JP3325132B2 - Combustion state detection method using ion current - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a combustion state by an ionic current in an internal combustion engine for automobiles.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional ignition device for an internal combustion engine. In FIG. 3, a power transistor 2 is connected to a primary side of an ignition coil 1 composed of a step-up transformer, and an ignition plug 3 is connected to a secondary side of the ignition coil 1 via a backflow preventing diode 4. The ignition plug 3 is connected to an ion current detecting diode 5. The cathode of this diode 5 is
The output terminal 8 of the ion current detection device 6 is connected to the input terminal 10 of the ion current calculation processing device 9. The ion current arithmetic processing unit 9 has an interface 11, and is connected to the interface 13 of the electronic control unit 12 via the interface 11.

FIG. 4 shows a signal waveform obtained from each point in FIG. Hereinafter, the operation of the ignition device and the ion current detection device of FIG. 3 will be described. As is well known, a pulse waveform (ignition signal) S1 shown in FIG. 4A is supplied to the base of the power transistor 2, and when the pulse waveform falls, a high voltage is applied to the secondary side of the ignition coil 1. Is generated, and the ignition plug 3 is ignited by this high voltage, and the mixed gas in each cylinder (not shown) of the internal combustion engine burns. This combustion generates ions in each cylinder,
At this time, by applying a predetermined voltage, the ion current becomes
It is detected by the ion current detector 6. At the output terminal 8 of the ion current detection device 6, an ion current output S2 as shown in FIG. This ion current output S2
Is supplied to the input terminal 10 of the ion current arithmetic processing unit 9 to perform arithmetic processing. This calculation processing includes, for example, the ion current detection amplification output S2 and a set value (threshold) previously held by the ion current calculation processing device shown in FIG.
S3 is compared, and the interval (d) until S2 finally falls below the set value is converted into a digital signal, for example, (e) and (f), (g), (h) in FIG. The result is output from the interface 11 to the electronic control unit 12 as digital signals S4, S5, S6, and S7. S4 and S
In steps S5 and S6, the signal processing is performed inside the electronic control unit 12 after transmission to the electronic control unit 12, and the combustion state in the cylinder is determined. Therefore, for example, under certain operating conditions, FIG.
When the combustion is in a stable state, a constant signal is obtained, but when the combustion is in an unstable state, the signal changes to a signal with large variation.

[0004]

In the above-described conventional method for detecting a combustion state using an ionic current, the interval (d) until the ionic current shown in FIG. 4B finally falls below the set value shown in FIG. Is subjected to analog-to-digital (A / D) conversion processing by a microcomputer in the ion current arithmetic processing unit 9, and a microcomputer in the electronic control unit 12 is processed.
To determine the combustion state. In the detection of the ion current, the ion current shown in FIG. 4B is detected at every predetermined crank angle movement, for example, every 1 degree CA of the crank angle, and whether or not the ion current exceeds the set value (c) is determined. This is done by monitoring for

In the prior art, in order to accurately detect the position where the ion current finally falls below the set value, it is necessary to shorten the interval of the crank angle for detecting the ion current as much as possible. However, there is a limit due to the time restrictions involved in A / D conversion processing of the signal from the ion current operation processing device 9 and the time restrictions required for other operation processing. As a result, sufficient detection accuracy can be obtained. There is a problem that cannot be solved. In particular, in the case of processing in a plurality of cylinders or in the high engine speed region, the interval for measuring the ion current cannot be relatively shortened, and there has been a problem that accuracy has deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an ion current detection device capable of detecting an ion current with high accuracy even in a plurality of cylinders and in a high rotation speed region.

[0007]

SUMMARY OF THE INVENTION In an ignition device for an internal combustion engine having a power transistor, an ignition coil, and an ion current arithmetic processing unit for detecting and processing an ion current, a power transistor is provided on a primary side of the ignition coil, and An ion current arithmetic processing device is connected to the next side, the ion current arithmetic processing device detects an ion current, an ion current detection device, a set value comparison circuit that compares the ion current with a set value, and an ignition device. A saw-tooth wave oscillating circuit for shaping a signal into a saw-tooth wave; and a peak-hold circuit for converting an interval from the time of ignition to a point in time at which the ion current finally falls below a set value to a voltage value. An ion current detector is connected to the secondary side, a set value comparison circuit is connected to this output section, and a saw is connected to an ignition signal input section of the power transistor. Oscillator circuit is connected, the output of the set value comparison circuit and sawtooth oscillation circuit peak - Kuho - a combustion state detection method according to the ion current which is connected to the hold circuit.

[0008]

According to the ion current detecting device having the above-described structure, the period up to the final time point where the ion current is larger than the set value can be directly supplied to the electronic control unit without being divided into predetermined periods.

[0009]

FIG. 1 shows an embodiment of the present invention. In FIG.
A transistor 2 is connected, a spark plug 3 is connected to a secondary side of the ignition coil 1 via a backflow preventing diode 4, and an ion current detecting diode 5 is connected to the ignition plug 3. It is connected. The cathode of the diode 5 is connected to the ion current arithmetic processing unit 6A. The ion current calculation processing device 6A includes a sawtooth wave oscillation circuit 16, an ion current detection device 6, a peak hold circuit 17, and a set value comparison circuit 19, and the cathode of the ion current detection diode 5 is used to calculate the ion current. The processing device 6A is connected to the ion current detection device 6 via the ion current input terminal 7, and the base of the power transistor 2 is connected to the sawtooth wave oscillation circuit 16 via the ignition signal input terminal 14 of the ion current calculation processing device 6A. The output of the ion current detection device 6 is supplied to a set value comparison circuit 19,
The output of the set value comparison circuit 19 and the output of the sawtooth wave oscillation circuit 16 are connected to a peak hold circuit 17, and the output of the peak hold circuit 17, that is, the output terminal 15 of the ion current arithmetic processing device 6A is It is connected to an electronic control unit 12A having a current input terminal 20.

