Scroll compressor

Abstract

A scroll compressor includes a fixed scroll member fixed to a housing and a movable scroll member engaging the fixed scroll member. Each scroll member has a base plate and a spiral wall. A compression chamber between the fixed and movable scroll members reduces in volume by orbiting the movable scroll member, thus compressing gas. A back pressure chamber is defined in the housing on a back surface side of the movable scroll base plate between the movable scroll member and the a fixed wall of the housing. An introducing passage interconnects the back pressure chamber and a relatively high pressure region. A seal member on one of the movable scroll member and the fixed wall seals the back pressure chamber as being slidable on the other. The seal member includes a portion for lowering sealing performance, which interconnects the back pressure chamber and a relatively low pressure region.

What is claimed is:  
     
         1 . A scroll compressor comprising: 
 a housing including a fixed wall, the housing defining a relatively high pressure region and a relatively low pressure region;    a fixed scroll member having a base plate and a spiral wall extending from the base plate, the fixed scroll member being fixedly connected to the housing;    a movable scroll member having a base plate and a spiral wall extending from the base plate, the movable scroll member being engaged with the fixed scroll member, whereby a compression chamber is defined between the fixed scroll member and the movable scroll member, the compression chamber progressively reducing in volume by orbiting the movable scroll member relative to the fixed scroll member, thus compressing gas;    a back pressure chamber defined in the housing on a back surface side of the base plate of the movable scroll member between the movable scroll member and the fixed wall;    an introducing passage interconnecting the back pressure chamber and the relatively high pressure region; and    a seal member provided on one of the movable scroll member and the fixed wall for sealing the back pressure chamber as being slidable on the other of the movable scroll member and the fixed wall, the seal member including a seal lowering portion for lowering sealing performance, the seal lowering portion interconnecting the back pressure chamber and the relatively low pressure region.    
     
     
         2 . The scroll compressor according to  claim 1 , wherein the seal member has an annular shape, the seal lowering portion being formed by partially splitting the seal member.  
     
     
         3 . The scroll compressor according to  claim 1 , wherein the movable scroll member is accommodated in a scroll chamber, which is defined by connecting the fixed scroll member and the fixed wall at a joint, the scroll compressor further comprising: 
 a shim interposed at the joint between the fixed scroll member and the fixed wall for adjusting a thrust clearance between the movable scroll member and the fixed wall.    
     
     
         4 . The scroll compressor according to  claim 1 , further comprising: 
 a rotary shaft including a crankshaft for supporting the movable scroll member;    a shaft support member fixedly connected to the fixed wall on a side opposite to the movable scroll member in the housing, the shaft support member rotatably supporting the rotary shaft, a balancer chamber being defined between the fixed wall and the shaft support member; and    a balancer provided for the crankshaft, the balancer being accommodated in the balancer chamber.    
     
     
         5 . The scroll compressor according to  claim 1 , wherein the back pressure chamber communicates with the relatively low pressure region through a passage other than the seal lowering portion, the scroll compressor further comprising: 
 a differential pressure regulating valve arranged in the passage for opening the passage when pressure differential between the back pressure chamber and the relatively low pressure region is equal to or higher than a predetermined value.    
     
     
         6 . The scroll compressor according to  claim 1 , wherein the relatively high pressure region includes two volume-reducing compression chambers, which respectively communicate with the back pressure chamber through the introducing passage.  
     
     
         7 . The scroll compressor according to  claim 6 , wherein two volume-reducing compression chambers respectively communicate with the back pressure chamber through the respective independent introducing passages.  
     
     
         8 . The scroll compressor according to  claim 1 , wherein the introducing passage is formed in the base plate of the movable scroll member.  
     
     
         9 . The scroll compressor according to  claim 1 , wherein carbon dioxide is employed as refrigerant of the refrigeration cycle.  
     
     
         10 . The scroll compressor according to  claim 1 , wherein the compressor is driven by an electric motor.