Technical Field
[0001] The present invention relates to a compressor having a muffler which reduces a pressure
variation (pulsation) of a compressed fluid.
Background Art
[0002] A rotary compressor constituting an air conditioner or the like includes a compression
mechanism which compresses a refrigerant in a cylinder by a rotation of a piston rotor
and a muffler which suppresses noise caused by a pressure variation of the compressed
refrigerant.
[0003] As the muffler of the rotary compressor, a two-stage muffler having a first muffler
and a second muffler is adopted (for example, PTL 1). The compressed refrigerant is
discharged from a discharge port of a bearing to which the cylinder is fixed into
the first muffler, and is discharged from the inside of the first muffler into the
second muffler through a discharge opening of the first muffler. A space in the first
muffler and a space in the second muffler are operated as a resistance according to
a space volume by the compressed refrigerant, and thus, the compressed refrigerant
sequentially passes through the first muffler and the second muffler, and the pulsation
of the refrigerant is reduced.
Citation List
Patent Literature
[0004] [PTL 1] Japanese Unexamined Patent Application Publication No.
2014-173554
Summary of Invention
Technical Problem
[0005] Even if a general muffler or a two-stage muffler is installed in a compression mechanism,
it is not always possible to obtain a sufficient pulsation reduction effect with respect
to a frequency component of a pulsation of a compressed refrigerant.
[0006] Particularly, in a case of the two-stage muffler, it is difficult to take a sufficient
plate thickness of the muffler due to restrictions of weight or a cost and improve
rigidities, and thus, pressure waves of the pulsation of the refrigerant are easily
radiated to the outside of the muffler.
[0007] If an opening area of a discharge opening of the muffler is narrowed, a pressure
loss is applied to the refrigerant discharged from the muffler, and thus, pulsation
can be reduced. However, performance in the compressor decreases. Particularly, in
the case of the two-stage muffler, the pressure loss increase, and thus, there is
a limitation in the narrowing of the opening area of the discharge opening.
[0008] Accordingly, an object of the present invention is to provide a compressor capable
of sufficiently reducing an appropriate pulsation frequency component of a fluid by
a muffler while securing performance of the compressor.
Solution to Problem
[0009] According to an aspect of the present invention, there is provided a compressor including:
a compression mechanism which compresses a fluid; and a muffler which reduces a pulsation
of the fluid compressed by the compression mechanism, in which the muffler includes
a muffler body which receives the fluid from the compression mechanism into an inside
of the muffler body, and a cover which forms a cavity between an outer peripheral
portion of the muffler body and the cover and discharges the fluid received from the
inside of the muffler body, the muffler body includes a plurality of openings which
are formed to penetrate the muffler body in a plate thickness direction, separately
from a discharge opening through which the fluid passes from the inside of the muffler
body into the cavity, and sound is absorbed by establishing a Helmholtz resonance
with respect to an air mass existing inside each opening communicating with the cavity
from a relationship between a speed of sound C, a cross-sectional area S of each of
the openings, a plate thickness L, and a volume V of the cavity.
[0010] In the compressor of the present invention, preferably, the compression mechanism
includes a piston rotor which is provided in a rotary shaft and a cylinder in which
the piston rotor is disposed, and the muffler body and the cover are disposed around
an axis of the rotary shaft.
Advantageous Effects of Invention
[0011] According to the present invention, as described in detail later, a pulsation reduction
effect based on the Helmholtz resonance can be obtained while the pulsation reduction
effect is maintained by a two-stage muffler which repeats discharge of pulsation into
a space. A movement of the air mass inside the minute opening of the muffler body
generating the Helmholtz resonance does not affect a mainstream inside the muffler,
and thus, the pulsation of the fluid is sufficiently reduced and the sound is absorbed
while the performance of the compressor is secured, and it is possible to suppress
a noise caused by a pressure variation of the fluid.
[0012] According to the present invention, in the muffler, the muffler itself becomes a
sound source by the pulsation reduction and can suppress radiation of the sound pressure,
and thus, even if a plate thickness of the muffler body or the cover is thin, it is
possible to suppress the noise. Brief Description of Drawings
[0013]
Fig. 1 is a longitudinal sectional view of a rotary compressor according to an embodiment
of the present invention.
Fig. 2 is a view schematically showing an upper muffler shown in Fig. 1.
