JP2020199548A - Composite type guide pin in electric resistance-welding electrode - Google Patents

Abstract

To minimize electric conduction phenomenon at an abnormal contact part by utilizing electrical insulation property of a nitride layer formed on a guide pin and to improve heat resistance, wear resistance and so on of the guide pin.SOLUTION: A guide pin 17, which projects from an end face of an electrode body 5 and penetrates a prepared hole 16 of a steel plate component 7, is configured from a heat-resistant metallic material, a slide member 19, which is integrated with the guide pin 17, is configured from an insulative synthetic resin material, the guide pin 17 is press-fitted into an insertion hole 22 of the slide member 19, and the guide pin 17 is provided with a reception hole 18 in which a projection bolt 1 is inserted, or a tapered part 54 which relatively enters into a screw hole 52 of a projection nut 50 and positions the nut 50. The guide pin 17 is press-fitted into the insertion hole 22 of the slide member 19 after formation of a nitride layer 43 over the whole surface area thereof.SELECTED DRAWING: Figure 1

Description

The present invention relates to a composite guide pin in an electric resistance welded electrode in which a guide pin made of a heat-resistant metal material that enters a prepared hole of a steel plate component and a sliding member made of an insulating synthetic resin material are integrated.

Japanese Patent No. 6493847 describes a guide pin made of a heat-resistant metal material having a receiving hole for a projection bolt and a composite guide pin in an electric resistance welded electrode in which a sliding member made of an insulating synthetic resin material is integrated. ing. Further, in Japanese Patent No. 6395068, a guide pin with a tapered portion for locking a screw hole of a projection nut and a composite guide pin in an electric resistance welded electrode in which a sliding member made of an insulating synthetic resin material is integrated are described. Have been described.

Japanese Patent No. 6493847 Japanese Patent No. 6395068

In the technique described in the above patent document, when the guide pin is pushed down, if a force in the tilting direction acts on the guide pin for some reason, the outer peripheral portion of the guide pin comes into contact with the inner surface of the electrode body. When a welding current is applied in such a contact state, sparks are generated at the contact points, causing local melting damage and electrolytic corrosion, which shortens the life of the guide pin and the electrode body. There is.

The present invention has been provided to solve the above problems, and utilizes the electrical insulation of the nitrided layer formed on the guide pin to minimize the energization phenomenon at the contact point between the guide pin and the electrode body. , The purpose is to improve the heat resistance and abrasion resistance of the guide pin.

The invention according to claim 1
A guide pin with a circular cross section that protrudes from the end face of the electrode body and penetrates the pilot hole of the steel plate part is made of a heat-resistant metal material.
A sliding member with a circular cross section, which is integrated with the guide pin and fitted into the guide hole of the electrode body so as to be slidable, is made of an insulating synthetic resin material.
The guide pin and the sliding member are integrated by press-fitting the guide pin into the insertion hole provided in the sliding member.
The guide pin is provided with a receiving hole into which a projection bolt having a welding protrusion is inserted, or a tapered shape portion that relatively enters the screw hole of a projection nut having a welding protrusion to position the nut. Is provided,
The guide pin is a composite type guide pin in an electric resistance welding electrode characterized in that a nitride layer is formed over the entire surface and then press-fitted into an insertion hole of a sliding member.

When a force in the tilting direction acts on the guide pin for some reason, such as the deviation of the central axis of the movable electrode, the welding protrusions of the projection bolt and projection nut are pressed against the mating steel plate parts, and the outer circumference of the guide pin is pressed. The part makes abnormal contact with the inner surface of the electrode body. When the welding current is energized under such a situation, it is divided into two systems, the original welding current flowing from the welding projection to the steel plate component and the stray current or the invalid current to the abnormal contact point. Such diversion occurs, causing stray current corrosion and reactive current corrosion. It is considered that these corrosions are caused by melting damage of the energized local part due to the generation of sparks and generation of electrolytic corrosion.

The guide pin is press-fitted into the insertion hole of the sliding member after forming a nitride layer over the entire surface. Since the nitrided layer has excellent electrical insulation, the electrical conductivity at the abnormal contact point is minimized. That is, by utilizing the electrical characteristics of the nitrided layer, the energization is reduced to a level where there is no actual harm, and therefore, melting damage and electrolytic corrosion in the energized local portion are prevented. Therefore, the energization phenomenon at the abnormal contact point between the guide pin and the electrode body is minimized, and the heat resistance and wear resistance of the guide pin are improved.

The portion where the outer peripheral portion of the guide pin is in abnormal contact with the inner surface of the electrode body is not in a stable energization state, so that the energization is incomplete, which causes electrolytic corrosion. Since the nitrided layer formed on the guide pin substantially de-energizes the incomplete energization, it is possible to eliminate the spark generation and the electrolytic corrosion phenomenon, and the durability of the guide pin is improved.

The outer peripheral surface of the guide pin made of stainless steel or the like remains in a jagged state with cutting tool marks during finishing, which causes a large pressing force when the guide pin is press-fitted into the insertion hole of the sliding member. It is necessary and not preferable in terms of workability. When the nitriding guide pin is press-fitted into the insertion hole of the sliding member, the pressing force is significantly reduced, which is good in terms of workability. The reason why the pressing force decreases is that elements such as nitrogen diffuse and permeate during the nitriding process and react with stainless steel to form a nitride layer, but the angular parts are rounded during the diffusion and permeation of the elements. It is thought that it deforms into a tinged shape.

The present invention is a composite guide pin as described above, but as is clear from the examples described below, it can exist as a method invention that specifies an energization phenomenon of welding current and the like.

It is sectional drawing of an electrode and each part of an electrode. It is sectional drawing which shows the shape of the guide pin surface. It is sectional drawing which shows the guide pin press-fitting state. It is sectional drawing which makes contact with the inner surface of an electrode body with a guide pin. It is sectional drawing which shows the other guide pin.

Next, a mode for carrying out the composite guide pin in the electric resistance welding electrode of the present invention will be described.

1 to 4 show Example 1 of the present invention.

This embodiment is a case where a projection bolt is welded to a steel plate part by electric resistance welding. In the following description, the projection bolt may be simply referred to as a bolt.

First, the projection bolt will be described.

As shown in FIGS. 1 and 4, the iron projection bolt 1 includes a shaft portion 2 on which a male screw is formed, a circular flat flange 3 integrally provided on the shaft portion 2, and a shaft portion 2 side. It is composed of a plurality of welding protrusions 4 provided on the flange surface of the above. Three welding protrusions 4 are provided on the same circle at intervals of 120 degrees.

The dimensions of each part of the bolt 1 are that the diameter and length of the shaft part 2 are 8 mm and 30 mm, respectively, and the thickness and diameter of the flange are 3.2 mm and 20 mm, respectively.

Next, the electric resistance welding electrode will be described.

The entire electric resistance welded electrode is indicated by reference numeral 100. The electrode body 5 made of a conductive material made of a copper alloy such as chrome copper has a cylindrical shape and a circular cross section, and a fixing portion 6 to be inserted into the stationary member 11 and a steel plate component 7 are placed therein. The cap portion 8 is connected at the screw portion 9 to form an electrode body 5 having a circular cross section. A guide hole 12 having a circular cross section is formed in the electrode body 5, and the guide hole 12 is formed with a large diameter hole 13 formed in the fixing portion 6 and a cap portion 8 having a diameter smaller than the large diameter hole 13. A medium-diameter hole 14 and a small-diameter hole 15 having a diameter smaller than the medium-diameter hole 14 are formed, and the large-diameter hole 13, the medium-diameter hole 14, and the small-diameter hole 15 are aligned on the central axis OO of the electrode body 5. It is arranged in a coaxial state.

A guide pin 17 having a circular cross section, which protrudes from the end surface of the electrode body 5 on which the steel plate component 7 is placed and penetrates the prepared hole 16 of the steel plate component 7, is made of a heat-resistant metal material such as stainless steel. The guide pin 17 is provided with a receiving hole 18 into which the shaft portion 2 is inserted, and the depth dimension thereof is set shorter than the length of the shaft portion 2 as shown in FIG. 1 (A).

The sliding member 19 having a circular cross section, which is integrated with the guide pin 17 and fitted into the guide hole 12 of the electrode body 5 so as to be slidable, is an insulating synthetic resin material, for example, polytetrafluoroethylene (trade name = Teflon).・ It is composed of registered trademarks). As another material, it is also possible to use a resin having excellent heat resistance and abrasion resistance from the polyamide resins.

Next, the composite guide pin will be described.

The composite guide pin 21 is formed by integrating the guide pin 17 and the sliding member 19. The guide pin 17 is press-fitted into the insertion hole 22 provided in the center of the sliding member 19, and the guide pin 17 and the sliding member 19 are integrated.

A coupling bolt structure is used to ensure the integration. That is, a coupling bolt 23 is integrally formed at the lower end of the guide pin 17, the coupling bolt 23 is penetrated through the bottom member 24 of the sliding member 19, the washer 25 is assembled, and the lock nut 26 is tightened. The sliding member 19 is arranged so that when the movable electrode 27 paired with the electrode body 5 moves forward and a welding current is applied, the current flows only from the welding projection 4 of the flange 3 to the steel plate component 7. It has an insulating function.

The compression coil spring 28 is fitted between the washer 25 and the inner bottom surface of the guide hole 12, and the tension thereof acts on the sliding member 19. Reference numeral 29 indicates an insulating sheet fitted into the inner bottom surface of the guide hole 12. The tension of the compression coil spring 28 is used as a pressing force on the flow path opening / closing portion described later. The compression coil spring 28 is a pressurizing means, and the pressure of compressed air can be used instead.

FIG. 3 shows an assembly device for the guide pin 17 and the sliding member 19. The pedestal 40 of the sliding member 19 is fixed on the stationary member 11, and the guide pin 17 is press-fitted into the insertion hole 22 of the sliding member 19 fixed therein. The pressurizing piece 41 that pressurizes the guide pin 17 matches the guide pin 17, and is pushed down by a pressurizing means such as a hydraulic cylinder. When the connecting bolt 23 penetrates the bottom member 24 and the guide pin 17 bottoms out against the bottom surface of the insertion hole 22, press fitting is completed.

Next, the correspondence between each part of the sliding member and each part of the guide hole will be described.

A large diameter portion 31 and a medium diameter portion 32 are formed in the sliding member 19, and a guide pin 17 having a diameter smaller than that of the medium diameter portion 32 is integrated. The large-diameter portion 31 is fitted into the large-diameter hole 13 in a state where it can slide with substantially no gap between it and the inner surface of the large-diameter hole 13, and the small-diameter portion 38 is fitted with the inner surface of the medium-diameter hole 14. It is inserted with a ventilation gap 33 for cooling air left between the two.

The above-mentioned "... a state in which the sliding member can slide without a gap ..." means that even if a force in the radial direction of the electrode body 5 is applied to the sliding member 19, there is a rattling feeling. It means a state in which there is no sticking feeling and the sliding in the central axis OO direction is possible.

A guide pin 17 protrudes from the upper surface of the electrode body 1 through the small diameter hole 15. When the guide pin 17 is pushed down, a ventilation gap 34 through which the cooling air passes is formed between the small diameter hole 15 and the guide pin 17.

Next, the intermittent structure of the cooling air will be described.

A vent 35 is formed to guide the cooling air to the guide hole 12. In order to secure an air passage at the sliding portion between the large diameter portion 31 and the large diameter hole 13, a concave groove in the central axis OO direction can be formed on the outer peripheral surface of the large diameter portion 31. As shown in 1 (B), an air passage formed by forming a flat surface portion 36 in the central axis OO direction on the outer peripheral surface of the large diameter portion 31 and being composed of the flat surface portion 36 and the arc-shaped inner surface of the large diameter hole 13. 37 is formed. Such flat surfaces 36 are formed at 90-degree intervals, and air passages 37 are provided at four locations.

A flow path opening / closing portion 39 is formed at the boundary between the medium-diameter hole 14 and the large-diameter hole 13 of the guide hole 12, that is, at the boundary between the medium-diameter portion 32 and the small-diameter portion 38 of the sliding member 19. In the flow path opening / closing portion 39, a plane orthogonal to the central axis OO formed on the sliding member 19 and a plane orthogonal to the central axis OO formed on the cap portion 8 are brought into close contact with each other or separated from each other, so that air is formed. Open and close the flow path.

Next, the abnormal contact between the guide pin and the electrode body will be described.

In addition, the inclination angle and the void dimension of each part of FIG. 4 are exaggerated for easy understanding.

Various phenomena can be considered as factors for tilting the guide pin 17, but here, it is the case where the advancing / retreating axis of the movable electrode 27 is tilted. As shown in FIG. 4, the central axis (advance / retreat axis) XX of the movable electrode 27 is inclined to the state where the bolt 1 is not tilted as shown in FIG. 1, and is in the same direction as the central axis XX. When the movable electrode 27 advances in the direction of the arrow 46, the pressurized end surface 47 of the movable electrode 27 pressurizes the outer peripheral edge of the flange 3, and the bolt 1 tilts to the left side in FIG. FIG. 4B is an enlarged cross-sectional view of this tilted state. When a force in the tilting direction acts on the guide pin 17 due to the tilting displacement of the bolt 1, the sliding member 19 elastically deforms, so that the guide pin 17 The upper end portion contacts the inner surface of the small diameter hole 15. This contact point is indicated by reference numeral 48. Note that FIG. 4A does not show the inclination of the composite guide pin 21, and shows a state in which the guide pin 21 is offset to the left side.

The welding current is divided into two systems: the original welding current flowing from the welding projection 4 to the steel plate component 7, and the stray current or invalid current flowing to the abnormal contact portion 48. Such diversion occurs, causing stray current corrosion and reactive current corrosion. It is considered that these corrosions are caused by melting damage of the energized local part due to the generation of sparks and generation of electrolytic corrosion. As shown in FIG. 4C, such a damaged portion 49 has a portion near the upper end of the guide pin 17 formed over the entire circumference, and the surface is discolored black to have a rough surface state and is thick. Is also getting thinner. Further, a crack 42 is formed. It is considered that the crack 42 is generated by the tilting force of the shaft portion 2 acting on the upper part of the inner surface of the receiving hole 18.

Next, the nitrided layer of the guide pin will be described.

A nitride layer is formed over the entire surface of the guide pin 17. The nitrided layer is formed by a gas nitriding method, a salt bath soft nitriding method, an ionic nitriding method, or the like. Here, it is a salt bath soft nitriding method using a cyanide salt bath, and is also called tuftride. Air is blown into a mixed salt bath of cyanide and carbonate to perform the immersion treatment. By this treatment, nitrogen is thermochemically diffused and permeated from the surface of the guide pin 17.

The satin-like surface layer shown by fine dots in FIGS. 1 (C) and 2 (B) is a nitrided layer. On the outer peripheral surface of the guide pin 17, fine cutting tool marks 44 during finishing are left in a jagged state as shown in FIG. 2 (A), but after the nitriding treatment, the jagged portion 44 is shown in the same figure ( As shown in B), the rounded shape portion 45 is rounded. The cause of such deformation is that elements such as nitrogen diffuse and permeate during the nitriding process and react with stainless steel to form a nitride layer, but the angular parts are rounded during the diffusion and permeation of nitrogen. It is considered that the shape is transformed into a tinged shape.

The effects of Example 1 described above are as follows.

When a force in the tilting direction acts on the guide pin 17 for some reason, such as a deviation of the central axis XX of the movable electrode 27, the welding projection 4 of the projection bolt 1 is pressed against the mating steel plate component 7. , The outer peripheral portion of the guide pin 17 makes an abnormal contact with the inner surface of the small diameter hole 15 of the electrode body 5 at the location of reference numeral 48. When a welding current is applied under such a situation, the original welding current flowing from the welding projection 4 to the steel plate component 7 and a stray current or an ineffective current flowing to the abnormal contact portion 48 are divided into two systems. Such diversion occurs, causing stray current corrosion and reactive current corrosion. It is considered that these corrosions are caused by melting damage of the energized local part due to the generation of sparks and generation of electrolytic corrosion.

The guide pin 17 is press-fitted into the insertion hole 22 of the sliding member 19 after forming the nitrided layer 43 over the entire surface. Since the nitrided layer 43 has excellent electrical insulation, the electrical conductivity at the abnormal contact portion 48 is minimized. That is, by utilizing the electrical characteristics of the nitrided layer 43, the energization is reduced to a level at which there is no actual harm, and thus melting damage and electrolytic corrosion in the energizing local portion 48 are prevented. Therefore, the energization phenomenon at the abnormal contact portion 48 between the guide pin 17 and the electrode body 5 is minimized, and the heat resistance and wear resistance of the guide pin 17 are improved.

The portion 48 in which the outer peripheral portion of the guide pin 17 is in abnormal contact with the inner surface of the small diameter hole 15 of the electrode body 5 is not in a stable energized state, so that the energization is incomplete, which causes electrolytic corrosion. .. Since the nitrided layer 43 formed on the guide pin 17 substantially de-energizes the incomplete energization, it is possible to eliminate the spark generation and the electrolytic corrosion phenomenon, and the durability of the guide pin 17 is improved.

The outer peripheral surface of the guide pin 17 made of stainless steel or the like remains in a state where the cutting tool mark 44 at the time of finishing is jagged, so that when the guide pin 17 is press-fitted into the insertion hole 22 of the sliding member 19. , A large pressing force is required, which is not preferable in terms of workability and the like. When the nitriding guide pin 17 is press-fitted into the insertion hole 22 of the sliding member 19, the pressing force is significantly reduced, which is good in terms of workability. The reason why the pressing force decreases is that elements such as nitrogen diffuse and permeate during the nitriding process and react with stainless steel to form a nitride layer, but the angular parts are rounded during the diffusion and permeation of the elements. It is considered that the shape is deformed into a rounded shape portion 45.

FIG. 5 shows Example 2 of the present invention.

In the second embodiment, the shape of the guide pin 17 is changed for the projection nut. In the following description, the projection nut may be simply referred to as a nut.

The square iron nut 50 is provided with screw holes 52 in the nut body 51 and welding protrusions 53 at the lower four corners.

The guide pin 17 is provided with a tapered portion 54 that relatively enters the screw hole 52 to position the nut 50, and a guide small diameter portion 55 is provided above the tapered portion 54.

When the nitride layer is not formed on the guide pin 17, when the movable electrode 27 advances in the inclined state as shown in FIG. 4 (B), the upper portion of the inclined guide pin 17 comes into contact with the inner surface of the small diameter hole 15. , The damaged portion 49 shown in FIG. 5B is formed by this abnormal contact. The other configurations are the same as those in the first embodiment including the parts (not shown), and the same reference numerals are given to the members having the same functions.

The action and effect of Example 2 is the same as the action and effect of Example 1.

As described above, according to the composite guide pin of the present invention, the electrical insulation of the nitrided layer formed on the guide pin is utilized to minimize the energization phenomenon at the contact point between the guide pin and the electrode body, and the guide pin. Has improved heat resistance and abrasion resistance. Therefore, it can be used in a wide range of industrial fields such as a body welding process for automobiles and a sheet metal welding process for home appliances.

1 Projection bolt 2 Shaft 3 Flange 4 Welding protrusion 5 Electrode body 7 Steel plate part 15 Small diameter hole 16 Pilot hole 17 Guide pin 18 Receiving hole 19 Sliding member 21 Composite guide pin 22 Insert hole 27 Moving electrode 38 Small diameter part 43 Nitride Layer 48 Contact point 49 Damaged part 50 Projection nut 54 Tapered shape part 100 Electric resistance welding electrode

Claims (1)

A guide pin with a circular cross section that protrudes from the end face of the electrode body and penetrates the pilot hole of the steel plate part is made of a heat-resistant metal material.
A sliding member with a circular cross section, which is integrated with the guide pin and fitted into the guide hole of the electrode body so as to be slidable, is made of an insulating synthetic resin material.
The guide pin and the sliding member are integrated by press-fitting the guide pin into the insertion hole provided in the sliding member.
The guide pin is provided with a receiving hole into which a projection bolt having a welding protrusion is inserted, or a tapered shape portion that relatively enters the screw hole of a projection nut having a welding protrusion to position the nut. Is provided,
The guide pin is a composite type guide pin in an electric resistance welded electrode characterized in that a nitride layer is formed over the entire surface and then press-fitted into an insertion hole of a sliding member.

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