JPH0957455A - Backing material for spot welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate continuous use for a long term because of the difficulty of wearing, to eliminate electric leakage, to execute the positional adjustment to the change of spotting point of a welding without developing the welding mark on a material to be worked and to improve the working rate of the welding process. SOLUTION: A ceramic-made chip 3 excellent in wear resistance, electric insulation and thermal conductivity is supported on a backing material body 2 under condition of preventing fall-out. This ceramic-made chip 3 has an upward receiving surface 3a for abutting on a door D as a material to be worked and forms a spherical surface to at least one side of the lower surface 3b of the chip 3 and the upper surface 2a of the backing material body 2, and the upward receiving surface 3a is made to be inclinable corresponding to the inclination of the abutting surface J1 of the door D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot-welding backing material used for spot-welding a goby-folded joint portion such as a door of an automobile body, when it is intended for a welding part requiring an aesthetic appearance. Is suitable.

[0002]

2. Description of the Related Art In the series welding of doors for automobile bodies and the like, gob-folding is applied to the edge portion and spot welding is then performed in order to meet the requirements of appearance, safety and rust prevention. When performing such spot welding, a large pressing force is applied to the workpiece by the welding electrode, so that a backing material commonly called a back bar that withstands the pressing force is required. As the backing material, usually, a chromium copper alloy is often used in order to eliminate the influence of heat generated during welding, and the backing material itself to the electrode is prevented in order to prevent generation of welding marks on the outside of the door. The contact area was increased and the amount of current per unit area was decreased.

However, problems such as creep deformation of the backing material due to heat and heat during welding, generation of welding marks due to wear, and deformation of the door occur, and periodical adjustment of the mounting position of the backing material and re-contacting of the contact surface occur. A door polishing process was required after adjustment and welding. In addition, leakage from the backing material cannot be avoided due to structural problems.

Therefore, as a conventional back welding material for spot welding, the one as shown in FIGS.
It is proposed in Japanese Patent Publication No. 9819. The spot welding backing material 31 is formed by forming a backing material body 32 of an alumina ceramic insulating material and shrink-fitting a chromium copper alloy ring 33 on the outer peripheral surface of the upper portion excluding the supporting portion.

In the conventional spot welding backing material, the power source 3 is formed by mounting the joint portion J of the door D on the receiving surface 31a with the door inner plate D1 facing upward, and connecting the cathode to the door inner plate D1.
4 is used to connect a welding electrode 35 and to perform spot welding of the joint portion J of the door D in a state where a predetermined press pressure is applied to the electrode 35.

[0006]

In the case of the conventional backing material 31 for spot welding, such as a backing material made of a chromium-copper alloy, wear of the backing material, accompanying deformation of the door D, and generation of welding marks. Problems such as easy leakage are solved.

However, in the series welding of the door D, if the receiving surface 31a is not parallel to the contact surface J1 of the door D, the deformation of the door D cannot be avoided even when the chrome copper alloy ring is used. Therefore, it is necessary to process and incline the receiving surface 31a as shown in FIG. 12, or incline the main body 32 as shown in FIG. When processing the backing material 31, it is difficult to process the alumina-based ceramics into a plurality of shapes, and all the plurality of backing materials 31 must be processed into different shapes. It cannot be said to be efficient, and in the case of tilting the backing material 31, it is necessary to adjust the tilt and height of all a plurality of pieces at the same time, and therefore there is a drawback in that adjustment is difficult and time is wasted. It was Further, there is a problem that the welding electrode 35 is consumed and shortened due to long-term use, and it takes a long time to perform readjustment due to a change in welding spot.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to prevent wear, to be continuously used for a long period of time, to be free from electric leakage, and to be processed. It is an object of the present invention to provide a backing material for spot welding, in which welding marks are not generated, position adjustment for welding point changes can be performed in a short time, and the operating rate of the welding process can be improved.

