JPH10103189A - Connecting head part structure for high pressure injection pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax concentration of local stress in a bottom part of a pocket in the inside, effectively prevent bursting in the bottom part, and impede growth of a hair crack in the periphery of the pocket based on collapse deformation in a large thickness part by axial force according to tightening. SOLUTION: In a structure constituted by forming a connecting head part l in an end part of a metal pipe P formed by a large thickness fine diameter, and press fitting a cylindrical annular washer 2 to a back surface of the head part, an under neck part of the connecting head part is made to serve as tilt surface 1' to the rearward, by forming the head part in a counter bead shape, a bottom part of a pocket 1" in the inside is formed as a curved surface of large radius of curvature. Further, a washer, correspondingly positioned to the tilt surface to be press engaged, is formed in a shape of almost parallelogram section formed by large thickness, in this press fit connecting condition, this constitution is provided by respectively directing a normal region of a forward tapered surface 2' formed by the washer to at least a bottom part of a pocket in the connection head part and a normal region of a backward tapered surface 2" to in the vicinity behind the periphery of the pocket part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a diesel internal combustion engine or various machines and apparatuses, and has a pipe diameter of about 30 m / m or less and a wall thickness of 2.5 m provided as a high-pressure fuel supply path or the like. The present invention relates to an improvement in a connection head structure of a high-pressure injection pipe having a thin wall thickness of about 1 / m to 12.0 m / m.

[0002]

2. Description of the Related Art Conventionally, as this kind of connection head structure,
For example, as shown in FIG.
An upright wall (11 ') that vertically bulges the lower part of the neck made by 1)
Then, a washer or a sleeve (12) having a similar raised flange wall (12 ') positioned in contact with the raised wall portion is pressed and fitted. Reference numeral (11 ″) denotes an annular pocket inside the connection head (11) that appears as the connection head (11) buckles in the axial direction.

[0003]

However, in such a prior art, the vertical wall (11 ') formed by the lower part of the neck of the connecting head (11) is formed inside the vertical wall. The bottom of the pocket (11 ") has a small radius of curvature or, in extreme cases, edge-like,
Accordingly, local stress concentration due to high-pressure fuel is generated in the pocket portion with the increase of the fuel injection pressure based on the requirement of the exhaust gas regulation as in recent years, and naturally the radially outward from the bottom portion. Micro cracks (13) tend to occur, and the number of hair cracks that occur during the buckling of the connection head (11) around the pocket (11 ″) is also increased. Had.

[0004] The present invention has been made in view of the above-mentioned problems of the prior art, and in particular, the lower part of the neck formed by the connecting head is formed as an inclined surface, and the entire head is formed into an abacus bead. By forming the bottom of the pocket with a curved surface with a large radius of curvature and forming the washer into a generally parallelogram shape made of thick wall, stress concentration due to high pressure at the bottom of the pocket is reduced. The normal region on the front inclined surface formed by the washer is connected to at least the bottom of the pocket, and the normal region on the rear inclined surface is directed toward the rear near the pocket. As a result, the mechanical strength against crushing / deformation in the thick part due to the axial force accompanying the tightening force is increased, and the hair force around the internal pocket is increased by the component force via the washer. Tighten combined pressure dense click, it is an object to provide a connecting head structure for high-pressure injection pipe which can also inhibit the growth due to the fuel high pressure.

[0005]

In order to achieve the above object, the present invention forms a frusto-conical connection head at the end of a metal tube having a thick wall and a small diameter, and forms a tube on the back of the head. In a structure in which an annular washer is press-fitted, the lower portion of the neck of the connection head is formed as an inclined surface toward the rear, and the head is formed in an abacus shape, so that the bottom of the internal pocket has a large radius of curvature. And a washer which is pressed against a position corresponding to the inclined surface is formed into a thick parallelepiped shape having a substantially parallelogram cross-section, and is in a press-fitted connection state, and is formed by the washer. The connection head structure of the high-pressure injection pipe is configured such that the normal region of the tapered surface is directed to at least the bottom of the pocket of the connection head, and the normal region of the rear tapered surface is directed toward the rear near the pocket. It is an abstract.

Since the present invention is constructed as described above, a curved surface having a large radius of curvature at the bottom of the inner pocket formed by the abacus having the connecting head has a local portion against a high pressure at the bottom. The concentration of stress can be reduced to effectively prevent the breakage at the bottom portion, and at the same time, the normal region on the front inclined surface by the substantially parallelogram formed of the thick wall of the washer in the connected state is reduced. Since the normal region formed by the bottom or entirety of the pocket and the rear inclined surface is directed toward the rear portion around the pocket, the machine against crushing / deformation at the thick portion due to the axial force due to the tightening. Due to the increase in the mechanical strength, the component force causes the innumerable hair cracks around the pockets to be pressed and brought together through washers, and thus the growth of the hair cracks is also prevented. So that the can.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partially cutaway view of a connecting head structure according to an embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view of another embodiment,
Reference numeral (1) denotes a connection head, which is generally a high-pressure fuel injection pipe (P) made of carbon steel or stainless steel for pressure piping, having a pipe diameter of about 30 m / m or less and a wall thickness of 2.5 m / m to 1 m.
It has a thick and small diameter of about 2.0 m / m.

The lower part of the neck of the connection head (1) in the form of a truncated cone according to the prior art forms an inclined surface (1 ') toward the rear, so that the entire connection head (1) is formed in an abacus shape. Is what you do.

[0009] On the other hand, (1 ") is an annular pocket inside the connection head which is formed when the connection head (1) is subjected to buckling in the axial direction, and its bottom is formed as a curved surface having a large radius of curvature. It forms.

[0010] Further, (2) is a washer, which is formed by forming a thick wall made of a metal material into an annular shape having a substantially parallelogram cross section, and the abacus-shaped connecting head (1).
Of the lower part of the neck corresponding to the inclined surface (1 '). In this specification, "substantially parallelogram cross section" means not only a substantially equilateral parallelogram as shown in FIG. 1, but also a tapered surface (2 ') at the front and a tapered surface (2') at the rear as shown in FIG. )), The central angle (α) of the front tapered surface (2 ′) of the washer (2) is 45 to 90 °, and the central angle (β) of the rear tapered surface (2 ″). ) Is included in the range of 60 to 120 °.

Then, the washer (2) is connected to the connection head (1).
In a connection state in which the washer (2) is press-fitted to the inclined surface (1 ') of the lower part of the neck, the normal area of the forward tapered surface (2') formed by the washer (2) is the bottom of the pocket (1 "). Preferably, the entire pocket and the normal area at the rear tapered surface (2 ") are respectively formed toward the rear vicinity of the periphery of the pocket, thereby crushing and deforming at the thick part due to tightening. Due to the increase in mechanical strength, the innumerable hair cracks around the pockets (1 ") are pressed and brought together through the washers (2) by the component force, thereby preventing the growth of the hair cracks. .

Reference numeral (3) denotes a tightening nut, and (4) denotes a connected portion such as a nozzle holder, which is screwed with the tightening nut (3).

[0013]

As described above, the connecting head structure of the high-pressure injection pipe according to the present invention has a slant surface (1 ') at the lower part of the connecting head (1). In relation to the shape, the respective normal regions by the inclined surfaces (2 ′) and (2 ″) on both the front and rear due to the shape of the washer (2) made of a thick wall are directed toward the direction. Therefore, the curved surface of the bottom of the pocket (1 ") having a large radius of curvature can relieve the concentration of local stress due to high pressure, effectively preventing breakage at the bottom, and at the same time in the connection state. By increasing the mechanical strength against crushing / deformation in the thick part due to the axial force accompanying the tightening force, countless hair cracks around the pocket (1 ″) located in the normal area are pressed by the component force. Close together to prevent their growth Etc. can be a connection head structure of a very useful high-pressure injection pipe.

[Brief description of the drawings]

FIG. 1 is a partially cutaway sectional view of a connection state of a connection head structure of a high-pressure injection pipe according to an embodiment of the present invention in a connection state.

FIG. 2 is a partially enlarged cross-sectional view of another embodiment of the present invention.

FIG. 3 is a partially cutaway sectional view of a connection head structure of a high-pressure injection pipe showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 connection head 1 'inclined surface 1 "pocket 2 washer 2' taper surface 2" taper surface α, β central angle

Claims (1)

[Claims] 1. A structure in which a connection head is formed at an end of a metal tube having a large thickness and a small diameter, and a cylindrical annular washer is press-fitted on the back of the head. By forming the lower part of the neck as a rearward inclined surface (1 ') and forming the head in an abacus shape, the bottom of the inner pocket (1 ") is formed into a curved surface with a large radius of curvature. A washer (2) pressed against the inclined surface is formed into a thick parallelepiped shape having a substantially parallelogram cross section, and is in a press-fit connection state, and the forward tapered surface (2) formed by the washer is formed. ′) With the normal region facing at least the bottom of the pocket (1 ″) of the connecting head (1) and the normal region of the rear tapered surface (2 ″) facing the rear near the pocket. Connection head structure of high-pressure injection pipe characterized by the following.