JPH08113021A - Damping force control device of shock absorber using electroviscous fluid - Google Patents

Abstract

PURPOSE: To provide a damping force control device of a shock absorber by which the electric power consumption and a calorific value can be reduced and the fuel consumption and a damping force variable range can be secured and improved by reducing an average electric current value flowing in electroviscous fluid to be used as working fluid of the shock absorber. CONSTITUTION: Error voltage eERR between target charging voltage Ui of capacity 13C in an electric equivalent circuit of electroviscous fluid necessary to set viscosity of electroviscous fluid 13 of itself, that is, damping force of a shock absorber and actual charging voltage Uc h of the capacity 13 detected by a charging voltage detector 49, is detected by an error detector 50. When this error voltage eERR is larger than a reference chopping voltage eTRI from a chopping wave oscillator 51, a switch 53 is closed, and a primary side current carrying quantity of a transformer 54 is controlled thereby, and high frequency- high voltage steep in a rise and fall is generated on the secondary side, and a driving voltage signal Vi by rectifying only this positive electric current by a half-wave rectifier 55 is supplied to the electroviscous fluid 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an electrorheological fluid whose viscosity changes according to the frequency or voltage value of a supply voltage signal as a working fluid of a shock absorber, and the shock absorber responds to a vehicle momentum and an input physical quantity. Specifically, the present invention relates to a damping force control device that controls the supply voltage signal in order to express the damping force.

[0002]

2. Description of the Related Art An electrorheological fluid having a property of increasing its own viscosity by supplying a voltage signal is used as a working fluid of a shock absorber, and the vibration damping force of the shock absorber is controlled by controlling this voltage signal. An example of the damping force control device capable of adjusting and controlling is disclosed in Japanese Patent Laid-Open No. 61-
Some are described in Japanese Patent No. 253208. This is to increase or decrease the viscosity of the electrorheological fluid by providing an electrode in the flow path of the working fluid formed between the upper and lower chambers of the piston, that is, an orifice or in the vicinity thereof, and supplying a voltage signal from the electrode to the electrorheological fluid. The flow resistance of the electrorheological fluid flowing through the orifice is controlled to be increased / decreased to increase / decrease the damping force of the shock absorber. According to this damping force control device, on the contrary, it is sufficient to set a desired damping force according to a turning momentum such as lateral acceleration or yawing momentum during vehicle traveling or a physical quantity such as road surface bouncing input, and to achieve that damping force. By supplying a voltage signal to the electrorheological fluid, it is possible to control the damping force during traveling and improve the vehicle traveling characteristics such as turning characteristics and riding comfort.

Various proposals have been made on what kind of voltage signal should be supplied to the electrorheological fluid. For example, the one which uses this voltage signal as an AC voltage signal is described in, for example, JP-A-62-251539 and JP-A-3-144715. Of these, the former supplies the high voltage AC signal generated on the secondary coil side to the electrorheological fluid as it is by periodically interrupting the current on the primary coil side of the transformer. That is, in order to obtain an effective viscosity as a working fluid for a vehicle shock absorber with this type of electrorheological fluid,
It has been clarified that a high voltage of at least several kV is required, and on the other hand, since the viscosity of the electrorheological fluid increases as the effective supply voltage increases, the high voltage on the secondary coil side of the transformer is increased. By setting the effective voltage of the AC signal according to the desired damping force, the damping force of the shock absorber can be controlled. In the latter, the frequency of the high-voltage AC signal whose effective voltage is constant is changed and supplied to the electrorheological fluid. In this type of electrorheological fluid, it has been clarified that the viscosity of the electrorheological fluid increases as the frequency of the supply voltage signal increases. Therefore, the frequency of the high voltage AC signal is set according to the desired damping force. By doing so, it becomes possible to control the damping force of the shock absorber.

Regarding the use of a DC voltage signal as the voltage signal supplied to the electrorheological fluid, for example, Japanese Patent Laid-Open No. 62-
It is disclosed in Japanese Patent No. 242146. The invention described in this publication does not attempt to achieve a desired damping force of the shock absorber by supplying a DC voltage signal, but the shock absorber is obtained from the waveform of the current flowing in the electrorheological fluid when the DC voltage signal is supplied. The supply voltage signal is a DC voltage signal having a constant voltage value.

[0005]

By the way, there are several kinds of so-called electrorheological fluids having the property of increasing viscosity by supplying a voltage signal as described above. Whether or not they show the same characteristics
At present, it is unknown, but if the electrical characteristics of a certain electrorheological fluid are expressed by a simple equivalent circuit, resistance R and capacitance C
And can be represented as being connected in parallel. However, when an AC voltage signal is supplied to an electrorheological fluid as described in JP-A-62-251539 and JP-A-3-144715, the electro-rheological fluid becomes known as the frequency increases as the frequency increases. Own capacity C
Since the impedance of the electrorheological fluid decreases, the amount of current flowing through the electrorheological fluid increases, power consumption increases, and the temperature of the electrorheological fluid increases. When a DC voltage signal is supplied to the electrorheological fluid as described in JP-A-62-242146, the amount of current flowing through the resistance R of the electrorheological fluid itself increases and the temperature of the electrorheological fluid increases. Since the resistance value of the resistance R of the electrorheological fluid itself decreases as the temperature rises, as the temperature value rises, a certain value of the electrorheological fluid increases. The current flowing through the resistance R of the electrorheological fluid itself further increases, power consumption increases, and the temperature of the electrorheological fluid further rises.

[0006] When the vehicle is traveling, the temperature of the working fluid in the shock absorber rises if the condition of large road surface irregularities continues, but it is necessary to control the damping force of the shock absorber only in such a region of large road surface irregularities. is there. However, as described above, when the temperature of the working fluid composed of the electrorheological fluid becomes higher due to the voltage signal supplied for controlling the damping force, there arises a problem that the temperature range used as the working fluid is narrowed. . In addition, if an electrical load has a characteristic that the resistance value of the load decreases as the temperature rises, the load heats up due to the current flowing through the load itself, causing a further current flow, which exceeds the operating range of the load. There is a phenomenon called thermal runaway.
In order to avoid this thermal runaway, it is necessary to limit the current flowing through the electrorheological fluid, which is a load, but there is also the problem that the target damping force of the shock absorber is limited in such a case. Further, as described above, when the power consumption increases, the load of the generator, that is, the load of the engine increases, so that there is a problem that the distance that can be traveled with a constant fuel is shortened and the fuel consumption is deteriorated.

Further, as described above, a certain kind of electrorheological fluid is represented by an equivalent circuit in which a resistance R and a capacitance C are connected in parallel, so that a damping force is applied to a shock absorber using this electrorheological fluid. In increasing / decreasing the control, when the viscosity of the electrorheological fluid is increased to increase the damping force of the shock absorber, the voltage value of the supply voltage signal is increased so that the charging voltage of the capacity C of the electrorheological fluid itself is increased. A relatively good responsiveness can be obtained by, for example, increasing, but when the viscosity of the electrorheological fluid is reduced and the damping force of the shock absorber is reduced, it is accumulated in the capacity C of the electrorheological fluid itself. Even if the voltage value of the supply voltage signal is reduced so that the generated electric charge is discharged, the discharge time of the capacitance C of the electrorheological fluid itself depends on the capacitance value of the capacitance C and the resistance R.
Since it is determined by the discharge time constant according to the resistance value of, the good responsiveness may not be ensured depending on the characteristics of the electrorheological fluid used. Therefore, there is a possibility that sufficient damping force control responsiveness cannot be ensured, particularly for high-frequency vibration input in which small road surface irregularities are continuous.

The present invention has been developed in view of these problems. First, by reducing the amount of current flowing in the electrorheological fluid to reduce the power consumption and the amount of heat generation, a sufficient shock absorber can be obtained. Provided is a shock absorber damping force control device using an electrorheological fluid, capable of ensuring a variable control range of the damping force, preventing deterioration of fuel consumption, and ensuring sufficient responsiveness of damping force control. That is the purpose.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has obtained the following findings and developed the present invention. That is, since a certain kind of electrorheological fluid is represented by an equivalent circuit in which the resistance R and the capacitance C are connected in parallel as described above, it flows when a DC voltage signal is supplied to the electrorheological fluid. By controlling the current for intermittently charging the capacity C of the electrorheological fluid itself in comparison with the current value, the viscosity charged to the capacity C of the electrorheological fluid itself is the target viscosity, that is, the shock absorber. If the voltage is configured to achieve the damping force of
It was found that the current value flowing in the electrorheological fluid becomes small. The reason why the current value flowing in the electrorheological fluid becomes small has not been completely clarified yet, but it can be considered as follows. That is, as described above, the electrical characteristic of the electrorheological fluid is represented by an equivalent circuit in which the resistance R and the capacitance C are connected in parallel when the supply voltage signal has a relatively low frequency, When the supply voltage signal becomes higher than the predetermined frequency, the electric characteristic of the electrorheological fluid becomes a complicated shape which cannot be expressed only by the resistance R and the capacitance C. From these facts, it goes without saying that the impedance of the electrorheological fluid increases in the high frequency region of the supply voltage signal, but the resistance value of the resistance R of the electrorheological fluid itself increases with an increase in the frequency of the supply voltage signal. Therefore, when the frequency of charging the capacitance C of the electrorheological fluid itself is increased, the resistance value of the resistor R increases, and the value of the current flowing through the electrorheological fluid decreases. Therefore, in order to express these characteristics in the shock absorber of the vehicle, the desired damping force is set according to the turning momentum such as the lateral acceleration and yawing momentum during the vehicle running and the physical quantity such as the road surface bouncing input. A high frequency at which a target voltage is a charging voltage of an electrorheological fluid sufficient to generate force, and a voltage value corresponding to a deviation between the actual charging voltage charged in the actual electrorheological fluid and the target charging voltage is obtained. A high-frequency high-voltage signal, which is a high-voltage signal and is intended only to charge the capacity C of the electrorheological fluid itself, is a high-frequency high-voltage signal consisting of a current flowing in only one direction of charging the capacity C. It may be supplied at the timing of charging / discharging. Then, in order to further reduce the average current value flowing in the electrorheological fluid, the time required to charge the capacity C of the electrorheological fluid itself is shortened, and the current value flowing at that time is a cycle satisfying the predetermined high frequency. It can be averaged with. As described above, in order to shorten the charging time to the capacity C of the electrorheological fluid itself, the time required for the rising / falling of the supplied voltage signal should be shortened as much as possible. The intermittent period of the direct current flowing to the secondary side may be matched with the predetermined high frequency, and the high frequency AC high voltage signal generated on the secondary side may be half-wave rectified.

