JP2008023543A - Welding gun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy load type welding gun capable of reducing the stress in a base portion of a connection member and mitigating the stress concentration. <P>SOLUTION: The welding gun 10 comprises a bar-shaped electrode rod 13 on a gun arm 11 via a connection member 12. The connection member 12 is constituted of two components of an adapter 14 and an electrode holder 15. The adapter 14 includes a storage recess 16 for storing a base part of the electrode rod 15 and has a tapered shape having the sectional area increasing toward the gun arm 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a welding gun used for spot welding.

Many spot welders, which are a type of resistance welder, are arranged in a vehicle production line. Various structures of a welding gun for a spot welder have been proposed (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2005-161348 (FIG. 3)

Patent document 1 is demonstrated based on the following figure.
FIG. 5 is a diagram for explaining the basic configuration of the prior art. A welding gun 100 is formed by providing an electrode tip 103 via a connecting member 102 on a gun arm 101 supported by an arm of a robot. The electrode tip 103 has a cap shape and is attached to the connecting member 102 by being inserted into the tapered portion 104 provided at the tip of the connecting member 102 from above.
Spot welding is performed by supplying a welding current to the electrode tip 103 while strongly pressing the electrode tip 103 against the workpiece.

  The cap-shaped electrode chip 103 described above is widely used in practical use. On the other hand, for the purpose of reducing the weight of the vehicle and maintaining the rigidity of the vehicle body, high-tensile steel has been adopted for workpieces that are objects to be welded. When the workpiece is high-tensile steel, the pressing force at the electrode tip 103 needs to be higher than when the workpiece is normal steel. That is, a welding gun corresponding to a high load has become necessary.

Therefore, the present inventors have started the development of a high load type welding gun. The following figure shows the structure studied in the early stages of development.
FIG. 6 is a view for examining a welding gun. First, a conventional welding gun 110 shown in FIG. The welding gun 110 includes a gun arm 111, an adapter 112 that constitutes a part of the coupling member, an electrode holder 113 that constitutes the remainder of the coupling member, and an electrode cap 114.

  Reference numeral 115 denotes an axis of the electrode cap 114. It is desirable that the electrode cap 114 contacts the workpiece 116 at the position of the axis 115. However, in the production line, the contact may occur in a form inclined by an angle θ. When the angle θ is inclined, an external force is applied to the electrode cap 114 in a direction orthogonal to the axis 115.

In the electrode cap 114, the skirt portion 117 is inevitably thin and has low rigidity. When the work 116 is strongly pressed in a state where it is inclined by the angle θ, the skirt portion 117 is slightly deformed by the reaction force.
When a minute gap is generated between the electrode holder 113 and the skirt portion 117, the welding current is concentrated on the other part of the welding cap 114. The part where the current is concentrated becomes hotter than other parts.
By repeating the above, the life of the electrode cap 114 is remarkably shortened.

  Therefore, the electrode cap 114 was replaced with a rod-shaped electrode rod 118 as shown in FIG. This eliminates the problem with the electrode tip. However, this time, the male screw 119 provided at the base of the electrode holder 113 is deformed and is difficult to be detached from the adapter 112. The electrode holder 113 is a cantilever extending upward from the adapter 112, and it is considered that stress is easily concentrated on the base of the electrode holder 113.

  Therefore, a welding gun having a new structure in place of FIGS. 6A and 6B is required.

  An object of the present invention is to provide a high-load welding gun.

  The invention according to claim 1 is a welding gun in which an electrode tip is provided on a gun arm via a connecting member, wherein the electrode tip is a rod-shaped electrode rod, and the connecting member has a storage recess for storing a base portion of the electrode rod. And having a taper shape with a cross-sectional area increasing toward the gun arm.

  The invention according to claim 2 is characterized in that the connecting member is a truncated cone.

  The invention according to claim 3 is characterized in that the truncated cone has a bullet shape in which a conical surface bulges or a drum shape in which a conical surface is depressed.

  In the invention according to claim 1, the connecting member is tapered so that the cross-sectional area increases toward the gun arm. As a result, the stress at the base of the connecting member can be reduced, and the stress concentration can be reduced.

  In the invention according to claim 2, the connecting member is a truncated cone. Since the truncated cone has a simple shape, it can be easily cut and the manufacturing cost of the connecting member can be reduced.

In the invention which concerns on Claim 3, the truncated cone was made into the bullet shape with which the conical surface bulged, or the drum shape with which the conical surface was depressed. In the case of a cannonball shape, the base portion is substantially parallel to the axis, and when the screw portion is provided on the base portion, the screw portion and the conical surface can be smoothly connected.
In addition, if it is a drum shape, the weight can be reduced by the amount of concavity.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the following description, the taper angle refers to a single taper angle.
FIG. 1 is a side view of a welding gun according to the present invention. A welding gun 10 includes a gun arm 11 provided with a rod-shaped electrode rod 13 via a connecting member 12.

  The connecting member 12 includes two parts, an adapter 14 and an electrode holder 15. The electrode holder 15 has a storage recess 16 for storing the base of the electrode rod 13 and has a tapered shape with a cross-sectional area increasing toward the gun arm 11. The adapter 14 has a female threaded portion 18 that houses a male threaded portion 17 provided at the base of the electrode holder 15 and has a tapered shape with a cross-sectional area increasing toward the gun arm 11.

In the figure, α is a taper angle, and the bending stress at the base of the electrode holder 15 decreases as the angle α increases. The same applies to the adapter 14.
1 and 6 (b) as a model, α in FIG. 1 is 5 °, no taper is used in FIG. 6 (b), and other conditions are the same, and bending at the base of the electrode holder and the base of the adapter is performed. The stress was compared and examined. The examination results are shown in Table 1.

  In the comparative example, when the stress at the electrode holder base was set to 100, the stress at the electrode holder base was 52 in the example, and the effect of increasing the diameter of the base by the taper was remarkable.

Next, another embodiment of the present invention will be described.
FIG. 2 is a view for explaining another embodiment of FIG. 1. A welding gun 10 </ b> B is provided with a rod-shaped electrode rod 13 on a gun arm 11 via a connecting member 12. The connecting member 12 has a storage recess 16 for storing the base of the electrode rod 13 and has a tapered shape with a cross-sectional area increasing toward the gun arm 11. That is, the connecting member 12 is a truncated cone whose upper surface (upper base) has a diameter d and whose cross-sectional area increases from the upper base toward the gun arm 11 at a taper angle α.

The truncated cone is a solid formed by cutting the head of the cone, and the conical surface 19 is a simple curved surface, which is easy to cut and can reduce the manufacturing cost.
Using such a connecting member 12 as a model, an appropriate value of the angle α was examined.
The diameter d of the upper base was set to 30 mm, the height H was set to 60 mm, and the angle α was changed in the range of 1 ° to 10 °, and the change in the section modulus at the base portion of the connecting member 12 was examined. D is the diameter of the lower base.

  The section modulus (relative value) was determined by setting the section modulus in a model without a taper to 1.0. The section modulus (relative value) was obtained by the following formula: (section coefficient at a certain angle / section coefficient with no taper model). The results are shown in the following table.

  For the purpose of stress relaxation, the base section modulus should be at least 1.5 times that of the prior art (no taper). Those satisfying this condition were marked with ○, and those not satisfying the condition were marked with ×.

By the way, in FIG. 2, the size of the gun arm 11 is naturally limited in consideration of the burden on the robot. If the angle α is increased while keeping the size of the gun arm 11 constant, the wall thicknesses T and T at the upper part of the gun arm 11 are reduced, causing a problem in strength.
Therefore, the limit value of the angle α is examined.
The diameter d of the upper base was set to 30 mm, the height H was set to 60 mm, and the angle α was changed in the range of 1 ° to 11 °, and the change in the diameter at the base of the connecting member 12 was examined.

When α is 0, the ratio of the diameter of the lower base to the diameter of the upper base is 1.0. When α is 5 °, (the diameter of the lower base / the diameter of the upper base) is 1.3.
The upper dimension of the gun arm 11 is assumed to be about twice the diameter d (same as the diameter of the upper base) of the upper surface of the connecting member 12. When the wall thicknesses T and T are removed from about twice the diameter of the upper base, the diameter of the lower base is determined. The diameter of the lower base is about 1.6 times the upper base diameter d, and preferably 1.5 times. This is because if the thickness exceeds 1.7 times, the thicknesses T and T cannot secure a sufficient thickness.
If it is about 1.6 times, the angle α may be 9 ° or less, and if it is about 1.5 times, the angle α needs to be 7 ° or less.

  From Table 2 and Table 3, the taper angle α may be set in the range of 2 ° to 9 °, preferably 2 ° to 7 °.

Next, another embodiment will be described.
FIG. 3 is a view for explaining a modified example of FIG. 2, and this welding gun 10C bulges with a radius R1 so that the tapered surface (conical surface) 19 of the connecting member 12 protrudes outward, and the ammunition. It is characterized by its shape. Since the other elements are the same as those in FIG. 2, the reference numerals are used and the description is omitted.

  In the case of a cannonball shape, the base portion is substantially parallel to the axis 21 of the electrode rod 13, and when the male screw portion 17 is provided on the base portion, the male screw portion 17 and the conical surface 19 can be smoothly connected.

FIG. 4 is a diagram for explaining a further modification of FIG. 2, and the welding gun 10 </ b> D has a tapered surface (conical surface) recessed inward at a radius R <b> 2 in the connecting member 12. (Half) Shaped. Since the other elements are the same as those in FIG. 2, the reference numerals are used and the description is omitted.
In the case of the hourglass shape, the weight can be reduced as much as the conical surface 19 is recessed inward.

  As is clear from the above description, the connecting member 12 may be a single product or a combination of a plurality of components. When combining a plurality of parts, as described in FIG. 1, it is desirable that all the constituent parts have a tapered shape in which the cross-sectional area increases toward the gun arm.

  In addition, the present invention is suitable for a welding gun equipped in a spot welding machine arranged on a production line of a vehicle body, but the welding gun may be applied to other uses.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a welding gun equipped on a spot welding machine arranged on a production line for a vehicle body.

It is a side view of the welding gun concerning the present invention. It is a figure explaining another Example of FIG. It is a figure explaining the modification of FIG. It is a figure explaining the further modification of FIG. It is a figure explaining the basic composition of the conventional technology. It is an examination figure of a welding gun.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10B, 10C, 10D ... Welding gun, 11 ... Gun arm, 12 ... Connecting member, 13 ... Electrode rod, 16 ... Storage recessed part, 19 ... Conical surface.

Claims (3)

In a welding gun in which an electrode tip is provided on the gun arm via a connecting member,
The electrode tip is a rod-shaped electrode rod, and the connecting member has a storage recess for storing a base portion of the electrode rod and has a tapered shape with a cross-sectional area increasing toward the gun arm. gun.   The welding gun according to claim 1, wherein the connecting member is a truncated cone.   The welding gun according to claim 2, wherein the truncated cone has a bullet shape in which a conical surface bulges or a drum shape in which a conical surface is recessed.

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