JPH10196706A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the lowering of damping force in an area of a low piston speed by employing a structure which allows the opening of an orifice to remain opened when a check valve is closed but fills the opening with an elastic material when the back-flow pressure of electroviscous fluid is applied. SOLUTION: A check valve 20 to be used in the lower chamber of a cylinder for a shock absorber suitable for an automobile suspension with an adjustable damping force, is constituted by securing an orifice-forming plate 211 made of an elastic material to the face opposite to that depressed by a spring 203 of a main valve body 204, and the check valve 20 is pressed against the upper face of a valve body 207 by the force of a spring 203. This condition allows the electroviscous fluid coming from a center hole 208 to flow through an orifice 212 as shown by an arrow 209, and the flow amount is throttled. However, if the electroviscous fluid starts flowing from the upper side (back-flowing), the orifice-forming plate 211 is depressed against the valve body 207, thereby closing the orifice 212 and the back-flow is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber using an electrorheological fluid as a working fluid.

[0002]

2. Description of the Related Art Some shock absorbers used in automobiles use an electrorheological fluid as a working fluid. An electrorheological fluid is a fluid whose apparent viscosity changes when the electric field applied thereto changes. When the applied electric field is increased, the viscosity does not change, but the connection between the dispersed particles in the electrorheological fluid becomes stronger, and the yield stress increases. Therefore, apparently, the viscosity of the electrorheological fluid is increased (Japanese Unexamined Patent Application Publication No. 5-179270 is a reference concerning the electrorheological fluid).

A shock absorber used for a vehicle suspension generates a damping force for suppressing vibration of a vehicle body and wheels due to road surface input and suppressing a change in posture of the vehicle body due to starting, stopping, steering and the like. is there. In general, a low damping force is good for improving ride comfort (that is, for suppressing vibration of the vehicle body), and a high damping force is good for suppressing posture change. ing. That is, it is desirable that the damping force can be adjusted according to the condition of the road surface on which the vehicle is traveling or the traveling condition. In a shock absorber using an electrorheological fluid as a working fluid, the damping force can be adjusted by changing an applied electric field according to a road surface condition or a running condition, so that the shock absorber is suitable for a vehicle suspension.

FIG. 5 is a diagram showing such a conventional shock absorber. First, the configuration will be described. In FIG.
1 is a shock absorber, 2 is a piston rod, 3 is a sealing material, 4A
Is an upper housing, 4B is a middle housing, 4C is a lower housing, 4C-1 is a mounting portion, 5A is an upper holder portion, 5B is a lower holder portion, 6 is an electrode cylinder, 7 is a communication hole, 8 is an electrode terminal portion, 9 Is a cylinder, 10 is an electrode terminal, 11 is an upper cylinder, 12 is a control gap, 13 is a piston, 14 is a communication passage, 15 is a check valve, 16 is a lower cylinder, 17 is a reservoir, and 17-1 is gas. Room, 1
8 is a sealing material, 19 is a communication hole, 20 is a check valve,
21 is a communication passage.

The housing is made of a conductive material, and includes an upper housing 4A, a middle housing 4B, and a lower housing 4C. The lower portion of the cylinder 9 is supported by the lower housing 4C, and the upper portion is supported by the upper housing 4A. I have. The electrode cylinder 6 is disposed outside the cylinder 9 with a control gap 12 therebetween. The electrode cylinder 6 is made up of a cylinder 9 by an upper holder 5A and a lower holder 5B.
It is supported by. The gap between the outer peripheral surface of the electrode cylinder 6 and each housing is used as a reservoir 17 for storing an electrorheological fluid as a working fluid. An electrorheological fluid is stored in a lower portion of the reservoir 17, and a gas chamber 17-1 in which a gas such as air is stored above the liquid level.

[0006] A piston 13 connected to the piston rod 2 is inserted into the cylinder 9. Piston 13
A seal member 18 is provided on the side surface of the piston 1.
The cylinder upper chamber 11, which is a chamber above 3, and the cylinder lower chamber 16, which is a lower chamber, are liquid-tightly separated. The piston 13 is provided with a check valve 15 and a communication passage 14 communicating from the lower cylinder chamber 16 to the check valve 15. The check valve 15 is a valve that allows the flow only from the cylinder lower chamber 16 to the communication passage 14 (the direction of arrow C).

In the lower housing 4C, a reservoir 17 is provided.
There is provided a communication passage 21 that communicates with the lower chamber 16 of the cylinder. The check valve 20 is provided in the communication path 21 and is a valve that allows the flow only from the communication path 21 to the cylinder lower chamber 16 (the direction of arrow D). Also,
A communication hole 7 communicating from the upper cylinder 11 to the control gap 12 is provided on the upper side wall of the cylinder 9, and a communication hole 19 communicating from the control gap 12 to the reservoir 17 is provided on the lower side wall of the electrode cylinder 6. ing.

