Patent ID: 8598755

Claim:
An electric rotary actuator with a first axial end and a second axial end, comprising: an electric motor; a speed reducer that is integrally coupled to the electric motor at a first axial end side of the electric motor; and a housing that accommodates the electric motor and the speed reducer, wherein the housing includes a housing body having a stepped cylindrical shape, the housing body including a cylindrical motor housing body, a step surface portion extending radially inward from a first axial end side of the cylindrical motor housing body, and a speed reducer housing body extending from a radial inner periphery of the step surface portion toward the first axial end; a partition wall portion that is annularly formed integrally with an inner peripheral surface of the housing body so as to present a first surface facing the first axial end and a second surface facing the second axial end, and that partitions an inner space of the housing body into an electric motor accommodating space that is located on a second axial end side of the partition wall portion and that accommodates the electric motor, and a speed reducer accommodating space that is located on a first axial end side of the partition wall portion and that accommodates the speed reducer; and a cylindrical housing boss portion that extends from the second surface of the partition wall portion toward the second axial end, which is on an electric motor accommodating space side, the electric motor is an outer rotor electric motor, the electric motor includes an inner stator that is fixed to an outer peripheral surface of the housing boss portion, an inner peripheral surface of the inner stator abutting the outer peripheral surface of the housing boss portion; an outer rotor that is arranged radially between an outer peripheral surface of the inner stator and the inner peripheral surface of the housing body so as to be spaced apart from both the outer peripheral surface of the inner stator and the inner peripheral surface of the housing body; a motor output shaft that is inserted on an inner peripheral side of both the housing boss portion and the partition wall portion, and that is rotatable relative to the housing; and an outer rotor coupling portion that is arranged on the second axial end side with respect to the inner stator and the housing boss portion, that couples the outer rotor and the motor output shaft with each other, and that transmits rotation of the outer rotor to the motor output shaft, the speed reducer includes a plurality of gears, is coupled to a first axial end side portion of the motor output shaft, and reduces a speed of rotation of the output shaft through operation of the plurality of gears and then outputs the rotation, and at least one of the plurality of gears of the speed reducer is fixed to a portion of the partition wall portion of the housing on the first axial end side, and transmits at least part of the torque transmitted from the motor output shaft to the partition wall portion.