U.S. patent application number 10/742357 was filed with the patent office on 2004-07-15 for scroll compressor.
Invention is credited to Hishinuma, Yumin, Kimura, Kazuya, Shimizu, Izuru, Tarao, Susumu.
Application Number | 20040136854 10/742357 |
Document ID | / |
Family ID | 32463494 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040136854 |
Kind Code |
A1 |
Kimura, Kazuya ; et
al. |
July 15, 2004 |
Scroll compressor
Abstract
A scroll compressor includes a fixed scroll member fixed to a
housing and a movable scroll member engaging the fixed scroll
member. Each scroll member has a base plate and a spiral wall. A
compression chamber between the fixed and movable scroll members
reduces in volume by orbiting the movable scroll member, thus
compressing gas. A back pressure chamber is defined in the housing
on a back surface side of the movable scroll base plate between the
movable scroll member and the a fixed wall of the housing. An
introducing passage interconnects the back pressure chamber and a
relatively high pressure region. A seal member on one of the
movable scroll member and the fixed wall seals the back pressure
chamber as being slidable on the other. The seal member includes a
portion for lowering sealing performance, which interconnects the
back pressure chamber and a relatively low pressure region.
Inventors: |
Kimura, Kazuya; (Kariya-shi,
JP) ; Shimizu, Izuru; (Kariya-shi, JP) ;
Tarao, Susumu; (Kariya-shi, JP) ; Hishinuma,
Yumin; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
32463494 |
Appl. No.: |
10/742357 |
Filed: |
December 19, 2003 |
Current U.S.
Class: |
418/55.4 ;
418/55.5; 418/57 |
Current CPC
Class: |
F04C 23/008 20130101;
F04C 2210/261 20130101; F04C 27/005 20130101 |
Class at
Publication: |
418/055.4 ;
418/055.5; 418/057 |
International
Class: |
F04C 018/00; F04C
002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2002 |
JP |
2002-370997 |
Claims
What is claimed is:
1. A scroll compressor comprising: a housing including a fixed
wall, the housing defining a relatively high pressure region and a
relatively low pressure region; a fixed scroll member having a base
plate and a spiral wall extending from the base plate, the fixed
scroll member being fixedly connected to the housing; a movable
scroll member having a base plate and a spiral wall extending from
the base plate, the movable scroll member being engaged with the
fixed scroll member, whereby a compression chamber is defined
between the fixed scroll member and the movable scroll member, the
compression chamber progressively reducing in volume by orbiting
the movable scroll member relative to the fixed scroll member, thus
compressing gas; a back pressure chamber defined in the housing on
a back surface side of the base plate of the movable scroll member
between the movable scroll member and the fixed wall; an
introducing passage interconnecting the back pressure chamber and
the relatively high pressure region; and a seal member provided on
one of the movable scroll member and the fixed wall for sealing the
back pressure chamber as being slidable on the other of the movable
scroll member and the fixed wall, the seal member including a seal
lowering portion for lowering sealing performance, the seal
lowering portion interconnecting the back pressure chamber and the
relatively low pressure region.
2. The scroll compressor according to claim 1, wherein the seal
member has an annular shape, the seal lowering portion being formed
by partially splitting the seal member.
3. The scroll compressor according to claim 1, wherein the movable
scroll member is accommodated in a scroll chamber, which is defined
by connecting the fixed scroll member and the fixed wall at a
joint, the scroll compressor further comprising: a shim interposed
at the joint between the fixed scroll member and the fixed wall for
adjusting a thrust clearance between the movable scroll member and
the fixed wall.
4. The scroll compressor according to claim 1, further comprising:
a rotary shaft including a crankshaft for supporting the movable
scroll member; a shaft support member fixedly connected to the
fixed wall on a side opposite to the movable scroll member in the
housing, the shaft support member rotatably supporting the rotary
shaft, a balancer chamber being defined between the fixed wall and
the shaft support member; and a balancer provided for the
crankshaft, the balancer being accommodated in the balancer
chamber.
5. The scroll compressor according to claim 1, wherein the back
pressure chamber communicates with the relatively low pressure
region through a passage other than the seal lowering portion, the
scroll compressor further comprising: a differential pressure
regulating valve arranged in the passage for opening the passage
when pressure differential between the back pressure chamber and
the relatively low pressure region is equal to or higher than a
predetermined value.
6. The scroll compressor according to claim 1, wherein the
relatively high pressure region includes two volume-reducing
compression chambers, which respectively communicate with the back
pressure chamber through the introducing passage.
7. The scroll compressor according to claim 6, wherein two
volume-reducing compression chambers respectively communicate with
the back pressure chamber through the respective independent
introducing passages.
8. The scroll compressor according to claim 1, wherein the
introducing passage is formed in the base plate of the movable
scroll member.
