JPS6230868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a welding machine output control device having a slope control function for continuously transitioning a welding voltage or current from one level to another at a predetermined time.

Arc welding machines, especially TIG welding machines, use a Slope control is required to generate an arc with a small current, then gradually increase the welding current to a steady-state value, and then gradually decrease the welding current from the steady-state value to the small current required for crater treatment when welding is complete. Figure 1A
is _a time chart showing a typical example.
is the start current, I _W is the main welding current, I _C is the crater current, t _u is the upward slope time, and t _d is the downward slope time. Figure 1B is a time chart when slope control is applied to so-called low-pulse welding, in which the main welding current is changed in a low-frequency (approximately 1 to 10Hz) pulse to control the welding heat input.
_P is the peak current value of the main welding current, I _B is the base current value, and other symbols are the same as in FIG. 1A.

The structure and operation of a conventional welding machine output control device with a slope control function will be explained with reference to FIG. and is supplied to the welding load 4 through the current detection element 3. For example, a thyristor is used as the current control element 2, and its phase is controlled by the ignition signal generation circuit 6. The current detection element 3 generates an output proportional to the welding current, and the output is converted into a voltage signal by an amplifier 5, which becomes a feedback signal. The signal of the difference between this signal and the target value signal V ₀ for setting the welding current is non-inverted amplified by the error amplifier 8, and its output is applied to the ignition signal generation circuit 6 so that the welding current matches the target value. Feedback control. Therefore, if the target value signal V ₀ is changed, the welding current will change accordingly. 7 is a constant voltage DC power supply; 9, 10, 11, and 12 are peripheral resistances of the error amplifier 8; the error amplifier 8 operates with the negative side of the DC power supply 7 as a reference potential.

13 is a target value signal generation section, 14 is a slope signal generation section in the preceding stage, and 15 and 16 are constant voltage DC power supplies that power these two parts. Positive potential +
V, and the DC power supply 16 supplies negative potential -V.

The target value signal generating section 13 includes a welding current adjusting resistor 1
7, 18, current amplification transistors 19, 20, and resistors 21, 22, 23, 24,
The voltage between the sliders of the welding current adjusting resistors 17 and 18 is set as the target value signal V ₀ .

The slope signal generating section 14 is mainly composed of a slope time adjustment resistor 25, a slope start switch element 26, an operational amplifier 27, and a capacitor 28. The operational amplifier 27 works together with the capacitor 28 as an integrator. The output of the operational amplifier 27 is always 0V, and when the switch element 26 closes, the output voltage of the operational amplifier 27 increases linearly due to the negative voltage from the slope time adjustment resistor 25, and the output voltage from 0V to the output terminal increases. A slope signal is obtained that reaches the positive saturation voltage of operational amplifier 27 (approximately equal to +V). This time can be changed by the slope time adjustment resistor 25. 29 is a switch element for resetting the integrator, and 30 to 34 are peripheral resistors.

Transistors 19 and 2 of target value signal generation section 13
0 performs current amplification of the slope signal supplied from the operational amplifier 27 through the resistors 21 and 22. Here, if we consider that the characteristics of both transistors 19 and 20 are the same and the values of emitter resistors 23 and 24 are equal, points a and b on the emitter side of both transistors will have the same potential, so welding current adjustment resistor 17 ,1
8 is equivalently connected in series between both ends of the DC power supply 15, and a slope signal is applied to points a and b, which are the intermediate points. Therefore, in the state before the slope starts when the output of the operational amplifier 27 is 0, the voltage applied to the welding current adjustment resistor 18 is 0.
Then, the full voltage of the DC power supply 15 is applied to the welding current adjusting resistor 17, and the target value signal V ₀ is determined only by the partial voltage of this resistor ₁₇ . ) becomes the target value signal for setting.

On the other hand, after the slope rises when the output of the operational amplifier 27 reaches a saturated state, the voltage applied to the welding current adjustment resistor 17 becomes almost 0, and the welding current adjustment resistor 1
Since almost the entire voltage of the DC power source 15 is applied to 8, the setpoint value signal V ₀ is determined only by the partial voltage of this resistor 18, which sets, for example, the crater current [I _C in FIG. 1A]. This becomes the target value signal.

In the middle of the slope, the voltage divided by the resistor 17 (the voltage between the slider of the resistor 17 and point a) gradually decreases, and the voltage divided by the resistor 18 (the voltage between the slider of the resistor 18 and point b) gradually decreases. voltage) gradually changes significantly until V ₀
is the sum of these two. In the end, V ₀ changes continuously from the divided voltage determined only by the resistor 17 to the divided voltage determined only by the resistor 18, and the welding current also changes continuously from the main welding current to the crater current for a predetermined period of time. t _d ] in FIG. 1A.

However, in the conventional circuit configuration described above,
Since the target value signal V ₀ is obtained from between the sliders of the welding current adjusting resistors 17 and 18, the reference potential of the error amplifier 8 and the reference potential of the target value signal generator 13 and the slope signal generator 14 are made common. Therefore, it is necessary to provide separate power supplies for each of the power supplies 7, 15, and 16. Although shown in the drawings in a simplified manner, these power supplies require independent DC stabilized power supplies, and the larger the number of power supplies, the higher the cost.

In addition, since two transistors 19 and 20 are used for current amplification of the slope signal, it is necessary to match the temperature characteristics of these transistors in order to increase the accuracy of the target value signal V ₀ . requires additional elements such as a temperature compensation circuit, which increases the complexity of the circuit and the number of parts.

Although only one slope has been described in the above description, if both an upward slope at the start of welding and a downward slope at the end of welding are required, the above-mentioned target value signal generator 13 and slope signal generator 14 are required. It is necessary to provide one more set of welding circuits for switching operation, and in addition, when performing low pulse welding by periodically changing the main welding current in magnitude as shown in FIG. 1B, the circuit becomes even more complicated.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a welding machine output control device that can perform slope control with high precision using a simple and economical circuit configuration with a small number of parts.

In order to achieve the above object, the present invention includes at least two welding voltage or current regulating resistors connected in series between a reference potential line and a predetermined voltage source,
The midpoint of the above two adjustment resistors is 0 with respect to the reference potential.
Connect to the output line of the slope signal generator that changes continuously from V to a predetermined voltage or vice versa, input the voltage between the sliders of the two adjustment resistors to the differential amplifier, and calculate this difference. The welding voltage or current is controlled using the output of the dynamic amplifier as a target value signal.

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

FIG. 3 is a diagram showing a circuit configuration of an embodiment of the present invention, which includes a welding transformer 1, a current control element 2, a current detection element 3, a load 4, an amplification section 5, an ignition signal generation circuit 6,
A feedback control system consisting of an error amplifier 8, resistors 9 to 12, a slope time adjustment resistor 25, a slope start switch element 26, an operational amplifier 27, a capacitor 28, an integrator reset switch element 29, and resistors 30 to 34. The function of the constructed slope signal generating section 14 is the same as that of the conventional example shown in FIG. 2, and the explanation thereof will be omitted.

Unlike the conventional example, the target value signal generating section 13
The welding current adjustment resistor 17 and the second welding current adjustment resistor 18 are connected in series between the positive potential line +V of the power supply and the reference potential line 0V, and the midpoint c between both resistors 17 and 18 is connected to the slope signal of the previous stage. It is connected to the output line from the operational amplifier 27 of the generator 14, and the voltage V ₁ between the sliders of both resistors 17 and 18 is inputted to the differential amplifier 35.
The output voltage V ₀ of the differential amplifier 35 is configured to be used as a target value signal for the feedback control system. 36 to 39 are peripheral resistances of the differential amplifier 35;
Fixed resistors 40 and 41 are connected in series with the welding current adjusting resistors 17 and 18.

According to this configuration, since the target value signal V ₀ is a voltage with respect to the reference potential 0V, the error amplifier 8, the target value signal generator 13 and the slope signal generator 1
The four reference potential lines can be used in common, and therefore the DC power supplies 15 and 16 can also be used in common.

In the above configuration, the output voltage of the operational amplifier 27
In the state before the start of the slope when V ₂ is 0, the second
Since the voltage applied to the welding current adjustment resistor 18 is 0, the voltage applied between the input terminals of the differential amplifier 35
V ₁ is determined only by the partial voltage of the first welding current adjusting resistor 17, and the voltage V ₀ output from the differential amplifier 35 at this time sets the main welding current [I _W in FIG. 1A], for example. This becomes the target value signal.

On the other hand, in the state after the slope rises when the output of the operational amplifier 27 reaches the positive saturation voltage, the potential at point c becomes approximately +V, so the first welding current adjustment resistor 1
7 is approximately 0, and the voltage _V1 input to the differential amplifier 35 is applied to the second welding current adjustment resistor 18.
The output voltage V ₀ of the differential amplifier 35 at this time becomes a target value signal for setting, for example, the crater current [I _C in FIG. 1A].

