JP3854880B2 - Misfire detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine ignition device having an ion current detection function for detecting a combustion state of an internal combustion engine based on an ion current in a combustion chamber.
[0002]
[Prior art]
A method for detecting the combustion state of an internal combustion engine by an ionic current is widely known. For example, Japanese Patent Laid-Open No. 4-194367 discloses an example of an ion current detection device. This device charges a capacitor to a constant voltage by a secondary current generated when the primary current of the ignition coil is interrupted, and after spark discharge, closes the capacitor, the secondary winding of the ignition coil, a spark plug, and an ion current detection resistor. The current flowing in the circuit can be measured via an ion current detection resistor.
[0003]
[Problems to be solved by the invention]
Conventionally well-known techniques have been extensively studied on ion current detection methods and processing circuits. A method of amplifying waveform shaping of an ion current detection waveform and outputting the signal to a rectangular wave using an integration circuit is also known. As a method of constructing an integration circuit, it is common to use an operational amplifier. However, due to the effects of the offset voltage and bias current of the operational amplifier, holding of the integrated HIGH output at the time of ignition and the output of the integrated LOW output at the time of misfiring become problems. , Difficult to set.
[0004]
[Means for Solving the Problems]
The above problem is that a capacitor and a forward diode inserted in series in a secondary current path including a secondary side of a spark plug and an ignition coil, and a capacitor connected in parallel to the capacitor and charged by a secondary current. A zener diode that limits the charging voltage to a constant value, and to detect ion current generated when ions are generated in the cylinder during combustion of the air-fuel mixture and the charging voltage of the capacitor is applied to the spark plug, An ion current detection circuit having a current detection resistor connected in parallel to the forward diode, and a waveform processing circuit that detects the ion current and outputs a rectangular wave of a HIGH signal when the ion current flows. In the misfire detection device, the waveform processing circuit includes a circuit for masking an ion current output, and an ion current output after a period of the mask. And an integration period setting circuit for integrating the ionic current output, so that the integration time constant of the integration circuit becomes larger after the integration period than the integration period by the output of the integration period setting circuit. This is achieved by a misfire detection device using an ionic current characterized by switching.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows the configuration of an embodiment of the present invention. 1 is a battery, 2 is an ignition coil, and an ignition signal output from the ECU causes the igniter 3 to cut off current from the primary coil 2a of the ignition coil 2 to generate a high voltage in the secondary coil 2b. Discharge. On the other hand, on the low voltage side of the secondary coil, an ion current detection circuit 6 is constituted by a capacitor 6a, a diode 6b, a Zener diode 6c, and a resistor 6d. The waveform processing circuit 7 processes the ion current waveform detected by the ion current detection circuit into a rectangular wave and outputs it. The present invention is characterized in that an ion current detection circuit 6 and a waveform processing circuit 7 are packaged as one as the ion current processing unit 5 and are built in the ignition coil together with the igniter 3 as the ignition coil ASSY 8. The circuit operation of FIG. 1 will be described with reference to FIG. The igniter 3 is turned ON in synchronization with the ignition signal HIGH from the ECU, and the primary current Ic is supplied to the primary coil 2a of the ignition coil 2. A positive ON voltage is generated in the A part at the start of energization. When the primary current Ic is cut off, a negative high voltage is generated on the secondary side of the ignition coil and is discharged by the spark plug 4. At this time, when ignition occurs in the cylinder of the internal combustion engine and combustion, the electrodes of the spark plug are ionized. Due to the discharge of the spark plug, a secondary current flows to the secondary side of the ignition coil, and the voltage clamped by the Zener diode 6c of the ion current detection circuit 6 is charged in the capacitor 6a. As described above, when the electrode between the electrodes of the spark plug is ionized, an ion current is caused to flow to the secondary side of the ignition coil by the voltage charged in the capacitor 6a. The ion current is detected as a negative voltage by the resistor 6d. It is not detected at the time of misfire because the ionic current does not flow. The output of the ion current detection circuit is inverted and shaped by a waveform processing circuit and output as a rectangular wave using an integration circuit. The reason for using the integration circuit is to reliably output a signal even with a small ion waveform. This integral output is reset for each ignition by an ignition signal, and the combustion state for each ignition can be monitored. Further, since the output of the ignition current is generated before the output of the ion current waveform due to the ignition, the capacity discharge portion is masked so that a more accurate combustion state can be confirmed. Next, the integrating circuit of the present invention will be described with reference to FIGS. A waveform generated by capacitive discharge and an ion current waveform generated by the flow of ion current are generated at the output of the ion current detector. The ion current waveform differs in the generated voltage and timing depending on the state of combustion and operating conditions, and does not occur during a misfire. The output of the ion current detector is input to the signal inversion circuit and amplified. As an example, an operational amplifier is used for the inverting circuit. The output of the inverting circuit is input to the operational amplifier (comparator) 101 and compared with the reference voltage. At this time, the capacitive discharge portion has ON and OFF waveforms corresponding to the vibration frequency during capacitive discharge, and the ion current waveform becomes HIGH at ignition and LOW output at misfire. The SW1 is turned on and off by the output of the comparator 101, and the capacitor 32 is charged when the SW1 is turned on. The charge charged in the capacitor 32 when the SW1 is turned off is discharged through the resistor 31. The comparator 102 compares the discharge waveform with the reference voltage generated by the resistor 33 and the resistor 34 to determine the mask time. At this time, the discharge of the time constant circuit does not reach the reference voltage during the capacity discharge because the high-frequency ON / OFF waveform generated by the capacity discharge cannot completely discharge the time constant circuit. As a result, in the circuit of the present invention, a mask of a certain time is created after the capacity discharge waveform to be surely masked, so that a reliable and accurate mask circuit configuration can be obtained. The output of the comparator 102 is input to the gate of SW2, and operates so that the output of the signal inverting circuit, that is, the ionic current output is input to the inverting terminal of the operational amplifier 101 only during the set integration period. The operational amplifier 101 includes a capacitor 41 between its output and the inverting terminal, and constitutes an integrating circuit via a resistor between the inverting terminal and GND. An analog SW 42 is arranged in parallel with the capacitor 41. The analog SW 42 is turned on and off by an ignition signal, and the charge of the capacitor 41 is discharged every ignition cycle, thereby resetting the output of the integrating circuit. In the present invention, the resistor inserted between the operational amplifier and the GND constituting this integration circuit is divided into two systems, the integration period setting signal of the output of the comparator 102 is inverted and SW3 is turned on, so that the resistance 43 in the integration period is turned on. And an integration circuit having a time constant circuit having a resistance value determined by the parallel connection of the resistor 44, and switching to an integration circuit configuration having a time constant circuit of only the resistor 44 by turning off SW3 except during the integration period. At this time, the relationship between the resistor 13 and the resistor 44 is the resistance value of the resistor 43 << the resistor 44. In order to start up the integral output with a small voltage or a short time even at the time of ignition, it is better that the time constant is small. However, during a period when there is no integral input (other than the integral period), the integral output cannot be held if the time constant is small. In addition, when a misfire occurs, due to the offset and bias current of the operational amplifier, a spring-out voltage is generated in which the integration circuit output gradually increases without the integration input. To prevent this, a larger time constant is better.
[0006]
FIG. 2 shows a conventional configuration. Assuming that the same circuit configuration as that of the present invention is used, conventionally, the ionic current detection circuit 6 and the waveform processing circuit 7 are arranged separately from the ignition coil ASSY 11 in which only the ignition coil 2 and the igniter 3 are integrated. Alternatively, the ignition coil 2, the igniter 3, and the ion current detection circuit 6 are integrated with the ignition coil ASSY 10 and the waveform processing circuit 7 arranged separately. In this case, since the secondary side 2b of the ignition coil to the ion current detection circuit 6 and the ion current detection circuit 6 to the waveform processing circuit are very small currents, the output is attenuated and detected by impedance such as wiring routing, inductance, and stray capacitance. Accuracy will deteriorate. By integrating the ignition coil and the waveform processing circuit as in the present invention, the influence of the wiring is eliminated and accurate misfire detection becomes possible. FIG. 4 shows a block diagram of a waveform processing circuit configuration used in the present invention. From the beginning of the secondary winding of the ignition coil, the ion current detector converts the voltage of the ion current waveform, and the waveform shaping circuit inverts and detects the level to shape the waveform. The waveform shaping circuit output integrates the ion current waveform output only at the time of ignition by an integration circuit. At this time, since all of the ignition is output by the capacity discharge waveform at the time of ignition, this capacity discharge portion is masked by the mask circuit. Further, the integral output is reset for each ignition by the ignition signal. FIG. 5 shows a mounting state of the present invention. An ionic current processing unit 5 in which an igniter 3, an ionic current detection unit, and a waveform processing circuit are integrated is set on the head of a case 21 of an ignition coil and is integrally sealed with an insulating epoxy resin in a coil winding portion. From the outside, an ignition signal, a power supply, and GND are input by the connector terminal 22 and a processing signal is output. Although only one connector terminal 22 is shown because of a cross-sectional view, naturally, there are input / output terminals. Like the terminal 24, there are two ignition coils that are connected from the primary coil to the collector terminal of the igniter 3, and from the secondary coil to the ion current detector in the ion current processing unit. Reference numeral 25 denotes a center core, 26 denotes a primary bobbin, 27 denotes a primary winding, 28 denotes a secondary bobbin, and 29 denotes a secondary winding. The high pressure part structure is omitted.
[0007]
FIG. 8 shows an example of an assembly in which an ion current processing unit and an igniter using the present invention are built in an ignition coil. An igniter with a heat sink is set in the coil case in which the connector terminal is inserted, and the igniter and the ignition signal terminal and the GND terminal of the connector terminal are electrically connected by soldering or welding. The collector terminal of the igniter is connected with the end of the primary winding of the ignition coil and a relay terminal, and is connected by soldering or welding in the same manner as the connection terminal. Here, the ignition signal and the GND terminal are terminals shared with the ion current processing unit, and the terminals of the ion current processing unit are also connected by soldering or welding. After connecting the igniter terminals, the ion current processing unit is set in the coil case and connected to each terminal by soldering or welding. Here, the connection with the winding start of the secondary winding of the ignition coil is performed using a relay terminal in the same manner as the collector terminal of the igniter. Set in the coil case in the order of the igniter and ion current processing unit, connect each terminal by soldering or welding, etc., fix it in the coil case, and then fix it integrally with the insulating epoxy resin cast into the ignition coil .
[0008]
【The invention's effect】
According to the present invention, in the misfire detection method using an ionic current, the detected information can be output more accurately, the output can be easily processed, and the total cost of the system can be reduced.
[Brief description of the drawings]
FIG. 1 shows a configuration of an ignition device incorporating an embodiment of the present invention.
FIG. 2 is a configuration example of a conventional ignition device.
FIG. 3 is an operation timing when the present invention is used.
FIG. 4 is a block diagram of a waveform processing circuit according to the present invention.
FIG. 5 shows an embodiment of the implementation of the present invention.
FIG. 6 shows details of the operation timing of the present invention.
FIG. 7 shows a specific circuit example of the present invention.
FIG. 8 shows an embodiment of the implementation of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Battery, 2 ... Ignition coil, 2a ... Primary coil, 2b ... Secondary coil, 3 ... Igniter, 4 ... Ignition plug, 5 ... Ion current processing unit, 6 ... Ion current detection circuit, 6a, 32, 41 ... Capacitor , 6b ... diode, 6c ... Zener diode, 6d, 31, 33, 34, 35, 36, 43, 44, 45, 47 ... resistance, 7 ... waveform processing circuit, 8 ... ignition coil ASSY, 21 ... coil case, 22 Connector terminal 23 Epoxy resin for insulation 24 Connection terminal 25 Core core 26 Primary bobbin 27 Primary winding 28 Secondary bobbin 29 Secondary winding 42 Analog switch 46: Inversion buffer.

Claims (4)

A capacitor and a forward diode inserted in series in a secondary current path including the spark plug and the secondary side of the ignition coil;
A Zener diode connected in parallel to the capacitor and configured to limit a charging voltage of the capacitor charged by a secondary current to a constant value;
During combustion of the mixture in order to detect the ion current generated by the charge voltage of that and the capacitor ions in the cylinder is produced it is applied to the spark plug, connected to the current detection in parallel with the forward diode an ion current detection circuit and a use resistor, the misfire detection apparatus that includes a waveform processing circuit for outputting a rectangular wave of a HIGH signal when the flow ion current detecting an ion current,
Wherein the waveform processing circuit comprises a circuit for masking the ionic current output, an integrating circuit for integrating the ion current output after a period of the mask, an integration period setting circuit for integrating said ion current output,
Misfire detecting device using an ion current and switches the integration time constant of the integrating circuit by the output of the integration period setting circuit, so as to increase after the integration period than the integration period. The ion current detection circuit and the waveform processing circuit of claim 1 are configured as an integral package,
A misfire detection device using an ionic current, characterized in that it is built in an ignition coil together with an ignition device (hereinafter referred to as an igniter) having a switching element for energizing / cutting off the primary current of the ignition coil. The ignition coil according to claim 1 includes four input / output terminals including a power supply terminal, an ignition signal input terminal, a GND terminal, and an ion current processing signal output terminal as an integrated connector,
A misfire detection device using ion current, characterized in that the output of the ion current processing signal output terminal is a rectangular wave output. Ion current detection circuit and the waveform processing circuit according to claim 2 is constituted by the igniter integral package misfire detection apparatus characterized in that it is incorporated in the ignition coil.

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