Fluid pressure cylinder

Abstract

In a hydraulic cylinder (100), a cylinder tube (10) has: an annular body part (12); an annular connection part (13) to which the cylinder head (40) is connected; and an annular connecting part (14) which is formed so as to straddle between the main body part (12) and the connecting part (13), the thickness (T2) of the connecting part (13) in the radial direction being greater than the thickness of the main body part (12) in the radial direction and the thickness of the connecting part (14) in the radial direction, and the boundary between the main body part (12) and the connecting part (14) and the boundary between the connecting part (14) and the connecting part (13) being formed in a conical shape. The inclination angle of the connecting part (14) with respect to the body part (12), the inclination angle (alpha) of the boundary between the body part (12) and the connecting part (14), and the inclination angle (beta) of the boundary between the connecting part (14) and the connecting part (13) are formed to be smaller than each other, and the thickness (T3) in the radial direction of the end of the connecting part (14) on the connecting part (13) side is larger than the thickness in the radial direction of the body part (12). The thickness of the body part (12) in the radial direction is not more than twice the thickness of the body part (12).

Description

Technical Field

[0001] The invention relates to a fluid pressure cylinder. Background Art

[0002] In Japanese Patent Laid-Open No. JPH3-249415A, a cylinder device is disclosed, which includes: a cylinder having one end set as an opening; a cylinder cover, which is installed in a manner of closing the opening of the cylinder and fixed by a plurality of bolts; a piston rod, which passes through the cylinder cover and is slidably arranged in the cylinder; a piston, which is mounted on the piston rod; and a buffer ring, which is mounted on the cylinder cover side of the piston and constitutes a buffer mechanism together with the inner circumference of the cylinder cover. Summary of the invention

[0003] In the cylinder device described in Japanese Patent Publication No. JPH3-249415A, the cylinder has a cylindrical main body and a connecting portion connected to a cylinder head. Since bolts for fixing the cylinder head are fastened on the connecting portion, the radial thickness of the connecting portion is larger than that of the main body. Therefore, in the cylinder, the radial thickness of the main body and the radial thickness of the connecting portion are different. Therefore, for example, when the cylinder device is extended, a load acts on the cylinder head, and when tensile stress acts on the cylinder via the bolts, the stress is concentrated near the boundary between the main body and the connecting portion of the cylinder, and the cylinder may be damaged.

[0004] An object of the present invention is to reduce stress concentration in a cylinder barrel of a fluid pressure cylinder.

[0005] The piston rod of the piston rod is arranged in the cylinder barrel in a reciprocating manner; the piston is connected to the piston rod and is accommodated in the cylinder barrel in a freely slidable manner; the cylinder cover is connected to the open end of the cylinder barrel to close the open end and form a pressure chamber between the cylinder barrel and the piston, the cylinder barrel having: an annular main body; an annular connecting part, which forms the open end and is connected to the cylinder cover; an annular connecting part, which is formed to span between the main body and the connecting part, the cylinder cover is connected to the connecting part of the cylinder barrel by bolts, and the radial thickness of the connecting part is equal to the radial thickness of the main body and the radial thickness of the connecting part. The main body portion and the connecting portion are formed larger than the main body portion, the boundary between the connecting portion and the boundary between the connecting portion and the connecting portion are formed in a conical shape, the connecting portion is formed in a manner that the outer diameters are the same, or in a manner that the outer peripheral surface in the cross section along the central axis of the cylinder tube becomes a conical shape, the inclination angle of the connecting portion relative to the main body portion and the inclination angle of the boundary between the main body portion and the connecting portion and the inclination angle of the boundary between the connecting portion and the connecting portion are formed smaller than the inner diameters of the main body portion, the connecting portion, and the connecting portion, the radial thickness of the end portion on the connecting portion side in the connecting portion is larger than the radial thickness of the main body portion and is formed to be less than twice the radial thickness of the main body portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a partial cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention.

