`Hsu
`
`I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US006081059A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,081,059
`Jun.27,2000
`
`[54] OUTER-ROTOR ELECTRIC MOTOR
`HAVING INNER-STATOR FORMED BY
`CONCENTRICALLY WRAPPING
`FLATTENED STATOR ELEMENTS ON
`STATOR CORE
`
`[76]
`
`Inventor: Chun-Pu Hsu, 19, Wu-Chien Sixth
`Road, Wu-Ku Industrial Park, Wu-Ku,
`Taipei Hsien, Taiwan
`
`[21] Appl. No.: 09/296,691
`
`[22] Filed:
`
`Apr. 21, 1999
`
`Int. Cl.7 ............................. H02K 1/12; H02K 15/02
`[51]
`[52] U.S. Cl. .......................... 310/179; 310/216; 310/218;
`310/259; 310/269; 29/596; 29/597; 29/598
`[58] Field of Search ..................................... 310/254, 259,
`310/41, 216, 218, 269, 156, 194; 29/596,
`597, 598, 609, 605
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,577,851
`3,886,256
`4,102,040
`
`5/1971 Detheridge ................................ 29/596
`5/1975 Ohuchi et al. .......................... 310/216
`7/1978 Rich .......................................... 29/598
`
`4,350,914
`4,395,815
`4,712,035
`4,818,911
`5,642,011
`
`9 /1982 Searle . ... .... ... ... ... ... ... .... ... ... ... .. 310/194
`8/1983 Stanley et al. ............................ 29/598
`12/1987 Forbes et al. .. ... ... .... ... ... ... ... ... 310/269
`4/1989 Taguchi et al. ... ... .... ... ... ... ... ... 310/259
`6/1997 Fanning et al. ......................... 310/216
`
`Primary Examiner-Nestor Ramirez
`Assistant Examiner-Tran N Nguyen
`
`[57]
`
`ABSTRACT
`
`An electric motor of outer-rotor type includes: an inner
`stator mounted on a stator holder, an outer rotor rotatably
`circumferentially disposed around the inner stator, a shaft
`coaxially secured with the outer rotor, and a housing com(cid:173)
`bined with the stator holder for encasing the outer rotor and
`the inner stator within the housing; with the inner stator
`including an annular core made of magnetic conductor, a
`plurality of fin arrays made of magnetic conductors and
`formed as a fin array assembly concentrically wrapped on
`the annular core, and a plurality of insulating coil bobbins
`each coil bobbin pre-wound with the coil windings thereon
`and jacketed on each fin array, thereby forming an inner
`stator having a stable construction, a higher winding
`capacity, higher magnetic flux density and higher output
`power, as well as a lower production cost.
`
`11 Claims, 8 Drawing Sheets
`
`F
`
`A
`L1
`143
`141
`142
`
`X ·~
`
`Mitsuba - 1014
`Page 1 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 1 of 8
`
`6,081,059
`
`52
`
`5
`
`51
`so
`
`40
`
`J"-1
`I
`
`2
`
`FIG. 1
`
`Mitsuba - 1014
`Page 2 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 2 of 8
`
`6,081,059
`
`110A
`
`11
`
`)
`
`x
`L1
`143
`141
`142
`
`FlG.2
`
`Mitsuba - 1014
`Page 3 of 13
`
`
`
`110A
`
`113
`
`1121"'
`
`I /
`
`..--143 .,.+-144
`
`I
`
`14,4
`
`I 14 12 /F;
`
`F,
`
`I
`
`141
`
`I 143 144 I
`
`1_4
`
`14A
`
`FIG. 3
`
`F
`
`143
`
`___,.,
`
`11
`
`11
`
`I 14 143
`;~
`L1
`12
`
`1[,2
`
`d •
`r:JJ.
`•
`~
`~ .....
`~ = .....
`
`~ = ?
`
`N
`~-..J
`N
`C
`C
`C
`
`rF.J. =-~
`~ ....
`0 ....,
`00
`
`~
`
`FIG. 4
`
`114
`
`FIG. 5
`
`0--,
`
`.... = 00
`~ .... = Ul
`
`\C
`
`Mitsuba - 1014
`Page 4 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 4 of 8
`
`6,081,059
`
`,,
`
`14
`
`114
`
`,,
`
`111
`
`113
`
`112
`
`145
`
`114
`
`144
`
`FIG. 6
`
`Mitsuba - 1014
`Page 5 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 5 of 8
`
`6,081,059
`
`F'
`
`14
`~ 4 3 142
`FIG.8~
`
`F
`
`Mitsuba - 1014
`Page 6 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 6 of 8
`
`6,081,059
`
`22
`
`\
`
`-
`
`~
`~
`~
`~
`~
`~
`~
`~
`~
`~
`~
`"-
`
`I
`
`2
`
`-
`
`-
`
`5
`
`-
`
`-
`
`~
`~
`~
`~
`~
`~
`~
`' ....
`
`51
`
`"'-
`
`4
`
`41
`
`FIG.9
`
`Mitsuba - 1014
`Page 7 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 7 of 8
`
`6,081,059
`
`11 10J 16 21
`12
`
`14
`Fi G. 10
`
`13
`
`30
`
`16
`
`10
`11
`
`FIG. 11
`
`FIG. 12
`
`Mitsuba - 1014
`Page 8 of 13
`
`
`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 8 of 8
`
`6,081,059
`
`13
`
`I 't-r°
`
`.
`
`I
`
`•
`
`12
`141
`I
`14f ~43( ?/ rS
`
`I 1'
`.
`
`I
`
`/
`
`/
`I
`, r
`
`30
`I
`
`31
`\
`
`) 5
`
`16a
`
`4
`
`\ \
`, 22
`2
`
`I
`14
`
`M
`
`R
`
`~
`
`T
`
`\
`21
`FIG. 13
`
`)
`
`12
`
`A
`I
`
`112
`10
`FIG.14
`
`FIG. 15
`PRIOR ART
`
`w
`
`Mitsuba - 1014
`Page 9 of 13
`
`
`
`1
`OUTER-ROTOR ELECTRIC MOTOR
`HAVING INNER-STATOR FORMED BY
`CONCENTRICALLY WRAPPING
`FLATTENED STATOR ELEMENTS ON
`STATOR CORE
`
`BACKGROUND OF THE INVENTION
`
`6,081,059
`
`5
`
`2
`FIG. 4 is a sectional drawing of the hinge portion of the
`two linked bobbins.
`FIG. 5 is a sectional drawing of the hinge portion of the
`two linked fin members.
`FIG. 6 is a cross sectional drawing of the fin array
`assembly and coil bobbin assembly when annularly
`assembled.
`FIG. 7 is a perspective view of the inner stator as
`10 exploded.
`FIG. 8 is an illustration of the inner stator as assembled.
`FIG. 9 is a perspective view of the electric motor of this
`invention.
`FIG. 10 is a longitudinal sectional drawing of the present
`15 invention.
`FIG. 11 is a cross sectional drawing of the present
`invention as viewed from 11-11 direction of FIG. 10.
`FIG. 12 is a cross sectional drawing of the present
`invention as viewed from 12-12 direction of FIG. 10.
`FIG. 13 is a longitudinal sectional drawing of another
`preferred embodiment of the present invention.
`FIG. 14 shows another embodiment of the core and the fin
`member of this invention.
`FIG. 15 shows a conventional electric motor with outer
`rotor.
`
`20
`
`A conventional electric motor, such as disclosed in a
`Japanese invention patent application publication (Laid(cid:173)
`open) No. 6-351185 (copy enclosed) as illustrated in FIG.15
`of this application, includes: an inner stator S secured on a
`base B, a plurality of tooth member sets T radially secured
`to an annular yoke Y having coil windings W wound on each
`tooth member set T and limited between two stopping
`fasteners Fr clamped on the tooth member set T, and an outer
`rotor R having magnets M secured thereon rotatably cir(cid:173)
`cumferentially disposed around the inner stator S having a
`shaft A coaxially secured to the outer rotor R.
`However, such a conventional outer-rotor type electric
`motor has the following drawbacks:
`1. Each tooth member set T includes plural tooth members
`clamped by an inner and an outer stopping fastener Fr for
`limiting the coil windings W as wound on the tooth
`members, thereby reducing the winding area and decreas- 25
`ing the coil windings on the stator and decreasing the
`torque output from such an electric motor.
