JPH0747210Y2 - Variable damping force type 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 vehicles such as automobiles, and more specifically, it uses two piezoelectric elements to reduce damping force on the compression side and the damping side. The present invention relates to a damping force variable hydraulic shock absorber that can be independently varied.

(Prior Art) Generally, a shock absorber absorbs bumps due to unevenness of the road surface during normal traveling with a low compression side damping force to enhance riding comfort, and absorbs subsequent rebounds by increasing the extension side damping force. At the time of occurrence of such a dive (previous leaning phenomenon), it is required to prevent the vehicle body from leaning by a high compression side damping force to satisfy running stability. Therefore, the damping force variable type that adjusts the damping force according to the running state to generate a low damping force that improves riding comfort during normal running and a high damping force that enhances running stability when a vehicle dive occurs Hydraulic shock absorbers are also popular.

As a conventional damping force variable hydraulic buffer of this type, for example, the one described in Japanese Utility Model Laid-Open No. 62-66037 is known. In this device, a plurality of piezoelectric elements are arranged in series along the axial direction of the piston, and contact with a single disc valve provided at the lower end of the piston via a pressing member. These piezoelectric elements detect the hydraulic pressure transmitted from the disc valve when the piston moves toward the pressure side, and when a voltage is applied based on the detection signal, the piezoelectric elements respectively expand according to the applied voltage,
As a whole, a large displacement force is applied to the disc valve, the bending rigidity of the disc valve is changed, the opening area of the orifice is changed, and the damping force on the extension side is changed.

(Problems to be Solved by the Invention) However, in such a conventional damping force variable hydraulic shock absorber, a plurality of piezoelectric elements are arranged in series to generate a large displacement force as a whole when a voltage is applied. Since it is configured to generate and change only the damping force on the extension side, since the axial length of these piezoelectric elements is long, the axial length of the piston is also extremely long, and the total length of the shock absorber becomes long. There was a point.

Further, for the same reason as above, it is not possible to dispose the dedicated piezoelectric elements on the compression side and the expansion side, respectively, so that the damping forces on the compression side and the expansion side cannot be changed independently.

(Object of the Invention) Therefore, according to the present invention, the valve body is slidably housed in the hollow portion of the piston, and a pair of piezoelectric elements are arranged on both side surfaces of the valve body to transmit hydraulic pressure in the cylinder. By matching the direction and the transmission direction of the displacement force of the piezoelectric element, the displacement force of the piezoelectric element is increased by the hydraulic pressure in the cylinder when switching the damping force, and the damping force on the compression side and the extension side can be increased or decreased with fewer piezoelectric elements. In addition, the purpose is to shorten the overall length of the shock absorber.

(Means for Solving the Problem) In order to achieve the above object, a damping force variable hydraulic shock absorber according to the present invention is provided at a cylinder filled with hydraulic oil and at a tip of a piston rod inserted from one end of the cylinder. And a piston defining the inside of the cylinder into an expansion side liquid chamber whose volume is reduced during the expansion side stroke and a compression side liquid chamber whose volume is reduced during the compression side stroke, and a hollow portion provided in the piston. A flow path that connects the extension-side liquid chamber and the compression-side liquid chamber with each other, and a fluid chamber and a pressure-side liquid chamber that are slidably inserted into the hollow portion inside the piston and that communicates the hollow portion with the extension-side liquid chamber. And a valve body having an expansion side passage and a pressure side passage that separately communicate the two chambers with each other, and a valve body closely disposed on both sides of the valve body. Block according to its bending rigidity, and reduce according to its bending rigidity. The expansion-side disc valve and compression-side disc valve that generate a weakening force and the expansion-side disc valve and compression-side disc valve are arranged on the opposite side to the valve body side, and the expansion-side disc valve and compression-side disc valve are pressed against the valve body. Accordingly, the first and second piezoelectric elements that change the bending rigidity of the disk valve are provided.

