Cylinder device

Abstract

This cylinder device has: a first piston that is slidably fitted into a first cylinder; a piston rod that is connected to the first piston; and a stopper mechanism that operates when the first piston reaches a prescribed position on a first end section side in one axial end of the first cylinder in an expansion stroke or a contraction stroke. The stopper mechanism has a second cylinder that is provided on the first end section side of the first cylinder, and a second piston that moves along with the movement of the piston rod and is provided in a manner so as to be able to be fitted into the second cylinder. One end of the second piston on a first end section side is in contact with a rod flange part between a rod first outer diameter part of the piston rod and a rod second outer diameter part which is on the side opposite from a first end section of the rod first outer diameter part and is smaller than the rod first outer diameter part, and the other end of the second piston on the side opposite from the first end section is biased by a biasing part that biases the second piston toward the rod flange part.

Description

Cylinder Device

[0001] This application claims priority to U.S. Application No. 18 / 584,327, filed February 22, 2024, the contents of which are incorporated herein by reference.

[0002] There is a cylinder device that increases the damping force when the piston rod reaches a predetermined range on the limit side during the extension stroke in which the piston rod extends from the cylinder or during the compression stroke in which the piston rod is pushed into the cylinder (see, for example, Patent Documents 1 and 2 listed below).

[0003] Japanese Patent Application Publication No. 2015-161404

[0004] However, there is a demand for improved durability in cylinder devices. Therefore, an object of the present invention is to provide a cylinder device that can improve durability.

[0005] In order to achieve the above object, one aspect of the cylinder device of the present invention includes a first cylinder in which a working fluid is sealed, a first piston slidably fitted within the first cylinder to define the interior of the first cylinder, a piston rod connected to the first piston, and a stopper mechanism that is activated when the first piston reaches a predetermined position on a first end side of one axial end of the first cylinder during an extension stroke or a compression stroke, wherein the stopper mechanism includes a second cylinder provided on the first end side of the first cylinder and having a smaller diameter than the first cylinder, and a second piston that moves with movement of the piston rod and is provided so as to be fittable within the second cylinder, wherein one end of the second piston on the first end side abuts against a rod flange portion between a rod first outer diameter portion of the piston rod and a rod second outer diameter portion opposite the first end of the rod first outer diameter portion and having a smaller diameter than the rod first outer diameter portion, and the other end of the second piston opposite the first end is biased by a biasing portion that biases the second piston toward the rod flange portion.

[0006] According to the above aspect of the present invention, it is possible to improve durability.

[0007] 11 ; 12 ; 13 ; 14 ; 15 ; 16 ; 17 ; 18 ; 19 ; 20 ; 21 ; 22 ; 23 ; 24 ; 25 ; 26 ; 27 ; 28 ; 29 ; 30 ; 31 ; 32 ; 33 ; 34 ; 35 ; 36 ; 37 ; 38 ; 39 ; 40 ; 41 ; 42 ; 43 ; 44 ; 45 ; 46 ; 47 ; 48 ; 49 ; 50 ; 51 ; 52 ; 53 ; 54 ; 55 ; 56 ; 57 ; 58 ; 59 ; 60 ; 61 ; 62 ; 63 ; 64 ; 65 ; 66 ; 67 ; 68 ; 69 ; 70 ; 71 ; 72 ; 73 ; 74 ; 75 ; 76 ; 77 ; 78 ; 79 ; 80 ; 81 ; 82 ; 83 ; 84 ; 85 ; 86 ; 87 ; 88 ; 89 ; 90 ; 91 ; 92 ; 93 ; 94 ; 95 ; 96 ; 97 ; 98 ; 99 ; 100 ; 101 ; 102 ; 103 ; 104 ; 105 ; 106 ; 107 ; 108 ; 109 ; 110 ;

[0008] A cylinder device according to an embodiment of the present invention will be described with reference to the drawings. For ease of explanation, the upper side in Figures 1, 2, 4, 6, 7, 9, 11, 13, and 15 will be referred to as "upper" and the lower side in the drawings will be referred to as "lower."

[0009] First Embodiment A cylinder device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG.

[0010] As shown in Figure 1, the cylinder device 1 of the first embodiment is a twin-cylinder hydraulic shock absorber. The cylinder device 1 is used in a vehicle, specifically, a suspension device for an automobile. The cylinder device 1 includes a cylinder 2. The cylinder 2 has a first cylinder 3, a second cylinder 4, and a shell 5. The first cylinder 3 and the second cylinder 4 are cylindrical. The shell 5 is cylindrical and has a bottom.

[0011] The outer diameter of the second cylinder 4 is smaller than the inner diameter of the first cylinder 3. The second cylinder 4 is disposed radially inside a first end 3a, which is one axial end of the first cylinder 3 and the upper end of the first cylinder 3. The central axis of the first cylinder 3 and the central axis of the second cylinder 4 coincide with each other.

[0012] The inner diameter of the shell 5 is larger than the outer diameter of the first cylinder 3. The first cylinder 3 is disposed radially inside the shell 5. The central axis of the first cylinder 3 and the central axis of the shell 5 coincide. The inside of the first cylinder 3 forms an inner chamber 6. The space between the first cylinder 3 and the shell 5 forms a reservoir chamber 7. The second cylinder 4 is provided in the inner chamber 6.

[0013] The shell 5 has a cylindrical body 11 having an opening 10 at its upper end, which is one end in the axial direction, and a circular bottom (not shown) that closes the lower end, which is the other end of the body 11 opposite the opening 10. The opening 10 of the shell 5 is located above the upper end, which is one end in the axial direction, of the first cylinder 3.

[0014] The cylinder device 1 includes a first piston assembly 17. The first piston assembly 17 is disposed in a first cylinder 3 of the cylinder 2. The first piston assembly 17 includes a first piston 18. The first piston 18 of the first piston assembly 17 is slidably fitted in the first cylinder 3. The first piston 18 divides the inner chamber 6 of the first cylinder 3 into two chambers: an upper first chamber 19 on one side and a lower second chamber 20 on the other side. In the axial direction of the first cylinder 3, the first chamber 19 is closer to the opening 10 of the shell 5 than the first piston 18. In the axial direction of the first cylinder 3, the second chamber 20 is on the opposite side of the opening 10 of the shell 5 than the first piston 18. In the cylinder 2, oil L as a working fluid is sealed in the inner chamber 6 of the first cylinder 3. In the cylinder 2, oil L and gas G as working fluids are sealed in a reservoir chamber 7 between the first cylinder 3 and the shell 5.

[0015] The cylinder device 1 includes a piston rod 21 connected to a first piston assembly 17 including a first piston 18. One axial side of the piston rod 21 is inserted into the shell 5 and the first cylinder 3 through an opening 10 at the upper end, which is one axial end of the shell 5, and a portion of the other axial side extends from the shell 5 and the first cylinder 3 to the outside.

[0016] The piston rod 21 has a main shaft portion 25 on its upper side extending outward from the shell 5 and the first cylinder 3, a first mounting shaft portion 26 below the main shaft portion 25, and a second mounting shaft portion 27 below the first mounting shaft portion 26. One axial end of the piston rod 21, i.e., the lower part of the main shaft portion 25, the first mounting shaft portion 26, and the second mounting shaft portion 27, is disposed in the inner chamber 6 of the first cylinder 3 of the cylinder 2. The other axial end of the piston rod 21, i.e., the upper part of the main shaft portion 25, is disposed outside the cylinder 2. In other words, the piston rod 21 has, in order from the upper end side in the axial direction of the first cylinder 3 where the second cylinder 4 is provided, the main shaft portion 25, the first mounting shaft portion 26, and the second mounting shaft portion 27.

[0017] The radially outer portion of the main shaft portion 25 is a rod first outer diameter portion 31 whose outer circumferential surface is cylindrical.

[0018] The radially outer portion of the first mounting shaft portion 26 constitutes a rod second outer diameter portion 32. The outer diameter of the rod second outer diameter portion 32 is smaller than the outer diameter of the rod first outer diameter portion 31. As a result, the piston rod 21 has a first rod flange portion 33 (rod flange portion) between the rod first outer diameter portion 31 and the rod second outer diameter portion 32, which has a flat end surface that faces downward and extends perpendicular to the central axis of the piston rod 21.

[0019] The rod second outer diameter portion 32 of the first mounting shaft portion 26 has a first fitting portion 41 with a cylindrical outer circumferential surface at its end axially adjacent to the main shaft portion 25, and a first male thread portion 42 (biasing portion, screw) on the axial opposite side of the first fitting portion 41 from the main shaft portion 25. The rod second outer diameter portion 32 has an extension portion 44 with a cylindrical outer circumferential surface on the axial opposite side of the first male thread portion 42 from the first fitting portion 41. The first male thread portion 42 has a maximum thread diameter equal to or smaller than the outer diameter of the first fitting portion 41. The extension portion 44 has an outer diameter equal to or smaller than the thread root diameter equal to or smaller than the minimum diameter of the first male thread portion 42. The first rod flange portion 33 is provided between the rod first outer diameter portion 31 and the first fitting portion 41 of the rod second outer diameter portion 32.

[0020] The radially outer portion of the second mounting shaft portion 27 constitutes a rod third outer diameter portion 46. The outer diameter of the rod third outer diameter portion 46 is smaller than the outer diameter of the extension portion 44. As a result, the piston rod 21 has a second rod flange portion 47 between the first mounting shaft portion 26 and the second mounting shaft portion 27, the second rod flange portion 47 having a flat end surface that faces downward and extends perpendicular to the central axis of the piston rod 21.

