CN114440022A

CN114440022A - Pipe joint structure

Info

Publication number: CN114440022A
Application number: CN202111270236.3A
Authority: CN
Inventors: 柿元泰
Original assignee: Japan Engine Corp
Current assignee: Japan Engine Corp
Priority date: 2020-11-02
Filing date: 2021-10-29
Publication date: 2022-05-06
Also published as: JP2022073641A; KR20220059412A

Abstract

The invention provides a pipe joint structure capable of ensuring the sealing performance between a pipe and a joint. The pipe joint structure is provided with: a pipe having an internal flow path through which a fluid flows and a convex end portion having an opening end portion in which the internal flow path is formed and having a partially spherical shape protruding outward; a cylindrical portion formed in a cylindrical shape and attached to an outer peripheral surface of the pipe, the cylindrical portion having a seat portion in a partial spherical shape protruding toward a side opposite to the convex end portion in a central axis direction of the pipe; a joint part which has a tapered abutting part abutting against the convex end part and communicates the device for processing the fluid with the pipe; and a cap nut having a tapered pressing portion that is tapered toward the opposite side of the convex end portion in the direction of the central axis of the pipe, and that is screwed to the outer peripheral surface of the joint portion, and presses the convex end portion of the pipe against the abutting portion of the joint portion by pressing the seat portion of the cylindrical portion with the pressing portion. The center of curvature of each of the convex end portion of the tube and the seat portion of the cylindrical portion is located on the central axis of the tube.

Description

Pipe joint structure

Technical Field

The invention relates to a pipe joint structure.

Background

Conventionally, in the field of piping for internal combustion engines and the like, there has been disclosed a pipe joint structure in which a pipe through which a fluid such as a fuel flows is joined to a device such as a pump that processes the fluid via a joint (for example, see patent document 1). This pipe joint structure is generally a structure in which a pipe is fastened to a joint by a cap nut via a nipple screwed to an outer peripheral surface of the pipe. In such a pipe joint structure, a seat surface of the nipple projecting from the outer peripheral surface is formed on the outer peripheral surface of the pipe. The cap nut presses the pipe against the joint via the seat surface of the nipple and is screwed to the joint.

The joint portion of the pipe to the joint is formed in a substantially spherical shape projecting outward. The receiving portion of the joint that receives the joint portion of the pipe is formed in a concave tapered shape having a substantially truncated conical surface. Therefore, even if the pipe is inclined with respect to the central axis of the joint, the joint portion of the pipe and the receiving portion of the joint can be maintained in an abutting state by being in line contact with each other. This can increase the contact pressure between the joint portion of the pipe and the receiving portion of the joint to a pressure higher than the pressure of the fluid, thereby ensuring the sealing property between the pipe and the joint.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent application No. 2010-242709

Technical problem to be solved by the invention

However, in the above-described conventional pipe joint structure, both the seating surface of the nipple projecting from the outer peripheral surface of the pipe and the pressing surface of the cap nut pressing the seating surface are formed in a flat shape. Therefore, when the pipe is fastened by the cap nut in a state of being inclined with respect to the central axis of the joint, contact with the pressing surface of the cap nut is deviated on one side and the other side of the seat surface of the nipple through the central axis of the pipe. This causes a shift in the contact pressure between the joint portion of the pipe and the receiving portion of the joint, and even if the joint portion of the pipe and the receiving portion of the joint appear to be in a state of coming into contact with each other by line contact, there is a possibility that a portion having a lower contact pressure than the pressure of the fluid may be generated between the joint portion of the pipe and the receiving portion of the joint. As a result, there is a problem that the sealing property between the pipe and the joint is lowered.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pipe joint structure capable of ensuring sealability between a pipe and a joint.

Means for solving the problems

In order to solve the above-described problems and achieve the object, a pipe joint structure according to the present invention includes: a pipe having an inner flow path through which a fluid flows and a convex end portion which is formed with an opening end portion of the inner flow path and has a partially spherical shape protruding outward; a cylindrical portion formed in a cylindrical shape attached to an outer peripheral surface of the pipe and having a seat portion in a partially spherical shape protruding toward a side opposite to the convex end portion in a central axis direction of the pipe; a joint portion having a tapered abutting portion abutting against the convex end portion and communicating a device for processing the fluid with the pipe; and a cap nut having a tapered pressing portion that is reduced in diameter toward a side opposite to the convex end portion in a direction of a central axis of the pipe, the cap nut being screwed to an outer peripheral surface of the joint portion, and pressing the seat portion of the cylindrical portion by the pressing portion to press the convex end portion of the pipe against the abutting portion of the joint portion, respective centers of curvature of the convex end portion of the pipe and the seat portion of the cylindrical portion being located on the central axis of the pipe.

In the pipe joint structure of the present invention, a center of curvature of the seat portion of the cylindrical portion and a center of curvature of the convex end portion of the pipe are located at the same position.

In the pipe joint structure of the present invention, in the above invention, the cylindrical portion further includes a stopper portion that comes into contact with a step portion formed on an outer peripheral surface of the pipe to regulate a position of the cylindrical portion in a central axis direction of the pipe.

In the pipe joint structure of the present invention, in the above invention, the tapered surface of the pressing portion is a linear tapered surface.

In the pipe joint structure of the present invention, in the above invention, the tapered surface of the pressing portion is a curved tapered surface.

In the pipe joint structure of the present invention, in the above invention, the tapered surface of the pressing portion is a partially spherical tapered surface having the same center of curvature as the seat portion of the cylindrical portion.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the pipe joint structure of the present invention, the effect of ensuring the sealing property between the pipe and the joint is obtained.

