Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1998-07-20
2001-10-09
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S447000, C123S506000
Reexamination Certificate
active
06298831
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating a fuel supply system for an internal combustion engine, in particular of a motor vehicle, in which fuel is pumped by a pump into a pressure accumulator. The present invention also relates to a fuel supply system for an internal combustion engine, in particular of a motor vehicle, having a pressure accumulator and a pump with which fuel can be delivered to the pressure accumulator, and having a control device with which at least the pressure in the pressure accumulator can be controlled.
BACKGROUND INFORMATION
Continually increasing demands are being made on an internal combustion engine, for example of a motor vehicle, in terms of reduced fuel consumption and exhaust emissions, while greater output is also desired. To meet these demands, modern internal combustion engines are equipped with a fuel supply system in which the delivery of fuel into the combustion chamber of the internal combustion engine is controlled and/or regulated electronically, in particular by means of a computer-aided control device. It is possible in this context to inject the fuel into an air intake pipe of the internal combustion engine, or directly into the combustion chamber of the internal combustion engine.
With the latter method in particular, which is referred to as “direct injection,” the fuel must be injected under pressure into the combustion chamber. Provided for this purpose is a pressure accumulator into which the fuel is pumped by means of a pump and subjected to a high pressure. From there the fuel is then injected through injection valves into the combustion chambers of the internal combustion engine.
A number of operating states can occur while the internal combustion engine is in operation. At full load, the internal combustion engine produces its maximum output; at part load it produces a desired portion thereof. At idle, the rotation speed of the internal combustion engine is as low as possible. And in coastdown (overrun) mode, the internal combustion engine generates no output, but instead creates a certain braking action.
Coastdown mode occurs, for example, when the motor vehicle is traveling down a sloping road and the driver of the motor vehicle removes his or her foot from the accelerator pedal. As a result, no further fuel is injected into the internal combustion engine, and often, in addition, no further air is delivered to the internal combustion engine. The injection valves thus remain closed during a coastdown period of this kind. Thus not only is the desired braking effect achieved, but also fuel is thereby saved.
SUMMARY OF THE INVENTION
It is an object of the present invention to further improve the coastdown (overrun) mode operating state.
This object is achieved according to the present invention, in the case of a method and a fuel supply system of the kind cited initially, in that when the internal combustion engine is in coastdown (overrun) mode, the pump output of the pump is or can be reduced.
Reduction of the pump output of the pump is equivalent to reducing the pump load. Since a considerable proportion of the pump output is converted into heat, the result is that the reduction in pump output causes less heat to be generated. The result of this in turn is that the fuel is heated less. This reduced heating of the fuel decreases the risk of vapor bubble formation, as well as the risk of misfiring or uneven operation of the internal combustion engine.
With a lower pump output, the pump is moreover under a lesser load than at a high pump output. This has advantageous effects in terms of lower wear and therefore a longer pump service life.
In an advantageous embodiment of the present invention, the pressure accumulator is closed off when the internal combustion engine is in coastdown mode. This represents a simple possibility for reducing the pump output of the pump. Closing off the pressure accumulator means that the pump no longer needs to generate the high pressure at which it supplies fuel to the pressure accumulator. The pump output required for the purpose is thus lower.
According to the present invention, the fuel pumped to the pressure accumulator is shunted off via a switchover valve. A switchover valve that can be switched by the control device is thus provided between the pump and the pressure accumulator. During coastdown periods, this switchover valve is switched over by the control device in such a way that the pressure accumulator is closed off. Fuel that continues to be pumped by the pump toward the pressure accumulator is then shunted off by the switchover valve in a different direction.
It is particularly advantageous if the shunted-off fuel is conveyed into a fuel tank or to the input of the pump. This results, without major effort, in fuel recirculation, so that the fuel can be re-used immediately.
According to the present invention, the pressure in the pressure accumulator is reduced when the internal combustion engine is in coastdown mode. For this purpose, the pressure accumulator is equipped with a pressure control valve that can be switched by the control device. Because of the lower pressure in the pressure accumulator, the pump needs to generate a lower pump output. The reduction in pressure in the pressure accumulator thus represents a simple means of reducing the pump output of the pump.
According to the present invention, the pressure in the pressure accumulator is kept approximately constant while the internal combustion engine is in coastdown mode. When the period of coastdown then comes to an end, the required pressure in the pressure accumulator is then immediately available, for example, to transition into a part-load operating condition. Maintaining a constant pressure in the pressure accumulator, according to the present invention, thus results in an immediate and, at the same time, smooth transition to other operating conditions. Another result of the approximately constant pressure in the pressure accumulator is to prevent vapor bubbles or the like from occurring in the pressure accumulator, particularly in coastdown mode.
REFERENCES:
patent: 4430980 (1984-02-01), Pidgeon
patent: 4800859 (1989-01-01), Sagisaka et al.
patent: 5016181 (1991-05-01), Hayashida
patent: 5085193 (1992-02-01), Morikawa
patent: 5237975 (1993-08-01), Betki et al.
patent: 5284119 (1994-02-01), Smitley
patent: 5379737 (1995-01-01), Hu
patent: 5379741 (1995-01-01), Matysiewicz et al.
patent: 5636611 (1997-06-01), Frankle et al.
patent: 5735242 (1998-04-01), Kahlenbeck et al.
patent: 5797372 (1998-08-01), Sugimoto
Bauer Hartmut
Grob Ferdinand
Maienberg Uwe
Rembold Helmut
Scherrbacher Klaus
Kenyon & Kenyon
Moulis Thomas N.
Robert & Bosch GmbH
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