Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-06-01
2001-04-03
Arganbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S447000, C123S1980DA
Reexamination Certificate
active
06209523
ABSTRACT:
The invention relates to a control and safety valve arrangement in a fuel feeding system.
In common pressure injection systems or common rail systems utilized for feeding fuel in internal combustion engines there is need for valve arrangements of different kinds. Especially when heavy oil or the like is used as fuel the viscosity of the fuel has to be decreased sufficiently before the engine is started so as to make the injection of the fuel into a cylinder possible. This is accomplished by circulating the fuel through the fuel feeding system so that it is warmed up. On the other hand a common rail system requires also a valve function for restricting the pressures used and a valve, through which the system can be unpressurized in connection with stopping of the engine or in an emergency situation. Thus, implementation of these functions requires normally three different valve functions and separate valves therefor.
The aim of the invention is to provide a new valve arrangement which is advantageous as to its construction and by means of which the valve functions mentioned above can at least partly be integrated in a common construction for obtaining a compact entity which is advantageous as to its costs. A further aim is that the valve arrangement can be applied especially in fuel feeding systems utilizing heavy fuel oil as a fuel.
In a control and safety valve arrangement according to the invention the pressure accumulator unit is connect to the fuel tank with a separate return flow line, which is provided with valve means provided with two separate control arrangements operationally independent on each other so that the pressure accumulator unit can be connected to the fuel tank by means of a first control arrangement under the influence of a separate control pressure when necessary and in addition by means of a second control arrangement in case the pressure in the pressure accumulator unit exceeds a certain selected limit value. The solution makes it possible to implement different valve functions required in common rail systems by making use of common structures.
In case said first control arrangement comprises a precontrol valve, preferably a solenoid valve, for controlling said control pressure, the control pressure can be connected and disconnected quickly and exactly according to need. In practice said control pressure can with advantage be hydraulically implemented, whereby it can be for instance as a part of a servo oil circuit of the engine, which is generally needed in any event for controlling the operation of the fuel injection valves.
Said second control arrangement may simply comprise a valve spring, the spring force and prestress of which determine the opening pressure in accordance with said limit value.
In case the valve means are located in a common valve unit fixed to the pressure accumulator unit and comprising a valve chamber, through which said return flow line is led, a space saving compact construction is obtained.
In an advantageous embodiment of the invention the return flow line is provided with two valves arranged functionally in successive order and of which the first valve in the flow direction is controlled by said first control arrangement and located in said valve chamber. The latter valve in the flow direction is controlled by said second control arrangement so that its opening force is smaller than that of the first valve in the flow direction. Hereby the latter valve may serve as a pressure restricting valve independent on the operations of the first valve.
A valve member of the first valve can be arranged to divide said valve chamber into two parts isolated from each other so that the first chamber part forms a part of said return flow line and the second chamber part is connected to the pressure to be controlled by means of the precontrol valve. The valve member of the first valve may in addition comprise a chamber, which can be connected on the one hand to the pressure accumulator unit and on the other hand to said first chamber part. In this case a valve member of the latter valve, a seat surface of the valve and a valve spring can be located in said chamber in the valve member so that normally it closes the connection from the pressure accumulator unit through said first chamber part into the fuel tank.
In another embodiment of the invention the valve means include a valve member, which in its closed position closes said return flow line and which is located in said valve chamber. In this case said first control arrangement comprises a guiding member, which is movable under the influence of the pressure to be controlled by means of the precontrol valve between a position closing the valve member and a position opening the valve member, and said second control arrangement comprises a valve spring, against the force of which the valve member can be pressed. In this case the valve spring can with advantage be supported to said guiding member at its end opposite to the valve member so that the guiding member acts on the valve member through the valve spring.
The guiding member may be provided with a shaft part which is arranged inside the valve spring. Then the end of the guiding member at the side of the valve member can be provided with a turnable nut for adjusting the prestress of the valve spring.
The valve spring and the guiding member may in this case be located in a second chamber which is separated from said valve chamber by means of the valve member.
REFERENCES:
patent: 5727525 (1998-03-01), Tzuzuki
patent: 6085728 (2000-07-01), Grosser et al.
patent: 196 26 689 (1996-07-01), None
patent: 196 40 826 (1996-10-01), None
patent: 411062773 (1999-03-01), None
Arganbright Tony M.
Castro Arnold
Smith-Hill John
Smith-Hill and Bedell
Wartsila NSD OY AB
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