JPS623717B2 - - 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 rewound from a wire dispenser 4 by a feeding roll 3 driven by a push motor 2, and the rewound welding wire 1 is unwound from a wire dispenser 4. The wire 1 passes through a conduit 5 and is pulled out by a feed roll 7 driven by a pull motor 6 to a welding torch 8.
is fed 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 proportional to the load torque of the pull motor 6 is applied to the control device 9 of the push motor 2. The push motor 2 was operated with a torque corresponding to the load torque of the pull motor 6.

However, in the conventional welding wire feeding control device as described above, when the device is started, the output torque of the push motor is also small because the output has not yet been detected at the time when the pull motor is about to start rotating. . Therefore, when starting up the device, a quick start-up cannot be obtained, and especially when the wire dispenser is large, the output of the pull motor becomes vibrating, causing a problem in that the start-up is delayed.

The present invention has been made to eliminate the above-mentioned drawbacks. For example, in a control system such as a push motor in which torque is controlled according to the output of a pull motor, an operational amplifier to which a signal representing the output of the pull motor is applied. By supplying a predetermined input signal, for example, a signal that gradually decreases or a constant input signal corresponding to the start-up time, to the input terminal of the device for a certain period of time when the device is started, the torque shortage at the time of start-up can be eliminated and the It is an object of the present invention to provide a control device for a welding wire feeding device that can be started stably.

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

In FIG. 2, a signal that gradually decreases during startup is superimposed on the operational amplifier, and the output signal of the load detector (usually a load current detector) 11 of the pull motor 6 is input to the input side of the control device 9 of the push motor 2. It is applied to the input terminal of operational amplifier 12.

A charging circuit 13 composed of a capacitor C and a resistor R is connected to this input terminal, and the resistor R is connected to a relay 1 that is turned on when the wire feeding device is started.
The normally closed contact 14b of the relay 14 and the normally open contact 14 of the relay 14 are connected to the DC power supply via the resistor _R1 .
a is connected, and this normally open contact 14a is grounded. With the above configuration, while the relay 14 is off, the capacitor C is charged via the resistor R ₁ , the contact 14b, and the resistor R, and the relay 14 is charged when the wire feeding device is started. When turned on, the charge in the capacitor C is discharged via the resistor R and the contact 14a. Note that the charging voltage of the capacitor C is applied to the input terminal of the operational amplifier 12 summatively with respect to the output signal of the load detector 11.

15 is a torque regulator, which outputs the output signal of the operational amplifier 12 and the load detector 16 of the push motor 2.
The torque regulator 15 outputs a control signal that causes the push motor 2 to generate a torque corresponding to the load of the pull motor 6.

18 is a limiter that limits the output of the torque regulator 15 so that the output torque of the push motor 2 does not exceed a predetermined upper limit; 19 is a motor drive control device using a thyristor or the like. The motor drive control device 19 controls the firing phase of a thyristor (not shown) according to the magnitude of the output signal of the torque regulator 15 by a known method, and supplies a predetermined electric power to the feeding device. The voltage is applied to the push motor 2 through the normally open contact 20a of the operating relay, which is turned on during operation.

21 is a dynamic braking resistor for applying a brake to the push motor 2, and this resistor 21 is connected to the push motor 2 via a normally closed contact 20b of a driving relay.

22 is an upper limit setter that sets the upper limit of the output torque of the push motor 2 by setting the upper limit of the output of the limiter 18, and 23 is a push button switch for starting.

In the control device configured as described above, when the feeding device is stopped, the relay 14 is off and
A DC voltage is supplied to the capacitor C via the normally closed contact 14b and resistors R ₁ and R, and the capacitor C is charged with a predetermined voltage. Note that at this time, the contact 20a is off, and the push motor 2,
The pull motor 6 is stopped.

Now push button 23 to start the feeding device.
is turned on, and the relay 14 is turned on. At this time, the driving relay is also turned on by a circuit not shown, the contacts 20a are turned on and the contacts 20b are turned off, the push motor 2 is started, and the pull motor 6 is also started by the circuit not shown.

At this starting point, the load current of the pull motor 6 is not detected, so no signal is applied from the detector 11 to the input terminal of the operational amplifier 12, but the terminal voltage of the capacitor C of the charging circuit 13 is used as a signal to promote startup. 12 input terminals.

Therefore, a signal corresponding to the charging voltage of the capacitor C is generated at the output terminal of the operational amplifier 12, and this output signal is applied to the motor drive control device 19 via the limiter 18.
A predetermined electric power is output from 9, and the push motor 2
starts with high torque. The push motor 2 is therefore activated quickly and rapidly unwinds the welding wire from the wire dispenser 4 and feeds it into the conduit 5.

On the other hand, by turning on the relay 14,
The normally closed contact 14b is turned off and the normally closed contact 14a is turned on, and the charge in the capacitor C is discharged through the resistor R and the contact 14a, and the terminal voltage of the capacitor C gradually decreases and is applied from the capacitor C to the operational amplifier 12. The voltage applied will also be lower. On the other hand, by starting the pull motor 6, the output signal of the load detector 11 increases, and the charging voltage of the capacitor C and the load detector 11 increase.
is applied to the operational amplifier 12.

After a predetermined period of time has elapsed after startup, capacitor C
voltage is sufficiently reduced so that substantially only the output voltage of the load detector 11 is applied to the input terminal of the operational amplifier 12, and a signal corresponding to the output of the pull motor 6 is applied to the torque regulator 15. Then, a predetermined electric power is applied to the push motor 2 via the limiter 18 and the control device 19, and the push motor 2 is operated with a predetermined torque, that is, a torque corresponding to the load of the pull motor 6.

Note that the torque of the push motor 2 is detected by the torque detector 16 and applied to the operational amplifier 17, and a signal indicating the actual torque of the push motor 2 is differentially applied to the torque regulator 15. The torque of the push motor is controlled to a value corresponding to the load of the pull motor 6.

Furthermore, when the output voltage of the torque regulator 15 becomes larger than a predetermined value, the limiter 18 is activated and the output of the limiter 18 is suppressed to a predetermined upper limit value, causing the push motor 2 to operate with an unnecessarily large torque. This prevents the welding wire from buckling within the conduit 5.

Figure 3A shows an example of the wire feeding speed characteristic at startup of the wire feeding device to which this invention is applied, and FIG. 3B 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 3, 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 175 msec, and the startup time is 175/5.
70≒1/3, which is about 1/3.

Furthermore, in place of the circuit shown in FIG. 2 that superimposes a signal that gradually decreases at the time of startup on the operational amplifier 12, the same effect can be obtained by applying a constant signal for a certain period of time only at the time of startup as shown in FIG. can get.

In FIG. 4, a relay 15 that operates for a limited time at startup is connected to +Vc.c. through a normally closed contact 15b, and a voltage Vs set by a setting device 16 is applied to the operational amplifier 12 through a resistor R. If the starting push button 23 is now pressed, the normally closed contact 15b of the time-limited relay 15 is connected to +Vc.c. for a certain period of time, thereby increasing the starting torque.

As described in detail above, the present invention provides a push-pull type welding wire feeding device in which, at startup, a signal corresponding to the load of the pull motor is supplied with a predetermined signal for a certain period of time from startup, for example, a signal that gradually decreases corresponding to the startup characteristics. Alternatively, by superimposing a constant input signal, it is possible to increase the starting torque of the push motor. Therefore, even if the GD ² of the wire dispenser becomes large, the starting time can be easily shortened. 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 an embodiment of the present invention, and Fig. 3 is a graph showing startup characteristics of the welding wire feeding device of the present invention and a conventional welding wire feeding device. It is. FIG. 4 is a circuit diagram showing a part of an embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Welding wire, 2... Push motor, 6... Pull motor, 8... Welding torch, 9... Control device for driving push motor, 10... Control device for driving pull motor, 11... Load detector, 12... Operational amplifier,
13...Charging circuit, 14...Relay, R...Resistor, C...
capacitor.

Claims (1)

[Claims] 1. A first motor that inserts a welding wire into a conduit of a predetermined length, a second motor that pulls out the welding wire from the conduit and feeds it to the welding torch, and a control device that controls the drive torque of the second motor. , to which a signal representing the drive torque of the second motor is applied as an input signal, and an operational amplifier that outputs a signal for driving the first motor in response to the input signal; a speed control device that controls the motor at a constant speed; a start instruction switch that gives a start command for the first and second motors; A welding wire feeding device characterized in that the welding wire feeding device is provided with a starting circuit that supplies a starting promotion signal to the operational amplifier in order to generate a signal sufficient to start the first motor from the operational amplifier. control device.