JPH0379549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition system for an engine, and in particular, it charges a charging/discharging capacitor using the output of an exciter coil, and conducts a first switching element connected to the charging/discharging capacitor. The electric charge of this capacitor is then supplied to the primary coil of the ignition coil, and at this time, the high voltage generated in the secondary coil of the ignition coil is applied to the spark plug, thereby generating a spark and igniting. The present invention relates to an ignition device for an engine.

In a capacitor charging/discharging type ignition system, a capacitor is charged in advance to a predetermined voltage, and at the ignition timing, the charge of this capacitor is rapidly discharged to the primary coil of the ignition coil, and a high voltage is applied to the secondary coil of the ignition coil. is generated to cause sparks to fly.
In such an ignition device, if the generated output of the exciter coil is used to charge the charging/discharging capacitor, it becomes possible to construct the ignition device without using a battery.
Therefore, such ignition devices are widely used as ignition devices for small engines.

In such an ignition device, in order to improve the efficiency of the engine, it is desirable to change the ignition timing according to the engine speed. Conventionally, ignition devices have been known that advance the ignition timing in stages when the engine speed reaches a predetermined speed. However, such a conventional ignition device uses a signal coil in addition to the exciter coil, and is configured to advance the angle stepwise using the output from the signal coil. Therefore, a signal coil is required in addition to the exciter coil, which has the disadvantage of complicating the structure and increasing cost.

The present invention has been made in view of these problems, and uses only an exciter coil without using a signal coil to perform advance angle operation when the engine speed reaches a predetermined speed. conduct,
It is an object of the present invention to provide an engine ignition device that improves the efficiency of the engine.

In the present invention, a charging/discharging capacitor is charged by the output of an exciter coil, and a first thyristor connected to the charging/discharging capacitor is made conductive to transfer the electric charge of the charging/discharging capacitor to a primary coil of an ignition coil. In the ignition device, the high voltage generated in the secondary coil of the ignition coil is applied to the ignition plug, thereby generating a spark and igniting the first thyristor. A gate of the exciter coil is connected to a negative terminal of the exciter coil, and a first capacitor charged by the negative output of the exciter coil is connected to the gate of the first thyristor. A second thyristor is connected between the gate of the thyristor and the negative terminal of the exciter coil, and the negative output of the exciter coil is connected to the second thyristor.
is connected to the gate of the first thyristor through the thyristor of the first thyristor;
A second capacitor that is charged by the discharge current of the charging/discharging capacitor when the thyristor is conductive is connected to the gate of the second thyristor, and when the engine speed is low, the exciter coil is connected to the gate of the second thyristor. The output changes to the negative side, and the negative output of this exciter coil causes the first
After the capacitor is charged, the first thyristor is made conductive to perform the ignition operation, and when the engine rotation speed exceeds a predetermined rotation speed, the output of the exciter coil is turned to the negative side. The second thyristor is made conductive by the second capacitor until it turns over, and immediately after the output of the exciter coil turns to the negative side, the output of the exciter coil is turned on through the second thyristor by the negative output of the exciter coil. The first thyristor is made conductive to perform the ignition operation.

The present invention will be explained below with reference to an illustrated embodiment.
FIG. 1 shows a circuit configuration of an ignition device according to this embodiment, and this ignition device is equipped with an exciter coil 1. As shown in FIG. The iron core 2 of the exciter coil 1 faces the outer peripheral surface of the magnet rotor 4 in which the magnets 3 are embedded with a small air gap. Note that this magnet rotor 4 may also be used as a flywheel fixed to the crankshaft of the engine, for example. And the above exciter coil 1
is connected to a charging/discharging capacitor 6 via a diode 5. Furthermore, this capacitor 6 is connected in series with the primary coil 8 of the ignition coil 7. On the other hand, the secondary coil 9 of the ignition coil 7
is connected to the spark plug 10.

A diode 11 is connected in parallel to the series circuit of the charging/discharging capacitor 6 and the primary coil 8. Further, the positive side of the charging/discharging capacitor 6 is connected to the anode of the thyristor 12. The cathode of this thyristor 12 is connected to the negative terminal of the exciter coil 1 through a series circuit of a varistor 13 and a diode 14. Further, the connection point between the varistor 13 and the diode 14 is
It is connected to the connection point between the exciter coil 1 and the diode 5 via a diode 15.

Next, at the gate of the thyristor 12, a second
The cathode of the thyristor 16 is connected to the thyristor 16. The anode of the thyristor 16 is connected to the negative terminal of the exciter coil 1, and the gate of the thyristor 16 is connected to a diode 17 and a resistor 18 at the connection point between the cathode of the thyristor 12 and the varistor 13. are connected through a series circuit.
At the connection point between the diode 17 and the resistor 18, a capacitor 19 and a resistor 20 are connected in parallel with each other, and the capacitor 19 and resistor 20 are connected in parallel with the varistor 13. There is. The cathode side of the varistor 13 is connected to a capacitor 21 and a diode 22.
It is connected to the negative side of the exciter coil 1 through the above. The connection point between the capacitor 21 and the diode 22 is connected to a resistor 23.
It is connected to the gate of the first thyristor 12 via.

Next, the operation of this ignition system configured as above will be explained. As the magnet rotor 4 rotates, the exciter coil 1 generates a power generation output with waveforms as shown in FIGS. 2A and 3A due to the magnetic flux of the magnet 3 provided in the rotor 4. This will result in Note that FIG. 2A shows the change in the output voltage of the exciter coil 1 when the engine speed is low, and FIG. 3A shows the output voltage of the exciter coil 1 when the engine speed is high. Among the outputs of this exciter coil 1, the positive side a
Because a potential difference is generated between both ends of the coil 1, current flows through the exciter coil 1, the diode 5, the charging/discharging capacitor 6, the primary coil 8 of the ignition coil 7, and the exciter coil 1 in this order. The charging/discharging capacitor 6 is charged by this current. The operation of charging the capacitor 6 is the same whether the engine speed is low or high. The voltage of the capacitor 6 charged in this manner becomes as shown in FIGS. 2B and 3B.

As the magnet rotor 4 rotates, the output of the exciter coil 1 changes from the plus side to the minus side as shown in FIGS. 2A and 3A. Then, in the portion b where the speed changes to the negative side, when the engine speed is low, the following operation is performed. When the output of the exciter coil 1 is reversed to the negative side, current flows through the exciter coil 1, the diode 22, the capacitor 21, the diode 15, and the exciter coil 1 in this order. Capacitor 21 is charged by this current. When the capacitor 21 is charged, the exciter coil 1, diode 22, and resistor 2
3. Gate of thyristor 12, cathode of thyristor 12, varistor 13, diode 15, exciter coil 1
Current will flow in this order. What must be noted here is that even if the output of the exciter coil 1 turns negative, no gate current is supplied to the thyristor 12 until the capacitor 21 is charged. Therefore, Figure 2 A and B
As shown in FIG. 2, when the output of the exciter coil 1 reaches the portion b, near its peak, the thyristor 12 finally becomes conductive and the charge in the capacitor 6 is discharged.

To explain in more detail the discharging operation of the capacitor 6, the capacitor 21 is charged by the negative output of the exciter coil 1,
After that, when a current is supplied to the gate of the thyristor 12 and the thyristor 12 becomes conductive, the current flows through the capacitor 6, the thyristor 12, the varistor 13, the diode 14, the primary coil 8 of the ignition coil 7, and the capacitor 6 in this order. , the current in the primary coil 8 of the ignition coil 7 changes rapidly. Therefore, a high voltage is induced in the secondary coil 9 of the ignition coil 7, and this high voltage generates a spark in the ignition plug 10 connected to the secondary coil 9. This causes the engine to ignite. Furthermore, the above charge/discharge capacitor 6
As a result of the discharge, a current flows through the varistor 13, so that the capacitor 19 is charged by the potential difference across the varistor 13.

The charge in the capacitor 19 is transferred to the capacitor 19, the resistor 18, the gate and cathode of the thyristor 16, the gate and cathode of the thyristor 12,
It flows through a closed circuit consisting of a varistor 13 and a capacitor 19 and is discharged. At the same time, part of the charge of this capacitor 19 is consumed by a resistor 20 connected in parallel to this capacitor 19. Therefore, the change in the voltage of the capacitor 19 is the second
This results in a sawtooth change as shown in Figure C.

What should be noted here is that since the engine speed is low and the output of the exciter coil 1 is also small, the discharge of the capacitor 19 causes the gate of the thyristor 16 to temporarily have a higher current than the gate trigger current. A current flows, but since the gate trigger current of the thyristor 12 is larger than this, the thyristor 12 does not turn on at this time. Further, in this case, the charging voltage of the capacitor 19 is also low, and the voltage of the capacitor 19 becomes lower than the gate trigger voltage of the thyristor 16 before the output of the exciter coil 1 changes from the positive side to the negative side. Therefore, when the engine speed is below a predetermined speed, the capacitor 19 and the second thyristor 16 prevent the first thyristor 12 from becoming conductive, and the output voltage of the exciter coil 1 decreases. Ignition operation is not performed immediately after changing from the positive side to the negative side.

On the other hand, when the engine speed exceeds a predetermined speed, the output of the exciter coil 1 increases and the time required for one cycle is shortened, so the change in the voltage of the capacitor 19 is The result is as shown in Figure 3C. What should be noted in this graph is that even though the change is in the same sawtooth pattern, the voltage across the capacitor 19 when the output of the exciter coil 1 changes from the positive side to the negative side is higher than the gate trigger current of the thyristor 16. It's a familiar thing. Therefore, while a current greater than the gate trigger current is flowing from the capacitor 19 to the gate of the second thyristor 16, the engine rotates once and the output of the exciter coil 1 becomes a.
When changing from part to part b, the first thyristor 1 passes through this second thyristor 16.
A signal current is applied to the gate of 2. That is, when the output of the exciter coil 1 changes from the positive side to the negative side, current flows through the exciter coil 1, the anode of the thyristor 16, the cathode of the thyristor, the gate of the thyristor 12, the cathode, the varistor 13, the diode 15, and the exciter coil 1 in this order. As a result, the thyristor 12 becomes conductive, and the charging/discharging capacitor 6 is rapidly discharged. Therefore, a high voltage is induced in the secondary coil 9 of the ignition coil 7, a spark is generated in the ignition plug 10, and ignition is performed.

In this way, when the engine rotation speed exceeds a predetermined rotation speed and the output of the exciter coil 1 changes from the positive side to the negative side, the voltage of the capacitor 19 exceeds the gate trigger voltage of the second thyristor 16, Immediately after the output voltage of the exciter coil 1 changes from the positive side to the negative side, the thyristor 12 becomes conductive, and an ignition operation is performed. Therefore, compared to the case where the engine speed is low, the angle is advanced by the angle shown by θ in FIG. 3C. Therefore, the ignition angle changes with respect to the engine rotation speed as shown in FIG. 4, and the ignition angle advances in stages when the engine rotation speed exceeds a predetermined rotation speed.

As described above, according to the ignition system according to the present embodiment, when the engine speed exceeds a predetermined speed, the advance angle is advanced in stages, so that the advance angle operation is performed in a stepwise manner. This makes it possible to increase engine efficiency. Furthermore, according to the ignition device according to this embodiment, the advancing operation is mainly achieved by the capacitor 19 and the second thyristor 16, and when the rotation speed exceeds a predetermined number, When the output of the exciter coil 1 changes from the positive side to the negative side, the voltage of the capacitor 19 exceeds the gate trigger voltage of the thyristor 16, and as a result, the advance angle is performed in stages. There is. Therefore, with such a configuration, it is possible to perform an advance operation without using a signal coil by simply changing the circuit configuration. Therefore, it becomes possible to provide an ignition device that advances the angle at a low cost.

