Patent ID: 8768571

Claim:
A vehicle steering device comprising: a steering mechanism that steers a wheel upon steering operation of a steering wheel; an electric motor that is supplied with source power from an electric power source device and generates assist force that assists in the steering operation of the steering wheel; a steering torque sensor that detects steering torque that a vehicle driver inputs to the steering wheel; electric power abnormality detection circuitry that detects abnormality of source power supply capability of the electric power source device; a vehicle speed sensor that detects vehicle speed; and motor control circuitry that controls driving of the electric motor based on at least the steering torque detected by the steering torque sensor, wherein the motor control circuitry includes output restriction circuitry that decreases an output upper limit value of the electric motor as the vehicle speed detected by the vehicle speed sensor decreases while the abnormality of the source power supply capability of the electric power source device is detected by the electric power abnormality detection circuitry, wherein the output restriction circuitry stores relation-connecting information that indicates relation of the output upper limit value of the electric motor with the vehicle speed detected by the vehicle speed sensor, and the relation-connecting information is set so that if the vehicle speed decreases, the output upper limit value of the electric motor decreases, and the motor control circuitry controls such that output of the electric motor does not exceed the output upper limit value that is found based on the relation-connecting information.