JPH0699831A - Rear wheel steering gear of automobile - Google Patents

Abstract

PURPOSE:To offer an automobile rear wheel steering gear which controls the steering angle of rear wheels in accordance with the specially selected controlling rules. CONSTITUTION:An ECU 20, which is established as a controlling means of an electric motor which drives a rear wheel steering mechanism, is provided with target setting devices responding respectively to a plurality of controlling rules such as a front wheel steering proportional target setting device 251, a phase inversion proportional target setting device 252, a lateral G induction control target setting device 253, a yaw rate induction control target setting device 254 and a 2WS target setting device 255. One of the controlling rules is selected by a demand from a control target selecting device 211, a rear wheel steering target is found on the basis of a detection signal from a vehicle speed sensor 18 and a steering sensor 16, a rear wheel steering angle is set by a rear wheel steering angle target setting device 26 and the rear wheel steering angle is set to the target steering angle upon driving the electric motor with a motor control device 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear-wheel steering system for a four-wheel steering vehicle, and more particularly to a rear-wheel steering system in which the steering angle of the rear wheels is controlled by an electric motor.

[0002]

2. Description of the Related Art In an automobile with four-wheel steering, the front wheels are steered in response to steering operation, and the rear wheels are steered in accordance with the driving conditions of the automobile.
Such rear wheel steering basically aims at the steering stability of the vehicle, and is roughly classified into the rear wheel steering system, and the vehicle speed sensitive front wheel steering angle proportional control, phase inversion proportional control,
There are lateral G sensitive control, yaw rate sensitive control, and the like. In an actual vehicle, one of such control rules is selected and equipped based on the vehicle grade and the like.

In such a control rule, the phase inversion proportional control cuts the rear wheel into a phase opposite to that of the front wheel at the start of the lane change or the like to increase the turning ability, and the lateral G-sensitive control moves laterally. The rear wheel steering angle is determined by the acting acceleration to improve the steering stability.

As described above, there are many rear wheel steering control rules, but each of these control rules has its own characteristics. Therefore, the driver has his or her preference for each control law, and there is a demand for each driver to select a control law that suits his or her preference. However, in reality, at present, it is not possible to meet the demand for the driver to select the control law.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a driver can freely select and set a rear wheel steering control law in accordance with, for example, a driving environment. An object of the present invention is to provide a rear-wheel steering system for an automobile that can ensure more comfortable driving stability.

[0006]

A rear wheel steering system for a vehicle according to the present invention is configured to control a steering angle of a rear wheel of the vehicle by an electric motor, and detects a rotation angle of the electric motor. A motor rotation angle sensor, a rear wheel steering angle sensor, a steering sensor, a vehicle speed sensor, etc. are provided, and detection signals from the steering sensor and the vehicle speed sensor are supplied to the rear wheel steering angle target setting means. The target setting means receives a selection command from the control law selecting means operated by the driver. Then, the electric motor is controlled based on the rear wheel steering angle target set by the output from the rear wheel steering angle target setting means.

[0007]

In the rear wheel steering system of the automobile constructed as described above, the rear wheels are steered by the electric motor, so that the rear wheels can be steered based on the electronic control command. The steering angle can be freely controlled. Therefore, by setting a plurality of types of target setting control law for the rear wheel steering angle target setting means and selecting one of the setting control laws by the control law selecting means operated by the driver, this selection is made. The rear-wheel steering angle target is set according to the specified control law, the control law is set according to the driver's preference, and the optimum rear-wheel steering angle control law is selected for the driving environment such as the driving conditions of the vehicle. As a result, more stable steering control is performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a rear wheel steering system, in which a front wheel 12 is steered by a steering wheel 11 and a rear wheel steering mechanism 14 driven by an electric motor 13 drives the rear wheel.
15 is steered. The steering wheel 11 is provided with a steering sensor 16 for detecting the operation angle of the steering wheel 11, and the rear wheel steering mechanism 14 is provided with a rear wheel steering angle sensor 17, which corresponds to the front wheel 12 portion. Then, the vehicle speed sensor 18 is provided, and the electric motor 13 is further provided with a motor rotation angle sensor 19.

The detection signals of the steering angle, the rear wheel steering angle, the vehicle speed and the motor rotation angle detected by these sensors 16, 17, 18 and 19 are input to an electronic control unit (ECU) 20 composed of, for example, a microcomputer. The electric motor is operated by a command from the ECU 20.
A drive command is given to 13, and the ECU 20 sets the steering angle of the rear wheels 15 to the calculated target rear wheel steering angle.

Here, a control changeover switch 21 for setting the rear wheel steering control law is provided. The control changeover switch 21 is set corresponding to the driver's seat of the vehicle, and is appropriately changed by the driver. I am trying to operate it. Then, the control law selection command selected by the control changeover switch 21 is input to the ECU 20. When an alarm signal is generated from the ECU 20, the alarm is set to be emitted by the alarm lamp 22 set in the driver's seat.

FIG. 2 shows the structure of the ECU 20. The detection signal from the steering sensor 16 and the vehicle speed sensor 18 are shown in FIG.
A rear wheel steering angle target setting device 25, to which a detection signal from the vehicle is supplied, is provided. This rear wheel rudder angle target setting device 25 includes a front wheel rudder angle proportional target setting device 251, a phase inversion proportional target setting device 25.
2, target setting devices corresponding to a plurality of rear wheel control laws, such as the lateral G response control target setting device 253, the yaw rate response control target setting device 254, and the 2WS target setting device 255, are set. Then, the plurality of target setting devices 251-
One of the 255 control rules is selected by the control rule selection device 211 constituted by the control changeover switch 21.

In the rear wheel steering angle target setting device 25,
Based on the detection signals from the steering sensor 16 and the vehicle speed sensor 18, a rear wheel target steering angle corresponding to the selected control law is calculated and output to the rear wheel steering angle target setting device 26, and this phosphorus steering angle target is set. Set. Then, based on this set rear wheel steering angle target, a command is issued to the motor control device 27 to drive the electric motor 13 to rotate. In this case, the output of the motor rotation angle sensor 19 and the rear wheel steering angle sensor are output.
The rear wheel steering angle is detected by the detection signal from 17
Is set to the target steering angle.

FIG. 3 shows the flow of control in the ECU 20. In this ECU 20, the operation of the selection switch 21 of the control law selection device 211 operated by the driver is read in step 301, and in step 302 the vehicle speed sensor 18 and the steering sensor 16 are read. Read the detection signal of. And step 30
In 3, the rear wheel steering angle control target for the control law selected by the rear wheel steering angle target setting means 25 is set. Where, horizontal G
And the yaw rate is measured by the vehicle speed sensor 18 and steering sensor.
Estimate accordingly based on the detection value from 16.

When the rear wheel steering angle control target is set in this manner, the positioning control of the electric motor 13 with respect to this control target is performed in step 304. The driver controls the positioning control of the electric motor 13. Rear wheel steering corresponding to the desired control law is realized. Such control can be dealt with immediately in step 301 by operating the control changeover switch 21 even during traveling.

As shown in FIG. 4, a lateral G sensor 28 and a yaw rate sensor 29, or a wheel speed sensor 30 is added to the ECU 19, so that the lateral G estimated by the rear wheel steering angle target setting means 25 is estimated. It is also possible to compare the yaw rate and the sensor output value to estimate μ of the road surface, and switch and select the control law according to this μ value.

[0016]

As described above, according to the rear-wheel steering system for a vehicle according to the present invention, since the rear-wheel steering is performed by the electric motor, an arbitrary control law is selected. The rear wheel steering control corresponding to the control law can be performed, and the rear wheel steering according to the driver's preference can be performed in a stable state in which the maneuverability is more suitable for the driver. Further, the control law can be arbitrarily and automatically selected and set according to the driving environment of the vehicle, and the steering stability can be more effectively ensured.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a control system of a rear wheel steering system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating an electronic control unit in the above embodiment.

FIG. 3 is a flowchart illustrating a processing flow in the electronic control unit.

FIG. 4 is a diagram illustrating another embodiment of the present invention.

[Explanation of symbols]

11 ... Steering, 12 ... Front wheel, 13 ... Electric motor, 14 ... Rear wheel steering mechanism, 15 ... Rear wheel, 16 Steering sensor, 17 ...
Rear wheel steering angle sensor, 18 ... Vehicle speed sensor, 19 ... Motor rotation angle sensor, 20 ... Electronic control unit (ECU), 21 ... Control changeover switch.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B62D 137: 00 (72) Inventor Takashi Inaba 1-1-chome, Showa-cho, Kariya city, Aichi Prefecture NIPPON DENSO CORPORATION In the company

Claims (1)

[Claims] 1. An electric motor for controlling a steering angle of a rear wheel of an automobile, a steering mechanism for controlling a steering angle of a front wheel of the automobile, a motor rotation angle sensor for detecting a rotation angle of the electric motor, A rear wheel steering angle sensor that detects a steering angle of wheels, a steering sensor that detects a steering angle of the steering mechanism, a vehicle speed sensor that detects a traveling speed of the vehicle, the steering sensor, and a detection signal from the vehicle speed sensor. The rear wheel steering angle target setting means, the control law selecting means operated by a driver that outputs a selection command to the rear wheel steering angle target setting means, and the output from the rear wheel steering angle target setting means. Motor control means for controlling the electric motor based on the set rear wheel steering angle target and the detection outputs from the rear wheel steering angle sensor and the motor rotation angle sensor A plurality of target setting control laws are set in the rear wheel steering angle target setting means, and a rear wheel steering angle target is set in accordance with the control law selected by the control law selecting means operated by a driver. A rear-wheel steering system for an automobile, characterized in that