Scroll Fluid Machine

Abstract

A scroll fluid machine is configured by engaging a fixed scroll and an orbiting scroll having spiral bodies formed on base plates. A seal member is provided between a rear surface of the orbiting scroll and a frame member arranged opposite thereto to divide a rear side chamber into an inner space and an outer space. The inner space inside the seal member is subjected to a pressure substantially corresponding to a discharge pressure, and the outer space is subjected to a pressure lower than that of an inner back pressure chamber to press the orbiting scroll against the fixed scroll. The scroll members are formed such that the width of a groove and the thickness of a tooth of the spiral body formed inside the seal member are larger than those of the spiral body formed outside the seal member.

1 . A scroll fluid machine comprising two scroll members each of which has a spiral body formed on a base plate, the scroll members being engaged to relatively gyrate such that a hermetic space formed by both scroll members is increased or reduced to make fluid expand or compress the fluid, wherein:
 the scroll fluid machine is configured such that a seal member is provided between a rear surface of one of the scroll members and a stationary member to divide a space formed between the rear surface and the stationary member into an inner side space and an outer side space, the inner side space inside the seal member being subjected to a pressure substantially corresponding to a discharge pressure, the outer side space outside the seal member being subjected to a pressure lower than that in the inner side space to press the one scroll member against the other scroll member; and   the shape of the spiral body of each scroll member is configured such that the width of a groove of the spiral body of the scroll member and the thickness of a tooth of the spiral body decrease from a central portion toward an outer side of the spiral body over a part of or the whole of the spiral body.   
   
   
       2 . The scroll fluid machine according to  claim 1 , wherein a part of or the whole of the spiral body of each scroll member is formed by an involute of a circle (base circle) the radius of which varies depending on an involute angle. 
   
   
       3 . The scroll fluid machine according to  claim 1 , wherein each scroll member is formed such that the width of a groove and the thickness of a tooth of the spiral body formed inside the seal member are larger than those of the spiral body formed outside the seal member. 
   
   
       4 . The scroll fluid machine according to  claim 2 , wherein each scroll member is formed such that a radius of the base circle for forming the spiral body formed inside the seal member is larger than that of the base circle for forming the spiral body formed outside the seal member. 
   
   
       5 . The scroll fluid machine according to  claim 4 , wherein the spiral body of each scroll member is formed by an involute of a circle represented by the formula of:
     a=as+f (λ) ( f ′(λ)<0)   
     wherein a is a radius of the base circle, λ is an involute angle, and as is a radius of the base circle at a beginning portion of winding of the spiral body. 
   
   
       6 . A scroll fluid machine comprising a fixed scroll and an orbiting scroll each of which has a spiral body formed on a base plate, the fixed scroll and the orbiting scroll being engaged, wherein:
 the scroll fluid machine is configured such that a seal member is provided between a rear surface of the orbiting scroll and a frame member arranged opposite to the rear surface to divide a space formed between the rear surface and the frame member into an inner side space and an outer side space, the inner side space inside the seal member being subjected to a pressure substantially corresponding to a discharge pressure, the outer side space outside the seal member being subjected to a pressure lower than that in the inner side space to press the orbiting scroll against the fixed scroll; and   each of the orbiting scroll and the fixed scroll is formed such that the width of a groove and the thickness of a tooth of the spiral body formed inside the seal member are larger than those of the spiral body formed outside the seal member.