US20210231125A1

US20210231125A1 - Fan comprising a cooling body consisting of heat-conductive plastic

Info

Publication number: US20210231125A1
Application number: US15/734,809
Authority: US
Inventors: Thomas Heli; Peter Riegler; Daniel GEBERT; Valerius Schaaf
Original assignee: Ebm Papst Mulfingen GmbH and Co KG
Current assignee: Ebm Papst Mulfingen GmbH and Co KG
Priority date: 2018-08-03
Filing date: 2019-07-25
Publication date: 2021-07-29
Also published as: DE102018118925A1; EP3830425A1; WO2020025443A1; CN209398636U; CN112334668A

Abstract

The invention relates to a fan (1) comprising an electronic system on a printed circuit board (2) and a cover (10) arranged above the electronic system, which is embodied both as an active cooling body and a passive cooling body, wherein the cover (10) is designed substantially as a flat covering element consisting of a thin-walled plastic and has a form with a surface (11) which is effective for the cooling of the electronic system arranged beneath the cover (10), said surface being larger than the projected base area of the cover (10) by a factor of at least 2.

Description

The invention relates to a fan comprising a cooling body embodied as a plastic cover.
A cooling body has the task of absorbing heat from an element to be cooled and releasing it again to a surrounding medium. As such, a material of high thermal conductivity, such as aluminum or copper, is typically used for the cooling body.
Mass production of aluminum cooling bodies, in particular those whose form is adapted to a predetermined application, is typically done using the die casting process. For this purpose, heated aluminum in the liquid or sticky state is pressed, under high pressure, into a preheated steel mold which will later serve as a conductive cooling body.
Cooling bodies are also used for motors. For example, DE 19841583 A1 addresses a cooling body for cooling elements, in particular semiconductor components, motors and aggregates, in particular a cooling unit at least partially made of extruded aluminum or other light metal, consisting of at least two separate base profiles for mounting the electric components which are spaced apart from each other and interconnected by means of a plurality of separate cooling fins. Further, the assembly of at least one fan is provided between two adjacent base profiles.
It is convenient to utilize heat conduction for cooling. In physics, heat conduction—also known as heat diffusion or thermal conduction—is understood to mean the flow of heat induced by a difference in temperature. As such, according to the second law of thermodynamics, heat always only flows in the direction of the lower temperature, i.e., in the direction of the temperature sink. Heat conduction is a mechanism for transferring thermal energy without requiring a macroscopic flow of material as with the alternative mechanism of convection. Heat transfer through heat radiation is also considered as a separate mechanism. A measure of heat conduction in a particular substance is thermal conductivity.
It is therefore obvious that, for utilizing cooling by means of a cooling body, a substance or material of good to very good thermal conductivity is used. Copper and its alloys typically have thermal conductivity values of 100-400 W/mK: with 236 W/mK, aluminum is also within a range of high thermal conductivity. As a metal material, even unalloyed steel already has a significantly poorer heat conduction property and exhibits a thermal conductivity in the range of about 50 W/mK.
Industrial plastics, such as PUR or polyimide (PA), are known in the art to be unsuitable as heat conductors due to their significantly lower conductivity of not even 1/1000 of the value of copper. Thus, copper provides a conductivity which is better than that of conventional plastics by more than 1000 times.
In the case of fans and fan motors with an integrated electronic system, the electronic system naturally becomes warm or hot and must therefore be cooled to avoid damage to the electronic system and increase its lifetime. While typical metallic covers dissipate heat well, they are expensive to manufacture and not achievable in a cost-effective manner due to the high material price alone.
The object of the invention is therefore to provide cooling for the electronic system of a fan motor of a fan, which can be produced cost-effectively and works reliably.
This object is achieved by the combination of features according to claim 1.
A basic idea of the present invention is to cool the electronic system of a fan using a plastic cooling body instead of a metal cooling body. This approach, which is unknown in the prior art, can be realized by using the cooling body as a cover with a very thin wall thickness having a specific form and surface.
In addition to increasing the surface area, several effects are used in a targeted and cumulative manner, namely heat conduction, heat convection and the reduction of heat build-up, by using a thin-walled plastic material having a large efficient surface and a comparatively large proportion with a direct contact surface for heat-producing components.
In this way, in a departure from the prior art, a cover enabling the resulting heat to be thermally dissipated can also be obtained with a plastic material in a cheap and efficient manner.
According to the invention, for this purpose, a fan is provided, comprising an electronic system on a printed circuit board, wherein, above the electronic system, a cover is provided which works both as an active cooling body and a passive cooling body, wherein, for this purpose, the cover is designed substantially as a flat covering element consisting of a thin-walled plastic and has a form with a surface effective for the cooling of the electronic system arranged beneath the cover, said surface being larger than the projected base area of the cover by a factor of at least 2.
For this purpose, it is particularly advantageous if the cover has a cooling fin structure with a plurality of cooling fins which increase the effective surface.
It is further advantageous if the cover forms a plurality of recesses in which fastening holes are provided at which the cover is detachably fastened to the fan by releasable fastening means.
It is further advantageously provided that the cover has, in the area of the cooling fin structure, a flat contact side for directly contacting heat-producing components.
In a further advantageous embodiment of the invention it is provided that the cover has the cooling fin structure in one or more areas or forms a plurality of areas with such a cooling fin structure.
Furthermore, it is advantageous if the cooling fins are attached or formed to extend radially outwards, thereby implementing a structure open radially outwards and upwards which has an advantageous effect on production and the cooling effect.
A further improvement can be achieved in that the cooling fins have a changing, in particular outwardly decreasing, wall thickness. Other forms and configurations of the wall thickness are also conceivable to improve heat dissipation effects. In principle, contrary to the metal bodies with large wall thicknesses usually used in the prior art, according to the concept of the present invention, an overall smaller wall thickness is aimed for in order to achieve rapid heat dissipation and also to prevent heat build-up.
A further optimization is a solution in which the cover forms a flat contact surface on the bottom facing the electronic system and in which, in the assembled state, this contact surface at least partially abuts electronic components.
In an advantageous embodiment of the invention for a radial fan, the cover is formed from a substantially round section integrally joined to a projection (preferably with a linearly extending lateral edge).
It has also been shown to be advantageous if the material of the cover is a polyimide (PA), polyurethane (PUR), polycarbonate (PC) or polyethylene (PE).
In a further advantageous embodiment, it is provided that the thickness of the cover is smaller in the area parallel to the arrangement of the printed circuit board and/or the area of the flat contact surface than in a periphery or in the area of the cover extending towards the electronic system by a factor of at least 2. As a result, the essential stabilizing properties can be placed in the periphery and the essential thermal properties in the flat area and the areas with the cooling fins.

Other advantageous developments of the invention are characterized in the sub-claims or are shown in more detail below together with the description of the preferred embodiment of the invention with reference to the figures.

Therein:

FIG. 1 shows a schematic sectional view through a radial fan,

FIG. 2 shows a perspective view of the radial fan of FIG. 1,

FIG. 3 shows a top view of the cover of the electronic system of the radial fan of FIG. 1,

FIG. 4 shows a perspective view of the cover of FIG. 3,

FIG. 5 shows a sectional view of the cover of FIG. 3.

In the following, the invention will be explained in greater detail on the basis of an exemplary embodiment with reference to FIGS. 1 to 5, in which the same reference numerals indicate the same structural and/or functional features.
FIG. 1 shows a schematic sectional view through a fan 1, here a radial fan.
Fan 1 is embodied with an electronic system on a printed circuit board 2. Above the electronic system, a cover 10 according to the invention is shown which is embodied both as an active cooling body and a passive cooling body. As such, as can be seen in FIGS. 3 to 5, cover 10 is designed as a substantially flat covering element consisting of a thin-walled plastic and has a form with a surface 11 which is effective for the cooling of the electronic system arranged beneath cover 10, said surface being larger than the projected base area of cover 10 by a factor of at least 2 due to the cooling fin structure with a plurality of cooling fins 12 as can be seen in FIG. 2. As can also be seen, the cooling fins run or extend radially outwards.
The projected base area can be seen in the top view from the illustration in FIG. 3. As can also be seen in FIG. 5, the effective active surface is significantly increased by the fin structure. Cover 10 is formed from a substantially central round section 17 integrally joined to a projection 18 with a straight lateral edge.
In FIGS. 3 and 4, it can be seen that cover 10 forms a plurality of recesses 13 in which fastening holes 14 are provided.
Operatively connected to the electronic system, cover 20 is detachably fastened to fan 1 by releasable fastening means 15 (e.g., screws). On the bottom facing the electronic system, cover 10 forms a flat contact surface 19 by which it at least partially abuts electronic components in the assembled state.
In the sectional view through cover 10, as shown in FIG. 5, it has a flat contact side 16 for contacting heat-producing components of the electronic system in the area of the cooling fin structure. It can also be seen that cooling fins 12 have a changing wall thickness, in particular slightly decreasing from bottom to top, and taper slightly, so to speak.
The practice of the invention is not limited to the preferred exemplary embodiments specified above. Rather, it is conceivable, to adapt the form and configuration of the cover correspondingly to the respective requirement and, for example, the number of areas with fin structures to the specific cooling task.

Claims

1. A fan (1), comprising an electronic system on a printed circuit board (2) and a cover (10) arranged above the electronic system, which is embodied both as an active cooling body and a passive cooling body, wherein the cover (10) is designed substantially as a flat covering element consisting of a thin-walled plastic and has a form with a surface (11) which is effective for the cooling of the electronic system arranged beneath the cover (10), said surface being larger than the projected base area of the cover (10) by a factor of at least

2. The fan (1) according to claim 1, characterized in that the cover (10) has a cooling fin structure with a plurality of cooling fins (12).

3. The fan (1) according to claim 1, characterized in that the cover (10) forms a plurality of recesses (13) in which fastening holes (14) are provided at which the cover (20) is detachably fastened to the fan (1) by releasable fastening means (15).

4. The fan (1) according to claim 2, characterized in that the cover (10), in the area of the cooling fin structure, has a flat contact side (16) for contacting heat-producing components.

5. The fan (1) according to claim 2, characterized in that the cover (10) has the cooling fin structure in one or more areas.

6. The fan (1) according to claim 2, characterized in that the cooling fins (12) are attached or formed to extend radially outwards.

7. The fan (1) according to claim 2, characterized in that the cooling fins (12) have a changing, in particular outwardly decreasing, wall thickness.

8. The fan (1) according to claim 1, characterized in that the cover (10) forms a flat contact surface (19) on the bottom facing the electronic system, and in that, in the assembled state, this contact surface at least partially abuts electronic components.

9. The fan (1) according to claim 1, characterized in that the cover (10) is formed from a substantially round section (17) integrally joined to a projection (18).

10. The fan (1) according to claim 1, characterized in that the material of the cover (10) is a polyamide (PA), polyurethane (PUR), polycarbonate (PC) or polyethylene (PE).

11. The fan (1) according to claim 8, characterized in that the thickness of the cover (10) is smaller in the area parallel to the arrangement of the printed circuit board (2) and/or the area of the flat contact surface (19) than in a periphery (20) or in the area of the cover (10) extending towards the electronic system by a factor of at least 2.

12. The fan (1) according to claim 1, characterized in that the fan is a radial fan.