JPS59166371A - Controlling method of starting in current change welding method - Google Patents

Abstract

PURPOSE:To enable sure assignment of H- and L levels in the stage of starting welding and to prevent welding defect by setting a flip-flop circuit in the stage of starting the welding and resetting a counter so that the clocking is started from 0. CONSTITUTION:In the case of an L start, a switch is shifted to a contact L, and a terminal is dropped temporarily to a ground level in the stage of starting the welding, by which a flip-flop circuit 90 is reset to Q=L, Q'=H, and an NAND gate 88 is reset. A light emitting diode is then lighted and a resistance is selected so that the welding voltage is set at a low voltage. The one input terminal of the gate 92 is dropped to the ground through a diode 106 to produce the output of an H level. Counters 62, 64 are thus reset and the clocking is started from the welding start. Since the gate 88 opens, the period L1 when a switch group 70 outputs is selected and the first inversion of the flip-flop 90 takes place after the lapse of the period L1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a start control method for a current change welding method in which a welding current is periodically changed from a large current to a small current.

The current change welding method is equipped with a timer (counter) to periodically switch the welding voltage between high and low voltages, increasing the welding current and increasing the welding current.
Change it to small. The period of high voltage incoming current (hereinafter referred to as H level) and the period of low voltage and small current (also referred to as L level) are accurately regulated by the timer during welding, but at the start of welding Since the timer is not synchronized with the start and stop of welding, it is uncertain whether the timer will start from H (high) level or L (low) level, and where in the H1L level period the time will start. If there is variation in the bead formation during the welding process, and if it is possible to adopt a method of using a tab plate and forming the start bead on the tab plate, we recommend that you
In circumferential welding, the start bead is also aligned with the intermediate bead, which may result in a defective weld.

The present invention improves this point and does not attempt to make the H and L levels and the start timing constant at the time of welding start. Although it is often preferable to start welding at an H level, there are also cases where it is better to start welding at an L level. Therefore, in the present invention, the H1L level at the start can be arbitrarily selected. This will be explained in detail below with reference to the drawings.

FIG. 1 shows an outline of the electrical system of a welding device that performs a current change welding method. 10 is a transformer, 3-phase AC power supply R, S,
It is connected to T and outputs stepped-down three-phase AC. 12 is a rectifier including a control element such as a silice or a transistor, and outputs a variable DC voltage. 2 and 3 are output terminals of the variable DC voltage, to which the welding torch and the base metal are connected.

14 is a glue handle for preventing rush current, 16 is a shunt for current detection, 18 is an amplifier, and 20 is a current relay. 22 is connected to two phases R and S of a three-phase AC power supply via a control circuit transformer 24, and includes a wire feed motor 26, a shield gas solenoid valve 28, a voltage adjustment circuit 30, and a wire inching push button switch PBl. , welding start/stop push button switch PB2, etc. are connected.

Although not shown, a rectifier for control power supply is connected to the three-phase AC power supplies R, S, T, and the first and second control circuit networks 40 shown in FIG. 2 are supplied with power from the overflow device.

In this Figure 2, X2 is a control relay, which has a normally open contact X2a and a normally closed contact X2b, which are connected to the voltage regulator circuit 3 in Figure 1.
0 high voltage setting resistor 32, low voltage setting resistor 34,
and a light emitting diode 42 for indicating a high voltage period in FIG.
It is connected to a light emitting diode 44 etc. for displaying the same voltage period.

46 is a resistor, and 48 is a diode for absorbing back electromotive force.

Further, SWl is a mode selection switch, which selects H1 low current welding during large current welding, and moves the movable element to P during current change welding. During current change welding, the welding current is changed from large to small at a predetermined cycle, and this circuit provides three types of cycles. Switch SW3 is used to select this, and when the mover is brought into contact with contact 1, the H level period is H.
Condition 1: L level period is Ll; Condition 2: when contacting contact 2, H level period is H2, L level period is L2.
, when contacting the contact point 3, select condition 3 in which the H level period is H3 and the L level period is L3. 50, 52° and 54 are light emitting diodes, each of which emits light under the condition of 1.2°3. Switch SW2 is a mode selection switch when starting welding. Pushing it to the H side will start at the H level, and pushing it to the L side will start at the L level. Xlb is a normally closed contact of the current relay 20, Vcc is the high potential side of the power supply, and GND is the low potential side (ground) of the power supply.

FIG. 3 shows a specific example of FIG. 2, and the same parts are given the same reference numerals. 60 is a clock oscillator, and a counter 62 divides the frequency of the output clock of the oscillator and divides 0 to 0.9 seconds into 0.
Outputs a, b, shown in 4-bit 7-bit BCD code shown in 1 second vehicle position,
produces c and d. A power pump 64 divides the overflow output of the counter 62 to generate a 2-bit BCD code f indicating 0 to 3 seconds in 1 second positions. Reference numeral 66 denotes a cycle setting circuit, which includes a large number of switches 68, 70 . . . . and diodes 72, 74, . ...Take it out. Although only the Hl and Ll circuits are shown in the figure, H2, L2. H3
, L3 are also provided with similar circuits. Selection of these periods I(1, , Ll,...) is made using switch SW3.
etc. For example, when the movable element of the switch SW3 is moved to the contact point 1, the b output of the flip-flop circuit 80 becomes T-1, and the Nant gates 86 and 88 are opened.

When the movable element of the switch SW3 is moved to the contacts 2 and 3, the Q outputs of the flip-flop circuits 82 and 84 become H, and H2 (not shown), 2. The Nantes gate for H3 and L3 opens. The Q and Q outputs of the flip-flop circuit 90 are also input to the inputs of these Nant gates, and their role will be described later. Each Nantes gate 86.8B,...
The outputs of ・ are combined by a gate 92 with OR Rfil,
The signal is guided to the clock terminal C of the flip-flop circuit 90.

The cent terminal S and the recent terminal R of the flip-flop circuit 90 are connected to the terminals ■ and ■, and the switch SW2 in FIG.
is selectively connected to ground GND. Further, a photocoupler 96 is connected to the Q output terminal via an inverter 94, and this photocoupler energizes a relay CR corresponding to the aforementioned relay X2. The output of gate 92 is connected to inverter 98
The counters 62 and 64 are used for cents through the counters 62 and 64.

To explain the start control of the present invention, at the start of welding, switch SW2 in FIG. 2 is turned to either contact H or L depending on whether H start or L start is selected. In the neutral state shown in the figure, a random start occurs. Also switch SW3
Operate to select any of conditions 1, 2, and 3. Condition 1
If you select , the flip-flop circuit 80 in FIG.
b output becomes H, Nantes gate 86.88 opens,
Then, the output of the inverter 100 becomes Llζ and the light emitting diode 50 lights up, indicating that condition 1 has been selected. Next, when push button switch PB2 attached to the welding torch is pressed to instruct welding to start, shielding gas supply, power supply, wire feeding, etc. are performed and welding starts. At this time, the movable element of switch SW2 is The closed contact Xlb is temporarily connected to the ground GND via the push button switch PB2 (until the welding current flows and the current relay 20 opens the normally closed contact Xlb. The push button switch PB2 is normally opened after that), and the switch SW2 is connected to the ground GND. If the contact H side is selected, the terminal ■ will be momentarily dropped to the ground potential. As a result, the flip-flop circuit 90 is set to make the Q output H and the Q output L, and the gate 92 is grounded via the diode 102, causing the output to be H.
Make it.

The H output of this gate 92 is inverted by an inverter 98 to become L, and is input to the counters 62 and 64 to reset them. In this way, the counters 62 and 64 are reset at the start of welding and start counting from zero. These counters are so to speak synchronized with the start of welding at the start, and there is no problem that the H and L level periods at the start of welding are different in length as in the conventional method.

The H level Q output of the flip-flop circuit 90 is applied to the Nant gate 86, and the H level Q output of the flip-flop circuit 90 is applied to the H level Q output of the flip-flop circuit 90.
Along with the output, the Nant gate 86 is opened and inverted by the inverter 94 to generate a light emitting diode of the photocoupler 96, which turns on the phototransistor, turns on the relay control transistor 104, and energizes the relay CR. Relay CR corresponds to relay X2 in FIG. 2, and when energized closes contact X2a and opens contact X2b. Therefore, the light emitting diode 42 lights up indicating that the H level has been selected, and the high voltage setting resistor 32 in FIG.
is selected and the welding voltage is made high. The above-described operation of relay X2 in FIG. 2 occurs when the movable element of switch SWI is brought into contact with contact P. The L level Q output of flip-flop 9° in FIG. 3 is applied to Nandt gate 88, closing it. Therefore, the first selection is the H1 output from the switch group 68, which remains at L level for the time selected by the switch group 68 from the start of welding.
Therefore, the output of the Nant gate 86 is H, and the output of the gate 92 is L. When the period H1 elapses, the H1 output becomes H level, and therefore the output of the Nantes gate 86 and the gate 9
The output of 2 becomes H, which resets the counters 62 and 64 and starts counting again, and also inverts the flip-flop circuit 90 so that Q=L and Q-H. As a result, relay CR is deenergized, opening contact X2a, and X 2 b.

When the light emitting diode 42 indicating the H level is closed, the light emitting diode 42 turns off.
Instead, the light emitting diode 44 lights up, indicating that the switch has been made to the L level, and the resistor 32 that sets the high voltage is disconnected, and the resistor 34 that sets the low voltage is selected instead, and the welding voltage is reduced to a low voltage. do.

Also, the Nantes Gate 86 is closed, and the Nantes Gate 88 is replaced.
is opened, and Ll output by the switch group 7o is selected.

In this case, the output of the pull circuit 90 is inverted as in the case of the output H1. Thereafter, the same operation is repeated, and the welding voltage is kept high during the period L1 and low voltage during the period L1.

For L start, turn switch SW2 in Figure 2 to the contact position. As a result, the terminal ■ in Figure 3 is temporarily dropped to ground level at the start of welding, and the flip-flop circuit 9
0 is reset and Q=L.

Q=H, Nandt gate 88 is opened, relay CR is deenergized, contact 2Xb is closed, 2Xa is released, light emitting diode 44 is turned on, resistor 34 is selected and welding voltage is set to a low voltage. Also, through the diode 106, the gate 9
2 has its 1 input terminal grounded to produce an H level output. This resets the counters 62 and 64 and starts timing from the start of welding. Since the Nant gate 88 is opened, the period L1 in which the switch group 70 outputs is selected, and the first inversion of the flip-flop 90, etc. occurs after the period L1 has elapsed. The subsequent operation is the same as in the case of H level start.

In Figure 1, 35 is the wire feed amount setting circuit, and in Figure 3, ■
108 and 110 are terminals for monitoring, and 108 and 110 change the H2L period. For example, if you change from HI, L+ to H2, L2, and the change is made at H+', the period will change to L2 after the end of period H1. This is a delay mode circuit when switching timing.

As explained above, according to the present invention, in the current change welding method, it is possible to reliably specify the H level and L level at the start of welding, and also to start the period from the beginning, such as in circumferential welding. Even in such cases, welding can be performed without any welding defects at the start.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing an outline of a welding apparatus for carrying out a current change welding method, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. In the drawing, 62.64 is a counter that counts the clock;
6 is a cycle setter, CR, 32 and X2a. 34 and X2b are circuits for switching the welding voltage set value between high and low, 90 is a flip-flop circuit, and SW2 is an H/L level start selection switch. Applicant: Nippon Steel Welding Industry Co., Ltd. Representative Patent Attorney Minoru Aoyagi (LLIE)

Claims (1)

[Claims] In a start control method for a welding method in which welding current is periodically changed between a large current and a small current, the output of a counter that counts clocks is selected by a cycle setting circuit to determine the H level period and the L level period. The circuit that switches the welding voltage setting value between high and low is controlled by the output of the flip-flop circuit.
The state of the flip-flop circuit is reversed at the end of each H and L level period using the output of the period setting circuit to switch the welding voltage between high and low, and when welding starts, either H level restart or L level start is performed. A current characterized in that the set terminal or reset terminal of the flip-flop circuit is temporarily set at ground level according to the above, and the flip-flop circuit is set or reset, and the counter is reset to start timing from O. Variation welding methods.