JPH0142797B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding wire feeding control device.

BACKGROUND ART Conventionally, it has been known to provide a feeding device on a welding wire supply side and a welding position side, respectively, and to perform welding wire feeding control using a push-pull method.

As this kind of feeding control mechanism, for example, the first
As shown in the figure, for ease of synchronization, the drive motor 1 of the push feeder (hereinafter referred to as push motor) is controlled at a constant speed, and the drive motor 2 of the other pull speed feeder (hereinafter referred to as pull motor) is controlled at a constant speed. There is one in which the welding wire 3 is fed to the welding torch 6 through the conduit 5 while being rewound from the take-up reel 4 by constant torque control.

As shown in FIG. 2, the armature of the pull motor 2 is connected to a DC power source 8 through the collector emitter of a power transistor 9, and the negative terminal of the armature of the pull motor 2 is connected to a current detection terminal. It is grounded via a resistor 10 with a low resistance value.
Note that the DC power source 8 outputs a predetermined voltage set to match the feeding operation at the maximum speed so that the pull feeding device can follow the entire speed range of the feeding operation of the welding wire 3. It is something to do.

A differential amplifier 12 is connected to the base of the transistor 9. The positive input terminal of this differential amplifier 12 is connected to the potentiometer 11 that outputs a voltage corresponding to the set torque of the control target, and the negative input terminal is connected to the negative terminal of the armature of the pull motor 2. It is connected.

In this way, the differential amplifier 12 receives a voltage signal V1 corresponding to the control target torque arbitrarily set from the potentiometer 11, and a voltage signal V1 corresponding to the control target torque that is arbitrarily set from the potentiometer 11, and the current actually flowing through the armature of the pull motor 2 detected by the resistor 10. A voltage signal Vx indicating the magnitude is differentially received, and a differentially amplified signal of both signals V1 and Vx is applied to the base of the transistor 9. By this differential amplification signal, the current flowing between the collector emitter of the transistor 9, and therefore the armature of the pull motor 2, is controlled to be a constant current, so that the current flows to a value corresponding to the above-mentioned set torque value. It's summery.

In the conventional feed control device described above, as shown in FIG. 3, the maximum speed of the pull motor 2 (indicated by 15a) is faster than the drive speed 16 of the push motor 1 (indicated by a group of broken lines in the figure). It is set to be. In this way, conduit 5
The frictional force acting on the welding wire 3 inside is small,
When the load fluctuation on the welding torch side is small, the welding wire 3 advances through the conduit 5 in an elongated state, as shown in FIG. The welding wire 3 by the pull motor 2 has a rotation speed-torque characteristic curve 15 of the pull motor 2 and a rotation speed-torque characteristic curve 16 of the push motor 1 in FIG.
is fed at the speed and torque indicated by the intersection point 17 with .

However, if the resistance force based on the frictional force acting on the welding wire 3 within the conduit 5 increases, or if the load on the welding wire 3 on the welding torch side changes, the welding wire 3 within the conduit 5 , as shown in FIG. 4, and elongated as shown in FIG. 1. In this way, the welding wire 3 repeatedly sag and elongate. According to the conventional control method, the feeding speed of the welding wire 3 sent out from the pull feeding device is large, and can reach ±100% or more of the average feeding speed, resulting in a decrease in welding workability. It had the disadvantage of coming.

This invention has been made to eliminate the above-mentioned drawbacks, and in the push-pull type welding wire feeding method, in the speed range exceeding the upper and lower limits of the average speed of the motor that is controlled with constant torque, the torque is constant. It is an object of the present invention to provide a control device that can significantly reduce fluctuations in wire feeding speed by increasing or decreasing the torque of a control motor, thereby stably feeding a wire.

An embodiment of the present invention will be described below with reference to the drawings.

The push-pull welding wire feeding system of the present invention is similar to that shown in FIG. 1, in which the push motor 1 is driven at a predetermined set speed by a control device (not shown).

On the other hand, the pull motor 2 is controlled by a circuit shown in FIG. In FIG. 5, 20 is a DC constant voltage power source that supplies a predetermined DC voltage, 21 is a transistor that controls the voltage applied to the motor 2 to control the motor speed to a set speed, and 22 is a transistor that controls the torque of the motor 2. The collector of the transistor 21 is connected to the power supply 20, the emitter is connected to the collector of the transistor 22, and the base is connected to the output terminal of an operational amplifier 23 for speed control, which will be described later.

The base of the transistor 22 is connected to an operational amplifier 26, which will be described later, and the emitter is connected to the motor 2, so that the current of the motor 2 is controlled by the emitter output of the transistor 22, and the motor torque is controlled. It's getting old.

The collector voltage Vx and the emitter voltage Vx' of the transistor 22 are differentially applied to a summation point 40, and a signal Vx-Vx' indicating the speed of the motor 2 is applied to an averaging circuit 25 using an integrator. The average speed of 2 is calculated. A signal indicating the average speed of the averaging circuit 25 is applied to the - input terminal of the operational amplifier 23. The set voltage of an upper limit speed setter 24, which is a variable resistor, is applied to the + input terminal of the operational amplifier 23, and the average speed of the motor 2 is applied to the - input terminal. The output of an averaging circuit 25 that calculates .

On the other hand, the output voltage of a resistor 27 inserted in series with the armature of the motor 2 is applied to the negative input terminal of the operational amplifier 26, and the output voltage V1 of the torque setting device 28 and the motor speed are applied to the positive input terminal. The output voltage of an adder 30 that calculates the sum with the output voltage V4 of an increment setter 29 that sets an increment in torque when V is lower than a predetermined lower limit value is applied.

31 is a lower limit setter for setting a predetermined lower limit value of the speed of the motor 2; 32 is an operational amplifier that compares the setting value of the lower limit setter 31 with a signal indicating the actual speed of the motor 2; 33 is an operational amplifier 32; This transistor is turned off when the output is negative and turned on when the output is positive, and when this transistor 33 is turned on, the above-mentioned voltage V4 is generated in the increment setter 29.

In the above configuration, now motors 1 and 2
It is assumed that the welding wire 3 is being operated within the conduit 5 at a predetermined speed FO in the same manner as the known push-pull method, and predetermined welding is being performed.

In this state, the collector and emitter voltages of the transistor 22, Vx and Vx', are applied to a summing point 40, from which a voltage representing the speed of the motor 2 is extracted, one being the average circuit. 2
5, the average speed in a fixed time unit is calculated and applied to the operational amplifier 23, the difference from the set value V2 of the upper limit speed setter 24 is calculated, and the transistor 21 is controlled according to the difference output. The voltage at the emitter Ta of the transistor 21 is maintained at a value corresponding to V2+the average end voltage of the motor.

On the other hand, in a range where the speed of the motor 2 is higher than the value obtained by subtracting the speed corresponding to the set value V3 of the lower limit setter 31 from the upper limit speed corresponding to Vx, the output of the summing point 40 is lower than V3, and therefore the calculation Amplifier 3
The output of point 2 is negative, the transistor 33 is off, the output voltage of the incremental setting device 29 is 0, and the output of the summing point 30 corresponds to the set value V1 of the torque setting device 28. , this V1 is applied to the operational amplifier 26.

On the other hand, if the resistance value of the resistor 27 is R and the armature current of the motor 2 is Ia, the voltage Ia×R is applied to the operational amplifier 26, and the transistor 22 is controlled by its output so that Ia×R=V1. Torque control of motor 2 is performed. However, the voltage applied to the transistor 22 is a voltage corresponding to (the average speed of the motor 2 over a certain period of time + the speed margin), and the voltage applied to the armature Tb of the motor 2 is the voltage applied to the emitter Ta of the transistor 21. Since the voltage cannot be exceeded, when the speed exceeds F1, the voltage applied to the motor 2 is limited and the torque becomes small. The state during this period is shown by range A in FIG.

On the other hand, when the speed of the motor 2 falls below the value obtained by subtracting the speed corresponding to the output voltage V3 of the lower limit setter 31 from the upper limit speed and reaches the speed F2, the amplifier 32
The output becomes positive and the transistor 33 is turned on. Now, if the resistance of the setting device 29 is R2 and the collector load resistance 34 is R1, the terminal of the resistor 29 is
R2/R1+R2Vcc This voltage is divided by the setting device 29 and applied to the summing point 30 as the torque increase V4. is applied to the operational amplifier 26, the output voltage of the operational amplifier 26 increases from the value at the speed F0, the output voltage of the transistor 22 increases, and the output torque of the motor 2 also increases. This state is shown in FIG. 6B.
The increase in output torque prevents the speed of the motor 2 from decreasing.

This torque increase is preferably set to about 20% of the normal torque.

As described above, this invention changes the output torque of the motor at the upper and lower limits of the average speed, so that when the resistance during wire feeding increases, the speed of the motor on the torque control side will decrease. However, since the motor torque increases, the wire can be fed over the increased resistance as described above, and the wire does not sag. Similarly, in the opposite case, the motor torque becomes smaller, so that the wire is not fed too much and the welding wire can be stably fed.

Note that when the motor starts, the output voltage of the averaging circuit 25 is zero, so a high voltage is applied to the base of the transistor 21, and the emitter output voltage becomes the maximum, while Vx - Vx' is lower than the setting value of the lower limit setting device 31. also decreases and therefore transistor 3
3 is in the on state and the torque increase is added, so the output torque of motor 2 also increases and the starting characteristics are improved. Also, when the load increases during operation and the speed suddenly decreases, Vx is delayed for a certain period of time. As a result, only Vx′ drops rapidly, and Xx−Vx′ becomes the lower limit value.
It is larger than V3, and in this case too, the torque increases, increasing the feeding force and working to recover speed.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the outline of a conventional push-pull type welding wire feeding mechanism, FIG. 2 is a circuit diagram showing the main parts of a conventional welding wire feeding control mechanism, and FIG. The figure is a graph showing the torque-rotational speed characteristics in the circuit of Figure 2, Figure 4 is a diagram showing the state of the welding wire in the conduit, and Figure 5 is the welding wire feeding control according to the present invention. FIG. 6 is an electric circuit diagram showing essential parts of an example of the mechanism, and FIG. 6 is a graph showing the operating characteristics of the embodiment shown in FIG. 1... Push motor, 2... Pull motor, 3... Welding wire, 5... Conduit, 20... Constant voltage power supply,
21, 22... Transistor, 23... Operational amplifier (speed), 24... Upper limit speed setter, 25... Average circuit, 26... Operational amplifier (torque), 27... Resistor,
28... Torque setting device, 29... Increment setting device, 30
...adder, 31...lower limit setter, 32...operational amplifier, 33...transistor, 40...addition point.

Claims (1)

[Claims] 1. In a welding wire feeding control device that feeds welding wire in a push-pull manner using a motor that is controlled at a constant speed and a motor that is controlled at a constant torque, a power supply device that supplies power to a constant torque motor that is controlled at a constant torque; a constant torque control circuit that is connected to the device and controls the current supplied to the constant torque motor at a constant current; a detection circuit that detects the average driving speed of the constant torque motor per a certain period of time; , comprising a torque control means for reducing the motor current when the upper limit speed value corresponding to the average driving speed of the output of the detection circuit is exceeded and increasing the motor current when the motor current is below the lower limit speed value; A welding wire feeding control device characterized in that the welding wire feed control device controls the welding wire feed so that the speed is constant at