Fan and electric machine assembly and methods therefor

In one embodiment, a fan for a rotating device having a shaft with an axis of rotation is provided. The fan includes a base plate having a front surface, a rear surface, and a hub configured for coupling to the shaft. The fan further includes at least one blade projecting from the front surface of the base plate substantially perpendicular to the base plate. The base plate is contoured to direct air at an acute angle relative to the axis of rotation.

BACKGROUND

The field of the invention relates generally to fans and, more particularly, to cooling fans for motor assemblies.

Many known electric machines such as electric motors generate heat during operation. At least some known motors are provided with a cooling fan rotatably coupled thereto, and the fan rotates during operation of the motor to produce air flow over the motor housing to facilitate cooling the motor. However, these fans direct airflow in a manner that produces a less than optimal motor cooling effect.

BRIEF DESCRIPTION

In one embodiment, a fan for a rotating device having a shaft with an axis of rotation is provided. The fan includes a base plate having a front surface, a rear surface, and a hub configured for coupling to the shaft. The fan further includes at least one blade projecting from the front surface of the base plate substantially perpendicular to the base plate. The base plate is contoured to direct air at an acute angle relative to the axis of rotation.

In another embodiment, an electric machine assembly is provided. The electric machine assembly includes a motor including a housing and a shaft with an axis of rotation. The electric machine assembly further includes a fan including a base plate having a front surface, a rear surface, and a hub configured for coupling to the shaft. The fan further includes a plurality of blades projecting from the front surface of the base plate substantially perpendicular to the base plate. The base plate is contoured to direct air at an acute angle relative to the axis of rotation.

In yet another embodiment, a method of assembling an electric machine assembly is described. The method includes providing a motor including a housing and a shaft with an axis of rotation and coupling a fan to the shaft. The fan includes a base plate comprising a front surface, a rear surface, an outer rim, and a hub configured for coupling to the shaft. The fan further includes at least one blade projecting from the front surface of the base plate substantially perpendicular to the base plate. The base plate is contoured to direct air at an acute angle relative to the axis of rotation.

DETAILED DESCRIPTION

FIG. 1illustrates an exemplary embodiment of an electric machine assembly10including a motor12and a fan14. Motor12includes a housing18having a first end wall20, a second end wall22, and a sidewall24extending from first end wall20to second end wall22. In one embodiment, housing18is generally cylindrical. In other embodiments, housing18may be any suitable shape that enables fan14to function as described herein. In the exemplary embodiment, second end wall22and sidewall24are joined together at a rounded contour26having a continuously changing degree of curvature (e.g., a substantially elliptical contour). A plurality of cooling fins28project from sidewall24and are oriented along a length of housing18substantially from first end wall20to second end wall22. In an alternative embodiment, cooling fins28may extend along only a portion of housing18or may not be present at all.

In the exemplary embodiment, motor12has a rotating shaft30. Shaft30has a first end32, a second end34(FIG. 5), and an axis of rotation X oriented from first end32to second end34. Shaft30extends through first end wall20of housing18such that first end32of shaft30is exposed outside of housing18for coupling to a load (not shown). Shaft30also extends through second end wall22such that second end34of shaft30is exposed outside of housing18for coupling to fan14to facilitate producing a flow of cooling air over housing18for cooling motor12, as described below.

FIGS. 2-4illustrate an exemplary embodiment of fan14. Fan14includes a generally bowl-shaped base plate50having a hub60, an outer rim62, a first face56extending from hub60to outer rim62, and an opposite second face58extending from hub60to outer rim62. Base plate50further includes at least one blade52projecting from first face56, and at least one rib54projecting from second face58. In some embodiments, fan14has a plurality of circumferentially-spaced blades52(e.g., fifteen blades) and a plurality of circumferentially-spaced ribs54(e.g., fifteen ribs). In one embodiment, first face56is convex, and second face58is concave such that base plate50has a continuously changing degree of curvature along surface56(e.g., base plate50may be generally elliptical, generally parabolic, or generally hemispherical). In other embodiments, first face56and second face58may have any suitable contours that facilitate enabling fan14to function as described herein.

