Electrode for resistance welding

Abstract

The guide pin (20) is integrated with a sliding member (22) inserted into a guide hole (15) of the main cylindrical part (8) to form an advancing / retreating member (23), and the end of the steel plate member (2) is firmly held by a clamping mechanism (45) of a robot device (44). An inclined portion (21) is formed on the guide pin (20), and a through hole (17) through which the guide pin (20) passes is provided in a support plate (16) made of a synthetic resin material disposed on the cap portion (9). The outer diameter dimension of the guide pin (20) and the inner diameter dimension of the through hole (17) are set such that the guide pin (20) can advance and retreat while the outer peripheral surface of the guide pin (20) can rub against the inner peripheral surface of the through hole (17), whereby the advance and retreat member (23) is configured so that the advance and retreat member (23) does not substantially tilt or displace with respect to the center axis (O-O) of the electrode. The steel plate member (2) between the guide pin (20) and the clamping mechanism (45) is elastically deformed in the bending direction or the extension direction.

Description

Technical Field

[0001] The present invention relates to a resistance welding electrode, which comprises a guide pin protruding from an electrode body and a sliding member sliding in the electrode body to form an advance and retreat member, improve the position state of the advance and retreat member, and make a steel plate member produce the required elastic deformation. Background Art

[0002] Japanese Patent Application Laid-Open No. 10-118775 describes a resistance welding electrode for welding a projection nut to a steel plate member, and describes that an advance and retreat member integrating a guide pin and a sliding member is housed in an electrode body of the resistance welding electrode, and a portion of the guide pin protrudes from the electrode body.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-118775 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In such an electrode, a steel plate component such as the floor of a car held by a robot device is usually placed on the upper surface of the electrode body, but the steel plate component is required to be moved toward the electrode body while the center axis of the lower hole opened in the steel plate component is consistent with the center axis of the electrode guide pin, so that the guide pin can relatively pass through the lower hole. By achieving this requirement, the projection welding nut can be welded to the steel plate component in a state concentric with the lower hole or in a state equivalent to it.

[0008] However, if Figure 5A and Figure 5B As shown, from the perspective of the motion control of the robot device 53, it is difficult to accurately make the lower hole 51, for example, with a diameter of about 5 mm, opened in the base plate 50 and the guide pin 52 coaxial. The main reason for this difficulty is believed to be that when it is a large steel plate component such as the base plate 50, the steel plate component will bend and deform due to its own weight, and the position of the lower hole 51 relative to the guide pin 52 will be offset. When the steel plate component 50 is moved toward the end face of the electrode in a state where the lower hole 51 and the guide pin 52 are eccentric, the inner peripheral surface of the lower hole 51 and the guide pin 52 rub strongly, and the steel plate component 50 will be placed on the placement surface 54 of the electrode body in a state where the guide pin 52 is tilted (see Figure 5A In the structure described in Patent Document 1, the advancing and retreating member composed of the guide pin 52 and the sliding member is a structure in which only the sliding member portion slides in the guide hole of the electrode. Therefore, there is a problem that when the external force as described above acts on the guide pin 52, the guide pin 52 will tilt.

[0009] If the projection welding nut is welded to the steel plate component, when the guide pin is tilted and eccentric relative to the lower hole as described above, Figure 5B As shown, the threaded hole of the projection welding nut is welded at an eccentric position offset from the lower hole 51. Hereinafter, in this specification, the projection welding nut is sometimes simply expressed as a nut.

[0010] The present invention is provided to solve the above-mentioned problems. Its purpose is that, in an electrode for resistance welding that houses an advance and retreat component composed of a guide pin and a sliding component, even if a part of the steel plate component contacts the guide pin, the advance and retreat component is not easy to tilt, and the steel plate between the guide pin and the clamping mechanism of the robot device can be elastically deformed.

[0011] Means for solving problems

[0012] In one aspect of the resistance welding electrode of the present invention, the electrode body for carrying a steel plate component is composed of at least a main cylindrical portion and a cap portion integrated with the main cylindrical portion, the cap portion being composed of a cylindrical portion with a circular cross-section integrated with the main cylindrical portion and an end portion that functions as a cover portion of the electrode body, the end portion carrying the steel plate component, the guide pin with a circular cross-section protruding from the end portion being integrated with a sliding portion that is inserted into a guide hole formed in the main cylindrical portion in a slidable state to form an advance and retreat component, and being configured to firmly hold the end of the steel plate component by using a clamping mechanism of a robot device, the steel plate component being formed with a lower hole, the guide pin relatively passing through the lower hole when the steel plate component is placed on the electrode body, the front end portion of the guide pin being formed with an inclined portion whose diameter gradually decreases toward the front end of the guide pin, and the inner portion of the cap portion being arranged and made of synthetic resin material The support plate is provided with a through hole with a circular cross section, through which the guide pin passes, and the outer diameter of the guide pin and the inner diameter of the through hole are set so that the outer peripheral surface of the guide pin can rub against the inner peripheral surface of the through hole while the guide pin can move forward and backward, thereby constituting that the advance and retreat component does not substantially tilt relative to the central axis of the electrode, and the resistance welding electrode is constructed as follows: after the inner peripheral portion of the lower hole of the steel plate component contacts the inclined portion through the action of the robot device, when the steel plate component is placed on the end component while the inner peripheral portion of the lower hole rubs against the inclined portion due to the weight of the steel plate component, the guide pin does not substantially tilt, and the steel plate component between the guide pin and the clamping mechanism generates elastic deformation in a bending direction or an elongation direction, and the guide pin relatively passes through the lower hole while the steel plate component is placed on the end component.

[0013] In the resistance welding electrode of another aspect of the present invention, in the above-mentioned structure, an air vent for supplying cooling air to the guide hole is provided in the main cylindrical portion, an air passage is formed in the sliding component, and a ventilation gap is retained when the guide pin moves forward and backward while the outer peripheral surface of the guide pin rubs against the inner peripheral surface of the through hole. The support plate is disc-shaped, and the outer diameter of the support plate is set to be smaller than the inner diameter of the cylindrical portion of the cap portion, thereby a portion of the support plate is exposed in a state of protruding into the space inside the cap portion.

[0014] Effects of the Invention

[0015] In one aspect of the resistance welding electrode of the present invention, the advancing and retracting member is constructed by integrating a guide pin having a circular cross-section protruding from an end member of the cap with 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 guide pin can advance and retract while rubbing against the inner circumference of the through hole formed in a support plate within the cap. This configuration ensures that the advancing and retracting member does not undergo substantial tilting displacement 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 minimized to such an extent that even if the guide pin is moved in the radial direction, no rattling or gapping is felt. In other words, there is substantially no gap between the outer circumference of the guide pin and the inner circumference of the through hole, allowing for sliding.

[0016] The advance / retract member, which integrates a guide pin and a sliding member, is supported at two locations: where the sliding member slides against the guide hole and where the outer circumference of the guide pin rubs against the inner circumference of the through hole. When the steel plate member and the guide pin are mated, if the guide pin's central axis is offset from the central axis of the steel plate member's lower hole, friction occurs between the inner circumference of the steel plate member's lower hole and the inclined portion of the guide pin, exerting a force that could cause the guide pin to tilt. Even with this force, the support provided by these two locations prevents the central axis of the advance / retract member from tilting.

[0017] On the other hand, since the steel plate member is firmly held by the clamping mechanism of the robot device, positional deviation that would cause the steel plate member to escape from the clamping mechanism does not occur.

[0018] This prevents the guide pin from tilting and the steel plate component from slipping out of the clamping mechanism. Therefore, when the inner circumference of the lower hole slides along the inclined portion, the steel plate between the guide pin and the clamping mechanism undergoes elastic deformation. After this elastic deformation, when the steel plate component is placed on the end member, the lower hole of the steel plate component and the guide pin are substantially concentric, or have an eccentricity that does not substantially damage them.

[0019] The elastic deformation of the steel plate component is achieved through elastic deformation such as bending or elongation of the steel plate component. The ends of the steel plate component are securely held by the clamping mechanism of the robotic device. Therefore, when the lower hole of the steel plate component deviates from the guide pin, the steel plate component does not experience positional deviation such as sliding at the clamping mechanism, and the guide pin is less likely to tilt, resulting in bending or elongation of the steel plate component.

[0020] Typically, for example, in the case of a weld nut, the front end portion of the guide pin has an inclined portion, such as a tapered shape, with the diameter gradually decreasing toward the front end. Therefore, when the steel plate component moves toward the end member of the electrode due to its own weight, the inner circumference of the lower hole moves along the central axis of the electrode and rubs against the tapered portion. At this time, a force acting in the guide pin's diametrical direction, i.e., a force intended to tilt the guide pin, acts on the guide pin. However, due to the support provided by the two aforementioned locations, the guide pin is substantially prevented from tilting. Furthermore, there is no positional offset, such as sliding, in the area of the clamping mechanism. Therefore, elastic displacement of the guide pin in the diametrical direction occurs on the steel plate component side, reducing the eccentricity between the guide pin's central axis and the lower hole's central axis to a level that is substantially non-problematic. In other words, the inner circumference of the lower hole of the steel plate component, securely held by the clamping mechanism, rubs against the secure guide pin, which prevents tilting, thereby allowing elastic deformation of the steel plate component side.

[0021] The elastic displacement of the guide pin in the diameter direction of the steel plate component side as described above is ensured by causing the steel plate component to deform in the bending direction or the elongation direction. In the present invention, for example, the elastic deformation of a steel plate component such as the aforementioned bottom plate or door plate, which is thin and much larger than the size of the lower hole, is intentionally utilized. In other words, the eccentricity between the center axis of the lower hole and the center axis of the guide pin is absorbed by the elastic deformation of the steel plate component. As a form of this elastic deformation, when the distance between the guide pin and the clamping mechanism is to be shortened, the steel plate between the guide pin and the clamping mechanism is deformed in the bending direction. Furthermore, when the distance between the guide pin and the clamping mechanism is to be lengthened, the steel plate between the guide pin and the clamping mechanism is deformed in the elongation direction.

[0022] When the steel plate component is held by the aforementioned robot device, the steel plate component is grasped by the robot device's clamping mechanism, or by the clamping mechanism of a transport jig provided on the steel plate component. Because the positional offset between the guide pin and the lower hole is absorbed by the elastic deformation of the steel plate component, the robot device or transport jig can be easily used. In other words, because the guide pin is in a state that is not easily tilted and the clamping mechanism firmly holds the steel plate component, elastic deformation can be generated on the steel plate component side.

[0023] In another aspect of the resistance welding electrode of the present invention, cooling air flowing from the inlet into the electrode body passes through the air passages of the sliding member and the ventilation gaps in the guide pin portion, exposing a portion of the support plate protruding into the space within the cap. This effectively cools the synthetic resin support plate and is effective in improving its durability. This cooling effect is particularly important because the support plate is located within the cap, close to the area where welding heat is generated.

[0024] Furthermore, a portion of the support plate is exposed, protruding into the space within the cap. Therefore, when the support plate expands due to welding heat, the exposed portion bulges into the space within the cap. This expansion and deformation into the space mitigates the unusually strong contact between the inner circumference of the through-hole and the outer circumference of the guide pin, thereby reducing wear on the inner surface of the through-hole to zero or to a level that causes virtually no damage, effectively improving the durability of the support plate. This phenomenon is believed to be due to the internal stress within the support plate caused by thermal expansion being reduced by the dispersed expansion into the space.

[0025] The present invention improves the resistance of resistance welding electrodes with respect to the tilting displacement of guide pins, making it suitable for welding floor panels or door panels securely held by a robotic device's clamping mechanism. Furthermore, it can be used as a welding method that intentionally exploits the elastic deformation of thin steel plate components, such as the aforementioned panels, that are significantly larger than the size of the lower hole. In other words, it can be used as a welding method designed to absorb the eccentricity between the center axis of the lower hole and the center axis of the guide pin by utilizing the elastic deformation of the steel plate component. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A It is a cross-sectional view of the entire electrode.

[0027] Figure 1B It is along Figure 1A Cross-sectional view of line BB.

[0028] Figure 1C It is a cross-sectional view of a local portion of the electrode.

[0029] Figure 1D It is a cross-sectional view of a local portion of the electrode.

[0030] Figure 1E It is a three-dimensional view of the support plate.

[0031] Figure 1F It is a cross-sectional view of the exhaust passage.

[0032] Figure 2A This is an external view showing the inclined portion of the guide pin.

[0033] Figure 2B This is an external view showing the inclined portion of the guide pin.

[0034] Figure 2C This is an external view showing the inclined portion of the guide pin.

[0035] Figure 3A It is a cross-sectional view when the steel plate member is offset to the right of the guide pin, and shows the state before the steel plate member is lowered.

[0036] Figure 3B It is a cross-sectional view when the steel plate member is offset to the right of the guide pin, and shows a state where the steel plate member has been lowered.

[0037] Figure 3C It is a cross-sectional view showing a state before the nut is welded to the steel plate member.

[0038] Figure 4A It is a cross-sectional view when the steel plate member is offset to the left of the guide pin, and shows the state before the steel plate member is lowered.

[0039] Figure 4B It is a cross-sectional view when the steel plate member is offset to the left of the guide pin, and shows a state where the steel plate member has been lowered.

[0040] Figure 4C It is a cross-sectional view showing a state before the nut is welded to the steel plate member.

[0041] Figure 5A This is a cross-sectional view showing an exaggerated state in which the guide pin is abnormally tilted, and shows the state before welding pressurization.

[0042] Figure 5B This is a cross-sectional view showing an exaggerated state of abnormal tilt of the guide pin, and illustrates the state during welding pressurization. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the resistance welding electrode of the present invention will be described.

[0044] Example

[0045] Reference Figures 1A to 4C , an embodiment of the present invention is described.

[0046] First, the components to be welded will be described.

[0047] As welding target parts, open hole parts such as nuts and washers are often welded to steel plate parts. Here, projection welding nuts 3 are welded to large steel plate parts 2 such as the floor panel or door panel of an automobile.

[0048] The nut 3 has a threaded hole 5 formed in the center of a square nut body 4 and welding protrusions 6 provided at the four lower corners. A lower hole 7 is formed in the steel plate member 2, and a guide pin described later extends through the lower hole 7.

[0049] Next, the electrode body will be described.

[0050] The cylindrical electrode body 1 is composed of at least a main cylindrical portion 8 and a cap portion 9 integrated with the main cylindrical portion 8. Preferably, the main cylindrical portion 8 is made of a copper alloy such as chromium copper, and the cap portion 9 is made of a copper alloy such as beryllium copper having better heat resistance and wear resistance.

[0051] Cap 9 is composed of a cylindrical portion 11 having a circular cross section, integrated with main cylindrical portion 8 via a threaded portion 10, and an end member 13 that functions as a cover member for electrode body 1. Steel plate member 2 is placed on end member 13. Main cylindrical portion 8 is formed of a cylindrical member and has a guide hole 15 having a circular cross section.

[0052] The electrodes such as the electrode body 1 of this embodiment are fixed electrodes and are fixed to a stationary member 42 such as a machine frame. The movable electrode 41 that moves forward and backward corresponding to the fixed electrode is arranged on the central axis OO.

[0053] Next, the support plate will be described.

[0054] The diameter of the disc-shaped support plate 16 is smaller than the inner diameter of the cylindrical 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 inner side of the cap 9, and the support plate 16 is pressed into this hole. This pressing is carried out to the middle of the thickness of the support plate 16, thereby exposing a portion of the support plate 16 protruding into the space 31 inside the cap 9. Figure 1C As shown, reference numeral D1 denotes the dimension obtained by subtracting the diameter of support plate 16 from the inner diameter of cylindrical portion 11, and reference numeral L1 denotes the dimension of the projection of corner portion 19 of support plate 16 from the top surface inside cap portion 9. Support plate 16 is made of a synthetic resin material such as polyamide resin, and polytetrafluoroethylene (trade name = Teflon, registered trademark) is used here, which has excellent heat resistance and wear resistance.

[0055] Next, the advancing and retreating member will be described.

[0056] The guide pin 20 made of ceramic material or stainless steel is composed of a rod-shaped member with a circular cross section. At its front end, an inclined portion 21 is formed, the diameter of which gradually decreases toward the front end. The opposite side of the inclined portion 21 is a threaded structure. The sliding member 22 inserted into the guide hole 15 in a slidable state 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 advance and retreat member 23 (see Figure 1C ).

[0057] As a structure for integrating the guide pin 20 and the sliding member 22 , a method of insert-molding the end of the guide pin 20 when the sliding member 22 is injection-molded can be considered, but a screw structure is employed here.

[0058] A bolt 25 is formed at the end of the guide pin 20 . The bolt 25 passes through a bottom member 26 of the sliding member 22 , is fitted into a washer 27 , and is fastened with a nut 28 .

[0059] The guide pin 20 protrudes from the end member 13 , and the opening corner of the threaded hole 5 of the nut 3 coincides with the inclined portion 21 , so that the nut 3 is held by the guide pin 20 . Furthermore, the lower hole 7 of the steel plate member 2 and the guide pin 20 are concentric.

[0060] Figure 2A 、 Figure 2B as well as Figure 2C A modified example of the guide pin 20 is shown. Figure 2A In the case where the outer shape of the inclined portion 21 is curved, Figure 1A The embodiment shown is of this type. Figure 2B This is the case where the outer shape of the inclined portion 21 is linear. Figure 2C This is the case where the inclined portion 21 is arranged in the middle portion. Figure 2A 、 Figure 2B as well as Figure 2C In FIG, the steel plate member 2 is illustrated by two-dot chain lines, showing a state in which each lower hole 7 is offset to the right, and an inner peripheral portion of one side of the lower hole 7 is hooked on the inclined portion 21 .

[0061] Next, the ventilation structure will be described.

[0062] The ventilation structure is composed of an inlet 29 provided in the main cylindrical portion 8, a guide hole 15, an air passage 30 provided in the sliding member 22, a space 31 in the cylindrical portion 11, and a small gap 32 between the through hole 17 of the support plate 16 and the guide pin 20 (see FIG. Figure 1C ), the exhaust passage 33 opened along the diameter direction of the end member 13, the vent hole 24 and the lower hole 7 of the steel plate member 2. As for the portion where the guide pin 20 passes through the through hole 17, the flow path area required for ventilation may be insufficient. As a countermeasure, it is preferable to Figure 1D As shown, a vent groove 35 is provided on the inner peripheral surface of the through hole 17 .

[0063] An air passage 30 is provided between the sliding member 22 and the guide hole 15. This configuration can employ various methods, such as providing grooves on the outer circumference of the sliding member 22 aligned with the central axis OO of the electrode, or scraping the outer circumference of the sliding member 22. The latter scraping method is employed here. Specifically, four flat surfaces 36 oriented in the direction of the central axis OO are formed on the outer circumference of the sliding member 22. These flat surfaces 36 and the arcuate inner surface of the guide hole 15 form the air passage 30.

[0064] Regarding the intermittent cooling air flow from the inlet 29, the air flow is interrupted when the movable end surface 38 provided on the upper surface of the sliding member 22 comes into close contact with the stationary inner end surface 37 of the support plate 16. The air flow resumes when the movable end surface 38 moves away from the stationary inner end surface 37. The stationary inner end surface 37 and the movable end surface 38 lie on a virtual plane perpendicular to the central axis OO. The force pressing the movable end surface 38 against the stationary inner end surface 37 is provided by the tension of a compression coil spring 39 disposed within the guide hole 15. One end of the compression coil spring 39 presses against the washer 27, and the other end presses against the insulating sheet 34 embedded in the inner bottom surface of the guide hole 15.

[0065] After the support plate 16 is pressed into the insertion hole 18, the exhaust passage 33 in the electrode diameter direction is formed by drilling. Figure 1E As shown, a groove 40 having an arc-shaped cross section is formed to constitute a portion of the exhaust passage 33 .

[0066] Next, the case of carrying in steel plate components using a robot device will be described.

[0067] The robot device 44 is shown partially and is a typical six-axis device. Various types of clamping mechanisms 45 can be used to securely hold the ends of the steel plate member 2. This is a simplified illustration, but a pair of openable clamping pieces are constructed from a wear-resistant metal material, and the clamping pieces are opened and closed by an air cylinder. Therefore, when the clamping pieces are firmly clamped by the air cylinder, even if a force is applied to the steel plate member 2 in an attempt to remove it from the clamping mechanism 45, it will not easily come out.

[0068] Figure 3A 、 Figure 3B as well as Figure 3CThe illustrated situation shows lower hole 7 offset to the right relative to the central axis OO of guide pin 20, with the inner circumference of the left side of lower hole 7 hooked midway on inclined portion 21. From this position, due to the weight of steel plate component 2, the inner circumference of the left side of lower hole 7 rubs against inclined portion 21 while steel plate component 2 descends and rests on the upper surface of end member 13. As steel plate component 2 descends in this manner, guide pin 20 barely tilts, causing elastic expansion of the steel plate between guide pin 20 and clamping mechanism 45, allowing it to descend. This elastic expansion is indicated by arrow 46.

[0069] Therefore, if Figure 3C As shown, the threaded hole 5 of the nut 3 is slightly eccentric to the lower hole 7 of the steel plate member 2. The forward and backward movement of the movable electrode 41 compresses the compression coil spring 39 and applies pressure to the welding protrusion 6 against the steel plate member 2. Subsequently, the welding current is passed, completing the welding process. When the guide pin 20, or the advancing and retreating member 23, descends due to the forward and backward movement of the movable electrode 41, the movable end surface 38 separates from the stationary inner end surface 37, thereby performing a so-called valve-opening action.

