Patent Application
20070237656
1. Field of the Invention
The invention relates to heat transfer systems, more particularly to fan assemblies utilized for moving a fluid in a heat transfer system.
2. Background Art
Motor vehicles commonly utilize heat exchangers to dissipate heat collected in the operation of the motor vehicle to the ambient air. These heat exchangers include radiators for cooling an internal combustion engine, or a heater core for providing heat to a passenger compartment for climate control.
Internal combustion engine cooling systems that utilize a heat exchanger may also include a rotary axial fan for enhancing the movement of air through the heat exchanger. For example, a radiator in conventional motor vehicles includes a fan rearward or forward of the radiator for forcing air through the radiator. Typically, a shroud is provided to generally restrict the air to flow axially through the radiator and the fan. The fan may be driven directly from the operation of the internal combustion engine by a belt or the like. Also, the fan may be driven by an independent motor for rotating the fan and forcing the air through the heat exchanger, as commonly utilized for transversely mounted internal combustion engines. Air is commonly forced through a conventional heater core through a fan which is operated by the climate controls within the passenger compartment.
Fan assemblies often include a rotary axial fan that is supported by a hub on the shroud. The hub is supported by an array of stator fan blades extending inward from the shroud for structurally supporting the rotary axial fan and for permitting air to pass through the shroud. Often times, a motor may be mounted to the hub and supported by the stator fan blades of the shroud, for imparting rotation to the rotary axial fan.
An embodiment of the present invention provides a rotary axial fan assembly with a shroud that is adapted to be mounted proximate to a heat exchanger. The shroud is sized for conveying a flow of fluid through the heat exchanger and the shroud. At least one stator fan blade extends inward from the shroud. A hub is oriented generally centrally within the shroud and is supported by the stator fan blade. A motor stator is encapsulated within the hub. The motor stator is adapted for receiving a fan rotor with fan blades for forcing the flow of fluid to the heat exchanger and the shroud.
Another embodiment of the present invention provides a hub formed from a thermally conductive material for transferring heat from the motor stator into the flow of fluid for dissipating the heat into the flow of fluid.
A further embodiment of the present invention provides a hub formed from a material having a coefficient of thermal conductivity within a range of 10 to 175 Watts per meter*Kelvin.
Yet another embodiment of the present invention a shroud and stator fan blades that are formed unitarily from a thermally conductive material.
The above embodiments and other embodiments, aspects, objects, features, and advantages of the present invention are readily apparent from the following description of embodiments of the invention when taken in connection with the accompanying drawings.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.
With reference now to
Alternatively, the heat transfer system 10 may include any heat exchanger, such as a heater core which passes coolant therethrough while air is forced by a fan 14 for passing heated air into a passenger compartment of a vehicle, or any other heat transfer mechanism.
With reference now to
The stator fan 28 of the present embodiment includes a shroud 30, which is generally annular for limiting a direction of air flow through the fan assembly 24 to a generally axial direction L. The shroud 30 may be provided with a plurality of mounting flanges 32 for mounting the fan assembly 24 proximate to a heat exchanger, such as a radiator 12. The stator fan 28 may also include a radial array of stator fan blades 34 converging centrally inward to a hub 36. The hub 36 may be supported by the stator fan blades 34. Likewise, the rotary axial fan 26 may be mounted to the hub 36 for rotation of the fan 26 relative to the hub 36. The rotary axial fan 26 may include a series of rotary fan blades 38 extending from a fan hub 40. The rotary fan blades 38 may be inclined relative to the axial flow direction L at an attack angle, which is angled (non-radial) relative to the fan hub 40 such that rotation of the rotary axial fan 26 in a counter-clockwise direction, as illustrated by the arcuate arrow R in
Although the fan assembly 24 is illustrated as a puller fan assembly, wherein air is pulled through the radiator 12 and subsequently through the fan assembly 24, the invention contemplates that the rotary axial fan 26 may be rotated in a clockwise direction such that air is forced in a reversed linear direction relative to the arrow L depicted in
The fan assembly 24 illustrated in
For the embodiment of
With reference now to
In order to facilitate heat transfer from the motor 42 to the stator fan 28, a motor stator 44 of the motor 42 is encapsulated within the hub 36 of the stator fan 28. The motor stator 44 includes an end cap 46 with motor windings 47 that are disposed about lamination plates 48. The motor windings 47 are the primary source of heat and the lamination plates 48 may act as a heat sink for transferring heat from the motor windings 47. The lamination plates 48 are encapsulated within an inner diameter of the hub 36 for direct contact with the hub 36 as illustrated in
To further enhance the engagement between the motor stator 44 and the stator fan 28, a thermally conductive adhesive may be placed within the inner diameter of the hub 36 for providing direct contact therebetween. A room temperature vulcanizing (RTV) sealant may also be provided between a flange 50 of the end cap 46 and the hub 36 for sealing the motor 42 and preventing contaminants from getting within the motor 42.
To further enhance heat transfer from the motor stator 44 to the hub 36, the end cap 46 of the motor stator 44 may be insert molded to the motor windings 47 and the lamination plates 48 by an injection molding process thereby removing any air or space between the windings 47 of the motor stator 44. The windings 47 may be over molded by a material that functions as an electrical insulator between the windings 47, but also functions as a thermal conductor, such as a thermally conductive plastic. The insulator of the motor windings 47 may be molded separately or integrally with the end cap 46. The end cap 46 may be provided by a thermally conductive polymer, such as a polymer having a coefficient of thermal conductivity of one to three watts per meter*Kelvin (W/m*K). Thus the thermally conductive plastic ensures heat transfer from the windings 47 directly to the hub 36 without air gaps between the windings 47.
By utilizing the hub 36 of the stator fan 28 for partially housing the motor 42, the stator fan 28 functions as a heat sink for drawing heat from the motor 42. Accordingly, the shroud 30, stator fan blade 34 and the hub 36 may be formed of a thermally conductive material for transferring the heat from the motor 42 into the path of forced air. For example, the stator fan 28 may be die cast from aluminum which has a coefficient of thermal conductivity of approximately 110 W/m*K. Die cast aluminum provides optimal heat transfer characteristics and also provides adequate structural integrity for supporting the fan assembly 24 and resisting vibrations imparted by the motor 42.
Alternatively, the stator fan 28 may be sand cast from aluminum thereby having a coefficient of thermal conductivity of approximately 150 W/m*K. Of course, the invention contemplates that the stator fan 28 may be formed from any material having a suitable coefficient of thermal conductivity for acting as a heat sink and cooling the motor 42. Depending on the application of a particular fan assembly, a hub having a coefficient of thermal conductivity within the range of 10 to 175 W/m*K should be suitable for providing a heat sink by the hub 36 and stator fan blade 34 for cooling the motor 42. Other reasonably suitable conductive materials that meet the design tradeoffs between conductivity and structural integrity include wrought aluminum, which has a coefficient of thermal conductivity of approximately 167 W/m*K; steel, which has a coefficient of thermal conductivity of approximately fifty W/m*K; and magnesium, which has a coefficient of thermal conductivity of approximately sixty W/m*K.
The fan assembly 24 is further provided with a fan rotor 52 for driving the rotary axial fan 26. The fan rotor 52 includes a unitary shaft 54 and bearing assembly 56. The bearing assembly 56 is mounted within the hub 36 for supporting the shaft 54 for rotation relative to the hub 36. The bearing assembly 56 may be press fit within the hub 36 for assembling the fan rotor 52 and for sealing the hub 36. The bearing assembly 56 may be sized to withstand some unbalance of the fan assembly 24 thereby minimizing or eliminating a need to balance the fan assembly 24 and reducing manufacturing steps and overall cost of the fan assembly 24. Additionally, the bearing assembly 56 includes double-lipped seals 58 on each axial end of the bearing assembly 56 about the shaft 54 for preventing contaminates from getting within the motor 42. The double-lipped seals 58 render the bearing assembly 56 submersible such that the hub 36 may be exposed to various external contaminates such as inclement weather.
The fan rotor 52 also includes a magnet 60 mounted to an end of the motor shaft 54 centrally disposed within the motor stator 44. The motor stator 44 includes wiring 62, which may be sealed by the encapsulation of the motor 42 so that no additional seal is required. For example, the wiring 62 may be insert molded into the end cap 46 of the motor 42. The wiring 62 conveys a current through the windings 47 of the motor stator 44 for imparting an electromagnetic field for rotating the magnet 60 and consequently the shaft 54 within the bearing assembly 56 relative to the hub 36 of the stator fan 28.
The magnet 60 may be press fit upon the shaft 54 to provide a reliable connection and ease in assembly of the fan rotor 52. By pressing the magnet 60 flush with an end of the shaft 54 as illustrated in
A series of mechanical fasteners 64 are provided for fastening the flange 50 of the motor stator 44 to the hub 36 of the shroud 30. The mechanical fasteners 64 may be used to secure the motor stator 44 to the hub 36 and/or to resist vibration in the fan assembly 24. The mechanical fasteners 64 may also be utilized for sealing the flange 50 of the motor stator 44 against the hub 36 of the stator fan 28. The fasteners 64 may be utilized in combination with an adhesive or a thermally conductive glue, which may be utilized to fill the cavity within the hub 36 and the motor stator 44 for improving vibration resistance and aid heat transfer between the motor stator 44 and the hub 36. Depending on the particular application, the fasteners 64 may be utilized alone or in combination with the adhesive, or the fasteners 64 may be omitted if the adhesive is adequate for securing and sealing the motor stator 44 to the hub 36.
The rotary axial fan 26 is mounted to the distal end of the shaft 54. The rotary axial fan 26 may be assembled to the shaft 54 by utilization of a hub plate 66, which is formed, for example, from steel and may be press fit onto the motor shaft 54. The interference fit of the hub plate 66 and the shaft 54 provides a reliable connection that is easily assembled by pressing the hub plate 66 upon the shaft 54. The hub plate 66 may be pressed flush to the end of the shaft 54 to provide accurate axial rotation of the rotary fan blades 38 for optimizing efficiency of the fan assembly 24. Although any sequence of manufacturing operations may be contemplated within the spirit and scope of the present invention, the hub plate 66 may be assembled to the shaft 54 after the magnet 60 has been assembled to the shaft 54. Subsequently, the motor stator 44 may be assembled to the hub 36 of the stator fan 28, and the fan hub 40 may be fastened to the hub plate 66 by mechanical fasteners 68 or any suitable connection. By providing the hub plate 66 with a flat surface for receiving the fan hub 40 and with a reduced diameter pilot 70 that extends through the fan hub 40, unbalance of the fan assembly 24 may be minimized.
The rotary fan 26 may be formed of any suitable material for forcing air through the fan assembly 24. For example, the rotary fan 26 may be formed of a polymeric material that is sufficient to withstand the stresses associated with forcing air through the fan assembly 24, but is sufficiently lightweight for maximizing the efficiency of the motor 42. A retaining plate 72 can be utilized between the fasteners 68 and the fan hub 40 for distributing the load from the fasteners 68 to an expanded area upon the fan hub 40.
In summary, a fan assembly 24 is disclosed, which maximizes efficiency of the fan assembly 24 by minimizing components of the fan assembly 24 while maximizing heat transfer associated with the fan assembly 24 and for cooling a motor 42 for the fan assembly 24 thereby providing a low cost and efficient cooling system.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
