Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2000-06-08
2001-05-22
Kwon, John (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406250
Reexamination Certificate
active
06234145
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine control device for use in an internal combustion engine for performing a variety of controls such as ignition timing control, fuel injection timing control, etc., based on reference crank angles.
2. Description of the Prior Art
In an internal combustion engine, when the ignition timing is advanced or retarded or the fuel injection timing is advanced or retarded based on reference crank angles, it is usual to use a method of controlling by performing a predictive computation of the time required for reaching the target angle from the reference crank position based on the engine's rotational period. However, this method involves the following difficulties.
In the aforementioned method of performing predictive computation based on the rotational period, since the time from the latest reference crank angle signal to the necessary timing (e.g., the target ignition timing) is estimated based on the engine's rotational frequency (the time of one revolution) between the reference crank angle signal prior to the necessary timing and the reference crank angle signal one revolution before the former, the estimated value will be unstable with respect to the rotational variations (rotational changes) of the crankshaft.
In multi-cylinder engines, rotational variations occur due to combustion variations depending upon individual cylinders, which are attributed to intake amount scatter, the scatter in the sprayed amount of injected fuel, variation in the injector characteristics dependent on individual cylinders, variation in the carburetor characteristics dependent on individual cylinders. In particular, in the very low speed range in which lower amounts of fuel and intake air are used, the ratios of the above variations in the required amount of fuel and the amount of intake air become large and the rotational inertia is low, so that a slightest fluctuation in combustion for each cylinder may significantly affect the variations in rotation.
In a typical case where predictive computation is performed based on the rotational period of one revolution, for a four cycle engine, the period of one revolution (
FIG. 1
) for determining the target angle is affected by the combustion of other cylinders, hence the precision of the predictive computation is low in the very low rotational range where combustion fluctuations dependent on individual cylinders are liable to occur as stated above.
In the above predictive computing method, #1 ignition timing is controlled on the premise that the average rotational frequency during the period between #3&agr; and the previous #3&agr; is approximately equal to the average rotational frequency during the period from #3&agr; to the ignition timing, as is shown in
FIG. 2
, for example. In this case, the one revolution roughly corresponds to the combustion stroke of cylinder #3 and the compression and combustion strokes of cylinder #2. Since the average rotational frequency during this interval is used to estimate the average rotational frequency for the compression stroke of cylinder #1, the estimate naturally presents poor precision if there are variations in combustion dependent on individual cylinders.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above difficulties, and it is therefore an object of the present invention to provide an engine control device which is capable of performing engine control aiming at a target crank angle with high accuracy by detecting the periodicity of the variations in rotation of an internal combustion engine and estimating the variations in rotation.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, an engine control device includes:
a means for detecting crank angles;
a means for estimating the time required from a reference crank angle to a target crank angle based on the crank rotational frequency determined based on the detected crank angles;
a means for detecting crank rotational variations based on the signal inputs of crank angles;
a means for storing the rotational variations;
a means for detecting the periodicity of the rotational variations based on the stored rotational variations;
a means for correcting the estimated time from the reference crank angle to the target crank angle, based on the periodicity of the rotational variations; and
a means for outputting an engine control signal corresponding to the target crank angle based on the corrected time.
In accordance with the second aspect of the present invention, the engine control device having the above first feature is characterized in that the crank angle detecting means detects the rotational variations dependent on each cylinder.
In accordance with the third aspect of the present invention, the engine control device having the above first feature is characterized in that the estimation of the time is computed using the simple or weighted average of a multiple number of computed values.
In accordance with the fourth aspect of the present invention, the engine control device having the above second feature is characterized in that the estimation of the time is computed using the simple or weighted average of a multiple number of computed values.
In accordance with the fifth aspect of the present invention, the engine control device having the above first feature is characterized in that the estimated value or the control value is modified in accordance with the degree of advancement of the target crank angle.
In accordance with the sixth aspect of the present invention, the engine control device having the above second feature is characterized in that the estimated value or the control value is modified in accordance with the degree of advancement of the target crank angle.
In accordance with the seventh aspect of the present invention, the engine control device having the above first feature is characterized in that correction of the estimated time is made in a predetermined low rotational frequency range and will not be made in middle and high rotational frequency ranges, and engine control based on the rotational frequency is switched in accordance with a predetermined hysteretic scheme of rotational frequency.
In accordance with the eighth aspect of the present invention, the engine control device having the above second feature is characterized in that correction of the estimated time is made in a predetermined low rotational frequency range and will not be made in middle and high rotational frequency ranges, and engine control based on the rotational frequency is switched in accordance with a predetermined hysteretic scheme of rotational frequency.
In accordance with the ninth aspect of the present invention, the engine control device having the above third feature is characterized in that correction of the estimated time is made in a predetermined low rotational frequency range and will not be made in middle and high rotational frequency ranges, and engine control based on the rotational frequency is switched in accordance with a predetermined hysteretic scheme of rotational frequency.
In accordance with the tenth aspect of the present invention, the engine control device having the above fourth feature is characterized in that correction of the estimated time is made in a predetermined low rotational frequency range and will not be made in middle and high rotational frequency ranges, and engine control based on the rotational frequency is switched in accordance with a predetermined hysteretic scheme of rotational frequency.
In accordance with the eleventh aspect of the present invention, the engine control device having the above fifth feature is characterized in that correction of the estimated time is made in a predetermined low rotational frequency range and will not be made in middle and high rotational frequency ranges, and engine control based on the rotational frequency is switched in
Darby & Darby
Kwon John
Suzuki Motor Corporation
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