CA1045358A - Welding leads to commutator bars - Google Patents

Abstract

WELDING LEADS TO COMMUTATOR BARS
ABSTRACT OF THE DISCLOSURE
An improved method for electrically and mechan-ically bonding or otherwise uniting the armature windings of a dynamoelectric machine armature to the commutator of that armature is disclosed. After the armature wires have been aligned within the commutator riser slots, an ultrasonic welding tip is applied to the radially outer surface of the outermost wire within the riser slot and welding energy is transferred from the welding tip to the wire within the slot to weld those wires within the slot. The welding tip and armature assembly are then radially separated to remove the welding tip from the slot and the armature is indexed to place a subsequent riser slot, and its armature windings, in alignment with the welding tip for a further welding step.
Upon completion of sufficient indexing and welding steps to weld each pair of armature winding wires within their appropriate commutator riser slots the armature is withdrawn from the welding fixture and subsequent metal removal and finishing operations are applied thereto to provide a completed armature assembly.

Description

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, The present invention is directed to the field of dynamoelectric machines in general and particularly to that . portion of the above-noted field which is concerned with the manufacture of armatures or rotors for such machines. More paFticularly still, the present invention is dlrected to that , ~ ' '': ' , , . .

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portion of the above-noted field which is concerned with the method of attaching or otherwise suitably bonding the wires comprising the armature windings to the appropriate commutator segments of a brush-type dynamoelectric machine commutator.
More particularly still, the present invention is directed to that portion of the above-noted field which is primarily con-cerned with electrically and mechanically bonding the wires comprising the armature windings within slots or grooves provided therefor in the riser section of each commutator segment o~ a commutator having a unitary molded phenolic or plastic dielectric central portion.
Dynamoelectric machine armatures for use in dynamo-electric machines which include electrical brushes to transfer electrical energy to the machine windings are normally provid-ed with a plurality of ferromagnetic laminations mounted on a -rotary shaft, for rotation therewith, and a plurality of electrically conductive wi~es, forming the machine windings, passed through suitably provided grooves or bores extending in alignment through the plurality of laminations. Each end of each conductor of the windings is anchored to an electrical commutator. Due to the large amounts of eleictrical current flow through the armature windings, large wire size is required.
For example, .128 inch diameter wire, is frequently required in automotive starter motor dynamoelectric machines. A dynamo- -electric machine is arranged so that current flowing through selected ones of the armature windings may produce an electro- -magnetic fleld which coacts with an electromagnetic field pro- `~
duced by the surrounding stator structure so that the armature windings will be propelled in a rotary direction, that is, about the

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1 axis of the armature shaft. Conversely, rotation o~ the 2 armature can be arranged to cooperate with the electromagnetic

3 ~ield produced by the stator winding so that an electrical

4 current is caused to flow through the armature windings. This current may then be extracted from the armature through the 6 use of the commutator so that the electrical generator is 7 provided. Structures as briefly outlined hereinabove are 8 notoriously well known. United States Letters Patent 9 3,026,432 "Dynamoelectric Machinet' issued in the name D. ~.
Baumhart and United States Letters Patent 3,028,514 "Dyna-11 moelectric Machine" issued in the names of R. W. Burby et al., 12 both assigned to the assignee of the present invention, 13 illustrate two forms of such dynamoelectric machines. Two 14 other well known forms of such a machine are the alternator and the aforenoted starter motor~ both of which are normally 16 associated with the internal combustion engine of an auto-17 motive vehicle.
18 The prior art teaches that the armature winding ` `
19 wires may be electrlcally and mechanically bonded to the individual segments of an electric commutator through the 21 use of a soldered ~oint. Recently, the dynamoelectric machine 22 armatures have been formed with commutators having an 23 lntegral riser section which has been slotted to receive 24 pairs of armature winding wires. The solder has been applied by rolling the armature through a solder bath such that the 26 depth of penetration within the solder bath approximately 27 matches the depth of the slotted riser sections. Earlier 28 ~orms of dynamoelectric machine armatures provided an up-29 standlng tang portion with the armature winding wires wrapped around this portion with an individual drop of solder applied ~L~453S~3 1 to this Joint to provide for electrical and mechanical bonding.
2 While soldering produces a generally satisfactory ~oint, the 3 lead of the solder and the copper of the commutator or 4 conductors forms a galvanic junction which is susceptible to corrosion. Corrosion may also occur as a result o~ solder 6 flux entrapped in the interstices of the solder ~oint. The 7 corrosion will tend to reduce both the electrical conductivity 8 and the mechanical strength. Furthermore, soldered junctions 9 are temperature limited and the advent o~ automotive exhaust emissions requirements has caused vehicle under-hood ~1 temperatures to rise reduclng the margin of temperature between 12 the solder melting temperature and the maximum predictable 13 operating temperature. Heretofore, the advantages of 14 soldering which include easy availability of equipment and technology and the ease o~ application of a soldering step 16 to an overall manufacturing process have outweighed the 17 dlsadvantages attendant upon soldering. Howev~r, elimination 18 o~ the soldered ~unction is now seen to be desireable.
19 In order to provide for manufacturing and assembly efficiency and to reduce costs through the use of automated 21 equipment, commutators for dynamoelectric machines have been 22 formed from unitary conductor bodies which have been provided 23 with a central plastic or phenolic section having good 24 dielectric capability. Through various machining operations applied to the commutator body, a commutator having the 26 central plastic or phenolic portions with a plurality of 27 strips of commutator material on the periphery thereof 28 separated by bands on the dielectric material has been formed.
29 United States Letters Patent 3,423,819 "Method o~ Forming 3 Relatively Straight Lengths of Metal into Elongated Members"

3~58 1 issued in the names of Donald W. Carlson et al. 3 and assigned 2 to the assignee of the present invention is concerned with 3 one method of forming the unitary metallic portion of the 4 commutator body, while United States Letters Patent 3,468,020 ~Method of Anchoring a Metallic Member to Plastic~ issued in 6 the names of Donald W. Carlson et al., and assigned to the 7 assignee of this invention is concerned ~ith a method by 8 which the metallic portlon of the commutator body may be 9 suitably altered to receive the plastic or phenolic central section and may therea~ter be operated upon to provide for a 11 plurality of commutator segments separated by strips of the 12 dielectric plastic or phenolic material. In order to take 13 advantage of the manufacturing efficiencies and cost reductions 14 associated with the methods embodied in these two patents, a special grade of copper material has been required for 16 formatlon o~ the metallic portion of the commutator body. This e ~ ~ o 17 special copper is available under the tr~d~ma~l~of "Oxygen-18 ~ree Copper". Recently, the cost of copper in general and of 19 this ~orm of copper in particular has greatly increased, serlously eroding the cost and efficiency benefits derived 21 by the methods o~ the two patents noted above.
22 Commutators ~or use in dynamoelectric machines 23 typically comprise a plurality of conductive segments 24 equidistantly arranged about the periphery of a dielectric body portion with the segments separated from each other by 26 dielectric material. The radially outer surfaces of the 27 segments and interspersed dielectric material generally 28 de~ine a cylinder. Each segment normally includes an upstanding 29 or radially directed riser portion. The riser portions are slotted to receive one free end of each of a selected pair of 31 armature windings in radially disposed relationship. The 1 armature windings are arranged in the appropriate armature 2 lamination passages so that the current path from one commu-3 tator segment to the other through the armature winding wlll 4 produce the desired electromagnetic field for coaction with the stator field. In manufacturing the armatures, the 6 armature laminations and commutator body (having a molded 7 dielectric central portion and a unitary conductive outer 8 shell) are attached to an armature shaft for rotation there-9 with. The commutator body outer shell normally has, at this point in the armature fabrication process, discontinuous 11 rlser portions with each portion separated from the ad~acent 12 riser portion by dielectric material and with each riser 13 portion slotted to receive the free ends of the windings. The 14 windings are inserted within the appropriate armature lamination passages and the free ends are con~igured to be 6 generally positioned within the proper riser slots. These 17 operations may be carried out by hand assembly but preferably 18 are automated. This composite structure is thereafter rolled 19 through a solder bath such that the armature winding wires are electrically and mechanically coupled to the material from 21 which the slots have been formed. Thereafter, through a 22 machining operation, excess material is removed from the 23 commutator body outer shell portion in order to provide for 24 separation of the metallic commutator se~ments from each other by a band or strip of dielectric material.
26 One requirement for starter motors normally imposed 27 by the assignee of the present invention is that such motors 28 be capable of operating satisfactorily for an e~tended period 29 of time in a battery run-down test. Such a test requires that 3 the dynamoelectric machine be operated under normal load for -~ ~4S3~8 an ~xtended period o~ time which may approachJ, ror example, ~en 2 mlnute~, Operation o~ a ~tarter motor ror an 1nternal com-3 bu~tlo~ englne involve~ applylng normal battery voltage to the 4 bru~hes o~ the dynamoelectrlc machine and to the ~i~ld wlndlngs ~o~ the dynamoelectric machine ~o that the machlne become~
6 operatlve, The duration o~ the test 18 a ~unctlon of the tlme 7 lt take~ the nomlnal battery voltage to drop to a ~elected 8 level t rOr e~ample, an inop~ratlve volta~e condltlon. Normal g operat~on o~ a st~rter mo~or typ~cally requ~re~ le~s ~han 30 s~cond~ Or continuous operation. Durlng operatlon o~ a ~tarter 11 motor large amounts of' current, on the order of' hundred~ of' 12 . ampheres, f`low through the armature windings. The soldered 13 Jun¢tlons between the commutator ~egments and the armature 14 windings compri~e ~mall resistance~ 3 whlch begin to accumulate heat due to the normal I.R. heatlng a~ociated wlth an elec-16 trlcal curren$ passln~ through an ~lectr~cal resl~tance. Under 17 prolonged appllcatlon~ Or battery voltage ln per~ormance Or 18 th~ battery run-down te~t3, the heat at the commutator winding 19 lnter~ace may eas~ly ri~e to lelrels ~urf'lcient to cause the ~0 ~older at the Junctlon to become r"luld. Under the in~luence 21 0~ the centrl~ugal ~orce associated wlth the ro~ation Or the 22 dynamoelectrlo machlne armature at speed, the ~older i8 thrown 23 out o~ the rl~er 810t8 ¢auqlng the electrical resistance o~ the 24 elec~rlcal Junctlon to increase. An undesirable hlgh resis~ance Junction 1~ formed and in 80mo lnstance~, an open circult 26 conditlon re~ults. Thl~ may occur in l~s~ than the t~n mlnute~
27 requlred ror battery run-down. ~h- 8 oonstltutes a dynamo-28 ele¢trlc ma¢hlne ~ailure and, 1~ encountered by the operator 29 o~ a motor vehlole9 necessltate~ a 008tly and aggravatlng replaeeme~ of the start~r motor. Th~8 may occur under pro-31 longed startl~g attempts, partlcularly where the starter 32 motor 1~ energized by hlgher than normal ~oltages.

