U.S. patent application number 10/553847 was filed with the patent office on 2006-11-16 for hermetic compressor.
Invention is credited to Makoto Katayama, Ikutomo Umeoka, Junichiro Yabiki.
Application Number | 20060257274 10/553847 |
Document ID | / |
Family ID | 34968133 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060257274 |
Kind Code |
A1 |
Umeoka; Ikutomo ; et
al. |
November 16, 2006 |
Hermetic compressor
Abstract
A hermetic compressor including a housing containing oil and a
compression mechanism for compressing a refrigerant gas. In this
configuration, a cylindrical piston has under cuts which do not
communicate with at least a top surface at a cylinder side of the
piston and are formed on an outer circumferential surface of the
piston excluding a sliding surface existing in the axial direction
of a piston pin and the perpendicular direction of the piston pin
viewed from the axial direction of the piston, in which the under
cuts communicate with space inside the housing in the vicinity of
the bottom dead center. Since the sliding surface is provided in
the direction parallel to and perpendicular to the axis,
inclination of the piston in the vertical direction is suppressed
and at the same time oil supply to the sliding portion through the
under cuts is promoted. Therefore, the sealing property and
lubricant property are improved, and thus high efficiency of the
compressor can be realized.
Inventors: |
Umeoka; Ikutomo; (Kanagawa,
JP) ; Katayama; Makoto; (Kanagawa, JP) ;
Yabiki; Junichiro; (Kanagawa, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK L.L.P.
2033 K. STREET, NW
SUITE 800
WASHINGTON
DC
20006
US
|
Family ID: |
34968133 |
Appl. No.: |
10/553847 |
Filed: |
May 11, 2005 |
PCT Filed: |
May 11, 2005 |
PCT NO: |
PCT/JP05/09006 |
371 Date: |
October 20, 2005 |
Current U.S.
Class: |
417/415 |
Current CPC
Class: |
F04B 39/0005 20130101;
F04B 39/023 20130101 |
Class at
Publication: |
417/415 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2004 |
JP |
2004-159165 |
Claims
1. A hermetic compressor comprising a housing which contains oil
and houses a compression mechanism for compressing a refrigerant
gas, the compression mechanism comprising: a crankshaft disposed in
a vertical direction and having a main shaft and an eccentric
shaft; a block forming a cylinder; a piston reciprocating in the
cylinder in a direction of a cylinder axis; a piston pin disposed
on the piston in a way in which a center axis is in parallel to the
eccentric shaft; a connecting rod for connecting the eccentric
shaft to the piston pin; and an oil supplying structure for
supplying the oil to an outer circumferential surface of the
piston; wherein the piston has an under cut on the outer
circumferential surface excluding a sliding surface existing in a
parallel direction and a perpendicular direction of the piston pin
viewed from an axial direction of the piston; and the under cut
separated from a top surface at a cylinder side of the piston and
communicates with space inside the housing at least when the piston
is in a bottom dead center.
2. The hermetic compressor according to claim 1, wherein an area of
the under cut is not less than one half of an area of the outer
circumferential surface of the piston.
3. The hermetic compressor according to claim 1, wherein an angle
made by an edge of the under cut and the outer circumferential
surface of the piston is an acute angle.
4. The hermetic compressor according to claim 1, wherein the under
cut is formed continuously to a skirt surface.
5. The hermetic compressor according to claim 1, wherein the piston
has a circumferentially formed land in a predetermined width from
the top surface, and the circumferentially formed land is provided
with an annular groove.
6. The hermetic compressor according to claim 1, wherein the piston
has a taper in at least one of a boundary between the top surface
and the outer circumferential surface and a boundary between a
skirt surface and the outer circumferential surface.
7. The hermetic compressor according to claim 1, further comprising
a motor element for rotating the crankshaft, the motor element
being inverter-driven at plural operation frequencies including an
operation frequency that is at least power supply frequency or
less.
8. The hermetic compressor according to claim 1, wherein the
refrigerant gas is R600a.
