JPS6052311B2 - Plasma igniter for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma ignition device for an internal combustion engine such as an automobile, and more specifically, the ignition gap between positive and negative electrodes is surrounded by an electrical insulating material to form a discharge space. A plasma ignition device that supplies ignition energy from both power supply circuits for spark ignition and plasma ignition, and controls the plasma ignition in combination with plasma ignition in low engine load ranges, and stops plasma ignition in high engine load ranges, resulting in only spark ignition. Regarding.

An example of a conventional plasma ignition device will be explained with reference to FIG.

Plasma ignition devices are used to ensure reliable ignition and improve combustion safety in operating conditions where combustion tends to be unstable, such as in the low-load operating range of internal combustion engines and lean mixture combustion. As shown in the cross-sectional view at 6 in FIG. 1, the spark plug surrounds the ignition gap between the center electrode 1 and the side electrodes 2 with an electrically insulating material 3 such as ceramics to generate a small volume of discharge. The ignition plug 6 has a structure that forms a space 4.The ignition plug 6 is supplied with ignition energy from both a spark ignition power supply circuit 7 and a plasma ignition power supply circuit 8, and when a spark is discharged, there is a The generated plasma gas is ejected from the nozzle hole 5 to ignite and burn the air-fuel mixture.This spark plug 6 differs from a normal spark plug that ignites the air-fuel mixture only by spark discharge. A spark is generated between the side electrode 2 and the spark ignition power supply circuit 7 based on a high voltage (■KV to 20KV), and by utilizing the fact that the insulation is broken inside the discharge space 4 at this time, By applying a relatively low voltage (for example, -3000 V) between the electrodes from the plasma ignition power supply circuit 8, the discharge state is maintained, and based on the thermal expansion of the resulting high-temperature, high-energy plasma-like gas, the high-temperature High-pressure gas is ejected from the nozzle holes 5 to reliably ignite and burn the air-fuel mixture. Therefore, stable combustion can be achieved even during low-load operation where misfires are likely to occur.
On the other hand, since the ignition energy is high, the temperature of the ignition plug also rises rapidly, and the combustion temperature itself becomes quite high, especially in the engine's high-load operating range, so if high-energy ignition continues in this state, the center electrode 1 will wear out rapidly. In some cases, there is a risk of melting and damage.Furthermore, if high-energy ignition is performed in a region where the engine speed is high, power consumption will be extremely large, resulting in inconveniences such as the need to increase the capacity of the battery and alternator. occurs.

To deal with this, plasma ignition is used in conjunction with plasma ignition to generate high energy in low engine load ranges, but in high engine load operating ranges where combustion conditions are generally good, plasma ignition is stopped and only spark ignition is used. A device has been proposed.

That is, in FIG. 1, the spark ignition power supply circuit 7 is as follows:
The ignition coil is the same as that used in a normal spark discharge ignition system and consists of a contact point 75 that opens and closes in synchronization with engine rotation, a battery power source 71, a primary coil 72, and a secondary coil 73. 74, and generates a high-voltage ignition voltage (pulse) in synchronization with the opening and closing of the contact point 75. On the other hand, the plasma ignition power supply circuit 8 includes a capacitor 81 that stores the plasma generation current, a relay 83 and its contacts 84 that open and close the circuit connection between the capacitor 81 and the high voltage power supply 82, and the plasma generation current. This relay 83 receives an output signal from the plasma ignition control circuit 12 which outputs a command signal to perform or cancel plasma ignition depending on the load condition of the internal combustion engine 11. It is becoming more and more controlled. That is, in a low engine load range, a high level signal is output from the plasma ignition control circuit 12, the relay 83 is energized, the contact 84 is closed, and plasma ignition energy is supplied to the ignition plug 6.
In the engine high load operating range, a low level signal is output from the plasma ignition control circuit 12, the relay 83 is in a de-energized state, and the contact 84 is open, so that plasma ignition energy is not transferred from the plasma ignition power supply circuit 8 to the ignition plug 6. There is no supply of 9 and 10 are diodes for blocking backflow.

However, since the conventional plasma ignition system described above is configured to ignite the spark and ignite the plasma at the same time when starting the aircraft, for example, the fuel system or mechanical parts may be the cause. If the aircraft start operation is performed many times without knowing the cause of failure, the problem is that the battery power source is likely to over-discharge due to the large amount of power consumed for starting and driving and the large amount of power consumed for plasma discharge. The point was hot.

The present invention has been made by focusing on these conventional problems, and adds detection means for detecting cranking time and number of cranking times, and control means for controlling plasma discharge based on this detection signal to the conventional configuration. Accordingly, it is an object of the present invention to provide a plasma ignition device that solves the above problems.

That is, conventionally, plasma ignition has the effect of completing combustion within the cylinders of an engine, greatly expanding the lean combustion limit, and as a result, in addition to cleaning exhaust gas, it is possible to significantly improve fuel efficiency. Furthermore, especially when starting at low temperatures, even if the fuel is not completely atomized and becomes close to lean combustion, the combined use of plasma ignition has the effect of greatly improving startability. However, since cranking consumes a large amount of power from the battery power source during startup, plasma ignition, which consumes even more power, must be avoided for a long time. In particular, in the case of a failure where there is no problem with ignitability, that is, there is no possibility of starting even after cranking for a certain amount of time or a certain number of times (such as a fuel system failure), repeating cranking many times is a waste of effort. energy will be consumed. In contrast, the present invention (1) does not continuously ignite plasma for a certain period of time during aircraft start-up, and returns to normal spark ignition only after the certain period of time has elapsed; If cranking is repeated many times within a short period of time, the above problem can be solved by gradually decreasing the plasma ignition time, (3) controlling the plasma ignition energy depending on the number of repetitions of cranking, etc. This is an attempt to resolve the issue. That is, the features of the present invention include a plasma ignition control circuit that detects the engine load state and outputs a signal to control the start and stop of plasma ignition, and a start detection circuit that detects when the engine is in the start state and outputs a start signal. and a starting plasma ignition amount suppression circuit that processes the starting signal and the plasma ignition control circuit output signal to suppress the amount of ignition energy for plasma ignition during the starting period.

The present invention will be explained below with reference to the drawings.

Fig. 2 is a circuit diagram showing one embodiment of the present invention, and Fig. 3 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of the start detection circuit 13 shown in the figure.

In FIG. 2, 14 is an ignition key, ST is the position when the starter 15 is driven, ON is the position where the internal combustion engine is kept running after starting, and OFF is the position when the internal combustion engine is stopped. 13 is a start detection circuit that detects when the ignition key 14 is in the ST position.

Fig. 3 is a circuit diagram showing an example of the circuit, which is composed of a transistor Q1, a constant voltage diode ZDl, and resistors R1 to R4, and normally outputs a high level signal ゜“1゛, when the ignition key 14 is in the ST position. outputs a low level signal “0”. 16 is a timer circuit, 17 is an AND circuit, 18
is an OR circuit, and these 16, 17, and 18 constitute a starting plasma ignition amount suppression circuit.

That is, the timer circuit 16 detects that the output of the start detection circuit 13 is
This is a timer circuit that outputs an on signal for a preset period of time from the time it rises from 1 to 0, and is formed of, for example, a monostable multivibrator circuit, and is connected to an AND circuit 1.
7 sends a "1" signal to the OR circuit 18 when the outputs of both the start detection circuit 13 and the plasma ignition control circuit 12 are "1", and the output of the timer circuit 16 is connected to the relay 83 via the OR circuit 18. has been done. In the above configuration,
When the driver turns the ignition key 14 to the ST position and drives the starter 15 (actually operated via a relay, not shown), the start detection circuit 13 detects this start signal and the output signal changes to the level.゜"1" changes to ゜゜0゛, and triggered by this fall, the timer circuit 16 outputs an ON signal for a preset time T (for example, 2 seconds).This ON signal is output to the OR circuit 18. is input, and plasma ignition is performed by energizing the relay 83 for T seconds after starting.At the time of starting when the output of the starting detection circuit 13 is ゜゜0゛, even if the plasma ignition control circuit 1
Even if the “゜1” signal is output from 2, the output of the AND circuit 17 is ゜゛0. Therefore, the relay 83 is deenergized when the set time of the timer circuit 16 has elapsed, and the plasma ignition energy is controlled thereafter. Supply will be discontinued. In operating states other than starting, since the starting detection circuit 13 outputs a signal "1", normal plasma ignition control is performed through the plasma ignition control circuit 12, AND circuit 17, and OR circuit 18. FIG. 4 is a circuit diagram showing another embodiment of the present invention, in which the number of cranking operations within a certain period of time is counted, and the time constant T of the timer circuit 16 is gradually reduced based on this number of cranking operations. It is.

This is achieved, for example, as follows. inputting the output signal of the start detection circuit 13 to the plasma ignition control circuit 12;
A counter counts the falling edge of this input signal from 1゛→゜゜0゛, a D/A converter generates a DC voltage proportional to this counted value, and this DC voltage is sent to the timer circuit 16 to generate a monostable multi-channel signal. The time constant of the vibrator circuit may be made smaller according to the magnitude of the DC voltage. (D/
For example, the A converter is configured to reset the count value when the ignition key is in the OFF position.) FIG. In addition, a function is added to control the plasma ignition energy during cranking.

As for the configuration, as shown in FIG. 4, a "capacitor 81" for storing current for plasma generation is placed in parallel with the capacitor 81, and a relay 83" and a contact 8C are provided for opening and closing the capacitor 8". is configured to be controlled by the output of the plasma ignition control circuit 12. Immediately after starting cranking, the capacitor 8 is
1 and 8" into the circuit of the high-voltage power supply 82 to actively ignite them. In most cases, they ignite and start in an instant, resulting in extremely short cranking, and the battery In addition, by installing both capacitors 81 and 8'', in addition to controlling whether to perform or cancel plasma ignition during normal operation, it is possible to reduce plasma ignition energy. There is also the advantage of being able to use a control method that increases or decreases the amount.
If the circuit of the embodiment shown in FIG. 5 is used, it is also possible to adopt a method in which the capacitor 8' is controlled by the count value obtained by counting the number of starts.For example, a specific value of the count value of the number of starts can be determined by a gate circuit and the capacitor 8' For example, the plasma ignition energy is reduced until the second start (contact 8C is opened), the energy is increased for the third and fourth times (contact 8C is closed), and from the fifth time onwards, the energy is increased. It is possible to set the control method according to the starting characteristics of the internal combustion engine, such as setting the value to zero (opening the contact 84).As explained above, according to the present invention, the plasma ignition during cranking By adding a configuration to control energy, it is possible to limit wasteful rankings and start high-energy plasma ignition.Furthermore, by adopting the configuration of the embodiment, wasteful battery consumption due to repeated cranking can be avoided. This has the effect of preventing combustion, increasing ignitability, and shortening cranking time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the prior art, FIG. 2 is an embodiment of the present invention, and FIG. 3 is a diagram showing an example of the start detection circuit in FIG.
FIGS. 4 and 5 are explanatory diagrams of other embodiments of the present invention, respectively. Explanation of symbols, 1... Center electrode, 2...
Side electrode, 3... Electrical insulation material, 4...
Discharge space, 5... Nozzle hole, 6... Spark plug, 7
......Spark ignition power supply circuit, 8...
Plasma ignition power supply circuit, 11... internal combustion engine, 12.
...Plasma ignition control circuit, 13...Start detection circuit, 14...Ignition key, 15.
... Starter, 16 ... Timer circuit, 74.
...Ignition coil, 75...Contact point, 81,8 "...Capacitor, 82...
・・High voltage power supply, 83,83″ ・・Relay, 85・・
...Waveform shaping coil.

Claims (1)

[Scope of Claims] 1. A discharge space is formed by surrounding the ignition gap between the positive and negative electrodes with an electric insulating material, and ignition energy is supplied from both power supply circuits for spark ignition and plasma ignition, and the ignition gap is surrounded by an electrical insulating material, and ignition energy is supplied from both power supply circuits for spark ignition and plasma ignition, and the ignition gap is surrounded by an electrical insulating material, and ignition energy is supplied from both power supply circuits for spark ignition and plasma ignition. In a plasma ignition system that uses both spark ignition and plasma ignition and controls the plasma ignition to stop and only spark ignition in the high engine load range, we have developed a signal that detects the engine load condition and controls the start and stop of plasma ignition. A plasma ignition control circuit outputs a plasma ignition control circuit, a start detection circuit detects when the engine is started and outputs a start signal, and processes this start signal and the output signal of the plasma ignition control circuit to generate plasma during the engine start period. A plasma ignition device for an internal combustion engine, comprising: a starting plasma ignition amount suppression circuit that suppresses the amount of ignition energy for ignition. 2. The starting plasma ignition amount suppression circuit ignites plasma when the above set time has elapsed when the engine is started, based on the output signal of a timer circuit that outputs an on signal for a predetermined set time from the time when the engine start signal is generated. 2. The plasma ignition device for an internal combustion engine according to claim 1, characterized in that the plasma ignition amount suppressing circuit at the time of startup stops the plasma ignition amount. 3. A patent claim characterized in that the starting plasma ignition amount suppression circuit is a starting plasma ignition amount suppression circuit that detects the number of engine starts within a certain period of time and suppresses the plasma ignition amount in accordance with the number of engine starts. A plasma ignition device for an internal combustion engine according to item 1.