Apparatus and method for operating fluid displacement apparatus with variable displacement mechanism

A variable fluid displacement apparatus, comprising:

• a housing enclosing a crank chamber, a suction chamber, and a discharge chamber;
• a drive shaft rotatably supported in said housing;
• a plate in said crank chamber, said plate having a slant angle and tiltably connected to said drive shaft, said slant angle varies in response to a pressure differential between said crank chamber and said suction chamber;
• a first communication path communicating said crank chamber with said discharge chamber, said first communication path including a first opening area;
• a first valve device that senses a suction pressure of said suction chamber and adjusts said first opening area of said first communication path in response to said suction pressure;
• a bellows member in said first valve device for sensing said suction pressure, wherein said bellows member urges a valve means to open and close said first communication path;
• a second communication path communicating said crank chamber with said suction chamber, said second communication path having a second opening area;
• and
• a second valve device comprising a valve member, a valve seat receiving said valve member and a valve body supporting said valve seat, wherein said valve member closes said second opening area of said second communication path when said pressure differential between said crank chamber and said suction chamber is below a valve member's weight.

A method for adjusting compression capacity in a variable fluid displacement apparatus comprising a housing enclosing a crank chamber, a suction chamber, a discharge chamber, and drive shaft, the method comprising the steps of:

• communicating said crank chamber with said discharge chamber via a first communication path having a first opening area;
• communicating said crank chamber with said suction chamber via a second communication path having a second opening area;
• sensing a pressure in said suction chamber;
• adjusting said first opening area of said first communication path responsive to said sensed pressure in said sensing step;
• determining a pressure differential between said crank chamber and said suction chamber;
• and
• closing said second opening area of said second communication path when said pressure differential is below a valve member's weight.