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Abstract

To provide a small-sized shock absorber.SOLUTION: A backpressure chamber 72 in which inner pressure acts in a direction of closing a main valve 51 is formed at one side of a pilot case 73, and a pilot valve seat part 74 on which a valve body 82 of a pilot valve 71 for adjusting the inner pressure of the backpressure chamber 72 is removably seated is formed at the other side of the pilot case 73. That is, the pilot case 73 of a shock absorber 1 in an embodiment of the present invention is formed by integrating a pilot case and a pilot body of a conventional shock absorber. Therefore, an axial length of an attenuation force adjustment mechanism 31 can be shortened by a thickness (length in an axial direction) of a bottom of the pilot case of the conventional shock absorber, which receives the main body, and the shock absorber 1 can be thereby reduced in size.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a shock absorber, and more particularly to a damping force adjustable shock absorber that adjusts damping force by controlling the flow of working fluid generated by the stroke of a piston rod. [Background technology]

[0002] Patent Document 1 discloses a shock absorber (hereinafter referred to as a "conventional shock absorber") in which a pin portion 85 formed integrally with a pilot case 73 is inserted into the inner periphery of a main valve 51 and a main body 52, and a nut 87 attached to the pin portion 85 is tightened to integrate the main valve 51, the main body 52, and the pilot case 73. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 161980 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional shock absorbers, the internal pressure of the annular flow path 21 of the main valve 51 acts as a bending load on the main body 52. ​​Furthermore, conventional shock absorbers are configured separately from a pilot case 73 on one side of which a back pressure chamber 72 for the main valve 51 is formed, and a seat portion 102 (pilot valve seat portion) on which the pilot valve 71 seats on the other side. Here, because the pilot case 73 receives the bending load acting on the main body 52, it was necessary to form the bottom portion 75 with a large thickness (long axial length). This resulted in a long axial length for the damping force adjusting mechanism 31, which was a factor in increasing the size of the shock absorber.

[0005] An object of the present invention is to reduce the size of a shock absorber. [Means for solving the problem]

[0006] The shock absorber of the present invention is a shock absorber including a cylinder in which hydraulic fluid is sealed, a piston inserted into the cylinder to divide the interior of the cylinder into two chambers, an outer cylinder provided on the outer periphery of the cylinder, a reservoir formed between the cylinder and the outer cylinder and in which hydraulic fluid and gas are sealed, a connecting pipe provided between the cylinder and the outer cylinder and communicating with the interior of the cylinder, and a damping force generating mechanism housed in a valve case provided outside the outer cylinder and connected to the connecting pipe, wherein the damping force generating mechanism includes a main valve that generates damping force, a seat member against which the main valve abuts, and a pilot case formed on one side with a back pressure chamber in which internal pressure acts on the main valve in a valve closing direction, and on the other side with a pilot valve seat portion on which a pilot valve that adjusts the internal pressure of the back pressure chamber is seated. A pin portion formed integrally with the pilot case is inserted into the seat member and the main valve, and a fastening member for fastening the seat member, the main valve, and the pilot case together is provided on the pin portion. It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to shorten the axial length of the damping force adjusting mechanism, and to reduce the size of the shock absorber. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a damping force adjustable shock absorber according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the damping force adjusting mechanism in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will now be described with reference to the accompanying drawings. As shown in Fig. 1, this embodiment is a so-called horizontally mounted control valve damping force adjustable hydraulic shock absorber 1 (hereinafter referred to as "shock absorber 1") in which a damping force adjustment mechanism 31 is mounted horizontally on the side wall of an outer cylinder 3. For convenience, the up-down direction in Fig. 1 will be referred to as the "up-down direction" as it is.

