JP2016110701A - Manufacturing method of current interruption mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a current interruption mechanism for suppressing a welding defect between a reverse plate and a rivet.SOLUTION: The manufacturing method of the current interruption mechanism includes placing an outer edge 33 of a reverse plate 30 on a step 45 of a rivet 40. On a wall surface 33a or on the wall surface 33a and a bottom face 33b of the outer edge 33, a high melting point layer 71 is provided. A width (h) of the high melting point layer 71 that is provided on the wall surface 33a exceeds 0.05 mm and less than 0.2 mm. The manufacturing method of the current interruption mechanism also includes temporarily welding the outer edge 33 and the step 45 and finally welding the outer edge 33 and the step 45. Laser output during the temporary welding is equal to or higher than 1200 W and lower than 1500 W in the case where the high melting point layer 71 is provided on the wall surface 33a, or is equal to or higher than 1200 W and lower than 1800 W in the case where the high melting point layer 71 is provided on the wall surface 33a and the bottom face 33b. Laser output during the final welding is equal to or higher than 1200 W and lower than 1800 W.SELECTED DRAWING: Figure 7

Description

  The present invention generally relates to a method for manufacturing a current interrupting mechanism, and more specifically, a current interrupting mechanism that is used for a secondary battery and interrupts current when the pressure in a case housing a battery element increases. It relates to a manufacturing method.

  Regarding a conventional secondary battery current interruption mechanism, for example, Japanese Patent Laid-Open No. 2013-157200 discloses a current interruption device for a sealed secondary battery for the purpose of ensuring sealing performance even when there is poor welding. Is disclosed (Patent Document 1). The current interruption device disclosed in Patent Document 1 is an apparatus that interrupts current when the pressure in the battery case of the lithium ion secondary battery becomes higher than a set pressure. The current interrupting device has a reversing plate made of aluminum and made into a disk shape, and a rivet fixed to the reversing plate by all-around welding.

  In addition, International Publication No. 2013/2173 (Patent Document 2), Japanese Patent Application Laid-Open No. 2-247094 (Patent Document 3), Japanese Patent Application Laid-Open No. 2013-188787 (Patent Document 4), and Japanese Patent Application Laid-Open No. 2013-21178. (Patent Document 5) also discloses various secondary batteries and manufacturing methods thereof.

JP 2013-157200 A International Publication No. 2013/2173 JP-A-2-247704 JP 2013-188787 A JP 2013-2111178 A

  As disclosed in Patent Document 1 described above, there is known a current interrupting mechanism for interrupting current when the pressure in the case of the secondary battery increases. In such a method of manufacturing a current interrupting mechanism, when placing the outer peripheral edge portion of the reversing plate on the step portion of the rivet and welding the step portion and the outer peripheral edge portion, the interval in the circumferential direction of the outer peripheral portion is previously set. A method is assumed in which laser welding is performed at a plurality of points separated (temporary welding process), and then laser welding is performed on the entire circumference of the outer peripheral edge (main welding process).

  In the manufacturing method described above, air in the gap between the stepped portion and the outer peripheral edge is pushed out in the laser welding scanning direction during the main welding process. However, since the welded portion previously provided by the temporary welding process exists at the destination of the extruded air, the movement of the air is inhibited by the welded portion. In this case, blow holes (pores) are generated, which may cause poor welding.

  Accordingly, an object of the present invention is to solve the above-described problems and to provide a method for manufacturing a current interrupt mechanism that suppresses poor welding between the reversing plate and the rivet.

