JPH0341268B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an improvement of a spot welding device using an industrial robot, and particularly to an improved spot welding device that can handle deep and diverse workpieces. .

(Prior Art) A spot welding device equipped with a spot welding gun and used to spot weld the body of an automobile, for example, is well known as an end effector of an industrial robot. However, when spot welding a deep workpiece, such as an underbody of an automobile, where the spot welding point is far from the end of the workpiece and there are no holes along the way, the conventional equipment described above cannot be used. The spot welding gun became a large C-type spot welding gun with a deep pocket and heavy weight, which reached its practical upper limit. For this reason, for example,
As disclosed in No. 6582, while the robot is equipped with pressure electrodes, a large number of electrodes that will be on the plate side of the workpiece, that is, back electrodes, are arranged in advance according to the workpiece, and the industrial robot is connected to the robot from the outside of these back electrodes. It has been proposed that spot welding be performed by pressing a pressure electrode provided on the weld.

(Problem to be Solved by the Invention) However, in this proposal, if the types of workpieces are different, multiple back electrodes are separately provided.
Since the position of these back electrodes is changed and they are not moved until welding is completed, there is a limit to the degree of freedom when changing the type of workpiece, and the equipment space and cost increase as the number of types of workpieces increases. There is also the problem that the work becomes complicated.

The present invention aims to provide a spot welding device that can not only handle deep workpieces, but also eliminates the need to change the back electrode depending on the type of workpiece, and has a high degree of flexibility for handling many types of workpieces. ,
That purpose.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention targets the underbody of an automobile as a workpiece, and depending on the type of the workpiece, the projecting cross-sectional shape at the center of the vehicle width direction is A spot welding device for spot welding parts at a plurality of points is composed of a holding and transferring device for transferring the workpiece to a welding set position, and a pair of industrial robots individually installed for the welding set position. At the movable end of the industrial robot, a pressurizing unit having only one pressurizing electrode at its tip is attached, while at the movable end of the other industrial robot, only one back electrode for the pressurizing electrode is attached. Furthermore, upon receiving a signal indicating that the workpiece is set at the welding set position, the back electrode substantially contacts one surface of the workpiece at the welding position, while
Both industrial robots are operated synchronously for each welding position according to the type of workpiece so that the pressure electrode is positioned on the other side of the workpiece at the welding position with a gap, and after this operation is completed, the above-mentioned The pressurizing unit is equipped with a control device that issues a pressurizing signal to operate the unit.

(Function) As a result, in this invention, the back electrode is provided on one robot as the only one with respect to the pressurizing electrode even when the type of workpiece changes, and the control device allows the welding position to be set at multiple welding positions depending on the type of workpiece. Since each robot operates in synchronization with the other robot that has a pressure electrode, it is possible to easily spot weld even deep workpieces, and when spot welding multiple welding points on a workpiece, it is possible to There is no need to change it depending on the type of workpiece, and the degree of freedom when changing the type of workpiece is extremely high.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

R ₁ is one industrial robot, R ₂ is the other industrial robot, and W is an automobile underbody as a workpiece. A device P for holding and transferring a workpiece W is mounted across the robot _R2 . The holding and transferring device P moves the workpiece W in the left and right direction (first
The transfer position is determined in the direction perpendicular to the plane of the paper in the figures and FIG.

The robot _R1 has a rotating arm 3 which is pivotably supported on the upper part of the base 1 by a shaft 2 in the left and right direction so as to be freely rotatable in the vertical direction. A power source (Mα ₁ , not shown) that operates the arm 3 at a rotation angle α ₁ is provided. arm 3
A telescopic arm 4 that moves forward and backward in the axial direction is supported at the front part of the arm. A power source (MY, not shown) is provided that operates the arm 4 by extending and contracting the length Y.

Further, the tip of the arm 4 is configured as a wrist of the robot _R1 , and supports the end effector fixture 5 rotatably in the vertical direction about a shaft 6 in the left and right direction. A power source (Mα ₂ , not shown) that operates the fixture 5 at a rotation angle α ₂ is provided.

Thus, robot R ₁ has three degrees of freedom, and the end effector it holds can be rotated in the front and rear vertical planes (the first
The position can be controlled to an arbitrary posture at a movable position within a plane (plane parallel to the plane of paper in the drawings and FIG. 2).

The fixture 5, which serves as the movable end of the robot _R1 , includes:
A pressurizing unit is installed in which two pressurizing electrodes 7, 7 as end effectors are arranged vertically in parallel as shown in the figure, and are movable forward and backward via known pressurizing cylinder devices 8, 8. ing.

A welding power source transformer T for operating this pressurizing electrode 7 is provided. The transformer T is supported via a trolley 10 on a guide rail 9 provided on the ceiling in the front-rear direction (left-right direction in FIGS. 1 and 2), and is configured to be movable in the front-rear direction. The transformer T and the electrode 7 are electrically connected via a cable 11. A publicly known fluid switching valve 12 is further suspended from the trolley 10 and is connected to the cylinder devices 8, 8 via piping 13. In addition, the transformer T is connected to a commercial power source (not shown).
Further, the switching valve 12 is connected to a fluid pressure source (not shown).

