A battery box

Abstract

This invention discloses a battery box, including a cover and a box body. The cover includes a first cover shell upright plate, a second cover shell upright plate, and a cover shell flat plate, which are welded together to form the cover shell. A thin aluminum plate is placed inside the cover shell and the box body. Open-cell aluminum foam is filled between the thin aluminum plate, the steel plate, and the cover shell. A battery pack is installed inside the box body. Outer edges are welded to the upper part of the steel plate, the lower part of the first cover shell upright plate, and the second cover shell upright plate, and round holes are provided on the outer edges. Each connecting screw connects the cover and the box body through the corresponding round holes. A heat insulation layer is added to the cover and the box body. The heat insulation layer is composed of a thin aluminum plate bonded to polyurethane foam. This ensures reliable operation of the battery box. The energy absorption capacity of the open-cell aluminum foam mainly depends on its density ρ. f Thickness t f Its mechanical properties. In order to fully absorb the energy of the explosion of flammable gas in the battery box, a corresponding analytical process is provided to select open-cell aluminum foam with appropriate parameters.

Description

Technical Field

[0001] This invention relates to the field of battery boxes, and specifically to a battery box for a (mining rubber-wheeled vehicle). Background Technology

[0002] The steel plates currently used in battery boxes are thick, resulting in a large overall weight. Furthermore, due to the good thermal conductivity of steel, the temperature of the battery pack inside the box is low when the battery system operates in cold environments, affecting the performance of the battery pack. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a battery box. To prevent the battery from igniting flammable gases, actual operating conditions require the battery pack to be placed inside the battery box. The battery box designed in this invention utilizes open-cell aluminum foam to absorb the energy of an explosion of flammable gases inside the battery box, which helps reduce the impact of the exploding gases on the outer steel plate of the battery box, thereby reducing the thickness of the outer steel plate and the weight of the battery box. Based on the design process of this invention, parameters such as the thickness and density of the open-cell aluminum foam inside the battery box, as well as the thickness of the outer steel plate, can be appropriately obtained. The thickness of the outer steel plate of the battery box in this invention is less than the thickness of the steel plate in current battery boxes, and the density of the open-cell aluminum foam is less than the density of steel and aluminum. Therefore, the weight of the battery box designed in this invention is less than the weight of currently used battery boxes.

[0004] The present invention provides a battery box, comprising a box cover and a box body.

[0005] The box cover includes a first box cover shell upright plate, a second box cover shell upright plate, and a box cover shell flat plate, which are welded together to form the box cover shell.

[0006] The box body is formed by welding steel plates on all sides and bottom.

[0007] The box lid and the box body contain thin aluminum sheets; the space between the thin aluminum sheets and the box lid and steel sheets is filled with perforated aluminum foam.

[0008] The battery pack is installed inside the box; the upper part of the steel plate, the first box cover plate and the lower part of the second box cover plate are all welded with outer edges, and round holes are provided on the outer edges.

[0009] The round holes on the outer edge of the lid correspond one-to-one with the round holes on the outer edge of the box body. Each connecting screw connects the lid and the box body through the corresponding round hole (5).

[0010] An insulation layer is added to the lid and the outside of the box; the insulation layer is composed of thin aluminum plate and polyurethane foam bonded together.

[0011] The grasshopper buckle welded on the outer edge of the box lid is used for a tight connection between the box lid and the insulation layer of the box lid;

[0012] The insulation layers on the front and back sides and the left and right sides of the box are connected to each other by the second grasshopper buckle. The insulation layer covers the box and the second grasshopper buckle is welded to the thin aluminum plate of the insulation layer of the box.

[0013] When the flammable gas inside the battery box explodes, it first acts on the thin aluminum plates of the box cover and body, then compresses the open-cell aluminum foam. During the compression process, ε0 is the maximum strain corresponding to the linear elastic deformation of the open-cell aluminum foam. When the compressive strain is less than ε0, the open-cell aluminum foam is in the elastic deformation stage, and the stress increases linearly with the strain; when the compressive strain is greater than ε0 and less than ε... p At that time, ε p This represents the maximum plateau plastic strain in the open-cell aluminum foam. The open-cell aluminum foam is in the plateau plastic deformation stage, and the stress is approximately σ. p When the compressive strain is greater than ε p At this time, the open-cell aluminum foam is in the compaction stage, and the stress increases rapidly with strain;

[0014] The stress-strain curve of open-cell aluminum foam and the strain axis, i.e., the ε-axis, enclose an area representing the compressive energy W absorbed per unit volume of open-cell aluminum foam.

