Measuring and testing – Vehicle chassis – Steering
Patent
1993-06-18
1995-03-07
Raevis, Robert
Measuring and testing
Vehicle chassis
Steering
G01M 1500
Patent
active
053947428
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
A related application is International Application PCT/EP91/02140, filed 12 Nov. 1991, and filed for entry into the U.S. national phase simultaneously herewith.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a process for recognizing abnormal combustions in the 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, by means of 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 lowest and the highest crankshaft speed have to be determined experimentally on the engine test bench. In particular, they are dependent on the load and on the speed and are stored in this dependence in the control unit for carrying out the method.
Corresponding tests on the engine test bench have shown that it is difficult to fix these crankshaft positions. Particularly for the purposes of the diagnosis of abnormal combustions, it has not been possible, in specific load and speed ranges, to find any crankshaft positions which would give a speed-difference signal which can be evaluated with sufficient accuracy.
SUMMARY OF THE INVENTION
The object of the present invention is, therefore, to develop the method in such a way that the evaluation capability is improved.
The solution according to the invention is achieved by determining the speed of the internal-combustion engine by means of two crankshaft positions which are selected as different depending upon load and on speed, wherein the two crankshaft positions are selected so that, in relation to the case of abnormal combustion, as great a speed difference as possible is obtained, and recognizing abnormal combustion when, according to the selected speed difference, a chronologically later minus chronologically earlier rpm value or chronologically earlier minus chronologically later rpm value, either exceeds or does not reach a limit value. Advantageous developments of the invention are include selecting the two crankshaft positions in relation to the case of a combustion misfire. The method preferably includes determining the speed for each cylinder continuously over two crankshaft-position ranges and obtaining one of the two speeds respectively from these by averaging. Simplification is provided when the limit value is zero so that whether or not the speed difference has exceed the limit value or has not reaching the limit value is recognized from the sign of the speed difference. Preferably, the crankshaft positions are selected as different in a cylinder-specific manner.
The invention proceeds from the knowledge that the problems of evaluation arise as a result of the choice of the optimization strategy for the crankshaft positions. In the state of the art, those crankshaft positions in which the crankshaft is at the lowest and the highest speed respectively are sought.
These crankshaft positions are determined during the normal operation of the internal-combustion engine, so that evidence of the torque generated by it can be derived. In the event of faults occurring to a pronounced extent in specific load and speed ranges, however, the speed difference determined in the two crankshaft positions is often no longer sufficient.
According to the invention, therefore, this speed difference increases by optimizing the crankshaft positions not in terms of normal operation, but in terms of abnormal combustion. The second crankshaft position in particular is selected at a later stage than would correspond to the point of highest crankshaft speed during normal operation.
BRIEF DESCRIPTION O
REFERENCES:
patent: 3972230 (1976-08-01), Hanson et al.
patent: 4697561 (1987-10-01), Citron
patent: 5191788 (1993-03-01), Nishimura
patent: 5197325 (1993-03-01), Tamura et al.
Angermeier Anton
Wier Manfred
Raevis Robert
Siemens Aktiengesellschaft
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