Patent Application
20150091396
This disclosure relates generally to electrical motors, and more particularly, to end shields mounted to stators in electrical motors.
Electrical motors are comprised of a rotor that can be axially received within an opening in a stator. The stator typically has teeth that extend into the opening to form a diameter in which the rotor is received. Electrical conductors are mounted about the teeth to enable an electrical current in the conductors to generate a rotating magnetic field. The rotor is configured for rotation in response to the magnetic field generated by the stator. This rotor is fixedly mounted about a shaft that rotates with the rotor. This shaft is held by journal bearings positioned within end shields mounted at each end of the housing in which the stator and rotor are positioned. The journal bearings in the end shields hold the rotor in position and mounting members, typically bolts or other threaded members, pass through openings in one of the endplates and mounting holes within an outer portion of the stator to be received in a threaded opening in the other end shield to hold the stator in position. When the end shields are mounted about the rotor shaft and the bolts are received in the stator mounting holes and threaded openings in the end shield, the air gap established between the inside of the stator and the outside of the rotor is important for efficient operation of the motor.
Some electrical motors are used in common appliances. For example, clothes dryers and washers use an electrical motor to rotate a drum in which wet clothes are placed for drying or washing, respectively. To reduce the weight of the appliance, some parts of the motor are made of plastic materials or the like. For example, some electrical motors are assembled with end shields that are formed with plastic materials. One advantage of using end shields fabricated with plastic materials is that the end shields can be formed with other features integrated in the component. In some electric motors having plastic end shields, the end shield is formed using injection molding techniques to incorporate a motor mounting feature in the end shield.
The motor mounting feature incorporated in the end shield is typically resilient enough to withstand the vibrations that occur within the appliance during its operational life. Issues have arisen, however, during the shipping of appliances from the place of manufacture to the location where the appliance is put into its operational life. Drops and/or bumps may be severe enough to stress the motor mounting feature to the point where the feature cracks and, in some cases, disconnects from the appliance structure to which the motor is mounted. Dislodging of the motor can result in movement of the end shield and the rotor mounted to the bearing within the end shield that may be sufficient to alter the air gap between the stator and the rotor. Thus, the motor does not operate at its most efficient levels. Therefore, constructing an electrical motor with a motor mounting feature that is more resistant to transportation stresses without appreciably adding weight to the motor is desirable.
A mounting feature plate that can be mounted to a stator in a way that maintains the air gap between the rotor and the stator while providing a more resilient mounting feature has been developed. The mounting feature plate includes a planar member, an offset member extending from the planar member, a terminating portion of the offset member being configured to engage a portion of a frame in an appliance for mounting an electrical motor within an appliance, and a pair of flanges extending from the planar member in a direction that is generally orthogonal to the planar member, each of the flanges in the pair of flanges having an opening with a cylindrical extrusion aligned with and extending from the opening, the extrusion being configured to be received within a mounting hole within a stator and the opening being configured to enable a bolt to pass through the opening and the extrusion to be received within the mounting hole in the stator.
An electrical motor includes a mounting feature plate that can be mounted to a stator in a way that maintains the air gap between the rotor and the stator while providing a more resilient mounting feature stator. The motor includes an output shaft, a rotor mounted about the output shaft, an end shield with an opening through which the output shaft extends, a stator secured to the end shield, and a mounting feature plate interposed between the end shield and the stator. The mounting feature plate includes a planar member, an offset member extending from the planar member, a terminating portion of the offset member being configured to engage a portion of a frame in an appliance for mounting the electrical motor within an appliance, and a pair of flanges extending from the planar member in a direction that is generally orthogonal to the planar member, each of the flanges in the pair of flanges being interposed between a surface of the end shield and a surface of the stator, each flange having an opening with a cylindrical extrusion aligned with and extending from the opening, the extrusion being configured to be received within a mounting hole within the stator and the opening being configured to enable a bolt to pass through the opening and the extrusion to be received within the mounting hole in the stator.
A method for assembling the electrical motor with the mounting feature plate includes aligning openings in flanges of a hard metal mounting feature plate with threaded mounting holes in a stator to enable extrusions extending from the hard metal mounting feature plate to be received by the stator mounting holes, aligning mounting holes in an end shield with the openings in the flanges of the mounting feature plate, inserting a bolt into each of the mounting holes in the end shield and through the aligned opening in the mounting feature plate to position an end of each bolt in one of the threaded holes in the stator, and rotating each bolt to advance each bolt into one of the threaded holes in the stator to secure the end shield and the mounting feature plate to the stator.
An improved electrical motor construction is shown in
The end shield 104 is fabricated from thermoplastic materials using an injection molding machine or the like. The end shield 104 differs from the end shield 10 (
To assemble the electrical motor 100, the flanges 136 of the mounting feature plate 108 are interposed between a lower surface of the end shield 104 at the mounting hole 124 and an upper surface of the stator 112. A mounting bolt can then be inserted into the mounting hole 124, through a hole in the flange 136 and passed through a mounting hole in the stator 112 so the bolt can be rotated in a threaded opening in the other end shield to secure the end shield 104 and the mounting feature plate 108 to the stator 112.
One issue that can arise with the structure described in the previous paragraph is the interface between the smooth lower surface of the plastic end shield 104 and the smooth upper surface of the mounting feature plate flange 136. Some forces arising from shocks that the appliance receives during transit may move the end shield 104 with respect to the stator 112 as the steel mounting feature plate 108 tends to slide with respect to the plastic surface of the end shield. When the plate 108 slides, it can engage the bolt passing through the hole in the flange and skew the stator with reference to the rotor. This skewing can affect the air gap between the stator and the rotor and the efficiency of the electrical motor.
To address the possible sliding of the steel mounting feature plate, the flanges 136 have been formed to include extrusions at the holes in the flanges. Such a mounting feature plate 108 is shown in
The extrusion 144 is configured to fit within the clearance between a mounting bolt and mounting hole in the stator and the end shield. A cross-sectional view of a portion of an electrical motor having the mounting feature plate with a mounting hole extrusion is shown in
The extrusion 144 should be long enough that it attenuates movement of the mounting feature plate 108 and end shield 104 relative to the stator 112. In one embodiment, the extrusion is at least as long as a thickness of two laminations that form the stator 112 to secure the plate adequately to the stator, although the extrusion can have a length that is the thickness of one lamination or even less provided that the length of the extrusion is sufficient to keep the end shield 104 and plate 108 from moving relative to the stator 112. In this embodiment, each lamination is 0.31″ thick so the extrusion is 0.62″ in length. The length of the extrusion also needs to be sufficiently long to ensure that the extrusion is formed with a diameter during manufacture that satisfies the tolerance for the extrusion fitting within the mounting holes. The clearance between the stator mounting hole and the outer wall of the extrusion 144, and between the bolt and the inner wall of the extrusion 144 is such that the mounting feature plate is relatively rigidly mounted to the stator. Thus, a proper fit of the extrusion within a mounting hole is important so the extrusion needs to be long enough to ensure that during manufacture of the plate 108 the extrusion diameter is formed within the tolerance needed for fitting the extrusion into a mounting hole and enabling a mounting bolt to pass through the extrusion. The fixing of the plate 108 to the stator 112 helps prevent the mounting feature plate 108 from slipping with respect to the end shield 104 to maintain the integrity of the air gap between the stator and the rotor despite shocks encountered during appliance shipping.
A flow diagram of a process for assembling an electrical motor with a hard metal mounting feature plate is shown in
Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