Fig. 3 is a partially enlarged view of Fig. 2.
Figs. 4A and 4B are views for explaining a Helmholtz resonance.
Description of Embodiments
[0014] Hereinafter, an embodiment of the present invention will be described with reference
to the accompanying drawings.
[0015] A rotary type compressor 1 shown in Fig. 1 sucks a gas refrigerant in an accumulator
(gas-liquid separator) (not shown) through pipes 8 and 9 and compresses the gas refrigerant
by a compression mechanism 4.
[0016] The compressor 1 and the accumulator constitute a refrigerating cycle device such
as an air conditioner or a refrigerator and are connected to a refrigerant circuit
(not shown) through which the refrigerant circulates.
[0017] The compressor 1 includes a motor 2 which is a power source, a rotary shaft 3 (crank
shaft) which is rotated by a rotational driving force output from the motor 2, the
rotary type compression mechanism 4 which is driven by the rotational driving force
transmitted via the rotary shaft 3, mufflers 10 and 20 which are disposed around an
axis of the rotary shaft 3, and a housing 5.
[0018] The mufflers 10 and 20 suppress a noise caused by a pulsation of the refrigerant
compressed by the compression mechanism 4.
[0019] The housing 5 accommodates the motor 2, the rotary shaft 3, the compression mechanism
4, and the mufflers 10 and 20, and is formed in a cylindrical shape.
[0020] The motor 2 includes a stator 2A which is fixed to an inner peripheral portion of
the housing 5, and a rotor 2B which is disposed inside the stator 2A. The rotor 2B
rotates with respect to the stator 2A by supplying power to a coil 2C provided in
the stator 2A.
[0021] The rotary shaft 3 includes a main shaft portion 3A which is connected to the rotor
2B and protrudes downward from the rotor 2B, an upper crank pin 3B which is eccentric
to an axis center of the main shaft portion 3A, and a lower crank pin 3C which is
eccentric to the axis center of the main shaft portion 3A similarly to the upper crank
pin 3B. The lower crank pin 3C is eccentric to the axis center of the rotary shaft
3 in a direction which becomes a phase (180°) reverse to the upper crank pin 3B.
[0022] The upper crank pin 3B is disposed in an upper cylinder 412 of the compression mechanism
4, and the lower crank pin 3C is disposed in a lower cylinder 422 of the compression
mechanism 4.
[0023] The compression mechanism 4 (Fig. 1) will be described.
[0024] The compression mechanism 4 which is a so-called twin rotary type mechanism includes
an upper compression mechanism 41, a lower compression mechanism 42, a partition plate
4A, and an upper bearing 6 and a lower bearing 7 which rotatably support the rotary
shaft 3.
[0025] The partition plate 4A partitions an inside of a cylinder 412 of the upper compression
mechanism 41 and an inside of a cylinder 422 of the lower compression mechanism 42.
[0026] The upper compression mechanism 41 is constituted so as to include an upper piston
rotor 411 which is provided in the upper crank pin 3B, the upper cylinder 412 in which
the upper piston rotor 411 is disposed, and the upper muffler 10 which is disposed
around an axis of the main shaft portion 3A.
[0027] The upper piston rotor 411 is fitted to an outer peripheral portion of the upper
crank pin 3B and is turned in the upper cylinder 412 according to a rotation of the
rotary shaft 3.
[0028] The refrigerant is sucked into the upper cylinder 412 through the pipe 8.
[0029] The upper bearing 6 includes an abutment portion 6A which abuts against an upper
end surface of the upper cylinder 412 and a cylindrical bearing portion 6B which protrudes
upward from the abutment portion 6A and is positioned around the axis of the rotary
shaft 3 (main shaft portion 3A). The abutment portion 6A is fixed to the inner peripheral
portion of the housing 5.
[0030] The upper cylinder 412, the upper muffler 10, the lower cylinder 422, and the lower
muffler 20 are integrally assembled to the upper bearing 6 by a bolt 113.
[0031] The refrigerant sucked into the upper cylinder 412 is pressed to an outer peripheral
portion of the turning upper piston rotor 411 and is compressed in a space in front
of a blade (not shown) in a rotation direction. The compressed refrigerant is discharged
into the upper muffler 10 through a discharge port 6P (Fig. 2) formed in the abutment
portion 6A of the upper bearing 6, and is discharged to a space in the housing 5 below
the motor 2 from the inside of the upper muffler 10.
[0032] Similarly to the upper compression mechanism 41, the lower compression mechanism
42 (Fig. 1) is constituted so as to include a lower piston rotor 421 which is provided
in the lower crank pin 3C, the lower cylinder 422 in which the lower piston rotor
421 is disposed, and the lower muffler 20 which is disposed around the axis of the
main shaft portion 3A.
[0033] The gas refrigerant is sucked into the lower cylinder 422 through the pipe 9.
[0034] The lower bearing 7 includes an abutment portion 7A which abuts against a lower end
surface of the lower cylinder 422 and a cylindrical bearing portion 7B which protrudes
downward from the abutment portion 7A and is positioned around the axis of the rotary
shaft 3 (main shaft portion 3A).
[0035] The refrigerant sucked into the lower cylinder 422 is compressed according to turning
of the lower piston rotor 421. The compressed refrigerant is discharged into the lower
muffler 20 through a discharge port (not shown) formed in the abutment portion 7A
of the lower bearing 7 and into the inner space of the housing 5, and the compressed
refrigerant is discharged to the space below the motor 2 in the housing 5 through
a notch 61A or an opening (not shown) formed in the abutment portion 6A of the upper
bearing 6.
[0036] As described above, the refrigerant compressed by the upper compression mechanism
41 and the lower compression mechanism 42 is discharged to the space in the housing
5 below the motor 2. The refrigerant flows to a space above the motor 2 through a
notch provided in the stator 2A or the rotor 2B and is discharged to a refrigerant
circuit through a discharge pipe 5A provided on an upper portion of the housing 5.
[0037] Each of the upper compression mechanism 41 and the lower compression mechanism 42
discharges the refrigerant with a pressure variation (pulsation) from the discharge
port according to a turning period of each of the piston rotors 411 and 421. The pulsation
of the compressed refrigerant which are ejected to the mufflers 10 and 20 through
the discharge port by the upper compression mechanism 41 and the lower compression
mechanism 42 is reduced in the mufflers 10 and 20.
[0038] The compressor 1 of the present embodiment is characterized by a structure of the
upper muffler 10.
[0039] First, with reference to Figs. 2 and 3, a configuration of the upper muffler 10 (hereinafter,
referred to as a muffler 10) will be described.
[0040] The muffler 10 includes a muffler body 11 which forms a space 110 between the abutment
portion 6A of the upper bearing 6 and the muffler body 11 and a cover 12 which forms
a cavity 120 between an outer peripheral portion 11S of the muffler body 11 and the
cover 12.
[0041] For example, each of the muffler body 11 and the cover 12 is formed of a metal material
such as an aluminum alloy by deep drawing.
[0042] In the muffler body 11, the compressed refrigerant which is compressed in the upper
cylinder 412 (Fig. 1) and ejected from the discharge port 6P is received in the inner
space 110, and the pulsation of the compressed refrigerant is reduced. The inner space
of the muffler body 11 is operated as a resistance according to a space volume by
the refrigerant ejected into the muffler body 11, and thus, the pulsation of the refrigerant
is attenuated by the muffler body 11.
[0043] The muffler body 11 is disposed around the axis of the rotary shaft 3. The bearing
portion 6B supporting the rotary shaft 3 passes through an opening formed at a planar
center portion of the muffler body 11. A peripheral edge portion of the opening corresponds
to an inner peripheral end 111 of the muffler body 11.
[0044] The muffler body 11 extends from the inner peripheral end 111 toward a radially outer
side of the rotary shaft 3 by a predetermined diameter and is formed in an approximately
cylindrical shape in a plan view. An end portion on a radially outer side of the muffler
body 11 is fastened to the upper bearing 6 by the bolts 113 at a plurality of locations
in a circumferential direction.
[0045] A dimension or a volume of the muffler body 11 can be appropriately determined so
as to conform to an audible frequency component of the pulsation of the compressed
refrigerant. This is similarly applied to the cover 12.
[0046] The muffler body 11 includes a portion 11A which extends radially outward from the
inner peripheral end 111 positioned above the abutment portion 6A and a portion 11B
which extends downward from the portion 11A toward the abutment portion 6A and is
disposed on the abutment portion 6A. The refrigerant ejected from the discharge port
6P is mainly sprayed to the portion 11A.
