JPH0729612B2 - Front and rear wheel steering system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an improvement of a front and rear wheel steering device for a vehicle capable of automatically and variably controlling a steering angle of a rear wheel with respect to a front wheel.

<Prior Art> The applicant of the present invention steers the rear wheels in relation to the steering of the front wheels, and continuously changes the steering angle ratio of the rear wheels to the front wheels according to the vehicle speed. 59-26363) has already been proposed. The outline of this device is as follows: In the low speed range, the rear wheels are steered to the opposite phase or almost zero to the front wheels, and in the high speed range, the rear wheels are made to have the same phase as the front wheels. Steer. Then, by making this steering angle ratio a continuous function with respect to the vehicle speed as shown by the curve D in FIG. 6, the steering angle ratio is positive, that is, the same, in the region where the vehicle speed is higher than this with the predetermined vehicle speed d as the boundary. Changes continuously on the phase side,
In a region where the vehicle speed is lower than this, the steering angle ratio is negative, that is, it continuously changes on the opposite phase side. In this way, the continuous control of the steering angle ratio is performed in accordance with the function curve D, so that the optimum characteristics of the steering device are compatible throughout the entire vehicle speed. As a result, the minimum turning radius of the vehicle and the inner ring difference are greatly reduced in the low speed range, and the maneuverability of the vehicle is drastically improved when entering the garage, traveling on a narrow bend, and making a U-turn. In addition to being able to achieve, it is possible to dramatically improve the steering response in the high speed range.

By the way, when the front wheels and the rear wheels are steered in opposite phases when performing parallel parking or narrowing in a narrow place in a low-speed traveling range, the rear part of the vehicle may shake laterally. Since it occurs, it may be easier to steer the steering wheel by turning the steering wheel in the same phase. Further, even in the high speed traveling range, it may be desired to keep the steering angle ratio between the front and rear wheels at a certain constant value according to the driver's preference. In other words, since one standard function curve shown by the curve D in FIG. 6 cannot necessarily meet the various preferences of the driver, a manual switching means that can arbitrarily select various steering angle ratio characteristics can be used as the front and rear wheel steering device. It is considered that it is preferable to provide the above.

However, depending on the driving situation of the vehicle, when the steering angle ratio characteristic is switched by activating the manual switching means, the steered angle of the rear wheels may suddenly change and the driver may feel uncomfortable. For example, if the steering angle ratio changes while the driver is steering steeply to make a sharp turn, the turning characteristics of the vehicle change abruptly, which does not force the driver to perform agile correction steering. Not necessarily.

<Problems to be Solved by the Invention> In view of such a problem, the main object of the present invention is to make the maneuverability of the vehicle compatible with a wider driving condition over the entire range of the vehicle speed, and It is an object of the present invention to provide a front / rear wheel steering device for a vehicle configured such that the manual switching can be performed only in a state where there is no fear of causing a sudden change in the motion of the vehicle even if the manual switching is performed.

<Means for Solving the Problems> According to the present invention, the object is to provide a front and rear wheel steering system for a vehicle that automatically and variably controls a steered angle of rear wheels according to a predetermined condition. A storage unit that stores a plurality of pieces of steering angle ratio information representing a relationship between a front wheel steering angle and a rear wheel steering angle that have been set in advance, and one of the plurality of steering angle ratio information is selected, and the selected rudder is selected. Manual switching means for giving a rear wheel steering command based on the angular ratio information, and manual switching of the plurality of steering angle ratio information only when the steering angular speed of the front wheels is detected and the steering angular speed is less than a predetermined value. It is achieved by providing a front and rear wheel steering device for a vehicle, which is provided with a restricting means for enabling the execution of the above.

<Operation> Under normal circumstances, the driver cannot operate the manual switching means during steering, but there is a possibility that a passenger may accidentally operate the manual switching means or the manual switching means is mechanical. It cannot be denied that when the contact point is configured, the contact point may be switched against the driver's intention due to a malfunction of the contact point or the like. Whatever the cause, if the turning angular velocity of the front wheels exceeds a certain predetermined value, that is, when a sudden steering operation is performed, it is possible that manual switching between a plurality of steering angle ratio information is executed. Regulate,
By allowing the manual switching only when the vehicle is moving straight or in a motion close to a steady turning motion, an inconvenience that may occur with a sudden change in the steering angle of the rear wheels, that is,
It is possible to prevent the vehicle from exhibiting a behavior that forces the driver to perform agile correction steering.