[0015] W=∫σdε (1);

[0016] In formula (1), σ represents the compressive stress of open-cell aluminum foam, and ε represents the compressive strain of open-cell aluminum foam.

[0017] During the elastic compression stage, the strain of the open-cell foamed aluminum decreases, and the energy absorbed is relatively small and can be ignored. During the compaction stage, the compressive stress increases rapidly, exceeding the stress limit requirements of the cover and the steel plate of the box body. During the platform plastic deformation stage, the compressive stress of the open-cell foamed aluminum absorbs the greatest compressive energy. In order to ensure the service reliability of the battery box, it is necessary to utilize the platform plastic deformation process of the open-cell foamed aluminum to absorb energy.

[0018] During the plastic deformation stage of the platform, the compressive stress of the open-cell aluminum foam is approximately constant, and the energy absorbed per unit volume of open-cell aluminum foam is:

[0019] W p =σ p (ε p -ε0) (2);

[0020] In formula (2), σ p The compressive plateau stress of open-cell aluminum foam;

[0021] During compression, the compression plateau stress of the open-cell aluminum foam is:

[0022] σ p =0.3σ s (ρ f / ρ s )3 / 2 (3);

[0023] In formula (3), σ s ρ is the yield strength of aluminum. f ρ is the density of open-cell aluminum foam. s This is the density of aluminum;

[0024] During compression, the maximum plateau plastic strain of open-cell aluminum foam is

[0025] ε p =(1-1.4ρ) f / ρ s (1-1 / D) (4);

[0026] In formula (4), D is the performance constant of open-cell aluminum foam;

[0027] Since the maximum strain ε0 corresponding to the elastic deformation of the open-cell aluminum foam wire during compression is small, it is ignored. Substituting equations (3) and (4) into equation (2), we get...

[0028] W p =0.3σ s (ρ f / ρ s ) 3 / 2 (1-1.4ρ f / ρ s (1-1 / D) (5);

[0029] Let ΔW be the energy increment resulting from the explosion of flammable gas inside the battery box;

[0030] To absorb all the explosion energy, the total volume of the perforated aluminum foam inside the battery box is:

[0031] V f ≥ΔW / W p (6);

[0032] Let the internal length, width, and height of the designed battery box be a, b, and c, respectively. Since the thickness of the perforated aluminum foam used in the box cover and body is the same, the thickness of the perforated aluminum foam used in the box cover and body is:

[0033]

[0034] Substituting equations (5) and (6) into equation (7), we get

[0035]

[0036] When the flammable gas inside the battery box explodes, the open-cell foamed aluminum is compressed. The stress amplitude of the battery box cover and the outer steel plate of the box body mainly depends on the plateau stress of the open-cell foamed aluminum. When the plateau stress increases, the stress amplitude of the battery box cover and the outer steel plate of the box body increases. The outer steel plate of the battery box includes the cover upright plate (1), the cover upright plate (2), the cover flat plate (3), and the steel plates around and at the bottom of the box body. When the plateau stress decreases, the stress amplitude of the battery box cover and the outer steel plate of the box body decreases relatively. In order to fully reduce the stress on the outer steel plate of the battery box, open-cell foamed aluminum with low plateau stress is selected. As can be seen from equation (3), the plateau stress of the open-cell foamed aluminum is σ. s ρ f and ρ s The function, where σ s and ρ s The yield strength and density of solid aluminum are constants, so the plateau stress of open-cell aluminum foam mainly depends on its density ρ. f Adjust density ρ f This allows for lower stress and strain in steel plates;

[0037] From equation (8), it can be seen that the thickness t of the open-cell aluminum foam f It is its density ρ f The function is given by equation (8), so the thickness of the open-cell aluminum foam is appropriately selected to ensure that the open-cell aluminum foam can fully absorb the energy during the explosion of flammable gas.

[0038] Preferably, in the event of an explosion of flammable gas inside the battery box, the energy absorption and buffering effect of the open-cell aluminum foam ensures reliable service of the battery box; the battery box is a non-circular cross-section box, and its membrane stress and bending stress should be calculated during the design; the parameters of the steel plate thickness are obtained through stress calculation.

[0039] Taking the front and rear steel plates of the box as an example, due to the energy absorption and buffering effect of the open-cell aluminum foam and its stress-strain characteristics, the stress acting on the steel plate is considered to be the plateau stress of the open-cell aluminum foam; the membrane stress of the front and rear steel plates of the box is...

[0040]

[0041] In formula (9), a is the distance between the front and rear steel plates, and t is the thickness of the steel plate;

[0042] The maximum bending stress on the front and rear steel plates of the box body is:

[0043]

[0044] In formula (10), α is a coefficient related to the side length of the steel plate;

[0045] To ensure the service requirements of the steel plate, the total stress of the steel plate must meet the following conditions.

[0046]

[0047] In formula (11), σ lim Where is the ultimate stress of the steel plate, n is the safety factor, and φ is the weld joint coefficient;

[0048] Substituting equations (9) and (10) into equation (11), we get

[0049]

[0050] By solving the inequality in equation (12), the range of steel plate thickness t can be obtained. In order to reduce the weight of the designed battery box, the minimum value of t is taken within the allowable range.

[0051] Similarly, the thickness of the lid and other steel plates of the box body can be obtained.

[0052] Preferably, the lower the thermal conductivity of the polyurethane foam, the better for heat insulation. The thermal conductivity mainly depends on the thermal conductivity of the polyurethane foam, the thermal conductivity of the gas in the pores of the polyurethane foam, and radiation. Its thermal conductivity is...

[0053]

[0054] In formula (13), C p ρ represents the thermal conductivity parameters of polyurethane. p ρ is the density of the polyurethane foam. sp λ is the density of the polyurethane solid. p Let λ be the thermal conductivity coefficient of the polyurethane solid. g β is the thermal conductivity of air, β is the emission factor of polyurethane foam, and σ is a constant, σ = 5.67 × 10⁻⁸ W / (m²). 2 ·K 4 T is the average of the temperature inside the battery box T1 and the ambient temperature outside the battery box T2, T=(T1+T2) / 2, t p Where is the thickness of the polyurethane foam, and K is the attenuation coefficient of the polyurethane solid.

[0055] The thickness and density of polyurethane foam are key physical quantities affecting its thermal conductivity. To improve the insulation of the battery box, the thermal conductivity of the polyurethane foam needs to be reduced. This can be achieved by selecting the appropriate thickness of the polyurethane foam to decrease its thermal conductivity. Let λ be the thermal conductivity of the polyurethane foam relative to t. p The derivative is zero;

[0056]

[0057] When this condition is met, the optimal thickness of the polyurethane foam is:

[0058]

[0059] By selecting a density that reduces the thermal conductivity of polyurethane foam, let λ be relative to ρ. p The derivative is zero;

[0060]

[0061] When this condition is met, the optimal density of polyurethane foam is:

[0062]

[0063] From equations (15) and (17), we get

[0064]

[0065] From equation (18), we get

[0066]

[0067] Therefore, the thickness and density of the polyurethane insulation layer are obtained according to equations (17) and (19).

[0068] Preferably, triangular reinforcing plates are welded between the first box cover upright plate and its outer edge, the second box cover upright plate and its outer edge, and the outer edge of the box body and the steel plate.

[0069] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0070] The main function of the perforated aluminum foam in the battery box lid and body is to absorb the energy of an explosion of flammable gases inside the box, reducing the impact of the exploding gases on the steel plates of the lid and body, thus ensuring the reliable operation of the battery box. f Thickness t f Its mechanical properties. In order to fully absorb the energy of the explosion of flammable gas in the battery box, a corresponding analytical process is provided to select open-cell aluminum foam with appropriate parameters.

[0071] Polyurethane foam is selected for battery box insulation. Based on the design process in this invention, appropriate dimensional and density parameters of the polyurethane foam can be obtained, enabling the battery pack inside the box to maintain high performance within a relatively high temperature range even in cold environments. The insulation layer, which provides the insulation function, is composed of polyurethane foam and a thin aluminum plate bonded together. The polyurethane foam provides insulation, while the thin aluminum plate, with its higher strength, protects the internal polyurethane foam. The insulation layer is easy to install, which is beneficial for engineering applications. Attached Figure Description

[0072] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0073] Figure 1 The present invention provides a battery box cover structure. Figure 1 ;

[0074] Figure 2 The present invention provides a battery box cover structure. Figure 2 ;

[0075] Figure 3 This is a structural diagram of the battery box housing according to the present invention;

[0076] Figure 4 This is a structural diagram of the separate body and insulation layer of a battery box according to the present invention.

[0077] Figure 5 This is a structural diagram of the battery box body and insulation layer of the present invention.

[0078] In the diagram: 1. First box cover upright plate; 2. Second box cover upright plate; 3. Box cover flat plate; 4. Outer edge; 5. Round hole; 6. Triangular reinforcing plate; 10. Steel plate; 18. Grasshopper buckle; 19. Second grasshopper buckle. Detailed Implementation

[0079] The following drawings will disclose several embodiments of the present invention. For clarity, many physical details will be described in the following description. However, it should be understood that these physical details are not intended to limit the invention. That is, in some embodiments of the invention, these physical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0080] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, such a combination should be considered nonexistent and not within the scope of protection claimed by this invention.

[0081] like Figure 1-5The battery box shown includes a cover and a body. The cover includes a first cover shell upright plate 1, a second cover shell upright plate 2, and a cover shell flat plate 3. The first cover shell upright plate 1, the second cover shell upright plate 2, and the cover shell flat plate 3 are welded together to form an internal length of a, an internal width of b, and an internal depth of t. f The box cover shell, the first box cover shell upright plate 1, the second box cover shell upright plate 2 and the box cover shell flat plate 3 are made of steel plate;

[0082] The box body is formed by welding steel plates 10 on all sides and bottom.

[0083] The box lid and the box body are lined with thin aluminum plates; the space between the thin aluminum plates and the box lid and steel plate 10 is filled with perforated aluminum foam.

[0084] The box lid is filled with material of length a, width b, and thickness t. f The perforated aluminum foam, thin aluminum sheet is bonded to the first box cover upright plate 1, the second box cover upright plate 2 and the perforated aluminum foam.

[0085] The box contains a battery pack; the upper part of the steel plate 10, the lower part of the first box cover plate 1 and the second box cover plate 2 are all welded with an outer edge 4.

[0086] The round holes 5 on the outer edge 4 of the lid correspond one-to-one with the round holes 5 on the outer edge 4 of the body. Each connecting screw connects the lid and the body through the corresponding round holes 5.

[0087] The enclosure consists of three layers around its perimeter and bottom. The outer layer is welded from steel plate 10; the inner layer is welded from thin aluminum plate; and the thickness of the filler between the steel plate 10 and the thin aluminum plate is t. f The battery pack is placed on a support base. Multiple cylindrical support bases are located at the bottom of the enclosure. One end of each cylindrical support base is welded to the bottom steel plate of the enclosure, and the other end of each cylindrical support base passes through the perforated aluminum foam and thin aluminum plate at the bottom of the enclosure to support the battery pack.

[0088] The sealing strip 9 between the outer edge of the box and the outer edge of the lid is used to achieve a seal between the box and the lid.

[0089] Inside the battery box, the distances between each surface of the battery pack and the thin aluminum plate at the bottom, around, and on the lid of the box are equal.

[0090] The steel plates, perforated aluminum foam, and thin aluminum sheets that make up the battery pack cover and body have good thermal conductivity. When the battery pack system operates in a cold environment for extended periods, the temperature inside the battery pack will equalize with the outside temperature, affecting the battery pack's performance. To fully improve the battery pack's performance, an insulation layer is added to the cover and body. This insulation layer is composed of thin aluminum sheets bonded together with polyurethane foam.

[0091] like Figure 4 As shown, the insulation layer of the box lid is made of material with a thickness of t.p Polyurethane foam and thin aluminum sheets are bonded together to form a shell shape. This insulation shell can be fitted onto... Figure 4 The outer layer of the box lid shown provides insulation. The thin aluminum sheet on the outer layer of the insulation shell is stronger than polyurethane foam and is used to protect the polyurethane foam. For example... Figure 4 As shown, the grasshopper buckle 18 welded to the outer edge of the box cover is used for a tight connection between the box cover and the insulation layer of the box cover.

[0092] The bottom, front and back sides, and left and right sides of the enclosure are insulated with a layer of polyurethane foam and thin aluminum sheet bonded together to achieve insulation. The insulation layer at the bottom of the enclosure is permanently installed. The insulation layers on the front and back sides and the left and right sides are interconnected by a second fastener 19, covering the enclosure's perimeter. The second fastener 19 is welded to the thin aluminum sheet of the insulation layer. The thin aluminum sheet has higher strength than the polyurethane foam and can be used to protect the polyurethane foam.

[0093] When the flammable gas inside the battery box explodes, it first acts on the thin aluminum plates of the box cover and body, then compresses the open-cell aluminum foam. During the compression process, when the compressive strain is less than ε0, the open-cell aluminum foam is in the linear elastic deformation stage, and the stress increases linearly with the strain; when the compressive strain is greater than ε0 and less than ε... p At that time, the open-cell aluminum foam is in the plateau plastic deformation stage, and the stress is approximately σ. p When the compressive strain is greater than ε p At this time, the open-cell aluminum foam is in the compaction stage, and the stress increases rapidly with strain.

[0094] The area enclosed by the stress-strain curve and the strain axis (i.e., the ε-axis) of open-cell aluminum foam represents the compressive energy absorbed per unit volume of open-cell aluminum foam.

[0095] W=∫σdε (1);

[0096] In formula (1), σ represents the compressive stress of open-cell aluminum foam, and ε represents the compressive strain of open-cell aluminum foam.

[0097] During the elastic compression stage, the strain of open-cell aluminum foam is small, and the energy absorbed is relatively small and can be ignored. During the compaction stage, the compressive stress is large and easily exceeds the stress limit allowed by the cover and body steel plate. During the platform plastic deformation stage, the compressive stress of open-cell aluminum foam can be kept within an appropriate range, and the absorbed compressive energy is the greatest. In order to ensure the service reliability of the battery box, the energy is absorbed by the platform plastic deformation process of open-cell aluminum foam.

[0098] During the plastic deformation stage of the platform, the compressive stress of the open-cell aluminum foam is approximately constant, and the energy absorbed per unit volume of open-cell aluminum foam is...

[0099] W p =σ p (εp -ε0) (2);

[0100] In formula (2), σ p The compressive plateau stress of open-cell aluminum foam;

[0101] During compression, the compression plateau stress of the open-cell aluminum foam is

[0102] σ p =0.3σ s (ρ f / ρ s ) 3 / 2 (3);

[0103] In formula (3), σ s ρ is the yield strength of aluminum. f ρ is the density of open-cell aluminum foam. s This is the density of aluminum;

[0104] During compression, the maximum plateau plastic strain of open-cell aluminum foam is

[0105] ε p =(1-1.4ρ) f / ρ s (1-1 / D) (4);

[0106] Since the maximum strain ε0 corresponding to the elastic deformation of the open-cell aluminum foam during compression is small, it is ignored. Substituting equations (3) and (4) into equation (2), we get:

[0107] W p =0.3σ s (ρ f / ρ s ) 3 / 2 (1-1.4ρ f / ρ s (1-1 / D) (5);

[0108] Let ΔW be the energy increment resulting from the explosion of flammable gas inside the battery box.

[0109] To absorb all the explosion energy, the total volume of the perforated aluminum foam inside the battery box is [missing information].

[0110] V f ≥ΔW / W p (6);

[0111] Let the internal length, width, and height of the designed battery box be a, b, and c, respectively. Since the thickness of the perforated aluminum foam used in the box cover and body is the same, the thickness of the perforated aluminum foam used in the box cover and body is:

[0112]

[0113] Substituting equations (5) and (6) into equation (7), we get

[0114]

[0115] When the flammable gas inside the battery box explodes, the open-cell foamed aluminum is compressed. The stress amplitude of the battery box cover and the outer steel plate of the box body mainly depends on the plateau stress of the open-cell foamed aluminum. When the plateau stress is large, the stress amplitude of the battery box cover and the outer steel plate of the box body is high. The outer steel plate of the battery box includes the first cover shell upright plate 1, the second cover shell upright plate 2 and the cover shell flat plate 3, as well as the steel plates 10 around and at the bottom of the box body. When the plateau stress is small, the stress amplitude of the battery box cover and the outer steel plate of the box body is relatively small. In order to fully reduce the stress on the outer steel plate of the battery box, it is necessary to select open-cell foamed aluminum with a small plateau stress. As can be seen from equation (3), the plateau stress of the open-cell foamed aluminum is σ. s ρ f and ρ s The function, where σ s and ρ s The yield strength and density of aluminum are constants, so the plateau stress of open-cell aluminum foam mainly depends on the density ρ. f Adjusting density ρ f This can achieve lower stress and strain in steel plates.

[0116] From equation (8), it can be seen that the thickness t of the open-cell aluminum foam f It is its density ρ f The function is given by equation (8), so the thickness of the open-cell aluminum foam is appropriately selected to ensure that the open-cell aluminum foam can fully absorb the energy during the explosion of flammable gas.

[0117] Furthermore, since the battery box has a non-circular cross-section, the membrane stress and bending stress of its outer steel plate should be calculated during the design process. Parameters such as the steel plate thickness can be obtained through stress calculation.

[0118] Taking the front and rear steel plates of the enclosure as an example, due to the energy absorption and buffering effect of the open-cell aluminum foam and its stress-strain characteristics, the stress acting on the steel plate is considered to be the plateau stress of the open-cell aluminum foam. The membrane stress of the front and rear steel plates of the enclosure is...

[0119]

[0120] In formula (9), a is the distance between the front and rear steel plates, and t is the thickness of the steel plate.

[0121] The maximum bending stress on the front and rear steel plates of the box is

[0122]

[0123] In formula (10), α is a coefficient related to the side length of the steel plate.

[0124] To ensure the deformation and strength requirements of the steel plate, the total stress of the steel plate must meet the following requirements.

[0125]

[0126] In formula (11), σ lim φ is the allowable ultimate stress of the steel plate, n is the safety factor, and φ is the weld joint coefficient.

[0127] Substituting equations (9) and (10) into equation (11), we get

[0128]

[0129] By solving the inequality in equation (12), the range of steel plate thickness t can be obtained. In order to reduce the weight of the designed battery box, the minimum value of t is taken within the allowable range.

[0130] Similarly, the thickness of the lid and other steel plates of the box body can be obtained.

[0131] Furthermore, the lower the thermal conductivity of the polyurethane foam, the better it is for insulation. The thermal conductivity mainly depends on the thermal conductivity of the polyurethane foam, the thermal conductivity of the gas in the pores of the polyurethane foam, and radiation. Its thermal conductivity coefficient is...

[0132]

[0133] In formula (13), C p ρ represents the thermal conductivity parameters of polyurethane. p ρ is the density of the polyurethane foam. sp λ is the density of the polyurethane solid. p Let λ be the thermal conductivity coefficient of the polyurethane solid. g β is the thermal conductivity of air, β is the emission factor of polyurethane foam, and σ is a constant, σ = 5.67 × 10⁻⁸ W / (m²). 2 ·K 4 T is the average of the temperature inside the battery box T1 and the ambient temperature outside the battery box T2, T=(T1+T2) / 2, t p Where is the thickness of the polyurethane foam, and K is the attenuation coefficient of the polyurethane solid.

[0134] The thickness and density of polyurethane foam are key physical quantities affecting its thermal conductivity. To improve the insulation of the battery box, it is necessary to reduce the thermal conductivity of the polyurethane foam. This can be achieved by selecting the appropriate thickness of the polyurethane foam to reduce its thermal conductivity, assuming λ versus t. p The derivative is zero;

[0135]

[0136] When this condition is met, the optimal thickness of the polyurethane foam is:

[0137]

[0138] By selecting a density that reduces the thermal conductivity of polyurethane foam, let λ be relative to ρ. p The derivative is zero;

[0139]

[0140] When this condition is met, the optimal density of polyurethane foam is:

[0141]

[0142] From equations (15) and (17), we get

[0143]

[0144] From equation (18), we get

[0145]

[0146] Therefore, the thickness and density of the polyurethane insulation layer are obtained according to equations (17) and (19).

[0147] The above analysis allows us to determine the thickness t of the outer steel plate of the battery box and the density ρ of the perforated aluminum foam inside the battery box. f and thickness t f The density ρ of the polyurethane foam in the insulation layer of the box lid and body p and thickness t p .

[0148] Furthermore, triangular reinforcing plates 6 are welded between the first box cover upright plate 1 and the outer edge 4, the second box cover upright plate 2 and the outer edge 4, and the outer edge 4 and the steel plate layer 10.

[0149] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A battery box characterized by, Including the lid and body of the box. The box cover includes a first box cover shell upright plate (1), a second box cover shell upright plate (2), and a box cover shell flat plate (3), which are welded together to form the box cover shell. The box body is formed by welding steel plates (10) around its sides and bottom; The box cover and the box body contain thin aluminum plates; the space between the thin aluminum plates and the box cover and the steel plate (10) is filled with perforated aluminum foam. The box contains a battery pack; the upper part of the steel plate (10), the lower part of the first box cover plate (1) and the second box cover plate (2) are all welded with an outer edge (4), and a round hole (5) is provided on the outer edge (4); The round holes (5) on the outer edge (4) of the box cover correspond one-to-one with the round holes (5) on the outer edge (4) of the box body. Each connecting screw connects the box cover and the box body through the corresponding round holes (5). An insulation layer is added to the lid and the outside of the box; the insulation layer is composed of thin aluminum plate and polyurethane foam bonded together. The grasshopper buckle (18) welded on the outer edge (4) of the box lid is used for the tight connection between the box lid and the insulation layer of the box lid; The insulation layers on the front and back sides and the left and right sides of the box are connected to each other by the second grasshopper buckle (19). The insulation layer covers the box and the second grasshopper buckle (19) is welded to the thin aluminum plate of the insulation layer of the box. When the flammable gas inside the battery box explodes, it first acts on the thin aluminum plates of the box cover and body, then compresses the open-cell aluminum foam. During the compression process, ε0 is the maximum strain corresponding to the linear elastic deformation of the open-cell aluminum foam. When the compressive strain is less than ε0, the open-cell aluminum foam is in the elastic deformation stage, and the stress increases linearly with the strain; when the compressive strain is greater than ε0 and less than ε... p At that time, ε p This represents the maximum plateau plastic strain in the open-cell aluminum foam. The open-cell aluminum foam is in the plateau plastic deformation stage, and the stress is approximately σ. p When the compressive strain is greater than ε p At this time, the open-cell aluminum foam is in the compaction stage, and the stress increases rapidly with strain; The stress-strain curve of open-cell aluminum foam and the strain axis, i.e., the ε-axis, enclose an area representing the compressive energy W absorbed per unit volume of open-cell aluminum foam. W=∫σdε (1); In formula (1), σ represents the compressive stress of open-cell aluminum foam, and ε represents the compressive strain of open-cell aluminum foam. During the elastic compression stage, the strain of the open-cell foamed aluminum decreases, and the energy absorbed is relatively small and can be ignored. During the compaction stage, the compressive stress increases rapidly, exceeding the stress limit requirements of the cover and the steel plate of the box body. During the platform plastic deformation stage, the compressive stress of the open-cell foamed aluminum absorbs the greatest compressive energy. In order to ensure the service reliability of the battery box, it is necessary to utilize the platform plastic deformation process of the open-cell foamed aluminum to absorb energy. During the plastic deformation stage of the platform, the compressive stress of the open-cell aluminum foam is approximately constant, and the energy absorbed per unit volume of open-cell aluminum foam is: W p =s p (e p -ε0) (2); In Equation (2), σ p is the compressive plateau stress of the open-cell aluminum foam; During compression, the compression plateau stress of the open-cell aluminum foam is: σ p = 0.3σ s (ρ f / ρ s ) 3 / 2 (3); In Equation (3), σ s is the yield strength of aluminum, p f is the density of the open-cell aluminum foam, p s is the density of aluminum; During compression, the maximum plateau plastic strain of open-cell aluminum foam is ε p = (1 - 1.4p f / p s )(1 - 1 / D) (4); In formula (4), D is the performance constant of open-cell aluminum foam; Since the maximum strain ε0 corresponding to the elastic deformation of the open-cell aluminum foam wire during compression is small, it is ignored. Substituting equations (3) and (4) into equation (2), we get... W p = 0.3σ s (ρ f / ρ s ) 3 / 2 (1-1.4ρ f / ρ s )(1-1 / D) (5); Let ΔW be the energy increment resulting from the explosion of flammable gas inside the battery box; To absorb all the explosion energy, the total volume of the perforated aluminum foam inside the battery box is: V f ≥ΔW / W p (6) Let the internal length, width, and height of the designed battery box be a, b, and c, respectively. Since the thickness of the perforated aluminum foam used in the box cover and body is the same, the thickness of the perforated aluminum foam used in the box cover and body is: Substituting equations (5) and (6) into equation (7), we get When the flammable gas inside the battery box explodes, the open-cell foamed aluminum is compressed. The stress amplitude of the battery box cover and the outer steel plate of the box body mainly depends on the plateau stress of the open-cell foamed aluminum. When the plateau stress increases, the stress amplitude of the battery box cover and the outer steel plate of the box body increases. The outer steel plate of the battery box includes the cover upright plate (1), the cover upright plate (2), the cover flat plate (3), and the steel plates (10) around and at the bottom of the box body. When the plateau stress decreases, the stress amplitude of the battery box cover and the outer steel plate of the box body decreases relatively. In order to fully reduce the stress on the outer steel plate of the battery box, open-cell foamed aluminum with low plateau stress is selected. As can be seen from equation (3), the plateau stress of the open-cell foamed aluminum is σ. s ρ f and ρ s The function, where σ s and ρ s The yield strength and density of solid aluminum are constants, so the plateau stress of open-cell aluminum foam mainly depends on its density ρ. f Adjust density ρ f This allows for lower stress and strain in steel plates; From equation (8), it can be seen that the thickness t of the open-cell aluminum foam f It is its density ρ f The function is given by equation (8), so the thickness of the open-cell aluminum foam is appropriately selected to ensure that the open-cell aluminum foam can fully absorb the energy during the explosion of flammable gas.

2. The battery box of claim 1, wherein When a flammable gas explodes inside the battery box, the energy absorption and buffering effect of the open-cell aluminum foam ensures the reliable operation of the battery box. The battery box is a non-circular cross-section box, and its membrane stress and bending stress should be calculated during the design. The parameters for the steel plate thickness are obtained through stress calculation; Taking the front and rear steel plates of the box as an example, due to the energy absorption and buffering effect of the open-cell aluminum foam and its stress-strain characteristics, the stress acting on the steel plate is considered to be the plateau stress of the open-cell aluminum foam; the membrane stress of the front and rear steel plates of the box is... In formula (9), a is the distance between the front and rear steel plates, and t is the thickness of the steel plate; The maximum bending stress on the front and rear steel plates of the box body is: In formula (10), α is a coefficient related to the side length of the steel plate; To ensure the service requirements of the steel plate, the total stress of the steel plate must meet the following conditions. In equation (11), σ lim is the ultimate stress of the steel plate, n is the safety factor, and φ is the coefficient of the welded joint. Substituting equations (9) and (10) into equation (11), we get By solving the inequality in equation (12), the range of steel plate thickness t can be obtained. In order to reduce the weight of the designed battery box, the minimum value of t is taken within the allowable range. Similarly, the thickness of the lid and other steel plates of the box body can be obtained.

3. The battery box of claim 1, wherein, A lower thermal conductivity coefficient of the polyurethane foam is more beneficial for heat insulation. The thermal conductivity mainly depends on the thermal conductivity of the polyurethane foam, the thermal conductivity of the gas in the pores of the polyurethane foam, and radiation. Its thermal conductivity coefficient is... In formula (13), C p ρ represents the thermal conductivity parameters of polyurethane. p ρ is the density of the polyurethane foam. sp λ is the density of the polyurethane solid. p Let λ be the thermal conductivity coefficient of the polyurethane solid. g β is the thermal conductivity of air, β is the emission factor of polyurethane foam, and σ is a constant, σ = 5.67 × 10⁻⁸ W / (m²). 2 ·K 4 T is the average of the internal temperature T1 and the external ambient temperature T2 of the battery box, T = (T1 + T2) / 2, t p Where is the thickness of the polyurethane foam, and K is the attenuation coefficient of the polyurethane solid. The thickness and density of polyurethane foam are key physical quantities affecting its thermal conductivity. To improve the insulation of the battery box, the thermal conductivity of the polyurethane foam needs to be reduced. This can be achieved by selecting the appropriate thickness of the polyurethane foam to decrease its thermal conductivity. Let λ be the thermal conductivity of the polyurethane foam relative to t. p The derivative is zero; When this condition is met, the optimal thickness of the polyurethane foam is: By choosing the thermal conductivity of the density-reduced polyurethane foam, set λ against ρ p the derivative of which is zero; When this condition is met, the optimal density of polyurethane foam is: From equations (15) and (17), we get From equation (18), we get Therefore, the thickness and density of the polyurethane insulation layer are obtained according to equations (17) and (19).

4. The battery box of claim 1, wherein, A triangular reinforcing plate (6) is welded between the first box cover upright plate (1) and the outer edge (4), the second box cover upright plate (2) and the outer edge (4), and the outer edge (4) of the box body and the steel plate (10).

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