JPH084936B2 - Welding electrode wire feeding speed control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a control device for feeding a consumable welding electrode wire at a predetermined speed, and particularly to a signal proportional to the rotation speed. In order to control the power supplied to the armature such that the armature voltage is detected and compared with a reference value so that the difference signal becomes zero, a control device of a system that compensates for a voltage drop due to internal resistance in the armature It is about improvement.

[Prior Art] In a control device for feeding a welding electrode wire at a constant speed using a DC shunt winding motor, since the armature voltage of the motor is substantially proportional to the rotation speed as a means for detecting the feeding speed. The method of detecting the armature voltage and determining the supply voltage to the armature based on the difference between this and the reference value is adopted. However, the armature voltage includes not only the voltage based on the armature reaction that is proportional to the rotation speed, but also the resistance drop due to the wiring cable to the armature and the internal resistance of the armature. This resistance drop changes because the current flowing changes, and a voltage proportional to the true rotation speed cannot be obtained. Therefore, as a control device for the welding electrode wire feed speed, which has large load fluctuations and requires a large adjustment of the set speed, it is proportional to the true rotation speed by compensating for the voltage drop due to this armature resistance. It is necessary to obtain a signal, conventionally detecting the armature current,
An apparatus has been proposed in which this detected value is subtracted from the armature voltage and used as a rotation speed proportional signal. (For example, JP-A-49
-23151) FIG. 5 is a connection diagram showing an example of these conventional devices,
Reference numeral 1 is a speed setter which outputs a voltage signal e _r for setting an adjustable wire feeding speed. A comparator 2 calculates the difference between the speed setting signal e _r and a speed feedback signal e _f described later. An amplifier 3 amplifies the output of the comparator 2 and supplies it to the armature 4 of the wire feeding motor. A semi-fixed resistor 5 for detecting the armature current as a voltage signal is connected in series to the armature 4, and the terminal voltage of the semi-fixed resistor 5 is amplified by another amplifier 6 and The voltage signal e _i is proportional to the current. Here, the semi-fixed resistor 5 and the amplifier 6 constitute an armature current detection circuit. The output e _i of the armature current detection circuit is supplied to another comparator 7 and the difference from the terminal voltage e _a of the armature 4 is calculated to obtain the speed feedback signal e _f = e _a −e _i . A wire feeding roll 8 is driven by the armature 4 and feeds the wire 9 toward the workpiece 10. The field circuit of the electric motor is not shown.

In the device of the same figure, the internal resistance value of the circuit of the armature 4 is
r _a, the resistance value of the semi-fixed resistor 5 r _e, the induced voltage due to armature reaction V _a, when the armature current is i, the terminal voltage e _a of the armature 4 is _{e a = V a + i (} r _a + a r _e). Since the terminal voltage e _i of the semi-fixed resistor 5 is (i · r _e ), the output e _i is e _i = A · i · r _e , where A is the amplification factor of the amplifier 6. output e _f of the comparator 7 becomes _{e f = e a -e i =} e a -A · i · r e = V a + i (r a + r e) -A · i · r e. Therefore, adjust the variable resistor 5 When set so that e _f = V _a , the true armature voltage is obtained as a feedback signal. As a result, the armature correctly rotates at the speed corresponding to the set value.

To set the semi-fixed resistor 5 so that the resistance value r _e values satisfying the way above formula (1) [0005] the particular which had been actually rotated electric motor It is necessary to change the feeding load variously when setting the speed, measure the wire feeding speed each time, and determine the semi-fixed resistor 5 by trial and error so that the speed becomes constant in all load conditions. Is. For this reason, it takes an extremely large number of steps to obtain an accurate setting state. Furthermore, after such a great deal of effort and adjustment, for example, if the length or thickness of the wiring for the armature is changed, the resistance in this wiring is added to the internal resistance of the armature. The above adjustment was also meaningless, and it was necessary to repeat the complicated adjustment again.

INDUSTRIAL APPLICABILITY The present invention solves the above-mentioned drawbacks of the conventional device, is easy to adjust, and enables accurate setting even in a place where there are few measuring instruments, such as a welding site, and also enables automation of these settings. It is a thing.

[Means for Solving the Problems] The present invention supplies an appropriate voltage to an armature instead of feedback control at the time of adjustment, and puts the armature in a stopped state to obtain a voltage proportional to the detected value of the armature voltage and the armature current. Adjust the gain of the armature voltage detection circuit or armature current detection circuit so that the signal becomes equal, and perform the above adjustment only once and with a simple voltage source (for example, tester) measuring instrument. In addition, the up-down counter is driven by the sign of the signal of the difference between the detected value of the armature voltage and the voltage proportional to the armature current,
The automatic adjustment is made possible by switching a plurality of resistors for switching the gain of the armature current detection circuit by the output of the up / down counter.

