Patent ID: 8128388

Claim:
A scroll-type expansion machine wherein a refrigeration cycle is constituted with a main compression mechanism for compressing a refrigerant, a gas cooler for cooling the refrigerant, and an evaporator for evaporating the refrigerant; said scroll-type expansion machine comprising: an expansion mechanism disposed within a hermetic vessel and including an orbiting scroll and a first fixed scroll for expanding a refrigerant from said gas cooler and recovering a power; and a scroll-type sub-compression mechanism disposed within said hermetic vessel and including an orbiting scroll including a base plate in common with the orbiting scroll of said expansion mechanism and coupled with a second fixed scroll for compressing the refrigerant compressed by said main compression mechanism by the power recovered by said expansion mechanism; wherein said first fixed scroll and said second fixed scroll define within said hermetic vessel an upper space, an orbit scroll moving space, and a lower space; said sub-compression mechanism includes a discharge port open within said upper space; said upper space and said lower space are connected together by an oil flow path; an outer circumference seal is disposed between said fixed scroll and said orbiting scroll of said sub-compression mechanism; said oil flow path is an oil return bore communicating said upper space and said lower space together without passing through said orbiting scroll moving space; and wherein said orbiting scroll moving space is at an expanded pressure and said upper space and said lower space each is at a compressed pressure of said sub-compression mechanism.