Variable displacement mechanism for scroll type compressor

Abstract

In a scroll type compressor having a movable scroll member and a fixed scroll member, the movable scroll member and the fixed scroll member defines compression chambers therebetween. The compression chambers reduce in volume in accordance with orbital motion of the movable scroll member relative to the fixed scroll member. Thus gas is compressed. A variable displacement mechanism for the scroll type compressor has a by-pass passage, a pivotal plate and an actuator. The by-pass passage serves to interconnect the compression chamber in a process of volume-reducing and a suction pressure region. The pivotal plate has a communication hole that partially constitutes the by-pass passage and is selectively pivoted between a first pivotal position for opening the by-pass passage by the communication hole and a second pivotal position for closing the by-pass passage. The actuator serves to pivot the pivotal plate.

What is claimed is:  
     
         1 . A variable displacement mechanism in a scroll type compressor having a movable scroll member and a fixed scroll member, the movable scroll member and the fixed scroll member defining compression chambers therebetween, the compression chambers reducing in volume in accordance with orbital motion of the movable scroll member relative to the fixed scroll member, whereby gas is compressed, a suction pressure region being defined in the scroll type compressor, the variable displacement mechanism comprising: 
 a by-pass passage provided for interconnecting the compression chamber in a process of volume-reducing and the suction pressure region;    a pivotal plate having a communication hole that partially constitutes the by-pass passage, the pivotal plate being pivotally switched between a first pivotal position for opening the by-pass passage by the communication hole and a second pivotal position for closing the by-pass passage; and    an actuator for pivoting the pivotal plate.    
     
     
         2 . The variable displacement mechanism according to  claim 1 , wherein the by-pass passage is configured to regularly interconnect the compression chamber in the process of volume-reducing and the suction pressure region until volume of the compression chamber in the process of volume-reducing is reduced to a predetermined value in a state where the pivotal plate is switched to the first pivotal position.  
     
     
         3 . The variable displacement mechanism according to  claim 1 , wherein the by-pass passage is plurally formed.  
     
     
         4 . The variable displacement mechanism according to  claim 3 , wherein the scroll type compressor includes a rotary shaft that has a central axis, the by-pass passages being distributed around the central axis and along an orthogonal direction relative to the central axis.  
     
     
         5 . The variable displacement mechanism according to  claim 1 , wherein the by-pass passage is configured to interconnect the compression chamber in the process of volume-reducing and the suction pressure region after the volume of the compression chamber in the process of volume-reducing has been reduced to a predetermined value in a state where the pivotal plate is switched to the first pivotal position.  
     
     
         6 . The variable displacement mechanism according to  claim 1 , wherein the fixed scroll member includes a base plate and a spiral wall that extends from the base plate, the pivotal plate being slidably laid on a back surface of the base plate.  
     
     
         7 . The variable displacement mechanism according to  claim 6 , wherein the back surface of the base plate of the fixed scroll member includes an accommodating recess, a discharge hole opening to the accommodating recess for communicating with the compression chamber near a center of the spiral wall, a discharge chamber being defined in such a manner that the accommodating recess is closed by laying the pivotal plate on the back surface of the base plate.  
     
     
         8 . The variable displacement mechanism according to  claim 7 , wherein the suction pressure region is defined on a side that is opposite to a side of the base plate relative to the pivotal plate, the pivotal plate serving as a partition wall for partitioning the suction pressure region and the discharge chamber.  
     
     
         9 . The variable displacement mechanism according to  claim 7 , wherein the pivotal plate has a donut-shape, a through hole being formed at the center of the pivotal plate, a discharge passage extending through the through hole for discharging the gas in the discharge chamber.  
     
     
         10 . The variable displacement mechanism according to  claim 9 , wherein adherence between the pivotal plate and the fixed scroll member seals the by-pass passage.  
     
     
         11 . The variable displacement mechanism according to  claim 10 , wherein a layer of lubricating oil is interposed between the pivotal plate and the base plate of the fixed scroll member.  
     
     
         12 . The variable displacement compressor according to  claim 1 , wherein the scroll type compressor is used for a vehicle air conditioner, the scroll type compressor being a hybrid type that is selectively driven by power from an engine for traveling a vehicle and by power from an internal electric motor.