9. A hermetic compressor comprising a housing which contains oil
and houses a compression mechanism for compressing a refrigerant
gas, the compression mechanism comprising: a crankshaft disposed in
a vertical direction and having a main shaft and an eccentric
shaft; a cylinder; a cylindrical piston reciprocating in the
cylinder in a direction of a cylinder axis; and a connecting
portion for connecting the piston to the eccentric shaft; the
piston comprising: a skirt surface at a side of the connecting
portion; a top surface at a side of the cylinder; and an outer
circumferential surface parallel to the cylinder; wherein the outer
circumferential surface includes a land that is on the same surface
as the outer circumferential surface of the piston and an under cut
that is recess with respect to the outer circumferential surface;
the land comprising: a circumferentially formed land formed in a
predetermined width from the top surface toward the skirt surface
around the piston; and an axially formed land formed in a
predetermined width on an outer circumferential surfaces at
0.degree., 90.degree., 180.degree. and 270.degree. with respect to
the cylinder axis as a center, and continuously formed from the
circumferentially formed land to the skirt surface.
10. The hermetic compressor according to claim 9, wherein the under
cut is formed continuously to the skirt surface.
11. The hermetic compressor according to claim 9, wherein the under
cut is formed discontinuously to the skirt surface, and when the
piston is at least in a bottom dead center, the under cut
communicates with space inside the housing.
Description
TECHNICAL FIELD
[0001] The present invention relates to a hermetic compressor used
in a refrigerating cycle of a Refrigerator Freezer, etc.
BACKGROUND ART
[0002] Recently, reduction in power consumption of this kind of
hermetic compressors has been strongly demanded. In a hermetic
compressor disclosed in International Publication WO 02/02944, by
improving an outer shape of a piston, sliding loss between the
piston and a cylinder is reduced so as to achieve efficiency.
[0003] Hereinafter, a conventional hermetic compressor is described
with reference to drawings.
[0004] FIG. 7 is a longitudinal sectional view showing a general
hermetic compressor described in US Pat. No. 5,228,843; and FIG. 8
is a perspective view showing a piston described in International
Publication WO 02/02944.
[0005] As shown in FIG. 7, hermetic housing 1 houses motor element
4 consisting of stator 2 having winding portion 2a and rotor 3, and
compression element 5 driven by motor element 4. Moreover, in the
lower part of hermetic housing 1, oil 6 is contained.
[0006] Crankshaft 10 includes main shaft 11 to which rotor 3 is
press-fitted and fixed and eccentric shaft 12 formed eccentric to
main shaft 11. Inside main shaft 11, oil pump 13 is housed and an
opening portion of oil pump 13 is disposed in oil 6. Block 20
provided at the upper side of motor element 4 has cylinder 21
having a substantially cylindrical shape and bearing 22 for
supporting main shaft 11. Piston 30 is inserted into cylinder 21 of
block 20 capable of reciprocating sliding and coupled to eccentric
shaft 12 via connecting means 41.
[0007] Next, a conventional piston is described with reference to
FIG. 8. Piston 30 includes top surface 31, skirt surface 32 and
outer circumferential surface 33. Furthermore, outer
circumferential surface 33 includes seal surface 34, two guide
surfaces 35 and removed portions 36. Herein, seal surface 34 is a
surface in the circumferential direction, which is formed so as to
be brought into close contact with the inner circumferential
surface of cylinder 21. Guide surface 35 is formed so as to be
brought into close contact with a part of the inner circumferential
surface of cylinder 21 and extends substantially in parallel in the
direction of the movement of piston 30.
[0008] Removed portion 36 is a concave portion that is not brought
into close contact with the inner circumferential surface of
cylinder 21. Furthermore, an angle made by lines respectively
connecting between central axis 37 of cylindrical piston 30 and two
boundary edges 35a and 35b of guide surface 35 in the direction of
the radius of piston 30 is generally 40.degree. or less and
preferably 30.degree. or less.
[0009] Next, an operation of a conventional hermetic compressor
shown in FIG. 7 is described.
[0010] During operation, piston 30 reciprocates in the horizontal
direction in the drawing. In the vicinity of the bottom dead
center, a part of the skirt side of piston 30 is protruded to the
outside of cylinder 21. From this state, when piston 30 enters
cylinder 21, that it is to say, when piston 30 moves in the right
direction of FIG. 7, piston 30 is guided by guide surface 35 and
thereby can enter cylinder 21 smoothly.
[0011] However, in a conventional hermetic compressor, inclination
in the vertical direction of piston 30 with respect to cylinder 21
is regulated by space between outer circumferential surface 33 and
cylinder 21 only in short section 34A between the edge of top
surface 31 and the edge of seal surface 34. Therefore, piston 30 is
likely to be inclined in the vertical direction. In particular,
during the compression stroke from the bottom dead center to the
top dead center (movement in the right direction in FIG. 7), top
surface 31 of piston 30 undergoes compression load of a refrigerant
gas and furthermore, crankshaft 10 is pressed in the direction that
is not the direction of a piston (downward direction in FIG. 7) via
connecting means 41, and thereby the inclination of piston 30 in
the vertical direction is likely to be increased. As a result,
there has been a problem that leakage of refrigerant increases, and
the refrigerating capacity is deteriorated so as to lower the
efficiency.
[0012] In particular, when low-density refrigerant Isobutane
(R600a) was used, the outer diameter of piston 30 was increased and
leakage of refrigerant was likely to occur, and therefore the
efficiency was lowered remarkably.
SUMMARY OF THE INVENTION
[0013] In order to solve the above-mentioned problems with a prior
art, a hermetic compressor of the present invention includes an
under cut that does not communicate with at least a top surface of
a piston on an outer circumferential surface of the piston
excluding a sliding surface provided in the axis direction and in
the perpendicular direction of the piston pin, in which the under
cut communicates with space inside a housing at least in the
vicinity of the bottom dead center. This configuration makes it
possible to reduce sliding loss due to the reduction in a sliding
area. Furthermore, by the sliding surface provided in the parallel
and in the perpendicular direction of the piston pin, the
inclination of the piston with respect to the cylinder is
suppressed, thus suppressing the leakage of refrigerant.
Furthermore, by supplying the sliding portion with oil through the
under cut, the sealing property can be improved. With the above
mentioned effect, a hermetic compressor with high efficiency can be
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a longitudinal sectional view showing a hermetic
compressor in an exemplary embodiment of the present invention.
[0015] FIG. 2 is an enlarged sectional view showing an element
around a piston used for a hermetic compressor in an exemplary
embodiment.
[0016] FIG. 3 is a front view showing a piston used for a hermetic
compressor in an exemplary embodiment.
[0017] FIG. 4 is a sectional view of a part along line 4-4 of FIG.
3.
[0018] FIG. 5 is an enlarged sectional view showing an end face of
an under cut of a piston used for a hermetic compressor in an
exemplary embodiment.
[0019] FIG. 6 is an enlarged sectional view showing a tip of a
piston used for a hermetic compressor in an exemplary
embodiment.
[0020] FIG. 7 is a longitudinal sectional view showing a
conventional hermetic compressor.
[0021] FIG. 8 is a perspective view showing a piston used for a
conventional hermetic compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Hereinafter, an exemplary embodiment of the present
invention is described with reference to drawings. Note here that
the present invention is not limited by the exemplary
embodiment.
Exemplary Embodiment
[0023] FIG. 1 is a longitudinal sectional view showing a hermetic
compressor in an exemplary embodiment of the present invention;
FIG. 2 is an enlarged sectional view showing an element around a
piston; FIG. 3 is a front view showing a piston; FIG. 4 is a
sectional view of a part along line 4-4 of FIG. 3; FIG. 5 is an
enlarged sectional view showing an end face of an under cut of a
piston; and FIG. 6 is an enlarged sectional view showing a tip of a
piston.
[0024] As shown in FIGS. 1 to 6, housing 101 houses motor element
104 and compression mechanism 105 driven by motor element 104, and
moreover contains oil 106. Motor element 104 includes stator 102
and rotor 103, and enables inverter driving by using a control
circuit, etc. controlled at plural operational frequencies
including operation frequency that is not higher than power supply
frequency.
[0025] The hermetic compressor of this exemplary embodiment uses
hydrocarbon-based refrigerant Isobutane (or R600a). Refrigerant
R600a is a natural refrigerant with low global warming
potential.
[0026] Crankshaft 110 includes main shaft 111 and eccentric shaft
112 and is disposed in substantially the vertical direction.
Herein, rotor 103 is press-fitted and fixed to main shaft 111 and
eccentric shaft 112 is disposed eccentric to main shaft 111.
[0027] Oil supplying structure 120 includes centrifugal pump 122,
vertical hole 123, and lateral hole 124. One end of centrifugal
pump 122 formed inside of crankshaft 110 is opened in oil 106 with
another end connected to viscosity pump 121. One end of vertical
hole 123 is connected to one end of viscosity pump 121 with another
end opened in space inside housing 101.
[0028] Block 130 includes substantially cylindrical cylinder 131,
main bearing 132 for supporting main shaft 111 and
collision-portion 134 provided on the upper side of cylinder 131.
Cylinder 131 includes notch 135 provided on the upper side of the
edge at the side of crankshaft 110.
[0029] Piston 140 is inserted into cylinder 131 capable of
reciprocating sliding. Piston 140 has piston pin hole 141 formed in
parallel to the center axis of eccentric shaft 112. Into piston pin
hole 141, hollow cylindrical piston pin 142 is fitted. Piston pin
142 is fixed to piston 140 by hollow cylindrical lock pin 143.
Piston pin 142 is connected to eccentric shaft 112 via connecting
rod 146.
[0030] Hollow part 144 of piston pin 142 communicates with space
inside housing 101 via vent hole 145.
[0031] On outer circumferential surface 150 of piston 140, under
cut 153 is formed. Under cut 153 does not reach top surface 151 of
piston 140 but reaches skirt surface 152. FIG. 4 is a sectional
view of a part of piston 140 taken along line 4-4 of FIG. 3,
showing a state of cylindrical central axis 170 of the piston seen
from the left direction. As shown in FIG. 4, under cut 153 is
formed excluding a region with a predetermined width in parallel
direction 147 with respect to the axis of piston pin 142 and a
region with a predetermined width in the perpendicular direction
148 with respect to the axis of piston pin 142. Total area of under
cut 153 is not less than one half of an area of outer
circumferential surface 150 of the piston. Furthermore, as shown in
FIG. 5 that is an enlarged view showing the vicinity of edge 180 of
under cut 153, angle .theta. made by edge 180 of under cut 153 and
outer circumferential surface 150 of the piston is set to be an
acute angle.
[0032] Furthermore, as shown in FIG. 3, the right end portion of
piston 140 is provided with circumferentially formed land 190, on
which under cut 153 is not formed, in a predetermined width from
top surface 151. Furthermore, outer circumferential surface 150
that does not belong to any of circumferentially formed land 190
and under cut 153 is referred to as axially formed land 192. In
FIG. 3, axially formed land 192 is provided in parallel to
cylindrical central axis 170 and extends from circumferentially
formed land 190 and reaches skirt surface 152. As shown in FIG. 4,
axially formed lands 192 are formed in a predetermined width on an
outer circumferential surfaces at 0.degree., 90.degree.,
180.degree. and 270.degree. with respect to the cylinder axis as a
center.
[0033] Furthermore, as shown in FIG. 4, it is preferable that the
width of axially formed land 192 is set so that angle .omega. made
by two lines linking between cylindrical central axis 170 of piston
140 and two boundary portions of axially formed land 192 in the
direction of radius of the piston is set to 40.degree. or less and
preferably 30.degree. or less.
[0034] As shown in FIG. 4, in outer circumferential surface 150 of
the piston, upper sliding surface 154 and lower sliding surface 155
are provided in the vertical direction and side sliding surface 160
is provided in the direction of the side surface. These correspond
to one or both of circumferentially formed land 190 and axially
formed land 192.
[0035] Furthermore, on circumferentially formed land 190, two
annular grooves 191 are provided in the outer circumferential
direction of the piston. Furthermore, on outer circumferential
surface 150 of the piston, at both end portions of top surface 151
side and skirt surface 152 side, minute tapers 201 and 202 are
provided.
[0036] In this exemplary embodiment, as shown in FIG. 1, in the
vicinity of the bottom dead center, a part of the skirt side of
piston 140 is protruded from cylinder 131. With such a
configuration, even in a shape in which under cut 153 does not
reach skirt surface 152, under cut 153 is opened in space inside
the housing when at least piston 140 is in the bottom dead
center.
[0037] Next, the operation and action of the hermetic compressor of
the exemplary embodiment are described.
[0038] When rotor 103 of motor element 104 rotates crankshaft 110,
the rotation movement of eccentric shaft 112 is transmitted to
piston 140 via connecting rod 146 and piston pin 142 as a
connecting portion, and thereby piston 140 reciprocates in cylinder
131. When piston 140 reciprocates, a refrigerant gas is sucked from
a cooling system (not shown) into cylinder 131, compressed and then
discharged into the cooling system, again.
[0039] Next, an operation of oil supplying structure 120 is
described. By the rotation of crankshaft 110, centrifugal pump 122
is rotated so as to generate centrifugal force. By the centrifugal
force, oil 106 moves upwardly in centrifugal pump 122 to reach
viscosity pump 121. Oil 106 which reached viscosity pump 121
further moves upwardly in viscosity pump 121 and are scattered in
housing 101 via vertical hole 123 and lateral hole 124.
[0040] Oil 106 scattered in housing 101 collides with
collision-portion 134 and moves along notch 135 so as to be
attached to outer circumferential surface 150 of the piston.
