WO2005123320A1

WO2005123320A1 - Spot welding robot system

Info

Publication number: WO2005123320A1
Application number: PCT/JP2005/011475
Authority: WO
Inventors: Tadashi Takamaru
Original assignee: Takamaru Engineers Co., Ltd.
Priority date: 2004-06-15
Filing date: 2005-06-15
Publication date: 2005-12-29
Also published as: JP2006000864A; JP4733367B2

Abstract

High-precision, high-quality spot welding is automated by utilizing an articulated general-purpose robot, or the like. The spot welding robot system comprises a spot welding gun unit (9) fixed to an articulated general-purpose robot (1), or the like, and having a servo motor (14) as the open/close drive source of spot welding chips (11, 13), a robot controller (17), a welding current control section (29), and a main controller (19). The main controller (19) comprises a chip drive program (28) for controlling the motor (14), a welding current control program (27) for controlling the welding current control section (29), and one timer (25) common to both programs and providing time information to both programs (27, 28). The open/close driving of the spot welding chips (11, 13) and welding current control between them are performed on a common time axis according to both programs (27, 28).

Description

Specification

Robot system for spot welding

The present invention relates to a robot system for spot welding that can automate highly accurate spot welding by using a multi-joint general-purpose robot. Background art

As disclosed in Patent Document 1, a spot welding robot unit having an electric servomotor as an opening / closing drive source for a spot welding tip is a robot system for spot welding. The spot welding tip (specifically, a movable chip that is driven linearly in a reciprocating manner by a screw mechanism, etc.) is attached to a step robot, As a single-axis core to which a robot is added, a configuration is known in which a robot control device that controls the robot is configured to perform control in synchronization with another robot axis. Of course, in this case, a welding control device for controlling the welding current at the time of welding by the spot welding gun nit is used in combination with a conventional general spot welding machine.

[Patent Document 1] Japanese Utility Model Publication No.

Spot welding is usually performed between two spot welding tips (in general, a combination of a fixed tip and a movable tip driven in a distance direction with respect to the fixed tip). A metal plate is sandwiched at a predetermined pressure, and in this state, a predetermined welding current is passed through the tip to the welding position of the statement to be welded, so that the welding portion is heated and melted, and the two welding objects (metal plate) ) Are welded together. Therefore, when performing spot welding, the required welding strength and appearance of the welded parts are ensured. In order to be able to do so, the welding force and welding current at the welding point must be set according to the physical properties of the welding object such as the material and thickness. Nowadays, high quality appearance is demanded, especially high strength spot welding to aluminum plate.

To meet such demands, it is no longer a simple matter that a constant welding current should be applied while the welding target is pressurized at a constant pressure.

In one welding cycle (the time from the start of pressurization to the end of pressurization of the welded part), the pressing force ゃ the current value during energization is changed, the welding current energization time, It is theorized that it is necessary to change What is important in this case is that the applied force and the welding current are closely related to each other, so that the applied force and the welding current that are changed in accordance with the elapsed time are changed on a common time axis. This must be performed so that the temporal relationship between the change in the pressing force and the change in the welding current during one welding cycle is as set. on the other hand,

Since one welding cycle is usually very short, not milliseconds, but milliseconds, the control of the applied pressure and welding current during that one welding cycle must be performed with high accuracy in milliseconds. Naturally, the time difference between the time when the applied pressure changes and the time when the welding current changes during one welding cycle described above must be accurate as set in ms.

Thus, in the robot system for spot welding as described above, the pressure applied to the welding location is controlled by the control of the electric servomotor which is a driving source for opening and closing the spot welding tip. Therefore, in the configuration described in Patent Document 1, the control of the pressing force is performed by the robot control device that controls the robot, while the welding current is controlled by a separate device from the robot control device. It will be controlled by the welding control device. That is As a result, the robot driving program set in the robot control device is executed based on the time information from the timer provided in the robot control device, and as a result, the spot welding gun unit is set at a predetermined spot welding point. At the same time, the electric servo motor, which is a driving source for opening and closing the spot welding tip, is controlled by the robot drive program, and the spot welding tip presses the welding portion of the welding object across the welding portion. Start. At this time, a welding start command is output from the mouth robot control device (robot drive program) to the welding control device, and a welding program provided in the welding control device, that is, an evening image provided in the welding control device is provided. The welding program executed based on the time information from the beginning operates, a welding current is applied to the welding location, and spot welding is performed on the welding location.

