Hydraulic cylinder

Abstract

To provide a hydraulic cylinder in which a plug is fixed in a simple form.SOLUTION: A hydraulic cylinder 1A includes: a cylinder tube 2; a piston rod 5 which has a rod end 10 disposed at the inner side of the cylinder tube and moves in an axial direction; a first rod passage 21 which is formed within the piston rod and connects a hydraulic power source with a first opening 23 formed at the rod end; a plug 7 which is inserted into the first rod passage through the first opening; and a piston 6 which is fixed to the piston rod while covering at least a part of the plug and partitions the inner side of the cylinder tube into a bottom chamber 11 at one axial side and a head chamber at the other axial side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a hydraulic cylinder. [Background technology]

[0002] In the technical field related to hydraulic cylinders, there is known a hydraulic cylinder such as that disclosed in Patent Document 1. The hydraulic cylinder disclosed in Patent Document 1 includes a plug that is inserted from an open end of a passage in the rod that opens into a cylinder tube. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-025506 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the pressure on the plug increases, it may come loose. Known methods for threaded plugs require thread machining and measures to prevent loosening, which require additional space, parts, and machining, resulting in increased costs. Furthermore, threaded parts are difficult to clean, so foreign matter generated during machining cannot be completely removed from small-diameter parts like the plug, increasing the likelihood of foreign matter remaining, making it difficult to stabilize quality.

[0005] The technology disclosed in this specification aims to fix the plug in a simple shape. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a hydraulic cylinder including: a cylinder tube; a piston rod having a rod end disposed inside the cylinder tube and moving in an axial direction; a first rod passage formed inside the piston rod and connecting a hydraulic source to a first opening formed in the rod end; a plug inserted into the first rod passage via the first opening; and a piston fixed to the piston rod while covering at least a portion of the plug and dividing the inside of the cylinder tube into a bottom chamber on one axial side and a head chamber on the other axial side. [Effects of the Invention]

[0007] According to the technology disclosed in this specification, the plug is fixed in place with a simple shape. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a hydraulic cylinder according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a part of the hydraulic cylinder according to the first embodiment. [Figure 3] FIG. 3 is a perspective cross-sectional view showing a part of the piston rod and the plug according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing a part of the piston rod and the plug according to the first embodiment. [Figure 5] FIG. 5 is a perspective cross-sectional view showing a part of the piston rod, a plug, and a piston according to the first embodiment. [Figure 6] FIG. 6 is a view of the piston rod, plug, and piston according to the first embodiment as viewed from the bottom side. [Figure 7] FIG. 7 is a cross-sectional view showing a part of a hydraulic cylinder according to the second embodiment. [Figure 8] FIG. 8 is a perspective view showing a plate according to the second embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a part of a hydraulic cylinder according to the third embodiment. [Figure 10]FIG. 10 is a view of the piston rod and piston according to the third embodiment as viewed from the bottom side. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiments. The components of the embodiments described below can be combined as appropriate. In addition, some components may not be used.

[0010] [First embodiment] A first embodiment will be described. Fig. 1 is a cross-sectional view showing a hydraulic cylinder 1A according to this embodiment. As shown in Fig. 1, the hydraulic cylinder 1A includes a cylinder tube 2, a bottom 3, a cylinder head 4, a piston rod 5, a piston 6, and a plug 7.

[0011] The cylinder tube 2 is a substantially cylindrical member. The bottom 3 is a substantially columnar member. The cylinder head 4 is a substantially cylindrical member. The piston rod 5 is a substantially columnar member. The piston 6 is a substantially cylindrical member. The central axes of the cylinder tube 2, the bottom 3, the cylinder head 4, the piston rod 5, and the piston 6 are substantially aligned.

[0012] In the embodiment, the central axis of the cylinder tube 2, the central axis of the bottom 3, the central axis of the cylinder head 4, the central axis of the piston rod 5, and the central axis of the piston 6 are collectively referred to as the central axis AX as appropriate.

[0013] In addition, in the embodiments, the direction parallel to the central axis AX will be referred to as the axial direction, the radial direction of the central axis AX will be referred to as the radial direction, and the direction circumferentially around the central axis AX will be referred to as the circumferential direction.

[0014] A position on one side in the axial direction or a direction approaching one side will be referred to as "one axial side" or "bottom side," and a position on the other side in the axial direction or a direction approaching the other side will be referred to as "other axial side" or "head side." In the radial direction, a position close to the central axis AX or a direction approaching the central axis AX will be referred to as "inner radial direction," and a position farther from the central axis AX or a direction away from the central axis AX will be referred to as "outer radial direction."

[0015] The cylinder tube 2 supports a piston 6 so that it can move. A bottom 3 is connected to one axial end of the cylinder tube 2. A cylinder head 4 is connected to the other axial end of the cylinder tube 2. The bottom 3 is welded to the cylinder tube 2. The cylinder head 4 is disposed around a piston rod 5. The cylinder head 4 supports the piston rod 5 so that it can move. A plurality of seal members 8 are disposed between the cylinder head 4 and the piston rod 5. The cylinder head 4 is fixed to the cylinder tube 2 with bolts 9.

[0016] The piston rod 5 moves in the axial direction relative to the cylinder tube 2 and the cylinder head 4. At least a portion of the piston rod 5 is disposed inside the cylinder tube 2. The piston rod 5 has a rod end 10 on one axial side. At least the rod end 10 of the piston rod 5 is disposed inside the cylinder tube 2.

[0017] The piston 6 is fixed to the piston rod 5. The piston 6 divides the inside of the cylinder tube 2 into a bottom chamber 11 on one axial side and a head chamber 12 on the other axial side. The piston 6 is slidably supported on the inner surface of the cylinder tube 2. The piston 6 is axially movable inside the cylinder tube 2.

[0018] A first rod passage 21 and a second rod passage 22 are formed inside the piston rod 5. The first rod passage 21 and the second rod passage 22 are each formed to extend in the axial direction. The second rod passage 22 is formed adjacent to the first rod passage 21. In the embodiment, the first rod passage 21 and the second rod passage 22 are substantially parallel. Note that as long as the first rod passage 21 and the second rod passage 22 are formed inside the piston rod 5, the first rod passage 21 and the second rod passage 22 do not have to be parallel.

[0019] The rod end portion 10 disposed inside the cylinder tube 2 has a first opening 23 and a second opening 24 formed therein.

[0020] The head side end of the first rod passage 21 is connected to the hydraulic power source 13 via a first connection passage 25. The bottom side end of the first rod passage 21 is connected to a first opening 23. The first rod passage 21 connects the hydraulic power source 13 and the first opening 23 formed in the rod end portion 10.

[0021] The head side end of the second rod passage 22 is connected to the hydraulic power source 13 via a second connection passage 26. The bottom side end of the second rod passage 22 is connected to a second opening 24. The second rod passage 22 connects the hydraulic power source 13 and the second opening 24 formed in the rod end portion 10.

[0022] The plug 7 is inserted into the first rod passage 21 through the first opening 23. The plug 7 closes the first opening 23. The piston 6 is fixed to the piston rod 5. The piston 6 is arranged to cover the plug 7 from the bottom side. The piston 6 is fixed to the piston rod 5 while covering at least a portion of the plug 7 from the bottom side. The piston 6 can contact at least a portion of the plug 7. In the embodiment, a small gap is formed between the plug 7 and the piston 6. The plug 7 slides in the axial direction due to hydraulic pressure acting on the plug 7. When the hydraulic pressure in the first rod passage 21 on the head side of the plug 7 is higher than the hydraulic pressure on the bottom side, the plug 7 abuts against an abutment surface 63 (see FIG. 2, etc.) of the piston 6, which will be described later. When the hydraulic pressure in the first rod passage 21 on the head side of the plug 7 is lower than the hydraulic pressure on the bottom side, the plug 7 abuts against a support surface 213 (see FIG. 2, etc.) of the piston rod 5, which will be described later.

