JP2863343B2 - guide pin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic guide pin mainly used for welding positioning.

[0002]

2. Description of the Related Art When resistance welding is performed by applying a current between members to be welded while clamping the welding positions of a pair of members to be welded to each other with an electrode, the welding positions of the members are individually set. 2. Description of the Related Art A positioning guide pin for resistance welding for fitting into a provided positioning hole and relatively positioning the members to be welded has been conventionally used. Normal,
Such positioning guide pins are made by spraying an insulator on the surface of a metal guide pin main body or using an insulating material such as ceramics so that welding current is not bypassed by the positioning pins.
Under such circumstances, the metal guide pin has a disadvantage that the insulating layer on the surface is peeled off by use and the insulating property is deteriorated, and the arc generated by this causes the outer diameter to be reduced and the positioning accuracy to be lowered. In recent years, ceramic guide pins have been frequently used. (See, for example, JP-A-62-142086, Japanese Utility Model Application Laid-Open No. 61-182683, Japanese Utility Model Application Laid-Open No. 1-80276)

[0003]

However, the ceramic guide pin is extremely brittle even if it is a high-strength ceramic as compared with a metal pin, and the top or the tapered pedestal is in contact with the member to be welded during the welding operation. There is a drawback that breakage is likely to occur from the connecting portion between the cylindrical portion (the truncated cone-shaped tapered seat) and the cylindrical body. 4 and 5 show a front view of a conventional ceramic guide pin and a view showing the positional relationship between the lower electrode for locking and the guide pin during resistance welding. As shown in FIGS. 4 and 5, the conventional ceramic guide pin has a small R (eg, R = 0.3) at the corner 2 where the root of the cylindrical body 5 and the frustoconical tapered seat 6 are formed and connected. ~ 0.
Therefore, the contact end 54 of the contact surface where the tapered seat 6 and the lower electrode 7 for locking come into contact with each other is close to the R portion minimum diameter position 53 of the corner 2.

As described above, the contact end 54 and the R portion minimum diameter position 5
When the welded member comes into contact during use, the bending stress (tensile stress) is concentrated at the R-portion minimum diameter position 53, and is concentrated around the contact end by contact with the lower electrode 7. When the generated bending stress (tensile stress, so-called Hertz stress) overlaps, the stress is concentrated at the R portion minimum diameter position 53, causing breakage at this portion. In general, it is known to increase the radius of the connecting portion in order to prevent the breakage of the connecting portion. However, as shown in FIG. 5, it is simply increased because the clearance between the lower electrode 7 and the tapered seat 6 is small. It is not possible.

[0005] In addition, the breakage at the top of the guide pin is easy to find, and the guide pin can be replaced immediately. However, the breakage at the R portion is difficult to find because it is inside the electrode. There was a problem that the failure continued.
Therefore, the present invention has been made to solve the above-mentioned conventional problems, and prevents the concentration of stress at the R part minimum diameter position by moving the contact end between the tapered seat and the lower electrode away from the R part minimum diameter position. It is an object of the present invention to provide a ceramic guide pin having improved strength.

[0006]

Means for Solving the Problems] To achieve the above object, according to the present invention, the conical top, Ri Do a cylindrical body portion and frusto-conical frustum tapered seat, the placing head frustoconical tapered seat
Is used for welding positioning where the
In the ceramic guide pins that Re, only the curve of R shape smoothly continuous from a side surface of the cylindrical body portion to the outer peripheral portion of said cylindrical body portion and a front wherein the head frustoconical tapered seat to connect
And a ceramic guide pin provided with a relief constituted by:

[0007]

The ceramic guide pin of the present invention is shown in FIGS.
As shown in the figure, the cylindrical body 5 and the truncated cone-shaped tapered seat 6
By providing a relief 3 composed of only an R-shaped curve at the outer peripheral portion where the taper seat 6 is connected, the tapered seat 6 is formed.
The contact end 4 between the electrode and the lower electrode 7 is kept away from the R portion minimum diameter position 33. Here, " Construct only with R-shaped curve
The term “relief” refers to the R portion 3 formed such that the contact end 4 between the tapered seat 6 of the ceramic guide pin and the lower electrode 7 is kept away from the R portion minimum diameter position 33. And the like. The R shape of the R portion 3 has a radius of curvature R of usually 1 to 5 mm, preferably 2 to 3 mm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the illustrated embodiments, but the present invention is not limited to these embodiments. FIG. 1 is a front view of a ceramic guide pin of the present invention, FIG. 2 is an enlarged view of a main part of the ceramic guide pin of the present invention, and FIG. It is explanatory drawing which shows a relative positional relationship. In the figure, reference numeral 1 denotes a ceramic guide pin, and the ceramic guide pin 1 has a conical top 8,
It comprises a cylindrical body 5 and a truncated cone-shaped tapered seat 6. Then, an R-shaped relief is provided on the outer peripheral portion 2 where the cylindrical body portion 5 and the truncated cone-shaped tapered seat 6 are connected (R portion).
3 are provided. By adopting this configuration, the contact end 4 between the truncated cone-shaped tapered seat 6 and the lower electrode 7 is kept away from the R portion minimum diameter position 33 to avoid stress concentration.

Next, a specific example will be described. A silicon nitride guide pin 1 of the present invention was manufactured in contrast to a conventional silicon nitride guide pin having a cylindrical body diameter of 6.7 mmφ and a radius of curvature of 1 mm. The fabrication method is described below. The granulated powder of Si ₃ N ₄ to which sintering aids such as yttria and magnesia are added is rubber-pressed into a cylindrical shape at a pressure of at least 1 ton / cm ² , and cut by a lathe into a guide pin shape that allows for sintering shrinkage After processing, the surface was finished with sandpaper, and after removing the binder, it was baked at 1700 ° C. in a nitrogen atmosphere. Next, 50 pieces of the obtained sintered bodies are put in a 7.5-liter hexagonal columnar steel container, and alumina ball media of φ3 mm to φ5 mm are further charged until the container reaches 60 vol%, and water is further added to 80 vol%. Then, a trace amount of a surfactant was added thereto, and the container was closed. The container was set in a centrifugal barrel polishing machine manufactured by Tipton Co., Ltd., and was rotated at a rotation speed of 150 to 200 rpm for 10 minutes or more. A guide pin 1 made of the same was manufactured.

The silicon nitride guide pin 1 has an R portion 3 having a cylindrical body diameter of 6.7 mmφ which is the same as the conventional shape and a radius of curvature of 2.0 to 2.2 mm. The point where the curve of the R portion 3 intersects the side surface of the tapered seat 6 is the contact end 4.
The straight side portion of the cylindrical body portion 5 and the R portion 3 smoothly transition from a straight line to a curved line and are continuous. The clearance between the outer diameter of the cylindrical body 5 and the lower electrode 7 for locking is 300.
μm or less. The manufacturing method of the ceramic dyed pin according to the present invention is the same as that of the conventional shaped product except that the shape is different from that of the conventional shaped product, so that it can be mass-produced at the same cost as the conventional product. Further, for comparison, as shown in FIG. 6, a ceramic guide pin (comparative example) in which the radius of curvature of the R portion 3 was formed as large as 5.2 to 5.5 mm was produced.
For each ceramic guide pin obtained above,
A Charpy impact strength test and a cantilever bending test according to JIS standards were performed. The test results are shown in Table 1.

[0011]

[Table 1]

As is clear from Table 1, the radius of curvature is 2.
In the case of the ceramic guide pin of 0 to 2.2 mm, both the impact strength and the static strength of the embodiment are increased as compared with the conventional shape,
In particular, it was found that the impact resistance was significantly improved. Further, the examples show that the static strength is slightly inferior to the comparative examples, but the examples have the same impact resistance as the comparative examples. In the comparative example, the value of R of the R portion 3 was increased, and the static bending strength and the shear strength increased as the value of R increased. Therefore, although it is preferable in terms of strength, it is necessary to chamfer the lower electrode 7 on the other side, and it has been found that there is a problem in practical use. That is, the guide pin is the one to which the work to be welded comes into contact in a practical manner,
Even if R was not made unnecessarily large unlike the comparative example, it was found that the example was practically sufficient.

[0013]

As described above, the ceramic guide pin of the present invention is provided with an R-shaped relief at the outer peripheral portion where the cylindrical body and the frusto-conical tapered seat are connected to each other, so that the tapered seat can be provided. The contact end with the lower electrode can be kept away from the minimum radius position of the R portion, so that there is an effect that stress concentration at a portion where the cylindrical body and the frustoconical tapered seat intersect can be avoided. In addition, the lower electrode of the counterpart is not required to be chamfered, and it is possible to prevent mutual interference, one-sided contact, and occurrence of local stress, and as a result, there is an effect that positioning accuracy is improved. This contributes not only to the guide pin positioning accuracy but also to the nut positioning accuracy.

[Brief description of the drawings]

FIG. 1 is a front view of a ceramic guide pin of the present invention.

FIG. 2 is an enlarged view of a main part of the ceramic guide pin of the present invention.

FIG. 3 is an explanatory view showing a relative positional relationship between a body portion and a tapered seat of a ceramic guide pin of the present invention and a counterpart lower electrode.

FIG. 4 is a front view of a conventional ceramic guide pin.

FIG. 5 is an explanatory diagram showing a relative positional relationship between a conventional ceramic guide pin and a counterpart lower electrode.

FIG. 6 is a front view of a ceramic guide pin of a comparative example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 ceramic guide pin 2 outer peripheral portion where cylindrical body and frustoconical tapered seat are connected 3 R portion 4,54 contact end 5 cylindrical body 6 frustoconical tapered seat 7 lower electrode 8 conical Top 33, 53 R part minimum diameter position (lower end of cylindrical body)

Claims (1)

(57) [Claims] 1. A conical top, cylindrical body portion and frusto-Ri Do from frustoconical tapered seat, the placing head frustoconical tapered seat and locking
In the ceramic guide pins that are used in the welding positioning and use lower electrode contacts, smoothly from the cylindrical barrel portion side face of the outer peripheral portion of said cylindrical body portion and a front wherein the head frustoconical tapered seat to connect Consists only of continuous R-shaped curves
A ceramic guide pin characterized by a relief provided.