JPH0487882A - Distribution of driving power to front and rear wheel and composite control device for auxiliary steering angle - Google Patents

Abstract

PURPOSE:To obtain the most suitable steering characteristics and to control the idle running of an inner wheel by distinguishing a change caused by the idle running of the inner wheel in the distribution of driving power from a changed caused by the variation of the friction u of a road surface in the distribution of the driving power, and correctively controlling an auxiliary steering angle according to the idle running quantity of the inner wheel at the time, when the idle running of the inner wheel occurs, of turning at highly increasing acceleration. CONSTITUTION:A control device (a) for distributing front and rear wheel driving power controls the driving power so that it may be distributed to front and rear wheels according to a difference in the rotating speeds of the front and rear wheels. An auxiliary steering angle control device (b) controls the steering angle of at least either of the front and the rear wheel at the time of steering the front wheel. In addition to that, an inner wheel idle running detecting means (c) detects the idle running quantity of the inner wheel or its equivalent quantity of the front and rear wheels at the time of turning. A corrective control means (d) for an auxiliary steering angle controls the auxiliary steering angle so that, in the case of the large detected quantity of the inner wheel idle running of the front wheel, the auxiliary steering angle may be corrected according to the idle running quantity of the inner wheel so as to reduce the lateral slip angle of a body, and in the case of the large detected quantity of the inner wheel idle running of the rear wheel, the auxiliary steering angle may be corrected according to the idle running quantity of the inner wheel so as to increase the lateral slip angle of the body.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for integrating front and rear wheel drive force distribution and auxiliary steering angle of a vehicle in which a front and rear wheel drive force distribution control device and an auxiliary steering angle control device are simultaneously installed. Regarding a control device.

(Prior Art) Conventionally, as a comprehensive control device for front and rear wheel drive force distribution and auxiliary steering angle, a device described in, for example, Japanese Patent Application Laid-open No. 120276/1983 is known.

This conventional source aims to optimize steering characteristics regardless of the driving force distribution ratio, calculates the driving force distribution ratio by looking at the rotation speed of the front and rear wheels, and corrects the front and rear wheel steering angle ratio accordingly. A device is shown.

(Problems to be Solved by the Invention) However, the above-mentioned conventional device has the following problems.

■ No consideration has been given to optimally controlling the vehicle's steering characteristics when turning at high lateral accelerations, where inner wheel slip occurs.

In other words, the amount of change in steering characteristics due to inner wheel slipping is not only due to the change in driving force distribution, but also due to the reduction of the driving force generated in the wheel due to the inner wheel slipping, and the oversteer moment (hereinafter referred to as LSD moment) due to the LSD effect. ) is also included, whereas the LSD moment decrease is not taken into account at all.

For example, if the rear inner wheels spin during a turn with high lateral acceleration, the understeer component due to the decrease in LSD moment due to the decrease in rear wheel drive force will remain (Figure 13).
.

Similarly, if the front inner wheels idle during a turn with high lateral acceleration, an understeer component due to the decrease in LSD moment due to the decrease in front wheel drive force remains.

■ If the front wheel drive force distribution ratio increases due to a change in the road surface μ, etc. without the inner wheels idling, turning stability will decrease.In other words, as the front wheel drive force distribution ratio increases, the front and rear wheel steering angle ratios will be reversed. If the control characteristics are set to keep the steering characteristics constant by correcting to the side, in situations where the front wheel drive force distribution becomes large on low μ roads such as snowy roads or frozen roads, the steering characteristics will be overcorrected and the turning stability will deteriorate. We cannot secure enough.

In other words, if the inner wheels do not spin when driving on a low μ road, as shown in Figure 14, the ideal control would be to correct the front wheels to the same phase side on the side where the front wheel drive force distribution is high to obtain stability. It is.

Therefore, when using conventional control to correct the auxiliary steering angle along the ideal line, when the front wheel drive force distribution becomes large due to inner wheel slipping, even if the road is not low μ, By adding correction on the in-phase side, the steering characteristic becomes strong understeer, and it is not possible to suppress the inner wheel slip.

The present invention has been made by focusing on the above-mentioned problems, and is aimed at improving the overall balance between front and rear wheel drive force distribution and auxiliary steering angle of a vehicle in which a front and rear wheel drive force distribution control device and an auxiliary steering angle control device are installed simultaneously. An object of the present invention is to obtain optimal steering characteristics in a control device during high lateral acceleration turns where driving force distribution changes due to inner wheel slipping, and to suppress inner wheel slipping.

(Means for Solving the Problems) In order to solve the above problems, in the comprehensive control device for front and rear wheel drive force distribution and auxiliary steering angle of the present invention, changes in drive force distribution due to inner wheel slipping are replaced by changes in drive force due to changes in road surface μ, etc. Distinguishing this from changes in distribution, the system corrects and controls the auxiliary steering angle according to the amount of inner wheel slip during high lateral acceleration turns where inner wheel slip occurs.

That is, as shown in the complaint correspondence diagram of FIG. 1, there is a front and rear wheel drive force distribution control device a that distributes drive force between the front and rear wheels according to the difference in rotational speed of the front and rear wheels, and a steering angle of at least one of the front wheels or the rear wheels. When the auxiliary steering angle control device controls the front wheel steering,
An inner wheel slip detecting means C detects the amount of inner wheel slip of the front and rear wheels or an equivalent amount of inner wheel slip when turning, and when the detected amount of inner wheel slip of the front wheels is large, an auxiliary steering angle is provided in accordance with the amount of inner wheel slip in a direction to reduce the vehicle body sideslip angle. and an auxiliary steering angle correction control means d for correcting the auxiliary steering angle in accordance with the amount of inner wheel slip in a direction of increasing the sideslip angle of the vehicle body when the detected amount of inner wheel slip of the rear wheels is large. do.

(Function) When turning with high lateral acceleration and the amount of front wheel slip detected by the inner wheel slip pressure detection means C is large, the auxiliary steering angle correction control means d
At this point, a command is output to correct the auxiliary steering angle in a direction that reduces the vehicle sideslip angle in accordance with the amount of inner wheel slip.

Therefore, when the inner wheels of the front wheels are spinning, the steering characteristics change in the oversteer direction due to an increase in the rear wheel drive force distribution, but the auxiliary steering angle is corrected in the understeer direction that reduces the vehicle sideslip angle. Steering angle correction takes into consideration both the change in driving force distribution and the reduction in SD moment exerted on the front wheels, so it is not enough to obtain optimal steering characteristics when turning with high lateral acceleration. This also suppresses the inner wheels of the front wheels from spinning.

When turning with high lateral acceleration and the amount of inner wheel slipping of the rear wheels detected by the inner wheel slipping detection means C is large, the auxiliary steering angle correction control means d
At this point, a command is output to correct the auxiliary steering angle in a direction that increases the vehicle sideslip angle in accordance with the amount of inner wheel slip.

Therefore, when the inner wheels of the rear wheels are idling, the steering characteristics change in the understeer direction due to an increase in the front wheel drive force distribution, but the auxiliary steering angle is corrected in the oversteer direction, which increases the vehicle sideslip angle. Since the steering angle correction takes into account both the change in driving force distribution and the reduction in LSD moment on the rear wheel side, it not only provides optimal steering characteristics when turning with high lateral acceleration. Inner wheel spinning of the rear wheels is also suppressed.

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

First, the configuration will be explained.

FIG. 2 is an overall system diagram showing a vehicle equipped with a front and rear wheel drive force distribution control device and a front and rear wheel steering angle control device (an example of an auxiliary steering angle control device).

The vehicle equipped with each control system is a rear-wheel drive based torque split four-wheel drive vehicle, with left and right rear wheels IR, +L
The engine 2. Transmission 3. Rear propeller shaft 4. Rear differential 5. Engine driving force is transmitted via left and right rear dry shafts 6R, 6L.

A front propeller shaft 9. is connected to the left and right front wheels 7R, 7L from a transfer 8 provided in the middle of the rear propeller shaft 4. Front differential 10. Engine driving force is transmitted via the left and right front drive shafts 11R911L.

A front wheel hydraulic power cylinder 13 is provided in the front steering gear device 12 that steers the front wheels 7R, 7L, and provides an auxiliary steering angle to the front wheels 7R, 7L by a piston stroke using supplied hydraulic pressure. A rear wheel hydraulic power cylinder 14 is provided which provides an auxiliary steering angle to the rear wheels +R and +L with a piston stroke.

Further, the transfer 8 includes a hydraulic multi-plate clutch 15 as a front and rear wheel drive force distribution control actuator that provides variable transmission torque to the front wheels through engagement pressure control.

The hydraulic pressure supplied to the hydraulic multi-disc clutch 15 is controlled by the driving force distribution controller 2 for the driving force distribution control valve 21.
This is performed by the valve operation control command from 2.
The driving force distribution controller 22 includes a right front wheel rotation sensor 23.
．． Left front wheel rotation sensor 24. Right rear wheel rotation sensor 25. Left rear wheel rotation sensor 26. A detection signal from a lateral acceleration sensor 27 or the like is input.

Fig. 3 is a system diagram showing only the front and rear wheel drive force distribution control device, Fig. 4 is a front wheel drive force distribution characteristic chart, and Fig. 5 is a control gain characteristic chart showing the front and rear wheel rotational speed difference. Δ
Drive power distribution is rear wheel drive (0:100) according to the increase in N.
The control is continuously performed up to the color rigidity 4WD (5o:50), and the road surface friction coefficient is detected as the magnitude of the lateral acceleration Y6, and the control gain K is decreased as the lateral acceleration Y6 increases. In other words, when starting or accelerating straight ahead, driving performance is improved by suppressing the drive shaft slip of the rear wheels +R and 11, and when turning, the distribution of drive force to the front wheels 7R and 7L is reduced so that the vehicle tends to drive the rear wheels. We are trying to improve turning performance.

The hydraulic pressure supplied to the front wheel hydraulic power cylinder 13 and the rear wheel hydraulic power cylinder 14 is controlled by a valve operation control command from the steering angle control controller 18 to the hydraulic control valve 17.
8 is a front wheel steering angle sensor 19. Vehicle speed sensor 20. Detection signals are input from each vehicle rotation sensor 23, 24, 25, 26, and a driving force distribution command from the driving force distribution controller 22 is input.

Fig. 6 is a system diagram showing only the front and rear wheel steering angle control device, and Fig. 7 is a correction control characteristic diagram of the front and rear wheel steering angles when no inner wheel slip occurs.The basic front and rear wheel steering angle control is as follows. The vehicle's yaw rate response model and lateral acceleration response model (reference model) are set, and the control is performed by applying auxiliary steering angles to the front and rear wheels so that the vehicle response matches these models, and the dynamic characteristics of yaw rate and lateral acceleration are highly refined. We are trying to achieve ideal turning performance by achieving both.

The steering angle control controller 18 receives the driving force distribution command from the driving force distribution controller 22 and also inputs the detection signals from the wheel rotation sensors 23, 24, 25, and 26 of each vehicle to prevent inner wheel slipping. Sometimes, considering the influence of changes in the driving force distribution on the steering characteristics, as shown in Figure 7, the larger the front wheel driving force distribution ratio, the more the steering characteristics become understeer.This is corrected to the opposite phase side. In addition to preventing changes in steering characteristics, in regions where the front wheel drive force distribution ratio is large, if too much negative phase correction is given, stability will be lost, so the steering angle correction control unit corrects it to the same phase side when inner wheel slipping does not occur. Sometimes, a steering angle correction control section when an inner wheel slip occurs is incorporated as a correction control program to obtain optimal steering characteristics and suppress inner wheel slip.

Next, the effect will be explained.

First, we will explain why the inner wheels spin during turns with high lateral acceleration.

The roll stiffness of the front and rear wheels of a vehicle is usually determined to optimize the steering characteristics during cornering, and the roll stiffness of the front and rear wheels is rarely the same, and one of the wheels is set to have a larger roll stiffness. Lateral G is generated when turning, causing a load shift in the left and right direction, but this load shift occurs on the front and rear wheels in proportion to the roll stiffness, so the load shift is greater on the front and rear wheels with greater roll stiffness. big. As the lateral G increases, the amount of load movement increases, and when the amount of load movement exceeds the wheel load of one wheel in a steady state, the inner ring lifts up and idles. Therefore, due to the front-rear distribution of roll stiffness, one of the front and rear wheels will idle with high lateral G.

In addition, when the rear wheels are controlled by a steering angle control device, for example, during reverse phase control, the sideslip angle of the vehicle body increases, the lateral G has a component from the front to the rear, the rear outer wheels sink, and vice versa. The front inner wheel side will lift up, making it easier for the front inner wheel to spin (Figure 8).

Conversely, during in-phase control, the vehicle sideslip angle decreases and the lateral G has a component from the rear to the front, causing the front outer wheels to sink and the rear inner wheels to rise, making the rear inner wheels more likely to spin (Figure 9). ).

FIG. 10 is a flowchart showing the flow of the correction control process performed by the steering angle controller 18, and each step will be explained below.

In step 101, the front inner wheel slip detection value Nfv, the rear inner wheel slip detection pressure value Nrv, and the driving force distribution command value are read.

Note that the front and rear inner wheel slip detection values Nfv and Nrv are calculated in advance from the absolute value of the difference between the rotation speeds of the front and rear wheels.

In step 102, it is determined whether the front inner wheel slipping detection pressure value Nfv is greater than or equal to a predetermined value (inner wheel slipping determination threshold).

In step 103, it is determined whether the rear inner wheel slip detection value Nrv is greater than or equal to a predetermined value (inner wheel slip determination threshold).

If the inner wheels do not spin, which is determined as No in step 102 and step 103, the process proceeds to step 104, where the control characteristics are corrected as shown in FIG. The control command value is pressured.

When it is determined in step 102 that the front inner wheel slip detection value Nfv is equal to or higher than a predetermined value and that the front inner wheel is in a slip state,
Proceeding to step 106, as shown in step 114, the control characteristics are corrected to the understeer side, which reduces the vehicle body slip angle, depending on the magnitude of the front inner wheel slip.

When it is determined in step 103 that the rear inner wheel slip detection value Nrv is greater than a predetermined value and that the rear inner wheel is in a slipping state, the process proceeds to step 107, and as shown in FIG. Accordingly, the control characteristics are corrected toward oversteer, which increases the vehicle body slip angle.

Through the above correction control, the following turning performance is achieved when the inner wheel does not slip and when the inner wheel slips.

(B) When inner wheel slipping does not occur When inner wheel slipping does not occur, the steering characteristics are kept constant by correcting the front and rear wheel steering angle ratio to the opposite phase side as the front wheel drive force distribution ratio increases, as shown in Figure 7. By correcting the control characteristics in the direction of steering, changes in steering characteristics due to driving force distribution are corrected, and the driver does not feel any discomfort in steering.

Furthermore, in situations where the front wheel drive force distribution becomes extremely large on low μ roads such as snowy roads or frozen roads, the front and rear wheel steering angle ratios are changed from negative phase side correction to stable side in-phase side correction. This ensures turning stability.

(b) When front inner wheel slip occurs When front inner wheel slip occurs, steering characteristics change in the oversteer direction due to an increase in rear wheel drive force distribution.

On the other hand, in correction control, as shown in FIG.
5. Front wheel auxiliary steering angle and rear wheel auxiliary steering angle in accordance with the amount of inner wheel slip in the understeer direction to reduce the vehicle sideslip angle.6. is corrected.

Therefore, the change in steering characteristics due to front inner wheel slipping is corrected, and this supplementary steering angle correction takes into account both the change in driving force distribution and the reduction in LSD moment on the front wheel side. This not only provides optimal steering characteristics during high lateral acceleration turns where front inner wheel slip occurs, but also suppresses front inner wheel slip.

(c) When rear inner wheel slip occurs When inner wheel slip occurs in the rear wheels, the front wheel side drive force distribution increases and becomes the four wheel drive force distribution direction, thereby changing the steering characteristic in the understeer direction.

On the other hand, in the correction control, as shown in FIG.
The front wheel auxiliary steering angle and the rear wheel auxiliary steering angle are corrected in accordance with the amount of inner wheel slip in the oversteer direction that increases the insect sideslip angle.

Therefore, the change in steering characteristics due to the rear inner wheel slipping is corrected, and this auxiliary steering angle correction takes into account both the change in driving force distribution and the reduction in LSD moment on the rear wheel side. As a result, not only is optimal steering characteristics obtained when turning at high lateral accelerations where rear inner wheel slip occurs, but also the rear inner wheel slip is suppressed.

As explained above, the comprehensive control device for front and rear wheel drive force distribution and auxiliary steering angle according to the embodiment exhibits the effects listed below.

■ Changes in driving force distribution due to inner wheel slipping are distinguished from changes in driving force distribution due to changes in road surface μ, etc., and when turning at high lateral acceleration where inner wheel slipping occurs, the inner wheel Since the device is designed to correct and control the auxiliary steering angle according to the amount of wheel slip, it is possible to obtain optimal steering characteristics during turns with high lateral acceleration, where the drive force distribution changes due to inner wheel slip, and to suppress inner wheel slip. I can do it.

■ Changes in driving force distribution due to inner wheel slipping are distinguished from changes in driving force distribution due to changes in road surface μ, etc. When inner wheel slipping does not occur and driving force distribution changes due to changes in road surface μ, etc., the change is shown in Figure 7. As shown in the figure, the device corrects and controls the auxiliary steering angle according to the front wheel drive force distribution ratio, which maintains the stability of the steering characteristics despite changes in the drive force distribution, eliminating steering discomfort and greatly reducing drive wheel slip. It is possible to achieve stability when the front wheel drive force distribution ratio increases.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment.

For example, in the embodiment, an example of a device that controls the steering angle of both the front and rear wheels is shown as the auxiliary steering angle control device, but it may also be an auxiliary steering angle control device that controls the steering angle of only one of the front wheels or the rear wheels. (In this case, if you want to reduce the vehicle sideslip angle, you can do so by giving the front wheels an auxiliary steering angle that reduces the front wheel steering angle, or by giving an auxiliary steering angle that turns the rear wheels in the same direction as the front wheels. When it is desired to increase the front wheel steering angle, an auxiliary steering angle is given to the front wheels to increase the front wheel steering angle, or an auxiliary steering angle is given to the rear wheels to steer the rear wheels in the opposite phase to the front wheels.

In addition, although an example of a rear wheel drive-based front and rear wheel drive force distribution control device is shown as a front and rear wheel drive force distribution control device, it can be similarly applied to a front and rear wheel drive force distribution control device based on a front wheel drive. First, as long as it is a four-wheel drive vehicle in which driving force is distributed based on the difference in rotational speed between the front and rear wheels, a heavy vehicle using a viscous coupling, a fluid pump type coupling, or the like may be used.

Further, in the embodiment, an example was shown in which inner wheel slipping is directly detected by wheel rotation speed, but inner wheel slipping may be estimated and detected by detecting lateral acceleration of a predetermined value or more, front and rear distribution of roll rigidity, etc.

(Effects of the Invention) As explained above, in the present invention, the front and rear wheel drive force distribution and the auxiliary steering angle of a vehicle in which the front and rear wheel drive force distribution control device and the auxiliary steering angle control device are simultaneously installed are as follows. The integrated control system distinguishes changes in drive force distribution due to inner wheel slip from changes in drive force distribution due to changes in road surface μ, etc., and corrects the auxiliary steering angle according to the amount of inner wheel slip during high lateral acceleration turns where inner wheel slip occurs. Since this is a control means, it is possible to obtain the optimum steering characteristics during turns with high lateral acceleration where the driving force distribution changes due to the inner wheel slipping, and also to suppress the inner wheel slipping.

[Brief explanation of the drawing]

Fig. 1 is a complaint-corresponding diagram showing a comprehensive control device for front and rear wheel drive force distribution and auxiliary steering angle of the present invention, and Fig. 2 is a diagram showing a system in which a front and rear wheel drive force distribution control device and a front and rear wheel steering angle control device are installed simultaneously. Figure 3 is a system diagram showing a specific example of the front and rear wheel drive force distribution control device, Figure 4 is a front wheel drive force distribution characteristic diagram, and Figure 5 is a control gain characteristic of drive force distribution. Fig. 6 is a system diagram showing a specific example of the front and rear wheel steering angle control device, Fig. 7 is a correction control characteristic diagram when inner wheel slipping does not occur, and Fig. 8 is a front inner wheel slipping state when turning with high lateral acceleration. FIG. 9 is an explanatory diagram of the operation showing the rear inner wheel slipping state during a turn with high lateral acceleration. FIG. 10 is the flow of the correction control operation of the front and rear wheel auxiliary steering angle control performed by the steering angle control controller. FIG. 11 is a characteristic diagram of the auxiliary steering angle correction control of the front and rear wheels when front inner wheel slip occurs, and FIG.
The figure is a characteristic diagram of the auxiliary steering angle correction control for the front and rear wheels when the rear inner wheel is slipping, FIG. 13 is an operation block diagram illustrating how the steering characteristics become understeer when the rear inner wheel is slipping, and FIG.
The figure is a characteristic diagram of auxiliary steering angle correction control in conventional constant steering characteristic control. a... Front and rear wheel drive force distribution control device b... Auxiliary steering angle control device C... Inner wheel slip detection means d... Auxiliary steering angle correction control device

Claims (1)

[Claims] 1) A front and rear wheel drive force distribution control device that distributes drive force between the front and rear wheels according to the difference in rotational speed between the front and rear wheels, and an assistant that controls the steering angle of at least one of the front wheels or the rear wheels when the front wheels are steered. a steering angle control device; an inner wheel slip detecting means for detecting the amount of inner wheel slip or an equivalent amount of inner wheel slip of the front and rear wheels during a turn; to correct the auxiliary rudder angle,
A front and rear wheel characterized by comprising: auxiliary steering angle correction control means for correcting an auxiliary steering angle according to the amount of inner wheel slip in a direction that increases the sideslip angle of the vehicle body when the detected amount of inner wheel slip of the rear wheels is large. Comprehensive control device for driving force distribution and auxiliary steering angle.