JPH0316286B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention adjusts the transmission force transmitted to the vehicle body via the shock absorber by controlling the damping force of the shock absorber, and adjusts the transmission force that is generated when switching the damping force. The present invention relates to a shock absorber control device that can suppress the impact force caused by a vehicle, thereby improving ride comfort and handling stability of a vehicle.

[Prior art]

As a conventional shock absorber control device,
For example, there is one disclosed in Japanese Patent Application Laid-Open No. 58-30542.

The shock absorber control device includes a variable orifice that is incorporated in a hydraulic shock absorber and whose flow cross-sectional area can be adjusted to change the damping force of the shock absorber, and a variable orifice that is capable of adjusting the flow cross-sectional area of the variable orifice to change the damping force of the shock absorber. A solenoid built into the shock 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 control the flow cross-sectional area of the variable orifice. and a control circuit that increases the damping force of the shock absorber under predetermined vehicle height conditions, thereby improving ride comfort by controlling the damping force of the shock absorber according to driving conditions. That's what I do.

[Problem that the invention seeks to solve]

However, with such conventional shock absorber control devices, the damping force of the shock absorber can be adjusted to one of two levels, large and small, using an ON-OFF solenoid, depending on the driving conditions, regardless of the uneven shape of the road surface. Because the structure was configured to perform binary control by continuously maintaining the Otherwise, phenomena such as rolling of the vehicle body occur, making it impossible to improve ride comfort.

On the other hand, there is Japanese Patent Application No. 106294/1982, which was previously proposed by the applicant of the present application as a solution to these problems. The vehicle height sensor detects the relative displacement between the sprung mass and the unsprung mass, and when the relative displacement moves away from the neutral position (in the excitation direction), the shock absorber is damped. The shock absorber is configured to reduce the force and, on the contrary, increase the damping force of the shock absorber when the relative displacement moves in a direction approaching the neutral position (damping direction), regardless of the magnitude of the relative displacement. First, the damping force is abruptly switched between two levels, large and small, depending on the direction of relative displacement. However, the bushing for connecting the shock absorber to the vehicle body, which is bent when the damping force is large, is released when switching to the small damping force, thereby generating an impactful moving force on the shock absorber. As a result, the shock absorber acts to vibrate the vehicle body due to its own weight, which causes an impact noise in the vehicle body and impairs the quietness of the vehicle interior.

[Means for solving problems]

This invention was made by focusing on these conventional problems, and as shown in the basic configuration diagram in Figure 1, the magnitude of the damping force is continuously adjusted according to the value of the input control signal. A variable damping force shock absorber that can be changed by changing the damping force, and a relative displacement amount between the sprung and unsprung portions of the vehicle connected by the variable damping force shock absorber, or a displacement amount that outputs a detection signal according to the force transmitted to the vehicle body. or a transmission force detection means;
a direction determining means for outputting a detection signal according to the direction of the relative displacement or transmitted force; and a direction determining means for outputting a detection signal according to the direction of the relative displacement or transmitted force; and a direction determining means for determining whether the relative displacement or transmitted force of the vehicle body is The damping force of the variable damping force shock absorber is increased when the damping direction is to suppress a change in attitude, and the variable damping force is increased when the relative displacement or transmission force is in the excitation direction to impart a change in attitude to the vehicle body. The value of the control signal is continuously changed and outputted so as to reduce the damping force of the shock absorber and to gradually switch the damping force at least when increasing the damping force or decreasing the damping force. By configuring a shock absorber control device including a control means,
The purpose is to solve the above problems.

[Effect]

Therefore, the present invention detects the amount of relative displacement between the sprung mass and the unsprung mass based on the transmission force applied to the vehicle by a displacement detection means, or detects the transmission force to the vehicle body by the transmission force detection means. The relative displacement or the direction of the transmitted force of the shock absorber is determined by the direction determining means, and the relative displacement or the transmitted force is determined by the control means based on each detection signal from the displacement amount detecting means or the transmitted force detecting means and the direction determining means. When the damping force is in the vibration excitation direction, the damping force of the variable damping force shock absorber is reduced, and when the relative displacement or transmission force is in the damping direction, the damping force is increased, and at least when the damping force is increased or decreased. On the other hand, by changing the value of the control signal continuously and outputting it to gradually switch the damping force, the shock at the time of switching the damping force is suppressed and the ride comfort and quietness of the vehicle are improved.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIGS. 2 to 11a and 11b are diagrams showing an embodiment of the present invention.

First, to explain the configuration, 1 shown in FIG.
A vehicle speed detector that outputs a detection signal according to the vehicle speed of the vehicle; 2a to 2d are displacement detection means that detect the relative displacement between the sprung and unsprung portions of the vehicle; 3 is a control device; 4a to 4d are: These are electromagnetic solenoids for variable damping force shock absorbers 6a to 6d, which will be described later.

As shown in FIG. 3, each of the displacement amount detection means 2a to 2d includes variable damping force shock absorbers 6a to 6a installed between each wheel 5a to 5d of the vehicle and the vehicle body.
It is attached to 6d.

Each variable damping force shock absorber 6a to 6d
As shown in FIG. 4, a piston 9 attached to the lower end of a piston rod 8 and a free piston 10 are slidably disposed in a cylinder tube 7. Therefore, the inside of the cylinder tube 7 is defined into three fluid chambers A, B and C. and,
The two fluid chambers A and B are filled with a working fluid such as hydraulic oil, and the other fluid chamber C is filled with high pressure gas.

