JPS5825581A - Plasma ignition system - Google Patents

Abstract

PURPOSE:To prevent mismatched discharge and enable energey to be poured positively even in high temperature of a plug by oscillating discharge voltage by the use of a capacity discharge system and providing a power source for plasma for pouring energy in the ignition timing of each cylinder. CONSTITUTION:Since a capacity discharge system (CDSI) constituted from an ignition coil 3, a boosting transformer 17, a capacitor C2 and a thyristor Q2 is used for a spark discharging power source, voltage applied to ignition plugs 8A-8D is oscillated by the capacitor C2 and inductance of the ignition coil 3 so that plasma energy can be positively poured even when the ignition plugs 8A- 8D have high temperature. Also, since a circuit consisting of diodes D1-D3, provided in every cylinder inductor L1, capacitor C1 and thyristor Q1 for controlling current and a boosting transformer 18 are used for a plasma power source, the plasma energy is poured only into cylinders corresponding to the ignition timing so that mismatching discharge in cylinders at non-ignition timing can be prevented.

Description

[Detailed description of the invention] The present invention relates to improvements in plasma ignition devices for internal combustion engines.

Recently, plasma ignition devices have been developed as ignition devices for internal combustion engines. As a conventional plasma ignition device, there is one as shown in FIG. 1, for example.

In FIG. 1, 1 is a battery that serves as the main power source.

2 is a key switch. Also, ignition coil 3. The contact points 4, etc. constitute a normal spark discharge power supply, and include a booster 9 (DC-DC converter), and a booster 10.
．． The inductor 11 and the like constitute a plasma power source.

Others 5 and 6A to 6D are diodes for backflow prevention, 7
is a distributor.

88 to 8D are spark plugs.

In the device shown in Fig. 1, when a spark discharge occurs at the spark plugs 8A to 8D due to the high voltage of 20 to 3 kV applied from the ignition coil 3 of the spark discharge power source during one ignition, the insulation in the discharge space is destroyed. As a result, the high energy (several joules) stored in the capacitor 10 of the plasma power supply is injected in a short period of time (several hundreds of μs). , plasma-like gas is generated.

A large number of flame kernels are generated in the air-fuel mixture in the combustion chamber by the high-temperature, high-energy plasma-like gas generated by the above-mentioned discharge, and even a lean air-fuel mixture is ignited reliably.

Note that the booster 9 has 9 oscillators 12. Transformer 15. It is composed of transistors 13 and 14 for switching and diodes 16 for rectification. Then, a constant frequency switching signal output from the oscillator 12 causes the transistor 1 to
3.14 are turned on alternately, and as a result, current flows through the primary winding of the transformer 15, causing a boosted high voltage (negative high voltage in the case of Figure 1) to be transferred to the secondary winding. ◇ By the way, in the apparatus shown in Fig. 1, the charge stored in the capacitor 1o of the plasma power supply is as follows.

Four spark plugs 88~ through diodes 6A~6D
It is constantly applied to all 8D, but the distribution
It was thought that only the spark plug selected by Tough to cause a spark discharge would cause dielectric breakdown, and that only that spark plug would automatically generate a plasma discharge.

However, 1. the dielectric breakdown voltage of the ignition plug tends to decrease as the atmospheric pressure decreases, so 2. For example, when the pressure in the cylinder decreases during the intake stroke, dielectric breakdown occurs in the ignition plug due to only the voltage of the plasma power supply, causing spark discharge. may occur.

Also, if the insulation level of the spark plug is reduced due to the influence of carbon adhering to the spark plug, spark discharge may occur in the same way as above.If irregular discharge occurs at a time other than the normal ignition timing,
If the charge in the capacitor 10 is insufficient at the normal ignition timing, the effectiveness of plasma ignition will be reduced. Furthermore, if spark discharge occurs due to irregular discharge in a cylinder during the intake stroke, there is a risk that the air-fuel mixture in the intake air will ignite, resulting in a backfire.

Further, in the apparatus shown in FIG. 1, since an inductive discharge type so-called Kettering type ignition device is used as a power source for spark discharge, the voltage applied from one ignition coil 3 to the spark plug has a fixed polarity.

By the way, when the spark plug electrode becomes hot.

It has the characteristic that the discharge sustaining voltage (the voltage required to maintain the discharge after dielectric breakdown) increases.

When the discharge sustaining voltage becomes higher than the output voltage of the plasma power supply (output voltage of the capacitor 10), if an inductive discharge type ignition device with the above characteristics is used, the energy of the capacitor 10 will no longer be injected. The present invention has been made to solve the problems of the prior art as described above, and there is no risk of causing irregular discharge.
Another object of the present invention is to provide a plasma ignition device that can reliably inject energy even when the ignition plug reaches a high temperature.

In order to achieve the above object, the present invention has the following features.

Capacitive discharge method (so-called CDI) as a power source for spark discharge
Each cylinder is provided with a plasma power source that uses the power source to oscillate the discharge voltage and injects energy to the ignition timing of each cylinder.

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

FIG. 2 is a diagram showing an embodiment of the present invention.

In FIG. 2, two ignition coils 6, a booster 17. A capacitive discharge device (hereinafter referred to as CDI) consisting of a capacitor C2 and a thyristor Q2 is used.

Further, as a plasma power source, diodes D1 to D5 . Inductor L4 for current limiting. A circuit consisting of a capacitor C1 and a thyristor Q, and a booster 18 are used.

Also, as an ignition signal generator, the crank angle of one engine is 1.
18 that outputs an 18o° signal S1 every time it rotates 80°
0" sensor 19. 7 every 7200 rotations of the angle of rotation
A 72D° sensor that outputs a 20° signal S2.

4-bit counter 21 and monostable multivibrator 2
A device consisting of 2 to 27 is used.

Next, FIG. 3 is a signal waveform diagram of the circuit of FIG. 2.

The circuit operation in FIG. 2 will be explained below with reference to FIG. 3.

explain about.

First, in the ignition signal generator, the 4-bit counter 21
counts the 180° signal S1 and outputs the signal S? as the output of each bit. lAI 85B 'S50' Outputs S50 one after another, and returns to the initial state (outputs S5A) when four 180° signals S are input. Furthermore, each time the monostable multivibrators 22 to 25 receive the signals S3A to S3D, the pulse signals S4A to S4D (for example,
For example, a pulse width of 100 μs) is output. This pulse signal S4A'' S4D becomes an ignition signal for each cylinder.

Note that the 720° signal S2 is a signal for cylinder discrimination, and is output at each ignition timing of the first cylinder, for example.

The 4-bit counter 21 is reset when the 720° signal S2 is applied, and returns to the initial state (outputting S3A). Therefore, the cylinders can be accurately discriminated at the time of starting, and even if a malfunction occurs due to noise or the like during normal operation, it can be immediately restored to normal operation.

In addition, the monostable multivibrator 26 has a 180 signal S
, outputs a pulse signal S5 every time it is input. This pulse signal S5 becomes the ignition signal for the CDI.O Also, the monostable multivibrator 27 outputs a pulse signal S6 (for example, pulse width 1 m5) every time the 180"5 signal S1 is input. This pulse signal S6 is This serves as a stop signal to stop the boosting operation of the booster 1B.

Next, in CDI, the booster 17 boosts the voltage 12V of the battery 1 to about 300V and outputs it. When the thyristor Q2 is off, the capacitor C2 is charged by the output of the booster 17.

Then, when the pulse signal S5 is applied and the thyristor Q2 is turned on, the charge in the capacitor C2 is rapidly discharged and a large current flows through the primary coil of the ignition coil 30, so that the peak value in the secondary coil is -20 to -60kV. A high voltage pulse is generated. This high voltage pulse is applied via the distributor 7 to one of the spark plugs 88 to 8D that corresponds to the ignition timing, and the spark plug (e.g. 8A)
・Next, in the plasma power supply, the booster 18 is connected to the battery 1.
12V is boosted to about 1500V and output.

When thyristor Q1 is off, the above 1500cm is connected to diode D5. Capacitor C1 is charged via D2.

Then, pulse signal S4A is applied to thyristor Ql.
When turned on, the X point is suddenly grounded.

1'I 500V is generated at 7 points.

Pulse signal S4A is synchronized with pulse signal s5.

At this time, as in the previous period, spark discharge is occurring at the ignition plug 8A, so the charge on the capacitor c1 is:

The plasma is injected into the spark plug 8A via the inductor L1 and diode D1, and plasma ignition is performed.

In other spark plugs 8B to 8D, similarly to the above,
Pulse signal 84B given at each ignition timing of each cylinder
” Energy injection from the capacitor occurs in response to S4D.

Further, while the pulse signal s6 is being applied, the booster 1
8 stops the boosting operation, so that the thyristor Q returns to OFF after the charge in the capacitor C4 is discharged.

Note that the 180' signal S is an ignition timing signal for a 4-cycle, 4-cylinder engine, and is a 120° signal for a 6-cylinder engine.

As mentioned above, in the device shown in Fig. 2, a plasma power source is provided for each cylinder, and plasma energy is injected only into the cylinder that corresponds to one ignition timing, so the cylinders that are not at one ignition timing There is no possibility that irregular discharge will occur.

In addition, since CDI is used as a power source for spark discharge, the voltage applied to the second spark plug oscillates due to the capacitor C2 and the inductance of the ignition coil, so even if the second spark plug becomes hot, plasma energy can be reliably injected. It is done.

FIG. 4 is a voltage waveform diagram of the spark plug in the above operation, and (a) shows the normal operation of the circuit in FIG. 1.

(b) shows the characteristics of the present invention shown in FIG. 2 when the spark plug of the circuit shown in FIG. 1 is at a high temperature, and (c).

In FIG. 4, W indicates the plasma energy injection period.

As can be seen from Fig. 4 (a), in the circuit shown in Fig. 1, when the spark plug becomes hot, the inductive energy stored in one ignition coil causes the discharge sustaining voltage to gradually rise from about 12 kV (approaching the D potential). ) will be the waveform.

As a result, the output voltage of the plasma power supply continues to be higher than that of the plasma power source, making it impossible to inject plasma energy.

On the other hand, in the case of the present invention, the voltage of one spark plug is detected as shown in FIG. 4(c).

The output voltage of the plasma power supply is always lower than that of the plasma power source, and plasma energy is reliably injected.

Next, FIG. 5 is a diagram showing another embodiment of the present invention.

The device of Figure 5 can be operated at two different voltages (e.g.
A booster 2B that outputs 1500 V and 1500 V) is used, and the respective voltages are used for CDI and plasma, which has the advantage that only one booster is required.

Note that in the booster 2B, 29 is an oscillator.

By alternately opening and closing two transistors using the output from the oscillator 29, a high voltage is generated on the secondary side of the transformer 29.

Furthermore, while the pulse signal S6 is being applied, the 1 oscillator 29 is stopped, and therefore there is no output from the booster 28.

In addition, in the embodiments shown in FIGS. 2 and 5, Cyrisk Q
It goes without saying that other semiconductor switching elements such as transistors may be used in place of Q2.

As explained above, according to the present invention, there is no risk of irregular discharge occurring and plasma energy can be reliably injected even when the ignition plug reaches a high temperature, resulting in the effect that 9 ignition performance can be improved. The device of the present invention is a two-spark plug type in which the ignition gap between the center electrode and the side electrodes is surrounded by an electrically insulating material such as ceramic to form a small volume discharge space. Although it is suitable for use in the case where a semiconductor is provided between the center electrode and the side electrodes (a so-called low tension plug), it can also be applied.

[Brief explanation of the drawing]

FIG. 1 is an example of a conventional device, FIG. 2 is an embodiment of the present invention, FIG. 5 is a signal waveform diagram of the circuit in FIG. 2, and FIG. 4 is a comparison diagram of spark plug voltage waveforms. The figure shows another embodiment of the present invention. Explanation of symbols 1...Battery 6...Ignition coil 7...
・Distributor 8A to 8D... Spark plug 17.18... Booster 19... 180' sensor 20... 720° sensor 21... 4-bit counter 22 to 27... Monostable multi-pipe leak 28・
...Booster 29...Oscillator C4, C2...
・Capacitor Q,,C2...Thyristor D1~D
5...Diode Figure 1

Claims (1)

[Scope of Claims] 1. A capacitive discharge type spark discharge power supply that applies high voltage to the spark plug at the ignition timing via a distributor to cause dielectric breakdown between the spark plug electrodes, and a spark discharge power source for each cylinder. and a plasma power source that applies the charge stored in the capacitor to the spark plug of the cylinder each time an ignition signal is applied. An ignition device that outputs an ignition signal that activates the spark discharge power source at each ignition timing of all cylinders, and an ignition signal that sequentially activates the plasma power source connected to the spark plug of each cylinder at each ignition timing of each cylinder. A plasma ignition device equipped with a signal generator. 2. The spark discharge power source is a series circuit of the primary coil of the two ignition coils, the first capacitor, and the first thyristor.
The output end of a booster that boosts the battery voltage is connected to the connection point between the first capacitor and the first thyristor, and the output end of the secondary coil of the ignition coil is connected to the rotor electrode of the distributor. A plasma ignition device according to claim 1, characterized in that: 3. The plasma power source includes a series circuit of a first diode, a second capacitor, and a second diode, and a thyristor W2 connected between the connection point of the first diode and the second capacitor and the ground. the second capacitor and the second
The first diode is connected to the output terminal of a booster that boosts the battery voltage. A plasma ignition device-4 according to claim 1, characterized in that a booster for the spark discharge power source and a booster for the plasma power source are shared by one booster. A plasma ignition device according to claim 2 or 3. 5. The ignition signal generating device includes a sensor that outputs a first signal at each ignition timing of all cylinders, and a sensor that outputs a second signal at each ignition timing of a specific cylinder. A counter that counts the first signal and has the same number of focus points as the number of cylinders that is reset by the second signal, and a first unit that has the same number of focus points as the number of cylinders connected to each pit of the counter. It consists of a stable multivibrator group and a second monostable multivibrator that is triggered every time the first signal is applied, and each output of the first monostable multivibrator group is provided for each cylinder. Claim 1, characterized in that the output of the second monostable multivibrator is used as an ignition signal for each of the plasma power sources, and the output of the second monostable multivibrator is used as an ignition signal for the spark discharge power source.
The plasma ignition device according to any one of items 1 to 4.