JPS60161261A - Controller for steering rear wheels - Google Patents

Abstract

PURPOSE:To prevent a tire and a steering system in steering operation from being put with a strain, by permitting rear wheels to be steered only when the rear wheels are at neutral position. CONSTITUTION:A position sensor 14 is installed into a steering system for rear wheels 3, and a controlling microcomputer 29 is installed onto a chassis 1, and each output of the position sensor 14, car-speed sensor 28, steering-wheel angle sensor 26, and a rear-wheel steering-mode selecting switch 27 is input into the controlling microcomputer 29. Only when the rear wheels 3 are at neutral position, the output for steering the rear wheels 3 in the mode selected by the rearwheel steering-mode selecting switch 27 is input into a servoamplifier 25 through a mixer 30. Threfore, the situation where rear wheels 3 in the largely steered state are largely steered state are largely steered to the reverse side is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a control device for rear wheel steering in a vehicle.

(Prior art) Figure 1 shows an example of a conventional rear wheel steering control device
No. 64926). In the figure, 1 is the vehicle body, 2 is the front wheel, 8 is the rear wheel, 4 is the steering wheel, 5 is the gearbox for the front wheel, 6 is the steering wheel for the front wheel, 11 is the front wheel steering wheel.
1 is a solenoid valve, 11a and llb are solenoids thereof, 12 is a power source, and 18 is a hand switch located near the driver's seat.

The state shown in the figure shows the state in which the rear wheel 8 is in the neutral position, but if the hand switch 18 is now switched to contact a from this state, the solenoid will open.

11a is energized, the solenoid valve 11 is switched to pattern A, and as a result, the rear wheel 8 is turned to the left in the figure by the operation of the power cylinder 7.

When the hand switch 18 is switched to the contact position, the solenoid llb is energized and the solenoid valve 11 is switched to pattern B, and as a result, the rear wheel 8 is turned to the right in the figure by the operation of the power cylinder 7.

This conventional device steers the rear wheels 8 by selecting one of the modes of in-phase, opposite-phase, and neutral position relative to the front wheels 2 as described above, and also controls the degree of change in direction of the rear wheels 8. The front wheel steering angle is detected by the steering sensor 4' provided on the steering wheel 4, and the variable throttle valve 91 provided in the oil passage for steering the rear wheels is controlled based on this signal, depending on the degree of direction change of the front wheels 2. It's starting to change. Therefore, when the front wheels 2 are returned to the neutral position by operating the handle 4, the rear wheels 8, which had been changing direction until then, are also returned to the neutral position.

However, in the conventional device described above, in order to reduce the turning radius when parking, for example, the front wheels 2 are turned significantly by operating the handle 4, the rear wheels 8 are switched to the opposite phase by the device, and the vehicle is parked as it is. If the vehicle stops in this state, both the front wheels 2 and the rear wheels 8 will remain in opposite phases and largely changed direction. Therefore, in such a state, for example, if the hand switch 18 is switched to the same phase side,
The rear wheels 8 will change their direction more to the same phase than to the opposite phase. However, a large change in direction of the wheels while the vehicle is stopped is a so-called stationary steering condition, and must be avoided as it puts strain on the tires and steering system.

(Purpose) The present invention was made in order to eliminate the occurrence of the above-mentioned problems, and solves the above problems by enabling the rear wheels to be steered only when the rear wheels are in a substantially neutral position. The purpose is to

(Configuration) In order to achieve the above object, the present invention has a plurality of control modes for rear wheel steering for the front wheels, and selects one of them to switch and steer the rear wheels using a mode switching device. In a rear wheel steering system, the mode switching device is connected to a position sensor that detects that the rear wheels are in a substantially neutral position, and the mode is switched only when the rear wheels are in a substantially neutral position according to a signal from the position sensor. A rear wheel steering control device is configured to enable switching.

(Example) The present invention will be described in detail below with reference to FIGS. 2 to 6. In the figure, the same reference numerals as the above-mentioned reference numerals indicate equivalent parts.

FIG. 2 shows a first embodiment of the invention. In this embodiment, a position sensor 4 and a comparator 15 for detecting the position of the rear wheel 8 are provided on the vehicle body l, and after the position of the rear wheel 8 is detected by the position sensor 14, The position of the wheel 8 is compared with the set value of the comparator 15, and only when the rear wheel 8 is in a substantially neutral position, the comparator 15 outputs a signal, and in cooperation with the switching of the hand switch 18, the solenoid valve 11 is output.
is configured to switch to a desired pattern. That is, in the figure, 16.17 is an AND circuit, TR, TR, are transistors, and Hz s Rg is a relay.

(Operation) The operation will be explained according to FIG. 2(a) and the time chart of the logic circuits 16 and 17 shown in FIG. 2(b).

Now, when the front wheels 2 and rear wheels 8 of the vehicle are in the state shown in FIG. is within the set value range, 1 is output to the position signal a in the figure, that is, 1 is input to the logic circuit 16. (Initial state t.) At this time, operate the hand switch 18 and, for example, contact x0.
When connected to, the signal 1 is sent from this contact X□ to the logic circuit 16.
enters. (t□) As a result, the output signal Q of the logic circuit 16 changes from 0 to 1, and the solenoid lla is energized to switch the solenoid valve 11 to pattern A in order to close the relay R□ via the transistor TR. Therefore, the rear wheels 8 change direction to the left in the diagram according to the degree of change in direction of the front wheels 2. Here, even if the rear wheels are largely steered and exceed the set value range of the rear wheel position, a changes from 1 to 1. However, while the contact x0 is connected and the pattern signal is 1, the output of the logic circuit 16 does not change.

(t,) Only when the contact X□ is disconnected, the output of the logic circuit 16 changes from 1 to 0, so that the function of pattern A can be canceled. (t,) Also, when the position of the rear wheel 8 is not approximately neutral, the hand switch 18
Even if contact X is connected by operating , the rear wheel steering pattern A function remains disabled and pattern switching becomes impossible. (1, -1.) That is, the pattern can only be switched after the rear wheels are returned to the substantially neutral position. (t7) Furthermore, by operating the hand switch 18, contact
, the logic circuit 17 and TR operate in the same manner as in pattern B when connected to .

In this way, there is no fear that strain will be applied to the tires or the steering device due to the rear wheels 8 making a large change in direction in the stationary steering condition as described above.

(Embodiment) Figures 8 to 5 show a second embodiment of the present invention, in which 18 is an engine, 19 is a gear shift i, 20 is a servo valve of the power cylinder 7 for steering the rear wheels, and 21 is a servo valve of the power cylinder 7 for steering the rear wheels. A pipe for supplying the hydraulic pressure of the hydraulic pump 9 to the servo valve 2o, 22 is an unloading valve inserted in the middle of this pipe 21, 28
is also an accumulator, 24 is a return oil pipe provided from the servo valve 20 to the oil tank IO, and 25 is a servo amplifier for driving the servo valve 20. In this embodiment, a vehicle speed sensor 28t [
A steering wheel angle sensor 26 is provided on the column 4a of the steering wheel 4, and a rear wheel steering mode changeover switch 27 is further provided.

There are eight types of rear wheel steering modes as shown in (r) t (n) in FIG. 4. In other words, the characteristic I in Fig. 4 (I), which shows the steering angle ratio γ of the front and rear wheels on the ordinate and the vehicle speed V on the abscissa, is mode (I). The rear wheels 8 and 8 are steered in opposite phases, and are steered in the same phase at a predetermined vehicle speed or higher.

Characteristic (2) in FIG. 4 (II) is a mode (If) in which the wheels are steered in the same phase when the vehicle speed is below a predetermined speed, and the rear wheels 8 are maintained in the neutral phase when the speed is above a predetermined speed.

Characteristic (2) in FIG. 4 (I[l) is mode (II), in which the rear wheels 8 maintain the neutral position at all vehicle speeds.

Further, in this embodiment, the position sensor 14 is provided in the steering system of the rear wheels 8, and a control microcomputer 29 is provided in the vehicle body 1, and the position sensor 14. The outputs of the vehicle speed sensor 28, the steering wheel angle sensor 26, and the rear wheel steering mode changeover switch 27 are input to the control microcomputer 29, and the rear wheel steering mode changeover switch 27 is activated only when the rear wheels 8 are in a substantially neutral position.
The output for steering the rear wheels 8 in the selected mode is input to the servo amplifier 26 via the mixer 80. Note that a part of the output of the position sensor 14 is fed back to the mixer 80.

(effect) Next, the operation of the embodiment configured as described above will be explained.

FIG. 5 shows the control flowchart. That is, as shown in block 81, when a desired mode is selected by operating the rear wheel steering mode changeover switch 27, a signal of the selected mode is input to the control microcomputer 29. Further, the vehicle speed at that time is detected by the vehicle speed sensor 28, and the signal thereof is also inputted to the microcomputer 29. On the other hand, the steering wheel angle at that time is inputted to the microcomputer 29 by the steering wheel angle sensor 26, and furthermore, the position sensor 14 detects the rear wheel 8 at that time. The position is input to the microcomputer 29, and a portion thereof is input to the mixer 80.

Then, within this control microcomputer 29, as shown by the book 82 in FIG. , the mode selected by the rear wheel steering mode selector switch 27 is referenced as shown in block 88 of FIG. 6, and then that mode is set to black as shown in block 84. As shown in block 86 within block 85, data corresponding to the mode is read, and further, in block 87, a rear wheel steering angle control signal corresponding to the front wheel steering angle is output from the control microcomputer 29. As shown in the figure, the power cylinder 7 is controlled via a servo amplifier 25 and a servo valve 20, thereby steering the rear wheels 8 to suit the selected mode.

Further, when the rear wheels 8 are not in the substantially neutral position, the control of the blocks 88 and 84 described above is not performed, and the rear wheels 8 only respond to the steering of the front wheels 2 by operating the handle 4. When the rear wheels 8 return to the substantially neutral position, switching to each motor mode as described above becomes possible.

(Effects) Since the device of the present invention is as described above, according to this, selection is made by the hand switch 18 or the rear wheel steering mode changeover switch 27 only when the rear wheels 8 are in a substantially neutral position (for example, within 5 degrees left and right). In other conditions, that is, when the rear wheels 8 are not in a substantially neutral position, the above-mentioned steering of the rear wheels 8 becomes impossible. Therefore, according to the present invention, it is possible to eliminate a situation where the rear wheels 8 are steered from a state where they are largely steered to the opposite side in a stationary state. Therefore, the device of the present invention has an excellent safety effect in that it eliminates the risk of straining the tires and steering system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional device; FIG. 2(a) is an explanatory diagram showing a first embodiment of the uninvented device;
(in the figure) is a time chart of the logic circuit, FIG. 8 is an explanatory diagram showing the second embodiment of the uninvented device, and FIG. 4 (I) *
(II) + (m) is a characteristic diagram showing an example of rear wheel steering mode. FIG. 5 is a control flowchart thereof. 1... Vehicle body 2... Front wheel 80, rear wheel 4... Han F Lua,... Power cylinder 9... Hydraulic pump 10.
...Oil tank 11...Solenoid valve 11a, ll
b... Solenoid 12... Power supply 18... Hand switch 14... Position sensor 16... Comparator 20... Servo pulp
25... Servo amplifier 2B... Handle angle sensor 27... Rear wheel steering mode changeover switch 28...
Vehicle speed sensor 29...Controlling microcomputer Fig. 2(b) Fig. 3 Fig. 4

Claims (1)

[Claims] L Has multiple control modes for rear wheel steering for the front wheels,
In a rear wheel steering device that selects one of the modes and steers the rear wheels by switching the rear wheels using a mode switching device, the mode switching device is connected to a position sensor that detects that the rear wheels are in a substantially neutral position, A rear wheel steering control device characterized in that the mode can be switched only when the rear wheels are in a substantially neutral position in accordance with a signal from the position sensor.