Patent Description:
In housings (or casings) of battery systems, in particular high-voltage battery system, such as those used in motor vehicles, temperature and pressure changes result in pressure differences between the housing of the battery system and the environment.

These pressure differences must be balanced in normal operation. To provide thermal control of the enclosed components a thermal management system may be used to efficiently emit, discharge and/or dissipate heat generated within the casing. If such thermal management system is omitted or the heat drain from the casing is not sufficiently performed, an increase of the internal temperature can lead to abnormal reactions occurring therein.

In addition, there is a risk, especially in high-voltage battery systems with a large capacity, that one or more cells in the battery will fail due to overloading or other technical defects. This can result in large amounts of harmful gas, which must be discharged in a controlled manner. Thus, an emergency venting in case of technical defect within the battery has to be provided.

One can use two different devices for both functions, pressure compensation in normal operation and emergency venting in case of technical defects. However, two devices increase the weight of the assembly as well as the maintenance.

Document <CIT> discloses a device combining both functions. The device comprises a pressure equalization element. The pressure equalization element has an element body and a membrane arranged on the element body. The device comprises a connecting element for the airtight connection of the pressure compensation element to the housing. The element body rests airtight on the connecting element when there is an internal pressure which is lower than a limit pressure. Besides, the element body opens an aperture for exchanging gas when there is an internal pressure which is greater than the limit pressure. <CIT>, <CIT> and <CIT> also disclose ventilation units comprising a first ventilation body and a second ventilation body. The first ventilation body permits gas to flow from an inside of a housing to an outside of the housing when internal pressure is higher than external pressure by a value not less than a predetermined value, and is capable of returning to block flow of the gas from the inside of the housing to the outside of the housing. The second ventilation body permits gas to flow between the inside of the housing and the outside of the housing even when a pressure difference between the internal pressure and the external pressure is less than the predetermined value.

Such devices are adapted to deal with the pressure compensation function with the element body and the emergency venting with the membrane. However, a need still exists to improve such devices.

It is an object of the present invention to provide a venting device which fulfils both functions (emergency degassing in the event of damage as well as differential pressure compensation in normal work environment) and which is robust, easy to manufacture, to mount and to maintain, with as less parts as possible.

Accordingly, the present disclosure is directed to a ventilation device for a battery with a battery casing having a vent opening according to claim <NUM> and to a battery system according to claim <NUM>.

More particularly, the ventilation device comprises a housing, a cap cooperating with the housing, a first membrane adapted to ensure pressure balance between the inside of a battery system and its environment during normal operation conditions of the battery system. The device further comprises a second membrane adapted to ensure an emergency venting in case of technical defect within the battery system, wherein the cap comprises a first portion connected to the first membrane and a second portion connected to the second membrane. Thus, the cap is connected to both membranes, which renders the valve easy to mount and to maintain.

In an embodiment, the first membrane is a breathable membrane. Thus the membrane can easily ensure the pressure balance in a normal environment.

In an embodiment, the cap is airtight ultrasonically welded to the first membrane. The ultrasonic welding ensures a robust fixation, is easy to realize.

In an embodiment, the second membrane is press-fitted between the housing and the cap. The press-fittings have high connection strength and anti-vibration. The assembly can be automated and is reliable and consistent. Besides, such connections have the ability to withstand thermal expansion during thermal cycling.

According to the invention, the cap is substantially circular with a central portion adapted to be covered by the first membrane and an outer annular portion adapted to be partly covered by the second membrane. The cap is integral but ensures different functions depending on the portion linked to the first or the second membrane.

According to the invention, the central portion comprises a plurality of ventilation holes. The ventilation holes are facing the first membrane to ensure a correct pressure balance.

In an embodiment, the second outer annular portion comprises a plurality of openings regularly distributed. The openings are curved. The openings are facing the second membrane.

In an embodiment, the cap comprises a rim covering at least partly an outer periphery of the housing. Thus, the cap is a protective cap and can surround the housing.

