Integrated rotor yoke

A rotor yoke includes a casing attachment ring, a sensor ring, and an over-molded body disposed between the casing attachment ring and the sensor ring. The over-molded body couples the sensor ring to the casing attachment mechanism.

TECHNICAL FIELD

The present disclosure relates to a rotor used in a motor.

BACKGROUND

A typical magnetic motor includes a yoke which is a cylindrical structure which is provided to: mechanically support the poles; provide a path of low reluctance for flux; protect the motor; and/or form part of the magnetic circuit. A yoke may be used affix magnets thereto as well.

However, in electric motors, reducing the number and complexity of machined parts leads to a reduction in costs and manufacturing time. Further, it is advantageous to reduce the weight of moving motor components to diminish the moment of inertia of the motor when operating in dynamic situations for quick start and stop application.

SUMMARY

This disclosure relates in general to the rotor of an electric motor. More specifically, this disclosure pertains to a yoke for a permanent magnet rotor wherein an independent yoke formed with over-molded plastic and is secured to a magnet casing. The disclosure further relates to a method for producing the yoke and rotor.

In one embodiment of the present disclosure, a rotor yoke includes a casing attachment ring, a sensor ring, and an over-molded body disposed between the casing attachment ring and the sensor ring. The over-molded body couples the sensor ring to the casing attachment ring. The over-molded body may optionally defines one or more protrusions on an outer surface of the over-molded body. The aforementioned protrusion(s) are configured to balance the rotor yoke. Specifically, the protrusion or protrusions may be removable from the over-molded body so as to balance the rotor. Where there are a plurality of protrusions, these protrusions may be defined across an outer surface of the over-molded body. The casing attachment ring of the yoke is configured to be secured to one of a magnet casing or a magnet carrier.

In yet another embodiment of the present disclosure, a rotor assembly for a motor may be provided which includes a sensor ring, a casing attachment ring, an over-molded body and a magnet casing. The over-molded body may be disposed between the sensor ring and the casing attachment ring. The casing attachment ring and the magnet casing are affixed to one another. It is understood that the over-molded body configured to couple the sensor ring to the casing attachment ring.

The rotor assembly of the present embodiment may further optionally include at least one removable protrusion configured to balance the rotor yoke. Where there is a plurality of protrusions, the protrusions may optionally be defined across an outer surface of the over-molded body. Moreover, such protrusions may optionally be defined in a spiral pattern over the outer surface of the over-molded body. The protrusions may be removeable from the over-molded body so as to balance the rotor.

DETAILED DESCRIPTION

Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present disclosure, which constitute the best modes of practicing the present disclosure presently known to the inventors. The figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the present disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the present disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

It is also to be understood that this present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any manner.

The terms “comprising”, “consisting of”, and “consisting essentially of” can be alternatively used. Where one of these three terms is used, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

Referring now to the drawings, there is illustrated inFIG. 1a yoke assembly, indicated generally at10. The yoke assembly10is the top portion of a permanent magnet rotor driven by a stator (not shown). The yoke assembly10comprises a casing attachment ring40at a base of the yoke assembly10. Casing attachment ring40is a generally annular shaped metallic support that is formed as a single part. The casing attachment ring40may be created as a machined part, sintered, deep-drawn, or by other manufacturing means. For example, the casing attachment ring40can be machined from a block of metal or formed from a sheet of metal and into an annular shape. Additionally, the casing attachment ring40may also have two ends welded to create the annular shape or may have interlocking tabs42as an attachment mechanism to an enable the casing attachment ring40to engage with the magnet support32or core32. The casing attachment ring40may be press-fitted onto the magnet support32or core32. (seeFIG. 6c).

The casing attachment ring40is configured to attach to a magnet support32as shown inFIGS. 6aand6. As best illustrated inFIGS. 2cand3, the casing attachment ring40may comprise several tabs42on a top portion. As shown inFIG. 6cone end of the casing attachment ring40is pressed-fitted into the magnet casing150. However, it is within the scope of the disclosure that other securing means between the casing attachment ring40and the magnet casing150can be utilized. As shown inFIG. 2a, the other end of the casing attachment ring40top portion is secured to a body80.

