JPH01266013A - Variable damping force type hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To improve initial responsibility, the riding comfortableness and travelling steadiness of a car even against continuous vibration by determining the rate of variation in hydraulic pressure on the each hydraulic pressure on compression and elongation sides in a variable damping force type shock absorber, and varying the damping force according to the above mentioned rate of variation. CONSTITUTION:Detecting means (a), (b) detect each hydraulic pressure on compression and elongation sides in a variable damping force type shock absorber respectively. Each output of the means (a), (b) is inputted into a controlling means C, which determines the rate of variation in the hydraulic pressure, and then computes control value to make the shock absorber turn into high damping force and to determine the value of the high damping force according to extreme value when the rate of variation has attained the extreme value, and to make the shock absorber turn into a fixed low damping force when the rate of variation has lowered to a fixed value. After that, operating means (d), (e) very the damping force on the compression and elongation sides in the shock absorber according to the output of the controlling means C respectively.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a variable damping force type hydraulic shock absorber for vehicles such as automobiles, and more specifically, to a variable damping force type hydraulic shock absorber that can vary the damping force for each cycle of road vibration. The present invention relates to a type hydraulic shock absorber.

(Prior Art) In recent years, as demands for vehicles have become more sophisticated, there has been a trend toward a need for both comfort and running stability.

Therefore, the damping force variable type increases or decreases the damping force depending on the driving condition, producing a low damping force that improves riding comfort during normal driving, and a high damping force that increases driving stability when the vehicle body rolls. Hydraulic shock absorbers are also popular.

As a conventional variable damping force type hydraulic shock absorber of this type, one described in, for example, Japanese Patent Laid-Open No. 61-85210 is known. In this device, a single piezoelectric element (i.e., four pieces) installed in each of the four shock absorbers detects the hydraulic pressure in the cylinder that is generated in response to road vibration.
The controller applies a voltage to the piezoelectric element based on the magnitude of the detection signal to switch the damping force from soft to hard.

The damping force is switched between soft and hard when the vibration frequency is low enough to cause displacement of the vehicle body and the electromotive force generated in two of the four piezoelectric elements exceeds a set value. Time is maintained.

That is, the damping force is maintained hard regardless of the pressure stroke or extension stroke within the predetermined time, and no hydraulic pressure is detected within the predetermined time.

(Problem to be Solved by the Invention) However, in such conventional variable damping force hydraulic shock absorbers, the magnitude of vibration is determined by using the magnitude of hydraulic pressure, that is, the amplitude of vibration, as vibration information. As a result, it is only possible to distinguish between large and small vibrations when the amplitude actually increases, making it impossible to control road vibrations at the initial stage. There was a problem with it being damaged.

For example, when the car body begins to roll, the shock absorber is actually compressed and then the damping force is switched to hard, so the recovery from the compression state is delayed and the car body is allowed to tilt, and until the slope recovers, the damping force is switched to hard. Running stability will be impaired.

Furthermore, a single piezoelectric element is used as a sensor for detecting fluid pressure and as an actuator for increasing or decreasing damping force by voltage application, and is configured to maintain hardness for a predetermined period of time according to a detection signal. Since sensing is not possible, the initial response is poor, and appropriate control cannot be performed in real time against continuous vibration input.

For example, in response to an input in the opposite direction to the first input within the above time period, a high damping force becomes a source of vibration, resulting in poor damping performance and poor riding comfort. Stability cannot be achieved at the same time.

In other words, in the case of the conventional device, the damping force is changed on the average by so-called prospective control over a certain period of time, and independent control cannot be performed for each of the compression stroke and extension stroke. Note that the compression stroke and extension stroke are when the piston moves in the direction of compression and in the direction of extension with respect to the cylinder, and hereinafter may be simply referred to as compression side and expansion side. .

(Objective of the Invention) Therefore, the present invention detects the compression side and expansion side hydraulic pressures separately and varies the damping force based on the rate of change.
The aim is to improve initial response, precisely change the damping force for each cycle of road vibration, and achieve both ride comfort and driving stability even in the face of continuous vibration input.