In the exemplary embodiment, each blade52is oriented substantially radially from hub60toward outer rim62and projects substantially perpendicularly from base plate50to a blade edge72. In this manner, fan14is an axial fan that is configured for bi-directional operation. Alternatively, each blade52is oriented at any angle between 0° and 90° from first surface56of base plate50. In the exemplary embodiment, blades52are substantially flat or linear. Alternatively, each blade52may have any curvature as blade52extends from base plate50and/or as blade52extends between hub60and rim62that enables fan14to function as described herein.

In the exemplary embodiment, blade edge72has a first portion68that extends from hub60at a substantially orthogonal orientation to axis of rotation X, and blade edge72has a second portion70that extends curvilinearly from first portion68toward outer rim62. In one embodiment, first portion68of blade edge72is substantially perpendicular to axis X. In another embodiment, first portion68of blade edge72may have any suitable contour that facilitates enabling fan14to function as described herein. In one embodiment, second portion70of blade edge72is substantially elliptical. In another embodiment, second portion70of blade edge72may have any suitable contour that facilitates enabling fan14to function as described herein.

In the exemplary embodiment, each rib54is also oriented substantially radially from hub60toward outer rim62and projects substantially perpendicularly from base plate50such that each rib54is generally aligned with one respective blade52. Alternatively, each rib54is oriented at any angle between 0° and 90° from second surface58of base plate50. In the exemplary embodiment, ribs54are substantially flat or linear. Alternatively, each rib54may have any curvature as rib54extends from base plate50and/or as rib54extends between hub60and rim62that enables fan14to function as described herein. Furthermore, in the exemplary embodiment, each rib54extends radially outward from hub60toward rim62. Alternatively, ribs54may be oriented substantially radially from hub60, but not coupled to hub60. In the exemplary embodiment, each rib54has an equal length. Alternatively, at least one rib54may have a different length than an adjacent rib54.

In the exemplary embodiment, base plate50further includes a plurality of apertures80, and each aperture80is located between a pair of adjacent blades52and/or a pair of adjacent ribs54. Apertures80are sized to permit airflow into an interior82of bowl-shaped base plate50to facilitate cooling second end wall22of motor12(e.g., each aperture has tapered edges84and86that enable a smoother flow of air into interior82). Apertures80may have any suitable size or shape that facilitates enabling fan14to function as described herein (e.g., apertures80may be sized in accordance with a desired RPM rating of fan14). In the exemplary embodiment, fan14includes at least one aperture80between each pair of adjacent blades52. Alternatively, fan14may include at least one aperture80between every other pair of adjacent blades52. Furthermore, fan14may include a plurality of apertures80between at least one pair of blades52. In the exemplary embodiment, apertures80are positioned proximate hub60on base plate50. Alternatively, each aperture80may be located anywhere on base plate50between hub60and rim62that facilitates operation of fan14as described herein.

FIG. 5illustrates a cross-sectional view of electric machine assembly10. In the exemplary embodiment, a generally bowl-shaped shroud16is coupled to housing18in a stationary manner such that shroud16is disposed over fan14, with fan14rotatably disposed between shroud16and second end wall22of housing18. Shroud16facilitates protection of fan14and increased cooling performance along housing18. In the exemplary embodiment, shroud16includes a plurality of air inlets90that are oriented substantially parallel to axis of rotation X. Alternatively, inlets90may be of any size, orientation, and shape that facilitates operation of shroud16as described herein. Shroud16is sized to envelop at least a portion of second end wall22of housing18to define an annular air outlet92along sidewall24of housing18. In one embodiment, outlet92is shaped to facilitate channeling a maximum amount of cooling airflow through outlet92and over sidewall24. In other embodiments, outlet92may be shaped in any suitable manner.

