JPH0241913A - Damping force variable type liquid pressure shock absorber - Google Patents

Abstract

PURPOSE:To make comfortability and a travel stability quality coexist, by detecting by means of two piezoelectric elements pressures at liquid chambers on the extension side and on the pressure side which are different in pressure size in opposition to the movement direction of the piston of a liquid pressure shock absorber, and arranging so that an operation direction may be decided by its result. CONSTITUTION:Liquid pressure at an expansion side liquid chamber 14 or at a pressure side liquid chamber 15 which is inputted through disk values 56, 57 opposing the movement direction of a piston 5 which is in the process of shock absorbing action, and liquid pressures on the sides of the back surfaces of opposing disk valves 56, 57, are detected by means of the 1st and 2nd piezoelectric elements 80, 90, and liquid pressure singnals Sp, Ss which are in accordance with liquid pressures are inputted into a controller 100. The controller 100 decides the operation direction of a shock absorber 1 by means of the sizes of liquid pressure signals Sp, Ss to be inputted, and outputs controlling signals SA, SB into piezoelectric elements 80, 90. As a result, comfortability and a travel stability quality can be made to coexist.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a variable damping force type hydraulic shock absorber for vehicles such as automobiles, and more specifically, the present invention relates to a variable damping force type hydraulic shock absorber for vehicles such as automobiles. This invention relates to a variable damping force hydraulic shock absorber that can be varied independently.

(Prior Art) In general, shock absorbers absorb bumps caused by irregularities on the road surface during normal driving with a low compression side damping force to provide a comfortable ride, and then absorb the subsequent rebound by increasing the rebound side damping force. When vehicle body roll occurs, a high compression damping force is required to prevent the vehicle body from tilting to ensure running stability. Therefore, the damping force can be increased or decreased 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 car body dives. Variable hydraulic shock absorbers are also popular.

As a conventional variable damping force type hydraulic shock absorber of this type, the one described in, for example, Japanese Patent Application Laid-open No. 85210/1983 is known. In this device, a single piezoelectric element installed in a variable damping force shock absorber detects the hydraulic pressure in the cylinder in response to road vibration and outputs a detection signal, and the controller adjusts the magnitude of the detection signal. Based on this, a voltage is applied to the piezoelectric element to uniformly switch the damping force from soft l- to hard regardless of the compression stroke or extension stroke. Note that switching between soft and hard damping force is performed when the magnitude of the detection signal exceeds a set value, and is maintained for a predetermined period of time.

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 a conventional variable damping force hydraulic shock absorber, a single piezoelectric element detects the absolute value of the hydraulic pressure and determines the pressure stroke and extension stroke. Since the configuration was such that a detection signal was output according to the absolute value of the hydraulic pressure being questioned, pressure stroke and extension stroke could not be determined from the magnitude of the detection signal that was uniformly output regardless of the stroke. There was a problem in that independent control could not be performed for each extension stroke, and compression side and rebound side damping forces could not be appropriately controlled against road vibration.

For example, on a bumpy road, if the damping force is switched to hard for a predetermined period of time in response to a detection signal in order to attenuate road surface vibrations, running stability will be satisfied against vibration input on the extension side of the continuous human vibration input, but on the compression side. In response to vibration input, the high damping force conversely becomes a source of vibration, worsening ride comfort, and ultimately making it impossible to achieve both ride comfort and running stability.

(Objective of the Invention) Therefore, the present invention uses two piezoelectric elements to simultaneously detect the hydraulic pressures of the expansion side and compression side liquid chambers, which have different sizes in accordance with the moving direction of the piston, and thereby detects the hydraulic pressure based on the output of the piezoelectric element. The purpose of this invention is to accurately determine the direction of movement of the piston and appropriately change the damping force on the compression side and the expansion side, respectively, independently.

