Press-fitting structure of pipe joint

Abstract

To properly engage a step part of an outer cylinder with a slipping-out preventive projection by getting over the slipping-out preventive projection of an inner cylinder when externally installing the outer cylinder on the inner cylinder by press-in in assembling a pipe joint.SOLUTION: The press-fit structure includes the inner cylinder 12, the retaining protrusion 14 protruding radially outward from the outer peripheral surface of the inner cylinder 12, and the outer cylinder 16 including the first cylinder portion 41 made of a material having a lower hardness than the inner cylinder 12 and externally fitted to the inner cylinder 12 by press-fitting, and the second cylinder portion 42 extending from the first cylinder portion 41 in the axial direction and having an inner diameter larger than the inner diameter of the first cylinder portion 41 to form a space between the inner cylinder 12 and the second cylinder portion 42 into which the tubular body is inserted. And a step part 18 engaged with the coming-off prevention projection 14.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a press-fit structure for a pipe joint. [Background technology]

[0002] Patent Document 1 discloses a pipe joint in which a joint base having a tubular base portion (inner tube) is made mainly of a metal material, a retaining projection is formed on the outer peripheral surface of the tubular base portion, a resin collar (outer tube) is press-fitted onto the joint base, and a stepped portion of the resin collar is engaged with the retaining projection. In the resin collar, the area between the first and second tubular portions is formed as a stepped portion. The inner peripheral surface of the stepped portion connects the inner peripheral surfaces of the first and second tubular portions and is inclined with respect to the center line of the pipe joint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-224652 Summary of the Invention [Problem to be solved by the invention]

[0004] When the outer cylinder is press-fitted onto the inner cylinder, the step portion of the outer cylinder rides over the retaining protrusion, causing the step portion of the outer cylinder to engage with the retaining protrusion of the inner cylinder. However, the step portion, which is softer than the inner cylinder, may deform and stretch in the press-fitting direction during press-fitting. This may result in the press-fitting ending with the step portion riding on the retaining protrusion rather than riding over it. To prevent this riding-on, it may be possible to provide a slope on the step portion as in the conventional example described above, but there is also concern about localized stress increases due to the corners of the retaining protrusion hitting the slope.

[0005] The present invention aims to ensure that when the outer tube is press-fitted onto the inner tube during assembly of a pipe fitting, the stepped portion of the outer tube overcomes the anti-slip protrusion of the inner tube and properly engages with the anti-slip protrusion. [Means for solving the problem]

[0006] The press-fit structure of a pipe fitting according to the first aspect comprises an inner tube, a retaining protrusion protruding radially outward from the outer peripheral surface of the inner tube, a first tubular portion made of a material lower in hardness than the inner tube and fitted onto the inner tube by press-fitting, and an outer tube having a second tubular portion extending axially from the first tubular portion and having an inner diameter larger than the inner diameter of the first tubular portion, forming a space between the first tubular portion and the inner tube into which a pipe is inserted; and a step portion formed in a stepped shape in the axial cross section between the first tubular portion and the second tubular portion on the inner circumference of the outer tube, which engages with the retaining protrusion.

[0007] In this pipe fitting press-fit structure, the outer cylinder is made of a material with a lower hardness than the inner cylinder. The inner cylinder has a retaining projection that projects radially outward, and the inner periphery of the outer cylinder is provided with a stepped portion that engages with the retaining projection. Because this stepped portion is formed in a stepped shape, deformation of the stepped portion is suppressed when the outer cylinder is press-fitted into the inner cylinder. This prevents the stepped portion from riding over the retaining projection when press-fitting is complete, and the stepped portion can ride over the retaining projection and engage with it.

[0008] In a second aspect, in the press-fit structure of the pipe fitting according to the first aspect, the step portion has an intermediate step portion having a diameter larger than that of the first cylindrical portion and smaller than that of the second cylindrical portion, and where the overall radial height of the step portion is h and the radial height from the first cylindrical portion to the intermediate step portion is h1, 0.3≦h1 / h≦0.5.

