JPH08132250A - Spot welding gun and body assembling method - Google Patents

Abstract

PURPOSE: To apply the most suitable spot welding to various welding parts by arranging freely movably a movable mount on the tip end of a gun arm and radially providing plural electrode tips on this movable mount. CONSTITUTION: A shaft hole 4 for a rotary mount 4 is put through on the tip end shaft of the gun arm 2 of a spot welding gun 1, and the rotary mount 4 is supported freely rotatably. The rotary mount 4 is ring-shaped with plural electrode tips 6-9 of different shapes radially attached at equal spaces apart on the outer circumference. In addition, the rotary mount 4 is rotated by the operation of a servo motor 3 based on signals from the controller of a spot welding robot, selecting tips with a shape suitable for a welding part. A cylinder 5 is provided with a cap tip 10 at the tip end of the cylinder rod 10, and spot welding is performed with the electric current made to flow between the cap tip and the selected electrode tip of the rotary mount 4 while a pressing force is imparted to a welding base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for joining vehicle body panels to each other in, for example, assembling a vehicle body of an automobile, and a spot welding gun capable of switching and welding electrode tips according to a joining portion, and The present invention relates to a method for assembling a vehicle body using the spot welding gun.

[0002]

2. Description of the Related Art The electrode tip of a spot welding gun is usually fixed to the gun, and under the present circumstances, dedicated guns are prepared for each purpose and used properly according to the object to be welded.

That is, a 16 mmφ cap tip is standard for the electrode tip of the spot welding gun, a gun equipped with the 16 mmφ tip is used at a normal welding position, and a 13 mmφ at a welding portion having a narrow flange width. A gun with a cap tip of is used. Also, in terms of appearance quality, spot welding guns with a large radius of curvature such as a semi-cylindrical radius tip or a flat back bar are used at locations where it is desired to prevent dents from occurring. Moreover, it is necessary to change the shape and type of the tip depending on the target part, and the welding gun is selected and replaced each time.

On the other hand, in assembling a vehicle body of an automobile, when a step portion formed at a joint portion of a vehicle body panel such as a roof, a rear fender, a front pillar, and a side roof rail is built up and smoothed, for example, an actual flat plate 1 is used. -8
No. 9885, or brass braze, as described in the right column on page 1-43 of "New Edition Automotive Engineering Handbook <Vol. 9>" issued by the Society of Automotive Engineers of Japan on May 31, 1983. The above-mentioned arc brazing fills the joint portion of the vehicle body panel to eliminate the joining line of the panel to improve the appearance of the vehicle body.However, in recent years, prevention of distortion of the vehicle body panel due to heat of brazing, grinding after brazing and From the viewpoint of reducing the polishing work, for example, thermal spraying with a zinc-based material has been performed (Japanese Patent Laid-Open No. 4-1).
7656).

At this time, if the accuracy of each panel is poor, a large step will be formed on the joint surface, and the appearance quality after overlaying will be deteriorated. Must be reinforced. Further, in this case, it is necessary to prevent spot dents by using a radius tip, a back bar or the like so as not to impair the appearance quality of the vehicle body. It is desirable that the spot welding for reinforcement be performed again upstream of the additional driving step in the vehicle body assembly line from the viewpoint of improving the joining accuracy of the panels in the overlay portion.

[0006]

However, since the spot welding robot for additional striking in the striking step of the vehicle body assembly line is equipped with a welding gun equipped with a tip for general striking, the spot striking mark is increased. It is necessary to separately prepare a welding gun equipped with a radius tip, a back bar, etc. and carry the gun with a hand changer in order to also perform spot welding for reinforcement of the overlaid part that requires prevention of Has a problem that the operation rate of the robot is reduced and the work efficiency is reduced. It is also possible to prepare a dedicated robot for overlay reinforcement for each type of gun, or to deal with it with a multi-welding gun or manual hammering, but there are problems in terms of equipment cost or work efficiency, respectively. Resolving this point has been a problem in performing spot welding for reinforcement of the overlay in the additional driving process.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in the conventional vehicle body assembling method, and is provided with a plurality of electrode tips, and the shape and type of the tips can be switched according to the welding site. For the purpose of providing a spot welding gun capable of performing optimum spot welding on various welding parts without sacrificing welding efficiency, and a vehicle body assembly method using such a spot welding gun. There is.

[0008]

A spot welding gun according to claim 1 of the present invention comprises a movable mount movably disposed at a tip end portion of a gun arm, a mount drive mechanism for activating the movable mount, and a mount drive mechanism. In the embodiment of the spot welding gun according to the present invention, the movable mount has a plurality of electrode tips having different shapes and arranged in parallel on the movable mount. And the movable mount is a rotary mount, or the rotary movable mount is equipped with a water cooling jacket for cooling the electrode tip and a contact plate for feeding power to the electrode tip, and the gun arm is Water hole that communicates with the water cooling jacket of the movable mount through an annular groove formed between the contact surface between the movable mount and the movable mount, and the welding current. It may be provided with a contact which is connected to a secondary cable for supply and is in sliding contact with the contact plate of the movable mount, and such a structure of the spot welding gun is used as means for solving the above-mentioned conventional problems. There is.

In the method of assembling a vehicle body according to a fourth aspect of the present invention, after the joint portions of the vehicle body panel are joined by spot welding, the step portion formed in the joint portion is overlaid to form the step portion. In the method for assembling a vehicle body for smoothing, a spot welding gun having at least one of a radius tip and a back bar together with a cap tip is used by a welding robot for increasing the spot welding, and an electrode tip of the spot welding gun is used. In the embodiment of the method for assembling a vehicle body according to the present invention, the radial tip or the back bar is used before welding the flange portion of the vehicle body panel. The feature is that the central part of the panel is welded.

[0010]

In the spot welding gun according to the first aspect of the present invention, the movable mount movably disposed at the tip of the gun arm, the mount drive mechanism for operating the movable mount, and the cap tip, for example, Since a plurality of electrode tips having different shapes such as a radius tip and a back bar and arranged in parallel on the movable mount are provided, for example, the mount drive mechanism is operated by a signal from the controller of the spot welding robot. By moving the movable mount, the electrode tip can be switched according to the welding location, and even if one welding robot carries out welding at different welding point with different applied tip specifications, the operating rate of the robot may decrease. Absent.

As an embodiment of the spot welding gun according to the present invention, in the welding gun according to claim 2, a movable mount is a rotary type in which the movable mount is rotatably arranged at the tip of the gun arm, and a plurality of electrode tips are provided. Since the chips are radially attached to the movable mount, the chips can be smoothly switched, and the pressing force is evenly applied without the interference of the adjacent chips with the panel as compared with the slide type, for example.

As another embodiment of the spot welding gun according to the present invention, in the welding gun according to claim 3, a rotary movable mount is provided for a water cooling jacket for cooling the electrode tip and a power supply to the electrode tip. The contact plate is provided, and cooling water is supplied from the water passage hole formed in the gun arm to the water cooling jacket of the movable mount through the annular groove formed between the contact surface of the gun arm and the movable mount, and the welding current is also supplied. Is supplied from the secondary cable to the contact plate of the movable mount through the contact formed on the gun arm, so that the cooling water and welding current can be smoothly supplied to the tip without using a flexible tube. The rotation of the mount and the working range of the spot welding gun are not restricted by the flexible tube.

In the method of assembling the vehicle body according to the fourth aspect of the present invention, the spot welding gun is used, for example.
Spot welding of the build-up part is performed concurrently with normal over-strike while switching the tip of the welding gun to the cap tip, back bar, etc. by the over-welding welding robot. The joining accuracy of the panel is improved without generating a mark.

Further, as an embodiment of the vehicle body assembling method according to the present invention, in the vehicle body assembling method according to claim 5, the welding of the panel center portion is prioritized over the welding of the flange portion of the vehicle body panel. Therefore, even if the curvature accuracy of the panel is low, the center portion of the panel does not rise, and the bonding accuracy of the panel is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 and 2 are explanatory views showing an embodiment of a spot welding gun according to the present invention.

That is, in the spot welding gun 1 shown in FIG. 1A, a rotary mount 4 (movable mount) mounted together with a servo motor 3 as a mount drive mechanism at the tip of the gun arm 2 and the middle of the gun arm 2. It is mainly composed of a cylinder 5 attached to the tip of a cylinder arm 2a branched from.

The rotary mount 4 has a ring shape as shown in FIG. 1 (b), and four electrode chips having different shapes on the outer periphery thereof, that is, in this embodiment, a cap chip 6 of 16 mmφ and a cap of 13 mmφ. A tip 7, a radius tip 8 and a back bar 9 are radially attached at 90 ° intervals.

A shaft 2b is formed at the tip of the gun arm 2, and the rotary mount 4 is rotatably supported by inserting the shaft hole 4a of the rotary mount 4 into the shaft 2b. Is rotated by 90 ° by the operation of the servo motor 3 based on a signal from the controller of the spot welding robot, and the four electrode tips 6,
A tip having a shape suitable for the welding site can be selected from 7, 8 and 9.

The cylinder 5 is provided with a cap tip 10a at the tip of a cylinder rod 10 and is interposed between one of the electrode tips selected by the rotation of the rotary mount 4 by the pushing operation based on the air supply, for example, a 16 mmφ cap tip 6. Then, the welding base metal is energized while applying a predetermined pressing force, thereby performing spot welding.

FIG. 2 is an enlarged cross-sectional view showing a cooling system and an energization system for the electrode tip of the spot welding gun 1 according to the present invention.

That is, the rotary mount 4 of the spot welding gun 1 is provided with a water cooling jacket 11 inside, and as shown in FIG. 1B, two annular grooves are formed on the sliding contact surface with the gun arm 2. 12 and 13 are formed concentrically, and these annular grooves 12 and 13 are respectively formed in the inlet holes 11a.
And, it communicates with the inside of the water cooling jacket 11 through the outlet hole 11b.

On the other hand, the annular groove 12 is formed on the gun arm 2.
And water communication holes 14 (supply side) and 15 communicating with 13 and 13, respectively.
(Drain side) is formed, and from the water passage hole 14 to the annular groove 12
The cooling water supplied into the water cooling jacket 11 through the inlet hole 11a and the inlet hole 11a is drained to the water passage hole 15 through the outlet hole 11b and the annular groove 13. , 7, 8 and 9 will be effectively cooled. Incidentally, packings 16, 17, and 18 made of three O-rings are arranged on the sliding contact surface of the gun arm 2 with the rotary mount 4 to prevent water leakage from the sliding contact surface. There is.

A contact 20 connected to a secondary cable 19 for supplying a welding current is provided on the shaft 2b of the gun arm 2, and the electrode tips 6, 7, 8, 9 of the rotary mount 4 are provided.
Since it comes into sliding contact with the contact plate 21 electrically connected to, the power supply to the electrode chips 6, 7, 8, 9 is smoothly performed regardless of the rotational position of the rotary mount 4.

Although the servo motor 3 is provided on the tip side of the gun arm 2 in the above embodiment, the servo motor 3 is provided on the base end side of the gun arm 2 and the drive shaft penetrating the gun arm 2 is provided. It is also possible to actuate the rotary mount 4 via.

The spot welding gun 1 having such a structure is mounted on, for example, a robot for additional welding in a vehicle body assembly line, and a body side frame, a roof and the like have been temporarily assembled on the floor in the body main process. It is used to build up a complete car body by over-welding the required parts of the body.

At this time, spot welding for reinforcing and maintaining accuracy is also performed in the subsequent process, for example, at the joints between the roof panel and the rear fender panel, which are subjected to overlaying by thermal spraying, and the roof panel and the front pillar panel. For welding this part, a specially shaped electrode tip different from the general overstrike part is used.

That is, FIG. 3 is a vertical cross-sectional view showing a joint portion between the roof panel 30 and the rear fender panel 31, and at such a joint portion, the one-step joggle shown in FIG. The two-step joggle as shown in (b) is applied, but especially in the case of the one-step joggle, a special electrode such as a radius tip or a back bar is used so that the dents of spot welding are not exposed on the surface of the vehicle body. Must use chips.

The additional welding robot sequentially welds predetermined welding spots in response to a command from the controller based on teaching, and operates the servomotor 3 of the spot welding gun 1 in response to a signal from the controller. By rotating the rotary mount 4, the electrode tips 6, 7,
Since the electrode tip can be freely selected from 8 and 9 according to the welding location, the welding gun is required each time when welding the build-up portion that requires the special tip such as the radius tip 8 and the back bar 9. Since it is not necessary to change the position, it is possible to perform spot welding of the overlay portion concurrently with other over-welding without lowering work efficiency.

At this time, depending on the curvature accuracy of the roof panel 30 and the rear fender panel 31, FIG.
As shown in (a), the flange portions 3 of the panels 30 and 31.
If 0a and 31a are welded first, the central portions of the panels 30 and 31 may float, and in addition, a radius tip or a back bar should be used in the welding of the central portions of the panels to avoid dents in spot welding. Due to the use, the pressing force becomes small, so that the central portions of the panels 30 and 31 may not be welded. Therefore, by using the radius tip 8 or the back bar 9,
As shown in (b), the central portions of the panels 30 and 31 are welded first, and then the 16 mmφ cap tip 6 or 13 is welded.
By switching to the mmφ cap chip 7, the flange portions 30a and 31a are welded as shown in FIG. 4 (c).

As described above, by using the spot welding gun 1 according to the present invention, the optimum electrode tip corresponding to the welding site, that is, the cap tip 6 of 16 mmφ for a normal overstrike, and the narrow flange portion are used. Is 13 mmφ
The cap tip 7, the radius tip 8 and the back bar 9 which do not produce dents on the overlaid portion can be used by switching to each, so that the normal overdip welding and overlay welding of the overwelding robot can be performed. Since the welding order is not constrained by the tip shape and can be freely set in the welding order that emphasizes the prevention of welding distortion, the welding accuracy of each body panel is improved and distortion is prevented. can do.

In the next step, the joint portion is subjected to a degreasing treatment and a grid blast treatment (base treatment) for improving the adhesion to the overlay metal, and then, for example, by a thermal spray gun as shown in FIG. ) And (b), a build-up layer 32 is formed, and finally, a surplus part of the build-up layer 32 is removed by a grinder or a sander to finish the surface smoothly.

[0033]

As described above, according to the first aspect of the present invention.
The spot welding gun according to (1) has a movable mount movably arranged at the tip end of the gun arm, a mount drive mechanism for operating the movable mount, and a plurality of parallel mounts having different shapes and arranged side by side on the movable mount. Since it is equipped with an electrode tip, it is possible to switch the electrode tip according to the welding location, and it is possible to promptly deal with welding of welding points with different application tip specifications without changing the spot welding gun. It has an excellent effect.

As an embodiment of the spot welding gun according to the present invention, in the welding gun according to claim 2,
Since the movable mount is a rotary type and a plurality of electrode chips are radially arranged on the movable mount, the chips can be switched smoothly, there is no interference by adjacent chips, and the pressing force between the chips is reduced. Can be uniform. In a welding gun according to a third aspect of the present invention, the rotary movable mount is provided with a water cooling jacket for cooling the electrode tip and a contact plate for supplying power to the electrode tip. The water flow hole formed in the gun arm was supplied to the water cooling jacket of the movable mount through the annular groove formed between the contact surfaces of the gun arm and the movable mount, and the welding current was formed in the gun arm from the secondary cable. Since it is supplied to the contact plate of the movable mount via the contact, cooling water and welding current are smoothly supplied to the tip, and the rotation of the movable mount and the operating range of the spot welding gun are flexible tubes for water supply and power supply. Has the effect of not being constrained by.

In the method of assembling a vehicle body according to claim 4 of the present invention, for example, by using the spot welding gun, the spot welding of the built-up portion is increased by the welding robot for the additional hitting, the tip of the welding gun is capped, for example, Chip,
Since the back bar or the radius tip is changed over and the normal overstrike is performed in parallel, it is possible to improve the joining accuracy of the panel without lowering the working efficiency or generating spot dents.

As an embodiment of the vehicle body assembling method according to the present invention, in the vehicle body assembling method according to claim 5, the welding of the panel center portion is prioritized over the welding of the flange portion of the vehicle body panel. Therefore, even when the curvature accuracy of the panel is low, it is possible to prevent the center portion of the panel from being lifted up, and it is possible to improve the joining accuracy of the panel.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view showing one embodiment of a spot welding gun according to the present invention. (B) It is explanatory drawing which shows the shape of the rotary mount of the spot welding gun shown in FIG. 1, and the arrangement | positioning state of an electrode tip.

FIG. 2 is a cross-sectional explanatory view of a rotary mount portion showing a water supply and power supply structure of the spot welding gun shown in FIG.

3 (a) and 3 (b) are cross-sectional explanatory views of a vehicle body panel showing a shape of a build-up portion and a spot welding position.

4 (a), (b) and (c) are cross-sectional explanatory views of a vehicle body panel showing a spot welding procedure of a built-up portion.

[Explanation of symbols]

 1 Spot Welding Gun 2 Gun Arm 3 Servo Motor (Mount Drive Mechanism) 4 Rotation Mount (Movable Mount) 6 16mmφ Cap Tip (Electrode Tip) 7 13mmφ Cap Tip (Electrode Tip) 8 Radius Tip (Electrode Tip) 9 Back Bar (Electrode Tip) ) 12,13 Annular groove 14,15 Water passage hole 19 Secondary cable 20 Contact point 21 Contact plate

Claims (5)

[Claims] 1. A movable mount movably arranged at the tip of a gun arm, a mount drive mechanism for operating the movable mount, and a plurality of electrode chips having different shapes and arranged in parallel on the movable mount. Spot welding gun characterized by having. 2. The movable mount is rotatably disposed at the tip of the gun arm, and the movable mount is provided with a plurality of electrode chips radially.
Spot welding gun described. 3. The movable mount has a water cooling jacket for cooling the electrode tip and a contact plate for supplying power to the electrode tip, and the gun arm has an annular groove formed between the contact surfaces of the gun arm and the movable mount. And a water hole that communicates with the water cooling jacket of the movable mount, and 2 for supplying welding current.
3. The spot welding gun according to claim 2, further comprising a contact which is connected to the next cable and is in sliding contact with the contact plate of the movable mount. 4. A method for assembling a vehicle body, wherein a joint portion of a vehicle body panel is joined by spot welding, and then a step portion formed at the joint portion is padded to smooth the step portion. With the welding robot for over-strike, a spot welding gun equipped with at least one of a radius tip and a back bar together with a cap tip is used, and the electrode tip of the spot welding gun is switched and it is possible to perform in parallel with general over-strike. Characteristic vehicle body assembly method. 5. The method for assembling a vehicle body according to claim 4, wherein the spot center welding is performed by welding the center portion of the panel with a radius tip or a back bar prior to welding the flange portion of the vehicle body panel.