Buffer

Abstract

To provide a buffer which enables easy fitting control between a sleeve and a valve spool and can secure slidability of the valve spool.SOLUTION: In a buffer, a sleeve 111 (a second member) is fixed to a piston bolt body 12 (a first member) by press-fitting parts 125, 126 which are provided spaced apart from each other in an axial direction and a slide part 128 where an inner peripheral surface 112 (a hole) of a first cylindrical part 114 of the sleeve 111 and a slide shaft part 32 of a valve spool 31 slidably contact with each other is arranged so as not to overlap with the press-fitting parts 125, 126 in the axial direction. The structure can secure a fitting dimension allowable tolerance between the inner peripheral surface 112 of the first cylindrical part 114 of the sleeve 111 and the slide shaft part 32 of the valve spool 31 in the slide part 128 and secure slidability between the sleeve 111 and the valve spool 31 even when an inner diameter of the sleeve 111 is reduced in the press-fitting parts 125, 126.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a shock absorber that adjusts damping force by controlling the flow of hydraulic fluid relative to the stroke of a piston rod. [Background technology]

[0002] Patent Document 1 discloses a piston-embedded damping force adjustable shock absorber 1 (hereinafter referred to as a "conventional shock absorber") in which a pilot valve 131 controls the flow of working fluid in a common passage 101 formed in a piston bolt 11. In a conventional shock absorber, in a manufacturing process, a sleeve 111 in which an axial passage 72 is formed is fixed (joined) by brazing to a sleeve press-fit hole 15 formed in a body of the piston bolt 11 (hereinafter referred to as a "piston bolt body"). That is, a brazing material melted by heating enters between the sleeve 111 and the sleeve press-fit hole 15 formed in the piston bolt body, and the piston bolt body and the sleeve are fixed together by cooling in this state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-152580 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional shock absorbers, when the piston bolt body and the sleeve are brazed and then cooled, the inner diameter of the sleeve tends to shrink. As a result, it becomes difficult to manage the fit of the sliding part between the sleeve and the valve spool, and there is a problem that the sliding performance between the sleeve and the valve spool is reduced. Therefore, in conventional shock absorbers, the sliding performance between the sleeve and the valve spool is ensured by machining the inner diameter of the sleeve after the piston bolt body and the sleeve are brazed, but this leads to problems such as increased manufacturing costs and reduced quality due to burrs remaining.

[0005] An object of the present invention is to provide a shock absorber in which the fit of the sliding portion between the sleeve and the valve spool can be easily controlled and the slidability of the valve spool can be ensured. [Means for solving the problem]

[0006] The shock absorber of the present invention includes a cylinder in which a working fluid is sealed, a piston slidably fitted within the cylinder and dividing the interior of the cylinder into two chambers, a piston rod having one end connected to the piston and the other end extending from the cylinder to the outside, an extension side passage and a compression side passage provided in the piston, a piston bolt inserted into a shaft hole of the piston, an extension side main valve provided in the extension side passage, an extension side back pressure chamber that adjusts the valve opening pressure of the extension side main valve, a compression side main valve provided in the compression side passage, a compression side back pressure chamber that adjusts the valve opening pressure of the compression side main valve, a common passage that communicates the extension side back pressure chamber and the compression side back pressure chamber, and a valve mechanism that controls the flow of the working fluid in the common passage. a pilot valve for opening the piston bolt, an actuator for controlling the valve opening pressure of the pilot valve, an extension side exhaust passage connecting a passage of the common passage closer to the compression side back pressure chamber than the pilot valve with the compression side passage, and a compression side exhaust passage connecting a passage of the common passage closer to the extension side back pressure chamber than the pilot valve with the extension side passage, wherein a second valve portion is provided on the other axial end side of a valve body of the pilot valve for restricting the flow of working fluid between the second valve seat formed in the piston bolt and the second valve portion when the actuator is energized, and the piston bolt is composed of a first member and a second member, and the second member has a hole into which a shaft member is slidably inserted, and is partially press-fitted into the first member. Effect of the Invention

[0007] According to the present invention, it is possible to provide a shock absorber in which the fit of the sliding portion between the sleeve and the valve spool can be easily controlled and the slidability of the valve spool can be ensured. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of a portion of the shock absorber according to the embodiment. [Diagram 2] FIG. 2 is an enlarged view of a main part in FIG. [Diagram 3] FIG. 3 is a further enlarged view of a portion of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will now be described with reference to the accompanying drawings. For convenience, the up-down direction in Fig. 1 is referred to as the "up-down direction" as it is. Although a mono-tube type damping force adjustable shock absorber will be described below as an example, the shock absorber 1 according to this embodiment can also be applied to a twin-tube type damping force adjustable shock absorber having a reservoir.

[0010] As shown in FIG. 1, the shock absorber 1 has a cylinder 2 filled with a working fluid, and a piston 3 slidably fitted in the cylinder 2 to divide the inside of the cylinder 2 into an upper cylinder chamber 2A and a lower cylinder chamber 2B. The piston 3 has an extension-side passage 5 whose upper end opens into the upper cylinder chamber 2A, and a compression-side passage 6 whose lower end opens into the lower cylinder chamber 2B. The shock absorber 1 has a piston rod 4 whose one end is connected to the piston 3 and whose other end extends outward from the cylinder 2. A free piston (not shown) capable of moving up and down within the cylinder 2 is provided within the cylinder 2. The free piston divides the inside of the cylinder 2 into a lower cylinder chamber 2B on the piston 3 side (upper side) and a gas chamber (not shown) on the bottom side (lower side).

[0011] The shock absorber 1 has a damping force adjustment unit that varies the damping force characteristics by controlling the flow of hydraulic oil (working fluid) that accompanies the movement of the piston 3. The damping force adjustment unit has a valve mechanism 10 and a solenoid 170. The valve mechanism 10 has an extension side valve mechanism 41 that controls the flow of hydraulic oil in the extension side passage 5, and a compression side valve mechanism 71 that controls the flow of hydraulic oil in the compression side passage 6. The damping force adjustment unit also has a piston bolt 11 whose shaft portion 13 is inserted into a shaft hole 7 of the piston 3.

[0012] 2, the extension side valve mechanism 41 has a cylindrical extension side pilot case 42 with a bottom. The extension side pilot case 42 has a bottom 43 attached to the shaft portion 13 of the piston bolt body 12 of the piston bolt 11, and a cylindrical portion 44 that opens on the piston 3 side. The extension side valve mechanism 41 has an extension side main valve 45 provided on the piston 3 side of the extension side pilot case 42. The extension side valve mechanism 41 has an extension side back pressure chamber 46 formed between the extension side pilot case 42 and the back surface of the extension side main valve 45.

[0013] The extension side valve mechanism 41 has a seat portion 59 formed on the outer circumferential side of the lower end surface of the piston 3, against which the extension side main valve 45 can be seated and released. The pressure in the extension side back pressure chamber 46 acts on the extension side main valve 45 in the valve closing direction. The extension side main valve 45 is a packing valve in which an annular packing 47 made of an elastic body is in contact with the inner circumferential surface of the cylindrical portion 44 of the extension side pilot case 42 over the entire circumference.

[0014] The extension side back pressure chamber 46 is connected to the cylinder lower chamber 2B via a passage 48 formed in a bottom portion 53 of the extension side pilot case 42 and a sub-valve 49. The sub-valve 49 opens when the pressure in the extension side back pressure chamber 46 reaches a predetermined pressure, and applies resistance to the flow of hydraulic oil from the extension side back pressure chamber 46 to the cylinder lower chamber 2B. The extension side back pressure chamber 46 is connected to a first pressure receiving chamber 50 formed between the extension side pilot case 42 and the sub-valve 49 via the passage 48. The first pressure receiving chamber 50 is divided into a sector shape by a plurality of annular first seats 51 provided on the lower end surface of the extension side pilot case 42 (the surface opposite to the extension side main valve 45 side). The passage 48 opens to the inside of the first seat 51.

[0015] The extension side pilot case 42 is provided with a back pressure introduction passage 52 through which hydraulic oil flows from the cylinder lower chamber 2B to the extension side back pressure chamber 46 during the compression stroke of the piston rod 4. An annular seat portion 53 is provided on the upper end surface (the surface on the extension side main valve 45 side) of the extension side pilot case 42. The seat portion 53 defines an annular pressure receiving chamber 54 formed on the outer periphery of the inner periphery of the bottom portion 43. A second pressure receiving chamber 55 isolated from the first pressure receiving chamber 50 is provided on the lower end surface of the extension side pilot case 42. The back pressure introduction passage 52 opens into the second pressure receiving chamber 55. The second pressure receiving chamber 55 is defined by a second seat portion 56.

[0016] The second seat portion 56 extends in an arc shape between the pair of adjacent first pressure receiving chambers 50. The second seat portion 56 is provided with a first orifice 57 that communicates the second pressure receiving chamber 55 and the cylinder lower chamber 2B. As a result, an extension side communication passage that communicates the cylinder lower chamber 2B and the extension side back pressure chamber 46 is formed in the extension side valve mechanism 41. The extension side communication passage introduces the hydraulic oil from the cylinder lower chamber 2B into the extension side back pressure chamber 46 via the first orifice 57, the second pressure receiving chamber 55, the back pressure introduction passage 52, the pressure receiving chamber 54, and the check valve 58 during the compression stroke of the piston rod 4.

[0017] On the other hand, the compression side valve mechanism 71 has a cylindrical compression side pilot case 72 with a bottom. The compression side pilot case 72 has a bottom 73 attached to the shaft portion 13 of the piston bolt 11, and a cylindrical portion 74 that opens on the piston 3 side. The compression side valve mechanism 71 has a compression side main valve 75 provided on the piston 3 side of the compression side pilot case 72. The compression side valve mechanism 71 has a compression side back pressure chamber 76 formed between the compression side pilot case 72 and the back surface of the compression side main valve 75.

[0018] The compression side valve mechanism 71 is formed on the outer circumferential side of the upper end surface of the piston 3, and has a seat portion 89 against which the compression side main valve 75 is able to seat and unseat. The pressure in the compression side back pressure chamber 76 acts on the compression side main valve 75 in the valve closing direction. The compression side main valve 75 is a packing valve in which annular packing 77 made of an elastic body is in contact with the inner circumferential surface of the cylindrical portion 74 of the compression side pilot case 72 over the entire circumference.

[0019] The compression back pressure chamber 76 is connected to the cylinder upper chamber 2A via a passage 78 formed in the bottom 73 of the compression pilot case 72 and a sub-valve 79. The sub-valve 79 opens when the pressure in the compression back pressure chamber 76 reaches a predetermined pressure, and applies resistance to the flow of hydraulic oil from the compression back pressure chamber 76 to the cylinder upper chamber 2A. The compression back pressure chamber 76 is connected to a first pressure receiving chamber 80 formed between the compression pilot case 72 and the sub-valve 79 via the passage 78. The first pressure receiving chamber 80 is partitioned into a sector shape by a plurality of annular first seat portions 81 provided on the upper end surface of the compression pilot case 72 (the surface opposite to the compression main valve 75 side). The passage 78 opens to the inside of the first seat portion 81.

[0020] The compression side pilot case 72 is provided with a back pressure introduction passage 82 through which hydraulic oil flows from the cylinder upper chamber 2A to the compression side back pressure chamber 76 during the extension stroke of the piston rod 4. An annular seat portion 83 is provided on the lower end surface of the compression side pilot case 72 (the surface on the compression side main valve 75 side). The seat portion 83 defines an annular pressure receiving chamber 84 formed on the outer periphery of the inner periphery of the bottom portion 73. A second pressure receiving chamber 85 isolated from the first pressure receiving chamber 80 is provided on the upper end surface of the compression side pilot case 72. The back pressure introduction passage 82 opens into the second pressure receiving chamber 85. The second pressure receiving chamber 85 is defined by a second seat portion 86.

