Fluid pressure cylinder

Abstract

A hydraulic cylinder (100) is provided with a cylinder tube (10). The cylinder tube (10) has a body part (12), an annular connection part (13), and a welding part (14) formed between the body part (12) and the connection part (13). The outer peripheral surface of the connection part (13) has a first curved surface (13b) that is formed so as to have a larger diameter as the distance from the welding part (14) increases, a second curved surface (13c) that is formed closer to an end surface (11) than the first curved surface (13b) is and that is formed so as to have a larger diameter as the distance to the end surface (11) decreases, a shoulder surface (13e) that is formed continuously from an end part of the second curved surface (13c) close to the end surface (11) and that extends radially outward, a large-diameter part (13f) that is formed continuously toward the end surface (11), and an inclined surface (13g) that is formed between the large-diameter part (13f) and the shoulder surface (13e). The first curved surface (13b) has a larger radius of curvature than the second curved surface (13c).

Description

Fluid Pressure Cylinder

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

[0002] JPH3-249415A discloses a cylinder device including a cylinder with an opening at one end, a cylinder head attached to close the cylinder opening and fixed with a plurality of bolts, a piston rod that passes through the cylinder head and is slidably disposed within the cylinder, and a piston attached to the piston rod. The cylinder has a cylindrical main body and a connecting part to which the cylinder head is connected. Bolts for fixing the cylinder head are fastened to the connecting part, and the connecting part has a radial thickness greater than that of the main body.

[0003] In a cylinder device such as that described in JPH3-249415A, a weld is formed between the main body and the connecting portion. Because stress concentration is likely to occur at the weld, providing a curved portion at the connecting portion can be considered to reduce the stress concentration at the weld. In this case, increasing the radius of curvature of the curved portion further reduces the stress concentration. However, increasing the radius of curvature of the curved portion increases the area where the curved portion is formed (specifically, the axial length where the curved portion is formed), which increases the area of ​​the cylinder where the curved portion is machined, resulting in more wasted cylinder material. As such, it is difficult to achieve both reduced stress concentration and reduced material waste.

[0004] An object of the present invention is to achieve both a reduction in stress concentration and a reduction in material waste in a fluid pressure cylinder.

[0005] According to one aspect of the present invention, there is provided a fluid pressure cylinder comprising: a cylinder tube; a piston rod reciprocally disposed within the cylinder tube; a piston connected to the piston rod and slidably housed within the cylinder tube; and a cylinder head connected to the cylinder tube and slidably supporting the piston rod. The cylinder tube has a cylindrical main body portion, an annular connecting portion whose end surface is connected to the cylinder head, and a welded portion formed between the main body portion and the connecting portion. The outer circumferential surface of the connecting portion has: a first curved surface formed so as to increase in diameter with increasing distance from the welded portion; a second curved surface formed on the end face side of the first curved surface and so as to increase in diameter with increasing distance to the end face; a shoulder surface formed continuous with an end of the second curved surface on the end face side and extending radially outward; a large diameter portion formed continuous with the end face; and an inclined surface formed between the large diameter portion and the shoulder surface. The first curved surface has a larger radius of curvature than the second curved surface.

[0006] Fig. 1 is a partial cross-sectional view of a fluid pressure cylinder according to an embodiment of the present invention, and Fig. 2 is an enlarged cross-sectional view of part A shown in Fig. 1.

[0007] A fluid pressure cylinder according to an embodiment of the present invention will be described with reference to the drawings. In the following, a case will be described in which the fluid pressure cylinder is a hydraulic cylinder 100 that is driven using hydraulic oil as a working fluid.

[0008] First, the overall configuration of a hydraulic cylinder 100 will be described with reference to FIG.

[0009] As shown in FIG. 1, the hydraulic cylinder 100 includes a cylinder tube 10, a piston rod 20 provided reciprocally within the cylinder tube 10, a piston 30 connected to the piston rod 20 and housed slidably within the cylinder tube 10, and a cylinder head 40 connected to the cylinder tube 10 and supporting the piston rod 20 slidably.

[0010] The cylinder tube 10 is formed in a cylindrical shape. The interior of the cylinder tube 10 is divided into a rod-side chamber 2 and an anti-rod-side chamber 3 by a piston 30. The rod-side chamber 2 and the anti-rod-side chamber 3 are connected to a hydraulic pump (not shown) or a tank (not shown) serving as a hydraulic supply source via a selector valve (not shown). When one of the rod-side chamber 2 or the anti-rod-side chamber 3 is connected to the hydraulic pump, the other is connected to the tank. The hydraulic cylinder 100 expands and contracts as hydraulic oil (working fluid) is introduced from the hydraulic pump to the rod-side chamber 2 or the anti-rod-side chamber 3, causing the piston rod 20 to move axially. Note that a working fluid such as a water-soluble substitute liquid may be used instead of hydraulic oil. Hereinafter, the axial direction of the cylinder tube 10 will also be simply referred to as the "axial direction," and the radial direction of the cylinder tube 10 will also be simply referred to as the "radial direction."

[0011] One opening of the cylinder tube 10 (the left side in FIG. 1 ) is closed by a cylinder head 40, and the other opening (the right side in FIG. 1 ) is closed by a cylinder bottom (not shown). The piston rod 20 is inserted through the cylinder head 40 and slidably supported by the cylinder head 40. The cylinder head 40 has an annular flange portion 41 and an annular fitting portion 42 that fits onto the inner circumferential surface of the cylinder tube 10. The flange portion 41 is fastened to the end surface 11 of the cylinder tube 10 via a plurality of fastening members 50, such as bolts. A supply / discharge port 45 extending radially is formed in the flange portion 41 and connected to a hydraulic pipe (not shown). An annular passage 46 connecting the supply / 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. Hydraulic oil is supplied to and discharged from the rod-side chamber 2 through the supply / discharge port 45 and the annular passage 46.

[0012] The piston rod 20 has a small diameter portion 21 formed at the tip end and to which the piston 30 is fastened, a large diameter portion 22 that slides on the inner circumferential surface of the cylinder head 40 and is formed with a diameter larger than the small diameter portion 21, and a medium diameter portion 23 that is formed between the small diameter portion 21 and the large diameter portion 22 and is provided with an annular cushion ring 81 described below. The cushion ring 81 is sandwiched between the piston 30 and the large diameter portion 22.

[0013] The piston 30 is formed in an annular shape and is provided on the outer periphery of the small diameter portion 21 of the piston rod 20. A seal member 31 is provided on the outer periphery of the piston 30. This blocks communication between the rod-side chamber 2 and the anti-rod-side chamber 3 through a gap between the inner periphery of the cylinder tube 10 and the outer periphery of the piston 30.

[0014] When the rod side chamber 2 is connected to the hydraulic pump and the anti-rod side chamber 3 is connected to the tank, hydraulic oil is supplied to the rod side chamber 2 through the supply / discharge port 45, and hydraulic oil in the anti-rod side chamber 3 is discharged to the tank. This causes the piston rod 20 to move to the right in Figure 1 and the hydraulic cylinder 100 to contract.

[0015] On the other hand, when the hydraulic pump is connected to the anti-rod-side chamber 3 and the rod-side chamber 2 is connected to the tank, hydraulic oil is supplied to the anti-rod-side chamber 3 and the hydraulic oil in the rod-side chamber 2 is discharged to the tank through the supply / discharge port 45. This causes the piston rod 20 to move to the left in Figure 1 and the hydraulic cylinder 100 to extend.

[0016] The hydraulic cylinder 100 further includes a cushion ring 81 for decelerating the piston rod 20 near the stroke end when hydraulic oil is discharged from the rod-side chamber 2 and the piston rod 20 strokes. The cushion ring 81 is provided on the outer periphery of the medium diameter portion 23 of the piston rod 20, and has an inner diameter larger than that of the medium 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 medium diameter portion 23 and the inner circumferential surface of the cushion ring 81. The cushion ring 81 is formed so that its outer diameter is smaller on the tip end side (left side in FIG. 1 ), and a groove 81a is formed on the base end side (right side in FIG. 1 ). The cushion ring 81 enters the annular passage 46 near the stroke end.

[0017] As shown in FIG. 1 , when the hydraulic cylinder 100 is extended and the piston rod 20 is in a normal stroke range (not at the stroke end), the hydraulic oil in the rod-side chamber 2 is guided through the annular passage 46 to the supply / discharge port 45 and discharged. On the other hand, when the hydraulic cylinder 100 is extended and the piston rod 20 is near the stroke end, the cushion ring 81, which has a diameter larger than the large-diameter portion 22, enters the annular passage 46. Therefore, the hydraulic oil in the rod-side chamber 2 is guided through the groove 81 a of the cushion ring 81 and the flow path 82 to the supply / discharge port 45 and discharged. Because the flow path 82 has a smaller flow path cross-sectional area than the annular passage 46, the pressure in the rod-side chamber 2 increases, and the piston rod 20 decelerates. In this way, the cushion ring 81 provides a cushioning effect.