The piston 9 has a central opening 12 whose upper end communicates with the fluid chamber A via a fluid passage 11 formed in the piston rod 8, and a central opening 12 which communicates with this and has a fluid chamber B.
A fluid passage 13 is bored in the center opening 12, and two fluid passages 11 and 1 are formed in the central opening 12.
A cylindrical spool 15 provided with a through hole 14 that communicates with the spool 3 is slidably disposed. This spool 1
5 is normally urged downward by a return spring 16, and its lower end surface contacts a plunger 17, and the lower end of this plunger 17 contacts the bottom surface of the case 18 to restrict its movement. In this state, the through hole 14 and the opening end of the fluid passage 13 are in the same position and are completely opened, so that the opening end of the fluid passage 13 is completely opened.
The two fluid passages 11 and 13 are in communication with each other with the maximum opening area.

Further, the plunger 17 is energized by applying an excitation current to the electromagnetic solenoids 4a to 4d disposed around it by the control device 3 via the lead wire 19, so that the plunger 17 is energized in proportion to the value of the excitation current. is moved upward. As a result, the spool 15 is displaced upward against the return spring 16, and the through hole 1
4, the opening area between the fluid passages 11 and 13 becomes smaller continuously depending on the value of the excitation current.

The attraction force characteristics of such electromagnetic solenoids 4a to 4d are shown in FIG.

That is, in FIG. 5, the value of the excitation current output by the control device 3 is plotted on the horizontal axis, the attractive force generated by the excitation current is plotted on the upper vertical axis, and the value of the plunger 17 is plotted according to the value of the excitation current. The stroke is plotted on the lower vertical axis. Here, the attractive force of the electromagnetic solenoids 4a to 4d with respect to an increase in the excitation current initially rises slowly in a curved manner, and soon changes linearly. Then, from around the time when the excitation current starts increasing linearly, the plunger 17 changes proportionally against the spring force of the return spring 16.

The graph showing the relationship between the excitation current and the stroke is stored in the form of a storage table in a predetermined storage area of the storage device of the microcomputer 30, which will be described later, and the output lookup table is referred to to determine the stroke size. The corresponding excitation current value is output as a digital signal to the output circuits 33a to 33d.

Therefore, the electromagnetic solenoid 4a~ from the control device 3
4d, when the spool 15 is urged downward by the return spring 16 and the two fluid passages 11 and 13 communicate with each other through the maximum opening area, each variable damping force shock absorber 6a The damping force of ~6d is set to a small damping force as shown by the solid line curve _lL in FIG.

On the other hand, the electromagnetic solenoids 4a to 4d are energized with a predetermined maximum value of excitation current to move the plunger 17 to the maximum, and the gap between the fluid passages 11 and 13 where the through hole 14 is at a position inconsistent with the open end of the fluid passage 13 is removed. When in communication, each variable damping force shock absorber 6
The damping forces a to 6d are set to a large damping force as shown by the curve _lH indicated by a broken line in the figure. Then, by continuously increasing the value of the excitation current by the control device 3, the plunger 17 moves upward in proportion to the increase in the excitation current. the result,
In response to the plunger 17, the spool 15 is displaced upward against the biasing force of the return spring 16, and the opening area between the two fluid passages 11 and 13 by the through hole 14 is made continuous according to the value of the excitation current. The damping force continuously increases steplessly, as represented by the curve _lJ indicated by the dashed line and the curve _l1 indicated by the dashed double dotted line in the figure.

The output value of the excitation current is stored in a predetermined storage area of the storage device of the microcomputer 30, which will be described later, in the form of a storage table, such as the graph shown in FIG. Calculate by referring to That is, the stroke of the plunger 17 corresponding to the relative displacement amount detected by the displacement amount detection means 2a to 2d is read with reference to the stroke lookup table, and then the output lookup table is referred to based on the stroke read value. Determine the output value of the excitation current.

However, the value shown in the graph of FIG. 7 may be calculated by the arithmetic processing unit of the microcomputer 30, and the output value of the excitation current may be determined based on the calculated value.

Further, a cylindrical cover 20 whose lower end reaches the cylinder tube 7 and covers it is integrally attached to the upper end of the piston rod 8. A displacement detecting coil 21 is wound around the vehicle to detect the relative displacement amount (that is, the relative displacement amount between the sprung portion and the unsprung portion of the vehicle) as an inductance change due to a change in the amount of overlap between the cover 20 and the cylinder tube 7. ing.

As shown in FIG. 8, the displacement detection coil 21 is incorporated into the LC oscillator 22 as a coil that determines the oscillation frequency of the LC oscillator 22.
From, cylinder tube 7 and piston rod 8
An oscillation output with a frequency corresponding to the amount of relative displacement between the two is output. The oscillation output is the frequency-voltage conversion circuit 2
3, and from now on as shown in Figure 9,
A displacement detection signal consisting of a voltage according to the relative displacement between the cylinder tube 7 and the piston rod 8
Sa to Sd are output. These displacement amount detection coil 21, LC oscillator 22, and frequency-voltage conversion circuit 23 constitute displacement amount detection means 2a to 2d.

As shown in FIG. 2, the control device 3 includes a microcomputer 30 having input/output ports, a processing unit (CPU), storage devices such as RAM, ROM, etc., and the vehicle speed detector is connected to the input port of the microcomputer 30. The vehicle speed detection signal DV of 1 is directly supplied, and the displacement detection signal Sa of each displacement detection means 2a to 2d is directly supplied.
-Sd are supplied to low-pass filters 24a-24d having a cutoff frequency of 10-15Hz, and filter output signals Fa-Fd that have passed through each of these low-pass filters 24a-24d are sent to a multiplexer 31.
and is supplied via the A/D converter 32.

The low-pass filters 24a to 24d are provided to prevent malfunctions due to fluctuations in the detection signals supplied thereto. That is, although the unsprung resonance frequency of general vehicles is 10 to 15 Hz, high frequency vibrations are superimposed on this and supplied, so the high frequency vibrations are transmitted to each of the low pass filters 24a to 24.
By cutting at d, it is intended to realize damping force control according to the unevenness of the road surface.

The microcomputer 30 transmits a control signal corresponding to the relative displacement output from the output port as a digital value to each variable damping force shock absorber 6.
Four output circuits 33a, 33b, 33c each having a D/A converter configuration installed corresponding to a to 6d.
and 33d, respectively. Switching type drive transistors 34a to 3d are individually connected to these four output circuits 33a to 33d.
Electromagnetic solenoids 4a to 4d of variable damping force shock absorbers 6a to 6d connected to a DC power source (not shown) are connected to 4a to 34d, respectively.

The output circuits 33a to 33d output drive signals to the drive transistors 34a to 34 according to the value of the control signal CSa supplied from the microcomputer 30.
d, and thereby an excitation current corresponding to the value of the control signal is supplied to each electromagnetic solenoid 4a-4d via the operation of each drive transistor 34a-34d.

Then, the microcomputer 30
The arithmetic processing is executed in accordance with a timer interrupt processing program stored in advance in, for example, the timer interrupt processing program shown in FIG. 10, which is executed every 5 msec, for example.

That is, in a step, the vehicle speed detection signal DV is read, for example, the number of pulses per unit time is measured to calculate the vehicle speed, and this is temporarily stored as the vehicle speed detection value V in the RAM of the storage device.

Next, the process moves to step and it is determined whether or not the vehicle is stopped. The determination in this case is made by reading out the vehicle speed detection value V stored in the above step and determining whether or not V≠0. Here, when the vehicle is stopped and V=0, the process moves to step and outputs the control signals CSa to CSd to the circuits 33a to 33d to control all variable damping force shock absorbers 6a to 6d to a large damping force.
output and then return to the main program.

On the other hand, if the determination result in the step is that the vehicle is running and V≠0, the process shifts to the damping force control processing after the step.

In the damping force control process, first, in step, the detection signal Sa of each displacement amount detection means 2a to 2d is
~Sd is processed by low-pass filters 24a to 24d to read the filter output signals Fa to Fd, and these are used as displacement detection values Xi (i = a, b, c, and d) of the relative displacement between the sprung mass and the unsprung mass. The data is temporarily stored in a predetermined storage area of the storage device. Next, the process moves to step and calculates the amount of change X〓i (i=a, b, c, and d) per unit time, which is the differential value of the detected displacement value Xi.

Next, the process moves to a step where the detected displacement value Xi stored in the step and the neutral position at the boundary position between the extension side and the contraction side of each variable damping force shock absorber 6i (i=a, b, c, and d) are calculated. Position displacement amount
A difference value D from Xn is calculated, and it is determined whether the difference value D is positive or negative. The determination in this case is to determine whether the relative displacement between the cylinder tube 7 and the piston rod 8 is in the extension side region or the contraction side region of the shock absorber 6i, and the extension side region where D≧0 is determined. In the state of , it moves to step.

In this step, the amount of change X〓i stored in the previous step is read, and it is determined whether these values are negative or positive. In this case, the judgment is made as to whether the relative displacement amount X〓i of the shock absorber 6i is in the excitation direction that applies a transmission force to the vehicle body (direction away from the _neutral position If X〓i _≦ 0, it is determined that the relative displacement is in the damping direction, and the process moves to step.

In the step, a control signal CSi is applied to control the variable damping force shock absorber 6i to a large damping force.
(i=a, b, c, and d) is outputted to the drive transistor 34i via each output circuit 33i, and the interrupt processing is then terminated and the process returns to the main program.

Further, when the determination result of the step is X〓i>0, it is determined that the relative displacement is in the excitation direction, and the process moves to the step. In this step, it is determined whether the value I of the excitation current supplied to the electromagnetic solenoid 4i of the variable damping force shock absorber 6i is the minimum current value Imin (0 may be used) when the damping force is small. In this case, the determination is based on the control signal output by the microcomputer 30 itself.
This can be done by looking at the value of CSi.

The result of this determination is that an excitation current of a value greater than the minimum current value is supplied to the electromagnetic solenoid 4i.
When Imin, move to step,
A predetermined correction current value ΔI set in advance is subtracted from the current value I of the excitation current, and then the process moves to step, where I=Imin, where the minimum current value of the excitation current is supplied to the electromagnetic solenoid 4i. Sometimes it goes directly to the step. In this step, a control signal CSi for controlling the damping force of the variable damping force shock absorber 6i to a small damping force is outputted to the drive transistor 34i via the output circuit 33i, and the interrupt processing is completed and the main program returns to the main program. Return.

