Patent ID: 6948316

Claim:
A Rankine cycle system comprising a working medium circulation circuit ( 110 ) through which a working medium is circulated and that includes an evaporator ( 112 ) that makes a working medium of a high-temperature, high-pressure gas-phase by heating the working medium in a liquid-phase by means of waste heat of an internal combustion engine ( 111 ), an expander ( 113 ) in the circuit ( 110 ) that converts the heat and pressure of the working medium of a gas-phase supplied from the evaporator ( 112 ) into mechanical energy, a condenser ( 114 ) in the circuit ( 110 ) that cools the gas-phase working medium whose temperature and pressure have decreased in the expander ( 113 ) to turn the working medium back into the liquid-phase working medium, and a feed pump ( 115 ) in the circuit ( 110 ) that supplies the liquid-phase working medium discharged from the condenser ( 114 ) to the evaporator ( 112 ), a lubricating medium circulating passage ( 91 ) through which a lubricating medium that is different from the working medium is circulated, wherein the expander ( 113 ) has a sliding section thereof lubricated by the lubricating medium, the Rankine cycle system further comprising: working medium separating means ( 118 ) for separating from the lubricating medium the working medium that has become mixed with the lubricating medium in the expander ( 113 ), and the working medium separating means ( 118 ) is provided in the lubricating medium circulating passage ( 91 ) at a position where the working medium is in a liquid-phase state, and lubricating medium separating means ( 137 ) for separating from the working medium the lubricating medium that has become mixed with the working medium in the expander ( 113 ), wherein the lubricating the medium separating means ( 137 ) is provided at a position on the downstream side of the expander ( 113 ) where the working medium is in a liquid-phase state.