[0007] Figure 2 This is a partial cross-sectional view of the fluid pressure cylinder according to the embodiment of the present invention, and shows a state in which the fluid pressure cylinder is extended and the piston rod is located near the stroke end. DETAILED DESCRIPTION

[0008] A fluid pressure cylinder according to an embodiment of the present invention will be described with reference to the drawings. Hereinafter, a case where the fluid pressure cylinder is a hydraulic cylinder 100 driven by a working fluid as a working fluid will be described.

[0009] First, refer to Figure 1 , Figure 2 , the overall structure of the hydraulic cylinder 100 is described.

[0010] like Figure 1 , Figure 2As shown, the hydraulic cylinder 100 comprises: a cylinder tube 10; a piston rod 20, which is arranged in the cylinder tube 10 in a manner that allows reciprocation; a piston 30, which is connected to the piston rod 20 and is accommodated in the cylinder tube 10 in a freely slidable manner; a cylinder head 40, which is connected to the open end 11 of the cylinder tube 10 to close the open end 11 and forms a rod side chamber 2 as a pressure chamber between the cylinder head 40 and the piston 30.

[0011] The cylinder 10 is formed in an annular shape. No reinforcement components or the like are provided on the outer peripheral surface of the cylinder 10. The inside of the cylinder 10 is divided into a rod side chamber 2 and a rod opposite side chamber 3 by a piston 30. The rod side chamber 2 and the rod opposite side chamber 3 are connected to a hydraulic pump (omitted from the illustration) or a fluid tank (omitted from the illustration) as a hydraulic supply source via a switching valve (omitted from the illustration). When one of the rod side chamber 2 and the rod opposite side chamber 3 is connected to the hydraulic pump, the other is connected to the fluid tank. The hydraulic cylinder 100 moves the piston rod 20 in the axial direction and thereby retracts and contracts by guiding the working fluid (working fluid) from the hydraulic pump to the rod side chamber 2 or the rod opposite side chamber 3. In addition, as the working fluid, a working fluid such as a water-soluble substitute fluid may be used instead of oil.

[0012] One side of the cylinder 10 ( Figure 1 , Figure 2 The opening of the left side of the cylinder head 40 is closed, and the opening of the other side ( Figure 1 , Figure 2 The opening of the cylinder head 40 (on the right side in the figure) is closed by the bottom of the cylinder (not shown). The cylinder head 40 allows the piston rod 20 to be inserted in a freely sliding manner and supports the piston rod 20. The cylinder head 40 has a flange portion 41 and a cylindrical portion 42 that fits with the inner circumferential surface of the cylinder barrel 10. The flange portion 41 is fastened to the cylinder barrel 10 by a plurality of fastening components 50 such as bolts. In the present embodiment, the fastening component 50 is only inserted through the later-described connecting portion 13 of the cylinder barrel 10, and the cylinder head 40 is connected to the cylinder barrel 10. In addition, it is also possible to connect without using the fastening component 50, for example, by screwing a threaded portion provided on the outer circumferential surface of the cylindrical portion 42 and a threaded portion provided on the inner circumferential surface of the cylinder barrel 10. The flange portion 41 is provided with a supply and discharge port 45 extending in the radial direction and connected to a hydraulic pipe (not shown). An annular passage 46 connecting the supply and discharge port 45 and the rod side chamber 2 is formed between the outer circumferential surface of the piston rod 20 and the inner circumferential surface of the through portion 42. The working fluid is supplied and discharged to the rod side chamber 2 via the supply and discharge port 45 and the annular passage 46. The rod side chamber 2 is divided by the cylinder barrel 10, the cylinder head 40, and the piston 30, and the rod opposite side chamber 3 is divided by the cylinder barrel 10, the cylinder bottom, and the piston 30.

