JP3882951B2 - High pressure injection pipe connection head structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention generally relates to a diesel internal combustion engine or various machines and devices, and has a pipe diameter of about 30 m / m or less and a wall thickness of 2.5 m / m to 12.0 m / The present invention relates to an improvement in the connection head structure of a high-pressure injection pipe having a thick and thin diameter of about m.
[0002]
[Prior art]
Conventionally, as this type of connecting head structure, as shown in FIG. 3, for example, there is an upright wall (11 ′) in which the lower part of the neck formed by the truncated conical connecting head (11) bulges vertically. Further, a washer or sleeve (12) having a similar raised wall (12 ') located in contact with the upright wall portion is pressed to form a press fit. Incidentally, (11 ″) is an annular pocket inside the head which appears as the connecting head (11) is bent in the axial direction.
[0003]
[Problems to be solved by the invention]
However, in such a conventional technique, the bottom of the pocket (11 ″) formed inside is related to the upright wall (11 ′) formed by the vertical part of the lower part of the neck of the connection head (11). It has a small radius of curvature or an edge in extreme cases, and as a result, the concentration of local stress due to high pressure fuel is increased in the pocket as the fuel injection pressure is increased based on the requirement of exhaust gas regulations as in recent years. Naturally, there is a tendency that micro cracks (13) tend to occur outward from the bottom in the radial direction, and the connecting head (11) is buckled around the pocket (11 "). There were problems such as incurring the growth of countless hair cracks that sometimes occurred.
[0004]
The present invention has been made in view of the above-described problems of the prior art, and in particular, by forming the lower part of the neck formed by the connecting head as an inclined surface and making the entire head into an abacus bead shape, By forming the bottom of the wall as a curved surface with a large radius of curvature and forming the washer into a substantially parallelogram shape made of thick wall, stress concentration against high pressure at the bottom of the pocket is alleviated and simultaneously connected Tightening by forming the normal region on the front inclined surface formed by the washer in the state toward at least the bottom of the pocket and the normal region on the rear inclined surface toward the rear vicinity around the pocket. The mechanical strength against crushing / deformation in the thick wall due to the axial force due to the force increases, and the hair cracks around the inner pocket are pressed and sealed by the component force through the washer. Allowed, 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]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention is formed by forming a truncated conical connecting head at the end of a metal tube having a thick and thin diameter and press fitting a cylindrical washer on the back of the head. In the structure, the bottom part of the neck of the connection head is inclined backward and the head is made into an abacus bead, so that the bottom of the inner pocket is a curved surface with a large radius of curvature, and further the inclination The washer that is engaged and pressed at a position corresponding to the surface has a substantially parallelogram shape with a thick cross section and is in the press-fitted connection state, and connects the normal region of the tapered surface in front of the washer. The gist of the present invention is a connecting head structure of a high-pressure spray pipe configured such that at least the bottom of the pocket of the head and the normal region of the rear tapered surface are directed toward the rear of the pocket.
[0006]
Since the present invention is configured as described above, the curved surface having a large radius of curvature at the bottom of the inner pocket due to the abacus bead shape formed by the connection head causes concentration of local stress against high pressure at the bottom. Can be effectively prevented from breaking at the bottom, and at the same time, the normal region on the inclined surface in front of the pocket by the substantially parallelogram made of the thick wall of the washer is connected to the bottom of the pocket. Alternatively, since the normal region formed by the rear inclined surface is directed toward the rear and the vicinity of the pocket, the mechanical strength against the crushing / deformation in the thick wall portion due to the axial force due to tightening is exerted. As a result of the increase, the result is that the innumerable hair cracks around the pockets are pressed and brought in close contact with each other by a washer, and therefore the growth of the hair cracks can be prevented. And thus.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially cutaway sectional view in a connected state according to an embodiment of a connection head structure of a high pressure injection pipe of the present invention, and FIG. It is a partial expanded sectional view of other examples, (1) is a connection head, and generally has a pipe diameter of about 30 m / m or less as a high pressure fuel injection pipe (P) made of carbon steel material for pressure piping or stainless steel material. The wall thickness is about 2.5 m / m to 12.0 m / m.
[0008]
And the neck part of the said connecting head (1) of the truncated cone shape by a prior art becomes an inclined surface (1 ') to back, and this connecting head (1) whole is formed in an abacus bead shape. is there.
[0009]
On the other hand, (1 ″) is an annular pocket inside the connecting head which is generated when the connecting head (1) is bent in the axial direction, and its bottom is formed as a curved surface with a large curvature radius. is there.
[0010]
Further, (2) is a washer, which has a thick wall made of a metal material and is formed into an annular shape having a substantially parallelogram in cross section, and is formed on the neck portion of the abacus-shaped connecting head (1). The position is corresponding to the inclined surface (1 ′) and is press-fitted.
In this specification, the “substantially parallelogram in cross section” means not only a substantially regular parallelogram as shown in FIG. 1, but also a front tapered surface (2 ′) and a rear tapered surface (2) as shown in FIG. The center 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. ) Includes those in the range of 60 to 120 °.
[0011]
The washer (2) is in a connected state in which the washer (2) is press-fitted to the inclined surface (1 ') of the lower part of the neck of the connection head (1), and the front tapered surface (2') formed by the washer (2). The normal region is formed at the bottom of the pocket (1 ″), preferably the whole pocket, and the normal region at the rear tapered surface (2 ″) is directed toward the back of the periphery of the pocket. Due to the increase in mechanical strength against crushing and deformation at the thick wall portion due to tightening, the countless hair cracks around the pocket (1 ″) are pressed and intimately joined through the washer (2) by the component force, This also prevents the growth of hair racks.
[0012]
Incidentally, (3) is a tightening nut, and (4) is a connected portion such as a nozzle holder, which is screwed with a tightening nut (3).
[0013]
【The invention's effect】
As described above, the connection head structure of the high-pressure injection pipe according to the present invention is particularly suitable for making the lower part of the neck of the connection head (1) an inclined surface (1 ') and making the head an abacus bead. In relation to the pockets (1), the normal regions of the inclined surfaces (2 ') and (2 ") on both sides of the washer (2) made of thick wall are oriented in the direction. ”) Can reduce the concentration of local stress against high pressure by the curved surface with a large radius of curvature at the bottom, effectively preventing breakage at the bottom, and at the same time in connection with the tightening force With the increase in mechanical strength against crushing / deformation in the thick wall portion due to axial force, countless hair cracks around the pocket (1 ″) located in the normal region are press-contacted and intimately bonded by the component force. To prevent growth Such that a connection head structure of a very useful high-pressure injection pipe.
[Brief description of the drawings]
FIG. 1 is a partially cutaway cross-sectional view of an embodiment of a connection head structure of a high pressure injection pipe according to an embodiment of the present invention in a connected state.
FIG. 2 is a partially enlarged 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]
1 Connecting head 1 ′ Inclined surface 1 ″ Pocket 2 Washer 2 ′ Tapered surface 2 ″ Tapered surfaces α, β Center angle

Claims (1)

In a structure in which a connection head is formed at the end of a metal tube having a thick and thin diameter and a cylindrical washer is press-fitted to the back of the head, the neck portion of the connection head (1) is By forming an inclined surface (1 ') to the rear and making the head into an abacus bead, the bottom of the internal pocket (1 ") has a curved surface with a large radius of curvature, and a position corresponding to the inclined surface. The washer (2), which has been subjected to pressure, has a substantially parallelogram-shaped cross section with a thick wall and is in the press-fitted connection state, and the normal line of the front tapered surface (2 ') formed by the washer The region is configured such that the region is at least at the bottom of the pocket (1 ″) of the connecting head (1) and the normal region of the rear tapered surface (2 ″) is directed toward the rear of the periphery of the pocket. Connecting head structure of high pressure injection pipe.

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