In the above description, the ion current detector 6 and the set value comparison circuit 19 are a resistor and an operational amplifier, the sawtooth wave oscillation circuit 16 is a diode and a variable resistor, a variable capacitor and an operational amplifier, and the peak hold circuit 17 is a transistor and a capacitor. It is composed of a resistor.

Next, the operation of the above configuration will be described with reference to FIG. FIG. 2 shows signal waveforms obtained from each point in FIG. As described in the background art, the base of the power transistor 2
A pulse waveform (ignition signal) S1 shown in FIG.
When the pulse waveform falls, a high voltage is generated on the secondary side of the ignition coil 1, and the ignition plug 3 is ignited by the high voltage, and the mixed gas in each cylinder (not shown) of the internal combustion engine is generated. Burns. This combustion produces ions in each cylinder.

The waveform of the ion current flowing by applying a voltage to the gas containing ions at the output of the operational amplifier of the ion current detector 6 is as shown in FIG.
This waveform is supplied to the set value comparison circuit 19. In this set value comparison circuit 19, the set value S3 shown in FIG.
Is compared with the waveform from the ion current detector 6, and the output of the set value comparison circuit 19 outputs the waveform shown in S4 of FIG. This waveform is formed by forming H and L with the portion above the threshold value shown in FIG.

The ignition signal S1 supplied to the ignition signal input terminal 14 of the ion current arithmetic processing unit 6A is synchronized with the rotational speed of each cylinder (not shown) by the sawtooth oscillation circuit 16 in FIG. It is shaped into the sawtooth waveform S5 shown. This shaping is performed so as to linearly connect from the pulse end portion of the ignition signal S1 to the next pulse generation portion.

When the waveforms from the sawtooth wave oscillation circuit 16 and the set value comparison circuit 19 are shaped by the peak hold circuit 17, the waveform shown in S6 of FIG. The waveform of S6 is a peak
The voltage changes in accordance with the state of charge of the capacitor in the hold circuit 17 and is converted by the transistor into a voltage value proportional to the slope of the sawtooth waveform S5. That is, as described with reference to FIG. 2, an ion current is generated after the falling of the pulse of the ignition signal S1, a waveform of S4 appears, and when the waveform is H, the capacitor is charged, and when the waveform is L, the capacitor is charged. Is held until the next ignition signal S1 pulse is input. As described above, in the output waveform S6, the interval from the time of ignition until the ion current finally falls below the set value S3 is converted into a voltage value proportional to the slope of the sawtooth waveform S5 and output. The output S6 is supplied to the electronic control unit 13 to determine the combustion state in the cylinder (not shown). Accordingly, for example, under certain operating conditions, FIG. 2 (g) shows that when combustion is in a stable state, a voltage value with a constant peak value is obtained, but when combustion becomes unstable, a voltage value with a large variation in peak value is large. Is obtained.

[0015]

As described above, according to the present invention, the value of the ionic current flowing in the cylinder immediately after ignition is compared with the set value, and the period from ignition to the final point in time when the ionic current is larger than the set value is determined. By converting the voltage into a voltage value and directly supplying it to the electronic control unit without dividing it into a predetermined crank angle period, a combustion state detection device using ion current with higher accuracy than before can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ignition device showing an embodiment of the present invention.

FIG. 2 is a signal waveform for describing the operation of FIG. 1;

FIG. 3 is a configuration diagram showing a conventional ignition device.

FIG. 4 is a signal waveform for explaining the operation of FIG. 3;

5 shows an example of a combination of signals output from the interface of FIG.

[Explanation of symbols]

 In the drawings, the same reference numerals indicate the same or corresponding parts. DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Power transistor 3 Spark plug 5 Ion current detection diode 6 Ion current detection device 6A, 10 Ion current calculation processing device 12, 12A Electronic control device 16 Saw wave oscillation circuit 17 Peak hold circuit 19 Set value comparison circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02P 17/12

Claims (1)

(57) [Claims] 1. An ignition device for an internal combustion engine comprising a power transistor, an ignition coil, and an ion current arithmetic processing unit for detecting and processing an ion current.
A power transistor is connected to the secondary side, and an ion current arithmetic processing unit is connected to the secondary side. The ion current arithmetic processing unit compares the ion current with a set value. A comparison circuit, a sawtooth wave oscillating circuit for shaping an ignition signal into a sawtooth wave, and a peak hold for converting an interval from the time of ignition to a point in time at which the ion current finally falls below a set value to a voltage value. An ion current detector is connected to the secondary side of the ignition coil, a set value comparison circuit is connected to this output section, and a sawtooth oscillation circuit is connected to an ignition signal input section of the power transistor, A combustion state detecting method using an ion current, wherein the output of the set value comparing circuit and the output of the sawtooth oscillation circuit are connected to a peak hold circuit.