Attached oil 106 moves around outer circumferential surface 150,
under cut 153, annular groove 191 and minute tapers 201 and 202 in
accordance with the reciprocating movement of piston 140, and works
as a lubricant between outer circumferential surface 150 and
cylinder 131.
[0041] In the hermetic compressor of this exemplary embodiment, as
shown in FIG. 1, in the vicinity of the bottom dead center, a part
of the skirt side of piston 140 is protruded from cylinder 131.
Therefore, when piston 140 comes to the bottom dead center, at
least a part of under cut 153 is protruded from cylinder 131 and
can be brought into direct contact with oil 106 scattered in
housing 101. Thus, enough amount of oil 106 is always supplied to
under cut 153.
[0042] As shown in FIG. 5, oil 106 entering under cut 153 is
accumulated in the vicinity of edge 180 of under cut 153. When
piston 140 moves from the bottom dead center to the top dead
center, oil 106 is carried to an inner part of cylinder 131. On the
other hand, when piston 140 moves from the top dead center to the
bottom top dead center, in accordance with the movement of piston
140, oil 106 is drawn into between cylinder 131 and outer
circumferential surface 150 of the piston so as to efficiently
lubricate the vicinity of circumferentially formed land 190.
[0043] Furthermore, since angle .theta. made by edge 180 and outer
circumferential surface 150 of the piton is made to be an acute
angle, in accordance with the movement of piston 140, oil 106 is
efficiently drawn into between cylinder 131 and outer
circumferential surface 150 of the piston.
[0044] In this exemplary embodiment, since four under cuts 153 are
provided in the axial direction of piston 140, through under cut
153, oil 106 is supplied to the wide range of outer circumferential
surface 150 of the piston.
[0045] With the synergistic effect of them, the lubricant property
of piston 140 is improved, and extremely high sealing property can
be obtained so as to suppress leakage of refrigerant. Therefore,
high efficiency can be realized.
[0046] In general, when piston 140 is in the vicinity of the top
dead center, the inside of cylinder 131 becomes high pressure due
to a compressed refrigerant, so that a refrigerant gas is about to
leak from between cylinder 131 and outer circumferential surface
150 of the piston. At this time, by compression load generated
inside cylinder 131, via piston pin 142 and connecting road 146,
crankshaft 110 is pressed toward the opposite direction to the
piston and may be inclined. When crankshaft 110 is inclined, piston
140 may be inclined in the vertical direction with respect to
cylinder 131, thereby forming a part in which space between
cylinder 131 and outer circumferential surface 150 of the piston
may be broadened. As a result, leakage of a refrigerant gas from
the part may be accelerated. Furthermore, the inclination of piston
140 may deteriorate the lubricant state between piston 140 and
cylinder 131 and may increase a sliding noise.
[0047] However, in this exemplary embodiment, since upper sliding
surface 154 and lower sliding surface 155 of piston 140 are
provided over the full length of piston 140 from top surface 151 to
skirt surface 152 as shown in FIGS. 3 and 4, the inclination in the
vertical direction of piston 140 is regulated, and thus the
generation of inclination of piston 140 can be effectively
suppressed. As a result of suppression of the inclination, leakage
of refrigerant gas from cylinder 131 to housing 101 is suppressed,
the behavior of piston 140 becomes stable, and it is possible to
reduce sliding loss and to suppress the increase in noise.
Consequently, high efficiency and low noise property can be
achieved.
[0048] Furthermore, the sliding loss generated when piston 140
reciprocates in cylinder 131 is in a state of fluid lubricant in
which the loss is reduced in proportion to reduction of the sliding
area. In this exemplary embodiment, since the area of under cut 153
is set to not less than one half of the area of outer
circumferential surface 150 of the piston, sliding loss of piston
140 is about one half. Thus, high efficiency by remarkable input
reduction can be realized.
[0049] Furthermore, during the compression stroke, a high pressure
gas inside cylinder 131 leaks out to under cut 153. However, since
under cut 153 always communicates with space inside housing 101 at
skirt surface 152 side, leaked refrigerant gas is not accumulated
in under cut 153. Therefore, jet noise is not generated when the
under cut comes out from the cylinder and a high pressure gas is
released into low pressure space inside housing 101 at once in the
case of a piston having a structure in which an under cut does not
communicates with space inside housing 101. Furthermore, a high
pressure gas accumulated in the under cut does not backflow into
cylinder 131 to increase re-expansion loss during the suction
stroke.
[0050] Note here that, in this exemplary embodiment, under cut 153
always communicates with skirt surface 152. However, another
configuration mentioned below can provide the same effect because a
high pressure gas is released into space inside housing 101. That
is to say, without allowing under cut 153 to communicate with skirt
surface 152, under cut 153 may be allowed to communicate with space
inside housing 101 only in the vicinity of the bottom dead center,
or under cut 153 may be allowed to communicate with piston pin hole
141.
[0051] Furthermore, when circumferentially formed land 190 is
provided with annular groove 191 and oil 106 is allowed to be
brought into direct contact with annular groove 191 in the vicinity
of the bottom dead center in which piston 140 is protruded from
cylinder 131, attached oil 106 is spread over the entire part of
annular groove 191 by the capillary phenomenon. Thereafter, during
the movement of piston 140 from the bottom dead center to the top
dead center, when a refrigerant gas reaches annular groove 191 and
is joined together with oil 106 in groove 191, great viscosity
resistance acts on the refrigerant gas. Furthermore, joined oil 106
and the refrigerant gas are expanded and contracted repeatedly, so
that the pressure is reduced, whereby a so-called labyrinth seal
effect is generated and the sealing property with respect to the
leakage of refrigerant from cylinder 131 is improved. From the
effect mentioned above, oil supply to the circumferentially formed
land is further promoted, the lubricant property can be more
improved, and furthermore, high efficiency can be achieved.
[0052] Next, the role of minute tapers 201 and 202 provided at the
end portions both at top surface 151 side and skirt surface 152
side of piston 140 is described. When the piston moves from the
bottom dead center to the top dead center, by the wedge effect of
minute taper 201 at top surface 151 side of piston 140, oil 106
moves around circumferentially formed land 190 of piston 140 so as
to improve the lubricant property of piston 140 and to also improve
the sealing property. On the other hand, when piston 140 moves from
the top dead center to the bottom dead center, by the wedge effect
of minute taper 202 at the skirt surface 152 side, oil 106 enters
minute taper 202 so as to form an oil film and lubricant property
and sealing property are improved. That is to say, the presence of
minute tapers 201 and 202 suppresses the leakage of refrigerant and
reduces the sliding loss. Furthermore, high efficiency can be
achieved.
[0053] Furthermore, in the case where the motor element is inverter
driven at plural operation frequencies including operation
frequency that is not more than power supply frequency,
reciprocating movement speed of piston 140 is reduced during low
speed operation. Furthermore, since an amount of oil 106 scattered
in housing 101 is reduced, leakage of refrigerant from space
between outer circumferential surface 150 of the piston and
cylinder 131 is likely to be increased. On the other hand, in the
hermetic compressor of this exemplary embodiment, since oil 106 can
be accumulated in under cut 153 and inclination in the vertical
direction of piston 140 can be suppressed, high efficiency can be
maintained also during the low speed operation.
[0054] The density of refrigerant R600a used in the hermetic
compressor of this exemplary embodiment is smaller than the density
of refrigerant R134a (1,1,1,2-tetrafluoroethane), which has been
conventionally used in refrigerators. Therefore, when refrigerating
ability that is the same as in a hermetic compressor using
refrigerant R134a is intended to be obtained by using refrigerant
R600a, cylinder capacity is increased and the outer diameter of
piston 140 may be increased. Necessarily, the flow passage area for
a refrigerant is increased and the amount of refrigerant leaking
into housing 101 from cylinder 131 is likely to increase. However,
in the hermetic compressor of this exemplary embodiment, since the
inclination of piston 140 with respect to cylinder 131 can be
suppressed, the efficiency can be improved.
[0055] Note here that crankshaft 110 may be provided with secondary
axis which is provided on the same axis as main shaft 111 and
opposed to main shaft with eccentric shaft 112 therebetween, and at
the same time, a secondary bearing for supporting the secondary
axis may be provided. With such a configuration, since crankshaft
110 is supported at both ends with eccentric shaft 112 sandwiched
therebetween, resulting in effectively suppressing the inclination
of piston 140 in the vertical direction with respect to cylinder
131. Consequently, since the behavior of piston 140 becomes stable,
sliding loss can be reduced and the increase in noise can be
suppressed, it is possible to realize a hermetic compressor with
high efficiency and low noise property.
INDUSTRIAL APPLICABILITY
[0056] As mentioned above, since a hermetic compressor according to
the present invention yields high productivity, and can increase
efficiency and reliability, it can be widely applied to an
application of a hermetic compressor of, for example, an air
conditioner, a vending machine, and the like.
* * * * *