JPH0545354B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a locating structure used for positioning panels to be welded during spot welding. (Prior Art) As a conventional locate structure, there is one shown in FIG. 4, for example. This is a locate structure for spot welding, and in Fig. 4,
101 is a locate pin having a conical head 101a at the upper part, a flange part 101b at the middle part, and a threaded part 101c at the lower part;
01 is inserted into the fixture 102 from above and fixed with a nut 103.
This locate pin 101 is used, for example, to spot-weld two panels 104 and 105 to be welded while positioning them at a predetermined location. Conventionally, such locating pins 101 have been made of steel, the entire body of which is made highly hard with only wear resistance in mind, or steel whose surface is thermally sprayed with alumina powder or zirconia powder (such as those made of steel with alumina powder or zirconia powder sprayed on the surface).
55-33639), steel with a chromium oxide film formed on the surface (Japanese Patent Application Laid-open No. 60-68181), etc. (Problems to be Solved by the Invention) However, among the locating structures using such conventional locating pins 101, for example, the locating pins 101 are made entirely of steel with high hardness considering only wear resistance. If it consists of
When the locate pin 101 is on or near the current flow path, the panel 10 to be welded
An arc is generated between the workpiece to be welded, such as 4, 105, etc., and the locate pin 101, and as a result, as the workpiece is repeatedly used, the outer diameter of the locate pin 101 that comes into contact with the workpiece becomes smaller, resulting in lower positioning accuracy. Furthermore, spatter adhering due to arc generation makes it difficult to remove the workpiece after welding. For example, on an automobile body assembly line, it is necessary to frequently replace the locate pin 101. There is a problem in that the productivity is significantly lowered, and an operation for removing the spatter is also required, which also causes a problem in that the productivity is significantly lowered. On the other hand, when alumina powder or zirconia powder is thermally sprayed onto the surface of the locate pin, thermal spraying cannot reduce the porosity of the ceramic layer on the surface of the locate pin, resulting in low strength and wear resistance, and the problems caused by arc generation. Although this problem can be resolved at least in the initial stage of spot welding, as the electrical insulating film on the surface is used repeatedly, there is a possibility that the electrical insulating film on the surface will be damaged or peeled off. There was a problem with the decline. Further, even in the case of steel locate pins having a chromium oxide film on the surface, problems of damage and peeling of the chromium oxide film on the surface cannot be avoided. This invention was made by focusing on the above-mentioned conventional problems, and it is possible to prevent arcing during spot welding, prevent wear and tear caused by arcing, and maintain positioning accuracy over a long period of time. The purpose is to provide a locate structure using a certain locate pin. [Structure of the Invention] (Means for Solving the Problems) The locate structure according to the present invention has a porosity of 5.
% and has a specific resistance of 500Ω・cm or more, the impact is absorbed by the elasticity of the membrane-like elastic body through a flat or circular arc surface and a membrane-like elastic body provided on the flat or circular arc surface. It is characterized by a configuration in which it can be attached. This type of locating pin used in locating structures for spot welding, for example, must have excellent electrical insulation to prevent arcing during spot welding, and be of high strength and strength so as not to break during repeated use. It is required to have excellent impact resistance, excellent abrasion resistance to prevent wear and tear during repeated use, good workability, and low cost. Therefore, ceramics are suitable as materials that have all of these properties.Among the various ceramics, from the viewpoint of having excellent electrical insulation properties, ceramics are the most suitable.
It has been confirmed through various experiments that a material with a porosity of 5% or less must be used because it is required to use a material with a porosity of 500Ω・cm or more and to have high strength and excellent impact resistance. did. Specifically, we confirmed that pressureless sintered bodies or hot press molded bodies of partially stabilized zirconia sintered bodies (PSZ-ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), and silicon carbide (SiC) were preferable. Ta. In addition, from the viewpoint of electrical insulation, locate pins made of bakelite or steel locate pins coated with ceramics are also effective, but those made of bakelite have problems with wear resistance and can produce worse results than conventional products. In addition, thermal spraying cannot form a ceramic layer with low porosity, so the impact when setting the object to be welded causes the thermal sprayed layer to break or peel, and the wear resistance is poor, so it is difficult to solve this problem fundamentally. I reconfirmed that I would not get it. Furthermore, when changing the material of the locate pin from steel to ceramics, in order to overcome the "brittleness" which is the biggest drawback of ceramics, it is especially required to use it in a stress-free state and avoid stress concentration. For this reason, it is desirable that all the edge portions of the locate pin be rounded, and it is particularly desirable that the stress concentration portions have a large radius. Furthermore, in the conventional case shown in FIG. 4, the locating pin is attached using a nut 103 with a male threaded portion 101c formed directly on the locating pin 101.
If the locating pin is formed directly, stress will be applied in the attached state, so it is more desirable to have a mounting structure in which the threaded portion is not directly formed on the locating pin. More preferably, the locating pin is attached via a film-like elastic body such as rubber in order to reduce the impact when setting the object to be welded. The locating structure according to the present invention can be used not only for positioning objects to be welded such as panels to be welded, but also for positioning spot welding electrodes, molds, and the like. Embodiment 1 FIG. 1 shows a first embodiment of this invention.
The locate pin 1 is entirely made of ceramic with a porosity of 5% or less and a resistivity of 500Ω・cm or more, which has excellent toughness and electrical insulation properties, and has a conical head 1a at the top and an enlarged conical head at the bottom. base 1b
All edges are rounded. This locate pin 1 is fitted into a fixture 2 which has a locate pin fitting hole 2a made of a circular arc surface with a large radius rounded to match the rounded shape of the locate pin 1, through a membrane-like elastic body 8 such as rubber. A fixed platen 3 is also applied to the flat bottom surface via a film-like elastic body 9 such as rubber, and a hexagonal socket bolt 5 is inserted into the bolt hole 3a formed in the fixed platen 3 via a washer 4. 5 is formed on the fixture 2 and screwed into the internal threaded hole 2b to fix the locate pin 1 to the fixture 2. In addition, Fixture 2
is fixed to a welding pin fixing stand (not shown). During spot welding, the fixture 2 is inserted into the positioning holes 6a and 7a formed in the panels 6 and 7 to be welded, with the locating pin 1 fitted into the positioning holes 6a and 7a.
Place it on top. Therefore, during spot welding, like the conventional locate pin 101 made entirely of steel,
Since no arc is generated between the panels 6 and 7 to be welded, there is no change in diameter or adhesion of spatter due to arc generation, and it is possible to maintain high positioning accuracy.
7 can be removed extremely easily, and there is no need to remove spatter. Further, in this embodiment, since there is no stress concentration on the locate pin 1 in the attached state, both strength and durability are excellent. Furthermore, locate pin 1
By interposing the membrane-like elastic bodies 8, 9 on the arcuate surface or flat surface on which the panels are attached, when the panels 6, 7 to be welded are set on the fixture 2,
The locate pin 1 can move by the elasticity of the elastic bodies 8 and 9, and the impact force applied to the locate pin 1 can be alleviated, making it possible to more effectively prevent damage to the locate pin 1. At the same time, the locate pin 1 only moves by the elasticity of the membrane elastic bodies 8 and 9, so that excessive movement is suppressed and the durability of the locate pin 1 is significantly improved. Embodiment 2 FIG. 2 shows a second embodiment of this invention,
The locate pin 11 is entirely made of ceramic with a porosity of 5% or less and a resistivity of 500Ω・cm or more, which has excellent toughness and electrical insulation properties. It has a mounting recess 11b, and all edges are rounded. This locate pin 11 is fitted into a fixture 12 having a locate pin fitting hole 12a, and a fixing pin 13 which is inserted into a fixing pin fitting hole 12b formed in the fixture 12 and whose outer periphery is covered with a membrane-like elastic body 14 such as rubber. a part of the locate pin 11
By engaging the concave portion 11b formed of an arcuate surface, the membrane-like elastic body 14 is interposed on the arcuate surface between the locate pin 11 and the fixing pin 13, and the fixture 12 is moved without causing stress concentration on the locate pin 11. Fixed. During spot welding, the panels 6, 7 to be welded are placed on the fixture 12 with the positioning holes 6a, 7a formed in them fitted into the locating pins 11. Therefore, in this case as well, as in Example 1, no arc is generated between the panels 6 and 7 to be welded, and no stress concentration occurs in the locate pin 1, so that it can withstand long-term use. Become something. Furthermore, by interposing the elastic body 14 in this way, the locate pin 1 can move by the elasticity of the elastic body 14, so that the impact force applied to the locate pin 11 can be alleviated. This makes it possible to more effectively prevent breakage of the locate pin 11, and since the locate pin 11 only moves by an amount corresponding to the elastic force of the membrane elastic body 14, excessive movement is suppressed. As a result, the durability of the locate pin 11 is significantly improved. Embodiment 3 FIG. 3 shows a third embodiment of this invention.
Locate pin 21 has a porosity of 5% or less and a specific resistance.
The locate pin 21 is formed into a cap shape using ceramics with excellent toughness of 500 Ω・cm or more and excellent electrical insulation properties. It is fixed to a support body 23, and a membrane-like elastic body 22 is interposed on the plane of the upper end and the circular arc surface of the side part. The support body 23 has a male thread 23a at its lower part, passes through the welding pin fixing base 24, and is fixed to the fixing base 24 with a nut 25. In addition, 26 is an electrode tip for spot welding, and 27 is a back electrode. According to this embodiment, as in the first embodiment, arc generation is prevented, and the impact force generated when the panels 6 and 7 to be welded are set on the locating pin 21 is suppressed by using the highly tough steel support 23 and the membrane elastic material. body 2
2, the locate pin 21 itself has high strength and high abrasion resistance, as well as superior durability. Test Example 1 In Test Example 1, a test was conducted on the locate structure shown in FIG. 1. The locating pin 1 was made of materials, densities (porosity), three-point bending strengths, and specific resistances shown in Table 1, and the results of evaluation tests in spot welding used in car body assembly are shown.

