JP2821402B2 - Resistance welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a resistance welding apparatus for performing lap resistance welding in a state where a joint work is positioned with respect to a work to be joined, such as projection welding of a nut to a panel.

[0002]

2. Description of the Related Art Conventionally, as this kind of resistance welding apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-238461, a projection-type welding of a nut with a projection at a position of a mounting hole of a panel is known. Are known. This has a fixed lower rod-shaped electrode on which a guide pin can protrude and retract from the tip end (upper end), a movable rod-shaped upper electrode that moves up and down in opposition to the lower electrode, and a lateral side of the upper electrode. A cylinder having a piston rod arranged and having a tip end contacting and separating from the upper electrode, and extending in synchronization with the lower electrode when the upper electrode moves downward to advance the piston rod;
It is provided at the tip of the piston rod of this cylinder, receives the nut from the nut transfer device when the cylinder is contracted, and loads it on the upper side. A nut transfer mechanism for transferring the nut, a panel is placed on the lower electrode, a guide pin is projected from the mounting hole, and a nut moved down with the upper electrode to the guide pin is positioned outside. Thus, welding is performed by applying a welding current while pressing the nut and the panel from both upper and lower sides by both electrodes.

[0003]

However, in the above-mentioned conventional device, since the nut is positioned by the guide pin of the lower electrode, it is difficult to position the nut in a fixed direction. For this reason, for example, when welding by aligning the outer peripheral portion of the nut with the edge of the panel, the direction of the nut is shifted, and a part of the projection is not welded to the panel portion. In this case, the torque becomes insufficient.

When the nut is a nut with a lid in which a part of the screw hole is sealed, if the guide pin of the lower electrode is inserted and positioned in the screw hole of the nut, the lid portion is moved by the guide pin. Since there is a possibility that the guide pin may be broken, it is necessary to reduce the length of the protrusion of the guide pin.
However, at that time, the mounting of the nut on the electrode becomes poor, and there is a problem that the nut is likely to be displaced.
That is, there is room for improvement in the above-mentioned conventional device.

Incidentally, it is conceivable to position the nut with respect to the electrode by the magnetic force of the magnet. However, it is inevitable that the nut becomes magnetic, and there is a possibility that the nut may be misaligned due to its magnetization. In addition, since the temperature of the electrode becomes high at the time of welding, even if it is cooled with cooling water, the magnet is thermally degraded and its magnetic force is apt to decrease, and a stable positioning effect over a long period of time cannot be expected. .

The present invention has been made in view of the above points, and a main object of the present invention is to perform resistance welding of a joined work to a work to be joined, such as in the case of welding a nut to a panel as described above. In such a case, it is an object of the present invention to improve the configuration for positioning the joint work so that the work can be accurately positioned and welded in a stable state for a long period of time.

[0007]

In order to achieve the above object, according to the present invention, a positioning portion for a joint work is provided on an electrode, and the joint work before welding is suction-held at the positioning portion by a negative pressure. In the suction state, resistance welding between the workpieces is performed between the electrodes.

More specifically, according to the first aspect of the present invention, there is provided a fixed electrode and a movable electrode which is disposed so as to be capable of coming into contact with and separating from the fixed electrode. A resistance welding device is premised on that the joint work supplied by the work supply means is sandwiched and pressed in a superimposed state, and a welding current is passed between the electrodes to weld both works by contact resistance heat. is there.

[0009] One of the fixed electrode and the movable electrode is a work holding electrode having a positioning portion for positioning a joint work with respect to the electrode at a tip end thereof .
This work holding electrode has a tapered taper at the tip.
Electrode body and a tape corresponding to the tapered portion of the electrode body.
A tapered concave portion, and the tapered concave portion
Removed and replaced at the tip of the electrode body by taper fitting
An electrode that is mounted so as to be capable of having the above-described positioning portion on the distal end surface
And a chip.

Further, a negative pressure suction means for holding the suction by the negative pressure in a state of positioning the bonded workpiece against the positioning portion of the workpiece holding electrode provided, the negative pressure adsorption means one
One end of which penetrates the electrode tip and opens at its tip
On the other hand, the other end communicates with the negative pressure source through the electrode body.
Road.

According to the above configuration, in a state before the welding, in which the movable electrode is separated from the fixed electrode, the workpiece to be joined is set to the electrode on the side that is not the workpiece holding electrode, and the workpiece holding electrode is set to the workpiece holding electrode. When the joined work is supplied by the work supply means, the joined work is positioned and held by the positioning portion of the work holding electrode by the negative pressure of the negative pressure suction means. In this suction holding state, the movable electrode approaches the fixed electrode, the work to be joined and the joined work are overlapped between the two electrodes and pressurized, and the two workpieces are resistance-welded by applying a welding current between the two electrodes. As described above, the joint work supplied by the work supply means is suction-held in the positioning state by the negative pressure in the positioning section of the work holding electrode, so that the joint work is accurately positioned on the positioning section without displacement. The workpiece is welded to the workpiece in the state, and the workpiece and the workpiece can be accurately and reliably positioned and welded.

