JPH10264636A - Camber angle control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability of the behavior of a vehicle body by comparing the detected value of the side slip angle of wheels with the critical side slip angle, and making variable the stroke of a lower arm or an upper arm according to the result so as to regulate the camber angle of the wheels. SOLUTION: When the camber angle of front wheels 1, 2 and rear wheels are controlled, in an electronic control device, vehicle body speed, steering angle, acceleration of the vehicle body in the lateral direction, and yaw rate are computed from the detected signals and the like from respective sensors. Then vehicle body side slip angular speed is computed, and it is integrated so as to compute vehicle side slip angle. Next front wheel side slip angle and rear wheel side slip angle are computed, and the critical side slip angle and the front wheel side slip angle are comparatively computed so as to obtain the difference of the front wheel side slip angles. Similarly the difference of the rear wheel side slip angles is computed. Thereafter it is judged whether the front wheel side slip angle difference is smaller than a fixed value or not, and in the case of YES, a front camber angle is controlled into the negative camber angle direction. Meanwhile in the case of NO, when the rear wheel side slip angle difference is smaller than a fixed value, a rear camber angle is controlled into the negative direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camber angle control device for a vehicle, which can adjust the behavior of the vehicle body by controlling the camber angle of the vehicle wheels.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No.
As described in the official gazette, the turning force of the vehicle body is enhanced by making the grip force of the front wheel larger than that of the rear wheel when turning at low speed, and it is stable by making the grip force of the rear wheel larger than the front wheel when turning at high speed. A device that sets the camber angle of each wheel so as to enhance the performance is known.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 5-96925, the steering angle and the operating speed of the steering wheel are detected, and the direction in which the operating speed of the steering wheel is generated coincides with the direction in which the steering angle is generated. Sometimes, the camber angle is controlled to oversteer, and when the direction of operation of the steering wheel is different from the direction of steering angle, the camber angle is controlled to understeer, thereby controlling transient steering characteristics. Possible devices are known.

[0004]

However, in such a conventional technique, the camber angle is adjusted according to the vehicle speed, the steering angle, etc., so that the camber angle according to each road surface condition under a plurality of wheels. It was difficult to control. Therefore, the present invention provides a camber of a vehicle that can control the camber angle in consideration of the sideslip angle (slip angle) of the front and rear wheels so that the front wheel or the rear wheel can appropriately increase the tire limit, thereby stabilizing the vehicle body behavior. It is an object to provide an angle control device.

[0005]

In order to solve the above-mentioned problems, a camber angle control device according to the present invention controls a square wheel according to a side slip angle of a wheel in order to suppress the tendency of the vehicle to spin or drift. Control the camber angle.
For example, when the rear wheel slips significantly with respect to the front wheel and is in a spin state, the camber angle of the rear wheel is set to the negative camber angle to increase the grip force, and the camber angle of the front wheel is set to the positive camber angle. To counteract spin moments by reducing grip. Conversely, if the slip state of the front wheel is more likely to drift out than the rear wheel, the camber angle of the rear wheel is set to the negative camber angle and the camber angle of the front wheel is set to the positive camber angle. A yaw moment of the vehicle can be generated. In the present invention, the sideslip angle of each wheel is adopted as a parameter that directly indicates the slip state of the wheel during turning.

Further, by performing the camber angle control with respect to the target limit side slip angle, it is possible to perform the camber angle control in consideration of the margin for the maximum friction circle of each wheel.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic front view of a vehicle in which the present invention is applied to a vehicle having a double wishbone type suspension system. In FIG. 1,
The hydraulic circuit and the like shown in FIG. 2 are omitted.

An upper arm 5A, 7A and a lower arm 6A, 8A are attached to the front wheel 1 and the front wheel 2, and are swingably fixed to the frame 101. The vehicle body 100 is supported by a well-known coil spring (not shown). Also, upper arm 5
A, 7A and lower arms 6A, 8A are provided with cylinders 5, 6, 7, 8 that extend and contract the lengths of upper arms 5A, 7A and lower arms 6A, 8A themselves.
The camber angles θ of the wheels 1 and 2 are varied by the expansion and contraction of the cylinders 5, 6, 7, and 8 substantially in the left-right direction of the vehicle body. The state of the camber angle shown in FIG. 1 is the camber angle θ in the normal stop state or the straight road traveling state. Here, when the cylinders 5, 7 are operated in the direction in which the upper arms 5A, 7A are extended and the cylinders 6, 8 are operated in the direction in which the lower arms 6A, 8A are contracted, each wheel has a positive camber angle. Conversely, when the lower arms 6A, 8A are extended and the cylinders 5 to 8 are actuated in the direction of contracting the upper arms 5A, 7A, each wheel has a negative camber angle. The camber angle can be varied by operating only one of the upper arm and the lower arm without operating both.

FIG. 2 shows an example of a specific hydraulic circuit for operating the lower arms 6, 8, 10, 12 and the upper arms 5, 7, 9, 11. Although only the hydraulic circuit for the cylinder 5 of the front wheel 1 is shown, the same configuration can be adopted for the other cylinders and the rear wheels 3 and 4, so that illustration and description will be omitted.

A pump 13 driven by an engine (not shown) normally draws oil from a reservoir 14 and
5. The switching valve 16 is returned to the reservoir 14 through the switching position 16a and the pipe 17 in this order. In the camber angle control, when the control in the positive camber angle direction is performed, the oil discharged from the pump 13 is switched to the pipe 15 and the switching valve 1 by switching the switching valve 16 to the switching position 16b.
6, oil is supplied to the head-side oil chamber 5b of the cylinder 5 through the pipe 19, the pilot check valve 20, and the pipe 21 in this order. At this time, the pilot check valves 20 and 23 are switched to the switching positions 20a and 23a by the pilot oil pressure from the pipe 15 via the pilot pipes 18 and 29. On the other hand, the rod-side oil chamber 5a of the cylinder 5
The oil of the pipe 22, the pilot check valve 23, the pipe 2
4. Returned to the reservoir 14 through the switching valve 16 and the pipe 17. Therefore, since the volume of the head-side oil chamber 5b expands and the volume of the rod-side oil chamber 5a decreases, the pistons 5c that divide each oil chamber and are connected to the upper arm extend outwardly of the vehicle body and positively adjust the camber angle θ. Adjust in the camber angle direction.

If the pilot check valves 20 and 23 which can change the switching position by the pilot oil pressure are employed, the oil in the cylinder can be reliably held in the cylinder chamber when the camber angle control is completed. Further, the relief valve 27 determines the pressure of the high-pressure circuit, and plays a role of returning excess oil to the reservoir 14 via the pipes 26 and 28 when the pressure is excessively increased.

The stroke sensor 30 provided in the cylinder 5 detects the amount of expansion and contraction of the cylinder 5, that is, the position of the piston 5c, and can be used when performing feedback control. In the camber angle control, when setting the negative camber angle, the switching position of the switching valve 16 is set to the position 16c, and oil flows into the rod-side oil chamber 5a.
The oil in the head-side oil chamber 5b is drained into the reservoir 14. Thereby, the piston 5c can be contracted and adjusted in the negative camber angle direction.

Next, a flow for performing the camber angle control based on the configuration shown in FIGS. 1 and 2 will be described with reference to the flowchart of FIG. This flow is executed based on an output signal of each sensor input to an input / output interface arranged in an electronic control unit (ECU) (not shown) and a calculation result in a central processing unit (CPU) in the ECU. Note that ROM and RAM are usually provided in the ECU.
Are also configured.

O (not shown) of an ignition switch or the like
The flow starts with the N operation and the like.
At 00, a vehicle speed VB is calculated using a detection signal from a wheel speed sensor or the like (not shown) or an integrated value of the vehicle acceleration as an output result from a vehicle acceleration sensor or the like (not shown). In step 110, the steering sensor 31
Is calculated based on the output signal from the steering wheel.

In step 120, the lateral acceleration G of the vehicle body is determined based on the output signal of a lateral acceleration sensor (not shown).
Calculate y. In step 130, a yaw rate γ based on the center of the vehicle body is detected based on an output signal from a yaw rate sensor (not shown). In step 140,
The vehicle side slip angular velocity dβ / dt = γ-Gy / V is calculated. In step 150, the vehicle body skidding angular velocity dβ / dt
To calculate the vehicle body sideslip angle β.

Next, at step 160, the vehicle body side slip angle β, the steering angle δf, the yaw rate γ, the vehicle body speed VB,
The side slip angle βf with respect to the front wheels is calculated based on the following formula 1 based on the distance If from the front wheel to the vehicle center of gravity and the distance lr from the rear wheel to the vehicle center of gravity.

[0017]

Βf = β + δf−γ * lf / VB In step 170, a side slip angle βr with respect to the rear wheel is calculated based on Expression 2.

[0018]

Βr = β + γ * lr / VB Next, in step 180, a comparison is made between the limit side slip angle β0 and the front wheel side slip angle βf, which are determined in advance based on the vehicle and tire specifications, based on Equation 3. The front wheel slip angle difference Eβf is determined. The limit side slip angle β0 varies depending on the characteristics of the tire, but if a value from about 6 ° at which the cornering power of the tire is maximized to about 20 ° at which the cornering force CF of the tire is maximized is selected. Good.

[0019]

Eβf = β0−βf In step 190, a rear wheel side slip angle comparison operation is performed based on Equation 4 to calculate a rear wheel side slip angle difference Eβr.

[0020]

Eβr = β0−βr In step 200, the front wheel side slip angle difference Eβf is set to a predetermined value K
It is determined whether it is smaller than (here K = 0). Here, if the determination is affirmative, the cornering force CF is no longer increased even if the front wheel sideslip angle βf is increased.
Can not be expected to increase, so step 230
To control the front camber angle in the negative camber angle direction. As a result, the grip force TG of the front wheel tires
Increase. Therefore, the tendency of the vehicle to drift out can be suppressed.

Next, if a negative determination is made in step 200, the routine proceeds to step 210, where the rear wheel side slip angle difference E
It is determined whether βr is smaller than a predetermined value K (here, K = 0). Here, if a positive determination is made, the rear wheel sideslip angle βr is excessive, and the rear wheelslip angle β
Even if r is increased, it is not possible to further increase the cornering force CF, so the routine proceeds to step 220, where the rear camber angle is controlled in the negative direction. As a result, the tire grip force TG of the rear wheels can be increased, and the spin tendency of the vehicle is suppressed.

In step 220, the front camber angle may be controlled in the positive direction because there is a margin in the grip force TG of the front tire. In this manner, the cornering force CF of the front wheels can be reduced, and the tendency of the vehicle to spin can be suppressed. If a negative determination is made in step 210, there is room in the tire grip force TG for both the front and rear wheels, and the routine returns without executing the camber angle control.

When the process proceeds to step 230 and the front camber angle is controlled in the negative direction as described above, the process may proceed to step 240 and subsequent steps. In step 240, it is determined whether or not the rear wheel side slip angle difference Eβr is smaller than a predetermined value K (here, K = 0). Here, if a positive determination is made, the rear wheel side slip angle βr is excessively large, and even if the rear wheel side slip angle βr is increased, the cornering force CF cannot be further increased, so that the rear camber angle is also negative. Control in the direction. As a result, the tire grip force TG of the rear wheels can also be increased, and the tendency of the vehicle to drift out of four wheels can be further suppressed as compared with the control of only the front wheels.

If a negative determination is made in step 240, the rear camber angle is controlled in the positive direction to reduce the tire cornering force CF of the rear wheel because there is room in the tire grip force TG of the rear wheel. As a result, the tendency of the vehicle to drift out of four wheels is further suppressed as compared with the control using only the front wheels. As shown in FIG. 4, the camber angle control amount (adjustment angle) is determined by the front wheel side slip angle difference Eβf.
Alternatively, it may be changed according to the magnitude of the rear wheel side slip angle difference Eβr. By doing so, more detailed control can be realized, and the layered vehicle body can be stabilized.
Also, as shown in FIG. 5, instead of the camber angle control amount,
By feedback control using the output of the stroke sensor, the piston stroke PS may be controlled according to the magnitude of the front wheel side slip angle difference Eβf and the rear wheel side slip angle difference Eβr. In FIG. 5, the predetermined value K is shown as K = 2.

