JPH0717523Y2 - Variable damping force hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a variable damping force type hydraulic shock absorber for a vehicle such as an automobile, and more specifically, performs detection of hydraulic pressure and increase / decrease of damping force at the same time. The present invention relates to a variable damping force type hydraulic shock absorber.

(Prior Art) In recent years, there is a strong demand for compatibility between riding comfort and traveling stability as the demands on vehicles increase. for that reason,
Variable damping hydraulic pressure that increases and decreases damping force according to the running state to generate low damping force that improves riding comfort during normal running and high damping force that enhances running stability when rolling of the vehicle body occurs Shock absorbers are also popular.

As a conventional damping force variable type hydraulic buffer device of this type, for example, one disclosed in Japanese Patent Laid-Open No. 61-85210 is known. In this device, a single piezoelectric element provided in the shock absorber detects the hydraulic pressure in the cylinder and outputs a detection signal, and the controller detects the magnitude of the detection signal input from the hydraulic pressure detection circuit. When it exceeds, a high voltage is applied to the piezoelectric element from the drive circuit, and the damping force is switched from soft to hard for a predetermined time regardless of the pressure stroke and the extension stroke. It should be noted that within the predetermined time, the switch of the hydraulic pressure detection circuit built in the controller is closed and the magnitude of the detection signal is not determined.

(Problems to be solved by the invention) However, in such a conventional damping force variable hydraulic shock absorber, when the magnitude of the detection signal exceeds a set value, the controller sets the switch of the hydraulic pressure detection circuit to a predetermined value. It is closed for a certain period of time, and a high voltage is applied from the drive circuit to the piezoelectric element to uniformly switch the damping force.Therefore, the magnitude of the detection signal cannot be determined within the above specified time. There was a problem that the compression side and extension side damping forces could not be controlled appropriately.

For example, if the damping force is uniformly switched to a hard one on uneven roads, running stability is satisfied for the vibration input on the extension side input within the predetermined time, but the riding comfort deteriorates for the vibration input on the compression side, Riding comfort and running stability cannot be achieved at the same time.

(Purpose of the Invention) Therefore, the present invention provides a signal separating means that allows only an AC component of the signal output from the piezoelectric element to pass, so that the moving direction of the piston, the moving speed, etc. can be determined from the detection signal from the piezoelectric element. It is an object of the present invention to provide a damping force variable type hydraulic shock absorber capable of constantly determining and controlling the driving of the piezoelectric element according to the magnitude of the detection signal to appropriately vary the damping force.

(Means for Solving the Problem) In order to achieve the above object, a damping force variable hydraulic shock absorber according to the present invention has a cylinder filled with hydraulic fluid and a tip side of a piston rod inserted from one end of the cylinder. Is provided in the cylinder, and defines the inside of the cylinder into an expansion side fluid chamber whose volume is reduced during the expansion side stroke of the hydraulic shock absorber, and a compression side fluid chamber whose volume is reduced during the compression side stroke of the fluid pressure shock absorber A piston having a passage for communicating with the liquid chamber, a damping force varying means for varying the generated damping force by varying the flow resistance of the passage, and the damping force varying means for pressing according to the applied voltage, and , A damping force variable hydraulic pressure provided with a piezoelectric element for receiving a hydraulic pressure in any one of the liquid chambers via the damping force varying means and outputting a signal according to the hydraulic pressure, and a control means for driving the piezoelectric element In the shock absorber, the control means is a piezoelectric element. The signal separating means for cutting off the direct current component and passing only the alternating current component of the output signal from the device is provided, and the hydraulic pressure in the hydraulic buffer is detected through the signal separating means.

(Operation) In the present invention, a piezoelectric element that detects the hydraulic pressure in the fluid chamber of the variable damping force type hydraulic buffer and outputs an AC signal is provided in the hydraulic buffer, and the signal separating means detects the piezoelectric element. Only the AC component of the signal is allowed to pass, the operating direction and operating speed of the hydraulic shock absorber are determined from the detection signal, and a DC applied voltage is applied to the piezoelectric element according to the magnitude of the detection signal. Is controlled to increase or decrease the damping force.

Therefore, even when the piezoelectric element is being driven and controlled, the magnitude of road surface vibration is constantly monitored from the output signal of the piezoelectric element, the damping force is appropriately controlled according to the road surface vibration, and riding comfort and running stability are improved. Both sexes can be achieved.

The expansion side and the compression side in the scope of utility model registration claims refer to the case where the piston moves in the direction in which the piston extends relative to the cylinder and the case where the piston moves in the direction toward compression. Sometimes referred to as.

Further, the operating direction of the hydraulic shock absorber referred to in the claims of utility model is the direction in which the piston moves with respect to the cylinder, and may be hereinafter referred to as the moving direction of the piston.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

1 to 5 are views showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention.

First, the configuration will be described. FIG. 1 is an overall configuration diagram of a shock absorber, FIG. 2 is a sectional view of an essential part thereof, FIG. 3 is an overall configuration diagram of a system, and FIG. 4 is a diagram showing a control circuit of one system thereof.

In FIG. 1, reference numeral 1 is a damping force type shock absorber. The shock absorber 1 is 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, a piston 5 provided at the tip of the piston rod 4 and sliding axially on the inner wall of the cylinder 3. A bottom valve 6 provided at the lower end of the cylinder 3, a reservoir chamber 7 formed by the inner wall of the outer cylinder 2 and the cylinder 3, a rod guide 8 that supports the piston rod 4, and an upper portion of the rod guide 8. The piston seal 9 and a stopper plate 10 that closes the upper portion of the outer cylinder 2 are included. The outer cylinder 2 has a bottomed cylinder shape, accommodates the cylinder 3, the rod guide 8 and the piston seal 9, and is formed by crimping the upper end. Further, an eye bush 11 and an eye 12 for attaching to an axle of a vehicle are fixed to the lower end of the outer cylinder 2. The piston 5 defines the inside of the cylinder 3 into an expansion side liquid chamber 14 whose internal volume is reduced during the stroke, and a compression side liquid chamber 15 whose internal volume is reduced during the pressure stroke. The pressure in the expansion side liquid chamber 14 and the pressure side liquid chamber 15 is generated according to the magnitude of the road surface vibration, and the input state of the road surface vibration, that is, the running state can be detected by detecting the pressure. The cylinder 3 has a bottom body 17 whose upper end opening is closed by a rod guide 8 and a communication hole 16 at a 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 an 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 a pressure stroke, and an orifice 21 that generates a damping force when the pressure side valve 20 opens. And the stopper plate 22 that regulates the opening of the check valve 18, and the check valve 18 on the bottom body 17.
And a crimping pin 23 for fixing the like. In the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 18 by the negative pressure in the pressure side liquid chamber 15 and flows into the pressure side liquid chamber 15. At this time, the opening of the check valve 18 is regulated by the stopper plate 22. In the pressure stroke, the hydraulic fluid in the pressure side liquid chamber 15 opens the pressure side valve 20, the damping force corresponding to the positive pressure in the pressure side liquid chamber 15 is generated by the orifice 21, and the reservoir chamber 7 passes through the communication hole 16. Flow into. A seal member 24 formed of a low friction material such as Teflon is provided on the outer peripheral portion of the piston 5, and the seal member 24 is the cylinder 3
Sliding against the inner wall of the. Further, a retainer 25 is fixed to the piston rod 4, and the retainer 25, together with an elastic rebound stopper 26 provided on the upper portion, alleviates the collision between the piston 5 and the rod guide 8. A main lip 27, which is in elastic contact with the piston rod 4 and maintains liquid tightness inside, and a dust lip 28, which prevents muddy water from the outside, are formed on the inner periphery of the piston seal 9. A lower portion of the stopper plate 10 is fitted to the upper end of the cylinder 3, and the piston rod 4 is slidably guided by a bush (not shown) in the central through hole 10a. The wiring 30 drawn out from the upper end of the piston rod 4 is connected to the control unit 100.

FIG. 2 shows a cross section of the periphery of the piston 5, in which the upper side is the vehicle body side and the lower side is 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 is gradually expanded and screwed with the piston 5 at the screw portion 41a at the lower end. The piston 5 has a main body 42 screwed to the piston rod 4, and a sleeve 43 screwed to the lower end of the main body 42, and an adjust nut 44 is screwed and fixed to the lower end of the sleeve 43. A hollow portion 45 and communication holes 46, 47 are formed in the main body 42, and the working fluid in the expansion side fluid chamber 14 and the lower hydraulic chamber 15 passes through the hollow portion 45 and the communication holes 46, 47. Flow to each other. A communication hole 48 is formed in the sleeve 43. In addition, storage holes 49 and 50 having circular cross sections are formed inside the piston 5, and the storage holes 4 and
9 and 50 communicate with the hollow portion 45.

A valve body 51 is slidably inserted inside the hollow portion 45. The valve body 51 includes an upper liquid chamber 52 that communicates the hollow portion 45 with the expansion side liquid chamber 14 and a lower liquid chamber that communicates with the pressure side liquid chamber 15. Divide into chamber 53. Further, the valve body 51 is provided with an expansion side flow path 54 and a compression side flow path 55 that separately communicate the upper liquid chamber 52 and the lower liquid chamber 53, and the expansion side flow passage 54 stores the working fluid in the expansion side liquid chamber 14. The pressure side flow passage 55 causes the hydraulic fluid in the pressure side liquid chamber 15 to flow out from the pressure side liquid chamber 15 during the pressure side stroke. An expansion side disk valve 56 and a compression side disk valve 57 are provided in the expansion side flow path 54 and the compression side flow path 55, respectively.
The expansion side and compression side disk valves 56, 57 are formed of a plurality of thin plates and have a predetermined bending rigidity, and adhere to the valve body 51 according to the bending rigidity to close the expansion side flow path 54 and the compression side flow path 55. To do. Also, expansion side and compression side disc valves 56, 57
Opens according to the liquid pressure in the extension side liquid chamber 14 and the pressure side liquid chamber 15,
The opening areas of the expansion-side flow path 54 and the compression-side flow path 55 are changed according to the bending rigidity, and a predetermined damping force according to the opening area is generated. The expansion side and compression side disc valves 56, 57
A slider 58 and a valve core 59 are arranged on both sides of
The slider 58 and the valve core 59, together with the valve body 51, grip the expansion side and compression side disk valves 56, 57, and when pressed in the vertical direction in the figure, change the bending rigidity of the expansion side and compression side disk valves 56, 57, and bend them. Depending on the rigidity, the opening area of the expansion side flow path 54 and the compression side flow path 55 is reduced to increase the generated damping force. Further, the slider 58 and the valve core 59 contact the first piezoelectric element 80 and the second piezoelectric element 90 via the plates 61 and 62. The first piezoelectric element 80 is supported by a plate 63, a cap 64 and a slider 58, and the second piezoelectric element 90 is a valve core 59 and a cap 65.
Supported by. Cap 65 in the pressure stroke
Receives the hydraulic pressure in the pressure side liquid chamber 15 from the hole 66 of the adjusting nut 44 on the lower surface and displaces upward, and the displacement is caused by the second piezoelectric element 90.
Communicate to. In the pressure stroke, the pressure side disk valve 57 receives the hydraulic pressure in the pressure side liquid chamber 15 and transmits the hydraulic pressure to the first piezoelectric element 80 via the slider 58. In the extension stroke, the extension-side disk valve 56 receives the hydraulic pressure in the extension-side liquid chamber 14 and transmits the hydraulic pressure to the second piezoelectric element 90 via the valve core 59.

The first piezoelectric element 80 and the second piezoelectric element 90 utilize a piezoelectric effect and a reverse piezoelectric effect (also referred to as an electrostrictive effect) of a predetermined ceramic (hereinafter referred to as a piezoelectric material) and have a thin pair of electrodes. It is formed by laminating a large number of piezoelectric materials (for example, about 100 sheets). The piezoelectric effect is a phenomenon that when a voltage is applied to an electrode of a piezoelectric material, the piezoelectric material expands and contracts in the vertical direction in the figure (hereinafter referred to as displacement) according to the change of the applied voltage, and is a phenomenon unique to the piezoelectric material. .

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, and the bending rigidity of the pressure side disk valve 57 is changed to change the pressure side flow path.
The opening area of 55 is reduced, and a predetermined damping force (hereinafter, soft) is increased to switch to a high damping force (hereinafter, hard). On the other hand, in the pressure stroke, the second piezoelectric element 90 generates a predetermined displacement force according to the applied voltage to generate the valve core 59.
Is pressed to change the bending rigidity of the expansion side disc valve 56 to reduce the opening area of the expansion side flow path 54 and switch the damping force from soft to hard.

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

That is, in the pressure stroke, the first piezoelectric element 80 detects the hydraulic pressure in the pressure side liquid chamber 15 transmitted from the pressure side disk valve 57 via the slider 58, and outputs the pressure side signal Sp according to the hydraulic pressure.

In the pressure stroke, the second piezoelectric element 90 detects the liquid pressure in the pressure side liquid chamber 15 transmitted through the cap 65, and outputs the pressure side signal Sp corresponding to the liquid pressure. On the other hand, the second
The piezoelectric element 90 detects the hydraulic pressure in the expansion side liquid chamber 14 transmitted from the expansion side disc valve 56 via the valve core 59, and outputs an expansion side signal Ss corresponding to the hydraulic pressure.

That is, the first piezoelectric element 80 has a function as a hydraulic pressure sensor for detecting the hydraulic pressure in the pressure side liquid chamber 15, and the second piezoelectric element 80.
90 has a function as a hydraulic pressure sensor for detecting the hydraulic pressure in the extension side liquid chamber 14 and the pressure side liquid chamber 15.

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 100. Housing hole 49
An adjusting mechanism 67 is housed inside the adjusting mechanism 67, and the adjusting mechanism 67 is composed of an adjusting screw 68 formed at the upper end of the main body 42 and an adjusting nut 69 screwed to the adjusting screw 68. When moved, it moves in the vertical direction in the figure and changes the axial position of the first piezoelectric element 80. Further, outside the piston 5, there are provided an extension side valve 70 that generates a damping force in the extension stroke and a spring 71 that urges the extension side valve 70 upward, and the lower end of the spring 71 has an adjust nut 72 and a lock nut. It is fixed to the piston 5 by 73. In the extension stroke, the hydraulic pressure in the lower liquid chamber 53 increases in accordance with the hydraulic pressure in the extension side liquid chamber 14, the hydraulic fluid in the lower liquid chamber 53 presses the extension side valve 70 through the communication hole 48, Overcome the urging force of spring 71 and extend side valve 70
Is moved downward and a predetermined damping force is generated by the extension side valve 70 in accordance with the hydraulic pressure.

The signals from the first and second piezoelectric elements 80 and 90 are input to the control unit 100, and the control unit 100 has a function as a control means and a signal separation means. The control unit 100 separates the output signals of the first and second piezoelectric elements 80 and 90 into a DC component and an AC component, and determines the moving direction of the piston 5 (compression side and extension side) depending on the presence or absence of the output signal of the first piezoelectric element 80. ) Is determined and pressure side and extension side control signals S _A and S _B corresponding to the magnitudes of the pressure side and extension side signals Sp and Ss are output.

Turning to FIG. 3, the inside of the control unit 100 will be described. In the figure, the control unit 100 is an I / O
It includes a port (signal separating means) 101, an input circuit 110, an arithmetic circuit 120, a drive circuit 130, and a drive power supply circuit 140. Shock absorber 1 is wired to I / O port 101
Connected via 30 and each control unit
It exchanges signals with 100.

To explain this detail, turn to FIG. In the figure, the shock absorber 1 includes a pair of piezoelectric elements 80,
One of the piezoelectric elements 80, 90 has a cord 81, 91 that is grounded, and the other cord 82, 92 that is connected to the I / O port 101. The first piezoelectric element 80 detects the hydraulic pressure, outputs an alternating pressure side signal Sp, and outputs it to the I / O port 101. I / O port 101
Has diodes D ₁ and D ₂ and a capacitor C. The capacitor C blocks the DC component of the pressure side signal Sp and allows the AC component to pass through. The diodes D ₁ and D ₂ block the compression side signal Sp, and when a high DC voltage (hereinafter referred to as a drive voltage) capable of expanding the piezoelectric element is output from the drive circuit 130, the diodes D ₁ and D ₂ respond to the expansion side control signal S _A. Then, a drive voltage is applied to and discharged from the first piezoelectric element 80. The input circuit 110 is a buffer 112
, Resistor R ₁ , diode D ₃ , transistor Tr ₁ , and
It is configured to include. Transistor Tr ₁ is arithmetic circuit 1
When the extension side control signal S _A is output from 20, it is turned on, and the increase of the pressure side signal Sp due to the drive voltage is cut, and the pressure side signal Sp is maintained at an appropriate signal level. Diode D ₃ and resistance
R ₁ stabilizes the signal level of the pressure-side signal Sp by removing minute fluctuations of the pressure-side signal Sp due to the fluctuation of the hydraulic pressure, and protects the buffer 112 from a short circuit on the input side. Buffer 112
Amplifies the AC component of the pressure side signal Sp and outputs the pressure side signal Sp having an appropriate signal level to the arithmetic circuit 120. The arithmetic circuit 120 is composed of, for example, a microcomputer, takes in external data in accordance with a program written in the internal memory, and based on the taken-in data and the data written in the internal memory, performs a variable control of the damping force. Calculate the required processed value. That is, the arithmetic circuit 120 determines the operating direction of the piston 5 from the input signal, and outputs the extension side control signal S _A corresponding to the input signal to the drive circuit 130. The drive circuit 130 includes an application unit 131 that applies a drive voltage and a discharge unit 132 that discharges electric charges. When the extension side control signal S _A is input to one end of the comparator 133, the applying unit 131 turns on the transistors Tr ₂ and Tr ₃ to drive the power supply circuit 140 for driving.
Drive voltage (DC voltage) of the diode D ₁ of I / O port 101
The damping force is switched from soft to hard by applying it to the first piezoelectric element 80 via. At this time, the resistor R ₂ limits the current flowing from the driving power supply circuit 140 to the transistors Tr ₂ and Tr ₃ , and the resistors R ₃ and R ₄ divide the voltage applied to the first piezoelectric element 80 to divide the voltage. The generated voltage is input to the other end of the comparator 133. The comparator 133 detects the voltage level (hereinafter referred to as the application level) of the first piezoelectric element 80 from the voltage divided by the resistors R ₃ and R ₄ , and the application level is the extension side control signal S _A.
The drive voltage is applied to the first piezoelectric element 80 until the value becomes equal to. The discharge unit 132 outputs the extension side control signal to one end of the comparator 134.
When S _A is input, the transistor Tr ₄ is turned on, the electric charge applied to the first piezoelectric element is discharged through the diode D ₂ of the I / O port 101, and the damping force is returned from hard to soft. At this time, the comparator 134 detects the voltage level (hereinafter, referred to as a discharge level) of the first piezoelectric element 80 from the voltage divided by the resistors R ₅ and R ₆ , and the discharge level is equal to the extension side control signal S _A. Discharge until At this time, the resistance
The R ₇ and the diode D ₄ appropriately control the current supplied from the driving power supply circuit 140 to the transistor Tr ₄ and hold the transistor Tr ₄ in the ON state. The drive power supply circuit 140 is formed of, for example, a DC-DC converter, and outputs a high DC voltage (drive voltage) capable of extending the first and second piezoelectric elements 80 and 90. The circuits connected to the second piezoelectric element 90 are given the same numbers as above, and the description thereof is omitted.

Further, the position adjustment of the piezoelectric element is performed as follows. That is, after a predetermined voltage is applied to the piezoelectric element, the piezoelectric element is discharged, the adjusting nut 69 is rotated to press the piezoelectric element, and the voltage generated by the pressing of the piezoelectric element is adjusted to a certain value. In addition, the extension side and the pressure side are adjusted by the same procedure.

Next, the operation will be described with reference to FIG.

In the extension stroke, as the piston 5 moves toward the extension side, a fluid pressure is generated in the extension side fluid chamber 14, the fluid pressure in the upper fluid chamber 52 rises, the extension side disc valve 56 opens, and the valve core 59 opens. The hydraulic pressure is transmitted from the expansion side disk valve 56 to the second piezoelectric element 90 (first hydraulic pressure sensor), and the expansion side signal Ss corresponding to the hydraulic pressure is output from the second piezoelectric element 90 ( (See FIG. 7C). The expansion side signal Ss is separated into a DC component and an AC component by the capacitor C of the I / O port 101 (signal separating means), and only the AC component of the signal passes through the capacitor C and the input circuit 110
Of the expansion side signal Ss is amplified to an appropriate signal level by the buffer 112 and input to the arithmetic circuit 120. At this time, the arithmetic circuit 120 causes the first piezoelectric element 80 to
It is determined that the extension side signal Ss is not output from the extension side, the control value for controlling the extension side damping force is calculated according to the magnitude of the extension side signal Ss, and the extension side control according to the control value is calculated. The signal S _A is output to the drive circuit 130, and a DC drive voltage corresponding to the extension side control signal S _A is output from the drive power supply circuit 140 to the I / O port 10.
The bending rigidity of the extension side disk valve 56 is changed according to the displacement force generated by the first piezoelectric element 80 via the diode D ₁ of _1, and the bending rigidity is changed according to the bending rigidity. The opening area of the expansion side channel 54 is reduced, and the damping force on the expansion side is switched from soft to hard (see section H).

Further, at the same time as the damping force is switched, the expansion side control signal S _A is output from the arithmetic circuit 120 to the input circuit 110, the transistor Tr ₁ of the input circuit 110 is turned on, and the voltage increase of the expansion side signal Ss accompanying the switching of the damping force. The amount is removed, the expansion side signal Ss is maintained at an appropriate signal level, and the arithmetic circuit 120 constantly determines the magnitude of the hydraulic pressure. When the hydraulic pressure decreases, the extension side control signal S _A
Is input to the drive circuit 130, the electric charge stored in the first piezoelectric element 80 is discharged through the diode D ₂ of the I / O port 101, and the extension side damping force is returned to soft.

Further, even during the extension stroke, when the piston 4 moves toward the pressure side, the pressure side control signal S _B is output and the driving voltage is the first piezoelectric element.
The damping force on the compression side is switched to hard by being applied to 80.
At this time, the drive voltage superimposed on the extension side signal Ss is removed by the action of the capacitor C of the I / O port 101, and the extension side signal Ss is maintained at an appropriate signal level.

As described above, in this embodiment, since the signal separating means (I / O port 101) for separating the AC component and the DC component is provided, the DC drive voltage is applied to the first and second piezoelectric elements 80 and 90. The magnitude of the output signals of the first and second piezoelectric elements can be constantly determined even when the voltage is applied, and the operating direction of the piston 5 (extension stroke and pressure stroke) can be determined from the output signal.
It is possible to appropriately control the compression side and extension side damping forces according to the operating direction.

On the other hand, in the pressure stroke, as the piston 5 moves to the pressure side, a hydraulic pressure is generated in the pressure side liquid chamber 15, the second piezoelectric element 90 is pressed by the hydraulic pressure, and the second piezoelectric element 90 changes to the hydraulic pressure. Accordingly, the pressure side signal Sp is output (see FIG. 5 (c)). At the same time, the fluid pressure in the lower fluid chamber 53 rises and the pressure side disc valve
57 is opened, hydraulic pressure is transmitted from the pressure side disk valve 57 to the first piezoelectric element 80 via the slider 58, and the first piezoelectric element is opened.
A pressure side signal Sp corresponding to the hydraulic pressure is output from 80 (see (b) in the figure). In this way, the pressure side signal from both piezoelectric elements
Since Sp is output, the arithmetic circuit 120 determines that it is the pressure stroke, and the driving voltage corresponding to the magnitude of the pressure-side signal Sp is the second value.
Applied to the piezoelectric element 90 of the second piezoelectric element 90, the bending rigidity of the pressure side disk valve 57 changes according to the displacement force generated by the second piezoelectric element 90, and the opening area of the pressure side flow passage 55 decreases according to the bending rigidity. The damping force is switched to hard (section H).

