US Patent 9822876 Axial piston device

A housing of an axial piston device is provided with a drain port for discharging the retained oil to the outside and a supply oil passage for guiding lubricating oil, which has been supplied from an oil source, toward a first hydraulic axial piston member. The drain port is arranged so as to bring about such a retained-oil level that a second hydraulic axial piston member, which is disposed below the first hydraulic axial piston member, is partially or entirely immersed in the retained oil while the first hydraulic axial piston member is not immersed in the retained oil.