JPH07251269A - Consumable electrode arc welding machine - Google Patents

Abstract

PURPOSE:To make a welding current almost constant ana to uniform a penetration depth on a welding part by comparing a detecting signal from a detecting means and a set signal of its welding current set in a welding current setting circuit, amplifying a wire feeding speed signal in a specific amplifying ratio, and controlling a motor driving circuit. CONSTITUTION:An operation amplifier OPI in a welding current feed back circuit 13 amplifies with comparing a welding current signal I and a welding current set signal i, and outputs a voltage Vd as its result to a comparator CP. The comparator CP compares the voltage Vd and a voltage Vk in a saw tooth like wave generating circuit 16, and outputs a signal a to a multiplication circuit 21 and a buffer BF. Then, the multiplication circuit 21 amplifies the wire feeding speed setting signal s in the amplification factor Z with the signal a and the signal b, and makes it into a signal m. The amplification factor to is, in comparing the detecting signal a and the set signal b, that it is 1 to 1.3 times in a case or b>=a, 1 time in a case of b=a, 1 to 0.7 times in a case of b<=a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode type arc welder.

[0002]

2. Description of the Related Art In a consumable electrode type arc welder having a constant voltage external characteristic, a wire is fed at a constant speed. In recent years,
An consumable electrode type arc welder is provided in which an output current feedback circuit for comparing a preset welding current value with a detected welding current is provided and the wire feeding speed is controlled by the output of the output current feedback circuit. ◆ According to the consumable electrode type arc welder having the above function, the welding current becomes substantially constant even if the wire protrusion length changes, and the penetration depth of the welded portion can be made uniform. ◆

[0003]

However, when the wire feeding speed is controlled by comparing the preset welding current value with the detected welding current, there are the following problems.
◆ It is difficult to control the start of welding. That is, since the welding current is fed back, the comparison cannot be made at the start of welding when the welding current is not flowing, and therefore the wire feeding speed cannot be set. ◆ Control becomes unstable because the output of the output current feedback circuit for the change of the wire protrusion length is the whole range of the wire feeding speed control range. The object of the present invention is to solve the above-mentioned problems and to make the welding current substantially constant over the entire welding time including the start time with respect to the change in the wire protrusion length, and to make the weld penetration depth uniform. An object is to provide a consumable electrode type arc welder.

[0004]

According to the present inventor, the amount that needs to be corrected for the change in the wire protrusion length is ± 30 with respect to the welding wire feeding speed at the standard wire protrusion length.
We found that it was good within%. As a result, the problems described above include a welding current setting circuit, a wire feeding speed setting circuit that outputs a wire feeding speed signal according to the welding current set in the welding current setting circuit, and a welding current detection unit. When,
When the detection signal from the welding current detection means and the welding current setting signal set by the welding current setting circuit are compared, setting signal ≧ detection signal, 1 to 1.3 times, setting signal = detection signal 1 time, 1 to 0.7 when setting signal ≤ detection signal
This is solved by providing an amplifier circuit for double-amplifying and a motor drive circuit, and controlling the motor drive circuit by amplifying the feed speed signal of the wire by the amplifier circuit. Further, by further providing means for setting the amplification factor to 1 when the detection signal from the welding current detecting means is 0, the problem can be solved more effectively.

[0005]

When the welding is started, the wire feeding speed signal set by the wire feeding speed setting circuit is used as it is, so that the start becomes stable. Also, during welding, the wire feeding speed is kept within ± 30% of the wire feeding speed set by the wire feeding speed setting circuit even if the wire protrusion length changes, so that it stabilizes as a feedback system. , The arc becomes stable.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. ◆ In the figure, 1 is an output voltage setting circuit for setting the output voltage of the consumable electrode type arc welding machine. Reference numeral 2 denotes a DC power supply whose external characteristic is a constant voltage characteristic, and applies the voltage set in the output voltage setting circuit 1 between the contact tip 3 and the base material 4. A wire feeding roller 5 feeds a wire 7 by a wire feeding motor 6. A motor drive circuit 8 drives the wire feeding motor 6 according to the value of the motor control signal m output from the control circuit 9. Then, the control circuit 9 is configured as follows. That is, 11 is a welding current setting circuit, which outputs a welding current setting signal i. ◆ 13
Is a welding current feedback circuit, which compares and amplifies the welding current signal I from the shunt 14 and the welding current setting signal i, and outputs the result to the + side of the comparator CP. A signal generator 15 outputs a signal j when the welding current signal I is zero. R1 in the welding current feedback circuit 13 is a feedback resistor. D1 and D2 are diodes. ZD1,
ZD2 is a Zener diode, which prevents saturation of the operational amplifier OP1 and at the same time limits the output voltage range of the operational amplifier OP1. C1 is an electrolytic capacitor, which is a delay element of 0.1 to 1 second. SW1 is an analog switch, which is turned on by a signal j when the welding current I is not flowing to make the output of the operational amplifier OP1 approximately 0V. R2 is a current limiting resistance due to the discharge of C1. Further, R3 to R5 are resistors. ◆
Reference numeral 16 is a sawtooth wave generating circuit, which has ZD1, centered at 0V.
A sawtooth voltage having a frequency of 1 kHz that changes to a voltage substantially equal to ZD2 is generated and output to the negative side of the comparator CP. The signal a output from the comparator CP is input to the multiplication circuit 21 and the buffer BF. Reference numeral 19 denotes a wire feeding speed setting circuit, which outputs a wire feeding speed setting signal s which is a wire feeding speed according to the value of the welding current setting signal i. Reference numeral 21 denotes a multiplication circuit which receives the wire feeding speed setting signal s and the signal a and the signal b output from the buffer BF and outputs the motor control signal m. The wire feeding speed setting signal s is an analog switch SW.
OP amp OP through one terminal of 2 and resistor R6
It is input to the + side of 2. Also, analog switch SW2
The other terminal of the resistor R7 is connected to one terminal of the analog switch SW3 and one terminal of the resistor R7. The other terminal of the resistor R7 is one terminal of the resistor R8 and the operational amplifier OP2.
Is connected to the + side of. Also, analog switch SW
The other terminal of 3 and the other terminal of the resistor R8 are grounded. C2 is a capacitor, which is a delay element. R8 is a voltage dividing resistor. R9 and R10 are feedback resistors. Further, the analog switch SW2 is turned on when the signal b is H,
That is, it turns on when the signal a is L, and the analog switch SW3 turns on when the output signal a is H.

