Method for filling a cavity

Abstract

Method for filling a cavity (24), in particular a cavity (24) in a battery arrangement (12) comprising a battery tray (14) and a battery (16) received in the battery tray (14), with a thermal paste, wherein the cavity (24) is evacuated before the thermal paste is introduced, characterized in that the quantity of air evacuated from the cavity (24) is measured and the volume of the cavity (24) is calculated from it.

Description

The invention relates to a method for filling a cavity according to the preamble of claim 1. Such methods (see DE 10 2019 210 437 A1) are particularly useful in the automotive industry when a cavity in a battery assembly is filled with a viscous material, especially thermal paste. The battery assembly comprises a battery tray and a battery housed within the tray. A cavity between the battery and the tray is regularly filled with thermal paste so that heat generated during charging can be effectively dissipated from the battery assembly. However, a common problem with known methods is that the volume of the cavity is often unknown due to manufacturing tolerances of the battery and / or the tray. If too much thermal paste is introduced into the cavity, it can damage the battery tray and / or the battery. If too little thermal paste is introduced, heat dissipation is insufficient.On the other hand, it can also be problematic that air located in the cavity has to be displaced from the cavity when the thermal paste is introduced, so that there is further resistance to the introduction of the thermal paste. Further prior art is disclosed in DE 10 2020 206 607 A1, which describes a battery housing for a traction battery device for a motor vehicle and a method for filling an intermediate gap. DE 10 2013 209 702 A1 discloses a connection device and a method for testing the tightness of a battery housing. JP H09-102 443 A discloses a method for filling with an electrolyte solution. It is therefore an object of the invention to further develop a method of the type mentioned above in such a way that the cavity can be filled more reliably with the viscous material. This problem is solved according to the invention by a method having the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims. The invention is based, firstly, on the finding that the introduction of the viscous material is facilitated if the cavity is evacuated prior to introduction. The evacuation is expediently carried out at least one evacuation opening. It is preferred that each evacuation opening is closed by means of an air-permeable cover element, so that the introduced viscous material cannot escape from it, or only in small quantities. The at least one cover element is expediently made of a nonwoven fabric or a selectively permeable membrane. It preferably has a thickness of at least 0.5 mm and at most 3 mm, and more preferably 1 mm to 2 mm. Depending on the introduced viscous material, the cover element is expediently selected to have a selective permeability for the viscous material that is at most 1 / 20 of the permeability for air, this value preferably being based on mass. The viscous material is advantageously introduced through at least one filling opening. It is preferred that each filling opening is arranged at a distance from each of the evacuation openings. To prevent the viscous material from escaping the filling opening, a sealing element is advantageously arranged at each filling opening. This element opens when there is overpressure into the cavity outside and closes when there is overpressure inside the cavity. This sealing element may, for example, be a slotted plastic film. It is preferred that the vacuum in the cavity is maintained until the viscous material has been introduced. This can be achieved by closing the evacuation opening(s) or by continuing evacuation. Secondly, evacuating the cavity allows for measuring the amount of air evacuated, thus enabling the calculation of the cavity's volume. This method according to the invention is based on the idea that a quantity of viscous material can be introduced into the cavity, the volume of which corresponds to the calculated volume of the cavity. The quantity of the introduced viscous material can then be dosed more precisely. The amount of air evacuated from the cavity is expediently measured using a flow meter or a piston meter. Both are proven and precise measuring devices available on the market. According to a further development of the method according to the invention, the pressure in the cavity is measured, and at least the pressure prevailing in the evacuated cavity is used to calculate the cavity's volume.It is then unnecessary to assume an approximate perfect vacuum after evacuation; instead, the residual air volume in the cavity can be deduced from the pressure prevailing in the cavity after evacuation. Similarly, the pressure prevailing in the cavity before evacuation can be used to calculate the cavity volume, so that atmospheric pressure does not need to be used as an approximation. Furthermore, it can be provided that the pressure in the cavity is measured by means of a pressure sensor located in a supply line for the viscous material, and that the introduction of the viscous material is stopped when the measured pressure exceeds a predetermined setpoint. Exceeding the setpoint can be used as a shutdown criterion with equal, primary, or secondary priority to the shutdown criterion for the introduction of the calculated volume of viscous material. The invention will now be explained in more detail with reference to an exemplary embodiment shown schematically in the drawing. Fig. 1 shows a battery box with four battery arrangements and a filling device. The battery box 10 shown in Fig. 1 has four battery assemblies 12, each containing a battery 16 (shown here only schematically) housed in a battery tray 14. The battery trays 14 are connected by a common base 18, a common circumferential side wall 20, and internal partitions 22. In each battery assembly 12, there is a cavity 24 between the battery tray 14 and the battery 16 housed therein, which must be filled with thermal paste. A filling device 26 is provided for introducing the thermal paste, which has two vent ports 28 and a filling port 30. The vent ports 28 are connected via a flow meter (not shown) to a vacuum pump, a Venturi nozzle, or a similar device for generating a vacuum. The filling port 30 is connected to a metering device 34 for the thermal paste. Each of the battery trays 14 has a ceiling wall 32 with two evacuation openings 36 spaced apart from each other, to each of which one of the venting nozzles 28 is connected. Each ceiling wall 32 also has a filling opening 38 spaced apart from the evacuation openings 36 and located midway between them, to which the filling nozzle 30 is connected. Before filling the cavity 24 with thermal paste, it is evacuated via the evacuation openings 36, with the flow meter determining the amount of evacuated air. A pressure gauge also measures the pressure prevailing in the cavity, and a data processing unit calculates the volume of the cavity 24 from the amount of air measured by the flow meter, the pressure prevailing in the cavity 24 before the start of evacuation, and the pressure prevailing in the cavity 24 after the completion of evacuation. Subsequently, the thermal paste is introduced into the cavity via the filling nozzle 30 and the filling opening 38 by means of the metering device 34 in a quantity whose volume corresponds to the volume of the cavity 24 determined by the data processing unit.The pressure gauge is located in the dosing device 34 or in the filling nozzle 30 and is capable of detecting when a predetermined target pressure is exceeded, which necessitates stopping the filling of the cavity 24. During the introduction of the thermal paste, the vacuum in the cavity 24 is maintained. To prevent the thermal paste from escaping through the evacuation openings 36, these are each sealed by an air-permeable cover element whose permeability for the thermal paste is significantly lower than its permeability for air.The filling opening 38 is also provided with a sealing element that opens when there is an external overpressure, so that the thermal paste can be introduced under pressure into the cavity 24, but closes when there is an overpressure in the cavity 24, so that the thermal paste cannot escape again through the filling opening 38 when the filling nozzle 30 is removed from the filling opening 38. In the present embodiment, two evacuation openings 36 and two venting ports 28, as well as a filling opening 38 and a filling port 30, are provided. It is understood that, particularly depending on the geometry of the battery trays 14, a different number of evacuation openings 36 and venting ports 28, as well as a different number of filling openings 38 and filling ports 30, may also be provided. In summary, the following can be stated: The invention relates to a method for filling a cavity 24, in particular a cavity 24 in a battery arrangement 12 comprising a battery tray 14 and a battery 16 received in the battery tray 14, with a viscous material, in particular with a thermal paste. According to the invention, the cavity 24 is evacuated before the viscous material is introduced.

