US2074545A - Magneto - Google Patents

Description

March 23, 193% K. A. HARMON ET A1..

MAGNETO Original Filed June 15, 1935 www.

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MAGNETO Original Filed June 15, 1935 2 Sheets-Sheet 2 INVENTOR. .KFM/fm1 A fw/my AWA ATTOR 'EYS.

Patented Mar. 23, 1937 UNITED STATES PATENT OFFICE MAGNET() Kenneth A. Harmon, Longmeadow, and Terrence G. Louis, West Springfield, Mass., assignors to Wico Electric Company,

West Springfield,

26,726. Divided and 11, 1935, Serial No. 27, 1936 3 Claims.

This invention relates to improvements in magnetos and is a division of our application filed June 15, 1935 under Serial No. 26,726, patented Sept. 15, 1936, No. 2,054,461.

The magneto is disclosed in the aforesaid application in connection with a dual ignition apparatus, wherein the primaryand secondary coils of the magneto and their core are utilized as an induction coil during the starting period-battery current being directed through the primary coil for this purpose.

'Ihis invention has for one object to provide a magneto which is primarily designed for use in such an apparatus although capable of use a apart from such apparatus, if desired.

The invention is characterized by the use of an electromagnet rather than a permanent magnet, for intermittently magnetizing the core of the magneto,-such electromagnet having the distinct advantage that its magnetizing action can readily be discontinued, when desired, so as not to interfere for example with the magnetization effected by the battery-energized primary coil, when operating on the induction coil prin- I) ciple for starting.

The invention has for an object to provide an improved mounting for the magnet coil, characterized in that it is maintained stationary although encompassing the rotor shaft, thereby avoiding the use of slip rings which would other- Wise be necessary to conduct battery current to the magnet coil if it turned with the rotor, as well as the expense of such rings and the troubles experienced with them in operation due to faulty contacts. y

The invention has for another object the provision of a single and stationary energizing coil with laminated rotors or flux distributers, one on each side thereof and xed to an engine driven shaft, together with pairs of stationary pole pieces, one pair for each rotor, a pair of bridges each magnetically connecting one pole piece of one pair to the corresponding pole piece of the other pair, and a core spanning the two bridges and carrying the primary and secondary coils. This arrangement contributes to the production of a compact, light weight unit, with the Weight of rotating parts reduced to a minimum.

A further object is to provide an improved mounting of the magnet coil in the magneto casing.

These and other objects will more particularly appear as the detailed description proceeds and will be pointed out in the appended claims,

this application October 44,567. Renewed August The invention will be disclosed with reference to the accompanying drawings, in which:

Fig. 1 is a central sectional elevational view of an ignition apparatus embodying the invention;

Fig. 2 is an end elevational view of the breaker point mechanism;

Fig. 3 is a cross sectional view taken on the line 3 3 of Fig. 1;

Fig. 4 is a fragmentary top plan view, showing the ignition coils,-the cover therefor having been removed;

Fig. 5 is a view, taken similarly to Fig. 4 except that the ignition coils and their core have been removed to reveal the pole pieces;

Fig. 6 is a fragmentary cross sectional view taken on the line 6 6 of Fig. 4; and

Fig. 7 is a diagrammatical view of the electrical connections.

Referring to Fig. 1 of these drawings, the apparatus is contained in a casing l, having a cylindiical bore 2 closed at one end by a head 3, in which a suitable anti-friction bearing "-.4 is mounted. A removable head 5, held to casing l by cap screws 6, closes the other end of bore 2 and has mounted therein an anti-friction bearing i. Rotatably mounted in these bearings is a shaft 8 adapted to be driven from the engine which the ignition apparatus serves, and usually from the cam shaft. This shaft 8 is made of magnetizable metal. It passes centrally through the coll 9 of an electromagnet and forms a core therefor adapted to be magnetized by the coil when the latter is energized. Coil 9 is stationarily supported in the bore 2 intermediate the ends thereof. Shaft 8 has fixed to it in axially spaced relation two flux distributers i0 and l0', disposed one on each side of the energizing coil 9 of the electromagnet. As shown in Fig. 3, these flux distributers are of like construction but one is angularly spaced from the other. Each is made up of soft iron laminations (Fig. 1) held together as by rivets l l, and each includes a plurality (three in the form shown in Fig. 3) of arms radially projecting from the shaft. These radial arms, in the form disclosed, are equally spaced around shaft 8. The members i9 and I0' are keyed to the shaft (Fig. 1) and each is also clamped in axial position against a shoulder l2 by a nut i3, threaded on the shaft. In the form herein shown, each radial arm of the distributer l0 is angularly spaced from the corresponding arm of distributer l0 by an angle of 60 degrees.

These ux distributers are adapted to direct flux from the electromagnet to and from a core M, made up of soft iron laminations, suitably held together as by rivets I4'. On this core are mounted primary and secondary coils I5 and I6, respectively. The distributers not only make and break a magnetic circuit through this core a plurality of times during each revolution of shaft 8 but, preferably also, elect this result by creating reversals of flux through the core, as will later appear. For these purposes the flux distributers cooperate with pole pieces made up of soft iron laminations and suitably fixed in the casing I and in this instance embedded therein during the process of casting the casing. There are two pairs of these pole pieces (Fig. 5), one pair for each distributer, the members of one pair being marked I1 and I8 and the corresponding members of the other pair being marked I1 and I8', respectively. The pole pieces I1 and I8 lie in the same transverse plane as the distributer I0 (Fig. 1) and the pole pieces I1' and I8 lle in the same transverse plane as the distributer I0'. The casing I has a dat face I9, approximately tangential to the cylindrical portion thereof and through this face is an opening leading into bore 2 (Figs. 3 and 5). Each pole piece has one end formed with a flat face 20 lying in the plane of said at face I9. The other end of each is formed with an arcuatesurface 2| concentric with the shaft 8 and adapted to cooperate with the arcuate ends of its flux distributer. 'Ihe pole pieces I1 and l1' are interconnected by a bridge 22 (Figs. 3 and 4), made up of soft iron laminations, suitably held together as by rivets 23. The pole pieces I8 and I 8 are similarly connected by a similar bridge 213. The ends-of each bridge rest directly on the*l flat faces 2D of the pole pieces. The core I li lnterconnects the bridges 22 and 24 (Figs. 3 and 4) and its ends rest directly on top of the bridges in seats provided for this purpose as shown in Figs. 1 and 3. Clamps 25, one at each end of core I4, are secured to casing I by screws 26 and act to press the core ends tightly against the bridges and the latter tightly against the faces 20 of the pole pieces.

The arms of each ux distributer and the pair of pole shoes, with which it cooperates, are so spaced that when one arm is covered to any substantial extent by one pole piece of a pair, the other arms are entirely out of covering relation with the other pole piece of, the pair. And the two distributers are angularly spaced so that when one arm of one, as Il), ls covered by a pole piece, as I8,. one arm of the other, as I0', ls covered by the opposite pole piece, as I1. Thus, with the distributers positioned as described, ux

' will then ow from the distributer of north polarity, say I0, through pole piece I8 and bridge .24 to,the right hand end (as viewed in Fig. 3) of core I4 and return from the opposite end of the core through bridge 22 and pole piece I1 to distributer I 0. Flux cannot at this time pass from pole piece I1 to distributer I0 nor from pole piece I 8' to distributer I 0'. oncontinued rotation of shaft 8, that arm of distributer I0 which was covered by pole piece I8 moves out of covered relation therewith and a succeeding arm becomes covered by pole piece I1 and the arm of distributer I0', which was covered by pole piece I1' moves ahead and becomes covered by pole piece I8. Flux then flows from distributer IB through pole piece I1 and bridge 22 to the left hand end of core I4 and returns from the opposite end of the core through bridge 24 and pole piece I8' to distributer I0'. Flux cannot then pass from pole piece I1' to distributer I0 nor from pole piece I8 to distributer I 0. Thus, each arm of each distributer cooperates successively with its pair of pole pieces to establish magnetic ux in core I4 first in one direction and then in the opposite direction. Three times during each revolutlon of shaft 8, magnetic flux is established ln one direction through core I4 and three times during each revolution flux is established in the opposite direction in core I4. The result is that ux ls built up in the core six times during each revolution but alternately in opposite directions so that the transition is from a maximum in one direction to a maximum in the other direction, whereby a large effective flux change can be utif lized in the core to induce a current in the coils thereon. The reversal of flux in core I6, while important and preferred, is not essential to the broader features of the invention.

The arrangement described is suitable for a six cylinder engine in which the cam shaft, travelling at one-half the crankshaft speed, drives the shaft 8. It is contemplated that the arrangement may' be varied to suit engines having a greater or less number of cylinders by varying the number of arms on the ilux distributer and the angular extent of the arcuate surfaces 2| of the several pole pieces.

The casing I is, of course, made of non-magnetic metal, such as aluminum for example. Cooperating with the casing I to enclose the core I 8 and coils I5 and IB, is a cap 21 of insulating material such as bakelite. 'Ihis cap rests on the surface I9 of casing I and is secured thereto by screws 28. The cap 21 has mounted therem a metallic socket 29 to which one end of a high tension Wire 30 is connected. This socket carries a contact nger 3l which presses against the high tension terminal 32 of the secondary coil I6. The other terminal of coil I6 is grounded in any suitable way. Y

A suitable breaker point mechanism (Fig. 2) is mounted on the outer face of. head 3 and operated by a cam 3l mounted on the outer end of shaft 8. This cam is clamped against one end face of the rotatable race of ball bearing l by a screw 32, threaded into shaft 8, the head of the screw being received in the counterbored end of the cam as shown. The stationarybreaker point 33 is carried by a metallic bracket 34 fixed to head 3 and thereby grounded. The movable breaker point 35 is fixed to one end of an arm 36 of insulating material. This arm is pivoted intermediate its ends on a stud 31 xed to head 3 and the other end of the arm serves as a follower to be engaged and moved by cam 3l. A flat spring 38 is secured at one end to arm 36 in electrical contact with point 35 and at the other end by a screw 39 to a block 39 of insulation, fixed to head 3. This spring tends to hold the breaker points engaged and also to electrically connect the terminal 39 to the movable breaker point 35. The bracket 34 is pivoted on stud 31 but is normally held against turning on this pivot' by a screw 40 which clamps the bracket to head 3. The bracket is slotted to receive screw 40 and the slot enables a limited degree of. swinging movement of the bracket, when screw 40 is loosened, for the purpose of adjusting the breaker point 33 relatively to its companion breaker point 35. An eccentric stud 4I, mounted to turn in head 3, engages in a slot in bracket 34, and when this stud is turned the bracket will be swung on its pivot. The cam 3|, as shown, is of hexagonal cross sectional shape and its six projections successively engage and move the arm 36 and cause the break` er points to separate six times during each revolution of shaft 8. The breaker point mechanism is given merely as an illustrative example of one suitable form and any other suitable form may be used as desired.

On the outer face of head 3 and encompassing the breaker point mechanism described is a circular ange 42 (Fig. 2) on which is seated a distributer cap 43 (Fig. 1) of insulating material. Spring clips 44 (Fig. 2), each pivoted to and between a pair of lugs on flange 42, engage in recesses in cap 43 (Fig. 4) in the usual way and hold the cap to its seat on flange 42 against axial and turning movement. The cap (Fig. 1) has a circular series, six in this case, oi' contacts 45 each connected to an exterior binding screw 46. To the screws 46 are connected the high tension wires 41 leading to the spark plugs s of the engine (see Fig. 7). The case also carries a central terminal 48 to which the lead wire 3|) from the secondary coil I6 is connected. This terminal on its inner end carries a spring pressed plunger 49 which engages the inner end of a conducting strip 5U mounted on the distributer brush arm 5|. I'he brush arm, which is of insulating material, telescopes over the outer end of the breaker point cam 3| and has a projection 52 fitting in a recess in the cam to effect an operable driving engagement. The outer end of strip 50 is movable suocessively into close proximity to the contacts 45 and thus the high tension current is distributed in proper order to the several spark plugs s.

Variations in the timing of the spark may be effected in any desired way. All that is necessary is to turn the breaker point mechanism relatively to its operating cam 3| and this may be done either by turning the casing l relatively to shaft 8 or by turning shaft 8 relatively to the casing. A timing adjustment of the breaker point mechanism results in a corresponding adjustment of the distributer because the distributer brush is fixed to the cam 3| and the distributer cap is fixed to the head 3 which carries the breaker points.

In Fig. 1 we have shown a cup-shaped casing` 53, secured in abutting relation with the head 5, to casing by the described screws 6. The casing 53 houses a centrifugal governor of well known form for advancing the shaft 8 relatively to the shaft which drives it,-in this case a shaft 54 mounted in a hub-like extension 55 of casing 53. Fixed to the inner end of shaft 54 is a member 56 to which are pivoted at diametrically opposite points on studs 5'! two weights 58, which at relatively high speeds fly outwardly. Two pins 59 engaged one with each of these weights are fixed to a plate 60, secured as indicated to one end of shaft 8. The arrangement is such that as the weights 58 fly outwardly they turn shaft 8 ahead of shaft 54 and effect an automatic advance of the spark. It is not thought necessary to describe this device in detail as it is not in itself a feature of novelty and is mentioned herein simply to show that provision may be made for an automatic spark advance mechanism.

The hub 55 is intended to t into the usual socket provided in the engine crankcase and is usually mounted therein for limited turning movement, whereby the casings 53 and may be turned by any suitable means, automatically or otherwise, to secure variations in the timing of the spark. Either or both forms of spark advance means may be used as desired. Within the described socket is located one end of an engine driven shaft and the shaft 54 is shaped, as indicated, for a coupling engagement with such engine driven shaft, when hub 55 is inserted in said socket.

Referring to Fig. 1, the casing I, at a point near the head 3 is provided with a chamber 62 in which is mounted a condenser 64. The condenser is supported by its grounded terminal screw 65 which passes through the lower wall of the chamber and is clamped thereto by a nut 61.

The magnet coil 9 (Figs. 1 and 3) is mounted within a short cylindrical casing 'H of insulating material, including a cover 18. This casing has diametrically disposed lugs 'I9 (Figs. 1 and 3), projecting radially outward and engaged in grooves formed in the bore 2 of casing and paralleling the axis thereof. The casing may thus slide in an axial direction in the casing and the grooves 88 extend from the open end of bore 2 to a point about midway thereof. In the assembling operation, shaft 8 with the casing 'l1 loosely mounted thereon between the rotors, is slid into the bore 2 with the lugs 75 riding in grooves 8B. After the rotor is in place the casing ll is pushed in until the lugs 'i9 abut the ends of the grooves 8|), as shown in Fig. 1, whereby the casing Tl will be properly located between the rotors and in position to be fastened in place. This casing Tl is fastened by cap screws @i and 82 (Fig. 3) which extend through casing i at diametrically opposite points and thread into metallic inserts 83 (see also Fig. 6) molded in the casing. The terminals of the magnet coil 9 are connected one to each insert 83. The screws 8i and 82, which are insulated from casing l by washers 84, thus hold the casing l1 in place and also serve as terminals for the magnet coil.

The electrical connections are shown diagrammatically in Fig. 7. One terminal of the magnet coil 9 is grounded and the other terminal is connected by wires |88 and |09 and an interposed switch I to one terminal of a battery B, the other terminal of which is grounded. One terminal of primary coil i 5 is grounded and the other terminal is connected by a wire 'i5 to the ungrounded terminal of condenser 64 and by a wire 'I6 to the terminal 39' of the breaker point mechanism. One terminal of secondary coil i6 is grounded and the other is connected by wire Sil to the brush 58 of the distributor.

In operation, when the ignition switch I is closed, current from battery B will flow through coil 9 magnetizing shaft 5 and its rotating distributers l0 and i0' cause magnetic circuits to be made and broken at properly timed intervals as above described. It should be noted, however, that the flux from the electromagnetic source 9 is allowed to build up in core iii under conditions as favorable as possible. That is, the primary circuit is kept open for relatively long intervals to allow the ux to build up in the coro Without the opposing inuence of a short circuited primary coil. The breaker points, in the form of apparatus herein disclosed, complete one cycle of operation in one-sixth of a revolution of shaft 8 or in 60 degrees. During this interval, the breaker points are closed about twothirds of the time and open only about one-third of the time. In Fig. 3, the flux distributers are shown in the positions which they occupy at the moment the breaker points open. Flux will then build up in core i4, flowing from right to left, the circuit being from the nearly vertical distributer arm I0 through pole piece i8, bridge 24, core i 4, bridge 22, pole piece H' to that distributer arm i0' which in Fig. 3 lies immediately to the left of the aforesaid arm i0. The

breaker points remain open until these two arms l and i0' become completely covered by their respective pole pieces I8 and Il' and until ,these 5 arms start to leave such pole pieces. Then the breaker points close and the then short circulted primary coil tends to resist a. change of ux in core I4. This condition continues until the aforesaid two arms Ill and I0' have moved far enough away from the forward edges of their respective pole pieces to create substantial gaps, such as those shown at g and g' in the magnetic circuit. Then the breaker points again open and a sudden change of ux occurs in core I4. But this change is not simply from a maximum to zero but from a maximum in one direction to zero and beyond to approach as near as possible to a maximum in the other direction. For at the time of the opening of the breaker points, the aforesaid arm lo' has moved into partially covered relation with pole piece I8' while a succeeding arm i0 has moved into partially covered relation with the pole piece Il. Flux then ows from left to right in core I4 and thus in the opposite direction to the flow of ilux previously established. Hence, in the magnetic change, a`

reversal of flux is secured. Such a flux change in core I6 is eifected six times during each revolution of shaft 8 to produce an ignition spark in the usual manner. This gives the three sparks per revolution 'required for the six cylinder engine.

The magneto is compact and of light weight. It utilizes an energizing coil in place of the more expensive magnets of cobalt steel which would be necessary to use to secure a degree of compactness approaching that herein disclosed. But the use of the coil is important for the reason that the action of the magnetic source can be discontinued during periods of induction coil operation Y so as not to interfere therewith, whereas the harmful action of permanent magnets at such periods cannot be so easily avoided. It is deemed important that the coil d be stationary. Use of sliprings is avoided as Well as their initial cost and the troubles in operation likely to arise from their use. The weight of the rotating parts is also reduced by not mounting the coil 9 on the shaft 8 and it is important to keep the weight of rotating parts as low as possible and reduce the wear on the moving parts. The pole piece arrangement, with the bridge pieces and the core which interconnects them, is important in that it enables the use of ux distributers of simple and inexpensive form and of a form which can be made up of laminated soft iron stampings as is desired for their excellent magnetic qualities. Specially shaped and expensive forgings, which are also-less desirable because of their poorer magnetic qualities, are avoided.

What we claim is: `1. An ignition apparatus, comprising, a magnet coil, a shaft extending axially through said coil and magnetizable thereby when said coil is energized, means for energizing said coil, flux distributers flxed to said shaft one on each side of said coil and each comprising a plurality of angularly-spaced radially-extending arms, a pair of pole pieces for each distributer, the pole pieces of each such pair being angularly spaced adjacent the circular path of travel of the arms of its distributer, a pair of bridges each magnetically connecting one pole piece of one pair to the corresponding pole piece of the other pair, a core interconnecting the two bridges, primary and secondary coils mounted on the core, and breaker point mechanism in circuit with the primary coil and operated by said shaft.

2. An ignition apparatus, comprising, a magnet coil, a shaft extending axially through said coil and .magnetizable thereby when said coll is energized, means for energizing said coil, flux distributers xed to said shaft one on each side of said coil and each comprising a plurality of angularly-spaced radially-extending arms, one distributer being angularly offset from the other so that each arm of one lies in a radial plane intermediate the radial planes of two adjacent arms of the other, a pair of pole pieces for each distributer, the pole pieces of each such pair being angularly spaced adiacent the circular path of travel of the arms of its distributer, each pole piece of one pair occupying the same angular position with reference to the axis of said shaft as the corresponding pole piece of the other pair, a pair of bridges each magnetically connecting one pole piece of one pair tothe corresponding pole piece of the other pair, a core interconnecting the two bridges, primary and secondary coils mounted on the core, and breaker point mechanism in circuit'with the primary coil and operated by said shaft.

3. An ignition apparatus, comprising, a casing of non-magnetic material having a cylindrical bore closed at opposite ends by heads at least one of which is removable, the wail of saidbore having a groove therein extending from the removable head inwardly to a position intermediate the heads, a second casing slidably itting the bore and having a lug engaged in said groove to hold it against rotation, a coil in said second casing, both the coil and second casing having a central axial opening, a magnetizable shaft passing through said opening and journalled in said heads, radially-extending flux-distributing members fixed to said shaft one on each side of said coil, a core mounted outside said bore and having pole pieces for cooperation with said members to periodically make and break a magnetic circuit through said core, primary and secondary coils on said core, a breaker point mechanism operated by said shaft and in circuit with the primary coil, and a battery for energizing the rst-named coil and magnetizing said shaft.

KENNETH A. HARMON. TERRENCE G. LOUIS.

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