`2. Each tooth member has only an inner lug Tl insertably
`fixed in the annular yoke Y, leaving the outer portion of
`the tooth member unstably suspending (without being 30
`supported) in the air to thereby easily cause vibrational
`shock or influence the magnetic fields between the stator
`and the rotor.
`3. Due to the unstable structure and assembly complexity
`when making the inner stator of such a conventional
`motor, it is merely suitable for making a "thin" or "flat"
`miniature motor, unable for producing a motor of higher
`torque output.
`The present inventor has found the drawbacks of the
`conventional electric motor and invented the present motor 40
`having higher torque output and efficiency.
`
`35
`
`DETAILED DESCRIPTION
`As shown in FIGS. 1-12, the present invention com-
`prises: an inner stator 1, a stator holder 2 for mounting the
`inner stator 1 thereon, an outer rotor 3 rotatably circumfer(cid:173)
`entially disposed around the inner stator 1, a shaft 4 coaxi(cid:173)
`ally secured with the outer rotor 3 about a longitudinal axis
`X defined at a longitudinal center of the stator holder 2, and
`a housing 5 combined with the stator holder 2 for encasing
`the outer rotor 3 and the inner stator 1 within the housing 5
`and the holder 2. The housing 5 may also be eliminated in
`this invention.
`The stator holder 2 includes: a central stem 21 protruding
`longitudinally from a base 22 of the holder 2, with the base
`22 combinable with the housing 5 for encasing the stator 1
`and the rotor 3 within the housing 5 and the holder 2.
`The inner stator 11 includes: an annular core 100 secured
`on the central stem 21 of the stator holder 2, a fin array
`assembly HOA radially mounted on and concentrically
`disposed around the core 100, an insulating coil bobbin
`assembly 14A embedded with the fin array assembly HOA
`and provided for winding a plurality of magnetizing coil
`windings 12 on each insulating coil bobbin 14 of the bobbin
`assembly 14A having electric wires 13 electrically con(cid:173)
`nected between the coil windings 12 and an external power
`supply source (not shown), and a retaining disk 15 for fixing
`the core 100 on the stem 21 of the stator holder 2 by bolts
`16.
`The annular core 100 is formed by laminating a plurality
`of central collar members 10 along a longitudinal axis X
`defined at a longitudinal center of the central stem 21 of the
`stator holder 2; each central collar member 10 made of
`60 magnetic conductor and each including: a central hole 101
`formed in a central portion of the collar member and
`engageable with the central stem 21 of the stator holder 2,
`a plurality of recesses 102 circumferentially recessed and
`equally spaced in a periphery of the collar member each
`65 recess 102 being formed as a "1" shape, an inversed T (not
`shown) shape or any other suitable shapes, and a plurality of
`bolt holes 103 formed in the collar member 10 adapted for
`
`SUMMARY OF THE INVENTION
`
`The object of the present invention is to provide an
`electric motor of outer-rotor type including: an inner stator 45
`mounted on a stator holder, an outer rotor rotatably circum(cid:173)
`ferentially disposed around the inner stator, a shaft coaxially
`secured with the outer rotor, and a housing combined with
`the stator holder for encasing the outer rotor and the inner
`stator within the housing; with the inner stator including an 50
`annular core made of magnetic conductor, a plurality of fin
`arrays made of magnetic conductors and formed as a fin
`array assembly concentrically wrapped on the annular core,
`and a plurality of insulating coil bobbins each coil bobbin
`pre-wound with the coil windings thereon and jacketed on 55
`each fin array, thereby forming an inner stator having a
`stable construction, a higher winding capacity, higher mag(cid:173)
`netic flux density and higher output power, as well as a lower
`production cost.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an exploded view showing the elements of the
`present invention.
`FIG. 2 is an illustration showing flattened fin array
`assembly and coil bobbin assembly of the present invention.
`FIG. 3 is a front view from FIG. 2.
`
`Mitsuba - 1014
`Page 10 of 13
`
`
`
`6,081,059
`
`3
`passing each bolt 16 through each bolt hole 103 for coaxially
`fixing the core 100 on the stem 21 of the stator holder 2 as
`shown in FIGS. 10 and 8; with all the recesses 102 longi(cid:173)
`tudinally or linearly aligned when all the core members 10
`are laminated to form the core 100 as shown in FIGS. 7 and
`8. Besides, other joining methods, rather than the
`lamination, may be used for forming the core 100 including
`at least a core member 10.
