United States Patent [191
`Marshall et al.
`
`[11]
`[45]
`
`Patent Number:
`Date of Patent:
`
`4,922,604
`May 8, 1990
`
`[54]
`
`[75]
`
`[73]
`
`[21]
`[22]
`[51]
`[52]
`
`[5 8]
`
`[5 6]
`
`METHOD OF FABRICATING AN
`ENCAPSULATED MOTOR
`Inventors: James W. Marshall, Towson, Md.;
`David Gotchy, Roscoe; Bradley L.
`Uffelman, Rockford, both of I11;
`Wendell B. Leimbach, Baltimore;
`Albert A. Wilhelmi, Baldwin, both of
`Md.
`Assignee: Paci?c Scienti?c Company,
`Rockford, Ill.
`Appl. No.: 323,507
`Filed:
`Mar. 13, 1989
`
`Int. Cl.5 ........................................... .. H02K 15/02
`U.S. Cl. ...................................... .. 29/598; 29/596;
`264/2722; 310/42; 310/43; 310/90
`Field of Search ............................... .. 29/596, 598;
`264/272.19, 272.2; 310/42, 43, 9O
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,156,076 11/1964 Origoni et a1. ................. .. 29/596 X
`4,015,154 3/1977 Tanaka et al_ ..
`29/596 X
`
`4,029,977 6/1977 Chai et a1. . . . . . . .
`
`. . . . . .. 310/49
`
`310/217
`4,538,084 8/1985 Kawada et a1. .
`310/ 89
`4,626,725 12/1986 Kawada et a1. .
`310/49
`4,712,028 v12/1987 Horber .......... ..
`310/154
`4,713,570 12/1987 Mastromattei ..
`4,763,034 8/1988 Gamble ............................. .. 310/181
`
`Primary Examiner—Carl E. Hall
`Attorney, Agent, or Firm—Leydig, Voit & Mayer
`[57]
`ABSTRACT
`A method of fabricating an electrical motor, such as a
`hybrid permanent magnet stepping motor or a variable
`> reluctance motor. A rotor is assembled on a rotor shaft
`and includes at least one lamination stack and a pair of
`supporting bearings, with the outer diameter of the
`bearings being slightly larger than that of the lamination
`stack. A stator is assembled from a stator lamination
`stack including a pole con?guration and a pair of unma
`chined end caps registered and secured to the lamina~
`tion stack such as by thru bolts. The registered stator
`assembly is potted to unitize the assembly, ?xing the
`relationship between the end caps and the lamination
`stack, and providing a smooth continuous bore through
`the center of the stator assembly. The thus potted as
`sembly is then machined as by diamond lapping to form
`a continuous bore accurately machined through the
`center of the stator, concurrently forming bearing sur
`faces in the end caps and an intermediate machined
`section in the lamination stack. The rotor assembly is
`inserted into the stator assembly with the machined
`bore providing bearing mounting surfaces in the end
`caps and an air gap for rotation of the rotor in the lami
`nation stack.
`
`30 Claims, 7 Drawing Sheets
`
`BMW-1016
`Page 1 of 17
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`

`

`US. Patent May 8,1990
`US. Patent
`May 8,1990
`
`Sheet 1 of 7
`Sheet 1 of 7
`
`4,922,604
`4,922,604
`
`
`
`BMW-1016
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`Page 2 of 17
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`BMW-1016
`Page 2 of 17
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`

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`US. Patent
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`' May 8,1990
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`BMW-1016
`Page 3 of 17
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`

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`May 8, 1990
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`BMW-1016
`Page 4 of 17
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`US. Patent May 8,1990
`US. Patent May 8, 1990
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`Sheet 4,0f 7'
`et 4 of 7'
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`4,922,604
`4,922,604
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`Page 5 of 17
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`US. Patent May 8, 1990
`US. Patent May 8, 1990
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`Sheet 5 0f 7
`Sheet 5 of 7
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`4,922,604
`4,922,604
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`US. Patent May 8, 1990
`US. Patent May 8, 1990
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`Sheet 6 of 7
`Sheet 6 0f 7
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`4,922,604
`4,922,604
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`BMW-1016
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`US. Patent May 8,1990
`US. Patent May 8, 1990
`
`Sheet 7 of7
`Sheet 7 0f 7
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`BMW-1016
`Page 8 of17
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`1
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`BMW-1016
`Page 8 of 17
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`

`

`1
`
`METHOD OF FABRICATING AN
`ENCAPSULATED MOTOR
`
`4,922,604
`
`FIELD OF THE INVENTION
`This invention relates to electrical motors, and more
`particularly to motor structures and assembly tech
`niques which provide relatively small size motors of
`simple and inexpensive construction.