DISCLOSURE OF THE INVENTION

As described above, in the conventional robot system for spot welding, the pressurization control of the spot welding tip by the electric servomotor is performed based on time information given from the timer provided in the robot control device. The welding current is controlled by the robot driving program to be executed, and the welding current is controlled by the welding current control program executed based on the time information provided by the timer provided in the dragon control device. That is, the pressurization control and the welding current control, which are essential requirements for spot welding, are executed based on different time information given from different timers. Even if the program is set up precisely using the time axis in ms units, when the pressurization control and the welding current control are independently verified, the pressurization control and the welding current are controlled on the time axis used by each program. Only the control is executed according to the program, and the welding program consisting of the combination of pressurization control and welding current control takes time. Due to the characteristics (accuracy) of the timer that gives the information or the error in the reference time at the start of the program, there is a deviation in the temporal relative relationship between the change in the pressing force during one welding cycle and the welding current. Since it becomes impossible in reality to accurately reproduce the temporal relationship between the change in the applied pressure and the change in the welding current in one welding cycle as set in ms, Accurate spot welding could not be achieved.

An object of the present invention is to provide a robot system for spot welding that can solve the conventional problems as described above, and its means are denoted by reference numerals in the embodiments described later. The robot 1 is attached to the robot arm 8 at the last stage of the robot 1 and has a motor-driven servo motor 14 as an open / close drive source for the spot welding tips 11 and 13. Welding gun unit 9, robot control unit 17 for controlling robot 1 based on robot drive program 22, welding for controlling welding current at the time of welding by gun unit 9 for spot welding A current control device (welding current control unit 29); a main control device 19; and the main control device 19 includes a tip drive program 28 for controlling the electric servomotor 14 and the welding current control. Welding current control program 27 that controls the welding position (welding current control unit 29), and one timer 25 that provides time information to both programs 27 and 28 Based on the start command (weld point arrival signal 22 a), it operates according to the common time information 25 a given from the tip drive program 28, the welding current control program 27 and the timer 25, and spot welding is performed. The opening / closing drive of the chips 1 to 13 and the control of the welding current therebetween are performed on a common time axis in accordance with both programs 27 and 28.

In order to facilitate understanding, the tip drive program 28 and the welding current control program 27 are shown to exist independently of each other. Since these two programs 27 and 28 are recorded in the memory of one hardware called the main control leaving 19, a chip driving program consists of a driving program section and a welding current control program section. It can be designed and recorded as one program (welding program 24). In addition, the main controller 19 and the welding current controller (welding current controller 29) do not need to be separately separated as hardware. It can also be implemented as a welding machine with a built-in drive program 28, welding current control program 27, control unit (servo amplifier, etc.) 26 of the electric servomotor 14. Further, the mouth robot 1 is not limited to the multi-joint general-purpose robot employed in the embodiment described later, but includes a final-stage robot arm that can reciprocate only in one-dimensional direction such as a vertical movement. It may be provided. That is, the system of the present invention includes a stationary foot-stepping start type spot welding machine provided with an elevating handle for driving the movable tip up and down, and the elevating and lowering drive for moving the welding object and the movable tip. The present invention can also be applied to an automatic spot welding machine or the like that can automatically change a welding position on a workpiece by sequentially moving one of the handles.

According to the spot welding ffl robot system of the present invention having the above-described configuration, a tip drive program (pressurization control program) for controlling an electric servomotor for opening and closing a spot welding tip is separated from the robot control device. The main control unit is installed together with the welding current control program that controls the welding current control unit, and one timer is used to provide common time information to both programs. Both programs can be operated on a common time axis. In other words, the change over time in the pressing force (the number of rotations of the electric servomotor) and the change over time in the welding current value due to the tip drive during one welding cycle are calculated. Since it can be set on a common time axis and can be reproduced as set, the relative time relationship between the change in welding pressure and the change in welding current during a welding cycle can be expressed in ms. With this, it is possible to reproduce spots exactly as programmed and to automate spot welding with extremely high precision and high quality while using multi-joint general-purpose robots.

[Brief description of the drawings]

FIG. 1 is a side view of a multi-joint general-purpose robot to which a welding gun unit is attached, and a block diagram illustrating an external device used in combination.

FIG. 2 is a block diagram illustrating the configuration of the entire robot system of the present invention.

FIG. 3 is a graph illustrating the contents of a tip drive program (pressurization control program) and a welding current control program. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a specific embodiment of the present invention will be described with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a six-axis multi-joint general-purpose robot having a vertical axis 2a with respect to a base 2. The first turntable 3 rotatably mounted around the first turntable 3, the first robot arm 4 supported movably around the horizontal axis 3 a with respect to the first turntable 3, and the first a-bottom Arm 5 connected to the distal end of the arm 4 in such a manner as to be capable of circulating around a horizontal axis 4a parallel to the horizontal axis 3a. The distal end of the joint arm 5 is perpendicular to the horizontal axis 4a. Sigma-bottom arm 6 rotatably connected around the axis 5a of the second robot arm 6 at the end of the second robot arm 6 around the axis 6a perpendicular to the axis 5a. A third robot arm 7 connected to the third robot arm 7 and an axis perpendicular to the axis 6 a at the tip of the third robot arm 7. Pivotally connected around heart 7a The final stage robot arm 8 is constructed.

A spot welding gun unit 9 is attached to the end of the final robot arm 8. As shown in FIG. 2, the spot welding gun unit 9 has a fixed chip 11 attached to the inside of the lower end of the C-shaped member 10. The C-shaped member is opposed to the fixed tip 11. Chip open / close driving means 12 attached to the upper end side of 10; movable chip 13 supported by this chip open / close drive means 12 and driven in the near / far direction with respect to fixed chip 11; It consists of a motor-driven boom as a drive source, a transformer for welding current, and a welding current supply transformer. As the tip opening / closing drive means 12, a screw feed mechanism using a ball screw can be used. The screw feed mechanism is driven by the electric servomotor 14 to drive the movable tip 1. 3 can be moved in the distance direction with respect to the fixed tip 11. An encoder 16 (see FIG. 2) for detecting the current position of the movable chip 13 is interlocked with the electric servo motor 14.

A conventionally well-known robot controller 17 is used in combination with the multi-joint general-purpose robot 1. For the spot welding gun unit 9, a welding power source 18 for supplying a welding current to the movable chip 13 via the transformer 15 and the main control device 19 are used in combination.

Explaining the hardware configuration of the entire system based on FIG. 2, the multi-joint general-purpose robot 1 is equipped with a robot axis driving means 20 and an α-bot axis position detector 21 as is well known in the art. ing. Further, the robot control device 17 includes a robot driving program 22 for controlling the robot axis driving means 20 and a spot welding program based on signals from the robot axis position detectors 21. It is provided with a welding gun current position calculator 23 that calculates and outputs current position information (three-dimensional coordinate values and attitude data) of the gun unit 9. Robot drive program The robot 22 moves the spot welding gun unit 9 in the home position to the spot welding point of the welding object set in the fixed position with respect to the multi-joint general-purpose robot 1 based on the activation finger. On the other hand, the current position information of the spot welding gun unit 9 which is fed back in real time from the welding gun current position calculation unit 23 in order for the fixed tip 11 to move to the corresponding position and posture in a predetermined posture 2 3. A conventionally well-known program for controlling the drive of each axis drive means 20 based on a, and is set based on a learning operation performed by manual operation of each axis drive means 20 of the robot.

The main controller 19 includes a welding program 24, one timer 25, and a servo motor controller 26. The welding program 24 is composed of a welding current control program 27 and a tip drive program 28, and both the programs 27 and 28 are provided with the common time information 25a from the timer 25. The welding current control program 27 controls the welding current control unit 29 included in the welding power source 18, and pressurizes the fixed tip 11 and the movable tip 13 included in the spot welding gun unit 9. It controls the welding current flowing to the spot welding point of the sandwiched welding object. The tip drive program 28 includes a position control based on the tip current position information 16a which is fed back in real time from the encoder 16 included in the spot welding gun unit 9, and a movable tip (not shown). Pressurization control started just before 13 starts to pressurize the welding object, that is, an application based on the current torque value measured and fed back from the load current value acting on the electric servomotor 14 Pressure control is performed via the servo motor-one control unit 26 to the electric servo motor 14 provided with the spot welding gun unit 9. As a result, the electric servo motor 14 The driven tip opening / closing drive means 12 drives the movable tip 13 in the perspective direction with respect to the fixed tip 11 1 in accordance with the programmed opening / closing operation. The spot welding point of the object to be welded can be pressurized at a predetermined pressure between the welding program and the welding process. Based on FIG. 3, the configuration of the welding program 24 will be described in more detail. It is a graph which shows the change of the pressing force with respect to the spot welding point set by program 28, and a horizontal axis is time and a vertical axis is a pressure value. FIG. 3B is a graph showing a change in welding current with respect to a spot welding point set by the welding current control program 27, in which the horizontal axis represents time and the vertical axis represents current value.

