JPH0534166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a rocking suppressing means for suppressing rocking of a vehicle body in response to road surface irregularities.

[Prior art]

As a conventional road surface detection device, for example,
There is one disclosed in Japanese Patent No. 30542 (title of invention: variable shock absorber device). This device is incorporated into a hydraulic shock absorber, and includes a variable orifice whose flow cross-sectional area can be adjusted in order to change the damping force of the shock absorber, and a shock absorber to change the flow cross-sectional area of the variable orifice. A solenoid built into the absorber, a vehicle height sensor that electrically detects the vehicle height value, and an excitation current supplied to the solenoid based on the detection signal of the vehicle height sensor to reduce the flow cross-sectional area of the variable orifice. a control circuit to
The damping force of the shock absorber is increased under a predetermined vehicle height condition, and the damping force of the shock absorber is increased when driving on a rough road to obtain a good driving condition.

[Problems with conventional technology]

However, such conventional road surface detection devices are configured to detect the amplitude of vertical movement of the vehicle body using a vehicle height sensor and control the damping force of the shock absorber based on this. There is a problem in that it is not possible to distinguish between a road surface that causes sprung mass vibration at a relatively low frequency, such as a road surface that causes unsprung mass vibration, and a road surface that causes unsprung mass vibration that occurs at a relatively high frequency, such as a rough road.

For this reason, for example, when controlling the damping force of a shock absorber, it is necessary to increase the damping force even at a relatively low level on a undulating road to suppress pitching and housing of the vehicle and improve ride comfort. Although it is desirable to control the damping force to increase the damping force to improve ground contact and suppress unsprung vibration after reaching a relatively high level on the road, it is detected at the same level, and the level is increased on rough roads. There was a problem that when combined with undulating roads, the damping force was too low on undulating roads, and conversely, when combined with undulating roads, the damping force was too high on rough roads.

[Purpose of the invention]

This invention detects the vertical vibration of the vehicle body using a vertical vibration detector, determines the levels of high-frequency components and low-frequency components contained in the detection signal using separate determining means, and then detects the low-frequency components based on the determination results. It is an object of the present invention to solve the problems of the above-mentioned conventional example by changing the determination level of the component determination means.

[Structure of the invention]

In order to achieve the above object, the present invention provides a vehicle rocking control device that includes a rocking suppressing means for suppressing the rocking of a vehicle body, and that changes the suppressing force of the rocking suppressing means according to the unevenness of the road surface. , a vertical vibration detector that detects vertical vibration of a vehicle body depending on road surface conditions, and a low frequency component determination that determines whether a low frequency component in a detection signal of the vertical vibration detector is equal to or higher than a predetermined determination level. means, control means for increasing the suppressing force of the rocking suppressing means when the judgment result of the low frequency component judging means is that the low frequency component is equal to or higher than a predetermined judgment level; high frequency component determining means for determining whether or not the high frequency component of is equal to or higher than a predetermined determination level; and determination level setting means for changing the determination level of the low frequency component determining means in accordance with the determination result of the high frequency component determining means. It is characterized by having the following.

[Action of the invention]

In the vehicle rocking control device of the present invention, a vertical vibration detector detects the vertical vibration of the vehicle body depending on the road surface condition, and when the level of the low frequency component included in the detection signal is equal to or higher than a predetermined determination level. When the low frequency component determining means determines that the vibration exists, the control means increases the suppressing force of the rocking suppressing means, thereby suppressing the rocking of the vehicle body. Here, the high frequency component determination means can detect whether the road surface is a rough road by determining the level of the high frequency component included in the detection signal of the vertical vibration detector,
When the road is rough, the judgment level of the low frequency component judgment means is changed, so it is possible to change the judgment level of the low frequency component judgment means when the road surface is relatively low frequency and generates sprung mass vibration, such as a undulating road, and when it is relatively high frequency, such as a rough road. It is possible to control the vehicle's oscillation according to the road surface with the generation of an unsprung signal.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example of a variable damping force shock absorber, and FIGS. 3 and 4 are signals for explaining the operation of the present invention. FIG.

In Fig. 1, reference numeral 1 denotes a vehicle height detector, which is composed of an ultrasonic distance measuring device attached to the lower surface of the front end of the vehicle body. Measures the time it takes for the reflected wave to be received by an ultrasonic receiver, multiplies the measured time by the speed of sound, and outputs a vehicle height detection signal DH corresponding to the distance between the vehicle body and the road surface, that is, the vehicle height. It is configured as follows.

The vehicle height detection signal DH from the vehicle height detector 1 is supplied to a low frequency band pass filter 2 that passes relatively low frequency signal components and a high frequency band pass filter 3 that passes relatively high frequency signal components. Ru. The cutoff frequency of the low frequency band pass filter 2 is selected so as to cut out signal components other than the sprung resonance frequency f ₁ (for example, 1 to 2 Hz), and the high frequency band pass filter 3 has a
The cutoff frequency is selected to cut signal components other than the unsprung resonance frequency f ₂ (for example, 12 to 13 Hz).

Then, the low frequency signal component LF output from the low frequency band pass filter 2 is transferred to the AC-DC conversion circuit 4.
The DC level signal LV is converted into a DC level signal LV, which is then supplied to the comparison signal input side of a comparison circuit 6 as a low frequency component determining means.

Further, the high frequency signal component HF output from the high frequency band pass filter 3 is supplied to the AC-DC conversion circuit 5 and converted into a DC level signal HV, which is then supplied to the comparison signal input side of the comparison circuit 7 as high frequency component determination means. has been done.

On the other hand, the reference voltage input sides of the comparison circuits 6 and 7 are provided with judgment level setting circuits 32 and 3, which will be described later.
Setting level signals LL and HL from 3 are supplied. Therefore, when the level of the output signal LV of the AC-DC conversion circuit 4 exceeds the set level signal LL from the judgment level setting circuit 32, the comparison circuit 6 outputs a comparison output of, for example, a logical value of "1". signal
LC is output as a road condition detection signal. Also,
When the level of the output signal HV of the AC-DC conversion circuit 5 exceeds the set level signal HL from the judgment level setting circuit 33, the comparison circuit 7 outputs, for example, a comparison output signal HC with a logical value of "1". be done.

The comparison output signal LC of the comparison circuit 6 is supplied to a damping force control circuit 8 that controls the damping force of the variable damping force shock absorbers 10a to 10d, and in this damping force control circuit 8, the comparison output signal LC is The control signal CS, which has a logic value of "0", reduces the damping force of the variable damping force shock absorbers 10a to 10d when the logic value is "0", and when the comparison output signal LC has a logic value of "1", the damping force is changed. A control signal CS having a logical value of "1" for increasing the damping force of the shock absorbers 10a to 10d is output to the drive circuit 9, respectively.

The drive circuit 9 operates variable damping force shock absorbers 10a to 1 in response to a control signal CS supplied thereto.
An excitation current is output that makes the solenoid 20 at 0d de-energized and excited. Here, the damping force control circuit 8
The drive circuit 9 and the drive circuit 9 constitute a control means, and the variable damping force shock absorbers 10a to 10d constitute a swing suppressing means.

Damping force variable shock absorber 10a to 10d
has a configuration shown in FIG. 2, which is incorporated into a suspension device disposed between each wheel of a vehicle and the vehicle body to absorb transient vertical vibrations of the wheels depending on road surface conditions.

That is, the variable damping force shock absorber 10
a to 10d each include a cylinder 13 composed of an inner cylinder 11 and an outer cylinder 12, a piston rod 14 that is slidable inside the cylinder, and a damping force generating bottom valve 15 disposed at the bottom of the cylinder 13. It is configured with The piston rod 14 is divided in the axial direction into an upper piston rod 16 and a lower piston rod 17. A bypass passage 19 is formed to allow direct communication between B and C, and an actuator 22 having a solenoid 20 and a plunger 21 is installed inside the upper piston rod 16. Further, the plunger 21 is positioned so as to penetrate into the bypass passage 19, and the plunger 21 is actuated in accordance with whether the solenoid 20 in the actuator 22 is energized or de-energized;
Then, the bypass passage 19 is opened and closed to open and close the liquid chambers B and C.
It connects or blocks direct communication between the two. Here, the solenoid 20 is connected to the drive circuit 9 via a lead wire 23, and operates the plunger 2 in response to a control signal CS from the damping force control circuit 8.
1, it becomes possible to switch and control the damping force between high and low. In addition, in the figure,
24, 25 and 26, 27 are damping force generating orifices on the compression side and expansion side, respectively; 28, 29 are
The non-return valve 30 is a return spring.

