Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2002-05-21
2004-03-09
Vo, Hieu T. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406390
Reexamination Certificate
active
06701894
ABSTRACT:
The present disclosure relates to a subject matter contained in Japanese Patent Application No.2001-165403 filed on May 31, 2001, which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knocking control apparatus used preferably in ignition timing control of an internal combustion engine, etc.
2. Description of the Related Art
The spark ignition internal combustion engine can get the higher output if the compression ration of the mixed gas is increased higher. In this case, if the compression ration is increased, sometimes the unburned gas is burst up prior to the flame during the propagation of the flame in the cylinder after the spark is sent off into the mixed gas being sucked into the cylinder, i.e., the so-called knocking occurs. If the knocking occurs in the internal combustion engine, not only the engine operates irregularly because the pressure is applied irregularly to the piston but also the engine temperature is increased to lower the thermal efficiency, so that the engine output is lowered. Therefore, in the internal combustion engine, it is decided whether or not the knocking is occurring and then the control to suppress the knocking occurrence is executed by adjusting the ignition timing, for example, if the knocking is occurring.
There is the method that the knock sensor made of the piezoelectric element, or the like is provided in the cylinder and then the decision of the knocking in the internal combustion engine is carried out based on the output of the knock sensor. When the spectrum of the output of the knock sensor is picked up, the output sensed when the knocking occurs becomes larger than that sensed when the knocking does not occur. The difference between the output obtained when the knocking occurs and the output obtained when the knocking does not occur is not uniform over the full frequency of the output of the knock sensor, and appears prominently at the particular frequencies. The frequency at which the difference of the outputs appears remarkably is called the resonance frequency.
The knock sensor whose sensing range is limited only to the resonance frequency band in which the difference of the outputs is large is called the resonance-type knock sensor. In the resonance-type knock sensor, the particular frequency is decided previously by the setting of the sensor itself. That is, the resonance frequency is identified/set to the frequency band, in which it is roughly predicted that the difference of the outputs is increased commonly, at the sacrifice of the characteristics, which are different every cylinder of the internal combustion engine, the states such as the engine speed, etc., and the S/N ratio. Therefore, such resonance frequency of the resonance-type knock sensor employed in the mass-produced same-type internal combustion engine is set equal. However, as described above, the resonance frequency is different every type of the internal combustion engine, and is different based on the engine speed of the internal combustion engine and the individual cylinder of the internal combustion engine. As a result, the resonance-type knock sensor, whose resonance frequency is uniformly fixed, cannot sense the knocking, which occurs in the case that such resonance frequency is not suited to the cylinder, the rotation speed, etc., with good precision.
Therefore, the flat sensor in which the frequency of the knock sensor is not fixed to the particular frequency is employed such that the setting of the flat sensor itself can be changed every type of the internal combustion engine, every engine speed, and every cylinder, i.e., the different resonance frequency can be set every flat sensor. However, since the resonance frequency being set once in one flat sensor is fixed in such flat sensor, the resonance frequency set in one flat sensor is deviated from the frequency at which the knocking occurs even if such frequency at which the knocking occurs is varied due to the time-dependent change, etc. As a result, the knocking cannot be sensed with good precision. That is, there is the problem that, even if the flat sensor is employed, the knocking cannot be sensed continuously for a long term with good precision.
The related art for overcoming this problem is disclosed in Patent Application Publication (KOKAI) Hei 8-177697, for example. According to this related art, the standard deviation is calculated in the level distribution of the output of the knock sensor, then the standard deviation is compared with the predetermined value, then it is decided that the resonance frequency is deviated if the standard deviation is below the predetermined value, and then the knocking sensing precision can be improved by correcting the resonance frequency.
This related art has following problems. The knocking decision period, i.e., the time point and the period to start the extraction of the output of the knock sensor, is fixed every knock sensor. Therefore, since the knocking occurring timing is shifted in the cycle of the internal combustion engine with the time-dependent change of the internal combustion engine, in some cases the output of the knocking is positioned on the outside of the knocking decision period, and thus there is the problem such that the knocking cannot be sensed.
Also, in the cycle of the internal combustion engine, there is the phenomenon such that the vibration is generated at the ignition timing, the seating timing of the suction and exhaust valve, etc. based on the causes except the knocking. These outputs of the vibration by the knock sensor due to the ignition timing, the seating timing of the suction and exhaust valve, etc. are the noises that act as the trouble in sensing the knocking. Because the knocking occurring timing is shifted, there is the case where both the output of the vibration due to the knocking and the noise are contained in the knocking decision period. If both the output of the knocking and the noise are contained in the knocking decision period, it is difficult to discriminate the output of the knocking from the noise. Thus, there is the problem such that the knocking sensing precision is lowered.
It is an object of the present invention to provide a knocking control apparatus for an internal combustion engine, capable of correcting a knocking decision period so as to respond to a variation in a knocking occurring timing and also achieving an excellent knocking sensing precision.
SUMMARY OF THE INVENTION
The present invention provides a knocking control apparatus for an internal combustion engine, having a knock sensor for sensing a knocking of the internal combustion engine, a crank angle sensor for sensing a rotation angle position of a crank provided to the internal combustion engine, a setting unit for setting a decision period in which an output of the knock sensor is extracted to decide whether the knocking occurs in response to an output of the crank angle sensor, a storing unit for storing the decision period, a changing unit for changing the set decision period to contain the output of the knock sensor in response to the knocking with a situation in which the knocking occurs, a calculating unit for calculating a difference between the decision period, which is changed to contain the output of the knock sensor in response to the knocking, and the decision period, which is stored in the storing unit, and a correcting unit for correcting the decision period stored in the storing unit in response to an output of the calculating unit to reduce an absolute value of the difference.
According to the present invention, the previously-set decision period can be changed by the changing unit to contain the output of the vibration generated by the knocking, and also the difference between the changed decision period and the decision period stored in the storing unit is calculated and then the decision period stored in the storing unit can be corrected based on the calculated result. According to this, even if the knocking occurring timing
Fujitsu Ten Limited
Huynh Hai
Oliff & Berridg,e PLC
Vo Hieu T.
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