VEHICLE STEERING SYSTEM

• US 20190315390A1
• Filed: 04/08/2019
• Published: 10/17/2019
• Est. Priority Date: 04/12/2018
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: SHIRAUCHI, Yousuke
• Granted Patent: US 11,072,362 B2
• Time in Patent Office: Days
• CPC Class Codes: B62D 5/0406 including housing for electronic control unit
• CPC Class Codes: B62D 5/0424 the axes of motor and final driven element of steering gear, e.g. rack, being parallel
• CPC Class Codes: B62D 5/0448 Ball nuts
• CPC Class Codes: B62D 5/0481 monitoring the steering system, e.g. failures

Abstract

The vehicle steering system includes a rack shaft and a conversion mechanism that converts rotation of a rotating shaft of the motor into reciprocating motion of the rack shaft. The conversion mechanism includes a drive pulley that rotates with the rotating shaft, a driven pulley rotatable about an axis of the rack shaft and a toothed belt extending around the drive pulley and the driven pulley, and converts rotation of the rotating shaft into reciprocating motion of the rack shaft when rotation of the drive pulley is transmitted to the driven pulley via the toothed belt. The vehicle steering system further includes a determination circuit that determines tooth skipping that is a change in meshing position between the drive pulley and the toothed belt, and a calculation circuit that calculates an integrated value obtained by integrating a prescribed value indicating that tooth skipping is determined by the determination circuit.

Claims

1. A vehicle steering system comprising:

a steered shaft that reciprocates in an axial direction to steer steered wheels;

a motor that generates power for reciprocating the steered shaft;

a conversion mechanism that converts rotation of a rotating shaft of the motor into reciprocating motion of the steered shaft;

a control circuit that controls power supply to the motor;

a determination circuit; and

a calculation circuit, wherein;

the conversion mechanism includes a drive pulley that rotates with the rotating shaft, a driven pulley rotatable about an axis of the steered shaft, and a toothed belt extending around the drive pulley and the driven pulley, and converts rotation of the rotating shaft into reciprocating motion of the steered shaft when rotation of the drive pulley is transmitted to the driven pulley via the toothed belt;

the determination circuit determines tooth skipping that is a change in meshing position between the drive pulley and the toothed belt; and

the calculation circuit calculates an integrated value obtained by integrating a prescribed value indicating that tooth skipping is determined by the determination circuit.

2. The vehicle steering system according to claim 1, wherein the prescribed value is a fixed value indicating a number of times tooth skipping is determined by the determination circuit.

3. The vehicle steering system according to claim 1, wherein the prescribed value is a variable that is set in accordance with a rotational speed of the rotating shaft and that indicates a load applied to the conversion mechanism when tooth skipping is determined by the determination circuit.

4. The vehicle steering system according to claim 1, wherein:

the control circuit includes the determination circuit and the calculation circuit; and

a threshold that is set for the integrated value and that indicates a degree of deterioration of the conversion mechanism is preset in the control circuit.

5. The vehicle steering system according to claim 4, wherein the control circuit further includes a notification instruction circuit that instructs a notification device mounted on a vehicle to notify that the integrated value is greater than the threshold.