Rotary compressor of variable displacement type

A rotary compressor of variable displacement type comprises a cylinder, a rotor accommodated in the cylinder in an eccentric relationship therewith, at least one vane incorporated in the rotor through an outer periphery of the latter and movable relative to the rotor reciprocatively in a longitudinal direction of the vane, and two side plates closing the cylinder at both axial ends of the latter. A suction port is formed in at least one of the side plates, while an opening portion is formed in a rear side portion of the vane as viewed in a direction of rotation of the rotor and being opened at a surface of the vane making sliding contact with the rotor. This opening portion is repeatedly communicated with and interrupted from a working space in the compressor according to the reciprocative movement of the vane relative to the rotor. A suction passage is formed in the vane, or in the vane and the rotor, for establishing communication between the suction port and the opening portion in a predetermined range of rotation of the rotor.

BACKGROUND OF THE INVENTION 
The present invention relates to a rotary compressor of variable 
displacement type, and in particular, to a rotary compressor of variable 
displacement type suitably used in an air-conditioning system for a 
vehicle. 
In a conventional rotary compressor of variable displacement type as 
disclosed in Japanese Utility Model Unexamined Publication No. 57-58791, 
an eccentric rotor rotates in a housing having a suction port and vanes 
arranged in the rotor compress the fluid suctioned through the suction 
port and exhaust the compressed fluid through an exhaust port, an inner 
sleeve being rotatably arranged on the inner surface of the housing. The 
vanes contact the inner surface of the inner sleeve in a sliding manner, 
and the inner sleeve is formed with an adjusting port which cooperates 
with the suction port. The exhaust displacement or volume is controlled by 
rotating the inner sleeve, i.e. by changing the amount of overlap of the 
adjusting port with the suction port, in other words, by changing the 
substantial opening range of the suction opening. 
In the above-mentioned prior art, a communication between the suction port 
and the working space starts when the front vane crosses over the starting 
point of the opening area formed by the suction port and the adjusting 
port, and finishes when the rear vane crosses over the terminal point of 
the opening area. In other words, a suction stroke starts when the front 
vane crosses over the starting point of the suction port opening range and 
finishes when the rear vane crosses over the terminal point of the suction 
port opening range. Consequence, denoting the angular range of the opening 
area of the suction port with respect to the rotor rotation center by 
.theta.p, and the angle between adjacent vanes, i.e. the pitch angle of 
vanes in a circumferential direction by .theta.v, the angular extent or 
range of the suction stroke is expressed by the sum of .theta.p .theta.v. 
In the conventional volume control technique, the suction port opening 
range .theta.p may be changed, possibly to zero, by rotating the inner 
sleeve. However, the vane pitch angle .theta.v can not be changed, because 
the vane pitch angle is determined by the number of vanes. Accordingly, 
the suction stroke is achieved at least in an angular range .theta.v. 
Thus, the minimum volume of the working space can not be made smaller than 
the volume determined by the angle .theta.v, thereby causing a problem 
that the minimum volume is limited in a volume control operation. 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a rotary compressor of variable 
displacement type in which a sufficiently decreased minimum volume and a 
wide range of volume control can be realized. 
A variable displacement rotary compressor to the invention, comprises a 
cylinder having an inner peripheral surface and both axial ends, with 
rotor means including a rotor being accommodated in the cylinder in an 
eccentric relationship therewith, and at least one vane incorporated in 
the rotor through an outer periphery of the rotor. The vane being is 
reciprocably movable relative to the rotor in a longitudinal direction of 
the vane, and two side plates close the cylinder at both ends thereof with 
the vane dividing a working space defined by the rotor, the cylinder, and 
the side plates into a plurality of spaces Suction port means are formed 
in at least one of the side plates and are opened at a surface of the side 
plate making siding contact with the rotor opening means are formed in a 
rear side portion of the vane as viewed in a direction of rotation of the 
rotor and are opened at a surface of the vane making sliding contact with 
the rotor The opening means being adapted to be repeatedly communicated 
with and interrupted from the working space according to the reciprocating 
movement of the vane relative to the rotor. A suction passage means is 
formed in the rotor means for establishing a communication between the 
suction port means and the opening means in a predetermined range of 
rotation of the rotor means. 
