US2922903A - Ignition apparatus - Google Patents

Description

4 Sheets-Sheet 1 Filed Sept. 11, 1956 IN V EN TOR. &(Zz2wo Kama A0721 ATTORNEYS Jan. 26, 1960 G. J. KNUDSON :cnmou APPARATUS 4 Sheets-Sheet 2 Filed Sept. 11, 1956 INVENTOR.

54AM Md J ATTORNEYS Jan. 26, 1960 G. J. KNUDSON 2,922,903

mnmon APPARATUS Filed Sept. 11, 1956 4 Sheets-Sheet s INVENTOR. %(Z$n% /1 /nud4m AT TOR Y5 Jan. 26, 1960 G. J. KNUDSON 2,922,903 IGNITION APPARATUS Filed Sept. 11, 1956 4 Sheets-Sheet 4 IN V EN TOR.

fwm a/dnwm ATTORNEYS United States Patent IGNITION APPARATUS Giltner J. Knudson, Guilford, N.Y., assignor to Bendix Aviation Corporation, Sidney, N.Y., a corporation of 7 Delaware This invention relates to electrical apparatus and more particularly to apparatus for generating current such as that required for the ignition system of internal combustion engines.

One of the objects of the present invention is to provide a novel current generating apparatus of increased efliciency.

Another object of the invention is to provide current generating apparatus, such as a magneto, wherein the pole members of the stator are of novel configuration and allow the marked conservation of overall size of the apparatus.

Still another object of the invention is to provide current generating apparatus, such as a magneto, wherein the pole members of the stator are of such configuration and interact with the pole pieces of the rotor in such manner as to yield appreciable greater current generating efficiency.

A further object is to provide a magneto of decreased girth while allowing ready accessibility to the current generating coil thereof.

Still another object is to provide a magneto having a stator provided with pole members of such configuration that the coil lies beyond an end of the rotor and at least partially overlies such end of the rotor.

A still further object is to provide a magneto for supplying the ignition needs of a multi-cylinder engine wherein each pole member on one of the relatively movable parts of the magneto interacts simultaneously with a plurality of pole pieces of like polarity on the other part of the magneto, whereby the magneto has an increased magnetic efiiciency.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, where like characters refer to like parts throughout the several views,

Fig. 1 is a view in longitudinal section through one form of magneto embodying the invention, the section being taken generally along the axis of the magneto shaft, certain parts including the magneto shaft and a portion of the distributor cap on the magneto being shown in elevation.

Fig. 2 is a rear end elevation of a magneto taken along the line 2-2 of Fig. 1, the rear shaft-supporting end member and the breaker point assembly having been removed.

Fig. 3 is a view in perspective of an assembly of pole members before its incorporation as an insert in the housing of the magneto.

v Fig. 4 is a view in transverse section through the magneto, the section being taken generally along the line 4-4 of Fig. 1, the pole pieces of the rotor being shown in neutral position with respect to the pole shoes of the stator.

Fig. 5 is a view in perspective of the rotor of the magneto, the view being taken in a direction from the rear to the front end thereof.

Fig. 6 is a view in rear end elevation of the rotor of the magneto.

Fig. 7 is a view in rear end elevation of the pole member assembly of the magneto, portions of the assembly being partially broken away at the location of the pole shoes of the pole members.

Fig. 8 is a view in rear end elevation of the rotor and pole member assembly of the stator in operative relationship, the pole pieces of the rotor being shown in registry with the pole shoes of the stator.

The embodiment of the invention illustrated in the drawings, by way of example, is in the form of a magneto for an eight-cylinder internal combustion engine wherein combustible charges are ignited by timed electrical discharges across the spark gaps in the respective cylinders. In Fig. 1 the magneto is shown as having a housing 10 carrying a shaft 11 in a front bearing 12 and a rear bearing 13 supported in such housing. Affixed to shaft 11 is a rotor 14 having eight equally angularly spaced outer pole pieces thereon.

The pole pieces of the rotor interact with the stator having opposed pole members 37 and 37 (Fig. 3) carried by the housing 10, in a manner to be explained, thereby producing cyclically varying flux in the pole members. Legs 15, leading from the pole shoes of the pole members, and lying offset from the axis of the rotor as shown in Fig. l, are bridged by the core 16 of a current generating coil .17 having a primary and a secondary winding.

The rear or outer end of housing 10 is provided with a seat 18, best shown in Fig. 2, which receives the inner or rear end member 19 supporting bearing 13. Cap 19 carries an inwardly directed flat spring of generally U- shape, the opposed legs 20 (one shown in Fig. 1) lie outwardly of the ends of coil 17 and press core 16 of coil 17 firmly into engagement with the outer ends of legs 15. Preferably, the flat spring is made of non-mag netic metal such as a copper-beryllium alloy.

The magneto includes a conventional breaker point assembly 21, which opens and closes the primary circuit of the coil at pre-determined times in the cycles of flux variation in the magneto, and a condenser 22 connected across the breaker points. The outer end of shaft 11 carries a distributor rotor 23 which cooperates successively with fixed contacts (not shown) on the inner face of distributor cap 24, the rotor successively connecting the spark gaps of the engine cylinders to a high tension lead wire (not shown) connected to terminal 32 of coil 17. The cap is provided with eight terminal housings 25 for receiving wires leading to the spark gaps of the respective cylinders.

The rotor 14 of the magneto has an annular magnet 26 aflixed thereto, a first generally cup-shaped fourarmed member 27 being positioned on the rotor shaft at one end of the magnet and a second, similar four-armed member 28 being positioned on the shaft at the other end of the magnet. Members 27 and 28 are non-rotatably affixed to shaft 11 so that the arms 30 of member 27 and the arms 29 of member '28, which overlie the outer surface of magnet 26, are parallel to and equally angularly spaced from each other The opposite ends of magnet 26 have opposite magnetic polarities so that the arms 29 constitute, for example, magnetic pole pieces having a north polarity and arms 30 constitute pole pieces having a south polarity. It will be evident that adjacent pole pieces of the rotor have their centers displaced throughout an angle AOB (Fig. 6), of 45 from g a each other in the same central transverse plane through the rotor.

In the embodiment of thezmagneto shown the opposed polemembers. of the: stator. each includes two pole shoes: displaced 90 from each other about the axis of the stator and so positioned as to coact simultaneously. with two pole pices on therotor having the same. magnetic polarity, the pole shoes of the opposed pole members coacting with polepieces of opposite polarity.

The construction of the opposed pole members, and of the assembly thereof prior to their incorporation as a unit in the housing of the magneto, willbest be to designate parts of the left hand pole member 37.

(Fig. 3), as those used in connection with the right hand pole member. 37. Detailed description of the pole members will be primarily confined to pole member 37.

The pole shoes and their extensions are made of lami nations. ofmagnetic metal such as iron or steel. Pole member 37 has an upper pole shoe 34, thecenter of which lies in an axial plane displaced 22 /2 above the horizontal (Fig. 7). Pole member 37 has a second, lower pole shoe 35, the center of which lies in an axial plane displaced 22 /z from the vertical and on the same side of a vertical axial plane as pole shoe 34. Consequently, pole shoes 34 and 35 are displaced 90 from each other, and are thus in position to confront alternate rotorpole pieces of the same magnetic polarity. Lower pole shoes 35 and 35' are displaced 45 from each other. The pole shoes 34'and 35 when connected parallel in the magnetic circuit produce a much greater flux density in such circuit than yielded by either of such pole shoes alone. Pole shoes 34 and 35 are connected by extensions of the'pole shoes, such extensions including a leg 42 andai leg 46, respectively, which extend outwardly or ,rearwardly parallel to the axis of the rotor and close to each other. to form a combined leg 15. In the form shown, the outer ends of legs 42 and 46 are riveted together. The upper leg 42 has its inner face 43 or tapering beveled in'a forward direction, so that the inner end of the leg is of reduced width. Such inner end of the leg is connected with a sweeping right angle band to a circumferential extending extension part 44. The radially inner face of extension part 44 is spaced appreciably outwardly from the rotor, the shoe 34 constitutinga radially inwardly projecting part on member 44. To improve the magnetic efficiency of the device, pole member 37 is provided with side filler laminations or. plates 45 at both sides thereofthroughout the Zone of'the pole shoe 34 and extension part 44, thereby increasing the effective cross section area of the polemember in such zone.

The bottom pole shoe 35 is, as we have seen, connected in parallelwith pole shoe 34 by an extension including leg 46. Leg 46 extends forwardly from the'fr'ee end of combined leg generally parallel to leg 42 to a location generally below member 44. At such position the extension is bent sweepingly downwardly into a first leg 47 of a U-shaped portion of the extension. Such U-shape portion. lies generally in the central transverse plane containing pole shoes 34 and 35. The other leg 49 of such U-shaped portion lies generally parallel to leg 47 andrises to terminate at its top in the generally radially directed lower pole shoe 35. Side filler plates 50 are provided at the lower pole shoe, such filler plates also overlyingthe'l'eg 49 of the extension. I

The two opposed pole members- 37 and 37' are retained the desired relationship by end retainer plates which are made, for-"example; or brass: A rear upper.

retainer plate 40 having a general central rotor-receiving aperture therethrough is connected to the pole members by rivets extending through ears on plate 40 and through the extensions of the upper pole shoes. A lower rear plate 39 is connected to legs 49 and 43 of the lower pole shoes by rivets as shown, A unitary forward retaining plate 41 made, in effect; to combine the shapes of the rear plates 39 and 40, is connected tothe assembly by the same rivets, which connect plates 39 and 40 to the polemembers.

- As-will be clearxinFig. 4; the pole member assembly 36 is imbedded in the housing 10 of the magneto; In the embodiment shown, the housing'ltlis an'integral'casting made of a non-magnetic metal, suchras aluminum, having a melting point appreciablylower'than the melting point of the pole members and their retaining plates. The pole member assembly 36 is disposed as an insert in a suitably shaped mold, and the metal-to form housingltlis' then cast about such insert. The pole member assembly and the opposed pole members 37 and 37 thereofitorming parent from the above description and from the drawings, particularly Figs. 4 and 8. In Fig; 4 the. rotor, whichis assumedtobe rotating clockwise, is in neutral position, that is, pole pieces of the rotorlie midway} betweenthe pole-shoes of the stator. In such position the flux density in the pole pieces is substantially 'zero. Whenthe rotor has turned 22 /z from theneutral position of. Fig. 4 into the full register position of Fig. 8,. pole pieces of'the rotorlie opposite the pole shoes or the stator, so that the flux density in the pole shoesis now at a. maximum. It will be understood. that theprimary circuit of the coil 17 is opened by the breaker. assembly 21 eachtime the'rotor travels from a neutral to a full. register position, and that the primary circuit is also opened each time the rotor travels troma full register to a neutral position. Since with the-magneto shown there are four complete cycles of flux variations per revolution of the rotor, the primary circuitof the coil is opened and closed eight times during each revolutionof therotor. The magneto-thus supplies the ignition needs of an eight cylinder, four cycle internal. combustion engine when the rotor of the magneto is rotated in synchronism with the engine at one-half the crankshaft speed. I

It will'alsobe evident from the Figs. 4 and 8 that the two pole shoes 34, 35 and 34, 35' ofrthe two respective opposed pole members 37 and '37 are connected in parallel, so that the flux in each of combined legs' 15' is essentially thesum of the flux in the two pole shoes of each pole member. The two pole members are alternately confrontedby opposed pairs of pole pieces on the rotor so that the flux through core 16 of the coil '17 alternates in polarity, thereby inducing voltage in the coil.

The electric current generating apparatus of the invention is of advantage because of its compactness and itseihciency of operation. The illustrative magneto has a generally rounded configuration, it being necessary merely to provide relatively low side and bottom bulges inthe housing 1!) to accommodate the pole member assembly rotor, makes possible the positioning. of the coil'so as atleast partially to overlie an end of the. rotor. Con.- seque'ntl'y, the overall girth of the apparatus is decreased" while retaining high efficiency of the apparatus and ready accessibility of the coil.

Although only one embodiment of the invention is illustrated in the drawings and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, in some instances, particularly with a small number of pole pieces on the rotor, only one set of opposed pole shoes 34 and 34', or 35 and 35 may be employed. Also, the opposed, pole members need not be connected as a unit prior to their incorporation in the housing, since the housing itself adequately locates and secures the pole members. Various changes may also be made in the design and arrangement of the parts illustrated as well as in the materials herein suggested as suitable without departing from the spirit and scope of the invention as it will now be understood by those skilled in the art.

What is claimed is:

l. A magneto comprising a rotor carrying a plurality of spaced magnetic pole pieces, a stator having two opposed sets of pole members cooperating with said rotor, the two sets of pole members being generally mirror images of each other, each set of pole members having one pole shoe located on one side of the axis of the rotor and another pole shoe located on the other side of the axis of the rotor, the pole shoes of both sets of pole members lying generally in the same plane transverse to the axis of the rotor, means magnetically connecting the pole shoes of each set together including an extension on each p'ole shoe having a leg extending parallel to the axis of the rotor, a coil, and a core for the coil having one end thereof magnetically connected to the legs of the extensions of one set of pole members and the other end thereof magnetically connected to the legs of the extensions of the other set of pole members, the sets of pole members being offset toward each other around the axis of the rotor, and the outer ends of the legs being offset toward each other around the axis of the rotor in I the same direction as the offset of the sets of pole mema plurality of spaced magnetic pole pieces, a stator in the housing having two opposed pole members each having a pole shoe cooperating with the pole pieces, each pole member including an extension connected to the pole shoe and including a leg, the legs of both pole members extending in the same direction generally parallel to the axis of the rotor, the outer ends of the legs lying outwardly beyond one end of the body of the rotor and being offset laterally to one side of the axis of the rotor, a

coil partially axially overlying the body of the rotor, a removable core for the coil extending between and magnetically connecting the legs of the extensions, and a removable end plate on one end of the housing overlying the rotor and the core, the end plate carrying a bearing journalling the rotor, the coil and the rotor being removable from the housing axially thereof in the direction toward said one end of the housing upon removal of the end plate from the housing.

4. Apparatus as defined in claim 3, comprising thrust means interacting between the core and the end plate to retain the core against the ends of the legs when the end plate is in operative position.

5. Apparatus as defined in claim 3, wherein said one end of the housing is the rear end thereof, the rotor has a rotor shaft, the rotor shaft has a driving portion extending forwardly from the rotor, the legs of the pole members extend rearwardly, the outer ends of the legs lie outwardly beyond the rear end of the body of the rotor, and the coil is laterally offset from and partially axially overlies the body of the rotor at the rear end thereof.

6. Apparatus as defined in claim 3, wherein the pole shoes lie in the same plane transversely of the axis of the rotor and are offset angularly around the axis of the rotor in the same direction as the direction of offset of the outer ends of the legs of the extensions.

References Cited in the file of this patent UNITED STATES PATENTS 1,693,345 Perry Nov. 27, 1928 1,922,824 Schick Aug. 15, 1933 2,285,463 Ridgway June 9, 1942 FOREIGN PATENTS 263,287 Great Britain Dec. 30, 1926 837,814 France Nov. 18, 1938

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