Patent Application
20070092376
Electronic systems and equipment such as computer systems, network interfaces, storage systems, and telecommunications equipment are commonly enclosed within a chassis, cabinet or housing for support, physical security, and efficient usage of space. Electronic equipment contained within the enclosure generates a significant amount of heat. Thermal damage may occur to the electronic equipment unless the heat is removed.
Electronic systems commonly include heat-dissipating components such as processors, central processing units (CPUs), signal processors, and others. One or more fans are used to push air through the system and over components to avoid overheating of the heat-dissipating components. In recent years electronic systems have become more densely packaged so that system design within power and heat dissipation allowances has become more difficult. This system evolution creates design challenges in aspects of power consumption and the effect of fans on overall system heat dissipation characteristics.
An electronics system may have multiple fans including, for example, multiple fans arranged in series to supply sufficient cooling and redundancy in case of failure of one or more fans. If one or more of the series-connected fans fails due to any of various mechanical or electrical failures, power failure or shutdown due to attempts to operate above a system power budget, physical obstruction of a fan rotor, or the like, the failed fan may create a drag on cooling airflow through the system. Drag in the airflow pathway can result in increased demand on other fans, overheating of electronic components and devices, and degradation in electronics performance. Electronics cooling fans typically fail when motor bearing lubricant dries, which may result in a locked rotor. Fan failure may create heavy resistance to airflow through the electronics system due to blockage created by stationary fan blades.
In accordance with an embodiment of an electronics cooling fan, the electronics cooling fan comprises at least one collapsible fan blade driven by centrifugal force to extend radially as the fan spins and driven by elastic force to retract as spinning slows or stops.
Embodiments of the invention relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings whereby:
Referring to
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Retraction of the collapsible fan blades 204 when the fan 200 stops spinning reduces or minimizes obstruction to airflow through the fan. In contrast, a traditional fan, upon failure, has fan blades that stop spinning and block airflow through the fan.
The electronics cooling fan 200 comprises a hub 206 adapted for rotational motion and multiple collapsible fan blades 204 coupled to the hub 206. In various implementations, embodiments and forms the collapsible fan blades 204 comprise an airfoil surface 208 and a spring-and-mass element 210. The airfoil surface 208 and the spring-and-mass element 210 may be distinct elements in some configurations and may be combined in inseparable elements in other configurations.
The spring-and-mass element 210 is designed with a selected mass configuration and a selected elasticity so that, as the hub 206 spins, the centrifugal force exceeds spring force and drives the mass away from the hub 206, thereby extending lateral edges 212 of the airfoil surface 208 outward from the hub 206. The rotation speed of fans in many high performance applications is sufficient to generate a centrifugal force that enables extension of the collapsible fan blades 204.
The selected mass configuration and selected elasticity of the spring-and-mass element 210 are further designed so that, as the hub spin speed is reduced or stopped, the spring force retracts the mass inward toward the hub 206 and collapses the collapsible fan blades 204 and forming an open annular area radially outward from the hub 206. The open annular area 214 enables airflow through the electronics cooling fan 200.
The fan blades may be implemented in any suitable shapes and/or sizes, and are commonly formed with known aerodynamic contours. For illustrative purposes, some of the fan blades depicted herein are shown in simple rectangular forms to describe aspects of spring-and-mass elements related to generation of centrifugal and spring forces with little complexity. Typically, collapsible fan blades are to be implemented with common aerodynamic shapes.
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In various other configurations, the flexible elastic member 310 may be arranged with other mass distributions, such as a uniform mass throughout without an increased mass at the distal end of the member 310. Any suitable mass distribution may be implemented to produce a selected behavior during application of centrifugal force.
The flexible elastic member 310 is typically configured in aerodynamic fan blade geometry.
In some embodiments, the flexible elastic member 310 is designed with a mass configuration and elastic spring force adapted to respond to fan rotation by producing a centrifugal force that exceeds the spring force during fan rotation with the elastic spring force selected to limit excursion of the collapsible fan blade 304 to a selected radial distance. Radial excursion is limited to prevent the extended blades 304 from striking a fan housing for fan assemblies contained within a housing.
Other embodiments may include a mechanical restraint or stopper element, for example a tab at the end of a rod, which limits blade excursion.
Referring to
The telescoping sheeting layers 412 form the fan blade 404 in multiple sections constructed from a suitable material such as plastic or metal that unfold or unfurl outward under centrifugal force and that collapse or retract when the fan stops spinning. Collapse of the metal or plastic sheets reduces or minimizes the cross-sectional area of the blade 404. In some implementations, the metal or plastic sheets may comprise a suitable mass upon which the centrifugal force acts and the fan may spin sufficiently fast so that the blade extends without addition further material or mass. In other implementations, additional weight or mass may be added to the structure to ensure extension. In contrast to the embodiment employing an elastic material for usage as a fan blade 304 depicted in
The telescoping sheeting layers 412 may be configured as very thin and rigid flat plates, each having a form selected to create an aerodynamic fan blade shape as centrifugal force expands the blade 404.