[0021] The rod third outer diameter portion 46 of the second mounting shaft portion 27 has a second fitting portion 48 with a cylindrical outer peripheral surface on the axial side facing the first mounting shaft portion 26, and a second male thread portion 49 on the radially outer side opposite the first mounting shaft portion 26. The second male thread portion 49 has a maximum thread diameter that is equal to or smaller than the outer diameter of the second fitting portion 48. The second rod flange portion 47 is provided between the extension portion 44 of the rod second outer diameter portion 32 and the second fitting portion 48 of the rod third outer diameter portion 46.

[0022] The piston rod 21 is seamlessly formed from a single material into the above-described shape, and therefore the first rod outer diameter portion 31, the second rod outer diameter portion 32, and the third rod outer diameter portion 46 are integrally formed.

[0023] The first piston assembly 17 is attached to the second mounting shaft portion 27 of the piston rod 21. The piston rod 21 is connected to the first piston assembly 17 and passes through the first chamber 19 to extend out of the first cylinder 3, the second cylinder 4, and the shell 5, i.e., the cylinder 2. The first piston assembly 17 divides the inner chamber 6 into the first chamber 19 on the main shaft portion 25 and first mounting shaft portion 26 side in the axial direction of the piston rod 21, and the second chamber 20 on the opposite side to the main shaft portion 25 and first mounting shaft portion 26.

[0024] The cylinder device 1 is connected to the vehicle body with the portion of the piston rod 21 extending from the cylinder 2 disposed at the top, and the body 11 of the shell 5 disposed at the bottom, and connected to the wheel side of the vehicle.

[0025] The first piston 18 is fixed to the second mounting shaft portion 27 of the piston rod 21. Therefore, the first piston 18 and the piston rod 21 move together. In the cylinder device 1, the stroke in which the piston rod 21 moves in a direction to increase the amount of extension from the cylinder 2 is the extension stroke, in which the overall length increases. In the cylinder device 1, the stroke in which the piston rod 21 moves in a direction to decrease the amount of extension from the cylinder 2 is the compression stroke, in which the overall length contracts. In the cylinder device 1, the first piston 18 moves toward the first chamber 19 during the extension stroke. In the cylinder device 1, the first piston 18 moves toward the second chamber 20 during the compression stroke.

[0026] A rod guide 51 is fitted to the upper end opening side of the first cylinder 3 and to the upper end opening 10 side of the shell 5. A seal member 52 is fitted to the shell 5 above the rod guide 51. Both the rod guide 51 and the seal member 52 are annular. The piston rod 21 has a first rod outer diameter portion 31 of the main shaft portion 25 inserted radially inside the rod guide 51 and the seal member 52. The piston rod 21 has a first rod outer diameter portion 31 of the main shaft portion 25 slide along the axial direction relative to the rod guide 51 and the seal member 52. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 52.

[0027] The rod guide 51 restricts radial movement of the piston rod 21 relative to the first cylinder 3, the second cylinder 4, and the shell 5 of the cylinder 2. The piston rod 21 is fitted into the rod guide 51 at the rod first outer diameter portion 31 of the main shaft portion 25, and the first piston 18 is fitted into the first cylinder 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the first cylinder 3. The rod guide 51 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 52 is in close contact with the shell 5. The inner periphery of the seal member 52 is in close contact with the rod first outer diameter portion 31 of the main shaft portion 25 of the piston rod 21. The piston rod 21 slides relative to the seal member 52 in the axial direction of the seal member 52. The seal member 52 prevents the oil L in the inner chamber 6 and the high-pressure gas G and oil L in the reservoir chamber 7 from leaking to the outside.

[0028] The rod guide 51 has a large diameter portion 55, an intermediate diameter portion 56, and a small diameter portion 57 on its outer periphery. The large diameter portion 55 has an outer diameter larger than that of the intermediate diameter portion 56. The intermediate diameter portion 56 has an outer diameter larger than that of the small diameter portion 57. The intermediate diameter portion 56 of the rod guide 51 is located closer to the first piston assembly 17, i.e., lower, than the large diameter portion 55. The small diameter portion 57 of the rod guide 51 is located closer to the first piston assembly 17, i.e., lower, than the intermediate diameter portion 56. The intermediate diameter portion 56 of the rod guide 51 fits into the inner periphery of the upper end of the first cylinder 3. At this time, the first end 3a, which is the upper end of the first cylinder 3, abuts against the large diameter portion 55 of the rod guide 51 in the axial direction. The upper large diameter portion 55 of the rod guide 51 fits into the inner periphery of the upper part of the body portion 11 of the shell 5.

[0029] A body valve assembly (not shown) is positioned radially and placed on the bottom (not shown) of the shell 5 on the axial side opposite the opening 10, i.e., on the lower side. The body valve assembly (not shown) fits into the lower end of the first cylinder 3 while positioning it radially. The body valve assembly (not shown) separates the second chamber 20 from the reservoir chamber 7.

[0030] An engagement portion (not shown) that protrudes radially inward is formed at the upper end of the body portion 11 of the shell 5. The seal member 52 is fixed to the cylinder 2 by being sandwiched between this engagement portion (not shown) and the rod guide 51.

[0031] The main shaft portion 25 of the piston rod 21 slides along the axial direction of the rod guide 51 and the seal member 52 at the rod first outer diameter portion 31 .

[0032] As described above, the first piston assembly 17 is connected to the second mounting shaft portion 27 of the piston rod 21 .

[0033] A through hole 70 is formed in the radial center of the first piston 18 of the first piston assembly 17. The through hole 70 passes through the first piston 18 in the axial direction of the first piston 18. In the first piston 18, the second fitting portion 48 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 of the piston rod 21 is fitted into the through hole 70.

[0034] A first passage 71 and a second passage 72 are formed in the first piston 18 outside the through-hole 70 in the radial direction of the first piston 18. The first passage 71 and the second passage 72 penetrate the first piston 18 in the axial direction of the first piston 18. A plurality of first passages 71 and a plurality of second passages 72 are formed in the first piston 18. The first passages 71 and the second passages 72 are arranged alternately in the circumferential direction of the first piston 18. Both the first passage 71 and the second passage 72 can communicate between the first chamber 19 and the second chamber 20.

[0035] The first piston assembly 17 has a first damping valve 75 and a second damping valve 76 .

[0036] The first damping valve 75 is a disc valve formed by stacking multiple annular discs. The second fitting portion 48 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 of the piston rod 21 is fitted to the radially inner side of the first damping valve 75. The first damping valve 75 is disposed on the second chamber 20 side of the first piston 18 in the axial direction of the piston rod 21. During the extension stroke in which the piston rod 21 moves toward the extension side, the outer peripheral portion of the first damping valve 75 separates from the first piston 18 to open the first passage 71. As a result, the first damping valve 75 allows hydraulic fluid 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 hydraulic fluid L to generate a damping force. The first damping valve 75 is disposed in the first passage 71 and suppresses the flow of hydraulic fluid L in the first passage 71 during the extension stroke to generate a damping force. An outer peripheral portion of the first damping valve 75 abuts against the first piston 18 to close the first passage 71. A fixed orifice (not shown) is provided in a portion between the first damping valve 75 and the first piston 18. This fixed orifice allows oil L to flow from the first chamber 19 to the second chamber 20 via the first passage 71 even when the outer peripheral portion of the first damping valve 75 abuts against the first piston 18.

[0037] The second damping valve 76 is a disc valve formed by stacking multiple annular discs. The second fitting portion 48 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 is fitted to the radially inner side of the second damping valve 76. The second damping valve 76 is disposed on the first chamber 19 side of the first piston 18 in the axial direction of the piston rod 21. During the compression stroke in which the piston rod 21 moves toward the compression side, the outer peripheral portion of the second damping valve 76 separates from the first piston 18 to open the second passage 72. As a result, the second damping valve 76 allows hydraulic fluid 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 hydraulic fluid L to generate a damping force. The second damping valve 76 is disposed in the second passage 72 and suppresses the flow of hydraulic fluid L in the second passage 72 during the compression stroke to generate a damping force. The second damping valve 76 has an outer peripheral portion abutting against the first piston 18 to close the second passage 72. A fixed orifice (not shown) is provided in a portion between the second damping valve 76 and the first piston 18. This fixed orifice allows oil L to flow from the second chamber 20 to the first chamber 19 via the second passage 72 even when the outer peripheral portion of the second damping valve 76 abuts against the first piston 18.

[0038] The first piston assembly 17 has an annular restricting ring 77 on the axial side of the first damping valve 75 opposite the first piston 18, which restricts deformation beyond a specified level when the first damping valve 75 is opened. The second fitting portion 48 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 is fitted into the radially inner side of the restricting ring 77.

[0039] The first piston assembly 17 has an annular restricting ring 78 on the axial side of the second damping valve 76 opposite the first piston 18, which restricts deformation beyond a specified level when the second damping valve 76 is opened. The second fitting portion 48 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 is fitted onto the radially inner side of the restricting ring 78.

[0040] The first piston assembly 17, which includes the first piston 18, the first damping valve 75, the second damping valve 76 and the regulating rings 77, 78, moves integrally with the piston rod 21 when the piston rod 21 moves in the axial direction of the first cylinder 3 relative to the first cylinder 3, thereby generating a damping force.

[0041] The first piston assembly 17 has a restriction ring 78 at its upper axial end abutting against the second rod flange portion 47 of the piston rod 21, and a restriction ring 77 at its lower axial end abutting against a nut 79 that is threaded onto the second male thread portion 49 of the rod third outer diameter portion 46 of the second mounting shaft portion 27 of the piston rod 21. When the nut 79 is tightened onto the second male thread portion 49 of the second mounting shaft portion 27, the fastening axial force of the nut 79 urges the first piston assembly 17 toward the second rod flange portion 47 so as to abut against the second rod flange portion 47. The piston rod 21 has an extension portion 44 with a cylindrical outer peripheral surface at the outer diameter portion of the second rod flange portion 47 that receives the urging force of the nut 79.

[0042] The second cylinder 4 constitutes a stopper mechanism 81 that is activated when the first piston 18 reaches a predetermined position on one axial end side of the first cylinder 3. The stopper mechanism 81 is activated when the first piston 18 reaches a predetermined position on the extension side, i.e., the first end 3a side, which is the upper end, of the first cylinder 3 during the extension stroke of the cylinder device 1. The stopper mechanism 81 has a second cylinder 4 that is provided on the first end 3a side of the first cylinder 3 and has a smaller diameter than the first cylinder 3.

[0043] The second cylinder 4 is connected by being fitted into the small diameter portion 57 of the rod guide 51. The second cylinder 4 is cylindrical. The second cylinder 4 is disposed radially inside the first cylinder 3. The second cylinder 4 is fixed to the rod guide 51 by fitting the inner periphery of the upper end portion on the first end 3a side into the small diameter portion 57 of the rod guide 51. At this time, the first end 3a of the second cylinder 4 abuts against the intermediate diameter portion 56 of the rod guide 51 in the axial direction. At this time, the central axis of the second cylinder 4 and the central axis of the first cylinder 3 coincide. The second cylinder 4 is disposed in the first chamber 19 with a radial gap between it and the first cylinder 3.

[0044] As shown in Figure 2, the second cylinder 4 has a cylindrical portion 85 and an expanded diameter portion 86. The cylindrical portion 85 is cylindrical with a constant inner diameter and a constant outer diameter, and extends from one end, i.e., the upper end, on the first end 3a side in the axial direction of the second cylinder 4 to an intermediate portion on the other end, i.e., the lower end. One axial end of the cylindrical portion 85 of the second cylinder 4 is fitted into the small diameter portion 57 of the rod guide 51. The other end of the second cylinder 4, opposite the first end 3a, extends downward from the rod guide 51 from the intermediate portion in the axial direction of the cylindrical portion 85.

[0045] The expanded diameter portion 86 is provided at the other end, i.e., the lower end, of the second cylinder 4, opposite the first end 3a in the axial direction. The inner diameter of the expanded diameter portion 86 increases as it approaches the lower end. The outer diameter of the expanded diameter portion 86 increases as it approaches the lower end. The diameter of the expanded diameter portion 86 increases in the direction away from the cylindrical portion 85 in the axial direction of the second cylinder 4. The second cylinder 4 opens on the opposite side of the first end 3a in the axial direction, i.e., downward.

[0046] The second cylinder 4 has a groove 87 extending in the axial direction of the second cylinder 4 on its inner periphery opposite the first end 3a in the axial direction. The groove 87 is provided on the inner periphery near the lower end of the second cylinder 4. The groove 87 is recessed radially outward from the inner periphery of the second cylinder 4. The groove 87 extends from the expanded diameter portion 86 to the end of the cylindrical portion 85 opposite the first end 3a, i.e., the lower end. The second cylinder 4 has a plurality of grooves 87 formed at equal intervals in the circumferential direction of the second cylinder 4. The grooves 87 each have a different length from the lower end of the second cylinder 4. In other words, the grooves 87 each have a different length in the axial direction of the second cylinder 4.

[0047] The stopper mechanism 81 has a second piston assembly 90 attached to the piston rod 21. The second piston assembly 90 has a second piston 91. The second piston 91 has a second piston body 94 having two parts, a third piston 92 (first restricting portion) and a fourth piston 93 that is separate from the third piston 92, and a piston ring 95. The piston ring 95 is made up of a piston ring body 96 and a seal ring 97.

[0048] The third piston 92 of the second piston body 94 is molded seamlessly and integrally, and has the shape shown in FIGS. 3 to 5 . The third piston 92 is a perforated disk with a through-hole 101 formed in the radial center and penetrating in the axial direction. As shown in FIGS. 4 and 5 , the third piston 92 has a circular groove 102 that is coaxial with the through-hole 101 and recessed axially inward, formed outside the radial through-hole 101 at one axial end. As shown in FIG. 4 , the third piston 92 has an inner seat portion 103 that protrudes axially outward beyond the bottom surface of the radial groove 102 at one axial end. The inner seat portion 103 is disposed so as to surround the through-hole 101 radially outward. The third piston 92 has a valve seat portion 104 that protrudes axially outward beyond the bottom surface of the radial groove 102 at one axial end. The valve seat portion 104 protrudes from the bottom surface of the recessed groove 102 to a greater height than the inner seat portion 103 .

[0049] 3 and 4, the third piston 92 has an annular groove 106 that is coaxial with the through hole 101 and recessed axially inward, formed outside the radial through hole 101 at the other end opposite the axial inner seat portion 103 and the valve seat portion 104. The third piston 92 has a passage hole 107 that connects the bottom surface of the annular groove 106 and the bottom surface of the recessed groove 102 and extends in the axial direction of the third piston 92. The third piston 92 has a plurality of passage holes 107 of the same shape formed at equal intervals around the circumference of the third piston 92, as shown in FIGS.

[0050] The fourth piston 93 of the second piston body 94 shown in Fig. 2 is molded seamlessly as a single piece and has the shape shown in Figs. 6 to 8. As shown in Figs. 7 and 8, the fourth piston 93 is cylindrical with a through-hole 111 that penetrates in the axial direction formed in its radial center. The fourth piston 93 has a cylindrical main body portion 112 with the through-hole 111 that penetrates in the axial direction formed in its radial center, and a fourth piston flange portion 113 (second restricting portion) that extends radially outward from one axial end portion of the main body portion 112.

[0051] As shown in FIG. 8 , the fourth piston 93 is formed with an axial groove 115 having a generally semicircular cross section that is recessed radially inward from the radially outer end of the fourth piston flange portion 113, penetrates the fourth piston flange portion 113 in the radial direction, and reaches the inside of the outer periphery of the main body portion 112. As shown in FIG. 6 , the axial groove 115 extends in the axial direction of the fourth piston 93 and is formed in the fourth piston flange portion 113 and the main body portion 112 so as to penetrate the fourth piston flange portion 113 in the axial direction. The axial groove 115 extends from a predetermined intermediate position near the end of the main body portion 112 opposite the fourth piston flange portion 113 in the axial direction to the end on the fourth piston flange portion 113 side, and exits from this end. As shown in FIG. 8 , the fourth piston 93 is formed with a plurality of axial grooves 115 of the same shape at equal intervals around the circumferential direction of the fourth piston 93.

[0052] As shown in Fig. 7 , the main body portion 112 is formed with a passage hole 116 that passes through the main body portion 112 in the axial direction, radially outward of the through hole 111. As shown in Fig. 8 , the main body portion 112 is formed with a plurality of passage holes 116 of the same shape that are equally spaced apart in the circumferential direction of the main body portion 112. The fourth piston 93 is provided with the same number of passage holes 116 as the axial grooves 115, and the passage holes 116 and the axial grooves 115 are alternately arranged at equal intervals in the circumferential direction of the fourth piston 93.

[0053] 2 , in the second piston body 94, the fourth piston 93 is fitted into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21 in the through hole 111. At this time, the fourth piston 93 abuts the end of the main body portion 112 on the axial side of the fourth piston flange portion 113, i.e., the upper end, against the first rod flange portion 33.

[0054] In the second piston body 94, the third piston 92 is fitted into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21 in the through hole 101. At this time, the inner seat portion 103 and the valve seat portion 104 of the third piston 92 are oriented axially away from the fourth piston 93, and the end portion of the third piston 92 opposite the inner seat portion 103 and the valve seat portion 104 in the axial direction abuts against the end portion of the main body portion 112 of the fourth piston 93 opposite the fourth piston flange portion 113 in the axial direction, i.e., the lower end portion. An end portion of the main body portion 112 of the fourth piston 93 on the fourth piston flange portion 113 side, which is one end of the second piston 91 on the first axial end portion 3a side, abuts against the first rod flange portion 33 between the rod first outer diameter portion 31 of the piston rod 21 and the rod second outer diameter portion 32 having a smaller diameter than the rod first outer diameter portion 31. The passage hole 116 of the fourth piston 93 is disposed radially outward of the rod first outer diameter portion 31 .

[0055] In the second piston body 94 fitted to the piston rod 21 in this manner, the outer diameter of the third piston 92 is equal to the outer diameter of the fourth piston flange portion 113 of the fourth piston 93. These outer diameters are smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4. The outer diameter of the main body portion 112 on the third piston 92 side of the fourth piston flange portion 113 in the axial direction of the fourth piston 93 is smaller than the outer diameter of the third piston 92 and the outer diameter of the fourth piston flange portion 113 of the fourth piston 93. Thus, the second piston 91 has the third piston 92 and the fourth piston 93, the outer diameter of which on the third piston 92 side is smaller than the outer diameter of the third piston 92.

[0056] The second piston body 94 fitted onto the piston rod 21 has the annular groove 106 of the third piston 92 and the passage hole 116 of the fourth piston 93 aligned radially on the second piston body 94. Thus, the passages in the recessed groove 102 of the third piston 92, the passages in the plurality of passage holes 107, and the passages in the annular groove 106 communicate with the passages in the plurality of passage holes 116 of the fourth piston 93, thereby forming a communication passage 118 that passes through the second piston body 94 in the axial direction.

[0057] The piston ring body 96 is made of, for example, metal and has a cylindrical shape. The seal ring 97 is made of, for example, rubber and has an annular shape. The seal ring 97 is made of an elastic material with high sealing properties.

[0058] The piston ring body 96 has the main body portion 112 of the fourth piston 93 inserted inside it, and in this state is disposed between the fourth piston flange portion 113 of the fourth piston 93 and the third piston 92. The seal ring 97 has the main body portion 112 of the fourth piston 93 inserted inside it, and in this state is disposed between the piston ring body 96 and the third piston 92. In other words, the seal ring 97 is disposed on the axial side of the piston ring body 96 toward the third piston 92.

