JPH0542573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic shock absorber for a vehicle whose damping force can be freely adjusted, and in particular is controlled using an electrostrictive element.

(Prior Art) A conventional variable damping force shock absorber, as disclosed in, for example, Japanese Unexamined Patent Publication No. 58-194609, connects two upper and lower hydraulic chambers defined in a cylinder with a passage. The damping force was adjusted by changing the area of this passage using a rotary valve.

However, the above-described conventional rotary valves have a problem in that high-speed response cannot be achieved because the rotary valves are operated by a drive source such as a small motor. In particular, when controlling a variable damping force shock absorber based on the vehicle's running speed and the amount of displacement in the steering angle (for example, as disclosed in Japanese Patent Application Laid-Open No. 168039/1983), it is necessary to sufficiently cope with rapid changes. Since it becomes difficult to control the variable damping force shock absorber, this has the disadvantage that the riding comfort for the occupant is impaired. In order to solve these problems, the same applicant as the present inventor proposed a basic configuration for controlling a variable damping force shock absorber using an electrostrictive element with excellent responsiveness (Japanese Patent Application No. 59-206699).
No.) has been devised.

The above-mentioned device drives a valve body by expanding the displacement of an electrostrictive element, which expands and contracts by a minute amount in response to an applied voltage, using the so-called Pascal principle via a sealed incompressible fluid. Although it is controlled,
According to research conducted by the present inventors, it has some disadvantages as follows. It is necessary to seal incompressible fluids. Further, since the displacement amount of the electrostrictive element is based on Pascal's principle, there is a problem in that the magnification is about several tens of times. In addition, since it seals an incompressible fluid, there are problems with its sealability.
Another problem is that it is affected by thermal expansion due to temperature changes.

Therefore, the present invention has been made in view of the above points, and its purpose is to utilize an electrostrictive element with an extremely fast response speed, and to reduce the amount of minute displacement of the electrostrictive element without sealing an incompressible fluid. The object of the present invention is to provide a variable damping force shock absorber that operates with sufficiently expanded damping force.

(Example) Hereinafter, a first example of the present invention will be described based on the drawings.

FIG. 1 is a partial vertical sectional view of a variable damping force shock absorber showing a first embodiment.

An absorber piston 4 is provided inside the cylinder 2 of the shock absorber so as to be slidable in the axial direction, and the inside of the cylinder 2 is separated by the piston 4 into a first hydraulic chamber 6 and a second hydraulic chamber 8. There is. A piston 4 is provided at one end of a piston rod 10. The other end of the piston rod 10 is coaxially fixed to one end of the shaft 12,
The other end of the shaft 12 projects outward from the upper end of the cylinder 2.

The piston 4 is provided with a fixed orifice 14 on the extension side and an orifice 16 on the contraction side that communicate the hydraulic chambers 6, 8, and valves 18, 20 are engaged with these orifices 14, 16 to determine the direction of flow. ing. Therefore, when the piston 4 moves upward or downward relative to the cylinder 2, the pressure oil in the first and second hydraulic chambers 6, 8 flows through the fixed orifices 14, 16.
The shock absorber has a predetermined damping force. The basic structure of the hydraulic shock absorber explained above is the same as the conventional one.

Next, the main parts of the present invention will be explained.

The piston rod 10 has a hole drilled in the axial direction, and the electrostrictive element stack 2 is inserted into the hole.
2 and a center rod 44 constituting a variable orifice 46.

The electrostrictive element laminate 22 is disposed in a cylindrical hole 10a bored in the rod 10, and its upper end is fixed to a disc-shaped mounting plate 24 with adhesive or the like, and its lower end surface is provided with a piston 26. The piston 26 is located within the hole 10a,
It is provided slidably in the axial direction and in an oil-tight manner, and is driven in the vertical direction in the figure by the electrostrictive element stack 22. Further, the electrostrictive element laminate 22 is formed by laminating several dozen thin (approximately 0.5 mm) disc-shaped electrostrictive elements into a cylindrical shape. The electrostrictive element is a ceramic called PZT, whose main component is lead titanate-zirconate, and has a voltage of several hundred V in the thickness direction.
When a voltage of 1 is applied, it extends by several μm. When several tens of electrostrictive elements are stacked and the above voltage is applied in the thickness direction of each element, an elongation of several tens of micrometers can be obtained as a whole. If this voltage is removed or a slight negative voltage is applied, it will shrink and return to its original length. still,
A voltage is applied to the electrostrictive element stack 22 through a hole 12a provided in the shaft 12 in the axial direction through a lead wire.

An O-ring 28 is provided along the outer periphery of the lower end surface of the piston 26, and the O-ring 28 deforms as the piston 26 moves. A pump chamber 30 is defined on the lower end surface of the piston 26, and this pump chamber communicates with the first hydraulic chamber 6 via a passage 32 and a suction check valve 34, and also communicates with the passage 36a of the valve case 36 and the suction check valve 34. It communicates with the working chamber 40 via the discharge check valve 38. Inhalation check valve 3
Reference numeral 4 designates a check valve that allows oil in the first hydraulic chamber 6 to flow in only one direction into the pump chamber 30, and the discharge check valve 38 allows oil to flow in the opposite direction to the suction check valve 36, that is, the pump chamber. This is a check valve that allows only one flow of oil in 30 to flow into the working chamber 40.

A center rod 44 that adjusts the flow area of the flow path 42 is slidably inserted into a hole provided along the axial direction of the piston rod 10, thereby forming a variable orifice 46. The center rod 44 has an axial hole 44a and a radial hole 44b, and the center rod 44 of the variable orifice 46
moves downward in the figure, the flow path area of the flow path 42 decreases, and the flow path 4 moves from the first hydraulic chamber 6 to the second hydraulic chamber 8.
5, 47, or flow in the opposite direction to squeeze out the oil. Conversely, when the rod 44 moves upward,
The flow area of the flow path 42 is increased, and one end of the rod 44 is urged upward by a spring 43 so that the flow area of the flow path 42 is normally maximized.

At one end above the center rod 44, there is a rod 4
A spool 48 having a smaller diameter than 4 is integrally provided, and the upper end surface of this spool 48 is connected to the working chamber 4.
It receives the pressure oil in the working chamber 40 and slides in the vertical direction based on the amount of oil in the working chamber 40.

A small groove 48a as shown in FIG. 2 is provided on the outer circumference of the spool 48 in its axial direction, and the groove 48a communicates the working chamber 40 and the space 50.

Note that the space 50 is configured to communicate with the outside through the small diameter 52 and not be in an oil-tight state.

Next, the basic operation will be explained based on the above configuration.

When a high voltage of approximately 800 V is applied to the electrostrictive element stack 22, the stack 22 will expand by several tens of μm in its axial direction.
The piston 26 is moved downward by extension displacement. When the piston 26 moves downward, the volume inside the pump chamber 30 decreases, and the oil inside the pump chamber 30 flows into the passage 36a.
and flows out into the working chamber 40 through the discharge check valve 38. Then, as the amount of oil in the working chamber 40 increases, the spool 48 and the center rod 44 move downward against the spring 46. At this time, the amount of displacement of the electrostrictive element stack 22 is determined based on Pascal's principle, that is, between the piston 26 and the spool 48.
It is enlarged according to the area ratio of , and is transmitted to the spool 48 and the center rod 44 . When the center rod 44 moves downward in this manner, the variable orifice 46 is constricted and the flow area of the flow path 42 is reduced.

However, when the laminated body 22 is fully extended after applying a voltage to the laminated body 22, the oil flowing out from the pump chamber 30 to the working chamber 40 is stopped. Then, due to the biasing force of the spring 43, the oil in the working chamber gradually flows out from the small groove 48a on the outer periphery of the spool 48 into the space 50 and decreases.
It is moved upward by the spring 43 according to the amount of oil in the 0, and finally returns to the initial state and opens the variable orifice 46 again.

