JPH04308361A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a misfire detecting device capable of detecting an ion current and discriminating misfire using the detection of the ion current with simple structure. CONSTITUTION:This misfire detecting device for an internal combustion engine is formed of a series circuit formed of a condenser 41 and a resistance 42 and provided between the secondary circuit 12 of an ignition coil 1 and earth G, a constant voltage diode 43 parallel-connected to this series circuit, a diode 44 provided parallel to the resistance 42, a current detecting means provided between the resistance 42 and the condenser 41, and a discriminating means 5 for discriminating the current waveform detected by the current detecting means.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device for detecting ignition errors (misfires) in internal combustion engines by generating an ion current in a spark plug.

0002

[Prior Art] A negative voltage is applied to the ignition circuit of an internal combustion engine to generate an ionic current in the discharge gap of a spark plug.
Ion current waveforms are detected through diodes to determine pre-ignition and detect knocking. Additionally, in response to demands for purifying exhaust gas and improving fuel efficiency, there is a need for a device that can detect the ignition state of each cylinder of an engine and take measures to prevent misfires in all cylinders.

0003

Conventional ion current detection devices have complicated and expensive configurations, and no device has been devised for use in determining misfires. SUMMARY OF THE INVENTION An object of the present invention is to provide a misfire detection device for an internal combustion engine that uses ionic current detection and is capable of detecting ionic current with a simple configuration and also enables misfire determination.

0004

[Means for Solving the Problems] A misfire detection device for an internal combustion engine according to the present invention includes a series circuit of a capacitor and a resistor provided between a secondary circuit of an ignition coil and ground, and a series circuit connected in parallel to this series circuit. A constant voltage diode, a diode connected in parallel with the resistor, a current detecting means provided between the resistor and the capacitor, and a means for determining the current waveform detected by the current detecting means.

[0005]

[Operations and Effects of the Invention] In the present invention, a constant voltage capacitor is charged with the current generated in the secondary circuit of the ignition circuit and used as an ion current power source, and a misfire in the cylinder is determined based on the discharge current of this power source. Therefore, a misfire in an internal combustion engine can be detected with an extremely simple configuration.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an ignition system 100 for an internal combustion engine, in which a primary coil 11 is connected to a battery B and an interrupter D.
, an ignition coil 1 having a secondary coil 12, a distributor 2, and a spark plug 3 attached to each cylinder and to which a high voltage generated in the secondary coil 12 is applied via the distributor 2. Equipped with. A diode 21 is connected in parallel to the power distributor 2, one end of the secondary coil 12 is connected to the power distributor 2, and the ion current detection device 4 is attached to the other end. The ion current detection device 4 outputs an output to a microcomputer 5 which is a current waveform discrimination means, and controls a monitor circuit M and a control means N.

The ion current detection device 4 includes a capacitor 41 and a resistor 42 between the secondary coil 12 and the ground G.
are connected in series, a constant voltage diode 43 is connected in parallel to this series circuit, and a diode 44 is connected to the resistor 42.
are connected in parallel, and the ion current is detected by the voltage across the resistor 42.

The operation of this misfire detection circuit will be explained with reference to FIG. When the ignition is done smoothly. When the ignition current flows due to the high voltage generated in the secondary coil of the ignition coil, the capacitor 41 is charged to the discharge voltage level of the constant voltage diode 43, so that a positive charging voltage a is generated. A diode 44 constitutes a charging circuit for this capacitor 41. Subsequently, a negative peak voltage b occurs due to the end of the spark discharge, and the ion current c falls during or after the end of this discharge waveform. The charge in the capacitor 41 generates an ionic current c in the discharge gap of the spark plug 3, is discharged in a discharge circuit consisting of the diode 21, the secondary coil 12, and the resistor 42, and appears as a voltage across the resistor 42. , the voltage waveform shown in (a) of FIG. 2 is detected.

[0009] When a misfire occurs. When ignition and combustion occur smoothly in the cylinder due to spark discharge, conductivity occurs in the spark discharge gap due to ionization of the fuel, so the ion current c flows as described above, but even if spark discharge occurs, When ignition does not occur smoothly due to low temperature or a lean air-fuel ratio of the air-fuel mixture, the charging voltage a and the peak voltage b flow, but the ion current c does not occur. A voltage waveform shown in (b) of FIG. 2 is detected.

[0010] The microcomputer (discrimination means) 5 includes:
Comparing the data of the current waveform pattern obtained by measurement or calculation and stored in advance with the above (a) and (b), a misfire is determined, the monitor circuit M makes the driver aware of the misfire situation, and the engine Control means N such as an ignition timing adjustment device, a fuel injection timing control device, an air-fuel ratio control device, etc.
output to adjust engine operating conditions to prevent misfires from occurring again.

[Brief explanation of drawings]

FIG. 1 is an ignition circuit diagram of an internal combustion engine equipped with a misfire detection device according to the present invention.

FIG. 2 is a waveform diagram for explaining operation.

[Explanation of symbols]

1 Ignition coil 2　Power distributor 3 Spark plug 4 Ion current detection device 5. Microcomputer 41 Capacitor 42 Resistance 43 Constant voltage diode 44 Diode

Claims (1)

[Claims] 1. A series circuit of a capacitor and a resistor provided between a secondary circuit of an ignition coil and ground, a constant voltage diode connected in parallel to the series circuit, a diode parallel to the resistor, A misfire detection device for an internal combustion engine, comprising a current detection means provided between a resistor and a capacitor, and a means for determining a current waveform detected by the current detection means.