[0059] The piston ring 95 has a combined axial length of the piston ring body 96 and the seal ring 97 that is shorter than the axial length between the fourth piston flange portion 113 of the fourth piston 93 and the third piston 92. Therefore, the piston ring 95 is axially slidable relative to the second piston body 94 between the fourth piston flange portion 113 and the third piston 92. In other words, the piston ring 95 is provided around the outer periphery of the second piston 91 so as to be axially movable. The third piston 92 is provided on the side opposite the first axial end 3 a of the piston ring 95 to restrict the axial movement of the piston ring 95. The fourth piston flange portion 113 of the fourth piston 93 is provided on the side of the first axial end 3 a of the piston ring 95 to restrict the axial movement of the piston ring 95. The seal ring 97 of the piston ring 95 is capable of abutting against the third piston 92 over the entire circumference. When the seal ring 97 abuts against the third piston 92, the seal ring 97 closes the gap between the third piston 92 and the third piston 92 over the entire circumference.

[0060] The piston ring body 96 has an outer diameter slightly smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4 and is provided so as to be able to be fitted inside the second cylinder 4. The seal ring 97 has an outer diameter slightly smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4 and is provided so as to be able to be fitted inside the second cylinder 4. Therefore, the second piston 91 including the piston ring 95 moves in accordance with the movement of the piston rod 21 and is provided so as to be able to be fitted inside the second cylinder 4. The piston ring body 96 and the seal ring 97 of the piston ring 95 are both able to slide axially inside the cylindrical portion 85 of the second cylinder 4.

[0061] The second piston assembly 90 has a valve body 120 arranged on the opposite side of the third piston 92 from the fourth piston 93 in the axial direction, a small diameter disc 121 arranged on the opposite side of the valve body 120 from the third piston 92 in the axial direction, and a large diameter disc 122 arranged on the opposite side of the small diameter disc 121 from the valve body 120 in the axial direction.

[0062] The valve body 120 is configured by stacking multiple annular disks. The small diameter disk 121 has an outer diameter smaller than that of the valve body 120. The large diameter disk 122 has an outer diameter equal to that of the valve body 120.

[0063] The valve element 120, the small diameter disc 121, and the large diameter disc 122 are fitted into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21. The valve element 120 abuts against the inner seat portion 103 of the third piston 92 over its entire circumference and is able to abut against the valve seat portion 104 over its entire circumference. When the valve element 120 is seated over its entire circumference on the valve seat portion 104 of the third piston 92, it closes the communication passage 118 of the second piston body 94. When the valve element 120 is released from the valve seat portion 104 of the third piston 92, it opens the communication passage 118 of the second piston body 94. The outer diameter of the valve element 120 is slightly smaller than the outer diameter of the second piston body 94, and is able to advance into the tubular portion 85 of the second cylinder 4.

[0064] The second piston assembly 90 has an annular member 123 provided on the axially opposite side of the large-diameter disc 122 from the small-diameter disc 121. The annular member 123 is annular, and is fitted into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21. The outer diameter of the annular member 123 is smaller than the outer diameter of the large-diameter disc 122. The annular member 123 restricts deformation of the valve body 120 beyond a specified level when the valve is open.

[0065] The stopper mechanism 81 has a nut 124 (biasing portion) that fixes the second piston assembly 90 to the piston rod 21. The nut 124 is provided on the opposite side of the annular member 123 from the large diameter disk 122 in the axial direction.

[0066] The nut 124 is annular in shape with a through hole 131 formed in the radial center and penetrating in the axial direction. The through hole 131 has a female thread portion 132 formed on the inner periphery on one axial side, and a fitting portion 133 with a cylindrical inner periphery on the other axial side.

[0067] The nut 124 has the female thread portion 132 threadedly engaged with the first male thread portion 42 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21. At this time, the nut 124 has the fitting portion 133 facing the annular member 123 in the axial direction relative to the female thread portion 132, and the fitting portion 133 fits into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26. The second piston 91 has one axial end, i.e., an upper end of the fourth piston 93 opposite to the third piston 92, which abuts against the first rod flange portion 33 of the piston rod 21, and the other axial end, i.e., a lower end of the third piston 92 opposite to the fourth piston 93, which is supported by the nut 124 via the valve body 120, the small diameter disc 121, the large diameter disc 122, and the annular member 123.

[0068] When the nut 124 is tightened onto the first male thread portion 42 of the rod second outer diameter portion 32 of the first mounting shaft portion 26, the second piston 91 has one end on the side of the first axial end 3a brought into contact with the first rod flange portion 33 of the piston rod 21. The other end of the second piston 91 opposite the first axial end 3a is urged toward the first rod flange portion 33 by the nut 124 via the annular member 123, the large-diameter disk 122, the small-diameter disk 121, and the valve body 120. In other words, the other end of the second piston 91 opposite the first axial end 3a is urged by the first male thread portion 42 and the nut 124, which urge the second piston 91 toward the first rod flange portion 33. In other words, the end of the second piston 91 opposite the first axial end 3a is biased toward the first rod flange portion 33 by the first male thread portion 42 and the nut 124, so that the end on the first axial end 3a side is pressed against the first rod flange portion 33.

[0069] The second piston assembly 90 and the nut 124 move with the piston rod 21 .

[0070] Here, when the piston rod 21 is in a first predetermined range in which the piston ring 95 of the second piston 91 is positioned below the second cylinder 4 and the piston ring 95 is not fitted into the second cylinder 4, the entire interior of the second cylinder 4 becomes the first chamber 19.

[0071] From this state, during the extension stroke, the piston rod 21 moves into a second predetermined range that is closer to the extension side than the first predetermined range. Then, the stopper mechanism 81 moves such that the piston ring 95 of the second piston 91, which moves integrally with the piston rod 21, enters the enlarged diameter portion 86 of the second cylinder 4 and then fits into the cylindrical portion 85 of the second cylinder 4. At the initial stage of this fitting, the seal ring 97 of the piston ring 95 is pressed against the third piston 92 by friction with the second cylinder 4 and the flow of oil L flowing from the rod guide 51 side of the piston ring 95 in the second cylinder 4 to the opposite side of the rod guide 51. As a result, the seal ring 97 of the piston ring 95 abuts against the third piston 92 in the axial direction, blocking the passage between the piston ring 95 and the third piston 92. Then, the flow of oil L flowing from the rod guide 51 side of the piston ring 95 to the opposite side of the rod guide 51 through the passages in the multiple axial grooves 115 of the fourth piston 93 shown in FIG. 6 is restricted. When the second piston 91 is positioned in the second cylinder 4 and the piston ring 95 is advanced into the second cylinder 4, the second piston 91 divides the interior of the second cylinder 4 into one side chamber 141 located closer to the rod guide 51 than the second piston 91, and another side chamber 142 located on the opposite side of the rod guide 51 than the second piston 91. In other words, when the second piston 91 is positioned in the second cylinder 4, the second piston 91 divides the interior of the second cylinder 4 into one side chamber 141 located closer to the first end 3 a in the axial direction than the second piston 91, and another side chamber 142 located on the opposite side of the first end 3 a than the second piston 91.

[0072] During the extension stroke in the second predetermined range, the second piston assembly 90 of the stopper mechanism 81 moves the second piston 91 toward the rod guide 51 with the piston ring 95 blocking the passage between the second piston 91 and the third piston 92 as described above. In the lower part of the second predetermined range, the piston ring 95 is located at the position of the plurality of grooves 87 provided in the second cylinder 4, and oil L flows through the plurality of grooves 87. At this time, as the second piston 91 approaches the rod guide 51, the number of open grooves 87 decreases, eventually reaching zero. This causes the damping force generated by the second cylinder 4 and the second piston 91 to increase in stages.

[0073] As the second piston assembly 90 moves further toward the extension side, the piston ring 95 slides above any of the plurality of grooves 87 in the second cylinder 4 to approach the rod guide 51, while still blocking the passage between the second piston assembly 90 and the third piston 92. Then, the second piston assembly 90 slides inside the second cylinder 4 to approach the rod guide 51, with the piston ring 95 blocking the gap between the second piston assembly 90 and the second cylinder 4.

[0074] When the pressure in one side chamber 141 becomes higher than the pressure in the other side chamber 142 by a predetermined value or more while the second piston assembly 90 is sliding toward the extension side within the second cylinder 4, the valve body 120 of the second piston assembly 90 opens, generating a damping force and causing the oil liquid L in the one side chamber 141 to flow into the other side chamber 142 through the connecting passage 118.

[0075] As described above, the second piston 91 is provided with a communication passage 118 that can communicate, when the second piston 91 is located in the second cylinder 4, one side chamber 141 that is closer to the first end 3 a in the axial direction than the second piston 91 in the second cylinder 4 with the other side chamber 142 that is on the opposite side of the first end 3 a in the axial direction than the second piston 91 in the second cylinder 4. The second piston 91 is provided on the other side chamber 142 side with a valve element 120 that opens to communicate the one side chamber 141 and the other side chamber 142 via the communication passage 118 when the pressure in the one side chamber 141 reaches a predetermined pressure that is higher than the pressure in the other side chamber 142 by a predetermined value or more.

[0076] When the second piston assembly 90 of the stopper mechanism 81 is at the upper limit position of the second predetermined range, the second piston 91 stops by abutting the end of the fourth piston 93 opposite the third piston 92 in the axial direction against the rod guide 51.

[0077] During the compression stroke within the second predetermined range, the second piston assembly 90 of the stopper mechanism 81 moves from a state in which the piston ring 95 of the second piston 91 is fitted in the second cylinder 4 to a state in which the second piston body 94 moves in a direction away from the rod guide 51. Then, the piston ring 95, together with the seal ring 97 and the piston ring body 96, moves axially away from the third piston 92 due to frictional force with the second cylinder 4 and the flow of oil liquid L flowing from the other side chamber 142 to the one side chamber 141, opening a passage between the piston ring 95 and the third piston 92, and connecting this passage to the passages in the plurality of axial grooves 115 of the fourth piston 93 shown in FIG. 6. During the subsequent compression stroke, the second piston assembly 90 shown in FIG. 2 moves in a direction away from the rod guide 51 shown in FIG. 2 while maintaining a state in which the piston ring 95 opens the passage between the piston ring 95 and the third piston 92, connecting this passage to the passages in the plurality of axial grooves 115 shown in FIG. 6. As a result, the second piston 91 causes the oil L in the other side chamber 142 to flow into the one side chamber 141 through the passage between the piston ring 95 and the third piston 92 and the passages in the plurality of axial grooves 115. This reduces the damping force acting on the retraction movement of the piston rod 21.

[0078] When the second piston 91 moves a predetermined distance away from the rod guide 51 during the compression stroke from a state in which the piston ring 95 is closer to the rod guide 51 than all of the grooves 87 in the second cylinder 4, the grooves 87 provided in the second cylinder 4 open. Then, in addition to the flow through the passage between the piston ring 95 and the third piston 92 and the passages in the multiple axial grooves 115, oil L flows through the grooves 87, reducing the damping force acting on the compression movement of the piston rod 21. At this time, the farther the second piston 91 is from the rod guide 51, the more of the multiple grooves 87 through which the oil liquid L flows. This causes the damping force acting on the compression movement of the piston rod 21 to gradually decrease.

[0079] The body valve assembly (not shown) that separates the second chamber 20 from the reservoir chamber 7 is provided with a damping force generating mechanism that regulates the flow of oil L from the reservoir chamber 7 to the second chamber 20 while generating a damping force by flowing oil L from the second chamber 20 to the reservoir chamber 7, and a suction valve mechanism that regulates the flow of oil L from the second chamber 20 to the reservoir chamber 7 while flowing oil L from the reservoir chamber 7 to the second chamber 20 without generating any substantial damping force.

[0080] Next, the main operation of the cylinder device 1 will be described.

[0081] "An extension stroke within a first predetermined range in which the piston rod 21 does not allow the piston ring 95 of the second piston 91 to fit into the second cylinder 4"

[0082] {First Speed ​​Region Where Piston Speed ​​is Slower than First Predetermined Value} In this first speed region of the extension stroke, the hydraulic fluid L from the first chamber 19 flows from the first passage 71 to the second chamber 20 through a fixed orifice (not shown) between the first damping valve 75 and the first piston 18 in the first piston assembly 17. Therefore, in the first speed region of the extension stroke, a damping force with orifice characteristics is generated.

[0083] {Second Speed ​​Region Where Piston Speed ​​is Greater than or Equal to First Predetermined Value} In this second speed region of the extension stroke, the hydraulic fluid L from the first chamber 19 flows from the first passage 71 to the second chamber 20 in the first piston assembly 17, opening the first damping valve 75. Therefore, in the second speed region of the extension stroke, a damping force with valve characteristics is generated by the first damping valve 75.

[0084] "Compression stroke when the piston rod 21 is in the first predetermined range"

[0085] {Third Speed ​​Region Where Piston Speed ​​is Slower than Second Predetermined Value} In this third speed region of the compression stroke, oil L from the second chamber 20 flows into the first chamber 19 from the second passage 72 in the first piston assembly 17 through a fixed orifice (not shown) between the second damping valve 76 and the first piston 18. Therefore, in the third speed region of the compression stroke, a damping force having an orifice characteristic (wherein the damping force is approximately proportional to the square of the piston speed) is generated.

[0086] {Fourth Speed ​​Region Where Piston Speed ​​is Greater than or Equal to Second Predetermined Value} In this fourth speed region of the compression stroke, oil L from the second chamber 20 flows from the second passage 72 to the first chamber 19 in the first piston assembly 17, opening the second damping valve 76. Therefore, in the fourth speed region of the compression stroke, a damping force is generated by the second damping valve 76 with valve characteristics (the damping force is approximately proportional to the piston speed).

[0087] "An extension stroke in a second predetermined range in which the piston rod 21 engages the piston ring 95 of the second piston 91 with the second cylinder 4."

[0088] During this extension stroke, the first piston assembly 17 operates in the same manner as in the first predetermined range. Then, the second piston 91 of the second piston assembly 90 moves in the axial direction of the first cylinder 3 toward the rod guide 51, fitting the piston ring 95 into the second cylinder 4. Then, in the early stage of this movement, the seal ring 97 of the piston ring 95 closes the passage between the piston ring 95 and the third piston 92.

[0089] With the piston ring 95 thus blocking the passage between the second piston 91 and the third piston 92, the second piston 91 moves toward the rod guide 51. Then, the oil L is constricted by the multiple grooves 87 provided in the second cylinder 4 and flows from the one side chamber 141 to the other side chamber 142 within the second cylinder 4. At this time, the damping force generated by the second cylinder 4 and the second piston 91 increases. Moreover, as the second piston 91 approaches the rod guide 51, the number of grooves 87 through which the oil L flows decreases, eventually reaching zero. As a result, the generated damping force increases stepwise, and the damping force against the movement of the piston rod 21 in the extension direction also increases stepwise.

[0090] When the pressure in one side chamber 141 becomes higher than the pressure in the other side chamber 142 by a predetermined value or more while the second piston assembly 90 is sliding toward the extension side within the second cylinder 4, the valve body 120 of the second piston assembly 90 opens, generating a damping force and causing the oil liquid L in the one side chamber 141 to flow into the other side chamber 142 through the connecting passage 118.

[0091] The damping force generated by the stopper mechanism 81 is increased relative to the damping force generated by the first piston assembly 17 .

[0092] "Compression stroke when the piston rod 21 is in the second predetermined range" During this compression stroke, the first piston assembly 17 operates in the same manner as in the first predetermined range. Then, the second piston 91 moves in a direction away from the rod guide 51. Then, at the beginning of this movement, the seal ring 97 of the piston ring 95 opens the passage between it and the third piston 92.

[0093] In this manner, with the piston ring 95 opening the passage between the second piston 91 and the third piston 92, the second piston 91 moves in a direction away from the rod guide 51. Then, oil L flows from the other-side chamber 142 to the one-side chamber 141 through the passage between the piston ring 95 and the third piston 92 and the passages in the plurality of axial grooves 115 of the fourth piston 93.

[0094] When the piston ring 95 passes the position of the groove 87 formed in the second cylinder 4 from a state in which it is closer to the rod guide 51 than all of the grooves 87 formed in the second cylinder 4, oil L flows from the other-side chamber 142 to the one-side chamber 141 through the groove 87 in addition to flowing through the passage between the piston ring 95 and the third piston 92 and the passages in the plurality of axial grooves 115 of the fourth piston 93. At that time, the farther the second piston 91 is from the rod guide 51, the more of the plurality of grooves 87 through which the oil L flows. As a result, the damping force against the movement of the piston rod 21 in the retraction direction is gradually reduced.

[0095] The aforementioned Japanese Patent Application Publication No. 2015-161404 discloses a cylinder device having a second cylinder and a second piston that increases damping force when the piston rod reaches a predetermined limit range during the extension stroke in which the piston rod extends from the cylinder. In this cylinder device, the second piston is directly fixed to the piston rod by plastically deforming the second piston, which raises concerns about reduced durability due to high pressure. Furthermore, U.S. Patent Application Publication No. 2015 / 0330475 discloses a cylinder device having a second cylinder and a second piston that increases damping force when the piston rod reaches a predetermined limit range during the compression stroke in which the piston rod is pushed into the cylinder. In this cylinder device, the second piston abuts against a flange portion of the piston rod. However, increasing the pressure-receiving area of ​​the flange portion would reduce the rigidity of the piston rod, making it impossible to do so. This raises concerns about reduced durability due to the high pressure received by this flange portion.

[0096] The cylinder device 1 of the first embodiment includes a first cylinder 3 filled with a working fluid, a first piston 18 slidably fitted within the first cylinder 3 to define the interior of the first cylinder 3, a piston rod 21 connected to the first piston 18, and a stopper mechanism 81 that is activated when the piston rod 21 reaches a predetermined position on a first end 3a of the first cylinder 3 during an extension stroke. The stopper mechanism 81 includes a second cylinder 4 that is provided on the first end 3a side of the first cylinder 3 and has a smaller diameter than the first cylinder 3, and a second piston 91 that moves with the movement of the piston rod 21 and is provided so as to be able to be fitted within the second cylinder 4. One end of the second piston 91 on the first end 3a side abuts against a first rod flange 33 between a rod first outer diameter portion 31 of the piston rod 21 and a rod second outer diameter portion 32 that is smaller in diameter than the rod first outer diameter portion 31. Additionally, the other end of second piston 91 opposite first end 3a is biased by nut 124, which biases second piston 91 toward first rod flange portion 33. As a result, cylinder device 1 is structured such that nut 124 biases the other end of second piston 91 opposite first end 3a, which receives high pressure from first end 3a when stopper mechanism 81 is activated, toward first rod flange portion 33, i.e., in a direction against the high pressure, thereby enabling to improve durability.

[0097] In the cylinder device 1, the rod first outer diameter portion 31 and the rod second outer diameter portion 32 are integrally formed, so that coaxiality can be easily achieved.

[0098] In the cylinder device 1, the second piston 91 is provided with a communication passage 118 that can communicate, when the second piston 91 is positioned in the second cylinder 4, one side chamber 141 that is closer to the first end 3a than the second piston 91 in the second cylinder 4 with another side chamber 142 that is closer to the first end 3a than the second piston 91 in the second cylinder 4. The cylinder device 1 also has a valve element 120 on the other side chamber 142 side of the second piston 91 that opens when the pressure in the one side chamber 141 reaches a predetermined pressure to communicate the one side chamber 141 and the other side chamber 142 via the communication passage 118. Therefore, in the cylinder device 1, the valve element 120 opens when the pressure in the one side chamber 141 reaches a predetermined pressure to allow the oil L to flow from the one side chamber 141 to the other side chamber 142 via the communication passage 118, thereby further improving durability.

[0099] The cylinder device 1 urges the second piston 91 toward the first rod flange portion 33 using the first male thread portion 42 formed on the rod second outer diameter portion 32 and the nut 124 that screws onto the first male thread portion 42, making it possible to improve durability with a simple structure.

[0100] In the cylinder device 1, the second piston 91 has a piston ring 95 provided around the outer periphery thereof so as to be movable in the axial direction, and a third piston 92 on the opposite side from the first end 3a and a fourth piston flange portion 113 of the fourth piston 93 on the first end 3a side, which limit the axial movement range of the piston ring 95. This makes it possible to limit the axial movement range of the piston ring 95.

[0101] In the cylinder device 1, the second piston 91 has a third piston 92 and a fourth piston 93 whose outer diameter on the third piston 92 side is smaller than that of the third piston 92, and the third piston 92 on the opposite side to the first end 3a and a fourth piston flange portion 113 formed on the fourth piston 93 on the opposite side to the third piston 92 limit the axial movement range of the piston ring 95. Therefore, the axial movement range of the piston ring 95 can be limited with a simple structure.

[0102] In the cylinder device 1, the outer diameter portion of the second rod flange portion 47, which receives the biasing force from the nut 79 of the piston rod 21, is an extension portion 44 with an outer peripheral surface having a cylindrical surface, which prevents damage to the threaded portion due to the force applied from the first piston assembly 17, thereby making it possible to further improve durability.

[0103] Second Embodiment Next, a cylinder device according to a second embodiment will be described, focusing on differences from the first embodiment, mainly with reference to Figures 9 to 15. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0104] 9, the cylinder device 1A has a stopper mechanism 81A that is partially different from the stopper mechanism 81 in place of the stopper mechanism 81. The stopper mechanism 81A has a second piston assembly 90A that is partially different from the second piston assembly 90 in place of the second piston assembly 90. The second piston assembly 90A has a second piston 91A that is partially different from the second piston 91 in place of the second piston 91.

[0105] The second piston 91A has a second piston body 200, a ring member 201, and a piston ring 95A.

[0106] The second piston body 200 of the second piston 91A is molded seamlessly as a single unit and has the shape shown in Figures 10 to 13. As shown in Figures 10, 12, and 13, the second piston body 200 is cylindrical with a through-hole 211 that penetrates in the axial direction at its radial center. The second piston body 200 has a cylindrical main body portion 212 (shown in Figures 10 and 13) that has a through-hole 211 that penetrates in the axial direction at its radial center, and a second piston flange portion 213 (first restricting portion) that extends radially outward from one axial end of the main body portion 212 as shown in Figures 11 and 13.

[0107] As shown in FIG. 13 , the second piston body 200 has a groove 222 that is coaxial with the through hole 211 and recessed axially inward, formed outside the radial through hole 211 at one end of the second piston body 200 on the axial side of the second piston flange portion 213. The inner side of the radial groove 222 at the end of the second piston body 200 on the axial side of the second piston flange portion 213 forms an inner seat portion 223 that protrudes axially outward from the bottom surface of the groove 222. The inner seat portion 223 is provided to surround the through hole 211 on the radial outside. The second piston body 200 has a valve seat portion 224 that protrudes axially outward from the bottom surface of the groove 222 at the end of the second piston body 200 on the axial side of the second piston flange portion 213. The valve seat portion 224 protrudes axially outward from the bottom surface of the groove 222 to a greater height than the inner seat portion 223.

[0108] The second piston body 200 has a fitting groove 231 (groove) having a semicircular cross section and recessed radially inward, formed coaxially with the through-hole 211, on the outer periphery near the end of the main body 212 on the opposite axial side from the second piston flange 213. Furthermore, the second piston body 200 has a passage groove 232 having a rectangular cross section and recessed radially inward, formed coaxially with the through-hole 211, on the outer periphery closer to the second piston flange 213 than the axial fitting groove 231 of the main body 212.

[0109] As shown in Fig. 11 , the second piston body 200 has an axial groove 235 recessed radially inward of the main body portion 212 over the entire axial range of the main body portion 212 that does not overlap with the second piston flange portion 213. The axial groove 235 extends in the axial direction of the second piston body 200 and is formed in the main body portion 212 so as to axially penetrate the fitting groove 231 and the passage groove 232. The axial groove 235 exits from the end of the main body portion 212 on the axial side opposite the second piston flange portion 213. As shown in Fig. 10 , the axial groove 235 has a semicircular cross section, and a plurality of axial grooves 235 of the same shape are formed in the second piston body 200 at equal intervals around the circumference of the second piston body 200.

[0110] As shown in Fig. 13 , the second piston body 200 is formed with a passage hole 236 that penetrates the second piston body 200 in the axial direction, radially outward of the through hole 211 in the main body portion 212. The second piston body 200 is formed with a plurality of passage holes 236 of the same shape, equally spaced around the circumference of the second piston body 200, as shown in Figs. 10 and 12 . As shown in Fig. 10 , the second piston body 200 is provided with the same number of passage holes 236 as the axial grooves 235, and the passage holes 236 and the axial grooves 235 are alternately arranged at equal intervals around the circumference of the second piston body 200. As shown in Fig. 13 , the axial end of the passage hole 236 on the second piston flange portion 213 side opens to the bottom surface of the recessed groove 222.

[0111] The ring member 201 of the second piston 91A shown in FIG. 9 has the shape shown in FIGS. 14 and 15 . The ring member 201 has a C-shaped mounting portion 241, which is broken at one location around its circumference to form a broken portion 240, and a restricting portion 242 provided on the outer periphery of the mounting portion 241. As shown in FIG. 9 , the mounting portion 241 has a semicircular cross section whose axial width narrows toward the radially inward direction of the mounting portion 241. As shown in FIGS. 14 and 15 , the restricting portion 242 has a square prism shape and protrudes radially outward from the outer periphery of the mounting portion 241 and also protrudes on both axial sides as shown in FIG. 15 . The ring member 201 has a plurality of restricting portions 242 of the same shape provided at approximately equal intervals around the circumferential direction of the mounting portion 241, as shown in FIG. 14 .

[0112] As shown in FIG. 9 , the second piston body 200 is fitted into the first fitting portion 41 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21 in the through hole 211. At this time, the second piston body 200 abuts the first rod flange portion 33 at the end of the main body portion 212 opposite the second piston flange portion 213 in the axial direction. Then, the second piston body 200 has the second piston flange portion 213 formed on the side opposite the first axial end 3a, and a fitting groove 231 formed on the first end 3a side. The end of the main body portion 212 opposite the second piston flange portion 213 in the axial direction, which is one end of the second piston body 200 on the first axial end 3a side, abuts the first rod flange portion 33 between the rod first outer diameter portion 31 of the piston rod 21 and the rod second outer diameter portion 32, which has a smaller diameter than the rod first outer diameter portion 31. The outer diameter of the second piston flange portion 213 of the second piston body 200 fitted to the piston rod 21 in this manner is smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4. In addition, the passage hole 236 of the second piston body 200 is disposed radially outward of the rod first outer diameter portion 31.

[0113] The ring member 201 is fitted into the fitting groove 231 at the mounting portion 241 of the second piston body 200. The outer diameter of the ring member 201 attached to the second piston body 200 is smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4. The ring member 201 attached to the second piston body 200 has lower ends of the plurality of restricting portions 242 that overlap with upper ends of the passage grooves 232 in the axial direction of the second piston body 200.

[0114] In the second piston body 200, the passage in the recessed groove 222 and the passage in the plurality of passage holes 236 form a communication passage 248 that passes through the second piston body 200 in the axial direction.

[0115] The piston ring 95A is made of, for example, metal and has a cylindrical shape. The main body 212 of the second piston body 200 is inserted into the piston ring 95A, and in this state, the piston ring 95A is disposed between the second piston flange 213 of the second piston body 200 and the ring member 201.

[0116] The axial length of the piston ring 95A is shorter than the axial length between the second piston flange portion 213 of the second piston body 200 and the restricting portion 242 of the ring member 201, and therefore the piston ring 95A is axially movable relative to the second piston body 200 and the ring member 201 between the second piston flange portion 213 and the restricting portion 242 of the ring member 201. In other words, the piston ring 95A is provided on the outer periphery of the second piston body 200 so as to be axially movable, the second piston flange portion 213 of the second piston body 200 is provided on the side opposite to the first axial end 3 a of the second piston body 200 and restricts the axial movement of the piston ring 95A, and the restricting portion 242 of the ring member 201 is provided on the side of the first axial end 3 a of the second piston body 200 and restricts the axial movement of the piston ring 95A. The piston ring 95A is capable of contacting the second piston flange portion 213 of the second piston body 200 over its entire circumference, and when it contacts the second piston flange portion 213 in this manner, it closes the gap with the second piston flange portion 213 over its entire circumference.

[0117] The piston ring 95A has an outer diameter slightly smaller than the inner diameter of the cylindrical portion 85 of the second cylinder 4, and is provided so as to be able to be fitted inside the second cylinder 4. Therefore, the second piston 91A including the piston ring 95A moves in accordance with the movement of the piston rod 21, and is provided so as to be able to be fitted inside the second cylinder 4. The piston ring 95A is able to slide axially inside the cylindrical portion 85 of the second cylinder 4.

[0118] In the second piston assembly 90A, the valve element 120 abuts against the inner seat portion 223 of the second piston body 200 of the second piston 91A over the entire circumference. The valve element 120 can abut against the valve seat portion 224 of the second piston body 200 over the entire circumference. When the valve element 120 is seated over the entire circumference on the valve seat portion 224 of the second piston 91A, it closes the communication passage 248 of the second piston 91A. When the valve element 120 is released from the valve seat portion 224 of the second piston 91A, it opens the communication passage 248 of the second piston 91A. The outer diameter of the valve element 120 is slightly smaller than the outer diameters of the second piston flange portion 213 and the ring member 201 of the second piston 91A, and is capable of entering the tubular portion 85 of the second cylinder 4.

[0119] In the stopper mechanism 81A, the nut 124 is also threaded onto the first male thread portion 42 of the rod second outer diameter portion 32 of the first mounting shaft portion 26 of the piston rod 21. The second piston 91A has one axial end, that is, an upper end of the main body portion 212 of the second piston body 200 opposite to the second piston flange portion 213, in contact with the first rod flange portion 33 of the piston rod 21, and the other axial end, that is, a lower end of the second piston body 200 on the first rod flange portion 33 side, supported by the nut 124 via the valve body 120, the small diameter disk 121, the large diameter disk 122, and the annular member 123.

[0120] When the nut 124 is tightened onto the first male thread portion 42 of the rod second outer diameter portion 32 of the first mounting shaft portion 26, the second piston 91A has one end on the side of the first axial end 3a brought into contact with the first rod flange portion 33 of the piston rod 21. The other end of the second piston 91A opposite the first axial end 3a is urged toward the first rod flange portion 33 by the nut 124 via the annular member 123, the large-diameter disk 122, the small-diameter disk 121, and the valve body 120. In other words, the other end of the second piston 91A opposite the first axial end 3a is urged by the first male thread portion 42 and the nut 124, which urge the second piston 91A toward the first rod flange portion 33. In other words, the end of the second piston 91A opposite the first axial end 3a is biased toward the first rod flange portion 33 by the first male thread portion 42 and the nut 124, so that the end on the first axial end 3a side is pressed against the first rod flange portion 33.

[0121] The second piston assembly 90A and the nut 124 move together with the piston rod 21.

[0122] Here, during the extension stroke, the piston rod 21 moves from a state in which the piston ring 95A of the second piston 91A is located below the second cylinder 4 and is in a first predetermined range in which the piston ring 95A is not fitted into the second cylinder 4 to a second predetermined range that is further toward the extension side than the first predetermined range. Then, the stopper mechanism 81A causes the piston ring 95A of the second piston assembly 90A, which moves integrally with the piston rod 21, to enter the enlarged diameter portion 86 of the second cylinder 4 and then fit into the cylindrical portion 85 of the second cylinder 4. At the beginning of this fitting, the piston ring 95A is pressed against the second piston flange portion 213 of the second piston body 200 by the frictional force with the second cylinder 4 in contact with the piston ring 95A and the flow of oil L that flows from the rod guide 51 side of the piston ring 95A in the second cylinder 4 to the opposite side from the rod guide 51. As a result, the piston ring 95A comes into axial contact with the second piston flange portion 213, blocking the passage between the piston ring 95A and the second piston flange portion 213. This restricts the flow of oil L from the rod guide 51 side of the piston ring 95A in the second cylinder 4 to the opposite side of the rod guide 51 via the passage in the passage groove 232 of the second piston body 200 and the passages in the plurality of axial grooves 235 shown in Fig. 11. When the second piston 91A is positioned in the second cylinder 4 and the piston ring 95A is advanced into the second cylinder 4, the second cylinder 4 is divided into a one side chamber 141 on the rod guide 51 side of the second piston 91A and a other side chamber 142 on the opposite side of the rod guide 51 of the second piston 91A. In other words, when the second piston 91A is positioned within the second cylinder 4, it divides the interior of the second cylinder 4 into one side chamber 141 on the axial side of the first end 3a of the second piston 91A, and another side chamber 142 on the opposite side of the first end 3a of the second piston 91A.

[0123] During the extension stroke within the second predetermined range, the second piston 91A of the stopper mechanism 81A moves toward the rod guide 51 together with the piston rod 21, with the piston ring 95A blocking the passage between the second piston flange portion 213 of the second piston body 200 as described above. In the lower part of the second predetermined range, the piston ring 95A is located at the position of the plurality of grooves 87 provided in the second cylinder 4, and oil L flows through the plurality of grooves 87. At this time, as the second piston 91A approaches the rod guide 51, the number of open grooves 87 among the plurality of grooves 87 decreases, eventually reaching zero. This causes the damping force generated by the second cylinder 4 and the second piston 91A to increase stepwise.

[0124] As the second piston assembly 90A moves further toward the extension side, the piston ring 95A slides above any of the plurality of grooves 87 in the second cylinder 4 to approach the rod guide 51, while still blocking the passage between the second piston assembly 90A and the second piston flange portion 213 of the second piston body 200. Then, the second piston assembly 90A slides inside the second cylinder 4 to approach the rod guide 51, with the piston ring 95A blocking the gap between the second piston assembly 90A and the second cylinder 4.

[0125] When the pressure in one side chamber 141 becomes higher than the pressure in the other side chamber 142 by a predetermined value or more while the second piston assembly 90A is sliding toward the extension side within the second cylinder 4, the valve body 120 of the second piston assembly 90A opens, generating a damping force and causing the oil liquid L in the one side chamber 141 to flow into the other side chamber 142 through the connecting passage 248.

[0126] As described above, the second piston 91A is provided with a communication passage 248 that can communicate, when the second piston 91A is located in the second cylinder 4, one side chamber 141 that is closer to the first end 3a in the axial direction than the second piston 91A in the second cylinder 4 with the other side chamber 142 that is closer to the first end 3a than the second piston 91A in the second cylinder 4. The valve element 120 is provided on the other side chamber 142 side of the second piston 91A and opens to communicate the one side chamber 141 and the other side chamber 142 via the communication passage 248 when the pressure in the one side chamber 141 reaches a predetermined pressure that is higher than the pressure in the other side chamber 142 by a predetermined value or more.

[0127] At the upper limit position of the second predetermined range, the second piston assembly 90A of the stopper mechanism 81A stops when the ring member 201 abuts the end of the multiple regulating portions 242 opposite the axial second piston flange portion 213 against the rod guide 51, and then the second piston body 200 abuts the end of the second piston body 200 opposite the axial second piston flange portion 213 against the rod guide 51.

[0128] During the compression stroke within the second predetermined range, the second piston 91A of the stopper mechanism 81A moves from a state in which the piston ring 95A of the second piston 91A is fitted in the second cylinder 4 to a direction in which the second piston 91A moves together with the piston rod 21 in a direction away from the rod guide 51. Then, due to the frictional force with the second cylinder 4 and the flow of oil liquid L flowing from the other side chamber 142 to the one side chamber 141, the piston ring 95A of the second piston 91A moves away from the second piston flange portion 213 of the second piston body 200 in the axial direction, opening the passage between the second piston flange portion 213 and the second piston flange portion 213, and connecting this passage to the passages in the plurality of axial grooves 235 and the passage groove 232 of the second piston body 200 shown in FIG. During the subsequent compression stroke, the piston ring 95A opens the passage between itself and the second piston flange portion 213, and moves in a direction away from the rod guide 51 while maintaining this passage in communication with the passages in the plurality of axial grooves 235 of the second piston body 200 and the passage in the passage groove 232. As the second piston 91A moves in a direction away from the rod guide 51, the oil L in the other-side chamber 142 flows into the one-side chamber 141 through the passage between the piston ring 95A and the second piston flange portion 213, the passages in the plurality of axial grooves 235, and the passage in the passage groove 232. This reduces the damping force acting on the compression movement of the piston rod 21.

[0129] When the piston ring 95A of the second piston 91A is moved a predetermined distance away from the rod guide 51 during the compression stroke from a state in which the piston ring 95A is closer to the rod guide 51 than all of the grooves 87 in the second cylinder 4, the grooves 87 provided in the second cylinder 4 open. Then, oil L flows through the grooves 87 in addition to the flow through the passage between the piston ring 95A and the second piston flange portion 213, the passages in the multiple axial grooves 235, and the passages in the passage groove 232, reducing the damping force acting on the compression movement of the piston rod 21. At this time, the farther the second piston 91A is from the rod guide 51, the more of the multiple grooves 87 through which the oil L flows. This gradually reduces the damping force acting on the compression movement of the piston rod 21.

[0130] Next, the main operation of the cylinder device 1A will be described.

[0131] "An extension stroke in which the piston rod 21 is in a second predetermined range in which the piston ring 95A of the second piston 91A is fitted into the second cylinder 4"

[0132] 1 operates in the same manner as in the first predetermined range. Then, the second piston 91A of the second piston assembly 90A shown in FIG. 9 moves toward the rod guide 51 in the axial direction of the first cylinder 3, causing the piston ring 95A to enter the second cylinder 4. Then, in the initial stage, the piston ring 95A closes the passage between the piston ring 95A and the second piston flange portion 213 of the second piston body 200.

