JP2004314098A - Arc welder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the application of a high no-load voltage during downtime of work which occurs in coated arc welding (manual welding) with an arc welding machine. <P>SOLUTION: The arc welding machine comprises a welding power source main circuit which converts and supplies the voltage suitable for arc working, an auxiliary power source circuit which supplies the auxiliary voltage lower than the no-load voltage of the welding power source main circuit, a short circuit detection circuit which discriminates the contact of a welding rod with welded objects, an arcing discrimination circuit which discriminates the output current of the welding power source main circuit as arcing when the output current is outputted within the time for monitoring the output current, and a main control circuit which supplies the auxiliary voltage when a manual welding mode is selected, drives the welding power source main circuit and stops driving of the auxiliary power source circuit when a short circuit detection signal is outputted, continues the driving of the welding power source main circuit when an arcing discrimination signal is outputted, stops the driving of the welding power source main circuit and supplies the auxiliary voltage by again driving the auxiliary power source circuit unless the above signal is outputted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an arc welding machine capable of selectively switching between two types of high and low no-load voltages.
[0002]
[Prior art]
When performing covered arc welding (hand welding) with the conventional arc welding machine shown in FIG. 6, the first thyristor 2 and the third thyristor 4 are used at both ends of the total number of turns of the secondary winding of the welding transformer 1. The first tap having half the total number of turns is connected to the current-carrying portion 9 of the manual welding holder 8, and when performing CO2 arc welding, the second thyristor is connected to the number of turns of N1 turns. 3 and a first thyristor 2 connected to the winding start side are used, and the CO2 welding torch 10 is connected to a third tap having half the number of turns of N1 turns from the winding start.
[0003]
That is, the torch 10 for CO2 welding and the current-carrying part 9 of the holder 8 for manual welding are directly connected to the neutral point of the secondary winding of the welding transformer 1 through which current flows by the thyristors 3 and 4 selected by each welding method. Because of the connection, the output of the CO2 welding torch 10 having a low no-load voltage characteristic suitable for CO2 arc welding is output to the energizing portion 9 of the manual welding holder 8 having a high no-load voltage suitable for manual welding. Each output is output. (See Patent Document 1)
[0004]
[Patent Document 1]
JP-A-11-58009
[Problems to be solved by the invention]
In covered arc welding (manual welding) of a commonly used arc welding machine, a high no-load voltage is applied when the work is stopped. As a countermeasure, a welding power supply using an inverter circuit controls the average voltage of no-load voltage during work suspension to a low level, detects that the covered arc welding rod has contacted the workpiece, and immediately reduces the no-load voltage immediately after the detection. And the welding was started. However, even if the average voltage of the no-load voltage is controlled to be low, a pulse waveform having a short pulse width and a high peak voltage is applied. Further, a bleeder resistor having a large capacity is required to maintain the stability of the constant voltage control, which leads to an increase in the size of the device and an increase in cost.
[0006]
[Means for Solving the Problems]
A welding power supply main circuit INV that rectifies an AC power supply and converts it into a DC voltage, converts the converted DC voltage into a voltage suitable for arc machining, and supplies the voltage to the workpiece, An auxiliary power supply circuit AD for supplying an auxiliary voltage lower than the no-load voltage of the welding power supply main circuit INV between the rod ES and the workpiece WT; When the value of the auxiliary voltage is lower than a predetermined short-circuit reference value upon contact, the short-circuit detection circuit SD that outputs the short-circuit detection signal Sd by determining that the contact has occurred, and outputs the short-circuit detection signal Sd with a predetermined value. An output current monitoring time T1 is provided and the output current of the welding power supply main circuit INV is monitored. When the output current is output within the output current monitoring time T1, it is determined that an arc has occurred, and an arc generation determination signal is generated. d, an arc generation discrimination circuit ED that outputs d, and when the covering arc welding mode is selected, the auxiliary power supply circuit is driven to supply an auxiliary voltage. When Sd is output, the welding power supply main circuit INV is driven and the driving of the auxiliary power supply circuit AD is stopped. When the arc generation determination circuit ED outputs the arc generation determination signal Ed, the welding power supply main circuit INV is driven. If the arc generation discrimination signal Ed is not output, the main control for stopping the driving of the welding power supply main circuit INV and subsequently performing the sequence control for driving the auxiliary power supply circuit AD again to supply the auxiliary voltage is performed. An arc welding machine comprising a circuit SC.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an electrical connection diagram of the arc welding machine of the present invention. In FIG. 1, a welding power source main circuit INV converts an input voltage into a voltage suitable for arc machining and supplies the voltage to a coated arc welding rod ES.
[0008]
The welding power supply main circuit INV shown in FIG. 4 includes a primary rectifier circuit DR1 for rectifying an AC power supply AC and converting it to a DC voltage, a smoothing capacitor C1 for smoothing the DC voltage, and converting the smoothed voltage to a high-frequency AC voltage. An inverter circuit IV for converting, a main transformer INT for converting the high-frequency AC voltage into a voltage suitable for arc machining, a secondary rectifier circuit DR2 for converting an output of the main transformer INT to a DC voltage, and a DC reactor L And formed. Further, although the welding power supply main circuit INV uses the inverter system, it goes without saying that the thyristor system can be used.
[0009]
The changeover switch SW is a changeover switch having two contacts, a contact a and a contact b, for selecting a welding method. TIG is selected by selecting the above-mentioned a-contact, covering arc welding (manual welding), and selecting the b-contact. It becomes welding. When the covering arc welding (manual welding) is selected, the main control circuit SC outputs a covering arc welding control signal Th, and in accordance with the covering arc welding control signal Th, a short-circuit detection circuit SD and an arc generation shown below. The detection circuit TC is operated and the output of the welding power supply main circuit INV is controlled according to the value of the output current detection signal Id. When the changeover switch SW is selected as the b-contact and TIG welding is performed, the operations of the auxiliary power supply circuit AD, the short-circuit detection circuit SD, and the arc occurrence determination circuit TC are stopped, and the operations are started according to the torch switch TS.
[0010]
The output current detection circuit ID detects an output current and outputs an output current detection signal Id, and the output voltage detection circuit VD detects an output voltage and outputs an output voltage detection signal Vd.
[0011]
The short-circuit detection circuit SD shown in FIG. 2 includes a short-circuit reference value setting circuit VR, a comparison circuit CP, and a second AND circuit AND2. The short-circuit reference value setting circuit VR has a predetermined short-circuit reference value Vr. The comparison circuit CP compares the value of the output voltage detection signal Vd with the short circuit reference value Vr, and determines that a short circuit occurs when the value of the output voltage detection signal Vd is smaller than the short circuit reference value Vr. Then, the comparison signal Cp is set to High level and output. The second AND circuit AND2 performs an AND logic operation between the High level of the covered arc welding control signal Th and the High level of the comparison signal Cp to output the short-circuit detection signal Sd at the High level.
[0012]
The arc occurrence determination circuit ED shown in FIG. 2 is formed by an output current reference value setting circuit IR, a second comparison circuit CP2, a delay circuit DL, a timer circuit MM, and an arc occurrence detection circuit TC. Sets an output current reference value Ir of a predetermined value, and the second comparison circuit CP2 compares the value of the output current detection signal Id with the output current reference value Ir to calculate the output current detection signal Id. Is larger than the output current reference value Ir, it is determined that the output current has been output by the covered arc welding (manual welding), and the output current detection signal Wcr is set to High level and output. The delay circuit DL delays the output current detection signal Wcr by a predetermined time and outputs the output current detection signal Wcr as an output current delay signal Wl.
[0013]
The timer circuit (monostable multivibrator) MM shown in FIG. 2 outputs the timer signal Mm of the output current monitoring time T1 having a predetermined value when the short-circuit detection signal Sd becomes High level, and the arc delay signal W1 becomes High level. , The timer signal Mm is set to the low level. The arc generation detection circuit TC enters an operation start state when the covering arc welding control signal Th becomes High level, and changes the arc generation detection signal Tc to Low level when the timer signal Mm is input. During the period when the timer signal Mm is at the high level, the output current detection signal Wcr is sequentially monitored. When the output current detection signal Wcr is at the high level, it is detected that an arc has occurred, and the low level of the arc occurrence detection signal Tc is detected. To maintain. The AND circuit AND shown in FIG. 1 takes the AND logic of the coating arc welding control signal Th and the arc occurrence detection signal Tc to set the arc occurrence determination signal Ed to a low level.
[0014]
The auxiliary power supply circuit AD shown in FIG. 3 is formed by an auxiliary transformer TI, a rectifier circuit DR3, a smoothing capacitor C2, a switching element TR1, and a current limiting resistor R. The auxiliary transformer TI covers the input voltage by arc welding (hand welding). ), The rectifier circuit DR3 rectifies the output voltage of the auxiliary transformer TI, and the smoothing capacitor C2 smoothes the rectified voltage. The switching element TR1 outputs an auxiliary voltage of the auxiliary power supply according to the arc occurrence determination signal Ed, and the current limiting resistor R limits the output current of the auxiliary power supply. Further, the value of the auxiliary voltage of the auxiliary power supply is set by the auxiliary transformer TI so as to be lower than the value of the no-load voltage of the welding power supply main circuit INV.
[0015]
FIG. 5 is a timing chart for explaining the operation when the arc welding machine of the present invention shown in FIG. 1 is selected in the covering arc welding mode (manual welding). The operation of the present invention shown in FIG. 1 will be described with reference to the timing chart shown in FIG. 5A shows the output voltage detection signal Vd, FIG. 5B shows the covering arc welding control signal Th, FIG. 5C shows the short-circuit detection signal Sd, and FIG. Shows a timer signal Mm, FIG. 5E shows an arc occurrence detection signal Tc, and FIG. 5F shows an arc occurrence determination signal Ed. FIG. 5G shows the output current detection signal Wcr, and FIG. 5H shows the output current delay signal Wl.
[0016]
At time t = t1 shown in FIG. 5A, when the covered arc welding rod ES comes into contact with the workpiece WT and starts covered arc welding, the output voltage detection circuit VD detects the output voltage and detects the output voltage. A signal Vd is output, and the short-circuit detection circuit SD compares the value of the output voltage detection signal Vd with the short-circuit reference value Vr and determines that contact has been made when the value of the output voltage detection signal Vd is smaller than the short-circuit reference value Vr. Then, the short-circuit detection signal Sd shown in FIG.
[0017]
At time t = t1, when the short-circuit detection signal Sd becomes High level, the timer circuit MM changes the timer signal Mm to High level during the output current monitoring time T1 shown in FIG. When the timer signal Mm becomes High level, the arc occurrence detection circuit TC makes the arc occurrence detection signal Tc Low level. Further, when the arc occurrence detection signal Tc goes low, the AND circuit AND also outputs an arc occurrence determination signal Ed of the output signal low. When the arc occurrence determination signal Ed goes to a low level, the switching element TR1 of the auxiliary power supply circuit AD shown in FIG. 3 is cut off to stop supplying the auxiliary voltage. Further, the arc generation discrimination signal Ed changes from a low level to a high level by the inverting circuit IN and is input to the main control circuit SC. The main control circuit SC drives the welding power supply main circuit INV when the input signal becomes High level.
[0018]
The arc occurrence detection circuit TC sequentially monitors the output current detection signal Wcr during the output current monitoring time T1 shown in FIG. 5D, and outputs the output current detection signal Wcr during the output current monitoring time T1. If the level does not reach High level, it is determined that the arc generation has failed, and at time t = t2, the arc generation detection signal Tc is set to High level.
[0019]
At time t = t2, the AND circuit AND takes the AND logic of the covered arc welding control signal Th and the arc occurrence detection signal Tc to set the arc occurrence determination signal Ed to a high level. When the arc occurrence determination signal Ed becomes High level, the switching element TR1 shown in FIG. 3 is turned on to supply the auxiliary voltage of the auxiliary power supply circuit AD again. Further, when the inversion signal of the arc generation determination signal Ed becomes Low level by the inversion circuit IN, the main control circuit SC stops driving the welding power supply main circuit INV.
[0020]
At time t = t3 shown in FIG. 5 (A), when the covered arc welding rod ES again comes into contact with the workpiece WT, the covered arc welding starts, and the output voltage detection circuit VD detects the output voltage and detects the output voltage. A signal Vd is output, and the short-circuit detection circuit SD compares the value of the output voltage detection signal Vd with the short-circuit reference value Vr, and determines that a contact has occurred when the value of the output voltage detection signal Vd becomes smaller than the short-circuit reference value Vr. Then, the short-circuit detection signal Sd shown in FIG.
[0021]
At time t = t3, when the short-circuit detection signal Sd shown in FIG. 5C goes high, the timer circuit MM changes the timer signal Mm to high level and outputs it. When the timer signal Mm becomes High level, the arc occurrence detection circuit TC makes the arc occurrence detection signal Tc Low level. Further, when the arc occurrence detection signal Tc goes low, the AND circuit AND also outputs an arc occurrence determination signal Ed of the output signal low. When the arc occurrence determination signal Ed goes to a low level, the switching element TR1 of the auxiliary power supply circuit AD shown in FIG. 3 is cut off to stop supplying the auxiliary voltage. Further, when the arc occurrence determination signal Ed changes from the low level to the high level and is input by the inversion circuit IN, the main control circuit SC drives the welding power supply main circuit INV.
[0022]
At time t = t4, when the value of the output current detection signal Id becomes larger than the output current reference value Ir, the second comparison circuit CP2 changes the output current detection signal Wcr to a high level and outputs it. When the output current detection signal Wcr goes high within the output current monitoring time T1, the arc occurrence detection circuit TC determines that an arc has occurred, and maintains the low level of the arc occurrence detection signal Tc. Further, an arc generation discrimination signal Ed obtained by taking an AND logic of the covered arc welding control signal Th and the arc generation detection signal Tc by the AND circuit AND is also maintained at a low level. The inversion signal maintains the High level, and the main control circuit SC continues to drive the welding power supply main circuit INV.
[0023]
At time t = t5, the output current detection signal Wcr is output by the delay circuit DL as an output current delay signal Wl delayed by a predetermined time T2 shown in FIG. 5G, and the timer circuit MM outputs the output current delay signal Wl. The timer signal Mm is set to the Low level when the signal becomes the High level.
[0024]
At time t = t6, when the value of the output current detection signal Id becomes smaller than the output current reference value Ir, the second comparison circuit CP2 changes the output current detection signal Wcr to a low level and outputs it. When the output current detection signal Wcr goes to a low level, the arc occurrence detection circuit TC determines that the arc has been cut and sets the arc occurrence detection signal Tc to a high level. Further, the arc generation determination signal Ed obtained by taking the AND logic of the covered arc welding control signal Th and the arc generation detection signal Tc by the AND circuit AND becomes High level, the switching element TR1 shown in FIG. Is supplied again. Further, when the inverted signal of the arc occurrence determination signal Ed becomes low level by the inverting circuit IN, the main control circuit SC stops driving the welding power supply main circuit INV.
[0025]
【The invention's effect】
In the present invention, by providing the auxiliary power supply circuit that outputs an auxiliary voltage lower than the no-load voltage of the welding power supply, a high no-load voltage is prevented from being applied when the work in the covered arc welding (manual welding) is stopped. Further, a bleeder resistor having a large capacity for maintaining the stability of the constant voltage control is not required, so that the device can be prevented from being increased in size and cost.
[Brief description of the drawings]
FIG. 1 is an electrical connection diagram of the arc welding machine of the present invention.
FIG. 2 is a detailed connection diagram of a power supply control circuit and a short-circuit detection circuit shown in FIG.
FIG. 3 is a detailed connection diagram of the auxiliary power supply circuit shown in FIG. 1;
FIG. 4 is a detailed connection diagram of the welding power source main circuit shown in FIG.
FIG. 5 is a timing chart for explaining an operation when the arc welding machine of the present invention shown in FIG. 1 is selected in a covered arc welding output mode (manual welding).
FIG. 6 is an electrical connection diagram of a conventional arc welding machine.
[Explanation of symbols]
AD auxiliary power supply circuit AND AND circuit AND2 Second AND circuit C1 Smoothing capacitor C2 Smoothing capacitor CP Comparison circuit CP2 Second comparison circuit DL Delay circuit DR1 Primary rectifier circuit DR2 Secondary rectifier circuit DR3 Rectifier circuit ED Arc occurrence determination circuit ES Arc welding rod HH Hand welding holder ID Output current detection circuit IN Inversion circuit IR Output current reference value setting circuit IV Inverter circuit INT Main transformer INV Welding power supply main circuit L DC reactor MM Timer circuit (monostable multivibrator)
R Current limiting resistor SC Main control circuit SD Short circuit detection circuit SW Changeover switch TC Arc generation detection circuit TI Auxiliary transformer TR1 Switching element TS Torch switch VR Short circuit reference value setting circuit VD Output voltage detection circuit WT Workpiece Ed Ed Arc discrimination Signal Id Output current detection signal Ir Output current reference value Mm Timer signal (monostable multivibrator signal)
Sc Main control signal Sd Short circuit detection signal Th Covered arc welding control signal In Inversion signal Vr Short circuit reference value Ts Start signal Vd Output voltage detection signal Wcr Output current detection signal Wl Output current delay signal T1 Output current monitoring time

Claims (1)

A welding power supply main circuit that rectifies an AC power supply, converts the converted DC voltage into a DC voltage, converts the converted DC voltage into a voltage suitable for arc machining, and supplies the voltage to the workpiece, and a coated arc welding rod and the workpiece. An auxiliary power supply circuit for supplying an auxiliary voltage lower than the no-load voltage value of the welding power supply main circuit between the welding power source and the covered arc welding rod in contact with the workpiece; If the value is lower than the value, a short-circuit detection circuit that determines that contact has occurred and outputs a short-circuit detection signal, and provides an output current monitoring time of a predetermined value when the short-circuit detection signal is output and monitors the output current of the welding power supply main circuit. When the output current is output within the output current monitoring time, an arc occurrence determination circuit that determines that an arc has occurred and outputs an arc occurrence determination signal; When the auxiliary circuit is supplied by driving the power supply circuit, and then the short-circuit detection circuit determines that there is a contact and outputs a short-circuit detection signal, the welding power supply main circuit is driven and the driving of the auxiliary power supply circuit is stopped. When the arc occurrence determination circuit outputs an arc occurrence determination signal, the driving of the welding power supply main circuit is continued.When the arc generation determination signal is not output, the driving of the welding power supply main circuit is stopped. And a main control circuit for performing a sequence control for supplying the auxiliary voltage by driving the arc welding machine again.

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