JP3496366B2 - Resistance welding equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding apparatus or the like in which one surface of a material to be welded and one electrode are brought into contact with each other, and then the other surface of the material to be welded The present invention relates to a resistance welding device in which the other electrode is brought into contact with a portion corresponding to the electrode and the welding current and pressure are applied to the material to be welded through these electrodes.

[0002]

2. Description of the Related Art FIG. 13 (a) conceptually shows a resistance welding apparatus of this type. With this resistance welding device,
After one surface Wa of the material to be welded W is brought into contact with the upper surface of the back electrode B arranged on the jig, the other surface of the material to be welded W is pressed through a pressing mechanism such as a link mechanism or an actuator (not shown). An electrode tip T is brought into pressure contact with the surface Wb, and a prescribed welding current and pressure are applied to the workpiece W through the back electrode B and the electrode tip T, whereby welding is performed by resistance heat generated in the workpiece W. I am trying.

In this type of resistance welding apparatus, in order not to leave a welding mark on one surface Wa of the material to be welded W that comes into contact with the back electrode B, which is usually the outer surface Wa of the product, the material to be welded The shape of the back electrode B is set so that the contact area with the material W is large.

Further, in this type of resistance welding apparatus,
Since the back electrode B and the electrode tip T have the same required characteristics, the electrodes B and T are usually made of the same material, for example, chromium copper (Cu-Cr).

[0005]

By the way, as described above, in the resistance welding apparatus, both the back electrode B and the electrode tip T are formed of the same kind of material, and the pressurizing means such as the link mechanism and the actuator (not shown). No. 3), the electrode tip T is pressed against the back electrode B via the material W to be welded. Therefore, as shown in FIG.
The upper surface of the back electrode B may easily be deformed such as the recess C.

In the above resistance welding apparatus, the back electrode B
If even a slight deformation of the recess C etc. occurs on the upper surface of the
Due to the shape mismatch with the electrode tip T, the electrode tip T
Since the energization point when the material W to be welded is pressed and sandwiched between and, the welding current and the flow of heat are disturbed, the electrode tip T is easily deteriorated. Deterioration of the electrode tip T not only causes deterioration of conductivity and hardness and causes a severe wear, but also causes poor welding due to insufficient energization. Therefore, it is necessary to take measures early to prevent this. There is.

Here, as a means for preventing the alteration of the electrode tip T, the electrode tip T or the back electrode B is used.
It is conceivable to dress one of the two to correct its shape or replace the electrodes T and B themselves.

However, first, when the back electrode B is dressed or replaced, the back electrode B is replaced.
However, since it has a function of contacting the outer surface Wa of the workpiece W first and positioning the same, it is possible to perform height adjustment work and surface adjustment work with the workpiece W after dressing or replacement is completed. This is necessary and causes a significant complication of work, and also causes a decrease in productivity due to the great amount of time required for these adjustment works. Particularly, in the case where a plurality of back electrodes B are fixedly arranged on a welding jig as in a multi-spot welding apparatus, height adjustment work and face adjustment work between these back electrodes B are also necessary. Therefore, the above-mentioned complication of work and reduction in productivity become more remarkable.

On the other hand, when the electrode tip T is dressed or replaced, the electrode tip T is replaced by the back electrode B.
Since it comes into contact with the inner surface Wb of the material to be welded W after contacting with, it is not necessary to perform the above-described height adjustment work and face-to-face adjustment work with the welded material W after the dressing or replacement is completed, Moreover, as shown in FIG. 13C, by applying a dressing for shaping the tip portion to an acute angle, regardless of whether the upper surface of the back electrode B is deformed or not, the welding current of It becomes possible to improve so that pressure is applied.

However, even when the electrode tip T is dressed or replaced, the back electrode B is still in a deformed state, so that the electrode tip T deteriorates very early as shown in FIG. 13 (d). Therefore, it is necessary to frequently repeat dressing and replacement.

[0011]

According to the present invention, after one surface of a material to be welded and one electrode are brought into contact with each other, a portion corresponding to the one electrode on the other surface of the material to be welded. In the resistance welding apparatus for applying the welding current and pressure to the material to be welded through these electrodes by abutting the other electrode on the electrode, at least a portion of the one electrode that abuts on one surface of the material to be welded The contact portion formed of a material having a conductivity equal to or higher than that of the other electrode and having a mechanical strength higher than that of the other electrode is provided.

It is preferable that the other electrode is formed of a chromium-based copper alloy and the contact portion of the one electrode is formed of a silver-based copper alloy, particularly a silver precipitation type copper alloy.

Further, it is preferable that a spherical convex portion is formed at a tip end portion of the other electrode, and a spherical concave portion corresponding to the convex portion is formed at a portion of the one electrode facing the convex portion. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments. 3 to 5 conceptually show an embodiment of the resistance welding apparatus according to the present invention, in which an inner panel component having a plate thickness of 0.65 mm ⁺ is subjected to hemming by a press machine (not shown). Di and outer panel component Do with a plate thickness of 0.75 mm ⁺
1 illustrates a multi-spot welding device for forming a door panel (material to be welded) D of a four-wheeled vehicle by welding and welding each other.

As shown in FIG. 3, this multi-spot welding apparatus has a main table 1 formed in an outer shape larger than the door panel D.
Clamping means 10 are provided at portions corresponding to the upper edge and the lower edge of the door panel D in the upper portion of the door panel D, and power feeding means 20 is provided at portions corresponding to both front and rear edges of the door panel D. There is.

The clamping means 10 is, as shown in FIG.
Each of the movable clampers 12 opens and closes with respect to the fixed clamper 13 based on the operation of the clamping cylinder actuator 11, and after the door panel D is placed on the fixed clamper 13 with the outer panel component Do arranged below. , By closing and moving the movable clamper 12 with respect to the fixed clamper 13, the door panel D is inserted between the movable clamper 12 and the fixed clamper 13.
To position and hold.

Although not shown in the drawing, the power feeding means 20 has a power feeding tip 23 held at the tip of the operating rod 22 in the power feeding cylinder actuator 21 via an insulating member. As shown in FIG. 2, the actuators 21 are arranged substantially horizontally, and as shown in FIG. 2, they serve to move the respective feed chips 23 to and from the side surface of the inner panel component Di with respect to the door panel D which is positioned and held by the clamp means 10. .

Further, as shown in FIG. 3, the multi-spot welding apparatus is provided with a plurality of pressurizing means 30 at portions corresponding to both front and rear edges of the door panel D, respectively. Since each of the plurality of pressurizing means 30 has a common constituent element, only one of them will be described below.

As shown in FIGS. 5 and 6, the pressurizing means 30 includes a fixed base 31 standing on the upper surface of the main table 1 and the fixed base 3 via a cylinder body 32.
The pressurizing cylinder actuator 33 held on the outer surface of the No. 1 and the upper end of the fixed base 31 are swingably supported, and the operating rod 34 of the pressurizing cylinder actuator 33 is connected to the outer end thereof. A pressure arm 35 is provided, and an electrode tip (electrode) 38 is held at an inner end of the pressure arm 35 via an insulating member 36 and a tip holder 37. A back electrode (electrode) 39 is held on the inner surface of the fixed base 31 via an insulating member 36.

The electrode tip 38 is made of chromium copper (Cu-Cr) as in the conventional one, and as shown in FIG. 1, a cylindrical base portion 38a and this base portion 38a.
And a hemispherical portion 38b which is spherically protruded from the tip of the base portion 38a with the same radius r as the base portion 38a, and is larger than the hemispherical portion 38b in a predetermined range from the axial extension line of the base portion 38a in the hemispherical portion 38b. It has a partial spherical convex portion (convex portion) 38c projecting in a spherical shape with a radius R, and the partial spherical convex portion 38c is opposed to the main table 1 through the base portion 38a. It is attached to the pressure arm 35. In the multi-spot welding apparatus, specifically, a hemispherical portion 38b having a radius r of 8 mm is formed at the tip of a base portion 38a having a diameter φ of 16 mm, and the axis of the base portion 38a is further formed in the hemispherical portion 38b. The electrode tip 38 in which the partial spherical convex portion 38c having the radius R of 40 mm is formed in the range of the diameter φ'of 6 mm from the core extension line is applied.

On the other hand, the back electrode 39 has a structure shown in FIGS.
As shown in FIG. 2, the silver deposition type has higher mechanical strength such as tensile strength and proof stress than chromium copper, which is a material of the electrode tip 38 described above, and has electrical conductivity and thermal conductivity equal to or higher than the chromium copper. It is formed of a copper alloy (Cu-Ag). This silver precipitation type copper alloy is a eutectic type or solid solution type silver copper alloy in which silver is precipitated by processing or heat treatment. As shown in FIGS. 1, 5 and 6, It has an integral prismatic shape, and is attached to the fixed base 31 in such a manner that one end surface 39a thereof faces the tip of the electrode tip 38. In the multi-spot welding apparatus, specifically, a copper alloy containing 0.1% of silver, preferably a copper alloy containing 0.15% or more of silver is used to provide a width: w = 32 mm and a depth: l. = 25 mm, length:
The back electrode 39 formed in a prism shape of h = 80 mm is applied.

Further, as is apparent from FIG. 1, the back electrode 39 has a partial spherical concave portion (recess) 39b on one end face 39a thereof. The partial spherical concave portion 39b is formed with the same radius R within the same range as the partial spherical convex portion 38c of the electrode tip 38, that is, the diameter φ '.
Is formed with a radius R of 40 mm within a circular range of 6 mm, and is arranged at a position facing the partial spherical convex portion 38c.

In the multi-spot welding apparatus configured as described above, the movable clamper 12 is opened with respect to the fixed clamper 13 by retracting the clamping cylinder actuator 11 of the clamping means 10 in the stand-by state, and the feeding means 20 of the power feeding means 20 is opened. When the power feeding cylinder actuator 21 is retracted, the power feeding tip 23 is retracted from the mounting area of the door panel D, and when the pressure applying cylinder actuator 33 of the pressure applying means 30 is retracted, the electrode tip 38 is moved to the back electrode 39. It is kept in a separated state.

When spot welding is applied to the preset welding point of the door panel D from the above-mentioned standby state, first, the clamp cylinder actuator 11 of the clamp means 10 is extended to position the door panel D on the main table 1. After that, the power feeding cylinder actuator 21 of the power feeding means 20 is extended to hold the tip end portions of the power feeding tips 23 in contact with the side surfaces of the inner panel component Di. In this state, the back electrodes 39 of the pressing means 30 are in contact with the lower surface of the outer panel component Do, that is, the outer surface of the door panel D, via the respective one end surfaces 39a.

From this state, the pressurizing cylinder actuator 33 of the pressurizing means 30 is extended to bring the hemispherical portions 38b of the electrode tips 38 into pressure contact with the upper surface of the inner panel component Di, that is, the inner surface of the door panel D, respectively. Further, from this state, when an alternating voltage of 8V10 cycles is applied as shown in FIG. 2 in order to flow a welding current of 8000A between the power supply tip 23 and the electrode tip 38, the electrode tip 38 and the electrode tip 38 are formed at the edge portion of the door panel D. Resistance heat is generated at each welding point pressed against the back electrode 39, and the inner panel component Di and the outer panel component Do are welded to each other via the portion where the resistance heat is generated.

When the welding operation for the door panel D is completed, the multi-spot welding apparatus returns to the standby state if the cylinder actuators 11, 21, 33 are retracted in the reverse order of the above procedure. The door panel D after welding can be taken out.

The welding operation for the door panel D can be repeatedly performed by sequentially repeating the above-described operation.

By the way, in the conventional resistance welding apparatus, as described above, both the back electrode and the electrode tip are formed of the same material, and the electrode tip is passed through the door panel through the door panel by the operation of the pressurizing cylinder actuator. Since the back electrode is pressed into contact with the back electrode, the one end surface of the back electrode may be easily deformed.

However, according to the above multi-spot welding apparatus, the back electrode 39 is formed by a silver precipitation type copper alloy having higher mechanical strength such as tensile strength and proof stress than the chromium copper which is the material of the electrode tip 38. Since one is applied, there is no fear that the one end surface 39a of the back electrode 39 is easily deformed, and shape correction such as dressing for the one end surface 39a becomes unnecessary.

Moreover, since the back electrode 39 has the electrical conductivity and thermal conductivity equal to or higher than that of chromium copper,
There is no occurrence of welding defects such as burn (overmelting) due to poor cooling on the door panel D after welding and welding defects such as unwelding due to insufficient energization.

