JP3676662B2 - Internal combustion engine ignition 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 device that detects 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.
[0003]
For example, Japanese Patent Laid-Open No. 4-194367 discloses an example of an ion current detection device.
[0004]
This device charges a capacitor to a constant voltage by a secondary current generated when the primary current of the ignition coil is cut off, and after spark discharge, this capacitor, the secondary winding of the ignition coil, and an ignition plug and an ion current detection resistor. The current flowing through the closed circuit can be measured through an ion current detection resistor.
[0005]
[Problems to be solved by the invention]
Conventionally well-known techniques have been extensively studied on ion current detection methods and processing circuits.
[0006]
However, when an ion current detection device is provided on the low voltage side of the ignition coil and the ion current is detected using the secondary current of the ignition coil, a positive secondary voltage (hereinafter, It is not possible to install a diode that blocks the ON voltage).
[0007]
If the plug is discharged by this ON voltage, pre-ignition may occur.
[0008]
The ON voltage is determined by the power supply voltage, the primary and secondary turns ratio of the ignition coil, the conversion efficiency, etc., but to lower the ON voltage, the normal ignition performance must also be reduced, so the ON voltage is usually around 1 KV. Will occur. Furthermore, a capacitor serving as a power source for detecting the ionic current is charged with a secondary current generated at the time of secondary discharge, and is not discharged even when the ionic current flows, and raises the ON voltage. As a result, there is a problem that premature ignition due to the ON voltage increases.
[0009]
An object of the present invention is to forcibly discharge a charging voltage of a capacitor serving as a power source for detecting an ionic current using a switching element in a period in which the ionic current is not detected in order to prevent premature ignition due to an ON voltage. Thus, the actual ON voltage is reduced.
[0010]
[Means for Solving the Problems]
To achieve the above object, as shown in FIG. 1, a switching element 6 is connected to a capacitor 5b serving as a power source for ion current detection, and the switching element 6 is switched by a reset signal shown at the operation timing in FIG. Thus, the charging voltage (C) of the capacitor 5b can be prevented from raising the ON voltage while securing the voltage C as a power source for detecting the ion current.
[0011]
Further, as shown in FIG. 4, the switching element 6 can be easily selected by blocking the leakage current of the switching element 6 with the resistor 11.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0013]
FIG. 1 shows an embodiment of the present invention.
[0014]
Reference numeral 1 denotes a battery, 2 denotes an ignition coil, and the switching element 3 cuts off the current through the primary coil 2a of the ignition coil 2 according to the ignition signal, generates a high voltage in the secondary coil 2b, and discharges it through the ignition plug 4. On the other hand, on the low voltage side of the secondary coil, an ion current detection circuit 5 is constituted by a Zener diode 5a, a capacitor 5b, a diode 5c, and a resistor 5d. The switching element 6 is one means of the present invention for extracting the charging voltage of the capacitor 5b.
[0015]
The circuit operation of FIG. 1 will be described with reference to FIG.
[0016]
The switching element 3 is turned on in synchronization with HIGH of the ignition signal, 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.
[0017]
When the present invention is not carried out, the voltage B determined by the voltage (Vce) between the collector 3C and the emitter 3B of the switching element 3, the turn ratio of the ignition coil, the conversion efficiency, etc. is generated. Further, by interrupting the primary current Ic, the secondary current generated together with the secondary voltage in the secondary coil 2b charges the capacitor 5b by the Zener voltage of the Zener diode 5a, and the charge voltage C is raised to the ON voltage.
[0018]
Therefore, the actually generated ON voltage is a B + C voltage. In order to avoid the danger of premature ignition, it is desirable that this ON voltage is low.
[0019]
However, in order to reduce the voltage of B, it is necessary to reduce the turn ratio of the primary coil 2a and the secondary coil 2b of the ignition coil 2 as described above.
[0020]
Decreasing the turn ratio of the ignition coil to lower the voltage of B also lowers the output on the negative side of the ignition coil, which has a great influence. On the other hand, lowering the charging voltage of the C capacitor 5b affects the detectability of the ionic current. That is, there is a contradictory relationship between lowering the ON voltage while improving the ignition performance and improving the detection of ion current.
[0021]
In the present embodiment, as means for achieving both of them, a switching element 6 for discharging the capacitor 5b is provided, and the capacitor 5b is discharged by a reset signal generated in the period D in FIG. As a result, it is possible to substantially reduce the ON voltage by discharging the charge voltage of the capacitor 5b when the ON voltage is generated while securing the charge voltage of the capacitor 5b when the ion current is detected.
[0022]
FIG. 2 shows a circuit configuration of a conventional ignition device. Conventionally, the generation of the ON voltage is prevented by providing the diode 10.
[0023]
However, when ion current detection is performed with the configuration shown in FIG. 1, the diode 10 cannot be provided because the path through which the ion current flows is hindered.
[0024]
FIG. 4 shows another embodiment of the present invention, in which a resistor 11 is provided between the collector of the switching element 6 for discharging the capacitor 5b. The switching element 6 is desirably completely open when the switch is OFF, such as a mechanical switch, for the purpose, but actually leak current is generated. It is difficult to select an element that has a breakdown voltage that takes into account the charge voltage of the capacitor 5b and that has a small leakage current, and element restrictions may occur.
[0025]
Thus, the switching element 6 can be easily selected by providing the resistor 11 as in this embodiment and limiting the leakage current of the switching element 6.
[0026]
【The invention's effect】
According to the present invention, in an ignition device having an ion current detection device, a substantial ON voltage is reduced without deteriorating ignition performance and without affecting the detectability of ion current. Can reduce the risk.
[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 diagram showing a configuration example of a conventional ignition device.
FIG. 3 is an operation timing chart of FIG. 1;
FIG. 4 is a configuration diagram of an ignition device showing another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Battery, 2 ... Ignition coil, 2a ... Primary coil, 2b ... Secondary coil, 3 ... Ignition coil control switching element, 4 ... Ignition plug, 5 ... Ion current detector, 5a ... Zener diode, 5b ... Capacitor, 5c ... Diode, 5d ... Resistance, 6 ... Switching element, 10 ... ON voltage prevention diode, 11 ... Resistance, A ... Ignition coil high voltage side (secondary voltage), B ... ON voltage, C ... Capacitor charge voltage, D ... Reset Signal application period.

Claims (4)

A capacitor and a forward diode inserted in series in a secondary current path including the secondary side of the spark plug and the ignition coil, and a constant charging voltage of the capacitor connected in parallel to the capacitor and charged by the secondary current A zener diode that limits the value, and the forward diode to detect ionic current generated by the generation of ions in the cylinder during combustion of the air-fuel mixture and the charging voltage of the capacitor applied to the spark plug In the internal combustion engine ignition device having an ion current detection device having a current detection resistor connected in parallel to the capacitor, the internal combustion engine ignition device has means for discharging the charging voltage of the capacitor during a period in which no ion current is detected. An internal combustion engine ignition device. 2. The internal combustion engine ignition device according to claim 1, wherein the capacitor is discharged using a switching element. 3. The internal combustion engine ignition device according to claim 2, wherein a resistor is disposed between the switching element for discharge and the capacitor. The internal combustion engine ignition device according to claim 2, wherein the switching element of the internal combustion engine ignition device has a breakdown voltage equal to or higher than a Zener voltage of the Zener diode.

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