Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2000-02-09
2001-12-11
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406370, C073S035040, C073S035050, C073S035080
Reexamination Certificate
active
06328016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knock suppression control apparatus for an internal combustion engine, which apparatus is so arranged as to detect occurrence of knocking or knock event in the engine on the basis of level change of an ion current which flows by way of a spark plug upon combustion of an air-fuel mixture within a cylinder of the engine to thereby correct an engine control quantity so that occurrence of such knock event can be suppressed. More particularly, the present invention is concerned with a knock suppression control apparatus for an internal combustion engine, which apparatus is designed to avoid erroneous detection of the knock event notwithstanding of change or variation of the ion current which may be brought about due to retrofitting of the spark plugs and/or compositional difference of the air-fuel mixture charged in the engine cylinders and/or sooting state of the spark plug, to thereby ensure the knock suppression control with high reliability.
2. Description of Related Art
Heretofore, in the knock suppression control apparatus for the internal combustion engine, the control quantity or quantities for the engine have been so corrected as to suppress knock occurrence (e.g. by retarding the ignition timing, a typical one of engine control quantities) upon detection of the knock event in an effort to protect the engine against damage or injury due to the occurrence of knock event.
Further, the knock suppression control apparatus for the internal combustion engine in which the ion current flowing across the electrodes of the ignition plug is utilized for detecting the knock event can certainly detect occurrence of the knock on a cylinder-by-cylinder basis without resorting to any particular sensor dedicated for the knock detection, which is of course advantageous from the standpoint of cost reduction. For this reason, there have heretofore been proposed various types of knock suppression control apparatuses which can operate on the basis of the ion current.
In general, in the internal combustion engine, an air-fuel mixture charged into a combustion chamber defined within each of the engine cylinders is compressed by a piston moving reciprocatively within the cylinder, and a high voltage is applied to the spark plug disposed within the cylinder and exposed to the combustion chamber, whereby a spark is generated between the electrodes of the spark plug due to electric discharge. Thus,combustion of the compressed air-fuel mixture is triggered. Explosion energy resulting from the combustion is then converted into every for motion of the piston in the direction reverse to that in the compression stroke, which motion is translated into an output torque of the engine taken out therefrom via a crank shaft.
Upon combustion of the compressed air-fuel mixture within the combustion chamber in the engine cylinder, molecules prevailing within the combustion chamber are ionized. Thus, when a high voltage is applied to an ion current detecting electrode which is constituted by one of the electrodes of the spark plug, migration of ions carrying electric charges takes place between both the electrodes of the spark plug, which gives rise to flow of the ion current.
As is known in the art, magnitude of the ion current varies with a high sensitively in dependence on variation of the pressure prevailing within the combustion chamber and thus the ion current carries vibration components which are ascribable to the knock event. Thus, it is possible to decide on the basis of the ion current whether the knock event has occurred or not.
For having better understanding of the present invention, description will first be made of the technical background thereof in some detail.
FIG. 3
is a circuit diagram showing generally and schematically a structure of a hitherto known or conventional knock suppression control apparatus for an internal combustion engine which is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 9108/1998 (JP-A-10-9108). In the apparatus shown in
FIG. 3
, a high voltage is applied distributively to spark plugs of individual engine cylinders, respectively, through the medium of a distributor
7
.
The conventional apparatus shown in
FIG. 3
is so designed as to extract vibration components ascribable to the knock event and superposed on an ion current i for counting knock pulses which are resulted from waveform shaping of the knock vibration components, to thereby make knock decision (i.e., decision as to occurrence or non-occurrence of the knock event) on the basis of the number of the counted pulses (hereinafter also referred to as the pulses number).
Referring to
FIG. 3
, there is provided in association with a crank shaft (not shown) of an internal combustion engine (not shown either, hereinafter also referred to simply as the engine) a crank angle sensor
1
designed to output a crank angle signal SGT which contains a number of pulses generated at a frequency depending on a rotation number or speed (rpm) of the engine.
The leading edges of the individual pulses contained in the crank angle signal SGT indicate reference positions for the individual engine cylinders (not shown) in terms of the crank angles, respectively. The crank angle signal SGT is supplied to an electronic control unit (ECU)
2
which includes by a microcomputer or the like to be used for performing various controls as well as arithmetic operations therefor.
More specifically, the electronic control unit (ECU)
2
further includes a counter
21
for counting the number of pulses (also referred to as the pulses number) N of a knock pulse train Kp inputted from a waveform processing means (described later on) and a CPU (central processing unit)
22
constituting a major part of the microprocessor for deciding occurrence or non-occurrence of the knock on the basis of the pulses number N.
The counter
21
, the CPU
22
and the waveform processing means cooperate to serve as a knock detecting means.
The electronic control unit
2
is so designed or programmed as to fetch the engine operation information signals from various sensors (not shown) in addition to the crank angle signal SGT outputted from the crank angle sensor
1
and execute various arithmetic operations in dependence on the engine operation states, to thereby generate driving signals for a variety of actuators and devices inclusive of an ignition coil
4
and others.
An ignition signal P for driving the ignition coil
4
is applied to a base of a power transistor TR connected to a primary winding
4
a
of the ignition coil
4
for turning on/off the power transistor TR. More specifically, the power transistor TR is turned of f in response to the driving signal P, whereby a primary current i
1
flowing through the primary winding of the ignition coil
4
is interrupted.
Upon interruption or breaking of the primary current i
1
, the primary voltage v
1
making appearance across the primary winding
4
a
rises up steeply, as a result of which a secondary voltage v
2
further boosted up is induced in a secondary winding
4
b
of the ignition coil
4
and makes appearance thereacross as a voltage of high level for ignition, which voltage is usually on the order of several ten kilovolts. Hereinafter, this voltage will also be referred to as the high ignition voltage or simply as the ignition voltage. In this manner, the ignition coil
4
generates the secondary voltage V
2
(high ignition voltage) in conformance with the ignition timing of the engine.
The distributor
7
which is connected to an output terminal of the secondary winding
4
b
operates to apply distributively and apply the secondary voltage V
2
sequentially to spark plugs
8
a
, . . . ,
8
d
installed in the engine cylinders, respectively, in synchronism with the rotation of the engine, whereby spark discharges take place within the combustion chambers defined in the engine cylinders, respectively, triggering combustion or burning of the air-fuel mixture confined within the combus
Koiwa Mitsuru
Ohashi Yutaka
Okamura Koichi
Takahashi Yasuhiro
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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