[0070] Thus, the air 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 in the cylindrical portion 11, the small gap 32 between the through hole 17 of the support plate 16 and the guide pin 20 (see Figure 1C Cooling air flows through the ventilation structure formed by the exhaust passage 33, the vent holes 24, and the lower holes 7 of the steel plate member 2, which are opened along the diameter of the cover member 13. Furthermore, spatter scattered from the molten zone is discharged to the outside through the exhaust passage 33 via the lower holes 7 and the vent holes 24.

[0071] Therefore, if Figure 3C As shown, the threaded hole 5 of the nut 3 and the lower hole 7 of the steel plate member 2 have a slight, non-destructive eccentricity. The advancement and retraction of the movable electrode 41 compresses the compression coil spring 39 while applying pressure to the welding protrusion 6 against the steel plate member 2. Subsequently, the welding current is passed, completing the welding process. When the guide pin 20, or the advancing and retracting member 23, is lowered by the advancement and retraction of the movable electrode 41, the movable end surface 38 separates from the stationary inner end surface 37, thereby performing a so-called valve-opening action.

[0072] Figure 4A 、 Figure 4B as well as Figure 4CThe situation shown is a state in which the lower hole 7 is offset to the left relative to the central axis OO of the guide pin 20, and the inner peripheral portion of the right side of the lower hole 7 is hooked in the middle of the inclined portion 21. From this state, due to the weight of the steel plate component 2, the inner peripheral portion of the right side of the lower hole 7 rubs against the inclined portion 21 while the steel plate component 2 descends and sits on the upper surface of the end component 13. When the steel plate component 2 descends in this way, the guide pin 20 is almost not tilted, so the steel plate between the guide pin 20 and the clamping mechanism 45 produces elastic bending deformation in the bulging direction, allowing it to descend. Regarding the bending deformation in the bulging direction, as shown in the image deformation shown by the double-dotted line 47 in Figure 4, it is elastically deformed in the direction of the arrow 48.

[0073] like Figure 4C As shown, the eccentricity between the threaded hole 5 and the lower hole 7 of the steel plate member 2 is a small value that does not cause any actual damage. The cooling air circulation function and the discharge of the sputtering in the ventilation structure are Figure 3A 、 Figure 3B and Figure 3C The same goes for the situation.

[0074] Figure 5A 、 Figure 5B This is a cross-sectional view illustrating problems of the conventional technology, and the reference numerals used in the above-described embodiment are described in this figure for easier understanding.

[0075] The effects of the above-described embodiments are as follows.

[0076] The advance / retract member 23 is an integrated structure consisting of a guide pin 20, which has a circular cross-section and protrudes from the end member 13 of the cap 9, and a sliding member 22, which is slidably inserted into the 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 guide pin 20 can advance and retract while rubbing against the inner circumference of the through hole 17 formed in the support plate 16 inside the cap 9. This ensures that the advance / retract member 23 does not substantially tilt relative to the center axis OO of the electrode. The difference between the outer diameter of the guide pin 20 and the inner diameter of the through hole 17 is minimized to the point where no rattling or other clearance is felt even when the guide pin 20 moves in the radial direction. In other words, there is virtually no clearance between the outer circumference of the guide pin 20 and the inner circumference of the through hole 17, allowing for sliding movement.

[0077] The advance / retract member 23, which integrates the guide pin 20 and the sliding member 22, is supported at two locations: the location where the sliding member 22 slides against the guide hole 15, and the location where the outer peripheral surface of the guide pin 20 rubs against the inner peripheral surface of the through hole 17. When the steel plate member 2 and the guide pin 20 are mated, if the central axis OO of the guide pin 20 is offset from the central axis of the lower hole 7 of the steel plate member 2, friction occurs between the inner peripheral portion of the lower hole of the steel plate member 2 and the inclined portion 21 of the guide pin 20, exerting a force that tends to tilt the guide pin 20. Even with this force, the support at these two locations prevents the central axis OO of the advance / retract member 23 from tilting.

[0078] On the other hand, since the steel plate member 2 is firmly held by the clamping mechanism 45 of the robot device 44 , positional deviation that would cause the steel plate member 2 to escape from the clamping mechanism 45 does not occur.

