JPH1130264A - Variable damping characteristic type shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and to reduce weight so as to improve car-mountability and to reduce energy consumption in a damping characteristic changing type shock absorber of such structure that damping characteristic changing mechanism driven by an actuator so as to change a damping characteristic is provide outside of a cylinder. SOLUTION: A pilot valve 60 controls hydraulic pressure of a pilot pressure chamber 50 forming hydraulic pressure of a back pressure chamber 53 for controlling deflection of a variable valve 30 provided outside of a cylinder 1 so as to change the ail flow rate from an upper chamber of a cylinder 1 toward reservoir 4a via an expanding side pressure chamber 3a at the time of an expansion stroke. In this case, a laminated piezoelectric element 40 is used as an actuator for driving a spool 39 for switching the opened/closed state of the pilot valve 38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber whose attenuation characteristics can be changed between high attenuation characteristics and low attenuation characteristics.

[0002]

2. Description of the Related Art Various types of variable damping characteristics type shock absorbers have heretofore been proposed. Among them, a mechanism in which a mechanism for changing the damping characteristics is provided outside a cylinder is, for example, a special type. The thing described in Unexamined-Japanese-Patent No. 5-118374 is known. In this conventional device, a damping characteristic changing mechanism (pressure regulating valve assembly) is provided in the middle of the fluid flow path of the shock absorber.
Is provided, the damping characteristic changing mechanism includes a deflectable disk that controls the flow of the fluid flow path, a pilot pressure chamber in which a fluid pressure acts to resist bending of the disk,
A solenoid assembly for controlling the fluid pressure in the pilot pressure chamber.

[0003]

However, the above-mentioned prior art has a structure in which the fluid pressure in the pilot pressure chamber is controlled by a solenoid assembly. In this case, it is necessary to increase the fluid pressure in the pilot pressure chamber, and in such a case, it is necessary to generate the driving force of the solenoid in a direction against the high pressure generated in the shock absorber. Therefore, in order to generate a high damping force in the shock absorber, it is necessary to increase the driving force of the solenoid,
In this case, it is necessary to increase the size of the members forming the coil and the magnetic path of the solenoid, which leads to an increase in the size and weight of the device, resulting in a reduction in vehicle mountability, and an increase in the energy consumption of the solenoid. There was a problem of inviting. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and is directed to a damping characteristic changing type shock absorber having a structure provided with a damping characteristic changing mechanism that changes the damping characteristic by driving an actuator outside the cylinder. Another object of the present invention is to reduce the size and weight of the vehicle, thereby improving the on-board performance and reducing energy consumption.

[0004]

Means for Solving the Problems In order to achieve the above object, according to the first aspect of the present invention, a cylinder is defined by a piston into an upper chamber and a lower chamber, and a reservoir is provided outside the cylinder. And an expansion-side fluid flow path connecting the upper chamber and the reservoir and a pressure-side fluid flow path connecting the lower chamber and the reservoir are formed. Each of the fluid flow paths is a variable valve that can open and close the fluid flow path. A variable damping characteristic changing mechanism and a compression damping characteristic changing mechanism for controlling the flow of fluid to change the damping characteristic are provided. Each of the damping characteristic changing mechanisms is formed on the back surface of the variable valve and has an internal pressure. Is a back pressure chamber that serves as a resistance of the opening of the variable valve, and a pilot pressure chamber that is connected to the back pressure chamber and that can adjust the internal pressure according to the opening and closing of a pilot valve provided in a passage that bypasses the variable valve. And have And the pilot valve includes a valve seat,
A pressure member configured to be able to directly or indirectly press and separate from the valve seat, and an actuator that applies a driving force in a direction to press the pressure member against the valve seat; When the pilot member cannot be opened by directly or indirectly pressing the pressurizing member against the valve seat based on the above, when a pressure difference occurs such that a flow toward the reservoir occurs in the fluid flow path, As the pressure in the pilot pressure chamber rises, the pressure in the back pressure chamber also rises, and the valve opening resistance of the variable valve increases, resulting in a high damping characteristic. On the other hand, when the pilot valve can be opened, the fluid flow path to the reservoir When there is a pressure difference that causes a head-to-head flow, the pilot pressure chamber does not rise due to the opening of the pilot valve, so the back pressure chamber does not rise and the pressure is variable. In the variable damping characteristic type shock absorber configured so that the valve opening resistance of the lube is reduced to have low damping characteristics, as the actuator, a laminated piezoelectric element that elongates and deforms in a direction of pressing a pressing member against a valve seat when energized is used. Is used. According to a second aspect of the present invention, in the variable damping characteristic type shock absorber according to the first aspect, the pilot valve has a plate-shaped valve body interposed between a valve seat and a pressurizing member. I do. According to the third aspect of the present invention, in the variable damping characteristic type shock absorber according to the first or second aspect, an outer tube is provided on an outer periphery of the cylinder, and an outer cylinder is provided on an outer periphery of the outer tube. The reservoir is formed between a cylinder and an outer tube, and a space between the cylinder and the outer tube is defined by an defining member as an upper extension-side pressure chamber and a lower compression-side pressure chamber, In the cylinder,
A communication port for communicating the upper chamber and the extension side pressure chamber and a communication port for communicating the lower chamber and the pressure side pressure chamber are formed, and each pressure chamber constitutes a part of the fluid flow path, and the piston has A passage connecting the upper chamber and the lower chamber is formed, and expansion side damping force generating means for restricting the flow of fluid from the upper chamber to the lower chamber of the passage to generate a predetermined high damping force is provided. The base provided at the bottom of the cylinder is provided with a passage for communicating the lower chamber with the reservoir, and restricts the flow of fluid from the lower chamber of the passage toward the reservoir to a predetermined height. A pressure-side damping force generating means for generating a damping force is provided. According to a fourth aspect of the present invention, in the variable damping characteristic type shock absorber according to the third aspect, the damping characteristic changing mechanism is fixed to an outer surface of the outer cylinder and accommodates a component member, and is pressed by the piezoelectric element. A first valve body that is supported by the housing while being restricted from moving in the first direction;
A check valve formed in the valve body and provided to open only from the reservoir toward the one pressure chamber with respect to a passage communicating with the reservoir and the one pressure chamber; and a reservoir formed in the first valve body. A variable valve that is provided to open only from the one pressure chamber to the reservoir with respect to a passage communicating with the one pressure chamber, and a back pressure chamber is formed on the back surface of the variable valve to open the valve in the valve opening direction. A ring member movably provided, a return spring for urging the ring member in a valve closing direction, and the valve seat are formed in series with the first valve body, and the valve seat is formed to constitute the pilot valve. A second valve body supporting a valve element to be closed, a spool having a bottomed cylindrical shape provided at a position facing the valve seat as the pressurizing member, and one end supported by the bottom of the spool. And the other end of which is supported on the housing and a, and the piezoelectric element housed in the spool.

[0005]