As described above, even after the wheel side force or grip force reaches the limit, the tire limit is further increased in consideration of the margin of the sideslip angle (slip angle) of each wheel according to each parameter. By executing such control as described above, it is possible to widen a control range capable of realizing a target vehicle body behavior. For example, even if suspension control is added to such camber angle control, the effect of the layer can be obtained.

For example, by increasing the roll stiffness of the front wheels and lowering the roll stiffness of the rear wheels when a spin tendency occurs, the cornering force of the front wheels, which has been reduced by the positive camber angle control, can be further reduced. Can be increased, so that the spin tendency can be suppressed. Similarly, when the vehicle tends to drift, if the suspension control for lowering the roll stiffness of the front wheels and increasing the roll stiffness of the rear wheels is added, a more effective layer can be expected.

In the above-described embodiment, the cylinders are arranged on both the upper arm and the lower arm. However, the cylinders may be arranged on one of the upper arm and the lower arm for control. Further, in the above-described embodiment, the camber angle control is performed using the result of comparing the limit sideslip angle with the front wheels and the rear wheels sideslip angles. The camber angle control may be executed according to the magnitude and the sign.

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of a vehicle to which the present invention is applied.

FIG. 2 is a configuration diagram showing one configuration example for implementing the present invention.

FIG. 3 is a flowchart illustrating camber angle control according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a front wheel slip angle difference, a rear wheel slip angle difference, and a camber angle control amount.

FIG. 5 is a characteristic diagram showing a relationship between a front wheel slip angle difference, a rear wheel slip angle difference, and a piston stroke adjustment amount.

[Description of Signs] 1, 2 Front wheel 3, 4 Rear wheel 5-12 Cylinder 5A, 7A Upper arm 6A, 7A Lower arm 13 Pump

Claims (6)

[Claims] 1. A mechanism provided on a lower arm or an upper arm of a vehicle for varying a stroke of the lower arm or the upper arm, a detecting means for detecting a side slip angle of a wheel of the vehicle, and a limit side slip preset for the wheel. Comparing means for comparing the angle with the detection result of the detecting means; and, in accordance with the comparison result of the comparing means, varying the stroke in the variable mechanism and setting the camber angle of the wheel in the negative camber angle direction or positive. Control means for adjusting the camber angle in the chimney angle direction. 2. A mechanism provided on a lower arm or an upper arm of a vehicle for varying a stroke of the lower arm or the upper arm; a detecting means for detecting a side slip angle of a vehicle wheel; and a side slip angle which is a detection result from the detecting means. Control means for varying the stroke and adjusting the camber angle of the wheel in the negative camber angle direction or the positive camber angle direction in the variable mechanism according to the magnitude and the sign of Angle control device for vehicle. 3. The variable mechanism includes a cylinder having two chambers disposed on at least one of the lower arm and the upper arm for varying the stroke, and a pump for flowing and discharging fluid to and from the two chambers of the cylinder. The camber angle control device for a vehicle according to claim 1, wherein the camber angle control device comprises a valve and a valve. 4. The control means determines the sideslip angle independently for the front wheels and the rear wheels, and independently controls the front and rear wheels to a camber angle on the side that suppresses the tendency of spin or drift in the variable mechanism. The camber angle control device for a vehicle according to any one of claims 1 to 3. 5. The control means does not perform camber angle control when the limit sideslip angle is larger in the comparison between the limit sideslip angle and the actual sideslip angle detected by the detection means. The camber angle control device for a vehicle according to claim 2. 6. The control means independently compares the limit sideslip angle with the actual sideslip angle detected by the detection means for the front wheels and the rear wheels. The camber angle control device according to claim 2, wherein the camber angle control is not performed when is larger.