Ventilation – Electronic cabinet
Reexamination Certificate
1999-11-11
2001-11-20
Wayner, William (Department: 3744)
Ventilation
Electronic cabinet
C095S014000, C096S420000, C165SDIG119, C236S049300
Reexamination Certificate
active
06319114
ABSTRACT:
FIELD OF INVENTION
This invention relates to a thermal management system including a fan disposed to force air through a filter over heat generating components such as electronic circuit cards and a control subsystem which monitors the temperature of the air inside the cabinet and/or the air flow rate through the cabinet and which also simultaneously monitors the condition of the fan and/or the filter and which provides an indication when the fan is not working properly and/or when the filter is clogged.
BACKGROUND OF INVENTION
Thermal management systems generally include an enclosure such as a housing or cabinet for heat generating electronic component circuit cards or boards which must be cooled to prevent damage to the electronic components. A variable speed fan is disposed to force air over the components and a temperature sensor and/or an air flow sensor monitors the temperature and/or air flow rate of the air or other cooling gas inside the cabinet.
A filter is used to reduce particulate matter in order to eliminate contaminants which could otherwise foul the circuit cards. A controller, connected to the fan and responsive to the temperature sensor and/or the air flow sensor, continuously monitors the temperature of the electronic circuit cards and adjusts the speed of the fan to keep the electronic components cool.
Such prior art systems, however, do not include means to determine the fan's condition or health. When the fan's bearings or motor begins to fail, the fan, operating at even full capacity, may not properly cool the electronic components and by the time this condition is detected manually, certain electronic components may have already failed, become thermally stressed, or degraded to the point where failure is imminent.
Prior art systems also fail to include any means for determining whether the filter is clogged to the point where cooling is no longer effective. Again, when the filter is clogged, the air flow rate through the cabinet may be less than optimal even at the highest fan speed resulting in component failure, thermal stress, or degradation which may not be detectable.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a more complete thermal management system for enclosures or cabinets housing electronic components.
It is a further object of this invention to provide such a thermal management system which automatically monitors the condition of the fan or its components and which provides an output signal when the fan is incapable of providing sufficient air flow to keep the electronic components cool.
It is a further object of this invention to provide such a thermal management system which automatically detects when the filter is clogged and when the air flow rate through the cabinet is less than optimal.
It is a further object of this invention to provide such a thermal management system which is simple in design, easy to implement, and which can be added to existing thermal management systems at little cost to the customer.
This invention results from the realization that since the controller of most thermal management systems automatically adjusts the speed of the fan until the air temperature inside the enclosure is optimal, the controller can be modified to also automatically determine the condition of the fan by comparing the input (e.g., voltage) signal to the fan with the speed of the fan since, in poorly operating fans, fan speed will be normally lower for a given input signal; and from the further realization that the controller can be modified to also automatically determine the condition of the air filter in the enclosure for dirty or clogged conditions by comparing, for example, the enclosure air flow rate with the speed of the fan since a clogged filter results in a lower air flow rate at a given fan speed.
The controller monitors the fan's speed, the voltage level applied to the fan, and the temperature(s) inside the enclosure and provides some kind of a notification when these signals indicate a poorly working fan and/or a clogged filter, in addition to functioning to speed up the fan to provide more air flow as needed to keep heat generating devices such as circuit boards cool to prevent component failures.
This invention features a thermal management system comprising an enclosure housing devices which generate heat; a fan whose speed is responsive to an input signal, the fan having a gas flow output in communication with the enclosure; a filter disposed in the gas flow path of the fan's output; at least one temperature sensor disposed in the enclosure for measuring the temperature inside the enclosure; a controller for adjusting the speed of the fan until the temperature inside the enclosure is within a predetermined range to ensure that the devices inside the enclosure do not overheat; means for comparing the signal input to the fan with the speed of the fan to determine the condition of the fan; and means, responsive to the temperature sensor, for determining the condition of the filter.
If the input signal to the fan is a voltage signal, the means for comparing includes a processor programmed to compare the voltage signal with the speed of the fan and to provide an output signal indicative of a poorly operating fan when the voltage signal exceeds a predetermined threshold for a predetermined fan speed.
There are several embodiments of the means for determining the condition of the filter. In one embodiment a processor is programmed to compare the temperature inside the enclosure with the speed of the fan and to provide an output signal indicative of a clogged filter when the temperature inside the enclosure exceeds a predetermined threshold for a predetermined fan speed. In another embodiment, the means for determining the condition of the filter includes a second temperature sensor disposed to measure the temperature of a gas flow entering the enclosure and a processor, responsive to the second temperature sensor, programmed to compare the temperature of the gas flow entering the enclosure with the temperature inside the enclosure and to provide an output signal indicative of a clogged filter when the difference between the two temperatures exceeds a predetermined threshold at a predetermined fan speed. In still another embodiment, the means for determining the condition of the filter includes at least one gas flow rate sensor disposed to measure the gas flow rate through the enclosure and a processor programmed to provide an output signal indicative of a clogged filter when the gas flow rate is less than a predetermined level at a predetermined fan speed.
Typically, the enclosure and even the fan and filter are not necessarily components of the thermal management system of this invention which includes at least one temperature sensor disposed in the enclosure for measuring the temperature inside the enclosure; a controller for adjusting the speed of the fan until the temperature inside the enclosure is within a predetermined range to ensure that the devices inside the enclosure do not overheat; means for determining the condition of the fan; and means, responsive to the temperature sensor, for determining the condition of the filter.
In most embodiments, the thermal management system comprises a temperature sensor for measuring the temperature inside an enclosure to be cooled with a fan whose speed depends on a fan input signal; and a controller responsive to the temperature sensor and connectable to the fan for monitoring the temperature inside the enclosure and adjusting the speed of the fan until the temperature inside the enclosure is within a predetermined range, the controller including: means for comparing the fan input signal with the speed of the fan to determine the condition of the fan; and means, responsive to the temperature sensor, for determining the condition of the filter. A thermal management system for detecting a poorly operating fan in accordance with this invention includes a temperature sensor for measuring the temperature inside an enclosure to
Gagnon David
Holman Roger
Nair Rajesh
Degree Controls, Inc.
Iandiorio & Teska
Wayner William
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