JPS6234466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding trace detection device employing a wire sense method that can automatically confirm the position of a weld joint.

In a welding wire type arc welding robot or automatic arc welding machine, an appropriate power supply voltage is applied between the welding wire and the workpiece, and the wire tip and workpiece are connected in accordance with a preset procedure (program). By short-circuiting the surface and detecting changes in the circuit current (or voltage) and reading the coordinates at that time, the weld joint (groove) position can be automatically confirmed. A wire sense method is used.

FIGS. 1a and 1b show different configuration examples for explaining the conventional wire sensing method. In Figure a, a welding power source Pw and a wire sense power source Ps are provided separately, and these are switched by a changeover switch Sw to apply a power source voltage between the welding wire 2 and the workpiece 1. be. In other words, changeover switch SW is connected to contact a-1,
Switch to the a-2 side and apply the voltage of the wire sense power supply Ps between the welding wire 2 and the material to be welded 1,
The circuit current (or voltage) at that time is detected by the wire sense detector Is (or Vs). In addition, in Fig. 1b, a welding contact C in which a series resistor Rs for wire sense is connected in parallel is provided in the power circuit connecting the welding power source Pw, the welding wire 2, and the workpiece 1, and the welding power source Pw is connected to the wire. It is also used as a sense power source, and the welding conductor C is opened to set the wire sense state, and the circuit current (or voltage) at that time is detected by the wire sense detector I (or V). .

However, in the configuration shown in FIG. 1a, the power source Ps for wire sense and the power source Pw for welding are switched to apply the power source voltage between the terminals of the welding wire 2 and the material to be welded 1. A changeover switch SW is required between the wire sense power source Ps and the welding power source Pw.

What is common to the configurations shown in Fig. 1 a and b is that there are variations in the electrical contact resistance between the two due to variations in the surface condition near the welding wire tip or the joint of the welded material, and in order to absorb this variation, requires a fairly high voltage to be applied.
This requires special consideration for the insulation performance of the equipment and, in some cases, for human safety.
This has become a factor of complexity and high cost.

The present invention alleviates these drawbacks, and provides a welding device that has a simple mechanism, is easy to install and handle, and can exhibit a stable detection function regardless of the contact state between the welding wire and the workpiece. The object of the present invention is to provide a tracing detection device.

In order to achieve such an object, the present invention is designed to form a high frequency short circuit through the welding wire, the material to be welded, and the welding cable when the tip of the welding wire and the material to be welded come into contact in the wire sense method. A high-frequency bypass capacitor is provided in the short circuit, and an induction coil whose inductance changes is provided in the short circuit, and the rate of change in inductance due to a change in the weak high-frequency current applied to the induction coil in advance is detected. By discriminating, contact between the welding wire and the material to be welded can be instantly detected.
It has the following characteristics:

Since this is an indirect application/detection method using a high-frequency induction coil, there is an extremely low possibility of interference from noise generated during operation of the main unit.

Installation to an existing mother machine is extremely easy, and there is no need for any modifications such as installing a changeover switch as in the conventional system.

The high-frequency oscillation circuit that includes an induction coil has extremely high detection sensitivity because the C, R, and L constants in the circuit are set so that the oscillation amplitude changes greatly depending on the presence or absence of contact between the welding wire and the welded material. Therefore, a stable detection function can be achieved without being affected by the surface condition near the wire tip or the joint of the welded material.

Since the rate of change in inductance of the induction coil due to contact between the welding wire and the welded material is detected and discriminated, it is not greatly influenced by the absolute value of inductance of the circuit including the detected circuit, resulting in excellent operability.

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

FIG. 2 shows an example of the configuration of a welding tracing detection device according to the present invention. Figure a shows an example of a block configuration when this detection means is applied to a butt welded joint, in which 1 is the material to be welded, 2 is the welding wire, 2a is the welding side cable, 3 is the induction coil, 3a is the connection cable, CHF is a high frequency bypass capacitor for preventing high frequency current detour. Further, 4 is a matching transformer, 5 is a characteristic adjustment circuit, 6 is a high frequency oscillation circuit, and 7
8 is a detection circuit, 8 is an amplitude change rate discrimination circuit, 9 is a discrimination threshold setting circuit, 10 is a discrimination result storage circuit,
11 is a discrimination display circuit, and 12 is a discrimination memory reset circuit. FIG. 2B shows a case in which a fillet weld joint is targeted, and the circuits of the detection section are the same as those in FIG. 2A, so they are omitted.

Figure 2c shows the induction coil 3 in Figures 2a and b.
This figure shows the detailed configuration of .

Next, FIG. 3 shows a specific electric circuit according to the block configuration example shown in FIG. 2a. 3
a is the connection cable (corresponds to 3a in Figure 2 a), 4
is a matching transformer (corresponding to 4 in FIG. 2a), and a matching high frequency transformer T1 is used. 5 is a characteristic adjustment circuit (corresponding to 5 in Figure 2 a) variable resistor
The electrical characteristics of the high frequency circuit are adjusted by VR1 and variable capacitor VC1. Reference numeral 6 denotes an oscillation circuit (corresponding to FIG. 2a), which is composed of an oscillation coil T2, an oscillation high-frequency transistor TR1, an emitter follower transistor TR2, and the like. 7
is a detection circuit (corresponding to 7 in Figure 2 a), and D in the figure
1 and D2 indicate diodes. 8 is an amplitude change rate discrimination circuit (corresponding to FIG. 2a), which is an integrating circuit consisting of an operational amplifier IC1 as a discrimination comparator, a resistor R provided at the non-inverting input stage of this operational amplifier IC1, and a capacitor C. It consists of 9 is a discrimination threshold setting circuit (corresponding to 9 in Fig. 2a);
A potentiometer VR2 for adjusting the set threshold value is used. 10 is a storage circuit (second
(corresponding to 10 in figure a), transistor TR3 and
It consists of a flip-flop circuit using TR4. 11 is a display circuit for the discrimination result (corresponding to 11 in Figure 2a), which is a light emitting diode LED for display.
1. Consists of 2 LEDs. 12 is a reset circuit for discrimination memory (corresponding to 12 in FIG. 2a);
A reset push button switch PB1 is used.

Next, the operation of the welding tracing detection device configured as described above will be explained.

Figure 4 shows A, B, C in Figure 3 when operated with the circuit configuration shown in Figures 2 and 3.
It shows the actual voltage measurement results at each point D, E, and F.

Now, in FIGS. 2 and 3, when the material to be welded 1 and the welding wire 2 come into contact with each other from the isolated state, the material to be welded 1, the welding wire 2, the high frequency bypass capacitor C _HF , the welding cable 2a, and the welding wire 2 are separated. A closed circuit reaching the welding material 1 is formed, and the inductance of the induction coil 3 changes. When the inductance of the induction coil 3 changes, the circuit constant of the high frequency oscillation circuit network consisting of the induction coil 3, matching transformer 4, characteristic adjustment circuit 5 and high frequency oscillation circuit 6 changes, and the voltage at point A in FIG. As shown in Figure a, the amplitude (voltage) of the oscillated high frequency wave changes. When this point A voltage is input to the detection circuit 7, it is detected by the detection action, and the welding wire 2 and the welded material 1 are detected at the point B in FIG.
A DC voltage as shown in FIG. 4b appears, which varies in response to the high frequency oscillation voltage caused by contact with the contact point. This DC voltage at point B is applied to the inverting side input terminal of the discrimination comparator IC1 of the amplitude change rate discriminating circuit 8, and the non-inverting side input terminal of the discrimination comparator IC1 is applied to the point B. A voltage as shown in FIG. 4d, which is obtained by integrating the voltage by an integrating circuit composed of C and R, is applied. Further, a voltage adjusted in advance by a threshold setting circuit 9 is applied to the discrimination comparator IC1 as an offset voltage. Therefore, when the voltages shown in FIG. 4c and d are applied to the inverting input terminal and the non-inverting input terminal of the discrimination comparator IC1, the output of the discrimination comparator IC1 becomes a negative value with respect to the in-phase input, Further, for an input in which the non-inverting input voltage is higher than the inverting input voltage, a pulse-like output having a positive value only during that period is obtained, and a voltage as shown in FIG. 4e is obtained. In this case, the pulse width of the pulsed output (Δt in FIG. 4d) is approximately determined by the time constant of the C and R integration circuits related to point D in FIG. 3. This kind of pulse-like output is the third
When input to the flip-flop memory circuit 10 from point E in the figure, this flip-flop memory circuit 10
is set, and an output voltage as shown in FIG. 4 f appears at point F in FIG. This output voltage is
As can be seen from Figure f, welding wire 2 and workpiece 1
It does not pay much attention to the amount of change in the high frequency oscillation voltage caused by contact with the object, but focuses on the point where the rate of change is large, and outputs this as a clear change in DC voltage. Therefore, by automatically reading the coordinates of the welding torch using this output voltage, the correct position of the weld joint is memorized. In addition, in the display circuit 11, the display light emitting diode LED 2 lights up during the period when the welding wire 2 and the workpiece 1 are isolated, and the display light emitting diode LED 2 lights up from the moment the two come into contact.
1 lights up, and has the function of displaying the relative positional relationship between the two.

