Heat exchange – With retainer for removable article – Electrical component
Reexamination Certificate
2000-04-05
2001-10-23
Flanigan, Allen (Department: 3743)
Heat exchange
With retainer for removable article
Electrical component
C165S185000, C165S109100, C029S890030
Reexamination Certificate
active
06305464
ABSTRACT:
The present invention relates to method according to the preamble of claim
1
for manufacturing cooling elements for power electronic components and other electric appliances.
The invention also relates to a cooling element manufactured according to the invention.
Description of Background Art
Cooling elements for electric appliances are most commonly made of long, extruded aluminium profile cut into suitable lengths. By extruding, it is easy to produce many kinds of profiles, wherefore it is simple to produce a suitable profile for different intended uses, and in this manner, a large number of different kinds of cooling elements can be manufactured. However, elements made from extruded profile have a number of disadvantages relating particularly to the cooling of power electronic components. With modern components, high electric power can be handled with relatively small equipment. When such high power is led through a semiconductor component, naturally, power loss results, heating the component. This heat is generated within a small area and air cooling is usually employed to remove it. The heat transmission capacity of an air-cooled cooling component depends especially on the area of the surface to be cooled and on the distance from the heat source to the surface, i.e. the length of conduction. As the size of the element is as good as always restricted due to structural reasons, the cooling capacity of a cooler of certain dimensions depends on how large an area to be cooled can be packed into a certain volume. The cooling capacity can be essentially increased by means of a forced air flow, but the element must hereby be designed such that it does not prevent the flow of cooling air to the other elements.
Cooling elements are also manufactured by casting. Die casting, for example, can be applied to effectively and at a reasonable cost manufacture large numbers of cooling elements, wherefore this is an advantageous method for the series production of similar elements needed in large numbers. The casting can be shaped more freely than an extruded profile but because the fins of the cooling element must be shaped by means of the mould and cores placed in the mould, the maximum density of the fins as well as the thickness of the fins are restricted. All parts of the casting must have a certain cross-section to enable the filling of the mould and to prevent deformations occurring while the casting becomes solid from destroying the casting. The casting tool must withstand several castings and a hot casting alloy, wherefore there must not be any very thin surfaces in the mould, such surfaces being subject to rapid wear due to the stresses affecting the mould. Therefore, it is not possible to apply the present casting methods to manufacture cooling elements having a high fin density.
Cooling elements must be made of a material having good heat transmission properties. Thus, copper would constitute a good raw material for cooling elements but it is expensive and heavy, wherefore cooling elements are usually made of aluminium-based light metal alloys. As a rule, light metal alloys have good castability properties and are particularly suited for pressure die-casting.
SUMMARY AND OBJECTS OF THE INVENTION
The aim of the present invention is to provide a method for manufacturing cooling elements having a high fin density using pressure die-casting techniques.
The invention is based on placing an insert assembled of lamella sheets in the core of the casting mould and fixing the body of the cooling element to the lamella package by pressure moulding, whereby an integral element comprising a body and an array of cooling fins is formed.
In more detail, the method according to the invention is characterized by what is stated in the characterizing part of claim
1
.
The invention offers considerable benefits.
The method according to the invention makes it possible to manufacture an array of cooling fins having a considerably higher density than one manufactured by conventional pressure moulding. This is of utmost importance because the ratio of the power handled by the power electronic components to the size of the components is on constant increase, wherefore a great cooling capacity must be fitted into a compact space. The body of the element is tightly adhered to the lamella package and thus, no air passage hampering the transmission of heat is formed between the body and the lamella package. Under advantageous conditions the surface of the lamella package can be melted by the aid of the casting material, thus forming a completely seamless piece. The insert and the casting material are of the same material or alloys of at least essentially similar type, preventing the generation of stresses due to the different thermal expansion of the materials in the casting. The production method is easily automated.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and of the scope of the invention will become apparent to those skilled in the art from thie detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
REFERENCES:
patent: 4785522 (1988-11-01), Biro
patent: 5247734 (1993-09-01), Lubbe et al.
patent: 5533257 (1996-07-01), Romero et al.
patent: 5562146 (1996-10-01), Harmon et al.
patent: 6003586 (1999-12-01), Beane
Miettinen Erkki
Smalen Matti
ABB Industry OY
Birch & Stewart Kolasch & Birch, LLP
Flanigan Allen
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