Patent Application
20120242187
The present invention relates, generally, to a rotor assembly for an electric motor assembly.
Electric motors include rotor assemblies which have a rotor stack formed from magnets and laminated layers of discs stacked together. The rotor stack is assembled on a rotor hub for stability within an electric motor. The rotor stack and the rotor hub rotate together as an assembly relative to the stator for the electric motor. Therefore, to ensure optimal operation of the electric motor, the rotor stack must be rotationally aligned with the rotor hub at the time of assembly.
The rotor hub and the rotor stack are typically aligned by broaching a rotor key on the laminates that form the rotor stack. The key is inserted into a keyway on the rotor hub when the rotor hub and rotor stack are assembled together. The rotor key and keyway ensure rotational alignment and prevent relative rotation between the rotor hub and the rotor stack. However, the rotor stack requires a skewing progress for the magnets and the laminate layers that form the stack which makes forming the key on to the laminate layers difficult.
An electric motor comprises a rotor hub defining a first slot and a rotor stack defining a second slot. A rotor key has a shape corresponding to the cross-sectional shape of the first slot such that the rotor key is removably retained within the first slot. The rotor key is inserted into the first slot on the rotor hub and the second slot on the rotor stack.
A rotor assembly comprises a rotor hub defining a first slot having a generally dovetail cross-sectional shape. A rotor key has a shape corresponding to the generally dovetail cross-sectional shape of the first slot. The rotor key is inserted into the first slot on the rotor hub.
A method of assembling a rotor assembly comprises inserting a rotor key having a trapezoidal shape in a first slot defined by a rotor hub, wherein the first slot has a dovetail shape corresponding to the shape of the rotor key such that the rotor key is retained within the first slot. A second slot defined by a rotor stack is aligned with the rotor key. The rotor stack is mounted on the rotor hub, such that a portion of the rotor key is received within the second slot.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the Figures, wherein like reference numbers refer to the same or similar components throughout the several views,
Referring to
Sloping sides 25 on the rotor key 18 follow the shape of the sloping sides 24 on the hub 14 forming the first slot 20. The sides 24 and 25 assist in retaining the rotor key 18 in the first slot 20. The rotor key 18 is retained in the first slot 20 by the corresponding shapes. Alternative to the dovetail or trapezoidal cross-sectional shape of the first slot 20 and the rotor key 18 both may have a generally rectangular cross-section shape. In either instance, a staking operation may be performed to retain the rotor key 18 within the first slot 20. That is, a small amount of material on the rotor key 18 or rotor hub 14 may be upset to retain the rotor key 18 within the rotor hub 14 prior to assembly of the rotor hub 14 and the rotor stack 16.
Alternatively, the rotor key 18 may be removable from the rotor hub 14 prior to assembly of the rotor stack 16, by axially sliding the rotor key 18 out of the first slot 20. In this manner the rotor key 18 and the rotor hub 14 are partially assembled to remain together prior to assembly of the rotor assembly 12 (shown in
The rotor hub 14 has a base 28 which has a larger outer diameter than the core portion 30 of the rotor hub 14. A relief groove 32 is formed around the outer diameter of the rotor hub 14 between the core portion 30 and the base 28. The groove 32 allows for oil and/or lubricants during operation of the electric motor 10. The first slot 20 is formed in the core portion 30 of the rotor hub 14 and extends past the groove 32 into the base 28. A rounded end 26 of the first slot 20 allows the rotor key 18 to bottom out and rest on the base 28 when the key is assembled with the rotor hub 14. The rotor key 18 may have a corresponding shape or taper to interfit with the bottom of the first slot 20 formed by the rotor hub 14.
As can be seen in
The rotor stack 16 has a generally annular shape such that the rotor stack may be mounted on the rotor hub 14 by axially moving the rotor stack 16 over the core position 30 of the rotor hub 14. Typically, the rotor stack 16 is press fit onto the rotor hub 14. Similar to the rotor key 18, the rotor stack 16 may be fully seated on the rotor hub 14 when the rotor stack 16 is contacting the end ring 17 which is resting on the base 28 of the rotor hub. Thus, the rotor stack 16 may be assembled on the rotor hub 14 in a manner that allows a portion of the rotor key 18 to be inserted in the second slot 22. The rotor key 18 is then located within the first slot 20 and the second slot 22 at the same time. Relative rotational alignment between the rotor stack 16 and the rotor hub 14 is, therefore, achieved. Further, the rotor key 18 prevents relative rotation between the rotor hub 14 and the rotor stack 16 once assembled, as shown.
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