(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 cylinder filled with hydraulic fluid and a tip of a piston rod inserted from one end of the cylinder. a piston that defines the inside of the cylinder into a rebound side liquid chamber whose volume is decreased during the expansion side stroke of the hydraulic pressure buffer and a pressure side liquid chamber whose volume is decreased during its compression side stroke; A compression side flow path for causing the working fluid in the compression side liquid chamber to flow out from the compression side liquid chamber during the compression side stroke; , an expansion side disc valve and a compression side disc valve that generate a damping force according to their bending rigidity, and a corresponding expansion side disc valve or compression side disc valve that changes the generated damping force by changing the bending rigidity, and responds accordingly. A second valve that generates an output signal in response to the hydraulic pressure in the expansion side liquid chamber or the pressure side liquid chamber inputted via the disc valve, and the hydraulic pressure in the compression side liquid chamber or the expansion side liquid chamber on the rear side of the corresponding disc valve. 1
and a second piezoelectric element, the operation direction of the hydraulic shock absorber is determined based on the output signals from the first and second piezoelectric elements, and the drive control of the first and second piezoelectric elements is performed. There is.

(Function) In the present invention, the hydraulic pressure in the expansion side liquid chamber or the pressure side liquid chamber input via the disc valve corresponding to the moving direction of the piston, as well as the hydraulic pressure in the compression side liquid chamber or the expansion side on the back side of the corresponding disc valve. The hydraulic pressure in the liquid chamber is detected by the first and second piezoelectric elements, a hydraulic pressure signal having a different magnitude is output depending on the hydraulic pressure, and the operating direction of the hydraulic shock absorber is determined based on the hydraulic pressure signal. , a driving voltage is applied to the first and second piezoelectric elements to control the damping force on the compression side and the expansion side.

Therefore, the compression-side and rebound-side damping forces are independently increased or decreased in response to road vibrations, making it possible to achieve both ride comfort and driving stability against road vibrations.

In addition, the compression side stroke and the expansion side stroke referred to in the claims of the utility model registration refer to the cases where the piston moves in the direction of compression and the case where the piston moves in the direction of extension with respect to the cylinder. It is sometimes abbreviated as extension stroke, compression side, and extension side.

Furthermore, the operating direction of the hydraulic shock absorber referred to in the claims of the utility model registration refers to the direction in which the piston moves relative to the cylinder, and hereinafter may also simply be referred to as the moving direction of the piston.

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

1 to 6 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. 1 is an overall configuration diagram of the shock absorber, FIG. 2 is a sectional view of its main parts, FIG. 3 is an overall configuration diagram of the system, and FIG. 4 is a diagram showing one system of the control circuit.

