JPH0549512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a front and rear wheel steering device for a vehicle, particularly a four-wheeled vehicle.

The applicant has already proposed a vehicle steering system (Japanese Patent Application No. 134889/1989, etc.) that steers the rear wheels in conjunction with the steering of the front wheels and varies the steering ratio of the rear wheels to the front wheels according to the vehicle speed. did. To give you an overview of this device, at low speeds, the rear wheels are steered in the opposite phase to the front wheels, or almost to zero, while at high speeds, on the other hand, the rear wheels are steered in the same phase as the front wheels. This steering ratio is a continuous function of the vehicle speed, and if the vehicle speed is higher than a certain vehicle speed as a boundary, the steering ratio is positive, that is, in the same phase, and if the vehicle speed is lower than this, the steering ratio is The steering ratio is continuously controlled so that it is negative, that is, in opposite phase (see line Q in Figure 5), and the functions of the steering system are achieved at both low and high speeds. As a result, both the minimum turning radius and the inner wheel difference of the vehicle are significantly reduced at low speeds, and the maneuverability of the vehicle is dramatically improved when entering a garage, driving on narrow curved roads, making U-turns, etc. At high speeds, maneuvering response when changing lanes, etc. can be dramatically improved.

By the way, according to such a device, the steering ratio is variably controlled based on a single characteristic curve data set in advance, which is set for the vehicle speed.

However, in road conditions, such as highways where there is little need for small turns, even if you are forced to drive at low speeds due to traffic jams, it is possible to drive easily without having to make small turns by changing lanes, or On normal roads, depending on subjective factors such as the driver's preference and physical condition while driving, the steering ratio is set to the opposite phase when driving at low speeds to enable tight turning when driving at medium speeds, etc. Alternatively, when driving at a certain high speed, the front and rear wheels may be steered in a flexible and arbitrary manner by not setting the steering ratios to the same phase side, but rather by setting them to slightly opposite phases to give a sporty feel. It would be extremely convenient for the driver if it could be changed to

In view of the above circumstances, the present invention aims to improve this type of front and rear wheel steering device. To provide a front and rear wheel steering device for a vehicle, which allows the most appropriate steering to be selectively performed and allows comfortable driving while maintaining the advantages of front and rear wheel steering.

To achieve the above object, the present invention steers the rear wheels in conjunction with the steering of the front wheels, and variably controls the steering ratio of the rear wheels to the front wheels based on a steering ratio function that changes according to the vehicle speed. It is applied to the front and rear wheel steering systems of vehicles such as four-wheeled vehicles, and its main component is a changing means that manually changes the characteristics of the steering ratio function that changes according to the vehicle speed, such as an on-board computer and a memory. The present invention is characterized in that it is configured with a switching means that selectively sets the characteristic data of a plurality of steering ratio function characteristics that are set and stored in advance, and that the driver can manually change the characteristics of the steering ratio function.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, in order to clarify the present invention, an overview of an example of the configuration and operation of a front and rear wheel steering device in a vehicle will be explained with reference to FIGS. 1 to 3. Fig. 1 is a perspective view showing the general basic structure of a vehicle equipped with a front and rear wheel steering system according to the present invention, Fig. 2 is an enlarged perspective view of the rear wheel steering system in Fig. 1, and Figs. 3 a, b, and c. is a principle diagram for explaining the operation.

The handle shaft 2 of the handle 1 is built 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 shaft 4, and front wheels 7, 7 are supported at the outer ends of both tie rods 5, 5. The knuckle arms 6, 6 are connected to steer the front wheels 7, 7 in the steering direction of the steering wheel 1 in a known manner.

On the other hand, a pinion shaft 8 is led out rearward from the gear box 3, and a long linkage shaft 10 is connected to the rear end of the shaft 8 via a universal joint 9. An input shaft 12 is connected to the rear end of the linkage shaft 10 via a universal joint 11, and this input shaft 12 is arranged on the left-right center line of the rear part of the vehicle body, and is connected to a bearing bracket 13.
It is rotatably supported.

