US20050053474A1

US20050053474A1 - Capacity control valve for variable displacement compressor

Info

Publication number: US20050053474A1
Application number: US10/918,420
Authority: US
Inventors: Hisatoshi Hirota; Morimitsu Kajiwara; Ryosuke Yoshihiro
Original assignee: TGK Co Ltd
Current assignee: TGK Co Ltd
Priority date: 2003-09-04
Filing date: 2004-08-16
Publication date: 2005-03-10
Also published as: EP1512871A1; JP2005098197A

Abstract

To provide a capacity control valve for a variable displacement compressor of a Pd-Ps differential pressure-controlled type, which suppresses overshooting of the differential pressure between the discharge pressure Pd and the suction pressure Ps which can occur when the differential pressure is changed in response to a stepwise change in the solenoid current. The capacity control valve includes a valve section having a Pd-Pc valve for control of the flow rate of refrigerant flowing from a discharge chamber to a crankcase and a Pc-Ps valve for control of the flow rate of refrigerant flowing from the crankcase to a suction chamber operating in a manner interlocked with the Pd-Pc valve. A spool valve element is provided on a valve element of the Pc-Ps valve, whereby in a stroke region where the Pd-Pc valve is toward the fully-closed position, refrigerant is allowed to pass through the clearance between the spool valve element and the valve hole of the Pc-Ps valve, to cause the Pc-Ps valve to have a characteristic that the opening area thereof does not change in response to a change in stroke. This makes it possible to suppress sharp changes in the pressure Pc in the crankcase due to the existence of the clearance, even if the solenoid current is stepwise sharply changed.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY

This application claims priority of Japanese Application No.2003-312369 filed on Sep. 4, 2003 and entitled “CAPACITY CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR” and No. 2003-332652 filed on Sep. 25, 2003, entitled “CAPACITY CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention
The present invention relates to a capacity control valve for a variable displacement compressor, and more particularly to a capacity control valve for use in a variable displacement compressor that compresses a refrigerant gas in a refrigeration cycle of an automotive air conditioner.
(2) Description of the Related Art
A compressor used for compressing refrigerant in a refrigeration cycle of an automotive air conditioner is driven by an engine, which makes it impossible to perform rotational speed control of the compressor. To overcome the inconvenience, a variable displacement compressor which is capable of changing displacement of compressed refrigerant is employed so as to obtain adequate refrigerating capacity without being constrained by the rotational speed of the engine.
In such a variable displacement compressor, compression pistons are connected to a wobble plate fitted on a shaft driven by the engine for rotation, and the angle of the wobble plate is changed to change the stroke of the pistons for changing the discharge amount of the refrigerant, i.e. the displacement of the compressor.
The angle of the wobble plate is continuously changed by introducing part of the compressed refrigerant into an airtight crankcase and changing the pressure Pc in the crankcase, thereby changing the balance between pressures applied to the opposite ends of each piston.
The pressure Pc in the crankcase of the variable displacement compressor can be changed by forming refrigerant passages, respectively, between a discharge chamber and the crankcase of the compressor and between the crankcase and a suction chamber of the same, and thereby controlling the flow rate of refrigerant flowing from the discharge chamber into the suction chamber via the crankcase at respective locations upstream and downstream of the crankcase. More specifically, a capacity control valve is provided in one of the passages between the discharge chamber and the crankcase and between the crankcase and the suction chamber, and an orifice is provided in the other of the passages, whereby control is provided such that the capacity control valve allows or blocks the communication via the associated refrigerant passage, so as to control the pressure Pc in the crankcase.
Further, a capacity control valve is also known which comprises two control valves disposed in respective refrigerant passages between a discharge chamber and a crankcase and between the crankcase and a suction chamber, such that they operate in a manner interlocked with each other (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2003-35269 (Paragraph numbers [0023] to [0034], FIG. 2)). The capacity control valve for a variable displacement compressor described in Japanese Unexamined Patent Publication (Kokai) No. 2003-35269 controls the discharging capacity of the compressor such that the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps of the compressor is held a predetermined value, and comprises a first control valve (hereinafter also referred to as “the Pd-Pc valve”) for high pressure which controls the flow rate of refrigerant flowing from the discharge chamber into the crankcase, a second control valve (hereinafter also referred to as “the Pc-Ps valve”) for low pressure which controls the flow rate of refrigerant flowing from the crankcase into the suction chamber in a manner interlocked with operation of the Pd-Pc valve, and a solenoid which is capable of externally setting a predetermined differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps by a current value.
FIG. 7 is a diagram showing characteristics of the conventional capacity control valve, and FIG. 8 is a diagram showing characteristics of the variable displacement compressor using the conventional capacity control valve.
The capacity control valve equipped with the two control valves for high pressure and low pressure has the characteristics, as shown in FIG. 7, that when the Pd-Pc valve is changed from its closed state in an opening area-increasing direction, the Pc-Ps valve is changed from its fully-open state in an opening area-decreasing direction in a manner interlocked with the operation of the Pd-Pc valve, and that inversely when the Pd-Pc valve is changed from its fully-open state in an opening area-decreasing direction, the Pc-Ps valve is changed from its closed state in an opening area-increasing direction in a manner interlocked with the operation of the Pd-Pc valve.
In such a capacity control valve, when the stroke position is changed according to the value of electric current supplied to the solenoid, the respective opening areas of the Pd-Pc valve and the Pc-Ps valve are changed in opposite directions, which increases the amount of change in the pressure Pc in the crankcase with respect to the same amount of change in the stroke compared with a case where the orifice having fixed opening area is provided between the discharge chamber and the crankcase or between the crankcase and the suction chamber of the compressor, which makes it possible to promptly change the variable displacement of the compressor.
However, the variable displacement compressor using the conventional capacity control valve, characteristics of which are illustrated in FIG. 8, suffers from the problem that when the current (solenoid current) supplied to the solenoid is stepwise changed, the pressure Pc in the crankcase is largely changed according to a change in the solenoid current, which causes a large change in the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps, which is to be controlled, causing a large overshoot, so that torque consumed by the compressor is largely changed only at the moment in time at which the solenoid current is changed, resulting in large variation in load on the engine.
More specifically, when the solenoid current is stepwise increased as illustrated in FIG. 8, the Pd-Pc valve is changed in the valve-closing direction and the Pc-Ps valve is changed in the valve-opening direction, which causes a too rapid drop in the pressure Pc in the crankcase, so that the pressure Pc in the crankcase once undergoes a sharp drop and then changes such that it settles in the predetermined pressure. The variable displacement compressor has its discharging capacity excessively increased in response to the sharp drop in the pressure Pc in the crankcase, which results in a sharp increase in the torque consumed by the compressor and causes an overshoot.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described points, and an object thereof is to provide a capacity control valve for a variable displacement compressor, which suppresses a overshoot which can occur when the differential pressure between the discharge pressure and the suction pressure is changed in response to a stepwise change in the solenoid current.
To solve the above problem, the present invention provides a capacity control valve for a variable displacement compressor, for controlling pressure in a crankcase to thereby vary discharging capacity of the variable displacement compressor such that differential pressure between pressure in a suction chamber and pressure in a discharge chamber is held at a predetermined differential pressure, comprising a first control valve for controlling a flow rate of refrigerant flowing into the crankcase from the discharge chamber, a second control valve for controlling a flow rate of refrigerant flowing out of the crankcase into the suction chamber, the second control valve having flow rate-restricting means operable to provide an opening area which does not change in the case where the second control valve is moved more than a predetermined value of stroke amount when the second control valve is moved in an opening area-increasing direction in a manner interlocked with operation of the first control valve, and a solenoid section for applying a solenoid force corresponding to the predetermined differential pressure to the first control valve and the second control valve.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central longitudinal cross-sectional view showing a capacity control valve according to a first embodiment of the present invention.
FIG. 2 is a diagram showing characteristics of the capacity control valve according to the first embodiment.
FIG. 3 is a diagram showing characteristics of a variable displacement compressor using the capacity control valve according to the first embodiment.
FIG. 4 is a central longitudinal cross-sectional view showing a capacity control valve according to a second embodiment of the present invention.
FIG. 5 is a central longitudinal cross-sectional view showing a capacity control valve according to a third embodiment of the present invention.
FIG. 6 is a central longitudinal cross-sectional view showing a capacity control valve according to a fourth embodiment of the present invention.
FIG. 7 is a diagram showing characteristics of a conventional capacity control valve.
FIG. 8 is a diagram showing characteristics of a variable displacement compressor using the conventional capacity control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a central longitudinal cross-sectional view showing a capacity control valve according to a first embodiment of the invention, FIG. 2 a diagram showing characteristics of the capacity control valve according to the first embodiment, and FIG. 3 a diagram showing characteristics of a variable displacement compressor using the capacity control valve according to the first embodiment.
The capacity control valve is formed by a valve section 1 and a solenoid section 2. The valve section 1 includes a body 3 having an opening in the top thereof, and a plug 4 is fitted in the opening. The plug 4 has a hole axially extending therethrough, with an opening in the upper end thereof as viewed in FIG. 1 forming a port 5 for receiving refrigerant at discharge pressure Pd from a discharge chamber of the variable displacement compressor, and a lower end thereof as viewed in FIG. 1 forming a valve seat 6. In opposed relation to the valve seat 6, a ball valve element 7 is disposed in a manner movable to and away therefrom. Space within which the ball valve element 7 is disposed communicates with the crankcase of the variable displacement compressor via a port 8 formed in the body 3. Therefore, the ball valve element 7 and the valve seat 6 forms a Pd-Pc valve (first control valve) that controls the flow rate of refrigerant at the discharge pressure Pd to thereby fill the crankcase with refrigerant at pressure Pc.
The body 3 is also provided with a port 9 which communicates with a suction chamber of the variable displacement compressor, and a valve seat 10 is integrally formed with the body 3 in a passage between the port 8 and the port 9. A valve element 11 which holds the ball valve element 7 of the Pd-Pc valve is disposed in opposed relation to the valve seat 10 in a manner movable to and away therefrom. Interposed between the valve element 11 and the plug 4 is a spring 12 for urging the ball valve element 7 in the valve-opening direction and the valve element 11 in the valve-closing direction. The valve element 11 and the valve seat 10 form a Pc-Ps valve (second control valve) which controls the flow rate of refrigerant at pressure Pc in the crankcase to fill the suction chamber with refrigerant at suction pressure Ps.
The capacity control valve is characterized in that it includes a spool valve structure whose opening area does not change in a region in which the Pd-Pc valve is toward the fully-closed position. To realize the structure, a spool valve element 11 a disposed within a valve hole of the Pc-Ps valve is integrally formed with the valve element 11 in an end face thereof opposed to the valve seat 10. Therefore, this Pc-Ps valve forms a spool valve in which in a stroke region where the valve element 11 is moved axially to start opening the Pd-Pc valve, the opening area of the Pc-Ps valve defined by a clearance between the spool valve element 11 a and the valve hole does not change, but in a stroke region in which the Pd-Pc valve is toward the fully-open position, the opening area between the valve element 11 and the valve seat 10 changes. The clearance which does not change its opening area forms flow rate-restricting means of the present invention.
Further, the body 3 has a strainer 13 capped on the upper end thereof as viewed in FIG. 1, and the port 9 is provided with a passage 14 for transmitting the suction pressure Ps to the inside of the solenoid 2. It should be noted that in the valve section 1, the Pc-Ps valve is formed such that the diameter of the valve hole thereof is larger than that of the valve hole of the Pd-Pc valve, thereby enabling refrigerant to instantly flow at a large flow rate.
The solenoid section 2 has a core 15 disposed in the center thereof which has an upper end thereof screwed into a lower end of the body 3, and a yoke 16 is arranged in a manner enclosing the core 15, with an upper end thereof screwed into the body 3. A sleeve 17 is disposed inward of the yoke 16, and a hollow cylindrical holder 18 is provided on the lower ends of the yoke 16 and the sleeve 17 as viewed in FIG. 1. The holder 18 has an adjustment screw 19 screwed into an opening thereof.
The core 15 has a through hole formed in the center thereof, and a shaft 20 is disposed in a manner extending through the through hole. This shaft 20 has one end thereof supported in a through hole formed in the body 3, and the other end thereof supported in a recess formed in the adjustment screw 19. The shaft 20 has a shaft 21 integrally formed therewith at the one end thereof, which is reduced in diameter and inserted into the valve element 11 for centering the valve element 11 and the ball valve element 7 held thereby. The shaft 20 has the same diameter as that of the valve hole of the Pd-Pc valve, whereby a pressure-receiving area of the ball valve element 7 where the discharge pressure Pd is received and a pressure-receiving area of the lower end of the shaft 20 as viewed in FIG. 1 where the suction pressure Ps introduced into the solenoid section 2 via the passage 14 is received are equal to each other.
The solenoid section 2 further includes a plunger 22 fixed to the shaft 20 at a location between the core 15 and the adjustment screw 19, a spring 23 disposed between the core 15 and the plunger 22, a spring 24 disposed between the plunger 22 and the adjustment screw 19, and a coil 25 disposed between the sleeve 17 and the yoke 16. The coil 25 is electrically connected to a harness 27 extending out of the solenoid section 2 via a water-proof coupler 26.
In the capacity control valve having the Pd-Pc valve and the Pc-Ps valve, described above, when the solenoid current is not supplied to the coil 25 of the solenoid section 2, such as when an automotive air conditioner is not in operation or when refrigerating load is the minimum, the plunger 22 is urged by the spring 23 in a direction away from the core 15, and the ball valve element 7 and the valve element 11 are urged by the spring 12 in a direction toward the solenoid section 2, which places the Pd-Pc valve for high pressure in the fully-open position and the Pc-Ps valve for low pressure in the fully-closed position. If the discharge pressure Pd is introduced at this time from the discharge chamber of the compressor, the discharge pressure Pd is introduced into the crankcase via the Pd-Pc valve. Since the refrigerant passage extending from the crankcase to the suction chamber is closed by the Pc-Ps valve, so that the pressure Pc in the crankcase becomes closer to the discharge pressure Pd, minimizing the differential pressure between the pressures applied to the opposite end faces of each piston of the compressor. This places the wobble plate at an inclination angle which minimizes the stroke of the piston, whereby the compressor is controlled to the minimum displacement operation.
Now, as the solenoid current supplied to the coil 25 of the solenoid section 2 increases, the plunger 22 is attracted by the core 15 to be moved upward as viewed in FIG. 1, and the shaft 20 fixed to the plunger 22 as well is moved upward as viewed in FIG. 1. Therefore, the capacity control valve has the characteristics, as shown in FIG. 2, that the opening area of the Pd-Pc valve is changed in a decreasing direction from the maximum since the ball valve element 7 is moved toward the valve seat 6, while the opening area of the Pc-Ps valve is changed in an increasing direction from zero since the valve element 11 is moved in a direction away from the valve seat 10. Accordingly, the pressure Pc in the crankcase progressively decreases, so that the variable displacement compressor is controlled to operation with displacement dependent on the solenoid current.
When the solenoid current continues to be increased, the opening area of the Pd-Pc valve continues to be decreased but the increase in the opening area of the Pc-Ps valve stops at a time point the opening area between the valve element 11 and the valve seat 10 becomes larger than the opening area defined by the clearance between spool valve element 11 a and the valve hole of the Pc-Ps valve. Thereafter, even if the solenoid current is increased, the Pc-Ps valve has a flat characteristic that the opening area thereof does not change relative to the travel or stroke amount of the valve element since the opening area of this valve is restricted by the opening area between the spool valve element 11 a and the valve hole.
When the capacity control valve is controlled by the supply of the predetermined solenoid current, the Pd-Pc valve and the Pc-Ps valve are controlled to respective stroke positions dependent on the solenoid current. At this time, when the differential pressure between the discharge pressure Pd received by the ball valve element 7 and the suction pressure Ps received by the shaft 20 varies due to a change in the rotational speed of the engine, i.e. the rotational speed of the compressor, the capacity control valve changes the travel or stroke amount of the valve elements of the Pd-Pc valve and the Pc-Ps valve to vary the displacement of the compressor, thereby providing control such that the differential pressure between the discharge pressure Pd and the suction pressure Ps is held at a predetermined differential pressure set by the solenoid current.
As described above, the Pc-Ps valve is caused to have the flat characteristic that the opening area thereof does not change in a region where the opening area of the Pd-Pc valve is small, whereby when the solenoid current is changed stepwise, the pressure Pc in the crankcase does not largely change relative to the change in the solenoid current, as shown in FIG. 3. If the solenoid current is increased e.g. stepwise in a region where the opening area of the Pc-Ps valve changes, the ratio of change in opening area in a opening direction of the Pc-Ps valve with respect to a stroke amount is larger than that of change in opening area in a closing direction of the Pd-Pc valve with respect to the same stroke amount, so that the pressure Pc in the crankcase is about to be sharply decreased, but the range of this change is restricted by the flat characteristic of the Pc-Ps valve so that overshooting of the pressure Pc in the crankcase is prevented. As a result, overshooting of the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps does not occur, either, which reduces variation in torque consumed by the compressor and hence reduces variation in load on the engine.
Similarly, if the solenoid current is increased e.g. stepwise in a region where the opening area of the Pc-Ps valve does not change, the Pc-Ps valve does not undergo a change relative to a stroke amount even though the Pd-Pc valve undergoes a change in the valve-closing direction relative to the same stroke amount, which reduces the range of variation in the pressure Pc in the crankcase. Therefore, the pressure Pc in the crankcase, the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps, and torque consumed by the compressor are reduced, which makes it possible to reduce variation in load on the engine. Of course, even when the solenoid current is stepwise decreased, occurrence of the overshooting can be suppressed in the same manner.
