Patent ID: 7671500

Claim:
A motor comprising: an inner-peripheral rotor having permanent magnets which are arranged along a circumference thereof; an outer-peripheral rotor, which has permanent magnets arranged along a circumference thereof, and is arranged on an outer periphery of the inner-peripheral rotor in a manner such that the outer-peripheral rotor is coaxial and relatively rotatable with respect to the inner-peripheral rotor; and a phase varying device for relatively rotating the inner-peripheral rotor and the outer-peripheral rotor so as to vary a relative phase between thereof, wherein the phase varying device includes: a forward-angle working chamber for relatively rotating the inner-peripheral rotor in a forward-angle direction with respect to the outer-peripheral rotor, by using pressure of a working fluid supplied to the forward-angle working chamber; a backward-angle working chamber for relatively rotating the inner-peripheral rotor in a backward-angle direction with respect to the outer-peripheral rotor, by using pressure of a working fluid supplied to the backward-angle working chamber; a fluid supply source for supplying each working fluid; a passage switching valve having a spur, for performing distribution with respect to a process of supply and drainage of the working fluid between the forward-angle working chamber and the backward-angle working chamber, in accordance with a position of the spur; and an electromagnetic pressure control valve for controlling pressure of the working fluid supplied from the fluid supply source, and controlling the position of the spur in the passage switching valve based on the controlled pressure of the working fluid, wherein the passage switching valve further comprises: a forward-angle feedback chamber which communicates with the forward-angle working chamber, and applies thrust to the spur, the thrust corresponding to pressure in the forward-angle working chamber; and a backward-angle feedback chamber which communicates with the backward-angle working chamber, and applies thrust to the spur in a direction opposite the thrust applied by the forward-angle feedback chamber, the thrust corresponding to pressure in the backward-angle working chamber; and in the spur, the area of a pressure-receiving face which contacts the forward-angle feedback chamber is identical to the area of a pressure-receiving face which contacts the backward-angle feedback chamber.