JPH0828620A - Hydraulic shock absorber - Google Patents

Abstract

(57) [Abstract] [Purpose] In a hydraulic shock absorber, the diameter of a disc valve and the passage area of an extension side and a contraction side communication passage communicating with the cylinder upper and lower chambers are increased. [Structure] A piston 15 in which a piston rod 16 is connected is fitted in a cylinder 13 in which an oil liquid is sealed. The extension side communication passage 22 and the contraction side passage 23 (oblong holes) are passed through the piston 15. At both ends of the piston 15, expansion-side communication passages 22 are connected to expansion-side communication passages 22 by connecting expansion-side and compression-side valve seat members 26, 27 each having a substantially bottomed cylindrical shape having a bottom having a diameter slightly smaller than the inner diameter of the cylinder 13.
The contraction side chamber 27a is communicated with the contraction side communication passage 23. At the bottom of the expansion side valve seat member 26, the expansion side passage 31 (long hole)
Further, a disk valve 33 is provided, and a compression side passage 35 (long hole) and a disk valve 37 are provided at the bottom of the compression side valve seat member. Since the diameters of the disc valves 33 and 34 and the passage areas of the passages can be increased, the inclination of damping force characteristics can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hydraulic shock absorber mounted on a suspension system of a vehicle such as an automobile.

[0002]

2. Description of the Related Art Generally, a hydraulic shock absorber mounted on a suspension system of an automobile will be described with reference to FIGS.

As shown in FIGS. 11 and 12, in a hydraulic shock absorber 1, a piston 3 is slidably fitted in a cylinder 2 in which an oil liquid is sealed. Is divided into two chambers, a cylinder upper chamber 2a and a cylinder lower chamber 2b. One end of a piston rod 4 is connected to the piston 3 by a nut 5, and the other end of the piston rod 4 is connected to a rod guide (not shown) and an oil seal (not shown) provided at the end of the cylinder 2. ) Has been extended to the outside. Further, the cylinder 2 is connected to a reservoir (not shown) that compensates for a volume change due to expansion and contraction of the piston rod 4 by compressing and expanding gas.

The piston 3 is provided with a plurality of expansion side communication passages 6 and a plurality of compression side communication passages 7 (four in the illustrated example) which communicate with the cylinder upper chamber 2a and the cylinder lower chamber 2b along the circumferential direction. It is set up. The extension side communication passage 6 is opened at the cylinder upper chamber 2a side at the outer peripheral portion of the end surface of the piston 3, and at the cylinder lower chamber 2b side is opened at the inner peripheral portion of the end surface of the piston 3. The compression-side communication passage 7 is opened on the cylinder upper chamber 2a side on the inner peripheral portion of the end surface of the piston 3, and on the cylinder lower chamber 3b side is opened on the outer peripheral portion of the end surface of the piston 3.

On the end surface of the piston 3 on the cylinder lower chamber 2b side, an annular valve seat 8 is provided so as to project from the inner and outer circumferences of the opening of the extension side communication passage 6, and the disc valve 9 is opposed to the valve seat 8.
Is provided. The end surface of the piston 3 on the cylinder upper chamber 2a side has an annular valve seat on the inner and outer circumferences of the opening of the compression side communication passage 7.
A disc valve 11 is provided so as to face the valve seat 10.

The operation of the hydraulic shock absorber 1 thus constructed will be described below.

During the expansion stroke of the piston rod 4, the compression side communication passage 7 is closed by the disc valve 11, the oil liquid on the cylinder upper chamber 2a side passes through the extension side communication passage 6 and opens the disc valve 9 to open the cylinder lower chamber 2b. And the damping force is generated according to the opening of the disc valve 9. Also, during the compression stroke, the expansion side communication passage 6 is closed by the disc valve 9, and the oil liquid on the cylinder lower chamber 2b side flows through the compression side communication passage 7 and opens the disc valve 11 to flow to the cylinder upper chamber 2a side. A damping force is generated according to the opening degree of the valve 11. At this time, the disc valves 9 and 11 open at an opening degree corresponding to the pressure of the oil liquid, so that a damping force having a valve characteristic in which the damping force linearly increases in proportion to an increase in the piston speed is generated. .

The damping area characteristics of the expansion side and the compression side are respectively determined by the passage area of the extension side communication passage 6 and the spring characteristic of the disc valve 9, and the passage area of the contraction side communication passage 7 and the spring characteristic of the disc valve 11. Can be set.

[0009]

However, the conventional hydraulic shock absorbers shown in FIGS. 11 and 12 have the following problems. That is, the extension side communication passage 6 and the compression side communication passage 7 are opened at the inner peripheral portion and the outer peripheral portion of the end surface of the piston 3, and are opposed to the inner peripheral side opening portions so as to face the disc valves 9, 11.
The outer diameters of the disc valves 9 and 11 are limited by the openings on the outer peripheral side of the expansion-side communication passage 6 and the compression-side communication passage 7, and the outer diameters of the disc valves 9 and 11 cannot be increased. . For this reason, the pressure receiving areas of the disc valves 9 and 11 cannot be made sufficiently large, so that it is difficult to set the inclination of the valve characteristic small, and the degree of freedom in setting the damping force characteristic decreases.

Further, generally, the piston 3 is molded by sintering, but since the expansion side communication passage 6 and the compression side communication passage 7 are provided so as to be inclined with respect to the axial direction of the piston 3, the piston 3 is formed. After molding, it is necessary to drill the expansion-side communication passage 6 and the contraction-side communication passage 7, and there is a problem in that the machining takes time. In particular, when setting a low damping force, it is necessary to provide a large number of extension side communication passages 6 and contraction side communication passages 7 in order to increase the passage area, which is a problem.

In Japanese Utility Model Laid-Open No. 59-142538, a first piston having an extension side communication passage and a compression side communication passage is slidably fitted in a cylinder, and one end of the first piston is attached. A second piston having a large-diameter disk valve facing the contraction-side passage, and a small-diameter oil liquid passage communicating with the extension-side communication passage at the other end at the other end. And a large-diameter disk valve is provided at the end of the second piston so as to face the oil passage, and a hydraulic shock absorber having large-diameter expansion-side and contraction-side disk valves is disclosed. .

However, even in the hydraulic shock absorber disclosed in the above publication, the expansion side passage and the contraction side passage need to be drilled, and therefore, there are the same problems as those in FIGS. 11 and 12.

The present invention has been made in view of the above points, and is a hydraulic shock absorber in which the disc valve has a large diameter and the passage areas of the extension side and the contraction side communication passages can be made sufficiently large. The purpose is to provide.

[0014]

In order to solve the above-mentioned problems, a hydraulic shock absorber according to the present invention comprises a cylinder in which an oil liquid is sealed, and a slidable fit in the cylinder. A cylindrical piston defined in two chambers, a piston rod having one end penetrating and fixed to the piston and the other end extending to the outside of the cylinder, and a position facing each other with the piston rod of the piston interposed therebetween. A pair of extension side communication passages formed along the axial direction of the piston, and a pair of extension side communication passages of the piston, and the piston rod is sandwiched between the pair of extension side communication passages. A pair of contraction-side communication passages and a tubular shape, and one end of the cylindrical portion abuts one end surface of the piston so as to enclose the piston rod and the pair of extension-side communication passages and not enclose the pair of compression-side communication passages. Abut, the other end of the tube An extension-side valve seat member that serves as a valve seat, an extension-side disk valve that is provided on the other end side of the extension-side valve seat member and closes the tubular portion, and is tubular and has one end of the tubular portion. Is a contraction-side valve seat member in which the piston rod and the pair of compression-side communication passages are surrounded and contact the other end surface of the piston so as not to surround the pair of extension-side communication passages, and the other end of the tubular portion serves as a valve seat. And a disc valve provided on the other end side of the contraction-side valve seat member so as to close the cylindrical portion.

[0015]

With the above construction, according to the hydraulic shock absorber of the present invention, during the expansion stroke of the piston rod, the oil liquid in the cylinder flows through the expansion side communication passage due to the sliding of the piston and the expansion side disc. The damping force is generated by the valve, and during the compression stroke, the fluid in the cylinder flows through the compression side communication passage due to the sliding of the piston, and the damping force is generated by the compression side disc valve. At this time, since the expansion-side and contraction-side valve seat members are provided, the diameters of the expansion-side and contraction-side disc valves can be increased, and the expansion-side and contraction-side communication passages and the expansion-side and contraction-side valves can be increased. Since the two chambers in the cylinder are communicated with each other through the tubular portion of the seat member, it is possible to increase the passage area of the oil liquid during the extension stroke and the contraction stroke. Further, since the expansion side communication passage and the compression side communication passage of the piston are provided along the axial direction, they can be easily molded.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2,
The hydraulic shock absorber 12 has a double cylinder structure in which an outer cylinder 14 is provided outside the cylinder 13, and a piston 15 is slidably fitted in the cylinder 13 so that the piston 15 moves the inside of the cylinder 13 above the cylinder. It is divided into two chambers, a chamber 13a and a cylinder lower chamber 13b. One end side of a piston rod 16 is connected to the piston 15 by a nut 17, and the other end side of the piston rod 16 is inserted into a rod guide 18 and an oil seal 19 mounted on the upper ends of the cylinder 13 and the outer cylinder 14. Is extended to the outside of the cylinder 13.

A reservoir 20 is formed between the cylinder 13 and the outer cylinder 14, and the reservoir 20 and the cylinder lower chamber 13 are formed.
The base valve 21 communicates with b with an appropriate flow resistance. The cylinder 13 is filled with an oil liquid, and the reservoir 20 is filled with an oil liquid and a gas, so that the volume change in the cylinder 13 due to the expansion and contraction of the piston rod 16 causes the compression of the gas in the reservoir 20. , It is designed to compensate by expansion.

As shown in FIG. 3, the piston 15 is provided with a pair of extension-side communication passages 22 and contraction-side communication passages 23 with the central axis interposed therebetween. The extension-side communication passage 22 and the contraction-side communication passage 23 are long holes that penetrate along the axial direction of the piston 15 and are opened along the circumferential direction, and are arranged annularly along the circumferential direction. Further, the extension-side communication passage 22 and the contraction-side communication passage 23 are arranged at positions different by 90 °. The piston 15 has a mounting hole for inserting the piston rod in the center.
24 is provided, and a seal ring 25 is attached to the outer peripheral portion. 1 and 2 are longitudinal sectional views taken along a line (orthogonal line) passing through the extension-side communication passage 22 and the contraction-side communication passage 23.

An extension side valve seat member 26 and a contraction side valve seat member 27 each having a substantially bottom cylindrical shape are provided at both ends of the piston 15. The extension side valve seat member 26 and the contraction side valve seat member 27 have openings abutting against both ends of the piston 15, and one end side of the piston rod 16 is attached to mounting holes 28 and 29 provided at the center of the bottom. It is connected to the piston rod 16 integrally with the piston 15 by inserting it and screwing a nut 17 at its tip. Then, the extension side chamber is provided inside the extension side valve seat member 26.
26a is formed, and the contraction side chamber 27 is formed inside the contraction side valve seat member 27.
a is formed.

Here, as shown in FIGS. 4 to 9, by forming recesses 15a and 15b at both ends of the piston 15 into which the expansion side valve seat member 26 and the contraction side valve seat member 27 are fitted, The extension side valve seat member 26 and the contraction side valve seat member 27 can be reliably positioned with respect to the rotation around the axis, and the assembling workability can be improved.

As shown in FIGS. 7 to 9, the extension side valve seat member 26 has a large diameter such that the side wall (cylindrical portion) of the opening abuts on the outer peripheral side of the extension side communication passage 22 at one end of the piston 15. Part 30a,
It has a shape in which it is combined with a small diameter portion 30b that abuts on the inner peripheral side of the contraction side communication passage 23.
The compression side communication passage 23 is directly communicated with the cylinder lower chamber 13b. The bottom of the extension side valve seat member 26 is
An extension side passage 31 that is slightly smaller than the inner diameter of the cylinder 13 and connects the extension side chamber 26a to the cylinder lower chamber 13b is provided along the axial direction. On the outer end surface of the bottom of the extension side valve seat member 26, an annular valve seat 32 is projectingly provided on the inner and outer circumferences of the extension side passage 31, and the extension side disc valve is opposed to the valve seat 32.
33 is installed.

Similarly, in the compression side valve seat member 27, the side wall (cylindrical portion) of the opening is in contact with the outer peripheral side of the compression side communication passage 23 at the other end of the piston 15 and the expansion side 34a. It has a shape that combines with a small diameter portion 34b that abuts on the inner peripheral side of the communication passage 22, the compression side communication passage 23 communicates with the compression side chamber 27a, and the extension side communication passage 22 directly communicates with the cylinder upper chamber 13a. It is like this. The bottom of the compression-side valve seat member 27 has a diameter slightly smaller than the inner diameter of the cylinder 13, and a compression-side passage 35 that connects the compression-side chamber 27a and the cylinder upper chamber 13a is provided along the axial direction. On the outer end surface of the bottom of the contraction-side valve seat member 27, an annular valve seat 36 is projectingly provided on the inner and outer circumferences of the contraction-side passage 35.
A contraction side disc valve 37 is mounted so as to face 36.

The operation of the first embodiment constructed as above will be described below.

During the extension stroke of the piston rod 16, the compression side passage 35 is closed by the compression side disk valve 37,
The oil liquid on the cylinder upper chamber 13a side is connected to the extension side communication passage 22 and the extension side chamber.
26a and extension side passage 31, pass through the extension side disc valve 3
3 is opened to flow to the cylinder lower chamber 13b side, and a damping force is generated according to the opening degree of the extension side disc valve 33. During the compression stroke, the expansion side disc valve 33 is used to
31 is closed, the oil liquid on the cylinder lower chamber 13b side flows through the compression side communication passage 23, the compression side chamber 27a and the compression side passage 35, opens the compression side disc valve 37, and flows to the cylinder upper chamber 13a side.
A damping force is generated according to the opening degree of the compression side disc valve 37.

At this time, the extension side disc valves 33, 37
Receives the pressure of the oil liquid and bends away from the valve seats 32 and 36 to open at an opening corresponding to the pressure of the oil liquid. As a result, a damping force having a valve characteristic in which the damping force linearly increases in proportion to an increase in piston speed is generated. Then, the extension side communication passage 22, the extension side passage 31 and the disc valve 33,
Compression side communication passage 23, compression side passage 35 and disc valve 37
By the characteristics of, the damping force characteristics on the extension side and the contraction side can be set respectively.

Further, by providing the extension side valve seat member 26 and the contraction side valve seat member 27, the diameters of the valve seats 32 and 36 and the extension side disc valves 33 and 37 are increased, and the disc valves 32 and 37 are provided. The pressure receiving area can be increased. In addition, the cylinder upper chamber 13a and the cylinder lower chamber 13b are
Since they are communicated with each other via 26a and the contraction side chamber 26b, the passage areas of the extension side communication passage 22, the compression side communication passage 23, and the extension side passages 31, 35 can be made sufficiently large. This allows
The inclination of the damping force characteristics on the extension side and the contraction side can be reduced, and it becomes easy to set a low damping force.

Further, the extension side communication passage 22 and the compression side communication passage 23 of the piston 15, the extension side passage 31 of the extension side valve seat member 26,
In addition, since the contraction-side passages 35 of the contraction-side valve seat member 27 are respectively provided along the axial direction, the piston 15, the extension-side valve seat member 26, and the contraction-side valve seat member 27 are molded by sintering or the like. Since the molding can be performed at the same time, it is not necessary to perform a separate process, and the productivity can be improved and the manufacturing cost can be reduced. Further, since the extension side valve seat member 26 and the contraction side valve seat member 27 can have the same shape, it is not necessary to prepare two kinds of parts.

In the above embodiment, the extension side communication passage 22 of the piston 15, the compression side communication passage 23, the extension side passage 31 of the extension side valve seat member 26 and the compression side passage 35 of the compression side valve seat member 27 are Although they are long holes, they may be a plurality of round holes.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment is an application of the present invention to a damping force adjustable hydraulic shock absorber capable of selecting different types of damping force characteristics on the extension side and the contraction side. Regarding the valve seat member, the contraction side valve seat member, the expansion side and the contraction side disk valve,
Since the structure is the same as that of the first embodiment, the same reference numerals as those of the first embodiment will be given and described. Further, FIG. 10 is a vertical cross-sectional view taken along an orthogonal line passing through the expansion side communication passage and the compression side communication passage of the piston, as in FIGS. 1 and 2.

As shown in FIG. 10, the damping force adjusting type hydraulic shock absorber 38 includes an extension side valve seat member 26 and a compression side valve seat portion seat 27 provided at both ends of the piston 15 and an extension side auxiliary valve. Seat member 39
And a contraction side sub-valve seat member 40 are provided so as to overlap each other, and one end side of the piston rod 41 is inserted therethrough, and a nut 42 is screwed to the tip end portion of the piston rod 41 to form the piston rod 41.
Are integrally connected to.

A cylindrical guide portion 41a is formed at one end of the piston rod 41, and a cylindrical shutter 43 is rotatably fitted on the guide portion 41a. Shutter
The operation rod 44 is connected to the operation rod 44.
Is inserted into the piston rod 41 and extended to the outside along the axis thereof, so that the shutter 43 can be rotated from the outside. Inside the shutter 43, the extension side shutter chamber
Two chambers 43a and a shrink side shutter chamber 43b are formed.

An extension side valve seat member is provided on the side wall of the guide portion 41a.
An extension side port 45 communicating with the extension side chamber 26a in 26 and a port 46 communicating with the compression side chamber 27a in the compression side valve seat member 27 are provided. Further, the cylinder lower chamber 13b is provided via the passage 47 and the orifice 48 provided in the extension side sub valve seat member 39.
A port 52 communicating with the cylinder upper chamber 13a is provided through a compression side port 49 communicating with the cylinder side, a passage 50 provided in the compression side auxiliary valve seat member 40 and an orifice 51.

On the side wall of the shutter 43, an extension side opening portion which faces the extension port 45 and communicates with the extension side shutter chamber 43a.
Shrink side shutter chamber facing 53 and contract side port 46
A contraction side opening 54 communicating with 43b is provided. In addition, an opening 55 that allows the extension-side shutter chamber 43a to always communicate with the port 49 and an opening 56 that allows the contraction-side shutter chamber 43b to always communicate with the port 52 are provided.

The extension side opening 53 and the contraction side opening 54 are formed in a substantially wedge shape, and the communication passage area between the extension side opening 53 and the extension side port is determined according to the rotational position of the shutter 43. When the (expansion side communication passage area) is the maximum, the communication passage area between the contraction side opening 54 and the contraction side port 46 (contraction side communication path area) becomes the minimum, and by rotating the shutter 43 to one side from this state. , The expansion side communication passage area gradually decreases and the contraction side communication passage area gradually increases,
The contraction side communication passage area is maximized when the expansion side communication passage area is minimum.

The extension side sub-valve seat member 39 includes a disc valve 57 (check valve) for allowing only the flow of the oil liquid from the passage 47 to the cylinder lower chamber 13b side to generate a damping force, and an orifice.
A check valve 58 that allows only the flow of oil liquid from the cylinder 48 to the cylinder lower chamber 13b side is provided. Further, the compression-side auxiliary valve seat member 40 has a disc valve 59 for generating a damping force by allowing only the oil liquid to flow from the passage 50 to the cylinder upper chamber 13a side.
A (check valve) and a check valve 60 which allows only the flow of the oil liquid from the orifice 51 to the cylinder upper chamber 13a side are provided. The disc valves 57 and 59 are provided on the extension side valve seat member 26.
And expansion side disc valves 33 and 37 of the compression side valve seat member 27
It is set to generate a smaller damping force.

The extension side port 45 and the extension side opening 5
3, extension side shutter chamber 43a, opening 55, port 49, passage 4
The expansion side bypass passage is constituted by 7 and the orifice 48, and the contraction side port 46, the contraction side opening 54, the contraction side shutter chamber 43b, the opening 56, the port 52, the passage 50 and the orifice 51 constitute the contraction side bypass passage. And
Further, the guide portion 41a and the shutter 43 constitute a damping force adjusting mechanism.

In FIG. 7, reference numeral 61 is a thrust bearing for supporting the shutter 43, and 62 and 63 are orifices for preventing the vertical movement of the shutter 43 by applying the positive pressure of the cylinder lower chamber 13b to the shutter 43 and the reverse. It is a stop valve.

The operation of the second embodiment constructed as above will be described below. The arrow on the right side of the drawing in FIG. 7 indicates the flow of the oil liquid during the expansion stroke of the piston rod 41, and the arrow on the left side indicates the flow of the oil liquid during the contraction stroke.

During the expansion stroke of the piston rod 41, the compression side disc valves 37, 59 and the check valve 60 are closed, and the oil liquid on the cylinder upper chamber 13a side is expanded as shown by the arrow on the right side in FIG. Pass the passage 22 through the extension side chamber 26a and the extension side passage 31 and open the extension side disk valve 33 to open the cylinder lower chamber 13b.
Flow toward the side, and also from the extension side chamber 26a to the extension side port 45 which is the extension side bypass passage, the extension side opening 53, the extension side shutter chamber 43a, the opening 55, the port 49, the passage 47 and the orifice 48, and the disc valve 57. And the check valve 58 is opened to flow to the cylinder lower chamber 13b side. At this time, a damping force is generated according to the openings of the orifice 48 and the expansion side disc valves 33 and 57, and the rotation of the shutter 43 changes the communication passage area between the expansion side opening 53 and the port 45 to reduce the damping force. Can be adjusted.

During the compression stroke of the piston rod 41, the extension side disc valves 33, 57 and the check valve 58 are closed, and the oil liquid on the cylinder lower chamber 13b side is closed as shown by the arrow on the left side in FIG.
The compression-side communication passage 23, the compression-side chamber 27a, and the compression-side passage 35 are opened to open the compression-side disk valve 37 to flow toward the cylinder upper chamber 13a, and the compression-side chamber 27a is a compression-side bypass passage port 46 and the compression-side opening. Part 54, contraction side shutter chamber 43
b, through the opening 56, the port 52, the passage 50 and the orifice 51, the disc valve 59 and the check valve 60 are opened to flow to the cylinder upper chamber 13a side. At this time, a damping force is generated according to the openings of the orifice 51 and the compression side disc valves 37 and 59, and the rotation of the shutter 43 causes the compression side opening 54 and the port 46.
It is possible to adjust the damping force by changing the area of the communication path between and.

Then, the operation rod 44 is operated from the outside to rotate the shutter 43, and the extension side opening 53 and the extension side port 53
Damping the expansion side by maximizing the communication path area with 45 (expansion side communication path area) and minimizing the communication path area between the contraction side opening 54 and the contraction side port 46 (contraction side communication path area) The force is minimum (soft characteristic), and the damping force on the contraction side is maximum (hard characteristic). When the shutter 43 is rotated to one side from this state to gradually decrease the expansion side communication passage area and gradually increase the contraction side communication passage area, the extension side damping force gradually increases and the contraction side damping force increases. Becomes smaller gradually. Then, by minimizing the expansion-side communication passage area and maximizing the contraction-side communication passage area, the expansion-side damping force becomes maximum (hard characteristic) and the contraction-side damping force becomes minimum (soft characteristic).

In this way, it is possible to select different types of damping force characteristics on the extension side and the contraction side, and to adjust continuously.

Similar to the first embodiment, the inclination of the damping force characteristic can be set small, and the number of processing steps can be reduced to improve the productivity and reduce the manufacturing cost.
Further, the piston 15, the extension side valve seat member 26 and the contraction side valve seat member 27 can be shared with the type in which the damping force is not adjusted as shown in the first embodiment, and the side wall of the guide portion 41a of the piston rod 41 is provided. Since the expansion-side and contraction-side bypass passages can be easily configured only by providing the ports 45 and 46, the number of parts can be reduced and the manufacturing cost can be reduced.

[0045]

As described in detail above, according to the hydraulic shock absorber of the present invention, during the expansion stroke of the piston rod, the oil liquid in the cylinder flows through the expansion side communication passage due to the sliding of the piston, and the expansion side A damping force is generated by the disc valve,
During the contraction stroke, the piston slides to cause the oil liquid in the cylinder to flow through the contraction-side communication passage, and the contraction-side disk valve generates a damping force. At this time, since the expansion-side and contraction-side valve seat members are provided, the diameters of the expansion-side and contraction-side disc valves can be increased, and the expansion-side and contraction-side communication passages and the expansion-side and contraction-side valves can be increased. Since the two chambers in the cylinder are communicated with each other through the tubular portion of the seat member, it is possible to increase the passage area of the oil liquid during the extension stroke and the contraction stroke. As a result, the inclination of the damping force characteristics on the extension side and the contraction side can be reduced, and it becomes easy to set a low damping force. Furthermore, since the extension side communication passage and the compression side communication passage of the piston are provided along the axial direction, it is possible to easily mold, and it is possible to improve the productivity and reduce the manufacturing cost. Play.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view taken along an orthogonal line passing through an extension side communication passage and a contraction side communication passage of a main part of a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view taken along a line orthogonal to the extension-side communication passage and the contraction-side communication passage of the hydraulic shock absorber of FIG.

FIG. 3 is an exploded perspective view showing a part of a piston, an extension side valve seat member and a contraction side valve seat member of the apparatus of FIG.

4 is a vertical cross-sectional side view of another embodiment of the piston of the apparatus of FIG.

5 is a plan view of the piston of FIG.

FIG. 6 is a bottom view of the piston of FIG.

7 is a vertical cross-sectional view of the extension side valve seat member of the apparatus of FIG. 1 taken along the line AA of FIG.

8 is a plan view of the extension side valve seat member of FIG. 7. FIG.

9 is a bottom view of the extension side valve seat member of FIG. 7. FIG.

FIG. 10 is a vertical cross-sectional view of the side surface of the essential part of the second embodiment of the present invention, taken along the same orthogonal line as in FIG.

FIG. 11 is a side view of a piston portion of a conventional hydraulic shock absorber.
It is a longitudinal cross-sectional view taken along the line CC of FIG.

12 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 12 Hydraulic shock absorber 13 Cylinder 15 Piston 16 Piston rod 22 Expansion-side communication passage 23 Compression-side communication passage 26 Expansion-side valve seat member 27 Compression-side valve seat member 33 Expansion-side disc valve 37 Compression-side disc valve

Claims (1)

[Claims] 1. A cylinder in which an oil liquid is sealed, a cylindrical piston slidably fitted in the cylinder and defining two chambers in the cylinder, and one end of which is fixed to penetrate the piston. And a piston rod having the other end extended to the outside of the cylinder, a pair of extension side communication passages formed along the axial direction at positions facing each other with the piston rod of the piston interposed therebetween, and the piston A pair of contraction side communication passages formed along the axial direction at positions facing each other with the piston rod sandwiched between the pair of extension side communication passages, and a tubular shape, one end of which is the piston rod. And an extension side valve seat member that surrounds the pair of extension side communication passages and abuts one end surface of the piston so as not to surround the pair of compression side communication passages, and the other end of the tubular portion serves as a valve seat, and the extension side valve seat member. Provided on the other end of the side valve seat member An expansion side disc valve provided so as to close the cylindrical portion, and a tubular shape, and one end of the cylindrical portion encloses the piston rod and the pair of contraction side communication passages and does not enclose the pair of extension side communication passages. And a contraction side valve seat member in which the other end of the cylinder portion serves as a valve seat, and the other end side of the contraction side valve seat member is provided so as to close the cylinder portion. A hydraulic shock absorber, comprising: