JPH10288123A - Common rail - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a maximum stress generated at a main pipe rail opening end part of a branch pipe and enhance internal pressure fatigue strength by forming pressure receiving surfaces which cane into contact with the outer peripheral surface of the main pipe rail symmetrically with a shaft core of a branch hole as a center on the inner peripheral surface on the opposite side to a screw wall part of a ring- shaped coupling hardware which is externally fitted to the main pipe rail. SOLUTION: When a branch pipe 2 is branch-connected with a main pipe rail 1, a nut 4 is screw-fastened to a screw wall 3-1 of a ring-shaped coupling hardware 3 which is externally fitted to the main pipe rail 1 after a pressing bearing surface 2-3 of a connection head part 2-2 on the side of the branch pipe 2 is made to abut on a pressure receiving bearing surface 1-3 opening outward in a branch hole 1-2 part. As a result, the main pipe rail 1 is compressed by the pressure receiving surface 3-2 provided symmetrically on the inner peripheral surface of the ring-shaped coupling hardware 3 because the ring-shaped coupling hardware 3 is attracted to the side of the branch pipe 2 at the same time that the pressing bearing surface 2-3 is made press-contact with the pressure receiving bearing surface 1-3. Thus, high compression pressure is imparted to the branch hole 1-2 of the main pipe rail 1 and internal pressure fatigue strength is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to common rails such as high pressure fuel manifolds or block rails in diesel internal combustion engines.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, for example, a common hole of this type has a branch hole 11- communicating with an internal flow passage 11-1 provided in a peripheral wall portion on a side of a main rail 11 having a circular cross section.
A pressure receiving seat surface 11-3 having two portions opened outwardly, and a ring-shaped joint fitting 13 surrounding the outer peripheral portion of the main rail 11 near the pressure receiving seat surface is used. Connection head 12-
2 is pressed into contact with the pressing seat surface 12-3, and the connection head is screwed together with a screw wall 13-1 protruding from the joint fitting 13 and a nut 14 previously assembled on the branch pipe 12 side. 12-2
There is a type in which a connection is made by tightening in accordance with pressing under the neck. Reference numeral 15 denotes a sleeve washer.

[0003]

However, in the case of the above-mentioned conventional common rail, when the internal pressure acts on the main pipe rail 11, the open end of the main pipe rail flow path 11-1 of the flow path 12-1 of the branch pipe 12 is formed. The largest stress is generated in the portion P, and the opening end portion P serves as a starting point to easily cause a crack, which may lead to fuel leakage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional common rail. The present invention has been made to reduce the maximum stress value generated at the end of the main pipe rail opening of the branch pipe flow path to improve the internal pressure fatigue strength. It is intended to provide a common rail that can be improved.

[0005]

In a common rail according to the present invention, a plurality of branch holes are provided at intervals in an axial peripheral wall portion of a main rail having a flow passage inside a shaft core. A pressure seating surface is formed at the end of the branch pipe, and a pressure seating surface is formed at an end of the branch pipe. And a threaded wall of the ring-shaped joint fitting externally fitted to the main pipe rail and a nut assembled in advance on the branch pipe side are screwed together with the pressing at the connection head to tighten. In the connected common rail, on the inner peripheral surface opposite to the screw wall portion of the ring-shaped joint fitting, the pressure receiving surface in contact with the outer peripheral surface of the main pipe rail is centered on the axis of the branch hole of the main pipe rail. The ring is formed symmetrically and the ring is tightened with the nut incorporated into the branch pipe. Main rail at the pressure receiving surface provided on the inner peripheral surface of the joint fitting is characterized in that no structured to be pressed.

In the present invention, the ring-shaped joint fitting is pulled toward the branch pipe side as the nut assembled on the branch pipe side is tightened, so that the inner peripheral surface of the ring-shaped joint fitting opposite to the screw wall portion. The pressure receiving surface provided symmetrically to the left and right and the outer peripheral surface of the main pipe rail are pressed against each other, so that the compressive stress on the main pipe rail can be further increased. As a result, it is possible to effectively suppress the generation of stress due to the internal pressure in the branch hole of the main pipe rail, and it is possible to significantly improve the internal pressure fatigue strength at each branch pipe mounting portion.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial longitudinal sectional view showing an example of a connection structure of a branch pipe in a common rail according to the present invention, wherein 1 is a main pipe rail as a common rail, 2 is a branch pipe, and 3 is a ring-shaped. The fittings 4, 4 are nuts, and 5 is a sleeve washer.

The main pipe rail 1 as a common rail is made of a thick steel pipe material such as a carbon steel pipe or a stainless steel pipe for a pressure pipe having a pipe diameter of about 30 m / m or less, as in the prior art. m, thickness 6m / m,
A relatively thick metal tube made of material STS480, and the inside of its axis is formed as a flow passage 1-1, and a space is maintained in the peripheral wall portion in the axial direction, and the metal tube is positioned on the center line of the flow passage 1-1. Flow passage 1
There is provided a branch hole 1-2 having an outer peripheral surface that opens to the outside and communicates with the pressure-receiving surface 1 as a pressure receiving seat surface 1-3.

The branch pipe 2 is composed of a branch pipe or a branch fitting, has a flow path 2-1 communicating with the flow passage 1-1 therein, and has a tapered conical crush at its end. A press seat surface 2-3 formed by a connection head 2-2 whose diameter has been expanded by bending is formed. The connection structure surrounds the outer peripheral portion of the main rail 1 like the common rail shown in FIG. The connection head 2 is formed by screwing a screw wall 3-1 protruding from a ring-shaped joint fitting 3 and a nut 4 previously assembled on the branch pipe 2 side.
-2 This is a method of fastening and connecting with the pressing under the neck.

A ring-shaped joint fitting 3 surrounding the outer periphery of the main rail 1 has an inner peripheral surface opposite to the screw wall 3-1 of the ring-shaped fitting, and an outer peripheral surface of the main rail 1. The contacting pressure receiving surface 3-2 is formed symmetrically about the axis of the branch hole 1-2 of the main pipe rail. This pressure receiving surface 3-2
Is formed so that a compressive force acts on the main rail 1 when the nut 4 is tightened, and a part of the inner peripheral surface of the lower half of the ring-shaped joint fitting 3 has a flat surface. -2 is formed. The angle θ of the pressure receiving surface 3-2, that is, the angle formed by the horizontal center line orthogonal to the axis of the branch hole 1-2 of the main pipe rail is not particularly limited, but is 3 °.
It is 0 to 70 degrees, preferably about 45 to 60 degrees.

In the common rail having the above-mentioned structure, the connection head 2 on the side of the branch pipe 2 whose diameter is expanded by buckling forming in the shape of a tapered cone.
2 is brought into contact with a pressure receiving seat surface 1-3 which is open to the outside of the branch hole 1-2, and protrudes from a ring-shaped joint fitting 3 which is externally fitted to the main pipe rail 1. When the nut 4 is screwed together with the screw wall 3-1 provided and the nut 4 previously assembled on the branch pipe 2 side, and the nut 4 is tightened, the lower part of the connection head 2-2 is necked through the sleeve washer 5. The pressing seat surface 2-3 formed by the connection head 2-2 is pressed against the pressure receiving seat surface 1-3 of the branch hole 1-2 portion of the main pipe rail 1 and connected to the main pipe rail 1 with the pressing of the main rail 1. At the same time, the main joint rail 1 is compressed by the pressure-receiving surface 3-2 provided symmetrically on the inner peripheral surface of the ring-shaped joint fitting 3 by the ring-shaped joint fitting 3 being attracted to the branch pipe 2 side. . That is, the main pipe rail 1 has a pressure receiving seat surface 1-3.
The compressive force is received at three places, that is, two pressure receiving surfaces 3-2 symmetrically provided on the inner peripheral surface of the ring-shaped joint fitting 3 and the inner peripheral surface of the ring-shaped joint fitting 3. This 3
Branching hole 1- of main pipe rail 1
Higher compressive stress is generated in the two parts, and the stress generated in the open end P of the main pipe rail flow path 1-1 due to the internal pressure of the flow path 1-1 is suppressed.

[0012]

As described above, the common rail of the present invention reduces the compressive stress on the main pipe rail by the press-contact action between the pressure receiving surface provided symmetrically on the inner peripheral surface of the ring-shaped joint fitting and the outer peripheral surface of the main pipe rail. As a result, it is possible to effectively suppress the generation of stress due to internal pressure in the branch hole of the main pipe rail, and the internal pressure fatigue strength in each branch hole is high, the durability is excellent, and the fuel due to cracking is generated. A stable function can be surely exhibited without any leakage, and it is extremely useful as a common rail.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing an example of a connection structure of a branch pipe in a common rail according to the present invention.

FIGS. 2A and 2B illustrate a conventional common rail using a symmetrical ring-shaped joint fitting of the present invention, wherein FIG. 2A is a front view showing a branch pipe connection part partially cut away, and FIG. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main rail 1-1 Flow passage 1-2 Branch hole 1-3 Pressure receiving seat surface 2 Branch pipe 2-1 Flow passage 2-2 Connection head 2-3 Pressing seat surface 3 Ring joint fitting 3-1 Screw wall 3-2 Pressure receiving surface 4 Nut 5 Sleeve / Washer

Claims (1)

[Claims] 1. A plurality of branch holes are provided in an axial peripheral wall portion of a main pipe rail having a flow passage inside a shaft core while maintaining a space therebetween.
And a connecting head provided at an end of the branch pipe by forming a pressure-receiving seat surface that opens outward to connect a branch pipe having a flow path communicating with the flow passage to a peripheral surface of the branch hole. With the pressing seat surface portion being made to abut and engage, with the pressing at the connection head by the screwing of the screw wall portion of the ring-shaped joint fitting externally fitted to the main pipe rail and the nut previously assembled on the branch pipe side. In a common rail which is fastened and connected, a pressure receiving surface which is in contact with an outer peripheral surface of the main pipe rail is provided on an inner peripheral surface of the ring-shaped joint fitting opposite to the screw wall portion, and an axial center of the branch hole of the main pipe rail. The main pipe rail is pressed by the pressure receiving surface provided on the inner peripheral surface of the ring-shaped joint fitting by tightening the nut incorporated on the branch pipe side symmetrically with respect to the center. Common rail characterized by doing.