JP2619902B2 - Shock absorber damping force control device - Google Patents

Description

[Detailed Description of the Invention] [Industrial application field] The present invention controls the switching of the damping force of a shock absorber installed between a vehicle body and wheels according to a running state and a road surface state. The present invention relates to a damping force control device for a shock absorber.

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open Publication No. H10-15064 discloses a technique for improving the ride comfort of a vehicle by switching and controlling a damping force of a shock absorber.
According to No. 61-85210, a piezoelectric body is arranged on a piston in a shock absorber, and a sliding member for changing a passage area of a communication passage between a first oil chamber and a second oil chamber is provided to transmit displacement of both. The squat, dive and roll phenomena are detected by the voltage of the piezoelectric body generated based on the pressure change of the hydraulic chamber in the shock absorber, and the sliding member is displaced and moved based on the voltage applied to the piezoelectric body. In order to control the damping force of a shock absorber, a method has been proposed.

Also, according to Japanese Patent Application No. 62-169169, the force received by the shock absorber from the vehicle body side or the wheel side is detected by the load detecting means, and the load is applied when the damping force of the shock absorber is switched or when the shock absorber is activated according to the driving state of the vehicle. If the predetermined change in damping force is not detected by the detecting means, the control that switches the damping force of the shock absorber is stopped, or the control is changed to the control at the time of abnormality to prevent a decrease in ride comfort and maneuverability due to inappropriate control. Proposed.

[Problems to be Solved by the Invention] However, in such a conventional device, if an abnormality occurs in any one of the piezoelectric bodies or the load detecting means,
For example, when the piezoelectric body or the load detecting means on the left side of the front wheel fails, the normal damping force switching control is not performed, or the shock absorbers of all the wheels are uniformly switched to the same level of damping force, and the When unevenness, scout, dive and roll phenomena occur, there is a problem that ride comfort and maneuverability may not be sufficiently improved.

Therefore, an object of the present invention is to solve the above-mentioned problems, and even if the road surface condition cannot be detected normally, when a road surface unevenness or a squat-dive-roll phenomenon occurs, the damping force of the shock absorber is reduced. The present invention is to provide a shock absorber damping force control device that can control the switching of the vehicle and improve the ride comfort and maneuverability.

Configuration of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following configurations as means for solving the problems. That is, as illustrated in FIG. 1, a damping force variable shock absorber M3 provided between each wheel M1 of the vehicle and the vehicle body M2 and capable of switching the damping force, and a traveling state detection for detecting the traveling state of the vehicle Means M4
The shock absorber M3 provided for each wheel M1
A road surface state detecting means M5 for detecting a road surface state based on an acting force for expanding and contracting, and a driving state detected by the driving state detecting means M4 and a road surface state detected by the road state detecting means M5. In the shock absorber damping force control device for switching and controlling the damping force of each of the shock absorbers M3 in response to the change of the running state by the running state detecting means M4, the road surface state by the road state detecting means M5 at that time. The abnormality is detected by the normal road surface state detecting means M5 except for the abnormality detecting means M6 which detects the abnormality of the road surface state detecting means M5 from the change in the road surface state detecting means M5, and the abnormality is detected by the abnormality detecting means M6. Abnormal damping force control that performs switching control of the damping force of the shock absorber M3 according to the road surface state and the running state detected by the running state detecting means M4. Construction of the damping force control apparatus for a shock absorber, characterized in that it comprises a means M7, a is it.

[Operation] In the shock absorber damping force control device having the above-described configuration, the traveling state detecting means M4 detects the traveling state of the vehicle, and the road surface state detecting means M5 detects the road surface based on the acting force for expanding and contracting the shock absorber M3. The state is detected, and the abnormality detecting means M6 detects abnormality of each road surface state detecting means M5 from the change of the road surface state by the road surface state detecting means M5 at that time based on the change of the running state by the running state detecting means M4. The abnormal damping force control means M7 is detected by the normal road surface state detection means M5 and the traveling state detection means M4, except for the road surface state detection means M5 in which the abnormality is detected by the abnormality detection means M6. The switching control of the damping force of the shock absorber M3 is performed in accordance with the running state. Therefore, even if the road surface state detecting means M5 becomes abnormal, when a road surface unevenness or a scout / dive / roll phenomenon occurs, the road surface state detecting means M5 responds to the road surface state and the traveling state detected by the other normal road surface state detecting means M5. By controlling the damping force of the shock absorber, ride comfort and maneuverability can be improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic configuration diagram showing the configuration of the entire damping force control device of the present embodiment.

As shown in the drawing, the vehicle damping force control device 1 of the present embodiment
Is provided with a variable damping force type shock absorber (hereinafter simply referred to as a shock absorber) 2FL, 2FR, 2RL, 2RR, and an electronic control unit 4 for controlling these damping forces.

