Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/12—Stationary parts of the magnetic circuit
  • H02K1/18—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/27—Rotor cores with permanent magnets
  • H02K1/2706—Inner rotors
  • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
  • H02K1/2726—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of a single magnet or two or more axially juxtaposed single magnets
  • H02K1/2733—Annular magnets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/28—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K5/00—Casings; Enclosures; Supports
  • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
  • H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
  • H02K5/173—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings
  • H02K5/1732—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings radially supporting the rotary shaft at both ends of the rotor
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K5/00—Casings; Enclosures; Supports
  • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
  • H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
  • H02K5/173—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings
  • H02K5/1735—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings radially supporting the rotary shaft at only one end of the rotor
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K5/00—Casings; Enclosures; Supports
  • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
  • H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
  • H02K5/173—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings
  • H02K5/1737—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using bearings with rolling contact, e.g. ball bearings radially supporting the rotor around a fixed spindle; radially supporting the rotor directly
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K5/00—Casings; Enclosures; Supports
  • H02K5/24—Casings; Enclosures; Supports specially adapted for suppression or reduction of noise or vibrations

Definitions

• the present invention relates generally to vibration and noise damping in electromotive devices such as electric motors and generators .
• the components of a conventional electromotive device are rigid and are in direct contact .
• These rigid parts are typically metal. Having these rigid parts in direct contact is desirable in some respects: for example, the direct contact of metal parts facilitates heat transfer and allows the device to cool sufficiently during operation.
• the direct coupling of rigid parts helps to keep moving parts in proper alignment.
• the direct contact of rigid parts also facilitates the transmission of vibrations and consequently results in significant levels of noise.
• the conventional brushless direct current (“DC") motor illustrated in FIG. 2 provides an example of this direct contact. Because the rotor magnet 24 in the motor shown in FIG. 2 is inside the stator 20, the motor is called an "inside" design. In a conventional inside motor, the bearings 22 are in direct contact with the rotor shaft 18, and the motor housing 16 and the stator stack 20 are connected directly to the motor housing.
• the shaft 18 of the rotor is typically made of steel.
• the bearings 22 are also typically made of steel .
• the housing 16 is typically aluminum or steel.
• Any vibration that is generated in the rotor is transmitted to the motor stator by variation in the motor air gap.
• This variation in air gap changes the radial forces on the stator because of the change in magnetic attraction between the stator and rotor.
• Stator vibration is then transmitted to the motor housing and then to the frame of the machine to which the motor is fastened.
• stator laminations are constantly being stressed from round to oval as each stator pole pair is electrically energized.
• the magnetic stress caused by the current flowing through successive coils 33 distorts the stator stack 20 as shown in FIG. 3. This variation in stack stress moves the motor housing, thereby generating audible noise as in an audio speaker.
• FIG. 4 depicts a conventional outside motor with a rotating shaft 42.
• Rotor assembly 40 connects rotor magnet 44 and rotor shaft 42.
• Stator 46, bearings 50 and housing 38 are connected to support structure 51.
• Rotor shaft 42 is supported for rotation by bearings 50.
• FIG. 5 depicts a conventional fixed-shaft outside motor.
• shaft 62 is directly affixed to base 72, cover 54, stator 68 and bearings 64.
• Rotor magnet 58 is directly attached to rotor 56, which is supported for rotation by bearings 64.
• All of the contacts indicated in FIGS. 4 and 5 are metal-to-metal and therefore tend to transmit noise and vibrations between connected parts.
• urethane bushings around the rotor bearings to dampen noise from the bearings.
• Model No. D1H18-23- 004Z sold by BEI, Kimco Magnetics Division included such urethane bushings.
• the use of urethane bushings around the rotor bearings has met with limited success in that it did not result in a significant reduction in vibration or noise.
• vibration damping material is used to decouple vibrations in the electromotive device which would otherwise be transmitted to other parts of the device.
• This vibration damping material may be composed of any substance which will cause a significant reduction in the transmission of vibrations, such as silicon rubber, urethane, the "ISODAMP” material manufactured by E-A-R Specialty Composites of Indianapolis, Indiana or material such as the "CHO-THERM” products manufactured by the Chomerics Division, Parker Hannifin PLC of Woburn, Massachusetts .
• vibration damping material used to isolate numerous rigid parts which were formerly in contact or otherwise vibrationally coupled, including: (1) the stator and housing or support structure, as described above; (2) the rotor bearings and housing; (3) the housing and front flange/end bell or other structural element; and (4) the rotor and the rotor magnet .
• FIG. 1 illustrates a conventional motor 10 mounted to a frame.
• FIG. 2 is a partial cross-section of conventional motor 10 of FIG. 1, taken from the center line 18 of the shaft 12, radially to the mounting frame 14 of the motor 10.
• FIG. 3 is a radial cross-section of the stator 20 partially depicted in FIG. 2, which illustrates the magnetostrictive force caused by the sequential excitation of opposing stator windings.
• FIG. 4 is a partial cross-section of a rotating- shaft outside motor.
• FIG. 5 is a cross-section of a fixed-shaft outside motor.
• FIG. 6 is a partial cross-section of an inside motor illustrating bearing damping inserts 26 and 28, stator damping insert 30 and flange damping insert 32, in accordance with one embodiment of the present invention.
• FIG. 7 illustrates magnet damping insert 36 between rotor shaft 12 and rotor magnet 24, in accordance with one embodiment of the present invention.
• FIG. 8 is a partial cross-section of a rotating- shaft outside motor with housing damping insert 39, magnet damping insert 45, stator damping insert 48 and bearing damping inserts 52, in accordance with another embodiment of the present invention.
• FIG. 9 is a cross-section of a fixed-shaft outside motor with magnet damping insert 60, bearing damping inserts 66 and stator damping insert 70, in accordance with another embodiment of the present invention.
• vibration damping material is used to damp vibrations of the stator, rotor magnet and bearings. Vibration damping material may also be placed between other parts of the electromotive device, such as the housing and support structure or between the housing and the front flange or end bell.
• vibration damping material When vibration damping material is used to damp vibrations to or from a particular part of an electromotive device, the vibration damping material so used forms a "vibration damping insert" which is named according to the part.
• vibration damping material used to damp vibrations to or from a bearing is called a “bearing damping insert.”
• vibration damping inserts may be formed from any material suitable for damping vibrations, such as material which has the property of converting a substantial amount of the impinging mechanical energy into heat energy. Examples of such material include silicon rubber and urethane. "ISODAMP” material, manufactured by E-A-R Specialty Composites of Indianapolis, Indiana, has proven to be particularly suitable for fabricating vibration damping inserts. Vibration damping material composed of "SORBOTHANE” material, manufactured by Sorbothane, Incorporated of Kent, Ohio, has also proven to be useful for fabricating vibration damping inserts.
• elements 26 and 28 are vibration damping inserts which block vibrations from leaving the rotor and rotor bearings of an inside motor, which vibrations would otherwise enter the housing 16 or the flange 14. Elements 26 and 28 are positioned between the outer race of bearings 22 and the flange 14 and housing 16.
• Element 30 of FIG. 6 is a stator damping insert which provides a layer of vibration damping material between the stator lamination 20 and the housing 16. This layer blocks the vibration from the stator magnetostriction and rotor pull effects from being transmitted to the motor housing 16.
• the thickness of the layer of vibration damping material surrounding the stator can be important : the layer must be thin enough to fit into the space between the stator and the housing and to allow the motor to cool sufficiently during operation, yet thick enough to provide a significant degree of vibration damping.
• the layer thickness can be especially important for vibration damping materials which are inefficient in heat transfer. In this configuration, the need for heat dissipation must be balanced against the degree of noise suppression.
• the applicant has found that forming the stator damping insert 30 with a thickness in the range of 4 mils to 100 mils (.004 inches to .10 inches) allows for sufficient heat dissipation yet provides a significant level of noise suppression.
• the 4 mil to 100 mil thickness range is dependent on various factors, including: the type of material used for the stator damping insert; the size of the motor; the amount of heat produced by the motor during operation; and manufacturing considerations. In general, if the vibration damping material used also has the ability to efficiently conduct heat away from the stator, then a thicker layer can be used.
• the cross-sectional shape of the stator damping insert 30 resembles a railroad spike.
• the shape of the preferred embodiment of the entire stator damping insert 30 is similar to that of a cylinder with a tapered rim, a thicker wall in the bottom and a circular hole cut in the bottom.
• the tapered rim allows for the stator 20 to slide more easily into the stator damping insert 30 to permit an interference fit between the stator 20 and the housing 16.
• stator damping insert 30 for inside motors, the bottom wall is thickened to form a "shoulder" against which the end of stator 20 is pressed after stator 20 is inserted into stator damping insert 30.
• this shoulder is adjacent to the arrow indicating the position of stator 20.
• Element 32 of FIG. 6 is a flange damping insert formed of vibration damping material, the dimensions of which may be adjusted in accordance with the dimensions of the flange 14.
• the flange damping insert 32 is placed between the motor housing 16 and front flange 14 or end bell. This vibration damping insert blocks the axial vibration reaching the end bell and provides vibration damping for the flat end cap.
• FIG. 7 Another useful vibration damping insert of the preferred embodiment, disposed between the rotor shaft 12 and the rotor magnet 24, is shown in FIG. 7.
• Magnet damping insert 36 can be attached to the shaft 12 by an interference fit or with epoxy. When epoxy is used, the magnet 24 slides on to the shaft 12 and epoxy and vibration damping material 36 are squeezed in between the magnet 24 and the shaft 12.
• FIG. 8 illustrates another embodiment of the present invention in which vibration damping material has been added to a rotating-shaft outside motor, as follows: bearing damping inserts 52 have been placed between bearings 50 and support structure 51; stator damping insert 48 has been placed between stator 46 and support structure 51; magnet damping insert 45 has been placed between rotor magnet 44 and rotor assembly 40; and housing damping insert 39 has been disposed between housing 38 and support structure 51.
• FIG. 9 illustrates yet another embodiment of the present invention in which vibration damping material has been added to a fixed- shaft outside motor, as follows: bearing damping inserts 66 have been placed between bearings 64 and fixed shaft 62; stator damping insert 70 has been placed between stator 68 and fixed shaft 62; and magnet damping insert 60 has been placed between rotor magnet 58 and rotor 56. Note that bearing damping inserts 66 and stator damping insert 70 may be formed as one piece.
• vibration damping material may be disposed between fixed shaft 62 and cover 54, and/or between fixed shaft 62 and base 72.
• This vibration damping material could be connected to bearing damping inserts 66 and/or stator damping insert 70, and may be formed as one piece which extends the length of shaft 62.
• Additional vibration damping material may be situated between bearings 64 and cover 54 and/or base 72.
• the factors which cause noise and/or vibration in the electromotive device should be reduced to a minimum: 1) the rotor balance should be improved, if possible; 2) the air gap distance should be held constant; 3) the windings should be impregnated; and 4) the best bearings and grease lubricants available should be used.
• the next step is to block the transmission of the vibration through various rigid barrier transitions of the electromotive device, using one or more of the following steps:
• the bearings should be supported on vibration damping material, blocking the vibration from leaving the bearings and entering the housing or support structure;
• stator should be supported on a layer of vibration damping material between the stator and the housing or support structure, blocking the vibration from the stator magnetostriction and rotor pull effects from being transmitted to the housing or support structure;
• Vibration damping material should be placed between the rotor and the rotor magnet ;
• Vibration damping material should be placed between the housing and front flange/end bell or support structure of rotating-shaft devices, or between the shaft and base and/or cover of fixed-shaft devices.
• the noise level of a conventional motor, over ambient was 20-30 dB .
• the noise level of the embodiment of the present invention shown at FIG. 6 was 8-10 dB over ambient, a ratio of about 3:1.
• the absolute improvement of 12-20 dB represents a reduction of noise energy to between 1/16 and 1/64 of the conventional design.
• the machine noise reduction because of this change is equally significant: the resulting noise level was from 1/16 to 1/64 of the original noise level.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Motor Or Generator Frames (AREA)
• Vibration Prevention Devices (AREA)
• Apparatuses For Generation Of Mechanical Vibrations (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Dc Machiner (AREA)

Priority Applications (5)

Applications Claiming Priority (4)

Publications (1)

Family

ID=26905736

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (2)

Citations (5)

• 1999
  • 1999-12-13 AU AU21796/00A patent/AU2179600A/en not_active Abandoned
  • 1999-12-13 JP JP2000588880A patent/JP2002533051A/ja active Pending
  • 1999-12-13 WO PCT/US1999/029561 patent/WO2000036730A1/en active IP Right Grant
  • 1999-12-13 DE DE69910618T patent/DE69910618T2/de not_active Expired - Lifetime
  • 1999-12-13 AT AT99966191T patent/ATE247875T1/de not_active IP Right Cessation
  • 1999-12-13 EP EP99966191A patent/EP1142083B1/en not_active Expired - Lifetime

Patent Citations (5)

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