Scroll-type compressor

Abstract

An orbiting scroll 6 is provided with a second communication passage 64 feeding refrigerant gas in a compression chamber 15 toward a back pressure chamber 16. One of or each of an outer circumferential surface of a bush 4 and an inner circumferential surface of a bearing 5 is provided with a first communication passage 41 communicating an upstream side space 16 a and a downstream side space 16 b. The first communication passage 41 is formed so as to avoid an area at which the bush 4 receives a largest load from the plain bearing 5. A part of the refrigerant gas compressed in the compression chamber 15 flows into the downstream side space 16 b via the second communication passage 64, the upstream side space 16 a and the first communication passage 41.

What is claimed is: 
     
         1 . A scroll-type compressor comprising:
 a rotation shaft;   an eccentric shaft fixed to the rotation shaft, the eccentric shaft being offset from a rotation center of the rotation shaft;   a cylindrical bush fitted onto the eccentric shaft;   a bearing disposed rotatably relative to the bush;   an orbiting scroll supported by the bush via the bearing;   a fixed scroll disposed to face the orbiting scroll; and   a shaft supporting member supporting the rotation shaft and being disposed to face the orbiting scroll at an opposite side from the fixed scroll,   wherein   a compression chamber is formed between the orbiting scroll and the fixed scroll,   a back pressure chamber is formed between the orbiting scroll and the shaft supporting member, the orbiting scroll is pressed toward a fixed scroll by pressure of refrigerant gas in the back pressure chamber,   refrigerant gas in the compression chamber is compressed in accordance with orbiting motion of the orbiting scroll caused by rotation of the rotation shaft through revolution of the eccentric shaft,   the bearing is a plain bearing,   the back pressure chamber is divided into an upstream side space and a downstream side space by the bearing,   at least one of an outer circumferential surface of the bush and an inner circumferential surface of the bearing comprises a first communication passage communicating the upstream side space and the downstream side space,   the orbiting scroll comprises a second communication passage feeding the refrigerant gas in the compression chamber toward the back pressure chamber,   a part of the refrigerant gas compressed in the compression chamber flows into the downstream side space via the second communication passage, the upstream side space and the first communication passage, and   the first communication passage is formed so as to avoid an area at which the bush receives a largest load from the plain bearing.   
     
     
         2 . The scroll-type compressor according to  claim 1 , wherein
 a balance weight is integrally attached to the bush, and   an opening of the first communication passage is located in an area not opposing the balance weight.   
     
     
         3 . The scroll-type compressor according to  claim 1 , wherein
 a imaginary line set to include a rotation shaft axis and a bush axis defines a first side on which an eccentric shaft axis exists and a second side on which the eccentric shaft axis does not exist, and   the first communication passage is formed on the second side.   
     
     
         4 . The scroll-type compressor according to  claim 1 , wherein
 the first communication passage extends along one of or each of an axial direction and a circumferential direction of the bush, and an axial direction and a circumferential direction of the bearing.   
     
     
         5 . The scroll-type compressor according to  claim 1 , wherein
 the first communication passage is formed on the bush.   
     
     
         6 . The scroll-type compressor according to  claim 1 , wherein
 the first communication passage is formed on the bearing.   
     
     
         7 . The scroll-type compressor according to  claim 1 , wherein
 the bearing comprises an inner sliding member in contact with the bush and an outer sliding member in contact with the orbiting scroll, and   the first communication passage is formed on the inner sliding member.   
     
     
         8 . The scroll-type compressor according to  claim 1 , wherein
 the rotation shaft comprises a discharging passage through which the refrigerant gas in the back pressure chamber is discharged.