Battery shell and sealing performance detection method

Abstract

The invention relates to a battery housing (3) for a traction battery (1), comprising at least two housing parts (4, 5) surrounding an inner volume, a connecting element (6) for connecting the housing parts (4, 5) in an interface region, and a sealing element (7) for sealing the interface. The battery housing according to the invention is characterized in that at least one detection volume (8), which is sealed against the interior volume and against the surroundings, is formed in the interface region by means of a sealing element (7) and has at least one detection connection (11), an electrically conductive and gas-permeable elastic element (9) being arranged in the detection volume (8), said elastic element (9) being arranged in the non-stressed state. The width of the electrically conductive and gas-permeable elastic element is transverse to the direction of extension of the detection volume (8) and is greater than the cross-section thereof. According to the method of the invention, a pressure is applied to the detection volume (8) and the tightness is detected on the basis of a pressure-time curve.

Description

Technical Field

[0001] The invention relates to a battery housing for a traction battery of the type specified in the preamble to claim 1. In addition, the invention relates to a method for testing the tightness of an assembled battery housing according to the invention. Background Art

[0002] Vehicle traction batteries for providing driving power for at least partially electric vehicles are known from the prior art. Generally, such traction batteries are composed of one or more battery modules, which are installed in a battery housing or a traction battery housing.

[0003] In order to manufacture the battery and maintain the battery as needed, multiple housing parts are always installed in the battery housing, generally at least two housing parts, namely the bottom for accommodating the battery module and the cover for closing the housing. Interfaces are then formed between these housing parts, which include, for example, flange surfaces, screw seat surfaces, etc. On the one hand, these interfaces must be sealed to prevent moisture intrusion and possible gas leakage, so the sealing of the housing interface has significant safety and technical importance. For this reason, the housing interface generally has a seal.

[0004] Therefore, when manufacturing a battery with a battery housing or when maintaining a battery in a battery housing, it must be ensured that it is reliably sealed after the manufacturing or maintenance is completed. This is usually done by testing the interface.

[0005] For testing the tightness of components, it is generally known to place them under overpressure and observe how the pressure changes over time. If the pressure in the closed volume decreases, there is a leak. DE 40 34 106 A1 describes such a procedure for starter batteries.

[0006] However, such leak tests are not practically applicable for the housings of traction batteries, since for technical reasons these batteries can only withstand relatively low overpressures, typically only 50 mbar. Pressure drops cannot therefore be detected within a time frame acceptable for production and maintenance.

[0007] Therefore, in practice, a test gas (e.g. helium) is usually introduced into the installed and sealed battery housing at such a low overpressure that is harmless to the battery. Subsequently, the interface is scanned using a test gas detector with a sniffer probe to determine safety-related leaks at the battery housing interface. This is relatively complicated and can still be implemented in production, but the workload is quite large for the re-tightness test after battery maintenance (when the battery housing has been opened).

[0008] Another problem in such battery housings is that the housing bottom and the housing top are generally designed as metal grooves, or have electrical conductivity or conductive coatings in other ways. The connection between the two housing parts is therefore also used for electromagnetic field shielding, because the components form a Faraday cage. It is therefore important to connect these components electrically. Usually, this is achieved by connecting the components with bolts. However, in modern manufacturing methods, the housing parts of the battery housing are increasingly connected only by bonding, so additional measures are required to achieve electrical contact of the housing parts, which causes corresponding expenses in terms of assembly, required components and required structural space.

[0009] DE 10 2020 107 043 A1 discloses a battery housing for a motor vehicle battery. The battery housing comprises two housing parts, an inner seal arranged in the interface between the housing parts, and an outer seal arranged at a distance therefrom, the inner seal being arranged between the housing interior and the screw connection, and the outer seal being arranged between the outer area of ​​the housing and the screw connection. Furthermore, a tab is described which enables electrical contact between the housing parts when the housing parts are connected. Summary of the invention

[0010] The object of the present invention is now to specify an improved battery housing which avoids the above disadvantages and enables a simple and efficient leak-tightness test while providing simple electrical contact. In addition, the object of the present invention is to specify a leak-tightness test method for such a battery.

[0011] According to the invention, this object is achieved by a battery housing having the features of claim 1, in particular the features of the characterizing part of claim 1. In addition, this object is achieved by a method according to claim 9. Advantageous embodiments and developments of the battery housing or of the method are derived from the respective dependent claims.

[0012] The battery housing according to the present invention provides that the housing is at least two-piece, and an interface is provided between the housing parts. The housing parts are connected by sealing and / or adhesive materials. Here, a plurality of seals for sealing the interface are provided in the interface area, that is, the internal volume of the battery housing is sealed relative to the external environment. Now, according to the present invention, at least one detection volume is formed in the interface area, which is sealed relative to the internal volume and relative to the environment by a seal, and has at least one detection connection. That is, a detection volume is provided, which is sealed relative to the internal space and relative to the environment by a seal. The detection volume can now be subjected to pressure. Here, a higher overpressure can be applied in the detection volume area, because if everything is well sealed, it will neither reach the internal volume of the battery housing and the components installed therein, nor the environment. Since the detection volume is located in the interface area, its total volume is much smaller than the internal volume of the battery. Therefore, even in the case of leakage relative to the internal space of the battery, the applied higher pressure will not cause technical damage to the battery.

[0013] Now, the test volume can be subjected to a higher pressure and a common test medium (such as compressed air). Due to the higher pressure, a possible pressure drop in the event of a leak can be detected relatively simply and quickly, so that an efficient test of the tightness of the test volume can be achieved. Since the test volume is sealed by the seal relative to the internal volume of the battery housing and to the environment, the tightness relative to both the internal volume of the battery housing and to the environment can be determined by the closed test volume in the interface area when no unexpected pressure drop occurs. The tightness of the entire interface can therefore be tested and verified very simply and efficiently by the test volume. Here, since no special equipment is required, it can be carried out in almost any workshop, and since a higher pressure is used in the test volume area, the test can be carried out quickly and convincingly.

[0014] In order to ensure the electrical contact between the two housing parts, it is now also provided that an electrically conductive and gas-permeable elastic element is inserted into the detection volume. It is dimensioned so that in its unloaded state its width is transverse to the direction in which the detection volume extends and is greater than the cross-sectional extension of the detection volume in this direction. The electrically conductive elastic element thus completely fills the detection volume and protrudes at least slightly, so that when the housing parts are placed against one another and bonded together, for example by means of an adhesive forming a seal, it contacts both one housing part and the other housing part and deforms elastically in the process. Due to its elasticity and restoring force, it thus reliably contacts the two housing parts and electrically connects them to one another.

[0015] The conductive elastic element can be designed, for example, as a hose consisting of a metal braid, or as a metal wire spiral, a spiral spring, or other structures consisting of metal wire or metal braid. It can smoothly allow the detection gas (for example, compressed air) to pass through and has sufficient elastic deformation capacity, does not hinder the closure of the housing parts, and at the same time ensures reliable abutment between the two housing parts, preferably over most of the length in the extension direction of the detection volume, thereby ensuring safe electrical contact between the housing parts. This can ideally meet the requirements for electromagnetic compatibility (EMC).

[0016] Here, according to a very advantageous design of the battery housing of the present invention, the interface can be designed to surround the internal volume. Thus, according to a very advantageous design of this improved solution of the battery housing of the present invention, it can be provided that the detection volume is designed as an annular detection volume, which is interrupted by a sealing device transverse to the circumference. The detection volume therefore does not completely surround the entire circumference, but is interrupted by the corresponding sealing device, so that it is approximately surrounded by the entire circumference of the sealing device in one direction from one side of the sealing device to the opposite side. In this very advantageous improved solution, a detection connector is provided on both sides of the circumferentially adjacent sealing device. Using two detection connectors, in addition to actually detecting the sealing, it is also allowed to check the function of the detection volume. If the gas can pass from one detection connector to another detection connector, it is confirmed that the detection volume itself is not blocked. If the detection volume then surrounds the entire circumference, it can also be ensured in this way that the entire circumference is detected, rather than only detecting a part of the circumference when the detection volume may be blocked, so that the part connected to it is actually never detected.

[0017] Another very advantageous design of the battery housing according to the invention provides that the detection volume is formed by two parallel material strips formed of a sealing and / or adhesive material. Therefore, two parallel strips formed of a sealing and / or adhesive material can be applied to the flange that ideally forms the interface between the two housing parts, so as to form the detection volume on the one hand and reliably seal the structure between the two housing parts on the other hand. Here, for example, the outer strip can be a sealing and adhesive material, which not only realizes the sealing, but also ensures the mechanical stability of the connection, while the inner strip, i.e. the strip located on the side of the interface facing the inner volume, is designed as a pure sealing strip. Then, if necessary, the above-mentioned sealing device can be added between the material strips, extending transversely to the other strips in the form of a material strip, preferably installed between the two detection connectors.

[0018] As an alternative thereto, such a seal can also be achieved by two material strips crossing between the two test connections, if the sealing and / or adhesive material strips are respectively formed from the same material during assembly of the battery housing.

[0019] According to a very advantageous design of the battery housing of the present invention, the conductive elastic element can be designed as a metal braid, a metal wire part or a spring part as mentioned above. According to a very advantageous improvement scheme, the metal braid can be designed as a hose, a roll wound transversely to its extension direction or an element with a U-shaped or S-shaped cross section relative to the extension direction. It is particularly simple and efficient to adopt a hose consisting of a metal braid or a metal mesh, and the hose is therefore easily available on the market as a standard component. Alternatively, a roll wound transversely to its extension direction can be adopted, that is, similar to a metal hose, but not in a closed ring shape in the circumferential direction, but with a seam in the circumferential direction. The entire circumference of the roll can correspond to the circumference of the metal hose here, but more material can also be used so that the roll is therefore more than one circle in the circumferential direction. It can also be provided that the two ends overlap only slightly in the circumferential direction. As an alternative, a metal braid of corresponding shape can be added, which is, for example, preformed into a U-shape or an S-shape and placed in the detection volume.

[0020] In addition to the use of such a metal braid, which can also be referred to as a wire braid or mesh, it is also conceivable to use a wire element consisting only of bent wires, for example designed as a spiral extending in the extension direction and having a certain inherent elasticity due to the spiral shape. In principle, spring elements are also conceivable, in particular, for example, helical springs extending around the entire circumference of the interface, thus ensuring good electrical contact. Other forms of spring elements are also conceivable, such as helical springs with protruding ends, so that the ends can be placed between the flange planes of the two housing parts and are correspondingly compressed and closed during installation due to the elasticity of the spring element in order to continuously contact the flange of the interface.

[0021] Another very advantageous design provides that the interface is formed by two flanges of the housing parts, i.e., a respective flange of each housing part. At least one of the flanges can have a groove for accommodating a seal and / or an electrically conductive and gas-permeable elastic element. Therefore, positioning becomes easier, especially when an applied material strip is used as a seal and / or adhesive material during installation. The groove for the electrically conductive and gas-permeable elastic element can ensure that it remains in the desired area during installation, for example between two seals or material strips in the center of the detection volume, thus ensuring reliable functionality. Stable center positioning can prevent the seal and / or adhesive material from entering at least over a large area between the elastic element and the flange material, so that electrical contact can be simply and reliably achieved without a lot of assembly work.

[0022] The method for detecting the tightness of such a battery housing according to the present invention now provides that the detection volume is connected directly or via an adaptation volume to a pressure source and a pressure sensor, wherein the pressure variation curve at the pressure sensor is evaluated. Therefore, the application of pressure can be detected by evaluating the pressure-time variation curve at the pressure sensor. If the system is then closed and the temperature remains approximately constant, the pressure should also remain constant. And if it decreases significantly, it should be determined that there is a leak in the battery housing.

[0023] Another very advantageous design of the method of the present invention provides that in the case of using two detection connectors, the continuity of the detection volume is checked in advance, that is, before the actual pressure detection and pressure-time curve evaluation, through at least these two detection connectors. This can be done, for example, in that the adaptation volume is not only connected to one detection connector, but also to another detection connector. If the pressure source is now connected, the first adaptation volume is filled, followed by the detection volume, and finally the second adaptation volume. If the pressure sensor is placed in the second adaptation volume, the continuity of the detection volume can be determined when the pressure rises in an expected manner. If the pressure does not rise despite the passage connected to the pressure source, it can be directly inferred that the detection volume is abnormal, and thus reliable detection cannot be performed. However, if the detection is reliable and feasible, the detection is performed similarly to the above-mentioned setting, that is, the pressure-time curve is evaluated accordingly, and it is preferably evaluated in the second adaptation volume. After reaching the desired rated pressure, this should remain constant for a period of time, otherwise there will be leakage in the detection volume and the battery housing seal.

[0024] The test can preferably be carried out with a test gas, but can in principle also be carried out with a test liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further advantageous embodiments of the battery housing and the method according to the invention also result from the following exemplary embodiments described in detail with reference to the figures, wherein:

[0026] Figure 1 A schematic diagram showing a battery with a battery housing according to an embodiment of the present invention,

[0027] Figure 2 Shown before battery housing installation Figure 1 Enlarged view of middle section II,

[0028] Figure 3 Shown after battery housing installation Figure 1 Enlarged view of middle section II,

[0029] Figure 4 A top view showing the Figure 2 Design of seals and detection volumes,

[0030] Figure 5 A schematic diagram showing a first pressure detection possibility,

[0031] Figure 6 A schematic diagram shows another possibility for pressure detection. DETAILED DESCRIPTION

[0032] exist Figure 1 The diagram of shows schematically a battery 1 which is to be designed as a traction battery for providing driving power in a vehicle. The battery 1 is designed here as a so-called high-voltage battery and generally comprises a plurality of battery modules, each of which is designated here by 2, which are arranged in a battery housing 3. The battery housing 3 comprises at least two housing parts 4, 5, which are designed here as a housing lower part 5 and a cover 4. They can be made, for example, as deep-drawn sheet metal parts. The two housing parts 4, 5 have flanges 4', 5' formed at least partially around the battery housing 3, for connecting the housing parts 4, 5. This can be done, for example, by bonding.

[0033] exist Figure 2 A possible embodiment is now shown in detail in the enlarged illustration of . The two housing parts 4, 5 form a flange respectively designated by 4' or 5'. On the outer side of the lower flange 5', i.e. on the side facing away from the inner volume of the battery housing 3, a glue strip 6 is applied for firmly bonding and additionally sealing the connection. In addition, another glue strip is arranged as a pure seal 7 on the side of the flange 5' facing the inner volume. The positions of the two elements 6, 7 can also be interchanged, or both can assume two functions at the same time. Therefore, for the sake of simplicity, both will be collectively referred to as seals 6, 7 below, but this should not exclude that they have a bonding effect sufficient to achieve a structural load-bearing connection. The seals 6, 7 are preferably produced during installation by applying a pasty, preferably elastically cured sealing and adhesive material.

[0034] Between the two seals 6, 7 there remains a gap which will subsequently serve as detection volume 8. In the area which will subsequently serve as detection volume 8, an electrically conductive and gas-permeable elastic element 9 is now introduced before the other flange 4' of the housing upper part 4 is mounted on the flange 5' of the housing lower part 5. The element 9 can be designed in a variety of ways. Particularly preferably, a hose consisting of a metal braid or a metal mesh is used. After the two seals 6, 7 have been mounted on the lower flange 5' and the electrically conductive and gas-permeable elastic element 9 has been introduced into the detection volume 8 which subsequently arises between them, the housing upper part 4 is mounted with its flange 4'. Figure 3 The assembled state can be seen in the illustration of FIG. The seals 6, 7 now seal the two flanges 4' and 5' and glue them together to close the battery housing 3. The detection volume 8 with the electrically conductive and gas-permeable elastic element 9 arranged therein is enclosed between the seals 6, 7 and the two flanges 4, 5. Figure 3 As can be seen in the figure, the element 9 is elastically deformed in the installation direction of the upper flange 4, i.e. transversely to the extension direction of the detection volume 8 (perpendicular to the drawing plane), so that it rests reliably on the surface of the flange 5' and the surface of the flange 4 at the same time, thus electrically connecting the two housing parts 4, 5 to each other and thus ensuring good shielding of electromagnetic radiation. Figure 2 and 3 As shown in the figure, grooves for seals 6, 7 and / or elements 9 can be provided in flange 5' and / or flange 4' to facilitate their positioning during installation. Such grooves are preferably designed in the shape of circular arc segments.

[0035] exist Figure 2 and 3 In both figures, the test connection 10 in the upper flange 4 ′ can also be seen, by means of which the test volume 8 can now be used in particular to test the tightness of the battery housing 3 in a manner which will be described in detail below.

[0036] In principle, a single test connection 10 is sufficient to test the test volume 8 around the entire circumference of the battery housing. However, due to the application of the seals 6, 7 as pasty adhesive strips and / or sealing strips during installation, it may happen that the test volume 8 is interrupted at multiple locations, for example when pasty sealing material enters between two strips of sealing material 6, 7. This may occur in particular if the element 9 is not designed to be continuous, but is only installed in a plurality of individual sections distributed in the circumferential direction, which is in principle possible.

[0037] In order to cope with such a fault scenario, provision may be made accordingly for two test connections 10 , 11 to be provided. Figure 4 Shown with Figure 2 4 shows a top view of a similar flange 5' section. The flange 5' section has two test connections 10, 11, which can obviously also be arranged in the flange 5' instead of the flange 4'. Figure 4 In the illustration, the detection volume 8 extends along the upper side, and the seal 7 extends on the lower side. The detection volume 8 should be designed to be annular and partially filled by the annular element 9. A sealing device 12 is formed between the two detection connectors 10, 11 by sealing and adhesive materials, which divides the detection volume 8 into an annular detection volume 8 and two ends facing each other. Two detection connectors 10, 11 are arranged in the respective end areas. In this way, not only the sealing of the detection volume 8, or the sealing of the part of the detection volume 8 connected to each detection connector 10, 11 can be checked, but also the permeability of the detection volume 8 can be checked to ensure that it is not blocked by the sealing material and / or adhesive material, thereby avoiding possible unidentified leakage in the area that cannot be approached from the detection connectors 10, 11.

[0038] Now combine Figure 5A first simple variant of the tightness test is described with reference to the schematic diagram of . Here, the pressure source 13 is connected to the adaptation volume 15 via a valve mechanism 14, in the region of which a pressure sensor 16 is provided. In a structure with only one such test connection 10, the test volume 8 is connected via the test connection 10. By opening the valve 14, the adaptation volume 15 is now first filled with the test medium (preferably compressed air) and then the test volume 8. After the valve mechanism 14 is closed, the pressure measured by the pressure sensor 16 should remain constant in the test volume 8 connected to the adaptation volume 15 or in the volume formed by the two volumes 8 and 15 as long as the ambient temperature remains constant. If this is the case, the tightness of the test volume 8 and ultimately the tightness of the battery housing 3 can be reliably determined, because the test volume 8 is sealed relative to the internal volume of the battery housing 3 and relative to its environment. If there is a leak, the pressure will drop because the test medium escapes into the internal volume or the environment of the battery housing 3.

[0039] exist Figure 6 An alternative improved variant of the method is shown in the diagram of FIG. Here again, a pressure source 13 and a valve 14 are used. Via a first adapter volume 15 and a test connection 10, the test volume 8 (here designed as a test channel around one of the flanges 5 ′, as described in connection with FIG. 1 ) is connected to the test volume 8 (here designed as a test channel around one of the flanges 5 ′, as described in connection with FIG. 1 ). Figure 4 and 5 The second adapter volume 17 with the pressure sensor 16 is then connected via the second test connection 11. When the valve 14 is open, the test gas first fills the first adapter volume 15 and then passes through the test volume 8 to the second adapter volume 17. If the pressure sensor 16 shows a pressure increase after the valve 14 is opened, it can be determined that the test volume 8 is connected. Figure 4 , it can thus be ensured that the interface between the two housing parts 4, 5 of the battery housing 3 can be reliably detected over approximately the entire circumference. If this is the case, the valve mechanism 14 is closed and the pressure-time curve is evaluated at the pressure sensor 16. Here, too, the following is true: under constant temperature and ambient conditions, a constant pressure over a certain time range indicates tightness, while a drop in pressure indicates a leak in the interface region between the two housing parts 4, 5 or their flanges 4', 5'.

Claims

1. A battery housing (3) for a traction battery (1), comprising: at least two housing parts (4, 5) surrounding an inner volume, a connecting element (6) for connecting the housing parts (4, 5) in the region of an interface, and a sealing element (6, 7) for sealing the interface, Its characteristics are: In the region of the interface, at least one detection volume (8) is formed by the seal (6, 7) which is sealed both relative to the inner volume and relative to the environment, and the detection volume has at least one detection connection (10, 11), wherein an electrically conductive and gas-permeable elastic element (9) is arranged in the detection volume (8), and in the unstressed state, the width of the electrically conductive and gas-permeable elastic element is transverse to the extension direction of the detection volume (8) and is greater than the cross-sectional extension dimension of the detection volume (8) in this direction.

2. The battery housing (3) according to claim 1, characterized in that: The interface is designed to be annular around the inner volume.

3. The battery housing (3) according to claim 2, characterized in that: The detection volume (8) is designed as an annular detection volume (8) which is interrupted only transversely to the circumference by a sealing device (12), wherein a detection connection (10, 11) is respectively provided on both sides adjacent to the sealing device (12) in the circumferential direction.

4. The battery housing (3) according to claim 1, 2 or 3, characterized in that: The detection volume (8) is formed between two parallel material strips formed from sealing material and / or adhesive material.

5. The battery housing (3) according to any one of claims 1 to 4, characterized in that: The electrically conductive elastic element (9) is formed of a metal braid or a metal mesh, is formed as a metal wire element or is designed as a spring element.

6. The battery housing (3) according to claim 5, characterized in that: The metal braid is designed as a hose, is formed as a roll wound transversely to its extending direction, or its cross-sectional shape is U-shaped or S-shaped relative to the extending direction.

7. The battery housing (3) according to claim 6, characterized in that: The metal wire member or the spring member has a coil extending along the extending direction.

8. The battery housing (3) according to any one of claims 1 to 7, characterized in that: The interface is formed by two flanges (4', 5') of the housing parts (4, 5), at least one of the flanges (4', 5') having a groove for accommodating the seal (6, 7) and / or the electrically conductive and gas-permeable elastic element (9).

9. A method for detecting the tightness of an installed battery housing (3) according to any one of claims 1 to 8, characterized in that: The detection volume (8) is connected directly or via at least one adaptation volume (15, 17) to a pressure source (13) and a pressure sensor (16), wherein after applying pressure to the detection volume (8), the pressure-time curve at the pressure sensor (16) is evaluated.

10. The method according to claim 9, characterized in that In the case of at least two test connections (10, 11), the continuity of the test volume (8) between the test connections (10, 11) is first tested.

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