Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a switching apparatus
for a machine responsive to a source of DC power, and more
particularly the type of machine having interacting rotor
and s-tator assemblies which rotate relative to each other
wherein the stator has a winding having a plurality oE
energizeable coils, the coils having an annular array of
commutator bars associated therewith for supplyina
electrical power thereto, and the rotor having a `
magnetic assembly associated therewith. ~ -
This is a division of copending Canadian Patant
Application Serial Number 234,456, filed August 29, 1975.
According to the apparatus of the present invention,
there is provided first and second annular brush rings
associated with the rotor and first an~ second brush means
associated with the stator for respectively coupling the
first and second brush rings to opposite polarities of
the DC source. First roller contact means is associated ;
with the rotor and is electrically connected to the first -
brush ring for progressively and sequentially engaging the
commutator bars to thereby momentarily couple the commutator
bars to the first brush ring. Second roller contact means
is assa~i~ted with the rotor and is electrically connected
to the second brush ring for progressively and sequentially
engaging the commutator bars thereby momentarily couple the -~
commutator bars to the second brush ring. The first and
second roller contact means having contoured outer surfaces
adapted to mate with the complementary contoured inner
surfaces of the commutator bars.
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BRIE~ DFSCRIPTION OF THE DR~WINGS
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Figure 1 is a sec-tional view of a DC machine
of the "inside-~ut" type;
Figure 2 is a partially sectionalized detail .
view of the roller contact assembly of Figure l;
Figure 2a is a partial end view of the roller
contac-t assembly of Figure 2; . :-
Figure 3 is an end view of the rotor permanent
magnet assembly of Figure l;
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Figure 3a is a side view of the permanent magnet
assembly of Figures 1 and 3 illustrating the manner of assembly;
Figure 4 is a partially sectionalized end view of
a molded commu-tator array;
Figure 4a is a partial front view of the commutator
bar array of Figure 4;
Figure 4b shows a detailed sectional view of one
bar of the commutator bar array of Figure 4;
Figure 5 is a simplified diagrammatic view of a DC
machine of modular design;
Figure 6 is a simplified diagrammatic view of a DC
machine for use in high speed operation;
Figure 7 is a partially sectlonalized detail view
of another roller contact assembly for use with the machine
of the Figure l;
Figure 8a is a top view of a rotor lamination
for use in the present invention, and ~ :
Figure 8b is a sectional view of a machined, cast
rotor of the present invention employing the lamination of
20 Figure 8a. `~
DETAILED DESCRIPTION
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Figure 1 shows an inside-out DC motor 10 which is ~:
comprised of hous~ng members 11 ~nd 12 which are eachprovided :~ :
with openings lla and 12a for receiving bearings 13 and 14
which surround a rotatably mounted rotor shaft 15. The inner
ends of housing members 11 and 12 are hollow and are contoured ~: ~
or otherwise formed to receive and suppor-t the stator and :
rotor assemblies.
The stator assembly is comprised of a laminated core
16 formed of individual laminations 16a. The stator winding
is comprised of a plurality of coils 17 (not shown in detail
for purposes of simplicity) which, when energized, create
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magnetic fields in -the stator core which interact with the
magnetic fields set up ;n the rotor assembly to effect rotor
rotation.
Housin~ member 12 is further adaptecl to receive the
commutator assernb]y 18 whieh includes a plurality of comrnu-tator
bars 19 mounted in radial fashion (see Figures 4-4b) within
annular-shaped molded insulating ma-terial 42, Selected ones
of the commutator bars are electrically connected to the encl
terminals of associated stator coils. As shown in Figure ~a,
the commutator bars 19 are skewed at a small angle ~ so that
a roller contact moving left to right with respect to Figure
4a will effect a make-before-break contact with the commutator `~
bars. In addition, skewing the commutator bars provides à
smooth rolling surfaee for the roller contact so that it w~ill
mate smoothly with the inside surface of the commutator.~
As shown in Figure 1, the rotor assembly comprises
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a permanent magnet arrary secured to shaft 15. The outer peri-
phery of the permanent magnet array lies a small, spaced dis- -~
tanee from the interior periphery of the stator core 16 to form
a hollow, annular-shaped air gap G therebetween
Referring now to Figures 2-2a, the details of roller
eontaet assemblies 22 will be explained. Unitary insulating
sleeve 20 is mounted on rotor shaft 15 (see also Figure 1)
- and has an annular reeess 20a for positioning floating roller
platform 30 whieh is resiliently mounted to sleeve 20 by
springs 31 and 31'. Support arms 30a and 30b respectively
support roller shaft 32 and contact 33. Spring 3~ urges -
roller 35 towards eontact 33. In the event of excessive wear,
that portion of roller 35 bearing against contact 33 may be
fitted with a plug of highl~ conductive, low resistance material.
The arms 30a and 30b are slidably supported by the slo-ts 20c
provided in upright supports 20b arranged at spaced intervals
about sleeve 20.
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Conductive roller 35 is provided with hollow elongat-
ed passageways 35a parallel to the rotating axis and which
extend to both sidewalls of the roller. The passageways
communicate with radially aligned passageways 35b which open
onto the cylindrical surface of the roller.
Fan blades 36 are molded into sleeve 20 and are
interspersed between adjacent pairs of rollers.
Sleeve 20 supports continuous brush rings 23 and 24,
each of which is electrically connected to selected ones of
10 the roller assemblies 22 by flexible conductors 37, 37a
Brushes 25 and 26 are spring loaded and mounted upon the stator
assembly. They engage brush rings 23 and 24 respectively.
The brushes are, in turn, connected to opposite polarities -~
of a DC power source ~not shown). While depicted in Figure 1
as disposed to one side of the roller contact assemblies 22,
brush rings 23 and 24 may be positioned on opposite sides of
the roller contact assemblies, if desired.
The rolling engagement between rollers 35 and the
bars 19 of the commutator array rotates the rollers creating
a centrifugal force which causes air to be drawn into the
side openings of passageways 35a and urged out of radial
passageways 35b. The rapidly moving air blows dust and/or
other conductive particles away from the commutator array. ~;
Blades 35 serve the same function.
Rollers 35 of roller contact assemblies 22 progress-
ively rollingly engage the commutator bars 19 while brushes
25 and 26 wipingly engage conductive rings 23 and 24, whereby
the electrical path extends from one terminal of the DC source
to brush 25, brush ring 23, flexible conductor 37, contac-t 33,
conducting roller 35 and the commutator bars 19. The opposite
polarity of the DC source is coupled to brush 26, brush ring 24,
flexible conductor 37a, roller (spaced from roller 35 of
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Figure 2) and commuta-tor bars 19. The end terminals of the
stator winding are thus progressively energized and the mag-
netic field generated thereby interacts with the magnetic field
of the rotor permanent magnet structure to sustain rotation.
The commutator bar array of Figures 4-4b contributes ,!
to the blower action by providing gaps 40 between adjacent
bars 19. Each commutator bar has a roller contact portion l9a
and upright arms l9b and l9c. Arm l9b extends inwardly at l9d
to secure commutator bar l9 to insulating material 42, Terminals
10 of the stator windings are connected to commutator bars l9 at ~ -
l9e. The bars l9 are embedded in an insulating material 42
which extends partially into each gap 40 and engages one wall of
each bar. For example, molded portion 40a engages one sidewall
of bar l9' and is spaced from the adjacent sidewall of bar l9''.
Particles falling into gap 40' and collecting in the bottom-
most portion are prevented from creating an electrical path
between bars l9' and 13'' due to the presence of molded insulat-
ing portion 40a. The blower action created by fan blades 38
and~or rollers 35 keeps gaps 40' clear of particles.
Figures 3 and 3a show the rotor permanent magnet
structure in greater detail. The permanent magnet structure -;
comprises a plurality of laminated ironpole piece assemblies
44 each having individual pole pieces 45 ~see also Figure l)
and each having an arcuate outer periphery and radially aligned
s~des 44b and 44c. Each pole piece is provided with an opening
44e. The s~dewalls of laminated assemblies 44 are em~raced
by solid rectangular-shaped permanent magnets 46.
- Rotor shaft 15 has a hexagonal-shaped cross section
extending the length of the permanent magnet assembly and is
preferably formed of a magnetic material such as, for example,
soft iron. Elongated rectangular-shaped permanent magnets 47
are positioned in pole pieces 45 and an associated surface lSa
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oE rotor shaEt 15. The magnets 46 are preEerably rare-earth
magnets whlch resist demagneti~ation, provide be-tter impedance
matching and serve to increase flux density across -the air gap
G ~see Figure 1). ~lagne-ts ~7 are preferably Alnico-8 magne-ts.
T~le magnet members 46, 47 and 46 embrace pole pieces 45 and
serve to concentrate the flux density in the air gap G.
Figure 3a shows the manner of assembly of the rotor
permanent magnet structure. End caps 49 and 50, rods 51 and
fastening nuts 52 hold the permanent magnet assembly together.
Set screws 53 and 54 engage tapped openings in collar portions
49a and 50a of the end caps 49 and 50 to lock the assembly to
shaft 15.