[0009]

In order to achieve the above object, the present invention as set forth in claim 1, is a spot welding used for supporting and spot welding a work piece by a metal backing material body. In the backing material for use, a ceramic chip having excellent wear resistance, electrical insulation and thermal conductivity is supported on the main body of the backing material in a fall-preventing state, and a work piece is mounted on the ceramic chip. It is characterized in that it has an upward receiving surface that abuts, and that the upward receiving surface is tiltable according to the inclination of the abutting surface of the workpiece. The present invention according to claim 2 provides:
The backing material for spot welding according to claim 1, wherein a spherical surface is formed on at least one of the lower surface of the ceramic chip and the upper surface of the backing material body, and the back welding material according to claim 3, The present invention is the backing material for spot welding according to claim 1, wherein a ceramic spherical member having a spherical surface is interposed between the backing material main body and the ceramic chip. The present invention according to claim 4 relates to claim 1, claim 2 or claim 3.
In the backing material for spot welding according to any one of the above items, the fulcrum of the ceramic chip supported by the backing material main body can be moved according to the change of the welding point position of the welding electrode.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A backing material for spot welding according to an embodiment of the present invention will be described in detail with reference to the drawings, taking a case where an automobile door is used as a workpiece. FIG. 1 is a side sectional view showing a spot welding backing material according to a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram showing a usage state of the spot welding backing material.

A door D, which is spot-welded using the spot welding backing material 1 according to this embodiment, includes a door inner plate D1 and a door outer plate D2, and a door outer plate D at an edge thereof.
The second portion is folded back inward to form a bent piece B, and the joint portion J of both is formed in a state in which the edge of the door inner plate D1 is sandwiched between the bent pieces B.

The backing material 1 for spot welding comprises a backing material body 2
And a ceramic chip 3 installed on the backing material body 2.

The backing material body 2 is made of carbon steel (JI
It is made of a metal rectangular parallelepiped using S symbol S45C) and has a flat upper surface 2a, and the upper surface 2a is surrounded by captive prevention walls 2b integrally provided on four sides of the upper surface 2a,
The chip 3 installed on the upper surface 2a is supported in a state in which it is prevented from falling off by a falling prevention wall.

The chip 3 is made of a quadrangular silicon nitride sintered ceramics, has a flat upward receiving surface 3a which is slightly smaller than the upper surface 2a of the backing material body 2, and has a lower surface 3b having a convex downward spherical shape. The lower surface 3b is abutted on the upper surface 2a of the backing material body 2 and is tiltably supported.
The contact surface J1 of the joint portion J abuts on the upward receiving surface 3a, and the door D
Is placed.

The chip 3 preferably has the following properties. It has excellent wear resistance. This is for maintenance-free. Excellent electrical insulation. This is to prevent leakage. High strength and high toughness. This is to prevent chipping and damage. Excellent thermal conductivity.
This is to prevent changes in the material of the weld and creep deformation. Low reactivity with the work piece.

A test example of spot welding using the backing material 1 for spot welding according to the first embodiment of the present invention will be described. In FIG. 2, the door D is placed by contacting the contact surface J1 of the joint portion J with the door inner plate D1 on the receiving surface 3a of the tip 3 of the spot welding backing material 1 and placing the cathode inside the door. The welding electrode 8 is connected to the power source 7 connected to the plate D1, and the bending strength of the ceramic chip 3 is 600 MPa.
Then, a pressing pressure of 250 kg was applied to the electrode 8 to perform spot welding of the joint portion J of the door D.

The reliability of the spot welding backing material 1 increases as the volume of the ceramic tip 3 decreases. Further, the smaller the area of the upward receiving surface 3a of the chip 3, the easier the alignment adjustment. In the series welding using the backing material 1 with the tip 3 attached, the effective current increased due to complete insulation and no leakage, and the required current value during welding could be greatly reduced. Further, since the backing material 1 is hardly worn, the readjustment of the mounting position of the backing material 1 and the polishing step after welding are not necessary.

FIG. 3 is a side sectional view showing a backing material for spot welding according to a modified example of the first embodiment, in which parts corresponding to those in FIG. 1 are designated by the same reference numerals. In this spot welding backing material 1, an upper surface 2a surrounded by a falling prevention wall 2b of the backing material body 2 is formed into a convex spherical surface, and a lower surface 3b of a chip 3 is a plane parallel to a receiving surface 3a. 1 is different from that shown in FIGS.

FIG. 4 and FIG. 5 are side sectional views showing spot welding backing materials according to different modifications of the first embodiment. The backing material 1 for spot welding shown in FIG.
A concave spherical surface is formed on the upper surface 2a of the backing material body 2 which is surrounded by the fall prevention wall 2b, and the lower surface 3b of the chip 3 is a flat receiving surface 3
Unlike a, it has a convex spherical surface adapted to the concave upper surface 2a. In the spot welding backing material 1 shown in FIG. 5, a convex spherical surface is formed on the upper surface 2a of the backing material body 2, and the lower surface 3b of the tip 3 is a concave spherical surface adapted to the convex upper surface 2a.

In the case of this embodiment, the chip 3 has an advantage that it can withstand a large load. In both cases, the concave spherical surface needs to have a radius of curvature equal to or greater than that of the convex spherical surface, and when the two radii of curvature are different, the difference is as small as possible. Smaller is desirable.

FIG. 6 is a side sectional view showing a backing material for spot welding according to the second embodiment of the present invention. This spot welding backing material 11 is provided with a blind hole 13 having a circular cross section in the upper surface 12a of the backing material body 12 at a substantially central portion, and a ceramic sphere 4 having a diameter slightly larger than the depth thereof is provided in the blind hole 13. The ceramic chip 3 having a flat lower surface 3b is placed on the spherical body 4 by loose fitting, and the spherical body 4 is sandwiched between the backing material body 12 and the flat lower surface 3b of the chip 3. This has the advantage that the degree of freedom in position adjustment and tilt angle adjustment is further improved.

FIG. 7 is a side sectional view showing a backing material for spot welding according to a modification of the second embodiment of the present invention. This spot welding backing material 11 is made of a ceramic sphere 4.
Instead of the above, a ceramic hemisphere 5 with the plane 5a facing upward is used, and the flat lower surface 3b of the chip 3 is brought into contact with the plane 5a. In FIG. 7, the other points are almost the same as those shown in FIG. 6, and therefore the same portions are denoted by the same reference numerals.

With long-time use, the welding electrode is consumed and shortened, and the welding spot changes. At that time, if the welding spot and the fulcrum of the tip 3 are misaligned, the tip 3 of the tip 8 will be in contact with the electrode 8. Since it receives a twisting force due to the load applied from, it shifts from the position tilted according to the door,
The door is damaged. In that case, there is no problem if the structure is such that the length of the arm supporting the welding electrode 8 can be adjusted, but if not, a structure in which the fulcrum of the tip 3 can be moved according to the change of the welding point is used. There is a need to. Since the hitting point moves linearly toward the arm due to the consumption of the electrode 8, the fulcrum of the tip 3 may be moved accordingly.

FIG. 8 is a side sectional view showing a spot welding backing material according to a third embodiment of the present invention in which the tip fulcrum can be moved, and FIG. 9 is taken along line AA in FIG. FIG. This spot welding backing material 21 includes a backing material body 22.
Is composed of a lower member 23 and an upper member 25, and the position of the upper member 25 can be adjusted with respect to the lower member 23 by an adjusting bolt 27. The same ceramic chip 3 as shown in FIGS. Are using.

The lower member 23 has an upward straight guide groove 24.
To form a through hole 2 in both end walls 24a of the straight guide groove 24.
4b, and the adjusting bolt 27 is inserted into the through hole 24b. Adjusting bolt 27 has circlip 28 on the tip side.
Is fitted to restrain the movement in the axial direction, and a washer 29 is arranged on the head side.

The upper member 25 is a fall prevention wall 25b surrounding a flat upper surface 25a, and the lower member 2 is formed substantially at the center of the lower surface.
3 has a downward projecting portion 26 that projects into the straight guide groove 24, and a screw hole 26a into which the adjusting bolt 27 is screwed is provided in the downward projecting portion 26. The position can be adjusted in any direction.
Therefore, with this backing material 11 for spot welding, the fulcrum of the ceramic chip 3 can be moved according to the change of the hitting position of the welding electrode 8.

FIG. 10 is a side sectional view showing a backing material for spot welding according to a modification of the third embodiment of the present invention, and FIG.
FIG. 11 is a sectional view taken along line BB of FIG. 10. The backing material 21 for spot welding is used to prevent the backing material body 22 from falling off.
A straight guide groove 24 is provided substantially in the center of a flat upper surface 22a surrounded by 2b, and screw holes 22c, 22c communicating with the straight guide groove 24 from both outer surfaces are provided, and the adjustment bolts 27 are provided in the holes.
Are screwed together, and the ceramic chip 3 is supported via the same ceramic sphere 4 as shown in FIG.

