Cooling structure for compressor

A compressor having a compression mechanism within a housing for compressing a refrigerant gas according to the rotation of a rotary shaft operatively connected to an external power source. A pulley is mounted on the rotary shaft and located on one side of the housing for transmitting power from the external power source to the shaft. A fan sends air to the outer surface of the housing by rotating with the pulley. Heat transferring fins are provided on the housing adjacent to the fan.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to compressors, and more particularly, to 
compressors that have a cooling structure. 
2. Description of the Related Art 
Typically, compressors are mounted in vehicles to air-condition the 
passenger compartments. It is preferable to employ a compressor, the 
displacement of which is adjustable, to accurately control the temperature 
in the interior of the vehicle to maintain an environment comfortable to 
the passengers. A typical compressor has a swash plate, which is mounted 
tiltably on a rotary shaft. The inclination of the swash plate is 
controlled by the difference between the pressure in a crank chamber and 
the suction pressure. The rotation of the swash plate is converted to a 
reciprocal linear movement of pistons. 
Lubricating oil, which lubricates the inside of the compressor, is mixed 
with the refrigerant gas and flows together with it. The interior of the 
compressor is sealed by a rubber seal. To cope with deterioration of the 
lubricating oil and the seal, which is caused by heat produced in the 
compressor, various measures have been taken in the prior art. One of 
these measures is described in Japanese Unexamined Utility Model 
Publication 50-86312. Heat transferring fins are provided on the outer 
surface of the compressor of this publication. 
The 50-86312 publication describes a compressor that transmits the drive 
force of a vehicle's engine to a rotary shaft through an electromagnetic 
clutch. Longitudinally extending fins are provided on the outer periphery 
of the compressor housing. A fan, which sends ambient air to the fins, is 
mounted on a pulley. Since a solenoid, used for a clutch, is located 
between the pulley and the compressor housing, the fan is arranged around 
the periphery of the pulley. The outer diameter of the pulley is about the 
same as the outer diameter of the housing. Therefore, it is required that 
the fins project a long distance in the radial direction of the compressor 
to efficiently cool the fins with the fan. However, such structure 
enlarges the compressor thus using valuable engine compartment space. 
SUMMARY OF THE INVENTION 
It is an objective of the present invention to provide a compressor having 
an enhanced heat releasing capability without increasing its size. 
To achieve the above objective, a compressor has a compression mechanism 
within a housing for compression of refrigerant gas according to the 
rotation of a rotary shaft operatively connected to an external power 
source. The compressor includes a rotary member, a fan, and a heat 
transferring fin. The rotary member is mounted on the rotary shaft and 
located on one side of the housing for transmitting power from the 
external power source to the rotary shaft. The fan sends air to the outer 
surface of the housing by rotating with the rotary member. The heat 
transferring fin is provided on the housing and located adjacent to the 
fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first embodiment of a compressor according to the present invention will 
now be described with reference to FIGS. 1 to 5. 
As shown in FIG. 1, a front housing 2 is coupled to the front end of a 
cylinder block 1 and a rear housing 3 is coupled to the rear end of the 
block 1. The cylinder block 1, front housing 2, and rear housing 3 
constitute a compressor housing. A crank chamber 2.sub.-1 is defined 
inside the front housing 2 and the block 1. A rotary shaft 4 is rotatably 
supported in the front housing 2 and block 1 with its front end protruding 
externally from the crank chamber 2.sub.-1. A rubber lip seal 47 is 
located between the front section of the shaft 4 and the front housing 2. 
The lip seal 47 prevents the escape of pressure from the crank chamber 
2.sub.-1. 
A hollow boss 2.sub.-2 is formed integrally on the front housing 2. A 
rotating member, or pulley 5, is rotatably supported by an angular contact 
bearing 6 on the boss 2.sub.-2. The bearing 6 carries the load in both 
axial and radial directions. The pulley 5 is connected to an engine (not 
shown), serving as an external drive source, by a belt 7. In this 
structure, a clutch mechanism is not employed to connect the pulley 5 with 
the engine. The front end of the shaft 4 is coupled to the pulley 5 by a 
bolt 9. As shown in FIG. 2, a fan 5.sub.-1 is provided integrally with the 
pulley 5. The fan 5.sub.-1 is formed inside the periphery of the pulley 5 
and thus has an outer diameter smaller than the pulley 5. The outer 
diameter of the pulley 5 is approximately equal to the outer diameter of 
the front housing 2. The pulley 5 rotates in a direction indicated by 
arrow R, as shown in FIG. 2, and the fan 5.sub.-1 sends ambient air in a 
direction indicated by arrow S, as shown in FIG. 1. 
A drive plate 8 is secured to the shaft 4. A swash plate 13 is mounted on 
the shaft 4 and is supported in a manner such that it slides and tilts in 
the axial direction of the shaft 4. As shown in FIG. 4, the connection 
between the support arm 8.sub.-1 of the drive plate 8 and a pair of guide 
rods 15, 16 enables the tilting of the swash plate 13. The tilting of the 
swash plate 13 is guided by the support arm 8.sub.-1, the rods 15, 16 and 
the shaft 4. 
The block 1 has a retaining hole 19. The rear end of the shaft 4 is 
supported in the inner peripheral surface of the hole 19 by a bearing 17 
and a cup-shaped spool 18. The bearing 17 carries the load in both radial 
and axial directions. A suction passage 20 is defined in the center of the 
rear housing 3. The suction passage 20 communicates with the retaining 
hole 19. A positioning surface 21 is defined about the outlet of the 
suction passage 20. The distal end of the spool 18 abuts against the 
positioning surface 21. As the spool 18 moves away from the swash plate 
13, abutment of the distal end of the spool 18 against the positioning 
surface 21 restricts the movement of the spool 18 and disconnects the 
suction passage 20 from the retaining hole 19. 
As the swash plate 13 tilts toward the spool 18, the swash plate 13 abuts 
against a bushing 22 and pushes the bushing 22 and the bearing 17 toward 
the positioning surface 21. This moves the spool 18 against the urging 
force of a spring 23, arranged inside the retaining hole 19, until its 
distal end abuts against the positioning surface 21. 
As shown by the chain line of FIG. 1, the minimum inclined position of the 
swash plate 13 is almost but not exactly perpendicular to the shaft 4. The 
minimum inclined position of the swash plate 13 is obtained when the spool 
18 is moved to a closing position where the spool 18 disconnects the 
suction passage 20 from the retaining hole 19. The maximum inclined 
position of the swash plate 13 is restricted by the abutment of the swash 
plate 13 against a restricting projection 8.sub.-2 provided on the drive 
plate 8. The rotation of the swash plate 13 is converted to reciprocal 
linear movement of a single-headed piston 25, which is accommodated in 
each cylinder bore 1.sub.-1, through shoes 24. 
As shown in FIGS. 1 and 5, a suction chamber 3.sub.-1 and a discharge 
chamber 3.sub.-2 are defined inside the rear housing 3. Refrigerant gas in 
the suction chamber 3.sub.-1 is drawn into each cylinder bore 1.sub.-1 via 
suction ports 26 and suction valves 27 when the associated piston 25 moves 
away from the suction chamber 3.sub.-1. After the gas is compressed in the 
cylinder bore 1.sub.-1 when the piston 25 moves in a reversed direction, 
the gas flows through a discharge port 28 and a discharge valve 29 and is 
discharged into the discharge chamber 3.sub.-2. The suction chamber 
3.sub.-1 is connected to the retaining hole 19 through a passageway 31. 
When the spool 18 is moved to the closing position, the passageway 31 is 
disconnected from the suction passage 20. 
A thrust bearing 30 is located between the drive plate 8 and the front 
housing 2. The bearing 30 carries the reaction force, which is produced 
during compression of the gas inside the bores 1.sub.-1 and applied to the 
drive plate 8 by way of the pistons 25, shoes 24, swash plate 13, and 
guide pins 15, 16. 
