Vehicle electronic power steering device

Abstract

In the event of failure in a first assist system or a second assist system, a failure assist amount computing unit (35) computes an assist amount (Tf) while decreasing a maximum assist amount (upper limit for failure) as a limit value for when a vehicle is stopped compared with a maximum assist amount as a limit value for when the vehicle is running. For example, when it is determined that a failure, such as disconnection or switching element seizure, is present in the first assist system or the second assist system on the basis of a result of determination by a failure determine function, an assist amount switching unit (36) supplies the assist amount (Tf) inputted from the failure assist amount computing unit (35) to a first motor drive control unit (37) and a second motor drive control unit (38). When the failure is present in the second assist system, the drive control unit (37) drives an EPS motor (15) in accordance with the assist amount (Tf). When the failure is present in the first assist system, the drive control unit (38) drives the EPS motor (15) in accordance with the assist amount (Tf).

Description

technical field [0001] The present invention relates to an electric power steering device for a vehicle including an electric motor that provides a predetermined assist force for assisting a driver's steering wheel operation, and more particularly relates to an electric power steering device including a plurality of electric motors that are configured to include an electric motor and electromagnetically drive the electric motor. The electric power steering device of the auxiliary system vehicle. Background technique [0002] Conventionally, for example, a control device for a multi-phase rotating machine disclosed in Patent Document 1 below, and an electric power steering device using the control device for a multi-phase rotating machine are known. In this conventional control device for a multi-phase rotating machine, the control unit is configured such that a conduction failure occurs in any one of the plurality of MOSs constituting the first inverter unit and the pluralit...

AI Technical Summary

Problems solved by technology

[0004] However, in the case of having a plurality of inverter units (auxiliary systems) as in the conventional apparatus described above, if one of the plurality of inverter units (auxiliary systems) fails, there is a problem of driving the electric motor. Possibility of torque (assist force) being lower than normal

In addition, in such a situation where the torque (assist force) generated by the electric motor is reduced, especially when the steering wheel is turned while the vehicle is stopped, a large load will be generated on the electric motor. Therefore, the electric motor, drive circuit ( Inverter) is prone to heat and become high temperature

In this case, in order to prevent overheating, the magnitude of the torque (assist force) applied by the electric motor drive may be limited or reduced.

[0005] Moreover, from this situation, especially immediately after the vehicle starts running, the electric motor is still at a high temperature, and there is a possibility that the limitation of torque (assist force) will continue.

In this case, when the driver operates the steering wheel to turn the steering wheel, the torque (assist force) is insufficient compared to usual, and there is a possibility of feeling uncomfortable due to the lack of torque (assist force).

Images