JPS61220974A - All-wheel steering gear for vehicles - Google Patents

Abstract

PURPOSE:To improve a degree of steering responsiveness so better, by installing a mechanical type decelerating device in an actuator steering rear wheels, while detecting displacement at the rear-wheel side of this device, and making it perform steering control, in case of a device controlling each steering angle of front and rear wheels variably in response to a car speed. CONSTITUTION:When a rack shaft 4 inside a gearbox 3 is slidden in both directions with rotation of a steering wheel 1 and symmetrical front wheels 7 are steered via a tie rod 5 and a knuckle arm 6, a motor 13 is driven and controlled by a computer 16 according to each output of a front steering angle sensor 14, a car speed sensor 17 and a manual select switch 18 selecting a steering ratio. With this constitution, a rack shaft 9 inside the gearbox 8 is slidden in both direction whereby symmetrical rear wheels 12 are steered. Then, a steering angle of these rear wheels is detected by a steering angle sensor 15 detecting displacement of the rack shaft 9, and the rear-wheel actual steering angle data obtained by this detection is fed back to the computer 16, thereby coming in useful for accurate steering control over the rear wheels 12.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a front and rear wheel steering device for a vehicle that can variably control the steering angle of the rear wheels relative to the front wheels.

<Prior Art> The present applicant has already developed a vehicle steering device ( Special application 1986-13
No. 4888, etc.). 1Ai like this
At low speeds, the rear wheels are steered in the opposite phase to the front wheels, and at high speeds, on the other hand, the rear wheels are steered in the same phase as the front wheels or approximately at zero. ing. Furthermore, if desired, the functional characteristic of the steering angle ratio of the rear wheels relative to the vehicle speed can be changed in accordance with the acceleration of the vehicle or manually, or a fixed mode can be selected by manual selection.

As a result, at low speeds, both the minimum turning radius and the difference between the inner wheels of the vehicle are significantly reduced, making it easier to quickly enter the vehicle, drive on narrow curved roads, and
It is possible to dramatically improve the maneuverability of the vehicle when making turns, and on the other hand, it is also possible to dramatically improve maneuverability when changing lanes at high speeds.

<Problems to be Solved by the Invention> Generally, in a vehicle steering system, the lateral displacement of the vehicle is given as an integral value of the steering amount, so if the error in the detected value of the actual steering angle is large. good control becomes difficult.

Based on such knowledge, the main object of the present invention is to provide front and rear wheel steering of a vehicle with excellent maneuverability by making it possible to accurately control the amount of steering of the rear wheels in a front and rear wheel steering device of a vehicle. The goal is to provide equipment.

<Means for Solving the Problems> According to the present invention, such an object is to steer the rear wheels in relation to the steering of the front wheels, and to adjust the steering angle of the rear wheels with respect to the front wheels in accordance with the vehicle speed. In vehicle front and rear wheel steering systems that are subject to variable control,
An actuator for steering a rear wheel has a mechanical deceleration means, and a displacement on the rear wheel side of the deceleration means is detected as a control input of a control device that controls the actuator. This is achieved by providing front and rear wheel steering devices.

In this way, by using the amount representing the actual steering amount of the rear wheels as the control input, errors in the control input due to operational errors of the actuator for rear wheel steering, elastic deformation play, etc. are eliminated. Stable and accurate control of the amount of wheel turning becomes possible.

<Embodiments> Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the configuration of a front and rear wheel steering device to which the present invention is applied. On the front wheel side, the handle shaft 2 of the handle 1 is incorporated into a rack and pinion type gear box 3, and tie rods 5.5 are connected to the left and right ends of the rack @4, and the outer ends of both tie rods 5.5 are connected to the left and right ends of the rack @4. A knuckle arm 6.6 supporting a front wheel 7.7 is connected to the knuckle arm 6.6, and as is known, the front wheel 7.7 is steered in the steering direction of the steering wheel 1.

On the other hand, on the rear wheel side, a rack and pinion gear box 8 similar to that described above is installed horizontally, and tie rods 10°10 are connected to the left and right ends of the rack shaft 9, and both tie rods 10. A knuckle arm 11.11 supporting a rear wheel 12.12 is connected to the outer end of the rear wheel. An output shaft of a motor 13 is connected to a pinion shaft of the gear box 8 . In this way, the rear wheels 12, 12 are steered using the rotational force of the motor 13 as power.

A displacement sensor 14.15 consisting of, for example, a sliding resistor or a differential transformer is installed between the casing of the front wheel side and rear wheel side gearbox 3.8 and the rack shaft 4.9, and is used to detect the actual steering angle. This is so that the displacement of the rack shaft 4.9 can be detected. These displacement sensors 14.15
The output of is connected to the control device 16. For example, the output of the vehicle speed sensor 17 provided on the non-driving wheel is also connected to the control bag [16], and furthermore, the push button type selection switch 18 installed on the dash board is connected to the control bag H1.
6.

The control device 16 has a built-in in-vehicle combiner 19 (FIG. 2), and this computer 19 receives information from steering angle sensors 14 and 15 that detect the steering angles of the front and rear wheels and a vehicle speed sensor 17 that detects the vehicle speed. Upon receiving the signal, an appropriate operation signal corresponding to the vehicle speed is sent to the motor 13 via the output bag e20, and its rotation is changed to i,13 In. A manual selection switch 18 is further connected to the computer 19 so that the steering ratio of the rear wheels can be controlled based on the function characteristic selected by the manual selection switch.

Next, the operation of the above embodiment will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows the functional configuration of the computer 9.
The vehicle speed detected by the vehicle speed sensor 7 is input to the computer 9 as a predetermined vehicle speed signal U. This vehicle speed signal U is converted into a preset steering angle ratio signal f(u) by conversion processing (a). The function giving the steering angle ratio signal f(u) is selected from a plurality of functional formula data f1, f, . . . stored in the memory (b), that is, it is selected by the selection switch 18. The selected selection information is processed through selection processing (
The plurality of characteristic curves shown in FIG. 3, that is, the characteristics 1k, 2k, . Functional formula data f 1 , f , . . . corresponding to - are selected. Each of these characteristics corresponds to each of the push buttons 21 to 24 of the selection switch 18.

In this way, the steering ratio function is set in the conversion process (a), and the target value y of the rear wheel steering angle is determined relative to the actual steering angle X obtained from the front wheel steering angle sensor 4. y o = X−f (I
J).

On the other hand, since the rear wheel steering angle sensor 15 detects the displacement of the rack shaft 9, the detection output of (() accurately corresponds to the actual rear wheel steering ratio. The actual wheel steering angle data y is input to the comparison process (d) in the computer 19.

This contact wheel actual steering angle data yIIl and the rear wheel steering angle target value y
A relative difference Δy between yl and yo is obtained by the comparison process (d) based on y and o. This difference Δy is input from the computer 19 to the output control device 20 as data corresponding to the amount of steering angle correction required to realize the required rear wheel steering angle.

The output side of this output control device 20 is connected to the motor 13 and supplies a control signal S corresponding to the difference Δy. In this way, the motor 13 is rotated in a direction that realizes a rear wheel steering angle corresponding to the current vehicle speed.

As shown in Fig. 3, the characteristics of the steering ratio function corresponding to the vehicle speed are obtained by dividing the curve corresponding to nk into multiple curves that are substantially parallel to each other at 1k, 2, 3k, etc., respectively. They are set to correspond to the characteristic curve 1, with the side corresponding to the sportier movement characteristics, 2k, 3k, etc.
...The larger the number, the easier the steering becomes.

In the above embodiment, each process in the computer 19 is executed by a predetermined &+ control program (software) stored in the computer; You can also do that. Furthermore, although the selection switch is configured as a push button, it may also be a sliding changing means that can continuously change the selection switch.

Further, the present invention is not limited to the above-mentioned embodiments, and may be applied to an actual steering angle sensor or a steering angle ratio in a hydraulic front and rear wheel steering device that hydraulically controls the steering of the rear wheels and transmits front wheel steering angle information hydraulically. In a configuration in which a variable mechanical structure is provided on the rear wheel side, and the rear wheels are steered by the rotational force mechanically transmitted from the front wheels in accordance with the steering angle ratio set in the variable steering angle ratio structure. The present invention can also be applied to a sensor that detects the actual steering angle of the rear wheels for the purpose of feedback. Further, as the deceleration means for the actuator that steers the rear wheels, a screw type or other known mechanical element whose steering angle does not change due to an external force applied to the rear wheels may be used.

<Effects> As described above, according to the present invention, the error in controlling the steering angle of the rear wheels is minimized, so the advantage of front wheel steering, that is, good steering response when driving at high speeds is achieved. Moreover, the basic effect of good maneuverability of the vehicle can be maintained at low speeds, and extremely good maneuverability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing the basic structure of a vehicle equipped with a front and rear wheel steering device to which the present invention is applied. FIG. 2 is a block diagram showing the functional configuration of the on-vehicle computer. FIG. 3 is a steering angle ratio output characteristic diagram in the above embodiment. 1... Handle 2... Handle shaft 3...
Gear box 4...Rack shaft 5...Tie rod 6...Knuckle arm 7...Front wheel
8... Gear box 9... Rack shaft 10
... Tie rod 11 ... Knuckle arm 12 ...
Rear wheel 13... Motor 14.15... Rudder angle sensor 16... Control device 17... Vehicle speed sensor 1
8...Manual selection switch 19...Computer 20...Output device 21-2
4...Push button

Claims (1)

[Scope of Claims] A front and rear wheel steering device for a vehicle that steers the rear wheels in conjunction with the steering of the front wheels and variably controls the steering angle of the rear wheels with respect to the front wheels in accordance with vehicle speed. Front and rear wheel steering of a vehicle, characterized in that an actuator for steering has a mechanical deceleration means, and displacement of a rear wheel side of the deceleration means is detected as a control input of a control device that controls the actuator. Device.