JPS61257367A - Rear wheel steering control device for car - Google Patents

Abstract

PURPOSE:To prevent the abnormal motion of rear wheels such as derailing by controlling the steering angle of rear wheels nearly to zero independently of the steering of front wheels nearly to zero independently of the steering of front wheels when the detected height of part of a car body from the travel road surface is not within the predetermined tolerance. CONSTITUTION:A speed sensor 20a detects the rotating speed of a front wheel 10b, and a displacement sensor 20b detects the displacement quantity of the rod 13a of an actuator 13. Distance sensors 20c, 20d are provided on a car near rear wheels 10c, 10d and detect the height from part of the travel road surface directly below them. A microcomputer 30 has input ports 32, 33, 34a, 34b, a CPU 35, a ROM 36, a RAM 37, and an output port 38 and outputs the calculated result from the CPU 35 to the actuator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vehicle equipped with a rear wheel steering mechanism, and particularly relates to a steering angle ratio of a rear wheel steering angle to a front wheel steering angle (referred to simply as a steering angle in this specification). The present invention relates to a rear wheel steering control device for a vehicle that changes and controls the ratio (referred to as a ratio) according to vehicle speed.

(Prior Art) Conventionally, as disclosed in Japanese Unexamined Patent Publication No. 57-11173, this type of device has been used to control the rear wheel steering angle to be in opposite phase to the front wheel steering angle when the vehicle is running at low speed. The steering angle of the rear wheels is controlled to be in phase with the front wheel steering angle when the vehicle is running at high speeds, improving the steering stability of the vehicle.

[Problem that the invention seeks to solve]

However, in such a configuration, if there are curbs, grooves, etc. on the road surface on which the vehicle is traveling, for example, if the rear wheel steering angle is controlled in the opposite phase to the front wheel steering angle, the rear wheels will , grooves, etc., and there is a risk of the wheels coming off the road surface.

In order to deal with this problem, the present applicant filed a patent application in 1983.
In the rear wheel steering control method for a four-wheeled vehicle filed as No. 0-7988, the height of a part of the vehicle body from the road surface is detected, and when this detected height is out of a predetermined tolerance range, the rear wheel steering angle is adjusted. We proposed a method to control the steering to almost zero. According to this method, it is possible to prevent the rear wheels from coming off the road surface or other abnormal movements, but when the vehicle turns at high speed or travels on an uneven road, the vehicle body may undergo rolling, pitching, or other movements. Therefore, the detected height may deviate from a predetermined allowable range and the rear wheel steering angle may be controlled to zero. As a result, when the vehicle is traveling at high speed, the rear wheel steering angle may not be controlled according to the vehicle speed.
This type of device cannot fully demonstrate its functions.

The purpose of the present invention is to reduce the detection height as described above in the low vehicle speed region, in view of the fact that when a vehicle passes near a ditch, curb, etc., the vehicle is normally driven at a low speed. Accordingly, the rear wheel steering angle is controlled to prevent the rear wheels from moving off the road surface or other abnormal movements, and the rear wheel steering angle is controlled regardless of the detected height at high vehicle speeds to steer the vehicle. It is an object of the present invention to provide a rear wheel steering control device for a vehicle that maintains safety.

Means for Solving Problem c] In solving this problem, the structural features of the present invention, as shown in FIG. 1, include vehicle speed detection means 1 for detecting vehicle speed;
Based on the detected vehicle speed, a steering angle ratio is determined such that the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle speed is low, and the rear wheel steering angle is in phase with the front wheel steering angle when the same vehicle speed is high. steering angle ratio determination means for determining a steering angle ratio; output means 3 for outputting a control signal according to the determined steering angle ratio; In a vehicle rear wheel steering control device having a wheel steering mechanism 4, a height detecting means 5 detecting the height of a part of the vehicle body from the running road surface;
When the detected vehicle speed is less than a predetermined value and the detected height is above a predetermined allowable range, a control signal for controlling the rear wheel steering angle to approximately zero is output in place of the control signal according to the determined steering angle ratio. This is because the steering angle ratio change control means 6 is provided to control the output means 3 so that the output means 3 is controlled.

[Action/Effect]

Therefore, as described above, the rear wheel steering for a vehicle is such that the rear wheels are steered in the opposite phase to the front wheels in a low vehicle speed region, and the rear wheels are steered in the same phase as the front wheels in a high vehicle speed region. In the control device, a height detection means 5 detects the height of a part of the vehicle body from the road surface, which changes due to curbs, grooves, etc. on the road surface where the rear wheels are located, and calculates the detected height. When the steering angle ratio changes out of a predetermined allowable range, the steering angle ratio change control means 6 controls the rear wheel steering angle to almost zero regardless of the front wheel steering, so that the rear wheels do not interfere with curbs, grooves, etc. As a result, it is possible to reliably prevent the rear wheels from coming off the road surface and other abnormal movements.