In the middle of the slope, the voltage divided by the resistor 17 gradually becomes smaller, and the voltage divided by the resistor 18 gradually changes to a larger value.The sum of both becomes _V1 , so _V1 is the divided voltage determined only by the resistor 17. voltage to resistance 1
The welding current changes continuously from the main welding current to the crater current due to the corresponding change in the target value signal V ₀ . Starting current [I _S in Figure 1 A]
A setpoint signal for the rising slope from to the main welding current can also be obtained by a similar circuit.

FIG. 4 shows another embodiment of the present invention, in which various current controls such as ascending slope, descending slope, and periodic variation of the main welding current necessary for low pulse welding can be performed by one set of circuits. It is something. In FIG. 4, parts corresponding to those in FIG. 3 are designated by the same reference numerals.

In this embodiment, the number of power supplies is further reduced, and one DC power supply 15 is shared.

The target value signal generating section 13 is basically the same as the embodiment shown in FIG. 3, but it is capable of switching the welding current set value during upward slope and downward slope, and between the peak current value and base current during low pulse welding. To enable switching of values, third and fourth welding current adjusting resistors 42 and 43 are connected in parallel with the first and second welding current adjusting resistors 17 and 18, respectively. The slider is connected to the differential amplifier 35 via analog switches 44 and 45 which are turned on and off by a signal from the current switching signal generator 48.
The analog switch 4 is connected to the non-inverting input side of the analog switch 4, and the sliders of the resistor 18 and the resistor 43 are turned on and off by a signal from the current switching signal generator 49.
6 and 47 to the inverting input side of the differential amplifier 35. These analog switches 44 to 47 are connected to resistors 17 and 42.
It may be connected to the power supply side of the resistor 18 and the ground side of the resistor 43.

The slope signal is generated by the operational amplifier 27 and the capacitor 2.
However, in order to switch between an upward slope and a downward slope, a series circuit of slope time adjustment resistors 50, 51 and diodes 52, 53 is connected in anti-parallel to the inverting input terminal of the operational amplifier 27. Also, the power supply voltage +V is connected to the non-inverting input terminal of the operational amplifier 27 through the resistors 32 and 56.
The voltage is applied after being divided into parts. The anode side of the diode 52 and the cathode side of the diode 53 are connected to the resistor 3.
3 and 34, and further connected to a slope start signal generating section 55 via a diode 54.

When the output of the slope start signal generator 55 is always at a low level of 0V, the diode 53 is turned on and the diode 52 is turned off, so that the operational amplifier 27
The potential at the non-inverting input terminal becomes higher than the potential at the inverting input terminal, and the output of the operational amplifier 27 has reached a positive saturation voltage.

The non-inverting input terminal of the operational amplifier 57 is connected to the positive potential line +V of the power supply via a resistor 58, and the inverting input terminal is connected to the reference potential line 0V via a resistor 59, so that its output is always positively saturated. are doing. The saturation voltages of the operational amplifier 27 and the operational amplifier 57 are approximately equal, and the intermediate point c connected to the output line of the operational amplifier 27 and the power supply side end of the resistor 40 connected to the output line of the operational amplifier 57 have approximately the same potential. Therefore, almost no voltage is applied to the welding current adjusting resistors 17 and 42. In this state, welding current adjustment resistor 18,
A partial pressure is generated only at 43. This partial pressure can be selectively taken out by analog switches 46 and 47, for example, by analog switches 45 and 47.
When turned on, the voltage V ₁ taken out between the slider of the resistor 17 and the resistor 18 is input to the differential amplifier 35, and its output V ₀ is used as the target value for setting the starting current ( _IS ), for example. It becomes a signal.

Next, when the output of the slope signal generator 55 changes to a high level +V, the operational amplifier 27 operates as an integrator due to the current flowing through the diode 52 and the slope time adjustment resistor 50, and the output V ₂ changes from the positive saturation voltage to 0V. gradually change to Output _V2
When becomes 0V, the saturation voltage of the operational amplifier 57 is applied only to the resistor 17 and the resistor 42, and the voltage divided by these two resistors can be selectively taken out by the analog switches 44 and 45. For example, when the analog switches 45 and 47 are on, the resistor 1
Voltage extracted from between the sliders of 7 and resistor 18
V ₁ is input to the operational amplifier 35, and its output V ₀
becomes a target value signal for setting, for example, the main welding current (I _W ).

The welding current changes from the start current (I _S ) to the main welding current (I
_W ), the time (t _u ) of which can be varied by the slope time adjustment resistor 50 .

The output of the slope start signal generator 55 is set to low level again, the analog switch 46 is closed by the current switching signal generator 49, and the analog switch 47 is closed.
When opened, the capacitor 28 is discharged through the slope time adjustment resistor 51 and the diode 53, and the output voltage V ₂ of the operational amplifier 27 gradually increases from 0V to reach a positive saturation voltage. At this time, the input voltage V ₁ of the differential amplifier 35 changes continuously from the voltage divided by the resistor 17 to the voltage divided by the resistor 43, and the output voltage V ₀ generated in the differential amplifier 35 due to the voltage divided by the resistor 43 becomes This becomes a target value signal for setting the crater current (I _C ). In other words, the welding current is the main welding current (I
The downward slope continuously changes from _W ) to the crater current (I _C ), and the time (t _d ) can be changed by the slope time adjustment resistor 51.

FIG. 5 is a time chart showing the operation of each part described above.

If the input of the integrator of the slope signal generator 14 is switched between high level and low level as in the embodiment shown in FIG. As a result, the circuit can be greatly simplified, and the integrator input circuit can be made contactless, improving reliability.

Furthermore, in the embodiment shown in FIG. 4, after the upward slope ends, the signal level of the current switching signal generator 48 is periodically changed, and the analog switches 44 and 45 are turned on and off alternately. It is also possible to obtain a target value signal for low pulse welding. Here, for example, 42 is the adjustment resistor for the peak current value (I _P ), and 17 is the base current value (I P ).
_B ) Used as an adjustment resistor.

The saturation voltage of the operational amplifier 27 used as an integrator does not exactly match the power supply voltage +V due to the internal voltage drop of the amplifier. Therefore, in the embodiment shown in FIG. 4, the operational amplifier 5 having the same characteristics as the operational amplifier 27 is
7 as a predetermined voltage source, this operational amplifier 5
By applying the saturation voltage of 7 to the power supply side end of the fixed resistor 40, it is possible to improve the accuracy of the target value signal without adjusting the circuit. Another voltage-adjusted DC power supply may be used as the predetermined voltage source, or if current control does not require much precision, the voltage +V of the DC power supply 15 may be fixed as is, as in the embodiment shown in Fig. 3. It may also be applied to the power supply side end of the resistor 40.

In the above embodiment, slope control using a feedback method has been described, but open-loop slope control is also possible by using the target value signal. Moreover, the present invention can be applied not only to current control but also to voltage control.

As explained above, in the present invention, at least two
A slope signal is applied to the midpoint of the two welding voltage or current adjusting resistors, and the voltage between the sliders of the two adjusting resistors is amplified by a differential amplifier and converted into a target value signal. The reference potential line in the circuit can be shared, and as a result, the conventional example shown in Fig. 2 requires three DC power supplies, but the embodiment shown in Fig. 3 reduces the number to two, and the embodiment shown in Fig. 4 reduces the number to one. This makes it possible to simplify the circuit and reduce costs. In addition, since it is not necessary to connect individual transistors to each adjustment resistor to amplify the current of the slope signal, it can be replaced with a differential amplifier integrated as an IC as a single component, so a special temperature compensation circuit, etc. This has the effect that a highly accurate target value signal for slope control with good temperature characteristics can be obtained without adding.

[Brief explanation of the drawing]

Figures 1A and 4 are time charts showing examples of slope control, Figure 2 is a circuit diagram of a conventional example of a welding machine output control device equipped with a slope control function, and Figures 3 and 4 are different diagrams of the present invention. A circuit diagram showing an example,
FIG. 5 is a time chart showing the operation of each part in FIG. 4. 1... Welding transformer, 2... Current control element, 3...
... Current detection element, 4 ... Welding load, 8 ... Error amplifier, 13 ... Target value signal generation section, 14 ... Slope signal generation section, 17, 18, 42, 43 ... Welding current adjustment resistor, 35 ... ...Differential amplifier, 27...
Operational amplifier constituting an integrator, 28... Integrating capacitor, 55... Slope start signal generating section, 1
5... DC power supply which is an example of a predetermined voltage source, 57
...An operational amplifier, which is another example of a predetermined voltage source, 0
V...Reference potential line.

Claims (1)

[Scope of Claims] 1. A welding machine output control device equipped with a slope control function that continuously shifts welding voltage or current from one level to another in a predetermined time,
At least two welding voltage or current regulating resistors are connected in series between a reference potential line and a predetermined voltage source, and the midpoint of the two regulating resistors is set to a predetermined voltage from 0V to the reference potential. or vice versa, and input the voltage between the sliders of the two adjusting resistors to a differential amplifier, and output the output of this differential amplifier. A welding machine output control device characterized by using a target value signal for slope control. 2. The slope signal generation section includes an integrator and a slope start signal generation section that switches the input of the integrator between a high level and a low level, and selects both the upward slope and downward slope slope signals by one integrator. The welding machine output control device according to claim 1, wherein the welding machine output control device is configured to be able to generate the following.