The mass distribution of the sheeting layers 412 and the elastic characteristics of the spring or springs 414 are selected in combination with selected fan speed specifications to produce appropriate response to centrifugal forces. Mass and elastic properties are balanced to extend the collapsible fan blades 404 during fan rotation at a selected minimum speed and otherwise collapsing the blades. In some arrangements, the multiple sheeting layers may have the same mass distribution. In other embodiments, sheets may have differing mass distributions. Similarly, sheets with a mass distribution varies in planar space may be used. Some implementations may use mass elements, for example weight blocks, attached selectively to the sheeting layers. The illustrative embodiment has a mass element 416 attached to the distal edge of the sheeting layer most distal from the hub 406.
The telescoping sheeting layers 412 are configured with a mass configuration and the one or more springs 414 selected to have a spring force appropriate to create a centrifugal force that exceeds the spring force during fan rotation. The telescoping sheeting layers 412 have flanges 418, shown in
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In some configurations, the spring force may limit excursion to a selected radial distance. In other arrangements, a mechanical stop element may be added to limit excursion to a selected radial distance.
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The electronics cooling apparatus is designed by configuring and forming the electronics cooling fans 604 in an arrangement selected to create rotational motion and generate an axial airflow pathway. Typically the number and type of fans is selected to produce appropriate cooling for a particular functional configuration. High performance electronics systems typically include one or more integrated circuit components that produce a large amount of heat. The number of electronics cooling fans 604 and motors driving the fans 604 is selected to produce suitable cooling airflow.
Fan selection is based on functional specifications of the system. Fans typically run at faster speeds and with higher phase motors due to meet cooling specifications for systems with increased functionality. Higher performance fans that run at faster speeds generate more power and thus a higher centrifugal force, enabling operation of the disclosed collapsible fan blades. The illustrative fans with collapsible fan blades 606 exploit the centrifugal force naturally produced by the fans to enable the fan blades to automatically expand during operation and automatically collapse and thereby retract when the fan is not longer rotating. The collapsible character of the fan blades is typically attained by usage of airfoils constructed from a flexible material or fabric, or by usage of articulating joints in rigid fan blade structures.
Based on the selection of fan motor, the collapsible fan blades 606 may be designed so that the blades 606 are driven by centrifugal force to extend radially as the fan spins and driven by elastic force to retract as spinning slows or stops. Accordingly, the spring-and-mass elements 612 forming the fan blades 606 are configured so that as the hub 608 spins at a selected minimum fan speed, the centrifugal force exceeds spring force and drives the mass away from the hub 608, extending airfoil surface lateral edges 614 outward from the hub 608. The spring-and-mass elements 612 can be further designed so that as the hub spin is reduced or terminated, the spring force retracts the mass inward toward the hub 608, forming an open annular area radially outward from the hub that enables airflow through the annular area.
For fans 604 that are contained within a housing, the collapsible fan blades 606 are generally designed to limit extension or excursion so that the spinning fans do not contact the housing. Various types of retaining or stopping devices may be used to limit flexible fan blade excursion. For example, for a flexible fan blade constructed of an elastic material such as a rubber or synthetic elastomer, the material may be selected according to elastic properties so that the material extends a selected known distance under the maximum operating speed of the fan motor. In other embodiments, a mechanical stop such as a flange or tab may be implemented that limits extension beyond a predetermined length. Collapsible fan blade implementations that include a spring which is distinct from fan blade sheeting or panels may have a stop mechanism configured to limit extension of the spring, thereby limiting length of the blade. Collapsible fan blade embodiments in the form of a frame or rigid sheeting layers may be constructed with built-in stops.
While the present disclosure describes various embodiments, these embodiments are to be understood as illustrative and do not limit the claim scope. Many variations, modifications, additions and improvements of the described embodiments are possible. For example, those having ordinary skill in the art will readily implement the steps necessary to provide the structures and methods disclosed herein, and will understand that the process parameters, materials, and dimensions are given by way of example only. The parameters, materials, and dimensions can be varied to achieve the desired structure as well as modifications, which are within the scope of the claims. For example, although particular types of collapsible fan structures and techniques are illustrated and described, any suitable collapsible fan including an element adapted for elastic collapse may be used. Similarly, various fan arrangements are shown to facilitate expression of the structures and techniques. Any suitable number and arrangement of fans may be used and remain within the scope of the description. Also the illustrative structures and techniques may be used in any suitable electronics application including, for example, computers, blade systems, desktop personal computers or workstations, rack-mounted servers or other rack-mounted devices, storage systems, communication systems, and the like.
In the claims, unless otherwise indicated the article “a” is to refer to “one or more than one”.
