Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2000-02-01
2001-10-09
Solis, Erick (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C324S399000
Reexamination Certificate
active
06298823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knock control apparatus for an internal combustion engine, which apparatus is designed for sensing or detecting 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 the engine cylinder to thereby correct an engine control quantity for suppressing the knocking. More particularly, the invention is concerned with a knock control apparatus for an internal combustion engine, which apparatus is arranged for suppressing erroneous detection of knock event in a sooting state of the spark plug to thereby evade erroneous knock suppression control.
2. Description of Related Art
Heretofore, in the knock control apparatus for the internal combustion engine, the control quantity or quantities for the engine have been so controlled as to suppress knock occurrence (e.g. by retarding the ignition timing, a typical one of engine control quantities) upon detection of knock event with a view to protect the engine against damage or injury due to the knock occurrence.
Further, the knock control apparatus for the internal combustion engine in which the ion current flowing by way of the ignition plug is made use of for the detection of knock event is capable of detecting magnitude of the knock on a cylinder-by-cylinder basis without resorting to the use of a knock sensor, which is advantageous for realizing cost reduction. Heretofore, various types of knock control apparatuses operative on the basis of the ion current have been proposed.
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. Subsequently, a high voltage is applied to a spark plug disposed within the cylinder and exposed to the combustion chamber, whereby a spark is generated between 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 a movement of the piston in the direction reverse to that of the compression stroke, which motion is translated into a torque outputted from the engine 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 an electrode of the spark plug, migration of ions carrying electric charges takes place between the electrodes of the spark plug, which gives rise to generation of an ion current.
As is known in the art, magnitude of the ion current varies with a high sensitively in dependence on the variation in pressure within the combustion chamber and contains 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 in some detail.
FIG. 5
is a block diagram showing generally a configuration of a hitherto known or conventional knock 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. 5
, a high voltage is applied distributively to spark plugs of individual engine cylinders, respectively, through the medium of a distributor.
The conventional apparatus shown in
FIG. 5
is so designed as to extract knocking vibration components superposed on an ion current i for counting knock pulses after waveform shaping of the known vibration components, to thereby make knock decision (i.e., decision as to knock occurrence) on the basis of the pulse counts number.
Referring to
FIG. 5
, there is provided in association with a crank shaft (not shown) of an internal combustion engine (not shown either and hereinafter also referred to simply as the engine) a crank angle sensor
1
which is adapted to output a crank angle signal SGT containing a number of pulses generated at a frequency which depends 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 angular reference positions for the individual engine cylinders in terms of crank angles, respectively. The crank angle signal SGT is supplied to an electronic control unit (ECU)
2
which may be constituted by a microcomputer, to be used for performing various controls and arithmetic operations therefor.
The electronic control unit
2
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
for deciding presence or absence of knocking on the basis of the pulses number N.
The counter
21
and the CPU
22
cooperate with the waveform processing means to constitute 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) as well as the crank angle signal SGT outputted from the crank angle sensor
1
and perform 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 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 off in response to the driving signal P, whereby a primary current i
1
is interrupted.
Upon interruption or breaking of the primary current i
1
, a primary voltage V
1
appearing 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 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 other words, the ignition coil
4
generates the secondary voltage V
2
(high ignition voltage) in conformance with the ignition timings of the engine.
The distributor
7
which is connected to an output terminal of the secondary winding
4
b
operates so as to distribute and apply the secondary voltage V
2
sequentially to spark plugs
8
a
, . . . ,
8
d
mounted in the engine cylinders, respectively, in synchronism with the rotation of the engine, whereby spark discharges take place within combustion chambers defined within the engine cylinders, respectively, triggering combustion or burning of the air-fuel mixture confined within the combustion chamber.
More specifically, with the spark discharges occurring across the spark plugs
8
a
, . . . ,
8
d
, respectively, in response to the application of the secondary voltage V
2
in conformance with the ignition timing of the engine, the air-fuel mixture within the cylinders is fired or ignited.
Connected between the other end of the primary winding
4
a
of the ignition coil
4
and the ground is a series circuit which is composed of a rectifier diode D
1
, a current limiting resistor R, a capacitor
9
connected in parallel with a voltage limiting Zener diode DZ and a rectifier diode D
2
. The series circuit mentioned above constitutes a path for allowing a charging current to flow to the capacitor
9
which constitutes a bias voltage source serving for supplying a bias voltage for detecting an ion current.
More spec
Koiwa Mitsuru
Morishita Tsutomu
Okamura Koichi
Takahashi Yasuhiro
Mitsubishi Denki & Kabushiki Kaisha
Solis Erick
Sughrue Mion Zinn Macpeak & Seas, PLLC
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