Fluid pressure cylinder

Abstract

A fluid pressure cylinder (100) is provided with a cylinder tube (10). The cylinder tube (10) has: an annular connection part (13); a welded part (14) formed between the main body part (12) and the connecting part (13), the outer peripheral surface of the connecting part (13) having: a first curved surface (13b) formed so that the diameter increases as the distance from the welded part increases; a second curved surface (13c) which is formed on the end surface (11) side of the first curved surface (13b), and which is formed so that the diameter increases as the second curved surface approaches the end surface (11); a shoulder surface (13e) formed so as to be continuous with an end surface on the end surface (11) side of the second curved surface (13c), the shoulder surface (13e) extending radially outward; a large-diameter section (13f) formed so as to be continuous with the end surface (11); and an inclined surface (13g) formed so as to straddle between the large-diameter section (13f) and the shoulder surface (13e), the radius of curvature of the first curved surface (13b) being larger than the radius of curvature of the second curved surface (13c).

Description

Technical Field

[0001] This invention relates to a fluid pressure cylinder. Background Technology

[0002] Japanese Patent Application Publication No. JPH3-249415A discloses a cylinder assembly comprising: a cylinder with one end open; a cylinder head installed to close the opening of the cylinder and secured by a plurality of bolts; a piston rod passing through the cylinder head and slidably disposed within the cylinder; and a piston mounted on the piston rod. The cylinder has a cylindrical body and a connecting portion connected to the cylinder head. Bolts for securing the cylinder head are fastened to the connecting portion, and the radial thickness of the connecting portion is larger than that of the body. Summary of the Invention

[0003] In the cylinder assembly described in Japanese Patent Application Publication No. JPH3-249415A, a welded portion is formed between the main body and the connecting portion. Since stress concentration easily occurs in the welded portion, it is advisable to provide a curved surface in the connecting portion to reduce stress concentration in the welded portion. In this case, increasing the radius of curvature of the curved surface further reduces stress concentration. However, increasing the radius of curvature of the curved surface increases the area for forming the curved surface (specifically, the axial length for forming the curved surface), and the area for machining the curved surface in the cylinder increases, thus increasing material waste in the cylinder. Therefore, it is difficult to simultaneously reduce stress concentration and reduce material waste.

[0004] The purpose of this invention is to simultaneously reduce stress concentration and material waste in a fluid pressure cylinder.

[0005] According to one aspect of the present invention, a fluid pressure cylinder comprises: a cylinder barrel; a piston rod disposed within the cylinder barrel in a reciprocating manner; a piston connected to the piston rod and slidably housed within the cylinder barrel; and a cylinder head connected to the cylinder barrel and slidably supporting the piston rod. The cylinder barrel has: a cylindrical body portion; an annular connecting portion connected to the cylinder head at an end face; and a welded portion formed between the body portion and the connecting portion, the outer peripheral surface of the connecting portion having: A first curved surface is formed such that its diameter increases with distance from the welded portion; a second curved surface is formed on the end face side of the first curved surface and is formed such that its diameter increases with distance from the end face; a shoulder surface is formed in a manner continuous with the end face side of the second curved surface and extends radially outward; a large-diameter portion is formed in a manner continuous with the end face; an inclined surface is formed in a manner spanning between the large-diameter portion and the shoulder surface, wherein the radius of curvature of the first curved surface is larger than that of the second curved surface. Attached Figure Description

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

[0007] Figure 2 for Figure 1 An enlarged sectional view of part A shown. Detailed Implementation

[0008] Referring to the accompanying drawings, a fluid pressure cylinder according to an embodiment of the present invention will be described. Hereinafter, the case where the fluid pressure cylinder is a hydraulic cylinder 100 that uses a driving working fluid as the working fluid will be described.

[0009] First, refer to Figure 1 The overall structure of the hydraulic cylinder 100 will be described.

[0010] like Figure 1 As shown, the hydraulic cylinder 100 includes: a cylinder barrel 10; a piston rod 20 which is disposed within the cylinder barrel 10 in a reciprocating manner; a piston 30 which is connected to the piston rod 20 and is housed within the cylinder barrel 10 in a freely sliding manner; and a cylinder head 40 which is connected to the cylinder barrel 10 and slidably supports the piston rod 20.

[0011] The cylinder 10 is formed in a cylindrical shape. 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 via a switching valve (not shown) to a hydraulic pump (not shown) or a fluid tank (not shown) as a hydraulic supply source. When one of the rod-side chamber 2 or the rod-opposite-side chamber 3 is connected to the hydraulic pump, the other is connected to the fluid tank. The hydraulic cylinder 100 is guided from the hydraulic pump to the rod-side chamber 2 or the rod-opposite-side chamber 3 by a working fluid, causing the piston rod 20 to move axially, thereby extending and retracting. Alternatively, a working fluid such as a water-soluble alternative fluid can be used instead of the working fluid. Hereinafter, the axial direction of the cylinder 10 will be simply referred to as "axial," and the radial direction of the cylinder 10 will be simply referred to as "radial."

[0012] One side of cylinder 10 ( Figure 1 The opening on the left side is blocked by the cylinder head 40, while the other side ( Figure 1The opening on the right side of the cylinder head 40 is blocked by the bottom of the cylinder (not shown). The piston rod 20 is inserted through the cylinder head 40 and supported on the cylinder head 40 in a freely sliding manner. The cylinder head 40 has an annular flange 41 and an annular fitting portion 42 that fits into the inner circumferential surface of the cylinder 10. The flange 41 is fastened to the end face 11 of the cylinder 10 by a plurality of fastening components 50 such as bolts. A supply and discharge port 45 extending radially and connected to a hydraulic hose (not shown) is formed on the flange 41. 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 fitting 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.

[0013] The piston rod 20 has: a small-diameter portion 21 formed at the top end for securing the piston 30; a large-diameter portion 22 that slides on the inner circumferential surface of the cylinder head 40 and is formed to be larger in diameter than the small-diameter portion 21; and a medium-diameter portion 23 formed between the small-diameter portion 21 and the large-diameter portion 22 for housing an annular cushion ring 81 (described later). The cushion ring 81 is held between the piston 30 and the large-diameter portion 22.

[0014] The piston 30 is formed in an annular shape and is disposed on the outer periphery of 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. This cuts off the communication between the rod-side chamber 2 and the opposite-side chamber 3 of the piston 30 via the inner peripheral surface of the cylinder 10 and the outer peripheral surface of the piston 30.

[0015] When the hydraulic pump is connected to the rod-side chamber 2 and the fluid tank is connected to the opposite-side chamber 3, the working fluid is supplied to the rod-side chamber 2 via the supply and discharge port 45, and the working fluid in the opposite-side chamber 3 is discharged to the fluid tank. This causes the piston rod 20 to... Figure 1 As the cylinder moves to the right, hydraulic cylinder 100 retracts.

[0016] On the other hand, when the hydraulic pump is connected to the opposite side chamber 3 of the rod and the fluid tank is connected to the rod side chamber 2, the working fluid is supplied to the opposite side chamber 3, and the working fluid in the rod side chamber 2 is discharged to the fluid tank through the supply and discharge port 45. In this way, the piston rod 20 moves towards... Figure 1 When the cylinder moves to the left, hydraulic cylinder 100 extends.

[0017] The hydraulic cylinder 100 also includes a buffer ring 81 for discharging working fluid from the rod-side chamber 2 and for decelerating the piston rod 20 near the end of its stroke. The buffer ring 81 is disposed on the outer periphery of the intermediate diameter portion 23 of the piston rod 20, with its inner diameter being larger than that of the intermediate diameter portion 23 and smaller than that of the inner circumferential surface of the fitting portion 42 of the cylinder head 40. A flow path 82 is formed between the outer circumferential surface of the intermediate diameter portion 23 and the inner circumferential surface of the buffer ring 81. The buffer ring 81 is positioned at the top end (… Figure 1The outer diameter is smaller on the left side of the middle section, at the base end ( Figure 1 A groove 81a is formed on the right side of the middle section. The buffer ring 81 enters the annular passage 46 near the end of the stroke.

[0018] like Figure 1 As shown, when the hydraulic cylinder 100 extends and the piston rod 20 is in its normal stroke range (not at the end of its stroke), the working fluid in the rod-side chamber 2 is guided to the supply and discharge port 45 via the annular passage 46 and discharged. On the other hand, when the hydraulic cylinder 100 extends and the piston rod 20 is near the end of its stroke, the buffer ring 81, which has a larger diameter than the large-diameter portion 22, enters the annular passage 46. Therefore, the working fluid in the rod-side chamber 2 is guided to the supply and discharge port 45 via the groove 81a of the buffer ring 81 and the flow path 82. Since the cross-sectional area of ​​the flow path 82 is smaller than that of the annular passage 46, the pressure in the rod-side chamber 2 is increased, and the piston rod 20 decelerates. Thus, a buffering effect is generated by the buffer ring 81.

[0019] Next, the cylinder 10 will be described in detail.

[0020] The cylinder 10 has: a cylindrical body portion 12; an annular connecting portion 13 connected to the cylinder head 40 at an end face 11; and a welded portion 14 formed between the body portion 12 and the connecting portion 13. The inner diameter of the cylinder 1 is formed to be the same, spanning the body portion 12, the welded portion 14, and the connecting portion 13.

[0021] The outer diameter of the body portion 12 is formed to be the same. The weld portion 14 is formed by welding and is formed at the boundary between the body portion 12 and the connecting portion 13. The weld portion 14 is formed in such a radially protruding manner from the outer peripheral surfaces of the body portion 12 and the connecting portion 13.

[0022] like Figure 2As shown, the outer peripheral surface of the connecting portion 13 has: a flat surface 13a, which is formed continuously with the welding portion 14; a first curved surface 13b, which is formed continuously with the flat surface 13a; a second curved surface 13c, which is formed on the end face 11 side of the first curved surface 13b; a conical surface 13d, which is formed across the space between the first curved surface 13b and the second curved surface 13c; a shoulder surface 13e, which is formed continuously with the end face 11 side of the second curved surface 13c and extends radially outward; a large diameter portion 13f, which is formed continuously with the end face 11; and an inclined surface 13g, which is formed across the space between the large diameter portion 13f and the shoulder surface 13e. Thus, on the outer peripheral surface of the connecting portion 13, starting from the welding portion 14 side, a flat surface 13a, a first curved surface 13b, a conical surface 13d, a second curved surface 13c, a shoulder surface 13e, an inclined surface 13g, and a large-diameter portion 13f are formed sequentially and continuously. The connecting portion 13 is formed such that it gradually becomes larger in diameter from the welding portion 14 toward the end face 11. Furthermore, in Figure 2 In the diagram, dashed lines represent the boundaries of the flat surface 13a and the first curved surface 13b, the first curved surface 13b and the conical surface 13d, and the boundary of the conical surface 13d and the second curved surface 13c.

