JPS6115272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved engine ignition system, particularly an engine ignition system that performs spark ignition and plasma ignition by ejecting plasma gas in the same cylinder.

2. Description of the Related Art Conventionally, plasma ignition devices have been proposed that perform ignition by ejecting plasma gas generated by plasma discharge into a combustion chamber. This plasma ignition device has the advantage of having greater ignition energy and improving engine combustibility than normal spark ignition, but on the other hand, high energy is supplied to the plug and the structure of the plug. The temperature of the plug was high due in part to poor cooling performance, which caused practical difficulties in terms of the durability of the plug.

For this reason, conventionally, for example, plasma ignition is performed only in a specific operating range (low load range) where engine combustibility deteriorates, and spark ignition is performed in other operating ranges (high load range) to lower the plug temperature. A device that prevents excessive rise is known. (Japanese Unexamined Patent Publication No. 55-96587).

However, uniformly setting specific operating ranges does not adequately correspond to engine operating conditions; for example, when operating at high altitudes, the air becomes thinner, so the areas where combustibility deteriorates may occur at low altitudes. As the plasma ignition device expands beyond the above range, it cannot be said that the original advantage of the plasma ignition device, which is to improve the combustibility of the engine, is effectively utilized.

The present invention has been made by focusing on such a problem, and when igniting plasma in a specific operating range, it is possible to identify whether or not the operation is at a high altitude, and when operating at a high altitude, the plasma operating range due to plasma discharge is determined. By making the area larger than that during normal low-altitude operation, it is possible to perform plasma ignition that is responsive to engine high-altitude operation by taking advantage of the inherent advantages of the plasma ignition device without excessively increasing the plug temperature. Its purpose is to provide an ignition system for engines.

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

In the drawing, 1 is a cylinder of a reciprocating engine in which a piston 2 is reciprocated within a cylinder 3 to obtain rotational output, and 4 is screwed and fixed to a cylinder head 6 that defines the upper part of a combustion chamber 5, with the tip thereof being fixed. A normal spark ignition plug faces the combustion chamber 5, and 7 is a plasma ignition plug screwed into the cylinder head 6 with its tip facing the combustion chamber 5. This plasma ignition plug 7 is well known. As shown, a discharge space 11 is formed inside by partitioning the center electrode 8 and the side electrodes 9 whose outer peripheries are threaded with an insulating material 10 such as ceramic, and a high voltage is first applied between both electrodes 8 and 9. After dielectric breakdown of the discharge space 11 occurs, a low voltage is applied between the electrodes 8 and 9 to cause plasma discharge, and the plasma gas generated by this discharge is ejected from the nozzle hole 12 into the combustion chamber 5. It has a structure that allows

The spark ignition plug 4 is provided with an ordinary spark ignition circuit 13, and a primary coil 16a connected to the positive terminal of a battery 15 via a key switch 14.
is intermittent by opening and closing point 18 with the rotation of cam 17 synchronized with the rotation of the engine, and at the timing of opening of point 18, the secondary coil 16b is
A high voltage of about 20 KV is generated and applied to the spark ignition plug 4 via the backflow prevention diode 19 and the first power distribution section 20 to cause spark discharge.

On the other hand, for the plasma ignition plug 7, a high voltage generation circuit 21 is provided to generate a high voltage of about 50 KV to cause dielectric breakdown in the discharge space 11 of the plasma ignition plug 7, and a To perform plasma discharge
Low voltage generation circuit 22 that applies a low voltage of about 3KV
has been established.

The high voltage generation circuit 21 described above has a circuit configuration similar to a normal spark ignition circuit, and has a key switch 23.
The primary coil 25a connected to the positive pole of the battery 24 is connected to the positive terminal of the battery 24 through the cam 26, which is synchronized with the rotation of the engine, by opening and closing the point 27.
A high voltage is generated and applied to the plasma ignition plug 7 via the backflow prevention diode 28 and the second power distribution section 29.

On the other hand, the low voltage generation circuit 22 connects a capacitor 33 to the negative electrode of the battery 32 via a switch 30 and a resistor 31 whose opening/closing is controlled according to the operating state of the engine, and also connects each wiring of the second power distribution section 29. A resistor 35 and a coil 36 are connected between the connected backflow prevention diode 34 and the capacitor 33.
It has a basic configuration in which the switch 30 is connected in series.
is turned on, following the application of high voltage by the high voltage generation circuit 21, the capacitor 33 is discharged for a predetermined time determined by the capacitor 33, the resistor 35, and the coil 36, and the plasma ignition plug 7 is charged with a predetermined voltage. A low voltage is applied to cause plasma discharge.

The opening and closing of the switch 30 is controlled by a plasma operating range setting device 37, which receives as an input signal the output signal of a conventionally known, for example, bellows type high altitude detection sensor 38 that detects atmospheric pressure. The output signal of the controller 39, the throttle opening sensor 40 that detects the opening of the carburetor throttle valve, and the output signal of the rotation speed sensor 41 that detects the engine speed are used as input signals to determine the operating range in which plasma ignition is performed (plasma operation area),
When the operating state of the engine is in the plasma operating range, the switch 30 is closed to allow the low voltage generation circuit 22 to function.

The plasma operating range is set based on a control signal from the controller 39 based on the output signal of the high altitude detection sensor 38, and the plasma operating range is expanded when the engine is operated at high altitude.

That is, as shown in Fig. 2, in normal low-altitude operation, the low-load operation range where the throttle opening is, for example, 30 degrees or less is the plasma operation range, while in high-altitude operation, the plasma operation range is For example, the throttle opening is expanded to a line of 40 degrees, and plasma operation is performed in this expanded plasma operation range.

Therefore, when operating at high altitudes, the plasma ignition plug 7 generates spark discharge (spark discharge) due to the high voltage generated by the high voltage generation circuit 21 in the low load operating range until the throttle opening reaches 40 degrees. ), and then plasma discharge is performed by the low voltage generating circuit 22 to compensate for combustibility at high altitudes where the air is thin. In this case, at high altitudes, the outside temperature is lower than at low altitudes, and the engine temperature is lower.
Even if the plasma operating range is expanded, the plug temperature of the plasma ignition plug will not rise excessively.

In addition, outside the plasma operation range, the switch 30 of the low voltage generation circuit 22 is connected to the plasma operation range setting device 3.
7, the capacitor 33 is not charged and the low voltage generation circuit 22 is disabled. As a result, the plasma ignition plug 7 is activated by the high voltage generation circuit 21, like the normal spark ignition plug 4. Perform only spark discharge.

In the above embodiment, the spark ignition plug 4 was installed in parallel with the plasma ignition plug 7, but as is clear from the above, the plasma ignition plug 7 also has a spark ignition function. A one-plug system is also possible.

Further, in the above embodiment, the plasma operating range was set to a throttle opening of 30° or less and 40° or less, respectively, but it goes without saying that such values are not limited to these. Furthermore, although we have shown an example in which the range of the plasma operating range is changed depending on the throttle opening state, this range may also be changed depending on the state of each parameter representing the operating state, such as the engine speed and intake pipe negative pressure. .

As is clear from the above description, the present invention provides a control system that expands the specific operating range in which plasma ignition is performed by ejecting plasma gas during high-altitude operation compared to normal low-altitude operation. An object of the present invention is to provide an engine ignition device that compensates for engine combustibility by performing plasma ignition in an expanded plasma operating range.

Therefore, according to the present invention, plasma ignition control suitable for high-altitude operation can be performed, the advantages of the plasma ignition plug can be more effectively exhibited, and engine operability at high altitudes can be improved.

[Brief explanation of the drawing]

FIG. 1 is an overall explanatory diagram of an engine ignition system according to an embodiment of the present invention, and FIG. 2 is a graph showing an example of changing the plasma operating range. 1...Cylinder, 4...Spark ignition plug, 7...Plasma ignition plug, 21...High voltage generation circuit, 2
2...Low voltage generation circuit, 30...Switch, 37
...Plasma operating range setting device, 38...High altitude detection sensor, 39...Controller, 40...Throttle opening sensor.

Claims (1)

[Scope of Claims] 1. An ignition device for an engine that performs spark ignition and plasma ignition by ejecting plasma gas in the same cylinder, which includes a detection means for detecting the operating state of the engine, and a signal from the detection means is inputted. a plasma operating range setting means for igniting plasma in a specific operating range; a high-altitude driving detecting means for detecting a high-altitude driving state by detecting atmospheric pressure, etc.; An engine ignition device characterized by having a control means for expanding a plasma operating range.