Control valve for variable displacement compressor

Abstract

In order to reduce the amount of refrigerant circulating within a variable displacement compressor to thereby improve compression efficiency, a control valve is configured to comprise a ball valve for controlling the flow rate of refrigerant flowing from a discharge chamber to a crankcase, a spool valve for controlling the flow rate of refrigerant flowing from the crankcase to a suction chamber, a diaphragm for sensing suction pressure, and a solenoid for setting the suction pressure, wherein the spool valve starts flow rate control after the ball valve is fully closed or nearly fully closed, and the ball valve starts flow rate control after the valve lift of the spool valve is minimized or nearly minimized. As a result, a region is almost eliminated in which the ball valve and the spool valve are both open simultaneously during switching of flow rate control between the ball valve and the spool valve, which makes it possible to minimize the flow rate of the refrigerant circulating within the compressor without contributing to a refrigerating operation, to thereby improve the efficiency of the compressor.

Description

[0001] This application is a continuing application, filed under 35 U.S.C. §111(a), of International Application PCT / JP2004 / 000505, filed Jan. 21, 2004.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 used in a refrigeration cycle of an automotive air conditioner. [0004] 2. Description of the Related Art [0005] The rotational speed of an engine as a drive source of an automotive air conditioner is not constant, and hence the air conditioner is required to be controlled such that refrigerating power thereof is held constant regardless of the engine rotational speed. To meet this requirement, a swash plate variable displacement compressor capable of changing the discharge amount of refrigerant is generally used in an automotive air conditioner. In the variable displacement compressor, a swash plate d...

AI Technical Summary

Benefits of technology

[0013] The present invention has been made in view of the above points, and an object thereof is to provide a control valve for a variable displacement compressor, which is capable of reducing the amount of refrigerant circulating within the compressor to thereby improve compression efficiency, while ensuring stable controllability.

Problems solved by technology

Consequently, in the variable displacement compressor using one of the above-described control valves, increased amount of refrigerant circulates therein, which inevitably causes degradation of compression efficiency.

Consequently, the flow rate of refrigerant circulating in the compressor can only be reduced to a limited degree, which makes it impossible to obtain sufficiently improved compression efficiency.

As a consequence, when the pressure in the crankcase rises excessively, gaseous refrigerant compressed in the crankcase cannot be reduced by changing the valve lift of the valve on the inlet side, and not until the suction pressure spontaneously becomes higher than a second set pressure with decrease in the displacement of the compressor to open the outlet-side refrigerant passage, does the pressure in the crankcase fall.

As described above, the latter control valve cannot ensure stable controllability.

Images