Measuring and testing – Engine detonation – Specific type of detonation sensor
Reexamination Certificate
1999-05-28
2001-03-27
Kwok, Helen (Department: 2856)
Measuring and testing
Engine detonation
Specific type of detonation sensor
Reexamination Certificate
active
06205844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combustion state detecting device that detects a combustion state of an internal combustion engine by detection of a change in the quantity of ions which are produced at the time of burning in the internal combustion engine, and more particularly to a combustion state detecting device for an internal combustion engine which is capable of diversifying detection functions by producing a plurality of currents analogous to an ion current to be detected.
2. Description of the Related Art
In general, in an internal combustion engine driven by a plurality of cylinders, the fuel-air mixture consisting of air and fuel introduced into the combustion chambers of the respective cylinders is compressed by moving up pistons, electric sparks are generated by applying an ignition high voltage to ignition plugs located in the respective combustion chambers, and an explosion force developed at the time of burning the fuel-air mixture is converted into a piston push-down force, to thereby extract the piston push-down force as an rotating output of the internal combustion engine.
There has been known that since molecules within the combustion chambers are ionized when the fuel-air mixture has been burned within the combustion chambers, ions having electric charges flow between the ignition plugs as an ion current upon application of a bias voltage to ion current detection electrodes (as usual, ignition plug electrodes are used) located within the combustion chambers.
Also, there has been known that the combustion state of the internal combustion engine can be detected by detection of a state in which the ion current occurs because the ion current is sensitively varied according to the combustion state within the combustion chambers.
FIG. 6
is a structural diagram showing one example of a conventional combustion state detecting device for an internal combustion engine.
In the figure, one end of a primary winding
1
a
of an ignition coil
1
is connected to a power supply terminal VB whereas the other end thereof is connected to the ground through a power transistor
2
having an emitter thereof grounded, which serves as a switching element for interrupting the supply of a primary current I
1
.
A secondary winding
1
b
of the ignition coil
1
constitutes a transformer in cooperation with the primary winding
1
a
, and a high-voltage side of the secondary winding
1
b
is connected to one end of an ignition plug
3
corresponding to each cylinder (not shown) to output a high voltage of negative polarity at the time of controlling ignition.
Each ignition plug
3
made up of counter electrodes is applied with an ignition high voltage to discharge and fire the fuel-air mixture within each of the cylinders.
It should be noted that the ignition coil
1
and the ignition plug
3
are disposed in parallel for each of the cylinders, however, in this example, only one pair of ignition coil
1
and ignition plug
3
are representatively shown.
A low-voltage side of the secondary winding
1
b
is connected to a bias circuit
6
through a resistor
4
and a diode
5
which are connected in parallel and constitute current limiting means.
The resistor
4
suppresses a discharge current that flows into the ignition plug
3
through the secondary winding
1
b
from the bias circuit
6
and suppresses a voltage developed at the high-voltage side of the secondary winding
1
b
at the time of starting the supply of the current to the primary winding
1
a.
The diode
5
is provided so that a direction in which the secondary current (ignition current) flows at the time of applying the ignition high voltage becomes forward, and is arranged so as to suppress a potential difference between both ends of the resistor
4
at the time of controlling ignition.
The bias circuit
6
applies a bias voltage of a polarity reverse to the ignition polarity, that is, the positive polarity to the ignition plug
3
through the resistor
4
and the secondary winding
1
b
to substantially detect an ion current corresponding to the quantity of ions generated at the time of burning.
The bias circuit
6
is connected to a current-voltage converter circuit
7
, and the current-voltage converter circuit
7
converts the ion current allowed to flow by the bias voltage into a voltage and applies the voltage thus converted to a voltage signal distributor circuit
8
as an ion current detection signal.
The voltage signal distributor circuit
8
distributes the ion current detection signal (ion signal) which has been converted into a voltage to a knock detection signal generator circuit
9
that extracts a knock signal from the ion signal and a combustion/misfire signal generator circuit
10
that produces a signal used for judging combustion/misfire according to the ion signal, respectively.
Then, output signals from the knock detection signal generator circuit
9
and the combustion/misfire signal generator circuit
10
are supplied to an ECU (electronic control unit)
11
. The ECU
11
judges the combustion state of the internal combustion engine on the basis of the output signal from the combustion/misfire signal generator circuit
10
, and conducts adaptive control appropriately so as not to cause inconvenience when detecting the deterioration of the combustion state.
Also, the ECU
11
arithmetically operates an ignition timing, etc., on the basis of drive conditions obtained from a variety of sensors (not shown) such as the knock detection signal generator circuit
9
or a crank angle sensor
12
to output not only an ignition signal V
1
to the power transistor
2
but also a fuel injection signal to an injector (not shown) for each of the cylinders and drive signals to a variety of actuators (a throttle valve, an ISC valve, etc.)
FIG. 7
is a circuit structural diagram showing an example of a specific circuit structure of the bias circuit, the current-voltage converter circuit and the voltage signal distributor circuit shown in FIG.
6
.
In the figure, the bias circuit
6
includes a capacitor
6
a
connected to a low-voltage side of the secondary winding
1
b
through the resistor
4
and the diode
5
which are connected in parallel, a diode
6
b
disposed between the capacitor
6
a
and the ground, and a Zener diode
6
c
for limiting bias voltage which is connected in parallel with the capacitor
6
a.
A series circuit consisting of the capacitor
6
a
and the diode
6
b
and the Zener diode
6
c
connected in parallel with the capacitor
6
a
are disposed between the low-voltage side of the secondary winding
1
b
and the ground through the diode
5
to constitute a charging path for charging the capacitor
6
a
with the bias voltage at the time of generating the ignition current.
The capacitor
6
a
is charged with the secondary current flowing therein through the ignition plug
3
which is discharged at a high voltage outputted from the secondary winding
1
b
when the power transistor
2
is off (when the supply of the current to the primary winding
1
a
is interrupted). The charge voltage is limited to a predetermined bias voltage (for example, about several hundreds V) by the Zener diode
6
c
and substantially functions as bias means for ion current detection, that is, a power supply.
A resistor
7
a
which is connected in parallel with the diode
6
b
and serves as the current-voltage converter circuit
7
converts the ion current allowed to flow by the bias voltage into a voltage, and supplies the voltage thus converted to the voltage distributor circuit
8
as the ion current detection signal.
The voltage signal distributor circuit
8
includes a plurality of buffers
8
a
and
8
b
, and the output side of the buffer
8
a
is connected to the knock detection signal generator circuit
9
while the output side of the buffer Bb is connected to the combustion/misfire signal generator circuit
10
.
Subsequently, the operation of the conventional combustion state detecting device for an internal combustion engine shown in
FIGS. 6 and 7
Koiwa Mituru
Morita Shingo
Ohashi Yutaka
Okamura Koichi
Kwok Helen
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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