JPH01190976A - Variable displacement swash plate-type compressor - Google Patents

Abstract

PURPOSE:To surely further promptly control a discharge capacity by providing a pressure limiting value, which prevents a pressure in a control pressure chamber from excessively increasing, in a spool forming the control pressure chamber. CONSTITUTION:A spool 30 is arranged slidably in the axial direction in a cylinder part 65 of a rear cylinder block 6 and in a cylinder part 135 of a rear housing 13. A control pressure chamber 200 is formed between these spool 30 and rear housing 13, and a pressure limiting valve 300 is provided in the spool 30. Thus because a pressure in the control pressure chamber 200 can be prevented from rising more than necessary, the spool 30 can be driven in a good response. Accordingly, a delivery capacity can be surely further promptly controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to capacity control of a swash plate compressor.
For example, it is effective when used as a refrigerant compressor for an automobile air conditioner.

[Background of the invention]

As a method for continuously varying the discharge capacity of a swash plate type pressure ll1i machine, the present inventors previously proposed a system for continuously variable control of the reciprocating stroke of a piston.

This causes the swash plate to be swingably and displaceably engaged with the shaft, and the inclination angle of the shaft and the swash plate's 11
J! The oblique angle and the center point position of the swash plate are continuously varied by displacement of the spool.

In the variable displacement compressor previously proposed by the present inventors, the spool is displaced by adjusting the pressure in a control pressure chamber formed on the back surface of the spool. The spool is displaced by increasing or decreasing the pressure in the control pressure chamber on the back of the spool, thereby making the tilt angle and center of rotation of the swash plate variable.

However, according to the experimental studies conducted by the present inventors, it has been confirmed that when the spool is displaced from the maximum discharge capacity state of the compressor to the reduced state, there is a state in which the spool does not shift with good response.

The inventors of the present invention conducted various studies regarding the cause of this problem, and found that it is due to the fact that sufficient pressure is required in the control pressure chamber in order to reliably displace the spool. In other words, the differential pressure between the high pressure side pressure and the low pressure side pressure of the compressor is used as the signal pressure for displacing the spool, but the compressor high pressure side pressure and low pressure side pressure are It changes depending on the situation.

In order to be able to reliably displace the spool regardless of the fluctuations caused by the compressor operation, it is necessary to set the driving force applied to the spool by the signal pressure to a sufficient value.

As a result of making the pressure introduced into the control pressure chamber sufficient in this way, if you try to lower the pressure in the control pressure chamber and displace the spool toward the control pressure chamber, the pressure in the control pressure chamber will decrease. It will take a lot of time to reduce it. the result,
When attempting to move the spool from the maximum displacement position, a situation arises in which the spool valve does not immediately move despite the switching of the signal pressure by the control valve.

[Problem to be solved by the invention]

The present invention was devised in view of the above points, and is designed to ensure sufficient signal pressure required to displace the spool, and to move the spool from its maximum displacement position with good responsiveness. The purpose is to

[Structure and Operation] In order to achieve the above object, the swash plate compressor according to the present invention is provided with a pressure limiting valve that prevents the pressure in the control chamber from becoming excessive.

With this pressure limiting valve, in the compressor of the present invention, the signal pressure in the control pressure chamber is maintained at a pressure sufficient for driving the spool, and at the same time, the signal pressure is prevented from becoming excessively high than that required for driving the spool. Therefore, in the compressor of the present invention, the spool can be reliably displaced and the capacity of the compressor can be adjusted satisfactorily regardless of the condition of the compressor.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a longitudinal sectional view of a variable displacement swash plate compressor. The aluminum alloy front housing 4, front side plate 8, suction valve 9, front cylinder block 5, rear cylinder block 6, suction valve 12, rear side plate 11, and rear housing I3 are integrally fixed by through bolts (not shown). It forms the outer shell of the compressor.

