JPH03253416A - Shock absorber control device - Google Patents

Abstract

PURPOSE:To improve steering stability by stopping the switching of a damping force characteristic or correcting the standard range of a damping force characteristic switching means and time until returning damping force characteristic when the abnormality of a vehicle speed sensor is detected in a shock absorber control device switching the damping force characteristic according to a road surface condition. CONSTITUTION:The exceeding a standard value of the irregular condition of a road surface, detected with a road surface condition detection means M2, causes the damping force characteristic of a shock absorber M1 to be switched with a damping force characteristic switching means M4. The standard range of the standard value and/or time until returning the damping force characteristic is set by a detected vehicle speed with a standard range-time setting means M5. The detection of the abnormality of a vehicle speed detection means M3 with an abnormality detection means M6 causes an abnormality treating means M7 to stop the switching with the damping force characteristic switching means M4, or to correct a standard range and/or time until returning damping force. This constitution can ensure steering stability even at the time of vehicle speed sensor failure.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a shock absorber control device that switches the damping force characteristics of a shock absorber according to road surface conditions.

[Prior Art] Conventionally, in order to improve ride comfort when a vehicle is running, the damping force characteristics of a shock absorber have been changed from large (hard) to small (soft) or small (soft) depending on the unevenness of the road surface. A shock absorber control device that switches from high to high (hard) is known.

For example, as shown in Japanese Patent Application Laid-Open No. 64-67407, the unevenness of the road surface is detected based on the rate of change in damping force obtained from the output value of a piezoelectric load sensor, and the damping force characteristics of the shock absorber are detected. There is something to switch between.

This technology compares the damping force change rate of the shock absorber with a threshold set according to the vehicle speed, and when the damping force change rate exceeds this threshold, the damping force characteristics are softly set. The period (soft retention time) is being switched.

This threshold value is set to a larger value as the vehicle speed increases, and the soft retention time is set to a shorter value as the vehicle speed increases. The period during which the damping force is maintained is also short. Conversely, the lower the speed of travel, the softer the damping force tends to be for the same damping force change rate, and the longer the period during which the damping force is maintained is longer.

As a result, both ride comfort and steering stability are maintained well.

[Problems to be Solved by the Invention] However, in the conventional device described above, when the vehicle speed sensor that detects the vehicle speed fails (hereinafter referred to as vehicle speed sensor fail), the vehicle speed is determined to be O and the damping force characteristic is switched. The threshold value and soft holding time for this are set to values corresponding to the vehicle speed O. Therefore, the damping force characteristic is set to the side where it is easy to switch to the soft one.Furthermore, the soft holding time also remains set for a long time. Therefore,
The shock absorber control device of the present invention solves the above problem and ensures steering stability even when the vehicle speed sensor fails. With the goal.

[Means for Solving the Problems] As illustrated in FIG. 1, the shock absorber control device of the present invention is provided between the wheels and the vehicle body of a vehicle, and has two damping force characteristics at least large and small. A shock absorber M1 that can be switched in two stages; a road surface condition detection means M2 that detects unevenness of the road surface; a vehicle speed detection means M3 that detects the vehicle speed of the vehicle; and a road surface unevenness detected by the road surface condition detection means M2. damping force characteristic switching means M4 for switching the damping force characteristic of the shock absorber M1 when the condition exceeds a reference range; In the shock absorber control device, the shock absorber control device is equipped with a reference range/time setting means M5 that is set accordingly, and an abnormality detecting means M6 that detects an abnormality in the vehicle speed detecting means M3, and an abnormality detecting means M6 that detects an abnormality in the vehicle speed detecting means M3; The gist of the present invention is to include an abnormality processing means M7 for canceling the switching or correcting the reference range of the damping force characteristic switching means M4 and/or the time until the damping force characteristic is restored.

[Function] The shock absorber control device of the present invention having the above-mentioned configuration table has the damping force characteristic switching means M4 when the uneven state of the road surface detected by the road surface state detecting means M2 exceeds the reference range.
switches the damping force characteristics of the shock absorber M1.

