JPS6138352B2 - - Google Patents

Description

Detailed Description of the Invention The present invention rectifies the AC output of a charging generator of a magnet generator driven in synchronization with the engine, charges a capacitor, and transfers the charge of this capacitor to a signal generator. The so-called capacitor discharge type uses a signal voltage to turn on a thyristor such as an SCR, causing a sudden discharge to the primary coil of the ignition coil, which generates high voltage in the secondary coil of the ignition coil to ignite the engine. This invention relates to a non-contact ignition device that can effectively prevent engine overspeed.

In general, small engines such as chainsaws may suddenly change from a loaded state to an unloaded state based on the operating conditions of the engine, and in this case the engine overspeeds, causing the engine itself and the power generated by the engine to machine, etc.) will be shortened.

Therefore, in order to solve this problem, in the past, as shown in FIG. However, the conventional device shown in Fig. 1 has a thyristor S2 of an overspeed prevention device U2 in parallel with the thyristor S1 of the non-contact ignition device U1, and prevents the engine rotation speed from exceeding a predetermined level. When the thyristor S2 of the overspeed prevention device U2 is turned on, the ignition operation of the non-contact ignition device U1 is disabled. However, the overall size of the device was large, and the manufacturing cost was extremely high.

The present invention has been particularly devised with attention to the above points, and its purpose is to effectively prevent overspeeding of the engine, have an extremely simple configuration, and increase the size of the entire device. Without,
To provide an excellent non-contact ignition device that can be manufactured at low cost.

A non-contact ignition device according to an embodiment of the present invention shown in FIG. 2 will be described below. In this figure, 1 is a charging generator such as a magnet generator driven in synchronization with the engine, 2 is its generating coil, 3 is a diode that rectifies the AC output of the generating coil 2, 4 is a capacitor, and 5 is a primary An ignition coil consisting of a coil 6 and a secondary coil 7, 8 a spark plug, 9 a thyristor such as an SCR, 10 a protection diode for the thyristor 9, 11 a signal generator such as a magnet generator,
12 is a generator coil of the signal generator 11, 14 is a rectifying diode, and 15 is a time constant circuit that maintains the on state of the thyristor 9 for a predetermined period of time.This time constant circuit 15 includes a capacitor 16 and a gate resistor. 17, a variable resistor 18, and a thermistor 20 for temperature compensation, which are connected as shown in the figure.

Next, 19 is a diode, and this diode 1
9 is connected between the generating coil 12 and the anode of the thyristor 9, and after the thyristor 9 is turned on,
The voltage generated by the generator coil 12 is transferred to its diode 19.
By short-circuiting the capacitor 16 and the anode and cathode of the thyristor 9, it is possible to prevent a voltage higher than a predetermined voltage from being applied to the capacitor 16.

(A) When the engine rotational speed is in a normal rotational state First, when the engine is rotated manually or by another method, the charging generator 1 and the signal generator 11 are driven in synchronization with the engine. The alternating current voltage generated in the generator coil 2 of the charging generator 1 is rectified by the diode 3, charges the capacitor 4 to the polarity shown in the figure, and is then applied to the signal generator 11.
The alternating current voltage generated in the generator coil 12 is rectified by the diode 14, charges the capacitor 16 of the time constant circuit 15 to the polarity shown in the figure, and when the charging voltage of the capacitor 16 exceeds a predetermined value, it is connected to the thyristor via the gate resistor 17. Turn on 9. Therefore, the charge in the capacitor 4 is suddenly discharged to the primary coil 6 of the ignition coil 5 through the anode and cathode of the thyristor 9, and as a result, a high voltage is generated in the secondary coil 7 of the ignition coil 5. This high voltage causes a spark to fly to the spark plug 8 and ignite it.

Therefore, during normal rotation when the engine speed is below a predetermined level, the above ignition operation is repeated and the engine rotates, but the charging voltage of the capacitor 4 during this normal rotation,
The relationship between the signal voltage applied to the thyristor 9 and the on/off state of the thyristor 9 is as shown in FIG. 3A.

In this FIG. 3A, VA1 is the waveform of the positive direction voltage of the generator coil 2 applied to the capacitor 4, VC1 is the waveform of the charging voltage of the capacitor 4,
VA2 represents the waveform of the positive voltage of the generator coil 12 applied to the capacitor 16, and VC2 represents the waveform of the charging voltage of the capacitor 16 applied to the gate of the thyristor 9.

Therefore, time t1 (time t
3), the charging voltage waveform VC2 of the capacitor 16 reaches the gate trigger voltage Vg1 of the thyristor 9, and the thyristor 9 turns on, and then the on state changes to the capacitor 1.
Until the charging voltage waveform VC2 of 6 drops to the gate holding voltage Vg2 of thyristor 9, that is, from time t1 to t2 (from time t3 to t4
TgA continues for a predetermined period of time (the same applies to the above), and then turns to the OFF state.

After the thyristor 9 turns off, that is, after time t2 (time t4 is also the same), the waveform VA1 of the positive voltage of the generator coil 2 applied to the capacitor 4 rises to charge the capacitor 4, as shown in the figure. I'm starting to do that.

(B) When the engine rotational speed is in an overspeeding state, then when the engine rotational speed increases abnormally and becomes in an overspeeding state, the charging generator 1 and the signal generator 11 also become high speed, and the high frequency In order for the output to be generated, from time t1 to t3 shown in FIG. 3A,
The time TA from t5 to t8 shown in FIG. 3B has a relationship of TA>TB, but the predetermined time TgA shown in FIG. TgB to maintain the on state of the thyristor 9 shown in Fig. 3B
is in the relationship TgA≒TgB, so the charging voltage waveform VC2 of the capacitor 16 decreases to the gate holding voltage Vg2 of the thyristor 9, and the thyristor 9
Before the time t6 (time t9 is the same) when the generator coil 2 turns off, the waveform VA1 of the positive voltage of the generator coil 2 starts to rise, and this positive voltage of the generator coil 2 is applied to the thyristor without charging the capacitor 4. As a result, the on state of the thyristor 9 continues until the waveform VA1 of the positive voltage of the generating coil 2 almost disappears, that is, for the time t7 (the same goes for the time t10). and then turn off.

Therefore, when the engine rotational speed increases abnormally and exceeds a predetermined level, the capacitor 4 is no longer charged as shown in FIG. 3B, so the engine is no longer ignited and the rotational speed decreases. Therefore, over-speeding of the engine can be effectively prevented.

In the embodiment of the present invention shown in FIG. 2, a capacitor 16 and a variable resistor 18 are connected in parallel through a gate resistor 17 between the gate and cathode of the thyristor 9, and the variable resistor 1
8 is convenient for adjusting variations in the predetermined time period during which the thyristor 9 remains on, but the present invention is not limited to this, and for example, a fixed resistor may be used. In that case, a plurality of fixed resistors with different resistance values are prepared, and the most suitable one is selected from among the plurality of fixed resistors and installed so that the thyristor 9 remains on for a predetermined time. All you have to do is do it.

Furthermore, the thermistor 20 for temperature compensation maintained between the gate and cathode of the thyristor 9 may be omitted if the temperature change is small or if variation in characteristics with respect to temperature change is acceptable. It is obvious that there is no need to explain it.

As described above, according to the present invention, the AC output of the charging generator 1 driven in synchronization with the engine is rectified to charge the capacitor 4, and the charge of the capacitor 4 is transferred to the signal generator 11. By turning on a thyristor 9 such as an SCR with a signal voltage of In the non-contact ignition device, the gate of the thyristor 9;
A capacitor 16 and a resistor 18 are connected in parallel between the cathodes via a gate resistor 17, and a connection point between the gate resistor 17 and the capacitor 16 is connected to the output end of the signal generator 11 via a diode 14, Furthermore, by connecting the output terminal to the anode of the thyristor 9 via a diode 19, the charging voltage of the capacitor 16 can be maintained approximately even if the output voltage of the signal generator 11 fluctuates due to fluctuations in the rotational speed of the engine. The on state of the thyristor 9 can be maintained for a predetermined period of time after the thyristor 9 is turned on, so that when the rotational speed of the engine exceeds a predetermined level, the capacitor 4 is turned on by the charging generator 1. Since the charging voltage can be diverted via the thyristor 9, overspeeding of the engine can be effectively prevented.

Furthermore, compared to the conventional device shown in Fig. 1, in which the overspeed prevention device thyristor S2 is provided in addition to the non-contact ignition device thyristor S1, the number of parts is greatly reduced and the configuration is simple. This not only makes it possible to downsize the entire device, but also significantly reduces manufacturing costs, which has significant practical effects.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a conventional device of this type, FIG. 2 is an electric circuit diagram of a device according to an embodiment of the present invention, and FIGS. 3A and 3B are time charts illustrating the operation of the same device. In the figure, 1 is a charging generator, 3 is a diode, 4 is a capacitor, 5 is an ignition coil, 8 is a spark plug, 9 is a thyristor, 11 is a signal generator,
14 is a diode, 15 is a time constant circuit, 16 is a capacitor, 17 is a gate resistor, and 20 is a thermistor.

Claims (1)

[Claims] 1 Rectifying the AC output of the charging generator 1 driven in synchronization with the engine to charge the capacitor 4,
The charge of this capacitor 4 is transferred to a signal generator 11.
The primary coil 6 of the ignition coil 5 is turned on by turning on the thyristor 9 such as an SCR with a signal voltage of
The secondary coil 7 of the same ignition coil
In the non-contact ignition device that generates high voltage to ignite the engine, the thyristor 9
A capacitor 16 and a resistor 18 are connected in parallel between the gate and cathode of the signal generator 11 via a gate resistor 17, and a connection point between the gate resistor 17 and the capacitor 16 is connected via a diode 14 to the signal generator 11.
By connecting the output end of the thyristor 9 to the anode of the thyristor 9 through a diode 19, the on state of the thyristor 9 is maintained for a predetermined period of time after the thyristor 9 is turned on, and the rotational speed of the engine is increased. A non-contact ignition system for an engine, characterized in that when the charging voltage exceeds a predetermined level, the charging voltage of the capacitor 4 by the charging generator 1 is bypassed via the thyristor 9 to prevent over-speeding of the engine.