JPH0815664B2 - Welding point detection method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a welding point detection device suitably used for a welding robot, an automatic welding machine, and the like.

[Background technology]

A conventional welding point detecting device of this type is disclosed in, for example, Japanese Patent Laid-Open No. 60-
As disclosed in No. 96370, a voltage is applied between a welding wire and a work through a current limiting resistance from another power supply device different from the welding power source, and a short-circuit current flows due to the contact between the wire and the work, resulting in a current limiting resistance. It is configured to detect the voltage change occurring at both ends of the welding wire.However, in the case of using such a detection method, the contact resistance between the welding wire and the work piece is generally generated by the slag generated at the tip of the welding wire at the end of welding. Is likely to increase, resulting in erroneous welding point determination.

For example, since the contact resistance between the welding wire and the work increases due to the generation of slag, even when the welding wire and the work contact each other, a sufficient voltage change does not occur in the current limiting resistance, and it is often determined that the contact is not made. .

As a countermeasure against such a problem, it is possible to apply a voltage higher than the output voltage of the welding power source during welding to destroy the slag.However, if such a method is adopted, a new safety measure such as electric shock is required. Cause problems.

[Object of the Invention]

The present invention has been made in view of such circumstances, while safely performing the destruction of the slag that occurs at the tip of the welding wire, the welding tip can be brought close to the workpiece to detect the welding point, safety and reliability. It is an object of the present invention to provide an improved welding detection method on both sides and an apparatus for implementing the method.

[Disclosure of Invention]

The welding point detection method of the present invention proposed to achieve the above object is configured to detect a welding point to be welded by bringing a welding tip with a protruding welding wire close to a work before starting welding. In the welding point detection method, welding is performed while applying a pulse voltage between the welding wire and the workpiece, which has a peak value sufficient to destroy the slag of the welding wire and whose effective value does not exceed the output voltage of the welding power source. The feature is that an unexpected accident due to electric shock can be prevented by detecting the short-circuit current generated when the wire is brought close to the work and the welding wire comes into contact with the work to detect the welding point.

Further, the welding point detection device of the present invention proposed at the same time,
A pulse generator circuit that applies a pulse voltage between the welding wire and the work while the welding wire is not in contact with the work after the completion of welding and before the start of the next welding. Detects voltage changes that occur when the welding wire contacts the work. Sometimes a signal generating circuit for outputting a welding point detection signal to another circuit section is provided, and in particular, the pulse generating circuit has a peak value sufficient to destroy the slag generated at the tip of the welding wire. In addition, it is characterized in that a pulse voltage having an effective value that does not exceed the output voltage of the welding power source applied to the welding wire during the welding operation is generated.

Example Hereinafter, the method of the present invention will be described together with the configuration of the apparatus with reference to the accompanying drawings.

FIG. 1 is an electric circuit diagram of 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 work, 6 is a welding torch, and 7 is a controller.

The welding power source 1 is a DC power source, and when the welding start switch SW of the control device 7 is turned on, the contact ms1 of the electromagnetic contactor MS is closed and the contact ms2 is opened, welding is performed between the welding wire 4 and the workpiece 5. It is configured to supply a voltage.

The pulse generation circuit 2 is configured by combining a pulse generation circuit 20, a transistor TR, a step-up transformer RT, a diode D2, and a driving power source E1. The pulse generation circuit 20 generates a pulse signal generated in a predetermined cycle from the transistor TR. The voltage pulse is generated on the secondary side of the step-up transformer PT by applying ON to the base of the transistor TR and controlling the ON / OFF of the transistor TR. The voltage pulse generated in this way is detected by the welding start switch SW of the control device 7. Open, contact of magnetic contactor MS ms
1 is open and ms2 is applied to the welding wire 4 through the closed special diode D2. As shown in FIG. 3, the pulse voltage generated in the pulse generating circuit 2 has a peak value Vp of a magnitude sufficient to destroy the slag generated at the tip of the welding wire 4 at the end of welding. In addition, its effective value VRMS is set so as not to be higher than the output voltage Vo of the welding power source during welding work in order to suppress electric shock. For example, a pulse voltage satisfying such a condition may have a crest value of several hundred V under normal welding conditions. A specific example is a pulse voltage pulse having a crest value Vp of 400 V. The width T1 is 0.5 msec and the pulse period T2 is 5
It can be realized by setting 0 msec, but needless to say, it is not limited to such an example.

On the other hand, the welding point detection signal generation circuit 3 is composed of 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 magnetic contactor MS
Is closed to form a drive circuit. In the drive circuit of the formed SCR, the welding start switch SW is opened, the contact ms2 of the electromagnetic contactor MS is closed, and the above-mentioned voltage pulse is supplied to the welding wire 4, the welding wire 4 and the work 5 are When a contact is made and a short-circuit current flows through the current limiting resistor R to cause a voltage change, the SCR is turned on to drive the relay CR. Note that E2 is a driving power supply. When the relay CR is driven, the contact cr provided in the control device 7 is closed, so that the welding point detection signal is output to another circuit section as a transfer signal. When the welding point detection signal output in this manner is sent to another circuit section, control necessary for the next welding operation is performed, and at the start of welding, the same operation as described above is repeated.

FIG. 2 shows another embodiment of the present invention. Since the basic structure is the same as that of the first embodiment, the same reference numerals are given to corresponding parts, and only the structures and operations of different parts will be described.

In this embodiment, since the welding point detection signal generating circuit 3 is configured as a relay drive circuit using a transistor without a latching function, if the pulse voltage supplied from the pulse generating circuit 2 has a small pulse width, When the welding wire 4 and the workpiece 5 contact each other, the transistor TR is turned on by the voltage change generated at both ends of the limiting resistance R, and the relay
CR can not work. Therefore, another diode D4 in parallel with the diode D2 is connected to the pulse generation circuit 2 so that the cathode becomes common, and another power source Eo is provided on the side opposite to the arnode of the diode D4 and the diode D2 of the step-up transformer PT. Is provided so that the voltage generated in the current limiting resistance R when the welding wire 4 contacts the work 5 becomes a voltage higher than the level at which the transistor TR1 is continuously turned on.

FIG. 4 is an explanatory diagram of the voltage pulse output from the pulse generating circuit 2 in this embodiment, and a crest value that destroys the slag generated at the tip of the welding wire as in the first embodiment. Set the value that has Vp and the effective value VRMS that does not exceed the output voltage Vo of the welding power source during welding.
The slag is destroyed and the electric shock is suppressed.

According to the device of the present invention configured as described above, the control device 7
In order to start the next welding process by opening the welding start switch SW, the welding power source 1 stops the application of the welding voltage, the pulse generation circuit 2 generates the welding point. The generated voltage pulse is applied between the welding wire and the workpiece to destroy the slag generated at the tip of the welding wire and the welding point can be searched in a safe state. It is highly reliable because there is no possibility that the welding point will not be detected due to the increase of
Moreover, since it is possible to detect a welding point safely, it is extremely useful when applied to a welding robot or an automatic welding machine.

〔The invention's effect〕

As can be understood from the above description, according to the welding point detection method of the present invention, the welding work is completed, and in the period until the next welding work, the slag generated at the tip of the welding wire is made safe. Since it can be destroyed reliably, it is possible to realize a highly safe and reliable welding point detection.

[Brief description of drawings]

1 and 2 are circuit configuration diagrams showing an embodiment of the present invention, and FIGS. 3 and 4 are waveforms of pulse voltages output from the pulse generating circuits corresponding to FIGS. 1 and 2. The figure is shown. (Explanation of symbols) 1 ... Welding power supply 2 ... Pulse generation circuit 3 ... Welding point detection signal generation circuit 4 ... Welding wire 5 ... Work 6 ... Welding torch 7 ... Control device

Claims (2)

[Claims] 1. A welding point detecting method for detecting a welding point to be welded by bringing a welding tip with a protruding welding wire close to a work before starting welding, and destroying the slag of the welding wire. The pulse voltage that has a sufficient peak value for the effective value and does not exceed the output voltage of the welding power source is applied between the welding wire and the work, the welding wire is brought close to the work, and the welding wire contacts the work. A method for detecting a welding point, which detects a short-circuit current that sometimes occurs to detect a welding point. 2. A pulse generation circuit for applying a pulse voltage between the welding wire and the work during a period until the welding wire and the work come into contact with each other, and a welding point is detected when a voltage change generated at the time of contact between the welding wire and the work is detected. And a welding point detection signal generating circuit for outputting a signal, wherein the pulse voltage has a peak value sufficient to destroy the slag generated at the tip of the welding wire, and is applied to the welding wire during welding operation. Welding point detection device characterized by an effective value that does not exceed the output voltage of the welding power source used.