Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-9278708-B2
Application number	US-201214131809-A
Country	US
Kind code	B2
Filing date	Sep 3, 2012
Priority date	Feb 6, 2012
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

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.

First claim

The invention claimed is:

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, and
an addition section that adds said substrate temperature and said relay-spring-portion-temperature and outputs said relay-spring-portion-temperature estimated-value.

2. An electric power steering apparatus according to claim 1 , wherein a decrease rate in control of said motor current is set to ½ of a normal time, and an increase rate in control of said motor current is set to double of said normal time.

3. The electric power steering apparatus according to claim 1 , further comprising a processor, which includes the temperature estimation section, the comparing section, and the motor current control section.

4. An electric power steering apparatus for calculating 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;
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-coil-portion-temperature estimating section, said relay-coil-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-coil-portion-temperature calculating section that calculates a relay-coil-portion-temperature based on a sum of said maximum value and a relay-coil-portion-temperature estimated-value, and
an addition section that adds said substrate temperature and said relay-coil-portion-temperature and outputs said relay-spring-coil-portion-temperature estimated-value.

5. An electric power steering apparatus according to claim 4 , wherein a decrease rate in control of said motor current is set to ½ of a normal time and an increase rate in control of said motor current is set to double of said normal time.

6. The electric power steering apparatus according to claim 4 , further comprising a processor, which includes the temperature estimation section, the comparing section, and the motor current control section.

7. An electric power steering apparatus comprising:
a memory storing executable instructions; and
a processor configured to execute the stored instructions comprising:
estimating a temperature of a relay spring portion of an electromagnetic type motor relay based on a substrate temperature, detected by a sensor, and is of a substrate that is equipped with said electromagnetic type motor relay,
comparing the estimated temperature with a given temperature, and
controlling a motor current flowing in said electromagnetic type motor relay based on said comparing,
wherein said estimating the temperature comprises:
accumulating detected each-phase current values of a three-phase brushless DC motor,
selecting a maximum value of said accumulated detected each-phase current values,
calculating a relay-spring-portion-temperature based on a sum of said maximum value and a relay-coil-portion-temperature estimated-value, and
adding said substrate temperature and said relay-spring-portion-temperature, and
outputting said relay-spring-portion-temperature estimated-value.

Assignees

• Kouichi Satoh
• Kashimoto Keiji
• Kamiguchi Haruhiko
• Nsk Ltd

Inventors

• Kouichi Satoh
• Kashimoto Keiji
• Kamiguchi Haruhiko

Classifications

• B62D5/0469

  End-of-stroke control · CPC title

• B62D5/0496

  by using a temperature sensor · CPC title

• H02P6/002

  Electricity · mapped topic

• H02P29/028

  the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault · CPC title

• B62D5/0463 Primary

  calculating assisting torque from the motor based on driver input · CPC title