In the arrangement of the invention, a suction stroke suctioning a fluid 
into the working space through the opening means starts when the suction 
passage means starts to establish communication between the suction port 
means and the opening means, and finishes when this communication is 
interrupted. Accordingly, denoting the angle of opening range or area of 
the suction passage means with respect to the rotor center by .theta.s, 
and the angular range of the suction port means by .theta.p, the angular 
extent of the suction stroke is expressed as the sum of .theta.s + 
.theta.p. 
The angle .theta.s can be sufficiently small in comparison with the angle 
.theta.v. As a result, it become possible to make the suction stroke 
.theta.s + .theta.p sufficiently small by sufficiently decreasing the 
angle .theta.p, and a smaller minimum exhaust volume and a wider control 
range can be attained. 
Further, in the present invention, the opening means is formed in the rear 
side portion of the vane as viewed in the direction of rotation of the 
rotor, and this opening means repeatedly communicates with and is 
interrupted from the working space according to the forward and rearward 
motions of the vane relative to the rotor. The opening means is closed due 
to the rearward motion of the vane into the inside of the rotor when the 
working space arrives at its maximum volume and the volume is just 
starting to decrease. By virtue of this arrangement, the high pressure gas 
produced in a compression stroke of the working space is prevented from 
flowing into the suction passage means through the opening means and 
leaking toward a low pressure side in the following suction stroke. Thus, 
an internal leakage in the compressor is prevented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
As shown in FIGS. 1 and 2, according to the present invention, a rotor 1 
has an integrally formed shaft 1A, and a pair of vane grooves 1a 
penetrating through the rotor 1 at positions circumferentially spaced 
apart from each other by 180 degrees. The rotor shaft 1A extends from one 
end surface of the rotor 1, and through the other end surface 1b of the 
rotor 1 formed with a large recess 1c extending from the middle portion of 
the end surface 1b toward the inside of the rotor. 
The rotor shaft 1A is rotatably supported by two bearings 4a, 4b which are 
spaced apart from each other and disposed on an inner surface of a front 
cover 3 arranged adjacent to one of side plates or a front plate 2. 
The front plate 2, a cylinder 5, and the other side plate or a rear plate 6 
are axially stacked one upon another, and define a working space 7 in 
cooperation with the outer surface of the rotor 1. 
The working space 7 is divided into three working spaces 7a, 7b, and 7c by 
a vane 8, which is received in the vane grooves 1a of the rotor 1. 
A rear cover 12 is provided on the rear side of the rear plate 6, and the 
rear cover 12, rear plate 6, cylinder 5, front plate 2, and front cover 3 
are clamped together by a bolt 9. A low pressure suction chamber 13 is 
defined between the rear plate 6 and the rear cover 12. 
The vane 8 includes a projection 8a at a longitudinally middle portion 
thereof, which is accommodated in the internal space or the recess 1 of 
the rotor 1, and the projection 8a is formed with a cylindrical sliding 
surface 8b extending in a direction substantially perpendicular to the 
longitudinal direction of the vane 8 or the vane grooves 1a. 
A slider 10 is disposed within the projection 8a in a manner to make 
sliding contact with the sliding surface 8b, and is permitted to 
reciprocate along this surface 8b. The slider 10 includes at its middle 
portion a bearing 10a which supports a slider pin 11 extending from the 
rear plate 6 in a cantilever-fashion, thereby allowing the slider 10 to 
rotate around the slider pin 11. 
The slider pin 11 has an axis parallel to the rotational axis of the rotor 
shaft 1A and radially spared from the same, and is secured to the rear 
plate 6. 
The inner surface of the cylinder 5 is shaped to have a contour 
substantially equal to the locus drawn by the tips of the vane 8 when the 
latter is rotated, and a fine clearance is maintained therebetween for 
assuring an oil film sealing. 
As shown in FIGS. 1 and 3, the vane 8 is formed with suction passages 8c 
having a depth smaller than the plate thickness of the vane 8. Each 
suction passage 8c has at one end thereof, an aperture 8e opening to a 
rotationally rear surface 8d of the vane 8 contacting with the vane groove 
1a of the rotor 1, and at the other end thereof, an opening part 8g 
opening at a rear side surface 8f of the vane 8 making sliding contact 
with the rear plate 6. 
The rear plate 6 is formed, as shown in FIG. 4, with a first suction port 
6a, which overlaps with the opening 8g of the suction passage 8c in a 
predetermined angular range, and penetrates the rear plate 6 from a side 
surface thereof adjacent to the suction chamber 13 to the other side 
surface adjacent to the end surface 1b of the rotor 1. 
The rear plate 6 is further formed with a second suction port 6b, which 
penetrates the rear plate 6 and opens at its one end to the suction 
chamber 13 and at the other end to the working space 7. The second suction 
port 6b is so located that a communication with the working space 7 can be 
maintained until a maximum volume of the space has been reached (as 
indicated in FIG. 1 with numeral 7b). Further, as shown in FIGS. 4-7, the 
second suction port 6b has a construction which makes it possible to 
establish or interrupt the communication between the suction chamber 13 
and the working space 7 by means of a solenoid valve 14. The breadth of 
the second suction port 6b, measured in the rotational direction of the 
rotor 1, is determined to be smaller than the thickness of the vane 8 for 
preventing two working spaces divided by the vane 8 from communicating 
with each other through the suction port 6b. It is possible to provide a 
plurality of second suction ports 6b for reducing suction resistance. 
An electromagentic clutch 15 is provided on an end of the rotor shaft 1A 
remote from the rotor 1. When the clutch 15 is in the "ON" state, a 
driving force is transmitted from a pulley 16. 
When electric current is supplied to the solenoid valve 14 with the second 
suction port 6b maintained in an open state as shown in FIGS. 4 and 5, the 
compressor performs, as shown in FIG. 8, a suction stroke from a state (b) 
shown in FIG. 8 to a state (f) of maximum volume where the second suction 
port 6b is closed by a portion of the vane 8 located on the rear side of 
the working space, and then compression and exhaust strokes follows, 
thereby assuring a maximum compression volume or displacement. 
On the other hand, when an electric current supply to the solenoid valve 14 
is interrupted and the second suction port 6b is brought to a "close" 
state, the compressor performs, as shown in FIG. 9, a suction stroke from 
a state (b) to a state (c) where the first suction port 6a communicates 
with the suction passage 8c of the vane, and thereafter, an adiabatic 
expasion in a closed space is carried out until the state (f). Thereafter, 
the compression and exhaust stroke are performed. Since the suction stroke 
is performed only until reaching the state (c), the exhaust volume or 
displacement of the compressor is significantly decreased in comparison 
with the case of FIG. 8. 
As mentioned above, in this embodiment, it is possible to vary an exhaust 
volume of the compressor by an on or off switching of the solenoid valve 
14. 
In this embodiment, the minimum exhaust volume can be decreased as compared 
with the case where the inlet port is opened to the inner peripheral 
surface of the cylinder (housing) as proposed in Japanese Utility Model 
Unexamined Publication No. 57-58791, resulting in a wider control range 
for the exhaust volume. 
Namely, as shown in FIG. 10A, it is possible to finish suction stroke 
before the volume of the working space becomes maximum, even in the case 
where the first suction port 6a' is opened to the inner peripheral surface 
of the cylinder or to a surface of the side plate which is exposed to the 
working space. In this case, however, the suction stroke starts when a 
front vane vf reaches the starting edge or rear edge of the suction port 
6a' as indicated by two-dot chain lines, while it finishes when a rear 
vane vr has passed the ending edge or front edge of the suction port 6a' 
as indicated by solid lines. Accordingly, denoting the angle of opening 
area of the suction port 6a' with respect to the rotation center of the 
rotor by .theta.p, and the angle between the vanes vf and vr (i.e. the 
pitch angle in a circumferential direction of the vanes) by .theta.v, the 
suction stroke is carried out in an angular range of .theta.p + .theta.v. 
