Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-03-01
2001-06-12
Wolfe, Willis R. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C123S406380, C073S035080
Reexamination Certificate
active
06246952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine control signal processing system for signal processing for various kinds of control by using a knock signal of an internal combustion engine.
2. Related Art
A conventional internal combustion engine control signal processing system is disclosed in JP-A-6-159129. Much like the signal processing using a known vibration type knock sensor, in this system, a knock current having a specific frequency characteristic is separated from an ion current generated in the internal combustion engine by an analog circuit and integrated for the purpose of knock determination based on a result of the integration. When the amplitude of a knock signal appearing in an ion current decreases due to an operating condition or a noise component which is generated by an external source and superposed on the ion current, accurate knock determination using an analog circuit becomes difficult. Such a noise component is generated at a time a vehicle passes another vehicle or at a time the horn is operated.
In addition, another internal combustion engine control signal processing system is disclosed in JP-A-6-281523 is also known. In this system, an FFT (Fast Fourier Transform) frequency analysis is carried out for a specific range centered at a maximum amplitude waveform of a knock detection signal or a knocking waveform. As a result, processing can be carried out by a processor having a relatively low processing speed and the size of a memory used for the processing can be reduced. The knock detection signal attenuates gradually after its maximum amplitude. For this reason, the knock detection signal produced for the same time periods immediately before and after the maximum amplitude of the waveform are picked up for an analysis purpose. If the signal in the period immediately after the maximum amplitude is not available in the analysis due to a limitation on the size of the memory, accurate knock determination is impossible.
Also in the case of the internal combustion engine control signal processing system disclosed in JP-A-62-81523, the waveform of a knock detection signal is subjected to A/D-conversion with predetermined timing during a gate period. Values obtained as a result of the A/D-conversion are stored in a RAM. In the FFT (Fast Fourier transform) frequency analysis, typically 128 values stored in the RAM selected during a period in which a knock is actually generated are used. Since the number of values is small, the processing time can be shortened. If a knock center frequency or a sampling frequency is shifted, however, desired FFT processing values (spectrum intensities) can not be obtained.
SUMMARY OF THE INVENTION
It is thus a first object of the present invention to provide an internal combustion engine control signal processing system that is capable of determining a variety of control signals for an internal combustion engine appearing in an ion current with a high degree of accuracy without being affected by a noise component or the like generated by an external source.
It is a second object of the present invention to provide an internal combustion engine control signal processing system capable of picking up data at points in a range of a knock detection signal required for a frequency analysis and capable of processing signals with a higher degree of accuracy through the frequency analysis by using a memory with only a small storage capacity.
It is a third object of the present invention to provide an internal combustion engine control signal processing system capable of processing signals with a higher degree of accuracy by performing a frequency analysis using few values obtained as results of A/D-conversion carrying out at points for processing frequencies.
According to the present invention, a knock detection signal is produced from a knock sensor such as an ion current flowing between an ignition plug and the ground by filtering. This knock detection signal is then subjected to A/D-conversion in an A/D-converter to generate A/D-converted values which are subsequently supplied to a processing unit employed in a digital signal processor. In the processing unit, the A/D-converted values are subjected to a frequency analysis by Fourier transformation thereby to detect an engine state such as an occurrence of knock.
Preferably, in the frequency analysis, signal waveforms produced after a maximum amplitude waveform of the knock detection signal are used more in number than those produced before the maximum amplitude waveform.
Preferably, in the frequency analysis, a discrete Fourier transform algorithm is executed for a specific frequency of the knock detection signal, and a fast Fourier transform algorism is executed for other frequencies of the knock detection signal. More preferably, in the discrete Fourier transform algorithm, the A/D-converted values are used more in number than the number of the A/D-converted values.
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patent: 6-159129 (1994-06-01), None
patent: 6-281523 (1994-10-01), None
Denso Corporation
Nixon & Vanderhye P.C.
Wolfe Willis R.
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