Abstract: A steering system includes a rack shaft, a housing, an electric motor, a control device, and a speed reduction mechanism that applies a moving force in the axial direction to the rack shaft with the speed of rotation of the electric motor reduced. The housing has a rack shaft housing portion and a speed reduction mechanism housing portion. The electric motor has: a motor case fixed to the housing; a plurality of stator cores disposed annularly in the motor case; coil windings wound around the plurality of stator cores; and a rotor. The motor case is formed with a water introduction hole that introduces water that has entered the speed reduction mechanism housing portion into the motor case. The control device has a detector that detects entry of water into the motor case.

Abstract: Provided is a motor apparatus in which an increase in its size in a radial direction of a rotation shaft of a motor can be suppressed while securing redundancy of control of driving of the motor. A motor apparatus includes a motor having a rotation shaft, a first control circuit board where a first power circuit and a first control circuit are mounted, and a second control circuit board where a second power circuit and a second control circuit are mounted. The control circuit boards are arranged with an overlapping portion when viewed along an axial direction on an extension line of an axis of the rotation shaft. The overlapping portion intersects the extension line of the rotation shaft of the motor.

Abstract: A motor device that can secure the detection precision of the rotational angle of a motor is provided. A motor device has a motor housing, a heat sink, a motor cover, a motor, and a substrate. An opening portion of the motor housing is covered by the motor cover which is made of a magnetic body such as iron in a roofed tubular shape. A choke coil is provided on a surface of the substrate on the side opposite to the motor. A magnetic sensor is provided on a surface of the substrate on the side of the motor. A housing portion is provided at a roof portion of the motor cover. The choke coil, which is mounted on the substrate, is surrounded by the housing portion.

Abstract: Provided is a motor device that prevents an increase in size in the radial direction of a motor while providing redundancy in controlling driving of the motor. A motor device includes: a motor including a motor shaft; a first control board on which a first power circuit and a first control circuit are mounted in combination, and a second control board on which a second power circuit and a second control circuit are mounted in combination, as control boards constructing a circuit that controls driving of the motor; and a housing that accommodates the motor and the control boards together. Each of the control boards is disposed to cross a radial direction that is orthogonal to an axial direction of the motor.

Abstract: A semiconductor device is provided that allows an IC chip and a heat sink to be prevented from being short-circuited even if facing surfaces of the IC chip and the heat sink are located closest to each other due to manufacturing variations and other variations. A controller for a motor apparatus includes a substrate on which MOSFETs are mounted and a heat sink provided facing the substrate and the MOSFETs so as to dissipate heat generated by the MOSFETs. Insulating portions are each provided on a facing surface of each MOSFETs. Protruding portions are each provided on a facing surface of the heat sink so as to protrude from the heat sink toward the insulating portion of the corresponding MOSFET. A second clearance smaller than the first clearance is formed between each of the insulating portions and the corresponding protruding portion.