[0010] Shock absorber 1 has a twin-cylinder structure in which cylinder 2 is provided inside outer cylinder 3, and reservoir 4 is formed between outer cylinder 3 and cylinder 2. A piston 5 is slidably fitted inside cylinder 2, dividing the interior of cylinder 2 into two chambers, an upper cylinder chamber 2A and a lower cylinder chamber 2B. The lower end of piston rod 6 is connected to piston 5. The upper end of piston rod 6 passes through upper cylinder chamber 2A and is further inserted into a rod guide 8 and an oil seal 9 attached to the upper ends of cylinder 2 and outer cylinder 3, protruding outside of cylinder 2.

[0011] The piston 5 is provided with an extension passage 11 and a compression passage 12 that connect the upper cylinder chamber 2A and the lower cylinder chamber 2B. The compression passage 12 is provided with a check valve 13 that allows the flow of hydraulic fluid from the lower cylinder chamber 2B to the upper cylinder chamber 2A. The extension passage 11 is provided with a disk valve 14 (relief valve) that opens when the pressure in the upper cylinder chamber 2A reaches a set pressure, releasing the pressure in the upper cylinder chamber 2A to the lower cylinder chamber 2B.

[0012] A base valve 10 is provided at the lower end of the cylinder 2, separating the cylinder lower chamber 2B from the reservoir 4. The base valve 10 is provided with an extension passage 15 and a compression passage 16 that connect the cylinder lower chamber 2B to the reservoir 4. The extension passage 15 is provided with a check valve 17 that allows hydraulic fluid to flow from the reservoir 4 to the cylinder lower chamber 2B. The compression passage 16 is provided with a disc valve 18 (relief valve) that opens when the pressure in the cylinder lower chamber 2B reaches a set pressure, releasing the pressure in the cylinder lower chamber 2B to the reservoir 4. Hydraulic fluid is sealed in the cylinder 2, and hydraulic fluid and gas are sealed in the reservoir 4.

[0013] A separator tube 20 (connecting pipe) is attached to the outer periphery of the cylinder 2 via a pair of upper and lower seal members 19, 19. An annular flow path 21 is formed between the cylinder 2 and the separator tube 20. The annular flow path 21 is connected to the cylinder upper chamber 2A via a passage 22 provided at the upper end of the side wall of the cylinder 2. A cylindrical connection port 23 that protrudes laterally and has an open tip is provided at the lower end of the side wall of the separator tube 20. A mounting hole 24 is formed in the side wall of the outer cylinder 3 at a position opposite the connection port 23. The mounting hole 24 is arranged coaxially with the connection port 23 and has an inner diameter larger than the outer diameter of the connection port 23. A substantially cylindrical valve case 25 is provided in the side wall of the outer cylinder 3 so as to surround the mounting hole 24. A damping force adjustment mechanism 31 is housed in the valve case 25.

[0014] 2, the damping force adjustment mechanism 31 includes a back pressure type main valve 51 that generates a damping force, an annular main body 52 (seat member) against which the main valve 51 abuts, a back pressure chamber 72 formed at the back of the main valve 51 and whose internal pressure acts on the main valve 51 in a valve closing direction, a pilot case 73 on one side (the side approaching the cylinder 2, the left side in FIG. 2) of which the back pressure chamber 72 is formed, a pilot valve 71 that controls the valve opening pressure of the main valve 51 by adjusting the internal pressure of the back pressure chamber 72, a pilot valve seat portion 74 formed on the other side of the pilot case 73 (the side facing away from the cylinder 2, the right side in FIG. 2) and on which the pilot valve 71 is seated, a fail-safe valve 111 provided downstream of the pilot valve 71, and a solenoid 121 that controls the valve opening pressure of the pilot valve 71.

[0015] An annular seat portion 53 is formed on the outer peripheral edge of the other end face (the "right end face" in FIG. 2) of the main body 52, against which the outer peripheral edge of the main valve 51 can removably seat. An annular recess 55 is formed on the inner peripheral side of the seat portion 53, in other words, on the upstream side of the main valve 51. On the other hand, a recess 56 is formed on one end face (the "left end face" in FIG. 2) of the main body 52, into which the connection port 23 of the separator tube 20 is fitted (inserted). The recess 56 has an inner peripheral surface 57 that is an inner cylindrical surface coaxial with the main body 52.

[0016] A seal ring 58 is provided in an annular groove (reference numeral omitted) formed in an inner circumferential surface 57 of the main body 52 (recess 56) to seal between the inner circumferential surface 57 of the main body 52 and the connection port 23 of the separator tube 20. The recess 56 on one side of the main body 52 and the annular recess 55 on the other side are connected by a plurality of passages 59 extending along the axial direction of the main body 52 (the axial direction of the connection pipe 23, the left-right direction in FIG. 2 ).

[0017] The inner periphery of the disk-shaped main valve 51 is sandwiched between the inner periphery 54 of the main body 52 and the bottom 75 of the pilot case 73, which is formed in a generally cylindrical shape with a bottom. An annular packing 60 (elastic seal member) is joined to the back side of the outer periphery of the main valve 51. An annular recess 77, which forms the back pressure chamber 72, is formed in one end face (the "left end face" in FIG. 2) of the pilot case 73 (bottom 75). The outer periphery wall surface of the annular recess 77 is an inner cylindrical surface coaxial with the axis (center line) of the pilot case 73, and forms the sliding surface for the packing 60 of the main valve 51.

[0018] An annular seat portion 79 is formed on the inner peripheral edge of the annular recess 77 on one end face of the pilot case 73. The outer peripheral edge of a disk-shaped back pressure introduction valve 81 is in releasable contact with the seat portion 79. The inner peripheral portion of the back pressure introduction valve 81 is sandwiched between the inner peripheral portion 54 of the main body 52 and the bottom portion 75 of the pilot case 73. The main valve 51, a retainer, a spacer, another retainer (reference numerals omitted), and the back pressure introduction valve 81 are interposed, in this order from one side to the other, between the inner peripheral portion 54 of the main body 52 and the bottom portion 75 of the pilot case 73. A pin portion 85, which is formed integrally with the pilot case 73, is inserted into axial holes of the main valve 51, the retainer, the spacer, the retainer (reference numerals omitted), and the back pressure introduction valve 81.

[0019] The pin portion 85 is provided coaxially with the pilot case 73 and protrudes to one side (the left side in FIG. 2 ) from the bottom portion 75 of the pilot case 73. The pin portion 85 is inserted through the axial hole 61 of the main body 52, and one end portion (tip portion) is located inside the recessed portion 56 of the main body 52, in other words, inside the connection port 23. A threaded portion 86 is formed at one end portion of the pin portion 85, and a nut 87 (fastening member) is screwed onto the threaded portion 86. The nut 87 is located (housed) inside the connection port 23, in other words, inside the recessed portion 56 of the main body 52.

[0020] By tightening a nut 87 that is threaded onto the threaded portion 86, an axial force is applied to the upstream valve parts between the washer 88 and the pilot case 73. When tightening the nut 87, a tool is engaged with a width across flats 89 (only one side is shown in FIG. 2 ) formed on the outer circumferential surface of the pilot case 73. A passage 33, which will be described later, is formed between the width across flats 89 of the pilot case 73 and the yoke 122.

[0021] The pilot case 73 has a recess 91 of a certain depth (axial length) formed on the other side (the "right side" in FIG. 2 ) of the bottom 75. The recess 91 has an inner cylindrical surface 92 that is coaxial with the axis (center line) of the pilot case 73. A valve chamber 93 for the pilot valve 71 and the fail-safe valve 111 is formed inside the inner cylindrical surface 92. A pilot valve seat portion 74 is formed in the center of the bottom of the recess 91, on which the valve body 82 of the pilot valve 71 is seated and releasably seated. A recess 94 (introduction passage) of a certain depth (axial length) is formed in the center of the pilot valve seat portion 74. In other words, the pilot valve seat portion 74 is formed on the periphery of the opening of the recess 94.

[0022] Meanwhile, the pilot case 73 has an annular groove 95 (annular recess) formed inside a seat portion 79 on which the back pressure introduction valve 81 is seated. The cross section of the annular groove 95 taken along the axial plane of the pilot case 73 is formed in a substantially right-angled triangle. The annular groove 95 is formed in the pilot case 73 and communicates with the recess 94 via a plurality of passages 96 that are evenly spaced around the axis of the pilot case 73. The passages 96 are inclined (60° in this embodiment) with respect to the axis of the pilot case 73 and are provided so as to be perpendicular to the inner peripheral surface (reference numeral omitted) of the annular groove 95.

[0023] The recess 94 is connected to the annular flow passage 21 via an axial hole 97 (introduction passage) of the pin portion 85. An introductory orifice 98 is formed at one end of the axial hole 97 (the tip of the pin portion 85) to introduce working fluid (hydraulic pressure) from the annular flow passage 21 to the back pressure chamber 72. The working fluid in the annular flow passage 21 is introduced into the back pressure chamber 72 via an introduction passage, that is, the introduction orifice 98, the axial hole 97, the recess 94, the passage 96, the annular groove 95, and the back pressure introduction valve 81. A plurality of orifices 99 that constantly connect the back pressure chamber 72 and the annular flow passage 21 are formed on the outer circumferential edge of the back pressure introduction valve 81.

[0024] The valve element 82 of the pilot valve 71 is formed in a substantially cylindrical shape with one end formed in a tapered shape. An outer flange-shaped spring bearing portion 83 is formed on the other side of the valve element 82. The valve element 82 is elastically supported by a pilot spring 112, a fail-safe spring 113, and a fail-safe disk 114 so as to be axially movable opposite the pilot valve seat portion 74. The pilot spring 112 and the fail-safe spring 113 can be formed as a single nonlinear spring.

[0025] On the other side (the "right side" in FIG. 2 ) of the pilot case 73, there are formed an inner cylindrical surface 92 (recess 91), an inner cylindrical surface 100, and an inner cylindrical surface 102, whose inner diameters increase stepwise from one side to the other side (opening side). The inner cylindrical surfaces 92, 100, and 102 are arranged coaxially. The inner cylindrical surface 102 is the inner circumferential surface of a cylindrical portion 101 provided on the other end face of the pilot case 73.

[0026] The outer peripheral edge of the pilot spring 112 is supported by a step (reference numeral omitted) between the inner cylindrical surface 92 and the inner cylindrical surface 100. On the other hand, the fail-safe spring 113, the fail-safe disk 114, and the washer 115 housed inside the inner cylindrical surface 102 are supported by a step (reference numeral omitted) between the inner cylindrical surface 100 and the inner cylindrical surface 102. The fail-safe spring 113, the fail-safe disk 114, and the washer 115 housed inside the inner cylindrical surface 102 are fixed to the other side of the pilot case 73 by a cap 117 attached to the outer cylindrical surface 103, which is the outer peripheral surface of the cylindrical portion 101.

[0027] A plurality of notches 118 are formed in the cap 117. The notches 118 connect the valve chamber 93 to an annular flow passage 37 formed on the outer periphery of the cap 117. The valve chamber 93 connects to the reservoir 4 via the axial hole 116 of the washer 115, the notches 118 of the cap 117, the flow passage 37, a passage 33 formed between the width across flats 89 of the pilot case 73 and the cylindrical portion 123 of the yoke 122, and an annular flow passage 35 formed on the inner periphery of the valve case 25 and on the outer periphery of the main body 52.

[0028] The pilot case 73 and the yoke 122 are fastened together by rotating a threaded portion 76 (external thread) formed on the outer peripheral surface of the pilot case 73 and a threaded portion 124 (internal thread) formed on the inner peripheral surface of the cylindrical portion 123 of the yoke 122 relative to each other in the fastening direction. As a result, an axial force is applied to downstream valve parts between the pilot case 73 and the yoke 122, i.e., the pilot spring 112, the failsafe spring 113, the failsafe disk 114, the washer 115, the cap 117, and the like.

[0029] Meanwhile, a coil 126, a core 127, a core 128, a plunger 129, and a hollow operating rod 130 are assembled to the other side of the yoke 122 (the "right side" in FIG. 2). The operating rod 130 is formed integrally with the plunger 129, but may be a separate body. A valve body 82 of the pilot valve 71 is fixed to one end of the operating rod 130. A spacer 131 and a cover 132 are inserted into the other end of the yoke 122, and an axial force is applied to the internal components of the solenoid within the yoke 122 by plastically working (caulking) the other peripheral edge of the yoke 122.

[0030] The yoke 122 has a cylindrical portion 123 on one side fitted into the large inner diameter portion 26 that opens to the other side of the valve case 25. The yoke 122 is axially positioned with respect to the valve case 25 when one end face of the cylindrical portion 123 abuts against a step portion 27 (the bottom of the large inner diameter portion 26) of the valve case 25. A seal ring 134 attached to the outer peripheral surface of the cylindrical portion 123 of the yoke 122 provides a seal between the valve case 25 and the cylindrical portion 123 of the yoke 122. The valve case 25 and the yoke 122 are fastened together by tightening a nut 135 attached to the valve case 25 and compressing a retaining ring 137 attached to an annular groove (reference number omitted) in the yoke 122. The valve case 25 and the yoke 122 are sealed together by a seal ring 29 attached to the outer peripheral surface of the valve case 25.

[0031] When the coil 126 is not energized, the valve element 82 is urged in a direction away from the pilot valve seat portion 74 (to the right in FIG. 2 ) by the spring force of the fail-safe spring 113. As a result, the spring receiving portion 83 of the valve element 82 abuts (seats) on the fail-safe disk 114, thereby closing the fail-safe valve 111. At this time, the pilot spring 112 is separated from a step (reference number omitted) between the inner cylindrical surface 92 and the inner cylindrical surface 100 of the pilot case 73.

[0032] Furthermore, when the coil 126 is energized, the operating rod 130 is urged in the seating direction of the valve element 82 (to the left in FIG. 2 ) against the spring forces of the pilot spring 142 and the fail-safe spring 113. As a result, the pilot spring 142 abuts against a step (reference numeral omitted) between the inner cylindrical surfaces 92 and 100 of the pilot case 73, and the valve element 82 seats on the pilot valve seat 74. The valve-opening pressure of the valve element 82 is controlled by changing the value of the current passed through the coil 126. Note that in the soft mode, in which the value of the current passed through the coil 126 is small, the spring force of the pilot spring 142 and the thrust of the plunger 129 are balanced, and the valve element 82 is spaced apart from the pilot valve seat 74 (see FIG. 2 ).

[0033] Next, the operation of the shock absorber 1 will be described. The shock absorber 1 is provided between the sprung part (vehicle body) and the unsprung part (wheels) of a vehicle suspension device (not shown). In normal operation, the on-vehicle controller adjusts the opening pressure of the pilot valve 71 by controlling the current flowing to the coil 126 of the solenoid 121 of the damping force adjusting mechanism 31.

[0034] During the extension stroke of the piston rod 6, the pressure rises in the cylinder upper chamber 2A, causing the check valve 13 of the piston 5 to close, and before the disc valve 14 opens, the hydraulic fluid in the cylinder upper chamber 2A is pressurized. The pressurized hydraulic fluid passes through the passage 22 and the annular flow path 21 and is introduced into the damping force adjustment mechanism 31 from the connection port 23 of the separator tube 20 (connecting pipe). At this time, the hydraulic fluid equivalent to the amount of hydraulic fluid displaced by the piston 5 flows from the reservoir 4 into the cylinder lower chamber 2B, opening the check valve 17 of the base valve 10. When the pressure in the cylinder upper chamber 2A reaches the opening pressure of the disc valve 14 of the piston 5 and the disc valve 14 opens, the pressure in the cylinder upper chamber 2A is relieved to the cylinder lower chamber 2B. This prevents an excessive pressure rise in the cylinder upper chamber 2A.

[0035] On the other hand, during the compression stroke of the piston rod 6, the pressure rises in the cylinder lower chamber 2B, causing the check valve 13 in the piston 5 to open and the check valve 17 in the passage 15 of the base valve 10 to close. Before the disc valve 18 opens, the hydraulic fluid in the piston lower chamber 2B flows into the cylinder upper chamber 2A, and the hydraulic fluid equivalent to the volume of the hydraulic fluid that has entered the cylinder 2 by the piston rod 6 is introduced from the cylinder upper chamber 2A through the passage 22, the annular flow path 21, and the connection port 23 of the separator tube 20 (connecting pipe) into the damping force adjustment mechanism 31. When the pressure in the cylinder lower chamber 2B reaches the opening pressure of the disc valve 18 and the disc valve 18 opens, the pressure in the cylinder lower chamber 2B is relieved to the reservoir 4. This makes it possible to prevent an excessive pressure rise in the cylinder lower chamber 2B.

[0036] The hydraulic fluid introduced into the damping force adjusting mechanism 31 flows into the annular groove 95 via an introduction orifice 98 formed in the pin portion 85 (pin member), an axial hole 97 of the pin portion 85, a recess 94 in the pilot case 73, and a passage 96, and when the pressure in the opening direction of the back pressure introduction valve 81 (the pressure inside the annular groove 95) exceeds a set pressure, the back pressure introduction valve 81 opens and the hydraulic fluid is introduced into the back pressure chamber 72. Before the main valve 51 opens (when the piston speed is in the low speed range), the hydraulic fluid introduced into the damping force adjusting mechanism 31 passes through the introduction orifice 98, the axial hole 97, and the recess 94, opening the valve element 82 (pilot valve 71), and flows into the valve chamber 93 in the pilot case 73.

[0037] The hydraulic fluid that has flowed into the valve chamber 93 flows through the gap between the valve element 82 and the failsafe disk 114, the axial hole 116 of the washer 115, the notch 118 of the cap 117, the flow path 37, the passage 33 between the pilot case 73 and the yoke 112, the annular flow path 35, and the outer periphery of the main body 52 to the reservoir 4. When the piston speed increases and the pressure in the annular recess 55, which is connected to the connection port 23 via a passage 59 in the main body 52, reaches the valve opening pressure of the main valve 51, the main valve 51 opens and the hydraulic fluid in the annular flow path 21 flows through the connection port 23, the passage 59, the annular recess 55, and the main valve 51 to the reservoir 4.

[0038] In this way, during both the extension stroke and compression stroke of the piston rod 6, the damping force adjustment mechanism 31 generates a damping force by the valve-opening pressure of the inlet orifice 98 and the pilot valve 71 (valve element 82) before the main valve 51 opens (when the piston is moving at a low speed), and generates a damping force according to the opening degree of the main valve 51 after the main valve 51 opens (when the piston is moving at a medium speed). The damping force can be directly controlled regardless of the piston speed by adjusting the valve-opening pressure of the pilot valve 71 by controlling the supply of current to the coil 126. Furthermore, by adjusting the valve-opening pressure of the pilot valve 71 by controlling the supply of current to the coil 126, the back-pressure introduction valve 81 is opened, thereby adjusting the pressure of the hydraulic fluid introduced into the back-pressure chamber 72, and the damping force characteristics can be adjusted over a wide range.

[0039] Furthermore, if the thrust of the plunger 129 is lost due to a failure such as a broken coil 126 or a malfunction of the on-board controller, the spring force of the fail-safe spring 113 will move the valve element 82 backward, opening the pilot valve 71 and causing the spring receiving portion 83 of the valve element 82 to abut against the fail-safe disk 114, thereby blocking communication between the valve chamber 93 and the annular flow path 35 inside the valve case 25.

[0040] As a result, the flow of hydraulic fluid from the annular flow path 21 through the inlet orifice 98, the axial hole 97 of the pin portion 85, the recess 94, the valve chamber 93, the axial hole 116 of the washer 115, the notch 118 of the cap 117, the flow path 37, the passage 33, the annular flow path 35, and the outer periphery of the main body 52 to the reservoir 4 is controlled by the fail-safe valve 111. Here, the desired damping force can be obtained by varying the valve opening pressure of the fail-safe disk 114. At the same time, the internal pressure of the back pressure chamber 72, i.e., the valve opening pressure of the main valve 51, can be adjusted, allowing an appropriate damping force to be obtained even in the event of a failure.

[0041] In conventional shock absorbers, the internal pressure of the main valve's valve chamber acts as a bending load on the main body. Furthermore, conventional shock absorbers are constructed with a pilot case, which forms the main valve's backpressure chamber on one side, and a pilot valve seat on which the pilot valve sits on the other side, which are separate components. Because the pilot case bears the bending load acting on the main body, it was necessary to make the bottom wall thicker (longer in the axial direction). This resulted in a longer axial length for the damping force adjustment mechanism, which in turn led to an increase in the shock absorber's size.

[0042] In contrast to this, in this embodiment, a back pressure chamber 72 is formed on one side of the pilot case 73, in which internal pressure acts in a direction to close the main valve 51, and a pilot valve seat portion 74 is formed on the other side of the pilot case 73, in which the valve body 82 of the pilot valve 71 that adjusts the internal pressure of the back pressure chamber 72 is seated and releasably seated. In other words, the pilot case and pilot body in a conventional shock absorber are integrated into the pilot case 73 in the shock absorber 1 of this embodiment, so that the axial length of the damping force adjusting mechanism 31 can be shortened by the thickness (axial length) of the bottom part of the pilot case in a conventional shock absorber that received the main body. This makes it possible to reduce the size of the shock absorber 1, and improves the degree of freedom in designing a vehicle suspension device. In addition, in this embodiment, the pilot case and pilot body are integrally formed, which is required in conventional shock absorbers. This eliminates the need for a seal ring to seal between the pilot case and pilot body and the need to machine an annular groove to fit the seal ring. This reduces the number of parts and the number of steps (machining and assembly), thereby reducing manufacturing costs. Furthermore, eliminating the seal ring to seal between the pilot case and pilot body improves the reliability of the damping force adjusting mechanism 31 and, ultimately, the shock absorber. [Explanation of symbols]

[0043] 1 shock absorber, 2 cylinder, 3 outer cylinder, 4 reservoir, 5 piston, 20 separator tube (connecting pipe), 31 damping force adjustment mechanism, 51 main valve, 52 main body (seat member), 71 pilot valve, 72 back pressure chamber, 73 pilot case, 74 pilot valve seat portion

Claims

1. a cylinder filled with hydraulic fluid; a piston inserted into the cylinder to divide the interior of the cylinder into two chambers; an outer cylinder provided on the outer periphery of the cylinder; a reservoir formed between the cylinder and the outer tube and containing a hydraulic fluid and a gas; a connecting pipe provided between the cylinder and the outer cylinder and communicating with the inside of the cylinder; a damping force generating mechanism housed in a valve case provided outside the outer cylinder and connected to the connecting pipe; A shock absorber comprising: The damping force generating mechanism includes: A main valve that generates damping force; a seat member against which the main valve abuts; a pilot case having a back pressure chamber formed on one side thereof, in which internal pressure acts on the main valve in a valve closing direction, and a pilot valve seat portion formed on the other side thereof, on which a pilot valve for adjusting the internal pressure of the back pressure chamber is seated; and a pin portion formed integrally with the pilot case is inserted into the seat member and the main valve, and a fastening member that fastens the seat member, the main valve, and the pilot case together is provided on the pin portion.

2. 2. The shock absorber according to claim 1, A shock absorber characterized in that an inlet orifice for introducing hydraulic fluid into the back pressure chamber is formed in the pin portion.

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