Further, a swing shaft 15 shown in detail in FIG. 2 is connected to the rear end of the input shaft 12 via a universal joint 14, and a joint member 16 is loosely fitted in the middle of the swing shaft 15. As shown in the figure, this joint member 16 has an arm member 17 whose length direction is in the vehicle width direction.
Fix the central part of the The right end of this arm member 17 is connected to the vehicle body via a link member 18 and a link bracket 19, and the left end is connected to a link member 20,
21 and link bracket 22 to the vehicle body side. Then, the pivot shaft 2 of the link member 21
3 rotates together with the link member 21.

The joint member 16 connects the inner ends of left and right rear wheel steering tie rods 25, 25 via ball joints 26, 26, and the outer ends of both tie rods 25, 25 are shown in FIG. Gotoku rear wheel 2
7, 27 are connected to knuckle arms 28, 28 which support them.

On the other hand, a motor 31 is disposed on the vehicle body side at the outer left end of the arm member 17 , and a worm gear 32 is disposed on the output shaft of the motor 31 and meshed with the sector gear 24 . In addition, the vehicle is equipped with an on-board computer 33, and this computer 3
3 receives signals from a vehicle speed sensor 34 that detects the vehicle speed and a position sensor 35 that detects the rotational position of the link member 21, and sends an appropriate control signal corresponding to the vehicle speed to the motor 31 to control its rotation.

When the pivot point P of the joint member 16 coincides with the center O of the input shaft 12 as schematically shown in FIG. 3a, the input shaft 12 and the swing shaft 15 rotate concentrically. At this time, the joint member 16 does not swing from side to side, and the tie rods 25, 25
In this case, only the front wheels 7, 7 are steered, and the rear wheels 27, 27 are not steered at all as in the conventional vehicle.

Also, when the vehicle speed is lower than the set speed and is running at low speed, the computer 33 receives a signal from the vehicle speed sensor and makes a judgment, and controls the rotation of the motor 31.
The worm gear 32 formed on the output shaft of the worm gear 32 causes the sector gear 24 that meshes with the worm gear 32 to respond, and the link member 21 that rotates together with the sector gear 24 swings downward about the pivot shaft 23, and as a result, the arm member 17 As shown in FIG. 3b, the left end is inclined downward. Due to the inclination of the arm member 17, the pivot point P is located below the shaft center O. At this time, if the input shaft 12 is rotated, for example, in the counterclockwise direction by θ, the tie rods 25, 25 will be moved to the position shown in FIG. 3b. The vehicle then moves slightly to the right as shown by the broken line, and the rear wheels 27, 27 are steered in the opposite direction to the front wheels 7, 7, and the front/rear wheel steering ratio at this time is continuously changed in accordance with the vehicle speed.

Furthermore, if the vehicle speed increases beyond the initial setting value, the computer 33 causes the motor 31 to reverse, so that the arm member 17 is tilted in the opposite direction as shown in FIG. 3c, so that the pivot point P is If the input shaft 12 is positioned above the shaft center O and rotated by an angle (θ) counterclockwise as described above, the tie rods 25, 25 will be moved as shown by the broken line in FIG. 3c. Working in the opposite manner, the rear wheels 27, 27 are also steered in the same direction as the front wheels 7, 7, and the front/rear wheel steering ratio at this time is continuously changed in accordance with the vehicle speed.
The characteristics of the steering ratio function for the above vehicle speeds are shown by curve Q in FIG.

Next, the main structure and functions of the present invention will be specifically explained with reference to FIGS. 2, 4, and 5. FIG. 4 is a functional block diagram of the rear wheel steering control system, and FIG. 5 is a characteristic diagram of the front/rear wheel steering ratio function with respect to vehicle speed.

First, the configuration will be explained. As shown in FIG. 2, the in-vehicle computer 33 has a plurality of push buttons 36, 3.
7, 38, 39, 40 and 41 are connected to manual selection switches 42 arranged horizontally. This selection switch 42 is used to arbitrarily change the steering function set according to the vehicle speed described above using a specific manual, and is installed, for example, on an instrument panel in the vehicle interior so that the driver can operate it while seated. Make it.

Next, the function of the rear wheel steering control system will be explained. As shown in FIG. 4, the vehicle speed signal detected from the vehicle speed sensor 34 is input to the computer 33 as predetermined vehicle speed data (u). This vehicle speed data (u) is converted into corresponding preset steering ratio data (k0) (=f(u)) by conversion process A.

To explain this process in detail, first, the steering ratio data (k0) corresponding to this vehicle speed data (u) is set and stored in advance as conversion data in the memory of the computer 33, and this conversion data is This is represented by a plurality of conversion characteristics shown in FIG.

On the other hand, the selection information selected by the selection switch 42 is given to the conversion process A to produce a plurality of characteristic curves shown in FIG. 2k), (3k), (4k)
One characteristic is selected from … (NK), and each characteristic (1k), (2k) … (NK) is selected by selection switch 4.
Corresponding to each of the push buttons 36, 37, . . . , 41 in FIG. Become. On the other hand, the position sensor 35 detects the rotational position of the link member 21, and this rotational position is proportional to the steering ratio in the actual steering state, and this detection result is the actual steering ratio data (km). input to the computer 33 as follows. Then, by comparing this actual steering ratio data (km) and the aforementioned steering ratio data (k0), (km)
- Obtain relative difference data (△k) of (k0). This difference data (Δk) is data for correcting the steering ratio to a required value, and is output from the computer 33 and input to the output control device 43. This output control device 4
The output side of 3 is connected to the motor 31 and supplies a control signal s corresponding to the difference data (Δk). Thus, the motor 31 is rotated and corrected until the steering ratio corresponds to the current vehicle speed.

Note that the characteristics of the steering ratio function corresponding to vehicle speed are as follows:
The settings are as shown in the diagram, and the characteristic curve (1k) side has a sporty feel, and the larger the number (2k), (3k), etc., the easier the steering becomes. Further, each process in the computer 33 is executed by a predetermined control program (software) stored in the computer 33.

In the above embodiment, the in-vehicle computer 33
However, the same function may be configured by an electric circuit consisting of a combination of other functions. Further, although the selection switch is configured by a push button, it may be a sliding type changing means that can change the selection switch instead of continuously. Furthermore, the present invention is not limited to the embodiments, and may include a front and rear wheel steering device that hydraulically controls the front and rear axles and transmits front wheel steering angle information using hydraulic pressure, or transmits the front wheel steering angle to the computer 33 as an electrical signal. The present invention can be similarly applied to a front and rear wheel steering device, etc.

As described above, the present invention provides front and rear wheel steering in which the rear wheels are steered in conjunction with the front wheel steering, and the steering ratio of the rear wheels relative to the front wheels is variably controlled based on a steering ratio function that changes in accordance with the vehicle speed. In the device, the characteristics of the steering ratio function that is set according to the vehicle speed can be manually changed arbitrarily, so it is possible to manually change the characteristics of the steering ratio function that is set according to the vehicle speed. The most appropriate steering for the driving conditions can be selectively performed depending on the subjective factors of It is possible to drive comfortably while maintaining the basic effect of good maneuverability of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the general basic structure of a vehicle equipped with a front and rear wheel steering device according to the present invention, and FIG.
An enlarged perspective view of the rear wheel steering system in Figure 3a,
b and c are principle diagrams for explaining the operation, Fig. 4 is a functional block diagram of the rear wheel steering control system showing the main configuration of the present invention, and Fig. 5 is a characteristic diagram of the front/rear wheel steering ratio function with respect to vehicle speed. It is. In the drawing, 33 is an in-vehicle computer, 34 is a vehicle speed sensor, 35 is a position sensor, 36, 37, 3
8, 39, 40, and 41 are push buttons, 42 is a selection switch (changing means), A is a conversion process, C is data for conversion, and D is a comparison process.

Claims (1)

[Scope of Claims] 1. Front and rear wheels of a vehicle in which the rear wheels are steered in relation to the steering of the front wheels, and the steering ratio of the rear wheels to the front wheels is variably controlled based on a steering ratio function that changes according to the vehicle speed. The steering system is characterized in that the steering system is provided with a changing means for manually changing the steering ratio function of the front and rear wheel steering system of the vehicle to a steering ratio function that has other characteristics that change according to the vehicle speed. Wheel steering device. 2. The first aspect of the present invention is characterized in that the changing means is constituted by a switching means for selectively setting from characteristic data of a plurality of steering ratio functions corresponding to vehicle speeds that are preset and stored in a memory of an on-vehicle computer.
Front and rear wheel steering device for the vehicle described in Section 3.