Vent valve for battery pack assembly for a vehicle

Abstract

A vent valve (16) for venting gas from a battery pack (10) with: a first part (20) comprising: a plate (24) with a first opening (32), a lateral wall (34); and a second part (22), adapted for being mounted on the first part (20), comprising in turn: a membrane carrier (23), which is essentially annular in shape; a first membrane (28), supported on an inner edge of the membrane carrier (23), which is porous and is adapted to allow the passage, therethrough, of gases but not liquids; a second membrane (30), supported on an outer edge of the membrane carrier (23), which is flexible between a first configuration in which it closes the passage of gases, and a second configuration in which it is laid out and opens the passage of gas for venting overpressure.

Description

[0001] Vent valve for battery assembly for a vehicle

[0002] The present invention relates to a vent valve, in particular, which can be used to allow the venting of overpressure gas from inside a casing of a battery pack assembly.

[0003] Generally, a battery pack assembly, e.g. for supplying electrical power to an engine and / or utilities in a vehicle, comprises a casing and inside it a battery pack, or a series of battery cells. Such a battery pack assembly must be constructed in such a way that - in the event of a battery cell failure or even just in the event of pressure surges, e.g. due to changes in altitude - any internal overpressure is allowed to vent outwards to prevent the battery pack assembly from exploding or swelling. For this purpose, according to the prior art, battery pack assemblies for vehicles are equipped with at least one hole in which a vent valve is installed. Clearly, especially in the event of a battery cell failure that can lead to the development of dangerous gases, venting should be carried out not towards the inside of the vehicle, but to the outside air, but the fact that battery pack assemblies are generally arranged below the vehicle floor complicates the design. Clearly, this poses serious problems when crossing fords, or in general when the water level below the vehicle floor is not negligible.

[0004] In addition, to date, vent valves for these applications are tested separately, and not when they are already installed on a respective hole in the battery pack assembly, making it essentially impossible to assess the quality of the vent valve installation on the hole.

[0005] The object of the present invention is to provide an alternative vent valve to the known ones, and one that does not, therefore, suffer from the disadvantages of the prior art.

[0006] This and other objects are fully achieved according to the present invention by means of a vent valve as defined in the appended independent claim 1.

[0007] Advantageous embodiments of the vent valve according to the invention are specified in the dependent claims, the contents of which are to be understood as an integral part of the following description. In summary, the invention is based on the idea of providing a vent valve for venting gas from a hole in a casing of a battery pack assembly, the vent valve comprising: a first part, adapted for being attached to the hole of the casing of the battery pack assembly, the first part comprising in turn: a plate, through which a first, through-hole opening is defined, the plate being adapted to rest on an outer surface of the casing so as to define a sealing strip on said outer surface of said casing; a lateral wall connecting the edge of the first opening to the edge of a second opening extending from said plate, and defining a first chamber, wherein the first opening puts the inside of the first chamber in fluid communication with the inside of the casing through the hole of the casing, a third opening being defined through the lateral wall; a second part, adapted for being mounted on the first part, comprising in turn: a membrane carrier, essentially annular in shape; a first membrane, supported on an inner edge of the membrane carrier, the first membrane being porous and adapted for being arranged in said second opening to allow the passage, therethrough, of gas but not of liquids; a second membrane, supported on an outer edge of the membrane carrier, the second membrane being flexible between a first configuration wherein the difference between the pressure inside the casing and therefore the first chamber and the external pressure is less than a predetermined pressure threshold value, and wherein the second membrane closes the passage of gas through the third opening, and a second configuration wherein the pressure inside the casing and therefore the first chamber exceeds the external pressure by said pressure threshold value and, therefore, the second membrane is laid out and opens the passage of gas through the third opening for venting any overpressure.

[0008] According to a preferred embodiment of the invention, the second part comprises a cap portion, and when the pressure inside the casing and thus the first chamber exceeds the outer one at least by said pressure threshold value, the second membrane goes into contact with said cap portion of the second part and defines, jointly with it and with the first membrane, a second chamber. According to a preferred embodiment of the invention, the second part is adapted for being mounted on the first part by screwing or in such a way as to be fit on it by a bayonet coupling.

[0009] According to a preferred embodiment of the invention, this pressure threshold value is comprised between 200 and 400 mbar and preferably is of about 300 mbar.

[0010] According to a preferred embodiment of the invention, the first membrane is a micro-porous membrane having a porosity adapted to ensure a gas flow rate of at least 3 litres per minute in the range of a pressure difference on its two sides comprised between -100 and +200 mbar.

[0011] According to a preferred embodiment of the invention, the sealing strip defined by the plate on the outer surface of the casing is obtained by contact of two surfaces and interposition of a sealing in-between, preferably an annular, rubber sealing or an O-ring.

[0012] According to a preferred embodiment of the invention, the first membrane is mounted on said membrane carrier detachably, to be replaced when necessary.

[0013] In accordance with a preferred embodiment of the invention, the plate has, on the side opposed to the lateral wall, one or more protrusions adapted to allow snap fastening or screwing of the first part in the hole of the casing of the battery pack assembly.

[0014] According to a preferred embodiment of the invention, the vent valve has an axial-symmetric shape about an axis passing through the centre of the first opening and of the second opening, when the second part is mounted on the first part.

[0015] Finally, according to a further aspect of the invention, a battery pack assembly for a vehicle is part of the invention, comprising: a battery pack adapted to store energy and supply electric energy to a motor and / or to users of the vehicle; a casing, adapted to enclose said battery pack and having a hole passing through it for venting gas from the inside of the casing; and a vent valve according to the first aspect of the invention, the first part of the vent valve being fixed in the hole of the casing, or being fixed on the casing so that the first opening constitutes an extension of the hole of the casing.

[0016] Further features and advantages of the present invention will become clearer from the following detailed description, which is provided by way of non-limiting example with reference to the accompanying drawings, in which:

[0017] Figure 1 is a cross-sectional side view of a vent valve according to an embodiment of the invention, in which the second diaphragm is shown in the first configuration;

[0018] Figure 2 is a view of what is shown in Figure 1, in which, however, the second membrane is shown in the second configuration;

[0019] Figure 3 is a partial sectional perspective view of what is shown in Figure 1;

[0020] Figure 4 is a sectional view of a detail of a battery pack assembly according to an embodiment of the second aspect of the invention; and

[0021] Figure 5 is a view of what is shown in Figure 4, in which the vent valve is shown separately, or not mounted on the assembly casing, or in which the first part is shown mounted on the casing but the second part is shown in a configuration not yet mounted on the first part.

[0022] With reference to the accompanying figures, the battery pack assembly according to the second aspect of the invention is indicated by reference number 10. The battery pack assembly 10 can be used, for example, in an electrically powered or partially electrically powered vehicle. Typically, a battery pack assembly 10 is installed under the floor of such a vehicle.

[0023] The battery pack assembly 10 essentially comprises a battery pack 12, a casing 14 and a vent valve 16. The vent valve 16 itself constitutes a first aspect of the invention because of its innovative features.

[0024] The battery pack 12 is itself known, and comprises a plurality of cells, adapted to store energy and deliver that energy in the form of electrical energy, for users and / or motors of the vehicle. The casing 14 is adapted to enclose or house the battery pack 12 inside it, in a manner known per se. The casing 14, therefore, has a hole 18 passing through it to allow the venting of gas from the inside of the casing 14 to the outside, or to the environment, via the vent valve 16 which is mounted at said hole 18. In fact, as mentioned above, since the battery pack 12 - in the event of cell failure or even pressure surges, e.g. due to changes in altitude - can generate gas and thus overpressure, it is necessary for the casing 14 to be equipped with a hole 18 for venting such overpressure and a respective vent valve 16. It is also possible that the battery pack assembly 10 comprises more than one through-hole 18, at each of which a respective vent valve 16 is arranged according to the first aspect of the invention.

