US3435264A

US3435264A - Magneto flywheel ignition

Info

Publication number: US3435264A
Application number: US569357A
Authority: US
Inventors: Guenter Brand; Gustav Pfrommer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1965-08-13
Filing date: 1966-08-01
Publication date: 1969-03-25
Anticipated expiration: 1986-03-25
Also published as: NL6611389A; DE1488401A1

Description

- March 25, 1969 i a. BRAND ET AL 3,435,264

MAGNETO FLYWHEEL IGNITION Filed Aug. 1. 1966 FIG] I I I I I I I h- 2000 4000 6000 u/min United States Patent Int. Cl. H02k 7/00, 21/22 US. Cl. 31070 9 Claims ABSTRACT OF THE DISCLOSURE An ignition system for a combustion engine of the flywheel magneto type. The system including an interrupter'connected in series with the primary winding in such a manner that a spark will only be generated when the magneto is operated in the desired direction.

The present invention relates to a magneto flywheel ignition for two-cycle combustion engines, and more specifically to a magneto flywheel ignition with a rotating four-pole symmetrically magnetized flywheel magneto and a'stationary armature plate on which an interrupter as well as an ignition armature and a light armature are mounted.

It is known that two-cycle combustion engines may rotate in one and in the reverse direction and may be prevented for rotating in the reverse direction, for instance, by a magneto ignition with asymmetrically magnetized flywheel magneto. In this construction there occurs in the ignition armature only one change of magnetic flux during each rotation of the magneto flywheel, which induces the necessary voltage for the ignition. In flywheel magneto ignitions which carry not only an ignition armature but also a light armature, the flywheel magneto is, however, provided with, for instance, four permanent magnets which, in view of the light current to be produced, are symmetrically magnetized so that four flux changes will occur in the armatures mounted on the armature plate during each revolution of the flywheel magnets which can be used for production of energy. Two-cycle combustion engines of this type which operate with a pre-ignition of 30 tend to oscillate during start and to continue rotation in the wrong direction. The ignition spark which initiates rotation of the engine in the reverse direction is produced in an interrupter with a closing angle of 230 by opening the primary current interrupter in a position which during rotation of the engine in the right direction is the closing position. In an interrupter having a 115 closing angle, faulty ignition sparks are produced by a voltage induced in the ignition armature by the magneto flywheel when the primary current interrupter is open.

It is an object of the present invention to prevent occurrence of an ignition spark during reverse oscillating movement of the combustion engine so as to prevent the engine to continue rotation in the wrong direction.

With this object in view the flywheel magneto ignition according to the present invention mainly comprises a rotating four-pole symmetrically magnetized flywheel magneto, a stationary armature plate, an ignition armature and a light armature mounted on the stationary plate, a primary current interrupter mounted on the plate and connected in series with the ignition armature, and a rectifier connected in parallel to the aforementioned interrupter. The rectifier is so connected as to short-circuit the primary winding of the ignition armature in one direction of current flow when the primary circuit interrupter is open to thereby prevent induction of a voltage in the secondary winding of the ignition armature which could 3,435,264 Patented Mar. 25, 1969 produce an ignition spark between the electrodes of the spark-plug.

It has been noted that the ignition voltage of the flywheel magneto ignition is reduced by the rectifier arranged parallel to the primary circuit interrupter when the engine rotates at high speed. In order to prevent such a drop in the ignition voltage the arrangement preferably also includes a resistance connected in series with the rectifier.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a partially sectioned plan view of the flywheel magneto ignition according to the present invention;

FIG. 2 is a wiring diagram of the ignition magneto according to the present invention; and

FIG. 3 is a diagram showing ignition voltage curves with and without a resistance in series with the rectifier of the ignition in dependence on the speed of rotation of the engine.

Referring now to the drawings, and more specifically to FIG. 1 of the same, it will be seen that the flywheel magneto ignition according to the present invention mainly comprises a rotating flywheel magneto 10 and a stationary armature plate 11 on which an ignition armature 12, a light armature 13 and a primary circuit interrupter 14 are mounted. The flywheel magneto 10 comprises a potshaped steel housing 15 in which four radially magnetized oxide magnets 16 having pole shoes 17 are arranged angularly displaced through an angle of from each other and fastened to the peripheral wall of the housing 10' by screws as clearly shown in FIG. 1. The magnets are magnetized in such a manner that the inner ends of adjacent magnets have respectively opposite polarities. Fixedly connected to the drive shaft 18 of the rotating flywheel magneto is a cam 19 having a cam face cooperating with the primary current interrupter 14 and being constructed in such a manner that the interrupter 14 is in a circuit closing position during rotation of the shaft 14 through an angle of 230 C. A lubricating felt 20 engages the cam face of the cam 19 to properly lubricate the same. Connected to the secondary winding of the ignition armature 12 is an ignition cable 21 which leads to a spark-plug not shown in FIG. 1. A conductor 22 connects the primary Winding of the ignition armature 12 to a condenser 23 mounted on the armature plate 11 and the condenser 23 is in turn connected by a conductor 24 with the interrupter 14.

A rectifier 25, preferably in the form of a silicon diode,

r is over a resistance 26 and a conductor 27 connected to the condenser 23 and serves to prevent rotation of the combustion engine in the reverse direction. The resistance 26 is preferably soldered to a pair of soldering taps 29 riveted to the frame 28 of the light armature 13, whereas the silicon diode 25 is provided with a serrated cylindrical projection 25a which is pressed in a corresponding opening formed in the armature plate 11 to properly secure the diode 25 to the armature plate and to connect the diode 25 at the same time to ground.

As can be seen from the wiring diagram of FIG. 2, the secondary winding 31 of the ignition armature 12 is connected at one end thereof to one end of the primary winding 30 of the ignition armature, whereas the other end of the secondary winding is connected to the sparkplug 32. Connected in series with the aforementioned end of the primary winding 30 is the primary current interrupter 14, whereas the condenser 23 and the diode 25 with the resistance 26 connected in series thereto, are respectively connected in parallel to the interrupter 14. The silicon diode 25 is so connected that during rotation of the combustion engine in the desired direction, as for instance indicated by the full line arrow in FIG. 1, and during opening of the primary current interrupter 14 at a preignition of 30, passage of current through the diode will be prevented so as not to impede the production of an ignition spark at the spark-plug 32, since the primary current is interrupted by the interrupter 14. During rotation of the engine in the opposite direction, as indicated by the dotted arrow in FIG. 1, the silicon diode 25 will permit passage of current therethrough during opening of the primary current interrupter 14 at about 100 before the piston of the combustion engine reaches its upper dead center position. Therefore, the impulse created in the ignition armature will be dampened to such an extent so that a faulty ignition spark on the spark-plug 32 will be positively prevented.

Prevention of rotation of the engine in the wrong direction is also assured with a primary current interrupter which has a closing angle of 115 since during rotation of the engine in the reverse direction the voltages induced in the ignition armature are short-circuited by the diode at about 120 before the piston of the engine reaches its upper dead center position.

The resistance 26 has to be dimensioned in such a way that, on the one hand, the ignition voltage during rotation of the engine at high speed will not drop too much, and that, on the other hand, the induced voltages during reverse rotation of the engine will be sufficiently dampened. The dotted line of the diagram in FIG. 3 illustrates the ignition voltage curve in dependence on the revolutions per minute of the engine for a magneto ignition with a closing angle of 230 without resistance connected in series to the diode, whereas the full line of FIG. 3 illustrates this curve in such an arrangement in which a resistance of 13 ohms is connected in series with the diode. As can be seen from the diagram of FIG. 3, the resistance provides an increase of the ignition voltage during high speed rotation of the engine.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of magneto ignitions differing from the types described above.

While the invention has been illustrated and described as embodied in a magneto ignition having an ignition armature and a light armature, it is not intended to be limited to the details shown, various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An ignition system for a combustion engine comprising, in combination, a flywheel magneto including a stationary stator, a rotatable rotor and a flywheel secured to said rotatable rotor, said rotatable rotor and flywheel rotatable in a predetermined direction and rotatable also in opposite direction; electric terminals on said flywheel magneto; a transformer having a primary and a secondary winding, said primary winding being connected between said terminals of said flywheel magneto; a spark gap connected in series with said secondary winding; an interrupter connected in series with said primary winding; and current flow adjusting means connected in series with said primary winding and in parallel with said interrupter in such a manner as to be non-conductive when said flywheel is rotating in said predetermined direction so as to permit operation of said interrupter and to be conductive when said flywheel is rotating in said opposite direction so as to short circuit and thereby prevent operation of said interrupter, thus preventing creating a spark across said spark gap while said flywheel is rotating in said opposite direction.

2. An ignition system as defined in claim 1, wherein said current flow adjusting means comprise a rectifier.

3. An ignition system as defined in claim 2, and including a resistance connected in series with said rectifier.

4. An ignition system as defined in claim 3, wherein said rectifier is a silicone diode.

5. An ignition system as defined in claim 4, wherein said diode and said resistance are mounted on said stationary stator.

6. An ignition system as defined in claim 4, wherein said diode has a portion serrated at the outer periphery thereof and said stator being formed with a corresponding opening into which said serrated portion of said diode is pressed.

7. An ignition system as defined in claim 4 and including a light armature mounted on said stator and including a frame, said electrical terminals comprising a pair of soldering taps fixed to said frame, said resistance being soldered to said taps.

8. An ignition system as defined in claim 1, and including a condenser connected in parallel with said interrupter.

9. An ignition system as defined in claim 1, wherein said flywheel magneto includes a hollow cylindrical steel housing and four radially magnetized oxide magnets connected to and projecting radially inwardly from the inner periphery of said housing uniformly spaced from each other, adjacent magnets having respectfully opposite polarities at the radial inner ends.

References Cited UNITED STATES PATENTS 2,688,101 8/1954 Harsch 310 70.1 2,790,914 4/1957 Dingman 310- 3,037,148 5/1962 Gayler 310--70 FOREIGN PATENTS 701,583 3/1931 France. 883,673 6/ 1953 Germany.

J D MILLER, Primary Examiner.

U.S. Cl. X.R.