JPH0891031A - Shock absorber for vehicle - Google Patents

Abstract

PURPOSE: To reduce the electric power consumption without lowering the responsiveness, by preventing temperature rise of the electric viscous fluid and spreading the range of the damping force which can be set as an object. CONSTITUTION: A shock absorber is equipped with a vehicle operation detecting means (displacement sensor 113 and a spring upper acceleration sensor 115) for detecting the operation state of a vehicle, objective voltage detecting means (control circuit 112) for determining the objective voltage applied to an electric viscous fluid 106 on the basis of the detection value of the vehicle operation detecting means, high voltage power source means (control circuit 112) which boosts the battery voltage of the vehicle and outputs the high voltage, and a charging means (control circuit 112) for charging the electroviscous fluid 106 with the high voltage outputted from the high voltage power source means. Further, a comparison means (control circuit 112) for comparing the objective voltage determined by the objective voltage determining means and the voltage value outputted from the high voltage power source means, and an electric discharge means (control circuit 112) for discharging the electric charge stored in the electric viscous fluid, on the basis of the result of the comparison of the comparison means are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention changes the viscosity of an electrorheological fluid by filling the cylinder with the electrorheological fluid as a working fluid and applying a voltage to the electrorheological fluid.
The present invention relates to a shock absorber for a vehicle that changes the damping force of the vibration acting between the piston and the cylinder by increasing or decreasing the resistance generated when the piston slides in the cylinder.

[0002]

2. Description of the Related Art Generally, a vehicle shock absorber is mounted on a vehicle as a mechanism for attenuating vibration during traveling to ensure a comfortable ride. At this time, since the road surface condition changes momentarily while the vehicle is traveling, it is desired to change the damping force of the vehicle shock absorber in accordance with the road surface condition.

One of such conventional vehicle shock absorbers is disclosed, for example, in JP-A-61-253208. This vehicle shock absorber uses an electrorheological fluid as a working fluid to change the vibration damping force. Specifically, the cylinder is filled with an electrorheological fluid as a working fluid, and an electrode is provided in the flow path communicating between the upper and lower chambers of the piston to apply a high voltage to the electrorheological fluid. Is to increase the damping force.

Further, as a voltage application method for changing the viscosity of the electrorheological fluid, there is, for example, Japanese Patent Laid-Open No. 3-144715 "Viscosity control method for electrorheological fluid". this is,
An AC high voltage is applied to the electrorheological fluid, and the applied frequency is changed to change the viscosity.

By the way, in order to apply a high voltage frequency to an electrorheological fluid having a capacitive load, it is necessary to use a device such as a high voltage amplifier having a low output impedance. The frequency to be applied needs to be a frequency that is as high as or higher than the viscosity change response speed of the electrorheological fluid due to the AC high voltage. This is because when the applied AC voltage is near zero, the viscosity of the electrorheological fluid does not change, and therefore the delay from the time when the signal that commands the applied voltage is generated until the viscosity actually changes becomes large.

[0006]

However, according to the above-mentioned conventional technique, when a high frequency due to an AC voltage is applied to the electrorheological fluid, a large current flows, and the temperature of the electrorheological fluid rises to operate. Since it exceeds the region, it is necessary to limit the current flowing in the electrorheological fluid,
As a result, there is a problem that the range of damping force that can be set is limited.

That is, there are several kinds of fluids having a property that the viscosity is changed by applying a voltage, but some electrorheological fluids have a relatively large capacity. Therefore, when a high frequency due to an AC voltage is applied to this type of electrorheological fluid, a large current flows and the temperature rises, and the resistance value decreases as the temperature rises. In an electrorheological fluid that has an electrical load, if the resistance as a load decreases as the temperature rises, heat will be generated by the current flowing through itself. Then, when a current flows through the electrorheological fluid, a phenomenon called thermal runaway that exceeds the operating region occurs. In order to avoid this thermal runaway, the current flowing in the electrorheological fluid must be limited, so the range of damping force that can be set as a target is limited.

Further, when a high voltage amplifier which outputs a high frequency to a certain extent at a high voltage is used, it is necessary to drive the element of the output stage with a low impedance in order to secure the responsiveness, which causes an increase in power consumption. was there.
In this case, the current value is a small value to some extent, but the applied voltage is very high, and therefore it becomes a large value when converted into power consumption.

Further, since the high voltage amplifier is complicated, large and expensive, there is a problem that the device becomes complicated, large and expensive.

The present invention has been made in view of the above, and an object thereof is to prevent the temperature rise of the electrorheological fluid and to expand the range of the damping force that can be set as a target.

The present invention has been made in view of the above, and an object of the present invention is to reduce power consumption without lowering responsiveness.

[0012]

In order to achieve the above-mentioned object, a shock absorber for a vehicle according to claim 1 comprises:
An electrorheological fluid is filled in the cylinder as a working fluid, and a voltage is applied to the electrorheological fluid to change the viscosity of the electrorheological fluid and increase or decrease the resistance generated when the piston slides in the cylinder. Thus, in the vehicle shock absorber that changes the damping force of the vibration that acts between the piston and the cylinder,
A vehicle operation detecting means for detecting an operation state of the vehicle; a target voltage determining means for determining a target voltage applied to the electrorheological fluid based on a detection value of the vehicle operation detecting means; and a battery voltage of the vehicle. High voltage power supply means for boosting and outputting a high voltage, charging means for charging the electrorheological fluid with the high voltage output from the high voltage power supply means, the target voltage determined by the target voltage determining means, and the Comparing means for comparing the level of the voltage applied to the electrorheological fluid,
Discharge means for discharging the electric charge stored in the electrorheological fluid based on the comparison result of the comparison means.

