Variable capacity vane compressor

A variable capacity vane compressor has a cylinder within which a pair of compression spaces are defined between the cylinder and a rotor rotatably received within the cylinder at diametrically opposite locations, and a control element disposed in the cylinder for rotation about its own axis in circumferentially opposite directions in response to a difference between pressure from a lower pressure zone and pressure from a higher pressure zone. The control element has its outer peripheral edge formed with a pair of cut-out portions at substantially diametrically opposite locations, which each have a leading end in the direction of rotation of the rotor. The rotation of the control element causes a change in the circumferential position of each cut-out portion to thereby vary the timing of commencement of compression in the corresponding compression space and hence vary the compressor capacity. The leading ends of the cut-out portions are located at diametrically asymmetric locations to provide a difference in the timing of commencement of compression between the compression spaces. Therefore, the compressor as a whole is free from insufficient compression and can provide sufficient discharge pressure even when it assumes the minimum capacity position.

BACKGROUND OF THE INVENTION 
This invention relates to vane compressors for use as refrigerant 
compressors in automotive air conditioning systems or like systems, and 
more particularly to variable capacity vane compressors of the type that 
the compressor capacity is controlled by varying the timing of 
commencement of compression. 
Variable capacity vane compressors of this type have been proposed e.g. by 
Japanese Provisional Patent Publication (Kokai) Nos. 62-20688 and 
62-129593. These proposed vane compressors are constructed as shown in 
FIG. 1 through FIG. 4. As shown in FIGS. 1 and 2, a rotor B is rotatably 
fitted within a cylinder formed by a cam ring A and two side blocks 
closing opposite ends of the cam ring A, and carries vanes D.sub.1 
-D.sub.5 radially slidably fitted in respective slits formed in the outer 
peripheral surface thereof. Two compression spaces C.sub.1 and C.sub.2 are 
defined within the cylinder by the inner peripheral surface of the cam 
ring A and the outer peripheral surface of the rotor B at diametrically 
opposite locations. During the suction stroke when compression chambers 
each defined between adjacent two vanes increase in volume, compression 
fluid is drawn from a suction chamber into the compression chambers 
through refrigerant inlet ports E and E, as shown in FIG. 3. During the 
compression stroke following the suction stroke, when the compression 
chambers decrease in volume, the drawn compression fluid is compressed to 
be discharged through refrigerant outlet ports F and F and discharge 
valves G and G into a discharge pressure chamber. An annular recess I is 
formed in an end face of one H of the side blocks formed with the 
refrigerant inlet ports E and E, which end face faces the rotor B. Two 
pressure working chambers J and J are defined in the annular recess I at 
diametrically opposite locations, which communicate with the suction 
chamber and the discharge pressure chamber. A control element L is 
rotatably fitted in the annular recess I, which has a side surface thereof 
formed with two pressure-receiving protuberances K and K slidably fitted 
in the respective pressure working chambers J and J to divide each of them 
into a first pressure chamber communicating with the suction chamber and a 
second pressure chamber communicating with the discharge pressure chamber, 
such that the control element is rotatable in opposite directions in 
dependence on the difference in pressure between the first and second 
pressure chambers, between a maximum capacity position and a minimum 
capacity position. The control element L has an outer peripheral edge 
thereof formed with two arcuate cut-out portions L.sub.1 and L.sub.2 at 
diametrically opposite locations, which determine the timing of 
commencement of compression stroke such that the fluid compression starts 
when a trailing one of two adjacent vanes passes a leading end of each 
cut-out portion L.sub.1, L.sub.2 in the direction of rotation of the rotor 
B. The timing of commencement of compression can thus be varied through 
the whole range as the control element L is rotated between the maximum 
capacity position as indicated by the solid lines in FIGS. 1 and 3 and the 
minimum capacity position as indicated by the two-dot chain lines in FIGS. 
2 and 3 so that the compression amount or capacity varies between the 
maximum value as shaded in FIG. 1 to the minimum value as shaded in FIG. 
2. 
However, according to the above proposed vane compressors, if the location 
of the leading end of each cut-out portion L.sub.1, L.sub.2 is shifted so 
as to further retard the timing of commencement of compression when the 
compressors are in the minimum capacity position and hence further 
decrease the minimum compression amount in order to increase the variable 
range of the compressor capacity, this causes insufficient compression, 
because there is a fixed "dead volume", that is, a non-compressed volume, 
in each refrigerant outlet port F, F, and therefore if the minimum 
compression amount is decreased, the ratio of the dead volume to the 
minimum compression amount increases, causing insufficient compression. 
Furthermore, since the two cut-out portions of the control element L are 
located at diametrically opposite locations and accordingly the two 
compression spaces C.sub.1 and C.sub.2 have the same timing of commencemnt 
of compression, the above-mentioned insufficient compression will take 
place in both of the two compression spaces C.sub.1 and C.sub.2 if the 
minimum compression amount is decreased as above. As a result, the 
compressors cannot provide desired discharge pressure when they are in the 
minimum capacity position. 
SUMMARY OF THE INVENTION 
It is therefore the object of the invention to provide a variable capacity 
vane compressor in which the timing of commencement of compression is 
different between the two compression spaces to thereby obtain a large 
variable range of capacity as well as sufficient discharge pressure even 
in the minimum capacity position in which the minimum compression amount 
is obtained. 
To attain the above object, the present invention provides a variable 
capacity vane compressor having a cylinder, a rotor rotatably received 
within the cylinder, a pair of compression spaces being defined between 
the cylinder and the rotor at diametrically opposite locations, a 
plurality of vanes carried by the rotor, a control element disposed in the 
cylinder for rotation about an axis thereof in circumferentially opposite 
directions, the control element having an outer peripheral edge thereof 
formed with a pair of cut-out portions at substantially diametrically 
opposite locations, the cut-out portions each having a leading end in the 
direction of rotation of the rotor, a lower pressure zone, a higher 
pressure zone, and means for rotating the control element in response to a 
difference between pressure from the lower pressure zone and pressure from 
the higher pressure zone, wherein compression of compression fluid 
commences when each of the vanes passes the leading end of each of the 
cut-out portions, whereby the rotation of the control element causes a 
change in the circumferential position of each of the cut-out portions to 
thereby vary the timing of commencement of compression in a corresponding 
one of the compression spaces and hence vary the capacity of the 
compressor. 
The variable capacity vane compressor according to the invention is 
characterized by an improvement wherein the leading ends of the cut-out 
portions of the control element are located at diametrically asymmetric 
locations to provide a difference in the timing of commencement of 
compression between the compression spaces. 
The above and other objects, features, and advantages of the invention will 
be more apparent from the ensuing detailed description taken in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
The invention will now be described in detail with reference to the 
drawings showing embodiments thereof. 
FIGS. 5 through 14 show a variable capacity vane compressor according to 
the first embodiment of the invention, wherein a housing 1 comprises a 
cylindrical casing 2 with an open end, and a rear head 3, which is 
fastened to the casing 2 by means of bolts, not shown, in a manner closing 
the open end of the casing 2. A discharge port 4, through which a 
refrigerant gas is to be discharged as a thermal medium, is formed in an 
upper wall of the casing 2 at a front end thereof, and a suction port 5, 
through which the refrigerant gas is to be drawn into the compressor, is 
formed in an upper portion of the rear head 3. The discharge port 4 and 
the suction port 5 communicate, respectively, with a discharge pressure 
chamber 19 and a suction chamber 17, both hereinafter referred to. 
A pump body 6 is housed within the housing 1. The pump body 6 is composed 
mainly of a cylinder formed by a cam ring 7, and a front side block 8 and 
a rear side block 9 closing open opposite ends of the cam ring 7, a 
cylindrical rotor 10 rotatably received within the cam ring 7, and a 
driving shaft 11 which is connected to an engine, not shown, of a vehicle 
or the like, and on which is secured the rotor 10. The driving shaft 11 is 
rotatably supported by a pair of radial bearings 12 provided in the side 
blocks 8 and 9, respectively. 
The cam ring 7 has an inner peripheral surface with an elliptical cross 
section, as shown in FIG. 6, and cooperates with the rotor 10 to define 
therebetween a pair of compression spaces 13.sub.1 and 13.sub.2 at 
diametrically opposite locations. 
The rotor 10 has its outer peripheral surface formed with a plurality of 
(five in the illustrated embodiment) axial vane slits 14 at 
circumferentially equal intervals, in each of which a vane 15.sub.1 
-15.sub.5 is radially slidably fitted. Adjacent vanes 15.sub.1 -15.sub.5 
define therebetween five compression chambers 13a-13e in cooperation with 
the cam ring 7, the rotor 10, and the opposite inner end faces of the 
front and rear side blocks 8, 9. 
Refrigerant inlet ports 16 and 16 are formed in the rear side block 9 at 
diametrically opposite locations as shown in FIGS. 6 and 7. These 
refrigerant inlet ports 16, 16 are located at such locations that they 
become closed when the respective compression chambers 13a-13e assume the 
maximum volume. These refrigerant inlet ports 16, 16 axially extend 
through the rear side block 9 and through which the suction chamber (lower 
pressure chamber) 17 defined in the rear head 3 by the rear side block 9 
and the compression chamber 13b on the suction stroke are communicated 
with each other. 
Refrigerant outlet ports 18 are formed through opposite lateral side walls 
of the cam ring 7 and through which compression chambers 13c and 13e on 
the discharge stroke are communicated with the discharge pressure chamber 
(higher pressure chamber) 19 defined within the casing 2, as shown in 
FIGS. 5 and 6. These refrigerant outlet ports 18 are provided with 
respective discharge valves 20 and valve retainers 21, as shown in FIG. 6. 
The rear side block 9 has an end face facing the rotor 10, in which is 
formed an annular recess 22 larger in diameter than the rotor 10, as shown 
in FIGS. 7 and 9 to 11, particularly in FIG. 11. A pair of pressure 
working chambers 27 and 27 are formed in the annular recess 22 at 
diametrically opposite locations, as best shown in FIG. 10. One end 
(trailing end in the direction of rotation of the rotor 10) of each of the 
pressure working chambers 27 and 27 is communicated with the suction 
chamber 17 by way of a corresponding one of the refrigerant inlet ports 16 
and 16, and the other end (leading end in the direction of rotation of the 
rotor 10) of each of the pressure working chambers 27 and 27 is 
communicated with the discharge pressure chamber 19 by way of a 
high-pressure passage 28 referred to hereinbelow. An annular control 
element 24 as shown in FIGS. 10 and 12 is received in the annular recess 
22 for rotation about its own axis in opposite circumferential directions 
as shown in FIG. 7. The control element 24 has its outer peripheral edge 
formed with a pair of approximately diametrically opposite arcuate cut-out 
portions 25.sub.1 and 25.sub.2, and its one side surface formed integrally 
with a pair of diametrically opposite pressure-receiving protuberances 26 
and 26 axially projected therefrom and acting as pressure-receiving 
elements. The pressure-receiving protuberances 26, 26 are slidably 
received in respective pressure working chambers 27 and 27. The interior 
of each of the pressure working chambers 27, 27 is divided into first and 
second pressure chambers 27.sub.1 and 27.sub.2 by the associated 
pressure-receiving protuberance 26 as shown in FIG. 8. The first pressure 
chamber 27.sub.1 communicates with the suction chamber 17 through the 
corresponding inlet port 16, and the second pressure chamber 27.sub.2 
communicates with the discharge pressure chamber 19 through the 
high-pressure passage 28. The two chambers 27.sub.2, 27.sub.2 are 
communicated with each other by way of a communication passage 30 as shown 
in FIGS. 5 and 8. The communication passage 30 comprises a pair of 
communication channels 30a, 30a formed in a boss 9a projected from a 
central portion of the rear side block 9 at a side remote from the rotor 
10, and an annular space 30b defined between a projected end face of the 
boss 9a and an inner end face of the rear head 3. The communication 
passages 30a, 30a are arranged symmetrically with respect to the center of 
the boss 9a. Respective ends of the communication passages 30a, 30a are 
communicated with the respective second pressure chambers 27.sub.2, 
27.sub.2, and the other respective ends are communicated with the annular 
space 30b. 
The high-pressure passage 28 is formed in the rear side block 9 as shown in 
FIG. 5. Arranged in the high-pressure passage 28 is a control valve device 
31 responsive to pressure within the suction chamber 17. When the valve of 
the control valve device 31 is open, pressure within the second pressure 
chambers 27.sub.2, 27.sub.2 is allowed to leak into the suction chamber. 
The control valve device 31 comprises a flexible bellows 32, a valve 
casing 33, a ball valve body 34, and a coiled spring 35 urging the ball 
valve body 34 in its closing direction. The bellows 32 is disposed in the 
suction chamber 17, with its axis extending parallel with that of the 
driving shaft 11. When the suction pressure within the suction chamber 17 
is above a predetermined value, the bellows 32 is in a contracted state, 
and when the suction pressure is below the predetermined value the bellows 
32 is in an expanded state. The valve casing 33 is fitted in a bore 29 
formed in the midway of the high-pressure passage 28 and is opposed to the 
bellows 32. The valve casing 33 has communication holes 33b, 33c formed in 
opposite end walls thereof, and the communication holes 33b, 33c 
communicate with each other through a hollow interior 33a of the valve 
casing 33. The ball valve body 34 arranged in the hollow interior 33a of 
the valve casing 41 is disposed to close and open the communication hole 
33c. The coiled spring 35 is arranged in the hollow interior 33c of the 
valve casing 33 and urges the ball valve body in its closing direction. 
When the pressure within the suction chamber 17 is above the predetermined 
value, and therefore when the bellows 32 is in the contracted state, the 
communication hole 33c of the valve casing 33 is closed by the ball valve 
body 34 by the force of the coiled spring 35. When the pressure within the 
suction chamber 17 is below the predetermined value, and therefore when 
the bellows 32 is in the expanded state, the ball valve body 34 is urgedly 
biased to open the communication hole 33c against the force of the coiled 
spring 35 through a rod 32a loosely fitted through the communication hole 
33c. 
A sealing member 36 of a special configuration as shown in FIG. 9 is 
mounted in the control element 24 and disposed along an end face of its 
central portion and radially opposite end faces of each pressure-receiving 
protuberance 26, to seal in an airtight manner between the first and 
second pressure chambers 27.sub.1 and 27.sub.2, as shown in FIG. 8, as 
well as between the end face of the central portion of the control element 
24 and the inner peripheral edge of the annular recess 22 of the rear side 
block 9, as shown in FIG. 5. 
The control element 24 is urged in the counterclockwise direction as viewed 
in FIG. 7, by a torsion coiled spring 37 fitted around the hub 9a of the 
rear side block 9 axially extending toward the suction chamber 17. The 
torsion coiled spring 37 has an end 37a thereof engaged in an engaging 
hole 24a which is formed in an end face of the control element 24. The 
other end 37b of the torsion coiled spring 37 is engaged in an engaging 
hole 9b formed in an end face of the hub 9a. 
Thus the control element 24 is rotatable in opposite directions in response 
to the difference between the sum of the pressure within the first 
pressure chamber 27.sub.1 and the urging force of the torsion coiled 
spring 37, and the pressure within the second pressure chamber 27.sub.2, 
within the range between the extreme positions, i.e. the maximum capacity 
position indicated by the solid lines in FIG. 7 at which the maximum 
capacity of the compressor can be obtained (in this position, a left end 
wall of the pressure-receiving protuberance 26 abuts against a maximum 
capacity stopper 27a), and the minimum capacity position indicated by the 
two-dot chain lines in FIG. 7 (in this position, a right end wall of the 
pressure-receiving protuberance 26 abuts against a minimum capacity 
stopper 27b). During the suction stroke, the volume of a compression 
chamber (e.g. the compression chamber 13a) defined between two adjacent 
vanes (e.g. the vanes 15.sub.1 and 15.sub.2) of the plurality of vanes 
15.sub.1 to 15.sub.5 is increased to thereby draw refrigerant into the 
compression chamber from the suction chamber 17 through the refrigerant 
inlet port 16. In the meanwhile, a trailing vane of the two adjacent vanes 
(e.g. the trailing vane 15.sub.2 of the two adjacent vanes 15.sub.1 and 
15.sub.2) passes a leading end (25.sub.10 or 25.sub.20) of a cut-out 
portion (25.sub.1 or 25.sub.2), whereupon communication between the 
compression chamber defined between the two adjacent vanes and the 
refrigerant inlet port 16 is cut off, and at this instant the compression 
stroke starts. This timing of commencement of compression stroke is 
retarded as the control element 24 angularly moves in the clockwise 
direction as viewed in FIG. 7 from the maximum capacity position to the 
minimum capacity position, whereby the compressor capacity can be 
continuously decreased. 
Further, as shown in FIG. 7, the leading ends 25.sub.10 and 25.sub.20 of 
the respective cut-out portions 25.sub.1, 25.sub.2 are located at 
asymmetric locations which are circumferentially offset by a predetermined 
degree of angle from the diametrically symmetric locations. This provides 
a difference in the time of commencement of compression stroke between the 
compression space 13.sub.1 which is controlled by the leading end 
25.sub.10 of the cut-out portion 25.sub.1 and the compression space 
13.sub.2 which is controlled by the leading end 25.sub.20 of the cut-out 
portion 25.sub.2. More specifically, as is clearly shown in FIG. 7, the 
leading end 25.sub.10 of the cut-out portion 25.sub.1 is located at a 
location which is offset backward in the direction of rotation of the 
rotor 10 (in the clockwise direction as viewed in FIG. 7) by a 
predetermined degree of angle with respect to symmetry in location of the 
leading ends 25.sub.10 and 25.sub.20, so that in the compression space 
13.sub.1 under the control of the leading end 25.sub.10 of the cut-out 
portion 25.sub.1 of the control element 24, the compression stroke of a 
compression chamber starts later than in the compression space 13.sub.2 
under the control of the leading end 25.sub.20 of the cut-out portion 
25.sub.2. The predetermined degree of angle may be, for example, 10 
degrees, whereby in the compression space 13.sub.2 under the control of 
the leading end 25.sub.20 of the cut-out portion 25.sub.2, the compression 
stroke of a compression chamber in the compression space 13.sub.2 starts 
at such a timing that when the control element 24 is in the minimum 
capacity position, compression of refrigerant is positively carried out to 
such a degree as to give a sufficient discharge pressure, and accordingly 
the variable range of the compressor capacity is kept small. At the same 
time, in the compression space 13.sub.1 under the control of the leading 
end 25.sub.10 of the cut-out portion 25.sub.1, the compression stroke of a 
compression chamber starts at such a timing that when the control element 
24 is in the minimum capacity position, the commencement of compression of 
refrigerant is so delayed as to hardly effect compression of refrigerant, 
and accordingly the variable range of he compressor capacity is increased. 
The operation of the above-described first embodiment of the invention will 
now be explained. 
As the driving shaft 11 is rotatively driven by a prime mover such as an 
automotive engine to cause clockwise rotation of the rotor 10 as viewed in 
FIG. 6, the rotor 10 rotates so that the vanes 15.sub.1 -15.sub.5 
successively move radially out of the respective slits 14 due to a 
centrifugal force and back pressure acting upon the vanes and revolve 
together with the rotating rotor 10, with their tips in sliding contact 
with the inner peripheral surface of the cam ring 7. During the suction 
stroke a compression chamber (e.g. compression chamber 13a) defined by 
adjacent ones (e.g. vanes 15.sub.1 and 15.sub.2) of the vanes 15.sub.1 to 
15.sub.5 increases in volume so that refrigerant gas as thermal medium is 
drawn through the refrigerant inlet port 16 into the compression chamber. 
The compression stroke starts when the trailing vane of the adjacent vanes 
(e.g. the trailing vane 15.sub.2 of the vanes 15.sub.1 and 15.sub.2) 
passes the leading end (25.sub.10 or 25.sub.20) of a cut-out portion 
(25.sub.1 or 25.sub.2) to thereby cut off the communication between the 
compression chamber defined by the adjacent vanes and the refrigerant 
inlet port 16. During the discharge stroke at the end of the compression 
stroke the high pressure of the compressed gas forces the discharge valve 
20 to open to allow the compressed refrigerant gas to be discharged 
through the refrigerant outlet port 18 into the discharge pressure chamber 
19 and then discharged through the discharge port 4 inot a heat exchange 
circuit of an associated air conditioning system, not shown. 
During the operation of the compressor described above, low pressure or 
suction pressure within the suction chamber 17 is introduced into the 
first pressure chamber 27.sub.1 of each pressure working chamber 27 
through the refrigerant inlet port 16, whereas high pressure or discharge 
pressure within the discharge pressure chamber 19 is introduced into the 
second pressure chamber 27.sub.2 of each pressure working chamber 27 
through the high-pressure passage 28. The control element 24 is 
circumferentially displaced in opposite directions between the maximum 
capacity position indicated by the solid lines in FIG. 7 and the minimum 
capacity position indicated by the two-dot chain lines in same depending 
upon the difference between the sum of the pressure within the first 
pressure chamber 27.sub.1 and the biasing force of the torsion coiled 
spring 37 (which acts upon the control element 24 so as to urge same 
toward the minimum capacity position, i.e. in the clockwise direction as 
viewed in FIG. 7) and the pressure within the second pressure chamber 
27.sub.2 (which acts upon the control element 24 so as to urge same toward 
the maximum capacity position, i.e. in the counter-clockwise direction as 
viewed in FIG. 7). At the same time, the leading ends 25.sub.10, 25.sub.20 
of the cut-out portions 25.sub.1, 25.sub.2 are displaced accordingly, 
whereby the timing of commencement of compression stroke is varied to 
continuously change the delivery quantity of refrigerant gas or the 
compressor capacity. 
For instance, when the compressor is operating at a low speed, the 
refrigerant gas pressure or suction pressure within the suction chamber 17 
is so high that the bellows 32 of the control valve device 31 is 
contracted to bias the ball valve body 34 to close the communication hole 
33c, as shown in FIG. 5. Accordingly, the pressure within the discharge 
pressure chamber 19 is introduced into the second pressure chamber 
27.sub.2. Thus, the pressure within the second pressure chamber 27.sub.2 
surpasses the sum of the pressure within the first pressure chamber 
27.sub.1 and the biasing force of the torsion coiled spring 37 so that the 
control element 24 is circumferentially displaced toward the maximum 
capacity position indicated by the solid lines in FIG. 7 in the 
counter-clockwise direction as viewed in same. 
When the control element 24 is in the maximum capacity position, the 
leading ends 25.sub.10 and 25.sub.20 of the respective cut-out portions 
25.sub.1 and 25.sub.2 are in the most backward positions in the direction 
of rotation of the rotor 10. Therefore, the timing the trailing vane of 
two adjacent vanes (e.g. the trailing vane 15.sub.2 of the vanes 15.sub.1 
and 15.sub.2) on the suction stroke passes the leading end (2510 or 2520) 
of the cut-out portion (25.sub.1 or 25.sub.2) to thereby cut off the 
communication between the compression chamber defined by the two adjacent 
vanes and the refrigerant inlet port 16 is the earliest, i.e. the earliest 
timing of commencement of the compression stroke is obtained. Therefore, 
when the control element 24 is in the maximum capacity position, the 
maximum compression volume X.sub.1 is obtained in the compression space 
13.sub.1 under the control of the leading end 25.sub.10 of the cut-out 
portion 25.sub.1, whereas the maximum compression volume X.sub.2 which is 
larger than the maximum compression volume X.sub.1 is obtained in the 
compression space 13.sub.2 under the control of the leading end 25.sub.20 
of the cut-out portion 25.sub.2. 
Incidentally, although the leading ends 25.sub.10 and 25.sub.20 are 
circumferentially offset from their diametrically symmetrical locations by 
about 10 degrees so that the timing of commencement of compression in the 
compression space 13.sub.1 differs from that in the compression space 
13.sub.2 by about 10 degrees when the control element assumes the maximum 
capacity position, almost the same capacity and almost the same discharge 
pressure can be obtained between the two compression spaces 13.sub.1 and 
13.sub.2, because the suction efficiency is the same between the two 
compression spaces. 
When the compressor is brought into high speed operation, the suction 
pressure within the suction chamber 17 is so low that the bellows 32 of 
the control valve device 31 is expanded so that the rod 32a biases the 
ball valve body 34 in the opening direction against the force of the 
coiled spring 35 to thereby open the communication hole 33c. Thus, the 
pressure within the second pressure chamber 27.sub.2 is allowed to leak 
into the suction chamber 17 through the high-pressure passage 28, the bore 
29, the communication hole 33b, the hollow interior 33a, and the 
communication hole 33c. This causes a sudden drop in the pressure within 
the second pressure chamber 27.sub.2, whereby the control element 24 is 
immediately angularly moved in the clockwise direction as viewed. FIG. 7 
toward the minimum capacity position indicated by the two-dot chain lines 
in FIG. 7. 
When the control element 24 is in the minimum capacity position, the 
leading ends 25.sub.10 and 25.sub.20 of the respective cut-out portions 
25.sub.1 and 25.sub.2 are in the most forward position in the direction of 
rotation of the rotor 10. Therefore, the timing the trailing vane of two 
adjacent vanes (e.g. the trailing vane 15.sub.2 of the vanes 15.sub.1 and 
15.sub.2) on the suction stroke passes the leading end (2510 or 2520 ) of 
the cut-out portion (25.sub.1 or 25.sub.2) to thereby cut off the 
communication between the compression chamber defined by the two adjacent 
vanes and the refrigerant inlet port 16 is the latest, i.e. the latest 
timing of commencement of the compression stroke of the compression 
chamber is obtained. Therefore, when the control element 24 is in the 
minimum capacity position, the minimum compression volume Y.sub.1 is 
obtained in the compression space 13.sub.1 under the control of the 
leading end 25.sub.10 of the cut-out portion 25.sub.1, whereas the minimum 
compression volume Y.sub.2 which is larger than the minimum compression 
volume Y1 is obtained in the compression space 13.sub.2 under the control 
of the leading end 25.sub.20 of the cut-out portion 25.sub.2, as shown in 
FIG. 14. 
The minimum compression volume Y.sub.1 is such a volume that the ratio of 
the dead volume to the volume Y.sub.1 is so great that compression of 
refrigerant gas hardly takes place. In other words, when the control 
element is in the minimum capacity position, the timing of commencement of 
the compression stroke in the compression space 13.sub.1 which is under 
the control of the leading end 25.sub.10 of the cut-out portion 25.sub.1 
is retarded by such a large amount that compression of refrigerant gas 
hardly takes place, whereby a large variable range of the compressor 
capacity is obtained. 
On the other hand, the maximum compression volume Y.sub.2 is such a volume 
that the ratio of the dead volume to the volume Y.sub.2 is so smaller than 
the maximum volume Y.sub.1 that compression of refrigerant gas can 
positively take place. In other words, when the control element is in the 
minimum capacity position, the timing of commencement of the compression 
stroke in the compression space 13.sub.2 which is under the control of the 
leading end 25.sub.20 of the cut-out portion 25.sub.2 is retarded by such 
a small amount that positive compression of refrigerant gas can take place 
and sufficient discharge pressure can be produced, whereby a relatively 
small variable range of the compressor capacity is obtained. 
As noted before, the control element 24 can assume any positions between 
the maximum capacity position and the minimum capacity position in 
response to the difference in pressure between the first pressure chamber 
27.sub.1 and the second pressure chamber 27.sub.2, and as the control 
element 24 moves between the maximum and minimum capacity positions, the 
positions of the leading ends 25.sub.10 and 25.sub.20 of the cut-out 
portions 25.sub.1 and 25.sub.2 vary correspondingly so that the delivery 
quantity or capacity varies. 
As described above in detail, according to the variable capacity vane 
compressor of the invention, the two cut-out portions of the control 
element at substantially diametrically opposite locations have their 
leading ends in the direction of rotation of the rotor located at 
diametrically asymmetric locations so as to provide a difference in the 
timing of commencement of compression between the two compression spaces. 
That is, in one of the two compression spaces the timing of commencement 
of compression is relatively early such that positive compression can take 
place to provide sufficient discharge pressure with the compressor in the 
minimum capacity position, whereby a moderately small variable range of 
the compressor capacity is obtained, whereas in the other compression 
space the timing of commencement of compression is relatively late such 
that compression can hardly take place with the compressor in the minimum 
capacity position, whereby a large variable range of the compressor 
capacity is obtained. Therefore, the compressor as a whole is free from 
insufficient compression and can provide sufficient discharge pressure 
even when it assumes the minimum capacity position, thus being practically 
very useful. 
FIGS. 15 shows a second embodiment of the invention. A variable capacity 
compressor of the second embodiment is different from the compressor of 
the first embodiment mainly in that the casing 2 is omitted from the 
compressor, thereby making the compressor compact in size and reduced in 
weight. The control element 24 according to the first embodiment can be 
applied to the compressor of the second embodiment. In FIG. 15, like 
reference numerals designate elements or parts similar to those in FIG. 5, 
and description thereof is omitted. 
In FIG. 15, the cam ring 7 forms a casing of the compressor together with 
the front head 8 and rear head 9. The cam ring 7 has e.g. two sets of 
refrigerant outlet ports 122, 122 (only one set of which is shown) formed 
through a peripheral wall thereof and arranged at circumferentially 
opposite locations with respect to the axis of the compressor. The 
refrigerant outlet ports 122, 122 have one end thereof opening into 
compression spaces 13.sub.1, 13.sub.2 in the neibourhood of portions with 
reduced diameter of the peripheral wall of the cam ring 7. Onter 
peripheral surface portions 123, 123 of the cam ring 7 formed with the 
refrigerant outlet ports 122, 122 are cut in the form of flat surfaces for 
mounting covers 125, 125 thereon (only one of the surfaces is shown). The 
cover-mounting portions 123, 123 have respective recesses 124, 124 (only 
one of which is shown) formed therein which each have e.g. three 
circumferantially extending grooves with arcuate bottom surfaces formed 
therein. The refrigerant outlet ports 122, 122 have other ends thereof 
opening into the respective recesses 124, 124. 
The covers 125, 125 (one of which is shown) are screwed respectively to the 
cover-mounting portions 123, 123 of the cam ring 7 by means of e.g. four 
mounting bolts 126 (two of which are shown). O-rings 114 are interposed 
between the covers 125, 125 and the cover-mounting portions 123, 123 of 
the cam ring 7, to maintain airtightness between the recesses 124, 124 and 
the outside. The covers 125, 125 have respective arcuate recesses formed 
in inner peripheral surfaces thereof, which form spaces 127, 127 for 
accommodating discharge valves 129, 129 (one of the spaces is shown), 
together with the recesses 124, 124 of the cam ring 7. The covers 125, 125 
have six stopper portions 128 (two of which are shown) projecting 
integrally therefrom toward the cam ring 7 and opposed to the respective 
refrigerant outlet ports 122. 
In the spaces 127, 127, the discharge valves 129, 129 (one of which is 
shown) are arranged as is known from Japanese Utility Model Publication 
(Kokai) No. 62-132289. The discharge valves 129, 129 are formed of a 
single elastic sheet member rolled in a form of cylinder. The cylinder has 
a slit, not shown, axially extending therethrough and resiliently fit and 
secured on an axial ridge, not shown, formed on the inner surface of the 
cover 125, thus being supported by the latter. 
The discharge valves 129, 129 have cylindrical end faces thereof in contact 
with the other ends of the respective refrigerant outlet ports 122, 
thereby closing the ports 122 except during the discharge stroke of the 
compressor. 
The discharge pressure chamber (higher pressure chamber) 19 and the 
discharge valve-accommodating spaces 127, 127 are communicated with each 
other through communicating passages 130, 130 (one of which is shown) 
formed in the cam ring 7 and the front side block 8. Respective ends of 
the passages 130, 130 opening into the spaces 127, 127 are arranged 
radially inwardly of an O-ring 115 which is interposed between the cam 
ring 7 and the front side block 8 for maintaining airtightness between the 
communicating passages 130, 130 and the outside. 
The annular control element 24 is receined in the annular recess 22 formed 
in the rear side block 9 for rotation about its own axis in opposite 
circumferential directions. The control element 24 in the second 
embodiment has substantially the same shape and function as that in the 
first embodiment, detailed description of which is therefore omitted. 
With the above construction, during the discharge stroke, the discharge 
valves 129, 129 are urgedly deformed by the force of compressed 
regrigerant gas until they are brought into contact with the stopper 
portions 128, whereby the compressed gas is discharged into the spaces 
127, 127. The gas discharged into the spaces 127, 127 is then delivered 
into the discharge pressure chamber 19 through the communicating passages 
130, 130, and then discharged out of the compressor through the discharge 
port 4. 
As described above, according to the ninth embodiment of the invention, the 
recesses 124, 124 into which the refrigerant outlet ports 122, 122 open 
are formed in the outer peripheral surface of the cam ring 7, the covers 
125, 125 are mounted on the cam ring so as to cover the respective 
recesses 124, 124, whereby the spaces 127, 127 are formed between the cam 
ring 7 and the covers 125, 125, in which the discharge valves 129, 129 are 
arranged, and the communicating passages 130, 130 are formed in the cam 
ring 7 and the side block to communicate with the spaces 127, 127 with the 
dischange pressure chamber 19. The casing of the compressor is thus 
omitted, thereby making the compressor compact in size and reduced in 
weight. Further, also the compressor of the second embodiment can obtain a 
large variable range of capacity as well as sufficient discharge pressure 
even in the minimum capacity position in which the minimum compressor 
amount is obtained, by virtue of employment of the control element 24 as 
employed in the first embodiment.