As is clear from the above-described embodiments, the present invention introduces a welding wire sensing method using induced application of high-frequency current and inductance discrimination, so that the following effects can be obtained.

Since this is an indirect application/detection method using a high-frequency induction coil, there is an extremely low possibility of interference from noise generated during operation of the main unit.

It is extremely easy to install on an existing mother machine, and there is no need for any modifications such as installing a changeover switch as in the conventional system.

A high-frequency oscillation circuit including an induction coil has C,
Since the R and L constants are set, the detection sensitivity is extremely high, and therefore a stable detection function can be achieved without being affected by the surface condition near the wire tip or the joint of the welded material.

It also detects the rate of change in inductance of the induction coil due to contact between the welding wire and the material to be welded,
Since the discrimination is made, the absolute value of inductance of the circuit including the circuit to be detected does not affect much, resulting in excellent operability.

Furthermore, since the main parts are composed of simple analog circuits, it can not only be realized at low cost, but also
Automation and robotization of welding-related equipment can provide a powerful clue to realizing labor savings.
Moreover, there is also the advantage that market competitiveness is strengthened by improving the functionality and reducing costs of welding robots or automatic welding equipment.

As described above, according to the present invention, when the tip of the welding wire and the material to be welded come into contact in the wire sense method, a high frequency short circuit is formed by the welding wire, the material to be welded, and the welding side cable. A high-frequency bypass capacitor is provided, and a stray coil whose inductance changes when a closed circuit is formed is provided, and the speed of change (rate of change) of the inductance is detected by changes in the weak high-frequency current applied to this induction coil in advance. Since the contact between the welding wire and the material to be welded is detected instantaneously, it is easy to install and handle with a simple mechanism, and it does not depend on the state of contact between the welding wire and the material to be welded. Therefore, it is possible to provide a welding tracing detection device that can exhibit a stable detection function without any interference, and has excellent operability and is not significantly influenced by the absolute value of inductance including the circuit to be detected.

[Brief explanation of the drawing]

Figures 1a and 1b are block diagrams for explaining different conventional wire sense systems, and Figures 2a to 2c show an embodiment of the present invention, where a is a block diagram when applied to a butt welded joint. Block diagram, b is a block diagram when applied to a fillet welded joint, c is a block diagram showing details of the induction coil, Figure 3 is a specific circuit diagram of the same embodiment, and Figures 4 a to f are the same implementation. FIG. 4 is a voltage waveform diagram of each part in FIG. 3 used to explain the operation of the example. 1... Material to be welded, 2... Welding wire, 2a...
Welding side cable, 3... Induction coil, 3a... Connection cable, 4... Matching transformer, 5... Characteristic adjustment circuit, 6... High frequency oscillation circuit, 7... Detection circuit, 8... Amplitude change rate discrimination circuit , 9...discrimination threshold setting circuit, 10...discrimination result storage circuit, 1
1... Discrimination display circuit, 12... Reset circuit.

Claims (1)

[Claims] 1. Provided so that when the welding wire of the welding wire type arc welding robot or the welding wire type automatic arc welding machine comes into contact with the welded material, a high frequency short circuit is formed via the welding wire, the welded material, and the welding cable. a high-frequency bypass capacitor connected to the high-frequency short-circuit closed circuit; an induction coil connected to the electric path of the high-frequency short-circuit closed circuit so that the inductance changes when the high-frequency short circuit closed circuit is formed; A high-frequency oscillation circuit that obtains an output with a changed amplitude of the oscillation frequency, a detection circuit that detects the output of this high-frequency oscillation circuit to obtain a DC voltage, and a comparator or operational amplifier that has an inverting input terminal and a non-inverting input terminal, respectively. Different time constant circuits are provided, and the DC voltage detected by the detection circuit is applied in phase to the inverting input terminal and the non-inverting input terminal of the comparator or operational amplifier to adjust the voltage change rate due to the change in inductance of the induction coil. 1. A welding tracing detection device comprising: an amplitude change rate discrimination circuit that discriminates and outputs the amplitude change rate discrimination circuit.