[0023] The flat surface 13a has the same outer diameter and is formed to be approximately the same diameter as the body portion 12. The first curved surface 13b is formed such that it becomes larger in diameter as it moves away from the weld portion 14. The second curved surface 13c is formed such that it becomes larger in diameter as it approaches the end face 11. The first curved surface 13b has a larger radius of curvature than the second curved surface 13c and slopes more gently than the second curved surface 13c. The conical surface 13d is formed to connect the first curved surface 13b and the second curved surface 13c and becomes larger in diameter as it approaches the second curved surface 13c. The conical surface 13d expands in diameter at a certain angle of inclination. The shoulder surface 13e is formed to extend perpendicularly to the axial direction. The outer diameter of the large-diameter portion 13f is formed to be the same, and the outer diameter is the largest in the connecting portion 13. The inclined surface 13g is formed as a cone shape that expands in diameter at a certain angle of inclination. A curved chamfer is formed at the boundary C between the large-diameter portion 13f and the inclined surface 13g. Thus, the outer peripheral surface of the connecting portion 13 is formed such that it gradually becomes a large diameter from the first curved surface 13b to the conical surface 13d, and abruptly becomes a large diameter from the second curved surface 13c to the conical surface 13g. Furthermore, one side of the boundary C between the large diameter portion 13f and the inclined surface 13g is... Figure 2 The intersection point D of the extension line of the first curved surface 13b, indicated by the double-dotted line, and the large-diameter portion 13f is closer to the welded portion 14 than the welded portion 14.

[0024] When axial tensile stress is generated in the cylinder 10, stress concentration is likely to occur in the weld 14. When the area prone to stress concentration is located adjacent to the weld 14, greater stress concentration occurs in the weld 14, thus reducing the strength of the cylinder 10. However, in this embodiment, the weld 14 is adjacent to the first curved surface 13b with a large radius of curvature. Therefore, the area prone to stress concentration is not located adjacent to the weld 14, reducing the stress concentration generated in the weld 14. Furthermore, the distance between the weld 14 and the first curved surface 13b is separated by the flat surface 13a, further reducing the stress concentration generated in the weld 14.

[0025] in addition, Figure 2 Arrow B indicates the line of force when axial tensile stress is generated in the cylinder 10. Since the outer diameter of the second curved surface 13c, which separates from the weld 14, is larger than that of the first curved surface 13b, and it separates from the line of force indicated by arrow B, stress concentration is unlikely to occur. Therefore, even though the radius of curvature of the second curved surface 13c is small, the strength of the cylinder 10 is ensured.

[0026] Here, assuming that the outer peripheral surface of the connecting portion 13 does not have a conical surface 13d, a second curved surface 13c, a shoulder surface 13e, and an inclined surface 13g, and that the first curved surface 13b is formed in a manner spanning between the flat surface 13a and the large-diameter portion 13f, the radius of curvature of the first curved surface 13b is large. Therefore, the area for forming the first curved surface 13b (specifically, the axial length for forming the first curved surface 13b) becomes larger. Consequently, the area for machining the first curved surface 13b in the cylinder barrel 10 becomes larger, resulting in more material waste in the cylinder barrel 10. Furthermore, the cylinder barrel 10 is subjected to buffering pressure generated by the buffer ring 81. Therefore, when the area for forming the first curved surface 13b is large, the wall thickness of the area in the cylinder barrel 10 (connecting portion 13) subjected to buffering pressure becomes smaller, which may reduce the strength of the cylinder barrel 10. In contrast, when the radius of curvature of the first surface 13b is reduced, the area formed by the first surface 13b becomes smaller. Therefore, although the material waste of the cylinder 10 is reduced, the stress concentration generated in the first surface 13b and the welded part 14 increases. Thus, it is difficult to simultaneously reduce stress concentration and reduce material waste in the cylinder 10.

[0027] However, in this embodiment, the outer peripheral surface of the connecting portion 13 has a first curved surface 13b and a second curved surface 13c, with the radius of curvature of the first curved surface 13b being larger than that of the second curved surface 13c. The first curved surface 13b reduces stress concentration in the welded portion 14. Furthermore, since the second curved surface 13c and the large-diameter portion 13f are connected via a shoulder surface 13e and an inclined surface 13g, the axial length of the connecting portion 13 can be shortened while ensuring the strength of the cylinder 10. Thus, both stress concentration reduction and material waste reduction can be achieved simultaneously.

[0028] Furthermore, the shoulder surface 13e extends perpendicularly to the axial direction of the cylinder 10, thus further shortening the axial length of the connecting portion 13 and reducing the amount of material cut during the machining of the cylinder 10.

[0029] According to the above implementation method, the following effects are achieved.

[0030] Although stress concentration is prone to occur in the welded portion 14 of the hydraulic cylinder 100, the stress concentration in the welded portion 14 is reduced by the proximity of the welded portion 14 to the first curved surface 13b. Furthermore, the radius of curvature of the second curved surface 13c, which separates from the welded portion 14, is smaller than that of the first curved surface 13b, and the second curved surface 13c and the large-diameter portion 13f are connected via a shoulder surface 13e and an inclined surface 13g. Therefore, the axial length of the connecting portion 13 can be shortened while ensuring the strength of the cylinder 10. Thus, both stress concentration reduction and material waste reduction can be achieved simultaneously.

[0031] Next, variations of this embodiment will be described. The following variations are also within the scope of this invention, and it is possible to combine the structures shown in the variations with the structures described in the above embodiments, or to combine the structures described in the following different variations with each other.

[0032] <Variation Example 1>

[0033] In the above embodiment, the outer peripheral surface of the connecting portion 13 has a conical surface 13d formed across the space between the first curved surface 13b and the second curved surface 13c. However, the conical surface 13d is not a necessary structure, and it can also be formed in a continuous manner between the first curved surface 13b and the second curved surface 13c. Alternatively, a curved surface can be formed between the first curved surface 13b and the second curved surface 13c to replace the conical surface 13d which is expanded at a certain angle. Even with this structure, it achieves the same effect as the above embodiment.

[0034] <Variation Example 2>

[0035] In the above embodiment, the outer peripheral surface of the connecting portion 13 has a flat surface 13a formed in a manner continuous with the welding portion 14. However, the flat surface 13a is not a necessary structure, and it can also be formed in a manner continuous with the welding portion 14 and the first curved surface 13b. In addition, the flat surface 13a may not be formed with a diameter approximately the same as that of the body portion 12, and may be formed with a smaller or larger diameter than that of the body portion 12.

[0036] <Variation Example 3>

[0037] In the above embodiment, the shoulder surface 13e is formed to extend perpendicularly to the axial direction. However, the shoulder surface 13e may not be formed to extend perpendicularly to the axial direction, as long as it is formed to extend radially outward. In other words, the shoulder surface 13e may also be formed to be inclined relative to the radial direction. The inclination angle α of the shoulder surface 13e relative to the axial direction (refer to...) Figure 2 The tilt angle β of the inclined plane 13g relative to the axis (refer to) Figure 2 The size of the sample is relatively large compared to the sample size.

[0038] <Variation Example 4>

[0039] In the above embodiment, the inclined surface 13g is formed as a cone with an expanded diameter at a certain inclination angle. However, it is not limited to this; the inclined surface 13g can also be curved. That is, the inclined surface 13g includes conical and curved structures.

[0040] <Variation Example 5>

[0041] In the above embodiment, a first curved surface 13b is formed between the flat surface 13a and the conical surface 13d, and a second curved surface 13c is formed between the conical surface 13d and the shoulder surface 13e. Alternatively, a curved surface may also be formed between the shoulder surface 13e and the inclined surface 13g.

[0042] <Variation Example 6>

[0043] In the above embodiment, the connecting portion 13 is formed sequentially from the welding portion 14 side with a flat surface 13a, a first curved surface 13b, a conical surface 13d, a second curved surface 13c, a shoulder surface 13e, an inclined surface 13g, and a large-diameter portion 13f. Alternatively, other flat surfaces, conical surfaces, or curved surfaces may be formed on the outer peripheral surface of the connecting portion 13. For example, a conical surface with a smaller inclination angle than the conical surface 13d may be formed at the end of the first curved surface 13b on the end face 11 side, and a curved surface may be formed between this conical surface and the conical surface 13d.

[0044] The structure, function, and effects of the embodiments of the present invention as described above are summarized and explained.

[0045] The hydraulic cylinder 100, as a fluid pressure cylinder, includes: a cylinder barrel 10; a piston rod 20 disposed within the cylinder barrel 10 in a reciprocating manner; a piston 30 connected to the piston rod 20 and housed within the cylinder barrel 10 in a freely sliding manner; and a cylinder head 40 connected to the cylinder barrel 10 and slidably supporting the piston rod 20. The cylinder barrel 10 has: a cylindrical body portion 12; an annular connecting portion 13 connected to the cylinder head 40 at an end face 11; and a welded portion 14 formed between the body portion 12 and the connecting portion 13. The outer peripheral surface of the connecting portion 13 has: a first curved surface 13b, which... The first curved surface 13b is formed such that it becomes larger in diameter as it moves away from the weld portion 14; the second curved surface 13c is formed on the side closer to the end face 11 than the first curved surface 13b, and is formed such that it becomes larger in diameter as it moves closer to the end face; the shoulder surface 13e is formed such that it is continuous with the end face 11 side of the second curved surface 13c, and extends radially outward; the large-diameter portion 13f is formed such that it is continuous with the end face 11; the inclined surface 13g is formed such that it spans between the large-diameter portion 13f and the shoulder surface 13e, and the radius of curvature of the first curved surface 13b is larger than that of the second curved surface 13c.

[0046] Although stress concentration is prone to occur in the welded portion 14 in this structure, the proximity of the welded portion 14 to the first curved surface 13b reduces this stress concentration. Furthermore, the radius of curvature of the second curved surface 13c, separated from the welded portion 14, is smaller than that of the first curved surface 13b, and the second curved surface 13c and the large-diameter portion 13f are connected via a shoulder surface 13e and an inclined surface 13g. Therefore, the strength of the cylinder 10 can be ensured while shortening the axial length of the connecting portion 13. Thus, both stress concentration reduction and material waste reduction can be achieved simultaneously.

[0047] In addition, the outer peripheral surface of the connecting portion 13 has a conical surface 13d formed in a manner that spans between the first curved surface 13b and the second curved surface 13c.

[0048] In addition, the shoulder surface 13e extends perpendicularly to the axial direction of the cylinder 10.

[0049] In this structure, the axial length of the connecting part 13 can be further shortened, and the amount of material cut during the machining of the cylinder 10 can be reduced.

[0050] The embodiments of the present invention have been described above. However, the above embodiments are merely some examples of the application of the present invention and are not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

[0051] This application claims priority based on Japanese Patent Application 2023-138850 filed with the Japan Patent Office on August 29, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A fluid pressure cylinder, wherein, Possessing: a cylinder; a piston rod which is disposed in the cylinder in a reciprocally movable manner; a piston which is linked to the piston rod and is housed in the cylinder in a freely slidable manner; a cylinder head which is linked to the cylinder and supports the piston rod in a slidable manner, the cylinder has: a body portion which is cylindrical; a ring-shaped linking portion which is linked to the cylinder head at an end face; a welding portion which is formed between the body portion and the linking portion, an outer peripheral surface of the linking portion has: a first curved surface which is formed so as to increase in diameter as it moves away from the welding portion; a second curved surface which is formed on the end face side of the first curved surface and is formed so as to increase in diameter as it moves closer to the end face; a shoulder surface which is formed so as to be continuous with the end face on the end face side in the second curved surface and extends toward the radially outer side; a large-diameter portion which is formed so as to be continuous with the end face; an inclined surface which is formed so as to straddle between the large-diameter portion and the shoulder surface, the radius of curvature of the first curved surface is larger than the second curved surface.

2. The fluid pressure cylinder according to claim 1, wherein the outer peripheral surface of the linking portion has a tapered surface which is formed so as to straddle between the first curved surface and the second curved surface.

3. The fluid pressure cylinder according to claim 1, wherein the shoulder surface extends perpendicularly with respect to the axial direction of the cylinder.

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