JPH01266014A - Variable damping force type hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To make the riding comfortableness of a car compatible with its travelling steadiness 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 minutely 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 shook 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 a fixed high damping force when the rate of variation has attained extreme value and a fixed low damping force when the rate of variation has lowered to a fixed value. After that, operating means (d), (e) vary the each damping force on the compression and elongation sides in the shock absorber according to the output of the controlling means C respectively. Thus the damping force can be minutely varied to make the riding comfortableness of a car compatible with its travelling steadiness even against continuous vibration.

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 technology) Recently, the damping force is increased or decreased depending on the driving condition of the vehicle, and a low damping force is used to improve ride comfort during normal driving, and a high damping force is used to improve driving stability when the vehicle body rolls. Variable damping force type hydraulic shock absorbers that generate each of these are becoming 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 heart at a vibration frequency low enough to cause displacement of the vehicle body, and when two of the four piezoelectric elements
This occurs when the magnitude of the electromotive force generated by the individual exceeds a set value, and is maintained for a predetermined period of time.

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

(Problem to be Solved by the Invention) However, in such a conventional variable damping force hydraulic shock absorber, a single piezoelectric element is used to sense the liquid pressure and act as an actuator for increasing or decreasing the damping force by applying a voltage. The damping force characteristic was configured to be hard for a predetermined period of time according to the detection signal, and the sensing function could not be used when hard was selected within the predetermined period of time, so continuous input from the road surface was not possible. However, there is a problem in that sufficient control cannot be performed for the second and subsequent input vibrations. For example, in response to an input in the direction opposite to the initial input, a high damping force becomes a vibration source, deteriorating vibration damping performance, and ultimately making it impossible to achieve both ride comfort and running stability.

In other words, in the case of the conventional device, the damping force is replaced on an average basis over a certain period of time by so-called prospective control, and precise control in real time is not possible. In addition, 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 precisely change the damping force with each cycle of road vibration, achieving both ride comfort and driving stability even in the face of continuous vibration input.

(Means for Solving the Problem) In order to achieve the above object, the variable damping force type hydraulic shock absorber according to the present invention has a basic conceptual diagram shown in FIG. The first to detect pressure
and a second detection means for detecting the hydraulic pressure on the extension side of the variable damping force shock absorber.The rate of change in hydraulic pressure is determined from the outputs of the first detection means a and the second detection means A. a control means C that calculates a control value that sets the shock absorber to a predetermined high damping force when the rate of change reaches an extreme value, and sets the shock absorber to a predetermined low damping force when the rate of change decreases to a predetermined value; The first operating means d changes the damping force on the compression side based on the output of the control means, and the second operating means e changes the damping force on the rebound side based on the output of the control means C.

(Function) In the present invention, the rate of change in the hydraulic pressure is determined by separately detecting the hydraulic pressure on the compression side and the expansion side, and when the rate of change reaches an extreme value, the hard damping force is selected, and the rate of change is determined. When it drops to a predetermined value, it is switched to soft.

Therefore, the damping force is finely increased or decreased in real time for each cycle of road vibration, independently on the rebound side and the compression side, making it possible to achieve both ride comfort and running stability.

(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 top of the front 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, the upper end opening of which is closed by a rod 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 connected to the piston 4 by an adjusting pad 18 and a clockwise counter 9.
is fixed to the lower end of the piston 4.
0 is screwed together.

The bottom valve 5 includes a check valve 21 that opens during the extension stroke.
A boat 22 that allows hydraulic fluid to flow in when the check valve 21 opens, a pressure side valve 23 that opens during the pressure stroke, and 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 the negative pressure in the lower fluid chamber 15, and the hydraulic fluid in the lower fluid chamber 1
5. At this time, the check valve 21 is regulated by a stopper plate 25 so as not to 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 and flows through the orifice 24 into the lower liquid chamber 1.
A damping force corresponding to the positive pressure inside 5 is generated, and the damping force flows into the reservoir chamber 7 through the communication hole 11. The pressure in the upper liquid chamber 14 and the lower liquid chamber 15 is generated depending on the magnitude of road vibration from the outside, 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,
The retainer 27, together with a rebound stopper 28 of an elastic body provided on the upper part, alleviates the collision between the piston 4 and the mouth/nod guide 8.

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 has a cylindrical shape with a bottom, and includes a cylinder 3 and a front guide 8.
and a piston seal 9, and is formed by crimping the upper end. On the inner circumference of the piston seal 9, there are a main rift 29 that comes into elastic contact with the piston rod 6 and maintains internal liquid tightness, and a dust lip 30 that prevents muddy water etc. from entering from the outside.
is formed.

Furthermore, an insulator 31 and a mounting ring 32 are fixed to the lower end of the outer cylinder 2 for mounting on 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 threaded portion 41a at the lower end. 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. The expansion side valve 16 connects the communication hole 48 to i1!
When the hydraulic pressure of the operating fluid increases, it overcomes the biasing force of the spring 17 and moves downward, generating a damping force in the hydraulic pressure. Further, inside the piston 4, there is a housing hole 4 having a circular cross section.
9.50 is formed, and the accommodation hole 49.50 is the space 4.
It communicates with 5.

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
passes through plate 54 and camp 55 to plate 5
6, and the plate 56 is fixed to the upper end of the first piezoelectric element 60. The first piezoelectric element 60 is a camp 55
and damping means 70, and is supported by the receiving hole 4
Move up and down within 9.

The cord 61.62 of the first piezoelectric element 60 together with the cord 91.92 of the second piezoelectric element 90 forms the wiring 35;
Wiring 35 is connected to 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,
The elongation corresponding to the elongation side control signal S is transmitted 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. ,
It is configured to include a valve core 72 and an expansion side valve 75 held between a valve body 73. Orifices 76 and 77 are formed in the valve body 73, and the upper side of the orifice 76 is closed by a pressure side valve 74- which has elasticity, and the lower side of the orifice 77 is closed by an expansion side valve 75 which has elasticity. Orifice 76 is space 4
A space 79 defined by the inner wall of the valve body 5 and the upper surface of the valve body 73 (hereinafter referred to as the first liquid chamber) communicates with the communication hole 47, and when the pressure side valve 74 bends and opens during the pressure stroke, a predetermined damping force is applied. Occur. The orifice 76 is closed during the extension stroke and no hydraulic fluid passes therethrough. Orifice 77 is space 45
A space defined by the inner wall of the valve body 73 and the lower surface of the valve body 73 (hereinafter referred to as the second liquid chamber) communicates with the first liquid chamber 79. generates a damping force of The orifice 77 is closed during the pressure stroke and no hydraulic fluid passes therethrough.

The compression side pulp 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 60, 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 a predetermined damping force (hereinafter referred to as "hard") 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 adjusting nand 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 the magnitude of the pressure or displacement applied to the piezoelectric material can be detected 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. The second piezoelectric element 90 receives the pressure side control signal SS in the pressure stroke.
When output from the control unit 100, it expands and contracts, giving displacement to 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.

During the extension stroke, the second piezoelectric element 90 detects the hydraulic pressure in the first liquid chamber 79 transmitted from the damping means 70 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. The control unit 100 also includes a first piezoelectric element 60
Compression side and expansion side signals Sp, S depending on the presence or absence of signals from
s is determined, the rate of change of the signal is calculated, and control signals SA and SB are output in accordance with 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 calculation 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 expansion side control signal S corresponding to the magnitude of the rate of change is generated.

is output to the drive circuit 130. When the expansion side control signal SA is input to the buffer 131, the drive circuit 130 turns on the transistor Tr, and applies the drive voltage of the drive power supply circuit 140 to the diode D of the I10 port 101.

is applied to the first piezoelectric element 60 via the damping force to switch the damping force from soft to hard. Further, 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 I/O.
○Discharge occurs through the diode D2 of the boat 101, returning 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 9o are given the same numbers as above, and the explanation thereof will be omitted.

Note that 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 adjusting 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 at P. The pressure side signal Sp corresponds to external vibration input, and the hydraulic pressure inside the cylinder 3 is detected in real time by the first piezoelectric element 6o.

Next, in P2, 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 near the center of vibration with small amplitude, and becomes 0 at the peak of vibration with large amplitude (boundary between compression stroke and extension stroke). 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 can be determined whether the amplitude is large or not at the initial stage of vibration.

Next, in P3, it is determined whether the rate of change is an extreme value.

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 refer to vibrations that cause the vehicle body to suddenly lean and impair running stability, such as roll, swivel, and dive.

Driving stability is best when the car body is in a horizontal state, and maneuverability is good, and it is worst when the car body is tilted significantly or sharply, and maneuverability is poor.

When the value is at the extreme value at P3, the compression side control signal Sl is output 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 the drive voltage, and depending on the setting of the drive voltage, it can be made stepless. Then P,
It is determined whether the drive voltage level has been reached. here,
The driving voltage level means the voltage value when the driving voltage is applied and the damping force is switched to hard. If the drive voltage level has not been reached, the process returns to P4, the drive voltage is applied again at P4, and when the drive voltage level is reached, the current routine ends. By executing steps P and ~P, vibrations with large amplitude can be determined at the initial stage of vibration, and unlike the conventional example, the damping force can be immediately switched to hard.

On the other hand, if the rate of change is not an extreme value at P3, move to P6, and P
In step 6, it is determined whether the rate of change is 0 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 O. Therefore,
By determining whether the rate of change is O, it is possible to determine whether the compression stroke has ended or not, and it is possible to easily distinguish between the compression stroke and the extension stroke of the vibration cycle. 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 compression 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 P6, it is determined that the pressure stroke has ended, and the process moves to P7, where the pressure side control signal S8 is outputted,
The charge on the second piezoelectric element 90 is discharged. Next, in P6, 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 in P7, and when the discharge is sufficiently performed, the current routine is ended. 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 changes from hard to soft, and when the charge is below the predetermined value, the second piezoelectric element 90 Restores its function as a detection means. Furthermore, if the damping force is soft from the beginning, the damping force will not change.

By executing steps P and ~P, 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. That is, switching is performed between hard in the compression stroke and soft in the extension stroke.

In this way, in this example, the hydraulic pressure on the compression side and the extension side is detected in real time, so the damping force can be controlled based on the rate of change of the detection signal, and the damping force can be controlled in the compression stroke and extension stroke of the vibration cycle. can be controlled independently.

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 large amplitude vibration 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 (detection signal) in the cylinder 3 rises by the amount of increase in damping force (drive voltage) as shown by the -dotted chain line, and changes in the same way as the software shown by the dotted line (see figure (b)). ). At this time, the movement of the piston 4 is restricted by a high damping force, that is, a high flow resistance, and its amplitude is reduced compared to the conventional example in which the piston 4 maintains a soft state up to point B.

Further, at point F, the rate of change becomes O, the damping force in the normal process is switched to soft, and the piston quickly returns to the center of vibration due to low flow resistance (section FG). 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, in this embodiment, unlike the conventional example in which the hard force is maintained for a predetermined period after point B, even during the period (section AG) in which the rebound damping force is maintained hard, the compression side damping force is maintained hard against continuous vibration input. The damping force can be made softer, and the damping force can be improved to improve the ride comfort. (Intervals BC and DE). This is because the spring can sufficiently absorb vibrations due to low flow resistance, and generally the compression side damping force is set lower than the rebound side damping force.

In this way, in this example, the hydraulic pressure on the compression side and the expansion side are detected in real time using separate piezoelectric elements, and the damping force is controlled according to the magnitude of the rate of change, so that the hydraulic pressure on the compression side and the expansion side can be detected independently. The damping force can be controlled to achieve both ride comfort and driving stability even in the face of continuous road vibration.

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. Also, the construction 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 O, but is not limited to this. It may be.

(Effects) According to the present invention, the hydraulic pressure on the compression side and the expansion side are detected separately to determine the rate of change, and when the rate of change reaches an extreme value, hard damping force is selected, and the rate of change is set to a predetermined value. Since the damping force is switched to soft mode when the damping force decreases to 100%, the damping force can be finely increased or decreased on the compression side and the rebound side for each cycle of road vibration, allowing both ride comfort and running stability to be achieved.

[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 a program for variable damping force control, 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... damping means (first operation means, second operation means), 90... second piezoelectric element (second detection means, first operation means), 90... second piezoelectric element (second detection means, first operation means) means), 94...cap, 100...control unit) (control 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) Determine 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, set the shock absorber to a predetermined high damping force, and set the rate of change to a predetermined high damping force. a control means that calculates a control value such that the damping force becomes a predetermined low damping force when the damping force decreases to a predetermined value; d) a first operating means that changes the compression side damping force based on the output of the control means; e) a control means A variable damping force type hydraulic shock absorber comprising: a second operating means for changing the damping force on the rebound side based on the output of the damping force variable hydraulic shock absorber.