JPH10213045A - Connecting structure for branch connecting body in common rail - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a maximum stress value generated on an opening end part so as to improve inner pressure fatigue strength by chamfering a common rail side opening end part of a branch hole in a circular arc shape so as to form a round chamfering part not having an edge part. SOLUTION: A main pipe rail 1 consists of a narrow diameter metal pipe, and its axial core inner part is formed as a circular section flow passage 1-1. A plurality of branch holes 1-2 whose circumferential surface opened outward holding a clearance on an axial direction circumferential wall part is formed as a pressure receiving seat surface 1-3, are arranged by communicating with the circulating passage 1-1. An opening end part of the circulating passage 1-1 of the branch hole 1-2 is chamfered in a circular arc shape so as to form an R-shaped chamfering part 1-2a not having an edge part. It is thus possible to sharply reduce a maximum stress generated on the opening end part of a common rail 1 of a flow passage of a joint part. Inner pressure fatigue strength is improved in each branch hole 1-2, durability is improved, and leakage of fuel caused by generation of cracking is eliminated so as to exhibit a stable function surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch connection such as a branch pipe or a branch fitting on a common rail such as a main rail or block rail generally comprising a manifold for high pressure fuel in a diesel internal combustion engine. Related to the connection structure.

[0002]

2. Description of the Related Art Conventionally, as a connection structure of this kind of branch connection body, for example, as shown in FIG. 6, a circular cross section provided inside a main rail 1 made of a manifold as a common rail. A ring-shaped joint fitting 3 surrounding the outer periphery of the main pipe rail 1 near the pressure-receiving seat surface is formed with a pressure-receiving seat surface 1-3 that opens outwardly at a branch hole 1-2 that communicates with the flow passage 1-1.
And a connection head 2- on the side of the branch pipe 2 as an enlarged branch connection body formed by, for example, tapering conical buckling molding at the end.
2, a screw wall 3-1 part which protrudes outward from the main rail 1 provided on the joint fitting so as to protrude in the radial direction of the main rail 1 by making the pressing seat surface 2-3 formed by abutment engagement. A method in which a nut 4 previously assembled to the branch pipe 2 side via a sleeve washer 5 is screwed together with the connection head 2-2 by being screwed together with a press under the neck, 7, instead of the ring-shaped joint fitting 3 as shown in FIG. 8, the cylindrical sleeve nipples 3a, 3b are respectively protruded outwardly in the radial direction of the main pipe rail 1, and are threaded by uneven fitting, welding, etc. To the outer peripheral wall of the main pipe rail 1 so that the pressing seat surface 2-3 formed by the connecting head 2-2 on the branch branch pipe 2 abuts on the pressure receiving seat face 1-3 on the main rail 1 side. There is also known a method in which a nut 4 screwed to the sleeve nipples 3a and 3b is tightened and connected to the sleeve nipples 3a and 3b. There.

Further, as shown in FIG. 9, a boss 3c integral with the main pipe rail 1 is formed on the main pipe rail 1 as a common rail, and a pressing seat surface 2 formed by a connection head 2-2 of the branch pipe 2 is formed.
-3 is brought into contact with a pressure receiving seat surface 1-3 on the main pipe rail 1 side, and a cap nut 6 screwed into a screw portion 3-2 provided on the outer peripheral surface of the boss 3c is tightened and connected. There are also known types.

[0004]

In each of the above-described conventional connection structures of a branch connection body, the center of a circular passage section 1-1 of a common rail such as the main pipe rail 1 and the branch branch pipe 2 are connected.
Has a structure in which the center of the flow path 2-1 of the branch connecting body coincides with the center of the flow path 2-1.
2 is a flow path 1-1 of the main rail 1 as a common rail.
And the opening end has an edge. When an internal pressure acts on the inside of the common rail, the largest stress is generated at the opening end P of the flow passage 1-1 having a circular cross section of the common rail. The opening end P serves as a starting point to easily cause cracks, which may lead to fuel leakage.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to reduce the maximum stress value generated at the end of the common rail opening of the flow path of the branch connector to further improve the internal pressure fatigue strength. It is an object of the present invention to provide a connection structure of a branch connector in a possible common rail for high-pressure fuel.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a common rail having a flow passage having a substantially circular cross section in the longitudinal direction. At the end of the branch connector, a hole is formed, and a pressure receiving seat surface that opens outward is formed by connecting a branch connector having a flow path that communicates with the flow passage on the peripheral surface of the branch hole. With the pressing seat surface portion formed by the provided connection head is brought into abutting engagement with the joint rail, which is integral with or separate from the common rail, and is pressed by the connection head by screwing of a nut previously incorporated into the branch connection body side. In the connection structure of the branch connection body which is fastened and connected, the common rail side opening end of the branch hole is chamfered in an arc shape to form an R-chamfered portion having a curved surface having no edge portion. Features connection structure of connection body Is shall.

[0007] In the present invention, the open end of the common rail formed on the curved surface having no edge portion may be such that the contour of the inner peripheral surface of the R chamfered portion is an elliptical shape having a longer diameter in the diameter direction of the flow passage. A cross-sectional shape of the R chamfered portion has a tapered surface continuous with the inner peripheral surface of the branch hole in a smooth curved surface, and a shape in which the tapered surface and the inner peripheral surface of the common rail flow passage are connected in a smooth curved surface. The cross-sectional shape may be a rotating arc surface, a spheroidal surface, a paraboloid of revolution, or a hyperboloid of revolution.

Further, in the present invention, the joint part separate from the common rail comprises a joint fitting or a cylindrical sleeve nipple attached to the common rail, or the joint part integral with the common rail comprises a boss or a circular groove. Wherein the common rail is
There is a main rail or a block rail, and the branch connection body is a branch branch pipe or a branch fitting.

Here, the radius R of the R chamfer at the opening end of the branch hole on the common rail side is not particularly limited, and is appropriately set according to the thickness of the common rail.

According to the present invention, as described above, in the common rail of the connection structure in which the center of the flow passage having a substantially circular cross section of the common rail coincides with the center of the flow passage of the joint part integral with or separate from the common rail, Since the common rail side opening end is an R-chamfer without an edge, the maximum stress generated at the common rail flow passage opening end of the flow path at the joint portion can be reduced.

[0011]

FIG. 1 is an enlarged cross-sectional view of a common rail according to the present invention, in which a main rail as a common rail is partially cut away, and FIG. 2 is a connection structure shown in FIG. FIG. 1 is a view showing an example of the contour of the inner peripheral surface of the R chamfered portion of the common rail side opening end of the branch hole in the example, and FIG. 3 is a view of the R chamfered portion of the branch hole in the connection structure example shown in FIG. The cross-sectional shape is exemplified, and (A) shows an R formed by a tapered surface connected to the inner peripheral surface of the branch hole by a smooth curved surface, and a shape formed by connecting the tapered surface and the inner peripheral surface of the common rail flow path by a smooth curved surface. FIG. 4B is a cross-sectional view of a common rail side opening end showing a cross-sectional shape of a chamfered portion, FIG. 4B is a cross-sectional view of a common rail side opening end showing a cross-sectional shape of an R-chamfered portion formed of a paraboloid of revolution, and FIG. The cross-sectional shape of the R chamfered section composed of hyperbolic surfaces Sectional view of the to the common rail side opening end portion, FIG. 4 is a perspective view showing a block rail as the common rail, Figure 5 is a cross-sectional view of FIG. 4, (A) is in Fig 4 A-
FIG. 5B is a cross-sectional view taken along line A ′, and FIG. 5B is a cross-sectional view taken along line BB ′ in FIG. Here, a tubular sleeve nipple is used as a joint part formed separately from a main pipe rail composed of a manifold as a common rail, and this sleeve nipple is directly welded to the main rail to form a branch shown in FIG. An example in which the invention is applied to a connection structure of a connection body will be described.

The connection structure of the branch connector shown in FIG. 1 is shown in FIG.
In the same manner as shown in FIG.
A cylindrical sleeve nipple 3b provided on the inner peripheral surface with a screw surface 3-1b for screwing with the nut 4 incorporated on the side is formed as a joint portion, and its base end is connected to a book near the pressure receiving seat surface 1-3. The pressure seat surface 2-3 formed by the connection head 2-2 on the branch branch pipe 2 side is welded to the outer peripheral wall of the pipe rail 1 so as to surround the pressure receiving seat surface part and concentrically with the branch hole 1-2. The pressure receiving seat surface 1-3 of the rail 1 is brought into contact with and engaged with the pressure receiving seat surface 1-3, and a nut 4 screwed to the sleeve nipple 3b is tightened to form a connection. here,
The main rail 1 as a common rail has a pipe diameter of, for example, 20 mm.
A relatively thick and small-diameter metal tube having a thickness of about 8 m / m and a wall thickness of about 8 m / m. A branch hole 1-2 having a plurality of outwardly open peripheral surfaces as pressure receiving seat surfaces 1-3 is provided so as to communicate with the flow passage 1-1. on the other hand,
The branch connection body is formed of the branch branch pipe 2 or the branch fitting as described above, and has therein the flow passage 1-1.
Bearing surface 2 formed by a connection head 2-2 having a diameter enlarged by tapering conical buckling molding at an end thereof, having a flow path 2-1 communicating with the flow path 2-1.
-3.

In the present invention, the outer peripheral surface of the peripheral wall of the main rail 1 is formed as a pressure receiving seat surface 1-3, and the branch hole communicates with the circular passageway 1-1 of the main rail 1. An R-chamfered portion 1-2a is formed by chamfering an open end of the flow passage 1-1 of the 1-2 in an arc shape and forming a curved surface having no edge portion. The contour of the inner peripheral surface of the R chamfered portion 1-2a is not limited to a perfect circle, but may be an elliptical shape having a longer diameter in the diameter direction of the flow passage 1-1 having a substantially circular cross section as shown in FIG.
As the cross-sectional shape of the R chamfered portion, Fig. 3 as (A), the tapered surface 1 continuous with the inner peripheral surface 1-2b and smooth curved surface 1-2c of the radius r ₁ of the vertical portion of the branch hole -2d
When, as shown in the shape the tapered surface and the main rail flow passage peripheral surface 1-1a is continuous smooth curved surface 1-2e radius r _2, or the, (B), the inner periphery of the vertical portion of the branch hole Surface 1
Rotation parabolic surface smooth curved 1-2f and the main rail flow passage peripheral surface 1-1a is continuous smooth curved surface 1-2 of the radius _{R 1} of the radius _{r 3} in which continuous and 2b, shown in (C) As shown, the radius R connected to the inner peripheral surface 1-2b of the vertical portion of the branch hole
₂ smooth curved surface 1-2h and main pipe rail flow path inner peripheral surface 1
-1a can be a rotating hyperbolic surface continuous with a smooth curved surface 1-2i radius _{r 4.} The radius R, R ₁ , R ₂ , r ₁ , r ₂ , r ₃ , r ₄ of each of the R chamfers is not particularly limited, and the thickness of the main rail or block rail as a common rail is not limited. Set appropriately according to the thickness.

As described above, when the opening end of the flow passage 1-1 of the branch hole 1-2 communicating with the flow passage 1-1 having a substantially circular cross section of the main pipe rail 1 is an R-chamfer without an edge. When the internal pressure acts on the main pipe rail 1, the flow path 1 of the branch hole 1-2 is formed.
-1 The maximum stress generated at the open end is greatly reduced.
Therefore, the problem that a crack starts from the opening end P is almost eliminated.

Although FIGS. 1 to 3 show an example in which the main rail is used as the common rail, a block rail 1 'can be used as the common rail as shown in FIGS. The block rails 1 'are formed with flow passages 1-1 and 1-1' having a circular cross section which communicate with each other (not shown).
The opening end on the -1 'side is an R-chamfered portion 1-2a having no edge, and a branch hole 1-2 is provided, the outer peripheral surface of which is open to serve as a pressure receiving seat surface 1-3. A circular groove 7 having a threaded surface on the inner peripheral surface is formed by drilling outward from the pressure receiving seat surface 1-3 to form a joint portion. The nut 4 previously assembled on the branch connecting body 2 side is provided with a circular groove. 7 is screwed into a screw surface provided on the inner peripheral surface of the block 7 so that the pressing seat surface 2-3 formed by the connection head 2-2 of the branch connection body 2 contacts the pressure receiving seat surface 1-3 of the block rail 1 '. The nuts 4 are brought into contact and fastened to form a connection.
Reference numeral 8 denotes a washer incorporated behind the connection head 2-2 of the branch connection body 2.

[0016]

As described above, the connection structure of the branch connector in the common rail according to the present invention is such that the flow passage opening end of the branch hole communicating with the flow passage having a substantially circular cross section of the common rail is chamfered in an arc shape. Due to the curved surface having no edge portion, the maximum generated at the common rail opening end of the flow path of a separate joint portion such as a branch fitting or a sleeve nipple, or an integral joint portion such as a boss or a circular groove is formed. Since the stress can be greatly reduced, the internal pressure fatigue strength in each branch hole is high, the durability is excellent, and fuel leakage due to the generation of cracks can be eliminated to ensure a stable function. The connection structure of a branch connector according to the present invention is also applicable to branch pipe joints other than common rails, hydraulic manifolds, and hydraulic manifolds.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing a main rail side as a common rail in a common rail connection structure example of the present invention, partially cut away.

2 is a view taken along the arrow in FIG. 1 showing an example of a contour of an inner peripheral surface of an R chamfered portion of a common rail side opening end of a branch hole in the connection structure example shown in FIG. 1;

3A and 3B illustrate a cross-sectional shape of an R-chamfered portion of a branch hole in the connection structure example shown in FIG. 1; FIG. 3A illustrates a tapered surface connected to an inner peripheral surface of the branch hole by a smooth curved surface; The cross-sectional view of the common rail side opening end showing the cross-sectional shape of the R-chamfered portion formed by connecting the surface and the inner peripheral surface of the common rail flow path with a smooth curved surface, and (B) is the R-chamfer formed by a paraboloid of revolution. FIG. 7C is a cross-sectional view of a common rail-side opening end showing a cross-sectional shape of a portion, and FIG. 7C is a cross-sectional view of a common rail-side opening end showing a cross-sectional shape of an R chamfer formed of a hyperboloid of revolution.

FIG. 4 is a perspective view showing a block rail as a common rail.

5A is a cross-sectional view taken along line AA ′ of FIG. 4; FIG. 5B is a cross-sectional view taken along line BB ′ of FIG. 4;

FIG. 6 is a cross-sectional view showing a connection structure example of a branch connection body in a conventional common rail using a ring-shaped joint fitting, partially cut away.

FIG. 7 is a cross-sectional view partially cut away showing an example of a connection structure of a branch connection body in a conventional common rail having a configuration in which a cylindrical sleeve nipple is attached to a main rail as a common rail by an uneven fitting screwing method. is there.

FIG. 8 is a cross-sectional view, partially cut away, showing an example of a connection structure of a branch connection body in a conventional common rail having a configuration in which a tubular sleeve nipple is attached to a main pipe rail as a common rail by welding.

FIG. 9 is a cross-sectional view showing an example of a connection structure of a branch connection body in a conventional common rail having an integral boss protruding therefrom.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Main rail 1 'Block rail 1-1, 1-1' Flow passage 1-1a Inner peripheral surface of flow passage 1-2 Branch hole 1-2a R chamfered portion 1-2b Inner peripheral surface of vertical portion of branch hole 1-2c radius _{r 1} of the smoothly curved surface 1-2d tapered surface smooth curved surface of 1-2e radius _{r 2} of a smooth curved surface 1-2f radius _{r 3} 1-2 g radii smoothly curved 1-2h radius _{R 1} R ₂ Smooth curved surface 1-2i Smooth curved surface with radius r ₄ 1-3 Pressure receiving seat surface 2 Branch branch pipe 2-1 Flow path 2-2 Connection head 2-3 Press seat surface 3 Joint fitting 3-1 Screw wall 3-2 Screw part 3a, 3b Tubular sleeve nipple 3c Boss 4 Nut 5 Sleeve washer 6 Cap nut 7 Circular groove 8 Washer P Open end R Radius of chamfer

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI F16L 41/08 F16L 41/02 Z

Claims (5)

[Claims] 1. A common rail having a flow passage having a substantially circular cross section in a longitudinal direction, a plurality of branch holes are provided in a circumferential wall portion of the flow passage in an axial direction of the flow passage, and a plurality of branch holes are provided in a peripheral surface portion of the branch hole. A pressure receiving seat surface that opens to the outside is formed by connecting a branch connecting body having a flow path communicating with the flow passage, and a pressing seat surface portion formed by a connection head provided at an end of the branch connecting body is abutted. A connection structure of a branch connection body which is joined together and tightened and connected together with the joint head, which is integral with or separate from the common rail, and pressed by the connection head by screwing a nut previously incorporated into the branch connection body side. 3. The connection structure for a branch connector in a common rail according to claim 1, wherein the common rail side opening end of the branch hole is chamfered in an arc shape to form a curved surface having no edge. 2. A common rail-side opening end formed on a curved surface having no edge portion, wherein a contour of an inner peripheral surface of an R-chamfered portion has an elliptical shape having a longer diameter in a diameter direction of the flow passage. The connection structure of a branch connection body in the common rail according to claim 1. 3. The cross-sectional shape of the R-chamfered portion is a tapered surface that is continuous with the inner peripheral surface of the branch hole in a smooth curved surface, and the tapered surface is a continuous curved inner surface of the common rail flow passage. The connection structure of a branch connection body in a common rail according to claim 1 or 2, wherein: 4. A cross-sectional shape of the R chamfered portion is a rotating arc surface,
The connection structure of a branch connection body in a common rail according to any one of claims 1 to 3, wherein the connection structure has a shape of a spheroid, a paraboloid of revolution, and a hyperboloid of revolution. 5. A joint part separate from the common rail,
The common rail according to any one of claims 1 to 4, wherein the common rail is formed of a joint fitting or a tubular sleeve nipple attached to the common rail, or a joint part integral with the common rail is formed of a boss or a circular groove. Connection structure of the branch connection body in FIG.