Hydraulic cylinder

Abstract

To suppress deterioration of maintainability of a hydraulic cylinder.SOLUTION: A hydraulic cylinder 1 includes a cylinder tube 2, a cylinder head 3 having a large diameter portion 31 and a small diameter portion 32, a piston rod 4, a bolt 5, a dust seal 6, and a cover 11 covering at least a part of the cylinder head 3. The cover 11 includes a first portion 13 arranged around an outer surface on a radial direction outer side of the small diameter portion 32, and a second portion 14 arranged around an outer surface on a radial direction outer side of the large diameter portion 31. An end of the first portion 13 on one side in an axial direction is arranged on the other side in the axial direction compared to an end of the small diameter portion 32. The first portion 13 has a tilt surface 11c tilted to the other side in the axial direction from the end of the first portion 13 to the radial direction outer side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to hydraulic cylinders. [Background technology]

[0002] The construction machine includes a working machine and a hydraulic cylinder that expands and contracts to operate the working machine. As disclosed in Patent Document 1, the hydraulic cylinder includes a dust seal disposed between a cylinder head and a piston rod. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-224732 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the time required for maintenance of a hydraulic cylinder becomes long, the availability rate of a construction machine equipped with the hydraulic cylinder decreases.

[0005] The present disclosure aims to suppress a decrease in the maintainability of a hydraulic cylinder. [Means for solving the problem]

[0006] According to the present disclosure, there is provided a hydraulic cylinder comprising: a cylinder tube having an end face facing one axial side; a cylinder head having a large diameter portion having an opposing surface opposing the end face of the cylinder tube and a support surface facing the one axial side; and a small diameter portion protruding from the support surface to the one axial side; a piston rod at least a portion of which is disposed inside the cylinder head and moves in the axial direction; a bolt having a head disposed on the one axial side of the support surface and fixing the cylinder tube and the cylinder head; a dust seal disposed radially inside the small diameter portion; and a cover covering at least a portion of the cylinder head, wherein the outer diameter of the small diameter portion is smaller than the outer diameter of the large diameter portion, a tip end of the small diameter portion on the one axial side is disposed on the one axial side of the head, the cover has a first portion disposed around an outer surface of the radially outer side of the small diameter portion and a second portion disposed around an outer surface of the radially outer side of the large diameter portion, a tip end of the first portion on the one axial side is disposed on the other axial side of the tip end of the small diameter portion, and the first portion has an inclined surface that inclines radially outward from the tip end of the first portion to the other axial side. Effect of the Invention

[0007] According to the present disclosure, deterioration in maintainability of the hydraulic cylinder is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a part of a hydraulic cylinder according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a part of the hydraulic cylinder according to the first embodiment. [Diagram 3] FIG. 3 is a view for explaining a method of assembling the hydraulic cylinder according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing a part of the hydraulic cylinder according to the second embodiment. [Diagram 5] FIG. 5 is a cross-sectional view showing a part of the hydraulic cylinder according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] [First embodiment] A first embodiment will be described. Fig. 1 is a perspective view showing a part of a hydraulic cylinder 1 according to this embodiment. Fig. 2 is a cross-sectional view showing a part of the hydraulic cylinder 1 according to this embodiment. As shown in Figs. 1 and 2, the hydraulic cylinder 1 includes a cylinder tube 2, a cylinder head 3, a piston rod 4, a bolt 5, a dust seal 6, a rod packing 7, a buffer ring 8, a first bearing 9, a second bearing 10, and a cover 11.

[0011] The cylinder tube 2 is a substantially cylindrical member. The cylinder head 3 is a substantially cylindrical member. The piston rod 4 is a substantially columnar member. The central axes of the cylinder tube 2, the cylinder head 3, and the piston rod 4 substantially coincide with each other. The piston rod 4 may be a hollow member.

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

[0013] In the embodiments, the direction parallel to the central axis AX is referred to as the axial direction, the radial direction of the central axis AX is referred to as the radial direction, and the direction going around the central axis AX is referred to as the circumferential direction.

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

[0015] The cylinder tube 2 has an end face 2A facing one axial side. A cylinder head 3 is connected to the end face 2A of the cylinder tube 2. A bottom (not shown) is connected to the end face of the cylinder tube 2 facing the other axial side. The cylinder tube 2 movably supports a piston (not shown) connected to the other axial side of a piston rod 4. The piston divides the inside of the cylinder tube 2 into a head chamber on one axial side and a bottom chamber on the other axial side. The cylinder tube 2 has a threaded hole 21 provided in the end face 2A of the cylinder tube 2. A plurality of threaded holes 21 are provided at intervals in the circumferential direction.