FIG. 4 is a central longitudinal cross-sectional view showing a capacity control valve according to a second embodiment of the invention. In FIG. 4, component elements identical to those in FIG. 1 are designated by identical reference numerals, and detailed description thereof is omitted.
Although the capacity control valve according to the first embodiment attains the flat characteristic of the Pc-Ps valve by the spool valve structure, the capacity control valve according to the second embodiment attains the same by providing an orifice 28 as flow rate-restricting means whose opening area does not change.
That is, the Pc-Ps valve has a valve element 11 whose surface opposed to the valve seat 10 is formed to have a tapered shape, and the orifice 28 is provided between the downstream side of the valve element 11, and the port 9 and the passage 14. The orifice 28 is disposed in series with the Pc-Ps valve, and therefore, when the opening area of the Pc-Ps valve becomes larger than the opening area of the orifice 28, even if the valve element 11 of the Pc-Ps valve further travels in a direction of increasing the opening area thereof, the opening area of the Pc-Ps valve is limited by the orifice 28 whose opening area does not change, and hence this capacity control valve has the same characteristics as shown in FIG. 2. Therefore, the capacity control valve according to the second embodiment operates in the same manner as the capacity control valve according to the first embodiment, and therefore reduces undesired variations in the pressure Pc in the crankcase, the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps, and torque consumed by the variable displacement compressor, thereby making it possible to decrease variation in load on the engine.
FIG. 5 is a central longitudinal cross-sectional view showing a capacity control valve according to a third embodiment of the invention. In FIG. 5, component elements identical to those in FIG. 1 are designated by identical reference numerals, and detailed description thereof is omitted.
Compared with the capacity control valve according to the first embodiment shown in FIG. 1, the capacity control valve according to the third embodiment is configured such that the operation of the Pc-Ps valve is not adversely affected by the pressure Pc in the crankcase.
More specifically, the capacity control valve is provided with a passage 14 which causes a space between the Pd-Pc valve and the Pc-Ps valve, which is connected to the crankcase via the port 8, to communicate with the inside of the solenoid section, whereby the pressure Pc in the crankcase is transmitted to the inside of the solenoid section 2. This causes the valve element 11 of the Pc-Ps valve to receive the pressure Pc in the crankcase in the valve-closing direction, and receive the pressure Pc in the crankcase introduced via the passage 14 into the solenoid section 2, via the shaft 20 in the valve-opening direction. Therefore, the pressure Pc in the crankcase received by the valve element 11 in the opposite directions is cancelled off, so that even when the pressure Pc in the crankcase is changed, the change in the pressure does not adversely affect the operation of the Pc-Ps valve.
It should be noted that the pressure received by the valve element 11 of the Pc-Ps valve in the valve-opening direction is the sum of the pressure Pc in the crankcase received from the solenoid section 2 and the suction pressure Ps. At this time, the area where the pressure Pc in the crankcase is received is equal to the cross-sectional area of the shaft 20, and the area where the suction pressure Ps is received is equal to an area obtained by subtracting the cross-sectional area of the shaft 20 from the opening area of the valve hole of the Pc-Ps valve, and at the same time, equal to the area where the discharge pressure Pd is received by the Pd-Pc valve, i.e. the opening area of the valve hole of the Pd-Pc valve.
The capacity control valve according to the third embodiment also has the valve characteristic shown in FIG. 2, similarly to the capacity control valves according to the first and second embodiments, so that when the solenoid current is stepwise changed, the clearance between the spool valve element 11 a and the valve hole restricts the flow rate of refrigerant which is about to be stepwise changed, whereby an undesired variation in the pressure Pc in the crankcase is suppressed. As a result, undesired variations in the differential pressure (Pd-Ps) between the discharge pressure Pd and the suction pressure Ps and torque consumed by the variable displacement compressor are reduced, which makes it possible to reduce variation in load on the engine.
FIG. 6 is a central longitudinal cross-sectional view showing a capacity control valve according to a fourth embodiment of the invention. In FIG. 6, component elements identical to those in FIG. 4 are designated by identical reference numerals, and detailed description thereof is omitted.
Compared with the capacity control valve according to the second embodiment shown in FIG. 4, the capacity control valve according to the fourth embodiment is configured such that the operation of the Pc-Ps valve thereof is not adversely affected by the pressure Pc in the crankcase.
More specifically, the capacity control valve is provided with a passage 14 which causes space between the Pd-Pc valve and the Pc-Ps valve connected to the crankcase via the port 8 to communicate with the inside of the solenoid section, whereby similarly to the capacity control valve according to the third embodiment, the pressure Pc in the crankcase is transmitted to the inside of the solenoid section 2. This causes the pressure Pc in the crankcase received by the valve element 11 in the opposite directions to be cancelled off, so that even when the pressure Pc in the crankcase is varied, the change in the pressure does not adversely affect the operation of the Pc-Ps valve. The capacity control valve according to the fourth embodiment also operates similarly to the capacity control valves according to the first to third embodiments to provide the same advantageous effects.
Due to provision of the flow rate-restricting means in the second control valve, the capacity control valve for a variable displacement compressor according to the present invention is capable of suppressing overshooting of the pressure in the crankcase, which can occur when the solenoid current is stepwise changed. This makes it possible to reduce undesired variation in the differential pressure to be controlled, and undesired variation in torque consumed by the compressor. As a result, it is possible to reduce variation in load on the engine that drives the compressor.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.

Claims

1. A capacity control valve for a variable displacement compressor, for controlling pressure in a crankcase to thereby vary discharging capacity of the variable displacement compressor such that differential pressure between pressure in a suction chamber and pressure in a discharge chamber is held at a predetermined differential pressure, comprising:

a first control valve for controlling a flow rate of refrigerant flowing into the crankcase from the discharge chamber;

a second control valve for controlling a flow rate of refrigerant flowing out of the crankcase into the suction chamber, the second control valve having flow rate-restricting means operable to provide an opening area which does not change in the case where the second control valve is moved more than a predetermined value of stroke amount when the second control valve is moved in an opening area-increasing direction in a manner interlocked with operation of the first control valve; and

a solenoid section for applying a solenoid force corresponding to the predetermined differential pressure to the first control valve and the second control valve.

2. The capacity control valve according to claim 1, wherein the flow rate-restricting means comprises a spool valve element provided on a valve element of the second control valve to form a clearance between the spool valve element and a valve hole such that an opening area of the clearance does not change.

3. The capacity control valve according to claim 1, wherein the flow rate-restricting means is an orifice provided on a downstream side of the second control valve.

4. The capacity control valve according to claim 1, comprising a passage communicating between a space connected to the crankcase and an inside of the solenoid section, and

wherein the second control valve causes the pressure in the crankcase introduced via the passage into the solenoid section to be received by a valve element thereof in a valve-opening direction, to thereby cancel out the pressure in the crankcase received by the valve element in a valve-closing direction.

5. The capacity control valve according to claim 4, wherein a pressure-receiving area of the second control valve obtained by subtracting an area where the pressure in the crankcase is received via the solenoid section from an opening area of a valve hole of the second control valve is set equal to an opening area of a valve hole of the first control valve.