[0018] Next, the cylinder tube 10 will be described in detail.

[0019] The cylinder tube 10 has a cylindrical main body 12, an annular connecting portion 13 whose end face 11 is connected to the cylinder head 40, and a welded portion 14 formed between the main body 12 and the connecting portion 13. The cylinder tube 10 has a uniform inner diameter throughout the main body 12, the welded portion 14, and the connecting portion 13.

[0020] The main body 12 has a uniform outer diameter. The welded portion 14 is formed by welding at the boundary between the main body 12 and the connecting portion 13. The welded portion 14 is formed by protruding radially from the outer circumferential surfaces of the main body 12 and the connecting portion 13.

[0021] 2 , the outer peripheral surface of the connecting portion 13 has a flat surface 13a formed continuously with the welded portion 14, a first curved surface 13b formed continuously with the flat surface 13a, a second curved surface 13c formed closer to the end surface 11 than the first curved surface 13b, a tapered surface 13d formed between the first curved surface 13b and the second curved surface 13c, a shoulder surface 13e formed continuously with the end of the second curved surface 13c on the end surface 11 side and extending radially outward, a large diameter portion 13f formed continuously with the end surface 11, and an inclined surface 13g formed between the large diameter portion 13f and the shoulder surface 13e. Thus, on the outer peripheral surface of the connecting portion 13, from the welded portion 14 side, the flat surface 13a, the first curved surface 13b, the tapered surface 13d, the second curved surface 13c, the shoulder surface 13e, the inclined surface 13g, and the large diameter portion 13f are formed continuously in this order. The connecting portion 13 is formed so that its diameter gradually increases from the welded portion 14 toward the end surface 11. In Fig. 2, the boundaries between the flat surface 13a and the first curved surface 13b, the first curved surface 13b and the tapered surface 13d, and the tapered surface 13d and the second curved surface 13c are indicated by dotted lines.

[0022] The flat surface 13a has a uniform outer diameter, approximately the same as that of the main body portion 12. The first curved surface 13b is formed so that its diameter increases with increasing distance from the welded portion 14. The second curved surface 13c is formed so that its diameter increases with increasing distance from the end surface 11. The first curved surface 13b has a larger radius of curvature than the second curved surface 13c and is more gently inclined than the second curved surface 13c. The tapered surface 13d is formed so that its diameter increases with increasing distance from the second curved surface 13c, connecting the first curved surface 13b and the second curved surface 13c. The tapered surface 13d expands in diameter at a constant inclination angle. The shoulder surface 13e is formed to extend perpendicular to the axial direction. The large diameter portion 13f has a uniform outer diameter, with the largest outer diameter at the connecting portion 13. The inclined surface 13g is formed in a tapered shape that expands in diameter at a constant inclination angle. A curved chamfer is formed at the boundary C between the large diameter portion 13f and the inclined surface 13g. In this manner, the outer circumferential surface of the connecting portion 13 is formed so that the diameter gradually increases from the first curved surface 13b to the tapered surface 13d, and then the diameter suddenly increases from the second curved surface 13c to the inclined surface 13g. Note that the boundary C between the large diameter portion 13f and the inclined surface 13g is closer to the welded portion 14 than the intersection D between the extension of the first curved surface 13b and the large diameter portion 13f, as shown by the two-dot chain line in Figure 2.

[0023] When axial tensile stress occurs in the cylinder tube 10, stress concentration is likely to occur at the welded portion 14. If a portion where stress is likely to concentrate is located adjacent to the welded portion 14, even greater stress concentration will occur at the welded portion 14, thereby reducing the strength of the cylinder tube 10. However, in this embodiment, the welded portion 14 is adjacent to the first curved surface 13b, which has a large radius of curvature, so that a portion where stress is likely to concentrate is not located adjacent to the welded portion 14, thereby reducing stress concentration at the welded portion 14. Furthermore, the flat surface 13a increases the distance between the welded portion 14 and the first curved surface 13b, further reducing stress concentration at the welded portion 14.

[0024] 2 indicates the line of force when axial tensile stress occurs in the cylinder tube 10. The second curved surface 13c, which is away from the welded portion 14, has a larger outer diameter than the first curved surface 13b and is away from the line of force indicated by arrow B, so stress concentration is less likely to occur. Therefore, even if the radius of curvature of the second curved surface 13c is small, the strength of the cylinder tube 10 is maintained.

[0025] Here, if the outer peripheral surface of the connecting portion 13 does not have the tapered surface 13d, the second curved surface 13c, the shoulder surface 13e, and the inclined surface 13g, and the first curved surface 13b is formed between the flat surface 13a and the large-diameter portion 13f, the first curved surface 13b has a large radius of curvature, and therefore the area where the first curved surface 13b is formed (specifically, the axial length where the first curved surface 13b is formed) is large. Therefore, the area of ​​the cylinder tube 10 where the first curved surface 13b is machined is large, resulting in a large amount of wasted material of the cylinder tube 10. Furthermore, because the cylinder tube 10 is subjected to cushion pressure generated by the cushion ring 81, if the area where the first curved surface 13b is formed is large, the thickness of the area of ​​the cylinder tube 10 (connecting portion 13) that is subjected to the cushion pressure is reduced, which may reduce the strength of the cylinder tube 10. On the other hand, if the radius of curvature of the first curved surface 13b is reduced, the area where the first curved surface 13b is formed becomes smaller, and therefore, although the amount of material wasted from the cylinder tube 10 is reduced, stress concentration occurring at the first curved surface 13b and the welded portion 14 increases. Thus, it is difficult to achieve both a reduction in stress concentration and a reduction in material wastage in the cylinder tube 10.

[0026] 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, and the first curved surface 13b has a larger radius of curvature than the second curved surface 13c. The first curved surface 13b reduces stress concentration at the welded portion 14. Furthermore, the second curved surface 13c and the large-diameter portion 13f are connected via the shoulder surface 13e and the inclined surface 13g, so that the axial length of the connecting portion 13 can be shortened while ensuring the strength of the cylinder tube 10. This makes it possible to achieve both reduced stress concentration and reduced material waste.

[0027] Furthermore, since the shoulder surface 13e extends perpendicular to the axial direction of the cylinder tube 10, the axial length of the connecting portion 13 can be made shorter, and the area where material is removed when processing the cylinder tube 10 can be made smaller.

[0028] According to the present embodiment described above, the following advantageous effects are achieved.

[0029] In the hydraulic cylinder 100, stress concentration is likely to occur at the welded portion 14, but the proximity of the welded portion 14 to the first curved surface 13b reduces the stress concentration at the welded portion 14. Furthermore, the second curved surface 13c, which is away from the welded portion 14, has a smaller radius of curvature than the first curved surface 13b, and the second curved surface 13c and the large diameter portion 13f are connected via the shoulder surface 13e and the inclined surface 13g, so that the axial length of the connecting portion 13 can be shortened while ensuring the strength of the cylinder tube 10. This makes it possible to achieve both a reduction in stress concentration and a reduction in material waste.

[0030] Next, modified examples of this embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, or to combine the configurations described in the following different modified examples.

[0031] <Modification 1> In the above embodiment, the outer peripheral surface of the connecting portion 13 has a tapered surface 13d formed between the first curved surface 13b and the second curved surface 13c. However, the tapered surface 13d is not an essential configuration, and the first curved surface 13b and the second curved surface 13c may be formed continuously. Furthermore, a curved surface may be formed between the first curved surface 13b and the second curved surface 13c instead of the tapered surface 13d that expands in diameter at a constant inclination angle. Even with this configuration, the same effects as the above embodiment can be achieved.

[0032] <Modification 2> In the above embodiment, the outer peripheral surface of the connecting portion 13 has the flat surface 13a formed continuously with the welded portion 14. However, the flat surface 13a is not an essential component, and the welded portion 14 and the first curved surface 13b may be formed continuously with each other. Furthermore, the flat surface 13a does not have to be formed to have approximately the same diameter as the main body portion 12, and may be formed to have a smaller or larger diameter than the main body portion 12.

[0033] <Modification 3> In the above embodiment, the shoulder surface 13e is formed to extend perpendicular to the axial direction. However, the shoulder surface 13e does not have to be formed to extend perpendicular to the axial direction, as long as it is formed to extend radially outward. In other words, the shoulder surface 13e may be formed to be inclined with respect to the radial direction. The inclination angle α (see FIG. 2) of the shoulder surface 13e with respect to the axial direction is larger than the inclination angle β (see FIG. 2) of the inclined surface 13g with respect to the axial direction.

[0034] <Modification 4> In the above embodiment, the inclined surface 13g is formed in a tapered shape that increases in diameter at a constant inclination angle. However, the inclined surface 13g may be curved. In other words, the inclined surface 13g may have a tapered or curved configuration.

[0035] In the above embodiment, the first curved surface 13b is formed between the flat surface 13a and the tapered surface 13d, and the second curved surface 13c is formed between the tapered surface 13d and the shoulder surface 13e. In addition, a curved surface may also be formed between the shoulder surface 13e and the inclined surface 13g.

[0036] <Modification 6> In the above embodiment, the flat surface 13a, the first curved surface 13b, the tapered surface 13d, the second curved surface 13c, the shoulder surface 13e, the inclined surface 13g, and the large diameter portion 13f are formed continuously in this order in the connecting portion 13 from the welding portion 14 side. In addition, another flat surface, tapered surface, or curved surface may be formed on the outer circumferential surface of the connecting portion 13. For example, a tapered surface having a smaller inclination angle than the tapered 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 the tapered surface and the tapered surface 13d.

[0037] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0038] The hydraulic cylinder 100 as a fluid pressure cylinder includes a cylinder tube 10, a piston rod 20 provided reciprocally within the cylinder tube 10, a piston 30 connected to the piston rod 20 and slidably housed within the cylinder tube 10, and a cylinder head 40 connected to the cylinder tube 10 and supporting the piston rod 20 slidably. The cylinder tube 10 includes a cylindrical main body 12, an annular connecting portion 13 to which the cylinder head 40 is connected at an end surface 11, and a welded portion 14 formed between the main body 12 and the connecting portion 13. The outer peripheral surface of the connecting portion 13 has a first curved surface 13b that is formed so that its diameter increases with increasing distance from the welded portion 14, a second curved surface 13c that is formed closer to the end face 11 than the first curved surface 13b and that is formed so that its diameter increases closer to the end face 11, a shoulder surface 13e that is formed continuous with the end of the second curved surface 13c on the end face 11 side and extends radially outward, a large diameter portion 13f that is formed continuous with the end face 11, and an inclined surface 13g that is formed between the large diameter portion 13f and the shoulder surface 13e, and the first curved surface 13b has a larger radius of curvature than the second curved surface 13c.

[0039] In this configuration, although stress concentration is likely to occur at the welded portion 14, the proximity of the welded portion 14 to the first curved surface 13b reduces the stress concentration at the welded portion 14. Furthermore, the second curved surface 13c, which is away from the welded portion 14, has a smaller radius of curvature than the first curved surface 13b, and the second curved surface 13c and the large diameter portion 13f are connected via the shoulder surface 13e and the inclined surface 13g, so that the axial length of the connecting portion 13 can be shortened while ensuring the strength of the cylinder tube 10. Therefore, it is possible to achieve both a reduction in stress concentration and a reduction in material waste.

[0040] The outer peripheral surface of the connecting portion 13 further has a tapered surface 13d formed between the first curved surface 13b and the second curved surface 13c.

[0041] The shoulder surface 13 e extends perpendicular to the axial direction of the cylinder tube 10 .

[0042] In this configuration, the axial length of the connecting portion 13 can be made shorter, and the amount of material removed when machining the cylinder tube 10 can be made smaller.

[0043] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0044] This application claims priority based on Japanese Patent Application No. 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 comprising: a cylinder tube; a piston rod provided reciprocally within the cylinder tube; a piston connected to the piston rod and slidably housed within the cylinder tube; and a cylinder head connected to the cylinder tube and supporting the piston rod slidably, wherein the cylinder tube has: a cylindrical main body portion; a ring-shaped connecting portion whose end face is connected to the cylinder head; and a welded portion formed between the main body portion and the connecting portion, and an outer circumferential surface of the connecting portion has: a first curved surface formed so as to become larger in diameter with increasing distance from the welded portion; a second curved surface formed on the end face side of the first curved surface and formed so as to become larger in diameter with increasing distance to the end face; a shoulder surface formed continuously with an end of the second curved surface on the end face side and extending radially outward; a large diameter portion formed continuously with the end face; and an inclined surface formed between the large diameter portion and the shoulder surface, and the first curved surface has a larger radius of curvature than the second curved surface.

2. A fluid pressure cylinder as set forth in claim 1, wherein the outer peripheral surface of the connecting portion further has a tapered surface formed between the first curved surface and the second curved surface.

3. A fluid pressure cylinder according to claim 1, wherein the shoulder surface extends perpendicular to the axial direction of the cylinder tube.

Images