Electric power steering system

• US 20020014877A1
• Filed: 05/31/2001
• Published: 02/07/2002
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Original Assignee: Koyo Seiko Co., Ltd. (Toyota Motor Corporation)
• Inventors: Yoshida, Kazuyuki, Kaji, Hiroaki, Sasaguchi, Nobuyuki
• Granted Patent: US 6,690,138 B2
• Time in Patent Office: Days
• US Class Current: 318/783
• CPC Class Codes: B62D 5/0496 by using a temperature sensor
• CPC Class Codes: H02H 7/0852 directly responsive to abnormal temperature by using a temperature sensor in a control circuit H02H7/0833

Abstract

An electric power steering system is provided which assists a steering operation by applying a driving force generated by an electric motor to a steering mechanism of a motor vehicle. The system includes a sensor (e.g., a torque sensor) for acquiring information necessary for controlling the electric motor, and a board provided adjacent the electric motor and having a sensor signal processing circuit for processing a signal from the sensor. A temperature sensor for acquiring temperature information necessary for controlling the electric motor is mounted on the board.

Claims

1. An electric power steering system which assists a steering operation by applying a driving force generated by an electric motor to a steering mechanism of a motor vehicle, the electric power steering system comprising:

a sensor for acquiring information necessary for controlling the electric motor;

a board provided adjacent the electric motor and having a sensor signal processing circuit for processing a signal from the sensor; and

a temperature sensor mounted on the board for acquiring temperature information necessary for controlling the electric motor.

2. An electric power steering system as set forth in claim 1, wherein the temperature sensor is connected to a ground line of the sensor signal processing circuit.

3. An electric power steering system as set forth in claim 1, further comprising a motor controlling circuit for controlling the electric motor on the basis of a signal processed by the sensor signal processing circuit and a detection signal of the temperature sensor.

4. An electric power steering system as set forth in claim 3, wherein the motor controlling circuit limits an electric current flowing through the electric motor on the basis of an output signal of the temperature sensor to prevent the electric motor from being overheated to a predetermined abnormally high temperature.

5. An electric power steering system as set forth in claim 1, wherein the temperature sensor includes a temperature sensor of a board-mounting type.

6. An electric power steering system as set forth in claim 1, wherein the board is housed in a water-tight case.

7. An electric power steering system as set forth in claim 6, wherein a signal line of the temperature sensor and a signal line connected to the sensor signal processing circuit are led out of the case through a water-tight grommet.