Internal-combustion engines – Combustion chamber means combined with air-fuel mixture...
Patent
1995-05-11
1996-05-21
Nelli, Raymond A.
Internal-combustion engines
Combustion chamber means combined with air-fuel mixture...
F02P 514
Patent
active
055179690
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a device for detecting faults, of the generic type of the main claim.
It is known that, in internal combustion engines with knocking control, it is necessary to monitor the operational capability of the knocking sensor which makes detection of knocking possible. Otherwise, there is the risk that in the event of the knocking sensor or a component of the associated evaluation circuit failing knocking is not detected and the working point of the internal combustion engine is erroneously shifted into the knocking range, which can result in a hazard for the internal combustion engine itself.
Therefore, in DE-PS 31 28 475 a testing device for a knocking control apparatus on an internal combustion engine is proposed, in which testing device a knocking sensor with an evaluation circuit which is connected downstream and triggers shifting of the ignition angle when knocking occurs is tested for correct operational capability.
In the known device, the knocking detection takes place during a measuring phase. For this purpose, the output signal of the knocking sensor is compared in a known manner with an adaptable reference value. Knocking is detected from the result of the comparison. During a test phase, the output signal of the knocking sensor is compared with another, lower reference value. Operational faults are then detected from this comparison result if the output signal does not exceed the reference signal.
The known testing device for a knocking control apparatus on an internal combustion engine has the disadvantage that a measuring phase and a test phase are required and testing is not possible in the measuring phase, while in the test phase detection of knocking cannot be carried out.
ADVANTAGES OF THE INVENTION
The device according to,the invention for detecting faults in an apparatus for detecting knocking in an internal combustion engine has, in contrast, the advantage that the detection of knocking and the detection of faults can proceed alongside one another without interruption so that the occurrence of knocking can be detected at any time and also the detection of faults can be carried out without interruption.
These advantages are achieved in that the reference level, the exceeding of which is the criterion for the detection of knocking, is initially normalized in such a way that it rises as the engine noise increases. Here, this reference level is, on the one hand, used for the detection of knocking and, on the other hand, a comparison is made as to whether the normalized reference level lies within a permitted reference level band. The permitted reference level band is specified in a suitable manner, in particular as a function of the engine speed. A fault is detected if the normalized reference level leaves the permitted reference level band. Here, it is advantageous that detection of faults can only occur if the normalized reference level not only leaves the range permitted for the normalized reference level but also exceeds an upper limit value which is dependent on the engine speed or drops below a lower limit value which is also dependent on engine speed.
Further advantages of the invention are achieved with the measures disclosed in the subclaims. Here, an advantageous feature for increasing the reliability of the detection of faults is that a fault is only detected if the normalized reference level lies outside the permitted reference level band for a specific, selectable time.
It is particularly advantageous that after detection of a fault safety measures are automatically initiated which ensure that the internal combustion engine is always operated in a non-hazardous range. For this purpose, the detection of faults is followed for example by an ignition angle adjustment which is maintained at least until it is detected that the apparatus for detecting knocking is functioning again correctly.
So that the safety measures initiated after detection of a fault are not terminated too early, in a further advantageous embodiment of the invention the cancell
REFERENCES:
patent: 4521769 (1985-06-01), Dudeck et al.
patent: 4599982 (1986-07-01), Sugiura
patent: 5020499 (1992-06-01), Kojima et al.
patent: 5134980 (1992-08-01), Sakakibara et al.
patent: 5287837 (1994-02-01), Hashimoto et al.
patent: 5388560 (1995-02-01), Hisaki et al.
Baeuerle Michael
Haeming Werner
Hilbert Wolfgang
Rothhaar Ulrich
Sloboda Robert
Nelli Raymond A.
Robert & Bosch GmbH
Striker Michael J.
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