JPS6397367A - Welding point detecting method and its device - Google Patents

Abstract

PURPOSE:To safely destroy slag and to detect a welding point by providing a crest value to destroy the slag generating on the welding wire tip to the voltage which is impressed on between a welding wire and a work during a noncontact period of both of them and besides, setting the crest value to the value not exceeding the welding voltage at the time of welding. CONSTITUTION:A pulse signal produced from a pulse generation circuit 20 is impressed on the base of a transistor TR which is ON/OFF controlled and a voltage pulse is produced at the secondary side of a step-up transformer PT. This voltage pulse has the crest value with the size enough for destroying the slag generating on the tip of the welding wire 4 at the time of finishing the welding and besides, its effective value is controlled so as not to exceed the output voltage of a welding source 1 at the time of welding to control an electric shock. Then, during the period when the welding point at the time of the next welding is being retrieved, the voltage pulse produced by the pulse generation circuit 20 is impressed on between the welding wire 4 and the work 5 and the slag of the welding wire 4 tip is destroyed and the welding point can be retrieved in a safe state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an improvement in a welding point detection device suitably used in welding robots, automatic welding machines, and the like.

[Background technology]

A conventional welding point detection device of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 1986-
As disclosed in No. 96370, a voltage is applied between the welding wire and the workpiece through a current limiting resistor from a power supply device different from the welding power source, and a voltage is generated across the current limiting resistor due to contact between the wire and the workpiece. The device is configured to detect changes, but in general, in devices that adopt this type of detection method, the contact resistance between the welding wire and the workpiece increases due to slag generated at the tip of the welding wire at the end of welding, and the welding There is a high risk of misjudging the points.

For example, the contact resistance between the welding wire and the workpiece increases due to the formation of slag, so even when the welding wire and the workpiece come into contact, a sufficient voltage change does not occur in the current limiting resistance, and it may be determined that there is no contact. many.

As a countermeasure to this problem, it is possible to destroy the slag by applying a voltage higher than the output voltage of the welding power source during welding, but when taking such a method, there is a new risk of electric shock from a safety perspective. cause problems.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and provides a welding detection method and method which are improved in terms of both safety and reliability, and which are capable of safely destroying slag generated at the tip of a welding wire. The purpose is to provide equipment for implementing this.

[Disclosure of the invention]

The welding point detection method of the present invention proposed to achieve the above object is to apply a voltage between the welding wire and the workpiece during a period in which they are not in contact with each other to destroy the slag generated at the tip of the welding wire. By setting the effective value to a value that does not exceed the output voltage of the welding power source during welding work, it is possible to prevent unexpected accidents due to electric shock. There is.

Further, the welding point detection device of the present invention proposed at the same time generates a pulse that applies a pulse voltage between the welding wire and the workpiece while the welding wire and the workpiece are not in contact after the end of welding and before the start of the next welding. The circuit is equipped with a signal generating circuit that outputs a welding point detection signal to other circuit parts when detecting a voltage change that occurs when the welding wire contacts the workpiece. The structure generates a pulse voltage that has a peak value sufficient to destroy slag generated at the tip and has an effective value that does not exceed the output voltage of the welding power source applied to the welding wire during welding work. It is characterized by

EXAMPLES Below, the method of the present invention will be explained together with the configuration of the apparatus with reference to the accompanying drawings.

FIG. 1 is an electrical circuit diagram showing a first embodiment of the device of the present invention.

1 is a welding power source, 2 is a pulse generation circuit, 3 is a welding point detection signal generation circuit, 4 is a welding wire, 5 is a workpiece, 6 is a welding torch, and 7 is a control device.

The welding electric power 'a1 is a DC power source, and when the welding start switch SW of the control device 7 is turned on, T! :, is configured to supply a welding voltage between the welding wire 4 and the workpiece 5 when the contact msl of the magnetic contactor MS is closed and the contact ms2 is opened.

The pulse generation circuit 2 includes a pulse generation circuit 20, a transistor TR, a step-up transformer PT, a diode D2 . It is configured by combining a driving power source E1, and a pulse generating circuit 2.
A pulse signal generated at a predetermined period from 0 is applied to the base of the transistor TR, and the transistor TR is turned on.
By performing OFF control, a voltage pulse is generated on the secondary side of the step-up transformer PT, and the voltage pulse thus generated causes the welding start switch SW of the control device 7 to open, and the contact msl of the electromagnetic contactor MS to open. ms2
When the voltage is closed, the voltage is applied to the welding wire 4 via the diode D2.

The pulse voltage generated in this pulse generation circuit 2 is
As shown in FIG. 3, the peak value Vp is large enough to destroy the slag generated at the tip of the welding wire 4 at the end of welding, and its effective value V RMS suppresses electric shock. For this reason, the output voltage of the welding power source during welding work is set not to exceed 0.For example, under normal welding conditions, the pulse voltage that satisfies these conditions is:
It is sufficient that the pulse voltage has a peak value of several hundred V. To give a specific example, the pulse width TI of a pulse voltage with a peak value Vp of 400 V is sufficient.
is 0.5m5ec, and the pulse period T2 is 5Qms.
This can be realized by using e c, but it goes without saying that this is not limited to this example.

On the other hand, the welding point detection signal generation circuit 3 is configured with an SCR drive circuit, and when the welding start switch SW provided on the control device 7 side is opened, the contact ms3 of the electromagnetic contactor MS closes to form a drive circuit. be done. SC formed
In the drive circuit R, the welding wire 4 and the workpiece 5 are in contact with each other during a period when the welding start switch SW is opened, the contact ms2 of the electromagnetic contactor MS is closed, and the above voltage pulse is supplied to the welding wire 4, The configuration is such that when a short circuit current flows through the current limiting resistor R and a voltage change occurs, the SCR is turned on and the relay CR is driven. In addition, E2
is the driving power source. When the relay CR is driven, the contact Cr provided in the control device 7 closes, so that the welding point detection signal is outputted to other circuit sections as a transfer signal. When the welding point detection signal thus output is sent to other circuit sections, the necessary control for the next welding operation is performed, and the same operation as above is repeated at the start of welding.

FIG. 2 shows another embodiment of the invention.

Since the basic structure is the same as that of the first embodiment, corresponding parts are given the same reference numerals, and only the structure and operation of the different parts will be explained.

In this embodiment, the welding point detection signal generation circuit 3 is configured as a relay drive circuit using a transistor without a latching function, so if the pulse voltage supplied from the pulse generation circuit 2 has a small pulse width, When the welding wire 4 and the workpiece 5 come into contact, the voltage change that occurs across the limiting resistor R turns on the transistor TR, making it impossible to operate the relay CR. For this reason, another diode D4 is connected in parallel to the diode D2 in the pulse generation circuit 2 so that the cathode is common, and another T: i'1REo is provided so that the voltage generated across the current limiting resistor R when the welding wire 4 comes into contact with the workpiece 5 becomes a voltage higher than the level that turns on the transistor TRI continuously.

FIG. 4 is an explanatory diagram of the voltage pulse output from the pulse generation circuit 2 in this embodiment, and the peak value is such that it destroys the slag generated at the tip of the welding wire, similar to that in the first embodiment. Vp and the effective value V IIMS
is set to a value that does not exceed the output voltage Vo of the welding power source during welding to destroy the slag and break the electric shock.

According to the apparatus of the present invention having the above configuration, the welding start switch SW of the control device 7 is opened, the application of the welding voltage by the welding power supply device l is cut off, and the welding process is started in order to start the next welding process. During the point search period, a voltage pulse generated by the pulse generation circuit 2 is applied between the welding wire and the workpiece to destroy the slag generated at the tip of the welding wire and safely locate the welding point. Since it can be searched, there is no risk of the welding point becoming impossible to detect due to an increase in contact resistance due to slag generated at the tip of the welding wire, making it highly reliable.
Moreover, since it is possible to safely detect welding points, it is extremely useful if applied to welding robots and automatic welding machines.

〔Effect of the invention〕

As can be understood from the above explanation, according to the welding point detection method of the present invention, the slag generated at the tip of the welding wire can be safely removed during the period from the end of the welding operation to the start of the next welding operation. , and can be destroyed reliably, making it highly safe (,
In addition, highly reliable welding point detection can be realized.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit configuration diagrams showing an embodiment of the present invention, and Figures 3 and 4 are waveforms of pulse voltages output from pulse generation circuits corresponding to Figures 1 and 2. Show the diagram. (Explanation of symbols) 1...Welding power source 2...Pulse generation circuit 3...Welding point detection signal generation circuit 4...8 contact wire 5...Workpiece 6...? 8 contact torch 7...control device

Claims (2)

[Claims] (1) During the period when the welding wire and the workpiece are in a non-contact state, the voltage between the welding wire and the workpiece is sufficient to destroy the slag generated at the tip of the welding wire, and the voltage applied to the welding wire during welding work. A pulse voltage with an effective value that does not exceed the output voltage of the welding power source is applied, and the welding point is detected by detecting the voltage change that occurs when the welding wire comes into contact with the workpiece during the application period of this pulse voltage. A method for detecting welding points. (2) During the period until the welding wire and the workpiece come into contact, the pulse generation circuit applies a pulse voltage between the welding wire and the workpiece, and the welding point detection signal is activated when detecting the voltage change that occurs when the welding wire and the workpiece come into contact. and a welding point detection signal generating circuit for outputting the welding point detection signal, the pulse voltage has a peak value sufficient to destroy slag generated at the tip of the welding wire, and is applied to the welding wire during welding work. A welding point detection device characterized by having an effective value that does not exceed the output voltage of a welding power source.