In FIG. 1, 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 rod 4 inserted from one end of the cylinder 3, and a piston rod 4.
A piston 5 provided at the tip of the cylinder 3 and sliding in the axial direction on the inner wall of the cylinder 3, a bottom valve 6 provided at the lower end of the cylinder 3, and 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 4, an oil seal 9 provided on the top of the front guide 8, and a stopper plate 10 that closes the top of the outer cylinder 2. The outer cylinder 2 has a cylindrical shape with a bottom, houses the cylinder 3, the rod guide 8, and the oil seal 9, and is formed by crimping the upper end. Furthermore, an eye bush 11 and an eye 12 are fixed to the lower end of the outer cylinder 2 for attachment to a vehicle axle or the like. The piston 5 connects the inside of the cylinder 3 to a rebound side fluid chamber 14 whose internal volume is reduced during the shock absorber 1's rebound stroke (hereinafter referred to as the extension stroke) and an internal volume during the compression side stroke (hereinafter referred to as the pressure stroke). and a pressure side liquid chamber 15 whose volume is reduced. The pressure in the expansion side liquid chamber 14 and the pressure side liquid chamber 15 is generated according to the magnitude of road vibration, and by detecting the pressure, it is possible to detect the input state of road vibration, that is, the driving state. The cylinder 3 has a bottom body 17 whose upper end opening is closed by a rod guide 8 and has a communication hole 16 at its lower end, and a bottom valve 6 is attached to the bottom body 17. The bottom valve 6 includes a check valve 18 that opens during the extension stroke, a port 19 that allows hydraulic fluid to flow in when the check valve 18 opens, a pressure side valve 20 that opens during the pressure stroke, and an orifice 21 that generates a damping force when the pressure side valve 20 opens. , a stopper plate 22 for regulating the opening degree of the check valve 18 , and a caulking pin 23 for fixing the check valve 18 and the like to the bottom body 12 . During the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 18 due to the negative pressure in the pressure side fluid chamber 15, and flows into the pressure side fluid chamber 15. At this time, check valve 18
The opening degree is regulated by the stopper plate 22. In addition, in the pressure stroke, the hydraulic fluid in the pressure side liquid chamber 15 opens the pressure side valve 20, generates a damping force corresponding to the positive pressure in the pressure side liquid chamber 15 at the orifice 21, and passes through the communication hole 16 to the reservoir chamber 7. flows into. A seal member 24 made of a low-friction material such as Teflon is provided on the outer circumference of the piston 5, and the seal member 24 slides in contact with the inner wall of the cylinder 3. Further, a retainer 25 is fixed to the piston rod 4, and the retainer 25 is connected to the piston 5 and the front guide 8 together with a rebound stopper 26 of an elastic body provided at the upper part.
Alleviate conflicts with. On the inner circumference of the oil seal 9,
A main lip 27 that comes into elastic contact with the piston rod 4 and maintains internal liquid tightness, and a dust lip 28 that prevents muddy water and the like from coming in from the outside are formed. The stopper plate 10 has a lower part fitted to the upper end of the cylinder 3, and a through hole 10a in the center.
The piston rod 4 is slidably guided by a bushing (not shown) inside. A wiring 30 drawn out from the upper end of the piston rod 4 is connected to a control unit 100.

FIG. 2 shows a cross section around the piston 5, 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 30 is formed in the center of the piston rod 4, and the wiring passage 41 gradually expands and is screwed into the piston 5 at a threaded portion 41a at the lower end. The piston 5 includes a main body 42 that is screwed onto the piston rod 4, and a main body 42.
A sleeve 43 is screwed to the lower end of the sleeve 43, and an adjustment nut 44 is screwed and fixed to the lower end of the sleeve 43. The main body 42 has a hollow part 45 and communication holes 46 and 47.
are formed, an extension side liquid chamber 14 and a lower side liquid pressure chamber 1.
The hydraulic fluid in 5 flows into each other via the hollow part 45 and the communicating holes 46,47. A communication hole 48 is formed in the sleeve 43 . Further, a housing hole 49.50 having a circular cross section is formed inside the piston 5.
0 communicates with the hollow portion 45. A valve body 51 is slidably inserted into the hollow part 45, and the valve body S1 has an upper liquid chamber 52 which communicates the hollow part 45 with the expansion side liquid chamber 14, and a lower liquid chamber 52 which communicates with the compression side liquid chamber 15. It is divided into a chamber 53. Further, the valve body 51 is provided with a growth side flow path 54 and a pressure side flow path 55 that separately communicate the upper liquid chamber 52 and the lower liquid chamber 53. The hydraulic fluid in the compression side liquid chamber 15 is caused to flow out from the expansion side liquid chamber 14 during the extension stroke, and the pressure side flow path 55 causes the hydraulic fluid in the compression side liquid chamber 15 to flow out from the compression side liquid chamber 15 during the compression side stroke. Growth side flow path 54 and compression side flow path 5
5 is provided with a growth-side disc valve 56 and a compression-side disc valve 57, respectively, and the growth-side and compression-side disc valves 5G and 57 are formed of a plurality of thin plates and have a predetermined bending rigidity. It comes into close contact with the body 51 and closes the growth side flow path 54 and the compression side flow path 55. In addition, the expansion side and compression side disc valves 56 and 57 each have a predetermined pressure receiving area on both the front and back surfaces, and respond to the liquid pressure in the expansion side liquid chamber 14 and the compression side liquid chamber 15 that are received from the surface on the bottom valve 51 side. The extension side flow path 54 is opened according to its bending rigidity.
Then, the opening area of the pressure side flow path 55 is changed to generate a predetermined damping force according to the opening area. In addition, a slider 58 and a valve core 59 are arranged on both sides of the expansion side and compression side disc valves 56.57, and the slider 58 and the valve core 59 grip the expansion side and compression side disc valves 56.57 together with the valve body 51. When pressed from above and below, the expansion side and compression side disc valves 56.5
7, and the opening areas of the expansion side flow path 54 and the compression side flow path 55 are reduced in accordance with the bending rigidity to increase the generated damping force. Further, the slider 58 and the valve core 59 are connected to the first piezoelectric element 8 via the plates 61 and 62.
0 and the second piezoelectric element 90. In the pressure stroke, the slider 58 transmits the hydraulic pressure in the pressure side liquid chamber 15 transmitted from the pressure side disc valve 57 to the first piezoelectric element 80 . The slider 58 also includes a pressure side disc valve 5.
A pressure-receiving surface 53a having a smaller pressure-receiving area than 7 is provided, and during the extension stroke, the slider 58 receives the liquid pressure in the extension-side liquid chamber 14 with the pressure-receiving surface 58a and transfers the pressure to the first The signal is transmitted to piezoelectric element P80. During the extension stroke, the valve core 59 receives the hydraulic pressure in the expansion side liquid chamber 14 transmitted from the expansion side disc valve 56 and transmits the hydraulic pressure to the second piezoelectric element 90 . Further, the valve core 59 is provided with a pressure receiving surface 59a having a predetermined pressure receiving area on the expansion side disc valve 56 side, and the valve core 59 receives the liquid pressure in the pressure side liquid chamber 15 on the pressure receiving surface 59a during the pressure stroke. and is transmitted to the second piezoelectric element 90 on the back side.

The first piezoelectric element 80 is supported by the plate 63, cap 64 and slider 58, and the second piezoelectric element is supported by the valve core 59 and camp 65.

The first piezoelectric element 80 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 (hereinafter referred to as displacement) in response to changes in the applied voltage, and is a phenomenon unique to piezoelectric materials. .

That is, in the extension stroke, the first piezoelectric element 80 generates a predetermined displacement force according to the applied voltage to press the slider 58, change the bending rigidity of the extension side disc valve 56, and open the extension side flow path 54. The area is frozen, 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, in the compression stroke, the second piezoelectric element 90 generates a predetermined displacement force according to the applied voltage to press the valve core 59, and changes the bending rigidity of the compression side disc valve 57 to increase the opening area of the compression side flow path 55. reduce the damping force and switch the damping force from soft to hard.

Furthermore, when pressure or displacement force is applied to the piezoelectric material in the vertical direction, the piezoelectric material is displaced, and the piezoelectric material generates an electromotive force in response to the displacement. This phenomenon is called an inverse piezoelectric phenomenon, and from the magnitude of this electromotive force, it is possible to detect the magnitude of the pressure or displacement force applied to the piezoelectric material.

That is, in the pressure stroke, the first piezoelectric element 80 detects the hydraulic pressure in the pressure side liquid chamber 15 that is transmitted via the slider 58 according to the pressure receiving area of the pressure side disc valve 57, and detects the hydraulic pressure in the pressure side liquid chamber 15 that is transmitted according to the pressure receiving area and the hydraulic pressure. outputs a pressure side signal Sp.

At the same time, the second piezoelectric element 90 receives the hydraulic pressure in the pressure side liquid chamber 15 on the back side of the corresponding expansion side disc valve 56 according to the pressure receiving area of the valve core 59, and the pressure side disc valve 56
Pressure side signal S according to pressure receiving area smaller than 7 and liquid pressure
Output p.

That is, in the pressure stroke, the first piezoelectric element 80 outputs a larger output signal than the second piezoelectric element 90 depending on the pressure receiving area.

