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 a shock absorber. This application claims priority based on U.S. Patent Application No. 17 / 954,389, filed in the United States on September 28, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] There is a shock absorber that increases 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

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a shock absorber, there is a desire to suppress an increase in cost.

[0005] Therefore, an object of the present disclosure is to provide a shock absorber capable of suppressing an increase in cost.

Means for Solving the Problems

[0006] To achieve the above objective, one embodiment of the shock absorber of the present disclosure comprises a tube whose inner side forms an inner chamber; a first valve assembly connected to one axial end of the tube; a piston assembly dividing the inner chamber into a first chamber and a second chamber; a piston rod connected to the piston assembly at an intermediate axial position 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 comprises 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 provided between the sleeve and the first valve assembly.

[0007] Another embodiment 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 housing 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 internal or inner circumferential side, and a seat for the second valve formed on one end face facing the primary piston, the second piston member having a second communication passage communicating with the first communication passage and the inside of the second tube, and a ring housing groove for housing 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 abut. [Effects of the Invention]

[0008] According to each of the above embodiments of this disclosure, it is possible to suppress cost increases. [Brief explanation of the drawing]

[0009] [Figure 1]This is a diagram showing a shock absorber of the first embodiment according to the present disclosure, and is a cross-sectional view taken in a section including the central axis CL. [Figure 2] This is a diagram showing the main parts of the shock absorber, and is a partially enlarged cross-sectional view of Figure 1. [Figure 3] This is a diagram showing the main parts of the shock absorber, and is a partially enlarged cross-sectional view of Figure 2. [Figure 4] This is a diagram showing a shock absorber of a second embodiment according to the present disclosure, and is a partially enlarged cross-sectional view taken in a section including the central axis CL. [Figure 5] This figure shows a shock absorber of a third embodiment relating to the present disclosure, and is a cross-sectional view taken in a section including the central axis CL. [Figure 6] This is a diagram showing the main parts of the shock absorber, and is a partially enlarged cross-sectional view of Figure 5. [Modes for carrying out the invention]

[0010] [First Embodiment] The shock absorber of the first embodiment relating to this disclosure will be described with reference to Figures 1 to 3. For the sake of explanation, the upper side of the drawings will be referred to as "top" and the lower side as "bottom" in the following description. The symbol CL shown in each figure indicates the central axis of the shock absorber.

[0011] As shown in Figure 1, the shock absorber 1 of the first embodiment is a twin-tube hydraulic shock absorber. The shock absorber 1 is used in the suspension system of a vehicle, specifically an automobile. The shock absorber 1 comprises 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 a bottomed cylinder. The inner diameter of the shell 5 is larger than the outer diameter of the tube 3. The tube 3 is positioned radially inward of 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 is an inner chamber 6. The space between the tube 3 and the shell 5 is a reservoir chamber 7.

[0012] The shell 5 has a body portion 11 and a bottom portion 12. The body portion 11 and the bottom portion 12 are formed integrally without seams. The body portion 11 is cylindrical. The bottom portion 12 closes the lower part of the body portion 11.

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

[0014] The shock absorber 1 includes a piston rod 21. One end of the piston rod 21 in the axial direction is located inside the tube 3 of the cylinder 2. This one end of the piston rod 21 is connected to a piston assembly 17. The other end of the piston rod 21 in the axial direction extends from the cylinder 2 to the outside of the cylinder 2. The piston rod 21 extends out of the cylinder 2 through the first chamber 19 to the tube 3 and shell 5, and thus out of the cylinder 2, with the piston assembly 17 connected to it.

[0015] The shock absorber 1 has a piston rod 21 with an extension from the cylinder 2 positioned at the top and connected to the vehicle body. At the same time, the shock absorber 1 has a mounting bracket 22 fixed to the body 11 of the shell 5, positioned at the bottom and connected to the vehicle's wheel side.

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

[0017] A rod guide 23 is fitted to the upper end opening side of the tube 3 and the upper end opening 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 through the radially inner sides of the rod guide 23 and the seal member 24 respectively. The piston rod 21 slides along the axial directions of the rod guide 23 and the seal member 24 respectively. The piston rod 21 extends from the inside of the cylinder 2 to the outside of the cylinder 2 beyond the seal member 24.

[0018] The rod guide 23 restricts the piston rod 21 from moving radially with respect to the tube 3 and the shell 5 of the cylinder 2. The piston rod 21 fits into the rod guide 23 and the piston 18 fits into the tube 3. Thereby, the central axis of the piston rod 21 coincides with the central axis of the tube 3. The rod guide 23 supports the piston rod 21 so as to be movable in the axial direction of the piston rod 21. The outer peripheral portion of the seal member 24 is in close contact with the shell 5. The inner peripheral portion of the seal member 24 is in close contact with the outer peripheral portion of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 24 with respect to the seal member 24. The seal member 24 suppresses the leakage of the oil fluid L in the tube 3, the high-pressure gas G and the oil fluid L in the reservoir chamber 7 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 provided below the large-diameter portion 28. The rod guide 23 fits into the inner peripheral portion of the upper end of the tube 3 at the lower small-diameter portion 29. At that time, the upper end portion 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 peripheral portion 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 with respect to the shell 5. The seat member 32 has a large-diameter portion 33 and a small-diameter portion 34. The outer diameter of the large-diameter portion 33 is larger than the outer diameter of the small-diameter portion 34. The large-diameter portion 33 of the seat member 32 is provided below the small-diameter portion 34. The seat member 32 fits into the inner peripheral portion of the lower end of the tube 3 at the upper small-diameter portion 34. At that time, the lower end portion of the tube 3 abuts against the large-diameter portion 33 in the axial direction of the tube 3. Thereby, the first valve assembly 31 is connected to one axial end of the tube 3.

[0021] A clamping portion 35 is provided at the upper end portion of the shell 5. The clamping portion 35 is formed by clamping the upper end portion of the shell 5 inward in the radial direction of the shell 5. The seal member 24 is fixed to the cylinder 2 by being sandwiched between this clamping portion 35 and the rod guide 23. When forming the clamping portion 35, with the bottom 12 of the shell 5 placed on a base, the seal member 24 is pressed against the rod guide 23 along the axial direction of the shell 5. Then, the seal member 24, the rod guide 23, the tube 3, and the seat member 32 abut against each other without a gap in their axial directions. Thereby, an axial force is generated in the seal member 24, the rod guide 23, the tube 3, and the seat member 32. In this state, the clamping portion 35 is formed. Therefore, after the clamping portion 35 is formed, an axial force is generated in the seal member 24, the rod guide 23, the tube 3, and the seat member 32.

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

[0023] The rod body 41 has a main shaft portion 51 and a mounting shaft portion 52. Both the main shaft portion 51 and the mounting shaft portion 52 are 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 located inside the tube 3. The piston rod 21 slides along the axial direction of the rod guide 23 and the sealing member 24, respectively, as the main shaft portion 51 of the rod body 41 slides against them.

[0024] As shown in Figure 2, the mounting shaft portion 52 has a threaded shaft portion 54 at the end opposite to the main shaft portion 51 in the axial direction. The threaded shaft portion 54 has male threads formed on its outer circumference. The mounting shaft portion 52 has a fitting shaft portion 55 in the portion between the main shaft portion 51 and the threaded shaft portion 54 in the axial direction. The outer surface of the fitting shaft portion 55 is cylindrical.

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

[0026] The main shaft portion 61 has a screw hole 64 formed at the end opposite to the mounting shaft portion 62 in the axial direction. The screw hole 64 is formed at the radial center 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 mounting shaft portion 62 has a threaded shaft portion 65 at the end opposite to the main shaft portion 61 in the axial direction. The threaded shaft portion 65 has male threads formed on its outer circumference. The mounting shaft portion 62 has a fitting shaft portion 66 in the portion between the main shaft portion 61 and the threaded shaft portion 65 in the axial direction. The outer surface of the fitting shaft portion 66 is cylindrical.

[0028] The rod body 41 is screwed into the threaded hole 64 of the extender 42 by screwing its threaded shaft portion 54 into it. This connects the rod body 41 and the extender 42 with their central axes aligned. This forms the piston rod 21. The entire extender 42 is located inside the tube 3.

[0029] A piston 18 is attached to the mounting shaft portion 52 of the rod body 41 on the piston rod 21. The piston 18 is positioned between the main shaft portion 51 of the rod body 41 and the extender 42. The piston 18 fits 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 its radial direction. The through hole 70 penetrates the piston 18 in the axial direction. The fitting shaft portion 55 of the rod 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 penetrate the piston 18 in the axial direction. Multiple first passages 71 and 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 passages 71 and the second passages 72 can connect the first chamber 19 and the second chamber 20.

[0031] The piston assembly 17 includes 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 composed of multiple stacked annular discs. The fitting shaft portion 55 of the rod body 41 is fitted into the radially inner side of the first damping valve 75. The first damping valve 75 is positioned between the piston 18 and the extender 42. The outer circumference portion of the first damping valve 75 separates from the piston 18 and opens the first passage 71. As a result, the first damping valve 75 allows the oil liquid L to flow 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 the oil liquid L and generates a damping force. The first damping valve 75 is provided in the first passage 71 and generates a damping force by suppressing the flow of oil liquid L that occurs in the first passage 71 during the extension stroke. The outer circumference portion of the first damping valve 75 abuts against the piston 18 and closes 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 liquid 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 comes into contact with the piston 18.

[0033] The second damping valve 76 is a disc valve composed of multiple stacked annular discs. The second damping valve 76 has a fitting shaft portion 55 fitted to its radially inner side. The second damping valve 76 is positioned between the main shaft portion 51 of the rod body 41 and the piston 18. The outer circumference portion of the second damping valve 76 separates from the piston 18 and opens the second passage 72. As a result, the second damping valve 76 allows the oil liquid L to flow from the second chamber 20 to the first chamber 19 through the second passage 72. At this time, the second damping valve 76 suppresses the flow of the oil liquid L and generates a damping force. The second damping valve 76 is provided in the second passage 72 and generates a damping force by suppressing the flow of oil liquid L that occurs in the second passage 72 during the compression stroke. The outer circumference portion of the second damping valve 76 abuts against the piston 18 and closes 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 oil liquid 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 comes into contact with 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 body 41 by the extender 42. Therefore, the piston assembly 17 is positioned between the main shaft portion 51 of the rod body 41 and the extender 42. The piston assembly 17 is connected to the piston rod 21 at an axial intermediate position. The piston 18, the first damping valve 75, and the second damping valve 76 are positioned on the piston rod 21.

[0035] The first valve assembly 31 includes, in addition to the seat member 32 described above, a disc valve 82, a disc valve 83, a bolt 84, and a nut 85. The disc valve 82 is located below the seat member 32. The disc valve 83 is located above the seat member 32. The bolt 84 is inserted from above into the disc valve 83, the seat member 32, and the 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 the disc valve 83 to the seat member 32.

[0036] The sheet member 32 is annular in shape. The sheet member 32 has a base portion 88 and a projection portion 89. The base portion 88 is disc-shaped. As shown in Figure 3, the base portion 88 has a through hole 90 formed in its radial center. The through hole 90 penetrates the base portion 88 in the axial direction of the sheet member 32. A bolt 84 is inserted through the through hole 90 into the sheet member 32. The sheet member 32 has passage holes 91 and passage holes 92 formed outside the through hole 90 in the radial direction of the sheet member 32. The passage holes 91 and passage holes 92 penetrate the base portion 88 in the axial direction of the sheet member 32. The passage holes 92 are located outside the passage holes 91 in the radial direction of the sheet member 32. Multiple passage holes 91 and passage holes 92 are formed in the sheet member 32.

[0037] The protruding portion 89 protrudes downward from the outer circumference of the base portion 88. The protruding portion 89 is positioned outside the radial passage hole 92 of the base portion 88. The sheet member 32 has the protruding portion 89 in contact with the bottom portion 12 of the shell 5. The protruding portion 89 has a passage groove 93 formed therein that penetrates the sheet member 32 radially. Multiple passage grooves 93 are provided on the sheet member 32 at equal intervals in the circumferential direction of the sheet member 32. As a result, the space between the sheet member 32 and the bottom portion 12 of the shell 5 communicates with the portion between the body portion 11 of the shell 5 and the tube 3 shown in Figure 1. Therefore, the space between the sheet member 32 and the bottom portion 12 of the shell 5 also constitutes the reservoir chamber 7.

[0038] As shown in Figure 2, the shock absorber 1 has a cup 101. The cup 101 is located 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 positioned 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 positioned in the second chamber 20 with a radial gap between it and the tube 3.

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

[0041] The sleeve 102 has a groove 116 extending in the axial direction of the sleeve 102 on the inner circumference of one axial end of the sleeve 102. The groove 116 is located on the inner circumference of the upper end of the sleeve 102. The groove 116 is recessed outward in the radial direction of the sleeve 102 from the inner circumferential surface of the sleeve 102. The groove 116 extends from the enlarged diameter portion 112 to the upper part of the main body portion 111. Multiple grooves 116 are provided on the sleeve 102 at equal intervals in the circumferential direction of the sleeve 102. Each of the multiple grooves 116 has a different length from the upper end of the sleeve 102. In other words, each of the multiple grooves 116 has a different length in the axial direction of the sleeve 102.

[0042] The base adapter 103 is annular in shape. The base adapter 103 has a main plate portion 121, a press-fit portion 122, and a leg portion 123.

[0043] The main plate portion 121 is disc-shaped. As shown in Figure 3, the main plate portion 121 has a recess 131 formed in the radial center on one side of its axial direction, which is 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 base adapter 103 is pressed into the lower end of the sleeve 102 by the press-fit portion 122. At this time, the upper surface of the main plate portion 121 comes into contact with 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 to the press-fit portion 122 in the axial direction. The leg portion 123 protrudes downward from the outer circumference of the main plate portion 121. The leg portion 123 is cylindrical. The leg portion 123 is positioned outside the radial recess 131 of the main plate portion 121. The inner circumference 135 of the leg portion 123, on its radially inner side, becomes larger 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 circumference 135 of the leg portion 123 expands in diameter as it moves away from the main plate portion 121 in the axial direction.

[0046] Communication grooves 136 are formed in the outer periphery of the main plate portion 121 and the leg portion 123, penetrating the main plate portion 121 and the leg portion 123 in the axial direction of the base adapter 103. The communication grooves 136 open to the radially outward side of the base adapter 103. The communication grooves 136 are formed radially outward from the sleeve 102 of the main plate portion 121. The communication grooves 136 penetrate the leg portion 123 in the radial direction of the base adapter 103. Therefore, the communication grooves 136 open to the upper surface of the main plate portion 121, the outer periphery of the main plate portion 121, the outer periphery of the leg portion 123, the lower surface of the leg portion 123, and the inner periphery of the leg portion 123. Multiple communication grooves 136 are provided on the base adapter 103 at equal intervals in the circumferential direction of the base adapter 103.

[0047] The cup 101, consisting 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 end of the leg portion 123 of the base adapter 103 in contact with the upper surface of the outer circumference of the base portion 88 of the seat member 32. At this time, the base adapter 103 avoids contact with the bolt 84 of the first valve assembly 31 by the recess 131. Also, at this time, the leg portion 123 of the base adapter 103 surrounds the disc valve 83 of the first valve assembly 31 radially outward. In other words, the leg portion 123 is positioned spaced radially outward 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-fitted 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 inner circumference 135 of the leg portion 123 expands in diameter in the axial direction of the base adapter 103 as it approaches the first valve assembly 31.

[0049] A third chamber 141 is located 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 connects the second chamber 20 and the third chamber 141.

[0050] The first valve assembly 31 has multiple passage holes 91 through which the oil liquid L flows between the third chamber 141 and the reservoir chamber 7. Multiple passage holes 92 also allow the oil liquid 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 oil L from the third chamber 141 to the reservoir chamber 7 through the passage hole 91. On the other hand, the disc valve 82 restricts the flow of oil L from the reservoir chamber 7 to the third chamber 141 through the passage hole 91. The disc valve 82 opens during the compression stroke of the shock absorber 1, allowing oil L to flow from the second chamber 20 and the third chamber 141 to the reservoir chamber 7 and generating damping force.

[0052] The disc valve 83 on the third chamber 141 side allows the flow of oil L from the reservoir chamber 7 to the third chamber 141 through the passage hole 92. On the other hand, the disc valve 83 restricts the flow of oil L from the third chamber 141 to the reservoir chamber 7 through the passage hole 92. The disc valve 83 maintains constant communication between the third chamber 141 and the passage hole 91. The disc valve 83 opens during the extension stroke of the shock absorber 1, allowing oil L to flow from the reservoir chamber 7 to the third chamber 141 and the second chamber, and generating damping force. Alternatively, the disc valve 83 may be used as a suction valve that allows oil L to flow from the reservoir chamber 7 to the third chamber 141 and the second chamber without substantially generating 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 located in the second chamber 20 and connected to the piston rod 21. The second valve assembly 151 is mounted on the mounting shaft 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 includes a valve base 152 (secondary piston), a fitting member 153 (ring), and a third damping valve 154 (second valve).

[0055] As shown in Figure 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 constructed by combining the first base member 161 and the second base member 162. The first base member 161 constitutes the upper part of the valve base 152. The second base member 162 constitutes the lower part of the valve base 152.

[0056] The first base member 161 is annular. A notch 171 is formed on the lower outer circumference 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 its radial center. The through hole 172 penetrates the first base member 161 in the axial direction. 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 is provided with a passage groove 173 outside the through hole 172 in the radial direction of the first base member 161. The first base member 161 is provided with a passage groove 174 and a passage hole 175 between the through hole 172 and the notch 171 in the radial direction of the first base member 161.

[0058] The passage groove 173 is formed at the upper end 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 is annular in shape, surrounding the through hole 172 radially outward. The passage groove 173 opens upward.

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

[0060] The passage groove 174 is formed at the lower end 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 is annular in shape and surrounds the through hole 172 radially outward. The passage groove 174 opens downward.

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

[0062] The first base member 161 has a passage in the passage groove 173, a passage in the plurality of passage holes 175, and a passage in the passage groove 174 that together constitute a connecting passage 178 (first connecting passage) that penetrates the first base member 161 in the axial direction. The first base member 161 has the connecting passage 178 on the interior or inner circumferential surface side, rather than on the outer circumferential surface side. Specifically, the first base member 161 has the connecting passage 178 on its interior side. The first base member 161 may also have a connecting passage 178 on its inner circumferential surface side, i.e., between itself and the fitting shaft portion 66 of the extender 42.

[0063] The second base member 162 is annular. A notch 181 is formed on the upper outer circumference 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] The second base member 162 has grooves 182 formed on its lower outer circumference. The grooves 182 are recessed inward in the radial direction of the second base member 162 from the outer surface of the second base member 162. The grooves 182 open radially outward from the second base member 162. The grooves 182 open into the notch 181. The grooves 182 open downward. Multiple grooves 182 are formed on 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 its radial center. The through hole 183 penetrates the second base member 162 in the axial direction. 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 is provided with a passage groove 184 on the outside of the through hole 183 in the radial direction of the second base member 162. The second base member 162 is provided with a passage hole 185 between the through hole 183 and the notch 181 in the radial direction of the second base member 162.

[0066] The passage groove 184 is formed at the upper end 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 is annular in shape, surrounding the through hole 183 radially outward. 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. Multiple passage holes 185 are formed in the second base member 162 at intervals in the circumferential direction of the second base member 162.

[0068] The second base member 162 has a passage in the passage groove 184 and passages in the multiple passage holes 185 that constitute a connecting passage 186 (second connecting passage) that penetrates the second base member 162 in the axial direction. The second base member 162 has the connecting passage 186 on the interior or inner circumferential surface side, rather than on the outer circumferential surface side. Specifically, the second base member 162 has the connecting passage 186 on its interior side. The second base member 162 may also have a connecting passage 186 on its inner circumferential surface side, i.e., between it and the fitting shaft portion 66 of the extender 42.

[0069] With the valve base 152 fitted onto the fitting shaft portion 66 of the extender 42, the first base member 161 abuts against the upper end surface 162a of the second base member 162 at its lower end surface 161b. As a result, the passage groove 173, passage hole 175, and passage groove 174 of the first base member 161 communicate with the passage groove 184 and passage hole 185 of the second base member 162. These passage grooves 173, 174, 184 and passage holes 175, 185 constitute the third passage 191. The third passage 191 is provided in the valve base 152 and penetrates the valve base 152 in the axial direction. The third passage 191 consists of a connecting passage 178 of the first base member 161 and a connecting passage 186 of the second base member 162.

[0070] The communication passage 186 of the second base member 162 has one end that communicates with the communication passage 178 of the first base member 161. When the valve base 152 is inside 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] The valve base 152 has a notch 171 in the first base member 161 and a notch 181 in the second base member 162 that forms a mounting groove 195 (ring housing groove). The mounting groove 195 is provided on the outer circumference 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 mounting groove 195 is recessed inward in the radial direction of the valve base 152 from the outer circumference of the valve base 152. The mounting groove 195 is annular. The mounting groove 195 opens radially outward. Multiple grooves 182 open into the mounting groove 195. The communication passage 178 of the first base member 161 is provided inside the mounting groove 195 in the radial direction of the first base member 161. The connecting passage 186 of the second base member 162 is located inside the radial arrangement groove 195 of the second base member 162.

[0072] The arrangement groove 195 may be located on the outer circumferential side of the first base member 161, specifically 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 located on the outer circumferential side of the second base member 162, specifically 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 located on the outer circumferential side of at least one of the first base member 161 and the second base member 162, specifically on the side of the lower end surface 161b and upper end surface 162a where the first base member 161 and the second base member 162 abut.

[0073] The fitting member 153 is annular in shape. The outer diameter of the fitting member 153 is larger than the outer diameter of the valve base 152. The fitting member 153 is positioned between the notches 171 and 181 when the first base member 161 and the second base member 162 are assembled to the extender 42. This positions the fitting member 153 within the placement groove 195 of the valve base 152. The fitting member 153 is axially movable relative to the valve base 152 within the placement groove 195. The placement 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 interfacing member 197 is provided between the inner circumference of the fitting member 153 and the bottom of the arrangement groove 195. The interfacing member 197 coaxially holds the fitting member 153 with respect to the valve base 152. The interfacing member 197 has an axial passage 196 that penetrates axially. The interfacing member 197 is, for example, cylindrical with multiple grooves formed on its outer circumference that penetrate axially. This interfacing member 197 is press-fitted into the inner circumference of the fitting member 153. In this way, the interfacing member 197 is fixed to the fitting member 153. The multiple grooves formed on the outer circumference of the interfacing member 197 constitute the axial passage 196.

[0075] The third damping valve 154 is a disc valve composed of multiple stacked 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 positioned between the main shaft portion 61 of the extender 42 and the valve base 152. The third damping valve 154 rests on the valve seat 177 of the valve base 152. In other words, the valve base 152 has a valve seat 177 formed on its upper end surface 161a facing the piston 18, on which the third damping valve 154 rests. The outer circumference portion of the third damping valve 154 moves away from the valve seat 177 of the valve base 152, opening the third passage 191. The outer circumference portion of the third damping valve 154 contacts the valve seat 177 of the valve base 152, closing the third passage 191.

[0076] A nut 201 is screwed onto the threaded shaft portion 65 of the extender 42. The second valve assembly 151, which includes the valve base 152 and the third damping valve 154, is attached to the mounting shaft portion 62 of the extender 42 by the nut 201. Therefore, as shown in Figure 2, the second valve assembly 151 is located on the side of the first valve assembly 31 that is located on the piston rod 21, relative to the piston assembly 17. The valve base 152 is fixed to the piston rod 21. As a result, the valve base 152 and the piston rod 21 move together. The valve base 152 and the third damping valve 154 are positioned on the piston rod 21. The sleeve 102 is capable of housing the valve base 152.

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

[0078] From this state, during the compression stroke, the piston rod 21 moves to a second predetermined range that is closer to the base adapter 103 than the first predetermined range. Then, the second valve assembly 151 enters the sleeve 102 from the side of the enlarged diameter portion 112 of the sleeve 102. In other words, the sleeve 102 has an enlarged diameter portion 112 on the side into which 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 enlarged diameter portion 112 of the sleeve 102, it fits the fitting member 153 into the sleeve 102. In the initial stages of this fitting, the fitting member 153 moves upward relative to the arrangement groove 195 of the valve base 152 due to the frictional force with the sleeve 102 it contacts. 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 compression 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 within 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 within the second predetermined range, the second valve assembly 151 moves toward the base adapter 103 together with the piston rod 21, with the axial passage 196 closed as described above. In the upper part of the second predetermined range, the fitting member 153 is positioned at the location of the multiple grooves 116 provided in the sleeve 102, and the oil liquid L flows from the fourth chamber 211 to the fifth chamber 212 through the multiple grooves 116. At this time, as the second valve assembly 151 approaches the base adapter 103, the number of grooves 116 that carry the oil liquid L from the fourth chamber 211 to the fifth chamber 212 decreases, and eventually becomes zero.

[0081] Furthermore, during the compression stroke within the second predetermined range, the second valve assembly 151 moves toward the base adapter 103 while the axial passage 196 is closed as described above. At that time, depending on the piston speed, which is the movement speed of the piston rod 21, piston 18, and valve base 152 relative to the tube 3, the third damping valve 154 opens. As a result, the oil liquid L flows from the fourth chamber 211 to the fifth chamber 212 via the third passage 191. In this way, the third damping valve 154 suppresses an excessive rise in pressure in the fourth chamber 211. The third damping valve 154 is provided in the third passage 191 and suppresses the flow of oil liquid L that occurs during the compression stroke, generating a damping force while allowing the oil liquid 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, generating a higher damping force than the second damping valve 76.

[0082] With the fitting member 153 fitted into the sleeve 102 of the cup 101, the second valve assembly 151 moves together with the piston rod 21 to the side opposite to the base adapter 103. As a result, the fitting member 153 moves downward relative to the arrangement groove 195 of the valve base 152 due to the frictional force with the sleeve 102. Consequently, the upper surface of the fitting member 153 is separated from the valve base 152. This opens the axial passage 196. In the subsequent extension stroke, the fitting member 153, with the axial passage 196 open, is pushed by the valve base 152 and slides inside the sleeve 102 to the side opposite to the base adapter 103. When the second valve assembly 151 moves to the side opposite to the base adapter 103, it allows the oil liquid L to flow from the axial passage 196 through the passage in the groove 182 of the valve base 152 from the fifth chamber 212 to the fourth chamber 211. This reduces the resistance force to the extension movement of the piston rod 21.

[0083] The second valve assembly 151 moves from a state where the fitting member 153 is closer to the base adapter 103 than all the grooves 116 in the sleeve 102 to a predetermined distance away from the base adapter 103 during the extension stroke. As a result, the grooves 116 in the sleeve 102 open into the fourth chamber 211. Then, the oil liquid L flows from the fifth chamber 212 to the fourth chamber 211 through the grooves 116. At this time, the further the second valve assembly 151 moves away from the base adapter 103, the more grooves 116 allow the oil liquid L to flow from the fifth chamber 212 to the fourth chamber 211. This gradually reduces the resistance force to the extension movement of the piston rod 21.

[0084] Next, we will explain the main operation of shock absorber 1.

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

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

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

[0088] "A compression stroke in which the piston rod 21 is in a first predetermined range."

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

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

[0091] "A compression stroke in which the piston rod 21 is in a 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, fitting the fitting member 153 into the sleeve 102. Initially, the fitting member 153 closes the axial passage 196.

[0092] With the axial passage 196 blocked in this manner, the second valve assembly 151 moves toward the base adapter 103. Then, the oil liquid L flows from the fourth chamber 211 to the fifth chamber 212 through the multiple grooves 116 provided in the sleeve 102. At this time, as the second valve assembly 151 approaches the base adapter 103, the number of grooves 116 that allow the oil liquid L to flow from the fourth chamber 211 to the fifth chamber 212 decreases, and eventually becomes zero. As a result, the damping force of the second valve assembly 151 increases in stages, and the resistance force against the compression movement of the piston rod 21 increases in stages. Here, the press-fit shaft 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, as the second valve assembly 151 moves toward the base adapter 103, the third damping valve 154 opens depending on the piston speed. As a result, the oil liquid L flows from the fourth chamber 211 to the fifth chamber 212 via the third passage 191. This suppresses an excessive rise in pressure in the fourth chamber 211.

[0094] "Extension stroke in which the piston rod 21 is in a 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 opposite side from the base adapter 103. Initially, the fitting member 153 opens the axial passage 196.

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

[0096] U.S. Patent No. 9,605,726, mentioned above, discloses a shock absorber that increases damping force when the rod reaches a predetermined limit range during the compression stroke in which the rod is pushed into the cylinder. However, there is a demand to suppress cost increases in shock absorbers. For example, Figure 13 of U.S. Patent No. 9,605,726 discloses a structure in which a tube is connected to a cup, and the cup is connected to a valve assembly. When assembling the shock absorber, an axial force is applied to the tube from the shell. In the structure disclosed in Figure 13 of U.S. Patent No. 9,605,726, the axial force of the tube must be borne by the cup. Therefore, the strength of the cup needs to be increased. As a result, costs increase.

[0097] The shock absorber 1 of the first embodiment comprises 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 inside of the tube 3 forms an inner chamber 6. The first valve assembly 31 is connected to one axial end of the tube 3. The piston assembly 17 divides the inner 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 axial 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 positioned in the second chamber 20 and connected to the piston rod 21, and moves in and out of the cup 101. The cup 101 has a sleeve 102 and a base adapter 103. The sleeve 102 is positioned 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, the shock absorber 1 receives axial force from the crimped portion 35 and bottom portion 12 of the shell 5 via the sealing member 24, rod guide 23, and first valve assembly 31 to the tube 3. In the shock absorber 1, the first valve assembly 31 is connected to one end of the tube 3 in the axial direction. Therefore, the axial force of the tube 3 can be received by the first valve assembly 31. This eliminates the need for the base adapter 103 to receive the axial force of the tube 3. As a result, the strength of the base adapter 103 can be reduced compared to when it receives the axial force of the tube 3. Consequently, the degree of freedom in the material of the base adapter 103 is increased, allowing for the selection of a low-cost material. Therefore, the shock absorber 1 can suppress cost increases. Furthermore, a lightweight material can be selected for the base adapter 103. Therefore, the shock absorber 1 can suppress weight increases.

[0099] The shock absorber 1 has a base adapter 103 that is press-fitted into a sleeve 102. Therefore, the base adapter 103 and the sleeve 102 can be integrated before assembly to the shock absorber 1. Thus, the base adapter 103 and the sleeve 102 can be treated as a single part, making handling easier and assembly to the shock absorber 1 easier.

[0100] The shock absorber 1 has a press-fit portion 122 at one axial end of the base adapter 103 that is press-fitted into the sleeve 102, and a leg portion 123 at the other axial end of the base adapter 103 that is placed on the first valve assembly 31. The leg portion 123 is provided with a communication passage 142 that connects the third chamber 141 between the first valve assembly 31 and the base adapter 103 and the second chamber 20. By providing the communication passage 142 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 the case where the communication passage is provided inside the leg portion 123 in the radial direction of the main plate portion 121.

[0101] The shock absorber 1 has an inner circumference 135 of the leg portion 123 that widens towards the first valve assembly 31. This allows the outer diameter of the disc valve 83 of the first valve assembly 31 to be larger compared to the case where the inner circumference 135 has a constant diameter. Therefore, the variable range of the damping force of the disc valve 83 can be increased. In particular, when the disc valve 83 is a suction valve that does not generate damping force substantially, the damping force can be brought close to zero by increasing the diameter of the disc valve 83.

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

[0103] Japanese Patent 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 an extension rod.

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

[0105] International Publication No. 2017 / 089425 shows a configuration in which the outer perimeter of the ring serves as a passageway.

[0106] Incidentally, in shock absorbers, there is a desire to create a compact structure that increases the damping force near the moving end position of the piston rod.

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

[0108] During the compression stroke, the shock absorber 1 has a valve base 152 and a fitting member 153 that enter the sleeve 102. The frictional force with the sleeve 102 causes the fitting member 153 to move relative to the valve base 152, closing the axial passage 196 between the fitting member 153 and the valve base 152 and generating damping force. The shock absorber 1 is equipped with a third damping valve 154 on the valve base 152. When the hydraulic pressure in the fourth chamber 211 rises above a predetermined pressure during the compression stroke, the third damping valve 154 opens, relieving the hydraulic pressure in the fourth chamber 211 to the fifth chamber 212 via the connecting passages 178 and 186. As a result, the shock absorber 1 can suppress an excessive rise in hydraulic pressure during the compression stroke when the valve base 152 enters the sleeve 102 and generates damping force. Furthermore, during the extension stroke, the shock absorber 1's fitting member 153 moves relative to the valve base 152 due to frictional force with the sleeve 102, opening the axial passage 196 between it and the valve base 152, allowing the oil liquid L to flow smoothly from the fifth chamber 212 to the fourth chamber 211. This facilitates the movement of the valve base 152 and the fitting member 153 within the sleeve 102 during the extension stroke.

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

[0110] The shock absorber 1 has a fitting member 153 made of brass or glass fiber reinforced plastic.

[0111] The shock absorber 1 has a sleeve 102 with an enlarged diameter portion 112 on the side into which the second base member 162 is inserted. This allows the shock absorber 1 to smoothly increase the damping force when increasing the damping force near the compressed end position of the piston rod 21.

[0112] [Second Embodiment] Next, the shock absorber of the second embodiment will be described, mainly based on Figure 4, focusing on the differences from the first embodiment. Parts common to both the first and second embodiments will be represented by the same designation and reference numerals. Furthermore, the numeral 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 which is partially different from the cup 101, in place of the cup 101. The cup 101A has a sleeve 102A (second tube) which is partially different from the sleeve 102, in place of the sleeve 102. The sleeve 102A has a main body 111A which is partially different from the main body 111, in place of the main body 111.

[0114] Like sleeve 102, sleeve 102A has multiple grooves 116 extending in the axial direction of sleeve 102A on the inner circumference of one axial end of sleeve 102A. Sleeve 102A also has grooves 116A extending in the axial direction of sleeve 102A on the inner circumference of the other axial end of sleeve 102A. Grooves 116A are provided on the inner circumference of the lower end of sleeve 102A. Grooves 116A are recessed outward in the radial direction of sleeve 102A from the inner circumferential surface of sleeve 102A. Multiple grooves 116A are provided on sleeve 102A at equal intervals in the circumferential direction of sleeve 102A. Multiple grooves 116A have the same length from the lower end of sleeve 102A. In other words, multiple grooves 116A have the same length in the axial direction of 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 comes into contact with 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 where 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. In the initial stages 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 closed in this manner, the second valve assembly 151 moves toward the base adapter 103 together with the piston rod 21. In the upper part of the second predetermined range, the fitting member 153 is positioned at the location of the multiple grooves 116 provided in the sleeve 102A, and the oil liquid L flows from the fourth chamber 211 to the fifth chamber 212 through the multiple grooves 116. At this time, as the second valve assembly 151 approaches the base adapter 103, the number of grooves 116 that carry the oil liquid L from the fourth chamber 211 to the fifth chamber 212 decreases, and eventually becomes zero.

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

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

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

[0121] When the fitting member 153 of the second valve assembly 151 is positioned on the opposite side from the base adapter 103 from all the grooves 116A in the sleeve 102A, the oil liquid L flows from the fifth chamber 212 to the fourth chamber 211 only through the passage 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 circumference 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 circumference of the other axial end of the sleeve 102A. As a result, at the beginning of the compression stroke within the second predetermined range, the rate of change of the damping force becomes gradual due to the groove 116 at the upper end. Since there is no groove in the middle of the axial direction of the sleeve 102A, the damping force becomes larger at the middle position of the compression stroke within 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 act as a relief.

[0123] In this embodiment, a hydraulic shock absorber was shown as an example of the shock absorber 1,1A, but the above structure can also be used for shock absorbers that use water or air as the working fluid.

[0124] [Third Embodiment] Next, the shock absorber of the third embodiment will be described, mainly based on Figures 5 and 6, focusing on the differences from the first embodiment. Parts common to both the first embodiment and the third embodiment will be represented by the same designation and reference numerals. Furthermore, the numeral CL shown in each figure indicates the central axis of the shock absorber.

[0125] As shown in Figure 5, the shock absorber 1B of the third embodiment does not have the cup 101 that the shock absorber 1 of the first embodiment had. The shock absorber 1B is equipped with a rod guide 23B, which is partially different from the rod guide 23, in place 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 outer diameter of the intermediate-diameter portion 29B is smaller than the outer diameter of the large-diameter portion 28. The outer diameter of the small-diameter portion 231 is smaller than the outer diameter of the intermediate-diameter portion 29B. The intermediate-diameter portion 29B of the rod guide 23B is located below the large-diameter portion 28. The small-diameter portion 231 of the rod guide 23B is located below the intermediate-diameter portion 29B. The rod guide 23B fits into the upper inner circumference of the shell 5 at its upper large-diameter portion 28. The rod guide 23B fits into the inner circumference of the upper end of the tube 3 at its intermediate-diameter portion 29B. At this 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 is equipped with 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 positioned radially inward of the tube 3B. The inner circumference of the upper end of the sleeve 102B fits into the smaller 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 positioned in the first chamber 19 with a radial gap between it and the tube 3.

[0128] As shown in Figure 6, the sleeve 102B has a main body 111B and an enlarged diameter portion 112B. The main body 111B is cylindrical and extends from the upper end to the lower end of the sleeve 102B. The enlarged diameter portion 112B is located at the lower end of the sleeve 102B. The inner diameter of the enlarged diameter portion 112B increases as it approaches the lower end. The outer diameter of the enlarged diameter portion 112B increases as it approaches the lower end. The enlarged diameter portion 112B expands in the axial direction of the sleeve 102B, away from the main body 111B.

[0129] The sleeve 102B has a groove 116B extending in the axial direction of the sleeve 102B on the inner circumference of one axial end of the sleeve 102B. The groove 116B is located on the inner circumference of the lower end of the sleeve 102B. The groove 116B is recessed outward in the radial direction of the sleeve 102B from the inner circumferential surface of the sleeve 102B. The groove 116B extends from the enlarged diameter portion 112B to the lower part of the main body portion 111B. Multiple grooves 116B are provided on the sleeve 102B at equal intervals in the circumferential direction of the sleeve 102B. Each of the multiple grooves 116B has a different length from the lower end of the sleeve 102B. In other words, each of the multiple grooves 116B has a different length in the axial direction of the sleeve 102B.

[0130] Shock absorber 1B replaces piston rod 21 with piston rod 21B, which is partially different from piston rod 21. Piston rod 21B consists of a rod body 41B and an extender 42B.

[0131] The rod body 41B has a main shaft portion 51B and a mounting shaft portion 52B. Both the main shaft portion 51B and the mounting shaft portion 52B are 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 located inside the tube 3. As shown in Figure 5, the piston rod 21B has the main shaft portion 51B of the rod body 41B sliding along the axial directions of the rod guide 23B and the seal member 24, respectively.

[0132] As shown in Figure 6, the mounting shaft portion 52B has a threaded shaft portion 54B at the end opposite to the main shaft portion 51B in the axial direction. The threaded shaft portion 54B has male threads formed on its outer circumference. The mounting shaft portion 52B has a fitting shaft portion 55B in the portion between the main shaft portion 51B and the threaded shaft portion 54B in the axial direction. The outer surface of the fitting shaft portion 55B is cylindrical.

[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, extending from the end opposite to 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 mounting shaft portion 62B has a threaded shaft portion 65B at the end opposite to the base shaft portion 61B in the axial direction. The threaded shaft portion 65B has male threads formed on its outer circumference. The mounting shaft portion 62B has a fitting shaft portion 66B in the portion between the base shaft portion 61B and the threaded shaft portion 65B in the axial direction. The outer surface of the fitting shaft portion 66B is cylindrical.

[0136] The rod body 41B is screwed into the threaded hole 64B of the extender 42B by screwing its threaded shaft portion 54B into the threaded hole 64B of the extender 42B. This connects the rod body 41B and the extender 42B with their central axes aligned. This forms the piston rod 21B. The entire extender 42B is placed inside the tube 3. The part of the rod body 41B that connects to the extender 42B is placed inside the tube 3, and the part opposite to the extender 42B extends outward from the cylinder 2.

[0137] A piston assembly 17, consisting 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 by 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 arranged on the piston rod 21B. The piston assembly 17, consisting of the piston 18, the first damping valve 75, and the second damping valve 76, is located at the tip end of the piston rod 21B.

[0138] The shock absorber 1B has a second valve assembly 151B. The second valve assembly 151B is located 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 body 41B. The second valve assembly 151B enters the sleeve 102B from below through the opening at the lower end of the sleeve 102B and exits downward.

[0139] The second valve assembly 151B includes 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 constructed by combining the first base member 161B and the second base member 162B. The first base member 161B constitutes the lower part of the valve base 152B. The second base member 162B constitutes the upper part of the valve base 152B.

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

[0142] The passage groove 173B is formed at the lower end 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 is an annular shape that surrounds the through hole 172B radially outward. The passage groove 173B opens downward.

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

[0144] The passage groove 174B is formed at the upper end 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 is an annular shape that surrounds the through hole 172B radially outward. The passage groove 174B opens upward.

[0145] The passage hole 175B is formed in the axial middle portion 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 opens at the bottom of the passage groove 174B. Multiple passage holes 175B are formed in the first base member 161B at intervals in the circumferential direction of the first base member 161B.

[0146] The first base member 161B has a passage in the passage groove 173B, passages in the multiple passage holes 175B, and passages in the passage groove 174B that together constitute a connecting passage 178B (first connecting passage) that penetrates the first base member 161B in the axial direction. The first base member 161B has the connecting passage 178B on its interior or inner circumferential surface, rather than on its outer circumferential surface. Specifically, the first base member 161B has the connecting passage 178B on its interior. The first base member 161B may also have a connecting passage 178B on its inner circumferential surface, i.e., between itself and the fitting shaft portion 55B of the rod body 41B.

[0147] The second base member 162B is annular. The second base member 162B has a notch 181B formed on its outer circumference from the axial middle portion to the lower part. The notch 181B is formed around the entire circumference of the second base member 162B. The notch 181B is annular.

[0148] The second base member 162B has a groove 182B formed at the lower part 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 from the second base member 162. The groove 182B opens into the notch 181. Multiple grooves 182B are formed on 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. The fitting shaft portion 55B of the rod body 41B is fitted into the through hole 183B of the second base member 162B. The second base member 162B abuts against the end face of the main shaft portion 51B of the rod body 41B on the mounting shaft portion 52B side at its upper surface 162Ba. The second base member 162B is provided with 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 is provided with a passage groove 235 outside the through hole 183B in the radial direction of the second base member 162B.

[0150] The passage groove 235 is formed at the upper end 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 is annular in shape and surrounds the through hole 183B radially outward. The passage groove 235 opens upward. The passage groove 235 opens radially outward from the main shaft portion 51B of the rod body 41B that 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 to the lower end surface 162Bb of the second base member 162B. Multiple passage holes 185B are formed in the second base member 162B at intervals in the circumferential direction of the second base member 162B.

[0152] The second base member 162B has a passage in the passage groove 235 and passages in the multiple passage holes 185B that constitute a connecting passage 186B (second connecting passage) that penetrates the second base member 162B in the axial direction. The second base member 162B has the connecting passage 186B on the inside or inner circumferential surface side, rather than on the outer circumferential surface side. Specifically, the second base member 162B has the connecting passage 186B on its inside. The second base member 162B may also have a connecting passage 186B on its inner circumferential surface side, i.e., between it and the fitting shaft portion 55B of the rod body 41B.

[0153] When the first base member 161B is fitted onto the fitting shaft portion 55B of the rod body 41B, its upper end surface 161Bb abuts against the lower end surface 162Bb of the second base member 162B. As a result, the passage groove 173B, passage hole 175B, and passage groove 174B of the first base member 161B communicate with the passage hole 185B and passage groove 235 of the second base member 162B. These passage grooves 173B, 174B, 235 and passage holes 175B, 185B constitute the third passage 191B. The third passage 191B is provided in the valve base 152B and penetrates the valve base 152B in the axial direction. The third passage 191B consists of a connecting passage 178B of the first base member 161B and a connecting passage 186B of the second base member 162B.

[0154] The communication passage 186B of the second base member 162B communicates with the communication passage 178B of the first base member 161B at one end. When the valve base 152B is inside 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] The valve base 152B has a notch 181B in the second base member 162B which forms a groove 195B (ring housing groove) with the first base member 161B. The groove 195B is located on the outer circumference side of the second base member 162B, and is provided on the lower end surface 162Bb side of the second base member 162B that abuts against the upper end surface 161Bb of the first base member 161B. The groove 195B is recessed inward in the radial direction of the valve base 152B from the outer circumference surface of the valve base 152B. The groove 195B is annular. The groove 195B opens radially outward. The communication passage 178B of the first base member 161B is located inside the groove 195B in the radial direction of the first base member 161B. The connecting passage 186B of the second base member 162B is located inside the radial arrangement groove 195B 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 lower end surface 162Bb sides where the first base member 161B and the second base member 162B abut. 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 abuts against 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 lower end surface 162Bb sides where the first base member 161B and the second base member 162B abut.

[0157] The first fitting member 153B is annular in shape. The outer diameter of the first fitting member 153B is larger than the outer diameter of the valve base 152B. The first fitting member 153B is positioned between the notch 181B of the first base member 161B and the second base member 162B when the first base member 161B and the second base member 162B are assembled to the rod body 41B. As a result, the first fitting member 153B is positioned 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, meaning it is not a continuous annular shape. This is because the first fitting member 153B expands in diameter due to internal pressure and slides against the main body 111B of the sleeve 102B.

[0158] The second fitting member 233 is annular in shape. The outer diameter of the second fitting member 233 is larger than the outer diameter of the valve base 152B. The second fitting member 233 is positioned between the notch 181B of the first base member 161B and the second base member 162B when the first base member 161B and the second base member 162B are assembled to the rod body 41B. As a result, the second fitting member 233 is positioned within the arrangement groove 195B of the valve base 152B. At that time, the second fitting member 233 is positioned 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, or steel, brass, etc. 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 slides against the main body 111B of the sleeve 102B. The second fitting member 233 does not have a slit like the first fitting member 153B and is annular in shape. The second fitting member 233 plays a role in preventing oil from flowing from the high-pressure side to the low-pressure side through the slit of the first fitting member 153B. Also, 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 circumference of the first fitting member 153B and the bottom of the arrangement groove 195B. A gap is also provided between the inner circumference of the second fitting member 233 and the bottom of the arrangement groove 195B. These gaps form an axial passage 196B that penetrates 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 composed of multiple stacked annular discs. The fitting shaft portion 55B of the rod body 41B is fitted into the radially inner side of the third damping valve 154B. The third damping valve 154B is attached to the rod body 41B by an extender 42B which is screwed into the threaded shaft portion 54B of the rod body 41B through a threaded hole 64B.

[0161] The third damping valve 154B rests on the valve seat 177B of the valve base 152B. In other words, the valve base 152B has a valve seat 177B formed on one end face facing the piston 18 on which the third damping valve 154B rests. The outer circumference portion of the third damping valve 154B moves away from the valve seat 177B of the valve base 152B, opening the third passage 191B. The outer circumference portion of the third damping valve 154B contacts the valve seat 177B of the valve base 152B, closing the third passage 191B.

[0162] As shown in Figure 5, the second valve assembly 151B is located on the opposite side of the piston assembly 17 of the piston rod 21B 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 positioned on the piston rod 21B. The sleeve 102B is capable of accommodating the valve base 152B.

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

[0164] From this state, during the extension stroke, the piston rod 21B moves to a fourth predetermined range that is closer to the rod guide 23B than the third predetermined range. Then, the second valve assembly 151B enters the sleeve 102B from the side of the enlarged diameter portion 112B of the sleeve 102B. In other words, the sleeve 102B has an enlarged diameter portion 112B on the side into which 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 enlarged diameter portion 112B of the sleeve 102B, it fits the first fitting member 153B and the second fitting member 233 into the sleeve 102B. In the initial stages of this fitting, the frictional force with the contacting sleeve 102B causes the first fitting member 153B to compress and deform the second fitting member 233, while moving downward relative to the arrangement groove 195B of the valve base 152B. As a result, the first fitting member 153B presses the lower surface of the second fitting member 233 against the valve base 152B. This closes the axial passage 196B with the second fitting member 233. In the subsequent extension stroke, the first fitting member 153B, while keeping the axial passage 196B closed by the second fitting member 233, is pushed by the valve base 152B via the second fitting member 233 and slides inside the sleeve 102B towards 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 within 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 within the fourth predetermined range, the second valve assembly 151B moves toward the rod guide 23B together with the piston rod 21B while the axial passage 196B is closed as described above. In the lower part of the fourth predetermined range, the first fitting member 153B is located in the position of the multiple grooves 116B provided in the sleeve 102B, and the oil liquid L flows from the third chamber 241 to the fourth chamber 242 through the multiple grooves 116B. At this time, as the second valve assembly 151B approaches the rod guide 23B, the number of grooves 116B that carry the oil liquid L from the third chamber 241 to the fourth chamber 242 decreases, and eventually becomes 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, depending on the piston speed, which is the movement speed of the piston rod 21B, piston 18, and valve base 152B relative to the tube 3, the third damping valve 154B opens. As a result, the oil liquid L flows from the third chamber 241 to the fourth chamber 242 via the third passage 191B. In this way, the third damping valve 154B suppresses an excessive rise in pressure in the third chamber 241. The third damping valve 154B is provided in the third passage 191B and generates a damping force by suppressing the flow of oil liquid L that occurs during the extension stroke, while allowing the oil liquid 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, generating a higher damping force than the first damping valve 75.

[0168] With the first fitting member 153B and the second fitting member 233 fitted into the sleeve 102B, during the compression stroke, the second valve assembly 151B moves together with the piston rod 21B to the side opposite to the rod guide 23B. As a result, the first fitting member 153B and the second fitting member 233 move upward relative to the arrangement groove 195B of the valve base 152B due to the frictional force with the sleeve 102B. Consequently, the lower surface of the second fitting member 233 is separated from the valve base 152B. This opens the axial passage 196B. In the subsequent compression stroke, the first fitting member 153B and the second fitting member 233, with the axial passage 196B open, are pushed by the valve base 152B and slide within the sleeve 102B to the side opposite to the rod guide 23B. As the second valve assembly 151B moves away from the rod guide 23B, it allows the oil L to flow from the fourth chamber 242 to the third chamber 241 through the axial passage 196B and the passages within the multiple grooves 182B. This reduces the resistance force to the compression movement of the piston rod 21B.

[0169] In the compression stroke, the second valve assembly 151B moves from a state where the first fitting member 153B and the second fitting member 233 are on the rod guide 23B side of all the grooves 116B in the sleeve 102B to a predetermined distance away from the rod guide 23B. As a result, the grooves 116B provided in the sleeve 102B open into the third chamber 241. Then, oil L flows from the fourth chamber 242 to the third chamber 241 via the grooves 116B. At this time, the further the second valve assembly 151B moves away from the rod guide 23B, the more grooves 116B allow oil L to flow from the fourth chamber 242 to the third chamber 241. This gradually reduces the resistance force to the compression movement of the piston rod 21B.

[0170] Next, we will explain the main operation of shock absorber 1B.

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

[0172] {Fifth region where 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 through the first passage 71 in the piston assembly 17 to the second chamber 20 through a fixed orifice (not shown) between the first damping valve 75 and the piston 18. Therefore, in the fifth region of the extension stroke, a damping force with orifice characteristics is generated.

[0173] {Sixth region where 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 into the second chamber 20 through the first passage 71 in the piston assembly 17, opening the first damping valve 75. Therefore, in the sixth region of the extension stroke, a damping force characteristic of the valve is generated by the first damping valve 75.

[0174] "The compression stroke in which the piston rod 21B is in the third predetermined range."

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

[0176] {The eighth region where the piston speed is above the fourth predetermined value} In the eighth region of this compression stroke, the oil L from the second chamber 20 flows into the first chamber 19 through the second passage 72 in the piston assembly 17, opening the second damping valve 76. Therefore, in the eighth region of the compression stroke, a damping force characteristic of the valve is generated by the second damping valve 76.

[0177] "Extension stroke in which the piston rod 21B is within 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, fitting the first fitting member 153B and the second fitting member 233 into the sleeve 102B. Initially, the first fitting member 153B and the second fitting member 233 close the axial passage 196B.

[0178] With the axial passage 196B blocked in this manner, the second valve assembly 151B moves toward the rod guide 23B. Then, the oil liquid L flows from the third chamber 241 to the fourth chamber 242 through the multiple grooves 116B provided in the sleeve 102B. At this time, as the second valve assembly 151B approaches the rod guide 23B, the number of grooves 116B that allow the oil liquid L to flow from the third chamber 241 to the fourth chamber 242 decreases, and eventually becomes zero. As a result, the damping force of the second valve assembly 151B increases in stages, and the resistance force against the extension movement of the piston rod 21B increases in stages. Here, the press-fit shaft 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] Here, as the second valve assembly 151B moves toward the rod guide 23B, the third damping valve 154B opens depending on the piston speed. As a result, the oil liquid L flows from the third chamber 241 to the fourth chamber 242 via the third passage 191B. This suppresses an excessive rise in pressure in the third chamber 241.

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

[0181] With the axial passage 196B and the passages within the multiple grooves 182B open in this manner, the second valve assembly 151B moves to the side opposite to the rod guide 23B. Then, the oil liquid L flows from the fourth chamber 242 to the third chamber 241 through the axial passage 196B and the passages within the multiple grooves 182B. When the first fitting member 153B of the second valve assembly 151B moves from a state where it is on the rod guide 23B side of all the grooves 116B provided in the sleeve 102B, and passes through the position of the grooves 116B provided in the sleeve 102B, the oil liquid L flows from the fourth chamber 242 to the third chamber 241 through the grooves 116B. At that time, the further the second valve assembly 151B moves away from the rod guide 23B, the more grooves 116B among the multiple grooves 116B that allow the oil liquid L to flow from the fourth chamber 242 to the third chamber 241. In other words, the damping force of the second valve assembly 151B decreases as it moves further away from the rod guide 23B, and the resistance to the compression movement of the piston rod 21B decreases.

[0182] The shock absorber 1B includes a tube 3, a piston rod 21B disposed inside the tube 3, a piston 18, a first damping valve 75 and a second damping valve 76 disposed on the piston rod 21B, a valve base 152B and a third damping valve 154B disposed on the piston rod 21B, and a sleeve 102B capable of housing the valve base 152B. The valve base 152B is constructed by combining a first base member 161B and a second base member 162B. The first base member 161B has a communication passage 178B inside. The first base member 161B has a valve seat 177B formed on its lower end surface 161Ba facing the piston 18, on which the third damping valve 154B rests. The second base member 162B has a communication passage 186B that communicates with the communication passage 178B and the inside of the sleeve 102B. On the outer circumference 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, there is an arrangement groove 195B for accommodating the first fitting member 153B and the second fitting member 233.

[0183] During the extension stroke, the shock absorber 1B has a valve base 152B, a first fitting member 153B, and a second fitting member 233 that enter the sleeve 102B. The frictional force 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 damping force. The shock absorber 1B also has a third damping valve 154B on the valve base 152B. When the hydraulic pressure in the third chamber 241 exceeds a predetermined pressure during the extension stroke, the third damping valve 154B opens, relieving the hydraulic pressure in the third chamber 241 to the fourth chamber 242 via the connecting passages 178B and 186B. This allows the shock absorber 1B to suppress an excessive rise in hydraulic pressure during the extension stroke when the valve base 152B enters the sleeve 102B and generates damping force. Furthermore, during the compression stroke, the shock absorber 1B's first fitting member 153B and second fitting member 233, housed in the arrangement groove 195B of the valve base 152B, move relative to the valve base 152B due to frictional force with the sleeve 102B, opening the axial passage 196B between them and the valve base 152B, thereby allowing the oil liquid L to flow smoothly from the fourth chamber 242 to the third chamber 241. This facilitates the movement of the valve base 152B, the first fitting member 153B, and the second fitting member 233 within the sleeve 102B during the compression stroke.

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

[0185] The shock absorber 1B has a first fitting member 153B made of brass or glass fiber reinforced plastic.

[0186] The shock absorber 1B has a sleeve 102B with an enlarged diameter portion 112B on the side into which the second base member 162B is inserted. This allows the shock absorber 1B to smoothly increase the damping force when increasing the damping force near the extension end position of the piston rod 21B.

[0187] In the shock absorber 1B of the third embodiment, the same modifications to sleeve 102B as to sleeve 102A may be applied to sleeve 102B.

[0188] According to the shock absorber in the above-described embodiment of this disclosure, it is possible to suppress cost increases. [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...Enlarged diameter section, 116 116A…groove, 122…press-fit portion, 123…leg portion, 135…inner circumference portion, 141…third chamber, 142…connecting 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 face (one end face), 161b…lower end face (contact surface), 161Ba…lower end face (one end face), 161Bb ...Upper end surface (contact surface), 162, 162B...Second base member (second piston member), 162a...Upper end surface (contact surface), 162Bb...Lower end surface (contact surface), 177, 177B...Valve seat (seat), 178, 178B...Connecting passage (first connecting passage), 186, 186B...Connecting passage (second connecting passage), 195, 195B...Placement groove, 233...Second fitting member (ring).

Claims

1. A tube with the inner side forming the inner chamber, A first valve assembly connected to one end of the tube in the axial direction, A piston assembly that divides the aforementioned internal chamber into a first chamber and a second chamber, The piston assembly is connected to the intermediate position in the axial direction and includes a piston rod that extends from the tube through the first chamber, The cup provided in the second chamber, A second valve assembly is positioned in the second chamber and connected to the piston rod, and moves in and out of the cup, Equipped with, The aforementioned cup, The second chamber comprises a sleeve positioned in the second chamber with a radial gap between it and the tube, and a base adapter that is press-fitted and fixed to the sleeve and provided between the sleeve and the first valve assembly. A third chamber is provided between the first valve assembly and the base adapter. A press-fit portion is provided at one end of the base adapter in the axial direction, which is press-fitted into the sleeve. A leg portion is provided at the other axial end of the base adapter, which is mounted on the first valve assembly. A connecting passage is provided in the leg portion that connects the second chamber and the third chamber. A shock absorber in which the inner circumference of the leg portion widens towards the first valve assembly.

2. A tube whose inner side is an inner chamber, A first valve assembly connected to one end of the tube in the axial direction, A piston assembly that divides the aforementioned internal chamber into a first chamber and a second chamber, The piston assembly is connected to the intermediate position in the axial direction and includes a piston rod that extends from the tube through the first chamber, The cup provided in the second chamber, A second valve assembly is positioned in the second chamber and connected to the piston rod, and moves in and out of the cup, Equipped with, The aforementioned cup, The second chamber comprises a sleeve positioned in the second chamber with a radial gap between it and the tube, and a base adapter that is press-fitted and fixed to the sleeve and provided between the sleeve and the first valve assembly. A third chamber is provided between the first valve assembly and the base adapter. A press-fit portion is provided at one end of the base adapter in the axial direction, which is press-fitted into the sleeve. A leg portion is provided at the other axial end of the base adapter, which is mounted on the first valve assembly. A connecting passage is provided in the leg portion that connects the second chamber and the third chamber. A shock absorber having a groove extending in the axial direction of the sleeve in a first inner circumference portion on one end of the sleeve in the axial direction and a second inner circumference portion on the other end of the sleeve in the axial direction.

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