Displacement control mechanism for variable displacement compressor

Abstract

A displacement control mechanism used in a variable displacement compressor for controlling a displacement of the compressor includes a first control valve located on a supply passage and a second control valve located on a first bleed passage. The second control valve includes a backpressure chamber having substantially the same pressure atmosphere as a region of the supply passage downstream of the first control valve and a spool including a back surface that is located in the backpressure chamber. The spool reduces an opening degree of the first bleed passage when a pressure in the backpressure chamber is increased. The spool blocks a communication between the backpressure chamber and the first bleed passage via a clearance formed around a cylindrical outer peripheral surface of the spool in the second control valve when the spool sets the first bleed passage at a minimum opening degree.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a displacement control mechanism for controlling the displacement of a variable displacement compressor that forms a part of a refrigerant circulation circuit of an air-conditioner. The displacement of the compressor is varied in accordance with the pressure in a crank chamber of the compressor. [0002] There is known a control mechanism shown in FIG. 15. According to the mechanism, the compressor displacement is controlled by adjusting the pressure in crank chamber 153 (or crank pressure Pc). Namely, in a swash plate type variable displacement compressor (hereinafter the compressor), the crank chamber 153 communicates with a suction chamber 155 via a bleed passage 154. A discharge chamber 151 of the compressor communicates with the crank chamber 153 via a supply passage 152 on which a control valve 156 is arranged. The amount of refrigerant gas introduced into the crank chamber 153 via the supply passage 152 is cont...

AI Technical Summary

Benefits of technology

[0012] The present invention provides a displacement control mechanism for a variable displacement compressor that prevents the operation failure of the spool of a second control valve that adjusts the opening degree of the bleed passage.

Problems solved by technology

However, the fixed throttle 158 provided in the bleed passage 154 causes the pressure in the crank chamber 153 to be slowly reduced, thereby deteriorating the response of the compressor in increasing the displacement.

However, foreign substances tend to be caught between the outer peripheral surface of the spool 162 and the inner peripheral surface of the spool-supporting recess 164, thereby causing poor sliding movement of the spool 162.

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