Electric power steering apparatus

摘要

An electric power steering apparatus for generating a PWM signal based on a calculated steering assist command value, PWM-controlling a motor via a motor drive circuit including switching elements, and assist-controlling a steering system that a motor relay is inserted between the motor drive circuit and the motor, includes a steering status detecting section that detects a steering status of a steering wheel, outputs a longtime steering holding signal when detecting that the steering status is a longtime steering holding status, and outputs a normal steering signal when detecting that the steering status is a normal steering status, and a motor current control section that determines a motor current control value for controlling a motor current flowing in the motor relay in accordance with the longtime steering holding signal or the normal steering signal.

主权项

1. An electric power steering apparatus for calculating a steering assist command value based on a steering torque and a velocity, generating a pulse-width modulation (PWM) signal based on said steering assist command value, PWM-controlling a three-phase brushless DC motor via a motor drive circuit comprised of switching elements, and assist-controlling a steering system that an electromagnetic type motor relay is inserted between said motor drive circuit and said three-phase brushless DC motor, comprising:
a temperature estimating section that estimates a temperature of a relay spring portion or a relay coil portion of said electromagnetic type motor relay, a comparing section that compares an estimated temperature value that is estimated by said temperature estimating section with a given temperature, and a motor current control section that controls a motor current flowing in said electromagnetic type motor relay in accordance with a comparison result of said comparing section; and a substrate temperature sensor that detects a temperature of a substrate that is equipped with said electromagnetic type motor relay; wherein said substrate temperature is inputted into said temperature estimating section, wherein said temperature estimating section is a relay-spring-portion-temperature estimating section, said relay-spring-portion-temperature estimating section comprises:
an each-phase current accumulating section that accumulates detected each-phase current values of said three-phase brushless DC motor,a maximum value selecting section that selects a maximum value of accumulated values of said detected each-phase current values,a relay-spring-portion-temperature calculating section that calculates a relay-spring-portion-temperature based on a sum of said maximum value and a relay-coil-portion-temperature estimated-value, andan addition section that adds said substrate temperature and said relay-spring-portion-temperature and outputs said relay-spring-portion-temperature estimated-value.