Electric power steering apparatus

• US 20050045414A1
• Filed: 05/16/2003
• Published: 03/03/2005
• Est. Priority Date: 07/02/2002
• Status: Active Grant

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Takagi, Masanori, Yoneda, Atsuhiko, Kuribayashi, Takashi
• Granted Patent: US 7,188,702 B2
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop

Abstract

An electric power steering apparatus is provided, which has a first device for detection of steering torque, a motor, a motor drive unit, a second device for determining a target current based upon at least a signal of steering torque, a third device for detection of a motor current, and a control unit for generating a signal for motor drive based upon at least a deviation between the target current and motor current and transmitting the signal for motor drive to the motor drive unit. The apparatus has a feature that the control unit includes a fourth device for weakening a magnetic field within the motor according to the deviation or a value computed based upon the deviation.

Claims

1. An electric power steering apparatus comprising:

a first device for detection of steering torque of a steering line;

a motor for exerting assist steering torque on the steering line;

a motor drive unit for driving the motor;

a second device for determining a target current to be supplied to the motor based upon at least a signal of steering torque delivered by the first device;

a third device for detection of a motor current running through the motor; and

a control unit for generating a signal for motor drive based upon at least a deviation between the target current and motor current and transmitting the signal for motor drive to the motor drive unit,

wherein the control unit comprises a fourth device for weakening a magnetic field within the motor according to one of the deviation and a value computed based upon the deviation.

2. An electric power steering apparatus comprising:

a first device for detection of steering torque of a steering line;

a motor for exerting assist steering torque on the steering line;

a motor drive unit for driving the motor;

a second device for determining a target current to be supplied to the motor based upon at least a signal of steering torque delivered by the first device;

a third device for detection of a motor current running through the motor; and

a control unit for generating a signal for motor drive based upon at least a deviation between the target current and motor current and transmitting the signal for motor drive to the motor drive unit,

wherein the control unit comprises a fourth device for weakening a magnetic field within the motor according to the motor current.

3. An electric power steering apparatus comprising:

a first device for detection of steering torque of a steering line;

a motor for exerting assist steering torque on the steering line;

a motor drive unit for driving the motor;

a second device for determining a target current to be supplied to the motor based upon at least a signal of steering torque delivered by the first device;

a third device for detection of a motor current running through the motor;

a fourth device for detection of a rotational velocity of the motor; and

a control unit for generating a signal for motor drive based upon at least a deviation between the target current and motor current and transmitting the signal for motor drive to the motor drive unit,

wherein the control unit comprises a fifth device for weakening a magnetic field within the motor according to the rotational velocity of the motor.