(Means for Solving the Problems) In order to achieve the above object, the variable damping force type hydraulic shock absorber according to the present invention includes a first detection means a for detecting the hydraulic pressure on the pressure side of a variable damping force type shock absorber, and a damping force variable type hydraulic shock absorber. The second detection means for detecting the hydraulic pressure on the extension side of the variable force shock absorber calculates the rate of change in the hydraulic pressure from the outputs of the first detection means a and the second detection means A, and determines whether the rate of change is When an extreme value is reached, the shock absorber is set to a predetermined high damping force, and the value of the high damping force is determined according to the extreme value, and when the rate of change decreases to a predetermined value, the shock absorber is set to a predetermined low damping force. a control means C that calculates a control value; a first operation means d that changes the damping force on the compression side based on the output of the control means C; and a second operation means d that changes the damping force on the rebound side based on the output of the control means C. an operating means e;
It is equipped with

(Function) In the present invention, the hydraulic pressure on the compression side and the rebound side are detected separately to determine the rate of change in the hydraulic pressure, and when the rate of change reaches an extreme value, the hard damping force is selected, and the hard damping force is selected. The value of the damping force is determined according to the extreme value, and when the rate of change decreases to a predetermined value at the peak of vibration, the damping force is switched to soft. Therefore, the value of the damping force in the hard state corresponds to the vibration input, improving damping performance, and the damping force is switched to a soft state at the peak of vibration, which is the boundary between the compression stroke and the extension stroke.

Therefore, the initial response is improved, and the damping force is finely increased or decreased in real time for each cycle of road vibration independently on the compression side and the rebound side, improving ride comfort and driving stability even in the face of continuous vibration input. You can balance your sexuality.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 7 are diagrams showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention.

First, the configuration will be explained. FIG. 2 is an overall configuration diagram of the shock absorber, FIG. 3 is a sectional view of its essential parts, FIG. 4 is an overall configuration diagram of the system, and FIG. 5 is a diagram showing one system of the control circuit.

In FIG. 2, reference numeral 1 denotes a variable damping force type shock absorber. The shock absorber 1 includes a sealed outer cylinder 2, a cylinder 3 built into the outer cylinder 2, a piston 4 that slides on the inner wall of the cylinder 3 in the axial direction, and a bottom valve 5 provided at the lower end of the cylinder 3. , a piston rod 6 that supports the piston 4, a reservoir chamber 7 formed by the inner wall of the outer cylinder 2 and the cylinder 3, a front guide 8 that supports the piston rod 6, and a piston seal provided on the upper part of the rod guide 8. 9 and a stopper plate 10 that closes the upper part of the outer cylinder 2.

The cylinder 3 has a bottom body 1 having a communication hole 11 at the lower end.
2, and the opening is closed by a front guide 8. The inside of the cylinder 3 is connected to the upper liquid chamber 1 by the piston 4.
The hydraulic fluid in these two chambers is divided into two chambers, a lower liquid chamber 15 and a lower liquid chamber 15.
mutually flowing through.

The piston 4 has an extension valve 1 that generates damping force during the extension stroke.
6 and the spring 1 that urges the expansion side valve 16 upward.
7 is provided. The lower end of the spring 17 is fixed to the piston 4 by an adjustment nut 18 and a lock nut 19, and an adjustment nut 20 is screwed into the lower end of the piston 4.

The bottom valve 5 includes a check valve 21 that opens during the extension stroke.
When the check valve 21 opens (when the check valve 21 opens, a boat 22 into which hydraulic fluid flows in, a pressure side valve 23 that opens during the pressure stroke, an orifice 24 that generates a damping force when the pressure side valve 23 opens,
It is configured to include a stopper plate 25 that regulates the opening degree of the check valve 21, and a caulking pin 26 that fixes the check valve 21 and the like to the bottom body 12. In the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 21 due to negative pressure in the lower fluid chamber 15, and the hydraulic fluid in the lower fluid chamber 15 opens the check valve 21.
flows into. At this time, the check valve 21 is regulated by a stopper plate 25 so that it does not open beyond a certain level. In addition, in the pressure stroke, the hydraulic fluid in the lower liquid chamber 15 opens the pressure side valve 23, generates a damping force corresponding to the positive pressure in the lower liquid chamber 15 at the orifice 24, and passes through the communication hole 11 to the reservoir. It flows into chamber 7. The pressure in the upper liquid chamber 14 and the lower liquid chamber 15 is generated according to the magnitude of road vibration from outside the shock, and by detecting this pressure, it is possible to detect the input condition of the road vibration, that is, the driving condition.

