A method for curing and bonding battery boxes

Abstract

This invention relates to the field of battery pack technology, specifically to a method for curing and bonding battery boxes. The method includes: sequentially applying expanding foam and sealant to sections of a liquid cooling plate and a bottom protective plate to obtain a connector to be cured; placing the connector into a mold and hot-pressing it to cure the expanding foam, obtaining an intermediate cured connector; wherein the area of ​​the mold corresponding to the expanding foam has a first mold temperature, and the area of ​​the mold corresponding to the sealant has a second mold temperature, the second mold temperature being lower than the first mold temperature; removing the intermediate cured connector from the mold and allowing it to stand at room temperature to allow the sealant to cure completely, obtaining a final cured connector. The curing process of this invention can balance the curing efficiency and sealing reliability of steel-aluminum battery packs.

Description

Technical Field

[0001] This invention relates to the field of battery pack technology, and more specifically to a method for curing and bonding battery boxes. Background Technology

[0002] Battery box materials exhibit a variety of dissimilar material connections, including ordinary steel-aluminum, high-strength steel-aluminum, profile-cast aluminum, and profile-profile connections. The bottom protective plate is a crucial component of the battery box, typically made of high-strength steel, while the liquid cooling plate, a vital component for heat dissipation, is generally made of aluminum alloy. The connection between the steel and aluminum materials often requires sealant for a tight seal, and expanding foam is also needed between the bottom protective plate and the liquid cooling plate to reduce noise and increase rigidity.

[0003] Currently, the biggest problem in steel-aluminum adhesive bonding processes is the difference in open time and curing temperature between the sealant and the foaming adhesive. Related technologies typically employ two solutions: the first involves sequentially applying and curing the two adhesives, requiring numerous fixtures and extended dwell times; the second is a compromise, using a single temperature close to the curing temperatures of both adhesives for long-term, constant-temperature curing. Both curing methods suffer from high production line investment and low curing efficiency. Furthermore, due to the different coefficients of thermal expansion of steel and aluminum, slight movement can occur between the aluminum alloy and the steel plate when different adhesives are cured at different temperatures. This can cause displacement of the battery box during adhesive curing, resulting in poor airtightness and insufficient bond strength. Summary of the Invention

[0004] The technical problem solved by this invention is that it is difficult to balance curing efficiency and sealing reliability when using two different types of adhesives for curing steel-aluminum battery packs.

[0005] To address the above problems, the present invention provides a method for curing and bonding a battery box, comprising:

[0006] Foam and sealant are applied sequentially between the liquid cooling plate and the bottom protective plate to obtain the joint to be cured.

[0007] The connector to be cured is placed in a mold and hot-pressed to cure the foam adhesive, thereby obtaining an intermediate cured connector; wherein, the area of ​​the mold corresponding to the foam adhesive has a first mold temperature, and the area of ​​the mold corresponding to the sealant has a second mold temperature, the second mold temperature being lower than the first mold temperature;

[0008] The intermediate cured connector is removed from the mold and left to stand at room temperature to allow the sealant to cure completely, resulting in the final cured connector.

[0009] Optionally, the first mold temperature ranges from 70 to 80°C, and the second mold temperature ranges from 5 to 10°C.

[0010] Optionally, the hot-press curing time of the connector to be cured is 8 to 12 minutes, and the room temperature curing time of the intermediate-cured connector is 15 to 20 minutes.

[0011] Optionally, the step of placing the connector to be cured into a mold for hot pressing and curing to obtain an intermediate cured connector further includes:

[0012] The molding pressure of the area corresponding to the foam in the mold is 450 to 500 N / cm. 2 The molding pressure of the mold corresponding to the sealant area is 180 to 250 N / cm. 2 .

[0013] Optionally, a heat insulation element is provided between the area corresponding to the foam and the area corresponding to the sealant within the mold.

[0014] Optionally, the surface of the mold corresponding to the area of ​​the sealant is provided with heat sink, and the surface of the mold corresponding to the area of ​​the foam is provided with heating pad.

[0015] Optionally, the mold is provided with a cooling channel inside the area corresponding to the sealant, and a cooling medium flows through the cooling channel.

[0016] Optionally, the step of sequentially applying expanding foam and sealant between the cold plate and the bottom protective plate to obtain the joint to be cured includes:

[0017] First, apply the foaming adhesive to the foaming area of ​​the surface of the liquid cooling plate near the bottom protective plate, and then apply the sealant to the sealing area of ​​the surface of the bottom protective plate near the liquid cooling plate.

[0018] Optionally, the foaming area is located in the middle of the surface of the liquid cooling plate, and the sealing area includes side sealing areas located on the four sides of the bottom protective plate.

[0019] Optionally, the side sealing area includes an inner adhesive channel and an outer adhesive channel, the inner adhesive channel and the outer adhesive channel are distributed in parallel and spaced apart, and the inner adhesive channel has an exhaust break point.

[0020] The advantages of this invention compared to related technologies include:

[0021] This invention employs zoned temperature control of the mold based on the corresponding positions of the expanding foam and sealant, creating temperature differences between different areas of the connector to be cured during the curing process. The expanding foam cures rapidly at a higher first mold temperature, achieving initial connection between the battery box's bottom protective plate and the liquid cooling plate, preventing product dimensional deformation. The lower second mold temperature extends the open time of the sealant. After the intermediate cured connector is removed from the mold, the sealant can continue to cure at room temperature. By adopting the zoned temperature control curing process of this invention, the curing rate of the expanding foam is accelerated while the open time of the sealant is extended, reducing the interfacial stress between steel and aluminum. This not only improves curing efficiency but also results in products with excellent airtightness and bonding strength. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a battery box curing and bonding method in an exemplary embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the battery box structure in an exemplary embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the zoned temperature control of the liquid cooling plate in an exemplary embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the zoned temperature control of the bottom guard plate in an exemplary embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the upper mold structure in an exemplary embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the lower mold structure in an exemplary embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the curing strength of the sealant versus curing time in an exemplary embodiment of the present invention;

[0029] Explanation of reference numerals in the attached drawings: 1. Bottom protective plate; 11. Sealing area; 111. Side sealing area; 111a. Inner glue channel; 111b. Outer glue channel; 111c. Exhaust break point; 112. Sleeve sealing area; 12. Sleeve hole; 2. Liquid cooling plate; 21. Foaming area; 3. Mold; 31. Upper mold; 32. Lower mold; 33. Heating pad; 34. Heat sink; 35. Cooling channel. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0032] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0033] In related technologies, when steel-aluminum battery packs are cured using adhesives made of two different materials, it is often difficult to simultaneously achieve both curing efficiency and sealing reliability due to the different coefficients of thermal expansion of steel and aluminum. Driven by cost-saving requirements, it is necessary to reduce investment in curing fixtures and equipment, and to combine curing processes as much as possible to shorten production time and reduce production line area and investment. Furthermore, the airtightness and adhesive strength of the product must be guaranteed. When performing single-temperature curing, if curing is carried out at a low temperature (e.g., 35°C), although the airtightness of the cured sealant is good, the curing time of the foamed adhesive usually exceeds 35 minutes, resulting in low curing efficiency. If curing is carried out directly at a high temperature (e.g., 70°C), the foamed adhesive can cure within 10 minutes. However, as the temperature drops, aluminum tends to shrink significantly, causing displacement and misalignment between aluminum and steel. This leads to cohesive failure within the sealant, making it prone to stress cracking and leakage, resulting in an airtightness compliance rate of less than 30%. Another related technology compromise is to use a single temperature that is close to the curing temperature of the two adhesives for constant temperature curing, such as curing at a constant temperature of 50°C for 35 minutes. However, this also requires a long curing time and it is difficult to ensure the curing quality of the two adhesives.

[0034] This invention provides a method for curing and bonding a battery box, referring to... Figures 1 to 4 As shown, it includes the following steps:

[0035] Step (1): Apply expanding foam and sealant sequentially to the liquid cooling plate 2 and the bottom protective plate 1 in sections to obtain the joint to be cured;

[0036] Step (2): Place the connector to be cured into the mold 3 and hot press it to cure the foam adhesive to obtain the intermediate cured connector; wherein, the area of ​​the mold 3 corresponding to the foam adhesive has a first mold temperature, and the area of ​​the mold 3 corresponding to the sealant has a second mold temperature, the second mold temperature being lower than the first mold temperature.

[0037] Step (3): Remove the intermediate cured connector from the mold 3 and let it stand at room temperature to allow the sealant to cure completely, thus obtaining the final cured connector.

[0038] This invention employs zoned temperature control in mold 3 based on the corresponding positions of the expanding foam and sealant, creating temperature differences between different areas of the connector to be cured. The expanding foam cures rapidly at a higher first mold temperature, achieving initial connection between the battery box's bottom protective plate 1 and the liquid cooling plate 2, preventing product dimensional deformation. The lower second mold temperature extends the open time of the sealant. After removing the intermediate-cured connector from mold 3, the sealant can continue to cure at room temperature. By adopting the zoned temperature-controlled curing process of this invention, the curing rate of the expanding foam is accelerated while the open time of the sealant is extended, reducing the interfacial stress between steel and aluminum. This not only improves curing efficiency but also results in a product with good airtightness and bonding strength.

[0039] In some optional embodiments, in step (2) above, the first mold temperature ranges from 70 to 80°C, preferably 70°C, and the second mold temperature ranges from 5 to 10°C, preferably 5°C. The hot-press curing time of the connector to be cured is 10 to 15 minutes, preferably 10 minutes.

[0040] In this embodiment, the expanding foam is accelerated to cure at a high temperature of around 70°C, while the sealant remains uncured at a low temperature of around 5°C. This creates a temperature difference of over 50°C between the foaming zone 21 and the sealing zone 11, achieving coordinated control of the dual temperature zones during the hot-pressing curing stage.

[0041] In some optional embodiments, in step (3) above, the room temperature curing time of the intermediate cured connector is 15 to 20 minutes, preferably 15 minutes. Through the zoned temperature control of the mold 3, since the sealant remains uncured during the hot-press curing process, the intermediate cured body continues to cure the sealant at room temperature after detaching from the mold 3, thus increasing the open time of the sealant to over 25 minutes. This avoids displacement between the aluminum and steel due to premature curing and cooling of the sealant, improving the adhesive strength and airtightness of the sealant.

[0042] In some optional embodiments, when the connector to be cured is placed in the mold 3 for thermosetting and curing, the molding pressure of the area of ​​the mold 3 corresponding to the expanding foam is 450 to 500 N / cm. 2 The molding pressure of mold 3 in the area corresponding to the sealant is 180 to 250 N / cm. 2 .

[0043] In this embodiment, by further applying pressure to the mold 3 in sections, the expanding foam cures rapidly under higher pressure, while the sealant exhibits good fluidity under this pressure. Specifically, pressure plates can be installed locally on the mold 3. By applying pressure to the area of ​​the mold 3 corresponding to the expanding foam, the mold 3 experiences greater pressure in the expanding foam area, thereby achieving a better curing effect.

[0044] In some optional embodiments, the zoned temperature control of mold 3 can be achieved as follows: First, the temperatures of the foam adhesive area and the sealant area of ​​mold 3 can be controlled separately by two mold temperature controllers. One mold temperature controller is used to raise the temperature of the foam adhesive area, rapidly increasing the temperature of the foam adhesive area of ​​the connector to be cured to a first mold temperature. Exemplarily, the heating power of the mold temperature controller used for heating can be 8 to 10 kW, the flow rate can be 15 to 18 L / min, and the medium is silicone oil. The other mold temperature controller is used to maintain the low temperature of the sealant area, keeping the temperature of the sealant area at around 5°C. Exemplarily, the cooling capacity of the mold temperature controller used for cooling can be 5 to 8 kW, using an aqueous ethylene glycol solution as the medium. Both mold temperature controllers can perform zoned temperature control using PID temperature control technology.

[0045] More specifically, refer to Figure 5 and Figure 6 As shown, mold 3 includes an upper mold 31 and a lower mold 32. To achieve more precise temperature control in different areas of mold 3, the foam area of ​​mold 3 can be subjected to corresponding heating treatment or the sealant area of ​​mold 3 can be subjected to corresponding cooling and heat dissipation treatment. For example, in an exemplary embodiment, heat sinks 34 are provided on the surface of mold 3 corresponding to the sealant area. The heat sinks 34 are preferably distributed on the surface of upper mold 31 corresponding to the sealant area to quickly dissipate heat from the sealant area of ​​the body to be bonded and cured. Heating pads 33 are provided on the surface of mold 3 corresponding to the foam area. The heating pads 33 are preferably distributed on the surface of lower mold 32 corresponding to the foam area to heat the foam area of ​​the body to be bonded and cured. In addition, a heat insulation component is provided between the area corresponding to the foam and the area corresponding to the sealant in mold 3 to fully isolate the heat between the sealant area and the foam area.

[0046] It should be noted that the heat sink 34 can be made of silicone, the thickness of the heat sink 34 can be 0.3 to 15 mm, the heat insulation can be made of bakelite, and the mold 3 can be made of aluminum.

[0047] To further achieve rapid heat dissipation in the sealant area of ​​the bonding assembly to be cured, refer to... Figure 5 As shown, the mold 3 also has a cooling channel 35 inside the area corresponding to the sealant, and a cooling medium flows through the cooling channel 35. Specifically, the width of the cooling channel 35 should be greater than 20mm, and the cooling medium can be cooling water.

[0048] In some embodiments, in step (1) above, when applying foam adhesive and sealant sequentially between the cold plate and the bottom protective plate 1, foam adhesive can be applied first to the foaming area 21 on the surface of the liquid cooling plate 2 near the bottom protective plate 1, and then sealant can be applied to the sealing area 11 on the surface of the bottom protective plate 1 near the liquid cooling plate 2.

[0049] Figure 3 and Figure 4 The specific distribution of the foaming area 21 and the sealing area 11 is shown respectively, such as Figure 3 As shown, the foaming area 21 is located in the middle of the surface of the liquid cooling plate 2, and the coverage area of ​​the foaming area 21 accounts for more than 80% of the total area of ​​the liquid cooling plate 2. It should be noted that the bottom protective plate 1 has sleeve holes 12 for fixing to the liquid cooling plate 2. The position in the middle of the liquid cooling plate 2 corresponding to the sleeve holes 12 is not coated with expanding foam; the expanding foam can be applied by robotic spraying. Figure 4 As shown, there are multiple sealing areas 11, including side sealing areas 111 and sleeve sealing areas 112. The side sealing areas 111 are located on the four sides of the bottom protective plate 1. It should be understood that when the connector to be cured is pressed together, the side sealing areas 111 are located around the foaming area 21 to achieve side sealing between the bottom protective plate 1 and the liquid cooling plate 2. The sleeve sealing area 112 is located inside the sleeve hole 12 of the bottom protective plate 1 to achieve sealing of the middle sleeve area.

[0050] Furthermore, in some embodiments, continuing Figure 4As shown, the side sealing area 111 includes an inner adhesive channel 111a and an outer adhesive channel 111b, which are distributed in parallel and spaced apart. The inner adhesive channel 111a has an exhaust breakpoint 111c. The thickness of both the inner and outer adhesive channels 111a is approximately 1 mm. The width of the inner adhesive channel 111a can be 6 to 8 mm, preferably 7.5 mm; the width of the outer adhesive channel 111b can be 10 to 12 mm, preferably 11.5 mm. In this embodiment, by forming two adhesive channels on the side, the inner adhesive channel 111a provides a channel for the air to be discharged from the internal cavity of the connector to be cured by providing an exhaust breakpoint 111c. When the connector to be cured is pressed, the air in the cavity is first squeezed towards the exhaust breakpoint 111c, thereby ensuring that the outer adhesive channel 111b can completely and densely fill the gap, avoiding sealing defects such as air bubbles and insufficient adhesive. The outer adhesive channel 111b is sealed with adhesive for a whole week. The amount of adhesive applied should be such that after pressing, the adhesive overflows by 0.5 to 3 mm.

[0051] In some optional embodiments, the expanding foam can be RUHL350+900, which is a mixture of Puropreg 569 / 1 LIT RG 350 Schwarz and Puropreg 900 in a ratio of 0.75:1. In step (1), the coating temperature of the expanding foam is controlled between 20 and 30°C, the coating speed is controlled between 50 and 200 mm / s, and the coating amount can be controlled at 150 g / s. The sealant can be DOW BETAFORCE™ 9050S, and the coating temperature of the sealant can be controlled between 18 and 28°C. The curing strength of the sealant as a function of curing time is shown in the curve. Figure 7 As shown in the figure, where the vertical axis represents shear strength, it can be seen that the adhesive strength of the sealant gradually increases with the extension of curing time. This invention can extend the curing time of the sealant to more than 25 minutes, which can significantly improve the bonding performance between the bottom protective plate 1 and the liquid cooling plate 2.

[0052] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for curing and bonding a battery box, characterized in that, include: Foaming adhesive and sealant are sequentially applied to the liquid cooling plate (2) and the bottom protective plate (1) in sections to obtain the joint to be cured; first, the foaming adhesive is applied to the foaming area (21) of the surface of the liquid cooling plate (2) near the bottom protective plate (1), and then the sealant is applied to the sealing area (11) of the surface of the bottom protective plate (1) near the liquid cooling plate (2); the foaming area (21) is located in the middle of the surface of the liquid cooling plate (2), and the sealing area (11) includes a side sealing area (111), which is located on the four sides of the bottom protective plate (1); the side sealing area (111) includes an inner adhesive channel (111a) and an outer adhesive channel (111b), which are distributed in parallel and spaced apart, and the inner adhesive channel (111a) has an exhaust break point (111c); The connector to be cured is placed in the mold (3) and hot-pressed to cure the foam adhesive, thereby obtaining an intermediate cured connector; wherein, the area of ​​the mold (3) corresponding to the foam adhesive has a first mold temperature, and the area of ​​the mold (3) corresponding to the sealant has a second mold temperature, the second mold temperature being lower than the first mold temperature; The intermediate cured connector is removed from the mold (3) and left to stand at room temperature to allow the sealant to cure completely, thus obtaining the final cured connector.

2. The battery box curing and bonding method according to claim 1, characterized in that, The first mold temperature ranges from 70 to 80°C, and the second mold temperature ranges from 5 to 10°C.

3. The battery box curing and bonding method according to claim 1, characterized in that, The hot-press curing time of the connector to be cured is 8 to 12 minutes, and the room temperature curing time of the intermediate-cured connector is 15 to 20 minutes.

4. The battery box curing and bonding method according to claim 1, characterized in that, The step of placing the connector to be cured into the mold (3) for hot pressing and curing to obtain an intermediate cured connector further includes: The molding pressure of the area corresponding to the foam adhesive in the mold (3) is 450 to 500 N / cm. 2 The molding pressure of the mold (3) in the area corresponding to the sealant is 180 to 250 N / cm. 2 .

5. The battery box curing and bonding method according to claim 1, characterized in that, The mold (3) has a heat insulation component between the area corresponding to the foam and the area corresponding to the sealant.

6. The battery box curing and bonding method according to claim 1, characterized in that, The mold (3) is provided with heat sink (34) on the surface of the area corresponding to the sealant, and the mold (3) is provided with heating pad (33) on the surface of the area corresponding to the foam.

7. The battery box curing and bonding method according to claim 6, characterized in that, The mold (3) has a cooling channel (35) inside the area corresponding to the sealant, and a cooling medium flows through the cooling channel (35).

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