JPS6213116B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a voltage compensation control device for a resistance welding machine, which not only simplifies the structure but also particularly applies to general spot welding machines, seam welding machines, and projection welding machines with 10 cycles or more. The purpose is to enable voltage compensation control without response delay even when used in combination with a short-time energizing machine such as a welding machine, or in the case of high-speed intermittent energization where even a 1/2 cycle compensation delay is not allowed. do.

In resistance welding, the welding current has a very large effect on the welding state and affects the quality of the product, and must be stably supplied without being affected by the energization of other welding machines. In order to stabilize the welding current, the most accurate method for compensating for fluctuations in welding current due to fluctuations in power supply voltage is to detect electrical quantities such as inter-electrode voltage and impedance from the secondary conductor and calculate these values. There is a method in which the detection signal waveform is compared with a standard waveform at any time, and if the detected signal waveform deviates from the standard waveform, a signal corresponding to the difference is fed back to match the standard waveform. However, since this method attempts to correct the detected signal waveform when it does not match the standard waveform,
A compensation delay occurs between signal detection and output for correction.

This compensation delay has been speeded up to 1/2 cycle response with the development of feedback control, but when using a thyristor etc. to control the welding current, it is difficult to compensate for this when power supply voltage fluctuations occur after ignition. Since it is for the next 1/2 cycle, the response delay of 1/2 cycle is the limit of accuracy for speeding up with the conventional method, and as long as this method is used, it is theoretically impossible to speed up the response any further. It is possible.

By the way, for example, when a plurality of seam welding machines are connected to one electric circuit and energized, a voltage drop generally occurs continuously due to the repetition of welding such as "energization for 1 to 2 cycles" and "pause for 1 cycle."

When one cycle of energization is considered, even if the next half cycle is completely compensated for with a 1/2 cycle response using the conventional method, a fluctuation of 50% remains. Another possible solution is to overcompensate the correction so that the current exceeds the set value in the next cycle to compensate for the shortfall due to fluctuations, so that the effective value is equalized during one cycle. If a power supply voltage fluctuation occurs during the half wave after , it cannot be compensated for. Also, if there is a voltage drop during the previous half wave of one cycle, the current will be small, so this will be compensated for in the next half wave, but at this time, unfortunately, if the power drop has returned, On the contrary, you end up overcompensating. Furthermore, in connection with the above-mentioned conventional method, ``Welding current control method and device in spot welding'' disclosed in Japanese Patent Publication No. 18313/1983 is known. First, the amount of voltage drop due to energization of each welding machine is calculated and determined in advance, and the total voltage drop when energized simultaneously is predicted by calculation.

Second, the no-load welding power supply voltage of the electric circuit is constantly monitored.

Third, the amount of compensation is sampled in multiple stages and a necessary voltage is selected.

Fourth, by performing complex calculations and control such as calculating the predicted value of voltage drop due to simultaneous energization, we can calculate in advance the amount of voltage drop when multiple welding machines are energized at the same time. The voltage is predicted by calculation, and the voltage is controlled in accordance with the actual welding operation.

However, when using this method, it is necessary to perform a large number of complex calculations as described above, which inevitably causes a delay in response. When used in combination with a short-time energizing device such as a welding machine, or in the case of high-speed intermittent energization where even a 1/2 cycle compensation delay is not allowed, it has the disadvantage that it is hardly effective, and as a result, the above-mentioned All of the conventional methods used have limitations in accuracy and are not satisfactory.

In the present invention, even if the above-mentioned limitations of the conventional method are met, that is, fluctuations in the power supply voltage are monitored and the response is made as short as possible, as long as a controlled rectifying element such as a thyristor is used, it is possible to overcome the fluctuations after ignition. It was devised recognizing that it is impossible to make corrections, and in the adjustment stage, the current reduction in the relevant machine due to the energization of other machines is adjusted in advance so that the decrease in current will be minimized while the other machine is energized. This amount is adjusted and added as a correction amount to the original phase control angle of the machine, and during actual operation, the correction amount is added only while the energization time signal of another welding machine is being input to perform predictive control. Therefore, it is an object of the present invention to provide a voltage compensation control device for a resistance welding machine that can perform compensation control with zero response delay for special spot, projection or seam welding that requires a short welding time.

The structure of the present invention will be explained below according to an embodiment shown in the drawings.

In Figure 1, 1 is a welding current setting device (or phase adjuster), which first sets the welding current and then energizes one of the other welding machines that are supplied with power from the same electrical circuit. , adjust the voltage compensation amount adjustment circuit 2 or 3 so that the current is the same when there is no voltage drop due to other equipment and when there is a drop in power supply voltage due to energization of other equipment. Adjust while checking the ammeter etc. Alternatively, in the case where the voltage compensation amount adjustment circuits 2 and 3 are provided with a compensation percentage scale corresponding to the percentage of power supply voltage fluctuation, the scale is adjusted based on the power supply voltage percentage or current reduction percentage if it can be measured. It is also possible.

Reference numerals 2 and 3 are voltage compensation amount adjusting circuits as described above, which are coupled to the welding current setting device 1. By the way, in general, the amount of correction for the same power supply voltage drop value when energizing at an advanced angle in phase control and when energizing at a delayed angle is approximately proportional. That is, the amount of voltage compensation when power is applied in a delayed phase needs to be proportionally smaller than when the power supply voltage drops while power is applied in an advanced phase. In order to reduce this, the inputs of the voltage compensation amount adjustment circuits 2 and 3 are taken from the output of the welding current setting device 1, and as a result, the setting value of the welding current setting device 1 becomes smaller, and the voltage increases. The amount of compensation of the compensation adjustment circuits 2 and 3 also becomes small. In this way, automatic compensation becomes possible without readjusting the voltage compensation adjustment circuits 2 and 3 every time the settings of the welding machine 13 are changed.

4 and 5 are energizing time signals of other welding machines, and the compensation amount of 2 or 3 is changed to 6 or 7 so that compensation due to power drop is performed only during the period when this signal is input.
is transmitted to the adder 8 via.

Reference numerals 9, 10, and 11 are phase control, energization time control, and ignition circuits, respectively, which perform phase control, etc. upon receiving the output of the adder 8, and are connected to the welding machine 13 via a control rectifying element 12 such as a thyristor. energize.

In this embodiment having the above configuration, the compensation operation will be explained. The output of the welding current setting device 1 is a voltage level, and also outputs a phase control angle approximately proportional to the input voltage level to the phase control circuit 9. Then, the phase control angle given by the output voltage level of the welding current setting device 1 is controlled by the phase control circuit 9, the ignition circuit 11, and the control rectifying element 12 such as a thyristor during the time set by the energization time control 10. The welding current flows through the welding machine. Next, when one of the other welding machines, for example, other welding machine A, is to be energized, the energization time signal of the other welding machine A is input, and S ₁
Close 6. At this time, the voltage compensation amount adjustment circuit 2 has previously been adjusted as a voltage amount to compensate for the voltage drop caused by the energization of another welding machine A, so the output of the voltage compensation amount adjustment circuit 2 and the welding current setting device 1 If the outputs of the welding machine A are added by the adder 8, and the phase control circuit 9, the ignition circuit 11, and the control rectifying elements such as the thyristor are applied to the welding machine 13, there will be no control delay with respect to voltage fluctuations caused by other welding machines A. can be compensated.
Next, the above operation will be explained according to the welding voltage waveform shown in FIG.

A shows the waveform of the current flowing through the other welding machine and the resulting voltage drop in the power supply. Note that this figure does not show the voltage drop caused by the welding machine. In other words, in reality, it would be a combination of voltage drops caused by other welding machines and the welding machine in question, but when considering fluctuations in the power supply voltage, a drop in the power supply voltage due to energization of the welding machine is considered a disturbance to the machine. Since this is not the case, there is no need to consider this.

B is a diagram showing the time relationship between the energization time signal and the firing phase of the current of another welding machine, and C is a diagram showing the relationship between the energization time signal and the ignition phase of the welding machine. Furthermore, in D, the time is divided into 0 to 11π, and each half wave of the current of the welding machine is designated as A to H, and the other currents are designated as I to O, and the phase control angle α of the welding machine is generated every time the power supply crosses 0. The synchronizing pulse that is the origin of the phase control angle α is set as the origin of the phase control angle α.

The predictive compensation at time 1π will be explained in terms of timing according to each of the above figures. Just before the current A of the welding machine in question is applied, the energization time signal of the other welding machine has been input to the circuit of the welding machine before that, and the phase with respect to the welding machine current A is not energized by the other welding machine. Sometimes, the ignition is performed by advancing the angle α ₂ which is advanced from the angle α ₃ to be ignited. Then, after the welding machine is ignited with current A, the current J of the other machine is ignited, causing a power supply voltage drop, but since current A is ignited at an advanced phase in anticipation of this, the power supply drop will cause the current A to ignite. No current reduction occurs in the welding machine.

The difference between the conventional voltage compensation method and the present invention, which monitors the power supply voltage and performs voltage compensation, is that in the conventional case, if K of another device fires after D starts energizing (ignition), the current of K Since the power supply voltage drop occurs after D is energized, the power supply voltage has not dropped when D is ignited, so the power supply drop cannot be recognized and voltage compensation for D cannot be performed. On the other hand, in the present invention, since the energization time signal of B is received before D is ignited, the voltage drop due to K is anticipated in advance and ignition is performed at an advanced phase. The machine current will not decrease.

FIG. 3 shows another embodiment, in which the present invention is implemented in constant current control using feedback control, in which 14 is a current detection circuit, 15 is an effective value conversion circuit, 16 is an adder or subtracter, 17 is a current compensation control signal circuit, and other components are the same as those in the embodiment shown in FIG.

In this embodiment having the above configuration, the primary or secondary current of the welding machine is detected by the current detection circuit 14, and this is converted to an effective value by the effective value conversion circuit 15, and the current is converted to an effective value by the current setting device 1. The difference from the set output is obtained by the first adder or subtracter 16, and the adder or subtracter 1
9 is applied to the current compensation control signal circuit 17 which works to reduce the current error with a high-speed response via the phase control circuit 9, and the output of the current compensation control signal circuit 17 and the voltage compensation described above are applied. The output voltages from adjustment circuits 2 and 3 are added by a second adder.
Further, the output of the current compensation control signal circuit 17 or the second adder 8 is connected to a circuit that generates a phase control signal pulse approximately proportional to the input voltage while the energization time control signal 10 of the welding machine is applied. It is given to a certain phase control circuit 9. The output of the phase control circuit 9 is
Ignition circuit 11, control rectifier element 12 such as a thyristor
A welding current is applied to the welding machine 13 through the welding machine 13. In this embodiment, the second adder 8 is configured independently, but the current compensation control signal circuit 17
It may be something that is added within.

According to this embodiment, the voltage drop of related welding machines that send and receive energization time signals is controlled with zero response delay, and other unrelated welding machines that are less affected by power supply voltage fluctuations are controlled. For slight fluctuations in power supply voltage due to energization, including load fluctuations, constant current can be realized by feedback control of one cycle or less.

Further, in the embodiments shown in FIGS. 1 and 3, the purpose is achieved by the configuration of the electronic circuit, but the electrical processing after receiving the energization time signal of another welding machine, for example, a predetermined Calculation of the amount of compensation, addition, phase control, effective value conversion, sequence timing management, etc. can be performed using microcomputer software. Therefore, it is also possible to implement the invention using means corresponding to the elements of the circuits and regulators described above.

Although the above description has focused on a seam welding machine, even spot welding machines where response delay is not a particular problem can be used to compensate for the power supply voltage with a simple circuit with zero response delay by using the first embodiment.
If used in combination with other particularly affected welding machines, it is possible to perform inexpensive high-response power supply voltage compensation. It can also be used as voltage compensation without response delay when used in combination with a general spot welding machine with a cycle capacity of 10 cycles or more and a short-time energizing machine such as a seam welding machine or projection welding machine. As explained in detail above, in the present invention, it is possible to realize voltage compensation with zero response delay, which was impossible with conventional methods, and eliminate current variations due to compensation delay, which are an obstacle to ensuring airtightness in seam welding. It is possible to see a significant improvement in the improvement of the welding process, and in turn, it is possible to improve the quality of the products to be welded and to make the quality uniform.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a welding voltage waveform diagram when the present invention is implemented, and FIG. 3 is a block diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1...Current setter, 8...Adder, 9...Phase control circuit, 11...Ignition circuit.

Claims (1)

[Claims] 1. In an electrical circuit that causes a voltage drop in one welding machine due to the energization of the other welding machine, when receiving an energization time signal from the other welding machine that foretells the occurrence of a voltage drop, the current due to the voltage drop a voltage compensation adjustment means for compensating for the decrease; and an addition means for adding the output of the voltage compensation adjustment means and the setting output of a welding current setting device for setting the welding current of the one welding machine;
It is composed of a phase control means and an ignition circuit that performs phase control in response to the output of the addition means, and a control rectifier such as a thyristor that performs phase control and opening/closing of the welding current in response to a signal from the ignition circuit. Voltage compensation control device for resistance welding machines.