BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a turbofan molded out of a thermoplastic resin and
an air conditioner on which the turbofan is mounted.
Description of the related art
[0002] There is a conventional turbofan molded out of a thermoplastic resin in which rigidity
of the turbofan is assured by ribs each constructed by a runner of injected resin
to realize lighter weight by reducing the thickness (refer to, for example, Japanese
Patent Application No.
3, 131,625 (p. 3 and 4 and FIGS. 1 and 3)).
There is also another turbofan in which the material is decreased by forming a recess
in an intersection of a blade and a main plate to realize cost reduction (refer to,
for example, Japanese Utility Model Application Laid-open No.
4-116698 (p. 1 and FIG. 1)).
There is further another turbofan including a plurality of blades having similar sectional
shapes in which thickness gradually increases from a shroud to a main plate, and the
distance between neighboring blades is gradually narrowed from the shroud to the main
plate. With the configuration, a time difference is created in release vortexes of
blowout flows from the shroud to the main plate at a blowout port of the turbofan,
thereby preventing noise resonance and the like and reducing noise (ref er to, for
example, Japanese Patent Application No.
3,544,325 (p. 7 to 9, FIGS. 5 and 6)).
There is further another turbofan using a thick hollow blade, thereby shortening cooling
and hardening time at the time of molding, preventing deformation at the time of cooling
and hardening, and reducing plastic material (refer to, for example, Japanese Utility
Model Application Laid-open No.
4-116699 (p. 1 and FIG. 1)).
DISCLOSURE OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0003] The conventional turbofan in the Japanese Patent Application No.
3,131,625 (p. 3 and 4 and FIGS. 1 and 3) has ribs for reinforcement to realize a thinner main
plate, the ribs also serving as a runner of a resin for improvement in moldability.
However, the strength of a resin merging portion, at which resins flowing from the
ribs merge at the time of molding, is low. Specifically, the resin merging portion
is positioned almost at the same distance from neighboring ribs, and the strength
of the portion is low. The conventional turbofan has a blade front-end rib positioned
near the front end of a blade and extending in the radial direction, a blade rear-end
rib positioned near the rear end of the blade and extending in the radial direction,
a connection rib for connecting the blade front-end rib and the blade rear-end rib,
and a blade reinforcement rib. For the ribs, resin is injected from one resin injection
port.
When the resin injected from the resin injection port flows to the ribs, in each of
the blade front-end rib and the blade rear-end rib, the resin flows in two ways in
the radial direction to the rotation center side and the outer periphery side. In
the connection rib, the resin flows in a direction having a radial-direction component
and a circumferential-direction component. In the blade reinforcement rib, the resin
flows in the direction opposite to the connection rib. That is, the resin injected
from one injection port flows in the plurality of ribs extending in the radial direction.
The resins flowing out from the ribs are merged and the resin merging portion is formed.
The resin merging portion is also formed between resins flowing out from neighboring
resin injection ports. Consequently, a number of resin marging portions are created
in the entire of the turbofan, and it limits improvement in strength of the turbofan.
Usually, a plurality of holes for cooling a motor are formed in a projected portion
of a main plate near the rotation axis. When the resin merging portion is formed on
a motor cooling hole as an opening portion having low strength, the strength becomes
lower. For example, when an impact in a direction parallel with the rotation axis
is applied to the turbofan during transportation or the like, a crack occurs in the
resin merging portion around the motor cooling hole. When the portions of low strength
are connected, a problem occurs such that the crack extends. With the configuration
of the runners, the resin merging portion may extend to the outer peripheral end of
the fan. It causes a problem such that the crack occurring in the resin merging portion
extends to the outer peripheral end, the fan is easily broken, and the product quality
deteriorates.
[0004] The configuration described in the Japanese Utility Model Application Laid-open No.
4-116698 (p. 1 and FIG. 1) in which a recess is formed in the intersection of a blade and
a main plate has the following problem. A flow along the surface of the main plate
is generated when the turbofan rotates. The flow on the surface of the main plate
leaves a corner R at the upstream end of the recess and then collides with a corner
R at the downstream end, so that noise is generated by pressure fluctuations.
[0005] In the turbofan described in the Japanese Patent Application No.
3,544,325 (p. 7 to 9, FIGS. 5 and 6), the blade does not have a hollow structure and the thickness
in portions of the blade largely varies, so that a temperature difference occurs in
the portions of the blade at the time of molding. Consequently, a cavity is generated
due to uneven flow of the resin and local thickness reduction (hereinbelow, called
locally small thickness) occurs. It causes a problem that moldability deteriorates.
Since the whole blade is made of a resin, as compared with a blade having a hollow
shape, a larger amount of resin is necessary. The fan becomes heavy and cost of the
fan becomes high. Accordingly, an air conditioner on which the turbofan is mounted
becomes heavy. There is a problem that portability for the worker is low.
[0006] A centrifugal fan described in the Japanese Utility Model Application Laid-open No.
4-116699 (p. 1 and FIG. 1) has a thick hollow blade. However, when the blade is too thick,
the air passage area of the fan is reduced. Consequently, there is the possibility
that noise increases due to increase in passage air velocity. The blade sections perpendicular
to the rotation axis are the same. When the blades is released from a mold at the
time of performing injection molding, there is no draft. The fan has a problem that
the resin is adhered to the mold and breakage occurs.
[0007] The present invention has been achieved to solve the problems as described above,
and an object of the invention is to obtain a reliable turbofan which is prevented
from being broken at the time of transportation or the like by realizing improvement
in moldability and strength of the turbofan made of a thermoplastic resin, and an
air conditioner on which the turbofan is mounted.
Another object of the invention is to obtain a turbofan realizing reduced noise and
an air conditioner on which the turbofan is mounted.
MEANS FOR SOLVING THE PROBLEM
[0008] A turbofan according to the present invention includes: a disc-shaped main plate;
a projected hub formed by making a center portion of the main plate project in a rotation
axis direction; a plurality of blades each of which is vertically provided in the
projecting direction of the hub using an outer-periphery-side flat part of the main
plate as a base; a plurality of motor cooling holes which are formed in the hub so
as to cool a motor disposed in a space having a projection shape surrounded by the
hub; a plurality of hub runners which are provided radially in the hub and into which
a thermoplastic resin is made to flow at the time of molding, so as to form the hub;
and a resin merging portions each of which is formed by merging the thermoplastic
resin flowing out from the neighboring hub runners at the time of molding, and is
characterized in that the motor cooling holes are disposed so as to avoid the resin
merging portion.
EFFECT OF THE INVENTION
[0009] According to the invention, a fan can be prevented from being broken by an impact
because of the configuration that the resin merging portion is not connected to the
motor cooling hole. Consequently, the strength can be improved, and an effect that
a reliable turbofan can be obtained is produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
FIGS. 1A and 1B are plan view and side view, respectively, of a turbofan according
to a first embodiment of the invention.
FIG. 2 is a perspective view of the turbofan according to the first embodiment of
the invention.
FIG. 3 is a view illustrating the turbofan according to the first embodiment of the
invention.
FIG. 4 is an enlarged view illustrating the turbofan according to the first embodiment
of the invention.
FIG. 5 is a view illustrating a cross section taken along line H1-H2 of FIG. 4, showing
the first embodiment of the invention.
FIG. 6 is an enlarged view illustrating a cross section taken along line O-O1-O2-O3
of FIG. 1B, showing the first embodiment of the invention.
FIG. 7 is a flowchart showing a fan molding process according to the first embodiment
of the invention.
FIG. 8 is a graph showing molding time (time from resin injection to taking out after
cooling) with respect to the ratio t1/t0 of the maximum thickness t1 of a hub runner
9a and the minimum thickness t0 of the other portion of a main plate 2 in the first
embodiment of the invention.
FIG. 9 is a graph showing molding time (time from resin injection to taking out after
cooling) with respect to the ratio t2/t0 of the maximum thickness t2 of a blade runner
9b and the minimum thickness t0 of the other portion of the main plate 2 in the first
embodiment of the invention.
FIGS. 10A and 10B are views showing a blade according to the first embodiment of the
invention. FIG. 10A is a side view showing a blade in the fan and FIG. 10B is a view
showing a transverse section taken along line Z-Z of FIG. 10A.
FIG. 11 is an explanatory view showing the blade according to the first embodiment
of the invention and showing a vertical section taken along line Y-Y of FIG. 10B.
FIG. 12 is a graph showing fan molding time (sec) and noise value (dB) when standing
faces on the outside of the blade and on the inside of the hollow are tilted at a
tilt angle θ toward the inside of the hollow with respect to the rotation axis and
the tilt angle θ is changed.
FIG. 13 is a bottom view showing a turbofan molded with another runner configuration
according to the first embodiment of the invention.
FIG. 14 is a bottom view showing a turbofan molded with further another runner configuration
according to the first embodiment of the invention.
FIG. 15 is a perspective view showing the turbofan having another configuration, viewed
from below, according to the first embodiment of the invention.
FIG. 16 is a partly enlarged perspective view showing a part of the turbofan according
to the first embodiment of the invention.
FIGS. 17A and 17B are views illustrating a blade according to the first embodiment
of the invention. FIG. 17A is a side view of a blade in a fan, and FIG. 17B is a view
showing a transverse section taken along line Z-Z of FIG. 17A.
FIG. 18A and 18B are views illustrating a blade according to the first embodiment
of the invention. FIG. 18A is a view showing a vertical section taken along line Y-Y
of FIG. 17B and FIG. 18B is a partially enlarged view of FIG. 18A.
FIG. 19 is a view illustrating a part of the bottom face of the turbofan according
to the first embodiment of the invention.
FIG. 20 is a graph showing the relation between the ratio of maximum opening diameter
F of a blade opening 3b having a hollow structure to the difference Δt between height
of a blade front runner 9ba and height of a blade rear runner 9bb and the noise value
with the same air volume according to the first embodiment of the invention.
FIG. 21 is a perspective view showing an air conditioner mounted, viewed from a room
according to the first embodiment of the invention.
FIG. 22 is a view showing a vertical cross section of the air conditioner according
to the first embodiment of the invention.
FIG. 23 is a view showing a horizontal cross section of the air conditioner according
to the first embodiment of the invention.
DESCRIPTION OF REFERENCE NUMERALS
[0011]
- 1
- turbofan
- 2
- main plate
- 2a
- hub
- 2b
- fan inner-radius-side face
- 2c
- boss
- 2d
- hub upper thick portion
- 3
- blade
- 5
- motor cooling hole
- 8
- motor
- 9
- runner
- 9a
- hub runner
- 9b
- blade runner
- 9ba
- blade front runner
- 9bb
- blade rear runner
- 9c
- connection runner
- 9d
- cooling hole runner
- 10
- resin injection port
- 12
- air conditioner body
- 15
- heat exchanger
- A
- resin merging portion
- B
- resin flowing direction at the time of molding
- C
- air current near blade opening
- D
- fan rotating direction
- E1, E2
- air currents
- F
- maximum opening width of blade opening 3b (diameter of inscribing circle of opening
in main plate)
- G
- air guided toward motor cooling hole via hub runner
- O
- rotation center
DESCRIPTION OF THE PREFERRED EMBODIMENT
First Embodiment
[0012] A turbofan (hereinafter, simply called a fan) according to a first embodiment of
the present invention will be described hereinafter with reference to the drawings.
