Measuring and testing – Engine detonation – Specific type of detonation sensor
Reexamination Certificate
1999-05-07
2001-03-06
Kwok, Helen C. (Department: 2856)
Measuring and testing
Engine detonation
Specific type of detonation sensor
C123S429000
Reexamination Certificate
active
06196054
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 accurately conducting knocking detection or misfire detection.
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. 8
is a circuit block diagram showing one example of a conventional combustion state detecting device for an internal combustion engine.
In the figure, an anode of a battery
1
mounted on a vehicle is connected to one end of a primary winding
2
a
of an ignition coil
2
whereas the other end of the primary winding
2
a
is connected to the ground through a power transistor
3
having an emitter thereof grounded for interrupting the supply of a primary current.
A secondary winding
2
b
of the ignition coil
2
constitutes a transformer in corporation with the primary winding
2
a
, and a high-voltage side of the secondary winding
2
b
is connected to one end of an ignition plug
4
corresponding to each cylinder (not shown) to output a high voltage of negative polarity at the time of controlling ignition.
The ignition plug
4
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.
The ignition coil
2
and the ignition plug
4
are disposed in parallel for each of the cylinders, however, in this example, only one pair of ignition coil
2
and ignition plug
4
are representatively shown.
A bias circuit
5
includes a capacitor
5
a
connected to a low-voltage side of the secondary winding
2
b
, a bias voltage limit Zener diode
5
b
connected in parallel with the capacitor
5
a
, and a diode
5
c
disposed between the capacitor
5
a
and the ground. A current-voltage convertor circuit
6
includes a resistor
6
a
connected in parallel with the diode
5
c.
A series circuit consisting of the capacitor
5
a
and the diode
5
c
and the Zener diode
5
b
connected in parallel with the capacitor
5
a
are disposed between the low-voltage side of the secondary winding
2
b
and the ground, to thus constitute a charging path for charging the capacitor
5
a
with the bias voltage at the time of generating the ignition current.
During the off state of the power transistor
3
(at the time of interrupting the supply of a current to the primary winding
2
a
), the capacitor
5
a
is charged with the secondary current that flows through the ignition plug
4
discharged by a high voltage outputted from the secondary winding
2
b
. The charge voltage is limited to a given bias voltage (for example, about several hundreds V) by the Zener diode
5
c
and functions as the ion current detection bias means, that is, a power supply.
The resistor
6
a
within the current-voltage convertor circuit
6
converts an ion current allowed to flow by the bias voltage into a voltage to output the voltage thus converted to a knock signal generator circuit
7
and a delay circuit
8
as an ion current detection signal. The knock signal generator circuit
7
is made up of a filter circuit
7
a
and a comparator circuit
7
b
. The filter circuit
7
a
extracts a high-frequency vibration component contained in an ion current detection waveform at the time of generating knocking. The comparator circuit
7
b
compares the output of the filter circuit
7
a
with a given reference value Vc and converts a comparison result into a rectangular wave.
The delay circuit
8
includes an operational amplifier
8
a
, a resistor
8
b
connected between a positive power supply terminal V
B
and the ground, and a capacitor
8
c
. The non-inverse input terminal of the operational amplifier
8
a
is connected to the output side of the current-voltage convertor circuit
6
, the inverse input terminal thereof is connected to a negative power supply terminal having a given reference value Va, and the output terminal thereof is connected to a node of the resistor
8
b
and the capacitor
8
c.
A comparator circuit
9
includes an operational amplifier
9
a
and a resistor
9
b
. The non-inverse input terminal of the operational amplifier
9
a
is connected to the output side of the delay circuit
8
, the inverse input terminal thereof is connected to a negative power supply terminal having a given reference value Vb, and the output terminal thereof is connected to the positive power supply V
B
through the resistor
9
b
and also connected to the base of the transistor
10
. The emitter of the transistor
10
is grounded, and the collector thereof is connected to the positive power supply terminal V
B
through a resistor
11
and also connected to the base of a transistor
12
.
The emitter of the transistor
12
is grounded, and the collector thereof is connected to the output side of the comparator circuit
7
b
, connected to the base of a transistor
14
and also connected to the positive power supply terminal V
B
through a resistor
13
. The emitter of the transistor
14
is grounded, and the collector thereof is connected to an ECU (electronic control unit)
15
. Structural elements
5
to
14
constitute a fuel state detector circuit
20
.
The ECU
15
made up of a microcomputer judges a combustion state of the internal combustion engine on the basis of the ion current detection signal, and if the ECU
15
detects the deterioration of the combustion state, it appropriately conducts adaptive control so as not to cause any inconvenience.
Also, the ECU
15
arithmetically operates an ignition timing, etc., on the basis of drive conditions obtained from a variety of sensors (not shown), and outputs not only an ignition signal to the power transistor
3
but also a fuel injection signal to an injector (not shown) for each cylinder, and drive signals to a variety of actuators (a throttle valve, an ISC valve, etc.).
Subsequently, the operation of the conventional combustion state detecting device for an internal combustion engine shown in
FIG. 8
will be described with reference to
FIGS. 9A
to
9
F. The left side of
FIGS. 9A
to
9
F shows signal waveforms appearing in the respective circuit portions when the internal combustion engine is in a low-revolution state, whereas the right side of
FIGS. 9A
to
9
F shows waveforms when it is in a high-revolution state.
In general, the ECU
15
arithmetically operates the ignition timing, etc., in accordance with the drive conditions, and supplies an ignition signal P shown in
FIG. 9A
to the base of the power transistor
3
at a desired control timing to control the on/off operation of the power transistor
3
.
As a result, the power tran
Koiwa Mituru
Ohashi Yutaka
Okamura Koichi
Kwok Helen C.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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