That is, the tip drive program 28 is a robot drive program of the robot controller 17 when the spot welding gun unit 9 (fixed tip 11) reaches the set spot welding point and stops. From the point when the welding point reaching signal (welding start command) 2 2a output from 2 2 is received, that is, from the start of welding, it can be moved by the electric servo motor 14 so that the applied pressure becomes P 1. After lowering the tip 13 and maintaining the state for a time X 1 ms, the movable tip 13 is further lowered by the electric servomotor 14 so as to increase the applied pressure from P1 to P2. Then, after maintaining the state of the pressing force P 2 for a time X 2 ms, the electric servomotor 14 is supported so that the movable chip 13 is lifted and opened by the electric servomotor 14. Control via motor control unit 26. On the other hand, the welding current control program 27 controls the welding current so that the welding current of A ampere flows between the chips 11 and 13 for the time Y 2 ms from the time delayed from the welding start time by the time Y 1 ms. Control part 29.

Therefore, the two programs of the welding current control program 27 and the tip drive program 28 operate based on the common time information 25 a given from one timer 25, and consequently, As shown in FIG. 3C, control of the welding current control unit 29 by the welding current control program 27 (welding 1 o

The current control) and the control of the electric servomotor 14 by the tip drive program 28 (pressing force control) are executed on a common time axis, and the change in the pressing force and the change in the welding current are performed. The temporal relationship between the two does not collapse. That is, when the tip drive program 28 and the welding current control program 27 operate on the basis of the time information given from the dedicated timers, both programs 27 , 28, there is a difference between the time axis of the graph of the pressure change shown in Fig. 3A and the time axis of the graph of the welding current change shown in Fig. 3B. Therefore, even if these two programs 27 and 28 are executed, as shown in Fig. 3C, the graph of the applied pressure change shown in Fig. 3A and the welding current shown in Fig. 3B will be obtained. The graph of the change is not superimposed, and the temporal relationship between the change in the applied pressure and the change in the welding current is broken. Does not occur.

One welding cycle is completed when the movable tip 13 is lifted and opened by the electric servomotor 14.At this time, the welding end signal 28a from the welding program 24 (chip drive program 28) is sent to the robot. This is output to the robot drive program 22 of the remote controller 17. Thus, when the next spot welding point is set, the robot drive program 22 operates again based on the welding end signal 28a, and the spot is moved toward the next spot welding point. In order to move the welding gun unit 9, the multi-joint general-purpose robot 1 is driven by each axis driving means 2 0. The force controlled by the next spot ^ The next spot Depending on the structure of the welding object at the welding point, etc. The electric servomotor 14 is controlled so that the ascending position of the movable tip 13 at the completion of the welding cycle is set to an intermediate position (closer to the fixed tip 11) lower than the ascending limit position (home position). Cycle at spot welding point Time can be reduced. Of course, when the spot welding for all the set spot welds is completed, the final welding end signal

Based on the output of 28a, the electric servomotor 14 is controlled so as to raise the movable tip 13 to the ascending position (home position), and the gun welding unit 9 for spot welding is controlled. The robot axis driving means 20 is controlled so as to return to the home position.

Claims

The scope of the claims

Claim 1

• A robot, a spot welding gun unit mounted on the last robot arm of the robot and provided with an electric servo motor as a driving source for opening and closing the spot welding tip, and a robot driving port for the robot. A robot control device for controlling based on a program, a welding current control device for controlling a welding current at the time of welding by the spot welding gun unit, and a main control device. A chip drive program for controlling the servomotor, a welding current control program for controlling the welding current control device, and a timer common to both programs for providing time information to both programs are provided. The chip driving program and the welding current control program are provided from the timer. Operates in accordance with the time information through a control of the opening and closing drive movement between them of welding current chip spot welding is performed Te 従Tsu on both programs on a common time axis robotic system for spot welding.