ELECTRIC POWER STEERING DEVICE FOR VEHICLE

摘要

An electric power steering device for a vehicle includes a plurality of assist systems electromagnetically driving an electric motor. When a first or second assist system malfunctions, a malfunction state assist amount calculation part calculates an assist amount while decreasing a limit value at the vehicle stopping, to an amount smaller than a limit value at the vehicle moving. When a malfunction such as a disconnection or a fixing of the switching elements occurs in the first or second assist systems on the basis of a judgment result of a malfunction judgment function, an assist amount switching part supplies an assist amount received from the malfunction state assist amount calculation part to first and second motor drive control parts. When a malfunction occurs in one of the first and second assist systems, one of the first and second motor drive control parts drives the motor by using the assist amount.

主权项

1. An electric power steering device for a vehicle, comprising:
at least one electric motor for adding a predetermined assist force for assisting a steering wheel manipulation by a driver; a plurality of assist systems including said electric motor, said assist systems electromagnetically driving said electric motor; assist control means for calculating an assist amount representing said predetermined assist force by using a manipulation force input by said driver via a steering wheel and controlling an assist to said steering wheel manipulation by using at least one of said assist systems on the basis of said calculated assist amount, wherein when a malfunction occurs in at least one of said assist systems, said assist control means is configured to: calculate an assist amount at one of vehicle stopping and moving while controlling a maximum assist amount at the vehicle stopping representing a maximum assist force added by said electric motor at the vehicle stopping to an amount smaller than a maximum assist amount at the vehicle moving representing a maximum assist force added by said electric motor at the vehicle moving; and control the assist to said steering wheel manipulation by using said assist system under a normal state other than said assist system under a malfunction state on the basis of said calculated assist amount at the vehicle stopping or moving.