Pack case having lower venting structure

Abstract

The disclosed pack case includes: a support plate having a plurality of battery assemblies mounted on an upper surface thereof, and having a plurality of venting holes penetrating a surface that is in contact with the plurality of battery assemblies; a pack lower plate arranged to be spaced downward from the support plate so as to form a lower venting passage; a cross beam supported on the support plate; and a bolt penetrating from the outside of the pack lower plate so as to be fastened to the cross beam, wherein the cross beam includes a first nut fastened to the bolt, the pack lower plate includes a second nut fastened to the bolt, and the strength of a first screw thread formed on the first nut is less than the strength of a bolt screw thread formed on the bolt and the strength of a second screw thread formed on the second nut.

Description

Pack case with bottom venting structure

[0001] The present invention relates to a pack case with a lower venting structure designed so that a venting channel for responding to a thermal event occurring in a battery pack flows into the lower space of the pack case, and to a pack case capable of reducing pressure by expanding the pack lower plate in response to the internal pressure increased by the thermal event.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0163977 filed on November 18, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Unlike primary batteries, secondary batteries are rechargeable and are currently the subject of extensive research and development due to their potential for miniaturization and high capacity. The demand for secondary batteries as an energy source is increasing rapidly due to the growing technological development and demand for mobile devices, as well as the rise of electric vehicles and energy storage systems driven by the contemporary need for environmental protection.

[0004] Rechargeable batteries are classified into coin batteries, cylindrical batteries, prismatic batteries, and pouch batteries according to the shape of the battery case. In rechargeable batteries, the electrode assembly mounted inside the battery case is a power generation device capable of charging and discharging, consisting of a laminated structure of electrodes and separators.

[0005] Since secondary batteries require continuous use over long periods, it is necessary to effectively control the heat generated during the charging and discharging process. To effectively dissipate the heat generated by secondary batteries, heat sinks (also called cooling plates) through which a refrigerant flows are widely used. Heat sinks are mounted on the bottom surface of a group of multiple secondary batteries, for example, a battery pack containing multiple batteries, and perform a cooling function by absorbing heat generated inside the pack using a refrigerant and releasing it to the outside.

[0006] However, if the amount of heat generated by the secondary battery is excessive and the cooling of the secondary battery is not carried out smoothly, a positive feedback chain reaction occurs in which the temperature rise of the secondary battery causes an increase in current, and the increase in current again causes a temperature rise, eventually leading to a catastrophic state of thermal runaway.

[0007] In addition, when secondary batteries are grouped in the form of modules or packs, a thermal propagation phenomenon occurs in which surrounding secondary batteries are continuously overheated due to thermal runaway occurring in one secondary battery. That is, when thermal runaway occurs in a battery module within a battery pack, a large amount of conductive dust, gas, and flames are ejected from the high-voltage terminal of the battery module, and consequently, dust accumulates on the high-voltage terminal of an adjacent battery module, and the thermal propagation phenomenon is triggered by heat transfer caused by the gas and flames.

[0008] When thermal propagation occurs within a battery pack, the internal pressure and temperature rise rapidly. To withstand this surge in pressure and temperature, the battery pack must maintain structural robustness for a significant period. If the battery pack collapses and external air enters, combustion reactions intensify rapidly, posing a major risk to the exterior of the pack, such as fire or explosion.

[0009] In order to maintain the structure of the battery pack for as long as possible in response to such thermal events, an appropriate venting structure is designed for the battery pack. By discharging high-pressure, high-temperature gas within the pack through the venting channel, the pressure is reduced to prevent structural collapse. However, since the high-temperature gas flowing along the venting channel can adversely affect other battery modules operating normally and cause heat propagation, this issue must be sufficiently considered in the design of the venting channel. As a countermeasure to this problem, a pack case with a bottom venting structure is being developed, designed so that the venting channel, which responds to thermal events occurring in the battery pack, flows into the lower space of the pack case.

[0010] Battery packs with a bottom venting structure utilize a bolt fastening structure between the pack's bottom plate and the cross beam to ensure safety against vibrations and shocks. In this type of pack fastening structure with a bottom venting design, the support plate and the cross beam supporting the battery module remain mutually fixed even during thermal runaway; consequently, the pack's bottom plate cannot bulge, making it difficult to relieve internal pressure, which can have an adverse effect on heat propagation.

[0011] The present invention aims to provide a pack case capable of relieving internal pressure in a battery pack with a bottom venting structure by implementing a structure in which the bottom plate of the pack can expand when thermal runaway occurs.

[0012] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description of the invention below.

[0013] The present invention relates to a pack case, wherein in one embodiment, a plurality of battery assemblies are mounted on the upper surface and a plurality of venting holes are formed through a support plate on a surface in contact with the plurality of battery assemblies, a pack lower plate spaced apart from the support plate and forming a lower venting passage, a cross beam supported on the support plate, and a bolt that penetrates from the outside of the pack lower plate and is fastened to the cross beam, wherein the cross beam has a first nut fastened to the bolt and the pack lower plate has a second nut fastened to the bolt, and the strength of the first thread formed on the first nut is less than the strength of the bolt thread formed on the bolt and the strength of the second thread formed on the second nut.

[0014] Under normal operating conditions designed for the above pack case, the fastening of the first nut and the second nut to the bolt is maintained.

[0015] And, under abnormal operating conditions where a thermal event occurs in the battery assembly mounted in the above-mentioned pack case, the fastening of the second nut to the bolt is maintained, and the fastening of the first nut to the bolt is destroyed.

[0016] With the fastening of the second nut to the bolt maintained and the fastening of the first nut to the bolt broken, the pack lower plate can expand due to an increase in internal pressure.

[0017] When the lower plate of the pack is expanded due to an increase in internal pressure, the fastening of the second nut to the bolt can be maintained.

[0018] The second nut above can be fixedly installed on the pack lower plate.

[0019] The second nut can be fixedly installed inside a nut hole formed in the lower plate of the pack.

[0020] The first nut can be installed embedded within the cross beam.

[0021] In one embodiment, the first nut may include a first nut body and a resin screw portion coupled within the first nut body and having the first screw thread formed therein.

[0022] The resin screw portion may be softened or melted by the heat transferred to the first nut under abnormal operating conditions in which a thermal event occurs in the battery assembly mounted in the pack case.

[0023] In one embodiment, the cross beam may have a heat transfer passage that exposes a portion of the embedded first nut body to the outside.

[0024] A heat conductor is filled inside the heat transfer passage, and the thermal conductivity of the heat conductor may be higher than the thermal conductivity of the cross beam.

[0025] The pack case of the present invention, having the above-described configuration, ensures the safety of the battery pack against vibrations, shocks, etc., by maintaining a tight double nut connection to the bolt under normal operating conditions, and under abnormal operating conditions where a thermal event occurs, the connection of the second nut to the bolt is maintained but the connection of the first nut is destroyed, thereby allowing the pack bottom plate to expand due to an increase in internal pressure, and thereby suppresses structural collapse of the battery pack by appropriately relieving the internal pressure.

[0026] However, the technical effects obtainable through the present invention are not limited to those described above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description of the invention below.

[0027] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0028] FIG. 1 is a perspective view of a pack case according to one embodiment of the present invention.

[0029] FIG. 2 is a cross-sectional view along the line "AA" of FIG. 1.

[0030] FIG. 3 is a schematic diagram illustrating the state in which the bottom plate of the pack is expanded due to a thermal event occurring within the pack.

[0031] FIG. 4 is a drawing illustrating one embodiment of a first nut provided on a cross beam.

[0032] FIG. 5 is a cross-sectional view of a pack case according to another embodiment of the present invention.

[0033] FIG. 6 is a cross-sectional view of a modified example of the pack case of FIG. 5.

[0034] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail below.

[0035] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0036] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0037] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0038]

[0039] The present invention relates to a pack case, wherein in one embodiment, a plurality of battery assemblies are mounted on the upper surface and a plurality of venting holes are formed through a support plate on a surface in contact with the plurality of battery assemblies, a pack lower plate spaced apart from the support plate and forming a lower venting passage, a cross beam supported on the support plate, and a bolt that penetrates from the outside of the pack lower plate and is fastened to the cross beam, wherein the cross beam has a first nut fastened to the bolt and the pack lower plate has a second nut fastened to the bolt, and the strength of the first thread formed on the first nut is less than the strength of the bolt thread formed on the bolt and the strength of the second thread formed on the second nut.

[0040] The pack case of the present invention, having the above-described configuration, ensures the safety of the battery pack against vibrations, shocks, etc., by maintaining a tight double nut connection to the bolt under normal operating conditions, and under abnormal operating conditions where a thermal event occurs, the connection of the second nut to the bolt is maintained but the connection of the first nut is destroyed, thereby allowing the pack bottom plate to expand due to an increase in internal pressure, and thereby suppresses structural collapse of the battery pack by appropriately relieving the internal pressure.

[0041] Hereinafter, specific embodiments of the pack case (10) according to the present invention will be described in detail with reference to the attached drawings. For reference, the directions of front, back, up, down, left, and right used to specify relative positions in the following description are intended to aid in understanding the invention, and unless otherwise specifically defined, the directions shown in the drawings are used as the reference.

[0042]

[0043] [First embodiment]

[0044] FIG. 1 is a perspective view of a pack case (10) according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view along the line "AA" of FIG. 1.

[0045] The illustrated pack case (10) includes a support plate (100) having a plurality of battery assemblies (510) mounted on its upper surface and a plurality of venting holes (110) formed through a surface in contact with the plurality of battery assemblies (510), and a pack lower plate (200) spaced apart from the support plate (100) to form a lower venting channel (220).

[0046] The support plate (100) has strength capable of supporting the load of a plurality of battery assemblies (510) which are heavy objects. Additionally, the plurality of battery assemblies (510) may include a lower housing (514) having a plurality of through holes (516) formed therein to implement directional venting. The through holes (516) of the lower housing (514) are aligned to match the venting holes (110) of the support plate (100). Thus, a large amount of venting gas and high-temperature particles resulting from a thermal event in a battery cell (512) of the battery assembly (510) are induced to move along a predetermined path leading to the through holes (516) and the venting holes (110).

[0047] Additionally, although not shown, a heat sink for external heat dissipation may be placed in close contact with the bottom surface of the support plate (100). Heat generated from the battery assembly (510) is transferred to the heat sink in the form of heat conduction through the support plate (100), and the transferred heat is dissipated to the outside through a refrigerant (e.g., cooling water) flowing through the cooling channels inside the heat sink. The support plate (100) and the heat sink may be manufactured as a single unit or manufactured separately and then joined together.

[0048] The pack lower plate (200) corresponds to a plate-shaped member forming the bottom surface of the pack case (10). The pack lower plate (200) is spaced downward from the support plate (100) to create a space between them, and this space forms a lower venting channel (220). That is, venting gas, etc. generated from the battery assembly (510) mounted on the support plate (100) flows downward through the venting hole (110), and this venting gas, etc. flows through the space between the pack lower plate (200) and is finally discharged to the outside of the battery pack (500).

[0049] Here, the battery assembly (510) referred to in this specification means a collection of battery cells in which a plurality of battery cells (512) are structurally and electrically connected. Depending on the method of structurally binding the plurality of battery cells (512), the battery assembly (510) may be referred to by various terms such as battery module, battery block, or battery unit, but the pack case (10) of the present invention is not limited to a specific structure of battery assembly (510). For example, the pack case (10) of the present invention may be a pack case (10) in which a battery module containing a plurality of battery cells (512) is mounted inside a closed housing, or it may be a pack case (10) of a Cell-to-Pack structure in which a plurality of battery cells (512) are bundled with a minimal structure and mounted directly into the pack case (10) without a modular structure that contains the plurality of battery cells (512) inside the housing.

[0050] And, the pack case (10) of the present invention includes a cross beam (300) supported on a support plate (100). The cross beam (300) improves the rigidity, for example, compressive strength, of the pack case (10) along its longitudinal direction. The cross beam (300) may be joined to the support plate (100) by welding or formed integrally by extrusion molding.

[0051] Since there is a space between the support plate (100) and the pack bottom plate (200), a bolt (400) penetrating from the outside of the pack bottom plate (200) is fastened to the cross beam (300) so as to maintain the upper and lower stacking structure between the support plate (100) and the pack bottom plate (200) well. In other words, the bolt (400) acts as a kind of pillar that distributes and bears the load applied to the support plate (100).

[0052] Referring to FIG. 2, the cross beam (300) is provided with a first nut (410) that is fastened to the bolt (400), and the pack bottom plate (200) is provided with a second nut (420) that is fastened to the bolt (400). Thus, the bolt (400) penetrates the pack bottom plate (200) while being fastened to the second nut (420), and reaches the cross beam (300) and is fastened to the first nut (410). Due to this double nut fastening structure, the bolt (400) firmly supports the support plate (100) against external vibrations, shocks, etc. The first nut (410) can be installed inside the cross beam (300), and structurally more stable load distribution can be achieved by accurately aligning the cross beam (300) and the bolt (400).

[0053] Here, the strength of the first thread (412) formed on the first nut (410) is less than the strength of the bolt thread (402) formed on the bolt (400) and the strength of the second thread (422) formed on the second nut (420). In other words, in the double nut fastening structure, the first thread (412) of the first nut (410) provided on the cross beam (300) is the weakest. For example, the bolt (400) and the second nut (420) can be made of steel, and the first nut (410) can be made of copper, which has lower hardness. Since the first nut (410) is the weakest, the fastening torque of the bolt (400) needs to be set based on the first nut (410).

[0054] FIG. 2 corresponds to a double nut fastening structure of a bolt (400) under normal operating conditions designed for a pack case (10). Under normal operating conditions of the battery pack (500), the temperature and pressure inside the pack satisfy the design criteria. Therefore, the bolt (400) firmly supports the support plate (100) against external vibrations, shocks, etc., and the pack case (10) is structurally stable.

[0055] FIG. 3 is a schematic diagram illustrating the state in which the pack bottom plate (200) has expanded due to a thermal event occurring within the pack. A thermal event refers to an abnormal accident occurring in a battery cell (512), such as thermal runaway or thermal propagation, and when a thermal event occurs, the temperature and pressure within the pack rise rapidly. Due to the rise in pressure within the pack, a strong tension is applied to the bolt (400) in a direction in which the support plate (100) and the pack bottom plate (200) move away from each other. If the strength of the first thread (412) is designed such that the tension acting on the bolt (400) during a thermal event exceeds the allowable limit of the first nut (410), the fastening of the second nut (420) to the bolt (400) is maintained, but the fastening of the first nut (410) to the bolt (400) is destroyed. FIG. 3 illustrates the state in which the double nut fastening structure of such a bolt (400) is destroyed.

[0056] As the restraint of the bolt (400) on the cross beam (300) is released, the pack lower plate (200) bends outward due to the pressure within the pack acting through the lower venting channel (220), thereby expanding the lower venting channel (220). As the volume increases due to the expansion of the pack lower plate (200), the pressure within the pack is appropriately reduced, and the structural collapse of the pack case (10) is suppressed or delayed.

[0057] As shown in FIG. 3, when the pack bottom plate (200) is expanded due to increased internal pressure, it may be desirable to maintain the fastening of the second nut (420) to the bolt (400). By keeping the bolt (400) and the second nut (420) fastened, the risk of external oxygen flowing in at the point where the bolt (400) penetrates the pack bottom plate (200) to promote the spread of a thermal event, or the risk of a fire caused by the ejection of venting gas and high-temperature particles, is prevented.

[0058] The second nut (420) can be fixedly installed on the pack bottom plate (200) so that the bolt (400) and the second nut (420) remain connected even when a heat event occurs. For example, the second nut (420) can be fixedly installed on the pack bottom plate (200) by means such as welding. In addition, the second nut (420) can be fixedly installed inside a nut hole (210) formed in the pack bottom plate (200) so that the second nut (420) does not protrude from the pack bottom plate (200) and unnecessarily occupy space.

[0059]

[0060] [Second embodiment]

[0061] FIG. 4 is a drawing illustrating one embodiment of a first nut (410) provided on a cross beam (300).

[0062] In the embodiment of FIG. 4, the first nut (410) provided on the cross beam (300) includes a first nut body (414) and a resin thread portion (416). The resin thread portion (416) is located in the part of the first nut (410) where the first thread (412) is to be formed. The resin thread portion (416) is coupled inside the first nut body (414) to form an integral part, and the first thread (412) is formed therein.

[0063] The resin screw portion (416) can be softened or melted by the heat transferred to the first nut (410) under abnormal operating conditions where a thermal event occurs in the battery assembly (510) mounted in the pack case (10). That is, when the first nut (410) of FIG. 4 is provided, the fastening structure of the first nut (410) can be more reliably removed by receiving the effect of temperature rise as well as pressure rise caused by the thermal event. Therefore, when a thermal event occurs, the release of the bolt (400) for the cross beam (300) occurs earlier, thereby promoting the expansion and pressure reduction effect of the pack lower plate (200).

[0064]

[0065] [Third Embodiment]

[0066] FIG. 5 is a cross-sectional view of a pack case (10) according to another embodiment of the present invention. In the embodiment of FIG. 5, the cross beam (300) has a heat transfer passage (310) that exposes a portion of the built-in first nut body (414) to the outside. Here, the first nut (410) is applied such that a first thread (412) is formed on the resin screw portion (416) described in the second embodiment.

[0067] A heat transfer passage (310) formed in the cross beam (300) exposes the first nut body (414) of the first nut (410), thereby transferring the effect of the temperature rise caused by a thermal event to the inner resin thread (416) through the heat transfer passage (310) and the first nut body (414). The heat transferred in this way induces the softening or melting of the resin thread (416) more quickly, and consequently, the release of the bolt (400) from the cross beam (300) is promoted.

[0068] FIG. 6 is a cross-sectional view of a modified example of the pack case (10) of FIG. 5. In the modified example of FIG. 6, a heat conductor (320) is filled inside the heat transfer passage (310) of the cross beam (300). The thermal conductivity of the heat conductor (320) is higher than that of the cross beam (300), and the heat conductor (320), which has a much higher thermal conductivity than air, can transfer heat caused by a thermal event to the first nut (410) more quickly. Accordingly, the release of the bolt (400) for the cross beam (300) can be achieved quickly.

[0069]

[0070] The present invention has been described in more detail above through drawings and embodiments. However, the configurations described in the drawings or embodiments described in this specification are merely one embodiment of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0071]

[0072] [Explanation of the symbol]

[0073] 10: Pack case

[0074] 100: Support plate

[0075] 110: Venting hole

[0076] 200: Pack bottom plate

[0077] 210: Nut hole

[0078] 220: Lower venting channel

[0079] 300: Cross Beam

[0080] 310; heat transfer path

[0081] 320: Thermal conductor

[0082] 400: Bolt

[0083] 402: Bolt threads

[0084] 410: 1st nut

[0085] 412: First thread

[0086] 414: First nut body

[0087] 416: Resin screw part

[0088] 420: Second nut

[0089] 422: Second thread

[0090] 500: Battery pack

[0091] 510: Battery Assembly

[0092] 512: Battery cell

[0093] 514: Lower housing

[0094] 516: Through hole

Claims

1. A support plate having a plurality of battery assemblies mounted on its upper surface and a plurality of venting holes formed through a surface in contact with the plurality of battery assemblies; A pack lower plate spaced downward from the above support plate to form a lower venting channel; A cross beam supported on the above support plate; and A bolt that penetrates from the outside of the pack lower plate and is fastened to the cross beam; Includes, The above cross beam is provided with a first nut that is fastened to the above bolt, and The above pack lower plate is equipped with a second nut that is fastened to the above bolt, and A pack case in which the strength of the first thread formed on the first nut is smaller than the strength of the bolt thread formed on the bolt and the strength of the second thread formed on the second nut.

2. In Paragraph 1, Under normal operating conditions designed for the above pack case, A pack case in which the fastening of the first nut and the second nut to the above bolt is maintained.

3. In Paragraph 2, Under abnormal operating conditions where a thermal event occurs in the battery assembly mounted in the above-mentioned pack case, A pack case in which the fastening of the second nut to the bolt is maintained, and the fastening of the first nut to the bolt is destroyed.

4. In Paragraph 3, With the fastening of the second nut to the bolt maintained and the fastening of the first nut to the bolt broken, The above pack lower plate is a pack case that can expand by increasing internal pressure.

5. In Paragraph 4, The lower plate of the above pack, in a state expanded by an increase in internal pressure, A pack case in which the fastening of the second nut to the above bolt is maintained.

6. In Paragraph 5, The above second nut is, Pack case, fixedly installed on the lower plate of the above pack, 7. In Paragraph 6, The above second nut is, A pack case fixedly installed inside a nut hole formed in the lower plate of the pack.

8. In Paragraph 1, The first nut above is, Pack case installed inside the above cross beam.

9. In Paragraph 8, The first nut above is, A pack case comprising a first nut body and a resin screw portion coupled within the first nut body and having the first screw thread formed therein.

10. In Paragraph 9, The above resin screw part is, A pack case that softens or melts due to heat transferred to the first nut under abnormal operating conditions in which a thermal event occurs in the battery assembly mounted in the pack case.

11. In Paragraph 10, The above cross beam is, A pack case having a heat transfer passage that exposes a portion of the built-in first nut body to the outside.

12. In Paragraph 11, A heat conductor is filled inside the above heat transfer passage, and Pack case, in which the thermal conductivity of the above thermal conductor is higher than the thermal conductivity of the above cross beam.

Images