JPH10166160A - Spot welding method and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a work from being deformed by the deflection of a C shaped arm by bringing an electrode at the side facing to a C shaped arm into contact with a work and fixing the work and successively pressing the work in spot welding using a welding gun having a C shaped arm. SOLUTION: A pressing start signal is inputted to a welding gun 19 side and then a rod side shaft 24 is started to descend. When an electrode 25 is brought into contact with a work, a load current of a motor 27 is increased so as to detect the electrode is brought into contact with the work. Rotation of the motor 27 is stopped and by driving a brake 31, the rod side shaft 24, at a state being brought into contact with the work, is positioned and fixed. The motor 34 is driven and welding force is started to apply to the work by the electrode 21 through the C shaped arm shaft 33. Discrimination as to whether the welding force is reached to a prescribed value is detected by a torque value of the motor 34. When completion signal of welding force application is outputted to a welding timer, a welding current is supplied from a power wire to upper/lower electrodes 25, 21, the work is subjected to welding by pressure in a spot shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding method for spot welding a work using a welding gun having, for example, a C-arm, and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, as the spot welding method and the apparatus of the above-mentioned example, for example, there is a spot welding method as shown in FIGS. That is, a C-arm 84 is attached to a robot arm 82 of a robot body 81 of a welding robot via a connection portion 83, and the C-arm 84
A cylinder 86 and a pressure shaft 87 are provided in opposition to the electrode 85, and an electrode 88 is disposed at the lower end of the pressure shaft 87. A welding gun 89 is constituted by the above-described elements 83 to 88. .

To weld the work 90 with the conventional welding gun 89, a pressing shaft 87 (so-called rod side) is pressed downward to weld the work 90 between the upper and lower electrodes 88 and 85. For this reason, the above-described pressing force causes the C-arm 84 to bend, causing the workpiece 90 to be deformed by a small amount, and causing the hitting position to move downward. Since the reference is supported by 82, there is a problem that the reference is shifted when the C-arm 84 is bent. C-arm 8
In the case where a spring 91 for equalizing (for height adjustment) is provided between the connecting member 4 and the connecting portion 83, the reaction force of the spring 91 is applied to the work 90 via the C-shaped arm 84, so that the work deformation amount is reduced. More.

[0004] In order to solve such a problem, there is a servo gun in which an equalizing section is constituted by a servo motor and a ball screw. This servo gun has a function of correcting the deflection of the C-arm 84 side, and in advance, anticipates the deflection of the C-arm 84, equalizes the entire gun upward, and controls so as not to move the hitting position.

However, in the welding method and apparatus using the servo gun, it is necessary to lift the work 90 so as to induce the deformation of the work 90, and the above-described arm deflection correction function and electrode wear correction function are indispensable.
There was a problem that control and structure became complicated.

[0006] On the other hand, a spot welding method and its apparatus as described in Japanese Patent Application Laid-Open No. Hei 7-314146 have already been invented. That is, as shown in FIG. 12, a pressing device 95 and a C-shaped arm 96 are attached to a robot arm 93 of a robot main body 92 of a welding robot via a connecting portion 94, and the above-described electrode 97 of the C-shaped arm 96 is The pressurizing shaft 98 and the electrode 99 pressurized by the pressurizing device 95 are provided to compensate for the equalizing operation of the spot welding gun 100 by program control on the robot side.

According to this conventional configuration, the work 101 is
Although welding is performed while backing up the electrode 97 on the mold arm 96 side while backing up, the pressing force of the pressurizing shaft 98 and the electrode 99 by the pressurizing device 95 causes the C-shaped arm 96 to flex. There was a point.

[0008]

According to the first aspect of the present invention, the electrode on the side (rod side) facing the C-arm is fixed by contacting with the work, and then the electrode on the C-arm is fixed. By moving and pressurizing the work, the position of the electrode on the rod side can be secured in accordance with the work, and welding can be performed at the correct position even if the C-arm is slightly bent. It is an object of the present invention to provide a spot welding method capable of preventing deformation of a workpiece.

According to a second aspect of the present invention, in addition to the object of the first aspect of the present invention, there is provided a moving means in which the electrode side on the side (rod side) facing the C-arm is supported by a robot. The object of the present invention is to provide a spot welding method in which the rod side that is not easily bent with respect to the robot can be used as a support standard by moving the robot, and the accuracy can be further improved.

According to a third aspect of the present invention, in addition to the object of the second aspect, the moving means is formed by a screw feed motor, and the work is controlled by a motor load such as a load current. By configuring to detect contact,
It is an object of the present invention to provide a spot welding method that does not require a teaching operation for a robot and can perform high-precision welding even when electrodes are worn.

According to a fourth aspect of the present invention, there is provided a rod-side electrode fixed in contact with a workpiece in advance, and a C-arm side for pressing the workpiece after the rod-side electrode contacts the workpiece. The electrode side of the rod is supported by the robot, and the moving means for moving the electrode on the rod side is provided, so that the position of the electrode on the rod side can be secured according to the work, and the C-shaped arm is provided. Welding can be performed at the correct position even if it slightly bends, preventing deformation of the work due to the bending of the C-arm, and also using the rod side that does not easily bend against the robot as a reference for welding. It is an object of the present invention to provide a spot welding apparatus capable of achieving high precision in welding.

[0012]

According to a first aspect of the present invention, there is provided a spot welding method using a welding gun having a C-shaped arm, wherein an electrode on the side facing the C-shaped arm is brought into contact with a workpiece. This is a spot welding method in which the workpiece is pressurized by moving the electrode on the C-arm side.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, a spot in which the electrode side facing the C-arm is moved by moving means supported by a robot. It is a welding method.

According to a third aspect of the present invention, in addition to the configuration of the second aspect of the present invention, the moving means is formed by a screw feed motor, and detects contact of a workpiece by a motor load. It is a spot welding method.

According to a fourth aspect of the present invention, there is provided a spot welding apparatus provided with a welding gun having a C-shaped arm. A C-arm-side electrode for pressing the work after the rod-side electrode comes into contact with the work, wherein the rod-side electrode is supported by a robot, and moving means for moving the rod-side electrode is provided. It is a spot welding device.

[0016]

According to the first aspect of the present invention, when performing spot welding on a work, first, the electrode on the side facing the C-shaped arm (ie, the rod side) is brought into contact with the work and fixed. Then, the workpiece is pressurized by moving the electrode on the C-arm side. In short, this is a method in which the rod side is positioned and fixed, and pressure is applied on the arm side. For this reason, the position of the electrode on the rod side can be ensured in accordance with the work, and even if the C-shaped arm slightly bends during welding pressurization, welding can be performed at the correct position, and deformation of the work due to the bending of the C-arm can be prevented. There is an effect that can be prevented. In addition, there is an effect that a correction function as in a conventional servo gun is not required.

According to the invention described in claim 2 of the present invention,
In addition to the effect of the first aspect of the present invention, the electrode side on the side (rod side) facing the C-shaped arm is moved by the moving means supported by the robot. That is, since the rod side that is hard to bend is supported by the robot and is used as a reference, even if the C-shaped arm is slightly bent, there is no bending deformation on the reference side, so that the effect of further improving the welding accuracy can be achieved. There is.

According to the third aspect of the present invention,
In addition to the effect of the second aspect of the present invention, the above-mentioned moving means is formed by a screw feed motor, and it is detected that the electrode has come into contact with the work by a motor load such as a load current. Has a detection function. Therefore, there is an effect that teaching (teaching) work for the robot is not required. If the electrode is polished every predetermined welding cycle, the electrode becomes shorter gradually.However, even when the electrode is worn in such a manner, it is detected that the electrode has come into contact with the workpiece by the above-described motor load. There is an effect that can be done.

According to the invention described in claim 4 of the present invention,
The rod-side electrode supported by the robot is moved by the moving means, and the electrode is brought into contact with the work and fixed. After the rod-side electrode comes into contact with the work, the work is carried out by the C-arm-side electrode. Since the pressure is applied, even if the C-shaped arm is slightly bent, the work is positioned on the rod side where there is no deformation, so that the position of the work is always constant. In this way, the position of the electrode on the rod side can be secured according to the workpiece,
This has the effect that welding can always be performed at the correct position, which prevents deformation of the work due to the bending of the C-arm, and that the rod side that does not bend with respect to the robot is used as a support standard, so that the welding work is high. There is an effect that accuracy can be achieved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawings show a spot welding method and its apparatus. First, the configuration of the spot welding apparatus will be described with reference to FIGS.

In FIG. 1, a welding robot 11 installed on the floor A is provided, and a robot arm 17 is attached to a robot body 12 of the welding robot 11 via indirect parts 13, 14, 15, and 16. A welding gun 19 is disposed at the tip of 17 via a connecting portion 18.

As shown in FIG. 2, the welding gun 19 has a C-shaped arm 20, and a gun body 22 is provided at a position vertically facing the electrode 21 on the C-shaped arm 20 side. Is supported on the robot arm 17 via the connection section 18 described above. The above-mentioned gun body 22 is provided with a rod-side shaft 24 integrally formed with a ball screw 23 at an upper portion, and the lower end (that is, the tip) of the rod 2
5 is attached.

Here, the ball screw 23 is screwed to a ball nut 26 via a sphere, and the rotational force of a screw feed motor 27 as a moving means is controlled by the pulley 28 and the belt 2.
9, transmitted through the pulley 30. The screw feed motor 27 described above is a reversible motor with a brake having a brake 31 as a braking device.

Further, another ball nut 32 is attached to the outside of the gun body 22, and a C-shaped arm shaft 33 having a ball screw structure is screwed to the ball nut 32 via a sphere. This C-shaped arm shaft 33 has a screw feed motor 34
Is transmitted through the pulley 35, the belt 36, and the pulley 37. The above-described screw feed motor 34 is constituted by a brakeless reversible motor.

In addition, this spot welding apparatus is configured so that the work 38 (see FIG. 5) is positioned and fixed on the rod side (see the rod-side shaft 24) and pressurized by the C-shaped arm 20. The configuration is such that the contact of the electrode 25 with the work 38 is detected by a motor load such as a load current of the motor 27. The above-mentioned welding robot 11 and welding gun 19 are provided with a ROM,
U and RAM are provided respectively.

Instead of the structure of the embodiment having the function of sensing the contact with the work 38 based on the detection of the motor load, the rod side shaft 24 is provided by a simple driving means having no contact sensing function. Also, the electrode 25 can be moved up and down. However, in this case, teaching needs to be performed on the welding robot 11, and thus the teaching processing will be described with reference to the flowchart of FIG.

In a first step S1, the motor of the rod side shaft 24 is rotated forward, and the rod side shaft 24 and the electrode 25 are lowered. In the second step S2, it is determined whether or not the electrode 25 of the rod-side shaft 24 has contacted the workpiece 38 under the condition of the minimum pressing force, and when NO determination (non-contact), the same process is repeated until the electrode 38 comes into contact. Then, the process returns to the first step S1, and when the determination is YES (at the time of contact), the next third step S3
Move to In the third step S3, the position of the rod side shaft 24 is stored, and this position is taught to the welding robot 11.

In the above-described embodiment (see FIGS. 1 and 2), since the function of detecting the contact with the work 38 based on the data load detection is provided, the teaching processing in FIG. 3 can be omitted. A method for performing spot welding using the spot welding apparatus configured as described above will be described in detail below with reference to a flowchart shown in FIG. 4 and explanatory diagrams shown in FIGS. 5, 6, and 7.

In the first step S11, the welding robot 11
When a spot number (data indicating a position to be spot-welded) and welding condition data (data such as a current value and a pressing force) are input from the side to the welding gun 19 side, the welding gun 1
Movement 9 is controlled by the robot arm 17 toward the position of the spot number to be welded (see FIG. 5). Next, in a second step S12, the welding gun 19 is received from the welding robot 11 side.
When the pressure start signal is input to the side, the rod-side shaft 24 starts descending at the hitting point number position.

In the next third step S13, the rod-side shaft 2
4 is further moved (downward) so that the electrode 25 comes into contact with the work 38, and in the next fourth step S14, the monitor 27 is moved.
It is determined whether the motor load such as the load current has reached a predetermined value set in advance. When the electrode 25 comes into contact with the work 38, the load current of the motor 27 increases. By comparing this load current with a predetermined value, it can be detected that the electrode 25 has come into contact with the work 38.

