US-12620677-B2 - Manufacturing method for welded structure, and battery

US12620677B2US 12620677 B2US12620677 B2US 12620677B2US-12620677-B2

Abstract

A manufacturing method for a welded structure includes preparing a stack in which a plate-shaped first welded member made of a first metal and a plate-shaped second welded member made of a second metal are stacked, and applying a laser beam to the first welded member such that multiple loop weld marks with the same central axis are provided. In applying the laser beam, the laser beam is applied such that irradiation energy gradually reduces from a predetermined one of the weld marks, located on an inner side, toward an outermost periphery.

Inventors

Seiko KUBOTA
Akio Sato
Seigo FUJISHIMA

Assignees

TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date: 20260505
Application Date: 20221230
Priority Date: 20220315

Claims (4)

1 . A battery comprising: a battery stack that includes a first single cell and a second single cell each having a plate-shaped positive electrode terminal made of a first metal and a plate-shaped negative electrode terminal made of a second metal and in which the first single cell and the second single cell are stacked such that each of the positive electrode terminals and an associated one of the negative electrode terminals are arranged in a stacking direction; and multiple loop weld marks welding each of the positive electrode terminals to the associated one of the negative electrode terminals, wherein the multiple loop weld marks are provided with a same central axis, the multiple loop weld marks include at least three loop weld marks, and a depth of each loop weld mark of the multiple loop weld marks progressively reduces from an innermost one of the multiple loop weld marks, located on an inner side, toward an outermost periphery of the multiple loop weld marks.
2 . The battery according to claim 1 , wherein an amount of alloy produced from the positive electrode terminal and the negative electrode terminal and contained in a weld mark of the multiple loop weld marks located at the outermost periphery is less than an amount of alloy contained in the innermost one of the multiple loop weld marks, located on the inner side.
3 . The battery according to claim 1 , wherein a width of the multiple loop weld marks reduces from the innermost one of the multiple loop weld marks, located on the inner side, toward the outermost periphery.
4 . The battery according to claim 1 , wherein the multiple loop weld marks include a first loop weld mark that is the innermost one of the multiple loop weld marks had has a first depth, a second loop weld mark adjacent the first loop weld mark and having a second depth that is less than the first depth, a third loop weld mark adjacent the second loop weld mark and having a third depth that is less than the second depth, and a fourth loop weld mark adjacent the third loop weld mark and having a fourth depth that is less than the third depth.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2022-040421 filed on Mar. 15, 2022, incorporated herein by reference in its entirety. BACKGROUND 1. Technical Field The disclosure relates to a manufacturing method for a welded structure, which welds a plate-shaped first welded member made of a first metal to a plate-shaped second welded member made of a second metal, and a battery in which a plate-shaped positive electrode terminal made of a first metal is welded to a plate-shaped negative electrode terminal made of a second metal. 2. Description of Related Art As a laser welding method of welding thin-plate welded members stacked on top of each other by application of a laser beam, WO 2015/186168 describes a method of applying a laser beam while moving the laser beam along preset multiple-loop weld lines, in which the laser beam is moved along an outer loop weld line before the laser beam is moved along an inner loop weld line. SUMMARY In the laser welding method described in WO 2015/186168, a laser beam is applied under constant welding conditions such that the inner areas of the weld lines are sequentially lowered by a predetermined amount to reliably weld the thin plates even with a gap between the thin plates. To perform welding in a state where portions to be welded are not clear due to the gap, the sheets can be actually welded in an outermost peripheral area. When the sheets are dissimilar metals, more than estimated amount of alloy may be produced at an outermost weld mark. In this case, alloy is formed at the outermost peripheral portion where stress tends to concentrate, so there are concerns that the strength of a joint decreases. The disclosure provides a manufacturing method for a welded structure, which is capable of maintaining good joint strength by reducing alloy to be formed at an outermost periphery, and a battery in which both terminals are joined with each other in a good condition. A manufacturing method for a welded structure according to the disclosure includes preparing a stack in which a plate-shaped first welded member made of a first metal and a plate-shaped second welded member made of a second metal are stacked, and applying a laser beam to the first welded member such that multiple loop weld marks with the same central axis are provided. In applying the laser beam, the laser beam is applied such that irradiation energy gradually reduces from a predetermined one of the weld marks, located on an inner side, toward an outermost periphery. With the above configuration, a laser beam is applied such that irradiation energy gradually reduces from a predetermined one of weld marks, located on an inner side, toward an outermost periphery. Therefore, it is possible to gradually reduce an alloy layer produced by application of a laser beam from the predetermined one of the weld marks toward the outermost periphery. Thus, it is possible to relatively firmly join the first welded member with the second welded member by allowing an alloy layer to some extent at the inner part where stress to be loaded is small, so it is possible to reduce the amount of alloy contained in the weld mark located at the outermost periphery where stress tends to concentrate. As a result, it is possible to reduce occurrence of cracks at the outermost periphery where stress tends to concentrate, so good joint strength is maintained. In the manufacturing method according to the disclosure, in applying the laser beam, multiple trajectories of laser beams respectively applied in association with the multiple loop weld marks may be discontinuous. With the above configuration, by providing discontinuous multiple trajectories of laser beams applied, irradiation energy of the laser beam for each trajectory is more easily changed. In the manufacturing method according to the disclosure, in applying the laser beam, each of the multiple trajectories may have a circular shape. With the above configuration, it is possible to uniformly apply a laser beam over in the circumferential direction. In the manufacturing method according to the disclosure, in applying the laser beam, the multiple loop weld marks may be provided such that a depth of the weld mark gradually reduces from the predetermined one of the weld marks, located on the inner side, toward the outermost periphery. With the above configuration as well, the depth of the weld mark gradually reduces from the predetermined one of the weld marks toward the outermost periphery. Therefore, the first welded member is relatively firmly joined with the second welded member by allowing an alloy layer to some extent at the inner part where stress to be loaded is small; whereas it is possible to reduce the amount of alloy contained in the weld mark located at the outermost periphery where stress tends to concentrate. In the manufacturing method according to the disclosure, in applying the laser beam, the laser beam may be