On the other hand, if the judgment result of the step is D<0 and the detected displacement value Xi is in the contraction side region, the process moves to the step, reads the change value X〓i stored in the previous step, and determines that value. Determine whether it is positive or negative. Similar to the determination in the step above, the determination in this case is to determine whether the relative displacement between the sprung mass and the unsprung mass is in the damping direction or in the vibration excitation direction with respect to the vehicle body, and X〓i
When ≧0, it is determined that the vibration is in the damping direction.
Then, as described above, the control signal CSi for controlling the variable damping force shock absorber 6i to a large damping force is outputted to the drive transistor 34i via the output circuit 33i, and the interrupt processing ends. and return to the main program.

Further, when the judgment result of the step is X〓i<0, it is judged that the vibration is in the excitation direction, and similarly to the step and step described above, the step moves to step and step, and the electromagnetic vibration of the variable damping force shock absorber 6i is performed. The value I of the excitation current supplied to the solenoid 4i is the minimum current value when the damping force is small.
Determine whether or not Imin, and the result of the determination is
When I≠Imin, the process proceeds to step, where a predetermined correction current value ΔI set in advance is subtracted from the current excitation current value I, and then the process proceeds to step; however, when I=Imin, Go directly to the step. Then, in step, a control signal CSi for controlling the damping force of the variable damping force shock absorber 6i to a small damping force is output to the circuit 3.
3i to the drive transistor 34i,
This ends the interrupt processing and returns to the main program.

Here, the direction determination means is constituted by the step ~ step and the processing of the step, and the step ~
The step, the step, the step processing, and the output circuit 33i constitute a control means.

Next, the effect will be explained.

Assume that the vehicle is currently parked or stopped, and in this state, when the interrupt process shown in FIG. The signal DV is read and the detected vehicle speed value V is calculated based on this. At this time, since the vehicle is stopped, V=0,
It is determined in step that the vehicle is stopped, and the process proceeds to step, where a control signal is generated to control all variable damping force shock absorbers 6a to 6d to a large damping force.
CSa is outputted to drive transistors 34a to 34d via output circuits 33a to 33d.

As a result, the drive transistor 34i is turned on, and the two fluid passages 1 are connected to the electromagnetic solenoids 4a to 4d of each variable damping force shock absorber 6i.
An excitation current having a maximum current value Imax is applied so that the opening area between 1 and 13 is the minimum value of 0. Therefore,
Since each electromagnetic solenoid 4i is energized and exerts the maximum suction force, the plunger 17 of each shock absorber 6i rises to the uppermost position, which causes the spool 15 to move to the uppermost position against the urging force of the return spring 16. rise to position.

As a result, the communication state between the through hole 14 and the fluid passage 13 is cut off, and the two are displaced to mutually inconsistent positions.
The two fluid passages 11 and 13 are completely cut off. Therefore, two fluid chambers A and B
The flow resistance between them becomes the largest, and the damping force of each variable damping force shock absorber 6i is increased to the maximum. Thereby, when the vehicle is stopped, it is possible to prevent the vehicle body from being tilted due to passengers getting on and off the vehicle, and to maintain a stable vehicle body posture.

This stop control state from step to step continues until the vehicle starts running.

Next, when the vehicle starts running, the value of the vehicle speed detection signal DV from the vehicle speed detector 1 changes in accordance with the vehicle speed, so the vehicle detection value V calculated in step becomes V≠0. Therefore, the displacement detection means 2a to 2d move from step to step.
The displacement amount detection signals Sa to Sd are read and temporarily stored in a predetermined storage area of the storage device as displacement amount detection values Xi of relative displacement.

Next, proceed to step, read out the detected displacement value Xi stored in the previous step, differentiate it to calculate the amount of change X〓i, which is the amount of relative displacement per unit time, and store these. It is temporarily stored in a predetermined storage area of the device. Next, the process moves to a step in which a preset neutral position displacement amount X _N is subtracted from the displacement amount detection value Xi, and the current cylinder tube value is determined depending on whether the difference value D is positive or negative. It is determined whether the relative displacement between the piston rod 7 and the piston rod 8 is in the extension side region or the contraction side region.

At this time, when one wheel of the vehicle (for example, the front left wheel 5a) passes through an unevenness on the road surface,
When the distance between the cylinder tube 7 and the piston rod 8 of the variable damping force shock absorber 6a changes relative to each other due to the relative displacement of the curve S shown by the broken line in FIG. The damping force of the shock absorber 6a changes as shown by a thick curve B, and at this time the damping force of the shock absorber 6a is controlled as shown in control mode I shown in FIG. In FIG. 11a, a curve L indicated by a one-dot chain line indicates a characteristic when a small damping force corresponds to a relative displacement, and a curve H indicated by a two-dot chain line indicates a characteristic when a large damping force corresponds to a relative displacement.

In other words, when the detected displacement value Xi of the relative displacement moves to the elongation side region, it is determined in the step that D>0. Determine if there is.
In this case, if the relative displacement is moving away from the neutral position _XN , that is, in the excitation direction, until time t1 in Figure 11a, then
It is determined that Therefore, moving to step, the value I of the excitation current energized to the electromagnetic solenoid 4a is set so that the opening area between the two fluid passages 11 and 13 is the minimum attraction force (the attraction force is 0).
It also includes the state of ) is the minimum current value Imin that generates. At this time, the relative displacement is moving in the excitation direction and the current excitation current value I is the maximum current Imax, so in step I
It is determined that ≠Imin. Therefore, proceeding to step, a predetermined correction current value ΔI set in advance is subtracted from the current excitation current value Imax, and then,
Move to step.

In this step, the damping force of the variable damping force shock absorber 6a is corrected from the maximum current value Imax in order to make it slightly smaller than the maximum damping force due to the maximum current value Imax supplied to the electromagnetic solenoid 4a based on the processing in the step. A control signal CSa having a value obtained by subtracting the current value ΔI is supplied from the microcomputer 30 to the output circuit 33a. As a result, the value of the excitation current supplied to the electromagnetic solenoid 4a of the variable damping force shock absorber 6a becomes smaller than the initial value by the corrected current value ΔI, and the biasing force of the electromagnetic solenoid 4a is slightly reduced by the corrected current value. reduced.

As a result, the spool 15 moves slightly downward, so that the space between the through hole 14 and the fluid passage 13 is slightly opened, and the small opening area, which is slightly larger than that in the completely closed state, is created between the two fluid passages 11 and 13. will be in a connected state. As a result, the fluid resistance between the two fluid chambers A and B changes to a small extent, and the damping force of the variable damping force shock absorber 6a decreases slightly.

This damping force correction control is continued until the value of the current flowing through the electromagnetic solenoid 4a reaches the minimum current value Imin. Therefore, the damping force of the variable damping force shock absorber 6a changes stepwise during the time p1 during which the damping force of the shock absorber 6a changes from a large damping force to a small damping force, as shown in FIG. 11b. , the damping force based on the relative displacement gradually changes from a large damping force to a small damping force over a predetermined period of time, as shown in FIG. Thereafter, the damping force changes along the curve L of small damping force until reaching time t1.

Next, beyond time t1, the relative displacement is at the _neutral position
When it changes in the direction approaching , that is, in the damping direction,
Since it is determined in step that X<i><0, the process moves to step and outputs a control signal CSa for controlling the variable damping force shock absorber 6a to a large damping force to the drive transistor 34a via the output circuit 33a. As a result, the drive transistor 34 is turned on, and an excitation current of the maximum current value Imax is applied to the electromagnetic solenoid 4a of the variable damping force shock absorber 6a.

Therefore, the electromagnetic solenoid 4a is energized and exerts the maximum attraction force, which causes the plunger 17 of the shock absorber 6a to rise to the uppermost position, causing the spool 15 to resist the urging force of the return spring 16. and rise to the top position. As a result, the communication state between the through hole 14 and the fluid passage 13 is cut off and the two fluid passages 11 and 13 are displaced to mutually inconsistent positions, and the two fluid passages 11 and 13 are completely cut off, so that the two fluid chambers A The fluid resistance between and B becomes the largest, and the variable damping force shock absorber 6a changes to a large damping force. This high damping force state of the variable damping force shock absorber 6a continues until time t2.

Then, beyond time t2, the relative displacement reaches the neutral position.
When moving from _XN to the contraction side region, it is determined in step that D<0, so the process proceeds to step and it is determined whether the amount of change in relative displacement X〓i is positive or negative. In this case, from time t2 to next time t3
In the state where the relative displacement is moving in the excitation direction up to , it is determined that It is determined whether the current value I is the minimum current value Imin.

At this time, at time t2, the excitation current value I is the maximum current value Imax, so in step I≠
It is determined that Imin is present, and therefore the process moves to step, where the corrected current value ΔI is subtracted from the current excitation current value Imax, and then the process moves to step.
In this step, as mentioned above, the damping force of the variable damping force shock absorber 6a is adjusted to the maximum current value.
In order to make it slightly smaller than the maximum damping force by Imax,
A control signal CSa having a value obtained by subtracting the corrected current value ΔI from the maximum current value Imax is supplied from the microcomputer 30 to the output circuit 33a.

As a result, the value of the excitation current supplied to the electromagnetic solenoid 4a is reduced by the correction current value ΔI,
Based on the corrected current value, the electromagnetic solenoid 4a
Since the biasing force of the spool 15 is slightly reduced, the spool 15 moves slightly downward, so that the through hole 14 and the fluid passage 13
The two fluid passages 1 are opened by a small opening area that is slightly larger than the completely closed state.
1 and 13 are connected. As a result, 2
The fluid resistance between the two fluid chambers A and B changes to a small extent, and the damping force of the variable damping force shock absorber 6a becomes a small damping force. This damping force correction control is performed so that the value of the current flowing through the electromagnetic solenoid 4a is the minimum current value.
It continues until it reaches Imin.

Therefore, in this case as well, the damping force of the variable damping force shock absorber 6a is stepped during the time p2 during which the damping force of the shock absorber 6a changes from the large damping force to the small damping force, as shown in FIG. 11b. The damping force based on the relative displacement gradually changes from a large damping force to a small damping force over a predetermined period of time, as shown in FIG. This small damping force state changes along the small damping force curve L until reaching time t3.

After that, when the relative displacement changes in the damping direction beyond time t3, it is determined that Control is executed to switch the damping force of the shock absorber 6a to a large damping force. This state of large damping force continues until time t4.

