shock absorber

Abstract

This shock absorber includes a first valve assembly connected to one axial end of the tube, a piston assembly dividing the interior of the tube into a first chamber and a second chamber, a piston rod connected to the piston assembly at an intermediate position in the axial direction and extending from the tube through the first chamber, a cup provided in the second chamber, and a second valve assembly disposed in the second chamber and connected to the piston rod and advancing and retracting relative to the cup. The cup has a sleeve disposed in the second chamber with a radial gap between it and the tube, and a base adapter fixed to the sleeve by press fitting and disposed between the sleeve and the first valve assembly.

Description

[Technical Field]

[0001] The present disclosure relates to shock absorbers. This application claims priority to U.S. patent application Ser. No. 17 / 954,389, filed in the United States on Sep. 28, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Some shock absorbers increase the damping force when the rod reaches a predetermined range on the limit side during the compression stroke in which the rod is pushed into the cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,605,726 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there is a demand for suppressing cost increases in shock absorbers.

[0005] Therefore, an object of the present disclosure is to provide a shock absorber that can suppress cost increases. [Means for solving the problem]

[0006] To achieve the above object, one aspect of a shock absorber of the present disclosure includes a tube having an internal chamber, a first valve assembly connected to one axial end of the tube, a piston assembly dividing the internal chamber into a first chamber and a second chamber, a piston rod connected to the piston assembly at an intermediate position in the axial direction and extending from the tube through the first chamber, a cup provided in the second chamber, and a second valve assembly disposed in the second chamber and connected to the piston rod and moving in and out of the cup. The cup has a sleeve disposed in the second chamber with a radial gap between it and the tube, and a base adapter press-fitted and fixed to the sleeve and provided between the sleeve and the first valve assembly.

[0007] Another aspect of the shock absorber of the present disclosure includes a first tube, a piston rod disposed within the first tube, a primary piston and a first valve disposed on the piston rod, a secondary piston and a second valve disposed on the piston rod, and a second tube capable of accommodating the secondary piston, wherein the secondary piston is formed by combining a first piston member and a second piston member, the first piston member having a first communication passage on its interior or inner circumferential surface side, and a seat for supporting the second valve on one end surface facing the primary piston, the second piston member having a second communication passage that communicates with the first communication passage and the inside of the second tube, and a ring accommodating groove for accommodating a ring provided on the outer circumferential side of at least one of the first piston member and the second piston member, on the contact surface side where the first piston member and the second piston member contact. [Effects of the Invention]

[0008] According to the above aspects of the present disclosure, it is possible to suppress cost increases. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a cross-sectional view showing a shock absorber according to a first embodiment of the present disclosure, taken along a cross section including a central axis line CL. FIG. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the shock absorber shown in FIG. 1, showing a main part of the shock absorber. [Figure 3] FIG. 3 is a diagram showing a main part of the shock absorber, and is a partially enlarged cross-sectional view of FIG. 2. [Figure 4] FIG. 10 is a partially enlarged cross-sectional view showing a shock absorber according to a second embodiment of the present disclosure, taken along a cross section including a center axis line CL. [Figure 5] FIG. 10 is a cross-sectional view showing a shock absorber according to a third embodiment of the present disclosure, taken along a cross section including a central axis line CL. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view of FIG. 5 showing a main part of the shock absorber. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] A shock absorber according to a first embodiment of the present disclosure will be described with reference to Figures 1 to 3. For ease of explanation, the upper side of the drawings will be referred to as "top" and the lower side of the drawings will be referred to as "bottom." Also, the symbol CL shown in each drawing indicates the central axis of the shock absorber.

[0011] As shown in FIG. 1, the shock absorber 1 of the first embodiment is a twin-tube hydraulic shock absorber. The shock absorber 1 is used in a suspension device for a vehicle, specifically an automobile. The shock absorber 1 includes a cylinder 2. The cylinder 2 has a tube 3 (first tube) and a shell 5. The tube 3 is cylindrical. The shell 5 is cylindrical with a bottom. The inner diameter of the shell 5 is larger than the outer diameter of the tube 3. The tube 3 is disposed radially inside the shell 5. The central axis of the tube 3 and the central axis of the shell 5 coincide. The inside of the tube 3 forms an inner chamber 6. A reservoir chamber 7 is formed between the tube 3 and the shell 5.

[0012] The shell 5 has a body 11 and a bottom 12. The body 11 and the bottom 12 are formed seamlessly as a single unit. The body 11 is cylindrical. The bottom 12 closes the lower part of the body 11.

[0013] The shock absorber 1 includes a piston assembly 17. The piston assembly 17 is disposed in the tube 3 of the cylinder 2. The piston assembly 17 includes a piston 18 (primary piston). The piston 18 of the piston assembly 17 is slidably fitted within the tube 3. The piston 18 divides the inner chamber 6 of the 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 tube 3, the first chamber 19 is located on the opposite side of the piston 18 from the bottom 12. In the axial direction of the tube 3, the second chamber 20 is located closer to the bottom 12 than the piston 18. In the cylinder 2, oil L is sealed in the inner chamber 6 of the tube 3 as a working fluid. In the cylinder 2, oil L and gas G are sealed in a reservoir chamber 7 between the tube 3 and the shell 5.

[0014] The shock absorber 1 includes a piston rod 21. One axial side of the piston rod 21 is disposed inside the tube 3 of the cylinder 2. This one side of the piston rod 21 is connected to the piston assembly 17. The other axial side of the piston rod 21 extends from the cylinder 2 to the outside of the cylinder 2. The piston rod 21 is connected to the piston assembly 17 and passes through the first chamber 19 to extend through the tube 3 and the shell 5, i.e., from the cylinder 2.

[0015] The shock absorber 1 is connected to the vehicle body with the portion of the piston rod 21 extending from the cylinder 2 located at the top, and the mounting bracket 22 fixed to the body 11 of the shell 5 located at the bottom, and connected to the wheel side of the vehicle.

[0016] The piston 18 is fixed to the piston rod 21. Therefore, the piston 18 and the piston rod 21 move together. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction of increasing the amount of extension from the cylinder 2 is the extension stroke, in which the overall length increases. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction of decreasing the amount of extension from the cylinder 2 is the compression stroke, in which the overall length shortens. In the shock absorber 1, the piston 18 moves toward the first chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves toward the second chamber 20 during the compression stroke.

[0017] A rod guide 23 is fitted to the upper open end side of the tube 3 and the upper open end side of the shell 5. A seal member 24 is fitted to the shell 5 above the rod guide 23. Both the rod guide 23 and the seal member 24 are annular. The piston rod 21 is inserted radially inside the rod guide 23 and the seal member 24. The piston rod 21 slides along the axial direction of each of the rod guide 23 and the seal member 24. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 24.

[0018] The rod guide 23 restricts radial movement of the piston rod 21 relative to the tube 3 and shell 5 of the cylinder 2. When the piston rod 21 is fitted into the rod guide 23, the piston 18 is fitted into the tube 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the tube 3. The rod guide 23 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 24 is in close contact with the shell 5. The inner periphery of the seal member 24 is in close contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 24 relative to the seal member 24. The seal member 24 prevents the oil L in the tube 3 and the high-pressure gas G and oil L in the reservoir chamber 7 from leaking to the outside.

[0019] The rod guide 23 has a large diameter portion 28 and a small diameter portion 29. The outer diameter of the large diameter portion 28 is larger than the outer diameter of the small diameter portion 29. The small diameter portion 29 of the rod guide 23 is located lower than the large diameter portion 28. The rod guide 23 fits into the inner periphery of the upper end of the tube 3 at the lower small diameter portion 29. At that time, the upper end of the tube 3 abuts against the large diameter portion 28 in the axial direction of the tube 3. The rod guide 23 fits into the inner periphery of the upper part of the shell 5 at the upper large diameter portion 28.

[0020] A first valve assembly 31 is placed on the bottom 12 of the shell 5. The first valve assembly 31 has a seat member 32. The seat member 32 is placed in contact with the upper surface of the bottom 12 of the shell 5. The seat member 32 is positioned radially relative to the shell 5. The seat member 32 has a large diameter portion 33 and a small diameter portion 34. The large diameter portion 33 has an outer diameter larger than the outer diameter of the small diameter portion 34. The large diameter portion 33 of the seat member 32 is located lower than the small diameter portion 34. The upper small diameter portion 34 of the seat member 32 fits into the inner periphery of the lower end of the tube 3. At that time, the lower end of the tube 3 abuts against the large diameter portion 33 in the axial direction of the tube 3. This connects the first valve assembly 31 to one axial end of the tube 3.

[0021] A crimped portion 35 is provided at the upper end of the shell 5. The crimped portion 35 is formed by crimping the upper end of the shell 5 radially inward. The seal member 24 is fixed to the cylinder 2 by being sandwiched between the crimped portion 35 and the rod guide 23. When forming the crimped portion 35, the bottom portion 12 of the shell 5 is placed on a table, and the seal member 24 is pressed against the rod guide 23 along the axial direction of the shell 5. This brings the seal member 24, rod guide 23, tube 3, and seat member 32 into contact with each other without any gaps in the axial direction. This generates an axial force among the seal member 24, rod guide 23, tube 3, and seat member 32. The crimped portion 35 is formed in this state. Therefore, after the crimped portion 35 is formed, an axial force is generated among the seal member 24, rod guide 23, tube 3, and seat member 32.

[0022] The piston rod 21 has a rod body 41 and an extender 42 .

[0023] The rod main body 41 has a main shaft portion 51 and a mounting shaft portion 52. The main shaft portion 51 and the mounting shaft portion 52 are both rod-shaped. The outer diameter of the mounting shaft portion 52 is smaller than the outer diameter of the main shaft portion 51. The mounting shaft portion 52 extends from one axial end of the main shaft portion 51. The central axis of the mounting shaft portion 52 coincides with the central axis of the main shaft portion 51. The entire mounting shaft portion 52 is disposed within the tube 3. In the piston rod 21, the main shaft portion 51 of the rod main body 41 slides relative to the rod guide 23 and the seal member 24 along the axial direction of these members.

[0024] As shown in Fig. 2, the end of the mounting shaft portion 52 opposite to the main shaft portion 51 in the axial direction of the mounting shaft portion 52 is a threaded shaft portion 54. A male thread is formed on the outer periphery of the threaded shaft portion 54. The portion of the mounting shaft portion 52 between the main shaft portion 51 and the threaded shaft portion 54 in the axial direction of the mounting shaft portion 52 is a fitting shaft portion 55. The outer periphery of the fitting shaft portion 55 is a cylindrical surface.

[0025] The extender 42 has a main shaft portion 61 and an attachment shaft portion 62. The main shaft portion 61 and the attachment shaft portion 62 are both rod-shaped. The outer diameter of the attachment shaft portion 62 is smaller than the outer diameter of the main shaft portion 61. The attachment shaft portion 62 extends from one axial end of the main shaft portion 61. The central axis of the attachment shaft portion 62 coincides with the central axis of the main shaft portion 61.

[0026] A screw hole 64 is formed in the main shaft portion 61 at the end opposite to the mounting shaft portion 62 in the axial direction of the main shaft portion 61. The screw hole 64 is formed at the radial center position of the main shaft portion 61. The screw hole 64 extends along the axial direction of the main shaft portion 61. The screw hole 64 opens upward.

[0027] The end of the mounting shaft portion 62 opposite to the main shaft portion 61 in the axial direction of the mounting shaft portion 62 is a threaded shaft portion 65. A male thread is formed on the outer periphery of the threaded shaft portion 65. The portion of the mounting shaft portion 62 between the main shaft portion 61 and the threaded shaft portion 65 in the axial direction of the mounting shaft portion 62 is a fitting shaft portion 66. The outer periphery of the fitting shaft portion 66 is a cylindrical surface.

[0028] The threaded shaft portion 54 of the rod main body 41 is threaded into the threaded hole 64 of the extender 42. This connects the rod main body 41 and the extender 42 with their central axes aligned, thereby forming the piston rod 21. The extender 42 is entirely disposed within the tube 3.

[0029] In the piston rod 21, the piston 18 is attached to the mounting shaft portion 52 of the rod main body 41. The piston 18 is disposed between the main shaft portion 51 of the rod main body 41 and the extender 42. The piston 18 is fitted into the fitting shaft portion 55 of the mounting shaft portion 52.

[0030] A through hole 70 is formed in the center of the piston 18 in the radial direction. The through hole 70 passes through the piston 18 in the axial direction of the piston 18. The fitting shaft portion 55 of the rod main body 41 is fitted into the through hole 70 of the piston 18. A first passage 71 and a second passage 72 are formed in the piston 18 outside the through hole 70 in the radial direction of the piston 18. The first passage 71 and the second passage 72 pass through the piston 18 in the axial direction of the piston 18. A plurality of first passages 71 and a plurality of second passages 72 are formed in the piston 18. The first passages 71 and the second passages 72 are arranged alternately in the circumferential direction of the piston 18. Both the first passage 71 and the second passage 72 can communicate between the first chamber 19 and the second chamber 20.

[0031] The piston assembly 17 has a first damping valve 75 (first valve) and a second damping valve 76 (second valve).

[0032] The first damping valve 75 is a disc valve formed by stacking multiple annular discs. The fitting shaft portion 55 of the rod main body 41 is fitted onto the radially inner side of the first damping valve 75. The first damping valve 75 is disposed between the piston 18 and the extender 42. The outer peripheral portion of the first damping valve 75 moves away from the piston 18 to open the first passage 71. This allows the first damping valve 75 to flow hydraulic fluid L from the first chamber 19 to the second chamber 20 through the first passage 71. At this time, the first damping valve 75 suppresses the flow of hydraulic fluid L to generate a damping force. The first damping valve 75 is disposed in the first passage 71 and suppresses the flow of hydraulic fluid L that occurs in the first passage 71 during the extension stroke to generate a damping force. The outer peripheral portion of the first damping valve 75 comes into contact with the piston 18 to close the first passage 71. A fixed orifice (not shown) is provided between the first damping valve 75 and the piston 18. This fixed orifice allows the oil L to flow from the first chamber 19 to the second chamber 20 via the first passage 71 even when the outer peripheral portion of the first damping valve 75 abuts against the piston 18 .

[0033] The second damping valve 76 is a disc valve formed by stacking multiple annular discs. The fitting shaft portion 55 is fitted onto the radial inside of the second damping valve 76. The second damping valve 76 is disposed between the main shaft portion 51 of the rod body 41 and the piston 18. The outer peripheral portion of the second damping valve 76 moves away from the piston 18 to open the second passage 72. This allows the second damping valve 76 to flow hydraulic fluid L from the second chamber 20 to the first chamber 19 via the second passage 72. At this time, the second damping valve 76 suppresses the flow of hydraulic fluid L to generate a damping force. The second damping valve 76 is disposed in the second passage 72 and suppresses the flow of hydraulic fluid L that occurs in the second passage 72 during the compression stroke to generate a damping force. The outer peripheral portion of the second damping valve 76 abuts against the piston 18 to close the second passage 72. A fixed orifice (not shown) is provided between the second damping valve 76 and the piston 18. This fixed orifice allows the hydraulic fluid L to flow from the second chamber 20 to the first chamber 19 via the second passage 72 even when the outer peripheral portion of the second damping valve 76 abuts against the piston 18 .

[0034] The piston assembly 17, which includes the piston 18, the first damping valve 75, and the second damping valve 76, is attached to the mounting shaft portion 52 of the rod main body 41 by the extender 42. Therefore, the piston assembly 17 is disposed between the main shaft portion 51 of the rod main body 41 and the extender 42. The piston assembly 17 is connected to the piston rod 21 at an axially intermediate position. The piston 18, the first damping valve 75, and the second damping valve 76 are disposed in the piston rod 21.

[0035] The first valve assembly 31 has a disc valve 82, a disc valve 83, a bolt 84, and a nut 85 in addition to the seat member 32 described above. The disc valve 82 is provided below the seat member 32. The disc valve 83 is provided above the seat member 32. The bolt 84 is inserted from above into the disc valve 83, seat member 32, and disc valve 82. In this state, the nut 85 is screwed onto the bottom of the bolt 84. In this way, the bolt 84 and the nut 85 attach the disc valve 82 and disc valve 83 to the seat member 32.

[0036] The seat member 32 has an annular shape. The seat member 32 has a base portion 88 and a protruding portion 89. The base portion 88 is disk-shaped. As shown in FIG. 3 , a through hole 90 is formed in the radial center of the base portion 88. The through hole 90 penetrates the base portion 88 in the axial direction of the seat member 32. In the seat member 32, a bolt 84 is inserted into the through hole 90. The seat member 32 has a passage hole 91 and a passage hole 92 formed outside the through hole 90 in the radial direction of the seat member 32. The passage hole 91 and the passage hole 92 penetrate the base portion 88 in the axial direction of the seat member 32. The passage hole 92 is located outside the passage hole 91 in the radial direction of the seat member 32. The seat member 32 has a plurality of passage holes 91 and a plurality of passage holes 92 formed therein.

[0037] The protrusion 89 protrudes downward from the outer periphery of the base portion 88. The protrusion 89 is disposed radially outward of the passage hole 92 of the base portion 88. The protrusion 89 of the seat member 32 abuts against the bottom portion 12 of the shell 5. The protrusion 89 is formed with a passage groove 93 that penetrates the protrusion 89 in the radial direction of the seat member 32. The seat member 32 is provided with a plurality of passage grooves 93 at equal intervals in the circumferential direction of the seat member 32. As a result, the space between the seat member 32 and the bottom portion 12 of the shell 5 is in communication with the portion between the body portion 11 of the shell 5 and the tube 3 shown in FIG. 1 . Therefore, the space between the seat member 32 and the bottom portion 12 of the shell 5 also constitutes the reservoir chamber 7.

[0038] 2, the shock absorber 1 has a cup 101. The cup 101 is provided in the second chamber 20. The cup 101 has a sleeve 102 (second tube) and a base adapter 103.

[0039] The sleeve 102 is cylindrical. The outer diameter of the sleeve 102 is smaller than the inner diameter of the tube 3. The sleeve 102 is disposed radially inside the tube 3. The central axis of the sleeve 102 coincides with the central axis of the tube 3. The sleeve 102 is disposed in the second chamber 20 with a radial gap between it and the tube 3.

[0040] The sleeve 102 has a main body portion 111 and an expanded diameter portion 112. The main body portion 111 is cylindrical and extends from the middle to the lower end in the axial direction of the sleeve 102. The expanded diameter portion 112 is provided at the upper end of the sleeve 102. The inner diameter of the expanded diameter portion 112 increases as it approaches the upper end. The outer diameter of the expanded diameter portion 112 increases as it approaches the upper end. The diameter of the expanded diameter portion 112 increases in the direction away from the main body portion 111 in the axial direction of the sleeve 102.

[0041] The sleeve 102 has a groove 116 formed on its inner periphery at one axial end thereof, the groove 116 extending in the axial direction of the sleeve 102. The groove 116 is formed on the inner periphery at the upper end of the sleeve 102. The groove 116 is recessed outward in the radial direction of the sleeve 102 from the inner periphery of the sleeve 102. The groove 116 extends from the expanded diameter portion 112 to the upper part of the main body portion 111. The sleeve 102 has a plurality of grooves 116 formed at equal intervals in the circumferential direction of the sleeve 102. The plurality of grooves 116 each have a different length from the upper end of the sleeve 102. In other words, the plurality of grooves 116 each have a different length in the axial direction of the sleeve 102.

[0042] The base adapter 103 has an annular shape and includes a main plate portion 121, a press-fit portion 122, and legs 123.

[0043] The main plate portion 121 is disk-shaped. As shown in Fig. 3, the main plate portion 121 has a recess 131 formed in the radial center of one axial side thereof, recessed upward from the lower surface of the main plate portion 121.

[0044] The press-fit portion 122 is provided at one axial end of the base adapter 103. The press-fit portion 122 protrudes upward from the upper surface of the main plate portion 121. The press-fit portion 122 is cylindrical. The outer diameter of the press-fit portion 122 is smaller than the outer diameter of the main plate portion 121. The press-fit portion 122 of the base adapter 103 is press-fitted into the lower end of the sleeve 102. At that time, the upper surface of the main plate portion 121 abuts against the lower end of the sleeve 102. This fixes the base adapter 103 to the sleeve 102. In this way, the base adapter 103 is fixed to the sleeve 102 by press-fitting.

[0045] The leg portion 123 is provided at the end of the base adapter 103 opposite the press-fit portion 122 in the axial direction. The leg portion 123 protrudes downward from the outer periphery of the main plate portion 121. The leg portion 123 is cylindrical. The leg portion 123 is disposed radially outward of the recess 131 of the main plate portion 121. The radially inner inner periphery 135 of the leg portion 123 increases in diameter as it moves away from the main plate portion 121 in the axial direction of the base adapter 103. In other words, the inner periphery 135 of the leg portion 123 increases in diameter as it moves away from the main plate portion 121 in the axial direction.

[0046] A communicating groove 136 is formed in the outer periphery of the main plate 121 and the leg portions 123, penetrating the main plate 121 and the leg portions 123 in the axial direction of the base adapter 103. The communicating groove 136 opens radially outward of the base adapter 103. The communicating groove 136 is formed radially outward of the sleeve 102 of the main plate 121. The communicating groove 136 penetrates the leg portions 123 in the radial direction of the base adapter 103. Therefore, the communicating groove 136 opens to the upper surface of the main plate 121, the outer periphery of the main plate 121, the outer periphery of the leg portions 123, the lower surface of the leg portions 123, and the inner periphery of the leg portions 123. A plurality of communicating grooves 136 are provided in the base adapter 103 at equal intervals in the circumferential direction of the base adapter 103.

[0047] The cup 101, which is made up of a base adapter 103 and a sleeve 102 fixed to the base adapter 103, is fixed by press-fitting the main plate portion 121 of the base adapter 103 into the tube 3. At this time, the cup 101 is placed with the lower ends of the leg portions 123 of the base adapter 103 in contact with the upper surface of the outer periphery of the base portion 88 of the seat member 32. At this time, the recesses 131 prevent the base adapter 103 from hitting the bolts 84 of the first valve assembly 31. Also, at this time, the leg portions 123 of the base adapter 103 surround the disc valve 83 of the first valve assembly 31 on the radially outer side. In other words, the leg portions 123 are positioned radially outward from and spaced apart from the disc valve 83. The base adapter 103 placed on the first valve assembly 31 is provided between the sleeve 102 and the first valve assembly 31.

[0048] As described above, one axial end of the base adapter 103 is provided with a press-fit portion 122 that is press-fit into the sleeve 102. The other axial end of the base adapter 103 is provided with a leg portion 123 that is placed on the first valve assembly 31. The diameter of an inner circumferential portion 135 of the leg portion 123 increases in the axial direction of the base adapter 103 as it approaches the first valve assembly 31.

[0049] A third chamber 141 is formed between the first valve assembly 31 and the base adapter 103. The third chamber 141 communicates with the portion of the second chamber 20 between the tube 3 and the sleeve 102 via a communication passage 142 in the communication groove 136 of the base adapter 103. In other words, the leg portion 123 of the base adapter 103 is provided with a communication passage 142 that communicates between the second chamber 20 and the third chamber 141.

[0050] In the first valve assembly 31, a plurality of passage holes 91 allow the oil L to flow between the third chamber 141 and the reservoir chamber 7. A plurality of passage holes 92 allow the oil L to flow between the reservoir chamber 7 and the third chamber 141.

[0051] The disc valve 82 on the reservoir chamber 7 side allows the flow of hydraulic fluid L from the third chamber 141 to the reservoir chamber 7 via the passage hole 91. On the other hand, the disc valve 82 restricts the flow of hydraulic fluid L from the reservoir chamber 7 to the third chamber 141 via the passage hole 91. The disc valve 82 opens during the compression stroke of the shock absorber 1 to allow the hydraulic fluid L to flow from the second chamber 20 and the third chamber 141 to the reservoir chamber 7 and generate a damping force.

[0052] The disc valve 83 on the third chamber 141 side allows the flow of hydraulic fluid L from the reservoir chamber 7 to the third chamber 141 via the passage hole 92. On the other hand, the disc valve 83 restricts the flow of hydraulic fluid L from the third chamber 141 to the reservoir chamber 7 via the passage hole 92. The disc valve 83 constantly communicates between the third chamber 141 and the passage hole 91. The disc valve 83 opens during the extension stroke of the shock absorber 1 to allow the hydraulic fluid L to flow from the reservoir chamber 7 to the third chamber 141 and the second chamber and generate a damping force. Note that the disc valve 83 may also be a suction valve that allows the hydraulic fluid L to flow from the reservoir chamber 7 to the third chamber 141 and the second chamber without generating any substantial damping force.

[0053] As shown in Figure 2, the cup 101 has a sleeve 102 that opens upward. The shock absorber 1 has a second valve assembly 151. The second valve assembly 151 is disposed in the second chamber 20 and connected to the piston rod 21. The second valve assembly 151 is attached to the mounting shaft portion 62 of the extender 42. The second valve assembly 151 enters the sleeve 102 of the cup 101 from above through the opening at the upper end of the sleeve 102 and exits upward.

[0054] The second valve assembly 151 has a valve base 152 (secondary piston), a fitting member 153 (ring), and a third damping valve 154 (second valve).

[0055] 3, the valve base 152 has a first base member 161 (first piston member) and a second base member 162 (second piston member). The valve base 152 is formed by combining the first base member 161 and the second base member 162. The first base member 161 forms the upper part of the valve base 152. The second base member 162 forms the lower part of the valve base 152.

[0056] The first base member 161 is annular. A notch 171 is formed in the outer periphery of the lower part of the first base member 161. The notch 171 is formed around the entire circumference of the first base member 161. The notch 171 is annular.

[0057] The first base member 161 has a through hole 172 formed in the center in the radial direction. The through hole 172 penetrates the first base member 161 in the axial direction of the first base member 161. The fitting shaft portion 66 of the extender 42 is fitted into the through hole 172 of the first base member 161. The first base member 161 has a passage groove 173 formed on the outer side of the through hole 172 in the radial direction of the first base member 161. The first base member 161 has a passage groove 174 and a passage hole 175 formed between the through hole 172 and the cutout portion 171 in the radial direction of the first base member 161.

[0058] The passage groove 173 is formed in the upper end portion of the first base member 161. The passage groove 173 is recessed downward from the upper end surface 161a (one end surface) of the first base member 161. The passage groove 173 has an annular shape that surrounds the through hole 172 on the radially outer side. The passage groove 173 opens upward.

[0059] At the upper end of the first base member 161, the portion inside the passage groove 173 in the radial direction of the first base member 161 is an annular inner seat 176, and the portion outside the passage groove 173 is an annular valve seat 177 (seat). The first base member 161 has the inner seat 176 and the valve seat 177 formed on an upper end surface 161a, which is one end surface facing the piston 18.

[0060] The passage groove 174 is formed in the lower end portion of the first base member 161. The passage groove 173 is recessed upward from the lower end surface 161b (contact surface) of the first base member 161. The passage groove 174 has an annular shape that surrounds the through hole 172 on the radially outer side. The passage groove 174 opens downward.

[0061] The passage hole 175 is formed in the axial middle portion of the first base member 161. The upper end of the passage hole 175 opens at the bottom position of the passage groove 173, and the lower end of the passage hole 175 opens at the bottom position of the passage groove 174. A plurality of passage holes 175 are formed in the first base member 161 at intervals in the circumferential direction of the first base member 161.

[0062] In the first base member 161, the passage in the passage groove 173, the passage in the plurality of passage holes 175, and the passage in the passage groove 174 constitute a communication passage 178 (first communication passage) that penetrates the first base member 161 in the axial direction. The first base member 161 has the communication passage 178 not on the outer peripheral surface but on the interior or inner peripheral surface side. Specifically, the first base member 161 has the communication passage 178 inside. The first base member 161 may have the communication passage 178 on the inner peripheral surface side, i.e., between it and the fitting shaft portion 66 of the extender 42.

[0063] The second base member 162 is annular. A notch 181 is formed in the outer periphery of the upper part of the second base member 162. The notch 181 is formed around the entire circumference of the second base member 162. The notch 181 is annular.

[0064] A groove 182 is formed in the outer circumferential portion of the lower part of the second base member 162. The groove 182 is recessed inward in the radial direction of the second base member 162 from the outer circumferential surface of the second base member 162. The groove 182 opens outward in the radial direction of the second base member 162. The groove 182 opens into the cutout portion 181. The groove 182 opens downward. A plurality of grooves 182 are formed in the second base member 162 at intervals in the circumferential direction of the second base member 162.

[0065] The second base member 162 has a through hole 183 formed in the center in the radial direction thereof. The through hole 183 penetrates the second base member 162 in the axial direction of the second base member 162. The fitting shaft portion 66 of the extender 42 is fitted into the through hole 183 of the second base member 162. The second base member 162 has a passage groove 184 formed on the outer side of the through hole 183 in the radial direction of the second base member 162. The second base member 162 has a passage hole 185 formed between the through hole 183 and the cutout portion 181 in the radial direction of the second base member 162.

[0066] The passage groove 184 is formed in the upper end portion of the second base member 162. The passage groove 184 is recessed downward from the upper end surface 162a (contact surface) of the second base member 162. The passage groove 184 has an annular shape that surrounds the through hole 183 on the radially outer side. The passage groove 184 opens upward.

[0067] The passage hole 185 is formed from the middle to the lower end in the axial direction of the second base member 162. The upper end of the passage hole 185 opens at the bottom position of the passage groove 184. A plurality of passage holes 185 are formed in the second base member 162 at intervals in the circumferential direction of the second base member 162.

[0068] In the second base member 162, the passage in the passage groove 184 and the passages in the multiple passage holes 185 form a communicating passage 186 (second communicating passage) that penetrates the second base member 162 in the axial direction. The second base member 162 has the communicating passage 186 not on the outer peripheral surface but on the interior or inner peripheral surface side. Specifically, the second base member 162 has the communicating passage 186 inside. The second base member 162 may have the communicating passage 186 on the inner peripheral surface side, i.e., between it and the fitting shaft portion 66 of the extender 42.

[0069] When the valve base 152 is fitted onto the fitting shaft portion 66 of the extender 42, the lower end surface 161b of the first base member 161 abuts against the upper end surface 162a of the second base member 162. This causes the passage groove 173, the passage hole 175, and the passage groove 174 of the first base member 161 to communicate with the passage groove 184 and the passage hole 185 of the second base member 162. These passage grooves 173, 174, and 184 and the passage holes 175 and 185 form a third passage 191. The third passage 191 is provided in the valve base 152 and passes through the valve base 152 in the axial direction. The third passage 191 is made up of the communication passage 178 of the first base member 161 and the communication passage 186 of the second base member 162.

[0070] One end of the communication passage 186 of the second base member 162 communicates with the communication passage 178 of the first base member 161. When the valve base 152 is inserted into the sleeve 102, the other end of the communication passage 186 of the second base member 162 communicates with the inside of the sleeve 102.

[0071] In the valve base 152, the notch 171 of the first base member 161 and the notch 181 of the second base member 162 form a positioning groove 195 (ring accommodating groove). The positioning groove 195 is provided on the outer peripheral sides of both the first base member 161 and the second base member 162, on the lower end surface 161b and upper end surface 162a sides where the first base member 161 and the second base member 162 abut. The positioning groove 195 is recessed inward in the radial direction of the valve base 152 from the outer peripheral surface of the valve base 152. The positioning groove 195 is annular. The positioning groove 195 opens radially outward. The multiple grooves 182 open into the positioning groove 195. The communication passage 178 of the first base member 161 is provided radially inward of the positioning groove 195 of the first base member 161. The communication passage 186 of the second base member 162 is provided on the inside of the arrangement groove 195 in the radial direction of the second base member 162.

[0072] The arrangement groove 195 may be provided on the outer periphery of the first base member 161, on a portion of the first base member 161 on the side of the lower end surface 161b that abuts against the upper end surface 162a of the second base member 162. Alternatively, the arrangement groove 195 may be provided on the outer periphery of the second base member 162, on a portion of the second base member 162 on the side of the upper end surface 162a that abuts against the lower end surface 161b of the first base member 161. In other words, the arrangement groove 195 is provided on the outer periphery of at least one of the first base member 161 and the second base member 162, on the side of the lower end surface 161b and the upper end surface 162a where the first base member 161 and the second base member 162 abut.

[0073] The fitting member 153 is annular. The outer diameter of the fitting member 153 is larger than the outer diameter of the valve base 152. When the first base member 161 and the second base member 162 are assembled to the extender 42, the fitting member 153 is disposed between the notch 171 and the notch 181. This causes the fitting member 153 to be disposed within the arrangement groove 195 of the valve base 152. The fitting member 153 is axially movable relative to the valve base 152 within the arrangement groove 195. The arrangement groove 195 of the valve base 152 accommodates the fitting member 153. The fitting member 153 is made of brass or glass fiber reinforced plastic.

[0074] An interposing member 197 is provided between the inner periphery of the fitting member 153 and the bottom of the arrangement groove 195. The interposing member 197 holds the fitting member 153 coaxially with respect to the valve base 152. The interposing member 197 has an axial passage 196 that penetrates in the axial direction. The interposing member 197 is, for example, cylindrical and has a plurality of grooves formed on the outer periphery that penetrate in the axial direction. This interposing member 197 is press-fitted into the inner periphery of the fitting member 153. As a result, the interposing member 197 is fixed to the fitting member 153. The plurality of grooves formed on the outer periphery of the interposing member 197 form the axial passage 196.

[0075] The third damping valve 154 is a disc valve formed by stacking multiple annular discs. The fitting shaft portion 66 of the extender 42 is fitted into the radially inner side of the third damping valve 154. The third damping valve 154 is disposed between the main shaft portion 61 of the extender 42 and the valve base 152. The third damping valve 154 rests on a valve seat 177 of the valve base 152. In other words, the valve base 152 has the valve seat 177, on which the third damping valve 154 rests, formed on its upper end surface 161a facing the piston 18. The outer peripheral portion of the third damping valve 154 separates from the valve seat 177 of the valve base 152 to open the third passage 191. The outer peripheral portion of the third damping valve 154 abuts against the valve seat 177 of the valve base 152 to close the third passage 191.

[0076] A nut 201 is threaded onto the threaded shaft portion 65 of the extender 42. A second valve assembly 151 including a valve base 152 and a third damping valve 154 is attached to the attachment shaft portion 62 of the extender 42 with the nut 201. Therefore, as shown in FIG. 2, the second valve assembly 151 is provided on the piston rod 21 closer to the first valve assembly 31 than the piston assembly 17. The valve base 152 is fixed to the piston rod 21. Therefore, the valve base 152 and the piston rod 21 move together. The valve base 152 and the third damping valve 154 are disposed on the piston rod 21. The sleeve 102 is capable of accommodating the valve base 152.

[0077] Here, when the piston rod 21 is in a first predetermined range in which the second valve assembly 151 is positioned above the sleeve 102 and is not fitted into the sleeve 102, the entire interior of the cup 101 becomes the second chamber 20.

[0078] From this state, during the compression stroke, the piston rod 21 moves from the first predetermined range to a second predetermined range that is closer to the base adapter 103. Then, the second valve assembly 151 enters the sleeve 102 from the side of the expanded diameter portion 112 of the sleeve 102. In other words, the sleeve 102 has the expanded diameter portion 112 on the side where the second valve assembly 151 including the valve base 152 is inserted. When the second valve assembly 151 enters the sleeve 102 from the side of the expanded diameter portion 112 of the sleeve 102, the fitting member 153 fits into the sleeve 102. At the beginning of this fitting, the frictional force between the fitting member 153 and the sleeve 102 moves the fitting member 153 upward relative to the arrangement groove 195 of the valve base 152. As a result, the upper surface of the fitting member 153 comes into contact with the valve base 152. Then, the axial passage 196 is closed. During the subsequent retraction stroke, the fitting member 153 is pushed by the valve base 152 while keeping the axial passage 196 closed, and slides within the sleeve 102 toward the base adapter 103 .

[0079] When the fitting member 153 of the second valve assembly 151 is fitted into the sleeve 102, the second chamber 20 is divided into a fourth chamber 211 and a fifth chamber 212. The fourth chamber 211 is the portion between the second valve assembly 151 and the base adapter 103 inside the cup 101. The fifth chamber 212 is the portion of the second chamber 20 excluding the fourth chamber 211. The fifth chamber 212 consists of the portion between the tube 3 and the cup 101 and the portion between the piston assembly 17 and the second valve assembly 151.

[0080] During the compression stroke in the second predetermined range, with the axial passage 196 closed as described above, the second valve assembly 151 moves together with the piston rod 21 toward the base adapter 103. In the upper part of the second predetermined range, the fitting member 153 is located at the position of the plurality of grooves 116 provided in the sleeve 102, and causes the oil L to flow from the fourth chamber 211 to the fifth chamber 212 through the plurality of grooves 116. At this time, as the second valve assembly 151 approaches the base adapter 103, the number of the plurality of grooves 116 that allow the oil L to flow from the fourth chamber 211 to the fifth chamber 212 decreases, eventually reaching zero.

[0081] Furthermore, during the compression stroke within the second predetermined range, the second valve assembly 151 moves toward the base adapter 103 with the axial passage 196 closed as described above. At that time, the third damping valve 154 opens depending on the piston speed, which is the moving speed of the piston rod 21, piston 18, and valve base 152 relative to the tube 3. Then, hydraulic fluid L flows from the fourth chamber 211 to the fifth chamber 212 via the third passage 191. As a result, the third damping valve 154 suppresses an excessive increase in pressure in the fourth chamber 211. The third damping valve 154 is provided in the third passage 191 and suppresses the flow of hydraulic fluid L that occurs during the compression stroke, thereby generating a damping force and causing hydraulic fluid L to flow from the fourth chamber 211 to the fifth chamber 212. Here, the third damping valve 154 has higher rigidity than the second damping valve 76 and is less likely to open. Therefore, the third damping valve 154 opens later than the second damping valve 76 and generates a higher damping force than the second damping valve 76.

[0082] From a state in which the fitting member 153 is fitted into the sleeve 102 of the cup 101, the second valve assembly 151 moves together with the piston rod 21 toward the opposite side from the base adapter 103. Then, the fitting member 153 moves downward relative to the arrangement groove 195 of the valve base 152 due to frictional force with the sleeve 102. As a result, the fitting member 153 moves its upper surface away from the valve base 152, thereby opening the axial passage 196. During the subsequent extension stroke, the fitting member 153 is pushed by the valve base 152 with the axial passage 196 still open, and slides within the sleeve 102 toward the opposite side from the base adapter 103. When the second valve assembly 151 moves toward the opposite side from the base adapter 103, the oil L flows from the fifth chamber 212 to the fourth chamber 211 through the axial passage 196 and the passage in the groove portion 182 of the valve base 152. This reduces the resistance to the movement of the piston rod 21 in the extension direction.

[0083] During the extension stroke, the second valve assembly 151 moves away from the base adapter 103 by a predetermined distance, from a state in which the fitting member 153 is closer to the base adapter 103 than all of the grooves 116 in the sleeve 102. As a result, the grooves 116 provided in the sleeve 102 open to the fourth chamber 211. Then, the oil L flows from the fifth chamber 212 to the fourth chamber 211 through the grooves 116. At this time, the farther the second valve assembly 151 moves from the base adapter 103, the more of the multiple grooves 116 that allow the oil L to flow from the fifth chamber 212 to the fourth chamber 211 increase. This gradually reduces the resistance to the movement of the piston rod 21 in the extension direction.

[0084] Next, the main operation of the shock absorber 1 will be described.

[0085] "Extension stroke during which the piston rod 21 is in the first predetermined range"

[0086] {First region in which the piston speed is slower than a first predetermined value} In this first region of the extension stroke, oil L from the first chamber 19 flows into the second chamber 20 through the first passage 71 and a fixed orifice (not shown) between the first damping valve 75 and the piston 18 in the piston assembly 17. Therefore, in the first region of the extension stroke, a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed) is generated.

[0087] {Second region in which the piston speed is equal to or greater than the first predetermined value} In this second region of the extension stroke, oil L from the first chamber 19 flows from the first passage 71 to the second chamber 20 in the piston assembly 17, opening the first damping valve 75. Therefore, in the second region of the extension stroke, a damping force with valve characteristics (where the damping force is approximately proportional to the piston speed) is generated by the first damping valve 75.

[0088] "Retraction stroke when the piston rod 21 is in the first predetermined range"

[0089] {Third region in which the piston speed is slower than the second predetermined value} In the third region of the compression stroke, hydraulic oil L from the second chamber 20 flows from the second passage 72 to the first chamber 19 through a fixed orifice (not shown) between the second damping valve 76 and the piston 18 in the piston assembly 17. Therefore, in the third region of the compression stroke, a damping force with orifice characteristics is generated.

[0090] {Fourth region in which the piston speed is equal to or greater than the second predetermined value} In the fourth region of the compression stroke, oil L from the second chamber 20 flows from the second passage 72 to the first chamber 19 in the piston assembly 17, opening the second damping valve 76. Therefore, in the fourth region of the compression stroke, a damping force with valve characteristics is generated by the second damping valve 76.

[0091] "Retraction stroke when the piston rod 21 is in the second predetermined range" During this compression stroke, the piston assembly 17 operates in the same manner as in the first predetermined range. Then, the second valve assembly 151 moves toward the base adapter 103 in the axial direction of the tube 3, and the fitting member 153 fits into the sleeve 102. Then, at the initial stage, the fitting member 153 closes the axial passage 196.

[0092] With the axial passage 196 thus blocked, the second valve assembly 151 moves toward the base adapter 103. This causes the oil L to flow from the fourth chamber 211 to the fifth chamber 212 via the multiple grooves 116 provided in the sleeve 102. As the second valve assembly 151 approaches the base adapter 103, the number of the multiple grooves 116 through which the oil L flows from the fourth chamber 211 to the fifth chamber 212 decreases, eventually reaching zero. This increases the damping force of the second valve assembly 151 in stages, thereby increasing the resistance to the retraction movement of the piston rod 21 in stages. The press-fit axial length between the press-fit portion 122 of the base adapter 103 and the sleeve 102 is set so that the sleeve 102 does not come out of the press-fit portion 122 even when the fourth chamber 211 reaches its maximum pressure.

[0093] Here, when the second valve assembly 151 moves toward the base adapter 103, the third damping valve 154 opens depending on the piston speed. Then, hydraulic fluid L flows from the fourth chamber 211 to the fifth chamber 212 via the third passage 191. This suppresses an excessive increase in pressure in the fourth chamber 211.

[0094] "Extension stroke when the piston rod 21 is in the second predetermined range" During this extension stroke, the piston assembly 17 operates in the same manner as in the first predetermined range. Then, the second valve assembly 151 moves to the side opposite the base adapter 103. Then, at the beginning of this movement, the fitting member 153 opens the axial passage 196.

[0095] With the axial passage 196 open in this manner, the second valve assembly 151 moves toward the opposite side from the base adapter 103. Then, the oil L flows from the fifth chamber 212 to the fourth chamber 211 via the axial passage 196 and the passage in the groove portion 182 of the valve base 152. When the fitting member 153 of the second valve assembly 151 passes the position of the groove 116 formed in the sleeve 102 from a state in which it is closer to the base adapter 103 than all of the grooves 116 formed in the sleeve 102, the oil L flows from the fifth chamber 212 to the fourth chamber 211 via the groove 116. At this time, the farther the second valve assembly 151 is from the base adapter 103, the more of the multiple grooves 116 that allow the oil L to flow from the fifth chamber 212 to the fourth chamber 211. In other words, the further the second valve assembly 151 is from the base adapter 103, the lower the damping force becomes, and the lower the resistance force against the movement of the piston rod 21 in the extension direction becomes.

[0096] The aforementioned U.S. Pat. No. 9,605,726 discloses a shock absorber that increases damping force when the rod reaches a predetermined limit during the compression stroke in which the rod is pushed into the cylinder. However, there is a demand for reducing costs associated with shock absorbers. For example, Figure 13 of U.S. Pat. No. 9,605,726 discloses a structure in which a tube is connected to a cup, and the cup is then connected to a valve assembly. During shock absorber assembly, axial force is applied to the tube from the shell. With the structure disclosed in Figure 13 of U.S. Pat. No. 9,605,726, the axial force of the tube must be borne by the cup. This requires increased cup strength, resulting in increased costs.

[0097] The shock absorber 1 of the first embodiment includes a tube 3, a first valve assembly 31, a piston assembly 17, a piston rod 21, a cup 101, and a second valve assembly 151. The tube 3 has an internal chamber 6 on its inside. The first valve assembly 31 is connected to one axial end of the tube 3. The piston assembly 17 divides the internal chamber 6 into a first chamber 19 and a second chamber 20. The piston rod 21 is connected to the piston assembly 17 at an axially intermediate position and extends from the tube 3 through the first chamber 19. The cup 101 is provided in the second chamber 20. The second valve assembly 151 is disposed in the second chamber 20 and connected to the piston rod 21, and moves in and out of the cup 101. The cup 101 includes a sleeve 102 and a base adapter 103. The sleeve 102 is disposed in the second chamber 20 with a radial gap between it and the tube 3. The base adapter 103 is fixed to the sleeve 102 by press fitting and is provided between the sleeve 102 and the first valve assembly 31 .

[0098] During assembly of the shock absorber 1, axial force is input to the tube 3 from the crimped portion 35 of the shell 5 and the bottom portion 12 via the seal member 24, the rod guide 23, and the first valve assembly 31. In the shock absorber 1, the first valve assembly 31 is connected to one axial end of the tube 3. This allows the first valve assembly 31 to bear the axial force of the tube 3. This eliminates the need for the base adapter 103 to bear the axial force of the tube 3. This allows the strength of the base adapter 103 to be lower than when the axial force of the tube 3 is borne by the base adapter 103. As a result, the flexibility in the material of the base adapter 103 is increased, allowing a lower-cost material to be selected. This allows the cost of the shock absorber 1 to be reduced. Furthermore, a lightweight material can be selected for the base adapter 103. This allows the weight of the shock absorber 1 to be reduced.

[0099] In shock absorber 1, base adapter 103 is fixed to sleeve 102 by press-fitting. Therefore, base adapter 103 and sleeve 102 can be integrated before being assembled to shock absorber 1. Therefore, base adapter 103 and sleeve 102 can be handled as a single component, which makes handling easy and assembly to shock absorber 1 easy.

[0100] In the shock absorber 1, a press-fit portion 122 that is press-fit into the sleeve 102 is provided at one axial end of the base adapter 103, and a leg portion 123 that is placed on the first valve assembly 31 is provided at the other axial end of the base adapter 103. The leg portion 123 is provided with a communication passage 142 that communicates between a third chamber 141 between the first valve assembly 31 and the base adapter 103 and the second chamber 20. Because the communication passage 142 is provided in the leg portion 123 in this way, it is possible to reduce the radial gap between the tube 3 and the sleeve 102 compared to when a communication passage is provided radially inward of the leg portion 123 of the main plate portion 121.

[0101] In the shock absorber 1, the inner periphery 135 of the leg portion 123 increases in diameter as it approaches the first valve assembly 31. This allows the outer diameter of the disc valve 83 of the first valve assembly 31 to be larger than when the inner periphery 135 has a constant diameter. This increases the variable range of the damping force of the disc valve 83. In particular, when the disc valve 83 is used as a suction valve that generates virtually no damping force, increasing the diameter of the disc valve 83 allows the damping force to approach zero.

[0102] US Pat. No. 9,651,110 discloses a configuration in which a piston rod is provided with, in addition to a first piston member, a second piston member as a hydraulic stopper mechanism for hydraulically locking the extension side.

[0103] Japanese Patent Application Laid-Open Publication No. 2022-133840 discloses a configuration in which a first piston member is provided on a rod, and a second piston member is provided on a holder corresponding to the extension rod.

[0104] European Patent No. 2910811 discloses a configuration in which a ring is sandwiched between two members.

[0105] WO 2017 / 089425 shows a configuration in which the outer periphery of a ring is used as a passageway.

[0106] In shock absorbers, it is desirable to have a compact structure that increases the damping force near the end of the piston rod's travel.

[0107] The shock absorber 1 has a tube 3, a piston rod 21 arranged in the tube 3, a piston 18 arranged in the piston rod 21, a first damping valve 75, a second damping valve 76, a valve base 152 and a third damping valve 154 arranged in the piston rod 21, and a sleeve 102 capable of accommodating the valve base 152. The valve base 152 is formed by combining a first base member 161 and a second base member 162. The first base member 161 has a communication passage 178 therein. A valve seat 177 on which the third damping valve 154 is placed is formed on an upper end surface 161a of the first base member 161 facing the piston 18. The second base member 162 has a communication passage 186 formed therein that communicates with the communication passage 178 and the inside of the sleeve 102. An arrangement groove 195 for accommodating the engaging member 153 is provided on the outer periphery of at least one of the first base member 161 and the second base member 162, on the lower end surface 161b and upper end surface 162a side where the first base member 161 and the second base member 162 abut.

[0108] During the compression stroke of the shock absorber 1, the valve base 152 and fitting member 153 enter the sleeve 102. Then, friction between the fitting member 153 and the sleeve 102 moves the fitting member 153 relative to the valve base 152, closing the axial passage 196 between the fitting member 153 and the valve base 152 and generating a damping force. By providing the third damping valve 154 in the valve base 152, the shock absorber 1 opens the third damping valve 154 to relieve the hydraulic pressure in the fourth chamber 211 to the fifth chamber 212 via the communicating passages 178, 186 when the hydraulic pressure in the fourth chamber 211 exceeds a predetermined pressure during the compression stroke. This allows the shock absorber 1 to suppress an excessive increase in hydraulic pressure during the compression stroke when the valve base 152 enters the sleeve 102 and generates a damping force. Furthermore, in the extension stroke of shock absorber 1, the frictional force between fitting member 153 and sleeve 102 causes fitting member 153 to move relative to valve base 152, opening axial passage 196 between fitting member 153 and valve base 152 and allowing oil L to flow smoothly from fifth chamber 212 to fourth chamber 211. This allows smooth movement of valve base 152 and fitting member 153 within sleeve 102 in the extension stroke of shock absorber 1.

[0109] As described above, the shock absorber 1 can be configured compactly by integrating the valve base 152, fitting member 153, and third damping valve 154, which increase the damping force near the end of travel of the piston rod 21 on the compression side.

[0110] In the shock absorber 1, the fitting member 153 is made of brass or glass fiber reinforced plastic.

[0111] In the shock absorber 1, the sleeve 102 has an expanded diameter portion 112 on the side where the second base member 162 is inserted. This allows the shock absorber 1 to smoothly increase the damping force near the end of travel of the piston rod 21 on the retracted side.

[0112] [Second embodiment] Next, the shock absorber of the second embodiment will be described mainly with reference to Fig. 4, focusing on the differences from the first embodiment. Note that parts common to the first embodiment will be designated by the same names and symbols. Also, the symbol CL shown in each figure indicates the central axis of the shock absorber.

[0113] The shock absorber 1A of the second embodiment has a cup 101A that is partially different from the cup 101, instead of the cup 101. The cup 101A has a sleeve 102A (second tube) that is partially different from the sleeve 102, instead of the sleeve 102. The sleeve 102A has a main body portion 111A that is partially different from the main body portion 111, instead of the main body portion 111.

[0114] Similar to the sleeve 102, the sleeve 102A has a plurality of grooves 116 formed on its inner periphery at one axial end thereof, extending in the axial direction of the sleeve 102A. The sleeve 102A also has a groove 116A formed on its inner periphery at the other axial end thereof, extending in the axial direction of the sleeve 102A. The groove 116A is formed on the inner periphery at the lower end of the sleeve 102A. The groove 116A is recessed outward in the radial direction of the sleeve 102A from the inner periphery of the sleeve 102A. The sleeve 102A has a plurality of grooves 116A formed at equal intervals around the circumference of the sleeve 102A. The grooves 116A have the same length from the lower end of the sleeve 102A. In other words, the grooves 116A have the same length in the axial direction of the sleeve 102A.

[0115] The press-fit portion 122 of the base adapter 103 is press-fitted into the lower end of the sleeve 102A. At this time, the upper surface of the main plate portion 121 abuts against the lower end of the sleeve 102A. This closes the lower ends of the multiple grooves 116A and fixes the base adapter 103 to the sleeve 102A. The multiple grooves 116A extend above the press-fit portion 122.

[0116] During the compression stroke, the piston rod 21 moves from a first predetermined range in which the second valve assembly 151 is not fitted into the sleeve 102A to a second predetermined range. Then, the second valve assembly 151 fits the fitting member 153 into the sleeve 102A. At the beginning of this fitting, the fitting member 153 closes the axial passage 196.

[0117] During the compression stroke within the second predetermined range, with the axial passage 196 thus blocked, the second valve assembly 151 moves together with the piston rod 21 toward the base adapter 103. In the upper part of the second predetermined range, the fitting member 153 is located at the position of the plurality of grooves 116 provided in the sleeve 102A, and causes the oil L to flow from the fourth chamber 211 to the fifth chamber 212 through the plurality of grooves 116. At this time, as the second valve assembly 151 approaches the base adapter 103, the number of the plurality of grooves 116 that allow the oil L to flow from the fourth chamber 211 to the fifth chamber 212 decreases, eventually reaching zero.

[0118] Furthermore, during the compression stroke within the second predetermined range, the second valve assembly 151 moves toward the base adapter 103 with the axial passage 196 closed as described above. At that time, depending on the piston speed, the third damping valve 154 opens. This causes hydraulic fluid L to flow from the fourth chamber 211 to the fifth chamber 212 via the third passage 191. As a result, the third damping valve 154 suppresses an excessive increase in pressure in the fourth chamber 211.

[0119] Here, during the compression stroke, when the second valve assembly 151 approaches the lower limit position of the second predetermined range, the fitting member 153 is positioned at the position of the plurality of grooves 116A provided in the sleeve 102A. Then, the oil L flows from the fourth chamber 211 to the fifth chamber 212 via the plurality of grooves 116A provided in the sleeve 102A. As a result, the plurality of grooves 116A suppress an excessive increase in pressure in the fourth chamber 211.

[0120] From this state, the second valve assembly 151 moves together with the piston rod 21 toward the opposite side from the base adapter 103. This causes the fitting member 153 to open the axial passage 196. When the second valve assembly 151 moves away from the base adapter 103 in this state, the oil L flows from the fifth chamber 212 to the fourth chamber 211 through the axial passage 196 and the passage in the groove portion 182 of the valve base 152. At the same time, the oil L flows from the fifth chamber 212 to the fourth chamber 211 through the multiple grooves 116A. This reduces the resistance to the movement of the piston rod 21 in the extension direction.

[0121] When the fitting member 153 of the second valve assembly 151 is positioned on the opposite side of the base adapter 103 from all of the grooves 116A in the sleeve 102A, the oil L flows from the fifth chamber 212 to the fourth chamber 211 only through the flow path from the axial passage 196 to the passage in the groove portion 182 of the valve base 152.

[0122] In the shock absorber 1A of the second embodiment, a groove 116 extending in the axial direction of the sleeve 102A is provided on the inner periphery of one axial end of the sleeve 102A, and a groove 116A extending in the axial direction of the sleeve 102A is provided on the inner periphery of the other axial end of the sleeve 102A. As a result, at the start of the compression stroke in the second predetermined range, the groove 116 on the upper end side slows the rate of change in the damping force. Because there is no groove in the axial middle of the sleeve 102A, the damping force increases at the middle position of the compression stroke in the second predetermined range. At the lower end of the second predetermined range, the groove 116A suppresses the increase in damping force. The groove 116A can serve as a relief.

[0123] In the embodiment, hydraulic shock absorbers are shown as examples of shock absorbers 1 and 1A, but the above structure can also be applied to shock absorbers that use water or air as the working fluid.

[0124] [Third embodiment] Next, a shock absorber according to a third embodiment will be described, focusing on differences from the first embodiment, mainly with reference to Figures 5 and 6. The same parts as those in the first embodiment are designated by the same names and symbols. The symbol CL in each figure indicates the central axis of the shock absorber.

[0125] 5, the shock absorber 1B of the third embodiment does not include the cup 101 that is included in the shock absorber 1 of the first embodiment. The shock absorber 1B includes a rod guide 23B that is partially different from the rod guide 23 instead of the rod guide 23.

[0126] The rod guide 23B has a large diameter portion 28, an intermediate diameter portion 29B, and a small diameter portion 231, similar to the rod guide 23. The intermediate diameter portion 29B has an outer diameter smaller than that of the large diameter portion 28. The small diameter portion 231 has an outer diameter smaller than that of the intermediate diameter portion 29B. The rod guide 23B has the intermediate diameter portion 29B located lower than the large diameter portion 28. The rod guide 23B has the small diameter portion 231 located lower than the intermediate diameter portion 29B. The rod guide 23B fits into the inner periphery of the upper part of the shell 5 at the upper large diameter portion 28. The rod guide 23B fits into the inner periphery of the upper end of the tube 3 at the intermediate diameter portion 29B. At that time, the upper end of the tube 3 abuts against the large diameter portion 28 in the axial direction of the tube 3.

[0127] The shock absorber 1B includes a sleeve 102B (second tube). The sleeve 102B is cylindrical. The outer diameter of the sleeve 102B is smaller than the inner diameter of the tube 3. The sleeve 102B is disposed radially inside the tube 3B. The inner peripheral portion of the upper end of the sleeve 102B is fitted into the small diameter portion 231 at the bottom of the rod guide 23B. At this time, the upper end of the sleeve 102B abuts against the intermediate diameter portion 29B in the axial direction of the sleeve 102B. The central axis of the sleeve 102B coincides with the central axis of the tube 3. The sleeve 102B is disposed in the first chamber 19 with a radial gap between it and the tube 3.

[0128] As shown in FIG. 6, the sleeve 102B has a main body portion 111B and an expanded diameter portion 112B. The main body portion 111B is cylindrical and extends from the upper end to the lower end of the sleeve 102B. The expanded diameter portion 112B is provided at the lower end of the sleeve 102B. The inner diameter of the expanded diameter portion 112B increases toward the lower end. The outer diameter of the expanded diameter portion 112B increases toward the lower end. The diameter of the expanded diameter portion 112B increases in the axial direction of the sleeve 102B in a direction away from the main body portion 111B.

[0129] The sleeve 102B has a groove 116B formed on its inner periphery at one axial end thereof, the groove 116B extending in the axial direction of the sleeve 102B. The groove 116B is formed on the inner periphery at the lower end of the sleeve 102B. The groove 116B is recessed outward in the radial direction of the sleeve 102B from the inner periphery of the sleeve 102B. The groove 116B extends from the expanded diameter portion 112B to the lower part of the main body portion 111B. The sleeve 102B has a plurality of grooves 116B formed at equal intervals in the circumferential direction of the sleeve 102B. The plurality of grooves 116B each have a different length from the lower end of the sleeve 102B. In other words, the plurality of grooves 116B each have a different length in the axial direction of the sleeve 102B.

[0130] The shock absorber 1B is provided with a piston rod 21B that is partially different from the piston rod 21, instead of the piston rod 21. The piston rod 21B has a rod main body 41B and an extender 42B.

[0131] The rod main body 41B has a main shaft portion 51B and a mounting shaft portion 52B. The main shaft portion 51B and the mounting shaft portion 52B are both rod-shaped. The outer diameter of the mounting shaft portion 52B is smaller than the outer diameter of the main shaft portion 51B. The mounting shaft portion 52B extends from one axial end of the main shaft portion 51B. The central axis of the mounting shaft portion 52B coincides with the central axis of the main shaft portion 51B. The entire mounting shaft portion 52B is disposed within the tube 3. As shown in FIG. 5, the piston rod 21B has the main shaft portion 51B of the rod main body 41B sliding relative to the rod guide 23B and the seal member 24 along the axial direction of these members.

[0132] As shown in Fig. 6, the end of the mounting shaft portion 52B opposite to the main shaft portion 51B in the axial direction of the mounting shaft portion 52B is a threaded shaft portion 54B. A male thread is formed on the outer periphery of the threaded shaft portion 54B. The portion of the mounting shaft portion 52B between the main shaft portion 51B and the threaded shaft portion 54B in the axial direction of the mounting shaft portion 52B is a fitting shaft portion 55B. The outer periphery of the fitting shaft portion 55B is a cylindrical surface.

[0133] The extender 42B has a base shaft portion 61B and a mounting shaft portion 62B. Both the base shaft portion 61B and the mounting shaft portion 62B are rod-shaped. The outer diameter of the mounting shaft portion 62B is smaller than the outer diameter of the base shaft portion 61B. The mounting shaft portion 62B extends from one axial end of the base shaft portion 61B. The central axis of the mounting shaft portion 62B coincides with the central axis of the base shaft portion 61B.

[0134] A screw hole 64B is formed in the base shaft portion 61B from the end opposite the mounting shaft portion 62B in the axial direction of the base shaft portion 61B to the middle portion. The screw hole 64B is formed at the radial center position of the base shaft portion 61B. The screw hole 64B extends along the axial direction of the base shaft portion 61B. The screw hole 64B opens upward.

[0135] The end of the mounting shaft portion 62B opposite to the base shaft portion 61B in the axial direction of the mounting shaft portion 62B is a threaded shaft portion 65B. A male thread is formed on the outer periphery of the threaded shaft portion 65B. The portion of the mounting shaft portion 62B between the base shaft portion 61B and the threaded shaft portion 65B in the axial direction of the mounting shaft portion 62B is a fitting shaft portion 66B. The outer periphery of the fitting shaft portion 66B is a cylindrical surface.

[0136] The threaded shaft portion 54B of the rod main body 41B is threaded into the threaded hole 64B of the extender 42B. This connects the rod main body 41B and the extender 42B with their central axes aligned. This forms the piston rod 21B. The entire extender 42B is disposed within the tube 3. The portion of the rod main body 41B that is connected to the extender 42B is disposed within the tube 3, and the side opposite the extender 42B extends from the cylinder 2 to the outside.

[0137] A piston assembly 17 made up of a piston 18 (primary piston), a first damping valve 75 (first valve), and a second damping valve 76 is attached to the mounting shaft portion 62B of the extender 42B on the piston rod 21B. At this time, the piston assembly 17 is fitted into the fitting shaft portion 66B of the extender 42B. The piston assembly 17 is attached to the extender 42B with a nut 201 that is screwed onto the threaded shaft portion 65B of the extender 42B. The piston 18, the first damping valve 75, and the second damping valve 76 are disposed on the piston rod 21B. The piston assembly 17 made up of the piston 18, the first damping valve 75, and the second damping valve 76 is provided on the tip side of the piston rod 21B.

[0138] The shock absorber 1B has a second valve assembly 151B. The second valve assembly 151B is disposed in the first chamber 19 and connected to the piston rod 21B. The second valve assembly 151B is attached to the mounting shaft portion 52B of the rod main body 41B. The second valve assembly 151B enters the sleeve 102B from below through an opening at the lower end of the sleeve 102B and exits downward.

[0139] The second valve assembly 151B has a valve base 152B (secondary piston), a first fitting member 153B (ring), a second fitting member 233 (ring), and a third damping valve 154B (second valve).

[0140] The valve base 152B has a first base member 161B (first piston member) and a second base member 162B (second piston member). The valve base 152B is formed by combining the first base member 161B and the second base member 162B. The first base member 161B forms the lower part of the valve base 152B. The second base member 162B forms the upper part of the valve base 152B.

[0141] The first base member 161B has an annular shape. A through hole 172B is formed in the radial center of the first base member 161B. The through hole 172B penetrates the first base member 161B in the axial direction of the first base member 161B. The fitting shaft portion 55B of the rod main body 41B is fitted into the through hole 172B of the first base member 161B. A passage groove 173B is formed in the first base member 161B outside the through hole 172B in the radial direction of the first base member 161B. A passage groove 174B and a passage hole 175B are formed in the first base member 161B outside the through hole 172B in the radial direction of the first base member 161B.

[0142] The passage groove 173B is formed in the lower end portion of the first base member 161B. The passage groove 173B is recessed upward from the lower end surface 161Ba (one end surface) of the first base member 161B. The passage groove 173B has an annular shape that surrounds the through-hole 172B on the radially outer side. The passage groove 173B opens downward.

[0143] At the lower end of the first base member 161B, the portion inside the passage groove 173B in the radial direction of the first base member 161B is an annular inner seat 176B, and the portion outside the passage groove 173B is an annular valve seat 177B (seat). The first base member 161B has the inner seat 176B and the valve seat 177B formed on a lower end surface 161Ba, which is one end surface facing the piston 18.

[0144] The passage groove 174B is formed in the upper end portion of the first base member 161B. The passage groove 173B is recessed downward from the upper end surface 161Bb (contact surface) of the first base member 161B. The passage groove 174B has an annular shape that surrounds the through-hole 172B on the radially outer side. The passage groove 174B opens upward.

[0145] The passage hole 175B is formed in the axial middle of the first base member 161B. The lower end of the passage hole 175B opens at the bottom of the passage groove 173B, and the upper end of the passage hole 175B opens at the bottom of the passage groove 174B. A plurality of passage holes 175B are formed in the first base member 161B at intervals in the circumferential direction of the first base member 161B.

[0146] In the first base member 161B, the passage in the passage groove 173B, the passage in the plurality of passage holes 175B, and the passage in the passage groove 174B constitute a communication passage 178B (first communication passage) that penetrates the first base member 161B in the axial direction. The first base member 161B has the communication passage 178B not on the outer peripheral surface but on the interior or inner peripheral surface side. Specifically, the first base member 161B has the communication passage 178B inside. The first base member 161B may have the communication passage 178B on the inner peripheral surface side, i.e., between the first base member 161B and the fitting shaft portion 55B of the rod main body 41B.

[0147] The second base member 162B is annular. A notch 181B is formed in the second base member 162B from the middle portion in the axial direction to the outer periphery of the lower portion. The notch 181B is formed around the entire circumference of the second base member 162B. The notch 181B is annular.

[0148] A groove 182B is formed in the second base member 162B at the bottom of the upper flange-shaped portion. The groove 182B is recessed upward from the lower surface of the flange-shaped portion of the second base member 162B. The groove 182B opens radially outward of the second base member 162. The groove 182B opens into the cutout portion 181. A plurality of grooves 182B are formed in the second base member 162B at intervals in the circumferential direction of the second base member 162B.

[0149] The second base member 162B has a through hole 183B formed in its radial center. The through hole 183B penetrates the second base member 162B in the axial direction of the second base member 162B. The fitting shaft portion 55B of the rod main body 41B is fitted into the through hole 183B of the second base member 162B. The upper surface 162Ba of the second base member 162B abuts against the end surface of the main shaft portion 51B of the rod main body 41B on the mounting shaft portion 52B side. The second base member 162B has a passage hole 185B between the through hole 183B and the notch 181B in the radial direction of the second base member 162B. The second base member 162B has a passage groove 235 formed outside the through hole 183B in the radial direction of the second base member 162B.

[0150] The passage groove 235 is formed in the upper end portion of the second base member 162B. The passage groove 235 is recessed downward from the upper surface 162Ba of the second base member 162B. The passage groove 235 has an annular shape that surrounds the through hole 183B radially outward. The passage groove 235 opens upward. The passage groove 235 opens radially outward of the main shaft portion 51B of the rod main body 41B, which abuts against the upper surface 162Ba of the second base member 162B.

[0151] The passage hole 185B is formed from the bottom surface of the passage groove 235 to the lower end surface 162Bb (contact surface) of the second base member 162B. In other words, the upper end of the passage hole 185B opens at the bottom position of the passage groove 235, and the lower end opens at the lower end surface 162Bb of the second base member 162B. A plurality of passage holes 185B are formed in the second base member 162B at intervals in the circumferential direction of the second base member 162B.

[0152] In the second base member 162B, the passage in the passage groove 235 and the passages in the multiple passage holes 185B form a communicating passage 186B (second communicating passage) that penetrates the second base member 162B in the axial direction. The second base member 162B has the communicating passage 186B not on the outer peripheral surface but on the interior or inner peripheral surface side. Specifically, the second base member 162B has the communicating passage 186B inside. The second base member 162B may have the communicating passage 186B on the inner peripheral surface side, i.e., between it and the fitting shaft portion 55B of the rod main body 41B.

[0153] When the first base member 161B is fitted onto the fitting shaft portion 55B of the rod main body 41B, the upper end surface 161Bb abuts against the lower end surface 162Bb of the second base member 162B. This allows the passage groove 173B, passage hole 175B, and passage groove 174B of the first base member 161B to communicate with the passage hole 185B and passage groove 235 of the second base member 162B. These passage grooves 173B, 174B, and 235 and the passage holes 175B and 185B form a third passage 191B. The third passage 191B is provided in the valve base 152B and passes through the valve base 152B in the axial direction. The third passage 191B is composed of the communication passage 178B of the first base member 161B and the communication passage 186B of the second base member 162B.

[0154] One end of the communication passage 186B of the second base member 162B communicates with the communication passage 178B of the first base member 161B. When the valve base 152B is inserted into the sleeve 102B, the other end of the communication passage 186B of the second base member 162B communicates with the inside of the sleeve 102B.

[0155] In the valve base 152B, the notch 181B of the second base member 162B forms a mounting groove 195B (ring accommodating groove) together with the first base member 161B. The mounting groove 195B is provided in a portion of the second base member 162B on the outer circumferential side of the first base member 161B and the second base member 162B, on the side of the lower end surface 162Bb of the second base member 162B that abuts against the upper end surface 161Bb of the first base member 161B. The mounting groove 195B is recessed inward in the radial direction of the valve base 152B from the outer circumferential surface of the valve base 152B. The mounting groove 195B is annular. The mounting groove 195B opens radially outward. The communication passage 178B of the first base member 161B is provided radially inward of the mounting groove 195B of the first base member 161B. The communication passage 186B of the second base member 162B is provided on the inside of the arrangement groove 195B in the radial direction of the second base member 162B.

[0156] The arrangement groove 195B may be provided on the outer periphery of both the first base member 161B and the second base member 162B, on the upper end surface 161Bb and the lower end surface 162Bb side where the first base member 161B and the second base member 162B come into contact. Alternatively, the arrangement groove 195B may be provided on the outer periphery of the first base member 161B, on the upper end surface 161Bb side where the first base member 161B comes into contact with the lower end surface 162Bb of the second base member 162B. In other words, the arrangement groove 195B is provided on the outer periphery of at least one of the first base member 161B and the second base member 162B, on the upper end surface 161Bb and the lower end surface 162Bb side where the first base member 161B and the second base member 162B come into contact.

[0157] The first fitting member 153B is annular. The outer diameter of the first fitting member 153B is larger than the outer diameter of the valve base 152B. When the first base member 161B and the second base member 162B are assembled to the rod main body 41B, the first fitting member 153B is disposed between the first base member 161B and the notch 181B of the second base member 162B. As a result, the first fitting member 153B is disposed within the arrangement groove 195B of the valve base 152B. The first fitting member 153B is axially movable relative to the valve base 152B within the arrangement groove 195B. The arrangement groove 195B of the valve base 152B accommodates the first fitting member 153B. The first fitting member 153B is made of brass or glass fiber reinforced plastic. The first fitting member 153B has a C-shaped cross section. In other words, a slit (not shown) is provided in a part of the radial direction, i.e., the shape is not a continuous ring, because the first fitting member 153B expands in diameter due to internal pressure and comes into sliding contact with the main body portion 111B of the sleeve 102B.

[0158] The second fitting member 233 is annular. The outer diameter of the second fitting member 233 is larger than the outer diameter of the valve base 152B. When the first base member 161B and the second base member 162B are assembled to the rod main body 41B, the second fitting member 233 is disposed between the first base member 161B and the notch 181B of the second base member 162B. As a result, the second fitting member 233 is disposed within the arrangement groove 195B of the valve base 152B. At this time, the second fitting member 233 is disposed below the first fitting member 153B. The second fitting member 233 is axially movable relative to the valve base 152B within the arrangement groove 195B. The arrangement groove 195B of the valve base 152B accommodates the second fitting member 233. The second fitting member 233 is made of an elastic material such as rubber, steel, brass, or the like. The outer diameter of the first fitting member 153B is larger than the outer diameter of the second fitting member 233. This is because the outer diameter of the first fitting member 153B is in sliding contact with the main body portion 111B of the sleeve 102B. The second fitting member 233 does not have a slit like the first fitting member 153B and is annular. The second fitting member 233 serves to prevent the outflow of oil that flows from the high-pressure side to the low-pressure side through the slit in the first fitting member 153B. Furthermore, the axial length of the second fitting member 233 is shorter than the axial length of the first fitting member 153B.

[0159] A gap is provided between the inner periphery of the first fitting member 153B and the bottom of the arrangement groove 195B. A gap is provided between the inner periphery of the second fitting member 233 and the bottom of the arrangement groove 195B. These gaps form an axial passage 196B that passes through the first fitting member 153B and the second fitting member 233 in the axial direction.

[0160] The third damping valve 154B is a disc valve configured by stacking multiple annular discs. The fitting shaft portion 55B of the rod main body 41B is fitted into the radial inside of the third damping valve 154B. The third damping valve 154B is attached to the rod main body 41B by an extender 42B that is screwed into the threaded shaft portion 54B of the rod main body 41B in a screw hole 64B.

[0161] The third damping valve 154B rests on a valve seat 177B of the valve base 152B. In other words, the valve base 152B has a valve seat 177B on which the third damping valve 154B rests formed on one end surface thereof facing the piston 18. The third damping valve 154B has an outer circumferential portion that separates from the valve seat 177B of the valve base 152B to open the third passage 191B. The third damping valve 154B has an outer circumferential portion that abuts against the valve seat 177B of the valve base 152B to close the third passage 191B.

[0162] As shown in Figure 5, the second valve assembly 151B is provided on the piston rod 21B on the opposite side of the piston assembly 17 from the first valve assembly 31. The valve base 152B is fixed to the piston rod 21B. Therefore, the valve base 152B and the piston rod 21B move together. The valve base 152B and the third damping valve 154B are disposed on the piston rod 21B. The sleeve 102B is capable of accommodating the valve base 152B.

[0163] When the piston rod 21B is in a third predetermined range in which the second valve assembly 151B is positioned below the sleeve 102B and is not fitted into the sleeve 102B, the inside of the sleeve 102B becomes the first chamber 19 as a whole.

[0164] From this state, during the extension stroke, the piston rod 21B moves from the third predetermined range to a fourth predetermined range that is closer to the rod guide 23B. Then, the second valve assembly 151B enters the sleeve 102B from the side of the expanded diameter portion 112B of the sleeve 102B. In other words, the sleeve 102B has the expanded diameter portion 112B on the side where the second valve assembly 151B including the valve base 152B is inserted. When the second valve assembly 151B enters the sleeve 102B from the side of the expanded diameter portion 112B of the sleeve 102B, the first fitting member 153B and the second fitting member 233 are fitted into the sleeve 102B. During the initial stage of this fitting, the first fitting member 153B moves downward relative to the arrangement groove 195B of the valve base 152B while compressing and deforming the second fitting member 233 due to frictional force with the sleeve 102B. As a result, the first fitting member 153B presses the lower surface of the second fitting member 233 against the valve base 152B. Then, the axial passage 196B is blocked by the second fitting member 233. During the subsequent extension stroke, the first fitting member 153B is pushed by the valve base 152B via the second fitting member 233, with the axial passage 196B still blocked by the second fitting member 233, and slides inside the sleeve 102B toward the rod guide 23B.

[0165] When the first fitting member 153B and the second fitting member 233 of the second valve assembly 151B are fitted into the sleeve 102B, the first chamber 19 is divided into a third chamber 241 and a fourth chamber 242. The third chamber 241 is the portion between the second valve assembly 151B and the rod guide 23B inside the sleeve 102B. The fourth chamber 242 is the portion of the first chamber 19 excluding the third chamber 241. The fourth chamber 242 consists of the portion between the tube 3 and the sleeve 102B and the portion between the piston assembly 17 and the second valve assembly 151B.

[0166] During the extension stroke in the fourth predetermined range, with the axial passage 196B closed as described above, the second valve assembly 151B moves together with the piston rod 21B toward the rod guide 23B. In the lower part of the fourth predetermined range, the first fitting member 153B is located at the position of the plurality of grooves 116B provided in the sleeve 102B, and causes the oil L to flow from the third chamber 241 to the fourth chamber 242 through the plurality of grooves 116B. At that time, as the second valve assembly 151B approaches the rod guide 23B, the number of the plurality of grooves 116B that allow the oil L to flow from the third chamber 241 to the fourth chamber 242 decreases, eventually reaching zero.

[0167] Furthermore, during the extension stroke within the fourth predetermined range, the second valve assembly 151B moves toward the rod guide 23B while the axial passage 196B is closed as described above. At that time, the third damping valve 154B opens depending on the piston speed, which is the moving speed of the piston rod 21B, piston 18, and valve base 152B relative to the tube 3. Then, hydraulic fluid L flows from the third chamber 241 to the fourth chamber 242 via the third passage 191B. As a result, the third damping valve 154B suppresses an excessive increase in pressure in the third chamber 241. The third damping valve 154B is provided in the third passage 191B and suppresses the flow of hydraulic fluid L that occurs during the extension stroke, thereby generating a damping force and allowing hydraulic fluid L to flow from the third chamber 241 to the fourth chamber 242. Here, the third damping valve 154B has higher rigidity than the first damping valve 75 and is less likely to open. Therefore, the third damping valve 154B opens later than the first damping valve 75, and generates a damping force higher than that of the first damping valve 75.

[0168] During the compression stroke, from a state in which the first fitting member 153B and the second fitting member 233 are fitted into the sleeve 102B, the second valve assembly 151B moves together with the piston rod 21B toward the opposite side from the rod guide 23B. Then, due to friction with the sleeve 102B, the first fitting member 153B and the second fitting member 233 move upward relative to the arrangement groove 195B of the valve base 152B. As a result, the lower surface of the second fitting member 233 moves away from the valve base 152B, thereby opening the axial passage 196B. During the subsequent compression stroke, the first fitting member 153B and the second fitting member 233 are pushed by the valve base 152B, with the axial passage 196B still open, and slide toward the opposite side from the rod guide 23B within the sleeve 102B. When the second valve assembly 151B moves in the opposite direction from the rod guide 23B, the oil L flows from the fourth chamber 242 to the third chamber 241 through the axial passage 196B and the passages in the plurality of grooves 182B. This reduces the resistance to the retraction movement of the piston rod 21B.

[0169] During the retraction stroke, the second valve assembly 151B moves away from the rod guide 23B by a predetermined distance from the rod guide 23B, from a state in which the first fitting member 153B and the second fitting member 233 are closer to the rod guide 23B than all of the grooves 116B in the sleeve 102B. As a result, the grooves 116B formed in the sleeve 102B open to the third chamber 241. Then, the oil L flows from the fourth chamber 242 to the third chamber 241 through the grooves 116B. At this time, the farther the second valve assembly 151B is from the rod guide 23B, the more of the multiple grooves 116B that allow the oil L to flow from the fourth chamber 242 to the third chamber 241 increase. This gradually reduces the resistance to the retraction movement of the piston rod 21B.

[0170] Next, the main operation of the shock absorber 1B will be described.

[0171] "Extension stroke when piston rod 21B is in the third predetermined range"

[0172] {Fifth region where the piston speed is slower than the third predetermined value} In the fifth region of the extension stroke, the oil L from the first chamber 19 flows from the first passage 71 to the second chamber 20 through a fixed orifice (not shown) between the first damping valve 75 and the piston 18 in the piston assembly 17. Therefore, in the fifth region of the extension stroke, a damping force with orifice characteristics is generated.

[0173] {Sixth region in which the piston speed is equal to or greater than the third predetermined value} In the sixth region of the extension stroke, the oil L from the first chamber 19 flows from the first passage 71 to the second chamber 20 in the piston assembly 17, opening the first damping valve 75. Therefore, in the sixth region of the extension stroke, a damping force with valve characteristics is generated by the first damping valve 75.

[0174] "Retraction stroke when piston rod 21B is in the third predetermined range"

[0175] {A seventh region in which the piston speed is slower than the fourth predetermined value} In the seventh region of the compression stroke, the oil L from the second chamber 20 flows from the second passage 72 to the first chamber 19 through a fixed orifice (not shown) between the second damping valve 76 and the piston 18 in the piston assembly 17. Therefore, in the seventh region of the compression stroke, a damping force with orifice characteristics is generated.

[0176] {Eighth region in which the piston speed is equal to or greater than the fourth predetermined value} In the eighth region of the compression stroke, the oil L from the second chamber 20 flows from the second passage 72 to the first chamber 19 in the piston assembly 17, opening the second damping valve 76. Therefore, in the eighth region of the compression stroke, a damping force with valve characteristics is generated by the second damping valve 76.

[0177] "Extension stroke when piston rod 21B is in the fourth predetermined range" During this extension stroke, the piston assembly 17 operates in the same manner as in the third predetermined range. Then, the second valve assembly 151B moves toward the rod guide 23B in the axial direction of the tube 3, and the first fitting member 153B and the second fitting member 233 fit into the sleeve 102B. Then, initially, the first fitting member 153B and the second fitting member 233 close the axial passage 196B.

[0178] With the axial passage 196B closed in this manner, the second valve assembly 151B moves toward the rod guide 23B. This causes oil L to flow from the third chamber 241 to the fourth chamber 242 through the multiple grooves 116B provided in the sleeve 102B. As the second valve assembly 151B approaches the rod guide 23B, the number of grooves 116B through which oil L flows from the third chamber 241 to the fourth chamber 242 decreases, eventually reaching zero. This increases the damping force of the second valve assembly 151B in stages, thereby increasing the resistance to the extension movement of the piston rod 21B in stages. The press-fit axial length between the small diameter portion 231 of the rod guide 23B and the sleeve 102B is set so that the sleeve 102B does not come out of the small diameter portion 231 even when the third chamber 241 reaches its maximum pressure.

[0179] When the second valve assembly 151B moves toward the rod guide 23B, the third damping valve 154B opens depending on the piston speed. Then, hydraulic fluid L flows from the third chamber 241 to the fourth chamber 242 through the third passage 191B. This prevents an excessive increase in pressure in the third chamber 241.

[0180] "Retraction stroke when piston rod 21B is in the fourth predetermined range" During this compression stroke, piston assembly 17 operates in the same manner as in the third predetermined range. Then, second valve assembly 151B moves to the side opposite rod guide 23B. Then, initially, first fitting member 153B and second fitting member 233 open axial passage 196B and the passages in multiple grooves 182B.

[0181] With the axial passage 196B and the passages in the plurality of grooves 182B open in this manner, the second valve assembly 151B moves toward the opposite side from the rod guide 23B. Then, oil L flows from the fourth chamber 242 to the third chamber 241 via the axial passage 196B and the passages in the plurality of grooves 182B. When the first fitting member 153B of the second valve assembly 151B passes the position of the grooves 116B formed in the sleeve 102B from a state in which it is closer to the rod guide 23B than all of the grooves 116B formed in the sleeve 102B, oil L flows from the fourth chamber 242 to the third chamber 241 via the grooves 116B. At this time, the farther the second valve assembly 151B is from the rod guide 23B, the more of the plurality of grooves 116B through which oil L flows from the fourth chamber 242 to the third chamber 241 increases. In other words, the further the second valve assembly 151B is from the rod guide 23B, the lower the damping force becomes, and the lower the resistance force against the movement of the piston rod 21B in the contraction direction becomes.

[0182] The shock absorber 1B includes a tube 3, a piston rod 21B disposed within the tube 3, a piston 18 disposed in the piston rod 21B, a first damping valve 75, a second damping valve 76, a valve base 152B and a third damping valve 154B disposed in the piston rod 21B, and a sleeve 102B capable of accommodating the valve base 152B. The valve base 152B is formed by combining a first base member 161B and a second base member 162B. The first base member 161B has a communication passage 178B therein. A valve seat 177B on which the third damping valve 154B is placed is formed on a lower end surface 161Ba of the first base member 161B facing the piston 18. The second base member 162B has a communication passage 186B formed therein, which communicates with the communication passage 178B and the interior of the sleeve 102B. An arrangement groove 195B for accommodating the first engaging member 153B and the second engaging member 233 is provided on the outer periphery of at least one of the first base member 161B and the second base member 162B, on the upper end surface 161Bb and lower end surface 162Bb side where the first base member 161B and the second base member 162B abut.

[0183] During the extension stroke of shock absorber 1B, the valve base 152B, first fitting member 153B, and second fitting member 233 enter the sleeve 102B. Then, friction with the sleeve 102B causes the first fitting member 153B and the second fitting member 233 to move relative to the valve base 152B, closing the axial passage 196 between them and the valve base 152B and generating a damping force. By providing a third damping valve 154B in the valve base 152B, shock absorber 1B opens the third damping valve 154B to relieve the hydraulic pressure in the third chamber 241 to the fourth chamber 242 via the communicating passages 178B and 186B when the hydraulic pressure in the third chamber 241 exceeds a predetermined pressure during the extension stroke. This allows shock absorber 1B to suppress an excessive increase in hydraulic pressure during the extension stroke when the valve base 152B enters the sleeve 102B and generates a damping force. Furthermore, during the compression stroke of shock absorber 1B, first fitting member 153B and second fitting member 233 housed in arrangement groove 195B of valve base 152B move relative to valve base 152B due to friction with sleeve 102B, opening axial passage 196B between them and valve base 152B, allowing oil L to flow smoothly from fourth chamber 242 to third chamber 241. This allows smooth movement of valve base 152B, first fitting member 153B, and second fitting member 233 within sleeve 102B during the compression stroke of shock absorber 1B.

[0184] As described above, the shock absorber 1B can be configured compactly by combining the valve base 152B, the first fitting member 153B, the second fitting member 233, and the third damping valve 154B, which increases the damping force near the end of the extension side of the piston rod 21B.

[0185] In the shock absorber 1B, the first fitting member 153B is made of brass or glass fiber reinforced plastic.

[0186] In shock absorber 1B, sleeve 102B has expanded diameter portion 112B on the side where second base member 162B is inserted, which allows shock absorber 1B to smoothly increase the damping force near the end of travel on the extension side of piston rod 21B.

[0187] In the shock absorber 1B of the third embodiment, the sleeve 102B may be modified in the same manner as the sleeve 102A.

[0188] According to the shock absorber according to the above aspect of the present disclosure, it is possible to suppress an increase in costs. [Explanation of symbols]

[0189] 1, 1A, 1B... shock absorber, 3... tube (first tube), 6... inner chamber, 17... piston assembly, 18... piston (primary piston), 19... first chamber, 20... second chamber, 21, 21B... piston rod, 31... first valve assembly, 75... first damping valve (first valve), 76... second damping valve (first valve), 101, 101A... cup, 102, 102A, 102B... sleeve (second tube), 103... base adapter, 112, 112B... expansion portion, 116 , 116A...groove, 122...press-fit portion, 123...leg portion, 135...inner peripheral portion, 141...third chamber, 142...communicating passage, 151...second valve assembly, 152, 152B...valve base (second piston member), 153...fitting member (ring), 153B...first fitting member (ring), 154, 154B...third damping valve (second valve), 161, 161B...first base member (first piston member), 161a...upper end surface (one end surface), 161b...lower end surface (abutment surface), 161Ba...lower end surface (one end surface), 161Bb ...upper end surface (abutment surface), 162, 162B...second base member (second piston member), 162a...upper end surface (abutment surface), 162Bb...lower end surface (abutment surface), 177, 177B...valve seat (seat), 178, 178B...communicating passage (first communicating passage), 186, 186B...communicating passage (second communicating passage), 195, 195B...positioning groove, 233...second fitting member (ring).

Claims

1. a tube whose inner side is an inner chamber; a first valve assembly connected to one axial end of the tube; a piston assembly that divides the internal chamber into a first chamber and a second chamber; a piston rod connected to the piston assembly at the axially intermediate position and extending from the tube through the first chamber; a cup provided in the second chamber; a second valve assembly disposed in the second chamber and connected to the piston rod, the second valve assembly extending into and out of the cup; Equipped with The cup is a sleeve disposed in the second chamber with a radial gap between the sleeve and the tube; a base adapter that is press-fitted and fixed to the sleeve and is provided between the sleeve and the first valve assembly; Shock absorber.

2. a third chamber is provided between the first valve assembly and the base adapter; a press-fit portion that is press-fitted into the sleeve is provided at one end of the base adapter in the axial direction, a leg portion to be placed on the first valve assembly is provided at the other axial end of the base adapter; A communication passage that communicates the second chamber with the third chamber is provided in the leg portion. The shock absorber according to claim 1 .

3. 3. The shock absorber according to claim 2, wherein the inner periphery of the leg portion increases in diameter toward the first valve assembly.

4. 2. The shock absorber according to claim 1, wherein a groove extending in the axial direction of the sleeve is provided on an inner peripheral portion of the sleeve at one end in the axial direction and on an inner peripheral portion of the sleeve at the other end in the axial direction.

5. A first tube; a piston rod disposed within the first tube; a primary piston and a first valve disposed on the piston rod; a secondary piston and a second valve disposed on the piston rod; a second tube capable of accommodating the secondary piston; the secondary piston is configured by combining a first piston member and a second piston member, the first piston member has a first communication passage on the inside or on the inner peripheral surface side, and a seat on which the second valve is placed is formed on one end surface facing the primary piston, the second piston member has a second communication passage formed therein that communicates with the first communication passage and the inside of the second tube; a ring receiving groove for receiving a ring is provided on an outer circumferential side of at least one of the first piston member and the second piston member, on a contact surface side where the first piston member and the second piston member contact each other; Shock absorber.

6. 6. The shock absorber of claim 5, wherein the ring is made of brass or glass fiber reinforced plastic.

7. 7. The shock absorber according to claim 5, wherein the second tube has an enlarged diameter portion on a side where the secondary piston is inserted.

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