Discharge structure for low-melting-point material that melts during the roasting of battery packs.

Abstract

This invention provides a discharge structure for low-melting-point material that melts during the roasting process of a battery pack, which is advantageous for efficiently removing battery cells after the roasting process. [Solution] When the spacer 20 melts, the closing member 22 and the fastening member 14 fall due to their own weight, and the lower surface of the head 1402 of the fastening member 14 comes into contact with the inner surface 1202A of the bottom wall 1202 around the fastening member insertion hole 16. As the fastening member 14 falls, the closing member 22 is positioned at a location lower than the outer surface 1202B of the bottom wall 1202, opening the discharge hole 18 located at the lowest point of the bottom wall 1202. The low-melting-point material, which has a melting point lower than the roasting temperature inside the battery case 10, falls downward from the discharge hole 18 together with the molten spacer 20 and flows out onto the closing member 22.

Description

Technical Field

[0001] The present invention relates to a discharge structure of a low melting point material that melts during baking of a battery pack.

Background Art

[0002] In electric vehicles such as electric cars and hybrid cars using a motor as a drive source, a battery pack that supplies power to the motor is used (see Patent Document 1). The battery pack includes an assembled battery having a plurality of battery modules each composed of a plurality of battery cells, and a steel case that houses the assembled battery. The battery cell is a secondary battery, and the battery element is sealed in a cell case. The battery element is composed of an electrode material containing rare metals with limited production amounts such as lithium, cobalt, and nickel. Therefore, from the viewpoint of effective utilization of resources, it is important to disassemble used battery cells to recover rare metals and recycle the recovered rare metals as battery elements of battery cells. In recent years, in such recycling, a baking process has been performed in which the battery pack is heated to a baking temperature of about 400 to 600 degrees without disassembling the battery pack to vaporize and remove the electrolytic solution inside the battery cell. Then, the battery pack after the baking process is disassembled, the battery cells are taken out from the case, and the rare metals are recovered.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, the inside of a battery pack case contains various components made of low-melting-point materials with a melting point lower than the roasting temperature, such as aluminum, including cooling fins for electrical components, brackets for fixing battery cells, and the case for the battery module. As a result of the roasting process, the low-melting-point materials melt and accumulate at the bottom of the case. When low-melting-point material accumulates at the bottom of the case, removing the battery cells from the accumulated material becomes a time-consuming process, and some kind of improvement is needed. The present invention has been made in view of the above circumstances, and aims to provide a discharge structure for low-melting-point material that melts during the roasting of a battery pack, which is advantageous for efficiently removing battery cells after the roasting process. [Means for solving the problem]

[0005] To achieve the above objective, one embodiment of the present invention provides at least two fastening member insertion holes provided at intervals in the wall portion constituting the battery case of the battery pack, a discharge hole provided in the wall portion located between the fastening member insertion holes, a plurality of spacers provided on the inner surface of the wall portion located inside the battery case, at the locations where the fastening member insertion holes are located, and a wall portion located outside the battery case, having a size that covers each of the fastening member insertion holes and the discharge hole, and having a plurality of fastening member coupling holes. The battery case comprises a closing member positioned on the outer surface of the wall portion, and a plurality of fastening members having a head and a shaft portion protruding from the head, each of which is inserted into the fastening member insertion holes for spacers, the shaft portion is connected to the fastening member coupling hole, and the closing member abuts against the outer surface of the wall portion around the fastening member insertion holes and the outer surface of the wall portion around the discharge hole, thereby closing the fastening member insertion holes and the discharge hole, wherein the spacer is formed of a material with a lower melting point than the wall portion, the fastening members and the closing member. Furthermore, one embodiment of the present invention is characterized in that two fastening member insertion holes are provided, and the two spacers, each positioned on the inner surface of the wall portion where the fastening member insertion holes are located, have different thicknesses. Furthermore, in one embodiment of the present invention, the fastening member insertion holes are provided in three locations such that they are at the vertices of a triangle when viewed from above, and three fastening members are also provided, the discharge holes are provided so as to be located inside the triangle, the thickness of the two spacers placed in the two fastening member insertion holes located at the vertices of both ends of one side of the triangle is the same, and the thickness of the one spacer placed in the fastening member insertion hole located at the remaining vertex is smaller than the thickness of the two spacers. Furthermore, in one embodiment of the present invention, the closing member is provided with three fastening member connection holes located at the vertices of the triangle when viewed from above, and a groove is provided on the inner surface of the closing member that abuts the outer surface of the wall portion, passing between the two fastening member connection holes located at the vertices of both ends of one side of the triangle, and extending from the outer edge of the closing member toward the remaining fastening member connection hole. Furthermore, one embodiment of the present invention is characterized in that the width of the groove differs on the inner surface of the closing member between the outer edge side of the closing member and the discharge hole side. Furthermore, in one embodiment of the present invention, the spacer comprises a spacer body disposed at a location on the inner surface of the wall portion where the fastening member insertion hole is located, and a spacer cylindrical portion having an outer diameter that protrudes from the spacer body and is inserted into the fastening member insertion hole, wherein the spacer fastening member insertion hole is formed extending from the spacer body to the spacer cylindrical portion. Furthermore, one embodiment of the present invention is characterized in that two fastening member insertion holes are provided, and the two spacer bodies, each positioned on the inner surface of the wall portion where the fastening member insertion holes are located, have different thicknesses. [Effects of the Invention]

[0006] According to one embodiment of the present invention, when the spacer melts due to the roasting of the battery pack, the closing member and fastening member fall, opening the discharge hole. As a result, the low-melting-point material inside the battery case falls downward through the discharge hole along with the molten spacer and flows out onto the closing member. Therefore, during battery pack recycling, it becomes possible to melt low-melting-point materials with melting points lower than the roasting temperature, such as aluminum alloys, and discharge them to the outside of the battery case through the discharge holes, which is advantageous for easily recovering rare metals. Furthermore, by providing two fastening member insertion holes and arranging the thickness of the two spacers, each positioned at the location of the fastening member insertion holes on the inner surface of the wall, when the spacers are melted by the roasting of the battery pack, the sealing member becomes inclined at a point lower than the outer surface of the wall. This allows the low-melting-point material, including the spacers, to flow out from the lowest point of the inclined sealing member's outer edge, which is advantageous for easily recovering the low-melting-point material. Furthermore, by providing three fastening member insertion holes located at the vertices of a triangle when viewed from above, and also providing three fastening members, and positioning the discharge holes inside the triangle, and by making the thickness of the two spacers placed in the two fastening member insertion holes located at the vertices of one side of the triangle the same, and making the thickness of the one spacer placed in the fastening member insertion hole at the remaining vertex smaller than the thickness of the two spacers, when the spacers are melted by the roasting of the battery pack, the closure member will be inclined at a point away from the outer surface of the wall, and the low-melting-point material including the spacers will flow out from the lowest point of the inclined closure member's outer edge, which is advantageous for easily recovering the low-melting-point material. In addition, since three fastening members are used, it is advantageous for more firmly attaching the closure member to the wall. Furthermore, if the closing member is provided with a groove that extends from the outer edge of the closing member toward the remaining fastening member connection hole, passing between the two fastening member connection holes located at the vertices of both ends of one side of the triangle, and the bottom surface of the groove is formed as a sloping surface that gradually becomes lower toward the outer edge of the closing member, then when the spacer is melted by the roasting of the battery pack, a large amount of the molten low-melting-point material is guided into the groove and flows out from the outer edge of the closing member through the groove, which is advantageous for easily recovering the molten low-melting-point material. Furthermore, if the width of the groove differs between the outer edge side of the closure member and the discharge hole on the inner surface of the closure member, it is advantageous for efficiently recovering the molten low-melting-point material. Furthermore, if the spacer comprises a spacer body and a spacer cylinder portion having an outer diameter that protrudes from the spacer body and is inserted into a fastening member insertion hole, and a spacer fastening member insertion hole is formed from the spacer body to the spacer cylinder portion through which a male threaded portion is inserted, then forming the outer diameter of the spacer cylinder portion to a size that allows it to be press-fitted into the fastening member insertion hole is advantageous in ensuring that the fastening member insertion hole is properly closed by press-fitting the spacer cylinder portion into the fastening member insertion hole when arranging the spacer body on the inner surface of the bottom wall. Furthermore, by providing two fastening member insertion holes and making the thickness of the two spacer bodies, which are positioned on the inner surface of the wall at the locations of the fastening member insertion holes, different, when the spacers are melted by the roasting of the battery pack, the closing member will be inclined at a point away from the outer surface of the wall. The low-melting-point material, including the spacers, will flow out from the lowest point of the inclined closing member's outer edge, which is advantageous for easily recovering the low-melting-point material. [Brief explanation of the drawing]