According to the present invention, when the extension side or the compression side is controlled to have high attenuation characteristics, the piezoelectric element of the extension side attenuation characteristic changing mechanism or the compression side attenuation characteristic changing mechanism is energized. This allows
The piezoelectric element expands and deforms to press the pressure member against the valve seat, thereby closing the pilot valve. Therefore, during the extension stroke of the piston, the pressure in the back pressure chamber of the variable valve that opens and closes the extension-side fluid flow path increases, and the valve opening resistance of the variable valve of the extension-side damping characteristic changing mechanism increases. When the piston is on the compression side stroke, the pressure in the back pressure chamber of the variable valve that opens and closes the compression side fluid flow path is increased, the valve opening resistance of the variable valve of the compression side attenuation characteristic changing mechanism is increased, and the compression side has high attenuation characteristics. At the time of this high damping characteristic control, the pressure of the pilot pressure chamber acts on the pilot valve in the valve opening direction, but the piezoelectric element is maintained in the expanded and deformed state even with a small electric power, that is, the state in which the pressing member is pressed against the valve seat. You. According to the second aspect of the invention, when the piezoelectric element is driven, the pressurizing member presses the plate-shaped valve element, and the valve element contacts the valve seat to close the pilot valve. Therefore, the pilot pressure chamber has a high sealing property and can be easily controlled to have a high damping characteristic. According to the third aspect of the invention, during the pressure stroke, the fluid in the lower chamber passes through the reservoir through one or both of the flow path passing through the pressure-side damping force generating means of the base and the pressure-side fluid flow path passing through the pressure-side damping characteristic changing mechanism. Flows to During high damping characteristic control, the number of flow paths in the pressure side fluid flow path is small, and a damping force is mainly generated in the pressure side damping force generating means of the base, resulting in high damping characteristics. Also,
At the time of the low damping characteristic control, the flow rate in the pressure side fluid flow path increases, and the low damping characteristic is obtained. On the other hand, during the extension stroke, the fluid in the upper chamber reaches the reservoir through the flow path reaching the lower chamber through the extension-side damping force generating means of the piston and the extension-side fluid flow path passing through the extension-side damping characteristic changing mechanism. It is movable in two flow paths including a flow path. When the high damping characteristic control is performed, the number of flow paths in the expansion-side fluid flow path is small, and a damping force is mainly generated in the expansion-side damping force generating means of the piston, thereby achieving high damping characteristics. Further, at the time of the low damping characteristic control, the flow rate in the extension-side fluid flow path increases, and the low damping characteristic is obtained. According to the fourth aspect of the present invention, when the piezoelectric element is driven, the spool as the pressure member is pressed in the direction of the valve seat, and the valve body is strongly contacted with the valve seat of the first valve body. Sealed against reservoir. At this time, the driving force of the piezoelectric element input to the first valve body is finally supported by the housing via the second valve body provided in series with the first valve body. On the other hand, when the piezoelectric element is not driven, when the valve element of the pilot valve is opened,
The spool is moved by being pushed by the valve body, and this movement is directly or indirectly regulated by the housing. The movement amount of the spool when the valve is opened is determined by the deformation amount when the piezoelectric element is driven. If it is smaller, the force acting on the valve element is not input to the piezoelectric element. Further, when the variable valve is opened, the ring member forming the back pressure chamber moves in the bending direction along with the bending of the variable valve, but when the hydraulic pressure difference before and after the variable valve disappears, the variable valve is closed. At this time, the ring member returns to the original position while maintaining contact with the variable valve by the biasing force of the return spring.

[0006]

Embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a sectional view showing a variable damping characteristic type buffer SA according to the embodiment of the present invention.
And a lower chamber 1b, a piston 2 is slidably provided. An outer tube 3 and an outer tube 4 are provided double on the outer periphery of the cylinder 1, and a reservoir 4 a is formed between the outer tube 4 and the outer tube 3. At the lower end of the cylinder 1, a base 5 is provided.
Thereby, the lower chamber 1b and the reservoir 4a are defined. The base 5 is formed with a communication hole connecting the reservoir 4a and the lower chamber 1b. The communication hole restricts the flow from the lower chamber 1b to the reservoir 4a to generate a damping force. Generating means 6) (see FIG. 7). The interior of the buffer SA is filled with oil, and the reservoir 4a is filled with gas at a predetermined pressure.

The piston 2 has a communication hole for communicating the upper chamber 1a and the lower chamber 1b, and this communication hole restricts the flow from the upper chamber 1a to the lower chamber 1b to reduce the damping force. It is opened and closed by the generated expansion-side hard valve (expansion-side damping force generating means) 7 (see FIG. 7). A piston rod 8 is connected to the piston 2, and the piston rod 8 is guided to slide by a guide member 9. Note that the guide member 9 defines an upper chamber 1a and a reservoir 4a.

