Battery unit and method

Abstract

The present disclosure relates to a battery unit (100) for an electric vehicle. The battery unit (100) includes a battery tray (1) made of a composite material that defines an interior space configured to receive a battery (2) including one or more battery cells. The interior space is bounded by a bottom wall (3) and one or more side walls (4). The side walls (4) also include lateral flanges (5) extending outwardly therefrom, the lateral flanges (5) including one or more metal inserts (6). The metal inserts (6) are configured to receive one or more fasteners for securing the battery tray (1) to a load-bearing structure of the electric vehicle. The disclosure also relates to a method (500) for manufacturing the battery unit.

Description

[Technical Field]

[0001] This application claims the benefit of European Patent Application No. EP22382911.0, filed September 30, 2022. This disclosure relates to a battery unit for a vehicle. More particularly, this disclosure relates to a battery unit comprising a battery tray made of a composite material. This disclosure further relates to a method for manufacturing such a battery unit. [Background technology]

[0002] Vehicles, such as cars, incorporate a structural skeleton designed to withstand all the loads the vehicle may be subjected to during its lifetime. The structural skeleton, or "body-in-white" (BIW), is further designed to withstand and absorb impacts (e.g., in the event of a collision with another vehicle). The structural skeleton is also designed to be as lightweight as possible to reduce the emission of pollutants (e.g., CO2) into the environment or to reduce power consumption in electric vehicles.

[0003] The structural skeleton or BIW of an automobile may include, for example, bumpers, pillars (e.g., A-pillars, B-pillars, C-pillars), side impact beams, and rocker panels. These and other structural members may have one or more regions with a substantially U-shaped (also known as a "hat" shaped) cross section. These structural members may be manufactured in a variety of ways and from a variety of materials. For example, rocker panels may be made of steel, particularly ultra-high strength steel (UHSS), and may be manufactured by press hardening.

[0004] Ultra-high strength steels (UHSS) are optimized for maximum strength per unit of weight and advantageous forming properties in the automotive industry for at least some of the structural framework of a vehicle or its components. In the present disclosure, UHSS may be considered to be steels with an ultimate tensile strength (after hot stamping) of at least 1000 MPa, preferably up to about 1500 MPa, or up to 2000 MPa or more. An example of a UHSS used in the automotive industry is 22MnB5 steel.

[0005] The processing of vehicle components can involve forming metal plates, especially steel plates, to give them a desired shape. One process that is particularly used in the automotive industry is Hot Forming Die Quenching (HFDQ). In the HFDQ process, a steel blank is heated above the austenitizing temperature, above Ac1, or above Ac3. After heating above the austenitizing temperature, the blank is placed in a hot forming press. The blank is deformed and quenched (rapidly cooled) at the same time. The cooling can usually be performed at a rate higher than the so-called critical cooling rate.

[0006] The rapid development of electric vehicles (EVs) and hybrid vehicles is forcing the industry to design new automotive components, particularly those that require lighter weight to increase vehicle range, as well as to house and protect the new components. To achieve safety and lightweighting goals, structural components with new geometries and alternative materials are being manufactured and incorporated into EVs.

[0007] Traction batteries are a critical component of electric and hybrid vehicles, providing power to the vehicle's electric motor. Their electrical and chemical properties make them particularly sensitive to high mechanical loads, such as crash impacts. To extend battery life and protect batteries from external impacts, the automotive industry has made considerable efforts to provide battery enclosures and load-bearing structures suitable for electric vehicles. Thus, a wide range of protective elements have been designed and constructed over the past few years to house and protect traction batteries.

[0008] Steel battery boxes or trays have been designed for this purpose. Polymer (plastic) or composite components have also been developed. Plastic and composite materials can be lighter than metal components, but must be designed and dimensioned to protect against severe impacts.

[0009] The present disclosure aims to provide an improved structure for protecting automotive batteries.

[0010] overview In a first aspect, a battery unit for a vehicle is provided. The battery unit includes a battery tray made of a composite material. The battery tray defines an interior space configured to receive a battery including one or more battery cells. The interior space of the battery tray is bounded by a bottom wall and one or more side walls. The side walls further include lateral flanges extending outwardly from the side walls. Additionally, the lateral flanges include one or more metal inserts embedded therein. The metal inserts are configured to receive one or more fasteners for securing the battery tray to a load-bearing structure of an electric vehicle.

[0011] The composite battery tray provides a lightweight structure for the disclosed battery unit. Furthermore, the composite material can be selected to provide tailored mechanical strength; for example, the composite material may provide greater strength in one direction than in another. Additionally, the introduction of embedded metal inserts into the side flanges of the battery tray provides a robust connection point between the battery tray and other structures of the electric vehicle (e.g., a load-bearing frame surrounding the battery tray or another portion of the vehicle framework). Thus, the provided battery unit benefits from the light weight of a unit made from composite or polymer materials, while simultaneously providing a secure connection between components and the ability to transmit mechanical loads through the load-bearing structure.

[0012] Throughout this disclosure, "electric vehicle" or "hybrid vehicle" may be understood to encompass any vehicle having a battery configured at least in part to power the vehicle's electric powertrain.

[0013] Also, throughout this disclosure, references to "mechanical properties of a structure" may be understood as the mechanical properties of the material forming said structure. Thus, unless stated otherwise, comparisons of mechanical properties of structures, components, or other structures are directed to the material and not to its geometry or other particularities.

[0014] In some examples, the composite material used to form the battery tray may include fiberglass, although other materials, such as carbon fiber or aramid fiber, may also be used.

[0015] In some examples, the battery trays can be made from sheet molding compound, which is a composite material that comes in sheet form. The sheets are typically made by spreading a resin paste onto a surface and distributing chopped fibers on top. Another layer of resin is then added on top of the chopped fibers, and the sheet is compressed and stored while it cures.

[0016] In some examples, the metal insert is a plate that includes at least two fastener holes. The fastener holes can be configured to receive fasteners and secure the battery tray to a load-bearing structure of the electric vehicle. In this way, the holes can serve as connection points between the plate and the load-bearing structure and can limit the forces and torques experienced by the battery tray during an impact.

[0017] In some instances, the metal insert may be perforated, which may enhance the connection strength of the composite metal plate, i.e., the composite material may at least partially flow into the perforations and harden therein, thereby increasing the contact surface between the components and creating a solid bridge of composite material between the two sides of the metal plate.

[0018] In some examples, the metal insert includes at least one pin protruding perpendicularly from the surface of the lateral flange. The pin may serve as an additional contact point between the metal insert and other components of the battery unit (e.g., a fixing bracket). A pin may be understood herein to cover any structural element used to fasten objects together or as a carrier by which one object can be suspended from another. A pin may be embodied herein, for example, as a stud or rod, or as a bolt.

[0019] In some examples, the battery unit may further include a load-bearing frame, which may include aluminum structural elements that may be relatively lightweight and may support and provide protection for the battery trays.

[0020] In some examples, the battery tray may further include reinforcing ribs located on the bottom wall. In some examples, the reinforcing ribs may define a substantially orthogonal grid. The ribs may increase the rigidity of the tray and may also promote air circulation between the bottom wall and the battery.

[0021] In some examples, the battery unit can further include one or more retaining brackets configured to couple with the metal insert and at least partially retain one or more battery cells in the interior space. The retaining brackets can thus be understood as components of the battery unit configured to at least partially cover the interior space of the battery tray and limit battery movement through geometric interference. The retaining brackets can also reduce vibration of the battery within the battery tray.

[0022] In some examples, the retaining bracket may include an internal channel configured to direct a cooling medium. Additionally, the retaining bracket may include an aluminum profile extending into an interior space in which the internal channel may be disposed. Thus, the retaining bracket with the cooling channel may help maintain the battery within an appropriate temperature range.

[0023] In some examples, aluminum profiles can be configured to be positioned adjacent to or between battery cells.

[0024] In some examples, the retention bracket includes at least one retention segment configured to receive the pin of the metal insert. The retention segment may be substantially horizontal. The retention bracket may then be connected to the load-bearing structure via the metal insert. This configuration allows loads to be transferred from the load-bearing structure or frame to the retention bracket without the composite battery tray having to withstand high mechanical loads.

[0025] Furthermore, in some examples, the fastening segments are configured to be coupled to one another by aluminum profiles, so that the fastening bracket can have fastening segments around the periphery of the battery cells.

[0026] In some examples, the battery unit may include a central separator bracket configured to be positioned between the rows of battery cells. The central separator may be configured to limit battery movement through geometric interference and may include an internal channel for directing a coolant for cooling the battery.

[0027] In another aspect, a method for manufacturing a battery unit for an electric vehicle is provided. The method includes providing a plurality of metal inserts in a mold. The method also includes providing a sheet molding compound in the mold. Thereafter, the method includes forming the battery unit by hot compression molding. It should be noted that the first and second steps of the method can be performed in the order listed above or in reverse order.

[0028] According to this aspect, the provided method allows for the production of battery units in a single molding process. This allows for the incorporation of metal inserts into the composite material, providing additional strength to the battery tray. Additionally, the resulting battery unit is lighter than similar battery units made primarily of metal, yet provides sufficient rigidity to withstand the weight and other mechanical loads associated with the battery. Furthermore, the disclosed method allows for the rapid and inexpensive manufacture of battery units. Additionally, the method allows for the use of at least partially recycled composite materials, contributing to the reduction of global CO2 emissions.

[0029] In some examples of this method, forming the battery tray may include heating the mold to 100-160°C. Further, the battery tray may be formed by applying a pressure of 30-120 bar to the sheet molding compound. Additionally, the sheet molding compound may include glass fiber.

[0030] Throughout this disclosure, ribs may be understood as elongated, substantially straight sections of the battery tray for localized reinforcement. The ribs may be manufactured during the formation of the battery tray by hot compression molding, or may be included in the battery tray after it has been manufactured. The ribs may be made of a composite material or any other material and may be embedded in the composite material during the formation of the battery tray.

[0031] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 1A and 1B schematically illustrate perspective views of an example battery unit according to the present disclosure. [Figure 2] 2 shows a schematic perspective view from above of the battery tray of FIG. 1; FIG. [Figure 3] 1 shows a schematic top perspective view of an example metal insert. [Figure 4] 2 shows a schematic cross section through the width of the battery unit of FIG. 1; [Figure 5] 1 is a flowchart of a method for manufacturing a battery unit according to the present disclosure.

[0033] These drawings refer to example implementations and are used only as an aid in understanding the claimed subject matter and are not to be used to limit the subject matter in any way.

[0034] Detailed explanation of the example FIG. 1 shows a schematic representation of a battery unit 100 for a vehicle, in particular for an electric or hybrid vehicle.

[0035] The battery unit 100 includes a battery tray 1 made of a composite material. The battery tray 1 defines an interior space configured to receive a battery 2 including one or more battery cells. The interior space of the battery tray 1 is bounded by a bottom wall 3 and at least one side wall 4. The side wall 4 further includes a lateral flange 5 extending outwardly therefrom. Additionally, the lateral flange 5 includes one or more metal inserts 6 embedded therein. The metal insert 6 is further configured to receive one or more fasteners for securing the battery tray 1 to a load-bearing structure of the electric vehicle.

[0036] Because the provided battery tray 1 is made of composite materials, it can be relatively lightweight. Furthermore, the composite materials can be selected and tailored to provide specific mechanical properties to the battery tray 1. For example, the composite materials can include biaxial or triaxial fiber layers to increase the tray's mechanical properties in a specific direction. Additionally, the fiber and resin materials can be selected to obtain a final product, i.e., the battery tray 1, with specific mechanical properties. For example, the fibers can include glass fiber, carbon fiber, or aramid fiber, among others. In some instances, different types of fibers can be incorporated into the same tray.

[0037] Additionally, metal inserts 6 embedded in the side flanges 5 of the battery tray 1 provide additional local strength to the battery tray 1. More specifically, the metal inserts 6 transfer loads acting on the battery units 100 through relatively strong components, limiting the magnitude of the loads acting on the composite battery tray 1. The metal inserts 6 may be made of steel.

[0038] 1 illustrates that the battery unit 100 may also include a load-bearing frame 8 that includes a structural element 81. The load-bearing frame 8 may substantially completely surround the battery tray. In this example, the load-bearing frame 8 may include two transverse members coupled to two longitudinal transverse members.

[0039] The load-bearing frame 8 may provide additional protection for the battery tray (and the batteries therein) against external impacts, such as side impacts. Additionally, the structural element 81 may provide protection at a relatively low weight, for example, the structural element 81 may be an aluminum extrusion profile with a low average density.

[0040] Additionally, the load-bearing frame 8 may also aid in the integration of the battery unit 100 in an EV. For example, the load-bearing frame 8 may include connection points to the body-in-white of the EV.

[0041] 1 further includes a retaining bracket 7 configured to be coupled with the metal insert 6. The retaining bracket 7 is configured to at least partially hold one or more of the battery cells within the interior space of the battery tray 1. The retaining bracket 7 may be made of metal, for example, stainless steel or aluminum.

[0042] In some examples, the retaining bracket 7 may include a retaining segment 72 or flange configured to receive the pin 62 of the metal plate 6 (as further described with reference to FIG. 3).

[0043] The fixing bracket 7 in the illustrated example comprises a substantially vertical portion 71 and a substantially horizontal flange or fixing segment 72. The flange or fixing segment 72 may extend inward to hold the cells of the battery.

[0044] 1, the retaining bracket 7, particularly the vertical portion 71, may include internal channels 73 configured to conduct a cooling medium. The cooling medium may be water and / or glycol, or another suitable heat exchange fluid. The retaining bracket 7 may extend into the interior of the tray next to the rows of cells of the battery, i.e., between the sidewalls of the tray and the rows of cells. The internal cooling channels may generally extend parallel to one another in the longitudinal direction.

[0045] In some examples, the retaining bracket may be made by extrusion, for example, aluminum extrusion. The extrusion profile may incorporate cooling channels.

[0046] Additionally, in some examples, the battery unit 100 may include a central separator bracket 74 configured to be positioned between the rows of battery cells, i.e., both sides of the separator bracket 74 may be adjacent to the battery cells.

[0047] Thus, in some examples, the battery unit 100 may include an aluminum profile 71 that at least partially surrounds the battery 2 and a central separator bracket 74 between the battery cells. In the example shown, the battery unit 100 includes two rows of cells in a battery tray. The central separator bracket 74 may be positioned between the two parallel rows. In the example shown, the central separator bracket 74 may include a horizontal portion or horizontal flange that helps retain the battery cells.

[0048] It will be apparent that the vertical separation between the bracket 74 and the cells of the battery is shown in an exaggerated manner in FIG.

[0049] The central separator bracket 74 may include internal cooling channels in the same manner as described for the fixing bracket 7. The arrangement of the uprights or profiles 71 and central separator bracket 74 relative to the battery cells can be seen in more detail in FIG.

[0050] Figure 2 is a schematic diagram of a battery tray 1 of the battery unit 100 of Figure 1. As previously mentioned, the battery tray 1 defines an interior space bounded by a bottom wall 3 and at least one or more side walls 4. In this example, the battery tray is rectangular and includes four side walls 4, although battery trays 1 of other shapes may also be provided.

[0051] The example battery tray 1 of Figure 2 also shows that the side walls 4 include lateral flanges 5 having one or more embedded metal inserts 6. In the example shown, all four lateral walls 4 include lateral flanges 5, but in other examples, some of the side walls 4 may not include lateral flanges 5.

[0052] The composite battery tray 1 can be manufactured using compression molding or sheet molding compound. In this case, sheet molding compound (SMC) can be cut into appropriately sized sheets and placed into a heated die of a mold. In some examples, the heated die can be at a temperature of 100-160°C. One or more mold dies are then closed together and a pressure of 30-120 bar is applied. As the viscosity of the material decreases, the SMC flows and fills the mold cavity. Note that other techniques can also be used in which the pressure applied to the SMC is significantly lower (i.e., below 30 bar).

[0053] Glass fiber SMC can cure in 30 to 150 seconds after the molding process begins, allowing for a total manufacturing cycle as fast as 80 seconds, including part loading and unloading, enabling mass production while reducing material costs.

[0054] The composition of the SMC can be tailored to provide composites with improved properties. For example, other fibers can be introduced into the SMC to increase the strength-to-weight and stiffness-to-weight ratios. Other additives can also be provided to prevent surface microcracking due to outgassing.

[0055] Many different types of thermosetting resins are available, such as polyester resin, vinyl ester resin, epoxy resin, or poly(methyl methacrylate) (PMMA). Fiber-reinforced composites can not only provide relatively lightweight structures, but can also act as electrical insulators if the right materials (especially the right resins) are used.

[0056] The battery tray 1 in the example of FIG. 2 also includes reinforcing ribs 11 located on the bottom wall 3. Note that the ribs 11 may provide rigidity to the bottom of the tray. The ribs 11 may be integrally formed with the battery tray 1. For example, the mold used to manufacture the battery tray may include an appropriate geometric shape, and the ribs may be formed from a composite material.

[0057] The reinforcing ribs 11 in this example define a substantially orthogonal grid to provide stiffness in two orthogonal directions, eg, the longitudinal and transverse directions.

[0058] The reinforcing ribs 11 can also provide a gap between the bottom wall and the battery 2, thereby enhancing air circulation and cooling of the battery 2. The height of the reinforcing ribs 11 can also be selected so that they are substantially aligned with the side flanges 5 when the battery 2 is resting on the reinforcing ribs.

[0059] In other examples, the composite battery tray 1 can be manufactured by hand layup, which involves manually placing layers of any dry fabric onto a tool (mold) to form a laminate stack. Resin can then be applied to the dry fabric, for example, by resin infusion or by injection using resin transfer molding (RTM). In a further example, prepreg (fabric pre-impregnated with resin) can be used. After the prepreg is placed, it can be heated to cure.

[0060] In other cases, the manufacturing process may involve laying down fabrics that have already been coated with resin, and then debulking the stack, which may be done manually using rollers or using vacuum-bagging techniques.

[0061] 3 shows a schematic perspective view from above of an example of a metal insert 6. In this example, the metal insert 6 is a plate including two fastening holes 61 for connecting the metal insert 6 to other components of the battery unit 100, more precisely to the load-bearing frame 8 shown in FIG.

[0062] The metal insert 6 shown in this example defines a substantially triangular shape with two fastener holes 61 at the vertices of the longest side and a pin 62 that protrudes perpendicular to the surface of the metal insert 6. In other examples, the metal insert 6 may have fastener holes 61 and pins 62 distributed in a different manner. For example, the metal insert 6 may have three fastener holes located substantially at the vertices of the triangular shape and the pin 62 in a substantially central position. The pin 62 may be configured to protrude perpendicular to the surface of the side flange 5 to engage with the fixing bracket 7 of the battery unit 100.

[0063] The pin 62 may be a simple rod, or in other instances may be configured as a stud or bolt, for example.

[0064] The metal plate illustrated in FIG. 3 may also be a perforated plate. Perforations in this specification may be understood to mean through-holes (which may generally be smaller than fastener holes). The perforations 63 may enhance the bond strength between the metal plate 6 and the battery tray 1. That is, the composite material of the battery tray 1 may at least partially flow into the perforations 63 and harden therein, thereby increasing the contact surface between the components and creating a solid bridge of composite material between the two sides of the metal plate. Thus, the bond may be not only chemical but also mechanical. In other examples, the metal plate 6 may also include surface ridges or surface depressions to strengthen the metal plate-battery tray connection.

[0065] FIG. 5 is a flowchart of a method 500 for manufacturing a battery unit 100 according to the present disclosure.

[0066] The method 500 includes providing a plurality of metal inserts 6 in a mold at block 501. The method further includes providing a sheet molding compound in the mold at block 502. The method further includes forming a battery tray 1 by hot compression molding at block 503.

[0067] As discussed above, the provided method 500 allows for a simple, fast, and reliable manufacturing of the battery unit 100. Furthermore, the method 500 can be easily automated for mass production, reducing human oversight and associated costs.

[0068] In some examples, as previously mentioned, forming the battery unit 100 may include heating a mold to 100-160°C and applying a pressure of 30-120 bar to a sheet molding compound. Additionally, the sheet molding compound may include glass fibers, which may result in a total manufacturing time of approximately 80 seconds.

[0069] Additionally, the method 500 may be adapted to form a battery unit 100 with any combination of the technical features discussed above.

[0070] After the tray is manufactured, a plurality of battery cells can be installed in the tray. In the example of the previous drawing, two rows of battery cells are provided. Stopper elements can be disposed at both ends of the rows of battery cells. Fixing brackets can be attached to the metal inserts along at least two sides of the battery tray.

[0071] The retaining brackets can be mechanically attached, for example by screwing them into a metal insert. The retaining brackets can also be joined to stop elements, which at least partially cover the battery cells and thus hold them in place. A central separator bracket can be positioned between the rows of cells and attached to the stop elements at both ends.

[0072] While only a number of examples are disclosed herein, there may be other alternatives, modifications, uses, and / or equivalents thereof. Furthermore, all possible combinations of the examples described are also covered. Thus, the scope of the present disclosure should not be limited by the specific examples, but should be determined solely by a fair reading of the following claims.

Claims

1. A battery unit (100) for a vehicle, wherein the battery unit (100) is A battery tray (1) made of composite material, defining an internal space configured to receive a battery (2) containing one or more battery cells. The interior space is divided by a bottom wall (3) and one or more side walls (4), The side wall (4) is provided with a lateral flange (5) extending outward from the side wall (4), and the lateral flange (5) is provided with one or more metal inserts (6) embedded in the lateral flange (5). The battery unit further comprises a load-bearing frame (8) that substantially completely surrounds the battery tray (1), The metal insert (6) is configured to receive one or more fasteners for securing the battery tray (1) to the load-bearing frame (8). Battery unit.

2. The battery unit according to claim 1, wherein the battery tray is made of a sheet-molded compound.

3. The battery unit according to claim 1, wherein the composite material includes glass fibers.

4. The battery unit according to claim 1, wherein the metal insert is a plate including at least two fastening holes (61).

5. The battery unit according to claim 1, wherein the metal insert is a perforated plate.

6. The battery unit according to claim 1, wherein the metal insert includes at least one pin (62) protruding perpendicularly from the surface of the lateral flange.

7. The battery unit according to claim 1, wherein the load-bearing frame includes an aluminum structural element (81).

8. The battery unit according to claim 1, wherein the battery tray further comprises reinforcing ribs (11) located on the bottom wall, the reinforcing ribs may define a substantially orthogonal grid.

9. The battery unit according to claim 1, further comprising one or more fixing brackets (7) configured to be coupled with the metal insert and to at least partially hold one or more of the battery cells in the internal space.

10. The battery unit according to claim 9, wherein the fixing bracket includes a substantially horizontal fixing segment configured to receive the pins of the metal insert.

11. The battery unit according to claim 9, wherein the fixing bracket further includes an internal channel (73) configured to guide a cooling medium.

12. The battery unit according to claim 11, wherein the fixing bracket includes a substantially vertical portion, the substantially vertical portion including the internal channel (73) configured to guide the cooling medium.

13. The battery unit according to claim 1, further comprising a central separator bracket (74) configured to be positioned between two rows of battery cells.

14. A method (500) for manufacturing an electric vehicle battery unit according to any one of claims 1 to 13, To prepare multiple metal inserts in the mold (501), (502) preparing a sheet molding compound in the mold, and Forming the battery unit by hot compression molding (503) Methods that include...

15. The method according to claim 14, wherein forming the battery unit comprises heating the mold to 100 to 160°C and applying a pressure of 30 to 120 bar to the sheet molding compound, wherein the sheet molding compound contains glass fibers.

Images