The above operation is shown in FIG. In FIG. 3, the horizontal axis shows time, and the vertical axis shows the voltage applied to the electrostrictive element stack 22 and the amount of movement of the center rod 44. The movement response time T _S of the center rod 44 is
This approximately corresponds to the response time from when a voltage is applied to the electrostrictive element stack 22 until it is completely extended, and the time T _S is several microseconds, which allows the center rod 44 to move in a very short time. Also, the return time Te for the center rod 44 to return to its initial state is
It can be arbitrarily adjusted by the flow area of the groove 48a of the spool 48 and the biasing force of the spring 43. Note that when comparing the flow rate flowing from the pump chamber 30 to the working chamber 40 due to voltage application to the laminate 22 and the flow rate flowing out from the working chamber 40 through the groove 48a due to the spring 43, the latter is smaller. Needless to say, it has been set.

Furthermore, assuming that the sufficient response time generally required to vary the damping force is several milliseconds, the response time T _S of the center rod 44, that is, the electrostrictive element stack 22
Since it takes a very short time (several tens of microseconds) for the voltage to fully extend, it is possible to apply the pulse voltage P ₁ at least several dozen times to the laminate 22 within the above response time.

Next, detailed operation of the first embodiment will be explained.

Normally, no voltage is applied to the electrostrictive element stack 22, and the center rod 44 is pushed upward in the figure by the biasing force of the spring 43, so that the flow path area of the variable orifice 46 is maximized. At this time, the damping force of the shock absorber is becoming smaller.

The electrostrictive element laminate 22 has a voltage of 800V as shown in FIG.
A pulse-like voltage P ₁ of a high voltage of about 100 mL is applied.
Note that the application time t ₁ of this pulse voltage P ₁ is
Since the response time is longer than the response time of No. 2, it is assumed that the laminate 22 is completely stretched. Then, the stacked body 22 expands and contracts in the vertical direction, driving the piston 26 up and down. When the piston 26 moves downward, oil is delivered from the pump chamber 30 to the working chamber 40, as described above, and the center rod 44 moves downward. On the other hand, when the piston 22 moves upward, the volume in the pump chamber 30 increases and flows from the hydraulic chamber 6 into the pump chamber 30 via the passage 32 and the suction check valve 34. That is, each time a pulse voltage is applied, the amount of oil in the working chamber 40 increases and the center rod 44 moves downward. Then, when the pulse voltage is applied repeatedly several times, the amount of oil in the working chamber 40 increases one by one, and the center rod 44 moves significantly downward, finally closing the variable orifice 46 completely. After that, when the pulse voltage is continued to be applied, the variable orifice 4
6 maintains the closed state. At this time, the area of the passage communicating the first and second hydraulic chambers 6, 8 of the shock absorber is reduced, so the damping force thereof is increased.

Then, when the application of the pulse voltage is stopped, the center rod is moved upward by the spring 43 as described above, the variable orifice 46 is gradually opened, and the damping force of the shock absorber returns to its original small state.

Next, a case will be described in which a desired damping force of the shock absorber is obtained by controlling the pulse voltage applied to the electrostrictive element stack 22.

Since the damping force of the shock absorber is determined by the flow path area of the variable orifice 46, that is, the position of the center rod 44, the explanation will be based on the relationship between the amount of movement of the rod 44 and the pulse voltage. By applying pulse voltage _P1 to the electrostrictive element stack 22 several times in a short period of time, the center rod 4 is
As described above, the amount of movement of the rod 44 can be arbitrarily controlled by using the pulse voltages P ₁ and P ₂ as shown in FIG. Since the application time t ₂ of this pulse voltage P ₂ is shorter than the application time t ₁ of the pulse voltage P ₁ described above and the response time t _S of the electrostrictive element stack 22, the pulse voltage P ₂ is not applied. The elongation of the laminate 22 stops before it is completely elongated. Therefore, the amount of movement of the center rod 44 when pulse voltage P ₂ is applied is smaller than that when pulse voltage P ₁ is applied.

