A first cylindrical part in which axial part passages for supplying a fluid to
or discharging a fluid from a fluid pressure chamber are formed is provided in
a rotor and, at the same time, a second cylindrical member in which cover passages
communicating with axial part passages and a fluid supplying and discharging means
are formed is provided. The first cylindrical part is overlaid on an inner side
relative to the second cylindrical member in a radial direction and is constructed
of an aluminium alloy, a sealing groove for accommodating a sealing member for
tight sealing between a first cylindrical part and a second cylindrical member
with an outer peripheral surface and a side surface thereof is provided, and a
friction A between a side of a sealing member and a sealing groove is set to be
greater than a friction B between an outer peripheral side of the sealing member
and an inner peripheral side of the second cylindrical member.