Further, a retainer 27 is fixed to the piston rod 6,
A rebound stopper 28 made of an elastic body is provided on the upper part of the retainer 27, and the rebound stopper 28 is arranged between the piston 4 and the lock guide 8.
Alleviate conflicts with.

The stopper plate 10 has a lower portion fitted into the upper end of the cylinder 3, and slidably guides the piston rod 6 with a bush (not shown) in a central through hole 10a.

The outer cylinder 2 accommodates a cylinder 3, a lock guide 8, and a piston seal 9 therein, and is formed by crimping the upper end. A main rift 29 that comes into elastic contact with the piston rod 6 and maintains internal liquid tightness, and a dust rift 30 that prevents muddy water and the like from entering the piston seal 9 from the outside are formed on the inner circumference of the piston seal 9. Furthermore, an eye bush 31 and an eye 32 are fixed to the lower end of the outer cylinder 2 for attachment to a vehicle axle or the like.

Also, the wiring 3 pulled out from the upper end of the piston rod 6
5 is connected to a control unit 100.

FIG. 3 shows a cross section around the piston 4, with the upper side of the figure being the vehicle body side and the lower side of the figure being the wheel side. In the figure, a wiring passage 41 for accommodating the wiring 35 is provided at the center of the piston rod 6, and the wiring passage 41 gradually expands and is screwed into the piston 4 at a lower threaded portion 41a. The piston 4 includes a main body 42 that is threadedly engaged with the piston rod 6, and a main body 42.
a sleeve 43 screwed together at the lower end and upper end of the
An adjustment nut 20 is screwed and fixed to the lower end of the sleeve 43. A sealing member 44 made of a low-friction material such as Teflon is provided on the outer periphery of the main body 42, and the sealing member 44 slides in contact with the inner wall of the cylinder 3. A space 45 and communication holes 46.47 are formed in the main body 42, and the hydraulic fluid in the upper liquid chamber 14 and the lower hydraulic pressure chamber 15 flows through the communication holes 46.47. A communication hole 48 is formed in the sleeve 43, and the hydraulic fluid in the space 45 flows through the communication hole 48 while generating a damping force at the extension valve 16. When the hydraulic pressure of the hydraulic fluid passing through the communication hole 48 increases, the expansion valve 16 overcomes the biasing force of the spring 17 and moves downward, generating a damping force on the hydraulic pressure. Furthermore, a housing hole 49.50 having a circular cross section is formed inside the piston 4, and the housing hole 49.50 communicates with the space 45.

Inside the accommodation hole 49 , 50 and the space 45 , an adjustment mechanism 51 , a first piezoelectric element 60 , a damping means 70 abutting the lower end of the first piezoelectric element 60 , and a first piezoelectric element 70 abutting the lower end of the damping means 70 . Two piezoelectric elements 90 and a cap 94 that supports the second piezoelectric elements 90 are housed.

The adjustment mechanism 51 is composed of an adjustment screw 52 formed at the upper end of the main body 42 and an adjustment nut 53 that is screwed into the adjustment screw 52. When the adjustment nut 53 is rotated, it moves in the axial direction and the first piezoelectric element 6
Change the axial position of 0. Adjust nut 53
is connected to plate 5 via plate 54 and cap 55.
6, and the plate 56 is fixed to the upper end of the first piezoelectric element 60. The first piezoelectric element 60 is connected to the cap 55
and damping means 7o, and is supported by the housing hole 4
Move up and down within 9.

The cords 61 , 62 of the first piezoelectric element 60 together with the cords 91 and 92 of the second piezoelectric element 90 form a wiring 35 , which is connected to the control unit 100 . Further, the first piezoelectric element 60 comes into contact with a slider 71 that constitutes a part of the damping means 70 via the plate 59, and transmits the expansion according to the extension side control signal SA to the damping means 70.

The damping means 70 includes a slider 71, a valve core 72 whose tip fits into the center 71a of the slider 71, a valve body 73 attached to the valve core 72, and a pressure side valve 74 held between the valve body 73 and the slider 71. , an expansion-side valve 75 held between a valve core 72 and a valve body 73. Valve body 73
Orifices 76 and 77 are formed in the upper side of the orifice 76, and the upper side of the orifice 76 is closed by an elastic pressure side valve 74, and the lower side of the orifice 77 is closed by an elastic expansion side valve 75.

The orifice 76 communicates the communication hole 47 with a space 79 (hereinafter referred to as first hydraulic pressure) defined by the inner wall of the space 45 and the upper surface of the valve body 73, and when the pressure side valve 74 bends and opens during the pressure stroke, a predetermined pressure is applied. generates a damping force of The orifice 76 is closed during the extension stroke and no hydraulic fluid passes therethrough. The orifice 77 is a space defined by the inner wall of the space 45 and the lower surface of the valve body 73 (hereinafter referred to as a second liquid chamber).
80 and the first liquid chamber 79, and during the extension stroke, the extension valve 75 bends and opens (and generates a predetermined damping force).

The orifice 77 is closed during the pressure stroke and no hydraulic fluid passes therethrough.

The compression side valve 74 and the expansion side valve 75 are formed of a plurality of thin plates and have a predetermined elasticity. During the extension stroke, the damping means 70 is compressed by the extension of the first piezoelectric element 6o, and changes the opening degree of the extension valve 75 to open the orifice 77.
The opening area of the damping force is reduced, a predetermined damping force (hereinafter referred to as "soft") is increased, and the damping force is switched to a high damping force (hereinafter referred to as "hard").

On the other hand, the damping means 70 is compressed by the expansion of the second piezoelectric element 90 during the compression stroke, changes the opening degree of the compression side valve 74 to reduce the opening area of the orifice 76, and switches the damping force from soft to hard.

Further, the damping means 70 comes into contact with the second piezoelectric element 90 via the plate 88, and transmits the hydraulic pressure in the first liquid chamber 79 to the second piezoelectric element 90 during the extension stroke. The lower end of the second piezoelectric element is in contact with the cap 94, and the upward displacement (corresponding to the liquid pressure in the lower liquid chamber 15) transmitted from the cap 94 during the pressure stroke is applied to the damping means 70 and the first piezoelectric element. to communicate. During the pressure stroke, the cap 94 receives on its lower surface the hydraulic pressure of the hydraulic fluid flowing in from the hole 95 of the adjustment nut 20 and is displaced upward, and transmits the displacement to the second piezoelectric element 90 .

The first piezoelectric element 60 and the second piezoelectric element 90 utilize the piezoelectric effect and inverse piezoelectric effect (also called electrostrictive effect) of a predetermined ceramic (hereinafter referred to as piezoelectric material). A large number of piezoelectric materials (for example, 10
(approximately 0 sheets) is formed by laminating them. The piezoelectric effect is a phenomenon in which when a voltage is applied to the electrodes of a piezoelectric material, the piezoelectric material expands and contracts in the vertical direction in the figure in response to changes in the applied voltage (hereinafter referred to as mechanical strain), and is a phenomenon unique to piezoelectric materials. It is.

On the other hand, when pressure or displacement is applied to the piezoelectric material in the vertical direction, mechanical strain is generated in the piezoelectric material, and the piezoelectric material generates an electromotive force in response to changes in the mechanical strain.

This phenomenon is called an inverse piezoelectric phenomenon, and it is possible to detect the pressure or displacement applied to the piezoelectric material from the magnitude of this electromotive force.

During the extension stroke, the first piezoelectric element 60 receives the extension side control signal S.
When A is output from the control unit 100, it expands and contracts, giving displacement to the damping means 70 and increasing or decreasing the damping force. In the compression stroke, the second piezoelectric element 90 receives the compression side control signal SI.
When I is an output from the control unit (100), it expands and contracts, displacing the damping means 70 and increasing or decreasing the damping force.

During the pressure stroke, the first piezoelectric element 60 detects the hydraulic pressure in the lower liquid chamber 15 transmitted from the damping means 70 and outputs a pressure side signal Sp.

The second piezoelectric element 90 detects the hydraulic pressure in the first liquid chamber 79 transmitted from the damping means 70 during the extension stroke, and outputs an extension side signal Ss.

The first piezoelectric element 60 has a function as a first detection means, and together with the damping means 70 constitutes a second operating means. Further, the second piezoelectric element 90 has a function as a second detection means, and together with the damping means 70 constitutes a first operation means.

