BATTERY HOUSING AND USE

Description

Technical area

[0001] The present invention relates to a battery housing for receiving one or more battery modules, in particular for an electrically powered vehicle or a vehicle with a hybrid drive, comprising a box with a frame and a base, which provides an interior space for receiving the battery module or modules, at least one mounting support which is connected at least in sections to the frame of the box on the side of the frame facing away from the interior space and which serves for the detachable connection of the battery housing to a vehicle, a lid for closing the box. Technical background

[0002] The increasing and ongoing electrification of vehicles, especially automobiles, and the simultaneous customer demand for long ranges in such vehicles, requires the development of high-performance battery concepts. In particular, battery housings, which accommodate the battery modules or in which the battery modules are housed, generally extend significantly in the vehicle's longitudinal and transverse directions and are usually mounted centrally, particularly below the passenger compartment under the vehicle (floor panel). The battery housing serves, among other things, to protect the battery modules from damage and to dissipate the heat generated by the battery modules while the vehicle is moving. This results in complex requirements with regard to installation space, crash performance, weight, tightness, etc.

[0003] The battery housing must protect the battery modules from water and therefore be waterproof. The requirements call for water resistance typically up to a depth of 1m. Below the vehicle (floor panel), the battery housing is exposed to splashing water, which may also be salted. To achieve this, the battery housing must be protected against rusting.

[0004] To ensure cost-effective production and high crash safety, battery housings are preferably made of ultra-high-strength steel. A generic battery housing constructed from multiple steel parts, as well as the mounting or fastening of the battery housing to a vehicle using detachable fasteners, preferably screws, is disclosed, for example, in DE 10 2016 110 330 A1 and WO 2018 210 420 A1.

[0005] The steel used should be coatable and weldable. The steel used, preferably coated, or the components made from it are joined together via welds, among other things, to form the interior of a battery housing for accommodating battery modules. It must be ensured that the welds seal the interior and are therefore leak-proof. This presents a conflict of objectives, because corrosion-protection coatings with a high protective effect can reduce process reliability during welding or the welded joint. Furthermore, the steel used should also exhibit a certain deformation resistance in order to meet the required requirements in the event of a crash. Summary of the invention

[0006] The invention is based on the object of providing a battery housing, in particular for an electrically powered vehicle or a vehicle with a hybrid drive, which is designed to be waterproof and corrosion-resistant and in particular has a high deformation resistance.

[0007] This problem is solved by a battery housing with the features of patent claim 1.

[0008] The components of the battery housing, such as the frame, the base, the mounting bracket, or the cover of the battery housing, are made of metal. According to the invention, at least one of the components (frame, base, mounting bracket, cover) is made of a steel sheet having a microstructure comprising ferrite and martensite and provided with a zinc-based coating on one or both sides. The combination of ferrite and martensite gives the respective component high deformation resistance coupled with very good coating suitability. The production of steel sheets with corresponding microstructures or properties is state of the art and known in the art. According to the invention, the steel sheet has a microstructure with at least 65% ferrite and martensite, with at least 20% ferrite and at least 5% martensite being present, with up to 35% bainite, pearlite, cementite, and / or retained austenite being possible.

[0009] The addition of martensite makes it clear that the steel sheets used to manufacture the respective components are subjected to only cold forming or tempering, which does not involve any structural transformation, in order to ensure that the advantageous properties already present in the steel sheet can also be utilized in the later, manufactured component. According to the invention, the steel sheets are coated on one or both sides with a zinc-based coating prior to production and prior to the assembly of the components to create the battery housing. This coating provides excellent protection against corrosion and, consequently, against rapid rust penetration.

[0010] The microstructure can in particular comprise at least 70% ferrite and martensite, preferably at least 80% ferrite and martensite, preferably at least 85% ferrite and martensite, wherein in particular up to 30%, preferably up to 20%, preferably up to 15% bainite, pearlite, cementite and / or retained austenite can be present.

[0011] Advantageous embodiments and variants of the invention emerge from the dependent claims and the following description.

[0012] According to one embodiment, the battery housing further comprises an underrun guard, which is arranged below the bottom of the box, in particular at a distance from the bottom. The underrun guard is made of a steel sheet having a microstructure comprising ferrite and martensite and is provided with a zinc-based coating on one or both sides. The underrun guard can, in particular, ensure additional protection of the battery modules from foreign bodies penetrating from below if the bottom of the box is or cannot be sufficiently dimensioned.The underrun protection is arranged in particular at a distance from the floor of the box so that, on the one hand, good use can be made of the available installation space for accommodating, for example, temperature control media for cooling and / or heating the battery modules and / or other means for operating / supplying the battery modules. On the other hand, the distance can slow down any foreign bodies penetrating from below before they reach and damage the sensitive battery modules, which can lead to a critical short circuit and, in the worst case, a fire. In order to be replaceable in the event of damage but also to ensure a certain degree of maintenance from below, the underrun protection should, according to a preferred embodiment, be detachably connected to the battery housing. By detachable is meant, for example, mechanical joining methods such as using clips and / or screws and / or adhesives.If no (additional) underrun protection is present, the floor of the box acts as the underrun protection. In an alternative design, the floor can be designed as a deep-drawn tray.

[0013] According to a preferred embodiment, the steel sheet has a microstructure with at least 60% ferrite and at least 5% martensite, with up to 35%, in particular up to 30%, preferably up to 25% bainite, pearlite, cementite, and / or residual austenite being present. Particularly preferably, the steel sheet has a microstructure with 70 to 90% ferrite and 10 to 30% martensite, with up to 20% residual austenite being present. This combination of the microstructure established in the steel sheet enables high deformation resistance and, at the same time, high coating suitability. Due to the martensite content in the microstructure of up to a maximum of 30%, cold forming of the steel sheet is nevertheless feasible using conventional plant technology.

[0014] According to an alternative embodiment, the steel sheet has a microstructure with at least 65% ferrite and martensite, wherein 20 to 95% ferrite and 5 to 80% martensite, in particular 40 to 80% ferrite and 20 to 60% martensite, are present, wherein up to 35%, in particular up to 30%, preferably up to 25% bainite, pearlite, cementite and / or retained austenite can be present.

[0015] The stated microstructure proportions in % refer to the area observed in the cross-section, with the exception of the information on the contents of (residual) austenite, which are usually determined by X-ray diffractometry and are therefore given in vol.%.

[0016] According to a further preferred embodiment, the steel sheet is provided with a zinc-based coating on one or both sides, which, in addition to zinc and unavoidable impurities, also contains at least one of the elements from the group aluminum and magnesium. Particularly preferably, the zinc-based coating consists of aluminum with 0.5 to 4 wt.% and / or magnesium with 0.5 to 4 wt.%, the remainder being zinc and unavoidable impurities, which offers improved corrosion protection compared to a coating consisting of pure zinc. Corrosion protection is further improved if both aluminum and magnesium are contained in the coating, so that according to a further preferred embodiment, the zinc-based coating consists of aluminum with 1 to 2.5 wt.% and magnesium with 1 to 2.5 wt.%, the remainder being zinc and unavoidable impurities.The improved corrosion protection has the significant advantage that the coating can be made thinner than with conventional (hot-dip) zinc coatings while still providing sufficient corrosion protection. This can improve process reliability during preferred welding, which can be crucial to ensure the tightness of the joints / welds in large-scale production.

[0017] In order to enable sufficient corrosion protection, according to one embodiment the zinc-based coating of the steel sheet for the production of the at least one component (frame, base, mounting bracket, cover) has a coating of at least 30 g / m 2< per side on one or both sides of the steel sheet, in particular with a coating of 40 g / m 2< to 90 g / m 2< per side on one or both sides. In the event that an underrun protection is used, according to one embodiment the zinc-based coating of the steel sheet for the production of the underrun protection has a coating of at least 30 g / m 2< , in particular of at least 60 g / m 2< , preferably of at least 90 g / m 2< per side on one or both sides of the steel sheet, preferably with a coating of 120 g / m 2< to 300 g / m 2< per side on one or both sides.

[0018] According to one embodiment, at least the frame and the base of the box are provided with an additional cathodic dip coating with a layer of at least 10 µm per side on one or both sides. The cathodic dip coating creates a barrier and slows the degradation of the zinc-based coating and can provide particularly effective protection against saline splash water. If an underrun guard is used, according to one embodiment, the underrun guard is provided with an additional cathodic dip coating with a layer of at least 15 µm per side on one or both sides, in particular at least 20 µm per side on one or both sides, preferably at least 30 µm per side on one or both sides.After production, the underrun bar is additionally coated with a cathodic dip coating as a single part. This provides a barrier against the degradation of the zinc-based coating and thus extends protection against base metal corrosion, especially when the underrun bar is exposed to (salt-containing) splash water. This coating can also be supplemented with additional, subsequently applied corrosion protection coatings / coatings.

[0019] The underrun protection is preferably coated with a higher layer of zinc-based coating, especially compared to the other components, because the corrosion protection requirements for this component are particularly high and, if the underrun protection is joined or attached using clips and / or screws and / or adhesives, the coating does not affect the tightness of the joint. If the underrun protection is joined or attached using welding, the coatings of the zinc-based coating and the cathodic dip coating described for the floor can be used.

