Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
1999-07-15
2001-08-28
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S179170, C137S527000
Reexamination Certificate
active
06279545
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply system for fuel supply of an internal combustion engine from a fuel container by means of a fuel supply unit.
Fuel supply systems of the above mentioned general type are known in the art, as disclosed for example in the German patent document DE 42 42 242 A1. The fuel supply unit of such a system is arranged in the fuel container and conventionally has a pressure limiting valve with adjustable maximum pressure. A pump in the fuel supply unit pumps the fuel from the supply container into a fuel supply conduit. Conventionally, the operational pressure of the fuel supply conduit is lower than the maximum pressure which is monitored by the pressure limiting valve. If the maximum pressure is exceeded, the pressure limiting valve which is usually located in the upper region of the housing of the fuel supply unit, supplies back the excessive fuel into the fuel container. The operational pressure in the fuel supply conduit is controlled by an adjustable pressure regulating valve which discharges the excessive fuel into the fuel return conduit for maintaining a regulated operational pressure, so that in the internal combustion engine conventionally only the operational pressure acts.
The known fuel supply system has the disadvantage that the fuel supply pressure increase over the operational pressure is not possible without adjustment of the pressure regulating valve for the fuel in the fuel supply conduit. A short-term excess of the operational pressure in the fuel supply conduit, which in particular is required in a cold start phase in an internal combustion engine or in a warm start phase, is thereby possible only via an adjustment of the nominal value for the regulated operational pressure of the pressure regulating valve or by an electrically operating additional pump. During adjustment of the operational pressure in each starting phase, the regulated operational pressure must be adjusted. There is the disadvantage for the known fuel supply systems that the operational pressure in the fuel supply conduit is not exactly reproducable after each starting step. In another case, an electrically operating additional pump which is switched off after the starting phase, has the disadvantage of increased cost and increased construction, maintenance and operational expenses for the additional pump.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel supply system for fuel supply of an internal combustion engine from a fuel container by a fuel supply unit, in which once adjusted nominal value of an operational pressure in the fuel supply conduit must not be changed for a starting or running-on phase of the internal combustion engine.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a fuel supply system of the above mentioned type, in which the pressure regulating valve is associated with a delay valve for loading the fuel supply conduit with an initial pressure which is higher than the operational pressure and preferably corresponds to the maximum pressure.
The inventive fuel supply system can provide a fuel supply of an internal combustion engine from a fuel container by means of a fuel supply unit. For a start or a running-on phase of the internal combustion engine, an initially increased pressure is obtained in that, a delay valve is pre-switched to the conventional pressure regulating valve. It first hinders a direct connection between the fuel supply conduit and the pressure regulating valve. Thereby in the fuel supply conduit an increased supplied pressure is built up, which reaches the adjustable maximum pressure of a pressure limiting valve which has the fuel supply unit, and thereby supplies the required pressure for the injection process in the starting phase of an internal combustion engine.
The inventive pressure increase by a short-time standby time of the pressure regulator has the advantage that, during a direct fuel injection the motor in the starting case can be supplied directly from the fuel supply unit so that no second additional pump is needed. Thereby a simple and efficient advantageous possibility is provided to increase the system pressure of the fuel supply system for the direct fuel injection in the starting case, until the delay valve lifts the standby of the pressure regulator.
In accordance with a preferable embodiment of the present invention, the delay valve has an inlet, a delayed operational pressure outlet, and a throttled outlet. The inlet of the delay valve is connected with a branch conduit of the fuel supply conduit. The operational pressure regulator which with conventional construction is directly connected with the branch conduit is in accordance with the present invention is switched later. In other words, when the fuel supply unit is turned into operation, its pump is started and the maximum pressure provided by the pressure regulating valve is built up and is available at the inlet of the delay valve. The maximum pressure can be adjusted to the starter conditions of a fuel direct injection by corresponding design of the pressure regulating valve or adjustment of the same within the limits of the pump power of the fuel supply unit. The additional maximum pressure is built up through the throttled outlet of the delay valve with a time delay, until the delay valve releases the operational pressure outlet. Prom this time point, through the branch conduit of the fuel supply conduit, the operational pressure is controlled and regulated by the pressure regulating valve. For this purpose the delayed operational pressure outlet of the delay valve is connected with the inlet of the pressure regulating valve, so that after the delayed time the pressure regulating valve is connected to the fuel supply conduit
The delayed buildup of the maximum pressure in the fuel supply conduit is obtained through the throttled outlet of the delay valve, which preferably is connected with the fuel container, so that the excessive fuel is supplied back into the fuel container. By a design of the throttle opening of the throttled outlet, the delayed time can be adjusted to the starter conditions.
In a preferable embodiment, the delayed valve has a housing with at least one prestressed turning element which in a first phase has an immovable position as long as the fuel in the fuel supply conduit is pressureless and with which in a second phase a delaying turning movement is carried out when the fuel supply conduit is set under pressure by the fuel supply unit and has a pressure which is higher than the operational pressure adjustable at the pressure regulating valve and lower or equal to the maximum pressure of the pressure regulating valve. Finally, the turning element in a third phase assumes an operational position in which the inlet of the delay valve is short-circuited directly with the operational pressure inlet of the pressure regulating valve through the delay valve.
For producing and adjusting a prestressing for the turning element, the delay valve is provided with a prestressing device which acts on the turning axis and is arranged outside the housing. Such a prestressing device has for example a spring element which, for producing different prestresses and thereby for adjusting the delay time, is adjustably connected with the axis of the turning element. Thereby there is the advantage that not only the throttling opening provided in the throttling out of the delay valve determines the delay time, but also the delayed time can be finally adjusted additionally by adjustment of the prestressing device. Such an embodiment has the advantage that no additional electrical drive for operation and for switching of the delay valve is needed. Instead the maximum pressure adjustable by the dimensioning and design or by the adjusting element is supplied into the supply conduit of the drive for switching of the delay valve.
A further preferable embodiment of the inve
Frank Kurt
Strohl Willi
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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