U.S. patent application number 10/676664 was filed with the patent office on 2004-07-01 for variable displacement swash plate type compressor.
Invention is credited to Ban, Takahisa, Kayukawa, Hiroaki, Koide, Tatsuya, Mizutani, Hideki, Murase, Masakazu.
Application Number | 20040123731 10/676664 |
Document ID | / |
Family ID | 31987213 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040123731 |
Kind Code |
A1 |
Murase, Masakazu ; et
al. |
July 1, 2004 |
Variable displacement swash plate type compressor
Abstract
A variable displacement swash plate type compressor includes a
bearing, a thrust bearing, a lug plate and urging means. The urging
means is placed between the bearing and the lug plate and has
urging force for reducing thrust force applied to the thrust
bearing. The bearing receives radial force and thrust force.
Inventors: |
Murase, Masakazu;
(Kariya-shi, JP) ; Kayukawa, Hiroaki; (Kariya-shi,
JP) ; Mizutani, Hideki; (Kariya-shi, JP) ;
Koide, Tatsuya; (Kariya-shi, JP) ; Ban, Takahisa;
(Kariya-shi, JP) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Family ID: |
31987213 |
Appl. No.: |
10/676664 |
Filed: |
October 1, 2003 |
Current U.S.
Class: |
92/70 |
Current CPC
Class: |
F04B 27/1063
20130101 |
Class at
Publication: |
092/070 |
International
Class: |
F01B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2002 |
JP |
P2002-292424 |
Claims
What is claimed is:
1. A variable displacement swash plate type compressor used in
connection with an external drive source comprising: a housing in
which a cylinder bore, a crank chamber, a suction chamber and a
discharge chamber are defined; a first bearing accommodated on a
front side of the housing, the first bearing receiving radial force
and thrust force; a drive shaft supported by the first bearing in
the housing rotatably; a lug plate fixed to the drive shaft in the
crank chamber; a swash plate supported by the drive shaft in the
crank chamber rotatably; a single-head piston accommodated in the
cylinder bore reciprocably and connected to the swash plate so as
to reciprocate in accordance with the rotation of the swash plate;
a control mechanism communicating with the crank chamber, the
suction chamber and the discharge chamber for controlling pressure
in the crank chamber; and urging means placed between the first
bearing and the lug plate having urging force for reducing thrust
force applied to the first thrust bearing.
2. The variable displacement swash plate type compressor according
to claim 1, wherein the drive shaft is urged by a force based on
the pressure in the crank chamber, the urging force being larger
than a maximum value of the force based on the pressure in the
crank chamber.
3. The variable displacement swash plate type compressor according
to claim 1, wherein the first bearing is a tapered roller
bearing.
4. The variable displacement swash plate type compressor according
to claim 1, wherein the first bearing has a race that is integrally
rotated with the drive shaft, the urging means being a coned disc
spring that is placed between the race and the lug plate.
5. The variable displacement swash plate type compressor according
to claim 4, wherein the race is an inner race, the first bearing
further having an outer race and a plurality of rollers, the outer
race being press-fitted into the housing, the rollers being
interposed between the inner race and the outer race.
6. The variable displacement swash plate type compressor according
to claim 1, wherein the first bearing has a radial bearing and a
second thrust bearing.
7. The variable displacement swash plate type compressor according
to claim 6, wherein rolling diameter of the radial bearing is equal
to that of the second thrust bearing.
8. The variable displacement swash plate type compressor according
to claim 1, wherein the drive shaft is continuously driven while
the external drive source drives.
9. The variable displacement swash plate type compressor according
to claim 1, wherein the refrigerant gas is carbon dioxide.
10. A variable displacement swash plate type compressor used in
connection with an external drive source comprising: a housing in
which a cylinder bore, a crank chamber, a suction chamber and a
discharge chamber are defined, the housing having a front side and
a rear side; a first bearing accommodated on the front side of the
housing, the first bearing receiving radial force and thrust force;
a second bearing accommodated on the rear side of the housing; a
drive shaft supported by the first bearing and the second bearing
in the housing rotatably, the drive shaft having a front end which
protrudes from the housing and being driven by the external drive
source; a lug plate fixed to the drive shaft in the crank chamber
so as to integrally rotate with the drive shaft; a first thrust
bearing placed between the front side of the housing and the lug
plate in the crank chamber; a swash plate supported by the drive
shaft in the crank chamber rotatably; a hinge mechanism interposed
between the lug plate and the swash plate, the hinge mechanism
through which the swash plate is rotated synchronously with the
drive shaft and inclines relative to the drive shaft; a single-head
piston accommodated in the cylinder bore reciprocably having a rear
side, on which a compression chamber is defined in the cylinder
bore, the piston being connected to the swash plate so as to
reciprocate in accordance with the rotation of the swash plate; a
control mechanism communicating with the crank chamber, the suction
chamber and the discharge chamber for controlling pressure in the
crank chamber, the control mechanism by which an amount of
refrigerant gas discharged from the compression chamber to the
discharge chamber is varied in accordance with the reciprocation of
the piston based on an inclination angle of the swash plate; and
urging means placed between the first bearing and the lug plate
having urging force for reducing thrust force applied to the first
thrust bearing.
11. The variable displacement swash plate type compressor according
to claim 10, wherein the drive shaft is urged from the rear side to
the front side by a force based on the pressure in the crank
chamber, the urging force being larger than a maximum value of the
force based on the pressure in the crank chamber.
12. The variable displacement swash plate type compressor according
to claim 10, wherein the first bearing is a tapered roller
bearing.
13. The variable displacement swash plate type compressor according
to claim 10, wherein the first bearing has a race that is
integrally rotated with the drive shaft, the urging means being a
coned disc spring that is placed between the race and the lug
plate.
14. The variable displacement swash plate type compressor according
to claim 13, wherein the race is an inner race, the first bearing
further having an outer race and a plurality of rollers, the outer
race being press-fitted into the housing, the rollers being
interposed between the inner race and the outer race.
15. The variable displacement swash plate type compressor according
to claim 10, wherein the first bearing has a radial bearing and a
second thrust bearing.
16. The variable displacement swash plate type compressor according
to claim 15, wherein rolling diameter of the radial bearing is
equal to that of the second thrust bearing.
17. The variable displacement swash plate type compressor according
to claim 15, wherein rolling diameter of the second thrust bearing
is smaller than that of the first thrust bearing.
18. The variable displacement swash plate type compressor according
to claim 1, wherein the drive shaft is continuously driven while
the external drive source drives.
19. The variable displacement swash plate type compressor according
to claim 1, wherein the refrigerant gas is carbon dioxide.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a variable displacement
swash plate type compressor that is applied to a vehicle air
conditioning system.
[0002] A compressor is installed in a refrigerant circuit for use
in a vehicle air conditioning system. The compressor compresses
refrigerant gas therein. In a prior art of Japanese Unexamined
Patent Publication No. 2002-13474, more specifically in FIG. 8
thereof, a typical variable displacement swash plate type
compressor is disclosed for use in a vehicle air conditioning
system. A housing of the compressor includes a front housing, a
cylinder block and a rear housing. The rear end of the front
housing is joined to the front end of the cylinder block. The rear
end of the cylinder block is joined to front end of the rear
housing through a valve mechanism that includes a suction valve
plate, a valve hole plate, a discharge valve plate and a retainer
plate. A plurality of cylinder bores extends through the cylinder
block so as to be parallel with each other. The front housing and
the cylinder block define a crank chamber therebetween. A suction
chamber and a discharge chamber are defined in the rear
housing.
[0003] A single-head piton is accommodated in each cylinder bore
for reciprocation. A compression chamber is defined in the
corresponding cylinder bore between the corresponding piston and
the valve mechanism. A first shaft hole extends through the front
housing. A first bearing is installed in the first shaft hole. A
second shaft hole extends through the cylinder block. A second
bearing is installed in the second shaft hole. That is, the first
bearing is located frontward than the second bearing. A drive shaft
is supported by the first and second bearings for rotation. The
front end of the drive shaft protrudes from the front housing and
is connected to an external drive source such as a vehicle engine
so as to be driven. A support spring is interposed between the rear
end of the drive shaft and the valve mechanism through a third
bearing in the second shaft hole. The rear end of the drive shaft
is in contact with the front end of the third bearing. The rear end
of the third bearing is in contact with the front end of the
support spring. The rear end of the support spring is in contact
with the front end of the valve mechanism. The support spring urges
the drive shaft frontward.
[0004] A lug plate is fixed to the drive shaft in the crank chamber
so as to integrally rotate with the drive shaft. A thrust bearing
is interposed between a front wall of the front housing and the lug
plate din the crank chamber. A swash plate is supported by the
drive shaft in the crank chamber for rotation. A hinge mechanism is
interposed between the lug plate and the swash plate. Thereby, the
swash plate is synchronously rotated with the drive shaft and is
inclinable with respect to a rotary axis of the drive shaft. Also,
the pistons engage with the periphery of the swash plate. Thus, the
piston is reciprocated in the corresponding cylinder bore in
accordance with the rotation of the swash plate. A control
mechanism is installed in the rear housing and communicates with
the crank chamber, the suction chamber and the discharge chamber.
The control mechanism controls the pressure in the crank
chamber.
[0005] In the compressor, while the drive shaft is driven, the
swash plate oscillates in accordance with the inclination angle of
the swash plate and thus the piston is reciprocated in the
corresponding cylinder bore. Therefore, refrigerant gas in the
suction chamber is drawn into the compression chamber, and the
refrigerant gas is compressed therein, and then the compressed
refrigerant gas in the compression chamber is discharged into the
discharge chamber. During the above process of the compressor, if
the control mechanism controls the pressure in the crank chamber,
since the inclination angle of the swash plate is varied, an amount
of the refrigerant gas discharged from the compression chamber to
the discharge chamber is also varied. That is, as the pressure in
the crank chamber is raised, the inclination angle of the swash
plate becomes small and the discharge amount of the refrigerant gas
is reduced. In contrast, as the pressure in the crank chamber is
lowered, the inclination angle of the swash plate becomes large and
the discharge amount of the refrigerant gas is increased.
[0006] On the other hand, during the above process of the
compressor, the first bearing and the second bearing receive radial
force that is applied to the drive shaft respectively in the front
housing and the cylinder block. The thrust bearing receives
compressive reaction force of the refrigerant gas through the
piston, the shoes, the swash plate and the lug plate in the front
housing. In addition, in the compressor, the crank chamber and the
second shaft hole are communicated via the second bearing, and the
support spring is interposed between the rear end of the drive
shaft and the valve mechanism. Therefore, the thrust bearing
receives the pressure in the crank chamber and urging force of the
support spring, which are applied to the drive shaft and the lug
plate.
[0007] In the above prior art, however, since only the thrust
bearing that is placed between the front housing and the lug plate
in the crank chamber receives all of the compressive reaction
force, the pressure in the crank chamber and the urging force of
the support spring and rolling diameter of the thrust bearing is
larger than that of the first bearing and the second bearing, power
loss of the thrust bearing is relatively large.
[0008] Meanwhile, in a compressor that is disclosed in the above
publication, a cylindrical regulating member is fitted around a
rear end of a drive shaft so as to have a slight clearance between
the cylindrical regulating member and a valve mechanism without the
support spring in the shaft hole of the cylinder block between the
rear end of the drive shaft and the valve mechanism. In the
disclosed compressor, a thrust bearing does not require receiving
the urging force of the support spring. Therefore, power loss is
reduced.