[Table] In Table 1, the material of test No. 1 is partially stabilized zirconia (ZrO ₂ ), and 3
Zirconia powder containing mol% of yttrium oxide (Y ₂ O ₃ ) was compacted and sintered in the atmosphere at 1450°C for 2 hours. Also, test No.
The material of No. 2 is alumina (Al ₂ O ₃ ), and alumina powder to which magnesium oxide (MgO) is added as a grain growth inhibitor is compacted and heated at 1600°C in the atmosphere.
Sintering was performed for 2 hours. Furthermore, the material of test No. 3 is pressureless sintered silicon nitride (Si ₃ N ₄ ), and Y 2 O 3 and Y ₂ O ₃ are added to Si ₃ N ₄ as a sintering aid.
A mixed powder containing MgO was compacted and sintered in _N2 gas at 1730°C for 1 hour. Furthermore, the material of sample No. 4 was hot-pressed silicon nitride (Si ₃ N ₄ ), and a compacted compact with the same composition as sample No. 3 was heated in N ₂ gas at 1700°C for 0.5 hours. It was hot pressed at a pressure of 250 kgf/cm ² . Furthermore, the material of test No. 5 is pressureless sintered silicon carbide (SiC), and a mixed powder of SiC with boron (B) and carbon (C) added is compacted and heated to 2050℃ in a vacuum. Sintering was performed under the conditions of ×0.5 hours. On the other hand, the material of test No. 6 is reactive sintered silicon nitride (Si ₃ N ₄ ), which is made by compacting metal silicon powder and molding it in nitrogen (N ₂ ) gas at 1200 to 1450°C for 70 hours. The porosity is 5.
%. In addition, the material of test No. 10 was reactive sintered silicon carbide (SiC), and a mixed powder of SiC and C was compacted and sintered in Si vapor at 1600°C for 4 hours. It is something. Furthermore,
Test Nos. 7 to 9 are made of the same reaction-sintered silicon carbide (SiC) as Test No. 10, but in order to reduce the amount of residual silicon and improve electrical insulation, the sintered bodies were further heated under high vacuum. It was kept under high temperature. The spot welding conditions were as shown in Table 2.

[Table] As shown in Table 1, no arc was observed when using the ceramic locating pins of test Nos. 1 to 7.
It became clear that a specific resistance of 500Ω・cm or more was required. However, among these, the porosity is 5%
In No. 6 and 7, which exceeds the above, arcing does not occur, but due to low strength and toughness, some breakage occurs during the process, and wear is also greater than in the inventive example, so the porosity should be 5% or less. I found out what was needed. Also, the specific resistance is smaller than 500Ω・cm
Arcing was observed in Nos. 8, 9, 10 and No. 11, which is a conventional steel locating pin, and favorable results were not obtained. Test Example 2 In this Test Example 2, the test sample in Test Example 1
It was decided to manufacture the locate pin using material No. 3 (pressure-pressure sintered silicon nitride), but in this case, locate pin 1 having the shape shown in Fig. 1 was manufactured and this
The locating pin 1, which has the same shape as the structure fixed between the fixture 2 and the fixed platen 3 without using the membrane elastic bodies 8 and 9 shown in the figure, is made of sheet-like natural rubber as shown in Fig. 1. A locating pin 11 having the shape shown in FIG. 2, which is fixed between the fixture 2 and the fixed plate 3 via the membrane elastic bodies 8 and 9, is manufactured and made of natural rubber as shown in FIG. An evaluation test was conducted on spot welding for car body assembly. The spot welding conditions in this case were a voltage of 15 to 30 V and a current of 12,000 to 13,000 A. The results are shown in Table 3.

[Table] As is clear from the results shown in Table 3, when the membranous end members 8, 9, and 14 are interposed when attaching the locate pins 1 and 11, the locate pins 1 and 11 are 11 did not break, whereas in the case where the membrane-like elastic body was not interposed, breakage of the locate pin 1 was observed up to 100,000 hits. Therefore, locate pin 1,
11, the membrane-like elastic bodies 8, 9, 14
It has been confirmed that the impact when the workpiece to be welded is set on the fixtures 2 and 12 can be alleviated by interposing it. [Effects of the Invention] As explained above, according to the locating structure according to the present invention, a locating pin made of ceramics having a porosity of 5% or less and a resistivity of 500 Ω·cm or more can be attached to a flat or arcuate surface and the locating structure described above. Since the structure is such that the shock can be absorbed by the elasticity of the film-like elastic body provided on a flat or arcuate surface, it is possible to prevent arcs from occurring at the locate pin during spot welding. This makes it possible to significantly reduce the work of replacing locate pins, which previously had to be done frequently, and eliminates the need to remove spatter.
Even when setting the object to be welded on the locating pin, the locating pin according to the present invention has excellent strength and wear resistance, so the locating pin will not be damaged even if the work is done somewhat roughly, improving positioning accuracy and productivity. In addition, it is possible to significantly improve the impact force applied to the locate pin by interposing the membrane elastic body, and to reduce the impact force applied to the locate pin.
A very excellent effect can be obtained in that damage to the locate pin can be more effectively prevented.

[Brief explanation of the drawing]

1 to 3 are cross-sectional explanatory views of a locate structure equipped with a locate pin according to a first embodiment to a third embodiment of the present invention, respectively, and FIG. 4 is a cross-sectional explanatory diagram of a locate structure equipped with a conventional locate pin. It is a diagram. 1, 11, 21... Locate pin, 6, 7...
Panels to be welded, 8, 9, 14, 22...membrane elastic bodies.

Claims (1)

[Claims] 1 Porosity is within 5% and specific resistance is 500Ω・cm
A locator characterized in that the locating pin made of ceramics as described above is attached to a flat or circular arc surface and a membrane elastic body provided on the flat or circular arc surface so as to be able to absorb shock under the elasticity of the membrane elastic body. Structure.