[0047] Shapes of the portions 11A and 11B are slightly different from those of other locations
at the locations at which the muffler body 11 is fastened by the bolts 113. The muffler
body 11 is not limited to the shape shown in Fig. 2 and can be formed in an appropriate
shape. For example, the muffler body 11 can be formed in a dome shape. This is similarly
applied to the cover 12.
[0048] In the muffler body 11, a discharge opening 11P and a plurality of openings 11H separately
from the discharge opening 11P are formed.
[0049] The refrigerant passes through discharge opening 11P from the inside of the muffler
body 11 to the inside of the cavity 120.
[0050] The discharge opening 11P penetrates the portion 11A of the muffler body 11 in a
plate thickness direction. In addition, a plurality of discharge openings are formed
at intervals in a circumferential direction of the muffler body 11.
[0051] A position of the discharge opening 11P is not particularly limited. However, preferably,
the discharge opening 11P is formed at a position at which a phase angle of the discharge
opening 11P is different from that of the discharge port 6P, or a position which is
away from the discharge port 6P such that the compressed refrigerant ejected from
the discharge port 6P is not discharged from the inside of the muffler body 11 as
it is. As described later, according to this, the refrigerant is introduced into the
plurality of openings 11H, and thus, a sound absorbing effect can be sufficiently
obtained using a Helmholtz resonance.
[0052] The number of discharge openings 11P, an opening area of each discharge opening 11P,
and a total opening area of the plurality of discharge openings 11P are determined
in consideration of a balance between a pressure loss for pulsation reduction and
the performance of the compressor 1. This is similarly applied to a discharge opening
12P of the cover 12.
[0053] In addition, the discharge opening 11P may be formed in an annular shape along the
axis (around an axis of the bearing portion 6B of the upper bearing 6) of the rotary
shaft 3.
[0054] Each of the plurality of openings 11H penetrates the muffler body 11 in the plate
thickness direction. In the example shown in Fig. 2, each opening 11H is formed in
the portion 11A. However, the opening 11H may be formed in the portion 11B or may
be formed in both the portions 11A and 11B.
[0055] A cross-sectional area (opening area) of the opening 11H is much smaller than a cross-sectional
area of the discharge opening 11P. For example, the cross-sectional area of the opening
11H is approximately 1/500 to 1/100 of the cross-sectional area of the discharge opening
11P. As described later, in order to increase the pulsation reduction effect by the
openings 11H and the cavity 120, preferably, a plurality of minute openings 11H are
formed in the muffler body 11.
[0056] As shown in Fig 4A, each opening 11H can be formed in a circular round hole. However,
the opening 11H is not limited to this, and the opening 11H can be appropriately constituted
as long as it causes the inside and the outside of the muffler body 11 to communicate
with each other.
[0057] In order to increase the pulsation reduction effect, preferably, the plurality of
opening 11H are formed over the entire surface of the muffler body 11.
[0058] In the cover 12 (refer to Figs. 2 and 3), the refrigerant is received in the cavity
120 between the cover 12 and the muffler body 11 from the space 110 in the muffler
body 11 and is discharged from the discharge opening 12P.
[0059] Similarly to the above-described muffler body 11, the cover 12 is disposed around
the axis of the rotary shaft 3, and the bearing portion 6B passes through an opening
formed at a planar center portion of the cover 12. An inner peripheral end 121 (peripheral
edge portion of the opening) of the cover 12 is slightly erected along the axial direction.
An annular gap between the inner peripheral end 121 and the bearing portion 6B becomes
the discharge opening 12P.
[0060] Preferably, the discharge opening 12P is formed at a position away from the discharge
opening 11P such that the refrigerant discharged from the discharge opening 11P of
the muffler body 11 into the cover 12 is not discharged to the outside of the cover
12 as it is. The discharge opening 12P may not be formed around the axis of the bearing
portion 6B and may be formed so as to penetrate the cover 12 in the plate thickness
direction.
[0061] The cover 12 covers the outer peripheral portion 11S of the muffler body 11 and is
fastened to the upper bearing 6 together with the muffler body 11 by the bolt 113.
[0062] The inner peripheral end 121 of the cover 12 is positioned at a position which is
positioned farther away from the abutment portion 6A of the upper bearing 6 in the
axial direction than where the inner peripheral end 111 of the muffler body 11 is
positioned. The cover 12 includes a portion 12A which faces the portion 11A of the
muffler body 11 and a portion 12B which extends downward from the portion 12A.
[0063] The cover 12 of the present embodiment covers the muffler body 11 so as to surround
the entirety thereof. However, the cover 12 may cover at least a portion of the muffler
body 11 as long as the cavity 120 is formed between the cover 12 and the muffler body
11.
[0064] According to a height of the cover 12, the inner peripheral end 121 does not face
the bearing portion 6B and may face an outer peripheral portion of the rotary shaft
3. In this case, the discharge opening 12P is formed between the inner peripheral
end 121 and the outer peripheral portion of the rotary shaft 3.
[0065] The lower muffler 20 (Fig. 1) is formed to be approximately similar to the upper
muffler 10 and is disposed around an axis of the lower bearing 7 in a direction in
which the lower muffler 20 is inverted to the upper muffler 10 in a vertical direction.
[0066] Unlike the upper muffler 10, the lower muffler 20 does not have the cover and is
formed of a single member. However, similarly to the upper muffler 10, the lower muffler
20 can be formed to have the muffler body and the cover.
[0067] Hereinafter, the pulsation reduction effect by the upper muffler 10 will be described.
[0068] As described above, the muffler body 11 forms the space 110 and the cover 12 forms
the cavity 120. Accordingly, the refrigerant compressed by the compression mechanism
41 is ejected to the space 110 and discharged to the cavity 120 from the discharge
opening 11P, and is discharged to the outside of the cover 12 through the discharge
opening 12P from the cavity 120. In this way, the refrigerant sequentially passes
through the inside of the muffler body 11 and the inside of the cover 12, and thus,
the pulsation of the refrigerant is reduced. That is, the muffler 10 having the muffler
body 11 and the cover 12 functions as a two-stage muffler which reduces the pulsation
through two stages.
[0069] The muffler 10 of the present embodiment further reduces the pulsation by establishing
the Helmholtz resonance by the openings 11H of the muffler body 11 and the cavity
120 while maintaining the performance of the pulsation reduction as the two-stage
muffler. The openings 11H and the cavity 120 constitute a Helmholtz resonator.
[0070] As shown in Fig. 4B, the Helmholtz resonance means that when air masses 15 (air columns)
existing inside the openings 11H passing through the cavity 120 move in directions
of hole axes, the air masses resonate at a predetermined frequency with the surrounding
air. In this case, the cavity 120 can be regarded as a spring provided in the air
masses 15. If the air masses 15 vibrate in a resonance state, frictions between air
and the inner peripheral portions of the openings 11H or frictions between air molecules
are remarkably generated, and thus, vibration energy attenuates and a sound pressure
decreases (sound is absorbed).
[0071] In order to establish the Helmholtz resonance, a cross-sectional area S (horizontal
cross-sectional area) of the opening 11H, a plate thickness L of the muffler body
11, and a volume V of the cavity 120 are determined so as to be a proper relationship
to each other.
[0072] A basic expression of the Helmholtz resonance is as follows. Here, f is a natural
frequency of the air mass 15 and C is a speed of sound.
[Expression 1]

[0073] Sound absorption by the Helmholtz resonance is assumed to be LS << V. That is, LS
which is an inner volume of the opening 11H is very small so as to be negligible compared
to the volume V of the cavity 120. For example, depending on the frequency f for reducing
the pulsation, a hole diameter of the opening 11H is approximately 0.15 mm, and the
plate thickness L is approximately 1.5 mm. Since each opening 11H is minute, the total
LS of the plurality of openings 11H is also very small as compared with the volume
V of the cavity 120.
[0074] As described above, since the cross-sectional area of the opening 11H is minute compared
to the discharge opening 11P or the discharge opening 12P, the openings 11 do not
affect a subject (mainstream) of a flow of the refrigerant involved in a basic pulsation
reduction mechanism of the muffler 10 in which the refrigerant received in the expanding
space 110 is discharged from the narrow discharge opening 11P and is received in the
cavity 120 to be discharged to the discharge opening 12P.
[0075] The cross-sectional area S or the plate thickness L can be determined in consideration
of an appropriate frequency f to be reduced.
