United States Patent [191
`Deavers et al.
`
`[54] SIMPLE BRUSHLESS DC FAN MOTOR
`[75]
`Inventors: Clyde J. Deavers, Woodstock; James
`Reffelt, Shokan, both of N.Y.
`[73] Assignee: Rotron Incorporated, Woodstock,
`N.Y.
`[21] Appl. No.: 690,401
`[22] Filed:
`Jan. 10, 1985
`
`[56]
`
`Related U.S. Application Data
`[63] Continuation of Ser. No. 629,753, Jul. 12, 1984, aban(cid:173)
`doned, which is a continuation of Ser. No. 416,504,
`Sep. 10, 1982, abandoned.
`[51]
`Int. CJ,4 ........................ H02P 7/36; H02K 29/02
`[52] U.S. CI •.................................... 318/254; 318/138;
`318/439; 310/62; 310/46; 310/156
`[58] Field of Search ....................... 318/254, 138, 439;
`310/62, 63, 68 R, 46, 156
`References Cited
`U.S. PATENT DOCUMENTS
`1,996,195 4/1935 Ferguson ............................ 230/273
`2,697,986 12/1954 Meagher ............................... 103/87
`3,083,314 3/1963 Ratajski ............................... 310/219
`3,098,958 7/1963 Katz .................................... 318/138
`3,230,434 1/1966 Bauerlein ........................ 310/156 X
`3,242,404 3/1966 Favre ................................ 310/46 X
`3,264,538 8/1966 Brailsford ............................ 318/138
`3,379,907 4/1968 Hollinger .............................. 310/77
`3,483,456 12/1969 Brunner et al ...................... 318/138
`3,577,049 5/1971 Madurski ............................ 318/138
`3,631,272 12/1971 Kirii .................................. 310/46 X
`3,662,196 5/1972 Ruschmanri ...................... 310/46 X
`3,845,334 10/1974 Harada et al ......................... 310/46
`3,891,905 6/1975 Muller ................................. 318/254
`4,025,831 5/1977 Webb .................................. 318/254
`4,115,715 9/1978 Miil1er ............................. 318/254 X
`4,130,769 12/1978 Karube .................................. 310/46
`4,164,690 8/1979 Muller et al ........................ 318/254
`4,217,508 8/1980 Uzuka ............................. 318/254 X
`4,322,666 3/1982 Miiller ................................. 318/254
`
`[II] Patent Number:
`[45] Date of Patent:
`
`4,563,622
`Jan. 7, 1986
`
`4,371,817 2/1983 Miiller ............................. 318/138 X
`4,459,087 7/1984 Barge .............................. 318/254 X
`FOREIGN PATENT DOCUMENTS
`EP18904 11/1980 European Pat. Off ............... 310/68
`3026797 2/1982 Fed. Rep. of Germany ........ 310/68
`OTHER PUBLICATIONS
`Air Currents, vol. 2, No. 1, Rotron, Inc., Copyright
`1977.
`Rotron Drawings, M500246, M500247 and PC027648.
`Rotron Photographs.
`Michael Oppenheimer, "In IC Form, Hall-Effect De(cid:173)
`vices Can Take on Many New Applications", Elec(cid:173)
`tronics/ Aug. 2, 1971.
`Jearl Walker, "The Amateur Scientist", Scientific Amer(cid:173)
`ican, Mar. 1982.
`Primary Examiner-Bernard Roskoski
`Assistant Examiner-Shik Luen Paul Ip
`Attorney, Agent, or Firm-Brumbaugh, Graves,
`Donohue & Raymond
`[57]
`ABSTRACf
`A simplified fan and brushless DC motor employs an
`annular permanent magnet magnetized in segments
`about its circumference. Each segment is ·oppositely
`radially magnetized with respect to the preceding seg(cid:173)
`ment as one proceeds around the magnet. Fan blades
`are located within the annular magnet. A coil and elec(cid:173)
`tromagnet structure defining two pole pieces reside
`outside the permanent magnet annulus. A Hall effect
`device switches the coil off and on in response to pas(cid:173)
`sage of the segments of the rotor magnet. Thus commu(cid:173)
`tated, the single coil affects rotation of the rotor and the
`fan blades. A permanent magnet supported on the stator
`structure serves to magnetically detent the permanent
`magnet of the rotor, bringing the rotor to rest correctly
`for restarting.
`
`22 Claims, 3 Drawing Figures
`
`PAGE 1 OF 6
`
`PETITIONERS' EXHIBIT 1130
`
`

`

`U.S. Patent
`
`Jan. 7, 1986
`
`4,563,622
`
`14
`
`34
`
`34
`
`2---j
`
`FIG.2
`
`CRI
`
`XI
`
`FIG. 3
`
`PAGE 2 OF 6
`
`

`

`SIMPLE BRUSHLESS DC FAN MOTOR
`
`20
`
`35
`
`1
`
`4,563,622
`
`This application is a continuation of application Ser.
`No. 629,753, filed on July 12, 1984, which is a continua(cid:173)
`tion of Ser. No. 416,504, filed Sept. 10, 1982, now aban(cid:173)
`doned.
`
`2
`ture extending from proximate the magnet to the hub
`and supporting the rotor hub for rotation. The housing
`encircles the annular magnet and the fan blades. The
`support structure includes mounting means formed in
`the housing about the periphery of the motor. A small
`compartment in the housing houses the stator coil, the
`electromagnet structure and all circuit elements of the
`relatively simple switching circuitry, including the
`BACKGROUND OF THE INVENTION
`commutation-effecting Hall device.
`This invention relates to brushless DC motors elec- 10
`Whereas, with its large annular rotor and external
`tronically commutated and more particularly to brush(cid:173)
`stator structure, the motor of this invention might not
`less DC fan motors that are of simple construction,
`be advantageous for certain other applications, it is
`inexpensive to manufacture, and reliable.
`particularly suitable for fans. The tips of fan blades
`A typical goal in the manufacture of fans is a motor
`ordinarily define a circular path and the area within the
`that is very simple and consequently has a low manufac- 15
`circle is necessarily used. Driving and fan blades di(cid:173)
`turing cost. In AC motors for fans, the side armature
`rectly from a magnet secured to the blade tips thus
`AC motor comes closest to achieving these goals. How(cid:173)
`requires little additional space and permits a narrow fan
`ever, recently, DC motors for fans have become more
`since there is no need to couple a motor to the hub or
`and more attractive, particularly for fans used to cool
`shaft supporting the blades centrally. The drive is effi(cid:173)
`electronics where DC power is available.
`cient and is economically accomplished in that the ro(cid:173)
`Brushless DC motors using Hall effect devices to
`tary force applied to the magnet is imparted directly to
`sense the commutation points as the rotor rotates are
`the blades. Less force is required to move the blades
`well known in the art. One or more stator coils are
`against a load than when force is applied where the
`repeatedly energized or have their energization re(cid:173)
`blades are centrally supported. Furthermore, using the
`versed to effect relocation of the electromagnetic field 25
`rotor of the current invention a large proportion of the
`produced by poles of the stator core. A permanent
`circular area from the blade tips inward can be devoted
`magnet rotor is continuously attracted to the new elec(cid:173)
`to air flow, inasmuch as no space therein is taken up by
`tromagnetic pole locations. For commutation, one or
`motor. The advantages of the combination fan and ro(cid:173)
`more Hall effect devices senses the location of the poles
`tor, then, surpass the apparent sum of the advantages of
`of the rotor permanent magnet to control the energiza- 30
`each.
`tion of the stator winding or windings, or a Hall device
`The above and further features of the invention will
`detects the position of one or more commutation mag(cid:173)
`be better understood with reference to the several fig(cid:173)
`nets mounted to rotate with the rotor and provided
`ures of the attached drawings and the following de(cid:173)
`especially to indicate, by changing the state of the Hall
`tailed description of a preferred embodiment.
`device, the commutation points as the rotor turns.
`DESCRIPTION OF THE DRAWINGS
`Many brushless DC motors have been complex in
`both their structure and their commutation circuitry.
`In the drawings:
`Where simple, low cost and reliable fan motors have
`FIG. 1 is a top plan view of the fan and motor accord(cid:173)
`been needed these brushless DC motors, which might
`ing to this invention and shows the rotor's annular per(cid:173)
`more appropriately have been used for, say, precise disc 40
`manent magnet magnetized in segments about its pe(cid:173)
`or tape drives, have been too expensive for the simple
`riphery and an external coil and electromagnet stator
`purpose of fan rotation.
`structure.
`FIG. 2 is a side elevational view of the fan and motor
`BRIEF SUMMARY OF THE INVENTION
`of FIG. 1, partially in section, along the line 2-2 of
`In accordance with this invention, a simple DC 45 FIG. 1, and illustrates the mounting of the rotor and fan
`brushless motor has a rotor with an annular permanent
`blades on a hub for rotation about a centr.al support
`magnet and a stator coil and electromagnet structure
`section of the stator.
`outside the annular magnet. The annular magnet of the
`FIG. 3 is a schematic diagram of an energizing circuit
`rotor is magnetized in segments about its circumference,
`for the stator coil.
`each succeeding segment being oppositely magnetized 50
`DETAILED DESCRIPTION OF THE
`in the radial direction. The electromagnet structure
`PREFERRED EMBODIMENT
`includes pole pieces magnetized by the coil and closely
`proximate the outer cylindrical surface of the annular
`In FIG. 1 a fan and motor combination 10 according
`magnet. A Hall effect device senses the passage of the
`to the invention includes a rotor 11 and a stator 12. The
`rotor magnet segments to turn the coil on and off. The 55
`rotor 11 has an annular permanent magnet 14, magne(cid:173)
`location of the electromagnet pole pieces and of the
`tized in segments about its circumference. As illus-
`Hall effect device are such that, each time the coil is
`trated, each succeeding segment about the circumfer(cid:173)
`energized, the correct magnetic polarities are estab(cid:173)
`ence is oppositely magnetized in the radial direction.
`lished at the pole pieces to attract the next approaching
`The magnet 14 is secured on a ring 16. Fan blades 17
`segments or poles of the annular magnet.
`60 extend from the ring 16 to a central hub 19 ..
`A further permanent magnet supported on the stator
`In FIG. 2, the hub 19 carries a shaft 21 supported in
`structure close to the periphery of the annular rotor
`the sleeve bearing 22 located in a bore 23 formed in a
`magnet magnetically detents the annular magnet so that
`central projecting portion 25 of the stator 12. C-rings 28
`the rotor is correctly positioned for start-up.
`and 29 retain the bearing and secure the rotor and stator
`In the fan of the invention, fan blades are located 65
`together. Spacers or shims 31 take up any excess end
`within and affixed to the annular magnet. The magnet
`play in the assembly. The particular mounting em-
`and the fan blades are mounted for rotation at a central
`ployed to locate the rotor assembly and fan blades rotat(cid:173)
`hub. The stator includes a housing and support struc-
`ably within the stator structure is exemplary only and
`
`PAGE 3 OF 6
`
`

`

`4,563,622
`
`3
`not to be construed as essential to the invention. For
`example, roller bearings or other bearing structure can
`be substituted for the sleeve bearing 22 and other ar(cid:173)
`rangements than the shaft 21 and bore 23 will readily be
`envisioned.
`Three struts 33 radiate outwardly from the central
`stator projection 25. These connect to a generally circu(cid:173)
`lar housing 34. Mounting bosses 35 define holes 36
`about the periphery of the housing, enabling the entire
`motor and fan to be mounted by, e.g., bolts passed 10
`through the holes 36.
`At one location, as seen at the bottom of FIG. 1, the
`housing 34 forms a compartment 40 housing a stator
`coil 41, electromagnet structure 42, a Hall effect device
`Xl, and the remaining circuit elements of the commuta- 15
`tion circuit, not shown in FIG. 1. The coil 41 is wound
`on a bobbin 43. A core 44 of magnetic material extends
`through the bobbin from end to end and forms a part of
`the electromagnet structure 42. Alternatively, the bob(cid:173)
`bin can be a part of the electromagnet structure. That 20
`structure also includes a pair of arms 46 and 47 secured
`in flux conducting relation to the magnetic core 44 and
`terminating in pole pieces 48 and 49 closely proximate
`the outer surface of the permanent magnet 14. As can be
`seen in FIG. 1, the spacing of the pole pieces 48 and 49 25
`is such that, with the magnet located as shown, energi(cid:173)
`zation of the coil 41 to make pole piece 48 north and
`pole piece 49 south will affect clockwise rotation of the
`rotor structure and the fan blades.
`A further permanent magnet 50 magnetically detents 30
`the annular rotor magnet in a position such that starting
`of the motor and fan is assured. At start-up, the coil is
`·· energized to apply, via the pole pieces 48 and 49, start(cid:173)
`ing torque to the annular magnet. The Hall effect device
`Xl controls energization of the coil41 such that the coil 35
`is energized to attract approaching poles of the annular
`rotor magnet and then deenergized when the magnetic
`field of the annular permanent magnet is reversed at the
`·: :; Hall device as a result of movement of a new, oppo-
`' sitely magnetically polarized segment into proximity 40
`· with the device. Deenergization of the coil allows pas(cid:173)
`sage of the next poles past the pole pieces 48 and 49 until
`the Hall device Xl senses the reversal of the magnetic
`field, signaling the approach of the next segments. The
`coil is reenergized and the pole pieces attract the next 45
`two segments. This sequ_ence repeats itself until the
`rotor comes to an equilibrium speed where the aerody(cid:173)
`namic load balances the motor power.
`This operation allows use of a simplified commuta(cid:173)
`tion circuit. In FIG. 3, the Hall device Xl, which can be 50
`a Hall switch, for example, is seen controlling a transis(cid:173)
`tor Ql whose collector-emitter circuit is in series with
`the stator coil 41. One such Hall switch is the sprague
`UGN-3013T of Sprague Electric Company, Worcester,
`Mass. Exposure of the Hall effect device Xl to a mag- 55
`netic field of the correct direction or polarity opens
`(breaks) a conduction path from a line 51 to ground.
`With this path thus open, a resistor Rl supplies base
`drive to Ql, biasing Ql into conduction and energizing
`the coil 41. When the Hall effect device Xl experiences 60
`a magnetic field of reverse direction or polarity, or no
`field at all, the current path from ground to Rl and the
`base of Ql closes. This path of conduction, now closed,
`starves Ql of base drive and Ql no longer conducts, the
`coil 41 is deenergized until Xl experiences a field of the 65
`appropriate direction again. Capacitor Cl damps tran(cid:173)
`sients that arise from the abrupt switching of the coil41.
`The diode CRl prevents current reversals back through
`
`4
`the input leads to, for example, the electronics being
`cooled. Typically, the input power to this simple circuit
`arrangement is taken from the DC bias voltage available
`nearby in the cooled electronics. In a preferred embodi(cid:173)
`ment, the circuit elements are mounted on a printed
`circuitboard of essentially the same shape as the cavity
`that forms the compartment 40 in FIG. 1. The circuit(cid:173)
`board is supported above the cavity with the circuit
`elements projecting downward and housed within the
`cavity so that the fan and motor has the compact shape
`seen in FIG. 1 and the narrow profile shown in FIG. 2.
`From the foregoing it will be seen that a simple and
`quite original combination of motor and fan has been
`provided. It will be readily apparent to those skilled in
`the art that many variations in the foregoing exemplary
`embodiment can be made without departing from the
`spirit and scope of the invention, as defined in the ap(cid:173)
`pended claims.
`We claim:
`1. A DC motor comprising:
`a rotor with an annular permanent magnet, the mag(cid:173)
`net defining magnetic segments, wherein segments
`of like polarization in the radial outward direction
`are spaced apart circumferentially about the rotor;
`a stator having an electromagnetic structure outside
`said annular magnet, proximate the periphery
`thereof, the electromagnet structure including, in a
`location to one side of the annular magnet and
`extending less than 180° around the magnet, coil
`means and electromagnetic flux conducting means
`in flux conducting relation to the coil and located
`to establish a magnetic field applying rotational
`torque to the annular magnet;
`position detecting means for commutating electrical
`current to the coil means to repeatedly produce
`said field and apply torque to succeeding segments
`as the rotor rotates.
`2. The motor according to claim 1, wherein the elec(cid:173)
`tromagnetic flux conducting means defines at least one
`pole piece of flux conducting material terminating adja(cid:173)
`cent the exterior of the annular magnet withi.n said
`location.
`3. The motor according to claim 2, wherein the elec(cid:173)
`tromagnet structure includes a flux path having a pair of
`arms associated with ends of the coil means and extend(cid:173)
`ing to said pole piece and a second pole piece spaced
`apart along the circumference of the annular magnet,
`said coil means and pole pieces occupying the location
`on one side of the annular magnet that extends less than
`180° around the magnet.
`4. The motor according to claim 3, wherein the pole
`pieces are spaced apart by such a distance as to each
`attract a separate magnetized segment of the annular
`magnet when the coil means is energized.
`5. The motor according to claim 4, wherein adjacent
`segments of the annular magnet are oppositely polar(cid:173)
`ized and the pole pieces are located to attract the adja(cid:173)
`cent; oppositely polarized segments when the coil
`means is energized.
`6. The motor according to claim 1, wherein the stator
`includes a housing defining a compartment at said loca(cid:173)
`tion on the periphery of the path of rotation of the
`annular magnet, said coil means and electromagnetic
`flux conducting means being located in said compart(cid:173)
`ment.
`7. The motor according to claim 6, wherein said
`compartment houses the position detecting means for
`commutating including a Hall effect device located
`
`PAGE 4 OF 6
`
`

`

`4,563,622
`
`50
`
`5
`proximate the annular magnet and switching circuit
`means for energizing the coil means when a magnetized
`segment of one polarity is adjacent the Hall effect de(cid:173)
`vice.
`8. The motor according to claim 6, wherein the stator
`housing encircles the annular magnet.
`9. The motor according to claim 1, further compris(cid:173)
`ing fan blades located within the annular magnet.
`10. A motor according to claim 9, wherein the fan
`blades extend from proximate the inside surface of the 10
`annular magnet to a central hub, said stator having a
`central member supporting, for rotation, the hub, the
`blades, and the rotor members, including the annular
`magnet, the st~tor further including struts extending
`outwardly from the central stator member to a housing 15
`encircling the fan blades, said housing supporting the
`coil proximate the annular rotor magnet and adjacent
`the outer surface thereon.
`11. A fan and motor combination including a central
`rotatable hub, fan blades radiating outwardly from the
`hub, an annular permanent magnet having segments 20
`polarized oppositely in the radial outward direction,
`said permanent magnet encircling the blades of the fan
`and secured to the blades, a housing encircling the an(cid:173)
`nular permanent magnet, a single electromagnet struc(cid:173)
`ture defming pole pieces supported by the housing out- 25
`side the annular magnet and including electromagnetic
`coil means wound thereon and electromagnetically
`coupled to the single electromagnet structure including
`the pole pieces, commutation means responsive to the
`position of the permanent magnet to repeatedly ener- 30
`gize the coil to apply a rotary force to segments of the
`annular magnet, and a second permanent magnet car(cid:173)
`ried by the housing and located proximate the annular
`magnet to bring the annular magnet to rest in a position
`such that the coil and electromagnet structure will 35
`apply start-up force on the annular magnet to begin
`rotation of the annular magnet when the stopped motor
`and fan is energized.
`12. In a brushless DC motor; a rotor having a perma(cid:173)
`nent magnet magnetized in segments proceeding cir- 40
`cumferentially on the magnet; a stator having only a
`single coil support structure having coil means includ(cid:173)
`ing a winding wound thereon at only one location along
`the periphery of the magnet and at least one pole piece
`proximate the magnet; means for supplying current to 45
`the winding in one direction only; and commutation
`means controlling the means for supplying to sequen(cid:173)
`tially and repeatedly energize the winding to attract a
`segment of a particular polarity, and then deenergize
`the winding until another segment of the particular
`polarity is rotated into position to be attracted.
`13. The motor according to claim 12, wherein the
`motor is a fan motor, the magnet is annular, and fan
`blades are located inside the annular magnet.
`14. The motor according to claim 1, wherein said
`location containing the coil means and flux conducting 55
`means extends less than 90° around the annular perma(cid:173)
`nent magnet.
`'15. The ·motor according to claim 14, wherein said
`coil means and flux conducting means in a location
`extending less than 90o around the annular permanent 60
`magnet is the only electromagnet structure of the stator.
`16. The motor according to claim 1, wherein the
`annular permanent magnet comprises a narrow ring
`having an internal radius at least twice the radial thick(cid:173)
`ness of the ring.
`17. The motor according to claim 16, wherein the
`magnet has at least six segments, adjacent segments
`being oppositely polarized, the electromagnet structure
`
`6
`terminating in two pole pieces producing oppositely
`directed magnetic fields at the outer circumference of
`the magnet when the coil means is energized with a
`direct current, the pole pieces being spaced apart to face
`adjacent oppositely polarized segments across an air
`gap to apply rotational torque thereto when the coil is
`energized.
`18. The motor according to claim 1, wherein means
`to be driven by the rotor are affixed to the annular
`magnet and extend inwardly thereof.
`19. A combination motor and fan comprising a rotor
`having an annular permanent magnet magnetized in
`segments with segments of like polarity being circum-
`ferentially spaced apart, the annular magnet defining a
`relatively large central opening through the motor; fan
`blades located in the central opening and connected to
`the annular magnet to be rotated by the magnet, for
`delivery of air through the central opening, stator struc(cid:173)
`ture in association with the magnet including electro-
`magnetic coil means for producing an electromagnetic
`field proximate the annular magnet to produce rota(cid:173)
`tional torque on the magnet, means for detecting the
`relative rotational position of the rotor and means re(cid:173)
`sponsive to the detection means for energizing the coil
`to produce the rotational torque.
`20. The motor and fan according to claim 21, wherein
`the stator structure further comprises struts projecting
`inward towards the center of the central opening, sup(cid:173)
`port means located centrally of the opening and affixed
`to the struts, a rotateable hub supported on the support
`means, the blades being affixed to the hub, the support
`means supporting the rotor for rotation, including the
`hub, the blades and the magnet.
`21. In a brushless DC motor having a permanent
`magnet rotor, stator electromagnet structure, and
`means for controlling energization of the stator perma(cid:173)
`nent magnet structure in dependence on the angular
`position of the rotor; the improvement comprising:
`the permanent magnet rotor including an annular
`rotor magnet magnetized in segments, circumfer(cid:173)
`entially adjacent segments having oppositely polar(cid:173)
`ized faces facing across a radial air gap to the sta-
`tor·
`the stator electromagnet structure including an as(cid:173)
`sembly comprising a coil wound onto an electro(cid:173)
`magnet support structure, and first and second pole
`pieces secured to the electromagnet support struc-
`ture at opposite ends of the coil and terminating in,
`respectively, first and second electromagnetic field
`producing portions facing the annular magnet
`across the air gap;
`the means for controlling energization being con(cid:173)
`nected with the coil to energize the coil with cur(cid:173)
`rent oppositely magnetizing the first and second
`electromagnetic field producing portions;
`said first and second electromagnetic field producing
`portions being spaced apart circumferentially of
`the magnet, and facing oppositely polarized faces
`of the magnet across the air gap to apply a rota(cid:173)
`tional magnetic force to magnet segments having
`oppositely polarized faces; and
`the assembly being confined at a location to one side
`of the annular magnet and extending less than 180°
`circumferentially thereof.
`22. The motor according to claim 21, wherein said
`assembly includes a bobbin on which the coil is wound,
`65 a core of electromagnetic material extending through
`the bobbin and joined to the pole pieces in flux conduct(cid:173)
`ing relation thereto.
`* * *
`
`PAGE 5 OF 6
`
`

`

`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`: 4,563,622
`PATENTNO.
`Jan. 7, 1986
`DATED
`INVENTOR(S) : Deavers et al.
`
`It is certified that error appears in the above-identified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`First page, Item
`the following
`--2,472,039
`2,912,609
`3,626,263
`3,909,647
`3,961,211
`4,358,245
`4,373,148
`
`56, add to the list of "U.S. PATENT DOCUMENTS"
`references:
`5/1949
`"230/259
`Zacharias
`11/1959
`Kassner ....... 310/156
`12/1971
`McBride .....•• 318/138
`9/1975
`Peterson ....•• 310,156
`6/1976
`Vergues ....... 310/68C
`11/1982
`Gray .......... .
`2/1983
`Gutz .......... 318/254--.
`
`Col. 6, ·line 25, "claim 21" should read --claim 19--.
`
`Signed and Sealed this
`
`Thirtieth Day of December, 1986
`
`Attest:
`
`Attesting Officer
`
`Commissioner of Patents and Trademarks
`
`DONALD J. QUIGG
`
`PAGE 6 OF 6
`
`