The time required for restoring this reference range and/or the damping force characteristic is set by the reference range/time setting means M5 in accordance with the vehicle speed detected by the vehicle speed detection means M3.

Then, when an abnormality in the vehicle speed detecting means M3 is detected by the abnormality detecting means M6, the abnormality processing means M7 stops switching the damping force characteristic, or the damping force characteristic switching means M4
The reference range and/or the time required to restore the damping force characteristics are corrected.

Therefore, when the vehicle speed detection means M3 is abnormal, the damping force characteristic is not switched in accordance with the vehicle speed as in the normal case as abnormal control, and steering stability can be ensured.

[Embodiments] In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the shock absorber control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the entire configuration of a shock absorber control device as an embodiment.

As shown in the figure, a vehicle shock absorber control device 1 (a variable damping force type shock absorber (hereinafter simply referred to as a shock absorber) of this embodiment is used.

) 2FL, 2FR, 2RL, 2RR1 It is composed of a vehicle speed sensor 3 that detects the running speed of the vehicle, and an electronic control device 4 that controls these.

Shock absorber 2FL, 2FR, 2RL,
2RR is shock absorber 2FL as described later.
, 2FR.

A piezo load sensor that detects the damping force acting on 2RL and 2RR, and shock absorbers 2FL and 2FR.
, 2RL, and 2RR are each equipped with a built-in piezo actuator for switching the damping force characteristics in two stages, large and small.

Also, each shock absorber 2FL, 2FR, 2RL
.

2 RRI, left and right front and rear wheels 5FL, 5FR, 5
RL, 5RR suspension lower arm 6FL
A coil spring 8 is installed between 6FR, 6RL, 6RR and the vehicle body 7.

It is attached to 8FR, 8RL, and 8RR.

The detection signals from the vehicle speed sensor 3 and the piezo load sensor are input to the electronic control device 4, and the electronic control device 4 outputs a control signal to the piezo actuator described above.

Next, each of the above shock absorbers 2FL, 2FR, 2
The structure of RL and 2RR will be explained. Since the structures of the above-mentioned shock absorbers 2FL, 2FR, 2RL, and 2RR are all the same, the shock absorber 2FL on the left front wheel 5FL side will be explained here as an example.

As shown in FIG. 3, the main piston 12 is fitted into the shock absorber 2FL [i cylinder 11 so as to be slidable in the axial direction (indicated by arrows A and B in the figure). 12 to the first hydraulic chamber 13
and a second hydraulic chamber 14. The main piston 12 is connected to one end of a piston rod 15, and the other end of the piston rod 15 is fixed to a shaft 16. The lower part (not shown) of the cylinder 1 is connected to the lower arm 6FL of the left front wheel 5FL, and the upper part (not shown) of the shaft 16 is connected to the vehicle body 7.

Next, a fixed orifice 17 on the extension side and a fixed orifice 18 on the contraction side are bored in the main piston 12 to communicate the first hydraulic chamber 3 and the second hydraulic chamber 14. On the exit side of 18 [L
Plate valve 1 that limits the flow direction to one direction
7a and 18a are provided, respectively.

Therefore, the main piston 12 moves inside the cylinder 11 as shown by the arrow A.
, When sliding in the axial direction indicated by B, the hydraulic oil inside the first hydraulic chamber ] 3 and the second hydraulic chamber 14 mutually flow through the fixed orifice 17 on the extension side and the fixed onofice 18 on the contraction side. Therefore, the damping force of the shock absorber 2FL is determined by the flow passage cross-sectional area of the hydraulic oil.

On the other hand, the piston rod 15 has a hollow part bored in its axial direction, and a piezo actuator 19 which is an electrostrictive element laminate made of piezoelectric ceramics such as PZT is installed in the hollow part.
Built-in FL. Also piezo actuator 19
A piston 20 is disposed at a position close to and facing the lower end surface of F[. Piston 20 (1 usually, plate spring 2
0a in the direction shown by arrow A in the same figure, it can slide inside the hollow portion of the piston rod 15 in its axial direction.

Therefore, when a voltage of several hundred V is applied to the piezo actuator 19FL to extend the piezo actuator 19F, the piston 20 moves several tens of μm in the direction shown by arrow B in the figure.
When the piezo actuator 19FL moves and conversely discharges the charge accumulated in the piezo actuator 19FL by applying a voltage and contracts the piezo actuator 19FL, the piston 20 moves in the direction shown by arrow A in the figure due to the bias of the plate spring 20a. . Furthermore, the charging and discharging of the piezo actuator 19F [
This is carried out via a lead wire 19a disposed in a passage bored inside the shaft 6 in the axial direction.

Next, the hollow part of the piston rod 5 and the bottom surface of the piston 20 form an oil-tight chamber 21, and a cylindrical plunger is provided in the through hole bored in the axial direction of the piston rod 15 and communicating with the bottom of the oil-tight chamber 21. 22 is slidably fitted into the lower end of the plunger 22 (the upper part of the spool valve 24 is slidably fitted into a fitting hole inside the housing 23 fixed to the piston rod 15). .

In addition, the spool valve 24 is biased by a spring 25 in the direction shown by arrow A in the same figure, and the lower part of the spool valve 24 has an annular groove 24a carved in the outer circumference, and the lowermost part is shaped into a cylindrical shape. There is.

Furthermore, an auxiliary flow path 26 is bored in the piston rod 5 to connect the first hydraulic chamber 13 and the second hydraulic chamber 4.
It is blocked by the lowest part of the spool valve 24 which is biased in the direction of the arrow by the spring 25.

For this purpose, a voltage of several hundred V is applied to the piezo actuator 191[ to extend the piezo actuator 19FL,
When the piston 20 is moved in the direction of arrow B, the oil-tight chamber 21
The internal pressure increases and plunger 22 and spool valve 2
4 also moves in the direction of arrow B, and the sub flow path 26 is connected to the spool valve 24.
The first hydraulic chamber 13 and the second hydraulic chamber 14 communicate with each other via this sub passage 26, and the main piston The flow path cross-sectional area of the hydraulic oil flowing through 12 becomes larger than usual, and its flow rate increases. Therefore, the damping force characteristic of the shock absorber 2FL at the time of 2 becomes smaller than normal.

That is, each of the above-mentioned shock absorbers 2FL, 2FR, 2
RL, 2 RRI;i Piezo actuators 19FL, 19FR, 19RL provided respectively,
By applying high voltage to 19RR, each piezo actuator 1
9FL, 19FR.

When extending 19RL and 19RR, the damping force characteristics change to the small (soft) side as shown in Figure 4.
It will be kept in the large (hard) state shown in the figure.

Next, attach the shock absorber 2 to the top of the shaft 16.
A piezo load sensor 31FL that detects the magnitude of the damping force acting on FL is provided.The piezo load sensor 31FL is fixed to the shaft 16 with a nut 32.

Piezo load sensor 31FLli Two thin plates 31A of piezoelectric elements made of piezoelectric ceramics such as PZT.

31B are stacked on top of each other with an electrode 31C in between.
The shaft 16 is connected to the electronic control device 4 via a lead wire 31a disposed in a passage bored inside the shaft 16.

Electronic control unit 4 (as shown in FIG. 5, CPU4a,
It is configured as a logic operation circuit mainly including ROM 4b and RAM 4c, and is connected to an input section 4e and an output section 4f via a common bus 4d to perform input/output with the outside. In addition, the electronic control circuit 4 (upper piezo load sensors 31FL, 31FR)
, 31RL, and 31RR from the charges generated by each shock absorber 2FL.

A damping force change rate detection circuit 35 that detects the rate of change in the damping force of 2FR, 2RL, and 2RR, and a waveform shaping circuit 36 that shapes the waveform of the detection signal from the vehicle speed sensor 3 are provided. The detection results are inputted to the input section 4e. Furthermore, each piezo actuator 19FL is controlled by the electronic control circuit 4 (by a control signal output from the CPU 4a via the upper output section 4f).
A drive circuit 37 is provided that expands and contracts the shock absorbers 2FL to 19RR and thereby switches the damping force characteristics of each of the shock absorbers 2FL to 2RR.

Here, the damping force change rate detection circuit 35 detects each shock absorber 2F based on detection signals from the piezo load sensors 31FL, 31FR, 31RL, and 31RR.

The road surface condition is detected by the expansion/contraction acceleration of 2FR, 2RL, and 2RR, and as shown in Fig. 6, four detection circuits 41FL and 41FR are provided corresponding to each piezo load sensor 31FL, 31FR, 31RL, and 31RR.
.

41RL, 41RR, and each detection circuit 41FL, 41
F.R.

A/D converters 42FL, 42FR, 42RL that convert the output signals from 41RL and 41RR into digital signals.
.

It is composed of 42RR.

Taking the detection circuit 41 FL as an example, each detection circuit 4IF
The operations of L, 41FR, 41RL, and 41RR will be explained.

As shown in FIG. 6, the detection circuit 41 FL is first provided with a resistor R1 connected in parallel to the piezo load sensor 31 FL. Since electric charges corresponding to the damping force are generated at both ends of the piezo load sensor 31FL due to the expansion and contraction of the shock absorber 2FL, the generated electric charges move through the resistor R1, and the shock absorber 2F is transferred to the resistor R1.
A current flows every time the damping force of L changes, and the current value becomes a value representing the rate of change in the damping force of the shock absorber 2FL. Therefore, in this embodiment (the detection circuit 41
FL detects the current flowing through the resistor R1 by the voltage across the resistor R1, and sends the detected value to the A/D converter 42 as a detection signal representing the damping force change rate of the shock absorber 2FL.
It is designed to be output after F.

That is, in the detection circuit 41 FL, the voltage signal across the resistor R1 first passes through the resistor R2 and then passes through the two coils.
．． High-frequency components such as radio noise are input to a radio noise removal filter EMI consisting of L2 and capacitor C1. The voltage signal from which radio noise has been removed is
Coupling capacitor C2 and offset voltage (2v)
is input to a bypass filter PF consisting of a resistor R3 to which 0. At the same time as the low frequency components below IHz are removed, the signal increases by 2V.It is further input to the low pass filter LPF consisting of resistor R4 and capacitor C3, and after removing high frequency components above 2 for 100 days, the voltage increases from the operational amplifier ○P1. A/D converter 42F via a buffer
Ll2 is output.

For this reason, the detection circuit 41F detects that there is a protrusion on the road surface as shown in FIG. The voltage at both ends (voltage at point a in FIG. 6) changes, and 0. 1
~100) Figure 7 (B
) will be generated as a damping force change rate signal.

In this way, the damping force change rate detection circuit 35 includes the piezo load sensors 31FL, 31FR, 31RL, 31
Four detection circuits 41FL and 41FR corresponding to RR
, 4IRL, and 41RR are provided in the hole detection circuit 41FL,
Detection signals representing the damping force change rate of each shock absorber 2FL, 2FR, 2RL, and 2RR are output from 4IFR, 41RL, and 41RR.

Next, the drive circuit 37 outputs the CPLJ4a via the output section 4f.
Each shock absorber from 2FL, 2FR, 2RL
, according to the damping force switching signal output every 2RR,
Each shock absorber 2FL, 2FR, 2RL,
Piezo actuator 19FL installed in 2RR,
19FR.

This is for driving 19RL and 19RR, and the 8th
As shown in the figure, the high voltage generating circuit 45 generates a high voltage table and the high voltage from the high voltage generating circuit 45 is applied to each piezo actuator 19 according to the damping force switching signal from the CPU 4a.
A charging/discharging circuit 47FL for applying voltage to FL, 19FR, 19RL, and 19RR, and conversely discharging.

It is composed of 47FR, 47RL, and 47RR.

Here, the high voltage generation circuit 45 (by increasing the battery voltage to 600
It is composed of a DC/DC converter 45a that converts the high voltage to V, and a capacitor 45b that stores the converted high voltage.

In addition, each charging/discharging circuit 47FL, 47FR, 47RL,
47RRLJ, when a low level signal is input as a damping force switching signal, a high voltage is applied to each piezo actuator 19FL, 19FR, 19RL, 19RR, and conversely, a high level signal is input as a damping force switching signal. When each piezo actuator is 19FL.

It is configured to discharge the high voltage charged in 19FR, 19RL, and 19RR.

That is, to explain this using the charging/discharging circuit 47FL as an example, when a low level signal is input as the damping force switching signal, the transistor Tr1 is turned off and the transistor Tr2 is turned on.
r2. When the high voltage generation circuit 45 and the piezo actuator 19F are connected via the resistor R10, and a high voltage is not applied to the piezo actuator 19FL, and conversely, a high level signal is input as the damping force switching signal, the transistor Since Tr1 is turned on and transistor Tr2 is turned off, high voltage generation circuit 45 and piezo actuator 1
9F bottom is cut off resistor RIO, diode DIO,
Piezo actuator 19 via transistor Trl
FL is grounded, and the charge stored in the piezo actuator 19FL is discharged.

Therefore, each of the above shock absorbers 2FL and 2FR.

Damping force characteristics of 2RL and 2RR (Piezo actuator 19FL, 19FR, 19RL, 19R)
By applying a high voltage to R, the piezo actuator 19FL,
When 19FR, 19RL, and 19RR are extended, they become small (soft), and piezo actuators 19FL,
Discharge the charges stored in 19FR, 19RL, and 19RR to actuate the piezo actuators 19FL, 19FR,
When 19RL and 19RR are contracted, they become large (hard), so each shock absorber 2FL, 2F
When making the damping force characteristics of R, 2RL, and 2RR small (soft), each charging/discharging circuit 47FL, 47FR, 47R
It is sufficient to input a low level damping force switching signal to L and 47RR, and conversely, to each shock absorber 2FL and 2FR.
, 2RL, and 2RR, each charging/discharging circuit 47FL, 47FR, 47RL
, 47RR may be input with a high level damping force switching signal.

Next, the shock absorber damping force switching control executed by the CPLJ4a will be explained.

Figure 9 shows each shock absorber 2FL, 2FR, 2
This shows the damping force switching process that is repeatedly executed by the CPU 4a to control the switching of the damping force characteristics (hereinafter simply referred to as damping force characteristics) tables of RL and 2RR.

First, in step 100, initialization processing is performed to initialize flags, timers, etc. used in subsequent processing. Next, in step 110, the damping force change rate signal DFC from the damping force change rate detection circuit 35 is read. Note that the damping force change rate signal DFC[i becomes 2v when the damping force change rate is O, and fluctuates with this value as the origin, but in the following explanation,
The damping force change rate signal DFC is defined with 2V as the origin O.

In other words, it is assumed that the distance varies around the origin O. Subsequently, in step 120, it is determined whether or not the flag "Fl&" is the value O.As shown in the processing described later, when it is determined that the vehicle speed sensor has failed based on the damping force change rate and the vehicle speed. The value is 1, and here the value is O because the damping force switching process has just started (it has been reset to the value O by the initialization process in step 100).
Then, the process moves to step 130.

In step 130, the vehicle speed is calculated based on the vehicle speed signal from the vehicle speed sensor 3. Next, in step 140, it is determined whether the absolute value of the damping force change rate signal DFC continues to be larger than a predetermined value for a certain period of time or more. l DFC
If l≦, the process moves to step 160, which will be described later, and l
If DFCl >K (ヱ Further 1: In step 150, it is determined whether the vehicle speed is present. In other words, it is determined whether the vehicle speed calculated in step 130 is greater than ○.If it is determined that the vehicle speed is present , or in step 140 the IDF
If it is determined that CI≦, the process moves to step 160, and based on the map shown in FIG.
and calculate the soft retention time Ts. Note that the soft switching threshold V ref is a threshold for detecting road surface irregularities from the damping force change rate signal DFC.

If it is determined in step 150 that there is no vehicle speed, there is no vehicle speed even though the absolute value of the damping force change rate signal DFC exceeds the predetermined value K, so it is determined that the vehicle speed sensor has failed, and step At step 170, the flag "is set to the value 1. Then, at step 180, the soft switching threshold value V
ref and software retention time Ts, abnormality software switching threshold Vrefs and abnormality software retention time Tss
Assign each. This abnormal software switching threshold Vr
efs and abnormal software retention time Tss (L 10th
．． As shown in Figure 11, it is a constant value regardless of the vehicle speed, and the abnormal soft switching threshold Vrefs is a large value.
The abnormality software retention time Tss is set to a small value.

When the process of step 180 or step 160 is completed, the process moves to step 190, and the damping force change rate signal DFC is
The absolute value of is the software switching threshold V ref calculated above.
Determine whether it is greater than or not.

If DFC>Vref, it is determined that there is a protrusion or depression on the road surface, and the process moves to step 200, where a low-level damping force switching signal is output to the drive circuit 37 in order to switch the damping force characteristic to small (soft). do. Next step 21
0, after switching the damping force characteristic to small (soft), a timer (not shown) starts the soft holding time T set above.
It is determined whether or not s has elapsed. Soft retention time Ts
This process is repeatedly executed until the software retention time Ts has elapsed, and when the software retention time Ts has elapsed, the process moves to step 220.

In step 190, if it is determined that IDFcI≦V ref, the process skips steps 200 and 210 and proceeds to step 220.In step 220, (
In order to switch the damping force characteristic to hard, a high level damping force switching signal is output to the drive circuit 37, and the process returns to step 110 again to repeat the above process. Therefore, after the damping force characteristic is switched to small (soft) in step 200 and the soft holding time Ts has elapsed, the damping force characteristic returns to large (hard).

Returning again to step 110, the damping force change rate signal DFC is read. Then, in step 120, it is determined whether or not the flag is F20.
If it is determined from the determination that the vehicle speed sensor has failed, the flag "1-knee straight" has been set in step 170, so the determination here is "No" and the process moves to step 180. That is, as an abnormality process, the soft switching threshold value V ref and the soft holding time Ts are set to predetermined values, and step 19 is performed based on these values.
The damping force characteristic is switched from zero.

Therefore, when a -1 vehicle speed sensor failure is detected, until this damping force switching process is completed (until the ignition switch (not shown) is turned off), the abnormality soft switching threshold Vrefs and the abnormality soft holding time Tss are used. Damping force characteristic switching processing is performed.

Shock absorber control device 1 of the present embodiment explained above
(As shown in Fig. 7, when the wheel runs over a protrusion on the road surface, the absolute value of the damping force change rate signal DFC detected by the damping force change rate detection circuit 35 is set according to the vehicle speed. If the soft switching threshold V ref is exceeded, it is estimated that the road surface is uneven and the vehicle body vibration increases, deteriorating the ride comfort.Then, during the soft switching time Ts, which is set according to the vehicle speed, the damping The force characteristics are switched to small (soft) to suppress vehicle body vibration.Moreover, if the absolute value of the damping force change rate signal DFC exceeds the predetermined value K It is determined that the sensor has failed, and the soft switching threshold V ref is set to a large value unrelated to the vehicle speed, and the soft holding time Ts is set to a small value unrelated to the vehicle speed.In other words, in the case of a vehicle speed sensor failure, the soft switching The threshold value V ref is set to the side where the damping force characteristics are difficult to switch to soft, and the soft holding time Ts is set short.As a result, even if the vehicle speed sensor fails when driving at high speed, the damping force is held soft. The time is shortened, good steering stability can be maintained, and the phenomenon of tilting can be prevented.

Furthermore, no special sensor or the like is required to detect vehicle speed sensor failure.

Here, in the above embodiment, both the soft switching threshold Vref and the soft holding time Ts are set, but a configuration may be adopted in which either one is set. Fortunately, when it is determined that the vehicle speed sensor has failed, the soft switching threshold V ref and the soft holding time Ts are set to constant values that are independent of the vehicle speed, but the damping force characteristics can be increased (hard) as shown below. The damping force switching process shown in FIG. 12 (as a second embodiment) is the same as that shown in FIG. 9 (using the same step numbers, Keep the explanation simple.

First, after initialization processing is performed in step 100, the damping force change rate signal DFC is read in step 110, and the vehicle speed is calculated based on the vehicle speed signal from the vehicle speed sensor 3 in step 130. Next, in steps 140 and 150, if there is no vehicle speed even though the absolute value of the damping force change rate signal DFC exceeds the predetermined value K, it is determined that the vehicle speed sensor has failed, and the process proceeds to step 220. and switches the damping force characteristic to large (hard).If it is not determined that the vehicle speed sensor has failed [1, proceed to the process from step 160,
Based on the map shown in Fig. 10.11, the soft switching threshold V ref and the soft holding time Ts of the damping force change rate according to the vehicle speed are calculated, and the damping force change rate signal DFC is calculated.
The damping force characteristics are switched according to the

By this process (ヱ) In case of vehicle speed sensor failure,
Because the damping force characteristics are always fixed to hard, the emphasis is on steering stability rather than ride comfort, allowing for safe driving.

In this embodiment, a configuration is adopted in which a vehicle speed sensor failure is detected from the damping force change rate signal and the vehicle speed, but a separate detection means for detecting a vehicle speed sensor failure may be provided. A piezo load sensor 31 FL that detects unevenness based on the rate of change in damping force.

Instead of using 31FR, 31RL, and 31RR, sensors that detect damping force, changes in vehicle height, etc. may be used, and it goes without saying that the present invention can be implemented in various ways without departing from the gist of the present invention. In addition, when a vehicle speed sensor failure is detected, a warning lamp (not shown) is configured to light up (the occupants can know that there is an abnormality in the vehicle speed sensor 3, and even if the timing of damping force switching is different from normal). There are no words that make me anxious.

As described in detail above, the shock absorber control device of the present invention (2) When an abnormality occurs in the vehicle speed detection means,
Since the switching conditions for the damping force characteristics and the time required to restore the damping force characteristics are corrected, steering stability can be improved even when traveling at high speeds.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the configuration of the present invention, FIGS. 2 to 12 illustrate embodiments of the present invention, FIG. 2 is a schematic configuration diagram showing the overall configuration of a shock absorber control device, and FIG. 3 4 is a characteristic diagram showing the damping force characteristics of the shock absorber, FIG. 5 is a block diagram showing the configuration of the electronic control device, and FIG. 6 is a diagram showing the damping force characteristics of the variable damping force type shock absorber. FIG. 7 is an explanatory diagram showing the operation of the damping force change rate detection circuit and the operation of damping force switching control; FIG. 8 is a circuit block diagram showing the structure of the drive circuit; FIG. 9 is a flowchart showing the damping force switching process, FIG. 10 is an explanatory diagram showing a map for setting the soft switching threshold from vehicle speed, and FIG.
FIG. 1 is an explanatory diagram showing a map for setting the soft holding time based on vehicle speed, and FIG. 12 is a flowchart showing damping force switching processing as a second embodiment. 2 FL, 2 FR, 2RL, 2 RR... Variable damping force shock absorber 3... Vehicle speed sensor 4... Electronic control unit 19FL, 19FR, 19RL, 19RR...
・Piezo actuator 31FL, 31FR, 31RL, 31RR...
・ Piezo load sensor 35... Damping force change rate detection circuit Figure 1

Claims (1)

[Scope of Claims] 1. A shock absorber that is provided between the wheels and the vehicle body of a vehicle and whose damping force characteristics can be switched in at least two stages, large and small; a road surface condition detection means that detects unevenness of the road surface; a vehicle speed detection means for detecting vehicle speed; a damping force characteristic switching means for switching the damping force characteristic of the shock absorber when the unevenness of the road surface detected by the road surface condition detection means exceeds a reference range; and/or abnormality detection for detecting an abnormality in the vehicle speed detection means in a shock absorber control device comprising reference range/time setting means for setting a time until the damping force characteristic is restored according to the detected vehicle speed. and abnormality processing for, when the abnormality is detected, canceling the switching of the damping force characteristic or correcting the reference range of the damping force characteristic switching means and/or the time required to restore the damping force characteristic. A shock absorber control device characterized by comprising: