Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-10-22
2001-09-11
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S467000
Reexamination Certificate
active
06286484
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for combustion engines, preferably Diesel engines, with at least one pilot valve by means of which a control piston is displaceable by a pressure medium in order to convey fuel through at least one line/channel toward a combustion chamber of the internal combustion engine.
For a reliable and clean mixture formation, internal combustion engines, Diesel engines in particular, require an injection process consisting of several individual injection actions. The injection processes are divided into pre-injection and main injection of the fuel quantity.
FIG. 3
illustrates the injection process. First, triggered by a switching pulse of the engine control, a pilot or pre-injection occurs. After a time period t, the pilot or pre-injection is terminated by a cut-off pulse and after a time period t, the main injection of the fuel is started by a switching pulse. The main injection has a longer duration than the pre-injection stage. Also, significantly more fuel is injected during the main injection than during the pre-injection stage. Particularly for producing the pre-injection quantity, a control unit is employed which, however, requires a high-cost electronic control system and which shows energetic losses. Frequently, a damper is employed for producing the pre-injection fuel quantity. This damper, however, cannot be fully utilized in each step of the operation. The reason for this is that the response times of the control hydraulic are too long in the event of small injection quantities due to the design of the control elements and a small pre-injection quantity can, therefore, be produced only with the help of a significant control-technical structural design and expenditure.
Therefore, it is an object of the present invention to provide a fuel injection device of the aforementioned kind such that a small pre-injection quantity can be produced with the fuel injection device having a simple structural design and only requiring a small control-technical expenditure and design.
SUMMARY OF THE INVENTION
This object is solved by the inventive fuel injection device by providing at least one accumulator in the flow path of the fuel or the pressure medium and connecting the accumulator space of the at least one accumulator with the connecting line for the fuel or the pressure medium.
With the inventive fuel injection device, the quantity of the fuel to be conveyed is, in addition to a minimum activation time of the control valve, minimized by the accumulator. A portion of the fuel to be conveyed to the combustion chamber or a portion of the pressure medium enters the accumulator. The accumulator volume for fuel or pressure medium is instantly available during a pre-injection action. When fuel is conveyed to the accumulator, only a minimum quantity of fuel needs to be conveyed to the combustion chamber via the connecting line. It is sufficient if the accumulator volume is smaller than the minimum quantity of fuel to be conveyed during the pre-injection stage. Therefore, only such a quantity of fuel needs to be conveyed to the combustion chamber during the pre-injection stage by the control piston which quantity equals the difference between the fuel amount that can be removed from the accumulator and the required pre-injection quantity. The accumulator can also be arranged such that it receives a portion of the pressure medium which acts upon the control piston. Also in this manner, the injection quantity of fuel can be limited. The accumulator volume can be selected to be equal to, larger or smaller than the minimum fuel volume to be conveyed during the pre-injection stage. If the accumulator volume is larger, any quantity of fuel can be conveyed. The accumulator does not require a high-cost electronic control system and no costly designed control elements. Therefore, even the smallest injection quantities can be reliably produced with the inventive injection device with a simple structural design and at lowest control-technical design and expenditure.
The accumulator can be provided within the inventive injection device, however, it can also be provided externally of the injection device. The accumulator volume can be designed to be fixed, however, it can also be designed to be variable. The accumulator makes a volume variation possible which results, depending on the respective adjustment of the accumulator, in a reduced quantity of fuel exiting when a hydraulic intake volume of fuel is predetermined time-wise.
REFERENCES:
patent: 4167168 (1979-09-01), Yamamoto
patent: 4711209 (1987-12-01), Henkel
patent: 5029568 (1991-07-01), Perr
patent: 5076236 (1991-12-01), Yu et al.
patent: 5195487 (1993-03-01), Zurner et al.
patent: 5718385 (1998-02-01), Fontell
Lenk Martin
Martin Steffen
Niethammer Bernd
Becker Robert W.
Hydraulik-Ring GmbH
Moulis Thomas N.
Robert W Becker & Associates
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