Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-08-07
2002-06-04
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S357000, C123S501000
Reexamination Certificate
active
06397821
ABSTRACT:
BACKGROUND AND SUMMARY OF INVENTION
This application claims the priority of German patent document 19937139.3, filed Aug. 6, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and device for controlling an internal combustion engine in which an injection start is determined as a function of input variables.
Such a device is disclosed, for example, in German Patent Document DE 42 08 002 A1 (corresponding U.S. Pat. No. 5,293,853). In the system described therein, the start of injection is determined as a function of a fuel amount to be injected and an additional input variable, e.g., the engine speed. In an internal combustion engine used to drive a ship or a generator, the problem is that the load on the power take-off may be abruptly reduced, e.g., when the ship's propulsion unit broaches. These internal combustion engines, as is well known, are operated at the nominal output point. For the nominal output point, the manufacturer of the internal combustion engine guarantees the maximum engine output for continuous operation. Since the nominal output point varies as a function of fuel quality and the drive system used, the manufacturer additionally indicates the range within which the nominal output point can lie. A significant load change on the power take-off in terms of a load rejection causes a rapid increase in the engine speed. Due to the small speed difference between the engine speed value at the nominal output point and the maximum speed, the time span for speed control is too short to prevent the maximum speed from being exceeded. In this case speed control via the set-point injection amount is not an effective protection. As an enforcement measure, when the maximum speed is exceeded, the internal combustion engine is tripped and a diagnostic entry occurs.
Based on the described prior art and the technical problem presented, it is an object of the invention to ensure a safe operation of the internal combustion engine.
According to the invention, for an internal combustion engine operated in the range of the nominal output point, this object is attained in that a significant load change on the power take-off of the internal combustion engine is detected if the engine speed exceeds a first limit value. In terms of the invention a significant load change is to be understood as a load rejection. When the load change is detected, the start of injection is shifted toward late in terms of smaller crankshaft angle values before the top dead centers. For this purpose the characteristics map for the start of injection has a first and second area. The first area is defined via engine speed values that are less than the first limit value and the second area via engine speed values that are greater than the first limit value. In the second area, the characteristics map is designed in such a way that each value of the engine speed is associated with only one value of injection start.
As an alternative, a characteristics map switchover is provided, according to which, at the nominal output point, the start of injection is determined according to a first characteristics map, and upon detection of a significant load change, the start of injection is determined according to a second characteristics map. This second characteristics map is designed as described above.
This special embodiment of the characteristics map for the start of injection has the advantage that the speed control is additionally supported. This prevents the engine speed from reaching the critical maximum speed. Since no additional input variables are required to convert the characteristics map, it can be readily integrated in the existing program.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
REFERENCES:
patent: 4368705 (1983-01-01), Stevenson et al.
patent: 4428341 (1984-01-01), Hassler et al.
patent: 5293853 (1994-03-01), Berger et al.
patent: 5680842 (1997-10-01), Schmid
patent: 3023350 (1982-01-01), None
patent: 4208002 (1993-09-01), None
Dölker Armin
Spägele Thomas
Argenbright Tony M.
Crowell & Moring LLP
MTU Friedrichshafen GmbH
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