Battery and manufacturing method thereof

Abstract

To provide a battery having a structure in which a through-hole is formed on a battery case and the through-hole is closed by a cap, and the joining of the cap is secure, and to provide a manufacturing method for the same.SOLUTION: In the battery, a battery case 5 has an annular first joint surface 12 on the surroundings of a through-hole 10 and an annular first surface 15 to be worked on its outside and external surface side. A cap 8 has a diameter smaller than the inner circumference of the first surface 15 to be worked, and has a second joint surface 22 facing the first joint surface 12 and an annular second surface 17 to be worked on the external surface side. An annular joint protrusion 18 is provided on at least one of the first joint surface 12 and the second joint surface 22. The first joint surface 12 and the second joint surface 22 are annularly joined to each other at a position of the joint protrusion 18. Machining traces are formed in annular shapes on both of the first surface 15 to be worked and the second surface 17 to be worked.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a battery and a method for manufacturing the same. [Background technology]

[0002] Some battery cases that house the contents of a battery have through holes formed therein for purposes such as filling. The through holes in the battery cases are closed with caps after the intended process, such as filling, is completed. During the battery manufacturing process, ultrasonic bonding is sometimes used as a technique for joining the caps to the battery cases for this purpose (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-68648 Summary of the Invention [Problem to be solved by the invention]

[0004] With the conventional technology described above, it was difficult to keep the incidence of poor bonding low. In ultrasonic bonding, it is necessary to stop the ultrasonic vibration once bonding is complete. If vibration is continued after bonding is complete, the bond that has been so well made will be destroyed. However, the length of time from the start of vibration to the completion of bonding varies from one piece to another. For this reason, there were inevitably some pieces where bonding was incomplete due to insufficient vibration, or where the bond was destroyed due to excessive vibration. As such, it was not easy to perform appropriate ultrasonic bonding without excess or deficiency.

[0005] The presently disclosed technology has been made to solve the problems of the conventional technology described above. That is, the object of the present disclosure is to provide a battery having a structure in which a through-hole is formed in a battery case and the through-hole is closed with a cap, and the cap is securely joined, together with a manufacturing method thereof. [Means for solving the problem]

[0006] A battery according to one embodiment of the disclosed technology has a battery case and a power generating element built into the battery case, and a through hole is formed in the battery case and closed with a cap. The battery case has a first annular bonding surface on the outer surface around the through hole and a first annular work surface that is outward and on the outer surface side from the through hole relative to the first bonding surface. The cap has a smaller diameter than the inner circumference of the first work surface and has a second bonding surface on the inner surface side facing the first bonding surface and a second annular work surface on the outer surface side. At least one of the first and second bonding surfaces has a circular bonding protrusion, and the first and second bonding surfaces are bonded in a circular shape at the bonding protrusion. Circular processing marks are formed on both the first and second work surfaces.

[0007] Another aspect of the disclosed technology is a method for manufacturing a battery, which includes: placing a cap so that the first bonding surface and the second bonding surface come into contact at the bonding protrusion, covering the through hole with the cap; placing a vibration tool having a vibration surface on the cap so that the vibration surface comes into contact with the second workpiece surface but does not come into contact with the first workpiece surface; vibrating the cap through the second workpiece surface with the vibration tool to bond the first bonding surface and the second bonding surface in a ring shape at the bonding protrusion; advancing the vibration tool toward the battery case until the vibration surface comes into contact with the first workpiece surface; and continuing to vibrate with the vibration tool until a ring-shaped machining mark is formed on both the first workpiece surface and the second workpiece surface, and then ending the vibration.

[0008] In the battery and its manufacturing method according to the above aspect, the end of vibration for bonding the first and second bonding surfaces is controlled by the amount of advancement of the cap before and after bonding, which, unlike control based on time, allows for good bonding quality and a high yield.

[0009] In the battery and its manufacturing method described above, it is desirable that both the first and second processed surfaces have convex inclined surfaces that are higher toward the center of the through hole. In this case, it is desirable that the vibration surface have a concave inclined surface that matches the inclination of the first and second processed surfaces. This ensures that the completed battery does not have many unnecessary irregularities or concave portions that can accumulate foreign matter.

[0010] In any of the above-described batteries and manufacturing methods thereof, it is desirable that the first work surface and the second work surface are flat surfaces without any steps. This prevents unnecessary steps from remaining in the completed battery. Furthermore, the vibration surface of the vibration tool may be a simple flat surface without any steps. [Effects of the Invention]

[0011] According to the disclosed technology, a battery having a structure in which a through hole is formed in a battery case and the through hole is closed with a cap, and in which the cap is securely joined, is provided along with a manufacturing method thereof. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing the appearance of a battery according to an embodiment; [Figure 2] FIG. 2 is a partial perspective view showing the state before the sealing cap of the battery in FIG. 1 is attached. [Figure 3] FIG. 3 is a cross-sectional view of a lid showing the structure of the liquid injection port. [Figure 4] FIG. 3 is a cross-sectional view showing the shape of the sealing cap. [Figure 5] FIG. 10 is a cross-sectional view showing the start of joining the sealing cap to the lid body. [Figure 6] 10 is a cross-sectional view showing the state when joining of the sealing cap to the lid body is completed. FIG. [Figure 7] FIG. 10 is an enlarged plan view showing the sealing cap and its surroundings after joining is completed. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments embodying the present disclosure will be described in detail with reference to the accompanying drawings. In this embodiment, the present disclosure is applied to a battery 1 shown in FIG. 1. The battery 1 in FIG. 1 includes a battery case 2 and a built-in power generating element 3. The power generating element 3 is formed by laminating positive and negative electrode sheets. The battery case 2 also contains an electrolyte.

[0014] The battery case 2 is composed of a box body 4 and a lid body 5. The power generating element 3 is housed in the box body 4. The lid body 5 is provided with positive and negative external terminals 6 and 7, a sealing cap 8, and a safety valve 9. The external terminals 6 and 7 are each connected to one of the positive and negative electrode sheets of the power generating element 3 inside the battery case 2. The sealing cap 8 is a cap that closes a liquid filling port, which is a through-hole provided in the lid body 5. The safety valve 9 is a weakened portion that is intentionally provided to break by itself when the internal pressure of the battery 1 rises to a certain level, preventing excessive internal pressure rise.

[0015] The sealing cap 8 will now be described. The sealing cap 8 is attached to the battery 1 after the liquid injection step during the manufacturing process of the battery 1. As shown in FIG. 2, a liquid injection port 10 is formed in the lid 5 of the battery 1 at the corresponding location before the sealing cap 8 is attached. The liquid injection port 10 is a through-hole for injecting electrolyte into the battery case 2. Naturally, the injection of electrolyte (the liquid injection step) is performed after the lid 5 is attached to the case 4. The attachment of the external terminals 6 and 7 to the lid 5 and the connection of the power generating element 3 to the external terminals 6 and 7 are performed even before that. The power generating element 3 is also housed in the case 4 when the lid 5 is attached to the case 4. The liquid injection port 10 is closed after the liquid injection step by joining the sealing cap 8 to the portion of the lid 5 where the liquid injection port 10 is located. The joining is performed by applying ultrasonic vibrations.

[0016] The structure of the liquid filling port 10 before closure will be described with reference to the cross-sectional view of FIG. 3. As shown in FIG. 3, a flange 11 is formed around the liquid filling port 10 in the lid 5. The outer surface of the flange 11 is called a joint surface 12. In this embodiment, the thickness of the flange 11 is thinner than the thickness of the lid 5 at locations other than the periphery of the liquid filling port 10. A protrusion 13 that protrudes outward is formed around the periphery of the flange 11. The inner surface of the protrusion 13 forms a vertical wall surface 14. The outer surface of the protrusion 13 forms an inclined surface 15. The inclined surface 15 is a surface that is inclined in a direction that is higher as it approaches the center of the liquid filling port 10. The inclined surface 15 is located outside the joint surface 12 when viewed from the liquid filling port 10, and is the outer surface of the lid 5. The flange portion 11, the joining surface 12, the protrusion 13, the wall surface 14, and the inclined surface 15 are all actually annular. The inclined surface 15 is a convex inclined surface shaped like the side surface of a cone. The inclined surface 15 is the first work surface.

[0017] The shape of the sealing cap 8 will be described. The overall shape of the sealing cap 8, viewed from above, is circular. As shown in the cross-sectional view of FIG. 4, the outer surface of the sealing cap 8 is provided with a flat portion 16 and an inclined surface 17 surrounding it. The inclined surface 17 is inclined so that it slopes higher toward the center. A connecting protrusion 18 with a tapered tip is formed on the back surface 22 on the inner side of the sealing cap 8. Both the inclined surface 17 and the connecting protrusion 18 are actually annular. The inclined surface 17 is a convex inclined surface resembling the side of a cone. The inclined surface 17 is the second work surface. The overall diameter of the sealing cap 8 is smaller than the diameter of the inner circumference of the inclined surface 15, i.e., the diameter of the wall surface 14. The diameter of the tip of the connecting protrusion 18 is smaller than the diameter of the wall surface 14 and larger than the diameter of the liquid inlet 10. The inclination of the inclined surface 15 and the inclined surface 17 is the same.

[0018] When closing the liquid filling port 10 with the sealing cap 8, the sealing cap 8 is placed on the location of the liquid filling port 10 in the lid body 5, as shown in the cross-sectional view of FIG. 5. With the sealing cap 8 placed in this manner, the joining surface 12 and the back surface 22 face each other. The joining surface 12 and the back surface 22 are in contact at the tip of the joining protrusion 18. The joining surface 12 is the first joining surface, and the back surface 22 is the second joining surface. This results in the liquid filling port 10 being covered with the sealing cap 8. At this time, there is a step between the inclined surface 15 and the inclined surface 17, with the lower end (outer periphery) of the inclined surface 17 being higher than the upper end (inner periphery) of the inclined surface 15. The protruding height of the joining protrusion 18 is set so as to create such a step.

[0019] In addition to the lid 5 and the sealing cap 8, Figure 5 also depicts a vibration tool 19. The vibration tool 19 is a tool that applies ultrasonic frequency vibrations to the workpiece. The vibration tool 19 has a vibration surface 20. The vibration surface 20 is a conical, concave, inclined surface. The degree of inclination matches the inclination of the inclined surfaces 15 and 17. The vibration surface 20 is a flat surface without any steps. The state in Figure 5 shows a state in which the vibration tool 19 is pressed against the sealing cap 8 from above. In this state, the vibration surface 20 is in contact with the inclined surface 17 but not with the inclined surface 15. This state is the state at the time when joining of the sealing cap 8 to the lid 5 begins.

[0020] The process of joining the sealing cap 8 to the lid body 5 is performed by moving the vibration tool 19 toward the lid body 5 while vibrating it from the state shown in Figure 5. The battery 1 itself is fixed at this time and does not move even when the sealing cap 8 is pressed down by the vibration tool 19. In the state shown in Figure 5, the vibration of the vibration tool 19 is transmitted only to the sealing cap 8 via the inclined surface 17, not to the lid body 5. Therefore, friction causes a local temperature rise at the contact point between the tip of the joining protrusion 18 and the joining surface 12, leading to melting and joining. In the state shown in Figure 5, the joining protrusion 18 and the joining surface 12 only contact a very narrow area at the tip of the joining protrusion 18. However, by pressing down the sealing cap 8 while vibrating it, the contact width, i.e., the joining width, increases.

[0021] As the sealing cap 8 is pressed down while being vibrated, it eventually reaches the state shown in FIG. 6. In the state shown in FIG. 6, the vibration tool 19 and the sealing cap 8 are slightly lowered compared to the state shown in FIG. 5. As a result, in the state shown in FIG. 6, the joining area at the joining protrusion 18 has a relatively wide width. The joining surface 12 and the back surface 22 are joined in a ring shape at the joining protrusion 18. This joining area surrounds the liquid injection port 10. In addition, the step between the inclined surface 15 and the inclined surface 17 has disappeared. As a result, the vibration surface 20 is in contact with both the inclined surface 17 and the inclined surface 15.

[0022] In this state, the vibration of the vibration tool 19 is transmitted to both the sealing cap 8 and the lid body 5 via the inclined surfaces 17 and 15. Therefore, the sealing cap 8 and the lid body 5 vibrate in the same manner. As a result, the already formed joint between the joining protrusion 18 and the joining surface 12 is not destroyed by the vibration. Furthermore, after this, the vibration tool 19 and the sealing cap 8 cannot be further lowered. This state indicates that the joining of the sealing cap 8 to the lid body 5 has been completed. Therefore, once this state is reached, the vibration by the vibration tool 19 can be stopped. After that, the vibration tool 19 is retracted from the battery 1, and the joining process is completed.

[0023] In the battery 1 after the joining is completed, the sealing cap 8 (inclined surface 17) and the lid body 5 (inclined surface 15) form a flat surface without any steps. Furthermore, as shown in FIG. 7 , a machining mark 21 is formed across the inclined surface 17 and the inclined surface 15. The machining mark 21 is a rough surface with some unevenness formed by contact with the vibrating vibration surface 20. The machining mark 21 can be easily identified with the naked eye in the areas of the sealing cap 8 and the lid body 5 that did not come into contact with the vibration surface 20. The portions of the machining mark 21 on the inclined surface 17 and the inclined surface 15 are both annular. It is sufficient for the vibration of the vibration tool 19 after the vibration surface 20 comes into contact with the inclined surface 15 to continue long enough to form the machining mark 21 on the inclined surface 17.

[0024] In the present embodiment, the timing for ending vibration by the vibration tool 19 is managed not by time but by the amount of sinking of the sealing cap 8. The amount of sinking refers to the difference in level between the inclined surface 15 and the inclined surface 17 in FIG. 5. Therefore, the bonding quality between the lid body 5 and the sealing cap 8 is low, resulting in a high yield and fewer defective products. This is because it is only necessary to properly manage the accuracy of the protruding height of the bonding protrusion 18, and individual differences do not have much of an effect.

[0025] As described above in detail, according to this embodiment, the filling port 10 of the battery 1 is closed with the sealing cap 8 by ultrasonic bonding after the filling. Then, only the sealing cap 8 comes into contact with the vibration tool 19 in the early stage of the bonding process, and the lid body 5 also comes into contact with the vibration tool 19 in the final stage of the bonding process. This ensures that batteries 1 in which the sealing cap 8 and the lid body 5 are bonded together in an annular shape and the filling port 10 is securely closed can be obtained with a high yield. In this way, a battery 1 in which the through hole 10 is formed in the battery case 2 and is closed by the cap 8, and in which the cap 8 is securely bonded, is realized, along with a manufacturing method thereof.

[0026] The present embodiment and examples are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be improved and modified in various ways without departing from the spirit and scope of the invention. For example, the type of battery 1 is not important. The safety valve 9 is not essential. During ultrasonic bonding, instead of fixing the battery 1 and pushing down the vibration tool 19, the vibration tool 19 may be fixed and the battery 1 may be pushed up.

[0027] The sealing cap 8 and its surroundings can be modified in various ways. It is not essential that the flange portion 11 be thinner than other portions of the lid body 5. The wall surface 14 of the lid body 5 does not have to be a strictly vertical surface. The flat portion 16 of the sealing cap 8 may be dome-shaped, or conversely, may be concave. The joining protrusions 18 may be provided on the joining surface 12 of the lid body 5 instead of on the back surface 22 of the sealing cap 8. The joining protrusions 18 may be double annular or multiple annular in shape. In this case, some of the joining protrusions 18 may be provided on the joining surface 12, and the remaining joining protrusions 18 may be provided on the back surface 22.

[0028] The relationship between inclined surface 15, inclined surface 17, and vibration surface 20 is not limited to that described above. The inclination of inclined surface 15 and inclined surface 17 may be different. In this case, however, vibration surface 20 must also have a shape in which the degree of inclination changes along the way. A configuration in which inclined surface 15, inclined surface 17, and vibration surface 20 are all flat is also possible. A configuration in which inclined surface 15 and inclined surface 17 are concave and vibration surface 20 is convex is also possible. However, from the viewpoint of minimizing unnecessary unevenness around sealing cap 8 in the completed battery 1 and avoiding concave areas where foreign matter may accumulate, the configuration of this embodiment in which inclined surface 15 and inclined surface 17 are convex is more advantageous.

[0029] It is not essential that there is a step between inclined surface 15 and inclined surface 17 at the start of processing in FIG. 5 and that there is no step between inclined surface 15 and inclined surface 17 at the end of processing in FIG. 6. A configuration in which there is no step at the start of processing but there is a step at the end of processing is also possible, or a configuration in which there is a step both at the start and the end of processing is also possible. In these cases, however, it is necessary for vibration surface 20 to have a stepped shape. Furthermore, from the viewpoint of not leaving a stepped area around sealing cap 8 in the finished battery 1 where foreign matter can accumulate, the configuration of this embodiment in which there is no step at the end of processing is advantageous. [Explanation of symbols]

[0030] 1 battery 15 slope 2 Battery case 17 Inclined surface 3 Power generating element 18 Joint protrusion 4 Box 19 Vibration tool 5 Cover 20 Vibration surface 8 Sealing cap 21 Machining marks 10 Filling port 22 Back side 12 Joint surface

Claims

1. A battery comprising a battery case and a power generating element housed in the battery case, wherein a through hole is formed in the battery case and the through hole is closed with a cap, The battery case is a first annular bonding surface on an outer surface side around the through hole; and an annular first work surface on the outer side of the through hole and on the outer surface side of the first joining surface, The cap is a diameter smaller than the inner periphery of the first work surface; a second bonding surface on an inner surface side opposite to the first bonding surface; and an outer annular second work surface, an annular joining protrusion is provided on at least one of the first joining surface and the second joining surface, the first bonding surface and the second bonding surface are bonded together in an annular shape at the bonding protrusion, a circular machining mark is formed on both the first machined surface and the second machined surface, A battery in which both the first processed surface and the second processed surface are convex inclined surfaces that become higher toward the center of the through hole.

2. 10. The battery of claim 1, A battery in which the first processed surface and the second processed surface are flat surfaces without any steps between them.

3. A method for manufacturing a battery having a battery case and a power-generating element housed in the battery case, wherein a through hole is formed in the battery case and the through hole is closed with a cap, the method comprising: The battery case is a first annular bonding surface on an outer surface side around the through hole; and an annular first work surface on the outer side of the through hole and on the outer surface side of the first joining surface, The cap is a diameter smaller than the inner periphery of the first work surface; a second bonding surface on an inner surface side opposite to the first bonding surface; and an outer annular second work surface, an annular joining protrusion is provided on at least one of the first joining surface and the second joining surface, the cap is disposed so that the first bonding surface and the second bonding surface come into contact with each other at the bonding protrusion, and the through hole is covered with the cap; a vibration tool having a vibration surface is applied to the cap so that the vibration surface contacts the second work surface but does not contact the first work surface; The vibration tool is used to vibrate the cap through the second workpiece surface to bond the first bonding surface and the second bonding surface together in an annular shape at the bonding protrusion, The vibration tool is advanced toward the battery case until the vibration surface contacts the first workpiece surface; A battery manufacturing method in which vibration by the vibration tool is continued until circular processing marks are formed on both the first processed surface and the second processed surface, and then the vibration is stopped.

4. A method for manufacturing the battery according to claim 3, comprising the steps of: the first work surface and the second work surface are both convex inclined surfaces that are higher toward the center of the through hole, A method for manufacturing a battery, wherein the vibration surface is a concave inclined surface that matches the inclination of the first processed surface and the second processed surface.

5. A method for manufacturing the battery according to claim 3 or claim 4, The vibration surface is a flat surface without any steps, A method for manufacturing a battery in which the first processed surface and the second processed surface are flat surfaces without any steps when the joining is completed.

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