On the other hand, the control signal CS of the damping force control circuit 8 is transmitted via an inverter 31 to a judgment level setting circuit 32 as judgment level setting means for setting the reference voltage of the comparison circuit 6 and a judgment level setting circuit 32 for setting the reference voltage of the comparison circuit 7. and a level setting circuit 33, respectively. The judgment level setting circuit 32 includes voltage dividing resistors R ₁ and R ₂ connected between the DC power supply and ground, and a resistor R 3 and a diode D connected between the connection point of these resistors R ₁ and R ₂ and the inverter ₃₁ . ₁ and a series circuit of a diode D ₂ and a resistor R ₄ inserted between the connection point of the resistors R ₁ and R ₂ and the comparison output side of the comparison circuit 7. and,
The inverter 31 is connected to the cathode of the diode _D1 .
The output side of the comparator circuit 7 is connected to the anode side of the diode _D2 , and the comparison output side of the comparator circuit 7 is connected to the anode side of the diode D2.Furthermore, the judgment level signal LL output from the connection point of the voltage dividing resistors _R1 and _R2 is connected to the anode side of the diode D2. is supplied to the reference voltage input side of the In this case, the determination level signal output from the determination level setting circuit 32
The value A of LL is as follows, where C is the value of the output signal IN of the inverter 31, and D is the value of the output signal of the comparator circuit 7.
It can be expressed by the following formula.

A= _A0 − _α1 ×C+ _α2 ×D……(1) Here, _A0 is the resistance _R1 for dividing the DC power supply voltage.
And the voltage value at the connection point of both divided by R ₂ , α ₁ is,
α 2 is a constant determined by the value of resistor R ₃ and α ₂ is a constant determined by resistor R ₄ .

Further, the judgment level setting circuit 33 includes voltage dividing resistors R ₁ , R ₂ , similar to the judgment level setting circuit 32 ,
It has a resistor R ₃ and a diode D ₁ , and a judgment level setting signal HL output from a connection point between the resistors R ₁ and R ₂ is supplied to the reference voltage input side of the comparator circuit 7 .
In this case, the value B of the determination level signal HL can be expressed by the following equation.

B=B ₀ −β×C ……(2) Here, B ₀ is the resistance R ₁ for dividing the DC power supply voltage.
And the voltage value at the connection point of both divided by R ₂ , β is,
It is a constant determined by the value of resistance _R3 .

Next, the effect will be explained. Now, the control signal CS from the damping force control circuit 8 has a logical value of "0", and each of the variable damping force shock absorbers 10a to 1
Assuming that the solenoid 20 at 0d is in a non-energized state, the plunger 21 is urged upward by the force of the return spring 30. As a result, the bypass passage 19 between the fluid chambers B and C is opened, facilitating the flow of the working fluid between the two chambers, and reducing the damping force of the variable damping force shock absorber.

In this state, as shown in Figure 3a, the vehicle height detector 1 outputs a relatively high-frequency vibration signal component HF that is transmitted from the road surface to the wheels according to the road surface condition, and a relatively low-frequency vibration signal component HF that is transmitted from the road surface to the wheels due to the vibration of the vehicle body. A detection signal DH on which the frequency vibration component LF is superimposed is output. Therefore, when the vehicle is traveling on a flat, good road, the high frequency signal component HF from the road surface is small, and the low frequency signal component LF due to the shaking of the vehicle is also small. Therefore, this vehicle height detection signal DH is supplied to the band pass filters 2 and 3, respectively, so that the band pass filters 2 and 3 detect the low frequency signal component LF and the high frequency signal as shown in FIG. 3b and c, respectively. The component HF is separated and extracted, and these are sent to AC-DC conversion circuits 4 and 5.
supplied to Therefore, relatively low level output signals LV and HV are outputted from these conversion circuits 4 and 5 as shown in FIG. 3d and e, respectively.
These are supplied to comparison circuits 6 and 7, respectively.

Here, the reference voltage input side of the comparator circuit 7 is supplied with the judgment level signal HL of the judgment level setting circuit 33, and as described above, this judgment signal HL is the control signal from the damping force control circuit 8. Since CS has a logic value of "0", the output signal IN of the inverter 31 has a logic value of "1". For this reason, diode _D1 is in a cut-off state, so
The current passing through the resistor _R3 is cut off, and the voltage value _B0 obtained by dividing the DC power supply voltage by the voltage dividing resistors _R1 and _R2 is output as the judgment level signal HL as shown in Figure 4b. .

Therefore, the comparison output signal HC of the comparison circuit 7
has a logical value of "0", and therefore, the judgment level setting circuit 32 receives a comparison output signal of a logical value of "0".
Since HC and the inverter output EIN of logical value “1” are supplied, this judgment level setting circuit 32
As shown by the solid line in FIG. 4a, the voltage value A ₀ obtained by dividing the DC power supply voltage by voltage dividing resistors R ₁ and R ₂ is output as the determination level signal LL. Therefore, the comparison output signal LC output from the comparison circuit 6 maintains the logical value "0",
Since this is supplied to the damping force control circuit 8, the control signal CS from the damping force control circuit 8 maintains the logical value "0". As a result, the damping force of each of the variable damping force shock absorbers 10a to 10d is maintained in a reduced state.

From this state, at time _t1 , when the vehicle is running on a undulating road with few road surface irregularities, the vehicle height detection signal DH output from the vehicle height detector 1 in this case
As shown in FIG. 3C, the high frequency signal component HF corresponding to the road surface condition included therein has a small amplitude because the road surface has few irregularities. Therefore,
The comparison output signal HC of the comparison circuit 7 has a logical value of “0”
, and the value of the judgment level signal LL from the judgment level setting circuit 32 is maintained at the divided voltage A ₀ .
As a result, when the undulation of the road surface is relatively slow, the vehicle does not shake much, and the vehicle height detector 1
Low frequency components included in the vehicle height detection signal DH from
Since the amplitude of LF is small, the level of the output signal of the AC-DC conversion circuit 4 is low, and the comparison output signal LC of the comparison circuit 6 maintains the logical value "0". Therefore, each variable damping force shock absorber 10a to 1
0b is maintained in a low damping force state. Furthermore, when the period of the road surface undulation is relatively short, the shaking of the vehicle becomes large, so the amplitude of the low frequency signal component LF included in the vehicle height detection signal DH from the vehicle height detector 1 becomes large. The level of the output signal of the AC-DC conversion circuit 4 becomes larger than the determination level signal LL, and the comparison output signal LC of the comparison circuit 6 becomes a logical value "1". Therefore, the control signal CS of the damping force control circuit 8 has a logical value of "1", increasing the damping force of each of the variable damping force shock absorbers 10a to 10d. That is, when the control signal CS of the damping force control circuit 8 becomes a logical value "1", an excitation current is output from the drive circuit 9, and this is supplied to the solenoids 20 of each of the variable damping force shock absorbers 10a to 10d. This solenoid 20 becomes energized, and in response, the plunger 21 descends against the return spring 30. As a result, the bypass passage 19 is closed by the lower end of the plunger 21, and the liquid chambers B and C are communicated only through the damping force generating orifices 24 and 26.
Movement of the hydraulic fluid between the two chambers is restricted, and the damping force of the variable damping force shock absorbers 10a to 10d is increased. In this way, when the damping force control circuit 8 outputs the control signal CS with the logical value "1" that increases the damping force of the variable damping force shock absorber, the output signal IN of the inverter 31 changes to the logical value "0" in response.
becomes. Therefore, a part of the current from the DC power source of the determination level setting circuit 33 flows through the resistor R ₃ and the diode D ₁ and further through, for example, a transistor in the inverter 31 to the ground side. Therefore, as shown in FIG. 4b, the voltage value at the connection point between the voltage dividing resistors R ₁ and R ₂ of the judgment level setting circuit 33 decreases by βC, and this is supplied to the comparator circuit 7 as the judgment level signal HL. be done. As a result, the value of the judgment level signal HL can compensate for the decrease in the amount of change in vehicle height caused by increasing the damping force of the variable damping force shock absorbers 10a to 10b, and provide an accurate road surface condition signal according to the road surface condition. It can be output from the comparison circuit 7.

