Housing for a vehicle battery, and motor vehicle

Abstract

The invention relates to a housing (10) for a vehicle battery, having a housing wall (16) that has at least one cavity (20) and delimits a receiving volume (12) of the housing (10), which receiving volume can accommodate vehicle batteries (14), and the cavity (20) is filled with a dilatant liquid.

Description

[0001] HOUSING FOR A VEHICLE BATTERY AND MOTOR VEHICLE

[0002] The invention relates to a housing for a vehicle battery and a motor vehicle with a vehicle battery.

[0003] It is already well known from series vehicle construction that vehicle batteries, particularly traction batteries for motor vehicles, are designed in such a way that they have a housing in which a large number of battery cells are accommodated. These battery cells must be protected from damage, particularly in the event of an accident. Furthermore, sufficient heat dissipation from the battery cells during operation must be ensured to reliably prevent thermal runaway of the battery cells. Another goal is to design the housing to be particularly lightweight in order to enable particularly low-energy propulsion of the motor vehicle with a particularly low vehicle weight.

[0004] The object of the present invention is to provide an improved solution for a housing for a vehicle battery of a motor vehicle.

[0005] The problem is solved by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the subclaims, the description, and the drawings. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0006] The invention relates to a housing for a vehicle battery, in particular a traction battery of a motor vehicle. This vehicle battery is in particular a high-voltage battery. The housing comprises a housing wall having at least one hollow space, which delimits a receiving volume of the housing. Battery cells of the vehicle battery can be accommodated in this receiving volume. In particular, the housing comprises a plurality of housing walls, which together delimit the receiving volume. The battery cells arranged in this receiving volume are particularly well protected by the respective housing walls against damage resulting from mechanical influences. The housing wall having the hollow space can, in particular, be completely hollow. This means that the hollow space extends through the entire housing wall.In particular, the housing wall is designed free of stiffening ribs that define the cavity or extend within the cavity and support it. The housing wall is therefore designed to be particularly lightweight. To ensure particularly good rigidity of the housing when forces act on the housing wall, for example as a result of an accident, the cavity is filled with a dilatant fluid. In rheology, dilatancy, also known as shear thickening, is the property of a non-Newtonian fluid to exhibit a higher viscosity when subjected to large changes in shear over time, and thus at high shear rates. In English, a dilatant fluid is also referred to as shear thickening.In a mechanically unloaded state, the dilatant fluid filling the cavity therefore has a lower viscosity than when a force acts on the housing wall, which leads to shear forces in the fluid and consequently to an increase in the fluid's viscosity. The greater the force acting on the dilatant fluid in the cavity, the higher the viscosity of this fluid and consequently the stiffness of the housing wall filled with the fluid. The greater the forces acting on the housing wall caused by the accident, the greater the stiffness of the housing due to the dilatant fluid, whereby the battery cells arranged in the receiving volume are particularly well protected from damage by the housing. At the same time, the housing is particularly lightweight, since no stiffening ribs are necessary to ensure the particularly high rigidity of the housing in the event of an accident.

[0007] In a possible development of the invention, the cavity is filled with a starch-water mixture or with a silica-polyethylene glycol mixture. The starch-water mixture has a particularly high specific heat capacity, in particular a specific heat capacity which is higher than that of water, whereby heat from the battery cells arranged in the receiving volume can be transported away into the environment particularly quickly by means of the starch-water mixture. Thus, excess heat from the battery cells arranged in the receiving space can be dissipated particularly quickly by means of the liquid consisting of the starch-water mixture arranged in the cavity, whereby the battery cells can be cooled particularly effectively.

[0008] In a further possible embodiment of the invention, the housing wall is made of aluminum. In this case, the housing wall can be extruded from aluminum. Because the housing wall is made of aluminum, the housing wall is particularly lightweight. As a result, the housing can be provided with a particularly low weight.

[0009] In an alternative possible embodiment of the invention, it is provided that the housing wall is made of steel parts, wherein the steel parts are directly connected to one another or the steel parts are designed as steel plates and are held together by injection-molded parts. Thus, several stamped steel plates can be welded together and sealed to produce the housing wall. Alternatively, flat steel plates can be used, which are connected to the steel plates by injection molding. Alternatively or additionally, the steel plates can be connected to a plastic housing of the vehicle battery by injection molding. By producing the housing wall from the steel parts, the housing wall is particularly robust, which in turn means that the battery cells accommodated in the receiving volume can be particularly well protected from damage by means of the housing wall.For example, the steel parts can be connected to each other via a form fit, such as flanging. Manufacturing the housing wall solely from interconnected steel parts allows for particularly cost-effective production. Furthermore, complex housing wall geometries can be implemented particularly easily. Furthermore, the steel parts enable particularly good heat transfer away from the battery cells arranged in the receiving volume.

[0010] By providing injection-molded parts by means of which respective steel parts are connected to one another and held in position relative to one another, the housing wall can be produced with particularly high precision. In addition, the housing wall can be designed to be particularly lightweight, since steel can be saved by providing the injection-molded parts to connect the steel parts. The housing wall formed from the steel plates connected to one another via injection-molded parts is also particularly lightweight and has particularly low production costs. Furthermore, this housing wall can be manufactured particularly quickly and easily. To produce the housing wall, the steel plates can be placed in a tool and the injection-molded parts can be injection-molded onto the steel plates to be connected to one another. The injection-molded parts, together with the steel parts, define the cavity filled with the dilatant liquid.In particular, the housing wall can be designed such that it comprises a first steel plate, which delimits the receiving volume of the housing and, when used as intended, rests against at least one battery cell accommodated in the receiving volume, and a second steel plate, which forms an outer side of the housing facing the environment, wherein the first steel plate and the second steel plate are connected to one another and held together by means of the injection-molded part. The injection-molded part thus provides the connection between the first steel plate and the second steel plate. Both the first steel plate and the second steel plate can each delimit the cavity, so that the dilatant liquid filling the cavity is in direct contact with the first steel plate and the second steel plate on the inside.In particular, the housing wall or the housing comprises several steel plates which are connected to one another via respective injection-molded parts.

[0011] In a possible further development of the invention, the injection-molded parts can be made of polypropylene resin. Polypropylene is a particularly lightweight plastic that is particularly easy to mold.

[0012] In a further possible embodiment of the invention, it is provided that the steel parts of the housing are arranged such that they are in direct contact with at least one battery cell when the receiving volume is filled with battery cells or are in direct contact with a heat sink of the vehicle battery. The heat sink is in particular an air-cooled outer side of the housing. This means that the respective steel part is either designed to rest against the at least one battery cell when used as intended in order to absorb heat from this battery cell, or is arranged on the outside of the housing, whereby heat can be dissipated via this steel part to the environment of the housing, in particular to the environment of the vehicle battery.This enables particularly good heat transfer from the battery cells to the housing and from the housing to the environment, allowing heat to be dissipated from the battery cells to the environment particularly easily and quickly. As a result, the battery cells can be cooled particularly efficiently, thus significantly reducing the risk of overheating of the vehicle battery's battery cells.

[0013] In a further possible embodiment of the invention, it is provided that an inner wall of the housing wall facing the receiving volume is flat. This flat inner wall of the housing wall thus faces the battery cells, provided these are arranged in the receiving volume, and delimits the cavity towards the receiving volume. Due to the flat design of this inner wall, the housing wall can lie flat against at least one battery cell. As a result, a particularly large contact area can be achieved between the at least one battery cell and the housing wall, via which contact area a particularly good heat transfer from the battery cell to the housing wall can be implemented. The larger the contact area between the at least one battery cell and the housing wall, the more efficient the heat transfer from the battery cell to the housing wall can be.The flat inner wall of the housing wall also enables a particularly even distribution of shear forces introduced into the liquid via mechanical influences on the housing wall. This causes a particularly even increase in the viscosity of the liquid as a result of the introduced shear forces. This even increase in the viscosity of the liquid, in turn, leads to a particularly even increase in the rigidity of the housing. A force applied externally to an outer wall of the housing wall can be conducted via the liquid to an inner wall facing the battery cells, whereby this force is in turn at least partially reflected by an inner side of the inner wall facing the liquid and thrown back into the liquid.The flat design of the inner wall distributes the force particularly evenly throughout the fluid, resulting in particularly uniform shear forces within the fluid. The outer wall of the housing defines the boundary between the cavity and the surrounding environment.

[0014] In a further possible embodiment of the invention, the housing wall is uneven at least on an outer side facing away from the receiving volume. In particular, the housing wall is uneven on an outer side facing the heat sink. The heat sink is an area surrounding the housing. The outer side can be air-cooled by an air stream flowing in this area. The uneven design of the outer side of the housing wall provides a particularly large heat transfer surface between the housing wall and the area surrounding the vehicle battery, via which heat can be dissipated from the housing wall to the area surrounding the housing. This particularly large heat transfer surface enables particularly rapid and efficient dissipation of heat from the housing wall to the area surrounding the housing, as a result of which the housing wall can be cooled particularly quickly.This allows the heat from the battery cells arranged in the receiving volume to be transported away from the battery cells particularly quickly via the housing wall and released into the surroundings of the housing. This allows the battery cells to be cooled particularly quickly and efficiently via the housing wall.

[0015] In this context, it can be provided, in particular, that the outer side facing away from the receiving volume is corrugated, in particular hyperbolic paraboloid. The hyperbolic paraboloids on the outer side can, for example, be embossed into the steel plates of the housing wall. Due to the hyperbolic paraboloids, the outer side has a particularly large surface area for heat transfer. Furthermore, the hyperbolic paraboloid design of the outer side achieves a particularly high strength of the housing wall. As a result, the housing wall can provide particularly good protection for the battery cells against damage.

[0016] The invention further relates to a motor vehicle, in particular a car, with a vehicle battery comprising a housing as already described in connection with the housing according to the invention. A plurality of battery cells are accommodated in the receiving volume of the housing. The housing wall of the housing provides particularly good protection for the battery cells against damage, particularly in the event of an accident.

[0017] Further features of the invention can be derived from the following description of the figures and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0018] The drawing shows: Fig. 1 a schematic sectional view of a section of a housing for a vehicle battery in a first embodiment;

[0019] Fig. 2 is a schematic sectional view of a section of the housing of the vehicle battery in a second embodiment; and

[0020] Fig. 3 is a schematic sectional view of a section of the housing of the vehicle battery in a third embodiment.

[0021] Identical or functionally equivalent elements are provided with the same reference numerals in the figures.

[0022] Figures 1 to 3 each show a section through a housing 10 of a vehicle battery of a motor vehicle in various embodiments. The vehicle battery is, in particular, a so-called high-voltage storage device. The vehicle battery is designed to provide electrical energy for an electric drive train of the motor vehicle. The motor vehicle can thus be driven by means of the electric drive train with electrical energy from the vehicle battery.

[0023] The housing 10 defines a receiving volume 12 in which a plurality of battery cells 14 can be accommodated. The housing 10 comprises one or more housing walls 16 which define the receiving volume 12. In the embodiment shown in Figure 1, the housing wall 16 is extruded from aluminum and is hollow. In the second embodiment of the housing 10 shown in Figure 2, the housing wall 16 comprises a plurality of steel parts 18, in particular a plurality of steel plates directly connected to one another. In the third embodiment of the housing 10 shown in Figure 3, the housing wall 16 comprises a plurality of steel parts 18 which are connected to one another via respective injection-molded components 30. The receiving volume 12 is closed at the top by means of a cover 28. The receiving volume 12 is thus completely enclosed by the cover 28 and the housing wall 16.

[0024] The respective housing walls 16 are each formed with a cavity 20. A

[0025] Stiffening the hollow housing walls 16 by means of stiffening ribs is not provided in the present case. This allows the respective housing walls 16 to be designed to be particularly lightweight. For particularly high rigidity of the respective housing walls 16, the cavity 20 is filled with an expanding fluid. In the present case, this expanding fluid is a starch-water mixture. Alternatively, the expanding fluid can be a silica-polyethylene glycol mixture. To manufacture the housing 10, the housing walls 16 are thus manufactured, and the cavity 20 provided in the housing walls 16 is filled with the expanding fluid.

[0026] A dilatant material, which can also be described as shear-thickening, is a material whose viscosity increases with increasing shear stress. A shear-thickening fluid is an example of a non-Newtonian fluid. In the starch and water mixture, water and cornstarch can be used in a ratio of 1 to 1.25. In dilatant fluids, the viscosity also increases with an increase in pressure. The pressure can be generated either in the form of temperature or mechanical stress. The dilatant fluid can thus transform into a solid when subjected to external stress or an increase in temperature. Dilatant fluids have a higher bulk modulus than water and steel. The bulk modulus is an intensive and material-inherent physical quantity from the theory of elasticity.The bulk modulus describes the all-round pressure change required to produce a specific volume change. No phase transition may occur. Furthermore, a dilatant fluid, especially a starch-water mixture, exhibits higher thermal conductivity and lower thermal resistance than water. At high temperatures, especially above the boiling point of water, the starch-water mixture separates into two layers: a cornstarch layer and a gel layer. These layers result in particularly high rigidity of the housing 10.

[0027] External stress creates a comparatively higher-viscosity or harder layer in the center of a liquid volume of the dilatant liquid. This comparatively harder layer is surrounded by a comparatively lower-viscosity layer. Heat transfer thus occurs primarily via the lower-viscosity layer, and structural strength is achieved by the harder, central region of the liquid volume and thus the higher-viscosity layer. The housing wall 16 in this case has an inner wall 22 and an outer wall 24. The inner wall 22 delimits the cavity 20 toward the receiving volume 12. The outer wall 24 delimits the cavity 20 toward the surroundings of the housing 10 and thus to the outside. The outer wall 24 forms an outer surface of the housing 10.The inner wall 22 of the housing wall 16 is flat in this case, at least on its side facing the receiving volume 12, whereby the battery cells 14 arranged in the receiving volume 12 can be placed against the inner wall 22 of the housing wall 16 over a large area. This allows for particularly good heat transfer from the battery cells 14 to the housing wall 16.

[0028] The outer wall 24 of the housing wall 16 can be flat, at least in some areas. The outer wall 24 is arranged facing away from the receiving volume 12. In particular, the outer wall 24 delimits the housing 10 from the surroundings of the housing 10. Due to the flat design of the outer wall 24 or the inner wall 22, a force acting on the housing wall 16 can be evenly distributed among the dilatant fluid arranged in the cavity 20. As a result of the application of a force and the resulting shear in the dilatant fluid, the viscosity of the dilatant fluid increases. Because the force is evenly introduced into the dilatant fluid in the cavity 20 due to the flat design of the inner wall 22 or the outer wall 24, this results in a uniform increase in the viscosity of the dilatant fluid and, consequently, a uniform stiffening of the housing 10.By increasing the rigidity of the housing 10, the battery cells 14 accommodated in the receiving volume 12 are particularly well protected against damage when this force is applied to the housing wall 16.

[0029] In order to enable particularly good heat dissipation from the battery cells 14 via the housing wall 16, the second and third embodiments of the housing 10 shown in Figures 2 and 3 provide for the outer wall 24 of the housing wall 16 to be corrugated in some regions, in this case hyperbolic paraboloid. This hyperbolic paraboloid region 26 of the outer wall 24 faces, in particular, a heat sink. In particular, the hyperbolic paraboloid region 26 of the outer wall 24 is an air-cooled region of the outer wall 24 of the housing wall 16. Due to the hyperbolic paraboloid design of the outer wall 24, there is a particularly large contact area between the air and the housing wall 16 in this area 26, thereby providing a particularly large heat transfer area.As a result, a particularly large amount of heat can be dissipated particularly quickly from the housing wall 16 to the environment via this hyperbolic paraboloid region 26.

[0030] The starch-water mixture, which in this case is the dilatant liquid, has a particularly high specific heat capacity, whereby the heat absorbed by the battery cells 14 via the housing wall 16 is transported particularly quickly by the dilatant liquid from the inner wall 22 to the outer wall 24, which in turn allows this heat to be dissipated particularly quickly to the environment. This allows for particularly effective cooling of the battery cells 14.

[0031] As can be seen particularly clearly in Figures 2 and 3, the steel parts 18 provide both the inner wall 22 and the outer wall 24. One of the steel parts 18, which provides the inner wall 22, can be configured to be applied to at least one battery cell 14 accommodated in the receiving volume 12. Another of the steel parts 18, which provides the outer wall 24, is configured to be in direct contact with a heat sink of the vehicle battery, in particular by the outer wall 24 being air-cooled through contact with the environment of the vehicle battery. As an alternative to the direct connection of the steel parts 18 to one another shown in Figure 2, the steel parts 18 can be connected to one another via the injection-molded parts 30, as shown in Figure 3. Direct contact between the respective steel parts 18 can thus be omitted.Instead, the steel parts 18 are positioned and held relative to one another via the injection-molded parts 30. These injection-molded parts 30 can, in particular, be injection-molded from polypropylene resin. In the present case, the injection-molded parts 30 are part of an injection-molded plastic housing of the vehicle battery. This plastic housing can be made of polypropylene. The plastic housing can be injection-molded onto the steel plates 18, or the steel plates 18 can be at least partially encapsulated by the plastic housing.

[0032] As shown in Figures 2 and 3, the housing wall 16 can have the hyperbolic paraboloid region 26 of the outer wall 24 on its underside and a flat region of the outer wall 24 in a lateral region. In the event of a lateral force acting on the housing wall 16, the flat design of the outer wall 24 in this region means that the force is distributed particularly evenly across the dilatant liquid arranged in the cavity 20. Due to the corrugated design of the underside region of the outer wall 24, air, and in particular airflow, can flow around this underside outer wall 24, particularly when the housing 10 or the vehicle battery is arranged in an underbody area of ​​the motor vehicle, whereby the housing wall 16 can be cooled particularly well due to the particularly large heat exchange surface.

[0033] Because the cavity 20 is filled with the dilatant liquid, stiffening ribs for stabilizing the hollow housing wall 16 are not necessary. As a result, the housing wall 16 can be provided with a particularly low weight. Furthermore, the particularly high thermal conductivity of the starch-water mixture enables particularly rapid heat dissipation from the battery cells 14 and, consequently, particularly good cooling of the battery cells 14. Furthermore, the high strength of the housing 10 enables particularly good protection of the battery cells 14 against damage. This results in particularly high vehicle efficiency due to the reduced weight of the vehicle battery, particularly good vehicle battery and motor vehicle performance due to the particularly good cooling of the battery cells 14, and particularly effective passive and cost-effective cooling of the battery cells 14 is enabled.

[0034] In the embodiment of the housing 10 shown in Figure 2, the housing wall 16 is formed from a stamped steel shell with inner walls 22 and outer walls 24, wherein the cavity 20 delimited by the inner walls 22 and the outer walls 24 is filled with the dilatant liquid.

[0035] Dilatant liquids heat up and cool from the inside. This means that heat absorbed by the dilatant liquid collects in the center of the liquid, causing the liquid in this central region to increase in viscosity and thus harden, or in other words, to solidify. Heat collects last in the respective outer regions of the liquid, causing the liquid in these outer regions to have a lower viscosity than in the center. As a result, heat can be transported particularly well in the outer regions by means of the dilatant liquid, particularly towards the center of the liquid. As the temperature of the dilatant liquid rises, the dilatant liquid solidifies first in the center, causing the housing wall 16 to have particularly high strength.In the respective edge regions of the dilatant fluid, it continues to exhibit a lower viscosity and a particularly high thermal conductivity compared to the central region. As a result, the dilatant fluid in the edge regions is particularly well suited to transporting heat away from the battery cells 14 particularly quickly and efficiently, or to dissipating heat to the environment via the outer wall 24. This increases the amount of heat absorbed by the dilatant fluid.

[0036] Heat increases the rigidity of the housing 10, while simultaneously ensuring particularly good heat dissipation from the battery cells 14 to the environment. Overall, the invention demonstrates how dilatant fluids can be used in a battery housing.

[0037] REFERENCE SYMBOL LIST

[0038] 10 housings

[0039] 12 Recording volume 14 Battery cell

[0040] 16 Housing wall

[0041] 18 steel part

[0042] 20 cavity

[0043] 22 Interior wall 24 Exterior wall

[0044] 26 hyperbolic paraboloid area

[0045] 28 lids

Claims

PATENT CLAIMS 1. Housing (10) for a vehicle battery, with a housing wall (16) having at least one cavity (20) which delimits a receiving volume (12) of the housing (10) in which battery cells (14) of the vehicle battery can be received, wherein the cavity (20) is filled with a dilatant liquid.

2. Housing (10) according to claim 1, characterized in that the cavity (20) is filled with a starch-water mixture or with a silica-polyethylene glycol mixture.

3. Housing (10) according to claim 1 or 2, characterized in that the housing wall (16) is made of aluminum.

4. Housing (10) according to claim 1 or 2, characterized in that the housing wall (16) is made of steel parts (18), wherein the steel parts (18) are directly connected to one another or the steel parts (18) are designed as steel plates and are held together by injection-molded parts.

5. Housing (10) according to claim 4, characterized in that the injection-molded parts are made of polypropylene resin.

6. Housing (10) according to claim 4 or 5, characterized in that the steel parts (18) of the housing (10) are arranged such that they are in direct contact with at least one battery cell (14) when the receiving volume (12) is filled with battery cells (14), or are in direct contact with a heat sink of the vehicle battery.

7. Housing (10) according to one of the preceding claims, characterized in that an inner wall of the housing wall (16) facing the receiving volume (12) is flat.

8. Housing (10) according to one of the preceding claims, characterized in that the housing wall (16) is uneven at least on an outer side (24) facing away from the receiving volume (12).

9. Housing (10) according to claim 8, characterized in that the outer side (24) facing away from the receiving volume (12) is corrugated, in particular hyperbolic paraboloid.

10. Motor vehicle with a vehicle battery, which comprises a housing (10) according to one of the preceding claims, wherein in the receiving volume (12) of the Housing (10) of a plurality of battery cells (14).

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