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The use of a soldering process to join the armature windings to the commutator segments has been used e~tensively since the art of soldering is well developed and a wide variety of equipment for soldering is available.
The ease of obkaining equipment and developing useful technology in the ~ield of soldering has strongly encouraged the continued use of copper conductors. As noted herein-ahove, the type of manufacturing process utilized by the assignee of the present invention in forming dynamoelectric machines, and in particular starter mo~ors, has also dlctated the use of a special form of copper. In our employ-ment by the assignee of the present invention, a continuous problem with which we are faced is the provision of improved manufacturing techniques by which the cost of manufacture of, for example, automotive starter motor dynamoelectric machines, may be reduced. q It is well known that aluminum material is relatively lower in weight than copper and closely approx-~. . .
imates the electrical conductivity of copper. On a per pound basis, aluminum is less expensive than copper and the mass of aluminum required to form a commutator which would ;
be electrically and mechanically comparable to the copper commutator presently in use would ~e significantly less than the mass of copper thereby engenderiny a dual cost savings in that ~1) aluminum is less costly on a per pound basis and (~) less poundage of aluminum would be required to fonm an equivalent commutator.
The presently used method of forming a commutator results in riser portions having relatively narrow, generally U-shaped, radially directed slots. These slots can most readily accommodate a pair of armature winding wire ends if .
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t~.e wire ends are radially disposed, i.e., positioned within the slot so that ~he wire~ are aligned in a direction which is radial with respect to the axis of rotation of the armature with one wire end in proximity to the bottom of the slot and the other wire end positioned in contact with the one wire end. In the case of circular cross-section wire, the bottom wire in the slot is in contact with a substantial portion of the slot while the other, or outer wire is at best only in line contact with the bottom wire and the sides of the slot. This arrangement, plus the high thermal conductivity of good electrical conductors requires that substantial quantities of heat be applied if bonding of the joints is to be achieved by heating (other than soldering) and the use of the phenolic or plastic central portion for the commutator bodies, renders application of substant~al quantities of heat undesirable.
The present invention provides a method for electrically and mechanically uniting or otherwise bonding the armature wires of a dynamoelectric machine armature to the commutator of the armature by ultrasonically welding the armature wires within slots provided for these wires on the riseir portion of the armature. The method is fully compatible with present methods of producing armatures and requires no modification in the commutator formation technology currently in use. The commutator body and the armature laminations are arranged on the armature shaft with thie armature field wires situated within the armature ..
laminations substantially following the present practiceO

In accordance with the present invention, there is provided an improvement in a method of manufacturing an armature for a dynamoelectric machine wherein the armature . . .

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~L~453S8 assemblage is formed havin~ an armature shaft provided with a plurality of laminations, and an electrical commutator ;~: -having a slotted riser portion and a plurality of insulated : :
electrical conductors are passed through the plurality of laminations to have their uninsulated free ~nds arranged in proximity to the riser portion of the commutator for bonding thereto in electrically conductive relation, the ` .
improvement wherein the step of bonding comprises the .-steps of: inserting selected pairs of conductor free ends in the slots in the commutator riser portion in a selected pattern, the conductor pair free ends being arranged in the .
riser slots in radially juxtaposed relation, the slots ;
being equidistantly spaced about the circumference of the ~ ~
riser portion and arran~ed to be substantially the same ~ -width as the conductor free ends; applying a welding tip to the radially remote free end of a first conductor pair within a first riser slot; ultrasonically energizing the welding tip to transfer welding energy from the welding tip to the conductor pair free ends whereby the conductor pair ree ends will become welded to the commutator riser portion; radially withdrawing the welding tip from the riser portion slot after sufficient wel~ding energy has been transferred to the conductox pair free ends within the slot;
indexing the assemblage to align a second slot with the welding tip; and repeating the steps of applying, energizing withdrawing and indexing until all conductor pair free ends have been welded to the respective slot portions of the ~:-commutator riser. .
The invention i5 described further, by way of illustration, with reference to the accompanying drawings, in which:

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; . . , . .. , . . .". ... ., . ... .. ~ , ,. ~ . , ., .. ;, ~ .- . . . , -~S35~3 Figure 1 illustrates, in an elevation~l perspective view, a dynamoelectric machine armature fabri-cated in accordance with the teachings of the present invention;
Figure 2 shows an enlarged elevational view of a single commutator riser segment from an armature fabri-cated in accordance with the teachings of the prior art;
Figure 3 illustrates a welding apparatus for performing the me~hod of the present invention in perspective view;
Figure 4 is a diagrammatic view illustrating a portion of the apparatus of Figure 3;
Figure 5 is a view taken along section line 5-5 of Figure 4, Figure 6 illustrates, i~ a fragmentary view of a commutator ~ody, a mechanism for indexing the armature assembly; and Figure 7 illustrates a view similar to that of Figure 2 but fabricated according to the teachings of the presen~ invention.
Referring now to the drawings, wherein like numbers designate like structure throughout the various views thereof, Figure l shows a perspective view of a :
completed dynamoele-tric , :, 1 machine armature 10 whlch has been generally fabricated in 2 accordance with the teachings of the prior art, but which 3 uses the present inventi~e method for electrically and 4 mechanically bonding the armature windings to the armature commutator riser slots. Armature 10 is provided with an 6 armature shaft 12 on which are mounted a plurality of armature 7 laminations one of which is shown as 14. For purposes of 8 clarity in the drawing the other armature laminations have 9 been omitted. Each armature lamination 14 is provided with a plurality of wire receiving apertures which are here 11 illustrated as ports 16. It will be appreciated that o~her 12 forms of apertures or passages, such as slots or grooves, 13 are also utilized. The armature larninations 14 are fixedly 14 mounted on the armature shaft 12 for rotation therewith and are aligned with each other so that the wire passages 16 o~
16 each lamination 14 are axially aligned. A commutator member 17 18 is attached to one end of armature shaft 12 and includes 18 a plurality of commutator segments 20 mounted on the surface 19 of, and retained by, an epoxy, phenolic, or other suitable plastic central hub portion 22. The commutator segments 20 21 are separated by ribs of hub material 24. As thus illustrated, 22 commutator member 18 may be fabricated in accordance with the 23 teachings of, for example, the aforenoted United States Letters 24 Patent 3,468,020. Each commutator segment 20 is provided with a riser portion 26 which extends from the surface of the 26 commutator segment 20 in a direction which is generally 27 radial with respect to the axis of rotation of armature shaft 28 12. Each riser sect~on 26 is provided with a riser slot 29 indicated generally as 28. Each riser slot 28 is arranged to receive one end of each of a pair of armature winding -la- , .

;;8 wires 30, 31 which are arranged to extend in opposite 2 directions ~rom one commutator riser slot 28 to the lamina-3 tions and l;hrough the plurality of laminations 14, across 4 the rear, or noncommutator, :Eace of the armature laminations 14 in opposite directions as at 29 back through different 6 armature winding passages 16 to connect with two separate and 7 distinct commutator riser slots 28. The particular winding 8 fashion, that is, the angular spacing between the commutator 9 riser slot 28 and the armature winding passage 16 and the angular spacing between the commutator segments 20 which 11 receive both ends of the same winding wire, is a function of 12 the design of the dynamoelectric machine for which armature 13 10 is intended. In the illustrated embodiment, the angular 14 spacing between a particular commutator riser slot 28a and the armature winding passage 16a is approximately 40 degrees.
16 The other end of armature winding 30a extends through 7 armature winding passage 16b which is approximately 75 degrees 18 from armatUre winding passage 16a. As illustrated in this 19 ~i~;ure, the radially irlner wires of each wire are separated and insulated from the radially outer wires o~ the wire 21 pairs by insulator 33 which is inserted between the radially 22 inner and radially outer wires.
23 With reference now to Figures 1 and 2~ the prior 24 art method of electrically and mechanically uniting armature windings 30, 31 with the side and bottom wall portions of a 26 commut~ator riser slot 28 is illustrated. ~ollowing the 27 insertion of the individual armature winding wires 30, 31 28 through the appropriate armature lamination passages 16, the 29 two ends of each wire are positioned within the appropriate 3 commutator riser slots 28. Since each commutator riser slot : ~`

5i3S8 1 must accommodate a pair of armature wires, the wires are 2 arranged in radially ~uxtaposed relations~lip. That is, one 3 wire end, ~or example the end o~ wire 31, is arranged in the 4 slot to be rad~ally more closely spaced to the axis of rotatiOn o~ the armature shaft 12 while the e~d of the other 6 Wire 30 is radially more remote from the axis of rotation 7 Of armature shaft 12. ~ollowing placement o~ two ends o~ each 8 associated pair of armature windings within their respective g commutatOr riser slots 28, the armature assembly is then positioned in a solder bath and rolled through the solder bath 11 so that each commutator riser slot 29 is filled with a suitable 12 solder solution such that the solder, here noted in Figure 2 as 13 32 will fili the voids within the commutator riser slots 28 to 14 surround each wire end 30, 31 and to provide a mechanical bond to position the armature wires 30, 31 within the riser slots 28.
16 $older 32 also serves to unite, in electrically conductive 17 relation, the armature wires 30, 31 and the commutator segment 18 20. It will be appreciated that this Junction constitutes a 19 small electrical resistance and passage of high values of current through the electrical Junction of the rlser 26 and the 21 armature wires 30, 31 ~ill result in electrical resistive 22 heating at these ~oints. In the event that the heating becomes 23 sufficientl~ se~ere, the solder 32 will be heated to a liquid 24 or fluid state. Since such heating is the result of elec-trical current flow through the ~unction and such electrical 26 current flow normally accompanies rotation of the armature 10 27 the result is the expulsion, under centrifugal force~ of the 28 solder 32 ~rom commutator riser slot 28. This results in 29 termlnation of the electrical and mechanical bonds between the armature wires 30, 31 and the commutator seg,ments 20. In ~1~453S~
1 order to accommodate the soldering step it is the ~ell known 2 practice to use copper ~or both the armature wires 30, 31 3 and the commutator segments 20. The technology of soldering 4 copper conductors into a mechanically and electrically unitary ~unction is well advanced and a great many solder 6 compositions and solder fluxes are available to accommodate 7 this step.
8 Referring now to Figures 3, 4, 5 and 6, the method g of the present invention is illustrated as being performed by one particular assemblage of apparatus. Other forms of the 11 various components of the assemblage are also contemplated.
12 An armature assembly 11 comprising an armature shaft 12 13 having laminations 14 and a commutator body attached thereto 14 ~or rotation therewith is provided with the necessary armature windings 30, 3] passed through the appropriate lamination 16 apertures 16. The ends of the armature windings 30, 31 are 17 suitably arranged, in radially directed pairs, within the 18 appropriate riser slots 28 of a commutator body. The 19 commutator body differs from commutator member 18 in that the commutator body has a unitary metallic shell. This is 21 fragmentarily illustrated in Figure 6. The commutator member 22 18 is ~ormed by machining or otherwise finishing the commutator 23 body to remove excess metal and to separate each commutator 24 segment from the ad;acent segments. This assembly may be made by the automatic equipment presently used and as thus described 26 conforms substantially to the assembly process presently in use.
27 The assembly, here denoted as number 11 to distinguish from 28 the completed armature denoted as 10, is placed within 29 ~-block 34 such that the noncommutator end of the armature 3 shaft 12 passes through support sleeve 36.

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1 The armature assembly 11 including the V~block 34 2 is placed upon indexing fixture 38 such that the V-block 34 3 is received within the V-shaped notch 40 of the indexing 4 fixture 38 while the generally cylindrical surface of laminations 14 are received and supported arranged side-by~
6 side one of which is shown as a pair of rollers 42. In-7 dexing fixture 38 includes indexing motor 44 which may be 8 for example a stepping motor arranged to step the desired 9 number of increments to represent slot spacing. Motor 44 is arranged to incrementally drive the armature assembly 11 11 to index the commutator body. This is best illustrated by 12 ~igure 6. Armature 11 is situated within indexing fixture 38 13 ~o as to position the commutator body within welding shield 14 means 46. Welding shield means 46 is arranged to receive the welding head o~ an ultrasonic welding apparatus 48. The 16 welding head is mounted at the free end of welding horn 50.
17 Welding shield 46 is operative to provide for protection of 18 the welding head while also providing some degree of muf~ling 19 for the apparatus. To remove any ~oreign matter which may accumulate within shield 46 an air ~low may be provided 21 through shield 46.
22 With particular re~erence now to ~igure 4, one ~orm 23 ~ o~ uItrasonic welding apparatus for performing the present 24 invention is illustrated and includes horn portion 50, electro/ultrasonic energy transducer section 52 and booster 26 section 54. A plurality, in this case two, o~ threaded 27 coupling members 58 are arranged to interconnect the horn 28 section 50 and transducer member 52 with the booster section 54.
29 Welding head 60 is attached as described hereinbelow to 3 horn section 50. A pair of support arms 62, 63 are interposed :

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1 between the booster section 54 and each Or the horn section 2 50 and the transducer section 52. Flrst ~upport arm 62 is 3 connected through a ~lrst connection 64 to ~ixed support 66.
4 Second support arm 63 is connected through a second connection 64 to flxed support 68. Connections 64~ and reed-llke ~upport 6 arms 62, 63 permlt oscillatory motion o~ welding apparatus 48 7 in the plane of Figure 4 in the dlrection of arrow 69 ln the 8 accompli~hment o~ the welding ~tep accordlng to the present 9 ln~entlon.
In order to provide relative radial displacement o~
11 the welding head 60 with respect to the slots 28, the lndexing 12 means 38 ls arranged on a support table for movement with 13 respect to weldln~ apparatus 48. Thls i~ denoted by double :.
14 ended arrow 70 in Figure 3. ~he apparatu~ ~or accomplishing the mo~ement Or the lndexin~ means 38 ls shown~ in Fi~ure 4, 16 ln schematlc ~orm ~ince the relative motion may be accompli~hed 17 by a large variety o~ means and mechanicm~. The illustrated 18 mech~ni~m operates through electromechanlcal means and lncludes 19 ~upport table 72 pivotally supported as at 74 and resillently bia~ed toward weldlng apparatu~ 48 by biasln~ means 76.
21 B.ia~lng mean~ 76 are selected to urge the welding head 60 and 22 the ~ree ends o~ wire palr 30, 31 together wlth a predetermined 23 level o~ ~orce. Wlth a lateral drlve ultrasonic w~lding means 24 a~ lllustrated, thls level o~ force is not crltlcal but may range between, for example~ three hundred ~i~ty and one 26 thou~and pounds load with the limlts determlned by ba~ic 27 requirement~ ~or cycle tlme and material strength llmitation~0 28 At lower levels Or rorce uneconomlcally higher acoustical 29 energy levels are required and at higher ~orce level~, the 30. conductor materlal will tend to extrude upon applicatlon o~
31 ultrasonic welding energy. Drlve motor 78 ls arranged to ,7 5i358 drlve cam mean3 80 ~o opera'ce agaln~t the force Or bla~lng means 76 to ral~e and lower indexlng mean~ 38. As illustrated, 3 cam mean~ 80 includes lobe 82 f'or lowering the inde~iLng mean~
4 38 ror indexlng operation. A~ illustrated, drlve motor 78 may contlnuously rotate cam mean~ 80 and the dwell time o~ the cam 6 means 80 with lndexing means 38 raised and lowered ~hould be 7 ad~usted ~o pro~tlde ~de~uate welding tlme and su~icien'c tlme 8 ~or indexlng. L~mlt ~w~ t~h 84 1~ provld~d to sens~ the changes 9 of' posltlon Or ~upport table 72 and is adap~ed to energize lnde~ing motor 44 when the ~uppor~ table 72 ha~ lowered the 11 lndexlng means 38 3u~rlalently ~o permlt lnterrerence ~ree 12 . rotation o~ the commutator body relative to the welding head 13 60. Power supply 86 18 arranged to energize drive motor 78 14 through ~tart-stop ~witch 88 an~ indexing motor 44 through limit ~witch 84. Resetable counter 90 i8 arranged to count the 16 number Or ind~xlng ~tep~ to automatically deenerglze dr~ve 17 motor 78 upon completlo~ o~ the des~red n~nber of welding step~
18 a~, ~or example, by deaatuating ~tart-stop ~wltch 88. Swi.t~h 19 as may be m~nually or automatically set to energize drlve motor 78 to initiate the rir~t welding step. As herelnabove de~cribed, 21 welding apparatus 48 and/or lndexing mean~ 38 may b~ hydrau-22 lic~lly, mochanlcally, pheumatlcally or electrlcally con-23 ~rolled to apply pres~ure to the wires to be welded or to 24 remove the weldlng tip from the weldment.
With particular rererence now to Fl~ure 5, an end 26 vlew Or the weldin~ hea~ 60 in a~soclation wlth a commutator 27 rlser slot 28 and ln contactive engagement wlth the radlally 28 outer ~ur~ace o~ the radlally outer conductor 30 o~ the partl-29 cular conductor palr reoeived wlthin the ~lot. As lllustrated in thls vlew, weldlng head 60 is a ~enerally clrcular body 31 hav~ng a plurallty, in thls ca3e slx, o~ welding tips 92a ., ., ., . ~ . " ~ ............................ .... .. . . . .
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1 through 92~. Welding head 60 is connected to horn ~ectlon 50 by 2 mean~ o~ n~t 94. The arrangement of the welding head 60 a~
3 thu~ descrlbed 1~ operative to provide rOr a plurality o~ weld-4 ing ~lp~ on the same welding head to permlt quick change

5 ;capability when a particular weldlng tip become~ too worn to be

6 serviceable. For examplej~ welding head 60 may be provided with

7 an lndex me¢hanlsrn ln the ~orm o~ a 3eparate tool arranged to

8 positlon the uppermost weldlng tlp, in thi~ instance weldlng

9 tip 92b, ln a selected orlentation wlth respect to the indexing mechanism 38 to prov~de a plurality o~, in this case ~lx, stable 11 positlon3 each one o~ whlch corre~pond to placement Or a weld-12 lng tlp 72 ln the proper locatlon with re~pect to the lndexing 13 me~hanlsm 38 o~ Flgure 3. Other arrangement~ are also contem-14 plated.
In per~ormlng the method Or the pre~ent inventlon, 16 armature a~embly 11 1~ pla¢ed within the lndexin~ mechanl3m 38 17 ~o that one o~ the commutator rl~er slot~ 18 aligned wlth the 18 operatlve weldlng tlp 70, as lllu~trated in Flgure 5 thls would 19 be weldlng tlp 70dj, and the first weldlng operatlon ls ~ider-taken, One convenlent mechanl~m o~ arranglng the alignment 21 would be to provlde an lndlcla on the ~ide Or, ror example 22 welding 3hlel~ 46, to be aligned wlth a suitable portlon or 23 lndlcla on the armature as3embly 11. Other initlal alignment 24 arrangements are also contemplated. The weldlng mechanlsm may therearter be automatlcally operated by actuatlon Or 3tart-3top 26 switch 88 to pro~lde weldlng energy ~o the condu~tor~ wlthin 27 the rlser portion 810t wlth which the weldlng tlp i~ engaged.
28 Followlng completlon Or the lnitial alignment and welding step, 29 the weldlng tip i~ extracked ~rom the riser portion slot by movlng the lndexing mechanlsm 38 radlally away ~rom the welding 31 tip 92e. The indexlng motor 44 i~ energlzed to rotate 32 armature as~embly 11 to present a di~erent ri3er portlon ~lot ., , ~45~8 1 for subsequent welding. The welding tip is reapplied, in an 2 automatic fashion, to the then promi.nent riser portion slot 3 and welding energy is applied. The sequence of operation is 4 repeated a su~icient number of times to transfer welding energy to, and hence to weld, each of the conductor pairs 6 within each of the riser portion slots.
7 With particular reference to Figure 6, the indexing 8 operation is illustrated in a fragmentary view of the 9 commutator bodyO As here shown, each of the commutator segments 22 is ~oined to its ad~acent segments by an outwardly 11 projecting ridge or flute 96 which is overlaying the plastic 12 ribs 24 in the axial direction. The radially extending 13 portions o~ plastlc ribs 24 is similarly covered by a solid 14 layer of conductor riser material which joins adjacent riser portions. Flutes 96 are accurately positioned on opposite 16 sides of each riser slot 28 and provide a convenient driven 17 indexing means. Driving indexing means 98 is shown in phantom 18 lines and is provided with indentations as at 100 which are 19 spaced about the periphery thereo~ to drivingly engage flutes 96. Driving indexing means 98 may be directly driven by 21 indexing motor 44. As here shown, the driving indexing means 22 98 is directly opposite the riser slot 28 to be welded, and if 23 supported by suitable bearings, will prevent any distortion 24 of the commutator body during welding. ~he presence of commutator riser portion material bridging the radially 26 directed portions of ribs 24, as at 102 will provide sub~
27 stantially greater circumferential strength for the commutator 28 riser portion during welding to avoid any damage to the 29 radially directed portions of ribs 24. Subsequent to the 3 welding operation, the armature assembly 11 may be situated ~53~
1 within a sultable fi~ture and may be machined to remove excess 2 metal from the commutator body such as the wire ends 3 illustrated in Figure 4 and the commutator body material 4 overlaying the ribs 24 such as the flutes 96 and the material ;at 102 as illustrated in Figure 6.
6 Referring now to Figure 7, an enlarged elevational 7 view of a commutator riser portion 26 having a pair o~
8 conductors 30, 31 electrically and mechanically bonded 9 according to the teachings of the present invention is illustrated. The application of ultrasonic welding energy 11 to the radially outer surface of the radially outer conductor 12 within the riser portion slot 28 has resulted in the metal 13 f each of the conductors 30 31 belng deformed to the extent 14 that the conductors now occupy substantially all of the lower two-thirds of the slot 28. Furthermore, metal o~ the 16 conductors has become closely joined by a solid state bond 17 with each other and with the sides o~ the riser portion slot.
18 Line 104 indicates the approximate demarcation between metal 19 which is uniquely that o~ one conductor, for example conductor 30, from metal which is uniquely that o~ the other, ~or 21 example conductor 31. Metal lying along line 104, as well as 22 metal lying along the line defining the slot boundary, is 23 indistinguishable as to source. That is, the source of the 24 metal lying along the~e defined boundaries cannot be defined with any accuracy and may be from either conductor or from 26 the riser portion or an alloy of both of the metals present 27 on either side of the boundary prior to the welding operation.
28 In practice, the material o~ riser portion 26 and o~ conductors 29 30, 31 would be indistinguishable except where dissimilar 3 material were used.

The bond produced between the upper and lower wires, and the wires and slot sides and bottom is achieved when the vibratory energy in the tip is transferred to the wires and slot. This sets up relative motion between the wires and wires and slot to the point of ~rictional heating at the contacting surfaces raising the contacting surface temperatures to somewhat less than the melting temperatures of the conducting materials. It is believed that the violent local vibration accelerates and attendant heating contacting surfaces mutual atomic diffusion of the conducting materials which break the surface barrier and allow the metallic bond to form. The mechanical strength and electrical current capacity of the solid state joint is proportional to the mutual bonded area of the wires and the commutator slot.
Examination of a large number of commutator welds accomplished according to the present invention has disclosed that welding energy is successfully transferred through the wire ends of conductors 30, 31 to the region of the bottom of riser portion slots 28. In the case of the exemplary wire dimensions, this is a distance of in excess of one ~uarter inch. Thus, welding is accomplished along the length and , width of the welding tip, as would be expected, but also along the entire d~Th of the riser portion slots 28.
Furthermore any materials tending to be entrapped within the riser portion slots 28, as for example, solder flux material predeposited on the wire ends has appeared to be hermetically sealed within weldment. Solder flux remaining within a soldered joint contributes greatly to galvanic corrosion upon exposure to air and no instances of galvanic corrosion have to be noticed. The level of heating of the commutator body -22- ;

, s,~ . ,.

~ 45i35~
produced by the welding operation is sufficiently low to permit handling of ~he commutator body immediately thereaf~er with special precautions and the force levels encountered ~ -by the plastic material of hub portion 22 and particularly ribs 24 may be maintained low enough that cracking or extrusion of the plastic material may be easily and regularly avoided. The welments so formed demonstrate substantially higher levels of mechanical strength and are not as susceptible to heat induced failures as the soldered joints. The use of the ultrasonic welding step in bonding commutator segments to the armature winding, particularly in dynamoelectric machines used as automotive starter motors admi~s of the use of dissimilar materials such as copper and aluminum, as well as being applicable to bonding similar materials, thereby permitting the use of less expensive material while con- -comitantly providing a superior bond between the commutator segments and the armature winding. Thus, the overall reliability of the resulting dynamoelectric machine is increased while material content may be decreased and labor content is virtually unchanged. The method described herein-above and claimed hereafter is fully compatible with the techniques presently in use for manufacturing dynamoelectric machine armatures and is relatively insensitive to wire size and to wire orientation within the riser portion slots.
In performing the method of the present invention, we have found that the strength of a completed weld is a function of the amount of energy transmitted to the welding tip, the time of application of the welding tip to the --weldment and the force of application of the welding tip to the weldment. Thus, for any given combination of materials to :.
' - \ :
S35~3 be welded and for a given electro/ultrasonic transducer, a large combination of vaxiables must be considered. The greater the amount of energy transferred to the welding tip, the quicker the welding step can be accomplished and the lower the clamping force. This permits a rapid cycle time but requires the maximum expenditure of energy by the equipment.
An equally strong weldment can be obtained with lower energy expenditure provided that increased clamping force is used and a longer cycle time is permitted. ~t will be appreciated that the variable may be combined in a large number of combinations and the particular combination selected for a particular welding operation may be optimiæed about cycle time or~k'~ energy expenditure or about clamping force.
Since clamping force can be relatively easily generated and controlled, it is expected that the optimum combination will result in a minimum cost per weldment when considering all labor, materials and energy cost variables. Under these conditions, it is expected that expeirimentation to arrive at the optimum values ~ the parameters applicable to a given welding operation will be undertaken. Other variables which in1uence the welding operation, although to lesser degrees, are surface and metallurgical conditions of the materials to be welded, geometry surface condition of the weldin~ tip, and frequency amplitude and type of utrasonic welding apparatus utilized.
In developing the present invention, a later~
drive ultrasonic ~elding machine was used. The transducer section was a parallel resonant driven electrostructive transducer producing a constant amplitude oscillation coupled to a titanium resonant transformer terminating in a tool steel -~4- -~' , 5i3~i~
head located at a longitudinal mechanical resonant node. The tip was driven at a frequency of abou~ 10 KHz with an amplitude of about 0.006 inches. The transducer received 4000 watts of power. In welding 0.128 inch diameter copper wire to a copper commutator having a riser portion slot slightly wider than 0.128 inches and about 0.250 inches long, satisfactory weldments were generated with clamping forces ranging ~rom about 350 pounds to about 1000 pounds and energy consumptions of about 1000 joules and about 500 joules respectively. Using copper wire having a diameter of 0.082 inches and a copper commutator with riser portion slots dimensioned accordingly, satisfactory weldment were formed with clamping pressures ranging from about 100 pounds to about 500 pounds and energy consumptions of about 300 joules and about 100 joules respectively, Using copper wire ha*~ng a diameter of about 0.128 inches and an aluminum commutator having suitably sized riser portion slots, suitable weldments were formed with clamping pressures ranging from about 300 pounds to about 450 pounds and energy consumption of about 900 joules and about 700 joules respectively.
It can thus be seen that the method of the present invention readily accomplishes its stated objective of providing a convenient and reliable replac~ment method for the previously used step of soldering. By ultrasonically welding the wire pair within the slot of the commutator riser portion a substantially stronger mechanically bond may be formed and the electrical union between the conductors 30, 31 and the commutator segment 20 is assured. Furthermore, the joint is free of any material having a melting temperature which is in any way approached by expected operating -25- ;

~45;~15~
temperatures genera~ed by resistive heatin~ or other sources at the boundary or which would promote corrosion. As a further advantage of the present method, armatures of dynamo-electric machines may now be fabricated using materials for either the commutator or the armature winding or both which had previously been precluded from use due to diff~culties in the soldering step. In particular, the commutator segments and/or the armature windings may now be fabricated from several readily commercially available grades of aluminum ~uch as the grades 2014, 2024, 6061 and 6063. By the use of aluminum in the commutator segments and~or the annature windings, particularly for a starter motor, the requirement for use of copper in any form is reduced thus producing a cost savings by using less expensive aluminum material and a further weight savings is achieved since the amount of aluminum required to carry the necessary levels of electric current in this class of dynamoelectric machine is less massive than the comparable quantity of copper is required.
An additional advantage encountered in those situations where a special class of copper has been required such as the previously mentioned oxygen-free copper is that multiple sources for the various commercial ~rades of aluminum are known whereas the sources of special grades of copper are .
limited.
We claim:
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i: ' ~ '' '~'':' ' ' '':

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

In a method of manufacturing an armature for a dynamoelectric machine wherein the armature assemblage is formed having an armature shaft provided with a plurality of laminations, and an electrical commutator having a slotted riser portion and a plurality of insulated electrical conductors are passed through the plurality of laminations to have their uninsulated free ends arranged in proximity to the riser portion of the commutator for bonding thereto in electrically conductive relation, the improvement wherein the step of bonding comprises the steps of:
inserting selected pairs of conductor free ends in the slots in the commutator riser portion in a selected pattern, the conductor pair free ends being arranged in the riser slots in radially juxtaposed relation, the slots being equidistantly spaced about the circumference of the riser portion and arranged to be substantially the same width as the conductor free ends;
applying a welding tip to the radially remote free end of a first conductor pair within a first riser slot;
ultrasonically energizing said welding tip to transfer welding energy from the welding tip to the conductor pair free ends whereby the conductor pair free ends will become welded to the commutator riser portion;

1 (contd) radially withdrawing said welding tip from the riser portion slot after sufficient welding energy has been transferred to the conductor pair free ends within the slot;
indexing the assemblage to align a second slot with the welding tip; and repeating the steps of applying, energizing withdrawing and indexing until all conductor pair free ends have been welded to the respective slot portions of the commutator riser.

The method of Claim 1 including the step of arranging the armature assemblage upon indexing and supporting means to present a first riser portion slot to the welding tip prior to the step of applying the welding tip to the radially remote free end of the conductor pair within the riser portion slot.

The method of Claim 2 wherein the step of radially withdrawing the welding tip includes the step of moving the indexing and supporting means relative to the welding tip.

The method of Claim 3 wherein the step of indexing is performed during performance of the step of moving the indexing and supporting means.

The method of Claim 1 wherein the welding tip is applied to the conductor pair with a predetermined level of pressure.

The method of Claim 5 wherein the pressure of application is selected to be greater than the minimum pressure necessary to accomplish welding.

The method of Claim 6 wherein the pressure of application is selected to be less than the pressure at which the application of welding energy would cause material of the wire pair to be forced in the axial direction.

The method of Claim 5 wherein the step of energizing the welding tip is performed for a period of time sufficient, when considering the pressure of application of the welding tip, to achieve welding.

The method of Claim 5 wherein the step of energizing is accomplished by transferring welding energy to the welding tip for a predetermined time period.

The method of Claim 9 wherein the step of energizing the welding tip is performed for a period of time selected to be sufficient to accomplish welding when considering the pressure of application and the level of energy transferred to the welding tip.