JPH06234315A - Damping coefficient control device for shock absordber - Google Patents

Abstract

PURPOSE:To control the damping coefficient of a shock absorber with good responsiveness according to the bound-rebound of a wheel so as to improve the riding comfort of a vehicle compared to the existing one. CONSTITUTION:In a damping coefficient control device for a shock absorber SA disposed between the sprung part and the unsprung part in correspondence with each wheel and formed in such a way that the damping coefficients of an expansion stroke and a contraction stroke are controlled independently, a load detecting device M1 detects load acting between the sprung part and unsprung part, and a load deviation computing device M2 computes the load deviation between the actual load, detected by the load detecting device M, and standard load. On the basis of the grade and code of the load deviation, a damping coefficient computing device M3 computes the damping coefficients of the expansion stroke and contraction stroke of the shock absorber SA so that the load deviation is decreased, thus reducing the increase/decrease quantity of load, generated in association with travel, from the standard load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber incorporated in a suspension of a vehicle such as an automobile, and more particularly to a damping coefficient control device for a variable damping force type shock absorber.

[0002]

2. Description of the Related Art As one of damping coefficient control devices for a variable damping force type shock absorber incorporated in a suspension of a vehicle such as an automobile, for example, as described in JP-A-61-163011, sprung acceleration is used. Detects and integrates sprung acceleration to calculate sprung speed, detects relative displacement between sprung and unsprung, and differentiates relative displacement to calculate relative speed between sprung and unsprung. Calculate,
2. Description of the Related Art A damping coefficient control device configured to increase or decrease the damping coefficient of a shock absorber according to the difference in sign (direction) of sprung speed and relative speed is conventionally known.

According to such a damping coefficient control device, the damping coefficient of the shock absorber is reduced when the sprung and unsprung parts move in the same direction, and the damping coefficient of the shock absorber when the sprung and unsprung parts move in the opposite direction. Therefore, the vibration of the vehicle body can be effectively damped and the riding comfort of the vehicle can be improved as compared with the case where the damping coefficient is not controlled according to the signs of the sprung speed and the relative speed.

[0004]

However, in the conventional damping coefficient control device as described above, the sprung mass velocity is calculated by integrating the detected sprung mass acceleration. Therefore, the sprung mass velocity is integrated by the integral calculation. Since the delay element caused by this is included, even if the damping coefficient of the shock absorber is controlled according to the sign of the sprung speed and the relative speed, the damping force of the shock absorber does not delay in response according to the actual sprung speed. There is a problem that the vehicle cannot be controlled, and therefore the riding comfort of the vehicle cannot be improved sufficiently.

In view of the above-mentioned problems in the conventional damping coefficient control device, the present invention controls the damping coefficient of the shock absorber responsively according to the bound and rebound of the vehicle as the vehicle travels. It is therefore an object of the present invention to provide an improved damping coefficient control device capable of improving the riding comfort of a vehicle as compared with the conventional one.

[0006]

According to the present invention, as described above, the above-mentioned objects are provided between the sprung portion and the unsprung portion, and the damping coefficient for the extension stroke and the compression stroke is provided. Shock absorber SA configured so that each of them is individually controlled
And a load deviation between the actual load and the standard load detected by the load detecting means M1 for detecting the load acting between the sprung portion and the unsprung portion. Load deviation calculation means M2 and damping coefficient calculation means M3 that calculates the damping coefficient of the extension stroke and the compression stroke of the shock absorber based on the magnitude and sign of the load deviation so as to decrease the magnitude of the load deviation. This is achieved by the damping coefficient control device of the shock absorber having.

[0007]

According to the above-mentioned structure, the load acting between the sprung portion and the unsprung portion is detected by the load detecting means M1,
The load deviation calculation means M2 calculates the load deviation between the actual load and the standard load, and the damping coefficient calculation means M3 reduces the load deviation based on the magnitude and sign of the load deviation. And the damping coefficient of the shrinkage stroke is calculated. In the present specification, "standard load" means a load corresponding to the load acting between the sprung portion and the unsprung portion when the vehicle is in a stopped state.

For example, when the load deviation becomes a positive value due to the fact that the wheel bounces from the neutral position and the actual load increases, the damping coefficient calculating means reduces the damping coefficient of the extension stroke of the shock absorber so that the magnitude of the load deviation decreases. When the load deviation becomes a negative value due to the fact that the wheel rebounds and the actual load decreases, the damping coefficient of the expansion stroke of the shock absorber is reduced by the damping coefficient calculation means. The damping coefficient of the reduction stroke is reduced and increased.

Therefore, in both cases of the wheel bouncing and rebounding, the magnitude of the deviation of the load acting between the sprung portion and the unsprung portion, that is, between the sprung portion and the unsprung portion is exerted. When the actual load increases or decreases as the vehicle travels, the amount of increase and decrease of the actual load from the standard load is reduced, which improves the riding comfort of the vehicle.

[0010]

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

FIG. 2 is a schematic block diagram showing one embodiment of the damping coefficient control device according to the present invention, and FIG. 3 is a block diagram showing the electronic control device of the embodiment shown in FIG. Figure 3
In the above, * is a symbol corresponding to each wheel, and the members indicated by the symbol with * are the right front wheel (* = 1) and the left front wheel (*
= 2), the right rear wheel (* = 3), and the left rear wheel (* = 4).

In FIG. 2, reference numeral 10 denotes a shock absorber of variable damping force, which comprises a cylinder 12 and a piston 14 reciprocally fitted into the cylinder 12, and the shock absorber 10 is provided at the lower end of the cylinder 12. The piston 1 is connected to a suspension member not shown in the figure.
The upper support 16 is connected to the vehicle body 18 at the upper end of the rod portion of No. 4 by the upper support 16 as described later.

Although not shown in FIG. 2, the shock absorber 10 is similar to the shock absorber described in Japanese Patent Application No. 4-293760 and the drawing filed by the same applicant as the applicant of the present application. The damping coefficient Cr for the expansion stroke is controlled by controlling the opening amount of the damping force control valve for the expansion stroke and the opening amount of the damping force control valve for the compression stroke provided on the base valve assembly. And the damping coefficient Cb of the compression stroke are individually the minimum damping coefficient Crl,
Cbl and the maximum damping coefficients Crh, Cbh are increased or decreased in multiple steps or continuously, and the damping coefficients Cr and Cb are the minimum damping coefficient Crl, respectively when the control signal is not output to the damping force control valve. It is set to Cbl.

A compression coil spring 24 as a suspension spring is elastically mounted between an upper spring seat 20 provided on the upper support 16 and a lower spring seat 22 fixed to the cylinder 12. A load sensor 2 is provided between the upper support 16 and the vehicle body 18.
6 is interposed and is fixed to the upper support and the vehicle body by bolts 28 and 29, respectively. Load sensor 26
Is the sum of the load acting between the vehicle body and the shock absorber along the axis 10A of the shock absorber 10, that is, the load Ps due to the spring force of the compression coil spring 24 and the load Pc due to the damping force generated by the shock absorber. Thus, the load acting between the sprung portion and the unsprung portion is detected.

The damping coefficient Cr for the expansion stroke and the damping coefficient Cb for the compression stroke of the shock absorber 10, that is, the opening amount of the damping force control valve for the expansion stroke and the compression stroke, is detected by the corresponding load sensor 26 and the vehicle speed V. A vehicle speed sensor 30, a steering angle sensor 32 for detecting the steering angle θ, a throttle position sensor 34 for detecting the throttle opening φ, and a brake switch (SW) 36 for detecting whether or not the brake pedal is depressed by a predetermined amount or more. The electronic control unit 38 controls the increase / decrease based on the above signal.

The electronic control unit 38 has a microcomputer 40 as shown in FIG. The microcomputer 40 may have a general structure as shown in FIG. 3, and the central processing unit (CPU) 4
2, read only memory (ROM) 44, random access memory (RAM) 46, and input port device 48
And an output port device 50, which are connected to each other by a bidirectional common bus 52.

The input port device 48 has a load sensor 26 *.
A signal indicating the load P * acting between the unsprung portion and the unsprung portion corresponding to each wheel detected by the vehicle speed sensor 30.
A signal indicating the vehicle speed V detected by the steering angle sensor 32
The steering angle θ detected by the throttle position sensor 34, the throttle opening φ detected by the throttle position sensor 34, and the brake switch 36 indicate whether the vehicle is in a braking state. ing.

The input port device 48 appropriately processes the signal input thereto, and in accordance with the instruction of the CPU 42 based on the program stored in the ROM 44, the CPU and the RAM.
The processed signal is output to 46. R
The OM 44 stores the control program shown in FIG. The CPU 42 is adapted to perform various calculations and signal processing based on the control program shown in FIG. 4, as will be described later. The output port device 50 follows the instructions of the CPU 42 and passes through the drive circuit 54 * and each shock absorber 10 *.
A control signal is output to the damping force control valve for the expansion stroke and the damping force control valve for the compression stroke.

Next, the control of the damping coefficient of the shock absorber in the illustrated embodiment will be described with reference to the flow chart shown in FIG. The routine shown in FIG. 4 is started by closing an ignition switch (not shown).

First, in step 10, the load detected by the load sensor 26 * when the vehicle is stationary, that is, the standard load Po * is read and stored in the RAM 46. At 20, the vehicle speed V detected by the vehicle speed sensor 30, the steering angle θ detected by the steering angle sensor 32, the throttle opening φ detected by the throttle position sensor 34, and the vehicle detected by the brake switch 36 are braked. A signal indicating whether or not there is a state is read.

In step 30, the vehicle travels requiring posture control based on the vehicle speed V, the steering angle θ, the throttle opening φ, and the signal indicating whether the vehicle is in the braking state read in step 20. It is determined whether or not the vehicle is in the state, that is, whether the vehicle is in the acceleration / deceleration state or the turning state that changes the posture of the vehicle body.

In this case, it is well known in the art to determine whether or not the vehicle is in a traveling state requiring attitude control, and it may be performed in any manner. For example, when the vehicle is in an accelerating state. The determination as to whether or not there is is made based on whether or not the time differential value of the throttle opening φ is greater than or equal to a reference value, and the determination as to whether or not the vehicle is in a decelerating state is made by a signal from the brake switch 36 in an on state. Whether or not the vehicle is in a turning state may be determined by whether or not the absolute value of the steering angle θ is greater than or equal to a reference value that is a function of the vehicle speed V.

When it is determined that the vehicle is in a traveling state requiring attitude control, the damping coefficient Cr * for the extension stroke and the damping coefficient Cb * for the compression stroke are maximum damping coefficients Crh * and Cbh, respectively, at step 40. The control signals corresponding to the damping coefficients set in step 40 are output to the damping force control valves of the corresponding shock absorbers set in step 50.
Return to 0.

When it is determined in step 30 that the vehicle is in a traveling state in which the posture control is not required, that is, the vehicle is in a substantially constant-speed straight traveling state, in step 60, a symbol corresponding to each wheel * Is set to 1, the actual load P * detected by the load sensor 26 * is read in step 70, and the actual load P * and the standard load P are read in step 80.
A deviation ΔP * (= P * -Po *) from o * is calculated.

In step 90, it is judged whether or not the absolute value of the load deviation ΔP * exceeds the reference value Pe *, that is, it is judged whether or not the damping coefficient of the shock absorber needs to be controlled. , | ΔP * |> Pe *, it returns to step 20, and | ΔP * |>
When it is determined that Pe *, step 10 is performed.
At 0, it is judged whether or not the load deviation ΔP * is positive.

When it is judged in step 100 that ΔP *> 0, that is, it is judged that the vehicle body is being lifted by the displacement of the wheels in the bounding direction relative to the vehicle body, the step is carried out. At 110, the damping coefficient Cr * of the extension stroke is Crl * + Kr, where Kr is a positive constant.
-Set to ΔP * and the damping coefficient Cb * of the compression stroke is set to the minimum damping coefficient Cbl *. If it is determined that ΔP *> 0 is not established, that is, the wheel is moving relative to the vehicle body in the rebound direction to lower the vehicle body, the extension stroke is determined in step 120. The damping Cr * is set to the minimum damping coefficient Crl *, and the damping coefficient Cb * of the contraction process is set to Cbl * + Kb.ΔP * with Kb being a negative constant.

Crl * + Kr in step 110
ΔP * and Cbl * + Kb in step 120 · ΔP
When * exceeds the maximum damping coefficient Crh * of the expansion stroke and the maximum damping coefficient Cbh * of the compression stroke, respectively, the damping coefficient Cr * of the expansion stroke is set to its maximum value Crh *, and the damping coefficient Cb * of the compression stroke. Is set to its maximum value Cbh *.

At step 130, a control signal corresponding to the damping coefficient calculated at step 110 or 120 is output to the damping force control valve of each shock absorber, and at step 140, it corresponds to each wheel. The symbol * is incremented by 1, and it is determined in step 150 whether * is 5 or not. If it is determined that * = 5 is not satisfied, the process returns to step 70 and * = 5. When the determination is made, the process returns to step 20.

Thus, according to the illustrated embodiment, the load Po * acting between the sprung and unsprung in step 10
Is read, and when the vehicle is in a substantially straight running state at a constant speed, the actual load P * acting between the sprung and unsprung is read in step 70, and the load deviation ΔP * is read in step 80. Is calculated, the load deviation ΔP * exceeds the reference value Pe * in steps 90 and 100, and it is determined that the vehicle body is about to be lifted because the wheels are displaced in the bounding direction relative to the vehicle body. When done,
In step 110, the damping coefficient Cr * of the extension stroke is increased by an increment proportional to the load deviation, and the damping coefficient Cb * of the contraction stroke is set to the minimum damping coefficient Cbl *.

Further, in steps 90 and 100, it is determined that the load deviation ΔP * is less than -Pe and the vehicle body is being lowered due to the displacement of the wheels in the rebound direction relative to the vehicle body. Sometimes step 1
At 20, the damping coefficient Cr * of the extension stroke is the minimum damping coefficient C.
While being set to rl *, the damping coefficient Cb * of the contraction stroke is increased in increments proportional to the magnitude of the load deviation.

Therefore, the wheels bounce and rebound, and the relative displacement between the sprung and unsprung parts changes,
If the actual load acting between the sprung and unsprung parts fluctuates,
In order to reduce the magnitude of the load deviation between the actual load and the standard load, the damping coefficient of the expansion stroke and the compression stroke of the shock absorber is controlled to increase / decrease with good responsiveness according to the fluctuation of the actual load.

For example, when the wheels bounce and rebound with high-frequency vibrations as the vehicle travels, the relative displacement between the sprung and unsprung portions fluctuates as shown in FIG. 5 (a). , Corresponding to this, compression coil spring 2
The load Ps generated by the change in the elastic deformation amount of No. 4 changes as shown in FIG. 5B when 0 is set when the wheel is in the neutral position.

If the damping coefficient of the shock absorber is not increased or decreased, the load Pc generated by the damping force of the shock absorber fluctuates as shown by the phantom line in FIG. Load deviation ΔP, that is, the actual load P (= Ps + Pc acting between the sprung and unsprung)
) And the standard load P0 fluctuate at 5 (d) as indicated by the phantom line.

On the other hand, according to the embodiment shown in FIG.
As shown in (e), the load deviation ΔP is the reference value Pe.
In the region exceeding .gamma., The damping coefficient Cr of the extension stroke is increased in increments proportional to the load deviation .DELTA.P and the damping coefficient Cb of the contraction stroke is set to the minimum damping coefficient Cbl, and the load deviation is less than the reference value -Pe. In the region of, the damping coefficient C of the extension stroke
Since r is set to the minimum damping coefficient Crl and the damping coefficient Cb in the compression stroke is increased by an increment amount proportional to the absolute value of the load deviation ΔP, the load Pc generated by the damping force of the shock absorber is shown in FIG. In FIG. 5C, the load deviation ΔP fluctuates as indicated by the solid line in FIG. 5D.

As can be seen from the comparison between the solid line and the phantom line in FIG. 5 (d), according to the illustrated embodiment, the bounding area and the rebounding area of the wheel are smaller than in the case where the damping coefficient of the shock absorber is not controlled to increase or decrease. In both cases, the magnitude of the load deviation ΔP is reduced and the integral value of the load deviation is also reduced, whereby the riding comfort of the vehicle is improved.

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

For example, in the above-described embodiment, the proportional constants Kr and Kb for calculating the damping coefficient are positive and negative constants, respectively, and these constants increase the vehicle speed V as shown in FIG. 6, for example. As a result, the magnitudes thereof may be calculated from the map prior to step 100 so as to increase gradually, and further, the damping coefficient Cr * of the extension stroke in step 110 and the damping coefficient Cb * of the compression stroke in step 120 are calculated. The calculation may be performed based on a three-dimensional map in which the damping coefficient ΔP * and the vehicle speed V are used as parameters, and the damping coefficient is set to gradually increase as the vehicle speed increases.

[0038]

As is apparent from the above description, according to the present invention, the load deviation calculating means M2 calculates the load deviation between the actual load and the standard load, and the damping coefficient calculating means M.
3, the damping coefficient for the expansion stroke and the compression stroke of the shock absorber is calculated so that the magnitude of the load deviation is reduced based on the magnitude and sign of the load deviation, and the integral calculation is not performed unlike the conventional damping coefficient control device. Therefore, the damping coefficient of the shock absorber bounces the wheels as the vehicle travels,
The responsiveness can be controlled according to the rebound, and the actual load acting between the sprung and the unsprung is accompanied by the traveling of the vehicle both when the wheel bounces and when the wheel rebounds. Reduce the amount of increase and decrease of the actual load when increasing or decreasing from the standard load,
As a result, the riding comfort of the vehicle can be improved.

Further, in the conventional damping coefficient control device, in order to calculate the relative speed between the sprung mass and the unsprung mass, the relative displacement between the sprung mass and the unsprung mass is detected corresponding to each wheel. According to the present invention, a sensor such as a vehicle height sensor is unnecessary, while a sensor such as a vehicle height sensor must be provided without fail, and therefore, the number of required sensors is greatly reduced, which makes it possible to reduce the number of required sensors. Thus, the damping coefficient control device can be greatly simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a damping coefficient control device according to the present invention in correspondence with the description of the claims.

FIG. 2 is a schematic configuration diagram showing one embodiment of a damping coefficient control device according to the present invention.

3 is a block diagram showing an electronic control unit of the embodiment shown in FIG. 2. FIG.

4 is a flow chart showing the control of the damping coefficient achieved by the electronic control device shown in FIG.

FIG. 5 is a time chart showing an example of the operation of the illustrated embodiment.

FIG. 6 is a graph showing a relationship between a vehicle speed V and proportional constants Kr and Kb for calculating a damping coefficient in another embodiment.

[Explanation of symbols]

 10 ... Shock absorber 16 ... Upper support 18 ... Vehicle body 24 ... Compression coil spring 26 ... Load sensor 30 ... Vehicle speed sensor 38 ... Electronic control device 40 ... Microcomputer

Claims (1)

[Claims] 1. A damping coefficient control device for a shock absorber, which is arranged between a sprung portion and an unsprung portion and is configured to individually control the damping coefficient for an extension stroke and a contraction stroke. Load detecting means for detecting a load acting between the load detecting means, a load deviation calculating means for calculating a load deviation between the actual load and the standard load detected by the load detecting means, and a magnitude of the load deviation and A damping coefficient control device for a shock absorber, comprising: damping coefficient calculation means for calculating a damping coefficient in an extension stroke and a contraction stroke of the shock absorber so as to reduce the magnitude of the load deviation based on a sign.