JPH06278B2 - Laminate resistance welding method and laminate resistance welding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to the resistance of laminated plates containing a non-conductive material, or the resistance of a laminated plate in which two or more laminated plates and metal materials are overlapped and welded by spot welding or the like. A welding method and a welding apparatus therefor.

[Prior art]

Generally, in a laminated plate, a non-conductive material is sandwiched in the middle in the plate thickness direction, so it is impossible to energize in the plate thickness direction, and resistance welding such as spot welding cannot be performed as it is. Therefore, conventionally, resistance welding has been performed by the method shown in FIG. 6 disclosed in Japanese Patent Laid-Open No. 59-113988. That is, a laminated plate 2 in which a metal material 1 is sandwiched between two steel plates 2a and 2c and a non-conductive material 2b such as a resin is sandwiched therebetween.
In the case of spot welding to a pair of welding electrodes 3a, 3b
In addition to the above, a pair of auxiliary electrodes 4a and 4b are provided and brought into contact with the steel plates 2a and 2c, respectively.
b is connected by a conductive member 5 so that the steel plates 2a and 2c are electrically conductive.

Further, as disclosed in Japanese Patent Application Laid-Open No. 59-42189, a proposal has been made in which the above proposal is further automated to improve the welding stability.

According to any of the above proposals, an electric current flows through at least one of the steel plates 2a and 2c, Joule heat is generated in the contact portion between the metal material 1 and the steel sheet 2a, and the non-conductive material in this portion is melted. At this time, when pressure is applied between the welding electrodes 3a and 3b, the steel plates 2a and 2c come into contact with each other and become conductive, and spot welding is performed.

However, in the manufacturing process of the laminated plate, the upper and lower steel plates 2 are mixed due to the fact that the fractured materials are mixed in during pressing such as cutting.
A minute short circuit part may occur between a and 2c. In such a case, the electric current at the time of welding is concentrated on this short-circuited portion, resulting in explosion or the like between the steel plates 2a and 2c, resulting in a hole. This means that 10V is applied between the steel plates 2a and 2c at the beginning of energization.
If there is a voltage difference of some magnitude and there is a short circuit, the current will flow
This is because there is a case where the current does not flow into the micro conductive portion and concentrates in the minute conductive portion and flows through 10,000 A or more. In general, when laminated plates are used for automobile parts, they are often used for parts that require airtightness such as oil pans and head covers, and there is a problem that quality defects such as oil leakage will occur if there are holes. It was Especially when dust or iron powder is mixed in the laminated board,
Not only cannot the amount, size, position, etc. be specified,
Even if a flat plate is in an insulated state, it may become conductive if it is deformed by pressing, etc., so it is necessary to visually inspect all and install expensive current waveform monitoring devices, which reduces man-hours and equipment costs. There was a problem that

[Problems to be solved by the invention]

As described above, the present invention, as a result of the inclusion of foreign matter during the manufacturing process of a laminated plate, which has been a problem in the resistance welding of conventional laminated plates, causes a bombardment during resistance welding to cause holes in the laminated plate. A resistance welding method for a laminated plate, which solves the problem that does not cause explosion even if the steel plates on both sides of the laminated plate are partially short-circuited and can perform resistance welding with high welding strength with an inexpensive device, and It is intended to provide a welding device for that purpose.

[Means for solving problems]

The present inventors, as a result of earnest research on means for solving the above-mentioned problems, when carrying out the main welding, an electric current is previously passed through the skin metal material of the laminated plate, and the non-conductive material layer of the laminated plate is caused by its Joule heat. The present invention has been completed by finding that the resistance welding of the laminated plate can be smoothly performed without the occurrence of the above-described bombardment by performing the resistance welding after melting and removing.

That is, the resistance welding method of the laminated plate of the present invention is a method of resistance-welding by sandwiching a laminated plate having a non-conductive material layer between metal skin materials between a pair of welding electrodes under pressure, and energizing, An auxiliary electrode for sandwiching the laminated plate separately from the welding electrode is provided so that the laminated plate can be abutted between the auxiliary electrode and one of the welding electrodes, and a current smaller than the welding current is applied to the metal skin material of the laminated plate in advance. After melting the non-conductive material layer in the welded part of the laminated plate to bring the pressure part of the laminated plate into a conductive state, there is a method of conducting a resistance welding by passing a welding current between the welding electrodes. The resistance welding device for a laminated plate of the invention is for opening and closing a pair of welding electrodes for sandwiching a laminated plate having a non-conductive material layer between metal skin materials under pressure to conduct a welding current and a conduction circuit between the welding electrodes. Welding current energizing circuit with switch mechanism A laminated plate having a channel and an auxiliary electrode for sandwiching the laminated plate so that the laminated plate can be abutted freely, and applying a current smaller than a welding current to the metal skin material of the laminated plate between the auxiliary electrode and one of the welding electrodes. A resistance welding apparatus comprising an auxiliary energizing circuit for melting a non-conductive material layer between them.

[Action]

According to the above configuration, the metal skin material is electrically heated in the first step, and the metal skin materials on both sides are brought into contact with each other by the pressure applied by the welding electrode to be in an electrically conductive state, and then in the second step, between the main electrodes. Since resistance welding is performed by energizing and pressurizing to the laminated plate, even if a short circuit portion is formed between the metal skin materials on both sides due to the inclusion of foreign matter in the laminated plate, almost no current flows in this short circuit portion, and most of the current is Since it flows between the welding electrodes, no bombardment occurs at the short-circuited portion. Therefore, it is possible to prevent the quality of the material to be welded from being deteriorated and to perform reliable welding.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a configuration diagram showing a first embodiment of a resistance welding apparatus for laminated plates according to the present invention. In the figure, parts that are the same as or equivalent to those of the conventional example shown in FIG.
The description is omitted. Output terminal 6a on the ten side of the power transformer 6
Is connected to the welding electrode 3a via a circuit 7. The output terminal 6b on one side of the power transformer 6 is connected to the welding electrode 3b by the circuit 9 via the contactor 8. The same metal skin material as the welding electrode 3a, that is, the auxiliary electrode 4a facing the same steel plate 2a is connected by a circuit 10 to an output terminal 6b on one side of the power transformer 6. In this case, the auxiliary electrode 4b only sandwiches the laminated plate 2 together with the auxiliary electrode 2a, and is not connected to the power transformer 6.
Reference numerals 11 and 12 denote contact guns for operating the auxiliary electrode 4 and the contactor 8 which is a switch, respectively. Reference numeral 13 is a positioning pin that determines the position of the material to be welded.

A welding method using the welding apparatus configured as described above and used in this embodiment will be described below.

In the first step, the contact gun 11 operates to bring the auxiliary electrode 4a into pressure contact with the steel plate 2a and close the circuits 7 and 10. At this time, the contactor 8 is open. As a result, the electric current flows through the welding electrode 3a, the metal material 1, the steel plate 2a and the auxiliary electrode 4a as indicated by the solid arrow, and the respective contact portions 1
4, 15 generate heat due to Joule heat. This heat usually reaches 600 to 800 degrees Celsius, and a pressing member (not shown) applies a pressure of about 300 kg to 6 between the welding electrodes 3a and 3b.
By adding 00 kg, the non-conductive material 2b of the laminated plate 2
Is melted and eliminated, and the steel plates 2a and 2c are electrically connected. At this time, even if foreign matter is present between the steel plates 2a and 2c and the short-circuit point 2d occurs, the welding electrodes 3a and 3b
Since no voltage is applied between the two electrodes and between the auxiliary electrodes 4a and 4b, no voltage is applied between the steel plates 2a and 2c, and no melting current flows through the short circuit point 2d. Therefore steel plate 2
No holes are made in a and 2d.

In the second step, the contact gun 11 is operated to separate the auxiliary electrode 4a from the steel plate 2a, and at the same time, the contact gun 12 is operated to close the contactor 8. At this time, since the steel plates 2a and 2c are in the conductive state in the above-described first step, the current flows through the circuits 7 and 9 through the welding electrodes 3a, the metal material 1, and the laminated plate 2 as shown by the dashed arrows. , Welding electrode 3b
As shown in FIG. 2, a complete nugget is formed in the contacting portion 14, and the metal plate 1 and the laminated plate 2 can be completely welded. At this time, even if the above-mentioned short circuit point 2d exists, the conductive portion 1 where the current easily flows immediately below the welding electrode 3a.
4, the large current does not concentrate at the short-circuit point 2d even if a voltage is applied between the welding electrodes 3a and 3b. Therefore, no holes are generated due to bombing or the like. The welding current in the first step is set to be much smaller than that in the second step, as shown in FIG.

According to the present embodiment, the same welding point is energized separately in two steps by different routes. Therefore, even if a minute foreign substance is mixed in the laminated plate and a short circuit exists, the bomb is blown. It is possible to carry out stable spot welding without generating a weld, and to obtain a stable product with high welding strength.

(Second Embodiment) FIG. 4 is a block diagram showing a second embodiment of the resistance welding apparatus for laminated plates according to the present invention. In the figure, the same or equivalent parts as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The difference from the first embodiment is that the welding nugget 15 is obtained also by the auxiliary electrodes 4a and 4b. Therefore, the electrode transformer 6 and the auxiliary electrode 4
In the circuit 10 connecting with a, the second contactor 17 operated by the contact gun 16 is provided, and the auxiliary electrode 4 is separately provided.
A second power transformer 18 having output terminals 18a, 18b connected to a, 4b was provided.

The first step in the present embodiment is the contact gun 11,
16 is operated to bring the auxiliary electrode 4a and the steel plate 2a into contact with each other, and at the same time, the second contact 17 is closed. As a result, the circuits 7 and 10 indicated by solid arrows are formed, and the welding electrode 3a, the metal material 1, the steel plate 2a, as in the case of the first embodiment, are formed.
A current flows through the auxiliary electrode 4a. And the welding electrodes 3a, 3
b between the auxiliary electrodes 4a and 4b and the steel plate 2
Electrical connection is established between a and 2c.

In the second step, at least one of the contact guns 11 and 16 is operated to open at least one of the auxiliary electrode 4a and the contactor 17, and the circuit 7,
Open ten. At the same time, the contact gun 12 is operated to close the contactor 8 and close the circuits 7 and 9 indicated by broken line arrows as in the case of the first embodiment, and the welding electrode 3a, the metal material 1, the laminated plate 2 and the welding electrode 3b are closed. A nugget 14 is obtained by passing an electric current through.

In the third step, the contact guns 12 and 16 are operated to open the contacts 12 and 16, and at the same time, the pressure applied to the welding electrodes 3a and 3b is released. The auxiliary electrodes 4 connected to the output terminals 18a and 18b of the second power transformer 18, respectively.
a, 4b are operated by the contact gun 11 to operate the steel plates 2a,
2b is contacted and pressed. This allows the circuits 19, 1
An electric current flows through the auxiliary electrodes 4a and 4b and the laminated plate 2 through 0 and 20 to obtain the welding nugget 15.

In this case, as shown in FIG. 5, the welding electrodes in each of the steps are made to flow the least in the first step and the most in the second and third steps.

According to the present embodiment, since the steel plates 2a and 2c at the positions of the auxiliary electrodes 4a and 4b are already in the conductive state in the first step, even if foreign matter is mixed and the short-circuit point 2d is formed, the bomb is not blown. A stable nugget 15 can be obtained without generating any holes in the laminated plate 2. The nugget 15 thus formed can be used as a ground point in other steps.

In any of the above-described embodiments, it is possible to completely prevent the occurrence of holes due to bombardment, so that it is not necessary to carry out a visual inspection of all the pieces after spot welding, and it is not necessary to provide an expensive current waveform monitoring device. Furthermore, all metal materials 1 and steel plates 2a
It is possible to form a complete nugget that welds the steel plate 2c together, as well as welding the welded steel sheets, and thus, the welding strength can be greatly improved.

Further, in the above-described embodiment, the case where the metal material 1 and the laminated plate 2 are spot-welded has been described, but the welding material is 3
Even if there are more than one layer, they can be welded in the same manner, and also applicable to resistance welding other than spot welding.

〔The invention's effect〕

As described above, according to the present invention, when two or more laminated plates containing a non-conductive material in the middle or two or more laminated plates and a metal material are overlapped and resistance-welded, one side of the metal skin material is used in the first step. To remove the non-conductive material in the welded portion to electrically conduct the metal skin materials on both sides, and in the second step, apply a large current between the welding electrodes to form a welded nugget in the welded portion. Therefore, even if foreign matter is present in the laminated plate, explosion does not occur, and resistance welding with high welding strength can be performed with an inexpensive device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a resistance welding apparatus for laminated plates according to the present invention, FIG. 2 is an enlarged sectional view showing a welded portion of FIG. 1, and FIG. 3 is a first embodiment. 4 is a graph showing the relationship between welding time and welding current in FIG. 4, FIG. 4 is a configuration diagram showing a second embodiment of the present invention, and FIG. 5 is a graph showing the relationship between welding time and welding current in the second embodiment. FIG. 6 is a configuration diagram showing a conventional resistance welding method for laminated plates. DESCRIPTION OF SYMBOLS 1 ... Metal material, 2 ... Laminated board, 2a, 2c ... Steel plate (metal skin material 1), 2b ... Non-conductive material, 3a, 3b ... Welding electrode, 4a, 4b ... Auxiliary electrode, 6, 18 ... Power transformer, 6a, 6b, 18a, 18b ... Output terminal, 8, 17 ... Contactor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-49-55548 (JP, A) JP-A-49-9447 (JP, A) JP-B-38-14465 (JP, B1)

Claims (2)

[Claims] 1. A method of resistance welding by sandwiching a laminated plate having a non-conductive material layer between metal skin materials between a pair of welding electrodes and energizing the same to form a resistance plate, the laminated plate being separated from the welding electrodes. Is provided with an auxiliary electrode that sandwiches the contact electrode freely, first opens a contactor for opening and closing the energization circuit between the welding electrodes, and by one of the auxiliary electrode and the welding electrode,
A current smaller than the welding current is applied to the metal skin material of the laminate in advance, the non-conductive material layer in each electrode contact portion is melted to bring the pressure portion of the laminate into a conductive state, and then the auxiliary electrode is attached. A resistance welding method for a laminated plate, characterized in that after separating from the laminated plate, the contact is closed and a welding current is passed between the welding electrodes to perform resistance welding. 2. A pair of welding electrodes for sandwiching a laminated plate having a non-conductive material layer between metal skin materials under pressure to conduct a welding current, and a contactor for opening and closing an energization circuit between the welding electrodes. A welding current energizing circuit having: and an auxiliary electrode for sandwiching the laminated plate so that the laminated plate can be contacted freely, and the metal skin material of the laminated plate between the auxiliary electrode and one of the welding electrodes has a welding current smaller than the welding current. A resistance welding apparatus for a laminated plate, comprising an auxiliary energizing circuit for applying an electric current to melt the non-conductive material layer between the metal skin materials of the laminated plate.