JPH0617871A - Shock absorber - Google Patents

Abstract

PURPOSE:To improve the general use of an automobile shock absorber by inserting a hollow rod, formed by disposing hollow pipes in multiple layers through insulators and forming spaces among the hollow pipes into control spaces, into a cylinder through a piston, then forming the respective pipes into alternately opposite electrodes, and communicating the control spaces with a piston side chamber and a rod side chamber. CONSTITUTION:A hollow piston rod 3 is formed by connecting plural hollow pipes 4a-4c in layers by insulating connecting plates 10a, 10b, and spaces among the pipes 4a-4c are formed into control spaces S. These control spaces S are communciated with a piston side chamber R1 through the hollow part A of the pipe 4c, the hollow part B of the insulating member 10b, the hollow part C of a connecting plate 11 and the hollow part D of a nut 12, and also communicated with a rod side chamber R through the communicating hole 3d of the piston rod 3. The pipes 4a-4c are alternately formed into one electrode and the other electrode, and voltage is applied to both electrodes to perform the change control of viscosity of an electroviscous fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber capable of generating a damping force and changing and adjusting the generated damping force by utilizing the property that an electrorheological fluid changes its viscosity by an applied voltage.

[0002]

2. Description of the Related Art In recent years, for example, a hydraulic shock absorber used as a shock absorber for an automobile is constructed so that the generated damping force is changed and adjusted according to the condition of the road surface of the automobile. Is desired.

In the hydraulic shock absorbers conventionally proposed for that purpose, in general, the damping force generated when the hydraulic oil, which is the working medium in the hydraulic shock absorber, passes through the damping valve. It is configured to adjust the height.

For example, in a conventional hydraulic shock absorber as shown in FIG. 3, the tip of a piston rod 2 which is inserted into and retractable from the cylinder 1 slides in the cylinder 1 and the cylinder 1 It has a piston portion 2a which divides and forms a rod side oil chamber A and a piston side oil chamber B therein, while a damping force adjusting portion V is provided in the piston rod 2.

The damping force adjusting portion V has a vertical hole 2b which is opened in the lower axial core portion of the piston rod 2 and communicates with the piston side oil chamber B, and a vertical hole 2b which communicates with the vertical hole 2b and the rod side oil chamber. While having a bypass passage L composed of a lateral hole 2c opened in the piston rod 2 so as to communicate with A, it is rotatable in the bypass passage L, that is, in the vertical hole 2b. It has a rotary valve V1 arranged.

The rotary valve V1 has a plurality of orifices communicating with the vertical hole 2b and selectively facing the horizontal hole 2c and having different diameters. It is assumed that it is connected to the tip of the control rod V2 that is rotatably inserted in the opened through hole 2d.

The base end of the rotary rod V2 projects outward from the upper end of the piston rod 2 under the distribution of the seal V3, and is rotatable by an actuator V4 connected to the base end. There is.

In the conventional example shown in the drawing, the piston portion 2a has an extension side damping valve 2e and a pressure side check valve 2f, and at the end of the bypass passage L on the piston side oil chamber B side. An extension side check valve 2g with an orifice is made to exist, and a base valve portion having a pressure side damping valve is arranged inside the lower end of the cylinder 1 although not shown.

Therefore, according to the above conventional hydraulic shock absorber,
When the piston rod 2 is retracted into and retracted from the cylinder 1, as long as the bypass L is closed, the expansion side damping valve 2e in the piston portion 2a and the compression side damping valve in the base valve portion are set respectively. Damping force will be generated.

When the bypass passage L is opened by allowing the hydraulic oil to pass through the damping force adjusting portion V during the above-described expansion / contraction operation, the flow rate of the hydraulic oil passing through the piston portion 2a is changed to change the piston. When the damping force generated in the portion 2a is changed and the orifice in the rotary valve V1 is selected when the bypass L is opened, the flow rate of the hydraulic oil passing through the bypass L is changed. The damping force generated in the piston portion 2a is changed and adjusted in multiple stages.

Therefore, when the hydraulic shock absorber is mounted on an automobile, it becomes possible to change and adjust the generated damping force according to the condition of the road surface on which the automobile travels, thereby improving the riding comfort of the automobile. Can be done.

[0012]

However, in the above-described hydraulic shock absorber as a conventional example, the responsiveness with respect to the generation of the damping force is poor, and it is impossible to smoothly change and adjust the damping force without steps. It has been pointed out that there is a drawback.

That is, in the operation of the damping force adjusting portion V, the actuator V4 is driven by energizing to rotate the control rod V2 with the seal V3 interposed, and the rotary valve V1 is rotated by rotating the control rod V2. Therefore, it is impossible to avoid the occurrence of friction due to the presence of the seal V3 and the sliding of members in the rotary valve V1 portion.

Therefore, the occurrence of the friction causes a so-called operation delay in the rotary valve V1,
The responsiveness with respect to the generation of the damping force is deteriorated, and the orifice is changed when the rotary valve V1 is rotated. However, at this time, the generated damping force is once returned to the old state, and the step is smooth without a step. It becomes impossible to change and adjust the damping force.

If the hydraulic shock absorber is equipped with the damping force adjusting unit V having the above-mentioned structure, not only the structure of the hydraulic shock absorber itself becomes complicated but also the number of expensive parts such as actuators is increased and the cost is increased. Is increased, and if the damping force adjusting unit V is operated with a more complicated structure in order to eliminate the above-mentioned operation delay, there is a disadvantage that the cost is further increased.

In view of the above-mentioned circumstances, the present invention takes into consideration the fact that an electrorheological fluid having a property that its viscosity changes with an applied voltage has been found in recent years.
It was invented, and its purpose is to prevent a so-called operation delay when changing and adjusting the damping force, and to make it possible to smoothly change and adjust the damping force without steps.
In addition, the structure of the shock absorber itself does not have to be complicated, and
It is an object of the present invention to provide a shock absorber using an electrorheological fluid, which can prevent an increase in cost due to the use of expensive parts and an unnecessary increase in the number of parts, and can be expected to improve its versatility.

[0017]

[Means for Solving the Problems] To achieve the above object,
According to the configuration of the present invention, a hollow piston rod is movably inserted into a cylinder via a piston portion, and a plurality of hollow pipe bodies are arranged in the hollow piston rod via an insulating material while being multiplexed. A series of control gaps is formed in the pipe, and the control gap communicates the rod side chamber and the piston side chamber, which are defined by the piston portion, through the through hole formed in the piston portion and the hollow piston rod, and the plurality of pipes are connected. Every other pipe body is used as one electrode member, while the remaining pipe bodies are used as the other electrode member, and the electric power is interposed in the control gap when voltage is applied to both electrode members. It is characterized in that it is configured so that the viscosity of the viscous fluid is changed.

[0018]

Therefore, during expansion and contraction of the shock absorber in which the hollow piston rod is retracted from the cylinder, the electrorheological fluid reciprocates between the rod side chamber and the piston side chamber in the cylinder through the control gap. At this time, at the time of operating the applied voltage to both electrode members consisting of the pipe body which is one electrode member and the pipe body which is the other electrode member, in the electrorheological fluid interposed in the control gap, The viscosity is instantly changed according to the applied voltage, and the electrorheological fluid with the changed viscosity becomes a so-called friction member.

By arranging a plurality of pipe bodies, the control gap formed between them becomes long, and the effective area of the viscous fluid effect becomes large.

Therefore, when a predetermined voltage is applied to both of the electrode members, the immersability of the hollow piston rod into the cylinder and the protruding property of the hollow piston rod from the cylinder are limited, which is the so-called damping action. Moreover, the damping action is immediately realized in response to the change of the applied voltage.

As a result, like the conventional hydraulic shock absorber, the damping force is adjusted by the damping force adjusting section having a rotary valve which is a sliding member, a control rod with a seal interposed, and an actuator which is driven by energization. Compared to the case of changing and adjusting, so-called operation delay is not caused, and
A predetermined damping force adjustment can be smoothly realized without a step by continuously changing the applied voltage.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the illustrated embodiments. The embodiment shown in FIG. 1 is a shock absorber for an automobile. The shock absorber comprises a cylinder 1 and a hollow. Piston rod 3 and hollow pipe bodies 4a, 4b, 4
c and the free piston 5.

The cylinder 1 is formed in a so-called single tube structure so as to have a chamber of a predetermined capacity therein, and inside thereof, a piston portion 3a connected to the tip of the hollow piston rod 3 is provided. Side chamber R1 partitioned by
And a piston side chamber R2.

The rod-side chamber R1 and the piston-side chamber R2 are filled with an electrorheological fluid whose viscosity changes when a voltage is applied.

Further, the cylinder 1 has a free piston 5 slidably accommodated inside the lower end side thereof so as to further partition the piston side chamber R2, and on the rear side of the free piston 5 is provided. The gas chamber G is partitioned and formed.

The cylinder 1 has its opening end closed by the bearing portion 1a, and allows the hollow piston rod 3 to pass through the shaft core portion of the bearing portion 1a.

A seal member 1b having a sealing function is disposed between the bearing portion 1a and the hollow piston rod 3.

The hollow piston rod 3 is made of an electrically conductive material and is formed into a substantially cylindrical head shape so that the hollow piston rod 3 has an inner space 3b having an appropriate capacity therein. The thick wall portion near the portion 3a has a communication hole 3d penetrating therethrough. The communication hole 3d communicates the inner space 3b with the rod side chamber R1.

The hollow piston rod 3 has a stopper member 3e on the outer periphery thereof close to the piston portion 3a, and the hollow piston rod 3 is extended from the inside of the cylinder 1 so that the extension stopper can be extended. It is supposed to be.

The pipes 4a, 4b, 4c are multiply arranged and are made of a current-carrying material, and the hollow space 3b of the hollow piston rod 3 has insulating materials 10a for the upper and lower ends thereof.
It is fixedly arranged under the distribution of 10b.

The insulating materials 10a and 10b and the respective pipe bodies 4a, 4b and 4c are integrally inserted into the hollow piston rod 3 and pushed up from the hollow portion in the center of the piston portion 3c, and these are insulatedly connected. It is supported by the plate 11 and the nut 12, and is tightened by the nut 12 screwed to the piston portion 3c.

The pipe body 4b penetrates the insulating material 10a so as to have the same pole as the piston rod 3 and is in contact with the piston rod 3.

In this embodiment, the piston rod 3 and the pipe body 4a, the pipe bodies 4a and 4b, and the pipe bodies 4b and 4c are connected in series at about 1 m / m. It is assumed that the connected control gap S is formed.

That is, the control gap S is determined in view of the fact that the shock absorber according to the present invention selects the electrorheological fluid as its working medium as described above, and therefore the control gap S The space S for use is preset to a size corresponding to the applied voltage.

As long as the size of the control gap S is secured, the structure of the pipe body 4 and the storage state of the pipe body 4 can be freely selected.

The pipe bodies 4a and 4c are provided at their upper ends with communication holes a and b which are opened so as to penetrate through the thickness thereof, and the pipe body 4b has a communication hole c at its lower end. The control gaps S are provided in series through the communication holes a, b, and c.

The control gap S is formed by the pipe bodies 4a, 4b, 4
Since it is formed between c and c, the passage becomes long and the effective area of the viscous fluid effect becomes large.

The control gap S communicates with the piston side chamber R2 through the hollow portion A of the pipe body 4c, the hollow portion B of the insulating material 10b, the hollow portion C of the connecting plate 11 and the hollow portion D of the nut 12, and the piston rod. It communicates with the rod side chamber R1 through the communication hole 3d. Piston rod 3 and pipe body 4
b is the same pole and is used as one of the electrode members.
a and 4b have the same polarity and are used as the other electrode member.