[0021] The second seat portion 86 extends in an arc shape between the pair of adjacent first pressure receiving chambers 80. A first orifice 87 that communicates the second pressure receiving chamber 85 and the cylinder upper chamber 2A is provided in the second seat portion 86. As a result, a compression side communicating passage that communicates the cylinder upper chamber 2A and the compression side back pressure chamber 76 is formed in the compression side valve mechanism 71. The compression side communicating passage introduces hydraulic oil from the cylinder upper chamber 2A into the compression side back pressure chamber 76 via the first orifice 87, the second pressure receiving chamber 85, the back pressure introduction passage 82, the pressure receiving chamber 84, and the check valve 88 during the extension stroke of the piston rod 4.

[0022] In addition, the valve parts that constitute the extension side valve mechanism 41 and the compression side valve mechanism 71 are pressurized between the head 14 of the piston bolt 11 and the washer 9 by tightening the nut 8 screwed onto the lower end of the shaft portion 13 of the piston bolt 11, generating axial force.

[0023] As shown in FIG. 2, the piston bolt 11 has a piston bolt body 12 (first member) and a sleeve 111 (second member) press-fitted into a spool hole 15 formed in the piston bolt body 12. A common passage 101 is formed in the piston bolt 11. The common passage 101 has an axial passage 102 formed in the inner lower part of a first cylindrical portion 114 (described later) of the sleeve 111, an axial passage 103 formed in a portion of the spool hole 15 below the lower end of the sleeve 111, and an axial passage 104 whose upper end opens into the spool hole 15 (axial passage 103). The inner diameter of the common passage 101 is largest for the axial passage 103, and decreases in order of the axial passage 102 and the axial passage 104.

[0024] The extension-side back pressure chamber 46 is connected to the extension-side passage 5 via the compression-side exhaust passage. The compression-side exhaust passage connects the extension-side back pressure chamber 46 to the extension-side passage 5 via a notch 60 formed in the check valve 58, a radial passage 105 formed in the shaft portion 13 of the piston bolt body 12, an axial passage 104, a radial passage 106 formed in the shaft portion 13 of the piston bolt body 12, and a notch 63 formed in the annular seat portion 62. The annular seat portion 62 is formed on the inner circumferential side of the piston 3 relative to the seat portion 59 and the opening of the extension-side passage 5. A compression-side check valve 61 that allows the flow of hydraulic oil from the extension-side back pressure chamber 46 side of the compression-side exhaust passage to the extension-side passage 5 is in releasable contact with the annular seat portion 62.

[0025] The compression back pressure chamber 76 is connected to the compression passage 6 via the extension discharge passage. The extension discharge passage connects the compression back pressure chamber 76 to the compression passage 6 via a notch 90 formed in the check valve 88, a passage 16 (groove extending in the axial direction) formed in the shaft portion 13 of the piston bolt body 12, and a notch 93 formed in the seat portion 92. The annular seat portion 92 is formed on the piston 3 on the inner circumferential side of the seat portion 89 and the opening of the compression passage 6. An extension check valve 91, which allows the flow of hydraulic oil from the compression back pressure chamber 76 side of the extension discharge passage to the compression passage 6, is in releasable contact with the annular seat portion 92.

[0026] The common passage 101 communicates between the compression side exhaust passage and the extension side exhaust passage. In other words, the common passage 101 communicates between the extension side back pressure chamber 46 and the compression side back pressure chamber 76. A plurality of ports 113 (only two are shown in FIG. 2 ) are formed in the side wall of the sleeve 111 (second member) to communicate between the outside and inside of the sleeve 111 of the passage in the common passage 101 closer to the compression side back pressure chamber 76 than the pilot valve 131. In other words, the axial passage 102 formed in the sleeve 111 is communicated with the radial passage 107 formed in the shaft portion 13 of the piston bolt body 12 by the ports 113.

[0027] The flow of hydraulic oil in the common passage 101 is controlled by a pilot valve 131. The pilot valve 131 has a valve spool 31 (shaft member) supported by the sleeve 111 so as to be axially movable. The valve spool 31 is formed of a solid shaft, and has a sliding shaft portion 32 slidably inserted into an inner circumferential surface 112 (hole) of a first cylindrical portion 114 (described later) of the sleeve 111, a head portion 35 provided at the upper end portion, a cylindrical valve element 33 formed at the lower end portion, and a connecting shaft portion 34 connecting the sliding shaft portion 32 and the valve element 33.

[0028] The pilot valve 131 has a first valve seat 132 formed on the periphery of the opening of the axial passage 102 in the sleeve 111, and a first valve portion 133 formed on the periphery of the upper end of the valve body 33. When the solenoid 170 (actuator) is not energized, the pilot valve 131 restricts the flow of hydraulic oil in the common passage 101 by having the first valve portion 133 seated (fitted) on the first valve seat 132. The pilot valve 131 also has a second valve seat 134 formed on the periphery of the opening of the axial passage 104 at the bottom of the spool hole 15, and a second valve portion 135 formed on the periphery of the lower end of the valve body 33. When the solenoid 170 is energized, the pilot valve 131 restricts the flow of hydraulic oil in the common passage 101 by having the second valve portion 135 seated on the second valve seat 134.

[0029] A first chamber 136 is formed on the outer periphery of the head 35 of the valve spool 31 inside the head 14 of the piston bolt body 11. An outer flange-shaped spring receiver 37 is formed on the peripheral edge of the lower end of the head 35. The inner periphery of a spring disc 143 that urges the valve spool 31 in the valve opening direction (the "upward direction" in FIG. 2) of the pilot valve 131 (second valve portion 135) is connected to the spring receiver 37. When the solenoid 170 is not energized, the head 35 of the valve spool 31 is brought into contact with (pressed against) the lower end surface of the operating rod 171 of the solenoid 170 by the urging force of the spring disc 143.

[0030] When the control current to the coil 174 of the solenoid 170 is 0 A (at the time of failure), the valve spool 31 moves in the valve opening direction of the pilot valve 131 by the biasing force of the spring disc 143, and the first valve portion 133 of the valve body 33 is seated (fitted) on the first valve seat 132. As a result, an orifice (not shown) that communicates between the axial passages 103, 102 is formed between the valve body 33 and the sleeve 111 (axial passage 102).

[0031] A cylindrical cap 151 with a bottom that opens upward is attached to the outer periphery of the head 14 of the piston bolt 11. A ring-shaped seal member 152 seals the gap between the cap 151 and the head 14 of the piston bolt 11, forming an annular second chamber 153 between the cap 151 and the piston bolt 11. The cap 151 has an insertion hole 154 through which the shaft 13 of the piston bolt 11 is inserted. The cap 151 has multiple notches 155 (only two are shown in FIG. 2 ) formed in the insertion hole 154. The notches 155 communicate with the passage 16 formed in the shaft 13.

[0032] The second chamber 153 is provided with a check valve 156 (spool back pressure relief valve) that allows hydraulic oil to flow from the first chamber 136 to the second chamber 153 via a passage 159. The outer peripheral edge of the check valve 156 is movably abutted against an annular seat portion 157 formed in the head 14 of the piston bolt 11. The inner peripheral edge of a retainer 158 that regulates the opening degree of the check valve 156 is formed with a plurality of notches 160 (only two are shown in FIG. 2 ) that communicate the second chamber 153 with the compression back pressure chamber 76 via notches 155, the passage 16, and notches 90 formed in the check valve 88.

[0033] 1, the solenoid 170 has an operating rod 171, cores 172 and 173, a coil 174, a cylindrical yoke 175 with a bottom, and a plunger 176 fixed to the outer periphery of the operating rod 171. The operating rod 171 is guided in the vertical direction (axial direction) by a bush 178 attached inside a core cap 177. The operating rod 171 has an inner rod passage 179. The lower end portion (one end) of the piston rod 4 is connected to the yoke 175.

[0034] The gap between the core 172 and the yoke 175 is sealed by a seal member 180. As a result, an annular passage 181 (see FIG. 2) is formed between the piston bolt 11, the core 172, and the yoke 175. The annular passage 181 is connected to the cylinder upper chamber 2A by a passage 182 formed in the head 14 of the piston bolt 11. A spool back pressure chamber 183 is formed in the center of the core 172 of the solenoid 170. The spool back pressure chamber 183 is connected to a rod back pressure chamber 185 via a notch 184 (see FIG. 2) formed in the operating rod 171 and the rod internal passage 179.

[0035] Next, the flow of hydraulic oil in the shock absorber 1 will be described. During the extension stroke, the hydraulic fluid in the cylinder upper chamber 2A is introduced into the extension back pressure chamber 46 via the extension passage 5, the notch 63 formed in the seat portion 62, the radial passage 106, the axial passage 104, the radial passage 105, and the notch 60 formed in the check valve 58. During the extension stroke, the hydraulic oil in the cylinder upper chamber 2A is introduced into the compression back pressure chamber 76 via the first orifice 87 formed in the second seat portion 86 of the compression pilot case 72, the second pressure receiving chamber 85, the back pressure introduction passage 82, and the check valve 88. This prevents the compression main valve 75 from opening due to the pressure in the cylinder upper chamber 2A during the extension stroke.

[0036] Here, the compression side back pressure chamber 76 is connected to the cylinder lower chamber 2B via the notch 90 formed in the check valve 88, the passage 16 (groove) formed in the shaft portion 13 of the piston bolt body 12, the notch 93 formed in the seat portion 92, and the compression side passage 6, so that before the extension side main valve 45 opens, that is, in the low piston speed region, a damping force due to the orifice characteristics of the notch 93 (orifice) and the valve characteristics of the extension side check valve 91 are obtained.

[0037] On the other hand, during the compression stroke, the hydraulic oil in the cylinder lower chamber 2B is introduced into the compression back pressure chamber 76 via the compression passage 6, the notch 93 formed in the seat portion 92, the passage 16, and the notch 90 formed in the check valve 88. Also, during the compression stroke, the hydraulic fluid in the cylinder lower chamber 2B is introduced into the extension back pressure chamber 46 via the first orifice 57 formed in the second seat portion 56 of the extension pilot case 42, the second pressure receiving chamber 55, the back pressure introduction passage 52, and the check valve 58. This makes it possible to prevent the extension main valve 45 from opening due to the pressure in the cylinder lower chamber 2B during the compression stroke.

[0038] Here, the extension side back pressure chamber 46 is connected to the cylinder upper chamber 2A via the notch 60 formed in the check valve 58, the radial passage 105, the axial passage 104, the radial passage 106, the notch 63 formed in the seat portion 62, and the extension side passage 5. Therefore, before the compression side main valve 75 opens, that is, in the low piston speed region, a damping force due to the orifice characteristics of the notch 63 (orifice) and the valve characteristics of the compression side check valve 61 are obtained.

[0039] Next, the main part of the embodiment will be described with reference to FIG. The sleeve 111 has a first cylindrical portion 114 and a second cylindrical portion 116 that is continuous with the upper end of the first cylindrical portion 114 via an expanded diameter portion 115. The second cylindrical portion 116 has an inner diameter larger than the inner diameter of the first cylindrical portion and an outer diameter larger than the outer diameter of the first cylindrical portion 114. An outer flange-shaped flange portion 117 (protruding portion) is formed at the upper end (one end) of the sleeve 111. The inner peripheral end of the flange portion 117 is continuous with the upper end of the second cylindrical portion 116 via an R portion 118. A small outer diameter portion 119 that has an outer diameter smaller than the outer diameter of the first cylindrical portion 114 is formed at the tip of the sleeve 111.

[0040] The inner diameter of the first cylindrical portion 114 is set to fit with the sliding shaft portion 32 of the valve spool 31 (shaft member) so that the sliding shaft portion 32 of the valve spool 31 can slide smoothly. A pair of upper and lower annular grooves 36, 36 (hydraulic oil filled grooves) are formed on the outer circumferential surface of the sliding shaft portion 32 of the valve spool 31 to ensure slidability with the inner circumferential surface 112 of the first cylindrical portion 114 of the sleeve 111.

[0041] On the other hand, the piston bolt body 12 has a recess 18 formed in the center of the end face 17 of the head 14 (the bottom surface of the first chamber 136). The recess 18 has an inner cylindrical surface 19 into which an outer circumferential surface 120 of the flange portion 117 of the sleeve 111 is fitted. The inner diameter of the inner cylindrical surface 19 and the outer diameter of the flange portion 117 of the sleeve 111 are set to be larger than the outer diameter of the head 35 of the valve spool 31.

[0042] An annular flange receiver 20 is formed at the bottom of the recess 18, extending circumferentially along the inner cylindrical surface 19. A lower end surface 121 of a flange portion 117 of the sleeve 111 abuts against the flange receiver 20. The sleeve 111 (second member) is positioned in the axial direction (the "up-down direction" in FIG. 3) with respect to the piston bolt body 12 (first member) by the flange portion 117 abutting against the flange receiver 20. The upper end of the spool hole 15 opens at the center of the bottom of the recess 18. A chamfered portion 21 is formed between the spool hole 15 of the piston bolt body 12 and the flange receiver 20 to avoid collision with the R portion 118 of the sleeve 111.

[0043] The sleeve 111 is fixed in the spool hole 15 of the piston bolt body 22 by a pair of press-fit portions 125, 126 formed with a gap in the axial direction. The upper press-fit portion 125 is formed by pressing the second cylindrical portion 116 of the sleeve 111 into the upper end portion 22 of the spool hole 15. The lower press-fit portion 126 is formed by pressing the lower end portion of the first cylindrical portion 114 of the sleeve 111 into the small inner diameter portion 23 formed in the lower portion of the spool hole 15. Note that a certain gap 127 is formed in the radial direction (the "left-right direction" in FIG. 3) between the press-fit portion 125 and the press-fit portion 126, between the spool hole 15 of the piston bolt body 12 and the first cylindrical portion 114 of the sleeve 111.

[0044] The sliding shaft portion 32 of the valve spool 31 and the inner circumferential surface 112 of the first cylindrical portion 114 of the sleeve 111 are in sliding contact (slidably contact) at a sliding portion 128. As shown in Fig. 3, the upper end of the sliding portion 128 is located lower than the lower end of the upper press-fit portion 125. In addition, the lower end of the sliding portion 128 is located higher than the upper end of the lower press-fit portion 126. In other words, the sliding portion 128 does not overlap with the press-fit portions 125 and 126 in the axial direction (the "up-down direction" in Fig. 3).

[0045] Here, in conventional shock absorbers, when the piston bolt body and the sleeve are brazed, the inner diameter of the sleeve tends to be reduced. As a result, it becomes difficult to manage the fit of the sliding part between the sleeve and the valve spool, and there is a problem that the sliding performance between the sleeve and the valve spool is reduced. In conventional shock absorbers, the sliding performance between the sleeve and the valve spool is ensured by machining the inner diameter of the sleeve after the piston bolt body and the sleeve are brazed, but there are problems such as increased manufacturing costs and reduced quality due to burrs remaining.

[0046] In contrast, in the present embodiment, the sleeve 111 (second component) is fixed to the piston bolt body 12 (first component) by pressing the sleeve 111 into the spool hole 15 of the piston bolt body 12, so that the degree of reduction in the inner diameter (diameter of the inner surface 112) of the sleeve 111 can be reduced compared to fixing by brazing. As a result, in this embodiment, it is easy to manage the fit between the inner circumferential surface 112 of the first cylindrical portion 114 of the sleeve 111 and the sliding shaft portion 32 of the valve spool 31 (shaft member), and it is possible to ensure the slidability between the sleeve 111 and the valve spool 31. In addition, since the process of machining the inner diameter of the sleeve 111 can be omitted, it is possible to avoid an increase in manufacturing costs and a decrease in quality due to the retention of burrs.

[0047] In this embodiment, the sleeve 111 (second member) is fixed to the piston bolt body 12 (first member) by press-fit portions 125, 126 that are spaced apart in the axial direction, and a sliding portion 128 where the inner surface 112 (hole) of the first cylindrical portion 114 of the sleeve 111 and the sliding shaft portion 32 of the valve spool 31 slide against each other is positioned so as not to overlap with the press-fit portions 125, 126 in the axial direction, and a radial gap 127 is formed between the inner surface 112 of the first cylindrical portion 114 of the sleeve 111 and the sliding shaft portion 32 of the valve spool 31 in the sliding portion 128. As a result, in this embodiment, even if the inner diameter of the sleeve 111 is reduced at the press-fit portions 125, 126, it is possible to ensure the fit dimensional tolerance between the inner surface 112 of the first cylindrical portion 114 of the sleeve 111 at the sliding portion 128 and the sliding shaft portion 32 of the valve spool 31, and ultimately to ensure the sliding ability between the sleeve 111 and the valve spool 31.

[0048] In this embodiment, the flange portion 117 (protruding portion) of the sleeve 111 abuts against the flange receiver 20 formed on the piston bolt body 12, so that the sleeve 111 can be positioned in the axial direction with respect to the piston bolt body 12. Also, in this embodiment, the outer peripheral surface 120 of the flange portion 117 of the sleeve 111 is fitted into the inner cylindrical surface 19 of the recess 18 formed in the piston bolt body 12, so that the flange portion 117 can be crimped into the recess 18 by applying axial pressure to the flange portion 117 using a jig or the like.

[0049] The embodiment is not limited to the above-described form, and can be configured as follows, for example. In the above-described embodiment, the flange portion 117 (protruding portion) is formed on the sleeve 111 (second member), but forming the flange portion 117 is not essential. [Explanation of symbols]

[0050] 1 shock absorber, 2 cylinder, 2A cylinder upper chamber, 2B cylinder lower chamber, 3 piston, 4 piston rod, 5 extension side passage, 6 compression side passage, 7 shaft hole, 11 piston bolt, 12 piston bolt body (first member), 31 valve spool (shaft member), 33 valve body, 45 extension side main valve, 46 extension side back pressure chamber, 75 compression side main valve, 76 compression side back pressure chamber, 101 common passage, 111 sleeve (second member), 112 inner surface (hole), 131 pilot valve, 132 first valve seat, 133 first valve portion, 134 second valve seat, 135 second valve portion, 170 solenoid (actuator)

Claims

1. A cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder and dividing the cylinder into two chambers; a piston rod having one end connected to the piston and the other end extending from the cylinder to the outside; an extension-side passage and a compression-side passage provided in the piston; a piston bolt inserted into a shaft hole of the piston; an extension side main valve provided in the extension side passage; an extension side back pressure chamber for adjusting the valve opening pressure of the extension side main valve; a compression side main valve provided in the compression side passage; a compression back pressure chamber that adjusts the valve opening pressure of the compression main valve; a common passage communicating the expansion-side back pressure chamber and the compression-side back pressure chamber; a pilot valve for controlling the flow of hydraulic fluid in the common passage; an actuator for controlling the opening pressure of the pilot valve; an extension-side exhaust passage communicating a passage of the common passage on the compression-side back pressure chamber side with respect to the pilot valve and the compression-side passage; a compression-side exhaust passage communicating the extension-side passage with a passage of the common passage that is located on the extension-side back pressure chamber side of the pilot valve; Equipped with a second valve portion is provided on the other axial end side of the valve body of the pilot valve, the second valve portion restricting the flow of working fluid between the second valve seat formed in the piston bolt and the second valve portion when the actuator is energized; The piston bolt is composed of a first member and a second member, The second member has a hole into which a shaft member is slidably inserted, and is a shock absorber that is partially press-fitted into the first member.

2. 2. The shock absorber according to claim 1, The second member is fixed to the first member by a plurality of press-fit portions spaced apart in the axial direction.

3. 3. The shock absorber according to claim 1 or 2, a sliding portion where the hole of the second member and a sliding shaft portion formed on the shaft member slide, The sliding portion is arranged so as not to overlap with the press-fit portion in the axial direction.

4. 2. The shock absorber according to claim 1, The press-fit portion has a large outer diameter portion formed on the sleeve.

5. 2. The shock absorber according to claim 1, The press-fit portion has a small inner diameter portion formed in the hole of the second member.

6. 2. The shock absorber according to claim 1, The second member has a protruding portion formed at one end, protruding in a radial direction, and abutting against the first member in the radial direction.

7. 2. The shock absorber according to claim 1, The second member has a protruding portion formed at one end, protruding radially, and abutting against the first member in the axial direction.

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