Measuring and testing – Vehicle chassis – Steering
Patent
1994-12-29
1996-04-02
Raevis, Robert
Measuring and testing
Vehicle chassis
Steering
G01M 1500
Patent
active
055030092
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a method for recognizing irregular combustions in a cylinder of an internal-combustion engine.
2. Description of the Related Art
U.S. Pat. No. 4,697,561 discloses a method in which the speeds for each cylinder are detected, during its work cycle, at the crankshaft positions in which the crankshaft is at the lowest and the highest speed respectively. The difference between these two speeds is a measure of the torque generated by the cylinder. This, when related to the averaged torque of all the cylinders, gives an indication of the operating efficiency of the cylinder in question, which is utilized for diagnostic purposes.
In this method, the crankshaft positions having the highest and the lowest crankshaft speed have to be determined experimentally on the engine test bench. Preferably, they are dependent on load and on speed and are stored in this dependence in the control unit for carrying out the method. These crankshaft positions have to be read out before each detection of speed. This means an increased outlay in terms of computing time in the detection of speed which in any case is critical with regard to time.
FR 2,301,691 describes a method for obtaining a measured quantity, indicating the approximation to a predetermined lean-running limit, during the operation of an internal-combustion engine.
For this purpose, a method and a device by which combustion misfires are to be recognized are described. For this, the crankshaft speed is measured at two points in time during the working stroke of a cylinder, one point in time being before the top dead center of combustion and the other being after the top dead center. The difference between the measured values is formed. These two measurements are made again during the next work cycle of the same cylinder. A difference is formed again from the two differences determined and a combustion misfire is recognized in the event of changes of these successively determined differences.
SUMMARY OF THE INVENTION
The object of the present invention is to describe a simplified method for recognizing combustion misfires, in which the outlay in terms of computing time is also reduced.
The solution according to the invention is achieved in a method for recognizing irregular combustions in a cylinder of an internal-combustion engine, the speed of the internal-combustion engine being determined for each cylinder at two crankshaft positions, at least one of the crankshaft positions being located after top dead center, a gradient of the speed curve, which is defined by the two speeds obtained, is respectively calculated from the two speeds obtained, and in that an irregular combustion is recognized when the speed gradient falls below a limit value. Advantageous developments of the invention are achieved when the speed for each cylinder is determined continuously over two crankshaft position ranges and one of the two speeds is obtained respectively from these by averaging. Preferably, the limit value is zero and the dropping of the speed gradient below the limit value is recognized by a change in the sign of the speed gradient. In a preferred embodiment, the limit value is varied depending upon the load and speed of the internal-combustion engine. A further development provides that the distance of the crankshaft positions from one another and from top dead center is varied depending upon load and on speed.
According to the invention, the speed for each cylinder is detected at two crankshaft positions, at least one or both crankshaft positions being located after the top dead center. An evaluatable speed difference must be present at these crankshaft positions, otherwise the positions are selectable at random.
During a proper combustion in a cylinder, some acceleration of the crankshaft must occur. If this does not occur or if it falls below a specific value, either no combustion at all or an insufficient combustion has taken place.
According to the invention, therefore, a speed gradi
REFERENCES:
patent: 3972230 (1976-08-01), Hanson et al.
patent: 4697561 (1987-10-01), Citron
patent: 5241480 (1993-08-01), Takaku et al.
Plapp et al., "Methods of On-Board Misfire Detection", Robert Bosch GmbH, Mar. 1990.
Angermeier Anton
Wier Manfred
Raevis Robert
Siemens Aktiengesellschaft
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