Resistance-welding method

Abstract

To provide a resistance-welding method which can suppress electric resistance of an electrode from increasing at an initial stage after electrode change and can improve weld quality at the initial stage after the electrode change.SOLUTION: A resistance-welding method repeatedly performs after exchanging a pair of electrodes (fixed electrode 1 and movable electrode 2) of a resistance-welding device 10: a welding step (S103) where member W to be welded is sandwiched and compressed between the pair of electrodes (fixed electrode 1 and movable electrode 2) to perform electric welding; and alignment step (S104) after welding where rotating alignment tool 21 is pushed against each tip of the pair of electrodes (fixed electrode 1 and movable electrode 2) for alignment. After exchanging the pair of electrodes (fixed electrode 1 and movable electrode 2) and before welding the member W to be welded at the first time, alignment step (S102) before welding is provided where the rotating alignment tool 21 is pushed against each tip of the pair of electrodes (fixed electrode 1 and movable electrode 2) for alignment.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a resistance welding method.

Background Art

[0002] Resistance welding is used as a means of joining a plurality of metal plates to each other. Welding is performed by sandwiching a member to be welded between a pair of electrodes and energizing while applying pressure. The tip of the electrode wears as welding is repeated. When the area of the tip of the electrode increases due to wear, the electrical resistance of the electrode decreases, resulting in a decrease in welding quality. Therefore, as disclosed in Patent Document 1, in order to maintain welding quality, a method of shaping the shape of the tip of the electrode after welding has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the resistance welding method disclosed in Patent Document 1, the inventors have found the following problems. In the resistance welding method disclosed in Patent Document 1, which repeats welding and electrode shaping after welding, at the initial stage after electrode replacement, the electrical resistance of the electrode increases due to electrode shaping after welding. Then, as welding and electrode shaping are repeated, the electrical resistance decreases and stabilizes. Therefore, due to the increase in electrical resistance at the initial stage after electrode replacement, the welding quality at the initial stage after electrode replacement deteriorates.

[0005] The present invention provides a resistance welding method capable of suppressing an increase in the electrical resistance of an electrode at the initial stage after electrode replacement and improving the welding quality at the initial stage after electrode replacement.

Means for Solving the Problems

[0006] A resistance welding method according to one aspect of the present invention is after exchanging a pair of electrodes of a resistance welding apparatus, a welding step of sandwiching a member to be welded between the pair of electrodes, applying pressure, and performing energization welding; a post-welding shaping step of pressing and shaping a rotating shaping tool against the tip of each of the pair of electrodes after the welding step, which is a resistance welding method that repeats these steps, and includes a pre-welding shaping step of pressing and shaping the rotating shaping tool against the tip of each of the pair of electrodes after exchanging the pair of electrodes and before first welding the member to be welded.

[0007] A resistance welding method according to one aspect of the present invention includes a pre-welding shaping step of shaping the tips of a pair of electrodes after exchanging the pair of electrodes of a resistance welding apparatus and before first welding a welding member. Therefore, an increase in the electrical resistance of the electrodes in the initial stage after electrode exchange can be suppressed, and the welding quality in the initial stage after electrode exchange is improved.

[0008] The rotation speed of the shaping tool in the pre-welding shaping step is preferably equal to or higher than the rotation speed of the shaping tool in the post-welding shaping step. With such a configuration, an increase in the electrical resistance of the electrodes in the initial stage after electrode exchange can be further suppressed, and the welding quality in the initial stage after electrode exchange is further improved.

[0009] The pressing force of the shaping tool against the tip of each of the pair of electrodes in the pre-welding shaping step is preferably equal to or higher than the pressing force of the shaping tool against the tip of each of the pair of electrodes in the post-welding shaping step. With such a configuration, an increase in the electrical resistance of the electrodes in the initial stage after electrode exchange can be further suppressed, and the welding quality in the initial stage after electrode exchange is further improved.