As described later, the shock absorbers 2FL, 2FR, 2RL, and 2RR include a piezo load sensor that detects a damping force acting on the shock absorbers 2FL, 2FR, 2RL, and 2RR, and a damping force of the shock absorbers 2FL, 2FR, 2RL, and 2RR. And a piezo actuator for switching between the two.

Further, each of the shock absorbers 2FL, 2FR, 2RL, 2RR is provided with a coil spring 8FL, 8FR, 8RL, It is attached to 8RR.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, 2RR will be described. Each of the above shock absorbers 2FL, 2FR, 2
Since the structures of RL and 2RR are all the same, here the left front wheel 5F
A description will be given taking the L-side shock absorber 2FL as an example.

As shown in FIG. 3 (A), shock absorber 2FL
The main piston 12 is slidably fitted in the cylinder 11 in the axial direction (indicated by arrows A and B in the figure).
The inside 1 is divided into a first hydraulic chamber 13 and a second hydraulic chamber 14 by a main piston 12. 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 11 is connected to the lower arm 6FL of the left front wheel 5FL,
The upper part (not shown) of the shaft 16 is connected to the vehicle body 7.

Next, an extension-side fixed orifice 17 and a contraction-side fixed orifice 18 that communicate the first hydraulic chamber 13 and the second hydraulic chamber 14 are formed in the main piston 12.
Plate valves 17a and 18a for restricting the flow direction to one direction are provided on the outlet side of the contraction side fixed orifice 18, respectively.

Therefore, the main piston 12 moves the arrows A and B
When sliding in the axial direction indicated by, the hydraulic oil in the first hydraulic chamber 13 and the second hydraulic chamber 14 flows mutually through the extension-side fixed orifice 17 and the contraction-side fixed orifice 18, The normal damping force of the shock absorber 2FL is determined by the flow area of the hydraulic oil.

On the other hand, the piston rod 15 has a hollow portion bored in the axial direction, and a piezo actuator 19FL, which is an electrostrictive element laminate made of piezoelectric ceramics such as PZT, is built in the hollow portion. Further, a piston 20 is provided at a position close to and opposed to the lower end surface of the piezo actuator 19FL. The piston 20 is normally urged by a leaf spring 20a in the direction indicated by the arrow A in the figure, but can slide in the hollow portion of the piston rod 15 in the axial direction.

Therefore, when a voltage of several hundred volts is applied to the piezo actuator 19FL to extend the piezo actuator 19FL, the piston 20 moves by several tens of μm in the direction indicated by the arrow B in FIG.
Conversely, when the electric charge accumulated in the piezo actuator 19FL is discharged by application of a voltage to contract the piezo actuator 19FL, the piston 20 moves in a direction indicated by an arrow A in FIG. The piezo actuator 19FL is charged / discharged via a lead wire 19a provided in a passage formed in the shaft 16 in the axial direction.

Next, the hollow portion of the piston rod 15 and the bottom surface of the piston 20 form an oil-tight chamber 21, and a through hole formed in the axial direction of the piston rod 15 and communicating with the bottom of the oil-tight chamber 21 has a cylindrical plunger 22. Are slidably fitted, and the lower end of the plunger 22 is further connected to a housing 23 fixed to the piston rod 15.
It is connected to the upper part of the spool valve 24 which is slidably fitted in the internal fitting hole.

The spool valve 24 is urged by a spring 25 in the direction indicated by the arrow A in the same figure, and an annular groove 24a is engraved on the outer periphery at the lower portion of the spool valve 24, and the lowermost portion is shaped into a cylindrical shape. ing.

Further, the piston rod 15 has a first hydraulic chamber 13 and a second hydraulic chamber 13.
A sub-flow path 26 for connecting to the hydraulic chamber 14 is formed, and is normally shut off by the lowermost part of the spool valve 24 urged in the direction of arrow A by a spring 25.

Therefore, when a voltage of several hundred volts is applied to the piezo actuator 19FL to extend the piezo actuator 19FL and move the piston 20 in the direction of arrow B, the pressure inside the oil-tight chamber 21 increases, and the plunger 22 and the spool valve 24 Moving in the direction of arrow B, the sub-flow passage 26 is communicated through an annular groove 24a formed in the outer periphery of the lower portion of the spool valve 24, and the first hydraulic chamber is connected through the sub-flow passage 26. The communication between the hydraulic pressure chamber 13 and the second hydraulic chamber 14 causes the flow area of the hydraulic oil flowing through the main piston 12 to be larger than usual, and the flow rate thereof increases. Therefore, the damping force of the shock absorber 2FL at this time becomes smaller than usual.

That is, each of the above shock absorbers 2FL, 2FR, 2RL, 2RR is
Piezo actuators 19FL, 19FR, 19R provided for each
Apply a voltage to L and 19RR to each piezo actuator 19FL and 1
When the 9FR, 19RL, and 19RR are expanded, the damping force is switched to the small (soft) side shown in FIG. 4, and normally the damping force is maintained at the large (hard) state shown in FIG.

