JPS6115271B2 - - 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 a large ignition energy and improving the combustion performance of the engine in normal spark ignition, but on the other hand, high energy is supplied to the plug and the structure of the plug makes it difficult to cool. In some cases, the temperature of the plug becomes high due to poor performance, which poses a practical problem in terms of the durability of the plug.

For this reason, conventionally, for example, plasma ignition is performed only in specific operating ranges (low load ranges) where engine combustibility deteriorates, and plasma ignition is performed only in other operating ranges (high load ranges).
It is known that spark ignition is used to prevent the plug temperature from rising excessively. (Japanese Patent Application Laid-open No. 55-96587).

However, uniformly setting a specific operating range does not adequately correspond to the operating condition of the engine, and it cannot be said that it effectively utilizes the inherent advantage of the plasma ignition device, which is to improve the combustibility of the engine. There was a problem.

The present invention has been made with attention to this problem, and when performing plasma ignition in a specific operating range, the present invention distinguishes the warm-up state of the engine, that is, before the warm-up is completed and after the warm-up is completed. Before engine completion, the plasma operating range due to plasma ignition is expanded from the area after warm-up, and the inherent advantages of the plasma ignition system are utilized to warm up the engine without excessively increasing the plug temperature. It is an object of the present invention to provide an engine ignition device that can perform prompt plasma ignition.

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 periphery is 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 makes it possible to

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 3 are connected between each connected diode 34 for backflow prevention and the capacitor 33.
It has a basic configuration in which switches 6 and 3 are connected in series.
0 is on, the high voltage generation circuit 21 applies a high voltage, and then the capacitor 33 is discharged for a predetermined time determined by the capacitor 33, the resistor 35, and the coil 36, and the plasma spark plug 7
A predetermined low voltage is applied to generate plasma discharge.

The opening and closing of the switch 30 is controlled by a plasma operating range setting device 37. This plasma operating range setting device 37 receives an output signal from a controller 39 which receives as an input signal an output signal from a water temperature sensor 38 that detects engine temperature, for example, engine cooling water temperature, and a throttle opening that detects the opening of a carburetor throttle valve. Using the output signals of the sensor 40 and the rotation speed sensor 41 that detects the engine rotation speed as input signals, an operating range (plasma operating range) in which plasma ignition is performed is set, and when the engine operating state is in the plasma operating range, the above-mentioned The switch 30 is closed to allow the low voltage generation circuit 22 to function.

The plasma operating range is set by a control signal from the controller 39 based on the output signal of the water temperature sensor 38 that detects the warm-up state of the engine, and the operating range is changed before and after the engine is warmed up. In other words, as shown in Fig. 2, after the engine has warmed up, the plasma operating range is set in the low-load operating range with a throttle opening of 30° or less, while when the engine is cold-started, the engine is warmed up. If the machine is not completed, the plasma operating range is expanded to the line of 40° throttle opening, and plasma operation is performed in this expanded plasma operating range.

Therefore, before the engine warm-up is completed, the plasma ignition plug 7 receives the high voltage generated by the high voltage generation circuit 21 in the low load operating range until the throttle opening reaches 40 degrees. by performing a spark discharge (spark discharge), and then by performing a plasma discharge by the low voltage generation circuit 22,
Compensate for flammability before warming up. In this case, since the engine temperature is low, even if the plasma operating range is expanded,
The plug temperature of the plasma spark plug does 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 the range of the plasma operating range has been exemplified as changing 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 engine speed, intake pipe negative pressure, etc.

As is clear from the above description, the present invention expands the specific operating range in which plasma ignition is performed by ejecting plasma gas before engine warm-up is completed compared to after engine warm-up is completed. The present invention provides an engine ignition device that compensates for engine combustibility by igniting plasma in an expanded plasma operating range.

Therefore, according to the present invention, plasma ignition can be controlled in accordance with the operating conditions of the engine, and the advantages of the plasma ignition plug can be more effectively exhibited.

[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...Water temperature 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 warm-up detecting means for detecting the warm-up state of the engine; and a warm-up detecting means for detecting the warm-up state of the engine. An ignition device for an engine, comprising a control means for expanding a plasma operating range from a plasma operating range after completion of warm-up.