JPS62116355A - Automatic steering angle correcting device - Google Patents

Abstract

PURPOSE:To secure the stability in high-speed turn traveling by judging the cornering limit on the basis of the differential values of the self aligning torque and the side force of the wheels and automatically steering front and rear wheels according to the result of the judgement. CONSTITUTION:The direction of turn of a steering wheel is detected by a means 70 in ordinary operation, and pressurized oil is sent into a front wheel actuator 79 by switching a front wheel control valve 77 by a means 73, and front wheels are steered in the same direction to the steering wheel. While, in turning traveling, the cornering limit is judged by a means 75 on the basis of the signals of a self aligning torque detecting means 71 and a side force detecting means 72. Therefore, when the front wheel side is in the vicinity of the cornering limit, rear wheels are steered in the reverse phase to the front wheels through a rear wheel control valve 78 by a steering angle correcting means 76. Further, when the rear wheel side is in the vicinity of the cornering limit, front wheels are steered in the direction for returning the steering wheel through a front wheel control valve 77.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a vehicle in which the front and rear wheels can be steered to automatically correct the steering angles of the front and rear wheels during cornering to improve driving stability. related to the equipment used.

(Prior Art) When a vehicle is cornering at a relatively high speed, if the steering wheel is turned too far, the wheels may slip on the outside of the turn, which may significantly impair cornering stability.

Generally, this condition is called the cornering limit, and driving the vehicle beyond the cornering limit makes it impossible to control the vehicle's attitude, which is extremely dangerous.

Therefore, according to the conventional Japanese Patent Application Laid-Open No. 59-223569,
A device has been proposed that determines the cornering limit from the differential values of self-lining torque and side force acting on the wheels, and issues a warning to the driver.

Figures 7 and 8 show the relationships between side force and slip angle, self-lining torque and slip angle. The relationship between this and the slip angle is that the slip angle changes linearly and proportionally up to a certain range, but beyond that, only the slip angle increases significantly relative to the side force, and within this limit range is called the cornering limit.
- Also, as shown in Figure 8, the relationship between the self-lining torque, which is the moment that attempts to return the direction of the wheel rotation surface to the direction of travel, which is the restoring torque of the steering, and the slip angle, changes to a certain point as the slip angle increases, as shown in Figure 8. The self-aligning torque also increases up to this point, but after that it decreases and its peak point is below the cornering limit.

Therefore, if we look at the differential value of the side force, we can see that while it is positive, it is within the cornering limit, and when it is negative, it is over the cornering limit.In contrast, the differential value of the self-lining torque It can be seen that when the value is 11-, the value is within the cornering limit, and when it changes from positive to negative, the value is approaching the cornering limit.

Therefore, in order to warn the vehicle so that it does not exceed the cornering limit, it should be determined that the cornering limit is near when the differential value of the side force is positive and the differential value of the self-lining torque changes from positive to negative. However, considering safety, it can be said to be practical.

Therefore, as described above, the cornering limit is determined from the sign of the differential value of the rain detection signal.

(Problems to be Solved by the Invention) In this way, in the conventional example described above, the cornering limit is determined during high-speed turning, etc., and a warning is issued to the driver based on this. Even when a general driver receives such a warning, it is technically difficult to perform a driving operation to quickly recover the vehicle from its cornering limit, so there is a problem in that the general driver cannot necessarily take appropriate measures.

The present invention solves this problem by adjusting the front wheels so that when approaching the cornering limit, the cornering limit is not exceeded.
The purpose is to automatically steer the rear wheels to ensure stability when turning at high speeds.

(Means for Solving the Problems) The present invention, as shown in FIG. a valve 77 and a rear wheel actuator 8 for redirecting the rear wheels;
0, a rear wheel control valve 78 for selectively controlling the supply of hydraulic oil to the rear wheel actuator 80, a means 70 for detecting the rotational direction of the steering wheel, and a means 70 for detecting the rotational direction of the steering wheel, and an operation of the front wheel control valve 77 according to the rotational angle of the steering wheel. Front wheel control means 73 for controlling and means 71 for detecting wheel self-lining torque
, a means 72 for similarly detecting side force, a means 74 for calculating the differential values of these respective detection signals, a means 75 for determining that the cornering limit is reached when the respective differential values have opposite signs, and a means 75 for determining the cornering limit when the respective differential values have different signs. Based on this, the rear wheel control valve 78 is operated to steer the rear wheels in an opposite phase to the front wheels when the front wheels are at the cornering limit, and the steering angle of the front wheels is reduced when the rear wheels are at the cornering limit. A steering angle correcting means 76 is provided for correcting the front wheel control valve 77 in the direction in which the front wheel control valve 77 is moved.