The operation will be described below. When the welding current is set by the welding current setting circuit 11, the wire feeding speed setting circuit 19 outputs the wire feeding speed setting signal s which is the wire feeding speed corresponding to the value of the welding current setting signal i. The wire feeding speed is experimentally obtained in advance in accordance with a suitable welding current when the wire protrusion length is set to a standard value. ◆ (1) During welding ◆ Operational amplifier OP1 of welding current feedback circuit 13
Compares and amplifies the welding current signal I and the welding current setting signal i, and outputs the resulting voltage Vd to the comparator CP. The comparator CP compares the voltage Vd with the voltage Vk of the sawtooth wave generation circuit 16, and outputs the signal a to the multiplication circuit 21 and the buffer BF. Then, the multiplication circuit 21 uses the signal a and the signal b to amplify the wire feeding speed setting signal s by the amplification factor Z.
Amplify to obtain signal m. ◆ That is, the amplification factor Z becomes maximum when the analog switch SW2 is always ON, that is, the analog switch SW3 is always OFF, and the analog switch SW2 is always OFF, that is, the analog switch SW.
The analog switches SW2 and SW3 change in the ratio of ON and OFF so that they become minimum when 3 is always ON. Then, the maximum value Z _MAX of the amplification factor Z is expressed by the equation 1, and the minimum value Z _MIN of the amplification factor Z is expressed by the equation 2. ◆

[0008]

[Equation 1]

In this embodiment, R6 to R10 have the same resistance value. As a result, Z _MAX = 1.3
3, Z _MIN = 0.67. (2) When welding is started ◆ Since the welding current signal I is 0, the signal j of the signal generator 15 is input to the analog switch SW1 and the voltage Vd becomes substantially 0. As a result, the ON times of the analog switch SW2 and the analog switch SW3 become the same, and the amplification factor Z≈
1, that is, the value of the wire feeding speed setting signal s is output as it is. ◆ In the present embodiment, the multiplication circuit 2
1 was used, but the detection signal of the welding current and the setting current set by the welding current setting circuit were compared, and when the setting signal ≥ the detection signal, 1 to 1.3 times, and when the setting signal = the detection signal, 1 times ，
It is also possible to use a microcomputer configured to amplify 1 to 0.7 times when setting signal ≦ detection signal. ◆ Also, the amplification factor Z was set to 0.7 to 1.3, but 0.85 to
It was confirmed that there was no practical problem even if it was set to 1.15.

[0010]

As described above, according to the present invention, the detection signal of the welding current is compared with the set current set by the welding current setting circuit, and the correction amount is adjusted according to the result. Within ± 30% of That is, the correction amount is not corrected by an absolute amount and is set to a value proportional to the welding wire feeding speed, so that there is an effect that the feedback system becomes stable and the arc becomes stable. Further, since the output of the wire feeding speed setting circuit is output as it is at the start of welding, there is an effect that the start becomes stable.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 7 wire 8 motor drive circuit 9 control circuit 11 welding current setting circuit 13 welding current feedback circuit 14 shunt 16 sawtooth wave generation circuit 19 wire feeding speed setting circuit 21 multiplication circuit CP comparator

Claims (2)

[Claims] 1. A welding current setting circuit, a wire feeding speed setting circuit for outputting a wire feeding speed signal according to the welding current set in the welding current setting circuit, a welding current detecting means, and The detection signal from the detection means is compared with the welding current setting signal set by the welding current setting circuit, and when setting signal ≧ detection signal, 1 to 1.3 times, when setting signal = detection signal, 1 times, 1 to 0.7 when setting signal ≤ detection signal
A consumable electrode type arc welding machine, comprising: an amplifier circuit for doubling the amplification and a motor drive circuit, wherein a feed rate signal of the wire is amplified by the amplifier circuit to control the motor drive circuit. 2. The consumable electrode type arc welder according to claim 1, further comprising means for setting an amplification factor to 1 when a detection signal from the welding current detecting means is 0.