On the other hand, in the extension stroke, the second piezoelectric element 90 detects the hydraulic pressure in the expansion side liquid chamber 14 that is transmitted via the valve core 59 according to the pressure receiving area of the expansion side disc valve 56, and detects the pressure receiving area and the hydraulic pressure. The extension side signal Ss corresponding to the output is output. At the same time, the first piezoelectric element 80 receives the hydraulic pressure in the expansion side liquid chamber 14 on the back side of the corresponding compression side disc valve 57 according to the pressure receiving area of the slider 58, and the expansion side disc valve 57
The expansion side signal Ss is output in accordance with the pressure receiving area smaller than 6 and the hydraulic pressure. That is, in the extension stroke, the second piezoelectric element 90 outputs a larger output signal than the first piezoelectric element 80 depending on the pressure receiving area.

In other words, the first and second piezoelectric elements 80.90 have a function as a hydraulic pressure sensor that detects the hydraulic pressure in the expansion side liquid chamber 14 and the pressure side liquid chamber 15, and also function as an actuator that increases or decreases the damping force. It has two functions and is used by switching between these two functions alternately. Note that the cords 81 and 82 of the first piezoelectric element 80 form the wiring 30 together with the cords 91 and 92 of the second piezoelectric element 90, and the wiring 30 is connected to the control unit 1004.1. Further, an adjustment mechanism 67 is housed inside the accommodation hole 49, and the adjustment mechanism 67 is composed of an adjustment screw 68 formed at the upper end of the main body 42, and an adjustment nut 69 screwed into the adjustment screw 68. When the adjustment nut 53 is rotated, it moves in the vertical direction in the figure and changes the position of the first piezoelectric element 80 in the axial direction. Additionally, an extension valve 70 is provided outside the piston 5 to generate a damping force during the extension stroke.
and a spring 71 that urges the expansion side valve 70 upward.
The lower end of the spring 71 is connected to the piston 5 by an adjustment nut 72 and a lock nut 73.
is fixed. In the extension stroke, the liquid pressure in the lower liquid chamber 53 increases in accordance with the liquid pressure in the extension side liquid chamber 14, and the lower liquid chamber 5
The hydraulic fluid in 3 passes through the communication hole 48 and presses the expansion-side valve 70, overcomes the biasing force of the spring 71, moves the expansion-side valve 70 downward, and the expansion-side valve 70 moves to a predetermined level according to the hydraulic pressure. Generates damping force.

The output signals from the first and second piezoelectric elements 70.90 are input to the control unit 100, and the control unit 100 connects the first and second piezoelectric elements 90.
The operating direction (compression stroke and extension stroke) of the shock absorber l is determined based on the magnitude of the output signal of
R is output to drive and control the first and second piezoelectric elements 70.90.

To explain the inside of the control unit 100, the third
Moving on to the figure. In the figure, a control unit 100
includes an I10 port 101, an input circuit 110, an arithmetic circuit 120, a drive circuit 130, and a drive power supply circuit 140. A shock absorber l is connected to the I10 port 101 via wiring 30, and signals are exchanged with the control unit 100, respectively.

In order to explain this in detail, we turn to FIG. 4. In the same figure,
The shock absorber 1 has first and second piezoelectric elements 80.90 inside, and the first and second piezoelectric elements 80.90.
One cord 81.91 of 90 is grounded and the other cord 82.92 is connected to I10 port 101.

The first piezoelectric element 80 detects the hydraulic pressure and outputs the pressure side signal Sp, and the capacitor C of the I10 port 101 outputs the pressure side signal s.
Blocks the DC component of p and allows the AC component to pass. The buffer 112 of the input circuit 110 amplifies the AC component of the pressure side 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 a control value for controlling the rebound damping force based on the magnitude of the rebound signal S, and generates a rebound control signal S, corresponding to the control value.
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 first piezoelectric element 80 via the diode D+ of the I10 boat 101. and 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 connects the 1-transistor Tr2.
is turned ON, the electric charge of the first piezoelectric element 80 is discharged through the diode D2 of the I10 boat 101, and the damping force is returned from hard to soft. The driving power supply circuit 140 is, for example, D
It is formed by a C-DC converter and outputs a direct current high voltage (hereinafter referred to as drive voltage) that can extend the first and second piezoelectric elements 70,90.

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 adjusting nut 53 is rotated to compress the damping means 60, 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 operation will be explained based on FIG.

The figure shows the dimensions around the valve body 51, with a first piezoelectric element 80 disposed in the upper part of the figure, and a second piezoelectric element 90 arranged in the lower part of the figure. In the extension stroke, as the piston 3 moves, a hydraulic pressure P is generated in the extension side liquid chamber 14.
When this occurs, the hydraulic fluid in the expansion side liquid chamber 14 flows into the upper liquid chamber 52 through the communication hole 46, the corresponding expansion side disc valve 56 opens according to the hydraulic pressure P, and the hydraulic fluid in the expansion side liquid chamber 14 flows according to its bending rigidity. The opening area of the expansion side flow path 54 changes, and a predetermined damping force (soft) is generated. At this time, the expansion side disc valve 56
A pressing force F corresponding to the pressure receiving area Ay7 is generated and transmitted to the second piezoelectric element 90 via the valve core 59,
An output signal V corresponding to the pressing force F is output. At the same time, the expansion side liquid chamber 14 on the back side of the corresponding disc valve
The pressure receiving area A, cc of the slider 58 due to the hydraulic pressure P within
A pressing force F corresponding to the pressing force F is generated and transmitted from the slider 58 to the first piezoelectric element 80, and an output signal V corresponding to the pressing force F is output.

Here, the pressure receiving area Acc of the pressure receiving surface 58a of the slider 58
The pressure receiving area ATT of the expansion side disc valve 56 is expressed by the following formula. That is, ACC-π/4 (Dcz"-Dc+") A, A=π/4 (DT, "-Dtz")+, tz L,
I) Outer diameter of C2 varnish slider 58, Dc: Pressure receiving surface 58a
DT4: Outer diameter of the growth side disc valve 56, D, 3 = Inner diameter of the growth side disc valve 5G, and pressure receiving area A of the slider 58 ((and pressure receiving area A of the growth side disc valve 56)
Pressure force F generated according to CT. and pressing force F are respectively expressed by the following equations.

FT = PXA, A pressing force F, and pressing force F are transmitted to the first piezoelectric element 80 and the second piezoelectric element 90, respectively, and output signals (2) and VT approximately corresponding to the pressing force are output. Here, as can be seen from the figure, the pressure receiving area ATo of the expansion side disc valve 56 is thicker than the pressure receiving area A((()) of the slider 53, and the following relationship exists between the above two equations.

Aa〉A, c... (2) As can be seen from (1) and (2) above, the pressing force Fa is larger than the pressing force Fc in accordance with the size of the pressure receiving area. Output signal V1 is greater than output signal V. Therefore, in the extension stroke, the second piezoelectric element 90 outputs a larger output signal than the first piezoelectric element 80.

On the other hand, in the pressure stroke, when hydraulic pressure P is generated in the pressure side liquid chamber 15 as the piston 3 moves, the hydraulic fluid in the pressure side liquid chamber 15 flows into the upper liquid chamber 52 through the communication hole 47, and The pressure-side disc valve 57 opens in response to the hydraulic pressure P, and the opening area of the pressure-side flow path 55 changes in accordance with its bending rigidity to generate a predetermined damping force (soft). At this time, a pressing force F corresponding to the pressure receiving area A (7) is generated in the pressure side disc valve 57, and is transmitted to the first piezoelectric element 80 via the slider 58, and an output signal vc corresponding to the pressing force F is generated. At the same time, the valve core 5 is
A pressing force Ft corresponding to the pressure receiving area ATC of 9 is generated and transmitted from the valve core 59 to the second piezoelectric element 90, and an output signal VT corresponding to the pressing force F7 is output.

Here, the pressure receiving area AcT of the pressure side disc valve 57 and the pressure receiving area A y (
is expressed by the following formula. That is, A, A=π/4 (Dtz” DTl2) A7.=
π/4 (DC42DC:l”) However, D, 2
: outer diameter of the pressure side disc valve 57, DTl: inner diameter of the pressure side disc valve 57, DC4: outer diameter of the valve core 59, I)ci: inner diameter of the pressure receiving surface 59a, and pressure receiving area A of the pressure side disc valve 57 (7 and valve core The pressing force F and the pressing force F1 corresponding to the pressure receiving area Aa of 59 are expressed by the following equation.

FT=PXA4C The pressing force FC and the pressing force FA are transmitted to the first piezoelectric element 80 and the second piezoelectric element 90, respectively, and an output signal VC and an output signal V7 substantially corresponding to the pressing force are output. Here, as can be seen from the figure, the pressure receiving area ATT of the pressure side disc valve 57 is the pressure receiving area A of the valve core 59.
It is formed larger than rc, and the following relationship exists between the above two equations.

ACT>ATc...-(4) As can be seen from equations (3) and (4) above, the pressing force F7 is the pressing force F corresponding to the size of the pressure receiving area.

Since it is larger than , the output signal V7 is the output signal ■. larger than Therefore, in the pressure stroke, the first piezoelectric element 80
outputs a larger output signal than the second piezoelectric element 90. In this way, in this embodiment, the hydraulic pressure in the cylinder 3 is received according to the pressure receiving area of the corresponding disc valve and the pressure receiving area of the slider 58 and the valve core 59 on the back side of the disc valve, and the pressure is received from the two piezoelectric elements. Since output signals corresponding to the area are outputted, the operating direction of the shock absorber 1 can be accurately determined based on these output signals. Therefore, the operating direction of road vibration can be accurately determined based on the output signal.
Damping force can be appropriately controlled according to road vibration.

A concrete timing chart of this is shown in FIG. 6. In this figure, the horizontal axis corresponds to the center of vibration, and the vertical axis corresponds to the amplitude of vibration.

As shown in the figure, in the middle stroke, the hydraulic pressure in the expansion side liquid chamber 14 is simultaneously detected by the first and second piezoelectric elements 80 and 90, and the first piezoelectric element is detected according to the pressure receiving area and hydraulic pressure of each. The output signal V of 80 and the output signal Vt (expansion side signal Ss) of the second piezoelectric element 90 are output. At this time, since the output signal ■ is larger than the output signal ■ according to the size of the pressure receiving area, the arithmetic circuit 120 determines that it is the extension stroke, and the extension side signal Ss (the output of the second piezoelectric element 90 control unit depending on the magnitude of the signal Vt).
A driving voltage is applied from 100 to the first piezoelectric element 80,
A predetermined displacement force is generated in accordance with the applied voltage, the bending rigidity of the growth side disc valve 56 changes, the opening area of the growth side flow path 54 is reduced, and the growth side damping force is switched from soft to hard.

On the other hand, in the pressure stroke, the liquid pressure in the pressure side liquid chamber 15 is
and the second piezoelectric element 80 and 90 simultaneously, and the first piezoelectric element 80 corresponds to the respective pressure receiving area and liquid pressure.
The output signal VC of the second piezoelectric element 90 and the output signal V of the second piezoelectric element 90
T (compression side signal Sp) is output. At this time, the output signal ■ corresponds to the size of the pressure receiving area. Since it is larger than the output signal V, the arithmetic circuit 120 determines that it is a pressure stroke, and the pressure side signal Sp (output signal VC of the first piezoelectric element 80)
from the control unit 100 depending on the size of the second
A driving voltage is applied to the piezoelectric element 90, and a predetermined displacement force is generated according to the applied voltage, changing the bending rigidity of the compression side disc valve 57, reducing the opening area of the compression side flow path 55, and changing the compression side damping force from soft to soft. Can be switched to hard.