`The fin array assembly 110A includes a plurality of fin
`arrays 110 juxtapositionally linked together to be a linear 10
`chain-like arrangement having a cross section defining a
`flattening line L2 (FIG. 2) projectively perpendicular to the
`longitudinal axis X of the stem 21 of the stator holder 2, with
`each fin array 110 generally parallel to the longitudinal axis
`X of the stator holder 2.
`Each fin array 110 is formed by laminating a plurality of
`radial fin members 11 juxtapositional or parallel to the
`longitudinal axis X of the stem 21 of the stator holder 2; each
`radial fin member 11 made of magnetic conductor, formed as
`an arcuate T shape and each including: a shank portion 111,
`an engaging root portion 112, which may be formed as a "1"
`shape, an inversed T shape, a ratchet tooth shape or any other
`suitable shapes, formed on a bottom end of the shank portion
`111 and engageable with each recess 102 (formed as "1" or
`inversed T shape, ratchet tooth shape or other shapes) in
`each collar member 10 for radially mounting the fin array
`110 on the annular core 100 of the inner stator 1, and a rod
`portion 113 perpendicularly formed on a top end of the
`shank portion 111 to form the T-shaped fin member 11; with
`all radial fin members 11 superimposed longitudinally to 30
`form the fin array 110 (FIG. 2) to be juxtapositional to the
`longitudinal axis X defined at the longitudinal center of the
`core 100 and of the stem 21 of the holder 2. Every two
`neighboring fin members 11 of the corresponding two fin
`arrays 110 are linked by a hinge portion 114 having thin 35
`thickness between two rod portions 113 of the two fin
`members 11 (FIG. 5) to form a folding line F' between the
`two fin members 11, with each folding line F' parallel to the
`longitudinal axis X of the holder 2; whereby upon a con(cid:173)
`centric curving of the fin array assembly 110A about the axis 40
`X, the fin array assembly 110A will be concentrically
`wrapped on the core 100 as packed by the coil bobbins 14
`of bobbin array 14A.
`The insulating coil bobbin assembly 14A includes a
`plurality of insulating coil bobbins 14 juxtapositionally 45
`linked together to be a linear chain-like arrangement having
`a cross section defining a flattening line Ll (FIG. 2) pro(cid:173)
`jectively perpendicular to the longitudinal axis X of the
`stator holder 2, with each coil bobbin 14 generally parallel
`to the longitudinal axis X of the holder 2. Each insulating 50
`coil bobbin 14 is made of electrically insulative material
`having its cross section generally formed as an I shape,
`including: a central slot 140 longitudinally formed in an
`elongate reel portion 141 and engageable with the shank
`portion 111 of each radial fin member 11 of the fin array 110 55
`when inserting each root portion 112 of each fin member 11
`through the central slot 140 to be protruded downwardly
`beyond the central slot 140, a centripetal flange 142 per(cid:173)
`pendicularly formed on a bottom portion of the reel portion
`141 and engageably ridable on a periphery of the core 100, 60
`and a peripheral flange 143 perpendicularly formed on a top
`portion of the reel portion 141 for retaining the rod portion
`113 of each radial fin member 11 when engaged with each
`coil bobbin 14; whereby upon insertion of the shank portions
`111 of the fin members 11 of the fin array 110 into the central 65
`slots 140 of the insulating coil bobbins 14 to protrude the
`root portions 112 of the fin members 11 of the fin array 110
`
`4
`beyond the centripetal flanges 142 of the bobbins 14, and
`upon engagement of the root portions 112 of the fin array
`110 with the recesses 102 as recessed in the collar members
`10 of the core 100; the fin array 110 will be radially mounted
`5 on the periphery of the core 100 having the insulating coil
`bobbins 14 packed and retained between the rod portions
`113 of the fin array 110 and the periphery of the core 100.
`Every two neighboring coil bobbins 14 are linked by a
`hinge portion 144 as shown in FIG. 4 having thin thickness
`between two peripheral flanges 143 of the two coil bobbins
`14 to form a folding line F between the two coil bobbins 14,
`with each folding line F parallel to the longitudinal axis X
`of the holder 2. Upon concentric curving of the bobbin
`assembly 14A, the bobbins 14 will be concentrically
`15 wrapped on the core 100.
`The coil bobbins 14 may be pre-wound with the magne(cid:173)
`tizing coil windings 12 on the bobbins 14. Then, the fin
`arrays 110 of the fin array assembly 110A are embedded into
`the slots 140 in the bobbins 14 of the bobbin assembly 14A
`20 to allow each fin array 110 to be engaged with each coil
`bobbin 14; whereby upon a concentric curving of the fin
`array 110A and the bobbin assembly 14A, an annular
`configuration by combining the fin array 110A with the
`bobbin assembly 14A is formed as shown in FIG. 6; having
`25 an inner ring 145 formed by concentrically connecting the
`centripetal flanges 142 of the bobbins 14, and an outer ring
`146 formed by concentrically curving the peripheral flanges
`143 of the bobbins 14.
`Each root portion 112 of each fin member 11 is engage(cid:173)
`ably inserted into each recess 102 recessed in each collar
`member 10 of the core 100. Upon engaging of the annular
`combination of the fin array assembly 110A and bobbin
`assembly 14A with the core 100 (FIGS. 7, 8, 10) by
`engaging the root portions 112 with the recesses 102 and by
`engaging the inner ring 145 of the bobbin assembly 14A
`with a collar periphery 104 of the core 100, the inner stator
`1 will be assembled. With the inner and outer rings 145, 146
`formed by radially assembling the bobbins around the core
`100 for concentrically "building" a cylindrical member like
`a "packing" strongly and stably cushioned between the core
`100 and the fin arrays 110 in order for forming the inner
`stator 1 with stable and strong construction.
`The bobbin assembly 14A may not be linked as that
`shown in FIG. 2, and the bobbins 14 are then individually
`engageable with the fin array 110 respectively. The coil
`windings 12 may be prewound on the bobbins 14 before
`engaged with the fin members 11; or the coil windings 12
`may be wound on the bobbins after being engaged with the
`fin members 11.
`By capping the retaining disk 15 on an end portion of the
`core 100 and by passing the bolts 16 through the bolt holes
`151 formed in the disk 15 and through the bolt holes 103
`formed through the core 100, the stator 1 will be firmly
`stably secured on the stem 21 of the stator holder 2 (FIG.
`10). The core 100 may have a polygonal periphery 104 to
`engage the bobbin assembly 14A formed as polygonal
`shape. Naturally, they may be formed as cylindrical shape or
`other shapes.
`The bolts 16 may be modified to be an axial (or unique)
`bolt 16a fixing the disk 15 and the core 100 on the stem 21
`of the holder 2 as shown in FIG. 13.
`The magnetic conductors of the collar members 10 and
`the radial fin members 11 may be made of laminated silicon
`steel sheets or ferromagnetic plates. The core 100 or the fin
`array 110 may also be formed by injection molding of
`magnetically conductive powder materials blended with
`
`Mitsuba - 1014
`Page 11 of 13
`
`
`
`6,081,059
`
`20
`
`30
`
`5
`resm materials. All the magnetic materials should have
`better permeability.
`The outer rotor 3 includes: a cylinder member 31 circum(cid:173)
`ferentially disposed around the inner stator 1 and a cylin(cid:173)
`drical magnetic conductor 30 secured to an inside wall of the 5
`cylinder member 31.
`The cylindrical magnetic conductor 30 may be made of
`permanent magnet, hysteresis ferromagnetic material, or any
`other materials which are magnetically conductive and may
`interact with the inner stator 1 to cause rotation of the outer 10
`stator 3 due to armature reaction between the inner stator 1
`and the outer rotor 3.
`The cylinder member 31 of the outer rotor 3 includes: a
`closed-end plate 32 formed on a first end of the cylinder
`member 31 having a central hub portion 321 coaxially 15
`secured with the shaft 4 about the longitudinal axis X of the
`central stem 21 of the stator holder 2, an open-end periphery
`33 formed on a second end of the cylinder member 31
`opposite to the closed-end plate 32 and rotatably engageable
`with the base 22 of the stator holder 2 by means of a bearing
`34 annularly formed between the open-end periphery 33 of
`the cylinder member 31 and the base 22.
`The base 22 of the stator holder 2 is annularly formed with
`a bearing groove or retaining portion 24 for fixing the
`bearing 34 therein for rotatably engaging and supporting the
`open-end periphery 33 of the cylinder member 31 of the
`outer rotor 3 for increasing the rotation stability of the rotor
`3 in the present invention and for preventing or minimizing
`vibrational shock caused during the rotation.
`The shaft 4 is rotatably mounted through a shaft hole 50
`formed in a central portion of a closed-end plate 51 of the
`housing by a shaft bearing 40, having an inner end portion
`41 of the shaft 4 coaxially secured with the central hub
`portion 321 of the cylinder member 31 of the outer rotor 3 35
`about the longitudinal axis X, and an outer end portion 42
`connected to any operational machine (not shown) driven by
`the motor of the present invention.
`The housing 5 has an open-end periphery 52 formed on a
`free end of the housing 5 opposite to the close-end plate 51 40
`to be combined with the base 22 of the stator holder 2 for
`encasing the inner stator 1 and the outer rotor 3 within the
`housing 5.
`The stator holder 2 is formed with a wire passage 23
`adjacent the base 22 for inserting the electric wires 13, 45
`electrically connected between the coil windings 12 and an
`external power supply source, into the wire passage 23.
`The coil windings 12 are pre-wound on the reel portions
`141 of the bobbin 14, neither on the fin extension 110 nor on
`the core 100, for a quicker assembly and production of the 50
`inner stator 1 of the present invention. Also, the bobbin 14
`is made of electrically insulative materials durable for high
`voltage electric current led into the coil windings 12 of the
`present invention.
`The present invention is superior to a conventional outer- 55
`rotor type motor with the following advantages:
`1. All the bobbins 14 can be flattened ("Ll" of FIG. 2) to be
`a linear chain-like arrangement for prewinding the mag(cid:173)
`netizing coil windings 12 on the bobbins 14, other than
`winding on the T-shaped fin arrays 110, thereby increas- 60
`ing the winding capacity and density of the inner stator for
`increasing a magnetic flux density of the magnetizing coil
`windings and increasing the output torque and efficiency
`of the motor.
`2. The bobbins are linearly flattened for an easy, faster, 65
`convenient and ergonomic winding operation for winding
`the coils 12 on the bobbins 14.
`
`6
`3. The fin arrays 110 are stably secured on the core 100 as
`packed by the bobbins 14, and the core 100 is in turn
`stably fixed on the stator holder 2, thereby forming a
`stably constructed inner stator and thereby preventing the
`vibrational shock and minimizing the variations of mag(cid:173)
`netic field for smoothly enhancing the armature reaction
`between the stator and the rotor.
`4. The coil windings are pre-wound on the insulating bob(cid:173)
`bins so that a higher voltage can be durably sustained
`between the windings and the T-shaped magnetic conduc(cid:173)
`tors (fin arrays) 110, ensuring a durability of high tension
`of the motor.
`5. Each bobbin may be pre-wound with the coil windings
`thereon and then inserted therethrough each T-shaped
`magnetic conductor (fin array). Then, the fin arrays and
`the bobbins are radially secured to the core 100 for a rapid
`assembly, easier installation and a lower production cost.
`The present invention may be further modified without
`departing from the spirit and scope of the present invention.
`The "fin member" (11) as defined in this invention may also
`be designated as a "stator tooth" or the like.
`As show in FIG. 14, the root portion 112 of the fin
`member 11 may also be formed as a dovetail shape to be
`engaged with a dovetail-shaped recess 102 as recessed in the
`25 collar member 10. So, the recess 102 of the collar member
`has an inner width adjacent to the axis X wider than an outer
`width adjacent the core periphery for forming an embedding
`portion for engaging the root portion 112 of the fin member
`11.
`I claim:
`1. An electric motor with outer rotor comprising:
`an inner stator secured on a central stem of a stator holder
`having a longitudinal axis defined at a longitudinal
`center of the central stem of the stator holder;
`an outer rotor circumferentially disposed around said
`inner stator and having a cylindrical magnetic conduc(cid:173)
`tor formed on an inside wall of said outer rotor opera(cid:173)
`tively interacting with said inner stator when magne(cid:173)
`tized to cause rotation of said outer rotor due to
`armature reaction between said inner stator and said
`outer rotor;
`a shaft coaxially secured with said outer rotor about said
`longitudinal axis;
`said inner stator including:
`an annular core including at least a central collar
`member and made of magnetic conductor secured on
`said central stem of said stator holder, having a
`plurality of recesses equally spaced and recessed in
`a core periphery of said collar member;
`a fin array assembly including a plurality of fin arrays
`juxtapositionally linked to be a linear chain-like
`arrangement when flattened, each said fin array
`being a magnetic conductor and generally parallel to
`said longitudinal axis, said fin array assembly, hav(cid:173)
`ing every two said fin arrays linked by a hinge
`portion therebetween having a folding line formed
`between said two fin arrays allowing a concentric
`curving of said fin arrays of said fin array assembly
`about said core, each fin array including at least a
`radial fin member having a cross section of T shape
`having a shank portion, and an engaging root portion
`formed on a bottom end of the shank portion to be
`engaged with each said recess in said collar member;
`an insulating coil bobbin assembly embedded with said
`fin array assembly therein and including a plurality
`of insulating coil bobbins juxtapositionally linked to
`be a linear chain-like arrangement when flattened,
`
`Mitsuba - 1014
`Page 12 of 13
`
`
`
`6,081,059
`
`7
`8
`each said coil bobbin made of electrically insulative
`bolt through at least a bolt hole formed in said core for stably
`material and being generally parallel to said longi(cid:173)
`fixing said core on said stator holder.
`tudinal axis of said stator holder, each said bobbin
`4. An electric motor according to claim 1, wherein said
`including a reel portion formed with a central slot
`collar member includes each said recess having an inner
`therein for inserting said shank portion of each said 5 width adjacent to the axis wider than an outer width adjacent
`fin member through said central slot in said reel
`to said core periphery of the collar member for forming an
`portion for winding magnetizing coil windings on
`embedding portion for engaging said root portion of each
`said reel portion of each said bobbin, having a
`said fin member.
`bobbin hinge portion formed between two said coil
`5. An electric motor according to claim 1, wherein said
`bobbins to define a bobbin folding line longitudi- 10
`core and said fin array is each made of ferromagnetic
`nally in the bobbin hinge portion allowing a concen(cid:173)
`materials including silicon steel plates which are laminated.
`tric curving of said coil bobbins to be concentrically
`6. An electric motor according to claim 1, wherein said
`wrapped on said core; said coil bobbin assembly
`core and said fin array are each made by injection molding
`flattened for prewinding magnetizing coil windings,
`of magnetically conductive powder materials as blended
`electrically connected to a power source, on said coil 15
`with resin materials.
`bobbins;
`7. An electric motor according to claim 1, wherein said
`whereby upon embedding of said fin array assembly in
`coil bobbins are linearly flattened for prewinding said coil
`said coil bobbin assembly prewound with said coil
`windings thereon, and then said coil bobbins are embedded
`windings thereon and upon concentric curving of
`with said fin arrays in said bobbins.
`said fin array assembly and said coil bobbin assem- 20
`8. An electric motor according to claim 1, wherein said
`bly about said core to be concentrically wrapped on
`coil bobbins are embedded with said fin arrays therein, and
`said core, said fin arrays are radially mounted on said
`then said coil bobbins are prewound with coil windings
`core; and
`thereon.
`a retaining disk capping an outer end portion of said
`9. An electric motor according to claim 1, wherein each
`core for stably fixing said core and said bobbins of 25
`said coil bobbin is independently prewound with coil wind(cid:173)
`said inner stator on said stator holder by a at least a
`ings thereon.
`bolt.
`2. An electric motor according to claim 1, wherein said
`10. An electric motor according to claim 1, wherein said
`core is secured on said central stem of said stator holder by
`coil bobbin assembly is broken down to be a plurality of
`said retaining disk retained on an outer end portion of said
`30 individnal coil bobbins, each said coil bobbin embedded
`with each said fin array therein.
`core, having an axial bolt fixing said retaining disk on said
`11. An electric motor according to claim 1, wherein said
`central stem of said stator holder for retaining said core on
`core includes a polygonal core periphery to be engaged with
`said central stem.
`3. An electric motor according to claim 1, wherein said
`the coil bobbin assembly formed as polygonal shape when
`core is secured to said central stem of said stator holder by
`35 concentrically wrapped on said core.
`passing at least a bolt through said retaining disk capped and
`retained on an end portion of said core and by passing said
`
`* * * * *
`
`Mitsuba - 1014
`Page 13 of 13
`
`