Furthermore, from this state, when the vehicle enters a state where it is traveling on a rough road with many road surface irregularities at time _t2 , a high frequency signal corresponding to the road surface irregularities included in the vehicle height detection signal DH output from the vehicle height detector 1 is generated. Since the amplitude of the component HF increases, the level of the output signal of the AC-DC conversion circuit 5 becomes higher than the determination level signal HL, and the comparison circuit 7 outputs a comparison output signal HC with a logical value of "1". Therefore, _the voltage dividing resistor R _{1 is}
and R ₂ , so that the voltage at that connection point becomes α ₂ ×D as shown by the dotted line in Figure 4a.
This is supplied to the comparator circuit 6 as the determination level signal LL. Therefore, the determination level in the comparator circuit 6 increases, and the amplitude of the low-frequency signal component LF due to vehicle rocking increases, causing the level of the output signal LV of the AC-DC conversion circuit 4 to become the determination level signal. When the value exceeds the value of LL, the comparison output signal LC of the comparison circuit 6 becomes the logical value "1". Therefore, the control signal of the damping force control circuit 8
CS becomes the logical value "1", and the damping force of each variable damping force shock absorber 10a to 10d is increased, and as a result, the unsprung vibration and sprung vibration of the vehicle caused by uneven road conditions are suppressed, and the The ride comfort of the vehicle and the ground contact of the wheels can be improved. In addition, when the road surface is uneven to the extent that the vehicle does not shake significantly, the amplitude of the low frequency signal component LF included in the vehicle height detection signal DH of the vehicle height detector 1 is small, so the AC-DC conversion circuit 4 output signal
The level of LV becomes less than the judgment level signal LL, and accordingly, the comparison output signal LC of the comparison circuit 6 becomes the logical value "0", and the control signal of the damping force control circuit 8
CS takes on a logical value of "0" and reduces the damping force of each variable damping force shock absorber 10a to 10d.

In addition, in the above embodiment, a case has been described in which the vehicle height detector 1 using ultrasonic waves is applied as a vertical vibration detector that detects vertical vibration of the vehicle body depending on the road surface condition, but the present invention is not limited to this. Instead, a vertical acceleration detector may be used to detect the vertical vibration of the vehicle body, or a vertical vibration detector that detects the amount of displacement of the piston rod of the shock absorber as a change in the inductance of a detection coil or a change in the load of a load cell, etc. . However, in this case, the variable damping force shock absorber 10a
The difference in the detected value of the vertical vibration of the vehicle body increases when the damping force is changed by ~10d, and when the damping force is increased, it changes in the direction of increasing.As shown in FIG.
While reversing the polarity of D ₁ , inverter 31
It is necessary to omit the control signal CS of the damping force control circuit 8 and supply it directly to the diode _D1 , thereby changing the determination level signals LL and HL as shown in FIGS. 6a and 6b.

Further, as a vibration suppressing means for suppressing vertical vibration of the vehicle body, a variable damping force shock absorber 10a is used.
The spring constant is not limited to ~10d, and the spring constant may be changed as shown in FIG. That is, the suspension device 35 in FIG. 7 is composed of a shock absorber 36 and an air chamber 37 that is integrally formed on the upper part of the shock absorber 36 and is expandable and retractable in the vertical direction. And this suspension device 35
is attached to the vehicle by attaching the upper end of the piston rod 38 of the shock absorber 36 and the upper end of the air chamber 37 to a member on the vehicle body side.

Here, when the on-off valve 39 is closed, the spring constant of the suspension device 35 is
determined solely by the volume of On the other hand, on-off valve 3
9 is opened to communicate the air chamber 37 and the reservoir tank 40, the spring constant of the suspension device 35 is determined by the volume of the air chamber 37 plus the volume of the reservoir tank 40. Therefore, by opening and closing the on-off valve 39, the spring constant of the air spring of the suspension device 35 can be switched between large and small. This change in spring constant is carried out by the drive circuit 9 which is supplied with the control signal CS from the damping force control circuit 8 in FIG.
This is done by opening and closing the on-off valve 39,
When the control signal CS is logical value “1”, the on-off valve 3
9 is in the closed state and the spring constant is increased, and on the other hand, when the control signal CS is the logical value "0", the on-off valve 39 is closed.
This is done by opening the spring and reducing the spring constant.

In the figure, 42 is an elastic body such as rubber, 43 is a passage, 44 is a passage communicating with other suspension devices, 45 is an intake/exhaust valve, and 46 is an air supply device. In addition, a variable torsional rigidity stabilizer whose torsional rigidity can be varied may also be used as the rocking suppression means.

〔Effect of the invention〕

As explained above, according to the present invention, a vehicle rocking control device includes a rocking suppressing means for suppressing the rocking of a vehicle body, and changes the suppressing force of the rocking suppressing means in accordance with the unevenness of the road surface. , a vertical vibration detector that detects vertical vibration of a vehicle body depending on road surface conditions, and a low frequency component determination that determines whether a low frequency component in a detection signal of the vertical vibration detector is equal to or higher than a predetermined determination level. means, a control means for increasing the suppressing force of the rocking suppression control means when the judgment result of the low frequency component judgment means is that the low frequency component is equal to or higher than a predetermined judgment level, and a detection signal of the vertical vibration detector. a high frequency component determining means for determining whether the middle high frequency component is equal to or higher than a predetermined level; and a determination level setting means for changing the determination level of the low frequency component determining means in accordance with the determination result of the high frequency component determining means. Since the configuration includes the following, it is possible to achieve the effect that the vehicle swing control can be performed depending on the undulating road and the rough road.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example of a variable damping force shock absorber applicable to the present invention, FIGS. 3 a to e, and FIGS. 4 a and b are signal waveform diagrams for explaining the operation of the present invention, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIGS. 6 a and b are diagrams showing the determination of the determination level setting circuit, respectively. FIG. 7, a waveform diagram showing a level signal, is a sectional view showing another example of a suspension device to which the present invention can be applied. 1...Vehicle height detector, 2...Low frequency band pass filter, 3...High frequency band pass filter, 4,
5... AC-DC conversion circuit, 6... Comparison circuit (low frequency component determining means), 7... Comparing circuit (high frequency component determining means), 8... Damping force control circuit, 9... Drive circuit, 10a~ 10d... Variable damping force shock absorber, 13... Cylinder, 14... Piston rod, 19... Bypass path, 20... Solenoid, 21... Plunger, 31... Inverter,
32... Judgment level setting circuit (judgment level setting means), 33... Judgment level setting circuit, 35... Suspension device.

Claims (1)

[Claims] 1 Equipped with a rocking suppression means for suppressing the rocking of the vehicle body,
A vehicle rocking control device that changes the suppressing force of the rocking suppressing means according to the unevenness of the road surface includes a vertical vibration detector that detects vertical vibration of a vehicle body depending on the road surface condition; low frequency component determining means for determining whether a low frequency component in a detection signal is at least a predetermined determination level; and when a determination result of the low frequency component determining means is that the low frequency component is at least a predetermined determination level; A control means for increasing the suppressing force of the vibration suppressing means, a high frequency component determining means for determining whether a high frequency component in a detection signal of the vertical vibration detector is equal to or higher than a predetermined determination level, and the high frequency component determining means. A swing control device for a vehicle, comprising: determination level setting means for changing the determination level of the low frequency component determining means according to a determination result of the means.