JPS6137982Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an ignition device used in a fluid fuel combustion device such as petroleum, and particularly relates to an improvement of a high frequency oscillation type capacitor discharge type ignition device.

In place of the leakage type high voltage transformer that has traditionally been used in the ignition system of fluid fuel combustion devices such as petroleum,
In recent years, it has become possible to obtain output energy comparable to that of the transformer described above by driving a capacitor discharge type ignition device to high frequency oscillation, and this is being used, but it is difficult to handle the surge voltage associated with the high frequency oscillation circuit. Since this is not sufficient, compromises have been made by using expensive semiconductor devices or unavoidably lowering the output energy, and the devices have been housed in cases of appropriate size.

This invention solves the above-mentioned problems by devising a circuit configuration and using a simple surge absorption circuit.

The figures showing the embodiments of this invention will be explained below. In the figure, 1 and 2 are input terminals from an AC power supply, and between these terminals 1 and 2, a series circuit consisting of a first choke coil 3 and a capacitor 4 is connected, and the capacitor 4 is connected to a second air-core choke coil. 5 and a thyristor 6 and a series circuit of the primary coil 71 of the ignition transformer 7 having primary, secondary and tertiary coils 71, 72 and 73; The primary coil 71 is also shunted by the capacitor 8.

The output terminal of the secondary coil 72 of the ignition transformer 7 is connected to a pair of spark plugs 9, and one end of the tertiary coil 73 is connected to the cathode of the thyristor 6.
It is connected to the connection contact of the next coil 71, and the other end is connected to the resistor 10, constant voltage diode 11, and capacitor 1.
It is connected to the gate of the thyristor 6 through a series circuit of two resistors 13 and 14, and a series circuit of resistors 13 and 14 is connected between the output terminals of the tertiary coil 73.

Further, the input terminal 1 is connected to the cathode of the thyristor 6 through a series circuit of a resistor 15 and a capacitor 16.
6 is connected to the gate of the thyristor 6 via a constant voltage switching element 17, and the capacitor 16 is further shunted by a series circuit of a resistor 18 and a transistor 19, the base of which is connected to the gate of the thyristor 6. At the same time, a protection diode 20 is connected to the connection point of the resistors 13 and 14.
is connected to the emitter of this transistor 19 via.

Further, a diode 21 and a resistor 22 are connected between the gate and cathode of the thyristor 6 for protection, and the voltage regulator diode 11 and the capacitor 1
The connection point of the thyristor 6 is connected to the cathode of the thyristor 6 via the constant voltage diode 23.

Next, the operation will be explained.

For convenience of explanation, suppose that a positive voltage is applied to the terminal 1 side and a negative voltage is applied to the terminal 2 side. At the same time, the capacitor 4 is charged through the choke coil 3, and at the same time, the resistor 15, the capacitor 16, and the primary coil of the ignition transformer 7 are charged. By the series circuit of 71, capacitor 1
When charging of the capacitor 16 starts and the charge of the capacitor 4 reaches a sufficient level, for example, when the phase angle reaches 45 degrees, the charge of the capacitor 16 reaches the threshold of the constant voltage switching element 17. , the element 17 is turned on and the thyristor 6 is turned on. Therefore, the electrical charge of the capacitor 4 is discharged through the series circuit of the choke coil 5, the thyristor 6, and the primary wire 71 of the ignition transformer 7.
Most of this discharge voltage is applied to the primary coil 71 of the ignition transformer 7, which has a large impedance, but prior to this, the capacitor 8 is rapidly charged via the air-core choke coil 5. Therefore, a high voltage is induced in the secondary coil 72 of the ignition coil 7, and spark discharge starts at the ignition plug 9. On the other hand, a voltage is induced with the dot side of the tertiary coil 73 being positive,
The base current of transistor 19 flows through resistor 13, turning on transistor 19 and discharging the residual charge in capacitor 16 through resistor 18.

Since the discharge of the capacitor 4 described above is accompanied by damped free vibration at a relatively high frequency of about 50 KHz, the thyristor 6 is turned off by an oscillating voltage in the opposite direction after being turned on for about 10 μs. However, the primary coil 71 of the ignition coil 7 has a capacitor 8 and
Since current flows through the circuit with a resonant frequency of about 14 KHz, the output voltage of the secondary coil 72 does not disappear due to changes in the core magnetic flux of the ignition transformer 7, and the ignition plug 9 Spark discharge continues.

By turning off the thyristor 6, the magnetic energy accumulated when the thyristor 6 was turned on and the voltage from the power supply are superimposed on the choke coil 3, and the capacitor 4 is charged again. On the other hand, the magnetic energy of the chiyoke coil 5 is released through the resistor 24.

Now, even after the thyristor 6 is turned off, a negative voltage is induced on the dot side of the tertiary coil 71 of the ignition transformer 7, so that
The capacitor 12 is charged through the diode 21 to a voltage limited by the constant voltage diode 23, but the polarity on the dot side is reversed,
When the polarity is reversed, the capacitor 12 is discharged through the gate of the thyristor 6, and the thyristor 6 is turned on again, discharging the charge in the capacitor 4 as described above, and discharging the primary wire 71 of the ignition coil 7.
and replenishes the energy of the resonant circuit of the capacitor 8. From now on, the same operation as above will be repeated,
The spark discharge from the spark plug 9 occurs when the polarity of the power supply voltage is set to terminal 1.
It continues without interruption until it changes from positive to terminal 2. Of course, the energy supplied to the spark plug 9 during this time is modulated by the power supply voltage. Also, when the power supply voltage drops extremely,
Since there is a possibility that the applied voltage for turning off the thyristor 6 may be insufficient, the gate trigger of the thyristor 6 is not applied before the power supply voltage becomes sufficiently small, that is, the capacitor 12 is
voltage regulator diode 1 so that charging is prevented.
1 is inserted. When the power supply voltage is reversed from negative to positive, the operation for ignition, which starts with charging the capacitor 16 again, starts.

As you can understand from the above explanation, the ignition coil 7
The thyristor 6 repeats switching depending on the frequency of the resonant circuit of the primary coil 71 and the capacitor 8, and each time the resonant energy of the resonant circuit is supplemented with the charge of the capacitor 4, but this supplementary current is It is necessary to limit the inflow current of the thyristor 6 to below the maximum rating, and the chiyoke coil 5 functions as an auxiliary coil to limit the above-mentioned current and to prevent the thyristor 6 from turning off incorrectly.
Although the inductance should be set large, if it is set unnecessarily large, the replenishment of energy to the resonant circuit will not be sufficient, and there is a risk that sufficient spark energy will not be obtained.

Therefore, in order to achieve the original purpose of the ignition device, the inductance of the choke coil 5 must be set appropriately small to increase the supplementary current to the resonant circuit. However, if the inductor tank is set small and the supplementary current is increased, the reverse surge voltage at turn-off during the switching operation of the thyristor 6 becomes extremely large, exceeding the maximum rated voltage of the thyristor 6.

Therefore, by inserting the resistor 24, the above-mentioned surge voltage absorption circuit is formed and the above-mentioned problem is solved. Here, the power consumption of the resistor 24 is relatively small, usually 1/3W, because it only absorbs the surge voltage with an extremely narrow pulse width of the air-core choke coil that occurs every time the thyristor 6 is switched.
That's about it.

On the other hand, the ignition transformer 7 which becomes another surge voltage source
A capacitor 8 is inserted between both terminals of the primary coil 7, and a capacitor 4 is inserted between both ends of the first chain coil 3 via a power supply to absorb each surge voltage. In order to suppress the large current from the power supply that occurs when the first thyristor 6 switches when thyristor 8 is not charged at all, an iron core made of ferrite or the like is inserted into the above-mentioned chiyoke coil 3 to reduce the load on the resistor 24. . Furthermore, the iron core also serves to absorb radio noise by about 5 to 10 dB.

As detailed above, according to this invention, a small and inexpensive ignition device that generates high output energy can be obtained without using any special elements by using a simple circuit configuration and a surge absorption circuit. be.

In the description of the embodiment, an alternating current is applied to the power input terminal, but a direct current voltage may also be applied, and therefore the starting trigger circuit constituted by the resistor 15, capacitor 16, element 17, etc. is not particularly restricted. Instead, various well-known circuits can be used.

It goes without saying that the resistor 24 for absorbing surges can be constructed of other elements, such as a series circuit of a resistor and a capacitor, or other surge absorbing means such as a varistor.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the ignition device of this invention. In the figure, 3... cored chiyoke coil, 5...
Air core chiyoke coil, 7...Ignition transformer, 9...
...Spark plug.

Claims (1)

[Scope of utility model registration request] A series circuit of a power supply, an iron-core chiyoke coil 3, and a first capacitor 4, an air-core chiyoke coil 5 and a thyristor 6 forming a closed circuit with the capacitor 4, and primary, secondary, and tertiary coils (71, 72, and 73). The air-core chiyoke coil 5 is shunted by the surge absorbing means 24, and the primary wire 71 is shunted by the second capacitor 8. A spark plug 9 is provided at the output terminal of the secondary coil 72, and the tertiary coil 73 and the primary coil 71 have polarities such that the thyristor 6 performs positive feedback operation. A resistor 22 is connected between the gate and the cathode of the thyristor through a series circuit of the thyristor 6 and the capacitor 12, and a resistor 22 is connected to the capacitor 12 with the gate side of the thyristor 6 as the positive terminal. A starting trigger circuit is connected to the gate of the thyristor 6, and a transistor 19 is connected to the gate of the thyristor 6 to stop the operation of the starting trigger. Base is resistor 13
an ignition device connected to the output end of the tertiary coil 73 through the ignition device.