Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2003-04-18
2004-06-15
Kwon, John (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C073S035080, C123S406210
Reexamination Certificate
active
06748922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knock control apparatus for an internal combustion engine that corrects control amounts or variables of the internal combustion engine in a direction to suppress knocking by detecting the occurrence of knocking in the internal combustion engine from an ionic current generated by combustion of an air fuel mixture therein. More particularly, it relates to a knock control apparatus for an internal combustion engine that is capable of preventing erroneous knock detection and detection miss when the magnitude of ionic current is varied due to differences among the rotational speed (or number of revolutions per minute) of the engine, load, environment, etc.
2. Description of the Related Art
Conventionally, in a knock control apparatus for an internal combustion engine, for the suppression of damage to the internal combustion engine due to the occurrence of knocking, a control amount or variable of the internal combustion engine is controlled such that it is corrected to a knock suppression side (for instance, an ignition timing retarding angle side)in accordance with the occurrence of knocking. In addition, a knock control apparatus for an internal combustion engine using an ionic current is limited in the difference in the knock detection sensitivity among the cylinders of the engine and hence effective to individually perform knock control on the respective cylinders, in view of which there have been conventionally proposed a variety of knock control apparatuses of such a type.
In general, in an internal combustion engine, a mixture of air and fuel introduced into the combustion chamber of each engine cylinder is compressed by the rising or compressing motion of a corresponding piston and fired by an electric spark generated by impression of a high voltage on a spark plug in the combustion chamber to produce a force that pushes down the piston so as to be taken out as output power. At this time, molecules in the combustion chamber are electrically dissociated or ionized when the mixture combusts in the combustion chamber, so an ionic current flows owing to the movements of ions through the spark plug when a high voltage is impressed on the spark plug (electrodes for ionic current detection) in the combustion chamber. It is known that the ionic current thus produced changes sensitively due to pressure fluctuations in the combustion chamber, and includes vibration components corresponding to knocking. Therefore, the presence or absence of knocking can be determined based on the ionic current.
In this kind of apparatus, a background level with respect to an ionic current detection signal is set so as to prevent erroneous knock detection due to noise superposed on an ionic current. In a known knock control apparatus, for an index of the magnitude of a knock (vibration) frequency that is obtained by subjecting a knock (vibration) frequency signal to waveform shaping processing, there is set a background level (i.e., noise level determination reference) that is calculated as the sum of the mean value of the index and a dead zone range (offset value) corresponding to the operating range of the engine (for instance, see a patent document: Japanese patent application laid-open No. 10-9108).
It is also known that the ionic current varies in its current level in accordance with differences in the environments such as the number of revolutions per minute (rpm) of the engine, load, temperature, etc. A vibration component superposed on the ionic current when knocking is taking place becomes large in its amplitude when the ionic current level is large, and small when the ionic current level is small. In other words, it will be understood that even if there took place knocking of the same magnitude, the result of an analysis on the frequency magnitude of an ionic current generated is varied according to a difference in the ionic current level. In the apparatus described in the above-mentioned patent document, when the knock frequency magnitude is varied in accordance with a variation in the level of the ionic current detection signal due to changes in the rotational speed (or number of revolutions per minute), load, environment, etc., an optimal offset value of the background level may often vary depending on the engine operating conditions. Thus, it is expected that if the offset of the background level is fixed over all the engine operating conditions, erroneous knock detection or detection miss will be caused. This problem can, however, be mostly solved if the offset value is mapped based on the relation between “the engine rotational speed (rpm)” and the “engine load”, for instance. However, it may be feared that when a difference between adjacent map values is great in the operating conditions between adjacent map axes, an optimal offset value cannot be obtained, thus making it impossible to ensure good knock controllability.
SUMMARY OF THE INVENTION
The present invention is intended to obviate the problems as referred to above, and has for its object to provide a knock control apparatus for an internal combustion engine which has substantially the same knock controllability in all the operating conditions of the internal combustion engine and does not need various corrections according to the operating conditions by normalizing the knock frequency magnitude and the level of background noise to substantially the same levels in all the operating conditions while taking into consideration a variation in the level of ionic current based on environments, the rotational speed (or the number of revolutions per minute) of the engine, engine load, etc.
Bearing the above object in mind, the present invention resides in a knock control apparatus for an internal combustion engine which includes: an ionic current detector for detecting an ionic current generated in a combustion chamber of the internal combustion engine immediately after ignition of an air fuel mixture therein; a frequency magnitude calculator for extracting the magnitude of a specific frequency from the ionic current; a knock determiner for determining based on the specific frequency magnitude whether the internal combustion engine is knocking; and a control parameter correction amount setter for setting an amount of correction for an ignition timing control parameter based on the result of the determination of the knock determiner. The frequency magnitude calculator includes: a frequency magnitude detector for detecting the specific frequency magnitude based on an output of the ionic current detector; an ionic current area calculator for calculating an ionic current area in a prescribed range within the combustion stroke of a cylinder concerned based on the output of the ionic current detector; and a corrector for correcting the detected specific frequency magnitude based on the calculation result of the ionic current area calculator. According to this arrangement, it becomes possible to perform knock control without being influenced by the magnitude of the ionic current level.
REFERENCES:
patent: 5836285 (1998-11-01), Aoki et al.
patent: 5900536 (1999-05-01), Mogi et al.
patent: 5905193 (1999-05-01), Hashizume et al.
patent: 5955664 (1999-09-01), Aoki et al.
patent: 6234146 (2001-05-01), Tanaya et al.
patent: 6311672 (2001-11-01), Morishita et al.
patent: 6427662 (2002-08-01), Tanaya et al.
patent: 6561163 (2003-05-01), Takahashi et al.
patent: 10-9108 (1998-01-01), None
Tanaya Kimihiko
Uchida Toshio
LandOfFree
Knock control apparatus for internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Knock control apparatus for internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Knock control apparatus for internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3298273