JPH0631460A - Positioning controller for spot welding robot - Google Patents

Abstract

PURPOSE:To suppress the quantity of wear of an electrode tip to the minimum by positioning a spot welding gun and detecting the quantity of wear of the electrode tip at the spot welding gun. CONSTITUTION:The positioning controller of the spot welding robot 1 constituted to position the spot welding gun 3 fitted on the tip of an arm based on teaching data and perform spot welding on materials to be welded is provided with a wear quantity detection means to detect the quantity of wear of the electrode tip 4 of the spot welding gun 3 and a correction means to correct the teaching data of the spot welding gun 3 according to the quantity of wear detected thereby. Consequently, the quantity of wear of the electrode tip can be detected while suppressing cost increase to the minimum and spot welding work of high quality with high reliability can always be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning control device for a spot welding robot having a function of automatically detecting the amount of wear of a tip of a spot welding gun mounted on the robot.

[0002]

2. Description of the Related Art For example, spot welding applied to a vehicle body is performed by a dedicated spot welding gun attached to a robot, but an electrode tip that directly performs spot welding wears depending on the number of times it is used. If this wear increases, problems may occur in terms of welding reliability.
The current situation is that humans regularly make diagnoses and exchange them.

[0003]

However, in the conventional method in which the human is regularly inspected as described above, in order to always obtain a highly reliable welding state, the frequency of the periodic inspection must be increased, and the work efficiency is high. There is a problem of decrease.

Further, if a special device such as a two-dimensional sensor for detecting this wear is provided, there is a problem that the cost is increased and it is not suitable for the current situation.

The present invention has been made in view of the above problems of the prior art, and a positioning control device for a spot welding robot capable of detecting the amount of wear while suppressing the cost increase to a minimum. For the purpose of providing.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention is configured to position a spot welding gun attached to the tip of an arm based on teaching data and spot weld a work piece. In the spot welding robot, the wear amount detecting means for detecting the wear amount of the electrode tip in the spot welding gun and the teaching data of the spot welding gun are corrected according to the wear amount detected by the wear amount detecting means. It has a correction means.

[0007]

In the present invention thus constructed, the wear amount detecting means detects the wear amount of the electrode tip of the spot welding gun, and the correcting means corrects the teaching data according to the wear amount. .

Since this correction is automatically performed, the electrode tip is always positioned at the optimum position, and it is possible to always ensure highly reliable welding.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a spot welding robot.

As shown in the figure, the operation of the spot welding robot 1 illustrated in the figure is performed by a robot controller 2.
Is controlled by. This spot welding robot is of a 7-axis type, and a spot welding gun 3 is attached to its working end. The first axis turns the entire spot welding robot 1 in the J1 direction, and the second axis moves the working end in the vertical direction, that is, the J2 direction with reference to the first axis. The third axis similarly moves the working end in the vertical direction, that is, the J3 direction, with the second axis as a reference. Fourth axis is third
The working end is turned in the J4 direction in the figure with the axis as a reference. The fifth axis shows the working end with reference to the fourth axis J5
It is to move in the direction. The sixth axis is for rotating the working end in the J6 direction in the figure with reference to the fifth axis. The seventh axis moves the electrode tip 4 of the spot welding gun 3 attached to the working end up and down in the direction J7 in the figure.

The robot controller 2 comprehensively controls the above-mentioned 7-axis operations based on the data taught in advance to position the electrode tip 4 at a predetermined position with respect to the workpiece. Spot welding is performed at that position.

FIG. 2 is a schematic block diagram of a positioning control device for a spot welding robot according to the present invention. In the robot control device 2, a control unit 5 that comprehensively controls the operation of the spot welding robot 1, and based on a signal from the control unit 5, the operation of each of the 7 axes is controlled for each axis. Servo control units 10A to 10G are provided. This servo control section 10A-
The six servo control units up to 10F control the operation of each axis arm of the main body of the spot welding robot 1, and the servo control unit 10G controls the operation of the electrode tip 4 of the spot welding gun 3. Is. The limit switch 15 constitutes a wear amount detecting means, is for obtaining a reference signal for detecting the wear amount of the electrode tip 4 described later, and is firmly attached to a predetermined reference position. Is.

FIG. 3 is a detailed block diagram of the servo control section. The servo control unit controls the operation amount of the connected servo motor 18,
The operation amount of the servo motor 18 is fed back by a signal from the encoder 19. The encoder 19 gives position feedback to the control unit 5 and at the same time, gives feedback of the position command and the speed command to the servo control unit itself.

The servo control unit calculates the rotation speed of the servo motor 18 based on the position command output from the control unit 5, and based on this speed command, the servo motor 18
Calculate the command of the current to flow to. Based on this current command, a predetermined voltage is applied to the servo motor 18 and a predetermined current is supplied. The current controller 20 controls the servo motor 18 based on the current limit command output from the controller 5.
Has a function of controlling so as not to supply a current exceeding the limit current, and a function of notifying the control unit 5 of the current currently supplied to the servo motor 18, that is, a function as a wear amount detecting means. It is a thing. The robot controller 2 wears the electrode tip 4 based on a signal input when the limit switch 15 is turned on or a signal that detects that the current flowing through the servomotor 18 has reached a predetermined value or more. It also has a function as a correction means for detecting the amount and at the same time automatically rewriting teaching data for the robot operation, which is pre-taught by the spot welding robot 1, based on the detected wear amount. ing.

