JP2004360655A - Branch joint structure of common rail - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complete and stable branch joint structure by preventing cracking from developing on a joint head portion as well as prevention of leakage or dust due to looseness at a mutual joint portion over a long period, in a common rail having a structure formed by welding a joint metal fitting to a main-piping rail. <P>SOLUTION: This common rail is structured so as to be tightened through a sleeve washer screwed into the joint head portion with the pressure at the joint head portion by screwing a tubular sleeve nipple of external thread system welded or brazed onto the main-piping rail with a box nut previously assembled into branch piping, and so that a thread between the sleeve nipple and the box nut may be inverse to a thread between the joint head portion and the sleeve washer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a common rail branch joint structure such as a high pressure fuel manifold or block rail in a diesel internal combustion engine.
[0002]
[Prior art]
Conventionally, as a joint structure of a branch pipe of this type, as shown in FIG. 3, for example, a through hole 11-2 portion communicating with an internal flow passage 11-1 provided in a peripheral wall portion on the main pipe rail 11 side is outwardly formed. A pressure receiving seat surface 11-3 which is open to the outside, a cylindrical sleeve nipple 14 of an external thread type having a diameter surrounding the pressure receiving seat surface portion is used, and a base end of the sleeve nipple 14 is connected to the pressure receiving seat surface 11-. 3 is welded or brazed to the outer peripheral wall of the main pipe rail 11 and has a flow passage 13-1 therein which communicates with the flow passage 11-1. The pressing seat surface (seat surface) 13-3 formed by the connection head 13-2 on the branch pipe 13 side provided with the enlarged connection head 13-2 contacts the pressure receiving seat surface 11-3 on the main pipe rail side. The sleeve nut 15 is screwed into the sleeve nipple 14. Which connection configuration via the sleeve washer 16 is known by the (see Patent Document 1).
[0003]
[Problems to be solved by the invention]
However, the joint structure according to such a conventional technique has the following problems.
That is, as a method of forming the connection head 13-2 having a truncated conical shape (or truncated arc shape) with the outer peripheral surface as a pressing seat surface (seat surface) 13-3 as shown in FIG. Generally, the end of the thick-walled steel pipe is formed by buckling due to pressing in the axial direction by a punch member from the outside. The connecting head formed by this forming method is formed by forming an annular pocket 17 inside the head by the outward expansion of the peripheral wall due to buckling by pressing, and has been used in such a state. However, due to cavitation erosion generated in the vicinity of the annular concave portion 17 due to the high-pressure fluid at the time of installation and use, radial cracks are generated in the connection head 13-2 starting from the annular pocket 17 or the annular pocket 17 is formed. There is a problem that a circumferential crack is generated around the periphery of the base.
[0004]
On the other hand, Patent Literature 2 discloses a branch joint structure employing a branch pipe having a connection head that does not have the pocket portion by buckling. As shown in FIG. 4, this branch joint structure has a pressure receiving seat surface 21-3 that opens outwardly through a through hole 21-2 that communicates with an internal flow passage 21-1 provided in a peripheral wall portion on the main pipe rail 21 side. A ring-shaped joint fitting 23 with a threaded hole surrounding the outer peripheral portion of the main pipe rail near the pressure receiving seat surface is used. A press seating surface 22-3 formed by the connection head 22-2 is brought into contact with and engaged with a pressure receiving seating surface 21-3 on the main pipe rail side. The branch pipe 22 is screwed into a screw surface of the branch pipe 22 and a screw hole of the joint fitting 23 to fasten and connect the branch pipe 22.
However, in the case of this joint structure, the use of the ring-shaped joint fitting 23 significantly increases the product weight at the connection part, and has the disadvantage that the product weight cannot be reduced. The fitting is simply fitted externally, so not only does it take a long time for positioning, but also there is a possibility that the fitting is displaced in the tube axis direction due to vibration, impact, etc., and this displacement is loosened. Causes the joint to become unstable by causing leakage, and when the branch pipe 22 is removed, the joint fitting 23 moves in the pipe axis direction, and dust adhering to the outer surface of the main pipe rail 21 is removed. Have a problem that there is a possibility of intrusion between the two.
[0005]
The present invention has been made in order to solve the above-described problems of the related art, and in a common rail having a structure in which a joint fitting made of a sleeve nipple is welded to a main pipe rail, a crack is not generated in a connection head. Further, it is an object of the present invention to provide a stable and stable branch joint structure by preventing leakage or dust from entering due to loosening at a mutual connection portion for a long time.
[0006]
[Patent Document 1] Japanese Patent Application Laid-Open No. H10-213044 [Patent Document 2] Japanese Utility Model Publication No. 5-33832
[Means for Solving the Problems]
The branch joint structure of a common rail according to the present invention is provided with a plurality of through-holes at intervals in an axial peripheral wall portion of a main pipe rail having a flow passage inside the shaft core, and each of the peripheral surface portions of the through-holes. A pressure formed by a connection head having an outer peripheral surface as a threaded surface, which is formed at an end of the branch pipe by forming an outwardly-opening pressure-receiving seat surface connecting a branch pipe having a flow path communicating with the flow passage. The connection head formed by screwing an externally threaded cylindrical sleeve nipple, which is brought into abutment engagement with the seat surface portion and connected to the main pipe rail by welding or brazing, and a cap nut previously incorporated in the branch pipe side. A joint between the sleeve nipple and the cap nut, wherein the connection head is connected by tightening via a sleeve washer screwed to the connection head in response to the pressure in the connection head. That the screw between the sleeve washer and the It is an.
[0008]
Further, according to the present invention, a plurality of through-holes are provided at intervals in an axial peripheral wall portion of a main pipe rail having a flow passage inside a shaft core, and each of the through-holes communicates with the flow passage in a peripheral surface portion thereof. A pressure receiving seat surface that opens to the outside connecting the branch pipe having the flow path is formed, and a pressing seat surface part formed by a connection head having an outer peripheral surface as a threaded surface provided at an end of the branch pipe abuts. An externally threaded cylindrical sleeve nipple connected to the main pipe rail by welding or brazing, a connection head forming a screw on the outer peripheral surface, and a cap nut previously incorporated in the branch pipe side. The joint between the sleeve nipple and the cap nut, and the screw between the connection head and the cap nut. Are reverse-threaded.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a longitudinal sectional side view showing an example of a common rail branch joint structure according to claim 1 of the present invention, and FIG. 1 is a longitudinal sectional side view showing an example of a common rail branch joint structure according to claim 2 of the present invention. A main pipe rail as a main body, 2 is a pressure receiving seat surface, 3 is a branch pipe, 4 is an external thread type cylindrical sleeve nipple, 5-1 and 5-2 are cap nuts, and 6 is a sleeve washer.
[0010]
The main pipe rail 1 as a common rail is a relatively thick and small-diameter metal pipe having, for example, a pipe diameter of 20 m / m and a wall thickness of about 6 m / m. A plurality of through-holes, each of which has a plurality of circumferentially open peripheral surfaces that are open to the outside and are spaced apart from each other in the axial direction and forms a pressure receiving seat surface 2, are provided in communication with the flow passage 1-1.
[0011]
In FIG. 1, a branch pipe 3 is formed of a branch branch pipe or a branch connector, and has therein a flow passage 3-1 communicating with the flow passage 1-1, and the end thereof is slightly expanded. A pressing seat surface 3-3 formed by the connection head 3-2 having a diameter is provided, and a male screw 3-4 is provided on an outer peripheral surface of the connection head 3-2.
An outer thread type cylindrical sleeve nipple 4 has a diameter surrounding the pressure receiving seat surface 2, and has a base end concentric with the pressure receiving seat surface 2 so as to surround the pressure receiving seat surface 2 of the main pipe rail 1. The part is welded or brazed. Reference numeral 4-1 denotes a male screw opposite to the male screw 3-4 of the connection head of the branch pipe 3.
The cap nut 5-1 is provided with an internal thread 5-1a which is screwed with the external thread 4-1 of the sleeve nipple 4 on the inner peripheral surface.
The sleeve washer 6 is provided on its inner peripheral surface with a female screw 6-1 which is screwed with a male screw 3-4 provided on the connection head on the branch pipe 3 side.
[0012]
In the case of the branch joint structure shown in FIG. 1, the pressing seat surface 3-3 formed by the connection head 3-2 on the branch pipe 3 is brought into contact with the pressure receiving seat surface 2 on the main pipe rail 1 side, and the branch is made in advance. After the sleeve washer 6 incorporated into the pipe 3 is screwed to the connection head 3-2, the cap nut 5-1 screwed to the sleeve nipple 4 is tightened to form a connection.
[0013]
That is, the branch joint structure of the common rail corresponding to claim 1 of the present invention shown in FIG. 1 is composed of the screws 4-1 and 5-1a between the sleeve nipple 4 and the cap nut 5-1 and the connection head 3-3. Since the screws 3-4 and 6-1 between the sleeve 2 and the sleeve washer 6 are reverse threads, even if the rigid nipple 4 is a common rail welded or brazed to the main pipe rail 1, There is no loosening at the joint.
[0014]
Further, in the branch joint structure according to the second aspect of the present invention shown in FIG. 2, the sleeve nipple 4 is pressed against the outer peripheral wall of the main pipe rail 1 near the pressure receiving surface 2 so as to surround the pressure receiving surface. A portion corresponding to the sleeve washer 6 is provided integrally with the cap nut 5-1 to form a cylindrical portion 5-1b by welding or brazing concentrically with the seating surface 2, and an inner periphery of the cylindrical portion 5-1b is formed. The female screw 5-1b 'which is screwed with the male screw 3-4 provided on the outer peripheral surface of the connection head 3-2 on the branch pipe 3 side is provided on the surface. In this case, the cylindrical portion 5- The screws 5-1b 'and 3-4 between the connection head 3a and the connection head 3-2 on the branch pipe 3 side are reverse screws to the screws 4-1 and 5-1a between the sleeve nipple 4 and the cap nut 5-1. ing.
Therefore, even in the case of the branch joint structure shown in FIG. 2, even when the sleeve nipple 4 having low rigidity is a common rail welded or brazed to the main pipe rail 1, no loosening occurs at the mutual joint portion.
[0015]
【The invention's effect】
As described above, the branch joint structure of the common rail according to the present invention can not only solve the problem of cracking due to the use of the branch pipe having the connection head that does not have a pocket portion due to buckling processing, but also can reduce the rigidity of the sleeve. Even if the nipple is a common rail welded or brazed to the main pipe rail, there is no loosening at the joints, so leakage and dust intrusion due to loosening at the mutual connection will not occur for a long time. An excellent effect is obtained that a stable and stable joint can be obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional side view showing an example of a common rail branch joint structure according to claim 1 of the present invention.
FIG. 2 is a longitudinal sectional side view showing an example of a common rail branch joint structure according to claim 2 of the present invention.
FIG. 3 is a longitudinal sectional front view showing an example of a conventional common rail branch joint structure.
FIG. 4 is a vertical sectional front view showing another example of a conventional common rail branch joint structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main rail 1-1 Flow passage 1-2 Through hole 2 Pressure receiving seat surface 3 Branch pipe 3-1 Flow passage 3-2 Connection head 3-3 Press seat surface 3-4, 4-1 Male screw 4 External screw system Cylindrical nipples 5-1 and 5-2, cap nuts 5-1b, cylindrical portions 5-1a, 5-1b ', and 6-1 internal thread 6 sleeve washers

Claims (2)

A branch pipe having a plurality of through-holes provided at intervals in an axial peripheral wall portion of a main pipe rail having a flow passage inside a shaft core, and a flow passage communicating with the flow passage in a peripheral surface portion of the through-hole. The pressure receiving seat surface which opens to the outside and is provided at the end of the branch pipe, and the pressing seat surface portion of the connection head having an outer peripheral surface as a screw surface is brought into contact with and engaged with the main pipe. The connection head is pressed by the connection head by screwing a cylindrical sleeve nipple of an external thread type connected to the rail by welding or brazing and a cap nut previously assembled on the branch pipe side. A joint between the sleeve nipple and the cap nut, and a screw between the connection head and the sleeve washer with a reverse screw. A branch joint structure of a common rail characterized by what has been done. A branch pipe having a plurality of through-holes provided at intervals in an axial peripheral wall portion of a main pipe rail having a flow passage inside a shaft core, and a flow passage communicating with the flow passage in a peripheral surface portion of the through-hole. The pressure receiving seat surface which opens to the outside and is provided at the end of the branch pipe, and the pressing seat surface portion of the connection head having an outer peripheral surface as a screw surface is brought into contact with and engaged with the main pipe. An externally threaded cylindrical sleeve nipple connected to the rail by welding or brazing, and a connection head having the outer peripheral surface as a screw surface and a cap nut previously incorporated in the branch pipe side, and the above-mentioned screwing is performed. A branch joint structure which is connected by being tightened and connected with the pressing at the connection head, wherein the screw between the sleeve nipple and the cap nut, and the screw between the connection head and the cap nut are reverse screws. A branch joint structure of a common rail characterized by what has been done.

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