[0025] The vent valve 16 thus allows the venting of gases from the inside of the casing 14 to the outside, while preventing the entry of liquids to the inside of the casing 14. The vent valve 16, according to the invention, essentially comprises a first part 20 and a second part 22.

[0026] The first part 20 is adapted to be screwed into hole 18 of the casing 14; for example, the first part 20 may be designed to be screwed into the hole 18 or to be fitted or coupled therein by some other type of mechanical coupling. In turn, the first part 20 essentially comprises a plate 24, from which a lateral wall 34 rises, which defines a first open volume, or a first chamber 26. The first chamber 26 is not itself closed or limited, but is delimited by the join of the first part 20 and the second part 22.

[0027] The plate 24 is adapted to be placed on an outer surface 14b of the casing 14, so as to make a sealing strip 24b on the outer surface 14b. The strip 24b extends around a first opening 32 that is defined through the plate 24. The sealing strip 24b ensures sealing through contact between two surfaces and preferably through the interposition of a sealing 24c placed between those two surfaces, such as a typical annular, rubber sealing or an O-ring.

[0028] In the battery pack assembly 10, the plate 24 is then placed on the casing 14 so that the first opening 32 is arranged aligned with, or in fluid communication with, the hole 18 defined through the casing 14.

[0029] Starting from the plate 24, and in particular from the edge of the first opening 32, the lateral wall 34 rises, which extends precisely from the edge of the first opening 32 to the edge of a second opening 36, and in this way defines an open volume corresponding to the first chamber 26; the first chamber 26 is then delimited when the second part 22 is mounted on the first part 20.

[0030] A third opening 38 is made through the lateral wall 34. The first opening 32 then puts the first chamber 26 in fluid communication with the inside of the casing 14, through the hole 18.

[0031] Preferably, the plate 24 may have, on the side opposite that from which the lateral wall 34 rises, one or more protrusions 40. These protrusions 40 may be adapted to allow the first part 20 of the vent valve 16 to be secured by interlocking or screwing into the hole 18 of the casing 14 of the battery pack assembly 10, for example by the provision of a suitable fin or trapezoid shape which is slightly flexible and which bends partially during assembly.

[0032] The second part 22 of the vent valve 16 is mounted on the first part 20, e.g. in such a way that it can be screwed onto the latter, or fitted by means of a bayonet mechanism, or even connected to it in a removable manner.

[0033] The second part 22 essentially comprises a membrane holder 23, a first membrane 28 and a second membrane 30.

[0034] The membrane holder 23 is essentially annular in shape and therefore has an inner edge, on which the first membrane 28 is supported, which therefore covers or occupies the inner space of the annular shape, and an outer edge, on which the second membrane 30 is supported, which is also essentially annular in shape.

[0035] The first membrane 28, which is made of porous, or microporous material, is adapted to allow gases but not liquids to pass through it. Advantageously, the first membrane 28 is mounted on the membrane carrier 23 in a removable manner, or in such a way that it can be removed and replaced, for example for maintenance or cleaning. In a preferred embodiment of the invention, the first membrane 28 is a micro-porous membrane having a porosity adapted to ensure a gas flow rate of at least 3 litres per minute in the range of a pressure difference on its two sides comprised between -100 and +200 mbar.

[0036] The second membrane 30 is made of a flexible material so that it can reconfigure itself between two configurations depending on the pressure exerted on it. In particular, the second membrane 30 may assume a first configuration in which the difference between the pressure inside the casing 14 - and thus inside the first chamber 26 which is in fluid communication with the inside of the casing 14 via the hole 18 and the first opening 32 - and the external pressure is less than a predetermined threshold value, and in which therefore the second membrane 30 is not pushed by a pressure sufficient to deform it outwards; this first configuration is shown in particular in Figures 1, 3 and 4. In this case, the second membrane 30 closes the gas passage via the third opening 38. Alternatively, the second membrane 30 may assume a second configuration, in which the pressure inside the casing 14 - and thus in the first chamber 26 which is in fluid communication with the inside of the casing 14 via the hole 18 and the first opening 32 - exceeds the external pressure by at least a value equal to said threshold pressure value, or it is greater than the external pressure by a certain amount, and in which therefore the second membrane 30 is pushed by a certain overpressure which is sufficient to deform it outwards; this first configuration is shown in particular in Figure 2. In this case, the second membrane 30 relaxes and opens the gas passage via the third opening 38, thus allowing the venting of this overpressure.

[0037] This threshold pressure value is preferably comprised between 200 and 400 mbar, and even more preferably about 300 mbar.

[0038] In this manner, when the pressure difference is insufficient or it does not exceed the pressure threshold value and the second membrane 30 is in its first configuration, a passage is defined for gas from within the casing 14 through the first opening 32 and the first membrane 28, whereas when the pressure difference exceeds this pressure threshold value and thus the second membrane 30 assumes its second configuration, a passage is defined for gas from within the casing 14 through the first opening 32 and the third opening 38 for venting the overpressure. As can be clearly seen in Figure 2, preferably, when the pressure inside the casing 14 - and thus in the first chamber 26 - is higher than the external pressure by at least one value greater than or equal to the pressure threshold value, the second membrane 30 may come into contact with an inner side of the second part 22, and in particular with a portion of the cap 25 thereof, and define jointly with this and with the first membrane 28 a second chamber 42.

[0039] In the preferred embodiment of the vent valve 16 according to the invention, the vent valve 16, when the second part 22 is mounted on the first part 20, has an essentially axial- symmetric shape around an axis passing through both the centre of the first opening 32 and the centre of the second opening 36.

[0040] As readily apparent from the foregoing description, the vent valve and the battery pack assembly comprising such a vent valve according to the invention enable the objects of the invention to be achieved.

[0041] In particular, the invention facilitates the validation and certification of the battery pack assembly in the related manufacturing process. In fact, one of the main problems in the production of battery pack assemblies is that the product must be able to guarantee a very high degree of sealing, generally higher than IPx7 according to the international standard IEC 60529, i.e. sealing of sufficient resistance to immersion. For this purpose, the battery pack assembly is subjected to a sealing test, in which an overpressure is applied to the casing, plugging all the holes and the relevant vent valves, to verify the correct tightness of the joints. In this test, however, the sealing of the vent valve itself on the casing is typically left unchecked: in fact, in the prior art this vent valve is only fitted downstream of the sealing test. In contrast to the prior art, thanks to the assembly of the first part of the vent valve, the sealing test can be carried out on the entire battery pack assembly, including the vent valve, or only its first part, thereby also validating and certifying the tightness of this vent valve and in particular the tightness of the first part on the casing, and even more in detail of the sealing strip of the plate on the outer surface of the casing. Therefore, the second part of the vent valve, being mounted downstream of the sealing test, ensures the tightness of the battery pack assembly with a grade better than IPx7 according to the aforementioned standard, preferably through the interlocking connection between the first porous membrane and the second flexible membrane, which, as such, do not allow liquids to enter but can allow the venting of any overpressure inside the casing.

[0042] Without prejudice to the principle of the invention, the embodiments and details of construction can vary widely with respect to what has been described and illustrated purely by way of non-limiting example, without departing from the scope of the invention as defined by the appended claims.

[0043] LIST OF REFERENCE NUMBERS

[0044] 10 battery pack assembly

[0045] 12 battery pack

[0046] 14 casing

[0047] 14b outer surface of the casing

[0048] 16 vent valve

[0049] 18 hole

[0050] 20 first part of the vent valve

[0051] 22 second part of the vent valve

[0052] 23 membrane carrier

[0053] 24 plate

[0054] 24b strip

[0055] 24c seal

[0056] 25 cap portion

[0057] 26 first chamber

[0058] 28 first membrane

[0059] 30 second membrane

[0060] 32 first opening

[0061] 34 lateral wall

[0062] 36 second opening

[0063] 38 third opening

[0064] 40 protrusion

[0065] 42 second chamber

Claims

CLAIMS1. Vent valve (16) for venting gas from a hole (18) of a casing (14) of a battery pack assembly (10), the vent valve (16) comprising: a first part (20), adapted for being attached to the hole (18) of the casing (14) of the battery pack assembly (10), the first part (20) comprising in turn: a plate (24), through which a first, through-hole opening (32) is defined, the plate (24) being adapted to rest on an outer surface (14b) of the casing (14) so as to define a sealing strip (24b) on said outer surface (14b) of said casing (14); a lateral wall (34) connecting the edge of the first opening (32) to the edge of a second opening (36) extending from said plate (24), the lateral wall (34) defining a first chamber (26), wherein the first opening (32) puts the inside of the first chamber (26) in fluid communication with the inside of the casing (14) through the hole (18) of the casing (14), a third opening (38) being defined through the lateral wall (34); a second part (22), adapted for being mounted on the first part (20), comprising in turn: a membrane carrier (23), essentially annular in shape; a first membrane (28), supported on an inner edge of the membrane carrier (23), the first membrane being porous and adapted for being arranged in said second opening (36) to allow the passage, therethrough, of gas but not of liquids; a second membrane (30), supported on an outer edge of the membrane carrier (23), the second membrane being flexible between a first configuration wherein the difference between the pressure inside the casing (14) and therefore the first chamber (26) and the external pressure is less than a predetermined pressure threshold value, and wherein the second membrane (30) closes the passage of gas through the third opening (38), and a second configuration wherein the pressure inside the casing (14) and therefore the first chamber (26) exceeds the external pressure by said pressure threshold value and, therefore, the second membrane (30) is laid out and opens the passage of gas through the third opening (38) for venting any overpressure.

2. Vent valve according to claim 1, wherein the second part (22) comprises a cap portion (25), and wherein when the pressure inside the casing (14) and thus the firstchamber (26) exceeds the outer one at least by said pressure threshold value, the second membrane (30) goes into contact with said cap portion (25) of the second part (22) and defines, jointly with it and with the first membrane (28), a second chamber (42).

3. Vent valve according to claim 1 or to claim 2, wherein the second part (22) is adapted for being mounted on the first part (20) by screwing or in such a way as to be fit on it by a bayonet coupling.

4. Vent valve according to any of the preceding claims, wherein said pressure threshold value is comprised between 200 and 400 mbar and preferably is of about 300 mbar.

5. Vent valve according to any of the preceding claims, wherein the first membrane (28) is a micro-porous membrane having a porosity adapted to ensure a gas flow rate of at least 3 litres per minute in the range of a pressure difference on its two sides comprised between -100 and +200 mbar.

6. Vent valve according to any of the preceding claims, wherein the sealing strip (24b) defined by the plate (24) on the outer surface (14b) of the casing (14) is obtained by contact of two surfaces and interposition of a sealing (24c) in-between, preferably an annular, rubber sealing or an O-ring.

7. Vent valve according to any of the preceding claims, wherein the first membrane (28) is mounted on said membrane carrier (23) detachably, to be replaced when necessary.

8. Vent valve according to any of the preceding claims, wherein the plate (24) has, on the side opposed to the lateral wall (34), one or more protrusions (40) adapted to allow snap fastening or screwing of the first part (20) in the hole (18) of the casing (14) of the battery pack assembly (10).

9. Vent valve according to any of the preceding claims, characterized in that an axial- symmetric shape about an axis passing through the centre of the first opening (32) and of the second opening (36).

10. Battery pack assembly (10) for a vehicle, comprising: a battery pack (12) adapted to store energy and supply electric energy to a motor and / or to users of the vehicle; - a casing (14), adapted to enclose said battery pack (12) and having a hole (18) passing through it for venting gas from the inside of the casing (14); and a vent valve (16) according to any of the preceding claims, the first part (20) of the vent valve (16) being fixed in the hole (18) of the casing (14).

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