Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-12-22
2001-09-18
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S495000, C417S273000
Reexamination Certificate
active
06289875
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority from Japanese patent application Nos. Hei 10-369731, filed Dec. 25, 1998, and Hei 11-315266, filed Nov. 5, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection pump for an internal combustion engine (hereinafter referred to as “the engine”).
2. Description of Related Art
One type of known radial pump has plural plungers radially provided at an outer periphery of a cam, and pressurizes fuel sucked into fuel pressurizing chambers formed on respective plungers. According to the radial pump, in general, pressure feed fuel passages for transferring high pressure fuel pressurized in the fuel pressurizing chambers are united together in a pump housing, and the fuel is supplied to a common-rail from the united pressure feed fuel passage.
However, when the plural pressure feed fuel passages are united in the pump housing to form one pressure feed fuel passage, the pump housing gets a corner portion at the united portion of the pressure feed fuel passage. Since a fuel injection pump for a common-rail-type diesel engine may pressurize fuel up to about 200 MPa, stress caused by fuel pressure concentrates on the corner portion of the pump housing to cause a damage on the corner portion if the corner portion is formed on an inner peripheral wall of the pump housing which forms the pressure feed fuel passage (“the inner peripheral wall of the pump housing which forms the pressure feed fuel passage” is called “passage inner peripheral wall” hereinafter).
Further, when the housing is drilled to form the pressure feed fuel passage, a corner portion is formed on the passage inner peripheral wall after drilling. If the stress caused by the fuel pressure concentrates on the corner portion, the passage inner peripheral wall other than the united portion may be damaged.
In order to prevent the stress concentration on the corner portion of the passage inner peripheral wall caused by the fuel pressure, a thin electrode may be inserted in the pressure feed fuel passage to discharge between the corner portion of the passage inner peripheral wall and the electrode thereby rounding the corner portion, or the corner portion may be polished to remove the corner portion by introducing a fluid including an abrasive material. However, the removal of the corner portion is difficult because the passage length becomes longer when the pressure feed fuel passages are directly united together in the pump housing.
Furthermore, reducing the size of the fuel injection pump has been requested according to the request for reducing engine in size to improve the fuel economy. However, it is difficult to reduce the fuel injection pump in size when the pressure feed fuel passages are united in the pump housing because the pump housing becomes bigger. Further, the weight of the fuel injection pump increases since a hard metal, such as iron, is used for the pressure feed fuel passage. Furthermore, an installation location of a large fuel injection pump is restricted by interference with an engine and engine peripheral components.
SUMMARY OF THE INVENTION
The present invention is made in light of the abovementioned problems, and it is an object of the present invention to provide a fuel injection pump which prevents a damage of a pressure feed fuel passage and which reduces the fuel injection pump in size and weight.
It is another object of the present invention to provide a fuel injection pump which facilitates an assembling operation to a cylinder head and which reduces the number of components and which reduces the manufacturing cost.
According to one aspect of a fuel injection pump of the present invention, the pressure feed fuel passages for feeding fuel from respective pressure chambers are formed in the housing without directly communicating each other in the housing. Accordingly, the length of each of the pressure feed fuel passages is shortened.
Furthermore, since each length of the pressure feed fuel passages is shortened, the fuel injection pump is reduced in size, and the installation degree of freedom for the fuel injection pump is improved.
According to another aspect of the present invention, the pressure feed fuel passage includes a check valve for allowing a fuel flow from a communication port toward a fuel outlet and for inhibiting a reversed fuel flow from the fuel outlet toward the communication port. Further, the cylinder head includes a fuel passage having a fuel opening provided at an outer peripheral wall of the cylinder head at a position different from the fuel outlet. Accordingly, when one of the fuel outlet and the fuel opening of a cylinder head is connected to one of the fuel outlet and the fuel opening of another cylinder head for transmitting fuel from the cylinder head to the other cylinder head and for feeding fuel with pressure unitarily from the other cylinder head, the reversed fuel flow from the pressure feed fuel passage to the fuel pressure chamber is prevented in the other cylinder.
Furthermore, fuel may be individually fed with pressure from respective cylinder heads, or fuel may be unitarily fed with pressure from one cylinder head by connecting each one of the fuel outlet and the fuel opening of a pair of cylinder heads, according to the installation space or installing position of the fuel injection pump. Accordingly, an interference between surrounding components and the fuel line is prevented by changing the combination of the fuel line connections, and the installation degree of freedom for the fuel injection pump is improved.
According to another aspect of the present invention, a pressure limiter is used as a sealing plug for closing the fuel outlet or the fuel opening. Accordingly, the pressure of fuel sent form the fuel injection pump is maintained lower than a predetermined pressure, and the number of components is reduced.
REFERENCES:
patent: 4712528 (1987-12-01), Schaffitz
patent: 5167493 (1992-12-01), Kobari
patent: 5383770 (1995-01-01), Hisahara
patent: 5688110 (1997-11-01), Djordjevic
patent: 5701873 (1997-12-01), Schneider
Furuta Katsunori
Kuroda Akihiro
Nishimura Hiroyuki
Shinohara Yukihiro
Watanabe Toshikazu
Denso Corporation
Gimie Mahmoud
Nixon & Vanderhye PC
Yuen Henry C.
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