A partition 10 is provided at an intermediate portion of the outer tube 3, and an upper extension side pressure chamber 3a and a lower side pressure chamber 3b are formed between the outer tube 3 and the cylinder 1. The extension side pressure chamber 3a is
Is communicated with the upper chamber 1a by a communication hole 1c opened at the upper part of the cylinder 1, while the pressure side pressure chamber 3b is communicated with the lower chamber 1b by a communication hole 1d (see FIG. 7) opened at the lower part of the cylinder 1. . An extension side damping characteristic changing mechanism (hereinafter referred to as “extension side mechanism”) 21 is attached to the extension side pressure chamber 3a, and a compression side damping characteristic changing mechanism (hereinafter referred to as “compression side mechanism”) 22 is attached to the compression side pressure chamber 3b. Installed.

The structure of the two mechanisms 21 and 22 will be described below. Both of them have the same structure. FIG. 1 is a cross-sectional view of these mechanisms 21 and 22. For convenience of explanation, the extension mechanism 21 will be described. . Openings 3c, 4c are formed concentrically on the side surfaces of the outer tube 4 and the outer tube 3, and a cylindrical housing tube 23 is formed in the opening 4c of the outer tube 4.
Are fixed by welding, and a housing 24 is fitted to the inner periphery of the open end of the housing tube 23. Therefore, the space formed by the housing tube 23 and the housing 24 communicates with the reservoir 4a and faces the extension-side pressure chamber 3a via the opening 3c. In addition, the movement of the housing 24 in the removal direction is as follows.
It is regulated by a cover 25 screwed to the open end of the housing tube 23. An oil seal 20a is provided between the housing tube 23 and the housing 24.

At the center of the housing 24, there is provided a housing portion 24a having a convex shape outward, and an inner ring portion 24b having a convex shape inward from the housing portion 24a. A through hole 24c is formed in the inner ring portion 24b, and the inner circumference of the large diameter portion 26a of the stator 26 is fitted to the inner circumference of the inner ring portion 24b. The stator 26 has a small diameter portion 26b extending in the axial direction from the center of the large diameter portion 26a.
, A central hole 26c is formed in the axial direction, and a small hole 26d is formed in a middle portion thereof so as to penetrate in the radial direction. The large diameter portion 26a has the central hole 2
A valve seat 26e is formed in an annular shape around the open end of 6c, and a support surface 26f is formed on the outer periphery thereof at the same height as the valve seat 26e. Incidentally, the large diameter portion 26a corresponds to the second valve body in the claims.

A return spring 27, a collar 28, an assist ring 29, a variable valve 30, a valve body (first valve body) 31, a check valve 32, and a collar 33 are sequentially mounted on the outer periphery of the small diameter portion 26b of the stator 27. Finally, the nut 34 is screwed and fastened.
The guide tube 3 is provided in the valve body 31.
5 is press-fitted, and the base end of the guide tube 35 is fitted to a joint 36 fixed to the opening 3 c of the outer tube 3. In addition, between the inner periphery of the joint 36 and the outer periphery of the guide tube 34,
An oil seal 20b is provided. Further, the valve body 31 is provided with the stepped portion 2 of the housing tube 23.
The axial movement toward the outer cylinder 4 by being engaged with the outer cylinder 4 is restricted. The nut 34 has a center height 26c.
A filter 37 for preventing foreign matter (contamination or the like) having a predetermined diameter or more from entering therein is attached. FIG. 4 is a perspective view of the return spring 27, and leg portions 27a for generating elastic force are provided at four locations as shown in the figure.

Returning to FIG. 1, the valve seat 26 of the stator 26 will be described.
e, and a plate-like pilot valve body 38
Is seated, and the valve seat 2 is mounted on the housing portion 24a.
A bottomed cylindrical spool (pressing member) 39 having a diameter opposite to 6e is slidably supported. The piezoelectric element 4 is located between the spool 39 and the housing 24.
0 is stored. The piezoelectric element 40 includes a harness 4
When a voltage is applied from No. 1, the axial dimension is extended. The spool 39 and the housing 24
Is sealed by an oil seal 20c, and the harness 41 is sealed by a grommet 42. FIG. 5 is a perspective view of the pilot valve body 38, which has a substantially C-shaped groove 38a as shown in FIG.
8b is configured to bend with respect to the annular support portion 38c.

A pilot bush 43 having a bottomed cylindrical shape is fitted into the central hole 26 c of the stator 26, and a pilot pressure chamber 50 is formed between the pilot bush 43 and the pilot valve body 38. An orifice hole 43a is formed in the bottom of the pilot bush 43.

With the structure described above, the outer chamber 51 communicated with the reservoir 4a is provided on the inner periphery of the housing tube 23.
Are formed on the inner periphery of the guide tube 35, and an inner chamber 52 communicated with the extension-side pressure chamber 3a is formed, and a back pressure chamber 53 for applying a back pressure to the variable valve 30 is formed. The back pressure chamber 53 has a small hole 26d formed in the stator 26.
In addition, it is communicated with the pilot pressure chamber 50 via a communication portion 28 a formed in the collar 28. The back pressure chamber 53 is formed in the outer chamber 51 by the oil seal 20 d and the close contact between the assist ring 29 and the variable valve 30.
(Reservoir 4a) is maintained in a sealing property.

In the extension mechanism 21 described above, as shown by a dotted arrow in FIG. 2, a constant orifice is formed from the outer chamber 51 through the hole 31a of the valve body 31 as a flow path from the reservoir 4a to the extension pressure chamber 3a. 31b or the check valve 32 is opened to open the inner chamber 52
From the pressure chamber 3a to the pressure chamber 3a. The flow path R1 has a small resistance and a large flow rate can be obtained. On the other hand, as a flow path from the expansion side pressure chamber 3a to the reservoir 4a, the variable valve 30 is opened from the inner chamber 52 through the constant orifice 31b and the hole 31a of the valve body 31, as shown by a solid line in FIG. The pilot valve body 38 is opened via the flow path R2 from the outer chamber 51 to the reservoir 4a and the pilot hole 50 from the center hole 26c, and the inner ring part 2 is opened.
A passage R3 is formed through the outer chamber 51 through the through hole 224c to the reservoir 4a.

The flow path resistance in the flow path R2 and the flow path R3 from the extension side pressure chamber 3a to the reservoir 4a is configured to be changeable by the piezoelectric element 40. That is, when the piezoelectric element 40 is not driven, as shown in FIG. 6B, the spool 39 can move until it comes into contact with the housing 24. Therefore, when the oil pressure of the extension side pressure chamber 3a becomes higher than the oil pressure of the reservoir 4a,
As shown in the figure, the pilot valve body 38 can be opened. In this case, since the flow of the flow path R3 is formed in FIG. 2, the hydraulic pressure of the pilot pressure chamber 50 becomes low, Also, the hydraulic pressure of the back pressure chamber 53 becomes low, so that the variable valve 30 can be easily opened, and the flow of the flow path R2 is formed. Therefore, these flow paths R
2 and R3 have low flow resistance.

On the other hand, when the piezoelectric element 40 is driven, the dimension of the piezoelectric element 40 becomes longer in the direction of the arrow as shown in FIG. 6A, and the spool 39 is pressed strongly against the valve seat 26e via the pilot valve body 38. Can be Therefore, even if the expansion side pressure chamber 3a becomes higher in pressure than the reservoir 4a and the pilot pressure chamber 50 becomes high in pressure, the pilot valve body 38 cannot be opened. The pressure in the back pressure chamber 53 also becomes high, making it difficult for the variable valve 30 to close, and the flow resistance of the flow paths R2 and R3 is high, and almost no flow rate occurs. The above-described valve seat 26 of the stator 26 is used.
e, pilot valve element 38, spool 39, piezoelectric element 40
Thus, a pilot valve 60 for adjusting the internal pressure of the pilot pressure chamber 50 is formed. Also, this piezoelectric element 4
0, the driving force of the piezoelectric element 40 is outwardly supported by the cover 25 via the housing 24, and inwardly, the driving force of the housing tube 23 via the stator 26, the valve body 31 and the like. 23a.

By the way, when the variable valve 30 is opened and closed, the contact state between the variable valve 30 and the assist ring 29 is maintained by the urging force of the return spring 27, so that the sealing property of the back pressure chamber 53 is maintained.

Next, the flow of oil in the variable damping characteristic type buffer SA of the embodiment will be described with reference to the schematic diagram of FIG.
At the time of the pressure stroke, as a flow path through which the oil in the lower chamber 1b whose volume is reduced flows out, as shown by a solid line in the drawing, a flow path that opens the pressure side hard valve 6 and moves to the reservoir 4a, From the chamber 1b to the pressure side mechanism 2 via the pressure side pressure chamber 3b
There is a flow path that opens the second variable valve 30 and moves to the reservoir 4a. The piezoelectric element 4 of the pressure side mechanism 22
In a state where the variable valve 30 can be opened without driving the hydraulic valve 0, the oil mainly flows out through the flow path passing through the variable valve 30, whereby the oil pressure in the lower chamber 1b does not increase, and the low damping characteristic (soft) is obtained. Become. On the other hand, when the piezoelectric element 40 is driven, the variable valve 30 is kept in the closed state.
The oil flows out in the flow path that opens the pressure-side hard valve 6, and has high damping characteristics (hard).

During the pressure stroke, the oil in the reservoir 4a is supplied to the expansion mechanism 21 in the upper chamber 1a whose volume is expanded.
The check valve 32 is opened and supplied through the extension-side pressure chamber 3a.

During the extension process, the upper chamber 1 whose volume is reduced
As shown by the dotted line in the figure, the flow path from which the oil in a flows out includes a flow path that opens the expansion-side hard valve 7 and moves to the lower chamber 1b, and a flow path that extends from the upper chamber 1a to the expansion-side pressure chamber 3a. The variable valve 30 of the extension side mechanism 21 is opened and the reservoir 4a is opened.
And a flow path that moves to Then, in a state where the variable valve 30 can be opened without driving the piezoelectric element 40 of the extension side mechanism 21, the oil flows out mainly through the flow path passing through the variable valve 30, so that the oil pressure of the upper chamber 1 a is high. And low attenuation characteristics (soft). On the other hand, the piezoelectric element 40
Is driven, the variable valve 30 is kept in the closed state, so that the oil flows out of the flow path in which the expansion-side hard valve 7 is opened, resulting in high damping characteristics (hard).

During the extension stroke, the oil in the reservoir 4a is supplied to the pressure side mechanism 22 in the lower chamber 1b whose volume is increased.
The check valve 32 is opened, and supplied through the pressure side pressure chamber 3b.

FIG. 8 shows the above-described low damping characteristics and high damping characteristics. In the present embodiment, the duty control of the piezoelectric elements 40, 40 of the extension / compression mechanisms 21, 22 is performed. . The high attenuation characteristic when the duty ratio is set to 100% is indicated by Hard, and the low attenuation characteristic when the duty ratio is set to 0% is indicated by Soft. The characteristic between Hard and Soft is shown in FIG. By controlling the duty ratio to a predetermined ratio within a range of 100% to 0%, the characteristics can be arbitrarily changed. In the figure, numerals of 10%, 25%, and 50% are added, respectively. The curved line indicates the attenuation characteristic when the duty ratio is set to each%.

As described above, in the present embodiment, the spool 39, which is the driving portion of the pilot valve 60, is driven by the piezoelectric element 40. Therefore, compared with the conventional structure driven by a solenoid, both damping characteristics are obtained. Change mechanism 2
The effect of reducing the size, weight, and cost of the shock absorber can be obtained by making it possible to reduce the size of the shock absorbers 1 and 22, thereby improving the vehicle mountability. Further, since the stacked piezoelectric element 40 has higher responsiveness and higher output than the solenoid, it is possible to obtain an effect that the controllability is excellent and the energy consumption can be reduced. In addition, pilot valve 6
0 when the piezoelectric element 40 is driven,
When the pressure acts in the valve opening direction, the valve can be maintained in a closed state with a small amount of electric power, and it is possible to reliably maintain high damping characteristics, which also has excellent controllability. Is obtained.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the embodiments of the present invention, and even if there is a design change or the like without departing from the gist of the present invention. Included in the present invention. For example, in the embodiment, the outer tube 3 and the outer cylinder 4 are provided, and the extension / compression-side pressure chambers 3a and 3b and the reservoir 4a are formed. However, the reservoir may be spherical or cylindrical outside the cylinder. In this case, the upper and lower chambers 1a and 1b of the reservoir and the cylinder may be provided.
Can be formed by a tube independent of the cylinder and the reservoir.

[0026]

According to the present invention, since a laminated piezoelectric element is used as the actuator of the extension-side / compression-side damping characteristic changing mechanism, both damping characteristic changing mechanisms can be miniaturized. This has the effect of reducing the size, weight, and cost of
The effect that the in-vehicle property is improved is obtained. Furthermore, since the laminated piezoelectric element has higher responsiveness and higher output than the solenoid, it has excellent controllability and can reduce energy consumption. Therefore, when the pressure of the pilot pressure chamber acts in the valve opening direction when the piezoelectric element is driven in the pilot valve, the valve closing state can be maintained with small electric power, and the high damping characteristics can be reliably maintained. Thus, it can be said that this also has excellent controllability. According to the second aspect of the present invention, since a plate-shaped valve body is interposed between the valve seat of the pilot valve and the pressurizing member, when the pressurizing member is pressurized in the valve seat direction, the valve is closed. There is an effect that the valve body is brought into close contact with the entire circumference by the valve body, and a high sealing property is obtained. According to the third aspect of the present invention, both the extension side and the compression side fluid flow paths are constituted by the extension side and the compression side pressure chambers formed by providing an outer tube on the outer periphery of the cylinder, and the reservoir is provided on the outer periphery of the outer tube. Since the shock absorber is configured with the outer cylinder, the overall structure of the shock absorber can be made compact and excellent in vehicle mounting. According to the fourth aspect of the invention, the merchantability of the present invention can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a damping characteristic changing mechanism as a main part of an embodiment.

FIG. 2 is an explanatory diagram of a flow of a fluid in the damping characteristic changing unit.

FIG. 3 is a cross-sectional view of the damping characteristic variable shock absorber according to the embodiment.

FIG. 4 is a perspective view of a main part of the embodiment.

FIG. 5 is a perspective view of a main part of the embodiment.

FIG. 6 is an explanatory diagram of an operation of a main part of the embodiment.

FIG. 7 is a schematic diagram showing a flow of oil during a stroke according to the embodiment.

FIG. 8 is an attenuation characteristic diagram of the embodiment.

[Explanation of symbols]

 SA damping characteristic variable type shock absorber 1 cylinder 1a upper chamber 1b lower chamber 1c communication hole 1d communication hole 2 piston 3 outer tube 3a extension side pressure chamber 3b pressure side pressure chamber 3c opening 4 outer cylinder 4a reservoir 4c opening 5 base 6 pressure side Hard valve (compression-side damping force generating means) 7 Extension-side hard valve (compression-side damping force generation means) 8 Piston rod 9 Guide member 10 Partition wall 20a, 20b, 20c, 20d Oil seal 21 Extension-side damping characteristic changing mechanism 22 Compression-side damping characteristic Change mechanism 23 Housing tube 23a Step portion 24 Housing 24a Housing portion 24b Inner ring portion 24c Through hole 25 Cover 26 Stator 26a Large diameter portion (second valve body) 26b Small diameter portion 26c Central hole 26d Small hole 26e Valve seat 26f Support surface 27 Return spring 27a Leg 28 Collar 28a Communication part 29 Assist ring 30 Variable valve 31 Valve body (first valve body) 31a Hole 31b Constant orifice 32 Check valve 33 Collar 34 Nut 35 Guide tube 36 Joint 37 Filter 38 Pilot valve body (Valve body) 38a Groove 38b Drive Part 38c Support part 39 Spool (pressing member) 40 Piezoelectric element 41 Harness 42 Grommet 43 Pilot bush 43a Orifice hole 50 Pilot pressure chamber 51 Outer chamber 52 Inner chamber 53 Back pressure chamber 60 Pilot valve

Claims (4)

[Claims] 1. A cylinder is defined by a piston into an upper chamber and a lower chamber, and a reservoir is provided outside the cylinder, and an extension-side fluid flow path and a lower chamber connecting the upper chamber and the reservoir. A pressure-side fluid flow path connecting to the reservoir is formed, and each fluid flow path has a variable valve that can open and close the fluid flow path to control the flow of the fluid and change the damping characteristic of the expansion side. A mechanism and a compression-side damping characteristic changing mechanism are provided, each of the damping characteristic changing mechanisms is formed on the back surface of the variable valve, and the internal pressure is a back pressure chamber in which the resistance of the variable valve opens.
A pilot pressure chamber that can communicate with the back pressure chamber and that can adjust an internal pressure in accordance with opening and closing of a pilot valve provided in a passage that bypasses the variable valve, wherein the pilot valve has a valve seat; A pressure member configured to be able to directly or indirectly press and separate from the valve seat, and an actuator that applies a driving force in a direction in which the pressure member is pressed against the valve seat; When the pilot member cannot be opened by directly or indirectly pressing the pressurizing member against the valve seat based on the above, when a pressure difference occurs such that a flow toward the reservoir occurs in the fluid flow path,
As the pressure in the pilot pressure chamber increases, the pressure in the back pressure chamber also increases, increasing the valve opening resistance of the variable valve, resulting in high damping characteristics.
On the other hand, when the pilot valve can be opened, when a pressure difference occurs such that a flow toward the reservoir occurs in the fluid flow path, the pilot valve is opened and the pilot pressure chamber does not increase in pressure. In the damping characteristic variable type shock absorber configured so that the pressure in the back pressure chamber does not increase and the valve opening resistance of the variable valve is reduced and the damping characteristic is low, the pressurizing member is pressed against the valve seat as the actuator when energized. A variable damping characteristic type shock absorber characterized by using a laminated piezoelectric element that expands and deforms in a direction. 2. The damping characteristic variable damper according to claim 1, wherein the pilot valve has a plate-shaped valve element interposed between a valve seat and a pressure member. 3. An outer tube is provided on an outer periphery of the cylinder, and an outer tube is provided on an outer periphery of the outer tube, and the reservoir is formed between the outer tube and the outer tube. The space between the tube, the upper extension side pressure chamber and the lower pressure side pressure chamber is defined by the defining member, the cylinder, a communication port for communicating the upper chamber and the extension side pressure chamber, and A communication port for communicating the lower chamber with the pressure-side pressure chamber is formed, each pressure chamber forms a part of the fluid flow path, and a passage is formed in the piston to communicate the upper chamber with the lower chamber. In addition, an extension side damping force generating means for restricting the flow of the fluid from the upper chamber to the lower chamber of the passage to generate a predetermined high damping force is provided, and a base provided at the bottom of the cylinder is , Lower chamber and And a pressure side damping force generating means for generating a predetermined high damping force by restricting the flow of the fluid from the lower chamber of the passage toward the reservoir. The variable damping characteristic type shock absorber according to claim 1 or 2, wherein: 4. A damping characteristic changing mechanism, wherein the housing is fixed to an outer surface of the outer cylinder and accommodates a component, and a first valve supported by the housing is restricted from moving in a pressing direction by the piezoelectric element. A check valve provided in the first valve body and formed in the first valve body so as to open only from the reservoir toward the one pressure chamber with respect to a passage communicating with the reservoir and the one pressure chamber; and the first valve A variable valve formed in the body and provided so as to open only from one pressure chamber toward the reservoir with respect to a passage communicating with the reservoir and one pressure chamber, and a back pressure chamber is formed on the back of the variable valve. A ring member movably provided in a valve opening direction, a return spring for urging the ring member in a valve closing direction, and a valve seat arranged in series with the first valve body, and Is formed, a second valve body supporting a valve body constituting the pilot valve, a spool having a bottomed cylindrical shape provided at a position facing the valve seat as the pressurizing member, and one end of the spool having a bottom end. 4. The variable damping characteristic type shock absorber according to claim 3, further comprising: the piezoelectric element supported by the bottom and the other end supported by the housing and housed in the spool.