JPH06299941A - Ion current detecting device - Google Patents

Abstract

PURPOSE:To provide an ion current detecting device which can detect desired ion current under good control by surely eliminating noise. CONSTITUTION:A transistor 3 and a current detecting resistor 4 are connected in series to the primary coil 2a of an ignition coil 2, a reverse current preventing diode 5 is arranged in the reverse direction in the secondary coil 2b, and an ignition plug 6 is connected to the diode 5. A base terminal of the transistor 3 is connected to a starting delay circuit 7, which inputs an ignition signal IGt. An ion current detecting circuit 8 provided with a bias power source 11 is connected to the ignition plug 6. A monostable circuit 14 for canceling noise during exciting and a monostable circuit 15 for canceling noise at the start of discharge and at the finish of discharge are arranged in a signal canceling circuit 22. An ion current voltage signal, in which a noise part is canceled, is detected in an output terminal 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion current detecting device provided in an internal combustion engine ignition device.

[0002]

2. Description of the Related Art Conventionally, in this type of ion current detecting device, a bias voltage is applied to a spark plug through a resistor and the voltage across the resistor is detected to generate a mixture during combustion. The ionic current was detected. Therefore, at the time of starting and ending the discharge of the ignition coil, the secondary discharge voltage waveform appears at both ends of the resistance and becomes noise, and the signal due to the noise is detected together with the ion current signal, so that the detection accuracy of the ion current signal is increased. There was a problem that was worse.

On the other hand, in the ion current detecting device disclosed in Japanese Patent Laid-Open No. 57-61930, a switch is connected to a bias power source connected to an ignition plug, and the switch is opened during ignition discharge. And
By the opening operation of the switch, the noise signal of the secondary side circuit generated by the ignition discharge is removed.

[0004]

However, in the above-mentioned conventional ion current detecting device, the switch is opened at the timing when the ignition discharge is started. Therefore, considering the delay time of the switching operation, the circuit is actually opened. The timing becomes later than the start of ignition discharge. as a result,
The noise at the time of starting the ignition discharge remains, which also causes a problem that the detection accuracy of the ion current deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to reliably remove noise so that a desired ion current can be detected with good control. It is to provide a detection device.

[0006]

In order to achieve the above object, the present invention relates to an ignition coil, a switching means connected to the primary side of the ignition coil and switching between energization and interruption of a primary current, and the ignition coil. Connected to the secondary side of the switching means, the secondary side high voltage generated by the interruption of the primary current by the switching means, the ignition plug for igniting the air-fuel mixture, and the bias voltage has been applied to the ignition plug. In an ion current detecting device having an ion current detecting means for detecting an ion current generated at the time of combustion, the invalidation of the output signal from the ion current detecting means is started at a timing before the primary current interruption of the ignition coil. At the same time, the gist of the present invention is to provide signal invalidating means for finishing the invalidation at a predetermined timing after the discharge of the ignition coil. A.

The signal invalidating means detects the primary current of the ignition coil, and when the primary current reaches a predetermined current value before reaching the cutoff current, the output signal from the ion current detecting means is invalidated. The conversion may be started.

Furthermore, the signal invalidating means may start invalidating the output signal from the ion current detecting means at a timing before the primary side energization of the ignition coil is started.

[0009]

When the primary current of the ignition coil is cut off by the switching means, a secondary high voltage is generated in the ignition coil, and the ignition plug ignites and burns the air-fuel mixture due to the secondary high voltage. At this time, the air-fuel mixture is ionized by the ionization action, and an ion current flows due to the bias voltage applied to the ignition plug. Then, this ion current is detected by the ion current detecting means. Also, the signal invalidating means is
The invalidation of the output signal from the ion current detection means is started at a timing before the primary current of the ignition coil is interrupted, and the invalidation is ended at a predetermined timing after the discharge of the ignition coil is completed.

In short, secondary current discharge occurs due to the interruption of the primary current of the ignition coil, and noise appears at the start and end of the discharge and is detected by the ion current detecting means.
On the other hand, according to the configuration of the present invention, since the output signal from the ion current detection means is invalidated at the start and end of the discharge, the noise is detected even if the ion current detection means detects the noise. Invalidated. As a result, of the output signal from the ion current detecting means, only noise is nullified and a desired ion current is detected.

On the other hand, when the invalidation of the output signal from the ion current detecting means is started according to the primary current, the invalidation is always started before the interruption of the primary current, that is, before the start of discharge. As a result, the noise generated at the start of discharge is surely nullified.

Further, when the invalidation of the output signal from the ion current detecting means is started before the start of the energization of the ignition coil primary side, the noise generated at the start of the energization of the ignition coil is surely invalidated. Will be done.

[0013]

【Example】

(First Embodiment) An ion current detecting device according to a first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a circuit diagram showing an outline of an ion current detecting device embodied in an independent ignition type ignition device. As shown in the figure, a transistor 3 and a current detection resistor 4 are connected in series to a primary coil 2a of an ignition coil 2 connected to a DC power supply 1. A backflow prevention diode 5 is arranged in the reverse direction on the secondary coil 2b of the ignition coil 2, and an ignition plug 6 is connected to the diode 5.

The ignition signal IGt is input to the rising delay circuit 7 which delays only the rising edge of the signal IGt. The delay circuit 7 is also connected to the base terminal of the transistor 3 as switching means. That is, the transistor 3 is controlled by the output signal of the rising delay circuit 7, and is turned on at a time later than the rising time of the ignition signal IGt, and is turned off at the falling time of the ignition signal IGt.
A primary current flows through the primary coil 2a of the ignition coil 2 when the transistor 3 is turned on, and a high ignition voltage is generated in the secondary coil 2b when the transistor 3 is cut off, causing the ignition coil 6 to move to a combustion chamber (not shown). ) Ignition and combustion of the air-fuel mixture.

The ignition signal IGt is delayed in rising, so that the energization time of the ignition coil 2 is shortened. However, the ignition signal IGt is preliminarily expected to account for this delay. It does not hinder energization.

On the other hand, in the ion current detection circuit 8 as the ion current detection means, the backflow prevention diode 9 connected to the ignition plug 6 is connected in series with a current detection resistor 10 and a bias power supply 11. Specifically, a negative bias voltage is applied to the spark plug 6 by the bias power supply 11. Then, when the air-fuel mixture is ignited and burned by the spark plug 6 and the air-fuel mixture is ionized by the ionization action, the bias voltage of the bias power supply 11 causes an ion current to flow in the path indicated by the broken line in FIG. It is detected at the connection point between the prevention diode 9 and the resistor 10.

Further, in the signal invalidating circuit 22 as the signal invalidating means, the non-inverting input terminal of the comparator 12 is connected to the emitter terminal of the transistor 3 and the current detecting resistor 4.
A point P2, which is a connection point with the, and the reference power source 13 is connected to the inverting input terminal. At the point P2, the primary current is detected as a voltage value by the current detecting resistor 4. Further, the output terminal of the comparator 12 has a monostable circuit 14
Are connected. Therefore, the comparator 12 outputs a pulse signal according to the result of comparison between the primary current of the ignition coil 2 and a predetermined threshold level. Also, monostable circuit 1
4 outputs a pulse signal for a predetermined time (for example, about 1 ms) corresponding to the rising edge of the pulse signal from the comparator 12.

The ignition signal IGt is input to the monostable circuit 15, and the monostable circuit 15 outputs a pulse signal for a predetermined time (for example, about 1 ms) corresponding to the rising edge of the ignition signal IGt. Further, the input terminals of the OR gate 16 are connected to the output sides of the monostable circuits 14 and 15, and the output terminal of the OR gate 16 is connected to the base terminal of the transistor 18 via the resistor 17.

Further, the point P of the above-mentioned ion current detection circuit 8
A capacitor 19 for cutting the DC component of the voltage signal at the same point P1 is connected to 1, and the capacitor 1
The collector terminal of the transistor 18 is connected to 9. The transistor 18 has its emitter grounded. Further, a resistor 20 and an output terminal 21 are connected to one end of the capacitor 19 (collector terminal of the transistor 18).

Therefore, when the transistor 18 is conductive, the output signal of the output terminal 21 is fixed to the ground voltage, and the ion current voltage signal at the point P1 is invalidated.
If the transistor 18 is cut off, the output terminal 2
The ion current voltage from 1 to the point P1 is detected.

Next, the operation of the ion current detecting apparatus of this embodiment will be described based on the time chart of FIG. In FIG. 2, the timing of t1 shows the rising time of the ignition signal IGt, the timing of t2 to t3 shows the energization time of the ignition coil 2, and the timing of t3 to t4 shows the discharge time of the spark plug 6.

As shown in the figure, the ignition signal IGt is raised at the timing of t1, and the output signal of the rising delay circuit 7 is raised at the timing of t2. When the output signal of the rise delay circuit 7 rises, the transistor 3 becomes conductive and the primary current starts to flow in the ignition coil 2. At this time, noise is generated in the secondary side circuit due to the change in the primary voltage, and the noise is transmitted through the path shown by the broken line in FIG.
Noise signal N1) appears.

After that, when the primary current increases with the energization on the primary side and the primary current reaches a predetermined breaking current (for example, 6.5 A), the constant current circuit (not shown) regulates the increase of the current.

At the ignition timing (timing of t3),
The transistor 3 is cut off by the falling edge of the output signal of the rising delay circuit 7. Then, a high voltage for ignition is generated in the secondary coil 2b by the action of the transformer, and a spark is generated between the electrodes of the spark plug 6. At this time, noise is generated in the secondary side circuit, and a noise signal (referred to as a second noise signal N2) appears again at the voltage at the point P1.

The spark generated at the timing of t3 continues for a predetermined discharge time, and the discharge ends at the timing of t4. At the end of this discharge, noise is generated in the secondary side circuit, and a noise signal (referred to as a third noise signal N3) appears again at the voltage at the point P1. Then, after a lapse of a predetermined time from the end of discharge, an ion current flows due to the ions attracted to the ignition plug 6, and an ion current voltage signal is detected at the point P1.

As described above, in the ion current detection circuit 8 of the present embodiment, the ion current voltage signal is detected after the end of discharge, and the noise signal is supplied at the start of energization, the interruption of the energization (at the start of discharge), and further discharge. It will be detected at the end.

On the other hand, in the signal invalidating circuit 22, the monostable circuit 1 is activated at the timing t1 when the ignition signal IGt is input.
5 operates and a pulse signal for a predetermined time is output. In addition,
The pulse length of the pulse signal of the monostable circuit 15 is set according to the noise duration at the start of energization.

Then, by this pulse signal, t1 to t
At the timing a, the transistor 18 is turned on and the output of the output terminal 21 is fixed to the ground voltage. That is, the timing of t1 to ta is the signal invalidation period, and the first noise signal N generated at the start of energization of the primary coil 2a.
1 is invalidated by the pulse signal of the monostable circuit 15 in this period (timing of t1 to ta).

At the timing tb when the primary current (voltage at the point P2) of the ignition coil 2 reaches the threshold level, the monostable circuit 14 outputs a pulse signal for a predetermined time at the rising edge of the output signal of the comparator 12. . The pulse length of the pulse signal of the monostable circuit 14 is set according to the noise duration at the start and end of discharge.

Then, by this pulse signal, tb to t
The transistor 18 is turned on again at the timing of c,
The output of the output terminal 21 is fixed to the ground voltage. That is, the timing from tb to tc is the signal invalidation period, and the second timing occurs at the start and end of the discharge of the spark plug 6.
And the third noise signals N2 and N3 are in this period (tb to t).
At the timing of c), the pulse signal of the monostable circuit 14 invalidates.

As described in detail above, in the ion current detector of this embodiment, the ignition signal IGt is delayed by the rising delay circuit 7 and the delay circuit 7 is delayed.
The power supply to the ignition coil 2 is started by the output signal of. Then, from the rising of the ignition signal IGt to the period including the duration of noise at the start of energization (t1 to ta in FIG. 2).
At the timing), the output of the output terminal 21 is fixed to the ground voltage so that the noise at the start of energization is nullified.

When the primary current of the ignition coil 2 is detected and the primary current reaches a predetermined current value before the cutoff current is reached,
Period including the duration of noise at the end of discharge (tb to tc
The output of the output terminal 21 is fixed to the ground voltage again to cancel the noise at the start and end of the discharge.

As a result, unlike the conventional ion current detecting device, the invalidation of the noise signal is started before the start of discharge,
It is possible to reliably remove noise signals at the start and end of discharge. Further, in the present embodiment, since the noise signal invalidation period is set even before the start of energization, the noise signal at the start of energization can be surely removed. Then, by removing these noise signals, the detection accuracy of the ion current can be significantly increased.

Further, according to the configuration of this embodiment, the ion current detecting device can be realized by adding a few components to the conventional ignition device, and the ion current detecting circuit 8 and the signal invalidation can be realized. By incorporating the circuit 22 in the ignition device, it is possible to provide a small-sized and inexpensive ion current detection device.

Below, a second modified version of the first embodiment will be described.
The differences between the fourth embodiment and the first embodiment will be mainly described. (Second Embodiment) In the first embodiment, a negative bias voltage is applied to the spark plug 6, but in the second embodiment, a positive bias voltage is applied to the spark plug 6. .

That is, as shown in FIG. 3, the spark plug 6
A current detection resistor 10 and a bias power supply 11 are connected in series via a backflow prevention diode 9 in the opposite direction. An inverting amplifier 31 is connected to the capacitor 19 connected to the point P1 of the ion current detection circuit 8.

Therefore, when the air-fuel mixture is ionized during combustion, an ionic current flows through the path indicated by the broken line in FIG. 3 (the path opposite to that in FIG. 1). Then, the ion current voltage detected at the point P1 is inverted and amplified by the inverting amplifier 31, and only noise is invalidated in accordance with the operation of the transistor 18 as in the first embodiment, and the output terminal 21 Detected at. (Third Embodiment) FIG. 4 is a diagram showing a third embodiment in which the ignition device is a simultaneous ignition system and the secondary side of the ignition coil 2 is a double coil system.

That is, as shown in FIG. 4, the ignition coil 2
A spark plug 6 is connected to each of the positive and negative electrodes of b.
An ion current detection circuit 8 having the same structure as that of the first embodiment is connected to the spark plug 6 connected to one electrode of the secondary coil 2b. (Fourth Embodiment) Next, a fourth embodiment in which an ion current voltage is detected from a specific cylinder of a distributor power distribution system
An example will be described with reference to FIGS. 5 and 6.

As shown in FIG. 5, a distributor 32 is connected to the secondary coil 2b of the ignition coil 2, and a distributor 32 is connected to the ignition plug 6 of each cylinder.
The ignition high voltage is distributed according to the rotation of the power distribution rotor 32a therein. Further, in this embodiment, the first
~ Unlike the third embodiment, the rising delay circuit 7, the monostable circuit 15 and the OR gate 16 are eliminated. Therefore, the transistor 3 operates according to the ignition signal IGt, and the transistor 18 operates according to the pulse signal from the monostable circuit 14.

The operation of the ion current detector of the fourth embodiment will be described with reference to the time chart of FIG. In FIG. 6, the timing of t11 to t12 shows the energization time of the ignition coil 2, and the timing of t12 to t13 shows the discharge time of the ignition plug 6.

First, at the timing of t11, the ignition signal IG
The energization of the ignition coil 2 is started with the rise of t.
Further, at the timing ta1 when the primary current of the ignition coil 2 reaches a predetermined threshold level, the monostable circuit 14 outputs a pulse signal for a predetermined time (timing ta1 to tb1) along with the rising edge of the output signal of the comparator 12. To be done.

On the other hand, a noise waveform is detected at point P1 at the start of discharge at the timing t12 and at the end of discharge at the timing t13. That is, in the configurations of the first to third embodiments, noise is generated not only at the start of discharge and at the end of discharge but also at the start of energization. However, in the case of the distributor power distribution as in the fourth embodiment, At the start of energization, the distribution rotor 32a has not yet reached the regular distribution position, and noise does not occur.

The pulse signal from the monostable circuit 14 causes the transistor 18 at the timing ta1 to tb1.
Are conducted, and the output of the output terminal 21 is fixed to the ground voltage. That is, the timing of ta1 to tb1 becomes a signal invalidation period, and noise generated at the start and end of discharge of the spark plug 6 is invalidated in this period and the output terminal 21
Not detected from.

As described above, in the fourth embodiment, in the ignition device of the distributor power distribution system, the structure for invalidating the noise signal at the start of coil energization is omitted, and the noise at the start of discharge and the noise at the end of discharge are eliminated. Only the signal is invalidated. As a result, similar to the above embodiment,
The noise can be removed to improve the detection accuracy of the ion current, and the configuration can be simplified by omitting the components such as the rise delay circuit 7.

The present invention is not limited to the above-mentioned embodiments, but may be arbitrarily modified within the scope not departing from the spirit of the invention.

[0047]

According to the present invention, by reliably removing noise, an excellent effect that a desired ion current can be detected with good control is exhibited.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an ion current detection device according to a first embodiment of the present invention.

FIG. 2 is a time chart for explaining FIG.

FIG. 3 is a circuit diagram showing an ion current detecting device of a second embodiment.

FIG. 4 is a circuit diagram showing an ion current detecting device of a third embodiment.

FIG. 5 is a circuit diagram showing an ion current detecting device according to a fourth embodiment.

FIG. 6 is a time chart for explaining FIG.

[Explanation of symbols]

2 ... Ignition coil, 3 ... Transistor as switching means, 6 ... Spark plug, 8 ... Ion current detection circuit as ion current detection means, 22 ... Signal invalidation circuit as signal invalidation means.

Claims (3)

[Claims] 1. An ignition coil, switching means connected to the primary side of the ignition coil for switching on / off of a primary current, and disconnection of a primary current by the switching means connected to a secondary side of the ignition coil. An ignition plug that ignites the air-fuel mixture due to the secondary high voltage that is generated along with the ignition plug, and an ion current detection unit that detects the ion current generated when the air-fuel mixture is burned by applying a bias voltage to the ignition plug. In the ion current detection device provided, the invalidation of the output signal from the ion current detection means is started at a timing before the primary current of the ignition coil is cut off, and the invalidation is made at a predetermined timing after the discharge of the ignition coil is completed. An ion current detecting device, characterized in that a signal invalidating means for ending the activation is provided. 2. The signal nullifying means detects the primary current of the ignition coil, and invalidates the output signal from the ion current detecting means when the primary current reaches a predetermined current value before reaching the cutoff current. The ion current detection device according to claim 1, wherein the ionization detection is started. 3. The ion current detecting device according to claim 1, wherein the signal invalidating means starts invalidating the output signal from the ion current detecting means at a timing before the primary side energization of the ignition coil is started. .