Therefore, NO in the above-described fourth step S14
If determined, the process proceeds to a fifth step S15, and if determined to be YES, the process proceeds to a sixth step S16. In the above-described fifth step S15, the forward rotation and lowering of the rod-side shaft 24 is executed via the motor 27 in order to continue the lowering of the rod-side shaft 24 and the electrode 25 until the motor load reaches a predetermined value.

In the above-described sixth step S16, the rotation of the motor 27 is stopped, and the brake 31 is driven to position and fix the rod-side shaft 24 in contact with the work 38 (see FIG. 6). Next, a seventh step S17
Then, the motor 34 is driven, and the pressurization of the work 38 by the C-arm 20 and its electrode 21 via the C-arm shaft 33 is started.

Next, in an eighth step S18, it is determined whether or not the work pressing force by the electrode 21 has reached a preset set value (specified value). When the determination is NO, the process returns to the seventh step S17 for the purpose of repeating the above processing until the welding pressure reaches the set value. When the determination is YES (see FIG. 7), the process proceeds to the next ninth step S19. .

Here, whether or not the above-mentioned pressing force has reached the set value can be detected by the torque of the motor 34. When the pressurization completion signal is output to the welding timer in the ninth step S19 described above, a welding current is supplied to the upper and lower electrodes 25 and 21 from the power supply line (not shown) under the work pressure condition, and two or three electrodes are supplied. A work 38 in which a plurality of plate materials such as sheets are combined is heated and melted by Joule heat, and a nugget 39 is formed and pressed in a point-like manner.

When the time set in advance by the above-mentioned welding timer expires, a welding completion signal is input to the welding gun 19 from the welding timer in a tenth step S20. Next, the process proceeds to the eleventh step S21 and the twelfth step S22, and the processes in these steps S21 and S22 are performed, for example, in parallel. That is, in the eleventh step S21, the control is performed so that the electrode 21 of the C-arm 20 is separated downward from the work 38 via the C-arm shaft 33 by the reverse rotation of the motor 34. Is controlled so that the electrode 25 is separated upward from the work 38 via the rod-side shaft 24 by the reverse rotation of.

Next, in a thirteenth step S23, the current chip open stroke (cos) by the above-mentioned separation control is performed.
(See FIG. 2, the separation stroke between the electrodes 21 and 24) is compared with a predetermined set value (however, it can be arbitrarily enlarged / reduced in accordance with the type of work to be welded and the position of the hit point). Judgment of OK or NG, C-shaped arm axis N
At G, the process returns to the eleventh step S21 and repeats the reverse rotation of the C-shaped arm shaft 33 until it becomes OK, and the rod-side shaft N
At G, the process returns to the twelfth step S22 and repeats the reverse rotation of the rod-side shaft 24 until it becomes OK. When OK, the process proceeds to the next fourteenth step S14, where the fourteenth step S14 is executed.
At 24, a pressure release signal is output to the welding robot 11,
Finish the spot welding operation corresponding to the specific spot number.

As described above, according to the spot welding method of the present embodiment, the electrode 25 on the side facing the C-shaped arm 20 (ie, the rod side) is brought into contact with the work 38 when performing the spot welding on the work 38. After fixing, the workpiece 21 is pressed by moving the electrode 21 on the C-arm 20 side. In short, this is a method in which the rod side is positioned and fixed, and pressure is applied on the arm side. For this reason, the position of the electrode 25 on the rod side can be secured in accordance with the work 38, and even if the C-shaped arm 20 is slightly bent during welding pressurization, welding can be performed at a correct position. There is an effect that deformation of the work 38 can be prevented. In addition, there is an effect that a correction function as in a conventional servo gun is not required.

Further, the electrode 25 side (see the gun body 22) on the side (rod side) facing the C-shaped arm 20 is moved by the moving means (see the motor 27) supported by the robot 11. That is, since the rod side that is difficult to bend is supported by the robot 11 and used as a reference, the C-arm 2
Even if 0 is slightly bent, there is no bending deformation on the reference side, so that there is an effect that the accuracy of welding can be further improved.