[Embodiment] FIG. 1 shows an embodiment of the present invention. 1-10 in the figure
Shows a device having the same function as that of the conventional device shown in FIG. Reference numeral 11 is for switching the power supplied to the armature 4, which is a changeover switch, between the time of adjustment (a) and the time of actual use (b). Reference numeral 12 denotes a DC power supply, which supplies a small current such that the armature 4 does not rotate by the resistor 13 connected in series. In the device shown in the figure, in order to adjust the semi-fixed resistor 5 for compensating the armature current, the changeover switch 11 is set to the (a) side. In this state, the armature 4
The feedback control for is suspended, the output of the amplifier 3 is not supplied to the armature 4, and the output of the DC power supply 12 is supplied to the armature 4. At this time, adjust the resistor 13 to adjust the armature 4
The current flowing through the armature 4 is limited to a small current such that the armature 4 does not rotate. The armature voltage e _a is e _a = V _a + i (r _a + r _e ) as described above, and since the armature is stopped, the induced voltage V _a due to the armature reaction is zero. Therefore, e _a = i (r _a + r _e ). The output of the result comparator 7 becomes _{e f = e a -A · e} i = i · r a + (1-A) · i · r e. Therefore, if a voltmeter is connected to point P in the figure and the semi-fixed resistor 5 is adjusted so that e _f = 0, the resistance value r _{e at} that time is Therefore, the above equation (1) is satisfied.

When the changeover switch 11 is set to the (b) side after adjusting the semi-fixed resistor 5 in this way, a feedback control circuit for the armature 4 is constructed and the armature 4 is accurately compensated for the voltage drop due to the armature current. Therefore, the motor rotates at a speed corresponding to the set value of the speed setter 1 correctly.

As can be seen from the above description, when adjusting the semi-fixed resistor 5, it is sufficient that the voltage V _a due to the armature reaction is zero.
If the armature 4 is mechanically restrained so as not to rotate, the current supplied from the DC power supply 12 may be increased during the adjustment. As a means for adjusting the voltage signal corresponding to the armature current, the resistance value is fixed except for adjusting the resistance value r _e of the resistor 5 connected in series as shown in FIG. Alternatively, the amplification factor A of the amplifier 6 for amplifying the terminal voltage may be adjusted. Alternatively, the resistance value r _e of the resistor 5 and the amplification factor A of the amplifier 6 may be fixed, and the armature terminal voltage may be passed through the amplifier. May be supplied to the comparator 7 to adjust the amplification factor of this amplifier.

FIG. 2 is a connection diagram showing another embodiment. Unlike the embodiment shown in FIG. 1, the changeover switch 11 switches the feedback signal to the comparator 2 so that the direct current used in the embodiment shown in FIG. The power supply 12 and the resistor 13 are removed, and at the time of adjustment, only the terminal voltage of the semi-fixed resistor 5 is supplied to the comparator 2 by the changeover switch 11. A description will be given of the time of adjustment when the changeover switch is set to the (a) side in the embodiment shown in FIG. If the speed setter 1 is adjusted to a low value such that the armature 4 does not rotate, or if the armature 4 is mechanically fixed and set to flow an appropriate small current, The terminal voltage i · r _{e of} the semi-fixed resistor 5, that is, a voltage proportional to the armature current is fed back to the comparator 2. As a result, the setting device 1 acts as an armature current setting device, so that it is easy to pass a current that does not rotate the armature 4. While the armature 4 is flowing a current that does not rotate, the terminal voltage i.
It is also supplied to r _e or amplifier 6. The amplifier 6 has a gain adjuster 14 and is capable of changing its amplification factor A. The output e _i = A · i · r _{e of the} amplifier 6 and the terminal voltage e _{a of the} armature 4 are input to the comparator 7 and the difference is calculated. A _{e a = V a + i (} r a + r e) , and _{e i = A · i · r} e , as described above, and therefore the armature 4 is at V _a = 0 because stopped e _a = i (R _a + r _e ) and the output of the comparator 7 becomes e _a −e _i = i · r _a + (1−A) · i · r _e . Therefore, if the gain adjuster 14 of the amplifier 6 is adjusted so that the voltage source is connected to the point P and the indication becomes zero, i · r _a + (1-A) · i · r _e = 0 When the changeover switch 11 is set to the (b) side, the feedback signal e _f is e _f = e _a −A · i · r _e = V _a + i (r _a + r _e ) −A · i · r Therefore, _e = V _a, and the correct voltage due only to the armature reaction is obtained.

In the above two embodiments, adjustment is performed by means, but when the switch 11 is adjusted to the (a) side, the gain of the amplifier 6 is automatically increased / decreased by the polarity of the voltage at the point P in each of the above embodiments. If so, these adjustments can be automated. FIG. 3 shows an automatic adjustment in the embodiment shown in FIG. 1. In FIG. 3, 1 to 13 show the same functions as in FIG. Further, 15 is a polarity discriminator for discriminating between positive, negative, and zero of the input voltage, 16 and 17 are changeover switches which are interlocked with the changeover switch 11, 18 is a pulse oscillator, and 19 is an up / down counter. Accordingly, it is an n-digit counter which counts up or down in synchronization with the pulse of the pulse oscillator 18 to the CL terminal, and is connected so as to open / close control the analog switches S1 to Sn by the output signal. R1 to Rn are resistors connected to the gain adjusting terminal of the amplifier 6 via the analog switches S1 to Sn. When all the changeover switches 11, 16 and 17 are set to the (a) side in the embodiment shown in the figure, the armature 4 is not rotated by the resistor 13 from the DC power source 12 as in the embodiment shown in FIG. A small current or an appropriate current is supplied while the armature 4 is mechanically fixed. This current is converted into a voltage signal by the semi-fixator 5, is detected, is amplified through the amplifier 6, becomes a voltage signal e _i , and is compared with the armature terminal voltage by the comparator 7. The output of the comparator 7 is discriminated by the discriminating circuit 15 as positive or negative, and the up / down counter 19 is set to up-count or down-count. Up-down counter
Since the pulse from the pulse oscillator 18 is supplied to 19 via the changeover switch 17, the up / down counter 19 counts up or down for each pulse of the pulse oscillator 18, and the analog switches S1 to Sn output the count output. The gain adjusting resistors R1 to Rn for the amplifier 6 are switched according to the above. As a result, the amplification factor of the amplifier 6 gradually changes, and the input e _{i of the} comparator 7 changes. As a result of the change in the amplification factor of the amplifier 6, when the output of the comparator 7 becomes zero, the discrimination circuit 15 becomes zero output, the up-down counter 19 stops counting, and the adjustment is completed. The time required for this adjustment is determined by the oscillation frequency of the pulse oscillator 18. However, since the counting speed of the up / down counter 19 and the response speed of the amplifier 6 are extremely fast, the oscillation frequency of the pulse oscillator 18 can be set to several hundreds hertz or higher. Therefore, the time required for this adjustment is completed in a very short time. Therefore, when the power is turned on, the short-time changeover switches 11, 16 and 17 are kept on the (a) side and then switched to the (b) side. Then, the automatic adjustment will be performed completely.

FIG. 4 is a diagram in which the method using the up / down counter of FIG. 3 is applied to the embodiment of FIG. 2, and a reference signal supplied at the time of adjustment (a small current such that the armature 4 does not rotate for complete automation). The setting device 1'is provided as a supply source of a signal for supplying the signal) and is switched by the switch 20 which is interlocked with the changeover switches 11, 16 and 17. The specific operation is shown in FIG. Details can be omitted since it can be easily understood from FIG.

[Advantages of the Invention] As described above, according to the present invention, the armature is stopped so that the feedback signal at that time is adjusted to zero. Therefore, it is possible to perform accurate adjustment for all load conditions and speed settings with one adjustment. Since the speed control is obtained, the adjustment work becomes extremely simple. Further, since the adjustment can be automated, the adjustment can be performed at any time even at the installation site of the device. This means that the length of the cable from the control unit to the motor can be changed freely. In particular, in the invention of claim 2 (FIGS. 3 and 4) in which automatic adjustment is performed by a timer for a very short time when the power is turned on or when a reset button or the like is used, the adjustment operation is almost apparent. Since it is present, the operator can freely change the cable without any knowledge about these adjustments.

[Brief description of drawings]

1 to 4 are connection diagrams showing an embodiment of the present invention, and FIG. 5 is a connection diagram showing an example of a conventional device. 1-speed setter, 2,7-comparator, 3,6-amplifier 4-armature, 5-semi-fixed resistor, 9-electrode wire 11,16,17,20-switch Switch 12 ... DC power supply, 15 ... Discrimination circuit 18 ... Pulse oscillator, 19 ... Up-down counter 14, R1 or Rn ... Gain adjustment resistor

Claims (2)

[Claims] 1. The difference (e _a −e _i ) between the output voltage e _a of the armature voltage detection circuit and the output voltage e _i of the armature current detection circuit with respect to the output voltage e _r of the feed rate setting device is calculated. Feedback to the difference signal _{{e r - (e a -e} i)} in feed rate control device of the welding electrode wire to make decisions to a constant speed control supply voltage for the armature by, electrical instead of the feedback control A switching circuit that supplies an arbitrary voltage to a child terminal and a difference (e _a −e _i) between the outputs of the detection circuits when the armature is in a stopped state during a period when the armature is not feedback-controlled by the switching circuit. ) For adjusting the ratio of the output voltage e _i of the armature current detection circuit to the output voltage e _a of the armature voltage detection circuit to a value at which) becomes zero. . 2. The up / down counter, the gain adjustment circuit for switching the gain of the armature current detection circuit according to the output of the up / down counter, and the feedback control of the up / down counter interrupted by the switching circuit. The driving circuit for driving in the up or down counting direction according to the sign of the difference (e _a −e _i ) between the output voltages of the detection circuits during Welding electrode wire feed speed control device.