Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-06-05
2001-07-03
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S458000
Reexamination Certificate
active
06253734
ABSTRACT:
The invention is based on a fuel delivery system for supplying fuel for an internal combustion engine.
Previously there have been fuel delivery systems in which a first fuel pump delivers fuel from a fuel tank to a second fuel pump by way of a fuel connection. The second fuel pump in turn delivers the fuel into a pressure line which is connected to at least one fuel valve. Usually, the number of fuel valves is equal to the number of cylinders of the internal combustion engine. The fuel delivery system can be designed so that the fuel valve injects the fuel directly into a combustion chamber of the internal combustion engine. During operation of this fuel delivery system, a high pressure is necessary in the pressure line that leads to the fuel valve.
Normally, the second fuel pump is mechanically driven directly by the internal combustion engine. The second fuel pump usually has a pump body that moves back and forth in a pump chamber, wherein the frequency of the pump body is rigidly coupled to the speed of the internal combustion engine. So that the delivery quantity to the second fuel pump can be controlled despite the rigid coupling of the pump body to the speed of the internal combustion engine, a control valve that controls the delivery quantity can be provided between the first fuel pump and the second fuel pump, and during a compression stroke of the pump body, this control valve permits part of the fuel from the pump chamber to flow back into the fuel connection between the first fuel pump and the second fuel pump. So that no vapor bubbles are produced inside the spaces that contain fuel, it is important that the control valve have a sufficiently large through flow cross section.
Because the through flow cross section must be relatively large, it has not been possible up to this point to construct the control valve so that the control valve switches rapidly enough to attain a sufficiently precise control or regulation of the pressure in the pressure line leading to the fuel valves even if the pump body has a high frequency.
Another disadvantage up to this point has been the fact that due to the size of the control valve, a relatively long time passes before the through flow cross section of the control valve is completely closed or completely opened so that in this transition time for the switching of the control valve, part of the fuel flows from the pump chamber of the second fuel pump into the fuel connection at a relatively high pressure, which involves a dissipation and consequently an undesirable energy loss and an undesirable heating of the fuel.
Despite the high cost, it has not previously been possible with sufficient precision to regulate or control the fuel quantity supplied by the second fuel pump even at high speeds of the internal combustion engine and to simultaneously assure that no gas bubbles are produced in the second fuel pump and that the second fuel pump does not require any excess fuel which likewise involves dissipation and consequently, further energy loss and heating of the fuel.
ADVANTAGES OF THE INVENTION
The fuel delivery system according to the invention, offers the exceptional feature that the electromagnet of the actuating drive that adjusts the valve member is supplied with current at an intermediate value while the control valve is still disposed in the starting position, i.e. for a certain amount of time before the valve member must be adjusted by the actuating drive, wherein the intermediate value of the current supply is at a level between the first value provided for the starting position and the second value provided for the end position. As a result, the valve member of the control valve does in fact remain in the starting position until the provided switching time, but subsequently, only a slight change in the current supply of the electromagnet is required to move the valve member from the starting position, which can occur within an extremely short period of time so that the valve member and therefore the control valve can be advantageously switched into the provided new end position in an extremely rapid fashion.
Advantageous improvements and updates of the fuel delivery system according are possible through the measures taken hereinafter.
While the valve member is still disposed in the starting position, i.e. for a certain amount of time before the control valve is to be actuated, the electromagnet of the actuating drive, which adjusts the valve member, is supplied with the current of an intermediate value that is adapted in a correspondingly different manner as a function of an operating condition of the internal combustion engine. As a function of a pressure inside the fuel delivery system, in particular as a function of a dynamic pressure acting on the valve member and/or as a function of time, in particular as a function of the momentary position of the pump body and/or as a function of a pump speed, then this achieves the advantage that, in a manner appropriate to the situation, the electromagnet produces just enough force that the valve member remains in its starting position. Only a slight change in the current supply must be carried out to move the valve member out of the starting position, which can occur within an extremely short period of time so that the control valve can be switched into the end position in an extremely rapid fashion.
By closing the through flow cross section as a function of an operating condition of the internal combustion engine, the fuel quantity supplied by the second fuel pump can be very simply and very precisely controlled or regulated with little dissipation. The control valve embodied according to the invention can be closed and opened in a particularly rapid and precisely timed fashion.
Through the use of the check valve that is hydraulically parallel to the control valve and conveys fuel from the fuel connection into the pump chamber of the second fuel pump, during an intake stroke, fuel can also travel from the fuel connection into the pump chamber in such a way that the fuel bypasses the control valve. This offers the adage that the through flow cross section of the control valve can be embodied as smaller without having to fear that during an intake stroke, the pressure in the pump chamber will drop too sharply and therefore result in the danger of gas bubbles.
If the control valve is embodied as a so-called seat valve, then a relatively large through flow cross section can advantageously be controlled or opened and closed with a relatively small adjustment path of the valve member.
REFERENCES:
patent: 4378775 (1983-04-01), Straubel et al.
patent: 4662825 (1987-05-01), Djordjevic
patent: 4884545 (1989-12-01), Mathis
patent: 5099814 (1992-03-01), Ament
patent: 5533481 (1996-07-01), Kronberger
patent: 5927322 (1999-07-01), Rosenau
patent: 3700358 (1988-07-01), None
Marquardt Werner-Karl
Rembold Helmut
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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