Brushless alternator

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could also be divided into more than two parts as like

BRUSHLESS ALTERNATOR wise shown in that copending application. FIELD OF THE INVENTION The major tooth portions bracketed by the pole pieces of the rotor advantageously include each a radi

The present invention relates to an electrical machine, ally extending web surrounded by the associated arma more particularly an alternator of the brushless type. ture winding and a pair of wings extending laterally BACKGROUND OF THE INVENTION from this web adjacent the pole pieces, a preferred wing span being about twice the width of the web as mea

Conventional alternators, in which slip rings and sured in the axial direction. The spacing of the teeth contact brushes are used to deliver the generated output 10 with reference to that of the pole pieces and the electri voltage from a rotating armature winding to a load or to cal interconnection of the armature depends, of course, energize an excitation coil of a rotating electromagnet, on the desired type of output voltage (e.g. single-phase are subject to various disadvantages such as noise, sensi or three-phase) as is well known per se. tivity to dust and oxidizing atmospheric conditions, and Although reference will be made only to an alternator sparking which makes such machines unsuitable for use 15 in the following description, it will be apparent that an in explosive atmospheres. The same drawbacks exist in analogous construction may be adopted for an electric electric motors provided with such slip rings and motor.

brushes.

Brief description of the drawing

OBJECTS OF THE INVENTION 20 The above and other features of my invention will The general object of my present invention, there now be described in detail in reference to the accompa fore, is to provide an improved electrical machine of the nying drawing in which:

brushless type which is of simple construction and obvi FIG. 1 is an elevational view, partly in axial section, ates the aforestated disadvantages. of an alternator embodying my invention; A more particular object is to provide an alternator, 25 FIG. 2 is a fragmentary side view of a stator, with of either the single-phase or the three-phase type, hav windings removed, forming part of the machine shown ing a higher power output than conventional alternators in FIG. 1;

of comparable weight and dimensions. FIG. 3 is a fragmentary axonometric view of a stator SUMMARY OF THE INVENTION tooth and a rotor pole piece included in the alternator of

An electrical machine according to my present inven FIG. 4 is a fragmentary developed view of the rotor tion comprises a magnetically permeable rotor on a and the stator of the alternator of FIG. 1; shaft which is journaled in a housing with a generally FIG. 5 is a view similar to FIG. 3, showing a modified cylindrical peripheral wall centered on the shaft axis, tooth;

this rotor including a magnetized central hub whose 35 FIG. 6 is a view similar to FIG. 1, illustrating another extremities are rigid with two axially spaced annular embodiment of my invention; arrays of pole pieces; the pole pieces of one array are FIG. 7 is a fragmentary side view of a stator forming peripherally offset from the oppositely polarized pole part of the alternator of FIG. 6; and pieces or the other array. A magnetically permeable FIG. 8 is a view similar to FIG. 7, illustrating a modi stator rigid with the housing includes a set of peripher fication.

ally spaced teeth which project radially inwardly from the peripheral housing wall between the arrays of pole SPECIFICDESCRIPTION pieces and carry armature windings for electromagnetic In FIG. 1 I have shown an alternator, i.e. an electrical interaction with these pole pieces, the teeth being me machine for the generation of an alternating voltage, chanically and magnetically interconnected by an annu 45 comprising a substantially cylindrical housing split into lar yoke centered on the housing axis. Unless the hub is two generally mirror-symmetrical halves 10a, 10b formed in whole or in part by a permanent magnet, its formed with venting apertures 11a, 11b. Journaled in magnetization is maintained by a stationary excitation coil concentrically surrounding it with intervening this rotor housing, by means of ball bearings 12a, 12b, is a shaft 13 with a threaded end adapted to receive a spacing, that coil being supported on the stator. 50 nonillustrated pulley driven from an external prime In an advantageous embodiment, the housing and the mover. The shaft may also carry a fan for blowing rotor are split into two halves along a transverse mid cooling air through the apertures 11a and 11b as illus plane which bisects an annular gap formed between the two arrays of pole pieces, the stator teeth being held in trated in my above-identified copending application. Shaft 13 carries a rotor split into two substantially position by extensions thereof clamped between the two 55 identical but relatively offset halves, comprising a hub housing halves. The two sets of pole pieces extend from 7a, 7b whose extremities are integral with radially ex opposite sides toward this midplane so as to form an tending arms 14a, 14b of generally L-shaped pole pieces annular space between themselves and the hub, this 2a, 2b having axially disposed cheeks. 15a, 15b which space preferably accommodating not only the excita terminate short of a transverse midplane P, as do the tion coil but also major portions of the teeth. This nest two housing ing of major tooth portions of the stator within the rotor between thesehalves 10a and 10b. Seated within a gap 16 housing halves, and fastened thereto by affords a particularly compact construction. An alterna soldering or other suitable means, are radially out tive arrangement, in which only the excitation coil lies wardly extending stems 1 of a set of generally T-shaped in that space and is held by extensions of the stator teeth teeth 17 which pass between the two peripheral arrays positioned for the most part outside the rotor, is de 65 pole pieces 2a and 2b into an annular space 29 defined scribed and illustrated in my copending application Ser. of by the pole pieces and the hub, the cross-bar of the "T" No. 624,934 of even date whose disclosure is incorpo having the shape of a web 3 of substantially greater rated by reference in the present application. The hub width than the stem 1 as measured in the direction of a 7 central axis A. Laterally extending wings 18a, 18b inte In FIG. 6 I have illustrated, in a machine otherwise gral with web 3 have a span substantially twice the axial similar to that of FIG. 1, a modified rotor and stator. width of the web. The outer edges of these wings pass The rotor teeth 17, integral with a yoke 6', are again close to the inner edges of pole pieces 2a and 2b, paral generally T-shaped and are each divided into a lami leling the axially extending faces 19a, 19b of their nated central section 1", forming the stem of the "T', cheeks 15a, 15b which are either flat or cylindrically and a pair of laminated lateral sections 3a' and 3b flank curved about axis A and which are advantageously ing the section 1'. As shown in FIG. 7, the lateral lami bounded by a parabolical outline, as seen in FIGS. 3 and nations are identical with the central laminations except 4, designed to induce a substantially sinusoidal voltage 10 for the radially outward stem-forming extensions of the in armature windings 4 surrounding the webs 3 of the latter which are held between the housing halves 10a teeth 17. The inner edges of these webs are fitted into and 10bperpendicular in gap 16. These laminations, all of which lie in axially extending slots of a pair of axially spaced rings planes together by to the housing axis, are again held spot-welding or possibly by riveting. The 6a, 6b forming a stator yoke, the teeth 17 also having radially inward extensions 8 sandwiched between these 15 three parts adjoining one another rotor pole pieces 2a", 2b' of the modified are divided into angles of approxi rings (see also FIG. 2). The yoke 6a, 6b supports an mately 45°. The arrangement shown in FIG. 6 is as excitation coil 5 which spacedly surrounds the hub 7a, compact as that of FIG. 1 but the effective confronting 7b and is conventionally energized via a nonillustrated rectifier from the output voltage of windings 4; these surface areas of the teeth and the pole pieces are some what reduced.

windings are bracketed by the yoke and the wings 18a, 20 As will be apparent from FIG. 4, the peripheral pitch 18b, Leads (not shown) from the stationary windings 4 of teeth 17 is one-third that of the relatively staggered and 5 pass outwardly through the gap 16 to a nonillus pole pieces 2a and 2b. This is consistent with a three trated load and the aforementioned rectifier.

All the rotor and stator parts 2a, 2b, 7a, 7b, 6a, 6b and tion ofalternator phase and also applies to the stator construc

FIG. 7. In FIG. 8 I have shown a similar stator 17 are made of magnetically permeable material 25 whereby the flux induced by the winding 5 in hub 7a, 7b construction with teeth 17" having radial extensions 1" can readily pass through, say, pole pieces 2a into the integral of thoseyoke and an annular 6' whose laminations are again of the teeth, the pitch of these teeth wings 18a of teeth 17 while moving past them, thence being three times that of the teeth 17" in FIG. 7 and through the webs 3 of these teeth and the yoke 6a, 6b corresponding therefore to that of the pole pieces. With into the webs of other teeth whose wings 18b then con 30 this modification, a single-phase output voltage is ob front pole pieces 2b, and back to the hub in a magnetic tained.

circuit with narrow air gaps of large width resulting in I claim:

a low flux density. 1. In an electrical machine comprising two relatively The stator parts are laminated as shown, with the rotatable members centered on a common axis, one of laminations of teeth 17 lying in planes parallel to axis A 35 said members having a magnetically permeable body and the laminations of yoke 6a, 6b extending perpendic which includes a magnetized hub and two axially ularly thereto. The laminations of the teeth are inter spaced annular arrays of pole pieces rigid with opposite connected by spot welding, preferably under a protec extremities of said hub, the other of said members in tive argon atmosphere, as indicated at 22; similar welds, cluding a set of peripherally spaced teeth intercon not shown, serve to hold the laminations of the yoke 40 nected by an annular yoke and positioned for magnetic together. Riveting could be used instead of spot-weld interaction with said pole pieces, said yoke and said 1ng. teeth being magnetically permeable, and armature Particularly in larger machines, it may be advanta windings surrounding said teeth, the pole pieces of one geous to insert insulating layers between the teeth and array having substantially axially extending faces on the yoke to provent the flow of eddy currents. 45 one side of a transverse midplane and being peripherally In assembling the alternator of FIG. 1, rotor half 2b, offset from the oppositely polarized pole pieces of the 7b is press-fitted onto shaft 13 with housing half 10a other array, the latter having substantially axially ex separated from half 10b. Next, the stator is secured to tending faces on the other side of said midplane, housing half 10b together with coils 4 and 5 whereupon the improvement wherein said hub and said pole rotor half 7a, 2a is positioned on shaft 13 with insertion 50 pieces together define an annular space surrounding of a spacer ring 23 between the rotor and bearing 12a. said hub, said annular space being bounded in part Screws diagrammatically illustrated at 24 hold the rotor by said axially extending faces, said teeth having together as housing half 10a is emplaced and secured to major portions interconnected by said yoke in said the stator. An end disk 25 is bolted onto housing half annular space and surrounded by said armature 10a as indicated at 26 to hold the bearing 12a in place. 55 windings.

As illustrated in FIGS. 2 - 4, the teeth 17 may be 2. The improvement defined in claim 1 wherein said provided with peripherally extending ledges 27 de one of said members is a rotor and said other of said signed to enlarge their surfaces which confront the members is a stator including a stationary housing hav cheeks 15a, 15b of pole pieces 2a, 2b, FIG. 4 also shows ing a generally cylindrical wall centered on said rotor, that the arrays of pole pieces 2a and 2 b are peripherally said teeth being provided with stems projecting radially offset from each other. inwardly from said wall into said annular space. FIG. 5 shows a slightly modified tooth whose wings 3. The improvement defined in claim 2 wherein said 18a, 18b lack the ledges 27 but are chamfered at their major portions include each a radially extending web ends as indicated at 28a, 28b. This measure also in substantially wider than said stems and a pair of wings creases, albeit to a smaller extent, the surface area con 65 extending laterally from said web adjacent said pole fronting the pole pieces as compared with the average pieces.

width of the tooth. Naturally, the two measures shown 4. The improvement defined in claim 3 wherein said in FIGS. 3 and 5 can be combined. armature windings surround the webs of said teeth, said 8 wings having a span in axial direction approximately lateral rings respectively integral with said central and twice the axial width of said web. lateral sections, said armature windings embracing all 5. The improvement defined in claim 3 wherein said said sections.

yoke comprises two axially spaced rings with axially 8. The improvement defined in claim 7 wherein said notched outer peripheries partly receiving the webs of 5 sections and said rings consist of laminations transverse said teeth, said webs being provided with inward pro to said axis.

jections disposed between said rings. 9. The improvement defined in claim 2 wherein said 6. The improvement defined in claim 5 wherein said housing and said rotor are split into two halves along teeth are composed of laminations parallel to said axis, said transverse midplane, said stems being held between said rings consisting of laminations transverse to said 10 the halves of said housing.

2XS. 10. The improvement defined in claim 2, further com 7. The improvement defined in claim 2 wherein said prising an extension coil centered on said axis and spac teeth are divided into a central section extending from edly surrounding said hub for maintaining the magneti said annular space to said wall and a pair of lateral zation thereof, said coil being supported in said annular sections entirely within said annular space flanking said 15 space by said yoke. is it is is k central section, said yoke being divided into central and