(Function) During normal driving, the front wheel control means 73 detects the rotation of the steering wheel and switches the front wheel control valve 77, thereby sending pressure oil to the front wheel actuator 79, and steering the front wheels in the same direction as the steering wheel. be done. At this time, the rear wheel control valve is held neutral, so the rear wheels are fixed at the neutral position, similar to a normal front wheel steered vehicle.

On the other hand, when the vehicle is turning, based on the signals from the self-lining torque detection means 71 and the side force detection means 72, the cornering limit determination means 75 determines whether the cornering limit has been approached or not based on the sign of the differential value. to judge.

As a result of this judgment, when the front wheels approach the cornering limit, there is a strong tendency for understeer, so in order to counteract this, the output of the steering angle correction means 76 causes the rear wheel control valve 78 to move the rear wheels in the opposite phase to the front wheels. When the steering wheel is turned and the rear wheels approach the cornering limit, there is a strong tendency for oversteer, so the front wheels are steered in the direction of returning the steering wheel via the front wheel control valve 77.

In this way, when the cornering limit is approached, the steering angles of the front and rear wheels are automatically corrected so as not to exceed the cornering limit, thereby improving driving stability during high-speed cornering.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figure 2 is a schematic configuration diagram, in which IA and IB are the front wheels,
A and 2B are rear wheels, and 3 is a +IIR wheel side child side steering link and a rear wheel side steering link, each of which is driven by a power cylinder 5 as a front wheel actuator and a power cylinder 6 as a rear wheel actuator.

The handle 7 is mechanically interlocked with the front wheel steering link 3, and a sensor 8 is attached to the handle 7 to detect the operating direction and the torque.

The steering angles of the front and rear wheels are determined by power cylinder 5.
．． Rudder angle sensors 9 and 10 are provided for detecting the displacement amount of 6.

In addition, in order to determine the cornering limit when the vehicle is turning, first, the side force (SF) acting on each wheel is determined.
), as shown in FIG. side force sensor 1.4 A
, ]71. B, i4c, 14D.

The side force that acts during turning acts as a load in the axial direction of the spindle 11, so by detecting this, the magnitude of the side force can be measured.

Further, in order to detect the self-lining torque of the wheels, self-lining torque sensors 15A and 15B are provided which are strain gauges that detect the axial stress applied to the steering link 3.4 as the restoring force of the wheels.

Self-lining torque is a torque that attempts to return the wheel to its original state, that is, a neutral state.When turning, this restoring torque acts on the steering link 3.4 as stress in the axial direction, so by detecting this, It can be determined how much self-lining torque is being generated.

Detection signals from each of these sensors are input to a control circuit 16 composed of a microcomputer, etc., and the control circuit 16
Based on these, it electromagnetically controls the front wheel control valve 18 and the rear wheel control valve 19 that control the operation of the power cylinder 5.6, and at the same time activates the alarm 17 as necessary.

That is, the control circuit 16 normally controls switching only the front wheels according to the operating direction of the steering wheel 7 and the operating l/ruq, and performs control equivalent to normal front-wheel power steering. The signs of the time differential values of Selfa lining torque and side force are determined, and when the signs are different, it is determined that the cornering limit is being approached.
The steering angle is automatically controlled to correct the steering angles of the front and rear wheels, regardless of the driver's intention.

The front wheel and rear wheel control valves 18 and 19 are electromagnetic valves that are switched by control signals, and the operating direction of the power cylinder 5.6 is freely controlled by a signal from the control circuit 16.

Pressure oil from the front wheel pump 2OA is selectively supplied to the left and right oil chambers of the front wheel power cylinder 5 via the front wheel control valve 18, and to the left and right oil chambers of the rear wheel power cylinder 6. Pressure oil from the rear wheel pump 20B is supplied to the rear wheel control valve 1.
9.

Note that the power cylinder 6 for the rear wheels is equipped with a neutral spring 24.
When the rear wheel control valve 19 is in the neutral state, it automatically returns to the neutral position and maintains that state, and in this case, the front wheel steering function is stably performed. It is configured.