  The method for manufacturing a current interrupting mechanism according to the present invention is a method for manufacturing a current interrupting mechanism that is used for a secondary battery and that interrupts current when the pressure in a case housing a battery element rises. A method of manufacturing a current interrupting mechanism includes a step of preparing a reversing plate including an outer peripheral edge and a rivet including a step having a step in the thickness direction of the reversing plate, and placing the outer peripheral edge on the step. . The outer peripheral edge portion is formed with a wall surface facing the outer peripheral side and contacting the step portion, and a bottom surface facing the step portion and facing the thickness direction of the reverse plate. A high melting point layer made of a metal or a metal oxide having a higher melting point than the reversal plate is provided on the wall surface, or the wall surface and the bottom surface. The width of the high melting point layer provided on the wall surface in the thickness direction of the reversal plate is in the range of more than 0.05 mm and less than 0.2 mm. A method of manufacturing a current interrupting mechanism includes a step of temporarily fixing an inversion plate to a rivet by laser welding the outer peripheral edge portion and the stepped portion at a plurality of positions spaced in the circumferential direction of the outer peripheral edge portion, After the step of temporarily fixing the rivet, a step of fixing the reverse plate to the rivet by laser welding the outer peripheral edge portion and the stepped portion around the entire circumference of the outer peripheral edge portion is provided. The laser output during the process of temporarily fixing the reversal plate to the rivet is in the range of 1200 W to less than 1500 W when the high melting point layer is provided only on the wall surface and the bottom surface, and the high melting point layer is provided on the wall surface and the bottom surface. In this case, the range is 1200 W or more and less than 1800 W. The laser output during the process of fixing the reversing plate to the rivet is in the range of 1200 W to less than 1800 W.

  According to the manufacturing method of the current interruption mechanism configured as described above, the wall surface of the outer peripheral edge portion of the reversing plate, or the wall surface and the bottom surface of the outer peripheral edge portion of the reversing plate has a high melting point that is difficult to melt compared to the reversing plate. While providing a layer, the outer peripheral edge part and the level | step-difference part are laser-welded with the laser output in a specific range. Thereby, the penetration by laser welding can be prevented from becoming more than the thickness of the reversal plate, and an air escape path can be ensured immediately below the welded portion. As a result, it is possible to suppress the occurrence of blowholes and suppress poor welding between the reversing plate and the rivet.

  As described above, according to the present invention, it is possible to provide a method of manufacturing a current interrupt mechanism that suppresses poor welding between the reversing plate and the rivet.

It is a top view which shows the external appearance of a secondary battery. It is a longitudinal cross-sectional view which shows the secondary battery in FIG. It is sectional drawing which shows the electric current interruption mechanism along the III-III line | wire in FIG. FIG. 4 is an exploded view of the current interrupt mechanism in FIG. 3. It is a perspective view which shows the 1st process in the manufacturing method of the electric current interruption mechanism in embodiment of this invention. It is sectional drawing which shows the contact part of the outer peripheral edge part of an inversion board, and the level | step-difference part of a rivet. It is sectional drawing which expands and shows the range enclosed with the dashed-two dotted line VII in FIG. It is a perspective view which shows the 2nd process in the manufacturing method of the electric current interruption mechanism in embodiment of this invention. It is sectional drawing which shows the outer peripheral part and the welding part of a level | step difference part. It is sectional drawing which shows the outer-periphery edge part and level | step-difference part at the time of this welding process along the XX line in FIG. It is sectional drawing which shows the outer peripheral part of an inversion board, and the welding part of the level | step-difference part of a rivet for the comparison. In Examples 1-6 and Comparative Examples 1-10, it is a table | surface which shows the formation result and welding conditions of a high melting point layer, and the evaluation result of the created electric current interruption mechanism.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment)
FIG. 1 is a plan view showing the appearance of the secondary battery. FIG. 2 is a longitudinal sectional view showing the secondary battery in FIG.

  With reference to FIG. 1 and FIG. 2, the whole structure of the secondary battery 100 is demonstrated first. The secondary battery 100 is a nonaqueous electrolyte secondary battery. As an example, a plurality of secondary batteries 100 are combined in series to form an assembled battery and are mounted on a hybrid vehicle. The assembled battery is used as a power source for a hybrid vehicle together with an internal combustion engine such as a gasoline engine or a diesel engine.

  The secondary battery 100 includes an exterior body 10 as a case, an electrode body 13 as a battery element, an external terminal 20 and a current collecting terminal 21 for a positive electrode, an external terminal 24 and a current collecting terminal 25 for a negative electrode, a negative electrode Current interrupting mechanism 200.

  The exterior body 10 is configured by combining the housing portion 11 and the sealing plate 12. The exterior body 10 has a bottomed cylindrical shape, and an electrode body 13 is accommodated therein. The sealing plate 12 is provided so as to close the opening of the exterior body 10. The external terminals 20 and 24 are attached to the sealing plate 12. The electrode body 13 includes a positive electrode core body, a negative electrode core body, and a separator (all not shown). The positive electrode core body and the negative electrode core body are wound via a separator. A positive electrode core exposed portion 14 and a negative electrode core exposed portion 15 are respectively provided at both ends of the electrode body 13.

  The positive electrode core exposed portion 14 is electrically connected to the external terminal 20 via the current collecting terminal 21. The negative electrode core exposed portion 15 is electrically connected to the external terminal 24 via the current collecting terminal 25 and the current interrupt mechanism 200. The current interruption mechanism 200 is an apparatus for interrupting the flow of current between the electrode body 13 and the external terminal 24 when the internal pressure of the exterior body 10 increases. Instead of the current interrupt mechanism 200 provided for the negative electrode, a current interrupt mechanism for the positive electrode may be provided.

  FIG. 3 is a cross-sectional view showing a current interrupting mechanism along the line III-III in FIG. 4 is an exploded view of the current interrupt mechanism in FIG.

  With reference to FIG. 3 and FIG. 4, the structure of the current interruption mechanism 200 which the secondary battery 100 has is demonstrated. The current interruption mechanism 200 includes a conductive plate 19, a reversing plate (also referred to as a diaphragm) 30, a rivet 40, and gaskets 16, 17, and 18.

  A through hole 12H is formed in the sealing plate 12. The through hole 12H is formed so as to communicate the space inside and outside the exterior body 10. The gaskets 17 and 18 are disposed inside the exterior body 10 and are interposed between the rivet 40 and the sealing plate 12. The conductive plate 19 is disposed outside the exterior body 10 and is provided directly above the sealing plate 12 via the gasket 16. The current collecting terminal 21 is electrically connected to the external terminal 20 in FIG. 2 via the reversing plate 30, the rivet 40, and the conductive plate 19.

  The rivet 40 is made of a conductive material. The rivet 40 is made of a metal such as aluminum. The rivet 40 is connected to the conductive plate 19 outside the exterior body 10 and is connected to the reversal plate 30 inside the exterior body 10. The rivet 40 is provided as a connecting member that electrically connects the external terminal 20 and the reversing plate 30.

  The rivet 40 includes a caulking portion 41, a small diameter portion 42, a connection portion 43, a large diameter portion 44, and a step portion 45 as its constituent parts.

  The small diameter portion 42 has a cylindrical shape and is inserted through the through hole 12H. The caulking portion 41 is provided at the tip of a small diameter portion 42 that extends toward the outside of the exterior body 10. The caulking portion 41 has a shape that spreads in a bowl shape from the tip of the small diameter portion 42. The connecting portion 43 is provided at the tip of the small diameter portion 42 extending toward the inside of the exterior body 10. Between the caulking portion 41 and the connecting portion 43, the conductive plate 19, the gasket 16, the sealing plate 12, the gasket 17 and the gasket 18 are fixed by caulking.

  The large diameter portion 44 is bent from the outer peripheral edge of the connection portion 43 and has a cylindrical shape having a larger diameter than the small diameter portion 42. The connecting portion 43 is provided so as to connect the small diameter portion 42 and the large diameter portion 44. The step portion 45 is provided at the tip of the large diameter portion 44. The step portion 45 is provided in an annular shape along the circumferential direction of the large-diameter portion 44 having a cylindrical shape. The step portion 45 has a step shape for receiving the reversing plate 30.

  The reverse plate 30 is made of a metal such as aluminum. The inversion plate 30 has a circular flat plate shape as a whole. The reversing plate 30 has a top surface portion 31, an inclined portion 32, and an outer peripheral edge portion 33 as constituent parts thereof.

  The top surface portion 31 is provided at the center of the reversing plate 30 in plan view. The top surface portion 31 is connected to the current collecting terminal 21. The outer peripheral edge 33 is provided on the outer peripheral edge of the reversing plate 30 in plan view. Preferably, the thickness of the outer peripheral edge 33 is substantially equal to the depth of the step 45 in the rivet 40. Preferably, the outer peripheral edge portion 33 has a thickness of 0.3 mm or more. The inclined portion 32 extends from the top surface portion 31 to the outer peripheral edge portion 33 while extending in an oblique direction on a plane on which the top surface portion 31 is disposed.

  In the method for manufacturing the current interrupt mechanism 200, the outer peripheral edge portion 33 is placed on the stepped portion 45, and the outer peripheral edge portion 33 and the stepped portion 45 are laser welded, whereby the reversing plate 30 is fixed to the rivet 40.

  The current collecting terminal 21 is made of a metal such as an aluminum alloy. The current collecting terminal 21 includes a thick portion 22, a thin portion 23, and a current collecting tab 24 as constituent parts. The thin portion 23 has a thickness smaller than that of the thick portion 22. The top surface portion 31 of the reversing plate 30 is connected to the thin portion 23 by laser welding. The current collecting tab 24 is connected to the positive electrode core exposed portion 14 in FIG.

  When the internal pressure of the exterior body 10 rises, the reverse plate 30 is reversely deformed in a direction away from the current collecting terminal 21. At this time, the connection between the thin portion 23 of the current collecting terminal 21 and the top surface portion 31 of the reversing plate 30 is released, and the current flow between the electrode body 13 and the external terminal 20 is interrupted.

  Next, a process of fixing the reversing plate 30 to the rivet 40 in the method for manufacturing the current interrupt mechanism 200 will be described.

  FIG. 5 is a perspective view showing a first step in the method of manufacturing the current interrupt mechanism in the embodiment of the present invention. FIG. 6 is a cross-sectional view showing the abutting portion of the outer peripheral edge portion of the reversing plate and the step portion of the rivet.

  With reference to FIGS. 5 and 6, first, a reversing plate 30 having an outer peripheral edge portion 33 and a rivet 40 having a stepped portion 45 are prepared, and the outer peripheral edge portion 33 is placed on the stepped portion 45.

  The step portion 45 has a step in the thickness direction of the reversing plate 30 (the direction indicated by the arrow 101 in FIG. 6). A wall surface 45 a and a step surface 45 b are formed on the step portion 45. The wall surface 45 a is an inner peripheral surface that forms a side portion of the stepped portion 45 and extends annularly with respect to the center of the reversing plate 30 in plan view. The step surface 45 b is a flat surface that forms the bottom of the step portion 45 and extends annularly with respect to the center of the reversing plate 30 in plan view.

  A wall surface 33 a and a bottom surface 33 b are formed on the outer peripheral edge portion 33. The wall surface 33a faces the outer peripheral side of the outer peripheral edge portion 33 and abuts on the step portion 45 (wall surface 45a). The bottom surface 33b faces the thickness direction of the outer peripheral edge portion 33 and abuts on the step portion 45 (step surface 45b). The wall surface 33 a is an outer peripheral surface extending in a ring shape with respect to the center of the reversing plate 30 in plan view, and the bottom surface 33 b is a plane extending in a ring shape with respect to the center of the reversing plate 30 in plan view.

  The contact surfaces of the outer peripheral edge portion 33 and the stepped portion 45 are configured by the contact surfaces of the wall surface 33a and the wall surface 45a and the contact surfaces of the bottom surface 33b and the stepped surface 45b.

  FIG. 7 is an enlarged cross-sectional view of a range surrounded by a two-dot chain line VII in FIG. Referring to FIG. 7, a high melting point layer 71p and a high melting point layer 71q are provided on the wall surface 33a and the bottom surface 33b of the outer peripheral edge portion 33, respectively. The high melting point layer 71p and the high melting point layer 71q are provided on the surface layer of the wall surface 33a and the bottom surface 33b.

  The high melting point layer 71p is provided over a predetermined range from the bottom surface 33b in the thickness direction of the reversing plate 30 (the direction indicated by the arrow 101 in FIG. 7). The width h of the high melting point layer 71 in the thickness direction of the reversing plate 30 is in the range of more than 0.05 mm and less than 0.2 mm (0.05 mm <h <0.2 mm).

  Furthermore, in the present embodiment, a high melting point layer 71r and a high melting point layer 71s are provided on the wall surface 45a and the step surface 45b of the step portion 45, respectively (hereinafter referred to as the high melting point layer 71p, the high melting point layer 71q, and the high melting point layer). When the layer 71r and the high melting point layer 71s are not particularly distinguished, they are referred to as the high melting point layer 71).

  The high melting point layer 71 is made of a metal or metal oxide having a higher melting point than the reversal plate 30. For example, when the reversal plate 30 is made of aluminum, the high melting point layer 71 is made of aluminum oxide, aluminum nitride, nickel, or the like having a melting point higher than that of aluminum.

  In the present invention, the high melting point layer 71r and the high melting point layer 71s provided in the stepped portion 45 are not essential components. Further, the high melting point layer 71 may be provided only on the wall surface 33a of the wall surface 33a and the bottom surface 33b of the outer peripheral edge 33.

  FIG. 8 is a perspective view showing a second step in the method of manufacturing the current interrupt mechanism in the embodiment of the present invention. FIG. 9 is a cross-sectional view showing a welded portion of the outer peripheral edge portion and the step portion.

  Referring to FIG. 8, next, the reversing plate 30 is temporarily fixed to the rivet 40 by laser welding the outer peripheral edge portion 33 and the stepped portion 45 at a plurality of locations spaced in the circumferential direction of the outer peripheral edge portion 33. (Temporary welding process) More specifically, the first welded portion 50j is provided by irradiating the outer peripheral edge portion 33 and the stepped portion 45 in a dot shape from directly above the contact surfaces of the wall surface 33a and the wall surface 45a.

  When the high melting point layer 71 is provided on the wall surface 33a and the bottom surface 33b of the outer peripheral edge portion 33, the laser output during the temporary welding process is set in a range of 1200 W or more and less than 1800 W. When the high melting point layer 71 is provided only on the wall surface 33a of the wall surface 33a and the bottom surface 33b of the outer peripheral edge 33, the laser output during the temporary welding process is set to a range of 1200 W or more and less than 1500 W.

  In the present embodiment, the first welded portion 50j by the temporary welding process is provided at four locations spaced in the circumferential direction of the outer peripheral edge portion 33. The number of the first welded portions 50j is not limited to four, and an optimal number for temporarily fixing the reversing plate 30 may be selected as appropriate. The plurality of places where the first weld 50j is provided may be equidistant or unequal.

  Referring to FIGS. 8 and 9, next, the reversing plate 30 is fixed to the rivet 40 by laser welding the outer peripheral edge portion 33 and the stepped portion 45 on the entire periphery of the outer peripheral edge portion 33 (main welding process). ). More specifically, the second welding is performed by scanning the outer peripheral edge portion 33 and the stepped portion 45 in the circumferential direction of the outer peripheral edge portion 33 while irradiating the outer peripheral edge portion 33 and the stepped portion 45 from directly above the contact surfaces of the wall surface 33a and the wall surface 45a. A portion 50k is provided. The outer peripheral edge portion 33 and the stepped portion 45 are coupled to each other by the welded portion 50 including the first welded portion 50j and the second welded portion 50k.

The laser output during the main welding process is set to a range of 1200 W or more and less than 1800 W.
Next, the mechanism of the occurrence of explosion that causes blowholes in the welded portion and the effect of suppressing the occurrence of such explosion by the method for manufacturing the current interrupt mechanism in the present embodiment will be described.

  With reference to FIG. 6 and FIG. 8, as described above, in the method of manufacturing a current interrupt mechanism, a temporary welding process is performed in which spot welding is performed on the contact portion of the outer peripheral edge portion 33 and the stepped portion 45 in advance. Then, the welding method which implements the main welding process which performs all-around welding to the contact part of the outer periphery part 33 and the level | step-difference part 45 is used.

  In the stage before the main welding process, the reversing plate 30 is placed on the stepped portion 45, and a minute gap exists at the contact portion between the reversing plate 30 and the stepped portion 45. The gap disappears by a main welding process in which the reversing plate 30 and the stepped portion 45 are welded and integrated. At this time, air in the gap is pushed out from the gap in the unwelded portion. For this reason, in the main welding process, the air in the gap is sequentially pushed out to the external space at the position excluding the place where the welding has been performed by the temporary welding process. The first welded portion 50j obstructs the movement of air at the location where the mark is applied.

  More specifically, during the main welding process, the air in the gap is surrounded by the wall surface 33a and the bottom surface 33b of the outer peripheral edge portion 33, the wall surface 45a and the step surface 45b of the step portion 45, and further scanned by the laser beam LB. There is a molten pool by laser irradiation at a position that is rearward with respect to the direction. Therefore, the air in the gap is blocked by the first welded portion 50j at a position that is forward with respect to the scanning direction of the laser beam LB, and an air pocket is generated. In this air reservoir, there is no escape space for air, and when scanning with the laser beam LB proceeds, air is compressed and explosion occurs due to rapid expansion due to heat during welding.

  FIG. 10 is a cross-sectional view showing the outer peripheral edge portion and the step portion along the line XX in FIG. 8 during the main welding process. FIG. 11 is a cross-sectional view showing a welded portion of the outer peripheral edge portion of the reversing plate and the step portion of the rivet for comparison.

  With reference to FIGS. 9 to 11, in the method of manufacturing the current interrupting mechanism in the present embodiment, in view of the explosion mechanism, the wall surface 33 a of the outer peripheral edge 33, or the wall surface 33 a and the bottom surface 33 b have a high height. The melting point layer 71 is provided, and the outer peripheral edge portion 33 and the stepped portion 45 are laser-welded with a laser output within a specific range. Thereby, in the temporary welding process and the main welding process, the depth of the penetration part by laser irradiation is prevented from being equal to or greater than the thickness of the reversing plate 30. For example, in the cross section showing the outer peripheral edge portion 33 and the stepped portion 45 in the main welding step in FIG. 10, the depth of the first welded portion 50j provided by the temporary welding step is larger than the plate thickness H1 of the reversing plate 30. The depth of the penetration portion 82 due to laser irradiation becomes smaller than the thickness H1 of the reversing plate 30. Thereby, at the time of the main welding process, it is possible to secure an air escape path in the non-welded portion 83 immediately below the penetration portion 82 and the first welded portion 50j, and the occurrence of explosion can be suppressed.

  At this time, the high melting point layer 71p is not provided on the entire surface of the wall surface 33a of the outer peripheral edge 33, and the width h of the high melting point layer 71p in the thickness direction of the reversal plate 30 exceeds 0.05 mm and is less than 0.00 mm. It is set to a range of less than 2 mm. By setting the width h of the high melting point layer 71p to a range exceeding 0.05 mm, it is possible to form the non-welded portion 83 necessary for securing the air escape path. Further, the unformed portion of the high melting point layer 71p on the wall surface 33a is melted and integrated during the main welding process, so that the welding strength of the outer peripheral edge portion 33 and the stepped portion 45, the conductivity between the reversing plate 30 and the rivet 40, This contributes to ensuring airtightness inside the rivet 40. By setting the width h of the high melting point layer 71p to a range of less than 0.2 mm, it is possible to sufficiently ensure the welding strength, conductivity, and airtightness.

  As shown in FIG. 11, when the high melting point layer 71 is not provided on the outer peripheral edge 33, a weld 50 having a depth H2 equal to or greater than the plate thickness H1 of the outer peripheral edge 33 of the reversing plate 30 is obtained (H2 ≧ H1), the occurrence of explosions becomes significant. On the other hand, according to the manufacturing method of the current interruption mechanism in the present embodiment, as shown in FIG. 9, the welded portion having a depth H2 smaller than the plate thickness H1 of the outer peripheral edge portion 33 of the reversing plate 30. 50 can be obtained (H2 <H1), and the occurrence of explosion can be effectively suppressed.

  According to the method of manufacturing the current interrupt mechanism in the embodiment of the present invention configured as described above, the welding structure between the reversing plate 30 and the rivet 40 having sufficient welding strength while suppressing the generation of blowholes. Can be obtained.

(Comparative example)
FIG. 12 is a table showing the formation conditions and welding conditions of the high melting point layer and the evaluation results of the created current interruption mechanism in Examples 1 to 6 and Comparative Examples 1 to 10. With reference to FIG. 12, an example of the method for manufacturing the current interrupt mechanism in the present embodiment will be described.

  In this embodiment, aluminum (A1050) having a thickness of 0.3 mm was used for the reversing plate 30. The rivet 40 was made of aluminum (A1050) having a thickness of 1.0 mm. The outer diameter of the outer peripheral edge portion 33 and the inner diameter (diameter) of the step portion 45 were 18 mm, and the depth of the step portion 45 was 0.3 mm.

  In the temporary welding step, the first welded portion 50j was provided by laser welding (keyhole welding) of the outer peripheral edge portion 33 and the stepped portion 45 at six equally spaced locations. As welding conditions in the main welding process, the processing speed was 300 mm / sec, and the beam diameter was 80 μm.

  The locations where the high melting point layer 71 is formed in each example and comparative example are shown in FIG. The case where the high melting point layer 71r is provided on the wall surface 45a of the stepped portion 45 is referred to as “A”, and the case where the high melting point layer 71q is provided on the bottom surface 33b of the outer peripheral edge portion 33 is referred to as “B”. The case where the high melting point layer 71 s was provided on the surface 45 b was designated as “C”, and the case where the high melting point layer 71 p was provided on the wall surface 33 a of the outer peripheral edge 33 was designated as “D”.

  In each of the examples and comparative examples, the widths of the high melting point layer 71p and the high melting point layer 71r were changed in the range of 0.05 mm to 0.2 mm. As the material of the high melting point layer 71, aluminum oxide (alumina) or nickel was used. The laser output at the time of temporary welding was changed in the range of 1200 W to 1800 W, and the laser output at the time of main welding was changed in the range of 750 W to 1800 W.

  The following evaluation was performed about 20 current interruption mechanisms created under the above conditions. First, airtightness was confirmed by a He leak test, and the number of current interrupting mechanisms in which airtight defects were recognized is shown in FIG. 12 (the number of airtight defects in 20). Next, the appearance of blowholes on the appearance was confirmed, and the number of confirmed blowholes is shown in FIG. 12 (occurrence frequency in 120 locations). Next, the welding strength was confirmed by destructive inspection, and the number of current interrupting mechanisms in which the welding strength was recognized as defective was shown in FIG. 12 (the number of defective welding strengths in 20).

  With reference to Comparative Example 1 and Comparative Example 2, the weld 50 reached a depth not less than the plate thickness of the outer peripheral edge 33, and a large number of blow holes were confirmed. In addition, increasing the laser output during the main welding process increased the number of blowholes.

  With reference to Comparative Example 3 and Comparative Example 4, by reducing the laser output during the main welding process, the number of blowholes generated was reduced, but sufficient welding strength could not be obtained due to insufficient welding depth.

  Referring to Comparative Example 5 and Comparative Example 6, since the laser output during the temporary welding process was too high, the high melting point layer 71 was melted, and the number of blow holes generated increased. In Example 5 in which the high melting point layer 71 is provided on the bottom surface 33 b of the outer peripheral edge 33 and the step surface 45 b of the step 45, the high melting point layer is provided on the bottom surface 33 b of the outer peripheral edge 33 and the step surface 45 b of the step 45. Compared with Comparative Example 5 in which 71 is not provided, the upper limit margin of the laser output during the temporary welding process is increased.

  In Comparative Example 7, since the laser output during the main welding process was too high, the high melting point layer 71 was melted, and the number of blow holes generated increased. In Comparative Example 7 and Example 6, the location where the blowhole occurred was not the first weld 50j, but the welding start location of the second weld 50k (a portion overlapping the first weld 50j). .

  In Comparative Example 8, because the width h of the high melting point layer 71p and the high melting point layer 71r was too large, the melting depth during welding was insufficient. As a result, sufficient welding strength could not be obtained.

  In Comparative Example 9, the high melting point layer 71 was provided only on the bottom surface 33b of the outer peripheral edge portion 33 and the step surface 45b of the step portion 45, and the generation of blow holes could not be sufficiently suppressed.

  In Comparative Example 10, since the width h of the high melting point layer 71p and the high melting point layer 71r was too small, the generation of blow holes could not be sufficiently suppressed.

  On the other hand, in Examples 1-6 according to the manufacturing method of the current interruption mechanism in the present embodiment, it was possible to obtain sufficient welding strength while suppressing the occurrence of blowholes.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is mainly used in a method for manufacturing a current interruption mechanism used in a secondary battery.

  DESCRIPTION OF SYMBOLS 10 exterior body, 11 accommodating part, 12 sealing board, 12H through-hole, 13 electrode body, 14 positive electrode core exposed part, 15 negative electrode core exposed part, 16, 17, 18 gasket, 19 electrically conductive plate, 20, 24 external terminal 21, 25 Current collecting terminal, 22 thick part, 23 thin part, 24 current collecting tab, 30 reversing plate, 31 top surface part, 32 inclined part, 33 outer peripheral edge part, 33a, 45a wall surface, 33b bottom surface, 40 rivets, 41 Caulking portion, 42 Small diameter portion, 43 Connection portion, 44 Large diameter portion, 45 Step portion, 45b Step surface, 50 Welded portion, 50j First welded portion, 50k Second welded portion, 71, 71p, 71q, 71r, 71s High melting point layer, 82 penetration site, 83 non-welded part, 100 secondary battery, 200 current interruption mechanism.

Claims (1)

A method of manufacturing a current interrupting mechanism that is used for a secondary battery and interrupts current when the pressure in a case containing a battery element rises,
Preparing a reversing plate including an outer peripheral edge and a rivet including a stepped portion having a step in the plate thickness direction of the reversing plate, and placing the outer peripheral edge on the stepped portion;
The outer peripheral edge portion is formed with a wall surface facing the outer peripheral side and contacting the step portion, and a bottom surface facing the step portion and facing the thickness direction of the reversing plate,
The wall surface or the wall surface and the bottom surface are provided with a high melting point layer made of a metal or metal oxide having a higher melting point than the reversal plate,
The width of the high melting point layer provided on the wall surface in the thickness direction of the reversal plate is in the range of more than 0.05 mm and less than 0.2 mm,
Temporarily fixing the reversal plate to the rivet by laser welding the outer peripheral edge and the stepped portion at a plurality of locations spaced in the circumferential direction of the outer peripheral edge; and
After the step of temporarily fixing the rivet to the reverse plate, the step of fixing the reverse plate to the rivet by laser welding the outer peripheral edge portion and the stepped portion on the entire circumference of the outer peripheral edge portion. ,
The laser output during the step of temporarily fixing the reversal plate to the rivet is in a range of 1200 W to less than 1500 W when the high melting point layer is provided only on the wall surface of the wall surface and the bottom surface. When provided on the wall surface and the bottom surface, the range is 1200 W or more and less than 1800 W,
The method of manufacturing a current interrupting mechanism, wherein a laser output during the step of fixing the reversing plate to the rivet is in a range of 1200 W or more and less than 1800 W.

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