A rotary fluid transmission device contains: a rotor, a drive shaft, a first holder, and a second holder. The first holder includes a circular bush and an annular chamber. The rotor includes a C-shaped piston which has an external face and an internal face. In addition, the annular chamber has a first reservoir defined between the internal face and the circular bush, and the annular chamber has a second reservoir defined between the external face and the inner fringe. The circular seat includes two clamp arms, and a respective clamp arm is rotatably engaged with a blade. The blade includes two abutting faces, and the C-shaped piston has two edge faces. The first holder includes two first conduits and two second conduits, the two first conduits are in communication with the first reservoir, and the two second conduits are in communication with the second reservoir.

The scroll compressor includes scroll members that include a compression chamber to compress working fluid, a housing that houses the scroll members, a second driving-side shaft portion that discharges the compressed working fluid from the compression chamber and is rotated around an axis with respect to the housing, a bearing that rotatably supports the housing with respect to the second driving-side shaft portion , and a seal member between the second driving-side shaft portion and the housing . A lubricant is provided between the bearing and the seal member.