Vibration damper and method for manufacturing vibration damper

Abstract

In the shock absorber, a piston has 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 valve seat, and a second valve seat. A first valve seat is in communication with the first passage, placing a first damper valve. The second damping valve is placed on the second valve seat. The second piston body has a third passage, a fourth passage, a third valve seat, and a fourth valve seat. The third valve seat is communicated with the fourth passage, and a third damping valve is placed. A fourth damping valve is placed on the fourth valve seat.

Description

Technical Field

[0001] The invention relates to a vibration damper and a method for manufacturing the vibration damper.

[0002] This application claims priority based on U.S. patent application No. 17 / 954,390, filed on September 28, 2022, the contents of which are incorporated herein. Background Art

[0003] A shock absorber is known in which a piston is constituted by a plurality of piston bodies (see, for example, Patent Documents 1 to 4 listed below).

[0004] Furthermore, there is a shock absorber including a valve and a valve that opens in a range where the piston speed is higher than the valve (for example, refer to Patent Documents 4 and 5 listed below).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-107003

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-129865

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2-113142

[0008] Patent Document 4: U.S. Patent Application Publication No. 2013 / 0037361

[0009] Patent Document 5: Japanese Utility Model Application Laid-Open No. 1-149037 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] However, in the vibration damper, it is required to suppress a decrease in productivity.

[0012] Therefore, an object of the present invention is to provide a vibration damper and a method for manufacturing the vibration damper that can suppress a decrease in productivity.

[0013] Technical solutions for solving technical problems

[0014] In order to achieve the above-mentioned purpose, one scheme of the shock absorber of the present invention comprises: a cylinder, which seals a working fluid; a piston, which is slidably embedded in the cylinder, dividing the cylinder into two chambers; a piston rod, which is connected to the piston and extends to the outside of the cylinder; the piston has a first piston body and a second piston body, the first piston body has: a first passage and a second passage, which allow the working fluid to flow between one chamber and the other chamber in the cylinder through the movement of the piston; a first valve seat, which is connected to the first passage and is placed on a first damping valve that opens when the piston speed is low; a second valve seat, which has a larger diameter than the first valve seat and is arranged on the side close to the chamber. , a second damping valve is placed to open after the first damping valve opens; the second piston body has: a third passage and a fourth passage, which allow the working fluid to flow between one chamber and another chamber in the cylinder through the movement of the piston; a third valve seat, which is connected to the fourth passage, and is placed on the third damping valve that opens when the piston speed is low; a fourth valve seat, which has a larger diameter than the third valve seat and is arranged on the side of the chamber, and is placed on the fourth damping valve that opens after the third damping valve opens; the first piston body and the second piston body are connected in a way that the first passage is connected to the third passage and the second passage is connected to the fourth passage.

[0015] In one embodiment of the manufacturing method of a shock absorber of the present invention, the shock absorber comprises: a cylinder, which seals a working fluid; a piston, which is slidably embedded in the cylinder, dividing the cylinder into two chambers; a piston rod, which is connected to the piston and extends to the outside of the cylinder; the piston has a first piston body, a second piston body and a piston band arranged on the first piston body and the second piston body, the first piston body having: a first passage and a second passage, which allow the working fluid to flow between one chamber and another chamber in the cylinder through the movement of the piston; a first valve seat, which is connected to the first passage and is placed on a first damping valve that opens when the piston speed is low; a second valve seat, which is larger in diameter than the first valve seat and is arranged on the side of the chamber, and is placed on a second damping valve that opens after the first damping valve opens; the second piston body having: a third passage and a fourth passage, which allow the working fluid to flow between one chamber and another chamber in the cylinder through the movement of the piston a third valve seat which is connected to the fourth passage and is placed on a third damping valve which opens when the piston speed is low; a fourth valve seat which is larger in diameter than the third valve seat and is arranged on the side of the chamber and is placed on a fourth damping valve which opens after the third damping valve opens; a method for manufacturing the shock absorber comprising: a first step of connecting one surface of the first piston body to one surface of the second piston body in such a way that the first passage is connected to the third passage and the second passage is connected to the fourth passage; a second step of processing the end of the first passage opposite to the third passage, the end of the third passage opposite to the first passage, the end of the second passage opposite to the fourth passage, the end of the fourth passage opposite to the second passage, and a groove for assembling the piston belt; and a third step of assembling the piston belt in the groove.

[0016] Effects of the Invention

[0017] According to the above-described aspects of the present invention, it is possible to suppress a decrease in productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a cross-sectional view showing a shock absorber according to an embodiment of the present invention.

[0019] Figure 2 It is a cross-sectional view showing a main part of a shock absorber according to an embodiment of the present invention.

[0020] Figure 3 It is a partial cross-sectional view showing a main part of a shock absorber according to an embodiment of the present invention.

[0021] Figure 4 It is a partial cross-sectional view showing a main part of a shock absorber according to an embodiment of the present invention.

[0022] Figure 5 It is a partial cross-sectional view showing a main part of a shock absorber according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] A shock absorber according to an embodiment of the present invention will be described based on the drawings. It should be noted that, for the convenience of description, the upper side in the drawings is referred to as "upper" and the lower side in the drawings is referred to as "lower" in the following description.

[0024] like Figure 1 As shown, the shock absorber 1 of the embodiment is a multi-tube type hydraulic shock absorber. The shock absorber 1 is used in a vehicle, specifically, in a suspension device of an automobile. The shock absorber 1 includes a cylinder 2. The cylinder 2 includes an inner cylinder 3 and an outer cylinder 4. The inner cylinder 3 is cylindrical. The outer cylinder 4 is cylindrical with a bottom. The inner diameter of the outer cylinder 4 is larger than the outer diameter of the inner cylinder 3. The inner cylinder 3 is arranged radially inward of the outer cylinder 4. The central axis of the inner cylinder 3 coincides with the central axis of the outer cylinder 4. A storage chamber 6 is formed between the inner cylinder 3 and the outer cylinder 4.

[0025] The outer tube 4 has a body 11 and a bottom 12. The body 11 and the bottom 12 are seamlessly formed in one piece. The body 11 is cylindrical. The bottom 12 blocks the lower part of the body 11.

[0026] The shock absorber 1 includes a piston 18. The piston 18 is inserted into the inner tube 3 of the cylinder 2. The piston 18 is slidably embedded in 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 side opposite to the bottom 12 compared to the piston 18. 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 as a working fluid is sealed in the first chamber 19 and the second chamber 20 in the inner tube 3. In the cylinder 2, oil L and gas G as a working fluid are sealed in the storage chamber 6 between the inner tube 3 and the outer tube 4.

[0027] The shock absorber 1 includes a piston rod 21. One end of the piston rod 21 in the axial direction is disposed in the inner tube 3 of the cylinder 2. The one end of the piston rod 21 is connected to the piston 18. The other end of the piston rod 21 in the axial direction extends from the cylinder 2 to the outside of the cylinder 2.

[0028] The piston 18 is fixed to the piston rod 21. Therefore, the piston 18 and the piston rod 21 move integrally. The stroke in which the piston rod 21 moves in the direction in which the protrusion amount from the cylinder 2 increases is a stretch stroke in which the full length of the shock absorber 1 is extended. The stroke in which the piston rod 21 moves in the direction in which the protrusion amount from the cylinder 2 decreases is a contraction stroke in which the full length of the shock absorber 1 is shortened. The piston 18 of the shock absorber 1 moves toward the first chamber 19 side during the stretch stroke. The piston 18 of the shock absorber 1 moves toward the second chamber 20 side during the contraction stroke.

[0029] A rod guide 22 is fitted on the upper opening side of the inner tube 3 and the upper opening side of the outer tube 4. A sealing member 23 is fitted on the outer tube 4 at the upper side of the rod guide 22. The rod guide 22 and the sealing member 23 are both annular. The piston rod 21 is inserted through the radial inner side of each of the rod guide 22 and the sealing member 23. The piston rod 21 slides along the axial direction of the rod guide 22 and the sealing member 23. The piston rod 21 extends from the inside of the cylinder 2 to the outer side of the cylinder 2 at the side closer to the sealing member 23.

[0030] The rod guide 22 restricts the piston rod 21 from moving in the radial direction relative to the inner tube 3 and the outer tube 4 of the cylinder 2. The piston rod 21 is fitted in the rod guide 22, and the piston 18 is fitted in the inner tube 3. As a result, the center axis of the piston rod 21 coincides with the center axis of the inner tube 3. The rod guide 22 supports the piston rod 21 so as to be movable in the axial direction of the piston rod 21. The outer peripheral portion of the sealing component 23 is in close contact with the outer tube 4. The inner peripheral portion of the sealing component 23 is in close contact with the outer peripheral portion of the piston rod 21. The piston rod 21 moves in the axial direction of the sealing component 23 relative to the sealing component 23. The sealing component 23 prevents the oil L in the inner tube 3 and the high-pressure gas G and oil L in the storage chamber 6 from leaking to the outside.

[0031] The upper portion of the outer periphery of the rod guide 22 has a larger diameter than the lower portion. The rod guide 22 fits into the inner periphery of the upper end of the inner tube 3 at the lower portion with a smaller diameter. The rod guide 22 fits into the inner periphery of the upper portion of the outer tube 4 at the upper portion with a larger diameter. A base member 26 of a bottom valve 25 is provided on the bottom 12 of the outer tube 4. The base member 26 is positioned in the radial direction relative to the outer tube 4. The upper portion of the outer periphery of the base member 26 has a smaller diameter than the lower portion. The base member 26 fits into the inner periphery of the lower end of the inner tube 3 at the upper portion with a smaller diameter. Thus, the central axis of the inner tube 3 coincides with the central axis of the outer tube 4. The base member 26 separates the second chamber 20 from the storage chamber 6.

[0032] The upper end portion of the outer tube 4 is constricted inward in the radial direction of the outer tube 4. The seal member 23 is fixed to the cylinder 2 by being sandwiched between the constricted portion and the rod guide 22.

[0033] The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28. Both the main shaft portion 27 and the mounting shaft portion 28 are rod-shaped.

[0034] The outer diameter of the mounting shaft portion 28 is smaller than the outer diameter of the main shaft portion 27. The mounting shaft portion 28 is arranged in the cylinder 2. The piston 18 is mounted on the mounting shaft portion 28. The main shaft portion 27 has a shaft step portion 29. The shaft step portion 29 is provided at the end of the mounting shaft portion 28 side in the axial direction of the main shaft portion 27. The shaft step portion 29 extends in a direction orthogonal to the central axis of the piston rod 21. On the mounting shaft portion 28, the end of the mounting shaft portion 28 on the opposite side of the main shaft portion 27 in the axial direction is a threaded shaft portion 31. The threaded shaft portion 31 is formed with an external thread on the 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 is a mating shaft portion 32. The outer peripheral surface of the mating shaft portion 32 is a cylindrical surface. The piston 18 is mated with the mating shaft portion 32.

[0035] The shock absorber 1 is configured such that the portion of the piston rod 21 protruding from the cylinder 2 is disposed at the upper portion and connected to the vehicle body. At the same time, the shock absorber 1 is configured such that the mounting bracket 33 fixed to the trunk 11 of the outer cylinder 4 is disposed at the lower portion and connected to the wheel side of the vehicle. The shock absorber 1 may be a single-cylinder type instead of a multi-cylinder type. The single-cylinder type is a structure in which the outer cylinder 4 and the bottom valve 25 are not provided with respect to the shock absorber 1, a bottomed cylindrical cylinder is provided in addition to the inner cylinder 3, and a free piston is provided between the bottom of the cylinder and the piston 18. In addition, gas is sealed between the bottom of the cylinder and the free piston. In the case of such a single-cylinder type shock absorber, it is also possible to connect the cylinder side to the vehicle body and connect the piston rod 21 to the wheel side.

[0036] like Figure 2 As shown, 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 formed metal products. The first piston body 36 and the second piston body 37 are both annular. The piston 18 connects the first piston body 36 and the second piston body 37 to the mounting shaft portion 28 of the piston rod 21. At this time, the first piston body 36 is arranged on the side opposite to the main shaft portion 27 compared to the second piston body 37 in the axial direction of the piston rod 21. And, at this time, the second piston body 37 is arranged between the first piston body 36 and the shaft step portion 29.

[0037] The first piston body 36 is formed with a joint surface 41 on the second piston body 37 side in the axial direction. The joint surface 41 is a flat surface extending perpendicularly to the central axis of the first piston body 36 .

[0038] A through hole 42 is formed in the radial center of the first piston body 36. The through hole 42 penetrates the first piston body 36 in the axial direction of the first piston body 36. In the through hole 42 of the first piston body 36, the mounting shaft portion 28 of the piston rod 21 is fitted.

[0039] The first piston body 36 includes a main body portion 43 , an inner valve seat 45 , a first valve seat 46 , and a second valve seat 47 .

[0040] The main body 43 is annular in shape, and the radial inner side of the main body 43 is a part of the through hole 42 .

[0041] The inner valve seat 45 is annular and protrudes from the main body 43 to the side opposite to the joining surface 41 in the axial direction of the first piston body 36 . The inner side of the inner valve seat 45 in the radial direction is a part of the through hole 42 .

[0042] The first valve seat 46 is annular. The first valve seat 46 protrudes from the main body 43 to the side opposite to the joint surface 41 in the axial direction of the first piston body 36. The first valve seat 46 has a larger diameter than the inner valve seat 45. The first valve seat 46 is arranged on the outer side of the inner valve seat 45 in the radial direction of the first piston body 36 so as to surround the inner valve seat 45. The front end surface of the first valve seat 46 is arranged on the side opposite to the joint surface 41 in the axial direction of the first piston body 36 compared with the front end surface of the inner valve seat 45.

[0043] The first piston body 36 has a passage groove 51 formed between the inner valve seat 45 and the first valve seat 46 in the radial direction of the first piston body 36. The passage groove 51 is annular and extends in the circumferential direction of the first piston body 36.

[0044] A passage hole 52 is formed on the main body 43 of the first piston body 36 between the inner valve seat 45 and the first valve seat 46 in the radial direction of the first piston body 36. The passage hole 52 is arranged closer to the first valve seat 46 than the inner valve seat 45 in the radial direction of the first piston body 36. One end of the passage hole 52 opens to the joint surface 41, and the other end opens to the passage groove 51. A plurality of passage holes 52 of the same shape are provided on the first piston body 36 at equal intervals along the circumferential direction of the first piston body 36.

[0045] The second valve seat 47 is annular. The second valve seat 47 protrudes from the main body 43 to the side opposite to the joint surface 41 in the axial direction of the first piston body 36. The second valve seat 47 is larger in diameter than the first valve seat 46. The second valve seat 47 is arranged on the outside of the first valve seat 46 in the radial direction of the first piston body 36 so as to surround the first valve seat 46. The second valve seat 47 is arranged on the side opposite to the joint surface 41 in the axial direction of the first piston body 36 compared to the first valve seat 46.

[0046] 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 43.

[0047] The first piston body 36 has an opening groove portion 62 on its radially outer peripheral portion. The opening groove portion 62 is recessed toward the radially inner side of the first piston body 36 compared to the outer peripheral surface 61. The opening groove portion 62 is annular centered on the central axis of the first piston body 36. The opening groove portion 62 is arranged between the center of the first piston body 36 in the axial direction and the second valve seat 47. The bottom surface of the opening groove portion 62 overlaps with the second valve seat 47 at the radial position of the first piston body 36.

[0048] A passage hole 65 is formed on the main body 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 opening groove 62. A plurality of passage holes 65 of the same shape are arranged at equal intervals along the circumference of the first piston body 36 on the first piston body 36. On the first piston body 36, the passage holes 52 and the passage holes 65 are arranged alternately and at equal intervals in the circumference of the first piston body 36. Therefore, the same number of passage holes 52 and passage holes 65 are provided on the first piston body 36.

[0049] The main body portion 43 has a concave portion 72 that is recessed from the joint surface 41 toward the inner valve seat 45 side in the axial direction of the first piston body 36 .

[0050] On the first piston body 36, the passages in the plurality of passage holes 52 and the passages in the passage grooves 51 constitute the first passage 75. The first passage 75 includes the space portion between the inner valve seat 45 and the first valve seat 46. Therefore, the first valve seat 46 is communicated with the first passage 75. The first passage 75 includes the space portion between the first valve seat 46 and the second valve seat 47. Therefore, the second valve seat 47 is also communicated with the first passage 75.

[0051] In the first piston body 36 , the passages in the plurality of passage holes 65 and the passage in the opening groove portion 62 constitute a second passage 76 .

[0052] The second piston body 37 is formed with a joint surface 81 on the first piston body 36 side in the axial direction thereof. The joint surface 81 is a flat surface extending perpendicularly to the central axis of the second piston body 37 .

[0053] A through hole 82 is formed in the radial center of the second piston body 37. The through hole 82 penetrates the second piston body 37 in the axial direction of the second piston body 37. In the through hole 82 of the second piston body 37, the mounting shaft portion 28 of the piston rod 21 is fitted.

[0054] The second piston body 37 includes a main body portion 83 , an inner valve seat 85 , a third valve seat 86 , a fourth valve seat 87 , and a convex portion 89 .

[0055] The main body 83 is annular in shape, and the radial inner side of the main body 83 is a part of the through hole 82 .

[0056] The inner valve seat 85 is annular and protrudes from the main body 83 to the side opposite to the joining surface 81 in the axial direction of the second piston body 37. The inner side of the inner valve seat 85 in the radial direction is a part of the through hole 82.

[0057] The third valve seat 86 is annular. The third valve seat 86 protrudes from the main body 83 to the side opposite to the joint surface 81 in the axial direction of the second piston body 37. The third valve seat 86 has a larger diameter than the inner valve seat 85. The third valve seat 86 is arranged on the outer side of the inner valve seat 85 in the radial direction of the second piston body 37 so as to surround the inner valve seat 85. The front end surface of the third valve seat 86 is arranged on the side opposite to the joint surface 81 in the axial direction of the second piston body 37 compared with the front end surface of the inner valve seat 85.

[0058] The second piston body 37 has a passage groove 91 formed between the inner valve seat 85 and the third valve seat 86 in the radial direction of the second piston body 37. The passage groove 91 is annular and extends in the circumferential direction of the second piston body 37.

[0059] A passage hole 92 is formed on the main body 83 of the second piston body 37 between the inner valve seat 85 and the third valve seat 86 in the radial direction of the second piston body 37. The passage hole 92 is arranged on the third valve seat 86 side of the inner valve seat 85 in the radial direction of the second piston body 37. One end of the passage hole 92 opens to the joint surface 81, and the other end opens to the passage groove 91. A plurality of passage holes 92 of the same shape are provided on the second piston body 37 at equal intervals along 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.

[0060] The fourth valve seat 87 is annular. The fourth valve seat 87 protrudes from the main body 83 to the side opposite to the joint surface 81 in the axial direction of the second piston body 37. The fourth valve seat 87 is larger in diameter than the third valve seat 86. The fourth valve seat 87 is arranged at an outer side than the third valve seat 86 in the radial direction of the second piston body 37 so as to surround the third valve seat 86. The fourth valve seat 87 is arranged on the side opposite to the joint surface 81 in the axial direction of the second piston body 37 compared with the third valve seat 86.

[0061] The second piston body 37 is formed with an outer peripheral surface 101 at its radial outer end. The outer peripheral surface 101 is a cylindrical surface centered on the central axis of the second piston body 37. The outer peripheral surface 101 is provided on the main body 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.

[0062] The second piston body 37 has an opening groove 102 on its radially outer peripheral portion. The opening groove 102 is recessed radially inward of the second piston body 37 compared to the outer peripheral surface 101. The opening groove 102 is annular centered on the central axis of the second piston body 37. The opening groove 102 is arranged between the center of the second piston body 37 in the axial direction and the fourth valve seat 87. The bottom surface of the opening groove 102 overlaps with the fourth valve seat 87 at the radial position of the second piston body 37.

[0063] A passage hole 105 is formed on the main body 83 of the second piston body 37. One end of the passage hole 105 opens to the joint surface 81, and the other end side opens to the opening groove portion 102. A plurality of passage holes 105 of the same shape are arranged on the second piston body 37 at equal intervals along the circumference of the second piston body 37. On the second piston body 37, the passage holes 92 and the passage holes 105 are arranged alternately and at equal intervals in the circumference of the second piston body 37. Therefore, the same number of passage holes 92 and passage holes 105 are provided on the second piston body 37. The number of passage holes 105 is the same as the number of passage holes 65 of the first piston body 36.

[0064] The convex portion 89 protrudes from the joint surface 81 toward the side opposite to the inner valve seat 85 in the axial direction of the second piston body 37 .

[0065] In the second piston body 37 , the passages in the plurality of passage holes 105 and the passage in the open groove portion 102 constitute a third passage 106 .

[0066] On the second piston body 37, the passages in the plurality of passage holes 92 and the passages in the passage grooves 91 constitute a fourth passage 107. The fourth passage 107 includes a space portion between the inner valve seat 85 and the third valve seat 86. Therefore, the third valve seat 86 is communicated with the fourth passage 107. The fourth passage 107 includes a space portion between the third valve seat 86 and the fourth valve seat 87. Therefore, the fourth valve seat 87 is also communicated with the fourth passage 107.

[0067] The first valve seat 46 and the third valve seat 86 have the same shape. The second valve seat 47 and the fourth valve seat 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 opening groove portion 62 and the opening groove portion 102 have the same shape. The passage hole 65 and the passage hole 105 have the same shape.

[0068] For the first piston body 36 and the second piston body 37, the convex portion 89 of the second piston body 37 is engaged with the concave portion 72 of the first piston body 36. As a result, the joint surface 41 of the first piston body 36 and the joint surface 81 of the second piston body 37 are in surface contact. In this state, the central axis of the first piston body 36 and the central axis of the second piston body 37 are consistent.

[0069] Furthermore, 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 is connected to the third passage 106 of the second piston body 37, but not to the fourth passage 107.

[0070] Furthermore, 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 is connected to the fourth passage 107 of the second piston body 37, but not to the third passage 106.

[0071] In this way, the first piston body 36 and the second piston body 37 are matched in position when the convex portion 89 is engaged with the concave portion 72. The first piston body 36 and the second piston body 37 are not matched in position in other connection states. In other words, 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 are connected, the second passage 76 and the fourth passage 107 are connected, and the joint surface 41 and the joint surface 81 are in surface contact as described above in other states.

[0072] The convex portion 89 and the concave portion 72 constitute a positioning portion 121. The positioning portion 121 is provided on the mutually connected joint surfaces 41, 81 of the first piston body 36 and the second piston body 37. The positioning portion 121 makes the positions of the first passage 75 and the third passage 106 consistent with each other in the circumferential direction and radial direction of the first piston body 36 and the second piston body 37, and makes the positions of the second passage 76 and the fourth passage 107 consistent.

[0073] The first piston body 36 and the second piston body 37 are fixed to each other and integrated by pressing 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 in the circumferential direction and the radial direction by the alignment portion 121, so that the first passage 75 is connected to the third passage 106, the second passage 76 is connected to the fourth passage 107, and the joint surface 41 is in surface contact with the joint surface 81. In other words, the first piston body 36 and the second piston body 37 are connected in a manner that the first passage 75 is connected to the third passage 106 and the second passage 76 is connected to the fourth passage 107.

[0074] Thus, the first piston body 36 is cut to form the inner valve seat 45, the first valve seat 46 and the second valve seat 47 while being integrated with the second piston body 37. In other words, the first piston body 36 is cut to form the end of the first passage 75 opposite to the third passage 106.

[0075] The second piston body 37 is cut to form the inner valve seat 85, the third valve seat 86 and the fourth valve seat 87 while being integrated with the first piston body 36. In other words, the second piston body 37 forms the end of the fourth passage 107 opposite to the second passage 76 by cutting.

[0076] After these processes, the first valve seat 46 and the third valve seat 86 are mirror-symmetrical. Also, after these processes, the second valve seat 47 and the fourth valve seat 87 are mirror-symmetrical. Also, after these processes, the height difference between the inner valve seat 45 and the first valve seat 46 is greater than the height difference between the inner valve seat 85 and the third valve seat 86 by a predetermined amount.

[0077] Furthermore, the first piston body 36 and the second piston body 37 in an integrated state are cut together at their respective outer circumferences. At this time, the opening groove 62 of the first piston body 36 is formed, and the opening groove 102 of the second piston body 37 is formed. In other words, the first piston body 36 is cut to form the end of the second passage 76 opposite to the fourth passage 107. The second piston body 37 is cut to form the end of the third passage 106 opposite to the first passage 75. In addition, the outer circumference of the first piston body 36 is cut to form the opening groove 62 of the first piston body 36, and the opening groove 102 of the second piston body 37 is formed. In other words, the first piston body 36 is cut to form the end of the second passage 76 opposite to the fourth passage 107. The second piston body 37 is cut to form the end of the third passage 106 opposite to the first passage 75. Figure 3 The deep groove 131 (groove) shown in the figure. At the same time, the outer peripheral surface 61, 101 and a plurality of (specifically, 4) shallow grooves 132 (grooves) are formed by cutting on the outer peripheral portion of the first piston body 36 and the outer peripheral portion of the second piston body 37. The outer peripheral surface 61, 101 is formed in a manner that constitutes the same cylindrical surface.

[0078] The deep groove 131 is recessed radially inward of the first piston body 36 relative to the outer peripheral surface 101. The deep groove 131 is annular centered on the central axis of the first piston body 36. The deep groove 131 is formed in a portion of the first piston body 36 that is closer to the second piston body 37 than the opening groove 62 in the axial direction.

[0079] The plurality of shallow grooves 132 are of the same shape and are recessed radially inward of the first piston body 36 and the second piston body 37 compared to the outer peripheral surfaces 61 and 101. The plurality of shallow grooves 132 are all annular in shape with the central axis of the first piston body 36 and the second piston body 37 as the center. The depth of the plurality of shallow grooves 132 from the outer peripheral surfaces 61 and 101 is shallower than the depth of the deep grooves 131 from the outer peripheral surfaces 61 and 101. In other words, the depth of the deep grooves 131 from the outer peripheral surfaces 61 and 101 is deeper than the depth of the plurality of shallow grooves 132 from the outer peripheral surfaces 61 and 101. In other words, the diameter of the bottom of the deep groove 131 is smaller than the diameter of the bottom of the plurality of shallow grooves 132.

[0080] The plurality of shallow grooves 132 are formed in the portion of the first piston body 36 that is closer to the second piston body 37 than the deep groove 131 in the axial direction and in the portion of the second piston body 37 that is closer to the first piston body 36 than the opening groove 102. In other words, the deep groove 131 is located closer to the first piston body 36 and the second piston body 37 in the axial direction than the plurality of shallow grooves 132. Figure 4 The second valve seat 47 side is shown. Figure 3 As shown, the plurality of shallow grooves 132 are arranged at equal intervals in the axial direction of the first piston body 36 and the second piston body 37 .

[0081] The piston band 38 is made of synthetic resin and is formed in an endless band shape. The piston band 38 includes a base portion 141 , a deep groove fitting portion 142 , and a plurality of (specifically, four) shallow groove fitting portions 143 .

[0082] The base portion 141 is in the shape of an endless belt with a constant thickness.

[0083] 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 continuous and has no joints over the entire circumference of the base portion 141.

[0084] The plurality of shallow groove fitting parts 143 are of the same shape and protrude from the inner circumferential surface 151 of the base part 141 to the inner side in the radial direction of the base part 141. The plurality of shallow groove fitting parts 143 are arranged at the middle position in the axial direction of the base part 141. The plurality of shallow groove fitting parts 143 are all continuous and jointless annular rings throughout the entire circumference of the base part 141. The plurality of shallow groove fitting parts 143 are arranged to be arranged at equal intervals in the axial direction of the base part 141. The protruding height of the plurality of shallow groove fitting parts 143 protruding from the inner circumferential surface 151 of the base part 141 is lower than the protruding height of the deep groove fitting part 142 protruding from the inner circumferential surface 151. In other words, the inner diameter of the plurality of shallow groove fitting parts 143 of the piston band 38 is larger than the inner diameter of the deep groove fitting part 142.

[0085] The piston band 38 is mounted on the outer periphery of the first piston body 36 and the second piston body 37 which are integrated by press-fitting as described above, so as to cover the outer periphery. At this time, the piston band 38 is elastically deformed in a manner of expanding the diameter, with the side opposite to the deep groove fitting portion 142 in the axial direction as the front, and is extended from the inner periphery of the piston band 38. Figure 4 The second valve seat 47 shown covers the first piston body 36 and Figure 3 The second piston body 37 shown. In addition, the deep groove fitting portion 142 of the piston band 38 first fits with the deep groove portion 131 of the first piston body 36 by releasing the diameter expansion, and then the plurality of shallow groove fitting portions 143 respectively fit with the shallow groove portions corresponding to the plurality of shallow groove portions 132 by releasing the diameter expansion. As a result, the inner peripheral surface 151 of the base portion 141 makes surface contact with and is in close contact with the outer peripheral surfaces 61, 101 of the first piston body 36 and the second piston body 37.

[0086] In this way, the piston band 38 is integrally mounted on the outer peripheral surfaces 61 and 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.

[0087] The piston 18 is formed in a manner including a first step, a second step, and a third step. The first step is as follows Figure 2 As shown in the figure, one surface of the first piston body 36, that is, the joint surface 41, is connected to one surface of the second piston body 37, that is, the joint surface 81, in such a manner that the first passage 75 is connected to the third passage 106 and the second passage 76 is connected to the fourth passage 107. The second step is to connect the end of the first passage 75 opposite to the third passage 106, the end of the third passage 106 opposite to the first passage 75, the end of the second passage 76 opposite to the fourth passage 107, and the end of the fourth passage 107 opposite to the second passage 76, as shown in the figure. Figure 3 The third step is to assemble the piston belt 38 to the deep groove 131 and the plurality of shallow grooves 132. In the third step, the piston belt 38 is assembled to the deep groove 131 and the plurality of shallow grooves 132. Figure 2 The second valve seat 47 shown is assembled in the deep groove portion 131 and then assembled in the plurality of shallow groove portions 132 .

[0088] The piston 18 is engaged with the engaging shaft portion 32 of the piston rod 21 in such a manner that the second piston body 37 is arranged 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 engaging the through hole 82 of the second piston body 37 and the through hole 42 of the first piston body 36 with the engaging shaft portion 32.

[0089] The piston 18 is connected to the piston rod 21, and the first valve seat 46 and the second valve seat 47 of the first piston body 36 are arranged on the second chamber 20 side, and the third valve seat 86 and the fourth valve seat 87 of the second piston body 37 are arranged on the first chamber 19 side. The piston 18 slides relative to the inner tube 3 in a state where the piston band 38 contacts the inner circumferential surface of the inner tube 3 on its outer circumferential surface.

[0090] like Figure 4 As shown, on the inner valve seat 45 of the piston 18, one disk 161, one disk 162, one disk 163, one disk 164, one disk 165, one disk 166, a plurality of (specifically, 6) disks 167, a plurality of (specifically, 3) disks 168, one disk 169, one disk 170, and one annular member 171 are stacked in order from the inner valve seat 45 side in the axial direction of the piston 18. The number of disks illustrated here is one embodiment, and can be appropriately adjusted according to the desired damping force characteristics.

[0091] The disks 161 to 170 and the annular member 171 are all made of metal. The disks 161 to 170 are all circular flat plates with holes of a constant thickness. The annular member 171 is annular. The disks 161 to 170 and the annular member 171 are fitted with the fitting shaft portion 32 of the piston rod 21 on the inner side.

[0092] The outer diameter of the disk 161 is larger than the outer diameter of the inner valve seat 45 of the piston 18 and smaller than the inner diameter of the first valve seat 46 .

[0093] The outer diameter of the disk 162 is larger than the outer diameter of the first valve seat 46 of the piston 18 and smaller than the inner diameter of the second valve seat 47. The disk 162 opens and closes the first passage 75 by using the position of the first valve seat 46 by moving away from the first valve seat 46 or contacting the first valve seat 46. The disk 162 is provided with a passage hole 182 at a position between the inner valve seat 45 of the piston 18 and the outer peripheral portion of the disk 161. The passage hole 182 penetrates the disk 162 in the axial direction of the disk 162. The passage hole 182 is an arc-shaped long hole extending in the circumferential direction of the disk 162. The passage hole 182 is opened and closed by the disk 161.

[0094] The outer diameter of the disk 163 is equal to the outer diameter of the disk 162. A cutout portion 183 is formed on the disk 163 at the outer periphery. The cutout portion 183 penetrates the disk 163 in the axial direction of the disk 163. The cutout portion 183 opens at the outer periphery of the disk 163. A plurality of cutout portions 183 are formed on the disk 163 at equal intervals in the circumferential direction of the disk 163. The plurality of cutout portions 183 are connected to the passage hole 182 of the disk 162 at the inner side portion in the radial direction of the disk 163. The plurality of cutout portions 183 and the passage hole 182 constitute a fixed throttle hole 184. The fixed throttle hole 184 is opened and closed by the disk 161. The disks 161 and 162 constitute a one-way valve 185. The one-way valve 185 allows the oil L to flow from the fixed throttle hole 184 to the passage in the passage groove 51, and restricts the oil L from flowing from the passage in the passage groove 51 to the fixed throttle hole 184.

[0095] The outer diameter of the disk 164 is equal to the outer diameter of the disk 163. The disk 164 forms a fixed throttle hole 184 by covering the plurality of cutout portions 183 of the disk 163 on the side opposite to the disk 162. Therefore, the fixed throttle hole 184 and the one-way valve 185 that allows the flow of the oil L in only one direction in the fixed throttle hole 184 are composed of the stacked plurality of disks 161 to 164.

[0096] The outer diameter of the disk 165 is smaller than the outer diameter of the disk 164 and slightly larger than the outer diameter of the inner valve seat 45 .

[0097] The outer diameter of the disk 166 is equal to the outer diameter of the second valve seat 47 of the piston 18. The disk 166 opens and closes the first passage 75 by utilizing the position of the second valve seat 47 by moving away from the second valve seat 47 or contacting the second valve seat 47. A cutout portion 186 is formed on the outer periphery of the disk 166. The cutout portion 186 penetrates the disk 166 in the axial direction of the disk 166. The cutout portion 186 opens at the outer periphery of the disk 166. A plurality of cutout portions 186 are formed on the disk 166 at equal intervals in the circumferential direction of the disk 166. The plurality of cutout portions 186 extend so as to cross the second valve seat 47 in the radial direction. The plurality of cutout portions 186 form a fixed throttle hole 187 in the first passage 75 when the disk 166 contacts the second valve seat 47. The flow path cross-sectional area of ​​the fixed throttle hole 187 is larger than the flow path cross-sectional area of ​​the fixed throttle hole 184.

[0098] The plurality of disks 167 have the same outer diameter, and each outer diameter is equal to the outer diameter of disk 166. The disk 167 closest to disk 166 among the plurality of disks 167 covers the plurality of cutouts 186 of disk 166 on the side opposite to second valve seat 47 to form a fixed orifice 187.

[0099] The plurality of disks 168 have the same outer diameter, and each disk 168 has an outer diameter that is smaller than the outer diameter of the disk 167 and larger than the outer diameter of the disk 165 .

[0100] The outer diameter of disk 169 is smaller than that of disk 168 and is equal to the outer diameter of disk 165 .

[0101] The outer diameter of disk 170 is larger than the outer diameter of disk 169 and is equal to the outer diameter of disk 167 .

[0102] The outer diameter of annular member 171 is smaller than that of disk 170 and larger than that of disk 169. Annular member 171 is thicker than disks 161 to 170 and has higher rigidity than disks 161 to 170.

[0103] Figure 2 The first passage 75 and the third passage 106 shown are flow passages for supplying the oil L from the first chamber 19 to the second chamber 20 during the extension stroke. The third passage 106 is always in communication with the first chamber 19.

[0104] like Figure 4 As shown, the disks 162 to 164 constitute a first damping valve 191 that opens and closes the first passage 75 by being placed on the first valve seat 46 and separated from the first valve seat 46 or contacting the first valve seat 46. The first damping valve 191 is provided with a fixed orifice 184 and a check valve 185.

[0105] The disks 166 to 168 constitute a second damping valve 192 that opens and closes the first passage 75 by being placed on the second valve seat 47 and being separated from the second valve seat 47 or abutting against the second valve seat 47. A fixed throttle hole 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 disks 166 to 168 of the second damping valve 192 is thicker than the total thickness of the disks 162 to 164 of the first damping valve 191. The second damping valve 192 has a higher rigidity than the first damping valve 191.

[0106] When the first damping valve 191 is separated from the first valve seat 46 and opens, the oil L flows from Figure 2 The first chamber 19 shown flows toward the second chamber 20 side via the third passage 106, the passages in the plurality of passage holes 52 that all constitute the first passage 75, the passages in the passage groove 51, and the passage between the first damping valve 191 and the first valve seat 46. At this time, the first damping valve 191 suppresses the flow of the oil L and generates a damping force. The first damping valve 191 is provided in the first passage 75, suppresses the flow of the oil L generated in the extension stroke and generates a damping force.

[0107] The second damping valve 192 has a higher rigidity than the first damping valve 191, so after the first damping valve 191 is separated from the first valve seat 46 and opened, the second damping valve 192 is separated from the second valve seat 47 and opened. When the second damping valve 192 is separated from the second valve seat 47 and opened, the oil L flows from the first chamber 19 to the second chamber 20 side via the third passage 106, the passages in the plurality of passage holes 52 that all constitute the first passage 75, the passages in the passage groove 51, the passages between the first damping valve 191 and the first valve seat 46, the passages between the first valve seat 46 and the second valve seat 47, and the passages between the second damping valve 192 and the second valve seat 47. At this time, the second damping valve 192 suppresses the flow of the oil L and generates a damping force. The second damping valve 192 is provided in the first passage 75, suppresses the flow of the oil L generated in the extension stroke, and generates a damping force.

[0108] The first damping valve 191 is provided on the upstream side of the second damping valve 192 in the flow direction of the oil L in the extension stroke. The first damping valve 191 has lower rigidity and lower valve opening pressure than the second damping valve 192. Therefore, the first damping valve 191 opens in a range where the moving speed of the piston 18 (hereinafter referred to as piston speed) is lower than that of the second damping valve 192.

[0109] According to the above, the first piston body 36 has a first valve seat 46 and a second valve seat 47. The first valve seat 46 is connected to the first passage 75, and is placed on the first damping valve 191 that opens when the piston speed is low. The second valve seat 47 has a larger diameter than the first valve seat 46 and is arranged closer to the second chamber 20 than the first valve seat 46, and is placed on the second damping valve 192 that opens after the first damping valve 191 opens.

[0110] The check valve 185 provided in the first damping valve 191 closes the flow in the direction from the first chamber 19 to the second chamber 20 generated during the extension stroke.

[0111] like Figure 5 As shown, on the inner valve seat 85 of the piston 18, a disk 201, a plurality of (specifically, two) disks 202, a disk 203, a disk 204, a plurality of (specifically, three) disks 205, a plurality of (specifically, two) disks 206, a disk 207, a disk 208, and a ring member 209 are stacked in order from the inner valve seat 85 side in the axial direction of the piston 18. The number of disks illustrated here is one embodiment, and can be appropriately adjusted according to the desired damping force characteristics.

[0112] The disks 201 to 208 and the annular member 209 are all made of metal. The disks 201 to 208 are all circular flat plates with holes of a constant thickness. The annular member 209 is annular. The disks 201 to 208 and the annular member 209 are all fitted with the fitting shaft portion 32 of the piston rod 21 on the inner side.

[0113] The outer diameter of the disk 201 is larger than the outer diameter of the third valve seat 86 of the piston 18, and smaller than the inner diameter of the fourth valve seat 87. The disk 201 opens and closes the fourth passage 107 by using the position of the third valve seat 86 by leaving the third valve seat 86 or contacting the third valve seat 86. A cutout 221 is formed on the outer periphery of the disk 201. The cutout 221 penetrates the disk 201 in the axial direction of the disk 201. The cutout 221 opens at the outer periphery of the disk 201. A plurality of cutouts 221 are formed on the disk 201 at equal intervals in the circumferential direction of the disk 201. The plurality of cutouts 221 extend in a manner of crossing the third valve seat 86 in the radial direction. The plurality of cutouts 221 form fixed throttle holes 222 in the fourth passage 107 when the disk 201 contacts the third valve seat 86.

[0114] The plurality of disks 202 have the same outer diameter, and each outer diameter is equal to the outer diameter of the disk 201. The disk 202 closest to the disk 201 among the plurality of disks 202 covers the plurality of cutouts 221 of the disk 201 on the side opposite to the third valve seat 86 to form a fixed orifice 222.

[0115] The outer diameter of the disk 203 is smaller than the outer diameter of the disk 202 and is slightly larger than the outer diameter of the inner valve seat 85 .

[0116] The outer diameter of the disk 204 is larger than the outer diameter of the fourth valve seat 87 of the piston 18. The disk 204 opens and closes the fourth passage 107 by using the position of the fourth valve seat 87 by leaving the fourth valve seat 87 or contacting the fourth valve seat 87. A cutout 225 is formed on the outer periphery of the disk 204. The cutout 225 penetrates the disk 204 in the axial direction of the disk 204. The cutout 225 opens at the outer periphery of the disk 204. A plurality of cutouts 225 are formed on the disk 204 at equal intervals in the circumferential direction of the disk 204. The plurality of cutouts 225 extend so as to cross the fourth valve seat 87 in the radial direction. The plurality of cutouts 225 form a fixed throttle hole 226 in the fourth passage 107 when the disk 204 contacts the fourth valve seat 87. The flow path cross-sectional area of ​​the fixed throttle hole 226 is larger than the flow path cross-sectional area of ​​the fixed throttle hole 222.

[0117] The plurality of disks 205 have the same outer diameter, and each outer diameter is equal to the outer diameter of the disk 204. The disk 205 closest to the disk 204 among the plurality of disks 205 covers the plurality of cutouts 225 of the disk 204 on the side opposite to the fourth valve seat 87 to form a fixed orifice 226.

[0118] The plurality of disks 206 have the same outer diameter, and each disk 206 has a smaller outer diameter than the outer diameter of the disk 205 and a larger outer diameter than the outer diameter of the disk 203 .

[0119] The outer diameter of disk 207 is smaller than that of disk 206 and is equal to that of disk 203 .

[0120] The outer diameter of disk 208 is larger than that of disk 207 and is equal to that of disk 205 .

[0121] The outer diameter of the annular member 209 is smaller than that of the disk 208 and larger than that of the disk 207. The thickness of the annular member 209 is thicker than that of the disks 201 to 208 and the annular member 209 has higher rigidity than the disks 201 to 208.

[0122] like Figure 2 As shown, the fourth passage 107 and the second passage 76 are flow passages for supplying the oil L from the second chamber 20 toward the first chamber 19 mainly during the contraction stroke. The second passage 76 is always in communication with the second chamber 20.

[0123] Figure 5 The disks 201 and 202 shown constitute a third damping valve 231 that opens and closes the fourth passage 107 by being placed on the third valve seat 86 and moving away from the third valve seat 86 or contacting the third valve seat 86. The third damping valve 231 is provided with a fixed orifice 222.

[0124] The disks 204 to 206 constitute a fourth damping valve 232 that opens and closes the fourth passage 107 by being placed on the fourth valve seat 87 and moving away from the fourth valve seat 87 or abutting against the fourth valve seat 87. A fixed throttle hole 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 disks 204 to 206 of the fourth damping valve 232 is thicker than the total thickness of the disks 201 and 202 of the third damping valve 231, and the fourth damping valve 232 has higher rigidity than the third damping valve 231.

[0125] When the third damping valve 231 is separated from the third valve seat 86 and opens, the oil L flows from Figure 2 The second chamber 20 shown flows toward the first chamber 19 side via the second passage 76, the passages in the plurality of passage holes 92 that all constitute the fourth passage 107, the passages in the passage groove 91, and the passages between the third damping valve 231 and the third valve seat 86. At this time, the third damping valve 231 suppresses the flow of the oil L and generates a damping force. The third damping valve 231 is provided in the fourth passage 107, suppresses the flow of the oil L generated in the contraction stroke and generates a damping force.

[0126] The fourth damping valve 232 has a higher rigidity than the third damping valve 231. Therefore, after the third damping valve 231 is separated from the third valve seat 86 and opened, the fourth damping valve 232 is separated from the fourth valve seat 87 and opened. When the fourth damping valve 232 is separated from the fourth valve seat 87 and opened, the oil L flows from the second chamber 20 to the first chamber 19 side via the second passage 76, the passages in the plurality of passage holes 92 that all constitute the fourth passage 107, the passages in the passage groove 91, the passages between the third damping valve 231 and the third valve seat 86, the passages between the third valve seat 86 and the fourth valve seat 87, and the passages between the fourth damping valve 232 and the fourth valve seat 87. At this time, the fourth damping valve 232 suppresses the flow of the oil L and generates a damping force. The fourth damping valve 232 is provided in the fourth passage 107, suppresses the flow of the oil L generated in the contraction stroke, and generates a damping force.

[0127] The third damping valve 231 is provided on the upstream side of the fourth damping valve 232 in the flow direction of the oil L in the contraction stroke. The third damping valve 231 has lower rigidity and lower valve opening pressure than the fourth damping valve 232. Therefore, the third damping valve 231 opens in a range where the movement speed of the piston 18 is lower than that of the fourth damping valve 232.

[0128] like Figure 4 As shown, the one-way valve 185 provided in the first damping valve 191 is in contact with the flow from the second chamber 20 to the first damping valve 191 during the contraction stroke. Figure 2 The valve is opened by controlling the flow of the oil L in the first chamber 19 shown. Figure 4 The one-way valve 185 shown in the figure does not generate a damping force substantially and allows the oil L to flow. Figure 2 The valve is opened for the flow in the first chamber 19 shown, and is closed for the flow in the opposite direction.

[0129] According to the above, the second piston body 37 has a third valve seat 86 and a fourth valve seat 87. The third valve seat 86 is connected to the fourth passage 107, and is placed in the third damping valve 231 that opens when the piston speed is low. The fourth valve seat 87 has a larger diameter than the third valve seat 86 and is arranged closer to the first chamber 19 than the third valve seat 86, and is placed in the fourth damping valve 232 that opens after the third damping valve 231 opens.

[0130] The first piston body 36 has a first passage 75 and a second passage 76 for allowing 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 by the movement of the piston 18. The second piston body 37 has a third passage 106 and a fourth passage 107 for allowing 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 by the movement of the piston 18.

[0131] The annular member 209 is placed on the shaft step portion 29 on the piston rod 21 so that the mounting shaft portion 28 is inserted into the inner side. Figure 5 As shown, the disk 208, disk 207, multiple disks 206, multiple disks 205, disk 204, disk 203, multiple disks 202, disk 201 and piston 18 are stacked in this order on the annular member 209 so that the mounting shaft portion 28 is inserted into each inner side. Figure 4 As shown, on the piston 18, disk 161, disk 162, disk 163, disk 164, disk 165, disk 166, multiple disks 167, multiple disks 168, disk 169, disk 170, and annular component 171 are stacked in this order in a state where the mounting shaft portion 28 is inserted into each inner side. In this state, the parts from the annular component 209 to the annular component 171 are engaged with the engaging shaft portion 32 of the mounting shaft portion 28. In this state, as Figure 2 As shown, the nut 241 is screwed to the threaded shaft portion 31 of the mounting shaft portion 28 protruding from the annular member 171. Thus, the inner circumferential sides of the parts from the annular member 209 to the annular member 171 are clamped in the axial direction by the shaft step portion 29 of the piston rod 21 and the nut 241.

[0132] like Figure 1 As shown, a base member 26 of the bottom valve 25 is provided between the bottom 12 of the outer tube 4 and the inner tube 3. The bottom valve 25 includes a disk valve 252, a disk valve 253, and a mounting pin 254 in addition to the base member 26. The disk valve 252 is provided on the lower side of the base member 26, that is, on the storage chamber 6 side. The disk valve 253 is provided on the upper side of the base member 26, that is, on the second chamber 20 side. The mounting pin 254 mounts the disk valve 252 and the disk valve 253 to the base member 26.

[0133] The base member 26 is annular, and a mounting pin 254 is inserted through the center in the radial direction. A plurality of passage holes 255 and a plurality of passage holes 256 are formed in the base member 26. The plurality of passage holes 255 allow the oil L to flow between the second chamber 20 and the reservoir 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 6. The disk valve 252 on the reservoir 6 side allows the oil L to flow from the second chamber 20 to the reservoir 6 via the passage hole 255. On the other hand, the disk valve 252 inhibits the oil L from the reservoir 6 to flow to the second chamber 20 via the passage hole 255. The disk valve 253 allows the oil L to flow from the reservoir 6 to the second chamber 20 via the passage hole 256. On the other hand, the disk valve 253 suppresses the flow of the oil L from the second chamber 20 to the reservoir chamber 6 via the passage hole 256 .

[0134] The disk valve 252 forms a damping valve mechanism 257 through the base member 26. The damping valve mechanism 257 opens during the contraction stroke of the shock absorber 1 to allow the oil L to flow from the second chamber 20 to the reservoir chamber 6 and generate a damping force. The disk valve 253 forms a suction valve mechanism 258 through the base member 26. The suction valve mechanism 258 opens during the extension stroke of the shock absorber 1 to allow the oil L to flow from the reservoir chamber 6 to the second chamber 20. It should be noted that the suction valve mechanism 258 mainly serves to compensate for the insufficient amount of liquid caused by the extension of the piston rod 21 from the cylinder 2 and allows the oil L to flow from the reservoir chamber 6 to the second chamber 20 in a manner that substantially does not generate a damping force.

[0135] Next, the main operation of the shock absorber 1 will be described.

[0136] "Stretching Stroke"

[0137] {First range where piston speed is slower than first specified value}

[0138] In the first range of the extension stroke, the oil L from the first chamber 19 does not flow to the second chamber 20 via the third passage 106 and the first passage 75 because the check valve 185 of the first damping valve 191 is closed. Therefore, the oil L from the first chamber 19 flows to the second chamber 20 via the second passage 76 through the fixed orifice 226 of the fourth damping valve 232, the passage between the third valve seat 86 and the fourth valve seat 87, the fixed orifice 222 of the third damping valve 231, the passage in the passage groove 91, and the passage in the plurality of passage holes 92, which all constitute the fourth passage 107. Therefore, in the first range of the extension stroke, a damping force based on the orifice characteristic (damping force is substantially proportional to the square of the piston speed) of the flow passage cross-sectional area a of the fixed orifice 222 is generated.

[0139] {A second range in which the piston speed is greater than or equal to the first predetermined value and slower than a second predetermined value greater than the first predetermined value}

[0140] In the second range of the extension stroke, the oil L from the first chamber 19 flows to the second chamber 20 through the third passage 106, the passages in the plurality of passage holes 52 that all constitute the first passage 75, the passages in the passage groove 51, the passages between the opened first damping valve 191 and the first valve seat 46, the passages between the first valve seat 46 and the second valve seat 47, and the fixed orifice 187 of the second damping valve 192. The oil L from the first chamber 19 flows to the second chamber 20 through the fixed orifice 226 of the fourth damping valve 232 that all constitute the fourth passage 107, the passages between the third valve seat 86 and the fourth valve seat 87, the fixed orifice 222 of the third damping valve 231, the passages in the passage groove 91, and the passages in the plurality of passage holes 92 through the second passage 76. Therefore, within the second range of the stretching stroke, a damping force is generated that is a combination of the valve characteristics of the first damping valve 191 (the damping force is roughly proportional to the piston speed) and the throttle hole characteristics based on the flow path cross-sectional area a of the fixed throttle hole 222 (the damping force is roughly proportional to the square of the piston speed).

[0141] {A third range in which the piston speed is greater than or equal to the second predetermined value and is slower than a third predetermined value greater than the second predetermined value}

[0142] In the third range of the extension stroke, the oil L from the first chamber 19 flows to the second chamber 20 through the third passage 106, the passage in the plurality of passage holes 52 that all constitute the first passage 75, the passage in the passage groove 51, the passage between the first damping valve 191 that opens and the first valve seat 46, the passage between the first valve seat 46 and the second valve seat 47, and the fixed throttle hole 187 of the second damping valve 192. At this time, the flow of the oil L is restricted at the fixed throttle hole 187. On the other hand, the oil L from the first chamber 19 flows to the second chamber 20 through the fixed throttle hole 226 of the fourth damping valve 232 that all constitute the fourth passage 107, the passage between the third valve seat 86 and the fourth valve seat 87, the fixed throttle hole 222 of the third damping valve 231, the passage in the passage groove 91, and the passage in the plurality of passage holes 92 through the second passage 76. Therefore, within the third range of the extension stroke, a damping force having a characteristic that combines the orifice characteristics based on the flow path cross-sectional area B of the fixed orifice 187 and the orifice characteristics based on the flow path cross-sectional area a of the fixed orifice 222 is generated.

[0143] {Fourth range where the piston speed is greater than or equal to the third predetermined value}

[0144] In the fourth range of the extension stroke, the oil L from the first chamber 19 flows to the second chamber 20 through the third passage 106 and through the passages in the plurality of passage holes 52, which all constitute the first passage 75, the passages in the passage groove 51, the passages between the first damping valve 191 which is opened and the first valve seat 46, the passages between the first valve seat 46 and the second valve seat 47, and the passages between the second damping valve 192 which is opened and the second valve seat 47. On the other hand, the oil L from the first chamber 19 flows to the second chamber 20 through the fixed throttle hole 226 of the fourth damping valve 232, which all constitute the fourth passage 107, the passages between the third valve seat 86 and the fourth valve seat 87, the fixed throttle hole 222 of the third damping valve 231, the passages in the passage groove 91, and the passages in the plurality of passage holes 92 through the second passage 76. Therefore, within the fourth range of the extension stroke, a damping force having a characteristic that is a combination of the valve characteristic of the second damping valve 192 and the orifice characteristic based on the flow path cross-sectional area a of the fixed orifice 222 is generated.

[0145] "Contraction Stroke"

[0146] {Fifth range where the piston speed is slower than the fifth specified value}

[0147] In the fifth range of the contraction stroke, the oil L from the second chamber 20 flows to the first chamber 19 through the second passage 76, the passage in the plurality of passage holes 92, which all constitute the fourth passage 107, the passage in the passage groove 91, the fixed orifice 222 of the third damping valve 231, the passage between the third valve seat 86 and the fourth valve seat 87, and the fixed orifice 226 of the fourth damping valve 232. On the other hand, the oil L from the second chamber 20 flows to the first chamber 19 through the fixed orifice 187 of the second damping valve 192, which all constitute the first passage 75, the passage between the first valve seat 46 and the second valve 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 passage in the plurality of passage holes 52, and flows to the first chamber 19 through the third passage 106. Therefore, within the fifth range of the contraction stroke, a damping force is generated that combines the throttle hole characteristics of the flow path cross-sectional area a based on the fixed throttle hole 222 of the third damping valve 231 and the throttle hole characteristics of the flow path cross-sectional area b based on the fixed throttle hole 184 of the first damping valve 191.

[0148] {A sixth range in which the piston speed is greater than or equal to the fifth prescribed value and is slower than a sixth prescribed value greater than the fifth prescribed value}

[0149] In the sixth range of the contraction stroke, the oil L from the second chamber 20 flows to the first chamber 19 through the second passage 76, the passage in the plurality of passage holes 92 all constituting the fourth passage 107, the passage in the passage groove 91, the passage between the third damping valve 231 and the third valve seat 86, the passage between the third valve seat 86 and the fourth valve seat 87, and the fixed orifice 226 of the fourth damping valve 232. On the other hand, the oil L from the second chamber 20 flows to the first chamber 19 through the fixed orifice 187 of the second damping valve 192 all constituting the first passage 75, the passage between the first valve seat 46 and the second valve seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passage in the passage groove 51, the passage in the plurality of passage holes 52, and the third passage 106. Therefore, in the sixth range of the contraction stroke, a damping force having a characteristic obtained by combining the valve characteristic of the third damping valve 231 and the orifice characteristic based on the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191 is generated.

[0150] {A seventh range in which the piston speed is greater than or equal to the sixth prescribed value and is slower than a seventh prescribed value greater than the sixth prescribed value}

[0151] In the seventh range of the contraction stroke, the oil L from the second chamber 20 flows to the first chamber 19 through the second passage 76, the passage in the plurality of passage holes 92 that all constitute the fourth passage 107, the passage in the passage groove 91, the passage between the third damping valve 231 and the third valve seat 86 that is open, the passage between the third valve seat 86 and the fourth valve seat 87, and the fixed orifice 226 of the fourth damping valve 232. At this time, the flow of the oil L is restricted at the fixed orifice 226. On the other hand, the oil L from the second chamber 20 flows to the first chamber 19 through the fixed orifice 187 of the second damping valve 192 that all constitute the first passage 75, the passage between the first valve seat 46 and the second valve 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 passage in the plurality of passage holes 52, and flows to the first chamber 19 through the third passage 106. Therefore, within the seventh range of the contraction stroke, a damping force is generated that combines the throttle hole characteristics of the flow path cross-sectional area A based on the fixed throttle hole 226 of the fourth damping valve 232 and the throttle hole characteristics of the flow path cross-sectional area b based on the fixed throttle hole 184 of the first damping valve 191.

[0152] {The eighth range where the piston speed is greater than the seventh specified value}

[0153] In the eighth range of the contraction stroke, the oil L from the second chamber 20 flows to the first chamber 19 through the second passage 76, and through the passages in the plurality of passage holes 92, which all constitute the fourth passage 107, the passages in the passage groove 91, the passages between the third damping valve 231 and the third valve seat 86, the passages between the third valve seat 86 and the fourth valve seat 87, and the passages between the fourth damping valve 232 and the fourth valve seat 87. The oil L from the second chamber 20 flows to the first chamber 19 through the fixed orifice 187 of the second damping valve 192, which all constitute the first passage 75, the passages between the first valve seat 46 and the second valve seat 47, the fixed orifice 184 of the first damping valve 191, the open check valve 185, the passages in the passage groove 51, and the passages in the plurality of passage holes 52, and through the third passage 106. Therefore, in the eighth range of the contraction stroke, a damping force having a characteristic obtained by combining the valve characteristic of the fourth damping valve 232 and the orifice characteristic based on the flow path cross-sectional area b of the fixed orifice 184 of the first damping valve 191 is generated.

[0154] In the shock absorber 1, the check valve 185 is provided in one of the first damping valve 191 and the third damping valve 231, both of which are opened at a low piston speed, and the check valve 185 is provided in the first damping valve 191, and the check valve is not provided in the other third damping valve 231. Therefore, as described above, in the extension stroke, the orifice characteristics of the first damping valve 191 before the valve is opened are characteristics based only on the flow path cross-sectional area a of the fixed orifice 222 of the third damping valve 231, and the orifice characteristics of the first damping valve 191 after the valve is opened are characteristics based on 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, in the contraction stroke, the throttle hole characteristics of the third damping valve 231 before opening are based on the characteristics of the flow path cross-sectional area a of the fixed throttle hole 222 of the third damping valve 231 and the flow path cross-sectional area b of the fixed throttle hole 184 of the first damping valve 191, and the throttle hole characteristics of the third damping valve 231 after opening are based on the characteristics of the flow path cross-sectional area A of the fixed throttle hole 226 of the fourth damping valve 232 and the flow path cross-sectional area b of the fixed throttle hole 184 of the first damping valve 191.

[0155] It should be noted that the above description is based on the case where the fixed orifice 184 and the check valve 185 are provided in the first damping valve 191. On the contrary, the same fixed orifice and check valve can also be provided in the third damping valve 231. In this case, for example, the first damping valve 191 including the check valve 185, the piston 18 and the third damping valve 231 are turned over in the axial direction relative to the above structure as a whole in the original state and are fitted with the fitting shaft portion 32. Then, the first damping valve 191 including the fixed orifice 184 and the check valve 185 and turned over becomes the third damping valve including the third fixed orifice and the third check valve, and the turned over third damping valve 231 becomes the first damping valve. In this way, the third check valve provided in the third damping valve allows the flow of the 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. Furthermore, the third check valve restricts the flow of the 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.

[0156] Furthermore, the second damping valve 192 may be provided with a structure in which a second fixed orifice is formed by a laminated disk and a second check valve that allows the oil L to flow in only one direction in the second fixed orifice. In this case, the second check valve allows the oil 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. Furthermore, the second check valve restricts the flow of the oil 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 check valve 185 may not be provided in the first damping valve 191, and only the fixed orifice may be provided. Furthermore, 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.

[0157] Furthermore, the fourth damping valve 232 may be provided with a structure in which a fourth fixed orifice is formed by a laminated disk and a fourth check valve that allows the oil L to flow in only one direction in the fourth fixed orifice. In this case, the fourth check valve allows the oil 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 the oil 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 including the third fixed orifice and the third check valve and the fourth damping valve 232 including the fourth fixed orifice and the fourth check valve may be provided.

[0158] The above-mentioned patent documents 1 to 4 disclose shock absorbers in which a piston is composed of a plurality of piston bodies. In addition, 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 high compared to the valve. However, in the shock absorber, it is required to suppress the increase in the number of parts and suppress the decrease in productivity. For example, a shock absorber is formed to have a first damping valve on the tension side and a second damping valve that opens in a range where the piston speed is high compared to the first damping valve, and a third damping valve on the contraction side and a fourth damping valve that opens in a range where the piston speed is high compared to the third damping valve. In this case, the number of valves is large, which is likely to lead to a decrease in productivity. Therefore, it is desired to suppress the increase in the number of parts and suppress the decrease in productivity.

[0159] The piston 18 of the shock absorber 1 of the embodiment includes a first piston body 36, a second piston body 37, and a piston band 38. The first piston body 36 includes a first passage 75, a second passage 76, a first valve seat 46, and a second valve seat 47. The first passage 75 and the second passage 76 allow the oil 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 by the movement of the piston 18. The first valve seat 46 is connected to the first passage 75, and a first damping valve 191 that opens when the piston speed is low is placed. The second valve seat 47 has a larger diameter than the first valve seat 46 and is provided on the side of the second chamber 20, and a second damping valve 192 that opens after the first damping valve 191 opens is placed. The second piston body 37 includes a third passage 106, a fourth passage 107, a third valve seat 86, and a fourth valve seat 87. The third passage 106 and the fourth passage 107 allow the oil L as the 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 through the movement of the piston 18. The third valve seat 86 is connected to the fourth passage 107, and the third damping valve 231 that opens when the piston speed is low is placed. The fourth valve seat 87 has a larger diameter than the third valve seat 86 and is arranged on the side of the first chamber 19. The fourth damping valve 232 that opens after the third damping valve 231 opens is placed. Since the piston 18 has the first piston body 36, the second piston body 37 and the piston band 38, the components of the piston 18 can be reduced. Therefore, the man-hours for manufacturing the various parts constituting the piston 18 and the man-hours for assembling can be reduced. In addition, the piston 18 can be assembled into a subassembly in advance before being assembled to the piston rod 21. Therefore, the man-hours for assembling the parts to the piston rod 21 can be reduced. Therefore, the productivity can be suppressed from decreasing. The shock absorber 1 is 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 placed on the piston 18, which is a structure that is particularly prone to causing a decrease in productivity. Therefore, suppressing the decrease in productivity as described above greatly contributes to the effect of suppressing an increase in the product cost of the shock absorber 1.

[0160] Furthermore, the shock absorber 1 is provided with an alignment portion 121 on the mutually connected joint surfaces 41, 81 of the first piston body 36 and the second piston body 37. The alignment portion 121 makes the positions of the first passage 75 and the third passage 106 consistent, and makes the positions of the second passage 76 and the fourth passage 107 consistent. Therefore, these alignments can be easily performed. Furthermore, the inner diameter of the first piston body 36 of the shock absorber 1 is different from the inner diameter of the second piston body 37, so by fitting the first piston body 36 and the second piston body 37 with the smaller inner diameter, the piston 18 can be positioned on the piston rod 21. Therefore, when connecting the first piston body 36 and the second piston body 37, it is not necessary to align the inner circumferential surfaces with each other. Therefore, the decrease in productivity can be further suppressed.

[0161] Furthermore, the shock absorber 1 is provided with a check valve 185 in the first damping valve 191 or the third damping valve 231, and the check valve 185 opens with respect to the flow toward the first chamber 19 or the second chamber 20, and closes with respect to the flow in the opposite direction. Therefore, the orifice characteristics before the first damping valve 191 or the third damping valve 231 is opened can be made different in the extension stroke and the contraction stroke. For example, in the case where the check valve 185 is provided in the first damping valve 191 as described above, in the extension stroke, the orifice characteristics before the first damping valve 191 is opened are based on the flow path cross-sectional area a of the fixed orifice 222, and the orifice characteristics after the first damping valve 191 is opened are based on 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. In the contraction stroke, the third damping valve 231 has a throttling hole characteristic based on the flow cross-sectional area a of the fixed throttling hole 222 and the flow cross-sectional area b of the fixed throttling hole 184 before opening, and has a throttling hole characteristic based on the flow cross-sectional area A of the fixed throttling hole 226 and the flow cross-sectional area b of the fixed throttling hole 184 after opening.

[0162] The manufacturing method of the shock absorber 1 of the embodiment includes the first to third steps. In the first step, the joint surface 41 of the first piston body 36 and the joint surface 81 of the second piston body 37 are connected in such a manner that the first passage 75 is connected to the third passage 106 and the second passage 76 is connected to the fourth passage 107. In the second step, the end of the first passage 75 opposite to the third passage 106, the end of the third passage 106 opposite to the first passage 75, the end of the second passage 76 opposite to the fourth passage 107, the end of the fourth passage 107 opposite to the second passage 76, the deep groove 131 and the shallow groove 132 for the piston band 38 to be assembled are processed. In the third step, the piston band 38 is assembled to the deep groove 131 and the shallow groove 132. In this way, the first piston body 36 and the second piston body 37 are processed in the second step in a state where the first piston body 36 and the second piston body 37 are connected in the first step, so that the relative accuracy of each part can be easily ensured. Furthermore, by performing the first to third steps, the piston 18 can be assembled into a subassembly before being assembled to the piston rod 21. Therefore, the man-hours for assembling the parts to the piston rod 21 can be reduced. Therefore, a decrease in productivity can be suppressed.

[0163] The third step is to fit the piston band 38 to the plurality of shallow grooves 132 having a depth shallower than that of the deep grooves 131 after being fitted to the deep grooves 131 via the second valve seat 47. Therefore, the piston band 38 can be properly and smoothly fitted to the first piston body 36 and the second piston body 37.

[0164] In addition, in the embodiment, a hydraulic shock absorber is exemplified as the shock absorber 1 , but the above-mentioned structure can also be adopted in a shock absorber using water or air as a working fluid.

[0165] Industrial Applicability

[0166] According to the above-described embodiment of the present invention, a vibration damper and a method for manufacturing the vibration damper can be provided, which can suppress a decrease in productivity. Therefore, the present invention has high industrial applicability.

[0167] Description of Reference Numerals

[0168] 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 belt, 41, 81… joint surface, 46… first valve seat, 47… second valve seat, 75… first passage, 76… second passage, 86… third valve seat, 87… fourth valve seat, 106… third passage, 107… fourth passage, 121… counter-position portion, 185… check valve, 191… first damping valve, 192… second damping valve, 231… third damping valve, 232… fourth damping valve.

Claims

1. A shock absorber comprising: a cylinder in which a working fluid is sealed; A piston slidably mounted in the cylinder to divide the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; The piston has a first piston body and a second piston body, The first piston body has: a first passage and a second passage for allowing working fluid to flow between one chamber and another chamber in the cylinder by movement of the piston; A first valve seat, which is in communication with the first passage and is provided with a first damping valve that opens when the piston speed is low; A second valve seat having a larger diameter than the first valve seat and disposed near the chamber, and being placed on a second damping valve that opens after the first damping valve opens; The second piston body has: a third passage and a fourth passage for allowing the working fluid to flow between one of the chambers and the other chamber in the cylinder by movement of the piston; a third valve seat, which is in communication with the fourth passage and is provided with a third damping valve which opens when the piston speed is low; a fourth valve seat having a larger diameter than the third valve seat and disposed near the chamber, and being placed on a fourth damping valve that opens after the third damping valve opens; The first piston body and the second piston body are connected in such a manner that the first passage communicates with the third passage and the second passage communicates with the fourth passage.

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 with respect to a flow toward the chamber and closes with respect to a flow in the opposite direction.

3. 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 with respect to a flow toward the chamber and closes with respect to a flow in the opposite direction.

4. A method for manufacturing a shock absorber, the shock absorber comprising: a cylinder in which a working fluid is sealed; A piston slidably mounted in the cylinder to divide the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; The piston comprises a first piston body, a second piston body and a piston band arranged on the first piston body and the second piston body. The first piston body has: a first passage and a second passage for allowing working fluid to flow between one chamber and another chamber in the cylinder by movement of the piston; A first valve seat, which is in communication with the first passage and is provided with a first damping valve that opens when the piston speed is low; A second valve seat having a larger diameter than the first valve seat and disposed near the chamber, and being placed on a second damping valve that opens after the first damping valve opens; The second piston body has: a third passage and a fourth passage for allowing the working fluid to flow between one of the chambers and the other chamber in the cylinder by movement of the piston; a third valve seat, which is in communication with the fourth passage and is provided with a third damping valve which opens when the piston speed is low; a fourth valve seat having a larger diameter than the third valve seat and disposed near the chamber, and being placed on a fourth damping valve that opens after the third damping valve opens; The manufacturing method of the shock absorber comprises: A first step of connecting one surface of the first piston body with one surface of the second piston body in such a manner that the first passage is connected to the third passage and the second passage is connected to the fourth passage; The second step is to process the end of the first passage opposite to the third passage, the end of the third passage opposite to the first passage, the end of the second passage opposite to the fourth passage, the end of the fourth passage opposite to the second passage, and the groove for the piston band to be assembled; The third step is to fit the piston band to the groove.

5. The method for manufacturing a vibration damper according to claim 4, wherein: The groove has: A plurality of shallow grooves; a deep groove portion located on the second valve seat side relative to the plurality of shallow groove portions and having a depth greater than that of the plurality of shallow groove portions; The third step is to mount the piston band in the plurality of shallow grooves after mounting the piston band in the deep groove via the second valve seat.

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