BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a motor of one embodiment, portions being omitted for clarity.
FIG. 2 is an exploded view of the motor of FIG. 1.
FIG. 3 is a perspective of the stator shown in FIG. 2.
FIG. 3A is a perspective of a sensor assembly.
FIG. 4 is a perspective of the stator of FIG. 3 but with portions omitted for clarity.
FIG. 5 is a perspective of a stator/sensor configuration of another embodiment.
FIG. 6 is a perspective like FIG. 5 but with the sensor omitted.
FIG. 7 is a perspective of a stator/sensor configuration of still another embodiment.
FIG. 8 is a perspective like FIG. 7 but with the sensor omitted.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to FIGS. 1-3, a motor of one embodiment of the invention is generally designated 11. The motor generally comprises a rotor generally designated 13 and a stator generally designated 15. The stator includes a center hub 17 and a plurality of teeth 19 extending outward from the center hub. Windings 21 are wound around each tooth 19. The motor may also include a controller and wires 23 for power connection and the like. Other details of construction need not be shown or described herein but will be understood by those of ordinary skill in the art. Also, the motor 11 of this embodiment is an outer rotor brushless permanent magnet motor, but many other types of motors, including for example, inner rotor motors, are contemplated within the scope of the invention.
The rotor 13 includes a rotor can 27 having magnets 29 mounted on an inwardly facing surface. There is an air gap between the magnets and outward faces of the stator teeth, the air gap generally designated 31 in FIG. 1. Note that a variety of other magnet configurations are contemplated.
A sensor assembly of this embodiment is designated 35 and is generally disposed atop the windings 21 and the teeth 19, as viewed in FIGS. 1 and 2. As will be further described below, the sensor assembly 35 includes a housing 37 having at least one sensor 39 therein adjacent the magnets 29 for sensing the magnets of the rotor. The housing 37 covers and protects the sensor 39, among other functions.
As best shown in FIGS. 3-4, each tooth 19 has a T-shape when viewed in cross-section taken transverse to a longitudinal axis of the stator 15. A first or long section 41 of the T-shape extends radially outward from the center hub 17 and a second or crossing section 42 extends circumferentially and generally symmetrically from the long section. An outward face 42o of the crossing section of each tooth is curved or “crowned” to generally conform to, or be complementary to, the shape of the magnets.
As noted above, the T-shape of the teeth 19 of this embodiment results in a small gap G between the crossing sections 42 of adjacent teeth, the gap between the teeth being smaller than the width of the sensor assembly 35 so that the sensor assembly cannot fit between the majority of the teeth. Alternatively, the gap may be smaller or roughly equal to the size of the sensor itself. Note that the gap G is different from the air gap 31 discussed above.
In this embodiment, a small notch or recess 45 is shaped into two adjacent “distinct” teeth 19a so that the voids are spaced apart a predetermined distance. These two teeth have a shape that is different or distinct from the other teeth 19 of the stator 15. The two teeth are optionally made to be “mirror image”, or symmetric about the gap G, but they need not be.
The housing 37 of the sensor assembly 35 is generally received in the recesses 45. As shown in FIGS. 3 and 3A, the housing has two tabs 47 that engage edges of the recess, and each tab has one of the sensors 39. The sensor 39 is thus disposed adjacent the magnets 29, or across the air gap 31 from the magnets so that the sensor can sense each magnet as the magnet passes the sensor. In this case, each sensor 39 is mounted inside the tab 47, as by molding the sensor into the housing 37 during molding of the housing. However, the sensor may be mounted in many other ways.
An alignment leg 49 (broadly, alignment feature) extends downward from the main portion of the housing 37 between the tabs 47. The alignment leg 49 is sized and shaped to engage the inward surfaces of the crossing sections 42 of the teeth 19a. The alignment leg 49 helps ensure that the sensor assembly 35, especially the sensors 39 are properly disposed relative to the teeth 19a and to the rotor 13.
In another embodiment shown in FIGS. 5-6, a stator 115 includes only one tooth 119a having a recess 145. (In other words, only one tooth is “distinct” from the rest of the teeth.) The recess is formed generally centrally in the crowned section 142 of the tooth 119a so that the sensor 139 of sensor assembly 135 is disposed generally at an end of the long section 141 of the distinct tooth. Thus, the long section 141 extends inward from the sensor 139 of this embodiment. Note no alignment feature is shown, but may be added. Other features of the motor of this embodiment may be substantially similar to that of the first embodiment.
In still another embodiment shown in FIGS. 7-8, a stator 215 has three teeth 219a-219c, each including at least one recess. A first distinct tooth 219a includes a recess 245a somewhat offset from its center at its top edge. A second distinct tooth 219b adjacent the first has one recess 245b1 along its top edge and extending to the edge facing the first tooth, and a smaller recess 245b2 along the top edge that faces a third distinct tooth 219c. The third distinct tooth has a small recess 245c along its top edge that faces the second tooth. As shown in FIG. 7, the sensor assembly 235 has a housing 237 that extends over the three teeth 219a-c. The housing has three tabs 247 that engage the respective recesses, and has three sensors 239 that are disposed in respective gaps G, similar to that of the first embodiment. Thus, the recesses 245a-c and sensors 239 are equally spaced apart a predetermined distance. Note that the spacing may depend, for example, on the number of poles and the number of sensors used, among other possible factors. Also, three alignment legs 249 are included and function as described above.
The recess in each “distinct” tooth may be formed in a variety of ways. For example, the recess may be formed by machining of the tooth. Alternatively, the laminations that make up the stator may be formed with the recess therein, as during stamping of the laminations.
The sensors of the various embodiments may be of a variety of types. For example, the sensor may be a hall-effect sensor, and may be of the type that senses speed, position or both for the rotor. It is contemplated that the housings of the various embodiments include any number of sensors, and further, it is contemplated that the housing be omitted altogether. As will be understood by those of ordinary skill, the sensor assembly may include additional components within the scope of the invention. Also, the sensor and/or sensor assembly may be described as being adjacent a magnet, even though the sensor is only momentarily adjacent a particular magnet as the rotor rotates during normal operation of the motor.
When introducing elements of various aspects of the present invention or embodiments thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top” and “bottom”, “front” and “rear”, “above” and “below” and variations of these and other terms of orientation is made for convenience, but does not require any particular orientation of the components.
As various changes could be made in the above constructions, methods and products without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Further, all dimensional information set forth herein is exemplary and is not intended to limit the scope of the invention.
Patent Application
20080084139
