JPH0435204Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] 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 the vehicle and improve the 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 attempts to solve]

However, with such conventional shock absorber control devices, the damping force of the shock absorber can be controlled at high speed in two stages, high and low, using an ON-OFF solenoid according to the driving conditions, regardless of the uneven shape of the road surface. Because the system was configured to perform binary control, it was not possible to appropriately attenuate the excitation force transmitted to the vehicle body due to the unevenness of the road surface. There was a problem in that this phenomenon occurred and the riding comfort could not be improved.

Therefore, the applicant of the present application filed the previously filed patent application
-106294, a 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 We have proposed a shock absorber control device configured to reduce the damping force of the shock absorber, and to increase the damping force of the shock absorber when the relative displacement moves in a direction approaching the neutral position (damping direction).

However, even in this device, the damping force is switched between high and low levels depending on the direction of the relative displacement, regardless of the magnitude of the relative displacement. Therefore, even when the relative displacement is small, the bushing that connects the shock absorber to the vehicle body, which is bent during high damping force, is released when switching to low damping force, and this causes an impactful moving force to be applied to the shock absorber. Occur. As a result, the shock absorber acts to vibrate the vehicle body due to its own weight, giving the occupant a bumpy feeling, which impairs the ride comfort of the vehicle, which is an unresolved problem.

[Means for solving problems]

This idea was made by focusing on these unresolved points in the past, and as shown in the basic configuration diagram in Figure 1, the magnitude of the damping force can be adjusted according to the value of the input control signal. A variable damping force shock absorber that can continuously change the damping force and outputs a detection signal according to the amount of relative displacement between the sprung and unsprung parts of the vehicle connected by the variable damping force shock absorber or the force transmitted to the vehicle body. A means for detecting the amount of displacement or transmitted force, and a direction for detecting the relative displacement or transmitted force detected by the detecting means is an excitation direction that causes a change in attitude of the vehicle body or a damping direction that suppresses a change in attitude of the vehicle body. a direction determining means for determining the damping force of the variable damping force shock absorber, and a relative displacement or magnitude of the transmission force based on a detection signal from the detecting means when the determination result of the direction determining means is in the vibration damping direction; The above-mentioned unsolved problem can be solved by configuring a shock absorber control device including a control means for outputting the control signal that continuously changes the damping force according to the vibration direction and maintains the damping force at a low level in the excitation direction. The purpose is to resolve the issue.

[Effect]

Therefore, this 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 the displacement detection means, or detects the transmission force to the vehicle body by the transmission force detection means, The detection signal is supplied to a direction determining means, which determines whether the relative displacement of the shock absorber or the direction of the transmitted force is an excitation direction that causes a change in attitude of the vehicle body, or a damping direction that suppresses a change in attitude of the vehicle body. When the damping direction is determined, the control means continuously changes the damping force of the variable damping force shock absorber according to the relative displacement or the magnitude of the transmitted force to suppress changes in the attitude of the vehicle body, In some cases, regardless of the relative displacement or the magnitude of the transmitted force, the damping force of the variable damping force shock absorber is set to a low damping force to suppress changes in the attitude of the vehicle body, and the damping force is optimally controlled according to changes in the attitude of the vehicle. This improves the ride comfort and handling stability of the vehicle.

〔Example〕

This invention will be explained below based on illustrated embodiments.

FIGS. 2 to 11 are diagrams showing an embodiment of this 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 parts of the vehicle; 3 is a control device; 4a to 4d are: These are electromagnetic solenoids of 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 case 18 is normally urged downward by a return spring 16, and its lower end surface abuts the plunger 17, and the lower end of the plunger 17 contacts the case 18. It comes into contact with the bottom of the body and restricts its movement. In this state, the through hole 14 and the open end of the fluid passage 13 are in the same position and are completely opened, so that the two fluid passages 11 and 13 are in communication.

Further, the plunger 17 is energized by applying excitation currents Ia to Id through the control device 3 via the lead wires 19 to the electromagnetic solenoids 4a to 4d disposed around the plunger. Moved upward in proportion to the value of Id. As a result, the spool 15 is displaced upward against the return spring 16, and the opening area between the fluid passages 11 and 13 formed by the through hole 14 becomes smaller continuously.

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

That is, in FIG. 5, the values of the excitation currents Ia to Id output by the control device 3 are plotted on the horizontal axis,
The attraction force generated by Ia to Id is plotted on the upper vertical axis, and the plunger 1 is plotted according to the value of the exciting current Ia to Id.
7 strokes are taken on the lower vertical axis. Here, the attractive force of the electromagnetic solenoids 4a to 4d with respect to the increase in the excitation currents Ia to Id initially rises slowly in a curved manner, and soon changes linearly. Then, from around the time when the excitation currents Ia to Id start 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 from the microcomputer 30 to the output circuits 33a to 33d.

Therefore, the electromagnetic solenoid 4a~ from the control device 3
Excitation current Ia~Id is not output to 4d, and spool 1
5 is urged downward by the return spring 16 and the two fluid passages 11 and 13 are in communication through the maximum opening area, the damping force of each variable damping force shock absorber 6a to 6d is as shown in FIG. The damping force is set to be low as shown by the curve shown by the solid line _L.

On the other hand, the exciting current Ia is applied to the electromagnetic solenoids 4a to 4d.
When the plunger 17 is moved to the maximum by energizing a predetermined maximum value of ~Id and the fluid passages 11 and 13 are brought into a state of non-communication between the fluid passages 11 and 13 where the through hole 14 takes a position inconsistent with the opening end of the fluid passage 13, each damping force The damping force of the variable shock absorbers 6a to 6d is indicated by the broken line l _H in the figure.
The damping force is set to high as shown by the curve shown in . Then, by continuously increasing the values of the excitation currents Ia to Id by the control device 3, the excitation current Ia
~The plunger 17 moves upward in proportion to the increase in Id. As a result, the spool 15 is displaced upward in response to the plunger 17 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 increased by the excitation currents Ia to Id. The damping force increases continuously according to the value, and the damping force becomes
In the figure, the damping force is continuously and steplessly increased, as represented by the dashed-dotted line _lJ and the dashed-double line _lI .

The output values of the excitation currents Ia to Id are calculated by referring to a stroke up table in which, for example, the graph shown in FIG. do. That is, the displacement amount detection means 2a is determined by referring to the stroke pickup table.
The stroke of the plunger 17 corresponding to the relative displacement amount detected in steps 2d to 2d is read, and then, based on the stroke read value, the output value of the excitation current is determined by referring to the output lookup table.

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 circuit 22 as a coil that determines the oscillation frequency of the LC oscillator 22.
2 outputs an oscillation output with a frequency corresponding to the amount of relative displacement between the cylinder tube 7 and the piston rod 8. The oscillation output is supplied to the frequency-voltage conversion circuit 23, and from this, as shown in FIG.
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 detection coils 21, LC oscillation circuit 22, and frequency-voltage conversion circuit 23 provide displacement detection means 2a to 2d.
It consists of

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 is multiplexer 31 and A/D converter 3
2.

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 34d are individually connected to these four output circuits 33a to 33d, and each drive transistor 34a
to 34d are connected to electromagnetic solenoids 4a to 4d of variable damping force shock absorbers 6a to 6d, respectively, which are connected to a DC power source (not shown).
Each of the output circuits 33a to 33d controls each electromagnetic solenoid 4a to 4d of the variable damping force shock absorber 6a to 6d in accordance with the value of the supplied control signal.
The current value that can flow through the transistors 34a to 34d is adjusted, and a drive signal is output to each of the drive transistors 34a to 34d. As a result, an exciting current having a value corresponding to the magnitude of the relative displacement is supplied to the electromagnetic solenoids 4a to 4d.

