TECHNICAL FIELD

The present disclosure relates to a vent assembly. More particularly, but not exclusively, the present disclosure relates to a vent assembly for a battery pack. The present disclosure also relates to a battery pack; a battery pack thermal management system; and to a vehicle.

BACKGROUND

It is known to provide a vehicle with a traction battery for supplying electrical energy to a traction motor. The battery packs are typically sealed. In the event of an internal thermal event, gases are vented to avoid excessive pressure within the battery pack. In order to vent gases, it is known to provide the battery pack with a vent system. A frangible membrane, such as a burst vent, may be provided within the vent system to prevent the ingress of water.

If the battery pack experiences an internal thermal event, gases released within the battery pack cause an increase in pressure which ruptures the frangible membrane. The gases are vented through the ruptured membrane, thereby preventing the build-up of pressure within the battery pack.

A potential shortcoming of known frangible membranes is ensuring that they behave consistently as small variations during production may lead to different operating characteristics. For example, the load required to rupture the membrane may vary.

At least in certain embodiments the present invention seeks to overcome or ameliorate at least some of the shortcomings of prior art arrangements.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a vent assembly, to a vent assembly for a battery pack, to a battery pack having one or more vent assembly, to a battery pack thermal management system and to a vehicle having one or more vent assembly.

According to a one aspect of the present invention there is provided a vent assembly for a battery pack, the vent assembly comprising:

a vent disc; and

an annular support frame having an annular recess;

wherein an outer edge of the vent disc is located in said annular recess to releasably mount the vent disc in the annular support frame. The vent disc is demountable from the annular support frame. The vent disc can be displaced from the annular support frame to open the vent system without rupturing or bursting. The vent disc may be displaced out of the annular recess in dependence on a pressure change. The annular recess may be an annular groove or an open channel formed in said annular support frame. When used in conjunction with a battery pack, the vent system can be configured such that the vent disc is demounted from the annular support frame due to an increase in pressure within the battery pack. The increased pressure may, for example, result from an internal thermal event in the battery pack which causes gases to be expelled. By venting the gases to atmosphere, the pressure within the battery pack may be controlled. At least in certain embodiments the vent disc may form a seal to prevent the ingress of water or condensation into the battery pack. The vent assembly has particular application for an automotive traction battery housing.

The annular recess may comprise opposing first and second sidewalls. The first sidewall may be configured to inhibit displacement of the vent disc out of the annular recess in a first direction ; and the second sidewall may be configured to enable displacement of the vent disc out of the annular recess in a second direction, the first and second directions being opposite to each other. The first sidewall may be a first annular sidewall having a first internal diameter and the second sidewall may be a second annular sidewall having a second internal diameter. The first internal diameter may be smaller than the second internal diameter. The first sidewall may be formed by a first annular flange and the second sidewall may be formed by a second annular flange.

At least in certain embodiments the vent disc may withstand high force from external pressure and/or objects, whilst allowing internal pressure to escape rapidly. In this manner, the vent disc exhibits anisotropic behaviour in response to forces or pressures acting thereon in dependence on whether the force or pressure is external or internal. The annular support frame is configured to enable the vent disc to be displaced in only one direction. The application of a force in said first direction displaces the vent disc towards the first sidewall. The displacement of the vent disc in said first direction is inhibited by the first sidewall. The application of a force in the second direction displaces the vent disc out of the annular recess, thereby opening the vent assembly. The displacement of the vent disc in said second direction is enabled by the relative size of the aperture formed in the second sidewall.

The vent disc resists the application of external forces and/or pressure. The application of internal forces and/or pressure opens the vent assembly. The vent disc may undergo deformation when demounted from the annular support frame. In particular, the application of an internal force and/or pressure may deform the vent disc allowing it to be displaced out of the annular recess. The vent assembly does not rely on melting of the vent disc, instead relying on the internal pressure to displace the vent disc. At least in certain embodiments, the vent disc is not affected by high ambient temperatures or other external heat sources, for example a component fire.

The vent disc may be an interference fit in said annular recess. The vent disc may be mounted and supported within said annular recess solely by the interference fit between the outer edge of the vent disc and the annular recess. The vent disc may be deformed to locate within said annular recess.

The vent disc may be movable relative to the annular support frame. The annular support frame may be configured to inhibit radial movement of the vent disc whilst allowing axial movement. The vent disc may float relative to the annular support frame.