FIG. 1A is a plan view of a fan according to the embodiment viewed from a shroud side,
and shows a blade by partly cutting the shroud away. FIG. 1B is a side view of the
fan of FIG. 1A. The left half of FIG. 1B shows a side face, and the right half shows
a longitudinal section taken along O-O1-O2-O3 of FIG. 1A.
FIG. 2 is a perspective view showing an under face of the fan according to the embodiment,
that is, viewed from the side opposite to the shroud.
[0013] As shown in FIGS. 1A and 1B and FIG. 2, a fan 1 is constructed by a disc-shaped main
plate 2. A center portion of the main plate 2 has a projected shape which is projected
in the rotation axis direction, and a motor (not shown) is disposed in the space surrounded
by the projection. The projection will be called a hub 2a. A boss 2c is formed in
the center of the hub 2a, that is, in the center of the main plate 2, and the shaft
of a motor is fixed to the boss 2c. A portion in which the motor is mounted is called
a fan outside of the main plate 2. In a flat plate portion on the outer peripheral
side of the fan inside opposite to the fan outside, a plurality of, for example, seven
blades 3 are provided. In a portion connected to the boss 2c of the main plate 2,
a hub upper thick portion 2d is provided, which is thicker than a thickness t0 of
an inclined face of the hub 2a.
[0014] The blade 3 uses, as a base portion, a flat portion on the outer peripheral side
of the main plate 2 and has a hollow bag shape which is upright from a blade opening
3b in the base portion in the projection direction of the hub 2a. In the base portion,
a blade opening 3b is positioned between a blade inner-radius-side end 3a and a blade
outer-radius-side end 3c. A center line 3a-3c of the blade opening 3b and the radius
of the main plate 2 are disposed so as to intersect at a predetermined angle of, for
example, about 45°. As shown in FIG. 1A, a plurality of blades 3 are disposed at variable
pitches so that at least part of circumferential-direction mounting pitch angles σ1,
σ2, σ3, ..., and σ7 with respect to the rotational axis varies. In FIG. 1A, for example,
σ1=σ4 < σ3=σ6=σ7 < σ2=σ5.
[0015] The fan 1 is driven by the motor and rotates in the direction of the arrow D around
a rotation center O. A shroud 4 is provided around a the fan 1 as shown in FIG. 1B
and is fixed to each of the blades 3 from above in FIG. 1B.
[0016] A fan internal air duct 6 is formed by being sandwiched between the shroud 4 and
the main plate 2 near the hub 2a, and a fan external air duct 7 is constructed by
the hub 2a on the side where motor is disposed. In the hub 2a, motor cooling holes
5 which are constituted of a plurality of openings are formed at almost equidistant
positions from the rotation center O around the rotation center O, thereby providing
communication between the fan internal air duct 6 and the fan external air duct 7.
In FIG. 1A, for example, seven motor cooling holes 5 are provided. Each of the motor
cooling holes 5 is arranged on a straight line O-3a connecting one blade inner-radius-side
end 3a and the rotation center O. Like the blades 3, the plurality of motor cooling
holes 5 are also formed so that at least part of circumferential-direction mounting
pitch angles γ1, γ2, γ3, ..., and γ7 of the plurality of motor cooling holes 5 varies.
In this case, the circumferential-direction mounting pitch angles γ1, γ2, γ3, ...,
and γ7 of the motor cooling holes 5 are set as, for example, γ1= γ4 < γ3 = γ6 = γ7
< γ2 = γ5 in a manner similar to the circumferential-direction mounting pitch angles
σ of the blades 3.
[0017] The main plate 2 and the blades 3 are integrally molded by using a thermoplastic
resin such as ABS or ASG (hereinbelow, simply called resin). In FIG. 2, reference
numeral 10 denotes a mark of a resin injection port used for injecting the resin at
the time of molding the main plate 2 and the blades 3. The mark 10 is positioned near
a folding part between the hub 2a and the flat part of the main plate 2 and near the
blade inner-radius-side end 3a in the flat part and will be called a resin injection
port 10. Runners 9 serving as paths of the resin at the time of molding are formed
in the fan. In a mold, the runner 9 corresponds to a portion which is a space larger
in the thickness direction than main parts of the main plate 2 so that the resin can
pass easily. In the fan as a finished article, the resin in the runner 9 is solidified
and remains, and the thickness of the runner portion is larger than the minimum thickness
t0 of the portion other than the runner in the main plate 2.
[0018] One of the runners 9 is a hub runner 9a for forming the hub at the time of molding.
For example, seven hub runners 9a are radially formed in the hub 2a and extend linearly
in the radial direction of the fan from the resin injection ports 10 toward the rotation
center O without crossing other runners to positions near the motor cooling holes
5. The hub runner 9a is thicker than the minimum thickness t0 in the inclined face
of the hub 2a and has a predetermined thickness t1 (> t0). The motor cooling holes
5 are disposed near ends on the fan center side of the hub runners 9a, and the blade
inner-radius-side ends 3a of the blades 3 are disposed near the other ends on the
outer radius side of the fan of the hub runners 9a. Further, a center line 11 in the
width direction of each of the linear hub runners 9a is arranged so as to extend on
the motor cooling hole 5. The blade inner-radius-side end 3a, the resin injection
portion 10, the hub runner 9a, and the motor cooling hole 5 are disposed so as to
position on an almost straight line extending in the radial direction using the rotation
center O as a start point. In the embodiment, the mounting pitch angles σ in the circumferential
direction of the blades 3 are set as unequal pitch angles, so that the motor cooling
holes 5, the hub runners 9a, and the resin injection ports 10 are similarly formed
at unequal pitches with respect to the rotation center O. When the mounting pitch
angles σ of the blades 3 are identical pitch angles, the mounting pitch angles in
the circumferential direction of the motor cooling holes 5, the hub runners 9a, and
the resin injection ports 10 are similarly identical pitch angles.
[0019] In the outer-radius-side flat plate portion of the main plate 2 as the base of the
hollow blade 3, a blade runner 9b is formed around the blade opening 3b. The blade
runner 9b is a runner for forming the blade 3 when the resin is made to flow in at
the time of molding. Like the hub runner 9a, the blade runner 9b has a predetermined
thickness t2 (> t0) larger than the thickness t0 of the outer-radius-side flat plate
portion of the main plate 2. A connection runner 9c is a runner for connecting the
hub runner 9a and the blade runner 9b. The connection runner 9c is formed, for example,
with the same thickness t1 as that of the hub runner 9a and a width smaller than that
of the hub runner 9a and that of the blade runner 9b.
[0020] When the fan 1 rotates in the direction D, the ambient air is guided into the blades
3 by the shroud 4 and sucked to the inside of the shroud 4, passes through a fan internal
air duct 6, and blows out from spaces between the blades 3 at the periphery of the
fan as shown by the arrows E1 in FIG. 2. At this time, the pressure in a fan internal
air duct 6 is negative with respect to the pressure in a fan external air duct 7 in
which the motor is attached. As shown in FIGS. 1B and 2, a part E2 of the air blowing
out from the fan 1 passes through the motor cooling holes 5 connecting the fan internal
air duct 6 to the fan external air duct 7 and flows in the fan external air duct 7
while turning due to friction with the hub 2a. The part E2 of air current passes through
the motor cooling holes 5 and flows in the fan internal air duct 6 under negative
pressure. A motor is mounted on the side of the fan external air duct 7 surrounded
by the hub 2a and fixed to the fan 1 at the boss 2c. With the air current E2, the
motor is cooled.
[0021] At the time of integrally molding the turbofan with such a configuration by using
a resin, the resin is injected from the plurality of resin injection ports 10 to a
mold having a space of a fan shape. The resin injected from the resin injection ports
10 is led to the runners 9 as thick portions, flows in the whole fan, and the main
plate 2 and the blades 3 are integrally formed. FIG. 3 is a bottom view of the fan.
The hub runners 9a are runners each provided between a center-side end 9a1 to a fan
outer-radius-side end 9a2. The motor cooling holes 5 are disposed near the fan center-side
ends 9a1 and the blade inner-radius-side ends 3a are disposed near the fan outer-radius-side
ends 9a2.
A part of the resin flows in the hub runners 9a and, after that, flows in the hub
2a in the main plate and forms the portion. Another part flows from the connection
runners 9c to the blade runners 9b, flows to the blades 3 and the main plate 2 around
the blades 3, and forms the portions. The flow of resin is shown by the arrow B in
FIG. 3. The resin flows via the runners 9 to the mold as shown by the arrows B, and
the resin flowing from neighboring runners 9 collides and merges at a resin merging
portion located so as to be almost equidistant from the neighboring runners. The resin
merging portion is indicated by a broken line A.
[0022] The resin injected from the resin injection ports 10 and led to the hub runners 9a
flows smoothly in one direction toward the rotation center O in the radial direction.
Further, the resin flowing in a hub runner 9a flows toward a neighboring hub runner
9a, so that a resin merging portion A is formed between neighboring hub runners 9a.
Since the motor cooling holes 5 are arranged so as to avoid resin merging portions
A, a resin merging portion A near a motor cooling hole 5 is formed, not in connection
with the motor cooling hole 5, but between the neighboring motor cooling holes 5.
Since the resin merging portion A is not coupled to the motor cooling hole 5 as an
opening having low strength against impact, occurrence of a crack connected to the
motor cooling hole 5 and the resin merging portion A can be prevented, and the strength
of the molded fan 1 can be improved. Therefore, even if an impact is applied in the
direction of the rotation axis of the fan 1 at the time of transportation or the like,
for example, in the vertical direction of FIG. 1B and a crack occurs in the periphery
of the motor cooling hole 5, extension of the crack in the radial direction of the
main plate 2 can be prevented. Consequently, the fan 1 can be prevented from being
broken, and reliability against the impact on the fan 1 can be improved.
In particular, in the embodiment, by forming the motor cooling hole 5 on the extension
line of the hub runner 9a, formation of the resin merging portion A near the motor
cooling hole 5 can be surely avoided.
[0023] The runners 9 are not complicatedly branched. A runner 9 is branched to two runners;
the hub runner 9a, and the connection runner 9c at the resin injection port 10, and
is branched into the blade runner 9b in two directions at the connection part of the
connection runner 9c and the blade runner 9b. Since the strength is low in the resin
merging portion A as described above, it is preferable to set the number and length
of the resin merging portions A as small as possible. In the configuration of the
runners 9 according to the embodiment, the resin merging portion A is not formed by
the resin injected from the one resin injection port 10 but is formed by the contact
portion of the resin injected from the neighboring resin injection ports 10. Consequently,
the number of the resin merging portions A can be decreased as a whole. As described
above, the runners 9 are constructed relatively simply, the resin flows along the
runners 9 more easily, occurrence of shrinkage is reduced, and moldability can be
improved.
[0024] Further, in the fan according to the embodiment, one end of the resin merging portion
A is in contact with the boss 2c.
The resin merging portion A extends in the radial direction between the neighboring
motor cooling holes 5. The other end is in contact with the center of the blade 3.
In the conventional configuration in which the resin merging portion A extends straight
to the outer periphery, in the case where a crack occurs along the resin merging portion
A, there is the possibility that the crack extends to the outer periphery of the fan
1 and the fan 1 is broken down. In contrast, in the embodiment, the outer-radius-side
end of the resin merging portion A formed in the main plate 2 is in contact with the
blade runner 9b.
Consequently, the resin merging portion A formed in the main plate 2 can be made shorter,
that is, the portion with low strength can be shortened. Thus, the fan 1 with high
reliability in strength can be obtained. Even if a crack occurs near the resin merging
portion A and extends along the resin merging portion A at the time of transportation
or the like, since the outer-radius-side end of the resin merging portion A is in
contact with the thick blade runner 9b, the crack stops at this part. Further, in
the case where the crack does not stop by the blade runner 9b, the whole blade 3,
which is connected to the blade runner 9b and has height in the axial direction, serves
as a strength member. Consequently, the fan 1 can be prevented from being completely
broken down, and reliability against an impact can be improved.
[0025] The configuration of the resin merging portion A and the runners 9 will be described
in detail hereinbelow. The number of pieces, the shape, and the angle with respect
to the radius of the blades 3, the shape and configuration of the runners 9, the positions
of the resin injection ports 10, the shape and position of the motor cooling hole
5, and the like are set as described above. That is, one end of the resin merging
portion A is in contact with the boss 2c, the resin merging portion A extends in the
radial direction between the neighboring motor cooling holes 5, and the other end
is in contact with the center of the blade 3. With the configuration, the fan 1 having
reliability against an impact can be obtained.
FIG. 4 is a partly enlarged view of FIG. 3. FIG. 5 is s view illustrating a cross
section taken along line H1-H2 of FIG. 4. The resin injection port 10 is provided,
for example, in the hub runner 9a at a position close to the connection runner 9c.
Two neighboring resin injection ports 10m and 10n will be described as an example.
The resin injection port 10m is connected to a hub runner 9am, a blade runner 9bm,
and a connection runner 9cm. The resin is injected from the resin injection port 10m
to mold the blade 3m and the main plate 2 around the blade 3m. On the other hand,
a resin injection port 10n is connected to a hub runner 9an, a blade runner 9bn, and
a connection runner 9cn. The resin is injected from the resin injection port 10n to
mold the blade 3n and the main plate 2 around the blade 3n. The blade 3 formed upright
on the main plate 2 has a predetermined thickness t3 (> t0) and the thickness in the
blade 3 is almost uniform.
[0026] In the case where the blade 3m is positioned ahead of the blade 3n in the fan rotation
direction (the arrow D direction), to prevent the resin merging portion A formed between
the two blades 3m and 3n from being connected to the fan outer periphery, the area
L should be formed with the resin injected from the resin injection port 10n. In particular,
when the resin injected from the resin injection port 10n, not the resin injected
from the resin injection port 10m, is used as the resin for forming a flat part 3cmt
of the blade outer-radius-side end of the blade 3m, the resin merging portion A formed
between the hub runners 9an and 9am is surely brought in contact with the blade 3m.
To realize it, the runners 9 should be constructed so that the distance from the resin
injection port 10n is shorter than the distance from the resin injection port 10m
with respect to the lengths of the flow paths of the resin flowing to the flat part
3cmt at the blade outer periphery.
[0027] Concretely, the number of pieces and the shape of the blades 3, the shape and configuration
of the runners 9, the positions of the resin injection ports 10, the shape and position
of the motor cooling hole 5, resin injection speed, and the like, are fittingly set
and, for example, a simulation is performed. In such a manner, a part in which the
resin merging portion A is to be formed in the fan at the time of molding can be examined.
The configuration should be so constructed that one end of the resin merging portion
A obtained by the simulation comes in contact with the boss 2c and extends in the
hub 2a between the neighboring motor cooling holes 5, and the other end comes in contact
with the blade runner 9b.
[0028] As described above, the turbofan includes: the disc-shaped main plate 2; the projected
hub 2a formed by making a center portion of the main plate 2 project in the rotation
axis direction; the plurality of blades 3 each using the outer-periphery-side flat
part of the main plate 2 as the base and vertically provided in the projecting direction
of the hub 2a; the plurality of motor cooling holes 5 formed in the hub 2a and for
cooling a motor disposed in a space having a projection shape surrounded by the hub
2a; the plurality of hub runners 9a which are provided radially in the hub 2a and
into which a resin is made to flow at the time of molding, thereby forming the hub
2a; and the resin merging portion A formed by merging the resin flowing out from the
neighboring hub runners 9a at the time of molding. By disposing the motor cooling
holes 5 so as to avoid the resin merging portion A, there is an effect that the turbofan
having high reliability against an impact can be obtained.
[0029] The plurality of motor cooling holes 5 provided in the hub 2a is disposed at portions
on extended lines of the hub runners 9a to the rotation center O so that coupling
between the motor cooling holes 5 having low strength to impact and the resin merging
portion A is surely prevented, and the f an having high reliability against an impact
is obtained.
[0030] By forming the hub runners 9a radially around the rotation center O, the resin flows
to the boss 2c around the rotation center more easily, and moldability can be improved
[0031] Each runner 9 as a path of the resin is formed so as to be separated to a hub runner
9a and a blade runner 9b. A connection runner 9c for connecting the runners 9a and
9b is provided and, further, the resin is injected from the resin injection port 10
provided in any one of the runners 9a, 9b, and 9c. Specifically, either of the resin
flowing in the hub runner 9a and the resin flowing in the blade runner 9b necessarily
flows via the connection runner 9c. Consequently, the balance between the amount of
the resin flowing in the hub runner 9a and that of the resin flowing in the blade
runner 9b can be adjusted according to settings of the width and thickness of the
connection runner 9c. By adequately adjusting the injection amounts of the resin flowing
in the hub runner 9a and the blade runner 9b, occurrence of cavity or locally small
thickness due to uneven flow can be prevented, and deterioration in strength can be
prevented.
Although the resin injection port 10 is directly provided in the hub runner 9a in
the embodiment, the resin injection port 10 may be provided in the blade runner 9b
or the connection runner 9c. In the case of providing the resin injection port 10
in the connection runner 9c, by making the thickness and width of the runner between
the resin injection port 10 and the hub runner 9a and those of the runner between
the resin injection port 10 and the blade runner 9b different from each other in accordance
with the flow rate of resin required, the balance of the resin amounts can be adjusted.
[0032] Since the blade 3 has the hollow shape and the blade opening 9b is provided around
the opening 3b, the weight can be reduced because of the hollow shape, and the resin
runs to the whole mold more easily at the time of molding the blades 3.
Consequently, the blade 3 can be made thinner and lighter. By the reduction in weight,
the weight in the fan peripheral portion with respect to the rotation center is reduced.
Therefore, the centrifugal force at the time of rotation is reduced and a stress applied
to the root of the main plate as the base of the blade 3 is reduced. As a result,
the strength of the fan 1 can be improved, and breakage at the time of rotation can
be prevented. Since the portion of the blade runner 9b remains as the resin in a molded
body, the thickness of the connected part of the blade 3 and the main plate 2 on which
stress is concentrated can be increased by the blade runner 9b. As described above,
the resin flowability is improved by the blade runner 9b, moldability can be improved,
and strength of the turbofan can be improved.
[0033] As described above, by providing the plurality of hub runners 9a which are provided
radially in the hub 2a and in which a resin is made to flow at the time of molding,
thereby forming the hub 2a; the plurality of blade runners 9b which are respectively
provided around the bases of the blades 13 and in which the resin is made to flow
at the time of molding, thereby forming the blade 3; and the connection runners 9c
for respectively connecting the hub runners 9a and the blade runners 9b positioned
close to the respective hub runners 9a, each of the runners 9 is continuously formed
in the radial direction from the rotation center side to the outer periphery of the
main plate 2. Consequently, the resin injected from the resin injection port 10 is
branched to the resin flowing toward the rotation center and the resin flowing toward
the outer periphery side in main flow directions. After that, the resin does not flow
backward but flows to the main plate 2 in the periphery while flowing through the
runners 9.
As described above, the resin flow directions are relatively simple, so that a portion
in which the resin merging portion A is formed can be predicted clearly. There are
also effects that the resin can flow smoothly, moldability can be improved, and the
very reliable fan 1 can be obtained. Further, the distance of the resin merging portion
A can be shortened, and deterioration in the strength of the turbofan can be prevented.
[0034] As compared with the conventional configuration in which the resin merging portions
are formed by the resin injected from a single resin injection port, in the embodiment,
the number of the resin merging portions A can be decreased, the mold design can be
simplified, and occurrence of cavity and locally small thickness due to uneven flow
can be prevented.
[0035] FIG. 6 is a partly enlarged view of FIG. 1B. As shown in the figure, in the fan according
to the embodiment, the hub runner 9a having the thickness t1 is projected from the
hub 2a having the thickness t0 to the fan external air duct 7 side only by the thickness
difference (t1-t0) in the wall face constructing the hub 2a of the fan external air
duct 7. The motor cooling hole 5 is positioned on the extension line of the hub runner
9a on the rotation center side. Consequently, the hub runner 9a functions as an air
guiding plate and induces air current G toward the motor cooling hole 5. The hub runner
9a serves as an air guiding plate to the air current G, thereby increasing the current
of air flowing on the surface of a motor mounted in the portion surrounded by the
hub 2a and accelerating cooling of the motor. Usually, temperature protection control
is performed such that power supply to the motor is stopped when the temperature increases
to certain temperature in temperature rise of the motor. However, by accelerating
cooling of the motor, the motor can be efficiently driven without executing the temperature
protection control. Further, breakage of the motor caused by the high temperature
of the motor can be also prevented.
[0036] As described above, by the projection of the hub runner 9a from the face of the main
plate 2 of the hub 2a to the fan external air duct 7 side as the motor mounting side,
the current of air to the surface of the motor is increased, cooling of the motor
can be accelerated, and there is an effect that the very reliable turbofan can be
obtained.
[0037] With respect to the shape of the fan according to the embodiment, a plurality of
sets each constructed by the blade 3, the blade runner 9b, the hub runner 9a, the
connection runner 9c, and the motor cooling hole 5 are provided radially around the
rotation axis O as a center. Specifically, all of the blades 3 constructing the fan
1 have almost the same arrangement that the resin injection port 10, the hub runner
9a, the blade runner 9b, the connection runner 9c, and the motor cooling hole 5 are
prepared for the blade. Therefore, by injecting almost the same amount of resin to
the plurality of resin injection ports 10, the resin flows in similar directions in
the entire disc-shaped fan 1, and the blades 3 can be formed under similar molding
conditions. Consequently, there is an effect such that, in a fan completed by molding,
occurrence of cavity and locally small thickness caused by uneven flow can be prevented
as a whole, and a turbofan having high reliability in strength is obtained.
For example, when the necessary resin amount is different among the sets each constructed
by the blade 3, the blade runner 9b, the hub runner 9a, the connection runner 9c,
and the motor cooling hole 5 due to, for example, variations in the pitches in the
circumferential direction, by changing the amount of resin injected from the resin
injection port 10 in accordance with the necessary amount, the molding can be performed
under similar molding conditions, and an effect similar to the above is produced.
[0038] By providing equal numbers of the motor cooling holes 5 and the hub runners 9a, the
disposal relation of the blade 3 to the motor cooling hole 5 can be made almost similar
to the motor cooling holes 5 constructing the fan 1. Consequently, turbulent air flow
E2 from the fan external air duct 7 to the fan internal air duct 6 via the motor cooling
hole 5 goes to the rear side of the blade 3 formed by the blade runner 9b connected
to the hub runner 9a closest to the motor cooling hole 5. The turbulent air flows
E2 from the motor cooling holes 5 flow between the blades 3 and 3 respectively and
they do not directly collide with each other. Therefore, without being subjected to
large pressure fluctuations, the turbofan realizing reduced noise can be obtained.
Although equal numbers of the motor cooling holes 5 and the hub runners 9a are provided
here, the number of motor cooling holes 5 may be smaller than that of the hub runners
9a. For example, the motor cooling holes 5 may not be provided on the rotation center
O side of all of the hub runners 9a. By providing the motor cooling holes 5 in positions
avoiding the resin merging portions A of the hub 2a and in uniform positions with
respect to the rotation center O, the turbofan having high reliability in strength,
which can be molded under substantially uniform molding conditions and in which occurrence
of cavity and locally small thickness due to uneven flow can be prevented as a whole,
is obtained. Obviously, by providing equal numbers of the motor cooling holes 5 and
the hub runners 9a, the turbofan can be molded under more uniform molding conditions,
and the very reliable turbofan is obtained.
[0039] The fan shape is so constructed as shown in FIG. 1 that a plurality of sets each
made of the blade 3, the blade runner 9b, the hub runner 9a, the connection runner
9c, and the motor cooling hole 5 are provided radially around the rotation axis O
as a center, and at least one of angles each formed between neighboring sets is different
from the other angles. With the configuration, the air current E2 released to the
outside from the motor cooling hole 5 and the air flow E1 blowing off from the blade
3 are prevented from having periodicity. Therefore, noise due to the number of revolutions
of the fan can be prevented and quietness in the sense of hearing is maintained.
[0040] As described above, by providing a plurality of sets each constructed by the blade
3, the blade runner 9b, the hub runner 9a, the connection runner 9c, and the motor
cooling air 5 radially arranged around the rotary shaft as a center, each of the blades
3 has almost the same arrangement with respect to the resin injection port 10, the
hub runner 9a, the blade runner 9b, and the motor cooling hole 5. Therefore, the molding
conditions can be made almost the same, occurrence of cavity and locally small thickness
caused by uneven flow can be prevented, and the turbofan having high reliability in
strength is obtained.
In the sets each constructed by the blade 3, the blade runner 9b, the hub runner 9a,
the connection runner 9c, and the motor cooling hole 5, by making at least one of
the angles each formed between neighboring sets different from the other angles, an
effect that noise can be reduced is obtained.
[0041] By providing the motor cooling holes 5 of the same number as that of the hub runners
9a, the positional relations between the motor cooling holes 5 and the blades 3 can
be made equal, the air current E2 flowing from the fan external air duct 7 to the
fan internal air duct 6 can smoothly pass between the blades and to the outside. Effects
that noise can be reduced and, further, moldability is high are produced.
[0042] A fan molding process will now be described with reference to FIG. 7. FIG. 7 is a
flowchart showing the fan molding process. A mold for molding the fan 1 having the
shape shown in FIGS. 1 to 6 is fixed (ST1), and the thermoplastic resin is injected
from the resin injection ports 10 (ST2). The injected resin flows through the hub
runners 9a, the connection runners 9c, and the blade runners 9b and, further, spreads
from the runners 9 to the main plate 2 and the blades 3. The whole fan is filled with
the resin in a few msec. Next, the fan is cooled to harden the thermoplastic resin
(ST3). After the thermoplastic resin is completely hardened, the molded fan 1 is released
and removed from the mold (ST4). After that, the shroud 4 is fixed to the suction
side of the fan 1 (ST5) . Further, the program advances to a process such as attachment
of the shaft of a motor.
[0043] The thicknesses of the parts of the resin forming the fan 1 will now be described.
As shown in FIGS. 5 and 6, the minimum thickness of the part other than the runners
9 of the main plate 2 is t0, the thickness of the hub runner 9a is t1, the thickness
of the blade runner 9b formed around the opening 3b of the blade having a hollow shape
is t2, and the thickness of the blade 3 having a hollow shape is t3. At least the
thicknesses t1, t2, and t3 are set to be larger than the thickness t0. Although there
is a case that the runners 9 have an error at the time of molding or their corner
portion has an R shape, a portion having the maximum thickness is set as the thickness
of the runner 9. As shown in the diagrams, the thicknesses of the runners 9 include
the thickness of the main plate 2 and the thickness of the portion projected from
the main plate face.
FIG. 8 is a graph showing molding time with respect to the ratio t1/t0 of the thickness
t1 of the hub runner 9a to the minimum thickness t0 of the portion other than the
runner in the main plate 2. The axis of abscissa shows t1/t0, and the axis of ordinate
indicates the molding time (sec) . The molding time denotes time required for ST2
to ST4 in the flowchart shown in FIG. 7, which is the time from the resin injection
to the removing from the mold after cooling.
[0044] As shown in the graph of FIG. 8, in the case where t1/t0 is 1.0 or less, that is,
the thickness t1 of the hub runner 9a is equal to or less than the minimum thickness
t0 of the portion other than the runners in the main plate 2, the runner 9a is thinner,
flow of the resin is not good, it takes time for the resin to flow in the whole mold,
and molding time increases. In the case where t1/t0 is larger than 2.0, that is, the
thickness t1 of the hub runner 9a is larger than twice as large as the minimum thickness
t0 of the portion other than the runners in the main plate 2, it takes time to cool
down the resin, and the time until removing increases. As a result, when the ratio
t1/t0 lies in the range of 1.1 ≤ t1/t0 ≤ 2, the molding time can be made shorten at
least more than the case where the thicknesses t1 and t0 are the same (t1/t0 = 1.0)
. By shortening the molding time, the production amount can be increased. Further,
electricity used by a molding machine can be also reduced so that energy can be saved.
[0045] FIG. 9 is a graph showing molding time with respect to the ratio t2/t0 of the thickness
t2 of the blade runner 9b to the minimum thickness t0 of the portion other than the
runners in the main plate 2. The axis of abscissa shows t2/t0, and the axis of ordinate
indicates the molding time (sec) . The molding time denotes time required for ST2
to ST4 in the flowchart shown in FIG. 7, which is the time from the resin injection
to the removing after cooling.
As shown in the graph of FIG. 9, in the case where t2/t0 is 1.0 or less, that is,
the thickness t2 of the blade runner 9b is equal to or less than the minimum thickness
t0 of the portion other than the runners in the main plate 2, the runner 9b is thinner,
flow of the resin is not good, it takes time for the resin to flow in the whole mold,
and molding time increases. In the case where t2/t0 is larger than 2.0, that is, the
thickness t2 of the blade runner 9b is larger than twice as large as the minimum thickness
t0 of the portion other than the runners in the main plate 2, it takes time to cool
down the resin, and the time until removing increases. As a result, when the ratio
t2/t0 lies in the range of 1.1 ≤ t2 /t0 ≤ 2, the molding time can be made shorten
at least more than the case where the thicknesses t2 and t0 are the same (t2 /t0 =
1.0) . By shortening the molding time, the production amount can be increased. Further,
electricity used by a molding machine can be also reduced so that energy can be saved.
[0046] Therefore, by setting the ratio t1/t0 between the thickness t1 of the hub runner
9a and the minimum thickness t0 of the portion other than the runners 9 in the main
plate 2 in the range of 1.1 ≤ t1/t0 ≤ 2, the molding time can be shortened as compared
with the case where the thicknesses t1 and t0 are the same (t1/t0 = 1.0). Similarly,
by setting the ratio t2/t0 between the thickness t2 of the blade runner 9b and the
minimum thickness t0 of the portion other than the runners 9 in the main plate 2 in
the range of 1.1 ≤ t2/t0 ≤ 2, the molding time can be shortened as compared with the
case where the thicknesses t2 and t0 are the same (t2 /t0 = 1.0). Particularly, by
setting the upper limit of the thicknesses t1 and t2 of the runners 9 to double of
the minimum thickness t0 of the main plate 2, the molding time can be shortened, the
amount of the resin can be decreased, and reduction in the weight and cost of the
fan 1 can be also achieved.
Although the thickness t1 of the hub runner 9a and the thickness t2 of the blade runner
9b have been described separately, it is also possible to satisfy one of the thicknesses
or both of them. In the configuration where both of the thicknesses t1 and t2 are
satisfied, the molding time can be further shortened effectively.
[0047] As described above, when at least one of the thickness of the hub runner 9a and the
thickness of the blade runner 9b is set as "t" and the thickness of the portion other
than the runners 9 in the main plate 2 is t0, by setting the ratio t/t0 to be in the
range of 1.1 ≤ t/t0 ≤ 2, the molding time can be shortened as compared with the case
where the thicknesses t and t0 are the same (t/t0 = 1.0).
[0048] The shape of the blade 3 will be described hereinbelow.
FIGS. 10A and 10B and FIG. 11 show the configuration of one blade 3. FIGS. 10A and
10B and FIG. 11 are diagrams illustrating the blade 3 according to the embodiment.
FIG. 10A is a side view of one blade. FIG. 10B is a view illustrating a transverse
section taken along line Z-Z of FIG. 10A. FIG. 11 is an explanatory view illustrating
vertical section taken along line Y-Y of FIG. 10B.
As shown in FIG. 10A, a blade inner-radius-side hollow 3dc and a blade outer-radius-side
hollow 3dd of a blade hollow 3d tilt to the inside of the hollow shape with respect
to a linear line X parallel with the rotation axis at arbitrary angles θ1 and θ2,
respectively, that is, the blade hollow 3d is tapered from the blade opening 3b, as
a base, formed in the main plate 2 to the blade suction-side end 3e toward the inside
of the hallow shape. Since the blade 3 has almost uniform thickness, the blade inner-radius-side
end 3a and the blade outer-radius-side end 3c also tilt to the inside of the hollow
shape, with respect to the linear line X parallel with the rotation axis at the arbitrary
angles θ1 and θ2, respectively, that is, the blade ends 3a, 3c are tapered from the
blade opening 3b to the blade suction-side end 3e toward the inside of the hallow
shape.
As shown in FIG. 11, a blade front hollow 3da in the rotation direction D of the blade
3 and a blade rear hollow 3db as a side face in the inverse rotation direction of
the blade 3 tilt to the inside of the hollow shape with respect to the linear line
X parallel with the rotation axis at arbitrary angles θ3 and θ4, respectively, that
is, the side surfaces 3da, 3db of the blade hollow 3d are tapered from the blade opening
3b to the blade suction-side end 3e toward the inside of the hallow shape. Since the
blade 3 has almost uniform thickness, the blade inner-radius-side surface 3f and the
blade outer-radius-side surface 3g also tilt with respect to the linear line X parallel
with the rotation axis, at the arbitrary angles θ3 and θ4, respectively, that is the
blade hollow 3d is tapered from the blade opening 3b to the blade suction-side end
3e toward the inside of the hallow shape.
[0049] In short, the blade 3 and the blade hollow 3d have a tapered shape from the main
plate 2 to the shroud 4 and tilt to the inside of the hollow at the predetermined
angles θ1 and θ2, and the predetermined angles θ3 and θ4. Consequently, at the time
of releasing the mold from the fan mold body in the rotation axis direction, the resin
and the mold can be smoothly separated from each other because of the tilt. The blade
3 can be prevented from being adhered to the mold and broken, so that moldability
can be improved. On completion of cooling and hardening of the resin, the mold is
in close contact with the standing faces 3a, 3c, 3f, and 3g of the fan mold body on
the outside of the blade 3 having the hollow shape, and further with the standing
faces 3dc, 3dd, 3da, and 3db of the fan mold body on the inside or the hollow side
of the blade 3. The standing faces on both of the outside and inside of the hollow
are tapered from the base in the vertical direction. Consequently, the mold can be
easily released on both of the outside of the blade 3 and inside of the hollow of
the blade 3.
In addition, the weight of the blade 3 having the hollow shape can be reduced as compared
with that of the blade 3 which does not have a hollow shape. In the case where the
thickness of the blade 3 is not uniform, poor molding due to variations in cooling
and hardening time of the resin occurs, and there is a problem of low moldability.
However, the thickness of the blade 3 is made almost uniform, so that the cooling
and hardening time of the resin can be made almost uniform, poor molding can be prevented,
and moldability can be improved.
[0050] As described above, the turbofan includes: the disc-shaped main plate 2; the projected
hub 2a formed by making the center portion of the main plate 2 project in the rotation
axis direction; and the plurality of blades 3 each of which has the hollow shape,
and is provided so as to stand on the outer-periphery-side flat part of the main plate
2 as a base in the projecting direction of the hub 2a, the base having the opening
3b. The standing faces 3a, 3g, 3c, and 3f on the outside of the blade 3 having the
hollow shape and the standing faces 3da, 3db, 3dc, and 3dd on the inside or the hollow
side of the blade 3 tilt to the inside of the hollow, and the outside of the blade
3 and the hollow inside are tapered from the base. With the configuration, the mold
can be easily released, and the damage of the blade 3 caused by adhesion of the blade
3 to the mold can be prevented.
Further, by making the thickness of the blade 3 almost uniform, the cooling and hardening
time of the resin can be made uniform, and the turbofan having excellent moldability
can be obtained.
In addition, by forming the blade 3 in the hollow shape, the whole fan 1 can be made
lighter.
[0051] FIG. 12 is a graph showing fan molding time (sec) and noise value (dB) when all of
the angle θ1 of the blade inner-radius-side end 3a with respect to the rotation axis,
the angle θ2 of the blade outer-radius-end 3c with respect to the rotation axis, the
tilt angle θ3 of the blade front hollow 3da with respect to the rotation axis, and
the tilt angle θ4 of the blade rear hollow 3db with respect to the rotation axis are
set to the same tilt angle 6, and the tilt angle θ is changed. The axis of abscissa
denotes the tilt angle θ and the axis of ordinate indicates the molding time (sec)
and the noise value (dB). The noise value (dB) was measured at a point located just
below the fan and apart from the fan by 2 m. The molding time is time corresponding
to ST2 to ST4 in the flowchart showing the molding process shown in FIG. 7.
[0052] The molding time will be described on the basis of the graph shown in FIG. 12.
In the case where the tilt angle θ < 0°, the blade 3 has a shape widened from the
main plate 2 side toward the shroud 4 side, so that the mold cannot be released, and
the configuration is impossible. In the case where θ = 0°, that is, in the case where
the blade 3 is not tilted with respect to the rotation axis, friction between the
blade 3 and the mold is large. If the mold is not released slowly, the blade 3 is
broken due to adhesion to the mold, so that long molding time is necessary. In contrast,
by employing the tilt angles θ, mold release is facilitated, and mold release time
can be shortened. Further, the surface area of the blade 3 increases, and cooling
area also increases, so that cooling time is shortened. Consequently, by employing
the tilt angles θ, the molding time can be shortened.
When the tilt angle θ is 1°, the molding time becomes about the half of that in the
case where the tilt angle θ is 0°. Therefore, when the tilt angle θ is 1° or larger,
the molding time is shortened, and moldability is high.
[0053] The noise value will now be described on the basis of the graph shown in FIG. 12.
When the tilt angle θ is too large in the relation between the tilt angle θ and the
noise value, the flow path between the neighboring blades 3 and 3 is narrowed, velocity
of air passing in the path increases, and it increases noise. According to the result
of measurement in FIG. 12, when the tilt angle θ is larger than 3°, noise increases.
Consequently, when the tilt angle θ is set in the range of 1° ≤ θ ≤ 3°, a preferable
noise value can be maintained.
As a result, by setting the tilt angle θ in the range of 1° ≤ θ ≤ 3°, the turbofan
having small noise change and high moldability is obtained.
[0054] As described above, by making the standing faces 3a, 3g, 3c, and 3f on the outside
of the blade 3 having the hollow shape and the standing faces 3da, 3db, 3dc, and 3dd
on the inside or the hollow side of the blade tilt to the inside of the hollow, each
of the predetermined tilt angles θ is set in the range of 1°≤ θ ≤ 3°. It produces
an effect that the turbofan having small noise change and high moldability is obtained.
[0055] In the above, all of the blade inner-radius-side hollow 3dc, the blade outer-radius-side
hollow 3dd, the blade front hollow 3da, and the blade rear hollow 3db of the blade
are tilted to the inside of the hollow at the same tilt angle θ with respect to the
rotation axis. However, even when they are tilted at angles different from each other,
a similar effect is produced.
The blade inner-radius-side end 3a, the blade outer-radius-side end 3c, the blade
suction-side end 3e, the blade front side 3f on the front side in the blade rotation
direction, and the blade rear side 3g on the rear side in the blade 3 have almost
uniform thickness. However, the invention is not limited to the configuration, and
they may be slightly different from each other due to molding error and the like.
In the blade inner-radius-side end 3a and the blade outer-radius-side end 3c, since
the width in the rotation direction is small, and it is difficult to make the thicknesses
uniform in this part. It is sufficient to make the thickness of the blade 3 almost
uniform with fluctuation to a certain extent. By making the thickness uniform, the
resin is injected uniformly and cooled uniformly. Thus, a preferable mold body can
be obtained.
[0056] In the embodiment, by making the center portion of the blade 3 upright in the projection
direction of the hub 2a from the base of the main plate 2 and tilting the standing
faces on the outside of the blade 3 and on the inside or the hollow side to the inside
of the hollow, the above effects are obtained. In the configuration, the mold is released
in the rotation axis direction and in parallel with the rotation axis. For example,
the mold may be also released in the rotation axis direction while slightly turning
the mold around the rotation axis as a center. In the case of releasing the mold while
rotating it, the configuration in which the center portion of the blade 3 is upright
in the projection direction of the hub 2a from the base of the main plate 2 is not
employed, but a shape in which the center portion of the blade 3 tilts from the base
of the main plate 2 to the blade suction-side end 3e in the rotation release direction
by predetermined angle is employed. Also in the case of employing the configuration
that the blade 3 tilts, by tilting the standing faces on the outside of the blade
3 and the inside or the hollow side to the inside of the hollow, mold release can
be performed easily, and effects similar to the above are produced.
[0057] The turbofan 1 in which the runners 9 are formed with another configuration will
be described. FIG. 13 is a bottom view of the turbofan 1 molded with another runner
configuration. In FIG. 13, the same reference numerals as those of FIG. 3 express
the same or corresponding parts.
In FIG. 13, runners 9d for cooling holes, each formed so as to surround the motor
cooling hole 5 are provided. By connecting the runner 9d and the hub runner 9a, an
integral runner is formed.
[0058] In the turbofan constructed as described above, part of the resin injected from the
resin injection port 10 at the time of molding flows from the hub runner 9a to the
runner 9d for a cooling hole and further flows to the hub 2a and the boss 2c. At this
time, the resin flowing in the hub runner 9a is branched to two directions in the
cooling hole runner 9d, and flows in the cooling hole runner 9d provided around the
motor cooling hole 5. After the resin flows around the motor cooling hole 5, the resin
merges again with reliability on the side of the boss 2c of the motor cooling hole
5, and flows toward the boss 2c. As described above, by providing the cooling runner
9d, the flowability of the resin around the motor cooling hole 5 improves, so that
moldability can be improved.
By providing the cooling hole runner 9d around the motor cooling hole 5, the resin
in the cooling hole runner 9d is hardened to remain around the motor cooling hole
5 as an opening, and the periphery of the motor cooling hole 5 is made thick.
Consequently, the strength around the motor cooling hole 5, which tends to decrease
due to the opening, can be improved. Thus, the turbofan having durability against
a breakage even with an impact applied is obtained.
[0059] FIG. 14 is a bottom view of the turbofan 1 molded with further another runner configuration.
In FIG. 14, the same reference numerals as those of FIG. 3 express the same or corresponding
parts.
In FIG. 14, the linear hub runner 9a is connected to the cooling hole runner 9d around
the motor cooling hole 5 and is further connected to a hub upper thick portion 2d.
The rotation center side of the motor cooling hole 5 is the hub upper thick portion
2d which is thicker than the portion other than the runners in the main plate 2.
[0060] In the turbofan constructed as described above, part of the resin injected from the
resin injection port 10 at the time of molding flows from the hub runner 9a to the
runner 9d for a cooling hole and further flows to the hub upper thick portion 2d,
thereby forming the portion. In a manner similar to the configuration of FIG. 13,
the resin flowing in the hub runner 9a is branched to two ways in the cooling hole
runner 9d, and flows in the cooling hole runner 9d provided around the motor cooling
hole 5. After the resin flows around the motor cooling hole 5, the resin flows to
the hub upper thick portion 2d connected to the periphery of the motor cooling hole
5, thereby forming the hub upper thick portion 2d.
[0061] Like the configuration of FIG. 13, by providing the cooling hole runner 9d around
the motor cooling hole 5, the resin in the cooling hole runner 9d is hardened to remain
around the motor cooling hole 5 as an opening, and the periphery of the motor cooling
hole 5 is made thick. Consequently, the strength around the motor cooling hole 5,
which tends to decrease due to the opening, can be improved. By providing the cooling
hole runners 9d, moldability and strength can be improved by improvement in the flowability
of the resin around the motor cooling hole 5. The turbofan having durability against
a breakage even with an impact applied is obtained.
Further, in the configuration, the cooling hole runner 9d is directly connected to
the hub upper thick portion 2d around the boss, which is thicker than the hub inclination
face.