Further, since the above-mentioned moving means is formed by the screw feed motor 27 and detects that the electrode 25 has come into contact with the work 38 by a motor load such as a load current, a function of detecting the contact of the electrode 25 with the work 38 is provided. Have. For this reason, there is an effect that teaching (teaching) work for the robot 11 becomes unnecessary. When the electrode 25 is polished every predetermined welding cycle, the electrode 25 is gradually shortened. However, even when the electrode 25 is worn as described above, it is detected that the electrode 25 has come into contact with the work 38 due to the motor load described above. This has the effect that high-precision welding can be performed.

In addition, according to the spot welding apparatus of this embodiment, the rod-side electrode 25 (see the gun body 22) supported by the robot 11 is moved by the moving means (see the motor 27), and the electrode is moved. 25 is brought into contact with the workpiece 38, and after the electrode 25 on the rod side contacts the workpiece 38, the workpiece 38 is pressed by the electrode 21 on the C-arm 20 side.
Even if the C-shaped arm 20 is slightly bent, the work 38 is positioned on the rod side that is not deformed.
The position of 8 is always constant. In this manner, the position of the electrode 25 on the rod side can be secured in accordance with the work 38, and there is an effect that welding can always be performed at a correct position. In addition, since the rod side that does not bend easily with respect to the robot 11 is used as a support standard, there is an effect that high precision welding can be achieved.

FIGS. 8 and 9 are partial views corresponding to FIGS. 6 and 7 of a welding gun 19 showing another embodiment of the spot welding apparatus. In this embodiment, the deformation of the C-arm 20 due to pressurization is shown. A predetermined angle θ is set in advance between the axis α of the rod-side shaft 24 and the axis β of the electrode 21 on the C-arm 20 side when the work 38 is pressed by the electrodes 25 and 21. (See FIG. 9), the shaft cores α and β are configured to be on a straight line. Even in such a configuration, accurate welding can be performed at a correct position. Therefore, in FIGS.

In correspondence between the structure of the present invention and the above-described embodiment, the electrode (rod-side electrode) on the side facing the C-arm of the present invention is the electrode 2 located at the top of the embodiment.
5, the electrode on the C-arm side corresponds to the electrode 21 located at the lower part, the electrode side supported by the robot corresponds to the gun body 22, and the moving means includes a screw feeder. Although corresponding to the motor 27, the present invention is not limited to only the configuration of the above-described embodiment.

[Brief description of the drawings]

FIG. 1 is a side view of the entire spot welding apparatus used in the spot welding method of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1;

FIG. 3 is a flowchart showing a teaching process.

FIG. 4 is a flowchart showing a spot welding method of the present invention.

FIG. 5 is an explanatory view showing the movement of the electrode to the hitting number position.

FIG. 6 is an explanatory view showing contact and fixation of a rod-side electrode to a workpiece.

FIG. 7 is an explanatory view showing pressurization of a work by a C-arm.

FIG. 8 is a partial view showing another embodiment of the spot welding apparatus of the present invention.

FIG. 9 is an explanatory view showing pressurization of a work by a C-arm of the welding gun of FIG. 8;

FIG. 10 is a side view showing a conventional spot welding method and its device.

FIG. 11 is an enlarged view of a main part of FIG. 10;

FIG. 12 is a side view showing a conventional spot welding method and its device.

[Explanation of symbols]

 11 Welding robot 19 Welding gun 20 C-arm 21, 25 Electrode 27 Motor 38 Work

Claims (4)

[Claims] 1. A spot welding method using a welding gun having a C-shaped arm, wherein an electrode on a side facing the C-shaped arm is brought into contact with a work and fixed, and then the electrode on the C-shaped arm is moved. A spot welding method that presses the workpiece by pressing. 2. The spot welding method according to claim 1, wherein the electrode side opposite to the C-arm is moved by a moving means supported by a robot. 3. The spot welding method according to claim 2, wherein said moving means is formed by a screw feed motor, and detects contact of a workpiece by a motor load. 4. A spot welding apparatus provided with a welding gun having a C-shaped arm, wherein a rod-side electrode fixed in contact with a workpiece prior to the workpiece and the rod-side electrode contact the workpiece. A spot welding apparatus comprising: a C-arm-side electrode that pressurizes a workpiece later; the rod-side electrode side is supported by a robot; and a moving unit that moves the rod-side electrode is provided.