US2753389A - Electric ignition system - Google Patents

Description

July 3, 1956 w. B. SMITS 2,753,389

ELECTRIC IGNITION SYSTEM Filed Feb. 12, 1952 //Vl E/V7 0/? 144 725 505 5/1/73 By Qua United States Patent ELECTRIC IGNITION SYSTEM Wytze Beye Smits, Voorburg, Netherlands, assignor to Smitsvonk N. V., Rijswijk (S. H.), Netherlands Application February 12, 1952, Serial No. 271,117

2 Claims. (Cl. 123-148) The invention relates to an electric ignition system with a surface discharge spark plug, a condenser, a magneto for charging this condenser, and a switch by means of which the spark plug can be periodically connected in parallel with the condenser.

The invention aims at providing an electric ignition system which is extremely simple in construction and particularly suitable for the internal combustion engine of a bicycle with a light motor. It is characterized in that the magneto consists of a rotatable permanent magnet and a stationary armature provided with a winding, a cam for operating the switch is provided on the rotatable member with the permanent magnet, the condenser is connected on the one hand to the contact of said switchwhich contact can be moved by means of said cam-and on the other hand to the ground, the spark plug is connected on the one hand to a fixed contact of the switch and on the other hand to the ground, and the condenser is connected in parallel with the armature winding of the magneto at least during the period that the connection with the spark plug is broken.

In this system the armature of the magneto need only be provided with a single coil, to which the ignition condenser is connected at least during the large part of the revolution of the permanent magnet. The switch provides for the condenser being connected to the spark plug at the moment when the former holds a charge. The cam for operating the switch should therefore be adjusted and designed in such a way that the switch is operated at the moment when the voltage generated in the armature coil exceeds a given value, for example when it has attained almost its maximum value. The said cam is preferably so designed and operates the moving contact of the switch in such a manner that this contact is passed from the position of rest to the position in which the spark plug is connected to the condenser by a rotation of the permanent magnet through at most The condenser may be permanently connected to the armature coil. In that case the switch may be an ordinary switch, while the armature coil, with the condenser connected via it, is connected on the one hand to the ground and on the other hand to the moving switch contact.

In many cases it is to be preferred to disconnect the condenser from the armature winding before it is connected to the spark plug. A pure condenser discharge is thus obtained. The switch should then be a changeover switch, with the moving contact connected to the condenser and the fixed contacts to the armature Winding and the spark plug respectively.

It is advantageous for the permanent magnet to be provided on the flywheel of the internal combustion engine, and for this flywheel to enclose a space in which at least the armature, the switch and the cam for operating the switch are accommodated. The condenser may also be located in the space enclosed by the flywheel.

In the system according to the invention not only is the current impulse required for the ignition generated direct by the flywheel, but the flywheel also serves to produce the ignition spark at the right moment. Some readjustment of the moment at which the spark is produced is possible when the fixed contacts of the switch are adjustable in the direction of rotation of the moving switch contact.

The invention is explaned with reference to the drawing, which illustrates two embodiments of the invention in a very diagrammatic way. In this drawing Fig. 1 is a diagram of an electric ignition system which is accommodated in the flywheel of an internal combustion engine and operates by means of a switch,

Fig. 2 is a diagram of a variant of the system according to Fig. 1, and

Fig. 3 shows a voltage curve.

In Fig. l, the numeral 1 designates the flywheel of an internal combustion engine, for example a light motor of a bicycle. 2 and 3 are the poles of a permanent magnet provided in the rim of this flywheel 1. The numeral 4 designates a stationary armature, which cooperates with the permanent magnet 2, 3 and is provided with a single coil 5. In the space enclosed by the rim of the flywheel, a change-over switch consisting of a reciprocating switch arm 6 and two adjustable fixed switch contacts 7, 8 has been accommodated. The fixed contact 7 is connected to the armature coil 5, the other end of which is connected to a spark plug 9, which is likewise connected to the ground. The moving switch arm 6 is connected to the ground. On the shaft 11 of the flywheel a cam 12 for operating the switch arm 6 has been provided.

Whenever the flywheel 1 moves with the poles 2, 3 of the permanent magnet past the ends of the armature 4, an alternating voltage is generated in the coil 5. The cam 12 is provided on the shaft 11 in such a way and has such a shape that the switch arm 6 of the contact 7 is forced from and against the contact 8 when the voltage generated in the coil 5 has a given value, for example when it is practically equal to the maximum amplitude of this voltage. The condenser 10 is therefore first charged, then disconnected from the coil 5, and subsequently connected to the spark plug 9, so that it can discharge via this spark plug. The cam 12 has such a shape that the change-over takes place within an angle of rotation of 10 of the flywheel.

In Fig. 2 the condenser remains connected in parallel with the armature coil 4. The advantage of this is that the switch need not be a change-over switch, and the switching need not take place with the same high degree of accuracy as in the case according to Fig. 1. Further it will not be possible for the voltage peak in the armature coil to attain an inadmissible value when the flywheel rotates very rapidly, as in the first case, because the condenser remains connected to the armature coil. A safety spark gap, which will frequently have to be provided in the case according to Fig. 1, is now superfluous. A drawback of the switching device according to Fig. 2 is that all the energy generated in the armature coil is conducted through the spark plug, and that consequently the consumption of the electrode material of the spark plug is greater than in the case according to Fig. 1. This switching device therefore does not produce a pure condenser discharge on the spark plug.

Fig. 3 shows the curve of the voltage on the condenser in the switching device according to Fig. 2.

I claim:

1. An ignition system for an internal combustion engine in which low voltage surface discharge spark plugs are utilized, in combination, a condenser, rotatable means including a camshaft for alternately connecting said condenser with a source and a low voltage spark plug, said source comprising a stationary armature and a rotatable permanent magnet, said rotatable permanent magnet being mounted in the rim of a flywheel disposed on said camshaft. V

2. An ignition system for an internal combustion engine comprising in combination a low-voltage surface discharge spark plug, a condenser, a source for charging said condenser, switch means for alternately connecting said condenser with said source and said low-voltage spark plug, a camshaft, rotatable cam means for actuating said switch mounted on said camshaft, said source comprising a stationary armature and a rotatable permanent magnet, said rotatable permanent magnet being mounted in the rim of a flywheel mounted on said camshaft.

References Cited in the file of this patent UNITED STATES PATENTS Reichenbach Dec. 27, 1904 Apple June 6, 1905 Kent Nov. 13, 1917 Plumm June 19, 1923 Smits July 26, 1938 Scott May 3, 1949 Raliegh Jan. 9, 1951

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