[0023] The piston rod (5) has a head chamber passage (27) that connects the first rod passage (21) and the head chamber (12) on the head side of the piston (6).

[0024] The piston 6 has a bottom chamber passage 28 that connects the second rod passage 22 and the bottom chamber 11.

[0025] In the embodiment, the hydraulic oil supplied from the hydraulic source 13 to the first rod passage 21 is supplied to the head chamber 12 via the head chamber passage 27. The hydraulic oil supplied from the hydraulic source 13 to the second rod passage 22 is supplied to the bottom chamber 11 via the bottom chamber passage 28.

[0026] The piston rod 5 moves axially so as to be removed from or inserted into the cylinder tube 2. When the piston rod 5 moves so as to be removed from the cylinder tube 2, the hydraulic cylinder 1A extends. When the piston rod 5 moves so as to be inserted into the cylinder tube 2, the hydraulic cylinder 1A contracts. When the piston rod 5 moves toward the head side, the hydraulic cylinder 1A extends. When the piston rod 5 moves toward the bottom side, the hydraulic cylinder 1A contracts. When hydraulic oil is supplied to the bottom chamber 11, the hydraulic cylinder 1A extends. When hydraulic oil is supplied to the head chamber 12, the hydraulic cylinder 1A contracts.

[0027] Fig. 2 is a cross-sectional view showing a portion of the hydraulic cylinder 1A according to this embodiment. Fig. 3 is a perspective cross-sectional view showing a portion of the piston rod 5 and the plug 7 according to this embodiment. Fig. 4 is a perspective view showing a portion of the piston rod 5 and the plug 7 according to this embodiment. Fig. 5 is a perspective cross-sectional view showing a portion of the piston rod 5, the plug 7, and the piston 6 according to this embodiment. Fig. 6 is a view of the piston rod 5, the plug 7, and the piston 6 according to this embodiment as viewed from the bottom side.

[0028] The piston 6 has a cylindrical portion 61 and an opposing portion 62. The cylindrical portion 61 is disposed around the piston rod 5. A screw thread 14A is provided on the outer peripheral surface of the piston rod 5. A screw groove 14B is provided on the inner peripheral surface of the cylindrical portion 61. The screw thread 14A and the screw groove 14B are coupled together. The piston rod 5 and the piston 6 are fixed together via a threaded portion 14 including the screw thread 14A and the screw groove 14B.

[0029] The facing portion 62 is connected to the bottom end of the cylindrical portion 61. The facing portion 62 is disposed on the bottom side of the piston rod 5 and the plug 7. The facing portion 62 faces the rod end portion 10.

[0030] The plug 7 has a first plug end face 71 facing the bottom side, a second plug end face 72 facing the head side, and an outer circumferential surface 73.

[0031] The first plug end face 71 abuts against an abutment surface 63 defined on at least a portion of the piston 6. The second plug end face 72 abuts against a support surface 213 arranged inside the first rod passage 21. The abutment surface 63 faces the head side. The support surface 213 faces the bottom side.

[0032] The contact surface 63 is disposed on the opposing portion 62 .

[0033] The first rod passage 21 has a large diameter portion 211 connected to the first opening 23, and a small diameter portion 212 arranged closer to the head than the large diameter portion 211. The support surface 213 is arranged at the boundary between the large diameter portion 211 and the small diameter portion 212.

[0034] A seal member 15 is disposed between the outer peripheral surface 73 of the plug 7 and the inner peripheral surface of the large diameter portion 211. The seal member 15 is disposed in a groove 74 provided in the outer peripheral surface 73. The seal member 15 includes an O-ring 15A, a backup ring 15B disposed on the bottom side of the O-ring 15A, and a backup ring 15C disposed on the head side of the O-ring 15A.

[0035] The surface roughness of the inner peripheral surface of the large diameter portion 211 is smaller than the surface roughness of the inner peripheral surface of the small diameter portion 212. Note that as long as the sealing performance between the seal member 15 and the inner peripheral surface of the large diameter portion 211 is ensured, the surface roughness of the inner peripheral surface of the large diameter portion 211 may be the same as or larger than the surface roughness of the inner peripheral surface of the small diameter portion 212.

[0036] A seal member 16 is disposed at the boundary between the cylindrical portion 61 and the piston rod 5, closer to the head than the threaded portion 14. The seal member 16 is disposed in a groove 65 provided on the inner circumferential surface of the cylindrical portion 61. The seal member 16 includes an O-ring 16A, a backup ring 16B disposed on the bottom side of the O-ring 16A, and a backup ring 16C disposed on the head side of the O-ring 16A. Note that the seal member 16 may be omitted.

[0037] When the piston 6 is fixed to the piston rod 5, the piston 6 is rotated with a tool inserted in the tool insertion hole 64 provided in the opposing portion 62 of the piston 6. Due to the relative rotation between the cylindrical portion 61 and the piston rod 5, the opposing portion 62 moves toward the head side. The opposing portion 62 is disposed so as to cover the plug 7 from the bottom side. In the embodiment, a small gap is formed between the first plug end face 71 of the plug 7 and the abutment surface 63 of the piston 6. The plug 7 slides in the axial direction due to hydraulic pressure acting on the plug 7. When the hydraulic pressure in the first rod passage 21 on the head side of the plug 7 is higher than the hydraulic pressure on the bottom side, the plug 7 abuts against the abutment surface 63 of the piston 6. When the hydraulic pressure in the first rod passage 21 on the head side of the plug 7 is lower than the hydraulic pressure on the bottom side, the plug 7 abuts against the support surface 213 of the piston rod 5. Furthermore, the opposing portion 62 contacts at least a portion of the rod end 10.

[0038] When the plug 7 is removed from the first rod passage 21, a tool is inserted into the tool insertion hole 75.

[0039] As shown in Figures 3, 4, and 5, the rod end 10 includes a rod end surface 101 facing the bottom side and a recess 102 provided in the rod end surface. At least a portion of the first opening 23 is provided in the rod end surface 101. At least a portion of the first opening 23 is provided inside the recess 102. At least a portion of the first opening 23 is provided in a bottom surface 103 of the recess 102 facing the bottom side. That is, at least a portion of the first opening 23 is provided so as to be exposed to the recess 102 and the bottom surface 103. At least a portion of the second opening 24 is provided in the rod end surface 101. At least a portion of the second opening 24 is provided inside the recess 102. At least a portion of the second opening 24 is provided in the bottom surface 103 of the recess 102 facing the bottom side.

[0040] It should be noted that the first opening 23 does not necessarily have to be exposed to the recess 102 or the bottom surface 103 .

[0041] As shown in Fig. 6, the bottom chamber passage 28 and at least a portion of the plug 7 overlap in a plane perpendicular to the central axis AX. In the plane perpendicular to the central axis AX, the range of the bottom chamber passage 28 through which hydraulic oil can pass is a non-overlapping portion 29, which is the bottom chamber passage 28 excluding the plug 7 and the rod end face 101, as shown in Fig. 6. The area of the non-overlapping portion 29 is 80% or more of the cross-sectional area of the second rod passage 22.

[0042] 3, 4, and 6, in the embodiment, the diameter Da of the second rod passage 22 is 20 mm, the depth Db of the recess 102 is 11 mm, the diameter Dc of the recess 102 is 27.5 mm, and the diameter Dd of the bottom chamber passage 28 is 26 mm. Also, the outer diameter De of the plug 7 is 20 mm.

[0043] As described above, the hydraulic cylinder 1A includes the cylinder tube 2, the piston rod 5 having the rod end 10 arranged inside the cylinder tube 2 and moving in the axial direction, the first rod passage 21 formed inside the piston rod 5 and connecting the hydraulic source 13 and the first opening 23 formed in the rod end 10, the plug 7 inserted into the first rod passage 21 via the first opening 23, and the piston 6 fixed to the piston rod 5 while contacting at least a portion of the plug 7 and dividing the inside of the cylinder tube 2 into a bottom chamber 11 on one axial side and a head chamber 12 on the other axial side.

[0044] According to the embodiment, the plug 7 is covered by at least a portion of the piston 6. As described above, if the plug 7 is movable in the axial direction, when the plug 7 moves to the bottom side, the plug 7 comes into contact with the piston 6. This prevents the plug 7 from coming out of the first rod passage 21 even if the pressure applied to the plug 7 increases.

[0045] The plug 7 has a first plug end face 71 facing one axial side and a second plug end face 72 facing the other axial side. The first plug end face 71 abuts against an abutment surface 63 defined on at least a portion of the piston 6. The second plug end face 72 abuts against a support surface 213 arranged inside the first rod passage 21. The plug 7 is disposed between the abutment surface 63 of the piston 6 and the support surface 213 of the piston rod 5.

[0046] The first rod passage 21 has a large diameter portion 211 connected to the first opening 23, and a small diameter portion 212 arranged on the other axial side of the large diameter portion 211. The support surface 213 is arranged at the boundary between the large diameter portion 211 and the small diameter portion 212.

[0047] A seal member 15 is disposed between the outer peripheral surface 73 of the plug 7 and the inner peripheral surface of the large diameter portion 211. This prevents the hydraulic oil that has flowed through the first rod passage 21 from flowing out from the first opening 23.

[0048] The surface roughness of the inner peripheral surface of the large diameter portion 211 is smaller than the surface roughness of the inner peripheral surface of the small diameter portion 212. This suppresses damage or deterioration of the seal member 15. Note that as long as the sealing performance between the seal member 15 and the inner peripheral surface of the large diameter portion 211 is ensured, the surface roughness of the inner peripheral surface of the large diameter portion 211 may be the same as the surface roughness of the inner peripheral surface of the small diameter portion 212, or may be larger than the surface roughness of the inner peripheral surface of the small diameter portion 212.

[0049] The piston 6 is arranged around the piston rod 5 and has a cylindrical portion 61 having a screw groove 14B that is coupled to a screw thread 14A provided on the piston rod 5, and an opposing portion 62 that is arranged on one axial side of the piston rod 5. An abutment surface 63 is arranged on the opposing portion 62. Relative rotation between the cylindrical portion 61 and the piston rod 5 moves the opposing portion 62 to the other axial side. As a result, the plug 7 and the opposing portion 62 face each other, preventing the plug 7 from slipping out of the first rod passage 21.

[0050] The opposing portion 62 comes into contact with at least a part of the rod end portion 10. This stabilizes the fixation of the piston rod 5 and the piston 6.

[0051] The piston rod 5 has a head chamber passage 27 that connects the first rod passage 21 and the head chamber 12 on the other axial side of the piston 6. As a result, the hydraulic oil that flows through the first rod passage 21 is supplied to the head chamber 12 via the head chamber passage 27.

[0052] A second rod passage 22 is formed inside the piston rod 5, connecting the hydraulic source 13 and a second opening 24 formed in the rod end 10. A bottom chamber passage 28 is provided in the piston 6, connecting the second rod passage 22 and the bottom chamber 11. As a result, the hydraulic oil that flows through the second rod passage 22 is supplied to the bottom chamber 11 via the bottom chamber passage 28.

[0053] The rod end 10 includes a rod end face 101 facing one axial side and a recess 102 provided in the rod end face 101. At least a portion of the second opening 24 is provided inside the recess 102. The recess 102 reduces pressure loss of the hydraulic oil flowing from the second opening 24 to the bottom chamber 11 via the bottom chamber passage 28.

[0054] [Second embodiment] A second embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment will be denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0055] Fig. 7 is a cross-sectional view showing a part of a hydraulic cylinder 1B according to this embodiment. As shown in Fig. 7, the hydraulic cylinder 1B includes a plate 30 disposed between the rod end portion 10 and the piston 6B.

[0056] 8 is a perspective view showing the plate 30 according to this embodiment. As shown in FIGS. 7 and 8, the plate 30 has a first plate end face 31, a second plate end face 32, and an outer peripheral surface 33.

[0057] The piston rod 5B has a first rod passage 21 and a second rod passage 22. A first opening 23B and a second opening 24B are formed in the rod end portion 10. The plug 7 is inserted into the first opening 23B.

[0058] The piston 6B has a cylindrical portion 61B and an opposing portion 62B. The opposing portion 62B is provided with a bottom chamber passage 28B.

[0059] The plate 30 has a connecting passage 34 that connects the second opening 24B and the bottom chamber passage 28B. The plate 30 also has a recess 35 in which the plug 7 is placed.

[0060] The first plate end face 31 contacts the opposing portion 62B. The second plate end face 32 contacts the rod end portion 10 of the piston rod 5B. The outer peripheral surface 33 contacts at least a portion of the inner peripheral surface of the cylindrical portion 61B. By inserting the plug 7 into the first opening 23B of the piston rod 5B and the recess 35 of the plate 30, rotation of the plate 30 is suppressed.

[0061] The hydraulic oil that has flowed through the second rod passage 22 flows through the connecting passage 34 of the plate 30, and is then supplied to the bottom chamber 11 via the bottom chamber passage 28B.

[0062] As described above, according to this embodiment, the plate 30 having the connecting passage 34 is disposed between the rod end 10 of the piston rod 5B and the piston 6B. The connecting passage 34 is inclined with respect to the central axis AX so as to connect the second opening 24B and the bottom chamber passage 28B. The connecting passage 34 reduces pressure loss of the hydraulic oil.

[0063] [Third embodiment] A third embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description of these components will be simplified or omitted.

[0064] Fig. 9 is a cross-sectional view showing a part of a hydraulic cylinder 1C according to this embodiment. Fig. 10 is a view of a piston rod 5C and a piston 6C according to this embodiment as seen from the bottom side.

[0065] 9 and 10, the piston rod 5C has a first rod passage 21 and a second rod passage 22. A first opening 23C and a second opening 24C are formed in the rod end portion 10. The plug 7 is inserted into the first opening 23C.

[0066] The piston 6C has a cylindrical portion 61C and an opposing portion 62C. The opposing portion 62C is provided with a bottom chamber passage 28C.

[0067] In a plane perpendicular to the central axis AX of the cylinder tube 2, the second opening 24C and the bottom chamber passage 28C at least partially overlap each other.

[0068] The hydraulic oil that has flowed through the second rod passage 22 is supplied to the bottom chamber 11 via the bottom chamber passage 28B.

[0069] As described above, according to this embodiment, the bottom chamber passage 28C is formed at a position shifted from the center of the opposing portion 62C, and the second opening 24C and the bottom chamber passage 28C at least partially overlap, thereby reducing pressure loss of the hydraulic oil. [Explanation of symbols]

[0070] 1A...hydraulic cylinder, 1B...hydraulic cylinder, 1C...hydraulic cylinder, 2...cylinder tube, 3...bottom, 4...cylinder head, 5...piston rod, 5B...piston rod, 5C...piston rod, 6...piston, 6B...piston, 6C...piston, 7...plug, 8...sealing member, 9...bolt, 10...rod end, 11...bottom chamber, 12...head chamber, 13...hydraulic source, 14...threaded portion, 14A...thread thread, 14B...thread groove, 15...sealing member, 15A...O-ring, 15B...backup ring, 15C...backup ring, 16...sealing member, 16A...O-ring, 16B...backup ring, 16C...backup ring, 21...first rod passage, 22...second rod passage, 23...first opening, 23B...second 1 opening, 23C...first opening, 24...second opening, 24B...second opening, 24C...second opening, 25...first connecting passage, 26...second connecting passage, 27...head chamber passage, 28...bottom chamber passage, 28B...bottom chamber passage, 29...non-overlapping portion, 30...plate, 31...first plate end surface, 32...second plate end surface, 33...outer circumferential surface, 34...connecting passage, 35...recess, 61...cylindrical portion , 61B...cylindrical portion, 61C...cylindrical portion, 62...opposing portion, 62B...opposing portion, 62C...opposing portion, 63...abutment surface, 64...tool insertion hole, 65...groove, 71...first plug end face, 72...second plug end face, 73...outer surface, 74...groove, 75...tool insertion hole, 101...rod end face, 102...recess, 103...bottom surface, 211...large diameter portion, 212...small diameter portion, 213...support surface, AX...central axis.

Claims

1. A cylinder tube; a piston rod having a rod end disposed inside the cylinder tube and moving in an axial direction; a first rod passage formed inside the piston rod and connecting a hydraulic pressure source and a first opening formed at an end of the rod; a plug inserted into the first rod passage through the first opening; a piston fixed to the piston rod in a state of covering at least a portion of the plug, and dividing the inside of the cylinder tube into a bottom chamber on one axial side and a head chamber on the other axial side; Hydraulic cylinder.

2. the plug has a first plug end face facing one axial side and a second plug end face facing the other axial side, the first plug end face contacts an abutment surface defined on at least a portion of the piston; the second plug end face contacts a support surface disposed inside the first rod passage; The hydraulic cylinder according to claim 1 .

3. the first rod passage has a large diameter portion connected to the first opening and a small diameter portion disposed on the other axial side of the large diameter portion, The support surface is disposed at the boundary between the large diameter portion and the small diameter portion. The hydraulic cylinder according to claim 2.

4. a seal member disposed between an outer circumferential surface of the plug and an inner circumferential surface of the large diameter portion; The hydraulic cylinder according to claim 3.

5. the surface roughness of the inner peripheral surface of the large diameter portion is smaller than the surface roughness of the inner peripheral surface of the small diameter portion; The hydraulic cylinder according to claim 4.

6. the piston includes a cylindrical portion disposed around the piston rod and having a thread groove coupled to a thread provided on the piston rod, and an opposing portion disposed on one axial side of the piston rod, The abutment surface is disposed on the opposing portion. The hydraulic cylinder according to any one of claims 2 to 5.

7. The opposing portion contacts at least a portion of the rod end portion.

7. The hydraulic cylinder according to claim 6.

8. the piston rod has a head chamber passage connecting the first rod passage and the head chamber on the other axial side of the piston; The hydraulic cylinder according to any one of claims 1 to 7.

9. a second rod passage formed inside the piston rod and connecting a hydraulic pressure source and a second opening formed at the rod end; a bottom chamber passage provided in the piston and connecting the second rod passage and the bottom chamber; The hydraulic cylinder according to any one of claims 1 to 8.

10. the rod end includes a rod end surface facing one axial direction and a recess provided in the rod end surface, At least a portion of the second opening is provided inside the recess.

10. The hydraulic cylinder according to claim 9.

11. a plate disposed between the rod end and the piston; The plate has a connecting passage that connects the second opening and the bottom chamber passage.

10. The hydraulic cylinder according to claim 9.

12. The second opening and at least a portion of the bottom chamber passage overlap in a plane perpendicular to the central axis of the cylinder tube.

10. The hydraulic cylinder according to claim 9.

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