JP2002070712A - Ignition system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of ON voltage at the start of energization of an ignition coil because an ON voltage protection diode is not equipped for the ignition system which has an ion current detecting system in the low voltage side of the ignition coil to detect the ion current using a secondary current of the ignition system and prevent the possibility of preignition caused by being ignited earlier than normal because the charged voltage of a condenser used for the power source of the ion current detection is increased to the level of ON voltage. SOLUTION: The decrease of substantial ON voltage becomes possible by forcing the charging voltage of condenser to pull off during it is not used for the power source for the ion current detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine having an ion current detection device for detecting a combustion state of an internal combustion engine based on an ion current in a combustion chamber.

[0002]

2. Description of the Related Art A method for detecting a combustion state of an internal combustion engine using an ionic current is widely known.

For example, Japanese Patent Laying-Open No. 4-194467 discloses an example of an ion current detecting device.

In this device, a capacitor is charged to a constant voltage by a secondary current generated when the primary current of the ignition coil is cut off. After spark discharge, the capacitor and the ignition coil secondary winding, and the ignition plug and the ionic current detection resistor are connected. It is configured such that the current flowing through a closed circuit composed of a device can be measured via an ion current detection resistor.

[0005]

In the prior art which has been widely known, a method for detecting an ion current and a circuit for processing have been widely studied.

However, when an ion current detecting device is provided on the low voltage side of the ignition coil to detect the ion current using the secondary current of the ignition coil, a positive secondary voltage generated by energizing the primary current of the ignition coil is used. (Hereinafter referred to as ON voltage) cannot be provided with a diode.

When the plug is discharged by this ON voltage,
Premature ignition may occur.

The ON voltage is determined by the power supply voltage, the primary / secondary turns ratio of the ignition coil, the conversion efficiency, and the like.
In order to lower the voltage, the normal ignition performance must also be reduced, so that an ON voltage of about 1 KV is normally generated.
Further, a capacitor serving as a power supply for detecting an ion current is charged with a secondary current generated at the time of a secondary discharge, and is not discharged even if an ion current flows, thereby increasing the ON voltage. As a result, there is a problem that premature ignition due to the ON voltage increases.

An object of the present invention is to prevent a premature ignition caused by an ON voltage by changing a charging voltage of a capacitor serving as a power supply for detecting an ion current during a period in which the ion current is not detected.
It is to reduce an actual ON voltage by forcibly discharging using a switching element.

[0010]

In order to achieve the above object,
As shown in FIG. 1, the switching element 6 is connected to a capacitor 5b serving as a power supply for detecting an ion current, and the switching element 6 is switched by a reset signal shown in the operation timing of FIG. While securing the voltage C as the power supply for the
It is possible to prevent the charging voltage (C) of b from raising the ON voltage.

Further, as shown in FIG. 4, the leakage current of the switching element 6 is blocked by the resistor 11, so that the switching element 6 can be easily selected.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention.

Reference numeral 1 denotes a battery, 2 denotes an ignition coil, and a switching element 3 cuts off current supply to a primary coil 2a of the ignition coil 2 according to an ignition signal to generate a high voltage in a secondary coil 2b. Discharge. On the other hand, on the low voltage side of the secondary coil, an ion current detection circuit 5 is configured by a Zener diode 5a, a capacitor 5b, a diode 5c, and a resistor 5d. Switching element 6
Is one means of the present invention for extracting the charging voltage of the capacitor 5b.

The operation of the circuit shown in FIG. 1 will be described with reference to FIG.

The switching element 3 is turned on in synchronization with the ignition signal HIGH, and a primary current Ic is supplied to the primary coil 2a of the ignition coil 2. At the start of energization, a positive O
N voltage is generated.

When the present invention is not implemented, the ON voltage is a voltage B determined by the voltage (Vce) between the collector 3C and the emitter 3B of the switching element 3, the turns ratio of the ignition coil, the conversion efficiency, and the like. Further, the interruption of the primary current Ic causes the secondary current generated in the secondary coil 2b together with the secondary voltage to charge the capacitor 5b by the Zener voltage of the Zener diode 5a, and the charging voltage C is raised to the ON voltage.

Therefore, the ON voltage actually generated is B + C
Voltage. In order to avoid the risk of premature ignition, it is desirable that this ON voltage be low.

However, in order to reduce the voltage of B, it is necessary to reduce the turns ratio between the primary coil 2a and the secondary coil 2b of the ignition coil 2 as described above.

Decreasing the voltage of B by lowering the turns ratio of the ignition coil also lowers the output on the negative side of the ignition coil, which has a great effect. On the other hand, if the charging voltage of the capacitor 5b of C is reduced, the detectability of the ion current is affected. In other words, there is a contradictory relationship to reduce the ON voltage while improving the ignition performance and the ion current detectability.

In this embodiment, as a means for achieving both of them, the switching element 6 for discharging the capacitor 5b is used.
And the capacitor 5b is discharged by a reset signal generated during the period D in FIG. Thereby, the charge voltage of the capacitor 5b is discharged when the ON voltage is generated while the charge voltage of the capacitor 5b is secured while the ion current is detected, so that the ON voltage can be substantially reduced.

FIG. 2 shows a circuit configuration of a conventional ignition device. Conventionally, the generation of the ON voltage has been prevented by providing the diode 10.

However, when the ion current is detected by the configuration as shown in FIG. 1, the diode 10 cannot be provided because the path for flowing the ion current is obstructed.

FIG. 4 shows another embodiment of the present invention, in which a resistor 11 is provided between the capacitor 5b and the collector of the switching element 6 for discharging. The switching element 6
For that purpose, like a mechanical switch, the switch
In the case of the FF, it is desirable to be completely open, but a leak current actually occurs. It is difficult to select an element having a withstand voltage in consideration of the charge voltage of the capacitor 5b and a small leak current, and there may be restrictions on the element.

Therefore, a resistor 11 is provided as in this embodiment,
By limiting the leakage current of the switching element 6, it is possible to easily select the switching element 6.

[0026]

According to the present invention, in the ignition device having the ion current detecting device, the substantial ON voltage can be reduced without lowering the ignition performance and without affecting the detectability of the ion current. Thus, the risk of premature ignition can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating 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, 2
b ... secondary coil, 3 ... switching element for controlling ignition coil, 4 ... ignition plug, 5 ... ion current detector, 5a ...
Zener diode, 5b ... capacitor, 5c ... diode, 5d ... resistor, 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.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Onuki, Hitachi, Ltd. 3G019 CA02 CD06 FA02 FA04 FA05 GA16 LA05

Claims (4)

[Claims] 1. A capacitor and a forward diode inserted in series in a secondary current path including a spark plug and a secondary side of an ignition coil, and the capacitor connected in parallel to the capacitor and charged by a secondary current. A zener diode for limiting the charging voltage to a constant value, and an ion current generated by the generation of ions in the cylinder when the air-fuel mixture burns and the charging voltage of the capacitor being applied to the spark plug. An internal combustion engine ignition device comprising an ion current detection device having a current detection resistor connected in parallel to the forward diode.
An ignition device for an internal combustion engine, comprising: means for discharging a charging voltage of the capacitor during a period in which an ionic current is not detected. 2. The ignition device for an internal combustion engine according to claim 1, wherein said capacitor is discharged using a switching element. 3. The internal combustion engine ignition device according to claim 2,
An ignition device for an internal combustion engine, wherein a resistor is arranged between the discharge switching element and the capacitor. 4. The internal combustion engine ignition device according to claim 2, wherein the switching element of the internal combustion engine ignition device according to claim 2 has a breakdown voltage equal to or higher than a Zener voltage of the Zener diode.