JPS5847567A - Electric power source for welding - Google Patents

Abstract

PURPOSE:To perform welding work stably by providing a setter for regulation of welding outputs, a detector for actual welding voltage and current, and an operating device for comparison thereof to an electric power supply device for welding devices, and controlling control elements for output voltage and a motor for feeding a welding wire in accordance with the compared values thereof. CONSTITUTION:In an output terminal 14 from a smoothing circuit 13 for DC secondary current in an electric power supply section of a welding device, the welding voltage and current under welding work are drawn out and detected with a shunt 19 for detection and the values thereof are inputted via an input circuit part 21 to a logical arithmetic circuit 22 of a microcomputer. At the same time, the set values of voltage and current are inputted from a setter 20 for regulation of welding outputs to the circuit 22. Both input values are compared and subjected to feedback operation. The voltage of the welding output and the driving of a motor 18 for feeding a welding wire are controlled by control circuits 23, 24 in such a way that the welding output is brought close to the set value infinitely, whereby the welding work is performed stably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a set value i of welding voltage or welding current set by a welding operator (hereinafter referred to as set value) and a detection signal of the voltage value or current value of welding output (hereinafter referred to as detected value). The present invention relates to a welding power supply device equipped with an arithmetic circuit that determines a welding output based on a value (referred to as a value).

Conventionally, this type of output feedback control type welding power supply device uses an operational amplifier 1' to compare and amplify a set value 2 and a detected value 3, as shown in Fig. 1, and the resulting output is used as the welding output. The control element command signal 4 was used. In addition, 6.
6 is a resistor and a capacitor for response time constant, response gain, and gain adjustment. In the method using the operational amplifier shown in FIG. 1, it is difficult to easily interrupt output feedback control and switch to open loop control. i.e. 5
Considering the output characteristics of the welding power supply device and the characteristics of the welding arc, if accurate welding output is not expected or if there is almost no fluctuation in the input power supply voltage, it is better not to perform output feedback control for smoother welding. In some cases, stable surface welding can be maintained by appropriately switching the presence or absence of feedback control depending on whether an arc is obtained or the state of the welding arc.

Therefore, direct feedback control of the welding output can be avoided by others.

The welding power supply system was completely open-loop, in which the welding output was corrected in accordance with the method, and in extreme cases, the welding output was not corrected. This has been dealt with by increasing the response time constant, or by preparing other simulated settings in addition to the settings set by the welding operator depending on the state of the welding arc, and switching the settings at appropriate times. That is, the output characteristic So of the welding power supply device shown in FIG.
, 81.82, if a set value corresponding to ijV+ is applied to one input of the operational amplifier, control can be performed to maintain a constant operating point even in the face of disturbances such as fluctuations in the input power supply voltage. be done. However, if the setting value corresponding to the same vl is inputted for the °C time until the welding arc is generated at the start of welding, the welding arc cannot be generated due to the feedback control function! . In addition, when a welding arc is generated at point M1 and the arc is cut off for some reason and moves to point M0, it is moved to point M3 by feedback control.
As a result, when an arc occurs in this method, a point is reached and the stable range is deviated from.

Therefore, as shown in Fig. 3, when the welding current is not detected, the set values 2 and 2' are switched by the cutoff element 7, and the vO
This was handled by inputting a set value 2' corresponding to Va, or inputting a set value 2' corresponding to Va at the time of so-called high voltage start, which generates an arc at a higher output voltage than during steady welding.

However, if the set value is changed for each state of the welding arc in this way, the switching circuit becomes complicated and expensive.

Further, even if the set value is changed depending on whether or not the welding current is detected, the welding current waveform at the start of welding is generally irregular as shown in FIG. 4a. Therefore, if the welding output during this period is detected and feedback controlled, there is a risk that the welding output will be disturbed.
□For this reason, in conventional control circuits, the response time constant of feedback control is set larger than, for example, the value ts9 in Fig. 4, and as a result, even when a welding arc is generated, the same time constant remains, and the response time constant is set in small steps. It was not possible to perform proper feedback control, and it was not possible to adequately deal with disturbances such as sudden changes in input power supply voltage.

In consideration of the output characteristics of a welding power supply device and the characteristics of a welding arc, which have a slight degree of droop, the present invention compares and calculates a set value and a detected value and outputs a command signal to bring the welding output as close to the set value as possible. It is possible to select between output feedback control to control the set value and control to change the set value to the detected value by switching with a switching element, and simultaneously achieves feedback control with good accuracy and responsiveness and a stable welding arc. be. Below, FIGS. 6 to 6 show an embodiment of the present invention.
Figure 7? This will be explained using drawings.

FIG. 6 shows a block circuit of a welding power supply device according to a first embodiment of the present invention. In FIG. Input/output voltage control element, 13 is a reactor section for adjusting welding characteristics, 14 is an output terminal for welding current waveform, 16 is a workpiece to be welded, 16 is a current supply tip, 17 is a welding wire,
18 is a wire feeding motor, 19 is a shunt for detecting welding current value, 20 is a setting device for adjusting welding output, 21 is welding current,
22 is a logic operation circuit section using a microcomputer or the like; 23 is a control circuit section for the output voltage control element 12; 24 is a motor control circuit section for the wire feeding motor 18; 26 is a feedback circuit section. This is a switching element that selects whether or not to control.

In the block circuit shown in FIG. 6, the output voltage of the welding power supply device is input to the input circuit section 21 together with the welding current value by the shunt 19 that detects the welding current value.

These detected values are input from the input circuit section 21 to a logic operation circuit section 22 composed of a microcomputer or the like.

On the other hand, the set value of the welding voltage or welding current set by the welding operator is inputted to the logic operation circuit section 22 by the setting device 20. By employing this logic operation circuit section 221i, such as a microcomputer, logic operations are executed in a predetermined procedure. In other words, if the switching element 26 that selects the presence or absence of -feedback control is in the null state, the output voltage control element 12 uses the set value from the setter 22 as a command signal, regardless of the detected value from the input circuit section 21. control circuit section 23 or motor control circuit section 24. Also, when the switching element 26 is on the right side of feedback control, the set value from the setting device 2o and the detected value from the input circuit section 21 are compared and feedback calculation is performed, so that the welding output reaches the set value without limit. The command signal is corrected so as to approach the command signal and transferred to the control circuit section 23 and the motor control circuit section 24.

A program flowchart that determines the order of the above tasks.

FIG. 6 shows a case where the switching element 26 of the above example is used as a switching element for detecting welding current. In other words, feedback control is not performed when the welding current is not detected, and feedback control is performed when the welding current is detected.
It is possible to perform highly responsive and accurate welding control.

In addition, in FIG. 7, a welding current multiplying element is used as the switching element 26, a counter buffer 1 is provided in the logic operation circuit section 22, and feedback control is performed after a certain period of time has passed after detecting the welding current. 5 shows a program flowchart.

As described above, the welding power supply device of the present invention is provided with a switching element that switches between feedback control and open-loop control, so when no welding current is detected, feedback control is not performed and the open-loop control number is switched on. open-loop control is performed when the welding current is detected and no welding current is detected, and within a certain period of time after the welding current is detected, and after a certain period of time after the welding current is detected, that is, when the welding arc is It is possible to estimate the time and perform feedback control thereafter. This eliminates the need to prepare and switch alternative setting values for times other than steady welding arc, frees the circuit from complexity, and provides special features for starting welding. Open loop control is used while the welding arc is not stable, and feedback control is applied after the welding arc is sufficiently stabilized. By reducing the response frequency, it is possible to perform feedback control of the welding arc with high accuracy and responsiveness. Moreover, such open loop control,
Automatic switching of feedback control can also be easily performed.

[Brief explanation of drawings]

A circuit diagram of the main parts of the welding power supply device, Fig. 2 is a diagram showing the relationship between the output characteristics and welding arc characteristics of the same welding power supply device for 1°, and Fig. 3 is a diagram showing the main parts of another conventional welding power supply device. 4a and 4b are signal waveform diagrams showing waveform examples of welding current and welding voltage at the time of welding arc start, and FIG. 6 is a block circuit diagram of a welding power supply device according to an embodiment of the present invention. , FIG. 6 is a flowchart showing an example of the block. 19...Shunt device, 2o...Setting device, 2
1... Input circuit section, 22... Logical operation circuit section, 23... Control circuit section, 24...
- Motor control circuit section, 26... switching element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 1111--Time- Figure 6 Figure 7

Claims (1)

[Scope of Claims] (1) Welding in which a welding voltage set by a welding operator or a welding chamber flow set value signal and a detected value signal of a welding output voltage value or current value are input and the welding output is determined. Feedback control includes an arithmetic circuit that outputs one command signal for voltage and welding current, compares and calculates the set value signal and the detected value signal, and outputs a command signal so that the welding output approaches the set value signal as much as possible. A welding power supply device comprising a switching element for switching between open loop control that outputs a set value signal as a command signal without a leap year in the detected value signal.
'(2) The switching element is switched by detecting welding current, and when no welding current is detected, open loop control is performed, and when welding current is detected, feedback control is performed. Range 1
Welding power supply device as described in section. (3) The switching element is switched by detecting the welding current, and open-loop control is performed when no welding current is detected and for a certain period of time after the welding current is detected. The welding power supply device according to claim 1, which performs feedback control after a certain period of time after detecting the welding current.