(Operation) In the present invention, since the valve body is slidably inserted in the hollow portion inside the piston, when one of the expansion side fluid chamber or the compression side fluid chamber becomes high pressure due to the action of the hydraulic shock absorber, The valve body is pressed to the other liquid chamber side. At this time, the piezoelectric elements are arranged on both sides of the valve body, and since both side surfaces of the valve body are in contact with the respective disc valves, the disc valve on the other liquid chamber side is moved to the other liquid chamber side by the valve body. Will be pressed toward the piezoelectric element.

Furthermore, at this time, if applied to the piezoelectric element on one liquid chamber side,
The piezoelectric element presses the valve body in the same direction as the hydraulic pressure of one side together with the one disk valve in contact with the piezoelectric element,
The other disc valve is also pressed by the piezoelectric element, and consequently, the other disc valve is given a large set load by the pressing force of both the output of the piezoelectric element and the hydraulic pressure.

Further, the piezoelectric element on the other side also receives the pressing force of both of them and is distorted, and outputs a voltage commensurate with this distortion. By outputting this voltage to the controller and applying it to one piezoelectric element to calculate the difference from the voltage, one liquid chamber is detected in real time.

Therefore, the damping force on the compression side and the damping force on the expansion side are independently increased / decreased by the two piezoelectric elements, the number of piezoelectric elements having a long axial length is reduced, and the overall length of the shock absorber is shortened. The pressure side stroke and extension side stroke of the hydraulic shock absorber referred to in the utility model registration claim mean that the piston moves relative to the cylinder in the direction of compression and the direction of extension thereof. Hereinafter, the pressure stroke, the extension stroke, and the compression side and the extension side may be abbreviated and used.

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

1 to 4 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 in the outer cylinder 2, a bottom valve 4 provided at the lower end of the cylinder 3, a piston rod 5 inserted from the upper end of the cylinder 3, and a piston rod 5 provided at the tip of the cylinder rod 3. A piston 6 that slides axially on the inner wall of the cylinder, 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 5, and an upper portion of the rod guide 8. It is configured to include an oil seal 9 and a stopper plate 10 that closes the upper portion of the outer cylinder 2. The outer cylinder 2 accommodates the cylinder 3, the rod guide 8 and the oil seal 9 inside, and is formed by swaging the upper end. The cylinder 3 has a bottom body 12 having a communication hole 11 at the lower end, and the opening is closed by a rod guide 8. The inside of the cylinder 3 is partitioned by the piston 6 into the expansion side liquid chamber 14 and the compression side liquid chamber 15, and the internal volumes of the expansion side liquid chamber 14 and the compression side liquid chamber 15 are reduced by the piston 6 during the expansion stroke and the compression stroke, respectively. . A seal member 16 made of a low friction material such as Teflon is provided on the outer peripheral portion of the piston 6, and the seal member 16
Slides in contact with the inner wall of the cylinder 3. Bottom valve 4
Is a check valve 21 that opens during the extension stroke, and a check valve 21
, A port 22 through which hydraulic fluid flows when opening, a pressure side valve 23 that opens in a pressure stroke, an orifice 24 that generates a damping force when the pressure side valve 23 opens, and a stopper plate 25 that regulates the opening degree of the check valve 21, The bottom body 12 includes a crimp pin 26 for fixing the check valve 21 and the like. In the extension stroke, the hydraulic fluid in the reservoir chamber 7 opens the check valve 21 by the negative pressure in the pressure side liquid chamber 15 and flows into the pressure side liquid chamber 15. At this time, the check valve 21 is regulated by the stopper plate 25 so as not to open above a certain level. Further, in the pressure stroke, the hydraulic fluid in the pressure side liquid chamber 15 opens the pressure side valve 23, and the orifice 24 generates a damping force corresponding to the positive pressure in the pressure side liquid chamber 15 and passes through the communication hole 11 to reach the reservoir chamber 7. Flow into. 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.

On the inner peripheral portion of the oil seal 9, there are formed a main lip 29 that elastically contacts the piston rod 5 and maintains the liquid tightness inside, and a dust lip 30 that blocks muddy water and the like from the outside. A lower portion of the stopper plate 10 is fitted on the upper end of the cylinder 3, and the piston rod 5 is slidably guided by a bush (not shown) in the central through hole 10a. An eye bush 31 and an eye 32 are attached to the lower end of the outer cylinder 2 for attachment to the axle of the vehicle. The wiring 35 drawn from the upper end of the piston rod 5 is connected to the control unit 100.

FIG. 2 shows a cross section around the piston 6, in which the upper side in the figure is the vehicle body side and the lower side in the figure is the wheel side. In the figure, the piston rod 5 has a wiring passage 41 for accommodating the wiring 35 therein, and is screwed into the piston 6 by the screw portion 5a at the lower end.
The piston 6 has a main body 42 screwed to the piston rod 5, and a sleeve 43 screwed to the lower end of the main body 42, and is fixed to the piston rod 6 with a set screw 44 for rotation. Body
Communication holes (flow paths) 46 and 47 and a hollow portion 48 are formed in 42, and the communication holes 46 and 47 communicate with the extension side liquid chamber 14 and the pressure side liquid chamber 15 via the hollow portion 48. The hydraulic fluids in the extension side liquid chamber 14 and the compression side liquid chamber 15 flow mutually through the communication holes 46, 47 and the hollow portion 48. Further, the piston 6 is formed with accommodation holes 49, 50 having a circular cross section inside, and the accommodation holes 49, 50 communicate with the hollow portion 48.

A valve body 51 is slidably inserted inside the hollow portion 48, and the valve body 51 has an upper liquid chamber 52 that communicates the hollow portion 48 with the expansion side liquid chamber 14 and a lower side that communicates with the compression side liquid chamber 15. Liquid chamber 53,
To define. Further, the valve body 51 is formed with an expansion side passage 54 and a compression side passage 55 for separately communicating the upper liquid chamber 52 and the lower liquid chamber 53. An expansion-side disk valve 56 and a compression-side disk valve 57 are arranged on both sides of the valve body 51, and the expansion-side and compression-side disk valves 56 and 57 are formed of a plurality of thin plates and have a predetermined bending rigidity, The flexural rigidity closely contacts the valve body 51 and closes the extension side passage 54 and the compression side passage 55, respectively. The expansion side and compression side disk valves 56, 57 open according to the pressure in the expansion side liquid chamber 14 and the compression side liquid chamber 15, and generate a predetermined damping force according to the bending rigidity thereof. Also, the expansion side and compression side disc valves 56,
A slider 58 and a valve core 59 are arranged on both sides of the 57, and the extension side and compression side disk valves 56, 57 are mounted on the slider 58.
When the valve core 59 is pressed from above and below in the figure, its bending rigidity is changed to increase the damping force. The valve body 51, the expansion side passage 54, the compression side passage 55, the expansion side disc valve 56, the compression side disc valve 57, the slider 58 and the valve core 59 constitute a damping means 60. In the extension stroke of the hydraulic shock absorber 1, the inside of the extension side liquid chamber 14 has a high pressure, which is introduced into the upper side liquid chamber 52 from the communication hole 46, presses the valve body 51 downward, and extends the side disc valve 56. Is pressed against the valve core 59. At this time, when the extension side control signal S _A is output from the control unit 100 and a voltage is applied to the first piezoelectric element 70, the sleeve 63 accommodating the first piezoelectric element 70 contacts the lower end of the piston rod 5. Therefore, it is expanded and displaced downward, and the valve body 51 is pressed downward together with the pressure side disc valve 57 via the plate 61 and the slider 58, and the extension side disc valve 56 is pressed against the valve core 59. Eventually, the expansion side disc valve 56 is strongly urged against the seat surface 59a of the valve core 59 by the pressing force of both the pressure of the expansion side liquid chamber 14 and the output of the first piezoelectric element 70, and the set load of the spring increases. . For this reason, the flow resistance of the hydraulic fluid from the expansion side liquid chamber 14 to the compression side liquid chamber 15 increases, and the damping force is switched to a hard one. At the same time, the valve core 59 presses the second piezoelectric element 90 via the plate 62. This second piezoelectric element
Since the lower end of 90 is supported by the sleeve 42, it is compressed and distorted between the sleeve 43 and the sleeve 43 and outputs a voltage corresponding to this distortion. In this case, the second piezoelectric element 90 is extended. The control unit 100 controls the extension side signal S _{S corresponding} to the sum of the pressing force of the hydraulic pressure in the side liquid chamber 14 and the pressing force of the first piezoelectric element 70.
Output to. The control unit 100 uses the value of the expansion side signal S _{S in} the arithmetic circuit 120 thereof to determine the first piezoelectric element 70.
The pressure in the extension side liquid chamber 14 is calculated by subtracting the value of the extension side control signal S _A output to. The behavior of the vehicle is determined based on this calculated value, the required control amount is calculated, and the extension side control signal S _A is sent to either the first piezoelectric element 70 or the second piezoelectric element 90.
Alternatively, the pressure side control signal S _B is output.

In the pressure stroke, the second piezoelectric element 90 acts as an actuator to press the pressure side disc valve 57, and the first piezoelectric element 70 acts as a sensor for detecting the pressure side hydraulic pressure. Act on.

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 101, an input circuit 110, an arithmetic circuit 120, a driving circuit 130, and a driving power supply circuit 140. The shock absorber 1 is connected to the I / O port 101 via a wiring 35, and exchanges signals with the control unit 100.

To explain this detail, we turn to FIG. In the figure,
The shock absorber 1 has a pair of piezoelectric elements 70 and 90 therein. One cord 71, 91 of the piezoelectric element 70, 90 is grounded, and the other cord 72, 92 is connected to the I / O port 101. . The first piezoelectric element 70 detects the hydraulic pressure and the pressing force of the second piezoelectric element 90, and the first piezoelectric element 70 is detected from the value of the extension side signal S _S.
The value of the expansion side control signal S _A output to 70 is subtracted to output the pressure side signal S _P, and the capacitor C of the I / O port 101 blocks the DC component of the pressure side signal S _P and passes the AC component. . The buffer 112 of the input circuit 110 amplifies the AC component of the pressure signal S _P and outputs it 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, the variable control of the damping force is performed. Calculate the required processed value. That is, the arithmetic circuit 120 calculates a control value for driving and controlling the extension side damping force based on the magnitude of the input signal, and outputs the extension side control signal S _A corresponding to the control value to the drive circuit 130. The drive circuit 130 sends the expansion side control signal S _A to the buffer 131.
Is input, the transistor Tr ₁ is turned on, the drive voltage of the drive power supply circuit 140 is applied to the first piezoelectric element 70 via the diode D ₁ of the I / O port 101, and the damping force is changed from soft to hard. Switch. Further, the drive circuit 130 turns on the transistor Tr ₂ when the expansion side control signal S _A is input to the buffer 132, and discharges the electric charge of the first piezoelectric element 70 through the diode D ₂ of the I / O port 101. , Return the damping force from hard to soft. The drive power supply circuit 140 is formed of, for example, a DC-DC converter, and outputs a high DC voltage (hereinafter referred to as a drive voltage) capable of expanding the first and second piezoelectric elements 70 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 applying a predetermined voltage to the piezoelectric element, it is discharged and the main body
The voltage from the piezoelectric element generated by rotating 42 to press the damping means 60 is adjusted to a certain value.
In addition, the extension side and the pressure side are adjusted by the same procedure.

Thus, in this embodiment, the valve body 51 (the damping means 6
0) is slidably accommodated in the hollow portion 48 of the piston 6, and a pair of piezoelectric elements 70, 90 are arranged on both sides of the hollow portion 48 so that the transmission direction of hydraulic pressure in the cylinder 3 and displacement force of the piezoelectric element is transmitted. Since they are matched, the displacement force of the piezoelectric element can be increased by the hydraulic pressure in the cylinder 3, and the damping force can be increased or decreased with a smaller number of piezoelectric elements than the conventional example in which the transmission directions of these two forces are different. it can. That is, unlike the conventional example in which a plurality of piezoelectric elements are arranged in series, this embodiment can reduce the number of piezoelectric elements having a long axial length, shorten the piston 6, and shorten the overall length of the shock absorber 1. it can.

Further, in this embodiment, the first and second piezoelectric elements 70 and 90 are made to function as a sensor for detecting a hydraulic pressure and an actuator for operating a damping force, and both of them are output based on the outputs of the first and second piezoelectric elements 70 and 90. Since the functions are alternately switched and used, the damping force on the compression side and the damping force on the extension side can be independently increased / decreased by the two piezoelectric elements.

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 valve body is slidably inserted into the hollow portion of the piston, when one of the expansion side fluid chamber and the compression side fluid chamber becomes high pressure due to the action of the hydraulic shock absorber. The valve body is pressed toward the other liquid chamber. At this time, since piezoelectric elements are arranged on both sides of the valve body and both side surfaces of the valve body are in contact with the respective disc valves,
The disc valve on the other liquid chamber side is pressed by the valve body toward the piezoelectric element on the other liquid chamber side. Further, at this time, when a voltage is applied to the piezoelectric element on the one liquid chamber side, the piezoelectric element contacts the piezoelectric element. With one disc valve in contact with the other, the valve body is pressed in the same direction as the hydraulic pressure of one, and the other disc valve is also pressed by the piezoelectric element. A large set load is given by the pressing force of both the output of the piezoelectric element and the hydraulic pressure. As a result, the total number of the hydraulic shock absorbers can be shortened by reducing the number of piezoelectric elements having a long axial length.

[Brief description of drawings]

1 to 4 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 sectional configuration diagram, FIG. 3 is an overall configuration diagram of the system, and FIG. 4 is a circuit diagram of a part thereof. 1 ... Shock absorber, 3 ... Cylinder, 5 ... Piston rod, 7 ... Piston, 14 ... Extension side liquid chamber, 15 ...
… Pressure side fluid chamber, 46, 47 …… Communication hole (flow passage), 48 …… Hollow part, 51 …… Valve body, 52 …… Upper fluid chamber (fluid chamber communicating with extension side fluid chamber), 53 …… Lower liquid chamber (liquid chamber communicating with pressure side liquid chamber), 54 …… extension side passage, 55 …… compression side passage, 56 …… extension side disc valve, 57 …… compression side disc valve, 58 …… slider, 59… ... Valve core, 60 ... Damping means, 70 ... First piezoelectric element, 90 ... Second piezoelectric element, 100 ... Control unit.

Claims (1)

[Scope of utility model registration request] 1. A cylinder filled with hydraulic oil, and an extension side liquid chamber provided at the tip of a piston rod inserted from one end of the cylinder and having a volume reduced in the cylinder during extension side stroke of the hydraulic shock absorber. And a piston that defines a pressure side liquid chamber whose volume is reduced during the pressure side stroke, a flow path that connects the extension side liquid chamber and the pressure side liquid chamber via a hollow portion provided in the piston, and a piston The expansion-side passage that is slidably inserted into the hollow part and defines the hollow part into a liquid chamber that communicates with the expansion-side liquid chamber and a liquid chamber that communicates with the compression-side liquid chamber, and that communicates both chambers separately. And a valve body provided with a compression side passage, and closely arranged on both side surfaces of the valve body, and the expansion side passage or the compression side passage is closed according to its bending rigidity, and an expansion side that generates a damping force according to the bending rigidity. Disc valve and compression side disc valve, and expansion side disc A first piezoelectric element and a second piezoelectric element, which are arranged on the opposite side of the valve body of the valve and the pressure side disc valve, and change the bending rigidity of the disc valve by pressing both disc valves against the valve body. A variable damping force type hydraulic shock absorber.