Scroll compressor and method for controlling back pressure for the same

Abstract

A scroll compressor has a fixed scroll member, a movable scroll member, a housing. The housing is secured to the fixed scroll member. The housing accommodates the movable scroll member to define a back pressure chamber. Pressure in the back pressure chamber is applied to the back surface of a movable scroll base plate of the movable scroll member. The back pressure chamber communicates with a region through a communication passage. The region is lower in pressure than the back pressure chamber. The communication passage relieves the pressure in the back pressure chamber to the region. The communication passage includes a valve. The valve varies an opening amount of the communication passage due to difference between the pressure in the compression region in the predetermined period of a compression process of the gas, and the pressure in the back pressure chamber.

What is claimed is:  
     
         1 . A scroll compressor for compressing gas introduced from an inlet, the gas being compressed and discharged through a discharge port, the scroll compressor comprising: 
 a fixed scroll member;    a movable scroll member having a movable scroll base plate, wherein the fixed scroll member and the movable scroll member cooperatively form a compression region and an intake space communicating to the inlet;    a housing secured to the fixed scroll member, the housing accommodating the movable scroll member to define a back pressure chamber, pressure in the back pressure chamber being applied to the back surface of the movable scroll base plate, the back pressure chamber communicating with a region through a communication passage, the region being lower in pressure than the back pressure chamber, the communication passage relieving the pressure in the back pressure chamber to the region; and    a valve for varying an opening amount of the communication passage due to difference between the pressure in the compression region in the predetermined period of a compression process of the gas, and the pressure in the back pressure chamber.    
     
     
         2 . The scroll compressor according to  claim 1  wherein the region is the compressor intake system.  
     
     
         3 . The scroll compressor according to  claim 1  wherein the region is a compression region of the compressor.  
     
     
         4 . The scroll's compressor according to  claim 3  wherein the pressure in the back pressure chamber is relieved to the region where gas compression in the compression region has just begun.  
     
     
         5 . The scroll compressor according to  claim 1  wherein the valve is a spool valve.  
     
     
         6 . The scroll compressor according to  claim 5  wherein the valve has a first end surface and a second end surface in the axial direction of the valve, the first end surface being smaller in area than the second end surface.  
     
     
         7 . The scroll compressor according to  claim 1  wherein the valve is a poppet valve.  
     
     
         8 . The scroll compressor according to  claim 1  further comprising an auxiliary spring for varying the opening amount of the communication passage, wherein the valve varies the opening amount of the communication passage due to the pressure difference and resilient force of the auxiliary spring.  
     
     
         9 . The scroll compressor according to  claim 1  wherein the discharge port is formed in the movable scroll member, 
 wherein the back pressure chamber is constituted of a first pressure chamber, a second pressure chamber and a third pressure chamber, the first pressure chamber receiving the discharged gas in the vicinity of the discharge port, the third pressure chamber communicating with the intake space in the vicinity of the inlet, the second pressure chamber being defined between the first pressure chamber and the third pressure chamber, and  
 wherein the valve varies the opening amount of the communication passage due to difference between the pressure in the compression region in the predetermined period of the compression process of the gas, and the pressure in the back pressure chamber.  
 
     
     
         10 . The scroll compressor according to  claim 1  wherein the communication passage and the valve are formed in the movable scroll base plate.  
     
     
         11 . The scroll compressor according to  claim 10  wherein the movable scroll base plate forms a valve chamber for accommodating the valve.  
     
     
         12 . The scroll compressor according to  claim 1  wherein the valve is an opening and closing valve for opening and closing the communication passage.  
     
     
         13 . A method for controlling the pressure in a back pressure chamber of a scroll compressor for compressing gas in a compression region comprising the step of: 
 communicating the back pressure chamber with a region that is lower in pressure than the back pressure chamber in accordance with the difference between the pressure in the compression region in the predetermined period of a compression process of the gas, and the pressure in the back pressure chamber.    
     
     
         14 . The method according to  claim 13  wherein the lower-pressure region is the compressor intake system.  
     
     
         15 . The method according to  claim 13  wherein the lower-pressure region is a compression region of the compressor.  
     
     
         16 . The method according to  claim 13  wherein the communicating step includes passing through a movable scroll base plate.  
     
     
         17 . The method according to  claim 13  further comprising the step of accommodating a valve in the movable scroll base plate.  
     
     
         18 . The method according to  claim 13  further comprising the step of providing an auxiliary spring in the movable scroll base plate.