JPS6215492Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an internal combustion engine ignition device having an overspeed prevention function.

A conventional internal combustion engine ignition system is shown in FIG. 1st
In the figure, reference numeral 1 denotes a power generation coil that also serves as an ignition coil and generates an electromotive force in synchronization with the rotation of an internal combustion engine (not shown), and is disposed within a generator (not shown). 1a and 1b are the primary and secondary coils of the power generation coil 1, 2 is a first transistor whose collector and emitter are connected to both ends of the primary coil 1a of the power generation coil 1, and 3 is the first transistor 2.
4 is a resistor connected between the base and collector of the first transistor 2; 5 and 6 are connected to the base of the second transistor 3 and a power generating transistor; 4 is a resistor connected between the base and collector of the first transistor 2; This is a bias resistor connected between each end of the primary coil 1a of the coil 1 for determining the operating point of the second transistor 3.

Next, the operation of such a conventional device will be explained. That is, when the internal combustion engine (not shown) rotates, an electromotive force indicated by the dotted line A in FIG. 2 is generated in the generator coil 1 in synchronization with this rotation. The first transistor 2 receives the positive electromotive force of this electromotive force via a resistor, and becomes conductive when a base current is applied thereto. Therefore, both ends of the primary coil 1a of the generator coil 1 are short-circuited, a short-circuit current flows between the collector and emitter of the first transistor 2, and the voltage drop across the resistor 4 increases. Therefore, the voltage across resistors 5 and 6 also increases, and when the predetermined ignition timing is reached, in other words, when the starting force reaches VT (trigger voltage) in FIG. 2, the voltage across resistor 6 increases. A voltage is reached which can make transistor 3 of 2 conductive.

Then, when the second transistor 3 becomes conductive, the first transistor 2 is suddenly cut off, and a sudden change in magnetic flux occurs within the generating coil 1. For this reason, an ignition voltage shown by the solid line B in FIG. 2 is generated in the secondary coil 1b of the generator coil 1, and an ignition spark is generated in a not-shown ignition plug connected to the secondary coil 1b.

However, in such a conventional device, as the rotational speed of the internal combustion engine (not shown) increases, the cycle of the voltage generated by the generator coil 1, indicated by the dotted line A in FIG. As a result, the rotational speed of the internal combustion engine increases more and more, eventually leading to overspeeding.

This invention was made to eliminate the above-mentioned drawbacks, and the purpose is to provide an internal combustion engine ignition device that can prevent overspeeding of the internal combustion engine by simply adding an extremely simple and inexpensive circuit. shall be.

An embodiment of this invention will be described below with reference to FIGS. 3 and 4. Figure 3 is a circuit diagram showing an embodiment of the internal combustion engine ignition system according to this invention.
.about.6 are the same as in FIG. 1, respectively. 7 connects the base and emitter of the second transistor 3 to the collector and
A third transistor 8, each having its emitter connected, is a capacitor circuit connected between the base of the third transistor 7 and the base of the first transistor 2, and here is constituted by a single capacitor 8a.

Next, the operation of the above-mentioned device of the present invention will be explained. Since the operation from the rotation of the internal combustion engine (not shown) to the generation of ignition spark in normal conditions is the same as that of the above-mentioned conventional device, here, we will explain the operation of the above-mentioned internal combustion engine. We will mainly discuss the over-speed prevention operation when the speed increases. That is, the electromotive force of the generating coil 1 is
Depending on the rotational speed of the internal combustion engine, when the engine rotates at low speed, the dotted line waveform C in FIG.
The temporal rise slope changes. That is,
As the rotational speed of the internal combustion engine increases, the frequency of the electromotive force of the generator coil 1 also increases.

On the other hand, a capacitor 8a connected between the bases of the third transistor 2 and the third transistor 7
has the property that its impedance is inversely proportional to frequency. Therefore, when the rotational speed of the internal combustion engine is low, the impedance of the capacitor 8a is high and does not affect the ignition operation in any way, but as the rotational speed of the internal combustion engine increases, the impedance of the capacitor 8a becomes low, and therefore the first When the base potential of the third transistor 2 rises, the base potential of the third transistor 7 also rises. That is, when the internal combustion engine rotates at high speed, the first transistor 2 is made conductive.
Even if the positive electromotive force +e of the generating coil 1 is applied to its base via the resistor 4, the base potential of the third transistor 7 is simultaneously increased via the capacitor 8a, and the third transistor 7 becomes conductive. Make it. Therefore, the base potential of the second transistor 3 is low, the second transistor 3 is not conductive, and the first transistor 2 is therefore maintained in a conductive state, causing a magnetic flux change in the generating coil 1. Things will disappear. Therefore, over-speeding of the internal combustion engine is prevented, and if the engine speed drops appropriately thereafter, the impedance of the capacitor 8a becomes high and the normal ignition operating state is restored.

The rotational speed of the internal combustion engine at which ignition sparks will not be generated is set by selecting a capacitor 8a with a capacity that matches the waveform of the electromotive force generated in the generator coil 1. Insert the capacitor circuit 8, that is, the capacitor 8
The rotational speed of the internal combustion engine may be adjusted by constructing a series circuit consisting of a and a resistor.

As described above, according to this invention, when the rotational speed of the internal combustion engine increases, no electromotive force is generated in the generator coil 1, and the ignition operation is no longer performed, thereby preventing overspeeding of the internal combustion engine. Furthermore, the configuration is extremely simple and inexpensive, as it only requires adding one transistor 7 and a capacitor circuit 8 to the conventional device, and one capacitor 8a in the above embodiment.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional device, Fig. 2 is a voltage waveform diagram for explaining the operation of the device, Fig. 3 is a circuit diagram showing an embodiment of an internal combustion engine ignition device according to this invention, and Fig. 4 FIG. 2 is a diagram showing a rising portion of a voltage waveform for explaining the operation of the device. 1...Generating coil, 1a...Primary coil, 1b
...Secondary coil, 2...First transistor, 3
...Second transistor, 4-6...Resistor, 7...
...Third transistor, 8...Capacitance circuit, 8a...
...capacitor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A generator coil that generates an electromotive force in synchronization with the rotation of an internal combustion engine, and a device that short-circuits the primary side of this generator coil when electrically connected, and the ignition timing of the internal combustion engine is short-circuited. a first transistor that is cut off in response to and generates an ignition voltage on the secondary side of the power generation coil;
A second transistor for controlling conduction of the first transistor, whose collector and emitter are respectively connected to the base and emitter of the first transistor, and whose base is connected to the primary side of the power generation coil via a bias resistor. an internal combustion engine ignition device comprising: a third transistor whose collector and emitter are respectively connected to the base and emitter of the second transistor; and between the base of the third transistor and the base of the first transistor. An internal combustion engine ignition device, characterized in that it comprises a capacitive circuit connected thereto and having at least a capacitor. (2) The internal combustion engine ignition system according to claim 1, wherein the capacitive circuit is a series circuit of a capacitor and a resistor.