Then, the microcomputer 30
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 50 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 the vehicle is stopped. The determination in this case is made by reading out the vehicle speed detection value V stored in the step above 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 high damping force.
output and then return to the main program.

On the other hand, when the determination result in step is V≠0, which means that the vehicle is running, the process moves to the damping force control process 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 and convert them into detected displacement values Xi (i=a, b, c
and d), temporarily stored in a predetermined storage area of the storage device. Next, the process moves to step and calculates the amount of change Xi (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 determined. 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 contraction side region where D<0 is determined. In the state of , it moves to step.

In step, the amount of change Xi stored in the previous step is read, and it is determined whether these values are positive or negative. In this case, _the determination is made whether the relative displacement amount Xi 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 Xi<0, it is determined that the relative displacement is in the excitation direction, and the process moves to step.

In the step, a control signal CSi for controlling the variable damping force shock absorber 6i to a low damping force is provided.
(i=a, b, c, and d) is output to each output circuit 33i, and the interrupt processing is then terminated to return to the main program.

Moreover, when the determination result of the step is Xi≧0, it is determined that the relative displacement is in the damping direction, and the process moves to the step. In this step, an output value corresponding to the displacement amount at the peak of the relative displacement calculated in the previous step is calculated by referring to a stroke lookup table and an output lookup table stored in a predetermined storage area of the storage device in advance. do.

Next, the process proceeds to step, where the output circuit outputs a control signal CSi for controlling the damping force of the variable damping force shock absorber 6i to a damping force corresponding to the amount of change at the peak time from the low damping force to the high damping force. 3
3i, which ends the interrupt processing and returns to the main program.

On the other hand, if the judgment result of the step is D≧0 and the detected displacement value Xi is in the elongation side region, the process moves to the step, reads the change amount Xi stored in the previous step, and if the value is negative. Determine whether it is true or not. 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 vibration excitation direction or vibration damping direction with respect to the vehicle body.
When ≧0, it is determined that the vibration is in the excitation direction.
Then, as described above, the control signal CSi for controlling the variable damping force shock absorber 6i to a low damping force is output to the output circuit 33i, and the interrupt processing is completed and the main program is returned to. do.

Further, when the step determination result is Xi<0, it is determined that the vibration is in the damping direction, and as described above, the process moves to step and step.
An output value corresponding to the displacement amount at the peak of the relative displacement calculated in the step is calculated by referring to the two lookup tables, and then the damping force of the variable damping force shock absorber 6i is calculated according to the displacement amount at the peak time. Control signal CSi to control the damping force according to
is outputted to the output circuit 33i, the interrupt processing is ended, and the process returns to the main program.

Here, the direction determination means is constituted by the processing of step ~ step and step, and 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 in a parked or stopped state, and in this state, when the interrupt process shown in FIG. Load the DV,
Based on this, the vehicle speed detector V is calculated. At this time, since the vehicle is stopped, V=0, and it is determined in step that the vehicle is stopped, and the process proceeds to step, where a control signal is sent to control all variable damping force shock absorbers 6a to 6d to a high damping force. CSa～
CSd is output to output circuits 33a to 33d.

In this way, when the control signal CSi is supplied to the output circuits 33i, these output circuits 33i adjust the amount of current supplied to each electromagnetic solenoid 4i of the variable damping force shock absorber 6i when the drive transistor 34i is activated, and also A drive signal is output to the transistor 34i to operate the drive transistor 34i. As a result, the drive transistor 34
i is turned on, and the maximum excitation current within a predetermined range is applied to the electromagnetic solenoids 4a to 4d of each variable damping force shock absorber 6i. Therefore, each electromagnetic solenoid 4i is energized and exerts the maximum suction force, so that in each shock absorber 6i, the plunger 17 rises to the uppermost position, which causes the spool 15 to move toward the return spring 1.
It rises to the top position against the urging force of 6.