[0076] For example, when the natural frequency (resonance frequency) of air mass 15 is 250
Hz, the hole diameter of the opening 11H can be set to 0.15 mm, the plate thickness
of the muffler body 11 to 1.5 mm, and the volume V of the cavity 120 to 200 mm
3.
[0077] Here, in order to obtain a pulsation reduction effect (sound absorbing effect), it
is necessary that the hole diameter of the opening 11 H is sufficiently small, and
an upper limit of a sum of the cross-sectional areas S of the plurality of openings
11H is 1% of the surface area of the muffler body 11.
[0078] Since the air mass 15 in the opening 11H moves so as to draw the surrounding air,
it is necessary to correct the length (plate thickness L) of the air mass 15 according
to the shape around the opening 11H (opening portion correction). For example, if
a radius of the opening 11H is defined as a, L' obtained from L + 1.7a = L' can be
applied to the Expression (1).
[0079] According to the compressor 1 of the present embodiment, the pulsation of the refrigerant
compressed by the upper compression mechanism 41 and the lower compression mechanism
42 can be sufficiently reduced by the mufflers 10 and 20. As described above, according
to the muffler 10, the pulsation reduction effect based on the Helmholtz resonance
can be obtained while the pulsation reduction effect of the two-stage muffler which
repeats the discharge of pulsation into the space is maintained. The movement of the
air mass 15 inside the minute opening 11H does not affect the mainstream inside the
muffler.
[0080] Therefore, according to the present embodiment, the pulsation of the refrigerant
is sufficiently reduced while the performance of the compressor 1 is secured, and
thus, it is possible to suppress a noise caused by the pressure variation of the refrigerant.
[0081] In the muffler 10, the muffler 10 itself becomes a sound source by the pulsation
reduction and can suppress radiation of the sound pressure, and thus, even if the
plate thickness of the muffler body 11 or the cover 12 is thin, it is possible to
suppress the noise.
[0082] In addition, as long as the gist of the present invention is not deviated, it is
possible to select configurations described in the embodiment or to appropriately
change the configurations to other configurations.
[0083] The compression mechanism mounted on the compressor of the present invention is not
limited to the twin rotary type compression mechanism 4. That is, the compression
mechanism may be a single rotary type compression mechanism having a pair of cylinder
and piston rotor and a muffler.
[0084] The compressor of the present invention is not limited to the rotary compressor and
may be a scroll compressor. In this case, the configuration of the present invention
may be applied to the muffler (also referred to as a discharge cover) which receives
the compressed refrigerant discharged from the scroll type compression mechanism.
That is, the discharge cover (muffler) includes a muffler body and a cover, and the
minute opening 11H may be formed in the muffler body.
[0085] As the power source of the compressor of the present invention, in addition to the
motor, for example, an engine or the like may be used.
Reference Signs List
[0086]
- 1:
- compressor
- 2:
- motor
- 2A:
- stator
- 2B:
- rotor
- 2C:
- coil
- 3:
- rotary shaft
- 3A:
- main shaft portion
- 3B:
- upper crank pin
- 3C:
- lower crank pin
- 4:
- compression mechanism
- 4A:
- partition plate
- 5:
- housing
- 5A:
- discharge pipe
- 6:
- upper bearing
- 6A:
- abutment portion
- 6B:
- bearing portion
- 6P:
- discharge port
- 7:
- lower bearing
- 7A:
- abutment portion
- 7B:
- bearing portion
- 8, 9:
- pipe
- 10:
- upper muffler
- 11:
- muffler body
- 11A:
- portion
- 11B:
- portion
- 11P:
- discharge opening
- 11H:
- opening
- 11S:
- outer peripheral portion
- 12:
- cover
- 12A:
- portion
- 12B:
- portion
- 12P:
- discharge opening
- 15:
- air mass
- 20:
- lower muffler
- 41:
- upper compression mechanism
- 42:
- lower compression mechanism
- 61A:
- notch
- 110:
- space
- 111:
- inner peripheral end
- 113:
- bolt
- 120:
- cavity
- 121:
- inner peripheral end
- 411:
- upper piston rotor
- 412:
- upper cylinder
- 421:
- lower piston rotor
- 422:
- lower cylinder
- L:
- plate thickness
- S:
- cross-sectional area
- V:
- volume