[0013] The piston rod 20 has a small diameter portion 21 formed at the top end and fastened to the piston 80; a large diameter portion 22 that slides on the inner peripheral surface of the cylinder head 40 and is formed to have a larger diameter than the small diameter portion 21; and a middle diameter portion 23 formed between the small diameter portion 21 and the large diameter portion 22 and provided with an annular buffer ring 81 described later. The outer diameter of the middle diameter portion 23 is larger than that of the small diameter portion 21 and smaller than that of the large diameter portion 22. The buffer ring 81 is sandwiched between the piston 30 and the large diameter portion 22.

[0014] The piston 30 is formed in an annular shape and connected to the small diameter portion 21 of the piston rod 20. A sealing member 31 is provided on the outer peripheral surface of the piston 30. Thereby, the communication between the rod side chamber 2 and the opposite rod side chamber 3 via the inner peripheral surface of the cylinder 10 and the outer peripheral surface of the piston 30 is cut off.

[0015] On the other hand, when the hydraulic source is connected to the rod side chamber 2 and the fluid tank is connected to the opposite rod side chamber 3, the hydraulic fluid is supplied to the rod side chamber 2 through the supply and discharge port 45, and the hydraulic fluid in the opposite rod side chamber 3 is discharged to the fluid tank. Figure 1 , Figure 2 The hydraulic cylinder 100 moves to the right side and contracts.

[0016] On the other hand, when the hydraulic source is connected to the opposite-rod side chamber 3 and the fluid tank is connected to the rod side chamber 2, the working fluid is supplied to the opposite-rod side chamber 3 and the working fluid of the rod side chamber 2 is discharged to the fluid tank through the supply and discharge port 45. Figure 1 , Figure 2 The hydraulic cylinder 100 moves to the left and extends.

[0017] The hydraulic cylinder 100 further includes a buffer mechanism 80 (see FIG. 8 ) for decelerating the piston rod 20 near the stroke end when the working fluid in the rod side chamber 2 is discharged and the piston rod 20 performs a stroke. Figure 2 ). Figure 1 The state in which the buffering effect produced by the buffer mechanism 80 is not produced is shown. Figure 2 The diagram shows a state in which the hydraulic cylinder 100 is extended and a buffering action is generated by the buffer mechanism 80 .

[0018] like Figure 2 As shown, the buffer mechanism 80 includes: a buffer ring 81, which is arranged on the middle diameter portion 23 of the piston rod 20 and enters the annular passage 46 near the stroke end; and a buffer passage 82, which guides the working fluid of the rod side chamber 2 to the supply and discharge port 45 when the buffer ring 81 enters the annular passage 46.

[0019] The buffer ring 81 is formed to have a larger diameter than the large diameter portion 22 of the piston rod 20, and is formed to have a smaller diameter than the inner circumferential surface of the cylindrical portion 42 of the cylinder head 40. When the hydraulic cylinder 100 is extended and the piston rod 20 is in the normal stroke region (not at the stroke end), as shown in FIG. Figure 1 As shown, the working fluid of the rod side chamber 2 is guided to the supply and discharge port 45 through the annular passage 46 formed between the outer peripheral surface of the large diameter portion 22 of the piston rod 20 and the inner peripheral surface of the through portion 42 and discharged. On the other hand, when the hydraulic cylinder 100 is extended and the piston rod 20 is located near the stroke end, as shown in FIG. Figure 2 As shown, the buffer ring 81 having a larger diameter than the large diameter portion 22 enters the annular passage 46. Therefore, the working fluid of the rod side chamber 2 is guided to the supply and discharge port 45 and discharged through the buffer passage 82 formed between the outer peripheral surface of the buffer ring 81 and the inner peripheral surface of the round through portion 42. Since the flow path cross-sectional area of ​​the buffer passage 82 is smaller than that of the annular passage 46, the pressure of the rod side chamber 2 rises and the piston rod 20 is decelerated. In this way, a buffering effect is generated by the buffer mechanism 80. In addition, the buffer mechanism 80 is not limited to a structure having a buffer ring 81 and a buffer passage 82.

[0020] Next, the cylinder 10 will be described in detail.

[0021] In the present embodiment, the cylinder 10 is formed of a material having a yield point of 400 MPa or more, such as a modulated material of S45C, SM570, SCM430, etc. The cylinder 10 has: an annular main body 12; an annular connecting portion 13, which is formed with an open end 11 and is connected to a cylinder head 40; an annular connecting portion 14, which is formed to span between the main body 12 and the connecting portion 13. The main body 12, the connecting portion 14, and the connecting portion 13 are formed continuously, and the cylinder 10 spans the main body 12, the connecting portion 14, and the connecting portion 13, and the inner diameters are formed to be the same. The outer diameters of the main body 12, the connecting portion 13, and the connecting portion 14 are formed to be the same. The boundary between the main body 12 and the connecting portion 14 and the boundary between the connecting portion 14 and the connecting portion 13 are formed in a conical shape. In other words, the first conical portion 18 is formed at the boundary between the main body portion 12 and the connecting portion 14, and the second conical portion 19 is formed at the boundary between the connecting portion 14 and the connecting portion 13. The axial length of the connecting portion 14 is longer than the axial length of the connecting portion 13, and is also longer than the axial lengths of the first conical portion 18 and the second conical portion 19.

[0022] The inclination angle of the connecting portion 14 relative to the main body 12 (in this embodiment, the outer diameters of the main body 12 and the connecting portion 14 are formed to be the same, and therefore, it is 0 degrees) is formed smaller than the inclination angle α of the boundary between the main body 12 and the connecting portion 14 and the inclination angle β of the boundary between the connecting portion 14 and the connecting portion 13. In addition, the inclination angle of the connecting portion 13 relative to the main body 12 (in this embodiment, the outer diameters of the main body 12 and the connecting portion 14 are formed to be the same, and therefore, it is 0 degrees) is formed smaller than the above-mentioned inclination angle α and inclination angle β.

[0023] Here, the radial thickness dimensions of the main body 12, the connecting portion 13, and the connecting portion 14 are set to T1, T2, and T3, respectively. The thickness T2 of the connecting portion 13 is formed larger than the thickness T1 of the main body 12 and the thickness T3 of the connecting portion 14 in a manner that the fastening component 50 can be fastened. The thickness T3 of the connecting portion 14 is formed larger than the thickness T1 of the main body 12. That is, the outer diameter of the cylinder 10 increases in the order of the connecting portion 13, the connecting portion 14, and the main body 12. Specifically, the thickness T3 of the connecting portion 14 is formed to be less than twice the thickness T1 of the main body 12. In addition, the thickness T3 of the connecting portion 14 is formed to be less than 2 / 3 times the thickness T2 of the connecting portion 13.

[0024] Here, in the hydraulic cylinder 100, when the piston 30 and the piston rod 20 are extended, Figure 1 , Figure 2 When the cylinder 42 of the cylinder head 40 moves to the left, the load acts on the cylinder 42 of the cylinder head 40. Figure 1 , Figure 2 The load to the left in the middle acts on the cylinder head 40. Since the cylinder head 40 is connected to the connecting portion 13 of the cylinder tube 10 through the fastening member 50, when such a load acts on the cylinder head 40, tensile stress acts on the cylinder tube 10 through the fastening member 50. When it is assumed that the cylinder tube 10 has a structure without the connecting portion 14 in the hydraulic cylinder 100, the difference between the thickness T1 of the body portion 12 and the thickness T2 of the connecting portion 13 is large, and therefore, stress is concentrated near the boundary between the body portion 12 and the connecting portion 13, and the cylinder tube 10 may be damaged.

[0025] However, in the hydraulic cylinder 100, as described above, the cylinder tube 10 has the connection portion 14, and the thickness T3 of the connection portion 14 is smaller than the thickness T2 of the connecting portion 13 and larger than the thickness T1 of the main body 12. Therefore, the radial thickness of the cylinder tube 10 changes slowly compared to the case where the connection portion 14 is not formed. Therefore, even if tensile stress acts on the cylinder tube 10, stress concentration in the cylinder tube 10 is reduced. Thus, damage to the cylinder tube 10 is prevented. In addition, as described above, the thickness T3 of the connection portion 14 of the cylinder tube 10 is formed to be less than twice the thickness T1 of the main body 12. Therefore, in the cylinder tube 10, the difference between the thickness T1 of the main body 12 and the thickness T3 of the connection portion 14 is small. Therefore, stress concentration between the main body 12 and the connection portion 14, which have the smallest radial thickness and are prone to reduced strength, is reduced. In this way, the stress concentration between the main body portion 12 and the connecting portion 14 having the smallest radial thickness is further reduced compared with the stress concentration between the connecting portion 13 and the connecting portion 14 having the largest radial thickness, thereby further effectively preventing the cylinder 10 from being damaged.

[0026] That is, in the present embodiment, stress concentration is not reduced by simply forming a conical shape between the main body 12 and the connecting portion 13 having different wall thicknesses (radial thicknesses), but in addition to slowly changing the wall thickness by forming the connecting portion 14, stress concentration generated between the main body 12 and the connecting portion 14 and between the connecting portion 13 and the connecting portion 14 can be controlled by adjusting the wall thickness of the connecting portion 14. Specifically, as described above, by further reducing stress concentration between the main body 12 and the connecting portion 14, damage to the cylinder 10 can be further effectively prevented.

[0027] In addition, in the present embodiment, the cylinder tube 10 has the connection portion 14, and the axial length of the connection portion 14 is longer than the axial length of the connecting portion 13. Thus, the cylinder tube 10 has two steps of the connection portion 14 and the connecting portion 13, and has a structure in which the wall thickness changes gradually, so that the stress concentration generated in the cylinder tube 10 is reduced compared with a structure without the connection portion 14 or a structure in which the axial length of the connection portion 14 is short.

[0028] Furthermore, in the present embodiment, the inclination angle α of the boundary between the main body 12 and the connecting portion 14 is formed to be smaller than the inclination angle β of the boundary between the connecting portion 14 and the connecting portion 13. Specifically, the boundary between the main body 12 and the connecting portion 14 and the boundary between the connecting portion 14 and the connecting portion 13 are formed in a conical shape. The inclination angle α is an acute angle formed by the boundary between the main body 12 and the connecting portion 14 and the extension line of the main body 12, and the inclination angle β is an acute angle formed by the boundary between the connecting portion 14 and the connecting portion 13 and the extension line of the connecting portion 14. Thereby, the stress concentration between the main body 12 and the connecting portion 14, which have the smallest radial thickness, is further reduced compared with the stress concentration between the connecting portion 13 and the connecting portion 14, which have the largest radial thickness.

[0029] In addition, in this embodiment, if Figure 2 As shown, the connection portion 14 is formed so as to face the rod side chamber 2 when the piston rod 20 is decelerated by the buffer mechanism 80. Therefore, when the piston rod 20 is decelerated by the buffer mechanism 80, the buffer pressure (the higher pressure in the rod side chamber 2 when the buffer action occurs) acts on the connection portion 14. Therefore, strength is required for the connection portion 14. That is, from the viewpoint of strength, it is preferable that the thickness T3 of the connection portion 14 is large.

[0030] In addition, as described above, the thickness T3 of the connection portion 14 is formed to be less than 2 / 3 times the thickness T2 of the connection portion 13. This is possible because the cylinder 10 is formed of a high-strength material having a yield point of 400 MPa or more as described above, and the strength of the connection portion 14 can be ensured even if the thickness T3 of the connection portion 14 is small. As a result, the thickness T3 of the connection portion 14 is small, and therefore, the amount of material used in the cylinder 10 can be reduced. As a result, while ensuring the strength of the cylinder 10, it is possible to reduce stress concentration in the cylinder 10 and reduce the amount of material used when manufacturing the cylinder 10.

[0031] According to the present embodiment described above, the following effects are achieved.

[0032] In the hydraulic cylinder 100, the cylinder tube 10 has a connection portion 14 formed between the main body portion 12 and the connection portion 13, and the thickness T3 of the connection portion 14 is smaller than the thickness T2 of the connection portion 13 and larger than the thickness T1 of the main body portion 12. Thus, in the cylinder tube 10, the thickness in the radial direction changes slowly, so even if tensile stress acts, stress concentration is reduced. In addition, the thickness T3 of the connection portion 14 of the cylinder tube 10 is formed to be less than twice the thickness T1 of the main body portion 12. Thus, in the cylinder tube 10, the difference between the thickness T1 of the main body portion 12 and the thickness T3 of the connection portion 14 is small, so that stress concentration between the main body portion 12 and the connection portion 14, which have the smallest thickness in the radial direction and are prone to reduced strength, is reduced.

[0033] In the hydraulic cylinder 100, the thickness T3 of the connection portion 14 is formed to be 2 / 3 times or less of the thickness T2 of the coupling portion 13. As a result, the thickness T3 of the connection portion 14 is small, and thus the amount of material used in the cylinder tube 10 can be reduced.

[0034] In the hydraulic cylinder 100 , the inclination angle α of the boundary between the body portion 12 and the connection portion 14 is formed to be smaller than the inclination angle β of the boundary between the connection portion 14 and the coupling portion 13 , thereby further reducing stress concentration between the body portion 12 and the connection portion 14 where the radial thickness is the smallest.

[0035] In the hydraulic cylinder 100, when the piston rod 20 is decelerated by the buffer mechanism 80, the buffer pressure acts on the connection portion 14. Since the cylinder tube 10 is formed of a material having a yield point of 400 MPa or more, the strength of the connection portion 14 can be ensured even if the thickness T3 of the connection portion 14 is small. Thus, while ensuring the strength of the cylinder tube 10, it is possible to reduce the stress concentration in the cylinder tube 10 and reduce the amount of material used for the cylinder tube 10.

[0036] Next, a modification of the present embodiment will be described.

[0037] <Variation 1>

[0038] In the above embodiment, the hydraulic cylinder 100 is provided with the buffer mechanism 80. However, the buffer mechanism 80 is not a necessary structure, and the hydraulic cylinder 100 may not be provided with the buffer mechanism 80. Even with this structure, as in the above embodiment, the stress concentration in the cylinder tube 10 is reduced, and the stress concentration between the main body portion 12 and the connecting portion 14, which have a smaller radial thickness, is reduced. In addition, if the hydraulic cylinder 100 is a structure without the buffer mechanism 80, no buffer pressure acts on the connecting portion 14, and therefore, the cylinder tube 10 does not necessarily need to be formed of a material having a yield point of 400 MPa or more. That is, it is not a necessary structure that the cylinder tube 10 is formed of a material having a yield point of 400 MPa or more.

[0039] <Variation 2>

[0040] In the above-mentioned embodiment, the thickness T3 of the connecting portion 14 of the cylinder 10 is formed to be less than 2 / 3 times the thickness T2 of the connecting portion 13. Thereby, the amount of material used in the manufacture of the cylinder 10 can be reduced. However, although the amount of material used in the manufacture of the cylinder 10 is increased, the thickness T3 of the connecting portion 14 can also be formed to be smaller than the thickness T2 of the connecting portion 13, and can be formed to be larger than 2 / 3 times the thickness T2 of the connecting portion 13. In other words, it is not a necessary structure that the thickness T3 of the connecting portion 14 is formed to be less than 2 / 3 times the thickness T2 of the connecting portion 13.

[0041] <Variation 3>

[0042] In the above embodiment, the connection portion 14 is formed in a manner that the outer diameter is the same. Figure 1 , Figure 2The outer peripheral surface is formed in a conical shape in the cross section of the center axis of the cylinder 10 shown. In this case, the radial thickness of the connecting portion 14 is formed to be smaller at the end on the main body 12 side, and the radial thickness is formed to be larger at the end on the connecting portion 13 side. In addition, the radial thickness T3 of the connecting portion 14 is the maximum thickness in the end on the connecting portion 13 side. In addition, the inclination angle of the connecting portion 14 relative to the main body 12 and the inclination angle α of the boundary between the main body 12 and the connecting portion 14 and the inclination angle β of the boundary between the connecting portion 14 and the connecting portion 13 are formed to be smaller. Even with this structure, as in the above-mentioned embodiment, stress concentration in the cylinder 10 is reduced, and stress concentration between the main body 12 and the connecting portion 14, which have the smallest radial thickness, is reduced.

[0043] In the above embodiment, the connecting portion 13 is formed so as to have the same outer diameter. Figure 1 , Figure 2 The outer peripheral surface of the cross section of the central axis of the cylinder tube 10 shown in the figure is formed in a conical shape. In this case, the radial thickness of the connecting portion 13 is formed to be smaller at the end portion on the connecting portion 14 side, and the radial thickness is formed to be larger at the opening end 11. In addition, the radial thickness T2 of the connecting portion 13 is the maximum thickness at the opening end 11. In addition, the inclination angle of the connecting portion 13 relative to the main body portion 12 is formed to be smaller than the above-mentioned inclination angle α and inclination angle β.

[0044] The structure, function, and effect of the embodiment of the present invention configured as above will be summarized and described.

[0045] The hydraulic cylinder 100 of the composition fluid pressure cylinder comprises: a cylinder tube 10; a piston rod 20, which is disposed in the cylinder tube 10 in a manner that allows reciprocal movement; a piston 30, which is connected to the piston rod 20 and is accommodated in the cylinder tube 10 in a freely slidable manner; a cylinder head 40, which is connected to the open end 11 of the cylinder tube 10 to close the open end 11 and forms a rod side chamber 2 as a pressure chamber between the cylinder tube 10 and the piston 30. The cylinder tube 10 has: an annular body portion 12; An annular connecting portion 13 is formed with an open end 11 and is connected to a cylinder head 40; an annular connecting portion 14 is formed to span between the main body portion 12 and the connecting portion 13, a radial thickness T2 of the connecting portion 13 is formed to be larger than a thickness T1 of the main body portion 12 and a thickness T3 of the connecting portion 14, a radial thickness T3 of the connecting portion 14 is larger than a thickness T1 of the main body portion 12 and is formed to be less than twice the thickness T1 of the main body portion 12.

[0046] In this structure, the cylinder 10 has a connecting portion 14 formed between the main body 12 and the connecting portion 13, and the radial thickness T3 of the connecting portion 14 is smaller than the thickness T2 of the connecting portion 13, and the radial thickness T3 is larger than the thickness T1 of the main body 12. Therefore, compared with the case where the connecting portion 14 is not provided, the radial thickness of the cylinder 10 changes slowly. Therefore, the stress concentration in the cylinder 10 is reduced. In addition, the radial thickness T3 of the connecting portion 14 of the cylinder 10 is formed to be less than twice the thickness T1 of the main body 12. Therefore, in the cylinder 10, the difference between the radial thicknesses T1 and T3 of the main body 12 and the connecting portion 14 is small. Therefore, the stress concentration between the main body 12 and the connecting portion 14, which have the smallest radial thickness and are prone to reduced strength, is reduced.

[0047] Furthermore, the thickness T3 of the connection portion 14 in the radial direction is formed to be not more than 2 / 3 times the thickness T2 of the coupling portion 13 .

[0048] In this structure, the thickness T3 of the connection portion 14 of the cylinder 10 in the radial direction is small, so the amount of material used in the cylinder 10 can be reduced.

[0049] Furthermore, in the hydraulic cylinder 100 , the inclination angle α of the boundary between the body portion 12 and the connection portion 14 is formed to be smaller than the inclination angle β of the boundary between the connection portion 14 and the coupling portion 13 .

[0050] In this structure, stress concentration between the body portion 12 and the connecting portion 14 , which have the smallest thickness in the radial direction, is further reduced.

[0051] In addition, in the hydraulic cylinder 100 , the axial length of the connection portion 14 is longer than the axial length of the coupling portion 13 .

[0052] In this structure, stress concentration generated in the cylinder 10 is reduced.

[0053] In addition, the hydraulic cylinder 100 also has a buffer mechanism 80 for decelerating the piston rod 20 near the stroke end when the working fluid in the rod side chamber 2 is discharged and the piston rod 20 performs a stroke. The connecting portion 14 is formed in a manner facing the rod side chamber 2 when the piston rod 20 is decelerated by the buffer mechanism 80, and the cylinder tube 10 is formed of a material with a yield point of 400 MPa or more.

[0054] In this structure, when the piston rod 20 is decelerated by the buffer mechanism 80, the buffer pressure acts on the connection portion 14 of the cylinder tube 10. Therefore, strength is required for the connection portion 14. Since the cylinder tube 10 is formed of a material having a yield point of 400 MPa or more, the strength of the connection portion 14 can be ensured even if the radial thickness T3 of the connection portion 14 is small. Thus, while ensuring the strength of the cylinder tube 10, it is possible to reduce the stress concentration in the cylinder tube 10 and reduce the amount of material used in the cylinder tube 10.

[0055] Although the embodiments of the present invention have been described above, the above embodiments merely represent a part of application examples of the present invention and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0056] This application claims priority based on Japanese Patent Application No. 2022-167458 filed with the Japan Patent Office on October 19, 2022, and all the contents of the application are incorporated into this specification by reference.

Claims

1. A fluid pressure cylinder, wherein: have: Cylinder barrel; A piston rod is disposed in the cylinder in a reciprocating manner; A piston connected to the piston rod and accommodated in the cylinder in a freely slidable manner; a cylinder head connected to the open end of the cylinder tube to close the open end and forming a pressure chamber between the cylinder head and the piston, The cylinder has: a ring-shaped main body; an annular connecting portion, which is formed with the open end and is connected to the cylinder head; an annular connecting portion formed to span between the main body portion and the connecting portion, The cylinder head is connected to the connecting portion of the cylinder tube by bolts. The radial thickness of the connecting portion is formed to be larger than the radial thickness of the main body portion and the radial thickness of the connecting portion. The boundary between the main body and the connecting portion and the boundary between the connecting portion and the connecting portion are formed in a conical shape. The connecting portion is formed so as to have the same outer diameter or so as to have an outer peripheral surface in a conical shape in a cross section along the central axis of the cylinder. The inclination angle of the connection portion relative to the main body portion is formed to be smaller than the inclination angle of the boundary between the main body portion and the connection portion and the inclination angle of the boundary between the connection portion and the coupling portion. The main body, the connecting portion, and the connecting portion have the same inner diameter. The radial thickness of the end portion of the connection portion on the coupling portion side is larger than the radial thickness of the main body portion and is formed to be not more than twice the radial thickness of the main body portion.

2. The fluid pressure cylinder according to claim 1, wherein: The radial thickness of the connection portion is formed to be 2 / 3 times or less of the radial thickness of the coupling portion.

3. The fluid pressure cylinder according to claim 1, wherein: The inclination angle of the boundary between the main body portion and the connecting portion is formed to be smaller than the inclination angle of the boundary between the connecting portion and the coupling portion.

4. The fluid pressure cylinder according to claim 1, wherein: The axial length of the connecting portion is longer than the axial length of the coupling portion.

5. The fluid pressure cylinder according to claim 1, wherein: The invention further comprises a buffer mechanism for decelerating the piston rod near the stroke end when the working fluid in the pressure chamber is discharged and the piston rod performs a stroke. The connecting portion is formed so as to face the pressure chamber when the piston rod is decelerated by the buffer mechanism. The cylinder tube is formed of a material having a yield point of 400 MPa or more.

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