Patent ID: 8789645
Filing Date: 2014-07-29
Classification: B62D

Abstract:
1. An electric power steering device, comprising: electric-motor driving means for driving an electric motor for applying an assist torque to steering performed by a driver; at least one relay for interrupting power supply to the electric-motor driving means; steering-force detection means for detecting a steering force of the driver; control means for generating an electric-motor control signal for controlling an output torque of the electric motor based at least on results of detection by the steering-force detection means and outputting the electric-motor control signal to the electric-motor driving means; failure detection means for detecting an abnormality in the electric power steering device; and relay gradual interruption means including switch means connected in parallel to a drive coil included in the at least one relay and a diode connected in series to the switch means, wherein: the relay gradual interruption means is for turning the switching means ON so as to cause an amount of current corresponding to a back surge generated at ends of the drive coil to flow back to the diode when an exciting voltage of the drive coil of the at least one relay is turned OFF; and when the failure detection means does not detect the abnormality in the electric power steering device, the control means lowers a target value of a relay-contact energizing current, operates the relay gradual interruption means, and then interrupts the at least one relay, and when the failure detection means detects the abnormality in the electric power steering device, the control means interrupts the at least one relay without operating the relay gradual interruption means.