The cylinder block 5.6 has five cylinders 64 (641 to 645) as shown in FIG.
4 are formed parallel to each other. A shaft 1, which rotates under the driving force of an automobile engine (not shown), is rotatably supported by a front housing 4 and a front cylinder block 5 via bearings 2 and 3, respectively. Further, the thrust force applied to the shaft 1 (force acting in the left direction in the figure) is received by the front cylinder block 5 via the thrust bearing 15, and the movement of the shaft 1 in the right direction in the figure is restricted by the retaining ring 16. . Note that the retaining ring weight 6 is retained by an annular groove formed in the shaft 1.

The rear shaft 40 connects to the spool 3 via the bearing 14.
0 and is rotatably supported. The thrust force acting on the rear shaft 40 (the force acting in the right direction in the figure) is generated by the thrust bearing 1.
The rear shaft 4o is received by the spool 30 via the rear shaft 4o, and is prevented from coming off the spool 30 by a retaining ring I7. This retaining ring is also locked in an annular groove formed in the rear shaft 40. The spool 30 includes a cylindrical portion 65 of the rear cylinder block 6 and a cylindrical portion 13 of the rear housing 13.
5 so as to be slidable in the axial direction.

A spherical part 107 is formed in the center of the swash plate 10, and a spherical support part 405 fixed to the end of the rear shaft 40 is disposed on this spherical part 107. It is supported by a support section 405.

A slit 105 is formed on the side surface of the shaft 1 of the swash plate 1O, and a flat plate portion 16 is formed on the end surface of the shaft 1 on the swash plate 1O side.
5 is formed. And the flat plate part 165 is sulin)
By being disposed in surface contact with the inner wall of the shaft 105, the rotational driving force applied to the shaft 1 is transmitted to the swash plate 10.

Furthermore, shoes 18 and 19 are slidably disposed on both sides of the swash plate 10. On the other hand, a piston 7 is slidably disposed within the cylinder 64 of the front cylinder block 5 and the cylinder 64 of the rear cylinder block. As described above, the shoes 18 and 19 are slidably attached to the swash plate lO. Furthermore, the shoes 18 and 19 are rotatably engaged with the inner surface of the piston 7. Therefore, the rocking motion accompanying the rotation of the swash plate 10 is transmitted to the piston via the shoes 18 and 19 as a reciprocating motion. The shoes 18 and 19 are formed so that their outer surfaces lie on the same spherical surface when assembled on the swash plate 10.

A long groove 166 is provided in the flat plate portion 165 of the shaft 1, and a bottle through hole is formed in the swash plate 10. After the flat plate portion 165 of the shaft 1 is arranged in the slit 105 of the swash plate 10, it is locked in the bottle through hole and the long groove 166 of the shaft l by the pin 80 and the retaining ring. The inclination of the swash plate changes depending on the position of the pin 80 in this long groove 166, and as the inclination changes, the center of the swash plate (the spherical part
The position of the spherical support portion 405) of No. 7 also changes. That is, in the second working chamber 60 on the right side in FIG. 1, even if the inclination of the swash plate lO changes and the stroke of the piston 7 changes, the top dead center of the piston 7 on the working chamber 60 side remains almost unchanged and remains dead. Long grooves 166 so that substantially no increase in volume occurs.
is provided. On the other hand, in the working chamber 50 on the left side in the figure, the top dead center of the piston 7 changes as the inclination of the swash plate changes, so the dead volume also changes.

In this example, as described above, the long groove 166 is formed in such a shape that even if the inclination angle of the swash plate 10 changes, the top dead center position of the piston 7 on the working chamber 60 side hardly changes. .

Therefore, strictly speaking, the long groove 166 has a curved shape, but in actual formation, it can be approximated by a substantially straight long groove. Furthermore, in this example, by forming the long grooves 166, the flat plate portion 1
In order to prevent the shape of the groove 65 from becoming too large, the long groove 166 is
is arranged on the axis of the shaft 1. In this way, the long groove 166 is formed on the axis of the shaft 1, and the flat plate part 165
It is particularly effective to reduce the size of the swash plate type compressor in which the flat plate portion 165 is disposed inside the piston 7.

Reference numeral 21 in the figure is a shaft sealing device, which prevents refrigerant gas and lubricating oil from leaking to the outside along the shaft 1. Reference numeral 24 in the figure opens into the working chamber 50.60, and the discharge chamber 90.60.
The discharge port 24 is opened and closed by the discharge valve 22 . The discharge valve 22 has a valve holder 23
It is also fixed to the front side plate 8 and the rear side plate 11 by bolts (not shown). In the drawing, reference numeral 25 denotes a suction port that communicates the working chamber 50.60 and the suction chamber 72.74, and is opened and closed by the suction valve 9 and the suction valve 12.

Reference numeral 400 in the figure is a control valve for controlling the internal pressure of the control pressure space 200, and is controlled by a control circuit 500.

One end of the control valve 400 is connected to the rear suction space 74 by a low pressure introduction passage 97. The other end is connected to the discharge space 93 via the throttle and high pressure introduction passage 96, and is also connected to the control pressure chamber 200 via the control pressure passage 98. When the control valve 400 is not energized, the space 200
and discharge space 93 are connected via a diaphragm 99.

A discharge space 90 on the front side in FIG. It is led to the discharge port 95. Since the discharge port 92 and the discharge port 95 are connected by external piping, the discharge space 90 and the discharge space 9
The three internal pressures are the same pressure. Further, the intake space 72 on the front side is guided by the intake passage 71 to the intake space 70 formed in the central part of the housing G, and similarly the intake space 74 on the rear side is guided to the intake space 70 by the intake passage 73. . In addition, the symbols 51, 52, 53゜54.55.56 in the figure
is the 0 ring.

Additionally, the spool 30 has a pressure limiting valve 3 as shown in FIG.
00 is arranged. That is, the spool 30 has a communication passage 3 that communicates the control pressure chamber 200 and the suction pressure space 74.
01 is formed, and this communication passage 301 is opened and closed by a pressure limiting valve body 302. The pressure limiting valve body 302 has a tapered sealing surface, and this sealing surface is attached to the valve seat portion 3 formed in the middle of the communication passage 301.
03, opening and closing of the communication passage 301 is switched. The pressure limiting valve body has an extension 3 at its tip.
30 is formed, and this extension part 330 connects to the through hole 33.
1 protrudes toward the suction space 74 side. Furthermore, the valve body 30
A spring 333 is disposed on the back side of the valve 2, and this spring presses the valve body 302 toward the valve seat 303. The spring 333 is held by a locking piece 340 fixed to the spool 30. Also, this locking piece 34
A communication hole 341 is opened at 0, and together with the communication passage 301, the control pressure space 200 and the suction pressure space 74 are communicated with each other.

The distal end 320 of the above-mentioned extension part 330 is such that the valve body 302 is connected to the valve seat 3.
03, the amount protrudes from the mold part 305 of the minute amount spool. Therefore, when the spool is displaced to the left by the amount shown in FIG.
0 comes into contact with the side plate 11. As a result, the valve body 302 can be removed from the valve seat 303 as the extension portion 330 and the side plate 11 come into contact with each other.

The operation of the compressor with the above configuration will be described.

When an electromagnetic clutch (not shown) is connected and driving force from the engine is transmitted to shirt +-1, the compressor is started.

When the compressor drive signal is input to the controller 500,
The controller 500 outputs an electric signal to the control valve to connect the low pressure introduction passage 97 and the signal pressure passage 98. Therefore, is it restricted at startup? Suction chamber 74 in II pressure chamber 200
Each time the pressure inside is introduced. Therefore, in this state, no pressure difference occurs before and after the spool 30.

That is, at the time of startup, no load is applied through the support portion 107 in the direction that makes the swash plate lO tilt.

When the shaft 1 starts rotating in this state, the rotation of the shirt l-1 causes the piston 7 to reciprocate via the swash plate 10. As the piston 7 moves back and forth, the refrigerant is sucked, compressed, and discharged within the working chamber 50, 60.

However, in this case, a force based on the pressure difference between the rear working chamber 60 and the front working chamber 50 is applied to the swash plate 10 via the piston 7 and the shoes 18, 19. In particular, since the swash plate 10 is swingably supported by the spherical support part 405 and receives the rotational force of the shaft l by fitting the slit 105 and the flat plate part 165, the force applied to the piston 7 acts as a moment in the direction of decreasing the inclination angle of the swash plate lO.

For example, when the pin 80 is located on the axis X in FIG. 2, the piston disposed in the first cylinder space 641 does not generate a moment that changes the inclination angle with respect to the swash plate lO. However, a rotational moment is generated from the pistons 7 disposed in the second to fifth cylinder spaces 642, 643, 644, 645 in a direction that reduces the inclination angle of the swash plate 10. This rotational moment FiXRi
is received by the moment FpmXr generated around the pin 80 (as shown in FIG. 4). Further, the rotational moment generated by this piston 7 is
The pressing force of FBx will be applied to 05.

That is, when the control valve introduces suction pressure into the control pressure chamber 200, the spherical support portion 405 and the spool 30 are displaced to the right in the figure. As a result, the swash plate 10 reduces its angle of inclination. However, the swash plate 10 is connected to the long groove 166 of the shaft 1.
Since the swash plate 10 is regulated by the pin 80, the inclination of the swash plate 10 is reduced and the ball portion 405 at the center of the swash plate 10 is regulated by the pin 80.
A force is applied to the right direction in the figure to move the ball portion 405 to the right. (rear shirt via the spherical support part 405) 40
The force acting in the right direction in the figure is transmitted to the spool 30 via the thrust bearing 16, and the spool 30 is connected to the rear housing 1.
The compressor moves until it hits the bottom of No. 3, and the discharge capacity of the compressor becomes minimum.

Then, the refrigerant gas sucked through a suction port (not shown) (connected to the evaporator of the refrigeration cycle) enters the central suction space 70, then passes through the suction passages 71 and 73.
Enter the front and rear suction chambers 72 and 74. after that,
During the suction stroke of the piston 7, air is sucked into the working chamber 50, 60 from the suction port 25 via the suction valve 12. The sucked refrigerant gas is compressed in the compression stroke, and when it is compressed to a predetermined pressure, the discharge valve 22 is pushed open from the discharge port 24 and the discharge chamber 9 is discharged.
It is discharged to 0.93. High-pressure refrigerant gas is discharged through the discharge passage 91
．． 94 and is discharged from discharge ports 92 and 95 to a condenser (not shown) of the refrigeration cycle.

At this time, since the first working chamber 50 on the front side has a large dead volume, the compression ratio is smaller than that of the second working chamber 60 on the rear side, and the pressure of the refrigerant gas in the first working chamber 50 is lower than that in the discharge space 90. The pressure is lower than the pressure (the discharge pressure of the second working chamber 60 on the rear side is led), and the suction and discharge of refrigerant gas in the first working chamber 50 on the front side is not performed.

When starting the compressor, the compressor discharge capacity is set to the minimum capacity as described above. However, when the compressor capacity required by the refrigeration cycle is high, the control valve 400 shuts off the control pressure passage 98 and the low pressure introduction passage 97. Here, in this example, the control pressure chamber 200 is connected to the control pressure chamber 200 through a throttle 99゛.
It communicates with the high pressure introduction passage 96. Therefore, in this state where the connection with the low pressure introduction passage 97 is cut off, the influence of the discharge pressure received from the high pressure introduction passage 96 on the control pressure chamber 200 increases. Therefore, the pressure within the control pressure chamber 200 increases.

Therefore, the force acting on the spool 30 to the left in the figure due to the pressure difference (due to the pressure difference between the control pressure chamber 200 and the suction space 74) gradually increases as the compressor rotates. When this force overcomes the force pushing the spherical support portion 405 to the right in the figure, the spool 30 gradually begins to move to the left in the figure.

Then, due to the action of the long groove 166 of the shaft 1 and the pin 80, the swash plate 10 increases its inclination while moving its center of rotation (spherical support portion 405) to the left in the figure. As the pressure inside the control pressure chamber 200 further increases, the spool 30 moves to the left in the figure until its shoulder 305 touches the rear side plate 11, achieving the maximum capacity state. This is the situation shown in FIG. In the state shown in FIG. 1, the refrigerant gas is sucked into the suction port 1- (not shown) in the central suction space.

