US2262323A - Dynamoelectric machine - Google Patents

Description

Nov. 11, 1941. R. M. HEINTZ 2,262,323

' DYNAMOELECTRIC MACHINE Original Filed Nov. 5, 1938 2 Sheets-Sheet 2 AC LOAD F0405 M 776/)772 2M Patented Nov. 11, 1941 DYNAMOELECTRIC MACHINE Ralph M. Heintz, Palo Alto, Calif., assignor to Bendix Aviation Corporation,'South Bend, Ind., a corporation of Delaware Original application November 5,1938, Serial No. 239,091. Divided and this application August 21, 1940, Serial No. 353,560

3 Claims. 01. 171-252) This invention relates to' a combined starting and generating unit for use with internal combustion engines and capable of functioning, first, to start an internal combustion engine by application of torque thereto, and thereafter to convert the power developed in the engine into electrical energy available for radio transmission and other purposes requiring alternating current of high, low or intermediate frequency and/or potential. 7

An object of the invention is the provision of a dynamo-electric machine of novel construction permitting most advantageous use thereof for multiple purposes including, for example, the initial turning over, or cranking, of an internal combustion engine, and the subsequent generation of alternating current of high frequency, by conversion of mechanical energy transmitted thereto by way of said internal combustion engine.

Among the novel features of the machine herein disclosed there is included that of a commutator adapted to be engaged by rotatable brushes, for transmission of current between the former and the latter at relatively low rotor speeds, the invention further including the concept of a novel method of manufacturing said commutator, and a novel mounting and mode of operation for said rotatable brushes, as a result whereof the said brushes remain in engagement with the commutator to feed low voltage direct current to the stator windings during the duration of the engine cranking, operation, but move out of engagement and thereby discontinue such direct current flow as soon as the engine crank-shaft accelerates sufllciently to render further cranking unnecessary. Thereafter the stator serves solely as a supply of alternating current for outside points of distribution and consumption.

These and other objects and features of the invention will become apparent upon consideration of the following detailed description, and upon reference to the accompanying drawings illustrating the preferred embodiment of the invention. It is to be understood, however, that the drawings are illustrative only, and that the claims at the conclusion of the specification rather than the drawings, measure the scope of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views:

Fig. 1 is a longitudinal sectional view of a housing enclosing a machine embodying the invencompleted commutator.

tion, some of the enclosed parts being shown in section and some in elevation;

Fig. 2 is a diagram of the electrical connections for the machine of Fig. 1, and including a schematic representation of the speed responsive brush shifting means;

Fig. 3 is a view showing part of the commutator and one of the brushes disengaged therefrom (the engaged position being shown in Fig. 1);

Fig. 4 is a view of the metallic annulus that eventually becomes the commutator, as said annulus appears at an intermediate stage of manufacture;

Fig. 5 is a view of one of the insulating segments as it appears at the time of insertion into the metallic annulus of Fig. 4; and Y Fig. 6 is a transverse view of a section of the In the drawings reference character Ill designates a source of direct current (battery, for ex ample) and ii designates an alternating current receiving apparatus, such as radio transmitters, transformers, receivers, rectifiers, motors, etc., to which alternating current of high frequency may be supplied upon rotation, at-

relatively high speed, of an engine driven dynamo-electric machine whose rotor shaft i2 is shown as direct-connected to the crank-shaft i3 of an internal combustion engine (not fully shown). Engines of a character adapted to drive high frequency alternators are commonly employed on aircraft as a power supply means for operation of electrical equipment ,of which the units above enumerated may be taken as examples.

Such aircraft installations ordinarily include a battery such as that shown at in, charged sufficiently to energize the rotor and stator windings i6 and II, respectively, for use as a starting motor in the initial cranking and acceleration of the engine crank-shaft i3 to self-sustaining speed. Attainment of this normal running speed produces a centrifugal force of sufficient magnitude to raise rotor brushesllB, i9, 20, and 2i out of contact with commutator 23, whereupon the passage of current therebetween is interrupted. Thereafter stator windings I! serve solely as a source of alternating current, to be fed to the A. C. load i i by way of multi-phase conductors 24, 25, and 26.

In order that the machine may function as a direct current shunt motor for engine starting purposes, the rotor windings l6, located in step formation about rotor poles 3i, are connected at segments in situ, and from a their ends to brushes l8, I9, 20 and 2|, two of said brushes being in turn connected with collector ring 33 of positive polarity while the other two connect with collector ring 34 of negative polarity. Brushes 36, mounted in brush assemblies secured to the housing 4| by suitable means (of which that shown at 42 in Fig. 1 is an example) engage collector ring 34, while brushes 31, correspondingly mounted, engage collector ring 33. Conductors 43 and complete the connections from battery I0 to the stationary brush sets, while aconductor 28 connects each of the rotating brushes l8 to 2| with its corresponding collector ring.

As hereinabove indicated, the stationary commutator assembly is made in a novel manner, including (as a step in the process) the union of two annular metallic members 23 and 21, of which the former eventually becomes the segmented commutator, per se, while the latter is the supporting core that is eventually secured to the housing by suitable means 29. A molding compound 30 is the uniting element for parts 23 and 21, the latter being provided, if desired, with compound receiving holes 41 to insure more complete union therebetween.

A preceding step in the process is to cut slots 48 (Fig. 4) extending part-way through the metallic annulus 23, and spaced around the inner periphery thereof, in accordance with a predetermined formula, to provide pockets for receipt of segments 50 (Fig. 5) of mica or equivalent insulating material. The annulus 23 (after union with core 21 inthe manner above described) is machined down to finished shape, (Fig. 6) in which process all metal located beyond (and, if desired, additional material within) the radially outermost part of the mica segments 50 (see line 5|, Fig. 4) is removed, thus exposing the mica edges to view, at the outer side, and likewise resulting in the creation of a corresponding number of spaced conducting segments to constitute the commutator. As shown each segment thereof has a final shape as indicated at 52 in Fig. 6, and each of said segments has now become electrically separate from every other metallic part.

By this process of fashioning the commutator single piece of metal, there are eliminated all problems of aciii curate fitting and positioning of segments individually; each segment is automatically caused to appear in its proper relative position, since all remain unshiftable from start to finish of the process.

In order to offset any tangling tendency, as between the conductors I5 and the rotating brush assemblies, I provide radially extending ribs forming pockets 49 in the housing 4|, along which pockets the conductors l5 are run, and to which they may be secured, thus preventing their dropping inwardly into contact with the brush assemblies l8 to 2|.

This application is related to my earlier filed applications Nos. 239,091 filed November 5, 1938. and 276,197 filed May 27, 1939; the former having issued as Patent No. 2,184,236 on December 19, 1939, and the latter having issued as Patent No. 2,221,707 on November 12, 1940.

What is claimed is:

1. In a dynamo-electric machine having a radially ribbed casing, the combination with said casing of a commutator secured thereto, and means including said commutator for feeding current to said machine, said current feeding means also including commutator connections running along the casing and separated, one from the other, by the radial ribs of said casing, said ribs constituting means for accommodating said commutator connections.

2. In a dynamo-electric machine, in combination, a housing, current feeding means including a commutator and commutator connections, and means projecting inwardly from the inner surface of said housing, in proximity to said commutator, for accommodating said commutator connections.

3. In a dynamo-electric machine, in combination, a housing, current feeding means including a commutator and commutator connections, and means projecting inwardly from the inner surface of said housing, in proximity to said commutator, for accommodating said commutator connections, said inwardly projecting means comprising rib-like sections spaced radially about that portion of the housing which is nearest to said commutator.

RALPH M. HEINTZ.

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