Compression capacity control apparatus for swash plate compressor

A swash plate compressor is disclosed which is provided with a compression capacity control apparatus capable of returning an output pressure of a high pressure chamber of one cover to a low pressure chamber of the same cover. The control apparatus comprises a delivery chamber which is communicated with a high pressure chamber of the other cover, isolated from the high pressure chamber of said one cover and connected to a delivery conduit. The control apparatus also comprises a compression capacity control passageway providing communication between the delivery chamber and the low pressure and high pressure chambers of said one cover. A valve member is disposed in the control passageway to interrupt the communication between the delivery chamber and the high pressure chamber of said one cover while establishing communication between the low pressure and high pressure chambers of said one cover.

BACKGROUND OF THE INVENTION 
The present invention relates to a multi-cylinder swash plate compressor 
and, more particularly, to an apparatus capable of controlling such a 
compressor into a part-capacity operation mode, as distinguished from the 
usual full-capacity operation mode. 
In a swash plate compressor with multiple cylinders, it is desirable, and 
possible, to render some of the cylinders ineffective to lower the 
compression capacity or output pressure in response to a decrease in load. 
A swash plate compressor usually includes low pressure and high pressure 
chambers for temporary storage of a gas which are formed in each of front 
and rear covers mounted on a cylinder block. It will therefore be easy to 
arrange the compressor such that a compressed gas discharged into the high 
pressure chamber in one of the covers is fed back into the lower pressure 
chamber, thereby halving the entire capacity of the compressor. However, 
since the high pressure chambers in both the front and rear covers are 
connected to a common delivery conduit and to each other, the gas from the 
high pressure chamber in one cover tends to be communicated back to the 
low pressure chamber of the other cover during a part-capacity operation 
mode of the compressor. An implement heretofore known for coping with such 
a tendency comprises a check valve which is located in the delivery 
passageway between the high pressure chambers in the opposite covers. The 
check valve prevents the high pressure gas from flowing in the reverse 
direction while the compressor is operated in the part-capacity mode. This 
is not acceptable because, in a full-capacity operation mode, the check 
valve creates resistance to the flow of the delivery pressure which 
results in significant falls of efficiency and frequent failures. 
SUMMARY OF THE INVENTION 
In a swash plate compressor having a cylinder block, front and rear covers 
mounted to the opposite ends of the cylinder block, and each being formed 
with a low pressure chamber for temporarily storing an incoming gas, a 
high pressure chamber for temporarily storing an outgoing gas and a 
delivery conduit for delivering the outgoing gas; a compression capacity 
control apparatus embodying the present invention comprises a delivery 
chamber formed in one of the front and rear covers to be communicated with 
the high pressure chamber in the other cover, isolated from the high 
pressure chamber in said one cover and connected with the delivery 
conduit. A compression capacity control passageway provides communication 
between the delivery chamber, high pressure chamber and low pressure 
chamber each in said one cover. A valve member is disposed in the control 
passageway and operable to block the communication between the delivery 
chamber and the high pressure chamber of said one cover while unblocking 
the communication between the high pressure chamber and the low pressure 
chamber of said one cover. 
In accordance with the present invention, a swash plate compressor is 
provided with a compression capacity control apparatus capable of 
returning an output pressure of a high pressure chamber of one cover to a 
low pressure chamber of the same cover. The control apparatus comprises a 
delivery chamber which is communicated with a high pressure chamber of the 
other cover, isolated from the high pressure chamber of said one cover and 
connected to a delivery conduit. The control apparatus also comprises a 
compression capacity control passageway providing communication between 
the delivery chamber and the low pressure and high pressure chambers of 
said one cover. A valve member is disposed in the control passageway to 
interrupt the communication between the delivery chamber and the high 
pressure chamber of said one cover while establishing communication 
between the low pressure and high pressure chambers of said one cover. 
It is an object of the present invention to provide a new compression 
capacity control apparatus for a swash plate compressor which eliminates 
all the drawbacks inherent in the prior art apparatus. 
It is another object of the present invention to provide a new compression 
capacity control means for a swash plate compressor which permits the 
compressor to operate in a part-capacity mode with a minimum of power loss 
and without any sacrifice to the efficiency attainable with a 
full-capacity operation mode. 
It is another object of the present invention to provide a generally 
improved compression capacity control apparatus for a swash plate 
compressor. 
Other objects, together with the foregoing, are attained in the embodiments 
described in the following description and illustrated in the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While the compression capacity control apparatus for a swash plate 
compressor of the present invention is susceptible of numerous physical 
embodiments, depending upon the environment and requirements of use, 
substantial numbers of the herein shown and described embodiments have 
been made, tested and used, and all have performed in an eminently 
satisfactory manner. 
Referring to FIGS. 1-3, a swash plate compressor includes a pair of 
cylinder blocks 10 and 12 which are connected together at one end in a 
predetermined relative position. A front cover 14 is rigidly mounted to 
the other end of the cylinder block 10 with a cylinder head 16 held 
therebetween. Likewise, a rear cover 18 is rigidly mounted to the other 
end of the cylinder block 12 through a cylinder head 20. A drive shaft 22 
extends along the axis of the aligned cylinder blocks 10 and 12 and 
protrudes from the front cover 14, as shown in FIG. 1. The drive shaft 22 
is in driven connection with a drive source (not shown). 
A swash plate 24 is mounted on the drive shaft 22 at an angle thereto and 
disposed in a crank case 26 which is defined by the cylinder blocks 10 and 
12. The swash plate 24 and drive shaft 22 are rotatably supported by the 
cylinder blocks 10 and 12 through thrust bearings 28 and 30 and radial 
bearings 32 and 34. 
A double acting piston 36 is bored at its axially central portion to 
straddle the peripheral edge of the swash plate 24. The opposite walls of 
the bore are formed with hemispherical ball pockets 38 and 40 in which 
balls 42 and 44 are received, respectively. The piston 36 hold the axially 
opposite ends of the swash plate 24 through the balls 42 and 44 and shoes 
46 and 48, which are engaged with the respective balls 42 and 44. The 
cylinder blocks 10 and 12 are provided with cylinder bores which may be 
three in number as designated by the reference numerals 48, 50 and 52 in 
FIG. 2. The cylinder bores 48, 50 and 52 extend in parallel with the drive 
shaft 22 at equally spaced locations along the circumference of the 
cylinder blocks 10 and 12. The piston 36 is slidably received in each of 
the cylinder bores 48, 50 and 52. With this arrangement, when the swash 
plate 24 oscillates on the drive shaft 22 as the latter is driven for 
rotation, it causes each piston 36 into reciprocal movement within the 
corresponding cylinder bore through the associated shoes 46 and 48 and 
balls 42 and 44. 
The cylinder bores 48, 50 and 52 are individually closed at the opposite 
ends by the cylinder heads 16 and 20 and communicated at an intermediate 
portion to the crank case 26. 
Annular walls 62 and 64 are formed integrally with the front and rear 
covers 14 and 18, respectively. The annular wall 62 defines a low pressure 
chamber 54 thereinside and a high pressure chamber 58 thereoutside. 
Likewise, the annular wall 64 defines a low pressure chamber 56 and a high 
pressure chamber 60 on the opposite sides thereof. The low pressure 
chambers 54 and 56 are communicated with the cylinder bores 48, 50 and 52 
through inlet openings 66 and 68 which are formed in the cylinder heads 16 
and 20, respectively. The high pressure chambers 58 and 60, on the other 
hand, are communicated with the cylinder bores 48, 50 and 52 through 
outlet openings 70 and 72 which are formed in the cylinder heads 16 and 
20, respectively. The inlet openings 66 and 68 and the outlet openings 70 
and 72 are blocked by delivery valves 74 and 76 which are located on the 
axially outer ends of the respective cylinder heads 16 and 20. 
A suction conduit 80 is communicated to the low pressure chamber 56 in the 
rear cover 18 through a coupling 78 which is fit in the rear cover 18. The 
low pressure chamber 56 is communicated to the low pressure chamber 54 in 
the front cover 14 by an inlet passageway 84 defined by openings which are 
formed through walls 80 and 82 (see FIG. 2) of the cylinder blocks 10 and 
12 and the cylinder heads 16 and 20. 
A delivery chamber 86 is formed in the rear cover 18. The delivery chamber 
86 is communicated with the high pressure chamber 58 in the front cover 14 
by an outlet passageway 92 defined by openings which are formed through 
walls of the cylinder blocks 10 and 12 and the cylinder heads 16 and 20. 
However, communication of the delivery chamber 86 with the high pressure 
chamber 60 in the rear cover 18 is prevented by a wall 94 which extends 
from the rear cover 18. A delivery conduit 98 is connected with the 
delivery chamber 86 through a coupling 96 fit in the rear cover 18. 
Lubrication oil is stored in a reservoir 100 which is defined below the 
crank case 26 (see FIG. 2). The peripheral edge of the swash plate 24 is 
dipped in the lubricant. 
A compression capacity control apparatus embodying the present invention is 
associated with the compressor described above and generally designated by 
the reference numeral 102. The control apparatus 102 functions to control 
intercommunication between the low pressure chamber 56, high pressure 
chamber 60 and delivery chamber 86 all of which are formed in The rear 
cover 18. In the illustrated embodiment, the rear cover 18 is formed with 
a vertical bore or capacity control passageway 104 and three openings 106, 
108 and 110. A cap 112 closes the upper end of the capacity control 
passageway 104. The opening 106 communicates the low pressure chamber 56 
to the passageway 104, the opening 108 communicates the high pressure 
chamber 60 to the passageway 104, and the opening 110 communicates the 
delivery chamber 86 to the passageway 104. 
A valve member 114 is slidably received in the control passageway 104. The 
valve member 114 is in the form of a pilot pressure-operated valve spool 
formed with lands 116 and 118 at its opposite sides. The lands 116 and 118 
define upper and lower pilot pressure chambers 120 and 122, respectively. 
When the pressure in the lower pilot pressure chamber 122 is higher than 
the pressure in the upper pilot pressure chamber 120, the valve spool 114 
is urged to the position shown in FIG. 1 where it blocks the communication 
between the low pressure chamber 56 and the high pressure chamber 60 with 
the lower land 118 while communicating the high pressure chamber 60 to the 
delivery chamber 86. As the pressure in the upper pilot pressure chamber 
120 rises beyond the pressure in the lower pilot pressure chamber 122, the 
valve spool 114 blocks the communication between the high pressure chamber 
60 and the delivery chamber 86 with the upper land 116 while communicating 
the low pressure chamber 56 to the high pressure chamber 60. 
Pilot conduits 124 and 126 are connected at one end to the pilot pressure 
chambers 120 and 122, respectively. The other end of each pilot conduit 
124 or 126 is communicable to the suction conduit 80 or the delivery 
conduit 98 through a solenoid-operated directional control valve 128. A 
control circuit 130 supplies the directional control valve 128 with a 
control signal to switch it from one position to the other. When applied 
to an automotive air conditioning system, the control circuit 130 will 
produce control signals in response to various parameters such as engine 
speed, intake vacuum, pressure in the suction conduit 80 or the delivery 
conduit 98 and temperature inside or outside the passenger compartment. 
While the directional control valve 128 is in a normal position, the upper 
pilot pressure chamber 120 is supplied with the low pilot pressure from 
the suction conduit 80 and the lower pilot pressure chamber 122 with the 
high pilot pressure from the delivery conduit 98. Under this condition, 
the valve spool 114 is moved upwardly to communicate the high pressure 
chamber 60 to the delivery chamber 86 and discommunicate the low pressure 
chamber 56 from the high pressure chamber 60 (see FIG. 4). Thus, in either 
the front or rear cover, a gas sucked in the cylinder bore 48, 50, 52 
through the low pressure chamber 54, 56 is compressed and communicated to 
the high pressure chamber 58, 60. The compressed gas from each cylinder 
bore is combined together in the delivery chamber 86. In this manner, all 
the cylinders are allowed to operate effectively in a full-capacity mode. 
When the control circuit 130 feeds a control signal to the directional 
control valve 128, the latter is switched to communicate the high pilot 
pressure from the delivery conduit 98 to the upper pilot pressure chamber 
120 and the low pilot pressure from the suction conduit 80 to the lower 
pilot pressure chamber 122. Then, the valve spool 114 is caused to stroke 
downward so that, in the rear cover 18, the high pressure chamber 60 
becomes discommunicated from the delivery chamber 86 while the low 
pressure chamber 56 is communicated to the high pressure chamber 60 (see 
FIG. 5). The compressed gas in the high pressure chamber 60 is now fed 
back to the low pressure chamber 56 via the control passageway 104. This 
makes only the cylinders on the front side effective thereby halving the 
total capacity of the compressor, i.e., establishes a part-capacity mode. 
Referring to FIG. 6, another embodiment of the present invention is shown 
which differs from the first embodiment in the provision of a rotary 
three-way valve 132 for the capacity control apparatus 102 and a safety or 
relief valve 134. The valve 132 comprises a body 136 mounted on the rear 
cover 18 and a rotatable valve member 138. The body 138 is formed with 
three passageways 140, 142 and 144 while the rotary valve member 138 is 
positioned at the junction between the three passageways 140-144. The 
valve member is rotatable 90.degree. to control the communication between 
the passageways 140-144. While the valve member 138 is moving from one 
position to another, the high pressure chamber 60 will become isolated 
from the others to have the pressure elevated therein. The relief valve 
134 passes such an elevated pressure into the delivery chamber 86. 
In each of the foregoing embodiments, the delivery chamber 86, control 
passageway 104 and valves 114 and 132, which form an essential part of the 
present invention, are commonly associated with the rear cover 18. It will 
be apparent, however, that they can be associated with the front cover 14 
without affecting the effects. 
In summary, it will be seen that the present invention provides a 
compression capacity control apparatus which permits a swash plate 
compressor to operate in a part-capacity mode with a minimum of power loss 
and without affecting the efficiency expected in a full-capacity mode. It 
will also be seen that the capacity control apparatus of the invention 
hardly involves the possibility of failure. 
Various modifications will become possible for those skilled in the art 
after receiving the teachings of the present disclosure without departing 
from the scope thereof.