Shock absorber and method for manufacturing the same

Abstract

In the shock absorber, a piston includes a first piston body, a second piston body, and a piston band. The first piston body has a first passage, a second passage, a first seat, and a second seat. The first seat communicates with the first passage and has a first damping valve mounted thereon. A second damping valve is mounted on the second seat. The second piston body has a third passage, a fourth passage, a third seat, and a fourth seat. The third seat communicates with the fourth passage and has a third damping valve mounted thereon. A fourth damping valve is mounted on the fourth seat.

Description

[Technical Field]

[0001] The present invention relates to a shock absorber and a method for manufacturing a shock absorber. This application claims priority to U.S. Patent No. 17 / 954,390, filed in the United States on September 28, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] There are shock absorbers in which the piston is made up of a plurality of piston bodies (see, for example, Patent Documents 1 to 4 listed below). There is also a shock absorber that has a valve and another valve that opens in a region where the piston speed is higher than that of the first valve (see, for example, Patent Documents 4 and 5 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-107003 [Patent Document 2] Japanese Patent Application Publication No. 2014-129865 [Patent Document 3] Japanese Patent Publication No. 2-113142 [Patent Document 4] US Patent Application Publication No. 2013 / 0037361 [Patent Document 5] Japanese National Publication No. 1-149037 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there is a demand for suppressing a decrease in productivity in shock absorbers.

[0005] Therefore, an object of the present invention is to provide a shock absorber and a method for manufacturing the shock absorber that can suppress a decrease in productivity. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of 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, and a piston rod connected to the piston and extending outside the cylinder, wherein the piston has a first passage and a second passage that allow the working fluid to flow between one chamber and the other chamber within the cylinder as the piston moves, a first seat that communicates with the first passage and on which a first damping valve that opens at a slow piston speed is mounted, and a second seat that has a larger diameter than the first seat and is provided on the chamber side and opens after the first damping valve opens. a first piston body having a second seat on which a second damping valve is mounted; third and fourth passages that allow working fluid to circulate between one chamber and the other chamber in the cylinder as the piston moves; a third seat that communicates with the fourth passage and on which a third damping valve that opens at a slow piston speed is mounted; and a fourth seat that has a larger diameter than the third seat and is provided on the chamber side and on which a fourth damping valve that opens after the third damping valve opens is mounted, and the first piston body and the second piston body are connected so that the first passage and the third passage communicate with each other and the second passage communicate with each other.

[0007] One aspect of a method for manufacturing a shock absorber of the present invention includes a cylinder filled with hydraulic fluid, a piston slidably fitted within the cylinder and dividing the interior of the cylinder into two chambers, and a piston rod connected to the piston and extending outside the cylinder, wherein the piston has a first piston body having a first passage and a second passage that allow hydraulic fluid to flow between one chamber and the other chamber within the cylinder as the piston moves, a first seat that communicates with the first passage and on which a first damping valve that opens at a slow piston speed is mounted, and a second seat that is larger in diameter than the first seat and is provided on the chamber side and on which a second damping valve that opens after the first damping valve opens is mounted, and a third passage and a fourth passage that allow hydraulic fluid to flow between one chamber and the other chamber within the cylinder as the piston moves, and a second passage that communicates with the fourth passage and on which a second damping valve that opens at a slow piston speed is mounted. a second piston body having a third seat on which a third damping valve is mounted, and a fourth seat which is larger in diameter than the third seat and is provided on the chamber side, the fourth seat mounting a fourth damping valve which opens after the third damping valve opens, and which is mounted on the second piston body; and a piston band which is provided on the first piston body and the second piston body, the method comprising: a first step of connecting one surface of the first piston body to one surface of the second piston body so that the first passage communicates with the third passage and the second passage communicates with the fourth passage; a second step of machining an end of the first passage opposite to the third passage, an end of the third passage opposite to the first passage, an end of the second passage opposite to the fourth passage, an end of the fourth passage opposite to the second passage, and a groove into which the piston band is attached; and a third step of attaching the piston band to the groove. [Effects of the Invention]

[0008] According to the above aspects of the present invention, it is possible to suppress a decrease in productivity. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a main part of a shock absorber according to an embodiment of the present invention. [Figure 3] 1 is a partial cross-sectional view of a main portion of a shock absorber according to an embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view of a main portion of a shock absorber according to an embodiment of the present invention. [Figure 5] 1 is a partial cross-sectional view of a main portion of a shock absorber according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] A shock absorber according to an embodiment of the present invention will be described with reference to the drawings. For ease of explanation, the upper side of the drawings will be referred to as "top" and the lower side of the drawings will be referred to as "bottom."

[0011] As shown in FIG. 1, the shock absorber 1 of this embodiment is a twin-tube hydraulic shock absorber. The shock absorber 1 is used in a suspension device for a vehicle, specifically an automobile. The shock absorber 1 includes a cylinder 2. The cylinder 2 has an inner tube 3 and an outer tube 4. The inner tube 3 is cylindrical. The outer tube 4 is cylindrical with a bottom. The inner diameter of the outer tube 4 is larger than the outer diameter of the inner tube 3. The inner tube 3 is disposed radially inside the outer tube 4. The central axis of the inner tube 3 and the central axis of the outer tube 4 coincide. A reservoir chamber 6 is formed between the inner tube 3 and the outer tube 4.

[0012] The outer cylinder 4 has a body 11 and a bottom 12. The body 11 and the bottom 12 are formed seamlessly as a single unit. The body 11 is cylindrical. The bottom 12 closes the lower part of the body 11.

[0013] The shock absorber 1 is equipped with a piston 18. The piston 18 is inserted into the inner tube 3 of the cylinder 2. The piston 18 is slidably fitted within the inner tube 3 of the cylinder 2. The piston 18 divides the inner tube 3 into two chambers: a first chamber 19 on one side and a second chamber 20 on the other side. In the axial direction of the cylinder 2, the first chamber 19 is located on the opposite side of the piston 18 from the bottom 12. In the axial direction of the cylinder 2, the second chamber 20 is located closer to the bottom 12 than the piston 18. In the cylinder 2, oil L is sealed in the first chamber 19 and the second chamber 20 within the inner tube 3 as a working fluid. In the cylinder 2, oil L and gas G are sealed in a reservoir chamber 6 between the inner tube 3 and the outer tube 4.

[0014] The shock absorber 1 includes a piston rod 21. One axial end of the piston rod 21 is disposed inside the inner tube 3 of the cylinder 2. This one end of the piston rod 21 is connected to the piston 18. The other axial end of the piston rod 21 extends from the cylinder 2 to the outside of the cylinder 2.

[0015] The piston 18 is fixed to the piston rod 21. Therefore, the piston 18 and the piston rod 21 move together. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to increase the amount of protrusion from the cylinder 2 is the extension stroke, in which the overall length increases. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to decrease the amount of protrusion from the cylinder 2 is the compression stroke, in which the overall length shortens. In the shock absorber 1, the piston 18 moves toward the first chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves toward the second chamber 20 during the compression stroke.

[0016] Rod guides 22 are fitted to the upper openings of the inner cylinder 3 and the outer cylinder 4. A seal member 23 is fitted to the outer cylinder 4 above the rod guide 22. Both the rod guide 22 and the seal member 23 are annular. The piston rod 21 is inserted radially inside the rod guide 22 and the seal member 23. The piston rod 21 slides along the axial direction of each of the rod guide 22 and the seal member 23. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 23.

[0017] The rod guide 22 restricts radial movement of the piston rod 21 relative to the inner cylinder 3 and outer cylinder 4 of the cylinder 2. When the piston rod 21 is fitted into the rod guide 22, the piston 18 is fitted into the inner cylinder 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the inner cylinder 3. The rod guide 22 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 23 is in close contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 23 relative to the seal member 23. The seal member 23 prevents the oil liquid L in the inner cylinder 3 and the high-pressure gas G and oil liquid L in the reservoir chamber 6 from leaking to the outside.

[0018] The rod guide 22 has an outer periphery with a larger diameter at its upper part than at its lower part. The rod guide 22's smaller-diameter lower part fits into the inner periphery of the upper end of the inner cylinder 3. The rod guide 22's larger-diameter upper part fits into the inner periphery of the upper part of the outer cylinder 4. A base member 26 of the base valve 25 is installed on the bottom 12 of the outer cylinder 4. The base member 26 is positioned radially relative to the outer cylinder 4. The base member 26 has an outer periphery with a smaller diameter at its upper part than at its lower part. The base member 26's smaller-diameter upper part fits into the inner periphery of the lower end of the inner cylinder 3. This causes the central axis of the inner cylinder 3 and the central axis of the outer cylinder 4 to coincide. The base member 26 separates the second chamber 20 from the reservoir chamber 6.

[0019] The upper end of the outer cylinder 4 is crimped radially inward of the outer cylinder 4. The seal member 23 is fixed to the cylinder 2 by being sandwiched between this crimped portion and the rod guide 22.

[0020] The piston rod 21 has a main shaft portion 27 and an attachment shaft portion 28. The main shaft portion 27 and the attachment shaft portion 28 are both rod-shaped.

[0021] The mounting shaft portion 28 has an outer diameter smaller than that of the main shaft portion 27. The mounting shaft portion 28 is disposed within the cylinder 2. The piston 18 is attached to the mounting shaft portion 28. The main shaft portion 27 has a stepped shaft portion 29. The stepped shaft portion 29 is provided at the end of the main shaft portion 27 on the mounting shaft portion 28 side in the axial direction. The stepped shaft portion 29 widens in a direction perpendicular to the central axis of the piston rod 21. The end of the mounting shaft portion 28 opposite the main shaft portion 27 in the axial direction of the mounting shaft portion 28 forms a threaded shaft portion 31. The threaded shaft portion 31 has a male thread formed on its outer periphery. The portion of the mounting shaft portion 28 between the main shaft portion 27 and the threaded shaft portion 31 in the axial direction of the mounting shaft portion 28 forms a mating shaft portion 32. The outer periphery of the mating shaft portion 32 is a cylindrical surface. The piston 18 fits into the mating shaft portion 32.

[0022] The shock absorber 1 is connected to the vehicle body with the portion of the piston rod 21 protruding from the cylinder 2 located at the top. At the same time, the shock absorber 1 is connected to the wheel side of the vehicle with the mounting bracket 33 fixed to the body 11 of the outer cylinder 4 located at the bottom. The shock absorber 1 may be a mono-tube type instead of a double-tube type. The mono-tube type eliminates the outer cylinder 4 and base valve 25 from the shock absorber 1, replaces the inner cylinder 3 with a cylindrical cylinder with a bottom, and provides a free piston between the bottom of the cylinder and the piston 18. Gas is sealed between the bottom of the cylinder and the free piston. With such a mono-tube shock absorber, it is possible to connect the cylinder side to the vehicle body and the piston rod 21 to the wheel side.

[0023] As shown in FIG. 2 , the piston 18 has a first piston body 36, a second piston body 37, and a piston band 38. The first piston body 36 and the second piston body 37 are both integrally molded from metal. The first piston body 36 and the second piston body 37 are both annular. The first piston body 36 and the second piston body 37 of the piston 18 are connected to the mounting shaft portion 28 of the piston rod 21. In this case, the first piston body 36 is disposed on the opposite side of the main shaft portion 27 from the second piston body 37 in the axial direction of the piston rod 21. In addition, in this case, the second piston body 37 is disposed between the first piston body 36 and the shaft step portion 29.

[0024] The first piston body has a joining surface 41 formed on the axial side thereof facing the second piston body 37. The joining surface 41 is flat and extends perpendicular to the central axis of the first piston body .

[0025] A through hole 42 is formed in the radial center of the first piston body 36. The through hole 42 passes through the first piston body 36 in the axial direction of the first piston body 36. The mounting shaft portion 28 of the piston rod 21 is fitted into the through hole 42 of the first piston body 36.

[0026] The first piston body 36 has a main body portion 43 , an inner seat 45 , a first seat 46 and a second seat 47 .

[0027] The main body portion 43 has an annular shape. The radially inner side of the main body portion 43 forms a part of the through hole 42.

[0028] The inner seat 45 is annular. The inner seat 45 protrudes from the main body 43 toward the opposite side of the joining surface 41 in the axial direction of the first piston body 36. The radially inner side of the inner seat 45 forms part of the through hole 42.

[0029] The first seat 46 is annular. The first seat 46 protrudes from the main body portion 43 on the opposite side of the joining surface 41 in the axial direction of the first piston body 36. The first seat 46 has a larger diameter than the inner seat 45. The first seat 46 is provided outside the inner seat 45 in the radial direction of the first piston body 36 so as to surround the inner seat 45. The tip end surface of the first seat 46 is provided on the opposite side of the joining surface 41 from the tip end surface of the inner seat 45 in the axial direction of the first piston body 36.

[0030] The first piston body 36 has a passage groove 51 formed between the inner seat 45 and the first seat 46 in the radial direction of the first piston body 36. The passage groove 51 has an annular shape extending in the circumferential direction of the first piston body 36.

[0031] A passage hole 52 is formed in the main body 43 of the first piston body 36 between the inner seat 45 and the first seat 46 in the radial direction of the first piston body 36. The passage hole 52 is arranged closer to the first seat 46 than the inner seat 45 in the radial direction of the first piston body 36. One end of the passage hole 52 opens to the joining surface 41, and the other end opens to the passage groove 51. The first piston body 36 is provided with a plurality of passage holes 52 of the same shape at equal intervals in the circumferential direction of the first piston body 36.

[0032] The second seat 47 is annular. The second seat 47 protrudes from the main body portion 43 on the opposite side of the joining surface 41 in the axial direction of the first piston body 36. The second seat 47 has a larger diameter than the first seat 46. The second seat 47 is provided on the outer side of the first seat 46 in the radial direction of the first piston body 36 so as to surround the first seat 46. The second seat 47 is provided on the opposite side of the joining surface 41 from the first seat 46 in the axial direction of the first piston body 36.

[0033] The first piston body 36 has an outer peripheral surface 61 formed at its radially outer end. The outer peripheral surface 61 is a cylindrical surface centered on the central axis of the first piston body 36. The outer peripheral surface 61 is provided on the main body portion 43.

[0034] The first piston body 36 has an open groove 62 on its outer periphery on the outside in the radial direction. The open groove 62 is recessed radially inward of the first piston body 36 relative to the outer periphery 61. The open groove 62 has an annular shape centered on the central axis of the first piston body 36. The open groove 62 is provided between the center of the first piston body 36 in the axial direction and the second seat 47. The bottom surface of the open groove 62 overlaps with the second seat 47 in the radial direction of the first piston body 36.

[0035] A passage hole 65 is formed in the main body portion 43 of the first piston body 36. One end of the passage hole 65 opens to the joint surface 41, and the other end opens to the open groove portion 62. The first piston body 36 is provided with a plurality of passage holes 65 of the same shape at equal intervals in the circumferential direction of the first piston body 36. The first piston body 36 is provided with passage holes 52 and passage holes 65 alternately at equal intervals in the circumferential direction of the first piston body 36. Therefore, the first piston body 36 is provided with the same number of passage holes 52 and passage holes 65.

[0036] The main body portion 43 has a recessed portion 72 recessed from the joining surface 41 toward the inner seat 45 in the axial direction of the first piston body .

[0037] In the first piston body 36, the passages in the multiple passage holes 52 and the passage in the passage groove 51 form a first passage 75. The first passage 75 includes the space between the inner seat 45 and the first seat 46. Therefore, the first seat 46 communicates with the first passage 75. The first passage 75 also includes the space between the first seat 46 and the second seat 47. Therefore, the second seat 47 also communicates with the first passage 75.

[0038] In the first piston body 36, the passages in the plurality of passage holes 65 and the passage in the open groove portion 62 form a second passage 76.

[0039] The second piston body 37 has a joining surface 81 formed on the axial side thereof facing the first piston body 36. The joining surface 81 is flat and extends perpendicular to the central axis of the second piston body 37.

[0040] A through-hole 82 is formed in the radial center of the second piston body 37. The through-hole 82 passes through the second piston body 37 in the axial direction of the second piston body 37. In the second piston body 37, the mounting shaft portion 28 of the piston rod 21 is fitted into the through-hole 82.

[0041] The second piston body 37 has a main body portion 83 , an inner seat 85 , a third seat 86 , a fourth seat 87 and a convex portion 89 .

[0042] The main body portion 83 has an annular shape. The inner side of the main body portion 83 in the radial direction forms a part of the through hole 82.

[0043] The inner seat 85 is annular. The inner seat 85 protrudes from the main body 83 toward the opposite side of the joining surface 81 in the axial direction of the second piston body 37. The radially inner side of the inner seat 85 forms part of the through hole 82.

[0044] The third seat 86 is annular. The third seat 86 protrudes from the main body portion 83 on the opposite side of the joining surface 81 in the axial direction of the second piston body 37. The third seat 86 has a larger diameter than the inner seat 85. The third seat 86 is provided outside the inner seat 85 in the radial direction of the second piston body 37 so as to surround the inner seat 85. The tip end surface of the third seat 86 is provided on the opposite side of the joining surface 81 from the tip end surface of the inner seat 85 in the axial direction of the second piston body 37.

[0045] The second piston body 37 has a passage groove 91 formed between an inner seat 85 and a third seat 86 in the radial direction of the second piston body 37. The passage groove 91 has an annular shape extending in the circumferential direction of the second piston body 37.

[0046] A passage hole 92 is formed in the main body 83 of the second piston body 37 between the inner seat 85 and the third seat 86 in the radial direction of the second piston body 37. The passage hole 92 is arranged closer to the third seat 86 than to the inner seat 85 in the radial direction of the second piston body 37. One end of the passage hole 92 opens to the joining surface 81, and the other end opens to the passage groove 91. The second piston body 37 is provided with a plurality of passage holes 92 of the same shape, spaced equally apart in the circumferential direction of the second piston body 37. The number of passage holes 92 is the same as the number of passage holes 52 of the first piston body 36.

[0047] The fourth seat 87 is annular. The fourth seat 87 protrudes from the main body portion 83 on the opposite side of the joining surface 81 in the axial direction of the second piston body 37. The fourth seat 87 has a larger diameter than the third seat 86. The fourth seat 87 is provided on the outer side of the third seat 86 in the radial direction of the second piston body 37 so as to surround the third seat 86. The fourth seat 87 is provided on the opposite side of the joining surface 81 from the third seat 86 in the axial direction of the second piston body 37.

[0048] The second piston body 37 has an outer peripheral surface 101 formed at its radially outer end. The outer peripheral surface 101 is cylindrical and has its center on the central axis of the second piston body 37. The outer peripheral surface 101 is provided on the main body portion 83. The outer diameter of the outer peripheral surface 101, i.e., the outer diameter of the second piston body 37, is equal to the outer diameter of the outer peripheral surface 61 of the first piston body 36, i.e., the outer diameter of the first piston body 36.

[0049] The second piston body 37 has an open groove 102 on its outer circumferential surface on the outside in the radial direction. The open groove 102 is recessed radially inward of the second piston body 37 relative to the outer circumferential surface 101. The open groove 102 has an annular shape centered on the central axis of the second piston body 37. The open groove 102 is provided between the center of the second piston body 37 in the axial direction and the fourth seat 87. The bottom surface of the open groove 102 overlaps with the fourth seat 87 in the radial direction of the second piston body 37.

[0050] A passage hole 105 is formed in the main body 83 of the second piston body 37. One end of the passage hole 105 opens to the joining surface 81, and the other end opens to the open groove portion 102. The second piston body 37 is provided with a plurality of passage holes 105 of the same shape at equal intervals in the circumferential direction of the second piston body 37. The second piston body 37 is provided with passage holes 92 and passage holes 105 alternately at equal intervals in the circumferential direction of the second piston body 37. Therefore, the second piston body 37 is provided with the same number of passage holes 92 and passage holes 105. The number of passage holes 105 is the same as the number of passage holes 65 of the first piston body 36.

[0051] The convex portion 89 protrudes from the joining surface 81 on the opposite side of the inner seat 85 in the axial direction of the second piston body 37.

[0052] In the second piston body 37, the passages in the plurality of passage holes 105 and the passage in the open groove portion 102 form a third passage 106.

[0053] In the second piston body 37, the passages in the plurality of passage holes 92 and the passage in the passage groove 91 form a fourth passage 107. The fourth passage 107 includes the space between the inner seat 85 and the third seat 86. Therefore, the third seat 86 communicates with the fourth passage 107. The fourth passage 107 also includes the space between the third seat 86 and the fourth seat 87. Therefore, the fourth seat 87 also communicates with the fourth passage 107.

[0054] The first sheet 46 and the third sheet 86 have the same shape. The second sheet 47 and the fourth sheet 87 have the same shape. The passage groove 51 and the passage groove 91 have the same shape. The passage hole 52 and the passage hole 92 have the same shape. The open groove portion 62 and the open groove portion 102 have the same shape. The passage hole 65 and the passage hole 105 have the same shape.

[0055] The first piston body 36 and the second piston body 37 are connected together such that the convex portion 89 of the second piston body 37 fits into the concave portion 72 of the first piston body 36. As a result, the mating surface 41 of the first piston body 36 and the mating surface 81 of the second piston body 37 come into surface contact with each other. In this state, the central axis of the first piston body 36 and the central axis of the second piston body 37 coincide with each other.

[0056] In this state, the passage hole 52 of the first piston body 36 overlaps with the passage hole 105 of the second piston body 37 in the circumferential and radial directions of the first piston body 36 and the second piston body 37. On the other hand, the passage hole 52 of the first piston body 36 does not overlap with the passage hole 92 in the circumferential and radial directions of the first piston body 36 and the second piston body 37. In other words, in this state, the first passage 75 of the first piston body 36 communicates with the third passage 106 of the second piston body 37, but does not communicate with the fourth passage 107.

[0057] In this state, the passage hole 65 of the first piston body 36 overlaps with the passage hole 92 of the second piston body 37 in the circumferential and radial directions of the first piston body 36 and the second piston body 37. On the other hand, the passage hole 65 of the first piston body 36 does not overlap with the passage hole 105 in the circumferential and radial directions of the first piston body 36 and the second piston body 37. In other words, in this state, the second passage 76 of the first piston body 36 communicates with the fourth passage 107 of the second piston body 37, but does not communicate with the third passage 106.

[0058] In this way, the first piston body 36 and the second piston body 37 are aligned when the convex portion 89 fits into the concave portion 72. The first piston body 36 and the second piston body 37 are not aligned in any other connection state. In other words, in any other state, the first piston body 36 and the second piston body 37 are not in a state where the first passage 75 and the third passage 106 communicate with each other, the second passage 76 and the fourth passage 107 communicate with each other, and the mating surfaces 41 and 81 are not in surface contact with each other, as described above.

[0059] The convex portion 89 and the concave portion 72 form an alignment portion 121. The alignment portion 121 is provided on the joining surfaces 41, 81 where the first piston body 36 and the second piston body 37 are connected to each other. The alignment portion 121 aligns the positions of the first passage 75 and the third passage 106, and also aligns the positions of the second passage 76 and the fourth passage 107, in the circumferential and radial directions of the first piston body 36 and the second piston body 37.

[0060] The first piston body 36 and the second piston body 37 are fixed to each other and integrated by press-fitting the convex portion 89 into the concave portion 72. At this time, the first piston body 36 and the second piston body 37 are positioned circumferentially and radially by the positioning portion 121, and the first passage 75 and the third passage 106 are communicated with each other, and the second passage 76 and the fourth passage 107 are communicated with each other, so that the mating surfaces 41 and 81 are in surface contact with each other. In other words, the first piston body 36 and the second piston body 37 are connected so that the first passage 75 and the third passage 106 are communicated with each other, and the second passage 76 and the fourth passage 107 are communicated with each other.

[0061] In this manner, the first piston body 36 is formed by cutting the inner seat 45, the first seat 46, and the second seat 47 in a state where it is integrated with the second piston body 37. In other words, the end of the first passage 75 of the first piston body 36 opposite to the third passage 106 is formed by cutting.

[0062] In addition, the second piston body 37 is formed by cutting the inner seat 85, the third seat 86, and the fourth seat 87 in a state where it is integrated with the first piston body 36. In other words, the second piston body 37 has the end of the fourth passage 107 opposite to the second passage 76 formed by cutting.

[0063] After these processes, the first sheet 46 and the third sheet 86 become mirror-symmetrical. Also, after these processes, the second sheet 47 and the fourth sheet 87 become mirror-symmetrical. Also, after these processes, the difference in height between the inner sheet 45 and the first sheet 46 becomes larger by a predetermined amount than the difference in height between the inner sheet 85 and the third sheet 86.

[0064] Furthermore, the outer peripheries of the integrated first piston body 36 and second piston body 37 are machined at the same time. At this time, the open groove portion 62 of the first piston body 36 is formed, and the open groove portion 102 of the second piston body 37 is formed. In other words, the end of the second passage 76 of the first piston body 36 opposite the fourth passage 107 is formed by machining. The end of the third passage 106 of the second piston body 37 opposite the first passage 75 is formed by machining. In addition, the deep groove portion 131 (groove) shown in FIG. 3 is formed on the outer periphery of the first piston body 36 by machining. At the same time, outer peripheries of the first piston body 36 and the second piston body 37 are formed with outer peripheries 61 and 101 and a plurality (specifically, four locations) of shallow groove portions 132 (grooves) by machining. The outer peripheries 61 and 101 are formed to form the same cylindrical surface.

[0065] The deep groove portion 131 is recessed radially inward of the first piston body 36 relative to the outer circumferential surface 101. The deep groove portion 131 has an annular shape centered on the central axis of the first piston body 36. The deep groove portion 131 is formed in a portion of the first piston body 36 closer to the second piston body 37 than the open groove portion 62 in the axial direction.

[0066] The shallow groove portions 132 have the same shape and are recessed radially inward of the first piston body 36 and the second piston body 37 relative to the outer peripheral surfaces 61, 101. Each of the shallow groove portions 132 has an annular shape centered on the central axis of the first piston body 36 and the second piston body 37. The shallow groove portions 132 are shallower in depth from the outer peripheral surfaces 61, 101 than the deep groove portions 131 are from the outer peripheral surfaces 61, 101. In other words, the deep groove portion 131 is deeper from the outer peripheral surfaces 61, 101 than the shallow groove portions 132 are from the outer peripheral surfaces 61, 101. In other words, the diameter of the bottom of the deep groove portion 131 is smaller than the diameter of the bottom of the shallow groove portions 132.

[0067] The shallow groove portions 132 are formed in a portion of the first piston body 36 closer to the second piston body 37 than the deep groove portion 131 in the axial direction of the first piston body 36, and in a portion of the second piston body 37 closer to the first piston body 36 than the open groove portion 102. In other words, the deep groove portion 131 is located closer to the second seat 47 shown in Fig. 4 in the axial direction of the first piston body 36 and the second piston body 37 than the shallow groove portions 132. As shown in Fig. 3, the shallow groove portions 132 are arranged side by side at equal intervals in the axial direction of the first piston body 36 and the second piston body 37.

[0068] The piston band 38 is made of synthetic resin and is formed in an endless band shape. The piston band 38 has a base portion 141, a deep groove fitting portion 142, and a plurality of (specifically, four) shallow groove fitting portions 143.

[0069] The base portion 141 is an endless strip of a constant thickness.

[0070] The deep groove fitting portion 142 protrudes radially inward from the cylindrical inner peripheral surface 151 of the base portion 141. The deep groove fitting portion 142 is provided at one axial end of the base portion 141. The deep groove fitting portion 142 is an endless annular shape that continues around the entire circumference of the base portion 141.

[0071] The shallow groove fitting portions 143 have the same shape and protrude radially inward from the inner circumferential surface 151 of the base portion 141. The shallow groove fitting portions 143 are provided at intermediate positions in the axial direction of the base portion 141. Each of the shallow groove fitting portions 143 is an endless ring shape that continues around the entire circumference of the base portion 141. The shallow groove fitting portions 143 are arranged side by side at equal intervals in the axial direction of the base portion 141. The shallow groove fitting portions 143 protrude from the inner circumferential surface 151 of the base portion 141 to a height that is smaller than the protrusion height of the deep groove fitting portions 142 from the inner circumferential surface 151. In other words, in the piston band 38, the inner diameters of the shallow groove fitting portions 143 are larger than the inner diameter of the deep groove fitting portions 142.

[0072] The piston band 38 is attached so as to cover the outer peripheries of the first piston body 36 and the second piston body 37 that have been integrated by press-fitting as described above. At this time, the piston band 38 is elastically deformed to expand in diameter, and is placed over the first piston body 36 and the second piston body 37 shown in FIG. 3 from the second seat 47 side shown in FIG. 4 , with the axial end opposite the deep groove fitting portion 142 leading. The deep groove fitting portion 142 of the piston band 38 is first released from its expanded diameter and fitted into the deep groove portion 131 of the first piston body 36. Then, the shallow groove fitting portions 143 are released from their expanded diameter and fitted into corresponding ones of the shallow groove portions 132. The inner periphery 151 of the base portion 141 then comes into surface contact with and closely contacts the outer peripheries 61, 101 of the first piston body 36 and the second piston body 37.

[0073] In this way, the piston band 38 is integrally attached to the outer peripheral surfaces 61, 101 of the first piston body 36 and the second piston body 37 to form the piston 18. The piston 18 is composed of only three parts: the first piston body 36, the second piston body 37, and the piston band 38.

[0074] The piston 18 is formed including a first step, a second step, and a third step. The first step is a step of connecting the mating surface 41, which is one surface of the first piston body 36, to the mating surface 81, which is one surface of the second piston body 37, so that the first passage 75 communicates with the third passage 106 and the second passage 76 communicates with the fourth passage 107, as shown in FIG. 2 . The second step is a step of machining an end of the first passage 75 opposite the third passage 106, an end of the third passage 106 opposite the first passage 75, an end of the second passage 76 opposite the fourth passage 107, an end of the fourth passage 107 opposite the second passage 76, and a deep groove portion 131 and a plurality of shallow groove portions 132 into which the piston band 38 is attached, as shown in FIG. 3 . The third step is a step of attaching the piston band 38 to the deep groove portion 131 and the plurality of shallow groove portions 132. In the third step, the piston band 38 is attached to the deep groove portion 131 via the second sheet 47 shown in FIG.

[0075] The piston 18 is fitted to the fitting shaft portion 32 of the piston rod 21 such that the second piston body 37 is disposed between the first piston body 36 and the shaft step portion 29 in the axial direction of the piston rod 21. At this time, the piston 18 is positioned radially relative to the piston rod 21 by fitting the fitting shaft portion 32 into the through hole 82 of the second piston body 37 and the through hole 42 of the first piston body 36.

[0076] With the piston 18 connected to the piston rod 21, the first seat 46 and the second seat 47 of the first piston body 36 are arranged on the second chamber 20 side, and the third seat 86 and the fourth seat 87 of the second piston body 37 are arranged on the first chamber 19 side. The piston 18 slides relative to the inner cylinder 3 with the piston band 38 in contact with the inner peripheral surface of the inner cylinder 3 at its outer peripheral surface.

[0077] 4, on the inner seat 45 of the piston 18, in order from the inner seat 45 side in the axial direction of the piston 18, one disc 161, one disc 162, one disc 163, one disc 164, one disc 165, one disc 166, a plurality of (specifically, six) discs 167, a plurality of (specifically, three) discs 168, one disc 169, one disc 170, and one annular member 171 are stacked. The number of discs shown here is one embodiment and can be adjusted as appropriate according to the desired damping force characteristics.

[0078] The discs 161 to 170 and the circular member 171 are all made of metal. The discs 161 to 170 are all circular flat plates with holes and a uniform thickness. The circular member 171 is annular. The fitting shaft portion 32 of the piston rod 21 is fitted inside each of the discs 161 to 170 and the circular member 171.

[0079] The disc 161 has an outer diameter that is larger than the outer diameter of the inner seat 45 of the piston 18 and smaller than the inner diameter of the first seat 46 .

[0080] The disc 162 has an outer diameter larger than the outer diameter of the first seat 46 of the piston 18 and smaller than the inner diameter of the second seat 47. The disc 162 moves away from and abuts against the first seat 46 to open and close the first passage 75 at the position of the first seat 46. A passage hole 182 is formed in the disc 162 at a position between the inner seat 45 of the piston 18 and the outer periphery of the disc 161. The passage hole 182 penetrates the disc 162 in the axial direction of the disc 162. The passage hole 182 is an arc-shaped elongated hole extending in the circumferential direction of the disc 162. The passage hole 182 is opened and closed by the disc 161.

[0081] The outer diameter of the disk 163 is equal to the outer diameter of the disk 162. A notch 183 is formed in the outer periphery of the disk 163. The notch 183 penetrates the disk 163 in the axial direction of the disk 163. The notch 183 opens to the outer periphery of the disk 163. A plurality of notches 183 are formed in the disk 163 at equal intervals in the circumferential direction of the disk 163. The inner portions of the plurality of notches 183 in the radial direction of the disk 163 communicate with the passage hole 182 of the disk 162. The plurality of notches 183 and the passage hole 182 form a fixed orifice 184. The fixed orifice 184 is opened and closed by the disk 161. The disks 161 and 162 form a check valve 185. The check valve 185 allows the oil liquid L to flow from the fixed orifice 184 to the passage in the passage groove 51 and restricts the flow of the oil liquid L from the passage in the passage groove 51 into the fixed orifice 184 .

[0082] The outer diameter of the disk 164 is equal to the outer diameter of the disk 163. The disk 164 covers the multiple cutouts 183 of the disk 163 on the side opposite to the disk 162 to form a fixed orifice 184. Therefore, the fixed orifice 184 and a check valve 185 that allows the oil liquid L to flow through the fixed orifice 184 in only one direction are made up of the multiple stacked disks 161 to 164.

[0083] The disc 165 has an outer diameter that is smaller than the outer diameter of the disc 164 and slightly larger than the outer diameter of the inner seat 45 .

[0084] The disc 166 has an outer diameter equal to the outer diameter of the second seat 47 of the piston 18. The disc 166 separates from and abuts against the second seat 47 to open and close the first passage 75 at the position of the second seat 47. A notch 186 is formed in the outer periphery of the disc 166. The notch 186 penetrates the disc 166 in the axial direction of the disc 166. The notch 186 opens to the outer periphery of the disc 166. A plurality of notches 186 are formed in the disc 166 at equal intervals around the periphery of the disc 166. The plurality of notches 186 extend radially across the second seat 47. The plurality of notches 186 form a fixed orifice 187 in the first passage 75 when the disc 166 abuts against the second seat 47. The flow path cross-sectional area of ​​the fixed orifice 187 is larger than the flow path cross-sectional area of ​​the fixed orifice 184.

[0085] The multiple disks 167 have the same outer diameter, and each outer diameter is equal to the outer diameter of disk 166. Of the multiple disks 167, the disk 167 closest to disk 166 covers the multiple cutouts 186 of disk 166 on the side opposite to second sheet 47, thereby forming a fixed orifice 187.

[0086] The plurality of disks 168 have the same outer diameter, and each outer diameter is smaller than the outer diameter of disk 167 and larger than the outer diameter of disk 165.

[0087] The outer diameter of the disk 169 is smaller than the outer diameter of the disk 168 and is equal to the outer diameter of the disk 165 .

[0088] The outer diameter of the disk 170 is larger than the outer diameter of the disk 169 and is equal to the outer diameter of the disk 167 .

[0089] The outer diameter of the circular ring member 171 is smaller than the outer diameter of the disc 170 and larger than the outer diameter of the disc 169. The thickness of the circular ring member 171 is greater than the thickness of each of the discs 161-170, and the rigidity of the circular ring member 171 is higher than that of the discs 161-170.

[0090] 2 are flow paths through which the oil L flows from the first chamber 19 to the second chamber 20 during the extension stroke. The third passage 106 is in constant communication with the first chamber 19.

[0091] 4, the discs 162 to 164 are placed on the first seat 46 and constitute a first damping valve 191 that opens and closes the first passage 75 by moving away from and into contact with the first seat 46. The first damping valve 191 is provided with a fixed orifice 184 and a check valve 185.

[0092] The discs 166-168 are placed on the second seat 47 and constitute a second damping valve 192 that opens and closes the first passage 75 by moving away from and into contact with the second seat 47. A fixed orifice 187 is provided in the second damping valve 192. The second damping valve 192 is provided closer to the second chamber 20 than the first damping valve 191. The total thickness of the discs 166-168 of the second damping valve 192 is greater than the total thickness of the discs 162-164 of the first damping valve 191. The second damping valve 192 has higher rigidity than the first damping valve 191.

[0093] When the first damping valve 191 lifts off the first seat 46 and opens, it causes hydraulic fluid L to flow from the first chamber 19 shown in FIG. 2 to the second chamber 20 side via the third passage 106, the passages in the plurality of passage holes 52, the passage in the passage groove 51, and the passage between the first damping valve 191 and the first seat 46, all of which constitute the first passage 75. At that time, the first damping valve 191 suppresses the flow of hydraulic fluid L to generate a damping force. The first damping valve 191 is provided in the first passage 75, and suppresses the flow of hydraulic fluid L that occurs during the extension stroke to generate a damping force.

[0094] The second damping valve 192 has higher rigidity than the first damping valve 191, and therefore, after the first damping valve 191 leaves the first seat 46 and opens, it leaves the second seat 47 and opens. When the second damping valve 192 leaves the second seat 47 and opens, hydraulic fluid L flows from the first chamber 19 to the second chamber 20 via the third passage 106, the passages in the multiple passage holes 52, the passage in the passage groove 51, the passage between the first damping valve 191 and the first seat 46, the passage between the first seat 46 and the second seat 47, and the passage between the second damping valve 192 and the second seat 47, all of which constitute the first passage 75. At this time, the second damping valve 192 suppresses the flow of hydraulic fluid L to generate a damping force. The second damping valve 192 is provided in the first passage 75, and suppresses the flow of hydraulic fluid L that occurs during the extension stroke to generate a damping force.

[0095] The first damping valve 191 is provided upstream of the second damping valve 192 in the flow direction of the hydraulic fluid L during the extension stroke. The first damping valve 191 has lower rigidity and a lower valve opening pressure than the second damping valve 192. Therefore, the first damping valve 191 opens in a region where the moving speed of the piston 18 (hereinafter referred to as piston speed) is lower than that of the second damping valve 192.

[0096] As described above, the first piston body 36 has a first seat 46 and a second seat 47. The first seat 46 communicates with the first passage 75, and a first damping valve 191 that opens at a low piston speed is mounted on the first seat 46. The second seat 47 has a larger diameter than the first seat 46 and is located closer to the second chamber 20 than the first seat 46, and a second damping valve 192 that opens after the first damping valve 191 opens is mounted on the second seat 47.

[0097] The check valve 185 provided in the first damping valve 191 closes against the flow from the first chamber 19 toward the second chamber 20 that occurs during the extension stroke.

[0098] 5, stacked on the inner seat 85 of the piston 18 are, in order from the inner seat 85 side in the axial direction of the piston 18, one disc 201, multiple (specifically, two) discs 202, one disc 203, one disc 204, multiple (specifically, three) discs 205, multiple (specifically, two) discs 206, one disc 207, one disc 208, and one annular member 209. The number of discs shown here is one embodiment and can be adjusted as appropriate depending on the desired damping force characteristics.

[0099] The discs 201 to 208 and the circular member 209 are all made of metal. The discs 201 to 208 are all circular flat plates with holes and a uniform thickness. The circular member 209 is annular. The fitting shaft portion 32 of the piston rod 21 is fitted inside each of the discs 201 to 208 and the circular member 209.

[0100] The disc 201 has an outer diameter larger than the outer diameter of the third seat 86 of the piston 18 and smaller than the inner diameter of the fourth seat 87. The disc 201 moves away from and abuts against the third seat 86 to open and close the fourth passage 107 at the position of the third seat 86. A notch 221 is formed in the outer periphery of the disc 201. The notch 221 penetrates the disc 201 in the axial direction of the disc 201. The notch 221 opens to the outer periphery of the disc 201. A plurality of notches 221 are formed in the disc 201 at equal intervals around the circumferential direction of the disc 201. The plurality of notches 221 extend radially across the third seat 86. The plurality of notches 221 form a fixed orifice 222 in the fourth passage 107 when the disc 201 abuts against the third seat 86.

[0101] The multiple disks 202 have the same outer diameter, and each outer diameter is equal to the outer diameter of disk 201. Of the multiple disks 202, the disk 202 closest to disk 201 covers the multiple cutouts 221 of disk 201 on the side opposite to third sheet 86, thereby forming a fixed orifice 222.

[0102] The disk 203 has an outer diameter smaller than that of the disk 202 and slightly larger than that of the inner seat 85 .

[0103] The disc 204 has an outer diameter larger than the outer diameter of the fourth seat 87 of the piston 18. The disc 204 moves away from and abuts against the fourth seat 87 to open and close the fourth passage 107 at the position of the fourth seat 87. A notch 225 is formed in the outer periphery of the disc 204. The notch 225 penetrates the disc 204 in the axial direction of the disc 204. The notch 225 opens to the outer periphery of the disc 204. A plurality of notches 225 are formed in the disc 204 at equal intervals around the periphery of the disc 204. The plurality of notches 225 extend radially across the fourth seat 87. The plurality of notches 225 form a fixed orifice 226 in the fourth passage 107 when the disc 204 abuts against the fourth seat 87. The fixed orifice 226 has a flow passage cross-sectional area larger than that of the fixed orifice 222 .

[0104] The multiple disks 205 have the same outer diameter, and each outer diameter is equal to the outer diameter of disk 204. Of the multiple disks 205, the disk 205 closest to disk 204 covers the multiple cutouts 225 of disk 204 on the side opposite to fourth sheet 87, thereby forming a fixed orifice 226.

[0105] The plurality of disks 206 have the same outer diameter, and each outer diameter is smaller than the outer diameter of disk 205 and larger than the outer diameter of disk 203.

[0106] The outer diameter of the disk 207 is smaller than the outer diameter of the disk 206 and is equal to the outer diameter of the disk 203.

[0107] The outer diameter of the disk 208 is larger than the outer diameter of the disk 207 and is equal to the outer diameter of the disk 205.

[0108] The outer diameter of the circular member 209 is smaller than the outer diameter of the disk 208 and larger than the outer diameter of the disk 207. The thickness of the circular member 209 is greater than the thickness of each of the disks 201 to 208, and the circular member 209 has higher rigidity than the disks 201 to 208.

[0109] 2, the fourth passage 107 and the second passage 76 are flow paths through which the oil L flows from the second chamber 20 toward the first chamber 19 mainly during the compression stroke. The second passage 76 is constantly in communication with the second chamber 20.

[0110] 5 constitute a third damping valve 231 that is placed on the third seat 86 and opens and closes the fourth passage 107 by moving away from and into contact with the third seat 86. A fixed orifice 222 is provided in the third damping valve 231.

[0111] The discs 204-206 are placed on the fourth seat 87 and constitute a fourth damping valve 232 that opens and closes the fourth passage 107 by moving away from and into contact with the fourth seat 87. A fixed orifice 226 is provided in the fourth damping valve 232. The fourth damping valve 232 is provided closer to the first chamber 19 than the third damping valve 231. The total thickness of the discs 204-206 of the fourth damping valve 232 is greater than the total thickness of the discs 201, 202 of the third damping valve 231, and the fourth damping valve 232 has higher rigidity than the third damping valve 231.

[0112] When the third damping valve 231 leaves the third seat 86 and opens, it causes hydraulic fluid L to flow from the second chamber 20 shown in FIG. 2 to the first chamber 19 side via the second passage 76, the passages in the multiple passage holes 92, the passage in the passage groove 91, and the passage between the third damping valve 231 and the third seat 86, all of which constitute the fourth passage 107. At that time, the third damping valve 231 suppresses the flow of hydraulic fluid L to generate a damping force. The third damping valve 231 is provided in the fourth passage 107, and suppresses the flow of hydraulic fluid L that occurs during the compression stroke to generate a damping force.

[0113] Because the fourth damping valve 232 has higher rigidity than the third damping valve 231, it lifts off the fourth seat 87 and opens after the third damping valve 231 lifts off the third seat 86 and opens. When the fourth damping valve 232 lifts off the fourth seat 87 and opens, hydraulic fluid L flows from the second chamber 20 to the first chamber 19 via the second passage 76, the passages in the multiple passage holes 92, the passage in the passage groove 91, the passage between the third damping valve 231 and the third seat 86, the passage between the third seat 86 and the fourth seat 87, and the passage between the fourth damping valve 232 and the fourth seat 87, all of which constitute the fourth passage 107. At this time, the fourth damping valve 232 suppresses the flow of hydraulic fluid L to generate a damping force. The fourth damping valve 232 is provided in the fourth passage 107 and suppresses the flow of hydraulic fluid L that occurs during the compression stroke to generate a damping force.

[0114] The third damping valve 231 is provided upstream of the fourth damping valve 232 in the flow direction of the hydraulic fluid L during the compression stroke. The third damping valve 231 has lower rigidity and a lower valve opening pressure than the fourth damping valve 232. Therefore, the third damping valve 231 opens in a region where the moving speed of the piston 18 is lower than that of the fourth damping valve 232.

[0115] As shown in Fig. 4, the check valve 185 provided in the first damping valve 191 opens to the flow of hydraulic fluid L from the second chamber 20 toward the first chamber 19 shown in Fig. 2 that occurs during the compression stroke. At this time, the check valve 185 shown in Fig. 4 allows the hydraulic fluid L to flow without generating any substantial damping force. The check valve 185 opens to the flow toward the first chamber 19 shown in Fig. 2, but closes to the flow in the opposite direction.

[0116] As described above, the second piston body 37 has a third seat 86 and a fourth seat 87. The third seat 86 communicates with the fourth passage 107, and a third damping valve 231 that opens at a low piston speed is mounted on the third seat 86. The fourth seat 87 has a larger diameter than the third seat 86 and is located closer to the first chamber 19 than the third seat 86, and a fourth damping valve 232 that opens after the third damping valve 231 opens is mounted on the fourth seat 87.

[0117] The first piston body 36 has a first passage 75 and a second passage 76 that allow the oil L to flow between the first chamber 19 on one side and the second chamber 20 on the other side in the cylinder 2 as the piston 18 moves. The second piston body 37 has a third passage 106 and a fourth passage 107 that allow the oil L to flow between the first chamber 19 on one side and the second chamber 20 on the other side in the cylinder 2 as the piston 18 moves.

[0118] A circular member 209 is placed on the shaft step 29 of the piston rod 21 with the mounting shaft portion 28 inserted inside. Then, as shown in Fig. 5, disc 208, disc 207, the plurality of discs 206, the plurality of discs 205, disc 204, disc 203, the plurality of discs 202, disc 201, and piston 18 are stacked in this order on the circular member 209 with the mounting shaft portion 28 inserted inside each of them. In addition, as shown in Fig. 4, disc 161, disc 162, disc 163, disc 164, disc 165, disc 166, the plurality of discs 167, the plurality of discs 168, disc 169, disc 170, and circular member 171 are stacked in this order on the piston 18 with the mounting shaft portion 28 inserted inside each of them. In this state, these parts from the circular ring member 209 to the circular ring member 171 are fitted onto the fitting shaft portion 32 of the mounting shaft portion 28. In this state, as shown in Fig. 2, a nut 241 is screwed onto the threaded shaft portion 31 of the mounting shaft portion 28 that protrudes beyond the circular ring member 171. As a result, the inner peripheral sides of the parts from the circular ring member 209 to the circular ring member 171 are clamped in the axial direction by the shaft step portion 29 of the piston rod 21 and the nut 241.

[0119] As shown in Figure 1, the base member 26 of the base valve 25 described above is provided between the bottom 12 of the outer cylinder 4 and the inner cylinder 3. In addition to the base member 26, the base valve 25 has a disc valve 252, a disc valve 253, and a mounting pin 254. The disc valve 252 is provided on the lower side of the base member 26, i.e., on the reservoir chamber 6 side. The disc valve 253 is provided on the upper side of the base member 26, i.e., on the second chamber 20 side. The mounting pin 254 attaches the disc valve 252 and the disc valve 253 to the base member 26.

[0120] The base member 26 has an annular shape, and a mounting pin 254 is inserted through its radial center. The base member 26 is formed with a plurality of passage holes 255 and a plurality of passage holes 256. The plurality of passage holes 255 allow the oil L to flow between the second chamber 20 and the reservoir chamber 6. The plurality of passage holes 256 are arranged outside the plurality of passage holes 255 in the radial direction of the base member 26. The plurality of passage holes 256 allow the oil L to flow between the second chamber 20 and the reservoir chamber 6. The disc valve 252 on the reservoir chamber 6 side allows the oil L to flow from the second chamber 20 to the reservoir chamber 6 via the passage hole 255. On the other hand, the disc valve 252 restricts the flow of the oil L from the reservoir chamber 6 to the second chamber 20 via the passage hole 255. The disc valve 253 allows the flow of oil L from the reservoir chamber 6 to the second chamber 20 via the passage hole 256. On the other hand, the disc valve 253 restricts the flow of oil L from the second chamber 20 to the reservoir chamber 6 via the passage hole 256.

[0121] The disc valve 252 and the base member 26 form a damping valve mechanism 257. The damping valve mechanism 257 opens during the compression stroke of the shock absorber 1, allowing hydraulic fluid L to flow from the second chamber 20 to the reservoir chamber 6 and generating a damping force. The disc valve 253 and the base member 26 form a suction valve mechanism 258. The suction valve mechanism 258 opens during the extension stroke of the shock absorber 1, allowing hydraulic fluid L to flow from the reservoir chamber 6 into the second chamber 20. The suction valve mechanism 258 mainly functions to allow hydraulic fluid L to flow from the reservoir chamber 6 to the second chamber 20 without generating any damping force, in order to make up for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0122] Next, the main operation of the shock absorber 1 will be described.

[0123] "Extension stroke"

[0124] {First region in which the piston speed is slower than a first predetermined value} In the first region of the extension stroke, the check valve 185 of the first damping valve 191 is closed, and therefore the hydraulic fluid L from the first chamber 19 does not flow to the second chamber 20 via the third passage 106 and the first passage 75. Therefore, the hydraulic fluid L from the first chamber 19 flows through the fixed orifice 226 of the fourth damping valve 232, the passage between the third seat 86 and the fourth seat 87, the fixed orifice 222 of the third damping valve 231, the passage in the passage groove 91, and the passages in the multiple passage holes 92, all of which constitute the fourth passage 107, and further through the second passage 76 to the second chamber 20. Therefore, in the first region of the extension stroke, a damping force is generated with orifice characteristics (the damping force is approximately proportional to the square of the piston speed) due to the flow path cross-sectional area a of the fixed orifice 222.

[0125] {A second region in which the piston speed is equal to or greater than a first predetermined value and is slower than a second predetermined value that is greater than the first predetermined value} In the second region of the extension stroke, the hydraulic fluid L from the first chamber 19 flows through the third passage 106, the passages in the plurality of passage holes 52, the passage in the passage groove 51, the passage between the first damping valve 191 that is open and the first seat 46, the passage between the first seat 46 and the second seat 47, and the fixed orifice 187 of the second damping valve 192, all of which constitute the first passage 75, to the second chamber 20. On the other hand, the hydraulic fluid L from the first chamber 19 flows through the fixed orifice 226 of the fourth damping valve 232, the passage between the third seat 86 and the fourth seat 87, the fixed orifice 222 of the third damping valve 231, the passage in the passage groove 91, and the passages in the plurality of passage holes 92, all of which constitute the fourth passage 107, and further through the second passage 76 to the second chamber 20. Therefore, in the second region of the extension stroke, a damping force is generated that has characteristics that combine the valve characteristics of the first damping valve 191 (where the damping force is approximately proportional to the piston speed) and the orifice characteristics of the flow path cross-sectional area a of the fixed orifice 222 (where the damping force is approximately proportional to the square of the piston speed).

[0126] {A third region in which the piston speed is equal to or greater than the second predetermined value and is slower than a third predetermined value that is greater than the second predetermined value} In the third region of the extension stroke, the hydraulic fluid L from the first chamber 19 passes through the third passage 106 and then through the passages in the multiple passage holes 52, the passage in the passage groove 51, the passage between the open first damping valve 191 and the first seat 46, the passage between the first seat 46 and the second seat 47, and the fixed orifice 187 of the second damping valve 192, all of which constitute the first passage 75, to flow to the second chamber 20. At that time, the flow of the hydraulic fluid L is throttled by the fixed orifice 187. On the other hand, the hydraulic fluid L from the first chamber 19 passes through the fixed orifice 226 of the fourth damping valve 232, the passage between the third seat 86 and the fourth seat 87, the fixed orifice 222 of the third damping valve 231, the passage in the passage groove 91, and the passages in the multiple passage holes 92, all of which constitute the fourth passage 107, and further through the second passage 76 to flow to the second chamber 20. Therefore, in the third region of the extension stroke, a damping force having characteristics that combine the orifice characteristics due to the flow path cross-sectional area B of the fixed orifice 187 and the orifice characteristics due to the flow path cross-sectional area a of the fixed orifice 222 is generated.

[0127] {Fourth region in which the piston speed is equal to or greater than the third predetermined value} In the fourth region of the extension stroke, the hydraulic fluid L from the first chamber 19 flows through the third passage 106 and then through the passages in the plurality of passage holes 52, the passage in the passage groove 51, the passage between the opened first damping valve 191 and the first seat 46, the passage between the first seat 46 and the second seat 47, and the passage between the opened second damping valve 192 and the second seat 47, all of which constitute the first passage 75, to the second chamber 20. On the other hand, the hydraulic fluid L from the first chamber 19 flows through the fixed orifice 226 of the fourth damping valve 232, the passage between the third seat 86 and the fourth seat 87, the fixed orifice 222 of the third damping valve 231, the passage in the passage groove 91, and the passages in the plurality of passage holes 92, all of which constitute the fourth passage 107, and then further through the second passage 76 to the second chamber 20. Therefore, in the fourth region of the extension stroke, a damping force having characteristics that are a combination of the valve characteristics of the second damping valve 192 and the orifice characteristics of the flow path cross-sectional area a of the fixed orifice 222 is generated.

[0128] "Retraction process"

[0129] {A fifth region in which the piston speed is slower than a fifth predetermined value} In the fifth region of the compression stroke, the hydraulic fluid L from the second chamber 20 flows through the second passage 76, the passages in the multiple passage holes 92, the passage in the passage groove 91, the fixed orifice 222 of the third damping valve 231, the passage between the third seat 86 and the fourth seat 87, and the fixed orifice 226 of the fourth damping valve 232, all of which constitute the fourth passage 107, to the first chamber 19. On the other hand, the hydraulic fluid L from the second chamber 20 flows through the fixed orifice 187 of the second damping valve 192, the passage between the first seat 46 and the second seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passage in the passage groove 51, and the passages in the multiple passage holes 52, all of which constitute the first passage 75, to the first chamber 19. Therefore, in the fifth region of the compression stroke, a damping force is generated that has characteristics that combine the orifice characteristics due to the flow path cross-sectional area a of the fixed orifice 222 of the third damping valve 231 and the orifice characteristics due to the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191.

[0130] {A sixth region in which the piston speed is equal to or greater than a fifth predetermined value and is slower than a sixth predetermined value that is greater than the fifth predetermined value} In the sixth region of the compression stroke, the hydraulic fluid L from the second chamber 20 flows through the second passage 76, the passages in the plurality of passage holes 92, the passage in the passage groove 91, the passage between the open third damping valve 231 and the third seat 86, the passage between the third seat 86 and the fourth seat 87, and the fixed orifice 226 of the fourth damping valve 232, all of which constitute the fourth passage 107, to the first chamber 19. On the other hand, the hydraulic fluid L from the second chamber 20 flows through the fixed orifice 187 of the second damping valve 192, the passage between the first seat 46 and the second seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passage in the passage groove 51, and the passages in the plurality of passage holes 52, all of which constitute the first passage 75, to the first chamber 19. Therefore, in the sixth region of the compression stroke, a damping force having characteristics that combine the valve characteristics of the third damping valve 231 and the orifice characteristics of the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191 is generated.

[0131] {A seventh region in which the piston speed is equal to or greater than a sixth predetermined value, but is slower than a seventh predetermined value that is greater than the sixth predetermined value} In the seventh region of the compression stroke, the hydraulic oil L from the second chamber 20 passes through the second passage 76, and then passes through the passages in the plurality of passage holes 92, the passage in the passage groove 91, the passage between the opened third damping valve 231 and the third seat 86, the passage between the third seat 86 and the fourth seat 87, and the fixed orifice 226 of the fourth damping valve 232, all of which constitute the fourth passage 107, before flowing into the first chamber 19. At that time, the flow of the hydraulic oil L is throttled by the fixed orifice 226. On the other hand, the oil L from the second chamber 20 passes through the fixed orifice 187 of the second damping valve 192, the passage between the first seat 46 and the second seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passage in the passage groove 51, and the passages in the multiple passage holes 52, all of which constitute the first passage 75, and then passes through the third passage 106 and flows into the first chamber 19. Therefore, in the seventh region of the compression stroke, a damping force is generated that has characteristics that are a combination of the orifice characteristics due to the flow path cross-sectional area A of the fixed orifice 226 of the fourth damping valve 232 and the orifice characteristics due to the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191.

[0132] {A seventh region where the piston speed is equal to or greater than a seventh predetermined value} In the eighth region of the compression stroke, the hydraulic fluid L from the second chamber 20 flows through the second passage 76, the passages in the plurality of passage holes 92, the passage in the passage groove 91, the passage between the open third damping valve 231 and the third seat 86, the passage between the third seat 86 and the fourth seat 87, and the passage between the open fourth damping valve 232 and the fourth seat 87, all of which constitute the fourth passage 107, to the first chamber 19. On the other hand, the hydraulic fluid L from the second chamber 20 flows through the fixed orifice 187 of the second damping valve 192, the passage between the first seat 46 and the second seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passage in the passage groove 51, and the passages in the plurality of passage holes 52, all of which constitute the first passage 75, to the first chamber 19. Therefore, in the seventh region of the compression stroke, a damping force having characteristics that are a combination of the valve characteristics of the fourth damping valve 232 and the orifice characteristics of the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191 is generated.

[0133] In the shock absorber 1, the first damping valve 191, which is one of the first damping valve 191 and the third damping valve 231, both of which open at low piston speeds, is provided with a check valve 185, while the other, the third damping valve 231, is not provided with a check valve. For this reason, as described above, during the extension stroke, the orifice characteristics before the first damping valve 191 opens are determined only by the flow path cross-sectional area a of the fixed orifice 222 of the third damping valve 231, and the orifice characteristics after the first damping valve 191 opens are determined by the flow path cross-sectional area a of the fixed orifice 222 of the third damping valve 231 and the flow path cross-sectional area B of the fixed orifice 187 of the second damping valve 192. In contrast to this, during the compression stroke, the orifice characteristic before the third damping valve 231 opens is determined by the flow path cross-sectional area a of the fixed orifice 222 of the third damping valve 231 and the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191, and the orifice characteristic after the third damping valve 231 opens is determined by the flow path cross-sectional area A of the fixed orifice 226 of the fourth damping valve 232 and the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191.

[0134] Note that the above description has been given taking an example where the first damping valve 191 is provided with the fixed orifice 184 and the check valve 185. Alternatively, it is also possible to provide a similar fixed orifice and check valve in the third damping valve 231. In that case, for example, the first damping valve 191 including the check valve 185, the piston 18, and the third damping valve 231 are all left as they are and fitted to the fitting shaft portion 32 while being inverted in the axial direction relative to the above configuration. Then, the inverted first damping valve 191 including the fixed orifice 184 and the check valve 185 becomes a third damping valve including a third fixed orifice and a third check valve, and the inverted third damping valve 231 becomes the first damping valve. The third check valve provided in the third damping valve in this way allows the flow of oil L from the first chamber 19 to the second chamber 20 via the third fixed orifice, the fourth passage 107, and the second passage 76. The third check valve also regulates the flow of oil L from the second chamber 20 to the first chamber 19 via the second passage 76, the fourth passage 107 and the third fixed orifice.

[0135] The second damping valve 192 may also be provided with a configuration in which a second fixed orifice and a second check valve that allows hydraulic fluid L to flow through the second fixed orifice in only one direction are formed using laminated discs. In this case, the second check valve allows hydraulic fluid L to flow from the second chamber 20 to the first chamber 19 via the second fixed orifice, the first passage 75, and the third passage 106. The second check valve also restricts the flow of hydraulic fluid L from the first chamber 19 to the second chamber 20 via the third passage 106, the first passage 75, and the second fixed orifice. In this case, the first damping valve 191 may be provided with only a fixed orifice, without the check valve 185. Alternatively, both the first damping valve 191 including the fixed orifice 184 and the check valve 185 and the second damping valve 192 including the second fixed orifice and the second check valve may be provided.

[0136] Furthermore, the fourth damping valve 232 may be provided with a configuration in which a fourth fixed orifice and a fourth check valve that allows hydraulic fluid L to flow through this fourth fixed orifice in only one direction are formed using laminated discs. In this case, the fourth check valve allows hydraulic fluid L to flow from the first chamber 19 to the second chamber 20 via the fourth fixed orifice, the fourth passage 107, and the second passage 76. Furthermore, the fourth check valve restricts the flow of hydraulic fluid L from the second chamber 20 to the first chamber 19 via the second passage 76, the fourth passage 107, and the fourth fixed orifice. Both the third damping valve 231 that includes the third fixed orifice and the third check valve, and the fourth damping valve 232 that includes the fourth fixed orifice and the fourth check valve may be provided.

[0137] The above-mentioned Patent Documents 1 to 4 disclose shock absorbers in which the piston is composed of multiple piston bodies. Furthermore, the above-mentioned Patent Documents 4 and 5 disclose shock absorbers having a valve and a valve that opens in a range where the piston speed is faster than that of the valve. However, there is a demand for suppressing an increase in the number of parts in shock absorbers to suppress a decrease in productivity. For example, a shock absorber may have a first damping valve and a second damping valve on the extension side that opens in a range where the piston speed is faster than that of the first damping valve, and a third damping valve and a fourth damping valve on the compression side that opens in a range where the piston speed is faster than that of the third damping valve. In this case, the large number of valves tends to result in a decrease in productivity. For this reason, it is desirable to suppress an increase in the number of parts to suppress a decrease in productivity.

[0138] In the shock absorber 1 of this embodiment, the piston 18 has a first piston body 36, a second piston body 37, and a piston band 38. The first piston body 36 has a first passage 75, a second passage 76, a first seat 46, and a second seat 47. The first passage 75 and the second passage 76 allow hydraulic fluid L, which is a working fluid, to flow between the first chamber 19 on one side and the second chamber 20 on the other side in the cylinder 2 as the piston 18 moves. The first seat 46 communicates with the first passage 75 and is fitted with a first damping valve 191 that opens at a low piston speed. The second seat 47 has a larger diameter than the first seat 46 and is located on the second chamber 20 side. The second seat 47 is fitted with a second damping valve 192 that opens after the first damping valve 191 opens. The second piston body 37 has a third passage 106, a fourth passage 107, a third seat 86, and a fourth seat 87. The third passage 106 and the fourth passage 107 allow hydraulic fluid L to flow between the first chamber 19 on one side and the second chamber 20 on the other side in the cylinder 2 as the piston 18 moves. The third seat 86 communicates with the fourth passage 107 and is fitted with a third damping valve 231 that opens at low piston speeds. The fourth seat 87 has a larger diameter than the third seat 86 and is located closer to the first chamber 19. A fourth damping valve 232 that opens after the third damping valve 231 opens is fitted with the fourth seat 87. Because the piston 18 has the first piston body 36, the second piston body 37, and the piston band 38, the number of components of the piston 18 can be reduced. This reduces the number of processes required to manufacture and assemble the components of the piston 18. Furthermore, the piston 18 can be assembled as a sub-assembly before being attached to the piston rod 21. This reduces the number of steps required to attach components to the piston rod 21. This makes it possible to prevent a decrease in productivity. The shock absorber 1 has a structure in which the first damping valve 191, the second damping valve 192, the third damping valve 231, and the fourth damping valve 232 are mounted on the piston 18, and this structure is particularly prone to a decrease in productivity. Therefore, preventing a decrease in productivity as described above greatly contributes to the effect of preventing an increase in the manufacturing cost of the shock absorber 1.

[0139] The shock absorber 1 also includes an alignment portion 121 on the mating surfaces 41, 81 where the first piston body 36 and the second piston body 37 are connected to each other. The alignment portion 121 aligns the first passage 75 with the third passage 106 and the second passage 76 with the fourth passage 107. This facilitates alignment. Furthermore, since the inner diameters of the first piston body 36 and the second piston body 37 are different in the shock absorber 1, the piston 18 can be positioned on the piston rod 21 by fitting the piston rod 21 with the smaller inner diameter of the first piston body 36 or the second piston body 37. Therefore, alignment of the inner circumferential surfaces of the first piston body 36 and the second piston body 37 is not required when connecting the first piston body 36 and the second piston body 37. This further reduces productivity degradation.

[0140] Furthermore, in the shock absorber 1, the first damping valve 191 or the third damping valve 231 is provided with a check valve 185 that opens for a flow toward the first chamber 19 or the second chamber 20 and closes for a flow in the opposite direction. Therefore, the orifice characteristics before the first damping valve 191 or the third damping valve 231 open can be made different between the extension stroke and the compression stroke. For example, if the check valve 185 is provided in the first damping valve 191 as described above, during the extension stroke, before the first damping valve 191 opens, the orifice characteristics are determined by the flow path cross-sectional area a of the fixed orifice 222, and after the first damping valve 191 opens, the orifice characteristics are determined by the flow path cross-sectional area a of the fixed orifice 222 and the flow path cross-sectional area B of the fixed orifice 187. During the compression stroke, before the third damping valve 231 opens, the orifice characteristics are determined by the flow path cross-sectional area a of the fixed orifice 222 and the flow path cross-sectional area b of the fixed orifice 184, and after the third damping valve 231 opens, the orifice characteristics are determined by the flow path cross-sectional area A of the fixed orifice 226 and the flow path cross-sectional area b of the fixed orifice 184.

[0141] The manufacturing method of the shock absorber 1 of this embodiment includes first to third steps. In the first step, the mating surface 41 of the first piston body 36 and the mating surface 81 of the second piston body 37 are connected so that the first passage 75 and the third passage 106 communicate with each other and the second passage 76 and the fourth passage 107 communicate with each other. In the second step, the end of the first passage 75 opposite the third passage 106, the end of the third passage 106 opposite the first passage 75, the end of the second passage 76 opposite the fourth passage 107, the end of the fourth passage 107 opposite the second passage 76, and the deep groove portion 131 and the shallow groove portion 132 to which the piston band 38 is attached are machined. In the third step, the piston band 38 is attached to the deep groove portion 131 and the shallow groove portion 132. In this way, the first piston body 36 and the second piston body 37 are connected in the first step, and then the first piston body 36 and the second piston body 37 are machined in the second step, so the relative precision of each part can be easily ensured. Furthermore, by performing the first to third steps, the piston 18 can be assembled as a sub-assembly before being attached to the piston rod 21. This reduces the number of steps required to attach parts to the piston rod 21. This makes it possible to suppress a decrease in productivity.

[0142] In the third step, the piston band 38 is attached to the deep groove portion 131 via the second sheet 47, and then attached to the shallow groove portions 132 that are shallower than the deep groove portion 131. Thus, the piston band 38 can be attached to the first piston body 36 and the second piston body 37 properly and smoothly.

[0143] In the embodiment, a hydraulic shock absorber is shown as an example of the shock absorber 1, but the above structure can also be applied to a shock absorber that uses water or air as the working fluid. [Industrial Applicability]

[0144] According to the above-described embodiment of the present invention, it is possible to provide a shock absorber and a method for manufacturing the shock absorber that can suppress a decrease in productivity, and therefore the present invention has great industrial applicability. [Explanation of symbols]

[0145] 1...shock absorber, 2...cylinder, 18...piston, 19...first chamber (chamber), 20...second chamber (chamber), 21...piston rod, 36...first piston body, 37...second piston body, 38...piston band, 41, 81...joint surface, 46...first seat, 47...second seat, 75...first passage, 76...second passage, 86...third seat, 87...fourth seat, 106...third passage, 107...fourth passage, 121...alignment portion, 185...check valve, 191...first damping valve, 192...second damping valve, 231...third damping valve, 232...fourth damping valve.

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder, The piston is a first passage and a second passage that allow working fluid to flow between the two chambers in the cylinder as the piston moves; a first seat on which a first damping valve is mounted, the first seat communicating with the first passage and opening at a low piston speed; and a second seat on which a second damping valve is mounted, the second seat having a larger diameter than the first seat and being provided on one side of the two chambers, the second seat opening after the first damping valve opens. a first piston body having a third passage and a fourth passage that allow the working fluid to circulate between the two chambers in the cylinder by movement of the piston; a third seat on which a third damping valve is mounted, the third seat communicating with the fourth passage and opening at a low piston speed; a fourth seat on which a fourth damping valve is mounted, the fourth seat having a larger diameter than the third seat and being provided on the other side of the two chambers, the fourth seat opening after the third damping valve opens; a second piston body having and the first piston body and the second piston body are connected so that the first passage and the third passage communicate with each other and the second passage and the fourth passage communicate with each other; The inner diameter of the first piston body and the inner diameter of the second piston body are different from each other, and the first piston body or the second piston body, whichever has a smaller inner diameter, is abutted against and attached to the piston rod.

2. 2. The shock absorber according to claim 1, wherein the first damping valve or the third damping valve is provided with a check valve that opens to a flow toward one of the two chambers or the other of the two chambers and closes to a flow in the opposite direction.

3. a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder, The piston is a first passage and a second passage that allow working fluid to flow between the two chambers in the cylinder as the piston moves; a first seat on which a first damping valve is mounted, the first seat communicating with the first passage and opening at a low piston speed; and a second seat on which a second damping valve is mounted, the second seat having a larger diameter than the first seat and being provided on one side of the two chambers, the second seat opening after the first damping valve opens. a first piston body having a third passage and a fourth passage that allow the working fluid to circulate between the two chambers in the cylinder by movement of the piston; a third seat on which a third damping valve is mounted, the third seat communicating with the fourth passage and opening at a low piston speed; a fourth seat on which a fourth damping valve is mounted, the fourth seat having a larger diameter than the third seat and being provided on the other side of the two chambers, the fourth seat opening after the third damping valve opens; a second piston body having a piston band provided on the first piston body and the second piston body; A method for manufacturing a shock absorber having a first step of connecting one surface of the first piston body and one surface of the second piston body so that the first passage communicates with the third passage and the second passage communicates with the fourth passage; a second step of machining an end of the first passage opposite to the third passage, an end of the third passage opposite to the first passage, an end of the second passage opposite to the fourth passage, an end of the fourth passage opposite to the second passage, and a groove into which the piston band is fitted; a third step of fitting the piston band into the groove; Including, The groove is a plurality of shallow groove portions; a deep groove portion that is located closer to the second sheet than the plurality of shallow groove portions and is deeper than the plurality of shallow groove portions; and the third step attaching the piston band to the deep groove portion via the second seat and then to the plurality of shallow groove portions; Shock absorber manufacturing method.

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