A steering device includes a clutch and a wheel-turning shaft. The clutch includes an input shaft, an output shaft, a planetary gear mechanism, a housing, and a restriction member. The planetary gear mechanism is coupled to each of the input shaft and the output shaft. The housing is configured to accommodate the planetary gear mechanism and at least part of the output shaft. The restriction member is secured to the housing or constitutes part of the housing. The restriction member is opposed to an outer surface of the output shaft through a gap so as to restrict inclination of the output shaft. The wheel-turning shaft is configured to be displaced in accordance with rotation of the output shaft so as to turn wheels of a vehicle.

Provided is an electric assisted power steering apparatus having a structure able to disconnect a worm shaft from any malfunctioning motor of motors connected to opposite end portions of the worm shaft, thereby preventing the worm shaft from rotating heavily or failing to rotate. Even in the case in which the worm shaft is disconnected from the malfunctioning motor, a target rotation speed of the properly-operating motor is increased to prevent sudden changes in auxiliary torque occurring on a steering shaft, thereby promoting the safety of a driver. Torque required for the worm shaft is distributed to the two motors, thereby increasing the rotation speeds of the motors and reducing the size and fabrication costs of the motors.

Provided is an electric assisted power steering apparatus having a structure able to disconnect a worm shaft from any malfunctioning motor of motors connected to opposite end portions of the worm shaft, thereby preventing the worm shaft from rotating heavily or failing to rotate. Even in the case in which the worm shaft is disconnected from the malfunctioning motor, a target rotation speed of the properly-operating motor is increased to prevent sudden changes in auxiliary torque occurring on a steering shaft, thereby promoting the safety of a driver. Torque required for the worm shaft is distributed to the two motors, thereby increasing the rotation speeds of the motors and reducing the size and fabrication costs of the motors.

Methods and systems are provided for a steer-by-wire system. In one example, a steer-by-wire system comprises an electric motor coupled to a steering axle via a bevel gear set, where a rotor of the electric motor is perpendicular to the steering axle, and the bevel gear set comprises a first bevel gear and a second bevel gear. The steer-by-wire system includes an overload protection arrangement, where the second bevel gear is normally coupled to a ball screw nut via a plurality of locking pins, the plurality of locking pins disengaging from the second bevel gear and allowing slipping of the ball screw nut in response to an external impact load acting on the ball screw nut exceeding a threshold.