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 cut off. Therefore, the fluid resistance between the two fluid chambers A and B is maximized, and the damping force of each variable damping force shock absorber 6i is maximized. 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 pulse interval of the vehicle speed detection signal DV from the vehicle speed detector 1 becomes shorter in accordance with the vehicle speed, so the vehicle speed detection value V calculated in the step becomes V≠0. Therefore, moving from step to step, reading the displacement detection signals Sa to Sd of the displacement detection means 2a to 2d,
These are 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 displacement detection value Xi stored in the previous step, differentiate it to calculate the change amount Xi of relative displacement per unit time, and store these in a predetermined storage area of the storage device. Memorize temporarily. Next, the process moves to step, and the preset neutral position displacement amount X _N is subtracted from the displacement amount detection value Xi, and depending on whether the difference value D is positive or negative, the current cylinder tube is determined. 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 cylinder tube 7 and piston rod 8 of the variable damping force shock absorber 6a relatively fluctuate due to the relative displacement shown by the broken line S in FIG. 11a, the detected displacement value Xa is on the extension side. When moving to the area, it is determined that D>0 in step. Therefore, the process moves to step and determines whether the amount of change Xa in relative displacement is negative or positive.

In this case, when the relative displacement up to time _t1 is moving away from the neutral position A control signal for controlling the damping force of the absorber 6a to a low damping force is supplied from the microcomputer 30 to the output circuit 33a.

The control signal in this case is a command signal that minimizes the damping force, and is set so that no current flows through the electromagnetic solenoid 4a by the operation of the output circuit 33a. Therefore, the variable damping force shock absorber 6
The supply of excitation current to the electromagnetic solenoid 4a of a is cut off, and the electromagnetic solenoid 4a is maintained in a non-energized state.

As a result, the through hole 14 maintains communication with the fluid passage 13 with the maximum opening area, and the two fluid passages 11 and 13 communicate with each other with the maximum opening area. As a result, the fluid resistance between the two fluid chambers A and B is minimized, and the damping force of the variable damping force shock absorber 6a is adjusted to the curve L representing the damping force characteristic at low damping force shown by the dashed line in FIG. The damping force is set to low by

Next, beyond time t1, the relative displacement is at the neutral position.
When it changes in the direction approaching _XN , that is, in the damping direction, it is determined in step that Xa<0, so the process moves to step and refers to the stroke pickup table stored in a predetermined storage area of the storage device. , the plunger 17 according to the displacement amount D of the relative displacement at the peak time calculated in the above step.
The value of the excitation current Ia at the peak is calculated by referring to the output lookup table stored in a predetermined storage area of the storage device based on this stroke value, and the control signal is
CSa is output to the output circuit 33a.

Next, proceeding to step, the output circuit 33
At step a, the amount of current supplied to the electromagnetic solenoid 4a is adjusted in accordance with the value of the control signal, and then the switching type drive transistor 34a is activated. As a result, the drive transistor 34a is turned on, and a value h corresponding to the magnitude of the relative displacement at that time is set.
The excitation current of 1 is applied to variable damping force shock absorber 6.
The electromagnetic solenoid 4a of a is energized. Therefore, the attraction force of the electromagnetic solenoid 4a becomes strong in accordance with the magnitude of the relative displacement, and the plunger 17 rises to a position corresponding to the strength of the attraction force.

In this case, if the magnitude of the relative displacement is greater than the reference value for controlling the damping force of the variable damping force shock absorber 6a to a high damping force, the attraction force of the electromagnetic solenoid 4a becomes maximum, and the plunger 17 moves to the top. rise to position. As a result, the spool 15 rises to the uppermost position against the biasing force of the return spring 16, so that the through hole 14 and the fluid passage 13 are completely cut off, and the two fluid passages 11 and 13 are No fluid movement. As a result, the flow of the working fluid between the two fluid chambers A and B becomes most difficult, and the damping force of the variable damping force shock absorber 6a at the high damping force shown by the two-dot chain line in FIG. A high damping force is set according to a curve H representing damping force characteristics.

Then, beyond time t2, the relative displacement reaches the neutral position.
When moving from X _N to the contraction side region, it is determined in step that D<0, so the process moves to step and it is determined whether the amount of change Xa in relative displacement is positive or negative. In this case, when the relative displacement is moving in the excitation direction from time t2 to the next time t3, it is determined that Xa<0,
Shifting to the step, the microcomputer 30 outputs the control signal CSa for controlling the damping force of the variable damping force shock absorber 6a to a low damping force to the output circuit 33a from the time t2 has passed.

Therefore, the supply of the excitation current Ia to the electromagnetic solenoid 4a is cut off by the operation of the output circuit 33a, so that the electromagnetic solenoid 4a changes to a non-energized state. As a result, the spool 15 is displaced to the lowered position by the return spring 16, so that the through hole 14 and the fluid passage 13 are aligned, and the fluid resistance between the two fluid chambers A and B is reduced and damped. The damping force of the force shock absorber 6a is changed to a low damping force again.

After that, when the relative displacement changes in the damping direction beyond time t3, it is determined that Xa≧0 after step determination, so the process moves to step and in the same manner as described above, at time t3. A stroke value of the plunger 17 is calculated according to the peak value of the relative displacement, and a control signal corresponding to the value of the excitation current for obtaining the stroke is output to the output circuit 33a. As a result, the output circuit 33a
The electromagnetic solenoid 4a adjusts the current value that can flow in accordance with the magnitude of the relative displacement, and then outputs a drive signal to the drive transistor 34a.

When the drive signal is supplied to the drive transistor 34a in this way, the drive transistor 34a is turned on, and an excitation current having a value h2 corresponding to the magnitude of the relative displacement is energized to the electromagnetic solenoid 4a of the variable damping force shock absorber 6a. Ru. Therefore, a suction force corresponding to the magnitude of the relative displacement is generated in the electromagnetic solenoid 4a, and the plunger 17 rises to a position corresponding to the suction force. As a result, the spool 15 rises against the biasing force of the return spring 16 to a position corresponding to the magnitude of the relative displacement, so that the opening area of the through hole 14 and the fluid passage 13 is slightly smaller than the maximum opening area. The fluid resistance between the two fluid passages 11 and 13 is moderate. As a result, two fluid chambers A,
The flow of working fluid between B and B becomes moderate, and the damping force of the variable damping force shock absorber 6a is set to a damping force corresponding to the current magnitude of relative displacement, which is slightly lower than that at the time t1. Ru.

Then, beyond time t4, the relative displacement reaches the neutral position.
When moving from _XN to the elongation side region, it is determined in step that D≧0, so the process moves to step and it is determined whether the amount of change in relative displacement Xa is negative or positive. When this time point t4 is exceeded, it is determined in step that Xa<0, so the control device 3 moves to step and controls the damping force of the variable damping force shock absorber 6a to a low damping force in the same manner as described above. do.

That is, since the drive signal is not outputted from the output circuit 33a to the drive transistor 34a, and the drive transistor 34a is turned off, the electromagnetic solenoid 4a is turned off. As a result, the spool 15 is displaced to the lowered position by the return spring 16, so that the through hole 14 and the fluid passage 13 are aligned, and the fluid resistance between the two fluid chambers A and B is reduced. The damping force of the variable damping force shock absorber 6a is changed to a low damping force again.

Next, when the relative displacement changes in the damping direction beyond time t5, it is determined that Xa < 0 at step after the step determination, so the process moves to step and, in the same manner as described above, time t5 A stroke value of the plunger 17 corresponding to the peak value of the relative displacement at is calculated, and a control signal corresponding to the stroke value is output to the output circuit 33a. Thereby, the output circuit 33a adjusts the current value that can flow through the electromagnetic solenoid 4a according to the value of the control signal, and outputs a drive signal to the drive transistor 34a.

As a result, an excitation current having a value h3 corresponding to the magnitude of the relative displacement at time t5 is applied to the electromagnetic solenoid 4a of the variable damping force shock absorber 6a. Therefore, an attractive force corresponding to the magnitude of the relative displacement is generated in the electromagnetic solenoid 4a, and the plunger 17 rises to a position corresponding to the attractive force.

This causes the spool 15 to move to the return spring 1.
6 to a position corresponding to the magnitude of the relative displacement, the through hole 14 and the fluid passage 13 are in communication with each other through a slightly larger opening area than when previously closed, two fluid passages 11,
The fluid resistance between 13 and 13 becomes small. As a result, 2
The working fluid flows between the two fluid chambers A and B to a small extent, and the variable damping force shock absorber 6a
The damping force is set to a damping force that is lower than that at the time t3 and corresponds to the current magnitude of the relative displacement.

After that, beyond time t6, the relative displacement is at the neutral position.
When moving from X _N to the contraction side region, from time t6 to time t7 when the relative displacement changes in the excitation direction, it is determined that D<0 in the step, and then it is determined that Xa<0 in the step. Therefore, the process moves on to step, and in the same manner as described above, the control device 3 outputs a control signal CSa for controlling the damping force of the variable damping force shock absorber 6a to a low damping force. Therefore, the spool 15 is displaced to the lowered position by the return spring 16, so that the through hole 14 and the fluid passage 13 are aligned, and the 2
The fluid resistance between the two fluid chambers A and B is reduced,
The damping force of the variable damping force shock absorber 6a is changed to a low damping force again.

Furthermore, when the relative displacement changes in the vibration damping direction beyond time t7, it is determined that Xa>0 in step after the step determination, so the process moves to step and in the same manner as described above, at time t7. A stroke value of the plunger 17 corresponding to the peak value of the relative displacement is calculated, and a control signal corresponding to the stroke value is output to the output circuit 33a. As a result, an excitation current having a value h4 corresponding to the magnitude of the relative displacement at time t5 is energized to the electromagnetic solenoid 4a of the variable damping force shock absorber 6a. 4a, and the plunger 17 rises to a position corresponding to the suction force.

This causes the spool 15 to move to the return spring 1.
6 to a position corresponding to the magnitude of the relative displacement, the through hole 14 is brought into communication with the fluid passage 13 through an opening area larger than the opening area at time t5, The fluid resistance between the two fluid passages 11 and 13 is further reduced, and the flow of working fluid between the two fluid chambers A and B is further increased. Therefore, the damping force of the variable damping force shock absorber 6a is set to a damping force that is lower than that at the time t5 and corresponds to the current magnitude of relative displacement.

Similar damping force variable shock absorber 6a
This control is repeated to suppress changes in vehicle attitude.

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 excitation direction causes a change in attitude of the vehicle, the damping force of the variable damping force shock absorber is set to a low damping force regardless of the magnitude of the relative displacement, and the damping force of the variable damping force shock absorber is set to a low damping force regardless of the magnitude of the relative displacement. Since the displacement is changed depending on the magnitude of the relative displacement in some cases, it is possible to suppress generation of an impulsive moving force on the shock absorber. Therefore, it is possible to suppress the vibration of the vehicle body due to the weight of the shock absorber, and it is possible to improve the riding comfort and steering stability of the vehicle.

In addition, in the above embodiment, the front left wheel 5a
Although the description has been made for the case where only one of the wheels passes through an uneven road surface, when the other wheels 5b to 5d pass through an uneven road surface, the variable damping force shock absorbers 6b to 6d are controlled in the same manner as described above.

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. 12, a variable damping force shock absorber 6i
The voltage shown in FIG. 13 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. 14. 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. 12, 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.

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. Particularly 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 the damping force characteristics of the front wheels are controlled depending on the vehicle speed. By changing continuously as described above, the steering stability of the vehicle can be further improved.

[Effect of idea]

As explained above, in this 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 the amount of relative displacement is transmitted to the vehicle body. The force is detected by the transmitted force detection means, and the detection signal is supplied to the direction determining means, which determines whether the relative displacement of the shock absorber or the direction of the transmitted force is the excitation direction that causes a change in attitude of the vehicle body. It is determined whether the damping direction is to suppress the vibration, and when it is the damping direction, the control means continuously changes the damping force of the variable damping force shock absorber according to the relative displacement or the magnitude of the transmitted force, The damping force of the variable damping force shock absorber is set to a low damping force to suppress changes in the attitude of the vehicle body regardless of the relative displacement or the magnitude of the transmitted force. Therefore, when the direction of relative displacement or transmitted force is the excitation direction that causes a change in attitude of the car body, the damping force is low, so the vibration damping that absorbs the excitation force transmitted to the car body and suppresses the change in attitude of the car body. In this direction, the damping force is set according to the relative displacement or the magnitude of the transmitted force to exert a damping effect, so it is possible to effectively suppress changes in the attitude of the vehicle body, and also to suppress vibrations in the damping direction. Since the damping force is set according to the magnitude of the relative displacement or transmitted force, when the relative displacement or transmitted force is small, a relatively low damping force will exert a damping effect, and when the relative displacement or transmitted force is large, the damping effect will be high. The damping force can exert a damping effect, and compared to the conventional case where a large damping force difference is always generated as a high damping force regardless of the relative displacement or the size of the transmitted force, it is possible to suppress the vibration when switching the damping force. The damping force difference between the shock absorbers and the vehicle body becomes smaller, and it is possible to suppress the occurrence of an impactful moving force on the shock absorber due to elastic deformation of the bush for elastically connecting the shock absorber to the vehicle body. This has the effect of preventing the vehicle body from being vibrated by its own weight, suppressing the feeling of a bumpy feeling imparted to the occupants, and improving the ride comfort and steering stability of the vehicle.

[Brief explanation of drawings]

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 that can be applied to this 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. 6 is a graph showing the characteristics of the electromagnetic solenoid. FIG. 7 is a graph showing the relationship between stroke and relative displacement, FIG. 8 is a block diagram showing an example of a displacement detection means, FIG. 9 is a graph showing the relationship between output voltage and relative displacement, and FIG. 10 is a control diagram. A flowchart showing the processing procedure of the device, FIGS. 11a and 11b are signal waveform diagrams for explaining the operation of this invention, FIG. 12 is a sectional view showing another embodiment of the displacement detection means, and FIG. 13 is a FIG. 14 is a graph showing the relationship between the output voltage and the vehicle body transmission force, and FIG. 14 is a graph showing the output voltage waveform when riding over uneven road surfaces. DESCRIPTION OF SYMBOLS 1...Vehicle speed detector, 2a-2d...Displacement detection means, 3...Control device, 4a-4d...Electromagnetic solenoid, 5a-5d...Wheel, 6a-6d...Damping force variable 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, 30...Microcomputer, 31...
Multiplexer, 32...A/D converter, 33a
~33d...Output circuit, 34a-34d...Drive transistor, 42...Piezoelectric element.

Claims (1)

[Scope of utility model registration request] 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 relative displacement between the sprung and unsprung portions 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 amount or transmission force to the vehicle body, and the direction of the relative displacement or transmission force detected by this detection means is the excitation direction that causes a posture change to the vehicle body. a direction determining means for determining whether the damping direction is a vibration damping direction for suppressing a change in attitude of the vehicle body; and a direction determining means for determining a damping force of the variable damping force shock absorber when a determination result of the direction determining means is in a vibration damping direction. A control means for outputting the control signal that continuously changes according to the magnitude of the relative displacement or transmission force based on the detection signal from the means, and maintains the damping force at a low damping force when the vibration is in the excitation direction. A shock absorber control device characterized by: