Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-04-05
2002-12-10
Le, Dang Dinh (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156130, C310S256000, C310S216006
Reexamination Certificate
active
06492756
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to rotary electric motors, more particularly to motors having first and second annular ring members concentrically arranged about an axis of rotation and separated from each other by an axial air gap, both of the members comprising groups of magnetically isolated structures, the groups of one of the members having permanent magnets affixed thereto and the other of the members comprising wound electromagnet poles.
BACKGROUND
Direct current motors have versatility in a wide range of applications. The availability of a battery power source for dc motor equipped devices facilitates a portability aspect that is not readily available for a-c motor drives. Electronic controls, such as microcontroller and microprocessor based systems, for a wide variety of functional applications have become commonplace. As development of the battery has progressed, and the versatility of electronic controls has expanded, the challenge of providing efficient direct current motor drives for vehicles, as a viable alternative to combustion engines, has become more compelling. U.S. Pat. No. 5,164,623 to Shkondin is one example of a proposed implementation in which a motor is mounted on the wheel of a vehicle for directly driving the vehicle. The patent proposes that such an arrangement can be applicable to electric cars, bicycles, wheelchairs and the like.
Electronically controlled energization of windings of direct current motors offers the prospect of more flexible management of motor characteristics. The use of permanent magnets in conjunction with such windings is advantageous in limiting current consumption. U.S. Pat. No. 4,754,207 to Heidelberg et al. describes a direct current motor having a rotor composed of a continuous ring of a plurality of permanent magnets successively alternating in polarity. The stator, comprising a plurality of electronically switchable electromagnet poles, is circumferentially separated from the rotor magnets by a radial air gap. Several adjacent stator electromagnets form a phase group. The inward base portions of adjacent electromagnet poles in each group are in surface area contact with each other to form a continuous magnetic flux path. The electromagnetic circuit is broken at transition points between adjacent groups of electromagnets. Sensors detect relative rotational position between rotor and stator elements to control electronic switching of the individual electromagnet windings. Electromagnets belonging to a common group are switched simultaneously with one common electronic switching means per group. Windings of the electromagnets in adjacent groups are of different phases and are switched at different times.
Of concern in implementation of stator winding switched energization is the avoidance of unfavorable consequences such as rotation irregularities. For example, simultaneous switching of all motor phase windings can cause pulsating output torque. Alleviation of these effects, with varying success, can be obtained by appropriately switching all phases at different times or by simultaneously switching certain winding combinations that are distributed symmetrically about the stator periphery and bear certain positional relationships with the permanent magnet poles of the rotor. However, switching of adjacent windings at different times leads to detrimental effects if the windings are linked to a continuous magnetic circuit path, as the flux changes due to the changed energization of the winding of one pole effects the flux of an adjacent pole.
Heidelberg et al. alleviates this problem to some extent by grouping pluralities of stator poles in separate magnetic circuit paths. The magnetic circuit path discontinuity between adjacent groups effects an isolation of magnetic flux, thus reducing transformer like magnetic flux interference between groups. However, where all poles of a group are wound and switched simultaneously, a torque ripple effect can still exist. Heidelberg et al. provides modifications in which some poles of a group are not wound and/or the pole structure of all poles within a group are not of uniform configuration, thus deterring the effects of torque ripple and flux interference between adjacent poles. Such modifications sacrifice torque characteristics and power capability. If fewer poles are wound, flux generation capability is reduced. The unwound poles do not contribute to torque and can detrimentally interact with rotor permanent magnets. Non-uniform pole configuration modifications in Heidelberg et al. are coupled with non-uniform pole windings. Such configurations complicate the manufacturing process and compromise motor efficiency.
The above-identified copending related U.S. patent application Ser. No. 09/826,422 identifies and addresses the need for an improved motor amenable to simplified manufacture and capable of efficient flexible operating characteristics. In the particular vehicle drive environment, it is highly desirable to attain smooth operation over a wide speed range, while maintaining a high torque output capability at minimum power consumption. Such a vehicle motor drive should advantageously provide ready accessibility to the various structural components for replacement of parts at a minimum of inconvenience. The copending related U.S. application incorporates electromagnet poles as isolated magnetic structures configured in a thin annular ring to provide advantageous effects. With this arrangement, flux can be concentrated, with virtually no loss or deleterious transformer interference effects in the electromagnet cores, as compared with prior art embodiments. While improvements in torque characteristics and efficiency are attainable with the structure of the identified copending application, further improvements remain as an objective.
DISCLOSURE OF THE INVENTION
The present invention fulfills the above-described needs and provides further advantages. A rotary electric motor comprises rotor and stator members each configured as annular rings and concentric with respect to each other about an axis of rotation. Either of the rotor or stator members is formed of groups of electromagnet pole pairs, the groups substantially equidistantly distributed along the angular extent of the annular ring, each of the groups comprising magnetic material magnetically isolated and separated from the other groups. The other member comprises a plurality of groups of permanent magnet poles substantially equidistantly distributed with alternating magnetic polarity along the angular extent of the radial air gap formed between the members. The groups of permanent magnet poles each comprise a common magnetic return path that is separate and magnetically isolated from adjacent permanent magnet pole groups. The poles of each group of electromagnet pole pairs are wound, the windings together being switchably energized for driving electromotive interaction between the stator and rotor. Thus, an even number of poles, two per pole pair, are provided for each electromagnet group. The poles of each pole pair are oppositely wound to provide opposite north/south polarities.
As described in the related copending application, isolation of the electromagnet groups permits individual concentration of flux in the magnetic cores of the groups, with virtually no flux loss or deleterious transformer interference effects with other electromagnet members. Operational advantages can be gained by configuring a single pole pair as an isolated electromagnet group. Magnetic path isolation of the individual pole pair from other pole groups eliminates a flux transformer effect on an adjacent group when the energization of the pole pair windings is switched. The lack of additional poles within the group eliminates precludes any such effects within a group.
By appropriately timing the switched winding energization for each of the pole pair groups, development of smooth electromotive force throughout the motor is attained. A precise optimum phase and sequence for timed switching of particular pole pair groups is depend
Maslov Boris
Pyntikov Alexander
Dinh Le Dang
McDermott & Will & Emery
Wavecrest Laboratories LLC
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