Patent ID: 7559208

Claim:
A displacement control mechanism used for a variable displacement compressor that adjusts a pressure in a pressure control chamber by introducing a refrigerant in a discharge pressure region into the pressure control chamber through a supply passage and releasing the refrigerant in the pressure control chamber to a suction pressure region through a bleed passage, thereby controlling displacement of the compressor, the displacement control mechanism comprising: a first valve hole partially forming the supply passage or the bleed passage; a first valve body operable to open and close the first valve hole; a pressure sensing means operable to sense a pressure of a first point in the discharge pressure region and a pressure of a second point in the discharge pressure region and to adjust a position of the first valve body based on pressure difference between the first and second points; and a pressure reducing means operable to increase the pressure difference between the first and second points when the pressure of the suction pressure region falls below a predetermined standard pressure, wherein the pressure sensing means displaces the first valve body in such a direction so as to increase an opening degree of the first valve hole according to increase of the pressure difference when the first valve hole is a part of the supply passage, wherein the pressure sensing means displaces the first valve body in such a direction so as to decrease the opening degree of the first valve hole according to the increase of the pressure difference when the first valve hole is a part of the bleed passage, wherein the pressure reducing means further has a pressure reducing valve operable to reduce a pressure of a low pressure side out of the sensed pressures of the first and second point thereby to increase the pressure difference between the first and second points, and wherein the pressure reducing valve is opened when the pressure of the suction pressure falls below the predetermined standard pressure.