Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2000-12-04
2002-11-05
Vo, Hieu T. (Department: 3754)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406280, C123S406130, C123S406370, C123S406160, C701S111000
Reexamination Certificate
active
06474302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knock control apparatus for internal-combustion engine, which detects ionization of combustion gas produced by combustion in an internal-combustion engine as ionic current, judges occurrence of a knock based on output from an ionic current detection device for detecting its combustion state, and performs control in order to avoid the knock.
2. Description of Related Art
In an ignition type internal-combustion engine (hereinafter, referred to as engine), a mixture of air and fuel to be introduced into a combustion chamber (hereinafter, referred to as cylinder) is compressed by a piston, and is burned by igniting with an ignition plug to take out power. The engine output and ignition timing relative to the cylinder position are closely related to each other, and generally when the ignition timing is advanced, high output can be obtained. In the case of excessive spark-advance, an abnormal combustion state called “knocking (knock)” occurs, and if the knocking continuously occurs, the engine may be broken.
When the mixture is burned within the cylinder, combustion gas is ionized, and therefore, when voltage is applied to it, current flows by the ionic action. This current is called “ionic current,” and sensitively varies in accordance with the combustion state within the cylinder. Therefore, it has been known that the combustion state (knocking state) can be detected by detecting the ionic current.
The ionic current is abruptly increased immediately after the ignition, and reaches the peak in a short time, and then gradually decreases. In the case where knocking occurs, a vibration component of several kHz is superimposed on the ionic current. On the basis of result of extraction of the vibration component corresponding to the knocking from the ionic current, the occurrence of knocking is judged, whereby when retard of the ignition timing is performed, high output can be obtained with the strength of the knocking and the frequency of its occurrence restrained.
As regards a knock control apparatus using ionic current, there has been previously proposed, by the present patent applicant, a knock control apparatus for internal-combustion engines provided with failure judgment means for judging an ionic current detection system for failure on the basis of, for example, the output from knocking strength detection means. When the output state of noise from each cylinder is judged in an operating range, in which noise ought to be detected, and the noise pulse output is obviously small, or when the filter value exceeds a predetermined value, this failure judgment means judges the cylinder concerned to be abnormal. Also, a retard angle for each cylinder will be determined in accordance with the number of cylinders which have been judged abnormal.
Hereinafter, with reference to
FIG. 6
, the detailed description will be made of a conventional example.
FIG. 6
is a flowchart showing failure judgment and control during failure according to the conventional example.
First, it is judged whether or not the operating condition is within a noise pulse judgment range (Step S
1
). If the noise pulse number is abnormally low or 0 (Step S
3
), this cylinder will be fail-judged (Step S
4
). Next, it is judged whether or not the operating condition is within a range in which the filter value is judged to be rising (Step S
2
). If the filter value is abnormally rising (Step S
5
), the cylinder will be fail-judged (Step S
6
).
Subsequently, the current number of fail cylinders is counted (Step S
7
), and it is judged whether or not the number of fail cylinders is equal to or less than a predetermined number of cylinders (Step S
8
). If not, the knock control will be inhibited to set a sufficient retard angle to all the cylinders (Step S
12
). If the number of fail cylinders is equal to or less than the predetermined number of cylinders, an average retard angle of the cylinders which are judged normal will be calculated (Step S
9
). A corrected retard angle corresponding to this cylinder will be acquired (Step S
10
), and the retard angle corresponding to this fail cylinder will be operated and set on the basis of the average retard angle of normal cylinders and the corrected retard angle (Step S
11
).
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
By the use of the knock control apparatus for internal-combustion engines proposed previously, it is possible to inhibit judgment of knocking for avoiding misjudgment of knocking and to perform ignition timing control based on safe ignition timing when, for example, high frequency noises are superimposed on ionic current to output a large quantity of noise signals, and when ionic current in some cylinders cannot be detected because of disconnected wiring in a vehicle body, failure of an ionic current detection circuit or the like.
In the conventional examples, however, there has not been proposed such a process as to stop failure judgment for returning to ordinary knock control when the detection state is continuously monitored and a normal state is recognized even after the failure judgment is performed. Therefore, for example, in the case where the engine is operated at a rich air fuel ratio, when soot temporarily adheres to plugs, when temporarily affected by radio wave of high intensity, when the engine has returned to a normal state by replacing the plugs although plug contamination advances and the degree of noise superimposition increases, or the like, temporarily noise superimposition has occurred, but when it is solved, the failure judgment cannot be stopped, but the engine cannot be returned to normal knock control.
In the case where the engine is operated at a rich air fuel ratio, when soot temporarily adheres to the plugs or the like, it has been experimentally found out that no noise superimposition occurs for each ignition, nor is the filter value so much raised, and it is difficult to judge failure by the filter value raised.
The present invention has been achieved in order to solve the above described problems, and is an object to obtain a knock control apparatus for internal-combustion engines having a function of judging whether or not the causes for failure have been solved for returning to ordinary knock control at the time of the solution, and capable of easily judging failure even in a failure mode in which it is difficult to raise the filter value and it is difficult to judge the failure in the conventional examples.
SUMMARY OF THE INVENTION
According to the invention of claim
1
, there is provided a knock control apparatus for internal-combustion engines, provided with: ionic current detection means for generating a signal corresponding to knocking based on the ionic current; background level setting means for filter-processing a knock detected signal value from the ionic current detection means to set a background level, which serves as a knocking criterion, based on the filter value; knock suppression and control means for judging the knocking based on the knock detected signal value and the background level to control at least ignition timing retard; and fail control means for performing control when knock detection cannot be properly performed, wherein the fail control means is provided with: failure judgment means for judging failure for each cylinder based on output from the background level setting means and the knock suppression and control means; number of fail cylinders judgment means for judging a number of fail cylinders based on the output from the fail judgment means; retard angle changing means for changing at least the retard angle of a fail cylinder based on the output from the knock suppression and control means, the fail judgment means and the number of fail cylinders judgment means; and normal judgment returning means for returning to normal ignition timing retard when a cylinder during fail judgment meets normal judgment requirements based on the output from the background level setting means and the retard angle changing
Koiwa Mitsuru
Morishita Tsutomu
Okamura Koichi
Takahashi Yasuhiro
Sughrue & Mion, PLLC
Vo Hieu T.
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