Variable delivery compressor

A variable delivery compressor having therein a plurality of compression chambers is adapted for compressing a refrigerant gas of a cooling circuit. The compressor has a first delivery chamber communicating with the compression chambers by way of a fixedly arranged valve and a second delivery chamber communicating with the compression chambers by way of a movably arranged delivery valve. This movable valve is formed to include a base portion, a plurality of reed portions formed to radially extend from the outer circumference of the base portion and arranged to face delivery ports, and at least one protrusion formed to radially extend from the outer circumference of the base portion for suppressing the warp of the base portion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a variable delivery compressor adapted 
mainly for use in a vehicular air-conditioning system. 
2. Description of the Prior Art 
As a vehicular air-conditioning system, there has been conceived a 
construction in which a compressor is run in an increased delivery state, 
when the temperature of a passenger's compartment is high as at an initial 
stage of the operation that a cooling load exerted upon the compressor is 
higher than the cooling capacity, but is run in a decreased delivery state 
when the compartment temperature drops to a point where the cooling load 
becomes lower than the cooling capacity. That variable delivery compressor 
is a swash plate type variable delivery compressor (as is disclosed in 
Japanese Patent Laid-Open No. 57-73877), which can alternately switch its 
delivery between 100% and 50%. Although not shown herein, a spool is 
axially movably mounted in the bore of a rear housing so that a delivery 
valve is pressed onto a valve plate by opening a first control valve to 
apply a delivery pressure to the back of the spool whereby the compression 
at the rear side is effective to perform a run of 100%, and so that the 
delivery valve is kept apart from the valve plate by closing the first 
control valve and opening a second control valve to apply a suction 
pressure to the back of the aforementioned spool whereby the compression 
at the rear side is made ineffective to switch the run to 50%. 
As shown in FIG. 9 herein, the compressor described in the above has its 
delivery valve 57 constructed of a base portion 57a and reed portions 57b. 
When the delivery valve 57 slightly leaves a valve plate 4 in the 
decreased delivery state, as shown in FIG. 10, a refrigerant gas of a 
delivery chamber 20 flows into a shaft bore 4a (i.e., the suction system) 
so that the base portion 57a and the reed portions 57b are sucked toward 
the valve plate 4 until their leading ends strike eventually the valve 
plate 4. These strikes roughen the surface of the valve plate 4 such that 
shortage of sealing occurs sensing a drop in the volumetric efficiency in 
the run of 100% capacity in which the base portion 57a is intended to shut 
off the shaft bore 4a, as shown in FIG. 11. Especially in the case whether 
spool 44 vibrates in the axial direction when the aforementioned delivery 
valve 57 is attracted, the strikes become particularly intense so as to 
increase the wear of the valve plate 4 thereby to reduce the sealing 
efficiency. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a variable 
delivery compressor which is capable of eliminating any incomplete sealing 
between its delivery chamber and suction system in the run of its cooling 
capacity at 100%, thereby to improve the volumetric efficiency and the 
durability of its delivery valve. 
The present invention provides a variable delivery compressor which has its 
delivery valve made liable to warp at its protrusions so that the shocks 
caused when the protrusions impinge upon a valve plate can be softened. 
The present invention also provides a variable delivery compressor which 
allows the leading ends of the protrusions of the delivery valve to 
impinge upon the valve plate in a face-to-face relationship thereby to 
reduce the wear on the same protrusions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be described in the following in connection with 
one embodiment, in which it is embodied as a swash plate type variable 
delivery compressor of a vehicular air-conditioning system, with reference 
to FIGS. 1 to 7. The front and rear ends of cylinder blocks 1 and 2 are 
respectively closed by front and rear housings 5 and 6 through valve 
plates 3 and 4, respectively. The two cylinder blocks 1 and 2, the two 
housings 5 and 6 and the two valve plates 3 and 4 are connected together 
by an appropriate number of bolts 7. At the connection portion of the 
cylinder blocks 1 and 2, there is formed a swash plate chamber 8 in which 
a swash plate 10 secured to a drive shaft 9 is received. The drive shaft 9 
extends axially through shaft bores 1a and 2a which are bored through the 
centers of the two connected cylinder blocks 1 and 2. In the shaft bores 
1a and 2a of the cylinder blocks 1 and 2, respectively, there are 
press-fitted radial bearings 11 and 12 for rotatably supporting the 
aforementioned drive shaft 9. Moreover, thrust bearings 13 and 14 are 
sandwiched between the cylinder blocks 1 and 2 and the swash plate 10. 
Each of the cylinder blocks 1 and 2 is formed with five cylinder bores 15 
extending in parallel with the drive shaft 9 and arranged at five radial 
positions around the drive shaft 9. Pistons 16 fitted in those cylinder 
bores 15 are engaged with the swash plate 10 through bearing members 
composed of balls 17 and shoes 18. Due to these engagements, the rotation 
of the swash plate 10 causes reciprocal sliding movements of the pistons 
16 within the cylinder bores 15. 
Within the front and rear housings 5 and 6, there are formed delivery 
chambers 19 and 20, which are arranged in the central portions of the 
housings 5 and 6, respectively, and substantially annular suction chambers 
21 and 22 which are arranged to encircle the respective delivery chambers 
19 and 20. Of these, the delivery chamber 19 formed at the front side has 
an annular shape, whereas the delivery chamber 20 has a generally circular 
shape, as better seen in FIG. 3. The suction chambers 21 and 22 are 
connected with the swash plate chamber 8 by way of suction passages 23 and 
24 which can also act as through-holes through which the aforementioned 
bolts 7 axially extend. The swash plate chamber 8 per se is fluidly 
connected to a suction flange 25 which is attached in the vicinity of the 
connecting portion of the cylinder blocks 1 and 2. 
As shown in FIG. 4, delivery passages 26 and 27 are formed in the cylinder 
blocks 1 and 2. The delivery passage 26 extends from that surface of the 
cylinder block 1 which contacts the valve plate 3, to the connecting 
portion of the cylinder blocks 1 and 2, whereas the delivery passage 27 
extends from the contacting surface of the cylinder block 2 with the valve 
plate 4 to the connecting portion of the cylinder blocks 1 and 2. These 
two delivery passages 26 and 27 are respectively and fluidly connected to 
a delivery flange 28, which is attached in the vicinity of the connecting 
portion of the two cylinder blocks 1 and 2, by way of connecting passages 
29 and 30. The delivery passages 26 and 27 are fluidly connected at their 
other ends to the delivery chambers 19 and 20, respectively, by way of 
connecting bores 31 and 32 which are formed in the valve plates 3 and 4, 
respectively. It should be understood that the delivery chambers 19 and 20 
have outwardly extended portions, respectively, at which they are fluidly 
connected to the delivery passages 26 and 27 (as better seen from FIG. 3). 
Moreover, the connecting passage 30 is equipped with a check valve 33 
which is set to close the connecting passage 30 when the delivery chamber 
20 at the rear side is kept under a low pressure condition and to open the 
passage 30 when the delivery chamber 20 is kept under a high pressure 
condition. 
The front and rear valve plates 3 and 4 are respectively bored with suction 
ports 34 and 35 for connecting the cylinder bores 15 and the suction 
chambers 21 and 22, respectively, and delivery ports 36 and 37 for 
connecting the cylinder bores 15 and the delivery chambers 19 and 20, 
respectively. The suction ports 34 and 35 are provided with suction valves 
38 and 39, respectively, and the delivery ports 36 and 37 are provided 
with delivery valves 40 and 41, respectively. The delivery valves 40 and 
41 are made deformable, but their deforming amounts are restricted within 
respective given limits by valve guards 42 and 43, respectively. The front 
delivery valve 40 together with the valve guard 42 is fixedly attached to 
the valve plate 3. On the other hand, the rear delivery valve 41 together 
with the valve guard 43 is movable between a normal closed position where 
the valve 41 closes the delivery ports 37 and an open position where the 
valve 41 opens the delivery ports 37. 
More specifically, the delivery valve 41 and the valve guard 43 are fixed 
to a cylindrical spool 44 by means of a bolt 46 and a washer 45 so that 
the valve 41, the valve guard 43 and the spool 44 are arranged to be 
concentric with one another. The spool 44 is axially slidably received in 
a circular recess 47 which is defined by an inwardly projecting wall 6a of 
the rear housing 6. The aforementioned delivery valve 41 is composed of, 
as shown in FIGS. 3 and 5, an annular base portion 41a, a plurality of 
(e.g., five in the present embodiment) reed portions 41b radially 
extending at a forming angle .alpha. to face the respective delivery ports 
37, and a plurality of (e.g., five in the present embodiment) protrusions 
41c radially extending between any two adjoining reed portions 41b and 
constituting the feature of the present invention. In other words, all the 
reed portions 41b and the protrusions 41c are made integral with the base 
portion 41a of the delivery valve 41 in a manner to outwardly project in 
radial direction. Each of the protrusions 41c has a generally rectangular 
front shape having a relatively large length L. On the other hand, the 
aforementioned valve guard 43 is formed to have the same shape as that of 
the delivery valve 41 except the aforementioned protrusions 41c. 
It should also be understood that the four members assembled by means of 
the bolt 46 are prevented from any rotation by a positioning pin 48 which 
is anchored in the wall 6a of the rear housing 6. In order to insert the 
positioning pin 48, one of the protrusions 41c of the delivery valve 41 
and the valve guard 43 are formed with holes 41d and 43a, respectively. 
The shaft bore 2a formed in the center of the rear cylinder block 2 is 
fluidly connected to the central portion of the delivery chamber 20 by way 
of a shaft bore 4a which is formed through the central portion of the 
valve plate 4. In the rear end portion of the shaft bore 2a, there is 
fitted a cylindrical spring holder 49 in which there is received a spring 
50 for urging the delivery valve 41 at all times toward its open position. 
The spring holder 49 is formed, in its bottom, with a through-hole 49a 
through which the delivery chamber 20 communicates with the swash plate 
chamber 8 in the state wherein the delivery valve 41 is kept in its open 
position. However, this communication is blocked to keep the seal 
therebetween when the delivery valve 41 is moved to the normal closed 
position to bring its annular base portion 41a (i.e., the hatched portion 
appearing in FIG. 5) into contact with the valve plate 4. 
The rear housing 6 is formed, at its central portion, with a pressure inlet 
hole 51 for introducing a pressure onto the back of the spool 44. The 
pressure inlet hole 51 communicates with the delivery flange 28 by means 
of a high pressure conduit 53 having therein a first electro-magnetic 
valve 52, and with the suction flange 25 by means of a low pressure 
conduit 55 having therein a second electro-magnetic valve 54. It should be 
noted here that the opening and closing controls of the first and second 
electro-magnetic valves 52 and 54 are conducted by the action of a 
pressure switch (although not shown) which is arranged in a part of the 
air-conditioning system such that they can be operated in response to a 
change in the temperature of the vehicular compartment. 
The operation of the variable delivery compressor having the construction 
thus far described will now be explained hereinafter. 
While the compressor is stopped, the rear delivery valve 41 is moved by the 
action of the spring 50 to its open position, and the check valve 33 
closes the connecting passage 30, as shown in FIG. 1. Moreover, the first 
electro-magnetic valve 52 is opened, and the second electro-magnetic valve 
54 is closed. 
When the compressor is driven in this state, the front side of the 
compressor immediately starts its normal compressing operation. Since the 
rear delivery valve 37 is opened, however, the refrigerant gas merely 
flows in a free and reciprocal manner between the respective cylinder 
bores 15 and the delivery chamber 20. Since the delivery chamber 20 and 
the swash plate chamber 8 are short-circuited via the by-pass aperture 
provided by the the shaft bores 2a and 4a, moreover, the rear side of the 
compressor performs no compressing operation and idles. Thus, at the start 
of the operation, the compressor exerts only 50% of its full compression. 
When the delivery pressure is applied by the normal compressing operation 
of the front side of the compressor to the back of the spool 44 through 
the high pressure conduit 53 (At this stage, the first electro-magnetic 
valve 52 is kept in its open state whereas the second electro-magnetic 
valve 54 is kept in its closed state), the rear delivery valve 41 is urged 
against the action of the spring 50 toward its closed position, in which 
the valve 41 is pressed against the rear valve plate 4, to close the 
respective delivery ports 37 of the cylinder bores 15 and the shaft bores 
2a and 4a. Accordingly, the rear side of the compressor also commences its 
normal compressing operation. Consequently, the check valve 33 is pressed 
toward its open position by the compressed gas delivered from the rear 
side of the compressor. As a result, the connecting passage 30 is opened 
so that the compressor is run to exert its entire compression performance 
of 100% (as shown in FIG. 2). 
Next, the steady state operation of the compressor will be explained in the 
following. Under a high load, i.e., when the cooling load is high, the 
compressor is run in the cooling capacity of 100%. 
When the cooling load applied to the air-conditioning system is reduced, 
namely, when the inside of the vehicular compartment is cooled to reduce 
the suction pressure, a pressure switch (although not shown) is turned on 
to close the first electro-magnetic valve 52 and open the second 
electro-magnetic valve 54. As a result, a low suction pressure acts upon 
the back of the spool 44 so that the rear delivery valve 41 is moved by 
the action of the spring 50 apart from the valve plate 4. Thus, the rear 
delivery port 37 is opened. Accordingly, the compressing operation of the 
rear side of the compressor becomes ineffective as at the aforementioned 
state. That is, the operation of the compressor is switched to the state 
where the compressor exerts 50% of its full compression performance. At 
this state, the check valve 33 is urged to its closed position by the 
delivery pressure delivered from the front side of the compressor. As a 
result, the connecting passage 30 is closed to prevent the compressed 
delivery gas from leaking from the front side to the rear side. 
In the aforementioned decreased capacity state from the performance of 100% 
to the performance of 50%, the delivery valve 41 is brought away from the 
valve plate 4, as has been described hereinbefore. At this stage, the high 
pressure gas flows from the delivery chamber 20 into the shaft bore 4a of 
the valve plate 4 to urge the delivery valve 41 toward the valve plate 4. 
At this stage, moreover, since the base portion 41a of the delivery valve 
41 has its inner circumference restricted by the washer 45, it is deformed 
from its outer circumference. Since the protrusions 41c are formed to 
integrally extend from the outer circumference of the base portion 41a, 
however, their leading ends first impinge upon the valve plate 4. It 
should be appreciated that the following three advantages can be obtained 
partly because the length L of those protrusions 41c continues to have a 
sufficient value, as better seen from FIGS. 5 and 6, and partly because 
the angle .theta. of the protrusions 41c with respect to the valve plate 4 
upon the impingement is small: 
(1) The protrusions 41c can warp so that the shocks due to the impingement 
can be absorbed. This shock absorbing effect is prominent especially in 
case the spool 44 axially vibrates while it is being moved. At this stage, 
the reed portions 41b also warp. Of these, the reed portions 41b during 
the delivery (i.e., the reed portions 41b in half of the number of the 
cylinders) can be prevented from impinging upon the valve plate 4. 
Moreover, no serious problem arises regarding wear around the delivery 
ports 37 because of an action which is similar to that described in the 
following advantage (2). 
(2) The impingement of the leading ends of the protrusions 41c is effected 
in a face-to-face relationship so that wear can be reduced. Even if wear 
is caused, as shown in FIG. 7, moreover, the surface of the valve plate 4 
facing the base portion 41a is not roughened so that the sealing 
efficiency of the base portion 41a is not deteriorated. 
(3) Since the warp of the base portion 41a of the delivery valve 41 is 
small, the durability of the valve 41 can be improved. 
It should be noted that the present invention can also be practised by the 
following embodiments: 
(A) It is desirable that the length L of the protrusions 41c of the 
delivery valve 41 be two or more times as large as the maximum floating 
distance D of the delivery valve 41, as better seen from FIG. 6. 
(B) It is also desirable that the protrusions 41c be provided, as shown in 
FIG. 5, where the forming angle .alpha. is 60 degrees or more. 
(C) As shown in FIG. 8, the leading ends of the protrusions 41c or the reed 
portions 41b are made straight. 
(D) The present invention can be applied not only to the aforementioned 
swash plate type compressor but also to a variable delivery compressor of 
the crank or waffle type. 
As has been described in detail hereinbefore, according to the present 
invention, since the delivery valve is formed with not only reed portions 
but also protrusions protruding from the base portion thereof, the 
incomplete sealing beteen the delivery chamber and the suction system 
during the entire capacity run of the compressor can be eliminated to 
improve the volumetric efficiency and the durability of the delivery 
valve. 
Although the present invention has been described by way of example only 
with reference to the preferred embodiments thereof, it is to be 
understood that variations or modifications may be easily made by anybody 
of ordinary skill in the art without departing from the scope of the 
invention which is defined by the appended claims.