[0007] [Figure 1] This is a longitudinal cross-sectional view of a discharge structure for low-melting-point material according to the first embodiment. [Figure 2] This is a plan view of Figure 1. [Figure 3] This is a longitudinal cross-sectional view of the spacer after melting in the discharge structure for low-melting-point material according to the first embodiment. [Figure 4]Vertical cross-sectional view of the low melting point material discharge structure according to the second embodiment. [Figure 5] Vertical cross-sectional view after spacer melting in the low melting point material discharge structure according to the second embodiment. [Figure 6] Vertical cross-sectional view of the low melting point material discharge structure according to the third embodiment, corresponding to the cross-section taken along line A-A in FIG. 7. [Figure 7] Plan view of FIG. 6. [Figure 8] Cross-sectional view of the closing member, corresponding to the cross-section taken along line B-B in FIG. 7. [Figure 9] Vertical cross-sectional view after spacer melting in the low melting point material discharge structure according to the third embodiment.

Embodiments for Carrying Out the Invention

[0008] (First Embodiment) The first embodiment of the present invention will be described with reference to FIGS. 1 - 3. The discharge structure of the low melting point material (hereinafter referred to as the low melting point material discharge structure) 100A that melts during baking of the battery pack in the present embodiment is mounted on an electric vehicle having only a motor as a drive source, or a hybrid vehicle, or a plug-in hybrid vehicle capable of external charging or external power supply, etc., and is applied to the battery case of the battery pack that supplies power to the motor.

[0009] As shown in FIGS. 1 and 2, the battery pack includes a battery case 10, a battery pack (not shown) composed of a plurality of battery modules housed in the battery case 10, a control device (not shown) for controlling the battery pack, a DC / DC converter (not shown), a cooling device (not shown) for cooling the battery modules, and the like. The battery case 10 is made of steel and includes a battery tray 12 with an open top and a battery cover (not shown) that closes the top of the battery tray 12. The battery tray 12 includes a bottom wall 1202 and a peripheral wall (not shown) that stands up from the periphery of the bottom wall 1202. On the bottom wall 1202, a battery pack, a control device, a DC / DC converter, a cooling device, etc., which are not shown, are accommodated. The bottom wall 1202 has an inner wall surface 1202A located inside the battery case 10 and an outer wall surface 1202B located outside the battery case 10.

[0010] In this embodiment, the center of the bottom wall 1202 is the lowest. And a discharge structure for a low melting point material that melts during baking of the battery pack of this embodiment is provided at the center of the bottom wall 1202. During baking of the battery pack, cooling fins for electrical components provided inside the battery case 10 of the battery pack, brackets for fixing battery cells, cases of battery modules, and other components formed of low melting point materials with melting points lower than the baking temperature are melted. A discharge structure 100A for such melted low melting point materials is provided at the center of the bottom wall 1202. The discharge structure 100A for the low melting point material includes a fastening member 14, a fastening member insertion hole 16, a discharge hole 18, a spacer 20, and a closing member 22.

[0011] Two fastening member insertion holes 16 are provided with a space therebetween across the center of the bottom wall 1202 that constitutes the battery case 10 of the battery pack. As the fastening member 14, various conventionally known ones such as bolts and steel rivets can be used. In this embodiment, a steel bolt is used as the fastening member 14. The fastening member 14 includes a hexagonal head 1402 and a male screw portion 1404 as a shaft portion protruding from the lower surface of the head 1402. The discharge hole 18 is provided at the center of the bottom wall 1202 that constitutes the wall portion of the battery case 10 of the battery pack and is located at the lowest position among the bottom walls 1202. That is, the discharge hole 18 is provided at a location on the bottom wall 1202 located between the two fastening member insertion holes 16. The bottom wall 1202 has an inner surface 1202A located inside the battery case 10 and an outer surface 1202B located outside the battery case 10. In this embodiment, two fastening members 14 are used, and correspondingly, two fastening member insertion holes 16 are provided in the bottom wall 1202, with a discharge hole 18 provided between the two fastening member insertion holes 16.

[0012] As shown in Figures 1 and 2, the spacer 20 is positioned on the inner surface 1202A of the bottom wall 1202 where the fastening member insertion hole 16 is located. The spacer 20 can be circular, rectangular, or polygonal in plan view. In this embodiment, the spacer 20 is disc-shaped, with a spacer fastening member insertion hole 24 formed in the center. Furthermore, in this embodiment, as shown in Figure 1, the thickness T1 of one spacer 20 is formed to be larger than the thickness T2 of the other spacer 20. The spacer 20 is made of a low-melting-point material that melts during the roasting process for recycling the battery pack. In other words, the spacer 18 is made of a low-melting-point material that has a melting point similar to that of various components such as cooling fins for electrical components that are melted during the roasting of the battery pack, brackets for fixing battery cells, and cases for battery modules. In other words, the spacer 18 is made of a material with a lower melting point than the fastening member 14, the bottom wall 1202 (wall portion), and the closing member 20. Examples of low-melting-point materials that make up the spacer 20 include aluminum alloys, rubber, and synthetic resins. In this embodiment, an aluminum alloy is used as the spacer 20. Furthermore, the roasting temperature during the recycling of the battery pack is set to a temperature above the melting point of the low-melting-point material used in the spacer 20.

[0013] As shown in Figures 1 and 2, the sealing member 22 is positioned on the outer surface 1202B of the bottom wall 1202 of the battery case 10 and is sized to cover the two fastening member insertion holes 16 and the discharge hole 18. The blocking member 22 is made of steel. Therefore, the spacer 20 is made of a material with a lower melting point than the bottom wall 1202, the fastening member 14, and the closing member 22. The closing member 22 has two female threaded portions 2202 which serve as fastening member connection holes. The female thread portion 2202 can be screwed onto the male thread portion 1404 of the fastening member 14. Spacers 20 are placed at locations where fastening member insertion holes 16 are provided on the inner surface 1202A of the bottom wall 1202 of the battery case 10. From inside the battery case 10, the male threaded portions 1404 of the two fastening members 14 are inserted into the spacer fastening member insertion holes 24 and the fastening member insertion holes 16, respectively, and screwed into the female threaded portions 2202. If rivets or the like are used as fastening members 14, the tip of the shaft of the rivet protruding from the fastening member coupling hole (female threaded portion 2002) is crushed, and the rivet is coupled to the closing member 20 via the fastening member coupling hole (female threaded portion 2002). As a result, the spacer 20 comes into contact with the inner surface 1202A of the wall, and the closing member 22 comes into contact with the outer surface 1202B of the wall, and the closing member 22 closes the two fastening member insertion holes 16 and the discharge hole 18. In this state, the spacer 20 is sandwiched between the head 1402 of the fastening member 14 and the inner surface 1202A of the wall portion. In this embodiment, a sealing member 26 is interposed between the closing member 22 and the outer surface 1202B of the bottom wall 1202 around the discharge hole 18, surrounding the discharge hole 18. The sealing member 26 is optional.

[0014] Next, I will explain the effects and benefits. During the recycling of the battery pack, it is roasted, and this roasting process melts the spacer 20. When the spacer 20 melts, as shown in Figures 1 and 3, the closing member 22 and the fastening member 14 fall due to their own weight, and the lower surface of the head 1402 of the fastening member 14 comes into contact with the inner surface of the bottom wall 1202 around the fastening member insertion hole 16. As the fastening member 14 falls, the closing member 22 is positioned at a location below the outer surface 1202B of the bottom wall 1202, opening the discharge hole 18 located at the lowest point of the bottom wall 1202. Low-melting-point materials such as cooling fins for electrical components, brackets for fixing battery cells, and battery module cases, which have a melting point lower than the roasting temperature and are in a molten state within the battery case 10, fall downward through the discharge hole 18 along with the molten spacers 20 and flow out onto the blocking member 22. In this embodiment, the thicknesses T1 and T2 of the spacer 20 are set to different values, so that the closing member 22 is inclined at a point away from the outer surface 1202B of the bottom wall 1202, the low-melting-point material including the spacer 20 flows out from the lowest point of the inclined closing member 22, which is advantageous for easily recovering the low-melting-point material. Therefore, during battery pack recycling, it becomes possible to melt low-melting-point materials with a melting point lower than the roasting temperature, such as aluminum alloys, and discharge them to the outside of the battery case 10 through the discharge hole 18, which is advantageous for easily recovering rare metals. Although the spacers 20 may be formed with equal thicknesses T1 and T2, in this case the blocking member 22 will be parallel to the bottom wall 1202 at a point away from the bottom wall 1202, and the low-melting-point material will flow out from the entire circumference of the blocking member 22, requiring a recovery container with a larger opening.

[0015] (Second Embodiment) Next, a discharge structure 100B for low-melting-point material according to a second embodiment will be described with reference to Figures 4 and 5. In the following description of the embodiments, the same reference numerals are used for parts and components as in the first embodiment, and their descriptions are simplified or omitted. The focus will be on describing the parts that differ from the first embodiment. In the second embodiment, the shape of the spacer 20 is different from that of the first embodiment. As shown in Figure 4, the spacer 20 comprises a spacer body 20A positioned on the inner surface 1202A of the wall portion where the fastening member insertion hole 16 is located, and a spacer cylindrical portion 20B protruding from the spacer body 20A and having an outer diameter that allows it to be inserted into the fastening member insertion hole 16 without rattling. A spacer fastening member insertion hole 24 is formed through the spacer body 20A and the spacer cylindrical portion 20B, through which the male threaded portion 1404 is inserted. In the second embodiment, the spacer bodies 20A of the two spacers 20 are placed on the inner surface 1202A of the wall portion surrounding the fastening member insertion hole 16, and the spacer cylindrical portion 20B is inserted into the fastening member insertion hole 16. The male threaded portion 1404 of the fastening member 14 is inserted through the fastening member insertion hole 16 of the spacer body 20A and the spacer cylindrical portion 20B, and the male threaded portion 1404 as the shaft portion is screwed into the female threaded portion 2202 as the fastening member coupling hole of the closing member 22, the discharge hole 18 is closed by the closing member 22 via the sealing member 26, and the fastening member insertion hole 16 is also closed by the closing member 22.

[0016] This second embodiment also provides the same effects as the first embodiment, as well as the following effects. In the second embodiment, since the spacer cylinder portion 20B is inserted into the fastening member insertion hole 16, the inner diameter of the fastening member insertion hole 16 can be made larger. Therefore, as shown in Figure 5, when the spacer 20 melts during roasting, the range in which the male thread portion 1404 directly below the head 1402 of the fastening member 14 can tilt within the fastening member insertion hole 16 becomes larger, which is advantageous in obtaining a greater inclination of the closing member 22 when the closing member 22 is inclined at a point further down from the outer surface 1202B of the bottom wall 1202. Furthermore, forming the outer diameter of the spacer cylinder portion 20B to a size that allows it to be press-fitted into the fastening member insertion hole 16, and then press-fitting the spacer cylinder portion 20B into the fastening member insertion hole 16 when positioning the spacer body 20A on the inner surface 1202A of the bottom wall 1202, is advantageous in ensuring that the fastening member insertion hole 16 is properly closed.

[0017] (Third embodiment) Next, a discharge structure 100C for low-melting-point material according to a third embodiment will be described with reference to Figures 6-9. The third embodiment differs from the first embodiment in that it uses three fastening members 14 and has grooves 28 formed in the closing member 22 to guide the molten low-melting-point material. The low-melting-point material discharge structure 100C comprises three steel fastening members 14, three fastening member insertion holes 16, one discharge hole 18, three spacers 20, one steel closing member 22, and one groove 28 for guiding the molten low-melting-point material. The spacers 20 are formed of a material with a lower melting point than the bottom wall (wall portion) 12, the fastening members 14, and the closing member 22.

[0018] As shown in Figures 6 and 7, three fastening member insertion holes 16 are provided so as to be located at the vertices of a triangle when viewed from above, and three fastening members 14 are also provided. In this embodiment, equilateral triangles and isosceles triangles are used as the triangle. The discharge hole 18 is located inside the triangle, specifically in the center of the triangle in this embodiment. Three spacers 20 are also provided, and each spacer 20 is provided with a spacer fastening member insertion hole 24. The thickness T1 of the spacers 20 placed at the vertices of both ends of one side of the triangle is greater than the thickness T2 of the spacers 20 placed at the remaining vertices.

[0019] The blocking member 22 is provided to be large enough to cover the discharge hole 18 and the three fastening member insertion holes 16. The closing member 22 is provided with female threaded portions 2202 at locations corresponding to the three fastening member insertion holes 16. In detail, the closing member 22 is provided with three female threaded portions 2202 into which the male threaded portion 1404 is screwed, so that when viewed from above, they are located at the vertices of the aforementioned triangle. As shown in Figures 7 and 8, a groove 28 is provided on the inner surface 2204 of the closing member 22 that abuts against the outer surface 1202B of the wall portion. The groove 28 extends from the outer edge of the closing member 22 toward the remaining female thread portion 2202, passing between the two female thread portions 2202 located at the vertices of both ends of one side of a triangle. The bottom surface 2802 of the groove 28 is formed as an inclined surface that gradually becomes lower towards the outer edge of the closing member 22. Furthermore, the width of the groove 28 is formed to gradually decrease as it approaches the outer edge of the closing member 22. In other words, the width of the groove 28 differs on the inner surface 2204 of the closing member 22 between the outer edge side of the closing member 22 and the side of the discharge hole 18.

[0020] As shown in Figures 6 and 7, three spacers 20 are placed on the inner surface 1202A of the wall portion where each fastening member insertion hole 16 is located, and a closing member 22 is placed on the outer surface 1202B of the wall portion so as to cover the discharge hole 18 and the three fastening member insertion holes 16. Then, the male threaded portion 1404 of the fastening member 14 is inserted into the spacer fastening member insertion hole 24 and screwed into the female threaded portion 2202 of the closing member 22, and the discharge hole 18 is closed by the closing member 22 via the sealing member 26, and the fastening member insertion hole 16 is also closed by the closing member 22.

[0021] Next, I will explain the effects and benefits. During the recycling of battery packs, the battery packs are roasted, and this roasting process melts the spacer 20 along with the cooling fins for electrical components made of low-melting-point material, the brackets that secure the battery cells, the battery module case, etc. As shown in Figures 6 and 9, when the spacer 20 melts, similar to the first embodiment, since the thicknesses T1 and T2 of the spacer 20 are set to different values, the closure member 22 becomes inclined at a point away from the outer surface 1202B of the bottom wall 1202. The low-melting-point material, including the spacer 20, flows out from the outer edge of the closure member 22, which is the lowest point of the inclined state, which is advantageous for easily recovering the low-melting-point material. Furthermore, since grooves 28 are provided on the inner surface 2204 of the inclined and lowered closure member 22, a large amount of molten low-melting-point material is guided into the grooves 28 and flows out from the outer edge of the closure member 22 through the grooves 28, which is advantageous for easily recovering the molten low-melting-point material. Furthermore, since the width of the groove 28 is formed to decrease as it approaches the outer edge of the closure member 22, the width of the outlet for the molten low-melting-point material can be narrowed, allowing the use of a recovery container with a small opening, which is advantageous for efficiently recovering the molten low-melting-point material. Furthermore, since three fastening members 14 are used, it is advantageous to attach the closing member 22 more firmly to the bottom wall 1202 of the battery case 10 compared to the second embodiment. Therefore, when recycling battery packs, it becomes possible to melt low-melting-point materials with melting points lower than the roasting temperature, such as aluminum alloys, and discharge them to the outside of the battery case 10, which is advantageous in easily recovering rare metals.

[0022] Furthermore, in the case where the width of the groove 28 differs on the inner surface 2204 of the closing member 22 between the outer edge side of the closing member 22 and the discharge hole 18 side, the width of the groove 28 may be formed to increase as it approaches the outer edge of the closing member 22. In this case, an area for heat reception of the molten low-melting-point material guided by the groove 28 can be secured, thereby ensuring the fluidity of the molten low-melting-point material and being advantageous for efficiently recovering the molten low-melting-point material. Furthermore, the groove 28 may be omitted, and the thicknesses of the three spacers 20 may be equal. However, providing the groove 28 and varying the thicknesses of the spacers 20, as in this embodiment, is advantageous for efficiently recovering the molten low-melting-point material.

[0023] Alternatively, as in the second embodiment, a spacer 20 having a spacer body 20A and a spacer cylindrical portion 20B may be used. When such a spacer 20 is used, the spacer cylindrical portion 20B is inserted into the fastening member insertion hole 16, which allows the inner diameter of the fastening member insertion hole 16 to be made larger. Therefore, during the roasting of the battery pack, the range in which the male thread portion 1404 directly below the head 1402 of the fastening member 14 can tilt within the fastening member insertion hole 16 becomes larger, which is advantageous in obtaining a greater inclination of the closing member 22 when the closing member 22 is inclined at a point further down from the outer surface 1202B of the bottom wall 1202. Furthermore, forming the outer diameter of the spacer cylinder portion 20B to a size that allows it to be press-fitted into the fastening member insertion hole 16, and then press-fitting the spacer cylinder portion 20B into the fastening member insertion hole 16 when positioning the spacer body 20A on the inner surface 1202A of the bottom wall 1202, is advantageous in ensuring that the fastening member insertion hole 16 is properly closed. [Explanation of Symbols]

[0024] Discharge structure for 100A-100C low-melting point materials 10 Battery Cases 12 Battery tray 1202 Bottom wall 1202A Inner surface of the wall 1202B Wall exterior 14 Fastening members 1402 Head 1404 Male threaded section 16 Fastening member insertion hole 18 Discharge hole 20 Spacers 20A Spacer Body 20B Spacer cylinder section 22 Closure member 2202 Female thread section 2204 Inner Self 24 Spacer fastening member insertion hole 26. Sealing member 28 grooves 2802 Bottom

Claims

1. At least two fastening member insertion holes are provided at intervals in the wall portion constituting the battery case of the battery pack, A discharge hole is provided in the wall portion located between the fastening member insertion holes, Multiple spacers are provided with fastening member insertion holes for spacers and are arranged on the inner surface of the wall portion located inside the battery case at the locations where the fastening member insertion holes are located, A closing member is provided on the outer surface of the wall portion located outside the battery case, having a size that covers each of the fastening member insertion holes and the discharge holes, and having a plurality of fastening member coupling holes, The battery case comprises a plurality of fastening members, each having a head and a shaft portion protruding from the head, and extending from the inside to the outside of the battery case, each spacer fastening member insertion hole, the shaft portion being inserted into the fastening member insertion hole and connected to the respective fastening member coupling hole, and the closing member abutting against the outer surface of the wall portion around the fastening member insertion hole and the outer surface of the wall portion around the discharge hole, thereby closing each fastening member insertion hole and the discharge hole. The spacer is made of a material with a lower melting point than the wall portion, the fastening member, and the closing member. A discharge structure for low-melting-point material that melts during the roasting of a battery pack, characterized by the above.

2. Two fastening member insertion holes are provided. The two spacers, each positioned on the inner surface of the wall portion where the fastening member insertion hole is located, have different thicknesses. A discharge structure for low-melting-point material that is melted during roasting of a battery pack according to feature 1.

3. The fastening member insertion holes are provided in three locations, positioned at the vertices of a triangle when viewed from above, and three fastening members are also provided. The discharge hole is provided so as to be located inside the triangle. The thickness of the two spacers, which are positioned in the two fastening member insertion holes located at the vertices of both ends of one side of the triangle, is the same. The thickness of one of the spacers positioned in the fastening member insertion hole at the remaining vertex is smaller than the thickness of the two spacers. A discharge structure for low-melting-point material that is melted during roasting of a battery pack according to feature 1.

4. The closing member is provided with three fastening member connection holes, which are positioned at the vertices of the triangle when viewed from above. A groove is provided on the inner surface of the closing member that abuts the outer surface of the wall portion, passing between the two fastening member connection holes located at the vertices of both ends of one side of the triangle, and extending from the outer edge of the closing member toward the remaining fastening member connection hole. The discharge structure for low-melting-point material that is melted during roasting of the battery pack according to feature 3.

5. The width of the groove differs on the inner surface of the blocking member between the outer edge side of the blocking member and the discharge hole side. The discharge structure for low-melting-point material that melts during roasting of the battery pack according to feature 4.

6. The spacer comprises a spacer body positioned on the inner surface of the wall portion where the fastening member insertion hole is located, and a spacer cylindrical portion having an outer diameter that protrudes from the spacer body and is inserted into the fastening member insertion hole. The spacer fastening member insertion hole is formed extending from the spacer body to the spacer cylindrical portion. A discharge structure for low-melting-point material that is melted during roasting of a battery pack according to feature 1.

7. Two fastening member insertion holes are provided. The two spacer bodies, each positioned on the inner surface of the wall portion where the fastening member insertion hole is located, have different thicknesses. The discharge structure for low-melting-point material that melts during roasting of the battery pack according to feature 6.

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