Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1998-12-23
2001-11-06
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C174S016300, C338S0220SD
Reexamination Certificate
active
06313996
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat radiation system for electric circuitry.
More specifically, the invention relates to a heat radiation system for electric circuitry including a “solid body releasing heat in balance, as it has a higher temperature than a surrounding body” (hereafter called “solid heat source body” or simply “heat source”), a “solid body receiving heat in balance, as it has a lower temperature than the heat source” (hereafter called “solid heat sink body” or simply “heat sink”), and a “body of medium or media conducting heat in balance in between, as it has a gradient or gradients of temperature continuously descending from the heat source to the heat sink” (hereafter called “heat conducting circuit” or simply “heat circuit”).
In particular, the invention is associated with electric circuitry having a “positive temperature coefficient thermistor” (hereafter called “PTC device”), and a heat radiation plate for the PTC device.
2. Description of Relevant Art
The PTC device is installed in an electric circuit connected to an electric load. The circuit conducts an electric current, which generates Joule's heat at “a positive temperature coefficient resistor element” (hereafter called “PTC element”) of the PTC device, whereby the PTC element is heated and has a temperature in accordance with an occasional heat balance. If the temperature exceeds a specified level, the PTC element trips to have a suddenly increased resistance so that the current is interrupted.
To restore the PTC element, its temperature needs to be lowered by dissipating heat through a heat radiation mechanism, in which the PTC element and electrodes in contact therewith release heat and one or more forced or natural heat-radiation members and large heat-capacity structural members near the PTC element receives heat.
A known PTC element comprises a body of thermally sensitive polymer and a system of electrically conductive particles suspended therein, and the body of polymer is adapted for a significant thermal expansion to have a decreased density of conductive particles to provide an increased resistance. A PTC device with such a PTC element is sometimes employed for electric or electronic control in an automobile.
Conventional techniques for radiating heat from a PTC device have been the provision of a metallic enclosure or wall with or without fins, see Japanese Patent Application Laid-Open Publication No. 4-78104, published Mar. 12, 1992, Japanese Patent Application Laid-Open Publication No. 61-234502, published Oct. 18, 1986, Japanese Utility Model Application Laid-Open Publication No. 62-163902, published Oct. 17, 1987, and Japanese Patent Publication No. 2-41161, published Sep. 14, 1990.
SUMMARY OF THE INVENTION
In view of the inventor, there has been provided a conventional heat radiation system for electric circuitry, the system comprising a combination of an electric-current conducting body and one or more significantly heat-conductive members in contact therewith as a “solid heat source body”, a surrounding structure or member in a vicinity of the solid heat source as a “solid heat sink body”, and an intervening body of air between the solid heat source and the solid heat sink as a “gaseous heat circuit”.
In the case of an electric circuit including a PTC device, the conventional heat radiation system comprises a combination of a PTC element and a pair of electrodes in contact therewith as a “solid heat source body with a tendency to thermally expand and contract”, a heat radiation member in a vicinity thereof as a “solid heat sink body”, and an intervening body of air therebetween as a “gaseous heat circuit”.
If the surrounding structure or member in a vicinity is metallic, the system comprises a combination of an electric-current conducting body and one or more significantly heat-conductive members such as electrodes in contact therewith as an “electrically conductive solid heat source body”, the surrounding structure or member in the vicinity as an “electrically conductive solid heat sink body”, and an intervening body of air therebetween as an “electrically non-conductive or insulating (i.e. dielectric) gaseous heat circuit”.
In any case, the gaseous heat circuit has a relatively small tendency to conduct heat, and is extremely susceptive to occasional factors so that it has an uncertain varying nature, unable to support a weight, and flees.
However, it has an extreme flexibility to occupy any form of space, accepts any intrusion or physical action, and never resists in a free space.
The present invention has been achieved with such points in view.
It therefore is an object of the present invention to provide a heat radiation system for electric circuitry including a heat circuit in which merits and demerits of a gaseous heat circuit are intentionally taken and improved, respectively.
To achieve the object, an aspect of the invention provides a heat radiation system for electric circuitry comprising a solid heat source body, a solid heat sink body, and a solid heat circuit interconnecting the solid heat source body and the solid heat sink body with each other, wherein the solid heat circuit comprises an elastic body having a larger tendency to conduct heat than the air.
In the heat radiation system for electric circuitry according to the aspect of the invention, the solid heat circuit can have an increased heat conductivity, hold the solid heat source body and the solid heat sink body within a desirable range of relative distance when either body is pushed toward the other, effectively eliminate influences of occasional factors, absorb displacements of and attenuate shocks to or vibrations of the solid heat source body and/or the solid heat sink body that may be a PTC element having a tendency to thermally expand and contract, provide a flexibility in design of outside dimensions and spacing, and have an improved handling nature.
The elastic body may preferably have a heat conductivity doner additionally suspended therein to have an increased heat conductivity, permitting a purpose-oriented control of heat conductivity.
The elastic body may preferably have an adhesive outer surface to permit an improved close contact with a sufficient retaining force.
The elastic body may preferably hold one of the solid heat source body and the solid heat sink body to eliminate a structural support therefor.
The elastic body may preferably have an adhesivity doner coated thereon and/or mixed therein so that the adhesive outer surface defines an application surface, permitting a decreased dust deposit.
The adhesive outer surface may preferably be coated with an exfoliative body to permit a post-application.
In the case of a metallic surrounding structure or member, the elastic body may preferably comprise a dielectric body and the solid heat source body and/or the solid heat sink body may preferably comprise a direct-current circuit such as a thermistor circuit, to avoid causing an undue induced current.
The solid heat source body may preferably comprise a PTC element.
The solid heat sink body may preferably comprise a metallic member.
The solid heat sink body may preferably comprise a ceramic member.
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IBM Tech Disol Bul vol. 19 No. 11 Apr. 1977 pp. 4279 “Conduction Path—Components
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Tolin Gerald
Yazaki -Corporation
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