Moreover, since the steering angle ratio change control means 6 controls the rear wheel steering angle to almost zero on the condition that the vehicle speed detected by the vehicle speed detection means 1 is less than a predetermined value, the rear wheel steering angle is controlled in the same phase as the front wheel steering angle, and even if the detected height deviates from a predetermined tolerance range due to a change in vehicle body posture such as rolling or pitching, the front wheel steering angle is the same as the rear wheel steering angle.

The improvement in maneuverability due to in-phase control of the vehicle is maintained.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.
The figure is a schematic view of the main parts of a four-wheeled vehicle to which the present invention is applied, and the left and right front wheels 10a, 10b move leftward (or rightward) in response to leftward (or rightward) steering operation of the steering wheel 11. ), and the left and right rear wheels 10c, 10d are both front wheels 10a.

Steering angle of 10b and rod 13a of actuator 13
The steering is controlled by rotating the link par 12 according to the amount of displacement. However, both front wheels 10a, 10b
If the steering angle of the rear wheels 10C and 10d is θf, and the steering angle of the rear wheels 10C and 10d is θf, then when the steering angle is leftward (or rightward) with respect to the straight-ahead direction of the vehicle, θf>0. θf>0 (or
θf<Q.

Let θf<0).

Next, the electric circuit configuration necessary for controlling the actuator 13 will be explained. The speed sensor 20a detects the rotational speed of the front wheel 10b and generates a pulse signal with a frequency proportional to this. The displacement sensor 20b detects the amount of displacement of the rod 13a of the actuator 13 and generates a displacement signal. The distance sensors 20c and 2Qd are provided in a part of the vehicle located near the rear wheels 10c and 10d, respectively. The height of the sensor is detected and generated as a distance signal.

The microcomputer 30 executes a computer program according to the flowchart shown in FIG. 2, and performs various calculation processes necessary for controlling the actuator 13. Note that, as shown in FIG.
(CPU 35) and read-only memory 36 (RO
M36) and random access memory 37 (RAM
37) and an output port 38, each input port
) 32. 33. 34a and 34b input a pulse signal from the speed sensor 20a, a displacement signal from the displacement sensor 20b, and a distance signal from the distance sensors 20c and 20d, respectively. In addition, the output port 38 is
Based on the calculation from step 5, this calculation result is sent to actuator 1.
Output to 3. .

In this embodiment configured as above, when the vehicle starts traveling at low speed on a flat road surface without curbs, grooves, etc.
The CPU 35 of the microcomputer 30 starts executing the computer program according to the flowchart in FIG. , the values of the distance signals from the distance sensors 20C and 20d are converted into digital height values hl.

It is stored in the RAM 37 as h2. Next, in step 43, the CPU 35 compares the calculated vehicle speed U with the predetermined speed uo, and while the vehicle is running at low speed, rNOJ based on U≧uO.
Then, the program proceeds to step 44. In addition,
The predetermined speed uo is set to about 10 kilometers per hour. The CPU 35 compares the detected height hl with the reference height H in step 44, and determines that H-ΔH< h 1 <H+ΔH
Based on this, it is determined as YESJ, and in step 45, the detected height h2 and the reference height H are compared, and H-ΔH<h2<H+ΔH
Based on this, it is determined as YESJ, and in step 46, a steering angle ratio pattern (fourth
(see figure), the target steering angle ratio = k i is determined according to the vehicle speed U in step 41, and in step 47, the value of the displacement signal from the displacement sensor 20b is A-D converted to a digital displacement amount, and the target The difference between the target displacement amount of the rod 13a of the actuator 13 corresponding to the steering angle ratio =k i and the digital displacement amount is generated through the output port 38 as an output signal. After that, the CPU 35 performs steps 41 to 47.
Performs a circular operation.

In such a case, the reference height H is the distance sensor 20c.

20d indicates a normal height from the running road surface, and the symbol ΔH indicates a height variation value corresponding to some unevenness of the running road surface. In addition, the steering angle ratio ki=θr/θf holds, and the target steering angle ratio k
That is, the target displacement amount corresponds to the target steering angle θro of both rear wheels 10c and 10d.

In this embodiment, the normal height H1 height fluctuation value ΔH and the steering angle ratio pattern are stored in the ROM 36 in advance. Therefore, while the vehicle speed U is in the low vehicle speed region of the vehicle, k-ki
<O (see FIG. 3) Therefore, the actuator 13 displaces the rod 13a according to the value of the output signal from the output boat 38 of the microcomputer 3o, and under the rotation of the link par 12, both rear wheels 10c, The steering angle θr of IOd is set θr in the opposite direction (opposite phase) to the steering angle θr of both front wheels Oa and 10b.
control towards o. This allows the vehicle to travel at low speeds and with a small turning radius.

In such a state, when the vehicle approaches a road with curbs, grooves, etc. on the road surface, the digital height value h1.
Both or one of h2 fluctuates, causing hl (or h2
)≦H−ΔH or hl (or h2)≧H+ΔH, the CPU 35 determines “NO” in the comparison in step 44 or step 45 during the cyclic calculations in steps 41 to 47, and the program proceeds to step 48. Proceed. CPU
35 is set to =o in step 48, and step 4
Actuator 130 rod 1 corresponding to -0 at 7
The difference between the target displacement amount of the displacement sensor 3a and the disicle displacement amount corresponding to the value of the displacement signal from the displacement sensor 20b is generated as an output signal through the output boat 38. Then, the actuator 13 changes the steering angle θr of both rear wheels 10c and 10d to θroζO by displacing the rod 13a according to the value of the output signal from the output boat 38 of the microcomputer 30 in cooperation with the linker 12. Control. As a result, the steering angle of both rear wheels 10c, 10d becomes almost zero, regardless of the steering angle of both front axles 10a, 10b.

For this reason, both rear wheels 10c and 10d do not interfere with each other's curbs, grooves, etc., and as a result, both rear wheels lOc and 10d
It is possible to prevent the occurrence of unexpected situations such as wheels falling off the road surface. In such a case, since the height variation value ΔH is taken into consideration in the determination in steps 44 and 45, slight variations in the running road surface will not be erroneously determined as being caused by curbs, grooves, etc.

On the other hand, when the vehicle speed U reaches the predetermined speed uo, the CPU 35 determines [YESJ] based on U≧uO in step 43, and in step 46.47, the link par 12. In cooperation with the actuator 13 and the displacement sensor 20b, the steering angle θr of both rear wheels 10c and 10d is set θr in the opposite direction (inverse phase) to the steering angle θf of both front axles 10a and 10b.
Control towards O. Furthermore, when the vehicle speed U becomes higher than the predetermined speed uo and enters the high vehicle speed region, since k=ki>0, the actuator 13 displaces the rod 13a according to the value of the output signal from the output boat 38 of the microcomputer 30. Under the rotation of the link par 12, both rear wheels 10c,
The steering angle θr of 10d is controlled toward θrO in the same direction (in phase) as the steering angle θf of both front 61Aloa and 10b. As a result, the vehicle can travel at high speed with improved maneuverability, regardless of the detected heights hl, h2 from the road surface.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the configuration of the invention described in the claims, FIG. 2 is a schematic diagram of the main parts of a four-wheeled vehicle to which the present invention is applied,
FIG. 3 is a flow chart showing the operation of the microcomputer in FIG. 2, and FIG. 4 is a steering angle ratio pattern diagram showing the relationship between the steering angle ratio ki and the vehicle speed U. Description of symbols 10a, 10b -- Front wheel, 10C910d -- Rear wheel, 13 -- Actuator, 2Qa -- Speed sensor, 20c, 20d -- Distance sensor, 30 -- Microcomputer.

Claims (1)

[Claims] a vehicle speed detection means for detecting vehicle speed; and a vehicle speed detection means for determining a steering angle ratio at which a rear wheel steering angle is in opposite phase to a front wheel steering angle when the same vehicle speed is low based on the detected vehicle speed, and a rear wheel steering angle when the same vehicle speed is high. steering angle ratio determination means for determining a steering angle ratio at which the steering angle is in phase with the front wheel steering angle; output means for outputting a control signal corresponding to the determined steering angle ratio; A rear wheel steering control device for a vehicle having a rear wheel steering mechanism that steers to a determined steering angle ratio, comprising: a height detecting means for detecting a height of a part of the vehicle body from a traveling road surface; and when the detected height is above a predetermined allowable range, the output means is controlled to output a control signal for controlling the rear wheel steering angle to approximately zero instead of the control signal according to the determined steering angle ratio. 1. A rear wheel steering control device for a vehicle, comprising: steering angle ratio change control means.