JPS6124693Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an ignition system for a small air-cooled engine used mainly in small agricultural machines such as brush cutters.

This type of ignition device has an ignition coil wrapped around an iron core placed opposite the magneto flywheel.
It also consists of an ignition circuit that has a heat generating element such as a power transistor. Conventionally, the above ignition circuit is manufactured as a circuit unit separate from the ignition coil, and in order to cool the heat generating element, the ignition circuit is manufactured on the outer surface of the engine. Or it was installed in a place with relatively good cooling inside.

However, if the ignition coil and ignition circuit are separate in this way, manufacturing is cumbersome and requires more man-hours to assemble into the engine, and the installation location of the ignition circuit unit is restricted due to dimensions. However, there were drawbacks such as the troublesome installation.

The object of this invention is to integrate the ignition coil and the ignition circuit to solve the above-mentioned conventional drawbacks and to sufficiently cool the heat generating elements of the ignition circuit.

An embodiment of this invention will be described below with reference to the drawings.

In Figures 1 and 2, 1 is the engine body, 2 is a magneto flywheel fixed to its crankshaft 3, and 4 is an air cooling blade fixed to this flywheel 2. Wheel 2 also serves as an air cooling fan. Reference numeral 5 denotes an iron core made of a laminated silicon steel plate, which is arranged opposite to the flywheel 2 and fixed to the engine cover 6 with bolts 7. 8 is an ignition coil wound around the central portion 5a of the iron core 5; 9 is an ignition circuit having a heat generating element 10 such as a power transistor;
Together with the ignition coil 8, it is integrally molded 11 with electrically insulating resin. Reference numeral 12 designates an envelope for the heat-generating element 10, which is made of a material with good thermal conductivity such as metal, and is exposed on the outer surface 13 of the molded part 11 and is connected to the air cooling fan 2.
It faces into the passage 14 of the cooling air A sent from the engine, that is, into the engine cover 6 that forms this passage 14. Here, it is common knowledge that molding is generally done to enclose all parts (ignition circuit parts) in order to prevent damage to them; however, in this invention, we have broken the above common sense and have molded the parts (ignition circuit parts) to prevent damage to the engine cover 6. A part of the envelope 12 is actively exposed.

16 is a recoil starter disposed adjacent to the flywheel 2, 17 is its inner drum, and 18 is a grip.

As an example of the ignition circuit 9, FIG. 3 shows a contactless ignition circuit widely used for two-stroke engines. In this figure, an ignition circuit 9 connected to the ignition coil 8 includes a thyristor 20, a power transistor 10 which is a heat generating element, etc., and has the same period as the crankshaft 3 applied to the primary coil 21 of the ignition coil 8. By detecting a predetermined value of the alternating current voltage and rapidly reducing the current flowing through the primary coil 21, a large voltage is induced in the secondary coil 22 and the spark plug 23 is ignited.

This invention has the above-mentioned configuration, and since the ignition coil 8 and the ignition circuit 9 are integrally molded, manufacturing is easy and the number of parts is small.
It is easy to install the heat generating element 10 in the engine, and since the envelope 12 of the heat generating element 10 of the ignition circuit 9 is exposed from the molded part 1 and faces into the passage 14 of the cooling air A, the heat generating element 10 can be easily attached to the engine. Since sufficient cooling is performed, malfunction of the ignition circuit 9 and deterioration of circuit characteristics do not occur.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side view showing an example of a small air-cooled engine implementing this invention, and Figure 2 is a side view of a small air-cooled engine incorporating this idea.
FIG. 3 is a front view showing the main parts of the figure, and an electric circuit diagram showing an example of the circuit of the ignition device. 1... Engine body, 2... Magneto flywheel (air cooling fan), 4... Air cooling fan blade, 5... Iron core, 5a... Center part, 6... Engine cover, 8... Ignition coil, 9... ...ignition circuit,
10... Heat generating element, 11... Mold part, 12
... Envelope, 13 ... Outer surface, 14 ... Passage, A
...cooling air.

Claims (1)

[Scope of utility model registration request] The central part of the iron core, which is placed opposite the magnetic flywheel that also serves as an air cooling fan, the ignition coil wrapped around this central part, and the ignition circuit, which has a heat-generating element such as a power transistor, are integrated. It is molded with electrically insulating resin, and a thermally conductive envelope containing the heat-generating element is exposed on the outer surface of the molded part so as to be exposed to the passage of cooling air sent from the air cooling fan. Let me,
This passage is the ignition system for the small air-cooled engine, which is formed inside the engine cover.