Figure 5 shows a DC machine 60 of modular design
comprised of a hermetically sealed housing 61 having internally
mounted bearings 62 and 63 for rotatably mounting shat 15.
The permanent magnet assembly 23, which is preferably of the
type shown in Figures 3 and 3a, is mounted upon rotor shaft 15.
The stator assembly has a laminated core 16 comprised of
individual laminations 16a. The stator winding is comprised
of a plurality of coils 17 ~not shown in detail) which,
when energized, create magnetic fields in the stator core
which interact with the magnetic fields set up by the
rotor permanent magnet assembly to effect rotor rotation.
The end terminalsl7a and 17b of the stator coils are led out
of the hermetically sealed housing and terminate at a hermeti-
cally sealed terminal assembly 64 molded into side face 61a
of housing 61.
A second housing 65 has molded or otherwise provided
along one side wall 55a a mating terminal assembly 66 which is
releasably inserted into terminal assembly 64. Housing 65
is provided with bearing assemblies 67 and 68 for rotatably
mounting shaft 69. Roller contact assemblies such as, for
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example, 70 and 70' and brush rings 71 and 72 are mounted on
insulating sleeve 73 which encircles shaft 69. S-tationary
mounted brushes 74 and 75 are secured within housing 65 and
respectively wipingly engzge rings 71 and 72. Opposite polarities
of a DC source are electrically connected -to brushes 74 and 75
by conductors 76 and 77 which extend between brushes 74 and 75
and the e~terior of housing 65. Flexible conductors 78 and 79
electrically connect brush rings 74 and 75 to spring loaded con-
tacts 80 and 81 which engage roller contacts 82 and 83 respect-
ively.
Roller contacts 82 and 83 are preferably of the typeshown in Figures 2 and 3 and operate to sequentially rollingly
engage stationary mounted commutator bars 84 mounted within
housing 65 and which are preferably of the type shown in
Figures 4-4b. The commutator bars are selectively coupled to
the stator coils 17 through conductors 85j terminal assemblies
66 and 64 and conductors 17a-17b. A permanent magnet member
86 is secured to rotor shaft 15 and is positioned in housing 61
immediately adjacent side wall 61a. A second permanent magnet
member 87 is secured to shaft 69 and is positioned in housing
65 immediately adjacent side wall 65a and ad~acent to member
86.
In operation, the DC source is progressively and
sequentially coupled to coils of the stator-mounted hermeti-
cally sealed housing 61 through leads 76-77, brushes 74-75,
brush rings 71-72, conductors 78-79, contacts 80-81, conduct-
ive rollers 82-83, commutator bars 84, leads 85-86, terminaI
assemblies 66 and 64 and conductors 17a-17b. The magnetic
fields created by coils 17 interact with the fields of the
permanent magnet structure 23 in air gap G to effect rotation.
The rotation of shaft 15 rotates magnetic member 86. The
magnetic coupling between members 86 and 87 imparts rotation
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to shaf-t 69 causiny the roller contac~ assemblies 70-70'
and commutator bars 84 to progressively switch DC power to
successive stator coils.
Hermetically sealed housing 61 keeps the rotor and
stator assemblies, which are practically wear-free, safe from
contamination by dust or dirt. Housing 65, ~owever, is design-
ed to be accessible for servicing. Alternatively, housing 65
may comprise a replaceable unit. Whlle housing 61 is shown as ~`
containing the load 88 driven by rotor shaft 15, rotor shaft
15 may extend beyond the left-hand side ~all 61b of housing 61
and an appropriate seal may be provided to ~eep the housing -~
interior hermetically sealed. The magnetic member 86 may also
be eliminated and lnstead rotor shaft 15 extended beyond the
right-hand side wall 65a upon providing a similar seal. The
magnet member 87 of shaft 69 may then be eliminated and replaced
by keying means on the left-hand end of shaft 69 for locking
shaft 69 to rotate with rotor shaft 15.
Figure 6 shows a DC motor 100 adapted ~or use in ~
high speed applications. It comprises a housing 101 which con- ~ `
tains bearings 62 and 63 for rotor sha~t 15 which has a perma-
nent magnet assembly 23 mounted thereon. The stator comprises
a laminated core 16 having lndi~idual laminations 16a. The
stator coils 17 are electrically connected to selected commu-
tator bars 84 by leads 17a-17b. A pair of brush rings 71 and 72
are ~ounted upon rotor shaft 15 and are respectively wipingly
engaged by brushes 74 and 75. Leads 76 and 77 electrically
connect brushes 74 and 75 to opposite polarities of a DC source.
P~oller support assemblles 102 and 103 support roller
contact shafts 104 and 105 which rotatably mount conductive
rollers 106 and 107. Spring mounted contacts 108 and 109
are secured to supports 102 and 103 and electrically connect
brush rings 71 a~d 72 to rollers 106 and 107 by conductors
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110 and 111. The bars 8~ of the co~nutator array are secured
in stationary fashion and are selectively connected to end
terminals of the stator coils 17 by leads 17a-17b. Conductive
rollers 106 and 107 which may be of the type shown in detail
in Figures 2 and 2a, rollingly engage the outer peripheries of
commutator bars 84.
The diameter of rotor shaft 15 is made as small as
practical under the commutator array while the outer diameter
of conductive rollers 106 and 107 is made as large as practical.
This arrangement, in one preferred embodiment, reduces the
angular velocity of the conductive rollers to less than one-half
the angular velocity of rotor shaft 15, thereby providing a
motor design which is advantageous for use in applications
requiring high speed rotation. Since the distance traveled
rollers 106 and 107 during one revolution of rotor shaft 15
is 2 ~f times the outer diameter of the commutator bar array,
then for the angular velocity of rollers 106 and 107 to be
less than the angular velocity of rotor shaft 15 the diameters
of rollers 106 and 107 must be greater than the outer diameter
of the commutator bar array.
It has been discovered in connection with the roller
commutating systems of the type disclosed in my U, S. Patent
No. 3,819,964 and in Figures 1, 2, 5 and 6 herein that if
the longitudinal axis of the roller contact is not parallel
to the longitudinal axis of the rotor then substantial forces
are generated which tend to drive the roller along its longi-
tudinal axis until slippage occurs be-tween the roller contact
and the commutator bar array. Indeed, at higher rotational
speeds when the centrifugal force on the roller is greater
and the roller is pressed harder against the commutator bar
array the forces tending to drive the roller along its axis
are increased. To overcome this difficulty a novel roller ,~
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commutating syste~ has been devised whereby both the roller
and the commu-tator bar array are contoured in complementary
fashion so as to contain the travel of the roller while ensur-
ing continued electrical contact therebetween.
This novel commutating system is illustrated in
Figure 7 wherein the same numerals designate the same parts
previously described in connection with Figures l, 2 and 4.
Attached to sleeve 20 is a flat, conducting spring 115 which
may be formed from a beryllium-copper alloy. Flexible conductor
37 connects spring 115 with brush ring 23. Attached to spring
115, e.g., by soldering, is a conducting tube 116 which also
may be formed from a beryllium-copper alloy. Roller contact 35
is fitted over conducting tube 116 and is free to rotate thereon.
The outer surface of roller 35 is curved and mates with the
complementary curved inner surface of commutator bars 19. In
this manner the roller is free to "rock" about its axis while
maintaining contact with the commutator bars. Although not
shown for purposes of simplicity, roller 35 has passageways
for blowing dust and dirt from the commutator bars as shown -
i~ Figures 2 and 2a and the commutator bars 19 have the confi-
guration shown in Figures 4, ~a, and 4b. In addition, Figure
7 illustrates but one of several pairs of similar roller
commutating assemblies which sequentially couple opposite
polarities of the DC sourcs to pairs of commutator bars connect-
ed to the ends of individual windings. ;
Turning now to Figure 8a there is shown full scalea rotor lamination 200 preferably of 1010-1020 steel and about
0.02 inches thick. Lamination 200 has a first set of equally
.
spaced openings 201 adapted to receive pieces of rare earth
magnet material. Lamination 200 also has a second set of
equally spaced openings 202 adapted to receive non-ferrous
casting material, preferably molten aluminum, during the ;;-
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casting step. Each of the first set of openings has lips or
flanges adapted -to retain the pieces of rare earth magnet
material. .
In manu~acturina the rare earth magnet rotor of the
present invention a stack of laminations 200 of desired size,
for example 4 inches, is assembled in a mold. ~ext, the
pieces of rare earth magnet material are inserted into the
slots 201 to build up a column the height of the stack of the
laminations. The pieces of rare earth magnet material are
typically 0.5 inches by 0.8 inches by 0.4 inches so that, in
the present illustrative embodiment, 10 pieces of the rare
earth magnet material would be required to fill each of the
slots 201. The rare earth magnet material employed is prefer-
ably a cobalt-rare earth intermetallic compound, the preparation
of such compounds and magnets therefrom being disclosed in
Benz U. S. Patent ~os. 3,655,~63, issued April 11, 1972, 3,655,
46~, issued April 11, 1972 3,695,945, issued October 3, 1972
and Benz et al U. S. Patent No. 3,684,593, issued ~ugust 15,
1972 and all granted to General Electric Company. The rare
earth magnet material for use in the present invention must
be "virgin", i.e., it must be processed so as not to contain
any significant magnetic field. It is permissible, however,
if the rare earth magnet material possess very weak residual
magnetic fields due, for example, to the presence of the
earth's magnetic field during formation of the virgin rare
earth magnet material. If the rare earth magnet material
is not virgin then the extxemely high coercive force of this
material renders impractical developing sufficient flux densities
to alter the magnetiZation thereof in situ, after casting.