Signals from the first and second piezoelectric elements 60.90 are input to the control unit 100, and the control unit 100 has a function as a control means. Further, when the control unit 100 receives the compression side and expansion side signals Sp and Ss, it calculates the rate of change of the signals and outputs control signals S, , S, corresponding to the magnitude of the rate of change.

The fourth section describes the inside of the control unit 100.
Moving on to the figure. In the figure, a control unit 100
includes an I10 board 101, an input circuit 110, an arithmetic circuit 120, a drive circuit 130, and a drive power supply circuit 140. The shock absorber 1 is connected to the I10 boat 101 via wiring 35, and signals are exchanged with the control unit 100, respectively.

In order to explain this in detail, we turn to FIG. In the same figure,
The shock absorber 1 has a pair of piezoelectric elements 60.9 inside.
0 and one code 61.9 of the piezoelectric element 60.90
1 is grounded, and the other cord 62.92 is connected to the I10 boat 101. The first piezoelectric element 60 detects the hydraulic pressure and outputs the pressure side signal Sp, and the capacitor C of the I10 boat 101 blocks the DC component of the pressure side signal Sp and allows the AC component to pass. The buffer 112 of the input circuit 110 amplifies the AC component of the pressure signal Sp and outputs it to the arithmetic circuit 120. The arithmetic circuit 120 is composed of, for example, a microcomputer, and takes in external data according to a program written in an internal memory, and performs variable control of the damping force based on the taken data and the data written in the internal memory. Calculate the necessary processing values.

That is, the arithmetic circuit 120 calculates the rate of change of the input signal based on the input signal, and when the rate of change is an extreme value, the arithmetic circuit 120 sends the expansion side control signal SA corresponding to the magnitude of the rate of change to the drive circuit 130.
Output to. When the expansion side control signal SA is input to the buffer 131, the drive circuit 130 turns on the transistor Tr, and changes the drive voltage of the drive power supply circuit 140 to I10 port 1.
The damping force is applied to the first piezoelectric element 60 through the diode D1 of No. 01, and the damping force is switched from soft to hard. Also,
When the expansion side control signal SA is input to the buffer 132, the drive circuit 130 turns on the transistor Tr, and transfers the charge of the first piezoelectric element 60 to the diode D of the I10 boat 101.
2 to return the damping force from hard to soft.

The driving power supply circuit 140 is formed of, for example, a DC-DC converter, and outputs a high DC voltage (hereinafter referred to as driving voltage) that can extend the first and second piezoelectric elements 60, 90. Note that the circuits connected to the second piezoelectric element 90 are given the same numbers as above, and the description thereof will be omitted. Moreover, the position adjustment of the piezoelectric element is performed as follows. That is, after applying a predetermined voltage to the piezoelectric element, it is discharged, and the adjustment nut 53 is rotated to compress the damping means 70, thereby adjusting the voltage from the piezoelectric element until it reaches a certain constant value.

The same procedure is used to adjust both the extension and compression sides.

Next, the effect will be explained.

FIG. 6 is a flowchart showing a program for variable damping force control, and this program is executed once every predetermined time. Note that, although the compression stroke will be described as an example here, the same process is performed in the extension stroke.

First, the pressure side signal Sp is read by the PI. The pressure side signal Sp corresponds to vibration input from the outside and is detected from the hydraulic pressure inside the cylinder 3 in real time.

Next, in P8, the rate of change of the pressure side signal Sp is calculated. The rate of change of the pressure side signal Sp (hereinafter referred to as the rate of change) is the pressure side signal S.
It is obtained by time differentiating p and corresponds to the speed of vibration. The speed of vibration is maximum at the initial stage of vibration (near the center) where the amplitude is small, and reaches O at the peak of vibration where the amplitude is maximum. Furthermore, the speed of vibration increases as the amplitude increases, and the speed of vibration increases as the period of vibration decreases. Therefore, if the rate of change (velocity of vibration) is used as vibration information, it is possible to judge whether the amplitude is large or not at the initial stage of vibration, and the damping force can be adjusted appropriately based on the magnitude of the rate of change. Can be controlled.

Next, it is determined whether the rate of change is an extreme value using Ps.

The reason for determining the extreme value is to determine vibrations with large amplitudes that progress in a short period of time (short period). Here, vibrations with large amplitudes mean vibrations that cause the vehicle body to suddenly lean, such as roll, swivel, and dive, which impair running stability. Driving stability is best when the vehicle body is horizontal, and maneuverability is good.
The worst situation occurs when the vehicle body is tilted significantly or when the vehicle body tilts rapidly, resulting in poor maneuverability.

When P is an extreme value, a compression side control signal Ss determined according to the extreme value is outputted at P4, and a drive voltage is applied to the second piezoelectric element 90 to switch the damping force from soft to hard.

Here, the value of the high damping force (hard) corresponds to an extreme value, and changes steplessly according to the amplitude (extreme value) of vibration input from the road surface. In other words, in this embodiment, the value of the high damping force changes in accordance with the magnitude of the amplitude, and is always appropriate for the vibration input. Determine whether it has been reached. Here, the drive voltage level is the compression side signal S when the damping force is switched to hard.
It means the voltage value of p. ! ! ! If the dynamic voltage is not at the voltage level, return to P4, apply the driving voltage again at P4,
When the drive voltage level is reached, the current routine ends.

By executing steps P and ~P, it is possible to determine vibrations with large amplitudes in the initial stage of vibration, and it is possible to hard switch the damping force in the initial stage of vibration. Furthermore, since the value of the high damping force is determined according to the extreme value, the damping force can be appropriately controlled to follow vibration input.
Vibration damping performance is improved, achieving both driving stability and ride comfort. That is, the present embodiment has improved initial response to vibrations compared to the conventional example in which control is performed in accordance with the magnitude of hydraulic pressure, and the tilting of the vehicle body that occurs in the conventional example hardly occurs.

On the other hand, if the rate of change is not an extreme value at P, move to P6, and P
, it is determined whether the rate of change is O or not.

When the amplitude of the vibration reaches the peak (the boundary point between the compression stroke and the extension stroke), the speed of the vibration, that is, the rate of change, becomes zero. Therefore,
By determining whether the rate of change is 0, it is possible to determine whether or not the compression stroke has ended, and it is possible to perform independent control in the compression stroke and extension stroke of the vibration cycle. That is, during the extension stroke, the damping force can be returned to a soft state to speed up recovery from the compressed state. If the rate of change is not O at P, it is determined that the pressure stroke has not ended, and the current routine is ended. If the pressure stroke has not been completed, the vibration is damped using the damping force set in the previous routine, and the damping force is not switched.

On the other hand, if the rate of change is O at P, it is determined that the pressure stroke has ended, and P9. Then, at P7, the compression side control signal S is outputted, and the charge of the second piezoelectric element 90 is discharged. Then, P
, the pressure side signal Sp is compared with a predetermined value, and if it is not less than the predetermined value, the process returns to P7, and the charge is discharged again at P7, and when the discharge is sufficiently performed, the current routine ends. Here, the predetermined value refers to a voltage value at which the length of the piezoelectric element returns to its original length and the damping force returns from hard to soft, and when the charge is below the predetermined value, the second piezoelectric element 90 detects Recovering its function as a means. Furthermore, if the damping force is soft from the beginning, the damping force will not change.

By executing steps P and -P8, it is determined that the compression stroke has ended or that vibration on the expansion side has been input, and the damping force can be independently controlled in the compression stroke and extension stroke of road surface vibration. In other words, the switching is made to be hard in the compression stroke and soft in the extension stroke, and together with the improvement in initial response, the tilt of the vehicle body is smaller than in the conventional example, and running stability is improved.

In this way, in this example, the damping force is finely changed based on the magnitude of the rate of change, so it is possible to independently control the compression stroke and extension stroke of the vibration cycle, and it is possible to control the damping force on a continuous road surface. It can also respond appropriately to vibrations. In addition, in this example, the value of the high damping force is determined according to the extreme value, so the value is always appropriate for the vibration input, such as a large value when the amplitude is large, and a small value when the amplitude is small. This improves vibration damping performance, making it possible to achieve both ride comfort and driving stability. A concrete timing chart of this is shown in FIG. 7. In the figure, the horizontal axis corresponds to the center of vibration, and the vertical axis corresponds to the amplitude of vibration. As shown in FIG. 5C, a vibration with a large amplitude is input at point A, and as soon as the rate of change reaches an extreme value, the damping force is switched from soft to hard (section H). Therefore, the hydraulic pressure (detected voltage) in the cylinder 3 rises by the amount of increase in damping force (drive voltage) as shown by the dashed line, and changes in the same way as the soft (driving voltage) shown by the dotted line.
(see figure (b)), at this time, the piston 4 has a high damping force,
That is, the movement is restricted by high flow resistance, and its amplitude is reduced compared to the conventional example in which the soft state is maintained up to point B.

Further, at point F, the rate of change becomes 0, the damping force in the pressure stroke is switched to soft, and the piston quickly returns to the center of vibration due to low flow resistance (section FC). Therefore, in this embodiment, the expansion of the shock absorber 1 due to road vibration is smaller than in the conventional example, and the shock absorber 1 recovers quickly, thereby preventing the vehicle from tilting and improving running stability (section AG).

In addition, since this embodiment detects the compression side and expansion side hydraulic pressures separately in real time, it is possible to improve the initial response and to appropriately control the damping force even in response to new vibration input. I can do it. In other words, in this embodiment, even during the period (section AG) in which the hardware is maintained to ensure running stability, unlike the conventional example in which the hardware is maintained for a predetermined period after point B, the hardware is maintained continuously in short cycles. The compression side damping force can be made soft in response to a vibration input, and vibration properties can be improved to improve riding comfort (sections BC and DE). This is because the flow resistance is reduced and vibrations can be sufficiently absorbed by the spring, and the compression damping force is generally set lower than the rebound damping force.

In this way, in this example, the damping force is controlled based on the size of the extreme value, and the value of the high damping force is determined according to the extreme value, so the damping force can be controlled independently on the compression side and the rebound side. Fine control is possible, and the value of the high damping force is always appropriate for vibration input, making it possible to achieve both ride comfort and running stability even in the face of continuous vibration input.

Further, in this embodiment, the first piezoelectric element 60 and the second piezoelectric element 90 are switched to the first and second detection means and the first and second operation means, but the present invention is not limited to this. The configuration method and mounting position of the second detection means and the first and second operation means are not limited to those in the above embodiment, and of course, for example, they may all be provided separately.

Note that the predetermined value referred to in the claims is a concept that includes O, and in this embodiment, this predetermined value is 0, but is not limited to this, and may include, for example, a concept that has a predetermined range, such as Fuwatai. It may be.

(Effects) According to the present invention, the hydraulic pressure on the compression side and the rebound side are detected separately to determine the rate of change in the hydraulic pressure, and when the rate of change reaches an extreme value, the hard damping force is selected and the hard damping force is selected. The value of the damping force is determined according to the extreme value, and when the rate of change decreases to a predetermined value, the damping force is switched to soft, improving initial response and making it possible to increase or decrease the damping force with each cycle of road vibration. This can be done in detail independently in real time for the compression side and the rebound side, and the damping force value at hard times is always an appropriate value for the vibration input, ensuring ride comfort and running stability even in the face of continuous vibration input. can be achieved at the same time.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention, and Fig. 2 shows the overall structure of the shock absorber. 3 is a cross-sectional diagram of the main parts, FIG. 4 is an overall configuration diagram of the system, FIG. 5 is a partial circuit diagram, and FIG.
The figure is a flowchart showing the damping force variable control program, and FIG. 7 is a diagram for explaining its operation. DESCRIPTION OF SYMBOLS 1... Shock absorber, 3... Cylinder, 4... Piston, 60... First piezoelectric element (first detection means, second operation means), 70...attenuation means (first operation means, second operation means), 90...second piezoelectric element (second detection means, I-th operation means), 90...second piezoelectric element (second detection means, I-th operation means), means), 94...camp, 100...control unit l-(control JI means).

Claims (1)

[Scope of Claims] a) A first detection means for detecting hydraulic pressure on the compression side of the variable damping force type shock absorber, and b) A second detection means for detecting hydraulic pressure on the rebound side of the variable damping force type shock absorber. c) determining the rate of change in hydraulic pressure from the outputs of the first detection means and the second detection means, and when the rate of change reaches an extreme value, sets the shock absorber to a predetermined high damping force; d) a control means that determines the value of the high damping force according to the extreme value and calculates a control value such that the damping force becomes a predetermined low damping force when the rate of change decreases to a predetermined value; and d) based on the output of the control means. A variable damping force hydraulic system comprising: a first operating means for changing the damping force on the compression side; and e) a second operating means for changing the damping force on the rebound side based on the output of the control means. Buffer device.