TECHNICAL FIELD
[0001] The present invention relates to a motor-mounted internal gear pump and electronic
equipment.
BACKGROUND ART
[0002] Internal gear pumps have long been known as pumps which discharge sucked liquid against
pressure, and particularly have been popular as hydraulic source pumps or oil feed
pumps.
[0003] An internal gear pump includes, as main active components, a spur gear type inner
rotor with teeth on its outer surface, and an annular outer rotor with teeth on its
inner surface which has almost the same width as the inner rotor. A pump casing, which
has flat inner surfaces facing both side faces of these rotors with a small gap, is
provided to house the rotors. The number of teeth of the inner rotor is usually one
smaller than that of the outer rotor, and the rotors rotate with their teeth meshed
with each other, like power transmission gears. As the groove area changes with this
rotation, the liquid trapped in the grooves is sucked or discharged so that the function
as a pump is performed. When one of the inner and outer rotors is driven, the other
rotor, meshed with it, rotates as well. Since the center of rotation is different
between the rotors, each rotor must be pivotally supported in a rotatable manner individually.
The pump casing has openings to flow channels communicated with the outside, called
a suction port and a discharge port. The suction port is designed to communicate with
a groove whose volume increases and the discharge port is designed to communicate
with a groove whose volume decreases. As for rotor profiles, typically, the outer
rotor profile includes an arc and the inner rotor teeth are trochoidal teeth.
[0004] Since the internal gear pump rotates with its inner rotor and outer rotor meshed,
when one rotor is driven, the other rotor rotates as well. When a motor part is integral
with the outer surface of a pump part and the rotator of the motor part is integral
with the outer rotor and the motor part drives the outer rotor, this structure can
be shorter than a structure in which the pump part and the motor part are arranged
in series along the axial direction and is thus suitable for a compact pump.
[0005] One example of this type of internal gear pump is the internal gear pump as disclosed
in Japanese Patent Application Laid-Open Publication No.
H2-277983 (Patent Document 1). According to Patent Document 1, the internal gear pump includes
an internal gear which combines an outer gear (outer rotor) having a rotor on its
outer surface to face and contact a stator fitted in a motor casing, with a given
gap inside the stator in the radial direction, and an inner gear (equivalent to an
inner rotor) to mesh with this outer gear, wherein both end faces of the internal
gear are liquid-tightly closed by end plates and one of the end plates has a suction
port and a discharge port which communicate with the internal gear. The end plates
(pump casings) include a front casing and a rear casing; disc thrust bearings are
disposed between the casings and both sides of the internal gear pump; and both sides
of the outer gear are supported by the thrust bearings; both ends of a support shaft
are fixed to the casings and the inner gear is rotatably supported by the support
shaft through a radial bearing; and also a liquid feed channel is provided to allow
some of the pressurized liquid on the discharge side to flow between the rotor and
stator and lubricate the bearings and flow back to the suction side.
[0006] Patent Publication 1: Japanese Patent Application Laid-Open Publication No.
H2-277983
DISCLOSURE OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0007] However, the internal gear pump described in Patent Document 1 has a problem that
since the outer gear and rotor are separate members, inevitably the size is considerable
and the cost is high.
[0008] Furthermore, Patent Document 1 neither discloses the materials of the rotor, outer
gear, inner gear and end plates which constitute the internal gear pump nor discloses
that it is used in electronic equipment. If this internal gear pump is used in electronic
equipment, such as a personal computer or server, it should meet the following requirements:
mass productivity, long service life, the ability to maintain high accuracy, less
friction in sliding parts, low cost and lightness. Also, it has been found that since
in consideration of the storage temperature of the electronic equipment, an antifreeze
liquid such as ethylene glycol is used as hydraulic fluid which flows in the pump
for use in electronic equipment, compatibility between the internal gear and the antifreeze
liquid must be taken into account.
[0009] An object of the present invention is to provide a motor-mounted internal gear pump
and electronic equipment which assure compactness, inexpensiveness and high reliability
taking advantage of the functionality as an internal gear pump suitable for high lift
application.
MEANS FOR SOLVING THE PROBLEMS
[0010] In order to achieve the above object, in a first mode of the invention, a motor-mounted
internal gear pump includes a pump part which sucks and discharges hydraulic fluid,
and a motor part which drives the pump part; the pump part includes an inner rotor
with teeth on its outer surface, an outer rotor with teeth on its inner surface to
mesh with the teeth of the inner rotor, and a pump casing which houses the inner rotor
and the outer rotor, and the motor part includes a rotator, and a stator which rotates
the rotator, wherein a common member of permanent magnet material as resin containing
magnetic powder serves as the rotator and the outer rotor.
[0011] Preferred concrete examples in the first mode of the present invention are as follows.
- (1) Water or a liquid containing water as an ingredient is used as hydraulic fluid
which is sucked and discharged by the pump part and the common member for the rotator
and the outer rotor is made of ferrite bond magnet containing ferrite magnetic powder.
- (2) The common member for the rotator and the outer rotor is formed as a member whose
magnetic force is strong on its outer surface side and weak on its inner surface side,
and the stator is located around and outside the common member.
- (3) In the example mentioned above in (1), an antifreeze liquid containing water and
an organic substance is used as the hydraulic fluid.
- (4) In the example mentioned above in (1), the common member is made of PPS/ferrite
bond magnet as PPS resin containing ferrite magnetic powder.
- (5) In the example mentioned above in (1), the pump casing consists of two casings,
a first casing and a second casing, which are connected; shoulder sections protruding
inward are formed on the first casing and the second casing respectively in a way
to face each other; and annular bracket sections axially extending from the inner
teeth are formed at both sides of the outer peripheral part of the common member;
the annular bracket sections are fitted to the outer surfaces of the respective shoulder
sections of the first casing and the second casing; and the stator is located around
and outside the common member.
- (6) In the example mentioned above in (1), the pump casing is made of PPS carbon fiber
resin as PPS resin containing carbon fiber or PPS glass fiber resin as PPS resin containing
glass fiber.
- (7) In the example mentioned above in (1), the inner rotor is made of PPS carbon fiber
resin as PPS resin containing carbon fiber, or POM resin.
- (8) In the example mentioned above in (5), the first casing and the second casing
are made of PPS carbon fiber resin as PPS resin containing carbon fiber.
- (9) In the example mentioned above in (8), an outer peripheral part of either of the
first casing and the second casing is extended axially to form a can for sealing between
the rotator and the stator, and the stator is fitted outside the can.
[0012] In a second mode of the present invention, a motor-mounted internal gear pump includes:
a pump part which sucks and discharges hydraulic fluid, and a motor part which drives
the pump part; the pump part includes an inner rotor with teeth on its outer surface,
an outer rotor with teeth on its inner surface to mesh with the teeth of the inner
rotor, and a pump casing which houses the inner rotor and the outer rotor, and the
motor part includes a rotator, and a stator which rotates the rotator, wherein the
rotator is made of PPS resin/ferrite bond magnet as PPS resin containing ferrite magnetic
powder.
[0013] A preferred concrete example in the second mode of the present invention is as follows.
- (1) The pump casing is made of PPS carbon fiber resin as PPS resin containing carbon
fiber and the inner rotor is made of PPS carbon fiber resin as PPS resin containing
carbon fiber.
[0014] A third mode of the present invention is electronic equipment in which one of the
above motor-mounted internal gear pumps is mounted as a liquid circulation source
and an antifreeze liquid composed of water and an organic substance is used as hydraulic
fluid.
EFFECT OF THE INVENTION
[0015] According to the present invention, it is possible to provide a motor-mounted internal
gear pump and electronic equipment which assure compactness, inexpensiveness and high
reliability taking advantage of the functionality as an internal gear pump suitable
for high lift application.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Next, a motor-mounted internal gear pump, a manufacturing method thereof and electronic
equipment according to an embodiment of the present invention will be described referring
to Figs. 1 to 6.
[0017] First, the general structure of a motor-mounted internal gear pump according to this
embodiment will be described referring to Figs.1 and 4. Fig.1 is a longitudinal sectional
view of a motor-mounted internal gear pump 80 according to an embodiment of the present
invention; Fig.2 is a sectional front view showing the left half of the pump 80 in
Fig. 1; Fig. 3 is an exploded perspective view of the pump part of the pump 80 in
Fig.1; and Fig. 4 is a sectional view showing how to connect the casings of the pump
80 in Fig.1.
[0018] The pump 80 is a motor-mounted internal gear pump which includes a pump part 81 which
sucks hydraulic fluid and discharges it, a motor part 82 which drives the pump part
81, and a control part 83 which controls the motor part 82.
[0019] The pump part 81 includes an inner rotor 1 made of resin, an outer rotor 2 made of
resin, a front casing (first casing) 3 made of resin, a rear casing (second casing)
4 made of resin and an internal shaft 5 made of metal. The front casing 3 and rear
casing 4 are members which constitute a pump casing: in other words, the pump casing
member consists of two separate pump casing members. The rear casing 4 includes a
can 6, a flange 18 and a cover 13. The internal shaft 5, which constitutes a shaft
for supporting the inner rotor, is a member separate from the front casing 3 or the
rear casing 4 in this embodiment.
[0020] The motor part 82 includes a rotator 11 as a permanent magnet, a stator 12, and a
can 6. The can 6 is shared by the pump part 81 and the motor part 82.
[0021] The inner rotor 1 of the pump part 81 is similar in shape to a spur gear and has
trochoidal teeth 1a on its outer surface. Strictly speaking the tooth surface is slightly
angled in the axial direction, making an angle called a "draft angle" which facilitates
drafting in injection molding. Also, the inner rotor 1 has, in its center, an axial
hole 1b with a smooth inner surface which penetrates it axially. Both end faces 1c
of the inner rotor 1 are flat and smooth and constitute sliding surfaces between the
flat inner faces 25, 26 as the end faces of shoulder sections 22 protruding inward
from the front casing 3 and rear casing 4.
[0022] The inner rotor 1 is made of a self-lubricating synthetic resin in which swelling
or corrosion caused by water or an aqueous solution is negligible. Concretely, it
is made of PPS carbon fiber resin as PPS (polyphenylene sulfide) resin containing
carbide fiber. Because of this, the inner rotor 1 has sufficient strength and wear
resistance and can be an inexpensive inner rotor 1. Instead of PPS carbon fiber resin,
POM (polyacetal) resin may be used. Since POM is low in friction resistance and low
in sliding resistance, it improves the pump efficiency. Also since it is a soft material,
it can alleviate impact load, thereby suppressing vibration noise caused by rotor
motion. Although these materials have a water-absorbing property and transmit water,
there is no problem since they are used for the inner rotor 1. When it absorbs hot
water, it may deform; however, if it is profiled to compensate for such deformation,
deformation is mitigated. At low temperatures, the gap between both rotors 1, 2 increases
but if an antifreeze liquid composed of water and an organic substance is used for
the hydraulic fluid, the viscosity of the antifreeze liquid increases and the pump
efficiency improves, thereby preventing performance deterioration.
