Venting device for a motor vehicle battery

Abstract

Ventilation device (1) for a battery of a motor vehicle, with - an opening (10) for fluidically coupling an interior space (3) of a battery housing (2) with an exterior space (4) of the battery housing (2), - a membrane (9) which closes the opening (10) and which bursts at a predetermined pressure difference in the form of an overpressure in the interior (3), so that a pressure reduction is possible in the interior (3), wherein a metal sheet (13) is attached to an edge of the opening (10) on an inner side of the membrane, which faces the interior (3) when the venting device (1) is used as intended, characterized in that - at least one part (11) of the sheet (13) is designed to be moved against the membrane (9) by the excess pressure in the interior (3) in order to tear open the membrane (9), and - the part (11) of the sheet (13) has at least one predetermined bending point (12) which extends over the part (11) of the sheet (13) to be moved against the membrane (9).

Description

[0001] The invention relates to a venting device for a battery of a motor vehicle, comprising an opening for fluidically coupling an interior of a battery housing with an exterior of the battery housing and comprising a membrane which closes the opening and which bursts at a predetermined pressure difference in the form of an overpressure in the interior, so that a pressure reduction is possible in the interior, according to the preamble of claim 1.

[0002] A venting device of this type can be found in US 2013 / 0 309 529 A1. In this known venting device for a battery, which is arranged in the opening region of a battery housing between its interior and exterior, a sealing unit comprises a lower valve plate facing the interior and an outer valve plate located above this toward the outside, which form parts of an electrical conduction mechanism that responds when the internal pressure in the valve housing increases and, when there is excess pressure in the interior of the battery housing, opens an opening for gas to escape to the outside. A central section of the upper valve plate is surrounded by a notch, and a central section of the lower valve plate is surrounded by two circumferential notches.The central section of the upper valve plate and the central section of the lower valve plate are welded together, whereby the upper valve plate and the lower valve plate are electrically connected to each other. When the internal pressure in the battery housing increases, the lower valve plate tears open along one or both of the notches and forms a hole. At the same time, a downwardly curved section of the central section of the upper valve plate is pushed upward so that it protrudes upward. As a result, the electrical connection between the upper valve plate and the lower valve plate is interrupted. If the internal pressure continues to increase in this state, the notch of the upper valve plate tears open and releases a hole in the valve through which gas flows from the interior to the outside.

[0003] WO 2013 / 121 990 A1 discloses a venting device for a battery arranged in a housing opening and having a venting membrane on the side facing the interior of the battery housing and a protective cover for the membrane on the side facing the exterior. The protective cover is provided with retaining projections on its outer edge, which are fixed in retaining receptacles of the venting device, and a diametrically extending weakening notch is present on the outer side of the protective cover. When the internal pressure in the battery housing exceeds a threshold, the membrane bulges outward, and the protective cover bends outward along the weakening notch, whereby the retaining projections emerge from the retaining receptacles and the protective cover is removed.

[0004] In another venting device for a battery, shown in US 2008 / 0 182 159 A1, a connecting plate is arranged in an opening region of a battery housing toward the interior, and a membrane is arranged on this opening toward the exterior. The membrane is electrically and mechanically connected to the connecting plate by resistance welding at a central portion in a connection region. As the internal pressure in the battery housing increases, the membrane is released from the connecting plate in the connection region to interrupt the flow of current. As the internal pressure increases even further, the membrane tears open along notches provided therein to create an opening for gas to escape from the interior of the battery housing to the outside.

[0005] In batteries for motor vehicles, especially batteries containing lithium-ion cells, a porous membrane, for example made of sintered polytetrafluoroethylene, is usually built into the battery housing. In an intact initial state, this membrane enables pressure equalization within the battery housing during temperature fluctuations or when traveling at high altitudes. If, for example, the lithium-ion cells of the battery become very hot or ignite, a large amount of gas must be discharged in a short time. For this purpose, the membrane is usually designed to burst in a controlled manner so that the gas can escape unhindered from the interior of the battery. In order to transport the gas flow out of the vehicle interior in a controlled manner, an exhaust pipe can be attached to an opening in the battery housing where the porous membrane is located, using a connecting piece.

[0006] In the event of a sudden overpressure inside the battery or battery casing, the porous membrane expands. Typically, to burst this membrane, a spike is positioned in such a way that the excess pressure pushes the membrane against the spike and pierces it. This causes the membrane to burst, and the opening becomes completely permeable to the gas. The excess pressure can then dissipate quickly. However, the membrane is often only punctured and does not burst. In this case, the excess pressure inside the battery casing is released uncontrollably by the battery casing bursting open.

[0007] For example, EP 0 798 793 A2 discloses a battery with a safety valve. In the event of overpressure, a membrane is pressed against a flat cap with a plurality of blades that cut the membrane in the event of such overpressure.

[0008] It is the object of the present invention to increase the safety of batteries in motor vehicles, in particular to provide an improved venting device for a battery of a motor vehicle.

[0009] This object is achieved by the subject matter of the independent patent claim. Advantageous embodiments emerge from the dependent patent claims, the description, and the figures.

[0010] The invention relates to a venting device for a battery of a motor vehicle. The venting device comprises an opening for fluidically coupling an interior of a battery housing with an exterior of the battery housing. The venting device also comprises a membrane which closes the opening and bursts when a predetermined pressure difference in the form of an overpressure in the interior occurs, thus enabling pressure relief in the interior. In order to provide an improved venting device, a metal sheet is attached to an edge of the opening on the inside of the membrane. The inside of the membrane is the side of the membrane that faces the interior when the venting device is used as intended. Part of the metal sheet or the entire metal sheet is designed to be moved against the membrane by the overpressure in the event of an overpressure in the interior in order to tear the membrane open.The part of the sheet has at least one predetermined bending point that extends over the part of the sheet that is to be moved against the membrane. The predetermined bending point can comprise an embossing or a partial punching out of the sheet or the part of the sheet to be moved. This has the advantage that the part of the sheet that is to be moved against the membrane is easier to deform. As a result, the part of the sheet to be moved or the sheet itself can be deformed by the excess pressure that is to be released, thus better opening the opening. For example, the part of the sheet to be moved can be pushed closer to an edge of the opening by the excess pressure. As a result, a larger part of the opening is opened, so that the excess pressure can be released more quickly. The safety of a battery equipped with such a venting device is thus increased.

[0011] In an advantageous embodiment, the opening has a round cross-section and the part of the sheet metal that is to move against the membrane is also round or essentially round. The predetermined bending point is particularly advantageous in the case of a round opening and a round part of the sheet metal that is to move against the membrane, since, for example, a round sheet metal attached at one point can only be bent to a limited extent in a round opening without deformation, so that a large part of the opening is then still blocked by the transverse part of the sheet metal. However, if the part of the sheet metal that is to be moved has a predetermined bending point, it can deform and, due to the excess pressure, come into contact with a round side 3 on the inside of the opening. This enables maximum gas flow through the opening and accordingly improves the venting device.

[0012] In a further advantageous embodiment, the desired bending point extends from one edge of the part of the sheet to be moved to a diametrically opposite edge of the part of the sheet to be moved. In this case, the desired bending point is particularly straight. It can also run through a center point of the part of the sheet. This has the advantage that even with a single such desired bending point, the part of the opening blocked by the part of the sheet to be moved after the membrane has been cut through and the movement or deformation has taken place is greatly reduced. Thus, a major effect, i.e. a significant improvement in the venting device, is achieved with relatively little effort.

[0013] In a further advantageous embodiment, the part of the sheet to be moved is fastened in an area which is located at one end of the desired bending point, i.e. at an edge of the sheet or part of the sheet. In particular, the part of the sheet to be moved is only fastened in exactly one area. In an initial state in which there is no or only slight excess pressure, in which both the membrane is intact and the sheet is in its initial position on the inside of the membrane, the desired bending point can be arranged parallel to an opening cross-section of the opening and perpendicular to a movement axis around which the sheet is to be moved to tear open the membrane. This has the advantage that the part of the sheet to be moved is particularly easy to move.The arrangement of the fastening at the end of the desired bending point promotes a space-saving deformation of the part of the sheet to be moved according to the desired bending point, i.e., exposing a large part of the opening. The described orientation of the desired bending point offers further special advantages, such as particularly efficient positioning on the inside of the opening.

[0014] In a further embodiment, the part of the sheet to be moved is fastened in two areas, in particular only in exactly two areas. These are each located in particular at one end of the desired bending point. Preferably, the two areas are each located at a different end of the desired bending point. In the initial position of the sheet, the desired bending point can run parallel to the cross-section of the opening and to a movement axis predetermined by the two areas in which the part of the sheet to be moved is fastened. It has been shown that with the said arrangement, in the event of excess pressure, an end state can be achieved which releases a particularly large part of the opening cross-section, so that excess pressure can be reduced particularly well and quickly.

[0015] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, 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.

[0016] Showing: Fig. 1 is a schematic representation of an exemplary embodiment of a venting device for a battery in an initial state; Fig. 2 a schematic representation of the embodiment of Fig. 1 in a final state; Fig. 3 a first exemplary embodiment of a sheet with a predetermined bending point; and Fig. 4 shows a further exemplary embodiment of a sheet with a predetermined bending point.

[0017] Identical or functionally identical elements are provided with the same reference symbols in different figures.

[0018] Fig. 1 shows a schematic representation of an exemplary embodiment of a venting device for a battery in an initial state. The venting device 1 is arranged on a battery housing 2 and couples an interior space 3 of the battery housing 2 with an exterior space 4 thereof. In the example shown, the venting device 1 is designed from a first component 5, which in this case is plugged or screwed into the battery housing 2, and a second component 6, which here is plugged or screwed into the first component 5. In the embodiment shown, the second component 6 has a connecting piece 7, onto which an exhaust pipe 8 is plugged in order to discharge gas escaping from the interior space 3 in a controlled manner in the event of excess pressure.

[0019] In this example, a membrane 9 is held between the first and second components 5, 6, which closes an opening 10 of side 4 of the venting device 1. On the inner side of the membrane facing the interior 3, a metal sheet 13 is arranged, with a part 11 of the metal sheet 13 that can be moved by excess pressure in the interior 3. In the event of slight pressure fluctuations, such as those that occur when a motor vehicle travels at high altitudes, the porous membrane 9 in this case enables air to be exchanged between the interior 3 and the exterior 4 of the battery housing 2. The same applies to temperature fluctuations that occur during normal operation.However, if, for example, a sudden heating of cells, such as lithium-ion cells, suddenly creates a large overpressure in the interior 3 of the battery housing 2, i.e., one that exceeds a predetermined threshold, the movable, i.e., the part 11 to be moved of the sheet 13 is pressed against the membrane 9 and tears it open, for example, with a sharp edge. The corresponding final state with the part 11 to be moved in a corresponding end position is shown here in . Fig. 2 shown.

[0020] In Fig. 2 is a schematic representation of Fig. 1 shows a known embodiment of a venting device in the final state after an overpressure has occurred. The part 11 to be moved is here in comparison to the Fig. 1 and is no longer arranged parallel to an opening cross-section of the opening 10. The membrane 9 is accordingly torn open in this case. Through the torn membrane 9, a gas can then flow out of the interior 3 of the battery housing 2 past the bent part 11, so that excess pressure is reduced as quickly and as controlled as possible. Because the part 11 of the sheet 13 has a predetermined bending point 12, the part 11 of the sheet 13, in the final state of the venting device 1 in its final position, is closely applied to an inner side of the second component 6, so that a gas flow from the interior 3 can flow unhindered through the opening 10.

[0021] In Fig. 3 shows an exemplary embodiment of a sheet metal part. The sheet metal part 13 extends in the drawing plane as an xy-plane. In the embodiment shown, the sheet metal part 13 has an outer ring 14, which can be inserted, for example, between the Fig. 1 and Fig. 2 shown first and second components 5, 6 of the venting device 1 ( Fig. 1) and thus can be secured. The part 11 of the sheet metal 13 to be moved is attached to the outer ring 14 via two material bridges 15. Otherwise, there is no material connection between the outer ring 14 and the part 11 to be moved. The two material bridges 15 are located in an area of ​​the sheet metal 13 that is located at one end of the predetermined bending point 12 of the sheet metal 13.

[0022] In the example shown, the desired bending point runs straight in the xy plane through the part 11 of the sheet 13 to be moved and thus runs in the xy plane perpendicular to a movement axis B, which is defined by the two material bridges 15.

[0023] When pressure is applied to part 11 of sheet 13, part 11 initially moves around the movement axis B. From a certain deflection, the part 11 of sheet 13 to be moved is pressed against an inner side, for example of the exhaust pipe 8 ( Fig. 1) or the second component 6 ( Fig. 1) of the venting device 1 ( Fig. 1). Then, the part 11 of the sheet 13 to be moved will deform due to the predetermined bending point 12, in this case bending along the bending axis A. The part 11 of the sheet 13 to be moved will thus essentially completely open the opening 10 and, thanks to the predetermined bending point 12, ensure a rapid reduction of the excess pressure.

[0024] In Fig. 4 shows another exemplary embodiment of the sheet. As in Fig. 3, the sheet 13 extends in the plane of the drawing as an xy-plane and has an outer ring 14, to which the part 11 of the sheet 13 to be moved is held via, in this example, two material bridges 15. In contrast to Fig. 3, however, the material bridges 15 are arranged at diametrically opposite points of the outer ring 14 and thus also of the part 11 of the sheet 13 to be moved. The desired bending point 12, which is designed as a punched-out section in this case, extends straight through the center of the sheet 13 and the part 11 to be moved, from one material bridge 15 to the opposite material bridge 15. This has the consequence that the movement axis B and the bending axis A coincide and, in the example shown, both run parallel to the x-axis.

[0025] If an overpressure is now applied to the part 11 of the sheet 13 to be moved, the ends of the part 11 to be moved in the positive and negative y-direction move the most, but the points of the part 11 located on the bending and movement axes A, B do not. Accordingly, a kind of folding of the part 11 of the sheet 13 to be moved takes place, so that the opening 10 ( Fig. 1) is released to the greatest possible extent by the part 11 of the sheet 13 to be moved, since the sheet 13 or the part 11 of the sheet 13 covers the opening 10 ( Fig. 1) only blocked according to the thickness of its edges. List of reference symbols 1 venting device 2 battery housings 3 Interior 4 Outdoor space 5 Component 6 Component 7 connecting pieces 8 Exhaust pipe 9 Membran 10 Opening Part 11 12 Target bending point 13 sheet metal 14 outer ring 15 material bridges A articulated axis B Movement axis QUOTES CONTAINED IN THE DESCRIPTION

[0026] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0027] EP 0798793 A2

[0004]

Claims

[1] Ventilation device (1) for a battery of a motor vehicle, with - an opening (10) for fluidically coupling an interior space (3) of a battery housing (2) with an exterior space (4) of the battery housing (2), - a membrane (9) which closes the opening (10) and which bursts at a predetermined pressure difference in the form of an overpressure in the interior (3), so that a pressure reduction is possible in the interior (3), wherein a metal sheet (13) is attached to an edge of the opening (10) on an inner side of the membrane, which faces the interior (3) when the venting device (1) is used as intended, characterized by , that - at least one part (11) of the sheet (13) is designed to be moved against the membrane (9) by the excess pressure in the interior (3) in order to tear open the membrane (9), and - the part (11) of the sheet (13) has at least one predetermined bending point (12) which extends over the part (11) of the sheet (13) to be moved against the membrane (9). [2] Ventilation device (1) according to claim 1, characterized by , that - the opening (10) has a round cross-section and - the part (11) of the sheet (13) which moves against the membrane (9) is also round. [3] Ventilation device (1) according to one of the preceding claims, characterized by that the desired bending point (12) extends in a straight line from one edge of the part (11) of the sheet (13) to be moved to a diametrically opposite edge. [4] Ventilation device (1) according to one of the preceding claims, characterized by that the part (11) of the sheet (13) to be moved is fastened in an area which is located at one end of the desired bending point (12). [5] Ventilation device (1) according to one of claims 1 to 3, characterized by that the part (11) of the sheet (13) to be moved is fastened in two areas, each of which is located at a different end of the desired bending point (12).

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