[0020] According to a second teaching, the invention relates to a use of a battery housing according to one of the aforementioned embodiments for detachable connection to a passenger vehicle, commercial vehicle, special vehicle, in particular a bus, omnibus or a track-bound vehicle, in particular a tram or passenger-carrying wagon or railcar. Short description of the drawings

[0021] The invention is explained in more detail below with reference to the drawings. Identical parts are provided with the same reference numerals. In detail: Fig. 1 a) a schematic side view of a battery housing, Fig. 1 b) a schematic plan view of the Fig. 1a ) battery case shown and Fig. 1 c) a schematic partial sectional view along section AA in Fig. 1b ). Description of the preferred embodiments

[0022] The battery housing (1) for accommodating one or more battery modules (not shown) can be designed in different ways. According to the invention, the battery housing (1) comprises a box (2) having a base (2.2) with a frame (2.1), in particular a surrounding frame (2.1) as a wall, which defines an interior space for accommodating the battery module(s) (not shown), and a lid (not shown) for closing the box (2). Furthermore, at least one mounting bracket (3) is arranged at least partially on the side of the frame (2.1) facing away from the interior space to the frame (2.1) of the box, which serves to detachably connect the battery housing (1) to a vehicle (not shown) via means (not shown), for example screws that can be passed through corresponding openings (3.1). The mounting bracket (3) is at least partially attached to the outside of the frame (2.1).1) of the box, in particular integrally connected, preferably welded. The mounting bracket (3) can also, as shown in the . Figures 1a) and 1b ), be arranged at least continuously on both sides of the battery housing (1) along the frame (2.1) in the vehicle's longitudinal direction (L). Alternatively or additionally, and not shown here, the mounting support (3) can also be connected to the frame (2.1) at least in sections in the vehicle's transverse direction (Q). The mounting support (3) can be dimensioned differently or as required, for example, it can be designed as an open or closed profile.

[0023] The box can be a built-up box (2), meaning that it is composed, in particular integrally connected, of individual components, such as at least one open or closed profile, which can be shaped to form a surrounding frame (2.1), or preferably of at least four profiles which have an open or closed cross-section and are connected to one another to form a surrounding frame (2.1), and a plate which is connected to the frame (2.1) and forms the base (2.2) of the box (2). In an alternative embodiment not shown, the base of the box can be designed as a deep-drawn tray.

[0024] The battery housing (1) can further comprise an underrun protection (2.3) which is arranged below the floor (2.2) of the box (2), in particular at a distance from the floor (2.2), see. Figures 1a) and 1c ), is arranged. In Figure 1b) At least one reinforcement element (in this embodiment, for example, exactly one reinforcement element is shown) is shown in dashed lines in the vehicle's longitudinal direction (L) and / or at least one reinforcement element (in this embodiment, for example, four reinforcement elements are shown) is shown in the vehicle's transverse direction (Q) in the interior of the box (2). These can be present if required and thus form compartments for accommodating battery modules. In this embodiment, for example, up to eight battery modules can be accommodated.

[0025] According to the invention, at least one of the components and / or parts, for example the frame (2.1), the floor (2.2), the underrun protection (2.3), the mounting support (3), the reinforcing element or the reinforcing elements (cf. Fig. 1b)) or the cover (not shown) is made from a steel sheet which has a microstructure comprising ferrite and martensite, preferably a microstructure with at least 60% ferrite and at least 5% martensite, wherein up to 35%, in particular up to 30%, preferably up to 25% bainite, pearlite, cementite and / or residual austenite can be present, particularly preferably a microstructure with 70 to 90% ferrite and 10 to 30% martensite, wherein up to 20% residual austenite can be present.

[0026] According to the invention, the steel sheet for the production of at least one component (frame, floor, underrun protection, mounting bracket, reinforcement element, cover) is provided with a zinc-based coating on one or both sides, wherein in particular, in addition to zinc and unavoidable impurities, at least one of the elements from the group aluminum and magnesium can also be present in the coating, particularly preferably the zinc-based coating consists of aluminum with 0.5 to 4 wt.% and / or magnesium with 0.5 to 4 wt.%, the remainder zinc and unavoidable impurities, further preferably the zinc-based coating consists of aluminum with 1 to 2.5 wt.% and magnesium with 1 to 2.5 wt.%, the remainder zinc and unavoidable impurities. The coating on the steel sheet or the component manufactured therefrom is at least 30 g / m² per side on one or both sides of the steel sheet. For the underrun protection (2nd3) A coating of at least 90 g / m² per side can be applied to one or both sides of the steel sheet. The zinc-based coating is applied to the steel sheet prior to production into a component, for example, in a conventional continuous coil coating process, preferably in a continuous hot-dip coating process.

[0027] Preferably, the frame (2.1) or the components for constructing the frame (2.1), the floor (2.2), the mounting support (3) and the underrun protection (2.3) are each made of a steel sheet which has a microstructure comprising ferrite and martensite and is provided with a zinc-based coating on one or both sides.