Further, since the partial spherical concave portion 39b corresponding to the partial spherical convex portion 38c of the electrode tip 38 is formed on the one end surface 39a of the back electrode 39 having high mechanical strength, the electrode tip 38 always has this partial spherical concave portion 39b. It will be deformed following the partial spherical concave portion 39b. Therefore, after the electrode tip 38 is dressed to correct its shape or after the electrode tip 38 is exchanged, only the height adjustment operation of the back electrode 39 needs to be performed. No need for adjustment work.

Incidentally, in products such as the door panel D,
Since the outer surface is often formed so as to be gently convex toward the outside, the shape correction is more likely to occur when a convex portion is formed than when a concave portion is formed on the outer surface. Wide tolerance. Therefore, even when the partial spherical concave portion 39b is formed on the one end face 39a of the back electrode 39 as in the above multi-spot welding apparatus, the shape correction work for the door panel D is not increased.

FIGS. 7 (a) and 7 (b) show the rate of change in the tip diameter of the electrode tip with respect to the number of welding points and the wear depth of the back electrode in the above-described multi-spot welding apparatus and the conventional resistance welding apparatus, respectively. It represents the relationship between. In the conventional resistance welding device, the back electrode is made of chrome copper and has a width: w = 32 mm and a depth: l.
= 25 mm, length: h = 80 mm formed in a prismatic shape, and the same electrode tip as the above multi-spot welding apparatus is applied.

First, as is clear from FIG. 7 (b),
In the conventional resistance welding device, the wear amount of both the electrode tip and the back electrode tends to increase as the number of welding points increases.

In the electrode tip, the tip diameter increases from around the point where the number of welds exceeds 250 shots, that is, the amount of wear becomes abrupt, and welding failure occurs on the door panel unless dressing is frequently performed from around 500 shots. Come to do.

On the other hand, at this point, the amount of wear of the back electrode also becomes remarkable, and pitching (dotted micro holes) is generated on one end surface of the back electrode, which causes scratches and irregularities on the door panel. Shape correction work is required for the rear door panel.

Therefore, the electrode tip itself was replaced when the number of welding points reached 2500 shots.

However, in the conventional resistance welding apparatus, since the back electrode is still in a worn state, the amount of wear of the electrode tip starts with a smaller number of welding points than the first time, resulting in an earlier dressing time. It was

On the other hand, in the above multi-spot welding apparatus, as is clear from FIG.
Although the wear amount of both No. 8 and the back electrode 39 tends to increase as the number of welding points increases, the amount of wear around the number of welding points exceeding 250 shots is suppressed to a level that does not require dressing. .

The electrode tip 38 exhibits flow wear at the initial stage of welding, but since it is shaped following the partial spherical concave portion 39b formed in the back electrode 39, the wear amount of the back electrode 39 is extremely small. The dressing does not wear out to the extent required.

Further, since the number of times of dressing the electrode tip 38 is small, it is possible to satisfactorily perform welding up to 5000 shots without the need for a shape correction work on the one end face 39a of the back electrode 39.

In the above embodiment, the resistance welding device for spot welding the door panel is illustrated, but the present invention can of course be applied to those that perform resistance welding on other works. Is. in this case,
It is not necessary to weld a plurality of welding points at the same time, and the welding method is not limited to the above-mentioned, so-called indirect method.

Further, in the above embodiment, one electrode is formed of a silver precipitation type copper alloy and the other electrode is formed of chromium copper, but the present invention is not limited to the combination of these materials. It is sufficient that one electrode has a conductivity equal to or higher than that of the other electrode and is formed of a material having higher mechanical strength than the other electrode. When a silver-based material is used as the material of one of the electrodes, the precipitation type is applied in the above embodiment, but the same effect can be obtained by applying the solid solution type or the eutectic type. Can be expected.

Further, in the above embodiment, one electrode having a prismatic shape is applied, but in the present invention, another shape may be applied. For example, in FIG.
As shown in, the flat portion 13 is formed around the partial spherical concave portion (recess) 139b on the one end surface 139a of the back electrode 139.
Chamfering 139d is applied to the periphery in a manner that leaves 9c,
As shown in FIG. 11, one end surface 239 of the back electrode 239
It is also possible to apply a small processing surface by providing a low step portion 239d on the peripheral edge in a mode in which the flat portion 239c is left around the partial spherical concave portion (recess) 239b.