The annular recess may accommodate expansion of the vent disc. In use, the vent disc may expand due to pressure changes. The vent disc may be movable within the annular recess. The vent assembly may comprise a sealing means for forming a seal between the vent disc and the annular support frame. The sealing means may comprise a resilient member, such as an O-ring. The resilient member may be disposed in the annular recess. The resilient member may bias the vent disc against the first sidewall. The vent disc may have a curved profile. The curved profile may extend at least substantially to the outer edge of the vent disc. The vent disc may have a domed, part-spheroidal or part- spherical profile. The curved profile may be substantially continuous over the surface of the vent disc. The vent disc may have a convex surface and a concave surface. The concave surface may face the first sidewall and the convex surface may face the second sidewall. The convex surface may be oriented outwardly and the concave surface may be oriented inwardly. The vent assembly may comprise an outlet and the first sidewall of the annular support frame may face towards the outlet of the vent assembly. When a force is applied to the convex surface, the vent disc deforms such that its outer diameter increases. The outer edge of the vent disc may be forced against the annular support frame. The annular recess may be sized to limit expansion of the vent disc. When a force is applied to the concave surface, the vent disc deforms such that its outer diameter decreases. The decrease in the diameter may facilitate displacement of the vent disc out of the annular support frame. The vent disc may be demounted from the annular support frame in order to vent gas from within the battery pack.

The vent disc may be formed from a sheet material. The vent disc may be formed from a resilient material. The vent disc may be formed from spring steel.

The annular recess and the vent disc may be arranged concentrically about a longitudinal axis of the vent assembly. The vent assembly may comprise retaining means for retaining the vent disc when it is displaced out of said annular support frame. The retaining means may comprise a coupling connected to said vent disc and/or a cage for catching the vent disc.

According to a further aspect of the present invention there is provided a vent assembly for a battery pack, the vent assembly comprising:

a vent disc releasably mounted in an annular support frame;

the annular support frame comprising an aperture, wherein the vent disc is an interference fit in said aperture. According to a further aspect of the present invention there is provided a battery pack thermal management system comprising:

a sealed battery pack comprising a plurality of battery cells; and

one or more vent assembly as described herein. According to a further aspect of the present invention there is provided a battery pack comprising one or more vent assembly as described herein.

According to a further aspect of the present invention there is provided a vehicle comprising one or more vent assembly as described herein.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1 shows a schematic representation of a vehicle incorporating a sealed battery pack;

Figure 2 shows a schematic representation of a vent assembly in accordance with an embodiment of the present invention;

Figure 3 shows a perspective view of a vent disc disposed in the vent assembly shown in Figure 2;

Figure 4 shows a vertical section through the vent disc shown in Figure 3;

Figure 5 shows an enlarged view of the mounting arrangement of the vent disc shown in Figures 3 and 4;

Figure 6 shows an alternate mounting arrangement for the vent disc in vent assembly; and

Figure 7 shows a schematic representation of a fermentation vessel comprising a vent assembly in accordance with another arrangement of the present invention.

DETAILED DESCRIPTION

A vent assembly 1 for a battery pack 2 in accordance with an embodiment of the present invention will now be described with reference to accompanying Figures 1 - 6. As shown schematically in Figure 1 , the battery pack 2 is disposed in a vehicle 3, such as an automobile or a sports utility vehicle. The battery pack 2 is a sealed unit and comprises a plurality of cells 4 arranged in an array. The battery pack 2 in the present embodiment is a traction battery configured to supply electrical energy to one or more traction machine 5 to propel the vehicle 3. The vehicle 3 is illustrated as having a front wheel drive configuration, but it will be appreciated that the battery pack 2 may be used in a vehicle 3 having a rear wheel drive configuration or a four wheel drive configuration.

The vent assembly 1 forms part of a thermal management system for venting gases from the battery pack 2 to an ambient environment external to the battery pack 2. The vent assembly 1 in the present embodiment is incorporated into a housing of the battery pack 2. The vent assembly 1 is configured to vent gases from the battery pack 2 in the event of an internal thermal event. As shown in Figure 2, the vent assembly 1 is connected to a vent conduit 6 having an inlet 7 and an outlet 8. The inlet 7 is open to an interior of the battery pack 2, and the outlet 8 is open to the ambient environment. For example, the outlet 8 may be open to atmosphere. As shown in Figure 3, the vent assembly 1 comprises a vent disc 9 and an annular support frame 10. As described herein, the vent disc 9 is mounted in the annular support frame 10 to close the vent conduit 6. The vent disc 9 is a circular disc formed from a resilient material, such as spring steel. The vent disc 9 has a substantially continuous, uninterrupted surface to prevent rupture or bursting under load.

With reference to Figures 4 and 5, the annular support frame 10 comprises a first annular flange 1 1 defining a first annular sidewall 12; and a second annular flange 13 defining a second annular sidewall 14. An annular recess (or channel) 15 is formed between the first and second annular flanges 1 1 , 13 such that the first and second annular sidewalls 12, 14 form opposing sides of the annular recess 15. The vent disc 9 is releasably mounted in the annular support frame 10. In particular, an outer edge 16 of the vent disc 9 is disposed within the annular recess 15. The vent disc 9 and the annular recess 15 are arranged concentrically about a longitudinal axis X of the vent assembly 1 . The annular support frame 10 has an outer diameter of 60mm in the present embodiment. The vent disc 9 has a curved profile (i.e. is curved out of plane). The curvature of the vent disc 9 extends to the outer edge 16 such that the vent disc 9 is curved over its entire surface. In the present embodiment the vent disc 9 has a domed configuration. The vent disc 9 has a convex surface S1 which faces outwardly and a concave surface S2 which faces inwardly. The convex surface S1 is juxtaposed to the second annular sidewall 14. The concave surface S2 is juxtaposed to the first annular sidewall 12.

As shown in Figures 4 and 5, the first annular sidewall 12 is arranged to inhibit displacement of the vent disc 9 out of the annular recess 15 in a first direction (represented by the arrow A1 in Figure 4). The second annular sidewall 14 is configured to enable displacement of the vent disc 9 out of the annular recess 15 in a second direction (represented by the arrow A2 in Figure 4). The first annular flange 1 1 has a first circular aperture 17 and the second annular flange 13 has a second circular aperture 18. The diameter of the first circular aperture 17 is smaller than the diameter of the second circular aperture 18 to inhibit displacement of the vent disc 9 in said first direction. In the present embodiment, the first circular aperture 17 has a diameter of 48mm and the second circular aperture 18 has a diameter of 50mm. The diameter of the vent disc 9 (when undeflected) is substantially equal to or larger than the diameter of the second circular aperture 18. In the present embodiment, the diameter of the vent disc 9 is 50.2mm. The vent disc 9 may be a light interference fit in the annular recess 15. In this case the vent disc 9 may be mounted and supported within the annular recess 15 of the vent assembly 1 solely by the light interference fit between the outer edge 16 of the vent disc 9 and the annular recess 15 (i.e. without mechanical assistance from the first annular sidewall 12 (defined by the first annular flange 1 1 ) or second annular sidewall 14 (defined by the second annular flange 13).

The annular support frame 10 comprises sealing means for forming a seal between the vent disc 9 and the annular support frame 10 to prevent the ingress of water and condensation into the battery pack 2. In the present embodiment the sealing means is in the form of an CD- ring 19 disposed in the annular recess 15. The O-ring 19 may also help to locate the vent disc 9 relative to the annular support frame 10. For example, the O-ring 19 may bias the vent disc 9 towards the first annular sidewall 12. In order to assemble the vent assembly 1 , the vent disc 9 may be inserted through the first circular aperture 17 to locate in the annular recess 15. As shown in Figure 5, the first annular flange 1 1 comprises a conical surface 20 which is tapered towards the longitudinal axis X of the vent assembly 1 in said second direction to facilitate insertion of the vent disc 9. The conical surface 20 helps to guide the vent disc 9 into position. Once assembled, the radial movement of the vent disc 9 relative to the annular support frame 10 is at least substantially inhibited. However, the vent disc 9 may undergo limited movement relative to the annular support frame 10 along said longitudinal axis X.

In use, the vent disc 9 is oriented within the annular support frame 10 such that the convex surface S1 faces outwardly (i.e. in said second direction); and the concave surface S2 faces inwardly (i.e. in said first direction). The application of a force to the convex surface S1 , for example due to an increase in the ambient pressure, deflects the vent disc 9 inwardly and reduces its curvature. The inward deflection causes radial expansion of the vent disc 9 which is accommodated by the annular recess 15. The increased diameter of the vent disc 9 further inhibits displacement of the vent disc 9 in said first direction. Conversely, the application of a force to the concave surface S2, for example due to an increase in the internal pressure within the battery pack 2, deflects the vent disc 9 outwardly and increases its curvature. The outward deflection causes radial contraction of the vent disc 9. It will be appreciated that sufficient increase in the pressure in the battery pack 2, for example due to an internal thermal event, will cause the vent disc 9 to be displaced through the second circular aperture 18 and out of the annular support frame 10. The vent conduit 6 would thereby open allowing gases to vent to the ambient surroundings through the vent assembly 1 .

The vent disc 9 provides a one-way blow-out vent which is demountable from the annular support frame 10 only in said second direction. Under normal operating conditions, the vent disc 9 and the O-ring 19 form a seal with the annular recess 15 to inhibit the ingress of water or condensation into the battery pack 2. In the event of an internal thermal event within the battery pack 2, the vent disc 9 allows excessive pressure to be released from the battery pack 2. The vent disc 9 is beneficial in that it can withstand very high force from external pressure or objects, whilst allowing pressure internal to the battery pack 2 to be released rapidly. In this manner, the vent disc 9 exhibits anisotropic behaviour in response to forces or pressures acting thereon in dependence on whether the force or pressure is external or internal. The vent disc 9 provides simpler construction than prior art devices and ease of resealing. The force required to open the vent conduit 6 can be calibrated by adjusting one or more of the following: the diameter of the vent disc 9, the diameter of the second circular aperture 18, the radius of curvature of the vent disc 9, and the material from which the vent disc 9 is formed.

The sealing means has been described as an O-ring 19 disposed in the annular recess 15. A modified arrangement is shown in Figure 6. Like reference numerals are used for like features. In the modified arrangement, the sealing means is in the form of a resilient insert 21 in said annular recess 15. The resilient insert 21 may be a resilient band or strip that is located in said annular recess 15, or may be moulded in situ, for example from an elastomeric material. In this arrangement, the vent disc 9 engages the resilient insert 21 to promote the seal formed by the vent assembly 1 .

As described herein, the vent disc 9 may be displaced from the annular support frame 10 in said second direction but not in said first direction. The relative dimensions of the first and second circular apertures 17, 18 help to promote this functionality. It will be understood that the curved profile of the vent disc 9 also helps to ensure that the vent disc 9 may be demounted in only one direction. In certain embodiments, the curved profile of the vent disc 9 may provide this functionality. For example, the first and second circular apertures 17, 18 could have the same diameter, but the curved profile would ensure that the vent disc 9 could be displaced from the annular recess 15 in only one direction. It will be appreciated that various changes and modifications may be made to the vent assembly 1 described herein without departing from the scope of the present application.

The first sidewall 12 and/or the second sidewall 14 may be tapered. For example, the first and second sidewalls 12, 14 may be tapered in opposite directions. The annular recess 15 could have a V-shaped profile for locating the vent disc 9.

In a further alternative, the annular recess 15 could have a concave profile. The first and second sidewalls 12, 14 may be formed in a continuous curve.

The vent assembly 1 could be incorporated into a manifold, for example to enable venting from a plurality of conduits in one direction. The manifold may comprise a plurality of said vent assemblies 1 . This arrangement could be used to prevent venting of gases between modules of the battery pack 2.

As will be readily apparent, the vent assembly 1 described herein has application beyond battery packs 2. For example, without limitation the vent assembly 1 may be usefully employed within a variety sealed storage containers, expansion vessels, fuel tanks, liquid storage tanks (especially water tanks for marine environments), and septic waste processing applications. Indeed the vent assembly 1 described herein may be used in any application which requires protection from internal overpressure while precluding ingress of contamination from an external environment.

By way of specific example, a vent assembly 1 for a brewery fermentation vessel in accordance with another arrangement of the present invention will now be described with reference accompanying Figure 7. Like reference numerals are used for like features.

In this arrangement, the vent assembly 1 forms part of an overpressure system for venting gases from a fermentation vessel 22 to an ambient environment external to the fermentation vessel 22. The vent assembly 1 in the present arrangement is incorporated into a housing of the fermentation vessel 22. The vent assembly 1 is configured to vent gases from the fermentation vessel 22 in the event of an internal overpressure condition (e.g. should an airlock or other pressure relief device fail to allow fermentation gases to escape safely from the vessel during the brewing process). As shown in Figure 7, the vent assembly 1 is connected to a vent conduit 6 having an inlet 7 and an outlet 8 as in the foregoing arrangement. The inlet 7 is open to an interior of the fermentation vessel 22, and the outlet 8 is open to the ambient environment. For example, the outlet 8 may be open to atmosphere. As shown in Figure 7, the vent assembly 1 comprises a vent disc 9 and an annular support frame 10. As described herein, the vent disc 9 is mounted in the annular support frame 10 to close the vent conduit 6. The vent disc 9 is a circular disc formed from a resilient material, such as spring steel. The vent disc 9 has a substantially continuous, uninterrupted surface to prevent rupture or bursting under load.

It will be appreciated that the vent assembly 1 described in the current arrangement in use in a fermentation vessel 22 may be the same in all respects as that described in the foregoing arrangement for use in a battery pack 2. Accordingly, the reader is referred to the earlier arrangement and Figures 3 - 6 for further details of the vent assembly 1 as described in relation to the current arrangement.