JP2002301574A - Method for detecting deposit in welding gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting deposit in a welding gun by which the deposit in the welding gun can accurately be judged by confirming beforehand erroneous detection and the possibility of detection of the deposit before detecting the deposit in the welding gun. SOLUTION: This method for detecting the deposit in the welding gun comprises confirming that there is no possibility of the erroneous detection of the deposit by giving a voltage signal to the gun side when the gun is opened in a stage before pressurizing a work, confirming that the deposit can be detected by giving the voltage signal to the gun side when a work is pressure- held, and checking whether the deposit is detected or not by giving the voltage signal to the gun side when the gun is opened after performing the above two confirming processes and welding the work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting welding of a welding gun in a welding gun in which a work is welded by pressurizing and holding the work with a welding gun and energizing the work.

[0002]

2. Description of the Related Art Conventionally, in a welding gun in which a work is welded by pressurizing and holding the work with a welding gun and energizing the work, the work is performed after the work is pressure welded by the welding gun. A method of applying a test voltage signal to the welding gun at the time when the welding gun is opened to detect welding of the welding gun is well known (for example, Japanese Utility Model Laid-Open No. 62-61379, Japanese Utility Model Application Laid-Open No. 2-3-3).
No. 2385).

[0003]

In the above-mentioned conventional technique, however, a test voltage signal for detecting welding is applied only after pressure welding of a work with a welding gun. If the gun is already short-circuited by spattering or the like, there is a risk that the detection will be a false detection,
If the test voltage signal supply wiring is disconnected or has poor contact, welding detection may not be possible, and there is a problem that it is difficult to accurately determine welding detection in a welding gun.

[0004] The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to make it possible to detect and detect erroneous welding in advance before detecting welding in a welding gun. It is an object of the present invention to provide a method for detecting welding in a welding gun so that accurate determination of welding in the welding gun can be made by checking whether or not the welding is performed.

[0005]

In order to achieve the above object, a method for detecting welding in a welding gun according to the present invention comprises:
When the gun is opened at the stage prior to pressurizing the work, a voltage signal is applied to the gun to confirm that there is no possibility of erroneous welding detection. Apply a voltage signal to confirm that welding detection is possible, and after both checks above, apply a voltage signal to the gun side when the gun is opened after welding the work to check for the presence of welding detection. It is characterized by doing so.

Further, in the case where there is a possibility of the erroneous detection and the case where the welding detection is impossible, an alarm output which can be classified is generated. is there.

[0007] Further, the present invention is characterized in that a short-time pulse-like voltage is applied as each voltage signal in each step without applying a long-time voltage.

[0008]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a welding detection circuit suitable for carrying out a welding detection method in a welding gun according to the present invention, and FIG. 2 is an explanatory diagram of a main part circuit for confirming the possibility of welding detection.

In FIG. 1, reference numeral 1 denotes a computer circuit, and an input / output circuit 2 is connected to the computer circuit 1. 3 is a detection line, 4 is a spot welding gun, 5
Is a work, 6 is a transformer, and 7 is a comparator (for example, a comparator or an operational amplifier).

Then, with the work 5 pressurized and held by well-known pressure holding means by the spot welding gun 4,
The work 5 is welded by the spot welding gun 4 by applying a welding current from the transformer 6 for a predetermined time.

By the way, when the work 5 is welded by the spot welding gun 4, the electrode of the spot welding gun 4 and the work 5 may be fused depending on welding conditions, resulting in a so-called welded state.

In order to detect this welding, when the welding gun 4 is opened after the welding of the work 5 by the welding gun 4, the input / output circuit 2 is instructed by the computer circuit 1.
, A short-time pulse-like voltage is applied from the detection line 3 to the welding gun 4 side. When this voltage is applied, i of comparator 7
A check is made to determine whether or not a voltage below a preset level is applied to the n side. If the voltage is below the set level, it is determined that welding has not been detected. If the voltage exceeds the set level, it is determined that welding has been performed. Then, an alarm is generated by the alarm generator A3 via the input / output circuit 2.

In FIG. 1 of the above embodiment, a voltage is applied from the input / output circuit 2 to the welding gun 4 side, and a change in the voltage is checked by the comparator 7, and the input / output circuit 2 and the wire are used. The connection line 3 may be used to electrically connect the welding gun 4 and the comparator 7 during the connection 5.

If the welding of the welding gun 4 is detected only when the welding gun 4 is opened after the welding of the work 5 by the welding gun 4 as described above, the gun opening before the welding of the work 5 by pressure is performed. Sometimes the position of work 5 or spatter
If an electric short circuit has already occurred with the work 5 on the gun 4 side due to the presence of dust or the like, even if the welding state is not generated when the welding gun 4 is opened after the welding, the comparator may be used. It is detected that the setting level exceeds the set level from 7, causing an erroneous detection.

Similarly, if the welding of the welding gun 4 is detected only when the welding gun 4 is opened after the welding of the work 5 by the welding gun 4, the detection wire 3 has a disconnection or poor contact. In this case, although the welding state is generated when the welding gun 4 is opened after the welding, the comparator 7 detects that the welding level is equal to or less than the set level, which causes the welding to be undetectable.

Therefore, according to the present invention, when the gun 4 is opened before the work 5 is press-welded, a voltage is applied to the gun 4 in the same manner as when the welding gun 4 is opened after welding the work 5. Give a signal. That is, when the gun is opened at the stage before the work 5 is press-welded, a short pulse voltage is applied from the detection line 3 to the welding gun 4 side via the input / output circuit 2 in response to a command from the computer circuit 1. Is applied. When this voltage is applied, the comparator 7
A check is made to see if a voltage below a preset level is applied to the in side of the switch. If the voltage is below the preset level, it is determined that there is no short circuit or the like between the welding gun 4 and the work 5, and the preset level is exceeded. If so, it is determined that a short circuit has occurred, and an alarm is issued by the alarm generator A1 via the input / output circuit 2. This makes it possible to confirm that there is no possibility of erroneous detection of welding detection.

FIG. 2 shows the stage of pressure welding the work 5.
When the welding gun 4 is in contact with the welding gun 4 and the work 5 is in contact with the welding gun 4 as shown in FIG. That is, in the step of welding the work 5 under pressure, first, a short pulse voltage is applied to the welding gun 4 side from the detection wire 3 via the input / output circuit 2 by a command from the computer circuit 1. You. When this voltage is applied, it is checked whether or not a voltage lower than a preset level is applied to the in side of the comparator 7. If the voltage is lower than the set level, it is determined that the detection line 3 has a disconnection accident or the like, and input / output is performed. The alarm is output by the alarm generator A2 via the circuit 2, and if the alarm level exceeds the set level, it is determined that the detection line 3 has no disconnection accident or the like. This makes it possible to confirm that welding can be detected.

As described above, in the present invention, prior to detection of welding in a welding gun, a voltage signal is applied to the gun 4 to check whether welding has been detected when the gun is opened after welding of the work 5. When the gun 4 is opened before the work 5 is press-welded and when the work 5 is pressed and held by the gun 4, a voltage signal is given to the gun 4 via the detection wire 3 in advance to detect welding. This is for confirming prevention of erroneous detection and confirming detectability.

Therefore, when the gun is opened after welding of the work 5 and a voltage signal is applied to the gun 4 to check whether or not welding has been detected, the determination is accurate.

In the case where the output of the alarm A1 or A2 which can be classified can be generated when there is a possibility of the erroneous detection and when the welding cannot be detected. Can be confirmed very easily and easily.

In the case where a short-time pulse-like voltage is applied without applying a long-time voltage as each voltage signal in each of the above-described confirmation step and welding check step,
If the conductor is prevented from being touched and the confirmation and the welding check are performed by applying a pulse voltage a plurality of times, the accuracy in probability is increased.

[0022]

In the present invention, prior to the detection of welding in a welding gun, a voltage signal is applied to the gun side to check the presence or absence of welding when the gun is opened after welding of the work. A voltage signal is applied to the gun side via a detection wire in advance when the gun is opened before pressurizing and welding the work and when the work is pressurized and held by the gun, so that misdetection of welding detection can be prevented and confirmed. Therefore, the method for detecting welding in the welding gun is such that accurate determination of welding in the welding gun can be made.

In the case where there is a possibility of erroneous detection and the case where welding detection is impossible, an alarm output that can be classified is generated. This is a very simple and easy welding gun welding detection method.

Further, when a short-time pulse-like voltage is applied without applying a long-time voltage as each voltage signal in each of the confirmation step and the welding check step, contact of the conductor is prevented, In addition, the method for detecting welding in a welding gun increases the accuracy of the probability of confirmation and welding check.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a welding detection circuit suitable for carrying out a welding detection method in a welding gun according to the present invention.

FIG. 2 is an explanatory diagram of a main circuit for confirming that welding detection is possible.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Computer circuit 2 I / O circuit 3 Detecting wire 4 Welding gun 5 Work 7 Comparator A1, A2, A3 Alarm

Claims (3)

[Claims] 1. A welding gun for welding a work by pressurizing and holding the work with a welding gun and applying an electric current to the welding gun. When the gun is opened before the work is pressurized, a voltage signal is applied to the gun side to confirm that there is no possibility of erroneous welding detection, b. Then, a voltage signal is applied to the gun side when the work is pressurized, and it is confirmed that welding can be detected; c. The above a. b. A welding detection method for a welding gun, wherein a voltage signal is applied to the gun when the gun is opened after welding of the work to check whether welding has been detected. 2. The method according to claim 2, wherein If there is a possibility of erroneous detection in b., And b. 2. The welding detection method for a welding gun according to claim 1, wherein when welding detection in the step (c) is not possible, an alarm output is generated so as to be able to distinguish each of them. 3. The a. b. c. 2. The welding detection method for a welding gun according to claim 1, wherein a short-time pulse-like voltage is applied without applying a long-time voltage as each of the voltage signals.