JPH0118264B2 - - Google Patents

Description

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

In general, in operating regions where the intake air charge increases rapidly, the combustion temperature also rises, leading to NOx, which contributes to air pollution.
It is well known that the amount of NOx generated increases, and there is a problem that a large amount of NOx is generated especially during acceleration driving, which is frequently used in city mode.

In other words, even during operation in the low to medium load range, when the transition to accelerated operation occurs, the air-fuel ratio of the mixture temporarily becomes leaner than the stoichiometric air-fuel ratio due to a delay in the response to the fuel increase, and becomes slightly leaner than the stoichiometric air-fuel ratio. The generation of NOx becomes a problem because the amount of NOx generated is at its maximum under these conditions.

On the other hand, as shown in Japanese Unexamined Patent Publication No. 55-96587, a discharge space is formed by surrounding the ignition gap between the positive and negative electrodes with an electrical insulating material, and the plasma-like gas generated in this discharge space is The plasma ignition plug is equipped with a plasma ignition plug that injects water into the combustion chamber from the nozzle hole, and the plasma ignition is stopped during high-load operation, which improves combustibility, thereby improving ignition performance and combustibility during low engine load. It is known that this method has the advantage of improving the durability of the spark plug under high loads.

In an engine equipped with such a plasma ignition device, the high ignition energy of plasma ignition can compensate for poor ignition performance and combustibility, especially in low-speed, low-load operation of an engine with poor ignition performance and combustibility. Thus, during accelerated operation in which the amount of NOx generated increases within the operating range where plasma ignition is performed, the ignition energy is high, so the combustibility is further increased, the combustion temperature rises further, and a large amount of NOx is generated. There is a problem that occurs when prompted.

The present invention has been made in view of this problem, and is designed to provide an ignition device with both a normal spark ignition function and a plasma ignition function by ejecting plasma gas. The object of the present invention is to provide an engine ignition device that cancels a plasma ignition function by ejecting plasma gas or reduces plasma ignition energy during accelerated operation even in an operating range where plasma ignition is performed.

Hereinafter, the present invention will be described in more detail based on illustrated embodiments.

In the figure, 1 is a reciprocating engine in which a piston 3 is reciprocated in the vertical direction within a combustion chamber 2, and 4 is a reciprocating engine that is screwed and fixed to a cylinder head 5 that defines the upper part of the combustion chamber 2. A normal spark plug that protrudes from the ignition plug, 6 is the spark plug 4.
As is well known, the plasma ignition plug 6 is a plasma ignition plug that is screwed and fixed to the cylinder head 5 at a distance from the center electrode 8 and the side electrodes 9 which are threaded on the outer periphery and are made of ceramic or the like. A discharge space 11 is formed inside by partitioning with an insulating material 10, and a high voltage is first applied between the center electrode 8 and the side electrodes 9 to cause a spark discharge to dielectrically break down the discharge space 11. A low voltage is applied between 8 and the side electrode 9 to cause plasma discharge, and the discharge space 11
It has a structure in which plasma-like gas generated therein is ejected from a nozzle hole 12 toward the combustion chamber 2.

The above-mentioned spark ignition plug 4 is provided with a normal ignition circuit 13, and a primary coil 16a of an ignition coil 16 connected to the positive terminal of a battery 14 via a key switch 15 is connected to a cam that rotates in synchronization with the rotation of the engine. By turning point 19 on and off at rotation 18, the point 19 is turned on and off, and when the point 19 is turned off, a high voltage of about 20 kV generated in the secondary coil 16b of the ignition coil 16 is applied to the spark ignition plug 4 via the first power distribution section 21. . Note that 17 is a diode connected between the secondary coil 16b and the first power distribution section 21 in order to prevent current from flowing in the opposite direction.

On the other hand, the plasma ignition plug 6 is provided with a high voltage generation circuit 22 and a low voltage generation circuit 23, as well as an acceleration sensor that detects when the engine is in accelerated operation and outputs an off signal. A control circuit 24 for disabling 23 is provided.

The high voltage generation circuit 23 includes a spark plug 4
The primary coil 2 of the ignition coil 28 has the same configuration as the ignition circuit 13 provided for the battery 26 and is connected to the positive electrode side of the battery 26 via the key switch 27.
8a is turned on and off by opening and closing the point 30 with a cam 29 that rotates in synchronization with the rotation of the engine, and when the cam 29 is turned off, a high voltage is generated in the secondary coil 28b of the ignition coil 28, and the second power distribution section 31 is turned on and off. is applied between the center electrode 8 and the side electrodes 9 through the
A spark discharge is generated between both electrodes 8 and 9, and dielectric breakdown of the discharge space 11 is performed. In this case, the ignition coil 28 is set so as to generate a high voltage, for example, 50 kV, sufficient to cause dielectric breakdown of the high voltage generating circuit 22 and the discharge space 11. Note that 32 is the secondary coil 28b of the high voltage generation circuit 22 and the second power distribution section 3.
This is a diode for backflow prevention connected between 1 and 1.

Further, the low voltage generation circuit 23 includes a capacitor 36 connected to the negative terminal of the power supply 33 whose positive terminal is grounded via a switch 34 and a resistor 35 whose on/off is controlled by the control circuit 24. , a resistor 38 and a coil 39 connected in series with a capacitor 36 in the forward direction of a diode 37 for preventing backflow with respect to the center electrode 8,
When the switch 34 is turned on, the power source 3
A relatively low voltage of, for example, about 3 KV is generated between the center electrode 8 and the side electrodes 9 by discharging the capacitor 36 charged by the capacitor 36, and a plasma discharge is generated in the discharge space 11 which has dielectric breakdown due to the spark discharge. This is performed to generate plasma-like gas, and the generated plasma-like gas is ejected from the nozzle hole 12 into the combustion chamber 2 to perform so-called plasma ignition.

In addition, the discharge time of plasma discharge, in other words,
The discharge time of the capacitor 36 is as follows:
It is set by a resistor 38 and a coil 39.

The control circuit 24 basically operates at a low voltage when acceleration is detected by a conventionally known acceleration sensor, for example, a sensor that detects acceleration from a change in intake negative pressure or a change in throttle opening. Generation circuit 23
It is sufficient to turn off the switch 34 that disables the plasma ignition, but it can also detect when the engine is operating under high load, which improves the ignitability and combustibility of the engine, and turns off the switch 34 even during such operation to prevent plasma ignition. It is preferable to disable it. In this way, the ignition energy during high-load operation can be significantly reduced, so it is possible to effectively prevent thermal deterioration of the plasma spark plug due to excessive temperature rise, especially during high-speed, high-load operation. .

In the above configuration, its operation will be explained next.

Now, in the low load operating state where the control circuit 24 turns on the switch 34, the low voltage generation circuit 23 is activated, so that the plasma ignition plug 6 is activated in parallel with the spark ignition of the spark ignition plug 4 by the normal ignition circuit 13. performs the original plasma ignition.

Therefore, the ignitability and combustibility of the engine are maintained in extremely good condition, and due to the multiple ignition sources and the high ignition energy of plasma ignition, especially at low rotation speeds and low loads, Ignitability and combustibility are improved.

On the other hand, when the engine accelerates, the acceleration sensor detects this, and the control circuit 24 turns off the switch 34 of the low voltage generation circuit 23, cutting off the current to the capacitor 36. is disabled, and due to the high voltage applied by the high voltage generating circuit 22, the plasma ignition plug 6 only performs spark ignition by normal spark discharge, and the substantial plasma ignition function is stopped. Therefore, during this operation, the spark ignition plug 4 and the plasma ignition plug 6 reduce their energy, thereby preventing an excessive rise in combustion temperature and suppressing the generation of NOx as much as possible. .

Note that, as described above, if the switch 34 is turned off by the control circuit 24 even during high-load operation of the engine, deterioration of the plasma ignition plug 6 can be effectively prevented.

Furthermore, in the above embodiment, the low voltage generation circuit 23 is disabled by turning off the switch 34, thereby canceling the actual plasma ignition. The plasma ignition energy may be reduced by reducing the voltage of the low voltage generating circuit 23. Furthermore, although the ignition device is configured with two spark plugs 4 and plasma ignition plugs 6, the plasma ignition plug 6 itself has both spark ignition and plasma ignition functions, so only the plasma ignition plug 6 is used. It goes without saying that the ignition device according to the present invention can be constructed using the following.

As is clear from the above description, the present invention provides means for detecting accelerated operation of an engine in an engine ignition device having a normal spark ignition function and a plasma ignition function by ejecting plasma gas, and a means for detecting accelerated operation of the engine. The present invention provides an engine ignition device including means for canceling plasma ignition or reducing plasma ignition energy in response to an output signal from the means.

According to the present invention, during acceleration operation of the engine,
Since plasma ignition is not performed, it is possible to prevent an excessive rise in combustion temperature and suppress the generation of NOx as much as possible.

Further, according to the present invention, during acceleration operation, the low
Even under medium load conditions, the plasma ignition is canceled or the ignition energy is reduced, so NOx accompanying accelerated operation is reduced regardless of the load.
It is possible to effectively suppress the temporary increase in .

[Brief explanation of drawings]

FIG. 1 is an overall schematic explanatory diagram of an engine ignition system according to an embodiment of the present invention. 1... Engine, 2... Combustion chamber, 4... Spark ignition plug, 6... Plasma spark plug, 13...
Spark ignition plug ignition circuit, 22...High voltage generation circuit, 23...Low voltage generation circuit, 24...Control circuit (acceleration detection means), 34...Switch.

Claims (1)

[Scope of Claims] 1. In an engine ignition device configured to perform spark ignition and plasma ignition by ejecting plasma gas in the same cylinder, a detection means for detecting accelerated operation of the engine and outputting a signal; and the detection means An ignition device for an engine, comprising means for canceling plasma ignition or reducing plasma ignition energy during accelerated operation in response to the output of the engine.