The electric wire E3 extended from the controller or the voltage source E is connected to the upper end portion of the hollow piston rod 3 which is one of the above-mentioned electrode members and is, for example, the plus side, and the other electrode member. Pipe body 4b, 4b
The electric wire E4 extended from the voltage source E is connected to the upper end of the negative side.

The electric wire E4 connected to the pipe bodies 4b, 4c extends through the hollow piston rod 3 through the upper end wall thickness thereof.
An appropriate insulating material 3f is distributed in the penetrating portion.

In the shock absorber using the electrorheological fluid formed as described above, during the compression side stroke in which the hollow piston rod 3 is retracted into the cylinder 1, the piston side chamber R
A part of the electrorheological fluid 2 of the rod side chamber R1
When the hollow piston rod 3 protrudes from the cylinder 1, the electrorheological fluid in the rod side chamber R1 reversely flows to the communication hole 3d of the hollow piston rod 3 for control. It will flow out into the piston side chamber R2 through the gap S.

Then, during the pressure side stroke, the piston side chamber R
The surplus electrorheological fluid in 2 is accommodated in the piston side chamber R2 due to the retraction of the free piston 5, and the electrorheological fluid that becomes insufficient in the piston side chamber R2 during the expansion side stroke is 5
Will be supplemented by the advance of.

On the other hand, at the time of expansion and contraction operation of the shock absorber, if, for example, a direct current applied voltage is appropriately applied to the hollow piston rod 3 serving as one electrode member and the pipe bodies 4b and 4c serving as the other electrode member, The viscosity of the electrorheological fluid interposed in the control gap S is instantaneously changed according to the applied voltage, and the electrorheological fluid with the changed viscosity acts as a so-called friction member.

At this time, since the control gap S is long and the effective area is large, it is possible to freely and freely change from a small damping force to a large damping force.

When a predetermined voltage is applied to both electrode members, the immersiveness of the hollow piston rod 3 into the cylinder 1 and the protruding property of the hollow piston rod 3 from the inside of the cylinder 1 are immediately limited. This is a so-called damping action, and the damping action is immediately realized according to the change of the applied voltage.

As a result, like the conventional hydraulic shock absorber, the damping force adjusting unit having the rotary valve as the sliding member, the control rod with the seal interposed, the actuator driven by the energizing operation, and the like can reduce the damping force. Compared to the case of changing and adjusting, a delay in generation of damping force due to a so-called operation delay is not caused, and if the applied voltage is changed continuously in high and low, predetermined damping force adjustment can be performed smoothly without steps. Will be done.

In the above-described embodiment, the gas chamber G is also provided in the cylinder 1, but instead of this, the gas chamber G is provided in the accumulator formed separately from the cylinder 1. It may be provided, or the gas chamber G may be provided together with the free piston 5 in a housing integrally formed with the cylinder 1.

FIG. 2 relates to another embodiment of the invention, which is suitable for alternating current use.

A pipe 14 made of an insulating material is inserted into the hollow piston rod 3 while abutting the outer periphery thereof, and the hollow pipe bodies 4a, 4b, 4c are multiply arranged in the pipe 14, and each pipe body is arranged. The upper ends of 4a, 4b and 4c are pressed against the upper surface of the piston rod 3 via an insulating material 15.

Inside the insulating material 15, two electrode terminals 16, 1 are provided.
7 is embedded, and one electrode terminal 16 is connected to the pipe bodies 4a and 4c, penetrates the insulating material 18, and is coupled to the electric wire E3 on the AC power source E side.

The other electrode terminal 17 is connected to the pipe body 4b and is also connected to the power source E4.

In this embodiment, the piston rod 3 is not used as an electrode member.

A control gap S is formed between each pipe body 4a, 4b, 4c, and each control gap is formed by each pipe body 4a, 4c.
b and 4c are communicated with each other through connecting holes d, e and f formed alternately in the upper and lower directions. Other structures, actions and effects are the same as those of the embodiment shown in FIG.

In the embodiment of FIG. 2, the polarity of the electrodes is constantly changed by using an AC power source, the movement of the dielectric particles dispersed in the electrorheological fluid becomes active, and the particles are less likely to settle. The sexual change can be kept constant.

Further, since the piston rod 3 is not used as an electrode member, it is possible to prevent the risk of electric leakage or electric shock.

The present invention can be used not only in the simple type but also in a double-cylinder type shock absorber.

Further, reliability can be improved because all the electrode portions can be set on the spring.

[0058]

As described above, according to the present invention, the following ideas can be obtained.

(1) A plurality of pipe bodies, which are electrode members, are arranged in the hollow piston rod to form control gaps between the electrode members, and in the control gaps when the shock absorber expands and contracts. The viscosity of the electrorheological fluid interposed in the electrode is instantaneously changed when a voltage is applied to both of the electrode members, and the electrorheological fluid whose viscosity has been changed serves as a friction member to form a hollow piston of the pipe body. Immediately limit the immersability into the rod and the retreat of the pipe body from the hollow piston rod, that is, to immediately provide a predetermined damping action.

(2) If the applied voltage is appropriately controlled, the viscosity of the electrorheological fluid interposed in the control gap is changed accordingly, and the conventional hydraulic shock absorber has the same viscosity. As described above, a so-called operation is performed as compared with a case where the damping force is adjusted by a damping force adjusting unit including a rotary valve that is a sliding member, a control rod with a seal interposed, and an actuator that is driven by energization. By delaying the generation of the damping force due to the delay, if the applied voltage is continuously changed in high and low, the predetermined damping force adjustment can be smoothly performed without a step.

(3) When the shock absorber is mounted on an automobile, the damping force can be adjusted according to the condition of the road surface of the automobile, the riding comfort of the automobile can be improved satisfactorily, and Since it does not have such a damping force adjusting section, the structure of the shock absorber itself does not have to be complicated, the use of expensive parts such as actuators can be avoided, and the cost increases due to an unnecessary increase in the number of parts. Can be prevented, and improvement in its versatility can be expected.

(4) Since a plurality of pipe bodies are multiply arranged, the control gap between the pipe bodies becomes long, the effective area of the characteristic fluid effect is large, and it is possible to freely move from a small damping force to a large damping force. Can be changed to.

(5) Further, as in the illustrated embodiment, when the electric wire extended from the controller is connected to the upper end side of the shock absorber, the wiring is concentrated on a so-called spring. Its durability is improved and maintenance management is easy, and many other effects are achieved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a shock absorber according to an embodiment of the present invention.

FIG. 2 is a partially cutaway sectional view of a hydraulic shock absorber according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional hydraulic shock absorber with a part thereof omitted.

[Explanation of symbols]

 1 Cylinder 2 Piston Rod 3 Hollow Piston Rod 3a Piston Part 3b Inner Space 3d Communication Holes 4a, 4b, 4c Pipe Body R1 Rod Side Chamber R2 Piston Side Chamber S Control Clearance

[Procedure amendment]

[Submission date] June 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

From the center of the piston portion 3a, the insulating material 10
a, 10b and the pipe bodies 4a, 4b, 4c are integrally inserted into the hollow piston rod 3 and pushed up,
These are supported by a conductive connecting plate 11 and a nut 12, and are tightened by a nut 12 screwed to the piston portion 3a.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

The pipe body 4 b penetrates through the insulating material 10 a so as to have the same pole as the piston rod 3, and the piston rod 3
Further, the pipe body 4c penetrates the insulating material 10b so as to have the same polarity as the pipe body 4a and contacts the pipe body 4a through the conductive connecting plate 11.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

The control gap S is the hollow portion A of the pipe body 4c.
Through the hollow portion B of the insulating material 10b, the hollow portion C of the connecting plate 11 and the hollow portion D of the nut 12, and the rod side chamber R1 through the communicating hole 3d of the piston rod 3. There is. The piston rod 3 and the pipe body 4b have the same pole and are used as one electrode member, and the pipe bodies 4a and 4c have the same pole and are used as the other electrode member.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

The electric wire E3 extended from the controller or the voltage source E is connected to the upper end of the hollow piston rod 3 which is one of the above electrode members and is, for example, on the plus side, and the other electrode member. The electric wire E4 extended from the voltage source E is connected to the upper end of the pipe body 4c to be the negative side.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction content]

The electric wire E4 connected to the pipe body 4c penetrates the upper end wall thickness of the hollow piston rod 3 and extends into the hollow piston rod 3. The insulating material 3f is distributed.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

In the shock absorber using the electrorheological fluid formed as described above, a part of the electrorheological fluid in the piston side chamber R2 is in the compression side stroke in which the hollow piston rod 3 is retracted into the cylinder 1. Is a communication hole 3d opened in the control gap S and the hollow piston rod 3 and communication holes a, c, opened in the pipe bodies 4a, 4b, 4c, respectively.
It will flow into the rod side chamber R1 via b. Also, during the expansion side stroke in which the hollow piston rod 3 is projected from the inside of the cylinder 1, the electrorheological fluid in the rod-side chamber R1 is, contrary to the above, the communication hole 3 of the hollow piston rod 3.
d, the piston side chamber R via the communication holes a, c, b opened in each of the pipe bodies 4a, 4b, 4c and the control gap S.
It will flow into the inside of 2.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

On the other hand, at the time of expansion / contraction operation of the shock absorber, by appropriately applying, for example, a direct current applied voltage to the hollow piston rod 3 which is one of the electrode members and the pipe body 4c which is the other of the electrode members, it is possible to control. The viscosity of the electrorheological fluid interposed in the gap S is instantly changed according to the applied voltage, and the electrorheological fluid with the changed viscosity acts as a so-called friction member.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction content]

In addition, in the embodiment of FIG. 2, since the hollow piston rod 3 is not set as an electrode member, there is an advantage that the risk of electric leakage or electric shock through the hollow piston rod 3 can be avoided. Instead of, as shown in FIG.
Insulating material 1 between the hollow piston rod 3 and the pipe body 4a
4 may be omitted and this portion may be set as a passage through which the electrorheological fluid passes, so that the entire length of the control gap S may be increased. In the case of the embodiment of FIG. 3, the hollow piston rod 3 is set as the electrode member as in the embodiment of FIG.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a shock absorber according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a shock absorber according to another embodiment.

FIG. 3 is a vertical sectional view showing a shock absorber according to another embodiment.

FIG. 4 is a front view showing a hydraulic shock absorber as a conventional example, partially broken away.

[Explanation of symbols] 1 cylinder 2 piston rod 3 hollow piston rod 3a piston part 3b inner space 3d communication hole 4a, 4b, 4c, pipe body R1 rod side chamber R2 piston side chamber S control gap

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 13]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

[Figure 4]

Claims (1)

[Claims] 1. A hollow piston rod is movably inserted into a cylinder via a piston portion, and a plurality of hollow pipe bodies are arranged in the hollow piston rod via insulating material while being multiplexed, and between the hollow pipes. A series of control gaps is formed in the pipe, and the control gap communicates the rod side chamber and the piston side chamber, which are defined by the piston portion, through the through hole formed in the piston portion and the hollow piston rod, and the plurality of pipes are connected. Every other pipe body is used as one electrode member, while the remaining pipe bodies are used as the other electrode member, and the electric current is interposed in the control gap when voltage is applied to both electrode members. A shock absorber, characterized in that the viscosity of a viscous fluid is changed.