Although it is possible to somewhat decrease the opening angle .theta.p of 
the suction port 6a', it is impossible to change the vane circumferential 
pitch angle .theta.v. Consequently, the suction stroke is performed in the 
range of at least the angle .theta.v, and the minimum volume of the 
working space can not be made smaller than that determined by the angle 
.theta.v (the volume being indicated by numeral 7' in FIG. 10A). Thus, the 
volume control range is narrower. 
On the other hand, in the above described embodiment, a suction stroke 
starts when the opening 8g of the suction passage 8c initiates to 
communicate with the suction port 6a of the rear plate or side plate 6, as 
indicated by two-dot chain lines in FIG. 10B, while it finishes when the 
communication has been cut off as indicated by solid lines. Accordingly, 
denoting the angle of the opening 8g of the suction passage with respect 
to the rotation center of the rotor by .theta.s, and the opening angle of 
the suction port 6a by .theta.p, the suction stroke is carried out in an 
angular range of .theta.s + .theta.p as measured in a direction of the 
rotor rotation. The opening angle .theta.s, which corresponds to the width 
of the opening 8g of the suction passage 8c measured on the surface of the 
vane contacting with side plate 6, can be made sufficiently small as 
compared with, the vane circumferential pitch angle .theta.v. 
Consequently, the range of the suction stroke, .theta.s + .theta.v, can be 
made significantly small by sufficiently decreasing the opening angle 
.theta.p of the first suction port 6a, as indicated by numeral 7 in FIG. 
10B. Thus, in controlling the volume to be discharged the minimum volume 
or displacement of lower level can be attained and hence a wide range of 
volume control can be effected. 
Further, in the above-described embodiment, the communication between the 
suction passage 8c and the working space 7 is interrupted just after a 
compression stroke starts as shown by (g) in FIG. 8, since the aperture 8e 
of the suction passage 8c is moved or drawn into the interior of the rotor 
1 together with the vane 8. As a result, in a compression stroke in the 
working space 7, the high pressure working gas is prevented from leaking 
into the suction passage 8c and causing an internal leakage of gas into 
the lower pressure side in the next suction stroke. 
Next, a second embodiment of the invention will be described by referring 
to FIGS. 11-13. In the first embodiment, the suction ports 8c for 
providing a communication between the first suction port 6a and the 
working space is formed only in the plate thickness of the vane 8. The 
second embodiment is different from the first embodiment in this point. 
Namely, in the second embodiment, a vane 8 is formed with grooves 8h in a 
rotationally rear surface 8d of the vane which makes sliding contact with 
one of the surfaces of each rotor groove 1a, with the grooves 8h 
constituting openings of a suction passage communicating with the working 
space. Further, the rotor 1 has axially extending grooves 1e formed in a 
surface 1d of each vane groove 1a which is in contact with the sliding 
surface 8d of vane 8. Each axial groove 1e has an opening portion 1f 
opening at a rear end surface 1b of the rotor 1 which makes sliding 
contact with the side plate or the rear plate 6, and forms a part of the 
suction passage. 
On the other hand, rear plate 6 is formed, as shown in FIG. 13, with a 
first suction port 60a penetrating the rear plate 6 from a suction chamber 
(not shown) to a surface of the plate 6 making a sliding contact with the 
end surface of the rotor. First suction port 60a extends circumferentially 
so as to overlap with the rear end opening 1f of the axial groove 1e of 
the rotor 1 in a predetermined angular range in a rotational direction of 
the rotor. 
Further, as shown in FIG. 13, there is formed a second suction port 6b, 
which is controlled to open or close by a solenoid valve 14 similarly to 
the first embodiment. 
In the second embodiment, when the second suction port 6b is in a closed 
state, the suction stroke in the working space is carried out only in a 
positional range where the groove 8h and the groove 1e each forming a part 
of the suction passage overlap with each other and the rear end opening 1f 
of the groove 1e overlaps with the first suction port 60a of the rear 
plate 6, thereby performing a partial load operation. The principle in 
controlling the volume is similar to that of the first embodiment 
described by referring to FIGS. 6-9. In this embodiment, however, since it 
is not required to provide the openings 8g in the rear end surface of the 
vane 8, there is no deterioration in sealing performance is caused, which 
may be possibly caused by a substantially decreased vane thickness due to 
the provision of the openings 8g. Thus, a volume control function may be 
achieved without lowering the cooling capacity of the compressor in a full 
load condition. 
Next, a third embodiment of the invention will be described by referring to 
FIGS. 14-18. In the first embodiment, the rear plate 6 is formed with a 
second suction port 6b which opens at a side surface of the plate 6 
directly exposed to the working space 7, and this second suction port can 
be switched to open or close for controlling the volume in two steps. In 
the third embodiment, a multi-step volume control can be achieved by an 
arrangement different from that of the first embodiment. 
In the third embodiment, a rear plate or side plate 61 includes a first 
suction port 61a, a second suction port 61b and a third suction port 61c 
arranged circumferentially one behind another and each opening at the rear 
plate surface contacting with the rotor 1. The first suction port 61a also 
opens at the rear plate surface on the suction room chamber side and 
communicates with the low pressure suction room 13 at all times, while the 
second and third suction ports 61b, 61c do not directly open to the 
suction room but communicate with the suction room 13 only through 
passages 61f and 61g, respectively, the passages 61f and 61g opening to 
the suction room 13 through opening portions 61d and 61e, respectively. 
The passages 61f, 61g are opened or closed by solenoid valves 141a, 141b. 
The states of the solenoid valves 141a and 141b in FIG. 14 are as shown in 
FIGS. 15 and 16, respectively. Namely, the solenoid valve 141a is in an 
electric current "ON" state, and the solenoid valve 141b is in an electric 
current `OFF` state, and accordingly, the second suction port 61b is in an 
`open` state and the third suction port 61c is in a `close` state. 
Similarly to the second suction port 6b of the first embodiment shown in 
FIG. 4, these suction ports of the third embodiments are so located as to 
have no direct communication with the working space 7. Further, the third 
suction port 61c is so arranged as to maintain communication with the 
suction passage 8c of the vane 8 until the volume of the working space 
becomes maximum. 
FIG. 17 shows an operation of the compressor when the latter is in a state 
shown in FIG. 14. The first suction port 61a or the second suction port 
61b communicates with the suction passage 8c of the vane 8 from a state 
(b) to a state (d) for performing a suction stroke, and then an expansion 
stroke is performed in a closed state until a state (f) corresponding to 
the maximum volume is reached. Thereafter, a compression stroke and an 
exhaust stroke follow. 
FIG. 18 shows an operation of the compressor which is in a state where both 
of the solenoid valves 141a and 141b are energized or in an `ON`, 
condition, and the first, second and third suction ports 61a, 61b and 61c 
are all communicating with the suction chamber 13. A suction stroke is 
performed from a state (b) to a state (f) corresponding to the maximum 
volume, and thereafter a compression stroke and an exhaust stroke follow. 
In this case, a maximum exhaust volume is obtained. 
Further, in the case where the solenoid valve 141a in FIG. 14 for opening 
and closing the second suction port 61b is also de-energized or made `OFF` 
and the first suction port 61a alone communicates with the suction room 
13, the compressor is operated in the same manner as that shown in FIG. 9. 
In this case, the suction stroke is achieved only from the state (b) to 
the state (c), resulting in a minimum exhaust volume of the compressor. 
As mentioned above, according to the third embodiment, the volume of the 
compressor can be varied in three steps. 
A fourth embodiment of the invention is described below by referring to 
FIGS. 19-22. In this embodiment, the volume control of the compressor is 
achieved continuously or steplessly. 
The compressor shown in FIG. 19 is the same as that of the first embodiment 
with respect to the structure located on the front side (left side in the 
figure) of the rear plate 62. The rear plate 62 in the fourth embodiment 
is formed with a ring-like groove 62a in a surface thereof on which an end 
surface lb of the rotor 1 slides. In this groove 62a is inserted a 
ring-like member 20 with its inner circumferential surface mounted on the 
inner circumferential surface of the groove. The thickness of the 
ring-like member 20 is substantially equal to the depth of groove 62a, and 
the outer diameter of the member 20 is smaller than the outer diameter of 
the groove 62a, thereby forming a ring-like space between the outer 
circumferential surface of the member 20 and the outer circumferential 
surface of the groove 62a. This ring-like space is divided into two spaces 
62b and 62c by two partition members 21 and 22 which are screwed secured 
to the rear plate 62 and the ring-like member 20, respectively, by bolts. 