[0133] With the piston ring 95A thus blocking the passage between it and the second piston flange portion 213, the second piston 91A moves toward the rod guide 51. Then, the oil L in one side chamber 141 of the second cylinder 4 is throttled by the multiple grooves 87 provided in the second cylinder 4 and flows to the other side chamber 142. Therefore, the damping force generated by the second cylinder 4 and the second piston 91A increases. At this time, as the second piston 91A approaches the rod guide 51, the number of grooves 87 through which the oil L flows decreases, eventually reaching zero. This causes the generated damping force to increase stepwise, and the damping force against the movement of the piston rod 21 in the extension direction also increases stepwise.

[0134] When the pressure in one side chamber 141 becomes higher than the pressure in the other side chamber 142 by a predetermined value or more while the second piston assembly 90A is sliding toward the extension side within the second cylinder 4, the valve body 120 of the second piston assembly 90A opens, generating a damping force and causing the oil liquid L in the one side chamber 141 to flow into the other side chamber 142 through the connecting passage 248.

[0135] The damping force generated by the stopper mechanism 81A is increased relative to the damping force generated by the first piston assembly 17.

[0136] "Compression stroke when piston rod 21 is in the second predetermined range" During this compression stroke, first piston assembly 17 shown in Fig. 1 operates in the same manner as in the first predetermined range. Then, second piston 91A of second piston assembly 90A shown in Fig. 9 moves in a direction away from rod guide 51. Then, in the early stage of this movement, piston ring 95A opens the passage between second piston flange portion 213 of second piston body 200.

[0137] With the piston ring 95A thus opening the passage between it and the second piston flange portion 213, the second piston 91A moves in a direction away from the rod guide 51. Then, oil L flows from the other side chamber 142 to the one side chamber 141 through the passage between the piston ring 95A and the second piston flange portion 213, the passages in the axial grooves 235, and the passage in the passage groove 232. When the piston ring 95A of the second piston 91A passes the position of the groove 87 provided in the second cylinder 4 from a state where it is closer to the rod guide 51 than all of the grooves 87 provided in the second cylinder 4, oil L flows from the other side chamber 142 to the one side chamber 141 through the groove 87 in addition to the flow through the passage between the piston ring 95A and the second piston flange portion 213, the passages in the axial grooves 235, and the passage in the passage groove 232. At this time, the farther the second piston 91A is from the rod guide 51, the more of the grooves 87 through which oil L flows. As a result, the damping force against the movement of the piston rod 21 in the contraction direction is reduced in stages.

[0138] The cylinder device 1A of the second embodiment includes a stopper mechanism 81A, a second cylinder 4 having a smaller diameter than the first cylinder 3 and provided on the first end 3a side of the first cylinder 3, and a second piston 91A that moves with the movement of the piston rod 21 and is provided so as to be able to be fitted into the second cylinder 4. One end of the second piston 91A on the first end 3a side abuts against a first rod flange portion 33 between a rod first outer diameter portion 31 of the piston rod 21 and a rod second outer diameter portion 32 having a smaller diameter than the rod first outer diameter portion 31. The other end of the second piston 91A opposite the first end 3a is biased by a nut 124 that biases the second piston 91A toward the first rod flange portion 33. As a result, the cylinder device 1A is structured so that the nut 124 biases the other end opposite the first end 3a of the second piston 91A, which receives high pressure from the first end 3a when the stopper mechanism 81A is activated, toward the first rod flange portion 33, i.e., in a direction that resists the high pressure, thereby improving durability.

[0139] In the cylinder device 1A, the second piston 91A is provided with a communication passage 248 that, when the second piston 91A is positioned in the second cylinder 4, can communicate between one side chamber 141 located closer to the first end 3a than the second piston 91A in the second cylinder 4 and another side chamber 142 located on the opposite side of the first end 3a than the second piston 91A in the second cylinder 4. The cylinder device 1A also has a valve element 120 on the other side chamber 142 side of the second piston 91A that opens when the pressure in the one side chamber 141 reaches a predetermined pressure to communicate the one side chamber 141 and the other side chamber 142 via the communication passage 248. Therefore, in the cylinder device 1A, the valve element 120 opens when the pressure in the one side chamber 141 reaches a predetermined pressure to allow the oil L to flow from the one side chamber 141 to the other side chamber 142 via the communication passage 248, thereby further improving durability.

[0140] The cylinder device 1A biases the second piston 91A toward the first rod flange portion 33 using a first male thread portion 42 formed on the rod second outer diameter portion 32 and a nut 124 that screws onto the first male thread portion 42, thereby enabling improved durability with a simple structure.

[0141] The cylinder device 1A includes a piston ring 95A that is axially movable around the outer periphery of the second piston 91A, and a second piston flange portion 213 on the opposite side from the first end 3a and a ring member 201 on the first end 3a side that limit the axial movement range of the piston ring 95A. This makes it possible to limit the axial movement range of the piston ring 95A.

[0142] In the cylinder device 1A, the second piston 91A has a second piston flange portion 213 formed on the side opposite to the first end 3a, and the second piston body 200 has a fitting groove 231 formed on the first end 3a side. The second piston flange portion 213 of the second piston body 200 limits the axial movement range of the piston ring 95A by the second piston flange portion 213 and the ring member 201 fitted in the fitting groove 231. Therefore, the axial movement range of the piston ring 95A can be limited with a simple structure.

[0143] In the above embodiment, an example has been described in which the second pistons 91, 91A are urged toward the first rod flange portion 33 by the first male thread portion 42 of the piston rod 21 and the nut 124 threaded thereon to press them against the first rod flange portion 33. However, the second pistons 91, 91A may be urged toward the first rod flange portion 33 by a spring supported by the piston rod 21 to press them against the first rod flange portion 33. Alternatively, the second pistons 91, 91A may be urged toward the first rod flange portion 33 by a C-shaped ring attached to the piston rod 21 to press them against the first rod flange portion 33.

[0144] Furthermore, in the above embodiment, an example has been described in which a second cylinder 4 that is separate from the first cylinder 3 and has a smaller diameter than the first cylinder 3 is provided on the first end 3a side of the first cylinder 3, but it is also possible to provide a second cylinder 4 that is smaller in diameter than the first cylinder 3 integrally with the first cylinder 3 on the first end 3a side of the first cylinder 3 by bulge molding.

[0145] In addition, in the above embodiment, the extension-side stopper mechanisms 81, 81A are described as examples that are activated when the piston rod 21 reaches a predetermined position on the first end 3a side of one axial end of the extension side of the first cylinder 3 during the extension stroke. However, the present invention is also applicable to a compression-side stopper mechanism that is activated when the piston rod 21 reaches a predetermined position on the first end side of the other axial end of the compression side of the first cylinder 3 during the compression stroke.

[0146] According to the above aspect, it is possible to provide a cylinder device that can improve durability, and therefore the industrial applicability is great.

[0147] REFERENCE SIGNS LIST 1, 1A...cylinder device, 3...first cylinder, 3a...first end, 4...second cylinder, 18...first piston, 21...piston rod, 31...first outer diameter portion of rod, 32...second outer diameter portion of rod, 33...first rod flange portion (rod flange portion), 42...first male thread portion (biasing portion, screw), 81, 81A...stopper mechanism, 91, 91A...second piston, 92...third piston (first restricting portion), 93...fourth piston, 95, 95A...piston ring, 113...fourth piston flange portion (second restricting portion), 118, 248...communicating passage, 120...valve body, 124...nut (biasing portion), 141...one side chamber, 142...other side chamber, 200...second piston body, 201...ring member (second restricting portion), 213...second piston flange portion (first restricting portion), 231...fitting groove (groove).

Claims

1. A cylinder device comprising: a first cylinder in which a working fluid is sealed; a first piston slidably fitted within the first cylinder and defining the interior of the first cylinder; a piston rod connected to the first piston; and a stopper mechanism that operates when the first piston reaches a predetermined position on a first end side of one axial end of the first cylinder during an extension stroke or a compression stroke, wherein the stopper mechanism comprises: a second cylinder having a smaller diameter than the first cylinder and provided on the first end side of the first cylinder; and a second piston that moves in conjunction with movement of the piston rod and is provided so as to be able to be fitted within the second cylinder, wherein one end of the second piston on the first end side abuts against a rod flange portion between a rod first outer diameter portion of the piston rod and a rod second outer diameter portion having a diameter smaller than the rod first outer diameter portion, and the other end of the second piston opposite to the first end is biased by a biasing portion that biases the second piston towards the rod flange portion.

2. The cylinder device according to claim 1, wherein the first outer diameter portion of the rod and the second outer diameter portion of the rod are integrally formed.

3. The cylinder device according to claim 1, wherein the second piston is provided with a communication passage that, when the second piston is positioned within the second cylinder, can communicate between one side chamber in the second cylinder that is closer to the first end than the second piston and another side chamber in the second cylinder that is closer to the first end than the second piston, and a valve body is provided on the other side chamber side of the second piston that opens when the pressure in the one side chamber reaches a predetermined pressure, thereby communicating the one side chamber with the other side chamber via the communication passage.

4. A cylinder device according to claim 1, wherein the biasing portion is composed of a screw formed on the second outer diameter portion of the rod and a nut that is screwed onto the screw.

5. A cylinder device as described in claim 1, wherein the second piston has a piston ring provided on the outer periphery so as to be movable in the axial direction, and a first restricting portion on the opposite side to the first end and a second restricting portion on the first end side, which restrict the axial movement range of the piston ring.

6. A cylinder device as described in claim 5, wherein the second piston has a third piston and a fourth piston whose outer diameter on the third piston side is smaller than the outer diameter of the third piston, the third piston is the first restricting portion, and a fourth piston flange portion formed on the side of the fourth piston opposite to the third piston is the second restricting portion.

7. A cylinder device as described in claim 5, wherein the second piston has a second piston flange portion formed on the side opposite the first end and a second piston body having a groove formed on the first end side, the second piston flange portion being the first restricting portion, and a ring member fitted into the groove being the second restricting portion.

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