JPH05213027A - Suspension control device - Google Patents

Abstract

PURPOSE:To keep a crew on board a vehicle free from uneasy feeling by automatically reducing the height of the vehicle at the time of turning. CONSTITUTION:This suspension control device has suspension control devices 14, 16 and 22 for each wheel, capable of changing roll center height according to a control signal, and an electronic control device 50 for outputting a control signal to the devices 14, 16 and 22, according to the turning state of a vehicle. Also, the electronic control device 50 controls the roll center height on the basis of data detected with a steering angle sensor or the like, so that a roll center height at the turning inner wheel side becomes larger than at the turning outer wheel side over a roll center height difference between both turning inner and outer wheel sides due to a wheel bound and rebound at the time of turning. The roll center of a body is thereby shifted to the turning inner wheel side actively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension of a vehicle such as an automobile, and more particularly to a suspension controller.

[0002]

2. Description of the Related Art As one of suspensions for vehicles such as automobiles, for example, as described in Japanese Patent Laid-Open No. 60-209315, the rate of change of the roll center height of the vehicle body due to the bouncing and rebounding of the wheels is the front suspension. Conventionally, there is known a suspension which is set to be small and is set to be large for a rear suspension and which is provided with a vehicle height adjusting device so that the vehicle height is reduced as the vehicle speed increases.

According to such a suspension, the rate of increase of the cornering force caused by the decrease of the roll center height in the front suspension at the time of high-speed turning is increased by the increase of the cornering force caused by the decrease of the roll center height in the rear suspension. Since it is smaller than the ratio, the change in the ground load due to the roll of the vehicle body during turning becomes larger on the front wheel side than on the rear wheel side, and the cornering force is greatly reduced on the front wheel side compared to the rear wheel side. Therefore, the understeer characteristic of the vehicle is strengthened, and therefore both the turning performance at low speed turning and the running stability at high speed turning can be improved.

[0004]

However, in the conventional suspension as described above, the vehicle height changes only in accordance with the vehicle speed, and the vehicle height becomes higher as the vehicle speed becomes lower. There is a problem that an occupant of the vehicle may feel anxiety when making a sharp turn, that is, when making a relatively sharp turn when the vehicle height is relatively high.

In view of the above-mentioned problems in the conventional suspension, the present invention has been improved so that the vehicle height automatically lowers when the vehicle turns, thereby preventing an occupant of the vehicle from feeling uneasy. It is intended to provide a suspension control device.

[0006]

According to the present invention, the above object is to provide a suspension device for each wheel capable of changing the roll center height according to a control signal, and a turning condition for detecting a turning condition of a vehicle. The detection means and the control means for outputting a control signal to the suspension device according to the turning state detected by the turning state detection means, and the control means turns when a vehicle turns, which is accompanied by a wheel bounce or rebound. The present invention is achieved by a suspension control device characterized in that the roll center height of the turning inner wheel side is controlled to be higher than the roll center height of the turning outer wheel side more than the difference between the roll center heights of the inner wheel side and the turning outer wheel side. It

[0007]

According to the above-described structure, when the vehicle turns, the roll center height on the turning inner wheel side is larger than the difference between the roll center heights on the turning inner wheel side and the turning outer wheel side due to the bouncing and rebound of the wheels. By controlling the roll center height to be higher than the center height, the amount of movement of the roll center of the vehicle body toward the turning inner wheel side is increased as compared with the case where the roll center heights are not actively controlled as described above, and the vehicle body is thus turned. Since the vehicle is tilted by the gravity and centrifugal force around the roll center that is positively moved to the inner ring side, the vehicle body is not only rolled to the turning outer ring side but also positively downward against the spring force of the suspension spring. The vehicle height is automatically urged, whereby the vehicle height during turning is automatically reduced.

[0008]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of a front suspension device for the right front wheel of a suspension control device according to the present invention.

In FIG. 1, reference numeral 10 denotes a carrier that rotatably supports a wheel 12. In addition, in FIG.
Reference numerals 16 and 16 respectively indicate an upper arm and a lower arm. The upper arm 14 is pivotally attached to the carrier 10 at the outer end and is pivotally attached to the middle portion of the lever 18 at the inner end. The lower arm 16 is pivotally attached to the carrier 10 at the outer end, and is pivotally supported on the vehicle body 20 at the inner end. Although not shown in the figure, a shock absorber and a suspension spring are arranged between the lower arm 16 and the vehicle body above it.

The lever 18 is pivotally supported on the vehicle body at its outer end, and a hydraulic actuator 22 is arranged between its inner end and the vehicle body 20. The actuator 22 is a cylinder 2 connected to the vehicle body 20 at one end in the illustrated embodiment.
4, a piston 26 fitted to the cylinder and connected to the outer end of the lever 18, and a compression coil spring 28 for urging the piston in the contracting direction. The hydraulic pressure in the chamber 30 is the hydraulic control device 32fr
It is designed to expand and contract by being increased or decreased by.

When the actuator 22 is in the contracted state shown, the upper arm 14 and the lower arm 16 extend substantially parallel to each other horizontally, so that the instantaneous center of the carrier 10 is located at infinity to the left in the figure. Roll center O bounded by the suspension device for the right front wheel
fr is an intersection of a straight line 34 drawn in parallel with the upper arm 14 and the lower arm 16 from the ground contact point P of the wheel 12 and the center plane 36 of the vehicle body, and the roll center height Hfr is low.

On the other hand, when the hydraulic pressure in the cylinder chamber 30 is increased by the hydraulic control device 32fr and the actuator 22 is extended, the lever 18 moves around its outer end as shown by the phantom line in FIG. Pivot downwards. Therefore, the instantaneous center of the carrier 10, which is the intersection of the axes of the upper arm 14 and the lower arm 16, moves upward, and the roll center defined by the suspension device for the right front wheel is indicated by Ofr 'in FIG. As described above, the roll center moves to a relatively high position, and the roll center height Hfr increases.

Although not shown in the figure, the front suspension device for the left front wheel is also constructed in the same manner as the front suspension device for the right front wheel, and the hydraulic pressure in the cylinder chamber of the actuator similar to the actuator 22 is By being controlled by the hydraulic control device 32fl, the height of the roll center Ofl of the left front wheel, that is, the roll center height Hfl is similarly controlled. The rear suspension device is also configured similarly to the front suspension device for the right front wheel described above, and the actuator 2
The hydraulic pressures in the cylinder chambers of the actuators similar to those in No. 2 are controlled by the hydraulic control devices 32rr and 32rl, respectively, so that the heights of the roll centers Orr and Orl of the right rear wheel and the left rear wheel, that is, the roll center heights Hrr and Hrl are the same. It is controlled by.

Hydraulic control devices 32fr, 32fl, 32rr, 3
In the illustrated embodiment, 2rl is a vehicle speed sensor 40, a steering angle sensor 42, and a steering angular velocity sensor 4 as shown in FIG.
4, vehicle speed V detected by yaw rate sensor 46, lateral acceleration sensor 48, steering angle θ, steering angular velocity θdo
Electronic control unit 50 based on t, yaw rate Y, and lateral acceleration G
Is controlled as described below. In the illustrated embodiment, the steering angle θ, the steering angular velocity θdot, the yaw rate Y, and the lateral acceleration G are detected with the right turning direction of the vehicle being positive.

The electronic controller 50 includes a microcomputer 52 as shown in FIG. The microcomputer 52 may be of a general configuration as shown in FIG. 2, and the central processing unit (CPU) 54
, Read only memory (ROM) 56, random access memory (RAM) 58, and input / output port device 60
And are connected to each other by a bidirectional common bus 62.

The input / output port device 60 includes a vehicle speed sensor 4
0, the steering angle sensor 42, the steering angular velocity sensor 44, the yaw rate sensor 46, and the lateral acceleration sensor 48 respectively input signals indicating the vehicle speed V, the steering angle θ, the steering angular velocity θdot, the yaw rate Y, and the lateral acceleration G. There is. The input port device 60 appropriately processes the signal input thereto, and executes the CP based on the program stored in the ROM 56.
According to the instruction from U54, the processed signal is output to the CPU and the RAM 58. ROM56 is shown in FIG.
The control program shown in FIG. 4 and the maps shown in FIGS. 4 and 5 are stored. The CPU 54 is adapted to perform various calculations and signal processing based on the control program shown in FIG. 3 as described later. I / O port device 60 is CP
According to an instruction from U54, control signals are output to the hydraulic control devices 32fr to 32rl via the drive circuits 64 to 70, respectively, and thereby the hydraulic pressure in the cylinder chamber of the corresponding actuator is controlled.

The operation of the illustrated embodiment will now be described with reference to the flow chart shown in FIG. The control by the electronic control unit 50 is started by closing an ignition switch (not shown).

First, in step 10, the vehicle speed sensor 40, the steering angle sensor 42, the steering angular velocity sensor 44,
The vehicle speed V, the steering angle θ, the steering angular velocity θdot, which are respectively detected by the yaw rate sensor 46 and the lateral acceleration sensor 48,
The yaw rate Y and lateral acceleration G are read, and then the process proceeds to step 20.

In step 20, based on the vehicle speed V read in step 10, the coefficients kf1, kf2, kf3, kf4 of the equation 1 and the coefficient kr1 of the equation 2 are used for the calculation in the step 30. kr2, kr3, kr4 are calculated by the map shown in FIG.

In step 30, the correction value ΔHf for the front wheel side roll center height and the correction value ΔHr for the rear wheel side roll center height are respectively expressed by the following equations 1 and 2.
Then, the process proceeds to step 40.

[0022]

[Equation 1] ΔHf = kf1 · θ + kf2 · θdot + kf3 · Y + kf4 · G

[Equation 2] ΔHr = kr1 · θ + kr2 · θdot + kr3 · Y + kr4 · G

In step 40, based on the vehicle speed V read in step 10, the coefficients Kf1 and Kf of the equations 3 and 4 used for calculating the roll center height in step 50 are calculated.
2, Kf3, Kf4 and the coefficients Kr1, Kr2, Kr of the equations 5 and 6
3, Kr4 is calculated by the map shown in FIG.

In step 50, the roll center height Hfr of the right front wheel, the roll center height Hfl of the left front wheel, the roll center height Hrr of the right rear wheel, and the roll center height Hrl of the left rear wheel are respectively expressed by the following formulas 3 to 3. The calculation is performed according to Equation 6, and then the process proceeds to step 60.

[0025]

[Equation 3] Hfr = Kf1 · | θ | + Kf2 · | θdot | + Kf3 · | Y | + Kf4 · | G | + ΔHf

[Equation 4] Hfr = Kf1 · | θ | + Kf2 · | θdot | + Kf3 · | Y | + Kf4 · | G | −ΔHf

[Equation 5] Hrr = Kr1 · | θ | + Kr2 · | θdot | + Kr3 · | Y | + Kr4 · | G | + ΔHr

[Equation 6] Hrl = Kr1 · | θ | + Kr2 · | θdot | + Kr3 · | Y | + Kr4 · | G | −ΔHr

In step 60, a control signal proportional to the roll center heights Hfr to Hrl calculated in step 50 is output to the hydraulic control devices 32fr to 32rl, whereby the hydraulic pressure in the cylinder chamber of the corresponding actuator is output. Is controlled to control the roll center heights of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel to Hfr, Hfl, Hrr, and Hrl, respectively, and then the process returns to step 10.

Thus, according to the illustrated embodiment, when the vehicle makes a right turn from the state of traveling straight at the vehicle speed Vs shown in FIGS. 4 and 5, the roll center heights Hfr and Hfl of the front wheels and the roll centers of the rear wheels are rolled. The center heights Hrr and Hrl change as shown in FIG. 6 as the vehicle is steered, and the roll center height on the inner turning wheel side during the turning of the vehicle is positively higher than the roll center height on the outer turning wheel side. Controlled.

Therefore, as shown in FIG. 7, the roll center Of on the front wheel side is located at a position Ofo when the vehicle is traveling straight and at a position inside the turning wheel Ofo 'when the hydraulic actuator 22 is not provided. And the roll center on the rear wheel side also moves to the inner wheel side during turning. As shown in FIG. 8, the vehicle body 20 is pivoted around the roll center thus moved to the inner wheel side of turning by the gravity M and the centrifugal force F acting on the vehicle body, and the center of gravity G is displaced obliquely downward to G ′. The vehicle body not only tilts and rolls toward the turning outer wheel side as shown by the phantom line, but also displaces downward to reduce the vehicle height.

According to the illustrated embodiment, when the vehicle is traveling straight ahead (including traveling on a rough road), the front wheel side roll center height Hf and the rear wheel side roll center height are as shown in FIG. Both of the Hr are controlled to be low, and the roll center shaft 72 defined by the front wheel roll center Of and the rear wheel roll center Or is set to a position sufficiently lower than the center of gravity G of the vehicle body. Good ride comfort is secured.

At the beginning of turning of the vehicle, as shown in FIG. 10, the roll center height Hf on the front wheel side is controlled to be high and the roll center height Hr on the rear wheel side is controlled to be low, whereby the roll center shaft 72 is tilted backward. Since the roll amount of the vehicle body is larger on the rear wheel side than on the front wheel side, and the turning performance of the vehicle body at the initial stage of turning is improved, good steering response of the vehicle is secured.

Further, after the vehicle reaches a steady turning state (after the absolute value of the steering angle reaches the maximum value), the roll center height Hf on the front wheels is low and the rolls on the rear wheels are low as shown in FIG. Since the center height Hr is controlled to be high, and the roll center shaft 72 is set to the forward tilted state, the roll amount of the vehicle body due to the turning is large on the front wheel side and small on the rear wheel side. Therefore, the slip angle of the vehicle body, that is, the angle formed by the center line passing through the center of gravity of the vehicle body and the locus of the center of gravity of the vehicle body is reduced. The yaw momentum may be small, which allows the course to be changed smoothly and stably.

In the illustrated embodiment, the upper arm 14
The position of the roll center is changed by changing the position of the inner end of the roll center in the vertical direction. However, the structure itself for changing the height of the roll center does not form the gist of the invention of the present application. It may be structural. In particular, when the vehicle turns, the load acting on the upper arm is mainly in the axial direction thereof, and in the illustrated embodiment, the actuator 22 cooperates with the lever 18 to substantially move the inner end of the upper arm 14 relative to the axis of the upper arm. Since it is designed to move in the vertical direction, the driving force of the actuator required to change the roll center height may be very small according to the illustrated embodiment, and the actuator may move via the lever 18 to the upper arm. It receives less power.

Further, according to the illustrated embodiment, when the roll center height is increased, the camber of the wheels is positively changed to the negative side and the toe-in is changed to the in side, so that the steering stability during turning of the vehicle is further improved. It is possible to further improve.

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art that it is possible.

[0035]

As is apparent from the above description, according to the present invention, when the vehicle turns, the turning inner wheel side of the turning inner wheel side is larger than the difference between the roll center heights of the turning inner wheel side and the turning outer wheel side due to the bouncing and rebound of the wheels. The roll center height is controlled to be higher than the roll center height on the turning outer wheel side, so that the roll center of the vehicle body moves to the turning inner wheel side as compared to the case where the roll center heights are not actively controlled as described above. The vehicle body is thus tilted by the gravity and centrifugal force around the roll center that is positively moved to the turning inner wheel side, which not only causes the vehicle body to roll to the turning outer wheel side but also positively moves downward. Since the vehicle is urged, it is possible to prevent the vehicle occupant from feeling uneasy by automatically lowering the vehicle height when turning.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of a front suspension device for a right front wheel of a suspension control device according to the present invention.

FIG. 2 is a block diagram showing an electronic control device for controlling the hydraulic control device shown in FIG.

FIG. 3 is a flowchart showing a control flow achieved by the electronic control device shown in FIG.

FIG. 4 is step 30 of the flowchart shown in FIG.
The coefficients kf1 and kf of the equations 1 and 2 used in the calculation in
2 is a graph showing 2, kf3, kf4, kr1, kr2, kr3, kr4.

5 is a step 50 of the flowchart shown in FIG.
The coefficients Kf1 and Kf of the equations 3 to 6 used in the calculation in
It is a graph which shows 2, Kf3, Kf4, Kr1, Kr2, Kr3, and Kr4.

FIG. 6 is a time chart showing changes in roll center height and roll center position when the vehicle is turning.

FIG. 7 is a schematic rear view of the vehicle showing the position of the roll center when the vehicle is traveling straight ahead and turning right.

FIG. 8 is a schematic rear view of the vehicle showing a posture change of the vehicle body when the vehicle turns right.

FIG. 9 is a schematic side view of the vehicle showing the position of the roll center shaft when the vehicle travels straight ahead.

FIG. 10 is a schematic side view of the vehicle showing the position of the roll center shaft in the initial stage of turning of the vehicle.

FIG. 11 is a schematic side view of the vehicle showing the position of the roll center shaft after the vehicle reaches the steady turning state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Carrier 14 ... Upper arm 16 ... Lower arm 18 ... Lever 20 ... Car body 22 ... Hydraulic actuator 32 ... Hydraulic control device 50 ... Electronic control device

Claims (1)

[Claims] 1. A suspension device for each wheel capable of changing a roll center height according to a control signal, a turning state detecting means for detecting a turning state of a vehicle, and a turning state detected by the turning state detecting means. And a control means for outputting a control signal to the suspension device according to the present invention, wherein the control means is greater than a difference between roll center heights of the turning inner wheel side and the turning outer wheel side due to wheel bound and rebound when the vehicle turns. The suspension control device is configured to control the roll center height on the side closer to the roll center height on the outer side of the turning wheel.