[0009] In the press-fit structure of this pipe fitting, the ratio of the radial height h1 of the intermediate step portion to the overall radial height h of the step portion is set appropriately, which prevents the step portion from riding up onto the anti-pullout protrusion when press-fitting is complete, while ensuring the engagement strength between the step portion and the anti-pullout protrusion in the axial direction. [Effects of the Invention]

[0010] According to the present invention, when the outer cylinder is press-fitted onto the inner cylinder to exteriorly mount the pipe joint, the stepped portion of the outer cylinder climbs over the retaining projection of the inner cylinder and properly engages with the retaining projection. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a half cross-sectional view showing a press-fit structure for a pipe joint according to an embodiment of the present invention and a pipe connected to the pipe joint. [Figure 2] 1 is an exploded half cross-sectional view showing a press-fitting structure for a pipe joint according to an embodiment of the present invention. [Figure 3] FIG. 4 is an enlarged cross-sectional view showing a step portion of the outer cylinder. [Figure 4] FIG. 10 is an enlarged cross-sectional view showing an early stage of a process of press-fitting an outer cylinder into an inner cylinder. [Figure 5] 10 is an enlarged cross-sectional view showing a state in which the retaining protrusion reaches a step portion during a process of press-fitting the outer cylinder into the inner cylinder. FIG. [Figure 6] 10 is an enlarged cross-sectional view showing a state in which the retaining protrusion has advanced to an intermediate step portion during a process of press-fitting the outer cylinder into the inner cylinder. FIG. [Figure 7] FIG. 10 is an enlarged cross-sectional view showing a state in which the outer cylinder has been press-fitted into the inner cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. Note that duplicated descriptions and reference numerals may be omitted in the embodiments described below. Furthermore, all drawings used in the following description are schematic, and the dimensional relationships and ratios of elements shown in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional relationships and ratios of elements between multiple drawings do not necessarily correspond to the actual ones.

[0013] 1 to 7, the press-fit structure S of the pipe fitting according to this embodiment relates to the press-fit structure of the inner tube 12 and the outer tube 16 in the pipe fitting 10, and includes the inner tube 12, the retaining protrusion 14, the outer tube 16, and the step portion 18.

[0014] The inner tube 12 is part of the joint base 20. The joint base 20 is formed in a cylindrical shape using a metal material, such as gunmetal or a copper alloy of bronze, which is harder than the outer tube 16, or a reinforced resin reinforced with glass fiber or the like. The interior of the joint base 20 forms a flow path 24 through which cold water and hot water for cold and hot water supply pass. A male threaded portion 26 for attachment to another joint member is formed at one axial end of the joint base 20. Note that a female threaded portion for attachment to another joint member may also be formed at one axial end of the joint base 20. A hexagonal portion 28, whose outer peripheral edge is hexagonal when viewed in the axial direction, protrudes from the outer periphery of the male threaded portion 26. A tubular base portion 30 extends toward the other axial side from the end face on the other axial side of the hexagonal portion 28. The outer tube 16 is press-fitted into this tubular base portion 30.

[0015] The inner cylinder 12 extends from the end face on the other axial side of the tubular base portion 30 and has a smaller diameter than the tubular base portion 30. Two grooves 34 are formed in the outer peripheral surface of the inner cylinder 12, spaced apart in the axial direction. Sealing O-rings 22 are fitted into the two grooves 34.

[0016] The retaining projection 14 protrudes radially outward from the outer peripheral surface of the inner cylinder 12. This retaining projection 14 is provided, for example, at the other axial end of the tubular base portion 30, is continuously formed in a flange-like shape in the circumferential direction, and protrudes radially outward from the outer peripheral surface of the tubular base portion 30. The retaining projection 14 functions to prevent the outer cylinder 16, which is press-fitted into the tubular base portion 30 of the inner cylinder 12, from coming out.

[0017] The outer cylinder 16 is made of a material with lower hardness than the inner cylinder 12, and includes a first cylindrical portion 41 that is press-fitted onto the outer surface of the inner cylinder 12, and a second cylindrical portion 42 that extends axially from the first cylindrical portion 41, has an inner diameter larger than that of the first cylindrical portion 41, and forms a space between the outer cylinder 16 and the inner cylinder 12 into which a tube is inserted. The outer cylinder 16 is formed into a cylindrical shape using a transparent resin material such as polyamide or polycarbonate.

[0018] One axial end of the outer cylinder 16 serves as a first cylindrical portion 41 that is press-fitted into the cylindrical base portion 30 of the joint base body 12. This first cylindrical portion 41 is arranged on the outer periphery of (exteriorly mounted on) the cylindrical base portion 30 when the outer cylinder 16 is fixed to the joint base body 12. The inner diameter of the first cylindrical portion 41 is D1 (FIG. 3).

[0019] The second cylindrical portion 42 is located on the other axial side of the first cylindrical portion 41 of the outer cylinder 16. When the outer cylinder 16 is fixed to the joint base 12, the second cylindrical portion 42 is arranged on the outer peripheral side of the retaining projection 14 and the outer peripheral side of the inner cylinder 12 of the joint base 12. The inner diameter D2 of the second cylindrical portion 42 is larger than the inner diameter D1 of the first cylindrical portion 41. That is, the outer diameter D3 of the retaining projection 14 is larger than the inner diameter D1 of the first cylindrical portion 41 and smaller than the inner diameter D2 of the second cylindrical portion 42. When the outer cylinder 16 is fixed to the joint base 12, an annular space into which the pipe 40 is inserted is formed between the second cylindrical portion 42 and the inner cylinder 12 of the joint base 12. An engaging recess 52 is formed on the outer periphery of the second axial side of the second cylindrical portion 42, and the cap 36, which will be described later, engages with the engaging recess 52.

[0020] A pipe holding member 38 is disposed on the other axial side of the outer tube 16. This pipe holding member 38 is formed in a ring shape that surrounds the pipe 40. The pipe holding member 38 has an L-shaped cross section, and the radially inner end of this pipe holding member 38 forms a claw portion 38A. When the pipe 40 moves in the direction to be removed, the claw portion 38A catches on the outer surface of the pipe 40, thereby preventing the pipe 40 from coming off the pipe fitting 10.

[0021] A release ring 48 is disposed on the other axial side of the pipe holding member 38. This release ring 48 is movable axially along the pipe 40. By moving the release ring 48 to one axial side, the release ring 48 enters between the claw portions 38A of the pipe holding member 38 and the outer surface of the pipe 40, separating the outer surface of the pipe 40 from the claw portions 38A. This makes it possible to remove the pipe 40 from the pipe fitting 10.

[0022] The cap 36 is formed into a cylindrical shape using polyacetal resin or the like. The cap 36 engages with the engaged recess 52 of the outer tube 16, preventing the release ring 48 from slipping out to the other axial direction. This limits the relative axial movement of the outer tube 16, pipe holding member 38, and release ring 48.

[0023] 3 to 7, the step portion 18 is provided in a stepped shape in the axial cross section between the first cylindrical portion 41 and the second cylindrical portion 42 on the inner periphery of the outer cylinder 16, and is a portion that engages with the retaining protrusion 14. The step portion 18 has an intermediate step portion 18A that is larger in diameter than the first cylindrical portion 41 and smaller in diameter than the second cylindrical portion 42. If the overall radial height of the step portion 18 is h and the radial height from the first cylindrical portion 41 to the intermediate step portion 18A is h1, then 0.3≦h1 / h≦0.5 is satisfied. The step portion 18, including the intermediate step portion 18A, is formed in an annular shape. Note that the heights h and h1 refer to the average heights in the circumferential direction of the outer cylinder 16.

[0024] (action) This embodiment is configured as described above, and its operation will be described below. In the pipe fitting press-fit structure S of this embodiment, the outer cylinder 16 is made of a material with a lower hardness than the inner cylinder 12. The inner cylinder 12 has a retaining projection 14 that protrudes radially outward, and the inner periphery of the outer cylinder 16 is provided with a stepped portion 18 that engages with the retaining projection 14. When the outer cylinder 16 is press-fitted onto the inner cylinder 12 during assembly of the pipe fitting 10, the stepped portion 18 of the outer cylinder 16 climbs over the retaining projection 14 of the inner cylinder 12 and properly engages with the retaining projection 14.

[0025] Because the stepped portion 18 is formed in a stepped shape, deformation of the stepped portion 18 is suppressed when the outer tube 16 is press-fitted onto the inner tube 12. Specifically, as shown in FIG. 4, the outer diameter D3 of the retaining projection 14 is larger than the inner diameter D1 of the first tubular portion 41. Therefore, when the outer tube 16 is press-fitted into the inner tube 12, the retaining projection 14 slides along the inner periphery of the first tubular portion 41 while deforming the outer tube 16, which has a relatively low hardness. Even when the retaining projection 14 approaches the stepped portion 18, the stepped portion 18 reduces stress concentration compared to when this portion is not stepped (FIG. 5). Furthermore, the retaining projection 14 abuts against the intermediate stepped portion 18A and then passes over the stepped portion 18 (FIG. 6), completing the press-fit (FIG. 7). The retaining projection 14 does not remain on the stepped portion 18 due to drag caused by deformation of the stepped portion 18.

[0026] In particular, as shown in Figure 3, by appropriately setting the ratio of the radial height h1 of the intermediate step portion 18A to the overall radial height h of the step portion 18, it is possible to ensure the engagement strength between the step portion 18 and the anti-pullout protrusion 14 in the axial direction while suppressing the step portion 18 from riding up onto the anti-pullout protrusion 14 when press-fitting is complete.

[0027] In this way, according to this embodiment, it is possible to prevent the step portion 18 from climbing up onto the anti-pullout protrusion 14 when the press-fitting is completed, and the step portion 18 can climb over the anti-pullout protrusion 14 and engage with it.

[0028] (Test example) The optimum h / h1 was verified by simulation. Software name: Solidworks 2023 simulation premium Analysis conditions: Unsteady analysis

[0029] [Table 1]

[0030] In Table 1, the analysis results are evaluated as follows: OK: Press fit completed MG: Press-in not completed due to overhang From this result, it was confirmed that the preferable range of h / h1 is 0.2≦h1 / h≦0.4.

[0031] [Other embodiments] The above describes one example of an embodiment of the present invention, but the embodiment of the present invention is not limited to the above, and it goes without saying that various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0032] 10...pipe joint, 12...inner tube, 14...anti-slip projection, 16...outer tube, 18...step portion, 18A...intermediate step portion, 41...first tube portion, 42...second tube portion, D1...inner diameter of first tube portion, D2...inner diameter of second tube portion, S...press-fit structure of pipe joint, h...total radial height of step portion, h1...radial height of intermediate step portion

Claims

1. An inner cylinder, a retaining protrusion protruding radially outward from the outer peripheral surface of the inner cylinder; an outer cylinder including a first cylindrical portion made of a material having a lower hardness than the inner cylinder and press-fitted onto the inner cylinder; and a second cylindrical portion extending from the first cylindrical portion in the axial direction, having an inner diameter larger than that of the first cylindrical portion, and forming a space between the first cylindrical portion and the inner cylinder into which a tube is inserted; a step portion provided in a stepped shape in an axial cross section between the first cylindrical portion and the second cylindrical portion on an inner periphery of the outer cylinder, the step portion being adapted to engage with the retaining projection; A press-fit structure for a pipe joint having the above structure.

2. the step portion has an intermediate step portion having a diameter larger than that of the first cylindrical portion and smaller than that of the second cylindrical portion, 2. The press-fit structure of a pipe fitting according to claim 1, wherein the overall radial height of the step portion is defined as h, and the radial height from the first cylindrical portion to the intermediate step portion is defined as h1, and the relationship is 0.2≦h1 / h≦0.4.

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