A conduit 32 is provided in the shaft 4. The conduit 32 connects the crank 
chamber 2.sub.-1 with the interior of the spool 18. A pressure releasing 
hole 18.sub.-1 is provided at the distal end of the spool 18. The hole 
18.sub.-1 connects the interior of the spool 18 with the interior of the 
retaining hole 19. 
As shown in FIG. 1, the crank chamber 2.sub.-1 and the suction chamber 
3.sub.-1 are connected to each other by a pressurizing passage 33. An 
electromagnetic valve 34 is provided in the pressurizing passage 33 to 
open or close the passage 33. Activation of a solenoid 35 in the 
electromagnetic valve 34 results in a valve body 36 closing the valve hole 
34.sub.-1. Deactivation of the solenoid 35 results in the body 36 opening 
the hole 34.sub.-1. 
A muffler chamber 10 extends along the peripheral surface of the block 1 
and the front housing 2. The muffler chamber 10 is defined by a wall 
1.sub.-2, formed integrally with the block 1, and a wall 2.sub.-3, formed 
integrally with the front housing 2. A cylindrical oil separator 11 is 
arranged in the muffler chamber 10. The separator 11 is formed integrally 
with the block 1 and extends parallel to the axis of the shaft 4. The 
inlet 11.sub.-1 of the separator 11 is faced toward the wall 2.sub.-3 and 
opens in the muffler chamber 10. The outlet 11.sub.-2 of the separator 11 
opens in the surface of the wall 1.sub.-2 and constitutes an outgoing port 
of the muffler chamber 10. 
As shown in FIGS. 3 and 4, a gas circulation compartment 10.sub.-1 and an 
oil reserve compartment 10.sub.-2 are defined by partitions 1.sub.-3, 
2.sub.-4 inside the muffler chamber 10. The compartments 10.sub.-1, 
10.sub.-2 are connected to each other by oil passages 1.sub.-4, 2.sub.-6 
defined in the partition 2.sub.-4. The circulation compartment 10.sub.-1 
and the discharge chamber 3.sub.-2 are connected by a discharge passage 
12, as shown in FIGS. 1 and 3. As shown in FIG. 3, an outlet 12.sub.-1 of 
the discharge passage 12 is located between the partition 1.sub.-3 and the 
separator 11. The outlet 12.sub.-1 serves as a port where refrigerant gas 
enters into the muffler chamber 10. The reserve compartment 10.sub.-2 is 
connected with the crank chamber 2.sub.-1 through a restricted passage 
2.sub.-5. 
A plurality of plate-like fins 46 are formed integrally on the outer 
periphery of the front housing 2. The fins 46 extend from the front end of 
the front housing 2 to the front end of the block 1 along the axial 
direction of the shaft 4. As shown in FIGS. 2 and 4, the rear ends of some 
of the fins 46 are connected to the wall 2.sub.-3 of the muffler chamber 
10. 
The suction passage 20, which is used to introduce refrigerant gas into the 
suction chamber 3.sub.-1, and the outlet 11.sub.-2 are connected to each 
other by an external refrigerant circuit 14. The circuit 14 includes a 
condenser 37, an expansion valve 38, and an evaporator 39. The expansion 
valve 38 controls the flow rate of the refrigerant gas in accordance with 
the change in gas temperature at the outlet side of the evaporator 39. A 
temperature sensor 40 is provided in the vicinity of the evaporator 39. 
The sensor 40 detects the temperature of the evaporator 39 and transmits 
the detected value to a computer C. The computer C controls the solenoid 
35 of the electromagnetic valve 34 in accordance with the temperature data 
from the sensor 40. 
When an operation switch 41 of an air-conditioning system is in a state 
that it is turned on, the computer C commands the deactivation of the 
solenoid 35 to prevent formation of frost in the evaporator 39 as the 
temperature falls below a predetermined value. An engine speed sensor 42 
is also connected to the computer C. When the switch 41 is in a state that 
it is turned on, the computer C receives the detected value of the engine 
speed from the sensor 42. The computer C deactivates the solenoid 35 when 
the engine speed exceeds a predetermined value. 
The computer C also deactivates the solenoid 35 when the switch is turned 
off. Deactivation of the solenoid 35 opens the pressurizing passage 33 and 
communicates the discharge chamber 3.sub.-2 with the crank chamber 
2.sub.-1. This causes the highly pressurized refrigerant gas in the 
discharge chamber 3.sub.-2 to flow into the crank chamber 2.sub.-1 and 
raise the pressure in the crank chamber 2.sub.-1. The pressure increase in 
the crank chamber 2.sub.-1 reduces the inclination of the swash plate 13. 
When the distal end of the spool 18 abuts against the positioning surface 
21, the inclination of the swash plate 13 is minimum and the flow of 
refrigerant gas from the refrigerant circuit 14 to the suction chamber 
3.sub.-1 is blocked. 
Since the minimum inclined position of the swash plate 13 is not 
perpendicular to the shaft 4, discharge of refrigerant gas from the bores 
1.sub.-1 to the discharge chamber 3.sub.-2 continues. The refrigerant gas 
in the suction chamber 3.sub.-1 is drawn into the bores 1.sub.-1 and 
discharged into the discharge chamber 3.sub.-2. Accordingly, when the 
swash plate 13 is at the minimum inclined position, a circulation passage 
is formed in the compressor between the discharge chamber 3.sub.-2, the 
pressurizing passage 33, the crank chamber 3.sub.-1, the conduit 32, the 
pressure releasing hole 18.sub.-1, the suction chamber 3.sub.-2, and the 
cylinder bores 1.sub.-1. The lubricating oil mixed with the refrigerant 
gas flows together with the gas in the circulation passage and lubricates 
the inside of the compressor. 
In this state, a pressure difference exists between the discharge and crank 
chambers 3.sub.-1, 2.sub.-1 and the suction chamber 3. Since the 
cross-sectional area of the pressure releasing hole 18.sub.-1 is not large 
enough to eliminate the pressure difference, the swash plate 13 is 
maintained at its minimum inclined position by the pressure difference. 
When the solenoid 35 is activated, the pressurizing hole 33 is closed. The 
pressure difference existing between the crank chamber 2.sub.-1 and the 
suction chamber 3.sub.-1 causes the gas in the crank chamber 2.sub.-1 to 
be conveyed to the suction chamber 3.sub.-1 through the conduit 32 and the 
pressure releasing hole 18.sub.-1. This lowers the pressure in the crank 
chamber 2.sub.-1 and increases the tilt of the swash plate 13 further from 
perpendicular. 
In a clutchless compressor that operates in the above manner, refrigerant 
gas discharged into the discharge chamber 3.sub.-2 from the compression 
chamber defined in each bore 1.sub.-1 is supplied to the muffler chamber 
10 through the discharge passage 12. After the gas is temporarily stored 
in the muffler chamber 10, the gas is returned to the external refrigerant 
circuit 14. The muffler chamber 10 reduces the pressure fluctuation of the 
gas. The refrigerant gas is helically routed about the separator 11 in the 
direction indicated by an arrow P shown in FIGS. 1 and 3. The gas moves 
toward the inlet 11.sub.-1 and enters the separator 11 from the inlet 
11.sub.-1. The gas then flows into the refrigerant circuit 14 from the 
outlet 11.sub.-2. When the refrigerant gas travels about the separator 11, 
mist-like lubricating oil is separated from the gas by centrifugal force. 
Accordingly, this efficiently prevents oil from being discharged 
externally together with the gas. The separated oil moves along the bottom 
of the circulation chamber 10.sub.-1 and flows into the reserve 
compartment 10.sub.-2 after passing through the oil passages 1.sub.-4, 
2.sub.-6. 
The lubricating oil in the reserve compartment 10.sub.-2 flows into the 
crank chamber 2.sub.-1 through the restricted passage 2.sub.-5 (shown in 
FIGS. 1 and 4), which restricts the flow of oil from the compartment 
10.sub.-2 to the crank chamber 2.sub.-1. This oil lubricates the various 
components inside the crank chamber 2.sub.-1. In addition, since the 
reserve compartment 10.sub.-2 is included in the area acted upon by 
discharge pressure, the pressure also acts on the surface of the 
lubricating oil therein. However, the oil in the passage 2.sub.-5 forms a 
film and thus closes the passage 2.sub.-5. Therefore, refrigerant gas with 
the discharge pressure applied thereto is substantially prevented from 
flowing into the crank chamber 2.sub.-1 through the passage 2.sub.-5. 
Preventing the deterioration of the lubricating oil, recovered in the above 
manner, is necessary for satisfactory lubrication. The heat produced in 
the compressor is one of the elements which cause deterioration of the 
lubricating oil. Heat of the compressor also starts the deterioration of 
the lip seal 47 at an early stage. In a clutchless compressor, such as the 
compressor of this embodiment, as long as the engine is operating, the 
swash plate 13 keeps rotating. Therefore, even if the compressor does not 
perform substantial discharging, that is, even if the swash plate 13 is at 
the minimum inclined position, the moving parts produce heat. Accordingly, 
a clutchless compressor generates more heat than a compressor that is 
clutched. 
However, the clutchless compressor does not require a solenoid for an 
electromagnetic clutch between the pulley 5 and the front housing 2. This 
allows the fins 46 to extend to the front end of the front housing 2 and 
also allows the fan 5.sub.-1 to be arranged inside the pulley 5. 
Therefore, when the compressor is operated, the fan sends air toward the 
front end of the fins 46. The air then flows rearward guided by the fins 
46 along the periphery of the front housing 2. Accordingly, the entire 
outer periphery of the clutchless compressor is cooled. This reduces 
deterioration of the lubricating oil and the lip seal 47. 
In this embodiment, the fan 5.sub.-1 is formed integrally with the pulley 
5.sub.-1. This reduces the length of the compressor. In addition, helical 
routing of the heated refrigerant gas in the muffler chamber 10 separates 
the lubricating oil and then reserves it. Thus, the oil in the muffler 
chamber 10 tends to be heated to a high temperature. To cope with this, 
some of the fins 46 are connected to the wall 2.sub.-3 to extend in the 
direction of air flow. This increases heat transfer from the walls 
2.sub.-3, 1.sub.-2, which define the muffler chamber 10, and prevents the 
chamber 10 from being excessively heated. 
In this embodiment, the boss 2.sub.-2 is press fitted into the inner race 
of the angular contact bearing 6 as the bearing is drive fitted onto the 
outer periphery of the boss 2.sub.-2. If the front end of the front 
housing 2 is deformed when press fitting the boss 2.sub.-2, it is possible 
that a reaction force will alter the position of the drive plate 8. This 
will alter the top dead center position of the pistons 25. This leads to a 
pressure imbalance in the compressor when the inclination of the swash 
plate 13 is minimum and may prevent the swash plate 13 from smoothly 
returning to the maximum inclined position from the minimum inclined 
position. 
However, in this embodiment, the fins 46, extending from the front end of 
the front housing 2 toward a rearward direction, reinforce the front end 
of the housing 2. This prevents deformation of the front housing 2 during 
installation of the angular contact bearing 6. 
A modification of the first embodiment will now be described with reference 
to FIGS. 6 and 7. Corresponding parts are denoted with the same numerals. 
In this modification, a portion of the muffler chamber 10 on the front 
housing 2 side is divided into cells 10.sub.-3 (three are defined in this 
example). Walls 10.sub.-4 of the cells 10.sub.-3 are formed integrally 
with some of the fins 46. Thus, the walls 10.sub.-4 form a part of the 
fins 46. This structure further improves the heat transfer performance of 
the muffler chamber 10. 
Another modification of the first embodiment will now be described with 
reference to FIGS. 8 and 9. Corresponding parts are denoted with the same 
numerals. In this modification, a muffler chamber 43 is defined by a 
cylindrical wall 1.sub.-5, which is formed integrally with the cylinder 
block 1 and projects in the radial direction from the peripheral surface 
of the block 1. A cylindrical oil separator 44 is formed in the muffler 
chamber 43 along the axis of the chamber 43. The bottom end of the oil 
separator 44 is separated from the bottom surface of the muffler chamber 
43. Thus, an inlet 44.sub.-1 located at the lower side of the separator 44 
is opposed to the bottom surface of the muffler chamber 43. An outlet 
44.sub.-2 located at the upper side of the separator 44 is connected to 
the external refrigerant circuit 14. The muffler chamber 43 is 
communicated with the crank chamber 2.sub.-1 through a restricted passage 
45. The outlet 12.sub.-1 of the discharge passage 12, which communicates 
the muffler chamber 43 with the discharge chamber 3.sub.-2, is directed 
toward the upper wall of the separator 44 and the inner side of the wall 
1.sub.-5. 
A plurality of second fins 48 are formed in the outer side of the wall 
1.sub.-5 extending in the radial direction of the muffler chamber 43. 
The refrigerant gas conveyed to the muffler chamber 43 from the discharge 
chamber 3.sub.-2 through the discharge passage 12 is helically routed 
about the separator 44 and is directed downward to the inlet 44.sub.-1, as 
shown by arrow Q in FIG. 8. The gas then passes through the interior of 
the separator 44 to be discharged to the external refrigerant circuit 14. 
The lubricating oil included in the refrigerant gas routed about the 
separator 44 is separated from the gas by centrifugal force. The separated 
oil falls to the bottom of the muffler chamber 43 and flows into the crank 
chamber 2.sub.-1 through the restricted passage 45. 
Efficiency in recovery of lubricating oil is similar to that of the first 
embodiment. The air sent from the fan 5.sub.-1, is guided along the fins 
46 and the second fins 48 and cools the muffler chamber 43 efficiently. In 
addition, the fan may be provided separately from the pulley. 
A fourth embodiment of the present invention will now be described with 
reference to FIGS. 10 through 12. Structure differing from the first 
embodiment will mainly be described. Corresponding parts will be denoted 
with the same numerals. 
In the fourth embodiment, the front housing 2, cylinder block 1, and rear 
housing 3 are fastened together by a plurality of bolts 50 (six are 
employed in this embodiment), as shown in FIG. 11. A plurality of recesses 
53 are formed in a front wall 52 of the front housing 2 to accommodate a 
head 51 of each bolt 50. This prevents the heads 51 from protruding from 
the surface of the front wall 52. The front and rear housings 2, 3, and 
the cylinder block 1 are made of an aluminum or aluminum alloy material. 
As shown in FIG. 10, a radial bearing 54 is arranged at the inner side of 
a boss 62 and supports the front side of the rotary shaft 4. The bearing 
54 is located between the lip seal 47 and the thrust bearing 30. The 
external refrigerant circuit 14 is connected to the discharge chamber 
3.sub.-2 by a discharge outlet 49. 
As shown in FIGS. 10 and 11, a flange 61, extending from the outer 
periphery of the boss 62, is formed integrally with the boss 62. A 
predetermined gap K1 is defined between the rear surface of the flange 61 
and the wall 52. A predetermined gap K2 is also defined between the front 
surface of the flange 61 and the pulley 5. Gap K1 is greater than K2 
(K1&gt;K2). 
A plurality of radially extending apertures 63 extend through the flange 61 
in the axial direction. A plurality of holes 64 (six are shown) are formed 
in the radially outer region of the flange 61 with the holes 64 
corresponding to the recesses 53. The fastening and unfastening of the 
bolts 50 is carried out through the holes 64 as shown in FIG. 11 by the 
arrow T. 
Fins 65 are defined between each aperture 63 on the flange 61. The fins 65 
extend in the radial direction with respect to the axis L. Connecting 
sections 66 are defined between the periphery of the flange 61 and the 
outer ends of adjacent fins 65. The space encompassed by the fins 65 and 
the connecting sections 66, that is, the apertures 63, constitute a 
venting passage 67. 
A fan section 68 is provided in the pulley 5. The fan section 68, defined 
at the rear side of the cup shaped pulley 5, extends along the 
circumferential direction of the pulley 5. Venting blades 70, which 
constitute a fan 69, are provided in the fan section 68. The blades 70 are 
arranged with a predetermined space between one another along the 
circumferential direction. As shown in FIG. 12, each blade 70 is inclined 
at an obtuse angle .theta. with respect to the inner bottom surface of the 
wall of the fan section 68. A plurality of air intake holes 71 (only one 
shown in FIG. 10) are formed extending through the wall of the fan section 
68 in the pulley 5. Each intake hole 71 corresponds to one of the blades 
70. Therefore, as shown in FIG. 12, air is drawn into the fan section 68 
through the intake holes 71 by the blades 70 when the pulley 5 is rotated 
in a direction indicated by the arrow. The drawn in air is then sent 
toward the venting passage 67 in the flange 61. 
The operation of the embodiment of FIG. 10 will now be described. In the 
state shown in FIG. 10, the solenoid 35 is activated and thus the 
pressurizing passage 33 is closed. Therefore, the highly pressurized 
refrigerant gas in the discharge chamber 3.sub.-2 is not conveyed to the 
crank chamber 2.sub.-1. In this state, the conduit 32 and the pressure 
releasing hole 18.sub.-1 release the pressure in the crank chamber 
2.sub.-1 to a value close to the pressure in the suction chamber 3.sub.-1, 
that is, the suction pressure. This causes the swash plate 13 to be 
maintained at the maximum inclined position and results in maximum 
displacement. 
While discharge is performed with the swash plate 13 retained at the 
maximum inclined position, a decrease in cooling load (requirement) lowers 
the temperature of the evaporator 39. When the temperature of the 
evaporator 39 becomes lower than a predetermined value, the solenoid 35 is 
deactivated and the pressurizing passage 33 is opened. This conveys the 
highly pressurized refrigerant gas in the discharge chamber 3.sub.-2 to 
the crank chamber 2.sub.-1 through the pressurizing passage 33 and raises 
the pressure in the chamber 2.sub.-1. The pressure increase in the crank 
chamber 2.sub.-1 immediately reduces the inclination of the swash plate 
13. That is, the swash plate 13 moves toward a perpendicular position. 
The reduction in the inclination of the swash plate 13 results in the spool 
18 disconnecting the suction passage 20 from the suction chamber 3.sub.-1. 
In this state, an internal circulating passage, constituted by the 
discharge chamber 3.sub.-2, the pressurizing passage 33, the crank chamber 
2.sub.-1, the conduit 32, the pressure releasing hole 18.sub.-1, the 
suction chamber 3.sub.-2, and the cylinder bores 1.sub.-1, is formed in 
the compressor. Since the minimum inclined position of the swash plate 13 
is not quite perpendicular, rotation of the rotary shaft 4 causes 
discharge of refrigerant gas into the discharge chamber 3.sub.-2 from the 
cylinder bores 1.sub.-1 even if cooling is not required. Accordingly, the 
discharged gas circulates in the circulating passage. The lubricating oil 
included in the gas lubricates the interior of the compressor. 
Friction between the lip seal 47 and the shaft 4 produces heat in the seal 
47. However, this heat is transferred through the boss 62 and to the fins 
65 provided in the flange 61. 
In addition, rotation of the pulley 5 causes the fan 69 to draw air into 
the fan section 68 through the intake holes 71 and toward the fins 65. 
This enhances the heat transfer effect of the fins 65. As a result, 
deterioration of the seal 47, which is caused by heat, is reduced and the 
sealing function is maintained. 
The structure of this embodiment also enables the following effects. The 
gap K1, defined between the fins 65 and the front wall 52 of the front 
housing 2, ensures that heat transferred from the crank chamber 2.sub.-1 
to the wall 52 is transferred to the ambient air without being conducted 
to the fins 65. Heat is transferred to the fins 65 from the crank chamber 
2.sub.-1 via the boss 62. Therefore, the seal 47 is not excessively 
heated. 
The venting passage 67 is defined by connecting the outer ends of the fins 
65. Thus, the air sent toward the fins 65 flows through the passage 67 and 
is then discharged externally from the gap K1. The connecting sections 66 
prevent the drawn in air from escaping in the radial direction. They also 
prevent external air currents from effecting the flow of the air between 
the fins 65. This enables the entire surface of the fins 65 to be cooled 
by the air and enhances the heat transfer effect of the fins 65. In 
addition, when the air is conveyed outward through the gap K1, the air 
contacts the front wall 52 of the front housing 1 and cools it. 
The fins 65 are formed integrally with the boss 62. Thus heat conducts 
effectively from the boss 62 to the fins 65. The drawn in air tends to 
flow outward through the gap K1, since gap K1 is greater than the gap K2. 
This suppresses the escape of air through the gap K2 before it reaches the 
venting passage 67 and enables air to be introduced into the passage 67 
efficiently. 
Since holes 64 through which the bolts 50 pass through are defined in the 
flange 61, integral formation of the flange 62 with the boss 62 does not 
interfere with the assembling of the front housing 1, the cylinder block 
2, and the rear housing 3. Thus, it is possible to enlarge the outer 
diameter of the flange 61 to a size larger than shown in FIG. 10. In this 
case, it is possible to provide sufficient surface area on the fins 65 to 
transfer a desired amount of heat even if the flange 61 is thin and the 
axial length of the compressor is shortened. 
Furthermore, since air may pass through the holes 64, the holes 64 have the 
same function as the air venting passages 67 (apertures 63). Thus, 
although the provision of the holes 64 shortens the length of those 
apertures 63 radially inward of the holes 64, the amount of air flowing 
through is not reduced. 
The head 51 of each bolt 50 is accommodated in the recess 53 and does not 
protrude from the surface of the front wall 52. Hence, the heads 51 do not 
interfere with the flow of ambient air. 
In addition to the lip seal 47, heat is produced in the radial bearing 54. 
However, since the fins 65 are located near the bearing 54, the heat of 
the bearing 54 is transferred to the fins 65 after being conducted through 
the boss 62. 
A modification of the embodiment illustrated in FIG. 10 is shown in FIG. 
13. In this modification, the location of the fan 72 differs from that 
shown in FIG. 10. More specifically, the outer diameter of the flange 61 
is smaller than the outer diameter of the pulley 5. Hence, an annular 
space is defined between the periphery of the flange 61, the periphery of 
the pulley 5, and the front wall 52 of the front housing 1. A plurality of 
blades 73 (only one shown) which constitute the fan 72 project from the 
rear side of the pulley 5 toward the front wall 52 in the annular space 
with a predetermined interval defined between one another. A gap K3 is 
defined between the fan 72 and the wall 52. The gap K3 is smaller than the 
gap K1. 
Integral rotation of the pulley 5 and the fan 72 causes a pressure 
difference between the inner and outer sides of the fan 72. This results 
in ambient air being drawn into the venting passages 67 through the intake 
holes 71 and then sent outward through the gaps K1, K3. This current 
enhances heat transfer from the fins 65 and the front wall 52. 
The rotating diameter of the fan 72 in this modification is larger than the 
fan 5.sub.-1 shown in FIG. 1. Thus, the amount of ambient air drawn in is 
increased. 
The present invention may also be modified in the manners described below. 
(1) The connecting sections 66 connecting the outer ends of the fins 65 may 
be omitted. 
(2) The flange 61 and the boss 62 may be constituted by separate bodies. In 
this case, the flange 61 is fixed to the boss 62 by press fitting, or the 
like. This simplifies the shape of the front housing 1 and facilitates 
machining. 
(3) The heads 51 of the bolts 50 may be arranged at the rear housing 3 
side. This omits the necessity for the holes 64 in the flange 61. 
(4) The air intake holes 71 may be inclined with respect to the rotary axis 
of the pulley 5. This facilitates the intake of air. 
(5) The present invention may be employed in a compressor with an 
electromagnetic clutch provided between the pulley and the rotary shaft 4. 
Although several embodiments of the present invention have been described 
herein, it should be apparent to those skilled in the art that the present 
invention may be embodied in many other specific forms without departing 
from the spirit or scope of the invention. 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.