In this way, in this embodiment, the expansion side liquid chamber 1 is controlled by two piezoelectric elements.
4 and the pressure side liquid chamber 15 are simultaneously detected, and the magnitude of the output signal generated by the piezoelectric element is changed depending on the pressure receiving area. Therefore, the moving direction of the piston 5 can be determined from the output signals of these piezoelectric elements. It is possible to accurately determine and control the damping force on the compression side and the rebound side. In addition, in this embodiment, two piezoelectric elements are used as a sensor for detecting hydraulic pressure and as an actuator for controlling damping force, so the damping force on the compression side and the expansion side can be adjusted based on the magnitude of the output signal. The damping force can be increased or decreased independently, and the damping force can be appropriately controlled according to road vibrations to achieve both ride comfort and driving stability.

Although piezoelectric elements are disposed on both sides of the damping means in this embodiment, the arrangement and construction method of the piezoelectric elements are not limited to this.

Further, in this embodiment, the damping force is switched between two stages, soft and hard, but the damping force is not limited to this, and may be changed steplessly, for example.

(Effect) According to the present invention, the liquid pressure in the pressure side liquid chamber and the expansion side liquid chamber is adjusted according to the pressure receiving area from the disk valve corresponding to the moving direction of the piston and the pressure receiving surface on the back side of the disk valve using two piezoelectric elements. The piston movement direction can be accurately determined from the output signals of these piezoelectric elements, and the damping force on the compression and rebound sides can be increased or decreased appropriately in response to road vibrations to improve driving stability and Both ride comfort can be achieved.

[Brief explanation of the drawing]

Figures 1 to 6 show variable damping force type hydraulic relaxation according to the present invention. FIG. 1 is a cross-sectional view showing the overall structure of the shock absorber, FIG. 2 is a cross-sectional view of the main parts, and FIG. 4
The figure is a partial circuit diagram, FIG. 5 is a diagram showing the dimensions of the main part, and FIG. 6 is a diagram showing its operation. ■... Shock absorber, 3... Cylinder, 4... Piston rod, 5... Piston, 14... Rebound side liquid chamber, 15...Pressure side liquid chamber, 45...Hollow part, 51...Valve body, 52...Upper liquid chamber, 53...Lower part Liquid chamber, 54... Growth side flow path, 55... Pressure side flow path, 56... Growth side disc valve, 57...
- Compression side disc valve, 53...Slider, 59...Valve core, 80...First piezoelectric element, 9o...Second piezoelectric element, 100 ······control unit. Agent Patent Attorney Ugagun Partial Diagram/IOC

Claims (1)

[Claims] A cylinder filled with hydraulic fluid, and a rebound fluid provided at the tip of a piston rod inserted from one end of the cylinder, whose volume is reduced during the rebound stroke of the hydraulic shock absorber inside the cylinder. a piston defined by a chamber and a compression side liquid chamber whose volume is reduced during the compression side stroke; a rebound side flow path through which the working fluid in the expansion side liquid chamber flows out from the expansion side liquid chamber during the expansion side stroke; and the pressure side liquid chamber. A compression side flow path that causes the hydraulic fluid to flow out from the compression side liquid chamber during the compression side stroke, and a compression side disc valve and a compression side disc valve that are provided in the expansion side flow path and the compression side flow path, respectively, and generate a damping force according to the bending rigidity of the expansion side flow path and the compression side flow path. and, the generated damping force is changed by changing the bending rigidity of the corresponding expansion side disc valve or the compression side disc valve, and the hydraulic pressure of the expansion side liquid chamber or the compression side liquid chamber is inputted via the corresponding disc valve, and first and second piezoelectric elements that generate an output signal in accordance with the hydraulic pressure of the pressure side liquid chamber or the expansion side liquid chamber on the back side of the corresponding disc valve, the first and second piezoelectric elements The direction of operation of the hydraulic shock absorber is determined based on the output signal from the first and second
A variable damping force hydraulic shock absorber characterized by driving and controlling a piezoelectric element.