Electrodynamic apparatus and method of manufacture
Electrodynamic apparatus such as a motor, generator or alternator is configured having a stator core assembly formed of pressure shaped processed ferromagnetic particles which are pressure molded in the form of stator modules. These generally identical stator modules are paired with or without intermediate modules to provide the stator core structure for receiving field winding components. In one embodiment, two sets of the paired stator modules are combined in tandem to enhance operational functions without substantial diametric increases in the overall apparatus.
Latest Patents:
Not applicable.
BACKGROUND OF THE INVENTIONInvestigators in the electric motor arts have been called upon to significantly expand motor technology from its somewhat static status of many decades. Improved motor performance particularly has been called for in such technical venues as computer design and secondary motorized systems carried by vehicles, for example, in the automotive and aircraft fields. With progress in these fields, classically designed electric motors, for example, utilizing brush-based commutation, have been found to be unacceptable or, at best, marginal performers.
From the time of its early formation, the computer industry has employed brushless d.c. motors for its magnetic memory systems. The electric motors initially utilized for these drives were relatively expensive and incorporated a variety of refinements, for instance as necessitated with the introduction of rotating disc memory. Over the recent past, the computer industry has called for very low profile motors capable of performing in conjunction with very small disc systems and at substantially elevated speeds.
Petersen, in U.S. Pat. No. 4,745,345, entitled “D.C. Motor with Axially Disposed Working Flux Gap”, issued May 17, 1988, describes a PM d.c. motor of a brushless variety employing a rotor-stator pole architecture wherein the working flux gap is disposed “axially” with the transfer of flux being in parallel with the axis of rotation of the motor. This “axial” architecture further employs the use of field windings which are simply structured, being supported from stator pole core members, which, in turn, are mounted upon a magnetically permeable base. The windings positioned over the stator pole core members advantageously may be developed upon simple bobbins insertable over the upstanding pole core members. Such axial type motors have exhibited excellent dynamic performance and efficiency and, ideally, may be designed to assume very small and desirably variable configurations.
Petersen in U.S. Pat. No. 4,949,000, entitled “D.C. Motor”, issued Aug. 14, 1990 describes a d.c. motor for computer applications with an axial magnetic architecture wherein the axial forces which are induced by the permanent magnet based rotor are substantially eliminated through the employment of axially polarized rotor magnets in a shear form of flux transfer relationship with the steel core components of the stator poles. The dynamic tangentially directed vector force output (torque) of the resultant motor is highly regular or smooth lending such motor designs to numerous high level technological applications such as computer disc drives which require both design flexibility, volumetric efficiency, low audible noise, and a very smooth torque output.
Petersen et al, in U.S. Pat. No. 4,837,474 entitled “D.C. Motor”, issued Jun. 6, 1989, describes a brushless PM d.c. motor in which the permanent magnets thereof are provided as arcuate segments which rotate about a circular locus of core component defining pole assemblies. The paired permanent magnets are magnetized in a radial polar sense and interact without back iron in radial fashion with three core components of each pole assembly which include a centrally disposed core component extending within a channel between the magnet pairs and to adjacently inwardly and outwardly disposed core components also interacting with the permanent magnet radially disposed surface. With the arrangement, localized rotor balancing is achieved and, additionally, discrete or localized magnetic circuits are developed with respect to the association of each permanent magnet pair with the pole assembly.
Petersen in U.S. Pat. No. 5,659,217, issued Aug. 19, 1997 and entitled “Permanent Magnet D.C. Motor Having Radially-Disposed Working Flux-Gap” describes a PM d.c. brushless motor which is producible at practical cost levels commensurate with the incorporation of the motors into products intended for the consumer marketplace. These motors exhibit a highly desirable heat dissipation characteristic and provide improved torque output in consequence of a relatively high ratio of the radius from the motor axis to its working gap with respect to the corresponding radius to the motors' outer periphery. The torque performance is achieved with the design even though lower cost or, lower energy product permanent magnets may be employed with the motors. See also: Petersen, U.S. Pat. No. 5,874,796, issued Feb. 23, 1999.
The above-discussed PM d,c, motors achieve their quite efficient and desirable performance in conjunction with a multiphase-based rotational control. This term “multiphase” is intended to mean at least three phases in conjunction with either a unipolar or bipolar stator coil excitation. Identification of these phases in conjunction with rotor position to derive a necessary controlling sequence of phase transitions traditionally has been carried out with two or more rotor position sensors. By contrast, simple, time domain-based multiphase switching has been considered to be unreliable and impractical since the rotation of the rotor varies in terms of speed under load as well as in consequence of a variety of environ mental conditions.
Petersen in application for U.S. patent Ser. No. 10/706,412, filed Nov. 12, 2003, entitled “Multiphase Motors With Single Point Sensing Based Commutation” describes a simplified method and system for control of multiphase motors wherein a single sensor is employed with an associated sensible system to establish reliable phase commutation sequencing.
Over the years of development of what may be referred to as the Petersen motor technology, greatly improved motor design flexibility has been realized. Designers of a broad variety of motor driven products including household implements and appliances, tools, pumps, fans and the like as well as more complex systems such as disc drives now are afforded an expanded configuration flexibility utilizing the new brushless motor systems. No longer are such designers limited to the essentially “off-the-shelf” motor varieties as listed in the catalogues of motor manufacturers. Now, motor designs may become components of and compliment the product itself in an expanded system design approach.
During the recent past, considerable interest has been manifested by motor designers in the utilization of magnetically “soft” processed ferromagnetic particles in conjunction with pressed powder technology as a substitute for the conventional laminar steel core components of motors. So structured, when utilized as a motor stator core component, the product can exhibit very low eddy current loss which represents a highly desirable feature, particularly as higher motor speeds and resultant core switching speeds are called for. As a further advantage, for example, in the control of cost, the pressed powder assemblies may be net shaped wherein many intermediate manufacturing steps and quality considerations are avoided. Also, tooling costs associated with this pressed powder fabrication are substantially lower as compared with the corresponding tooling required for typical laminated steel fabrication. The desirable net shaping pressing approach provides a resultant magnetic particle structure that is 3-dimensional magnetically (isotropic) and avoids the difficulties encountered in the somewhat two-dimensional magnetic structure world of laminations. See generally U.S. Pat. No. 5,874,796 (supra).
The high promise of pressed powder components for motors and generators initially was considered compromised by a characteristic of the material wherein it exhibits relatively low permeability. However, Petersen, in U.S. Pat. No. 6,441,530, issued Aug. 27, 2000 entitled “D.C. PM Motor With A Stator Core Assembly Formed Of Pressure Shaped Processed Ferromagnetic Particles”, describes an improved architecture for pressed powder formed stators which accommodates for the above-noted lower permeability characteristics by maximizing field coupling efficiencies.
As the development of pressed powder stator structures for electrodynamic devices such as motors and generators has progressed, investigators have undertaken the design of larger, higher power systems. This necessarily has lead to a concomitant call for larger press molded structures. The associated molding process calls for press pressures adequate to evolve requite material densities to gain adequate electrical properties. To achieve those densities, press pressures are needed in the 40 tons per square inch to 50 tons per square inch range. As a consequence the powdered metal pressing industry suggest that the design of molded parts exhibit aspect ratios (width or thickness to length in the direction of pressing) equal to or less than about 1:5. Thus as the length of stator core component structures increase, their thickness must increase to an extent that a resultant shape becomes so enlarged in widthwise cross section as to defeat the design goal, with attendant loss of both the economies of cost and enhanced performance associated with this emerging pressed powder technology.
BRIEF SUMMARY OF THE INVENTIONThe present invention is addressed to electrodynamic apparatus and a method of manufacturing the stator core assemblies thereof utilizing press powder technologies wherein requisite stator core material densities are achieved while part thicknesses and volumes are retained within desirable dimensional limits. Requisite ratios of component widths or thicknesses to corresponding lengths are maintained in proper combinations while minimizing thicknesses of core structures through the employment of two or more stator core modules or components which, following their press forming, are selectively combined to define a sequence of module core components over which field windings are positioned. Because the stator core modules may be geometrically identical, tooling costs may be conserved through employment, in effect, of a single mold to produce them.
In one embodiment of the invention, paired stator core modules are combined in tandem along the axis of the electrodynamic apparatus to achieve an enhanced functional capacity while minimizing the diametric extent of the device within which they perform. With this arrangement, two or more sets of phase defining field windings are utilized with wire diameters of smaller extent. These phase defining windings advantageously then may be combined for simultaneous excitation through employment of a series or parallel electrical interconnection.
Where stator assembly sizes are called for which are large, the stator core modules may be press formed in segmented fashion. The resulting segments then may be combined in mutually abutting fashion to form the stator modules. Further, the configuration of these segments may be selected such that segments otherwise aligned within paired stator modules can be pre-wound with field winding elements prior to being abuttably joined together.
A convenient feature of the stator assemblies resides in the utilization of electrically insulative shields positioned over the mutually outwardly disposed winding support surfaces of field winding core portions of the stator pole core member. In general, the pole core members are formed with wire receiver troughs within which field windings are retained. To facilitate the circuit association of the windings from pole-to-pole within the stator assembly, the insulative shield may be configured to extend outwardly to define an outwardly open wire receiving channel adjacent the inner surface of an associated back iron region of the stator structure. The stator structures revealed in the embodiments presented herein are all shown in the classical inward facing salient stator pole configuration. This should not be considered a limitation as U.S. Pat. No. 6,441,530 (supra) illustrates both inward and outward facing stators and is incorporated by reference herewith.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.
The invention, accordingly, comprises the apparatus and method possessing the construction, combination of elements, arrangement of parts and steps which are exemplified in the following detailed description.
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the discourse to follow radially salient pole stator structures and the techniques of their formation and assembly are described in conjunction with d.c. PM motors having an architecture for deriving relatively higher power outputs, for example, about 250 watts and above. The structuring and techniques apply additionally to other forms of motors such as doubly salient pole motors and to electricity generators. Thus, the term “electrodynamic apparatus” is utilized with the meaning that it incorporates motors and generators employing the noted techniques of stator formation. In developing such electrodynamic devices utilizing magnetically soft composite pressed powder technology for stator construction the developer will establish a variety of dimensional parameters for electrical reasons establishing, for instance, appropriate material thicknesses to achieve flux transfer and avoidance of saturation. These electrical criteria are generated by calculation. When those requisite thicknesses are so established with judicious safety factors, the utilization of pressed powder material above and beyond those thicknesses will contribute only to weight and cost without improvement in device performance. Once these dimensional parameters are established, then the developer is confronted with the mandates of the powder metal pressing industry requiring molded part aspect ratios calling for structural thicknesses well beyond those necessary for electrical performance criteria.
Looking to
Referring to
Shaft 24 supports a rotor represented generally at 44 which is formed having a cylindrical core 46 formed of aluminum extending to an outer cylindrical surface 48. Coupled with that surface 48 is a cylindrical back iron 50 formed of ferrous material and extending to a cylindrical back iron surface 52. Surface 52, in turn, supports a cylindrical radially magnetized permanent magnet 54 which extends to flux confronting surfaces 56. Those flux confronting surfaces provide, in this embodiment, a sequence of six magnetic regions of alternating polarity generally extending in parallel with the rotor axis 26.
Additionally supported for rotation upon shaft 24 is a polymeric annular disc 58 which rotationally supports an annularly-shaped sequence of sensible system permanent magnets shown in cross section at 60. The annular magnets sequence 60 is shown mounted within an annular steel back iron 62 supported, in turn, upon an annular shoulder 64 formed within disc 58. Mounted internally upon end cap 16 is a printed circuit board 66 which functions to carry an integrated circuit 68 along with appropriate driver transistors and one or more Hall effect sensors as shown at 70. Sensor 70 is positioned for magnetic field response to the magnetic regions of sensible system magnet 60.
An annular stator assembly is represented generally at 80. Assembly 80 is formed using a material composed of magnetically soft pressure shaped processed ferromagnetic particles which are generally mutually insulatively associated. These materials such as Somaloy 500, are sometimes referred to as involving soft magnetic composite technology and are marketed, inter alia, by North American Hoganas, Inc. of Hollsopple, Pa. Assembly 80 is configured as a radial salient pole stator having nine, angularly spaced apart identical stator pole core members. Looking additionally to
Core members 82a-82i and back iron 84 are not formed as a unitary part in their axial plane. Were they to be so formed, the widthwise dimensions required to meet the pressing criteria for pressure shaped processed ferromagnetic particles would increase significantly causing the resulting structure to be less desirable for its intended electrodynamic function. In accordance with the precepts of the invention, the back iron and core members are constructed, for the instant embodiment, as four identically structured modules, each of which is formed meeting press forming criteria and optimum electrical criteria. In this regard, the ratio of each of the noted predetermined widthwise or thickness dimensions with respect to their length in the direction of pressing is equal to or less than a ratio of about 1 to 5. Looking to
Certain of the winding core portions of module 110 are identified in general in
Looking additionally to
Returning to
The receiving troughs and associated shields are configured to carry windings below the noted tip or top surface regions of the back iron portions and flux interaction portions and thus permit module stackability. Additionally,
Turning now to the configuration of the windings 150a-150i provided with modules 110 and 111, reference is made to
Referring to
This approach of achieving higher power motors through the combining of components or modules to form the field wound stator is uniquely suited to powder metal technology. Since the module design is optimized for uniting the requirements of the powder metal pressing industry and the electrical requirements of the motor design under consideration the total number of modules may vary. Also, the stacking ability of the modules yields a versatility to the motor design unavailable with a typical steel lamination motor design. Referring to
Motor 200 is configured with an annular stator assembly represented generally at 234, the stator portion of which is formed of two annular modules formed of pressure shaped processed ferromagnetic particles and here represented in general at 236 and 237. Note that the profiles of components 236 and 237 are identical to those described earlier at 110 and 111 or 112 and 113. Using the identifying convention of the earlier figures, for a nine stator pole embodiment, stator pole core members 240c and 240g of module 236 are revealed. In similar fashion, core members 242c and 242g are illustrated in connection with module 237. As before, each of these modules is net shaped with back iron portions as shown respectively at 244c, 244g and 246c, 246g. The back iron portions are integrally formed with the winding core portions of the stator pole core members as seen at 248g and 250g. Those winding core portions are, in turn, integrally formed with flux interaction portions as at 252c, 252g and 254c, 254g. These flux interaction portions extend to arcuate flux interaction surfaces as at 256c, 256g in the case of module 236 and at 258c, 258g for the case of module 237. The surfaces define, with the flux confronting surface 230 of rotor 222 a functioning or working air gap 260. Note that as in the case of earlier embodiments, both the back iron portions and flux interaction portions of the core components extend to coplanar top and bottom surface regions. The bottom surface disposed tip regions are located in mutual adjacency and alignment while the top surface regions extend to define receiver troughs as represented at 262c, 262g for module 236 and at 264c, 264g as illustrated in connection with module 237. In each receiver trough, the winding core portions support a polymeric electrically insulative shield, each configured in the manner described above in connection with motor 10. Note that polymeric shields 266c, 266g are positioned within respective receiver troughs 262c and 262g while polymeric shields 268c, 268g are located within respective receiver troughs 264c, 264g. Field windings are shown, as before, at 270c, 270g, the winding starts and finishes thereof being carried about the motor via outwardly open channels formed within the shields 266c, 266g and 268c, 268g. Those open channels are represented, for instant illustration at 272c, 272g and 274c, 274g. As before, motor 200 incorporates a sensible system having a disc form and represented generally at 276 which performs in conjunction with printed circuit board mounted control circuit sensors. Such a printed circuit board is represented in general at 278. A preferred sensible system and sensor implementation for the motor as disclosed herein is described in a co-pending application for United States patent by Petersen entitled “Multi-Phase Motors With Single Point Sensing Based Commutation” (supra).
As in the previous embodiment, winding core regions 284g and 286g are recessed to help achieve the desired electrical characteristics while retaining a suitable safety factor in overall winding core area. Additionally, some material and weight economies are also achieved. It should be noted that the recess 284g and 286g as well as recesses in the winding core bottom surface; 130′-130″″ in the previous equipment are not required for proper or efficient motor assembly and may not be a necessary feature when designing for the optimum electrical characteristics, but are shown as an optional design feature available with pressed powder technology and suitable for many applications.
Referring to
The stator assembly for motor or device 300 is represented generally at 338 and is seen to be structured having three pre-formed stator core module components 340-342. Again utilizing the descriptive approach employed with motor or device 10 in
Each of the stator pole core members of each module 340-342 is configured with an inwardly depending receiver trough from each axial surface. For example, receiver troughs 376c, 376g and 388g are formed within respective core members 344c, 344g of module 340. Centrally disposed core members as at 346g also are formed having an identical receiver trough as represented at 378g and 389g, and core members 348c, 348g are seen to have respective receiver troughs 380c, 380g and 390g. For the present embodiment electrically insulative polymeric shields are inserted over the winding core portion in the outboard or outwardly opening receiver troughs of the module assembly. In this regard, shields 382c, 382g are inserted within respective receiver troughs 376c, 376g and shields 384c, 384g are inserted within respective receiver troughs 380c, 380g. Shields 382c and 384c are seen to support a more elongate field winding 386c. Similarly, shields 382g and 384g are seen to support field winding 386g.
As illustrated on the C numerated side of
Motor 300 also contains a sensible system represented as a disc at 392 which cooperates with a sensor arrangement and control circuit at a printed circuit board 394.
In the embodiment presented herein the individual stator core modules can be purposely slightly angularly misaligned or skewed within the cylindrical outer sleeve resulting in an offset between adjacent stator pole core members of adjacently stacked core modules yet still permitting the winding operation to occur in the same manner as if each individual stator core module was perfectly angularly aligned. This misalignment can be used in certain motor designs to reduce the effects of cogging or detent torque where desirable or required.
As the instant electrodynamic apparatus structures reach larger sizes the module components forming the stator structure may themselves be segmented, again to accommodate for the severe molding requirements at hand as well as to facilitate the winding of field coils about the winding core regions. One such segmentation approach is illustrated in connection with
Note that component 402 is not net shaped as a unit but is pre-formed in three arc shaped segments which are joined together in mutual abutment at edge locations 426-428. This form of abutment is intimate and touching inasmuch as the resultant three segments reside in flux transfer communication. Three segments are maintained in their arch-like structural orientation by the outer cylindrical sleeve 430 seen in
Note additionally in
Looking to
The rotor of motor or device 500 is represented in general at 516 and is configured in the same manner as rotor 44 described in connection with
Since certain changes may be made in the above-described apparatus and method without departing from the scope of the invention herein involved, it is intended that all matter contained in the description thereof or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Claims
1-39. (canceled)
40. A method for manufacturing a stator assembly for a multiphase electrodynamic apparatus having an axis, comprising the steps of:
- (a) providing a powdered metal pressing facility for producing by compressive molding a stator core module, said facility being configured to provide said stator core module as being formed of ferromagnetic particles which are generally mutually insulatively associated, and said stator core module comprising a back iron portion and a plurality of stator pole core members each formed integrally with said back iron portion said said back iron portion having a back iron widthwise extent and back iron length extending from a bottom surface to a top surface, said core members having a winding core portion with core widthwise extent and extending a core length between bottom and top winding core surfaces, and a flux interaction portion having an interaction widthwise extent, integrally formed with said winding core portion and extending an interaction length from a top surface to a bottom surface, said back iron widthwise extent and corresponding said back iron length, said winding core widthwise extent and corresponding said winding core length, and said interaction widthwise extent and corresponding said interaction length being selected to derive a said stator core module by said compressive molding wherein said particles of said stator core modules exhibit a density effective to achieve adequate operational permeability and avoidance of magnetic saturation under operating conditions;
- (b) molding at least a first and a second stator core module in a said powdered metal pressing facility;
- (c) symmetrically disposing said first and second stator core modules about said axis in a manner wherein said back iron portions are circumferentially aligned and said stator pole core members are axially aligned to an extent permitting stator pole winding to be applied over said axially aligned stator pole core members said winding core portion of said first and second stator core modules;
- (d) fixing said stator pole core members of said first and second stator core modules in such axially aligned orientation; and
- (e) providing a sequence of field windings each extending over and supported by the mutually outwardly disposed top surfaces of said winding core portions of said first and second stator core modules.
41. The method of claim 40 wherein:
- said back iron widthwise extent and corresponding back iron length are selected in step (a) to respectively exhibit a ratio equal to or less than about 1 to 5.
42. The method of claim 40 wherein:
- said winding core widthwise extent and corresponding winding core length are selected in step (a) to respectively exhibit a ratio equal to or less than about 1 to 5.
43. The method of claim 40 wherein:
- said interaction widthwise extent and corresponding interaction length are selected in step (a) to respectively exhibit a ratio equal to or less than about 1 to 5.
44. The method of claim 40 wherein:
- at least a third said stator core module is placed and aligned intermediate said first and second stator core modules; said field winding surmounting said winding core portions between said winding core portions of said first and second stator modules.
45. The method of claim 40 wherein:
- said step (b) further comprises molding at least a third and a forth stator core module in a said powdered metal pressing facility;
- said step (c) further comprises symmetrically disposing said first, second, third and fourth stator core modules about said axis in a manner wherein said back iron portions are circumferentially aligned and said third and fourth stator core modules' stator pole core members are axially aligned to an extent permitting stator pole winding to be applied over said axially aligned stator pole core members said winding core portion of said third and fourth stator core modules;
- said step (d) further comprises fixing said stator pole core members of said third and fourth stator core modules in such axially aligned orientation; and
- said step (e) further comprises providing a sequence of field windings each extending over and supported by the mutually outwardly disposed top surfaces of said winding core portions of said third and fourth stator core modules, said first and second stator core modules being connected in series or parallel electrical interconnection with said third and fourth stator core modules.
46. A method of enclosing a stator core module assembly comprising of two or more stator core modules each formed of pressure shaped ferromagnetic particles which are generally mutually insulatively associated comprising the steps of:
- (a) placing a rotor assembly central to said stator core modules;
- (b) affixing a first motor end cap over one end of the shaft of said rotor assembly and adjacent with an end surface of said stator core module assembly;
- (c) affixing a second motor end cap over the opposite end of said rotor shaft and adjacent with the other end of said stator core module assembly; and
- (d) installing two or more fastening devices through said rotor assembly from said first motor end cap to said second motor end cap and tightening said fastening devices such that the components of said stator core module assembly are firmly held in place and aligned.
47. The method of claim 46 further comprising the step of:
- (e) installing a sleeve over the outside surface of said stator core module assembly intermediate said first motor end cap and said second motor end cap, said sleeve aligning and enclosing said stator core module assembly.
48. The method of claim 46 wherein said step (d) further comprises installing said fastening devices as screws.
49. The method of claim 46 wherein said step (d) further comprises installing said fastening devices as fastening rods.
Type: Application
Filed: Jan 6, 2006
Publication Date: Jun 8, 2006
Applicant:
Inventor: Christian Petersen (Sandwich, MA)
Application Number: 11/326,487
International Classification: H02K 15/12 (20060101); H02K 47/00 (20060101); H02K 3/00 (20060101);