[0016] The cylinder head 3 movably supports the piston rod 4. The cylinder head 3 has a large diameter portion 31, a small diameter portion 32, and an insertion portion 33.

[0017] The large diameter portion 31 is substantially cylindrical. The large diameter portion 31 has an opposing surface 3A that faces the end surface 2A of the cylinder tube 2, and a support surface 3B that faces the opposite direction of the opposing surface 3A. The opposing surface 3A faces the other axial side. The support surface 3B faces one axial side. The large diameter portion 31 has a through hole 34 that is provided to connect the support surface 3B and the opposing surface 3A. A plurality of through holes 34 are provided at intervals in the circumferential direction.

[0018] The small diameter portion 32 is substantially cylindrical. The small diameter portion 32 protrudes from the support surface 3B of the large diameter portion 31 to one side in the axial direction. The central axis of the large diameter portion 31 and the central axis of the small diameter portion 32 coincide with each other. The outer diameter of the small diameter portion 32 is smaller than the outer diameter of the large diameter portion 31.

[0019] The insertion portion 33 is substantially cylindrical. The insertion portion 33 protrudes from the opposing surface 3A of the large diameter portion 31 to the other axial side. The central axis of the large diameter portion 31 and the central axis of the insertion portion 33 coincide with each other. The outer diameter of the insertion portion 33 is smaller than the outer diameter of the large diameter portion 31. The insertion portion 33 is disposed inside the cylinder tube 2. The insertion portion 33 is inserted into the inside of the cylinder tube 2 from an opening of the cylinder tube 2 on one axial side.

[0020] The piston rod 4 moves in the axial direction relative to the cylinder tube 2 and the cylinder head 3. At least a portion of the piston rod 4 is disposed inside the cylinder tube 2. At least a portion of the piston rod 4 is disposed inside the cylinder head 3. An annular rod head 41 is provided on one axial side of the piston rod 4. The piston rod 4 is connected to a working implement of the construction machine via the rod head 41.

[0021] The piston rod 4 moves in the axial direction so as to be removed from the cylinder tube 2 or inserted into the cylinder tube 2. When the piston rod 4 moves so as to be removed from the cylinder tube 2, the hydraulic cylinder 1 extends. When the piston rod 4 moves so as to be inserted into the cylinder tube 2, the hydraulic cylinder 1 contracts. When the piston rod 4 moves to one axial side, the hydraulic cylinder 1 extends. When the piston rod 4 moves to the other axial side, the hydraulic cylinder 1 contracts. In the embodiment, the one axial side is the extension direction side. The other axial side is the contraction direction side. Hydraulic oil is supplied to the bottom chamber or the head chamber in response to the extension and contraction of the hydraulic cylinder 1.

[0022] The bolts 5 fix the cylinder tube 2 and the cylinder head 3. The bolts 5 are inserted through the multiple threaded holes 21 of the cylinder tube 2 provided in the circumferential direction and through holes 34 of the cylinder head 3. The cylinder tube 2 and the cylinder head 3 are fixed by the multiple bolts 5. When the fixation by the bolts 5 is released, the cylinder head 3 is released from the cylinder tube 2.

[0023] The bolt 5 has a head 51, a shaft 52, and a threaded portion 53. The threaded portion 53 of the bolt 5 is inserted into the threaded hole 21 via the through hole 34. The cylinder tube 2 and the cylinder head 3 are fixed by the bolt 5 by engaging a threaded ridge on the threaded portion 53 with a threaded groove on the threaded hole 21. The head 51 is disposed on one axial side of the support surface 3B. A washer 12 is disposed between the head 51 and the support surface 3B. The washer 12 does not necessarily have to be disposed.

[0024] The tip end 3C of the small diameter portion 32 on one axial side is disposed on one axial side of the support surface 3 B. The tip end 3C of the small diameter portion 32 is disposed on one axial side of the head 51.

[0025] The dust seal 6 seals the boundary between the cylinder head 3 and the piston rod 4. The dust seal 6 scrapes off foreign matter adhering to the outer surface of the piston rod 4. The dust seal 6 prevents foreign matter present around the hydraulic cylinder 1 from entering the inside of the cylinder tube 2.

[0026] The dust seal 6 is disposed radially inside the small diameter portion 32. The dust seal 6 is disposed between the inner surface of the small diameter portion 32 and the outer surface of the piston rod 4. The dust seal 6 is a substantially annular member. The dust seal 6 has an outer annular portion 61 and a lip portion 62 protruding radially inward from the inner surface of the outer annular portion 61. The outer annular portion 61 is fixed to the inner surface of the small diameter portion 32. The lip portion 62 contacts the outer surface of the piston rod 4. In this embodiment, a plurality of dust seals 6 are disposed at intervals in the axial direction. A plurality of dust seals 6 may be disposed without any intervals, or only one dust seal 6 may be disposed.

[0027] The tip portion 6A of the dust seal 6 on one axial side is disposed outside the space defined by the inner surface of the small diameter portion 32 and the outer surface of the piston rod 4. In other words, the tip portion 6A of the dust seal 6 is disposed on one axial side of the tip portion 3C of the small diameter portion 32. The tip portion 6A of the dust seal 6 includes the lip portion 62 of the dust seal 6 that is disposed furthest on one axial side among the multiple dust seals 6.

[0028] The rod packing 7 and the buffer ring 8 each seal the boundary between the cylinder head 3 and the piston rod 4. The rod packing 7 and the buffer ring 8 each suppress the hydraulic oil inside the cylinder tube 2 from leaking to the outside of the cylinder tube 2. The rod packing 7 is disposed between the large diameter portion 31 and the piston rod 4. At least a portion of the buffer ring 8 is disposed between the insertion portion 33 and the piston rod 4.

[0029] The first bearing 9 and the second bearing 10 each support the piston rod 4 movably in the axial direction. The cylinder head 3 movably supports the piston rod 4 via the first bearing 9 and the second bearing 10. The first bearing 9 is disposed between the large diameter portion 31 and the piston rod 4. The second bearing 10 is disposed between the insertion portion 33 and the piston rod 4. The first bearing 9 and the second bearing 10 do not necessarily have to be disposed.

[0030] The cover 11 covers at least a part of the cylinder head 3. The cover 11 is a substantially cylindrical member. In this embodiment, the cover 11 is made of synthetic resin. An example of the synthetic resin forming the cover 11 is urethane resin. The cover 11 may be made of rubber.

[0031] The cover 11 has a first portion 13 and a second portion 14. The first portion 13 is disposed around the radially outer surface of the small diameter portion 32. The second portion 14 is disposed around the radially outer surface of the large diameter portion 31. The first portion 13 is disposed so as to cover at least a portion of the outer surface of the small diameter portion 32. The second portion 14 is disposed so as to cover the outer surface of the large diameter portion 31.

[0032] At least a part of the first portion 13 is disposed on one axial side of the head 51. At least a part of the second portion 14 is disposed radially outward of the head 51. The head 51 of the bolt 5 is covered by the cover 11.

[0033] A tip end 11A of the first portion 13 on one axial side is disposed on the other axial side of the tip end 3C of the small diameter portion 32. In other words, the cover 11 is disposed so as not to cover the dust seal 6. The tip end 6A of the dust seal 6 is exposed from the opening between the tip end 3C of the small diameter portion 32 and the piston rod 4.

[0034] In this embodiment, the position of the base end 11B of the second portion 14 on the other axial side coincides with the position of the base end 3D of the large diameter portion 31 on the other axial side. The position of the base end 11B may be disposed outside the cylinder tube 2.

[0035] The first portion 13 has an inclined surface 11C, a first sealing surface 11D, and a bolt-facing surface 11E.

[0036] The inclined surface 11C faces substantially one side in the axial direction. The inclined surface 11C inclines from the tip end 11A of the first portion 13 toward the outside in the radial direction to the other side in the axial direction.

[0037] The first seal surface 11D faces radially inward. The first seal surface 11D faces the outer surface of the small diameter portion 32. The first seal surface 11D and the outer surface of the small diameter portion 32 are substantially parallel. The first seal surface 11D contacts the outer surface of the small diameter portion 32.

[0038] The bolt-facing surface 11E faces the other axial side. The bolt-facing surface 11E faces the head 51 of the bolt 5. The bolt-facing surface 11E may come into contact with the head 51.

[0039] The second portion 14 has an outer surface 11F, a second sealing surface 11G, and a bolt-facing surface 11H.

[0040] The outer surface 11F faces radially outward. A peripheral portion of the inclined surface 11C of the first portion 13 is connected to the outer surface 11F of the second portion 14. A radially outer peripheral portion of the inclined surface 11C is connected to an end portion on one axial side of the outer surface 11F.

[0041] The second seal surface 11G faces radially inward. The second seal surface 11G faces the outer surface of the large diameter portion 31. The second seal surface 11G and the outer surface of the large diameter portion 31 are substantially parallel. The second seal surface 11G contacts the outer surface of the large diameter portion 31.

[0042] The bolt-facing surface 11H faces radially inward. The bolt-facing surface 11H and the second seal surface 11G are disposed substantially in the same plane. The bolt-facing surface 11E is disposed radially outward from the head 51 of the bolt 5. The bolt-facing surface 11H faces the head 51 via a gap. A radially outer end of the bolt-facing surface 11E and an end of the bolt-facing surface 11E on one axial side are connected to each other.

[0043] The first portion 13 has a first protrusion 13A protruding radially inward from the first seal face 11D. The first protrusion 13A is provided around the central axis AX over the entire circumferential area of ​​the first seal face 11D. The first protrusion 13A may be provided on only a portion of the circumferential area of ​​the first seal face 11D. In the axial direction, only one first protrusion 13A is provided on the first seal face 11D.

[0044] The small diameter portion 32 has a first recess 32A provided on the outer surface of the small diameter portion 32. The first recess 32A is provided around the central axis AX over the entire circumferential area of ​​the outer surface of the small diameter portion 32. The first recess 32A may be provided on a portion of the circumferential area of ​​the outer surface of the small diameter portion 32. Only one first recess 32A is provided on the outer surface of the small diameter portion 32 in the axial direction.

[0045] The first protrusion 13A is disposed in the first recess 32A. The first protrusion 13A is fitted into the first recess 32A.

[0046] The second portion 14 has a second protrusion 14A protruding radially inward from the second seal surface 11G. The second protrusion 14A is provided so as to surround the central axis AX. In the axial direction, only one second protrusion 14A is provided on the second seal surface 11G.

[0047] The large diameter portion 31 has a second recess 31A provided on the outer surface of the large diameter portion 31. The second recess 31A is provided so as to surround the central axis AX. In this embodiment, one second recess 31A is provided on the outer surface of the large diameter portion 31 in the axial direction. The number of second recesses 31A in the axial direction is not limited to one.

[0048] The second protrusion 14A is disposed to correspond to the second recess 31A. The second protrusion 14A is fitted into the second recess 31A.

[0049] 3 is a diagram for explaining a method of assembling the hydraulic cylinder 1 according to this embodiment. After the dust seal 6, the rod packing 7, the buffer ring 8, the first bearing 9, and the second bearing 10 are attached to the cylinder head 3, the insert part 33 is inserted into the inside of the cylinder tube 2. After the insert part 33 is inserted into the inside of the cylinder tube 2, the cylinder tube 2 and the cylinder head 3 are fixed by a plurality of bolts 5. The cylinder tube 2 and the cylinder head 3 are fixed so that the end surface 2A and the opposing surface 3A are in contact with each other. The threaded part 53 of the bolt 5 is disposed in the screw hole 21, the shaft part 52 of the bolt 5 is disposed in the through hole 34, and the head of the bolt 5 is supported on the support surface 3B via the washer 12.

[0050] The piston rod 4 is inserted into the cover 11, and then inserted into the cylinder head 3 and the cylinder tube 2. With the cover 11 disposed around the piston rod 4, the piston rod 4 is inserted into the cylinder head 3 and the cylinder tube 2.

[0051] After the piston rod 4 is inserted into the cylinder head 3 and the cylinder tube 2, the cover 11 is attached to the cylinder head 3. The cover 11 is attached to the cylinder head 3 such that the second portion 14 is disposed around the large diameter portion 31 and the first portion 13 is disposed around the small diameter portion 32.

[0052] The cover 11 is made of synthetic resin or rubber. The cover 11 can be elastically deformed. The cover 11 is attached to the cylinder head 3 so that the second portion 14 is arranged around the large diameter portion 31 and the first portion 13 is arranged around the small diameter portion 32 while elastically deforming. The second portion 14 arranged around the large diameter portion 31 elastically deforms so as to clamp the outer surface of the large diameter portion 31. The first portion 13 arranged around the small diameter portion 32 elastically deforms so as to clamp the outer surface of the small diameter portion 32. As a result, the outer surface of the large diameter portion 31 and the second seal surface 11G are in close contact with each other, and the outer surface of the small diameter portion 32 and the first seal surface 11D are in close contact with each other.

[0053] Moreover, the cover 11 is attached to the cylinder head 3 such that the first protrusion 13A is disposed in the first recess 32A and the second protrusion 14A is disposed in the second recess 31A. By disposing the first protrusion 13A in the first recess 32A and the second protrusion 14A in the second recess 31A, the cover 11 is prevented from slipping out of the cylinder head 3.

[0054] When the cover 11 is attached to the cylinder head 3, at least a portion of the cylinder head 3 is covered by the cover 11. The cover 11 is arranged so as to cover the outer surface of the large diameter portion 31, the support surface 3B of the large diameter portion 31, and the outer surface of the small diameter portion 32. The cover 11 is also arranged so as to cover the bolts 5. The cover 11 prevents foreign matter from adhering to the surface of the cylinder head 3 and the surface of the bolts 5. Examples of foreign matter include soil, sand, dust, rainwater, and muddy water.

[0055] Foreign matter adhering to inclined surface 11C falls from inclined surface 11C due to, for example, the effect of gravity. Similarly, foreign matter adhering to outer surface 11F falls from outer surface 11F due to, for example, the effect of gravity. Therefore, foreign matter is prevented from accumulating on the surface of cover 11.

[0056] The tip 6A of the dust seal 6 is not covered by the cover 11. Because the tip 6A of the dust seal 6 is not covered by the cover 11, an operator can easily remove foreign matter adhering to the tip 6A without removing the cover 11 from the cylinder head 3. Also, an inclined surface 11C of the cover 11 is disposed around the tip 6A of the dust seal 6. Therefore, foreign matter adhering to the tip 6A can fall from the tip 6A by running down the inclined surface 11C due to the action of gravity.

[0057] Since the cylinder head 3 and the bolts 5 are covered with the cover 11, the cylinder head 3 and the bolts 5 are prevented from being contaminated by foreign matter and from rusting.

[0058] When replacing the dust seal 6, the worker removes the cover 11 from the cylinder head 3, and then releases the bolts 5 that secure the cylinder tube 2 and the cylinder head 3 to each other. Because the cover 11 prevents foreign matter from adhering to the bolts 5 and prevents the bolts 5 from rusting, the worker can use a tool to smoothly rotate the bolts 5. After the bolts 5 have been released from securing the cylinder tube 2 and the cylinder head 3 to each other, the cylinder head 3 is removed from the cylinder tube 2. The worker can then replace the dust seal 6.

[0059] As described above, according to this embodiment, the cylinder tube 2 and the cylinder head 3 are fixed by the bolt 5 inserted into the through hole 34 of the large diameter portion 31. The dust seal 6 is disposed radially inside the small diameter portion 32. The cover 11 is disposed so as to cover the surface of the cylinder head 3 and the head 51 of the bolt 5. The cover 11 suppresses contamination of the cylinder head 3 and the bolt 5. Since contamination of the cylinder head 3 and the bolt 5 is suppressed, deterioration of the cylinder head 3 and the bolt 5 is suppressed. Since the cover 11 suppresses adhesion of foreign matter to the bolt 5 and rusting of the bolt 5, the worker can smoothly rotate the bolt 5 using a tool. The worker can smoothly perform the work of releasing the fixing of the cylinder tube 2 and the cylinder head 3 by the bolt 5.

[0060] The tip end 11A of the first portion 13 on one axial side is disposed on the other axial side of the tip end 3C of the small diameter portion 32. Since the tip end 6A of the dust seal 6 is not covered by the cover 11, an operator can easily remove foreign matter adhering to the tip end 6A without removing the cover 11 from the cylinder head 3.

[0061] For example, if the tip of the dust seal is covered with a cover, if a foreign object gets inside the cover and adheres to the dust seal, the worker needs to remove the cover from the cylinder head to remove the foreign object. This increases the time required for the foreign object removal work, and as a result, the time required for maintenance increases. Also, if foreign object is attached to the bolt 5 or the bolt 5 is rusted, the worker may not be able to smoothly rotate the bolt 5 using a tool. This increases the time required for the work of releasing the fixation between the cylinder tube 2 and the cylinder head 3, and as a result, the time required for maintenance increases.

[0062] In this embodiment, a worker can easily remove foreign matter adhering to the tip 6A without removing the cover 11 from the cylinder head 3. This reduces the time required for the foreign matter removal work. In addition, the cover 11 prevents contamination of the cylinder head 3 and the bolt 5. This reduces the time required for the work of releasing the fixation between the cylinder tube 2 and the cylinder head 3. This prevents the time required for maintenance of the hydraulic cylinder 1 from becoming long, and reduces the deterioration of the maintainability of the hydraulic cylinder 1. Since the deterioration of the maintainability of the hydraulic cylinder 1 is reduced, the deterioration of the availability of the construction machine equipped with the hydraulic cylinder 1 is reduced.

[0063] The inclined surface 11C of the cover 11 is disposed around the tip 6A of the dust seal 6. Therefore, foreign matter adhering to the tip 6A can fall from the tip 6A by gravity along the inclined surface 11C. This prevents foreign matter from accumulating on the tip 6A of the dust seal 6 and on the surface of the cover 11.

[0064] At least a part of the first portion 13 is disposed on one axial side of the head 51, and at least a part of the second portion 14 is disposed radially outward of the head 51. The head 51 is disposed in an enclosed space defined by the bolt-facing surface 11E of the first portion 13, the bolt-facing surface 11H of the second portion 14, and the outer surface of the small diameter portion 32. Therefore, contamination of the head 51 is suppressed.

[0065] The peripheral edge of the inclined surface 11C is connected to the outer surface 11F of the second portion 14. Therefore, foreign matter adhering to the inclined surface 11C can smoothly fall from the cover 11. Therefore, the accumulation of foreign matter on the surface of the cover 11 is suppressed.