In an embodiment, the central portion comprises an edge extending longitudinally along a longitudinal axis from the inner surface, wherein the edge defines one or a plurality of cavities. The edge forms a reinforcing structure for the rigidity of the device.

In an embodiment, the first membrane is fixed to the edge. The edge forms a surface and the first membrane can easily be fixed to this surface.

In an embodiment, the ventilation device further comprises a sealing ring extending around the housing. The sealing ring is adapted to sealingly fix the ventilation device to the casing.

In an embodiment, the second membrane is annular. In an embodiment, the first membrane has the shape of a disc. In an embodiment, the first membrane extends substantially in the centre of the second membrane. Thus a compact arrangement is provided.

In an embodiment, the first membrane is made of Polyethylene terephthalate (PET) or Polytetrafluoroethylene (PTFE) material. Such materials have high strength to weigh ratio and resistant to moisture.

In an embodiment, the second membrane is made of elastomer or thermoplastic elastomer material. Such materials are customizable in size, shape or flexibility.

The present invention is also directed to a battery system comprising a battery casing with a vent opening and a ventilation device, wherein the ventilation device (and more particularly its housing) is inserted in the vent opening.

A specific embodiment of the present invention will now be described, by way of example only and with reference to the accompanying drawings, of which:.

On the different figures, the same reference signs designate identical or similar elements.

<FIG> illustrates a schematic perspective view of a battery system <NUM> with a ventilation device <NUM>. The shape of the battery system <NUM> and the arrangement in <FIG> is for illustration purpose. The battery system <NUM> comprises a casing <NUM>. In the context of the present application, a battery system <NUM> is to be understood as one of a battery submodule, a battery module and a battery pack. Hence the battery casing <NUM> is to be understood to be a casing of one of a battery submodule, a battery module and a battery system. The casing <NUM> may consist of a metal alloy and/or a plastic material. The battery system <NUM> may comprise a plurality of attachment portions <NUM> for mounting the battery system to a fixing structure, for example an electric vehicle. The casing <NUM> comprises a vent opening <NUM>. More particularly, the casing may comprise <NUM> or <NUM> vent openings. Eventually more than <NUM> vent openings may also be provided.

The vent opening <NUM> is adapted to receive the ventilation device <NUM>. The ventilation device <NUM> is more particularly shown in <FIG> and <FIG>. In an embodiment, the ventilation device <NUM> is configured to be attached to the casing <NUM> for covering and/or overlapping the vent opening. In another embodiment, the ventilation device <NUM> is configured to be inserted into the vent opening <NUM>.

As depicted in <FIG>, the ventilation device <NUM> comprises a housing <NUM>, a cap <NUM>, a first membrane <NUM> and a second membrane <NUM>.

When the ventilation device <NUM> is configured to be inserted into the vent opening <NUM>, the housing <NUM> of the ventilation device <NUM> cooperates with the vent opening <NUM>. The housing <NUM> is for instance substantially annular around a longitudinal axis. However, in other embodiment, the shape of the housing <NUM> may be rectangular or oval. Actually, the shape of the housing <NUM> is complimentary with the shape of the vent opening <NUM>. The housing <NUM> for example comprises a first flange <NUM> (see for instance <FIG>) delimiting a central opening <NUM>, and a second flange <NUM> radially outwardly extending from the first flange <NUM>. A housing bent portion (housing elbow) <NUM> is arranged between the first and the second flange <NUM>, <NUM> and connects said flanges <NUM>, <NUM>. The second flange <NUM> may have a substantially flat surface, wherein the first flange <NUM> may be inclined. The first flange <NUM> has for instance a reduced diameter with regard to the second flange. The first flange <NUM> may be provided with first flange openings <NUM>. The housing <NUM> is adapted to cooperate with the cap <NUM> in a mounted state of the ventilation device <NUM>.

The cap <NUM> is for instance a protective cap. The cap <NUM> comprises an outer surface <NUM> and an inner surface <NUM>. The inner surface <NUM> faces the housing <NUM>, wherein the outer surface <NUM> is opposite the inner surface <NUM>. The cap <NUM> has a substantially circular shape. The cap has a first portion <NUM> which forms a central portion and a second portion <NUM> arranged around the first portion. The cap <NUM> is for instance integral. The first position <NUM> comprises an edge <NUM> which extends longitudinally from the inner surface <NUM> such as to delimit a cavity <NUM>. For instance the edge <NUM> delimit a cavity <NUM> having a circular cross-section. The bottom <NUM> of the cavity <NUM> comprises at least one, but for instance a plurality of ventilation holes <NUM>. A supporting structure <NUM> may extend between the edge <NUM> such as to delimit a plurality of sub-cavities and to render the cap <NUM> more rigid. The second portion <NUM> of the cap is an outer annular portion. The edge <NUM> is connected to the second portion <NUM> by a cap bent portion <NUM> (cap elbow), such that a groove <NUM> is formed at the outer surface <NUM> of the cap <NUM>, the groove <NUM> separating the first portion <NUM> and the second portion <NUM>. The second portion <NUM> may comprise a plurality of openings <NUM> regularly distributed, for instance around a longitudinal axis X. The cap <NUM> also comprises a rim <NUM> extending at its outer periphery from the inner surface <NUM>. The rim <NUM> is adapted to cover at least partly an outer periphery of the housing <NUM>. More particularly, as visible in <FIG>, the rim <NUM> may cover longitudinally the second flange <NUM> of the housing.

The first membrane <NUM> is a breathable membrane. The first membrane <NUM> is for instance made of Polyethylene terephthalate (PET) or Polytetrafluoroethylene (PTFE) material. The first membrane <NUM> has a disc shape.

The second membrane <NUM> has an annular shape. The second membrane is for instance made of elastomer or thermoplastic elastomer.

The cap, <NUM>, housing <NUM>, first membrane <NUM> and second membrane <NUM> are mounted together such as to form the ventilation device <NUM>. For example, all these parts have a substantially circular outer shape and their central axis (corresponding to the longitudinal axis X) coincide in a mounted state of the ventilation device.

The first membrane <NUM> is connected to the first portion <NUM> of the cap <NUM>. More particularly, the first membrane <NUM> is airtight ultrasonically welded to the cap <NUM>. For instance, the first membrane <NUM> is welded to the edge <NUM> of the cap <NUM>, such that it covers the cavity <NUM> (or all the sub-cavities). The edge <NUM> comprises an edge surface substantially parallel to the inner surface <NUM> of the cap and the first membrane <NUM> is welded to the edge surface. Thus, the first membrane <NUM> is at a non-zero distance from the ventilation holes <NUM> and faces said ventilation holes <NUM>. The diameter of the first membrane <NUM> corresponds substantially to the diameter of the edge <NUM> which delimits the cavity <NUM>. Thus, the first membrane <NUM> covers entirely the cavity <NUM>. As mentioned above, the supporting structure <NUM> may be arranged within the cavity. The supporting structure <NUM> may also support the first membrane <NUM>. Eventually the first membrane <NUM> may be welded to the supporting structure <NUM>.

The second membrane <NUM> is connected to the second portion <NUM> of the cap. The second membrane <NUM> has an annular shape, such that in the mounted state of the ventilation device <NUM>, it surrounds the edge <NUM>. More particularly, the surface defining the inner circle of the annular-shaped second membrane faces the edge <NUM> and is arranged under the cap bent portion <NUM>. The second membrane is press-fitted between the cap <NUM> and the housing <NUM>. More particularly the cap bent portion <NUM> comprises a cap edge <NUM>, and the first flange <NUM> of the housing comprises a housing edge <NUM>, facing the cap edge <NUM> in the mounted state of the ventilation device. The second membrane <NUM> is press-fitted between the cap edge <NUM> and the housing edge <NUM>. For instance, a segment of the second membrane in the vicinity of the inner circle of the annular-shaped second membrane is press-fitted between the edges <NUM>, <NUM>. An outer periphery <NUM> of the second membrane forms a free end, such that the second membrane <NUM> (and more particularly a segment in the vicinity of the free end) can freely move with regard to the cap and the housing. The free end or outer periphery <NUM> is movable between a rest position, in which it rests against a surface of the housing <NUM> and an open position, for instance to ensure an emergency venting in case of technical defect within the battery system <NUM>. The outer periphery <NUM> rests against the first flange <NUM>. The second membrane <NUM> faces for instance the first flange openings <NUM>. The portion of the second membrane which is movable faces the second portion <NUM> of the cap, and more particularly may face at least partly the plurality of second portion openings <NUM>.

The ventilation device <NUM>, notably when configured to be inserted into the vent opening <NUM>, further comprises a sealing ring <NUM> extending around the housing <NUM>. For instance, the housing <NUM> comprises on its external lateral surface a recess <NUM> adapted to receive the sealing ring <NUM>. The sealing ring <NUM> is for instance made of elastomer or thermoplastic elastomer. The sealing ring <NUM> is for instance an O-ring. The sealing ring <NUM> is arranged below the second flange. It has a flat surface <NUM> substantially parallel to the second flange, and a lateral surface <NUM>, orthogonal to the flat surface. The sealing ring <NUM> is such that the ventilation device <NUM> may be connected to the casing <NUM> in an airtight and watertight manner. The vent opening <NUM> has a shape complimentary to the shape of the housing <NUM> with the sealing ring <NUM>.

In a mounted state of the ventilation device <NUM>, the cap <NUM> cooperates with the housing <NUM> for instance with a snap fit connection. For example, as depicted in <FIG> the inner surface of the rim <NUM> is snap fitted with a portion of the housing <NUM>. More particularly the rim is in a snap-fit connection with the lateral surface of the second flange <NUM> of the housing <NUM>. In other embodiments, cap and housing may be press-fitted or glued or welded. The second membrane <NUM>, as mentioned above is sandwiched between the cap <NUM> and the housing <NUM>, wherein the first membrane <NUM> is fixed to the cap only. The inner diameter of the second membrane <NUM> is greater than the diameter of the first membrane <NUM>.

Said ventilation device, when in a mounted state, is compact and allows, to fulfil the two functions needed in a battery system (pressure balance in a normal work environment and emergency venting in case of technical defect). These two functions are fulfilled with only few elements, i.e. the cap <NUM>, the housing <NUM>, the first and second membranes <NUM>, <NUM> (and eventually the sealing ring <NUM>). No further element is necessary. Besides, the arrangement of the first membrane <NUM> with regard to the second membrane <NUM> allows to realize a compact device. In a normal work environment, the first membrane balances the pressure between the interior of the casing and the outside environment. The ventilation holes allow a regular and easy ventilation and their position - at distance from the first membrane - decreases the risks of humidity entering the casing. As depicted in <FIG>, the first membrane may be substantially below the housing, wherein the second membrane is arranged between the housing and the cap.

Claim 1:
Ventilation device (<NUM>) for a battery system (<NUM>) with a battery casing (<NUM>) having a vent opening (<NUM>), comprising:
- a housing (<NUM>) adapted to be attached to the battery casing (<NUM>),
- a cap (<NUM>) with an outer surface (<NUM>) and an inner surface (<NUM>), wherein the inner surface (<NUM>) faces the housing (<NUM>), and wherein the cap (<NUM>) cooperates with the housing (<NUM>),
- a first membrane (<NUM>) adapted to ensure pressure balance between the inside of the casing (<NUM>) and its environment during normal operation conditions of the battery system,
- a second membrane (<NUM>) adapted to ensure an emergency venting in case of technical defect within the battery system (<NUM>),
wherein the cap (<NUM>) comprises a first portion (<NUM>) connected to the first membrane (<NUM>) and a second portion (<NUM>) connected to the second membrane (<NUM>), the cap (<NUM>) being substantially circular with a central portion (<NUM>) adapted to be covered by the first membrane (<NUM>) and an outer annular portion (<NUM>) adapted to be partly covered by the second membrane and
characterized in that the central portion (<NUM>) comprises a plurality of ventilation holes (<NUM>).