Scroll-type compressor

A scroll-type compressor comprising:

• a first scroll member having a first spiral element;
• a second scroll member disposed for nonrotatable, orbital movement relative to said first scroll member and having a second spiral element, said first and second spiral elements interfitting at an angular and radial offset to make a plurality of line contacts which define at least one pair of sealed-off fluid pockets;
• a ball coupling provided as a rotation preventing mechanism for said second scroll member and having a pair of plates and a plurality of balls disposed between said plates, said pair of plates having ring-like ball rolling grooves for receiving said balls on respective surfaces facing each other, one of said pair of plates being fixed to a front housing, the other of said pair of plates being fixed to said second scroll member;
• and
• a driving mechanism for said second scroll member comprising a drive shaft, a crank pin provided eccentric to said drive shaft, and a driven crank mechanism being swingably fitted to said crank pin and being rotatably held by said second scroll member, said driven crank mechanism having a swing angle variation allowing mechanism for regulating a maximum amount of variation of a swing angle of said driven crank mechanism, said maximum amount of variation of said swing angle due to said swing angle variation allowing mechanism being set within a range predetermined in accordance with a diameter of a ring form of each of said ring-like ball rolling grooves, such that said balls are held within said ring-like ball rolling grooves during operation of said compressor.