The robot R ₂ has a first arm 1 which is rotatably supported in the front and back directions on the upper part of the base 14 about a left and right shaft 15.
It has 6. A power source (Mβ ₁ , not shown) that operates the arm 16 at a rotation angle β ₁ is provided.

A second arm 18 is further pivotally supported at the tip of the arm 16 by a left-right shaft 17 so as to be rotatable in the front-back direction. A power source (Mβ ₂ , not shown) that operates the arm 18 at a rotation angle β ₂ is provided.

A telescopic arm 19 that moves forward and backward in the axial direction is further supported at the tip of the arm 18. A power source (MZ, not shown) is provided that operates the arm 19 even when the arm 19 is extended or contracted.

Thus, the robot R ₂ also has three degrees of freedom, and the end effector it holds can be controlled to any desired posture in a movable position in the front-rear vertical plane. A back electrode 20 as an end _effector ,
20 corresponds to the pressurizing electrodes 7, 7, and the pressurizing electrodes 7,
It is fixedly installed in parallel with 7 at the same pitch. Note that the back electrodes 20, 20 are electrically connected to each other.

The transfer device P includes a guide 2 extending in the left-right direction.
It has a movable frame 23 that is guided by 1 and 22 and supported so as to be movable in the left and right direction. Guide 2
1 is provided on the front side of the robot R _2. On the other hand, a drive roller 24 supported by a horizontal axis on a movable frame 23 is in contact with the upper surface of the guide 21, and is supported by a vertical axis. Two supported pairs of guide rollers 25, 25 sandwich and contact the guide 21 from the left and right sides. MX is a power source that drives the roller 24,
As a result, the movable frame 23 is forcibly transferred to its left and right X positions (workpiece W mounting position, welding set position, and workpiece W removal position). The guide 22 is formed by arranging a large number of free rollers in the left-right direction, and supports the lower surface of the movable frame 23 on the other side. Movable frame 23
A plurality of workpiece positioning pins 26 are provided on the top of the pins 26 to project upward, and are configured to detect the presence or absence of a workpiece W on the pins 26 using an optical sensor SE (not shown).

Operation of robots R ₁ and R ₂ and pressurizing electrodes 7, 7;
Control of the moving position of the movable frame 23 and the like are executed by a control device C whose main component is a known microcomputer M. That is, as shown in FIG. 3, the power sources Mα ₁ , MY, Mα ₂ , Mβ ₁ , Mβ ₂ , MZ
and positioning servo system Sα ₁ including MX,
SY, Sα ₂ , Sβ ₁ , Sβ ₂ , SZ and SX, the switching valve 12 and the sensor SE are connected to the balance B of the microcomputer M, and the user program is stored in the memory of the microcomputer M in advance by a known teaching method. The above-mentioned components are controlled by the execution of (by the so-called playback method).

Hereinafter, by explaining the execution of the easer program mentioned above based on the flowchart of Fig. 4,
The operation of the embodiment of the present invention in the previous procedure will be explained.

The operator first activates the robots R ₁ and R ₂ , the control device C, the transfer device P, and other necessary components by energizing them, and then starts the control device C.

(1) The microcomputer M first moves the movable frame 23 of the transfer device P to the workpiece mounting position (not shown, but on the right side in the left-right direction)
Determine whether the position is being controlled by the
_P1 ).

(2) If the workpiece mounting position is not under position control (whether or not it is position controlled is determined based on the feedback information of the servo system. The same shall apply hereinafter), the position of the workpiece mounting position. The command information is commanded to the servo system SX to control the position of the movable frame 23 to the workpiece mounting position (processing P ₂ ).

(3) If the workpiece mounting position is controlled, it is further determined whether a workpiece is mounted on the movable frame 23, that is, whether there is a signal from the sensor SE (processing P ₃ ).

(4) If it is not installed, one of the workpieces W prepared in advance, although not shown in detail,
It is mounted on the movable frame 23 so that the positioning hole pin 26 drilled therein is fitted. Although this loading is not shown in detail, it is assumed that this loading is carried out by a known feeder (process P ₄ ).

(5) Once the workpiece W is loaded, the movable frame 23
is the welding set position at which spot welding is to be performed (memorized by the above-mentioned teaching)
(Processing)
_P5 ).

(6) If it is not positioned at the spot welding position (welding set position), the position command information of the spot welding position is commanded to the servo system SX to control the position of the movable frame 23 to the spot welding position (processing
_P6 ). When the movable frame 23 moves within the movable range of the robot R ₂ in this way, the robot R ₂ is temporarily retracted as shown by the two-dot chain line in FIG. 2 to prevent interference between the movable frame 23 and the robot R ₂ . put.

(7) Once the movable frame 23 is positioned at the position where the workpiece W is to be spot welded (welding set position), each electrode 7 is attached to the robots R ₁ and R ₂ in accordance with the type of the workpiece W. , 7 and 20, 20 to the spot welding position shown in the figure (memorized by the above-mentioned teaching), position command information is output to each required servo system to control the position ( process
_P7 ). This spot welding position is the back electrode 2
The tips of 0 and 20 are the parts of the workpiece W to be welded,
That is, this is a position in which the pressurizing electrodes 7, 7 face the workpiece W while being in contact with the back side of the central projecting cross section in the vehicle width direction, and is a spot welding standby position.

(8) Then, it is determined whether robots R ₁ and R ₂ are both positioned at the commanded position (processing
_P8 ).

(9) Once both are positioned, in synchronization with this, the switching valve 12 is switched for a certain period of time (process P ₉ ). By this switching, fluid pressure acts on the cylinder devices 8, 8, causing them to expand, and the tips of the pressurizing electrodes 7, 7 come into contact with the welding location of the workpiece W.
Then, the current from the transformer T flows in order from one pressure electrode 7 → one back electrode 20 → the other back electrode 20 → the other pressure electrode 7, spot welding the double stacked works W together. It is something.

The robots _R1 and _R2 are further position-controlled to the next welding position, and spot welding is performed in the same manner one after another.

(10) When welding of a plurality of points on one workpiece W is thus completed, position command information is output to the servo system SX in order to control the position of the movable frame 23 to the workpiece removal position (process P ₁₀ ). Although not shown, the workpiece removal position is on the left side in the left-right direction.

(11) Although the details are not shown, the workpiece W is removed from the pins 26, 26, . . . by the workpiece removal device and sent to the next conveyor (processing P ₁₁ ).

(12) Then, the movable frame 23 is returned to the workpiece mounting position described above (process P ₁₂ ).

(13) Furthermore, it is determined whether or not the workpiece W that has just been welded is all the workpieces to be welded using this user program (processing P ₁₃ ). If everything is completed according to this judgment, the program execution ends; if not, the process returns to process _P3 and repeats the above-mentioned operations.

The present invention is not limited to the embodiments described above, and various modifications described below are also possible.

(a) Both robots R ₁ and R ₂ are not limited to those in the above-mentioned embodiments, and may be robots with mechanical configurations of other control systems. Further increasing the degree of freedom,
If the position and orientation of the end effector can be controlled three-dimensionally, the movable frame 23 can be positioned at only one location when welding a large number of welding locations on one workpiece W.

(b) The control algorithm for both robots R ₁ and R ₂ may also be a method other than the above-mentioned embodiment.

(c) The means for pressurizing the workpiece W by the pressurizing electrodes 7, 7 is not limited to the cylinder devices 8, 8;
By controlling each control axis of Robot R ₁ itself,
The pressure electrodes 7, 7 may be advanced in the axial direction and pressed against the welding point of the workpiece W.

(d) The workpiece W transfer device P may also be capable of supplying, fixing, and removing the workpiece W by means other than the above-mentioned embodiments.

(E) It is also possible to replace each structure with equivalents within the scope of the technical idea of this invention.

(Effects of the Invention) This invention provides a single pressure electrode on one industrial robot, and a back electrode on the other industrial robot. The robot is installed as the only robot in the system, and both robots are operated synchronously at each welding position depending on the type of workpiece, so it is possible to handle deep workpieces and many different types of workpieces. Spot welding can be easily performed by simply changing control procedures such as user programs, and since both electrodes operate synchronously, spot welding can be reliably performed. Therefore, when spot welding multiple welding points on a workpiece, there is no need to change or install a new back electrode as a unit according to the type of workpiece as in the past, and it is possible to adapt to changes or increases in the type of workpiece. It can bring about unique and remarkable effects such as significantly increasing the degree of freedom, eliminating capital investment, and being advantageous in terms of equipment and work.

[Brief explanation of the drawing]

The drawings all show embodiments of the present invention; FIG. 1 is an overall side view, FIG. 2 is an enlarged view of the main part of FIG. 1, FIG. 3 is a block diagram, and FIG. 4 is a flowchart. _R1 ...one industrial robot, _R2 ...other industrial robot, 7...pressure electrode, 8...cylinder device, 20...back electrode, C...control device,
W...Work.

Claims (1)

[Scope of Claims] 1. A spot welding device that targets an underbody of an automobile as a workpiece and spot-welds a protruding cross-sectional portion in the center of the vehicle width direction at a plurality of points depending on the type of the workpiece, comprising: It consists of a holding and transferring device that transfers the workpiece to the welding set position, and a pair of industrial robots that are individually installed for the welding set position, and one of the industrial robots has a single pressure electrode at its movable end. At the same time, the only back electrode for the above-mentioned pressure electrode is attached to the movable end of the other industrial robot, and upon receiving a signal that the workpiece is set at the above-mentioned welding set position, The back electrode is synchronized at each welding position depending on the type of workpiece so that it is in approximate contact with one side of the workpiece at the welding position, while the pressure electrode is positioned at a distance from the other side of the workpiece at the welding position. A spot welding apparatus characterized in that it is equipped with a control device which operates both industrial robots and, after completion of the operation, issues a pressure signal to the pressure unit to operate the unit.