Patent ID: 12231023

DETAILED DESCRIPTION

FIG.1is a perspective view of an electric motor100. The electric motor100includes a stator102, a rotor104, end caps106and107, a shaft108to which the rotor104delivers torque during operation, and a casing109. The left end of the rotor includes a plurality of blades110in between which are a plurality of arrays of micro-features112. Each of the arrays includes projections that are arranged in a trapezoidal fashion, but can be in other configurations such as rectangular, circular, or triangular. The configurations could also be staggered or aligned. The projections of the micro-features112have a circular cross-section, but the cross-section of the micro-features112could be other shapes such as rectangular, circular, ovular, rhomboidal, or the shape of a hydrofoil or an airfoil. The right side of the rotor104also includes a plurality of blades118and a plurality of arrays of micro-features, which cannot be observed in this perspective view but will be shown in subsequent figures. Each array of micro-features112on the left side of the rotor104corresponds with an array of micro-features on the right side of the rotor. Specifically, each corresponding pair of micro-feature arrays are two ends of an insert made of conductive material, referred to herein as a spreader and described in more detail below. In the embodiment ofFIG.1, there are six spreaders inserted into the rotor104, and as a result, there are six corresponding pairs of micro-feature arrays. Additionally, the blades110and118can be integral with the spreaders, or alternatively the blades110and118can be integral with the rotor104. The blades110and118could also be discrete components attached to either the rotor104or the spreaders.

The end caps106and107includes a plurality of arrays of micro-features114and116respectively. Each array of micro-features114and116is arranged in a rectangular fashion but can be in other configurations such as circular, triangular, or trapezoidal. Like the micro-features112, the micro-features114and116have a circular cross-section, but the cross-section of the micro-features114and116could be other shapes such as rectangular, circular, ovular, or rhomboidal.

During operation of the motor100, the rotor104rotates and because the blades110and118and the micro-features112(and the corresponding micro-features on the right side of the rotor) are on the rotor, they also will rotate. Overtime, the rotor and stator will generate heat. The heat generated by the rotor will be conducted to the ends of the rotor104via the spreader. When the heat reaches the ends of the rotor, the blades110and118and the micro-features112(and the corresponding micro-features on the right side of the rotor104) will cool the rotor and stator by dissipating the heat generated in the rotor.

More specifically, the rotation of the blades110and118causes an axisymmetric circulation of air that goes from the rotor104, to the stator102, to the end caps106and107, and back to the rotor104. In this circulation, the heat from the rotor gets dissipated by flowing from the rotor along the described axisymmetric circulation. When the heat reaches the end caps106and107, the micro-features114and116of the end caps will cause the heat to dissipate to the ambient air outside the motor100.

The micro-features described enhance the cooling of the motor100. As described, heat generated by the rotor104will be thermally conducted to the ends of the rotor104via the spreaders. The blades110and118generate the axisymmetrical circulation of air, which will flow in between the gaps of, and around individual micro-features. The surface of the micro-features increases the area of the ends of the rotor (where generated heat is conducted to via the spreaders) and the flow of the circulating air increases its velocity as it flows in between and around individual micro-features. The increase in area and velocity enhances the heat dissipation from the rotor104.

Similarly, when the heat dissipated from the rotor flows along the axisymmetric airflow and reaches the micro-features114and116on the end caps106and107, the micro-features114and116will enhance the cooling of the motor100by dissipating the heat out to the ambient air outside the motor100due to the surface area of the micro-features and the increased velocity of the air flow in between and around the micro-features.

The arrangement of micro-features and blades described are useful in rotors that comprise permanent magnets. In permanent magnet machines, magnets can generate heat through eddy currents. These eddy currents generate heat on the magnets that can degrade their function. One problem is that magnets are not good thermal conductors, so the generated heat tends to stay with the magnet. When used in permanent magnet machines, the spreader acts as a thermal capacitance that conducts the heat from the magnets and moves it to the ends of the rotor, where it is dissipated as described.

FIG.2is a side view of motor100so that internal parts of the motor100can be observed.FIG.2illustrates the stator102, a rotor104, end caps106and107, a shaft108, and a casing109. On the left side of the rotor are blades110and micro-features112, and on the right side of the rotor are blades118and micro-features120. On the end caps106and107are micro-features114and116respectively.FIG.2shows arrows122and124which illustrate the generally axisymmetric circulation created by the blades110and118.

FIG.3is an axial view of components of the electric motor100. This figure shows the stator102inside of which is the rotor104. One of the ends of the rotor104includes blades110and micro-features112.FIG.3also shows end cap107having micro-features116.FIG.4is a perspective view of components of the electric motor100. This figure shows the stator102, rotor104, and the shaft108. On the rotor104are the blades110and micro-features112.

FIG.5is an axial view of end cap106andFIG.6is a side view of end cap106.FIG.5shows the array of micro-features114andFIG.6shows from the side, the projection of the micro-features114.FIG.7shows the micro-features on the end cap106from a perspective view, showing micro-features114.

FIG.8is a perspective view of an electric motor200. The electric motor200includes a stator202, a rotor204, end caps206and207, a shaft208to which the rotor204delivers torque during operation, and a casing209. The left end of the rotor includes a plurality of blades210in between which are a plurality of arrays of micro-features212. Each of the arrays include projections that are arranged in a trapezoidal fashion, but can be in other configurations such as rectangular, circular, or triangular. The projections of the micro-features212have a circular cross-section, but the cross-section of the micro-features212could be other shapes such as rectangular, circular, ovular, or rhomboidal. The right side of the rotor204also includes a plurality of blades218and a plurality of arrays of micro-features, which cannot be observed in this perspective view. The micro-features on the right side of the rotor204are symmetrical to those on the left side, as described inFIG.1. Each array of micro-features212on the left side of the rotor204corresponds with an array of micro-features on the right side of the rotor. Specifically, each corresponding pair of micro-feature arrays are two ends of an insert made of conductive material, referred to herein as a spreader and described in more detail below. In the embodiment ofFIG.8, there are six spreaders inserted into the rotor204, and as a result, there are six corresponding pairs of micro-feature arrays. Additionally, the blades210and218can be integral with the spreaders, or alternatively the blades210and218can be integral with the rotor204. The blades210and218could also be discrete components attached to either the rotor204or the spreaders.

The end caps206and207includes a plurality of arrays of micro-features214and216respectively. Each array of micro-features214and216is arranged in a rectangular fashion but can be in other configurations such as circular, triangular, or trapezoidal. Like the micro-features212, the micro-features214and216have a circular cross-section, but the cross-section of the micro-features214and216could be other shapes such as rectangular, circular, ovular, or rhomboidal.

During operation, the heat generated in rotor204is conducted to the ends of the rotor via the spreaders wherein the heat is dissipated via the blades and micro-features on the rotor204, similar to that described inFIG.1. InFIG.8, however, the motor200also includes ducts222and224. During operation, the blades210and218rotate to create a circulation of air. InFIG.1, the circulation created by the blades directed airflow axisymmetrically from the rotor to the stator and then to the end caps. In the embodiment inFIG.8, the circulated air does not flow to the stator due to the ducts222and224. Instead, inFIG.8, due to the ducts, the air circulates from the rotor204to the end caps206and207. With the ducts222and224, there is a close coupling convection between the rotor204and the end caps206and207such that the heat dissipated from the rotor204is directed to the micro-features214and216of the end caps206and207.

FIG.9is an axial view of components of the electric motor200. This figure shows the stator202inside of which is the rotor204. One of the ends of the rotor204includes blades210and micro-features212.FIG.9also shows the duct224and end cap207having micro-features216.

FIG.10is another axial view of components of the electric motor200, which shows the end cap207having micro-features216, and also shows the duct224. The duct224includes ribs226. The ribs226provide structural support for the duct224and also direct airflow to the micro-features216. During operation, some of the air flow from the rotor (via the blades210and218) will contact the ribs226at which point the ribs226will assist in direct the airflow to the micro-features216. The ribs226, therefore, increase the efficiency of the heat transfer from the rotor to the end caps and ultimately out of the motor200. While end cap207is shown inFIG.10, it will be appreciated that ribs, like ribs226, can be included on duct222on end cap206.

FIG.11is a side view of the end cap207showing the micro-features216and duct224and ribs226, andFIG.12is a perspective view showing these features. The ribs226are triangular, but it will be appreciated that other geometries such as cubical or pyramidal can be applied without departing from the scope of this disclosure.

The rotors described herein may be manufactured where the spreaders are machined to include the micro-features on each end; alternatively the micro-features and the spreader could be integrally casted, where the conductive material that forms the spreader and micro-features is poured and casted directly in the rotor.

The features described herein can be applicable to electic machines, including without limitations, induction machines, permanent magnet machines (including those that use segmented magnets or an array of segmented magnets), switch-reluctance machines, and field wound synchronous machines.

While embodiments have been illustrated and described herein, it is appreciated that various substitutions and changes in the described embodiments may be made by those skilled in the art without departing from the spirit of this disclosure. The embodiments described herein are for illustration and not intended to limit the scope of this disclosure. For example, while embodiments described here include micro-features on a rotor and micro-features on one or more end caps, it should be understood that motor design in accordance with the teachings of this disclosure may include micro-features on one or more end caps and no micro-features on the rotor. Alternatively, a motor design in accordance with the teachings of this disclusure may include micro-features on the rotor and not on the one or more end caps.