JPS6137825Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-type ignition device for an internal combustion engine.

Magneto type ignition devices, which obtain a high-voltage current from a magneto (magnet generator) without relying on batteries, have come to be widely used, for example, in internal combustion engines of lawn mowers and other agricultural machinery. Since such lawn mowers are required to be small and lightweight, manual starting methods have generally been adopted as they are easy to start.

However, with the manual starting method, it is not possible to sufficiently increase the rotational speed of the internal combustion engine due to solidification of lubricating oil, etc., so there are problems such as it takes a long time to start the engine in cold regions.

The present invention was made to improve such conventional drawbacks, and in particular, by replenishing current from the battery to the primary coil only in the low speed range of the internal combustion engine, it is possible to supply sufficient current even in the low speed range. An object of the present invention is to provide a magneto-type ignition device for an internal combustion engine that obtains ignition energy.

An embodiment of the present invention will be specifically described below with respect to the circuit shown in FIG.

In the figure, 1 is a primary coil that generates an induced voltage in synchronization with the internal combustion engine, 2 is a secondary coil 2 connected to one end of the primary coil 1, and a spark plug 3 is connected to one end of the secondary coil 2. The other end is grounded.

On the other hand, a battery 4, a transistor 5 as a first switching means, and a well-known current cutoff circuit 9 are connected in series between the connection midpoint P of both coils 1 and 2 and the ground (grounding point A). It forms a series circuit. The control pole of the transistor 5 serving as the first switching means, that is, the base of the transistor 5 is connected to the connection midpoint between the primary coil 1 and the battery 4, that is, the connection midpoint P via a resistor 10. There is. Also,
A bypass circuit having a thyristor 7 as a second switching means is provided between the connection midpoint P and the connection midpoint R between the transistor 5 and the current cutoff circuit 9. That is, the connection midpoint P
A diode 6, a thyristor 7, and a diode 8 are connected in series between and the connection midpoint R.
These constitute a low impedance bypass circuit for the transistor 5.

Furthermore, depending on the rotational speed of the internal combustion engine, the second
A control circuit is provided for controlling conduction/non-conduction of a thyristor 7, which is a switching means. The control circuit includes a third circuit which conducts when the reverse induced voltage of the primary coil 1 reaches a predetermined level and causes the thyristor 7 serving as the second switching means to conduct.
Zener diode 13 is the switching means for
The capacitor 14 charges the reverse induced voltage of the primary coil 1, and the capacitor 14 and the thyristor 7, which is the conductive second switching means, form a discharge circuit for the capacitor 14, and the conduction state of the thyristor 7 is set to a predetermined value. It is configured to include a resistor 16 for maintaining time. That is, a resistor 12 and a Zener diode 13 are connected in series between a connection point Q between the thyristor 7 and the diode 8 and a ground point A, and a connection point between the resistor 12 and the Zener diode 13 is connected to the thyristor 7. gate is connected. Further, a capacitor 14 and a diode 15 are connected in series between the connection midpoint Q and the grounding point A, and the connection midpoint P
A diode 11 is connected between the connection center point Q and the connection center point Q. Furthermore, a resistor 16 is connected between the connection midpoint between the diode 6 and the thyristor 7 and the connection midpoint between the capacitor 14 and the diode 15.

Further, the voltage waveform of the primary coil 1 generated at the point P due to the rotation of the engine is as shown in FIG.

Next, the operation of the circuit will be explained.

First, in the low rotational speed range of the engine, looking at the negative half period a in FIG. 2, the voltage generated in the primary coil 1 causes the current to flow from ground point A to diode 1.
5 → capacitor 14 → diode 11 → connection midpoint P, and charges the capacitor 14. At this time, since the potential across the Zener diode 13 has not reached the Zener potential, the Zener diode 13 remains off.

On the other hand, if we look at the positive half period b in Figure 2,
This time, the current flows from the connection middle point P to the resistor 10 to the base of the transistor 5 to the emitter of the transistor 5 to the current cutoff circuit 9 to the ground point A, and the collector and emitter of the transistor 5 are electrically connected. Therefore, current also flows from the battery 4 through the collector-emitter of the transistor 5 to the current cutoff circuit 9, and the primary current induced by the rotation of the engine and the current from the battery 4 flow in the primary coil 1 in a superimposed manner. becomes.

Thus, when the current cutoff circuit 9 is cut off at the ignition timing of the engine, the large superimposed current flowing through the primary coil 1 is suddenly cut off, generating a high voltage as a back electromotive force in the secondary coil 2.

That is, in the low rotation range of the engine, the current of the battery 4 is superimposed on the primary coil 1, so
Greater ignition energy can be supplied to the spark plug 3 than when only the induced voltage of the primary coil is used, and the engine can be started smoothly.

On the other hand, when the engine is operated in a high rotation range,
Since the magnetoelectric power generation is sufficient, the induced voltage in the primary coil 1 also becomes high. Therefore, the battery 4 becomes useless because it accelerates its consumption. For this reason, it is desirable to cut off the circuit of the battery 4 in a rotation range where the voltage of the primary coil 1 is sufficient.

That is, when the engine is operated in a high rotation range, looking at the negative half period a (the level is sufficiently large) in FIG. → Diode 11 → Connection midpoint P, and the capacitor 14 is charged in the same manner as described above. At this time, since the voltage level of the primary coil 1 is high, the capacitor 14 is charged to a voltage exceeding the Zener potential of the Zener diode 13, and the capacitor 14 is charged to a predetermined level.
That is, as soon as the Zener potential is exceeded, the series circuit of the capacitor 14 and the diode 15 is shunted by the Zener diode 13,
A current from the primary coil 1 flows from the ground point A to the Zener diode 13 to the resistor 12 and the gate/cathode of the thyristor 7 to the diode 11 to the connection midpoint P. Therefore, the thyristor 7 is turned on, and the charge in the capacitor 14 maintains the thyristor 7 in a conductive state for a certain period of time due to the time constant with the resistor 16.

On the other hand, if we continue to look at the positive half period b (the level is sufficiently large) in Fig. 2, the current from the primary coil 1 is from the connection midpoint P → diode 6 → thyristor 7 → diode 8 → current cutoff circuit 9 → Grounding point A
Therefore, the resistor 10 and the high impedance circuit between the base and emitter of the transistor 5 are bypassed, and the transistor 5 is maintained in an off state. Therefore, no current flows from the battery 4, and its consumption can be prevented. Note that in this state, the capacitor 14 and the resistor 16
The discharge time constant is maintained for an appropriately determined period of time. In this manner, sufficient induced voltage is obtained in the primary coil 1 in the high rotational speed range of the engine, so the use of the battery 4 can be stopped and unnecessary consumption of the battery 4 can be effectively prevented.

As explained above in detail, according to the present invention, by inserting the battery in series with the primary coil only in the low rotational speed range of the engine, the current flowing through the primary coil is increased, and the induced current in the secondary coil is increased. It is possible to increase the voltage and strengthen the ignition energy. In this way, an advantage is obtained in that the small and small capacity internal combustion engine for mowing grass can be started smoothly.

[Brief explanation of drawings]

FIG. 1 is a specific circuit diagram of the magneto-type ignition device of the present invention, and FIG. 2 is a waveform diagram of the induced voltage in the primary coil. 1...Primary coil, 2...Secondary coil, 3...
Spark plug, 4... Battery, 5... First switching means, 6, 8, 11... Diode, 7
... second switching means, 9 ... current cutoff circuit, 10, 12, 16 ... resistor, 13 ... third switching means, 14 ... capacitor.

Claims (1)

[Claims for Utility Model Registration] (1) For a series circuit consisting of a primary coil, a battery, a first switching means, and a current interrupting circuit that generate an induced voltage in synchronization with an internal combustion engine, A control pole is connected to a connection midpoint between the primary coil and the battery via a resistor, and a second
A bypass circuit having a switching means is provided, and further, when the reverse induced voltage of the primary coil reaches a predetermined level, conduction occurs to cause the second coil to conduct.
a third switching means for bringing the switching means into conduction, a capacitor for charging the reverse induced voltage of the primary coil, and a discharge circuit for the capacitor formed together with the capacitor and the second switching means which have been brought into conduction; 1. A magneto-type ignition device for an internal combustion engine, comprising a control circuit having a resistor for maintaining a conductive state of a switching means for a predetermined period of time. (2) A magneto-type ignition device for an internal combustion engine according to claim 1, wherein the first switching means is a transistor. (3) Claim 1 for utility model registration, characterized in that the second switching means is a thyristor
A magneto-type ignition device for an internal combustion engine according to paragraph 1. (4) A magneto-type ignition device for an internal combustion engine according to claim 1, wherein the third switching means is a Zener diode.