JP3291183B2 - Resistance welding control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding control device for supplying a predetermined alternating current to a resistance welding machine.

[0002]

2. Description of the Related Art In a resistance welding machine, a welding current is passed between a pair of electrodes to weld a work held between the two electrodes. And there are the following two types of resistance welding machines. As shown in FIG. 4, the first type of resistance welding machine 60 converts an alternating current supplied from the resistance welding control device 110 into a direct current by a transformer 70 and a pair of diodes 76, and the two electrodes 61 and 62. A DC current flows between them. As shown in FIG. 5, a second type resistance welding machine 80 transforms an alternating current supplied from a resistance welding control device 210 by a transformer 90 and passes the alternating current between both electrodes 81 and 82 as it is. It is.

[0003] Conventionally, as shown in FIG. 4, a first type resistance welding machine (DC resistance welding machine) 60 includes:
The following resistance welding control device 110 is used.
The resistance welding control device 110 has a DC power supply 112. The DC power supply 112 is formed by a three-phase AC power supply 114 and a diode 116. DC power supply 112
, An inverter 120 and a capacitor 150 are connected in parallel. Then, an alternating current flowing from the inverter 120 is supplied to the resistance welding machine 60. The ON / OFF of each transistor forming the inverter 120 is controlled by the control unit 140 so that a predetermined alternating current is supplied.

As shown in FIG. 5, a second type of resistance welding machine (AC resistance welding machine) 80 uses the following resistance welding control device 210. The thyristor 220 is bidirectionally connected to the AC power supply 214, and the AC current is supplied to the resistance welding machine 80.
Each thyristor 220 is controlled by the control unit 240 so that a predetermined alternating current is supplied.

The frequency of the alternating current supplied by the first type (for direct current) resistance welding control device 110 to the resistance welding machine 60 is determined by the second type (for alternating current) resistance welding control device 210. The frequency is about 10 times higher than the frequency of the alternating current supplied to the device 80.

The first type (for direct current) of the resistance welding machine 60 and the resistance welding control device 110 are:
Has the advantage that the current supplied to the electrode (and, consequently, the welding current flowing between the electrodes 61 and 62) can be finely controlled, the price of the entire apparatus is expensive, and the electrode wear is large (the welding current is large). Because it flows only in one direction). On the other hand, the second type (for AC) resistance welding machine 80 and resistance welding control device 21
On the contrary, 0 has the advantages that the price of the entire apparatus is low, the wear of the electrodes is small, and the current supplied to the resistance welding machine 80 (therefore, both electrodes 81 and 82).
It has the disadvantage that the control accuracy of the welding current flowing between them is coarse.

[0007]

In order to control both types of resistance welding machines 60 and 80, it is necessary to provide a dedicated resistance welding control device. However, that would result in high costs. Therefore, an object of the present invention is to provide a resistance welding control device capable of controlling both types of resistance welding machines.

[0008]

Means for Solving the Problems In order to solve this problem, the invention according to claim 1 comprises a DC power supply and a DC power supply.
An inverter that converts the DC current of the
And a control unit for controlling the inverter.
A resistor that supplies AC current from the inverter to the primary side of the lance
An anti-welding control device that switches between DC and AC
The switching unit is switched for DC.
If the inverter has been replaced,
DC resistor that allows DC current to flow through the electrode on the secondary side of the
Supply alternating current of welding machine frequency to primary side of transformer
If the switching unit is switched for AC,
From the inverter to the electrode on the secondary side of the transformer.
An alternating current having a frequency for AC resistance welding machine supplying a flow current
This is a resistance welding control device supplied to the primary side of the transformer.

In the present invention, the frequency of the AC current converted by the inverter is switched depending on the type of the resistance welding machine (for DC current or AC current). Therefore, both types of resistance welding machines can be handled.

The invention according to claim 2 is a DC power supply.
And convert the DC current from the DC power supply to a predetermined AC current.
And a control unit that controls the inverter.
To the primary side of the resistance welding machine transformer from the inverter.
A resistance welding control device for supplying a current
Supplies alternating current to the primary side of the resistance welding machine transformer.
When a current flows between the electrodes provided on the secondary side
Based on the primary current value of the
DC resistor that allows DC current to flow through the electrode on the secondary side of the
Replace the electrode on the secondary side of the transformer with a welding machine.
Determines whether the welding machine is an AC resistance welding machine that passes current and determines
From the inverter to the resistance welding machine transformer based on the results
Resistance welding that controls the frequency of alternating current supplied to the primary side
It is a control device.

In the present invention, when a current is supplied to a resistance welding machine, it is determined whether the resistance welding machine is for DC current or AC current, and the AC converted by the inverter is determined based on the result. The frequency of the current is switched. In this way, it is possible to automatically cope with either type of resistance welding machine, and it is convenient that the operator does not need to recognize the type of resistance welding machine and switch the frequency based on it.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the resistance welding control device 10 is connected to a DC resistance welding machine 60 and an AC resistance welding machine 80, and supplies a predetermined AC current thereto. The resistance welding control device 10 includes a DC power supply 12, an inverter 20, a control unit 40, a pair of resistance welding machine connection terminals 48, and a capacitor 50.

The DC power supply 12 is formed by a three-phase AC power supply 14 and a diode 16. The inverter 20 and the capacitor 50 are provided in parallel with the DC power supply 12.

The inverter 20 has four transistors (first transistor 21 to fourth transistor 24). A set of the first transistor 21 and the second transistor 22 and a set of the third transistor 23 and the fourth transistor 24 are connected to the DC power supply 12 in parallel. First transistor 21 and second transistor 2
2 is connected in series to the DC power supply 12, and both the third transistor 23 and the fourth transistor 24 are connected in series to the DC power supply 12. The energization directions of the transistors 21 to 24 are all the same. The bases of the transistors 21 to 24 are connected to the control unit 40.

A diode (first diode 31 to fourth diode 34) is connected in parallel to each of the transistors 21 to 24. Each transistor 21-2
The direction of conduction of the diode 4 and the direction of conduction of the diodes 31 to 34 are opposite to each other. The pair of resistance welding machine connection terminals 48 are connected to a portion between the first transistor 21 and the second transistor 22 and a portion between the third transistor 23 and the fourth transistor 24.

A current detection circuit 42 is provided for an electric wire connecting the DC power supply 12 and the inverter 20.
An AC / DC determination unit 44 is connected to the current detection circuit 42, and the AC / DC determination unit 44 is connected to the control unit 40. The switching unit 46 is connected to the control unit 40.

On the other hand, the DC resistance welding machine 60 has a pair of electrodes (a first electrode 61 and a second electrode 62) and a control device connection terminal 64. The transformer 70 is connected to the control device connection terminal 64, and both ends of the secondary coil 72 of the transformer 70 are both connected to the first electrode 61 via the diode 76 in the direction toward the first electrode 61. Secondary coil 7
The center of 2 is connected to the second electrode 62.

The AC resistance welding machine 80 also has a pair of electrodes (first
(Electrode 81, second electrode 82) and control device connection terminal 84. A transformer 90 is connected to the control device connection terminal 84. One end of a secondary coil 92 of the transformer 90 is connected to the first electrode 81, and the other end is connected to the second electrode 82.

The resistance welding machines 60 and 80 are connected to the resistance welding machine connection terminals 48 of the resistance welding control device 10 at their control device connection terminals 64 and 84, respectively. Receives AC current.

Next, the control contents of the resistance welding control device 10 will be described. First, the case of manual switching will be described. When the DC resistance welding machine 60 is connected, the switching unit 46 switches to DC. Thereby,
As described below, the resistance welding control device 10 to 400 to 120
An alternating current of about 0 Hz is supplied. That is, in the resistance welding control device 10, under the control of the control unit 40,
A state where the first and fourth transistors 21 and 24 are on (the second and third transistors 22 and 23 are off) (this state is referred to as a first state), and all the transistors 2
1 to 24 are in an off state (also in a second state), and the second and third transistors 22 and 23 are in an on state (first and fourth transistors 21 and 24 are off) (also in a third state).
State) and all transistors 21 to 24 are off (similarly, the fourth state) are repeated at the above frequency.

As a result, in the first state, a current flows from the DC power supply 12 → the first transistor 21 → the primary coil 71 → the fourth transistor 24 → the DC power supply 12.
The primary coil 71 flows downward from above in the figure. This is referred to as a direction. In the third state, the DC power supply 12 → the third transistor 23 → the primary coil 71 → the second
A current flows from the transistor 22 to the DC power supply 12. 1
In the next coil 71, it flows upward from below in the figure. This is referred to as the b direction. As described above, a predetermined high-frequency AC current is supplied to the DC resistance welding machine 60 (the secondary coil 72 side).

Based on this AC current, in the DC resistance welding machine 60 (the secondary coil 72 side), one end of the secondary coil 72 → the first electrode 61 → the second electrode 62 → the central portion of the secondary coil 72. → The other end of the secondary coil 72 → a current flows in a loop of the first electrode 61, a welding current flows between the two electrodes 61 and 62, and the work W, W sandwiched between the two electrodes is welded. Will be

When the AC resistance welding machine 80 is connected, the switching unit 46 switches to AC. Thereby, an alternating current of 50 or 60 Hz is supplied from the resistance welding control device 10 as follows. That is, in the resistance welding control device 10, under the control of the control unit 40, the first state (the first and fourth transistors 21, 24)
Is on), the third state (the second and third transistors 2
2 and 23 are ON), the above 50 or 60H
By repeating at the frequency of z , an alternating current of 50 or 60 Hz is supplied to the AC resistance welding machine 80. When the AC resistance welding machine 80 is connected, both the transistors 21 and 24 (or 22, 23) are duty-controlled from the microscopic viewpoint even in the first and third states. ON / OFF is repeated finely, and each waveform of the AC current is substantially rectangular.

On the basis of the alternating current supplied in this manner, an alternating welding current flows between the first electrode 81 and the second electrode 82 of the alternating-current resistance welding machine 80, and both electrodes 81, 82
The works W, W sandwiched therebetween are welded. In addition,
Also in this case, similarly to the above, the current flows in the primary coil 91 are defined as directions a and b, and the corresponding current flows in the secondary coil 92 are defined as directions a ′ and b ′. .

Next, the case of automatic switching will be described. First, the above-described first state, second state, third state, and fourth state are repeated at a predetermined frequency (high frequency). Then, the current detected by the current detection circuit 42 differs between the case where the AC resistance welding machine 80 is connected and the case where the DC resistance welding machine 60 is connected, as follows.

When the AC resistance welding machine 80 is connected, the operation is as follows. As shown in FIG. 3, when the first state (the first and fourth transistors 21 and 24 are turned on), the current flowing through the current detection circuit 42 (the DC power supply 12 → the first transistor 21 → 1) Next coil 9
1 (direction a) → fourth transistor 24 → DC power supply 12)
Is gradually increased from zero. The gradual increase is due to the coil in the circuit. As a result, the current value (a 'direction) flowing through the secondary coil 92 also gradually increases from zero. The current detection circuit 42
(Accurately, the direction in which the current detection circuit 42 measures the current) is defined as the direction A flowing from left to right in the drawing, and the opposite direction is defined as the B direction. In this case, it flows in the A direction.

Next, the transformer 9 is set in the second state (all the transistors 21 to 24 are turned off).
The current flow of the 0 primary coil 91 is about to stop.
However, it tends to continue to flow in the a 'direction on the side of the secondary coil 92 of the transformer 90 (depending on the coil).
Therefore, the primary coil 91 also tries to continue to flow in the a direction. At this time, on the primary coil 91 side, a current flows while charging the capacitor 50 in the order of the primary coil 91 → the third diode 33 → the capacitor 50 → the second diode 32 → the primary coil 91. In the current detection circuit 42, the current flows in the B direction. As the capacitor 50 is charged, the flow of this current gradually decreases, and when the charging of the capacitor 50 ends, the current stops on both the first coil side and the second coil side.

As described above, when the AC resistance welding machine 80 is connected, in the second state, not only the side of the secondary coil 92 of the transformer 90 but also the side of the primary coil 91 (resistance welding control). The current flow remains in the loop including the device 10). When the charging of the capacitor 50 ends, the flow of the current stops.

Next, the third state (the second and third transistors 22 and 23 are turned on) causes the current flowing through the current detection circuit 42 (direction A) to be the same as in the first state. The current value of (DC power supply 12 → third transistor 23 → primary coil 91 (b direction) → second transistor 22 → DC power supply 12) gradually increases from zero, and in the secondary coil 92 side, in the b ′ direction. The current value gradually increases from zero.

On the other hand, when the DC resistance welding machine 60 is connected, the operation is as follows. As shown in FIG.
State (the first and fourth transistors 21 and 24 are on)
As a result, similarly to the case where the AC resistance welding machine 80 is connected, the current flowing from the current detection circuit 42 (direction A) (DC power supply 12 → first transistor 21 → 1)
The current value of the next coil 71 (direction a) → the fourth transistor 24 → the DC power supply 12) gradually increases from zero. Further, the value of the current flowing through the secondary coil 72 (a 'direction) also gradually increases from zero.

Next, the transformer 7 is set in the second state (all the transistors 21 to 24 are turned off).
The current flow of the 0 primary coil 71 is about to stop.
Then, as in the case where the AC resistance welding machine 80 is connected, the same current as in the first state will continue to flow on the secondary coil 72 side of the transformer 70. However, in this case, on the secondary coil 72 side, 2
One end of the next coil 72 → first electrode 61 → second electrode 62 →
The current flows in a loop of the central part of the secondary coil 72 → the other end of the secondary coil 72 → the first electrode 61 (this has been described above). That is, in the secondary coil 72,
Current flows from the center of the secondary coil 72 to both ends. For this reason, the current induced in the primary coil 71 by the current flow in the secondary coil 72 is canceled in the directions a and b, so that little current flows on the primary coil 71 side. Therefore, on the primary coil 71 side, independently of the secondary coil 72 side, the primary coil 71 → the third diode 33 →
Capacitor 50 → second diode 32 → primary coil 71
Then, only the current flows while the capacitor 50 is being charged, and the current value is small and stops immediately. On the other hand, on the side of the secondary coil 72, the current tends to continue to flow in the above-mentioned loop independently of the primary coil 71, so that unlike the case where the AC resistance welding machine 80 is connected, When the resistance is small and the charging by the capacitor 50 ends, the current flow does not stop. For this reason, as shown in the figure, the current continues to flow on the side of the secondary coil 72 without stopping even in the second state. In addition,
The current value is slightly reduced by the resistance.

In this state, if the third state (the first and fourth transistors 21 and 24 are turned on) is established, the primary coil 72 is already (still) energized, so that the primary The current of the secondary coil 72 is not gradually induced from zero by the current of the coil 71. For this reason, on the side of the primary coil 71, the current value rises not from zero but from a predetermined current value, and then gradually increases.

As described above, when the AC resistance welding machine 80 is connected when shifting from the second state to the third state, the value of the current flowing through the primary coil 71 (ie, , The current value flowing through the current detection circuit 42) starts from zero, whereas when the DC resistance welding machine 60 is connected, it starts from a predetermined value other than zero. For this reason, the AC / DC determination unit 44 determines which resistance welding machine 60 or 80 is connected based on this difference. Then, based on the result of the determination, the control unit 40 switches between performing the control for DC or the control for AC, and performs the control suitable for the type of the resistance welding machines 60 and 80. The specific control content in each case is the same as that in the case of manual switching.

As described above, the resistance welding control device 10
Then, since both types of resistance welding machines 60 and 80 can be controlled, it is not necessary to prepare resistance welding control devices for each type of resistance welding machines 60 and 80, which is convenient and convenient. Since it is possible to automatically determine which type of the resistance welding machines 60 and 80 are connected and to automatically switch the control contents, the operator determines which type of the resistance welding machines 60 and 80 are connected. It is convenient because there is no need to switch manually.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of the resistance welding control device of FIG. 1; This is a case where an AC resistance welding control device is connected.

FIG. 3 is also a case where a DC resistance welding control device is connected.

FIG. 4 is a circuit diagram showing a conventional resistance welding control device.
For DC resistance welders.

FIG. 5 is also for an AC resistance welding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Resistance welding control apparatus 12 DC power supply 20 Inverter 40 Control part 44 AC / DC discrimination part 46 Switching part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 11/24 H02M 9/00

Claims (2)

(57) [Claims] 1. A DC power supply and a DC current from the DC power supply.
An inverter that converts the current into a predetermined alternating current;
And a control unit for controlling the primary of the transformer of the resistance welding machine.
Welding control device that supplies AC current from the inverter to the side
And a switching unit that is switched between DC and AC, and the control unit is configured to switch when the switching unit is switched to DC.
Is connected to the transformer provided on the secondary side of the transformer from the inverter.
AC at a frequency for a DC resistance welder with a DC current flowing through the poles
The current is supplied to the primary side of the transformer, and the switching unit is switched for AC.
If the inverter has been replaced,
AC resistor that allows AC current to flow through the electrode provided on the secondary side of the
Supply alternating current of welding machine frequency to primary side of transformer
To control the resistance welding. 2. A DC power supply and a DC current from the DC power supply.
An inverter that converts the current into a predetermined alternating current;
And a control unit for controlling the primary of the transformer of the resistance welding machine.
Welding control device that supplies AC current from the inverter to the side
The control unit applies an alternating current to the primary side of the transformer of the resistance welding machine.
When the current is supplied between the electrodes provided on the secondary side
Based on the primary current value of the transformer, the resistance welding machine
DC to apply DC current to the electrode provided on the secondary side of the lance
Resistance welding machine or a transformer provided on the secondary side of the transformer.
Determine whether it is an AC resistance welding machine that sends AC current to the pole
Based on the determination result,
Controls the frequency of the alternating current supplied to the primary side of the lance
A resistance welding control device.