Shock absorber and piston

Abstract

The present invention provides a buffer and piston that can suppress leakage of working fluid from the piston. [Solution] The shock absorber has a piston 21 that divides the inside of the cylinder into two chambers, a first chamber and a second chamber, and is composed of a first piston member 61 at one end in the axial direction and a second piston member 62 at the other end in the axial direction, and an extension-side passage 37 and a contraction-side passage 38 are formed that connect the first chamber and the second chamber, and on the opposing surfaces 81,121 where the first piston member 61 and the second piston member 62 face each other, there is a through hole 33 and a seal member 64 which is positioned between the extension-side passage 37 and the contraction-side passage 38, and recesses 84,124 and protrusions 85,125 which are positioned radially outward of the extension-side passage 37 and the contraction-side passage 38.

Description

【Technical Field】 【0001】 The present invention relates to a shock absorber and a piston. 【Background Art】 【0002】 Some shock absorbers have a piston composed of two piston members (see, for example, Patent Documents 1 and 2). 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 10-103512 【Patent Document 2】 Japanese Patent Application Laid-Open No. 2022-13016 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 By the way, in a shock absorber, when a piston is composed of two piston members, there is a possibility that the working fluid leaks through the gap between the opposing surfaces of the two piston members that abut against each other. 【0005】 An object of the present invention is to provide a shock absorber and a piston capable of suppressing the leakage of the working fluid generated in the piston. 【Means for Solving the Problems】 【0006】 To achieve the above objective, one embodiment of the shock absorber according to the present invention comprises a cylinder filled with working fluid, a piston slidably fitted inside the cylinder and dividing the inside of the cylinder into two chambers, a first chamber and a second chamber, and a piston rod fastened with one end inserted into a through hole provided in the piston, the other end extending to the outside through the first chamber, wherein the piston is composed of a first piston member at one axial end and a second piston member at the other axial end, and an extension-side passage and a compression-side passage are formed communicating the first chamber and the second chamber, and the opposing surfaces of the first piston member and the second piston member are provided with a sealing member disposed between the through hole and the extension-side passage and the compression-side passage, and recesses and protrusions disposed radially outward of the extension-side passage and the compression-side passage. 【0007】 One embodiment of the piston according to the present invention is a piston used in a shock absorber, which divides a cylinder filled with working fluid into a first chamber and a second chamber, and the piston is composed of a first piston member at one axial end and a second piston member at the other axial end, and has a through hole into which the piston rod of the shock absorber is inserted, and an extension-side passage and a compression-side passage that connect the first chamber and the second chamber, and the opposing surfaces of the first piston member and the second piston member that face each other are provided with a seal member disposed between the through hole and the extension-side passage and the compression-side passage, and recesses and protrusions disposed radially outward of the extension-side passage and the compression-side passage. 【0008】 Another embodiment of the piston according to the present invention is a piston used in a shock absorber that divides a cylinder filled with working fluid into a first chamber and a second chamber, wherein the piston is composed of a first piston member at one axial end and a second piston member at the other axial end, and has a through hole into which the piston rod of the shock absorber is inserted, and extension-side passages and compression-side passages that connect the first chamber and the second chamber, and has a recess and a protrusion arranged radially outward of the extension-side passage and the compression-side passage on the opposing surfaces of the first piston member and the second piston member facing each other. [Effects of the Invention] 【0009】 According to the present invention, it is possible to suppress leakage of working fluid from the piston. [Brief explanation of the drawing] 【0010】 [Figure 1] This is a cross-sectional view showing a buffer according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view along line II-II in Figure 4, showing the piston of a buffer according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view along line III-III in Figure 4, showing the piston of a buffer according to an embodiment of the present invention. [Figure 4] This is a plan view showing the opposing surface of the compression-side piston member of a shock absorber according to an embodiment of the present invention. [Figure 5] This is a plan view showing the opposing surface of the extension piston member of a shock absorber according to an embodiment of the present invention. [Modes for carrying out the invention] 【0011】 Embodiments will be described based on the drawings. The buffer 1 of this embodiment is a buffer used in the suspension systems of railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles, and more specifically, a buffer used in the suspension system of a four-wheeled automobile. As shown in Figure 1, the buffer 1 is a twin-cylinder type buffer comprising a cylinder 4 having a cylindrical inner cylinder 2 and a bottomed cylindrical outer cylinder 3 which has a larger diameter than the inner cylinder 2 and is provided radially outside the inner cylinder 2. A reservoir chamber 5 is located between the outer cylinder 3 and the inner cylinder 2. 【0012】 The outer cylinder 3 has a stepped cylindrical body member 8 whose axial ends are smaller in diameter than the axial middle section, and a bottom member 9 that closes one axial end of the body member 8, with the other end of the body member 8 opposite to the bottom member 9 being an opening. 【0013】 The shock absorber 1 includes an annular valve body 10 provided at one end of the inner cylinder 2 and outer cylinder 3 on the axial side of the bottom member 9, and an annular rod guide 11 provided at the other end of the inner cylinder 2 and outer cylinder 3 opposite to the axial side of the bottom member 9. The valve body 10 constitutes the base valve 12 and has a stepped outer circumference. The rod guide 11 also has a stepped outer circumference, and its large diameter portion is fitted into the body member 8. 【0014】 The inner cylinder 2 has one end on the axial side facing the bottom member 9 that is fitted to the small diameter portion of the outer circumference of the valve body 10, and engages with the bottom member 9 of the outer cylinder 3 via the valve body 10. The other end of the inner cylinder 2, opposite to the axial side facing the bottom member 9, is fitted to the small diameter portion of the outer circumference of the rod guide 11, and engages with the body member 8 of the outer cylinder 3 via the rod guide 11. In this state, the inner cylinder 2 is positioned radially relative to the outer cylinder 3. Here, the space between the valve body 10 and the bottom member 9 is in communication with the space between the inner cylinder 2 and the outer cylinder 3, and, similar to the space between the inner cylinder 2 and the outer cylinder 3, constitutes the reservoir chamber 5. 【0015】 The shock absorber 1 has an annular sealing member 13 on the side opposite to the axial bottom member 9 of the rod guide 11. This sealing member 13 is fitted to the inner circumference of the body member 8, similar to the rod guide 11. At the end of the body member 8 opposite to the axial bottom member 9, a locking portion (not shown) is formed by plastically deforming the body member 8 radially inward through crimping, such as curling. The radially outer portion of the sealing member 13 is sandwiched between this locking portion (not shown) and the rod guide 11. The sealing member 13 closes the opening of the outer cylinder 3 and is specifically an oil seal. 【0016】 The shock absorber 1 has a piston 21 located inside the cylinder 4. The piston 21 is slidably fitted into the inner cylinder 2 of the cylinder 4. The piston 21 divides the inner cylinder 2 into two chambers: a first chamber 22 and a second chamber 23. The first chamber 22 is located between the piston 21 and the rod guide 11 inside the inner cylinder 2, and the second chamber 23 is located between the piston 21 and the valve body 10 inside the inner cylinder 2. The second chamber 23 is defined as a reservoir chamber 5 by the valve body 10. Inside the cylinder 4, the first chamber 22 and the second chamber 23 are sealed with working fluid L, and the reservoir chamber 5 is sealed with gas G and working fluid L. 【0017】 The shock absorber 1 includes a piston rod 25, one end of which is positioned inside the cylinder 4 and connected to and fixed to the piston 21, while the other end of which extends outside the cylinder 4. The piston rod 25 is made of metal and passes through the first chamber 22, but not through the second chamber 23. Therefore, the first chamber 22 is the rod side chamber through which the piston rod 25 passes, and the second chamber 23 is the bottom side chamber on the bottom member 9 side of the cylinder 4. 【0018】 The piston 21 and piston rod 25 move together. During the extension stroke of the shock absorber 1, when the piston rod 25 increases the amount it protrudes from the cylinder 4, the piston 21 moves toward the first chamber 22, and during the compression stroke of the shock absorber 1, when the piston rod 25 decreases the amount it protrudes from the cylinder 4, the piston 21 moves toward the second chamber 23. 【0019】 The rod guide 11 and the seal member 13 are both annular. The piston rod 25 is slidably inserted inside each of these rod guide 11 and seal member 13 and extends from the inside to the outside of the cylinder 4. One axial end portion of the piston rod 25 is fixed to the piston 21 inside the cylinder 4, and the other axial end portion protrudes outside the cylinder 4 through the rod guide 11 and the seal member 13. 【0020】 The rod guide 11 supports the piston rod 25 with respect to the cylinder 4 so as to be axially movable while restricting its radial movement, and guides the movement of this piston rod 25. 【0021】 The outer peripheral portion of the seal member 13 is in close contact with the outer cylinder 3 of the cylinder 4, and the inner peripheral portion is in sliding contact with the outer peripheral portion of the piston rod 25 that moves axially. Thereby, the seal member 13 prevents the oil fluid L and gas G inside the cylinder 4 from leaking to the outside. 【0022】 The piston rod 25 has a columnar main shaft portion 30 and a columnar mounting shaft portion 31 having a smaller outer diameter than the main shaft portion 30. The mounting shaft portion 31 is provided at one axial end portion of the piston rod 25. The piston rod 25 has the main shaft portion 30 slidably fitted to the rod guide 11 and the seal member 13, and the mounting shaft portion 31 at one axial end portion is disposed inside the cylinder 4 and connected to the piston 21 and the like. The other end portion of the main shaft portion 30 of the piston rod 25, which is on the opposite side to the mounting shaft portion 31 in the axial direction, extends outside through the first chamber 22, the rod guide 11, and the seal member 13. 【0023】 The piston 21 is disc-shaped, with a through-hole 33 formed in its radial center, extending axially through it. The mounting shaft portion 31 of the piston rod 25 is inserted into the through-hole 33 of the piston 21. A male thread 34 is formed on the end of the mounting shaft portion 31 of the piston rod 25 opposite to the main shaft portion 30 in the axial direction, and the piston 21 is fastened to the piston rod 25 by a nut member 35 that is screwed onto this male thread 34. In other words, the piston rod 25 is fastened with one end inserted into the through-hole 33 provided in the piston 21, and the other end extends to the outside through the first chamber 22. 【0024】 The piston 21 is provided with an extension-side passage 37 that connects the first chamber 22 and the second chamber 23, and a retraction-side passage 38 that connects the second chamber 23 and the first chamber 22, located outside its radial through-hole 33. 【0025】 On the second chamber 23 side of the piston 21, a damping force generating mechanism 42 is provided, which generates damping force by opening and closing the extension-side passage 37 with a valve member 41. The extension-side passage 37 opens to the first chamber 22 on the side opposite to the damping force generating mechanism 42. Because the damping force generating mechanism 42 is positioned on the second chamber 23 side, the extension-side passage 37 becomes a passage through which the oil liquid L flows from the first chamber 22, which is upstream, to the second chamber 23, which is downstream, during the movement of the piston 21 toward the first chamber 22, i.e., the extension stroke. The damping force generating mechanism 42 provided for the extension-side passage 37 is an extension-side damping force generating mechanism that generates damping force by suppressing the flow of oil liquid L from the extension-side passage 37 toward the second chamber 23. The damping force generating mechanism 42 is provided with a fixed orifice (not shown) that keeps the extension-side passage 37 in communication even when the valve member 41 is in the closed state. 【0026】 On the second chamber 23 side of the extension-side passage 37, beyond the damping force generating mechanism 42, is a damping force generating mechanism 44 that generates damping force by opening the extension-side passage 37 via a valve member 43 when the damping force generating mechanism 42 is in the open state. The damping force generating mechanism 44 is also an extension-side damping force generating mechanism that generates damping force by suppressing the flow of oil L from the extension-side passage 37 to the second chamber 23. The damping force generating mechanism 44 has a higher opening pressure than the damping force generating mechanism 42 and opens after the damping force generating mechanism 42 opens. The damping force generating mechanism 44 is provided with a fixed orifice (not shown) that maintains communication with the extension-side passage 37 even when the valve member 43 is in the closed state. 【0027】 On the first chamber 22 side of the piston 21, a damping force generating mechanism 46 is provided, which generates damping force by opening and closing the compression-side passage 38 with a valve member 45. The compression-side passage 38 opens to the second chamber 23 on the side opposite to the damping force generating mechanism 46. Because the damping force generating mechanism 46 is positioned on the first chamber 22 side, the compression-side passage 38 becomes a passage through which the oil liquid L flows from the second chamber 23, which is upstream, to the first chamber 22, which is downstream, during the movement of the piston 21 toward the second chamber 23, that is, during the compression stroke. The damping force generating mechanism 46 provided for the compression-side passage 38 is a compression-side damping force generating mechanism that generates damping force by suppressing the flow of oil liquid L from the compression-side passage 38 toward the first chamber 22. The damping force generating mechanism 46 is provided with a fixed orifice (not shown) that keeps the compression-side passage 38 in communication even when the valve member 45 is in the closed state. 【0028】 On the first chamber 22 side of the compression-side passage 38 relative to the damping force generating mechanism 46, there is a damping force generating mechanism 48 that generates damping force by opening the compression-side passage 38 via a valve member 47 when the damping force generating mechanism 46 is in the open state. The damping force generating mechanism 48 is also a compression-side damping force generating mechanism that generates damping force by suppressing the flow of oil L from the compression-side passage 38 to the first chamber 22. The damping force generating mechanism 48 has a higher opening pressure than the damping force generating mechanism 46 and opens after the damping force generating mechanism 46 opens. The damping force generating mechanism 48 is provided with a fixed orifice (not shown) that maintains communication with the compression-side passage 38 even when the valve member 47 is in the closed state. 【0029】 The valve body 10 has fluid passages 51 and 52 that penetrate in the axial direction. Fluid passages 51 and 52 are able to communicate the second chamber 23 and the reservoir chamber 5. The base valve 12 has a compression-side damping force generating mechanism 55 on the axial bottom member 9 side of the valve body 10 that can open and close the fluid passage 51. The base valve 12 also has an extension-side damping force generating mechanism 56 on the side opposite to the axial bottom member 9 of the valve body 10 that can open and close the fluid passage 52. 【0030】 The base valve 12 operates when the piston rod 25 moves in the compression direction and the piston 21 moves in a direction that narrows the second chamber 23, causing the pressure in the second chamber 23 to become higher than a predetermined value than the pressure in the reservoir chamber 5. At this time, the damping force generating mechanism 55 opens the fluid passage 51, allowing the oil L from the second chamber 23 to flow into the reservoir chamber 5, thereby generating a damping force. The damping force generating mechanism 55 is a damping force generating mechanism for the compression side. 【0031】 The base valve 12, when the piston rod 25 moves in the extension direction and the piston 21 moves toward the first chamber 22, causing the pressure in the second chamber 23 to drop below the pressure in the reservoir chamber 5, opens the fluid passage 52, allowing the oil L from the reservoir chamber 5 to flow into the second chamber 23, thereby generating a damping force. The damping force generating mechanism 56 is an extension-side damping force generating mechanism. The damping force generating mechanism 56 may also function as a suction valve that flows the oil L from the reservoir chamber 5 into the second chamber 23 without substantially generating a damping force. 【0032】 In the shock absorber 1, for example, the portion of the piston rod 25 protruding from the cylinder 4 is positioned at the top and supported by the vehicle body, while the bottom member 9 of the cylinder 4 is positioned at the bottom and connected to the wheel side. In the case of a single-tube type, the opposite is possible: the cylinder 4 side is supported by the vehicle body, and the piston rod 25 is connected to the wheel side. 【0033】 The piston 21 is composed of a compression-side piston member 61 (one of the first and second piston members) provided on the second chamber 23 side, an extension-side piston member 62 (the other of the first and second piston members) provided on the first chamber 22 side and joined to the compression-side piston member 61, a sliding member 63 mounted on the outer circumferential surfaces of the compression-side piston member 61 and the extension-side piston member 62, and a sealing member 64 as shown in Figures 2 and 3. Both the compression-side piston member 61 and the extension-side piston member 62 are disc-shaped and made of metal. The sliding member 63 is cylindrical and made of synthetic resin. The sealing member 64 is made of an elastic material such as rubber. 【0034】 The piston 21 is formed by joining a compression-side piston member 61 and an extension-side piston member 62, with a seal member 64 held between them. In this state, a single cylindrical sliding member 63 is placed over the radially outer sides of both the compression-side piston member 61 and the extension-side piston member 62, thereby integrating them. The compression-side piston member 61 and the extension-side piston member 62 of the piston 21 are connected in contact with the mounting shaft portion 31 of the piston rod 25 shown in Figure 1, and the sliding member 63 slides against the inside of the inner cylinder 2 of the cylinder 4. 【0035】 The compression piston member 61 is formed, for example, by sintering, and is provided facing the second chamber 23. 【0036】 As shown in Figures 2 and 3, the retracting piston member 61 has a hole 70 in its radial center that forms part of the through hole 33, which is on the axial side of the second chamber 23 (the lower side in Figures 2 and 3), and penetrates the retracting piston member 61 in the axial direction. 【0037】 As shown in Figure 2, the retracting piston member 61 has passage holes 71 that penetrate the retracting piston member 61 axially, located outside the radial hole 70, and forming a part of the extension-side flow path 37 that is on the axial side of the second chamber 23 (lower side in Figure 2). As shown in Figure 4, the retracting piston member 61 has multiple passage holes 71, specifically five. All passage holes 71 are the same shape and are aligned radially with the retracting piston member 61, and are arranged at equal intervals in the circumferential direction of the retracting piston member 61. 【0038】 As shown in Figure 2, the retraction piston member 61 is provided with a passage hole 72 that forms part of the retraction flow path 38 on the axial side towards the second chamber 23 (lower side in Figure 2), outside the radial hole 70. The portion of the passage hole 72 opposite to the second chamber 23 in the axial direction (upper side in Figure 2) is aligned with the axial direction of the retraction piston member 61, and the end on the axial side towards the second chamber 23 (lower side in Figure 2) opens to the radial outer end on the second chamber 23 side, beyond the portion covered by the sliding member 63 of the retraction piston member 61. As shown in Figure 4, the retraction piston member 61 has multiple passage holes 72, specifically five in total. All passage holes 72 are the same shape and are arranged at equal intervals in the circumferential direction of the retraction piston member 61, with their radial positions aligned. 【0039】 The retractable piston member 61 has two passage holes, 71 and 72, which are provided alternately at equal intervals in the circumferential direction of the retractable piston member 61. 【0040】 As shown in Figure 2, the retracting piston member 61 has an annular groove 73 formed on the axial side of the second chamber 23 (lower side in Figure 2) that connects a plurality of passage holes 71. 【0041】 Furthermore, the retracting piston member 61 has an annular groove 74 formed radially and axially outward (on the second chamber 23 side) of the annular groove 73, surrounding the annular groove 73 radially outward. 【0042】 The annular grooves 73 and 74 also constitute the extended side flow path 37. 【0043】 An inner seat portion 75 is formed on the compression piston member 61, radially inward of the annular groove 73 on the axial second chamber 23 side (lower side in Figure 2). The valve member 41 shown in Figure 1 is placed on the inner seat portion 75. 【0044】 As shown in Figure 2, the compression piston member 61 has an intermediate seat portion 76 formed between the annular groove 73 and the annular groove 74 on the axial second chamber 23 side (lower side in Figure 2). The intermediate seat portion 76 causes the valve member 41 shown in Figure 1 to seat and dissipate, opening and closing the extension flow path 37, and together with the valve member 41, constitutes the damping force generating mechanism 42. 【0045】 As shown in Figure 2, the compression piston member 61 has an outer seat portion 77 formed radially outside the annular groove 74 on the axial second chamber 23 side (lower side in Figure 2). The outer seat portion 77 causes the valve member 43 shown in Figure 1 to seat and dissipate, opening and closing the extension flow path 37, and together with the valve member 43, constitutes the damping force generating mechanism 44. 【0046】 As shown in Figures 2 and 3, the compression piston member 61 has an opposing surface 81 on the side opposite to the axial second chamber 23 (the upper side in Figure 2) that faces the extension piston member 62. The opposing surface 81 has an end face 82 on the axial extension piston member 62 side, and this end face 82 is planar in the direction perpendicular to the axis of the compression piston member 61. 【0047】 As shown in Figure 4, all passage holes 71 and all passage holes 72 open into this end face 82. All passage holes 71 and all passage holes 72 have the same shape in the portion that opens into the end face 82, and are arranged alternately at equal intervals in the circumferential direction of the retraction-side piston member 61, with their radial positions aligned. 【0048】 The opposing surface 81 is provided with a groove 83, a recess 84, and a protrusion 85. 【0049】 The groove 83 is recessed inward in the axial direction from the end face 82 to the retracting piston member 61, as shown in Figures 2 and 3. The groove 83 has an annular groove 91 and a radial groove 92, as shown in Figure 4. 【0050】 The annular groove 91 is provided radially on the retracting piston member 61, between the hole 70 and the passage holes 71 and 72, and is separated from these holes 70, 71 and 72. The annular groove 91 is circular in shape and surrounds the hole 70 on the radially outer side of the retracting piston member 61. The annular groove 91 is concentric with the hole 70. 【0051】 The radial groove 92 runs along the radial direction of the retraction piston member 61 and is provided between adjacent passage holes 71 and 72 in the circumferential direction of the retraction piston member 61, at a distance from them. The radial groove 92 communicates with the annular groove 91 and extends radially outward from the annular groove 91 to just before the radial outer end of the retraction piston member 61. The radial groove 92 aligns the radial outer end position of the retraction piston member 61 with the same outer end position of the passage holes 71 and 72. The groove 83 has radial grooves 92 at positions between all combinations of adjacent passage holes 71 and 72 in the circumferential direction of the retraction piston member 61. Therefore, the groove 83 has multiple radial grooves 92, specifically 10 locations, the same number as the total number of passage holes 71 and 72. Multiple radial grooves 92 have the same shape and radiate outwards from the annular groove 91. 【0052】 As shown in Figure 2, the recess 84 is recessed inward in the axial direction from the end face 82 of the retraction-side piston member 61. The recess 84 is provided on the radially outer side of the retraction-side piston member 61 of the passage hole 71 that constitutes the extension-side flow path 37, with the circumferential position of the passage hole 71 and the retraction-side piston member 61 aligned. As shown in Figure 4, the recess 84 is arc-shaped with the central axis of the hole 70 as its center. The retraction-side piston member 61 has multiple recesses 84, specifically five recesses, the same number as the passage holes 71, and the recesses 84 are provided on the radially outer side of each of the passage holes 71 of the retraction-side piston member 61. All the recesses 84 are the same shape and are arranged at equal intervals in the circumferential direction of the retraction-side piston member 61, with their radial positions aligned. 【0053】 As shown in Figure 2, the protrusion 85 projects outward in the axial direction from the end face 82 of the retraction-side piston member 61. The protrusion 85 is provided on the radially outer side of the retraction-side piston member 61 of the passage hole 72 that constitutes the retraction-side flow path 38, with the circumferential position of the passage hole 72 and the retraction-side piston member 61 aligned. As shown in Figure 4, the protrusion 85 is arc-shaped with the central axis of the hole 70 as its center. The retraction-side piston member 61 has multiple protrusions 85, specifically five, the same number as the passage holes 72, and the protrusions 85 are provided on the radially outer side of each of the passage holes 72 of the retraction-side piston member 61. All the protrusions 85 are the same shape and are arranged at equal intervals in the circumferential direction of the retraction-side piston member 61, with their radial positions aligned. The protrusions 85 are aligned with the radial position of the retraction-side piston member 61 and the recess 84. 【0054】 The multiple protrusions 85 are provided at five locations, with three or more at equal intervals in the circumferential direction of the retracting piston member 61. Therefore, the retracting piston member 61 can be stably placed on the horizontal plane by the multiple protrusions 85. 【0055】 The retracting piston member 61 has recesses 84 and protrusions 85, which are provided alternately at equal intervals in the circumferential direction of the retracting piston member 61. 【0056】 The sealing member 64 is integrally molded without seams and has an annular sealing portion 101 and a radial sealing portion 102. 【0057】 The annular seal portion 101 is circular in shape. 【0058】 The radial sealing portion 102 extends outward from the annular sealing portion 101 in the radial direction. The sealing member 64 has multiple radial sealing portions 102, the same number as the radial grooves 92 of the groove portion 83, specifically 10 locations. The multiple radial sealing portions 102 are identical in shape and are arranged at equal intervals in the circumferential direction of the annular sealing portion 101. Therefore, the multiple radial sealing portions 102 radiate outward from the annular sealing portion 101. 【0059】 In its natural state, the thickness of the sealing member 64 before assembly to the compression piston member 61 and the extension piston member 62 is greater than the depth from the end face 82 of the groove 83 of the compression piston member 61. In its natural state, the outer diameter of the annular sealing portion 101 of the sealing member 64 is slightly smaller than the radially outer diameter of the annular groove 91 of the compression piston member 61, and the inner diameter of the annular sealing portion 101 in its natural state is slightly larger than the radially inner diameter of the annular groove 91 of the compression piston member 61. In its natural state, the circumferential width of the annular sealing portion 101 of the radial sealing portion 102 of the sealing member 64 is slightly smaller than the circumferential width of the annular groove 91 of the radial groove 92 of the compression piston member 61. In its natural state, the extension length of the radial seal portion 102 of the sealing member 64 from the annular seal portion 101 is slightly smaller than the extension length of the radial groove portion 92 from the annular groove portion 91 of the retractable piston member 61. 【0060】 The sealing member 64 is positioned within the groove 83 of the retracting piston member 61. In this configuration, the annular sealing portion 101 of the sealing member 64 is positioned within the annular groove 91, and all radial sealing portions 102 are positioned within their respective corresponding radial grooves 92. 【0061】 The extension piston member 62 is formed, for example, by sintering, and is provided facing the first chamber 22, as shown in Figure 1. 【0062】 As shown in Figures 2 and 3, the extension piston member 62 has a hole 110 in its radial center that forms part of the through hole 33, which is on the axial side of the first chamber 22 (upper side in Figures 2 and 3), and penetrates the extension piston member 62 in the axial direction. 【0063】 As shown in Figure 2, the extension piston member 62 has passage holes 111 that penetrate the extension piston member 62 axially, located outside the radial hole 110, and forming a part of the retraction flow path 38 that is on the axial side of the first chamber 22 (upper side in Figure 2). As shown in Figure 5, the extension piston member 62 has multiple passage holes 111, specifically five in total, the same number as the passage holes 72. All passage holes 111 are the same shape and are arranged at equal intervals in the circumferential direction of the extension piston member 62, with their radial positions aligned. 【0064】 As shown in Figure 2, the extension piston member 62 is provided with a passage hole 112 that forms part of the extension flow path 37, which is on the axial side of the first chamber 22 (upper side in Figure 2), outside the radial hole 110. The portion of the passage hole 112 opposite to the first chamber 22 in the axial direction (lower side in Figure 2) is aligned with the axial direction of the extension piston member 62, and the end on the axial side of the first chamber 22 (upper side in Figure 2) opens to the radial outer end on the first chamber 22 side of the extension piston member 62, beyond the covering position by the sliding member 63 of the extension piston member 62. As shown in Figure 5, the extension piston member 62 has multiple passage holes 112, specifically five in total, the same number as the passage hole 71. All passage holes 112 are the same shape and are arranged at equal intervals in the circumferential direction of the extension piston member 62, aligning the radial position of the extension piston member 62. 【0065】 The extension piston member 62 has passage holes 111 and passage holes 112, which are arranged alternately at equal intervals in the circumferential direction of the extension piston member 62. 【0066】 As shown in Figure 2, the extension piston member 62 has an annular groove 113 formed on the axial side of the first chamber 22 (upper side in Figure 2) that connects a plurality of passage holes 111. 【0067】 Furthermore, the extension piston member 62 has an annular groove 114 formed radially and axially outward (on the first chamber 22 side) of the annular groove 113, surrounding the annular groove 113 radially outward. 【0068】 The annular grooves 113 and 114 also constitute the contracted side flow path 38. 【0069】 An inner seat portion 115 is formed on the extension piston member 62, radially inward of the annular groove 113 on the axial first chamber 22 side (upper side in Figure 2). The valve member 45 shown in Figure 1 is placed on the inner seat portion 115. 【0070】 As shown in Figure 2, the extension piston member 62 has an intermediate seat portion 116 formed between the annular groove 113 and the annular groove 114 on the axial first chamber 22 side (upper side in Figure 2). The intermediate seat portion 116 causes the valve member 45 shown in Figure 1 to move away from and seat, opening and closing the compression flow path 38, and together with the valve member 45, constitutes the damping force generating mechanism 46. 【0071】 As shown in Figure 2, the extension piston member 62 has an outer seat portion 117 formed radially outside the annular groove 114 on the axial first chamber 22 side (upper side in Figure 2). The outer seat portion 117 causes the valve member 47 shown in Figure 1 to seat and dissipate, opening and closing the compression flow path 38, and together with the valve member 47, constitutes the damping force generating mechanism 48. 【0072】 As shown in Figures 2 and 3, the extension piston member 62 has an opposing surface 121 on the side opposite to the first chamber 22 in the axial direction (the lower side in Figure 2) that faces the retraction piston member 61. The opposing surface 121 has an end face 122 on the side of the retraction piston member 61 in the axial direction, and this end face 122 is planar in the direction perpendicular to the axis of the extension piston member 62. 【0073】 As shown in Figure 5, all passage holes 111 and all passage holes 112 open into this end face 122. All passage holes 111 and all passage holes 112 have the same shape in the portion that opens into the end face 122, and are arranged alternately at equal intervals in the circumferential direction of the extension piston member 62, with their radial positions aligned. The portions of passage holes 111 and passage holes 112 that open into the end face 122 have the same shape as the portions that open into the end face 82 of passage holes 71 and passage holes 72, and their radial positions are aligned with those of the piston 21. 【0074】 The opposing surface 121 is provided with a recess 124 and a protrusion 125. 【0075】 As shown in Figure 2, the recess 124 is recessed inward in the axial direction from the end face 122 of the extension piston member 62. The recess 124 is provided on the radially outer side of the extension piston member 62 of the passage hole 111 that constitutes the retraction flow path 38, with the circumferential positions of the passage hole 111 and the extension piston member 62 aligned. As shown in Figure 5, the recess 124 is arc-shaped with the central axis of the hole 110 as its center. The extension piston member 62 has multiple recesses 124, specifically five recesses, the same number as the passage holes 111 and the same number as the protrusions 85, and the recesses 124 are provided on the radially outer side of each extension piston member 62 of all the passage holes 111. The multiple recesses 124 are the same shape and are arranged at equal intervals in the circumferential direction of the extension piston member 62, with their radial positions aligned. 【0076】 As shown in Figure 2, the protrusion 125 projects outward in the axial direction from the end face 122 of the extension piston member 62. The protrusion 125 is provided on the radially outer side of the extension piston member 62 of the passage hole 112 that constitutes the extension flow path 37, with the circumferential position of the passage hole 112 and the extension piston member 62 aligned. As shown in Figure 5, the protrusion 125 is arc-shaped with the central axis of the hole 110. The extension piston member 62 has multiple protrusions 125, specifically five in total, the same number as the passage holes 112 and the same number as the recesses 84, and the protrusions 125 are provided on the radially outer side of each extension piston member 62 of the passage holes 112. The multiple protrusions 125 are of the same shape and are arranged at equal intervals in the circumferential direction of the extension piston member 62, with their radial positions aligned. The recessed portion 124 and the protruding portion 125 are aligned in the radial direction of the extension-side piston member 62, and the protruding portion 85 and the recessed portion 84 of the retraction-side piston member 61 are also aligned in the radial direction of the piston 21. 【0077】 The multiple protrusions 125 are provided at five locations, with three or more at equal intervals in the circumferential direction of the extension piston member 62. Therefore, the extension piston member 62 can be stably placed on the horizontal plane with respect to the multiple protrusions 125. 【0078】 The extension piston member 62 has recesses 124 and protrusions 125 arranged alternately at equal intervals in the circumferential direction of the extension piston member 62. 【0079】 All of the recesses 124 of the extension piston member 62 are capable of fitting into a corresponding protrusion 85 of the retraction piston member 61. 【0080】 The compression piston member 61 has the same shape as the extension piston member 62, except that it has a groove 83 and a different shape in the outer circumference to which the sliding member 63 is attached. 【0081】 As described above, the seal member 64 is positioned in the groove 83 of the retraction piston member 61. In this state, one corresponding protrusion 125 of the extension piston member 62 is fitted into each of the recesses 84 of the retraction piston member 61, and one corresponding protrusion 85 of the retraction piston member 61 is fitted into each of the recesses 124 of the extension piston member 62, so that the end face 82 of the retraction piston member 61 and the end face 122 of the extension piston member 62 abut against each other and make surface contact. In this state, the compression piston member 61 and the extension piston member 62 are positioned and integrated in the circumferential and radial directions. In other words, the compression piston member 61 and the extension piston member 62 are joined together by the recess 84 and the protrusion 125 fitting together, and the end faces 82 and 122 making surface contact, thereby restricting relative rotation in the circumferential direction and relative movement in the radial direction. The end faces 82 and 122 of the compression piston member 61 and the extension piston member 62 become the bonding surfaces. 【0082】 In this joined state, the inner circumferential surface of the hole 70 of the retracting piston member 61 and the inner circumferential surface of the hole 110 of the extension piston member 62 are arranged on a single cylindrical surface, forming a through hole 33. 【0083】 Furthermore, in this joined state, all the passage holes 71 of the retracting piston member 61 are in phase with and communicate with one of the corresponding passage holes 112 of the extension piston member 62, forming the extension flow path 37. At this time, the openings of all the passage holes 71 to the end faces 82 coincide with the openings of the corresponding passage holes 112 to the end faces 122. 【0084】 Furthermore, in this joined state, all the passage holes 72 of the retracting piston member 61 communicate with one of the corresponding passage holes 111 of the extending piston member 62 in phase with each other, forming the retracting flow path 38. At this time, the openings of all the passage holes 72 to the end faces 82 coincide with the openings of the corresponding passage holes 111 to the end faces 122. 【0085】 Furthermore, in this joined state, the recess 84 and the protrusion 125 are positioned radially outward of the piston 21 of the extension-side passage 37, and the recess 124 and the protrusion 85 are positioned radially outward of the piston 21 of the retraction-side passage 38. 【0086】 Furthermore, in this joined state, the entire seal member 64 is housed within the space enclosed by the groove 83 and the end face 122 of the extension piston member 62. In this joined state, the annular seal portion 101 of the seal member 64 abuts against the bottom surface of the annular groove 91 of the retraction piston member 61 and the end face 122 of the extension piston member 62 over its entire circumference, and all of the radial seal portions 102 abut against the bottom surface of the radial groove 92 where they are located and the end face 122 of the extension piston member 62. As a result, the annular seal portion 101 of the seal member 64 is positioned between the through hole 33 and the extension flow path 37 and the retraction flow path 38, sealing the space between them over its entire circumference. Additionally, the radial seal portions 102 are positioned between the extension flow path 37 and the retraction flow path 38, which are located adjacent to each other in the circumferential direction of the retraction piston member 61 and the extension piston member 62. 【0087】 With the compression piston member 61, extension piston member 62, and seal member 64 assembled in this manner, a single cylindrical sliding member 63 is mounted radially outward on the compression piston member 61 and the extension piston member 62, straddling them axially. As a result, the compression piston member 61, extension piston member 62, seal member 64, and sliding member 63 are integrated to form a piston 21. 【0088】 The piston 21 with the above configuration is composed of a compression-side piston member 61 at one axial end and an extension-side piston member 62 at the other axial end. In other words, the piston 21 is composed of an extension-side piston member 62 at one axial end and a compression-side piston member 61 at the other axial end. The piston 21 also has an extension-side passage 37 connecting the first chamber 22 and the second chamber 23, and a compression-side passage 38 connecting the first chamber 22 and the second chamber 23. Furthermore, the piston 21 is provided with a sealing member 64 positioned between the through hole 33 and the extension-side passage 37 and the compression-side passage 38 on the opposing surfaces 81 and 121 where the compression-side piston member 61 and the extension-side piston member 62 face each other, and recesses 84 and 124 and protrusions 85 and 125 positioned radially outward of the extension-side passage 37 and the compression-side passage 38. Furthermore, the piston 21 has a sealing member 64 provided in a groove 83 provided in the compression side piston member 61. In the compression side piston member 61, of the recess 84 and the protrusion 85, the recess 84 is provided on the radially outer side of the extension side passage 37, and the other protrusion 85 is provided on the radially outer side of the compression side passage 38. In the extension side piston member 62, of the recess 124 and the protrusion 125, the protrusion 125 is provided on the radially outer side of the extension side passage 37, and the other recess 124 is provided on the radially outer side of the compression side passage 38. 【0089】 With the piston 21 assembled to the piston rod 25, the piston 21 is clamped axially on its radially inward side, along with the valve members 41, 43, 45, 47, etc., by the main shaft portion 30 and nut member 35 of the piston rod 25. In this state, the recesses 84, 124 and protrusions 85, 125 of the piston 21 are located radially outward from the main shaft portion 30 and nut member 35. 【0090】 Patent documents 1 and 2, mentioned above, disclose a shock absorber in which the piston is composed of two piston members. When the piston is composed of two piston members in this way, there is a possibility that the working fluid may leak through the gap between the opposing surfaces of the two piston members that abut against each other. 【0091】 In contrast, the buffer 1 of this embodiment is provided with a through hole 33 into which the piston rod 25 is inserted, and a sealing member 64 positioned between the opposing surfaces 81 and 121 where the retraction-side piston member 61 and the extension-side piston member 62 of the piston 21 face each other, and the extension-side passage 37 and the retraction-side passage 38 that connect the first chamber 22 and the second chamber 23. As a result, the buffer 1 can suppress leakage of oil liquid L that occurs between the through hole 33 and the extension-side passage 37 and the retraction-side passage 38 within the piston 21 by having the sealing member 64 block it. This allows the buffer 1 to stabilize its performance. 【0092】 Furthermore, the shock absorber 1 is provided with recesses 84, 124 and protrusions 85, 125 on the opposing surfaces 81, 121 where the compression-side piston member 61 and the extension-side piston member 62 of the piston 21 face each other, and which are positioned radially outward of the extension-side passage 37 and the compression-side passage 38. Therefore, even if a sealing member 64 is provided to suppress leakage of oil L between the through hole 33 and the extension-side passage 37 and the compression-side passage 38, the shock absorber 1 can still position and integrate the compression-side piston member 61 and the extension-side piston member 62. 【0093】 In this case, when the piston is assembled to the piston rod, the axial force from the main shaft of the piston rod and the nut member is applied to the radially inward side of the piston. This causes deformation in which the outer diameter side of the compression side piston member and the extension side piston member bends backward, making it easy for a gap to form between the outer circumference of the opposing surface of the compression side piston member and the outer circumference of the opposing surface of the extension side piston member. In contrast, the shock absorber 1 has recesses 84, 124 and protrusions 85, 125 on the radially outward side of the extension side passage 37 and the compression side passage 38 of the opposing surfaces 81, 121 of the compression side piston member 61 and the extension side piston member 62. By fitting the recesses 84 and protrusions 125 together, the deformation in which the outer diameter side of the compression side piston member 61 and the extension side piston member 62 bends backward can be suppressed. As a result, the shock absorber 1 can suppress the gap that occurs between the outer circumference of the opposing surface 81 of the compression-side piston member 61 and the outer circumference of the opposing surface 121 of the extension-side piston member 62. Therefore, the shock absorber 1 can suppress the leakage of oil L that occurs between the outer circumference of the piston 21 and the extension-side passage 37 and the compression-side passage 38 within the piston 21. This allows the shock absorber 1 to stabilize its performance. 【0094】 Furthermore, since the shock absorber 1 has a seal member 64 provided in a groove 83 on the compression side piston member 61, the seal member 64 can be reliably positioned in a predetermined location on the compression side piston member 61. Therefore, assembly defects of the seal member 64 can be suppressed. In addition, since the shock absorber 1 has a groove 83 on the compression side piston member 61, it is easy to visually distinguish between the compression side piston member 61 and the extension side piston member 62, and it is possible to suppress incorrect assembly, such as assembling compression side piston members 61 together or extension side piston members 62 together. 【0095】 Furthermore, the same effect can be achieved by providing a similar groove 83 on the extension piston member 62 instead of the compression piston member 61, and providing a sealing member 64 in this groove 83. In this case, the groove 83 is provided on the opposing surface 121. Also, in this case, the entire groove 83 is recessed inward in the axial direction of the extension piston member 62 from the end face 122. Also, in this case, the annular groove 91 of the groove 83 is provided radially between the hole 110 and the passage holes 111 and 112 of the extension piston member 62, at a distance from these holes 110, 111 and 112. Also, in this case, the annular groove 91 is circular in shape, surrounding the hole 110 on the radially outer side of the extension piston member 62, and is concentric with the hole 110. In this case, the radial groove 92 of the groove 83 is aligned with the radial direction of the extension piston member 62 and is provided between adjacent passage holes 111 and 112 in the circumferential direction of the extension piston member 62, at a distance from them. In this case, the radial groove 92 of the groove 83 extends radially outward from the annular groove 91 to a point before the radial outer end of the extension piston member 62. In this case, the radial groove 92 of the groove 83 substantially aligns the radial outer end position of the extension piston member 62 with the same outer end positions of the passage holes 111 and 112. In this case, the radial groove 92 of the groove 83 is located between all combinations of adjacent passage holes 111 and 112 in the circumferential direction of the extension piston member 62. 【0096】 Furthermore, in the shock absorber 1, the compression piston member 61 has a recess 84 and a protrusion 85, with the recess 84 being provided on the radially outer side of the extension flow path 37 and the other protrusion 85 being provided on the radially outer side of the compression flow path 38. In the extension piston member 62, the protrusion 125 is provided on the radially outer side of the extension flow path 37 and the other recess 124 is provided on the radially outer side of the compression flow path 38. Thus, the fitting protrusion 85 and recess 124 can block communication between the compression flow path 38 and the outer circumference of the compression piston member 61 and the extension piston member 62, and the fitting protrusion 125 and recess 84 can block communication between the extension flow path 37 and the outer circumference of the compression piston member 61 and the extension piston member 62. This makes it possible to suppress leakage of oil L within the piston 21 between the outer circumference of the piston 21 and the extension-side passage 37 and the compression-side passage 38. As a result, the shock absorber 1 can stabilize its performance. 【0097】 Furthermore, the shock absorber 1 can recognize the extension-side flow path 37 which is in phase with the recess 84 provided on the compression-side piston member 61 and the protrusion 125 provided on the extension-side piston member 62, and can recognize the compression-side flow path 38 which is in phase with the protrusion 85 provided on the compression-side piston member 61 and the recess 124 provided on the extension-side piston member 62. Therefore, the shock absorber 1 can prevent incorrect assembly of the compression-side piston member 61 and the extension-side piston member 62. 【0098】 Furthermore, the same effect can be achieved even if, in the retraction-side piston member 61, the recess 84 aligns with the passage hole 72 constituting the retraction-side flow path 38 in the circumferential direction of the retraction-side piston member 61, and the protrusion 85 aligns with the passage hole 71 constituting the extension-side flow path 37 in the circumferential direction of the retraction-side piston member 61, and in the extension-side piston member 62, the recess 124 aligns with the passage hole 112 constituting the extension-side flow path 37 in the circumferential direction of the extension-side piston member 62, and the protrusion 125 aligns with the passage hole 111 constituting the retraction-side flow path 38 in the circumferential direction of the extension-side piston member 62. In other words, in the retraction piston member 61, one of the recess 84 and the protrusion 85 is provided on the radially outer side of the extension flow path 37, and the other is provided on the radially outer side of the retraction flow path 38. In the extension piston member 62, one of the recess 124 and the protrusion 125 is provided on the radially outer side of the extension flow path 37, and the other is provided on the radially outer side of the retraction flow path 38. In this case as well, the protrusion 125 of the extension piston member 62 fits into the recess 84 of the extension piston member 61, and the protrusion 85 of the extension piston member 61 fits into the recess 124 of the extension piston member 62. In this fitted state, all the passage holes 71 of the extension piston member 61 are aligned in phase with one of the corresponding passage holes 112 of the extension piston member 62 to form the extension flow path 37, and all the passage holes 72 of the extension piston member 61 are aligned in phase with one of the corresponding passage holes 111 of the extension piston member 62 to form the extension flow path 38. 【0099】 Furthermore, in the compression piston member 61 of the shock absorber 1, multiple recesses 84 and protrusions 85 are provided, and the recesses 84 and protrusions 85 are arranged alternately. For example, when transporting the shock absorber 1 on a belt conveyor with the protrusions 85 facing downwards during manufacturing, multiple protrusions 85 can make stable contact with the belt conveyor. Therefore, it is possible to prevent the compression piston member 61 from becoming unstable and rolling, which could cause damage to the inner seat portion 75, intermediate seat portion 76, and outer seat portion 77, where precision is required. Also, in the extension piston member 62 of the shock absorber 1, multiple recesses 124 and protrusions 125 are provided, and the recesses 124 and protrusions 125 are arranged alternately. For example, when transporting the shock absorber 1 on a belt conveyor with the protrusions 125 facing downwards during manufacturing, multiple protrusions 125 can make stable contact with the belt conveyor. Therefore, it is possible to prevent the extension piston member 62 from becoming unstable and rolling around, which could cause damage to the inner seat portion 115, intermediate seat portion 116, and outer seat portion 117, where precision is required. [Explanation of Symbols] 【0100】 1...buffer, 4...cylinder, 21...piston, 22...first chamber, 23...second chamber, 25...piston rod, 33...through hole, 37...extension side passage, 38...retraction side passage, 61...retraction side piston member (one of the first piston member and the second piston member), 62...extension side piston member (the other of the first piston member and the second piston member), 64...seal member, 81,121...opposing surfaces, 83...groove, 84,124...recess, 85,125...protrusion, L...oil (working fluid).

Claims

[Claim 1] A cylinder filled with working fluid, A piston is slidably fitted inside the cylinder and divides the inside of the cylinder into two chambers, a first chamber and a second chamber. A piston rod is fastened with one end inserted into a through hole provided in the piston, and the other end extends to the outside through the first chamber. It is a shock absorber equipped with, The piston is composed of a first piston member at one axial end and a second piston member at the other axial end, and has an extension-side passage and a retraction-side passage connecting the first chamber and the second chamber. On the opposing surfaces of the first piston member and the second piston member facing each other, A sealing member is disposed between the through hole and the extension-side flow path and the contraction-side flow path, The recess and protrusion are arranged radially outward of the extension-side flow path and the contraction-side flow path, A buffer is provided. [Claim 2] The buffer is as described in claim 1, The sealing member is a buffer provided in a groove provided in the first piston member or the second piston member. [Claim 3] A buffer according to claim 1 or 2, A buffer in which one of the recess and the protrusion is provided on the radially outer side of the extension-side flow path, and the other is provided on the radially outer side of the contraction-side flow path. [Claim 4] A buffer according to claim 1 or 2, A buffer in which multiple recesses and protrusions are provided, and the recesses and protrusions are arranged alternately. [Claim 5] A piston used in a shock absorber, which divides a cylinder filled with working fluid into a first chamber and a second chamber. The aforementioned piston is It consists of a first piston member at one end in the axial direction and a second piston member at the other end in the axial direction. The through hole into which the piston rod of the buffer is inserted, An extension-side channel and a contraction-side channel are formed to connect the first chamber and the second chamber. On the opposing surfaces of the first piston member and the second piston member facing each other, A sealing member is disposed between the through hole and the extension-side flow path and the contraction-side flow path, The recess and protrusion are arranged radially outward of the extension-side flow path and the contraction-side flow path, A piston equipped with a piston. [Claim 6] The piston according to claim 5, The sealing member is a piston provided in a groove provided in the first piston member or the second piston member. [Claim 7] The piston according to claim 5 or 6, A piston in which one of the recess and the protrusion is provided on the radially outer side of the extension-side flow path, and the other is provided on the radially outer side of the retraction-side flow path. [Claim 8] The piston according to claim 5 or 6, A piston in which multiple recesses and protrusions are provided, and the recesses and protrusions are arranged alternately. [Claim 9] A piston used in a shock absorber, which divides a cylinder filled with working fluid into a first chamber and a second chamber. The aforementioned piston is It consists of a first piston member at one end in the axial direction and a second piston member at the other end in the axial direction. The through hole into which the piston rod of the buffer is inserted, An extension-side channel and a contraction-side channel are formed that connect the first chamber and the second chamber. On the opposing surfaces of the first piston member and the second piston member facing each other, Recesses and protrusions are arranged radially outward of the extension-side flow path and the contraction-side flow path, A piston equipped with a piston.

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