JPH02256564A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To change the direction of a vehicle in nearly linear form for the steering quantity by steering only rear wheels in the reverse phase according to the steering, keeping the steering angle of front wheels constant, when a steering wheel is steered over a prescribed steering angle. CONSTITUTION:In a vehicle 1, front and rear wheel steering devices 10 and 20 for steering front and rear wheels by shifting racks 15 and 25 in the axial direction by the revolution of the pistons 17 and 27 installed onto the output shafts of servomotors 16 and 26 are provided, and the steering devices 10 and 20 are controlled by a control unit 30. Only the front wheel steering device 10 is drive-controlled so that the front wheels are steered according to the steering angle, until the steering angle detected by a steering angle sensor 8 becomes equal to a prescribed steering angle. Further, when a steering wheel 4 is steered over the prescribed steering angle, the rear wheel steering device 20 is drive-controlled so that the rear wheels are steered in the reverse phase according to the steering, keeping the steering angle of the front wheels constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rear wheel steering device for a vehicle equipped with an anti-phase steering mechanism.

[Prior Art] As is well known, in a four-wheel steering vehicle (4WS vehicle) that can steer not only the front wheels but also the rear wheels in response to steering wheel steering, the front wheel steering device used in the conventional 2WS vehicle is Additionally, it is equipped with a rear wheel steering device that steers the rear wheels in conjunction with the steering wheel. As such a rear wheel steering device, a device equipped with a so-called reverse phase steering mechanism that steers the rear wheels in a direction opposite to the steering direction of the front wheels is generally well known. In Publication No. 63-97468, a force plate is fixed to the input shaft of a rear wheel steering mechanism, and left and right driven levers for steering the rear wheels are brought into contact with the outer periphery of this cam plate. When the shaft rotates in conjunction with the handle, a driven lever is operated along the outer circumferential shape of the cam plate, and the rear wheels are steered in the opposite direction to the direction in which the front wheels are steered. , a cam-type rear wheel steering device equipped with a reverse phase steering mechanism is disclosed.

Such a rear wheel steering device usually operates in a region where the steering angle of the front wheels is larger than a predetermined value (in the case of a steering angle responsive type), or in a region where the running speed of the vehicle is lower than a predetermined value (in the case of a vehicle speed responsive type). The steering characteristics of the rear wheels are set so that the rear wheels are steered in the opposite phase to the front wheels, and when entering the garage or
When turning the vehicle with a small turning radius, such as when turning (
In other words, it is possible to significantly improve the vehicle's ability to turn in a tight corner (when turning the steering wheel significantly at low vehicle speeds).

However, in a 4WS vehicle equipped with the above-mentioned rear wheel reverse phase steering mechanism, when the front wheels are steered by steering the steering wheel from the neutral position to either the left or right, the rear wheels immediately shift in conjunction with the steering of the front wheels. If the steering wheel is turned, it may actually be difficult to drive. In other words, when turning the vehicle with a small turning radius by steering the rear wheels in the opposite phase, if the rear wheels are immediately turned in conjunction with the steering of the front wheels, the turning action of the vehicle may become excessively agile. This makes driving difficult, and may also have a negative effect on the stability of the vehicle when turning.

Regarding this problem, near the steering neutral position of the steering wheel,
A so-called dead zone, which is a zone in which the rear wheels are not steered and maintained in a neutral steering state even when the steering wheel is steered, is provided, and the rear wheels are not steered until the steering wheel is steered by a predetermined amount exceeding this dead zone. It is possible to do so.

[Problem to be Solved by the Invention] However, even when the above-mentioned dead zone is provided for rear wheel steering, when the steering wheel is largely steered beyond the dead zone in order to make a small turn of the vehicle, the problem occurs during front wheel steering. Then, the rear wheels begin to be steered in the opposite phase, and the direction of the vehicle no longer changes linearly in accordance with the amount of steering wheel steering, giving rise to a problem that the driver feels strange.