The shock absorber for a vehicle according to a second aspect of the invention is such that the current value charged by the charging means and the current value discharged by the discharging means can be set independently.

In the vehicle shock absorber according to the present invention, the discharging means comprises a discharging resistor and a discharging switch connected to a path for supplying a voltage from the high voltage power source means to the electrorheological fluid. , Based on the comparison result of the comparison means, when the voltage applied to the electrorheological fluid is less than or equal to the target voltage, the discharge switch is turned off, and the voltage applied to the electrorheological fluid is lower than the target voltage. If the discharge switch is turned on when it is large, the electric charge stored in the electrorheological fluid is discharged.

Further, in the vehicle shock absorber according to the present invention, the charging means comprises a charging resistor and a charging switch connected to a path for supplying a voltage from the high-voltage power supply means to the electrorheological fluid. , Based on the comparison result of the comparison means, when the voltage applied to the electrorheological fluid is less than or equal to the target voltage, the charging switch is turned on, and the voltage applied to the electrorheological fluid is lower than the target voltage. When it is larger, the charging switch is turned off to charge the electrorheological fluid with the high voltage output from the high voltage power supply means, and the discharging means applies voltage to the electrorheological fluid from the high voltage power supply means. A discharge resistor and a discharge switch connected to a path for supplying the electric voltage to the electrorheological fluid based on the comparison result of the comparison means. When the pressure is equal to or lower than the target voltage, the discharge switch is turned off, and when the voltage applied to the electrorheological fluid is higher than the target voltage, the discharge switch is turned on to store in the electrorheological fluid. The discharged electric charge is discharged.

According to a fifth aspect of the shock absorber for a vehicle, the viscosity of the electrorheological fluid is changed by filling the cylinder with the electrorheological fluid as a working fluid and applying a voltage to the electrorheological fluid. A vehicle shock absorber that changes the damping force of the vibration acting between the piston and the cylinder by increasing or decreasing the resistance generated when the piston slides in the cylinder, and detects the operating state of the vehicle. Based on the detected value of the vehicle motion detecting means and the vehicle motion detecting means,
Voltage determining means for determining a target voltage to be applied to the electrorheological fluid and a used high voltage used when generating the target voltage; and a battery voltage of the vehicle based on the used high voltage determined by the voltage determining means A high voltage power supply means for boosting the voltage to output a high voltage, and a high voltage output from the high voltage power supply means based on the target voltage determined by the voltage determination means and applied to the electrorheological fluid. And a voltage changing means for changing the voltage.

According to a sixth aspect of the present invention, in the vehicle shock absorber, the vehicle motion detecting means detects the vertical displacement amount and the vertical moving acceleration of the piston, and the voltage determining means controls the vehicle motion detecting means. Based on the detected value of, the energy parameter in the direction for damping the body posture is obtained, and the target voltage is determined based on the obtained energy parameter.

[0018]

In the vehicle shock absorber according to the present invention (claim 1), the target voltage determining means determines the target voltage to be applied to the electrorheological fluid based on the detection value of the vehicle operation detecting means. Further, the high voltage power supply means boosts the battery voltage of the vehicle to output a high voltage, and the charging means charges the electrorheological fluid with the high voltage output from the high voltage power supply means.
On the other hand, the comparison means compares the target voltage determined by the target voltage determination means with the level of the voltage applied to the electrorheological fluid, and the discharge means is stored in the electrorheological fluid based on the comparison result of the comparison means. Discharge electric charge. Therefore,
When the high voltage applied to the electrorheological fluid exceeds the target voltage, the electric charge stored in the electrorheological fluid is discharged, and the current flowing through the electrorheological fluid decreases. Further, the voltage charged in the electrorheological fluid is controlled to the target voltage.

Further, in the vehicle shock absorber according to the present invention (claim 2), the current value charged by the charging means and the current value discharged by the discharging means can be set independently.

Further, the vehicle shock absorber according to the present invention (claim 3) turns off the discharge switch when the voltage applied to the electrorheological fluid is equal to or lower than the target voltage based on the comparison result of the comparison means. , When the voltage applied to the electrorheological fluid is higher than the target voltage, the discharge switch is turned on to discharge the electric charge stored in the electrorheological fluid.

Further, the vehicle shock absorber according to the present invention (claim 4) turns on the charging switch when the voltage applied to the electrorheological fluid is less than the target voltage based on the comparison result of the comparison means. When the voltage applied to the electrorheological fluid is higher than the target voltage, the charging switch is turned off to charge the electrorheological fluid with the high voltage output from the high voltage power supply means. Further, based on the comparison result of the comparison means, the discharge switch is turned off when the voltage applied to the electrorheological fluid is equal to or lower than the target voltage, and the discharge switch is turned on when the voltage applied to the electrorheological fluid is higher than the target voltage. By turning on the switch, the electric charge stored in the electrorheological fluid is discharged.

In the shock absorber for a vehicle according to the present invention (claim 5), the voltage determining means generates the target voltage and the target voltage to be applied to the electrorheological fluid based on the detection value of the vehicle operation detecting means. Determine the high voltage used at times. Further, the high voltage power supply means boosts the battery voltage of the vehicle based on the used high voltage determined by the voltage determination means and outputs the high voltage. Further, the voltage changing unit changes the high voltage output from the high voltage power supply unit based on the target voltage determined by the voltage determining unit and applies the high voltage to the electrorheological fluid. Therefore, when it is not necessary to apply a voltage to the electrorheological fluid, it is possible to reduce the voltage output by the high-voltage power supply means and suppress power consumption.

Further, in the vehicle shock absorber according to the present invention (claim 6), the vehicle motion detecting means detects the vertical displacement amount and the vertical moving acceleration of the piston, and the voltage determining means controls the vehicle motion detecting means. Based on the detected value of
The energy parameter in the direction of damping the vehicle body posture is calculated, and the target voltage is determined based on the calculated energy parameter. Therefore, when the energy for damping the body posture is not generated, that is, when it is not necessary to apply the voltage to the electrorheological fluid, the target voltage can be set to zero to suppress the power consumption.

[0024]

[Examples] [Example 1], [Example 2], [Example 3] of a shock absorber according to the present invention
Will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic configuration diagram of a first embodiment. Note that, in FIG. 1, each configuration is illustrated as one for the sake of simplification of description, but in reality, except for the control circuit 112, there is one corresponding to each wheel of the vehicle. .

In the figure, 101 is a cylinder, 102 is a piston that slides in the cylinder 101, and 103 and 104.
Reference numeral 105 denotes a piston upper chamber and a piston lower chamber, which are vertically divided by the piston 102. Reference numeral 105 denotes a connecting path connecting the piston upper chamber 103 and the piston lower chamber 104. The piston upper chamber 103 and the piston lower chamber 104 in the cylinder 101. The connection path 105 is filled with the electrorheological fluid 106. 107 is the lower part of the cylinder 101 and the outer cylinder 1
It is a free piston provided in 08, and gas 109 is filled between the free piston 107 and the outer cylinder 108. Reference numeral 110 is a first electrode attached to the outer peripheral surface of the cylinder 101, and 111 is a second electrode attached to the inner peripheral surface of the outer cylinder 108. The first electrode 110 and the second electrode 111 electrically connect the electrodes. A voltage is applied to the viscous fluid 106.

Reference numeral 112 denotes a control circuit, which executes a predetermined calculation based on a signal from each sensor,
The viscosity of 6 is controlled. 113 is the cylinder 1
01 is a displacement sensor provided between the piston 102 and the cylinder 101, and outputs the displacement amount between the cylinder 101 and the piston 102, that is, the relative displacement amount 114 between the sprung portion and the unsprung portion of the vehicle to the control circuit 112. 115 is the piston 102
It is a sprung acceleration sensor provided in the above, and outputs a sprung acceleration signal 116 to the control circuit 112.

FIG. 2 is a block diagram of the control circuit 112. As shown in the figure, the control circuit 112 includes a microcomputer 200, a high-voltage power supply 201, and a voltage control unit 202.
a, 202b, 202c, 202d. The microcomputer 200 has a relative displacement amount 114 between the sprung portion and the unsprung portion corresponding to each wheel (not shown) (hereinafter, 114a, 114b, 114 corresponding to each wheel).
c and 114d) and sprung acceleration signal 11
6 (hereinafter, corresponding to each wheel 116a, 116b, 1
16c and 116d) are input.

Further, from the microcomputer 200 to the voltage control units 202a, 202b, 202c and 202d, target voltages 203a, 203b, 203c and 203d are provided.
Are output respectively. A preset high voltage 204 is output from the high voltage power supply 201 to the voltage control units 202a, 202b, 202c, 202d. The voltage control units 202a, 202b, 202c, 202d are
Target voltages 203a, 203b, 203c, 20 respectively
The high voltage is converted based on 3d and the first electrode 110
(Hereinafter, 110a, 110b, 11 corresponding to each wheel
0c, 110d), and the electrorheological fluid 10
A high voltage is applied to each of 6.

FIG. 3 is a circuit diagram of the voltage controller 202a. The voltage control units 202a to 202d are provided by the number corresponding to each wheel. However, since the respective configurations are the same, the circuit diagram will be described here by taking the voltage control unit 202a as an example. In the figure, 301 is a resistor provided between the high-voltage power supply 201 and the first electrode 110a, 302 and 303 are voltage dividing resistors for dividing the voltage applied to the first electrode 110a, 304 is a voltage dividing resistor 302, Connected to the middle point of 303 and battery 305, the divided voltage and target voltage 2
The comparison result is output to the discharge switch 306 by a comparator for comparing the magnitude with 03a. The discharge switch 306 is connected to the first electrode 110 via the resistor 307.
connected to a. 308 is a voltage dividing resistor 302, 303
It is a resistor provided between the midpoint and the output side of the comparator 304.

The operation of the first embodiment having the above configuration will be described. While the vehicle is running, the road surface condition changes and the cylinder 10
1 and the positional relationship between the piston 102 change, the relative displacement amount 114 between the sprung portion and the unsprung portion from the displacement sensor 113.
However, the sprung acceleration signal 116 is output from the acceleration sensor 115 and input to the control circuit 112.

In this case, since the displacement sensor 113 and the acceleration sensor 115 are provided for each wheel, the sprung-unsprung relative displacement amount 114a, 1 depending on each wheel.
14b, 114c, 114d and sprung acceleration signal 1
16a, 116b, 116c and 116d are control circuits 11
Entered in 2. Therefore, the microcomputer 200 of the control circuit 112 is activated and the target voltages 203a, 20
3b, 203c, and 203d are output, respectively. The target voltages 203a, 203b, 203c, 203d are input to the voltage control units 202a, 202b, 202c, 202d, respectively. On the other hand, the high-voltage power supply 201 outputs a high voltage that is carefully set, and the voltage control unit 202
a, 202b, 202c, 202d. In response to this, the voltage control units 202a, 202b, 202c, 2
02d is the target voltage 203a, 203b, 20 respectively.
The high voltage is converted based on 3c and 203d, and the high voltage is applied to the electrorheological fluid 106 through the first electrodes 110a, 110b, 110c and 110d, respectively.

Next, the operation of the voltage control units 202a to 202d will be described by taking the voltage control unit 202a as an example. The high voltage from the high voltage power source 201 passes through the resistor 301 to the first electrode 1
It is applied to 10a. The comparator 304 has a voltage dividing resistor 3
The voltage divided by 02 and 303 and the target voltage 203a
And the result of comparison is output to the discharge switch 306. The discharge switch 306 is turned on / off according to the output signal of the comparator 304. That is, the partial voltage value of the voltage charged in the electrorheological fluid 106 is the target voltage 2
If it is larger than 03a, the comparator 304 outputs "1" and the discharge switch 306 is turned on. As a result, the electric charge charged in the electrorheological fluid 106 is discharged through the resistor 307 and the discharging switch 306. On the contrary, when the divided voltage value of the voltage charged in the electrorheological fluid 106 is smaller than the target voltage 203a, the comparator 304 outputs "0" and the discharging switch 306 is turned off. By this,
A high voltage is applied to the electrorheological fluid 106 from the high voltage power source 201 via the resistor 301, and the electrorheological fluid 106 is charged.

FIG. 4 is a time chart of the target voltage applied to the electrorheological fluid 106 and the applied voltage. As shown in the figure, the applied voltage 401
Has a similar mountain shape. Here, the applied voltage 401
The gradual amplitude of is a result of the discharge and charge of the electrorheological fluid 106 by the voltage control unit 202a, whereby the voltage applied to the electrorheological fluid 106 (applied voltage 4
01) is controlled to match the target voltage 203a.

In the first embodiment, the comparator 304 compares the level of the voltage charged in the electrorheological fluid with the target voltage, and the discharge switch 306 is turned on / off according to the comparison result. The same operation can be realized by a configuration in which the discharge operation ratio is increased when the voltage charged in the electrorheological fluid is equal to or higher than the target voltage by intermittently operating 306 at a constant cycle.

[Second Embodiment] In the second embodiment, a voltage control unit 500 shown in FIG. 5 is arranged in place of the voltage control units 202a to 202d of the first embodiment. Since the other configurations and operations are the same as those in the first embodiment, illustration and description thereof will be omitted.

FIG. 5 is a circuit diagram of the voltage control unit 500 of the second embodiment, and as shown in the figure, the charging unit 501 and the discharging unit 502.
And a comparison unit 503. Charging part 50
1 is two resistors 5 connected in parallel to the high-voltage power supply 201.
04, 505 and a charging switch 506 connected to the first electrode 110a, and charges when the voltage of the first electrode 110a becomes lower than the target voltage 203a.

The discharging section 502 includes a discharging switch 509 connected to the first electrode 110a through a diode 507 and a resistor 508, and a diode 510 provided between the charging switch 506 and the discharging switch 509. And the voltage of the first electrode 110a is equal to the target voltage 203a
Discharge when higher.

The comparison unit 503 is connected to the voltage dividing resistors 511 and 512 for dividing the voltage applied to the first electrode 110a, the middle point of the voltage dividing resistors 511 and 512 and the battery 305, and the divided voltage. And a target voltage 203a, and a resistor 514 provided between the midpoint of the voltage dividing resistors 511 and 512 and the output side of the comparator 513.
And the target voltage 20 and the voltage of the first electrode 110a.
3a and height are compared. In this case, the charging unit 501 receives the current value for charging the first electrode 110a,
Is set to the current value discharged from the first electrode 110a.

The operation of the second embodiment having the above configuration will be described. Here, only the operation of the voltage control unit 500 will be described, and other operations are the same as those in the first embodiment, and thus the description thereof will be omitted. The comparator 513 has a voltage dividing resistor 51.
The voltage divided by 1, 512 and the target voltage 203a are compared in magnitude, and the comparison result is output to the discharge switch 509. The discharge switch 509 turns ON / OFF according to the output signal of the comparator 513. When the voltage charged in the electrorheological fluid 106a via the first electrode 110a is lower than the target voltage, the comparator 513 outputs "0" and the discharging switch 509 is turned off. As a result, the charging switch 506 is turned on, and the high voltage power source 201 causes the resistance 50
5, a high voltage is applied to the first electrode 110a (that is, the electrorheological fluid 106a) via the charging switch 506 and the resistor 508, so that charging can be performed. When the voltage charged in the electrorheological fluid 106a becomes higher than the target voltage, the comparator 513 outputs "1", and the discharge switch 5
09 turns on. As a result, the charging switch 506 is turned off, and the voltage charged in the electrorheological fluid 106a is
Resistor 508, diode 507, charging switch 509
Can be discharged through.

The above operation, that is, when the voltage charged in the electrorheological fluid becomes higher than the target voltage, the charge of the electrorheological fluid is discharged, and conversely, when the voltage charged in the electrorheological fluid becomes lower than the target voltage, Since the electrorheological fluid is charged, the target voltage can always be applied to the electrorheological fluid. Then, the damping force of the shock absorber can be adjusted by setting the current value flowing through the charging unit 501 and the discharging unit 502 to a desired value.

Here, the charging unit 501 and the discharging unit 502
The effect of independently setting the value of the current flowing to the desired value will be described. First, in the method of applying the target voltage to the electrorheological fluid by repeating charge and discharge as in the present invention, the discharge time constant becomes large when the discharge resistance is large, and the falling response (that is, the damping force of the shock absorber is reduced. Response speed) is delayed. On the contrary, if the discharge resistance is small, the discharge current increases and the power consumption increases. Therefore, it is desirable that the response speed that determines the discharge resistance and the capacity of the electrorheological fluid be within an allowable range and that the power consumption be small.

Further, in the present invention, the maximum voltage that can be applied to the electrorheological fluid is a value obtained by dividing the output voltage of the high voltage power source 201 by the charging resistors (resistors 504 and 505) and the impedance of the electrorheological fluid itself. Therefore, it is necessary to set the charging resistance value at which the divided voltage value reaches the target voltage. Furthermore, the rising response speed of the voltage applied to the electrorheological fluid is determined by the charging resistance and the capacity of the electrorheological fluid itself. Although the damping force of the electrorheological fluid can be changed by a few mS with respect to the applied voltage, it is desired to increase the charging resistance to such an extent that the response and the response speed required for the applied device are not affected. The reason for this is that when the charging resistance becomes small, the power consumed by the charging resistance becomes large when the target voltage applied to the electrorheological fluid is small, the power consumption increases, and the amount of heat generation also increases.

Therefore, it is necessary to make the speed of applying the voltage to the electrorheological fluid and the power consumption, and the speed of decreasing the voltage and the power consumption to be proper current values, respectively. The above requirements can be satisfied by independently setting the value of the current flowing through 502 to a desired value.

In the second embodiment, the voltage charged in the electrorheological fluid and the target voltage are compared by a comparator 513, and the discharge switch 509 is turned on and the charge switch 506 is turned off according to the comparison result. Alternatively, the discharge switch 509 is turned off and the charge switch 506 is turned on, but the discharge switch 509 is intermittently operated at a constant cycle, and when the voltage charged in the electrorheological fluid is equal to or higher than the target voltage, the discharge operation ratio is changed. The same can be achieved with a configuration in which the number is increased.

[Third Embodiment] FIG. 6 is a block diagram of a control circuit according to a third embodiment. Since the schematic configuration is the same as that of the first embodiment and the configuration of the voltage control unit is the same as that of the first or second embodiment,
Illustration is omitted. As shown in the figure, the control circuit 600 includes a microcomputer 601, a high-voltage power supply 602, and voltage control units 603a, 603b, 603c, and 603d, and executes a predetermined calculation based on the signals from the respective sensors, The voltage applied to the electrodes 110a to 110d is controlled.

The microcomputer 601 has a relative displacement amount 1 between the sprung portion and the unsprung portion corresponding to each wheel (not shown).
14a, 114b, 114c, 114d and sprung acceleration signals 116a, 116b, 116c, 116d are input. Further, the microcomputer 601 calculates the electrode applied target voltage value corresponding to each wheel, and outputs the applied target voltage (Vt) 604a, 604b, 604c, 604d to the voltage control units 603a, 603b, 603c, 603d, respectively.

Further, a high voltage instruction voltage (Vi) 605 is output from the microcomputer 601 to the high voltage power source 602. The high voltage instruction voltage (Vi) 605 is output from the high voltage power supply 602 by the voltage control units 603a, 603b, 603.
It is a voltage that indicates the voltage 606 to be output to c and 603d. That is, a high voltage 606 corresponding to the high voltage instruction voltage (Vi) 605 is output from the high voltage power source 602 to the voltage control units 603a, 603b, 603c, 603d, and in response to this, the voltage control units 603a, 603 are received.
b, 603c, 603d to the first electrodes 110a, 11
A high voltage is applied to each of 0b, 110c, and 110d. The voltage control units 603a, 603
For b, 603c and 603d, for example, a high voltage amplifier can be used.

FIG. 7 is a block diagram of the high voltage power source 602.
In the figure, 701 is a triangular wave oscillator, 702 is a differential amplifier connected to the microcomputer 601, and the triangular wave oscillator 701 and the differential amplifier 702 are connected to a comparator 703. 704 is a transformer connected to the comparator 703 via a switch 705, the switch 705 is provided on the primary side of the transformer 704, and the secondary side is a smoothing element 706.
Via the voltage control units 603a, 603b, 603c, 6
03d, respectively. 707 is a transformer 70
A voltage divider connecting the secondary side of 4 and the differential amplifier 702, 7
Reference numerals 08 and 709 denote a resistor and a smoothing capacitor connected to the secondary side of the transformer 704, respectively.

The operation of the third embodiment having the above configuration will be described. When the road surface condition changes while the vehicle is traveling, the first embodiment
Similarly, from the displacement sensor 113 and the acceleration sensor 115 provided for each wheel, the sprung-unsprung relative displacement amounts 114a, 114b, 114c, 114d and the sprung acceleration signals 116a, 116b, 116c, 11 are obtained.
6d is output and input to the microcomputer 601 of the control circuit 600.

Here, the operation of the microcomputer 601 will be described with reference to the flowchart of FIG. This operation is to repeat the processing every preset processing time, for example, every 1 mS. In the figure, first, the output value output from the sprung acceleration sensor 115, that is, the sprung acceleration signal 116 is read (S801), and the sprung acceleration signal 116 is integrated and converted into a sprung speed signal (S802). Next, the output signal from the displacement sensor 113, that is, the relative displacement amount 1 between the sprung portion and the unsprung portion of the vehicle.
14 is read (S803), the change amount of the relative displacement amount 114 per time is calculated, and converted into the relative speed between the sprung part and the unsprung part (S804).

Next, the sprung speed calculated in step S802 is multiplied by the relative speed calculated in step S804 to obtain a multiplication result (S805). It is determined whether the sign of the multiplication result is positive or negative (S806). In this determination result, when the multiplication result is determined to be negative, the target voltage applied to the electrorheological fluid is set to zero (S807: When the multiplication result is negative, it is desirable to set the damping force to a negative value). However, in a shock absorber that uses an electrorheological fluid, a negative damping force cannot be generated, so the applied voltage is set to zero and the minimum damping force is used).

On the other hand, when the multiplication result is determined to be positive, the target voltage applied to the electrorheological fluid is calculated (S8).
08: The shock absorber control is configured to increase the damping force and keep the vehicle body posture stable when, for example, energy in the direction for damping the vehicle body posture is generated. However, in the case of electrorheological fluid, the applied voltage is applied. To change the damping force, calculate the target voltage to be applied). With a certain type of electrorheological fluid, a damping force approximately proportional to the square root of the applied voltage can be obtained, so the applied target voltage (Vt) can be expressed by Equation 1.

[0054]

[Equation 1]

As a method of keeping the body posture stable,
For example, there is one described in JP-A-61-160311. This is the sign of sprung velocity and sprung −
The damping force is switched depending on whether or not the sign of the relative speed between the unsprung parts is the same. When the signs do not match, the damping force is low, and when they match, the damping force is high.

Next, the high voltage indicating voltage (Vi), which is the voltage to be output by the high voltage power supply, is calculated based on equation 2 (S8).
09). In this case, the voltage output from the high voltage power supply is the voltage supplied as the power supply for the high voltage amplifier.

[0057]

[Equation 2]

As described above, the microcomputer 60
1 operates, and the applied target voltage (Vt) 604a, 604
b, 604c and 604d are output respectively. The applied target voltage (Vt) 604a, 604b, 604c, 60
4d is a voltage control unit 603a, 603b, 603c, 60
3d is input respectively. Further, the high voltage instruction voltage (Vi) 605 is input from the microcomputer 601 to the high voltage power supply 602. From the high-voltage power supply 602 to the voltage control units 603a, 603b, 603c, 603d,
A high voltage 606 corresponding to the high voltage instruction voltage (Vi) 605 is output.

Next, the operation of the high voltage power source 602 will be described. The differential amplifier 702 has a high voltage instruction voltage (Vi) 60.
The difference between 5 and the high voltage 606 is output to the comparator 703. Receiving the output, the comparator 703 compares the output with the triangular wave oscillator 701. When the output of the differential amplifier 702 is smaller than the output of the triangular wave oscillator 701, the comparator 70
3 is the switch 705, the primary side of the transformer 704 is ON
It outputs a signal that increases the ratio. On the contrary, when the output of the differential amplifier 702 is larger than the output of the triangular wave oscillator 701, the comparator 703 controls the switch 705 and the transformer 70.
The signal of which the primary side ON ratio of 4 becomes small is output.

Based on the output signal of the comparator 703,
The switch 705 is turned ON / OFF to operate the transformer 704.
Is turned ON / OFF. Switch 705 is ON
Then, the smoothing capacitor 709 is charged via the smoothing element 706 by the voltage generated on the secondary side of the transformer 704. When the switch 705 is turned off, the electric charge charged in the smoothing capacitor 709 is discharged through the resistor 708 and the voltage control unit 603a (603b, 603c, 603d). Therefore, the high voltage 6 is applied from the high voltage power source 602 to the voltage control units 603a, 603b, 603c and 603d.
06 can be output respectively.

Voltage control unit 603a (603b, 603)
c, 603d) is the same as that of the first or second embodiment, except that the target voltage applied (Vt) 604a, 604b, 604c, 604d from the microcomputer 601.
When a high voltage 606 is input from the high voltage power supply 602, the electro viscous fluids 106a, 106
A high voltage can be applied to each of b, 106c, and 106d.

In the third embodiment, the electrorheological fluid 106
The voltage applied to the electro-rheological fluid 106 is calculated based on the absolute value of the relative displacement between the sprung part and the unsprung part. A voltage is applied. When no energy for damping the body posture is generated, the electrorheological fluid 106
There is no need to apply a voltage to. Therefore, it is not necessary to supply the power supply voltage to the voltage control unit (high voltage amplifier) 603,
The output of the high voltage power supply 602 is zero. However, although the voltage rising time of the high-voltage power supply 602 is fast, the voltage drop speed is discharged by the next constant determined by the smoothing capacitor 709 and the load, so that a delay occurs as described later.

Next, description will be made with reference to the operation time chart of FIG. When there is a road surface having a road surface shape 901 as shown in the figure, the sprung displacement changes as indicated by 902, and the relative displacement between the sprung portion and the unsprung portion changes as indicated by 903. The applied target voltage (Vt) obtained by multiplying the sprung mass velocity at that time by the relative velocity and multiplying the square root of the positive value of the multiplication result by a coefficient is 904. The high voltage indicating voltage (Vi) obtained by multiplying the absolute value of the relative displacement between the sprung part and the unsprung part by a coefficient is 905. The high voltage generated based on the high voltage instruction voltage (Vi) is configured to output a voltage higher than the voltage applied to the electrorheological fluid 106 based on the applied target voltage (Vt).
The high voltage output from the high-voltage power supply 602 is discharged with the next constant determined by the smoothing capacitor 709 and the load as described above, and therefore, as shown by the dotted line 905 in FIG. The voltage becomes as shown by the solid line and becomes the power supply voltage supplied to the voltage control unit (high voltage amplifier) 603. High voltage instruction voltage (Vi) and applied target voltage (V
t) changes like 906.

As can be seen from the relative displacement 903 and the applied target voltage (Vt) 904 in FIG. 9, the timing for changing the damping force is the time when a predetermined time has elapsed after the motion signal of the vehicle was detected. That is, in order to boost the battery voltage and obtain a preset high voltage, a certain rise time is required after the operation of the high-voltage power source 602 is started. However, since the operation of the high-voltage power supply 602 is started at the time when the vehicle motion signal is generated, a high voltage value set in advance is reached by the time when the damping force is changed, which is necessary for changing the target damping force. A high voltage can be generated.

In the third embodiment, the output of the high voltage power source 602 for boosting the battery voltage is changed based on the product of the absolute value of the detection signal detected by the displacement sensor 113 and the acceleration sensor 115 and the high voltage conversion coefficient. There is. However, a method in which a constant value is added to the absolute values of the detection signals detected by the displacement sensor 113 and the acceleration sensor 115 and the output of the high voltage power supply 602 is changed based on the product of the total value and the high voltage conversion coefficient, or the displacement sensor The same effect can be obtained also by a method of adding a constant value to the product of the absolute value of the detection signal detected by 113 and the acceleration sensor 115 and the high voltage conversion coefficient and changing the output of the high voltage power supply 602 based on the total value. Obtainable.

As described above, the present inventor rectifies an AC voltage of a short cycle in the electrorheological fluid with respect to the current flowing when the DC voltage is applied to the electrorheological fluid, and applies the same voltage as the DC voltage. Then, they found that the electric current flowing in the electrorheological fluid decreased. This phenomenon seems to be related to the following. When a DC voltage is applied to a certain type of electrorheological fluid and the applied voltage is changed, a current that is a phase advance of the applied voltage and a current that is in phase with the applied voltage change flows. Can be observed.

From this, it can be seen that the electric characteristics of the electrorheological fluid are such that the capacitance and the resistance are connected in parallel. However, it was also confirmed that this resistance is not a general resistance, and the resistance value changes depending on the applied frequency as shown in FIG. That is, when an AC voltage having a short cycle is rectified and applied to the electrorheological fluid, the voltage is applied in a state where the resistance is increased, and it is considered that the current consumption is reduced.

By utilizing the characteristics of the electrorheological fluid, when the charge stored in the electrorheological fluid itself is lower than the target voltage, the charging circuit charges the electrorheological fluid itself.
When the charge stored in the electrorheological fluid itself becomes higher than the target voltage, the discharge circuit discharges the charge of the electrorheological fluid itself. By alternately repeating the charging and discharging operations in a short cycle and controlling the voltage applied to the electrorheological fluid to the target voltage, the current flowing in the electrorheological fluid can be reduced. Therefore, as the current flowing through the electrorheological fluid decreases, the amount of heat generation also decreases, and the temperature rise of the electrorheological fluid can be prevented, and the range of damping force that can be set as a target can be expanded.

[0069]

As described above, in the vehicle shock absorber according to the present invention (claim 1), the target voltage determining means applies the target voltage to the electrorheological fluid based on the detection value of the vehicle motion detecting means. The high voltage power supply means
The battery voltage of the vehicle is boosted to output a high voltage, the charging means charges the electrorheological fluid with the high voltage output from the high voltage power supply means, and the comparison means determines the target voltage determination means. The target voltage is compared with the level of the voltage applied to the electrorheological fluid, and the discharging means discharges the electric charge stored in the electrorheological fluid based on the comparison result of the comparing means. Therefore, when the high voltage applied to the electrorheological fluid becomes higher than the target voltage, the charging / discharging is repeated according to the level of the target voltage and the voltage applied to the electrorheological fluid. Since the current flowing in the electrorheological fluid is smaller than that in the method of applying a high AC voltage, it is possible to prevent the temperature rise of the electrorheological fluid and expand the range of damping force that can be set as a target. In addition, power consumption can be reduced without lowering responsiveness. Furthermore, with the above configuration, a high voltage can be applied to a capacitive load without using a high voltage amplifier, which simplifies the device.
It is possible to reduce the size and price.

Further, in the vehicle shock absorber according to the present invention (claim 2), the current value charged by the charging means and the current value discharged by the discharging means can be set independently of each other. The speed can be set to the desired proper value.

Further, the vehicle shock absorber according to the present invention (claim 3) turns off the discharge switch when the voltage applied to the electrorheological fluid is equal to or lower than the target voltage based on the comparison result of the comparison means. , When the voltage applied to the electrorheological fluid is higher than the target voltage, the electric charge stored in the electrorheological fluid is discharged by turning on the discharge switch. It is possible to prevent and expand the range of damping force that can be set as a target.

Further, the vehicle shock absorber according to the present invention (claim 4) turns on the charging switch when the voltage output from the high voltage power supply means is less than the target voltage based on the comparison result of the comparison means. When the voltage output from the high voltage power supply means is higher than the target voltage, the charging switch is turned off to charge the electrorheological fluid with the high voltage output from the high voltage power supply means, and Based on the comparison result, turn off the discharge switch when the voltage applied to the electrorheological fluid is less than the target voltage, and turn on the discharge switch when the voltage applied to the electrorheological fluid is higher than the target voltage. Since the electric charge stored in the electrorheological fluid is discharged by this, the temperature rise of the electrorheological fluid is prevented with a simple configuration, and the range of damping force that can be set as a target is expanded. It can be.

In the vehicle shock absorber according to the present invention (claim 5), the voltage determining means generates the target voltage and the target voltage to be applied to the electrorheological fluid based on the detection value of the vehicle operation detecting means. The high-voltage power supply means used at times is determined, and the high-voltage power supply means boosts the battery voltage of the vehicle to output the high voltage based on the high-voltage use determined by the voltage determination means, and also changes the voltage. The means changes the high voltage output from the high voltage power supply means and applies it to the electrorheological fluid based on the target voltage determined by the voltage determining means, so that it is not necessary to apply the voltage to the electrorheological fluid. Can reduce the voltage output by the high-voltage power supply means to suppress power consumption.

Further, in the vehicle shock absorber according to the present invention (claim 6), the vehicle motion detecting means detects the vertical displacement amount and the vertical moving acceleration of the piston, and the voltage determining means determines the vehicle motion detecting means. Based on the detected value of
The energy parameter in the direction of damping the vehicle body posture is obtained, and the target voltage is determined based on the obtained energy parameter. Therefore, when the energy in the direction of damping the vehicle body posture does not occur, that is, the voltage is applied to the electrorheological fluid. When it is not necessary to apply the voltage, the target voltage can be set to zero to suppress power consumption.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is a block diagram of a control circuit according to the first embodiment.

FIG. 3 is a circuit diagram of a voltage control unit according to the first embodiment.

FIG. 4 is a time chart of a target voltage applied to an electrorheological fluid and an applied voltage.

FIG. 5 is a circuit diagram of a voltage controller according to a second embodiment.

FIG. 6 is a block diagram of a control circuit according to a third embodiment.

FIG. 7 is a configuration diagram of a high voltage power supply according to a third embodiment.

FIG. 8 is a flowchart showing the operation of the microcomputer of the third embodiment.

FIG. 9 is an operation time chart of the third embodiment.

FIG. 10 is an explanatory diagram showing a relationship between a frequency applied to an electrorheological fluid and a resistance value.

[Explanation of symbols]

101 cylinder 102 piston 106 electrorheological fluid 112,600
Control circuit 113 Displacement sensor 115 Sprung acceleration sensor 200,601 Microcomputer 201,602 High voltage power source 202a to 202d, 603a to 603d Voltage control unit 304,513,703 Comparator 305 Battery 306,509
Discharge switch 506 Charge switch

Claims (6)

[Claims] 1. A cylinder is filled with an electrorheological fluid as a working fluid, and a voltage is applied to the electrorheological fluid to change the viscosity of the electrorheological fluid so that when the piston slides in the cylinder. In a vehicle shock absorber that changes the damping force of the vibration acting between the piston and the cylinder by increasing or decreasing the generated resistance, vehicle operation detecting means for detecting the operation state of the vehicle, and the vehicle operation detecting means. Target voltage determining means for determining a target voltage to be applied to the electrorheological fluid based on the detected value of the means, and boosting the battery voltage of the vehicle,
High voltage power supply means for outputting a high voltage, charging means for charging the electrorheological fluid with the high voltage output from the high voltage power supply means, target voltage determined by the target voltage determining means, and the electrorheological fluid A shock for a vehicle, comprising: a comparison means for comparing the level of the voltage applied to the vehicle and a discharge means for discharging the electric charge stored in the electrorheological fluid based on the comparison result of the comparison means. absorber. 2. The shock absorber for a vehicle according to claim 1, wherein the current value charged by the charging means and the current value discharged by the discharging means can be set independently of each other. 3. The discharging means comprises a discharging resistor and a discharging switch connected to a path for supplying a voltage from the high voltage power source means to the electrorheological fluid, and based on a comparison result of the comparing means, Turning off the discharge switch when the voltage applied to the electrorheological fluid is less than or equal to the target voltage, and turning on the discharge switch when the voltage applied to the electrorheological fluid is greater than the target voltage The shock absorber for a vehicle according to claim 1, wherein the electric charge stored in the electrorheological fluid is discharged by the above. 4. The charging means comprises a charging resistor and a charging switch connected to a path for supplying a voltage from the high-voltage power supply means to the electrorheological fluid, and based on a comparison result of the comparison means, Turning on the charging switch when the voltage applied to the electrorheological fluid is less than or equal to the target voltage, and turning off the charging switch when the voltage applied to the electrorheological fluid is greater than the target voltage. The electro-rheological fluid is charged with the high voltage output from the high-voltage power supply means, and the discharging means is connected to a path for supplying a voltage from the high-voltage power supply means to the electro-rheological fluid. And a discharge switch, and based on the comparison result of the comparison means, the discharge switch is turned on when the voltage applied to the electrorheological fluid is equal to or lower than the target voltage. 2. The electric charge stored in the electrorheological fluid is discharged by turning off the switch and turning on the discharge switch when the voltage applied to the electrorheological fluid is higher than the target voltage. The vehicle shock absorber described. 5. A cylinder is filled with an electrorheological fluid as a working fluid, and a voltage is applied to the electrorheological fluid to change the viscosity of the electrorheological fluid so that the piston slides in the cylinder. In a vehicle shock absorber that changes the damping force of the vibration acting between the piston and the cylinder by increasing or decreasing the generated resistance, vehicle operation detecting means for detecting the operation state of the vehicle, and the vehicle operation detecting means. A voltage determining means for determining a target voltage to be applied to the electrorheological fluid and a high voltage to be used when the target voltage is generated, and a high voltage to be used determined by the voltage determining means. Based on the high voltage power supply means for boosting the battery voltage of the vehicle to output a high voltage, based on the target voltage determined by the voltage determining means. A shock absorber for a vehicle, further comprising: a voltage changing unit that changes the high voltage output from the high-voltage power supply unit and applies the voltage to the electrorheological fluid. 6. The vehicle operation detecting means detects an up-and-down displacement amount and an up-and-down moving acceleration of the piston, and the voltage determining means controls a vehicle body posture based on a detection value of the vehicle operation detecting means. The shock absorber for a vehicle according to claim 5, wherein an energy parameter in a shaking direction is obtained, and the target voltage is determined based on the obtained energy parameter.