As shown in FIG. 5, the rod 44 is moved to a desired position by applying the pulse voltage P ₁ the first few times using the pulse voltages P ₁ and P ₂ , and thereafter the pulse voltage P ₂ is applied. The position of rod 44 is maintained by applying it at appropriate intervals. When a pulse voltage P ₂ with a very short application time t ₂ is applied, the center rod is affected by its inertial force and the viscosity of the oil, so its position changes smoothly as shown in the enlarged diagram. Become. Therefore, if the pulse voltage P ₂ of application time t ₂ is applied at even shorter intervals, the center rod 44 will appear to be stationary and will be kept at the same position.

Here, the drive circuit will be explained based on FIGS. 17 and 18. First, the sawtooth wave generation circuit 101
As a result, a sawtooth wave as shown in FIG. 18a is generated at point A. Furthermore, the period of this sawtooth wave signal is t ₃
is set by variable resistor _R1 , and voltage _V3 is set by Zener diode _D2 . Next, this signal is converted to the reference voltage V ₄ by the comparator 102-1 of the voltage comparison circuit 102, as shown in FIG. 18b.
An output signal as shown in FIG. 18c is generated at point B. Note that this reference voltage _V4 is set by a variable resistor _R6 . This signal is input to the base of transistor Tr ₁ of high voltage application circuit 103 . A high voltage _V2 is applied to the electrostrictive element stack 22 via this transistor _Tr1 as shown in FIG. 18d.

In addition, the duty ratio (the time ratio at which the pulse voltage is applied) is set based on the period _t3 of the sawtooth wave and the reference voltage of the comparator 102-1, as described above.
This can be done by setting V ₄ to an arbitrary value. In other words,
By setting the variable resistor R ₁ of the sawtooth wave generation circuit 101 and the variable resistor R ₆ of the voltage comparison circuit 102 to predetermined resistance values, a desired duty ratio can be set. Here, e, f, g in Fig. 18 indicate the period t _1.
The signal is shown when shortened to t ₂ .

In addition, D ₁ and D ₂ shown in the figure are diodes, and R ₁ to _{R 9}
is a resistor, _C1 is a capacitor, _OP1 to _OP2 are operational amplifiers, _Tr1 is a transistor, _V1 is a reference voltage, and _V2 is a high-voltage power supply (electrostrictive element driving power supply) voltage.

Therefore, by applying pulse voltage P ₁ to the variable orifice 46 as shown in FIG. 6a, the variable orifice can be instantly changed from fully open to fully closed without making any special configuration arrangements. to do,
In other words, it is possible to change the damping force of the shock absorber in two stages, small and large, and by applying pulse voltages P ₁ and P ₂ as shown in Fig. 6b, the flow path of the variable orifice can be changed. It becomes possible to arbitrarily change the area, that is, to arbitrarily change the damping force of the shock absorber from small to large.

Therefore, by performing the above-described control according to the vehicle running conditions, it is possible to set the damping force of the shock absorber to the optimum damping force according to the running conditions.

In the above embodiment, the damping force of the shock absorber is rapidly increased by applying a pulse voltage to the electrostrictive element stack, but this generally occurs due to sudden steering, sudden braking, etc. This is because it is often desirable to suddenly increase the damping force of the shock absorber in order to suppress the tilt of the vehicle. However, by changing the position of the hole 44b provided in the center rod 44 upward in FIG. 1, when a pulse voltage is applied to the electrostrictive element stack, the variable orifice is opened and the damping force of the shock absorber is reduced. It is also possible to do so.

Next, other embodiments will be described.

FIG. 7 is a partial sectional view showing a second embodiment of the present invention, which differs from the first embodiment in the positions of the suction check valve 60 and the discharge check valve 62. The suction check valve 60 is provided in the middle of the passage 34 that communicates the pump chamber 30 and the working chamber 40, and allows flow in only one direction from the working chamber 40 to the pump chamber 30. The discharge check valve 62 is provided at one opening end of the passage 32 that communicates the pump chamber 30 and the hydraulic chamber 6, and allows flow in only one direction from the pump chamber 30 to the hydraulic chamber 6. Further, the spring 43 urges the center rod 44 downward in the figure. The rest of the configuration is the same as the first embodiment, so when a pulse voltage is applied to the electrostrictive element stack 22 and the piston 26 moves in the vertical direction, the oil in the working chamber 40 is pumped by the pumping action of the pump chamber 30. The oil flows into the hydraulic chamber 6 and the amount of oil decreases. Therefore, the spool 48 of the center rod 44 is drawn into the working chamber 40,
It moves upward against the spring 43 and squeezes the variable orifice 46. When the application of the pulse voltage is stopped, the oil in the space 50 flows into the working chamber 40 through the groove 48a of the spool 48 due to the action of the spring 43, so that the center rod 44 returns to its original position.

FIG. 8 is a partial sectional view showing the third embodiment.
The difference from the embodiment is that a space 64 around the outer periphery of the electrostrictive element stack 22 is filled with oil. That is, a passage communicating between the pump chamber 30 and the space 64 is formed on the outer periphery of the piston 26, and oil enters the space 64. Note that the oil filling this space 64 is insulating. The other configurations are the same as in the first embodiment. Therefore, when a pulse voltage is applied, the electrostrictive element stack 22 expands and its volume increases. Then, pump chamber 3
0 and the oil in the space 64 flows into the working chamber 40 and operates in the same manner as in the first embodiment described above. Note that if there is a minute gap between each electrostrictive element of the electrostrictive element stack 22, the oil that has entered the gap is pushed out by the expansion of each element due to the application of a pulse voltage and flows into the working chamber 4.
It contributes as oil flowing to 0.

9 and 10 show the fourth and fifth embodiments, and FIG. 9 shows a suction check valve 34 that allows flow only in the direction from the hydraulic chamber 6 to the pump chamber 30.
is provided, in which the pump chamber 30 operates in the same manner as the working chamber. In FIG. 10, a discharge check valve 38 is provided that allows only one flow from the pump chamber 30 to the working chamber 40, and its operation is the same as in the first embodiment.

FIG. 11 shows a sixth embodiment, which differs from the first embodiment in that a variable orifice 65 is constructed of a plurality of spools 63 instead of the center rod 44 of the variable orifice 46. The spool 63 slides perpendicularly to a plurality of passages 66 communicating with the first and second hydraulic chambers 6 and 8 by the hydraulic pressure of the working chamber 40, and its small hole 63a opens and closes the passages 66. One end of the spool 63 receives hydraulic pressure from the working chamber 40 and is pressed toward the working chamber 40 by a spring 68 at the other end. A space 72 in which the spring 68 is provided communicates with the hydraulic chamber 6 via a small hole 70. Note that a groove (not shown) is formed along the axial direction on the outer periphery of the spool 62, and other configurations and operations are the same as in the first embodiment. According to the above configuration, the working chamber 40 communicates with the hydraulic chamber 6 through the check valves 34 and 38, and the space 72 communicates with the hydraulic chamber 6 through the small hole 70.
Both ends of the spool 63 receive pressure from the hydraulic chamber 6. Therefore, the force acting on the spool 63 is canceled out by pressure fluctuations within the shock absorber, so the spool 63 can move without being affected by the hydraulic pressure in the hydraulic chambers 6 and 8. Further, FIG. 12 is similar to the sixth embodiment, but the spool 63 slides vertically in the figure to open and close the passage 66'. Since the passage 66' is bent in the middle, it has a large flow resistance with respect to the passage 66.

13a and 13b show a seventh embodiment, and FIG. 13b is a sectional view taken along line A--A in FIG. 13a. In this embodiment, the center rod 74
A notch 74a provided on the outer periphery of the
8 forms a variable orifice. This center rod is urged upward by a spring 80, and the space in which the spring 80 is provided is the passage 8.
It communicates with the flow path 76 via 2. At the upper part of the notch 74a of the center rod 74, an axial groove 74b is formed on the outer periphery of the notch 74a to communicate the working chamber 40 and the flow path 78. Therefore, in the illustrated state, the first and second hydraulic chambers 6 and 8 communicate with each other via the passage 76, the notch 74a of the center rod 74, and the passage 78. Note that the other configurations and operations are the same as in the first embodiment.

FIG. 14 shows an eighth embodiment, in which the suction and discharge check valves 34 and 38 of the first embodiment are replaced with
It uses fluid diodes 82 and 84 which have the same operation as a check valve, that is, they allow easy flow in one direction and have a large resistance to flow in the opposite direction. The fluid diode 82 is provided so that the fluid flowing from the hydraulic chamber 6 into the pump chamber 30 can flow therethrough easily, and has a large flow resistance against the flow in the opposite direction. The fluid diode 84 is provided so that the fluid flowing out from the pump chamber 30 toward the working chamber 40 can easily flow therethrough, but has a large flow resistance against the flow in the opposite direction. Therefore, when the piston 26 moves up and down, oil is delivered to the working chamber 40 by the action of the fluid diodes 82 and 84, and the center rod 44 moves downward. When the piston 26 stops moving, the oil in the working chamber 40 gradually flows out from the fluid diodes 82 and 84 under the action of the spring 43, and the center rod 44 returns to its original position. Note that the groove 48a provided on the outer periphery of the spool 48 of the center rod 44 in the first embodiment is no longer necessary. Further, FIG. 15a shows an enlarged view of the fluid diodes 82 and 84,
Other fluid diodes, such as those shown in FIGS. 15b, c, and d, may be used as the fluid diodes 82, 84. In FIG. 15, solid lines indicate the flow of fluid that flows easily, and dotted lines indicate the flow of fluid that is subject to flow resistance.

FIG. 16 shows a ninth embodiment, in which a light emitting and light receiving element 8 is used to detect the position of a center rod 44 that adjusts the opening degree of a variable orifice 46.
6,88. Light from the light emitting element 86 is detected by the light receiving element 88 through a hole 90 passing through the center rod 44 perpendicularly to its axis. The light-emitting element 86 starts emitting light at the same time as the first voltage is applied to the electrostrictive element stack 22, and the light-receiving element 88 detects that the amount of light received changes depending on the amount of movement of the center rod 44. Detect the position of. This signal is fed back to a control circuit (not shown) to produce an electrostrictive element stack 2.
By controlling the pulse voltage applied to the shock absorber 2, the damping force of the shock absorber can be easily controlled to a damping force suitable for the vehicle running conditions. Furthermore, a potentiometer or the like may be used as the detection device.

(Effects of the Invention) As explained in the above embodiments, the response time of the electrostrictive element stack is extremely short, several tens of microseconds. Even with this in mind, the valve body of the variable orifice can be driven at high speed. Furthermore, since the response time of the electrostrictive element stack is short, it is possible to apply the pulse voltage at least several dozen times within the response time required to vary the damping force of the shock absorber. Furthermore, as shown in Figure 4, the valve body of the variable orifice moves each time a pulse voltage is applied, so the valve body of the variable orifice sequentially moves and increases the amount of movement depending on the number of times the pulse voltage is applied. do. Therefore, it takes time depending on the number of times the pulse voltage is applied, but in reality, it only takes a few hundred microseconds even if the pulse voltage is applied several dozen times, so a large amount of movement of the valve body can be obtained almost instantly. .

In other words, in the previous application (Japanese Patent Application No. 59-20699) considered by the same applicant as the present application, the movement of the valve body could only be a few millimeters at most, whereas the present invention According to the method, it is possible to obtain a movement amount of about 10-odd millimeters almost instantaneously. Regarding the shock absorber, this applies to the valve body (center rod) of the variable orifice.
It is possible to take a large stroke and give flexibility in the design of variable orifices, etc. On the other hand, in order to expand the amount of displacement of the electrostrictive element stack and transmit it to the valve body, there is no need to ensure sealing performance or precise processing accuracy to seal the incompressible fluid as in the previous application. This also has the effect of facilitating the design of variable orifices and the like.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing a first embodiment of the variable damping force shock absorber according to the present invention, FIG. 2 is a partial perspective view of the spool 48 of the variable damping force shock absorber shown in FIG. 1, and FIG. 6 is a diagram showing the voltage applied to the electrostrictive element stack 22 and the amount of movement of the center rod 44, FIG. 7 is a partial vertical cross-sectional view showing the second embodiment, and FIG. 8 is a third embodiment. , FIG. 9 is a partial longitudinal sectional view showing the fourth embodiment, FIG. 10 is a partial longitudinal sectional view showing the fifth embodiment, and FIGS. 11 and 12 are respectively the sixth embodiment. 13 is a diagram showing the seventh embodiment, FIG. 13a is a partial longitudinal sectional view, FIG. 13b is a cross-sectional view taken along line A-A in FIG. 13a, 14 is a longitudinal sectional view showing the eighth embodiment, FIG. 15 is an enlarged view showing a fluid diode, FIG. 16 is a partial longitudinal sectional view showing the ninth embodiment, and FIG. 17 is an electrostrictive element stack 22.
FIG. 18 is a waveform diagram of FIG. 17. 2...Cylinder, 4...Piston, 6...First
Hydraulic chamber, 8... Second hydraulic chamber, 10... Piston rod, 14, 16... Fixed orifice, 22...
Electrostrictive element laminate, 30...pump chamber, 34, 60
... Check valve for suction, 38, 62 ... Check valve for discharge, 40 ... Working chamber, 42 ... Channel, 44 ... Center rod (valve body), 82, 84 ... Fluid diode.

Claims (1)

[Scope of Claims] 1. A shock absorber having first and second hydraulic chambers in which a piston is housed so as to be slidable relative to the cylinder, and a fixed orifice provided in the piston, comprising the steps of: a first flow path that communicates the first and second hydraulic chambers; a valve body that is slidably provided to change the area of this flow path; and a valve body that is provided on the piston or piston rod and that applies a voltage. an electrostrictive element laminate that expands and contracts according to a space that communicates between the space and the first flow path, such that the flow rate of oil flowing in and out between these spaces and the first flow path is such that the flow rate of oil flows from the one oil chamber to the space. a second flow path set to be slower than the flow rate of the oil entering the valve; and a biasing means for biasing the valve body to a state before voltage is applied to the electrostrictive element stack, A variable shock absorber with variable damping force in which the valve body slides and changes the flow path area according to the amount of oil in this space. 2. The space is a pump chamber that communicates with the hydraulic chamber through a one-way fluid flow means that changes in volume due to expansion and contraction of the electrostrictive element stack and easily allows flow in only one direction, inflow or outflow. and a working chamber that communicates with the pump chamber through a second one-way fluid flow means that easily allows fluid to flow only in the opposite direction to the one-way fluid means. The variable damping force shock absorber according to item 1. 3 The space is a pump chamber whose volume changes as the electrostrictive element expands and contracts, and this pump chamber facilitates only one-way flow of oil into or out of the hydraulic chamber. Claim 1, characterized in that the oil pressure chamber is in communication with the hydraulic chamber via a one-way fluid circulation means that allows the fluid to flow in one direction.
Variable damping force shock absorber as described in . 4. The variable damping force shock absorber according to claim 2 or 3, wherein the fluid one-way circulation means is a check valve. 5. The attenuation according to claim 2 or 3, wherein the fluid unidirectional flow means is a fluid diode that easily allows flow in only one direction and has flow resistance against flow in the opposite direction. Land variable shock absorber. 6. The variable damping force shock absorber according to claim 1, wherein the electrostrictive element laminate is driven to expand and contract by an intermittently applied pulse voltage. 7. The variable damping force shock absorber according to claim 6, wherein the amount of expansion and contraction of the electrostrictive element laminate is controlled by controlling the time during which a pulse voltage is applied. . 8. The valve body is provided with a detection means for detecting the amount of movement of the valve body, and the flow area of the flow path is detected based on a signal from the detection means, and the voltage applied to the electrostrictive element stack is adjusted. 8. The variable damping force shock absorber according to claim 7, wherein the damping force variable shock absorber controls the time of the shock absorber.