JPH08177703A - Method for detecting combustion state by ion current - Google Patents

Abstract

PURPOSE: To detect only real ion current without detecting reverse direction voltage as noise. CONSTITUTION: A power transistor is provided on the primary side of an ignition coil, a combustion state detecting device 6A is provided on a secondary side, the combustion state detecting device 6A is provided with an ion current detecting circuit 10, a discharge time detecting circuit 11, an electrification time detecting circuit 15, and a current time setting circuit 16 which is connected to the circuit 15, output parts of the discharging time detecting circuit 11 and the reverse current time setting circuit 16 are connected to a transistor in the ion current detecting circuit 10, and the transistor is connected to the output terminal of the combustion state detecting device 6A.

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 shows a circuit diagram of a conventional ignition device for an internal combustion engine. In FIG. 3, a power transistor 2 is connected to the primary side of an ignition coil 1 composed of a step-up transformer, and an ignition plug 3 is connected to the secondary side of the ignition coil 1 via a backflow prevention high-voltage diode 4. A high voltage diode 5 for ion current detection is connected to the spark plug 3. The anode of the diode 5 is connected to the combustion state detecting device 6. The combustion state detection device 6 is composed of an ion current detection circuit 10 and a discharge time detection circuit 11, and the cathode of the high voltage diode 5 for ion current detection is connected via an ion current input terminal 7 of the combustion state detection device 6. The ion current detection circuit 1
0, the collector of the power transistor 2 is connected to the ion current detection circuit 10 and the discharge time detection circuit 11 via the discharge signal input terminal 8 of the combustion state detection device 6, and the discharge time detection circuit 11 The output part of is connected to the ion current detection circuit 10.

The ion current detection circuit 10 is connected in parallel to the ion current input terminal 7 and the discharge signal input terminal 8.
There is a resistor connected in series and a diode 12, and the cathode of this diode 12 is connected to a resistor connected in series and a zener diode. The ion current input terminal 7 is connected to the cathode of the diode 12 and one end of the capacitor 13,
The other end of the zener diode is connected to the ground through a resistor, and the anode of the Zener diode is connected to the non-inverting input of the operational amplifier. The inverting input is connected to the ground through the resistor, and the non-inverting input is connected through the resistor. It is connected to this output. The output part of the operational amplifier is connected to the collector of the transistor 14 and the output terminal 9 via a resistor, the emitter is grounded, and the gate is a discharge time detection circuit 1 described later.
Connected to 1.

In the discharge time detection circuit 11, a diode connected to the discharge signal input terminal 8 and one resistor and another resistor connected in series are connected to the cathode, and the connection portion of each resistor is the second Is connected to the inverting input of the operational amplifier, the non-inverting input is connected to the connection of two voltage dividing resistors, and the output of the operational amplifier is connected to the gate of the transistor 14 in the ion current detection circuit 10. Has been done.

The operation of FIG. 3 will be described with reference to the waveforms shown in FIG. FIG. 4 shows the signal waveform obtained from each point in FIG. As is well known, the pulse waveform (ignition signal) shown in FIG. 4A is supplied to the base S1 portion of the power transistor 2, and when the pulse waveform falls, the secondary side of the ignition coil 1 A high voltage is generated at. At this time, in the collector of the power transistor 3, a pulse waveform (discharge signal) shown in (b) is generated in S2, the ignition plug 3 is ignited by the high voltage, and each cylinder of the internal combustion engine (not shown). The mixed gas inside burns. Due to this combustion, ions are generated in each cylinder. The gas containing this ion is charged in advance from the ion current input terminal 8 of the combustion state detection device 6 to the waveform (b) in advance by the charge / discharge capacitor 13
By applying the charged voltage to S4, a minute ion current shown in (d) is obtained in S4, and this ion current is amplified and output by the operational amplifier.

Further, S2 is an ion current detection circuit 1
It is also supplied to the discharge time detection circuit 11 at the same time as 0,
Discharge signal S2 supplied to the discharge time detection circuit 11
Is compared with the threshold value shown in (c) formed by the voltage dividing resistance of the S3 portion, and passed through the second operational amplifier,
The waveform of (e) shown by S5 is obtained. In (e), from the above (b) and (c), the part where (b) is (c) or more is H, and the other part is L, which results in a shaped waveform. There is.

Here, the waveform from S4 is the true ion current flowing by the ions due to the combustion of the mixed gas in each cylinder of the internal combustion engine, and the discharge plug 2 from the charging / discharging capacitor 13 during the discharging time of the spark plug 3. There are a charging current flowing at the time of charging and a current for the ignition signal shown by the waveform (a) given to the base of the power transistor 2. For this reason, the diode 12 and the backflow prevention high voltage diode are provided. The reverse current flowing for a moment is detected by the switching characteristic of the switch 4.

In the prior art, by inputting the waveform (e) output from the discharge time detection circuit 11 to the gate of the transistor 14, the waveform of (d) is partially masked to detect the S6 portion, that is, the combustion state. An output (f) close to the true ion current is obtained from the output terminal 9 of the device 6.

[0009]

The conventional device is configured as described above, and as described above, the output from the combustion state detecting device 6 is the sum of the two currents, the true ion current and the reverse current. ing. In the prior art, it is necessary that the diode in the ion current detection circuit and the high voltage diode for backflow prevention have good switching characteristics and a small reverse current, but there is a limit to such characteristics. In addition, since the true ion current flowing by the ions due to the combustion of the mixed gas in each cylinder of the internal combustion engine is extremely small, it is amplified several hundred times by the operational amplifier. Amplification is performed and current is detected. From the above, there is a demand for a highly accurate combustion state detection method that can detect only the true ion current without detecting noise such as reverse current.

The present invention has been made in view of the above problems, and provides a combustion state detecting method capable of detecting only a true ion current without detecting a reverse voltage which causes noise. To aim.

[0011]

In order to solve the above problems, according to the present invention, a power transistor 2 is provided on the primary side of an ignition coil 1, and a high voltage diode 4 for preventing backflow and an ignition plug 3 are provided on the secondary side. And combustion state detection device 6 based on ion current
In the ignition device for an internal combustion engine including A, the combustion state detection device 6A detects the ion current generated by applying a predetermined voltage to the ions generated in the combustion chamber, and the power source. A discharge time detection circuit 11 which is connected to the collector of the transistor 2 and detects the discharge time of the spark plug 3 by a discharge signal from this collector.
And a conduction time detection circuit 15 connected to the collector of the power transistor 2 to detect conduction time, and a conduction time detection circuit 15 connected to the conduction time detection circuit 15.
When the ignition signal is supplied to the base of the transistor 2 to energize the base, the switching current of the diode 12 in the ion current detection circuit 10 and the high-current diode 4 for preventing backflow causes a reverse current similar to that flowing for a moment. A reverse current time setting circuit 16 for shaping a pulse waveform of a width, and a gate is connected to the discharge time detection circuit 11 and an output portion of the reverse current time setting circuit 16 in the ion current detection circuit 10, and a collector is provided. Is connected to the part for outputting the ion current detection result, and the emitter is connected to the output part of the combustion state detection device 6A.

[0012]

As is well known, the base of the power transistor 2 is
When an ignition signal is supplied and the pulse waveform falls, a high voltage is generated on the secondary side of the ignition coil 1.
At this time, a discharge signal is generated at the collector of the power transistor 3. This discharge signal is the discharge time detection circuit 11
Is converted into a waveform composed of H and L, which are compared with the threshold values formed inside and inside the energization time detection circuit 15, respectively. Of these, the H portion of the output waveform from the energization time detection circuit 15 is further limited in H time by the reverse current time setting circuit 16 and waveform shaping is performed.

In the above, since the H portion of the waveforms of the discharge time detection circuit 11 and the reverse current time setting circuit 16 is masked from the waveform created inside the ion current detection circuit 10, as a result, only the true ion current component is obtained. It can be output from the output terminal 9.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 showing an embodiment of the present invention, a power is provided on the primary side of an ignition coil 1 composed of a step-up transformer.
A transistor 2 is connected, and a spark plug 3 is connected to a secondary side of the ignition coil 1 through a high voltage diode 4 for preventing backflow.
Further, a high voltage diode 5 for ion current detection is connected to the spark plug 3. This dio
The anode of the battery 5 is connected to the combustion state detection device 6A. The combustion state detection device 6A includes an ion current detection circuit 10, a discharge time detection circuit 11, and an energization time detection circuit 1
5, a reverse current time setting circuit 16, the cathode of the ion current detection high voltage diode 5 is connected to the ion current detection circuit 10 via an ion current input terminal 7 of a combustion state detection device 6A, The collector of the power transistor 2 is connected to the ion current detection circuit 10, the discharge time detection circuit 11, and the conduction time detection circuit 15 via the discharge signal input terminal 8 of the combustion state detection device 6A,
The output part of the discharge time detection circuit 11 is connected to the ion current detection circuit 10 and the output part of the conduction time detection circuit 15 is connected to the reverse current time setting circuit 16.
The output section 6 is connected to the discharge time detection circuit 11.

The ionic current detection circuit 10 is connected in parallel to the ionic current input terminal 7 and the discharge signal input terminal 8.
There is a resistor connected in series and a diode 12, and the cathode of this diode 12 is connected to a resistor connected in series and a zener diode. The ion current input terminal 7 is connected to the cathode of the diode 12 and one end of the capacitor 13,
The other end of the zener diode is connected to the ground through a resistor, and the anode of the Zener diode and the non-inverting input part of the operational amplifier are connected to each other. It is connected to the lever output. The output part of the operational amplifier is connected to the collector of the transistor 14 and the output terminal 9 via a resistor,
The emitter is connected to ground and the gate is connected to a discharge time detection circuit 11 described later.

In the discharge time detection circuit 11, a diode connected to the discharge signal input terminal 8 and one resistor and another resistor connected in series are connected to this cathode, and the connection portion of each resistor is the second Is connected to the inverting input of the operational amplifier, the non-inverting input is connected to the connection of two voltage dividing resistors, and the output of the operational amplifier is connected via a diode to the transistor 14 in the ion current detection circuit 10.
Connected to the gate. The cathode of this diode is also connected to the cathodes of other diodes, and this anode is connected to the output section of the reverse current time setting circuit 16 described later.

The energization time detection circuit 15 has a diode connected to the discharge signal input terminal 8 as in the discharge time detection circuit 11 and one and another resistors connected in series to the cathode. The connection part of the resistor is connected to the inverting input part of the third operational amplifier, this non-inverting input part is connected to the connection part of the two resistors for voltage division, and the output part of this operational amplifier is connected to the reverse current time setting circuit 16 It is connected to the.

The reverse current time setting circuit 16 has a series-connected capacitor and resistor connected to the conduction time detection circuit 15, and these connection parts are connected to the non-inverting input part of the fourth operational amplifier. The inverting input section is connected to the connection section of two resistors for voltage division, and the output section of this operational amplifier is connected to the anodes of the other diodes in the discharge time detection circuit 11.

The operation of FIG. 1 will be described with reference to the waveforms shown in FIG. FIG. 2 shows the signal waveform obtained from each point in FIG. As is well known, a pulse waveform (ignition signal) shown in (a) is supplied to the base S1 portion 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. Voltage is generated. At this time, a pulse waveform (discharge signal) shown in (b) is generated in the collector S2 portion of the power transistor 3, the ignition plug 3 is ignited by the high voltage, and the mixed gas in each cylinder of the internal combustion engine is burned. . Due to this combustion, ions are generated in each cylinder. By applying the voltage charged in the charging / discharging capacitor 13 in the ion current detection circuit 10 to the gas containing the ions, a minute ion current shown in (d) is obtained in S4, which is amplified by the operational amplifier. ing.

Obtained at the discharge signal input terminal 8 (b)
The waveform is supplied to the discharge time detection circuit 11 and the energization time detection circuit 15 in addition to the ion current detection circuit 10 described above.

It is supplied to the discharge time detection circuit 11 (b)
With respect to the waveform, the threshold value shown in (c) is created in S3, the second operational amplifier compares it with the waveform shown in (b), and outputs the value above this threshold value as H and the other part as L. This is the waveform (e) output to the S6 portion.

Supply to the energization time detection circuit 15 (b)
The waveform is compared with the threshold value shown in (e) created by the S5 portion, the third operational amplifier compares it with the waveform shown in (b), H is set below this threshold value, and the other portion is set to L. Output as. This is the waveform (g) output to the S7 portion.

In the reverse current time setting circuit 16, an ignition signal is supplied to the base of the power transistor 2 from the rising portion of the waveform (g) to energize the diode, thereby turning on the diode.
A width similar to a reverse current flowing for a moment due to the switching characteristics of the reverse current prevention high voltage diode 4 and, for example,
A waveform (h) having H for several tens of microseconds is output from the S8 portion. This H can be determined by the resistance value for voltage division connected to the inverting input section of the fourth operational amplifier.

Here, as described in the prior art, the waveform (d) produced by the ion current detection circuit 10 is the true ion current flowing by the ions due to the combustion of the mixed gas in each cylinder of the internal combustion engine, and the spark plug. The charging current flowing when the charging / discharging capacitor 13 is charged by the waveform (b) during the discharging time of 3 and the base of the power transistor 2 are shown in (a).
When the waveform is supplied and energized, the reverse current flowing for a moment is detected by the switching characteristics of the diode 12 and the high voltage diode 4 for backflow prevention. However, due to the action of the transistor 14, the discharge time detection circuit 11 is determined from the waveform (d) which is the output of the ion current detection circuit 10.
It is possible to mask (f) that is output from (f) and the portion (h) that is output from the reverse current time setting circuit 16. Therefore, at the portion S9, that is, at the output terminal 9, only the true ion current is left, and the amplified waveform (i) is output.

[0025]

As described above, according to the present invention, when the power transistor supplies the ignition signal to the base and energizes the diode, the diode in the ion current detecting circuit and the high voltage diode for preventing backflow are provided. A combustion state detection device capable of masking and outputting the reverse current that flows for a moment due to the switching characteristics of the battery and capable of detecting only the true ion current after noise removal is obtained.

Therefore, when the combustion state is detected by using the ion current, an unnecessary current output that becomes noise can be cut, and the ion current can be detected with high reliability, and the combustion state can be detected by this result. Also, desired control such as knock detection and lean limit detection can be reliably performed.

[Brief description of 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 explaining the operation of FIG.

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

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

[Explanation of symbols]

 In the drawings, the same reference numerals indicate the same or corresponding parts. 1 Ignition coil 2 Power transistor 3 Spark plug 4 High voltage diode for backflow prevention 5 High voltage diode for ion current detection 6A Combustion state detection device 10 Ion current detection circuit 11 Discharge time detection circuit 15 Energization time detection circuit 16 Reverse current time setting circuit

Claims (1)

[Claims] 1. An ignition device for an internal combustion engine comprising a power transistor on a primary side of an ignition coil, a high pressure diode for preventing backflow, an ignition plug and a combustion state detection device based on ion current on a secondary side of the ignition coil. The state detection device
An ion current detection circuit for detecting an ion current generated by applying a predetermined voltage to the ions generated in the combustion chamber and a discharge signal from the collector connected to the collector of the power transistor. Is connected to the collector of the power transistor to detect the energization time, and the energization time detection circuit is connected to the energization time detection circuit to determine the base of the power transistor from the energization time. A reverse current that forms a pulse waveform of the same width as the reverse current that flows momentarily due to the switching characteristics of the diode in the ion current detection circuit and the high-voltage diode for backflow prevention when the ignition signal is supplied and is energized. A time setting circuit, and a gate in the ion current detection circuit is the discharge time detection circuit and a reverse current time setting circuit. Is connected to the output unit, is connected to a portion of the collector outputs of said ion current detection result, the combustion state detection method according to the ion current that the emitter comprises a transistor connected to the output of the combustion state detecting device.