An electrorheological fluid as a working fluid fills the cylinder lower chamber 16, the communication passage 14, the cylinder upper chamber 11, the control gap 12, and the communication passage 21 and a reservoir 17
Is filled with some. The wires from the power supply (not shown)
It is connected to the electrode terminals 8 and 10. Either terminal may be a positive electrode or a negative electrode, but generally, the electrode terminal 10 is a positive electrode and the electrode terminal 8 is a negative electrode. The electrode terminal portion 10 is attached to a hole formed in the housing via an insulating material, and is in conductive contact with the electrode cylinder 6 by a contact 10-1. The electrode terminal portion 8
It is conductively connected to the cylinder 9 through the housing.
Therefore, when a voltage is applied to the electrode terminal portions 8 and 10, a voltage is applied between the electrode cylinders 6 and 9, that is, in the thickness direction of the control gap 12. The greater the voltage applied across the control gap 12, the greater the apparent viscosity of the electrorheological fluid between them.

Therefore, the larger the voltage that can be applied between the electrode terminal portion 8 and the electrode terminal portion 10, the larger the variable width of the damping force that can be generated in the shock absorber. However, this voltage is equally applied between both side walls forming the reservoir 17 (the electrode cylinder 6 and the housings 4A, 4B, 4C).

In order to generate a damping force that can be used as a suspension for an automobile, the control gap 1 is required.
2, several K over an electrode length of about 200 mm.
It is known that an electric field of about V / mm needs to be applied. The length of the electrode is determined by the size of the shock absorber, but the size of the shock absorber is limited by the installation space in the vehicle. Also, the higher the voltage of the power supply used, the higher the electric field can be generated, but the voltage of the power supply mounted on the vehicle is not so high. For this reason, in order to obtain the electric field, the thickness of the control gap 12 (that is, the distance between the electrodes) needs to be about 1 mm.

Next, the operation will be described. (1) Operation when the piston 13 descends (during compression) When the piston 13 attempts to descend, the cylinder lower chamber 16
Since the pressure applied to the check valve 15 from the side increases, the electrorheological fluid in the lower cylinder chamber 16 flows to the upper cylinder chamber 11 through the communication passage 14 and the check valve 15. On the other hand, the check valve 20 also receives pressure from the cylinder lower chamber 16 side, but since the check valve 20 blocks the flow from the cylinder lower chamber 16 to the communication path 21,
The electrorheological fluid does not flow into the communication passage 21.

The electrorheological fluid is displaced by the volume increase of the descending piston rod 2, enters the control gap 12 through the communication hole 7, flows therethrough, and flows into the reservoir 17 from the communication hole 19. In this case, if the electric field applied to the control gap 12 is large, the apparent viscosity of the electrorheological fluid will also be large, and it will not easily flow through the control gap 12. This acts as a large resistance to the downward movement of the piston 13. That is, it acts as a large damping force. Conversely, if the applied electric field is small, the apparent viscosity becomes small, the electrorheological fluid can easily flow through the control gap 12, and the damping force becomes small.

(2) Operation when the piston 13 rises (during extension) When the piston 13 tries to rise, the cylinder upper chamber 11
Therefore, the electrorheological fluid therein passes through the communication hole 7, enters the control gap 12, flows therethrough, and flows into the reservoir 17 through the communication hole 19. At the check valve 15, the electrorheological fluid tends to flow toward the cylinder lower chamber 16 through the communication passage 14, but does not flow out because this direction is the blocking direction of the check valve 15.

On the other hand, since the volume of the cylinder lower chamber 16 is increased, pressure is applied to the check valve 20 in the direction of arrow D. Since the check valve 20 can flow in this direction, the electrorheological fluid of the reservoir 17 flows into the cylinder lower chamber 16 through the communication passage 21 and the check valve 20 in order to fill the increase in volume. Also in this case, the damping force with respect to the force for moving the piston 13 can be adjusted by changing the electric field applied to the control gap 12.

FIG. 9A is a diagram showing ideal damping force characteristics of the conventional shock absorber using an electrorheological fluid.
However, this is a characteristic in the case where a check valve that opens and closes with high response when the moving direction of the piston changes is used as the check valve. The horizontal axis is the piston speed,
The positive direction is the piston extension side (extension side), and the negative direction is the piston compression side (compression side). The vertical axis is the generated damping force, the curve a ₁ represents the characteristics when no electric field is applied to the control gap 12, and the curve a ₂ represents the characteristics when the maximum allowable electric field is applied. ing. The length in the vertical axis direction between these curves (the length indicated by the arrow K in the figure) indicates the variable range of the damping force. By changing the applied electric field, the damping force can be arbitrarily changed within this range.

