Patent Application
20070152643
The present invention relates to circuit packs and, more particularly, to multiple air-cooled circuit packs installed in a receptacle, such as an electronics cabinet, workstation, or the like.
Circuit packs containing multiple electronic components have become extremely important to the electronics infrastructure of a wide range of industries, businesses, government entities, and other users of electronics. It is well known to arrange electronic circuitry, usually for accomplishing one or more functions (e.g. telecom, video processing) on a single card with purpose-appropriate inputs and/or outputs. The card (or circuit pack) is then installed in a slot or receptacle located in an electronics cabinet, workstation, or the like. The slot is sized to accommodate a standard-sized circuit pack, typically such that the inputs and/or outputs on the circuit pack engage with appropriate connections, allowing the circuit pack functionality to be available within a larger electronics system.
The use of circuit packs is beneficial for a number of reasons. Adding and upgrading the capabilities of the system can be done by adding additional circuit packs or replacing existing circuit packs with newer models. System down time for repairs is minimized because faults can readily be isolated to a circuit pack, allowing for easy replacement of the faulty circuit pack with minimal impact to the rest of the system.
The electronic components,on each circuit pack generate heat as a result of power dissipation. Unless a cooling means is supplied, excess heat can build up, leading to improper functioning and premature failure of circuit pack components. Typically, an electronics cabinet, workstation, or the like includes with one or more fans to facilitate cooling by forcing air through the circuit packs. However, with increasing miniaturization and increasing demands on the capabilities of individual circuit packs, the trend is toward an ever-increasing density of electronics components on circuit packs. Heat generation on these densely populated circuit packs is often very near the heat removal capacity of the conventional forced air methods.
Aggravating the problem is the fact that in cabinets, workstations, or the like with multiple circuit packs, airflow is greatest where the circuit pack density is lowest. This phenomenon occurs because resistance to airflow is typically lower in circuit packs with fewer electronic components and greater in densely populated circuit packs. Consequently, the most cooling air is being supplied to the circuit packs that generate the least heat, such that the circuit packs with higher heat generation have a greater probability of excessive heat build-up.
Attempts have been made to provide more cooling to these densely populated circuit packs first by using higher performance fans, and also by using liquid cooling and/or cold plates, but such cooling methods are typically expensive and complex, increase the time and skill required to replace circuit packs, and are often not adaptable for use with existing electronics cabinets, workstations, or the like. Accordingly, it can be seen that there is a need for an inexpensive method for optimizing the cooling of high density circuit packs, that preserves all the ease and convenience of readily interchangeable circuit packs, and allows the continued use of existing electronic cabinets, workstations, or the like.
According to an embodiment of the present invention, an electronics system includes an airflow generation means and a plurality of circuit packs installed in a receptacle, at least one of the circuit packs having a backpressure generation means, wherein the backpressure generation means is effective for increasing airflow to at least another of the circuit packs.
According to a further embodiment of the present invention, a circuit pack adaptable for installation in a circuit pack receptacle includes a circuit board, and a backpressure generation means associated with the circuit board.
According to an additional embodiment of the present invention, an airflow resistor has a resistor body adapted to reduce excess airflow when used in connection with a circuit pack.
In operation, it is determined if excess airflow is supplied to one of the circuit packs, and the airflow is then restricted to one of the circuit pack based on the determination, wherein airflow to another of the circuit packs in increased.
These and other features and advantages of the present invention will be better understood from the drawings and in light of the detailed description, below.
FIGS. 5 is a front view of a circuit pack having a backpressure generation means, according to a further embodiment of the present invention;
Referring to
Referring to
A backpressure generation means 46 is disposed on the airflow entrance end 38. In the depicted embodiment, the backpressure generation means is an airflow resistor 46 formed with a resistor body 50. Resistor body 50 at least partially defines a clearance area 54. In the depicted embodiment, clearance area 54 is discontinuous and includes a first partial clearance area 56, which is further defined by the airflow entrance end 38, and a second partial clearance area 58, which is further defined by a reference line 60. The airflow resistor 46 generates backpressure as airflow entering the circuit pack 22 from the direction of arrow 44 is impeded by resistor body 50. The backpressure thus generated resists the free flow of air through the circuit pack 22 and only some reduced airflow is able to enter through the clearance area 54. The smaller the clearance area defined by the resistor body, the greater the generated backpressure. In other words, generally speaking, the larger the overall area of the resistor body 50, the greater the backpressure generated.
Referring again to
Referring to
From the foregoing it can be seen that the novel apparatus of the present invention allows the optimization of airflow through a plurality of circuit packs such that the circuit packs with the highest heat generation experience the highest airflow. The tendency of higher heat generating circuit packs to experience relatively low airflow because of the typically greater density of electronic components in such circuit packs is alleviated by resistively controlling airflow to lower heat generation circuit packs using airflow resistors with smaller clearances, which generate greater backpressure. Airflow resistors with larger clearances, which generate lower backpressure, are included on higher heat generation circuit packs. Because no additional liquid cooling or additional structures, such as cold plates, are necessary, the present invention results in little, if any, additional expense, and maintains the easy interchangeability of circuit pack configurations. Furthermore, the usefulness of existing cooling fans, and electronics cabinets, workstations, and the like is extended.
It will be dear to those skilled in the art that the present invention is not limited to the described embodiments, but that numerous variations and modifications can be made within the scope of the present invention.
For instance, the present invention is not limited to a particular circuit pack receptacle, but any of the several well-known circuit pack receptacles may be used. Such receptacles include, but are not limited to: workstations, electronics cabinets, and equipment racks. Accordingly, the term “receptacle” is used generically, and does not itself imply a specific structure beyond the capacity to receive multiple circuit packs.
Additionally, the fans 20, depicted in
Various backpressure generation means 46 may also be employed, and various designs and placements of airflow resistors are possible and fall within the scope of the present invention. The airflow resistors depicted in
In
It is not necessary that the backpressure generation means be located at the airflow entrance end of the circuit pack, as in
Circuit pack 1222, referring to
Furthermore, various means may be employed to determine the heat generation of the circuit packs. The heat generation may be determined based on past knowledge or modeling based on factors such as component type and density. If heat generation is empirically determined, various other well-known methods of heat measurement may also be employed.
While resistively controlling airflow in inverse proportion to heat generation may tend to produce a more optimized airflow, a strict mathematical relationship need not be applied. In general, it is desirable to resistively limit airflow to lower heat generation circuit packs enough such that higher heat generation circuit packs receive a sufficient percentage of the overall available airflow to provide sufficient cooling, while still ensuring that the reduced airflow provided to the lower heat generation circuit packs remains sufficient. “Excess airflow,” as used herein, refers to airflow supplied to a circuit pack in excess of the airflow required to adequately cool the circuit pack.
Though the foregoing are some examples of variations of the described embodiment that fall within the scope of the present invention, it will be appreciated by those skilled in the art that numerous other variations and modifications are possible without departing from the scope of the present invention.
