Source: http://www.google.com/patents/US4482829?ie=ISO-8859-1
Timestamp: 2016-02-13 08:18:54
Document Index: 798234593

Matched Legal Cases: ['art.\n2', 'art 5', 'art 12', 'art 12', 'art 12', 'art 5']

Patent US4482829 - Brushless electric micromotor - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA brushless electric micromotor comprised of a rotor, a shaft and a tube-like part and permanent magnets rotatably mounted and hermetically sealed in a rotor housing, said shaft being supported in bearings. The permanent magnets have their co-axial surfaces coated with a layer of an electrically conductive...http://www.google.com/patents/US4482829?utm_source=gb-gplus-sharePatent US4482829 - Brushless electric micromotorAdvanced Patent SearchPublication numberUS4482829 APublication typeGrantApplication numberUS 06/433,526Publication dateNov 13, 1984Filing dateOct 8, 1982Priority dateOct 8, 1981Fee statusLapsedAlso published asDE3237196A1, DE3237196C2Publication number06433526, 433526, US 4482829 A, US 4482829A, US-A-4482829, US4482829 A, US4482829AInventorsPierre R. Tardieu, Yves H. Mulet-MarquisOriginal AssigneeKollmorgen Technologies CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (14), Referenced by (27), Classifications (15), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetBrushless electric micromotor
US 4482829 AAbstract
A brushless electric micromotor comprised of a rotor, a shaft and a tube-like part and permanent magnets rotatably mounted and hermetically sealed in a rotor housing, said shaft being supported in bearings. The permanent magnets have their co-axial surfaces coated with a layer of an electrically conductive metal. The micromotor further comprises a stator co-axially surrounding the rotor housing and comprising field windings regularly arranged with equal angular distances in the stator housing made of magnetic material.
1. A brushless electric micromotor comprising a rotor having a shaft, a tube-like member of a magnetic material on said shaft and permanent magnets mounted on said tube-like member, said shaft, said tube-like member and said magnets being rotatably mounted in a hermetically sealed in a rotor housing, said shaft being supported at its opposite ends in bearings mounted in said housing, said permanent magnets having outer surfaces coated with a layer of an electrically conductive metal, said permanent magnets extending beyond one of the ends of said shaft and the bearing supporting said shaft end and forming a magnetic drive for a second shaft magnetically coupled thereto and a stator unit co-axially surrounding said rotor housing, said stator unit having a housing of magnetic material and field winding coils in said magnetic material stator housing arranged regularly in said stator housing coaxially around said rotor with equal angular distances between said coils, said coils being embedded in insulating material, the hermetically sealed rotor housing being provided with a recessed end forming an axial, cylindrical cavity facing to the outside, and the end of said permanent magnets extend into a recess formed inside of said rotor housing by said recessed end and the outside wall of said housing, said end of said permanent magnets extending into said sleeve forming one part of a magnetic coupling for transmitting the torque of said rotor to said second shaft having a magnetic coupling counterpart.
2. The micromotor of claim 1 wherein said rotor housing is made of an insulating plastic material.
3. The micromotor of claim 1 wherein said field winding coils in said stator unit are embedded in, and the interspaces between said coils completely filled with, an insulating plastic material.
4. The micromotor of claim 1, 2, or 3, wherein the angular distance between said field winding coils is 2π/3 and said coils are connected to a tri-phase electric power supply having a phase difference between the phases of 2π/3 for creating a rotating field.
5. The micromotor of claim 1, 2 or 3 wherein the hermatically sealed rotor housing comprises a capsule and a flange.
6. The micromotor of claim 1, 2 or 3 wherein the electrically conductive layer on the permanent magnets is a copper layer.
7. The micromotor of claim 2 wherein said field winding coils of said stator are embedded in, and the interspaces between said coils completely filled with, an insulating plastic material.
8. The micromotor of claim 8 wherein the angular distance between said coils is 2π/3 and said coils are connected to a tri-phase electric power supply having a phase difference between the phases of 2π/3 for creating a rotating field.
9. The micromotor of claim 7 wherein the hermetically sealed rotor housing comprises a capsule and a flange.
10. The micromotor of claim 7 wherein the electrically conductive layer on the permanent magnets is a copper layer.
This invention relates to brushless electric micromotors and, more particularly, to brushless electric micromotors for use with hand held tools, for example, dental drills.
Brushless electric micromotors having position sensors for detecting the rotor position and for controlling the current supply to the field windings for effective starting and synchronizing the motor are known. Such motors require additional space for housing the sensor means and sealing of the motor with the sensors is difficult.
The instant invention provides a brushless electric micromotor without position sensors, eliminates the need for added motor housing sensor space and sensor sealing and provides a motor completely sealed, practically maintenance-free, which is easy to assemble and has a long life-span. The electric micromotor of the present invention includes a rotor with a shaft, a tube-like member and permanent magnets rotatably mounted and hermetically sealed in a rotor housing. The shaft is supported in bearings mounted in the housing. The housing is provided with the tube-like member which is made of magnetic material and carries the permanent magnets. The permanent magnets have coaxial surfaces coated with a layer of an electrically conductive metal. The stator co-axially surrounds the rotor housing and includes the stator part made of magnetic material and field winding coils arranged regularly with equal angular distances and embedded in insulating material.
The hermetically sealed rotor housing consists of a plastic capsule sealed at one of its ends by a flange-like part. Because the rotor is hermetically sealed, contaminates from the outside are excluded. The rotor bearings may be lubricated for their total life-span. The assembly of the motor is simplified. There are no brushes or sensors to install or assemble. The rotor is simply inserted into the stator.
The field windings of the stator of the micromotor of the instant invention are also embedded in plastic material. Thus, the entire motor is sealed, completely electrically isolating the motor and allowing the motor to be used in environments exposed to liquids and fluids.
In one embodiment of the motor of the present invention, three stator field windings are employed and are arranged regularly in an angular distance of 2π/3 from each other. The windings are powered with three-phase current with the phases differing from each other by 2π/3. A rotating field is thus generated. Because the rotor of the micromotor of the instant invention is completely sealed in the rotor housing, the motor of the invention is particularly adapted for transmitting torque by means of a magnetic coupling between the rotor shaft and the tool to be driven.
In another embodiment of the invention, one end of the housing is provided with an axial cavity. The permanent magnets of the rotor extend inside of the housing and into the axial cavity. A device provided with magnets is fitted into the axial motor housing cavity so that a magnetic coupling is formed between the permanent rotor magnets extending into the axial cavity and the magnets of such device for transmitting the torque of the motor shaft to the device and by the device to a tool outside the motor housing.
The micromotor, as aforesaid, operates without position sensors. The starting of the motors and the synchronization of the magnetic rotor field with the stator field is achieved through a layer of conductive metal, i.e., copper, on the outside surfaces of the permanent magnets of the rotor.
The instant invention will be more fully described and will be better understood from the following description, taken with the accompanying drawings in which
FIG. 1 is a side view, in section, of the micromotor of the present invention; and
FIG. 2 is a sectional view taken at II, II, FIG. 1.
As best shown in FIG. 1, the motor unit of the inventive micromotor comprises a hermetically sealed rotor housing 10 with bearings 3, 3', shaft 4, tube-like part 5, 6, and permanent magnets 6' in housing 10 and making up a freely rotating rotor. Housing 10 consists of capsule 11 and sealing flange part 12. Capsule 11 and flange part 12 are preferably produced by molding of plastic material. Capsule 11 is hermetically sealed by the sealing flange part 12. The use of synthetic plastic material, at the same time, electrically isolates the rotor. Rotor housing 10 is inserted into the stator unit, generally designated 2. Shaft 4 is rotatably supported by bearings 3, 3', lubricated and sealed in housing 10.
Tube-like part 5 of magnetic material with attached permanent magnets 6, 6', provided with a layer of conductive metal 8, such as copper, on their surfaces, is mounted on shaft 4. Stator unit 2 co-axially surrounds motor housing 10 and comprises field windings 13, 14, 15 regularly arranged with equal angular distances of 2π/3 (FIG. 2) and, when connected to a tri-phase electric power supply (not shown in the drawing), providing a phase difference between phases of 2π/3, generates a rotating magnetic field. Field windings 13, 14, 15 are completely embedding in synthetic resinous material 9, which is an electric insulator, and are arranged in the stator housing 16 made of magnetic material to close the magnetic circuit with magnets 6, 6'.
In the operation of the instant motor, stator unit 2 generates a rotating magnetic field in the manner well-known in the art. When starting the motor, the necessary torque for the rotor has to be generated.
In the motor of the instant invention, the torque for starting the motor is generated without using a position sensor. Copper layer 8 on the outer surfaces of the magnets 6, 6' of the rotor permits the starting of the rotor and the synchronization of the rotating field of the stator with the magnetic field of the rotor. If the rotor rotates at a different speed that the field of the stator, eddy currents are generated in copper layer 8. The reaction of the stator field and the field induced by the eddy currents causes the rotating torque of the rotor non-synchronous. The non-synchronous torque drives the rotor up to a speed which permits the synchronization of the rotor.
The motor speed depends on the rotation speed of the stator field, which is controlled by the frequency of the supply current. The frequency of the supply current can easily be adjusted by means well-known in the art.
The diameter of the rotor is very small so that very high speeds can be achieved. Speeds comparable to the speeds of air turbines can be attained. For example, if the power supplied to the stator has 2000 cycles, a speed of 120,000 rpm of the rotor is attained with a dipol motor. The high speed, as well as the complete electric insulation of the rotor and the stator of the invention motor, allow a wide field of applications especially in fields where high speed and safety are of importance, as, for example, in the field of dental surgery and microsurgery.
As the micromotor of the invention has a completely sealed rotor, magnetic coupling is provided, as described hereinafter. The ends of rotor magnets 6, 6' are extended by portions 7 beyond bearing 3 at the end of motor shaft 4 and into the recess of cavity 17. Cavity 17 is shaped to support bearing 3 in its inner part. Outer cavity 18 of cavity 17 is shaped to form a co-axial cavity and receives the end of shaft 21 having disc 22 having magnets 24, 26 for magnetic coupling of rotor shaft 4 and shaft 21. Extensions 7 of magnets 6, 6' of the rotor are arranged to be housed in the recessed part of 17 and adjacent to the wall of housing 10. The extensions 7 of magnets 6, 6' in rotor housing 10, when motor is started, extending beyond bearing 3 and the end of motor shaft 4 and into the outer periphery of cavity 17 for the magnetic coupling with magnet 24, 26 on disc 22 of shaft 21. Thus, the magnetic field of magnet extension 7, with the magnetic field of magnets 24, 26 of disc 22, cause shaft to rotate as the motor shaft rotates.
The exact shape of motor 16, and especially the shape of a mechanically connected device, depends on the field of application and is not part of this invention. In FIG. 1, motor 16 with coupling flange 19 for mounting the micromotor on device 20.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS1810844 *Nov 7, 1928Jun 16, 1931Emile MorelMagneto-electric machineUS2516901 *Feb 19, 1945Aug 1, 1950Wayne J MorrillRotor for dynamoelectric machinesUS2522233 *Dec 18, 1948Sep 12, 1950Gen ElectricRotor for permanent magnet dynamoelectric machinesUS2919359 *Mar 4, 1957Dec 29, 1959Us Electrical Motors IncDynamoelectric machine provided with sealing means, and process for making sameUS3164735 *Aug 16, 1961Jan 5, 1965AmpexIndexing synchronous motorUS3343017 *Oct 12, 1966Sep 19, 1967Peerless Electrical Division OLow inertia electric motorsUS3638055 *Jun 29, 1970Jan 25, 1972Sulzer AgElectrical apparatusUS3754844 *Jul 27, 1972Aug 28, 1973Bosch Gmbh RobertPump and electric drive motor unitUS3873861 *Jun 15, 1973Mar 25, 1975Halm RichardElectric motor, especially a squirrel-cage motorUS3974408 *Jan 20, 1975Aug 10, 1976Compagnie De Construction Mechanique SulzerAsynchronous synchronizable magnetic couplingUS4053983 *Apr 23, 1976Oct 18, 1977Flatland Lloyd PProphylactic angle head for use with a dental handpieceUS4115040 *May 25, 1977Sep 19, 1978Franz Klaus-UnionPermanent magnet type pumpUS4128527 *Apr 13, 1977Dec 5, 1978Hitachi, Ltd.Dynamoelectric machine having coil windings and core encapsulated with resin-filler compositionUS4339874 *Mar 10, 1980Jul 20, 1982The Garrett CorporationMethod of making a wedge-shaped permanent magnet rotor assembly* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS4823033 *Feb 26, 1988Apr 18, 1989Mabuchi Motor Co.Miniature motor having coated rubber permanent magnetUS4831615 *Jan 28, 1986May 16, 1989Nippon Columbia Co., Ltd.Dual differential optical system moving apparatusUS4984745 *Jun 20, 1989Jan 15, 1991Gmf Robotics CorporationElectric robot for use in a hazardous locationUS5046154 *Oct 9, 1990Sep 3, 1991Delco Electronics CorporationEncapsulated armature and shaft assemblyUS5054009 *Aug 4, 1989Oct 1, 1991Vdo Adolf Schindling AgMotor, in particular, for driving a clockworkUS5113102 *May 9, 1991May 12, 1992Huntington Mechanical Laboratories, Inc.Rotary motion transmitter and heat treatment method for sealed chamberUS5113114 *Dec 18, 1990May 12, 1992General Electric CompanyMultilam or belleville spring contact for retaining rings on dynamoelectric machineUS5327032 *Feb 18, 1993Jul 5, 1994Carter Automotive Company, Inc.Dual flux ring multiple position rotary actuatorUS5430340 *Apr 15, 1993Jul 4, 1995General Electric Co.Harmonic current path spring device between retaining ring and rotor wedge of a dynamoelectric generatorUS5486728 *Aug 13, 1993Jan 23, 1996Seiko Instruments Inc.MicromotorUS5814907 *May 5, 1997Sep 29, 1998Moog Inc.Electromagnetic force motor with internal eddy current dampingUS6058593 *Mar 31, 1998May 9, 2000Impella Cardiotechnick GmbhMethod for producing a micro motorUS6227853Jul 16, 1999May 8, 2001Edge Technologies, Inc.Magnetic coupling system and methodUS6477913Nov 22, 1994Nov 12, 2002Fanuc Robotics North America, Inc.Electric robot for use in a hazardous locationUS6531801Dec 2, 1999Mar 11, 2003Ispat Inland, Inc.Asynchronous motors having simple rotor structuresUS6713905 *Aug 30, 2001Mar 30, 2004S-B Power Tool CompanyElectric-motor rotary power tool having a light source with a self-generating power supplyUS6794789Nov 6, 2001Sep 21, 2004Impella Cardiosystems AgMiniature motorUS7429810 *Sep 15, 2005Sep 30, 2008Hitachi, Ltd.Electric rotary machineUS7679244 *Mar 13, 2007Mar 16, 2010Nidec Sankyo CorporationMotorUS8133053 *Mar 27, 2008Mar 13, 2012Kaltenbach & Voigt GmbhElectric motor for use in a dental, dental-medical or dental-technical handpiece and stator thereforUS20040046466 *Nov 6, 2001Mar 11, 2004Thorsten SiessMiniature motorUS20060138876 *Sep 15, 2005Jun 29, 2006Hitachi, Ltd.Electric rotary machineUS20070216243 *Mar 13, 2007Sep 20, 2007Ikuo AgematsuMotorUS20100261140 *Mar 27, 2008Oct 14, 2010Kaltenbach & Voigt GmbhElectric Motor for use in a Dental, Dental-Medical or Dental-Technical Handpiece and Stator ThereforEP0253398A1 *Jul 16, 1987Jan 20, 1988Haruo OhamaMagnetic health deviceWO1998044619A1 *Mar 31, 1998Oct 8, 1998Impella Cardiotech GmbhMethod for producing a micromotorWO2002041935A1 *Nov 6, 2001May 30, 2002Impella Cardiotech AgMiniature motor* Cited by examinerClassifications U.S. Classification310/105, 310/88, 310/40.0MM, 310/181, 310/89, 310/86, 310/156.75, 310/45International ClassificationH02K5/12, H02K21/46, H02K29/00, H02K21/14, H02K7/14Cooperative ClassificationH02K21/46European ClassificationH02K21/46Legal EventsDateCodeEventDescriptionOct 20, 1982ASAssignmentOwner name: KOLLMORGEN TECHNOLOGIES CORPORATION STE 300 2001 BFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:TARDIEU, PIERRE R.;MULET-MARQUIS, YVES;REEL/FRAME:004071/0048Effective date: 19821012May 4, 1988FPAYFee paymentYear of fee payment: 4May 13, 1992FPAYFee paymentYear of fee payment: 8Jun 18, 1996REMIMaintenance fee reminder mailedNov 10, 1996LAPSLapse for failure to pay maintenance feesJan 21, 1997FPExpired due to failure to pay maintenance feeEffective date: 19961113RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services