[0028] In the preferably assembled box (2), the individual components, such as the components for creating the frame (2.1), the base (2.2), and optionally the mounting support (3), are joined together by a material bond, whereby a welding process is used, in particular laser welding or optionally laser hybrid welding (with filler material). The combination of microstructure, coating, and joining process ensures high quality of the components (2.1, 2.2) connected by welds and thus the tightness of the battery housing (1). Thus, in particular after the completion of the box (2), with or without the mounting support (3), at least the box (2) can be subjected to a cathodic dip coating, so that at least the frame (2.1) and the base (2.2) of the box (2) are provided with an additional cathodic dip coating with a thickness of at least 10 µm per side on one or both sides.

[0029] The underrun protection (2.3) is preferably detachably connected to the battery housing (1) or to the box (2) and is preferably provided with an additional cathodic dip paint coating with a layer of at least 15 µm per side on one or both sides. If welding is not used to connect the underrun protection (2.3), the zinc-based coating and / or the cathodic dip paint coating can be applied with a high layer, in particular with a higher layer compared to the other components (2.1, 2.2, 3), which can lead to particularly good corrosion protection. In order to make the connection between the underrun protection (2.3) and the box (2) or battery housing (1) preferably tight, the connection area or contact area is additionally provided with adhesive and / or sealing agents, so that watertightness and corrosion protection against premature rust can be guaranteed here too.3) is joined or connected by welding, the zinc-based coating and cathodic dip coating described for the floor can be used.

[0030] The cover (not shown) can be made of sheet steel with the aforementioned properties. Alternatively, the cover can also be made of another steel material, a light metal, a (fiber-reinforced) plastic, or even a hybrid of these. For maintenance purposes, in particular to ensure accessibility to the interior of the box (2), the cover is preferably detachably connected to the box (2).

[0031] The invention is not limited to the embodiment shown, but the individual features can be combined with each other as desired, provided this is technically possible and within the scope of the claims.

Claims

1. Battery housing (1) for accommodating one or more battery modules, in particular for an electrically powered vehicle or a vehicle with hybrid drive, comprising - a box (2) with a frame (2.1) and a base (2.2), which provides an interior space for accommodating the battery module or modules, - at least one mounting support (3) which is connected to the frame (2.1) of the box (2) at least in sections on the side of the frame (2.1) facing away from the interior and which serves to detachably connect the battery housing (1) to a vehicle, - a lid to close the box (2), characterized in that the frame (2.1), the base (2.2), the mounting support (3) or the cover of the battery housing (1) is made from a sheet steel which has a microstructure comprising ferrite and martensite, the sheet steel having a microstructure with at least 65% ferrite and martensite, at least 20% ferrite and at least 5% martensite being present, up to 35% bainite, pearlite, cementite and / or retained austenite being present, and being provided with a zinc-based coating on one or both sides.

2. Battery housing according to claim 1, wherein the battery housing (1) further comprises an underride guard (2.5) which is arranged below the bottom (2.2) of the box (2), wherein the underride guard (2.5) is made of a steel sheet which has a microstructure comprising ferrite and martensite and is provided with a zinc-based coating on one or both sides.

3. Battery housing according to claim 2, wherein the underride guard (2.5) is detachably connected to the battery housing (2).

4. Battery housing according to one of the preceding claims, wherein the steel sheet has a microstructure with at least 60 % ferrite and at least 5 % martensite, wherein up to 35 % bainite, pearlite, cementite and / or retained austenite may be present.

5. Battery housing according to one of the preceding claims, wherein the steel sheet has a microstructure with 70 to 90 % ferrite and 10 to 30 % martensite, wherein up to 20 % retained austenite may be present.

6. The battery housing according to any one of the preceding claims, wherein the zinc-based coating comprises, in addition to zinc and unavoidable impurities, at least one of aluminum and magnesium.

7. Battery housing according to one of the preceding claims, wherein the zinc-based coating consists of aluminum with 0.5 to 4 wt.% and / or magnesium with 0.5 to 4 wt.%, balance zinc and unavoidable impurities.

8. The battery housing according to any one of the preceding claims, wherein the zinc-based coating has a coating of at least 30 g / m2 per side on one or both sides of the steel sheet.

9. Battery housing according to claim 2 or 3, wherein the zinc-based coating has a coating of at least 90 g / m2 per side on one or both sides of the steel sheet.

10. Battery housing according to one of the preceding claims, wherein at least the frame (2.1) and the bottom (2.2) of the box (2) are provided with an additional cathodic dip coating with a coating of at least 10 µm per side on one or both sides.

11. Battery housing according to any one of claims 2 to 9, wherein the underride guard (2.5) is provided with an additional cathodic dip coating with a coating of at least 15 µm per side on one or both sides.

12. Use of a battery housing (1) according to one of the preceding claims for detachable connection to a passenger vehicle, commercial vehicle, special vehicle or track-bound vehicle.