Further, since the joint work is positioned and held on the work holding electrode itself, a separate clamp device for positioning the work is not required, and the welding device can be simplified.

Furthermore, since the bonded work is attracted by the negative pressure and held at the electrode positioning portion, the misalignment due to the magnetization of the work and poor positioning due to the thermal deterioration of the magnet as in the case of using a magnet are not caused. In addition, the accurate positioning function of the workpiece can be stably maintained over a long period of time.

In addition, the work holding electrode is an electrode
Removed by taper fitting to the body and the tip of the electrode body
It is mounted so that it can be replaced and has the above-mentioned positioning part at the tip
One end of the negative pressure suction means.
While penetrating the electrode tip and opening at its tip,
The other end is connected to a negative pressure passage communicating with the negative pressure source through the inside of the electrode body.
Therefore, the configuration of the negative pressure adsorption means can be
Wear. Moreover, the taper fitting between the electrode tip and the electrode body
Remove and replace the electrode tip from the electrode body.
Can be. Therefore, positioning according to the type of joining work
If a plurality of types of electrode tips with
Each time the type of workpiece changes, the electrode body shall be the same.
Remove the electrode tip only from the electrode body
Can be replaced by a low-cost structure for various types of joining work.
I can deal with it.

[0015] In the present invention of claim 2, in the resistance welding apparatus of the invention of claim 1, while the opposite place the fixed electrode and the movable electrode in the vertical direction, the fixed electrode and the lower electrode, and a movable electrode in the upper electrode Work holding electrode. According to this configuration, after the work to be joined is set on the lower electrode, the work to be supplied supplied to the upper electrode is positioned and held by the positioning portion thereof, and both works are added between the two electrodes by the downward movement of the upper electrode. Pressed and welded. In this case, even with the upper electrode, it is possible to reliably position and hold the bonded workpiece by suction without dropping it.

According to a third aspect of the present invention, in the resistance welding apparatus according to the first or second aspect of the present invention, the joined work has a partially screwed screw hole and is projection-welded to the work to be joined by a projection. Use a nut with a lid. The positioning portion of the work holding electrode is a positioning recess in which the nut with the lid is fitted at the outer peripheral portion. In this way, even if the nut with a lid is fitted to the positioning recess of the work holding electrode, it can be positioned, and the structure for positioning and holding the nut with the lid on the work holding electrode is concrete and easy. Is obtained.

According to the invention of claim 4 , similarly, in claim 1 or
In the resistance welding apparatus according to the second aspect of the invention, the joining work is a nut having a threaded hole therethrough and projected and welded to the work to be joined by a projection, and the positioning portion of the work holding electrode is inserted into the screw hole of the nut. Possible positioning pins. By doing so, the nut can be positioned by inserting the screw hole of the nut into the positioning pin of the work holding electrode, and the structure for positioning and holding the nut having the penetrating screw hole to the work holding electrode is concrete. And easily obtained.

According to a fifth aspect of the present invention, in the resistance welding apparatus according to the third or fourth aspect , the workpiece to be joined has a mounting hole, and the nut is projection-welded in a state where the screw hole matches the mounting hole. Panel. In this case, the nut can be welded to the panel in a state where its screw hole is accurately positioned in the mounting hole of the panel.

[0019]

FIG. 3 shows an electrode structure of a projection welding apparatus as a resistance welding apparatus according to an embodiment of the present invention. This welding apparatus includes a copper cylindrical rod-shaped lower electrode 1 as a fixed electrode having an upper end surface serving as a pressurizing section, and a cylinder (not shown) capable of ascending and descending above the lower electrode 1, that is, the lower electrode 1. A copper cylindrical rod-shaped upper electrode 4 as a movable electrode having a lower end surface serving as a pressurizing section, when the upper electrode 4 is at a rising end position. A panel P (workpiece to be joined) whose lower surface contacts the lower electrode 1 and a projection nut N (jointwork) whose upper end abuts on the upper electrode 4 are positioned vertically between the electrodes 1 and 4. And then
The upper electrode 4 is lowered, the nut N and the panel P are sandwiched and pressed between the lower electrode 1 and the lower electrode 1 at the lower end position, and a welding current is applied between the electrodes 1 and 4 to apply the nut N.
The panel P is welded by contact resistance heat.

More specifically, the panel P has a plurality of mounting holes P1, P1,. on the other hand,
The nut N is composed of a square nut with projections having projections N1, N1,... As fusion parts at the corners of the joint surface with the panel P, and the screw holes N2 are matched with the mounting holes P1 of the panel P. Are welded to the panel P at the projections N1, N1,. In the screw hole N2 of each nut N, the opening end opposite to the projections N1, N1,... Is closed by a cover portion N3, and is used for mounting parts after welding each nut N to the panel P. Only for the nut N to which a member (not shown) is screwed and fastened, its cover N3 is removed by screwing in the screw member, and the other nuts N are left with the cover N3 remaining, and the mounting hole of the panel P is left. P1 is closed with a nut N.

A guide pin 2 is supported at the center of the lower electrode 1 so as to be able to protrude and retract from the upper end surface (tip surface). The length of the protrusion of the guide pin 2 is shorter than the length of the screw hole N2 of the nut N. Dimensions of the panel P and its mounting holes P
1 is set on the lower electrode 1 with the tip of the guide pin 2 inserted.

On the other hand, the upper electrode 4 constitutes a work holding electrode for positioning and holding the nut N.
As shown in FIG. 1, the upper electrode 4 includes a columnar electrode body 5 having a vertical central axis, and a columnar electrode tip 1 attached to a lower end portion (tip) of the electrode body 5.
The lower end of the electrode body 5 is formed with a tapered tapered portion 6 whose outer diameter becomes smaller toward the lower side. On the other hand, the electrode body 5
A tapered concave portion 19 whose inner diameter becomes smaller toward the lower side is formed so as to correspond to the tapered portion 6 at the lower end, and this tapered concave portion 19 is taperedly fitted to the tapered portion 6 of the electrode body 5 in a tightly contacting state. Due to the structure, the electrode tip 18 is detachably attached to the electrode body 5.

A positioning recess 20 is formed in the lower end surface (tip surface) of the electrode tip 18 as a positioning portion for positioning the nut N with respect to the lower electrode 1.
The positioning recess 20 is a circular recess having an inner diameter capable of fitting an approximately upper half portion of the nut N in a welding position with the projections N1, N1,... Facing downward, and is indicated by phantom lines in FIGS. As described above, the nut N in the above-described welding posture is fitted and positioned in the positioning recess 20 at the outer peripheral portion.

The positioning recess 20 of the upper electrode 4
A negative pressure suction device 27 for holding the nut N by suction with a negative pressure in a state where the nut N is positioned. The negative pressure suction device 27 has a negative pressure passage 26 for communicating the inside of the positioning recess 20 at the lower end surface (tip surface) of the electrode tip 18 with a negative pressure source 25 such as a negative pressure pump.

That is, a center hole 22 is formed in the center of the electrode tip 18 so as to penetrate between the tapered recess 19 on the upper surface and the positioning recess 20 on the lower surface. On the other hand, the electrode main body 5 is formed with a through hole 8 penetrating the center thereof,
The lower end of the through hole 8 has a large diameter portion 8a having an inner diameter larger than other portions, and the lower end of the large diameter portion 8a communicates with the center hole 22 of the electrode chip 18. On the other hand, the through hole 8
Is connected to a negative pressure inlet 9 opened at the upper end of the electrode body 5, and the negative pressure inlet 9 is connected to a negative pressure source 25 through a negative pressure pipe 24. A negative pressure passage 26 is formed by the hole 22, the through hole 8 in the electrode body 5, and the negative pressure pipe 24, and one end of the negative pressure passage 26 penetrates the electrode tip 18 and has a positioning recess 20 on the lower end surface thereof.
The other end passes through the electrode body 5 and the negative pressure source 2
5 is connected. The nut N is the electrode tip 18
When the nut N is supplied to the positioning recess 20, the nut N is positioned in the positioning recess 20 by the negative pressure generated by the air suction of the negative pressure source 25 and is suction-held.

A cooling water passage 11 is formed below the electrode body 5 of the upper electrode 4. That is, as shown in FIG. 2, the lower portion of the electrode body 5 has the tapered portion 6 formed at the lower end and has an inner cylindrical portion 12 having the through hole 8, and is externally fitted to the inner cylindrical portion 12. It has a double structure with the outer cylinder 13. A notch 1 formed by cutting out a portion facing the diametrical direction of the inner cylindrical portion 12 over a predetermined range in the vertical direction.
4 and 14 are formed between the notch 14 and the outer tube 13, and a forward path 11 a of the cooling water passage 11 is provided between the notch 14 and the outer tube 13. Passage 11
Of the cooling water passage 1
The outgoing path 11a and the return path 11b are connected to the notches 14, 1
At the lower end position of 4, the entire outer periphery of the inner cylindrical portion 12 is cut off in an annular shape to communicate with each other.

At the upper end of the outer cylindrical portion 13, a water inlet 15 communicating with the outward path 11a of the cooling water passage 11 and a drain port 16 communicating with the return path 11b are opened. The cooling water supplied from the cooling water passage 11 flows into the outward path 11a of the cooling water passage 11, and the cooling water flows through the return path 11b to the drain port 1a.
By discharging the gas from the inner tube 6, the inner cylindrical portion 12 of the electrode main body 5 and the electrode tip 18 attached thereto are cooled.

Each nut N welded to the panel P is supplied to the positioning recess 20 of the upper electrode 4 by a nut supply device 31 shown in FIG. The nut supply device 31 includes an air cylinder 32. The air cylinder 32 includes a cylinder body 33 extending in a horizontal direction along a vertical plane passing through the lower electrode 1 and the upper electrode 4, and electrodes 1 and 4 of the cylinder body 33. The upper electrode 4 protrudes from the front end (the right end in FIG. 4) which is the upper end when the cylinder 32 extends.
And a piston rod 34 advancing to a lower position.
In FIG. 4, 35 is an air supply port for contracting the cylinder 32, 36 is an air supply port for extending the cylinder 32, 37 is a proximity switch for detecting the stroke end of the contracting operation of the cylinder 32, A proximity switch 38 detects the stroke end of the extension operation of the cylinder 32.

A nut transfer mechanism 40 for transferring the nut N to the positioning recess 20 of the upper electrode 4 is attached to the tip of the piston rod 34. As shown in FIG. 5, the nut transfer mechanism 40 has a rectangular block 41, and a pair of cam block portions 42, 42 are integrally formed on the left and right sides of the lower portion of the block 41 on the rear side. A swinging piece 43 is supported at the front end of the block 41 by a horizontal shaft 44 so as to be swingable in a vertical plane. This rocking piece 43 is a pair of arm portions 4 extending rearward while sandwiching the front end of the block 41 from both left and right sides.
3a, 43a, the front end of the block 41 is disposed between the two arm portions 43a, 43a, and the two are connected by a shaft 44. As a result, the upper surface of the swinging piece 43 is substantially horizontal. , And a retractable posture in which the upper surface is oriented vertically. Although not shown, a torsion spring is arranged around the shaft 44,
The rocking piece 43 is urged by the torsion spring to rotate in the direction from the retracted position to the transfer position.

A nut receiving seat 45 is formed on the upper surface of the rocking piece 43 to support the nut N on the welding position in which the projections N1, N1,. The nut receiving seat 45 has a rectangular recessed groove 46 extending in the front-rear direction for fitting the nut N in a welding position so as not to rotate around the center of the screw hole N2. The nut N is provided in the groove 47 so as to project from the projection N.
, N1, ... side, and the screw hole N of the nut N
The nut N is inserted into the concave groove 46 by inserting the pin portion 47 into
It is immovably locked inside. On the other hand, on the lower surface of the swinging piece 43, an inclined cam surface 48 which is inclined downward toward the front side is formed.

At the front end of the body 33 of the cylinder 32, a large number of nuts N, N,... Sent from a nut sorting device (not shown) are transferred one by one to a nut receiving seat 45 of the transfer mechanism 40. Nut transfer mechanism 50 is provided. As shown in FIG. 6, the nut transfer mechanism 50 has a plate-shaped base 51 projecting from the lower end of the rectangular front cover 33a of the cylinder body 33 and extending forward. Column-shaped support portions 52, 52 are respectively provided on the left and right sides of the front and rear intermediate portion, and a swing member 53 is provided between the support portions 52, 52 by a horizontal shaft 55.
And is swingably supported through. This swing member 53
Is a substantially U-shaped member having a groove 54 extending in the front-rear direction on the lower surface.
4 is inserted.

On the left and right sides of the rear end of the upper surface of the base 51, columnar spring receiving portions 56, 56 having spring retaining pins 56a, 56a on the upper surface, respectively, are erected.
The lower end of a compression spring 57 composed of a coil spring is locked by a spring retaining pin 56 a on the upper surface of the upper surface 6, and the upper end of each compression spring 57 is in contact with the rear end of the lower surface of the swinging member 53. The swing member 53 is rotationally urged to a non-transferring posture in which the front end portion is downward by the spring force of the spring 57.

Further, at the front end of the lower surface of the swing member 53,
Inclined cam surfaces 58, 58 inclined upward toward the front side are formed. When the cylinder 32 contracts and the nut transfer mechanism 40 at the tip of the piston rod 34 retreats, the cams on the left and right sides of the block 41 are moved. Block part 4
By pushing the inclined cam surfaces 58, 58 of the swinging member 53 by means of the swinging members 2, 42, the swinging member 53 is rotated to the transfer position in which the front end is upward against the biasing force of the compression spring 57. It has become.

At the front end of the upper surface of the swinging member 53, a nut N
A nut inlet 60 having a rectangular cross section is formed, through which the protrusions N1, N1,... Can move in a forward posture, and has a rectangular cylindrical tube having the same inner surface shape as the nut inlet 60. The mounting portion 61 is attached and fixed by welding. The tube mounting portion 61 has a feeding tube 59 made of a rectangular tube that communicates with the nut selection device.
(See FIG. 4) is mounted, and a number of nuts N, N,... Are supplied from the nut selection device into the swinging member 53 via the feeding tube 59 and the tube mounting portion 61.

At the front end of the upper surface of the base 51, an inclined cam surface 62 inclined downward toward the front is formed. The cylinder 32 contracts and the nut transfer mechanism 40 at the tip of the piston rod 34 retreats. Sometimes, just before the retreat end position, the inclined cam surface 62 of the swinging piece 43 in the nut transfer mechanism 40 is formed by the inclined cam surface 62 on the base 51 side.
8, the swinging piece 43 is further rotated in the direction in which the front end is upward from the delivery posture, whereby a large number of nuts N, N,. Are hooked on the lower projections N1 and N1 so as to rotate to a welding position in which the projections N1, N1,.

At the front end of the bottom of the groove 54 of the rocking member 53, an inclined surface 63 is formed immediately after the nut inlet 60 and is inclined downward toward the rear. When the lowermost nut N is rotated in the vicinity of the retreat end position by the rotation of the rocking piece 43 beyond the delivery posture, the nut N is further rotated in cooperation with the inclined surface 63, and Groove 4 of nut receiving seat 45 on the upper surface of moving piece 43
The nut N is transferred to the nut 6 with its screw hole N2 locked by the pin portion 47.

A nut holding plate 64 made of a spring plate extending forward is attached to the front end of the swinging member 53, and the nut placed on the nut receiving seat 45 of the nut transfer mechanism 40 of the swinging piece 43. When N advances to the upper electrode 4 side by the extension operation of the cylinder 32, the moving nut N is slidably held from above by a nut holding plate 64 to prevent the nut N from falling off from the nut receiving seat 45. ing.

Next, the operation of sequentially supplying nuts N, N,... And welding to the panel P in the projection welding apparatus of the above embodiment will be described. In a normal state, a large number of nuts N, N,... From the nut sorting device swing through the feed tube 59, its mounting portion 61, and the nut inlet 60 in a movement posture in which the respective projections N1, N1,. It is supplied into the moving member 53. As shown in FIG. 9, when the cylinder 32 extends and the nut transfer mechanism 40 at the tip of the piston rod 34 advances, the lowermost nut N among the plurality of nuts N, N,. Is stopped in a state where it comes into contact with the piston rod 34 and is regulated. In other words, a large number of nuts N, N,.
The nuts N, N,... Are successively stacked on top of each other.

In this state, when the cylinder 32 contracts and the nut delivery mechanism 40 at the tip of the piston rod 34 retreats, as shown in FIG.
Is pulled by the retreating piston rod 34 and the projection N
Are rotated by a small angle in a direction in which 1, N1,. When the transfer mechanism 40 moves near the retreat end position, the left and right cam block portions 42 of the block 41,
42, the inclined cam surface 5 of the base 51 of the swing member 53
8 and 58 are pushed and the swinging member 53 is compressed by the compression springs 57 and 57.
Is rotated from the non-transferring posture to the transferring posture against the rotational urging force of the swinging member 53 and the base 51 with the front end thereof facing upward.
Are open between the front ends.

Thereafter, when the cylinder 32 further contracts and reaches the stroke end of the contracting operation and the nut transfer mechanism 40 reaches the retreat end position, as shown in FIG. 7, the base 5 in the front cover 33a of the cylinder body 33 is moved.
The nut transfer mechanism 40 is formed by the inclined cam surface 62 at one front end.
The inclined cam surface 48 of the oscillating piece 43 is pushed, and the oscillating piece 43 is rotated in a direction in which the front end is further upward than the delivery posture. As a result, the lowermost nut N in the rocking member 53 is first hooked on the rocking piece 43 by the lower protrusions N1 and N1 so that the protrusions N1, N1,. Then, the rear upper end portion of the nut N is further rotated while being guided by the inclined surface 63 on the bottom surface of the groove portion 54 of the swinging member 53, and then the projections N1, N1,
Are in the welding position located on the lower side, and in this welding position, the screw hole N2 is locked by the pin portion 47 in the concave groove 46 in the nut receiving seat 45 on the upper surface of the swinging piece 43 on the lower side. Will be transferred. At this time, the nut N is
5 is fitted around the screw hole N2 at the outer peripheral portion so as not to rotate around the screw hole N2, so that it is transferred and supported in a state where it is positioned at a predetermined position.

In the state where the transfer of the nut N to the transfer mechanism 40 is completed, the welding of the previous nut N is completed, the upper electrode 4 moves to the rising end position, and then the panel P on the lower electrode 1 is removed. The lower electrode 1 is moved to the position of the next mounting hole P1.
After the guide pin 2 is inserted, the nut N is welded to the position of the mounting hole P1. At this time, in response to a signal from the welding command, first, the cylinder 32 is extended and the delivery mechanism 40 moves forward with the nut N mounted on the nut receiving seat 45 of the rocking piece 43. With this advance,
Since cam engagement between the cam block portions 42, 42 of the transfer mechanism 40 and the cam surfaces 58, 58 of the swing member 53 is released, the swing member 53 rotates from the transfer position to the non-transfer position, and its front end. The part faces downward. For this reason, the nut holding plate 64 attached to the front end of the swinging member 53 pushes the nut N on the nut receiving seat 45 in the advancing delivery mechanism 40 from the upper side. It is possible to prevent the nut from falling off from the nut receiving seat 45.

Next, as shown in FIG.
Reaches the stroke end of the extension operation, and as soon as the nut transfer mechanism 40 reaches the forward end position, the upper electrode 4 moves downward. At the forward end position of the nut transfer mechanism 40, the nut N on the nut receiving seat 45 of the rocking piece 43 is located directly below the upper electrode 4 (directly above the lower electrode 1), so that the upper electrode 4 moves downward. On the way, it hits the nut N on the nut receiving seat 45. A positioning recess 20 is formed on the lower surface of the electrode tip 18 at the lower end of the upper electrode 4, and the inside of the positioning recess 20 is sucked by a negative pressure source 25 through a negative pressure passage 26 in the upper electrode 4 to create a negative pressure state. Therefore, as shown in FIG. 9, the nut N on the nut receiving seat 45 is delivered to the upper electrode 4 side, is fitted in the positioning recess 20 and is sucked and held in the positioning state. At this time, since the nut N has a cover in which a part of the screw hole N2 is closed by the cover N3, the suction effect by the negative pressure is enhanced.

After the delivery of the nut N, the upper electrode 4 continues to descend while holding the nut N by suction. Since the rocking piece 43 of the nut transfer mechanism 40 can rock, the nut N is transferred to the upper electrode 4 and at the same time, the nut itself is pushed down by the upper electrode 4 to rotate downward.
The posture changes to a standby posture that does not interfere with the upper electrode 4 that moves downward.

Thereafter, as shown in FIG.
Moves to the lower end position, the nut N sucked and held in the positioning recess 20 of the electrode tip 18 causes the tip end of the guide pin 2 of the lower electrode 1 to be slightly inserted from below into the screw hole N2. Are pressed around the mounting hole P1 of the panel P on the lower electrode 1 by the projections N1, N1,..., And the nut N and the panel P are pressed in a state of being vertically overlapped. When the welding current is applied between the electrodes 1 and 4 in this pressurized state, the protrusions N1, N1,... Of the nut N are melted and welded to the panel P, whereby the nut N is projection-welded to the panel P. During this welding, the cylinder 32 contracts in the same manner as described above, and the transfer mechanism 40 emptied by the transfer of the nut N to the upper electrode 4 is retracted. Thereafter, the same operation as described above is repeated for each of the plurality of nuts N, N,.

Therefore, in the case of this embodiment, the nut N supplied by the nut supply device 31 is positioned in the positioning recess 20 of the electrode tip 18 in the upper electrode 4 moving downward, and is sucked and held without dropping.
In this state, the projection is welded by being pressed against the panel P on the lower electrode 1, so that even if the nut N with the lid is accurately positioned and held on the upper electrode 4, it is surely sucked and held, and the mounting hole P 1 of the panel P is formed. It can be welded accurately without displacement.

Further, since the nut N is positioned and held on the upper electrode 4 itself, it is not necessary to separately provide a clamping device for the positioning, and the structure of the projection welding device can be simplified accordingly. Can be.

Further, since the nut N is attracted by the negative pressure from the negative pressure source 25 and held in the positioning concave portion 20 of the upper electrode 4, the nut N is attracted as in the case of attracting the nut N using a magnet. No misalignment due to magnetization or poor positioning due to thermal deterioration of the magnet does not occur, and the positioning and holding function of the nut N can be stably maintained for a long period of time.

Since the electrode tip 18 of the upper electrode 4 is detachable from the electrode body 5 and is replaceable, the electrode tip 18 can be replaced as needed. That is, when removing the electrode tip 18 from the electrode body 5,
The electrode tip 18 may be turned with a tool or the like to remove the tapered recess 19 from the tapered tapered portion 6 of the electrode body 5, and conversely,
When the electrode tip 18 is mounted on the electrode main body 5, the tapered recess 19 of the electrode tip 18 is externally fitted to the tapered portion 6 of the electrode main body 5 in close contact.

FIG. 11 shows a state where the electrode tip 18 'is replaced with another kind of electrode tip 18'. In this example, a nut N 'is used.
Are projection-welded to the panel P at the projections N1, N1,..., And the screw holes N2 penetrate therethrough. The lower surface of the electrode tip 18 'in the upper electrode 4 serving as a work holding electrode is flat, and the center hole 22 of the electrode tip 18' has a screw hole N2 projecting from the lower surface of the electrode tip 18 'and having a nut N'. The positioning pin 21 (positioning portion) that can be inserted through the center hole 22 and the negative pressure passage 26
Is inserted and held with a gap. The positioning pin 21 has a base end whose large-diameter portion 8 a at the lower end of the through hole 8.
It is immovably fixed and supported inside.

With this configuration, when the nut N 'is supplied to the upper electrode 4 by the nut transfer mechanism 40 at the forward end position, as shown by the phantom line in FIG.
The positioning pin 21 of the upper electrode 4 is inserted from above into the screw hole N2 to position the nut N '. In this positioning state, the nut N' is placed on the lower surface of the electrode tip 18 'by the negative pressure of the negative pressure passage 26. Adsorbed and held. Accordingly, the positioning and holding of the ordinary nut with projection N 'by the negative pressure can be easily realized.

By providing a plurality of types of electrode tips 18 and 18 'having positioning portions (positioning recesses 20 and positioning pins 21) corresponding to the types of nuts N and N', nuts N and N 'are provided. Each time the type of 'is changed, it is sufficient to remove and replace only the electrode tips 18, 18' from the electrode body 5 while maintaining the same electrode body 5, and to weld many types of nuts N, N '. Can be dealt with with a cheap structure.

In the above embodiment, the nuts N, N 'are positioned on the upper electrode 4 and held by suction, and are pressed against the panel P on the lower electrode 1. However, the nuts N, N' are conversely. May be positioned on the lower electrode 1 and held by suction, and pressed against the panel P set on the upper electrode 4 side.

Although the above embodiment is an example of a projection welding apparatus having electrodes 1 and 4 opposed in the vertical direction, the facing directions of the electrodes are not limited to the vertical direction.
INDUSTRIAL APPLICABILITY The present invention can be applied to a projection welding apparatus having electrodes that are opposed to each other in all directions.
In other words, it is sufficient that the nut N, N 'is supplied to the electrode from any direction, as long as it has a fixed electrode and a movable electrode arranged opposite thereto.
N ′ can be accurately positioned on the electrode and held by suction under a negative pressure.
1 increases the degree of freedom of the layout.

In the above embodiment, the projection-attached nuts N and N 'are welded to the panel P by projection welding. However, the present invention is not limited to such welding, and other joined workpieces may be replaced with non-joined workpieces. Needless to say, the present invention can be applied to the case of resistance welding.

[0055]

As described above, according to the first aspect of the invention, the work to be joined and the joint work supplied by the work supply means are sandwiched between the fixed electrode and the movable electrode in a state where they are overlapped with each other. to have so as to weld resistance welding device, the one electrode and a work holding electrode for positioning the bonding work, it and the electrode body, the tip
It is provided to be removable by taper fitting to the part,
An electrode tip having a positioning portion; and
The joining work is located at the positioning part at the tip of the work holding electrode.
Position the electrode tip or electrode body.
A vacuum suction hand having a vacuum passage penetrating therethrough and communicating with a vacuum source.
Workpieces are held in a state where the work pieces are accurately positioned and held on the electrodes while simplifying the welding equipment by eliminating the need for a separate clamping device for work piece positioning by holding the workpieces by the negative pressure generated by the step. , Welding quality can be improved, and the positioning effect can be stably maintained over a long period of time. Also, remove the electrode tip from the electrode body.
Each time the type of work to be joined changes,
Remove and replace only the electrode tip from
Can be dealt with with a cheap structure.

According to the second aspect of the present invention, since the fixed electrode is the lower electrode and the movable electrode is the upper electrode and the work holding electrode, the joint work is reliably positioned and sucked without dropping on the upper electrode. In the held state, it can be welded to the work to be joined on the lower electrode.

According to the third aspect of the present invention, the jointed work is a nut with a lid for projection welding in which a part of the screw hole is sealed, and the positioning portion of the work holding electrode is fitted with the nut with the lid at the outer periphery. Positioning recesses. Further, in the invention of claim 4 , the joint work is a normal projection welding nut having a penetrating screw hole, and the positioning portion of the work holding electrode is a positioning pin that can be inserted into the screw hole of the nut. According to these inventions, a structure for positioning and holding an ordinary nut for projection welding or a nut with a lid on the work holding electrode can be concretely and easily obtained.

According to the fifth aspect of the present invention, the workpiece to be joined is a panel in which the nut is projection-welded with the screw hole aligned with the mounting hole, so that the nut is accurately positioned in the mounting hole of the panel. Can be projection welded.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an upper electrode according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a perspective view showing a state where a nut is welded to a panel by both electrodes.

FIG. 4 is a front view showing the entire configuration of the nut supply device.

FIG. 5 is an enlarged perspective view showing a structure of a nut delivery mechanism.

FIG. 6 is an exploded perspective view showing an enlarged structure of a nut transfer mechanism.

FIG. 7 is a sectional view showing the operation of the nut transfer mechanism when the cylinder is at the contraction side stroke end.

FIG. 8 is a front view showing a state in which the cylinder is located at the extension-side stroke end and immediately before the nut transfer mechanism transfers the nut to the upper electrode.

FIG. 9 is a front view showing a state immediately after the nut delivery mechanism has delivered the nut to the upper electrode.

FIG. 10 is a front view showing a state in which an upper electrode presses and welds a nut to a panel.

FIG. 11 is an enlarged sectional view showing a main part of the upper electrode when the electrode tip is replaced.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lower electrode (fixed electrode) 4 upper electrode (movable electrode) 5 electrode body 18, 18 ′ electrode tip 20 positioning recess (positioning part) 21 positioning pin (positioning part) 25 negative pressure source 26 negative pressure passage 27 negative pressure suction device (Negative pressure suction means) 31 Nut supply device (Work supply means) 32 Air cylinder 40 Nut transfer mechanism 45 Nut receiving seat 50 Nut transfer mechanism 53 Swing member P Panel (workpiece to be joined) P1 Mounting hole N, N 'Projection Nut (joint work) N1 Projection N2 Screw hole N3 Cover

Claims (5)

(57) [Claims] A fixed electrode, and a movable electrode disposed so as to be able to contact and separate from the fixed electrode, wherein a work to be joined between the two electrodes and a joint work supplied by a work supply means are provided. In a resistance welding apparatus, the two workpieces are welded by contact resistance heat by applying a welding current between the electrodes, and pressing one of the electrodes, the one electrode being joined to the electrode. The work holding electrode is a work holding electrode having a positioning portion for positioning the work at the tip, and the work holding electrode has a tapered taper at the tip.
And a tapered recess corresponding to the tapered portion of the electrode body are formed.
And the tapered recess is taperedly fitted to the tapered portion.
Is detachably attached to the tip of the electrode body,
An electrode tip having the positioning portion on the tip end surface.
A negative pressure suction means is provided for sucking and holding by a negative pressure in a state where the joining work is positioned with respect to the positioning portion of the work holding electrode , and one end of the negative pressure suction means penetrates the electrode tip.
While opening to the tip, the other end passes through the inside of the electrode body
A resistance welding apparatus having a negative pressure passage communicating with a negative pressure source . 2. The resistance welding apparatus according to claim 1, wherein the two electrodes are vertically opposed to each other, the fixed electrode is a lower electrode, the movable electrode is an upper electrode, and the work holding electrode is Resistance welding equipment characterized by being performed. 3. The resistance welding apparatus according to claim 1, wherein the joining work is a nut with a lid that has a screw hole partially closed and is projection-welded to the work to be joined by a projection. The resistance welding device, wherein the positioning portion is a positioning recess for fitting the nut with the lid at an outer peripheral portion. 4. The resistance welding apparatus according to claim 1, wherein the joining work is a nut having a threaded hole therethrough and projection-welded to the work to be joined by a projection, and the positioning portion is a nut of the nut. A resistance welding device characterized by a positioning pin that can be inserted into the hole. 5. The resistance welding apparatus according to claim 3 , wherein the workpiece to be joined is a panel having a mounting hole and a nut being projection-welded in a state where the screw hole is aligned with the mounting hole. Characteristic resistance welding equipment.