Pump

A pump comprising:

• a cylindrical outer rotor having an inner peripheral surface on which a plurality of pendulum retaining grooves are formed, each pendulum retaining groove being of a letter C shape in cross section and being extended in an axial direction of the pump;
• an inner rotor disposed at an inner peripheral side of the outer rotor eccentrically to the outer rotor and having a plurality of slots formed on an outer peripheral surface of the inner rotor in a radial direction of the pump;
• and
• a plurality of pendulums, each pendulum having:
• a head section of a substantially circular shape in cross section slidably fitted into a corresponding one of the pendulum retaining grooves;
• and a body section of a substantially triangular shape in cross section connected to the head section via a neck section and slidably fitted into a corresponding one of the slots while contacting on side surfaces of both sides of the corresponding one of the slots and partitioning a space between the outer rotor and the inner rotor into a plurality of chambers, either of the outer rotor or the inner rotor being rotationally driven, wherein
• each of the pendulums has a torque transmission surface formed on one side surface of the body section opposed against a torque-transmission-side side surface of a corresponding one of the slots, the torque transmission surface having a profile such that a straight line section and a curved section extended from one end of an outer peripheral side of the straight line section to a side portion of the neck section are continued,
• the straight line section has a profile such that the straight line section makes a surface contact on the torque-transmission-side side surface of the corresponding one of the slots, at a reference angle position at which a perpendicular line orthogonal to an eccentric direction of the inner rotor and passing through a center of the inner rotor and the torque-transmission-side side surface of the corresponding one of the slots are made parallel to each other, and
• the curved section has a profile such that, at least, during a predetermined torque transmission angle including an angle into which 360° is equally divided by the number of pendulums, the curved section continues the contact on an opening edge of the torque-transmission-side side surface of the corresponding one of the slots and maintains rotational angles of both of the rotors mutually equally.