In the above embodiment, all of the back electrodes are formed of the same material, but as shown in FIG. 12, for example, the main body portion 300 formed of chrome copper into a prismatic shape and the silver deposition type. Molded into a thin plate with copper alloy,
And an abutting portion 301 having a partial spherical concave portion (recess) 301b on one end surface 301a, and the back electrode 339 is configured by joining the abutting portion 301 to the one end surface 300a of the main body portion 300. I don't mind.

[0046]

As described above, according to the present invention,
Since one of the electrodes that comes into contact with the material to be welded first is made of a material having higher mechanical strength than the other electrode, there is no fear that the one electrode will be easily deformed. , Its shape modification becomes unnecessary.

Moreover, since the one electrode has the electrical conductivity and the thermal conductivity equal to or higher than that of the other electrode, no welding failure or welding failure occurs in the material to be welded.

Further, since the concave portion corresponding to the convex portion of the other electrode is formed in one electrode having high mechanical strength, the other electrode is always deformed following this concave portion. Therefore, the other electrode is dressed to correct its shape, or after the other electrode is replaced, only the height adjustment work of one electrode may be performed.
The work of adjusting the surface alignment with the material to be welded becomes unnecessary.

[Brief description of drawings]

FIG. 1 is an enlarged view of main parts conceptually showing an embodiment of a resistance welding apparatus according to the present invention.

FIG. 2 is a diagram conceptually showing a usage mode of the resistance welding device shown in FIG.

FIG. 3 is a plan view conceptually showing the entire resistance welding apparatus shown in FIG. 1.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5 is a sectional view taken along line VV in FIG.

FIG. 6 is a VI view in the direction of arrow in FIG.

7A is a diagram showing the relationship between the rate of change of the tip diameter of the electrode and the wear depth of the electrode with respect to the number of welding points in the resistance welding apparatus shown in FIG. 1, and FIG. 7B is a conventional resistance welding apparatus. FIG. 6 is a diagram showing the relationship between the rate of change in the tip diameter of the electrode and the wear depth of the electrode with respect to the number of welding points in FIG.

FIG. 8 is a diagram showing the relationship between tensile strength and conductivity of various copper alloys.

FIG. 9 is a chart showing material properties of various copper alloys.

FIG. 10 is an enlarged view of essential parts conceptually showing a modified example of the resistance welding apparatus according to the present invention.

FIG. 11 is an enlarged view of a main part conceptually showing a modified example of the resistance welding apparatus according to the present invention.

FIG. 12 is an enlarged view of a main part conceptually showing a modified example of the resistance welding apparatus according to the present invention.

FIG. 13 is a view conceptually showing a main part of a conventional resistance welding device.

[Explanation of symbols]

38 ... Electrode tip 38c ... Partial spherical convex portion 39,139,239,339 ... Back electrode 39a, 139a, 239a ... One end surface 39b, 139b, 239b, 301b ... Partial spherical concave portion 139c, 239c ... Flat portion 301 ... abutting part D ... Door panel Di ... Inner panel parts Do ... Outer panel parts

Continuation of the front page (56) Reference JP-A-5-329662 (JP, A) JP-A-7-166274 (JP, A) JP-A-3-274235 (JP, A) JP-A-48-92249 (JP , A) Japanese Unexamined Patent Publication No. 63-236224 (JP, A) Actual development No. 63-116188 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 11/30

Claims (4)

(57) [Claims] 1. After bringing one surface of a material to be welded and one electrode into contact with each other, the other electrode is brought into contact with a portion of the other surface of the material to be welded corresponding to the one electrode. , In a resistance welding apparatus that applies a welding current and pressure to the material to be welded through these electrodes, at least at a portion of the one electrode that abuts one surface of the material to be welded, conductivity equal to or higher than that of the other electrode And a contact welding part formed of a material having a mechanical strength higher than that of the other electrode. 2. The resistance welding apparatus according to claim 1, wherein the other electrode is formed of a chromium-based copper alloy, and the contact portion of the one electrode is formed of a silver-based copper alloy. . 3. The resistance welding apparatus according to claim 2, wherein the contact portion of the one electrode is formed of a silver precipitation type copper alloy. 4. A spherical convex portion is formed at a tip portion of the other electrode, and a spherical concave portion corresponding to the convex portion is formed at a portion of the one electrode facing the convex portion. The resistance welding apparatus according to claim 1.