Control apparatus for variable displacement compressor

A control apparatus for controlling the displacement of a variable displacement compressor that forms a refrigerant circuit of an air-conditioning system, wherein the refrigerant circuit includes the compressor, an external circuit, and a discharge pressure zone, which communicate the compressor and the external circuit and is exposed to refrigerant gas that is discharged from the compressor to the external circuit, the control apparatus comprising:

• a control valve, wherein the control valve includes:
• a valve housing;
• a valve chamber defined in the valve housing;
• a valve body located in the valve housing;
• a pressure monitoring location in the discharge pressure zone in the refrigerant circuit;
• a pressure sensing mechanism, wherein the pressure sensing mechanism includes:
• a first and second pressure sensing chamber exposed to the pressure at the pressure monitoring location;
• a pressure sensing member for detecting the pressure difference between the first and second pressure sensing chambers, wherein the pressure sensing member is displaced in accordance with the fluctuations of the pressure difference at the pressure monitoring location such that the pressure difference is equal to a target pressure, which is a criteria for determining the position of the valve body, and the valve body moves accordingly to cancel the fluctuations of the pressure and thus the displacement of the compressor is changed;
• and
• a target pressure changing member, wherein the target pressure changing member changes the target pressure by controlling the external force applied to the pressure sensing member;
• and
• a pressure reducing mechanism for drawing the pressure at the pressure monitoring point to the first pressure sensing chamber, wherein the pressure reducing mechanism is located in a passage that connect the pressure monitoring point and the first pressure sensing chamber, and wherein, when the pressure at the pressure monitoring point abruptly increases, the pressure reducing mechanism reduces the increase of the pressure that is detected by the pressure sensing mechanism.