Measuring and testing – Vehicle chassis – Steering
Patent
1995-06-19
1997-04-01
Raevis, Robert
Measuring and testing
Vehicle chassis
Steering
G01M 1500
Patent
active
056168586
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a diagnostic method for recognizing combustion misfiring in an internal-combustion engine.
2. Description of the Related Art
The requirement to recognize misfiring under all the operating conditions of an internal-combustion engine, to make it possible to counteract increased emissions of harmful materials associated therewith or to perform protective functions with a catalytic converter, have increasingly becoming part of the corresponding regulations. Various methods have already become known for recognizing such combustion misfiring, such as, for example, the evaluation of erratic running or a lambda-probe signal or monitoring of the ignition current, etc.
It has been shown, however, that none of these methods can provide generally valid evidence of combustion misfiring. On the one hand, there is the problem that one method does not work with sufficient accuracy in all load and rotational-speed ranges, as, for example, in the consideration of erratic running. On the other hand, in some other methods, there is the problem that no reliable information about a proper combustion can be obtained, since only sub-functions necessary for the combustion method are diagnosed, as, for example, in ignition-current diagnosis.
SUMMARY OF THE INVENTION
In contrast to this, the object of the present invention is to provide a diagnostic method for detecting combustion misfiring, in such a way that information about a proper combustion in all the load and rotational-speed ranges of the internal-combustion engine can be obtained with greater reliability.
The solution according to the invention is provided by a diagnostic method for recognizing combustion misfiring in an internal-combustion engine, characterized in that a memory with a map of characteristics, in which characteristic numbers dependent on load and on rotational speed are filed, is provided, in that a selection device selects at least one diagnostic method from at least two diagnostic methods for detecting combustion misfiring depending on the read-out characteristic number, and in that the diagnostic device recognizes a combustion misfire when at least one of the diagnostic methods detects a combustion misfire. Advantageous developments of the invention are provided by the selection method selecting the diagnostic method from a group of diagnostic methods which evaluate method output quantities of the combustion method, such as erratic running, noise, vibrations, lambda-probe signal. A further improvement provides that the selection method selects the diagnostic method from a group of diagnostic methods which evaluate the method input quantities of the combustion method, such as ignition current or output signals from the output stages for the injection valves. The solution according to the invention proceeds from the consideration that diagnostic methods for detecting combustion misfiring can be divided into three groups.
The first group considers method output quantities, such as erratic running, noise, vibrations or the lambda-probe signal. The reaction of the internal-combustion engine to the combustion operation is therefore evaluated.
These methods are highly cost-effective since the sensors necessary for them are usually already present in engine control systems. The corresponding diagnosis therefore necessitates only additional software routines. However, the high dependence of many of these methods on load and on rotational speed is a problem, no reliable information being obtained in specific operating ranges, for example as a result of the influences of vibration and resonance.
The second group of diagnostic methods considers method input quantities, such as, for example, the ignition current or the output signals from the output stages for the injection valves. One of the preconditions for proper combustion is therefore respectively evaluated.
These methods are likewise highly cost-effective since only the corresponding electrical signals have to be evaluated. A pr
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"Kfz-Tester mit drahtloser MeBwertaufnahme", Elektronik, 38 (1989) 7 Jul., No. 14, pp. 78-80, 82.
Angermeier Anton
Wier Manfred
Raevis Robert
Siemens Aktiengesellschaft
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