JP2855826B2 - Caster angle control device for vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caster angle control device for a vehicle suspension, and more particularly, to appropriately improving vehicle performance according to lateral acceleration, longitudinal acceleration, and vertical acceleration applied to a vehicle body. The present invention relates to a caster angle control device for a vehicle, which can control a caster angle to cause the caster angle to be controlled.

[Conventional technology]

It is known that, in an automobile, by adjusting the suspension alignment, it is possible to change the running characteristics and the like of the vehicle, and by adjusting a caster angle (hereinafter simply referred to as a caster), which is one of the suspension elements,
Means for improving the running performance of vehicles have also been proposed.

As for such casters, increasing the angle improves the straight running stability and decreasing the angle improves the steering performance.
For example, it is possible to improve the straight running performance by controlling the casters to increase according to the vehicle speed, or to improve the steering performance by controlling the casters to decrease according to the magnitude of the steering angle. Proposed.

[Problems to be solved by the invention]

By the way, the ride comfort of the vehicle is greatly affected by the setting of the suspension, but it is conceivable to improve the ride comfort of the vehicle by adjusting the caster angle, which is one of the suspension elements.

The present invention has been devised in view of such a problem, and has a caster angle that can be appropriately controlled according to the running state of the vehicle so that the riding comfort of the vehicle can always be kept good. It is an object to provide a caster angle control device.

[Means for solving the problem]

For this reason, the caster angle control device for a vehicle of the present invention includes a caster angle adjustment mechanism that can adjust a caster angle by driving a mounting portion of the strut on the vehicle body side only in the vehicle front-rear direction in a strut type front suspension of the vehicle, Caster angle setting means for setting an optimum caster angle for a traveling state; and control means for controlling the caster angle adjusting mechanism so that the caster angle of the vehicle takes the caster angle set by the caster angle setting means. A vehicle speed detecting means for detecting a speed of the vehicle, a steering angle detecting means for detecting a steering angle of the vehicle, a lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle body, and a front and rear for detecting a longitudinal acceleration applied to the vehicle body An acceleration detecting means for detecting a vertical acceleration applied to the vehicle body; A value obtained by calculating a lateral acceleration accompanying the turning of the vehicle based on the detection information from the vehicle speed detecting means and the steering angle detecting means, and subtracting the turning lateral acceleration from the lateral acceleration information detected by the lateral acceleration detecting means. Is set as a lateral acceleration, and a correction coefficient relating to the lateral acceleration is set so that the caster angle increases in accordance with the increase in the lateral acceleration, and the detection information from the longitudinal acceleration detecting means and the vertical acceleration detecting means described above. , The correction coefficients for the longitudinal acceleration and the vertical acceleration are set so that the caster angle decreases in accordance with the increase in the longitudinal acceleration or the vertical acceleration.

(Operation)

In the above caster angle control device for a vehicle according to the present invention, the caster angle setting means calculates the lateral acceleration accompanying the turning of the vehicle based on the detection information from the vehicle speed detecting means and the steering angle detecting means. A value obtained by subtracting the turning lateral acceleration from the detected lateral acceleration information is set as the lateral acceleration, and a correction coefficient for the lateral acceleration is set so that the caster angle increases in accordance with the increase in the lateral acceleration.

Further, based on each detection information of the longitudinal acceleration detecting means and the vertical acceleration detecting means, the correction coefficients for the longitudinal acceleration and the vertical acceleration are respectively set so that the caster angle becomes smaller in accordance with the increase of the longitudinal acceleration or the vertical acceleration. I do. Then, under the control of the control means, the caster angle adjusting mechanism adjusts the caster angle of the vehicle to the caster angle set by the caster angle setting means, while driving the mounting portion of the strut on the vehicle body side in the longitudinal direction of the vehicle. Thereby, the straight running stability is improved in the control corresponding to the lateral acceleration,
In the control for the longitudinal acceleration and the vertical acceleration, the effect of kickback generated on the wheels on the vehicle body is reduced.

〔Example〕

A caster angle control device for a vehicle according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing the contents of the caster angle control, and FIGS. FIG. 6 is an exploded perspective view showing the caster angle adjusting mechanism, FIG. 7 is a perspective view showing a suspension provided with the caster angle adjusting mechanism, and FIG. 8 is a hydraulic circuit of the actuator. It is a block diagram.

