Resistance welding electrodes

Abstract

Invention details;

Description

Electrode for Electric Resistance Welding

[0001] The present invention relates to an electrode for electric resistance welding in which a guide pin protruding from an electrode body and a sliding member sliding within the electrode body form a reciprocating member, and the position state of this reciprocating member is improved to cause required elastic deformation in a steel plate component.

[0002] Japanese Patent Laid-Open No. 10-118775 describes an electrode for electric resistance welding for welding a projection nut to a steel plate component, in which a reciprocating member in which a guide pin and a sliding member are integrated is housed within the electrode body of the electrode for electric resistance welding, and moreover, it is described that a part of the guide pin protrudes from the electrode body.

[0003] Japanese Patent Laid-Open No. 10-118775

[0004] In such an electrode, usually, a steel plate component such as an automobile floor panel held by a robot device is placed on the upper surface of the electrode body. However, it is required that the steel plate component be moved toward the electrode body side with the central axis of the lower hole formed in the steel plate component and the central axis of the electrode guide pin aligned, and by realizing this, the projection nut is welded to the steel plate component in a concentric state with the lower hole or a state equivalent thereto.

[0005] However, as shown in FIGS. 5A and 5B, it is difficult to make the lower hole 51, for example, about 5 mm in diameter, formed in the floor panel 50 coaxial with the guide pin 52 in terms of the accuracy of the operation control of the robot device 53. The reason for such difficulty is that in the case of a large steel plate part such as the floor panel 50, it is considered that deflection deformation occurs due to its own weight, resulting in a shift in the position of the lower hole 51 with respect to the guide pin 52. When the steel plate part 50 is moved to the electrode end face side with the lower hole 51 and the guide pin 52 being eccentric, the inner peripheral surface of the lower hole 51 is strongly rubbed against the guide pin 52, and the steel plate part 50 is placed on the mounting surface 54 of the electrode body while the guide pin 52 is inclined (see FIG. 5A). In the structure described in Patent Document 1, the advancing and retreating member composed of the guide pin 52 and the sliding member has a structure in which only the sliding member part slides in the guide hole of the electrode. Therefore, when an external force as described above acts on the guide pin 52, there is a problem that the guide pin 52 inclines.

[0006] In the case of welding a projection nut to a steel plate part, if the guide pin is inclined and eccentric with respect to the lower hole as described above, as shown in FIG. 5B, the threaded hole of the projection nut is welded at an eccentric position shifted from the lower hole 51. Hereinafter, in this specification, the projection nut may be simply expressed as a nut.

[0007] The present invention is provided to solve the above problems. In an electrode for electric resistance welding in which an advancing and retreating member composed of a guide pin and a sliding member is accommodated, even if a part of the steel plate part contacts the guide pin, the purpose is to prevent the advancing and retreating member from easily inclining and to cause elastic deformation in the steel plate between the guide pin and the chuck mechanism of the robot device.

[0008] An electric resistance welding electrode according to one aspect of the present invention comprises: an electrode body on which a steel plate part is placed, which is composed of at least a main cylindrical part and a cap part integrated therewith; the cap part is composed of a tubular part with a circular cross section integrated with the main cylindrical part, and an end member on which the steel plate part is placed and which functions as a cover member for the electrode body; a guide pin with a circular cross section protruding from the end member is integrated with a sliding member inserted slidably into a guide hole formed in the main cylindrical part to form an advancing / retreating member; the electrode is configured to firmly hold an end of the steel plate part with a chuck mechanism of a robot device; a pilot hole through which the guide pin passes relatively when the steel plate part is placed on the electrode body is formed in the steel plate part; a sloped part is formed at the tip of the guide pin whose diameter gradually decreases towards the tip; a support plate disposed deep inside the cap part and made of a synthetic resin material is provided with a through hole with a circular cross section through which the guide pin passes; The outer diameter dimensions of the guide pin and the inner diameter dimensions of the through hole are set so that the guide pin can advance and retreat while its outer surface rubs against the inner surface of the through hole, thereby configuring the advance / retreat member to not substantially tilt relative to the central axis of the electrode; and after the inner periphery of the pilot hole of the steel plate part comes into contact with the inclined part due to the operation of the robot device, when the steel plate part is placed on the end member while the inner periphery of the pilot hole rubs against the inclined part due to the weight of the steel plate part, the guide pin does not substantially tilt and generates elastic deformation in the bending direction or extension direction in the steel plate part between the guide pin and the chuck mechanism, so that the guide pin relatively passes through the pilot hole and the steel plate part is placed on the end member.

