Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Analysis of complex waves
Reexamination Certificate
1999-02-12
2001-12-11
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Analysis of complex waves
Reexamination Certificate
active
06329807
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates of a device for detecting an erroneous signal characteristic of a load on an internal combustion engine and, more particularly, to a device comprising a first and second load signal generating means and means for recognizing whether or not the first and second load signal are characteristic of the same measured load value.
In the course of determining an essential measurement value it may become necessary to employ two sensor systems, which operate independently of each other, for the determination. It is then possible by means of such redundant systems to detect an error by means of a comparison of the signals provided by the sensor systems, for example if a signal exceeds an upper threshold value or falls below a lower threshold value.
However, it is also further possible to compare both signals and to monitor, for example, the distance between two signals in order to detect an error if the difference between the two signals exceeds a threshold value. Such a plausibility check is performed in DE-OS 43, 44 633, for example.
With this known plausibility check, the so-called main load signal and the so-called secondary load signal are compared with each other in connection with the load registration in an internal combustion engine. Here, the main load signal is determined by directly registering the air flow aspirated by the internal combustion engine with the aid of an air flow sensor. The registration of the main load signal can also be performed indirectly with an induction pipe pressure sensor. In the course of this, the aspirated quantity of fresh air is calculated, using the gas equation and taking into consideration the temperature of the aspirated air, the remaining gas portion and the cylinder stroke volume. The secondary load signal is formed in both methods (pressure sensor, or respectively air flow sensor) by evaluating the rpm and the angular position of the throttle of the internal combustion engine, for example with the aid of a throttle potentiometer. The main load signal as well as the secondary load signal must correspond to each other to a large extent when the air flow sensor or the pressure sensor, or respectively the throttle potentiometer operate correctly and are optimally matched. However, if deviations nevertheless occur, it is possible to conclude that one of the two sensor systems is in error.
SUMMARY OF THE INVENTION
The device in accordance with the invention for detecting an erroneous signal can, in an advantageous manner, surely and dependably recognize when one of two sensors which register the same measurement value provides an erroneous output signal. In this case it is particularly advantageous that an erroneous signal is recognized even if it lies within a range which is per se valid. It is therefore possible to recognize if one of the two sensors emits a constant signal which is still plausible, although the value to be measured changes, i.e. the lack of dynamics on the defective signal path is recognized.
These advantages are achieved in that the two signals are not directly compared with each other, but are initially filtered and the magnitude of the filtered signal is respectively formed. By forming the difference between the magnitudes of the filtered signals it is possible to generate particularly dependable conditions which are used for detecting errors. Thus it is possible in particular to detect an error in an advantageous manner by evaluating the sign of the difference of the two signals for error recognition. Therefore the error recognition, or respectively the plausibility monitoring, is based in an advantageous manner on the variance between the two signals. In comparison with the monitoring known from DE-OS 43 44 633, which is based on a comparison of signal levels, this monitoring has the advantage of being more dependable and of operating dependably even in case of small error functions of a sensor.
Further advantages are achieved by the features of the preferred embodiments. A particular advantage lies in that it is also possible to detect, which of the two signals is erroneous. This advantage is achieved in that, following the difference formation, a special plausibility check using logical means is performed.
In an alternative embodiment instead of a difference formation of the magnitude of the filtered signals, it is also possible to provide a quotient formation. The comparison of the quotient with at least one threshold value also makes the detection of an error possible.
REFERENCES:
patent: 4199799 (1980-04-01), Ostenso et al.
patent: 5223830 (1993-06-01), Romes
patent: 5706791 (1998-01-01), Mezger et al.
patent: OS 43 44 633 (1993-12-01), None
Pfitz Manfred
Wild Ernst
LeRoux Etienne
Metjahic Safet
Robert & Bosch GmbH
Striker Michael J.
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