On the other hand, the resistance value of the resistor R represented by the equivalent circuit of the electrorheological fluid of a certain type reduces the current value flowing through the resistor R by the high frequency half-wave high voltage signal supplied to the electrorheological fluid. In order to reduce power consumption and heat generation, the resistance value must be large to some extent. However, the capacitance C of the electrorheological fluid itself, which also appears in the equivalent circuit,
Since the electric charge stored in the capacitor is discharged through the resistor R in parallel with it, if the resistance value of the resistor R is large, the discharge time constant set by the capacitance value of the capacitor C becomes large as described above. This causes a delay in the response of the damping force control system, particularly in the direction of decreasing the damping force. Therefore,
An electric resistor corresponding to the discharge time constant of the electrorheological fluid, specifically, the resistance value of the resistance R and the capacitance value of the capacitance C of the equivalent circuit of the electrorheological fluid is used as a discharge path of the capacitance C of the equivalent circuit. By connecting the capacitor C in parallel, the discharge of the electric charge accumulated in the capacitor C can be promoted and the response of the damping force control can be secured. However, as described above, since the charging / discharging of the electrorheological fluid is switched by the supplied voltage value, the discharge path of the capacity C of the equivalent circuit of the electrorheological fluid is the same as the charging path. And therefore the capacitance C
The connection of the electrical resistor for promoting the discharge of 1 may be provided in parallel with the charging path of the capacitance C.

As described above, the damping force control device for the shock absorber using the electrorheological fluid according to the first aspect of the present invention, as shown in the basic configuration diagram of FIG. The electroviscous fluid whose viscosity changes accordingly is filled in the cylinder as the working fluid of the shock absorber, and when the piston slides in the cylinder, a damping force that damps the vibration between the two is generated near the orifice. In a damping force control device for a shock absorber using an electrorheological fluid controlled by the supply voltage supplied to the electrorheological fluid, a target charging voltage for charging the electrorheological fluid is set based on a physical quantity of motion generated in a vehicle. Target charging voltage setting means, actual charging voltage detecting means for detecting an actual charging voltage actually charged in the electrorheological fluid, and the target To the electrorheological fluid a supply voltage of a predetermined high frequency composed of a current in a predetermined one direction according to the target charging voltage set value set by the pressure setting means and the actual charging voltage detection value detected by the actual voltage detecting means. And a supply voltage output means for outputting.

In a shock absorber damping force control apparatus using an electrorheological fluid according to a second aspect of the present invention, the supply voltage output means has a primary side as shown in the basic configuration diagram of FIG. Which generates a predetermined AC high voltage on the secondary side by interrupting the DC current of the, the target charging voltage set value set by the target voltage setting means, and the actual charging detected by the actual voltage detecting means. The DC current on the primary side of the transformer is interrupted at the predetermined high frequency according to the detected voltage value,
An intermittent control unit for controlling the AC high voltage generated on the secondary side of the transformer to the AC high voltage of the predetermined high frequency, and the AC high voltage generated on the secondary side of the transformer to a half-wave high frequency high voltage. A half-wave rectifier for rectifying is provided.

According to a third aspect of the present invention, a damping force control device for a shock absorber using an electrorheological fluid has a discharge time constant of the electrorheological fluid in parallel with a discharge path to the electrorheological fluid. It is characterized in that an electric resistor having a predetermined resistance value set according to the connection is connected.

[0014]

In the shock absorber damping force control apparatus using the electrorheological fluid according to the first aspect of the present invention, the target charging voltage setting means, as shown in the basic configuration diagram of FIG. For example, a desired damping force of the shock absorber is set according to a turning physical momentum such as lateral acceleration or yawing momentum during vehicle traveling or a physical physical quantity such as a road surface bouncing input, and an electric fluid used as a working fluid in the shock absorber is set. In the viscous fluid, the target value of the charging voltage of the electro-rheological fluid sufficient to develop this damping force, more specifically, the charging voltage of the capacity C of the electro-rheological fluid itself in the electrical equivalent circuit as described above. The target value is set as the target charging voltage, while the actual charging voltage detecting means is the electro-rheological fluid used as the working fluid in the shock absorber. The actual charging voltage, more specifically, the actual charging voltage of the capacity C of the electro-rheological fluid itself in the electrical equivalent circuit is detected, and the supply voltage output means detects, for example, the target charging voltage set value and the actual charging voltage. A predetermined high frequency voltage signal having a voltage value corresponding to the deviation from the detected value and consisting of a current in only one direction of charging of the capacity C in the electrical equivalent circuit of the electrorheological fluid is used as the working fluid in the shock absorber. The electrorheological fluid used is supplied from an electrode provided near the orifice of the shock absorber. As a result, when the electrorheological fluid used as the working fluid in the shock absorber has a voltage value of the predetermined high frequency voltage signal larger than the actual charging voltage of the capacitance C in the electrical equivalent circuit of the electrorheological fluid. Only the current flows, and at other times, the capacity C is discharged. As a result, the charging voltage of the capacity C increases or decreases toward the target charging voltage set value, and the desired damping force appears in the shock absorber. As described above, the predetermined high frequency voltage signal is composed of a current flowing in one direction in which the capacitance C in the electrically equivalent circuit of the electrorheological fluid is charged. Therefore, the voltage value of the predetermined high frequency voltage signal is the electrorheological fluid. A current flows through the electrorheological fluid for a relatively short time, which is larger than the actual charging voltage of the capacitance C in the electrical equivalent circuit, and as described above, the electrical equivalent of the electrorheological fluid increases as the frequency of the voltage signal increases. Since the resistance value of the resistor R in the circuit increases, the current value itself flowing in the electrorheological fluid also decreases, so that the power consumed by the electrorheological fluid decreases and the amount of heat generation thereof decreases.

Further, in the damping force control device for a shock absorber using the electrorheological fluid according to the second aspect of the present invention, as shown in the basic configuration diagram of FIG. 1, the intermittent connection provided in the supply voltage output means. The control unit, depending on the target charging voltage setting value set by the target voltage setting means and the actual charging voltage detection value detected by the actual voltage detecting means, for example, when the deviation between them is large in the positive direction, the connection time , The DC current on the primary side of the transformer is interrupted at the predetermined high frequency so that the AC high voltage generated on the secondary side of the transformer is the AC high voltage of the predetermined high frequency. And, for example, the maximum voltage value in the charging direction of the capacity C in the electrical equivalent circuit of the electrorheological fluid is controlled to a high AC high voltage of a predetermined high frequency according to the deviation between the target charging voltage and the actual charging voltage, Half-wave rectifier Of the AC high voltage of the predetermined high frequency, the voltage component of the current which is not the charging direction of the capacitance C in the electrically equivalent circuit of the electrorheological fluid is removed to remove the charging direction of the capacitance C in the electrically equivalent circuit. The half-wave high-frequency high-voltage signal is effective for charging the capacitance C in the electrical equivalent circuit of the electrorheological fluid because it is rectified into half-wave voltage signal composed of only current. It is a high voltage signal generated on the secondary side at the moment when the secondary side is cut off or immediately after that, and the rising / falling edge thereof is extremely sharp. Therefore, the time for which the current flows for charging the capacitance C of the equivalent circuit is It becomes an extremely short time, and as a result, the average current value flowing in the electrorheological fluid becomes smaller, the power consumption becomes smaller, and the heat generation amount becomes smaller.

In the shock absorber damping force control apparatus using the electrorheological fluid according to the third aspect of the present invention, the discharge path of the electrorheological fluid, specifically, the electrical equivalent circuit of the electrorheological fluid. Discharge path of capacity C at
That is, since an electric resistor is connected in parallel with the electrorheological fluid itself, for example, the resistance value of this electric resistor is set to the resistance value of the resistance R and the capacitance value of the capacity C in the electrical equivalent circuit of the electrorheological fluid. By setting a resistance value sufficient to reduce the discharge time constant obtained from, the responsiveness is improved especially when the charging voltage of the electrorheological fluid is discharged to reduce the damping force of the shock absorber, and It becomes possible to secure the response of the damping force control to the road surface input.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing a first embodiment of the present invention, in which 10 is a vehicle body side member, and 11FL to 11FL.
RR indicates the front left to rear right wheels, and 12 indicates the damping force variable control type suspension.

The damping force controllable suspension 12 is
The viscosity of the vehicle body is changed between the vehicle body side member 10 and each wheel side member 14 of each of the wheels 11FL to 11RR, and the working fluid therein is changed in accordance with the frequency and the voltage value of the drive voltage signal supplied. Damping force variable shock absorbers 18FL to 18RR enclosing the electrorheological fluid 13 and vertical acceleration sensors 28FL to individually detect vertical accelerations on the vehicle body, that is, springs at positions corresponding to the wheels 11FL to 11RR, respectively. 28RR and front wheel side hydraulic cylinders 18FL and 18FR are arranged in parallel to each wheel 11FL to 11RR, that is, unsprung and vehicle body side member 1.
0, that is, the sprung vertical acceleration detection value Z of the stroke sensors 27FL to 27RR for detecting relative displacement with the sprung and the vertical acceleration sensors 28FL to 28RR.
_{1GFL to} Z _1GRR and stroke sensors 27FL to 27R
Based on the relative displacement detection values Z _{2XFL to} Z _2XRR between the sprung and unsprung portions of R, the damping force D / F of each damping force variable shock absorber 18FL to 18RR that achieves the desired vehicle behavior, that is, the sprung behavior, is achieved. So that the damping force variable shock absorbers 18FL to 18RR
And a control unit 30 for supplying the drive voltage signals V _{FL to} V _RR .

Variable damping force shock absorber 18F
Each of L to 18RR has a cylinder tube 18a as clearly shown in FIG. 3, and the inside of the cylinder tube 18a is located inside the upper fluid chamber 18a.
The piston 18c, which is separated between U and the lower fluid chamber 18L,
It is slidably arranged, and a piston rod 18b extends upward from the piston 18c. Then, the lower end of the cylinder tube 18a is the wheel-side member 14
The upper end of the piston rod 18b is attached to the vehicle body side member 10. A coil spring 36, which has a relatively low spring constant and supports a static load of the vehicle body, is disposed between the upper and lower springs of each of the damping force variable shock absorbers 18FL to 18RR.

In this embodiment, the upper fluid chamber 14U and the lower fluid chamber 14L separated by the piston 18c in each of the damping force variable shock absorbers 18FL to 18RR are the outer circumference of the piston 18c and the cylinder. It is connected via an orifice formed in the gap with the inner wall of the tube 18a, and the relative movement of the piston 18c and the cylinder tube 18a causes the viscous resistance of the working fluid to flow through this orifice (more strictly speaking, (Resistance force generated by viscosity against shear force due to flow)
However, the damping force is exerted on the vibration input that interacts between the unsprung part and the sprung part.

On the other hand, in this embodiment, the so-called electrorheological fluid 13 is used as the working fluid enclosed in the variable damping force shock absorbers 18FL to 18RR. When a voltage signal is supplied to the electrorheological fluid 13 as will be described in detail later, its viscosity changes in accordance with its frequency and voltage value. The damping force of the variable force shock absorbers 18FL to 18RR can be adjusted and controlled, and for that purpose, an electrode provided for supplying the voltage signal is provided in the orifice formed in the gap between the piston 18c and the cylinder tube 18a. Has been done. In this embodiment, as clearly shown in FIG. 3, each damping force variable shock absorber 18i (18FL
18RR), a backup material 18d longer than the longitudinal dimension of the piston 18c is attached to the outer circumference of the piston 18c, an inner electrode 24i is provided around the outer circumference, and the inner electrode is opposed to the inner electrode 24i. An outer electrode 24o longer than the longitudinal dimension of 24i is provided around the outer electrode 24o. Then, each damping force variable shock absorber 18
The inner electrode 24i of i is connected to the control unit 30 via the piston 18c and the piston rod 18b to be supplied with the drive voltage signal V _i (V _{FL to} V _RR ) and the outer electrode 24o is grounded. This electrode 24i, 24
Regarding the dimension setting of o, it is desired that the viscosity change range when a voltage signal is supplied to each electrode, that is, the damping force adjustment control range is wide, and for that purpose, a proposal is made in JP-A-62-15.
See Japanese Patent No. 1449 and Japanese Patent Laid-Open No. 63-83421. By the way, below the lower fluid chamber 18L,
A gas chamber 18f filled with high-pressure gas is formed by being tightly separated by a free piston 18e.

On the other hand, the vertical acceleration sensor 28FL
As shown in FIG. 4, each of the .about.28RL has a voltage of zero when the sprung vertical acceleration acting on the vehicle body is zero,
A sprung vertical acceleration detection value consisting of a positive analog voltage corresponding to the acceleration value when detecting an upward acceleration and a negative analog voltage corresponding to the acceleration value when detecting a downward acceleration. Z _{1GFL to} Z _1GRR are output to the control unit 30.

The stroke sensors 27FL-2FL are also used.
As shown in FIG. 4, each of the 7FR has the front wheel 11FL.
In order to detect the relative displacement between the vehicle body side member 10 and 11FR, that is, the relative displacement between the sprung portion and the unsprung portion, the vehicle height is calculated from the stroke sensors 27FL and 27FR with reference to the wheel side, that is, the unsprung portion. A neutral voltage of zero when the target vehicle height is set in advance, and a deviation when the vehicle height becomes higher than the target vehicle height, that is, a positive voltage according to the relative displacement between the sprung and unsprung, the vehicle height is the target. When the vehicle height becomes lower than the vehicle height, the deviation, that is, the sprung-unsprung relative displacement detection value Z _2XFL , which is a negative voltage according to the sprung-unsprung relative displacement
And Z _2XFR are output to the control unit 30.

The control unit 30 is shown in FIG.
As shown, the vertical acceleration sensors 28FL to 28FR
Sprung vertical acceleration detection value Z output from_1GFL~ Z
_1GRRAnd output from stroke sensors 27FL to 27RR
Relative displacement between sprung and unsprung Z_2XFL~ Z_2XRRIs input
Microcomputer 44 and this microcomputer
Target charge output from the computer 44 after D / A conversion
Voltage control signal U_FL~ U _RRAre supplied with each of these damping force
Inner electrode of variable shock absorber 18FL to 18RR
Drive voltage signal V for 24i_FL~ V_RRDrive to convert to
The circuits 46FL to 46FR are provided.

Here, the microcomputer 44 has an input side interface circuit 44a having at least an A / D conversion function, an output side interface circuit 44b having a D / A conversion function, an arithmetic processing unit 44c and a storage unit 44.
have d. Detections Z _{2XFL to} Z _2XRR and Z _{1GFL to} Z _1GRR from the sensors 27FL to 27RR and 28FL to _28RR are input to the input interface circuit 44a, and damping force variable shock absorbers 18FL to _18RR are output from the output side interface circuit 44b. The target charging voltages U _{FL to} U _RR for the electrorheological fluid 13 are output as control signals.

The arithmetic processing unit 44c will be described later.
6 is executed, and the predetermined sampling time ΔT (for example,
Every 5 msec), relative displacement Z between sprung and unsprung parts_2XFL~ Z
_2XRRAnd sprung vertical acceleration detection value Z_1GFL~ Z_1GRRTo
Read, from these, relative speed Z between sprung and unsprung_2VFL~
Z_2VRRAnd spring up-down velocity Z_1VFL~ Z_1VRRAnd calculate
Relative displacement between sprung and unsprung Z_2XFL~ Z_2XRREach dead zone
Threshold Z_2XFL0~ Z_{2XRR 0}Greater and sprung-unsprung
Relative speed Z_2VFL~ Z_2VRRIs the dead zone threshold Z _2VFL0~
Z_2VRR0Greater and velocity Z in the vertical direction of the spring_1VFL~
Z_1VRRAnd relative speed Z between sprung and unsprung_2VFL~ Z_2VRRWith
When the product is positive, for example in skyhook theory
According to the so-called Karnopp's law, etc., each damping force shock absorber
Sawber 18FL to 18RR for electrorheological fluid 13
Target charging voltage U_FL~ U_RRThe damping force variable shock absorber
The damping force D / F of Busorber 18FL to 18RR is high damping force.
Predetermined charging voltage U corresponding to_FLHiSet to the above
If the conditions are not satisfied, the damping force shock absorber
Sawber 18FL to 18RR for electrorheological fluid 13
Target charging voltage U_FL~ U_RRThe damping force variable shock absorber
Damping force D / F of Busorber 18FL to 18RR is low damping force
Predetermined charging voltage U corresponding to_FLLOSet these to
Target charging voltage U_FL~ U_RRThe applicable damping force variable shock
For the inner electrodes 24i of the absorbers 18FL to 18RR
Output.

Further, the storage device 44d stores a program necessary for the arithmetic processing of the arithmetic processing device 44c in advance, and has a high-speed RAM function for sequentially storing the arithmetic results required in the arithmetic process of the arithmetic processing device 44c. I have it. Next, the electrical characteristics of the electrorheological fluid described above will be described. There are several types of such electrorheological fluids that have the property of increasing viscosity by supplying a voltage signal, and it is currently unknown whether or not all of them have the same characteristics. FIG. 5 shows the electrical characteristics of a certain type of electrorheological fluid when a voltage signal of a relatively low frequency composed of a current flowing in one direction is supplied.
FIG. 5a shows the supplied voltage signal (referred to as applied voltage in the figure).
5a shows the current value flowing in the electrorheological fluid. As is clear from these, it can be seen that the current value flowing in the electrorheological fluid has a phase lead component with respect to the voltage signal supplied. Furthermore, the results of extensive verification of current flowing through the electro-rheological fluid, the current signal is the combined current of the current signal I _C flowing through the current signal I _R and the capacitor C through the resistor R as shown in FIG. 5c It can be seen that it is a signal, and therefore at least for such a relatively low frequency supply voltage signal, the electrical characteristics of this type of electrorheological fluid are represented by a simple equivalent circuit in which a resistance R and a capacitance C are connected in parallel. can do. Therefore, in the present embodiment, the charging voltage to the capacity C in the electrical equivalent circuit of the electrorheological fluid is adjusted and controlled to change and control the viscosity of the electrorheological fluid, whereby the damping force variable shock absorbers 18FL to 18FL. The damping force D / F of 18RR is adjusted and controlled. That is, if the voltage value of the voltage signal to be supplied is larger than the charging voltage of the capacity C in the electrical equivalent circuit of the electrorheological fluid, the capacity C is charged and the viscosity increases, and the damping force variable shock absorber 18FL ... If the damping force D / F of 18 RR becomes high and the voltage value of the voltage signal to be supplied is smaller than the charging voltage of the capacitance C in the electrically equivalent circuit of the electrorheological fluid, the capacitance C is discharged and the viscosity becomes Decreasing the damping force variable shock absorber 18F
The damping force D / F of L to 18RR becomes low.

On the other hand, the so-called Kar in the skyhook theory
According to the nopp rule, when the product value of the sprung vertical speed and the sprung-unsprung relative speed is positive, the damping force of the shock absorber is increased, and when the product value of both is negative, Since it is known that reducing the damping force of the shock absorber is ideal for vehicle motion characteristics including riding comfort, the microcomputer 44 of the control unit 30 performs the arithmetic processing shown in the flowchart of FIG. The damping force variable shock absorber 18F
A voltage control signal U _i (U _i = U _{FL to} U _RR ) sufficient for achieving the target damping force D / F of L to 18 _RR is set and output. In each of the damping force variable shock absorbers 18FL to 18RR using the electrorheological fluid 13, it is possible to change the damping force D / F to be variable, of course, but here, the damping force is simply set to be high or low. Setting adjustment control shall be performed depending on the damping force.

The arithmetic processing of FIG. 6 is executed by a timer interrupt which is interrupted at every predetermined sampling time ΔT (for example, 5 msec.) As described above. In addition, in this flow chart, no upper input / output step is provided,
The upper portion calculated or set by the arithmetic processing of the arithmetic processing device 44c is updated and stored in the storage device 44d at any time, and the upper portion stored in the storage device 52c is communicated and stored in the buffer of the arithmetic processing device 44c. It Moreover, during this processing, the sprung - dead zone threshold Z _2Xi0 between unsprung relative displacement _{(Z 2Xi0 = Z 2XFL0 ~Z 2XRR0} ) and the sprung - dead zone threshold between unsprung relative speed Z _2Vi0 (Z _2Vi0 = Z
_{2VFL0 to} Z _2VRR0 ), the control hunting between the low damping force and the high damping force as described above occurs with respect to the vibrations generated or input to the smaller damping force variable shock absorbers 18FL to 18RR, As a result, it is for preventing the excitation force from acting on the vehicle body.

In this calculation process, first, in step S1, the current value Z _{1Gi (n)} (Z _{) of} the sprung vertical acceleration detection value detected by the vertical acceleration sensors 28FL to 28RR is detected.
_{1Gi (n)} = Z _{1GFL (n) to} Z _{1GRR (n)} ) is read. Next, in step S2, the stroke sensor 27FL ...
_Current value of detected relative displacement between sprung and unsprung _parts detected at _27RR Z _{2Xi (n)} (Z _{2Xi (n)} = Z _{2XFL (n)} ~
Read Z _{2XRR (n)} ).

Next, in step S3, the current value Z _{1Gi (n) of} the sprung vertical acceleration detected value read in step S1 and the sprung vertical velocity updated and stored in the storage device 44d are stored. Previous value Z _{1Vi (n-1)} (Z _{1Vi (n-1)} = Z
_{1VFL (n-1) to Z1VRR (n-1)} ) and the current value of the sprung vertical velocity Z _{1Vi (n)} (Z _{1Vi (n)} = Z
_{1VFL (n) to} Z _{1VRR (n)} ) are calculated. Since this equation 1 integrates the sprung vertical acceleration detection value Z _1Gi to obtain the sprung vertical velocity Z _1Vi , for example, a digital low-pass filter or the like set to an appropriate cutoff frequency is used as a substitute. Of course, it is also possible to use known integration calculation processing.

Z _{1Vi (n)} = Z _{1Vi (n-1)} + Z _{1Gi (n) .ΔT} ... This time of the relative displacement detection value Z
_{2Xi (n)} and the previous value Z _{2Xi (n-1)} (Z
_{2Xi (n-1)} = _{Z2XFL (n-1) to Z2XRR (n-1)} ), and the current value Z of the sprung-unsprung relative velocity is calculated according to the following two equations.
_{2Vi (n)} ( _{Z2Vi (n)} = _{Z2VFL (n) to Z2VRR (n)} ) is calculated. Note that these two expressions differentiate the above-mentioned sprung-unsprung relative displacement detection value _Z2Xi to differentiate the sprung-unsprung relative velocity _Z2Vi.
Therefore, it is of course possible to substitute, for example, a digital high-pass filter or the like set to an appropriate cutoff frequency, and it is also possible to substitute known differential operation processing.

Z _{2Vi (n)} = (Z _{2Xi (n)} -Z _{2Xi (n-1)} ) / ΔT (2) Next, the process proceeds to step S5, and the _{sprung mass} read in step S2 is read. − It is determined whether or not the absolute value | Z _{2Xi (n)} | of the current value of the unsprung relative displacement detection value is equal to or less than the _preset dead zone threshold Z _2Xi0 of the sprung-unsprung relative displacement. If the absolute value | Z _{2Xi (n)} | of the current value of the relative displacement detection value between the sprung portion and the unsprung portion is equal to or less than the dead zone threshold Z _2Xi0 , the _{process proceeds} to step S6, and if not, the _{process proceeds} to step S7. Transition.

In step S6, the absolute value of the current value of the sprung-unsprung relative velocity calculated in step S4 |
It is determined whether Z _{2Vi (n)} | is equal to or less than the _preset dead zone threshold Z _2Vi0 of the sprung-unsprung relative velocity,
Absolute value of current value of relative speed between sprung and unsprung | Z
_{If 2Vi (n)} | is less than or equal to the dead zone threshold Z _2Vi0 , the _{process proceeds} to step S8, and if not, the above step S7.
Move to

In the step S7, the step S3
The _product value of the current value Z _{1Vi (n) of} the sprung vertical direction velocity calculated in step S4 and the current value Z _{2Vi (n)} of the sprung-unsprung relative velocity calculated in step S4 is larger than “0”. That is, it is determined whether the product value is positive, and if the product value is positive, the process proceeds to step S9, and if not, the step S8.
Move to

In step S8, the electrorheological fluid 1 of the damping force variable shock absorbers 18FL to 18RR is
The target charging voltage U _i for _{No. 3} is set to a predetermined value U _ilo of the low damping force sufficient to achieve a preset low damping force, and then the process proceeds to step S10. On the other hand, the step S
9, the damping force variable shock absorber 18FL ~
Target charging voltage U _i for electrorheological fluid 13 of 18 RR
_Is set to a high damping force side predetermined value U _iHi sufficient to achieve a preset high damping force, and then the process proceeds to step S10.

In the step S10, the step S
8 or the target charging voltage U _i set in step S9,
Applicable damping force variable shock absorber 18FL to 18
Output as a control signal to RR. Next in step S11
Then, the current value Z _{2Xi (n)} of the sprung-unsprung relative displacement detection value read in step S2 is changed to the previous value Z.
_It is updated and stored in the storage device 44d as _{2Xi (n-1)} .

Next, in step S12, the present value Z _{2Vi (n)} of the sprung-unsprung relative velocity calculated in step S4 is stored in the storage device 44d as the previous value Z _{2Vi (n-1).} After updating and storing, it returns to the main program. According to this arithmetic processing, for the vibration input and the vibration acting force of the sprung-unsprung relative displacement Z _2Xi and the sprung-unsprung relative velocity Z _2Vi that exceed the dead zone thresholds Z _2Xi0 and Z _2Vi0 , The sprung vertical velocity Z _1Vi and the sprung-unsprung relative velocity Z
_When the product value with _2Vi is positive, specifically, when the vehicle body goes up and the wheels relatively lower, or when the vehicle body goes down and the wheels relatively go up, the target charging voltage control signal U _i has a high damping force. side predetermined value U _IHI, and the sprung vertical velocity Z _1Vi and sprung - If the product value of the relative speed Z _2Vi between unsprung is negative, when in particular relatively wheels falls down the vehicle body When the vehicle body goes up and the wheels relatively go up, the target charging voltage control signal U _i becomes the low damping force side predetermined value U _iLO .
Therefore, each damping force variable shock absorber 18FL-1FL
The damping force D / F of 8RR is the Karnopp of Skyhook theory.
Since the control is performed according to the rules, it is considered that the vehicle motion characteristics including the riding comfort are improved. Further, each dead zone threshold Z _2Xi0, Z _2Vi0 on the following spring - between unsprung relative displacement Z _{2X i} and sprung - with respect to the vibration input and the vibration acting force relative speed Z _2Vi between unsprung, the target charging voltage Since the control signal U _i becomes the low damping force side predetermined value U _iLO , the damping force D / F of each damping force variable shock absorber 18 FL to 18 RR becomes a low damping force that does not vibrate the vehicle body, and also in a heavy vehicle. It is thought to achieve a comfortable and profound ride quality that can be seen.

Next, in the present embodiment, the damping force variable shock absorbers 18FL to 18R corresponding to the target charging voltage U _i are used.
To obtain a damping force D / F of R, a description will be given of the basic principle for supplying a driving voltage signal V _i from the inner electrode 24i to the electrorheological fluid 13 as a working fluid of the damping force control shock absorber 18FL～18RR. As described above, the electrical characteristics of a certain electrorheological fluid used in this embodiment can be represented by a simple equivalent circuit in which a resistance R and a capacitance C are connected in parallel. Therefore, when supplying a drive voltage signal to the electrorheological fluid, if the drive voltage signal is an AC voltage signal, as the frequency increases,
As is known, the impedance of the capacitance C of the electrorheological fluid itself decreases, so that the amount of current flowing through the electrorheological fluid increases, power consumption increases, and the temperature of the electrorheological fluid rises. When the drive voltage signal supplied to the electrorheological fluid is a DC voltage signal, the resistance R of the electrorheological fluid itself increases as the voltage value of the DC voltage signal increases.
The amount of current flowing through the electrorheological fluid increases and the temperature of the electrorheological fluid rises, and with some electrorheological fluid, the resistance value of the resistance R of the electrorheological fluid itself decreases with the temperature rise. Therefore (see FIG. 7), when the voltage value of the supplied DC voltage signal increases, the current flowing through the resistance R of the electrorheological fluid itself further increases, power consumption increases, and the temperature of the electrorheological fluid further increases. To do.

When the temperature of the working fluid composed of the electrorheological fluid is further increased by the voltage signal supplied for controlling the damping force of the shock absorber in this way, the operating temperature range of the working fluid is narrowed. Further, in the electrorheological fluid in which the resistance value of the resistance R of the electrorheological fluid itself in the equivalent circuit decreases as the temperature rises,
If the value of the current that flows to avoid the thermal runaway, that is, the voltage value of the supply voltage signal is limited, the target damping force of the shock absorber is limited. Furthermore, as described above, when the power consumption increases, the load of the generator (alternator), that is, the load of the engine (engine) increases, so that the distance that can be run with a constant fuel is shortened and the fuel consumption deteriorates.

Therefore, in this embodiment, since a certain type of electrorheological fluid is represented by an equivalent circuit in which the resistance R and the capacitance C are connected in parallel as described above, the capacitance of the electrorheological fluid itself. By controlling the current for intermittently charging C, the charging voltage of the capacitance C is set to a voltage sufficient to achieve the target viscosity, that is, the damping force of the shock absorber. It was found that the value of the flowing current was small. That is, as described above, the electrical characteristic of the electrorheological fluid is represented by an equivalent circuit in which the resistance R and the capacitance C are connected in parallel, because the supply voltage signal is the capacitance C concerned.
When the supply voltage signal is higher than a predetermined frequency at a relatively low frequency composed of a current flowing in the charging direction, the electric characteristics of the electrorheological fluid are complicated by the resistance R and the capacity C alone. It becomes a shape. From these facts, it goes without saying that the impedance of the electrorheological fluid increases in the high frequency region of the supply voltage signal, but as shown in FIG. 8, the resistance value of the resistance R of the electrorheological fluid itself is the frequency of the supply voltage signal. Since it has a characteristic that increases with the increase of
If the frequency of the supply voltage signal consisting only of the current that charges the capacitance C of the electrorheological fluid itself is increased as shown in b, the resistance value of the resistance R increases and the current flowing through the electrorheological fluid as shown in FIG. 9c. It is considered that the value (average current value) decreases. Therefore, the target charging voltage U _i, which is set by the processing of FIG. 6, to detect the actual charging voltage U _ch being charged to said electro-rheological fluid, the actual charging voltage with respect to the target charging voltage U _i U _A high-frequency high-voltage signal that is a high-frequency high-voltage signal that can obtain a voltage value according to the deviation e _ERR of _ch and that consists of a unidirectional current only in the charging direction of the capacity C of the electro-viscous fluid itself is The fluid may be supplied at the timing of charging / discharging the fluid. And
In order to further reduce the average current value flowing in the electrorheological fluid, the time required to charge the capacity C of the electrorheological fluid itself is shortened, and the current value flowing during that time is averaged in a cycle satisfying the predetermined high frequency. For that purpose, the time required for the rising / falling of the voltage signal to be supplied can be shortened as much as possible, and the intermittent period of the direct current flowing through the primary side of the transformer can be set to the above predetermined value. It suffices to perform half-wave rectification on the high-frequency AC high-voltage signal generated on the secondary side in accordance with the high frequency.

Based on the above-mentioned principle of the invention, by obtaining the target charging voltage U _i set in the calculation process of FIG. 6 for the electrorheological fluid 13 of each damping force variable shock absorber 18i (18FL to 18RR). , The damping force variable shock absorber 18i develops a desired damping force D / F, and the average current value flowing through the electrorheological fluid 13 is reduced to reduce power consumption and heat generation amount. Drive circuit 46i of unit 30
FIG. 10 shows a specific circuit configuration of (46i = 46FL to 46RR). In the figure, the electro-rheological fluid 13 which is the working fluid of each damping force variable shock absorber 18i is connected to the electrodes 24i and 24o with the capacitance 13C (impedance r _C ) and the resistor 13R (resistance r) in parallel. It is shown as an electrically equivalent circuit that is connected, but its function as a damper is not shown in the circuit.

This drive circuit 46i has a primary coil L ₁
Has one end connected to the DC battery voltage + B, the other end grounded via a switch (substantially a switching element) 53, and one end of the secondary coil L ₂ having a half-wave rectifier (specifically, a diode element). Is connected to the inner electrode 24i for supplying a voltage signal to the electrorheological fluid 13 via 55,
The transformer 54 whose other end is grounded, the charging voltage detector 49 for detecting the actual charging voltage U _ch of the electrorheological fluid 13 of each damping force variable shock absorber 18i, the target charging voltage U _i and the actual charging The error detector 50 for detecting the error voltage e _ERR with the voltage U _ch, and the triangular wave voltage e serving as the reference wave
A triangular wave oscillator 51 for generating _TRI and the error voltage e
_{The ERR} and the triangular wave voltage e _TRI are compared, and the switch 53 is compared.
Comparator 5 that generates switching voltage S _SW that controls switching
2 and.

The charging voltage detector 49 is stored in the actual charging voltage of the electrorheological fluid 13 which is the working fluid of each damping force variable shock absorber 18i, more specifically, in the capacity 13C of the electrorheological fluid 13 itself. The actual charging voltage U _ch is output by resistance division. The error detection value 50
The error value e _ERR is a voltage value obtained by subtracting the actual charging voltage U _ch detected by the charging voltage detector 49 from the target charging voltage U _i set in the microcomputer 44 by the calculation process of FIG. Output. The triangular wave oscillator 51 outputs a triangular wave voltage e _TRI as a reference wave which is composed of a current in a predetermined direction and which increases and decreases in a cycle T satisfying the predetermined high frequency (for example, about 10 kHz). The comparator 52 outputs the error voltage e _{ERR based} on the triangular wave voltage e _TRI.
Is larger, the logical value becomes "1", and the error voltage e
Logical value “0” when triangular wave voltage e _TRI is larger than _ERR
And outputs the switching voltage S _SW . The voltage value corresponding to the logical value “1” of the switching voltage S _SW is also _referred to as S _SWHi, and the voltage value corresponding to the logical value “0” is S _SWHi.
It is also indicated as _SWLO, and it is _{assumed that} the switch 53 is closed when the switching voltage S _SW has a logical value “1” or a voltage value S _SWHi corresponding thereto, and is opened otherwise. That is, in the drive circuit 46i, the charging voltage detector 49, the error detector 50, the triangular wave oscillator 51, and the comparator 52 control the pulse width modulation of the primary side current of the transformer 54, so-called PWM (Pulse Width Modulation). Control is made.

Therefore, in the drive circuit 46i, the target charging voltage U _i and the actual charging voltage U output from the error detector 50 are set.
_The greater the error voltage e _ERR with _ch , the longer it takes to exceed the triangular wave voltage e _TRI output from the triangular wave oscillator 51, and as a result, the switching voltage S _SW output from the comparator 52 becomes logical. Since the value “1” or the voltage value S _SWHi corresponding thereto becomes long, the switch 53 is closed for a correspondingly long time, and the amount of electricity supplied to the primary coil L _{1 of} the transformer 54 increases, and conversely. The time that the switch 53 is open becomes shorter. Generally, the maximum voltage value generated in the secondary coil when the direct current flowing in the primary coil is cut off is proportional to the energization amount of the primary coil (easy to understand if considered as electrical energy). Therefore, when the actual charging voltage U _ch is lower than the target charging voltage U _i as described above, the error voltage e _ERR exceeds the triangular wave voltage e _TRI for a long time, resulting in a voltage change. The time during which the DC voltage + B is flowing in the primary side coil L ₁ of the container 54 increases, and the amount of energization increases.
When the secondary coil L ₁ is cut off, the target charging voltage U _i
Voltage value V corresponding to the deviation of the actual charging voltage U _{ch from}
A drive voltage signal V _i having _iMAX is generated via the half-wave rectifier 55. That is, when the target charging voltage U _i increases from the low damping force side predetermined value U _iLO to the high damping force side predetermined value U _iHi , the maximum voltage value V _iMAX of the drive voltage signal V _i increases, so that the electrorheological fluid is generated. When the actual charging voltage U _ch matches or almost matches the target charging voltage U _i , the capacity 13C of the capacitor 13 is charged relatively quickly, and the damping force D / F of the damping force variable shock absorber 18i is a predetermined high damping force. become.

On the other hand, a current for charging (current i _C flowing in the capacity 13c in FIG. 10) flows through the electrorheological fluid 13, more specifically, the capacity 13C of the electrorheological fluid 13 itself, because it is the actual charging. Only when the driving voltage signal V _i supplied is larger than the voltage U _ch , and at other times, the discharge time constant corresponding to the capacitance value of the capacitance 13C and the resistance value of the resistor 13R in the electrical equivalent circuit. Is discharged (current i _R flowing through the resistor 13R in FIG. 10). However, since the value of the current flowing during discharging is extremely smaller than the value of the current flowing during charging, it is assumed here to be “0” or almost “0”. Further, according to this principle, the target charging voltage U _i is the predetermined value U on the high damping force side.
becomes smaller from _iHi to low damping force side predetermined value U _iLO, the time error voltage e _{ER R} becomes less time exceeds the triangular wave voltage e _TRI switch 53 is closed is shortened, resulting in drive Maximum voltage value V _iMAX of voltage signal V _i
Therefore, the actual charging voltage U _ch charged in the capacity 13C of the electrorheological fluid 13 is discharged at the discharge time constant, and the actual charging voltage U _ch eventually matches or substantially matches the target charging voltage U _i. Then, the damping force D / F of the damping force variable shock absorber 18i becomes a predetermined low damping force.

Next, the operation of the arithmetic processing of FIG. 6 and the drive circuit of FIG. 10 will be described with reference to the timing chart of FIG. This timing chart simulates each voltage and current before and after the target charging voltage U _i is changed from the low damping force side predetermined value U _iLO to the high damping force side predetermined value U _iHi at time t _07. FIG. 11a shows the change with time of the target charging voltage U _i , and FIG. 11b shows the triangular wave voltage e _TRI.
And the error voltage e _ERR with time, FIG. 11c shows the switching voltage S _SW with time, and FIG. 11d shows the actual charging voltage U _ch.
And the change over time of the drive voltage signal V _i , and FIG. 11e shows the change over time of the charging current i _C. Since the frequency of the triangular wave voltage e _TRI is a high frequency of about 10 kHz as described above, it should be understood that this timing chart is obtained by appropriately extending the time axis which is the horizontal axis. Also, FIG.
The drive voltage signal V _i which is the output voltage from the drive circuit 46i is shown by a thin solid line and a two-dot chain line in FIG.
The actual charging voltage U _ch and is supposed equivalent, where it is to be understood that conceptually shows the output voltage value of the voltage value or half-wave rectifier 55 of the secondary coil L ₂ of the transformer 54.

At the time shown in this timing chart, from time t ₀₁ to time t _06, it can be said that the damping force D / F of the damping force variable shock absorber 18i is a steady state in which the damping force is low. From time t ₀₆ to time t ₁₇ including time t ₀₇ when the target charging voltage U _i is changed, the damping force D / of the damping force variable shock absorber _{18 i} is
It can be said that F is a transitional state in which the damping force is changed and adjusted from the low damping force to the high damping force. From time t ₁₇ to time t ₂₅ , the damping force D / F of the variable damping force shock absorber 18i is the high damping force. It can be said that it is in a steady state.

First, the damping force variable shock absorber 18
Consider time t ₀₁ to time t _{06 when} the damping force D / F of i is constantly low. Here, the error voltage e _ERR between the low damping force side predetermined value U _iLO set to the target charging voltage U _i and the actual charging voltage U _ch is comparatively small, and therefore, the triangular wave voltage e _TRI which becomes the reference wave is The time being exceeded, for example, time t ₀₂ −t ₀₃ or time t ₀₄ −
t ₀₅ is the triangular wave voltage e that satisfies the predetermined high frequency.
Time t ₀₂ -t ₀₄ and time t ₀₄ -t corresponding to the cycle T of _{TRI
Since the} switching voltage S _SW output from the comparator 52 by the PWM control is a logical value “1” or a voltage value S _SWHi corresponding to the switching voltage S _SWHi because it is relatively shorter than ₀₆ (t ₀₂ −t ₀₃ , t ₀₄ −t ₀₅ ) becomes short, and therefore the amount of electricity to the primary coil L _{1 of the} transformer 54 is small, so that when the switch 53 is cut off, the transformer 54
The voltage signal generated in the secondary coil L ₂ is conceptually the drive voltage signal V _i indicated by the thin solid line and the chain double-dashed line in FIG. 11d.
, The maximum voltage value V _{iM AX} becomes relatively small, and the driving voltage signal V output from the half-wave rectifier 55
_i is conceptually supplied to the electrorheological fluid 13 only in the portion shown by the thin solid line in FIG. 11d.