In the exemplary embodiment, shroud16is contoured such that, when coupled to housing18, a central segment94of shroud16is oriented substantially perpendicular to axis of rotation X, and a peripheral segment96of shroud16is substantially parallel to axis of rotation X (e.g., shroud16is contoured to substantially complement the contour of, or envelop, housing18near second end wall22). In the exemplary embodiment, central segment94and peripheral segment96are joined together at a rounded contour98(e.g., a substantially elliptical contour). In other embodiments, rounded contour98may have any suitable contour that facilitates enabling shroud16to function as described herein.

In the exemplary embodiment, an electronics enclosure100is positioned within motor second end wall22. Electronics enclosure100is configured to house various electronics, controls and/or drive system components. Electronics enclosure100generates heat during operation and is cooled by air flowing through apertures80behind fan14. Alternatively, electronics enclosure100is positioned on second end wall22between fan14and second end wall22or anywhere on housing18that enables electronics enclosure100to be cooled by air flow.

During operation, fan14rotates about rotational axis X and draws air through air inlets90of shroud16. The continuously changing degree of curvature of base plate50facilitates airflow remaining attached along the entire surface of base plate50. Base plate50directs air at an acute angle A relative to rotational axis X as air passes over outer rim62, and the air is thereafter directed axially along housing18through outlet92by shroud16and effects of the contours of electric machine assembly10. Because the contour of blade outer edge72is substantially contiguous with, or matched to, rounded contour26, a smoother transition of air flow from base plate50over sidewall24of housing18is facilitated. More specifically, attachment of airflow over rounded contour26is facilitated through the Coanda Effect (tendency of a fluid to be attracted to a nearby surface) since air flow departing axial fan14is at angle A and, therefore, attaches to (or follows more smoothly over) rounded contour26of housing18. Attachment of air flow over rounded contour26is also facilitated through the Bernoulli Effect (an increase in flow velocity leads to a decrease in static pressure) since the acceleration and velocity of the angled air flow is increased. In this manner, fan14increases cooling air velocity, volume, and distance of travel over sidewall24of housing18.

Additionally, ribs54generate an area of low pressure within interior82of bowl-shaped base plate50during rotation of fan14such that air flow through apertures80and over second end wall22is increased to facilitate improved cooling of electric machine assembly10, motor12, and/or electronics enclosure100near second end wall22and behind fan14(e.g., a low pressure gradient develops within the interior82of base plate50due to ribs54, which draws air through apertures80due, at least in part, to the Bernoulli Effect and/or low pressure behind moving blades52, and the air flowing through apertures80is provided over second end wall22of housing18and/or electronics enclosure100behind fan14). The air flowing within interior82of base plate50is accelerated subsequently directed over rounded contour26and axially along sidewall24between cooling fins28. By tapering outlet92toward second end of housing, air flow can be accelerated through outlet92to improve cooling efficiency even more.

The methods and systems described herein facilitate providing an axial fan for cooling a rotating device such as a motor. The methods and systems described herein also facilitate providing an axial fan configured to direct air flow at an acute angle A relative to an axis of rotation X of a motor shaft to which the fan is coupled, thereby increasing air flow velocity and air flow attachment over the housing of the motor. The methods and systems described herein further facilitate providing an axial fan with a base plate contoured to better complement a contour of a motor housing, thereby improving air flow speed and attachment over the sidewall of the motor housing. Additionally, the methods and systems described herein facilitate providing an axial fan that produces a flow of air behind the fan for cooling the motor housing behind the fan. The methods and systems described herein also facilitate providing a shroud over an axial fan for accelerating airflow over a side wall of a motor housing via a tapered outlet formed by the shroud, thereby improving attachment of the airflow to the motor housing along the entire length of the housing. The methods and systems described herein therefore facilitate providing an axial fan that requires less torque for a given RPM, which facilitates improving the overall air moving and cooling efficiency of the fan.