JPH0376271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a front and rear wheel steering device for a vehicle such as a four-wheeled vehicle.

(Prior art) Vehicles that use general front wheel steering only, or recently proposed vehicles that perform front-rear steering by steering both the front wheels and the rear wheels (for example, Japanese Patent Application Laid-Open No. 1983-1983 proposed by the present applicant). No. 5270, etc.), in both cases, steering is performed only or primarily by the front wheels, and although the rear wheels are steered, this only performs an auxiliary steering action that is always smaller than the amount of steering of the front wheels.

Therefore, in the conventional steering system, when the vehicle turns in the backward travel mode, it draws a turning trajectory as shown in FIG. 4. In other words, the steering angle of the front wheels 40 is larger than the steering angle of the rear wheels 41, and the turning trajectory P1 of the center of gravity G1 of the vehicle 42 is
Since it swings greatly, it first bulges outward (arrow F1), and then moves inward, which is the direction in which it should turn.

Therefore, in a vehicle equipped with a conventional steering device, it is difficult to drive the vehicle in reverse, and the driver cannot stabilize the vehicle and drive the vehicle in reverse unless the vehicle is running at a very high speed.

(Object of the Invention) The object of the present invention is to improve a steering device when a vehicle turns in reverse driving mode.
An object of the present invention is to provide a front and rear wheel steering device for a vehicle that can stably and easily perform a backward turn by greatly improving the maneuverability of the vehicle during a backward turn.

(Structure of the Invention) In order to achieve the above object, the present invention is provided with a steering means for steering the front wheels and the rear wheels respectively, and a traveling direction detecting means for detecting the traveling direction of the vehicle, and the front wheels and the rear wheels can be steered by steering the steering wheel. In a front and rear wheel steering device for a vehicle that can steer wheels, the steering means on the traveling direction side detected by the traveling direction detection means steers the wheels on the traveling direction side according to the steering wheel angle, and the other steering means This fixes the other wheel in the straight-ahead position.

Further, a front and rear wheel steering device for a vehicle is provided with a steering means for steering the front wheels and the rear wheels, and a driving direction detection means for detecting the driving direction of the vehicle, and is capable of steering the front wheels and the rear wheels by steering the steering wheel. The steering means on the traveling direction side detected by the traveling direction detecting means steers the wheels on the traveling direction side according to the steering wheel angle, and at least when traveling in reverse, the front wheels are steered by an amount smaller than the amount of steering of the rear wheels. , and steers at a predetermined steering ratio with respect to the steering angle of the rear wheels.

(Example) Below, preferred examples that further embody the present invention will be described in detail with reference to the drawings.

In the drawings, FIG. 1 is a schematic plan view showing the basic structure of a vehicle equipped with a front and rear wheel steering device according to the present invention. First, in order to clarify the present invention, the overall schematic configuration of a front and rear wheel steering system of a vehicle will be described based on the same drawing.

The reference numeral 1 in the figure is a steering handle, and the steering shaft 2 of this handle 1 is coupled to a steering wheel angle sensor 3 that also detects the magnitude of the steering angle (steering wheel rotation angle) of the steering wheel 1.
From this, we obtain steering wheel angle data whose size is proportional to the steering wheel rotation angle.

On the other hand, the vehicle is equipped with an on-board computer 4,
The steering wheel angle data from the steering wheel angle sensor 3 is input to the computer 4 as input data. For example, in the forward running mode, the computer 4 generates and outputs front wheel steering control information S1 that is approximately proportional to the steering wheel angle data and turns the front wheels in the steering direction of the steering wheel 1, and controls the front wheel steering servo. is supplied to the actuator 5.

The front wheel steering servo actuator 5 constitutes a servo system including an amplifier circuit, a drive motor, etc., and rotates the transmission shaft 5a substantially in proportion to the front wheel steering control information S1. The transmission shaft 5a is connected to a front wheel gear box 6 which includes a steering gear mechanism of the rack and pinion type, for example. This gearbox 6 is provided with a tie rod 7 that penetrates through it and moves in the vehicle width direction by rotation of the transmission shaft 5a, and knuckle arms 8 are rotatably connected to both ends of the tie rod 7. The knuckle arms 8, 8 support the front wheels 9, 9, and rotate the front wheels 9, 9 in a desired direction approximately in proportion to the rotation of the transmission shaft 5a, that is, the steering rotation of the handle 1. Let me steer.

On the other hand, the computer 4 generates rear wheel steering control information S2 by varying a proportionality constant approximately proportional to the steering wheel angle data from the steering wheel angle sensor 3 and further based on vehicle speed data compared to the vehicle speed obtained from the vehicle speed sensor 10. Generate and output. This rear wheel steering control information has, for example, content for steering the rear wheels in the same phase direction as the front wheels when driving at high speed in forward driving mode, and steering the rear wheels in the opposite phase direction with respect to the front wheels when driving at low speed. .

This rear wheel steering control information S2 is then supplied to the rear wheel steering servo actuator 11. Like the front wheel steering servo actuator 5, this servo actuator 11 also constitutes a servo system including an amplifier circuit, a drive motor, etc., and rotates the transmission shaft 11a in response to the rear wheel steering control information S2. The transmission shaft 11a is connected to a rear wheel gear box 12 which includes a rear gear mechanism of the rack and pinion type, for example. A transmission shaft 11a passes through the gearbox 12.
Tie rod 1 moves in the vehicle width direction due to the rotation of
3 is provided, and knuckle arms 14, 14 are rotatably connected to both ends of this tie rod 13.
The knuckle arms 14, 14 support the rear wheels 15, 15, and thereby steer the rear wheels 15, 15 in the above-mentioned required direction in response to the rotation of the transmission shaft 11a, that is, the rear wheel steering control information S2. This allows the rear wheels to have an auxiliary steering function. For example, when driving at high speeds, in-phase steering can greatly improve steering response, while when driving at low speeds, anti-phase steering can greatly improve maneuverability. Construct a front and rear wheel steering system that can be used.

Next, the configuration and functions of the main parts of the present invention will be specifically explained with reference to FIGS. 1 and 2. Incidentally, FIG. 2 is a functional block diagram of an information processing system for front and rear wheel steering, which is a main part of the present invention.

First, the configuration of main parts and the functions of each part based on the first feature of the present invention will be described. In the present invention, the above-mentioned steering wheel angle sensor 3 and vehicle speed sensor 10 are connected to the computer 4 as input data. The vehicle speed sensor 10 obtains vehicle speed data proportional to the vehicle speed, and also functions as a traveling direction sensor that detects the traveling direction of the vehicle, that is, whether the vehicle is in the forward traveling mode or the backward traveling mode. Note that a traveling direction sensor may be provided separately. Therefore, the vehicle speed sensor 10 or the separately provided traveling direction sensor constitutes a traveling direction detecting means. Further, a manual selection switch 16 is connected to the computer 4 so that required input data can be input manually by the driver in the vehicle interior. This manual selection switch 16 will be explained in detail later.

The present invention relates to a configuration that can be used only in the backward traveling mode, and the forward traveling mode has the same general configuration as described above.

Now, assume that the driver operates the shift lever to switch to reverse driving mode. As a result, data d1 representing the traveling direction is input from the vehicle speed sensor 10 to the computer 4, and this data d1 is provided to the determination process 1. This discrimination process is based on data d.
1 is in reverse driving mode (read)
Then, this result d2 is given to the first arithmetic processing unit.
In the forward running mode, this first calculation process supplies the front wheel steering control information S1 to the front wheel steering actuator 5 in approximately proportion to the steering wheel angle data d3 of the steering wheel angle sensor 3, and is stored in the memory. Depending on the set data, for example proportionality constant K1,
It performs the calculation process of (S1)=(K1)・(d3). However, this proportionality constant K1 is fixed to zero based on the above-mentioned determination result d2. In other words, front wheels 9,9
is fixed in a straight running position where it is not steered to the left or right.

On the other hand, at the same time, the determination result d2 is applied to the second arithmetic processing. This second calculation process d corresponds to a predetermined function based on vehicle speed data d4 that is approximately proportional to the steering wheel angle data d3 from the steering wheel angle sensor 3 and proportional to the vehicle speed obtained from the vehicle speed sensor 10 in the forward running mode. and supplies the rear wheel steering control information S2 to the rear wheel steering actuator 11, and similarly to the front wheel side described above, a proportionality constant K2 and vehicle speed whose variables are the steering wheel angle (data d3) which is data in the memory. The function corresponding to (f(d4))
Computation processing is performed by However, in the backward running mode, based on the determination result d2, a proportionality constant K3, which is approximately the same size as the proportionality constant K1 in the forward running mode for the front wheels, is assigned to the second calculation process 2 from the data in the memory. The rear wheel steering control information S3 performs the calculation process of (S3)=(K3)·(d3).

The above is the configuration based on the first feature of the present invention, and next, the overall function of this configuration will be described. When the vehicle speed sensor 10 detects the reverse travel mode, the computer 4 also switches to the reverse travel mode. The front wheels 9, 9 are automatically fixed in the straight running position as described above, and the rear wheels 1
5 and 15 are steered in proportion to the steering angle of the handle 1. Moreover, by selecting the proportionality constant K3, the magnitude of this steering amount becomes approximately the same as the amount of steering of the front wheels in the forward running mode. In other words, in the reverse travel mode, the system becomes a system in which the front wheels and the rear wheels are respectively reversed in contrast to the conventional steering system that only controls the front wheels.

Next, the configuration and function based on the second feature of the present invention will be explained.

While the configuration based on the first feature described above fixes the front wheels in a straight-ahead running position, the second feature is that the front wheels also have an auxiliary steering function. In other words, the steering of the rear wheels is the same as the configuration according to the first feature, but the steering of the front wheels performs the following process based on the determination result d2. First, in the first arithmetic processing B, a proportionality constant K4 is given from the memory, and in order to obtain front wheel steering control information S4 (S4)=
Execute the arithmetic processing of (K4) and (d3). Note that this proportionality constant K4 is smaller than the proportionality constant K3 on the rear wheel side. In other words, the front wheels are steered at a predetermined steering ratio relative to the rear wheel steering angle so that (K4)<(K3). As a result, the amount of steering of the front wheels is always smaller than the amount of steering of the rear wheels, and the steering direction is set. This steering ratio may be automatically set using preset data, or may be manually selected by the driver using the manual selection switch 16 as shown in FIG. good.
In this case, a plurality of switch leads 16a, 16b, 1
6c... can be arbitrarily selected, for example, the specific constant K4 can be set to (+K4-2), (+K4-1), (0), (-
K4-1), (-K4-2), [However (+K4-2)>
(+K4-1)>(0)>(-K4-1)>(-K4-2)]
For example, even in reverse driving mode, the front wheels are steered in the opposite phase direction to the rear wheels, and the minimum turning radius at sharp curves such as on alleys is set. It is possible to greatly improve the maneuverability of the vehicle by making it as small as possible, or by steering the front wheels in the same phase direction as the rear wheels to make it easier to pull the wheels closer together when parking. can.

Next, the operation of the present invention will be explained with reference to FIG. FIG. 3 is a functional explanatory diagram showing a schematic plan view of a vehicle equipped with a front and rear wheel steering device according to the present invention.
As shown in the figure, the turning angle of the rear wheels 15, 15 is set in proportion to the steering angle of the steering wheel 1, and the front wheels 9, 9 are always turned smaller than the turning amount of the rear wheels 15, 15. Ru. FIG. 3 shows a state in which the front wheels 9, 9 are fixed in the straight running position based on the first feature.
In this case, the turning trajectory P of the center of gravity position G2 of the vehicle 17
2 obediently enters the inside direction (arrow (F2)), which is the direction in which it should turn, immediately after turning. Therefore,
Conventional (Fig. 4) The outside (fourth
No adverse effects such as swelling and shifting in the direction shown by the arrow (F1) in the figure occur.

As described above, each process in the computer 4 is executed according to the control program (software) stored in the memory in advance. Further, the drawings only show the minimum functions necessary to constitute the present invention, and other accessory devices such as input/output interfaces required to make the computer 4 function are omitted. Note that the computer 4 may be replaced by an electrical circuit having the same function, or by mechanically switching the connecting portions in a mechanical configuration. Also,
The proportionality constant set in the computer 4 can also be applied as a function corresponding to a predetermined variable.

(Effects of the Invention) As described above, the present invention can determine whether the vehicle is traveling forward or backward using the traveling direction detection means and obtain desirable steering characteristics, so that the driver can perform only normal driving operations. I can concentrate on it. Maneuverability of the vehicle when turning backwards is greatly improved, thereby achieving the effect that backward turns can be performed stably and easily even at relatively high vehicle speeds.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing the basic structure of a vehicle equipped with a front and rear wheel steering device according to the present invention, and FIG. 2 is a functional block diagram of an information processing system for front and rear wheel steering, which is the main part of the present invention. , FIG. 3 is an operational explanatory diagram showing a schematic plan view of a vehicle equipped with a front and rear wheel steering device according to the present invention, and FIG. 4 is an explanatory diagram showing a schematic plan view of a vehicle for explaining problems in the prior art. be. In the drawing, 1 is a steering wheel, 3 is a steering wheel angle sensor, 4 is an on-board computer, 5 is a front wheel steering servo actuator, 9 is a front wheel, and 10 is a front wheel steering servo actuator.
1 is a vehicle speed sensor, 11 is a rear wheel steering servo actuator, 15, 15 is a rear wheel, 16 is a manual selection switch, A is a discrimination process, B is a first calculation process, C is a memory, D is a second calculation process, S3 is rear wheel steering control information, and S4 is front wheel steering control information.

Claims (1)

[Scope of Claims] 1. A vehicle that is equipped with a steering means for steering the front wheels and the rear wheels, respectively, and a running direction detection means for detecting the running direction of the vehicle, and the front and rear wheels of the vehicle can be steered by steering the steering wheel. In the wheel steering device, the steering means on the traveling direction side detected by the traveling direction detecting means steers the wheels on the traveling direction side according to the steering wheel angle, and the other steering means moves the other wheel to a straight traveling position. A front and rear wheel steering device for a vehicle, characterized in that the steering device is fixed to the front and rear wheels of a vehicle. 2. A front and rear wheel steering device for a vehicle, which is equipped with a steering means for steering the front wheels and the rear wheels, respectively, and a running direction detection means for detecting the running direction of the vehicle, and is capable of steering the front wheels and the rear wheels by steering the steering wheel, as described above. The steering means on the traveling direction side detected by the traveling direction detecting means steers the wheels on the traveling direction side according to the steering wheel angle, and at least when traveling backward, the front wheels are steered by an amount smaller than the amount of steering of the rear wheels. A front and rear wheel steering device for a vehicle is characterized in that the front and rear wheels of the vehicle are steered at a predetermined steering ratio with respect to the steering angle of the rear wheels.