<Embodiment> Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the drawings, FIG. 1 is a perspective view showing a schematic basic structure of a vehicle equipped with front and rear wheel steering devices, FIG. 2 is an enlarged perspective view of a rear wheel steering system, and FIGS. 3 (a), (b) and (C) is a fractured side view showing the operating principle thereof.

First, in order to clarify the present invention, the configuration and operation of the front and rear wheel steering device will be described with reference to FIGS. 1 to 3. The handle shaft 2 of the handle 1 is incorporated in a rack and pinion type gear box 3, and tie rods 5 and 5 are connected to the left and right ends of the rack shaft 4 so that both tie rods 5 and 5 are connected.
At the outer end of the, the knuckle arm 6, which supports the front wheels 7, 7,
6, the front wheels 7, 7 are steered in the steering direction of the steering wheel 1, as is known.

On the other hand, a pinion shaft 8 is led out from the gear box 3 rearward, and a long linkage shaft 10 is connected to a 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. The input shaft 12 is arranged on the left and right centerlines at the rear part of the vehicle body and rotatably supported by a bearing bracket 13. Has been done. Further, a swing shaft 15 shown in detail in FIG. 2 is connected to the rear end of the input shaft 12 via a clevis 14, and a joint member 16 is loosely fitted to a member of the swing shaft 15. Tie rods 18, 18 are connected to the left and right ends of the joint member 16 via ball joints 17, 17, and the joint member 16 is a link.
It is swingably supported by the vehicle body side by 21, 22 and a bracket 23. In addition, rear wheels are attached to the outer ends of both tie rods 18, 18.
Knuckle arms 19, 19 supporting 20, 20 are connected. An arm 25 is fixed to the rear end of the swing shaft 15 so as to project downward, and a link 26 is pivotally attached to the lower end of the arm 25 so as to be vertically rotatable.
A slider 27 is also pivotally attached to the rear end of the slider 26 so as to be vertically rotatable. As shown in FIG. 3, an output shaft 30 of a motor 29 is screwed into the slider 27 via a ball screw mechanism 28 so that the output shaft 30 is positioned rearward coaxially with the input shaft 12. The motor 29 is fixed to the vehicle body.

On the other hand, the vehicle is equipped with an in-vehicle computer 31, which receives signals from a vehicle speed sensor 32 for detecting the vehicle speed and a position sensor 33 for detecting the position of the slider 27, and an appropriate control signal according to the vehicle speed. Is supplied to the motor 29.

Assuming that the steering angle ratio characteristic shown by the curve D in FIG. 6 is standard, for example, when the vehicle speed is the set value d, the slider 27 is in the position shown in FIG. The point P coincides with the axis of the input shaft 12. In this case, since the input shaft 12 and the swing shaft 15 rotate concentrically, the joint member 16 does not swing left and right, and the tie rod 18, 18 is also immobile. Therefore, only the front wheels 7, 7 are steered and the rear wheels 20, 20 are not steered at all.

When the vehicle speed is lower than the set value d, the computer 31 drives the motor 29 according to the vehicle speed signal from the vehicle speed sensor 32 to set the position of the slider 27 to the forward position as shown in FIG. 3 (b). . If the slider 27 is in the forward position, the swing shaft 15 tilts downward, and the pivot point P is offset (eccentric) by e1 below the axis of the input shaft 12,
The joint member 16 swings left and right according to the rotation of the input shaft 12, and the tie rods 18, 18 for the rear wheels are connected to the tie rods 5, 5 for the front wheels.
Displace in the opposite direction to. Therefore, the rear wheels 20, 20 are steered in the opposite phase to the front wheels 7, 7, and the steering angle ratios of the front and rear wheels continuously change according to the vehicle speed.

When the vehicle speed is higher than the set value d, the computer 31 reverses the motor 29 according to the vehicle speed at that time, and moves the slider 27 backward as shown in FIG. 3 (c). When the slider 27 retreats, the swing shaft 15 tilts upward, and the pivot point P is offset by e2 above the axis of the input shaft 12, so that the joint member 16 moves left and right according to the rotation of the input shaft 12. It swings to displace the rear wheel tie rods 18, 18 in the same direction as the front wheel tie rods 5, 5. Therefore, the rear wheels 20 and 20 are steered in the same phase as the front wheels 7 and 7, and the steering angle ratio between the front and rear wheels continuously changes according to the vehicle speed.