~ather than assembling a complete stack of laminations
followed by filling up the slots 201 with pieces of rare earth
magnet ma-terial, the formation of the stack and insertion of
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tne pleces of rare ear-th magnet ma-terial may proceed in-ter-
mit-tently. The order is not critical and is merely a matter
of choice.
~ fter tlle laminationsand pieces of rare earth magnet
material have been assembled a shaft is preferably positioned
at the center of the array, the longitudinal axis of the shaft
being coincident with the longitudinal axis o the stack of
laminations. The shaft may be of ferrous material such as steel.
The assembly comprising the laminations, the pieces
of virgin rare earth magnet material and the rotor shaft is
now ready for castiny using a non-ferrous material, preferably
aluminum because of its light weight, low cost, high strength
and high melting point. The molten aluminum flows into the
center section of the stack of laminations and into the second
set of slots 202, thereby rendering rigid the rotor structure.
It also locks the pieces of virgin rare earth magnet material
into the slots 201 and has the effect of reducing any retained
residual magnetism possessed by the rare earth magnet material.
Finally, it makes the rotor shaft an integral part of the rotor
structure.
After casting, the rotor is machined so as to remo~e
those portions of the laminations radially aligned with the
slots 201, thereby forming a plurality of separate pole pieces
equally spaced around the rotor. Figure 8b shows in cross
section the machined, cast rotor~ The slots 201 are now filled
with pieces of virgin rare earth magnet material 203 while
the slots 202 are filled with aluminum, which also surrounds
the rotor shaft 204.
The cast rotor with the virgin rare earth magnet ~;~
material is now ready for magnetization. This virgin rare
earth magnet material can be saturated with between about
12,000 and about 18,~00 oersteds to develop a field strength of
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be-tween about 9,000 and about 12,000 gauss. These low values
may be employed because the rare earth magnet material is in a
virgin state. The particular values selected depend on the
type of rare earth magnet material used. The fac-t tha-t the
rare earth material is magneti~e~ in situ in the cast rotor
places certain constraints on the design of the rotor structure.
For example, the rotor pole pieces should be formed fromlamina-
tions, otherwise the eddy current losses during magnetization
would be too great. Moreover, -there must be sufficient iron
available to carry the flux so as to saturate the pieces of
rare earth magnet material. Thus, the poles must contain more
iron than is necessary to carry the flux out from the rare
earth magnets into the stator during operation of the motor.
The amount of iron required in the poles also depends upon
the geometry of the pieces of rare earth magnet material.
The longer the dimension of the rare earth magnet material in
the radial direction, the more pole section area that is requir-
ed. Accordingly, to ensure proper magnetization of the rare
earth magnet material the rotor sections should have an area
adequate to provide full saturation to the innermost radial
por~ions of the rare earth magnet material. Thus, the rotor
pole section area may be 1.5 times that necessary to carry
the flux out from the rare earth magnets into the stator
during motor operation~ Depending on the geometry of the
rare earth magnet material, the area may be 2 to 3 times
gréater, or more.
After magnetization the field strength of the rare
earth permanent magnets may be adjusted or "trimmedl' by heating
the rotor structure in the absence of significant amounts of
ferrous material so that flux path will not be completed.
Thus, the rotor s-tructure is in an air-stabilized condition
with as low a B/H as practical, e.g., 0.5. This is because
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the per cent of irre~ersible magnetic loss in rare earth
magnets with increasing temperature is a function of the B/H
slope and the lower the slope the sharper the fall-off of both
B and H wi.th temperature. The rare earth magnets in the rotor
structure can be magnetized to increase their magnetic field
up to any portion oE the maximum flux by remagnetizing, pro-
vided that the magnetizing fixture is positioned so that it
energizes the poles in the same direction as during initial
magnetization.
The invention disclosed and claimed herein is not
limited to the specific mechanism and techniques herein shown
and described since modifications will undoubtedly occur to
those skilled in the art. Hence, departures may be made from
the form of the instant invention without departing from
the principles thereof.
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