US1638307A - Lighting and ignition magneto - Google Patents

Description

Aug.L 9, 1927. I 1,638,307

J. H. HUNT Lisanne AND IGNiTIoN MAGNETO i Filed Ju1y21, 1922 2 Sheets-sheetl Au 9 19 i g *'4 ..27 J. H, HUNT LIGHTING AND IGNITION MAGNETO Filed July 21. 1922 2 Sheng-sheet 2 Patented Aug. 9, 1927.

UNITED STATES 1,638,307 PATENT OFFICE;

JOHN H. HUNT, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TOV DELCO- REMY CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE.

LIGHTING AND IGNITION MAGNETO.

Application iled July 21, 1922. Serial No. 576,493.

This invention relates to electrical systems for automotive vehicles and particularly to apparatus for applying ignition current for the engine and current for lighting purposes.

This invention is particularly adapted for use on farm tractors andthe like which do not generally require electrical starting apparatus and, consequently, in which the storage battery is not necessary.

In electrical systems which supply current for engine ignition and vehicle lighting only, there is .usually provided one dynamo-electric-machine, a magneto, which furnishes current for ignition purposes, and a separate dynamo-electric-machine is provided for furnishing the vehicle with electric lighting. Sometimes the two machines are combined all in one unit, but such a machine has separate fields and `separate armatures so that the unitary structure is in effect two separate dynamo-electric-machines. Precaritions are sometimes taken to insulate magnetically the two `fields from one another so that the operation of one dynamo-electricmachine may not affect the operation of the other in the unitary structure. Vhere magnetos are used to supply ignition current for engines which are started by hand, it has been found necessary to use impulse starters so that the magneto may be operated with sufficient rapidity periodically, to supply ignit-ion current while the engine is being cranked by hand.

It is among the objects of the present invention to provide a dynamo-electric-machine having va permanent magnet field `and one rotor for supplying current both for ignition and for lighting purposes. n

It is a further object to provide a dynamoelectric-machine which will supply current sufficient for ignition purposes at engine speeds attained by cranking and without the use of an impulse starter drive or coupling between the magneto and some engine part operated by the hand crank.

Other and further objects of the present invention will be apparent from the follow-Y ing description, reference being had to the accompanying drawings, wherein ya preferred embodimentof the present invention is clearly shown.`

In the drawings:

Fig. l is an end elevation'of the ignition device, certain parts being shown in section for the sake of clearness.

Fig. 2 is a wiring diagram of a complete lighting and ignition system embodying the present invention.

The dynamo and ignition timer unit is designated as a Whole by numeral and includes a base 3l to which is attached, by means of screws 32, laminated pole shoes 33 and 34 each built up of a plurality of thin fiat punehings. The laminat-ions or punchings forming the pole shoe 33 are secured by rivets 35 and 36, while the laminations forming the shoe 34 are secured by rivets 37 and 3S. All `of these rivets pass through clamping .frames of non-magnetic material. bet-Ween which the pole shoes 33 and 34, of magnetizable material, are clamped together, the ends of the rivets 35, 36 and 37 being swedged to fill up the countersunk holes in the clamping frames through which these rivets pass. The pole shoe 33 is provided with teeth 4l, 42, 43 and 44 and the pole shoe 34 is provided with teeth 45, 46, 47 and 48, and when'the laminations forming the shoes 33 and 34 have been clamped together in the manner described, these teeth will all be equally spaced and will radiate from a common centerand the faces of these teeth will all be tangent to the same circular arc. This common center or center line from which the teeth radiate, is coincident with the axis of they armature shaft. In order to assist in accurately spacing the poles 33 and 34 so that teeth 4l and 48 and teeth 44 and may vbe correctly spaced, spacing blocks 49 and 50 of non-magnet-izable material are provided, and these blocks fit in between suitably formed recesses provided in the poles 33 and 34. A cover plate 51 of non-magnetizable material is attached by screws 51a to the pole shoes 33 and 34 to provide the top of a box-like structure for housing the dynamo armature.` The base 31 provides the bottom of this armature housing, the pole shoes themselves providing the side walls, and the end Walls are provided by the dynamo end frames t not shown).

Permanent magnets 55 and 56 are attached to the pole shoes 33 and 34 by means of screws 57 and 58. y

84 designates as a whole the armature core comprising a series of laminations or flat punchings which areheld upon the shaft 76 by a driven fit, these punchings being forced against'a shoulder, not shown, provided on the shaft 76,

The armature core 84 is laminated and the cylindrical periphery thereof is notched to provide a series of equally spaced teeth 220, the face of each tooth being approximately one-third the greatest width of the notch between adjacent teeth. It is desirable that the notches spacing the teeth be as wide as possible in order to reduce flux leakage to the minimum. But on the other hand, if the notches are too wide,'the teeth 220 will be too narrow to carryeliciently the flux from the various pole teeth of the permanent magnets. Satisfactory proportions of width of notch to width of armature tooth face have been found to be from Lto gi-0. The notches between certain of the armature teeth 220, 220", 220, 220e, and 220f, are made considerably deeper than other notches in order to provide for the armature winding, arranged in two coils 221 and 222 which are wound about ,armature core 84 after the fashion of the ordinary shuttle wound armatune windings, and these windings are connected in series and one end of the group of windings is grounded by attaching the same to the armature shaft 76, and the other end of the group of armature windings is onnected with the timer mechanism, not illustrated. By way of example, the followinf.r armature dimensions are given to show what proportions having been found satisfactory in one machine constructed in accordance with the present invention. Core length 3 inches. Core diameter 1.87 5 inches. twelve core teeth. Windings 221 and 222 have each 166 turns of No. 23 wire. It will be noted that the magneto armature Awindings differ from the ordinary shuttle Wound armature windings in that the windings include two coils which are separated by the relatively ,long armature core teeth 226b and 220e. This construction increases the time ot' duration of the short circuit current in the armature at values continuously above the minimum required for ignition and also reduces the indnctance per turn to a value substantially less than what it would be if the windings were concentrated. This arrangement permits a wider range of adjustment of the ignition timer than is possible where the armature turns are all concentrated between adjacent core teeth.

fr'[he windings in which current is generated for lighting purposes are 'divided into two groups, namely, the group of windings in an externally regulated circuit and a group of windings in an externally unregulated circuit. The first group of windings comprises coils 231. 232, 233, 234, 235., 236, 237, and 238, which are preferably wound upon a form and placed around the pole teeth 41. 42, 43, 44, 45, 46, 47 Vand 48,-respectively. These windings are fall connected in series and the connections between adjacent windings are such that at any instant the sign of the electromotive forces produced by the windings are the same so that the electromotive forces produced b the windin are cumulative in effect. The ends of t e group of windings 231 to 238, inclusive, are connected with terminals 239 and 24.-() supported by plate 51 but insulated therefrom. 'lhe center ot this group of windings indicated by dot 241 in Figs. 1 and 2, is connected with terminal 242.

The group of windings providing current for the externally unregulated lighting circuit includes two coils 243 and 244 surrounding the pole teeth 41 and 45 respectively. These windings are connected together 1n series and so that the electromotive produced by the separate windings will be accumulative in etl'ect. One end of the group of the windings 243 and 244 is connected with the terminal 242 and the other end with terminal 245 also supported b the plate 51. Terminal 242 is connected wit 1 the center of the windinggroup 231 to 238.

The following dimensions ot' pole face windings are given by way ot example: findings 232, 233, 234, 236, 237, 238 each 40 turns of No. 17 wire. findings 231, 235 each 30 turns of No. 17 wire. Windings 243, 244 each 150 turns of No. 27 Wire.

A wiring diagram showing an embodiment of the present invention is shown in F ig. 2. The ignition circuit includes thc windings 221 and 222 which are grounded through shaft 76 and grounding brush 261, 100 and are connected by brush 160 with the circuit hreaker which includes contacts 148 and 146. lontact 146 is connected by conductor 146 with contact 145 coo )erating with contact 147 which is grounded as indicated at 106 147 A condenser 250 is in parallel with breaker points 146 and148 and condenser 251 -is in parallel with breaker points 145 and 147. As shown in Fig. 2 the conductor 140 is connected by wine 17() with terminal 110 171 which fin turn is connected with ignition coil 252 having a primary 253 grounded at and having a secondary 255 grounded through the primary coil and connected with the center contact 194 of the distributor 115 head. From this center terminal 194. sparking impulses are distributed through the rotor contact 185 to the various terminals 192 connected with spark plugs indicated at 256. l

In Fig'. 2. the ignition switch 26() includes a ,sw-itch lever 261. carrying contacts 262 and 263 which are insulated from one another. Contact 263 is connected Vwith the pivot point of the lever 61 which is grounded 125 at 264, and contact 263 is arranged to engage stationary contacts .265, 266, or 2.67. Contact 262 is `arranged to connect two stationary contacts 268and 269. Contacts 269 and 265 are joined by wire 270; Contact 268 130 is joined with magneto terminal 239 by wire 27.1 stationary contact 265 is connected with brush 160; contact 266 is connected by wire 272 with magneto termiinl 242; and contact; 267 is connected by wire 273 with magneto terminal 24.0.

The externally regulated lighting circuit includes the group ot pole face windings 231 to 238, inclusive, having terminals at 239, and 240. The terminal 239 is connected by wire 280 witlra regulating transformer primary 281 which is connected with a switch blade 282 adapted to engage with contact 283 or to connect contactsy 28e and 285. Terminal 240 is connected by wire 286 with regulating transformer primary 287 which is connected with a switch blade 288 adapted to engage contact 289 or 290. Contacts 283 and 285 are connected with an electric lamp 291 grounded at 292 and contacts 289 and 290 are connected with an electric lamp 293 grounded at 291i. Contacts 281i and 289 are connected together through a dimmer resistance The externally regulating circuit includes regulatiligc transiiormer sccondary windings 296 and 297 connected together in series with a condenser 29S. Preferably the windings 296 and 297 are grouped together on one leg of a magnetic circuit while the windings 281 and 287 are mounted upon Yanother portion of the saine magnetic circuit.

In 2 the lever 261 is shown in run position, but `to start the engine this lever 261 is moved into the start position so that the contact 262 will engage contacts 268 and 269 and the contact. 263 will engage the contact 267. The pole tace windings are now connected up in parallel with the magneto armature windings so as to assist in produc` ing a. sparking impulse su'liicient for engine ignition even when the engine is cranked by hand and the magneto secondary rotates at a relatively slow speed. `Thepole face wind ings areconnected up in the 'following manner with the brush 160; ground 264, switch contact 263, contact 267, terminal 240` windings 238 to 231, terminal, 239, wire 271, contacts 266, 262. 269, wire 270, contact 265 which is connected toy the brush 160 The current wave oit the pole face windings includes a series olf peaks alternating above and below the zero line. In the ma-r chine disclosed, duringl a revolution oi" the armature. there will `be twelve positive peaks alternating with twelve negative peaks, and the peaks will extend approximately the same distance trom the zero line.

The current wave ot the arn'iature, when short-circuited also includes a series of peaks extending alternately above and below a certain mean line. This mean `line is not the zero current line but approximates a sine curve making a complete wave each revolution of the armature. During each revolution of the armature oil' the machine disclosed there will be twelve peaks in the armature current above this mean line alternating with twelve peaks below the mean line. Once a revolution there is a peak extending` above the mean line which has a positive value greater than any other ot the positive peaks in the armature shortcircuit current wave, and it happens that this peak occurs substantially in phase with one ot the positive peaks ot the pole lrace winding current wave.

This coincidence of these particular current wave peaks is taken advantage ot in providing rignition cuirrentduring slow cranking of the engine. When the pole tace windings are connected in parallel with the armature windings in the manner stated, these two peaks are added to produce a peak every'armature revolution having a current value sufficient for ignition purposes at engine speeds produced by hand cranking. After the engine has become self-operative these maximum positive peaks of the armature current will alone be suiiieientl'or ignition purposes, and halt way between maxi mum positive peaks, there will be a maximum negative peak ysufficient for engine sparking. Therefore during each armature revolution during normal engine running there will be at least two instants when sulicient current is available for ignition.

`The arrangement of the ignition timer de-r pends on the ratio of magneto speed to engine speed. Where the dimensions ot the magneto are limited by space requirements, it may be necessary to operate the magneto at speeds great-er than engine speed in order to provide sufficient output for lighting pur-- poses. Although the magneto disclosed constructed to be operated at twice engine speed, the invention is not thus limited, but includes magnetos operable at other speeds such as oneV operating at engine speed. y

After the engine becomes self-operative the speed of the magneto will be such that the value ot the maximum positive `peak et the armature current wave will be sufficient ior ignition purposes. The wave `form for the pole face winding current will remain substantially thesame but the height of the peaks will tend to increase with increasing engine speed. Regulation of the lighting circuit however is efected in a manner to be f described. f

It, 'for example, the magneto be one constructed to operate at engine speed, and :tire a tourl cylinder engine, then the timer would be constructed to use the maximum positive peak and maximum negative peak every magneto revolution so that there would be four sparking impulses for each engine cycle for a tour-stroke-cycle engine. The timer cam would have the-flats located 180o apartand the breaker levers arranged so that twice a revolution both breakers would be closed at the same time. The levers would need to be constructed so that the grounded breaker controlling contacts 145, 147 opens slightly ahead of the other one in order to preserve the feature of maintaining the arumtureopen circuited as long as possible.

It is to be undeistood also that the present invention is not limited to ignition for a four cylinder four-stroke-cycle engine, butcan be applied to ignition for other multicylinder engines with such changes as will be apparent to those skilled in the art.

The dividing of the armature windings into two coils separated by core teeth results .in the.maximum positive armature current peaks being of such ashapc that for a relatively great proportion of Vthe duration of the wave peak, the peak is at values greater than the minimum required for 'ignition purposes. Therefore, although the breaker lever rubbing block'may wear into a different shape and tend to change the ignition timing, a certain variation is permissible because of the character of the wave peak just described.

The advancing and reta rding of the ignition does not change the relation of the timer to the ignition current wave peak since the connecting' linkage, not shown, shifts both the armature core and the timer cam. Therefore ignition intensity for a given speed remains constant lregardless of advance and retard.

After the engine has become self-operative the lever 261 is moved into runposition slmwn in Fig. 2. Assuming the levers 282 and 288 to be in bright position, designated BRT in Fig. 2, the externally regulated lighting circuit will be as follows: Starting with terminal 239 this circuit includes windings 231 to 238 inclusive, terminal 240, wire 286, transformer primary 287, switch 288, contact 290, head lamp 293, ground 294 to ground 292, head lamp 291, contact 283, contact 282, transformer primary 281 and wire 280 back to terminal 239. As the speed of the engine driving the magneto varies, the frequency of the current in this circuit will vary and the potential of this circuit would vary were it not for the resonance circuit including the transformer secondaries 296, 297 and the capacity 298. Below a certain engine speed, the operation of this circuit is to increase the voltage in the primary circuit but above this engine speed the tendency is to oppose any increase inthe voltage of the primary circuit. The result is that within a relatively wide range of engine speed variation, the voltage of the regulated lighting circuit described will remain substantially constant.

The following dimensions of coils `and condenser in the regulating circuit are given by way of example for a 6 volt circuit: Condenser 298 .500 microfarads, windings 281, 287 turns, windings 296, 297, total 2280 turns. All these dimensions vary within a reasonable range. The transformation ratio should be such that the current into the condenser will have the desired regulating effect above a certain magneto speed. If the transformation ratio is relatively low, then the capacity of the condenser must be relatively large, and, if this ratio is relatively high then the condenser must be constructed to withstand a relatively high voltage. What is the best combination from a. practical point of view will be apparent to those skilled in the art.

In case it is desired to dim the head lamps 291 or 293, either of the switches 282 or 288 is moved to the dim position, thereby inserting a resistance 295 in parallel with the two head lamps 291 and 293 with the result that the current delivered to these lamps is considerably reduced. In case one of the head lamps burns out` for example, the lamp 291, current will still be supplied to the lamp 293 through the following circuit: starting with ground 264, the circuit continues through contact 263, contact 266, wire 272, center terminal 242 windings 235 to 238, wire 286, transformerv primary 287, switch 288, contact 290, lamp 293 and ground 294 back to ground 264. Obviously since only one lamp is burning, there should be impressed upon this lamp only half the voltage which was impressed upon both the lamps 291 and 293 when connected in series. This is brought about since the windings 231 and 234 are inoperative to impress any potential upon the head lamp 293 after the head lamp 291 has burned out.

By closing the switch 315'with contact 316, the tail lamp 317 will burn, this tail lamp or externally unregulated light circuit being as follows: starting with ground 264 the circuit continues through contact 263, contact 266, wire 272, terminal 242, pole tooth windings 243, and 244, terminal 245, switch 315, contact 316, lamp 317, and ground 318 back to ground 244. While it may be desirable to regulate the tail lamp circuit, this has not been found to be necessary as this lamp is relatively low in candle power compared -with the head lamps.

To stop the engine, lever 261 is moved to stop position wherein the contact 263 engages contact 265 and the armature is short circuited.

The following advantages are present in this invention:

The generating unit provides current for lighting and current for ignition by the use of but one magnetic circuit and source of magnetism and one set of rotating windings. The magnets and armature cooperate lili! to provide ignition current, and pole face windings and the armature teeth or inductor poles cooperate as a high frequency A. C. generator Ato produce lighting current.

- In high frequency A. C. machines, it has been the practice to employ more st-ator slots than inductor poles, but such practice could not be employed in the present invention as the winding space would be insufficient. Also the available flux is limited where permanent magnets are used. In the large inductor alternator more fiux is available in proportion than in a small magneto because the field is separately excitedvand the iron is worked much harder. But in a magneto there are limitations as to the number of permanent magnets used on account of expense, weight and space available. I-Ience it is necessary to use more windings in proporf tion inorder to secure the desired output. If the usual inductor alternator practice of two stator teeth 'to one rotor `tooth be followed in ai small unit using permanent magnets the stator winding space will be insufficient. This difficulty has been overcome by omitting two out of every three stator teeth and increasing the cross section of the remaining teeth in order toy carry the finir. For example, starting with a construction involving 24 stator teeth and 12 rotor teeth, the number of stator teeth was reduced to 8 While preserving the same frequency for a given engine speed, and resulting in three times the available Winding space and approximately three times the output. This 2 to 8 ratio and the use of 12 rotor teeth has been found to give a frequency which is satisfactory from a lighting viewpoint and also for inherent eX` ternal regulation by means of a resonant circuit. A two to five ratio could be employed, such as Ll stator teeth to l() rotor teeth, but the frequency and hence the potential might be too low unless machine be operated at a higher speed. An 8 to 20 combination could be used provided the diameter of the armature is large enough to permit a rotor tooth of sufficient width to carry the iuX, it being borne in mind that the rotor tooth spaces must be great enoughpto prevent fiuX leakage and the consequential inefficiency of the machine. Either combination of 8 to 12 or 8 to 20 or 4; to 10 (the 2 to 8 ratio or the 2 to 5 ratio) is possible depending on operating conditions and size. It is to be remembered that the number of rotor teeth should be divisible by half of the number of stator teeth so that the pulsations of flux from the permanent magnets will be minimized. In the combinations of stator and rot-or teeth mentioned, it is apparent that there will be a lineup of rotor teeth with stator teeth for every angular movement of the rotor through angle of 360 degrees divided by twice the number of rotor teeth and the number of line-ups will remain constant. Since the line-ups come at regular intervals and are constant in number, these other advantages just mentioned Will result. Of course it is necessary to minimize "ilux pulsations in the magnet in order that the magnetism may be retained for a long period. I

By employing a double slotted armature instead of a single winding slot as in the ordinary shuttle armature the form of ignition current Wave is improved and the inductance per turn of armature Winding is reduced, also improving ignition.

Regulation of the lighting circuit has been accomplished Without the use 0f moving parts. The resonant circuit operates below a certain frequency to cause a leading current to flow in the pole face Windings` thus tending to increase the output of the machine.` At slightly higher frequencies the resonant leading current decreases and the effect upon the main windings decreases and at still higher frequencies the coils of the controlling circuit react to hold down the current in the external circuit to the'desired value.

Satisfactory ignition is provided throughout the entire range of driving speeds and even at low speeds prevailing during cranking the .engine by hand. without the use of an impulse coupling. This is accomplished by using the pole face windings, to assist the armature windings during starting.

The armature circuit is established practically only as needed for ignition purposes by means of the double breaker mechanism, so that armature reaction causing a demagnetization of the permanent magnets is re duced to the minimum.

The advancing and retarding` of the spark does not affect the quality of the ignition since the relation of the timer to the armature remains unchanged. The. speed increasing gearing between the engine and magneto shaft includes a shifting member for changing the timing of the magneto shaft with respect to the engine.

Then one of the head lamps burns out the lother head lamp will not burn with appre ciably greater' intensity than before, since the central connection in the pole face windings provides an individual circuit for the remaining lamp.

IVhile the head lamp circuit is called an externally regulated circuit, and the tail lamp circuit an externally unregulated circuit, it is to be understood that as to both circuits the magneto pole face windings have some inherent regulation. In the case of the windings supplying current for the tail lamp. the number of turns per pole tooth is great enough and the inductance high enough for inherent regulation. Therefore an external regulatorhas not been found necessary. As the size of the machine is limited it is not of coils, each device. is connected in series with a portion of the group of coils.

Vhile the forni of mechanism herein shown and described constitutes a preferred form of embodiment of the invention, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

l'Vhat I claim is as follows :A

l. In a magneto, the combination with a pernianent magnet fiel-d including toothed poles, and pole face windings surrounding the pole teeth; of a toothed armature core carrying armature windings, the core being notched toy provide equally spaced core teeth of equal width at the periphery, certain diametrically opposite groups of notches being relatively deep to provide Winding space for groups of armature windin s.

2. In a magneto, the com ination with a permanent magnet field including toothed poles, and pol'e face windings surrounding the pole teeth; of' a toothed armature core carrying armature windings, the core being notched to rovi-de equally spaced core teeth of equal wie th at the periphery, two adjacent noteics and two other' adjacent notches diametrical'ly opposite the 'rst mentioned notches being relatively deep to provide winding space for two groups of armature windings` In a magneto, the combination with a permanent magnetfield including toothed poles, of a plurality of groups of pole face coils, one group including as many coils 'as there are pole teeth and each surrounding a pole tooth, and another group of two coils each surrounding diametricailly posite pole teeth, the groups being substantially of the same potential but of different current capacity; and a toothed inductor rotor.

In testimony whereof I hereto ax my signature. n

JOHN H. HUNT.

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