As described above, the present invention connects the gate of the first thyristor to the negative terminal of the exciter coil, and connects the first capacitor charged by the negative output of the exciter coil to the first capacitor. A second thyristor is connected to the gate of the thyristor, and a second thyristor is connected between the gate of the first thyristor and the negative terminal of the exciter coil so that the negative output of the exciter coil passes through the second thyristor. A second capacitor connected to the gate of the first thyristor and charged by the discharge current of the charging/discharging capacitor when the first thyristor becomes conductive is connected to the gate of the second thyristor. When connected and the engine speed is low, the output of the exciter coil turns to the negative side, and after the first capacitor is charged by the negative output of the exciter coil, the second thyristor becomes conductive. ignition operation is performed, and when the engine speed exceeds a predetermined speed, the second thyristor is made conductive by the second capacitor until the output of the exciter coil changes to the negative side; Immediately after the output of the exciter coil changes to the negative side, the first thyristor is made conductive by the negative output of the exciter coil through the second thyristor, thereby performing an ignition operation.

Therefore, according to such an ignition device, when the charging voltage of the second capacitor reaches the rotation speed to maintain the gate trigger voltage of the second thyristor until the output of the exciter coil changes from the positive side to the negative side, The engine will advance in stages. Since the engine is advanced in stages at a predetermined rotation speed in this way, it is possible to improve the efficiency of the engine. Furthermore, the advancing rotation speed can be arbitrarily changed depending on the charging/discharging characteristics of the second capacitor. In addition, since such an ignition device achieves a stepwise advance angle using a second capacitor and a second thyristor, it does not require a signal coil for advance angle. Therefore, it becomes possible to provide an ignition device that advances the angle at a low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an engine ignition system according to an embodiment of the present invention, and FIG. 2 is a graph showing changes in voltage of exciter coil 1, capacitor 6, and capacitor 19 when the engine speed is low. , Figure 3 shows the exciter coil 1, capacitor 6,
Graph showing changes in voltage of capacitor 19, 4th
The figure is a graph showing changes in the ignition angle with respect to the engine rotation speed of the ignition device according to the present embodiment. In addition, in the symbols used in the drawings, 1...exciter coil, 6...charging/discharging capacitor, 7...
Ignition coil, 8... Primary coil, 9... Secondary coil, 10... Spark plug, 12... First thyristor, 16... Second thyristor, 19... Second thyristor
capacitor, 21... is the first capacitor.

Claims (1)

[Claims] 1. A charging/discharging capacitor is charged by the output of the exciter coil, and a first thyristor connected to the charging/discharging capacitor is made conductive to transfer the electric charge of the charging/discharging capacitor to the ignition coil. In the ignition device, the high voltage that is supplied to the primary coil of the ignition coil and generated in the secondary coil of the ignition coil at this time is applied to the ignition plug, thereby generating a spark and igniting. A gate of the first thyristor is connected to the negative terminal of the exciter coil, and a first capacitor charged by the negative output of the exciter coil is connected to the gate of the first thyristor. A second thyristor is connected between the gate of the first thyristor and the negative terminal of the exciter coil, and the negative output of the exciter coil is connected to the second thyristor.
is connected to the gate of the first thyristor through the thyristor of the first thyristor;
A second capacitor that is charged by the discharge current of the charging/discharging capacitor when the thyristor is conductive is connected to the gate of the second thyristor, and when the engine speed is low, the exciter coil is connected to the gate of the second thyristor. The output changes to the negative side, and the negative output of this exciter coil causes the first
After the capacitor is charged, the first thyristor is made conductive to perform the ignition operation, and when the engine rotation speed exceeds a predetermined rotation speed, the output of the exciter coil is turned to the negative side. The second thyristor is made conductive by the second capacitor until it turns over, and immediately after the output of the exciter coil turns to the negative side, the output of the exciter coil is turned on through the second thyristor by the negative output of the exciter coil. An ignition device for an engine, characterized in that a first thyristor is made conductive to perform an ignition operation.