And this conceptually the thin solid line of FIG. 11d
Drive voltage signal V of only the part indicated by_iIs electrorheological fluid 13
Is supplied to the drive voltage signal V_iIs the electric viscosity
Actual charging voltage U of fluid 13_chOnly when it exceeds
The charging current i is applied to the capacitance 13C of the electrorheological fluid 13 itself._C
Flows and the charging voltage U_chAnd other times
According to the discharge time constant, the volume of the electrorheological fluid 13 itself is
The electric charge of 13C is discharged, and the discharge current i flows through the resistor 13R._R
Flows and the charging voltage U_chDecreases. Here as mentioned above
Discharge current i_RIs neglected, the
Supplied conceptual drive voltage signal V_iIs one of the transformers 54
Secondary coil L₁At the moment when the DC voltage + B of
Immediately after the secondary coil L₂Rise / fall that occurs in
The electrorheological fluid 13 becomes extremely steep.
Charge current i to its own capacity 13C_CTime is flowing
It gets shorter. Also, this damping force variable shock absorber
The damping force D / F of the bar 18i is constantly low.
Time t₀₁From time t₀₆Up to about the electroviscosity
Conceptual driving voltage signal V supplied to the fluid 13_iMaximum of
Voltage value V_iMAXIs also small, the electrorheological fluid 13 itself
Current i flowing in the capacitor 13C of_CMaximum current value i_CMAX
Is also smaller. Also, basically the triangular wave voltage e _TRICycle of
Shorten T and set the PWM control frequency to about 10kHz.
Because of the high frequency, as described above, the electrorheological fluid 13
The resistance value of its own resistor 13R may be large.
Thus, the conceptual drive supplied to the electrorheological fluid 13
Voltage signal V_iOn the other hand, the current value flowing through the resistor 13R is
Get smaller. From the above, this time t₀₁From time t₀₆Until
Average charging current i flowing in the electrorheological fluid of_CAVE(here
(Represented as a moving average value) is shown by a two-dot chain line in FIG.
Power consumption is reduced
At the same time, the amount of heat generated is also reduced.

Next, at time t ₀₇ , the target charging voltage U _i is changed from the low damping force side predetermined value U _iLO to the high damping force side predetermined value U _iHi , and the damping force variable shock absorber _{18 i} is changed.
The time t ₀₆ to the time t ₁₈ including the time t _{07 at} which the damping force D / F of the above transiently changes from the low damping force to the high damping force will be considered. Here, time t from time t ₀₆ to time t ₀₇
In ₀₆ -t _07, but changes over time in the same signal and the time t ₀₁ -t ₀₆ is continued, the target charging voltage U _i in this time t ₀₇
From the low damping force side predetermined value U _iLO to the high damping force side predetermined value U _iHi
In order to make a so-called step-up, after this time t ₀₇ , the error voltage e _ERR output from the error detector 50 becomes large. Therefore, this error voltage e _ERR is equal to the triangular wave voltage e
Increases the time t ₀₇ -t ₀₈ until time t ₀₈ below _TRI, thus switching voltage S _SW outputted from the comparator 52, the voltage value S _SWHi corresponding to "1" or the logic value
The time t ₀₆ -t ₀₈ becomes longer, and accordingly, the amount of electricity supplied to the primary coil L _{1 of the} transformer 54 increases, and when the switch 53 is cut off at the time t ₀₈ , the transformer concerned. The voltage signal generated in the secondary side coil L ₂ of 54 is a relatively large maximum voltage value V _iMAX , like the driving voltage signal V _i conceptually shown by the thin solid line and the two-dot chain line in FIG. Further, the driving voltage signal V _i output from the half-wave rectifier 55 is conceptually supplied to the electrorheological fluid 13 only in the portion shown by the thin solid line in FIG. 11d.

And this conceptually the thin solid line of FIG. 11d
Maximum voltage value V of only the part indicated by_iMAXLarge drive voltage signal
Issue V_iIs supplied to the electrorheological fluid 13, the same as above
This drive voltage signal V_iIs the actual filling of the electrorheological fluid 13.
Electric voltage U_chElectrorheological fluid 1 only when
Charging current i to the capacitance 13C of 3 itself._CIs flowing and charging
Pressure U_chHowever, the conceptual drive voltage signal
Issue V_iMaximum voltage value V _iMAXCapacity increases to 13C
The amount of accumulated charge also increases, and as a result, the actual charging voltage U_chIs
Increase relatively large. However, as mentioned above, the discharge current
i_RIs ignored, the electrorheological fluid 13 is supplied with
Conceptual drive voltage signal V_iIs the extreme rise / fall
Since it becomes steep, the volume of the electrorheological fluid 13 itself is
Charge current i to quantity 13C_CIs very short
Yes. Therefore, this conceptual drive voltage signal V_iIs the actual charging voltage
Pressure U_chWhen the temperature falls below the level, the capacity 13 of the electrorheological fluid 13 itself is again detected.
C starts discharging and the actual charging voltage U that continues discharging_chof
Target charging voltage U_iError voltage e_ERRIs the time t₀₉
And triangular wave voltage e_TRIExceeded. Error voltage e at this time
_ERRIs the actual charging voltage U of the electrorheological fluid 13._chIs increasing
The time t₀₇-T₀₈Actual charging voltage U_chThan
Is also small, but the time t is still₀₁-T₀₆Actual charging voltage U_ch
Correspondingly larger than.

Therefore, the time t ₀₉ -t ₁₀ until the time t ₁₀ when the error voltage e _ERR becomes lower than the triangular wave voltage e _TRI becomes longer, so that the switching voltage S _SW output from the comparator 52 has a logical value. The time during which the voltage value S _SWHi is "1" or equivalent (t ₀₉ -t ₁₀ ) is further lengthened, and therefore the amount of electricity to the primary coil L _{1 of the} transformer 54 is further increased. The conceptual drive voltage signal V generated when the switch 53 is cut off at the time t _10.
i becomes a larger maximum voltage value V _{iMAX in} only the portion shown by the thin solid line in FIG. 11d and is supplied to the electrorheological fluid 13. Then, when the driving voltage signal V _i having a conceptually larger maximum voltage value V _iMAX is supplied to the electrorheological fluid 13, the maximum voltage value V _{iMAX of the} conceptual driving voltage signal V _i is supplied.
The amount of electric charges accumulated in the capacitor 13C also increases with the increase of the charge current, and as a result, the actual charging voltage U _ch increases further greatly. However, as described above, the conceptual drive voltage signal V _i supplied to the electrorheological fluid 13 has an extremely steep rise / fall, so that the capacitance 1 of the electrorheological fluid 13 itself is increased.
The time during which the charging current i _C is flowing to 3C is extremely short, and the conceptual driving voltage signal V _i falls below the actual charging voltage U _ch , and at the same time when the actual charging voltage U _ch starts discharging, with respect to the target charging voltage U _i . The error voltage e _ERR exceeded the triangular wave voltage e _TRI at time t ₁₁ . The error voltage e _{ERR at} this time is because the actual charging voltage U _ch of the electrorheological fluid 13 increases,
It is smaller than the actual charging voltage U _{ch at} the time t ₀₉ -t ₁₀ .

Therefore, this error voltage e_ERRIs the triangular wave voltage
e_TRITime t below₁₂Time to₁₁-T₁₂Is the above
Time t₀₉-T_TenA little shorter than that of the comparator 52.
Switching voltage S output from_SWIs a logical value "1"
Or the voltage value S corresponding to it _SWHiHas become (t
₁₁-T₁₂) It becomes slightly shorter, and therefore the primary side of the transformer 54
Coil L₁The amount of electricity supplied to
₁₂Conceptually occurs when the switch 53 is cut off by
Drive voltage signal V_iIs the time T_TenMaximum voltage value V_iMAX
Only the part shown by the thin solid line in FIG.
Maximum voltage value V_{iM AX}To have electrorheological fluid 1
3 is supplied. Then, this conceptually maximum voltage value V
_iMAXLarge drive voltage signal V_iIs supplied to the electrorheological fluid 13.
When the power is supplied, the result is that the amount of charge increases accordingly.
Actually the actual charging voltage U_chIs relatively large. Only
However, as described above, the capacity 13 of the electrorheological fluid 13 itself
Charge current i to C_CIs flowing for a very short time,
Conceptual drive voltage signal V_iIs the actual charging voltage U_chBelow
The actual charging voltage U that continues to be discharged from_chTarget charging voltage U_iTo
Error voltage e_ERRIs the time t₁₃And triangular wave voltage e_TRI
Exceeded. Error voltage e at this time_ERRIs the electric viscosity
Actual charging voltage U of the oxidative fluid 13_chBecause of the increase in
Interval t₁₁-T₁₂Actual charging voltage U_chSmaller than.

Thereafter, at time t₁₃From the error voltage e_ERRBut
Triangle wave voltage e_TRITime t below₁₄After that,
Pressure e_ERRIs the triangular wave voltage e_TRITime t that exceeds_FifteenUntil
Interval t ₁₃-T_Fifteen, The time t_FifteenFrom the error voltage e_ERRIs a triangle
Wave voltage e_TRITime t below ₁₆And the error voltage e
_ERRIs the triangular wave voltage e_TRITime t that exceeds₁₇Time to
₁₃-T₁₇Actual charging voltage U_chGradually becomes the target charging voltage U
_iError voltage e of both_ERRGradually
While decreasing to the time t₁₁-T₁₃Similar to Figure 11d
Conceptual drive voltage signal V shown only by the thin solid line_i
Is supplied to the electrorheological fluid 13, however
Error voltage e_ERRIs gradually reduced, the comparator
Switching voltage S output from 52_SWIs a logical value
"1" or voltage value S corresponding to it_SWHiWhen
The distance between the two is gradually shortened, and as a result, the primary coil of the transformer 54 is
Le L₁The amount of electricity to the switch gradually decreases, and the switch 53
Drive voltage signal V generated when the power is cut off_i
Maximum voltage value V_iMAXBecomes gradually smaller, and the electric viscosity
Actual charging voltage U of fluid 13_chGradually becomes the target charging voltage U_iTo
Asymptotically, the damping force variable shock absorber 18i
The damping force D / F gradually approaches the target high damping force.

This damping force variable shock absorber 18i
At time t ₀₆ -t ₁₇ , which corresponds to a so-called transition period, in which the damping force D / F of the battery is changed and controlled from a low damping force to a high damping force, the maximum current value i _CMAX of the charging current i _C is as described above. Although it becomes large, the energizing time is short, and basically the cycle T of the triangular wave voltage e _TRI is shortened to set the PWM control frequency to the high frequency of about 10 kHz, similarly to the time t ₀₁ -t _06. Since the resistance value of the resistance 13R of the electrorheological fluid 13 itself is large, the electrorheological fluid 1
The current value flowing through the resistor 13R becomes smaller than the conceptual drive voltage signal V _i supplied to No. 3, and as described above, the average charging current i _CAVE flowing in the electrorheological fluid from time t ₀₆ to time t _17. Although the (moving average value) slightly increases as shown by the chain double-dashed line in FIG. 11e, it becomes a sufficiently small current value and the power consumption is reduced, and at the same time, the heat generation amount is also reduced.

Next, the damping force variable shock absorber 18
When the damping force D / F of i is steadily stable to a high damping force
Tick t₁₇From time t_{twenty five}Consider Here the goal
Charging voltage U_iHigh damping force side predetermined value U set to_iLO
And the actual charging voltage U_chError voltage e_ERRIs the low damping force
Time t corresponding to the stationary phase₀₁-T₀₆Error voltage e_ERRThan
Although it is also large, the time equivalent to the transition period of the damping force change setting
t₀₆-T₁₇Error voltage e_ERRSmaller than. Therefore this
Is the triangular wave voltage e that is the reference wave_TRIAbove
For example, here time t₁₇-T₁₈And time t₁₉-T
₂₀Is the triangular wave voltage e that satisfies the predetermined high frequency.
_TRITime t corresponding to the cycle T of₁₇-T₁₉And time t ₁₉-T
_{twenty one}It becomes a little short for. Therefore, according to the PWM control
The switching voltage S output from the comparator 52_SWBut
Logical value "1" or voltage value S corresponding to it _SWHiBecome
Time (t₁₇-T₁₈, T₁₉-T₂₀) Is the damping force change
Time t during the further setting transition period₀₆-T₁₇Relative to that of
To the primary coil L of the transformer 54.₁To
The switch 53 is cut off because the amount of electricity is rather large.
Sometimes the secondary coil L of the transformer 54₂Electricity generated in
The pressure signal is conceptually represented by a thin solid line and a two-dot chain line in FIG. 11d.
Drive voltage signal V shown_i, The maximum voltage value V_iMAXNoya
And the output from the half-wave rectifier 55.
Drive voltage signal V_iIs conceptually represented by the thin solid line in FIG. 11d.
Only the portion shown is supplied to the electrorheological fluid 13.

Then, the driving voltage signal V _{i of} this conceptually only the portion shown by the thin solid line in FIG.
To the drive voltage signal V _{i in the same} manner as described above.
Is above the actual charging voltage U _ch of the electrorheological fluid 13, the capacity 13C of the electrorheological fluid 13 itself is
A charging current i _C flows through the charging voltage U _ch to increase the charging voltage U _ch , and at other times, according to the discharging time constant, the electrorheological fluid 1 is discharged.
The electric charge of the capacitor 13C of 3 itself is discharged and the resistor 13R
The discharge current i _R flows through the charge current U _ch and the charge voltage U _ch decreases. Then, similarly to the above, since the conceptual drive voltage signal V _i supplied to the electrorheological fluid 13 has an extremely steep rise / fall, the capacitance 13C of the electrorheological fluid 13 itself is changed. The time during which the charging current i _C is flowing is extremely short. Also, as in the above, basically, the triangular wave voltage e _TRI
Of the PWM control frequency is set to 10 kHz by shortening the cycle T of
Since the resistance value of the resistance 13R of the electrorheological fluid 13 itself is large as described above because the frequency is set to a high frequency, the conceptual drive voltage signal V _i supplied to the electrorheological fluid 13 is generated. On the other hand, the current value flowing through the resistor 13R becomes smaller. From the above, from time t ₁₇ to time t
_The average charging current i _CAVE (moving average value) flowing in the electrorheological fluid during the time t ₁₇ -t _{25 up} to ₂₅ becomes a sufficiently small current value as shown by the chain double-dashed line in FIG. At the same time, the amount of heat generated is also reduced.

From the above, it is considered that the present embodiment is an implementation of the damping force control device for the shock absorber using the electrorheological fluid according to claims 1 and 2 of the present invention, and the calculation of FIG. The process and the microcomputer 44 of FIG. 4 or FIG. 10 correspond to the target charging voltage setting means of the damping force control device of the shock absorber using the electrorheological fluid of the present invention. Similarly, charging in the control unit of FIG. The voltage detector 49 corresponds to the charging voltage detecting means, and the error detector 50, the triangular wave oscillator 51, the comparator 52, and the switch 53 in the control unit of FIG.
Corresponds to the intermittent control unit.

Next, a second embodiment of the present invention will be described with reference to the drawings. The vehicle schematic configuration and operation of this embodiment are as follows.
Since it is similar or almost the same as that of the first embodiment shown in FIG. 2, its detailed description is omitted. Further, the configuration of the damping force variable shock absorber used in this embodiment is
Since it is similar or almost the same as that of the first embodiment shown in FIG. 3, its detailed description is omitted. Further, since the configuration and the action of the electrorheological fluid used as the working fluid of the variable damping force shock absorber in this embodiment are the same as or substantially the same as those of the first embodiment shown in FIG. I will omit the explanation. The electrode structure for supplying the driving voltage signal to the electrorheological fluid used as the working fluid of the variable damping force shock absorber in this embodiment is the same as or substantially the same as that of the first embodiment shown in FIG. Therefore, the detailed explanation is omitted.

Further, in the present embodiment, in order to adjust and control the damping force of the variable damping force shock absorber, the construction and operation of the vertical acceleration sensor for detecting the sprung vertical acceleration are the same as those of the first embodiment shown in FIG. The detailed description is omitted because it is the same as or substantially the same as that of the embodiment. Also,
In this embodiment, in order to adjust and control the damping force of the damping force variable shock absorber, the structure and operation of the stroke sensor for detecting the relative displacement between the sprung and unsprung portions are the same as those of the first embodiment shown in FIG. The detailed description is omitted because it is similar or almost the same.

Further, in the present embodiment, the configuration of the control unit that controls the damping force adjustment control of the variable damping force shock absorber is the same as that of the first embodiment shown in FIG. 4 except for the configuration of the specific drive circuit. The detailed description is omitted because it is similar or almost the same. The structure and the basic operation of the microcomputer that controls the calculation and setting output of the target charging voltage control signal in the control unit are the same as or substantially the same as those of the first embodiment shown in FIG. I omit the detailed explanation for that.

The electric characteristics of the electrorheological fluid used as the working fluid of the variable damping force shock absorber in this embodiment are similar to or substantially the same as those of the first embodiment shown in FIG. I will omit the detailed explanation. Further, since the basic principle of setting and controlling the damping force of each damping force variable shock absorber using the electrical characteristics of the electrorheological fluid is the same as or substantially the same as that described in the first embodiment. I will omit the detailed explanation. Further, based on the basic principle of setting and controlling the damping force of the damping force variable shock absorber, arithmetic processing executed by a microcomputer to calculate and output a target charging voltage control signal for the electrorheological fluid and its operation With respect to the above, the detailed description thereof will be omitted because it is similar or almost the same as that of the first embodiment shown in FIG.

Further, regarding the basic principle of the drive voltage signal setting output to be supplied to the electrorheological fluid used as the working fluid of the damping force variable shock absorber in this embodiment, the first embodiment using FIGS. The detailed description is omitted because it is similar or almost the same as the description in 1. Next, the basic principle of the damping force adjustment control responsiveness improvement when an electrorheological fluid is used as the working fluid of the damping force variable shock absorber in this embodiment will be described.

The response delay when the charging voltage charged in the electrorheological fluid is lowered as described above is obtained from the capacitance value of the capacitance C and the resistance value of the resistor R for smoothing in the electrical equivalent circuit. Although it will be determined by the discharge time constant, the resistance value of the resistor R related to the discharge time constant is set in order to reduce the current value flowing through the resistor R to reduce the power consumption and heat generation amount in the electrorheological fluid. In reality, the resistance value is relatively large, and the discharge time constant of the electrorheological fluid itself is relatively large. Therefore, by using only this electrorheological fluid, the target charging voltage control signal from the microcomputer is changed from the so-called logical value "1" corresponding to the high damping force side predetermined value to the low damping force side predetermined value as described above. When the setting is changed to the corresponding logical value "0", the charging voltage of the electrorheological fluid appears with a large response delay as shown by the broken line in FIG. Therefore, it can be seen that the responsiveness at the time of setting the change from the high damping force to the low damping force is inferior.

Therefore, an electric resistor is connected in parallel with the capacitance C of the electrorheological fluid itself in the electrical equivalent circuit, that is, in the discharge path of the capacitance C to force a response delay when the charging voltage is lowered. It is possible to secure the required responsiveness by making it faster. However, at this time, if the resistance value of the electrical resistor connected in parallel with the capacitance C of the electrorheological fluid itself is reduced, the current flowing through the electrical resistor itself increases, resulting in an increase in power consumption. Similarly, the fuel consumption may be deteriorated, so that the resistance value of the electric resistor needs to be set to an appropriate resistance value.

For example, the damping force variable shock absorbers 18FL to 18RR are filled with some kinds of electrorheological fluid 13 as working fluid, and the inner and outer electrodes 24i, 24o are filled.
When the capacitance value of the capacitance C of the electrorheological fluid 13 itself interposed therebetween was measured, the capacitance value was about 0.001 μF. Further, the damping force variable shock absorber 1 for vehicles is
8FL to 18RR is the unsprung resonance frequency 1
Since a response of about 3 Hz is required, the capacitance C
The resistance value r ₁ of the electric resistor corresponding to the impedance of ₁ is calculated according to the following formula (10).

R ₁ = 1 / (2πfC) = 1 / (2π130.0010.000001) = 12.24 MΩ ... (10) This resistance value r ₁ is the inner / outer electrode 24i, The effective area of 24o is equivalent to the damping force variable shock absorber 18FL
If the damping force required for the damping force variable shock absorbers 18FL to 18RR can be made smaller, the effective area of the inner and outer electrodes 24i, 24o can be reduced. Can be less than half. Therefore, when the electrode area is halved, the capacitance value of the capacitance C of the electrorheological fluid 13 itself between the inner and outer electrodes 24i, 24o becomes 0.0005 μF, so the resistance value r _{1 of the} electrical resistor is Is 24.48M
It will be Ω.

Further, the resistance value r of each electric resistor
_{Since 1} is when the resistance value of the resistance R of the electrorheological fluid itself in the electrical equivalent circuit is infinite,
The resistance value of the resistance R of the actual electrorheological fluid itself is about 50M.
Ω, the resistance value R ₁ of the electrical resistor is
It becomes about 50 MΩ. That is, if the resistance value of the electric resistor connected in parallel with the electrorheological fluid, that is, connected to the discharge path of the electrorheological fluid is 50 MΩ or less, the required responsiveness can be satisfied.

On the other hand, when the resistance value of the electric resistor is reduced to improve the responsiveness, attention must be paid to the above-mentioned problem of power consumption. Here, in setting the resistance value of the electric resistor, it is desired that at least a current equal to or lower than the charging current flowing through the electrorheological fluid itself flows through the electric resistor. Therefore, the electro-viscous fluid filled in the damping force variable shock absorbers 18FL to 18RR as working fluid is
Since a current flowing when a voltage signal of z, 5 kV is supplied is about 5 mA, the resistance value r _{1 of the} electric resistor is
It can be seen that is required to be 1 MΩ (= 5000 V / 0.005 A) or more.

Based on the above-described principle of the invention, the target charging voltage U _i set by the calculation process of FIG. 6 is obtained for the electrorheological fluid 13 of each damping force variable shock absorber 18i (18FL to 18RR). , A desired damping force D / F is exhibited by each damping force variable shock absorber 18i with required responsiveness, and the average current value flowing in the electrorheological fluid 13 is reduced to reduce power consumption and heat generation amount. FIG. 12 shows a concrete circuit configuration of the drive circuit 46i (46i = 46FL to 46RR) of the control unit 30 which can be lowered. In the figure, the electro-rheological fluid 13 which is the working fluid of each damping force variable shock absorber 18i has the capacitance 13C (impedance r _C ) and the resistance 13R (resistance value r) arranged in parallel with each electrode 24i,
Although it is shown as an electrically equivalent circuit connected to 24o, its function as a damper is not shown in the circuit.

The transformer 54 in this drive circuit 46i,
Switch 53, half-wave rectifier 55, charging voltage detector 49,
The configurations and operations of the error detector 50, the triangular wave oscillator 51, and the comparator 52 are the same as or substantially the same as those of the first embodiment shown in FIG. 10, and therefore detailed description thereof will be omitted. In this embodiment, the resistor 56 having the resistance value r ₁ calculated and set by the basic principle is provided in parallel with the capacitance 13C of the electrorheological fluid 13 itself in the electrical equivalent circuit, that is, in the discharge path of the capacitance 13C. The drive circuit 46
It was placed in i. As a result, the electric charge accumulated in the capacitance 13C of the electrorheological fluid 13 itself in the electrical equivalent circuit is discharged as the current i _R1 flowing in the resistor 56, resulting in the target charging. The _{electrorheological} fluid 13 when the voltage control signal U _i is changed from the high damping force side predetermined value U _{iH i} to the low damping force side predetermined value U _iLO
It is conceivable that the charging voltage U _ch of (1) rapidly drops as shown by the solid line in FIG. 12, and the responsiveness of the damping force control to a high-frequency vibration input such as an unsprung resonance frequency is improved.

Next, regarding the description of the operation of reducing the power consumption and the heat generation amount using the drive circuit 46i in the present embodiment, it is the same as or substantially the same as the description of the first embodiment using the timing chart of FIG. Therefore, the detailed explanation is omitted. Next, the operation of the damping force control device for the variable damping force shock absorber using the drive circuit 46i according to the present embodiment will be described with respect to vehicle motion characteristics including riding comfort. FIG. 14 shows a case where the resistor 56 is connected to the discharge path of the electrorheological fluid 13 (described as the present embodiment in the drawing) and a case where the resistor 56 is not connected (described as the conventional in the drawing) on the spring (vehicle body). The vertical acceleration acting on is shown by a power spectrum which is an energy evaluation value. As is clear from the figure, in the present embodiment in which the resistor 56 is connected to the discharge path of the electrorheological fluid 13, the vertical acceleration energy acting on the spring is reduced, and especially around 15 Hz which exceeds the unsprung resonance point. The reduction cost is large. This is because the discharge time constant of the electrorheological fluid 13 is shortened by the resistor 56 connected to the discharge path of the electrorheological fluid 13, and as a result, the damping force control response to the high frequency vibration input is improved. This means that unless there is a high damping force control response to such high-frequency vibration input, the vehicle motion characteristics such as riding comfort cannot be improved.

From the above, it is considered that the present embodiment is an implementation of the damping force control device for a shock absorber using the electrorheological fluid according to all of claims 1 to 3 of the present invention. 13 and the microcomputer 44 of FIG. 4 or 13 correspond to the target charging voltage setting means of the damping force control device of the shock absorber using the electrorheological fluid of the present invention. 13 corresponds to the charging voltage detecting means, and the error detector 50, the triangular wave oscillator 51, the comparator 52, and the switch 53 in the control unit of FIG. 13 correspond to the intermittent control unit, and in the control unit of FIG. The resistor 56 corresponds to an electrical resistor.

Particularly, in the damping control device for the shock absorber using the electrorheological fluid according to claim 1 of the present invention, the target charging voltage and the actual charging voltage in the actual charging voltage detecting means and the supply voltage outputting means are set. It is also possible to construct the means for providing a supply voltage signal in accordance with the above, with an arithmetic processing device such as a microcomputer as described above, but at least the current processing speed of the arithmetic processing device such as a microcomputer is nsec. On the other hand, since the frequency of the voltage signal required to reduce the resistance value of the resistance R of the electrorheological fluid itself is about 10 kHz as described above, the arithmetic processing for supplying the voltage signal is performed. It is necessary to pay attention to the speed, and at least, at present, it seems that an analog hard circuit such as the PWM control is required even if it is auxiliary.

In the above embodiment, the case where the damping force control of the variable damping force shock absorber is performed only on the basis of the vertical velocity has been described, but the present invention is not limited to this and other lateral acceleration sensors are used. Alternatively, a control signal for suppressing rolling motion or pitching motion may be calculated based on the acceleration detection value of the longitudinal acceleration sensor and the like, and these signals may be added or subtracted from each other to perform total control.

Further, in the above embodiment, the case where the control unit is constructed by the microcomputer has been described, but the present invention is not limited to this, and it is constructed by appropriately combining electronic circuits such as logic circuits and arithmetic circuits. Good.

[0078]

As described above, according to the damping force control device for a shock absorber using the electrorheological fluid of the present invention, the electrorheological fluid used as the working fluid of the shock absorber is By supplying a high-frequency supply voltage consisting of a current flowing in one direction of charging the viscous fluid, the viscosity of the electrorheological fluid is changed and controlled, and the damping force of the shock absorber is adjusted to a desired damping force. As a result, the power consumption of the electrorheological fluid can be reduced to improve the fuel consumption, and the calorific value of the electrorheological fluid can be reduced to suppress thermal runaway and secure a variable adjustment range of damping force. can do.

In generating a high-frequency supply voltage composed of a current flowing in one direction of charging the electrorheological fluid, the intermittent timing of the direct current flowing through the primary side of the transformer is adjusted and controlled, Rise that occurs on the secondary side /
Since it is configured to obtain a sharp falling voltage signal,
It is possible to shorten the time for which the charging direction current of the electrorheological fluid flows, and consequently reduce the average current value to promote the reduction of the power consumption and the heat generation amount.

By connecting an electric resistor having a resistance value related to the discharge time constant of the electrorheological fluid to the discharge path of the electrorheological fluid, the discharge time constant of the electrorheological fluid is reduced, It is possible to shorten the time to change and control the charge voltage by changing it to a smaller damping force, improve the response of damping force control to high frequency vibration input, etc., and improve the vehicle motion characteristics such as riding comfort. .

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a schematic configuration of a damping force control device for a shock absorber using an electrorheological fluid of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a damping force control device for a shock absorber using an electrorheological fluid of the present invention.

FIG. 3 is a configuration diagram of the damping force variable shock absorber of FIG.

FIG. 4 is a structural explanatory view of a control unit of FIG.

FIG. 5 is a characteristic diagram showing electrical characteristics of an electrorheological fluid.

6 is a flowchart showing a calculation process of setting a target charging voltage, which is executed by the control unit of FIG.

FIG. 7 is a characteristic diagram showing a DC voltage-DC resistance characteristic of an electrorheological fluid.

FIG. 8 is a characteristic diagram showing a supply voltage frequency-resistance characteristic of an electrorheological fluid.

9 is an explanatory diagram showing an average current characteristic when a positive current high frequency voltage signal is supplied to the electrorheological fluid by the control unit of FIG.

FIG. 10 is a configuration diagram of a drive circuit of the control unit of FIG. 2 showing a first embodiment of the damping force control device for a shock absorber using the electrorheological fluid of the present invention.

11 is a timing chart showing changes with time of a current signal and a voltage signal generated by the control unit of FIG.

FIG. 12 is a response characteristic diagram of an electrorheological fluid.

FIG. 13 is a configuration diagram of a drive circuit of the control unit of FIG. 2 showing a second embodiment of the shock absorber damping force control device using the electrorheological fluid of the present invention.

14 is a characteristic diagram showing sprung vertical acceleration characteristics by the drive circuit of the control unit of FIG.

[Explanation of symbols]

 10 is a vehicle body side member 11FL to 11RR wheels 12 is a damping force variable control type suspension 13 is an electrorheological fluid 13C is a capacity 13R is a resistor 14 is a wheel side member 18FL to 18RR is a damping force variable shock absorber 24i, 24o is an electrode 27FL 27 RR is a stroke sensor 28 FL to 28 RR is a vertical acceleration sensor 30 is a control unit 44 is a microcomputer 46 FL to 46 RR is a drive circuit 49 is a charging voltage detector 50 is an error detector 51 is a triangular wave oscillator 52 is a comparator 53 is a switch 54 is a switch 54 Transformer 55 is a half-wave rectifier 56 is a resistor

Claims (3)

[Claims] 1. A cylinder is filled with an electrorheological fluid whose viscosity changes according to the frequency and voltage value of a supply voltage as a working fluid of a shock absorber, and when the piston slides in the cylinder, both In a damping force control device for a shock absorber using an electrorheological fluid, the damping force for damping the vibration between the two is controlled by the supply voltage supplied to the electrorheological fluid in the vicinity of the orifice,
Target charging voltage setting means for setting a target charging voltage for charging the electro-rheological fluid based on a physical quantity of motion generated in the vehicle, and actual charging voltage detection for detecting an actual charging voltage actually charged in the electro-rheological fluid Means, and a predetermined high frequency supply voltage consisting of a current in a predetermined one direction according to the target charging voltage set value set by the target voltage setting means and the actual charging voltage detection value detected by the actual voltage detecting means. A damping force control device for a shock absorber using an electrorheological fluid, comprising: a supply voltage output means for outputting to the electrorheological fluid. 2. The supply voltage output means is a transformer for generating a predetermined AC high voltage on the secondary side by interrupting a direct current on the primary side, and a target charging set by the target voltage setting means. The DC current on the primary side of the transformer is interrupted at the predetermined high frequency according to the voltage setting value and the actual charging voltage detection value detected by the actual voltage detecting means, and the DC current is applied to the secondary side of the transformer. An intermittent control unit that controls the generated AC high voltage to the AC high voltage of the predetermined high frequency, and a half-wave rectifier that rectifies the AC high voltage generated on the secondary side of the transformer into a half-wave high-frequency high voltage. The damping force control device for a shock absorber using the electrorheological fluid according to claim 1. 3. An electric resistor having a predetermined resistance value set according to the discharge time constant of the electrorheological fluid is connected in parallel with the discharge path to the electrorheological fluid. Item 3. A damping force control device for a shock absorber using the electrorheological fluid according to Item 1 or 2.