Drawings

Fig. 1 is a schematic diagram showing an application example of a pipe joint structure according to an embodiment of the present invention.

Fig. 2 is a schematic sectional view showing a configuration example of a pipe joint structure according to an embodiment of the present invention.

Fig. 3 is a cross-sectional view showing an enlarged main portion of the pipe joint construction shown in fig. 2.

Fig. 4 is a schematic cross-sectional view showing a configuration example of a conventional pipe joint structure.

Fig. 5 is a schematic diagram for explaining a problem of the conventional pipe joint structure.

Fig. 6 is a schematic diagram for explaining the operation of the pipe joint structure according to the embodiment of the present invention.

Description of the symbols

1 pipe joint structure

5 Fuel injection pump

10 tube

11 internal flow path

11a open end

12 convex end part

13 screw part

14 step part

20 screw connecting sleeve

21 seat part

22 stop part

23 screw part

30 joint part

30a first engaging portion

30b second joint part

31 abutting part

32 internal flow path

33 screw part

34 bolt head

35 bolt screw portion

40 cap nut

41a, 41b openings

42 pressing part

43 screw part

44 nut part

101 conventional pipe joint structure

110 tube

112. 112a, 112b convex end

120 screw connecting sleeve

121. 121a, 121b seat

130 joint part

131. 131a, 131b contact part

140 cap nut

142 pressing part

Central axis of C1, C2, C11 and C12

S1, S2 imaginary sphere

Center of curvature P

Detailed Description

Hereinafter, preferred embodiments of the pipe joint structure according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiment. Note that the drawings are schematic, and it is to be noted that the relationship in size of each element, the ratio of each element, and the like may be different from the actual ones. The drawings may contain portions having different dimensional relationships and proportions from each other. In the drawings, the same components are denoted by the same reference numerals.

Fig. 1 is a schematic diagram showing an application example of a pipe joint structure according to an embodiment of the present invention. Fig. 2 is a schematic sectional view showing a configuration example of a pipe joint structure according to an embodiment of the present invention. Fig. 3 is a cross-sectional view showing an enlarged main portion of the pipe joint construction shown in fig. 2. As shown in fig. 1 to 3, a pipe joint structure 1 of the present embodiment includes: a pipe 10 and a joint 30 to be joined, and a nipple 20 and a cap nut 40 for fastening the pipe 10 to the joint 30.

The pipe 10 is a pipe (flow pipe) for flowing a fluid. Specifically, as shown in fig. 2, the pipe 10 is made of metal or the like, and has an internal flow path 11 and a convex end portion 12. The internal flow passage 11 is a flow passage through which a fluid such as fuel oil flows, and is formed in the tube 10 over the entire region from one end portion to the other end portion in the direction of the central axis C1 of the tube 10, for example. The convex end portion 12 is a joint end portion of the pipe 10 with respect to the joint portion 30. As shown in fig. 2 and 3, the convex end 12 is formed in a partially spherical shape projecting outward of the pipe 10. That is, the convex end 12 has a partially spherical shape in which the opening end 11a of the internal flow path 11 is formed in a part of a spherical surface and protrudes outward. For example, the convex end portions 12 are formed at both ends of the tube 10 in the direction of the central axis C1. In the present embodiment, as shown in fig. 3, the outer surface (tube end surface) of the convex end portion 12 is a partial spherical surface which is a part of an imaginary spherical surface S1 having a curvature center P. The center of curvature P is located on the central axis C1 of the tube 10.

The central axis C1 of the pipe 10 is a central axis in a direction (longitudinal direction) perpendicular to the radial direction of the pipe 10. The pipe 10 is a pipe capable of withstanding the pressure of the fluid flowing therethrough, and may be, for example, a high-pressure pipe capable of withstanding a pressure exceeding 35MPa or a low-pressure pipe capable of withstanding a pressure of 35MPa or less.

As shown in fig. 2 and 3, a screw portion 13 for attaching a nipple 20 is formed on the outer peripheral surface of the pipe 10. A stepped portion 14 for determining the attachment position of the nipple 20 is formed on the outer peripheral surface of the pipe 10 between the threaded portion 13 and the convex end portion 12. The threaded portion 13 of the pipe 10 is screwed to the threaded portion 23 of the nipple 20. The threaded

portions

13, 23 of the pipe 10 and nipple 20 are counter-threaded. This is because the screwing of the pipe 10 and the nipple 20 is loosened in order to prevent the nipple 20 from rotating (being rotated) in accordance with the rotation of the cap nut 40 when the screw portion 43 of the cap nut 40 and the screw portion 33 of the joint 30 are fastened.

The nipple 20 is an example of a cylindrical portion attached to the outer peripheral surface of the pipe 10, and specifically, as shown in fig. 2 and 3, the nipple 20 is formed in a cylindrical shape using metal or the like as a material, and includes a seat portion 21, a stopper portion 22, and a threaded portion 23.

The seat 21 is formed in one end of the nipple 20 in a partially spherical shape projecting outward of the nipple 20. That is, as shown in fig. 2 and 3, in a state where the nipple 20 is attached to the outer peripheral surface of the pipe 10, the seat portion 21 has a partially spherical shape protruding toward the opposite side of the convex end portion 12 in the direction of the central axis C1 of the pipe 10. As shown in fig. 3, the surface (seat surface) of the seat 21 is a partial spherical surface that is a part of the virtual spherical surface S2. The seat portion 21 is attached to the outer peripheral surface of the pipe 10 by a screw fitting 20, and forms the above-described partially spherical seat surface protruding from the outer peripheral surface of the pipe 10 along the circumferential direction around the central axis C1 of the pipe 10. The center of curvature of the convex end portion 12 of the pipe 10 and the seat portion 21 of the nipple 20 is located on the central axis C1 of the pipe 10. Preferably, as shown in fig. 3, the center of curvature of the seat portion 21 is located at the same position as the center of curvature P of the convex end portion 12. That is, the center of curvature P is preferably the center of curvature of the partially spherical outer surface (the imaginary spherical surface S1) of the convex end portion 12 and is also preferably the center of curvature of the partially spherical seat surface (the imaginary spherical surface S2) of the seat portion 21.

Further, as shown in fig. 3, for example, the seat portion 21 has a longer radius of curvature than the convex end portion 12. However, the radius of curvature of the seat portion 21 is not limited to this, and may be the same as the radius of curvature of the convex end portion 12 or may be shorter than the radius of curvature of the convex end portion 12.

As shown in fig. 2 and 3, the stopper 22 is formed near the other end (end opposite to the seat 21) of the nipple 20. For example, the stopper 22 is formed in a convex shape protruding inward from the inner peripheral surface of the nipple 20, and comes into contact with the step 14 formed on the outer peripheral surface of the pipe 10 to regulate the position of the nipple 20 in the direction of the central axis C1 of the pipe 10. The threaded portion 23 is formed in an area between the seat portion 21 and the stopper portion 22 on the inner peripheral surface of the nipple 20. The threaded joint 20 is screwed to the outer peripheral surface of the pipe 10 so that the threaded portion 23 engages with the threaded portion 13 of the pipe 10. The attachment position (screwing position) of the nipple 20 in the direction of the central axis C1 of the pipe 10 is determined by the contact between the step portion 14 of the pipe 10 and the stopper portion 22 of the nipple 20 being restricted. Thus, the center of curvature of the seat portion 21 of the nipple 20 is set to be simply the same position as the center of curvature P of the convex end portion 12 of the pipe 10.

The threaded

portions

13 and 23 of the pipe 10 and the nipple 20 are reverse threads as described above. Therefore, when the screw portion 43 of the cap nut 40 is fastened to the screw portion 33 of the joint 30, the stopper 22 of the nipple 20 abuts against the step portion 14 of the pipe 10, and the nipple 20 can be prevented from being rotated by the rotation of the cap nut 40. As a result, it is possible to prevent the center of curvature of the seat portion 21 from deviating from a target position (in the present embodiment, the same position as the center of curvature P of the convex end portion 12) associated with the screwing of the cap nut 40 and the joint portion 30.

The joint portion 30 communicates a device for treating a fluid with the pipe 10 through which the fluid flows. Specifically, as shown in fig. 2, the joint portion 30 is made of metal or the like, and integrally includes a first joint portion 30a joined to the pipe 10 and a second joint portion 30b joined to a device for processing a fluid. Examples of the device for treating the fluid include a fuel injection pump 5 (see fig. 1) for supplying (pressure-feeding) fuel oil to a fuel injection valve provided in a cylinder of an internal combustion engine. As shown in fig. 2, the joint portion 30 includes: an abutment portion 31, an internal flow passage 32, a screw portion 33, a bolt head 34, and a bolt screw portion 35.

The contact portion 31 is a tapered portion that contacts the convex end portion 12 of the pipe 10. Specifically, as shown in fig. 2 and 3, the abutting portion 31 is formed in a tapered shape at the end portion of the joint portion 30 on the first engagement portion 30a side. Examples of the taper shape of the contact portion 31 include a linear taper shape in which the diameter decreases linearly from one end side toward the other end side in the direction of the central axis C2 of the joint portion 30. As shown in fig. 2 and 3, the abutting portion 31 abuts against the convex end portion 12 of the tube 10 in a line contact state. The central axis C2 of the joint 30 is a central axis in a direction (longitudinal direction) passing through the end of the joint 30 on the first joint 30a side and the end of the joint 30 on the second joint 30b side.

The internal flow path 32 is a flow path through which a fluid flows, and is formed in the joint 30 over the entire region from the contact portion 31 of the joint 30 to the end portion on the second joint portion 30b side shown in fig. 2. The internal flow path 32 communicates the internal flow path 11 of the pipe 10 in a state in which the convex end portion 12 is in contact with the contact portion 31 of the joint 30 with the fuel injection pump 5 to which the second joint portion 30b of the joint 30 is joined. The screw portion 33 is used to screw the joint portion 30 and the cap nut 40 together. As shown in fig. 2, a threaded portion 33 is formed on the outer peripheral surface of the first engagement portion 30a of the joint portion 30.

As shown in fig. 1 and 2, the bolt head 34 is formed on the outer peripheral surface of the second engagement portion 30b of the joint 30. The bolt screw portion 35 is formed in a predetermined region of the outer peripheral surface of the joint portion 30 from the end portion on the second engagement portion 30b side toward the bolt head portion 34 side. The joint 30 is screwed to the fuel injection pump 5 as shown in fig. 1 by rotating the bolt head 34 around the center axis C2 using a tool such as a wrench and screwing the bolt screw portion 35 into a screw portion (not shown) of the fuel injection pump 5.

The cap nut 40 joins the pipe 10 and the joint portion 30 to be able to communicate with each other. Specifically, as shown in fig. 1 to 3, the cap nut 40 is formed in a cylindrical shape using a metal or the like as a material. The cap nut 40 has

openings

41a and 41b at both ends in a direction (longitudinal direction) perpendicular to the cylindrical radial direction, a pressing portion 42 and a threaded portion 43 inside, and a nut portion 44 on the outer peripheral surface.

The

openings

41a and 41b allow the inside and the outside of the cap nut 40 to communicate with each other. Specifically, as shown in fig. 2, one opening 41a is formed at one end of the cap nut 40. The tube 10 to be joined is inserted through the opening 41 a. The other opening 41b is formed in the other end of the cap nut 40. The joint portion 30 to be joined is inserted into the opening 41 b. For convenience of description, an end portion where one opening 41a of the cap nut 40 is formed is referred to as a pipe-side end portion, and an end portion where the other opening 41b of the cap nut 40 is formed is referred to as a joint-side end portion.

The pressing portion 42 is a tapered portion for pressing the pipe 10, to which the nipple 20 is attached on the outer peripheral surface, against the nipple 30. Specifically, as shown in fig. 2 and 3, the pressing portion 42 is formed inside the cap nut 40 so as to have a tapered shape that reduces in diameter in a direction from the joint-side end portion to the pipe-side end portion of the cap nut 40 (hereinafter, referred to as the central axis direction of the cap nut 40). That is, in a state where the tube 10 is inserted through the opening 41a of the cap nut 40, the pressing portion 42 has a tapered shape that is reduced in diameter toward the opposite side of the convex end portion 12 in the direction of the central axis C1 of the tube 10. As the cap nut 40 is screwed into the joint 30, the pressing portion 42 presses the seat portion 21 of the nipple 20 attached to the outer peripheral surface of the pipe 10, and presses the convex end portion 12 of the pipe 10 against the contact portion 31 of the joint 30 via the seat portion 21.

In the present embodiment, for example, as shown in fig. 2 and 3, the tapered surface of the pressing portion 42 is a linear tapered surface that linearly decreases in diameter toward the central axis direction of the cap nut 40. The tapered surface of the pressing portion 42 is preferably a curved tapered surface in order to increase the contact area with the seat portion 21 of the nipple 20 attached to the outer peripheral surface of the pipe 10 and reduce the surface pressure of the seat portion 21. Examples of the curved tapered surface include an exponential tapered surface that exponentially reduces in diameter in the central axis direction of the cap nut 40, a parabolic tapered surface that exponentially reduces in diameter in the central axis direction, and a spherical tapered surface that spherically reduces in diameter in the central axis direction. Among them, the tapered surface of the pressing portion 42 is particularly preferably a partially spherical tapered surface having the same center of curvature (in the present embodiment, the center of curvature P shown in fig. 3) as the seat portion 21 of the nipple 20.

As shown in fig. 2, the screw portion 43 is formed in a predetermined region (for example, a region corresponding to the inside of the nut portion 44) from the joint-side end portion toward the pipe-side end portion in the inner peripheral surface of the cap nut 40. The cap nut 40 is screwed to the outer peripheral surface of the joint 30 so that the screw portion 43 meshes with the screw portion 33 of the joint 30. The nut portion 44 is a portion to be gripped by a hand or a tool of an operator when the cap nut 40 is screwed to the outer peripheral surface of the joint portion 30. As shown in fig. 1 and 2, the nut portion 44 is formed in a polygonal shape on the outer peripheral surface of the screw portion of the cap nut 40 to be screwed with the joint portion 30.

The cap nut 40 having the above-described structure is screwed to the outer peripheral surface of the joint 30, and presses the seat portion 21 of the nipple 20 by the pressing portion 42, thereby pressing the convex end portion 12 of the pipe 10 against the contact portion 31 of the joint 30. Thus, the cap nut 40 fastens and engages the pipe 10 to the joint portion 30.

The pipe joint structure 1 of the present embodiment is applied to both end portions of the pipe 10 to be joined (specifically, both end portions in the direction of the central axis C1 of the pipe 10). For example, by applying the pipe joint structure 1 described above to one end portion of the pipe 10, as shown in fig. 1 to 3, the one end portion of the pipe 10 and the fuel injection pump 5 are joined so as to be able to communicate with each other via the joint portion 30. Although not particularly shown, a pipe joint structure 1 similar to one end of the pipe 10 is applied to the other end of the pipe 10. Thereby, the other end portion of the pipe 10 is joined to the fuel injection valve so as to be able to communicate therewith. The fuel injection valve is an example of a device for treating the fluid flowing through the pipe 10, and is provided in a cylinder of an internal combustion engine such as a marine diesel engine. As described above, when both end portions of the pipe 10 are respectively joined to the fuel injection pump 5 and the fuel injection valve via the pipe joint structure 1, it is possible to pressure-feed the fuel oil from the fuel injection pump 5 to the fuel injection valve via the pipe 10 and to inject the fuel oil from the fuel injection valve into the cylinder (combustion chamber) of the internal combustion engine.

The fluid processing device in the present embodiment is not limited to the fuel injection pump and the fuel injection valve described above. Examples of the device for treating the fluid include various devices that are connected to the internal combustion engine or a device other than the internal combustion engine by pipes, such as a fuel injection pump, a fuel injection valve, a water injection pump, a water injection valve, a hydraulic oil pump, a supercharger, an air supply device, and an exhaust device. Examples of the fluid flowing through the pipe 10 include liquids or gases such as fuel oil, water, working oil, lubricating oil, combustion gas, and exhaust gas.

Next, problems of the conventional pipe joint structure will be described. Fig. 4 is a schematic cross-sectional view showing a configuration example of a conventional pipe joint structure. Fig. 4 shows a cross section of a main portion of a conventional pipe joint structure 101. As shown in fig. 4, a conventional pipe joint structure 101 includes: a pipe 110 and a joint 130 to be joined, and a nipple 120 and a cap nut 140 for fastening the pipe 110 to the joint 130.

The pipe 110 is configured in the same manner as the pipe 10 of the pipe joint structure 1 of the present invention, except that the stepped portion 14 (see fig. 2 and 3) is not formed on the outer peripheral surface. For example, as shown in fig. 4, the pipe 110 has an internal flow path 11, an opening end 11a, and a screw portion 13, as in the pipe 10 of the present invention. For convenience of explanation, the convex end 112 of the pipe 110 is formed in a partially spherical shape protruding outward in the same manner as the pipe 10 of the present invention, except that the reference numeral is changed to distinguish it from the convex end 12 of the pipe 10 of the present invention. The center axis C11 of the tube 110 is a center axis in a direction perpendicular to the radial direction of the tube 110, similarly to the center axis C1 of the tube 10 of the present invention.

As shown in fig. 4, the screw nipple 120 has a flat seat portion 121, and does not have the above-described partially spherical seat portion 21 (see fig. 3) projecting outward. That is, the seat surface of the nipple 120 is a flat surface facing the middle portion side (the side opposite to the convex end portion 112) of the pipe 110, unlike the seat surface (partial spherical surface) of the nipple 20 of the pipe joint structure 1 of the present invention. The nipple 120 does not have the stopper 22 of the nipple 20 according to the present invention (see fig. 3). The nipple 120 has the same structure as the nipple 20 of the present invention, except for the structures of the seat portion 21 and the stopper portion 22 having the partially spherical shape. For example, as shown in fig. 4, the nipple 120 has a screw portion 23 on an inner peripheral surface thereof and is screwed to an outer peripheral surface of the pipe 110. Thus, the nipple 120 forms the above-described planar seat surface protruding from the outer peripheral surface of the pipe 110 in the circumferential direction around the central axis C11 of the pipe 110.

The joint portion 130 is configured in the same manner as the joint portion 30 of the pipe joint structure 1 of the present invention. For example, as shown in fig. 4, the joint portion 130 has a tapered abutting portion 131, as in the joint portion 30 of the present invention. The convex end 112 of the tube 110 contacts the abutment 131.

As shown in fig. 4, the cap nut 140 has a flat pressing portion 142, but does not have the tapered pressing portion 42 (see fig. 3). That is, the pressing surface of the cap nut 140 is a flat surface facing the joint portion 130 side (lower side of the paper surface in fig. 4), unlike the pressing surface (tapered surface) of the cap nut 40 of the pipe joint structure 1 of the present invention. The cap nut 140 has the same structure as the cap nut 40 of the present invention, except for the structure of the tapered pressing portion 42. For example, as shown in fig. 4, the cap nut 140 is screwed to the outer peripheral surface of the joint 130, and the flat pressing portion 142 presses the flat seat portion 121 of the nipple 120, thereby pressing the convex end portion 112 of the pipe 110 against the contact portion 131 of the joint 130.

Fig. 5 is a schematic diagram for explaining a problem of the conventional pipe joint structure. In the conventional pipe joint structure 101 (see fig. 4), the nipple 120 is screwed to the outer peripheral surface of the pipe 110, and the convex end portion 112 of the pipe 110 is brought into contact with the contact portion 131 of the joint portion 130 by a manual operation of an operator or the like. Then, a torque (manual torque) generated by the input of the operator is applied to the cap nut 140. Thus, the cap nut 140 is dummy on the outer peripheral surface of the joint 130, and the flat pressing portion 142 presses the flat seat portion 121 of the nipple 120, so that the convex end portion 112 of the tube 110 is pressed against the contact portion 131 of the joint 130 via the seat portion 121. Thereafter, a tightening torque is further applied to the cap nut 140 by a tool such as a wrench or a torque wrench. Thereby, the cap nut 140 is completely screwed to the outer peripheral surface of the joint 130, and the pressing portion 142 presses the convex end portion 112 of the tube 110 against the contact portion 131 of the joint 130 via the seat portion 121. As a result, the pipe 110 is completely fastened to the coupling portion 130 by the cap nut 140.

Here, as shown in fig. 5, when the convex end 112 of the pipe 110 contacts the contact portion 131 of the joint portion 130 in a state where the central axis C11 of the pipe 110 is inclined with respect to the central axis C12 of the joint portion 130, the nipple 120 screwed to the outer peripheral surface of the pipe 110 is in a state of being inclined integrally with the pipe 110 (state a 1).

In this state a1, the convex end 112 of the tube 110 is maintained in a state of being in contact with the contact portion 131 of the joint 130 by wire contact. On the other hand, since the seat portion 121 of the screw nipple 120 has a planar seat surface, as shown in fig. 5, the height position H2 of the seat portion 121 is changed to a position higher than the height position H1 of the seat portion 121 in the case where the center axis C11 of the tube 110 is not inclined with respect to the center axis C12 of the joint portion 130. That is, a step is generated between one side (right side in the drawing sheet of fig. 5) and the other side (left side in the drawing sheet of fig. 5) of the seat portion 121 via the center axis C11 of the pipe 110. The height positions H1 and H2 are positions in the height direction with reference to a predetermined position.

When the cap nut 140 is screwed to the joint 130 in a state where the height difference is generated in the seat portion 121 of the socket 120 as described above, the contact between the pressing portion 142 of the cap nut 140 and the seat portion 121 of the socket 120 is deviated. For example, as shown in fig. 5, the seat portion 121b of the height position H2 in the seat portion 121 can contact the pressing portion 142. However, the seat portion 121a on the opposite side of the seat portion 121b with respect to the central axis C11 of the tube 110 is not in contact with the pressing portion 142 (state a 2).

In the state a2, the pressing portion 142 of the cap nut 140 is biased to press the one seat 121b of the seat 121 of the nipple 120 through the center axis C11 of the tube 110. As a result, as shown in fig. 5, a rotational force is generated in the tube 110 due to the pressing force of the pressing portion 142 against the one seat portion 121 b. In this case, the convex end 112 of the tube 110 and the contact portion 131 of the joint 130 seem to be maintained in a state of being in contact by line contact. However, the contact pressure between the convex end 112 and the contact portion 131 is deviated by the rotational force. Specifically, of the contact pressures of the convex end 112 and the contact portion 131, the contact pressure of the seat portion 121b pressed by the pressing portion 142 on the opposite side across the center axis C11 of the tube 110, that is, the contact pressure of the convex end 112a and the contact portion 131a shown in fig. 5, is increased. Accordingly, the contact pressure on the same side of the seat portion 121b pressed by the pressing portion 142 with respect to the central axis C11 of the tube 110, that is, the contact pressure between the convex end portion 112b and the contact portion 131b shown in fig. 5 decreases.

As a result, a portion where a contact pressure lower than the pressure of the fluid flowing through the pipe 110 is generated at the contact portion between the convex end 112 of the pipe 110 and the contact portion 131 of the joint 130, and thus a problem arises in that the sealing performance between the convex end 112 and the contact portion 131 is lowered. In the conventional pipe joint structure 101, it is difficult to avoid a situation in which fluid leaks from between the pipe 110 and the joint portion 130.

In the conventional pipe joint structure 101, as illustrated in a state a2 of fig. 5, the pressing portion 142 of the cap nut 140 is biased toward one side of the seat portion 121 that contacts the threaded nipple 120. Therefore, even if the cap nut 140 is dummy-fitted to the joint portion 130 by manual torque, it is difficult to eliminate the displacement of the contact of the pressing portions 142 with the seat portion 121. This causes a problem that the fastening angle of the cap nut 140 varies from a state in which the cap nut 140 is dummy in the joint portion 130 by the manual torque to a state in which the cap nut 140 is completely fastened to the joint portion 130 by the fastening torque. In this case, it is difficult to manage the complete fastening of the cap nut 140 to the joint portion 130 by the fastening angle of the cap nut 140, and it is necessary to manage by the fastening torque of the cap nut 140. That is, the cap nut 140 has to be completely tightened with a larger torque wrench than a tool such as a wrench. As a result, in the conventional pipe joint structure 101, a wide operation space in which a torque wrench can be used is required for complete fastening of the cap nut 140, and therefore, for example, it is difficult to connect pipes in a place where the operation space is narrow, such as a cylinder head of an internal combustion engine, and the operability of pipe connection is degraded.

The fastening torque is a torque required to completely fasten (completely screw) the cap nut to the joint portion. The tightening angle is a rotation angle at which the cap nut is rotated around the central axis of the joint portion (see fig. 1, for example) from a state in which the cap nut is provisionally provided on the joint portion to a state in which the cap nut is completely tightened.

Next, an operation of the pipe joint structure 1 according to the embodiment of the present invention will be described. Fig. 6 is a schematic diagram for explaining the operation of the pipe joint structure according to the embodiment of the present invention. In the pipe joint structure 1 (see fig. 1 to 3) of the present embodiment, the nipple 20 is screwed to the outer peripheral surface of the pipe 10, and the convex end portion 12 of the pipe 10 is brought into contact with the contact portion 31 of the joint portion 30 by the hand operation of the operator or the like. Then, by applying a manual torque to the cap nut 40, the cap nut 40 is made to be fictive on the outer peripheral surface of the joint 30, and the tapered seat portion 21 of the nipple 20 is pressed by the partially spherical pressing portion 42. The cap nut 40 presses the protruding end portion 12 of the pipe 10 against the contact portion 31 of the joint 30 via the seat portion 21. Thereafter, the cap nut 40 is further applied with a tightening torque, whereby the cap nut 40 is completely screwed to the outer peripheral surface of the joint portion 30. At the same time, the cap nut 40 presses the convex end 112 of the pipe 10 against the contact portion 31 of the joint 30 via the seat portion 21 by the pressing portion 42. As a result, the pipe 10 is completely fastened to the joint portion 30 by the cap nut 40.

Here, as shown in fig. 6, in a state where the central axis C1 of the pipe 10 is inclined with respect to the central axis C2 of the joint 30, when the convex end portion 12 of the pipe 10 contacts the contact portion 31 of the joint 30, the nipple 20 screwed to the outer peripheral surface of the pipe 10 is in an inclined state integrally with the pipe 10 (state a 11).

In this state a11, the convex end 12 of the pipe 10 is maintained in a state of coming into contact with the contact portion 31 of the joint 30 by wire contact. The seat portion 21 of the screw nipple 20 has a partially spherical seat surface as described above. Therefore, as shown in fig. 6, the seat surface of the seat 21 maintains a state in which an imaginary spherical surface S2 included in the center of curvature (for example, the center of curvature P shown in fig. 3) is positioned on the central axis C1 of the tube 10. That is, the seat surface of the seat 21 is always located within the virtual spherical surface S2 regardless of the inclined state of the tube 10.

When the cap nut 40 is screwed to the joint 30 in a state where the pipe 10 is in contact with the joint 30 in an inclined manner as described above, the pressing portion 42 of the cap nut 40 is in uniform contact with the seat portion 21 of the nipple 20. That is, as shown in fig. 6, since the pressing portion 42 is the above-described tapered pressing surface and the seat portion 21 is the above-described partially curved seat surface, the pressing portion 42 and the seat portion 21 can be brought into contact with each other over the entire region in the circumferential direction (outer circumferential direction) around the center axis C1 of the pipe 10 (state a 12).

In such a state a12, the pressing portion 42 of the cap nut 40 uniformly presses the seat portion 21 of the nipple 20 over the entire region in the circumferential direction around the central axis C1 of the pipe 10. Thereby, as shown in fig. 6, the pressing force from the pressing portion 42 is uniformly transmitted to the convex end portion 12 of the tube 10 via the seat portion 21. As a result, the contact pressure of the convex end 12 of the pipe 10 and the contact portion 31 of the joint 30 is maintained at a high pressure equal to or higher than the pressure of the fluid flowing in the pipe 10 over the entire region of the contact portion between the convex end 12 and the contact portion 31. In the pipe joint structure 1, since the sealing performance between the convex end portion 12 and the contact portion 31 can be maintained high, a situation in which fluid leaks from between the pipe 10 and the joint portion 30 can be avoided. In particular, the pipe joint structure 1 of the present embodiment is effective for joining the pipe 10 and the joint portion 30 through which a fluid of high pressure (e.g., pressure exceeding 35 MPa) that is difficult to maintain sealability by a sealing member such as an O-ring flows.

In the pipe joint structure 1 of the present embodiment, as illustrated in the state a12 of fig. 6, the pressing portion 42 of the cap nut 40 contacts the seat portion 21 of the nipple 20 over the entire circumferential region around the central axis C1 of the pipe 10. Therefore, when the cap nut 40 is dummied to the joint portion 30 by the manual torque, the pressing portions 42 can be brought into close contact with the seat portion 21 over the entire region in the circumferential direction around the central axis C1 of the pipe 10. This can suppress variation in the fastening angle of the cap nut 40 from the state in which the cap nut 40 is virtually inserted into the joint 30 to the state in which the cap nut is completely fastened. In this case, the complete fastening of the cap nut 40 to the joint portion 30 can be managed by the fastening angle of the cap nut 40. As a result, since the cap nut 40 can be completely tightened without using a torque wrench and with a tool such as a wrench smaller than the torque wrench, it is possible to easily connect the pipe to a place having a narrow operation space such as a cylinder cover of an internal combustion engine, and to improve the operability of the pipe connection.

As described above, in the pipe joint structure 1 according to the embodiment of the present invention, the nipple 20 having the partially spherical seat portion 21 is attached to the outer peripheral surface of the pipe 10 having the internal flow path 11 through which the fluid flows and the partially spherical convex end portion 12 projecting outward, the convex end portion 12 of the pipe 10 abuts against the tapered abutting portion 31 of the joint portion 30, the device (for example, the fuel injection pump 5) for processing the fluid communicates with the pipe 10 via the joint portion 30, the cap nut 40 having the tapered pressing portion 42 inside is screwed onto the outer peripheral surface of the joint portion 30, and the pressing portion 42 presses the seat portion 21 of the nipple 20 to press the convex end portion 12 of the pipe 10 against the abutting portion 31 of the joint portion 30. In the pipe joint structure 1, the pressing portion 42 of the cap nut 40 has a tapered shape that is reduced in diameter toward the opposite side of the convex end portion 12 in the direction of the center axis C1 of the pipe 10. The seat portion 21 of the nipple 20 has a partially spherical shape projecting toward the opposite side of the convex end portion 12 in the direction of the central axis C1 of the pipe 10. The respective centers of curvature of the convex end portion 12 of the pipe 10 and the seat portion 21 of the nipple 20 are located on the central axis C1 of the pipe 10.

With the above configuration, regardless of the inclination of the joint 30 with respect to the pipe 10, the pressing portion 42 of the cap nut 40 can be uniformly brought into contact with the seat portion 21 of the nipple 20 over the entire region in the outer circumferential direction of the pipe 10 without one-side contact while maintaining the state in which the convex end portion 12 of the pipe 10 and the contact portion 31 of the joint 30 are brought into contact with each other by line contact. Therefore, the cap nut 40 can press the seat portion 21 of the nipple 20 uniformly over the entire region in the outer circumferential direction of the pipe 10 by the pressing portion 42 while being screwed into the nipple 30, and can press the convex end portion 12 of the pipe 10 against the contact portion 31 of the nipple 30 via the seat portion 21. Thus, the convex end portion 12 of the pipe 10 is brought into contact with the contact portion 31 of the joint portion 30 over the entire circumferential region around the central axis C2 of the joint portion 30 without being displaced, and the pipe 10 and the joint portion 30 can be joined by the cap nut 40. As a result, the contact pressure of the convex end 12 of the pipe 10 and the contact portion 31 of the joint 30 can be maintained at a high pressure equal to or higher than the fluid pressure over the entire contact area between the convex end 12 and the contact portion 31, and thus high sealability between the pipe 10 and the joint 30 joined thereto can be ensured.

In the pipe joint structure 1 according to the embodiment of the present invention, the pressing portion 42 of the cap nut 40 is in contact with the seat portion 21 of the nipple 20 over the entire region in the outer circumferential direction of the pipe 10. Therefore, the cap nut 40 can be dummied to the joint portion 30 by the manual torque, and the pressing portions 42 are brought into close contact with the seat portion 21 over the entire region in the outer circumferential direction of the pipe 10 without one-side contact. This can suppress variation in the fastening angle of the cap nut 40, and can control the complete fastening of the cap nut 40 to the joint 30 by the fastening angle of the cap nut 40. As a result, the cap nut 40 can be easily and completely tightened in a place with a narrow operation space without using a torque wrench, and thus, the operability of pipe connection can be improved.

In the pipe joint structure 1 according to the embodiment of the present invention, the center of curvature of the seat portion 21 of the nipple 20 is set to the same position as the center of curvature P of the convex end portion 12 of the pipe 10. Therefore, the imaginary spherical surface S2 including the partially spherical seat surface formed by the seat portion 21 of the nipple 20 can be a spherical surface concentric with the imaginary spherical surface S1 including the partially spherical pipe end surface formed by the convex end portion 12 of the pipe 10. This can reduce the displacement between the seat surface of the seat portion 21 and the virtual spherical surface S2 when the pipe 10 is tilted with respect to the joint portion 30. As a result, a structure in which the seat portion 21 of the nipple 20 and the pressing portion 42 of the cap nut 40 can be uniformly brought into contact can be easily realized.

In the pipe joint structure 1 according to the embodiment of the present invention, the stepped portion 14 is formed on the outer peripheral surface of the pipe 10, and the stopper portion 22 is provided on the nipple 20, and the stopper portion 22 comes into contact with the stepped portion 14 to regulate the position of the nipple 20 in the direction of the central axis C1 of the pipe 10. Therefore, the mounting position of the nipple 20 on the outer peripheral surface of the pipe 10 can be easily determined so that the center of curvature of the seat portion 21 of the nipple 20 and the center of curvature of the convex end portion 12 of the pipe 10 are at the same position.

In the above-described embodiment, the pipe 10 to be joined has the convex end portion 12 at one end portion and the other end portion in the direction of the central axis C1 as an example, but the present invention is not limited to this. For example, the pipe 10 may have the convex end portion 12 only at one of both ends in the direction of the central axis C1, or may be branched into a plurality of parts. The tube 10 may be a linear tube or a tube having a bent portion or a bent portion, and the shape of the tube 10 is arbitrary in the present invention.

In the above-described embodiment, the center of curvature of the partially spherical convex end portion 12 of the pipe 10 and the center of curvature of the partially spherical seat portion 21 of the nipple 20 are set at the same position on the central axis C1 of the pipe 10, but the present invention is not limited to this. In the present invention, the respective centers of curvature of the convex end portion 12 and the seat portion 21 may be the same position or different positions as long as they are located on the central axis C1 of the tube 10.

In the above-described embodiment, the nipple 20 is screwed to the outer peripheral surface of the pipe 10, but the present invention is not limited to this. For example, the nipple 20 may be attached to the outer peripheral surface of the pipe 10 by fitting, or may be attached to the outer peripheral surface of the pipe 10 by adhesion, welding, or the like.

In the above-described embodiment, the linear tapered abutting portion is exemplified as the abutting portion 31 of the joint portion 30, but the present invention is not limited thereto. For example, the tapered surface of the contact portion 31 may be a linear tapered surface or a curved tapered surface.

The above embodiments do not limit the present invention. The present invention also encompasses a structure in which the above-described respective components are appropriately combined. In addition, other embodiments, examples, operation techniques, and the like, which are realized by those skilled in the art based on the above-described embodiments, are all included in the scope of the present invention.

Claims

1. A pipe joint structure is characterized by comprising:

a pipe having an inner flow path through which a fluid flows and a convex end portion which is formed with an opening end portion of the inner flow path and has a partially spherical shape protruding outward;

a cylindrical portion formed in a cylindrical shape attached to an outer peripheral surface of the pipe and having a seat portion in a partially spherical shape protruding toward a side opposite to the convex end portion in a central axis direction of the pipe;

a joint portion having a tapered abutting portion abutting against the convex end portion and communicating a device for processing the fluid with the pipe; and

a cap nut having a tapered pressing portion that is reduced in diameter toward a side opposite to the convex end portion in a direction of a central axis of the pipe, the cap nut being screwed to an outer peripheral surface of the joint portion, and pressing the seat portion of the cylindrical portion with the pressing portion to press the convex end portion of the pipe against the abutting portion of the joint portion,

the respective centers of curvature of the convex end portion of the tube and the seat portion of the cylindrical portion are located on a central axis of the tube.

2. The pipe joint construction according to claim 1,

the center of curvature of the seat portion of the cylindrical portion is located at the same position as the center of curvature of the convex end portion of the tube.

3. The pipe joint construction according to claim 1,

the cylindrical portion further has a stopper portion that comes into contact with a step portion formed on an outer peripheral surface of the pipe, thereby restricting a position of the cylindrical portion in a central axis direction of the pipe.

4. The pipe joint construction according to claim 2,

5. The pipe joint construction according to any one of claims 1 to 4,

the conical surface of the pressing part is a linear conical surface.

6. The pipe joint construction according to any one of claims 1 to 4,

the conical surface of the pressing part is a curved conical surface.

7. The pipe joint construction according to claim 6,

the tapered surface of the pressing portion is a partially spherical tapered surface having the same center of curvature as the seat portion of the cylindrical portion.