At the upper part of the shaft 16, the magnitude of the damping force acting on the shock absorber 2FL is detected. FIG. 3 (B) is an exploded view. A piezo load sensor 31FL is provided, and the piezo load sensor 31FL is fixed to the shaft 16 by a nut 32. The piezo load sensor 31FL includes two thin plates 31A and 31B of a piezoelectric element made of piezoelectric ceramics such as PZT,
The detection signal is configured to be overlapped with the electrode 31C interposed therebetween.
Lead wire arranged in a passage drilled inside the shaft 16
It is output to the electronic control unit 4 via 31a.

Further, a steering sensor 33 for detecting a steering angle of a steering (not shown) as running state detecting means,
A vehicle speed sensor 34 for detecting the running speed of the vehicle, a neutral switch 35 for detecting a neutral position of the transmission for shifting and outputting the engine speed, and a stop lamp for emitting a signal when a brake pedal (not shown) is depressed. And a switch 36. Detection signals from the steering sensor 33, the vehicle speed sensor 34, the neutral switch 35, and the stop lamp switch 36 are input to the electronic control unit 4, and the electronic control unit 4 sends control signals to the above-described piezo actuators 19FL, 19FR, 19RL, and 19RR. Is output.

Next, as shown in FIG. 5, the electronic control unit 4
a, ROM4b, RAM4c is configured as a logical operation circuit around,
It is connected to the input unit 4e and the output unit 4f via the common bus 4d, and performs input / output with the outside.

Detection signals from the piezo load sensors 31FL, 31FR, 31RL, and 31RR are passed through a damping force detection circuit 37, and detection signals from the steering sensor 33, the vehicle speed sensor 34, the neutral switch 35, and the stop lamp switch 36 are sent to a waveform shaping circuit 38. Via the input unit 4e to the CPU 4a.

On the other hand, the CPU 4a outputs a signal from the output unit 4f via the drive circuit 39.
Control signals are output to the piezo actuators 19FL, 19FR, 19RL, and 19RR.

Here, as shown in FIG. 6, the damping force detection circuit 37 includes four detection circuits 41FL, 41FR, 41RL, 41RR provided corresponding to the respective piezo load sensors 31FL, 31FR, 31RL, 31RR. I have.

Hereinafter, taking the detection circuit 41FL as an example, each detection circuit 41FL, 41FR,
The configuration and operation of 41RL and 41RR will be described.

As shown in the figure, the detection circuit 41FL includes a piezo load sensor 31FL.
A damping force change rate detection circuit 50 for detecting a change rate of the damping force from a current flowing through the damper, a damping force change rate signal amplifying circuit 52 for amplifying an output signal from the damping force change rate detection circuit 50, and a damping force change rate signal. The damping force change rate signal output from the amplifier circuit 2 is
A / D converter 54 for A / D conversion, damping force estimation circuit 56 for estimating damping force by integrating output signals from damping force change rate detection circuit 50, and output from damping force estimation circuit 56 An A / D converter 58 for A / D converting the damping force signal and a voltage generating circuit 60 for generating a 2V reference voltage are provided.

Here, first, the damping force change rate detection circuit 50 is provided with a resistor R1 connected in parallel to the piezo load sensor 31FL. Since a charge corresponding to the damping force is generated at both ends of the piezo load sensor 31FL by the expansion and contraction of the shock absorber 2FL, the generated electric charge moves through the resistor R1, and the resistor R1 causes the shock absorber 2FL to expand and contract. Each time the damping force, which is the acting force, changes, a current flows, and the current value is a value representing the damping force change rate of the shock absorber 2FL. Therefore, the damping force change rate detection circuit 50 detects the current flowing through the resistor R1 based on the voltage across the resistor R1, and outputs the value as a signal representing the damping force change rate of the shock absorber 2FL.

That is, in the damping force change rate detection circuit 50, first, the resistor R1
The voltage generated at both ends is two coils via the resistor R2
The signal is input to a radio noise removal filter EMI composed of L1 and L2 and a capacitor C1, and high frequency components such as radio noise are removed. The voltage signal from which the radio noise has been removed is input to a high-pass filter HPF including a coupling capacitor C2 and a resistor R3 to which a reference voltage (2V) from a voltage generation circuit 60 is applied, and a low frequency of 0.1 Hz or less. After the frequency component is removed, the voltage rises by 2 V at the same time.After being input to a low-pass filter LPF composed of a resistor R4 and a capacitor C3 to remove the high-frequency component of 100 Hz or more, the voltage is externally passed through a buffer composed of an operational amplifier OP1. Is output.

