JPH0871771A - Dc mash seam welding machine - Google Patents

Abstract

PURPOSE: To prevent magnetization of a magnetic material near a secondary conductor by changing, each time one welding process completes, the direction of a current which flows to each secondary conductor that supplies a welding current from a rectification circuit to a rotating disc electrode, changing the direction of a magnetic flux generated in the secondary conductor in the next welding process and cancelling the remaining magnetic flux. CONSTITUTION: The direction of a DC welding current, which flows from each output terminal of a full wave rectification circuit composed of anti-parallelly connected thyristors 7a, 7b, 8a, 8b, to a pair of rotating disc electrodes oppositely facing through secondary conductors 4a, 4b, is changed by continuity- controlling the thyristors 7a, 7b, 8a, 8b each time one welding process completes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC mash seam welding machine, and more particularly, to a magnetic body around a secondary conductor by changing the direction of the magnetic flux generated in the secondary conductor which supplies a welding current to a rotating disk electrode. The present invention relates to a DC power supply device for supplying a welding current that can demagnetize a magnetic field.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a power supply unit of a conventional DC mash seam welder. In the figure, reference numeral 1 is a transformer having an intermediate tap CT in a secondary winding N2, and a thyristor 3 connected in antiparallel to the primary winding N1 of the transformer 1.
An AC power source 2 is connected through the diode D, and a cathode is commonly connected to the terminals T1 and T2 of the secondary winding N2.
The anodes 1 and D2 are connected. A full-wave rectification circuit for full-wave rectifying the secondary voltage is configured by these diodes D1 and D2.

Reference numeral 4a designates a full-wave rectifying circuit and an upper rotating disk electrode 5
4a is an upper secondary conductor that fastens a and 4b is a lower secondary conductor that fastens the full-wave rectifier circuit and the lower rotating disk electrode 5b.
The upper secondary conductor 4a fastens the cathode of the diode D1 and the upper rotating disc electrode 6a, and the lower secondary conductor 4b fastens the lower rotating disc electrode 6b and the intermediate tap CT of the secondary winding N2. Thus, the upper rotating disk electrode 5a, the strips 6a and 6b, the lower rotating disk electrode 5 are arranged from the upper secondary conductor 4a.
The welding current flowing through b returns to the intermediate tap CT through the lower secondary conductor 4b.

Next, the operation of the conventional DC mash seam welding machine will be described. First, each time the voltage polarity of the AC power supply 2 changes, the corresponding thyristor among the thyristors 3 connected in anti-parallel is triggered to supply AC power from the AC power supply 2 to the primary winding N1 of the transformer 1. . As a result, while the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive and the polarity of the terminal T2 is negative, the terminal T1 and the diode D
1, upper secondary conductor 4a, upper rotating disc electrode 5a, superimposed strips 6a, 6b, upper rotating disc electrode 5
A welding current flows to b, the lower secondary conductor 4b, and the intermediate tap CT.

Also, while the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T
2, diode D2, upper secondary conductor 4a, upper rotating disc electrode 5a, overlapped strips 6a, 6b, upper rotating disc electrode 5b, lower secondary conductor 4b, intermediate tap CT
Welding current flows to. Therefore, the upper secondary conductor 4a, the upper rotating disk electrode 5a, the stacked strips 6a,
A full-wave rectified direct current flows through 6b, the upper rotating disk electrode 5b, and the lower secondary conductor 4b, so that Joule heat is generated in the overlapped strips 6a, 6b to perform welding.

[0006]

Since the conventional DC mash seam welding machine is constructed as described above, the welding current flowing through the upper secondary conductor and the lower secondary conductor is a full-wave rectified DC current. Therefore, its polarity is 1 of the current waveform in Fig. 4.
There is no inversion as shown in 3b. As a result, a magnetic flux φ is generated in the upper secondary conductor according to the direction of current flow, and a magnetic flux φ is also generated in the lower secondary conductor according to the direction of current flow.

This magnetic flux φ passes through the input and output side clamps, shears, etc. (not shown) near each secondary conductor and magnetizes them. For this reason, when the iron piece adheres to the shear, there is a problem that the blade surface is chipped when the tip of the strip is cut, or the strip is damaged when the insert / exit clamp is performed.

The present invention has been made to solve the above problems, and an object thereof is to obtain a DC mash seam welding machine in which the magnetic material near the secondary conductor is not magnetized.

[0009]

A direct current mash seam welding machine according to the invention of claim 1 has a rectifier connected to two windings of a transformer for welding, and a rectifier connected to two rotating disc electrodes. Current switching means for alternately switching the polarities of the upper and lower secondary conductors supplying positive voltage and negative voltage and the voltage applied to each secondary conductor by the rectifier to change the direction of the current flowing through each secondary conductor. It is equipped with and.

A DC mash seam welder according to a second aspect of the present invention is the DC mash seam welder according to the first aspect, wherein a pair of anti-welding transformer secondary windings are connected in antiparallel to each other. A thyristor is connected to form a rectifier and a current switching means rectifier.

A DC mash seam welder according to a third aspect of the present invention is the DC mash seam welder according to the first aspect, wherein the current switching means has a first contact provided in the middle of the upper secondary conductor and a lower contact. A second contact provided in the middle of the secondary conductor and operating in the same operation as the first contact;
A third contact, which operates in reverse to the first contactor and is connected between the input side of the first contactor and the output side of the second contactor, and the input side of the second contactor. And a fourth contactor connected between the output side of the first contactor and operating in the same operation as the third contactor.

A DC mash seam welder according to a fourth aspect of the present invention is the DC mash seam welder according to the first aspect, wherein the current switching means is a first switch provided in the middle of the upper secondary conductor, and a lower switch. A second switch provided in the middle of the secondary conductor and operating in the same operation as the first switch;
A third switch, which operates in reverse to the first switch and is connected between the input side of the first switch and the output side of the second switch, and the input side of the second switch. And a fourth switch connected between the output side of the first switch and operating in the same operation as the third switch.

[0013]

In the DC mash seam welding machine according to the invention of claim 1, the direction of the current flowing through each secondary conductor is changed every time one welding process is completed, and the magnetic flux generated in the secondary conductor in the next welding process is changed. The magnetic flux in the vicinity of the secondary conductor is prevented by changing the direction of and canceling the residual magnetic flux.

In the DC mash seam welding machine according to the second aspect of the present invention, the thyristor is made to conduct in one direction to generate a DC welding current flowing through each secondary conductor, and the thyristor to be made conductive is brought into a non-conductive state. Thyristor 1
By changing the direction of the welding current flowing in the secondary conductor by changing it every time the welding process is completed, and as a result, changing the direction of the magnetic flux generated in the secondary conductor in the next welding process to cancel the residual magnetic flux Prevents magnetization of magnetic material in the vicinity of the conductor.

According to another aspect of the present invention, there is provided a direct current mash seam welder having a first contact and a second contact as a pair and a third contact and a fourth contact as a pair, each of which has a pair. The ON / OFF operation of the contact is changed every time one welding process is completed to change the direction of the welding current flowing in the secondary conductor, and as a result, the direction of the magnetic flux generated in the secondary conductor in the next welding process is changed. By canceling the residual magnetic flux, the magnetization of the magnetic material in the vicinity of the secondary conductor is prevented.

According to a fourth aspect of the present invention, there is provided a direct current mash seam welding machine in which a first switch and a second switch are paired with each other, and a third switch and a fourth switch are paired with each other. The ON / OFF operation of the switch is changed every time one welding process is completed to change the direction of the welding current flowing in the secondary conductor, and as a result, the direction of the magnetic flux generated in the secondary conductor in the next welding process is changed. By canceling the residual magnetic flux, the magnetization of the magnetic material in the vicinity of the secondary conductor is prevented.

[0017]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a DC mash seam welder according to this embodiment. In the figure, the same parts as those in FIG. 6 indicate the same or corresponding parts. In the figure, 7a and 7b are thyristors connected in anti-parallel, and these thyristors 7a and 7b
One connection point of b is connected to the terminal T1 of the secondary winding N2, and the other connection point of the other end is connected to one end of the upper secondary conductor 4a fastened to the upper rotating disk electrode 5a.

Reference numerals 8a and 8b denote thyristors connected in antiparallel. One connection point of these thyristors 8a and 8b is connected to the terminal T2 of the secondary winding N2, and the other connection point of the thyristor 8a is connected to the upper secondary conductor 4a. It is connected to one end. Thyristor 7
A, 7b, 8a, and 8b form a current switching means together with a full-wave rectifier circuit.

Next, the operation of this embodiment will be described.
First, the thyristors 7b and 8b are rendered conductive by a trigger signal from a gate circuit (not shown), and the thyristors 7a and 8a are rendered non-conductive. In this state, by triggering the thyristor 3 connected in anti-parallel, AC power is supplied from the AC power supply 2 to the primary winding N1 of the transformer 1. As a result, while the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive and the polarity of the terminal T2 is negative,
As shown by the solid line, to the terminal T1, the thyristor 7b, the upper secondary conductor 4a, the upper rotating disc electrode 5a, the stacked strips 6a and 6b, the upper rotating disc electrode 5b, the lower secondary conductor 4b, and the intermediate tap CT. Welding current flows.

While the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T2, the thyristor 8b and the upper secondary conductor are also shown by the solid line. Welding current flows to 4a, upper rotating disk electrode 5a, overlapped strips 6a and 6b, upper rotating disk electrode 5b, lower secondary conductor 4b, and intermediate tap CT. In this way, during one welding process, the thyristors 7b and 8b are brought into the conducting state and the full-wave rectified direct current is passed.

When one welding process is completed, the AC power source is temporarily cut off, the thyristors 7a and 8a are made conductive by a trigger signal from a gate circuit (not shown), and the thyristors 7b and 8b are made non-conductive. State. As a result, as long as the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is negative with respect to the polarity of the intermediate tap CT, the intermediate tap CT and the lower secondary coil are shown by a broken line in the opposite direction to the solid line. A welding current flows to the conductor 4b, the lower rotating disk electrode 5b, the overlapped strips 6b and 6a, the upper rotating disk electrode 5a, the upper secondary conductor 4a, the thyristor 7a, and the terminal T1.

While the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is negative with respect to the polarity of the intermediate tap CT, the intermediate tap CT, as shown by the broken line in the opposite direction to the solid line,
A welding current flows to the lower secondary conductor 4b, the lower rotating disk electrode 5b, the overlapped strips 6b and 6a, the upper rotating disk electrode 5a, the upper secondary conductor 4a, the thyristor 8a, and the terminal T2.

Therefore, a full-wave rectified direct current flows through the upper secondary conductor 4a, the upper rotating disk electrode 5a, the strips 6a and 6b that are superposed, the lower rotating disk electrode 5b, and the lower secondary conductor 4b. , Stacked strips 6
Joule heat is generated in the portions a and 6b and welding is performed.

As described above, the thyristors 7a and 8b and the thyristors 7b and 8b are brought into conduction every time one welding process is completed,
By switching to the non-conducting state alternately, the upper secondary conductor 4
The direction of the welding current flowing through both a and the lower secondary conductor 4b changes from (a) of FIG. 5 to (b) of the same figure. As a result, when the direction of the magnetic flux φ is reversed, the magnetic materials such as the input and output clamps that were once magnetized by passing through the magnetic flux φ are also magnetized with the opposite polarities, so that the residual magnetic flux does not have a coercive force and is retained in the atmosphere. It does not magnetically attract floating iron powder or iron pieces.

Example 2. In the first embodiment, the antiparallel thyristor connected to the secondary winding of the transformer 1 is used for the full-wave rectifier circuit and the current switching means. However, in the conventional DC mash seam welder, the upper and lower secondary conductors are A current switching means may be inserted in the.

FIG. 2 is a block diagram of the DC mash seam welder in this embodiment. In the figure, the same reference numerals as those in FIG. 6 indicate the same or corresponding portions. In the figure, 9a, 10a
Are a first contactor, a second contactor 9 inserted in the upper secondary conductor 4a and a lower secondary conductor 4b, respectively.
b is a third contactor 10 connected between the input side of the first contactor 9a and the output side of the second contactor 10a.
Is the output side of the first contactor 9a and the second contactor 1
It is a fourth contactor connected between the input sides of 0a.
The contactors 9a, 9b, 10a, 10b are tulip contactors having a large current capacity and are turned on and off by a control circuit (not shown).

Next, the operation of this embodiment will be described.
First, the first contactor 9a and the second contactor 10a
Is turned on, and the third contactor 9b and the fourth contactor 10b are turned off. In this state. By triggering the thyristors 3 connected in anti-parallel, AC power is supplied from the AC power supply 2 to the primary winding N1 of the transformer 1. As a result, while the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive and the polarity of the terminal T2 is negative,
Terminal T1, diode D1, first contactor 9a, upper secondary conductor 4a, upper rotating disc electrode 5a, superimposed strips 6a, 6b, upper rotating disc electrode 5b, lower secondary conductor 4b, second contactor 10a, intermediate tap C
Welding current flows to T.

Further, while the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T
2, diode D2, first contactor 9a, upper secondary conductor 4a, upper rotating disc electrode 5a, overlapped strips 6a, 6b, lower rotating disc electrode 5b, lower secondary conductor 4b, second contactor 10a. , Welding current flows to the intermediate tap CT. Thus, during one welding process,
The first and second contactors 9a, 10a are turned on, and a full-wave rectified welding current is passed.

Next, when one welding process is completed, the AC power source is once cut off, and then the first contactor 9a and the second contactor 9a.
The contactor 10a is turned off, and the third contactor 9b and the fourth contactor 10b are turned on. As a result, while the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive and the polarity of the terminal T2 is negative, the terminal T1, the diode D1, the third contactor 9b, the lower secondary conductor 4b, Lower rotating disk electrode 5b, stacked strips 6b,
6a, upper rotating disk electrode 5a, upper secondary conductor 4a, fourth
The welding current flows to the contactor 10b and the intermediate tap CT.

Further, while the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T
2, diode D2, third contactor 9ba, lower secondary conductor 4b, lower rotating disk electrode 5b, superimposed strips 6b, 6a, upper rotating disk electrode 5a, upper secondary conductor 4a, fourth contactor 10b. , Welding current flows to the intermediate tap CT.

In this way, every time one welding process is completed, the first welding process is performed.
And the second contactors 9a and 10a, and the third and fourth contactors 9b and 10b are alternately switched between the on-state and the off-communication state so that the upper secondary conductor 4a and the lower secondary conductor 4b.
The waveforms of the welding currents flowing through both of them are 13a and 13b in FIG.
And alternate. The direction of the welding current flowing through both the upper secondary conductor 4a and the lower secondary conductor 4b changes from (a) in FIG. 5 to (b) in FIG.
The direction of changes. As a result, the magnetic materials such as the input and output clamps that were once magnetized by the passage of the magnetic flux φ are also magnetized with the opposite polarity, so the residual magnetic flux does not have a holding force, so iron powder or iron pieces floating in the atmosphere can be removed. No magnetic attraction.

Example 3. Although the contactor is used as the current switching means in the above embodiment, it may be a mechanical switch (hereinafter referred to as a switch) that is turned on and off by a control signal from the outside. In this case, as the switch, a disconnecting switch (commonly called a decon) that is a switchgear for a high voltage circuit is most suitable.

FIG. 4 is a block diagram of the DC mash seam welder in this embodiment. In the figure, the same reference numerals as those in FIG. 6 indicate the same or corresponding portions. In the figure, 11a, 12
a is a first switch, a second switch, 11 inserted in the middle of the upper secondary conductor 4a and the lower secondary conductor 4b, respectively.
b is the input side of the first switch 11a and the second switch 1
A third switch 12 is connected between the output sides of 2a and 12 is a fourth switch connected between the output side of the first switch 11a and the input side of the second switch 12a.

Next, the operation of this embodiment will be described.
First, the first switch 11a and the second switch 12a are turned on by a control circuit (not shown), and the third switch 11b and the fourth switch 12b are turned off. In this state, by triggering the thyristor 3 connected in anti-parallel, AC power is supplied from the AC power supply 2 to the primary winding N1 of the transformer 1. As a result, the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive, and the terminal T
While the polarity of 2 is negative, the terminal T1, the diode D1, and the first
Switch 11a, upper secondary conductor 4a, upper rotating disc electrode 5a, overlapped strips 6a, 6b, upper rotating disc electrode 5b, lower secondary conductor 4b, second switch 1
2a, welding current flows to the intermediate tap CT.

While the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T
2, diode D2, first switch 11a, upper secondary conductor 4a, upper rotating disc electrode 5a, superimposed strips 6a, 6b, lower rotating disc electrode 5b, lower secondary conductor 4b, second switch 12a. , Welding current flows to the intermediate tap CT. In this way, during one welding process, the first and second switches 11a and 12a are turned on to flow the full-wave rectified welding current.

Next, when one welding process is completed, the AC power source is once cut off, and then the first switch 11a and the second switch 11a
Switch 12a is turned off, and the third switch 11
b, the fourth switch 12b is turned on. As a result, while the polarity of the secondary voltage appearing at the terminal T1 of the secondary winding N2 is positive and the polarity of the terminal T2 is negative, the terminal T1, the diode D1, the third switch 11b, the lower secondary conductor 4b, Lower rotating disc electrode 5b, overlapping strips 6b, 6
A welding current flows to a, the upper rotating disk electrode 5a, the upper secondary conductor 4a, the fourth switch 12b, and the intermediate tap CT.

Further, while the polarity of the secondary voltage appearing at the terminal T2 of the secondary winding N2 is positive and the polarity of the terminal T1 is negative, the terminal T
2, diode D2, third switch 11ba, lower secondary conductor 4b, lower rotating disk electrode 5b, stacked strips 6b, 6a, upper rotating disk electrode 5a, upper secondary conductor 4a, fourth switch 12b , Welding current flows to the intermediate tap CT.

[0038]

According to the invention of claim 1, a rectifier connected to the secondary winding of a transformer for welding and a rectifier connected to this secondary rectifier are provided.
Current flowing in each secondary conductor by alternately switching the polarities of the upper and lower secondary conductors supplying positive and negative voltages to the two rotating disk electrodes and the voltage applied to each secondary conductor by the rectifier. Since the current switching means for changing the direction of the secondary conductor is provided, the direction of the magnetic flux generated in the secondary conductor can be switched alternately.
There is an effect that it can be easily prevented from being magnetized by the generated magnetic flux.

According to the invention of claim 2, since the rectifier and the current switching means are composed of two thyristors connected in anti-parallel connection provided in the middle of each secondary conductor, a structure is provided in addition to the effect of claim 1. Has the effect of being simplified.

According to the invention of claim 3, the current switching means includes a first contactor provided in the middle of the upper secondary conductor,
A second contactor provided in the middle of the lower secondary conductor and interlocking with the first contactor in the same operation; and a second contactor that operates in reverse to the first contactor and is on the input side of the first contactor. The third contactor is connected between the output sides of the second contactors, and the third contactor is connected between the input side of the second contactors and the output side of the first contactors. In addition to the effect of the first aspect, there is an effect that switching of a large current is facilitated because the fourth contact element is linked with the same operation as the above.

According to the invention of claim 4, the current switching means includes a first switch provided in the middle of the upper secondary conductor,
A second switch provided in the middle of the lower secondary conductor and interlocking with the first switch in the same operation; and a second switch that operates in reverse to the first switch and operates on the input side of the first switch. A third switch connected between the output sides of the second switch, and a third switch connected between the input side of the second switch and the output side of the first switch Since it is composed of a fourth switch which is interlocked with the same operation as the above, there is an effect that switching of a large current is facilitated in addition to the effect of claim 1.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a DC mash seam welder according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a DC mash seam welder according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a DC mash seam welder according to another embodiment of the present invention.

FIG. 4 is a waveform diagram of a welding current flowing through each secondary conductor.

FIG. 5 is a diagram showing a direction of a welding current and a direction of a magnetic flux flowing in each secondary conductor.

FIG. 6 is a configuration diagram of a conventional DC mash seam welding machine.

[Explanation of reference numerals] 1 transformer, 2 power supply device, 3 antiparallel connection thyristors, 4a, 4b upper and lower secondary conductors, 5a, 5b
Upper and lower rotating disc electrodes, 7a, 7b, 8a, 8b
Thyristor, 9a, 9b, 10a, 10b Contactor, 11a, 11b, 12a, 12b Switch, D
1, D2 diode.

Claims (4)

[Claims] 1. A rectifier connected to a secondary winding of a transformer for welding, and upper and lower secondary conductors for feeding a positive voltage and a negative voltage to the two rotating disk electrodes from the rectifier. A direct current mash seam welding machine, comprising: current switching means for switching the polarity of the voltage applied from the rectifier to each of the secondary conductors alternately to switch the direction of the current flowing through each of the secondary conductors. 2. The rectifier and the current switching means are configured by connecting a pair of anti-parallel thyristors to each terminal of the secondary winding of the welding transformer. DC mash seam welder described. 3. The current switching means includes a first contactor provided in the middle of the upper secondary conductor and a second contactor provided in the middle of the lower secondary conductor and operating in the same operation as the first contactor. And a third contactor that operates in reverse to the first contactor and is connected between the input side of the first contactor and the output side of the second contactor. The fourth contactor is connected between the input side of the contactor and the output side of the first contactor and is interlocked with the third contactor in the same operation as the fourth contactor.
DC mash seam welder described in. 4. The current switching means includes a first switch provided in the middle of the upper secondary conductor and a second switch provided in the middle of the lower secondary conductor and operating in the same operation as the first switch. And a third switch, which operates in reverse to the first switch and is connected between the input side of the first switch and the output side of the second switch, 2. A fourth switch which is connected between an input side of the switch and an output side of the first switch and which operates in the same operation as the third switch.
DC mash seam welder described in.