The present invention has been made in view of the above problems, and provides a rear wheel steering device for a vehicle that can change the direction of the vehicle approximately linearly with respect to the amount of steering wheel steering even in the rear wheel reverse phase steering region. The purpose is to provide.

[Means for Solving the Problems] For this reason, the present invention provides a rear wheel steering system for a vehicle equipped with an anti-phase steering mechanism, in which the steering wheel is rotated until the amount of steering wheel steering reaches a predetermined steering angle. If only the front wheels are steered and the steering wheel is steered beyond the above-mentioned predetermined steering angle, only the rear wheels are turned to the opposite phase in response to the steering wheel steering while keeping the steering angle of the front wheels constant. It was designed to be steered.

[Effect of the invention] According to the invention, the rear wheels are not steered while the front wheels are being steered;
In addition, since the front wheel steering angle is kept constant when the rear wheels are steered to the opposite phase, by setting the change characteristic of the rear wheel steering angle to the steering wheel steering angle to be approximately linear, the rear wheels are steered to the opposite phase. Even in this area, the direction of the vehicle can be changed approximately linearly with respect to the amount of steering wheel steering, and there is no difference in turning caused by the front wheels being steered and the rear wheels being steered to the opposite phase at the same time. You can eliminate the sense of harmony.

In addition, in a small steering angle range where the amount of steering wheel steering does not reach the above-mentioned predetermined steering angle, the steering stability can be improved as a 2WS vehicle in which only the front wheels are steered. In the large steering angle range where the vehicle is steered, it is possible to demonstrate the good turning performance characteristic of JWS vehicles equipped with a rear wheel reverse phase steering mechanism.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a plan view schematically showing the overall configuration of the steering mechanism of an automobile according to this embodiment, and as shown in this figure,
The above-mentioned automobile 1 includes a steering device 2 including a steering shaft 3 rotatably supported with respect to the vehicle body, a steering wheel 4 fixed to the rear end of the steering shaft 3 and rotatably operated, and a knuckle. Arm 1
2 (front wheel steering device 10 that steers the left and right front wheels 11L11r via 2, 12r, and knuckle arms 2212, 2
Rear wheel steering device 20 that steers left and right rear wheels 2112, 21r via 2r, and a steering device 1O120 for these front and rear wheels.
and a control unit 30 for controlling.

The front wheel steering device IO is installed so as to be reciprocally movable in the vehicle width direction, and is connected to the left and right front wheels 11 (2, 11r) via knuckle arms 1212, 12r.
4, and a servo motor 16 connected to the control unit 30 so as to be able to send and receive signals, and an output shaft 16a of the servo motor 16 meshes with a rack 15 formed in the middle of the front wheel steering rod 14. A pinion 17 is fixed. Further, the rear wheel steering device 20 is also configured in the same manner as the front wheel steering device 10 described above, and the front wheel steering device! 0
The servo motor 2 is equipped with a rear wheel steering rod 24, a servo motor 26, and a heather, each of which performs the same function as that of the servo motor 2.
A pinion 27 fixed to the output shaft 26a of the rear wheel steering rod 24 meshes with a rack 25 formed on the rear wheel steering rod 24.

Although not specifically shown, the servo motor 1
6.26 is equipped with a speed reduction mechanism.

The rotation angle of the steering shaft 3 (i.e., the steering wheel steering angle θh) is provided at the front end of the steering shaft 3.
A steering wheel angle sensor 8 is provided to detect the steering angle. Also, in the vicinity of the front wheel steering rod 14 and the rear wheel steering rod 24, there are a front wheel 1112, llr and a rear wheel 21f2, 2, depending on the amount of movement of these steering rods 14 and 24 in the vehicle width direction.
Rudder angle sensors 1B and 2B are provided to detect the steering amounts θr and θr of 1r, respectively, and the steering wheel angle sensor 8 and the front and rear wheel steering angle sensors 18 and 28 are both electrically connected to the control unit 30. are connected, and each detection data is input as a signal to the control unit 30.

The control unit 30 is composed of a microcomputer as a main part, and the steering wheel angle sensor 8
A command signal is output to the servo motors 16.26 based on input data from the servo motors 16.2.
By rotating the output shafts 16a, 26a of the front wheels 1112. llr and the rear wheels 2112.21r can each be steered by a predetermined amount.

Further, the control unit 30 has a predetermined steering characteristic as shown in FIG. are stored in advance, and the front wheels 1112. Ilr and rear wheel 2IQ.

21r are respectively steered according to the above-mentioned steering characteristics in accordance with the steering of the handle 4. That is, in this embodiment, in the steering region where the steering wheel steering angle θh is less than or equal to the predetermined value α, the rear wheels 2
1L21r remains in the neutral steering state (steering angle θr-0), and only the front wheels 11(!, 11r) are steered substantially linearly in accordance with the steering wheel steering, while the steering wheel 4 is turned at the above-mentioned predetermined steering angle α. When the steering angle is significantly exceeded, only the rear wheels 21L21r are steered approximately linearly in response to the steering wheel steering while the front wheel steering angle θr is maintained at a predetermined value β corresponding to the above-mentioned predetermined steering wheel steering angle α. It is now possible to do so.

Therefore, as before, the front wheels 1112. During the steering of llr, the rear wheels 21f2 and 21r are steered to opposite phases (second
(See the dashed-dotted line in the figure). Therefore, even in the rear wheel antiphase region, the direction of the vehicle can be changed approximately linearly with respect to the amount of steering wheel steering, and the rear wheels can be steered to the antiphase to steer the vehicle. It is possible to eliminate the strange feeling when turning. Further, in a small steering angle region where the steering wheel steering amount θh does not reach the predetermined steering angle α, the steering stability can be improved as a 2WS vehicle in which only the front wheels 11LIIr are steered, while the steering stability is improved when the steering wheel 4 is turned to the above-mentioned predetermined steering angle. In the large steering angle region where the vehicle is steered beyond the steering angle α, it is possible to demonstrate the good turning performance characteristic of a JWS vehicle equipped with a rear wheel reverse phase steering mechanism.

In the above embodiment, the front wheel 11LIlr and the rear wheel 21Q are controlled by the drive control of the servo motor 16.26.

Although the present invention relates to a vehicle 1 equipped with a front and rear wheel motor type steering mechanism for steering 21r, other systems,
For example, the present invention can be applied to a vehicle equipped with a front and rear wheel cam type steering mechanism that uses a cam mechanism to control the amount of steering of the front wheels and rear wheels, respectively. in this case,
Regarding the front wheel steering device cam and the rear wheel steering device cam,
By appropriately setting the shape of each cam, the rotational phase and rotational speed of the cam, the same effects as in the above embodiment can be achieved.

[Brief explanation of drawings]

FIG. 1 is an explanatory plan view schematically showing the overall configuration of a steering mechanism of an automobile according to an embodiment of the present invention, and FIG. 2 is a graph showing the steering characteristics of the front wheels and rear wheels with respect to the steering angle of the steering wheel of the automobile. be. ! ...Automobile, 4...Steering wheel (steering wheel), 11Q, llr...Front wheel, 20...Rear wheel steering device, 2112.21r...IL30...Control unit, α...Predetermined Steering wheel angle, β...
Front wheel steering angle corresponding to a predetermined steering angle, θr...front wheel steering angle, θh...handle steering angle, θr...rear wheel steering angle.

Claims (1)

[Claims] (1) In a rear wheel steering system of a vehicle equipped with a reverse phase steering mechanism, only the front wheels are steered in accordance with the steering wheel until the amount of steering wheel steering reaches a predetermined steering angle. A rear wheel steering device for a vehicle, characterized in that when the vehicle is steered beyond a corner, only the rear wheels are steered in the opposite phase in accordance with steering wheel steering while keeping the steering angle of the front wheels constant. .