9. The scroll compressor according to claim 1, wherein carbon
dioxide is employed as refrigerant of the refrigeration cycle.
10. The scroll compressor according to claim 1, wherein the
compressor is driven by an electric motor.
Description
[0001] The present invention relates to a scroll compressor of a
refrigeration cycle in a vehicle air conditioner for compressing
refrigerant.
[0002] A scroll compressor of such type includes a fixed scroll
member and a movable scroll member. The fixed scroll member has a
spiral wall and a base plate, and is fixedly connected to a housing
of the compressor. The movable scroll member has a spiral wall and
a base plate, and is engaged with the spiral wall of the fixed
scroll member. As the movable scroll member orbits, compression
chambers defined between both the spiral walls progressively reduce
in volume, thus compressing refrigerant gas.
[0003] Recently, carbon dioxide is employed as refrigerant for the
refrigeration cycle. When carbon dioxide refrigerant is employed,
pressure in the refrigeration cycle becomes much higher than that
when fluorocarbon refrigerant is employed. Accordingly, in the
scroll compressor, relatively large thrust load based upon pressure
in the compression chambers is applied to the movable scroll
member. Thus, the movable scroll member slides under relatively
hard condition, so that reliability of the scroll compressor is
deteriorated.
[0004] In order to solve such a problem, for example, as disclosed
in Unexamined Japanese Patent Publication No. 2000-249086, the back
surface of the movable scroll member is recessed to form a pocket
for applying back pressure, and the pocket for applying back
pressure is shut by a fixed wall provided in a housing of the
compressor. Thus, a back pressure chamber is formed. A
volume-reducing compression chamber communicates with the back
pressure chamber through an introducing passage. Accordingly, force
(force based upon the back pressure) that resists against force
(thrust load) based upon pressure in the compression chambers is
applied to the movable scroll member due to the pressure in the
back pressure chamber, so that sliding resistance is reduced
between the movable scroll member and the fixed wall. Additionally,
the movable scroll member is pressed against the fixed scroll
member, so that sealing performance of the compression chambers
improve.
[0005] The pressure in the back pressure chamber is appropriately
adjusted by variation in the amount of a clearance (passing
cross-sectional area) between the movable scroll member and the
fixed scroll wall. In other words, for example, as the pressure in
the back pressure chamber rises, the clearance between the movable
scroll member and the fixed wall increases. Accordingly, the amount
of refrigerant gas delivered from the back pressure chamber to a
relatively low pressure region through the clearance increases, so
that an excessive rise in the pressure in the back pressure chamber
is prevented. On the contrary, as the pressure in the back pressure
chamber falls, the clearance between the movable scroll member and
the fixed wall reduces. Accordingly, the amount of refrigerant gas
delivered from the back pressure chamber to the relatively low
pressure region through the clearance reduces, so that undesirable
reduction in the pressure in the back pressure chamber is
prevented.
[0006] An unwanted feature is that in accordance with the
Unexamined Japanese Patent Publication No. 2000-249086, the entire
clearance between the movable scroll member and the fixed wall is
utilized as a passage for delivering the refrigerant gas from the
back pressure chamber to the relatively low pressure region.
Accordingly, in order to optionally and appropriately adjust the
pressure in the back pressure chamber by the variation in the
amount of the clearance, for example, a facing surface of the
movable scroll member and a facing surface of the fixed wall need
be manufactured in high accuracy. As a result, cost for
manufacturing the scroll compressor rises.
[0007] Particularly, when carbon dioxide refrigerant is employed,
the pressure in the back pressure chamber is adjusted in a much
higher range than that when fluorocarbon refrigerant is employed.
Accordingly, in order to appropriately adjust the pressure in the
back pressure chamber, the clearance between the movable scroll
member and the fixed wall need be much narrower at the maximum.
Thus, a rise in cost for manufacturing becomes a further serious
problem. Therefore, there is a need for providing a scroll
compressor that has a reasonable structure and optionally and
appropriately adjusts pressure in a back pressure chamber.
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention, a scroll
compressor has a housing, a fixed scroll member, a movable scroll
member and a seal member. The housing includes a fixed wall, and
defines a relatively high pressure region and a relatively low
pressure region. The fixed scroll member has a base plate and a
spiral wall extending from the base plate, and is fixedly connected
to the housing. The movable scroll member has a base plate and a
spiral wall extending from the base plate, and is engaged with the
fixed scroll member. A compression chamber defined between the
fixed scroll member and the movable scroll member progressively
reduces in volume by orbiting the movable scroll member relative to
the fixed scroll member, thus compressing gas. The back pressure
chamber is defined in the housing on a back surface side of the
base plate of the movable scroll member between the movable scroll
member and the fixed wall. The back pressure chamber and the
relatively high pressure region are interconnected through an
introducing passage. A seal member is provided on one of the
movable scroll member and the fixed wall for sealing the back
pressure chamber as being slidable on the other of the movable
scroll member and the fixed wall. The seal member includes a seal
lowering portion for lowering sealing performance. The seal
lowering portion interconnects the back pressure chamber and the
relatively low pressure region.
[0009] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention together with objects and advantages thereof, may
best be understood by reference to the following description of the
presently preferred embodiments together with the accompanying
drawings in which:
[0011] FIG. 1 is a longitudinal cross-sectional view of an electric
compressor according to a preferred embodiment of the present
invention;
[0012] FIG. 2 is a rear end view of a movable scroll member, which
is detached from the scroll compressor, according to the preferred
embodiment of the present invention;
[0013] FIG. 3A is a partially enlarged cross-sectional view around
a seal member of FIG. 1;
[0014] FIG. 3B is a partially enlarged cross-sectional view
illustrating a state when a passing cross-sectional area of a
portion for lowering sealing performance becomes small;
[0015] FIG. 4 is a rear end view of a movable scroll member
according to an alternative embodiment of the present invention;
and
[0016] FIG. 5 is a partially enlarged cross-sectional view of a
relevant portion of an electric compressor according to an
alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] A preferred embodiment of the present invention will now be
described with reference to FIGS. 1 through 3B. In the preferred
embodiment, a scroll compressor according to the present invention
is applied to an electric compressor for use in a refrigeration
cycle of a vehicle air conditioner. Incidentally, carbon dioxide is
employed as refrigerant of the refrigeration cycle. The left side
and the right side of FIG. 1 respectively correspond to the front
side and the rear side of the electric compressor.
[0018] As shown in FIG. 1, a housing 11 of the electric compressor
includes a first housing element 21 and a second housing element
22. The first housing element 21 and the second housing element 22
are fixedly connected with each other. The first housing element 21
has a cylindrical portion 23 and a bottom portion 24, which
connects with the rear end of the cylindrical portion 23 (on the
right side of FIG. 1). Thus, the first housing element 21 forms a
cylinder with a bottom at one end and is formed by die-casting an
aluminum alloy. The second housing element 22 forms a cylinder with
a bottom on the front side (the left side of FIG. 1) and is formed
by die-casting an aluminum alloy.
[0019] A cylindrical shaft support portion 24a extends from the
center of an inner wall surface of the bottom portion 24 in the
first housing element 21. A shaft support member 32, which has an
insertion hole 32a formed through the center thereof, is fixedly
connected to an opening end of the cylindrical portion 23 in the
first housing element 21. A rotary shaft 33 is accommodated in the
first housing element 21. The rear end (the right end) of the
rotary shaft 33 is rotatably supported by the shaft support portion
24a of the first housing element 21 through a bearing 34. The front
end (the left side) of the rotary shaft 33 is inserted through the
insertion hole 32a of the shaft support member 32, and is rotatably
supported by the shaft support member 32 through a bearing 35 in
the insertion hole 32a.
[0020] A motor chamber 12 is defined in the housing 11 and is
located on the rear side of FIG. 1 relative to the shaft support
member 32. In the motor chamber 12, a stator 36 is provided on the
inner circumferential surface of the cylindrical portion 23 of the
first housing element 21. In the motor chamber 12, a rotor 37 is
secured to the rotary shaft 33 so as to be located inside the
stator 36. The stator 36 and the rotor 37 constitute the electric
motor 13. The electric motor 13 integrally rotates the rotor 37 and
the rotary shaft 33 by electric power externally supplied to the
stator 36.
[0021] A fixed scroll member 41 is accommodated in the first
housing element 21 and is located near the opening end of the
cylindrical portion 23. The fixed scroll member 41 includes a
disc-shaped base plate 61, a cylindrical outer circumferential wall
62 and a spiral wall 63. The outer circumferential wall 62 extends
from the outer periphery of the base plate 61. The spiral wall 63
extends from the base plate 61 and is located inside the outer
circumferential wall 62. In the first housing element 21, a
disc-shaped center frame or a fixed wall 31 is arranged between the
fixed scroll member 41 and the shaft support member 32. A through
hole 31a is formed through the center of the center frame 31. An
annular contact portion 31b is located at the opening end near the
motor chamber 12 in the through hole 31a and protrudes inward.
[0022] The fixed scroll member 41 is connected to the outer
periphery of the center frame 31 by the distal end surface of the
outer circumferential wall 62. An annular shim 68 is interposed at
a joint between the fixed scroll member 41 and the center frame 31.
The base plate 61 of the fixed scroll member 41, the outer
circumferential wall 62 of the fixed scroll member 41 and the
center frame 31 surround to define a scroll chamber 15 in the
housing 11.
[0023] A crankshaft 43 is provided at the end surface of the rotary
shaft 33 near the center frame 31. The crankshaft 43 is mostly
arranged in the through hole 31a of the center frame 31. A bushing
44 is fixedly fitted around the crankshaft 43. A movable scroll
member 45 is accommodated in the scroll chamber 15 and is rotatably
supported on the bushing 44 through a bearing 46 so as to face the
fixed scroll member 41.
[0024] A balancer 44a is provided at the end of the bushing 44 near
the shaft support member 32. The balancer 44a relieves imbalance on
the rotary shaft 33 due to uneven arrangement of the movable scroll
member 45 around an axis L of the rotary shaft 33. The balancer 44a
is accommodated in a balancer chamber 14 outside the through hole
31a. The balancer chamber 14 is defined between the shaft support
member 32 and the center frame 31. The balancer chamber 14
communicates with the motor chamber 12 through a clearance of the
bearing 35. Accordingly, the balancer chamber 14 has the same
atmospheric pressure as that of the motor chamber 12.
[0025] The movable scroll member 45 includes a disc-shaped base
plate 65 and a spiral wall 66 that extends toward the fixed scroll
member 41. A boss 67 is provided near the center of a back surface
of the base plate 65 and protrudes therefrom. The boss 67 is fitted
around the bushing 44 through the bearing 46 in the through hole
31a of the center frame 31. An annular tip seal 77 is provided at
the distal end of the boss 67. In the through hole 31a, the boss 67
slidably contacts with the contact portion 31b of the center frame
31 by the tip seal 77. Accordingly, in the through hole 31a, the
tip seal 77 blocks communication between an inner space of the boss
67 communicating with the balancer chamber 14 and an outer space of
the boss 67.
[0026] The fixed scroll member 41 and the movable scroll member 45
engage with each other by the respective spiral walls 63, 66 in the
scroll chamber 15, while the distal end of the spiral wall 63 and
the distal end of the spiral wall 66 contact with the base plate 65
of the movable scroll member 45 and the base plate 61 of the fixed
scroll member 41, respectively. Accordingly, the base plate 61 and
the spiral wall 63 of the fixed scroll member 41 and the base plate
65 and the spiral wall 66 of the movable scroll member 45 define
compression chambers 47 in the scroll chamber 15.
[0027] A self-rotation blocking mechanism 48 is provided between
the base plate 65 of the movable scroll member 45 and the center
frame 31 facing the base plate 65. The self-rotation blocking
mechanism 48 includes a plurality of cylindrical holes 48a and a
plurality of pins 48b (only one of them is shown in FIG. 1). The
cylindrical holes 48a are recessed in radially outer portions of
the back surface 65a of the base plate 65 in the movable scroll
member 45. The pins 48b are buried in an end surface 31c of the
center frame 31 and are loosely fitted therein.
[0028] In the scroll chamber 15, a suction chamber 51 is defined
between the outer circumferential wall 62 of the fixed scroll
member 41 and the outermost circumferential portion of the spiral
wall 66 of the movable scroll member 45. A suction passage 39 is
formed in radially outer portions of the shaft support member 32,
the shim 68 and the center frame 31 for interconnecting the suction
chamber 51 and the motor chamber 12.
[0029] A suction port 50 is formed in the cylindrical portion 23 of
the first housing element 21 and is located to correspond with the
motor chamber 12. The suction port 50 connects with an external
conduit, which further connects with an evaporator (not shown) of
an external refrigerant circuit. The suction port 50 communicates
with the motor chamber 12. Accordingly, relatively low pressure
refrigerant gas from the external refrigerant circuit is introduced
into the suction chamber 51 through the suction port 50, the motor
chamber 12 and the suction passage 39.
[0030] In the housing 11, a discharge chamber 52 is defined between
the second housing element 22 and the fixed scroll member 41. A
discharge port 53 for communicating with the discharge chamber 52
is formed in the second housing element 22. The discharge port 53
connects with an external conduit, which further connects with a
gas cooler (not shown) of the external refrigerant circuit.
Accordingly, relatively high pressure refrigerant gas in the
discharge chamber 52 is delivered to the external refrigerant
circuit through the discharge port 53.
[0031] A discharge hole 41a is formed through the center of the
base plate 61 of the fixed scroll member 41. The compression
chamber 47 near the center communicates with the discharge chamber
52 through the discharge hole 41a. In the discharge chamber 52, a
discharge valve 55 constituted of a reed valve is arranged on the
base plate 61 of the fixed scroll member 41 for opening and closing
the discharge hole 41a. The opening degree of the discharge valve
55 is regulated by a retainer 56, which is fixedly arranged on the
base plate 61 of the fixed scroll member 41.
[0032] As the rotary shaft 33 is rotated by the electric motor 13,
the movable scroll member 45 orbits around the axis (the axis L of
the rotary shaft 33) of the fixed scroll member 41 through the
crankshaft 43. At the moment, the self-rotation of the movable
scroll member 45 is blocked by the self-rotation blocking mechanism
48, so that only the orbital movement of the movable scroll member
45 is permitted. Due to the orbital movement of the movable scroll
member 45, the compression chambers 47 reduce in volume as the
compression chambers 47 move from the radially outer side of the
spiral walls 63, 66 of the respective scroll members 41, 45 toward
the center of the spiral walls 63, 66. Thus, relatively low
pressure refrigerant gas introduced from the suction chamber 51 to
the compression chambers 47 is compressed. The compressed
refrigerant gas is discharged to the discharge chamber 52 through
the discharge hole 41a by pushing away the discharge valve 55.
[0033] The operation for adjusting back pressure of the movable
scroll member 45 will now be described.
[0034] As shown in FIG. 1, in the scroll chamber 15, a back
pressure chamber 16 is located on the side of the back surface 65a
of the base plate 65 of the movable scroll member 45. The base
plate 65 and the boss 67 of the movable scroll member 45 and the
center frame 31 surround to define the back pressure chamber 16.
Communication between the back pressure chamber 16 and the balancer
chamber 14 is blocked by the tip seal 77, which is interposed
between the boss 67 of the movable scroll member 45 and the contact
portion 31b of the center frame 31.
[0035] As shown in FIGS. 2 and 3A, in the back surface 65a of the
base plate 65 of the movable scroll member 45, an annular groove
65b for accommodating a seal is recessed in radially outer portion
relative to the cylindrical recesses 48a so as to surround the
cylindrical recesses 48a. An annular seal member 75 constituted of
a tip seal is fitted in the groove 65b. The back surface 65a of the
movable scroll member 45 slidably and elastically contacts with an
end surface 31c of the center frame 31 by the seal member 75.
Namely, the seal member 75 is interposed at a clearance CL between
the back surface 65a of the movable scroll member 45 and the end
surface 31c of the center frame 31. Communication between the back
pressure chamber 16 and the suction chamber 51 through the entire
clearance CL is blocked by the seal member 75.
[0036] Incidentally, a maximum distance of the clearance CL between
the movable scroll member 45 and the center frame 31, that is, a
thrust clearance between the movable scroll member 45 and the
center frame 31, is adjusted in an appropriate distance in such a
manner that a shim 68 having an appropriate thickness is selected
from a plurality of shims 68 having different thicknesses and is
assembled to the clearance CL when the electric compressor is
manufactured.
[0037] As shown in FIGS. 1 and 2, an introducing passage 76 is
formed in the base plate 65 of the movable scroll member 45 so as
to extend through the base plate 65 in thickness. Two introducing
passages 76 are provided. The back pressure chamber 16 and a
volume-reducing (compressing) compression chamber 47A, which is a
relatively high pressure region, are interconnected through one
introducing passage 76. The back pressure chamber 16 and a
volume-reducing compression chamber 47B, which is different from
the compression chamber 47A, are interconnected through the other
introducing passage 76. The introducing passages 76 are
symmetrically located in the base plate 65 from each other with an
angle of 180 degrees with respect to the axis of the crankshaft 43,
and respectively open to the corresponding compression chambers
47A, 47B.
[0038] A fixed throttle 76a is arranged in each of the introducing
passages 76. In the movable scroll member 45, the back surface 65a
of the base plate 65 forms two accommodating recesses 65c, with
which the opening of each introducing passage 76 on the side of the
back pressure chamber 16 communicates. A check valve 78 constituted
of a reed valve is accommodated in each of the accommodating
recesses 65c. The check valves 78 each permit refrigerant gas
supplied from the compression chambers 47A, 47B to the back
pressure chamber 16, and block the refrigerant gas returned from
the back pressure chamber 16 to the compression chambers 47A,
47B.
[0039] As shown in FIGS. 2 and 3A, a portion 75a for lowering
sealing performance (hereinafter, a seal lowering portion 75a)
relative to the other portion is provided for the seal member 75.
The seal lowering portion 75a is formed by splitting a portion of
the annular seal member. The back pressure chamber 16 and the
suction chamber 75, which is a relatively low pressure region, are
interconnected through the seal lowering portion 75a of the seal
member 75 in the clearance CL between the movable scroll member 45
and the center frame 31. Incidentally, in FIG. 2, dimensions of the
seal lowering portion 75a (a split portion in the seal member 75)
are exaggeratedly illustrated for easier understanding. Actually,
the seal lowering portion 75a is formed by an extremely narrow
clearance.
[0040] Incidentally, according to the present invention, a
relatively high pressure region means a region where relatively
high pressure refrigerant gas, which is compressed by the fixed
scroll member 41 and the movable scroll member 45, exists, while a
relatively low pressure region means a region where relatively low
pressure refrigerant gas, which is yet to be compressed by the
fixed scroll m ember 41 and the movable scroll member 45,
exists.
[0041] As shown in FIG. 1, as pressure in the volume-reducing
compression chambers 47A, 47B rises to exceed pressure in the back
pressure chamber 16 due to operation of the electric compressor,
the check valve 78 opens so that the relatively high pressure
refrigerant gas in the volume-reducing compression chambers 47A,
47B is introduced into the back pressure chamber 16 through the
respective introducing passages 76. Accordingly, the pressure in
the back pressure chamber 16 rises so that force (back pressure
force) F1 urging the movable scroll member 45 toward the fixed
scroll member 41 is applied based upon the pressure in the back
pressure chamber 16. On the other hand, force (thrust load) F2
based upon the pressure in the compression chambers 47 is applied
to the movable scroll member 45 toward a direction to leave the
fixed scroll member 41. Accordingly, a position of the movable
scroll member 45 relative to the center frame 31 is determined in
accordance with a balance between the force F1 and the force
F2.
[0042] As exaggeratedly shown in FIG. 3A, for example, as the force
F1 becomes greater than the force F2 (F1>F2) due to an increase
in the pressure in the back pressure chamber 16, the movable scroll
member 45 is displaced in a direction in which the back surface 65a
leaves the end surface 31c of the center frame 31. Accordingly,
sliding resistance between the back surface 65a of the movable
scroll member 45 and the end surface 31c of the center frame 31 is
reduced. In addition, when the force F1 becomes greater than the
force F2 (F1>F2), the movable scroll member 45 is pressed
against the fixed scroll member 41 so that sealing performance of
the compression chambers 47 improves.
[0043] As the movable scroll member 45 leaves the center frame 31
to increase the clearance CL between the movable scroll member 45
and the center frame 31, the passing cross-sectional area of
refrigerant gas increases at the seal lowering portion 75a of the
seal member 75. Accordingly, the amount of refrigerant gas
delivered from the back pressure chamber 16 to the suction chamber
51 increases so that the pressure in the back pressure chamber 16
falls to reduce the force F1.
[0044] As exaggeratedly shown in FIG. 3B, as the force F1 becomes
smaller than the force F2 (F1<F2) due to a reduction in the
pressure in the back pressure chamber 16, the movable scroll member
45 is displaced in a direction in which the back surface 65a
approaches the end surface 31c of the center frame 31. Accordingly,
sliding resistance between the movable scroll member 45 and the
fixed scroll member 41 is reduced.
[0045] As the movable scroll member 45 approaches the center frame
31 to reduce the clearance between the movable scroll member 45 and
the center frame 31, the passing cross-sectional area of
refrigerant gas reduces at the seal lowering portion 75a of the
seal member 75. Accordingly, the amount of refrigerant gas
delivered from the back pressure chamber 16 to the suction chamber
51 reduces so that the pressure in the back pressure chamber 16
rises to increase the force F1.
[0046] Thus, the movable scroll member 45 varies the clearance CL
(distance) between the back surface 65a and the end surface 31c of
the center frame 31 in such a manner that the force F1 based upon
the pressure in the back pressure chamber 16 becomes an appropriate
magnitude in a correspondence with the force F2 based upon the
pressure in the compression chambers 47. The passing
cross-sectional area of the seal lowering portion 75a is thereby
autonomously adjusted. Incidentally, in the preferred embodiment,
in order to enhance compression efficiency by improving sealing
performance of the compression chambers 47, the adjustment of the
pressure in the back pressure chamber 16 is predetermined in such a
manner that a state, where the force F1 applied to the movable
scroll member 45 slightly exceeds the force F2, is maintained for a
relatively long time.
[0047] According to the preferred embodiment, the following
advantageous effects are obtained.
[0048] (1) The movable scroll member 45 varies the clearance CL
between the movable scroll member 45 and the center frame 31 in
such a manner that the force F1 based upon the pressure in the back
pressure chamber 16 becomes an appropriate magnitude in a
correspondence with the force F2 based upon the pressure in the
compression chambers 47. Thus, the passing cross-sectional area of
the seal lowering portion 75a of the seal member 75 is autonomously
adjusted. In comparison to a prior art in which an entire clearance
CL between the movable scroll member 45 and the center frame 31 is
utilized as a passage for delivering refrigerant gas from the back
pressure chamber 16 to the suction chamber 51, the surfaces 31c and
65a respectively facing the movable scroll member 45 and the center
frame 31 need not be manufactured in high accuracy. Accordingly,
the pressure in the back pressure chamber 16 is appropriately
adjusted without an increase in cost for manufacturing the electric
compressor.
[0049] (2) The seal lowering portion 75a for lowering sealing
performance of the seal member 75 is formed by splitting a portion
of the annular seal member 75. Accordingly, the seal lowering
portion 75a is easily formed in the seal member 75.
[0050] (3) The shim 68 is interposed at a joint between the fixed
scroll member 41 fixed to the housing 11 and the center frame 31
also fixed to the housing 11 for adjusting a thrust clearance
between the movable scroll member 45 and the center frame 31. For
example, in comparison to the shim 68 interposed at a sliding
portion between the movable scroll member 45 and the center frame
31, the leakage of refrigerant gas at a portion where the shim 68
is interposed is prevented in the preferred embodiment. This leads
to improving compression efficiency of the electric compressor.
[0051] (4) The shaft support member 32, by which the rotary shaft
33 is supported through the bearing 35, is independently provided
from the center frame 31, on which the movable scroll member 45
slides. The balancer chamber 14 is defined between the shaft
support member 32 and the center frame 31, and the balancer 44a is
accommodated in the balancer chamber 14. For example, in comparison
to a structure in which the shaft support member 32 is integrated
with the center frame 31 as one component and the balancer 44a is
accommodated in the back pressure chamber 16 (This embodiment is
not a departure from the present invention.), sealing of the back
pressure chamber 16 becomes easy.
[0052] In other words, in a state of a comparative example, the
rotary shaft 33 is partially located in the back pressure chamber
16, so that the back pressure chamber 16 need be sealed by a lip
seal. The lip seal, in view of its characteristic, tightly fastens
the rotary shaft 33 for performing desirable sealing performance.
As a result, power loss of the rotary shaft 33 increases, and
appropriate seal of the back pressure chamber 16 and a reduction in
power loss are not performed at the same time.
[0053] Incidentally, in the above comparative example, as disclosed
in the Unexamined Japanese Patent Publication No. 2000-249086, a
pocket for back pressure is recessed in the back surface 65a of the
movable scroll member 45, and the back pressure chamber is formed
by covering the pocket for applying back pressure with the center
frame 31. Thus, the rotary shaft 33 need not be sealed by the lip
seal. However, in this state, since the suction pressure is
partially applied to the back surface of the movable scroll member
45 other than the pressure in the back pressure chamber, it becomes
complicated to appropriately set function for adjusting back
pressure. Additionally, the pocket for applying back pressure need
be recessed in the movable scroll member 45, so that cost for
manufacturing increases.
[0054] The relatively high pressure region includes two
volume-reducing compression chambers 47A, 47B. Two introducing
passages 76 are provided. One compression chamber 47A and the back
pressure chamber 16 are interconnected through one introducing
passage 76, while the other compression chamber 47B and the back
pressure chamber 16 are interconnected through the other
introducing passage 76. Thus, relatively high pressure refrigerant
gas is supplied from two compression chambers 47A, 47B to the back
pressure chamber 16, so that the inclination of the movable scroll
member 45 due to a reduction in pressure in the compression
chambers 47A, 47B by supplying the relatively high pressure
refrigerant gas is prevented.
[0055] Namely, for example, when one compression chamber 47A only
supplies relatively high pressure gas to the back pressure chamber
16 (this embodiment is not a departure from the present invention),
pressure in the compression chamber 47A is reduced by supplying the
relatively high pressure refrigerant gas to the back pressure
chamber 16, while pressure in the other compression chamber 47B,
which is located on a side opposite to the compression chamber 47A
relative to the axis (the axis of the crankshaft 43) of the movable
scroll member 45, is not reduced. Accordingly, force applied to the
movable scroll member 45 based upon pressure in the compression
chambers 47A, 47B becomes imbalance on each side relative to the
axis, so that the movable scroll member 45 tends to incline
relative to the axis of the movable scroll member 45.
[0056] (6) Carbon dioxide is employed as refrigerant for the
refrigeration cycle. As described in the prior art, when carbon
dioxide refrigerant is employed, passing cross-sectional area of a
refrigerant gas passage between the back pressure chamber 16 and
the suction chamber 51 need be much narrower at the maximum than
that when fluorocarbon refrigerant is employed. Such a setting is
easily handled by partially lowering sealing performance of the
seal member 75 with low cost.
[0057] The present invention is not limited to the embodiment
described above but may be modified into the following alternative
embodiments.
[0058] In alternative embodiments to the above preferred
embodiment, the balancer chamber 14 is defined as a relatively low
pressure region, while the tip seal 77 for separating the balancer
chamber 14 from the back pressure chamber 16 is defined as a seal
member. As shown in FIG. 4, the tip seal 77 is partially split to
form a seal lowering portion 77a for lowering sealing performance,
and the back pressure chamber 16 and the balancer chamber 14 are
interconnected through the seal lowering portion 77a.
[0059] In this state, as the operation being described with
reference to FIGS. 1 and 4, for example, as the force F1 becomes
greater than the force F2 (F1>F2) due to a rise in the pressure
in the back pressure chamber 16, the movable scroll member 45 is
displaced in a direction in which the distal end surface of the
boss 67 leaves the contact portion 31b of the center frame 31.
Accordingly, a clearance between the distal end surface of the boss
67 and the contact portion 31b of the center frame 31 increases, so
that the passing cross-sectional area for refrigerant gas increases
at the seal lowering portion 77a of the tip seal 77. The amount of
refrigerant gas delivered from the back pressure chamber 16 to the
balancer chamber 14 increases, and the pressure in the back
pressure chamber 16 falls to reduce the force F1.
[0060] As the force F1 becomes smaller than the force F2 (F1<F2)
due to a reduction in the pressure in the back pressure chamber 16,
the movable scroll member 45 is displaced in a direction in which
the distal end of the boss 67 approaches the contact portion 31b of
the center frame 31. Accordingly, a clearance between the distal
end surface of the boss 67 and the contact portion 31b of the
center frame 31 reduces, so that the passing cross-sectional area
for refrigerant gas reduces at the seal lowering portion 77a of the
tip seal 77. The amount of refrigerant gas delivered from the back
pressure chamber 16 to the balancer chamber 14 reduces, and the
pressure in the back pressure chamber 16 rises to increase the
force F1.
[0061] According to another embodiment, the same advantageous
effects, such as appropriate adjustment of pressure in the back
pressure chamber 16 with a relatively low-cost structure, are
obtained.
[0062] As shown in FIG. 5, in addition to the structure described
in the preferred embodiment, the back pressure chamber 16 and a
relatively low pressure region (the balancer chamber 14) are
interconnected not through the seal lowering portion 75a but
through another passage 81. A differential pressure regulating
valve 82 is arranged in the passage 81 for opening when
differential pressure between the back pressure chamber 16 and the
balancer chamber 14 is equal to or greater than a predetermined
value. Incidentally, the differential pressure regulating valve 82
includes a spherical valve body 82a, a coil spring 82b and a spring
seat 82c. The pressure in the back pressure chamber 16 and the
pressure in the balancer chamber 14 are respectively applied to the
front side and the rear side of the valve body 82a. The coil spring
82b urges the valve body 82a in a direction to close the valve.
[0063] As described in the preferred embodiment, the passing
cross-sectional area of the seal lowering portion 75a is adjusted
in response to a balance between the force F1 based upon the
pressure in the back pressure chamber 16 and the force F2 based
upon the pressure in the compression chambers 47. Namely, in the
embodiment of FIG. 5, the pressure in the back pressure chamber 16
is adjusted by utilizing two valves (the seal lowering portion 75a
and the differential pressure regulating valve 82) each having
different characteristic. Accordingly, a region where only one of
the valves 75a and 82 cannot appropriately adjust pressure may be
mutually covered by combination with the other of the valves 82 and
75a. Thus, the pressure in the back pressure chamber 16 is further
appropriately adjusted.
[0064] In the preferred embodiment, one portion of the annular seal
member 75 is split to form the seal lowering portion 75a. In
alternative embodiments, a plurality of portions of a seal member,
such as two, three, four, five or six portions, is split to form
portion for lowering sealing performance at plural portions of the
seal member.
[0065] In the preferred embodiment, the seal lowering portion 75a
is formed by partially splitting the annular seal member 75. In
alternative embodiments, the annular shape of the seal member is
maintained, while a groove is partially formed in the seal member.
Thus, a seal lowering portion for lowering sealing performance is
formed.
[0066] In the preferred embodiment, two volume-reducing compression
chambers 47A, 47B independently communicate with the back pressure
chamber 16 through the respective introducing passages 76. In
alternative embodiments, two introducing passages 76, which
respectively extend from two compression chambers 47A, 47B, are
integrated on the way and the integrated one introducing passage
communicates with the back pressure chamber 16. Thus, only one
portion of the movable scroll member 45 (the base plate 65) is
recessed to form the accommodating recess 65c, and the only one
check valve 78 is required. Accordingly, cost for manufacturing the
electric compressor is reduced.
[0067] In the preferred embodiment, relatively high pressure
refrigerant gas is introduced from the volume-reducing compression
chambers 47A, 47B to the back pressure chamber 16. In alternative
embodiments, the compression chamber 47 near the center (the
compression chamber 47 completes compression) or the discharge
chamber 52 is defined as a relatively high pressure region, while
the upstream portion of the introducing passage 76 communicates
with the relatively high pressure region, so that the high pressure
refrigerant gas, which is higher in pressure than the refrigerant
gas in the volume-reducing compression chambers 47A, 47B, is
introduced to the back pressure chamber 16.
[0068] In the preferred embodiment, a scroll compressor is embodied
as the electric compressor. The scroll compressor is not limited to
the electric compressor. In alternative embodiments, a scroll
compressor driven by an engine of a vehicle, a hybrid type scroll
compressor having an electric motor and an engine as drive sources,
may be employed.
[0069] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive, and the invention
is not to be limited to the details given herein but may be
modified within the scope of the appended claims.
* * * * *