Therefore, in the damping force change rate detection circuit 50, FIG.
When the left front wheel 5FL rides on the protrusion and the shock absorber 2FL expands and contracts as shown in FIG. 5, the voltage across the resistor R1 (the voltage at point a in FIG. 1) is increased according to the expansion and contraction acceleration. A voltage signal as shown in FIG. 7 (C), which changes as shown in FIG. 7 (B) and which is obtained by adding 2V to a signal component of 0.1 to 100 Hz among the voltage signals, is generated as a damping force change rate signal. Becomes

Note that the high-pass filter HPF and the low-pass filter LPF extract the voltage signal of the frequency component of 0.1 to 100 Hz from the voltage between both ends of the resistor R1 because the shock absorber 2FL is structurally in this frequency range. This is to expand and contract. In FIG. 6, the diodes D1 and D2 are connected so that the input voltage of the operational amplifier OP1 is in the range of 0 to 5V.
This is a protection diode for protecting the operational amplifier OP1.

Next, the damping force change rate signal amplifying circuit 52 amplifies the damping force change rate signal output from the damping force change rate detection circuit 50 and outputs the amplified signal to the A / D changer 54. The reference voltage (2V) from the voltage generating circuit 60 is applied to the non-inverting input terminal via the input terminal, and the inverting input terminal is connected to the frequency terminal of the damping force change rate signal amplifying circuit 52 via the capacitor C4 and the resistor R6. The inverting input terminal and the output terminal are configured as an inverting amplifier by an operational amplifier OP2 connected through a resistor R7.

For this reason, the damping force change rate signal amplifying circuit 52 outputs a damping force change rate signal VFL as shown in FIG. 7D in which the output signal from the damping force change rate detecting circuit 50 is inverted and amplified around 2 V. Is done.

The damping force change rate signal amplifying circuit 52 includes a capacitor C4
And a resistor R7 to function as a high-pass filter,
The low frequency component (frequency component of several Hz to 10 Hz or less) of the damping force change rate signal output from the damping force change rate detection circuit 50 is removed.

In other words, the damping force change rate signal VFL output from the damping force change rate signal amplifying circuit 52 is used to detect the unevenness of the road surface and to switch the damping force of the shock absorber softly, and is used as the undulation of the road surface. When the low-frequency components corresponding to long irregularities with a long period are taken in as the damping force change rate signal VFL, the damping force of the shock absorber is switched softly even for such irregularities, and the car body resonates with the irregularities on the road surface. This would adversely affect the ride comfort of the vehicle.

Next, the damping force estimation circuit 56
A voltage generating circuit for integrating the damping force change rate signal output from 50 to obtain a damping force signal representing the damping force of the shock absorber via a resistor R8 to a non-inverting input terminal.
A reference voltage (2 V) from the inverter 60 is applied, the inverted input terminal is connected to the output terminal of the damping force change rate signal amplifier circuit 62 via the capacitor C5 and the resistor R9, and the inverted input terminal and the output terminal are connected to the resistor. It is composed of operational amplifiers OP3 connected by R7 and capacitor C6, respectively.

This damping force estimation circuit 56 has a bandwidth of 0.1 to 1 as a whole.
A band pass filter of about 0 Hz is configured, the DC component of the damping force change rate signal output from the damping force change rate detection circuit 50 is cut by the capacitor C5, and the input signal is configured by the capacitor C6 and the resistor R9. Then, the signal is integrated by the integrating circuit and output to the A / D changer 58. For this reason, the damping force estimating circuit 56 integrates the frequency component of 0.1 to 10 Hz of the damping force change rate signal from the damping force change rate detection circuit 50, as shown in FIG. Is output.

Note that the damping force change rate signal
The reason for integrating only the frequency component of 0.1 to 10 Hz is that a low-frequency component that affects the vehicle body vibration may be detected as the damping force signal.

Next, the voltage generation circuit 60 is for generating the reference voltage of 2 V as described above. In the present embodiment, the power supply voltage 5 V is divided by the resistors R11 and R12, and the voltage of 2 V is supplied through the buffer including the operational amplifier OP4. It is configured to output a reference voltage.

Thus, the damping force detection circuit 37 includes four detection circuits 41FL, 41FL, 31FL, 31FR, 31RL, 31RR corresponding to the respective piezo load sensors 31FL, 31FR, 31RL, 31RR.
41FR, 41RL, 41RR are provided, and each detection circuit 41FL, 41FR, 41R
A detection signal indicating the damping force of each of the shock absorbers 2FL, 2FR, 2RL, and 2RR and the rate of change of the damping force is output from L and 41RR.

Since the shock absorber expands and contracts due to the detected damping force, each piezo load sensor 31FL, 31FR, 31RL, 31R
R and the damping force signal output from each of the above detection circuits 41FL, 41FR, 41RL, 41RR are based on the acting force for expanding and contracting each shock absorber, whereby the road surface condition can be detected. In this example, the road surface state detecting means M5 is constituted by the detection circuit and the piezo load sensor.

Next, the drive circuit 39 responds to the damping force switching signal output from the CPU 4a for each of the shock absorbers 2FL, 2FR, 2RL, and 2RR via the output unit 4f, and outputs the signal to each of the shock absorbers 2FL and 2FL.
Piezo actuators 19FL, 19F provided on FR, 2RL, 2RR
R, 19RL, and 19RR, and as shown in FIG. 8, a high voltage generating circuit 45 for generating a high voltage and a high voltage generating circuit 45 in response to a damping force switching signal from the CPU 4a. Apply high voltage to each piezo actuator 19FL, 19FR, 19RL, 19R
Charge / discharge circuits 47FL, 47 for applying to R or discharging reversely
FR, 47RL, 47RR.

Here, the high-voltage generating circuit 45 includes a DC / DC converter 45a that converts a battery voltage to 600 V, and a capacitor 45b that stores the converted high voltage.

Each charge / discharge circuit 47FL, 47FR, 47RL, 47RR applies a high voltage to each piezo actuator 19FL, 19FR, 19RL, 19RR when a low level signal is input as a damping force switching signal, and reversely attenuates. When a high level signal is input as a force switching signal, each piezo actuator 19F
It is configured to discharge the high voltage charged in L, 19FR, 19RL, and 19RR.

That is, the charge / discharge circuit 47FL will be described as an example. In the charging circuit 47FL, when a low-level signal is input as a damping force switching signal, the transistor Tr1 is turned off and the transistor Tr2 is turned on. R20
High voltage generation circuit 45 and piezo actuator 19FL via
Are connected, and a high voltage is applied to the piezo actuator 19FL. Conversely, when a high level signal is input as a damping force switching signal, the transistor Tr1 is turned on and the transistor Tr2 is turned off, so that the high voltage generating circuit 45 and the piezo actuator 19FL are cut off, and the resistor R20,
The electric charge charged in the piezo actuator 19FL via the diode D10 and the transistor Tr1 is discharged.

Therefore, the damping force characteristics of each of the shock absorbers 2FL, 2FR, 2RL, 2RR are determined by the piezo actuators 19FL, 19FR, 19RL, 1
Apply high voltage to 9RR to apply piezo actuators 19FL and 19F
When R, 19RL, 19RR is expanded, it becomes small (soft),
Discharges the charge in the piezo actuators 19FL, 19FR, 19RL, 19RR to discharge the piezo actuators 19FL, 19FR, 19R
When the shock absorber L, 19RR is contracted, it becomes large (hard). Therefore, when the damping force characteristic of each shock absorber 2FL, 2FR, 2RL, 2RR is made small (soft), each charge / discharge circuit 47FL, 47FR, 47
It is sufficient to input a low-level damping force switching signal to RL and 47RR. Conversely, if the damping force characteristics of each shock absorber 2FL, 2FR, 2RL, and 2RR are to be made large (hard), each charging and discharging circuit 47FL, A high-level damping force switching signal may be input to 47FR, 47RL, and 47RR.

Next, the shock absorber damping force switching control executed by the CPU 4a will be described.

FIG. 9 shows a damping force switching process that is repeatedly executed by the CPU 4a to switch and control the damping force of each of the shock absorbers 2FL, 2FR, 2RL, 2RR.

As shown in FIG. 9, in the damping force switching process, first, in step 100, after performing an initialization process of initial setting a counter used in the subsequent processes and a threshold value for detecting road surface unevenness. In step 110, based on the detection signals from the steering sensor 33, the vehicle speed sensor 34, the neutral switch 35, and the stop lamp switch 36, the steering angle θ as the traveling state, the vehicle speed S, the neutral switch on / off, and the stop lamp Read ON and OFF. In step 120, the damping force change rate signals VFL, VFR, VRL, VR of each of the shock absorbers 2FL, 2FR, 2RL, 2RR are based on the detection signal from the damping force detection circuit 37 as the road surface condition.
R and the damping force signals VaFL, VaFR, VaRL, VaRR are read.

Next, in step 130, the load sensors 31FL and 31FR as the road surface state detecting means M5 on the front wheels 5FL and 5FR side and the detection circuit 41F
It is determined whether any of L and 41FR is abnormal. This is determined by, for example, whether or not the damping force change rate signals VFL, VFR have changed in accordance with the operation of the brake or the steering. FIG. 10 (a) shows the change in the detection signals of the load sensors 31FL and 31FR in response to the brake operation, and FIG. 10 (b) shows the load sensors 31FL and 3FR in accordance with the steering operation.
The change of the detection signal of 1FR is shown. Solid line is load sensor 31FL, 31
Indicates the state where FR has detected normally. On the other hand, a dotted line shows a detection state when the load sensors 31FL and 31FR are abnormal. Changes in response to brake or steering operation can be detected after braking or steering operation by exhibiting greater amplitude variations. If there is a fluctuation, it is normal,
If the fluctuation is small or very large, it can be determined that the abnormality is abnormal. This is a load sensor
Not only 31FL and 31FR, but also a damping force change rate detection circuit 50, a damping force change rate signal amplifying circuit 52, and A / D converters 54 and 5 corresponding to these.
8. The same applies when either the damping force estimation circuit 56 or the voltage generation circuit 60 is abnormal. Alternatively, while the vehicle is running, the damping force change rate signals VFL, VFR,
The same determination can be made even when VaFL and VaFR are not input to the CPU 4a.

If it is determined in step 130 that there is no abnormality, in step 140, which of the load sensors 31RL, 31RR as the road surface state detecting means M5 on the rear wheels 5RL, 5RR side and the detection circuits 41RL, 41RR is abnormal is determined. It is determined whether or not. This is determined in the same manner as in step 130.

If it is determined in step 140 that there is no abnormality, then in step 150, normal control is performed based on the running state and the road surface state. In the case where the road surface has irregularities, as shown in FIG. 11, step 200 is first executed, and the vehicle speed S obtained in step 110 is greater than 0, as shown in FIG.
It is determined whether the vehicle is in a running state. If it is determined in step 200 that the vehicle is stopped, the process proceeds to step 210 to reset a time counter CTFL described later, and then proceeds to step 280.

On the other hand, if it is determined in step 200 that the vehicle is in a running state, the process proceeds to step 220 and the damping force change rate signal VFL of the shock absorber 2FL read in step 120 is read.
Is the upper limit value VreflF preset for each shock absorber
It is determined whether L has been exceeded. If VFL ≦ VreflFL, the process proceeds to step 230, and this time the damping force change rate signal VF
L is the lower limit Vre preset for each shock absorber
It is determined whether the value has dropped below f2FL.

The upper limit value VreflFL and the lower limit value Vref2FL are threshold values for detecting road surface unevenness from the damping force change rate signal VFL.

Next, when it is determined in step 220 that VFL> VreflFL, or when it is determined in step 230 that VFL <Vref2FL, it is determined that there is a protrusion or a depression on the road surface.
The process proceeds to step 240, in which a holding time (hereinafter, referred to as a soft holding time) Ts when the damping force set in advance in the time counter CTFL is switched to small (soft) is set, and then the process proceeds to step 250. In order to switch the damping force of the shock absorber 2FL to small (soft), a low-level damping force switching signal is output to the charge / discharge circuit 47FL.

The counter CTFL for which the soft holding time Ts is set in step 240 is a counter that counts down to 0 every predetermined time in a timing process (not shown), and a value corresponding to the soft holding time Ts is set in step 240. By setting, the soft holding time Ts is measured.

Next, when the damping force of the shock absorber 2FL is switched to small (soft) in step 250, step 260
Then, the switching counter CFL for counting the number of times the damping force is switched is counted up, and the routine proceeds to step 270.

Step 270 is also executed when it is determined in step 230 that VFL ≧ Vref2FL, and the time counter C
It is determined whether or not TFL is 0. That is, when the damping force is switched to small, the software holding time Ts is set in the timing counter CTFL, and then the countdown is performed at predetermined time intervals by a timing process (not shown). It is determined whether or not the state of the small damping force has elapsed for a predetermined time Ts or more by determining whether or not the state is set.

If CTFL> 0, the process is once terminated. Conversely, if CTFL = 0, the flow shifts to step 280 to control the damping force of the shock absorber 2FL to a large (hard) value.
After outputting a high-level damping force switching signal to the charge / discharge circuit 47FL and stopping the driving of the piezo actuator 19FL,
This process is temporarily ended.

That is, in the damping force switching control of this embodiment, as shown in FIGS. 7 (A), (B), and (C), the left front wheel 5FL rides on a protrusion on the road surface, and the acting force for expanding and contracting the shock absorber 2FL acts. , The damping force change rate signal VFL detected by the damping force change rate detection circuit 35 exceeds the upper limit value Vref1FL or the lower limit value.
If Vref2FL is exceeded, it is estimated that the road surface will be uneven and the vehicle body vibration will increase and the ride quality will deteriorate, and FIG. 7 (F)
As shown in (2), the damping force of the shock absorber 2FL is switched to a small (soft) value for a predetermined time Ts thereafter to suppress the vehicle body vibration.

Further, by an anti-roll control process (not shown), for example, when the vehicle speed S is equal to or more than a predetermined speed, the steering is operated, and the steering angle θ is equal to or more than the predetermined angle, and it is determined that the roll phenomenon occurs, the steering angle θ, Based on the vehicle speed S,
Upper limit value Vref1 and lower limit value Vref2 as threshold values described above
Is changed to a predetermined value, and the damping force change rate signals VFL, VFR, VR
When L and VRR exceed or fall below the upper limit value Vref1 and the lower limit value Vref2, the damping force of the shock absorber on the turning inner wheel is switched to small (soft), and the damping force of the shock absorber on the turning outer wheel is increased (hard). Execute the switching anti-roll control. Further, the same processing is executed in the anti-dive control processing and the anti-squat control processing.

On the other hand, in step 140, the load sensors 31RL, 31RR as the road surface state detecting means M5 on the rear wheels 5RL, 5RR side, the detection circuit 41RL,
If any of 41RR is determined to be abnormal, step
At 160, the shock absorbers 2FL and 2FR of the front wheels 5FL and 5FR perform the above-described normal restriction, and the shock absorbers 2RL and 2RR of the rear wheels 5RL and 5RR change the damping force of the piezo load sensors 31FL and 31FR of the front wheels 5FL and 5FR. Abnormal control is performed in accordance with the rate signals VFL and VFR. For example, when the vehicle passes through the above-described unevenness, the shock absorbers 2FL and 2FR of the front wheels 5FL and 5FR perform the control processing shown in FIG. 11, and the shock absorbers 2RL and 2RR of the rear wheels 5RL and 5RR perform the control of the front wheels. 5FL, 5
The rear wheels 5RL and 5RR pass through the unevenness after a certain period of time according to the vehicle speed S after the FR has passed the unevenness.
According to the damping force change rate signals VFL, VFR of the piezo load sensors 31FL, 31FR of FL, 5FR, the damping force of the shock absorbers 2RL, 2RR of the rear wheels 5RL, 5RR is switched after a certain period of time.

Alternatively, in the execution of the anti-roll control processing, similarly, the damping force of all the shock absorbers 2FL, 2FR, 2RL, 2RR is similarly determined according to the damping force change rate signals VFL, VFR of the piezo load sensors 31FL, 31FR of the front wheels 5FL, 5FR. Execute the control of.

When it is determined in step 130 that the load sensors 31FL, 31FR and the detection circuits 41FL, 41FR on the front wheels 5FL, 5FR are abnormal, in step 170, similar to step 140, the rear wheels 5RL, 5RR are detected. Load sensor 31RL, 31RR, detection circuit 41RL, 41RR
Is determined to be abnormal. If it is determined in step 170 that there is no abnormality, that is, if any of the load sensors 31FL, 31FR and the detection circuits 41FL, 41FR on the front wheels 5FL, 5FR are abnormal, the shock absorber 2F on the front wheels 5FL, 5FR is abnormal.
Abnormal control is performed for L and 2FR based on the running state, and normal control is performed for the shock absorbers 2RL and 2RR on the rear wheels 5RL and 5RR. For example, when passing through unevenness, only the shock absorbers 2RL and 2RR on the rear wheels 5RL and 5RR are
The control shown in FIG. 11 is executed, and in the execution of the anti-roll control processing, the piezo load sensors 31RL, 31RR of the rear wheels 5RL, 5RR are executed.
The control of the damping force of all the shock absorbers 2FL, 2FR, 2RL, 2RR is executed according to the damping force change rate signals VRL, VRR.

On the other hand, in step 170, the load sensors 3 on the rear wheels 5RL and 5RR side
If 1RL, 31RR and the detection circuits 41RL, 41RR are also determined to be abnormal, that is, the load sensors 31FL, 31FR on the front wheels 5FL, 5FR,
If any one of the detection circuits 41FL and 41FR and any of the load sensors 31RL and 31RR on the rear wheel 5RL and 5RR side and any one of the detection circuits 41RL and 41RR are abnormal, control based on the running state is executed in step 190. . For example, in the execution of the anti-roll control process, when the steering is operated and the steering angle θ is equal to or more than a predetermined angle and the vehicle speed S is equal to or more than a predetermined speed, the damping force of the shock absorber on the turning inner wheel side is reduced (soft). To execute the anti-roll control for switching the damping force of the shock absorber on the turning outer wheel to a large (hard) value.

After executing the processes of steps 150, 160, 180, and 190 described above, the processes of step 110 and subsequent steps are repeated.

As described above, in the shock absorber damping force control device of the present embodiment, the steering sensor 33, the vehicle speed sensor 34, the neutral switch 35, and the stop lamp switch 36 as the traveling state detecting means M4 detect the traveling state of the vehicle,
Load sensors 31FL, 31FR, 31R as road surface state detecting means M5
L, 31RR, the detection circuit 41FL, 41FR, 41RL, 41RR detects the road surface state based on the action force to expand and contract the shock absorbers 2FL, 2FR, 2RL, 2RR, step as abnormality detection means M6
By the processing of 130, 140, 170, each load sensor 31FL, 31FR, 31R
L, 31RR, detecting the abnormality of the detection circuit 41FL, 41FR, 41RL, 41RR, 160,180, as the abnormal time damping force control means M7
Any of the load sensors 31FL, 31FR, 31RL, 31RR, and the detection circuits 41FL, 41FR, 41RL, 41 for which an abnormality has been detected by the processing of 190
Any normal load sensor 31FL, 31FR, 31R except RR
L, 31RR, the road surface state detected by the detection circuits 41FL, 41FR, 41RL, 41RR and the steering sensor 33, the vehicle speed sensor 34,
The shock absorber 2 according to the traveling state detected by the neutral switch 35 and the stop lamp switch 36
Switching control of the damping force of FL, 2FR, 2RL, 2RR is performed.

The running state detecting means M4 is not limited to the steering sensor 33, the vehicle speed sensor 34, the neutral switch 35, the stop lamp switch 36, and may be a throttle opening sensor, an engine speed sensor, or the like.

As described above, according to the shock absorber damping force control device of the present embodiment, the load sensors 31FL, 31FR, 31RL, 31RR,
Even if the detection circuit 41FL, 41FR, 41RL, 41RR becomes abnormal, when a road surface unevenness or a scout / dive / roll phenomenon occurs, the other normal load sensors 31FL, 31FR, 31RL, 31RR,
The shock absorbers 2FL, 2FR, 2 are provided in accordance with the road surface condition and the traveling condition detected by the detection circuits 41FL, 41FR, 41RL, 41RR.
By controlling the damping force of RL and 2RR, it is possible to improve the riding comfort and driving quality. Further, abnormal control of the actuator system based on the detection signal of the failed sensor is not executed for a long period of time, so that breakage of the actuator can be prevented.

Although the embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention.

Effect of the Invention As described in detail above, the shock absorber damping force control device of the present invention is configured such that the abnormality detection means M6
Road condition detecting means based on the change of the running state by the road surface condition detecting means M5 at that time.
Since the abnormality of M5 is detected, the abnormality can be accurately detected even in the case of a failure in which a signal of a certain level is output from the road surface state detecting means M5. Further, even if the road surface condition detecting means M5 becomes abnormal, if a road surface unevenness or a scout / dive / roll phenomenon occurs, other normal road surface condition detecting means
The damping force of the shock absorber is controlled in accordance with the road surface state and the traveling state detected by M5, and the ride comfort and maneuverability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an overall configuration of a damping force control device of the present embodiment, and FIG. 3 (A) is a damping force of the present embodiment. Partial sectional view showing the structure of the variable shock absorber, FIG. 3 (B).
FIG. 4 is an enlarged perspective view of a cross section of a piezo load sensor of the shock absorber of the present embodiment, FIG. 4 is a characteristic diagram showing a damping force characteristic of the shock absorber, and FIG. 5 is a block diagram showing a configuration of an electronic control device of the present embodiment. 6, FIG. 6 is a circuit diagram showing the structure of the damping force detection circuit, FIG. 7 is a diagram for explaining the operation of the damping force detection circuit and the operation of damping force switching control, and FIG.
FIG. 9 is a circuit diagram showing the configuration of the drive circuit, FIG. 9 is a flowchart showing the damping force switching process, FIG. 10 is a timing chart showing the relationship between the output of the load sensor by the brake or steering operation, and FIG. 5 is a flowchart showing damping force switching control processing of FIG. M1: Wheels, M2: Body M3: Shock absorber M4: Traveling state detecting means M5: Road surface state detecting means M6: Abnormality detecting means M7: Abnormality damping force control means 2FL, 2FR2RL, 2RR ... Variable damping force type shock absorber 4. Electronic control device 19FL, 19FR, 19RL, 19RR… Piezo actuator 31FL, 31FR, 31RL, 31RR… Piezo load sensor 33… Steering sensor 34… Vehicle speed sensor 35… Neutral switch 36… Stop lamp switch 37… Damping force detection circuit 39… Drive Circuit 41FL, 41FR, 41RL, 41RR ... Detection circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Suzuki 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-61-85210 (JP, A) JP-A-62-151111 (JP, U)

Claims (1)

(57) [Claims] 1. A damping force variable shock absorber provided between each wheel of a vehicle and a vehicle body and capable of switching damping force, running state detecting means for detecting a running state of the vehicle, A road surface state detecting means for detecting a road surface state based on an acting force for expanding and contracting the shock absorber; and a traveling state detected by the traveling state detecting means and a road surface detected by the road surface state detecting means. In the shock absorber damping force control device for switching and controlling the damping force of each of the shock absorbers according to the state, based on a change in the running state by the running state detecting means, the road surface state detected by the road surface state detecting means at that time is changed. Abnormality detecting means for detecting an abnormality of the road surface state detecting means from a change; and a road surface state detecting means for detecting an abnormality by the abnormality detecting means. Abnormal damping force control means for performing switching control of the damping force of the shock absorber in accordance with the road surface state detected by the normal road surface state detecting means and the running state detected by the running state detecting means, A shock absorber damping force control device, comprising: