Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1998-03-03
2001-04-10
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S468000
Reexamination Certificate
active
06213095
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common rail such as a high pressure fuel manifold in an accumulator fuel injection system of a diesel internal combustion engine, a block rail or the like.
2. Description of the Prior Arts
Conventionally, there have been known common rails of this kind, for example, as illustrated by
FIGS. 21 and 22
. The common rail shown by
FIG. 21
is of a system constituted by perforating branch holes
21
-
2
each having a pressure receiving seat face
21
-
4
communicating with a flow path
21
-
1
of a main pipe rail
21
and opened outwardly at a plurality of boss portions
21
-
3
provided at intervals at a peripheral wall portion in the axial direction on the side of the main pipe rail
21
comprising a circular pipe, engageably bring pressing seat faces
22
-
3
constituted by connection head portions
22
-
2
on the side of branch pipes
22
into contact with the pressure receiving seat faces
21
-
4
on the side of the main pipe rail
21
and screwing fastening box nuts
23
previously integrated to the side of the branch pipes via washers
24
to male screws (outside screws)
21
-
5
provided on outer peripheral faces of the boss portions
21
-
3
to thereby fixedly fastening the branch pipes to the main pipe rail by pressing action at the connection head portions
22
-
2
. In
FIG. 21
, notation
22
-
1
designates a flow path of the branch pipe
22
.
Further, a common rail shown by
FIG. 22
is of a system constituted by machining bottomed holes to a plurality of boss portions
21
-
3
provided at intervals at a peripheral wall portion in the axial direction on the side of a main pipe rail
21
similar to
FIG. 21
, providing female screws (inside screws)
21
-
6
on inner peripheral faces of the bottomed holes and screwing fastening male nuts
25
to the female crews (inside screws)
21
-
6
to thereby fastening branch pipes to the main pipe rail
21
by pressing action at the connection head portions
22
-
2
. Incidentally, in
FIG. 22
, numeral
26
designates a sleeve washer.
However, in the case of a common rail having a structure where the branch hole
21
-
2
is installed to the boss portion
21
-
3
provided to the main pipe rail
21
comprising a circular pipe, large tensile stress is caused at an opening end portion P at the flow path of the main pipe rail in the branch hole
21
-
2
by high inner pressure of the main pipe rail
21
and cracks are liable to cause with the opening end portion P as onset which may give rise to leakage.
SUMMARY OF THE INVENTION
The present invention has been carried out in order to resolve the above-described conventional problem and it is an object of the present invention to provide a common rail and its fabrication method capable of promoting the inner pressure fatigue strength by decreasing a value of a maximum tensile stress generated at an inner peripheral edge portion of a lower end of a branch hole.
In order to achieve the above-described object, according to a first aspect of the present invention, there is provided a common rail comprising a main pipe rail comprising a flow path at inside of the main pipe rail in a direction of an axis center, and at least one boss portion provided to a peripheral wall portion in an axial direction of the main pipe rail, said boss portion including a branch hole communicated with the flow path and having a pressure receiving seat face opened outwardly, a branch pipe having a flow path communicating with the flow path, said branch pipe including a pressing seat face portion constituted by a connection head portion installed at an end portion of the branch pipe, wherein the pressing seat face portion of the branch pipe is engageably brought into contact with the pressure receiving seat face of the main pipe rail and the branch pipe is connected to the main pipe rail by fastening to screw a fastening nut previously integrated to a side of the branch pipe to the boss portion to thereby press the main pipe rail right under the connection head portion, and wherein a compressive residual stress is made to exist at a periphery of an opening end portion of the flow path of the main pipe rail at the branch hole.
According to a second aspect of the present invention, there is provided a method of fabricating a common rail, the common rail comprising a main pipe rail comprising a flow path at inside of the main pipe rail in a direction of an axis center, and at least one boss portion provided to a peripheral wall portion in an axial direction of the main pipe rail, said boss portion including a branch hole communicated with the flow path and having a pressure receiving seat face opened outwardly, a branch pipe having a flow path communicating with the flow path, said branch pipe including a pressing seat face portion constituted by a connection head portion installed at an end portion of the branch pipe, wherein the pressing seat face portion of the branch pipe is engageably brought into contact with the pressure receiving seat face of the main pipe rail and the branch pipe is connected to the main pipe rail by fastening to screw a fastening nut previously integrated to a side of the branch pipe to the boss portion to thereby press the main pipe rail right under the connection head portion, and wherein a compressive residual stress is generated at a periphery of an opening end portion of the flow path of the main pipe rail at the branch hole by applying a pressing force in a direction of an axis of the boss portion from outside preferably by a press system. It is preferable to apply the pressing force in the axial direction of the boss portion from outside by an outside pressing system and at the same time the branch hole is punched through.
Further, according to a third aspect of the present invention, there is provided a method of fabricating a common rail, the common rail comprising a main pipe rail comprising a flow path at inside of the main pipe rail in a direction of an axis center, and at least one boss portion provided to a peripheral wall portion in an axial direction of the main pipe rail, the boss portion including a branch hole communicated with the flow path and having a pressure receiving seat face opened outwardly, a branch pipe having a flow path communicating with the flow path, said branch pipe including a pressing seat face portion constituted by a connection head portion installed at an end portion of the branch pipe, wherein the pressing seat face portion of the branch pipe is engageably brought into contact with the pressure receiving seat face of the main pipe rail and the branch pipe is connected to the main pipe rail by fastening to screw a fastening nut previously integrated to a side of the branch pipe to the boss portion to thereby press the main pipe rail right under the connection head portion, and wherein a compressive residual stress is generated at a periphery of an opening end portion of the flow path of the main pipe rail at the branch hole by applying a pressing force on an inner peripheral face of the main pipe rail at a vicinity of the branch hole by an inside pressing system.
Further, according to a fourth aspect of the present invention, there is provided a method of fabricating a common rail, the common rail comprising a main pipe rail comprising a flow path at inside of the main pipe rail in a direction of an axis center, and at least one boss portion provided to a peripheral wall portion in an axial direction of the main pipe rail, said boss portion including a branch hole communicated with the flow path and having a pressure receiving seat face opened outwardly, a branch pipe having a flow path communicating with the flow path, said branch pipe including a pressing seat face portion constituted by a connection head portion installed at an end portion of the branch pipe, wherein the pressing seat face portion of the branch pipe is engageably brought into contact with the pressure receiving seat face of the main pipe rail and the branch pipe is connected to the main pipe ra
Asada Kikuo
Takikawa Kazunori
Usui Masayoshi
Watanabe Eiji
Casella Anthony J.
Gimie Mahmoud
Hespos Gerald E.
Kamen Noah P.
Porco Michael J.
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