JPS6268685A - Control unit for spot welding robot - Google Patents

Abstract

PURPOSE:To prevent the traces in spotting and of spatters by reducing the output of the electrically driven servo motor which performs the position correction while from the completion of the movement of a welding gun to the target value upto the start of welding current feeding and by returning on each completion of welding as well. CONSTITUTION:A memory part 11 stores the spot welding position of a work by teaching and arithmetic processing part 12 plays it back according to the program of the memory part 11. A servo motor driving part 13 drives an electrically driven servo motor by the command from the arithmetic processing part 12 and a pressure driving part 14 drives the pressure driving source of a welding gun by the command from the arithmetic processing part 12. A transformer 15 feeds the welding current to a welding electrode 2 by the command from the arithmetic processing part 12. A control means 16 reduces the output of the electric servo motor which performs the position correction by the deflection of the gun 1 while from the movement completion of the welding gun 1 upto the feeding start of the welding current by the command from the arithmetic processing part 12 and restores the output of the electric servo motor on each completion of the spot welding of the welding gun 1 as well.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a control device for a spot welding robot.

Conventional technology spot welding robots are known, for example, from August 10, 1980, published by Sankaido, “Internal Combustion Engine; vo121/16267
As shown in pages 51 and 52 of ``August Special Issue: Trends in Industrial Robot Technology'', an X-shaped welding gun is attached to the tip of the multi-axis arm, and the spot welding position of the workpiece is This spot welding robot (hereinafter referred to as
(Simply referred to as a welding robot) There are two types of moss playback drive sources: hydraulic type, which uses hydraulic pressure, and electric type, which uses electric power.However, hydraulic type requires maintenance and is slow to respond, and the equipment is large, making it difficult to save energy. However, electric models are increasingly being used.

However, in the case of the electric type described above, as shown in FIG. 3, the welding gun 1 is moved by calculating the distance and direction to the target value, which is the spot welding position. When the welding gun 1 reaches the target spot welding position, it is pressurized by the pressurizing drive source 1a, and when the workpiece 3 is held between the welding electrode rods 2 facing each other, the welding electrode rod 2 is supported by the applied force. The arm 1b that is in the position bends as shown by the imaginary line, and this bending
As a result, the arm 4 on which the welding gun 1 of the spot welding robot is attached is pushed back by the deviation Δg in the direction of arrow Then, in an attempt to correct the deviation Δe, the electric servo motor is driven while the welding gun 1 pressurizes and clamps the workpiece 3, and as a result of this drive, the welding electrode 2 moves around the clamped part with the workpiece 3. It is pushed in the direction of arrow Y, which is opposite to arrow X, and arrow F,
In addition to the required pressure shown by arrow F, spot welding is performed while applying an abnormal external force shown by arrow F, so as the spot welded part of workpiece 3 is softened by the welding current, it is pushed forward and raised, resulting in dents. 5, and some of the raised parts scatter and adhere to the area around the spot welding area, resulting in spatter marks 6. These dents 5 and spatter marks 6 are ground by a grinder ζ after spot welding, which requires only one surface finishing work and is also economically disadvantageous.

Therefore, the present invention focuses on the fact that the deflection of an X-shaped welding gun is proportional to the applied force, and provides a control device for a spot welding robot that can prevent the dents and spatter marks.

Means for Solving the Problems In the present invention, an X-shaped welding gun is attached to the arm,
A welding robot equipped with an electric servo motor as a drive source plays back the program f in which the spot welding position of the workpiece is memorized. A control means is provided for reducing the output of the electric servo motor to correct the position due to the deflection of the welding gun, and for returning the output of the electric servo motor to the original position every time the welding gun completes spot welding.

Function: Eliminates the push-back force from the welding robot to the workpiece due to the deflection of the welding gun, without interfering with the work speed of the welding robot's movement of the workpiece to the target value, which is the spot welding position, and the pressurizing operation of the welding gun. Perform spot welding.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, with the same reference numerals assigned to the same parts as in the conventional structure.

Figure 1 - As shown, 10 is an electric servo motor as a drive source that plays back spot welding positions on the workpiece according to a stored program! This is a welding robot equipped with a welding robot, which includes a storage section 11 that stores the welding position of the workpiece by teaching, an arithmetic processing section 12 that plays back according to the program in the storage section 11, and a command l from this arithmetic processing section. 'I! Servo motor drive section 13 that drives the ts servo motor, and arithmetic processing section 1
A transformer 1 that supplies a welding current to the welding rod 2I according to a command from the arithmetic processing section 12;
5, and an X-shaped welding gun 1 is attached to the tip of the arm 10a. [6 is a command from the arithmetic processing unit 12 to reduce the output of the electric servo motor that corrects the position according to the deflection ζ of the welding gun 1 from the end of the movement of the welding gun 1 to the start of supply of welding current, and 1
This is a control means for restoring the output of the electric servo motor each time spot welding is completed.

To explain the execution of the control in the above-mentioned embodiment according to the flowchart shown in FIG. The servo motor drive section, 131, is supplied. In the next section (1), it is determined whether the welding gun 1 has reached the target value.

If the target value of the welding gun 1 has not been reached, the processing in section (2) is continued. When welding gun 1 reaches the target value, welding gun 1 is pressurized and driven in section ■.
In section (2), the output voltage of the servo motor drive section 13, which attempts to correct the position of the deflection of the welding gun 1, is lowered to an extent that can prevent the arm from falling due to its own weight. In the next section (2), it is checked whether the pressurization of the welding gun 1 is completed or not, and in the section (2) it is determined whether the output voltage of the servo motor drive section 13 has decreased. When the welding gun 1 pressurizes at the required value and the output voltage of the motor drive unit 13 decreases, H-1
In '7', the transformer 15) outputs a welding current supply signal. If pressurization of welding gun 1 is not completed, proceed to section (2). If the output pressure of the servo motor drive unit 13 has not decreased, perform section ■ cell. Next, check whether the spot welding is completed in section ①. Then spot melting 1j 5E, if you have not done so, continue with section ■. When spot welding is complete, output a welding current cutoff signal to transformer 15 in section ■,
The pressurization of the welding gun 1 is released in section [phase], and the output voltage of the servo motor drive section is restored to the required value in section (2).

Next, check the operation of these sections ■, [phase], and σp using sections @, ◎, and ■. Once the operation is complete, check whether the spot welding position is the final spot welding position of the program using section If not, move on to the next program goal in section [phase] and compare sections ■ to section O by 1.

Effects of the Invention As described above, according to the present invention, it is possible to prevent the welding robot from moving to the workpiece due to the deflection of the welding gun, without impeding the working speed of the welding robot's movement to the target welding value and the pressurizing operation of the welding gun. Since the push-back force can be removed, dents and spatter marks that require finishing work can be prevented, and spot welding can be performed at low cost and with good quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart of the same embodiment, and FIG. 3 is an explanatory diagram of the operation of a conventional spot welding robot. 1. Welding gun, 10... Welding robot, 16... Control means.

Claims (1)

[Claims] An X-shaped welding gun is attached to the arm of the welding robot, which is equipped with an electric servo motor as a drive source that plays back spot welding positions on the workpiece according to a stored program. A control means is attached to reduce the output of the electric servo motor that corrects the position due to the deflection of the welding gun between the time and the start of supply of welding current, and to restore the output of the electric servo motor each time the welding gun completes spot welding. A control device for a spot welding robot, characterized in that: