JP2002086276A - Controller for servo gun for spot welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that arises in a controlling for a servo gun for a spot welding equipment in which the position of a servo control part driving the moving body part of a gun shaft is controlled, because a variance exists among works or tools for holding works, a fixing shaft of the gun strongly hits the work when the position is controlled, thus the work is deformed. SOLUTION: The moving part of the gun shaft is set to be stationary at an original position by a electric current limiting means of the servo control part for driving the moving body part of the gun shaft, the reaction force from the work occurring when the front end of the movable shaft of the gun hits the work is received by the main body part of the gun shaft and thereby the fixing shaft of the gun slowly advances toward the work, thus the fixing shaft of the gun holds the work with a light pressing force, and the work is not deformed even when a variance exists among works or tools for holding works.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding machine that holds a work using two axes, a movable gun axis and a fixed gun axis, and applies an optimum pressure to the workpiece from the movable gun axis to perform welding.

[0002]

2. Description of the Related Art In the prior art, a target position command is first given to a gun axis moving body driving servo control unit, and a gun fixed shaft advances toward a work. When the position control is completed, the gun fixed axis is stopped, and the difference between the current position of the gun fixed axis and the current position of the gun movable axis is calculated to determine the moving amount of the gun movable axis. The position of the gun movable shaft is also controlled, but since the gun movable shaft needs to apply an optimal pressing force to the work, the current output value is limited by the current limiting means so that an optimal torque can be output. The gun movable shaft advances toward the work, and advances even when the tip of the gun movable shaft hits the work until it reaches a set pressing force. When the pressing force reaches the predetermined value, the gun movable shaft stops. Through this series of operations, the work is held by both the gun fixed axis and the gun movable axis, and the welding sequence execution command is sent to the programmable sequence controller (hereinafter referred to as the "program") while the work is applied to the work optimally by the gun movable axis. PLC), and the welding starts.

[0003]

In a spot welding servo gun control device, the position of a servo control unit for driving a gun axis moving unit is controlled. However, there is a variation in the work and the tools for holding the work, so that when the position is controlled, there is a problem that the gun fixed shaft strongly hits the work and deforms the work.

[0004]

Means for Solving the Problems The configuration of the invention for solving the above-mentioned problems includes a mechanical mechanism means in which the gun fixed shaft and the gun movable shaft are respectively connected by a support base on a gun shaft moving body. A small current limit is set in the servo control unit for driving the gun shaft moving unit so that the torque that can overcome the static friction force of the gun shaft moving unit is not set, and the gun fixed shaft is kept stationary at the original position. Wherein said gun axis moving body control means is provided, and said gun movable axis control means is configured to set a current limit value capable of outputting an optimum pressing force during welding to said gun movable axis. .

[0005]

According to the invention of the present application, a small current limiting value is set by the current limiting means of the servo control unit for driving the gun shaft moving body so that the static friction force of the gun shaft moving body can be prevented from being overcome. Leave the fixed shaft stationary at the original position, set a current limit value for the gun movable shaft so that the optimum pressing force can be applied, move the gun movable shaft toward the workpiece, and set the tip of the gun movable shaft to the workpiece. The gun fixed shaft can move slowly toward the work when the gun shaft moving body receives the reaction force from the work when hitting, so the gun fixed shaft can lightly press the work. .

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a spot welding machine using the control device of the present invention. This apparatus comprises a gun fixed shaft support 102 with a gun fixed shaft 100 mounted thereon, and a gun movable shaft support 108 with a gun movable shaft 106 mounted thereon.
A gun shaft moving body 104 mechanically connecting the gun fixed shaft support 102 and the gun movable shaft support 108, and a ball screw 110 for driving the gun shaft moving body 104 back and forth. And a servo motor 100M for driving the gun moving body, which is attached to one end of the gun and is coupled to the ball screw 110, and a gun movable shaft 106 which is provided in the gun movable shaft support 108 and moves the gun movable shaft 106 left and right. It comprises a ball screw to be driven and the gun movable shaft driving servomotor 102M attached to one end of the ball screw and coupled to the ball screw. In other words, the present invention is a mechanism in which a feed servo control system for moving the gun movable shaft is mounted on a servo control shaft for driving the gun shaft moving unit that moves the gun fixed shaft.

FIG. 2 is a diagram showing a servo configuration used for an NC or the like according to the present invention. Reference numeral 200 indicates a management unit,
A PLC 210 and a console 212 (small operation panel for inputting programs, parameters, etc.) are connected to a main CPU 216 in a command generation unit denoted by reference numeral 202. The command generation unit 202 includes a ROM 218 and a BRAM 220 (battery backup RAM). Command generation unit 2
Reference numeral 02 is connected to the gun axis moving body servo control unit 204A and the gun movable shaft servo control unit 204B via a communication I / F. (Here, the servo control unit for the gun axis moving unit 204A and the reference numeral 2
Since the gun movable axis servo control unit of the 04B has exactly the same configuration, the hardware description of the gun movable axis servo control unit is omitted. )

The servo control unit for the gun axis moving unit includes a control CPU 232A, a DSP 236A (digital signal processor), and an inverter 238A.
It is connected to the gun axis moving body part driving servomotor 244A. The servomotor 244A for driving the gun axis moving unit is provided with an electromagnetic brake 246A and a position detector 24A.
8A is incorporated, and the signal of the position detector 248A is taken into the DSP 236A as current position data. The U-phase current and the V-phase current of the three-phase current flowing through the servomotor 244A for driving the gun axis moving unit are detected by the current detectors 242Aa and 242Ab, and the A / D converter 240
A is taken into DSP 236A through A.

Next, the function of the servo configuration diagram of FIG. 2 will be described. First, a welding command is output to the main CPU 216 of the command generation unit 202 from the PLC 210 in the control unit 200 that manages the entire system. The main CPU 216
Stores the program of the flowchart shown in FIG.
8 and executed. The index point and various parameters are stored in the BRAM and read out from the main CPU 216 at the time of executing the operation. First, step 300
Now, the servo motor 1 that drives the gun axis moving body 104
A position interpolation command is generated at 00M and output to the gun axis moving body part servo control unit 204A through the communication I / Fs 222 and 230A. The CPU 232A for controlling the servo control unit 204A of the gun axis moving body unit performs position control, and the DSP 236A outputs a PWM gate signal for controlling the inverter 238A from the DSP 236A that performs speed control, current control and current limitation.

From the inverter 238A, the servo motor 2
A three-phase current for generating a rotating magnetic field for rotating 44A is output. The actual current flowing through the servomotor 244A is detected by current detectors 242Aa and 242Ab, converted into a digital value by the A / D converter 240A, used for current control in the DSP 236A, and mounted on the same axis as the servomotor 244A. The signal output from the position detector 248A is taken into the DSP 236A, processed into a current position signal and an actual speed signal, and used by the speed control unit and the current control unit, and used by the position control unit in the control CPU 232A. In the present embodiment, since the current value is set to be very small, the output torque of the servomotor 100M is also small, and the output torque cannot overcome the static frictional force that hinders the forward movement of the gun shaft moving unit 104, and The body 104 remains stationary at the original position.

Next, in step 302, the gun movable shaft 10
A position interpolation command is generated in the servo motor 102M that drives the motor 2 and the communication I / F2 is transmitted to the gun movable axis servo controller 204B.
22, 230B. (Hereinafter, the hardware function of the gun movable axis servo control unit will be omitted because it is the same as that of the gun axis moving body unit servo control unit 204A.) However, the current value preset by the current limiting function of the gun movable unit 102 is not changed during spot welding. The value is large so that the optimal pressing force is applied from the gun movable portion 102. Therefore, the gun movable shaft 102 advances toward the workpiece 100W.
The forward end of the movable gun shaft 102 hits the work 100W, and a certain force is applied to the work 100W (arrow 10 in FIG. 1).
F). Then, a reaction force (arrow 20 in FIG. 1) is applied to the workpiece 100W.
F) occurs. The reaction force pushes the gun movable shaft 106 to the left. This reaction force is transmitted from the gun movable shaft 106 to the gun movable shaft support 108. Since the gun movable shaft support is mechanically connected to the gun shaft moving body 104, the reaction force is It acts as a force to move the moving body 104 forward. Since this force overcomes the static friction force that caused the gun axis moving body 104 to stand still, the gun fixed shaft 100 advances at a very low speed, reaches the work 100W, and slightly presses the right side surface of the work 100W. The right side of the work 100W is lightly pressed with the gun fixed shaft 100, and the monitoring of whether the left side of the work 100W is applied with the optimum pressing force for spot welding by the gun movable shaft 106 is executed in step 304, Step 3 when pressure is applied
Proceeding to 06, the welding sequence is executed by the PLC.

[0012]

Another embodiment of the present invention In the servo configuration diagram of FIG. 2, in this figure, a command generation unit and each servo control unit are separated and perform respective processes. However, if the processing capability of the main CPU 216 increases, the servo control is performed. Control CPU 232A,
B and the functions of DSPs 236A and B
The present invention can be carried out by itself.

[0013]

The present invention does not control the position of the servo unit for driving the gun shaft moving unit equipped with the gun fixed shaft as in the prior art, but sets a small current limit value to set the static friction force of the gun shaft moving unit. The gun fixed shaft is kept stationary at the original position, the current limit value is set so that the optimal pressure can be applied to the gun movable shaft, and the gun movable shaft moves forward toward the workpiece. When the work is pushed, the reaction force from the work pushes back the gun movable shaft, and the force acts as a force for pushing the gun moving body to the left, so that the gun fixed shaft moves forward and presses lightly on the work. Therefore, the gun axis moving body is positioned smoothly so that it floats to the center of the work. Can be used for welding.

[0014]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a servo gun according to a specific embodiment of the present invention.

FIG. 2 is a servo control device showing characteristics of the device of the embodiment.

FIG. 3 is a flowchart showing characteristics of the apparatus according to the embodiment.

[Explanation of symbols]

 10F: Pressing force 20F: Reaction force 100: Gun fixed shaft 100M: Servo motor for driving the gun shaft moving unit 100W ... Work 102: Gun fixed shaft support 102M: Servo motor for driving the gun movable shaft 104: Gun shaft moving unit 106: Gun movable shaft 108: Gun movable shaft support 110: Ball screw for driving the gun shaft moving body

Claims (1)

[Claims] 1. A spot welding machine having a servo control device for controlling two axes of a gun fixed shaft and a gun movable shaft for performing welding, wherein the gun fixed shaft and the gun movable shaft are arranged on a gun shaft moving body. Mechanical mechanism means respectively connected by a support base, and a current limit set so small as to be unable to output a torque overcoming the static friction force of the gun axis moving body part in the servo control unit for driving the gun axis moving body part, The gun axis moving body section control means configured to keep the gun fixed axis at the original position, and the gun movable section configured to set a current limit value capable of outputting an optimal pressing force at the time of welding to the gun movable axis. A servo control device for a spot welding machine, comprising: a shaft control means.