Ventilator for battery

Abstract

A battery system (10) comprising a battery casing having a vent opening (18) and a ventilation device (12, 12', 12"), wherein the ventilation device (12, 12', 12") is adapted to ensure a pressure balance between the inside of the battery casing (14) and the environment of the battery casing (14) during normal operating conditions of the battery system, and a second membrane (26, 26', 26") adapted to ensure emergency gas venting in the event of a technical defect within the battery system (10).

Description

Technical Field

[0001] The present invention relates to a ventilation device for a battery, and more particularly to a gas venting device for a casing of a battery sub-module, a battery module or a battery system, which is configured to be integrated with the casing. More specifically, the present invention relates to a device for equalizing the internal pressure of a housing, particularly an automotive battery housing, with the ambient pressure of the housing. Further, the present invention relates to a battery system including such a ventilation device.

Background Art

[0002] In a battery system such as those used in automobiles, particularly in the housing (or casing) of a high-voltage battery system, changes in temperature and pressure result in a pressure difference between the housing of the battery system and the environment.

[0003] In normal operation, these pressure differences must be balanced. To provide thermal control of the enclosed components, a thermal management system may be used to efficiently release, exhaust, and / or dissipate the heat generated within the casing. If such a thermal management system is omitted, or if the heat discharge from the casing is not sufficiently carried out, abnormal reactions may occur therein due to the increase in internal temperature.

[0004] Furthermore, particularly in a large-capacity high-voltage battery system, there is a risk that one or more batteries in the battery may fail due to overload or other technical defects. As a result, a large amount of harmful gases may be generated, and these harmful gases must be discharged in a controlled manner. Therefore, emergency gas venting in the case of a technical defect in the battery must be provided.

[0005] Two different devices can be used for both functions, i.e., pressure compensation in normal operation and emergency gas venting in the case of a technical defect. However, the two devices increase the weight and maintenance of the assembled product.

[0006] Document DE102017214754 discloses an apparatus that combines both functions. This apparatus comprises a pressure equalizing element. This pressure equalizing element has an element body and a membrane disposed on the element body. This apparatus comprises a connecting element for hermetically connecting this pressure compensation element to a housing. When an internal pressure lower than the limiting pressure exists, the element body rests on the connecting element while maintaining airtightness. Moreover, the element body opens an aperture for gas exchange when an internal pressure higher than the limiting pressure exists.

[0007] U.S. Patent Application Publication No. 2021396324 discloses a ventilation component attached to a housing at the ventilation opening of the housing, the ventilation component comprising a gas permeable membrane, a ventilation valve including an elastomer and opened and closed by elastic deformation of the elastomer, and a structural member supporting the gas permeable membrane and the ventilation valve. This structural member is disposed between the housing of the ventilation component and a cap.

[0008] EP3617570 is directed to a ventilation unit comprising a first ventilation body that allows gas to flow from the inside of the housing to the outside of the housing when the internal pressure is higher than the external pressure, and a second ventilation body. The first and second ventilation bodies are connected to a structural support disposed in the cavity of the housing of the ventilation unit.

[0009] U.S. Patent Application Publication No. 2018292020 discloses a pressure compensation device for a housing comprising a gas opening covered by a gas permeable membrane and a pressure relief valve. The gas permeable membrane and the pressure relief valve are both disposed in a lattice-shaped cage. This cage consists of an inner half 20 forming the housing and an outer half 21 forming a cap. The gas permeable membrane and the pressure relief valve are both connected to the housing.

[0010] Such apparatuses are adapted to handle the pressure compensation function by the element body and the emergency gas venting by the membrane. However, there is still a need to improve such apparatuses.

SUMMARY OF THE INVENTION

[0011] The object of the present invention is to provide a gas venting device that realizes both functions (emergency gas venting in case of damage and differential pressure compensation in normal operating environments), is robust, easy to manufacture, install, and maintain, and has as few components as possible. A further object of the present invention is to provide a gas venting device that exhibits satisfactory performance with respect to humidity management and service life.

[0012] Accordingly, the present disclosure is directed to a ventilation device for a battery comprising a battery casing having a vent opening as set forth in claim 1, and a battery system as set forth in claim 14.

[0013] More specifically, this ventilation device comprises a housing, a cap cooperating with the housing, a cap extending over the housing, and a first membrane adapted to ensure pressure equilibrium between the inside of the battery system and the environment of the battery system during normal operating conditions of the battery system. This device further comprises a second membrane adapted to ensure emergency gas venting in case of a technical defect within the battery system, and the cap comprises a first segment connected to the first membrane and a second segment connected to the second membrane. Accordingly, the cap is connected to both membranes, which makes this valve easy to install and maintain. Thus, this cap has two functions: protecting the inside of the housing and assembling the membranes.

[0014] In one embodiment, the first membrane is a breathable membrane. Accordingly, this membrane can easily ensure pressure equilibrium in normal environments.

[0015] In one embodiment, the cap is ultrasonically welded to the first membrane. Ultrasonic welding ensures a robust fixation and is easy to implement. Accordingly, this welding is airtight.

[0016] In one embodiment, the second membrane is press-fitted between the housing and the cap. The press-fitting has high connection strength and vibration resistance. Assembly can be automated, with high assembly reliability and consistent assembly. Moreover, such a connection has the ability to withstand thermal expansion during the thermal cycle. In one embodiment, the second membrane is movable between an open position and a closed position, and when the excessive pressure disappears, the second membrane is automatically returned to its closed position.

[0017] In one embodiment, the cap is substantially circular and includes a central portion adapted to be covered by the first membrane and an outer annular portion adapted to be partially covered by the second membrane. The cap is of an integral type, but guarantees different functions according to the portions connected to the first membrane or the second membrane. In one embodiment, the first membrane covers the central portion and the outer annular portion. In other words, in one embodiment, the first membrane extends over the second membrane.

[0018] In one embodiment, the central portion includes a plurality of ventilation holes. Those ventilation holes face the first membrane to ensure proper pressure balance.

[0019] In one embodiment, the second outer annular portion includes a plurality of regularly and dispersedly arranged openings. Those openings are curved. Those openings face the second membrane.

[0020] In one embodiment, the cap includes a rim that at least partially covers the outer peripheral portion of the housing. Thus, the cap is a protective cap and can surround the housing.

[0021] In one embodiment, the central portion includes an edge that extends longitudinally along the vertical axis from the inner surface, and the edge defines one or more cavities. This edge forms a reinforcing structure for enhancing the rigidity of the device.

[0022] In one embodiment, the first membrane is fixed to this edge. This edge forms a surface, and the first membrane can be easily fixed to this surface.

[0023] In one embodiment, the ventilation device further comprises a sealing ring extending around the housing. This sealing ring is adapted to seal and fix the ventilation device to the casing.

[0024] In one embodiment, the second membrane is annular. In one embodiment, the first membrane has the shape of a disc. In one embodiment, the first membrane extends substantially to the center of the second membrane. Thus, it is arranged compactly.

[0025] In one embodiment, the first membrane is made of polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) material. Such materials have a high strength-to-weight ratio and water resistance.

[0026] In one embodiment, the second membrane is made of an elastomer or thermoplastic elastomer material. Such materials can be customized in size, shape or flexibility.

[0027] In one embodiment, the lid and / or the cap and / or the housing are made of a metallic material. Thus, the lid and / or the cap and / or the housing are excellent in resistance to high temperatures.

[0028] In one embodiment, the lid is adapted to be automatically released from the cap in case of overpressure. In other words, the fixing of the lid to the cap is releasable.

[0029] In one embodiment, the second membrane is adapted to move from an open position to a closed position, so that gas can flow out of the battery but subsequently cannot return to the battery housing. Since some of these gases are highly flammable, in some cases this helps to prevent thermal runaway events. Thus, the second membrane is irreversible. The automatic movement from the open position to the closed position can occur up to a certain temperature.

[0030] The present invention also targets a battery system including a battery casing having a vent opening and a ventilation device, where the ventilation device (more specifically, the housing of the ventilation device) is inserted into the vent opening.

[0031] Next, with reference to the accompanying drawings, specific embodiments of the present invention will be described as mere examples.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0033] In different figures, the same reference numerals indicate the same or similar elements.

[0034] FIG. 1 shows a schematic perspective view of a battery system 10 including a ventilation device 12. The shape and arrangement of the battery system 10 in FIG. 1 are for illustration purposes. The battery system 10 includes a casing 14. In the context of this application, the battery system 10 should be understood as one of a battery sub-module, a battery module, and a battery pack. Thus, the battery casing 14 should be understood as the casing of one of a battery sub-module, a battery module, and a battery system. The casing 14 may be made of a metal alloy and / or a plastic material. The battery system 10 may include a plurality of attachment portions 16 for attaching the battery system to a fixed structure, such as an electric vehicle. The casing 14 includes a vent opening 18. More specifically, the casing may include two or three vent openings. In some cases, four or more vent openings may be provided.

[0035] The vent opening 18 is adapted to receive the ventilation devices 12, 12’, 12”. The ventilation devices 12, 12’, 12” can be connected to the vent opening 18 using a bayonet mount.

[0036] A first embodiment of the ventilation device 12 is shown in FIGS. 2 and 3. The ventilation device 12 may be configured to be attached to the casing 14 to cover and / or overlap the vent opening. Alternatively, the ventilation device 12 may be configured to be inserted into the vent opening 18.

[0037] As shown in FIG. 2, the ventilation device 12 includes a housing 20, a cap 22, a first membrane 24, and a second membrane 26. The cap 22 includes a first segment connected to the first membrane 24 and a second segment connected to the second membrane 26.

[0038] When the ventilation device 12 is configured to be inserted into the vent opening 18, the housing 20 of the ventilation device 12 cooperates with the vent opening 18. The housing 20 has, for example, a substantially annular shape around a longitudinal axis. However, instead, the shape of the housing 20 may be rectangular or oval. In fact, the shape of the housing 20 is complementary to the shape of the vent opening 18. The housing 20 includes, for example, a first flange 28 (see, e.g., FIG. 3) that defines the boundary of the central opening 30, and a second flange 32 that extends radially outward from the first flange 28. A housing bending portion (housing elbow) 34 is disposed between the first and second flanges 28, 32, and the housing bending portion (housing elbow) 34 connects the flanges 28, 32. The second flange 32 may have a substantially flat surface, and the first flange 28 may be inclined. The first flange 28 has, for example, a smaller diameter with respect to the second flange. The first flange 28 may include a first flange opening 36. The housing 20 is adapted to cooperate with the cap 22 when the ventilation device 12 is mounted.

[0039] The cap 22 is, for example, a protective cap. The cap 22 has an outer surface 38 and an inner surface 40. The inner surface 38 faces the housing 20, and the outer surface 38 is on the opposite side of the inner surface 36. The cap 22 has a substantially circular shape. The cap has a first portion 42 that forms a central portion and a second portion 44 disposed around the first portion. The cap 22 is, for example, integrally formed. The first position 42 has an edge 46 that extends vertically from the inner surface 40 to define the boundary of the cavity 48. For example, the edge 46 defines the boundary of a cavity 48 having a circular cross-section. The bottom 50 of the cavity 48 has at least one ventilation hole 52, for example, a plurality of ventilation holes 52. A support structure 54 may extend between the edges 46 so as to define the boundaries of a plurality of secondary cavities and to make the cap 22 more rigid. The second portion 44 of the cap is an outer annular portion. The edge 46 is connected to the second portion 44 by a cap bending portion 56 (cap elbow) in such a manner that a groove 58 separating the first portion 42 and the second portion 44 is formed on the outer surface 38 of the cap 22. The second portion 44 may have a plurality of regularly and dispersedly arranged openings 60, for example, a plurality of regularly and dispersedly arranged openings 60 around the longitudinal axis X. The cap 22 further has a rim 62 extending from the inner surface 40 at the outer peripheral portion of the cap 22. The rim 62 is adapted to at least partially cover the outer peripheral portion of the housing 20. More specifically, as shown in FIG. 3, the rim 62 may vertically cover the second flange 32 of the housing. The cap substantially covers the housing or extends over the housing and thus protects the housing.

[0040] The first membrane 24 is a breathable membrane. The first membrane 24 is made of, for example, polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) material. The first membrane 24 has a disc shape.

[0041] The second membrane 26 has a ring shape. The second membrane is made of, for example, an elastomer or a thermoplastic elastomer.

[0042] The first membrane 24 is connected to the first part 42 of the cap 22. The first part 42 forms a first segment. More specifically, the first membrane 24 is hermetically ultrasonically welded to the cap 22. For example, the first membrane 24 is welded to the edge 46 of the cap 22 in such a manner that the first membrane 24 covers the cavity 48 (or all sub-cavities). The edge 46 has an edge surface that is substantially parallel to the inner surface 40 of the cap, and the first membrane 24 is welded to this edge surface. Thus, the first membrane 24 is at a non-zero distance from the ventilation hole 52 and faces the ventilation hole 52. The diameter of the first membrane 24 substantially coincides with the diameter of the edge 46 that defines the boundary of the cavity 48. Thus, the first membrane 24 completely covers the cavity 48. As described above, a support structure 54 may be disposed within the cavity. The support structure 54 may further support the first membrane 24. In some cases, the first membrane 24 may be welded to the support structure 54.

[0043] The second membrane 26 is connected to the second part 44 of the cap. The second part forms a second segment. The second membrane 26 has an annular shape such that in the state where the ventilation device 12 is mounted, the second membrane 26 surrounds the edge 46. More specifically, the surface defining the inner circle of the annular second membrane faces the edge 46 and is disposed under the cap bending portion 56. The second membrane is press-fitted between the cap 22 and the housing 20. More specifically, the cap bending portion 56 has a cap edge 64, the first flange 28 of the housing has a housing edge 66, and in the state where the ventilation device is mounted, the housing edge 66 faces the cap edge 64. The second membrane 26 is press-fitted between the cap edge 64 and the housing edge 66. For example, a segment of the second membrane near the inner circle of the annular second membrane is press-fitted between the edges 64 and 66. The outer peripheral portion 68 of the second membrane forms a free end, and this free end is a free end in such a manner that the second membrane 26 (more specifically, the segment near the free end) can move freely with respect to the cap and the housing. This free end or outer peripheral portion 68 is movable between a resting position or a closed position on the surface of the housing 20 and an open position, for example, an open position for ensuring emergency gas venting in the case of a technical defect in the battery system 10. The outer peripheral portion 68 rests on the first flange 28. More specifically, the outer peripheral portion 68 rests on the curved portion of the first flange. In other words, the first flange 68 has a raised portion with a specific radius of curvature, and the outer peripheral portion of the membrane contacts and rests on this raised portion. The second membrane may have a surface with low roughness. More specifically, the average roughness depth Rz is important. The average roughness depth Rz is defined by the average value of the individual roughness depths of five consecutive individual measurement intervals of the roughness profile. For example, the surface of the second membrane has a porosity of less than 0.6 μm, particularly less than 0.4 μm. The small roughness (or porosity) of this surface makes it possible to enhance the performance of the second membrane, and in particular, to reduce the amount of moisture passing through the membrane when the second membrane is in the closed position.

[0044] The second membrane 26 faces, for example, the first flange opening 36. The movable portion of the second membrane faces the second portion 44 of the cap, and more specifically, may at least partially face a plurality of openings 60 in the second portion. The outer peripheral portion 68 of the second membrane is closer to the first membrane than the inner peripheral portion of the second membrane. In other words, the second membrane is not flat, but forms an inclined or curved shape, and when measured along the vertical axis, the outer peripheral portion of the second membrane is closer to the outer portion 38 of the cap than the inner peripheral portion of the second membrane. When viewed from above the ventilation device (or from the outer portion side of the cap), the second membrane 26 may have a concave shape. The shape of the second membrane enables reducing the amount of moisture passing through the membrane when the second membrane is in the closed position.

[0045] The second membrane can automatically move from the open position to the closed position up to a certain temperature, so that gas can flow out of the battery, but subsequently cannot return into the battery housing. In other words, in order to enable discharging the gas inside the battery housing or the battery casing to the outside, the second membrane can move from the closed position (where the free end of the second membrane is not in contact with the housing 20) to the open position (simultaneously the free end moves away from the housing 20, enabling discharging the gas from the inside to the outside of the battery casing). Then, after the gas is released, when the pressure inside the battery casing drops below a certain value, the second membrane can automatically return to its closed position. Since some of these gases are highly flammable, in some cases, this helps to prevent thermal runaway events. Therefore, the second membrane is reversible. The second membrane 26 forms a diaphragm that is fixed on only one side and is actuated by fluid pressure. The second membrane opens when excessive pressure is applied inside the battery casing and closes when the excessive pressure disappears.

[0046] When the ventilation device 12 is configured to be inserted particularly into the vent opening 18, it further comprises a sealing ring 70 extending around the housing 20. For example, the housing 20 comprises, on its outer surface, a recess 72 adapted to receive the sealing ring 70. The sealing ring 70 is made of, for example, an elastomer or a thermoplastic elastomer. The sealing ring 70 is, for example, an O-ring. The sealing ring 70 is arranged under the second flange. The sealing ring 70 has a plane 74 substantially parallel to the second flange and a side surface 76 perpendicular to this plane. The sealing ring 70 is a sealing ring in such a manner that the ventilation device 12 may be connected to the casing 14 in an airtight and watertight manner. The vent opening 16 has a shape complementary to the shape of the housing 20 to which the sealing ring 70 is attached.

[0047] In the state where the ventilation device 12 is mounted, the cap 22 cooperates with the housing 20, for example, by snap-fit connection. For example, as shown in FIG. 3, the inner surface of the rim 62 is snap-fitted to a portion of the housing 20. More specifically, the rim is snap-fitted to the side surface of the second flange 32 of the housing 20. In other embodiments, the cap and the housing may be press-fitted, or glued, or welded. The second membrane 26 is sandwiched between the cap 22 and the housing 20 as described above, and the first membrane 24 is fixed only to the cap. The inner diameter of the second membrane 26 is larger than the diameter of the first membrane 24.

[0048] The cap 22, the housing 20, the first membrane 22, and the second membrane 24 are mounted together to form a ventilation device 12. For example, all of these components have a substantially circular outer shape, and in the state where the ventilation device is mounted, their central axes (which coincide with the longitudinal axis X) coincide. The ventilation device 12 is mounted in the vent opening of the battery system in such a manner that the first membrane faces the inside of the casing and the outer surface of the cap extends outward. The second membrane is disposed between the cap and the housing and moves to an open position for emergency gas venting in the case of a technical defect. As shown in FIG. 3, the first membrane may be substantially under the housing, and the second membrane is disposed between the housing and the cap.

[0049] A second embodiment of the ventilation device 12' according to the present invention is shown in FIGS. 4, 5, and 6. As will be described in more detail later, the main difference between the first embodiment disclosed in FIGS. 2 and 3 and the second embodiment shown in FIGS. 4 to 6 is the size and position of the first membrane 24'. While the first membrane 24 of the first embodiment is disposed at the bottom of the cap, the first membrane 24' of the second embodiment is disposed on the upper side or the outer surface 38' of the cap, and thus, the surface area of the first membrane can be increased without increasing the size of the ventilation device. By increasing the surface area of the first membrane 24', the air flow rate can also be increased, and thus the performance of the ventilation device can be enhanced.

[0050] As shown in FIGS. 4 to 6, the ventilation device 12' includes a housing 20', a cap 22', a first membrane 24', and a second membrane 26'. The ventilation device 12' further includes a lid 78.

[0051] The housing 20' of the ventilation device 12' is adapted to cooperate with the vent opening 18. The housing 20', for example, has a substantially annular shape around a longitudinal axis. However, instead, the shape of the housing 20' may be rectangular or oval. In fact, the shape of the housing 20' is complementary to the shape of the vent opening 18. The housing 20' is, for example, similar to the housing 20' of the first embodiment. The housing 20' includes a first flange 28' that defines the boundary of the central opening 30', and a second flange 32' that extends radially outward from the first flange 28'. A housing bending portion (housing elbow) 34' is disposed between the first and second flanges 28', 32', and the housing bending portion (housing elbow) 34' connects the flanges 28', 32'. The second flange 32' may have a substantially flat surface, and the first flange 28' may be inclined. The first flange 28' has, for example, a smaller diameter with respect to the second flange 32'. The first flange 28' may include a first flange opening 36'. The housing 20' is adapted to cooperate with the cap 22' when the ventilation device 12' is mounted.

[0052] The cap 22' has an outer surface 38' and an inner surface 40'. The inner surface 38' faces the housing 20', and the outer surface 38' is on the opposite side of the inner surface 36'. The cap 22' has a substantially circular shape. The cap 22' has a first part that forms a central portion and a second part disposed around the first part. The cap 22' is, for example, of one-piece construction. The first part may include an edge 46' that extends vertically from the inner surface 40 to define the boundary of the cavity 48. For example, the edge 46' may define the boundary of a cavity having a circular cross-section. The cap 22' includes a plurality of ventilation holes 52. These ventilation holes are provided, for example, on the first part. The second part of the cap 22' is an outer annular part. The second part may include a plurality of regularly spaced-apart openings, for example, a plurality of regularly spaced-apart openings around the longitudinal axis X. Alternatively, these openings may be irregularly spaced-apart. The cap 22' further includes a rim 62' that extends from the inner surface at the outer peripheral portion of the cap 22'. The rim 62' is adapted to at least partially cover the outer peripheral portion of the housing 20'. More specifically, as shown in FIG. 5, the rim 62' may vertically cover the second flange 32' of the housing. The cap substantially covers or extends over the housing and thus protects the housing.

[0053] A slot or notch 80 may be provided between the rim 62’ and the second portion to cooperate with a tang or latch 82 provided on the lid 78. The lid 78 cooperates with the cap 22’ by snap fit connection. Alternatively, the lid may be adhered, welded, or press-fitted to the cap 22’. The lid 78 is provided with a plurality of holes to allow air to flow through the first membrane 24’. The plurality of holes are arranged, for example, at the center of the lid 78 as shown in FIG. 4. However, alternatively, the plurality of holes may be distributed over the entire surface of the lid 78. In another alternative embodiment, the lid may be made of a porous material. In the case of overpressure, the lid may be automatically released or discharged from the cap. The snap fit connection between the lid 78 and the cap 22’ is a connection in such a manner that the connection is releasable in the case of overpressure. The dimensions of this fit may be such that the lid is released from a certain predetermined pressure. The lid may be made of a plastic or metal material. Similarly, the housing and / or the cap may also be made of a plastic material or a metal material.

[0054] The first membrane 24' is connected to the first segment of the cap. More specifically, the first membrane 24' is disposed between the lid and the cap. More specifically, the first membrane 24' can be fixed to the cap by ultrasonic welding, or the first membrane 24' can be fixed to the cap 22' by a press-fit connection between the cap 22' and the lid 78. The first membrane extends over the upper side of the cap 22'. The first membrane extends over the outer portion 38' of the cap. The first membrane 24' extends over the entire surface area of the central portion and the outer annular portion. The upper side of the cap 224 is the surface on the opposite side of the lower side of the cap 22'. The lower side of the cap 22' is adapted to face the vent opening. More specifically, the first membrane 24' may extend to the rim 62', or may substantially extend to the rim 62'. The rim 62' forms a recess for disposing the first membrane 24' therein. The notch 80 remains open to connect the lid 78. Thus, the first membrane 24' faces the ventilation hole. The first membrane also faces a plurality of openings 60', and the plurality of openings 60' can function as ventilation holes. The diameter of the first membrane 24' substantially coincides with the diameter of the second portion 44'. The first membrane 24' is a breathable membrane. The first membrane 24' is made of, for example, polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) material. The first membrane 24 has a disc shape.

[0055] The cap 22' cooperates with the housing 20' by, for example, a snap-fit connection. The cap 22' extends over the entire housing to protect the housing. In other words, the cap covers the housing. For example, as shown in FIG. 5, the inner surface of the rim 62' is snap-fitted to a portion of the housing 20'. More specifically, the rim is snap-fitted to the side surface of the second flange 32' of the housing 20'. In other embodiments, the cap and the housing may be press-fitted or adhered or welded.

[0056] The second membrane 26’ has an annular shape. The second membrane is made of, for example, an elastomer or a thermoplastic elastomer. The second membrane 26’ is connected to a second segment formed by the second part of the cap. The second membrane 26’ has an annular shape in such a manner that in the state where the ventilation device 12’ is mounted, the second membrane 26’ surrounds the edge 46’. More specifically, the surface defining the inner circle of the annular second membrane faces the edge 46’. The second membrane is press-fitted between the cap 22’ and the edge of the housing 20’. Thus, the second membrane 26’ is fixed to the cap 22’. For example, a segment of the second membrane near the inner circle of the annular second membrane is press-fitted between the cap 22’ and the edge of the housing 20’. The outer peripheral portion 68’ of the second membrane forms a free end, and this free end is a free end in such a manner that the second membrane 26’ (more specifically, the segment near the free end) can move freely with respect to the cap and the housing. This free end or outer peripheral portion 68’ is movable between a resting position on the surface of the housing 20 and an open position, for example, an open position for ensuring emergency gas venting in the case of a technical defect in the battery system 10. The outer peripheral portion 68’ rests on the first flange 28’. The second membrane 26’ faces, for example, the first flange opening 36’. The movable part of the second membrane faces the second part of the cap, and more specifically, may at least partially face a plurality of openings in the second part. The outer peripheral portion 68’ of the second membrane is closer to the first membrane than the inner peripheral portion of the second membrane. In other words, the second membrane is not flat but forms an inclined or curved shape, and when measured along the longitudinal axis, the outer peripheral portion of the second membrane is closer to the outer part 38’ of the cap than the inner peripheral portion of the second membrane. When viewed from above (or from the outer part side) of the ventilation device, the second membrane may have a concave shape. This arrangement enables better emergency gas venting. The second membrane may have a surface with low roughness. More specifically, the average roughness depth Rz is important. The average roughness depth Rz is defined by the average value of the individual roughness depths of five consecutive individual measurement intervals of the roughness profile. For example, the surface of the second membrane has a porosity of less than 0.6 μm, particularly less than 0.4 μm.The small roughness (or porosity) of this surface enables to enhance the performance of the second membrane, and in particular, enables to reduce the amount of moisture passing through the membrane when the second membrane is in the closed position.

[0057] The first membrane 24' extends over the entire second membrane. In other words, the first membrane covers the second membrane.

[0058] The ventilation device 12' may include a sealing ring 70' extending around the housing 20'. For example, the housing 20' has a recess 72' on its outer surface adapted to receive the sealing ring 70'. The sealing ring 70' is made of, for example, an elastomer or a thermoplastic elastomer. The sealing ring 70' is, for example, an O-ring. The sealing ring 70' is disposed under the second flange 32'. The sealing ring 70' has a plane 74 substantially parallel to the second flange and a side surface 76 perpendicular to this plane. The sealing ring 70' is a sealing ring in such a manner that the ventilation device 12' may be connected to the casing 14' in an airtight and watertight manner.

[0059] The cap 22', the housing 20', the first membrane 22', the second membrane 24' and the lid 78 are mounted together so as to form the ventilation device 12'. For example, all these components have a substantially circular outer shape, and in the state where the ventilation device is mounted, their central axes (coinciding with the longitudinal axis X) coincide.

[0060] Figs. 7-9 show a ventilation device 12'' according to a third embodiment. The ventilation device 12'' includes a housing 20'', a cap 22'', a first membrane 24'', a second membrane 26'' and a lid 78' arranged in a similar or identical manner to the housing 20', the cap 22', the first membrane 24', the second membrane 26' and the lid 78 of the second embodiment. The ventilation device 12 further includes a sensor 84. The sensor 84 can be a gas sensor, a humidity sensor, a pressure sensor, a temperature sensor,... and can be, for example, a gas sensor, a humidity sensor, a pressure sensor, a temperature sensor,... for predictive diagnosis and predictive maintenance.

[0061] As shown in FIGS. 7, 8, and 9, the sensor may be disposed within a cavity formed by the cap 22”. More specifically, the sensor 84 may be disposed within a cavity 48” bounded by an edge 46” of the first portion 42”. More generally, the sensor 84 is disposed within the ventilation device in such a manner that the sensor 84 can collect the necessary data. In the case of the gas sensor 84, the presence of the sensor within the cavity enables the presence of the sensor within the main air flow path. Moreover, as shown in FIGS. 7 and 8, the sensor does not protrude from the remainder of the ventilation device (especially from the housing and the cap). Thus, the ventilation device 12” remains compact. This sensor disposed within the cavity formed by the cap is protected by the walls of the cavity. This reduces the risk of damage.

Industrial Applicability

[0062] When in the mounted state, the ventilation device is compact and enables the realization of two functions required for the battery system (pressure equilibrium in a normal operating environment and emergency gas venting in the case of a technical defect). These two functions are realized by only a few elements, namely, the cap 22, the housing 20, the first and second membranes 24, 26 (and optionally the sealing ring 70). No additional elements are required. Moreover, the arrangement of the first membrane 24 with respect to the second membrane 26 enables the realization of a compact device. The position and shape of the second membrane (concave shape when viewed from above) further reduce the overall dimensions of the ventilation device. Moreover, it reduces the ingress of moisture into the casing. The ventilation device is particularly flat so that it does not protrude in a non-functional or non-uniform manner. In a normal operating environment, the first membrane equalizes the pressure between the interior of the casing and the external environment. The ventilation holes enable regular and easy ventilation, and their positions spaced from the first membrane reduce the risk of moisture entering the casing. For example, in the case of emergency gas venting, the second membrane opens at an internal pressure between 0.05 and 0.15 bar.

Description of Symbols

[0063] 10 Battery system 12, 12’, 12” Ventilation device 14 Casing 16 Mounting part 18 Vent opening 20, 20’, 20” Housing 22, 22’, 22” Cap 24, 24’, 24” First membrane 26, 26’ Second membrane 28, 28’ First flange 30, 30’ Central opening 32, 32’ Second flange 34, 34’ Housing bending part 36, 36’ First flange opening 38, 38’ Outer surface 40, 40’ Inner surface 42 First part 44 Second part 46 Edge 48 Cavity 50 Bottom 52 Ventilation hole 54 Support structure 56 Cap bending part 58 Groove 60 Opening of the second part 62 Rim 64 Cap edge 66 Housing edge 68 Outer peripheral part 70 Sealing ring 72 Recess 74 Flat surface, plane 76 Side surface 78 Lid 80 Slot or notch 82 Tongue or latch 84 Sensor

Claims

1. A ventilation device (12, 12', 12") for a battery system (10) comprising a battery casing (14) having a vent opening (18), - A housing (20, 20', 20") adapted to be attached to the battery casing (14), - A cap (22, 22', 22") having an outer surface (38, 38', 38") and an inner surface (40, 40', 40"), wherein the inner surface (40, 40', 40") faces the housing (20, 20', 20"), and the cap (22, 22', 22") cooperates with the housing (20, 20', 20") and extends over the housing, - A first membrane (24, 24', 24") adapted to ensure pressure equilibrium between the inside of the casing (14) and the environment of the casing (14) under normal operating conditions of the battery system, - A second membrane (26, 26', 26") adapted to ensure emergency gas release in the event of a technical defect in the battery system (10) and In a ventilation device (12, 12', 12") comprising, A ventilation device (12, 12', 12") characterized in that the cap (22, 22', 22") comprises a first segment connected to the first membrane (24, 24', 24") and a second segment connected to the second membrane (26, 26', 26").

2. The ventilation device (12, 12', 12") according to claim 1, wherein the first membrane (24, 24', 24") is a breathable membrane.

3. The ventilation device (12, 12', 12") according to claim 1 or 2, wherein the second membrane (26, 26', 26") is press-fitted between the housing (20, 20', 20") and the cap (22, 22', 22"), and the second membrane has a ring shape having an inner peripheral portion and an outer peripheral portion, the outer peripheral portion being closer to the cap than the inner peripheral portion.

4. The ventilation device (12, 12', 12") according to claim 1, wherein the cap (22, 22', 22") is substantially circular and comprises a central portion (42, 42") fitted to be covered by the first membrane (24, 24', 24") and an outer annular portion (44, 44') fitted to be partially covered by the second membrane.

5. The ventilation device (12, 12', 12") according to claim 4, wherein the central portion (42) comprises a plurality of ventilation holes (52, 52').

6. The ventilation device (12, 12', 12") according to claim 4, wherein the outer annular portion (44) comprises a plurality of regularly distributed openings (60).

7. The ventilation device (12', 12") according to claim 4, wherein the first membrane covers the central portion (42') and the outer annular portion (44').

8. The ventilation device (12, 12', 12") according to claim 4, wherein the cap (22, 22', 22") comprises a rim (62).

9. The ventilation device (12, 12', 12") according to claim 4, wherein the central portion (42) is provided with a rim (46) that extends vertically from the inner surface along the vertical axis (X), and the rim (46) defines one or more cavities.

10. The ventilation device (12, 12', 12") according to claim 1, further comprising a sealing ring (70) extending around the housing (20).

11. The ventilation device (12, 12', 12") according to claim 1, wherein the second membrane (26) is annular and the first membrane (24) is substantially located at the center of the second membrane (26).

12. The ventilation device (12, 12', 12") according to claim 1, wherein the first membrane (24) is made of polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) material.

13. The ventilation device (12, 12', 12") according to claim 1, wherein the second membrane (26) is made of an elastomer or a thermoplastic elastomer.

14. The ventilation device (12, 12', 12") according to claim 1, wherein a sensor is located within the cavity of the ventilation device, and the sensor is a gas sensor, a humidity sensor, a pressure sensor, and / or a temperature sensor.

15. A battery system (10) comprising a battery casing having a vent opening (18) and a ventilation device (12, 12', 12") as described in claim 1, wherein the housing (20) is inserted into the vent opening (18).

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