The apparatus of the present invention thus constructed operates as follows based on the flowchart of FIG. 4 or FIG. This operation will be described with reference to FIG. 5 or FIG. First, a first embodiment will be described in which the wear amount of the electrode tip is detected based on the on / off timing of the limit switch 15 and the teaching data is corrected based on this.

When the robot controller 2 starts executing the program for detecting the wear amount of the electrode tip 4 according to a predetermined fixed period, the controller 5 is taught the electrode tip 4 in advance at the same time when the program is started. A signal for positioning at a predetermined position based on the teaching data is output to each of the servo control units 10A to 10G (S1). Servo control unit 10 receiving this signal
A to 10G slowly move the tip of the electrode tip 4 toward the limit switch 15 as shown in FIG. 5 (S
2). When the positioning is completed, the tip end of the electrode tip 4 is vertically moved based on another teaching data until the limit switch 15 is turned on as shown in FIG. 5 (S3). When the switch is turned on, the control unit 5 recognizes that this switch is turned on, and at the same time, inputs the position data of each axis arm from the encoder of the servo motor to which each servo control unit is connected, and from this input data, the electrode tip The wear amount of 4 is calculated. Since the coordinate at which the limit switch 15 is turned on is always constant (because the limit switch is firmly attached to the fixed dog 16), for example, when the limit switch 15 is turned on when the electrode tip 4 is replaced. By storing the position data of each axis arm, the wear amount can be easily calculated from the position data (S4 to
S6). The wear amount is detected for both the upper and lower chips, and the teaching data for spot welding is corrected by the wear amount. Specifically, the teaching data in the Z-axis direction shown in FIG. 5 is corrected, and the pressure contact force of the electrode tip 4 to the workpiece is corrected (S7, S).
8).

The flowchart shown in FIG. 6 shows a second embodiment in which the change in the current flowing through the servo motor is detected, the wear amount of the electrode tip is detected based on the change, and the teaching data is corrected. .

When the robot controller 2 starts executing the program for detecting the wear amount of the electrode tip 4 according to a predetermined fixed period, the controller 5 is taught the electrode tip 4 in advance at the same time when the program is started. A signal for positioning at a predetermined position based on the teaching data is output to each of the servo control units 10A to 10G. Servo control units 10A to 1 that received this signal
0G slowly moves the tip of the electrode tip 4 toward the limit switch 15 as shown in FIG. 5 (S1).
1). When this positioning is completed, only the electrode tip 4 is slowly moved in the pressing direction of the dog 16 (S12). At this time, the value of the current flowing through the servo motor 18 is detected by the current controller 20, and this is output to the controller 5. When this operation is continued and the electrode tip 4 hits the detection portion 16A of the dog 16, the current flowing through the servo motor 18 increases. When the control unit 15 detects this rise (S13), the control unit 5 inputs the position data of each axis arm from the encoder of the servo motor to which each servo control unit is connected, and the wear of the electrode tip 4 is detected from this input data. The amount is calculated in the same manner as in the first embodiment (S1
4, S15). The wear amount is detected for both upper and lower chips, and the teaching data for spot welding is corrected by this wear amount in the same manner as in the first embodiment (S16-).
S18). Whether or not the current flowing through the servomotor 18 has risen is recognized by the control unit 5 based on the current monitor feedback signal shown in FIG.

If the above operation is programmed so as to be performed at regular intervals during spot welding work, or periodically at the time of factory startup every day, it is not necessary for humans to perform regular inspections, and it is always optimal. Since the teaching data is automatically generated, it is possible to save labor in maintenance work and improve welding reliability.

In addition, although the limit switch is used in the first embodiment, the invention is not limited to this, and any device can be used as long as it can detect that the electrode tip 4 is in contact with a predetermined position of the dog 16. It may be something like this. For example, the contact may be detected by conduction.

In the second embodiment, there is an error from the contact of the electrode tip 4 to the detection unit 16A to the detection of the current rise. This error is given to the control unit 5 in advance as a correction amount. Of course, there is

[0022]

As described above, according to the present invention, the wear amount of the electrode tip is detected by the wear amount detecting means, and the teaching data is corrected by the correcting means based on this wear amount. High-quality spot welding work with high performance becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a spot welding robot.

FIG. 2 is a schematic block diagram of a positioning control device for a spot welding robot according to the present invention.

FIG. 3 is a detailed configuration diagram of a servo control unit shown in FIG.

FIG. 4 is a flowchart showing a first operation example of a positioning control device for a spot welding robot according to the present invention.

FIG. 5 is a diagram for explaining the operation of the flowchart of FIG.

FIG. 6 is a flowchart showing a second operation example of the positioning control device for the spot welding robot according to the present invention.

FIG. 7 is a diagram for explaining the operation of the flowchart in FIG.

[Explanation of symbols]

 1 ... Robot for spot welding 2 ... Robot controller 3 ... Gun for spot welding 4 ... Electrode tip 5 ... Control unit 15 ... Limit switch 18 ... Servo motor 19 ... Encoder 20 ... Current controller

Claims (1)

[Claims] 1. A spot welding robot configured to position a spot welding gun attached to the tip of an arm on the basis of teaching data and spot-weld an object to be welded. A spot welding robot comprising: a wear amount detecting means for detecting a wear amount; and a correcting means for correcting teaching data of the spot welding gun according to the wear amount detected by the wear amount detecting means. Positioning control device.