Claims

Method for filling a cavity (24), in particular a cavity (24) in a battery arrangement (12) comprising a battery tray (14) and a battery (16) received in the battery tray (14), with a thermal paste, wherein the cavity (24) is evacuated before the thermal paste is introduced, characterized in that the quantity of air evacuated from the cavity (24) is measured and the volume of the cavity (24) is calculated from it. Method according to claim 1, characterized in that the evacuation of the cavity (24) takes place at at least one evacuation opening (36). Method according to claim 2, characterized in that each evacuation opening (36) is closed by means of an air-permeable cover element. Method according to claim 3, characterized in that the at least one cover element is made of a nonwoven fabric or a selectively permeable membrane. Method according to claim 4, characterized in that the at least one cover element has a thickness of at least 0.5 mm and at most 3 mm and preferably 1 mm to 2 mm. Method according to one of claims 3 to 5, characterized in that the at least one covering element is adapted to the thermal paste in such a way that it has a selective permeability for the thermal paste which is at most 1 / 20 of the permeability for air. Method according to one of the preceding claims, characterized in that the thermal paste is introduced at at least one filling opening (38). Method according to claim 7 and according to one of claims 2 to 6, characterized in that each filling opening (38) is arranged at a distance from each of the evacuation openings (36). Method according to claim 7 or 8, characterized in that a sealing element is arranged at each filling opening (38) which opens into the cavity (24) when there is overpressure outside the cavity (24) and closes when there is overpressure in the cavity (24). Method according to claim 9, characterized in that the at least one sealing element has a slotted plastic film. Method according to one of the preceding claims, characterized in that the vacuum in the cavity (24) is maintained until the end of the introduction of the thermal paste. Method according to one of the preceding claims, characterized in that a quantity of thermal paste is introduced into the cavity (24) the volume of which corresponds to the calculated volume of the cavity (24). Method according to one of the preceding claims, characterized in that the quantity of air evacuated from the cavity (24) is measured by means of a flow meter or a piston dispenser. Method according to one of the preceding claims, characterized in that the pressure prevailing in the cavity (24) is measured and that at least the pressure in the evacuated cavity (24) is used to calculate the volume of the cavity (24). Method according to claim 14, characterized in that the pressure in the cavity (24) is measured by means of a pressure sensor arranged in a supply line for the thermal paste and that the introduction of the thermal paste is stopped when the measured pressure exceeds a predetermined setpoint.

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