70 and flows into suction chambers 72 and 74 through suction passages 71 and 73, respectively. In the suction stroke, the air enters the working chambers 50 and 60 from the suction port 25 through the suction valves 9 and 12, respectively, and is then compressed with the displacement of the piston 7, and flows from the discharge port 24 through the discharge valve 22 into the discharge space. 90 and 93, and discharge passages 91 and 94.
The gas is discharged from the discharge ports 92 and 95, and is merged with the external piping. In this state, both the working chamber 50 and the working chamber 60 perform the action of sucking in and discharging refrigerant gas.

A solid line a in FIG. 5 is a diagram showing the relationship between the piston stroke and the compressor capacity of the variable displacement swash plate compressor according to the present invention. In the capacity control system according to this example, by changing the inclination of the swash plate 10, the stroke of the piston 7 is changed and the center position of the swash plate 10 is also changed. There is almost no increase in Therefore, as shown by the - dotted chain line, the discharge capacity gradually decreases according to the piston stroke. Conversely, in the front side first working chamber 50, the dead volume increases as the piston stroke decreases, and as the dead volume increases, the compression ratio decreases, and the discharge capacity rapidly increases as shown by the broken line C in FIG. Decrease.

Then, when the maximum pressure (discharge pressure) in the first working chamber 50 on the front side becomes lower than the discharge pressure in the second working chamber 60 (point d in FIG. 5), the pressure in the first working chamber 50 on the front side becomes lower than the discharge pressure in the second working chamber 60. The suction and discharge actions are no longer performed, and the refrigerant gas suction, compression, and discharge actions are performed only in the rear working chamber 60.
The piston stroke d at which the working chamber 50 does not take in or discharge refrigerant gas is the maximum piston stroke,
Suction pressure Ps (kg/cj・abs), discharge pressure Pd
(kg/cffl - a b s), adiabatic index k of refrigerant gas, piston radius R1 pi, then P s ・(πR"L)"=P d - (z R2 ・(
It is expressed by L-d))', and the capacitance in this case is.

Here, Ps=3kg/c++1-abs, Pb=16k
g/cta-abs, K=1.14,
d=0.77L b=38.5(%).

Note that this piston stroke is almost proportional to the amount of movement of the spool 30, and the spool 3 in FIG.
If 0 is the state in which it goes all the way to the right in the figure, and 2 is the state in which it is all the way to the left in the figure, you can see the relationship between the amount of spool movement and the compressor capacity as shown in Figure 5. Loc I
! ,).

Now, the solid line part a in FIG. 5 is the capacity change characteristic of the compressor according to the present invention. In the movement distance e - e section of the spool 30, the capacity actually changes as tJia, and the thin line r in the figure Although the compressor capacity changes linearly with respect to the spool movement, the slope is steep and controllability is poor.
In the spool displacement amount e~0 section, the capacity is the solid line a in the figure.
2, the gradient is gentler than that of the thin line f, and the controllability is particularly excellent at low capacity.

Next, when the cooling load decreases, the control circuit 500 in FIG. 1 alternately switches the control valve 400 between the ON state and the OFF state (for example, duty ratio control).
The capacity can be reduced by gradually lowering the internal pressure of the space 200 from the discharge pressure and moving the spool 30 to the right in FIG. 1. In order to obtain the minimum capacity, the pressure inside the space 200 is communicated with the suction space 74 by the control valve 400 to maintain the suction pressure.

In this way, the compressor capacity is variably controlled according to the amount of displacement of the spool, but in order to actually maintain the displacement of the spool 30 at an appropriate position, a sufficient holding force must be applied to the spool 30. It is a premise.

Next, the thrust load applied to the spool 30 will be explained in more detail. FIG. 6 shows the state of the load applied to the spool 30. In the figure, FPSi indicates the sum of the forces holding down the swash plate 10 due to the compression of the piston 7. Further, FPN in the figure indicates the force applied to the pin 80. Furthermore, Ps indicates the pressure within the suction chamber 74, and Pc indicates the pressure within the control pressure chamber 200.

Furthermore, the thrust loads generated by these pressures Ps and Pc are indicated by FPS and FPC. Furthermore, FB in the figure,
FS and FO are the friction force between the spherical support part 107 and the swash plate lO, and m between the shaft l and the rear shaft 40, respectively.
The W force and the frictional force between the spool 30 and the housing inner surface 135 are shown.

As is clear from Fig. 6, in order to displace the spool 30 from a state in which it is operating at a certain capacity in a direction in which the amount of displacement further increases, in other words, in the left direction in the figure, FPS i + FPS < FPN + FPC + FB + FS + F.
O... (1) must hold true.

When selecting the diameter of the spool 30, as shown in Fig. 7, if the diameter is too small, the maximum capacity cannot be secured even if the discharge pressure Pd is introduced into the control pressure chamber 200, and conversely, if the diameter is too large. and the pressure change in the control room required to change the capacity between 01 and 02 because the dynamic range is too wide]
11 is as small as ΔPc, which makes delicate capacitance adjustment difficult.

Therefore, the diameter of the spool 30 needs to be designed to an appropriate size.

When focusing only on the pressure relationship, the control spool load FSP
is the thickest (this is when the pressure inside the first working chamber 501 on the front side of the piston is the discharge pressure Pd and the pressure in the second working chamber 60 on the rear side is the suction pressure Ps, and at this time, the pressure in the front side first working chamber 501 is the suction pressure Ps. The working load FPSi' is the number of pistons n (pieces)
, if the piston diameter is Dp, then FPS, '-nxπ(Dp)'' /4
' is FPC' = π (Ds)2/4X (Pd-I'
s)...(3) Therefore, from equation (1), the friction force at each part is calculated as FPS'.

It is ignored as a small value compared to FPC', and the spool 30
If FPSi' = FPC' is required to maintain , then Ds = fiV·Dp.

That is, it is desirable that the diameter of the spool 30 be approximately equal to or larger than the diameter of the piston.

By setting in this way, it is possible to avoid a situation where the spool diameter becomes too small as shown in FIG. 7, resulting in poor spool operation.

However, depending on the operating state of the compressor, a pressure greater than the pressure required to maintain or drive the spool may be maintained in the control pressure chamber 200. this is,
This is especially common when the compressor is at its maximum capacity.

In other words, when the compressor is set to maximum capacity, the control pressure chamber 2
The low pressure pipe 97 connecting the low pressure side space and the low pressure side space is closed, and the control pressure chamber 200 is communicated with the high pressure chamber 93 via the high pressure side pipe 96. Then, when the signal pressure Pc in the control pressure chamber 200 rises to approximately the discharge pressure Pd, the force FPC acting on the spool becomes greater than the load required to displace the spool 30.

If an attempt is made to move the spool 30 in a direction that reduces the capacity of the compressor in this state, the pressure within the control pressure chamber 200 will not drop to a low enough pressure to allow the displacement in a short period of time. It can happen.

However, since the compressor of this example is provided with the spool 32° pressure limiting valve 300, it is possible to immediately displace the spool 30 even in such a case.

In the compressor of this example, when the spool 30 is at its maximum capacity position, the valve body 300 of the pressure limiting valve 300 is connected to the communication passage 3.
01 will be opened. Therefore, in this state, the high pressure within the control pressure chamber 200 is released to the suction pressure chamber 74 side. As a result, the spool 30 is displaced in a direction that reduces the compressor capacity, that is, to the right in the figure. When the spool 30 is displaced, the valve body tip 320 of the pressure limiting valve 300 is separated from the side plate, and the valve body 302 closes the valve seat 303.

By repeating the above-described operation, if the spool valve 30 maintains the maximum capacity position of the compressor, the control pressure chamber 20
The pressure within 0 will be maintained at the minimum pressure necessary to maintain it. In other words, in the compressor of this example, even if the spool 30 is at one maximum capacity position of the compressor, excessive pressure within the control royal family 200 will not be maintained.

Therefore, in the compressor of this example, when the capacity of the compressor is to be reduced from the maximum capacity state, the spool 30 immediately starts to be displaced by the operation of the control valve 400.

In the above-described embodiment, when a solenoid valve is used as the control valve 400, only the conduction is interrupted between the control pressure passage 98 and the low pressure introduction passage 97, and the connection between the control pressure passage 98 and the high pressure introduction passage 9 is interrupted.
6 was always in communication with the control valve 400 through the throttle.
The passages 96° and 97 may be switched by.

Furthermore, a three-way valve that switches between the control pressure passage 98, the high pressure introduction passage 96, and the low pressure introduction passage 97 may be employed as the control valve 400. In this example.

When the solenoid valve is in the ON state, the control pressure passage 98 and the high pressure introduction passage 96 communicate with each other via the throttle 99. Also, the solenoid valve is OFF.
In state F, the control pressure passage 98 communicates with the low pressure introduction passage 97.

Furthermore, the control valve 400 may be replaced with a solenoid valve, and a diaphragm valve that utilizes a pressure difference may be used.

FIG. 8 shows an example using a diaphragm valve. It is known that the cooling load required for the refrigeration cycle is reflected in the suction side pressure of the compressor. When the load required from the refrigeration cycle is large and a large capacity of the compressor is drawn down, the suction pressure increases. On the other hand, when the load required by the refrigeration cycle is small and the discharge capacity of the compressor is small, the cooling pressure in the suction chamber 74 decreases. In the embodiment shown in FIG. 8, this pressure fluctuation is sensed by the diaphragm 440 of the control valve 400, and the ball valve body 441 opens and closes the signal passage 98 based on the displacement of the diaphragm 440.

When the compressor is required to have a large discharge capacity, the pressure in the suction pressure chamber 74 becomes high, and as a result, the diaphragm 8
Displaced upward in the figure. Therefore, the valve body 441 receives the biasing force of the spring 442 and comes into contact with the valve cover 443. In this state, the control pressure chamber 200 is connected to the discharge pressure chamber 93 through the throttle 99.
It will only communicate with Therefore, the pressure within the control pressure chamber 200 increases, and the spool 30 is displaced to the left in the figure.

Conversely, when the pressure within the suction pressure chamber 74 decreases, the differential pressure generated between both surfaces of the diaphragm 440 decreases. Therefore, the diaphragm 440 receives the urging force of the spring 448.
is displaced downward, and the valve body 441 is separated from the valve cover 443 via the rod 449. Therefore, the low pressure passage 97 and the signal pressure passage 98 are brought into communication with each other, and the control pressure chamber 200
The pressure inside is released to the suction pressure chamber 74 side.

In this manner, in the embodiment shown in FIG. 8, the position of the spool 30 is accurately controlled based on the pressure within the suction pressure chamber 74. Also in this example, since the pressure limiting valve 300 is disposed on the spool 30, the control pressure chamber 200
There will be no situation where the internal pressure increases more than necessary.

In the embodiment shown in FIG. 8, the shirt I-1 has a structure in which it passes through the spherical support portion 405. As a result, the shaft 1 is rotatably supported at both ends, making it possible to support the shaft 1 more reliably.

Furthermore, in the above example, the pressure limiting valve was incorporated into the spool 30, but the pressure limiting valve was incorporated into the side play 1-11.
Alternatively, it may be attached to the rear housing 13 side. In any case, the pressure limiting valve is sufficient as long as it prevents the pressure in the control pressure chamber 200 from exceeding the pressure required to hold the spool 30, and its location is not necessarily limited to the spool 30.
It is not limited to 0.

〔Effect of the invention〕

As explained above, in the compressor of the present invention, the pressure limiting valve is provided to prevent the pressure in the control pressure chamber from increasing more than necessary, so that the spool can be driven with good responsiveness. Therefore, the compressor of the present invention must have the excellent effect of being able to control the discharge capacity reliably and quickly.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the first embodiment of the compressor of the present invention;
The figure is a sectional view taken along the line ■-■ in Figure 1, Figure 3 is a sectional view showing the pressure limiting part of the compressor shown in Figure 1, and Figure 4 is an explanation showing the pressure state of the compressor shown in Figure 1. Figure 5 is an explanatory diagram showing the relationship between the spool displacement amount of the compressor shown in Figure 1 and the compressor capacity; Figure 6 is an explanatory diagram showing the pressure state applied to the spool of the compressor shown in Figure 1; The figure is an explanatory diagram showing the relationship between the pressure in the control pressure chamber and the compressor discharge capacity, and FIG. 8 is a sectional view showing another example of the compressor of the present invention. ■...Shaft, 5.6...Housing, 7...
Piston, 10... Swash plate, 30... Spool, 40
...Rear shaft 300...Pressure limiting valve, 400
···solenoid valve.

Claims (8)

[Claims] (1) A cylinder block having a cylinder chamber inside, a shaft rotatably supported within the cylinder block, a swash plate pivotally connected to the shaft and rotating integrally with the shaft, and within the cylinder chamber. a piston that is slidably disposed and reciprocates within the cylinder chamber in response to the rocking motion of the swash plate; a working chamber for suctioning, compressing, and discharging; a supporting part disposed coaxially with the shaft and swingably supporting the central point position of the swash plate; a spool to be displaced; a control pressure chamber formed in a portion of the spool on the opposite side of the support portion and configured to displace the spool in the axial direction of the shaft according to internal pressure; and a control pressure chamber that is supplied to the control pressure chamber. The spool controls the signal pressure supplied to the control pressure chamber so that the spool displaces the center point position of the swash plate in the axial direction of the shaft and also displaces the inclination angle of the swash plate. A variable capacity swash plate compressor, comprising: a control valve; and a pressure limiting valve that limits a value of signal pressure supplied to the control pressure chamber to a predetermined value or less. (2) The control valve controls switching of the signal pressure supplied to the control pressure chamber between the suction side pressure and the discharge side pressure of the compressor, and the control valve controls the discharge side pressure of the compressor. When introduced into the pressure chamber, the spool displaces the support portion in a direction that increases the inclination angle of the swash plate based on the pressure in the control pressure chamber, and the control valve adjusts the suction side pressure of the compressor to the control pressure chamber. When introduced into the piston, the support portion and the spool are displaced in a direction smaller than the inclination angle of the swash plate due to the compression reaction force of the piston, and a working chamber is formed on one end surface side of the piston in the working chamber. In the above, the piston is capable of moving forward to a predetermined position for sucking, compressing, and discharging fluid regardless of the tilt angle displacement of the swash plate, and the working chamber is formed on the other side of the piston behind the working chamber. The variable capacity swash plate compressor according to claim 1, wherein the variable displacement swash plate compressor is configured such that dead space in the working chamber increases depending on the inclination angle of the swash plate. (3) The variable displacement swash plate compressor according to claim 1 or 2, wherein a plurality of the cylinder chambers are formed in the cylinder block so as to be parallel to each other. . (4) The control valve includes a control pressure passage that communicates with the control pressure chamber, a high pressure introduction passage that introduces the discharge side pressure of the compressor, a low pressure introduction passage that introduces the suction pressure side pressure of the compressor, and the control pressure The variable capacity according to any one of claims 1 to 3, further comprising a switching valve that selectively switches a passage to either the high pressure introduction passage or the low pressure introduction passage. Swash plate type compressor. (5) The control pressure chamber communicates with the discharge pressure of the compressor via a predetermined flow resistance, and the control valve communicates with the control pressure passage communicating with the control pressure chamber, and the suction pressure side pressure of the compressor. Claims 1 to 4 include a low pressure introduction passage for introducing the low pressure, and a valve body for switching and controlling conduction/blocking between the low pressure introduction passage and the control pressure passage. A variable capacity swash plate compressor as described in any of the above. (6) The spool has a cylindrical shape, and its diameter D_s
6. The variable displacement swash plate compressor according to any one of claims 1 to 5, wherein D_p is about the square root of the number of pistons times the diameter D_p of the pistons. (7) The pressure limiting valve is disposed on the spool and releases the pressure in the signal pressure chamber to the low pressure side of the compressor when the spool is maximally displaced toward the support portion. A variable capacity swash plate compressor according to any one of claims 1 to 6. (8) A communication passage communicating the control pressure chamber and a low pressure part of the compressor is formed in the spool, and the pressure limiting valve is disposed in the communication passage, and the spool is disposed on the supporting part side. 8. The variable displacement swash plate compressor according to claim 7, wherein the pressure limiting valve is configured to open the communication passage when the pressure is displaced by a predetermined value or more.