To the ring-like member 20 is secured a stopper pin 23, which limits the 
rotation angle of the ring like member 20 in one direction. 
The ring-like member 20 is formed with gear teeth 20a on the inner 
peripheral surface thereof. A pinion gear 24 meshes with the gear teeth 
20a and is rotationally driven by a servo-motor 25 located outside of a 
rear cover 121. 
The divided space 62b defined by the front end surface (as viewed in the 
rotational direction of the rotor 1) of the partition member 21 fixed to 
the side plate 62 and the rear end surface of the partition member 22 
rotatable together with the ring-like member 20 communicates with a 
suction chamber 131 through a plurality of communication holes 62d at all 
times. The other divided space 62c does not communicate with the suction 
chamber 131. 
The circumferential length of the space 62b can be changed by rotating the 
ring-like member 20 and the partition member 22 integrated with the member 
20 as shown in FIGS. 22A, 22B and 22C. As a result of this length change, 
the volume to be suctioned into the working space can be continuously 
changed. 
The operations of the compressor in the states shown in FIGS. 22A, 22B and 
22C are substantially identical with those shown in FIGS. 9, 17 and 18, 
respectively. 
The servo-motor 25 for driving the ring-like member 20 and the partition 
member 22 is controlled by a controller 26 based on an evaporator fin 
temperature, a refrigeration cycle signal indicating an operational state 
of refrigeration cycle such as suction pressure, and a positional signal 
showing a position of the volume control means. 
According to the fourth embodiment, the volume can be changed continuously. 
Although, in the above described embodiments, the invention is applied to 
rotary vane compressors including a rotor of cantilever type and a vane 
penetrating the rotor, the invention may also be applied to compressors of 
different types As shown, for example, in FIGS. 23 and 24. 
In the embodiment shown in FIG. 23, the rotary compressor includes two 
vanes 81, each of which does not penetrate (or extend through) the rotor 
111, and two grooves in the rotor each having a bottom chamber 111c at one 
end thereof. The back pressure in the bottom chambers 111c push the vanes 
towards the outside of the rotor and bring the vanes into contact with the 
cylinder 5. The concept of the third embodiment is applied to this 
compressor. A rear plate (not shown) is formed with a first, a second, and 
a third suction ports 611a, 611b, and 611c, and each of the two vanes 81 
has a suction passage 81c. 
In the embodiment shown in FIG. 24, the rotary vane type compressor 
includes two vanes 82, each of which penetrates the rotor 111 and is 
freely movable in the rotor in a longitudinal direction of the vane 
without any restriction and with both ends of the vane contacting the 
cylinder 5. The two vanes are arranged perpendicular to each other. The 
concept of the first embodiment is applied to this compressor. The rear 
plate (not shown) is formed with a first and a second suction ports 611a 
and 611b, and each of the two vanes is formed with suction passages 82c 
near the both ends thereof. 
As mentioned above, the invention may be applied to all pipes of rotary 
vane type compressors regardless of the number of vanes, or the motion 
form of the vanes. 
Although, in the above described embodiments, all of the suction passages 
formed in the vane, or the vane and the rotor have opening portions 
opening at the rear side, and the suction ports associated with these 
suction passages are formed on the rear plate side, it is possible in 
principle to form these suction passages and suction ports on the front 
side or on both the rear and front sides. 
According to the invention, a variable volume rotary is obtained compressor 
of rotary vane type, wherein the volume can be adjusted over a wide range, 
thereby significantly decreasing the frequency in the operation of the 
magnet clutch in a low heat load operating condition, preventing 
acceleration and deceleration shock feelings caused by the magnet clutch 
operations. Further, an internal leakage of the high pressure gas into a 
lower pressure side may be prevented by providing the volume control 
means. By virtue of these features, it is possible to minimize the 
performance deterioration of the compressor in a full capacity operating 
condition, and to attain a maximum cooling capacity in a high heat load 
operating condition.