JP2000199588A - Connection structure of pipe end part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the connection structure of a pipe end part to shorten a seal peripheral length during threaded engaging fastening of a fastening nut against a mating coupling, prevent the occurrence of partial contact by absorbing a core deviation when the deviation occurs, and further prevent the decrease of the thickness of a flare part, and maintain a stable connection state during a long period by relieving concentration of a stress to the under-neck part of the flare part and effectively dispersing the stress. SOLUTION: The tip part side having a rounded acute angle α, and a ring member 5 having a slope 5-2 formed fronting on the outside is fitted in the vicinity of the pipe end part of a metallic pipe P. By bending the pipe end part of the metallic pipe P in a state to brace the ring member 5 and cover the slope 5-2, a flare wall 2 is formed. Meanwhile, the pressure receiving seat surface of a mating coupling 3 is formed such that the angle β of the mating coupling 3 with a central axial line is higher than the angle α and lower than 90 deg.. Further, it is preferable that the flare wall 2 consists of a double wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pipe having a relatively small diameter and a thin wall, which is generally provided as an oil supply or air supply path for an automobile or various machines and devices. The sealing is performed by pressing against the pressure receiving seat surface of the mating joint. For example, a high pressure fluid such as CNG (compressed natural gas) or dimethyl ether (DME) or a leaky fluid is effective for the end of the metal tube. It relates to a connection structure.

[0002]

2. Description of the Related Art Conventionally, a single flare or a double flare has been known as a connection structure of a pipe end of a metal pipe of this kind. In these flare structures, the flare portion is sandwiched between the inclined pressing seat surface of the tightening nut and the pressure receiving seat surface inclined corresponding to the inclined surface of the pressing seat surface of the mating joint. Is to connect.

[0003]

However, such a conventional flare structure has a structure in which the flare portion is sandwiched between the corresponding inclined surfaces, so that the tightening nut 11 is screwed into the mating joint 12 when tightening. As shown in FIG. 6, the initial seal portion S 'is subjected to the axial force of the tightening nut 11 on the flare portion 13 so that the initial seal portion S' has the two inclined surfaces 11-1,
12-1 and the seal portion S
, The circumferential length of the seal is increased (ie, the circular seal portion S 'shifts outward, resulting in a large-diameter circular seal portion S, and consequently the seal circumferential length increases). When the misalignment between the mating joint 12 and the metal pipe P 'occurs, the sealing surface may be partially contacted or the flare portion 13 may be thinned due to excessive tightening, thereby causing leakage of the internal fluid. Furthermore, there is a problem that the fatigue strength is concentrated on the lower part of the neck of the flare portion 13 due to the use for a long period of time under the vibrating state and the cracks and breakage are induced.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problem, and it is possible to prevent the seal circumferential length from being lengthened when screwing and tightening, and to reduce the misalignment even when there is misalignment. Absorbs to prevent the occurrence of one-sided contact, and further reduces the stress concentration at the lower part of the neck of the flare part without effectively reducing the thickness of the flare part, maintaining a stable connection state for a long time It is an object of the present invention to provide a connection structure of a pipe end which can be used for connection of an electric resistance welded pipe as a mating joint.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a metal pipe comprising a ring member having an acute angle (.alpha.) With a rounded front end and an inclined surface formed on the outside. Of the metal tube to form a flare wall so as to hold the ring member and cover the inclined surface, while forming a flare wall. The connection structure of a pipe end portion in which an angle (β) with respect to a center axis of a mating joint is larger than the angle (α) and smaller than 90 °, and the flare wall is formed of a double wall. Is preferred.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 is a half sectional view of a tube end connection structure according to one embodiment of the present invention, FIG. 2 is a half sectional view of a tube end connection structure according to another embodiment, and FIG. 3 is still another embodiment of the present invention. FIG. 4 is a half cutaway view showing the structure of the tube end portion of the example, FIG. 4 is a half cutaway view showing the structure of the tube end portion of still another embodiment of the present invention, and FIG. 5 shows the operation of the present invention for absorbing misalignment. In the drawing, P is a metal tube, 2 is a double flare wall, 2 'is a single flare wall, 3 is a mating joint, 4 is a cap nut as a fastening nut, and 5 is a ring member.

In the present invention, as shown in FIG. 1, an acute angle (α) having a rounded tip 5-1 near the pipe end of the metal pipe P.
A ring member 5 having a substantially right-angled triangular cross-section having an inclined surface 5-2 facing outward is fitted therein. The pipe end of the metal pipe P is bent outward so as to hold the ring member 5 and cover the inclined surface 5-2, and bend its free end inward again to form a double tube. The flare wall 2 is formed, and the tip of the pressing seat surface 2-1 of the double flare wall 2 is formed in an arc shape along the tip portion 5-1. The angle (β) of the mating joint 3 with respect to the center axis 3-2 is formed as a plane inclined at an angle larger than the angle (α). In the illustrated embodiment, an example is shown in which a cap nut is used as the tightening nut 4, but it goes without saying that a general male nut can be used.

When connecting the metal pipe P and the mating joint 3, the pipe end according to the present invention, in which the tightening nut 4 is previously assembled on the metal pipe P side, is connected to the pressing seat surface 2 of the double flare wall 2. As the inner thread portion 4-1 of the tightening nut 4 is screwed and fastened to the outer thread portion 3-3 of the mating joint 3 with the -1 abutting against the pressure receiving seat surface 3-1 of the mating joint 3, The surface 2-1 is pressed against and connected to the pressure receiving seat surface 3-1. At this time, since the pressing seat surface 2-1 is formed in an arc shape as described above, a circular line contact is made with the inclined pressure receiving seat surface 3-1 of the mating joint 3 so as to increase the surface pressure and ensure the pressure. The sealing effect can be exerted. Also, even if there is a misalignment between the pressing seat surface 2-1 and the pressure receiving seat surface 3-1 and the one-sided portion S "occurs, as shown in FIG. The pressure seating surface automatically moves to the position of the regular seal portion S to absorb the misalignment, so that leakage of the internal fluid due to one end of the seal portion can be prevented.

Further, the angle (β) of the pressure receiving seat surface 3-1 with respect to the center axis 3-2 of the mating joint 3 is formed to be larger than the acute angle (α) on the tip end 5-1 side of the ring member 5. Therefore, the flare wall 2 of the metal tube P is pressed in the axial direction by the screwing of the tightening nut 4, and the initial seal portion S '
(Solid line position) is shifted inward in the radial direction, and the regular seal portion S
(The position indicated by the two-dot chain line) to shorten the seal circumference (that is, the circular seal portion S 'is shifted inward to the position of the seal portion S, so that the circle has a small diameter, and as a result, the seal circumference is reduced). Therefore, the axial force generated by the tightening nut 4 is strongly transmitted to the seal portion S, and a stable and strong seal is obtained.

Unlike the embodiment of FIG. 1, the free end of the inside of the pressing seat 2-1 of the double flare wall 2 is shortened as shown in FIG. -1
Even if it is formed not in the shape of an arc along the line but in the shape of a straight line, the same operation and effect as the embodiment of FIG. 1 can be exhibited.

Next, FIG. 3 shows a pressure receiving seat having an angle (β) formed by the pressure receiving surface 3-1 with respect to the central axis 3-2 of the mating joint 3 larger than an acute angle (α) at the tip end side of the ring member 5. It is a figure which shows the example which forms the pressure receiving seat surface 3-1 as a plane orthogonal to the said center axis 3-2, ie, a vertical wall, instead of forming the surface 3-1. That is, in FIG. 3 as well, the ring member 5 in which the tip end 5-1 side forms a rounded acute angle (α) and has an inclined surface 5-2 facing outward is fitted near the end of the metal tube P in FIG. Have been. The pipe end of the metal pipe P holds the ring member 5 and the inclined surface 5
-2 double flare wall to bend to cover -2
And the tip of the pressing seat surface 2-1 of the double flare wall 2 is formed in an arc shape. On the other hand, the pressure receiving seat surface 3 of the mating joint 3
-1 is formed at an angle of 90 ° with respect to the center axis 3-2 of the mating joint 3.

In the embodiment of FIG. 3, when the metal pipe P is connected, since the tip of the pressing seat surface 2-1 is formed in an arc shape as described above, the vertical pressure receiving seat surface 3-1 of the mating joint 3 is connected.
Contact with the pressure receiving surface 2-1 and the pressure receiving surface 3-1 even if there is a misalignment between the pressure bearing surface 2-1 and the pressure receiving surface 3-1. Since the misalignment is automatically absorbed by the arc-shaped pressing seat surface, it is possible to prevent the internal fluid from leaking due to one-side contact. Further, the flare wall 2 of the metal tube P is pressed in the axial direction by the pressure receiving seat surface 3-1 perpendicular to the acute angle (α) on the tip portion 5-1 side of the ring member 5, and the initial seal portion S ′ (solid line) Position) shifts inward in the radial direction and becomes a regular position of the seal portion S (a position indicated by a two-dot chain line) to shorten the seal circumference, so that the axial force generated by the tightening nut 4 is strongly transmitted to the seal portion S. A stable and strong seal can be obtained.

As described above, in the present invention, the pressure receiving seat surface 3-1 of the mating joint 3 must be formed such that the angle (β) with respect to the central axis 3-2 of the mating joint 3 is larger than the angle (α) and smaller than 90 °. However, angle (β) is 5 times greater than angle (α).
It is preferable to be larger than 90 ° and less than 90 °. In the embodiment shown in FIG. 3, the whole is not a substantially right-angled triangular cross section as in the ring member 5 of FIGS. 1 and 2, but only the tip end side of the ring member 5 has a substantially right-angled triangular cross section. And a tightening nut 4 at the rear end.
An annular flange portion 5-3 is formed integrally and extends outward to transmit a stable axial force by enlarging a contact surface with the flange portion. As the metal pipe P having the double flared wall 2 shown in the embodiment of FIGS. 1 to 3, not only a seamless pipe and a double wound pipe but also an electric resistance welded pipe can be used. That is, when the pressing seat surface 2-1 is formed using the outer surface of the electric resistance welded tube, the pressure receiving seat surface 3-
The reason for this is that the reliability of internal fluid leakage is increased because the internal surface where the weld bead may be present is not used for 1.

FIG. 4 is a cross-sectional view of the double switch shown in FIGS.
It is the figure which showed the pipe end structure of the metal pipe P used for the connection structure of the pipe end which concerns on this invention which provided the single flare wall 2 'instead of the flare wall 2. FIG. That is, in FIG. 4, the ring member 5 formed on the inclined surface 5-2 facing the outside forms an acute angle (α) with a rounded end portion 5-1 near the end of the metal tube P. Have been. The pipe end of the metal pipe P holds the ring member 5 and the inclined surface 5
The single flare wall 2 'is formed to be bent outward so as to cover -2, and the tip of the pressing seat surface 2-1 of the single flare wall 2' has an arc shape. On the other hand, as in FIGS. 1 to 3, the shape of the pressure receiving seat surface 3-1 of the mating joint 3 is such that the angle (β) with respect to the central axis 3-2 of the mating joint 3 is inclined with an angle larger than the angle (α). It is formed as a flat surface, or formed at an angle of 90 ° with respect to the central axis 3-2 of the mating joint 3.

In this embodiment, when the metal tube P is connected,
Since the pressing seat surface 2-1 is formed in an arc shape as described above, the pressing seat surface 2-1 makes line contact with the inclined surface having a large angle (β) of the mating joint 3 or the vertical pressure receiving seat surface 3-1 to reduce the surface pressure. It is possible to enhance the sealing effect by increasing the pressure, and even if there is misalignment between the pressing seat surface 2-1 and the pressure receiving seat surface 3-1, the pressure receiving seat surface of the inclined surface having the large angle (β) Since the arc-shaped pressing seat automatically moves to the normal position, the misalignment is automatically absorbed, and the vertical pressure-receiving seat and the arc-shaped pressing seat automatically absorb the misalignment. In addition, leakage of the internal fluid due to one side contact can be prevented. Further, the flare wall 2 of the metal pipe P is oriented in the axial direction by the acute angle (α) on the tip end 5-1 side of the ring member 5 and the inclined surface or the vertical pressure receiving seat surface 3-1 having the large angle (β). The axial force generated by the tightening nut 4 is strongly transmitted to the seal portion S so that the seal portion S 'is shifted inward in the radial direction to be in the position of the regular seal portion S and shorten the seal circumference. Thus, a stable and strong seal can be obtained.

[0016]

As described above, according to the present invention, the circumferential length of the seal can be shortened when the tightening nut is screwed into the mating joint, and even if there is a misalignment, To prevent the occurrence of one-sided contact, further reduce the stress concentration at the lower part of the neck of the flare part without causing the flare part to become thinner, and effectively disperse it to ensure a stable connection state for a long time. It is possible to provide a pipe end connection structure that can be maintained and can also be used to connect an ERW pipe to a mating joint.

[Brief description of the drawings]

FIG. 1 is a half cutaway view of a pipe end connection structure according to an embodiment of the present invention.

FIG. 2 is a half cutaway view of a pipe end connection structure according to another embodiment of the present invention.

FIG. 3 is a half cutaway view showing a structure of a pipe end according to still another embodiment of the present invention.

FIG. 4 is a partially cutaway view showing a structure of a pipe end according to still another embodiment of the present invention.

FIG. 5 is a diagram illustrating an operation of absorbing misalignment according to the present invention.

FIG. 6 is a diagram showing an operation of a conventional example.

[Explanation of symbols]

 2 Double flared wall 2 'Single flared wall 2-1 Press seat surface 3 Mating joint 3-1 Pressure receiving seat surface 3-2 Center axis line 3-3 External thread 4 Tightening nut 4-1 Internal thread 5 Ring member 5 -1 Tip portion 5-2 Inclined surface 5-3 Annular flange portion P Metal tube S, S 'Seal portion S "One-side contact portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kasumitsu Mizuno 186-1 Yukawa Yukawa, Shimizu-cho, Sunto-gun, Shizuoka Prefecture (72) Inventor Hiroaki Kondo 75-1 Okamiya, Numazu-shi, Shizuoka F-term (reference) 3H014 EA02 EA07

Claims (2)

[Claims] 1. An almost acute angle (α) having a rounded tip portion
A ring member having an inclined surface facing outward is fitted near a tube end of the metal tube, and the tube end of the metal tube is held so as to hold the ring member and cover the inclined surface. Is bent to form a flare wall, while the pressure receiving seat surface of the mating joint has an angle (β) with respect to the central axis of the mating joint that is equal to the angle (α).
A pipe end connection structure formed to be larger than 90 °. 2. The pipe end connection structure according to claim 1, wherein said flare is formed of a double wall.