Scroll type fluid displacement apparatus with balanced drive means

Abstract

A scroll-type fluid displacement apparatus, in particular, a compressor unit is disclosed. The unit includes a housing with a fluid inlet port and a fluid outlet port. A fixed scroll with first end plate and first spiral element is fixedly disposed in the housing. An orbiting scroll with a second end plate and a second spiral element is disposed for orbiting motion in the housing. The first and second spiral elements interfit with one another at an angular offset to make a plurality of line contacts to define at least one pair of sealed off fluid pockets. A drive pin extends from an inner end of a drive shaft. The orbiting scroll has a boss which rotatably supports a bushing. An eccentric hole is formed in the bushing and the drive pin is received within this hole. The center of the drive pin is located on an opposite side to the center of the drive shaft with regard to a straight line, which passes through the center of the bushing and is perpendicular to a connecting line passing through the center of the drive shaft and the center of the bushing. The center of the drive pin also is beyond the connecting line in the direction of rotation of the drive shaft. The bushing has a balance weight for cancelling a centrifugal force which arises because of the orbiting motion of the scroll member and bushing. Dynamic balance is accomplished by the use of a pair of balance weights affixed to the drive shaft for generating a moment of the same amount, but opposite in direction, to the moment generated by a force due to the interaction of the centrifugal force of the orbiting parts and the first balance weight.