[0010] The pressing time of the shaping tool against the tip of each of the pair of electrodes in the pre-welding shaping process is preferably equal to or longer than the pressing time of the shaping tool against the tip of each of the pair of electrodes in the post-welding shaping process. With such a configuration, an increase in the electrical resistance of the electrodes in the initial stage after electrode replacement can be further suppressed, and the welding quality in the initial stage after electrode replacement can be further improved.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a resistance welding method capable of suppressing an increase in the electrical resistance of electrodes in the initial stage after electrode replacement and improving the welding quality in the initial stage after electrode replacement.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0013] Embodiment 1 Hereinafter, with reference to the drawings, a resistance welding method according to Embodiment 1 will be described.

[0014] <Configuration of Resistance Welding Apparatus> First, with reference to FIG. 1, a resistance welding apparatus used in the resistance welding method according to Embodiment 1 will be described. FIG. 1 is a schematic diagram of the resistance welding apparatus. The resistance welding apparatus 10 includes a fixed electrode 1, a movable electrode 2, a transformer 3, and a servo electric motor 4.

[0015] The fixed electrode 1 is fixed, for example, on the lower side of the resistance welding apparatus 10. The material of the fixed electrode 1 is made of, for example, copper, copper alloy, tungsten, tungsten alloy, etc. In the first embodiment, the shape of the fixed electrode 1 has a rounded tip, but it may also be flat at the tip or tapered towards the tip.

[0016] The movable electrode 2 is made of, for example, the same type of material as the fixed electrode 1 and has the same shape. The movable electrode 2 is disposed, for example, on the upper side of the resistance welding apparatus 10. That is, the fixed electrode 1 and the movable electrode 2 are oppositely installed in the resistance welding apparatus 10. The movable electrode 2 moves in the vertical direction by a servo electric motor 4. In other words, the servo electric motor 4 moves the movable electrode 2 in a direction approaching or moving away from the fixed electrode 1.

[0017] The transformer 3 converts the current supplied to the welding apparatus into a current supplied to the fixed electrode 1 and the movable electrode 2. The servo electric motor 4 is a drive source for moving the movable electrode 2 in the vertical direction. The workpiece to be welded W is a metal plate (for example, an iron plate or an aluminum alloy plate), and the number of welded sheets is two or more. The workpiece to be welded W is sandwiched between the fixed electrode 1 and the movable electrode 2 and is welded by energizing while applying pressure.

[0018] In this embodiment, there is no limitation on the type of welding gun of the resistance welding apparatus 10, and a C gun, an X gun, a horizontal gun, a vertical gun, etc. may be used.

[0019] <Shaping device> With reference to FIG. 2, an electrode shaping device used in the resistance welding method according to the first embodiment will be described. FIG. 2 is a schematic diagram of the electrode shaping device. The electrode shaping device 20 includes a shaping tool 21 for shaping the tip of the electrode and an electric motor 22 for rotating the shaping tool 21. The shaping tool 21 is rotatably mounted on the electrode shaping device 20 and is rotated by the electric motor 22.

[0020] The shaping tool 21 includes machining surfaces B1 and B2 for shaping the tip of the electrode. The machining surfaces B1 and B2 have, for example, cutting edges for shaping the tip of the electrode by cutting. In the first embodiment, in addition to the cutting edges, a shaping tool that shapes the tip of the electrode by crushing it with the machining surfaces B1 and B2 may be used as the shaping tool 21.

[0021] In the first embodiment, the tip of the electrode is shaped using a shaping device, but it is not limited thereto. For example, a cutting tool (dresser) for cutting the tip of the electrode may be used as the shaping tool 21.

[0022] <Resistance welding method> The resistance welding method according to the first embodiment will be described. FIG. 3 is a flowchart of the resistance welding method according to the first embodiment.

[0023] First, the electrodes of the resistance welding device 10 of the resistance welding device are replaced (step S101). After replacing the electrodes, a shaping process (hereinafter referred to as a pre-welding shaping process) is performed (step S102). Thus, by shaping the electrodes after replacing them and before the first welding process, an increase in the electrical resistance of the electrodes at the initial stage after electrode replacement can be suppressed.

[0024] Then, a welding process is performed using the shaped electrodes (step S103). An alloy layer is formed on the tip of the electrode after welding and is worn. Therefore, after the welding process, a shaping process of the electrodes (hereinafter referred to as a post-welding shaping process) is performed (step S104). By shaping the electrodes after welding, the worn tip of the electrode can be brought closer to the shape before welding.

[0025] After the post-welding shaping process, it is determined whether the shaped electrode can be used again in the welding process (step S103) (step S105). If it is determined that the electrode can be used in the welding process (step S103), the welding process (step S103) is performed again. The welding process (step S103) and the post-welding shaping process (step S104) are repeated until it is determined that the electrode cannot be used. If it is determined that the electrode cannot be used, the resistance welding using that electrode is terminated.

[0026] <Shaping process> Next, with reference to FIG. 2, the shaping processes (steps S102 and S104) for the resistance welding method shown in FIG. 3 will be described. By the operation of the electric motor 22, the shaping tool 21 is rotated at a predetermined rotational speed. Then, the tip of the fixed electrode 1 or the movable electrode 2 (hereinafter referred to as the electrode) is pressed against the machining surfaces B1 and B2 of the rotating shaping tool 21 with a predetermined pressing force for a predetermined time. Through the above operations, the electrode is shaped.

[0027] By changing the shaping conditions in the electrode shaping process between the pre-welding shaping process (step S102) and the post-welding shaping process (step S104), the change in the electrical resistance value can be more effectively suppressed. The rotational speed of the shaping tool 21 in the pre-welding shaping process (step S102) is preferably equal to or higher than the rotational speed in the post-welding shaping process (step S104). Also, the pressing force of the electrode against the machining surfaces B1 and B2 of the rotating shaping tool 21 in the pre-welding shaping process (step S102) is preferably equal to or higher than the pressing force in the post-welding shaping process (step S104). Further, the pressing time of the electrode against the machining surfaces B1 and B2 of the rotating shaping tool 21 in the pre-welding shaping process (step S102) is preferably equal to or longer than the pressing time in the post-welding shaping process (step S104). Regarding the above three conditions, it is preferable to satisfy two or more, or three or more of them.

[0028] Regarding the pressing time of the electrode against the machining surfaces B1 and B2 of the rotating shaping tool 21, if the total pressing time is the same, equivalent effects can be obtained by changing the single pressing time and the number of presses. For example, the effect is the same whether the single pressing time is 8 seconds and it is pressed only once, or the single pressing time is 2 seconds and it is pressed 4 times.

[0029] <Welding process> Next, with reference to FIG. 1, the welding process for the resistance welding method (step S103) shown in FIG. 3 will be described. First, the workpiece to be welded W is placed between a pair of fixed electrodes 1 and a movable electrode 2. Next, the movable electrode 2 is moved by the servo motor 4 to approach the fixed electrode 1. As a result, the fixed electrode 1 and the movable electrode 2 sandwich and electrically connect the workpiece to be welded W. Subsequently, the movable electrode 2 is pushed in, and electric resistance welding is performed while the workpiece to be welded W is pressurized. Finally, the movable electrode 2 is separated from the fixed electrode 1, and the resistance-welded workpiece to be welded W is taken out.

[0030] <Example> Hereinafter, an example of the resistance welding method according to Embodiment 1 will be described. FIG. 4 is an example showing the change in the electrical resistance value of the electrode from after the electrode exchange until it is determined that the electrode cannot be used in the welding process in Embodiment 1. FIG. 5 is a comparative example showing the change in the electrical resistance value of the electrode from after the electrode exchange until it is determined that the electrode cannot be used in the welding method disclosed in Patent Document 1. In the welding method of the example, a pre-welding shaping process (step S102) is performed, but in the comparative example, the pre-welding shaping process (step S102) is not performed.

[0031] Regarding the shaping conditions of the pre-welding shaping process (step S102) in the embodiment, the rotational speed of the shaping tool 21 was 1200 rpm, the pressing force of the electrode against the processing surfaces B1 and B2 of the shaping tool 21 was 4000 N, and the pressing time was 8 seconds. Regarding the shaping conditions of the post-welding shaping process (step S104) in the embodiment and the comparative example, the rotational speed of the shaping tool 21 was 1000 rpm, the pressing force of the electrode against the processing surfaces B1 and B2 of the shaping tool 21 was 2800 N, and the pressing time was 2 seconds.

[0032] In the comparative example where the pre-welding shaping process (step S102) was not performed, at the initial stage after electrode replacement, the electrical resistance of the electrode increased due to the post-welding shaping process (step S104). Then, as the welding process (step S103) and the post-welding shaping process (step S104) were repeated, the electrical resistance of the electrode decreased and stabilized. On the other hand, in the embodiment where the pre-welding shaping process (step S102) was performed, there was no increase in resistance at the initial stage after electrode replacement. And even when the welding process (step S103) and the post-welding shaping process (step S104) were repeated, the electrical resistance hardly changed and remained stable.

[0033] The reason for the presence or absence of an increase in electrical resistance in the comparative example and the embodiment is considered as follows. At the initial stage after electrode replacement in the comparative example, the atomic arrangement at the tip of the electrode is disrupted, so the electrical resistance of the electrode is high. And by repeating the welding process (step S103) and the post-welding shaping process (step S104), the disrupted atomic arrangement realigns. As the atomic arrangement realigns, the electrical resistance of the electrode decreases and stabilizes. On the other hand, in the embodiment, the pre-welding shaping process (step S102) can align the atomic arrangement at the tip of the electrode before welding. Therefore, the welding process (step S103) and the post-welding shaping process (step S104) can be started with the atomic arrangement at the tip of the electrode aligned. Thus, no increase in electrical resistance occurs, and the welding process (step S103) and the post-welding shaping process (step S104) can be repeated while remaining stable, so the welding quality is stable.

[0034] Note that the present invention is not limited to the above-described embodiments, and can be appropriately modified without departing from the gist thereof.

Description of Reference Numerals

[0035] 1 Fixed electrode 2 Movable electrode 3 Transformer 4 Servo motor 10 Resistance welding device 20 Shaping device 21 Shaping tool 22 Electric motor W Welded member

Claims

1. After exchanging a pair of electrodes of a resistance welding apparatus, a welding step of sandwiching a member to be welded between the pair of electrodes, applying pressure, and performing energization welding; a post-welding shaping step of pressing and shaping a rotating shaping tool against the tip of each of the pair of electrodes after the welding step, the resistance welding method being repeated, comprising a pre-welding shaping step of pressing and shaping the rotating shaping tool against the tip of each of the pair of electrodes after exchanging the pair of electrodes and before first welding the member to be welded. Resistance welding method.

2. The rotational speed of the shaping tool in the pre-welding shaping step is equal to or higher than the rotational speed of the shaping tool in the post-welding shaping step, The resistance welding method according to Claim 1.

3. The pressing force of the shaping tool against the tip of each of the pair of electrodes in the pre-welding shaping step is equal to or higher than the pressing force of the shaping tool against the tip of each of the pair of electrodes in the post-welding shaping step, The resistance welding method according to Claim 1.

4. The pressing time of the shaping tool against the tip of each of the pair of electrodes in the pre-welding shaping step is equal to or longer than the pressing time of the shaping tool against the tip of each of the pair of electrodes in the post-welding shaping step, The resistance welding method according to Claim 1.

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