[0066] The first portion 13 has a first seal surface 11D that faces the outer surface of the small diameter portion 32. This prevents the outer surface of the small diameter portion 32 from being contaminated.

[0067] The first seal surface 11D comes into contact with the outer surface of the small diameter portion 32. This prevents foreign matter from entering between the first seal surface 11D and the outer surface of the small diameter portion 32.

[0068] The first portion 13 has a first protrusion 13A protruding radially inward from the first seal surface 11D. The small diameter portion 32 has a first recess 32A provided on the outer surface of the small diameter portion 32 and in which the first protrusion 13A is disposed. This prevents the cover 11 from slipping out of the cylinder head 3.

[0069] The second portion 14 has a second seal surface 11G that faces the outer surface of the large diameter portion 31. This prevents the outer surface of the large diameter portion 31 from being contaminated.

[0070] The second seal surface 11G comes into contact with the outer surface of the large diameter portion 31. This prevents foreign matter from entering between the second seal surface 11G and the outer surface of the large diameter portion 31.

[0071] The second portion 14 has a second protrusion 14A protruding radially inward from the second seal surface 11G. The large diameter portion 31 has a second recess 31A provided on the outer surface of the large diameter portion 31 and in which the second protrusion 14A is disposed. This prevents the cover 11 from slipping out of the cylinder head 3.

[0072] [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 are denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0073] Fig. 4 is a perspective view showing a part of the hydraulic cylinder 101 according to this embodiment. Fig. 5 is a cross-sectional view showing a part of the hydraulic cylinder 101 according to this embodiment. The hydraulic cylinder 101 includes a cylinder tube 2, a cylinder head 3, a piston rod 4, a bolt 5, a dust seal 6, a rod packing 7, a buffer ring 8, a first bearing 9, a second bearing 10, and a cover 71.

[0074] The cover 71 covers at least a portion of the cylinder head 3. In this embodiment, the cover 71 is made of metal. An example of the metal that forms the cover 71 is iron.

[0075] The cover 71 has a so-called half structure. The cover 71 includes a first half cover 711 and a second half cover 712. The first half cover 711 and the second half cover 712 are fixed together by a fixing member 72. The fixing member 72 includes a screw. The first half cover 711 and the second half cover 712 are fixed together by the two fixing members 72. By fixing the first half cover 711 and the second half cover 712 together, the substantially cylindrical cover 71 is formed.

[0076] The cover 71 has a first portion 73 and a second portion 74. The first portion 73 is disposed around the outer surface of the small diameter portion 32. The second portion 74 is disposed around the outer surface of the large diameter portion 31. The first portion 73 is disposed so as to cover the outer surface of the small diameter portion 32. The second portion 74 is disposed so as to cover the outer surface of the large diameter portion 31.

[0077] At least a part of the first portion 73 is disposed on one axial side of the head 51. At least a part of the second portion 74 is disposed radially outward of the head 51. The head 51 of the bolt 5 is covered with the cover 71.

[0078] A tip end 71A of the first portion 73 on one axial side is disposed on the other axial side of the tip end 3C of the small diameter portion 32. The cover 71 is disposed so as not to cover the dust seal 6. The tip end 6A of the dust seal 6 is exposed from an opening between the tip end 3C of the small diameter portion 32 and the piston rod 4.

[0079] The stopper member 15 is disposed so as to face the tip end 71A of the first portion 73. The stopper member 15 prevents the cover 71 from slipping out of the cylinder head 3. The stopper member 15 is disposed in a groove 32B provided on the outer surface of the small diameter portion 32. The groove 32B is formed so as to surround the central axis AX. The stopper member 15 is an annular or arc-shaped member disposed in the groove 32B. Examples of the stopper member 15 include a snap ring or a circlip.

[0080] In this embodiment, the position of the base end 71B of the second portion 74 on the other axial side coincides with the position of the base end 3D of the large diameter portion 31 on the other axial side. The position of the base end 11B may be disposed outside the cylinder tube 2.

[0081] The first portion 73 has an inclined surface 71C, a first sealing surface 71D, and a bolt-facing surface 71E.

[0082] The inclined surface 71C faces substantially one axial direction side. The inclined surface 71C is inclined from the tip end 71A of the first portion 73 toward the radially outward side toward the other axial direction side.

[0083] The first seal surface 71D faces radially inward. The first seal surface 71D faces the outer surface of the small diameter portion 32. The first seal surface 71D and the outer surface of the small diameter portion 32 are substantially parallel to each other.

[0084] The bolt-facing surface 71E faces the head 51 of the bolt 5. The bolt-facing surface 71E faces the other axial side.

[0085] The second portion 74 has an outer surface 71F, a second sealing surface 71G, and a bolt-facing surface 71H.

[0086] The outer surface 71F of the second portion 74 is connected to the circumferential edge portion of the inclined surface 71C of the first portion 73. The outer surface 71F of the second portion 74 faces radially outward.

[0087] The second seal surface 71G faces radially inward. The second seal surface 71G faces the outer surface of the large diameter portion 31. The second seal surface 71G and the outer surface of the large diameter portion 31 are substantially parallel to each other.

[0088] The bolt facing surface 71H faces radially inward. The bolt facing surface 71H and the second seal surface 71G are disposed substantially in the same plane. The bolt facing surface 71E is disposed radially outward of the head 51 of the bolt 5.

[0089] The first seal member 16 is disposed between the first seal surface 71D and the outer surface of the small diameter portion 32. An example of the first seal member 16 is an O-ring.

[0090] The first portion 73 has a recess 73A provided in the first seal surface 71D. The recess 73A is provided to surround the central axis AX. At least a portion of the first seal member 16 is disposed in the recess 73A. When disposed in the recess 73A, the first seal member 16 contacts the outer surface of the small diameter portion 32.

[0091] A second seal member 17 is disposed between the second seal surface 71G and the outer surface of the large diameter portion 31. An example of the second seal member 17 is an O-ring.

[0092] The second portion 74 has a recess 74A provided in the second seal surface 71G. The recess 74A is provided to surround the central axis AX. At least a portion of the second seal member 17 is disposed in the recess 74A. When disposed in the recess 74A, the second seal member 17 contacts the outer surface of the large diameter portion 31.

[0093] Next, a method of assembling the hydraulic cylinder 101 will be described. After the dust seal 6, the rod packing 7, the buffer ring 8, the first bearing 9, and the second bearing 10 are each attached to the cylinder head 3, the insertion part 33 is inserted into the inside of the cylinder tube 2. After the insertion part 33 is inserted into the inside of the cylinder tube 2, the cylinder tube 2 and the cylinder head 3 are fixed together with a plurality of bolts 5.

[0094] After the piston rod 4 is inserted into the cylinder head 3 and the cylinder tube 2, the first seal member 16 and the second seal member 17 are disposed around the cylinder head 3, and the first half cover 711 and the second half cover 712 are disposed around the cylinder head 3. The first half cover 711 and the second half cover 712 are fixed by the fixing member 72, so that at least a portion of the cylinder head 3 is covered by the cover 71. The bolt 5 is also covered by the cover 71. After the cover 71 is attached to the cylinder head 3, the stopper member 15 is disposed in the groove 32B.

[0095] When replacing the dust seal 6, the fixing member 72 is released between the first half cover 711 and the second half cover 712. After the first half cover 711 and the second half cover 712 are released and the cover 71 is removed from the cylinder head 3, the bolts 5 are released between the cylinder tube 2 and the cylinder head 3. Since contamination of the bolts 5 is suppressed, the worker can smoothly rotate the bolts 5 using a tool. After the bolts 5 are released from the cylinder tube 2 and the cylinder head 3, the cylinder head 3 is removed from the cylinder tube 2. The worker can replace the dust seal 6.

[0096] As described above, in this embodiment as well, deterioration in the maintainability of the hydraulic cylinder 1 is suppressed.

[0097] A first seal member 16 is disposed between the first seal surface 71D and the outer surface of the small diameter portion 32. A second seal member 17 is disposed between the second seal surface 71G and the outer surface of the large diameter portion 31. The first seal member 16 and the second seal member 17 prevent foreign matter from entering the space inside the cover 71. The first seal member 16 and the second seal member 17 also seal the space inside the cover 71. The space inside the cover 71 includes a space in which the head 51 is disposed, which is defined by the bolt facing surface 71E, the bolt facing surface 71H, and the outer surface of the small diameter portion 32. The first seal member 16 and the second seal member 17 prevent contamination of the head 51.

[0098] The stopper member 15 is disposed so as to face the tip end 71A of the first portion 73. This prevents the cover 71 from coming off the cylinder head 3.

[0099] The cover 71 has a half-split structure, so that the cover 71 can be attached to the cylinder head 3 after the piston rod 4 is inserted into the cylinder head 3 and the cylinder tube 2.

[0100] [Other embodiments] In the first embodiment described above, the synthetic resin or rubber cover 11 may have a half structure. When the synthetic resin or rubber cover 11 includes a first half cover and a second half cover, an adhesive may be used to fix the first half cover and the second half cover together.

[0101] In the second embodiment described above, the metal cover 71 does not have to have a split structure, and may have an integral structure like the cover 11 described in the first embodiment described above. Even in the integral cover 71, the first seal member 16 and the second seal member 17 are disposed to prevent foreign matter from entering the space inside the cover 71. Also in the integral cover 71, the stopper member 15 is disposed to prevent the cover 71 from coming off the cylinder head 3. [Explanation of symbols]

[0102] 1...hydraulic cylinder, 2...cylinder tube, 2A...end surface, 3...cylinder head, 3A...opposing surface, 3B...support surface, 3C...tip portion, 3D...base end portion, 4...piston rod, 5...bolt, 6...dust seal, 6A...tip portion, 7...rod packing, 8...buffer ring, 9...first bearing, 10...second bearing, 11...cover, 11A...tip portion, 11B...base end portion, 11C...inclined surface, 11D...first seal surface, 11E...bolt opposing surface, 11F...outer surface, 11G...second seal surface, 11H...bolt opposing surface, 12...washer, 13...first portion, 13A...first convex portion, 14...second portion, 14A...second convex portion, 15...stopper member, 16...first seal member, 17...second seal member, 21...screw hole, 31...large diameter portion, 31A...second recess, 32...small diameter portion, 32A...first recess, 32B...groove, 33...insertion portion, 34...through hole, 41...rod head, 51...head, 52...shaft portion, 53...threaded portion, 61...outer ring portion, 62...lip portion, 71...cover, 71A...tip portion, 71B...base end portion, 71C...inclined surface, 71D...first seal surface, 71E...bolt-facing surface, 71F...outer surface, 71G...second seal surface, 71H...bolt-facing surface, 72...fixing member, 73...first portion, 73A...recess, 74...second portion, 74A...recess, 101...hydraulic cylinder, 711...first half cover, 712...second half cover, AX...central axis.

Claims

1. a cylinder tube having an end face facing one axial direction; a cylinder head including a large diameter portion having an opposing surface opposing an end surface of the cylinder tube and a support surface facing one axial direction, and a small diameter portion protruding from the support surface to one axial direction; A piston rod having at least a portion disposed inside the cylinder head and movable in an axial direction; a bolt having a head portion disposed on one axial side of the support surface, the bolt fixing the cylinder tube and the cylinder head; A dust seal disposed radially inside the small diameter portion; a cover that covers at least a portion of the cylinder head, The outer diameter of the small diameter portion is smaller than the outer diameter of the large diameter portion, a tip end portion of the small diameter portion on one axial direction side is disposed on one axial direction side of the head portion, the cover has a first portion disposed around a radially outer surface of the small diameter portion and a second portion disposed around a radially outer surface of the large diameter portion, a tip end portion of the first portion on one axial direction side is disposed on the other axial direction side with respect to a tip end portion of the small diameter portion, The first portion has an inclined surface that is inclined toward the other axial direction from a tip end portion of the first portion toward the radially outer side. Hydraulic cylinder.

2. At least a part of the first portion is disposed on one axial side of the head portion, At least a portion of the second portion is disposed radially outward of the head.

2. The hydraulic cylinder according to claim 1.

3. The peripheral edge of the inclined surface is connected to the outer surface of the second portion. The hydraulic cylinder according to claim 1 or 2.

4. The first portion has a first sealing surface facing an outer surface of the small diameter portion. A hydraulic cylinder according to any one of claims 1 to 3.

5. The first seal surface contacts an outer surface of the small diameter portion.

5. The hydraulic cylinder according to claim 4.

6. The first portion has a first protrusion protruding radially inward from the first seal surface, the small diameter portion has a first recess provided on an outer surface of the small diameter portion and in which the first protrusion is disposed; The hydraulic cylinder according to claim 4 or 5.

7. a first seal member disposed between the first seal surface and an outer surface of the small diameter portion; 5. The hydraulic cylinder according to claim 4.

8. The second portion has a second sealing surface facing an outer surface of the large diameter portion. A hydraulic cylinder according to any one of claims 1 to 7.

9. The second seal surface contacts an outer surface of the large diameter portion.

9. The hydraulic cylinder according to claim 8.

10. The second portion has a second protrusion protruding radially inward from the second seal surface, the large diameter portion has a second recess provided on an outer surface of the large diameter portion and in which the second protrusion is disposed; 10. A hydraulic cylinder according to claim 8 or claim 9.

11. a second seal member disposed between the second seal surface and an outer surface of the large diameter portion; 9. The hydraulic cylinder according to claim 8.

12. a stopper member disposed in the groove of the small diameter portion so as to face the tip end of the first portion; A hydraulic cylinder according to any one of claims 1 to 11.

13. The cover includes a first half cover and a second half cover, A fixing member is provided to fix the first half cover and the second half cover together. A hydraulic cylinder according to any one of claims 1 to 12.

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