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
  • H02K1/17—Stator cores with permanent 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
  • H02K1/12—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
  • H02K23/00—DC commutator motors or generators having mechanical commutator; Universal AC/DC commutator motors
  • H02K23/02—DC commutator motors or generators having mechanical commutator; Universal AC/DC commutator motors characterised by arrangement for exciting
  • H02K23/04—DC commutator motors or generators having mechanical commutator; Universal AC/DC commutator motors characterised by arrangement for exciting having permanent magnet excitation
• • 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
  • H02K5/08—Insulating casings
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/04—Details of the magnetic circuit characterised by the material used for insulating the magnetic circuit or parts thereof
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
  • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
  • H02K15/03—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies having permanent magnets
• • 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

Definitions

• the present invention relates to electric motors, and more particularly to stator assemblies for electric motors.
• stator assemblies for permanent magnet electric motors magnets are retained within the stator assembly.
• magnets are retained on a stator housing or a separate flux ring within the stator housing. This generally requires gluing or adhering each individual magnet to the flux ring or stator housing.
• the present invention provides a stator assembly for an electric motor.
• the stator assembly includes a stator housing, a split flux ring inserted into the stator housing and a plurality of magnets on an inner surface of the flux ring.
• An overmolding secures the magnets to the flux ring and asserts a radial force on the flux ring to secure it to the stator housing. Additionally, the overmolding fills the seam of the flux ring and prevents collapse of the flux ring.
• the material used to mold the overmolding is a plastic that is injection molded about the magnets on the flux ring after the flux ring and magnets have been placed in the stator housing.
• the pressure of the plastic as it is being injection molded exerts a radial pressure on the flux ring, expanding it against the stator housing and secures it to the stator housing.
• the overmolding also secures the magnets to the flux ring.
• the flux ring is aligned with the stator housing and is further secured to it by engagement of a dimple in one of the flux ring and stator housing with a hole in the other of the flux ring and the stator housing.
• At least one of a rear bearing support, front bearing support and fan baffle are integrally molded with the overmolding when the material used to mold the overmolding is molded.
• the overmolding is formed with slots of different widths between magnetic poles of the stator assembly to provide a keying feature for the stator assembly to key it, such as when it is placed in a magnetizer.
• the flux ring and housing are preformed as a unit by stamping them from blanks and rolling them together.
• the flux ring blank is rolled first to form the flux ring and the housing blank rolled around the flux ring with the flux ring acting as a rolling arbor.
• an electric motor has an armature and a stator assembly in accordance with the invention.
• a power tool has a housing including an electric motor having an output coupled to a transmission.
• the electric motor has an armature and a stator assembly in accordance with the invention.
• Figure 1 is a cross-sectional view of a power tool according to the present invention.
• Figure 2 is a perspective view of a stator assembly of the power tool of Figure 1;
• FIG. 3 is a cross-section view of the stator assembly of Fig. 2 taken along the line 3 - 3;
• Fig. 4 is a perspective view of a flux ring of the stator assembly of Fig. 2;
• Fig. 5 is a perspective view of a stator can or housing of the stator assembly of Fig. 2;
• Fig. 6 is a perspective view of the flux ring of Fig. 4 received in the stator can of Fig. 5;
• Fig. 7 is a perspective view of a variation of the flux ring of Fig.
• Fig. 8 is a cross-sectional view of an alternative configuration of the stator assembly of Fig. 2;
• Fig. 9 is a perspective view of an electric motor having an alternative configuration of the stator assembly of Fig. 2;
• Fig. 10 is a cross-sectional view of the electric motor of Fig. 9 taken along the line 10 - 10;
• Fig. 11 is a perspective view of an alternative stator assembly; and [0027] Fig. 12 is a perspective view of still another alternative stator assembly.
• the power tool 10 is illustrated as a drill, however, any type of power tool may be used in accordance with the present invention.
• the power tool 10 includes a housing 12 which surrounds a motor 14.
• An activation member 16 is coupled with the motor and a power source 18.
• the power source 18 includes either a power cord (AC current) or includes a battery (DC current) (not shown).
• the motor 14 is coupled with an output 20 that includes a transmission 22 and a chuck 24.
• the chuck 24 is operable to retain a tool (not shown).
• the motor includes a stator assembly 30.
• the stator assembly 30 The stator assembly
• the stator 30 includes a stator housing 32, a flux ring 34 and magnets 36.
• the flux ring 34 is an expandable or split flux ring.
• An armature 40 includes a shaft 42, a rotor 44 and a commutator 50 coupled with the shaft 42.
• the rotor 44 includes laminations 46 and windings 48.
• the motor 14 also includes end plates 52 and 54.
• End plate 52 includes a front bearing 56 which supports one end of a shaft 42.
• the shaft 42 is coupled with a pinion 60 that is part of the output 20.
• Brushes 62 and 64 are associated with the commutator 50.
• a rear bearing 70 is also coupled with the end plate 54 to balance rotation of the shaft 42.
• Stator housing 32 and flux ring 34 are illustratively made of soft magnetic material, such as cold rolled steel.
• the flux ring 34 has anchors 80 extending radially inward.
• the magnets 36 are disposed around an inner surface 82 of the flux ring 34 between anchors 80.
• An overmolding 84 secures the magnets 36 to flux ring 34 as described in more detail in WO 02/068235 A2.
• the flux ring 34 is discontinuous having a seam 86 extending therealong.
• the seam 86 enables the flux ring 34 to be compressed for insertion into the stator housing 32.
• the seam 86 is preferably disposed over one of magnetic poles P-i, P 2 of the stator assembly 30 to minimize magnetic losses.
• the flux ring 34 includes a projection or dimple 88 that engages a hole 90 in the stator housing 32.
• the stator housing 32 includes a projection or dimple 92 that engages a hole 94 in the flux ring 34.
• the dimple 88,92 and hole 90,94 are illustratively at ninety degrees to seam 86 to provide sufficient displacement of dimple 88 or hole 94, as applicable, in flux ring 34 with respect to stator housing 32 when flux ring 34 is compressed so that when flux ring 34 is uncompressed, dimple 88 will be urged into hole 90 (or hole 94 around dimple 92).
• the dimple 88, 92 and hole 90, 94 are ideally centered over one of the magnetic poles P- t , P 2 to reduce magnetic losses.
• Overmolding 84 is formed so there are slots 95, 96 on diametrically opposite sides of flux ring 34 between the overmolding 84 around magnets 36 of pole Pi, and the overmolding 84 around magnets 36 of pole P 2 .
• Slots 95, 96 illustratively extend axially along inner surface 82 of flux ring 34 between poles Pi and P 2 .
• Slots 95, 96 may be gaps in the overmolding 84 or regions of reduced thickness in the overmolding 84.
• stator assembly 30 has one pair of magnetic poles, with one of poles Pi and P 2 thus being a North pole and the other being a South pole. It should be understood that stator assembly 30 could have more than one pair of North and South poles.
• stator housing 32 and flux ring 34 are each preformed.
• stator housing 32 illustratively has interlocking fingers 33 as shown in Fig. 5.
• the flux ring 34 is slightly compressed and inserted into the stator housing 32 as shown in Fig. 6.
• the dimple 88,92 engages the hole 90,94 as described above.
• the magnets 36 are placed against the inner surface 82 of the flux ring 34 and are positioned between the anchors 80.
• the magnets 36 can be lightly magnetized so they are retained against the inner surface 82 of flux ring 34 during assembly.
• Overmold material 83 such as plastic, is injection molded into the stator assembly 30 to form the overmolding 84.
• the pressure of the overmold material 83 pushes against the magnets 36 and flux ring 34, expanding the flux ring 34 against the stator housing 32.
• the overmold material 83 fills the seam 86 of flux ring 34 and surrounds the magnets 36. Expansion of the flux ring 34 against the stator housing 32 provides the retention force for retaining the flux ring 34 within the stator housing 32. Further, because the overmolding 84 fills the seam 86 of the flux ring 34, compression of the flux ring 34 in the stator housing 32 is prevented after the overmold material 83 hardens, thus preventing the removal of flux ring 34 from the stator housing 32.
• stator assembly 30 The engagement of the dimple 88, 92 and hole 90, 94, held in place by the overmolding 84, further secures the flux ring 34 to the stator housing 32.
• the diameter and true position of the overmolding 84 are maintained closely relative to the inside diameter of the stator housing 32 to reduce tolerance stack-ups to the armature 40 (Fig. 1). It should be understood that there can be more than one dimple/hole arrangement in flux ring 34 and stator housing 32.
• slot 95 is wider than slot 96. This limits to two the orientations in which stator assembly 30 can be placed in a magnetizer (not shown) used to magnetize magnets 36 after stator assembly 30 is assembled.
• stator assembly 30 could be placed in the magnetizer in four orientations. That is, either end of stator assembly 30 could be placed in the magnetizer in two orientations that are 180 degrees apart.
• each end of the stator assembly 30 can be placed in the magnetizer in only one orientation, reducing to two the orientations in which the stator assembly 30 can be placed in the magnetizer. This makes sensing of the stator assembly 30 in the magnetizer fixture more robust and eliminates the possibility of magnetizing backwards due to placing the stator assembly 30 in the magnetizer in the wrong orientation. It should be understood that in stator assemblies having more than two poles, preferably the width of only one of the slots between the poles would be different than the widths of the rest of the slots between the poles to key the stator assembly to the magnetizer.
• the stator housing 32 and the flux ring 34 are preassembled as a unit according to an alternative assembly method. More specifically, the stator housing 32 and flux ring 34 are formed of separate blanks, such as steel blanks, and in this regard, the edges of the seams of flux ring 34 and stator housing 32 are formed to have interlocking fingers, such as interlocking fingers 33 shown in Fig. 5 for stator housing 32 and interlocking fingers 37 shown in Fig. 7 for flux ring 34. One or more holes 94 are stamped into the flux ring and matching mating dimple(s) 92 stamped in the stator housing 32, or vice-versa.
• the stator housing 32 and flux ring 34 are lain together in their flat, pre-rolled states with the holes and dimples engaged.
• the stator housing 32 and flux ring 34 are rolled and the seam of the flux ring 34 interlocks as does the seam of the stator housing 32.
• the holes and dimples maintain alignment of the stator housing 32 and flux ring 34 during the rolling process.
• the flux ring 34 can be rolled first and the stator housing 32 rolled about the flux ring 34. In this case, the flux ring 34 acts as a rolling arbor. Additionally, the holes and dimples maintain alignment as the stator housing 32 is rolled about the flux ring 34.
• stator housing 32 and flux ring 34 can be spot-welded together to form a sub-assembly. Regardless of how the stator housing 32 and flux ring 34 are assembled together, injection of the overmold material 83 not only secures the magnets 36 to the flux ring 34 but also secures the flux ring 34 to the stator housing 32 through the pressure exerted on the flux ring 34 therein. [0038]
• the stator assembly 30 of the present invention provides significant advantages in both assembly and manufacture of the power tool 10. In particular, the stator assembly 30 eliminates the need for welding equipment to secure the components together.
• the expansion of flux ring 34 against stator housing 32 induced by injection of the overmold material 83 secures the flux ring 34 to stator housing 32 and the overmolding 84 also secures the magnets to flux ring 34.
• the interlocking of the dimple/hole arrangement(s) further secure the flux ring 34 to the stator housing 32.
• injection of the overmold material 83 reduces tolerance stack-ups, improving ease of assembly. As a result, manufacturing equipment and floor space is reduced entailing cost savings.
• Another advantage of reduced tolerance stack-ups is that the magnet can be placed closer to the armature 40 thus maximizing motor performance.
• the keying feature provided by the different widths of slots 95, 96 improve the placement of stator assembly 30 in the magnetizer.
• the stator assembly 100 includes the stator housing 32, flux ring 34, and permanent magnets 36 as shown in the stator assembly 30 of Figs. 2 - 6.
• the stator assembly 100 further includes an integrally molded commutator end or rear bearing support 102 and an integrally molded fan baffle 104.
• An armature, such as armature 40 (Fig. 1), is received in stator assembly 100.
• a fan 112 is affixed at one end of shaft 42 of armature 40 and is disposed within fan baffle 104.
• An insulative sleeve 114 may illustratively be disposed between shaft 42 and laminations 46 and between shaft 42 and commutator 50.
• An end plate (not shown in Figs. 9 and 10), such as end plate 52 (Fig. 1 ), is affixed to fan baffle 104.
• the rear bearing support 102 includes a cap 106 integrally molded from the overmold material 83.
• the cap 106 includes a pocket 108 for receiving rear bearing 70 (Fig. 1). Integrally forming the cap 106 as part of the overmolding 84 from the overmold material 83 eliminates the need for separate fasteners to fix the rear bearing support 102 to the stator housing 32.
• the fan baffle 104 is likewise integrally molded from the overmold material 83.
• Fig. 11 an alternate embodiment of stator assembly 100 is shown and generally indicated by reference numeral 100'.
• Stator assembly 100' is substantially similar to the stator assembly 100 shown in
• a front bearing support 103 (shown in phantom in Fig. 11) for engaging a front bearing, such as bearing 56 (Fig. 1), may be integrally molded in a manner substantially similar to the rear bearing support 102.
• stator assembly 100 is illustrated and generally indicated by reference numeral 100".
• Stator assembly 100" is substantially similar to the stator assembly 100 shown in Figs. 9 and 10, however, only the fan baffle 104 is integrally molded as part of overmolding 84 from the overmold material 83.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Permanent Field Magnets Of Synchronous Machinery (AREA)
• Dc Machiner (AREA)
• Motor Or Generator Frames (AREA)
• Manufacture Of Motors, Generators (AREA)

Priority Applications (6)

Applications Claiming Priority (6)

Publications (2)

Family

ID=34381919

Family Applications (1)

Country Status (8)

Cited By (9)

Families Citing this family (4)

Citations (5)

Family Cites Families (12)

• 2003
  • 2003-12-10 CA CA002508260A patent/CA2508260A1/en not_active Abandoned
  • 2003-12-10 WO PCT/US2003/039145 patent/WO2004055956A2/en active Search and Examination
  • 2003-12-10 AU AU2003293467A patent/AU2003293467B2/en not_active Ceased
  • 2003-12-10 BR BR0317257-0A patent/BR0317257A/pt not_active IP Right Cessation
  • 2003-12-10 JP JP2005508313A patent/JP2006518177A/ja active Pending
  • 2003-12-10 KR KR1020057010492A patent/KR20050084230A/ko not_active Application Discontinuation
  • 2003-12-10 MX MXPA05006227A patent/MXPA05006227A/es active IP Right Grant
  • 2003-12-10 EP EP03790418.2A patent/EP1588469A4/en not_active Withdrawn

Patent Citations (5)

Non-Patent Citations (1)

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