JPH04309473A - Resistance welding device - Google Patents

Abstract

PURPOSE:To obtain the spot welding device which can increase a welding current contributed to heating/melting of a weld zone, and can execute film welding having resistance against vibration by heating and melting sufficiently its weld zone even in the case of welding a member to be welded having an insulating film on the surface of its weld zone and a member to be welded in a state of superposing several pieces. CONSTITUTION:A secondary coil 123 of a transformer 103 of a spot welding device is constituted by superposing copper plates so that an induction reactance component of the transformer is offset by an electrostatic capacity between a primary coil and a secondary coil, and as soon as an output voltage of the transformer 103 is generated, a large current whose rise is sharp is applied to a memer 111 to be welded held by a welding electrode 110.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding device for spot welding, butt welding, etc., and more particularly to improving welding performance by increasing the phase of welding current.

0002

[Prior Art] Spot welding or butt welding is a method of welding by applying resistance heat generated by passing an electric current between parts to be welded to heat the parts to be welded and at the same time pressing the two parts to be welded together. It is a type of welding, and generally the welding temperature is lower than arc welding, and it is performed in a shorter time, so the effect of heating can be limited to a narrow area near the joint, and there is less deformation and residual stress in the parts to be welded. It has the advantage of However, since heating is based only on resistance heat, it requires a current several tens of times larger than arc welding in a short period of time, and the capacity of the welding machine is large.

[0003] Furthermore, such resistance welding machines usually use single-phase AC power, and the apparent input power when energizing is large, resulting in a load with a low power factor.Therefore, various measures have been taken to improve the power factor. One of them is a capacitor discharge welding machine. This is done by rectifying the AC power supply with a rectifier to make it into DC, charging a capacitor with the DC current, discharging that charge to the primary side of the welding transformer, and reducing the momentarily generated large current on the secondary side. It is suitable for locations with small power supply capacity.

0004

[Problems to be Solved by the Invention] However, it is not suitable for welding thick plates that require a relatively long welding current (about 0.5 seconds), and the welding surface may be contaminated with oil or dust. or when the workpiece is welded with a rough surface.
Spot welding etc. was difficult. There is also the inconvenience that it is not possible to spot weld several aluminum plates stacked on top of each other, or to perform spot welding with a sealant or the like applied to the welding surfaces of the parts to be welded to prevent water from entering. Furthermore, the welded parts are brittle, and if a spot-welded member is used in a part of a mechanical device that experiences strong vibrations, it may come off. For this reason, spot welding, which has good workability, cannot be used for welding parts that require particularly high reliability, such as welding the wing parts of airplanes, and we have to use time-consuming riveting, that is, as shown in Figure 17. a) and Figure 1
Aluminum plates 801 and 80 to be joined as shown in 7(b)
Insert the rivet 804 into the rivet insertion hole 803 of No. 2, and press the head 8 of the rivet.
Two aluminum plates were joined by modifying 04a. However, in this case, the crack 8 is from the hole 803 where the stud 804 is attached.
10 (Fig. 17(c)), and there was a problem in that if this part was damaged, it would lead to a major accident.

On the other hand, in order to carry out spot welding, etc., a dedicated transformer for spot welding etc. was installed via a power company's pole transformer or a private high voltage power receiving transformer, and spot welding work was carried out. In welding, the output obtained on the secondary side is about 40% on average with respect to the primary input input to the primary side of the transformer, and the power conversion efficiency is also not favorable.

The present invention was made to solve the above-mentioned conventional problems, and it is possible to reduce the reactive current and increase the welding current that contributes to heating and melting the welded part. Even when welding parts that have some insulation coating on their surfaces, or even when welding several parts stacked on top of each other, the welded part must be sufficiently heated and melted to make it strong and resistant to vibration. The object of the present invention is to obtain a resistance welding device capable of performing welding.

[0007]

[Means for Solving the Problems] A resistance welding device according to the present invention connects the secondary coil of a transformer so that the inductive reactance component of the transformer is canceled out by the capacitance between the primary and secondary coils. It consists of a plurality of overlapping copper plates forming a circuit around an iron core, and the transformer applies a welding current that rises sharply at the same time as an output voltage is generated to a pair of welding electrodes.

[0008] The resistance welding device according to the present invention pressurizes the pair of welding electrodes with a pressure that changes in synchronization with the welding current, or with a pressure that is a constant pressure superimposed on the pressure. This is how it was done.

Further, in the resistance welding apparatus of the present invention, two sets of upper and lower welding electrodes are arranged close to each other as the welding electrodes, and the transformer is connected to each set of welding electrodes. A current flows between the upper and lower welding electrodes of each set and the secondary coil of the corresponding transformer between the adjacent upper and lower welding electrodes through the upper and lower workpieces, respectively. This is how the wires are connected.

[0010] Furthermore, the present invention provides the above resistance welding device with a phase control circuit for controlling the ignition of the three-phase AC supply for each phase on the input side of the transformer, and the transformer has a single-phase iron core. Three primary coils are wound on the primary side, a single-phase coil is wound on the secondary side, and each of the three primary coils is connected to each phase of a three-phase AC power source via the phase control circuit,
The phase control circuit controls the phase of each phase of the three-phase AC power supply to output single-phase AC to the secondary coil.

[0011]

[Operation] In this invention, the secondary coil of the transformer is
Because the structure consists of overlapping copper plates so that the reactance component of the transformer is canceled out by the capacitance generated between the primary coil and the secondary coil, at the same time as the output voltage of the transformer is generated,
A large current with a steep rise will flow through the workpiece held between the welding electrodes, and even if there is some insulation film on the surface of the workpiece, or if several workpieces are overlapped, Even if there is, the welded part can be sufficiently heated and melted to create a strong weld that is resistant to vibration.

Furthermore, since the pressure applied to the welding electrode is changed in synchronization with the welding current, the members to be welded can be effectively pressurized.

Further, in the present invention, as the welding electrodes, two sets of upper and lower welding electrodes are arranged close to each other, and each set of welding electrodes is provided with the above-mentioned transformer. Since the current flows between the upper and lower welding electrodes through the upper and lower welded parts, even if there is an insulating film between the welded parts, there is no difference between adjacent welding electrodes. The heat generation effect of the flowing current melts or carbonizes the insulating film, making it possible to conduct between the upper and lower welding electrodes, thereby enabling resistance welding.

Furthermore, in the present invention, the phase of the three-phase alternating current is controlled by a phase control circuit, and the three-phase alternating current is supplied to the three-phase primary coil wound around the primary side of the single-phase iron core, and Since single-phase alternating current is output to the secondary coil wound in As a result, a single-phase output consisting of the composite waveform can be generated on the secondary side of the transformer. Further, by controlling the phase, the obtained output waveform can be made into a waveform suitable for spot welding.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a spot welding device according to an embodiment of the present invention. In the figure, 100 is a spot welding device, which is a power source consisting of a single-phase AC power source 101, a transformer 103 that transforms the output thereof, and an on/off switch circuit 102 inserted between the single-phase AC power source and the transformer 103. 120, and a spot welding section 130 consisting of a pair of upper and lower welding electrodes 110 and a member to be welded 111 held between the welding electrodes. The transformer 103 has four secondary coils 123 and three primary coils 124 attached to an iron core 121 made of a laminated body of thin iron plates.

The structure of the transformer (hereinafter also referred to as transformer) will be explained in detail below with reference to FIGS. 1(b) to 1(d). In the figure, reference numeral 121 denotes the outer iron core of this transformer, 122 denotes two coil housing sections hollowed out inside the outer iron core 121, and 123 denotes the coil housing section 122 of the outer iron core 121. This is a secondary coil formed by hollowing out a copper plate, which is housed inside the coil.In this case, four copper plates (secondary coils) 123 are used to generate the reactance component of the transformer due to the capacitance generated between the primary coil and the secondary coil. These four copper plate secondary coils 123 are connected in parallel. 124 is a primary coil housed between the secondary coils 123 in the secondary coil storage section 122;
There are three, middle and bottom. Each primary coil 124 is formed by winding rectangular copper wire in two stages such that the winding start 124a and winding end 124b are located at the outermost circumference of the coil, and the three primary coils are connected in series. are doing. In addition, here, the outer iron type iron core 121 has a central iron core portion 121a.
The cross-sectional area is twice that of the side iron core portions 121b on both sides.

[0017] Also, here, the secondary coil 123 includes:
As shown in Figure 1(d), cut out the copper plate and make the central hole 1.
23a, and following this, both end sides 12 are formed.
A copper plate coil formed to have a slit portion 123b between 3c and 123d is used. Note 123
e is a screw hole for coil connection.

Next, the functions and effects will be explained. First, as shown in FIG. 1(e), a pair of welding electrodes 110 is used to
The material to be welded 111 is held under pressure and the switch circuit 102 is turned on. Then, the AC output of the AC power supply 101 is applied to the primary coil 124 of the transformer 103, and the secondary coil 1
03, a voltage is generated according to the turn ratio of the primary and secondary coils based on the principle of electromagnetic induction. As a result, a voltage on the secondary side is applied to the pair of welding electrodes 110, as shown in FIG. 1(f).
As shown in , a welding current I flows through the welded member 111,
The heat generated at this time heats and melts the pressure contact portion A of the electrode and joins it.

In a spot welding device using a transformer with such a configuration, copper plates are placed one on top of the other as a secondary coil, and the inductive reactance of the transformer is reduced by the capacitance generated between the primary coil and the secondary coil. Since the components are canceled out, it is possible to phase advance the welding current. In other words, conventionally, as shown in FIG. 2, the phase of welding current I2 was
Because of the inductive reactance component of the transformer, the welding current I1 lags behind the output voltage V0 and rises slowly.
The large current I1 rises sharply at the same time as 0 occurs, and the workpiece held between the welding electrodes receives a large current I1 with a steep rise.
will flow.

[0020] Furthermore, the central iron core portion 121a of the iron core 121 is
Since it has twice the cross-sectional area of the side iron core part 121b, the magnetic flux in the central iron core part does not become overcrowded, and the cross-sectional area of the central iron core part and the side iron core part are the same. In comparison, energy loss such as heat generation can be reduced. Furthermore, since the above-mentioned iron core has only two joints B1 and B2 on both sides of the center, 1
A transformer core with a high output power ratio on the secondary side to the input current on the next side, good performance, low contact resistance, and no loss can be obtained.

As a result, the welded portion of the welded member is efficiently and sufficiently heated and melted, making it possible to perform a strong spot welding that is resistant to vibrations. Specifically, even if there is oil or dust on the welding surface of the workpiece, welding can be performed without any problems even if the welding surface is somewhat rough, and it is possible to weld without any problems, such as pickling of aluminum plates, which was conventionally performed as a pretreatment for welding. Work can be omitted. Furthermore, even if a sealer or adhesive is applied to the welding surface of the aluminum plate to prevent moisture from entering, if it has not yet completely dried, some current will flow and the adhesive will melt or carbonize due to the heat generated. spot welding is possible because the welding current flows.

In other words, in the past, in the case of aluminum, it was impossible to spot weld the parts with oil or dust on them, so it was customary to clean the oil, wash with water, dry and weld within 2 hours. Also used in aircraft etc.
In contrast to welding within one hour, especially for important parts that require reliability, with the present invention, welding can be done even if there is oil or dust on the surface of the parts to be welded. Even if a sealant or an adhesive is applied to the entire surface, spot welding can be performed as long as it has not yet dried.

Furthermore, in spot welding of aluminum plates of different thicknesses, normally the thickness of the thick plate and the thin plate is limited to about 3:1, but in this example, aluminum foil as thin as 0.1 mm is It can also be spot welded to aluminum plates as thick as 10mm, which is twice as thick. As an example of welding when the thickness is different, for example, as shown in Fig. 3(a), the bone member 1
11c and an aluminum plate 111d, and of course there is no problem even if the adhesive 111e is present between these members as long as the adhesive 111e is not dried. As another example, FIG. 3(b) shows a case in which an aluminum plate 111d is spot-welded to the upper and lower surfaces of the I-shaped steel member 111f at the same time. Note that 110a is an auxiliary copper electrode connected to the middle point of the secondary coil 123 of the transformer to efficiently flow spot welding current. Still another example is shown in FIG. 3(c) in which the auxiliary copper electrodes 110a are arranged on both sides of the central longitudinal side of the I-shaped steel material.

Furthermore, spot welding of 20 layers of aluminum foil or titanium foil is possible, and copper alloy, platinum,
Such overlap welding is also possible for non-ferrous metals such as gold and silver.

If the adhesive or sealer material is dry, welding can be performed using a spot welding device (Japanese Patent Publication No. 1379/1983) using two pairs of upper and lower welding electrodes. FIG. 4 shows a second embodiment of the present invention in which the transformer of the first embodiment is used in this spot welding device. In the figure, 110c and 110d are connected to the secondary coil 123 of the first transformer 103b. a first pair of welding electrodes, 11;
0f and 110g are a second pair of welding electrodes connected to the secondary coil 123 of the second transformer 103a;
The members 111g and 111h to be welded, with a dry insulating film interposed therebetween, are overlapped and welded using a pair of welding electrodes. Here, the first and second transformers each have the same configuration as the transformer shown in FIG.
It is connected to a single-phase AC power source via a switch circuit (not shown).

In welding using this device, first, a current IP flows horizontally between the adjacent electrodes 111c and 111e, and between 111d and 111f, and the insulating film 11 is heated by the heat generated by the current IP.
1g is melted or carbonized. As a result, a welding current flows between the pair of upper and lower welding electrodes 111c and 111d, and between 111e and 111f, and spot welding is performed. In this way, spot welding can be performed even if there is an insulating film or the like between the members to be welded.

Furthermore, with this device, even if there is a dried adhesive 111a between stacked aluminum plates 111 as shown in FIG. 5, up to three stacked aluminum plates can be welded without any problem. FIG. 5(a) shows the state of the cross section of the welded member before welding, and FIG. 5(b) shows the state of the cross section of the welded member after welding.

Furthermore, as shown in FIG. 6, when four or more aluminum plates are stacked and there is an insulating film between each plate, it is necessary to adjust the time until the central insulating film 110b carbonizes and conducts. Overlap welding is possible, and if the insulating film is made of oil or the like, multilayer spot welding of about 10 sheets can be performed. Note that FIG. 6(a) shows the state of the cross section of the welded member before welding, and FIG. 6(b) shows the state of the cross section of the welded member after welding.

Examples of specific applications of such spot welding are shown below. FIGS. 18(a) to 18(c) respectively show examples of airtight or watertight containers made of, for example, aluminum and used in aircraft, automobiles, and the like. In the case shown in FIG. 18(a), a sealant or adhesive (not shown) is applied to the flange portions 711a and 712a of a pair of containers 711 and 712 with concave cross sections, and these are overlapped, and both flange portions are spotted. Welding. In addition, in the sealed container having the shape shown in FIGS. 18(b) and 18(c), the container body 720 and its lid member 721 are spot welded with a sealant or the like (not shown) sandwiched therebetween, and the sealed mouthpiece is sealed. 722 is spot welded to the opening of the lid member 721 via a sealer (not shown). Conventionally, these containers were welded across the entire joint using seam welding, argon welding, etc., which required a high degree of skill, and also caused thermal distortion, which required a master's skill to remove the distortion. There was also the problem of leaks occurring due to poor welding, but by using this spot welding equipment, spot welding can be performed with a sealant etc. applied as described above, which requires advanced technology. It is possible to perform welding with high mechanical strength and excellent airtightness without causing any damage, and it is possible to reduce manufacturing costs.

FIG. 19 shows a stainless steel sink manufactured using the present spot welding device. In the figure, reference numeral 730 is the sink, which has a container 732 with a concave cross section attached to the opening 731a of the top plate 731. be. This top plate opening 7
The flange portion 731b of the container 731a and the upper end portion 732a of the container 732 are spot welded via a sealing material or the like. In this case as well, the same effect as in the case of the container shown in FIG. 18 can be obtained.

FIG. 20 shows another example of a container.
In the case of (a), there is a gap between the upper end of the container body 740 having a substantially concave cross section and the cover member 741 and the container body 74.
The nipple portion 740a at the bottom of the pipe member 742 and the pipe member 742 are spot welded via a sealing material (not shown). In the case shown in FIG. 20(b), one end of a pipe member 743 is spot-welded to an opening 740b formed in the side surface of the container body through a sealing material (not shown).

Furthermore, FIGS. 21(a) to 21(d) show a bathtub having a heat insulating structure, and in the figure, 750
751 is a bathtub, and 751 is a base member with a generally concave cross section and a rectangular outline, which constitutes the bathtub body, and on the outer surface of its side wall,
A cover member 752 is attached whose central portion bulges outward so as to create a heat insulating space S between the cover member 752 and the side wall.
Further, a bottom cover member 753 is attached to the bottom surface of the bathtub body 751 so as to create a heat insulating space S between the bathtub body 751 and the bottom surface. The bottom cover member 753 and the bathtub body 7
A corrugated reinforcing member 754 for supporting the load applied to the bathtub is disposed between the bathtub and the bottom surface of the bathtub. In addition,
755 is a corrugated reinforcing member 754 and a bottom cover member 753
A screw member 756 connecting the two is a drain cap attached to the drain port 751a at the bottom of the bathtub body.

[0033] In this bathtub, especially the cover member 75
2,753, the drain fitting 756, and the bathtub body 751 are spot welded with a sealant applied to them, and spot welding is used to achieve the sealing effect of seam welding or argon welding. There is. Figure 21(a)
In the plan view, the spot welding parts of the reinforcing member 754 are shown by black circles, and the tightening parts of the screw members are shown by white circles. In addition, since we use spot welding, which does not generate much heat, it is easy to fill the insulation space S with insulation material to improve the insulation effect, and there is no discoloration due to welding burns and no thermal distortion. Therefore, it is possible to obtain a product with low manufacturing cost and excellent heat insulation, mechanical strength, appearance, etc. Although a bathtub is shown here, the same applies to industrial hot water containers, instantaneous water heaters, solar hot water tanks, etc.

Furthermore, this spot welding apparatus can also be used to join aluminum plate members that are constituent members of an aircraft. In other words, in the past, most aircraft accidents were caused by cracks arising from the holes in the riveted rivets.In recent years, as aircraft have become larger, vibration power has also increased. However, with the spot welding of the present invention, the spot weld is sufficiently melted and firmly joined, making it highly reliable and superior to the conventional riveting method. It can be used to join members instead of rivets, which not only eliminates the need for time-consuming work such as riveting, but also avoids accidents caused by metal fatigue in the riveted holes, which has been a problem with riveting. Further, such a spot welding device of the present invention,
It can also be widely used in the manufacture of future automobiles that will likely use aluminum plates.

FIG. 7 shows a transformer used in a spot welding apparatus according to a third embodiment of the present invention, which uses an inner iron core. FIG. 7(a) shows a conventional core type transformer, whereas FIG. 7(b) shows a core type transformer of a spot welding apparatus according to an embodiment of the present invention. In the figure, 201 is an iron core formed by a pair of cut cores 201a facing each other and butted against each other, and 203 is a secondary coil formed by hollowing out a copper plate in the same way as in the first embodiment. Three coils 203 are stacked one on top of the other and attached to the left and right legs 211 of the iron core 201, thereby canceling out the inductive reactance component of the transformer by the capacitance between the primary and secondary coils. ing. Reference numeral 204 denotes three primary coils installed between the upper and lower secondary coils 203. Similar to the first embodiment, rectangular copper wires are wound so that the winding start 204a and winding end 204b are located at the outermost periphery of the coils. It is formed by winding it in stages. Further, four secondary coils 203 are connected in parallel, and three primary coils 204 are connected in series.

In this way, even in a spot welding device using a core type transformer, as in the above embodiment, the effect of the phase advance capacitor is exerted, and the welding current of a sawtooth wave rises sharply at the same time as the output voltage is generated. is obtained, and strong spot welding is possible using large current.

It should be noted that the primary coil does not need to be a two-stage winding as shown in FIG. 7(d), and one-stage winding may be connected in series.

Next, as a fourth embodiment of the present invention, a spot welding apparatus in which the method of pressurizing the welding electrode in the first embodiment is improved will be described. FIG. 8 shows the fourth embodiment of the present invention.
shows a spot welding device according to an embodiment of the invention, in which:
The same reference numerals as in FIG. A coil 301 is wound. In addition, 321 is the second
321b is a solenoid whose solenoid coil 321a is connected to the secondary coil 301 of the solenoid 321.
The sliding rod 322 is a member that can be moved up and down about a fulcrum 323 by the up and down movement of the sliding rod 321b.

Next, the operation will be explained. Conventionally, in spot welding, the welding electrode is pressurized by pneumatic pressure or hydraulic pressure from a cylinder, and for example, for the welding current I0 as shown in FIG. 9(b), the dot-dashed line Pc1 in FIG. 9(a)
The actual welding current I1 was obtained by applying air pressure (pressure force P1) as shown in FIG. However, this was very wasteful because a large pressing force P1 was applied even at the zero point of the actual welding current waveform I1 and in the region where the current is small in the vicinity thereof. That is, in pressurizing spot welding, if the spot welding current I has a sine waveform I1, this is the maximum Im
When (t=tm), if the pressurizing force P is P1, good welding can be performed, and when the spot welding current I is 0, the pressurizing force P may also be 0, ideally as shown by the dotted line. It is sufficient if a pressurizing waveform Ps can be obtained.

For this reason, in this embodiment, the second secondary coil 301 is used to apply pressure with the same waveform Ps as the welding current I1 generated by the first secondary coil 123, thereby reducing power loss. It is very efficient. Also,
In spot welding, it is difficult to generate heat when pressure is applied, and the welding heat I2R becomes small when the pressure is large, but in this example, the pressure is usually small (other than when welding). Therefore, heat generation increases and good spot welding can be obtained. As a result, spot welding of Al, copper, titanium, etc., which was previously impossible, has become possible. For example, conventionally 3mm
100KVA was required to spot weld thick Al, but this is now possible with 50KVA in the present invention.

However, in welding in which spot welding current is applied and electrode pressure is applied in synchronization with this,
It is good when the spot welding current I1 and the pressure waveform Ps are completely synchronized, but when the two are out of synchronization, the resistance becomes large even if the current is small and the pressure is zero.
Sparks may create holes in the welded material or electrode. For this reason, in this embodiment, a constant pressure Pc0 (pressure force P0) is further applied by pneumatic or hydraulic pressure, and this constant pressure Pc0 is added to a pressure P synchronized with the welding current I1.
Vibration pressurization with superimposed s is obtained, thereby eliminating the risk of damage to the object to be welded or the electrode.

As described above, in addition to the effects of the first embodiment, this embodiment has the advantage that the members to be welded can be effectively pressurized.

[0043] In this fourth embodiment, the case where the waveform of the spot welding current is a sine waveform has been explained.
This may be a sawtooth waveform, and the same thing as in this embodiment can be said in this case as well. Further, the above-mentioned pressurizing method is not limited to spot welding equipment, but can also be applied to, for example, a forging machine that performs heat forming using an electric current.

[0044] Similar to the spot welding described above, a rod-shaped body butt welding method, which is a type of resistance welding, is also used, that is, Fig. 10
As shown in FIG.
0(a)), the end faces are brought into contact (Fig. 10(b)), and in this state welding is performed by applying welding voltage and pressure to the holder (Fig. 10(c), Fig. 10(d)). , as in the above embodiment, a sawtooth wave welding current that rises sharply at the same time as the welding voltage is generated is applied to the pair of holders 610a, 6.
By applying vibration pressure to the holder in synchronization with the welding current, six times the welding effect can be achieved.
In other words, it has become possible to weld workpieces that are six times as thick as conventional methods. Note that FIG. 10(e) shows the welded member subjected to finishing processing after welding.

FIG. 11 also shows T-shaped butt welding of aluminum pipes, etc. as another example of butt welding, and as shown in FIG. 11(a), one pipe 701
When the tip of the other pipe 702 is brought into contact with the middle part of the two pipes, and in this state, the above-mentioned welding current and vibration pressure synchronized with this are applied to these pipes, a T-shaped butt is formed as shown in Fig. 11(b). Welding is done. When welding is completed, both pipes that were in initial point contact are one pipe 7.
01 is recessed into the other pipe 702, and the contact portion 703 is in surface contact as shown in the figure.

In this case, non-ferrous metals such as aluminum are good conductors,
Because it has low resistance and good heat conduction, a large current is required in a very short period of time, and the current waveform is required to have a pulse-like or instantaneous rise curve. In other words, a very large and instantaneous welding current is required, but if this large welding current is applied at the beginning of welding, sparks are generated and the welding member 7
Since the contact portions 01 and 702 are scattered, the welding current is initially set to a small pulse waveform as shown in FIG. 13, and the pulse is gradually increased. In addition, the material of the pipe is
Examples include titanium, stainless steel, galvanized steel pipes, copper-plated iron pipes, and metal pipes with painted or plated films, and in any case, a pulse with a good rise is required.

FIG. 12 shows a case where two pipes are crossed and butt welded, with FIG. 12(a) showing the state before welding and FIG. 12(b) showing the state after welding. In this case as well, conditions such as the waveform and magnitude of the welding current are the same as those for T-shaped butt welding.

FIG. 14 is an explanatory diagram of a fifth embodiment of the present invention, which shows the configuration of a three-phase rectification type welding machine. In FIG. 14(a), 412 is the input terminal 401
This is a three-phase power supply on/off switch circuit in which a three-phase power supply is connected to 403, and a three-phase transformer 413 is connected to its output side. This transformer 413 is a 3-phase 1 in delta connection.
Secondary coil 413a and star-connected three-phase secondary coil 413
It has b. The anodes of three diodes 414a to 414c are connected to each phase output on the secondary side of the transformer 413, and a rectifier circuit 414 is configured by these diodes. The cathode sides of each of the diodes 414a to 414c are commonly connected to one of the pair of welding electrodes 410. The other welding electrode 410 is connected to the neutral point N of the three-phase secondary coil 413b.

Next, the structure of the above transformer will be explained in detail. FIG. 14(b) shows a three-phase transformer used in this fifth embodiment, and in the figure, 413 is a transformer.
, 473a, 473b are three seamless iron cores 413a
The primary and secondary coils are alternately stacked and wound around the first leg (the leg on the left side of the paper), and each coil has a central hole 472a cut out of the copper plate as shown in FIG. 14(c). , and following this, both end sides 472c and 472d are formed.
A copper plate coil 472 formed to have a slit portion 472b between the two is used. Note that 472e is a connection hole.

Further, 475a and 475b are primary coils wound around the second leg (center leg) of a three-phase transformer in a vertically overlapping manner.
The secondary coil is a copper plate coil 474 (Fig. 14(d)
) is rolled. 477a and 477b are the above 47
3a and 473b, it consists of a coil 476 (Fig. 14(e)) formed by hollowing out a copper plate, and is stacked vertically on the third leg (leg on the right side of the page) of a three-phase transformer. These are a wound primary coil and a secondary coil. Here, 474a to 474e and 476a to 476e are the same parts as each part 472a to 472e of the copper plate coil 472. In this embodiment, the capacitance between the primary and secondary coils is increased by arranging the primary and secondary coil copper plates of each leg of the iron core one on top of the other as described above. This cancels out the reactance component of

In this embodiment, as in the first embodiment, a steep large current can be applied to the welding electrode at the same time as the output voltage of the transformer rises, which was previously impossible. This has the effect of making spot welding possible.

[0052] In the above embodiment, the transformer has a seamless iron core, but as shown in Fig. 14(f), the transformer core has two hollowed out portions 461a and 461b in the center of a thin iron plate. Inner side portions 461c, 461
A thin iron core plate 461 may be used in which slits 462a and 462b are formed to cut the upper side of the thin iron plate 461 along the direction d. In this case, the iron core can be constructed only by the thin iron core plate 461. , manufacturing becomes extremely easy.

Furthermore, by setting the center leg of the iron core 413a of the transformer 413 to have a cross-sectional area twice that of the legs on both sides,
The efficiency of the transformer can be improved, but in this case, Fig. 14 (g
) A copper plate coil 478 having a wider center hole 478a than the copper plate coil 474 is used. Each portion 478b to 478e of this coil is the same as each portion 474b to 474e of the copper plate coil 474 described above.

Furthermore, in the above embodiment, a normal single-phase AC power source or three-phase AC power source is used as the power source for the spot welding device, and the output of the power source section is a sine wave. The output may be a sawtooth wave, in which case the efficiency can be further improved.

Next, as a sixth embodiment of the present invention, a spot welding apparatus using such a sawtooth single-phase output power supply device will be described. Figure 15(a) shows a power supply device (Japanese Patent Application No. 150585/1999) that the applicant has already applied for.
501 in the figure shows a spot welding device using
is a three-phase AC power supply, 504 is a phase control circuit that controls the supply of three-phase AC power only in the range of 120 degrees to 180 degrees for each phase, and 503 is three primary coils 505, 5 on the primary side.
06,507, a transformer having an iron core made of a laminated body of thin plates with one secondary coil 508 wound on the secondary side, 51
2 is a ground, and 500 is a power supply device consisting of the phase control circuit 504 and a transformer 509. In addition, in the phase control circuit 504, 520a, 520b, 520c in the figure
is a thyristor; 521 is a zero-crossing point detector for detecting the zero-crossing point of a sine wave in each layer of three-phase AC; 522a, 522
b, 522c are phase adjusters that receive the output of the zero cross point detector 521 and adjust the firing angles of the thyristors 520a, 520b, 520c in each layer.

The transformer 503 shown in FIG. 15(d)
As shown in the first embodiment, four secondary coils 50
8 and three primary coils 524a to 524c.
The central iron core part 1 is stacked vertically so that the reactance component of the transformer is canceled out by the capacitance generated between the
21a, but here all the secondary coils 508 are connected in parallel, both ends of which are connected to a pair of spot welding electrodes 110, and each primary coil 52
One end of 4a to 524c is connected to each of the above thyristors 520a to 520a.
20c, and the other end is all grounded. Further, as the primary coil and the secondary coil, a two-stage coil of rectangular copper wire and a copper plate coil are used, respectively, as in each of the above embodiments.

Next, the operation will be explained. The energization from the 3-phase AC power supply 501 to the 3-phase coils 505 to 507 of the transformer 500 is controlled by the phase controller 504 as shown in FIG.
b) The first, second and third coils 505,
AC sine waves X, Y, Z of each layer are shown at 506 and 507, respectively.
Each coil is energized only in the phase angle range of 120 degrees to 180 degrees (c and f for X, b and e for Y, and a and d for Z), and at other times, each coil is energized. is open.

[0058] When the three-phase first, second, and third coils 505, 506, and 507 are energized in sequence in this manner, triple-frequency waves are generated in the iron core as shown in Fig. 15(c). A magnetic flux having a drooping characteristic is induced, and as a result, a current having a frequency three times the sawtooth wave as shown in FIG. 15(c) is induced in the secondary coil 508.

This sawtooth triple frequency current is applied to both welding electrodes 110 of the welding part 130, and the current flows to the corresponding part of the welding member 111 sandwiched between the welding electrodes 110, so that the part is It is melted and spot welded. At this time, the following effects can be obtained in addition to the effects of the fifth embodiment.

[0060] Generally, spot welding requires a large amount of current, and the conventional method using single-phase alternating current causes the problem of three-phase imbalance, but in this example, the three-phase is converted to a single-phase. Therefore, the problem of three-phase unbalance does not occur. Furthermore, since the single-phase output has a sawtooth wave with triple frequency as shown in FIG. 15(c), extremely high quality welding can be achieved. In particular, welding of nonferrous metals such as Al, Cu, and Bs can be performed well.
Spot welding is possible even with a small amount of insulation film.

[0061] Since the frequency obtained by the power source used in the present invention is tripled, the transformer becomes smaller and weighs only one third of the conventional one, making it extremely small and lightweight. Furthermore, since the structure of the transformer is simple, small and lightweight, manufacturing costs can be significantly reduced.

■ The firing angle of the 1-phase AC sine waveform is 12
By appropriately adjusting the angle back and forth around 0 degrees, the strength of spot welding can be greatly adjusted.

[0063] By performing automatic control using a computer, finer adjustment than conventional commercial frequencies is possible, and greater welding stability can be obtained. Note that the waveform of the welding current is not limited to the one described above, but can be changed by adjusting the phase control circuit, for example, as shown in FIGS. 16(a) to 16(c).
A welding current with a waveform as shown in can be obtained.

[0064]

[Effects of the Invention] As described above, according to the resistance welding device according to the present invention, the reactance component of the transformer is canceled out by the capacitance between the primary and secondary coils of the transformer. Since the structure is made of overlapping copper plates, at the same time as the output voltage of the transformer is generated, a large current with a steep rise flows through the workpiece held between the welding electrodes.
As a result, even if the surface of the welded part has some unevenness, or even if several welded parts are stacked on top of each other,
This has the effect of sufficiently heating and melting the welded portion and making it possible to perform strong welding that is resistant to vibrations.

Further, since the welding electrode is pressurized in synchronization with the welding current, there is an effect that the welding member can be pressurized effectively.

Further, according to the present invention, two pairs of upper and lower welding electrodes are arranged close to each other as the welding electrodes, and the transformer is provided for each pair of welding electrodes, so that each adjacent pair of welding electrodes is provided with the transformer. Since the current flows between the upper and lower welding electrodes through the upper and lower workpieces, even when there is an insulating film between the welding workpieces, the current flows between the adjacent welding electrodes. The insulating film can be melted or carbonized by the heat generation effect of the current flowing through the welding electrode, thereby making it possible to conduct between the upper and lower welding electrodes, thereby making it possible to carry out resistance welding.

Further, according to the present invention, the phase of the three-phase alternating current is controlled by the phase control circuit, and the three-phase alternating current is supplied to the three-phase primary coil wound around the primary side of the single-phase iron core, and the Since I output single-phase AC to the secondary coil wound on the side, 3
It is possible to obtain a composite waveform equivalent to a single-phase output of a sawtooth wave with a frequency doubled, and thereby a single-phase output consisting of the composite waveform can be generated on the secondary side of the transformer. Moreover, the output waveform obtained by controlling the phase can be made into a waveform suitable for spot welding.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a spot welding device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the output voltage and output current of a transformer applied to the welding electrode of the spot welding device.

FIG. 3 is a diagram showing an example of welding members having different thicknesses.

FIG. 4 is a diagram for explaining a spot welding apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a method of welding three aluminum plates having an insulating film together.

FIG. 6 is a diagram showing a method of welding four aluminum plates having an insulating film together.

FIG. 7 is a diagram showing the structure of a core transformer of a spot welding device according to a third embodiment of the present invention.

FIG. 8 is a diagram for explaining a spot welding apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing the relationship between the welding current and the pressing force of the welding electrode in the spot welding apparatus.

FIG. 10 is a diagram for explaining butt welding.

FIG. 11 is a diagram showing a T-shaped butt welding method for aluminum pipes.

FIG. 12 is a diagram showing a method of welding aluminum pipes by crossing them.

FIG. 13 is a diagram showing the waveform of welding current required in the welding method shown in FIGS. 11 and 12 above.

FIG. 14 is a diagram for explaining a spot welding apparatus according to a fifth embodiment of the present invention.

FIG. 15 is a diagram for explaining a spot welding apparatus according to a sixth embodiment of the present invention.

FIG. 16 is a diagram showing an example of a waveform of a welding current that can be generated in the sixth embodiment.

FIG. 17 is an explanatory diagram of problems in conventional bonded aluminum plates.

FIG. 18 is a diagram showing an example of an airtight or watertight container made of aluminum, for example, used in aircraft, automobiles, etc.

FIG. 19 is a diagram showing a stainless steel sink manufactured using the present spot welding device. .

FIG. 20 is a diagram showing another example of a container manufactured using the present spot welding apparatus.

FIG. 21 is a diagram showing a bathtub with a heat insulating structure manufactured using the present spot welding device.

[Explanation of symbols]

Claims (7)

[Claims] Claim 1: A transformer that receives an AC input and outputs a voltage and current for welding, and a pair of welding electrodes to which the output of the transformer is applied and performs resistance welding by pressing and holding a member to be welded. A resistance welding device for resistance welding non-ferrous metal materials, wherein the transformer is equipped with A resistor having a secondary coil configured by overlapping a plurality of copper plates forming a circumferential circuit, and supplying the welding electrode with a welding current that rises sharply at the same time as the output voltage is generated. Welding equipment. 2. The resistance welding apparatus according to claim 1, wherein the secondary coil is formed by hollowing out a copper plate to form a circumferential circuit, and cutting a part of the circumferential circuit to form an outer iron core. Or it can be attached to the inner iron core,
The above-mentioned primary coil is wound in the space of the outer iron type or inner iron type iron core between the secondary coils made of the above copper plate so as to be located in a plane parallel to the surface of the copper plate of the secondary coil. A resistance welding device characterized by: 3. The resistance welding apparatus according to claim 1, wherein the transformer is a core type, and the primary coil is wound within a predetermined plane around a wound iron core consisting of a pair of opposing cut cores. 3. The resistance welding apparatus according to claim 2, wherein the secondary coil is made of a secondary copper plate attached to the wound iron core in a plane parallel to the primary coil. 4. The resistance welding apparatus according to claim 1, wherein the pressure applied between the pair of welding electrodes is a pressure that changes in synchronization with the welding current. 5. The resistance welding apparatus according to claim 4, wherein the pressure between the pair of welding electrodes is a constant pressure and an oscillating pressure that is a combination of a pressure that changes in synchronization with the welding current. A resistance welding device featuring: 6. The resistance welding apparatus according to claim 1, wherein the welding electrodes include two pairs of upper and lower welding electrodes disposed close to each other, and the transformed voltage is adjusted to correspond to each pair of welding electrodes. each pair of upper and lower welding electrodes and the corresponding secondary coil of the transformer,
A resistance welding device characterized in that adjacent upper and lower welding electrodes are connected so that current flows through upper and lower welded members, respectively. 7. The resistance welding apparatus according to claim 1, further comprising a phase control circuit for controlling the supply of three-phase AC power for each phase, and the transformer has a three-phase primary on the primary side. The transformer has a single-phase iron core with a single-phase secondary coil wound around the secondary side, and the three-phase primary coil of the transformer is connected to each phase of the three-phase AC power supply via the phase control circuit. , wherein the phase control circuit controls the phase of each phase of the three-phase AC power source to output single-phase AC to the secondary coil.