US2142094A - Magneto - Google Patents

Description

w. DRN

Jan. 3, 1939.

MAGNETO Filed Feb. 20, 1937 2 Sheets-Sheet l Jan. 3, 1939.

w. lDQRN 2,142,094

MAGNETO Filed Feb. 20, 1937 2 Sheets-Sheet 2 y INVENTOR. l/l/a /e f- 00./77

A TTORNE Y.

Patented Jan. 3, 1939 2,142,094 MAGNEro vWalter Dorn, Stuttgart. Germany, assgnor to Robert Bosch Gesellschaft mit beschrnkter Haftung, Stuttgart, Germany Application February 20, 1937, Serial No. 126,819 In Germany March 9, 1936 4 Claims.

This invention relates to' magneto electric generators -and more particularly to a magneto for supplying ignition sparks to an internal combustion engine.

In prior magnetos it has been necessary to provide an interrupter which periodically interrupts the circuit of the primary winding. 'I'he sudden cessation of current flow therein causes the collapse of the magnetic field produced thereby, which simultaneous with a reversal or reduction of the ux produced by the permanent magnet of the magneto, induced a sparking voltage in the associated secondary winding. In the invention to be described herein, no interrupter is required, and the necessity of adjustments in compensating for the wear occurring in parts thereof is eliminated, as well as the initial expense of the interrupter mechanism. Additionally, the present invention discloses a magneto which has a quicker time ratechange of ux in the magnetic circuit and in consequence is more emcient in the generation of sparking voltages at low speeds. The prior art magnetos were relatively ineilicient at low speed and sometimes required -additional special apparatus, such as impulse couplings, to achieve satisfactory ignition performance during the starting period of the engine.

One of the objects of this invention is, therefore, to provide a novel and improved magneto which is more economical in construction and eilcient in operation.

Another object is to provide a magneto which is more eiiicient at low rotational speeds.

Still another object is to provide an improved magneto which requires no associated interrupter mechanism.v

A further object is to provide a magneto having a novel and improved magnetic circuit therein.

Other objects and advantages will in part be specifically stated and in part be obvious when the following specification is read in connection with the drawings,l in which:

Fig, 1 is a schematic showing of the improved magneto, which has a rotating permanent magnet; Fig. 2 is a diagrammatic showing of the variations of magnetomotive force occurring during a full rotation of the rotor; Fig. 3 is a diagram showing the hysteresis loop of the coil core member; Fig. 4 is an enlarged cross section showing the preferred form of the coil core; and Fig. 5

is an enlarged cross section of an alternative construction of the coil core.

Referring now in more detail to Fig. 1, the reference numeral I indicates a rotatable permanent magnet preferably of high'coercive force. Adjacent the magnet are the pole faces 2 of the polepieces 3, and rmly secured between the upper extremities of the polepieces is a coil core l, carrying a primary winding 5 and a secondary winding 6. Secured to each polepiece 3 and extending inwardly below the coil are threaded stud bolts l. A turnbuckle member 8 is internally threaded to col-operate with the threads of the respective stud bolts 'igso as to be capable of applying force thereto, forl a reason later to be explained in detail. A frame 9 receives the lower ends of the polepieces 3 and maintains the gap between the rotor magnet 'ii and polefaces 2 at a constant value, regardless of any adjustment of the turnbuckle 8.

Fig. 2 shows the change in ileld intensity or magnetomotive forcev H, during a full rotation of the rotary magnet I; with the position as shown in Fig. 1 corresponding to position 0 thereof.

The coil core 4 is composed of an alloy having the hysteresis loop shown in Fig. 3, for instance a nickel-iron alloy which contains about 8% nickel and which is held under a mechanical tension of at least 6000 kilograms per square centimeter, as described in the book of Millier- Pouillet, Vol. 4, part 4 at page 146, entitled Lehr- -buch der Physik und Meteorlogie, 10th edition,

"tive force hasy been reduced through zero, and

then reversing, has risen in the opposite sense to a critical value. Thereupon the reversal of flux occurs abruptly in the alloy and the flux assumes substantially 80% of its full value almost instantaneously. This is shown in Fig. 3 where H represents magnetomotive force and B represents the value of the ilux lines per square centimeter. The hysteresis loop there shown has a right angle in each phase which illustrates the quick time rate of change of iiux never before available in a magneto.

The coil core l is composed of an alloy of the foregoing nature, and while it may be of laminatons, the preferred form is a single sheet which is folded upon itself as shown in Fig. 4, or is alternatively rolled into cylindrical form as shown in Fig. 5. The stud bolts 1 are forced apart by the turnbuckle member 8 in order to place the coil core 4 under the proper longitudinal tension.

It will be obvious that many modications and changes may be made by anyone skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.

Having described the invention, claimed is: l

1. In a magneto having a rotor, a current generating coil, a metallic core for said coil, pole pieces attached to each end of said core, means for forcing said polepieces apart, whereby said core is placed under tension, and means preventing displacement of the portion of the pole pieces adjacent said rotor.

2. In a magneto having a rotor, a current generating coil, a metallic core for said coil, pole pieces attached to each end of said core, a stud bolt secured to each pole piece, means engaging what is said stud bolts for forcing said pole pieces apart, whereby said core is placed under tension, and means preventing displacement of the portion of the pole pieces adjacent said rotor.

3. In a magneto, a current generating coil, a metallic core for said coil, a polepiece attached to each end of said core, a stud bolt secured to each polepiece, means engaging said stud bolts for forcing said polepieces apart, and a frame member securing said polepieces at a point remote from said core, whereby said core may be placed under tension.

4. In amagneto, a current generating coil, a metallic core for said coil, a polepiece attached to each end of said core, a stud bolt secured to each polepiece, a turnbuckle member engaging said 'stud bolts for forcing said polepieces apart, and a frame member securing said polepieces at a point remote from said core, whereby said core may be placed under tension.

WALTER DORN.

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