Control valve for variable displacement compressor

Abstract

To provide a control valve for a variable displacement compressor, based on a Pd−Ps differential pressure control method, which is capable of setting characteristics concerning the degree of influence of crank pressure on a change in the differential pressure between discharge pressure and suction pressure, to desired characteristics with ease. A control valve for a variable displacement compressor adjusts the difference between an effective pressure-receiving area A on a discharge pressure side of an intermediate in which a valve element and a shaft are integral with each other and an effective pressure-receiving area B on a suction pressure side of the intermediate, as required. This makes it possible to obtain desired differential pressure·crank pressure characteristics according to the specifications of the control valve. Changes in the effective pressure-receiving areas have almost no influence on electric current·differential pressure characteristics, i.e. the relationship between the value of electric current supplied to a solenoid and the differential pressure between discharge pressure and suction pressure, and hence it is possible to realize the changes in the effective pressure-receiving areas with ease.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY: [0001] This application claims priority of Japanese Application No. 2004-239161 filed on Aug. 19, 2004 and entitled “CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR”.BACKGROUND OF THE INVENTION [0002] (1) Field of the Invention [0003] The present invention relates to a control valve for a variable displacement compressor, and more particularly to a control valve for a variable displacement compressor, for controlling a discharge capacity of refrigerant discharged from a variable displacement compressor for an automotive air conditioner. [0004] (2) Description of the Related Art [0005] A compressor used in a refrigeration cycle of an automotive air conditioner is driven by an engine whose rotational speed varies depending on a traveling condition of the vehicle, and hence incapable of performing rotational speed control. To eliminate the inconvenience, a variable displacement compressor capable of changing the discharge capacity of...

AI Technical Summary

Benefits of technology

[0014] The present invention has been made in view of these problems, and an object thereof is to provide a control valve for a variable displacement compressor, based on a Pd−Ps differential pressure control method, which is capable of setting characteristics concerning the degree of influence of crank pressure on a change in the differential pressure between discharge pressure and suction pressure, to desired characteristics with ease.

Problems solved by technology

A compressor used in a refrigeration cycle of an automotive air conditioner is driven by an engine whose rotational speed varies depending on a traveling condition of the vehicle, and hence incapable of performing rotational speed control.

However, to perform the displacement control based on the suction pressure Ps as described above, it is necessary to movably arrange a flexible member, such as a diaphragm or a bellows, for sensing the suction pressure Ps in the control valve, which tends to make the control valve relatively large in scale.

Although the phenomenon may not be ideal when considering only the characteristics of the control valve, this is not always true when considering matching between the Pd−Ps differential pressure control and control of the variable displacement compressor.

This makes it difficult to perform the displacement control with stability.

For example, when the swash plate of the variable displacement compressor is difficult to move, it is required to increase the response to improve motion of the swash plate, whereas when the swash plate is excessively easy-to move, it is required to lower the response to stabilize motion of the swash plate.

However, when the characteristic of the spring or the attractive force characteristic of the solenoid is changed as described above, the differential pressure characteristics, i.e. the relationship between the value of electric current supplied to the solenoid and the differential pressure (Pd−Ps) can also be changed, which makes it difficult to perform a total tuning operation.

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