Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Patent
1998-12-17
2000-06-27
Solis, Erick
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
123506, F02B 310
Patent
active
060793880
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection system. In a system of this kind, which has been disclosed by DE-A-36 44 257, a distributor injection pump is provided as a fuel injection. A pump piston that is driven to reciprocate and rotate at the same time, which with its rotating motion and its pump stroke, respectively supplies one of a number of injection lines. Each injection lines lead to a fuel injection valve, to supply fuel that has been brought to injection pressure. For the division of the injection into a pre-injection and a main injection, the electrically controlled solenoid valve, is opened for a short time in order to thus discharge the pump work chamber and to temporarily decrease the fuel pressure generated. This means that a very rapidly switching solenoid valve is needed, which requires a considerable expenditure in the electrical control and construction of the valve. In this connection, it is particularly disadvantageous that the interruption of the injection must occur in a time-controlled manner by means of a solenoid valve. As a result, with increasing speed, an ever greater portion of the available cam stroke is used for interrupting the injection. In comparison to the possibilities of an in-line injection pump, in which a cam respectively drives only one pump piston, with a distributor injection pump, a significantly smaller stroke is available for each injection event because the cam stroke available is limited due to the limited length of the cam track. A time-controlled interruption of the injection by means of intermediate discharging of the pump work chamber by means of a solenoid valve therefore entails a significant limitation of the output produced by the fuel injection pump. Furthermore, a special pressure control valve is provided in the connection between the pump work chamber and the injection valve. This pressure control valve opens in the feed direction with the high-pressure fuel delivery to the fuel injection nozzle and closes at the end of injection. The valve is suitable for decreasing pressure waves between the pressure control valve and the fuel injection valve and for maintaining a desired constant standing pressure in this region during the injection pauses. In a divided fuel injection with one pre-injection and one main injection per work cycle of the respective cylinder of the engine to be supplied, it is advantageous to provide for a constant standing pressure in the injection pauses.
ADVANTAGES OF THE INVENTION
The embodiment according to the invention produces a reliable interruption of the injection between the pre-injection and main injection with low requirements as to the speed of a time-controlled valve. At the same time, none of or only a very small portion of the available cam stroke is used during the interruption of the injection between the pre-injection and the main injection. The interruption of the injection, which is supported structurally by way of the cam form, achieves the fact that even at a higher speed, a reliable interruption of the injection between the pre-injection and the main injection can be maintained without a loss in a cam stroke that can be supplied for the high-pressure delivery. The speed independent influence of the switching time is compensated for by means of the second partial region of the cam so that in addition, no excessive requirements have to be placed on the speed of the electrically controlled valve.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplary embodiment of the invention is represented in the drawings and will be explained in more detail in the description below.
FIG. 1 is a schematic representation of a fuel injection pump, which is controlled by a solenoid valve,
FIG. 2 shows a course of the cam track according to the invention, in the form of a cam lifting curve, over the rotation angle, with a first control sequence of the valve at a low speed of the engine, and
FIG. 3 shows a course of the cam track according to the invention over the rotation angle, with a second control sequence of the
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patent: 5070836 (1991-12-01), Wahl et al.
patent: 5325837 (1994-07-01), Laufer
patent: 5443047 (1995-08-01), Ishiwata et al.
patent: 5803049 (1998-09-01), Harcombe
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Solis Erick
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