JPS6234465B2 - - 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). Short circuit between the surface and the circuit current (or voltage)
The so-called wire sense method is used, which allows the position of the weld joint (bevel) to be automatically confirmed by detecting changes in the welding joint (groove) and reading the coordinates at that time.

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. It is. In other words, changeover switch SW to contact a-
1. Switch to the a-2 side and connect the wire sense power supply Ps
is applied between the welding wire 2 and the workpiece 1, and 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 shared as the sense power supply, and the welding conductor C is opened to set the wire sense state.
The circuit current (or voltage) at that time is detected by 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 Figures 1a and b is that there are variations in the electrical contact resistance between the two due to variations in the surface condition near the tip of the welding wire or the joint of the welded material. 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 with a simple mechanism that is easy to install and handle, and that can exhibit a stable detection function regardless of the contact state between the welding wire and the material to be welded. The object of the present invention is to provide a scanning detection device.

In order to achieve such an object, the present invention uses a wire sense method in which when the tip of a welding wire and a material to be welded come into contact, a high-frequency short circuit is formed through the welding wire, the material to be welded, and the welding side cable. A high-frequency bypass capacitor is provided in the short circuit, and an induction coil whose inductance changes is provided in the short circuit. By detecting the change in inductance caused by the change in the weak high-frequency current applied to the induction coil in advance, the welding wire and It has a configuration that can detect contact with the material to be welded, and 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 motherboard is extremely easy, and
There is no need for any modifications such as installing a changeover switch as in the conventional method.

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.

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
Reference numeral 8 indicates a detection circuit, 8 indicates an amplitude discrimination circuit, 9 indicates a discrimination threshold setting circuit, and 10 indicates a discrimination display 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.

FIG. 2c shows the detailed structure of the induction coil 3 in a and b.

Next, FIG. 3 shows a specific electric circuit according to the block configuration example shown in FIG. 2a. In the figure, 3a is a connection cable (corresponds to 3a in Figure 2a), 4 is a matching transformer (corresponds to 4 in Figure 2a)
In this case, a matching high frequency transformer T1 is used. 5 is a characteristic adjustment circuit (corresponding to a5 in Fig. 2);
The electrical characteristics of the high frequency circuit are adjusted using the variable resistor VR-1 and variable capacitor VC-1. 6 is an oscillation circuit (corresponding to 6 in Figure 2a), which includes an oscillation coil T2 and a high-frequency transistor TR for oscillation.
1. Consists of emitter follower transistor TR2, etc. 7 is the detection circuit (7 in Figure 2 a)
In the figure, D1 and D2 indicate diodes. 8 is an amplitude discrimination circuit (corresponding to 8 in Fig. 2);
In the figure, IC1 indicates an operational amplifier as a discrimination comparator. 9 is a discrimination threshold setting circuit (corresponding to Fig. 2 9), and a potentiometer for adjusting the setting threshold.
VR2 is used.

10 is a display circuit for the discrimination results (corresponding to 10 in Figure 2), which includes display light emitting diodes LED1 and LED2.
It consists of

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

FIG. 4 shows actual voltage measurement results at points A, B, C, and D in FIG. 3 when the circuit configuration shown in FIGS. 2 and 3 is operated.

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. When this DC voltage at point B is input to the amplitude discriminator circuit 8, the voltage at point C in FIG. 3 is as shown in FIG. Such a differential voltage is obtained, and this differential voltage is input to the discrimination comparator IC1. This discrimination comparator IC
In 1, the differential voltage at point C in Fig. 3 is discriminated, and the slight change in the high frequency oscillation voltage caused by contact with the welding wire is inverted and amplified and output as a clear change in DC voltage.
A voltage as shown in FIG. 4d appears at point D in the figure. Therefore, by automatically reading the coordinates of the welding wire 2 from this output voltage, the correct position of the weld joint is memorized.

Note that the display circuit 10 is a light emitting diode for displaying the period during which the welding wire 2 and the workpiece 1 are separated.
The LED 2 lights up, and the light emitting diode LED 1 lights up to indicate the period when the two are in contact, and has the function of displaying the relative positional relationship between the two.

As is clear from the above-mentioned 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.

In addition, since the main parts are composed of simple analog circuits, it can not only be realized at low cost, but also provide an effective clue for realizing labor savings through automation of welding-related equipment and robotization. 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 an induction coil whose inductance changes when a closed circuit is formed is provided. Changes in inductance are detected by changes in a weak high-frequency current applied to the induction coil in advance, and the welding wire and the Since it detects contact with the welding material, it is easy to install and handle with a simple mechanism, and provides stable detection function regardless of the contact state between the welding wire and the material to be welded. It is possible to provide a welding tracing detection device that can perform the following steps.

[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 d 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 discrimination circuit, 9 ...Discrimination threshold setting circuit, 10...Discrimination display 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 preset threshold value for the DC voltage detected by this detection circuit. and an amplitude discrimination circuit that compares and discriminates the welding wire and outputs a minute change in the high-frequency oscillation output due to contact of the welding wire as a change in DC voltage.