1. Field of the Invention
The present invention relates generally to a machine in which an electric motor is used. More specifically, the present invention concerns a machine having means by which an electric motor including a rotor and an insulated stator can be mounted directly to the machine.
2. Discussion of the Prior Art
Those of ordinary skill in the art will appreciate that electric motors are often used in home appliances such as dishwashers and washing machines. In a washing machine, for instance, an electric motor may be used to cause rotation of the washer basket to agitate the clothing contained therein. Although a variety of motor component arrangements may be used, one known embodiment of an electric motor includes a stator positioned at least in part radially inside a rotor. An electric motor having such a configuration is commonly referred to as an outer rotor motor or external rotor motor, although other names may be used. In the case of a washing machine having an electric motor of this sort, the rotor is typically coupled to the washer basket, whereas the stator is fixed to a tub mounting hub that is coupled to a stationary washer outer tub. To avoid potential electrical shock of the user, the stator is mounted in such a manner that it is electrically isolated from the tub.
The stator of an outer rotor motor typically includes a core and a plurality of coils. Conventionally, the core takes a generally toroidal form and is composed of a ferromagnetic metal such as iron or steel. The core typically includes a plurality of teeth projecting radially outwardly and defining slots therebetween. The coils are formed by the winding of electrically conductive wire multiple times around each tooth to at least partially fill the slots. Copper wire is commonly used due to its low electrical resistivity.
The rotor of an outer rotor motor typically includes a shaft, a support structure coupled to the shaft, and a plurality of permanent magnets supported by the support structure so that they circumscribe the stator in a spaced relationship. When an electrical current flows through the coils formed around each tooth of the stator core, the ferromagnetic material of the core is energized to form a plurality of magnetic fields corresponding to the teeth. These stator magnetic fields interact with the magnetic fields produced by the permanent magnets of the rotor to induce relative rotation between the rotor and stator. The direction of each magnetic field is dependent on the direction of the current flow around the respective tooth. Although a variety of approaches may be used to ensure appropriate field directions, one embodiment of an electric motor includes a stator having coils wound clockwise around some teeth and coils wound counter-clockwise around other teeth to produce oppositely directed magnetic fields within the same stator when the wires are exposed to a direct current.
Mounting of the outer rotor motor in the machine is conventionally done through alignment of openings in the stator core with corresponding openings in the tub mounting hub, followed by insertion of a fastener through each pair of openings. Such an approach is often inconvenient and expensive. For instance, traditional outer rotor motors are limited to a specific mounting arrangement incorporated into the core fabrication process. To use a conventional core in a different application requiring a different mounting arrangement, the core fabrication process must be varied (e.g., the lamination die for a laminated stator core must be re-machined). Furthermore, the metal core must be large enough to house the mounting openings, making it heavy and expensive. Even further, the increased number of components in the machine-motor system, including fasteners such as bolts or screws, slows the assembly process and increases the risk that a component necessary for assembly will be misplaced.
According to one aspect of the present invention, a machine is provided that includes a motor and motor mounting structure configured to support the motor within the machine. The motor includes a rotor rotatable about an axis and a stator spaced from the rotor. The stator presents axially spaced radial surfaces. The stator further presents radially spaced inner and outer circumferential faces. The motor mounting structure includes a mounting surface, a radially projecting shoulder, and a shiftable catch. The mounting surface engages at least one of the faces of the stator so as to restrict relative radial movement between the stator and mounting structure. The radially projecting shoulder engages one of the radial surfaces so as to prevent axial movement of the stator in a first axial direction. The shiftable catch removably engages the other one of the radial surfaces so as to prevent axial movement of the stator in a second axial direction opposite the first direction, when the catch is in a retaining position. The catch is moveable out of the retaining position to permit axial movement of the stator relative to the mounting structure.
According to another aspect of the present invention, a machine is provided that is configured to generally support a motor having a rotor rotatable about an axis and a stator spaced from the rotor, wherein the stator presents axially spaced radial surfaces and radially spaced inner and outer circumferential faces. The machine includes motor mounting structure configured to support the motor within the machine. The motor mounting structure includes a mounting surface, a radially projecting shoulder, and a shiftable catch. The mounting surface is configured to engage at least one of the faces of the stator, such that the mounting surface is operable to restrict relative radial movement between the stator and mounting structure. The radially projecting shoulder is configured to engage one of the radial surfaces, such that the shoulder is operable to prevent axial movement of the stator in a first axial direction. The shiftable catch is configured to removably engage the other one of the radial surfaces, such that the catch is operable to prevent axial movement of the stator in a second axial direction opposite the first direction, when the catch is in a retaining position. The catch is moveable out of the retaining position to permit axial movement of the stator relative to the mounting structure.