`
`5
`
`BACKGROUND OF THE INVENTION
`At the outset, it will be pointed out that the invention
`relates to constructional features and assembly tech
`niques for motors rather than the speci?c electromag
`netic mechanism which drives them. As a result, the
`present invention can be applied to a number of differ
`ent motor types including switched reluctance motors,
`permanent magnet brushless motors and hybrid step
`ping motors among others.
`Chai et al. U.S. Pat. No. 4,029,977 shows a relatively
`conventional construction for _ a variable reluctance
`stepping motor. It is seen that the motor includes an
`external case machined to register with a pair of end
`bells which also must be machined to register with both
`the case and the rotor bearings. The external case, in
`turn, serves to register a wound and insulated stator
`lamination stack. Thus, when the elements are assem
`bled, the rotor is held in its bearings in the machined
`surfaces in the end bells, the numerous registration de
`vices assure that the rotor is properly positioned within
`the stator. However, such an arrangement carries with
`it a degree of manufacturing expense because of all of
`the separate parts must be fairly precisely machined in
`order for all of the registration systems to function in
`properly aligning the rotor within the internal bore of
`35
`the stator.
`It has been proposed to produce a motor without an
`external case, exposing the exterior of the stator lamina
`tions. One such approach is illustrated in Kawada et al.
`U.S. Pat. No. 4,538,084, and another in Kawada et al.
`U.S. Pat. No. 4,626,725. The former uses threaded rods
`welded within the stator lamination assembly in order
`to appropriately register the end caps to the stator. The
`latter uses threaded rods of two lengths, one inter?tting
`into the end caps and the other on which the end caps
`bottom in order to maintain registration of the end caps
`to the stator. While those approaches save the expense
`of the motor housing, they add complication in the form
`of such elements for attaining and maintaining registra
`tion of the end caps (and therefore the rotor) to the
`stator.
`It is also applicants’ understanding that a motor of the
`general type illustrated in the aforementioned Chai et al.
`patent has been con?gured without a case, that is, with
`the stator laminations exposed intermediate a pair of end
`caps. As applicants understand it, in order to achieve
`the elimination of the case, the end caps were altered in
`two ways. First of all, tapered tabs were formed on the
`periphery of the end caps, projecting toward the lami
`nation stack at three points around each end cap in
`order to accurately register the end caps with the lami
`nation stack. Secondly, apertured mounting ears were
`also formed on the end caps, protruding at right angles
`from the tabs. The mounting ears received bolts which
`spanned the lamination stack between end caps to
`?rmly secure the end caps to the lamination stack,
`thereby not only providing register but also rigidity. In
`that registered rigid con?guration, means were then
`
`50
`
`60
`
`2
`provided to machine the bore which extended through
`the end caps and stator assembly. A multi-station lap
`ping machine was used to simultaneously machine bear
`ing surfaces in the end caps and the stator bore. The
`rotor was then positioned in the machined aperture with
`the rotor bearings mounted in the end caps and the
`rotor free to rotate within the stator.
`That approach suffers from certain problems. First of
`all, the exterior tabs and mounting ears on the end caps
`require the envelope occupied by the motor to be en
`larged; in many applications where space is at a pre
`mium the enlarged size could be unacceptable. More
`importantly, machining the bearing surfaces and stator
`ID with the stator fully assembled results in machining
`debris entering the motor. The motor was constructed
`of open con?guration, providing large apertures in the
`end caps which allowed the motor to be thoroughly
`washed in an effort to remove the machining debris. .In
`addition, machining debris could be trapped within the
`coils, fall between the end caps and the stator or other
`wise lodge itself in apertures in the stator assembly, and
`that machining debris could work loose during later
`operation of the motor to cause premature failure.
`The stator machining problem could be particularly
`severe for motors of the “enhanced” type which have
`permanent magnet segments interposed between rotor
`teeth, since machining of the rotor bore would then
`create machining debris which included highly mag
`netic particles. The magnetic particles would be ex
`tremely dif?cult to remove by standard washing tech
`niques and motor stators were sometimes varnished or
`otherwise internally coated to secure the magnetic par
`ticles which could not be removed in position. Thus,
`there was created a signi?cant cleanup problem and the
`possibility of motor failure by means of unremoved
`machining debris.
`One of the problems which has necessitated relatively
`elaborate registration devices is thermal cycling of the
`motor in the case where the end caps have a signi?
`cantly different coefficient of thermal expansion than
`the stator laminations. The stator laminations are typi
`cally steel. The end caps, however, must be nonmag
`netic and often made of aluminum which expands much
`more than the steel when the motor is operating and
`dissipating heat, and contracts much more than the steel
`when the motor is at rest and cools. If the end caps are
`not held in rigid and ?xed register with respect to the
`stator laminations, when the motor is cyclically heated
`and cooled during operation, the end caps can “walk”
`with respect to the stator, ultimately causing misalign
`ment of the rotor within the stator.
`
`SUMMARY OF THE INVENTION
`In view of the foregoing, it is a general aim of the
`present invention to provide a small and relatively inex
`pensive motor with exposed stator laminations which is
`simpler and more economical to fabricate than the prior
`art discussed above.
`.
`I
`In that regard, it is an object to minimize the cost and
`complexity of both the end caps and the lamination
`stack while still achieveing the necessary precision in
`final assembly.
`Accordingly to a more detailed aspect of the inven
`tion, it is an object to minimize pilot devices on the
`motor components to the greatest extent possible in
`order to produce a motor which is simple and easy to
`
`BMW-1016
`Page 9 of 17
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`

`

`4
`hanced by the potting material in the gaps between the
`teeth which serves as a backing member for the teeth,
`preventing distortion which can be caused by material
`shearing or slight tooth deformation during machining.
`The magnetic debris generated during machining of the
`inserted magnets is easily and reliably cleaned from the
`smooth continuous bore of the potted stator.
`Other objects and advantages will become apparent
`upon reference to the detailed description when taken
`in conjunction with the drawings, in which:
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a perspective view illustrating a completely
`assembled motor constructed in accordance with one
`embodiment of the present invention;
`FIG. 2 is a partly exploded view showing a motor
`according to the invention with the rotor assembly
`removed from the stator assembly;
`FIG. 3 is a process flowchart illustrating the steps of
`constructing a motor in accordance with the present
`invention;
`FIG. 4 is an elevational view illustrating a partially
`assembled rotor;
`FIG. 5 is an elevation illustrating a rotor assembly
`with bearings and bushings in place and ready for inser
`tion into a stator assembly;
`FIG. 6 is an elevation illustrating an individual stator
`lamination;
`FIG. 7 is a persspective view showing an assembled
`lamination stack made up of individual laminations as
`illustrated in FIG. 6;
`FIG. 8 is a perspective view illustrating the lamina
`tion stack of FIG. 7 with insulators and windings in
`place;
`FIG. 9 illustrates a wound stator assembly with end
`caps and printed circuit board in place;
`FIG. 10 is a perspective view illustrating the connec
`tor end of the lamination stack of FIG. 7;
`FIG. 11 is a partial view illustrating the relationship
`between the connectors of FIG. 10 and the mating
`circuit board;
`FIG. 12 is a partial view (without end cap) illustrat
`ing the partly completed stator assembly of FIG. 9 after
`potting; and
`FIG. 13 is a view similar to FIG. 12 illustrating the
`potted stator assembly after it has been machined and is
`thus ready for insertion of the rotor assembly.
`While the invention will be described in connection
`with certain preferred embodiments, there is no intent
`to limit it to those embodiments. On the contrary, the
`intent is to cover all alternatives, modi?cations and
`equivalents included within the spirit and scope of the
`invention as de?ned by the appended claims.
`
`4,922,604
`3
`assemble with a minimum of register machining on the
`parts to be assembled.
`It is a further object of the present invention to pro
`vide a small and relatively inexpensive electrical motor
`in which the end caps and rotor are machined after
`assembly and which can be easily and reliably cleaned
`of machining debris.
`According to another aspect of the invention, a fur
`ther object is to provide an electrical motor which,
`although it has end caps and stator of substantially dif
`ferent coefficient of thermal expansion, prevents or
`minimizes walking between those elements.
`These and other objects are achieved in accordance
`with the present invention by providing a motor fabri
`cation technique and the resulting motor which in an
`early stage of assembly achieves register of a pair of end
`caps with a wound stator lamination stack. Such regis
`tration can be achieved, for example, by bolts passing
`through clearance holes in one of the end caps, clear
`ance holes stamped in the laminations of the lamination
`stack, and into an aperture in the other end cap while
`those elements are held in position on an arbor. Having
`achieved this initial registration and created a unitized
`stator assembly, the stator assembly is then potted, ?x
`ing the positional relationship between the end caps and
`the stator lamination assembly. Following potting, the
`central bore is machined, preferably by lapping, to form
`bearing mounting surfaces in the end caps and to ma
`chine the internal bore of the stator lamination stack to
`provide a running air gap between the rotor and stator.
`A rotor assembly, comprising the rotor section itself
`and a pair of bearings, has the bearings of slightly larger
`outer diameter than the stator section. The rotor assem
`bly is inserted into the machined bore in the stator as
`sembly and ?xed in place to produce a completed mo
`I01‘.
`It is a feature of the invention that the potting mate
`rial ?xes the relationship between the end caps and
`stator lamination stack, and subsequent machining of
`the internal stator bore accommodates for any misregis
`40
`tration which might have occurred during the initial
`registration before potting.
`It is a further feature of the invention that the smooth
`continuous internal bore of the stator assembly prevents
`machining debris from falling into the motor and pro
`vides a stator assembly which can be'easily cleaned
`following machining.
`It is a further feature of the invention that heat trans
`fer from the motor is enhanced by virtue of the potting
`material which ?lls internal voids and has a better ther
`mal coef?cient than air which normally ?lls such voids
`in conventional motors.
`According to a further feature of the invention, the
`potting material prevents walking of the metallic stator
`components, particularly in the case where the end caps
`have signi?cantly different thermal coef?cents of ex
`pansion than the lamination stack.
`According to a optional feature of the invention, the
`motor can be produced in an “enhanced" con?guration,
`having permanent magnets inserted between the teeth
`of the stator poles. The potting material is allowed to
`envelope the stator poles, thereby securing the perma
`nent magnets into the gaps between the teeth. Subse
`quent machining of the bore removes some of the pot
`ting material and machines sharp square faces on the
`stator teeth while still allowing the potting material to
`assist in holding the permanent magnets in their pole
`slots. The sharpness of the stator teeth edges is en
`
`30
`
`35
`
`45
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Turning now to drawings, FIG. 1 shows a perspec
`tive view of a hybrid permanent magnet stepping mo
`tor, and FIG. 2 a partly exploded view showing the
`rotor and rotor retaining elements removed from the
`stator assembly. It will be noted at the outset, however,
`that while the invention will be described in connection
`with a hybrid stepping motor, it is also applicable to
`other motor types, particularly in the small size range.
`For example, a brushless variable reluctance stepping
`motor of the Chai et al. type could be constructed in
`accordance with the present invention by con?guring
`the rotor and stator assembly as a variable reluctance
`
`60
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`Page 10 of 17
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`5
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`20
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`25
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`35
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`4,922,604
`5
`motor. Similarly, theainvention is applicable to perma
`nent magnet brushless motor designs, switched reluc
`tance motors, enhanced variable reluctance motors, as
`well as enhanced and unenhanced stepping motors of
`the hybrid stepping type. Finally, induction motors
`could also utilize the present invention as could other
`motor types as will be apparent to those skilled in the art
`upon reading the following detailed description.
`Referring to FIGS. 1 and 2, there is shown a hybrid
`stepping motor generally indicated at 20 comprised of a
`stator assembly 21 and a rotor assembly 22. The rotor
`assembly is ?tted with bearings 23, 24 which in turn
`mount in end caps 25, 26 to support the rotor assembly
`22 for rotation in the stator assembly 21. The end caps
`25, 26, sandwich a central stator lamination stack 27
`which carries stator poles and windings (not shown in
`FIGS. 1 and 2). In the currently preferred embodiment,
`the end caps 25, 26, and the lamination stack 27 are
`secured together, initially by means of mounting bolts
`28 which preferably pass through clearance holes in
`front end cap 26 and lamination stack 27 and are secured
`in apertures in rear end cap 25. In a further embodiment,
`the bolts 28 and the end cap apertures for receiving
`those bolts can be eliminated (as illustrated in FIG. 1)
`and the end caps initially secured to the stator assembly
`by means of a suitable adhesive applied at the seams
`indicated by 28’. While that arrangement places greater
`emphasis on the initial securement by means of adhe
`sive, it is advantageous in eliminating the need for me
`chanical devices such as bolts and the necessary aper
`tures for providing the initial unitized assembly.
`As will be described in greater detail below, the unit
`ized elements after being joined by bolts, adhesive, or
`the like are further secured together by means of a
`potting compound which completely encapsulates the
`secured members and preferably projects partly into a
`central bore 30 after potting. The bore 30 is then ma
`chined as by lapping to form bearing surfaces 31, 32 in
`the end caps 25, 26 and also to form a smooth bore 33
`through the lamination stack 27, contiguous with the
`bearing surfaces 31, 32. Retaining rings 35, 36 secure the
`rotor assembly in the stator assembly. The front end cap
`26 has a flange 37 which in turn has a machined surface
`38 with a mounting boss 39 to locate the motor in a
`mounting bracket. Mounting holes 40 provide means
`45
`for mounting the motor to its bracket (not shown). The
`rear end cap 25 is provided with an electrical connector
`41 for supplying power to the stator windings.
`As shown in FIG. 2, the rotor assembly 22 includes a
`rotor shaft 50 which supports a rotor section 51, (i.e.,
`the portion of the rotor which is magnetically active)
`and outboard bearings 23, 24. In the illustrated embodi
`ment, the rotor comprises toothed lamination sections
`52, 53 separated by a permanent magnet 54. The magnet
`is positioned to provide the lamination sections 52, 53
`with opposite magnetic polarities, for example, making
`lamination section 52 a north pole and lamination sec
`tion 53 a south pole. The laminations are formed with
`external teeth, of the same pitch as the teeth associated
`with the stator assembly. The teeth of section 53 are
`offset by- one half pitch with respect to the teeth of the
`section 52 in order to form a hybrid permanent magnet
`rotor. Thus, when the stator windings are energized by
`drive current coupled through connector 41, the rotat
`ing magnetic ?eld which is produced in the stator tends
`to successively align the rotor lamination sections 52,
`53, with the ?eld, causing the motor to step in sequence
`with the rotor ?eld. Control of the rotational rate and
`
`6
`direction of the stator ?eld thus allows control of the
`rate and direction of rotor rotation.
`Turning now to FIG. 3, there is illustrated the pro
`cess for fabricating a motor in accordance with the
`present invention. Concentrating ?rst on the rotor as
`sembly, it is seen that the primary raw materials which
`go to make up the rotor are brought together at process
`step 100, and include rotor shafts, rotor laminations (or
`prestacks) and magnets. Those items are assembled at a
`step 101 and the assembled rotor which results is best
`illustrated in FIG. 4. There is shown a rotor shaft 50
`having a pair of lamination stacks 52, 53 disposed
`thereon, with a permanent magnet 54 interposed be
`tween the lamination stacks forming a rotor section 51
`intended to be driven by the rotating magnetic ?eld
`produced by the stator. In a hybrid permanent magnet
`stepping motor, the rotor laminations 52 and 53 have
`alternate teeth and valleys of a given pitch correspond
`ing to the stator pitch, and the teeth in the sections 52
`and 53 are offset with respect to each other by one-half
`pitch. The magnet 54 serves to magnetically polarize
`the stacks 52, 53 with, for example, the stack 52 being a
`north pole and the stack 53 being a south pole.
`The shaft 50 has a pair of machined sections 60, 61
`adapted to receive the inner race of bearings for support
`of the rotor. The shaft 50 can have its output end keyed
`as illustrated or unkeyed if desired, and the motor can
`also be con?gured with an output shaft on the rear end
`to form a double-ended motor. Such constructional
`details form no part of the present invention and will
`not be emphasized herein.
`Having assembled the rotor 22 in the step 101 (FIG.
`3), the rotor is then passed to a grinding station where
`step 102 is performed to grind the rotor outer diameter.
`Such grinding tends to produce teeth in the lamination
`stacks 52, 53 which have relatively sharp corners. In
`addition, the grinding step produces a rotor which is
`substantially concentric and therefore can operate in a
`carefully machined stator bore with a relatively small
`air gap.
`Having thus con?gured the rotor magnetic section
`51, and after machining debris is cleaned from the rotor,
`a step 103 is then performed in which bearings 22, 23 are
`assembled onto the bearing support surfaces 60, 61 of
`the rotor. In the exemplary embodiment, spacer bush
`ings 62, 63 are interposed between the bearings 23, 24
`and the lamination stacks 52, 53 respectively. The bush
`ings ride between the lamination stack and the inner
`race of the bearings to form a spacer element to prop
`erly locate the bearings on the shaft. The bearings are
`press ?t on the shaft, preferably in an appropriate ?x
`ture, in the step 103. Referring to FIG. 5, there is shown
`the rotor assembly including bearings 23, 24 and the
`spacing bushings 62, 63, providing a rotor assembly
`which is ready for insertion into a stator assembly. FIG.
`5 illustrates, in somewhat exaggerated fashion, the fact
`that the outer diameter of the bearings 23, 24 is slightly
`greater than the outer diameter of the rotor section 51.
`It was previously noted that the stator bore is a continu
`ous straight through bore formed in a single operation
`after assembly of the stator. Thus, providing the bear
`ings 23, 24 with a slightly greater outer diameter than
`the rotor section 51 allows the entire rotor assembly to
`be inserted into the bore, with the outer race of the
`bearing 23, 24 seating in the bearing surfaces in the end
`caps while the rotor section 51 has a suf?cient, although
`a very small, clearance for rotation. The precision thus
`achieved allows the motor to be con?gured with a
`
`55
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`65
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`Page 11 of 17
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`

`

`7
`relatively small air gap, thus allowing highly efficient
`operation.
`As illustrated in FIG. 3, the initial raw material com
`ponent for the stator assembly procedure is individual
`stator laminations which are assembled in a step 105. An
`individual lamination 27a is illustrated in FIG. 6. It is
`seen that each lamination, which can be formed by
`stamping, has a series of poles 66a with a plurality of
`teeth 670 formed on each of the poles. In a hybrid per~
`manent magnet stepping motor, the pitch of the teeth
`67a is the same as the pitch of the rotor teeth. The poles
`660 are separated by gaps 68a which provide an area for
`receiving the stator windings. The laminations also
`have punched clearance holes 69a through which the
`bolts 28 can pass for initially registering the stator as
`sembly. Preferably a clearance hole 69a is associated
`with each pole 660 such that the stator laminations are
`symmetrical and can be installed in any of eight orienta
`tions. Thus, it is possible in assembly to turn the stator
`laminations with respect to each other such that the
`grain of the steel from which the laminations are made
`is not in a single direction, allowing the magnetic prop
`erties of the lamination stack due to grain to be aver
`aged.
`As illustrated in FIG. 7, the step 105 (FIG. 3) is im
`plemented by assembling a stack of laminations of a
`predetermined height and af?xing the laminations to
`gether, in the illustrated embodiment by means of welds
`70. Alternatively, prestacks, i.e., groups of laminations
`joined by stamped dimples formed during the lamina
`tion stamping operation may be used. Using the welding
`technique, preferably a stack of laminations is placed
`under pressure, and automatic machinery gauges that
`the lamination stack is of the appropriate height before
`the welds are made. If it is not laminations are either
`added or removed until the desired height is obtained at
`which point automatic welding equipment preferably
`applies four welds 70 at comers of the lamination stack
`displaced 90 degrees from each other. As seen in FIG.
`7, the assembled lamination stack thereupon provides a
`pole structure 66 separated by inter-pole winding gaps
`68, each pole structure having axially disposed teeth 67
`of a predetermined pitch. It is also seen that the clear
`ance holes 69 are aligned such that an assembly bolt or
`potting injection needle can pass through the lamination
`stack at the appropriate point in the assembly process.
`After the lamination stack is assembled, and in the
`optional case where an “enhanced” motor is to be pro
`duced, in a step 105' elongate magnetic strips are in
`serted in each gap 85 between stator teeth 67 (see, for
`example, FIG. 12). As will be described below, the
`magnets which are inserted between stator teeth tend to
`enhance the magnetic properties of certain classes of
`motor. The magnetic strips have sufficient frictional
`engagement with and magnetic attraction for the gaps
`into which they are inserted to temporarily maintain the
`strips in place during subsequent manufacturing steps
`until they are ?rmly secured in their gaps by means of
`injected potting material.
`Following the magnet insertion step 105' if per
`formed, or the simple welding of the lamination stack
`105 for a non-enhanced motor, as shown in FIG. 3
`subsequent operations are performed on the assembled
`lamination stack to associate the stator electrical com
`ponents with the stack. In other words, the stack is
`insulated, wound, and the windings are terminated. In
`FIG. 3 the insulation step is indicated at 106. Preferably
`discrete insulators are supplied along with the welded
`
`45
`
`55
`
`65
`
`4,922,604
`
`b.
`
`25
`
`8
`stator lamination stack in order to provide appropriate
`insulation. Turning brie?y to FIG. 8, one end of the
`insulator assembly is schematically illustrated at 71 and
`is shown to completely line the slot 68 as well as to
`cover the face 72 of each pole 66. Upstar'iding insulator
`sections 71' will interface with the end cap when they
`are juxtaposed and bolt protectors 71" insulate the
`through-bolts 28 and prevent contact between the bolts
`and the windings. A mating end for the insulator is
`illustrated in FIG. 10 at 90. It is seen that the insulator
`90 is similar to the insulator 71 in that it provides protec
`tors 91 for the through bolts, a face 92 for insulating the
`end of the pole, channels 93 which completely line the
`inter-pole slots, and upstanding projections 93' for inter
`facing with the associated end cap. In addition, the
`insulator 90 includes connector means 94 for terminat~
`ing the windings as will be described below and up
`standing standards 94’ which serve two purposes. First
`of all, they provide a seat on which the circuit board
`which carries the connectors for mating with the con
`nector means 94 seats, and secondly they provide a path
`for jumper walkers connecting a pair of coils, keeping
`the jumper wires in a controlled safe location where
`they will not short with other elements of the’ motor.
`More particularly, in many motors the automatic wind
`ing equipment winds one coil and then is moved to
`another pole, carrying the wire along to wind a second
`coil before the second end of the wire is terminated. In
`that case, the wire is brought by automatic winding
`equipment around the outside of the adjacent standard
`94' and the inside of the bolt protector 91 so that it is
`restrained to the outside of the stator assembly but as
`sured to be free of contact with the through bolt.
`Having thus insulated the pole structure, windings
`schematically illustrated at 73 are applied, preferably
`automatically, to each of the poles in a step 107 (FIG.
`3). It will be appreciated that in the typical case a wind
`ing of signi?cant dimension (more significant than illus
`trated in FIG. 8) will build up in order to get the neces
`sary turns on each pole. It is seen, however, that the
`turns are insulated from the magnetic structure by
`means of the insulator 71. In addition, when the auto
`matic winding equipment winds two coils before termi
`nating the winding, the exposed inter-pole connection is
`routed between the standards 94' and the bolt protec
`tors 91 as described above. The automatic winding
`equipment which forms the coils 73 also preferably
`automatically terminates the coils in the connectors 94.
`In the preferred embodiment, the coils are bifllar
`wound, and each connector 94 provides for terminating
`two individual wires. Thus, at the start of the winding,
`the automatic winding equipment lays the beginning
`end of a coil into slot 95, then winds two of the poles,
`then lays the end of the coils in a further slot 950 in a
`second one of the connectors.
`With all of the coils wound, and the beginning and
`ending ends of the coils inserted in appropriate slots 95,
`950, a step 108 (FIG. 3) is then performed to terminate
`the windings. In the illustrated embodiment the termi
`nation is accomplished via a printed circuit board 75
`which carries the connector 41 and which also carries a
`plurality of tabs 76 connected to appropriate pins of the
`connector 41 by means of printed circuit board connec
`tions. In performing the termination step 108, as best
`shown in FIG. 11, the printed circuit board is put in
`place over the connectors 94, and the tabs 76 forced into
`the connectors 94. Using the illustrated terminating
`means, when