In the figure, 21A and 21B are leaf valves for adjusting the supply oil pressure, respectively, and 22 is a tank to which return oil is refluxed.

Next, the control operation in the control circuit 16 will be specifically explained according to the flowchart of FIG.

In the following explanation, the relationship between the side force (SF) and self-lining torque (SAT) with the steering direction is specifically defined as positive in the direction indicated by the arrow in Figure 5, and negative in the opposite direction. It will be explained as follows.

Furthermore, as shown in Fig. 4, these SF and SAT are different from those shown in Figs.
Since it shows the same tendency as shown in the figure, in other words, in the range where the time differential value of side force is positive, when the sign of the differential value of self-lining changes from positive to negative, it is determined that the cornering limit is approached. Therefore, these time differential values are actually used to determine the cornering limit.

First, in step 30 of the routine shown in FIG. The front wheel side SAT obtained from the detection value of the Selfa Lining Torque Sensor 1.5A is
The sign of each differentiated value is determined, and if the signs are different, it is determined that the cornering limit is near (1), as indicated by 0q, and if the signs are the same, it is determined that the cornering limit has not been reached.

Also, in step 31, the rear wheel side SF and SAT are
The detected value is differentiated, and the cornering limit on the rear wheel side is determined from the sign of the time differential value.

If both have the same sign =? - Since the steering limit has not been reached, the rear wheels 2A, 1l-2B are held in a neutral state in step 32, and the front wheels IA, IB are moved to the handlebar 7.
Normal power steering operation is performed according to the operation of the steering wheel.

That is, the front wheels IA, IB operate the front wheel control valve 5 in the operating direction based on the output of the steering sensor 8 that detects the operation of the handle 7.
8 is switched.

On the other hand, one rear wheel control valve is held in the neutral position so that the rear wheels 2A and 2B are kept in the neutral state, and as a result, normal front wheel steering is performed under normal driving conditions. This does not cause any discomfort to the driver in terms of steering sensation.

Next, when it is determined in step 30 that the front wheels are close to the cornering limit, the routine shifts to the routine shown in FIG. 6B.

In step 33, a front wheel limit detection alarm is issued, and specifically, the alarm 17 installed in the driver's seat is activated. In step 34, the turning direction of the front wheels is determined based on whether or not the front wheel side SF is positive. If it is positive (in the direction of the arrow in FIG. In other words, the vehicle is steered counterclockwise by Δθ°.

This rear wheel steering is performed while operating the rear wheel control valve 19 and detecting the actual steering angle with the steering angle sensor 10.
Control is performed so that the rear wheels are steered by θ°.

On the other hand, if the SF is negative, this means that the front wheels are being steered counterclockwise, so the rear wheels are steered clockwise by Δθ° in step 36.

This steering angle Δθ° is the value necessary to stably avoid the front wheel when it approaches the =1-knarling limit.
Since sudden steering impairs stability, it is set to an appropriate minute value.

In this state, Δ is held for only seconds in step 37. In other words, when the front wheels are close to their cornering limit, understeer becomes stronger, so to counteract this, the rear wheels are steered in the opposite phase to the front wheels.

After performing the corrective action in this way, the process moves to the routine shown in Figure 6C, and as a result of the rear wheel steering, the front wheels S F and S
It is determined in step 38 how the AT has changed.

In other words, it determines whether the differential values of SF and SAT have the same sign and have recovered from the cornering limit.
If it does not recover, the process returns to step 33 and the correction operation is repeated.

On the other hand, when recovering from the cornering limit,
Next, in order to return the corrected rear wheels to their original state, that is, return them to the neutral state, in step 3 it is determined whether the rear wheel steering angle is in the neutral position, and if it is not in the neutral position, in step 40 the front wheels are adjusted. If the total value of SF is positive, the rear wheels are steered clockwise by Δθ° in step 41 to return to the neutral side. If SF is negative, in step 42, the rear wheels are steered counterclockwise by Δθ° in order not to return to the neutral position.

In this way, once the front wheels have escaped the cornering limit, the steered rear wheels are returned to their original neutral position, and when they have completely returned to the neutral position, the front wheel limit detection alarm is canceled in step 43, that is, the alarm is turned off. Stop operation.

On the other hand, when it is determined in step 31 that the cornering limit of the rear wheels is approaching, a rear wheel limit detection alarm is issued in the sixth routine.

First, in order to determine the direction of the side force, it is determined in step 45 whether or not the rear wheel SF is positive, and the fourth
If the side force is acting to the right in the figure, the front wheels are steered counterclockwise by Δθ° in step 46, and if →noid force is acting to the left, step 4 is carried out.
Δθ clockwise at 7.

Turn the wheel.

In this way, when the rear wheels are at their cornering limit,
Since the over steer becomes stronger, the front wheels are corrected and steered in the direction in which the steering wheel 7 is returned.

In this case, the corrective steering of the front wheels is appropriately set within a range that does not abruptly change the turning characteristics, as described above.

In step 48, this state is bolded by Δ for seconds, and then, in step 49, the signs of the differential values of SF and SAT are determined again.

If the signs are the same, it is determined that the rear wheels have escaped the cornering limit, and the rear wheel limit detection warning is stopped in step 50. If they are not the same, the cornering limit is still reached. Since it is close, the process returns to step 44 and the subsequent operations are repeated, and the front wheels are further corrected and steered in the direction of returning the steering wheel 7.

By moving the front wheels back against the driver's steering wheel operation,
It feels like a kickback to the steering wheel to the driver, but at that point the driver is warned in advance of the cornering limit of the rear wheels, which prevents the driver from making mistakes such as not turning the steering wheel 7 in a hurry. be able to.

(Effects of the Invention) In this way, the present invention normally detects the direction of rotation of the steering wheel and controls the operation of the front wheel control valve according to the rotation angle of the steering wheel. Based on the differential value with the side force, it is determined that the cornering limit is reached when the signs of these are different from each other, and based on this judgment result, when the front wheels are at the cornering limit, the rear wheels are set opposite to the front wheels. activating the rear wheel control valve to steer the phase; and
The front wheel control valve is operated in a corrective manner to reduce the amount of steering of the front wheels when the rear wheels are at the cornering limit, so when the front wheels approach the cornering limit during turning, the rear wheels are automatically shifted to the opposite phase. By steering the front wheels without returning the steering wheel when the rear wheels approach the cornering limit, it is possible to avoid exceeding the respective cornering limits, improving turning stability during high-speed turns. It is possible to direct the

Furthermore, during normal driving, the rear wheels are maintained in a neutral state, so the driving sensation is no different from normal front wheel steering, and the driver does not feel uncomfortable.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic configuration diagram showing an embodiment, Fig. 3 is a sectional view showing how the sensor is attached to the wheel, and Fig. 4 is a diagram showing side force during turning. Characteristic diagram showing the generation state with Selfa lining torque, 5th
The figure is an explanatory diagram that defines the relationship between the generation direction and sign of side force and self-lining torque, and Figures 6A to 6
7 is a characteristic diagram showing the relationship between side force and slip angle, and FIG. 8 is a characteristic diagram showing the relationship between self-lining torque and slip angle. LA, IB...Front wheel, 2A, 2B...Rear wheel, 3.4
... Steering link, 5, 6... Power cylinder, 7... Handle, 8... Steering torque sensor, 9
．． 10... Rudder angle sensor, 1.4 A to 14D... Side force sensor, 15A, 15B... Self-lining torque sensor, 16... Control circuit, 17...
・Alarm, 18.19...Control valve, 2OA, 20B・
··pump. Patent applicant: Kayabae Gyo Co., Ltd. Figure 2 Figure 4 Figure 5 Figure 6 A

Claims (1)

[Claims] A front wheel actuator that turns the direction of the front wheels, a front wheel control valve that selectively controls the supply of hydraulic oil to the front wheel actuator, a rear wheel actuator that turns the direction of the rear wheels, and selects the supply of hydraulic oil to the rear wheel actuator. a rear wheel control valve for controlling the front wheel control valve, a means for detecting the rotation direction of the steering wheel, a front wheel control means for controlling the operation of the front wheel control valve according to the rotation angle of the steering wheel, and a means for detecting the self-aligning torque of the wheel. , a means for similarly detecting the side force, a means for calculating the differential values of these detection signals, a means for determining that the cornering limit is reached when the differential values have different signs, and a means for determining the cornering limit based on the result of this determination. The rear wheel control valve is operated to steer the rear wheels in an opposite phase to the front wheels when the rear wheels are at the cornering limit, and the rear wheel control valve is operated to reduce the steering amount of the front wheels when the rear wheels are at the cornering limit. An automatic steering angle correction device comprising: steering angle correction means for correcting a front wheel control valve.