Incidentally, such a buffer using an electrorheological fluid has a structure in which an electrorheological fluid is passed through the control gap 12 to generate a damping force, and the flow path is narrowed at a check valve. It is not a structure to generate. Accordingly, the check valves 15 and 20 used for this purpose must have no flow path resistance when opened, and have an infinite flow path resistance when closed. Since the apparent viscosity of the electrorheological fluid can be changed with a high response, if the check valve is operated with a high response, the buffer can have a high response.

In order to close the check valve instantly,
The structure must be closed with a strong spring. However, if it is made stronger, a force greater than that force is required to open it, and it will not open until the pressure of the electrorheological fluid applied to the check valve reaches that force, and the shock absorber will be in a stretched state. In other words, this is the same as the case where the shock absorber has static friction, and the vibration is transmitted as it is until the static friction is overcome. It is well known that shock absorbers with high static friction deteriorate ride comfort.

In order to prevent this, a structure has been proposed that allows the flow of the electrorheological fluid even if the pressure for opening the check valve is smaller than the pressing force of the spring. The structure is a structure in which an orifice (small cutout) is provided in a check valve. If the piston speed is low and the check valve is not opened, even if the pressure of the electrorheological fluid is low, the flow of the electrorheological fluid flowing through the orifice with almost no resistance is generated, and the buffer is not stretched.

Next, the check valve having such a structure will be described in detail. FIG. 6 is a diagram illustrating a first example of the check valve 20 used on the cylinder lower chamber side. In FIG. 6, 201 is a valve cover, 202 is a hole, 20
3 is a spring, 204 is a valve body, 205 is a hole, 2
Reference numeral 06 denotes an orifice, 207 denotes a valve body, 208 denotes a center hole, and 209 denotes an arrow indicating the flow of the electrorheological fluid.
6A is a cross-sectional view when the check valve is closed, FIG. 6B is a plan view of the valve body 204, and FIG.
(C) is a sectional view when the check valve is open.

A valve body 204 and a spring 203 are disposed in this order above a valve body 207 having a central hole 208 penetrating in the vertical direction, and a valve cover 201 is put on the valve body 204 and a spring 203. It is fixed to the body 207. A hole 202 is formed in the upper surface of the valve cover 201, and an appropriate number of holes 205 are formed in the side surface. This check valve 2
0, as shown in FIG.
The point of this is that several (four in the figure) orifices 206 are provided on the peripheral edge of the lower surface of 4.

The valve body 204 is pressed downward by a spring 203. The pressing force causes the valve body 204 to move the valve body 207 as shown in FIG.
Is in a state where the check valve 20 is closed. However, even if abutted, orifice 2
In the portion of 06, a small gap is opened between the valve body 207 and the upper surface. If the pressure of the electrorheological fluid that is to flow in the direction of pushing up the valve body 204 is greater than the pushing force of the spring 203, the valve body 204 is pushed up, and the pressure with the upper surface of the valve body 207 is increased. There is a large gap between them. This state is shown in FIG.
(C) is a state where the check valve 20 is open.

FIG. 7 is a view showing an example of the check valve 15 used on the piston side. Reference numerals correspond to those in FIG. 5, 152 is a valve cover, 152-1 is a notch, 15
2-2 is a piston rod through hole, 153 is a spring,
154 is a valve body, 154-1 is a piston rod through hole, 155 is an orifice, and 156 is a collar. FIG.
7A is a cross-sectional view when the check valve is open, FIG. 7B is a perspective view of the valve cover 152, and FIG. 7C is a plan view of the valve body 154.

As shown in FIG. 7B, the valve cover 1
52 is formed in a cup shape as a whole, has several cutouts 152-1 on its side surface, and one piston rod through hole 152-2 is opened in the center of the upper surface. As shown in FIG. 7 (C), a piston rod through hole 154-1 is provided at the center of the valve body 154, and several orifices 155 are provided at the peripheral edge of the lower surface. After fitting the valve cover 152 and the cylindrical collar 156 to the lower end of the piston rod 2, the spring 153, the valve body 154 and the piston body 130 are fitted in this order and fixed by the nut 131.

The valve body 154 is pressed downward by a spring 153 and abuts on the upper surface of the piston body 130. This state is a state in which the check valve 15 is closed, but a small gap is opened at the orifice 155 even when the check valve 15 is in contact. On the other hand, the piston body 13
When the pressure at which the electrorheological fluid flows upward from below the pressure of the valve body 0 becomes greater than the pressing force of the spring 153, the pressure passes through the communication passage 14 and the valve body 1
54, and as shown in FIG.
Push up 54. This state is a state where the check valve 15 is open. The electrorheological fluid that enters through the communication passage 14 passes through a gap between the valve body 154 and the piston body 130, and the notch 152-1 of the valve cover 152.
And flows out into the upper cylinder chamber 11.

The operation of the shock absorber when the valves shown in FIGS. 6 and 7 are used as the check valves 20 and 15 will be described.
This will be described with reference to FIGS. 5 and 9B. In addition,
FIG. 9B is a damping force characteristic diagram in this case. When the piston 13 is moved to the extension side, the check valve 2
0 is open and the electrorheological fluid in the reservoir 17 is
7 → communication passage 21 → check valve 20 → cylinder lower chamber 1
Flows to 6. This flow flows without resistance and generates no damping force. On the other hand, the check valve 15 is closed, and the electrorheological fluid in the upper cylinder chamber 11 flows from the upper cylinder chamber 11 → the communication hole 7 → the control gap 12 → the communication hole 19 → the reservoir 17 to reduce the resistance in the control gap 12. Generates damping force from receiving.

However, even when the check valve 15 is closed, the gap between the orifices 155 described with reference to FIG. 7 is open, so that a part of the electrorheological fluid is transferred to the upper cylinder chamber 11 → orifice 155 → communication passage. 14 → Cylinder lower chamber 1
Backflow to 6. For this reason, the damping force generated in the control gap 12 is reduced by an amount corresponding to the reverse flow that should have passed through the control gap 12. The greater the electric field applied to the electrorheological fluid and the more difficult it is for the control gap 12 to flow, the greater the amount of backflow. When no electric field is applied and the control gap 12 flows easily, the amount of backflow is reduced. Also, the lower the piston speed, the larger the proportion of the backflow, and the higher the piston speed, the smaller the proportion of the backflow. Therefore, as shown in FIG. 9B, when the applied electric field is small (curve a ₁ ), the damping force hardly decreases when the piston 13 is moved to the extension side. In the case of a large value (curve a ₂ ), the damping force decreases in a region where the piston speed is low (see the extension-side characteristic in FIG. 9B).

When the piston 13 is moved to the contraction side, the check valve 20 on the lower chamber side of the cylinder is closed, the check valve 15 on the piston side is opened, and a damping force is generated in the control gap 12. At the portion of the orifice 206 at 20 (see FIG. 6), backflow of the electrorheological fluid also occurs. Therefore, as in the case described above, when the applied electric field is large, the damping force decreases in a region where the piston speed is low (see the contraction side characteristic in FIG. 9B).

FIG. 8 is a view showing a second example of a check valve used on the lower chamber side of the cylinder. The reference numerals correspond to those in FIG. 6, and 210 is an orifice. FIG. 8A is a cross-sectional view when the check valve is closed, and FIG.
Is a plan view of the valve body 207, and FIG. 8C is a cross-sectional view when the check valve is opened. In the example of FIG. 6, the orifice is provided on the valve body 204 side, but in the example of FIG. 8, the orifice is provided on the valve body 207 side.

When the pressure of the electrorheological fluid for pushing and opening the check valve is smaller than the pushing force of the spring 203, the fluid slightly flows through the orifice 210 as shown by an arrow 209 in FIG. Although not shown,
Similarly, in the second example of the check valve 15, the orifice is not provided on the valve body 154 side but on the piston body 1
It is provided on the 30 side.

Conventional documents relating to such a shock absorber include, for example, JP-A-4-282040, JP-A-6-101737, JP-A-6-174001, and JP-A-6-174001.
-241264, JP-A-6-241265 and the like.

[0031]

(Problems to be Solved by the Invention) As described above, in the shock absorber using the electrorheological fluid using the check valve with the orifice described above,
There is a problem that the damping force when an electric field is applied is reduced in a low piston speed region.

(Explanation of the Problem) One of the features of the shock absorber using the electrorheological fluid is that, as shown in FIG. 9A, when the applied electric field is increased, it is large even in a region where the piston speed is low. That is, a damping force can be obtained.
However, if the check valve is provided with an orifice, the characteristics will be as shown in FIG. 9 (B). When the applied electric field is increased, the damping force is reduced due to the backflow at the check valve in a region where the piston speed is low. Another problem was that it had to be done. SUMMARY OF THE INVENTION In order to solve such a problem, it is an object of the present invention to minimize a decrease in damping force in a region where a piston speed is low without losing an advantage provided by an orifice.

[0033]

In order to solve the above-mentioned problems, according to the present invention, there is provided a cylinder in which a piston is inserted, and a control portion which is externally inserted in the cylinder and which is separated from the cylinder by a holder made of insulating material. And a reservoir formed by utilizing a gap between the electrode cylinder and the housing, and an electrorheological fluid flowing through the cylinder, the control gap, and the reservoir in accordance with the movement of the piston. A fluid, a first check valve attached to the piston, and allowing a flow of an electrorheological fluid from a chamber below the piston to an upper chamber of the cylinder, and a chamber below the piston from the reservoir. A second check valve installed in the middle of the flow path to allow the flow of the electrorheological fluid from the reservoir to the lower chamber; and a second check valve between the cylinder and the electrode cylinder. A voltage is applied to the buffer, and the apparent viscosity of the electrorheological fluid flowing through the control gap is adjusted to vary the damping force. At least one of the first and second check valves has a structure. A valve body pressed in the closing direction by a spring, and an orifice forming plate made of an elastic material and fixed to a surface of the valve body opposite to a surface pressed by the spring.

In the above-mentioned shock absorber, the first and second
A valve body pressed in a closing direction by a spring, an elastic plate fixed to a surface of the valve body opposite to a surface pressed by the spring, and a check valve closing mechanism. In some cases, the elastic plate may be provided with a member having an orifice formed on a surface in contact with the elastic plate.

Further, in the above-mentioned shock absorber, the first and second
At least one structure of the check valve, a valve body pressed in the closing direction by a spring, and a surface of the valve body opposite to the surface pressed by the spring,
A structure having a laminated structure in which a leaf valve, an elastic plate, and a leaf valve with an orifice are laminated in this order may be adopted.

(Summary of Action to be Solved) In a shock absorber using an electrorheological fluid, the structure of a check valve used for the same is as follows. When the backflow pressure is applied, the gap between the orifices is filled with the elastic material, so that the following operation is performed.

When the piston moves in the direction to open the check valve, the valve body is pushed up by the pressure of the electrorheological fluid, the check valve opens, and the electrorheological fluid flows without resistance. Even when the piston speed is extremely low and the pressure of the electrorheological fluid is small and the valve body cannot be pushed open, the electrorheological fluid flows through the orifice without resistance. When the piston moves in the direction to close the check valve, the damping force does not decrease because the orifice is filled with the elastic material and the backflow of the electrorheological fluid is prevented. In some cases, "completely" cannot be interrupted, in which case a slightly backflowing electrorheological fluid may cause a slight reduction in damping force. And explain).

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings. The overall structure of the shock absorber is the same as that of FIG. 5, but the structure of the check valves 15, 20 used therein is new. (First Embodiment) FIG. 1 is a view showing a check valve 20 used in a first embodiment of a shock absorber according to the present invention, and FIG. 2 is a view showing a check valve 15.

First, description will be made from FIG. The symbol is FIG.
Reference numeral 211 denotes an orifice forming plate, 212 denotes an orifice, and 213 denotes an opening. 6 have the same structure as that of FIG. 6 except for the valve main body 204 and operate, so that the description thereof will be omitted. In this check valve 20, no orifice is provided in the valve body 204, and the surface of the valve body 204 opposite to the surface pressed by the spring 203 (ie,
The orifice forming plate 211 made of an elastic material is fixed to the surface facing the valve body 207).

FIG. 1B is a plan view of the orifice forming plate 211, and several orifices 212 are provided on the peripheral edge of the lower surface thereof. The orifice forming plate 21
Since the central portion of 1 does not perform any special operation, the opening 213 is formed in a size that does not hinder the operation of the orifice, in order to save material. FIG. 1A is a cross-sectional view illustrating a state in which the orifice forming plate 211 is in contact with the upper surface of the valve body 207 by the pressing force of the spring 203. This state is a state in which the check valve is closed. The pressure of the electrorheological fluid from the central hole 208 overcomes the pressing force of the spring 203 and the valve body 204
While not pushing up, flows through the orifice 212 as shown by arrow 209. Thereby, the advantage of providing the orifice is secured.

FIG. 1C is a sectional view showing a state in which the pressure of the electrorheological fluid from the center hole 208 overcomes the pressing force of the spring 203 and pushes up the valve body 204. This state is a state where the check valve is open. FIG. 1D shows that the electrorheological fluid has an arrow 209.
If you are trying to flow from above like (that is,
(In the case of backflow). Valve body 204
Is a sum of the pressing force of the spring 203 and the backflow pressure, so that the orifice forming plate 211, which is an elastic material, is strongly pressed against the upper surface of the valve body 207. Therefore, the portion of the orifice 212 is also crushed and no gap is generated, so that the electrorheological fluid does not flow backward. Therefore, the damping force does not decrease due to the backflow.

Next, the check valve 15 shown in FIG. 2 will be described. Reference numerals correspond to those in FIG. 7, reference numeral 157 denotes an orifice forming plate, 158 denotes an orifice, and 159 denotes a piston rod through hole. 7 have the same structure as that of FIG. 7 except for the valve main body 154 and operate, so that the description thereof will be omitted. In this check valve 15, the valve body 154 has no orifice, and the surface of the valve body 154 on the opposite side to the surface pressed by the spring 153 (that is, the piston body 130).
Orifice forming plate 1 made of elastic material
57 is fixed.

When the electrorheological fluid is going to flow upward from below the piston 13, it operates in the same manner as in FIG. That is, when the pressure is smaller than the pressing force of the spring 153, the gas flows through the orifice 158 without resistance. When the pressure is larger, the orifice forming plate 157 and the valve body 154 are pushed up and flow without resistance. When the flow of the electrorheological fluid is reversed (the notch 152 of the valve cover 152)
-1 to flow downward through the communication passage 14), the spring 153 is provided in the valve body 154.
Is applied, and the orifice forming plate 157 which is an elastic material is attached to the piston body 13.
It is strongly pressed against the upper surface of 0. Therefore, the portion of the orifice 158 is also crushed and no gap is formed, so that the electrorheological fluid does not flow backward. Therefore, the damping force does not decrease due to the backflow.

Next, the check valve 15,
The operation of the shock absorber when 20 is used is shown in FIGS.
This will be described with reference to FIG. (1) Operation when the piston 13 moves to the extension side In this case, the pressure of the electrorheological fluid which pushes the check valve 20 to open it is applied. If the piston speed is very low, the pressure will
Although the check valve 20 cannot be pushed open because the pressure is smaller than the pressing force of FIG.
An electrorheological fluid can pass through the check valve 20 as indicated by an arrow 209 in FIG.

On the other hand, since the check valve 15 is subjected to the backflow pressure of the electrorheological fluid, the orifice forming plate 15
7 is strongly pressed against the upper surface of the piston body 130,
Orifice 158 is crushed. Therefore, the electrorheological fluid does not flow back through the orifice 158.
The piston 13 is provided with an orifice 21 of the check valve 20.
2 can be raised by the volume of the electrorheological fluid that has passed, and the electrorheological fluid can be sent to the control gap 12. When the supplied amount flows in the control gap 12, a damping force is generated. Since the back flow of the electrorheological fluid does not occur at the check valve 15, it is possible to generate a large damping force as compared with the conventional example in which the back flow has occurred.

(2) Operation when the piston 13 moves to the contraction side In this case, the pressure of the electrorheological fluid to push and open the check valve 15 is applied to the check valve 15. If the piston speed is very low, the pressure will
Although the pressure is smaller than the pressing force, the check valve 15 cannot be pushed open, but the electrorheological fluid can pass through the check valve 15 through the orifice 158.

On the other hand, since the check valve 20 is subjected to the backflow pressure of the electrorheological fluid, as shown in FIG.
The orifice forming plate 211 is strongly pressed against the upper surface of the valve body 207, and the orifice 212 is crushed. Therefore, the electrorheological fluid does not flow back through the orifice 212. The piston 13 can descend by the volume of the electrorheological fluid that has passed through the orifice 158 of the check valve 15, and can send the electrorheological fluid to the control gap 12. When the supplied amount flows in the control gap 12, a damping force is generated. Since the back flow of the electrorheological fluid does not occur in the check valve 20, it is possible to generate a large damping force as compared with the conventional example in which the back flow has occurred.

When the speed of the piston 13 increases, the pressure of the electrorheological fluid acts in the direction of opening the valve. In a check valve, the pressure becomes larger than the pressing force of the spring, and the valve opens. Can be passed without resistance. On the other hand, in the check valve where the backflow pressure acts,
The orifice is not crushed and backflow does not occur.

As described above, according to the present invention, since the piston speed is low, even when the pressure of the electrorheological fluid for pushing and opening the check valve is smaller than the spring pressing force in the direction to close the check valve, An electric field can be generated by preventing backflow at the check valve where the backflow pressure of the electrorheological fluid is applied, while securing the advantage of providing an orifice that allows the electrorheological fluid to flow without resistance. It is possible to prevent a decrease in damping force when applied. FIG. 9C is a diagram illustrating the damping force characteristic of the present invention. The decrease in the damping force in the region where the piston speed is low is almost eliminated, and is greatly improved as compared with the conventional example having an orifice in FIG. 9B.

(Second Embodiment) The check valve used in the shock absorber of the first embodiment has an orifice provided on the valve body side which is pressed by a spring. , Provided on the side facing the valve body. Next, a specific configuration of such a check valve will be described for the check valve 20 (in addition,
The configuration of the check valve 15 in this embodiment can be easily analogized in accordance with this, and thus the description is omitted).

FIG. 3 is a view showing a second example of the check valve 20. Reference numerals correspond to those in FIG. 8, reference numeral 214 denotes an elastic plate, and reference numeral 215 denotes an opening. The orifice 210 is provided on the upper surface of the valve body 207. The difference from the conventional check valve 20 of FIG.
4 is that an elastic plate 214 as shown in FIG. The reason why the center is the opening 215 is as follows.
This is for material saving.

FIG. 3A is a sectional view when the check valve is closed. The pressure of the electrorheological fluid acting upward from below the central hole 208 is applied to the spring 2.
When the pressing force is smaller than the pressing force of 03, the electrorheological fluid flows through the orifice 210 as indicated by an arrow 209 without resistance. FIG. 3C is a cross-sectional view when the check valve is open. When the piston speed is high and the pressure of the electrorheological fluid is higher than the pressing force of the spring 203, the valve body 204 and the elastic plate 214 are pushed up,
Electro-rheological fluid flows without resistance.

FIG. 3D is a cross-sectional view when the piston moves in the direction in which the check valve 20 is subjected to the backflow pressure (that is, when the piston moves to the contraction side). Spring 203
Due to the pressing force and the backflow pressure, a part of the elastic plate 214 is pushed into the orifice 210, and the gap between the orifices 210 is filled. Thereby, the orifice 210
Backflow through is prevented.

(Third Embodiment) The check valve used in the shock absorber according to the third embodiment has a structure in which a leaf valve and a leaf valve with an orifice are used together.
A specific configuration of such a check valve will be described with respect to the check valve 20 (the configuration of the check valve 15 in this embodiment can be easily analogized in accordance with this, and a description thereof will be omitted).

FIG. 4 is a view showing a third example of the check valve 20. The reference numerals correspond to those in FIG. 6, 217 is a leaf valve, 218 is an elastic plate, 219 is a leaf valve with an orifice, 220 is an orifice, 217-1 and 218
-1,219-1 is an opening. 6 is different from the surface of the valve body 204 opposite to the surface pressed by the spring 203 (that is, the valve body 207).
The leaf valve 217 and the elastic plate 2
18 and the leaf valve with orifice 219 are stacked in this order.

FIG. 4E shows a leaf valve 2 with an orifice.
19, FIG. 4 (F) is a plan view of the elastic plate 218, and FIG. 4 (G) is a plan view of the leaf valve 217. The leaf valve 217 and the leaf valve with orifice 219 are made of a flexible thin plate. Leaf valve with orifice 2
Several orifices 220 are provided on the periphery of the 19. When these are stacked as described above, the ceiling of the orifice 220 is formed by the elastic plate 218.

FIG. 4A is a sectional view when the check valve 20 is closed by the pressing force of the spring 203. When the piston 13 is moved to the extension side at a very low speed, the electrorheological fluid flows through the orifice 220 as indicated by an arrow 209. When the piston speed is slightly higher, the pressure of the electrorheological fluid is slightly higher.
As shown in (B), the elastic plate 2 at the orifice 220
18, the leaf valve 217 is slightly pushed up, and FIG.
More electrorheological fluid flows than in case (A).

When the piston speed is further increased, the pressure of the electrorheological fluid becomes larger than the pressing force of the spring 203.
The valve body 204 is pushed up as shown in FIG. FIG. 4D shows a case where the flow of the electrorheological fluid is in a reverse flow direction with respect to the check valve 20. Since the pressing force of the spring 203 and the backflow pressure of the electrorheological fluid are applied to the upper surface of the valve body 204, the elastic plate 218 is pushed into the orifice 220 of the leaf valve with orifice 219, and the orifice Close the gap. This prevents backflow. At this time, if the backflow is prevented, there may be a little gap without completely closing the gap between the orifices.

In each of the above-described embodiments, both of the two check valves 15 and 20 of the shock absorber have a structure in which the orifice is filled with the elastic material when the electrorheological fluid flows backward. Depending on the force characteristics, only one may be of the structure of the present invention and the other may be of a conventional structure. For example, when the piston moves to the extension side, it is not good that backflow occurs, but when it moves to the contraction side, it is acceptable to use it for applications such as
Only the check valve 15 has the structure of the present invention. On the other hand, when it is used for an application in which a reverse flow does not need to occur when moving to the contraction side, but may occur when moving to the extension side, only the check valve 20 is used in the structure of the present invention. What should be done.

