JPS628268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a so-called push-pull type welding wire feeding device.

FIG. 1 shows an example of this type of welding wire feeding device, in which a welding wire 1 is unwound from a wire 4 by a feed roll 3 driven by a push motor 2. is pulled out through a conduit 5 by a feed roll 7 driven by a pull motor 6 and fed to a welding torch 8 at a predetermined speed.

9 is a control device for driving the push motor 2;
0 is a control device that drives the pull motor 6.

In the welding wire feeding device as described above, the pull motor 6 is controlled at a constant speed or by arc voltage, and a signal indicating the output of the pull motor 6 is applied to the control device 9 of the push motor 2. was operated with a torque corresponding to the output of the pull motor 6.

FIG. 2 is a block diagram showing a control device for the push motor 2, in which numeral 11 is a load detector for the pull motor 6, numeral 12 is an operational amplifier that amplifies the output of the load detector 11, and numeral 13 is a torque regulator that performs arithmetic operation. The output signal of the amplifier 12 and the output signal of the amplifier 15 that amplifies the output of the torque detector 14 that detects the torque of the push motor 2 are applied differentially, and an output is generated according to the difference between the two signals.

16 is a torque limiter which limits the output voltage of the torque regulator 13 from exceeding a predetermined value and defines the upper limit of the torque of the push motor 2;
As a result, the welding wire is prevented from buckling within the conduit 5.

Reference numeral 17 denotes a drive control device that supplies a predetermined controlled power to the push motor 2.

As mentioned above, this type of welding wire feeding device is provided with the limiter 16, so the limiter 16 operates even when the feeding device is started, and the starting torque of the push motor 2 is limited, especially when the wire dispenser is started. When GD ² becomes large, there is a drawback that the start-up of the entire feeding device is delayed.

The present invention has been made to eliminate the above-mentioned drawbacks, and includes a push-pull type welding wire feeding device that includes a circuit that releases the torque limiter for a predetermined period of time when the device is started.
It is an object of the present invention to provide a control device that can start up and complete a feeding device in a short time.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, parts that are equivalent to those in FIGS. 1 and 2 are given the same reference numerals, and explanations of those parts will be omitted.

In FIG. 3, reference numeral 20 denotes a torque limiter circuit, and the anode of a Zener diode 21 is connected to the output terminal of the torque regulator 13 via a resistor 22 and to the drive control device via a resistor 23. The cathode of the Zener diode 21 is grounded via a capacitor 24, and a normally closed contact 30b of a relay 30, which is turned on when the feeding device is driven, is connected in parallel to the capacitor 24. The connection point 25 with the capacitor 24 is connected to the upper limit torque setting device 2.
It is connected to the sliding terminal of 6. One terminal of the upper limit torque setting device 26 is connected to +Vc.c via a resistor 27.
It is connected to the.

In FIG. 3, 18a is a normally open contact of an operating relay that is turned on when the feeding device is operating, and 18b
1 is a normally closed contact of the operation relay, and 19 is a resistor for dynamic braking.

In the above configuration, during normal operation, the load of the pull motor 6 is detected by the load detector 11, and this detection signal is converted into a positive signal via the operational amplifier 12, and is converted into a reference value for the output torque of the push motor 2. is applied to the inverting input terminal of the torque regulator 13 as .

A signal representing the output torque of the push motor 2 is fed back to the torque regulator as a negative polarity signal, and a negative polarity signal is generated at the output terminal of the torque regulator 13. The drive control device 17 receives this output signal and operates the push motor 2 at a predetermined torque.

In the above device, when the feeding device is stopped, the relay 30 is off, and the connection point 25 between the capacitor 24 and the Zener diode 21 is
is grounded via the normally closed contact 30b, and the anode of the Zener diode 21, that is, the connection point 40
The clamp voltage between the zener diode 21 and the ground point is the zener voltage of the zener diode 21. This Zener voltage is applied to the push motor 2 to prevent the welding wire from buckling in the conduit during normal operation.
The voltage is set so that the voltage is higher than the clamp value V _L for limiting the torque of the push motor 2, that is, the torque at the time of starting the push motor 2 is set to a sufficiently large value.

When the feeding device is started now, the relay 30b is turned off and the upper limit torque setting device 2 is connected to the capacitor 24.
Charging is performed to the positive polarity via 6.

Immediately after startup, the voltage at the connection point 25 is close to zero, so the Zener voltage of the Zener diode 21 becomes the clamp upper limit value at the connection point 40.

Therefore, when a high negative polarity voltage is generated from the torque regulator 13, if the voltage is less than the Zener voltage, it is directly applied to the drive control device, and the push motor 2 generates a large starting torque to accelerate starting. .

As time passes after startup, the capacitor 24
As charging progresses, the voltage at the connection point 25 gradually increases with positive polarity. Therefore, now the capacitor 24
When the charging voltage of the Zener diode 21 is Vc and the Zener voltage of the Zener diode 21 is Vz, the clamp voltage at the connection point 40 is Vz - Vc, which is lower than the clamp voltage immediately after startup.

When the predetermined starting time has elapsed, the charging voltage of the capacitor 24 becomes constant. As a result, after the normal operating state is reached, the upper limit of the output torque of the push motor 2 is limited to a value that does not cause buckling of the welding wire within the conduit.

Note that this upper limit torque can be adjusted as desired by changing the setting value of the upper limit torque setting device 26.

Further, the upper limit clamping value of the connection point 40 at the time of startup can be set by changing the Zener voltage of the Zener diode 21.

Note that in the above embodiment, the torque amplifier 13
If the output voltage of It may also be connected to the negative power supply -Vc.c.
Further, instead of the Zener diode, a diode 21' may be used as shown in FIG.

In addition, in order to improve the starting characteristics of the feeding device, the circuit shown at 50 in FIG. A predetermined voltage may be summarily superimposed to increase the input signal to the torque regulator 13 at startup.

Figure 6A shows an example of the wire feeding speed characteristic at startup of the wire feeding device to which the present invention is applied, and FIG. 6B shows an example of the wire feeding speed characteristic at startup of the conventional wire feeding device. , it has been shown that the wire feeding speed rises quickly at startup, and vibrations are also reduced.

The above data is for a wire dispenser.
This is when a 200Kg roll is used.

As can be seen from Figure 6, in the conventional device, after startup,
The time T ₁ until the speed stabilizes is 570 msec, whereas according to the device of the present invention, the time T ₂ until the speed stabilizes after startup is 75 msec, and the startup time is 175/57
0≒ 1/3, which is about 1/3.

As described in detail above, the present invention provides a push-pull type welding wire feeding device with a circuit that releases the output limit of the torque limiter in the control device for the motor that is torque-controlled at the time of startup. It is now possible to increase the torque of the wire dispenser.
Easily shorten startup time even when GD ² grows larger,
Moreover, stable starting characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a push-pull type welding wire feeding device, FIG. 2 is a circuit diagram showing a conventional control device for a welding wire feeding device, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. 4 and 5 are circuit diagrams showing a modification of the embodiment shown in FIG. 3, and FIG. 6 is a graph showing the starting characteristics of the welding wire feeding device of the present invention and the conventional welding wire feeding device. 1...Welding wire, 2...Push motor, 6
...Pull motor, 9, 10...Control device, 13...
...torque regulator, 20...torque limiter circuit,
21... Zener diode, 24... Capacitor, 30b... Normally closed contact of relay.

Claims (1)

[Claims] 1 Welding wire is fed in a push-pull manner using two motors located apart from each other, one motor is operated at a predetermined speed, and the other motor is adapted to handle the load of the one motor. An operational amplifier is provided to which a signal is applied to one input terminal and a signal corresponding to the load of the other motor is applied to the other input terminal, and the torque of the other motor is controlled by the output of the operational amplifier. A control device for a welding wire feeding device equipped with a torque limiter using a diode or Zener diode for controlling the torque of the other motor so as not to exceed a predetermined value during normal operation. A series circuit of a Zener diode and a capacitor, a relay that is turned on when a start command is received for the welding wire feeder, a short circuit between the capacitors when the relay is off, and a short circuit when the relay is on. 1. A control device for a welding wire feeding device, comprising a circuit that releases the torque limiter for a certain period of time when the feeding device is started.