Consequently, the resin smoothly flows to the hub upper thick portion 2d, and the
resin flowing in the cooling hole runner 9d reliably merges again on the front side
in the resin flowing direction of the motor cooling hole 5, that is, on the boss 2c
side of the motor cooling hole 5, and the merged resin flows to the hub upper thick
portion 2d. Therefore, the resin can be reliably injected to the periphery of the
motor cooling hole 5 as an opening by an amount of the thickness of the cooling hole
runner 9d. Thus, the strength around the motor cooling hole 5, which tends to decrease
due to the opening, can be improved.
[0062] As described above, by providing the cooling hole runner 9d connected to the hub
runner 9a and formed so as to surround the motor cooling hole 5, the turbofan realizing
improved moldability and strength by improvement in the flowability of the resin around
the motor cooling hole 5 can be obtained.
[0063] Next, the blade runner 9b will be described in detail. FIG. 15 is a perspective view
of the turbofan according to the embodiment and having another configuration, viewed
from below.
FIG. 16 is a partly enlarged perspective view showing a part of FIG. 15 . FIGS. 17A
and 17B and FIGS. 18A and 18B are explanatory views illustrating one blade 3. FIG.
17A is a side view of the blade 3 and FIG. 17B is a transverse section taken along
line Z-Z of FIG. 17A. FIG. 18A is a cross section taken along line Y-Y of FIG. 17B.
FIG. 18B is an enlarged view of the portion of a circle M in FIG. 18A. FIG. 19 is
an explanatory view illustrating a part of the bottom face of the turbofan 1.
[0064] The configuration of the turbofan shown here is another configuration of the blade
runner 9b provided around the blade opening 3b formed in the base of the blade 3.
For example, as shown in FIGS. 15 to 18B, the blade runner 9b is provided around the
opening in the blade 3 having a hollow shape, and the blade runner 9b on the front
side in the blade rotation direction is called a blade front runner 9ba, and the blade
runner 9b on the rear side in the blade rotation direction is called a blade rear
runner 9bb. The projection height from the face of the main plate 2 of the blade front
runner 9ba and that from the face of the main plate 2 of the blade rear runner 9bb
are made different from each other. The projection height in the rotation axis direction
of the blade front runner 9ba is set to be larger than that of the blade rear runner
9bb by a predetermined height, and the blade front runner 9ba is made project to the
outside of the fan.
[0065] An air current C near the main plate 2 at the blade opening 3b generated at the time
when the fan 1 rotates in the direction D collides with the blade front runner 9ba,
is curved outward, draws a parabola, and flows so as to approach the main plate 2
again on the blade rear runner 9b side. FIG. 16 is an enlarged view showing this state.
If the blade front runner 9ba and the blade rear runner 9bb have the same height,
at the time of rotation of the fan, the flow around the main plate 2 is apart from
the blade front runner 9ba and collides with the corner of the blade rear runner 9bb,
so that pressure fluctuation occurs, causing a problem such that noise occurs in the
narrow band.
[0066] In contrast, when the blade front runner 9ba is set to be higher than the blade rear
runner 9bb by predetermined height as shown in FIG. 18B, the flow near the blade opening
3b is as shown by the arrow C in FIG. 18A. Specifically, the flow after departing
from the blade front runner 9ba draws a parabola which curves to the outside of the
main plate 2 and flows so as to approach the main plate 2 again on the rear side in
the rotation direction of the blade rear runner 9bb. If the blade front runner 9ba
is set to be higher, the air current C curves to the outside from the surface of the
main plate 2 so that the departing distance from the main plate 2 increases. As a
result, a re-attachment point of the air current C shifts to the rear side of the
blade rear opening 3b . By making the air current C smoothly re-attached on the rear
side of the blade rear opening 3b, the air current C can be prevented from collision
with the corner of the blade rear runner 9bb, and noise can be reduced.
Since the blade front runner 9ba becomes thicker, the resin flows to the blade 3 more
smoothly. As a result, shrinkage can be prevented, and moreover, the strength in the
blade front runner 9ba improves, so that the strength of the fan also improves.
[0067] As described above, by making the blade front runner 9ba higher than the blade rear
runner 9bb by predetermined height so as to project toward the outside of the fan,
the light, strong, highly reliable, and low-noise turbofan, which can be prevented
from being broken at the time of rotation and transportation, is achieved.
[0068] The difference Δt (shown in FIG. 18B) between the height of the blade front runner
9ba and the height of the blade rear runner 9bb of the blade runner 9b formed' so
as to surround the blade 3, with respect to the maximum opening diameter F of the
blade opening 3b of the blade having a hollow structure shown in FIG. 19 will be described.
The maximum opening width F is the diameter of an inscribing circle of the opening
on the face of the main plate 2, and Δt denotes the difference between the height
of the blade front runner 9ba and the height of the blade rear runner 9bb.
When the height difference Δt is small, the flow departing from the blade front runner
9ba does not draw a parabola having a sufficient height but collides with the corner
of the blade rear runner 9bb. Consequently, noise occurs due to pressure fluctuations
in the blade opening 3b. On the contrary, when the blade front runner 9ba is too high,
that is, the difference Δt is too large, the flow is separated by the blade front
runner 9ba, and a peak sound due to the rotation speed is generated. As described
above, a desirable range of the difference △t between the height of the blade front
runner 9ba and the height of the blade rear runner 9bb exists.
[0069] The flow crossing the blade opening 3b relates to not only the difference △t between
the height of the blade front runner 9ba and the blade rear runner 9bb but also the
maximum opening diameter F of the blade opening 3b. Consequently, the ratio (Δt/F)
of the difference Δt between the height of the blade front runner 9ba and the height
of the blade rear runner 9bb to the maximum opening diameter F of the blade opening
3b is calculated.
FIG. 20 is a graph showing the relation between the ratio (Δt/F) % and the noise value
(dB) with the same air volume. The axis of abscissa denotes the Δt/F (%) and the axis
of ordinate indicates the noise value (dB). The noise value was measured just below
the fan and 2m apart therefrom.
[0070] By constructing the turbofan so that the ratio lies at least in the range of 4% ≤
Δt/F ≤ 22% on the basis of the measurement result shown in FIG. 20, the turbofan with
noise lower than that in the case where the projection height from the face of the
main plate 2 of the blade front runner 9ba and that of the blade rear runner 9bb are
the same, that is, Δt = 0 (Δt/F=0) is obtained.
In the case where Δt/F < 4%, the difference Δt of the runners is small with respect
to the maximum opening diameter F. Thus, the possibility that the flow departing from
the blade front runner 9ba collides with the corner of the blade rear runner 9bb becomes
high, and pressure fluctuation occurs so that noise is generated in the narrow band.
On the other hand, in the case where 22% < Δt/F, the difference △t of the projection
heights of the runners is large with respect to the maximum opening diameter F. Thus,
the flow departing from the blade front runner 9ba is separated, and noise increases
by a peak sound due to the rotational speed.
[0071] As described above, by forming the turbofan so that the difference between the projection
height of the blade front runner 9ba and the projection height of the blade rear runner
9bb with respect to the maximum opening diameter F of the blade opening 3b is set
in the range of 4% ≤ Δt/F ≤ 22%, the noise can be suppressed, which is generated in
the narrow band at the time of rotation of the fan since the flow around the main
plate 2 is apart from the blade front runner 9ba, collides with the corner of the
blade rear runner 9bb so that pressure fluctuation occurs. A re-attachment point of
the air current after departing from the blade front runner 9ba to the rear side in
the rotation direction of the blade rear runner 9bb is moved to the rear side of the
blade rear opening 3g, so that the air current C is smoothly re-attached on the rear
side of the blade rear opening 3g. Since the projection height of the blade front
runner 9ba is not too high, so that the flow is not separated by the blade front runner
9ba, occurrence of generation of a peak sound due to rotation speed is suppressed,
and deterioration in noise can be prevented.
Consequently, reduction in noise can be achieved.
[0072] Therefore, by forming the turbofan so that the ratio Δt/F of the difference Δt of
the projection heights of the blade front runner 9ba and the blade rear runner 9bb
to the maximum opening diameter F of the blade opening 3b of the blade having the
hollow structure lies in the range of 4% ≤ Δt/F ≤ 22%, noise can be reduced.
[0073] By providing the above-described configuration of the fan in addition to the configurations
of the blade opening 3b and the blade runner 9b, further effects can be obtained.
For example, by providing the motor cooling holes 5 so as to avoid the resin merging
portions, the turbofan having high reliability in strength is obtained. By providing
the hub runner 9a, the resin flows easily to the boss 2c near the top of the main
plate 2, and the resin flowability in the whole main plate can be improved. Since
the blade 3 has the hollow structure, the weight of the turbofan as a whole can be
reduced. Further, the blade hollow 3d has the tapered shape having a molding draft
angle, which is tilted at the predetermined angle θ from the main plate 2 toward the
shroud 4, so that the mold can be easily released, breakage of the blade due to adhesion
of the blade 3 to the mold can be prevented, and moldability is high. Since the thickness
of the blade 3 is almost uniform, the cooling and hardening time can be made uniform.
Therefore, occurrence of poor molding caused by unevenness due to variations in the
cooling and hardening time can be prevented to a certain degree.
[0074] In the embodiment, the fan in which the plurality of blades 3 are constructed by
seven blades and, accordingly, seven runners 9 and seven motor cooling holes 5 are
provided has been described. However, the number of blades 3, the number of runners
9, and the number of the motor cooling holes 5 are not limited to the above but may
be arbitrary.
Although the number of the motor cooling holes 5 is the same as that of the hub runners
9a, as described above, the number of motor cooling holes 5 may be set to be smaller
than the number of hub runners 9a. When the motor cooling hole 5 is disposed on the
extension line of the hub runner 9a, the motor cooling hole 5 and the resin merging
portion do not meet with each other, so that the strength is high. Consequently, even
in the case where the number of motor cooling holes 5 is set to be smaller than that
of the hub runners 9a, it is preferable to dispose the motor cooling hole 5 on the
extension line of the hub runner 9a. By decreasing the number of the motor cooling
holes 5, although the function of cooling the motor decreases, the strength of the
hub 2a of the fan can be increased.
[0075] FIGS. 21 to 23 show an example of the configuration in which the turbofan 1 described
in the embodiment is mounted on an air conditioner. FIG. 21 is a perspective view
showing a state where an air conditioner is mounted in the ceiling, viewed from a
room. FIG. 22 is a vertical cross section of the air conditioner. FIG. 23 is a horizontal
cross section of the air conditioner. An example of mounting the turbofan 1 in a recessed
air conditioner in the ceiling will be described.
[0076] The air conditioner shown in FIG. 21 is a recessed air conditioner in the ceiling
and faces a room 19 through a decorative panel 13 having an almost square shape. In
a center portion of the decorative panel 13, a suction grille 13a as an air suction
port to the air conditioner body, and a filter 20 for removing dust from air passing
through the suction grille 13a are disposed.
The decorative panel 13 also has panel's blowout ports 13b formed along sides of the
decorative panel 13. Each of the panel's blowout ports 13b has a wind direction vane
13c.
[0077] As shown in FIG. 22, an air conditioner body 12 is disposed with a top plate 12c
facing up for the room 19, side plates 12d are attached to the sides of the top plate
12c, and is mounted so that the lower side opens to the room 19. A body's suction
port 12a in the center portion of the under face of the air conditioner body 12 is
disposed so as to communicate with the suction grille 13a of the decorative panel
13. Body's blowout ports 12b disposed around the body's suction port 12a are disposed
so as to communicate with the panel's blowout ports 13b. The air conditioner body
12 has therein the fan 1, a bell mouth 14 forming a suction air path of the turbofan,
and a motor 8 for rotating the fan 1.
[0078] A heat exchanger 15 is disposed in a discharge air path extending from a part between
the blades as an air current blowing part in the fan 1 to the panel's blowout ports
13b. The heat exchanger 15 has aluminum fins 15a and heat transfer tubes 15b. The
heat exchanger 15 has a configuration that the plurality of aluminum fins 15a each
having a rectangular shape, which extend in the height direction of the air conditioner
body 12, that is, in the vertical direction are stacked at predetermined intervals
and the heat transfer tubes 15b in a plurality of stages penetrate the fins in the
stack direction.
As shown in FIG. 23, the heat exchanger 15 is formed almost in a C shape so as to
surround the periphery side of the turbofan 1. To the heat transfer tubes 15b at one
of two ends of the heat exchanger 15 having an almost C shape, a header 16 for adjusting
an amount of refrigerant to each of the heat transfer tubes 15b, a distributor 17,
and connecting pipes 18 connecting the distributor 17 with the outside unit are attached.
A refrigerant such as carbon dioxide is circulated in the heat transfer tubes 15b.
[0079] By the air conditioner constructed as described above, when the turbofan 1 rotates
in the rotation direction D, air in the room 19 passes through the suction grille
13a of the decorative panel 13 and the filter 20 and dusts are removed from the air.
The resultant air passes through the body's suction port 12a and the bell mouth 14
and is sucked in the turbofan 1. The air passes between the blades 3 of the turbofan
1 and is discharged toward the heat exchanger 15. The indoor air is heat-exchanged
with the refrigerant flowing in the heat transfer tubes 15b at the time of passing
through the heat exchanger 15, thereby performing heat exchange for heating, cooling,
or the like or dehumidification. After that, when the air blows out from the body's
blowout port 12b and the panel's blowout ports 13b into the room 19, the direction
of the air is controlled by the wind direction vanes 13c.
[0080] At the time of transporting the air conditioner, usually, the air conditioner is
held so that the rotation axis direction of the turbofan 1 is perpendicular, that
is, the rotary shaft of the fan motor 8 is perpendicular. Specifically, the air conditioner
body 12 is loaded onto a truck or the like and carried in a state where the body top
plate 12c becomes an under face or the bell mouth 14 side of the air conditioner body
12 becomes the under face.
[0081] By mounting the turbofan 1 according to the embodiment in the recessed air conditioner
shown in FIGS. 21 to 23, the following effects are produced. By the improvement in
the moldability of the turbofan 1, the turbofan 1 can be made thinner and lighter,
and the weight of the whole product can be reduced. Since the strength reliability
is improved, the turbofan 1 can be prevented from being damaged by an impact such
as vibration at the time of transportation. The product reliability of the air conditioner
can be also improved.
In the turbofan 1 in which the motor cooling holes 5 and the blades 3 are disposed
at unequal pitches, turbulent flow released from the motor cooling holes 5 to the
outside of the turbofan 1 and the flow blowing from the blades 3 do not have periodicity.
Therefore, noise due to the rotational speed of the fan can be reduced, and reduction
in noise can be achieved. By mounting the fan 1 on the air conditioner, the turbulent
flow flowing out from the fan 1 to the panel's blowout port 13b is also reduced. Consequently,
noise in the fan 1 is reduced and, in addition, noise in the air conditioner can be
further reduced, so that a quiet air conditioner is obtained. Since heat exchange
is performed with the refrigerant in the heat exchanger 15 in a state where the turbulent
flow is reduced, the efficient air conditioner is obtained.
[0082] The present invention is not limited to the recessed air conditioner shown in FIGS.
21 to 23. Although the air conditioner having the panel's blowout ports 13b in four
directions in the ceiling has been described here, two panel's blowout ports 13b may
be provided in two directions so as to face each other. The air conditioner may not
be entirely mounted in a recess in the ceiling but may be mounted in a state where
it is pro j ected downward from the surface of the ceiling. The air conditioner is
not limited to a ceiling mounting type but may be a wall mounting type. By applying
the turbofan according to the embodiment to an air conditioner having another configuration
on which the turbofan is mounted, in a manner similar to the above, breakage of a
fan during product transportation can be prevented, and a quiet and light air conditioner
with low noise, high product quality, and high portability is obtained.
[0083] As described above, by the configuration including at least any one of the turbofans
described in the embodiment and a heat exchanger, in which air sucked from a suction
port by the turbofan is heat-exchanged with a refrigerant in the heat exchanger, and
blowing the resultant from a blowout port, a lightweight air conditioner having high
reliability in strength and achieving reduced noise is obtained.
The invention is not limited to the air conditioner but can be also applied to a ventilation
fan and an air cleaner each including a turbofan, and effects similar to the above
can be obtained.
[0084] According to the present invention, the following effects can be obtained.
The plurality of hub runners 9a, which are connected to the resin injection ports
10 and extended linearly in the fan radial direction with a thickness larger than
that of the inclined face of the hub 2a of the main plate, are provided in predetermined
intervals in the side face on the motor side of the main plate 2. When resin flows
from the hub runners 9a to the hub upper thick portion 2d near the boss thicker than
the inclined face of the hub at the time of molding, the resin merging portion A is
not connected to the motor cooling hole 5 as an opening having low strength against
an impact but is formed between the motor cooling holes 5. Consequently, the resin
flows easily to the boss 2c to improve moldability, and the resin merging portion
formed in the main plate 2 can be made short. Thus, even if an impact is applied in
the axial direction (vertical direction in FIG. 1B) of the turbofan 1 at the time
of transportation or the like so that a crack occurs in the worst case, the turbofan
is resistant to breakage. The improved moldability and high reliability against an
impact of the turbofan can be achieved.
[0085] The motor cooling holes 5 are disposed near the fan center-side ends 9a1 of the hub
runners 9a, and at least the number of the motor cooling holes 5 and the number of
the hub runners 9a are the same. Further, the blade inner-radius-side ends 3a are
disposed near the fan outer-radius-side ends 9a2 of the hub runners 9a. The hub runners
9a and the blade runners 9b formed so as to surround the openings 3b of the blades
3 are connected to each other via the connection runners 9c, so that the resin merging
portion A made of the resin flowing from the hub runners 9a is formed between the
motor cooling holes 5 with reliability. As a result, even if an impact is applied
in the axial direction (vertical direction in FIG. 1B) of the turbofan 1 at the time
of transportation or the like so that a crack occurs in the worst case, the turbofan
is resistant to breakage. The improved moldability and high reliability against an
impact of the turbofan can be achieved. Since the hub runner 9a and the blade runner
9b are not integrally formed, the amount of injection of the resin injected from the
resin injection port 10 between the hub runner 9a and the blade runner 9b can be adjusted.
Therefore, occurrence of cavity and locally small thickness due to uneven flow can
be prevented, and thereby deterioration in strength can be prevented. Since the resin
flows more easily because of the blade runners 9b, the thickness of the blade 3 can
be reduced, and the thickness of the connection part of the blade 3 and the main plate
2 on which stress is concentrated can be increased. Thus, both improvement in moldability
and improvement in strength of the turbofan can be realized by improvement in the
resin flowability.
[0086] Since the neighboring linear hub runners 9a are formed so as not to overlap each
other, the main current direction of the resin is the radial direction so that the
flow direction is less complicated as compared with the conventional case where ribs
forming runners to one resin injection port 10 are numerous, the resin merging portion
A can be made clearer, the number of resin merging portions A can be reduced, the
mold design can be simplified, occurrence of cavity and locally small thickness due
to uneven flow can be prevented, and deterioration in strength of the turbofan can
be prevented.
[0087] Since the hub runner 9a is projected to the fan external air duct 7 side of the main
plate, the hub runner 9a can also serve as an air guide for inducing flow G toward
the motor cooling hole 5. With the configuration, air flowing on the surface of the
fan motor 8, which is mounted on the side of the fan external air duct 7 of the hub
2a and fixed to the turbofan 1 by the boss 2c, increases, so as to cool the motor
more easily. Therefore, the temperature protection control for coping with the motor
temperature rise is made unnecessary and, further, breakage of the motor due to high
temperature can be also prevented.
[0088] The resin injection port provided near the blade inner-radius-side end and the blade
runner formed so as to surround the main-plate-side opening of the blade having the
hollow shape are connected to each other via the connection runner. The blade inner-radius-side
hollow, the blade outer-radius-side hollow, the blade front hollow surface, and the
blade rear hollow surface of the blade hollow are faces tilted at an arbitrary angle
θ with respect to the rotation axis. The blade inner-radius-side end, the blade outer-radius-side
end, the blade suction-side end, and the blade front-side end on the front side and
the blade rear-side end on the rear side in the blade rotation direction are formed
so as to have almost the same thickness in the entire blade. The blade and the blade
hollow are formed so as to be tapered from the main plate toward the shroud. Since
the blade has a hollow structure, the weight of the blade can be reduced. Because
of almost uniform thickness, occurrence of poor molding caused by variations in the
cooling and hardening time of the resin due to non-uniform blade thickness is suppressed,
so that moldability is high. In addition, since each of the blade and the blade hollow
has a tapered shape at a molding draft angle, which is tilted at the predetermined
angle from the main plate toward the shroud, the mold can be easily released, breakage
of the blade due to adhesion of the blade to the mold can be prevented, and moldability
is high.
[0089] In a turbofan made of a thermoplastic resin including: a disc-shaped main plate having
a projected hub formed by making a center portion so as to cover a motor, a plurality
of motor cooling holes formed in the hub, for communicating the motor and the inside
of the fan, and a boss as a fixing part to a rotary shaft of a motor, which is provided
in the center portion of the hub; a plurality of blades; and a shroud for coupling
the plurality of blades to form an air intake wall, a plurality of hub runners each
of which is connected to a resin injection port formed in a main plate flat portion
near the blade inner-radius-side end, made thicker than the inclined face of the main
plate, and extended linearly in the radial direction of the fan, is provided in predetermined
intervals on the motor-side side face of the main plate. The hub runners are so formed
that a resin merging portion formed between neighboring hub runners is not connected
at least to the motor cooling holes. The blade inner-radius-side hollow, the blade
outer-radius-side hollow, the blade front hollow surface, and the blade rear hollow
surface of the blade hollow are faces tilted at an arbitrary angle θ with respect
to the rotation axis. The blade inner-radius-side end, the blade outer-radius-side
end, the blade suction-side end, and the blade front-side end on the front side and
the blade rear-side end on the rear side in the blade rotation direction are formed
so as to have almost the same thickness in the entire blade. The blade and the blade
hollow are formed so as to be tapered from the main plate toward the shroud. Because
of the hub runners, resin flowability in the hub and the main plate is high, and moldability
is high. Since the hub runners are formed so that the resin merging portion does not
communicate with at least the motor cooling holes, breakage of the fan due to an impact
at the time of transportation or the like is prevented. Since the blade has a hollow
structure, the weight of the turbofan as a whole can be reduced. Because of almost
uniform thickness, occurrence of poor molding caused by variations in the cooling
and hardening time of the resin due to non-uniform blade thickness is suppressed,
so that moldability is high. In addition, since each of the blade and the blade hollow
has a tapered shape at a molding draft angle, which is tilted at the predetermined
angle from the main plate toward the shroud, the mold can be easily released, breakage
of the blade due to adhesion of the blade to the mold can be prevented, and moldability
is high.
Further, because of reduction in the weight of the blades, the weight of the outer
peripheral portion of the turbofan relative to the rotation center of the turbofan
is reduced. Consequently, centrifugal force at the time of rotation is lessened, the
stress applied on the root of the blade on the main plate is reduced, and strength
can be improved. Thus, breakage of the turbofan at the time of rotation can be prevented.
As a result, the lightweight and high-reliability turbofan having high moldability
and strength is obtained.
[0090] The blade inner-radius-side hollow, the blade outer-radius-side hollow, the blade
front hollow surface, and the blade rear hollow surface of the blade hollow are faces
tilted at a tilt angle θ of 1° to 3° with respect to the rotation axis. The blade
inner-radius-side end, the blade outer-radius-side end, the blade suction-side end,
and the blade front-side end on the front side and the blade rear-side end on the
rear side in the blade rotation direction are formed so as to have almost the same
thickness in the entire blade. The blade and the blade hollow are formed so as to
be tapered from the main plate toward the shroud. Since the blade has a hollow structure,
the weight can be reduced. Because of almost uniform thickness, occurrence of poor
molding caused by variations in the cooling and hardening time of the resin due to
non-uniform blade thickness is suppressed, so that moldability is high. In addition,
since each of the blade and the blade hollow has a tapered shape at a molding draft
angle, which is tilted at the predetermined angle from the main plate toward the shroud,
the mold can be easily released, breakage of the blade due to adhesion of the blade
to the mold can be prevented, and moldability is high. A noise change is at least
small and does not deteriorate. As a result, when at least the tilt angle θ is 1°
to 3°, a turbofan with a small noise change and high moldability is obtained.
[0091] The mounting pitch angles σ in the circumferential direction of the blades 3 are
set as unequal pitch angles and, simultaneously, the pitch angles γ in the circumferential
direction of the motor cooling holes 5 are unequal pitch angles in correspondence
with the blades 3. The hub runners 9a extending linearly in the radial direction from
the fan rotation center O are also arranged at unequal pitches in correspondence with
the blades 3 and the motor cooling holes 5. One resin injection port 10, the hub runner
9a, the blade runner 9b, and the motor cooling hole 5 are disposed almost by the same
arrangement. Consequently, molding conditions hardly-change, occurrence of cavity
and locally small thickness due to uneven flow can be prevented, and deterioration
in strength of the turbofan can be prevented. Since the motor cooling holes 5 and
the blades 3 are disposed by the same arrangement, the turbulent flow E2 from the
fan outer air duct 7 to the fun inner air duct 6 via the motor cooling hole 5 does
not directly collide with the blade 3, the turbofan is not largely subjected to pressure
fluctuations so that noise can be reduced.
[0092] The resin flowing out from the resin injection port 10 flows from the hub runner
9a toward the cooling hole runner 9d and flows to the boss 2c. Since there is the
cooling hole runner 9d around the motor cooling hole 5, after the resin flows in,
the resin is merged again on the rear side in the resin flowing direction of the motor
cooling hole, and the merged resin flows to the boss 2c . Consequently, unlike the
conventional technique in which there is no cooling hole runner around the cooling
hole and the resin is not easily re-merged on the rear side in the resin flowing direction
of the cooling hole, the strength around the motor cooling hole 5, which tends to
decrease due to the opening, can be improved. As a result, improvement in both moldability
and strength is realized by improvement in the resin flowability around the motor
cooling hole, and the turbofan, which is resistive to breakage even when an impact,
is applied, is obtained.
[0093] When the ratio t1/t2 is in the range of 1.1 to 2, and the ratio t2/t0 is in the range
of 1.1 to 2 where t1 denotes the maximum thickness of the hub runner 9a, t2 denotes
the maximum thickness of the blade runner 9b, and t0 denotes the minimum thickness
of the other portion of the main plate 2, molding time can be shortened as compared
with the case where the thicknesses are the same (t1/t0, t2/t0=). The production amount
can be increased in the same time, electricity required for a molding machine can
be also reduced, and energy can be saved.
[0094] The blade front runner corresponding to the side face in the blade rotation direction
of the blade runner formed so as to surround the opening on the outer side of the
main plate of the blade having a hollow structure has a height larger than the blade
rear runner corresponding to the side face on the opposite side in the blade rotation
direction and is formed so as to project to the outside of the fan. Consequently,
the noise can be suppressed, which is generated in the narrow band at the time of
rotation since the flow around the main plate is apart from the blade front runner,
collides with the corner of the blade rear runner, so that pressure fluctuation occurs.
A re-attachment point of the air flow after departing from the blade front runner
to the rear side in the rotation direction of the blade rear runner is moved to the
rear side of the blade opening so that the air current is smoothly re-attached. Thus,
noise can be reduced.
[0095] In a turbofan made of a thermoplastic resin including: a disc-shaped main plate having
a projected hub formed by making a center portion so as to cover a motor, a plurality
of motor cooling holes formed in the hub for communicating the motor and the inside
of the fan, and a boss as a fixing part fixed to a rotary shaft of a motor, which
is provided in the center portion of the hub; a plurality of blades; and a shroud
for coupling the plurality of blades to form an air intake wall, a plurality of hub
runners each of which is connected to a resin injection port formed in a main plate
flat portion near the blade inner-radius-side end, made thicker than the inclined
face of the main plate, and extended linearly in the radial direction of the fan,
is provided in predetermined intervals on the motor-side side face of the main plate.
The hub runners are so formed that a resin merging portion formed between neighboring
hub runners is not connected at least to the motor cooling holes. The blade inner-radius-side
hollow, the blade outer-radius-side hollow, the blade front hollow surface, and the
blade rear hollow surface of the blade hollow are faces tilted at an arbitrary angle
θ with respect to the rotation axis. The blade inner-radius-side end, the blade outer-radius-side
end, the blade suction-side end, and the blade front-side end on the front side and
the blade rear-side end on the rear side in the blade rotation direction are formed
so as to have almost the same thickness in the entire blade. The blade and the blade
hollow are formed so as to be tapered from the main plate toward the shroud. The blade
runner formed so as to surround the opening on the outside of the main plate of the
blade having the hollow structure is connected via the connection runner. The blade
front runner corresponding to the side face in the blade rotation direction of the
blade runner has a height larger than that of the blade rear runner corresponding
to the side face on the opposite side in the blade rotation direction and is formed
so as to project to the outside of the fan. Because of the hub runners, resin flowability
in the hub and the main plate is high, and moldability is high. Since the hub runners
are formed so that the resin merging portion is not connected to at least the motor
cooling holes, breakage of the fan due to an impact at the time of transportation
or the like is prevented. Since the blade has a hollow structure, the weight of the
turbofan as a whole can be reduced. Because of almost uniform thickness, occurrence
of poor molding caused by variations in the cooling and hardening time of the resin
due to non-uniformblade thickness is suppressed, so that moldability is high. In addition,
since each of the blade and the blade hollow has a tapered shape at a molding draft
angle, which is tilted at the predetermined angle from the main plate toward the shroud,
the mold can be easily released, breakage of the blade due to adhesion of the blade
to the mold can be prevented, and moldability is high. The noise can be suppressed,
which is generated in the narrow band at the time of rotation, since the flow around
the main plate is apart from the blade front runner, collides with the corner of the
blade rear runner, so that pressure fluctuation occurs. A re-attachment point of the
air flow after departing from the blade front runner to the rear side in the rotation
direction of the blade rear runner is moved to the rear side of the blade opening
so that the air current is smoothly re-attached. Thus, noise can be reduced. Since
the blade front runner becomes thicker, the resin flows to the blade more smoothly
at the time of molding, and shrinkage can be prevented. Moreover, the strength in
the blade front runner improves, so that the strength of the turbofan also improves.
As a result, a lightweight, strong, and low-noise turbofan which can be prevented
from being broken at the time of rotation and transportation can be obtained.
[0096] The turbofan is formed so that the ratio Δt/F of the difference △t between the height
of the blade front runner 9ba and the height of the blade rear runner 9bb with respect
to the maximum opening diameter F of the blade opening 3b lies in the range of 4%
to 22%. At the time of rotation, the noise can be suppressed, which is generated in
the narrow band since the flow around the main plate is apart from the blade front
runner, collides with the corner of the blade rear runner so that pressure fluctuation
occurs. A re-attachment point of the air flow after departing from the blade front
runner to the rear side in the rotation direction of the blade rear runner is moved
to the rear side of the blade opening, so that the air current is smoothly re-attached
on the rear side of the blade rear opening, so that noise can be reduced. A peak sound
due to rotation speed, which is generated by separating the flow at the blade front
runner with a too large thickness, is suppressed, and deterioration in noise can be
prevented. Consequently, reduction in noise can be achieved.
[0097] An air conditioner including: the turbofan 1 having any one of the configurations
described in the first embodiment; and the heat exchanger disposed on the suction
side or the blowout side of the turbofan can be thinned because of improvement in
the moldability of the turbofan 1 and, accordingly, the weight can be reduced. In
addition, the air conditioner has high reliability in strength. Consequently, at the
time of mounting after transportation, the turbofan 1 is not found broken due to an
impact such as vibrations at the time of transportation, so that the product reliability
is high. The product weight can be also reduced only by the reduced weight of the
turbofan 1.
[0098] The present invention also provides an air conditioner recessed in a ceiling, having
the following configuration. Side plates and the top plate of the air conditioner
body are formed by plate members. The inside of the air conditioner body including
the side plates and at least a part of the ceiling serves as an air path wall using
heat insulating material. A motor and the turbofan 1 having at least one of the configurations
described in the first embodiment are mounted around the center of the air conditioner
body. A bell mouth constituting a suction port of the turbofan and a suction port
of the body is disposed in the center portion of the under face of the air conditioner
body. A heat exchanger is vertically arranged so as to surround the turbofan. A drain
pan made of foam is disposed under the heat exchanger. A body's blowout port is provided
in a position around the body's suction port and almost along the side plate of the
air conditioner body. A decorative panel having a panel's suction port and a panel's
blowout port communicating with the body's suction port and the body's blowout port,
respectively, is attached to the under face of the body. With the configuration, the
air conditioner can be thinned because of improvement in the moldability of the turbofan
1 and, accordingly, the weight can be reduced. In addition, the air conditioner has
high reliability in strength. Consequently, at the time of mounting after transportation,
the turbofan 1 is not found broken due to an impact such as vibrations at the time
of transportation, so that the product reliability is high. The product weight can
be also reduced only by the reduced weight of the turbofan 1.