Then, beyond time t4, the relative displacement reaches the neutral position.
When moving from _XN to the extension side region, as described above, the step and step are determined, then the step and step are entered, and the damping force variable shock absorber 6a is moved to the step.
Control is performed to successively reduce the damping force to a small damping force.

Below, similar variable damping force shock absorber 6
The control a is repeated, and in this way, changes in the attitude of the vehicle are suppressed.

Thus, in this embodiment, the relative displacement between the sprung and unsprung portions of the vehicle body due to the unevenness of the road surface is detected by the displacement detection means, and the direction of the relative displacement is determined by the direction determination means. When the damping direction is to suppress a change in attitude of the vehicle, the damping force of the variable damping force shock absorber is set to a large damping force, and when the relative displacement changes to the excitation direction that causes a change in attitude of the vehicle body, the large damping force is reduced to a small damping force. Since the shock absorber is gradually switched over a predetermined period of time to the shock absorber, it is possible to suppress generation of an impulsive moving force on the shock absorber at the time of the switch. Therefore, the vibration of the vehicle body due to the weight of the shock absorber can be suppressed, and the ride comfort and quietness of the vehicle can be improved.

In addition, in the above embodiment, the shock absorber 6
When the relative displacement of i changes from the damping direction to the excitation direction, the damping force of the shock absorber 6i is changed from a large damping force to a small one, regardless of whether the relative displacement is in the extension side region or the contraction side region. Although the damping force is gradually changed over a predetermined period of time, the control may be executed only when the relative displacement is in the expansion side region, as shown in FIGS. 11c and 11d.

This means that in a normal variable damping force shock absorber, the damping force generated when the relative displacement moves to the extension side area is more than twice as large as the damping force generated when the relative displacement moves to the contraction side area. It focuses on points. Such damping force switching control is the same as the timer interrupt processing program shown in FIG. 10, except for steps and step processing.

The timer interrupt processing program is executed by the microcomputer 30, and at this time, the curve S ₂ shown by the broken line in FIG. 12a (same as the curve S shown in FIG. 11a)
When the relative displacement between the cylinder tube 7 and the piston rod 8 of the variable damping force shock absorber 6a changes relative to each other, the damping force of the variable damping force shock absorber 6a relative to the relative displacement changes as shown by the thick line _B2 . At this time, the damping force of the shock absorber 6a is controlled as shown in the control mode shown in FIG. In FIG. 11a, the same parts as in FIG. 11a are given the same reference numerals.

That is, when the damping force switching control of this embodiment is executed, as shown in FIGS. The force changes rapidly from large damping force to small damping force,
Since the damping force in the compression side region is significantly smaller than the damping force in the extension side region, a very large shock does not occur when switching between the two, and therefore, this embodiment also has the same effect as the previous embodiment. can be obtained.

FIG. 13 shows another embodiment of the processing procedure of the microcomputer 30.

In this embodiment, when the relative displacement of the shock absorber 6i is in either the extension side region or the contraction side region, the large damping force is changed to the small damping force when the relative displacement changes from the damping direction to the vibration excitation direction. Not only is the damping force switched gradually by the damping force switching control, but also the small damping force is gently switched to the large damping force when the relative displacement changes from the vibration excitation direction to the damping direction.

In this embodiment, as shown in FIG. 14a, neutral regions of a predetermined width are provided above and below the neutral position _XN of the relative displacement, and when the relative displacement of the shock absorber 6a is in the damping direction, the In both the area and the contraction side area, the damping force is started to be switched when the neutral area displacement amount δ is reached, and the damping force switching is then finished when the neutral position X _N is reached. When the relative displacement is displacing in the excitation direction, the damping force starts to be switched when the rate of change of the relative displacement becomes a predetermined value K or -K or less in both the extension side region and the contraction side region, and then The switching of the damping force is completed when the relative displacement reaches the peak value.

An example of a flowchart for executing this damping force switching control is shown in FIG. In the same figure,
Steps that are the same as those shown in FIG. 10 are given the same reference numerals.

Of the timer interrupt processing program shown in FIG. 13, the steps that are different from the processing in FIG. 6
It is determined whether or not it is in the neutral region excluding the growth side neutral region (X _N ~+δ) of i.

That is, in the step, a predetermined neutral position displacement amount δ set from the neutral position X _N to the extension side is set to the neutral position displacement amount X _N , which is the boundary position between the extension side and the contraction side, in each variable damping force shock absorber 6i. Calculate the difference value _D1 by subtracting the added value (X _N + δ) from the detected displacement value Xi stored in step, and check whether the difference value _D1 is positive or negative. judge. As a result of this determination, if the state is in the elongation side region where D ₁ >0, the process moves to the step.

In the step, the amount of change X〓i, which is the differential value of the relative displacement stored in the step, is read, and it is determined whether or not the value is smaller than a predetermined value K set in advance. In this case, the judgment is made by checking whether the amount of change in the relative displacement of the shock absorber 6i, X〓i, has decreased to a predetermined value or less, thereby determining whether the relative displacement has reached a predetermined position at its peak. When X〓i≦K, it is determined that the relative displacement has reached a predetermined position before the peak value, and the process moves to step.

In this step, the value I of the excitation current supplied to the electromagnetic solenoid 4i of the variable damping force shock absorber 6i is the maximum current value when the damping force is large.
Determine whether it is Imax. The determination in this case can be made by looking at the value of the control signal CSi output by the microcomputer 30 itself.

