JP2000218377A - C-shaped welding gun controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a safe C-shaped welding gun for preventing deformation of a work during pressurization welding by providing a welding gun main body with an equalizing in correspond to the movement of the welding gun main body caused along with supply of a welding current. SOLUTION: This C-shaped welding gun is equipped with an equalizing mechanism 3 between a manipulator arm 1 and a welding gun main body 2. This gun also comprises a motor 11 which is fixed to the manipulator arm and equalizes the welding gun main body, and a motor 4 which is fixed to the welding gun body and drives a movable arm 6. In this case, a servo control action for providing the motor fixed to the manipulator arm with equalizing corresponding to the movement volume due to influences of a magnetic field of the welding gun arm main body accompanied by supply of the welding current, is started right before the welding current is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control method for a C-type welding gun having an equalizing mechanism between a manipulator arm of a robot or the like and a welding gun body.

[0002]

2. Description of the Related Art Conventionally, a C-type welding gun having an equalizing mechanism 23 between a manipulator arm 21 of a robot or the like and a welding gun body 22 as shown in FIG. In this gun, the pressurizing cylinder 24, the movable electrode 25, the fixed electrode 26 and the manipulator arm 21 are mechanically separated from each other. To keep each other floating. And 29 is the manipulator arm 2
The power is supplied from the transformer 29 to the movable electrode 25 and the fixed electrode 26 via a flexible conductor 30.

In the C-type welding gun, when a work current is supplied through the flexible conductor 30 while the work 31 is in a pressurized state by the electrodes 25 and 26, the flexible conductor 30 and the movable electrode 2 are moved.
5, a secondary loop circuit composed of the work 31, the fixed electrode 26, and the flexible conductor 30 is acted upon by an electromagnetic force to increase the electrical impedance, and the force for expanding the entire circuit is increased. appear. Due to this force, the welding gun body 22 is moved leftward or rightward with respect to the paper surface in FIG.

Meanwhile, a movable arm driven by a pressurizing device connected to a manipulator arm similar to the above-mentioned conventional example.
A C-type welding gun having a motor, comprising: a motor fixed to the manipulator arm for equalizing the welding gun body; and a motor fixed to the welding gun body to drive the movable arm, the motor being fixed to the manipulator arm. To the electric motor, the electric current taking into account the torque of the electric motor caused by the posture of the welding gun body at the welding position and the pressing force on the work by the electric motor, is set and applied to the electric motor fixed to the welding gun main body. An electric current taking into account the pressure applied to the work by the electric motor is set and applied so that the electric motor is held between the electric motors, as disclosed in Japanese Patent Application Laid-Open No. 9-70671, for example. It is known.

[0005]

In the case of the known gun, a specially complicated sensor mechanism for the posture, weight balance, etc. of the welding gun body is not required, and the control of the pressing force is simple. C that is possible and excellent in cost and performance
The welding gun becomes a die-type welding gun, but the welding gun body moves with respect to the work under the influence of the magnetic field generated with the supply of the welding current, and the one side of the work is strongly pressed in the same manner as in the conventional well-known technology. There is a risk of doing so. This tendency is particularly noticeable when the welding gun body is large and a large current is supplied as in welding of an aluminum plate.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to cope with the movement of the welding gun body which occurs with the supply of welding current. An object of the present invention is to provide a safe control method for a C-type welding gun that imparts equalizing to the welding gun body to prevent deformation of the work during pressure welding.

[0007]

In order to achieve the above-mentioned object, a method of controlling a C-type welding gun according to the present invention comprises a C-type welding gun having an equalizing mechanism between a manipulator arm and a welding gun body. A motor fixed to the manipulator arm for equalizing the welding gun body and a motor fixed to the welding gun body to drive the movable arm, wherein the motor fixed to the manipulator arm includes: A servo control operation for imparting equalization commensurate with the amount of movement caused by the magnetic field of the welding gun body accompanying the supply of the welding current is started immediately before the supply of the welding current.

Further, the servo control operation is terminated immediately before the supply of the welding current is completed.

[0009]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a main part of a C-type welding gun applied to the present invention.
The gun is substantially the same as that shown in the publication. In FIG. 1, reference numeral 1 denotes a manipulator arm of a robot or the like, and an equalizing mechanism 3 is disposed between the manipulator arm 1 and the welding gun main body 2.
The welding gun body 2 is connected to the manipulator arm 1 via the equalizing mechanism 3.

A movable arm 6 driven by an electric motor 4 and having an electrode 5 at its tip is provided on the welding gun body 2.
, A substantially C-shaped fixing arm 8 having an electrode 7 at the tip is formed, and constitutes a C-type welding gun as a whole.

The equalizing mechanism 3 comprises a bracket 9 fixed to the manipulator arm 1, a groove 10 in which the welding gun body 2 can slide, an electric motor 11 fixed to the bracket 9, and the welding gun. And a lead screw 13 screwed into a nut 12 fixed to the main body 2.

Reference numeral 14 denotes a nut fixed to the movable arm 6, and a lead screw from the electric motor 4 is provided.
15 is screwed. Reference numerals 16 and 17 denote connection terminals for supplying a welding current to the work 18 via the electrodes 5 and 7, which are connected to output terminals of a welding transformer (not shown). .

In the above-described C-type welding gun, when the welding gun main body 2 is moved by the manipulator arm 1, the welding gun main body 2 itself needs to be fixed to the manipulator arm 1; Servo-locking control is performed. When the welding gun body 2 is moved to a fixed welding position by the manipulator arm 1,
First, the current in the electric motor 11 is measured, and the posture of the welding gun body 2 and the state of its gravity balance can be determined from the magnitude and polarity of the current. That is, the current value at that time indicates a torque balanced with the gravitational force applied to the welding gun main body 2, and the polarity thereof is determined by the direction of the pressing direction of the electrode 5 with respect to the horizontal plane. The gravity referred to here is the gravity acting on a portion of the motor 11 other than the manipulator arm 1, the bracket 9 and the motor 11 in FIG.

Therefore, based on this data, the work 18
Is calculated (approximately 0 to 20 kg), and the current of the electric motor 11 is set to the calculated value. At this time, when the pressing direction of the electrode 5 is upward with respect to the horizontal plane, the set current and its direction are “measured current−workable current (current corresponding to the pressing force allowed for the work)”. In the counter-working direction ”, and when the pressing direction is downward with respect to the horizontal plane, it becomes“ measurement current + working allowable current in the working direction ”. The current set value of the motor 4 is a value corresponding to the pressing force required for welding the work.

After the currents are set and applied to the motors 4 and 11 as described above, when the motors 4 and 11 are driven to perform constant current control, the motor 4 causes the movable arm 6 and the electrode 5 to warp. Approach to the electrode 18 and the electric motor 11
Is in a stopped state or gradually slowly approaches the work 18,
After the electrode 5 contacts the work 18, the motor 4
The electrode 7 also approaches the work 18 due to the reaction force of the pressing force caused by the pressure, and contacts the work 18 to apply a pressing force to the work 18.
Since the weight of the welding gun body 2 is balanced by the electric motor 11 when the electrode 5 is moved, that is, when the welding gun body 2 is equalized, the deformation of the work 18 during the pressurizing operation can be almost completely prevented. is there.

When the work 18 is pressurized by the electrodes 5 and 7 and a welding current is supplied through the connection terminals 16 and 17, the connection terminal 16, the movable arm 6, the electrodes 5 and 5 are supplied as described above. An electromagnetic force acts to increase the electrical impedance of the secondary loop circuit composed of the work 18, the electrode 7, the fixed arm 8, and the connection terminal 17, and attempts to expand the entire circuit. Force is generated. This force causes the welding gun body 2 to move downward or upward as a whole in FIG. 1 (due to the position of the welding gun, the structure of the equalizing mechanism, etc.).
As a result, the work 18 may be further pressurized by the electrode 5 to damage the work 18.

Therefore, as shown in FIG. 2, the electric motor 11 is driven immediately before the supply of the welding current, and the drive of the electric motor 11 causes the welding gun body 2 to be supplied with the welding current and the above-mentioned expected movement amount X Servo control operation is performed to equalize upward or downward by the amount corresponding to. As a result, the movement of the welding gun body due to the magnetic field caused by the supply of the welding current is canceled, and the electrode 5 is prevented from being excessively pressurized on the work 18. In this case, the movement amount X
Is determined by the attitude of the welding gun at that time, the structure of the equalizing mechanism, and the like, and may be programmed according to the actual situation.

Also, immediately before the supply of the welding current is stopped, the electric motor 1
By performing control to reverse the drive of 1 and return it to the original position,
Since the welding gun body 2 returns to the original position by the amount corresponding to the movement amount X at the same time as the supply of the welding current is stopped, the influence of the magnetic field is eliminated by stopping the supply of the welding current, and the welding gun body is moved upward or downward. The portion to be moved is canceled out, and the extreme pressurization of the work 18 by the electrode 7 is also prevented.

Immediately before the supply of the welding current, the motor 1
As a timing for driving the motor 1, a welding dead time TS (for example, several milliseconds to several tens of milliseconds), which is a delay time from when a start signal is input to the electric motor 11 to when the electric motor 11 actually starts to move, is applied. The supply of the welding current is started in synchronization with the time when the main body equalizes by X (proportional to the supply current). Also, when the motor 11 is reversed just before the supply of the welding current is stopped, the motor 11
May be set in consideration of the return adjustment time TE (for example, several milliseconds to several tens of milliseconds) in which the welding gun body actually returns to the original state after the reverse rotation.

[0020]

According to the present invention, there is provided a servo control operation for imparting equalizing to the electric motor fixed to the manipulator arm in accordance with the amount of movement of the welding gun main body due to the magnetic field accompanying the supply of the welding current. Since the starting is performed immediately before the supply of the welding current, it is possible to prevent the work from being excessively pressurized and damaged by the supply of the welding current, and to provide a safe C-type welding gun control method. Becomes

If the servo control operation is terminated immediately before the end of the supply of the welding current in addition to the above control method, the work is extremely pressurized by stopping the supply of the welding current. Such damage can be prevented beforehand, and a safer control method for the C-type welding gun can be provided.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a C-type welding gun applied to the present invention.

FIG. 2 is an explanatory diagram showing a control relationship between a welding current and a motor in the present invention.

FIG. 3 is a schematic explanatory diagram of a C-type welding gun provided with a conventional equalizing mechanism.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Manipulator arm 2 Welding gun main body 3 Equalizing mechanism 4 Motor for driving movable arm 5, 7 Electrode 6 Movable arm 11 Motor for equalizing 18 Work

Claims (2)

[Claims] 1. A C-type welding gun having an equalizing mechanism between a manipulator arm and a welding gun main body. The motor is fixed to the manipulator arm and equalizes the welding gun main body. An electric motor for driving an arm, wherein the motor fixed to the manipulator arm is provided with an equalizing commensurate with the amount of movement of the welding gun body due to the influence of the magnetic field caused by the supply of the welding current. -A method for controlling a C-type welding gun, wherein a bob control operation is started immediately before the supply of the welding current. 2. Immediately before the end of the supply of the welding current, the
2. The control method for a C-type welding gun according to claim 1, wherein the control operation is terminated.