Next, with reference to FIG. 4 to FIG. 6, the configuration of the main part of the present invention will be described. FIG. 4 is a configuration diagram of main parts, FIG. 5 is a functional block diagram of FIG. 4, and FIG. 6 is a characteristic diagram of the steering angle ratio output in FIG.

In FIG. 4, reference numeral 34 indicates, for example, a plurality of push buttons 35a, 35b.
Is a selection switch as a manual switching means for manually switching the steering angle ratio between the front wheels and the rear wheels (or the absolute value of the rear wheel steering angle with respect to the front wheel steering angle, the same applies hereinafter) configured by arranging ... It is arranged on the instrument panel in the room so that the driver can manually operate it. The selection switch 34 is connected to the computer 31, and the selection result of the steering angle ratio selected by the selection switch 34 is displayed on the computer.
Entered in 31.

A steering angle sensor 36 for detecting the steering angle of the front wheels is arranged below the handle shaft 2. This sensor may be a resistor type sensor or an electromagnetic type sensor, and may be a sensor that can generate a signal representing the angular velocity of the handle shaft 2, that is, the steering angular velocity of the front wheels, by differentiating the output signal thereof. . The output of the steering angle sensor 36 is also connected to the computer 31.

Next, the selective switching of the steering angle ratio in the computer 31 will be described with reference to FIG.

First, the auto mode AT in which the steering angle ratio continuously changes according to the vehicle speed will be described. This automatic mode AT is selected by pressing the first push button 35a of the selection switch 34. The vehicle speed signal detected by the vehicle speed sensor 32 is input to the computer 31 and converted into target steering angle ratio data ka corresponding to the vehicle speed by the conversion processing section (a). The target rudder angle ratio data ka is read from the standard rudder angle ratio information corresponding to the curve D in FIG. 6 stored in advance in the conversion processing section (a). On the other hand, the actual steering angle ratio data kb is obtained from the position sensor 33. The two steering angle ratio data ka and kb are compared by the first comparison calculation processing section (b), and the steering angle ratio correction information b1 corresponding to the deviation at this time is obtained.

Here, when the automatic mode AT is selected by the selection switch 34 as described above, the steering angle ratio correction information b1 from the first comparison calculation processing section (b) is directly output from the selection processing section (c) and the vehicle speed is changed. The correction control signal S1 for setting the appropriate steering angle ratio according to the above is supplied to the motor 29 via the output circuit 37.

Next, the arbitrary selection mode will be described. This arbitrary selection mode includes pushbuttons 35b ...
Selected by pressing. On the other hand, the data storage unit (d) of the computer 31 stores steering angle ratio information different from the above-mentioned steering angle ratio information of the automatic mode AT. This rudder angle ratio information is composed of, for example, a plurality of rudder angle ratio data k1, k2, k3, ... Kn having arbitrary sizes. And select switch
For example, when the second push button 35b is pressed at 34, the selected steering angle ratio data k1 is read from the data storage unit (d), and this is read as the actual steering angle ratio data kb from the position sensor 33 and the second steering angle ratio data kb.
Comparison information at the comparison calculation processing unit (e), correction information at this time
b2 is obtained.

Here, in the selection processing section (c), when a push button other than the auto mode AT in the selection switch 34 is pressed, it is received and correction is made from the first comparison calculation processing section (b). The output of the information b1 is stopped, and the correction information b2 from the second comparison operation processing section (e) is selected to be output. This allows
The correction control signal S2 is supplied from the output device 37 to the motor 29,
The steering angle ratio of the rear wheels is set to k1.

This operation is the same for the other push buttons 35b, 35c ..., and the driver can manually select any of the steering angle ratios k1, k2, k3 ... Kn in FIG. .

By the way, the device of the present invention is provided with a means for restricting the switching operation of the manual selection. This is the above-mentioned steering angle sensor 36 and the differential for converting the data of the steering angle sensor 36 into the steering angular velocity data. The circuit section (h), a judgment processing section (f) for comparing the actual turning angular velocity of the front wheels with a preset reference value to judge the difference, and the judgment processing section (f) for actual steering When it is determined that the angular velocity exceeds the reference value, the selection processing unit ((2) that regulates either the output of the correction information b1 or b2 from the first and second comparison calculation processing units (B) and (E)). C)
It consists of

When the steering angle signal from the steering angle sensor 36 is differentiated in the computer 31 to obtain the steering angular velocity signal, the judgment processing unit (f) changes the steering angular velocity signal to a preset reference turning signal. It is compared with the steering angular velocity data to determine whether or not the reference steering angular velocity data is larger than the reference steering angular velocity data. Then, when the actual turning angular velocity exceeds the reference turning angular velocity data, a judgment result is given to the selection processing section (C), and the switching signal from the selection switch 34 is ignored. That is, when the front wheel turning angular velocity exceeds the predetermined value, even if the selection switch 34 is pressed, the selection processing unit (c) maintains the state before the selection switch 34 is pressed, and the steering angle ratio is switched. Prohibit that.

The reference steered angular velocity data for performing such regulation is selected in consideration of the steered angular velocity that does not cause a sudden change in the vehicle motion state. The various processes in the computer 31 described above may be executed by a predetermined control program (software) stored in the computer 31.

Although the vehicle-mounted computer 31 is used in the above-described embodiment, an electric circuit or mechanical structure having the same function may be used. Further, although the position sensor 33 obtains the steering angle ratio data between the front and rear wheels, the control may be performed based on the measured data of the rear wheel steering angle. Further, the present invention is not limited to the above-described embodiment, and the front and rear wheel steering device for steering the front and rear wheels by hydraulic pressure and transmitting the front wheel steering angle information by hydraulic pressure, or transmitting the front wheel steering angle to the computer 31 by an electric signal. The same can be applied to the front and rear wheel steering device and the like.

<Effect> As described above, according to the present invention, in the front and rear wheel steering device of a vehicle that can automatically change the steering angle ratio of the rear wheels to the front wheels according to the vehicle speed, a desired steering angle ratio can be set regardless of the vehicle speed. Since it is possible to manually change it arbitrarily, it is possible to prohibit manual switching under the situation where steering at a predetermined turning angular speed or more is being performed.
This has the effect of further improving the maneuverability of the vehicle and preventing the sudden change in the motion state of the vehicle, which is unpredictable by the driver, because the switching is not performed especially when the switching is inappropriate. .

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic basic structure of a vehicle equipped with front and rear wheel steering devices. FIG. 2 is an enlarged perspective view of the rear wheel steering system. 3 (a), (b), and (c) are broken side views showing the operating principle of the rear wheel steering system. FIG. 4 is a configuration diagram of the main part. FIG. 5 is a functional block diagram of FIG. FIG. 6 is a steering angle ratio output characteristic diagram in FIG. 1 ... Handle, 2 ... Handle shaft, 3 ... Gear box, 4
... rack shaft, 5 ... tie rod, 6 ... knuckle arm, 7
... front wheel, 8 ... pinion shaft, 9 ... universal joint, 10 ... linkage shaft, 11 ... universal joint, 12 ... input shaft, 13 ... bearing bracket, 14 ... clevis, 15 ... swing shaft, 16 ... joint member,
17 ... Ball joint, 18 ... Tie rod, 19 ... Knuckle arm, 20
... rear wheel, 21, 22 ... link, 23 ... bracket, 25 ... arm, 26 ... link, 27 ... slider, 28 ... ball screw mechanism, 29 ... motor, 30 ... output shaft, 31 ... computer, 32
… Vehicle speed sensor, 33… Position sensor, 34… Selection switch, 35
a to 35d ... push button, 36 ... rudder angle sensor, 37 ... output device,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Hamada 6-8-7 Motoimaizumi Utsunomiya City, Tochigi Prefecture No. 201 Eder Heights 201 (72) Inventor Manuya Serizawa 773-5, Sukugocho, Utsunomiya City, Tochigi Prefecture 2 Izumi Mansion 2 -201 (56) Reference JP-A-59-81264 (JP, A) JP-A-57-15066 (JP, A)

Claims (1)

[Claims] 1. A front-rear wheel steering system for a vehicle, which automatically and variably controls a rear-wheel steered angle according to a predetermined condition, and represents a preset relationship between a front-wheel steered angle and a rear-wheel steered angle. Storage means for storing a plurality of steering angle ratio information, and manual switching means for selecting one of the plurality of steering angle ratio information and giving a rear wheel steering command based on the selected steering angle ratio information And a regulation means for detecting the turning angular velocity of the front wheels and enabling the manual switching of the plurality of steering angle ratio information only when the turning angular velocity is equal to or less than a predetermined value. Front and rear wheel steering system for vehicles.