[0009] Another aspect of the present invention provides an electric resistance welding electrode having the above-mentioned configuration, wherein a vent hole for sending cooling air into the guide hole is provided in the main cylindrical portion, an air passage is formed in the sliding member, and an air gap is left in a state in which the outer surface of the guide pin advances and retreats while rubbing against the inner surface of the through hole, and the support plate is disk-shaped and its outer diameter is set smaller than the inner diameter of the cylindrical portion of the cap portion, so that a part of the support plate is exposed and protrudes into the space within the cap portion.

[0010] In one aspect of the electric resistance welding electrode according to the present invention, the advancing / retracting member is integrally formed by a guide pin having a circular cross section protruding from an end member of the cap portion and a sliding member slidably inserted into a guide hole formed in the main cylindrical portion. The outer diameter of the guide pin and the inner diameter of the through hole are set so that the outer surface of the guide pin advances and retreats while rubbing against the inner surface of the through hole formed in a support plate within the cap portion. This prevents the advancing / retracting member from substantially tilting relative to the center axis of the electrode. The difference between the outer diameter of the guide pin and the inner diameter of the through hole is small enough that no rattle is felt even when the guide pin is swayed diametrically. In other words, there is substantially no gap between the outer surface of the guide pin and the inner surface of the through hole, allowing for sliding movement.

[0011] The retractable member, which is an integrated unit of a guide pin and a sliding member, is supported at two points: the point where the sliding member slides against the guide hole, and the point where the outer surface of the guide pin rubs against the inner surface of the through hole. When fitting a steel plate part onto the guide pin, if the central axis of the guide pin and the central axis of the pilot hole in the steel plate part are misaligned and in an eccentric state, the inner periphery of the pilot hole in the steel plate part will rub against the inclined portion of the guide pin, causing a force that tries to tilt the guide pin. Even if such a force is applied, the central axis of the retractable member will not easily tilt due to the support at two points.

[0012] On the other hand, since the steel plate part is firmly held by the chuck mechanism of the robot device, there is no risk of the steel plate part being displaced out of the chuck mechanism.

[0013] In this way, the guide pin is not easily tilted, and the steel plate part is not easily released from the chuck mechanism, so when the inner periphery of the pilot hole slides along the inclined portion, elastic deformation occurs in the steel plate between the guide pin and the chuck mechanism. After such elastic deformation, when the steel plate part is placed on the end member, the pilot hole of the steel plate part may become substantially concentric with the guide pin, or may become eccentric to a harmless level.

[0014] The elastic deformation of the steel plate part is caused by bending deformation, elongation deformation, etc. that occurs in the steel plate part. Since the end of the steel plate part is firmly held by the chuck mechanism of the robot device, if the pilot hole of the steel plate part is misaligned with the guide pin, the steel plate part will not slip or be displaced at the chuck mechanism, and the guide pin will not tilt easily, causing bending deformation or elongation deformation on the steel plate part.

[0015] Typically, when welding a nut, the tip of a guide pin has a tapered shape, with the diameter gradually decreasing toward the tip. When the steel sheet component moves toward the electrode end member due to its own weight, the inner periphery of the pilot hole is displaced toward the central axis of the electrode and rubs against the tapered portion. At this time, a force acts on the guide pin in the diametric direction, i.e., a force tending to tilt the guide pin. However, because the two-point support prevents the guide pin from tilting, and there is no slippage or other misalignment of the steel sheet component at the chuck mechanism, the guide pin undergoes elastic radial displacement toward the steel sheet component, reducing the eccentricity between the central axis of the guide pin and the central axis of the pilot hole to a substantially negligible level. In other words, the inner periphery of the pilot hole of the steel sheet component, firmly held by the chuck mechanism, rubs against the guide pin, which is strong enough to prevent tilting, thereby causing elastic deformation toward the steel sheet component.

[0016] The above-described elastic displacement of the steel sheet part in the diametric direction of the guide pin is ensured by generating bending and elongation deformation in the steel sheet part. In the present invention, the elastic deformation of a thin steel sheet part, such as the floor panel or door panel, which is much larger than the size of the pilot hole, is intentionally utilized. In other words, the eccentricity between the central axis of the pilot hole and the central axis of the guide pin is absorbed by the elastic deformation of the steel sheet part. As a form of this elastic deformation, when the distance between the guide pin and the chuck mechanism is shortened, bending deformation occurs in the steel sheet between the guide pin and the chuck mechanism. Furthermore, when the distance between the guide pin and the chuck mechanism is lengthened, elongation deformation occurs in the steel sheet between the guide pin and the chuck mechanism.

[0017] When the above-mentioned robot device holds a steel plate part, the steel plate part is gripped by a chuck mechanism of the robot device or by a chuck mechanism provided on a conveying jig for the steel plate part, and since the misalignment between the guide pin and the pilot hole is absorbed by the elastic deformation of the steel plate part, it is easy to employ the robot device, conveying jig, etc. In other words, the guide pin is not easily tilted, and the chuck mechanism firmly holds the steel plate part, so elastic deformation can be caused on the steel plate part side.

[0018] In the electric resistance welding electrode according to another aspect of the present invention, the cooling air flowing into the electrode body from the inlet passes through the air passages of the sliding member and the ventilation gaps of the guide pin, and a part of the support plate is exposed in a protruding state into the space within the cap, thereby effectively cooling the support plate made of a synthetic resin material, which is effective in improving the durability of the support plate. In particular, since the support plate is located deep within the cap, i.e., near the location where welding heat is generated, the above-mentioned cooling effect is important.

[0019] Furthermore, since a portion of the support plate is exposed and protrudes into the space within the cap, when the support plate expands due to welding heat, the exposed portion bulges into the space within the cap. This expansion deformation toward the space reduces the abnormally strong contact between the inner surface of the through hole and the outer surface of the guide pin, thereby reducing the progression of wear on the inner surface of the through hole to zero or to a level that is essentially harmless, which is effective in improving the durability of the support plate. This phenomenon is thought to be due to the internal stress within the support plate caused by thermal expansion being reduced by the dispersed expansion toward the space.

[0020] The present invention improves the inclination displacement of the guide pin in an electric resistance welding electrode, and can be used to weld floor panels and door panels that are firmly held by a chuck mechanism of a robot device. The present invention can also be used as a welding method that intentionally utilizes the elastic deformation of thin steel sheet parts, such as the panels, that are much larger than the size of the pilot hole. In other words, the present invention can be used as a welding method that uses the elastic deformation of the steel sheet parts to absorb the eccentricity between the central axis of the pilot hole and the central axis of the guide pin.

[0021] 1A is a cross-sectional view of the entire electrode. FIG. 1B is a cross-sectional view taken along the line B-B of FIG. 1A. FIG. 1C is a cross-sectional view of a portion of the electrode. FIG. 1D is a cross-sectional view of a portion of the electrode. FIG. 1E is a perspective view of a support plate. FIG. 1F is a cross-sectional view of an exhaust passage. FIG. 1G is an external view showing an inclined portion of a guide pin. FIG. 1H is an external view showing an inclined portion of a guide pin. FIG. 1I is an external view showing an inclined portion of a guide pin. FIG. 1I is a cross-sectional view of a steel sheet part deviated to the right of the guide pin, showing the state before the steel sheet part is lowered. FIG. 1I is a cross-sectional view of a steel sheet part deviated to the right of the guide pin, showing the state after the steel sheet part is lowered. FIG. 1J is a cross-sectional view of a steel sheet part deviated to the left of the guide pin, showing the state before the steel sheet part is lowered. FIG. 1J is a cross-sectional view of a steel sheet part deviated to the left of the guide pin, showing the state after ... immediately before the nut is welded to the steel sheet part. FIG. 1J is an exaggerated cross-sectional view of an abnormally inclined guide pin, showing the state immediately before welding pressure is applied. 10 is an exaggerated cross-sectional view showing a state in which the guide pin is abnormally tilted, and shows the state when welding pressure is applied.

[0022] Hereinafter, an embodiment of the electric resistance welding electrode of the present invention will be described.

[0023] An embodiment of the present invention will now be described with reference to Figures 1A to 4C.

[0024] First, the parts to be welded will be described.

[0025] The parts to be welded are often perforated parts such as nuts and washers welded to steel plate parts, but in this case, a projection nut 3 is welded to a large steel plate part 2 such as an automobile floor panel or door panel.

[0026] The nut 3 has a square nut body 4 with a screw hole 5 drilled in the center and welding projections 6 provided at the four corners on the bottom. The steel plate part 2 has a pilot hole 7 drilled therein, through which a guide pin (described later) passes.

[0027] Next, the electrode body will be described.

[0028] The cylindrical electrode body 1 is composed of at least a main cylindrical portion 8 and a cap portion 9 integral with the main cylindrical portion 8. The main cylindrical portion 8 is made of a copper alloy such as chromium copper, and the cap portion 9 is preferably made of a copper alloy such as beryllium copper, which has better heat resistance and wear resistance.

[0029] The cap portion 9 is composed of a cylindrical portion 11 with a circular cross section that is integrated with the main cylindrical portion 8 via a threaded portion 10, and an end member 13 that functions as a lid member for the electrode body 1 and on which the steel plate part 2 is placed. The main cylindrical portion 8 is composed of a cylindrical member and has a guide hole 15 with a circular cross section formed therein.

[0030] In this embodiment, the electrodes such as the electrode body 1 are fixed electrodes, and are fixed to a stationary member 42 such as a machine frame. A reciprocating movable electrode 41 corresponding to the fixed electrode is disposed on the central axis O--O.

[0031] Next, the support plate will be described.

[0032] The diameter of the disk-shaped support plate 16 is smaller than the inner diameter of the tubular portion 11, and a through-hole 17 is provided in the center. An insertion hole 18 is formed in the end member 13 from the inside of the cap portion 9, and the support plate 16 is press-fitted into the insertion hole 18. This press-fitting extends partway through the thickness of the support plate 16, leaving a portion of the support plate 16 exposed and protruding into the space 31 within the cap portion 9. As shown in FIG. 1C , the dimension obtained by subtracting the diameter of the support plate 16 from the inner diameter of the tubular portion 11 is indicated by the symbol D1, and the dimension by which a corner portion 19 of the support plate 16 protrudes from the ceiling surface within the cap portion 9 is indicated by L1. The support plate 16 is made of a synthetic resin material such as polyamide resin; in this case, polytetrafluoroethylene (trade name: Teflon, registered trademark), which has excellent heat resistance and abrasion resistance, is used.

[0033] Next, the reciprocating member will be described.

[0034] The guide pin 20, made of ceramic or stainless steel, is a rod-shaped member with a circular cross section, and its tip is formed with a tapered portion 21 whose diameter gradually decreases toward the tip. The opposite side of the tapered portion 21 is a threaded portion. The sliding member 22, slidably inserted into the guide hole 15, is made of a synthetic resin material such as polytetrafluoroethylene (trade name: Teflon, registered trademark). Therefore, the guide pin 20 and the sliding member 22 are integrated to form the advancing / retreating member 23 (see FIG. 1C).

[0035] One possible structure for integrating the guide pin 20 and the sliding member 22 is to cast the end of the guide pin 20 in during injection molding of the sliding member 22, but here a screw structure is used.

[0036] A bolt 25 is formed at the end of the guide pin 20, and this bolt 25 passes through a bottom member 26 of the sliding member 22, a washer 27 is fitted on the bolt, and the bolt is tightened with a nut 28.

[0037] The guide pin 20 protrudes from the end member 13, and the opening corner of the screw hole 5 of the nut 3 matches the inclined portion 21, thereby holding the nut 3 on the guide pin 20. In addition, the pilot hole 7 of the steel plate part 2 is concentric with the guide pin 20.

[0038] 2A, 2B, and 2C show modified examples of the guide pin 20. In FIG. 2A, the outer shape of the inclined portion 21 is curved, and the embodiment shown in FIG. 1A is of this type. In addition, FIG. 2B shows the outer shape of the inclined portion 21 is linear. Furthermore, FIG. 2C shows the case where the inclined portion 21 is located in the middle. In FIGS. 2A, 2B, and 2C, the steel sheet part 2 is shown by a two-dot chain line, and each pilot hole 7 is shown shifted to the right, with the inner periphery on one side of the pilot hole 7 engaging with the inclined portion 21.

[0039] Next, the ventilation structure will be described.

[0040] The ventilation structure is composed of an inlet 29 provided in the main cylindrical portion 8, the guide hole 15, an air passage 30 provided in the sliding member 22, a space 31 inside the tubular portion 11, a small gap 32 (see FIG. 1C ) between the through hole 17 of the support plate 16 and the guide pin 20, an exhaust passage 33 opened in the diameter direction of the end member 13, the ventilation hole 24, and the pilot hole 7 of the steel plate component 2. The area of ​​the passage where the guide pin 20 passes through the through hole 17 may be insufficient to provide sufficient flow path area for ventilation. To address this issue, it is desirable to provide a ventilation groove 35 on the inner surface of the through hole 17, as shown in FIG. 1D .

[0041] An air passage 30 is provided between the sliding member 22 and the guide hole 15, and various structures can be used for this, such as providing a groove in the outer peripheral surface of the sliding member 22 in the same direction as the central axis O-O of the electrode, or by scraping off the outer peripheral surface of the sliding member 22. Here, the latter scraping type is used. That is, flat surfaces 36 are formed in four locations on the outer peripheral surface of the sliding member 22 in the direction of the central axis O-O, and the flat surfaces 36 and the arc-shaped inner surface of the guide hole 15 form the air passage 30.

[0042] The cooling air flow sent in through the inlet 29 is interrupted when the movable end face 38 provided on the upper surface of the sliding member 22 comes into close contact with the stationary inner end face 37 of the support plate 16, and the air flow is resumed when the movable end face 38 separates from the stationary inner end face 37. The stationary inner end face 37 and the movable end face 38 exist on an imaginary plane perpendicular to the central axis O-O. The force pressing the movable end face 38 against the stationary inner end face 37 is obtained by the tension of a compression coil spring 39 arranged in the guide hole 15. One end of the compression coil spring 39 is pressed against the washer 27, and the other end is pressed against an insulating sheet 34 fitted into the inner bottom surface of the guide hole 15.

[0043] After the support plate 16 is press-fitted into the insertion hole 18, the exhaust passage 33 is formed in the electrode diameter direction by drilling. Therefore, as shown in Fig. 1E, a recessed groove 40 having an arc-shaped cross section that forms part of the exhaust passage 33 is formed.

[0044] Next, the loading of steel plate parts by the robot device will be described.

[0045] The robot device 44 is a partial illustration of a typical six-axis type device. Various types of chuck mechanisms 45 are used to firmly hold the ends of the steel plate component 2. While shown simply here, a pair of openable clamping pieces are made of a metal material with excellent wear resistance, and the clamping pieces are opened and closed by an air cylinder. Therefore, when the clamping pieces tightly clamp the steel plate component 2 by the air cylinder, the steel plate component 2 does not easily come out even if a force acts on the steel plate component 2 to release it from the chuck mechanism 45.

[0046] 3A, 3B, and 3C, the pilot hole 7 is shifted to the right with respect to the central axis O-O of the guide pin 20, and the inner periphery on the left side of the pilot hole 7 is caught midway on the inclined portion 21. From this state, the steel plate part 2 descends due to its own weight, with the inner periphery on the left side of the pilot hole 7 rubbing against the inclined portion 21, until it seats on the upper surface of the end member 13. When the steel plate part 2 descends in this manner, the guide pin 20 is barely inclined, so elastic stretching occurs in the steel plate between the guide pin 20 and the chuck mechanism 45, allowing it to descend. The elastic stretching is indicated by the arrow 46.

[0047] 3C, the threaded hole 5 of the nut 3 and the pilot hole 7 of the steel plate part 2 are slightly eccentric, and the advancement of the movable electrode 41 compresses the compression coil spring 39 while the fusion bonding projection 6 is pressed against the steel plate part 2, and then the welding current is passed through to complete the welding. When the advancement of the movable electrode 41 causes the guide pin 20, i.e., the advancing / retracting member 23, to descend, the movable end face 38 separates from the stationary inner end face 37, performing a so-called valve-opening action.

[0048] This allows cooling air to circulate through the aforementioned ventilation structure formed by the inlet 29 provided in the main cylindrical portion 8, the guide hole 15, the air passage 30 provided in the sliding member 22, the space 31 inside the tubular portion 11, the small gap 32 (see FIG. 1C ) between the through hole 17 in the support plate 16 and the guide pin 20, the exhaust passage 33 opened in the diameter direction of the cover member 13, the vent hole 24, and the pilot hole 7 of the steel plate part 2. In addition, spatter scattered from the molten part is discharged to the outside through the exhaust passage 33 via the pilot hole 7 and the vent hole 24.

[0049] 3C, the screw hole 5 of the nut 3 and the pilot hole 7 of the steel plate part 2 are offset by a small, harmless amount, and the advancement of the movable electrode 41 compresses the compression coil spring 39 while the fusion bonding projection 6 is pressed against the steel plate part 2, and then the welding current is applied to complete the welding. When the advancement of the movable electrode 41 causes the guide pin 20, i.e., the advancing and retracting member 23, to descend, the movable end face 38 separates from the stationary inner end face 37, performing the so-called valve-opening action.

[0050] In the cases shown in Figures 4A, 4B, and 4C, the pilot hole 7 is shifted to the left with respect to the central axis O-O of the guide pin 20, and the inner periphery of the right side of the pilot hole 7 is caught midway on the inclined portion 21. From this state, the weight of the steel sheet part 2 causes the inner periphery of the right side of the pilot hole 7 to rub against the inclined portion 21, causing the steel sheet part 2 to descend and seat on the upper surface of the end member 13. Since the guide pin 20 is barely inclined when the steel sheet part 2 descends in this manner, elastic bending deformation in the bulging direction occurs in the steel sheet between the guide pin 20 and the chuck mechanism 45, allowing the descent. The bending deformation in the bulging direction is elastic deformation in the direction of the arrow 48, as shown by the dashed-dotted line 47 in Figure 4.

[0051] As shown in Fig. 4C, the eccentricity between the screw hole 5 and the pilot hole 7 of the steel plate part 2 is a small value that does not cause any actual harm. The circulation of cooling air and the discharge of spatter in the ventilation structure are performed in the same manner as in Figs. 3A, 3B, and 3C.

[0052] 5A and 5B are cross-sectional views showing the problems of the prior art, and the reference numerals used in the above embodiment are used in the figures to make it easier to understand.

[0053] The effects of the embodiment described above are as follows.

[0054] The advancing / retracting member 23 is integrally formed by a guide pin 20 having a circular cross section protruding from the end member 13 of the cap portion 9 and a sliding member 22 slidably inserted into a guide hole 15 formed in the main cylindrical portion 8. The outer diameter of the guide pin 20 and the inner diameter of the through hole 17 are set so that the outer peripheral surface of the guide pin 20 can advance and retreat while rubbing against the inner peripheral surface of the through hole 17 opened in the support plate 16 inside the cap portion 9, thereby preventing the advancing / retracting member 23 from substantially tilting relative to the central axis O-O of the electrode. The difference between the outer diameter of the guide pin 20 and the inner diameter of the through hole 17 is small enough that no rattle is felt even when the guide pin 20 is wobbled in the diametric direction. In other words, there is virtually no gap between the outer peripheral surface of the guide pin 20 and the inner peripheral surface of the through hole 17, allowing for sliding movement.

[0055] The advancing / retreating member 23, which is an integral combination of the guide pin 20 and sliding member 22, is supported at two points: the point where the sliding member 22 slides in the guide hole 15, and the point where the outer circumferential surface of the guide pin 20 rubs against the inner circumferential surface of the through hole 17. When the steel plate part 2 is fitted onto the guide pin 20, if the central axis O-O of the guide pin 20 and the central axis of the pilot hole 7 of the steel plate part 2 are misaligned and eccentric, a phenomenon occurs in which the inner circumferential portion of the pilot hole 7 of the steel plate part 2 rubs against the inclined portion 21 of the guide pin 20, and a force is applied that tries to knock down the guide pin 20. Even if such a force is applied, the central axis O-O of the advancing / retreating member 23 does not easily tilt due to the support at two points.

[0056] On the other hand, since the steel plate part 2 is firmly held by the chuck mechanism 45 of the robot device 44, the steel plate part 2 does not shift out of position and slip out of the chuck mechanism 45.

[0057] In this way, the guide pin 20 is not easily tilted, and the steel sheet component 2 is not easily removed from the chuck mechanism 45. Therefore, when the inner periphery of the pilot hole 7 slides along the inclined portion 21, elastic deformation occurs in the steel sheet between the guide pin 20 and the chuck mechanism 45. After such elastic deformation, when the steel sheet component 2 is placed on the end member 13, the pilot hole 7 of the steel sheet component 2 becomes substantially concentric with the guide pin 20, or becomes eccentric to a level that does not cause any practical harm. Comparing Figures 3A and 3B, a large difference is observed in the clearance of the pilot hole 7, with Figure 3B showing an eccentricity level that does not cause any practical harm. The same is true for Figures 4A and 4B.

[0058] The elastic deformation on the steel plate part 2 side is caused by elastic deformation such as bending deformation and elongation deformation that occurs in the steel plate part 2. Since the end of the steel plate part 2 is firmly held by the chuck mechanism 45 of the robot device 44, even if the pilot hole 7 of the steel plate part 2 is misaligned with the guide pin 20, displacement such as slippage of the steel plate part 20 does not occur at the location of the chuck mechanism 45, and the guide pin 20 does not easily tilt, so bending deformation and elongation deformation occur on the steel plate part 2 side.

[0059] Typically, for example, when welding a nut 3, the tip portion of the guide pin 20 has an inclined shape, e.g., a tapered shape, with the diameter gradually decreasing toward the tip, so that when the steel sheet component 2 moves toward the electrode end member 13 due to its own weight, the inner periphery of the pilot hole is moved in the direction of the central axis O-O of the electrode and rubs against the tapered portion. At this time, a force in the diameter direction of the guide pin 20, i.e., a force trying to tilt the guide pin 20, acts on the guide pin 20. However, since the support at two points described above prevents the guide pin 20 from moving in an inclined direction, and there is no positional displacement such as slippage of the steel sheet component 2 at the chuck mechanism 45, an elastic displacement in the diameter direction of the guide pin 20 occurs toward the steel sheet component 2, and the eccentricity between the central axis O-O of the guide pin 20 and the central axis O1-O1 of the pilot hole 7 is reduced to a level that is not substantially problematic. In other words, the inner periphery of the pilot hole 7 of the steel plate part 2 firmly held by the chuck mechanism 45 is rubbed against the strong guide pin 20, for which tilt displacement is not substantially a problem, so that elastic deformation can be caused toward the steel plate part 2 side.

[0060] The above-described elastic displacement of the steel sheet component 2 in the guide pin diameter direction is ensured by generating bending and elongation deformation in the steel sheet component 2. In this embodiment, the elastic deformation of the steel sheet component 2, such as the floor panel or door panel, which has a thin plate thickness and is much larger than the pilot hole size, is intentionally utilized. In other words, the eccentricity between the central axis O1-O1 of the pilot hole 7 and the central axis O-O of the guide pin 20 is absorbed by the elastic deformation of the steel sheet component 2. As for the mode of this elastic deformation, when the distance between the guide pin 20 and the chuck mechanism 45 is shortened, bending deformation occurs in the steel sheet between the guide pin 20 and the chuck mechanism 45. Furthermore, when the distance between the guide pin 20 and the chuck mechanism 45 is lengthened, elongation deformation occurs in the steel sheet between the guide pin 20 and the chuck mechanism 45.

[0061] When the steel plate component 2 is held by the robot device 44, the steel plate component 2 is gripped by the chuck mechanism 45 of the robot device 44 or by the chuck mechanism 45 provided on the conveying jig for the steel plate component 2, and since any misalignment between the guide pin 20 and the pilot hole 7 is absorbed by the elastic deformation of the steel plate component 2, it is easy to employ the robot device 44 or the conveying jig. In other words, the guide pin 20 is not easily tilted, and the chuck mechanism 45 firmly holds the steel plate component 2, so that elastic deformation can be caused on the steel plate component 2 side.

[0062] The cooling air flowing into the electrode body 1 from the inlet 29 passes through the air passage 30 of the sliding member 22 and the ventilation gap 32 of the guide pin portion, and part of the support plate 16 is exposed in a protruding state into the space 31 within the cap portion 9, so that the support plate 16 made of a synthetic resin material can be effectively cooled, which is effective in improving the durability of the support plate 16. In particular, since the support plate 16 is located deep within the cap portion 9, i.e., in a position close to the location where welding heat is generated, the above-mentioned cooling effect is important.

[0063] Furthermore, because a portion of the support plate 16 is exposed and protrudes into the space 31 within the cap portion 9, when the support plate 16 expands due to welding heat, the exposed portion bulges into the space 31 within the cap portion 9 as shown by the two-dot chain line. This expansion and deformation toward the space 31 reduces the abnormally strong contact between the inner surface of the through hole 17 and the outer surface of the guide pin 20, thereby eliminating wear on the inner surface of the through hole or reducing it to a level that causes virtually no damage, which is effective in improving the durability of the support plate 16. This phenomenon is thought to occur because the internal stress within the support plate 16 caused by thermal expansion is reduced by dispersed expansion toward the space.

[0064] As described above, the electrode of the present invention, which is an electric resistance welding electrode containing an advancing / retracting member consisting of a guide pin and a sliding member, prevents the advancing / retracting member from easily tilting even when a part of a steel plate part comes into contact with the guide pin, and causes elastic deformation in the steel plate between the guide pin and the chuck mechanism of the robot device. Therefore, the electrode can be used in a wide range of industrial fields, such as automobile body welding processes and sheet metal welding processes for home electrical appliances.

[0065] DESCRIPTION OF SYMBOLS 1 Electrode body 2 Steel plate part 3 Projection nut 5 Screw hole 7 Pilot hole 8 Main cylindrical part 9 Cap part 11 Cylindrical part 13 End member 15 Guide hole 16 Support plate 17 Through hole 19 Corner part 20 Guide pin 21 Inclined part 22 Sliding member 23 Advance / retract member 24 Vent hole 29 Inlet 30 Air passage 31 Space 32 Gap 33 Exhaust passage 37 Stationary inner end surface 38 Movable end surface 39 Compression coil spring 44 Robot device 45 Chuck mechanism O-O Central axis of electrode O1-O1 Central axis of pilot hole

Claims

DEPCT681. The electrical resistance welding electrode in which the main body of the electrode, on which the steel plate component is placed, shall include at least a main cylindrical section and a cover section that is integrated with the main cylindrical section. The cover section shall include a cylindrical section with a circular cross-section and be integrated with the main cylindrical section, and an end piece which serves as the cover piece of the main body of the electrode and on which the steel plate component is placed. A guide pin protruding from the end piece and having a circular cross-section shall be integrated with a sliding piece that is sliding into a guide hole formed in the main cylindrical section to form the sliding piece forward and backward. The end of the steel plate component shall be firmly held by a robotic gripping mechanism.The guide hole, through which the guide pin passes relatively far when the steel plate component is placed on the main body of the electrode, is molded into the steel plate component. An inclined section with a gradually decreasing diameter towards the end of the guide pin is molded at the end of the guide pin. The through hole, with a circular cross-section through which the guide pin passes, is arranged in a support plate positioned deeper in the cover section and manufactured with synthetic resin material. The guide pin is structured so that the outer diameter dimensions of the guide pin and the inner diameter dimensions of the through hole are set to allow the outer surface of the guide pin to slide forward and backward as it rubs against the outer surface of the through hole, where the sliding and retracting parts are not significantly displaced at an angle relative to the central axis of the electrode.And when the steel plate component is placed on the end piece, while the outer and inner surfaces of the pilot hole of the steel plate component rub against the inclined part by the weight of the steel plate component itself, after the outer and inner surfaces of the pilot hole of the steel plate component come into contact with the inclined part by the operation of the robotic device, the guide pin will cause elastic deformation in the bending or protruding direction in the steel plate component between the guide pin and the gripping mechanism without significant tilting displacement, and the guide pin will relatively penetrate the pilot hole to place the steel plate component on the end piece.

2. The electrical resistance welding electrode conforms to claim 1, where the vent channel through which cool air is sent into the guide hole is arranged in the main cylindrical part, the air passage is formed in the sliding part, and the vent gap in the state in which the outer surface of the guide pin slides forward and backward while rubbing against the outer and inner surfaces of the through hole is maintained, and the support plate is in the shape of a disc.And the outer diameter dimension of the support plate is set to be smaller than the inner diameter dimension of the cylindrical part of the cover section, so that the support plate section is open in a state of protrusion into the area of ​​the cover section;

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