Battery pack shell, battery pack assembling method and battery pack

Abstract

The invention discloses a battery pack shell, a battery pack assembling method and a battery pack, the battery pack shell comprises a shell body, the shell body is provided with an accommodating cavity for accommodating a plurality of cylindrical batteries, and the bottom of the accommodating cavity is provided with battery mounting grooves corresponding to the cylindrical batteries one by one; at least one glue overflowing groove used for containing and guiding overflowing liquid glue when a cylindrical battery is pressed in is formed in the inner wall of each battery installation groove, the glue overflowing grooves are perpendicularly formed along the groove walls of the battery installation grooves, and weak areas are arranged at the positions, corresponding to the battery installation grooves, of the bottom of the outer wall of the shell body. The shell thickness of the weak area is smaller than the shell thickness of the surrounding area. When the battery is pressed into the mounting groove after glue injection, liquid glue overflows upwards along the vertical glue overflowing groove and fills the mounting groove, so that uniform distribution and full filling of the adhesive in the circumferential direction of the side wall of the battery are ensured. The weak area with the structure thickness smaller than that of the surrounding area is arranged at the position corresponding to the battery pressure relief valve, and presetting and orientation of the pressure relief channel are achieved.

Description

Technical Field

[0001] This invention relates to the field of battery pack technology, specifically to battery pack housing, battery pack assembly method, and battery pack. Background Technology

[0002] As the core power unit in electric vehicles, energy storage systems, and other fields, the reliability, safety, and production efficiency of the battery pack's structural design are of paramount importance. Traditional battery pack lower casing designs typically face multiple challenges, including structural complexity, insecure battery mounting, and insufficient protection against thermal runaway.

[0003] For battery mounting, a common approach is to use independent metal or plastic brackets to position and hold the batteries. These brackets, as separate components, need to be first fixed to the lower casing of the battery pack using welding, screwing, or clipping, before the cylindrical batteries are individually placed into the bracket slots. This method not only involves a large number of parts and cumbersome assembly processes, leading to increased costs and reduced production efficiency, but also poses a safety hazard as the connection points may loosen under long-term vehicle vibration due to vibration. Another simplified approach is to omit the independent brackets and directly fill the space between the battery and the casing with structural adhesive for fixation. However, this simple adhesive method has significant drawbacks: if adhesive is only applied to the bottom of the battery, the bonding area is limited, resulting in insufficient fixing strength; if adhesive is applied to the entire battery after placement, the adhesive cannot evenly fill the narrow and irregular gaps between the battery and the casing, easily creating voids and leading to weak adhesion, and also requires a large amount of adhesive, resulting in high costs.

[0004] In terms of thermal safety protection, effectively managing the pressure relief process during battery thermal runaway is a key challenge. Some designs incorporate exhaust channels inside the battery module or direct pressure relief valves towards the internal cavities of the battery pack, hoping that the gas can be discharged along a predetermined path. However, these solutions often fail to achieve physical isolation of the cell-level pressure relief channels. The high-temperature, high-speed jets released from adjacent cells can easily directly impact neighboring cells, triggering a chain reaction of thermal runaway. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a battery pack housing, a battery pack assembly method, and a battery pack. By injecting liquid adhesive along the overflow groove, the uniform distribution and full filling of the adhesive in the circumferential direction of the battery sidewall are ensured. By setting a weak area with a structural thickness smaller than the surrounding area at the position corresponding to the battery pressure relief valve, the pre-setting and orientation of the pressure relief channel are achieved.

[0006] The technical solution adopted by the present invention is as follows: a battery pack housing, including the housing body, the housing body having a cavity for accommodating multiple cylindrical batteries, the bottom of the cavity having a battery mounting groove corresponding to each cylindrical battery, the inner wall of the battery mounting groove having at least one overflow groove for accommodating and guiding overflowing liquid adhesive when the cylindrical battery is pressed in, the overflow groove being vertically arranged along the groove wall of the battery mounting groove, the bottom of the outer wall of the housing body having a weak area corresponding to the position of each battery mounting groove, the housing thickness of the weak area being less than the housing thickness of the surrounding area.

[0007] Optionally, the outer bottom of the shell body is provided with multiple grooves, which constitute the weak area. The multiple grooves are arranged adjacent to each other in sequence, and the centers of two adjacent grooves are not located on the same straight line.

[0008] Optionally, the wall of the battery mounting slot extends upward into the cavity, and there are multiple battery mounting slots, the outline of which is adapted to the bottom outer outline of the cylindrical battery.

[0009] Optionally, there are multiple overflow grooves, which are evenly distributed at intervals along the circumference of the battery mounting groove.

[0010] Optionally, the outer bottom of the shell body is provided with reinforcing ribs, the reinforcing ribs including a central ring and a plurality of ribs extending outward from the central ring, the ribs dividing the groove into a plurality of sub-regions.

[0011] Optionally, the bottom of the battery mounting slot is also provided with a clearance groove for accommodating the bottom protrusion of the cylindrical battery.

[0012] Optionally, the thickness of the weak area meets a predetermined pressure relief and bursting condition, wherein the predetermined pressure relief and bursting condition is: under the pressure generated by the opening of the cylindrical battery pressure relief valve, the stress on the weak area is greater than or equal to the tensile strength of the shell material under this working condition.

[0013] Optionally, the thickness of the weak zone satisfies the following relationship:

[0014] (P vent * d weak ) / t weak ≥k * σ b (T vent )

[0015] Among them, P vent d is the rated discharge pressure of the cylindrical battery. weak σ is the equivalent stress diameter of the weak zone. b For the shell material at the pressure relief operating temperature T ventThe tensile strength is given by k, where k is a safety factor greater than 1.

[0016] This invention also discloses a battery pack assembly method based on the battery pack casing described above, comprising the following steps:

[0017] (1) Place the shell body vertically so that the opening of the cavity faces upward;

[0018] (2) Inject liquid adhesive into each of the battery mounting slots;

[0019] (3) Align the cylindrical battery with and press it into the corresponding battery mounting slot, so that the pressure relief valve at the bottom of the cylindrical battery is aligned with the weak area at the bottom of the shell body. During this process, the liquid glue is squeezed and overflows through the glue overflow groove.

[0020] (4) Let the shell body stand until it solidifies into a liquid state, thus completing the fixation of the cylindrical battery and the shell body.

[0021] The present invention also discloses a battery pack, including a cylindrical battery and the battery pack housing described above, wherein the cylindrical battery is installed in the battery mounting slot, and the pressure relief valve of the cylindrical battery faces the corresponding pressure relief weak area.

[0022] The beneficial effects of this invention are as follows: When the battery is pressed into the mounting groove after adhesive injection, the liquid adhesive overflows upwards along the vertical overflow groove and fills the groove, ensuring uniform distribution and full filling of the adhesive on the circumferential sidewall of the battery. After curing, a composite bonding structure is formed, including bonding to the bottom surface of the battery and circumferential bonding to the sidewall. The bonding area is maximized, and the fixing strength, vibration resistance, and impact resistance are fundamentally improved, eliminating battery loosening. By setting a weak area with a structural thickness smaller than the surrounding area at the position corresponding to the battery pressure relief valve, the pre-setting and orientation of the pressure relief channel is realized. Each battery's pressure relief valve is aligned with a dedicated weak area. When thermal runaway occurs in the cell, high-temperature and high-pressure gas can instantly break through the weak area shell below it, forming a directional and independent pressure relief port, directly exporting destructive energy and ejected material to the outside of the battery pack. This effectively blocks the direct impact of high-temperature ejected material on adjacent batteries, significantly suppressing the risk of chain reaction (thermal propagation) of thermal runaway, thereby greatly improving the overall safety and reliability of the battery pack. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the battery pack housing structure proposed in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the weak area of ​​the battery pack casing according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the battery pack proposed in an embodiment of the present invention.

[0026] The markings in the attached figures are as follows: 10, casing; 11, cavity; 20, battery mounting slot; 21, slot wall; 22, glue overflow slot; 23, clearance slot; 30, weak area; 31, groove; 40, reinforcing rib; 41, central ring; 42, rib; 300 cylindrical battery. Detailed Implementation

[0027] The present application will now be described in further detail with reference to the accompanying drawings and embodiments.

[0028] like Figures 1 to 3 As shown, this embodiment discloses a battery pack housing, mainly a housing body 10. The housing body 10 is an integrally injection-molded plastic part. The housing body 10 has a cavity 11 inside for accommodating multiple cylindrical batteries. At the bottom of the cavity 11, there are multiple battery mounting slots 20 corresponding to the cylindrical batteries to be installed. The outline of these battery mounting slots 20 is adapted to the bottom outer outline of the cylindrical battery 300 for initial reception and positioning of the batteries.

[0029] To ensure reliable battery mounting, the wall 21 of each battery mounting slot 20 extends upward into the cavity 11. The wall 21 itself restricts the radial displacement of the battery. Multiple overflow grooves 22 are evenly spaced circumferentially on the upper part of the wall 21. In this embodiment, each mounting slot has multiple overflow grooves 22, evenly distributed along the circumference of the mounting slot. Each overflow groove 22 is perpendicular to the wall 21 of the battery mounting slot 20, meaning its extension direction is parallel to the axis of the battery mounting slot 20. When the battery 300 is pressed into the mounting slot 20, the pre-injected liquid adhesive (such as thermally conductive epoxy resin adhesive) is compressed. Due to the vertical overflow grooves 22, the liquid adhesive can be orderly guided and fill these overflow grooves 22 along the gap between the wall 21 and the battery sidewall. This design ensures that the adhesive overflows evenly around the battery, rather than flowing randomly. After the adhesive cures, it not only forms a surface bond at the bottom of the battery, but also forms a uniform and firm ring bond around the side wall of the battery, solving the problem of unreliable fixation caused by uneven adhesive filling and small bonding area in traditional solutions.

[0030] At the bottom center of the battery mounting slot 20, there is also a clearance slot 23. This clearance slot 23 is used to accommodate electrode protrusions or other protruding structures that may exist at the bottom of the cylindrical battery 300. By adapting the contour of the battery mounting slot 20 to the outer contour of the bottom of the battery 300 and integrally molding it during manufacturing, separate battery bracket parts are eliminated, simplifying the system structure of the battery pack, reducing the number of parts, improving assembly efficiency, and reducing costs.

[0031] At the bottom of the outer wall of the casing 10, directly below each battery mounting slot 20, a weak area 30 is provided. The casing thickness of the weak area 30 is reduced, significantly less than the casing thickness of the surrounding area. Specifically, the weak area 30 is formed by injection molding a groove 31 on the bottom outer side of the casing 10. That is, the groove 31 directly constitutes the weak area 30. Multiple grooves 31 are arranged adjacent to each other, and the centers of two adjacent grooves 31 are not on the same straight line. This staggered arrangement of adjacent groove centers makes the pressure relief channels of each battery spatially staggered, rather than arranged on one or more straight lines. This effectively disperses potential thermal runaway eruption paths, avoids high-temperature jets concentrating on impacting a part of the casing or adjacent batteries, and greatly improves the overall thermal safety protection level of the battery pack.

[0032] Furthermore, on the outer bottom of the casing body 10, a reinforcing rib 40 is provided around the groove 31 (weak area 30). This reinforcing rib 40 includes a central ring 41 and multiple ribs 42 extending radially outward from the central ring 41. The radial ribs 42 naturally divide the circular groove 31 into multiple fan-shaped sub-regions. This design has dual advantages: firstly, the reinforcing rib significantly enhances the overall structural strength and deformation resistance of the casing bottom under conditions such as battery weight and vehicle vibration; secondly, since the orientation of the pressure relief valve at the bottom of the battery is random when it is placed in the mounting slot, the multiple sub-regions formed by the radial ribs ensure that regardless of the angle at which the pressure relief valve orifice faces, there is always a thinner sub-region defined by the ribs directly below it that can serve as an effective pressure relief channel.

[0033] Based on the aforementioned housing 100, this embodiment also provides a battery pack assembly method, including the following steps:

[0034] (1) Place the shell body 10 vertically with the opening of its cavity 11 facing upward. This position facilitates subsequent glue injection and battery installation.

[0035] (2) Using an automated adhesive dispensing device, a measured amount of liquid structural adhesive is injected into each of the battery mounting slots 20. The amount of adhesive injected is precisely calculated to ensure that the gaps are filled and an appropriate amount overflows into the overflow tank 22.

[0036] (3) Align the cylindrical battery 300 with the corresponding battery mounting groove 20 in a specific direction (ensuring that the pressure relief valve 301 at its bottom faces downward), and then apply axial pressure to press it in. During this process, it is necessary to ensure that the pressure relief valve 301 at the bottom of the cylindrical battery 300 is macroscopically aligned with the weak area 30 (groove 31) at the bottom of the casing body 10. When pressed in, the liquid adhesive is squeezed and overflows evenly upward through the gap between the battery and the groove wall 21, fully filling each adhesive overflow groove 22.

[0037] (4) Place the assembled shell body 100 at a specific work station until the internal liquid structural adhesive is completely cured. After curing, the cylindrical battery 300 is firmly bonded to the shell body 10 by a large area of ​​structural adhesive, and its pressure relief valve 301 is aligned with the weak area 30 at the bottom, completing the integrated assembly of fixing and explosion-proof alignment.

[0038] This embodiment also provides a complete battery pack product. The product includes the aforementioned battery pack housing 100 and a plurality of cylindrical batteries 300. The cylindrical batteries 300 are installed within the battery mounting groove 20 and are fixedly connected to the housing body 100 by cured structural adhesive. The pressure relief valve 301 of each cylindrical battery 300 faces the corresponding weak area 30 (groove 31).

[0039] To ensure that the high-temperature, high-pressure gas generated when the cylindrical battery experiences thermal runaway and the pressure relief valve opens can reliably breach the weak area and form an effective pressure relief channel, while preventing accidental rupture of the casing under normal operating conditions, the structural strength of the weak area needs to be specifically designed. The structural strength of the weak area must be lower than the total stress on the casing caused by the gas pressure and thermal shock generated when the pressure relief valve opens, but higher than the static pressure and general impact stress that the battery pack may withstand during normal use, transportation, and installation. In practical design, the mechanical and thermal loads during the pressure relief process should be comprehensively considered. Based on thin-plate bending theory and thermal stress analysis, the following strength verification criteria are established to determine the thickness and structural safety of the weak area:

[0040] σ total =σ m +σ th ≤[σ] T

[0041] Where, σ m The mechanical bending stress caused by the pressure relief can be approximately calculated using the following formula:

[0042] σ m =K*(P vent * R²) / t weak ²

[0043] In the formula, K is the stress coefficient, which depends on the constraint conditions at the edge of the weak zone (e.g., 3 / 4 when completely fixed); P vent R is the rated discharge pressure of the cylindrical battery; R is the equivalent radius of the weak zone; t weak This represents the minimum thickness of the weak zone.

[0044] σ th The thermal stress generated by the temperature gradient in the weak area due to the impact of high-temperature gas during the pressure relief can be approximately calculated using the following formula:

[0045] σ th≈[E(T)*α(T)*ΔT] / [2*(1-ν)]

[0046] In the formula, E(T) represents the shell material at the pressure relief temperature T. vent The elastic modulus at temperature T; α(T) is the coefficient of linear expansion of the material at temperature T; ΔT is the temperature difference between the upper and lower surfaces of the weak zone or the constrained part; ν is the Poisson's ratio of the material.

[0047] [σ]T is the material at the pressure relief temperature T. vent The allowable stress is determined by the following formula:

[0048] [σ]T=σ s (T vent ) / n

[0049] In the formula σ s (T vent ) represents the material at the pressure relief temperature T vent The yield strength (or tensile strength) under high temperature conditions; n is the safety factor under high temperature conditions, which is usually greater than the safety factor at normal temperature, for example, it can be selected in the range of 1.5 to 3.0.

[0050] By designing according to the above principles, it can be ensured that weak areas will reliably rupture during thermal runaway and pressure relief, while maintaining sufficient structural integrity during normal use.

[0051] It is understood that the specific embodiments described above are merely for explaining the relevant invention and not for limiting the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Multiple technical solutions in the same embodiment, as well as multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions that do not contradict or conflict with each other. Any equivalent structural transformations made based on the content of this specification and drawings, whether directly or indirectly applied to other related technical fields, are similarly included within the scope of protection of this invention.

Claims

1. A battery pack housing, characterized in that, The device includes a housing body, which has a cavity for accommodating multiple cylindrical batteries. The bottom of the cavity has a battery mounting groove corresponding to each cylindrical battery. The inner wall of the battery mounting groove has at least one overflow groove for accommodating and guiding the overflowing liquid adhesive when the cylindrical batteries are pressed in. The overflow groove is vertically arranged along the groove wall of the battery mounting groove. The bottom of the outer wall of the housing body has a weak area corresponding to the position of each battery mounting groove. The shell thickness of the weak area is less than the shell thickness of the surrounding area.

2. The battery pack housing according to claim 1, characterized in that, The outer bottom of the shell body is provided with multiple grooves, which constitute the weak area. The multiple grooves are arranged adjacent to each other in sequence, and the centers of two adjacent grooves are not located on the same straight line.

3. The battery pack housing according to claim 1, characterized in that, The wall of the battery mounting slot extends upward into the cavity, and there are multiple battery mounting slots. The outline of the battery mounting slot is adapted to the bottom outer outline of the cylindrical battery.

4. The battery pack housing according to claim 1, characterized in that, There are multiple overflow grooves, and the multiple overflow grooves are evenly distributed at intervals along the circumference of the battery mounting groove.

5. The battery pack housing according to claim 1, characterized in that, The outer bottom of the shell body is provided with reinforcing ribs, which include a central ring and a plurality of ribs extending outward from the central ring. The ribs divide the groove into a plurality of sub-regions.

6. The battery pack housing according to claim 1, characterized in that, The bottom of the battery mounting slot is also provided with a clearance groove for accommodating the protrusion at the bottom of the cylindrical battery.

7. The battery pack housing according to claim 1, characterized in that, The thickness of the weak zone meets the predetermined pressure relief and bursting condition, which is: Under the pressure generated by the opening of the cylindrical battery pressure relief valve, the stress on the weak area is greater than or equal to the tensile strength of the shell material.

8. The battery pack housing according to claim 7, characterized in that, The thickness of the weak zone satisfies the following relationship: σ total =σ m +σ th ≤[σ] T σ m = K * (P * R²) / t² σ th ≈ [E(T)*a(T)*DT] / [2*(1-v)] [σ]T=σ s (T vent ) / n In the formula, σ m For mechanical stress, σ th For thermal stress, [σ]T is the material stress at the pressure relief temperature T. vent The allowable stress is given by K, where K is the stress coefficient and P is the rated pressure of the cylindrical battery. vent R is the equivalent radius of the weak zone, R = d weak / 2, where t is the minimum thickness of the weak zone. weak E(T) is the elastic modulus of the shell material at temperature T, α(T) is the coefficient of linear expansion of the shell material at temperature T, ΔT is the temperature difference between the upper and lower surfaces of the weak area or the constrained part during pressure relief, ν is the Poisson's ratio of the material, and σ s (T vent ) represents the material at the pressure relief temperature T vent The yield strength is given by n, where n is the safety factor under high-temperature conditions.

9. A battery pack assembly method based on the battery pack casing according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Place the shell body vertically so that the opening of the cavity faces upward; (2) Inject liquid adhesive into each of the battery mounting slots; (3) Align the cylindrical battery with and press it into the corresponding battery mounting slot, so that the pressure relief valve at the bottom of the cylindrical battery is aligned with the weak area at the bottom of the shell body. During this process, the liquid glue is squeezed and overflows through the glue overflow groove. (4) Let the shell body stand until it solidifies into a liquid state, thus completing the fixation of the cylindrical battery and the shell body.

10. A battery pack, characterized in that, The battery pack includes a cylindrical battery and a battery pack housing as described in any one of claims 1 to 8, wherein the cylindrical battery is installed in the battery mounting slot and the pressure relief valve of the cylindrical battery faces the corresponding weak area.

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