[0060]

As described above, according to the present invention, the structure of the check valve used in the electro-rheological fluid-based shock absorber is such that when the check valve is simply closed, the gap between the orifices is open. When the backflow pressure of the electrorheological fluid is applied, the gap between the orifices is filled with the elastic material, so that the following effects are obtained.

When the piston moves in the direction to open the check valve, the electrorheological fluid passes through the orifice even if the piston speed is extremely low and the pressure of the electrorheological fluid is too small to push and open the valve body. When the piston moves in the direction to close the check valve, the orifice is filled with the elastic material and the backflow of the electrorheological fluid is prevented when the piston moves in the direction to close the check valve. Even in the case where it cannot be completely prevented, the reduction in the damping force can be made small by making the backflow small.)

[Brief description of the drawings]

FIG. 1 is a view showing a first example of a check valve used on a cylinder lower chamber side of a shock absorber according to the present invention.

FIG. 2 is a diagram showing a first example of a check valve used on the piston side of the shock absorber according to the present invention.

FIG. 3 is a diagram showing a second example of a check valve used on the cylinder lower chamber side of the shock absorber according to the present invention.

FIG. 4 is a diagram showing a third example of the check valve used on the cylinder lower chamber side of the shock absorber according to the present invention.

FIG. 5 is a diagram showing a conventional shock absorber;

FIG. 6 is a diagram showing a first example of a check valve used on the cylinder lower chamber side of a conventional shock absorber.

FIG. 7 is a diagram showing a first example of a check valve used on a piston side of a conventional shock absorber.

FIG. 8 is a diagram showing a second example of a check valve used on the cylinder lower chamber side of a conventional shock absorber.

FIG. 9 is a graph showing damping force characteristics of a conventional shock absorber and an inventive shock absorber using an electrorheological fluid.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Buffer, 2 ... Piston rod, 3 ... Seal material, 4A
... upper housing, 4B ... middle housing, 4C ... lower housing, 4C-1 ... mounting part, 5A ... upper holder part, 5B ... lower holder part, 6 ... electrode cylinder, 7 ... communication hole, 8 ... electrode terminal part, 9 ... Cylinder, 10 ... Electrode terminal part, 11 ... Cylinder upper chamber, 12 ... Control gap, 13 ... Piston, 14 ... Communication passage, 15 ... Check valve, 16 ...
Cylinder lower chamber, 17: reservoir, 18: sealing material, 19
... communication hole, 20 ... check valve, 21 ... communication passage, 13
0: piston body, 131: nut, 152: valve cover, 153: spring, 154: valve body, 15
Reference numeral 5: orifice, 156: collar, 157: orifice forming plate, 158: orifice, 159: piston rod through hole, 201: valve cover, 203: spring,
204: valve body, 206: orifice, 207: valve body, 208: central hole, 211: orifice forming plate, 212: orifice, 213: opening

Claims (3)

[Claims] 1. A cylinder having a piston inserted therein, an electrode cylinder externally inserted into the cylinder and supported by a holder made of insulating material with a control gap therebetween.
A reservoir formed using a gap between the electrode cylinder and the housing, an electrorheological fluid flowing through the cylinder, the control gap, and the reservoir according to the movement of the piston; A first check valve that allows the flow of an electrorheological fluid from a chamber below the piston to an upper chamber of the cylinder, and a first check valve that is installed in the middle of a flow path from the reservoir to a chamber below the piston; A second check valve that permits the flow of an electrorheological fluid from the reservoir to the lower chamber, and a voltage that is applied between the cylinder and the electrode cylinder to flow through the control gap. In a shock absorber that adjusts an apparent viscosity of a viscous fluid to vary a damping force, at least one structure of the first and second check valves is pressed in a closing direction by a spring. And the valve body, the surface to be pressed against the spring of the valve body is fixed to the opposite surface,
A shock absorber having a structure comprising an orifice forming plate made of an elastic material. 2. A structure in which at least one of the first and second check valves is mounted on a valve body pressed in a closing direction by a spring and on a surface of the valve body opposite to a surface pressed by the spring. 2. The shock absorber according to claim 1, wherein the shock absorber comprises a fixed elastic plate and a member having an orifice formed on a surface that comes into contact with the elastic plate when the check valve is closed. 3. A structure in which at least one of the first and second check valves is attached to a valve body pressed in a closing direction by a spring and a surface of the valve body opposite to a surface pressed by the spring. 2. A shock absorber according to claim 1, wherein the shock absorber has a structure in which a laminated body is laminated in the order of a leaf valve, an elastic plate, and a leaf valve with an orifice.