Capacity control valve for variable displacement compressor

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 [0001] 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 [0002] (1) Field of the Invention [0003] 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. [0004] (2) Description of the Related Art [0005] 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 ...

AI Technical Summary

Benefits of technology

[0015] 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.

Problems solved by technology

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.

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.

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.

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