Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1998-07-13
2001-07-24
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S468000
Reexamination Certificate
active
06263862
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a common rail comprising a block rail in an accumulator fuel injecting system of a diesel internal combustion engine.
2. Description of the Prior Arts
Conventionally, as a common rail of this kind, for example, as shown in
FIG. 12
, there has been known a common rail of the type which is structured such that a branch hole
11
-
2
communicating with an communication passage
11
-
1
of a block rail
11
and having a pressure receiving seat surface
11
-
3
open to an outer portion is punched in a bottom portion
12
-
2
of a plurality of connecting hole portions
11
-
4
provided in a peripheral wall portion of the block rail
11
having a rectangular cross section in an axial direction at an interval, a pressing seat surface
12
-
3
constituted by a connecting head portion
12
-
2
of a branch pipe
12
end is brought into contact with and engaged with the pressure receiving seat surface
11
-
3
of the block rail
11
end, and a fastening external screw nut
13
previously assembled in the branch pipe end is meshed with the connecting hole portion
11
-
4
, thereby fastening and connecting together with pressing under a neck of the connecting head portion
12
-
2
. In the drawing, reference numeral
12
-
1
denotes a flow passage of the branch pipe
12
. In this case, the cross sectional shape of the block rail is not limited to a rectangular shape, and various kinds of shapes such as a triangular shape and a trapezoidal shape can be employed.
However, in the case of the conventional common rail structured such that the branch hole
11
-
2
is provided in the connecting hole portion
11
-
4
disposed in the block rail
11
, a great tensional force is generated in an inner peripheral edge portion P of a lower end of the branch hole
11
-
2
due to a repeating high internal pressure within the block rail
11
and an axial force applied to the pressure receiving seat surface
11
-
3
together with a pressing of the connecting head portion
12
-
2
in the branch pipe
12
, so that a crack is easily generated from the inner peripheral edge portion P of the lower end and there is a possibility of causing a leak.
SUMMARY OF THE INVENTION
The present invention is made so as to solve the conventional problems mentioned above, and an object of the invention is to provide a common rail which can reduce a maximum tensile stress value generated in an inner peripheral edge portion of a lower end of a branch hole and can improve an internal pressure fatigue strength.
In order to achieve the object mentioned above, in accordance with the invention, there is provided a common rail structured such that a branch hole communicating with an communication passage of a block rail and having a pressure receiving seat surface open to an outer portion is provided in at least one connecting hole portion provided in a peripheral wall portion in an axial direction of the block rail having the communication passage in a longitudinal inner portion, a pressing seat surface constituted by a connecting head portion provided in an end portion of a branch having a flow passage communicating with the communication passage is brought into contact with and engaged with the pressure receiving seat surface, and the connecting hole portion and a fastening nut previously assembled in the branch pipe are meshed with each other so as to fasten and connect together with pressing under a neck of the connecting head portion, wherein a compression residual stress exists in a periphery of an end portion of the communication passage of the block rail of the branch hole.
Further, in a method of manufacturing a common rail in accordance with the invention which is structured such that a branch hole communicating with an communication passage of a block rail and having a pressure receiving seat surface open to an outer portion is provided in at least one connecting hole portion provided in a peripheral wall portion in an axial direction of the block rail having the communication passage in a longitudinal inner portion, a pressing seat surface constituted by a connecting head portion provided in an end portion of a branch having a flow passage communicating with the communication passage is brought into contact with and engaged with the pressure receiving seat surface, and the connecting hole portion and a fastening nut previously assembled in the branch pipe are meshed with each other so as to fasten and connect together with pressing under a neck of the connecting head portion, a first aspect of the invention is characterized in that a pressing force is applied to an axial direction of the connecting hole portion from an outer portion preferably by a press method so as to generate a compression residual stress in the periphery of an open end portion of the communication passage of the block rail of the branch hole, and a second aspect of the invention is characterized in that the branch hole is punched at the same time of applying the pressing force to the axial direction of the connecting hole portion from the outer portion by an external pressing method. Next, a third aspect of the invention is characterized in that the pressing force is applied to an inner peripheral surface of the block rail at a portion near the branch hole by an internal pressure method so as to generate a compression residual stress at a portion near the open end portion of the communication passage of the block rail of the branch hole, a fourth aspect of the invention is characterized in that the pressing force is applied to the inner peripheral surface of the block rail at a portion near the branch hole by a pipe expansion method structured such as to apply a pressure to an diametrical direction from the inner portion of the block rail so as to generate a compression residual stress at a portion near the open end portion of the communication passage of the block rail of the branch hole, and a fifth aspect of the invention is characterized in that the pressing force is applied to the inner peripheral surface of the branch hole by a pipe expansion method structured such as to apply a pressure to an diametrical direction from the inner portion of the branch hole so as to generate a compression residual stress at a portion near the open end portion of the communication passage of the block rail of the branch hole.
Further, in accordance with a sixth aspect of the invention, there is provided a method of manufacturing a common rail structured such that a branch hole communicating with an communication passage of a block rail and having a pressure receiving seat surface open to an outer portion is provided in at least one connecting hole portion provided in a peripheral wall portion in an axial direction of the block rail having the communication passage in a longitudinal inner portion, a pressing seat surface constituted by a connecting head portion provided in an end portion of a branch having a flow passage communicating with the communication passage is brought into contact with and engaged, and a nut previously assembled in the branch pipe is meshed so as to fasten and connect together with pressing under a neck of the connecting head portion, wherein a piece-like body formed in a spherical body or having a narrowed tip end is pressed to the open end portion of the communication passage of the block rail at a portion near the branch hole so as to generate a compression residual stress in a periphery of the open end portion of the communication passage of the block rail of the branch hole.
Accordingly, in accordance with the invention, by remaining a compression residual stress at a portion near the open end portion of the communication passage of the block rail in the branch hole, a tensile stress generated in an inner peripheral edge portion P of the lower end of the branch hole by a repeated high internal pressure within the block rail and an axial force applied to the pressure receiving seat surface together with a pressing by the connection head port
Asada Kikuo
Kusanagi Ryuichi
Takikawa Kazunori
Usui Masayoshi
Watanabe Eiji
Casella Anthony J.
Hespos Gerald E.
Miller Carl S.
Porco Michael J.
Usui Kokusai Sangyo Kaisha Limited
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