JPH1030541A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device which can eliminate the noise caused by an ion signal and detect misfire appropriately according to the combustion condition of each ignition. SOLUTION: This ignition device is provided with an ignition coil 1 involving a primary coil L1 and a secondary coil L2, an ignition control circuit 2 which is connected to the primary coil L1 to control primary current intermittently according to an ignition timing signal, an ignition plug 3 which involves at least a pair of electrodes and whose one electrode is connected to one end of the secondary coil L2, and an ion signal detecting circuit 4 which is provided through a secondary circuit including the ignition plug 3 and the secondary coil L2, and converts electric current corresponding to an ion in the vicinity of the ignition plug 3 into a voltage signal to detect an ion signal. For an operation amplifier OP1 which amplifies the ion signal for outputting, a gain in the operation amplifier OP1 is set so as to be low while voltage is being generated in the primary coil L1 and for a prescribed time after voltage disappearance by a gain setting circuit 6 and is adjusted by a gain adjustment circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine, and more particularly to an ignition device for an internal combustion engine capable of detecting misfire by ionic current.

[0002]

2. Description of the Related Art In general, an ignition device for an internal combustion engine interrupts a primary current of a primary coil in accordance with an ignition timing signal based on an operation state of the internal combustion engine by an ignition control circuit, thereby generating a secondary coil. A high voltage is supplied to a spark plug provided in each cylinder of the internal combustion engine to generate a spark discharge,
The mixture is ignited in each cylinder. Then, an ignition device in which an ignition coil is provided for each ignition plug has become widespread.

Further, in recent years, it has been required to establish a means for performing appropriate misfire detection in an ignition device, and there has been an urgent need to develop a misfire detection means instead of the so-called ΔNe method based on the conventional crankshaft rotation speed. I have. Among them, a misfire detection means using an ion signal detection circuit has attracted attention. This detection principle utilizes the fact that various ions are present in a flame in a cylinder of an internal combustion engine, and a current flows when an electrode having a potential is arranged in the flame.
Therefore, an ion signal detection circuit is used to detect an ion current or an ion signal obtained by converting the ion current into a voltage. Since the electrode of the ignition plug can be used for this current detection, it is not necessary to newly provide a sensor, and the current can be easily applied to the misfire detecting means.

For example, Japanese Patent Application Laid-Open No. 7-91357 discloses that combustion ionization measurement is synchronized with the engine position, combustion ionization measurement is performed, and it is determined whether misfire (misfire) has occurred based on the combustion ionization measurement. In addition, there has been proposed a method of detecting a misfire in a cylinder of an internal combustion engine by performing catalyst damage due to occurrence of misfire and a predetermined test.

[0005]

FIG. 6 shows a basic configuration of a general igniter provided with an ion signal detecting circuit. The capacitor charges a discharge current at the time of spark discharge by an ignition coil to a charging voltage. Is applied to the ignition plug as a bias voltage to provide an ion current. That is, the primary coil L1 and the secondary coil L
An ignition control circuit (also referred to as an igniter or an ignition module) 2 connected to one end of the primary coil L1 to interrupt the primary current;
An engine control unit ECU is connected to the ignition control circuit 2 and outputs an ignition timing signal according to an operation state of an internal combustion engine (not shown). A power supply Vcc is connected to the other end of the primary coil L1, and a secondary The ignition plug 3 is connected to one end of the coil L2. And the secondary coil L2
On the side, an ion signal detection circuit 4 is further provided. That is, the capacitor C1 is connected to the other end of the secondary coil L2, the resistor R1 is connected to the capacitor C1, and the Zener diode ZD1 is connected in parallel with the capacitor C1.
Are connected and these are Zener diodes ZD
2 is grounded.

In the ignition device shown in FIG. 6, an ignition timing signal IGt is supplied from the engine control unit ECU to the ignition control circuit 2, and the Darlington transistor DTR is turned on / off in accordance with the ignition timing signal, and the primary coil The primary current of L1 is interrupted. In response to the interruption of the primary current, a counter electromotive force is induced on the secondary coil L2 side to generate a high voltage, and this high voltage is applied between the electrodes of the ignition plug 3 to generate a spark discharge. Thereby, the spark plug 3, the secondary coil L2, the capacitor C
1. A current flows through the Zener diode ZD2 and the ground (ground side). At this time, the Zener diode Z
D1 limits the bias voltage to not more than the withstand voltage of the capacitor C1, and suppresses fluctuations in the bias voltage. Further, the capacitor C1 is quickly charged by the presence of the zener diode ZD2.

[0007] When spark discharge occurs in the spark plug 3 and combustion and explosion of the air-fuel mixture are normally performed in the cylinder, the pressure and temperature in the cylinder rise and the electrode of the spark plug 3 is increased. Ions are generated around the part as described above. At this time, the capacitor C1 has 100 to several hundred volts.
Since the charging voltage is applied to the ignition plug 3 as a bias voltage, a discharge current flows through a discharge circuit including the resistor R1, the capacitor C1, the secondary coil L2, the ignition plug 3, and the ground. This current is detected as a negative voltage by the resistor R1. On the other hand, when the combustion in the cylinder is insufficient and a normal explosion is not performed and a so-called misfire occurs, ions rise around the electrode portion of the ignition plug 3 because the pressure rise and the temperature rise in the cylinder are small. not exist. For this reason, the resistance of the air gap between the electrodes of the ignition plug 3 becomes large, so that the capacitor C
No discharge current of 1 flows, and no voltage change occurs in the resistor R1. Thus, misfire of the internal combustion engine is detected.

A misfire detection operation based on an ion signal in the ignition device of FIG. 6 will be described with reference to FIGS.
FIG. 7 shows the operation waveform of each signal shown in the circuit of FIG. First, an ignition timing signal IGt of a square wave voltage signal is output from the engine control unit ECU according to the rotation of an internal combustion engine (not shown). At time t1 when the ignition timing signal IGt becomes high level (H), the Darlington transistor DTR of the ignition control circuit 2 becomes conductive, supply of the primary current PRc to the primary coil L1 is started, and the ignition timing signal IGt becomes low level ( L)
Is supplied until time t3 when At time t2, the time when the constant current control for the primary current PRc is started is indicated.
v represents the voltage of the primary coil L1.

When the ignition timing signal IGt goes low (L) at time t3, a high voltage of about 35 kV is induced in the secondary coil L2. Thereby, the discharge voltage of the ignition plug 3 is reached, and a discharge current flows immediately after t3 (not shown). With this discharge, the capacitor C1 is charged by the secondary current flowing through the secondary coil L2, rises to the set voltage of the Zener diode ZD1, and the voltage is maintained as the bias voltage Vb. Thus, a spark discharge is generated in the electrode portion of the ignition plug 3, and the compressed air-fuel mixture in the cylinder is ignited. This explodes the air-fuel mixture, and an ion current flows as the temperature and pressure in the cylinder rise. This ion current is detected as a voltage drop of the resistor R1, and becomes an ion signal INv of a voltage signal shown in FIG.

That is, whether combustion has occurred in the cylinder (ignition or misfire) depends on the characteristics shown in FIG. 8 at the time of firing when the fuel is supplied to the internal combustion engine and the motor is driven without supplying the fuel. If the characteristics at the time of motoring driven by the above are compared, when combustion occurs, a voltage drop (hereinafter referred to as a spark discharge signal Fs) due to an ion current indicated by Fs in FIG.

However, in each of FIGS. 8 and 9, it is difficult to identify the spark discharge signal Fs because noise is included as indicated by Na, Nb, and Nc. For example, in the peak value determination method of comparing the peak values of the signals, the noise may be larger, and therefore the spark discharge signal Fs cannot be specified. Further, even if the difference between the spark discharge signal Fs and the noise is small, it is difficult to specify the spark discharge signal Fs by the area method in which the amount of change in the spark discharge signal Fs is converted into an area. As will be described later, various noises may occur depending on the circuit design, but these can be dealt with individually.

The above-mentioned noises Na, Nb, and Nc can each specify the generation time as shown in FIG. That is, the noise Na is the time when the supply of the primary current PRc is started, the noise Nb is the time when the discharge ends (after the ignition timing signal IGt becomes low level), and the noise Nc is the time when the constant current control for the primary current PRc is started. It can be seen from FIG. Therefore, by adjusting the ion signal detection circuit according to the generation time of each noise, it is possible to remove noise at the time of misfire detection. In particular, the noise Nb occurs exactly at the end point of the primary voltage, and the end point of the primary voltage varies depending on the combustion state for each ignition. For this reason, if the removal of noise is too long, ion signals may be removed. Therefore, it is desirable to remove noise based on the end point of the primary voltage.

Accordingly, the present invention provides an ignition device for an internal combustion engine provided with an ion signal detection circuit, which removes noise from the ion signal and reliably detects the ion signal, thereby enabling appropriate misfire detection. The task is to provide

Another object of the present invention is to provide an ignition device which can remove noise generated particularly near the timing of generation of an ion signal and can appropriately perform misfire detection according to the combustion state of each ignition. I do.

[0015]

In order to achieve the above object, the present invention provides an ignition coil having a primary coil and a secondary coil, and an intermittent control of a primary current connected to the primary coil and according to an ignition timing signal. An ignition control circuit, an ignition plug connected to the secondary coil and having at least a pair of electrodes, a secondary circuit including the ignition plug and the secondary coil, and the ignition plug interposed in the secondary circuit. In an ignition device for an internal combustion engine provided with an ion signal detection circuit for converting a current corresponding to nearby ions into a voltage signal and detecting the ion signal, the ignition device is connected to the ion signal detection circuit and amplifies and outputs the ion signal An operational amplifier, a gain adjusting circuit for adjusting the gain of the operational amplifier, and a voltage generated in at least the primary coil with respect to the gain adjusting circuit; and During a predetermined time after the voltage loss is obtained by a further comprising a gain setting circuit gain of the operational amplifier than when the voltage on the primary coil does not occur is set to be lower.

In the ignition device for an internal combustion engine, as set forth in claim 2, the gain adjustment circuit includes at least a first feedback resistor connected in parallel to the operational amplifier, and a first feedback resistor connected in parallel to the operational amplifier. And a second feedback resistor having a different resistance value and connected in parallel to the first feedback resistor, and conducting one of the first and second feedback resistors to the operational amplifier and the other The gain setting circuit detects a voltage of the primary coil and outputs a detection signal, and after the detection signal of the primary voltage detection circuit disappears, A delay circuit that outputs a delay signal for a predetermined time,
While the gain setting circuit is outputting at least the detection signal and the delay signal, the switch means conducts the feedback resistance of the first and second feedback resistances having a lower resistance value. It is better to switch to.

For example, the second feedback resistor having a smaller resistance value than the first feedback resistor and a normally open analog switch are connected in series, and these are connected in parallel to the operational amplifier. At least while the detection signal and the delay signal are being output, the switch means of the gain adjustment circuit can be configured to be closed. Alternatively, first and second analog switches are respectively connected in series to the first and second feedback resistors, and these are connected in parallel to the operational amplifier, respectively. The second analog switch is closed and the second analog switch is opened, and at least while the detection signal and the delay signal are being output, the first analog switch is opened and the second analog switch is closed. You can also.

Further, as set forth in claim 3, the gain setting circuit is configured to determine the logical sum of an ignition timing signal of the ignition control circuit, a detection signal of the primary voltage detection circuit, and a delay signal of the delay circuit. The switching means may be configured to be switched.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an ignition device for an internal combustion engine according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. An ignition coil 1 having a primary coil L1 and a secondary coil L2, and a Darlington transistor DTR connected to one end of the primary coil L1 to generate a primary current according to an ignition timing signal. An ignition control circuit 2 for intermittent control and an engine control unit ECU connected to the ignition control circuit 2 and outputting an ignition timing signal according to the ignition timing are provided. An ignition plug 3 having at least one pair of electrodes, one end of which is connected to one end of the secondary coil L2; and an ignition plug 3 and a secondary coil L2.
Is provided. An ion signal detection circuit 4 is interposed in the secondary circuit, and an ion current corresponding to ions near the spark plug 3 is detected here. This ion current is converted into a voltage signal via the resistor R1 and the operational amplifier OP1 as an operational amplifier and amplified. A power supply (Vcc) is connected to the other end of the primary coil L1, and the ignition plug 3
Is grounded.

In the ion signal detection circuit 4, a capacitor C1 is connected to the other end of the secondary coil L2, a resistor R1 is connected in series with the capacitor C1, and a zener diode ZD1 is connected in parallel with the capacitor C1. And these are grounded via a Zener diode ZD2. The resistor R1 is connected to an operational amplifier OP
1, the non-inverting input terminal of the operational amplifier OP1 is grounded, and an ignition signal is output from the output terminal OT. This operational amplifier OP1
In contrast, a first feedback resistor R2 is connected in parallel to form an inverting amplifier circuit, and a capacitor C2 is connected in parallel. A gain adjustment circuit 5 including the first feedback resistor R2 and the capacitor C2 to adjust the gain of the operational amplifier OP1 is configured.

Further, the gain adjustment circuit 5 includes a series circuit of a second feedback resistor R3, a capacitor C3, and an analog switch AS having a resistance much lower than that of the first feedback resistor R2. It is connected in parallel to the operational amplifier OP1 (and the first feedback resistor R2 and the capacitor C2). The capacitor C2 removes minute noise and constitutes a so-called low-pass filter. In addition, the capacitor C3 is provided to reduce a minute noise that remains even when the gain is adjusted as described later. Then, for the gain adjustment circuit 5,
A gain setting circuit 6 for setting the gain of the operational amplifier OP1 according to the ignition timing signal is provided.

The gain setting circuit 6 includes an OR circuit ORG,
It comprises an operational amplifier OP3 and the like connected to this input side,
A primary voltage detection circuit 6a and a delay circuit 6b are configured. As shown in FIG. 1, the OR circuit ORG is connected to receive the ignition input signal GIa synchronized with the ignition timing signal IGt as it is or via an appropriate buffer (not shown). ing. In the primary voltage detection circuit 6a, the ground side of the primary coil L1 is connected to the inverting input terminal of the operational amplifier OP2 via the resistors R4 and R5, and the connection point between the resistors R4 and R5 is grounded via the resistor R6. The non-inverting input terminal of the operational amplifier OP2 is connected to the connection point of the resistors R7 and R8, and a voltage obtained by dividing the power supply voltage Vcc is applied to the non-inverting input terminal. The output terminal of the operational amplifier OP2 is connected to the base of the transistor Tr1 whose emitter is grounded.
9 is connected to a power supply (Vcc). The connection point between the transistor Tr1 and the resistor R9 is connected to the OR circuit ORG.
And the base of the transistor Tr2 of the delay circuit 6b. Therefore, the operational amplifier OP2 outputs the primary voltage signal P as shown in FIG.
When Rv exceeds a predetermined threshold level, a detection signal GIc that becomes high level (H) is output, and this detection signal GIc is input to the OR circuit ORG.

In the delay circuit 6b, the transistor T
A capacitor C4 is connected in parallel between the collector and the emitter of r2, and the collector side is connected to the inverting input terminal of the operational amplifier OP3. The non-inverting input terminal of the operational amplifier OP3 is connected to a connection point between the resistors R10 and R11, and a voltage obtained by dividing the power supply voltage Vcc is applied to the non-inverting input terminal. The inverting input terminals of the capacitor C4, the transistor Tr2 and the operational amplifier OP3 are connected to a power supply (Vcc) via a constant current circuit SC1. Thus, as shown in FIG. 2, the delay signal GIb, which is the output signal of the operational amplifier OP3, is turned on (high level) for a predetermined time td after the detection signal GIc, which is the output of the operational amplifier OP2, falls. This predetermined time td
Is set to, for example, 100 μsec, and is set to a time that can include the noise Nb as shown in FIG.

The LC resonance reducing circuit 7 reduces the LC resonance at the end of the primary voltage to prevent the influence on the ion signal.
After the ignition timing signal IGt is turned off (low level), the primary coil L1 is short-circuited after elapse of, for example, 100 μsec until the next ignition timing signal IGt turns on (high level). Transistor T
A capacitor C5 is connected in parallel between the collector and the emitter of r3, and the collector is connected to the inverting input terminal of the operational amplifier OP4. The non-inverting input terminal of the operational amplifier OP4 is connected to a connection point between the resistors R12 and R13, and a voltage obtained by dividing the power supply voltage Vcc is applied to the non-inverting input terminal. The inverting input terminals of the capacitor C5, the transistor Tr3, and the operational amplifier OP4 are connected to a power supply (Vcc) via a constant current circuit SC2. The output terminal of the operational amplifier OP4 is connected to the base of the transistor Tr4, and the collector of the transistor Tr4 is connected to the power supply (Vcc) via the resistor R14. The connection point between the transistor Tr4 and the resistor R14 is connected to the field effect transistor FET. This field effect transistor FET is connected in parallel with the primary coil L1 together with the resistor R15. When the field effect transistor FET is turned on, the primary coil L1 is turned on.
1 is configured to be short-circuited.

According to the ignition device having the above configuration, the ignition timing signal IGt is output from the engine control unit ECU according to the rotation of the internal combustion engine (not shown). When the primary current of the primary coil L1 is interrupted in response to the ignition timing signal IGt, a high voltage is generated on the secondary coil L2 side and applied between the electrodes of the ignition plug 3. As a result, a spark discharge occurs in the spark plug 3, and when the combustion and explosion of the air-fuel mixture are normally performed in the cylinder, ions are present around the electrode portion of the spark plug 3. A discharge current flows through the circuit. This current is connected to the resistor R1
Can be detected as a voltage signal at this time, but at this time, the voltage is limited to the withstand voltage of the capacitor C1 or less by the Zener diode ZD1. Then, the voltage signal is inverted and amplified through the inverting amplifier circuit of the operational amplifier OP1, and is output from the output terminal OT as a voltage signal indicating normal ignition. On the other hand, if a misfire occurs in a cylinder (not shown),
No ions exist around the electrode portion of the spark plug 3. Accordingly, since the discharge current of the capacitor C1 does not flow and the voltage of the resistor R1 does not change, misfire of the internal combustion engine is detected.

The operation of the generation of noise accompanying the above-mentioned misfire detection and its removal will be described with reference to the waveform diagram shown in FIG. First, the engine control unit ECU
At the time t1 when the ignition timing signal IGt output from the IC becomes high level (H), the Darlington transistor DTR of the ignition control circuit 2 becomes conductive, supply of the primary current to the primary coil L1 is started, and the ignition timing signal IG
It is supplied until t3 when t becomes a low level (L).

At time t3, the ignition timing signal IG
When t becomes a low level (L), about 3 is applied to the secondary coil L2.
Since a high voltage of 5 kV is induced to reach the discharge voltage of the ignition plug 3, a discharge current flows immediately after time t3. With this discharge, the capacitor C1 is charged by the secondary current flowing through the secondary coil L2, and the set voltage of the Zener diode ZD1 is maintained as the bias voltage Vb. Thus, when a spark discharge is generated in the electrode portion of the ignition plug 3 and a compressed air-fuel mixture in a combustion chamber (not shown) is ignited, the air-fuel mixture explodes, and ions increase with an increase in temperature and pressure in the cylinder. Electric current flows. This ion current is detected as a voltage drop of the resistor R1, and is inverted and amplified by the operational amplifier OP1.

On the other hand, an ignition input signal GIa is input to the OR circuit ORG in synchronization with the ignition timing signal IGt. When the primary current of the primary coil L1 is no longer supplied, the transistor Tr1 is turned on by the output of the operational amplifier OP2, and the detection signal GIc shown in FIG. 2 is input to the OR circuit ORG. Further, after the detection signal GIc disappears (after the detection signal GIc goes low), a delay signal GIb that goes high for a predetermined time td is input to the OR circuit ORG. Eventually, in response to each of the above-mentioned input signals to the OR circuit ORG, the gain adjustment signal GO shown in FIG.
x is output, and while this is being output (during high level), the analog switch AS is turned on. Thus, the analog switch AS is turned on from the start of the ignition timing signal IGt to the lapse of a predetermined time td after the end of the primary voltage signal PRv. When the analog switch AS is turned on, the second feedback resistor R3 (<< R2) conducts with respect to the operational amplifier OP1, and the operational amplifier OP1
Therefore, as shown in FIG. 2, the ion signal INc (inversion of the ion signal INv of FIG. 7 and schematically shown in FIG. 2) loses noises Na to Nd as shown in FIG. Only the spark discharge signal Fs indicating the state is provided.
In this embodiment, noise Nd is generated at the end of the ignition timing signal IGt, in addition to the noises Na to Nc.
Noise Nd does not occur depending on the circuit configuration.

Next, the operation of the LC resonance reducing circuit 7 will be described. After the primary voltage ends and the ignition timing signal IGt turns off (low level), for example, 100 μsec.
After the lapse of time, the primary coil L1 is forcibly short-circuited until the next ignition timing signal IGt is turned on (high level). That is, after the ignition timing signal IGt is turned off, the field effect transistor FET is turned on for a predetermined time Te determined by the capacitor C5 and the resistors R12 and R13, and the primary coil L1 is short-circuited. As a result, a closed circuit including the primary coil L1 and the resistor R15 is formed, and the residual current of the primary coil L1 is consumed by the resistor R15, so that the noise of the primary voltage signal PRv, particularly immediately after the times t3 and t4 in FIG. The noise caused by the LC resonance occurring in the above is removed, and an accurate detection signal GIc is obtained.

Thus, in the above-described ignition device, the actual waveform of the ion signal INc is as shown in FIG. 3, and the combustion (ignition) can be easily performed by comparing with the reference voltage Sv.
The state is determined. In addition to the peak value determination method, the above-described area method may be applied. According to the latter method, the combustion (ignition) state is more easily determined. That is, the area of the spark discharge signal is calculated, and when the area is equal to or smaller than a predetermined value, the misfire is determined, so that the misfire can be easily detected.

FIG. 4 shows another embodiment of an ignition device for an internal combustion engine, in which the ignition timing signal IGt is omitted and the gain setting circuit 6 outputs the gain adjustment signal GOy shown in FIG. It is. As is apparent from FIG. 5, in the present embodiment, the noises Na and Nc cannot be removed, but they can be distinguished from the spark discharge signal Fs. can do. Other configurations are the same as those of the embodiment of FIG.

In each of the above embodiments, the analog switch AS is used as the switch in the gain adjustment circuit 5. However, the invention is not limited to this, and various switches can be used. Also, instead of the analog switch AS of FIG. 1, first and second analog switches (not shown) are connected in series to the first and second feedback resistors R2 and R3, respectively, and these are connected to the operational amplifier OP1. 2 are connected in parallel, and the first analog switch is normally closed and the second analog switch is opened at all times.
While the detection signal GIc and the delay signal GIb shown in (1) are being output (while high level), the first analog switch can be opened and the second analog switch can be closed.

[0033]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the ignition device for an internal combustion engine according to the present invention, the gain adjustment circuit for adjusting the gain of the operational amplifier is applied to at least a period when a voltage is generated in the primary coil and for a predetermined time after the voltage of the primary coil is lost. Has a gain setting circuit that sets the gain of the operational amplifier to be lower than when no voltage is generated in the primary coil, and can appropriately adjust the gain according to the state of the voltage of the primary coil. Therefore, the gain of only the signal portion including noise can be reduced without damaging the ion signal. Therefore, noise can be removed in accordance with the combustion state for each ignition, the ion signal can be reliably detected, and misfire detection can be appropriately performed.

In particular, in the ignition device for an internal combustion engine according to the second aspect, while the gain setting circuit outputs at least the detection signal and the delay signal, the switch means controls the first and second feedback circuits. Since the switching is made so as to conduct the feedback resistor having a lower resistance value among the resistors, noise generated in the vicinity of the generation timing of the ion signal is reduced by the gain of the operational amplifier based on the end point of the primary voltage. It is removed by adjustment, and misfire detection can be appropriately performed according to the combustion state of each ignition.

Further, in the ignition device for an internal combustion engine according to the third aspect, the switch means is switched based on the logical sum of the ignition timing signal, the detection signal, and the delay signal. Noise generated until the ion signal is generated can be easily removed by adjusting the gain of the operational amplifier.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an ignition device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a graph showing each signal when an ion signal is detected in the ignition device according to the embodiment of the present invention.

FIG. 3 is a graph showing an ion signal detected by the ignition device according to the embodiment of the present invention.

FIG. 4 is an electric circuit diagram of an ignition device for an internal combustion engine according to another embodiment of the present invention.

FIG. 5 is a graph showing each signal when an ion signal is detected in an ignition device according to another embodiment of the present invention.

FIG. 6 is an electric circuit diagram of a general ignition device of an internal combustion engine.

FIG. 7 is a graph showing each signal when an ion signal is detected in the ignition device of FIG. 6;

8 is a graph showing a voltage signal used for detecting an ion signal at the time of firing by the ignition device of FIG. 6;

9 is a graph showing a voltage signal used for detecting an ion signal at the time of motoring by the ignition device of FIG. 6;

[Explanation of symbols]

1 ignition coil, 2 ignition control circuit, 3 spark plug 4 ion signal detection circuit, 5 gain adjustment circuit,
6 gain setting circuit 6a primary voltage detection circuit, 6b delay circuit, 7
LC resonance reduction circuit

Claims (3)

[Claims] An ignition coil having a primary coil and a secondary coil, an ignition control circuit connected to the primary coil for intermittently controlling a primary current according to an ignition timing signal, and at least one pair connected to the secondary coil. A secondary circuit including the ignition plug and the secondary coil, and a current interposed in the secondary circuit and corresponding to an ion in the vicinity of the ignition plug is converted into a voltage signal to generate an ion signal. An ignition amplifier connected to the ion signal detection circuit for amplifying and outputting the ion signal; and a gain adjustment circuit for adjusting the gain of the operation amplifier. The voltage is applied to the primary coil with respect to the gain adjustment circuit at least as long as a voltage is generated in the primary coil and for a predetermined time after the voltage of the primary coil has disappeared. A gain setting circuit for setting the gain of the operational amplifier to be lower than when it does not occur. 2. The gain adjustment circuit according to claim 1, wherein said gain adjustment circuit has at least a first feedback resistor connected in parallel with said operational amplifier, and has a resistance value different from said first feedback resistor. And a second feedback resistor connected in parallel to the operational amplifier, and switch means for switching one of the first and second feedback resistors to the conductive amplifier and cutting off the other, and the gain setting circuit Comprises a primary voltage detection circuit that detects the voltage of the primary coil and outputs a detection signal, and a delay circuit that outputs a delay signal for a predetermined time after the detection signal of the primary voltage detection circuit disappears, wherein the gain setting While the circuit is outputting at least the detection signal and the delay signal, the switch means switches the first and second feedback resistors so as to conduct a feedback resistor having a lower resistance value. Characterized by The ignition device for an internal combustion engine according to claim 1. 3. The apparatus according to claim 2, wherein said gain setting circuit switches said switch means based on a logical sum of an ignition timing signal of said ignition control circuit, a detection signal of said primary voltage detection circuit and a delay signal of said delay circuit. The ignition device for an internal combustion engine according to claim 2, wherein: