Measuring and testing – Engine detonation – Specific type of detonation sensor
Reexamination Certificate
2000-02-01
2002-03-26
Kwok, Helen (Department: 2856)
Measuring and testing
Engine detonation
Specific type of detonation sensor
Reexamination Certificate
active
06360586
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for detecting the knocking of an internal combustion engine based on an ionic current that flows through a spark plug during the combustion in the internal combustion engine. More specifically, the invention relates to a device for detecting the knocking of an internal combustion engine by preventing erroneous detection of noise or erroneous detection of knocking in a state in which the engine is being shifted toward producing an increased number of the signals of the knocking level or a decreased number of the signals of the knocking level.
2. Prior Art
In a device for controlling an internal combustion engine, so far, it is accepted practice to judge the occurrence of knocking during the operation and, when the occurrence of knocking is detected, the control quantity for the internal combustion engine is corrected toward the side of suppressing the knocking (e.g., toward the side of delaying the ignition timing) depending upon the amount of knocking in order to prevent damage to the internal combustion engine.
In order to detect the knocking of the internal combustion engine, therefore, there has been proposed a device that utilizes a change in the amount of ions produced during the combustion of the internal combustion engine.
The device for detecting the knocking of the internal combustion engine based on the ionic current is capable of detecting the intensity of knocking in each of the cylinders without using knock sensor, and is effective in decreasing the cost.
In the device of this type, a background level is set for an ionic current detection signal in order to prevent erroneous detection of the knocking caused by noise superposed on the ionic current.
In a device disclosed in, for example, Japanese Patent Laid-Open No. 10-9108, a background level (reference for judging the noise level) operated from the sum of an average value of the detection signal intensities and an insensitive region (offset value) based on the operation condition, has been set for a signal that is obtained by shaping the waveform of a knock current detection signal.
FIG. 6
is a block diagram schematically illustrating a conventional device for detecting the knocking of an internal combustion engine.
FIG. 7
is a timing chart illustrating the operation waveforms of signals in FIG.
6
and shows a case where a knock signal Ki is superposed on a waveform-shaped signal Fi of an ionic current detection signal Ei.
In
FIG. 6
, the ignition device
1
of the internal combustion engine includes an ignition coil having a primary winding and a secondary winding, and a power transistor (both of which are not shown) for interrupting the flow of the primary current i
1
(see
FIG. 7
) into the ignition coil.
The power transistor in the ignition device
1
turns on and off (flows and interrupts) the primary current il to the ignition coil in response to an ignition signal P from an ECU
5
, and the ignition coil generates a high ignition voltage V
2
(see
FIG. 7
) through the secondary winding in response to the turn on and off of the power transistor.
Being impressed with a high spark voltage V
2
from the ignition device
1
, the spark plug
2
generates a spark to ignite the mixture at a predetermined timing in each of the cylinders of the engine.
In order to detect the ionic current that flows across a gap of the spark plug
2
at the time of combustion, the ionic current detecting circuit
3
includes a bias means (capacitor) for applying a bias voltage to the spark plug
2
through the ignition coil in the ignition device
1
, and a resistor (both of which are not shown) for producing an ionic current detection signal Ei.
Various sensors
4
include a known throttle opening sensor, a crank angle sensor, a temperature sensor and the like sensors, and produce various sensor signals that represent the operation conditions of the internal combustion engine. For example, the crank angle sensor which is one of the various sensors
4
produces a crank angle signal SGT (see
FIG. 7
) depending on the rotational speed of the engine.
Various sensor signals inclusive of the ionic current detection signal Ei and the crank angle signal SGT, are input to the ECU
5
that comprises a microcomputer.
The crank angle signal SGT has a pulse edge representing a reference crank angular position in each cylinder, and is used by the ECU
5
for executing various control operations.
The ECU
5
includes a knock detecting means
6
for detecting the knocking based on the ionic current detection signal Ei, and an ignition control means
7
that delays the spark signal P based on the result of detecting the knocking by the knock detecting means
6
.
The knock detecting means
6
in the ECU
5
includes a filter means
11
comprising a band-pass filter, a counter means
12
, an averaging means
13
, an offset means
14
, and a comparator means
15
.
The filter means
11
includes a waveform-shaping means, and picks up a knock signal Ki in a predetermined frequency band from the waveform-shaped signal Fi (see
FIG. 7
) of the ionic current detection signal Ei.
The counter means
12
includes a waveform-processing means, and counts the number N of the pulses of the knock signals Ki after their shapes have been processed.
The counter means
12
constitutes a knocking level operation means, and operates the number N of the pulses (signals of the knocking level) corresponding to the knocking state of the engine.
The number N of the pulses (signals of the knocking level) represents the amount of knocking occurring.
The averaging means
13
averages the number N of the pulses to operate an average knocking level AVE.
The offset means
14
offsets the average knocking level AVE and forms a background level BGL (reference for judging the noise level).
The offset means
14
includes an offset operation means for operating an offset value OFS for the average knocking level AVE depending on the operation conditions of the engine, and a background level operation means for operating the background level BGL by adding up the average knocking level AVE and the offset value OFS together.
The comparator means
15
constitutes a knock-judging means, and compares the number N of the pulses (signals of the knocking level) with the background level BGL to judge the knocking state of the engine. When the number N of the pulses exceeds the background level BGL, the comparator means
15
produces the result of comparison representing the occurrence of knocking.
Next, described below with reference to
FIGS. 6 and 7
as well as a flow chart of
FIG. 8
is the operation of the conventional device for detecting the knocking of the internal combustion engine.
First, the ECU
5
receives a crank angle signal SGT and the like signals from various sensors
4
, executes various operations depending upon the operation conditions, and produces drive signals to various actuators such as the ignition device
1
and the like.
For example, the ECU
5
turns the power transistor in the ignition device
1
on and off in response to the ignition signal P to flow and interrupt the primary current i
1
.
In this case, the bias power source (capacitor) in the ionic current detecting circuit
3
is electrically charged with the primary voltage V
1
that generates in the ignition coil when the primary current i
1
flows therein.
Further, the primary voltage V
1
rises when the primary current i
1
is interrupted (corresponds to an ignition timing of the engine), and a further elevated secondary voltage V
2
(several tens of kV) is generated from the secondary winding of the ignition coil. The secondary voltage V
2
is applied to the spark plug
2
of a cylinder in which the ignition is controlled to burn a mixture in the combustion chamber.
As the mixture burns, ions generate in the combustion chamber of the combustion cylinder, and a bias voltage electrically charged in the capacitor in the ionic current detecting circuit
3
is discharged through the spark plug
2
immediately
Koiwa Mitsuru
Morishita Tsutomu
Okamura Koichi
Takahashi Yasuhiro
Tanaya Kimihiko
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