JPH04311680A - Resin-molded ignition device - Google Patents

Abstract

PURPOSE:To provide a light and low-priced resin-molded ignition device of stable quality by providing a resin-made crankshaft web part with a magnet and a pole piece, and forming resin-made crankcases and an ignition coil assembly integrally. CONSTITUTION:A recoil starter side crankshaft 22 and a cooling fan side crankshaft 23 are deposition-molded out of synthetic resin, and a magnet 24 and a pole piece 25 are integrally formed at a crankshaft web part. A recoil starter side crankcase 26 and a cooling fan side crankcase 27 are also made of synthetic resin. An ignition coil iron core 30 is disposed opposedly, with a fixed gap, to the pole piece 25 and integrally formed at the coil starter side crankcase 26 after cutting the opposed face. An ignition coil 31 is wound onto the ignition coil iron core 30 but not molded at the crankcase 26. Magnetic paths can be thereby formed between the crankshafts 22, 23 and the crankcases 26, 27 so as to reduce the number of part items.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a magneto type ignition device molded onto a resin crankshaft and crankcase of an engine.

0002

2. Description of the Related Art A conventional two-stroke gasoline engine equipped with a flywheel magneto type ignition device will be explained with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view of a two-stroke gasoline engine equipped with a flywheel magneto type ignition device, and FIG. 4 is a front view of the same engine as that of FIG. 3. In the figure, 1 is a cylinder, which is integrated with the cylinder head. 2 is a piston, 3 is a connecting rod, 4 is a carburetor, 5 is a muffler, 6 is a recoil starter for starting, 7
Reference numeral 8 denotes a crankshaft on the recoil starter side, and 8 a crankshaft on the cooling fan side, which is combined with the recoil starter side crankshaft 7 by press-fitting a crank pin not shown in the figure. The material of this crankshaft is generally a magnetic material such as SCM material. 9 is the recoil starter side crankcase, and 10 is the cooling fan side crankcase, which are assembled with several bolts. The material is generally die-cast aluminum. Reference numeral 11 denotes a cooling fan, which is fastened to the crankshaft 8 on the cooling fan side. Reference numeral 12 denotes a flywheel magnet, which is positioned and tightened on the recoil starter side crankshaft 7 with a key, pin, etc., and is made of a thick disc made of non-magnetic material such as aluminum, with a magnet integrally molded near its outer periphery. Reference numeral 13 denotes an ignition coil iron core, which is attached to the crankcase at a position facing the flywheel magnet 12. An ignition coil 14 is wound around the ignition coil iron core 13. 17 is a spark plug screwed into the end of the cylinder 1. 15 is a high voltage cord connected to the ignition coil 14;
A high voltage is introduced to the spark plug 17. 16 is a screw that attaches the ignition coil iron core 13 to the recoil starter side crankcase 9. The ignition coil core 13, the ignition coil 14, and the high-voltage cord 15 constitute an ignition coil assembly, and the ignition coil assembly is connected to the recoil starter side crankcase with a screw 16, facing the magnet provided in the flywheel magneto. It is attached to 9.

[0003] The operation of the conventional example will be explained. Since the operation of power generation by the engine is well known, a description thereof will be omitted. Since the ignition circuit is also well known, it will be briefly described. Ignition coil iron core 13
When a magnet installed near the outer periphery of the flywheel magnet 12 passes through the end of the flywheel magnet 12, a current flows through the primary winding of the ignition coil 14, and by cutting off this current at a predetermined time, a current is generated in the secondary winding. The high voltage cord 1
5 leads to the spark plug 17.

0004

Problems to be Solved by the Invention In order to reduce variations in performance such as startability and output of conventional engines, it is necessary to keep the ignition timing within ±2 degrees of the value determined by the crank angle. Ignition timing in the flywheel magneto system is ultimately determined by the angle at which the pole pieces in the flywheel magneto are attached to the ignition coil iron core. Therefore, it is necessary to determine the dimensional tolerances of parts such as the piston, connecting rod, crankcase, crankshaft, key, flywheel magneto, ignition coil iron core, etc. so that the cumulative value of dimensional accuracy falls within the above-mentioned ±2° angle. The ignition energy is greatly influenced by the gap between the pole piece in the flywheel magnet and the ignition coil iron core, and ideally it is within a predetermined value of ±0.05 mm. However, improving the dimensional accuracy of the ignition coil core and improving the accuracy of the positioning dowel pin to reduce the variation within the above width will greatly increase the construction cost, so generally the mounting hole of the ignition coil core is made into a long hole to minimize the The gap between the piece and the ignition coil iron core is adjusted and tightened, and the variation width is ±0.1.
A compromise is made at about mm.

[0005] As mentioned above, conventional flywheel magnetos basically cannot reduce the number of parts and cannot compromise on dimensional accuracy, and user needs have increased in recent years for lighter weight, smaller size, and stable quality at lower prices. Some products have defects that cannot be addressed.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a resin molded ignition device that is lightweight, has stable quality, and is suitable for inexpensive engines.

[0007]

[Means for Solving the Problems] In order to solve the above problems, it is necessary to change the functions of each engine component from military functions to multi-functions. From this point of view, it has become possible to construct a magnetic path between the crankshaft and the crankcase, which was impossible with conventional flywheel magnets. The flywheel and key are abolished, and the crankshaft is made of synthetic resin, which is equipped with a magnet and a pole piece. In this invention, the crankshaft needs to be made of a non-magnetic material, and although aluminum is also available as a non-magnetic material, it is inferior in strength to synthetic resin, and according to trial calculations, it cannot be used due to insufficient strength, so synthetic resin is optimal. Where the flywheel has been eliminated, a simple disc is installed to transmit the torque of the recoil starter when starting the engine to compensate for the drop in the inertia factor. The crankcase is made of non-magnetic synthetic resin, eliminating the need for ignition coil mounting screws and molding the ignition coil assembly integrally with the crankcase, eliminating the need for assembly adjustments.

[0008]

[Function] The crankshaft is made of synthetic resin, and the magnet and pole piece are molded onto it to make it a rotating magnet, eliminating the need for a flywheel magnet, which can reduce weight. A simple disc that transmits the torque of the recoil starter when starting the engine is installed in the place where the flywheel has been abolished to compensate for the drop in inertia caused by the abolition of the flywheel. Since the crankcase is made of synthetic resin and the ignition coil assembly is integrally molded therein, the crankcase itself becomes lighter and the number of man-hours is reduced by eliminating the need for installation and adjustment of the ignition coil assembly. No need for installation screws for the ignition coil iron core, making it lighter. The magnetic path is made up of the magnet and pole pieces integrally molded on the crankshaft, and the ignition coil iron core integrally molded on the crankcase. No adjustment of the ignition coil assembly is required. This eliminates the need for machining the tapered shaft and keyway of the crankshaft, machining bolt holes for the ignition coil core, machining screw holes for attaching the ignition coil core in the crankcase, and machining the flywheel. The accurate positioning of parts can be determined without adjustment, reducing variations in ignition timing and ignition energy.

[0009] As the crankshaft rotates, the magnet and pole piece rotate, causing a change in magnetic flux in the ignition coil iron core. The ignition coil consists of a primary winding and a secondary winding. The current in the primary winding is interrupted by a transistor, etc., and a high voltage (
The operation of generating 15 to 30 kV) is the same as that of the conventional technology.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a two-stroke engine according to an embodiment of the present invention, and FIG. 2 is a front sectional view of the same engine as in FIG. (a) It is AA sectional view of figure. Since the general structure of a two-stroke gasoline engine is well known, its explanation will be omitted. The connecting rod 20 is preferably made of synthetic resin to reduce weight and prevent magnetic flux leakage. 21 is a crank pin, 22 is a recoil starter side crankshaft, and 23 is a cooling fan side crankshaft, and these are made of synthetic resin and are welded and molded. Reference numeral 24 denotes a magnet, and 25 a pole piece. These are closely attached, and the outer periphery of the pole piece 25 is exposed from the crank web portion and is integrally molded with the crank web portion. The pole piece 25 is formed by pressing a silicon steel plate, and the outer peripheral surface is processed to reduce the gap between the pole piece 25 and the opposing partner. The outer periphery of the synthetic resin can be left as it is, leaving just enough space to prevent it from colliding.

Reference numeral 26 denotes a crankcase on the recoil starter side, and numeral 27 denotes a crankcase on the cooling fan side. Both are made of synthetic resin and are welded together after the necessary parts have been assembled, but they may also be bolted together. 28 is a bearing made of non-magnetic material. 29 is an oil seal. Reference numeral 30 is an ignition coil iron core that faces the pole piece 25 with a predetermined gap therebetween, and its opposing surface is cut and integrally formed with the recoil starter side crankcase 26. Reference numeral 31 denotes an ignition coil, which has the same structure as the conventional technology, is wound around the ignition coil iron core 30, and is not molded into the crankcase to prevent thermal deterioration of the wire.

The magnet 24 and the pole piece 25 may be provided on either side of the crank web. The pole piece 25 may be taken out from the side of the web, and the ignition coil iron core 30 may be opposed thereto. The crankshaft and crankcase must be made of non-magnetic material. Non-magnetic materials include aluminum and zinc, but synthetic resin is most suitable for the following reasons. Synthetic resin is stronger and more reliable than aluminum for the crankshaft. It is also difficult to select the crank pin material. That is, aluminum is insufficient in strength, and even if steel is used, the strength of the press-fit assembly portion is insufficient. For the crankcase, the temperature at which the ignition coil assembly is integrally molded is important. The current temperature that the ignition coil assembly can withstand is about 100 degrees Celsius, and aluminum is no good.

Although there is nothing on the opposite side of the crank web on which the magnet 24 and pole piece 25 are not molded in FIG. 1, it is necessary to balance the mass of the piston, connecting rod, and crankshaft rotating part due to vibration. The shape should be determined by the conditions.

Next, the operation of the above embodiment will be explained. magnet 2
4. The pole piece 25 and the ignition coil iron core 30 form a magnetic path, and the magnet and pole piece rotate together with the crankshaft, so an ignition device can be constructed. Eliminating the flywheel magneto reduces mass. Since the crankshafts 21, 22, 23, the connecting rod 20, and the crankcases 26, 27 are made of synthetic resin, they are lighter, and the parts to be assembled can be integrally molded in precise positions, improving precision and reducing man-hours. That is, since the relative position between the pole piece 25 and the ignition coil core 30 can be determined accurately, variations in ignition timing can be reduced, and variations in the distance between the pole piece 25 and the ignition coil core 30 can be reduced, so variations in ignition energy can be reduced. can be made smaller. Also, the number of man-hours required for preparing screw holes for installing the ignition coil iron core can be saved.

[0015]

[Effects of the Invention] Although the ignition principle of the present invention is the same as that of the conventional technique, the weight can be significantly reduced compared to the conventional technique. It is possible to reduce the number of parts, reduce machining time, and improve productivity. Since there is no need to assemble and adjust the ignition system parts, product quality is stabilized and improved, and productivity is also improved. Therefore, the present invention can provide a resin molded ignition device that is lightweight, has stable quality, and is suitable for inexpensive engines.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a two-stroke gasoline engine according to an embodiment of the present invention.

FIG. 2 is a front sectional view of a two-stroke gasoline engine according to an embodiment of the present invention, (a) is a BB sectional view in FIG. 1;
(b) is an AA sectional view in (a) of FIG.

FIG. 3 is a cross-sectional view of a two-stroke engine equipped with a conventional flywheel magneto ignition system.

FIG. 4 is a front view of a two-stroke engine equipped with a conventional flywheel magneto ignition system.

[Explanation of symbols] 21 Crank pin 22 Recoil starter side crankshaft 23
Cooling fan side crankshaft 24 Magnet 25 Pole piece 26 Recoil starter side crankcase 27
Cooling fan side crankcase 30 Ignition coil iron core 31 Ignition coil

Claims (1)

[Claims] 1. A magnet (24) and a pole piece (25) integrally formed on the web portion of a resin crankshaft (22), and a magnet (24) and a pole piece (25) integrally formed on a resin crankcase (26) at a position facing the crankshaft web. Molded ignition coil assembly (30)
(31) A resin mold ignition device comprising: