Method for manufacturing a battery

Abstract

Method for manufacturing a battery (10) for an electric vehicle, comprising the steps: Providing a battery housing (12), Inserting at least one battery cell (21) into the battery housing (12), wherein an inner surface (15) of a housing wall (13) and the at least one battery cell (21) define a cavity (17), Filling the cavity (17) with a thermal conducting medium (40), wherein the thermal conducting medium (40) is introduced into the battery housing (12) and, during the filling process, progresses through the cavity (17) with a pouring front (41) until the cavity (17) is completely filled, characterized by the fact that the casting front (41) is detected by means of an ultrasonic sensor (52) which is arranged on an outer surface (19) of the housing wall (13) of the battery housing (12) and the ultrasonic waves emanating from the ultrasonic sensor (52) are introduced through the housing wall (13) into the cavity (17).

Description

[0001] The invention relates to a method for manufacturing a battery for an electric vehicle, comprising the steps of: providing a battery housing, inserting at least one battery cell into the battery housing, wherein an inner surface of a housing wall and the at least one battery cell define a cavity, filling the cavity with a thermal conducting medium, wherein the thermal conducting medium is introduced into the battery housing and, during the filling process, progresses through the cavity with a pouring front until the cavity is completely filled.

[0002] Such batteries, in particular traction batteries, are known from the prior art and serve to supply various consumers of an electric vehicle, in particular an electric drive unit, with electrical energy. The battery typically has a large number of battery cells, which are either arranged directly in a battery housing or are grouped into several battery modules, each of which has a battery module housing and is attached to a battery frame.

[0003] To dissipate heat from the battery, which can be generated during discharge or fast charging, the battery may, for example, have a cooling plate attached to an outer surface of the battery casing. This plate conducts the heat away from the casing. Typically, due to manufacturing and assembly processes, a cavity exists between the battery cells and an inner surface of the battery casing. This cavity results in relatively low heat transfer between the battery cells and the casing. To increase heat transfer between the battery cells and the casing, the cavity is filled with a thermally conductive medium, particularly a high-viscosity thermal paste, also known as a gap filler.

[0004] During the battery manufacturing process, the battery cells are inserted into the battery casing, and a cavity between the battery cells and an inner surface of the casing is filled with the thermal conductivity medium. To ensure sufficient heat transfer between the battery cells and the casing via the thermal conductivity medium, the gap should be completely filled with the medium. Therefore, the thermal conductivity medium is typically poured into the cavity on one side until it exits the casing through an outlet on the opposite side. At this point, the filling process is complete. A disadvantage of this filling method is that a separate outlet must be created, and complete filling of the cavity cannot be reliably guaranteed.For example, such a method for filling the thermal conducting medium is known in DE 10 2019 211 092 A1, wherein the cavity to be filled with the thermal conducting medium is located between a battery module housing and a cooling plate.

[0005] The object of the invention is therefore to provide a method for manufacturing a battery by which the cavity can be completely filled with the heat-conducting medium in a simple and reliable manner.

[0006] By detecting the casting front using an ultrasonic sensor, which is arranged on an outer surface of the battery housing wall, and by transmitting the ultrasonic waves emanating from the sensor through the housing wall into the cavity, the fill level of the cavity can be determined simply and cost-effectively, without requiring an outlet opening on the battery housing for the thermal conductivity. Furthermore, battery manufacturing is simplified because the thermal conductivity exiting the outlet opening does not need to be removed. In the inventive method, only the ultrasonic sensor needs to be positioned on the outside of the battery housing, either by being firmly mounted to the housing wall or by being pressed against it.

[0007] The operating principle of the ultrasonic sensor is such that ultrasonic waves, for example via a piezoelectric element, are introduced through the housing wall into the cavity. The ultrasonic waves introduced by the ultrasonic sensor or the piezoelectric element propagate as structure-borne sound within the housing wall and are thus introduced into the cavity or the heat-conducting medium. The ultrasonic sensor detects any reflection of the introduced ultrasonic waves. The reflection of the ultrasonic waves varies depending on the progress of the casting process.

[0008] This eliminates the need for additional measures to monitor the progress of the casting process and thus the fill level of the cavity with the heat-conducting medium. The ultrasonic sensor can be removed after the battery is manufactured.

[0009] Preferably, the ultrasonic waves are introduced into the cavity transversely to the flow direction of the heat transfer medium. In a preferred embodiment, the subsonic sensor is arranged at a predefined area, and the filling of the heat transfer medium is stopped when the area detected by the ultrasonic sensor is reached and the injection front is detected by the ultrasonic sensor. Ultrasonic waves are introduced into the housing wall transversely to the flow direction of the heat transfer medium and transmitted from the housing wall into the cavity or into the heat transfer medium. As long as air, i.e., no heat transfer medium, is present in the cavity in the area of ​​the ultrasonic sensor, the ultrasonic waves are strongly attenuated and reflected in a first way, so that the ultrasonic sensor does not transmit a measurable or a first electrical signal to an evaluation unit.As soon as the casting front reaches the area of ​​the ultrasonic sensor, the reflection of the ultrasonic waves detected by the sensor changes, thereby transmitting a second electrical signal from the sensor to the evaluation unit. Preferably, the ultrasonic sensor is located in an area that is reached last by the casting front.

[0010] Alternatively, only the excitation of the housing wall can be considered, whereby the reflection of the ultrasonic waves at the housing wall changes with the advancing casting front and increasing filling of the cavity, since this increases the damping of the housing wall with increasing filling of the cavity.

[0011] Preferably, the ultrasonic waves are introduced into the cavity in the flow direction of the heat transfer medium. Specifically, the ultrasonic waves are introduced into the housing wall in the flow direction of the heat transfer medium and then directed from the housing wall into the heat transfer medium in the flow direction of the heat transfer medium. The ultrasonic waves are reflected at the interface between the heat transfer medium and air, i.e., at the casting front, and this reflection is detected by the ultrasonic sensor. The travel time of the ultrasonic waves, i.e., the time between the emission of the ultrasonic waves and the reception of the reflections, allows the position of the casting front and thus the fill level of the cavity with the heat transfer medium to be determined. This enables not only the detection of the casting front at a predefined location but also the monitoring of its actual progress during the inflow process.In a preferred embodiment, the casting front is continuously monitored during the inflow process. This allows the fill level of the cavity containing the heat transfer medium to be reliably, simply, and cost-effectively monitored.

[0012] Preferably, the thermal conductivity medium is a viscous thermal paste, whereby a relatively high heat transfer can be achieved through the viscous thermal paste.

[0013] This method allows the fill level of the cavity to be detected in a simple and cost-effective way using the heat-conducting medium.

[0014] Two embodiments of the invention are explained in more detail with reference to the drawings. Fig. Figure 1 shows an exploded view of a battery. Fig. 2 indicates the battery is off Fig. 1 in cross-section, Fig. 3 shows the battery from the Fig. 1 and Fig. 2 during a filling process of a heat-conducting medium after a first execution, and Fig. 4 shows the battery from the Fig. 1 and Fig. 2 during a filling process of a heat-conducting medium after a second execution.

[0015] Fig. 1 and Fig. Figure 2 shows a battery 10 and a battery module of a battery 10, respectively. The battery 10 has a battery housing 12, which essentially consists of a base body 14 and two housing covers 16, 18. The base body 14 is made of aluminum and is designed as an extruded profile, with the base body 14 having two open ends. A first end is sealed fluid-tight by a first cover 16. A second end is sealed fluid-tight by a second cover 18, with a seal (not shown in the figures) arranged between each of the covers 16, 18 and the base body 14. Several battery stacks 20, 22, 24, 26 are arranged inside the battery housing 12, each battery stack 20, 22, 24, 26 comprising a plurality of interconnected battery cells 21.

[0016] During the assembly of the battery 10 or the battery module, the battery stacks 20, 22, 24, 26 are inserted into the battery housing 12 through their open ends. Two battery stacks 20, 22 are inserted through the first end, and two battery stacks 24, 26 through the second end. The battery stacks 20, 22, 24, 26 are then connected to each other. In a subsequent step, the ends are sealed fluid-tight by the covers 16, 18. The battery housing 12 is designed such that, when the battery stacks 20, 22, 24, 26 are assembled, there is the smallest possible gap (i.e., a cavity 17) between the battery cell stacks 20, 22, 24, 26 and an inner surface 15 of a housing wall 13 of the battery housing 12.

[0017] During operation of the battery 10, i.e., during charging and discharging of the battery 10 or the battery cells 21, the battery cells 21 heat up. The heat generated during charging and discharging must be dissipated. For this purpose, a cooling plate 30 is provided, which rests against an outer surface 19 of the housing wall 13. The cooling plate 30 is coolant-fluidized and has a coolant channel 36, a coolant inlet 32, and a coolant outlet 34, wherein the coolant inlet 32 ​​and the coolant outlet 34 are fluidically connected to a cooling circuit (not shown in the figures) with a pump and a radiator.

[0018] The cooling plate 30 allows the heat generated during charging and discharging of the battery cells 21 to be dissipated from the battery 10, whereby the heat is first transferred from the battery cells 21 to the battery housing 12, in particular to the housing wall 13, and from the housing wall 13 to the cooling plate 30, i.e. to the circulating coolant.

[0019] To increase heat transfer between the battery cells 21 and the housing wall 13, a thermal conductivity medium 40 is provided in the cavity 17, i.e., in the gap between the top surface of the battery cells 21 and the inner surface 15 of the housing wall 13. The thermal conductivity medium 40 is, in particular, a viscous thermal paste, also called a gap filler.

[0020] The Fig. 3 and Fig. Figure 4 shows the battery 10 during the filling process of the heat transfer medium 40 into the cavity 17. The second cover 18 has a filling opening 23. The heat transfer element 40 is filled into the cavity by an injector 38, which is attached to the filling opening 23, so that the heat transfer medium 40 flows into the cavity 17 via the filling opening 23. The cavity 17 is filled in the direction of flow X, whereby a pouring front 41 advances in the direction of flow X during the filling process until the cavity 17 is completely filled and the pouring front 41 reaches the first cover 16.

[0021] Because the battery housing 12 is completely closed, it is not visually apparent when the cavity 17 is completely filled and the filling process must be stopped. According to the invention, the fill level of the cavity 17 with the heat-conducting medium 40 and the pouring front 41 are detected by a detection device 50 arranged outside the battery housing 12. The detection device 50 comprises an ultrasonic sensor 52 and an evaluation unit 54, which are interconnected by signal.

[0022] Fig. Figure 3 shows a first arrangement of the ultrasonic sensor 52. The ultrasonic sensor 52 rests against the outer surface 19 of the housing wall 13 and is positioned in the flow direction X directly adjacent to the first cover 16, i.e., at the end opposite the filling opening 23. The ultrasonic sensor 52 is oriented transversely to the flow direction X. This arrangement detects complete filling of the cavity 17 by the heat-conducting medium 40, since the pouring front 41, due to the flow direction X, only reaches the first cover 16 and thus the area detected by the ultrasonic sensor 52 at the very end. The ultrasonic sensor 52, in particular via a piezoelectric element, transmits ultrasonic waves through the housing wall 13 into the cavity 17. The ultrasonic waves transmitted by the ultrasonic sensor 52 propagate as structure-borne sound in the housing wall 13 and are thereby transmitted into the cavity 17.The ultrasonic sensor 52 detects the reflection of the introduced ultrasonic waves, the reflection of which varies depending on the progress of the casting front 41. As long as there is air, i.e., no thermal conductivity, in the cavity 17 in the area of ​​the ultrasonic sensor 52, the ultrasonic waves are strongly attenuated, so that the ultrasonic sensor 52 does not transmit a measurable, or first, electrical signal to the evaluation unit 54. As soon as the casting front 41 reaches the area of ​​the ultrasonic sensor 52, the reflection of the ultrasonic waves detected by the ultrasonic sensor 52 changes, thereby transmitting a second electrical signal from the ultrasonic sensor 52 to the evaluation unit 54, indicating that the cavity 17 is completely filled with the thermal conductivity 40.

[0023] The Fig. Figure 4 shows a second arrangement of the ultrasonic sensor 52, wherein the ultrasonic sensor 52 is oriented in the flow direction X of the heat-conducting medium 40 and is arranged on an outer surface of the second cover 18, the cover 18 being part of the housing wall 13 of the battery housing 12. The ultrasonic sensor 52 is, as in the first arrangement according to Fig.3, connected to the evaluation unit 54 via a signal. Here, the ultrasonic waves are introduced by the ultrasonic sensor 52 in the flow direction X of the heat-conducting medium 40 into the second cover 18 and from the second cover 18 into the heat-conducting medium 40 in the flow direction X of the heat-conducting medium 40. The introduced ultrasonic waves are reflected at the interface between the heat-conducting medium 40 and air, i.e., at the casting front 41, with the reflection being detected by the ultrasonic sensor 52. From the transit time of the ultrasonic waves, i.e., the time between the introduction of the ultrasonic waves and the reception of the reflection of the introduced ultrasonic waves, the position of the casting front 41 and thus the fill level of the cavity 17 with the heat-conducting medium 40 can be determined.This allows not only the detection of the pouring front 41 at a predefined point, but also the recording of the actual progress of the pouring front 41 during the filling process. Preferably, the pouring front 41 is continuously recorded during the filling process.

[0024] By such a method, the fill level of the cavity 17 through the heat-conducting medium 40 can be detected in a simple and cost-effective manner.

[0025] Other constructive embodiments besides those described are also possible, which fall within the scope of protection of the main claim.

Claims

[1] Method for manufacturing a battery (10) for an electric vehicle, comprising the steps: Providing a battery housing (12), Inserting at least one battery cell (21) into the battery housing (12), wherein an inner surface (15) of a housing wall (13) and the at least one battery cell (21) define a cavity (17), Filling the cavity (17) with a thermal conducting medium (40), wherein the thermal conducting medium (40) is introduced into the battery housing (12) and, during the filling process, progresses through the cavity (17) with a pouring front (41) until the cavity (17) is completely filled, characterized by , that the casting front (41) is detected by means of an ultrasonic sensor (52) which is arranged on an outer surface (19) of the housing wall (13) of the battery housing (12) and the ultrasonic waves emanating from the ultrasonic sensor (52) are introduced through the housing wall (13) into the cavity (17). [2] Method according to claim 1, characterized by , that the ultrasound waves are introduced into the cavity (17) perpendicular to the flow direction (X) of the heat conducting medium (40). [3] Method according to claim 2, characterized by , that the subsonic sensor (52) is arranged in a predefined area, wherein the filling of the heat-conducting medium (40) is terminated when the area detected by the ultrasonic sensor (52) is reached and when the casting front (41) is detected by the ultrasonic sensor (52). [4] Method according to claim 1, characterized by, that the ultrasound waves are introduced into the cavity (17) in the flow direction (X) of the heat conducting medium (40). [5] Method according to claim 4, characterized by , that the pouring front (41) is continuously captured during the filling process. [6] Method according to any one of the preceding claims, characterized by , that the thermal conductivity medium (40) is a viscous thermal paste.

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