Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
2000-06-26
2002-05-21
Doerrler, William C. (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
C062S259200, C062S003300
Reexamination Certificate
active
06389817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of small temperature-sensitive devices, and in particular, to temperature control for small disk drives.
2. Background Information
Small, temperature-sensitive electronic and electromechanical devices, such as micro disk drives, are being developed and used. However, many potential applications for these devices, such as in automotive vehicles, are presently ruled out because of a mismatch between device operating temperature specifications/limitations and automotive operating temperatures. This is true at both the low temperature end and high temperature end of the respective operating temperatures. Besides vehicles, the temperature environment for the emerging market of wearable computers may also be outside of the normal specifications for such devices under certain circumstances.
Existing temperature control methods and adaptations are generally inadequate and/or have drawbacks which make them inapplicable to such devices in these environments. Therefore, there is a need for better temperature control methods and apparatus to adapt these temperature-sensitive devices to be used in a wider variety of operating environments having a wider range of temperatures, such as may be found in the automotive and wearable computer environments.
The present invention is directed to solving the problem of improving temperature control for small, temperature-sensitive devices. In particular, the present invention has been developed to control the temperature environment of ‘microdrives,’ such as those manufactured by IBM (IBM is a registered trademark of International Business Machines). Microdrives, as the term is used herein, are direct access storage devices (DASD's) in miniaturized form, e.g., packaged in a relatively small, thin housing, for example, having a thickness of approximately 5 mm or less, and outer dimensions of under 50 mm. In other words, about the size of a small match-box. It should be clear that the inherent small size and low power consumption that a microdrive can provide would clearly be advantageous in situations where these are at a premium, such as in a hand-held device, a wearable computer, or a vehicle.
However, one of the current unresolved issues with using a microdrive in an automotive setting is the mismatch between the automotive operating temperature specifications and those of the microdrive. Disadvantageous external cooling and/or heating apparatus may be required thereby destroying the size and power advantages the microdrive would otherwise provide. To date there have been no solutions proposed that are built into the microdrive. In order to gain rapid acceptance of the microdrive in automotive environments (and other stressed environments), it would be advantageous for the microdrive be a complete OEM entity, that is, having adequate temperature controls already built in.
As with regular-sized DASD's, microdrives have one or more storage disks which are rotated by a motor and one or more read/write heads. When ‘loaded,’ that is, positioned for operation with respect to the storage disks over data storage areas, the read/write heads operate to read and write data to and from the storage disks. When not loaded, the heads are ‘parked,’ that is, positioned at an area off the disk surfaces sometimes called a ‘load/unload ramp’, which is typically located adjacent to the outer edge of the disks in the disk drive.
In practice, based on tests, a microdrive motor can be started and spun without the heads loaded at a temperature as low as −30 C. After the drive reaches a temperature of 5 degrees C. (the lower operating temperature specification), the heads can be loaded and the drive is ready for use. Therefore, some means to warm the microdrive may be required in certain environments.
On the other hand, a microdrive disposed inside of an automobile, for example, might reach a high temperature of 75 degrees C. (non-operating). However, the upper operating temperature of a typical microdrive is around 55 degrees C. Therefore, some means to cool the microdrive down to its operating temperature range is required.
Solid state heating/cooling devices, for example the Peltier thermoelectric module, are known. These modules produce a temperature differential between two surfaces. The effect was discovered in 1834 by Peltier. When a current passes through the junction of two different conductors, it results in a temperature change. The Peltier effect is a thermocouple in reverse. Instead of producing a voltage proportional to temperature, a voltage is used to produce a temperature difference between the two metals in a thermocouple junction. In order to optimize the effect, Peltier devices today use semiconductors such as bismuth telluride. The devices that are commercially available are a sandwich structure as small as 2 millimeters (mm) square and 1 mm thick. Which of the plates is hot and which is cold depends ONLY on the direction of DC current flow.
SUMMARY OF THE INVENTION
It is, therefore, a principle object of this invention to provide a method and apparatus for controlling the internal temperature of a small device.
It is another object of the invention to provide a method and apparatus that solves the above mentioned problems so that small, temperature-sensitive devices can be used in a wider range of environments and applications.
These and other objects of the present invention are accomplished by the method and apparatus disclosed herein.
According to an aspect of the invention, an environmental shell is provided that operates in either a heating or cooling mode.
According to another aspect of the invention, heat transfer, either to or from the drive, is aided by the rotating disk or disks inside of the drive. By using the rotating disks as a means to circulate air, one of the limitations of solid state heating/cooling devices, such as a Peltier thermoelectric module, is advantageously overcome, since such devices require a fan or other air circulation mechanism.
According to another aspect of the invention a specially designed cover plate for a microdrive that incorporates a thermoelectric module is provided.
According to another aspect of the invention, a Peltier thermoelectric module is used. The thermoelectric module produces a temperature differential between two surfaces when a current passes through the junction of two different conductors, resulting in a temperature change. This effect was discovered in 1834 by Peltier.
According to another aspect of the invention, the thermoelectric module uses semiconductors such as bismuth telluride. Further, the module is a sandwich structure which may be as small as 2 millimeters (mm) square and 1 mm thick.
According to another aspect of the invention, the thermoelectric module has plates and which of the plates is hot/heated and which is cold/cooled depends only on the direction of direct current flow (DC).
According to another aspect of the invention, the thermoelectric module is integrated into the cover of a microdrive, so that the interior of the microdrive can either be heated or cooled.
According to another aspect of the invention, when cooling the interior, the outside of the microdrive is more efficiently cooled by providing a separate fan combined with fins on the drive.
According to another aspect of the invention, the thermoelectric cooling module can be placed either inside of the microdrive casting or on the outside. In a preferred embodiment, the cooling module is outside of the casting and attached to the top cover of the microdrive. In another preferred embodiment, the thermoelectric cooling unit may be provided with fins and integrated with the top cover of the microdrive.
According another aspect of the invention, miniature thermoelectric modules are used, having dimensions compatible with the size of the microdrive, and which are easily capable of providing over 10 watts of heating power. Since the mass of a typical microdrive is about 16 grams, the required heating or cooling energy
Bussan Matthew J.
Doerrler William C.
International Business Machines - Corporation
Lynt Christopher H.
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