Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2000-02-01
2001-05-22
Solis, Erick (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
Reexamination Certificate
active
06234146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for detecting a knock of an internal combustion engine on the basis of an ionic current which flows in an ignition plug by combustion of fuel and for correcting the controlled variable of the internal combustion engine when the knock is detected. More particularly, the present invention relates to a knock control device for an internal combustion engine in which a relative reference value (background level) for knock judgement is calculated on the basis of an maximum noise level which is arithmetically estimated from a knock level signal to always optimize the background level, thereby preventing a misjudgment and a control error which are caused by the fluctuation of the noise level at unsteady time.
2. Description of the Related Art
Up to now, a knock control device for an internal combustion engine is designed in such a manner that it is judged whether a knock occurs during running, or not, and when it is detected that the knock occurs, the controlled variable of the internal combustion engine is corrected to a knock suppression side (for example, an ignition timing is corrected to a spark delay side) in response to the knock quantity in order to prevent the internal combustion engine from being damaged.
Also, in order to detect the knock of the internal combustion engine, there has been proposed a device using a change in the ion quantity which is caused by combustion of fuel.
The knock control device for the internal combustion engine using the ionic current is effective in realization of the reduced costs since the knock intensity can be detected for each of cylinders without using a knock sensor.
In the device of this type, in order to prevent the knock from being erroneously detected due to the superimposed noises of the ionic current, a noise judgement reference level (background level) is set with respect to an ionic current detection signal.
For example, in a device disclosed in Japanese Patent Unexamined Publication No. Hei 10-9108, a background level (judgment reference of the noise level) which is calculated from a sum of an average value of the detection signal intensity and an insensitive region (offset value) responsive to a running state is set with respect to a signal resulting from subjecting a knock current detection signal to a waveform shaping processing or the like.
FIG. 12
is a block diagram schematically showing a conventional knock control device for an internal combustion engine. Also,
FIG. 13
is a timing chart showing the operating waveforms of the respective signals in
FIG. 12
, and shows a case in which a knock signal Ki is superimposed on a waveform shaping signal Fi of an ionic current detection signal Ei.
Referring to
FIG. 12
, an ignition unit
1
of an internal combustion engine (engine) includes an ignition coil having a primary winding and a secondary winding, and a power transistor that permits or interrupts the flow of a primary current i
1
in the ignition coil (refer to FIG.
13
), both of which are not shown.
The power transistor within the ignition unit
1
conducts the on/off control (permission/interruption of the flow) of the primary current i
1
in the ignition coil in response to an ignition signal P from an ECU
5
, and the ignition coil generates an ignition high voltage V
2
from the secondary winding in response to the on/off operation of the power transistor (refer to FIG.
13
).
An ignition plug
2
generates an ignition spark due to the ignition high voltage V
2
which is applied to the ignition plug
2
from the ignition unit
1
and ignites an air-fuel mixture within each of cylinders of the engine at a given timing. In other words, the ignition high voltage is applied to the ignition plug
2
of each cylinder to be controlled in response to the ignition timing.
An ionic current detecting circuit
3
includes, in order to detect an ionic current that flows in a gap of the ignition plug
2
at the time of combustion, a bias means (capacitor) (not shown) for applying a bias voltage to the ignition plug
2
through the ignition coil within the ignition unit
1
, and a resistor (not shown) that outputs an ionic current detection signal Ei.
A variety of sensors
4
include a known throttle opening sensor, a crank angle sensor, a temperature sensor and so on, and produce a variety of sensor signals indicative of the running state of the internal combustion engine. For example, the crank angle sensor among the various sensors
4
outputs a crank angle signal SGT in response to the r.p.m. of the engine (refer to FIG.
13
).
The various sensor signals including the ionic current detection signal Ei and the crank angle signal SGT are inputted to the ECU
5
made up of a microcomputer. The crank angle signal SGT has a pulse edge representative of a crank angle reference position of each cylinder and are employed for various control operation within the ECU
5
.
The ECU
5
includes a means for detecting a knock from a knock level signal (which will be described later) based on the ionic current detection signal Ei, and an ignition control means
7
for correcting the spark delay of the ignition signal P on the basis of a knock detection result from the knock detecting means.
The ignition control means
7
includes, in order to produce the ignition signal P on the basis of the running state from the various sensors
4
and a knock judgement result from a comparing means
15
, an ignition timing operating means for deciding an ignition timing of the engine in response to the running state thereof and an ignition timing correcting means for arithmetically operating a spark delay quantity responsive to the knock detection quantity and allowing the spark delay quantity to be reflected on the ignition timing when the occurrence of knock is detected.
The controlled variable operating means for arithmetically operating the controlled variable of the engine is not limited to the ignition control means
7
but includes a fuel injection control means (not shown) for arithmetically operating a fuel injection amount and an injection timing, and so on. Also, the control variable correcting means for suppressing the knock can correct the spark delay of the fuel injection timing.
A knock detecting means is made up of a filtering means
11
formed of a band-pass filter, a counter means
12
, an averaging means
13
within the ECU
5
, an offset means
14
and a comparing means
15
.
The filtering means
11
, which includes a waveform shaping means, extracts a knock signal Ki having a given frequency band from a waveform shaping signal Fi (refer to
FIG. 13
) of the ionic current detection signal Ei. The counter means
12
, which includes a waveform processing means, counts the number of pulses N of the knock signal Ki after waveform processing is performed.
The counter means
12
constitutes a knock level calculating means and calculates the number of pulses N (knock level signal) corresponding to the knock state of the engine on the basis of the knock signal Ki. The number of pulses N (knock level signal) represents the amount of knock occurrence.
The averaging means
13
averages the number of pulses N and calculates a knock level average value AVE. The offset means
14
offsets the knock level average value AVE and produces a background level BGL (noise level judgement reference).
The offset means
14
includes offset calculating means for calculating an offset value OFS with respect to the knock level average value AVE in response to the running state of the engine, and a background level calculating means for calculating the background level BGL by adding the knock level average value AVE and the offset value OFS.
The comparing means
15
constitutes a knock judging means and compares the number of pulses N (knock level signal) with the background level BGL to judge the knock state of the engine. The comparing means
15
outputs a comparison result indicative of a knock occurrence when the number of pulses N exceeds the background level BGL.
Hatazawa Yasuyoshi
Koiwa Mitsuru
Takahashi Yasuhiro
Tanaya Kimihiko
Mitsubishi Denki & Kabushiki Kaisha
Solis Erick
Sughrue Mion Zinn Macpeak & Seas, PLLC
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