First, the suspension of a vehicle equipped with this device will be described. The suspension of this embodiment is a strut type front suspension for a passenger car as shown in FIG. As is well known, a shock absorber 2 and a coil spring 3 are combined, and a portion of each strut 1, 1 is fixed to the vehicle body 4 side. A front wheel 7 is rotatably mounted on the lower end of each strut 1, 1 via a knuckle 5 and a hub 6.

The lower end of the strut 1 is connected via a lower arm 8 to a cross member 9 provided between the front wheels so as to also serve as a subframe, and constitutes a suspension using the shock absorber 2 as a part of a suspension link. ing.

Reference numeral 10 denotes a center member provided on the cross member 9, and reference numeral 11 denotes a disc brake.

A caster angle adjustment mechanism (slide) that allows the caster angle to be freely adjusted by sliding the heads 1A, 1A in the front-rear direction of the vehicle body 4 to the mounting portions of the heads 1A, 1A of the struts 1, 1 respectively. Mechanism) 12,12 are provided.

In FIG. 6, reference numeral 27 denotes a drive shaft, and 28 denotes a stabilizer.

Each of the caster angle adjusting mechanisms 12 has the same configuration, and as shown in FIG. 7, a slide base 14 attached to the vehicle body 4 on the upper surface of the strut tower;
Slide base 14 attached to the upper end of strut 1
And a slide plate 13 that can slide with respect to.

The slide base 14, for example, has a structure in which a substantially rectangular through hole 16 parallel to the vehicle longitudinal direction is provided in the center of a plate member 15 whose longitudinal side faces the vehicle longitudinal direction.
A pair of rail portions 17, 17 each having a substantially triangular cross section are provided upright on two sides corresponding to the vehicle width direction side 16 in parallel. Each of the rails 17, 17 is arranged inward, and the head 1A of the strut 1 penetrates between the opposed rails 17, 17 and inside the through hole 16. 17a is a rib for supporting the rail portion 17.

On the other hand, the slider plate 13 is
Substantially rectangular plate member 1 with dimensions corresponding to the distance between 17,17
8 and sliding walls 19, 19 which are provided on two parallel sides on the rail portion side of the plate member 18 and have a wedge shape which can be inserted into the rail portions 17, 17 respectively.

The sliding wall portions 19, 19 have a wedge-shaped cross section, for example, the plate member 1
A symmetrical triangular wall with the side of 8 as the top is integrally provided on the side of the plate member 18 and slides on the rails 17, 17 without rattling, whereby the slide plate
The rail 13 is guided by the rails 17, 17 between the rails 17, 17 and can slide in a certain direction.

In addition, between each sliding wall portion 19 and the corresponding rail portion 17, for example, a needle roller bearing 20 in which a plurality of roller bearings are arranged in parallel is interposed along the sliding direction, and the slide plate 13 is Stable and smooth sliding along the direction. In FIG. 7, reference numeral 21 denotes a bearing rolling surface provided on each of four outer surfaces of the sliding wall portion 19, and is formed of a rectangular recess.

The upper end of the strut 1 penetrates through the slide base 14 and is inserted into a circular opening 13a provided at the center of the slide plate 13. Also, fixed holes are provided before and after the opening 13a.
On the other hand, a pair (two) of mounting bolts 23, 2 is provided on the head portion 1A of the strut 1, for example, on the insulator portion 1a.
3 are projected, and these fixing bolts 23,2 are
By fastening 3, the head 1 </ b> A of the strut 1 is integrated with the slide plate 13. Thus, the casters of the front suspension can be made variable by sliding the slider plate 13 in the front-rear direction.
Numeral 24 indicates a nut for fastening the strut head.

And each slide plate 1 of such a slide mechanism 12,12
An actuator (drive device) 25 for moving the strut head in the longitudinal direction of the vehicle body is directly connected to 3. As the actuator 25, for example, a hydraulic actuator that drives a hydraulic cylinder 25B through a hydraulic supply / discharge system 25A having a hydraulic switching valve such as an electromagnetic valve as illustrated is conceivable.

In this case, for example, a hydraulic circuit configuration as shown in FIG. 8 is conceivable. In FIG. 8, 25a is a tank for storing hydraulic oil, 25b is a pump, 25c is a pump accumulator,
25d and 25e are main accumulator, 25f is filter, 25g
Is a relief valve, 25h is a check valve, 25i, 25j, 25
k and 25l are control valves, 25m and 25n are position sensors, and other symbols are the same as those described above.

A controller (comprising a microcomputer and its peripheral circuits) 26 as a control means is connected to the actuator 25, and various sensors (for example, a vehicle speed sensor, a steering angle sensor, a lateral acceleration sensor, Based on the information from the longitudinal acceleration sensor and the vertical acceleration sensor 29, the angle of the caster can be adjusted according to the vehicle speed V, the steering angle θ, the lateral acceleration gy, the longitudinal acceleration gx, and the vertical acceleration gz. .

In particular, the controller 26 controls a caster angle setting unit that sets an optimal caster angle based on detection information from each sensor, and a caster angle adjustment mechanism that takes the caster angle set by the caster angle setting unit. It has a control unit to perform.

The caster angle setting section sets the caster value C as follows.

That is, the value C of the caster angle can be set as follows: C = C ₀ + ΔC (1) where C ₀ = caster auxiliary setting value ΔC: correction auxiliary setting value.

The caster auxiliary set value C _0, as shown in FIG. 5, as the supplementary set value C ₀ the vehicle speed V is large in correspondence to the vehicle speed V
Is set to a large value. Therefore,
By adapt the vehicle speed V detected by the vehicle speed sensor in such a map (FIG. 5), it is possible to set the caster auxiliary setpoint C _0.

 Further, the correction auxiliary set value ΔC is as follows when traveling straight, ΔC = Kgx · Kgy · Kgz · C ′ (2), and when turning, ΔC = Kgx · Kgy · Kgz · C ″ (3) ).

Where Kgx: longitudinal acceleration correction coefficient Kgy: lateral acceleration correction coefficient Kgz: vertical acceleration correction coefficient C ′, C ″: correction auxiliary constant Note that the longitudinal acceleration correction coefficient Kgx is the magnitude of the longitudinal acceleration as shown in FIG. The lateral acceleration correction coefficient Kgy is a coefficient that decreases as the magnitude of the lateral acceleration | gy | increases, as shown in FIG. 3, and the vertical acceleration correction coefficient Kgz is: As shown in FIG. 2, the coefficient decreases as the magnitude | gz | of the vertical acceleration increases.

Therefore, the longitudinal acceleration gx and the lateral acceleration gx detected by the longitudinal acceleration sensor, the lateral acceleration sensor, and the vertical acceleration sensor
By associating y and the vertical acceleration gz with such a map (FIGS. 2, 3, and 4), the longitudinal acceleration correction coefficient Kgx, the lateral acceleration correction coefficient Kgy, and the vertical acceleration correction coefficient Kgz can be set.

However, at the time of turning, the centrifugal force accompanying the turning is applied to the vehicle as a lateral acceleration, so that the lateral acceleration gx needs to correct the value detected by the lateral acceleration sensor by this centrifugal force. That is, the present invention is to improve the straightness by changing the caster angle in accordance with the lateral acceleration caused by disturbance factors such as unevenness of the road surface and side wind, and excludes lateral acceleration caused by centrifugal force during turning. They are trying to do it.

Considering the centrifugal force, ma = mv ² / r, a = v ² / r = v ² / kθ = K · v ² / θ (4) where r: turning radius a: turning lateral acceleration ( = gy ') theta: the steering angle k, K: constant Accordingly, during turning, for its lateral acceleration g y, a lateral acceleration sensor at the detected lateral acceleration gy from the turning lateral acceleration a (= gy' subtracting) (Gy = gy-gy ')
The lateral acceleration correction coefficient Kg is obtained by associating the corrected lateral acceleration gy with a map (FIG. 3).
y is set.

Since the caster angle control device for a vehicle according to one embodiment of the present invention is configured as described above, the caster angle control is performed as shown in FIG.

That is, first, parameters related to control are initially set immediately after the ignition switch of the automobile is turned on (step S1), and the vehicle speed V, the steering angle θ, and the lateral acceleration gy are read from each sensor (step S2).

Then, in a succeeding step S3, it is determined whether or not the brake switch is turned on. If the brake switch is ON (that is, if the brake is depressed), the caster control (control corresponding to the acceleration applied to the vehicle body) is not performed, and the caster angle C is kept constant, or the caster angle C as C = C _0, performs control in accordance with only the vehicle speed.

On the other hand, if the brake switch has not been turned on (that is, the brake has not been depressed), the process proceeds to step S4.

Although the control corresponding to the acceleration is not performed during braking, it is desirable that the caster is large for braking stability when braking, but if the caster is large for turning braking etc. There is a fear that the driver may be out of the course, and control results are unclear, so control is excluded during braking.

In step S4, it is determined whether the steering angle θ is 0 or almost 0. When the steering angle θ is 0 or almost 0, it is determined that the vehicle is traveling straight, and the process proceeds to step S5. When the steering angle θ is not 0 or almost 0,
It is determined that the vehicle is turning, and the process proceeds to step S6.

In step S5, a longitudinal acceleration correction coefficient set corresponding to the longitudinal acceleration gx, the lateral acceleration gy, and the vertical acceleration gz detected by the longitudinal acceleration sensor, the lateral acceleration sensor, and the vertical acceleration sensor (see FIGS. 2, 3, and 4) Kgx, lateral acceleration correction coefficient Kgy
The auxiliary correction set value ΔC is set by substituting the vertical acceleration correction coefficient Kgz into the equation (2).

On the other hand, in step S6, a correction is made from the vehicle speed V detected by the vehicle speed sensor and the steering angle θ detected by the steering angle sensor based on equation (4) (that is, gy ′ = K · v ² / θ). Is calculated for the turning.

In the next step S7, the turning lateral acceleration gy 'is subtracted from the lateral acceleration gy detected by the lateral acceleration sensor (gy = gy-g
y ').

Then, in step S8, the longitudinal acceleration gx and the vertical acceleration gz detected by the longitudinal acceleration sensor vertical acceleration sensor and the corrected lateral acceleration gy obtained in step S7 (see FIGS. 2, 3, and 4). The longitudinal acceleration correction coefficient Kgx, the lateral acceleration correction coefficient Kgy, and the vertical acceleration correction coefficient Kgz are set, and the correction auxiliary setting value ΔC is set by substituting these coefficients into the above equation (2).

In this way, when the respective values are obtained from the correction auxiliary set values ΔC, the process proceeds to step S9, and the casters are calculated from the above-described equation (1). That is, the caster auxiliary setting value C ₀ is set from the map (FIG. 5) in accordance with the vehicle speed V, and the correction auxiliary setting value ΔC is added to the auxiliary setting value C ₀ .

Then, the control unit of the controller 26 controls the operation of the actuator 25 of the caster angle adjusting mechanism 12 so as to obtain the caster angles set as described above.

As a result, the caster becomes larger in accordance with the magnitude with respect to the lateral acceleration, so that there is an advantage that the straight running stability is improved, and the caster becomes smaller in accordance with the magnitude with respect to the longitudinal acceleration and the vertical acceleration. Therefore, there is an advantage that the effect of kickback generated on the wheels on the vehicle body can be reduced, and the riding comfort can be improved.

Further, in the present invention, since the lateral acceleration caused by the centrifugal force is excluded from the detected lateral acceleration, there is an advantage that the caster angle can be changed according to the lateral acceleration caused by a disturbance factor such as unevenness of a road surface or a side wind. There is.

The application of the caster angle control device is not limited to the suspension and the caster angle adjusting mechanism (slide mechanism) 12 having the configuration as in the present embodiment, but may be applied to the caster angle external force correction as described above. For example, the responsiveness adjustment of the caster control is not limited to the caster control as in the present embodiment, and the responsiveness adjustment of the caster control can be applied only to the vehicle speed corresponding control and the steering angle corresponding control conventionally proposed. It is also applicable to caster control and the like, and has an effect of improving driving feeling.

〔The invention's effect〕

As described in detail above, according to the caster angle control device for a vehicle of the present invention, in the strut type front suspension of the vehicle, the caster angle can be adjusted by driving the mounting portion of the strut on the vehicle body side only in the vehicle longitudinal direction. A caster angle adjusting mechanism; a caster angle setting means for setting an optimal caster angle for a traveling state; and a caster angle adjusting mechanism for controlling the caster angle of the vehicle to the caster angle set by the caster angle setting means. Vehicle speed detecting means for controlling the vehicle and detecting the speed of the vehicle;
Steering angle detecting means for detecting a steering angle of the vehicle, lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle body, longitudinal acceleration detecting means for detecting a longitudinal acceleration applied to the vehicle body, and detecting vertical acceleration applied to the vehicle body A caster angle setting means for calculating a lateral acceleration accompanying the turning of the vehicle based on detection information from the vehicle speed detecting means and the steering angle detecting means; A value obtained by subtracting the turning lateral acceleration from the lateral acceleration information detected in the above is set as a lateral acceleration, and a correction coefficient relating to the lateral acceleration is set so that the caster angle increases in accordance with the increase in the lateral acceleration. On the basis of the detection information from the longitudinal acceleration detecting means and the vertical acceleration detecting means, the caster angle is reduced in accordance with the increase in the longitudinal acceleration or the vertical acceleration. It is configured to set the correction coefficients for the longitudinal acceleration and the vertical acceleration respectively, so that the advantage of improving the straight running stability and the effect of kickback generated on the wheels on the vehicle body can be reduced, and the riding comfort of the vehicle can be reduced. There is an advantage that is improved.

Further, since the lateral acceleration caused by the centrifugal force is excluded from the detected lateral acceleration, there is an advantage that the caster angle can be changed according to the lateral acceleration caused by a disturbance factor such as unevenness of a road surface or a side wind.

[Brief description of the drawings]

1 to 8 show a caster angle control device for a vehicle as an embodiment of the present invention. FIG. 1 is a flowchart showing the contents of the caster angle control, and FIGS. Graph showing the characteristics of the coefficient according to the setting of
FIG. 6 is an exploded perspective view showing the caster angle adjusting mechanism, FIG. 7 is a perspective view showing a suspension provided with the caster angle adjusting mechanism, and FIG. 8 is a hydraulic circuit configuration diagram of the actuator. 1 ... Strut, 1A ... Head of strut 1, 1a ...
Insulator part, 2 ... Shock absorber, 3 ...
... Coil spring, 4 ... Vehicle, 5 ... Knuckle, 6
… Hub, 7… Front wheel, 8… Lower arm, 9… Cross member, 10… Center member, 11… Disc brake, 12… Caster angle adjustment mechanism (slide mechanism),
13: Slide plate, 13a: Opening, 14: Slide base, 15: Plate member, 16: Through hole, 17: Rail part, 17
a ... rail part, 18 ... plate member, 19 ... sliding wall part, 20 ...
... Needle roller bearing, 22 ... Fixed hole, 23 ... Mounting bolt, 24 ... Nut, 25 ... Actuator (drive unit), 25A ... Hydraulic supply / discharge system, 25B ... Hydraulic cylinder, 25
a… Tank, 25b… Pump, 25c… Pump accumulator, 25d, 25e …… Main accumulator, 25f …… Filter, 25g …… Relief valve, 25h …… Check valve, 25i, 25j, 25k, 25l …… Control valve, 25m, 25n
… Position sensor, 26… Controller, 27… Drive shaft, 28… Stabilizer, 29 …… Various sensors (vehicle speed sensor, steering angle sensor, lateral acceleration sensor, longitudinal acceleration sensor, vertical acceleration sensor, etc.).

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takao Morita 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-60-53416 (JP, A) JP-A-60-151181 (JP, A) JP-A-61-46702 (JP, A) JP-A-61-78705 (JP, U) JP-A-2-3979 (JP, U)

Claims (1)

(57) [Claims] 1. A caster angle adjusting mechanism that can adjust a caster angle by driving a strut-mounted portion of a strut only in the front-rear direction of a vehicle in a strut-type front suspension of a vehicle, and sets an optimum caster angle for a traveling state. And a control means for controlling the caster angle adjusting mechanism so that the caster angle of the vehicle takes the caster angle set by the caster angle setting means, and a vehicle speed for detecting the speed of the vehicle. Detecting means; steering angle detecting means for detecting a steering angle of the vehicle; lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle body; longitudinal acceleration detecting means for detecting a longitudinal acceleration applied to the vehicle body; A caster angle setting unit, comprising: a vehicle speed detection unit; and a steering angle. A lateral acceleration accompanying the turning of the vehicle is calculated based on the detection information from the detecting means, and a value obtained by subtracting the turning lateral acceleration from the lateral acceleration information detected by the lateral acceleration detecting means is set as a lateral acceleration.
A correction coefficient for the lateral acceleration is set so that the caster angle increases in accordance with the increase in the lateral acceleration. Based on the detection information from the longitudinal acceleration detecting means and the vertical acceleration detecting means, the longitudinal acceleration or the vertical acceleration is determined. A caster angle control device for a vehicle, wherein a correction coefficient for a longitudinal acceleration and a vertical acceleration is set so that a caster angle decreases as the acceleration increases.