[0009] Even in the compressor, however, the thrust bearing still
receives both of the compressive reaction force and the pressure in
the crank chamber. Therefore, the power loss is not sufficiently
reduced. In particular, in a state that the pressure in the crank
chamber is relatively high and displacement of the compressor is
relatively small, although the compressive reaction force is not so
large, since the drive shaft is urged frontward by force caused due
to the high pressure in the crank chamber, the power loss in the
state is not ignored.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a variable displacement
swash plate type compressor whose power loss is reduced.
[0011] The present invention has the following features. A variable
displacement swash plate type compressor is used in connection with
an external drive source. The compressor includes a housing, a
first bearing, a drive shaft, a lug plate, a swash plate, a
single-head piston, a control mechanism and urging means. In the
housing, a cylinder bore, a crank chamber, a suction chamber and a
discharge chamber are defined. The first bearing is accommodated on
a front side of the housing. The first bearing receives radial
force and thrust force. The drive shaft is supported by the first
bearing in the housing rotatably. The lug plate is fixed to the
drive shaft in the crank chamber. The swash plate is supported by
the drive shaft in the crank chamber rotatably. The single-head
piston is accommodated in the cylinder bore reciprocably and is
connected to the swash plate so as to reciprocate in accordance
with the rotation of the swash plate. The control mechanism
communicates with the crank chamber, the suction chamber and the
discharge chamber for controlling pressure in the crank chamber.
The urging means is placed between the first bearing and the lug
plate and has urging force for reducing thrust force applied to the
first thrust bearing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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:
[0013] FIG. 1 is a cross sectional view illustrating a variable
displacement swash plate type compressor according to a first
preferred embodiment of the present invention;
[0014] FIG. 2 is a partially enlarged view of FIG. 1;
[0015] FIG. 3 is a partially enlarged view of FIG. 1; and
[0016] FIG. 4 is a partial cross sectional view illustrating a
variable displacement swash plate type compressor according to a
second preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] A variable displacement swash plate type compressor
according to a first preferred embodiment of the present invention
is applied to a vehicle air conditioning system. The compressor
will now be described with reference to FIGS. 1 through 3. In FIG.
1, a left side of the drawing is a front side and a right side
thereof is a rear side.
[0018] Referring to FIG. 1, the rear end of a cup-shaped front
housing 2 is joined to the front end of a cylinder block 1. The
rear end of the cylinder block 1 is joined to the front end of a
rear housing 7 through a valve mechanism that includes a suction
valve plate 3, a valve hole plate 4, a discharge valve plate 5 and
a retainer plate 6. The cylinder block 1, the front housing 2 and
the rear housing 7 form a compressor housing. In the cylinder block
1, a plurality of cylinder bores 1a, a shaft hole 1b, a muffler
chamber 1c and an inlet 1d are defined. In the front housing 2, a
shaft hole 2a is formed. The cylinder block 1 and the front housing
2 define a crank chamber 8 therein.
[0019] Still referring to FIG. 1, a drive shaft 12 extends through
the crank chamber 8 and is supported by a first bearing 10 at the
shaft hole 2a and by a second bearing 11 at the shaft hole 1b
rotatably. A shaft seal device 9 seals a clearance between the
drive shaft 12 and the front housing 2. In the first embodiment, a
tapered roller bearing is adopted as the first bearing 10. Also, a
radial bearing is adopted as the second bearing 11.
[0020] As shown in FIGS. 2 and 3, the first bearing 10 includes an
inner race 10a, an outer race 10b, a plurality of rollers 10c and a
cage, which is not shown in the drawings. The drive shaft 12 is
press-fitted inside the inner race 10a so as to integrally rotate
with the inner race 10a. The outer race 10b is press-fitted into
the front housing 2. The plurality of rollers 10c is interposed
between the inner race 10a and the outer race 10b. A rolling
contact surface of the inner race 10a is formed on a cylindrical
surface whose central axis is the same as a rotary axis of the
drive shaft 12. A rolling contact surface of the outer race 10b is
formed on a tapered surface whose central axis is the same as the
rotary axis of the drive shaft 12. The rolling contact surface of
the outer race 10b is formed in such a manner that diameter of the
rolling contact surface of the outer race 10b on the front side of
the first bearing 10 becomes smaller than that on the rear side of
the first bearing 10. Each of the rollers 10c is formed in such a
manner that diameter of each of the rollers 10c on the front side
of the first bearing 10 becomes smaller than that on the rear side
of the first bearing 10. That is, each of the rollers 10c has the
shape of a circular truncated cone.
[0021] Referring back to FIG. 1, a lug plate 14 is fixed to the
drive shaft 12 in the crank chamber 8 so as to integrally rotate
with the drive shaft 12. A thrust bearing 13 is placed between a
front wall of the front housing 2 and the lug plate 14 in the crank
chamber 8. The drive shaft 12 extends though a coned disc spring 20
which is placed between the inner race 10a and the lug plate 14.
The coned disc spring 20 is served as an urging means. Urging force
f0 of the coned disc spring 20 is applied to the lug plate 14
rearward.
[0022] Still referring to FIG. 1, a pair of arms 15 protrudes from
the rear surface of the lug plate 14 rearward, although only one of
the arms 15 is shown in FIG. 1. A cylindrical guide hole 15a is
formed through each arm 15. The drive shaft 12 extends through a
swash plate 16 where a through hole 16a is formed. An inclination
angle of the swash plate 16 is defined as an angle between a
perpendicular plane to the rotary axis of the drive shaft 12 and
the swash plate 16. A spring 17 is interposed between the swash
plate 16 and the lug plate 14 for reducing the inclination angle of
the swash plate 16. A return spring 26 is interposed between the
swash plate 16 and a circular clip 25. A bearing 27 is placed at
the rear end of the drive shaft 12 in the shaft hole 1b of the
cylinder block 1. A support spring 29 is interposed between the
bearing 27 and the suction valve plate 3. A regulating member may
be used in place of the bearing 27 and the support spring 29.
[0023] A pair of guide pins 16b protrudes from the front end of the
swash plate 16 respectively to the pair of arms 15, although only
one of the guide pins 16b is shown in FIG. 1. A spherical guide
portion 16c is formed on the distal end of each guide pin 16b so as
to pivotally slide along the corresponding guide hole 15a. The
guide holes 15a of the lug plate 15 and the guide portions 16c of
the swash plate 16 constitute a hinge mechanism, through which the
swash plate 16 is rotated synchronously with the drive shaft 12 and
inclines relative to the drive shaft 12. A plurality of hollow
single-head pistons 19 is engaged with the periphery of the swash
plate 16. Each piston 19 has a pair of shoes 18, which is placed
respectively at the front and rear sides of the swash plate 16.
Each piston 19 is also accommodated in each cylinder bore 1a. A
compression chamber 30 is defined on the rear side of the piston 19
in the corresponding cylinder bore 1a.
[0024] A pulley 22 is fixed to the front end of the drive shaft 12,
which protrudes from the front housing 2 frontward, by a bolt 23.
The pulley 22 is supported by a ball bearing 24 on the front
housing 2 rotatably. A belt is partially wound around the pulley 22
so as to connect with an engine EG, which is served as an external
drive source.
[0025] In the rear housing 7, a suction chamber 7a is defined. The
suction chamber 7a and the inlet 1d of the cylinder block 1 are
communicated via a suction passage, which is not shown in FIG. 1.
The suction chamber 7a and the cylinder bores 1a are communicated
respectively via suction ports 31, which are formed through the
retainer plate 6, the discharge valve plate 5 and the valve hole
plate 4. The inlet 1d is connected to an evaporator EV of a
refrigerant circuit by a piping. The evaporator EV is connected to
a condenser CO through an expansion valve V by a piping. Also, in
the rear housing 7, a discharge chamber 7b is defined around the
suction chamber 1a. The discharge chamber 7b and the muffler
chamber 1c of the cylinder block 1 are communicated via a discharge
passage 7d, which extends through the retainer plate 6, the
discharge valve plate 5, the valve hole plate 4 and the suction
valve plate 3. The muffler chamber 1c is connected to the condenser
CO of the refrigerant circuit by a piping. The discharge chamber 7b
is connected to the cylinder bores 1a respectively by discharge
ports 32, which extends through the valve hole plate 4 and the
suction valve plate 3. Further, a control mechanism 34, which
communicates with the crank chamber 8, the suction chamber 7a and
the discharge chamber 7b so as to control the pressure in the crank
chamber 8, is accommodated in the rear housing 7. The control
mechanism 34 is capable of adjusting the pressure in the crank
chamber 8, for example, by detecting the pressure in the suction
chamber 7a. Thereby, an amount of refrigerant gas discharged from
the compression chamber 30 to the discharge chamber 7b is varied in
accordance with reciprocation of the piston 19 based on an
inclination of the swash plate 16.
[0026] The above structured compressor compresses carbon dioxide
filled in the refrigerant circuit. Carbon dioxide is served as a
refrigerant gas. Specifically, while the engine EG drives, since
the pulley 22 is rotated through the belt, the drive shaft 12 is
continuously driven. Thereby, the swash plate 16 is oscillated and
the piston 19 is reciprocated in the corresponding cylinder bore
1a. That is, the piston 19 is reciprocated in accordance with the
rotation of the swash plate 16. Thus, refrigerant gas of the
evaporator EV in the refrigerant circuit is drawn into the suction
chamber 7a through the inlet 1d and the refrigerant gas in the
suction chamber 7a is drawn into the compression chamber 30. After
the refrigerant gas in the compression chamber 30 is compressed
therein, the compressed refrigerant gas is discharged into the
discharge chamber 7b. The refrigerant gas in the discharge chamber
7b is discharged into the condenser CO through the muffler chamber
1c.
[0027] During the compressive process of the compressor, the first
and second bearings 10 and 11 receive radial force which is applied
to the drive shaft 12 respectively in the front housing 2 and the
cylinder block 1. Also, compressive reaction force of the
refrigerant gas is transmitted to the piston 19, the shoes 18, the
swash plate 16 and the lug plate 14. Further, in the compressor the
crank chamber 8 communicates with the shaft hole 1b of the cylinder
block 1 through the second bearing 11 and the support spring 29 is
interposed between the rear end of the drive shaft 12 and the valve
mechanism. Therefore, the pressure in the crank chamber 8 is
applied to the drive shaft 12 and the lug plate 14. In addition,
urging force of the support spring 29 is applied to the drive shaft
12 and the lug plate 14. Note that the force applied to the drive
shaft 12 frontward in accordance with the pressure in the crank
chamber 8 is f1. Also, note that the urging force of the support
spring 29 is f2, and that the compressive reaction force is f3. In
this case, the urging force f0 of the coned disc spring 20 is set
so as to be larger than resultant force of the force f1 which is
the maximum value and the urging force f2 of the support spring
29.
[0028] In such a compressor, when a vehicle is stopped and the
engine EG is stopped, or when the vehicle is accelerated, or when a
vehicle air conditioning system is switched off in a state that the
engine EG drives, the control mechanism 34 raises the pressure in
the crank chamber 8. Thereby, the inclination angle of the swash
plate 16 becomes minimum. Thus, a volume of the compression chamber
30 becomes minimum and the amount of refrigerant gas discharged
from the compression chamber 30 becomes minimum.
[0029] In the above state of the compressor, the force f1 based on
the pressure in the crank chamber 8 becomes the maximum value. The
urging force f2 is a fixed value. The compressive reaction force f3
is an extremely small value. Meanwhile, when the engine EG and the
compressor is started, or when the vehicle is normally run, or when
the vehicle air conditioning system is switched on in a state that
the engine EG drives, as shown in FIG. 2, the drive shaft 12 is
urged frontward by resultant force of the force f1, the urging
force f2 and the extremely small compressive reaction force f3.
Therefore, the lug plate 14 is also urged frontward. In the
compressor, however, since the urging force f0 of the coned disc
spring 20 is set so as to be larger than resultant force of the
maximum force f1, which is the maximum value, and the urging force
f2 of the support spring 29, the drive shaft 12 and the lug plate
14 are urged rearward. For this reason, a slight clearance is
produced between the lug plate 14, that is, the thrust bearing 13,
and the thrust bearing 13 does not receive thrust force.
Consequently, rolling frictional force of the thrust bearing 13 is
not generated and power loss is reduced.
[0030] In this case, the thrust force which is applied to the coned
disc spring 20 is received by the first bearing 10 through the
inner race 10a. In other words, since the inner race 10a prevents
the coned disc spring 20 from sliding over the drive shaft 12,
power loss is reduced due to sliding frictional force. Thus, in
this state, only the first bearing 10 receives thrust force and
radial force. Therefore, operation of the compressor is not
interrupted. In addition, since the tapered roller bearing is
adopted as the first bearing 10, the number of parts is
reduced.
[0031] Thus, when the compressor is started in such a manner that
displacement of the compressor is minimum, reduction of the power
loss accomplished by the first bearing 10 and the thrust bearing 13
is described as follows. If frictional force generated on the first
bearing 10 is F1, coefficient of friction of the first bearing 10
is .mu.1 and thrust force which is applied to the first bearing 10
is N1, F1 gives the following equation:
F1=.mu.1.times.N1
[0032] If the pressure in the crank chamber 8 is P and the diameter
of the drive shaft 12 is D, the thrust force, which is applied to
the first bearing 10, gives the following equation:
N1=P.times..pi./4.times.D.sup.2
[0033] Meanwhile, if the rolling diameter of the first bearing 10
is R1, torque T1 which is generated on the first bearing gives the
following equation:
T1=F1.times.R1
[0034] From the above equations, the torque T1, which is generated
on the first bearing 10, gives the following equation:
T1=.mu.1.times.P.times..pi./4.times.D.sup.2.times.R1
[0035] If frictional force generated on the thrust bearing 13 is
F2, coefficient of friction of the first bearing 10 is .mu.2,
thrust force which is applied to the first bearing 10 is N2 and the
rolling diameter of the second bearing 12 is R2, T2, which is
generated on the thrust bearing 13, gives the following
equation:
T2=.mu.2.times.P.times..pi./4.times.D.sup.2.times.R2
[0036] Thus, gross torque T that are generated on the first bearing
10 and the thrust bearing 13 gives the following equation: 1 T = T1
+ T2 = P .times. / 4 .times. D 2 .times. ( 1 .times. R1 + 2 .times.
R2 )
[0037] In the first embodiment, as described above, when the
compressor is started in such a manner that displacement of the
compressor is minimum, the torque T2 is not generated on the thrust
bearing 13. Therefore, the gross torque T gives the following
equation: 2 T = T1 = 1 .times. P + / 4 .times. D 2 .times. R1
[0038] From the above equations, in comparison with a case that
torque is generated on both of the first bearing 10 and the thrust
bearing 13, in a case that torque is generated only on the first
bearing 10 whose rolling diameter is relatively small, it is found
that relatively small torque is generated on the drive shaft 12.
That is, in the compressor of the first embodiment, power loss is
reduced. Therefore, when the compressor is started, load that is
applied to the engine EG is reduced. In the compressor especially
where carbon dioxide is used as a refrigerant gas in view of
environmental problem, the above effect is remarkable.
[0039] On the other hand, in the compressor, if the control
mechanism 34 lowers the pressure in the crank chamber 8 in a state
that the engine EG drives, the inclination angle of the swash plate
16 becomes maximum. Thus, the volume of the compression chamber 30
becomes maximum and the amount of refrigerant gas discharged from
the compression chamber 30 becomes maximum.
[0040] In the above state of the compressor, the force f1 becomes a
minimum value. The urging force f2 is a fixed value. The
compressive reaction force f3 is maximum. Therefore, as shown in
FIG. 3, the drive shaft 12 is urged frontward by resultant force of
the force f1, the urging force f2 and the maximum compressive
reaction force f3. Therefore, the lug plate 14 is also urged
frontward. In this case, the urging force f0 of the coned disc
spring 20 is defeated because the compressive reaction force f3
becomes maximum. Thereby, the coned disc spring 20 is squeezed
between the inner race 10a of the first bearing 10 and the lug
plate 14. Thus, the drive shaft 12 and the lug plate 14 are urged
frontward.
[0041] At this time, while the thrust bearing 13 receives the lug
plate 14, the urging force f0 of the coned disc spring 20 urges the
lug plate 14 rearward. Therefore, thrust force which the thrust
bearing 13 receives is restrained. That is, in the above equation,
the torque T2, which is generated on the thrust bearing 13, is
reduced. Therefore, in the compressor of the first embodiment, even
in a state that an amount of refrigerant gas discharged from the
compressor is relatively large, power loss is reduced. Thereby,
while the compressor is driven, load that is applied to the engine
EG is reduced. Thus, in the compressor of the first embodiment,
power loss is reduced.
[0042] Further, in the compressor, the coned disc spring 20 is
placed within a relatively short distance between the inner race
10a of the first bearing 10 and the lug plate 14 and operates the
urging force f0 therein. Therefore, the length of the drive shaft
12 is shortened. Thereby, a relatively compact compressor is
materialized.
[0043] Further, even in a case that an electromagnetic clutch is
used without directly placing the pulley 22 around the drive shaft
12 of the compressor, while the engine EG is connected to the drive
shaft 12, similar effects to the above described effects are
obtained.
[0044] A variable displacement swash plate type compressor
according to a second preferred embodiment of the present invention
is also applied to a vehicle air conditioning system. In the
compressor of the second embodiment, as shown in FIG. 4, a radial
bearing 40 and a thrust bearing 50 whose rolling diameter is
substantially equal to that of the radial bearing 40 are placed in
place of the first bearing 10 of the first embodiment. The rolling
diameter of the thrust bearing 50 is smaller than that of the
thrust bearing 13. The radial bearing 40 is placed in the rear side
of the shaft seal device 9. The thrust bearing 50 is placed in the
front side of the coned disc spring 20. In the second embodiment,
identical reference numerals to the first embodiment are applied to
the same or corresponding members in the second embodiment and
overlapped description is omitted.
[0045] In the above structured compressor, the thrust bearing 50
receives thrust force that is generated on the coned disc spring
20. The radial bearing 40 receives radial force caused by drive of
the drive shaft 12.
[0046] If torque that is generated on the radial bearing 40 is T1
and torque that is generated on the thrust bearing 50 is T2, as
mentioned above gross torque T gives the following equation: 3 T =
T1 + T2 = P .times. / 4 .times. D 2 .times. R1 .times. ( 1 + 2
)
[0047] where both of rolling diameters of the radial bearing 40 and
the thrust bearing 50 are R1.
[0048] Thus, even in the compressor of the second embodiment, gross
torque T is restrained by shortening the rolling diameter of the
thrust bearing 50 than that of the thrust bearing 13. Therefore,
load that is applied to the drive shaft 12 is reduced. Thereby,
power loss is reduced. Similar effects of the first embodiment are
also obtained.
[0049] 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.
* * * * *