JPS6221984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition system for an engine capable of performing spark ignition and plasma ignition in the same cylinder.

Conventionally, a plasma ignition device has been developed in order to obtain combustion stability in operating conditions where combustion tends to be unstable, such as in a low-load operating range of an engine (Japanese Patent Application Laid-Open No. 1987-96587).

That is, this plasma ignition device generates an arc by applying a high voltage between both electrodes in a discharge space surrounded by a center electrode and a ground electrode, and then continuously applies a low voltage between both electrodes. This maintains the discharge state and ejects plasma-like gas from the nozzle holes to reliably ignite and burn the air-fuel mixture.

Therefore, this plasma ignition device is extremely effective in obtaining good combustion performance even during low-load operation, where misfires are likely to occur.However, on the other hand, because the ignition energy is high, the temperature of the spark plug increases rapidly, especially during high-load operation. In this region, the combustion temperature itself is quite high, which causes severe wear on the electrodes and significantly reduces the durability of the spark plug.

Therefore, it is desirable to perform plasma ignition as described above in low and medium load operating ranges where combustibility is poor, and to stop it during idling when the alternator's power generation capacity is low and in high load operating ranges where combustibility is good. If there is a sudden change in the ignition energy when switching the plasma ignition, it is conceivable that engine rotational fluctuations may occur, causing problems in drivability, etc.

The present invention has been made in view of the above points, and is an ignition device for an engine capable of performing spark ignition and plasma ignition in the same cylinder. Receives the output of the operating state detection means,
plasma ignition switching means for switching between a first state in which the plasma ignition is performed and a second state in which the plasma ignition is stopped; Alternatively, when the second state changes to the first state, the ignition energy control means changes the plasma ignition energy so as to gradually decrease or increase the plasma state corresponding to the changed operating state. An object of the present invention is to provide an ignition device for an engine that eliminates the possibility of problems in drivability caused by sudden changes in ignition energy.

An embodiment of the present invention will be described below with reference to the drawings.

The drawing shows an engine ignition system according to an embodiment of the present invention. In the drawing, 1 is an engine composed of a cylinder 2 and a cylinder head 3. A piston 4 is inserted into the cylinder 2. A combustion chamber 5 is formed in the combustion chamber 5. A normal spark plug 6 is installed in the cylinder head 3 above.
The plasma ignition plug 7 includes a center electrode 8, a ground electrode 9, an insulating material 10 made of ceramic interposed between the electrodes 8 and 9, and a discharge formed by these. It has a space 11, and a nozzle hole 12 for ejecting plasma gas is formed at the tip thereof.
Further, 13 is a spark ignition circuit for igniting the spark ignition plug 6, and in this circuit 13, one end of the primary coil 14a of the ignition coil 14 is connected to the battery 16 via the key switch 15, and the other end is connected to the battery 16 via the key switch 15. is a point 18 that is opened and closed by a cam 17 connected to the output shaft of the engine.
It is connected to the. Further, the secondary coil 14b of the ignition coil 14 is connected to the first power distribution section 20 via a diode 19. The part surrounded by the dashed line in the figure shows the secondary coil 14b by cutting off the current flowing through the primary coil 14a at point 18.
A high voltage generation circuit 21a that generates high voltage is configured, and the high voltage generated by the circuit 21a is distributed to the spark plug 6 of each cylinder by the first power distribution section 20. There is.

Further, 22 is a plasma ignition circuit for igniting the plasma ignition plug 7, and this circuit 2
Reference numeral 2 denotes a high voltage generation circuit 21b similar to the spark ignition circuit 13, and a low voltage generation circuit 2 for continuously supplying low voltage for a predetermined time after spark ignition.
3, and a second power distribution section 25 that distributes the output voltage of the high voltage generation circuit 21b and the low voltage generation circuit 23 to the plasma ignition plug 7 of each cylinder via the diode 19 or the diode 24. The low voltage generating circuit 23 has a resistor 27
, variable capacitor 28, coil 29 and resistor 3
This T-type circuit is connected to the battery 16 via a switch 26.

The capacitance of the variable capacitor 28 is controlled by the control signal a from the capacitor capacity controller 31, and the switch 26 is controlled to open and close by the switch control signal b from the operating state detector 32. ing. This operating state detector 3
2 detects operating conditions such as the engine speed and load condition based on the output of the rotation sensor 33 and the output of the throttle opening sensor 34, and outputs a plasma ignition switching signal c to the capacitor capacity controller 31. It outputs the switch control signal b.

Next, the operation of this device will be explained.

While the engine is running, the rotation sensor 33 detects the engine rotation speed, the throttle opening sensor 34 detects the throttle opening, and both sensors 33,
The output of 34 is input to the operating state detector 32 to detect the operating state (second state) of the engine, such as high engine speed or low engine speed, or high load or low load. When the operating state is such that only spark ignition is required, such as during idling or high-load operation, the operating state detector 32
For example, the switch control signal b is set to "1", and the switch 26 is opened. Therefore, in this state, only the high voltage generation circuits 21a and 21b generate high voltage,
The high voltage is applied to the first power distribution section 20 and the second power distribution section 2
5 distributes power to the spark ignition plug 6 and plasma ignition plug 7 of each cylinder, and the spark ignition plug 6 performs normal spark ignition, and the plasma ignition plug 7 also performs spark ignition. That is, in this plasma ignition plug 7, an arc is created between the center electrode 8 and the ground electrode 9 due to the high voltage, but since the switch 26 is off, the low voltage generation circuit 2 is activated during normal plasma ignition.
The low voltage that should be applied from 3 is not applied, and therefore, even though the element is a plasma ignition plug, it performs the same spark ignition as the spark ignition plug 6.

By the way, when the operating state of the engine changes and becomes an operating state (first state) in which plasma ignition is required, such as during low-load or medium-load operation, the operating state detector 32 detects this through the output of the rotation sensor 33 and It is detected from the output of the throttle opening sensor 34, the switch control signal b is set to "0", and the capacitance control signal c is sent to the capacitor capacitance controller 31.
send. Then, at the same time as the switch 26 is closed, the capacitance of the capacitor 28 is gradually increased by the output a from the capacitor capacity controller 31, and the low voltage generating circuit 23 gradually increases the output voltage at its output terminal 23a. Therefore, in the plasma ignition plug 7, after a high voltage is applied from the high voltage generation circuit 21b and an arc is generated in the discharge space 11, a low voltage is continuously applied from the low voltage generation circuit 23, and a discharge occurs. Plasma ignition is performed by ejecting plasma gas generated in space 11 from nozzle hole 12 . Moreover, at this time, the low voltage generation circuit 2
Since the low voltage from 3 gradually increases, the ignition energy supplied to the spark plug 7 gradually increases,
Since there is no large change in ignition energy, there are no problems with driveability, etc.

Further, when the engine shifts from a state where plasma ignition is performed in a low load or medium load operating region to a high load operating region or an idling state, the operating state detector 32 detects this and outputs a plasma ignition switching signal c. Upon receiving this signal c, the capacitor capacity controller 31 reduces the capacitance of the capacitor 28 using the capacity control signal a, and gradually decreases the output voltage of the low voltage generation circuit 23. Furthermore, the operating state detector 32 receives the switch control signal b is “1”
The switch 26 is opened to stop plasma ignition and only spark ignition occurs.

According to the engine ignition system of this embodiment, the ignition energy is gradually increased or decreased when switching between plasma ignition and spark ignition, so that problems with drivability etc. due to sudden changes in ignition energy are avoided. This has the effect of avoiding the risk of this occurring.

In the above embodiment, the driving state detector 32 receives the output of the rotation sensor 33 and the output of the throttle opening sensor 34 as input, but it is also possible to use only the output of one of the two sensors as input. In addition, in the low voltage generating circuit 23, the capacitor 28 is made variable so that the output voltage can be gradually increased or decreased, but the output voltage may be made variable by other means.

In the above embodiment, a spark ignition plug 6 and a plasma ignition plug 7 are provided, and the spark ignition plug 6 always ignites the spark, and the plasma ignition plug 7 switches between spark ignition and plasma ignition. Alternatively, only the plasma ignition plug 7 may be provided, and when plasma ignition is required, this may be used to ignite the plasma, and when spark ignition is better, this may be used to ignite the spark.

As described above, according to the present invention, in an engine ignition device capable of performing spark ignition and plasma ignition in the same cylinder, the ignition energy is gradually increased or decreased when plasma ignition is started or stopped. This configuration has the effect of eliminating the possibility that problems in drivability or the like may occur due to sudden changes in ignition energy.

[Brief explanation of the drawing]

The drawing is a configuration diagram of an engine ignition system according to an embodiment of the present invention. 32... Operating state detector as plasma ignition switching means; 31... Capacitor capacity controller as ignition energy control means.

Claims (1)

[Claims] 1. In an engine ignition device capable of performing spark ignition and plasma ignition by ejecting plasma gas in the same cylinder, the engine ignition device includes an operating state detecting means for detecting the operating state of the engine, and an operating state detecting means that receives the output of the operating state detecting means and detects the operating state of the engine. plasma ignition switching means for switching between a first state in which plasma ignition is performed and a second state in which plasma ignition is stopped; ignition energy control means for changing plasma ignition energy to gradually decrease or increase when changing from the second state to the first state to bring the plasma into a plasma state corresponding to the changed operating state; An ignition device for an engine characterized by comprising: