Electric machine, stator assembly for an electric machine, and method of manufacturing the same

A stator for a motor having a rotor includes a plurality of laminations each formed in a first elongated arrangement. Each lamination includes a first leg, a second leg, and an intermediate portion that are configured to be rearranged and stacked in a stackwise direction to define a core having a second U-shaped arrangement. A coil is coupled to the first leg.

BACKGROUND

The invention relates to a stator assembly for an electric machine and a method of manufacturing the same. More particularly, the invention relates to an electric machine including a stator.

SUMMARY

In one embodiment, the invention provides a stator for a motor having a rotor. The stator includes a plurality of laminations each formed in a first elongated arrangement. Each lamination includes a first leg, a second leg, and an intermediate portion that are configured to be rearranged and stacked in a stackwise direction to define a core having a second U-shaped arrangement. A coil is coupled to the first leg.

In another construction, the invention provides a stator for a motor having a rotor. The stator includes a first leg including a first curved portion and a first substantially straight portion and a coil coupled to the first leg. The stator also includes a second leg formed as a separate piece from the first leg. The second leg includes a second curved portion and a second substantially straight portion. An intermediate portion is formed as a separate piece from the first leg and the second leg. The first leg, the second leg, and the intermediate portion are connected to one another to at least partially define a U-shaped magnetic circuit.

In yet another construction, the invention provides a stator for a motor. The stator includes a first leg formed from a first plurality of laminations. The first leg includes a first curved portion and a first substantially straight portion. A first coil is coupled to the first leg. A second leg is formed from a second plurality of laminations and is separate from the first leg. The second leg includes a second curved portion and a second substantially straight portion. A second coil is coupled to the second leg. An intermediate portion is formed from a third plurality of laminations and is separate from the first leg and the second leg. A first locking member is configured to connect the first leg and the intermediate portion and a second locking member is configured to connect the second leg and the intermediate portion. A bridge member is connected to the first curved portion and the second curved portion.

Other aspects and embodiments of the invention will become apparent by consideration of the detailed description and accompanying drawings.

DETAILED DESCRIPTION

As illustrated inFIG. 1, a motor10generally includes a rotor15disposed within a stator20. The rotor15includes a rotor core25and a shaft30that extends from one or both ends of the rotor core25to provide support points and to provide a convenient shaft power take off point. Generally, two or more bearings35engage the rotor shaft30and support the rotor15such that it rotates about a rotational axis40. The motor10also includes a housing45that supports the stator20. The stator20defines a substantially cylindrical aperture55that is centered on the rotational axis40. When the rotor15is in its operating position relative to the stator20, the rotor core25is generally centered within the aperture55such that a small air gap is established between the rotor core25and the stator20. The air gap allows for relatively free rotation of the rotor15within the stator20.

The motor10illustrated inFIG. 1is a permanent magnet brushless motor. As such, the rotor15includes permanent magnets that define two or more magnetic poles. The stator20includes conductors (e.g., wire) forming one or more phase windings that can be selectively energized to produce a varying magnetic field. The permanent magnets of the rotor15interact with the varying magnetic field of the stator20to produce rotor rotation. As one of ordinary skill will realize, the present invention is suited for other types of electric motors (e.g., induction motors, variable reluctance motors) and other arrangements of motors (e.g., outer-rotor motors). As such, the invention should not be limited to the permanent magnet brushless motors illustrated herein. Furthermore, one of ordinary skill will realize that the present invention can also be applied to many types of generators. In addition, figures and description presented herein are directed to a stator and/or a motor. However, many of the features described and illustrated could be applied to wound rotors. Thus, while the figures and description refer to a brushless motor and/or a stator, other applications are possible.

FIGS. 2-22illustrate various aspects of another stator805and electric machine810according to the invention. Before describingFIGS. 2-22in detail, it should be noted thatFIGS. 2-22illustrate a motor810referred to in the following as a U-frame motor. However, some aspects illustrated inFIGS. 2-22are applicable to other motor arrangements such as, for example C-frame motors as described in U.S. Pat. No. 6,982,532, which is fully incorporated herein by reference. As such, the aspects discussed with regard toFIGS. 2-22should not be limited to U-frame motors alone. Generally, the U-frame and C-frame motors described are permanent magnet brushless motors. However, other types of motors, such as, for example, shaded pole induction motors may employ features illustrated inFIGS. 2-22.

FIG. 2illustrates a U-frame motor810that includes a rotor815, the stator805, a printed circuit board (PCB)820, a first bearing arrangement825, and a second bearing arrangement830. The PCB820includes electrical components that allow for the control of the rotation of the rotor815. Specifically, the electrical components and the PCB820are designed to receive an input electrical signal at a predetermined voltage and frequency (such as, for example, standard utility power or 12V dc) and convert the input signal to an output signal at a second voltage and frequency to produce the desired rotation of the rotor815. In preferred constructions, the output signal is a high-frequency signal that produces rotation of the rotor815at a desired speed, as is well known in the motor art.

The rotor815includes a shaft835that supports a rotor core840. The shaft835can be coupled to a component to allow for the transmission of power to the component to be driven by the motor810. The rotor core840shown inFIG. 2consists of a permanent magnet cylinder magnetized to define at least two magnetic poles and attached to the shaft835. In other constructions the rotor core can include other components such as ferromagnetic laminations, electric conductors etc. as is known to those skilled in the art.

The first bearing arrangement825shown inFIG. 3includes a first bearing845, a first lubrication member850, and a first bearing retainer855. This arrangement is described in detail in U.S. Patent Application Publication No. 2006/0038452 fully incorporated herein by reference. The first bearing arrangement825is supported by the PCB820, as illustrated inFIG. 3. In the illustrated construction, the PCB820is encapsulated in a material (e.g., plastic) that also defines a bearing support portion (not shown). The encapsulating material defines a first encapsulation portion1145. The first bearing845is supported by the bearing support portion such that the bearing845is able to move slightly to align with the rotor shaft835. The shaft835extends into the bearing845and, in some constructions extends through a portion of the PCB820. In the illustrated construction, a journal bearing, also commonly referred to as a self-aligning sleeve bearing, or bushing, is employed. However, other constructions may employ other types of bearings (e.g., roller, ball, needle, etc.) if desired.

The first lubrication member850fits within the bearing support portion and substantially surrounds the bearing845. In preferred constructions, a lubricant soaked felt-like material is employed such that the felt-like material is able to deliver lubricant to the bearing845during the life of the motor810.

The first bearing retainer855covers the first lubrication member850and a portion of the first bearing845and engages the bearing support portion to retain the first lubrication member850and the first bearing845in their operating position. The first bearing retainer855includes a central aperture860and a plurality of radially extending slots865that cooperate to define flexible fingers870. The ends of the fingers870adjacent the central aperture860engage the bearing845and bias it toward its operating position.

With reference toFIG. 2, a second encapsulation portion875supports the second bearing arrangement830. The second bearing arrangement830includes a second bearing880, a second lubrication member885, and a second bearing retainer890that are each similar to the corresponding first bearing845, first lubrication member850, and first bearing retainer855of the first bearing arrangement825.

In one construction, the second encapsulation portion875is formed with a pocket that receives the second bearing880, the second lubrication member885, and the second bearing retainer890. Thus, the second bearing retainer890engages the second encapsulation portion875and biases the second bearing880toward its operating position. In other constructions, the pocket is formed around the second bearing arrangement830.

The stator805, illustrated inFIG. 4, includes a stator core895, first and second coils900,905, and two bridges910. The stator core895includes a base915, a first leg920that supports the first coil900, and a second leg925that supports the second coil905. The first leg920and the second leg925each include a substantially straight portion that receives the respective coil900,905, and curved portions926that extend beyond the coils and at least partially define a rotor space930. The curved portions926are substantially C-shaped such that they define two openings935in the rotor space930. The curved portions926are sized such that they surround a substantial portion of the circumference of the rotor (particularly the rotor core840) when it is installed in the stator. In preferred constructions, the curved portions926are arranged to surround at least about 65 percent of the circumference of the rotor.

Two slots940are formed in each of the curved portions and are sized to receive the bridges910. Each slot940is substantially circumferential and is disposed near the rotor space930adjacent the openings935. Preferably, the slots940are shaped and sized such that they do not detrimentally influence the path of the magnetic flux in the stator core895.

Bridges910and their use in U-frame motors are described in U.S. Pat. No. 6,975,049 and U.S. Patent Application Publication No. 2005/0223541, both of which are fully incorporated herein by reference.FIG. 5illustrates one common bridge910that could be employed in the stator805. The bridge910includes two engaging tabs945and an offset body portion950. The engaging tabs945engage the slots940of the curved portion to attach the bridge910and position the offset body portion950adjacent the rotor space930. The shape of the bridge910enhances the mechanical strength and reduces the vibration and noise that could be caused by electromagnetic forces. Also, the bridges910provide additional strength and rigidity to the stator805, reduce the variation of the air-gap magnetic permeance around the circumference of the rotor815and therefore reduce cogging torque, noise, and vibration of the electrical machine810. Also, the material used for the bridges910can be selected, and the shape and dimensions of the bridges910can be designed to improve other aspects of motor performance. For example, in one construction, discussed with regard toFIG. 9, the material characteristics and the design of the bridges910influence the parking position of the rotor815, thereby improving the starting capability of the electrical machine810.

FIG. 6illustrates another arrangement of a bridge955. In this construction, the bridge955includes two engaging tabs945and a body portion950. The engaging tabs945engage the stator core895in a manner similar to that described with regard to the bridge910ofFIG. 5. The body portion950is similar to the body portion950of the bridge910ofFIG. 5and also includes two corrugations960, or bumps that enhance the mechanical strength of the structure and modify the distribution of the air-gap magnetic permeance when compared to the construction incorporating bridge910ofFIG. 5. It should be noted that other bridge constructions may employ only one corrugation960or may employ more than two corrugations960as desired.

FIGS. 7-9illustrate three additional constructions of bridges suitable for use with the stator805ofFIG. 3. The bridge965ofFIG. 7includes a first portion970and a second portion975that are substantially similar to the bridge955ofFIG. 6, but which are narrower. The first portion970and the second portion975are interconnected in their width direction by a ligament980disposed in the body portion950between corrugations960. In the illustrated construction, a single ligament980is centered in the bridge955. While a single slot1050is illustrated inFIG. 9, other constructions may offset the ligament980to one side or may include two or more ligaments980.

The bridge985ofFIG. 8includes a first narrow end990, a second narrow end995, a first wide end1000and a second wide end1005. A first narrow body portion1010extends from the first narrow end990to the first wide end1000to define a first end portion1015. A second narrow body portion1020extends from the first wide end1000to the second wide end1005to define an inner portion1025. A third narrow body portion1030extends from the second wide end1005to the second narrow end995to define a second end portion1035. Thus, two slots1040are defined with one slot1040being between the first narrow body portion1010and the second narrow body portion1020and the second slot1040being between the second narrow body portion1020and the third narrow body portion1030. The wide ends1000,1005and narrow ends990,995are similarly shaped such that they may engage the slots940in the curved portions of the core895. In addition, the first end portion1015, the second end portion1035, and the inner portion1025include corrugations960to enhance the strength of the bridge985. It should be noted that other constructions may employ only one slot1040or more than three slots1040if desired.

Another construction of a bridge1045shown inFIG. 9includes first and second end portions that each define two engaging tabs945that are separated by a slot1050. The engaging tabs945engage the stator core895in a manner similar to that described with regard to the bridge910ofFIG. 5. The bridge1045also includes a body portion1055that is divided into three separate portions. A first portion1060extends from one end portion to a point slightly beyond the center of the bridge1045. The first portion1060extends across the full width of the bridge1045and includes a slot1065approximately centered within the first portion1060. A second portion1070extends from the second end portion and is substantially the full width of the bridge1045. A third portion1075interconnects the first portion1060and the second portion1070and is substantially thinner than the full width of the bridge1045. The third portion1075includes a corrugation960and is disposed substantially on one side of the bridge1045(see alsoFIG. 13). Other constructions may employ more slots1065if desired.

Magnetic bridges910,955,965,985,1045with a construction as illustrated inFIGS. 7-9enhance the electromagnetic and mechanical performance, as well as the manufacturability of the motor810. In preferred constructions, the bridges910,955,965,985,1045are manufactured using ferromagnetic material such as laminated electric steel. The bridges can be manufactured for example by stamping (punching) the laminations and then profile them by using a die. By corrugating the bridges the mechanical strength is increased and the vibration and noise, which could be caused by the electromagnetic forces acting on the bridge, is reduced. Furthermore, the corrugations960(bumps) are conveniently located to modify the distribution of the magnetic field in the motor air-gap and its surrounding regions. For example, the construction ofFIG. 9includes one corrugation960that increases the air-gap between the rotor815and the bridge1045and covers only part of the core axial length, thereby defining an effective magnetic opening of the air-gap, which reduces the magnetic leakage flux. The asymmetric position of the corrugation960and of the air-gap opening enhances the rotor parking capability and the shape of the motor back emf for electronic control.

The magnetic bridges965,985,1045ofFIGS. 7-9define slots that substantially divide the bridge965,985,1045into two or more axial sections that reduce the path of the induced eddy currents and minimize core losses. The slots are formed to maintain the one-piece integrity of the bridge965,985,1045and enhance manufacturability. The proportion between the width of the slots and the bridge965,985,1045is also conveniently designed to control the magnetic saturation in the bridge965,985,1045and enhance motor performance. Other combinations of slots and corrugations, different from those shown in the figures, are also possible.

While one-piece bridge constructions have been described, it should be noted that several bridge constructions may include two or more components that cooperate to define the bridge. For example, one construction illustrated inFIG. 27includes a first bridge portion955athat is disposed near the rotor and a second bridge portion1045athat is disposed on top of the first bridge portion955ato in effect define a thicker bridge1079. In the illustrated construction, two different bridge portions are employed. These two bridge portions can be made using similar or different materials if desired. Alternatively, other constructions may employ similarly shaped bridge portions and can be made from similar or different materials. Thus,FIG. 27illustrates a construction in which two bridge portions955a,1045aare stacked on top of one another to define a stacked bridge1079. In one construction, a substantially solid copper first bridge portion is placed near the rotor and a steel portion shaped like one of the bridges910,955,965,985,1045, or another suitable shape, is placed on top of the first portion to complete the bridge. Such an arrangement may provide electromagnetic or operational advantages that are desirable. For example, the aforementioned example would function like a shading coil and would improve the starting performance of a single-phase induction motor incorporating the stator.

In preferred constructions, the stator core895is formed from a plurality of stacked laminations1080. The laminations1080, shown inFIG. 10, are generally formed from electric steel or other suitable materials. In some constructions, the laminations1080are punched from grain-oriented steel with a preferred magnetization direction1081extending along the length of the laminations1080. When the lamination1080is reconfigured to its final operating position, the preferred magnetization direction is substantially U-shaped and matches the arrangement of the stator. Specifically, the metal has a grain structure oriented in a U-shaped direction when the lamination is in the U-shaped arrangement. This arrangement enhances the motor performance because in the finally assembled laminations (see for exampleFIG. 14) the magnetic field during motor operation is substantially aligned with the preferred magnetization direction of the steel. The lamination1080illustrated inFIG. 10, and arranged for forming (punching) as shown inFIG. 11, results in a very low scrap rate, thereby reducing the cost of a motor810produced with the laminations1080.

With continued reference toFIG. 10, each lamination1080includes an elongated body portion1085and two curved portions1090disposed at either end of the body portion1085. The body portion1085has a substantially constant width1095and defines two V-shaped reliefs1100that are positioned such that the apex of the “V” is positioned adjacent the intended corner of the stator core895when the lamination1080is reconfigured to a second U-shaped arrangement. In the illustrated construction, a circular aperture1105is positioned at the apex to provide additional relief that may be required during reconfiguration.

Each of the curved portions1090includes an inner arcuate surface1110and an outer arcuate surface1115. In preferred constructions the inner arcuate surface1110and the outer arcuate surface1115are substantially circular and as such define a diameter. The diameter is thus the average diameter of the particular surface. The inner arcuate surface1110and the outer arcuate surface1115are arranged such that they define a curved portion width1120. In preferred constructions the curved portion width1120is substantially constant and is substantially equal to the width1095of the body portion1085. The inner arcuate surface1110and the outer arcuate surface1115have substantially the same circular profile with the same diameter. The surfaces can have a relatively small variation from a circular profile (e.g., elliptical) in order to allow for a tapered or stepped rotor to stator air-gap that may enhance the motor performance.

Each curved portion1090also defines an attachment aperture1125that extends through the lamination1080and two circumferential slots1130. In the illustrated construction, the attachment apertures1125are circular apertures disposed near the outer arcuate surface1115, with other shapes, sizes and locations also being possible. The two circumferential slots1130are formed near the inner arcuate surface1110adjacent the ends of each curved portion1090.

The use of a lamination1080as illustrated inFIG. 10allows the laminations1080to be manufactured from a single sheet of material as illustrated inFIG. 11. The arrangement ofFIG. 10allows for the production of several laminations1080that are very closely spaced, thus greatly reducing the amount of scrap. In addition, the arrangement allows the outer arcuate surface1115to closely match the inner arcuate surface1110to enhance the nesting arrangement.

With reference toFIGS. 12-13, the assembly of the motor810ofFIG. 2will be described. A plurality of laminations1080are stamped or otherwise formed such that they resemble the laminations1080ofFIG. 10. Several of the laminations1080are stacked on top of one another to define the stator core895having a desired axial depth. In the illustrated construction, eight laminations1080are stacked on top of one another while still arranged in a first elongated arrangement.

Bobbin supports1135made of an electrically insulating material are then positioned on the stator core895as illustrated. In one construction, the stacked stator core895is positioned in a mold and a moldable material is formed around the stator core895to define the bobbin supports1135. For example, one construction injection molds plastic in the shape of the bobbin supports1135. The bobbin supports1135in these constructions provide a location for a coil1140to be wound from electric conductor (magnet wire) and could also serve to hold the various laminations1080together. In other constructions, the bobbin supports include two pieces with a snap fit or other attachment means, or plastic end portions with insulation between the plastic ends covering the steel. In one construction, electrostatically-deposited electrical insulation is applied to the steel to at least partially define bobbin supports.

Once the bobbin supports1135are positioned as desired, the magnet wire is wound to complete each coil.FIG. 12illustrates one bobbin support1135after the coil1140is wound and the second bobbin support1135before winding. With the bobbin supports1135and the laminations1080positioned as illustrated inFIG. 12, an inexpensive bobbin winder can be employed to wind the coils.FIG. 12does not illustrate the magnet wire which is repeatedly wound, but rather illustrates the space occupied by the coil1140as a block of material on the bobbin1135.

After the coils1140are wound, the laminations1080are bent, reconfigured or otherwise repositioned in a second U-shaped arrangement as illustrated inFIG. 13. The bridges1045are then coupled to the laminations1080to complete the stator assembly. While the preferred method of attaching the bridges is by inserting them in slots made into the stator core, it is understood that other known methods of coupling, such as pressing, gluing, screwing etc, may be employed. It should be noted thatFIG. 13illustrates the stator805as including the bridges1045ofFIG. 9. However, other constructions may include the bridges910,955,965or985illustrated inFIGS. 5-8rather than the bridges1045ofFIG. 9. Alternatively, a combination of the bridges910,955,965,985,1045illustrated inFIGS. 5-9may be employed. In still other constructions, no bridges, or other bridges not illustrated herein are employed.

With the stator assembly complete, the printed circuit board820and first bearing arrangement825are coupled to the stator805as illustrated inFIG. 2. The first bearing845and the first lubrication member850are positioned within the bearing support portion that is formed with the PCB820. The first bearing retainer855is then positioned such that it engages the first bearing support portion and holds the first bearing845in the desired position. The PCB820, including the first bearing845is then positioned adjacent the stator805as illustrated inFIG. 2. In some constructions, fasteners, stand-offs, pins, or other positioning members pass through the attachment apertures1125of the laminations1080and support the PCB820adjacent the stator805and in the desired position. The PCB820and stator805are then positioned within a mold and encapsulated in a material that defines the first encapsulation portion1145. In one construction, molded or injection-molded plastic encapsulates the stator805and the PCB820. Once encapsulated, the positioning members can be removed if desired, as the encapsulating material now performs all of the support and positioning functions.

As discussed, the second bearing arrangement830can be formed separate from the stator805and PCB820assembly if desired. Generally, in these constructions, the second encapsulation portion875is formed to include the pocket that receives the second bearing880, the second lubrication member885, and the second bearing retainer890. The second bearing880and second lubrication member885are positioned within the pocket and the second bearing retainer890engages the walls that define the pocket to hold the second bearing880in the desired position.

The rotor815, including the shaft835and the rotor core840, is positioned within the encapsulated stator805such that one end of the shaft835engages the first bearing845and the rotor core840is positioned within the rotor space930defined by the laminations1080and the bridges1045. The second bearing arrangement830is then positioned adjacent the encapsulated stator805and the rotor815such that the shaft835extends through the second bearing880and the second encapsulation portion875. The second encapsulation portion875is then attached to the first encapsulation portion1145using any suitable means including adhesives, welding, fasteners, and the like. In some constructions, the positioning members extend beyond the first encapsulation portion1145and engage the second encapsulation portion875to properly locate the second encapsulation portion875and the second bearing880. In the construction illustrated inFIG. 2, standoffs856are formed as part of the first encapsulation portion1145. The standoffs856extend from the first encapsulation portion and fit within apertures in the second encapsulation portion875. The standoffs856are then heat bonded, attached with an adhesive, or attached using other suitable means, to the second encapsulation portion875.

In another construction, the stator805, PCB820, and second bearing880are encapsulated simultaneously in one step. In this construction, the PCB820, including the first bearing845within the bearing support portion is supported in a mold adjacent the stator805, which is also supported in the mold. The rotor815and second encapsulation portion875are also supported in the mold such that encapsulating material can be molded around all of the components in a single step to complete the motor810. Variations in the order of operations and the techniques used to injection mold the entire assembly810are also possible. In other constructions, no plastic injection molding is employed and the motor is formed using conventional end-caps (brackets) as known to those skilled in the art. In still other constructions, injected molded parts, such as a PCB completely encapsulated in plastic, coils partially encapsulated in plastic and a plastic front cover, are combined with conventional parts, such as a zinc end-cap.

FIGS. 14 and 15illustrate another aspect of the invention that may be incorporated into some constructions.FIG. 14shows one of the laminations1080ofFIG. 10after it is bent into its operating position. As can be seen, the V-shaped openings1100close to provide the desired shape of the stator core895. The corners formed by the now closed V-shaped openings1100include a break or discontinuity, oriented at approximately 45 degrees, that may reduce the electromagnetic performance of the motor810slightly. In a motor with a rotor made substantially of permanent magnet material (e.g., ceramic ferrite, rare-earth NdFeB, etc.), the mmf drop caused by the introduction in the magnetic circuit of the aforementioned corner discontinuities is minimal. However, the arrangement described does allow the lamination to have a substantially constant width along the magnetic circuit, thus enhancing the electromagnetic performance of the motor810.

FIG. 15illustrates another lamination1150that is similar to the lamination1080ofFIG. 14. However, the lamination1150ofFIG. 15includes an open (cut-out) corner1155in which lamination material has been omitted. Modeling and testing has shown that very little magnetic flux passes through this particular corner1155during motor operation. The results of the electromagnetic finite element analysis are illustrated inFIGS. 21a-21cof U.S. Pat. No. 6,975,049 which is fully incorporated herein by reference. As such, the omission of this material has little effect on motor performance. However, the space created by the omitted material does provide space for electrical or other components such as a capacitor1156, thus further reducing the overall size of the completed motor810.

FIGS. 10-15describe one basic arrangement of laminations1080. However, one of ordinary skill in the art will realize that different variations in laminations are possible andFIGS. 16 and 17are exemplary of one such variation. The lamination1160ofFIG. 16includes a first end piece1165, a middle piece1170, and a second end piece1175that can be arranged adjacent one another to allow for their production with a very low scrap rate. In fact, the laminations1160can be arranged such that almost no scrap is produced (see alsoFIG. 11).

The first and second end portions1165,1175may, in some constructions be substantial mirror images of one another and include a curved portion1090that at least partially defines the rotor space930. A body portion1085extends from the curved portion1090and terminates at an angled surface1180. In the illustrated construction, the angle is approximately 45 degrees with respect to the body portion1085. An attachment aperture1185is formed in each of the body portions1085near the angled surface1180.

The middle piece1170is substantially trapezoidal with two angled surfaces1190that are angled to match the angles of the first and second end portion angled surfaces1180. Thus, in the illustrated construction, the angles are approximately 45 degrees with respect to the body portions1085. Two middle attachment apertures1195are formed in the middle piece1170with one adjacent each angled surface1190.

In some constructions, the end pieces1165,1175and the middle piece1170include interlocking members, such as tabs and slots, balls and sockets, and the like, that further enhance the connection between the components to improve both the mechanical strength and the electrical performance of the stator. For example,FIGS. 21-22illustrate a lamination1194in which the middle or intermediate piece1170includes balls1196that extend outward from the angled surface1190. Each of the end portions1165,1175includes a socket1197that extends inward from the angled surface1180and that is sized to receive the balls1196. InFIG. 21, a socket1197and its mating ball1196have a common centerline that is perpendicular to the corresponding angled surface1180. Because the angled surfaces1180,1190are arranged at about 45 degrees with respect to a longitudinal axis1198of the lamination1194and are perpendicular to one another, the intermediate portion1170is simply rotated 180 degrees about the longitudinal axis1198and the end portions1165,1175are connected to the intermediate portion1170such that the balls1196engage the sockets1197and the adjacent angled surfaces1180,1190are substantially parallel to one another to change the arrangement from the first elongated arrangement ofFIG. 21to the second U-shaped arrangement illustrated inFIG. 22.

A stator core1200assembled using the laminations1160ofFIG. 16is illustrated inFIG. 17. To assemble the stator core1200, the middle piece1170of each lamination1160is inverted and the first and second end portions1165,1175are moved such that their respective angled surfaces1180align with the angled surfaces1190of the middle piece1170. Several laminations1160are arranged as described and stacked on top of one another. Locking members1205are then positioned to lock the end portions1165,1175to the middle pieces1170. In constructions that employ the lamination ofFIGS. 21 and 22, the function of the locking member1205is performed by the engagement of the balls1196with the adjacent sockets1197.

In the illustrated construction ofFIG. 17, a first U-shaped locking member1205is inserted into the attachment apertures1185of each of the first end portions1165and the attachment apertures1195of the middle piece1170adjacent the first end portions1165, and a second U-shaped locking member1205is inserted into the attachment apertures1185of each of the second end portions1175and the attachment apertures1195of the middle piece1170adjacent the second end portions1175. In other constructions, a molding operation is used to mold the U-shaped locking members1205in the desired position and complete the assembly of the stator core1200ofFIG. 17. Other means could be used to assemble and hold the stator core1200if desired. Coils can be wound separately and slid on the lamination portions1165and1175prior to assembling the three-part U-frame core1200.

FIG. 18illustrates another more conventional lamination1210that includes a pocket1215sized and positioned to receive a bobbin1135or a wound conductor1140but that omits the outer curved surface and replaces it with a more conventional straight surface1220. Only one pocket1215is illustrated on the lamination1210. However, a second pocket1215could be employed if desired. In preferred constructions, the pocket1215receives the bobbin1135to fixedly locate and support the bobbin1135. However, other constructions may apply the conductor1140directly to the pocket1215and omit the bobbin1135. In addition, the pocket1215could be applied to differently arranged laminations, such as the lamination1160illustrated inFIG. 16, the lamination1194illustrated inFIG. 21, and/or the lamination1080illustrated inFIG. 10. Combinations of elements shown inFIGS. 10,16,18,19and21are also possible. For example, lamination1194ofFIG. 21can include pockets on legs1165and1175similarly to the pockets1215shown inFIG. 18.

FIGS. 19 and 20illustrate another lamination1225suitable for use with the invention. The lamination1225is similar to the lamination1080ofFIG. 10with the exception of the area adjacent the V-shaped spaces1100. Rather than employ a small circular aperture, the lamination1225ofFIG. 19includes a larger circular relief1230and a bump1235on the opposite side of the lamination1225from the V-shaped opening1100. The bump1235includes a partially-circular portion that shares a substantially common center with the circular relief1230as illustrated inFIG. 20. Thus, the bump1235serves to provide a material ligament1240that is large enough to facilitate the bending of the lamination1225without failing, and ensures good perpendicularity tolerances of the bent structure. In the construction illustrated inFIG. 20, the V-shaped portion defines an imaginary apex1245that rests on an extension of the outer surface1250of the lamination1225. This geometry allows for the consistent bending of the lamination1225to the desired final shape. Other constructions, may vary the size, width, or shape of the bump1235and the ligament1240as desired. In addition, other constructions may employ a shape other than a circle to define the relief1230.

While the constructions ofFIGS. 2-22have been described as including stator cores formed from laminations, one of ordinary skill in the art will realize that other constructions, including powdered metal components, could be employed if desired. For example, a stator core having a substantially constant magnetic path width could be formed, if desired, from a single powdered metal component, such as for example a soft magnetic composite. As such, the invention should not be limited to stator cores constructed from laminations.

FIGS. 23-26illustrate aspects of a stator1300suitable for use in a motor like the one illustrated inFIG. 1and incorporating a number of bridges1305similar to those described with regard to the constructions ofFIGS. 2-22. The stator is substantially circular and includes a number of teeth1310that extend radially inward. In the illustrated construction, the stator1300includes four teeth1310with other stators1300employing more or fewer teeth1310as required. The teeth1310are substantially uniform in width, as best illustrated inFIG. 24and as such define wide slot openings. Each tooth1310defines two slots1315that extend in an axial direction and that are sized to receive one of the bridges1305. The teeth1310extend inward to define a central aperture1320that receives a rotor1325much like conventional motors of this type.

The large slot openings allow a coil1327to be prewound and then slid onto the particular tooth1310if desired. Alternatively, the wide slot opening between the teeth1310facilitates the easy winding of the coil1327onto the tooth if desired.

Unlike conventional stators, the stator1300ofFIGS. 23 and 24includes bridges1305that extend across the slot openings to connect adjacent teeth1310. Thus, the teeth1310and the bridges1305cooperate to completely surround the circumference of the rotor1325, and particularly the rotor core.

While bridges configured as illustrated inFIGS. 5-9could be employed in the stator1300ofFIGS. 23 and 24, the stator1300ofFIGS. 23 and 24includes another bridge1305illustrated inFIG. 25. The bridge1305is similar to the bridge965ofFIG. 7and includes four tabs1330with two adjacent tabs1330arranged to engage one of the slots1315of the stator teeth1310. The bridge1305also includes four corrugations1335that extend in a substantially axial direction with respect to the stator1300. The bridge1305is divided into a first half1340and a second half1345by a pair of slots1350that extend in a circumferential direction and terminate at a ligament portion1355that maintains the connection between the first half1340and the second half1345. In some constructions, additional slots1350are employed to divide the bridge1305into more than two parts if desired.

FIG. 26illustrates yet another bridge1360that could be employed in the stator805ofFIG. 2or the stator1300ofFIG. 23. The bridge1360includes two tabs1365that engage the tooth slots1315, a single corrugation1370near one end of the bridge1360, and a slot1375near the opposite end. The bridge1360includes substantially continuous tabs1365that, when inserted into the stator teeth slots1315, ensure the continuity of the magnetic connection between the ferromagnetic core and the bridge1360. The slot1375and the corrugation1370increase the equivalent magnetic length of the air-gap between the stator1300and the rotor1325and introduce an asymmetry that may be beneficial for certain type of motors, such as single phase motors. The eddy current path in the bridge1360is reduced due to the slot1350.

The bridges can be manufactured from ferromagnetic material, such as cold rolled motor lamination steel that is non-grain oriented or from transformer laminated steel, which is grain oriented. If a grain oriented steel is employed, the slot leakage flux can be reduced by aligning the hard (non-preferential) magnetization axis of the steel with the circumferential direction surrounding the motor air-gap and the rotor.

It should be understood that each of the features described with respect to one or more of the bridge constructions illustrated herein could be applied to any other of the bridge constructions illustrated herein. As such, the lack of description with regard to any feature of a bridge should not be interpreted as an indication that the feature is not applicable to the particular bridge construction being described.

Thus, the invention provides, among other things, a new and useful stator for an electric motor. The constructions of the stator and the methods of manufacturing the stator described herein and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the invention.