Energy storage for a motor vehicle

Abstract

Energy storage device for a motor vehicle, with a plurality of energy storage cells (12, 14, 16, 18) which are electrically connected to one another and arranged side by side, and cooling plates (22, 24, 26) arranged between the energy storage cells (12, 14, 16, 18) and through which a coolant flows, wherein the cooling plates (22, 24, 26) each comprise a bent sheet (30) which, in a leg region (36), has two mutually parallel and mutually spaced legs (32, 34) and in a bending region (38) has a bending section (39) connecting the two legs (32, 34) to one another, characterized in that a first axial end face (35) of the cooling plate (22, 24, 26) is sealed fluid-tight exclusively in the leg region (36) and a second axial end face (37) of the cooling plate (22, 24, 26) is sealed fluid-tight in the leg region (36) and in the bending region (38).

Description

The invention relates to an energy store for a motor vehicle, having a plurality of energy store cells which are electrically connected to one another and are arranged next to one another, and cooling plates which are arranged between the energy store cells and through which a coolant flows.During the discharging and charging of energy stores, energy in the form of heat is released due to electrochemical processes in the energy storage cells, wherein the heat has to be dissipated in order to prevent a permanent loss of capacity of the energy store due to overheating. The cooling of the energy store is achieved by different known cooling concepts, wherein, for example, cooling plates are provided between the individual energy store cells. The cooling plates abut on the broad sides of the energy storage cells and are flowed through by a cooling medium, wherein the heat emitted by the energy storage cells is transferred to the cooling medium and is dissipated by the circulation of the cooling medium through a cooling circuit.Furthermore, when discharging and charging energy storage cells, it must be taken into account that the energy storage cells expand during charging and shrink again during discharging. This phenomenon known as "swelling" leads on the one hand to a mechanical load on the energy storage cells during the charging process if the energy storage cells are arranged in a fixed manner in a compact manner lying against one another in a battery frame or in a battery housing, and on the other hand to a reduction in cooling if the cooling plates arranged between the energy storage cells do not bear directly against the energy storage cells on account of shrinkage of the energy storage cells in the thickness direction and gaps are formed between the energy storage cells and the cooling plates.DE 10 2018 008 618 A1 discloses an electrical energy store for a motor vehicle. The electrical energy store comprises a plurality of energy storage cells, wherein a cooling plate through which a cooling medium flows is arranged between each two energy storage cells. The cooling plates have two rigid wall parts arranged parallel to one another and a deformable element connecting the wall parts to one another, wherein the elastic element deforms as a function of a change in the volume of the energy storage cell. When the energy storage cell expands in the thickness direction due to the charging of the energy storage cells, the elastic member deforms, thereby reducing the thickness of the cooling plate. The predefined contact pressure between the energy storage cells and the cooling plates is maintained in this case.DE 10 2016 219 283 A1 discloses a cooling plate for an energy store, wherein the cooling plate is arranged between two energy store cells and a coolant is passed through it. The cooling plate comprises a support frame, an elastic element radially surrounding the support frame and a film arranged on the broad sides of the cooling plate. The elastic element is designed such that it elastically deforms when the energy storage cells expand in the thickness direction and thus prevents an undesirable effect due to the "swelling".JP 2016-023893 A discloses a battery module with a battery cell stack, wherein a cooling plate is arranged on one side of the battery module, which cooling plate is produced from a bent metal sheet and has two limbs running parallel to one another and spaced apart from one another in a limb region and a bending section connecting the two limbs to one another in a bending region. A coolant inlet is arranged at a first end of the bending region and a coolant outlet is arranged at a second end of the bending region.Furthermore, U.S. Pat. No. 4,570,700 A discloses a heat exchanger which is produced from a bent sheet metal.A disadvantage of such energy stores is that the production of the cooling plates for cooling the energy storage cells is complicated and cost-intensive.The object of the invention is to provide an energy store for a motor vehicle, which has cooling plates which are simple and cost-effective to produce.This object is achieved by an energy store for a motor vehicle having the features of independent claim 1.Because the cooling plates each comprise a bent metal sheet which has in a leg region two limbs running parallel to one another and spaced apart from one another and in a bending region a bending portion connecting the two limbs to one another, wherein a first axial end side of the cooling plate is sealed off in a fluid-tight manner exclusively in the leg region and a second axial end side of the cooling plate is sealed off in a fluid-tight manner in the leg region and in the bending region, a cooling plate is provided which can be produced easily and cost-effectively. In this case, a rectangular sheet metal blank which can be produced cost-effectively is bent over in the bending region by a simple and cost-effective forming method, so that a bending section arranged in the bending region and two limbs arranged in the limb region and of equal length and arranged parallel to one another are produced. Subsequently, the second axial end face of the cooling plate is completely sealed, i.e. in the bending region and in the leg region, and the first axial end face of the cooling plate is sealed in a fluid-tight manner only in the leg region by an adhesive or another sealant known from the prior art, wherein the adhesive or the other sealant is applied in the edge region to the inner surface of the bent metal sheet. The cooling plate is thus a sheet metal and bent part which is produced simply and cost-effectively.Furthermore, such a configuration of the cooling plate leads to the fact that it can elastically deform as a function of an expansion of the energy storage cells in the thickness direction, as a result of which, on the one hand, the mechanical loading of the energy storage cells during the charging process and, on the other hand, the reduction of the cooling on account of "swelling" can be prevented.The bent metal sheet and the sealed axial end faces of the cooling plate delimit a coolant channel which extends through the cooling plate and through which a coolant flows and carries away the heat which arises during the charging or discharging process of the energy storage cell. The coolant is preferably introduced into the coolant channel at an unsealed region of the first axial end side forming a coolant inlet, flows through the coolant channel between the two limbs and is discharged again from the coolant channel at an open end opposite the bending section and forming the coolant outlet. As a result, the coolant outlet and the coolant inlet are produced in a cost-effective manner by omitting the seal in each case in a predefined region.In a preferred embodiment, the bending section has a fully circular cross section. Preferably, the diameter of the full circle-like cross section is greater than the distance between the two legs spaced apart from one another. As a result, the coolant inlet can be adapted to the flow cross section of the coolant channel between the limbs, such that a sufficiently high volume flow of the coolant through the coolant inlet can be provided and therefore sufficient cooling of the energy storage cells can be ensured.Preferably, a coolant-permeable, flexible wire mesh is arranged between the legs. The coolant-permeable, flexible wire mesh can, on the one hand, allow the elastic deformations of the cooling plate and, on the other hand, cause a swirling of the coolant flowing through the cooling plate. The swirling of the coolant has the effect that the coolant flowing through the cooling plate dwells in the cooling plate for a longer time and as a result more heat can be absorbed by the coolant. As a result, the cooling effect of the energy storage cells is increased.Preferably, the coolant-permeable wire fabric is designed in multiple layers, wherein the different wire fabric layers have different weaves from one another. This can improve the swirling of the coolant and the flow through the cooling plate.In a preferred embodiment, at least one perforated plate and at least one flexible foam element are arranged between the legs. The perforated plate serves for swirling the coolant flowing through the cooling plate, wherein the flexible foam element is provided in order to ensure the elastic deformation of the cooling plate. This creates a cost-effective cooling plate with swirling elements or coolant guide elements arranged therein.The bent metal sheet preferably has a wall thickness of 0.05 to 0.5 mm, as a result of which the metal sheet has such a small wall thickness that elastic deformation of the cooling plate can be ensured and an increase in the volume of the energy storage cell in the thickness direction can be compensated.The object is also achieved by a cooling plate for an energy store according to one of Claims 1 to 8 having the features of Claim 9. As a result, the cooling plate can be produced easily and cost-effectively.An energy store is thus provided which has a cooling plate which is simple and cost-effective to produce.An exemplary embodiment of the invention is explained in more detail with reference to the drawings. FIG. 1 shows an energy store in a perspective view, FIG. 2 shows a cooling plate of an energy store from FIG. 1 in a perspective view, FIG. 3 ashows a first embodiment of a cooling plate of an energy store from FIG. 1 in a sectional view, and FIG. 3 bshows a second embodiment of a cooling plate of an energy store from FIG. 1 in a sectional view.FIG. 1 shows an energy store 10, which is usually installed in an electric vehicle and serves for supplying power to an electric machine of the electric vehicle.The energy store 10 has a plurality of energy storage cells, wherein only four energy storage cells 12, 14, 16, 18 are shown by way of example in FIG. 1. The energy storage cells 12, 14, 16, 18 are lithium ion cells and are designed as pouch cells, wherein in pouch cells the stacked or folded active layers of the energy storage cells are enclosed by a flexible outer foil, which usually consists of aluminum.The energy storage cells 12, 14, 16, 18 are arranged next to one another and are electrically connected to one another in series or in parallel via a cell connector, not shown in FIG. 1. A cooling plate 22, 24, 26 is arranged in each case between two adjacent energy storage cells 12, 14, 16, 18, wherein the cooling plates 22, 24, 26 bear with their broad sides against the broad sides of the two adjacent energy storage cells 12, 14, 16, 18.The cooling plate 22, 24, 26 shown in FIG. 2 is produced from a bent sheet 30, wherein the bent sheet 30 has a bent section 39 and two legs 32, 34. The legs 32, 34 are arranged parallel to one another and spaced apart from one another by a distance A. Both legs 32, 34 have a common length L and depth T. The legs 32, 34 are connected to one another via the bending section 39, wherein the region in which the bending section 39 is arranged is referred to as bending region 38 and the region in which the legs 32, 34 are arranged is referred to as leg region 36.The first axial end face 35 of the cooling plate 22, 24, 26 is sealed in a fluid-tight manner in the bending region 38 by a sealing means 40, wherein the sealing means 40 is injected into the cavity between the two limbs 32, 34 in the region of the first end face 35.The second axial end face 37 of the cooling plate 22, 24, 26 is sealed in a fluid-tight manner by a sealing means 42 in the bending region 38 and in the leg region 36, so that the second axial end face 37 is completely closed by the sealing means 42.On the first axial end side 35, a coolant inlet 50 having a fully circular cross section and a diameter D is provided, wherein the coolant inlet 50 is formed by the unsealed bending region 38. The coolant inlet 50 is substantially radially delimited by the fully circular cross section of the bending section 39.A coolant outlet 52 is provided on the side opposite the bending section 39, wherein the coolant outlet 52 extends over the entire depth T of the cooling plate 22, 24, 26 and is radially delimited by the end regions of the limbs 32, 34 spaced apart from one another by the distance A and by the sealing means 40, 42 arranged on the end sides 35, 37. The distance A between the two legs 32, 34 is smaller than the diameter D of the coolant inlet 50.In FIGS. 1 and 2, the coolant flow through the cooling plate 22, 24, 26 is illustrated by dashed arrows. In this case, the coolant flows through the coolant inlet 50 formed in the bending region 38 into the cooling plate 22, 24, 26 and is deflected by 90°. The coolant then flows through a coolant channel 56 disposed between the legs 32, 34 before the coolant flows out of the cooling plate 22, 24, 26 through the coolant outlet 52.To improve the cooling effect of the cooling plates 22, 24, 26, further components are arranged in the coolant channel 56, wherein FIG. 3 ashows a first embodiment and FIG. 3 bshows a second embodiment of the cooling plates 22, 24, 26 with components arranged in the coolant channel 56.FIG. 3 ashows a cooling plate 22, 24, 26 with a coolant channel 56, in which a wire mesh 60 is arranged. The wire fabric 60 is embodied in multiple layers and has a first wire fabric layer 62 with a first weave, a second wire fabric layer 64 with a second weave, and a third wire fabric layer 66 with a third weave.FIG. 3 bshows an alternative to the wire mesh 60, wherein two perforated plates 74, 76 spaced apart from one another and two foam elements 70, 72 are arranged in layers in the coolant channel 56.The coolant flowing through the cooling plate 22, 24, 26 is swirled by the multilayer flexible wire mesh 60 shown in FIG. 3 aand the perforated plates 74, 76 shown in FIG. 3 b, whereby the coolant flowing through the cooling plate remains in the cooling plate longer, whereby more heat can be absorbed by the coolant and the cooling effect of the cooling plates 22, 24, 26 increases. Furthermore, the flexible wire mesh 60 from FIG. 3 aand the foam element 70, 72 from FIG. 3 b serve for elastic deformation of the cooling plate 22, 24, 26, wherein the cooling plates 22, 24, 26 elastically deform when the energy storage cells 12, 14, 16, 18 expand in the thickness direction during the charging process. Furthermore, the bent sheet 30 is made with a wall thickness of 0.1 mm, thereby permitting the elastic deformation of the cooling plates 22, 24, 26.Other structural embodiments than the described embodiments are also possible, which fall within the scope of protection of the main claim. For example, the coolant inlet 50 or the coolant outlet 52 can be designed differently.

Claims

Energy store for a motor vehicle, having a plurality of energy storage cells (12, 14, 16, 18) which are electrically connected to one another and are arranged next to one another, and cooling plates (22, 24, 26) which are arranged between the energy storage cells (12, 14, 16, 18) and through which a coolant flows, wherein the cooling plates (22, 24, 26) each comprise a bent metal sheet (30) which has, in a limb region (36), two limbs (32, 34) which run parallel to one another and are spaced apart from one another and has, in a bending region (38), a bending portion (39) which connects the two limbs (32, 34) to one another, characterized in that a first axial end side (35) of the cooling plate (22, 24, 26) is sealed in a fluid-tight manner exclusively in the limb region (36), and a second axial end side (37) of the cooling plate (22, 24, 26) is sealed in a fluid-tight manner in the limb region (36) and in the bending region (38).Energy store according to Claim 1, characterized in that a coolant inlet (50) is provided on the first axial end side (35) and in the bending region (38), and the coolant outlet (52) is provided on an open end opposite the bending section (39).Energy store according to Claim 1 or 2, characterized in that the bending section (39) has a fully circular cross section.Energy store according to Claim 3, characterized in that the diameter (D) of the fully circular cross section is greater than the distance (A) between the two limbs (32, 34) which are spaced apart from one another.Energy store according to one of the preceding claims, characterized in that a coolant-permeable, flexible wire mesh (60) is arranged between the limbs (32, 34).Energy store according to Claim 5, characterized in that the coolant-permeable, flexible wire fabric (60) is designed in multiple layers, the different wire fabric layers (62, 64, 66) having different types of weave.Energy store according to one of Claims 1 to 4, characterized in that at least one perforated sheet (74, 76) and at least one flexible foam element (70, 72) are arranged between the limbs (32, 34).Energy store according to one of the preceding claims, characterized in that the bent sheet (30) has a wall thickness of 0.05 to 0.5 mm.Cooling plate for an energy store (12, 14, 16, 18) according to one of Claims 1 to 8.

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