JPS5841153B2 - Welding current control device in resistance welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for controlling a welding current to a resistance welding machine via a silicon-controlled rectifying element.

Conventionally, in controlling the welding current via a silicon-controlled rectifying element, the ignition position of the silicon-controlled rectifying element is generally set by the OR time constant or the number of clock pulses counted by a counter. When using a time constant, the conduction angle tends to fluctuate due to the influence of external voltage fluctuations or temperature changes, and delicate adjustment of the conduction angle is difficult.Moreover, the dial position and conduction angle of the control device are different from each other. The disadvantage is that it varies depending on the characteristics of each individual welding machine or the characteristics of each welding machine.Also, when using a counter, although it is easy to adjust with a dial, the clock pulse must be synchronized with the power supply frequency, and the counting operation of the counter must be controlled by the power supply frequency. The disadvantage is that the circuit becomes quite complex because it must be synchronized with the frequency.

In addition, when the welding current is large, if this large current is passed rapidly, the excessive inrush current at this time may damage the welding current control cylinder.In addition, spatter may occur due to the sudden flow of the large current. As a countermeasure to prevent this, the welding current value at the start of energization is limited and the welding current is slowed down. The up characteristics change every time the power supply voltage fluctuates or the welding current changes, so readjustment is necessary, but as a practical matter, welding is performed without being readjusted when the power supply voltage fluctuates, resulting in variations in welding characteristics. However, if the slow-up is not readjusted when changing the welding current, the slow-up characteristics, including the current value at the start of energization, will also slide up and down as the welding current increases and decreases, resulting in an increase in the welding current. In this case, an increase in the inrush current due to an increase in the welding starting current may damage the welding current, and if the welding current decreases, it may not be necessary to slow up the welding current by limiting the welding starting current. However, there was a drawback that the welding characteristics changed significantly due to the greater slow-up effect.

The object of the present invention is to
In this case as well, it is an object of the present invention to provide a welding current control device for a resistance welding machine that can stabilize welding characteristics without readjusting the welding current slow-up. .

Next, the configuration of an embodiment of the present invention will be explained with reference to the drawings.

A square wave output synchronized with the power supply frequency from a power supply synchronization signal generation circuit 1, which inputs a sine wave of a commercial power supply AC and is made of, for example, a photocoupler, is sent to a frequency multiplier circuit 2, that is, a phase comparator circuit 3, and a voltage controlled oscillation circuit 4. and an n-divider counter 5, and the phase comparator circuit 3 divides the square wave output from the power synchronization signal generation circuit 1 and the oscillation frequency of the voltage controlled oscillation circuit 4 by n. An output corresponding to the phase difference l with the square wave output from the frequency counter 5 is generated, and by controlling the oscillation frequency by this output, a synchronized clock pulse of n times the power supply frequency is generated from the voltage controlled oscillator circuit 4. Ru.

Output data from the firing angle setting circuit 6, which sets the number of pulses corresponding to the firing angle of the SCR, using a BCD code, and the welding current. The welding current value at the start of energization corresponding to the slow-up of O is the initial firing angle corresponding to B.
When setting the CD code in the slope setting section 7, the output data from the slope setting circuit 9, which sequentially increases the set value of the preset counter 8 by a fixed number, in this case 1 count, every cycle of the power supply frequency, is the output data of the digital comparator. The data is input to a data comparison circuit 10 and a data selection circuit 11 of an AND-OR selection gate.

Therefore, data is selected by the comparison output from the data comparison circuit 10 (therefore, when the output data from the slope setting circuit 9 does not reach the setting value of the firing angle setting circuit 6), the output data of the slope setting circuit 9 is Further, after the output data of the slope setting circuit 9 reaches the setting value of the ignition angle setting circuit 6, the setting value of the ignition angle setting circuit 6 is output from the data selection circuit 11, and the preset counter 2 for counting the ignition angle At the same time, the preset counter 2 starts counting the Norita pulses from the voltage controlled oscillation circuit 4 with the output "H" of the n frequency division counter 5, and the preset counter 2 starts counting the Norita pulses from the voltage controlled oscillation circuit 4 when the count number reaches the set value (the preset value is Output "H" from counter 2 is - frequency division counter 3
The Σ frequency division counter 3 starts counting clock pulses from the voltage controlled oscillation circuit 4, and generates an output "H" at the end of counting clock pulses corresponding to a half cycle of AC.

In addition, an output control circuit 15 whose gate signal is an output from a timing control circuit 14 of a D-type FF whose inputs are the output of the n frequency division counter 5 and a start signal for starting welding current supply, that is, NANDI 6.17. IN
An output control circuit 15 consisting of VTlB, a negative input ORI 9, and an AND 20 generates an output rHJ at the time of output generation of the ignition angle counting preset counter 2 and the Σ frequency division counter 3, and generates an ignition pulse. A trigger voltage is applied to the gate l of the welding current control SCR through the transistor TR and pulse transformer PT of the generating circuit 21, and the NAND l6 controls the output of the preset counter 12 for the positive ignition cycle only for the positive cycle. Take out, NANDl7 takes out the output of the Σ frequency division counter 13 of the negative firing cycle only for the negative cycle, the negative input 0R19 takes out both of these two signals as output, and the AND20 outputs from the negative input ORI9. A gate for synchronizing the start of output of the positive and negative cycle firing signals with the power supply by taking an AND condition between the firing signals of the positive and negative cycles to be output and the start signal synchronized with the power supply output from the timing control circuit 14. be.

Next, the effect of this embodiment will be explained using the energization method shown in the waveform diagram in FIG. The slow-up energization method Q, in which the welding current is applied at the final ignition position while increasing the welding current, will be explained below.

For simplicity, the frequency multiplier circuit 2 generates a synchronized clock pulse 20 times the power supply frequency, and the slope setting section 7 has a setting value 8 of the firing angle corresponding to the initial energization current at the start of energization. is set, and the firing angle setting value 8 corresponding to the welding current (corresponding to the welding current) is set in the firing angle setting circuit 6. The relationship between the firing position of each setting value and the power supply phase is shown in FIG.
. Waveform is being output.

When the start signal is turned on in this state, a signal synchronized with the power supply frequency (C in Figure 3) is output from the timing control circuit 14, and the slope is set smaller than the setting value 8 of the ignition angle setting circuit 6. The setting data 3 from the circuit 9 is set via the data selection circuit 11 to a preset counter 12 for counting the ignition angle. The synchronizing signal is also applied to the output control circuit 15 by AND20's 1-f. Therefore, when the count reaches the set value of 3, the output from the preset counter 12 is NANDl6 by the output m' (Fig. 3D), and the negative input is AND via 0R19
20's output "H" (Fig. 3 F) generates a trigger voltage (Fig. 3 G) from the pulse transformer PT of the ignition pulse generation circuit 21, and the SCR for the positive half cycle changes as shown in Fig. 2. It turns on at the ignition angle corresponding to the setting data 8, and after half a cycle, the percentile counter 3 starts counting toward this ignition position. ) is generated, Oko, N
AND 1 7, the AND 20 output becomes "H" again (third
(F), the phase angle O corresponding to the setting data 3 of the negative half cycle is reached, and the SCR for the negative half cycle is triggered as shown in the second diagram and the third diagram G.

That is, as shown in FIG. 3H, the NANDl 6 receives the positive cycle firing signal output from the preset counter 2 (FIG. 3D) and the output of the n frequency division counter 5 synchronized with the power supply (FIG. 3A). Under the NAND AND condition, the firing signal is output at "L" level only in the positive cycle, and NANDl 7 is 0 as shown in Figure 3 (■), and the firing output of preset counter 2 (Figure 3 D) is output in the positive cycle. The negative cycle firing output of the Σ frequency division counter 13 (Fig. 3 E) that occurs with a delay and the IN
NAND condition with the power output from VT18 and the output with the opposite phase (J in Figure 3), the ignition signal is output at "L" level only in the negative cycle, and the negative input 0R19 is as shown in Figure 3. , these positive and negative ignition "L" level signals are combined and output as "H" level ignition signals for positive and negative cycles, and the AND 20 is connected to the timing control circuit 14 as shown in FIG. 3F. The synchronized start signal output synchronously when the power supply rises and the negative input O
The AND condition with the output from the RI 9 (K in FIG. 3) is taken to generate the firing signal for the SCR, and the same firing signal is output to the firing pulse generation circuit 21.

In this way (thus, in the second cycle after the ignition of the first cycle of the power supply frequency is completed), when the output of the n frequency division counter 5 becomes rHJ again, the setting data of the slope preset counter 8 becomes 4. (Since the set value 4 is smaller than the set value 8 of the ignition angle setting circuit 6, the set value 4 of the preset counter 8 is set to the ignition angle count preset counter 2 via the data selection circuit 11. As a result, the output control circuit 15 generates an output rHJ at a phase angle corresponding to the setting data 4 in each positive and negative half cycle, and outputs S for each positive and negative half cycle.
CR is triggered at the phase angle shown in FIG. 2E.

Similarly, as the number of cycles of the power supply frequency progresses, the conduction angle of the SCR increases as shown in FIG. The setting data 8 of the ignition angle setting circuit 6 is repeatedly set in the ignition angle preset counter 12 for each cycle of the power supply frequency because it matches the setting value of the slope preset counter 8 and is smaller than the setting value. .

As a result, from the 6th cycle onwards, the SCR for each positive and negative half cycle is triggered at the phase angle corresponding to the setting data 8 as shown in Figure 2 J to L, and the welding current through the SCR is After the start W generation period shown in FIG. 2M is pressed, the flow slows down as shown in FIG. 2N as a whole.

Furthermore, the welding current can be applied for a certain period of time or every certain cycle (here, the set value of the slope preset counter 8 can be sequentially decreased for each cycle (thereby, the welding current can be easily slowed down). .

Next, the effects of the present invention will be explained.

The present invention is a resistance welding machine that controls welding current according to the conduction angle of a silicon-controlled rectifying element connected to a commercial power supply, and a power supply synchronization signal generation circuit 1 that generates a square wave synchronized with the frequency of the commercial power supply. The square wave from the signal generation circuit 1 is sent to the voltage controlled oscillation circuit 4 via the phase comparator circuit 3.
to generate a clock pulse with a frequency n times the power supply frequency, and also input the same clock pulse to the phase comparison circuit 3/I via the n frequency division counter 5 to output the power supply frequency from the voltage controlled oscillation circuit 4. a frequency multiplier circuit 2 for generating n-multiplied synchronous pulses; a firing angle setting circuit 6 for setting the number of pulses corresponding to the specified firing angle of the silicon-controlled rectifier; and at least one for slowing up and slowing down the welding current. Correspondingly, a slope setting section 7 sets an initial value of the ignition angle that changes every arbitrary cycle of the commercial power supply, and the output of the n-divider counter 5 and the start signal for starting welding current application are manually operated. the timing control circuit 14 of the D-type FF, the output from the timing control circuit 14 (thus, the slope preset counter 8 that starts counting the slope, the firing angle setting circuit 6, and the slope preset counter 8). a data comparison circuit 10 that compares the magnitude of the number of pulses corresponding to the firing angle to be output and outputs one of the number of pulses corresponding to slow-up or slow-down;
A preset counter 12 for counting the firing angle that sets the number of pulses corresponding to the firing angle from the data comparison circuit 10, and a preset counter 12 for counting the firing angle.
Start counting by the output of n/2
Generate an output after a clock pulse count of n/
By using the outputs of the divide-by-2 counter 13, the ignition counting brisset counter 12, and the divide-by-n/2 counter 13 as inputs, the time point at which the output from the preset counter 12 is generated and n
/ an output control circuit 15 that triggers the silicon-controlled rectifier via the ignition pulse generation circuit 21 at each of the output generation points from the divide-by-2 counter 13;
There is a welding current control device that can be attached to a resistance welding machine equipped with both.

With this, the present invention can be used for controlling welding current with a simple circuit.
The CRO ignition position can be easily controlled in synchronization with the power supply frequency, and this allows the conduction angle to be easily and accurately set numerically, as well as to eliminate variations in characteristics between products. Not only can it eliminate differences in the characteristics of the welding machines being controlled, but it can also maintain stable operating characteristics even in the face of fluctuations in power supply voltage, temperature changes, etc. In addition to being able to
The value of the energized current at the start of energization and its slow-up characteristics are approximately the maximum value of safe inrush current determined by the capacity of Cyrisk, etc., that is, excessive inrush, regardless of fluctuations in power supply voltage or changes in welding current. Current (value corresponding to approximately the maximum value of safe inrush current required to prevent damage to the welded surface due to the risk of damage and generation of spatter) (
As a result, even when the power supply voltage fluctuates or the welding current changes, stable welding can be performed without having to make any adjustments to the welding current slow-up, including setting the energization start current. It's effective.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of an embodiment of the present invention, Fig. 2 A-N
and FIGS. 3A to 3G are waveform diagrams showing its operating state. 1...Power synchronization signal generation circuit, 2...
Frequency multiplier circuit, 3... Phase comparison circuit, 4...
...Voltage controlled oscillation circuit, 5...n frequency division counter, 6... Firing angle setting circuit, 7...
・Slope setting section, 8... Slope preset counter, 9... Slope setting circuit, 10.
... Data comparison circuit, 12 ... Preset counter for firing angle count, 13 ... Percentage counter, 14 ... Timing control circuit, 15 ... ...output control circuit, 21.
...Ignition pulse generation circuit.

Claims (1)

[Claims] 1 A resistance welding machine that controls the welding current according to the conduction angle of the silicon-controlled rectifier connected to the commercial power supply.
a power supply synchronization code generation circuit 1 that generates a square wave synchronized with the frequency of the commercial power supply, and a power supply synchronization signal generation circuit 1 for generating a square wave synchronized with the frequency of the commercial power supply.
A square wave from the input signal is input to the voltage controlled oscillation circuit 4 via the phase comparison circuit 3 to generate a clock pulse having a frequency n times the power supply frequency, and the same clock pulse is input to the phase comparison circuit via the n frequency division counter 5. 3 to generate a synchronizing pulse of n times the power supply frequency from the voltage controlled oscillation circuit 4; Angle setting circuit 6 and welding current slow-up/
A slope setting section 7 sets an initial value of the ignition angle that changes with each arbitrary cycle of the commercial power supply in response to a decrease in slowdown, and a slope setting section 7 that sets the initial value of the ignition angle that changes with each arbitrary cycle of the commercial power supply, and a slope setting section 7 that sets the initial value of the ignition angle that changes at every arbitrary cycle of the commercial power supply, D-type FF with start signal as input
a timing control circuit 14, a slope preset counter 8 that starts counting the slope according to the output from the timing control circuit 14, and a firing angle output from the firing angle setting circuit 6 and the slope preset counter 8. a data comparison circuit 10 that compares the magnitude of the number of pulses corresponding to the number of pulses and outputs one of the number of pulses corresponding to the slow-up or slow-down;
A brisset counter 12 for counting the ignition angle that sets the number of pulses corresponding to the ignition angle from the data comparison circuit 10, and a preset counter 12 for counting the ignition angle.
Start counting by the output of n/2
Generate an output after a clock pulse count of n/
The outputs of the 2 frequency division counter 13, the ignition count preset counter 12, and the n/2 frequency division counter 13 are input, and the output generation time from the preset counter 12 and the output generation time from the n/2 frequency division counter 13 are determined. 3. A welding current control device for a resistance welding machine, characterized in that an output control circuit 15 for triggering the silicon-controlled rectifying element via an ignition pulse generation circuit 21 is provided for each of the resistance welding machines.