As shown inFIG. 2a, the over-molded body80extends between the casing attachment ring40and a sensor ring50. In production, casing attachment ring40and the sensor ring50are placed in a mold. The body80is then created via an over-molding process that connects the sensor ring50to the casing attachment ring40.

Various elements of the yoke assembly10may have features that assist the over-molded body80to be secured to the elements. For example, the sensor ring50may have blind holes, tabs, or other features that allow the over-molded body80to further interface with the sensor ring50.

In addition, it is within the scope of the disclosure that the amount of plastic used in the over-molded body80can be adjusted. For example, the thickness of the over-molded body80can be made thinner for weight reduction or increased for balance and strength purposes. Further, the over-molded body can be made of a variety of materials. While standard plastics or nylon impregnated plastics can be utilized, it is with the scope of the disclosure that other materials can be present in the over-molded body.

The over-molded body80can further have additional elements or surface textures to allow balancing. As shown inFIG. 4, protrusions182can be provided on the outer surface of the over-molded body180that can then be removed to varying degrees to balance the yoke assembly10, and in turn the entire rotor assembly12. The protrusions182are shown in a rectangular shape inFIGS. 4-5. The protrusions182may optionally be removable to help balance the rotor. However, such protrusions182may be provided in various different shapes, such as, but not limited to dome-shaped protrusions (shown as elements182inFIG. 7). Alternatively, grooves or slots (not shown) may be made along the outer surface of the over-molded body80for similar balancing purposes.

Referring now toFIGS. 6a-6c, the yoke may be press-fitted onto the magnet casing (at the interface38(FIG. 6C) between the core32or magnet support32and the casing attachment ring40) in order to form the rotor assembly12.FIG. 6ais a perspective view of an example yoke and magnet casing of the present disclosure whileFIG. 6bis a cross sectional view of the magnet casing ofFIG. 6Calong line6B-6B.FIG. 6cis a side view of the yoke and magnet casing ofFIG. 6A. As indicated, the casing attachment ring40may have interlocking tabs42as an attachment mechanism to an enable the casing attachment ring40to engage with the magnet support32or core32. The casing attachment ring40may be press-fitted onto the magnet support32or core32. (seeFIG. 6c). As shown inFIG. 6b, the magnets30may be affixed to the magnet support (or core)32as shown.

In another embodiment, as shown inFIG. 7, the balancing protrusions182can be arraigned in a spiral shape (as dome shaped protrusions182) around the outer surface of the body180for improved balancing. These protrusions182may be removable. In addition, it is within the scope of the disclosure that the yoke assembly10may be balanced using additive methods.

In addition, the body over-molded body80can be adjusted as to how much engagement it has with each individual element. For example, the over-molded body80can extend to be flush with a top surface of the sensor ring50(as shown inFIG. 2a) or have a gap52from the top surface of the sensor ring50, as shown inFIG. 1. This further allows adjustment of the weight of the overall yoke assembly10as well as allowing mitigation of any fan effects created by the rotating sensor ring50.

As best shown inFIG. 2c, the sensor ring50is a generally annular shape with a planar body. The sensor ring50has a plurality of cut-outs54at the planar body portion which allows a sensor of the motor to determine rotation and/or position of the yoke assembly10. The sensor ring50is a metallic structure and can be formed by a variety of means. For example, the sensor ring50can be formed by a stamping process. Other yoke and rotor assemblies have previously formed a sensor ring as an integral part of a rotor body. These rotor assemblies are often deep-drawn to create the body. However, this process often causes uneven thickness of the sensor ring due to necking of the metal in a deep-draw process. This can have negative consequences in obtaining a signal from the sensor ring. In the present disclosure, a stamping process will result in a uniform thickness that is advantageous for signal reading of the sensor ring50.

The modular design of the present disclosure has further advantages over existing yoke and rotor assemblies that have an integral body, rotor shaft, and sensor ring. For example, the sensor ring50can be made of a material optimized for the sensor while the casing attachment ring40can be made of a different material optimized for strength or weight. Further, the components can be individually changed and optimized without requiring a change to the entire assembly.

The principle and mode of operation of this disclosure have been explained and illustrated in its preferred embodiment. However, it must be understood that this disclosure may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.