[0023] The outer rotor 2 takes the form of an annular internal gear having almost the same
tooth width as the inner rotor 1 and has arched teeth where the number of teeth is
one larger than the number of teeth of the inner rotor 1. The teeth 2a of the outer
rotor 2 as a spur gear have a sectional profile which is almost constant in the axial
direction; however, they may be slightly angled in the axial direction, or have an
angle called a "draft angle" to facilitate drafting in injection molding. In this
case, the inner rotor 1 should have a similar draft angle and the inner rotor 1 and
the outer rotor 2 are angled in opposite directions and the rotors 1, 2 are meshed
so that the inner teeth diameter of the outer rotor 2 increases in the direction in
which the outer teeth diameter of the inner rotor 1 increases. This can prevent the
meshing surfaces of the rotors 1, 2 from contacting each other unevenly in the axial
direction. Both end faces 2b of the teeth of the outer rotor 2 are flat and smooth
and constitute sliding surfaces between the flat inner faces 25, 26 of the front casing
3 and rear casing 4 and function as thrust bearings.
[0024] The outer rotor 2 has almost the same width as the inner rotor 1 except its outer
periphery, and the outer rotor 2 is disposed outside the inner rotor 1 in a way that
both end faces of the inner rotor 1 almost coincide with those of the outer rotor
2. Annular bracket sections 21, which protrude axially from the teeth portion (which
has almost the same tooth width as the inner rotor 1 located inside), are formed on
the outer periphery of the outer rotor 2. The inner surfaces of the bracket sections
21 are smooth and constitute sliding surfaces between the outer surfaces 27, 28 of
the shoulder sections 22.
[0025] The outer rotor 2 and inner rotor 1 are designed to rotate between the front casing
3 and rear casing 4 while meshed with each other. A bearing of the internal shaft
5 with a smooth outer surface is fitted into the central axial hole of the inner rotor
1 with a small gap, and thus the inner rotor 1 is pivotally supported by the internal
shaft 5 in a rotatable manner. The internal shaft 5 does not rotate because it is
tightly fitted into the front casing 3 and rear casing 4.
[0026] A permanent magnet as the rotator 11 of the motor part 82 is integrated with the
outside of the outer rotor 2. In this embodiment, resin mixed with magnetic powder
is used to form the rotator 11 integral with the outer rotor 2. In other words, the
rotator 11 of the motor part 82 and the outer rotor 2 of the pump part 81 constitute
a common member 112 made of permanent magnet containing magnetic powder. This means
that the rotator 11 and the outer rotor 2 can be compact and manufactured at low cost.
The rotator 11 provides alternate polarities in the radial direction and when viewed
from outside, it has N and S poles arranged alternately along its circumference.
[0027] In this embodiment, the common member 112 is made of ferrite bond magnet containing
ferrite magnet powder. Therefore, even if water or a liquid containing water as an
ingredient is used as hydraulic fluid, the magnet neither corrodes nor rusts and can
be manufactured at low cost. This common member 112 is also made of PPS/ferrite bond
magnet as PPS resin containing ferrite magnetic powder. Therefore, the magnetic property
as the rotator 11 of the motor part 82 is improved, high precision teeth for the pump
part 81 can be formed, and a low-friction , low-wear sliding property is achieved
in the portion which functions as a bearing, and also formability is high and stability
against corrosion in water is high.
[0028] In this embodiment, the common member 112 is formed cylindrically so that the magnetic
force of its outer surface is strong and that of its inner surface is weak, and since
the stator 12 is located outside the outer surface of the common member 112, magnetization
from the outer surface is easy and even if ferrite bond magnet, usually inexpensive
and weaker in magnetic force than neodymium magnet, is used, the function as the rotator
11 can be well performed.
[0029] Furthermore, in this embodiment, shoulder sections 22, protruding inward, are respectively
formed on the front casing 3 and rear casing 4 in a way to face each other; and annular
bracket sections 21, protruding axially from the teeth portion of the inner surface,
are formed at both sides of the outer periphery of the common member 112 and the annular
bracket sections 21 are fitted to the outer surfaces 27, 28 of the respective shoulder
sections 22 of the front casing 3 and rear casing 4, so that the portion which functions
as the rotator 11 can be increased in size axially, which helps the use of ferrite
bond magnet which is inexpensive and weak in magnetic force.
[0030] It is possible that a composite structure serves as both the outer rotor 2 and the
rotator 11 where the outer surface including the outer rotor 2's bracket sections
is of PPS/ferrite bond magnet and the teeth portion is of PPS carbon fiber. In that
case, if PPS/ferrite bond magnet, from which it is difficult to make a complicated
shape, is used to make a simple cylindrical shape and PPS resin is used to make the
teeth portion which requires accuracy, teeth with low loss and low wear are formed
without hard ferrite powder in the surface of meshing with the inner rotor 1.
[0031] The internal shaft 5 includes: a cylindrical bearing 51 which has an outside diameter
slightly smaller than the inside diameter of the axial hole 1b of the inner rotor
1 and is slightly longer than the tooth width of the inner rotor 1 in the axial direction;
and a fitting part 53 which extends from both end faces of the bearing 51 in both
axial directions and has an outside diameter smaller than the outside diameter of
the bearing 51. Concretely, the axial length of the bearing 51, located in the center
of the internal shaft 5, is slightly (for example, 0.05-0.1 mm) longer than the tooth
width of both rotors. The cylindrical fitting part 53, located at each end of the
bearing 51, is concentric with the bearing 51. The bearing 51 and the fitting part
53 are parts of the internal shaft 5 which are all made of the same metal material,
and integral with each other. The internal shaft 5, made of a metal material, is superior
in strength and dimensional accuracy to the inner rotor 1, outer rotor 2, front casing
3 and rear casing 4 which are made of synthetic resin.
[0032] The internal shaft 5 also has the function as a structural member which connects
the front casing 3 and the rear casing 4. Its fitting part 53 is inserted and fixed
into fitting holes 27a, 28a made in the flat inner surfaces 25, 26 of both casings
3, 4. In this condition, the step faces (both end faces of the bearing 51) 51a as
boundaries between the bearing 51 and the fitting part 53 are in close contact with
the flat inner surfaces 25, 26 of the casings. This means that the length of the bearing
51 is equal to the distance (interval) between both flat inner surfaces 25, 26, and
both rotors 1, 2 are inside the flat inner surfaces 25, 26 as the axial end faces
of the front casing 3 and rear casing 4, with a small gap. The fitting holes of the
front casing 3 and rear casing 4 are eccentric with respect to the outer surfaces
27, 28 of the shoulder sections 22 in a way to accommodate both rotors 1, 2 which
are meshed.
[0033] The shoulder sections 22 of the front casing 3 and rear casing 4 protrude inward
in a way to face each other. The outer surfaces 27, 28 of the shoulder sections 22
are fitted to the inner surfaces of the bracket sections 21 of the outer rotor 2 with
a small gap; and the shoulder sections 22 of the front casing 3 and rear casing 4
pivotally support both sides of the outer rotor 2 in a rotatable manner, functioning
as radial bearings. The shoulder sections 22 of the front casing 3 and rear casing
4 are in a positional relation as if they originated from a single cylinder.
[0034] The front casing 3, one of the two pump casing members, has a hole called a suction
port 8 and a hole called a discharge port 10 in its flat inner surface 25. The suction
port 8 and the discharge port 10 are holes whose profile extends inside the tooth-base
circle of the inner rotor 1 and outside the tooth-base circle of the outer rotor 2
(since the outer rotor 2 is an internal gear, its tooth-base circle diameter is larger
than its tooth-tip circle diameter). The suction port 8 faces a working chamber 23
whose volume increases and the discharge port 10 faces a working chamber 23 whose
volume decreases. When the volume of a working chamber 23 is maximized, either port
8, 9 does not face the working chamber 23 or is communicated with it only through
a small sectional area.
[0035] The suction port 8 and discharge port 10 are respectively communicated from the innermost
port grooves through an L-shaped flow channel with a suction hole 7 and a discharge
hole 9 which are open to the outside. Midway in the flow channel from the discharge
port 10 to the discharge hole 9, there is a branched communication path 9a which communicates
with an internal space 24 facing the outer surface of the outer rotor 2. The internal
space 24 is a space surrounded by the front casing 3 and the rear casing 4 including
the can 6.
[0036] The can 6, a thin-walled cylinder, is located with a small gap from the outer surface
of the rotator 11 (for example, gap of 1 mm or less), so that the rotator 11 can rotate
together with the outer rotor 2.
[0037] The rear casing 4, one of the two casing members, has a cylindrical can 6 covering
the outside of the outer rotor 2 and axially extending outward from the portion constituting
its flat inner surface 26, where the can 6 side is softer than the flat inner surface
26 side in terms of axial rigidity; and at the tip side of the can 6, it is connected
with the front casing 3, one of the two casing members. In other words, the can 6
is part of the rear casing 4 and refers to a cylindrical thin portion extending frontward
and outward from the portions constituting the flat inner surface and shoulder section.
[0038] The front casing 3 and rear casing 4 contact each other on a cylindrical surface
called a fitting surface 16, engaging with each other with freedom in axial movement
while binding each other in the radial direction. The fitting surface 16 consists
of a fitting surface between the inner surface of the tip of the can 6 and the outer
surface of the outer annular part 29 formed inside the front casing 3. A dent is formed
in the inner surface of the tip of the can 6 adjacent to the fitting surface 16 and
an O ring 14 inserted into this dent keeps confidentiality between the front casing
3 and rear casing 4. Such structure allows the front casing 3 and rear casing 4 to
be combined in a confidentiality manner while assuring freedom in the axial direction.
[0039] The front casing 3 and rear casing 4 are made of PPS carbon fiber resin, PPS resin
containing carbon fiber. The front casing 3 and rear casing 4 of PPS carbon fiber
resin are less water-absorbent and less deform due to water absorption and less deform
thermally and are corrosion-resistant against an antifreeze liquid and heat-resistant.
Since PPS carbon fiber resin is an insulating material, it is effective in prevention
of ground leakage and also it transmits less water and well slides on bearings so
that wear rarely occurs and long life and high reliability are expected and forming
can be done with high precision.
[0040] Plural welding projections 41 which are annular and oriented rearward are formed
near the outer surface of the front casing 3 and annular welding grooves 42 into which
the welding projections 41 are inserted are formed in the flange 18 of the rear casing
4. In this embodiment, as shown in Fig. 4, the tip of a welding projection 41 has
a slanted surface and the bottom of a welding groove 42 has a slanted surface to match
the abovementioned slanted surface and welding tools 43, 44 are pushed against the
outer surface of the front casing 3 and the flange 18 of the rear casing 4 from both
sides and micro-vibrations are given to the welding tools 43, 44 with a force applied
to the welding tools 43, 44. Concretely, the welding tools 43, 44 are attached to
an ultrasonic welder to give them ultrasonic vibrations. Consequently, the surface
of contact between both casings 3, 4 generates heat due to micro-vibration friction
and melts and they fuse with each other; after vibrations stop, as the temperature
goes down, they are re-solidified and connected. For this reason, the back side of
the welding projection 41 of the front casing 3 and the back side of the welding groove
42 of the rear casing 4 should be flat and open so that the welding tools 43, 44 can
be placed in tight contact with them.
[0041] The groove on the rear casing 4 into which the welding tool 44 is inserted is an
annular groove into which the stator 12 is inserted after welding and can be smaller
and simpler in shape than a groove dedicated to welding.
[0042] Any contact that limits axial movement, except two points of contact, contact between
the welding projection 41 and the welding groove 42 and contact between the internal
shaft 5 step and the flat inner surface 25, 26, should be eliminated before completion
of welding. The can 6 is thin-walled and the can and its vicinity are softer than
the flat inner surfaces, the shoulder sections and the areas around welding points.
This establishes a positional relationship among members in the following order.
[0043] First, the fitting part 53 of the internal shaft 5 is inserted in the rear casing
4; the inner rotor 1 and outer rotor 2 are fitted into the internal shaft 5; and the
front casing 3 with the O ring 14 fitted thereon is fitted to the rear casing 4. In
this condition, the welding tools 43, 44 are applied to both casings 4, 5 from both
sides and ultrasonic vibrations are given to them while they are pushed with a prescribed
force. Consequently the point of contact between the welding projection 41 and welding
groove 42 melts and the front casing 3 and rear casing 4 come closer to each other.
In this process, the step faces 51a of the internal shaft 5 come into tight contact
with the flat inner surfaces 25, 26. As welding goes on, the can 6 of the rear casing
4 and its vicinity are elastically deformed and welding goes deeper. Vibrations are
stopped with a force on the welding tools 43, 44 and the molten welded parts cool
down and solidify, settling into shape. Even after the welding tools are removed,
the step faces 51a of the internal shaft 5 remain in contact with the flat inner surfaces
25, 26 and that contact force remains a reactive force against elastic deformation
of the can 6 and its vicinity.
[0044] The internal shaft 5 is made of metal and easier to manufacture with required dimensional
accuracy in the axial direction than the resin casing members 3, 4. It is also advantageous
in that dimensional accuracy in the tooth width direction is assured in its central
part adjacent to the teeth of the rotors 1, 2. It is far easier to maintain accuracy
than in the method in which accuracy in the distance between both flat inner surfaces
25, 26 is assured only by dimensional accuracy of the casings 3, 4 through the outer
periphery of the can 6, etc. without relying on accuracy of the internal shaft 5.
Hence the structure in this embodiment is effective in keeping the gap at tooth end
faces, which has a large influence on pump performance and reliability, adequate
[0045] The welding projection 41 is annular but not a continuous circle and there are missing
parts in the circumference as shown in Fig. 2. The reason for this is that a pushing
force as applied to a limited area is more concentrated than as applied to the whole
circumference and thus welding is done more securely. The suction and discharge flow
channels lie in the missing parts in order to prevent interference between the welding
tool 43 and these flow channels.
[0046] Thanks to the function of the fitting surface 16, the two casings are combined with
high positioning accuracy in the radial direction, and their axial positional accuracy
is maintained by contact between the internal shaft 5 and the flat inner surfaces
25, 26. The internal space 24 is hermetically sealed by the O ring 14 and there are
no holes or fitting surfaces communicated with the outside except the suction hole
8 and discharge hole 10 and this simple structure is highly liquid-tight. Hence, it
prevents liquid leakage with reliability.
[0047] The cover 13 is integrally molded as a backwardly folded extension from the flange
18 on the front side of the can 6 which is continuous with the rear casing 4. The
cover 13, which covers the outer surface of the stator 12 of the motor part 82, is
useful in preventing electric shock, keeping a good appearance and shutting off the
noise.
[0048] The stator 12 is press-fitted into the outer surface of the can 6 outside the can
6 and opposite to the rotator 11 where the stator 12 consists of a winding around
a comb-shaped iron core. The stator 12 is fitted into a circular groove formed between
the can 6 and the cover 13. Since the motor part 82, composed of the rotator 11 and
the stator 12, is located around the pump part 81, composed of the inner rotor 1 and
the outer rotor 2, namely the motor part 82 and the pump part 81 are not arranged
in series along the axial direction, the pump 80 is thin and compact.
[0049] The control part 83, which is intended to control the motor part 82, is equipped
with an inverter electronic circuit for driving a brushless DC motor. Since the motor
part 82 is located around the pump part 81 as mentioned above, the control part 83
can be located on the rear side where the suction hole 7 and the discharge hole 9
of the pump part 81 are not located.
[0050] A power device 32 as a main electronic component is mounted on a circuit board 31,
constituting an inverter circuit for driving a brushless DC motor. The circuit board
31 is fixed to the rear casing 4 by caulking, or passing a projection 45 on the back
of the rear casing 3 through a hole in its center. The power device 32 contacts the
rear casing 4 through the circuit board 31. Consequently, heat generated in the inverter
circuit can be passed through the rear casing 4 into the hydraulic fluid in the pump
part 81. The circuit board 31 is connected with one end of the winding of the stator
12 and also with a power line 33 for external power supply, a rotation output line
34 for transmitting rotation speed information by pulses and a common grounding line
for them.
[0051] The brushless DC motor includes: the motor part 82 having the rotator 11 as permanent
magnet, and the stator 12; and the control part 83 having the inverter electronic
circuit. The structure that the rotator 11 is inside the thin-walled can 6 and the
stator 12 is outside the can 6 is called a "canned motor". Since the canned motor
does not require a shaft seal, etc. and transmits the turning force to the inside
of the so-called can 6 by the use of a magnetic force, it is suitable for the structure
of a positive displacement pump which pumps out the hydraulic fluid through change
in the volume of the working chambers 23 while isolating the fluid from the outside.
[0052] When the pump 80 has dimensional relations as shown in Fig. 5, the object of the
present invention is achieved better. When the width of the inner rotor 1 and the
tooth width of the outer rotor 2 are expressed as 1, the outside diameter of the inner
rotor should be 1.7-3.4, the inside diameter of the outer rotor bracket sections should
be 2.5-5, and the axial length of the outer rotor bracket sections should be 0.4-0.8.
[0053] If the outside diameter of the inner rotor 1 is above this range, the rate of internal
leakage (back flow from the higher pressure discharge port communicating side to the
suction port communicating side, which deteriorates pump performance) would increase,
deteriorating pump performance. If it is below the range, the velocity of flow would
increase at opening areas where the working chambers communicate with the suction
or discharge port, leading to increased pressure loss and deterioration in pump performance.
[0054] The inside diameter of the bracket section 21 of the outer rotor 2 must be geometrically
larger than the outside diameter of the inner rotor 1. At the same time, if it is
above this range, frictional force and internal leakage from bearing surfaces would
increase, leading to deterioration in pump performance.
[0055] If the axial length of the outer rotor bracket section 21 is below this range, the
bearing surface pressure might increase and thus frictional wear might increase, leading
to shorter pump life and lower reliability. If it is above this range, it is disadvantageous
because unevenness in contact easily occurs due to errors in bearing surface cylindricality
and concentricity, etc.
[0056] It is recommended that the inner rotor rotation speed be within the range of 2500-5000
rpm. If the rotation speed is slower than this, the ratio of internal leakage to transportation
flow rate would increase, leading to deterioration in pump efficiency. If it is faster
than this, vibration noise generated by the pump would increase.
[0057] Next, how the pump 80 works will be explained referring to Figs.1 to 5.
[0058] By giving 12 V DC power to the power line 33 to supply electric current to the motor
drive circuit of the control part 83, electric current is fed through the power device
32 to the winding of the stator 12. This starts the motor part 82 and controls it
to rotate it at a preset rotation speed. Since the power device 32 outputs rotation
information on the rotator 11 as a pulse signal through the rotation output line 34,
a higher-level control apparatus which receives the signal can confirm the operating
condition of the pump 80.
[0059] As the rotator 11 of the motor part 82 rotates, the outer rotor 2, united with it
also rotates; as the rotation is transmitted like an ordinary internal gear, the inner
rotor 1, meshed with it, also rotates. The volume of working chambers 23 formed in
the grooves of the two rotors 1, 2 increases or decreases as both rotors 1, 2 rotate.
As shown in Fig.2, when the teeth of the inner rotor 1 and outer rotor 2 are meshed
deepest, the volume of the working chamber 23 at the bottom is the minimum and the
volume of the working chamber 23 at the top is the maximum. Hence, when the rotors
rotate counterclockwise in Fig.2, the working chambers 23 in the right half move up
and their volume increases, while the working chambers 23 in the left half move down
and their volume decreases. All the sliding parts pivotally supporting both rotors
1, 2 are immersed in the hydraulic fluid and therefore their friction is small and
abnormal wear is prevented.
[0060] The hydraulic fluid passes through the suction hole 7 and then the suction port 8
and is sucked into the working chambers 23 whose volume is increasing. As the rotors
rotate, the working chamber 23 whose volume is maximized leaves the profile of the
suction port 8 and finishes its suction process, then communicates with the discharge
port 10. Then, the volume of the working chamber 23 begins to decrease and the hydraulic
fluid in the working chamber 23 is discharged through the discharge port 10. The discharged
hydraulic fluid is sent out through the discharge hole 9. Since the branched communication
path 9a lies midway in the discharge flow channel, the inner pressure of the internal
space 24 is maintained at a discharge pressure level.
[0061] In this embodiment, since the suction flow channel is short, the negative pressure
for suction is small, which prevents cavitation. In addition, a relatively high discharge
pressure is applied to the inner surface of the can 6 to push and expand it outward
and therefore even though the can 6 is thin-walled, it cannot be so deformed inward
as to touch the rotator 11. At the same time, leakage from the gap as a radial bearing
formed on the bracket section 21 of the outer rotor 2 can be reduced.
The reason is that although the outward force of leakage from this gap is increased
by a centrifugal force, if the inner pressure of the internal space 24 around it is
high, there is an action which pushes it back.
[0062] In the power device 32, which must be cooled because it generates heat during operation,
the heat passes through the wall of the rear casing 4 which the device contacts through
the circuit board 31, and moves to the hydraulic fluid flowing in the internal space
24 before being released outside. Since the hydraulic fluid in the internal space
24 is always stirred and successively replaced due to minor leaks from the radial
bearing surface, it carries away the heat efficiently. Since the inside of the pump
80 is cooled efficiently as described above, a heat sink or cooling fan for cooling
the power device 32 is not needed. Similarly, the heat generated by motor loss in
the rotator 11 or the stator 12 is carried away efficiently, which prevents an abnormal
temperature rise.
[0063] Next, electronic equipment which has the above pump 80 will be described referring
to Fig.6. Fig.6 is a perspective view showing a personal computer system configuration
with a computer in its upright position. The electronic equipment shown in Fig.4 is
a desk top personal computer system.
[0064] The personal computer system 60 includes a personal computer 61A, a display unit
61B, and a keyboard 61C. A liquid-cooling system 69 is housed in the personal computer
61A together with a CPU (central processing unit) 62 and consists of a closed loop
system in which a liquid reservoir 63, a pump 80, a heat exchanger 65, a heat radiating
plate A66 and a heat radiating plate B67 are connected in the order of mention by
tubing. This liquid-cooling system 69 is primarily intended to convey out the heat
generated by the CPU 62 housed in the personal computer 61A and keep the temperature
rise of the CPU 62 below a prescribed level. The liquid-cooling system 69, which uses,
as a heat transfer medium, water or an aqueous liquid such as an antifreeze liquid
composed of water and an organic substance (ethylene glycol, etc), features a higher
heat transfer capability and lower noise than an air-cooling system, so it is suitable
for cooling the CPU 62 which generates much heat.
[0065] The liquid being conveyed (hydraulic fluid) and air are filled in the liquid reservoir
63. The liquid reservoir 63 and the pump 80 are placed side by side where the outlet
of the liquid reservoir 63 and the suction hole of the pump 80 are connected by tubing.
The heat exchanger 65 is bonded to the heat radiating surface of the CPU 62 through
thermally conductive grease. The discharge hole of the pump 80 and the inlet of the
heat exchanger 65 are communicated by tubing. The heat exchanger 65 is communicated
with the heat radiating plate A66 by tubing; and the heat radiating plate A66 is communicated
with the heat radiating plate B67 by tubing; and the heat radiating plate B67 is communicated
with the liquid reservoir 63 by tubing. The heat radiating plate A66 and the heat
radiating plate B67 are so located as to allow heat radiation from different surfaces
of the personal computer 61A.
[0066] The pump 80 is connected with the power line 33 from a 12 V DC power supply usually
provided in the personal computer system 60 and the rotation output line 34 is connected
with the electronic circuit of the personal computer system 60 as a higher-level control
apparatus.
[0067] Next, how this liquid-cooling system 69 works will be explained. As the personal
computer system 60 is started, power is supplied, the pump 80 begins running and the
liquid being conveyed begins circulating. The liquid is sucked from the liquid reservoir
63 into the pump 80 and pressurized by the pump 80 and sent to the heat exchanger
65. The liquid sent from the pump 80 to the heat exchanger 65 absorbs the heat emitted
from the CPU 62 and the liquid temperature rises. Then, the heat of the liquid is
exchanged for outside air through the heat radiating plate A66 and the heat radiating
plate B67 (heat is released to the outside) and consequently the liquid temperature
falls, then the liquid returns to the liquid reservoir 63. This process is repeated
so that the CPU 62 is continuously cooled.
[0068] Since the pump 80 is an internal gear pump as a kind of positive displacement pump,
even if it is started in a dry (no liquid) condition, it has the ability to make the
suction hole have a negative pressure. Therefore, even when the liquid comes through
a tube above the liquid level inside the liquid reservoir 63 or when the pump 80 is
located at a higher position than the liquid level, the pump 80 has a self-priming
ability to suck liquid without priming water. The internal gear pump 80 has a higher
pressurizing ability than a centrifugal pump, etc, so it can also be used in such
a condition that the liquid passes through the heat exchanger 65 and the heat radiating
plates 66, 67 and thus liquid pressure loss increases. Particularly when the heat
density of the CPU 62 is high, in order to increase the heat exchange area, the flow
channel inside the heat exchanger 65 must be elongated by folding it; thus a liquid
cooling system which uses a centrifugal pump, etc. would be difficult to use because
of increased pressure loss in the liquid passing through the channel, while the liquid
cooling system 69 according to this embodiment can cope with such a situation.
[0069] In the liquid cooling system 69 according to this embodiment, the liquid being conveyed
passes through the heat radiating plates 66, 67 just after the outlet of the heat
exchanger 65 where the liquid temperature is highest, and the liquid temperature falls,
so the temperature of the liquid reservoir 63 and pump 80 is maintained at a relatively
low level. For this reason, the internal parts in the pump 80 provide higher reliability
than in a high temperature environment.
[0070] As a result of operation of the liquid cooling system 69, the temperature of each
of the components through which the liquid circulates is determined and the temperature
is monitored by a thermo sensor (not shown). If insufficiency of the cooling performance
is confirmed by detection of a temperature above a prescribed level, a command is
given to increase the rotation speed of the pump 80 to prevent an excessive temperature
rise. Contrarily, if the cooling performance is too high, the rotation speed is decreased.
The rotation output signal from the pump 80 is always monitored; if no rotation signal
is sent and there is an abnormal change in the liquid temperature, the pump 80 is
considered to be out of order and the personal computer system 60 enters an emergency
mode. In the emergency mode, a fatal hardware damage is prevented by taking minimum
necessary steps such as decreasing the CPU speed and saving current program data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0071]
[Fig.1] is a longitudinal sectional view of a motor-mounted internal gear pump according
to an embodiment of the present invention.
[Fig.2] is a sectional front view showing the left half of the pump in Fig. 1.
[Fig. 3] is an exploded perspective view of the pump part of the pump in Fig.1.
[Fig. 4] is a sectional view showing how to connect the casings of the pump in Fig.1.
[Fig. 5] is a dimensional drawing of the inner rotor and outer rotor of the pump in
Fig. 1.
[Fig. 6] is an explanatory view of electronic equipment with a cooling system having
the pump in Fig.1.
EXPLANATION OF REFERENCE NUMERALS
[0072]
1...Inner rotor
1a... Teeth
1b...Axial hole
1c...En face
2...Outer rotor
2a...Teeth
2b...End face
3...Front casing
4...Rear casing
5...Internal shaft
6...Can
7...Suction hole
8...Suction port
9...Discharge hole
9a...Communication path
10...Discharge port
11...Rotator
12...Stator
13...Cover
14...0 ring
16...Fitting surface
18...Flange
21...Bracket section
22...Shoulder section
23...Working chamber
24...Internal space
25...Front casing flat inner surface
26...Rear casing flat inner surface
27, 28...Shoulder section outer surfaces
27a, 28a...Fitting holes
29...Outer annular part
31...Circuit board
32...Power device
33...Power line
34...Rotation output line
41...Welding projection
42...Welding groove
43...Welding tool
44...Welding tool
51...Bearing
51a...Step face
53...Fitting part
60...Personal computer system
61A...Personal computer
61B...Display unit
61C...Keyboard
62...CPU
63...Liquid reservoir
65...Heat exchanger
66...Heat radiating plate A
67...Heat radiating plate B
69...Liquid-cooling system (cooling system)
80...Motor-mounted internal gear pump
81...Pump part
82...Motor part
83...Control part
112...Common member
1. A motor-mounted internal gear pump, comprising:
a pump part which sucks and discharges hydraulic fluid; and
a motor part which drives the pump part,
the pump part including:
an inner rotor with teeth on its outer surface;
an outer rotor with teeth on its inner surface to mesh with the teeth of the inner
rotor; and
a pump casing which houses the inner rotor and the outer rotor; and
the motor part including:
a rotator; and
a stator which rotates the rotator,
wherein a common member of permanent magnet material as resin containing magnetic
powder serves as the rotator and the outer rotor.
2. The motor-mounted internal gear pump according to Claim 1,
wherein: water or a liquid containing water as an ingredient is used as hydraulic
fluid which is sucked and discharged by the pump part; and
the common member for the rotator and the outer rotor is made of ferrite bond magnet
containing ferrite magnetic powder.
3. The motor-mounted internal gear pump according to Claim 1,
wherein: the common member for the rotator and the outer rotor is formed as a member
whose magnetic force is strong on its outer surface side and weak on its inner surface
side; and
the stator is located around and outside the common member.
4. The motor-mounted internal gear pump according to Claim 2,
wherein an antifreeze liquid containing water and an organic substance is used as
the hydraulic fluid.
5. The motor-mounted internal gear pump according to Claim 2,
wherein the common member is made of PPS/ferrite bond magnet as PPS resin containing
ferrite magnetic powder.
6. The motor-mounted internal gear pump according to Claim 2,
wherein: the pump casing consists of two casings, a first casing and a second casing
which are connected;
shoulder sections protruding inward are formed on the first casing and the second
casing respectively in a way to face each other;
annular bracket sections axially extending from the inner teeth are formed at both
sides of the outer peripheral part of the common member;
the annular bracket sections are fitted to the outer surfaces of the respective shoulder
sections of the first casing and the second casing; and
the stator is located around and outside the common member.
7. The motor-mounted internal gear pump according to Claim 2,
wherein the pump casing is made of PPS carbon fiber resin as PPS resin containing
carbon fiber or PPS glass fiber resin as PPS resin containing glass fiber.
8. The motor-mounted internal gear pump according to Claim 2,
wherein the inner rotor is made of PPS carbon fiber resin as PPS resin containing
carbon fiber, or POM resin.
9. The motor-mounted internal gear pump according to Claim 6,
wherein the first casing and the second casing are made of PPS carbon fiber resin
as PPS resin containing carbon fiber.
10. The motor-mounted internal gear pump according to Claim 9,
wherein: an outer peripheral part of either of the first casing and the second casing
is extended axially to form a can for sealing between the rotator and the stator;
and
the stator is fitted outside the can.
11. 1. A motor-mounted internal gear pump, comprising:
a pump part which sucks and discharges hydraulic fluid; and
a motor part which drives the pump part,
the pump part including:
an inner rotor with teeth on its outer surface;
an outer rotor with teeth on its inner surface to mesh with the teeth of the inner
rotor; and
a pump casing which houses the inner rotor and the outer rotor; and
the motor part including:
a rotator; and
a stator which rotates the rotator,
wherein the rotator is made of PPS resin/ferrite bond magnet as PPS resin containing
ferrite magnetic powder.
12. The motor-mounted internal gear pump according to Claim 11,
wherein: the pump casing is made of PPS carbon fiber resin as PPS resin containing
carbon fiber; and
the inner rotor is made of PPS carbon fiber resin as PPS resin containing carbon fiber.
13. Electronic equipment,
wherein the motor-mounted internal gear pump according to any of Claims 1 to 12 is
mounted as a liquid circulation source and an antifreeze liquid composed of water
and an organic substance is used as the hydraulic fluid.