JPS5828428B2 - plasma igniter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma ignition device for an internal combustion engine.

FIG. 1 is a schematic diagram of an example of a conventional plasma ignition device.

In Fig. 1, the ignition coil 3, transistor eveninger (or contact point) 4, etc. are the usual spark discharge power supply, and the booster 7 (e.g. DC-DC converter), capacitor 8, inductor 9 are used to generate the plasma. It is a power source for

At the time of ignition, a high voltage of 10 to 20 kV is applied to the ignition plug 1 from the ignition coil 3 of the spark discharge power source.
When a spark discharge occurs at 0, the insulation in the discharge space is destroyed and a state is created in which discharge is possible even at a relatively low voltage of 2 to 3 kV.As a result, the electric charge stored in the capacitor 8 of the plasma power supply causes the necessary The discharge lasts for a certain amount of time.

The high-temperature, high-energy plasma-like gas produced by this discharge generates a large number of flame kernels in the air-fuel mixture in the combustion chamber, ensuring reliable ignition even in a lean air-fuel mixture.

In FIG. 1, 1 is a battery, 2 is a key switch (main switch of an automobile), and 5 and 6 are diodes for blocking reverse current.

FIG. 2 also shows an example of a conventional plasma ignition device.

In the circuit of FIG. 2, the booster 7 outputs a positive voltage (for example, +3000V), and the capacitor 8 and diode
The capacitor 8 is charged by the thread 2.

When the capacitor 8 is charged, the A of the capacitor 8 is
The terminal (on the spark plug side) is almost at O■, but when the thyristor 11 is turned on, the B terminal (on the booster side) of the capacitor 8 goes from +3000V to O■, so the A terminal becomes 13000V.

Therefore, if the thyristor 12 is turned on when the ignition coil 3 of the spark discharge power source outputs a high voltage, plasma ignition similar to the circuit shown in FIG. 1 is performed.

In the circuit shown in Figure 2, the spark plug 1 is used only at the ignition timing.
Since the voltage of the capacitor 8 is applied to 0, there is an advantage that there is no possibility of erroneous discharge at times other than the ignition timing.

In conventional plasma ignition devices such as those described above, normal ignition by the spark discharge power supply and plasma ignition by the charge in the capacitor are performed only once at the same time, so the combustion promotion effect of plasma ignition is The problem was that it was not being fully utilized.

This will be explained in detail below.

Figure 3 is a diagram showing the relationship between crank angle and cylinder pressure.
Curve Y1 shows the characteristics in the case of no ignition, curve Y2 shows the characteristics in the case of ignition only by normal spark discharge, and curve Y3 shows the characteristics in the case of conventional plasma ignition.

In the case of only normal spark discharge, if ignition occurs before top dead center (TDO), the pressure will rise as shown by the curve ¥2.

In the case of plasma ignition, combustion is fast, so the ignition timing is ignited at L2, which is later than in the normal case, but the pressure rises rapidly as shown by the curve ¥3.

However, the increase in pressure before top dead center TDO has a negative effect on the output of the internal combustion engine, so if the pressure increase before top dead center is large as shown in curve ¥3, the output will be attenuated by that amount. become.

The present invention has been made in view of the above problem, and is configured to perform ignition by spark discharge multiple times, and perform plasma ignition at the last ignition of the ignition. It is an object of the present invention to provide a plasma ignition device capable of suppressing pressure rise as much as possible and improving output.

The present invention will be described in detail below based on the drawings.

FIG. 4 is a diagram showing one embodiment of the present invention, and FIG. 5 is a signal waveform diagram of the circuit of FIG. 4.

In FIG. 4, reference numeral 13 denotes an ignition signal generator, which is, for example, a signal generator of a normal transistor eveninger.

This ignition signal generator 13 generates an ignition signal S1 for spark discharge.
and the ignition signal S2 for plasma discharge.
As shown in the figure, the ignition signal S1 first falls at the ignition timing L1, and then τ.

After (about several Ins), it falls again.

Spark discharge occurs at this falling point.

Further, the ignition signal S2 is output with a delay of τ2 from the second ignition operation of the ignition signal S.

Therefore, in the circuit shown in Figure 4, spark discharge occurs twice with an interval of several ms, and from the second spark discharge τ
After a delay of 2, the thyristor 11 is turned on and plasma ignition occurs.

Note that the delay τ2 is a delay to ensure that a spark is generated in the spark plug 10 when the thyristor 11 is turned on, and has a value of about 0.1 ms.

The following FIG. 6 is a diagram of another embodiment of the present invention, and FIG. 7 is a signal waveform diagram of the circuit of FIG. 6.

The circuit shown in FIG. 6 shows a case where the spark discharge power source is a CDI type (capacitor discharge type).

In Fig. 6, 17 and 18 are CDI capacitors, 19.20 is a thyristor, 14 to 16 are capacitors,
21 is the ignition signal generator.

As shown in FIG. 7, the ignition signal generator 21 outputs the ignition signal S3 at the ignition timing L1, then outputs the ignition signal S4 after τ1, and then outputs the ignition signal S5 after a delay of τ2.
Output.

On the other hand, capacitors 17 and 18 are charged with high voltage applied from booster 7.

When the ignition signal S3 is output at the ignition timing, the thyristor 19 is turned on and the charge in the capacitor 17 is released, causing a spark discharge. is turned on,
Spark discharge occurs again.

Then, after τ2, the ignition signal S is output, the thyristor 11 is turned on, and plasma ignition is performed.

Therefore, when the circuits of FIGS. 4 and 6 are pressed, the first spark discharge occurs at Ll in FIG.
At step 3, plasma discharge occurs slightly after the second spark discharge, so the cylinder pressure changes as shown by curve ¥4.

As is clear from a comparison of the conventional plasma ignition curve ¥3 and the above curve Y4, in the case of the present invention, the pressure rises before the top dead center is small, and the pressure rises rapidly from around the top dead center. Since the amount that has a negative effect on the output of the internal combustion engine is reduced and the combustion promoting effect of plasma ignition can be fully utilized, the output of the engine can be improved.

In the above embodiment, the spark discharge is performed twice, but the spark discharge may be performed three or more times.

In either case, plasma discharge may be performed in synchronization with (in fact, slightly delayed) the last spark discharge.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams of an example of a conventional plasma ignition device;
Fig. 3 is a diagram of the relationship between cylinder pressure and crank angle, Fig. 4 is a diagram of one embodiment of the present invention, Fig. 5 is a signal waveform diagram of the circuit of Fig. 4, and Fig. 6 is a diagram of another embodiment of the present invention. Embodiment FIG. 7 is a signal waveform diagram of the circuit of FIG. 6. Explanation of symbols, 1...Battery, 2...
Key switch, 3...Ignition coil, 4...
...Transistor eveninger, 5,6...Diode, 7...Booster. 8... Capacitor, 9... Inductor, 10... Spark plug, 11... Thyristor, 12... Diode, 13...・・・
・Ignition signal generator, 14-16...Diode, 17.18...Capacitor, 19.20...
...Thyristor, 21...Ignition signal generator.

Claims (1)

[Claims] 1 A button is pressed on a plasma ignition device that causes a spark plug to perform a spark discharge using a high voltage from a spark discharge power source, and discharges the electric charge charged in a capacitor of a plasma power source in accordance with the spark discharge to ignite a plasma. , means for causing the spark discharge power supply to perform spark discharge multiple times at each ignition timing, and means for discharging the charge from the plasma power supply at the time of the last spark discharge of the plurality of spark discharges. A plasma ignition device characterized by comprising: