Vehicular steering apparatus and control method thereof

• US 8,504,243 B2
• Filed: 07/21/2009
• Issued: 08/06/2013
• Est. Priority Date: 07/22/2008
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kageyama, Hiromitsu
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): GOLDMAN, RICHARD A
• Application Number:
  US12/999,332
• Publication Number:
  US 20110106382A1
• Time in Patent Office: 1,477 Days
• Field of Search: None
• US Class Current: 701/41
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• CPC Class Codes: B62D 6/04 responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel
• CPC Class Codes: B62D 7/1509 with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

An electronic control unit determines that a vehicle is traveling in a straight line if a state in which the steering torque is less than a predetermined steering torque and an amount of change in the steering angle is less than a predetermined steering angle continues for a predetermined period of time when the vehicle speed is greater than a predetermined vehicle speed. Also, if the steering angle of the steering wheel is not 0, while the vehicle is traveling in a straight line, the electronic control unit calculates the steering amount of rear wheels that matches the steering amount of front wheels, using the steering angle of the steering wheel. Then the electronic control unit steers the rear wheels by driving an electric motor until a controlled neutral steering position of the rear wheels that corresponds to the steering amount matches an absolute neutral steering position.

Claims

1. A vehicular steering apparatus that includes a steering wheel which is operated by a driver, a front wheel steering mechanism which steers a front wheel in response to an operation of the steering wheel, and a rear wheel steering mechanism which steers a rear wheel in connection with the steering of the front wheel, the vehicular steering apparatus comprising:

a vehicle speed detecting portion that detects a speed of a vehicle;

an operating force detecting portion that detects operating force applied to the steering wheel;

a displacement amount detecting portion that detects an amount of displacement of the steering wheel;

a straight-line travel determining portion that determines that the vehicle is traveling in a straight line when a state in which i) the operating force detected by the operating force detecting portion is equal to or less than a predetermined operating force that is set in advance and ii) an amount of change in the amount of displacement detected by the displacement amount detecting portion is equal to or less than a predetermined amount of change that is set in advance, continues for a predetermined period of time that is set in advance or longer, when the vehicle speed detected by the vehicle speed detecting portion is equal to or greater than a predetermined vehicle speed that is set in advance;

an operating position determining portion that determines whether the operating position of the steering wheel that corresponds to the amount of displacement of the steering wheel detected by the displacement amount detecting portion is different than a neutral position of the steering wheel for aligning the direction in which the vehicle is traveling with the front-rear axial direction of a vehicle body such that the vehicle will travel in a straight line, when it is determined by the straight-line travel determining portion that the vehicle is traveling in a straight line; and

an operating position correcting portion that corrects the operating position of the steering wheel to the neutral position when it is determined by the operating position determining portion that the operating position of the steering wheel is different than the neutral position.

2. The vehicular steering apparatus according to claim 1,

wherein the rear wheel steering mechanism includes an actuator for steering the rear wheel, and a steering amount detecting portion that detects a relative steering amount of the rear wheel with respect to the vehicle body resulted from driving the actuator, and

wherein the operating position correcting portion is constructed with i) a rear wheel steering amount calculating portion that calculates a steering amount of the rear wheel that matches the steering amount of the front wheel, using the amount of displacement of the steering wheel detected by the displacement amount detecting portion and a ratio between the amount of displacement of the steering wheel in the front wheel steering mechanism and the steering amount of the front wheel, and ii) an actuator operation controlling portion that operates the actuator, using the relative steering amount detected by the steering amount detecting portion, until the steering position of the rear wheel that corresponds to the steering amount calculated by the rear wheel steering amount calculating portion comes to match a neutral steering position for aligning the direction in which the vehicle is traveling with the front-rear axial direction of the vehicle body such that the vehicle travels in a straight line.

3. The vehicular steering apparatus according to claim 1, wherein a first shaft that is connected to the steering wheel is able to rotate relative to a second shaft that is connected to the front wheel steering mechanism;

a front wheel steering actuator is provided which independently displaces the steering wheel with respect to the steering of the front wheel; and

the operating position correcting portion corrects the operating position of the steering wheel to the neutral position by controlling the operation of the front wheel steering actuator when it is determined by the straight-line travel determining portion that the vehicle is traveling in a straight line and it is determined by the operating position determining portion that the operating position of the steering wheel is different than the neutral position.

4. A control method for a vehicular steering apparatus that includes a steering wheel which is operated by a driver, a front wheel steering mechanism which steers a front wheel in response to an operation of the steering wheel, and a rear wheel steering mechanism which steers a rear wheel in connection with the steering of the front wheel, the control method comprising:

detecting a speed of the vehicle;

detecting operating force applied to the steering wheel;

detecting an amount of displacement of the steering wheel;

determining that the vehicle is traveling in a straight line when a state in which i) the detected operating force is equal to or less than a predetermined operating force that is set in advance and ii) an amount of change in the detected amount of displacement is equal to or less than a predetermined amount of change that is set in advance, continues for a predetermined period of time that is set in advance or longer, when the detected vehicle speed is equal to or greater than a predetermined vehicle speed that is set in advance;

determining whether the operating position of the steering wheel that corresponds to the detected amount of displacement of the steering wheel is different than a neutral position of the steering wheel for aligning the direction in which the vehicle is traveling with the front-rear axial direction of a vehicle body such that the vehicle will travel in a straight line, when it is determined that the vehicle is traveling in a straight line; and

correcting the operating position of the steering wheel to the neutral position when it is determined that the operating position of the steering wheel is different than the neutral position.