As a result of the determination, if I≠Imax, meaning that an excitation current larger than the minimum current value Imin is supplied to the electromagnetic solenoid 4i, the process moves to step 〓〓, where the current excitation current value I is preset. The predetermined correction current value ΔI is added, and then the process moves to step, but when the excitation current of the maximum current value Imax is supplied to the electromagnetic solenoid 4i,
Go directly to the step.

On the other hand, if the step judgment result is D ₁ ≦0 and the relative displacement detection value Xi is not in the extension side region excluding the extension side neutral region, the step is shifted to the change amount X stored in the previous step. Read 〓i and determine whether the value is negative or positive.

In this step, contrary to the determination in step, each variable damping force shock absorber 6i
A predetermined neutral position displacement amount δ set on _{the contraction side from the neutral position X N is} subtracted from the neutral position displacement amount X _N at A difference value D ₂ is calculated by subtracting from , and it is determined whether the difference value D ₂ is negative or positive. In this case, the judgment is that the cylinder tube 7
It is determined whether the relative displacement between the piston rod 8 and the piston rod 8 is in the contraction side region of the shock absorber 6i and excluding the contraction side neutral region (X _N −δ), and D ₂ < In the state where it is 0,
Move to step 〓〓.

In this step 〓〓, the amount of change X〓i stored in step 〓 is read, and it is determined whether the value is smaller than a predetermined value -K. In this case, the determination is made by checking whether the amount of change in the relative displacement of the shock absorber 6i has decreased to a predetermined value position, and thereby determining whether the relative displacement has reached a predetermined position before the peak value. If there is, and X〓i≦−K, it is determined that the relative displacement has reached a predetermined position before the contraction side peak value, and the process proceeds to the step described above. Then, control is performed to gradually switch the damping force of the variable damping force shock absorber 6i from the small damping force to the large damping force over a predetermined period of time.

Further, when the judgment result of the step 〓〓 is X〓i>-K, the process moves to the step and the damping force of the variable damping force shock absorber 6i is gradually increased over a predetermined period of time to a large damping force, as described above. Control is performed to switch from to small damping force.

Further, when the step determination result is D ₂ <0, the relative displacement X〓i is in the neutral region, so the process directly moves to the step.

Thus, according to this embodiment, when the relative displacement changes from the control direction to the excitation direction, the large damping force is not only gradually switched over a predetermined period of time to the small damping force, but also the relative displacement is controlled from the excitation direction. Even when changing in the vibration direction, the small damping force is gradually switched over a predetermined period of time to the large damping force, so it is possible to more effectively suppress the occurrence of an impactful moving force on the shock absorber during the switching. . Therefore,
It is possible to effectively suppress the vibration of the vehicle body due to the weight of the shock absorber, and the ride comfort and quietness of the vehicle can be greatly improved.

Incidentally, it is also possible to gradually change the damping force described above, for example, by providing a chamfer or spiral groove on the spool 15, and using mechanical means to moderate the change in fluid resistance when passing through these grooves. In this case, since there is no degree of freedom in damping force control, the switching time cannot be arbitrarily set, and tuning of the switching time is difficult.

In each of the above embodiments, the case where only the front left wheel 5a passes through an uneven road surface has been described, but when the other wheels 5b to 5d pass through an uneven road surface, the damping force variable shock absorber is used in the same manner as described above. 6b to 6d are controlled.

Further, in the above embodiment, a case has been described in which a detection coil is used as the displacement amount detection means 2a to 2d to detect the relative displacement between the cylinder tube 7 and the piston rod 8. However, the present invention is not limited to this. Instead, as shown in FIG. 15, a variable damping force shock absorber 6i
The voltage shown in FIG. 16 corresponds to the transmission force transmitted to the variable damping force shock absorber 6i by the piezoelectric element 42 inserted in the attachment part 41 to the vehicle body side member 40 at the tip of the piston rod 8. A displacement detection signal may also be obtained.

In this case, when the vehicle overcomes temporary irregularities on the road surface, it is possible to detect the transmission force transmitted from the piezoelectric element 42 to the vehicle body with pitching and bouncing as shown in FIG. 17. Therefore, by inputting the displacement amount detection signal from the piezoelectric element 42 to the control device 3 of FIG. 2, the same effects as in the above embodiment can be obtained. Moreover,
Since the force transmitted to the vehicle body is directly detected using a piezoelectric element, there is less response delay than when detecting relative displacement, enabling accurate vibration damping control and ensuring excellent ride comfort. In addition, since the piezoelectric element 42 is used as the detection element, it has the advantage that it is not only easy to assemble but also can be constructed at low cost.

In addition, in FIG. 15, 43 is a coil spring, 44 and 45 are spring seats, and 46 is a mount insulator.

Further, as other displacement detection means, it is possible to apply a displacement detection means such as a distance measuring device that measures the distance between the road surface and the vehicle body using ultrasonic waves provided at each wheel position of the vehicle body. can. Furthermore,
The variable damping force shock absorber 6i is not limited to the above configuration, and any variable damping force shock absorber may be used as long as it has a configuration that allows the damping force to be continuously changed by inputting a control signal. can do. Furthermore, as another example of the direction determining means, it is of course possible to use a gravitational acceleration sensor that detects acceleration applied to the vehicle body.

Further, the control device 3 is not limited to the above-mentioned configuration, but can also be configured with an electronic circuit such as a subtraction circuit, a comparison circuit, a logic circuit, etc.
The control device 3 outputs pulse outputs with different duty ratios to control the variable damping force shock absorber 6i.
It is also possible to continuously change the damping force according to the transmitted force. Furthermore, in the above embodiment,
Although the case has been described in which the neutral position displacement amount X _N is stored in advance, the vehicle height displacement amount when a passenger is on the vehicle may be detected while the vehicle is stopped, and the neutral position displacement amount may be calculated based on this. .

In the above embodiment, the damping force control is performed based only on the amount of relative displacement between the sprung and unsprung portions of the vehicle or the magnitude of the force transmitted to the vehicle body. It is also possible to control the damping force of the variable damping force shock absorber in consideration of other driving conditions. Especially in general bottoming control, rolling control, etc.
At high speeds, the front wheels are controlled with high damping force and the rear wheels with low damping force, but by continuously changing the damping force characteristics of the front wheels according to the vehicle speed as described above, it is possible to The steering stability of the vehicle can be further improved.

〔Effect of the invention〕

As explained above, in the present invention, the amount of relative displacement between the sprung portion and the unsprung portion of the vehicle based on the transmission force applied to the vehicle body via the shock absorber is detected by the displacement amount detection means or transmitted to the vehicle body. The force is detected by the transmitted force detection means, the direction of the relative displacement or the transmitted force is determined by the direction determining means, and the relative displacement or the transmitted force is applied by the control means based on the detection signals from the detecting means and the direction determining means. When the displacement is in the vibration direction, the damping force is decreased, and when the relative displacement or transmitted force is displaced in the vibration damping direction, the damping force is increased, and when the damping force is increased or the damping force is decreased. The damping force of the variable damping force shock absorber is continuously changed at least on one side when the damping force is changed, and the damping force is gradually changed over a predetermined period of time. Therefore, when switching the damping force, it is possible to effectively suppress generation of an impactful moving force on the shock absorber due to elastic deformation of the bush to elastically connect the shock absorber to the vehicle body. It is possible to prevent the car body from being vibrated by its own weight and eliminate impact noise from the car body.
Therefore, the effect of improving the riding comfort and quietness of the vehicle can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of this invention, FIG. 2 is a block diagram showing an embodiment of this invention, and FIG. 3 is a block diagram showing a schematic configuration of this invention.
FIG. 4 is a sectional view showing an example of a variable damping force shock absorber applicable to the present invention, FIG. 5 is a graph showing the characteristics of the electromagnetic solenoid, FIG. 6 is a characteristic curve diagram showing the damping force characteristics, and FIG. Figure 7 is a graph showing the relationship between the stroke and the relative displacement, Figure 8 is a block diagram showing an example of the displacement detection means, Figure 9 is a graph showing the relationship between the output voltage and the relative displacement, and Figure 10 is the control. A flowchart showing an example of the processing procedure of the device, FIGS. 11a and 11b are signal waveform diagrams for explaining the operation of the present invention,
FIGS. 12a and 12b are signal waveform diagrams for explaining another embodiment of the operation of the present invention, FIG. 13 is a flowchart showing another example of the processing procedure of the control device, and FIGS. 14a and b are FIG. 15 is a sectional view showing another embodiment of the displacement detection means, FIG. 16 is a graph showing the relationship between the output voltage and the vehicle body transmission force, and FIG. 17 is the road surface It is a graph showing an output voltage waveform when overcoming unevenness. DESCRIPTION OF SYMBOLS 1... Vehicle speed detector, 2a-2d... Displacement detection means, 3... Control device, 4a-4d... Electromagnetic solenoids, 5a-5d... Wheels, 6a-6d... Variable damping force shock absorber, 7 ...Cylinder tube, 8...Piston rod, 11, 13...
Fluid passage, 14...Through hole, 15...Spool, 1
7... Plunger, 21... Displacement detection coil,
22...LC oscillator, 23...Frequency-voltage conversion circuit, 24a to 24d...Low pass filter, 3
0... Microcomputer, 31... Multiplexer, 32... A/D converter, 33a to 33d
...Output circuit, 34a to 34d...Drive transistor, 42...Piezoelectric element.

Claims (1)

[Claims] 1. A variable damping force shock absorber that can continuously change the magnitude of damping force according to the value of an input control signal, and a relative relationship between the sprung and unsprung parts of the vehicle connected by this variable damping force shock absorber. a displacement amount or transmission force detection means that outputs a detection signal according to the displacement amount or the transmission force to the vehicle body; a direction determination means that outputs a detection signal according to the direction of the relative displacement or transmission force; and the displacement amount. or increasing the damping force of the variable damping force shock absorber when the relative displacement or the transmitted force is in a vibration damping direction that suppresses a change in attitude of the vehicle body based on each detection signal from the transmission force detection means and the direction determination means; Further, when the relative displacement or transmitted force is in an excitation direction that imparts a posture change to the vehicle body, the damping force of the variable damping force shock absorber is decreased, and the damping force is increased or the damping force is decreased. A shock absorber control device comprising: control means for continuously changing and outputting the value of the control signal so as to gently switch the damping force on at least one of the damping forces.