Then, the ceramic sphere 5 placed on the bottom surface 24a of the groove of the backing material main body 22 has two adjusting bolts 27,
It is sandwiched by the tip of 27, and by turning both adjusting bolts 27, 27, the backing material main body 2 along the straight guide groove 14
It is possible to freely adjust the position in the lateral direction with respect to 2.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

[0030]

According to the present invention as set forth in claim 1, a ceramic chip having excellent wear resistance, electrical insulation and thermal conductivity is supported on the backing material main body in a falling prevention state, and the ceramic chip is supported. Since the chip-made chip has an upward receiving surface against which the workpiece contacts, the backing material is electrically insulated,
The power consumption is reduced, the cost can be reduced, and the continuous usable period of the backing material is extended, so the operating rate of the welding process is improved and the upward receiving surface is By making it tiltable in accordance with the tilt, it is possible to reliably prevent the generation of welding marks, and therefore it is possible to omit the polishing step for eliminating the welding marks. According to the present invention as set forth in claim 2, since the spherical surface is formed on at least one of the lower surface of the ceramic chip and the upper surface of the backing material body, the chip is adjusted in accordance with the inclination of the contact surface of the workpiece. It can be tilted extremely smoothly. According to the third aspect of the present invention, since the ceramic spherical member having a spherical surface is interposed between the backing material body and the ceramic chip, the degree of freedom of inclination of the chip is significantly improved. In the present invention according to claim 4,
By making the fulcrum of the ceramic chip supported by the backing material body movable according to the change of the welding point position of the welding electrode, it is possible to adjust the position of the chip with respect to the work piece in a short time. Even if there is a position shift, there is an advantage that it is unlikely to be affected.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a main part of a spot welding backing material according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration side view showing a usage state of the spot welding backing material according to the first embodiment of the present invention.

FIG. 3 is a side sectional view showing a modified example of the backing material for spot welding according to the first embodiment of the present invention.

FIG. 4 is a side sectional view showing another modified example of the backing material for spot welding according to the first embodiment of the present invention.

FIG. 5 is a side sectional view showing another modified example of the backing material for spot welding according to the first embodiment of the invention.

FIG. 6 is a side sectional view showing a main part of a backing material for spot welding according to a second embodiment of the present invention.

FIG. 7 is a side sectional view showing an essential part of a backing material for spot welding according to a modification of the second embodiment of the present invention.

FIG. 8 is a side sectional view showing a main part of a spot welding backing material according to a third embodiment of the present invention.

9 is a plan sectional view taken along the line AA of FIG.

FIG. 10 is a side sectional view showing a main part of a spot welding backing material according to a modification of the third embodiment of the present invention.

11 is a plan sectional view taken along the line BB of FIG.

FIG. 12 is a schematic configuration side view showing a usage state of a conventional spot welding backing material.

FIG. 13 is a schematic configuration side view showing another usage state of a conventional backing material for spot welding.

[Explanation of symbols]

 D Door (workpiece) J Joint part J1 Abutment surface 1 Spot welding backing material (first embodiment) 2 Backing material body (first embodiment) 2a Upper surface 3 Ceramic chip 3a Upward Receiving surface 3b Lower surface 4 Sphere (spherical member) 5 Hemisphere (spherical member) 8 Welding electrode 11 Spot welding backing material (second embodiment) 12 Backing material body (second embodiment) 12a Upper surface 21 Backing material for spot welding (third embodiment) 22 Backing material body (third embodiment) 23 Lower member 24 Straight guide groove 25 Upper member

Claims (4)

[Claims] 1. A backing material for spot welding, which is used for supporting and spot welding an object to be processed with a metal backing material body, wherein wear resistance, electrical insulation and A ceramic chip having excellent thermal conductivity is supported in a falling-out prevention state, and the ceramic chip has an upward receiving surface against which a workpiece contacts, and the upward receiving surface is a contact surface of the workpiece. A backing material for spot welding, which can be tilted freely according to the tilt. 2. The spot welding backing material according to claim 1, wherein a spherical surface is formed on at least one of a lower surface of the ceramic chip and an upper surface of the backing material body. Backing material for welding. 3. The backing material for spot welding according to claim 1, wherein a ceramic spherical member having a spherical surface is interposed between the backing material body and the ceramic chip. Spot welding backing material. 4. The spot welding backing material according to claim 1, 2, or 3, wherein a fulcrum of the ceramic tip supported by the backing material body is a welding point of a welding electrode. A backing material for spot welding, characterized in that it can be moved according to changes in position.