Shock absorber

Abstract

To provide a shock absorber capable of exhibiting frequency sensitivity without enlarging a device.SOLUTION: By forming the frequency response unit 75 (a plurality of rows of serrations 76) on the outer periphery of the inner tube 2, a pressure loss due to the pipeline resistance of the frequency response unit 75 is generated in the hydraulic fluid flowing through the annular flow path 20. As a result, as the vibration frequency of the piston rod 6 increases, the pressure loss due to the pipe resistance of the frequency response unit 75 increases, and the flow rate of the hydraulic fluid introduced into the damping force generation mechanism 30 decreases, so that the damping force generation mechanism 30 generates the damping force of the soft characteristic. Therefore, it is possible to cause the damping force generated by the damping force generation mechanism 30 to exhibit frequency sensitivity in both the extension stroke and the compression stroke without increasing the size of the device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a shock absorber that is attached between two members that are movable relative to one another. [Background technology]

[0002] BACKGROUND ART Conventionally, shock absorbers having frequency sensitivity that reduces damping force against high frequency vibrations are known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-001488 Summary of the Invention [Problem to be solved by the invention]

[0004] In the shock absorber described in Patent Document 1 (hereinafter referred to as the "conventional shock absorber"), a frequency sensitive section is formed in the extension damping force generating section 31, so a first valve seat member 32, a relief valve 34, and a second valve seat member 33 are interposed between the piston 5 and the spacer, which increases the axial length of the extension damping force generating section 31 and causes the device to become larger.

[0005] An object of the present invention is to provide a shock absorber that can exhibit frequency sensitivity without increasing the size of the device. [Means for solving the problem]

[0006] In the shock absorber of the present invention, the annular flow path is formed in the vicinity of the communication port and has a frequency sensitive portion that varies the flow path resistance in accordance with the vibration frequency of the piston rod. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a shock absorber that can exhibit frequency sensitivity without increasing the size of the device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the shock absorber according to the embodiment. [Figure 2] FIG. 2 is an enlarged view of the damping force adjusting mechanism in FIG. [Figure 3] FIG. 2 is an explanatory diagram of the first embodiment, showing an enlarged view of the periphery of a frequency sensitive section. [Figure 4] FIG. 10 is an explanatory diagram of a second embodiment, showing an enlarged view of the periphery of a frequency sensitive section. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) A first embodiment of the present invention will be described with reference to the accompanying drawings. 1, the shock absorber 1 is a so-called horizontally mounted control valve type damping force adjustable hydraulic shock absorber in which a damping force generating mechanism 30 is mounted horizontally on the side wall of an outer tube 3. The shock absorber 1 has an inner tube 2 (cylinder) in which a working fluid is sealed as a working fluid, and an outer tube 3 provided on the outer periphery of the inner tube 2.

[0010] The shock absorber 1 has a reservoir 4 formed between an inner tube 2 and an outer tube 3, and has a working fluid, a working liquid, and a gas sealed therein. The shock absorber 1 has a piston 5 inserted into the inner tube 2, and dividing the interior of the inner tube 2 into two chambers, a first chamber 2A and a second chamber 2B. The shock absorber 1 has a piston rod 6 whose one end (the "lower side" in FIG. 1) is connected to the piston 5, and whose other end (the "upper side" in FIG. 1) is inserted through a rod guide 7 attached to the other end of the outer tube 3 and an oil seal 8, and which extends out of the inner tube 2.

[0011] The piston 5 is provided with an extension passage 9 and a compression passage 10 that connect the first chamber 2A and the second chamber 2B. The extension passage 9 is provided with a disc valve 11 (pressure adjustment valve) that opens when the pressure on the first chamber 2A side reaches a set pressure to release the pressure in the first chamber 2A to the second chamber 2B. The compression passage 10 is provided with a disc valve 12 (check valve) that allows the flow of hydraulic fluid from the second chamber 2B to the first chamber 2A.

[0012] A base valve 13 is provided at one end (the "lower side" in FIG. 1 ) of the inner tube 2, separating the second chamber 2B from the reservoir 4. The base valve 13 is provided with an extension-side passage 14 and a compression-side passage 15 that communicate between the second chamber 2B and the reservoir 4. The extension-side passage 14 is provided with a disc valve 16 (check valve) that allows the flow of hydraulic fluid from the reservoir 4 to the second chamber 2B. The compression-side passage 17 is provided with a disc valve 17 (pressure adjustment valve) that opens when the pressure in the second chamber 2B reaches a set pressure, releasing the pressure in the second chamber 2B to the reservoir 4.

[0013] The shock absorber 1 has a separator tube 18 that is provided between the inner tube 2 and the outer tube 3, and has both ends in the cylinder axial direction (the "up-down direction" in FIG. 1) fitted to the inner tube 2 via a pair of seal members 19, 19. The shock absorber 1 has an annular flow path 20 that is formed between the inner tube 2 and the separator tube 18. The shock absorber 1 has a communication port 21 that is formed in the side wall of the inner tube 2 and that communicates the other end (the "upper side" in FIG. 1) of the annular flow path 20 with the first chamber 2A.

[0014] The shock absorber 1 has a connecting pipe 22 formed at one end of the side wall of the separator tube 18 (the "lower side" in FIG. 1) and extending to the right (radially outward) in FIG. 1 toward the outer tube 3. The shock absorber 1 has an opening 23 formed in the side wall of the outer tube 3 and opening to face the connecting pipe 22. The shock absorber 1 has a cylindrical valve case 24 provided on the side wall of the outer tube 3 and protruding radially outward from the outer tube 3. The valve case 24 houses a damping force generating mechanism 30 connected to the connecting pipe 22. The inner diameter of the valve case 24 and the diameter of the opening 23 are set to be the same.

[0015] As shown in Fig. 2, the damping force generating mechanism 30 has a back-pressure type main valve 31 that generates a damping force. For convenience, the left side in Fig. 2 is referred to as the radially inner side of the cylinder, and the right side in Fig. 2 is referred to as the radially outer side of the cylinder. An annular packing 32 (elastic seal member) is joined to the outer peripheral edge of the radially outer surface of the main valve 31. The damping force generating mechanism 30 has a main body 41 against which the main valve 31 abuts, a back-pressure chamber 33 formed radially outward of the main valve 31 and in which internal pressure acts on the main valve 31 in a valve closing direction, and a pilot case 52 that forms the back-pressure chamber 33.

[0016] The damping force generating mechanism 30 includes a pilot valve 51 that controls the valve-opening pressure of the main valve 31 by adjusting the internal pressure of the back pressure chamber 33, a pilot body 53 against which the pilot valve 51 abuts, a fail-safe valve 81 that is provided downstream of the pilot valve 51, and a solenoid 91 that controls the valve-opening pressure of the pilot valve 51. The damping force generating mechanism 30 has an annular seat portion 42 that is formed on the outer peripheral edge of the end face of the main body 41 on the outer side in the cylinder radial direction and against which the outer peripheral edge of the main valve 31 abuts so as to be able to seat and lift off. An annular recess 43 is formed on the inner peripheral side of the seat portion 42 (upstream side of the main valve 31).

[0017] The main body 41 has a connecting portion 44 formed at the center of its radially inner end face, and connected (fitted) into the connecting pipe 22 of the separator tube 18. The main body 41 has a recess 45 formed at the radially inner end face of the connecting portion 44, and opening into the annular flow path 20. The main body 41 has a plurality of passages 46 (six in the first embodiment) that connect the recess 45 to the annular recess 43. The main body 41 has a pin portion 47 formed at the center of its radially outer end face, and inserted into a shaft hole 54 of the pilot case 52. The pin portion 47 has an introduction passage 48 that connects to the annular flow path 20 via the recess 45 and an introduction orifice 49.

[0018] The main valve 31, a retainer, a spacer (reference numerals omitted), and a back pressure introduction valve 34 are interposed between the main body 41 and the pilot case 52. The main valve 31, the retainer, the spacer (reference numerals omitted), and the back pressure introduction valve 34 are sandwiched between the main body 41 and the pilot case 52 by tightening a nut 35 that is threaded onto the tip of a pin portion 85.

[0019] The pilot case 52 has an annular recess 43 formed on its end surface in the cylinder radial direction. The packing 32 of the main valve 31 slidably abuts against the inner circumferential surface of the annular recess 43. The pilot case 52 has an annular seat portion 56 formed on the inner circumferential edge of the annular recess 43. The back pressure introduction valve 34 abuts against the seat portion 56 so that it can be seated and removed. An annular recess 57 is formed on the inner circumferential side of the seat portion 56. The annular recess 57 is connected to a small diameter recess 59 formed on the outer side of the pilot case 52 in the cylinder radial direction by multiple passages 58 (only two are shown in FIG. 2). Note that the back pressure introduction valve 34 has multiple orifices (reference numerals omitted) formed on its outer circumferential edge that connect the back pressure chamber 33 to the annular flow path 20.

[0020] The pilot body 53 is formed in a generally cylindrical shape with a bottom that is open on the outer side in the cylinder radial direction. The outer periphery of the pilot body 53 on the inner side in the cylinder radial direction is fitted into the large-diameter recess 60 of the pilot case 52. The pilot body 53 is positioned in the cylinder radial direction (the "left-right direction" in FIG. 2 ) relative to the pilot case 52 by being abutted against a step 61 formed between the large-diameter recess 60 and the small-diameter recess 59 of the pilot case 52.

[0021] A valve chamber 62 is formed inside the pilot body 53, and houses the pilot valve 51 and the fail-safe valve 81. Working fluid is introduced into the valve chamber 62 from the annular flow path 20 via the inlet orifice 49, the inlet passage 48, and a passage 63 formed in the center of the bottom of the pilot body 53. A seat portion 65 is formed around the opening periphery of the passage 63 on the outer side in the cylinder radial direction, against which a valve element 64 of the pilot valve 51 can be seated and released. The valve element 64 is formed in a substantially cylindrical shape, and its end on the inner side in the cylinder radial direction is tapered. An outer flange-shaped spring bearing portion 66 is formed on the outer periphery of the valve element 64 on the outer side in the cylinder radial direction. The valve element 64 is urged in the valve opening direction (outward in the cylinder radial direction) by a return spring 67 (non-linear spring) that integrates a pilot spring and a fail-safe spring.

[0022] A return spring 67, a spacer, a retainer (reference numerals omitted), and a washer 68 are stacked on the radially outer side of the pilot body 53. These stacked components are fixed to the pilot body 53 by a cap 69 attached to the outer periphery of the pilot body 53 in the radially outer side of the cylinder. The cap 53 is formed with a notch 71 (communication passage) that connects the valve chamber 62 to a passage 70 formed on the outer periphery of the cap 69. The valve chamber 62 is connected to the reservoir 4 via the notch 71, the passage 70, two passages 72 (only two are shown in FIG. 2 ) formed between a flat (reference numerals omitted) formed on the outer periphery of the pilot case 52 and a cylindrical portion 93 of a yoke 92 of the solenoid 91, a passage 73 formed on the outer periphery of the main valve 31, and the opening 23.

[0023] The coil 92, core 95, fixed core 96, movable core 97, and hollow operating rod 98 are assembled to the outside of the yoke 92 in the cylinder radial direction. The operating rod 98 is configured as one unit with the movable core 97, but may be configured as a separate unit. The valve body 64 of the pilot valve 51 is fixed to the end of the operating rod 98 on the inside of the cylinder radial direction. A spacer 99 and a cover 100 are inserted into the end of the yoke 92 on the outside of the cylinder radial direction, and an axial force is applied to the internal components of the solenoid within the yoke 92 by plastically processing (crimping) the opening on the outside of the cylinder radial direction.

[0024] The cylindrical portion 123 of the yoke 92 is fitted to the radially outer end of the valve case 24. The yoke 92 is positioned in the axial direction of the solenoid 91 (valve case 24) by being abutted against a step portion 25 of the valve case 24. The yoke 92 is fixed to the valve case 24 by tightening a nut 101 threaded onto the valve case 24 and compressing a retaining ring 102.

[0025] When the coil 94 is not energized, the spring force of the return spring 67 urges the valve element 64 in the unseating direction (diametrically outward in the cylinder), causing the spring bearing portion 66 of the valve element 64 to abut (seat) on the fail-safe disk 82, thereby closing the fail-safe valve 81. On the other hand, when the coil 94 is energized, thrust is generated in the movable iron core 97, and the operating rod 98 is urged in the seating direction of the valve element 64 (diametrically inward in the cylinder).

[0026] As a result, the actuation rod 98 is propelled against the spring force of the return spring 67, and the valve element 64 is seated on the seat portion 65. The valve-opening pressure of the valve element 64 at this time is controlled by the value of the current passed through the coil 94. Note that in the soft mode, in which the value of the current passed through the coil 94 is small, the spring force of the return spring 67 and the thrust of the movable iron core 97 (actuation rod 98) are balanced, and the valve element 64 is maintained in a state where it is spaced a certain distance from the seat portion 65 (see FIG. 2).

[0027] Here, the annular flow path 20, which is formed between the inner tube 2 (cylinder) and the outer tube 3 and communicates with the introduction passage 48 of the damping force generating mechanism 30, has a frequency sensitive section 75 that varies the flow path resistance in accordance with the vibration frequency of the piston rod 6. As shown in FIG. 3, the frequency sensitive section 75 in the first embodiment is configured by multiple rows (eight rows in the first embodiment) of serrations 76 formed on the outer periphery of the inner tube 2. The frequency sensitive section 75 is arranged closer to one end than the communication port 21 (the "lower side" in FIG. 3), and is arranged in the vicinity of the communication port 21. The multiple rows of serrations 76 are arranged at regular intervals in the cylinder axial direction (the "up-down direction" in FIG. 3). The shape of the teeth of the serrations 76 and the spacing between adjacent teeth in the circumferential direction are set appropriately as needed.

[0028] Next, the operation of the shock absorber 1 will be described. The shock absorber 1 is mounted vertically between the sprung (body) and unsprung (wheel) parts of the vehicle suspension system, and the opening pressure of the pilot valve 51 is adjusted by an on-board controller (not shown) controlling the current flowing to the coil 94 of the solenoid 91 of the damping force generating mechanism 30.

[0029] During the extension stroke of the piston rod 6, the pressure rises in the first chamber 2A, causing the disc valve 12 of the piston 5 to close, and before the disc valve 11 opens, the hydraulic fluid in the first chamber 2A is pressurized. As a result, the hydraulic fluid in the first chamber 2A is introduced into the damping force generating mechanism 30 via the communication port 21, the annular flow path 20, and the connecting pipe 22. At this time, the hydraulic fluid that has left the inner tube 2 (cylinder) by the piston rod 6 opens the disc valve 16 of the base valve 13 and flows from the reservoir 4 to the second chamber 2B. When the pressure in the first chamber 2A reaches the opening pressure of the disc valve 11 of the piston 5 and the disc valve 11 opens, the pressure in the first chamber 2A is relieved to the second chamber 2B, preventing an excessive pressure rise in the first chamber 2A.

[0030] On the other hand, during the compression stroke of the piston rod 6, the pressure in the second chamber 2B rises, opening the disc valve 12 of the piston 5 and closing the disc valve 16 in the passage 14 of the base valve 13. Before the disc valve 17 opens, hydraulic fluid flows from the piston under-chamber 2B to the first chamber 2A. At this time, the volume of hydraulic fluid that has entered the inner tube 2 by the piston rod 6 is introduced from the first chamber 2A through the communication port 21, the annular flow path 20, and the connecting pipe 22 into the damping force generating mechanism 30. When the pressure in the second chamber 2B reaches the opening pressure of the disc valve 17 of the base valve 13 and the disc valve 17 opens, the pressure in the second chamber 2B is relieved to the reservoir 4, preventing an excessive pressure rise in the second chamber 2B.

[0031] The hydraulic fluid introduced into the damping force generating mechanism 30 passes through the introduction orifice 49, the introduction passage 48, the small-diameter recess 59 of the pilot case 52, and the passage 58 and is introduced into the annular recess 57. When the pressure in the annular recess 57 reaches the valve-opening pressure of the back-pressure introduction valve 34, the back-pressure introduction valve 34 opens and hydraulic fluid is introduced into the back-pressure chamber 33. Before the main valve 31 opens (in the low-piston speed range), when the pressure upstream of the pilot valve 51 reaches the valve-opening pressure of the valve body 64, the pilot valve 51 (valve body 64) opens and hydraulic fluid is introduced into the valve chamber 62 via the introduction orifice 49, the introduction passage 48, the small-diameter recess 59, and the passage 63.

[0032] The hydraulic fluid introduced into the valve chamber 62 passes through the notch 71 in the cap 69, the flow path 70, the passage 72, and the flow path 73, and then flows from the opening 23 to the reservoir 4. When the piston speed increases and the main valve 31 opens, the hydraulic fluid in the annular flow path 20 passes through the recess 45, the multiple passages 67, the annular recess 43, the main valve 31, and the flow path 73, and then flows (is released) from the opening 23 to the reservoir 4.

[0033] In this way, during both the extension stroke and compression stroke of the piston rod 6, the damping force generating mechanism 30 generates a soft damping force according to the opening pressure of the inlet orifice 49 and the pilot valve 51 (valve body 64) before the main valve 31 opens (when the piston speed is low), and generates a hard damping force according to the opening degree of the main valve 31 after the main valve 31 opens (when the piston speed is medium).

[0034] The damping force can be directly controlled regardless of the piston speed by adjusting the valve opening pressure of the pilot valve 51 through controlling the energization of the coil 94. Furthermore, by adjusting the valve opening pressure of the pilot valve 51 through controlling the energization of the coil 94, it is possible to open the back pressure introduction valve 34 and adjust the pressure of the hydraulic fluid introduced into the back pressure chamber 33, thereby enabling adjustment of the damping force characteristics over a wide range.

[0035] On the other hand, if thrust from the movable iron core 97 (operating rod 98) is lost due to a failure such as a break in the coil 94 or a malfunction of the on-board controller, the spring force of the return spring 67 moves the valve element 64 backward to open the pilot valve 51, and the spring receiving portion 66 of the valve element 64 abuts against the fail-safe disk 82, thereby blocking communication between the valve chamber 62 and the flow path 73 inside the valve case 24. In other words, the fail-safe valve 81 controls the flow of hydraulic fluid from the annular flow path 20 to the reservoir 4 via the inlet orifice 49, the inlet passage 48, the small-diameter recess 59, the passage 63, the valve chamber 62, the notch 71, the flow path 70, the passage 72, the flow path 73, and the opening 23.

[0036] In this way, the damping force generating mechanism 30 can obtain a damping force according to the valve opening pressure of the fail-safe valve 81, and at the same time, can adjust the internal pressure of the back pressure chamber 33 and therefore the valve opening pressure of the main valve 31, so that a constant damping force can be obtained even when a failure occurs.

[0037] In the first embodiment, even when the piston speed is the same, frequency sensitivity is exhibited, which varies the flow path resistance according to the vibration frequency of the piston rod 6. That is, during both the extension stroke and the compression stroke, the working fluid is introduced from the first chamber 2A through the communication port 21, the annular flow path 20, and the connecting pipe 22 into the damping force generation mechanism 30. At this time, the working fluid flowing through the annular flow path 20 is subjected to line resistance by the frequency sensitive portion 75 (multiple rows of serrations 76) formed on the outer periphery of the inner tube 2 (cylinder), causing a pressure loss. As a result, the higher the vibration frequency of the piston rod 6, the greater the pressure loss due to the line resistance of the frequency sensitive portion 75, and the less the flow rate of the working fluid introduced into the damping force generation mechanism 30 via the connecting pipe 22, causing the damping force generation mechanism 30 to generate a damping force with soft characteristics.

[0038] In conventional shock absorbers, the frequency sensitive part is formed by placing a first valve seat member, a relief valve, and a second valve seat member between the piston and the spacer. This increases the axial length of the piston rod by the amount of parts placed between the piston and the spacer, which causes the device to become larger.

[0039] In contrast, in the first embodiment, a frequency sensitive portion 75 (multiple rows of serrations 76) is formed on the outer periphery of the inner tube 2 (cylinder), so that pressure loss occurs in the working fluid flowing through the annular flow path 20, in other words, in the working fluid introduced into the damping force generating mechanism 30, due to the pipeline resistance of the frequency sensitive portion 75. According to the first embodiment, as the vibration frequency of the piston rod 6 increases, the pressure loss due to the pipeline resistance of the frequency sensitive part 75 increases, and the flow rate of the working fluid introduced into the damping force generating mechanism 30 via the connecting pipe 22 decreases, so that the damping force generating mechanism 30 generates a damping force with soft characteristics. In this way, in the first embodiment, the damping force generated by the damping force generating mechanism 30 can be made to exhibit frequency sensitivity in both the extension stroke and the compression stroke without extending the axial length of the piston rod 6 and, consequently, without increasing the size of the device. Furthermore, in the first embodiment, by forming multiple rows of serrations on the outer periphery of the inner tube 2 without adding parts such as a free valve, it is possible to make the damping force generated by the damping force generating mechanism 30 frequency sensitive, thereby suppressing increases in manufacturing costs.

[0040] The first embodiment is not limited to the above-described aspects, and can be configured as follows, for example. In the first embodiment, the frequency sensitive portion 75 is configured by multiple rows of serrations formed on the outer periphery of the inner tube 2, but the frequency sensitive portion 75 may be any portion that has the effect of generating pressure loss due to pipeline resistance in the working fluid flowing through the annular flow path 20 (roughening the outer periphery surface of the inner tube 2), for example, by forming a male thread on the outer periphery of the inner tube 2.

[0041] (Second embodiment) Next, a second embodiment will be described with reference to FIG. The same names and symbols are used for parts common to the first embodiment, and duplicated explanations will be omitted. In the first embodiment, the frequency sensitive part 75 is configured by multiple rows of serrations formed on the outer periphery of the inner tube 2 (cylinder).

[0042] In contrast to this, in the second embodiment, the frequency sensitive portion 75 is configured as an annular protrusion 77 formed on the inner periphery of the outer tube 3. The protrusion 77 can be formed by intermediate swaging of the outer tube 3. The axial length (length in the cylinder axial direction) and height (gap in the cylinder radial direction with the inner tube 2) of the annular protrusion 77 are appropriately set as needed.

[0043] According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment described above. Furthermore, in the second embodiment, manufacturing costs can be reduced compared to the first embodiment in which the frequency sensitive portion 75 is formed by multiple rows of serrations 76. Note that, in the second embodiment, the frequency sensitive portion 75 is formed by annular convex portions 77 formed on the inner circumference of the outer tube 3, but the frequency sensitive portion 75 may be formed by any other means as long as it has the effect of generating a pressure loss due to pipeline resistance in the working fluid flowing through the annular flow path 20 (roughening the inner circumferential surface of the outer tube 3), such as by forming multiple rows of serrations (inner serrations) on the inner circumference of the outer tube 3. [Explanation of symbols]

[0044] 1 shock absorber, 2 inner tube (cylinder), 2A first chamber, 2B second chamber, 3 outer tube, 4 reservoir, 5 piston, 18 separator tube, 20 annular flow path, 21 communication port, 22 connecting pipe, 23 opening, 30 damping force generating mechanism, 75 frequency sensing part

Claims

1. A shock absorber attached between two relatively movable members, a cylinder in which a working fluid is sealed; a piston inserted into the cylinder and dividing the interior of the cylinder into a first chamber and a second chamber; a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder; an outer tube provided on the outer periphery of the cylinder; a reservoir formed between the cylinder and the outer tube and containing a working fluid; a separator tube provided between the cylinder and the outer tube, the separator tube having both ends fitted to the cylinder; an annular flow path formed between the cylinder and the separator tube; a communication port formed in a side wall of the cylinder, the communication port communicating the first chamber with the annular flow path; a connecting pipe formed on a side wall of the separator tube and extending toward the outer tube; a damping force generating mechanism provided on a side wall of the outer tube and connected to the connecting pipe; an opening formed in a side wall of the outer tube, facing the connecting pipe, and communicating between the reservoir and the damping force generating mechanism; A shock absorber comprising: The annular flow path is formed in the vicinity of the communication port and has a frequency sensitive portion that varies the flow path resistance in accordance with the vibration frequency of the piston rod.

2. 2. The shock absorber according to claim 1, The shock absorber, wherein the frequency sensitive portion is a serration formed on the outer periphery of the cylinder.

3. 2. The shock absorber according to claim 1, The shock absorber is characterized in that the frequency sensitive portion is a convex portion formed on the inner periphery of the outer tube.

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