As described above, in this embodiment, the shock absorber 1 includes the first piezoelectric element for detecting the hydraulic pressure in the expansion side fluid chamber 14 and the compression side fluid chamber 15 and the second piezoelectric element for detecting the hydraulic pressure in the compression side fluid chamber 15. In addition to being provided inside, a signal separating means for passing an AC signal from both piezoelectric elements is provided, so that the operation direction of the shock absorber 1 can be determined from the output signals of the first and second piezoelectric elements, and the operation can be performed. First and second depending on direction
By controlling the piezoelectric elements 80 and 90, the damping force on the compression side and the damping force on the expansion side can be independently increased / decreased. Therefore, unlike the conventional example in which the road surface vibration cannot be accurately determined in this embodiment, the road surface vibration can be accurately determined from the output signals of the first and second piezoelectric elements 80 and 90, and Accordingly, it is possible to appropriately control the damping force to achieve both riding comfort and running stability. Further, in the present embodiment, the first and second piezoelectric elements 80 and 90 are made to function as a hydraulic sensor and an actuator for increasing / decreasing the damping force, and the two functions are satisfied at the same time. It is possible to reduce the manufacturing cost.

Further, in the present embodiment, the damping force is switched between two levels, soft and hard, but the present invention is not limited to this, and it may be changed steplessly.

(Effect) According to the present invention, since the piezoelectric element for detecting the liquid pressure in the liquid chamber is provided and the signal separating means for passing the AC signal from the piezoelectric element is provided, the DC voltage is applied to the piezoelectric element. While controlling the damping force, at the same time, the output direction of the piezoelectric element can be used to constantly determine the operating direction and operating speed of the shock absorber, and the damping force can be controlled appropriately to generate the damping force according to road surface vibration. Both riding comfort and driving stability can be achieved.

[Brief description of drawings]

1 to 5 are views showing an embodiment of a variable damping force type hydraulic shock absorber according to the present invention. FIG. 1 is a sectional view showing the overall structure of the shock absorber, and FIG. 2 is a main part thereof. FIG. 3 is a cross-sectional configuration diagram, FIG. 3 is an overall configuration diagram of the system, FIG. 4 is a partial circuit diagram thereof, and FIG. 5 is a diagram for explaining its operation. 1 ... Shock absorber, 14 ... Extension side liquid chamber, 15 ... Pressure side liquid chamber, 80 ... First piezoelectric element, 90 ... Second piezoelectric element, 100 ... Control unit (control means, signal separation) Means), 101 ... I / O port (signal separation means), 110 ...
… Input circuit, 120 …… Arithmetic circuit, 130 …… Drive circuit, 140
...... Driving power supply circuit.

Claims (1)

[Scope of utility model registration request] 1. A cylinder filled with hydraulic fluid, and an extension side fluid which is provided on the tip side of a piston rod inserted from one end of the cylinder and whose volume is reduced in the cylinder during the extension side stroke of the hydraulic shock absorber. A chamber, and a piston having a passage that defines a pressure side liquid chamber whose volume is reduced during the pressure side stroke and that connects the extension side liquid chamber and the pressure side liquid chamber, and by changing the flow resistance of the passage. Damping force varying means for changing the generated damping force, and the damping force varying means is pressed according to the applied voltage, and the fluid pressure of any of the liquid chambers is received via the damping force varying means, depending on the fluid pressure. In the damping force variable hydraulic shock absorber including a piezoelectric element that outputs a signal and a control unit that drives the piezoelectric element, the control unit cuts off a DC component of an output signal from the piezoelectric element, Signal separation that allows only AC components to pass The stage is provided, the damping force variable hydraulic shock absorber, characterized in that through the signal separating means for detecting the hydraulic pressure in the hydraulic shock absorber.