Among other things, provision of motor mounting structure independent of the stator core allows the size of the stator core to be reduced and increases the ease with which the motor can be adapted for use with new mounting systems.
This summary is provided to introduce a selection of concepts in a simplified form. These concepts are further described below in the detailed description of the preferred embodiments. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
Various other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures.
A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:
The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiments.
The present invention is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments.
With initial reference to
Referring again to
In the preferred embodiment illustrated in
Preferably, the rotor 16 is rotationally supported on the tub 14 by a bearing assembly 46. In the preferred embodiment shown in
The tub 14 includes mounting structure 54 configured to fix the stator 18 to the tub 14, such that the stator 18 is fixed to and supported on the machine 12 by the mounting structure 54. In a preferred embodiment best shown in
In a preferred embodiment best shown in
The mounting structure 54 is preferably composed of a synthetic resin material, although a different type or types of material, preferably being at least substantially electrically insulative, could be used without departing from the spirit of the present invention
As best shown in
The stator core 58 preferably comprises a ferromagnetic material such as steel and is preferably a laminated structure. However, it is within the ambit of the invention for the core 58 to comprise an alternative material and be of an alternative structure. For instance, the core 58 could be integrally formed, be composed of iron, include a continuous annular base ring from which the teeth 66 project, or feature a combination of these or other variations known to one skilled in the art.
In a preferred embodiment, the stator core 58 is at least partly coated with an electrically insulative coating, preferably a powder coating. More preferably, the entire stator core 58 except the inner and outer circumferential faces 62,64 is powder coated. One suitable powder coating material is available from 3M′ under the designation Scotchcast™ Electrical Resin 5555. However, it is within the scope of the present invention for the stator core 58 to be insulated with other electrically insulative coatings (or low profile means that permit larger coils), as well as insulation arrangements that cover the core 58 to a lesser or greater degree than that shown.
The coils 60 of the stator 18 comprise electrically conductive wiring 82 wound multiple times around each individual tooth 66. The wiring 82 preferably substantially comprises a plurality of aluminum wires, although it is within the scope of the present invention to use other types of electrically conductive wires (such as copper). The wires may or may not be provided with coatings. (Note that the coils 60 are shown only schematically and have been removed from all or a plurality of the teeth 66 in some figures for the sake of clarity. However, in practice, the coils 60 would be found on each tooth 66 and would comprise multiple windings of the wiring 82.) As is customary, the wiring 82 is wound around the teeth 66 in a particular pattern according to phasing of the motor 10.
As best shown in
Preferably, the inner portion 83 at least partly defines the mounting structure 54. However, it is within the scope of the present invention for the mounting structure 54 to be fully distinct from the inner portion 83.
In one embodiment, one or more transitional portions may be present between the main tub portions 83,84,85. As shown in
Preferably, the tub portions are related such that the tub is a unitarily formed body that has an axis of rotational symmetry that is coaxial with the axis of rotation of the rotor 16.
The mounting structure 54 preferably comprises an annular projection 88, a tubular wall 90 that presents an outer mounting surface 91, a plurality of longitudinally extending connecting pins 92, and a plurality of latches 94. The annular projection 88 projects axially downwardly from the base portion 84 of the tub 14. The tubular wall 90 projects axially downwardly from the annular projection 88. The connecting pins 92 project radially outwardly from the tubular wall 90 and, in a preferred embodiment, extend at least substantially along the axial length thereof. Preferably, the connecting pins 92 are circumferentially spaced around the tubular wall 90. More preferably, the connecting pins 92 are evenly spaced around the circumference of the tubular wall 90. However, alternative spacing arrangements are within the scope of the present invention.
A shoulder 96 is formed by the annular projection 88 adjacent the mounting surface 91, such that the shoulder 96 projects radially outwardly from the tubular wall 90. In a preferred embodiment, the shoulder 96 extends continuously about the circumference of the tubular wall 90. However, discontinuous extension is permissible as long as the shoulder remains at least partly distinct from the collective connecting pins 92.
The latches 94 are preferably integral with the tubular wall 90 and cooperate to define respective parts of the mounting surface 91. Each of the latches 94 includes an arm 98 and a catch 100. Each arm 98 is defined between a pair of spaced apart longitudinal slits 102 in the tubular wall 90. In a preferred embodiment, the tubular wall 90 comprises a lower margin 104 from which the slits 102 extend axially upwardly. Preferably, each catch 100 comprises an angled cam surface 106 and a flat supporting surface 108.
As best shown in
If desired, grooves may also or alternatively be formed in the tubular wall of the mounting structure and configured to interact with connecting pins projecting from the inner circumferential face of the stator core.
If desired, the connecting pins 92 may be heat stake pins that, upon application of appropriate heat, create a permanent bond between the mounting structure 54 and the stator core 58. The provision of other means of adhesion between the connecting pins 92 and the grooves 110 is also acceptable. However, it is most preferred that the stator be removable for maintenance, replacement, etc.
As best shown in
In a preferred embodiment best shown in
For assembly of the preferred embodiment of the motor 10, the connecting pins 92 of the mounting structure 54 are first aligned with the grooves 110 in the inner circumferential face 62 of the stator core 58. No clocking is necessary beyond that required to align one of the pins 92 with one of the grooves 110, with the remaining pins 92 and grooves 110 automatically falling into alignment. The mounting structure 54 and the stator core 58 are then moved axially toward each other until the upper faces 76 of the teeth 66 are in contact with the angled cam surfaces 106 of the catches 100. The angle of each cam surface 106 is such that continued axial movement of the stator core 58 relative to the mounting structure 54 results in elastic flexing of each latch 94 in a radially inward direction. Preferably, each latch 94 is operable to flex in the radially inward direction to such a degree that continued axial movement of the stator core 58 relative to the mounting structure 54 is permitted without obstruction by the latches 94. Such flexing is enabled by the presence of the arms 98 and associated slits 102, in addition to the choice of material.
Although elastic flexing of the latches 94 based primarily on the properties of the material of construction is preferred, alternative modes of shifting are acceptable. For instance, spring-loaded latches could be used. The spring could be in a relaxed configuration when the latches are in the stator retaining position (shown in
As noted previously, the elastic flexing is preferably such that the latches 94 are positioned unobstructively for at least some degree of continued axial movement of the stator core 58 relative to the mounting structure 54. Such continued movement is preferably associated with the sliding engagement of the connecting pins 92 with the grooves 110. The continued relative axial movement preferably ceases when the shoulder 96 is positioned flush with the upper faces 76. Preferably, the engagement of the shoulder 96 with the upper faces 76 corresponds to the clearance of the catch 100 of each latch 94 relative to the lower faces 78 of the teeth 66. Such clearance preferably enables the previously flexed latches 94 to return to their unflexed configuration. The flat surface 108 of each catch 100 then engages the lower faces 78. Therefore, the shoulder 96 and the catches 100 cooperatively restrict further relative axial movement of the stator core 58 relative to the mounting structure 54 and, in turn, the tub 14 in either an upward or downward direction, respectively, while the connecting pins 92 and the corresponding grooves 110 cooperatively restrict relative rotation between the stator core 58 and the mounting structure 54 and, in turn, the tub 14.
Further means of restricting relative motion between the stator core 58 and the mounting structure 54 may be provided as well. In the illustrated embodiment, for instance, both the inner circumferential face 62 of the stator core 58 and the outer surface 91 of the tubular wall 90 are cylindrical, with the tubular wall 90 configured to fit snugly inside the stator core 58 when the machine 10 is assembled. Relative axial and rotational motion between the stator core 58 and the mounting structure 54 is therefore restricted by friction between the outer surface 91 and the inner circumferential face 62. Alternatively, the outer surface and the inner circumferential face could have dissimilar shapes. For instance, the outer surface could be polygonal and the inner face could be circumferential (as shown), so as to provide multiple discrete contact points between the components.
The stator core 58 can be removed from the mounting structure 54 after assembly. First, the latches 94 are disengaged (that is, flexed radially inwardly) to allow axial movement of the stator core 58 in a downward direction relative to the mounting structure 54. Such downward movement is associated with sliding removal of the connecting pins 92 from the grooves 110. When the upper faces 76 clear the catches 100, the stator core 58 is no longer engaged with the mounting structure 54; and the latches 94 return to their original, unflexed positions.
In operation of the preferred machine embodiment shown in
The preferred forms of the invention described above are to be used as illustration only and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention.
The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and access the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention set forth in the following claims.