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Home › Nissan-Datsun › 2004 › Sentra SE-R › Repair and Diagnosis › External Pages › Different car › Section 757 (Automatic Air Conditioner) › Refrigeration System › V-6 Variable Displacement Compressor › Description › Operation

V-6 Variable Displacement Compressor: Description: Operation

WARNING: This page is about a different car, the 2003 Infiniti M45. However, it is still accessible from the selected car via links, so may be relevant.
  1. Operation Control Valve 
    • By changing high-pressure valve lift amount, built-in compressor control valve executes the following:
      • Controls high-pressure valve discharge amount.
      • Changes crankcase pressure in compressor.
      • Changes angle of wobble (swash) plate.
    • Amount of high-pressure valve loft is determined by factors below.
      • Low pressure applied to diaphragm
      • Spring load of set spring
      • Balance of magnetic force generated in magnet coil
    • Electronic control valve (ECV) magnet coil receives electric signal (duty control) from auto amplifier. Then, magnetic force generated by electric current is changed to control high-pressure valve lift amount.
  2. Maximum Cooling 

    High-pressure valve is closed by magnetic force generated by electric signal sent from automatic amplifier. At this time, cylinder moves full stroke due to pressure balance between inside crankcase (Pc) and suction line (Ps).

    Under this condition, the wobble (swash) plate is set to the maximum stroke position.

    Fig 1: Identifying Operation Control Valve Of Variable Compressor For Increase Stroke
    G02025772Courtesy of NISSAN MOTOR CO., U.S.A.
  3. Capacity Control 

    When no electric signal is sent from automatic amplifier (current: OFF), high- pressure valve is opened by spring force.

    Since suction pressure is low, it makes the suction port close and the discharge port open. Thus, crankcase pressure becomes high as high pressure enters the crankcase.

    • The force acts around the journal pin near the wobble (swash) plate, and is generated by the pressure difference before and behind the piston.

      The drive lug and journal pin are located where the piston generates the highest pressure. Piston pressure is between suction pressure Ps and discharge pressure Pd, which is near suction pressure Ps. If crankcase pressure Pc rises due to capacity control, the force around the journal pin makes the wobble (swash) plate angle decrease and also the piston stroke decrease. In other words, crankcase pressure increase triggers pressure difference between the piston and the crankcase. The pressure difference changes the angle of the wobble (swash) plate.

    Fig 2: Identifying Operation Of Variable Compressor For Decrease Stroke
    G02025773Courtesy of NISSAN MOTOR CO., U.S.A.
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