[0079] In this way, the guide pin 20 is in a state that is not easy to tilt, and the steel plate component 2 is in a state that is not easy to escape from the clamping mechanism 45. Therefore, when the inner peripheral portion of the lower hole 7 slides on the inclined portion 21, the steel plate between the guide pin 20 and the clamping mechanism 45 is elastically deformed. After such elastic deformation, when the steel plate component 2 is placed on the end component 13, the lower hole 7 of the steel plate component 2 and the guide pin 20 are substantially concentric, or have an eccentricity to the extent that no actual damage is caused. Figure 3A and Figure 3B , it can be confirmed that there is a large difference in the space gap of the lower hole 7, Figure 3B It is the amount of eccentricity that does not cause any actual damage. Figure 4A and Figure 4B The same is true in .

[0080] The elastic deformation of the steel plate member 2 is achieved by elastic deformation such as bending deformation or elongation deformation of the steel plate member 2. The end of the steel plate member 2 is firmly held by the clamping mechanism 45 of the robot device 44. Therefore, when the lower hole 7 of the steel plate member 2 deviates from the guide pin 20, since the steel plate member 20 does not slide or other positional deviations at the clamping mechanism 45 and the guide pin 20 is not easily tilted, bending deformation or elongation deformation occurs on the steel plate member 2 side.

[0081] Typically, for example, in the case of a weld nut 3, the front end portion of the guide pin 20 is in the shape of an inclined portion, such as a tapered shape, whose diameter gradually decreases toward the front end. Therefore, when the steel plate component 2 moves toward the end component 13 of the electrode due to its own weight, the inner peripheral portion of the lower hole moves in the direction of the center axis OO of the electrode and rubs against the tapered portion. At this time, a force in the diameter direction of the guide pin 20, that is, a force that attempts to tilt the guide pin 20, acts on the guide pin 20. However, since the guide pin 20 is supported by the above two locations, it is in a state where substantially no tilting movement of the guide pin 20 occurs, and there is no positional offset such as sliding of the steel plate component 2 at the location of the clamping mechanism 45. Therefore, elastic displacement of the guide pin 20 in the diameter direction occurs on the steel plate component 2 side, and the above-mentioned eccentricity between the center axis OO of the guide pin 20 and the center axis O1-O1 of the lower hole 7 is reduced to a level that does not substantially become a problem. That is, the inner peripheral portion of the lower hole 7 of the steel plate component 2 firmly held by the clamping mechanism 45 rubs against the strong guide pin 20 for which tilt displacement is substantially not a problem, thereby enabling elastic deformation of the steel plate component 2 side.

[0082] The elastic displacement of the guide pin in the diameter direction of the steel plate component 2 side as described above is ensured by causing the steel plate component 2 to deform in the bending direction or the elongation direction. In this embodiment, for example, the elastic deformation of the steel plate component 2, which is thin and much larger than the size of the lower hole, such as the aforementioned bottom plate or door plate, is intentionally utilized. In other words, the eccentricity between the center axis O1-O1 of the lower hole 7 and the center axis OO of the guide pin 20 is absorbed by the elastic deformation of the steel plate component 2. As a form of this elastic deformation, when the distance between the guide pin 20 and the clamping mechanism 45 is to be shortened, the steel plate between the guide pin 20 and the clamping mechanism 45 is deformed in a bending direction. Furthermore, when the distance between the guide pin 20 and the clamping mechanism 45 is to be lengthened, the steel plate between the guide pin 20 and the clamping mechanism 45 is deformed in an elongation direction.

[0083] When the steel plate member 2 is held by the aforementioned robot device 44, the steel plate member 2 is grasped by the gripping mechanism 45 of the robot device 44, or by the gripping mechanism 45 of a transport jig provided on the steel plate member 2. Since the positional deviation between the guide pin 20 and the lower hole 7 is absorbed by the elastic deformation of the steel plate member 2, the robot device 44 or the transport jig can be easily used. In other words, since the guide pin 20 is in a state that is not easily tilted and the gripping mechanism 45 firmly holds the steel plate member 2, elastic deformation can be generated on the side of the steel plate member 2.

[0084] 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, leaving a portion of the support plate 16 exposed by protruding into the space 31 within the cap 9. This effectively cools the synthetic resin support plate 16 and is effective in improving the durability of the support plate 16. This cooling effect is particularly important because the support plate 16 is located inside the cap 9, close to the area where welding heat is generated.

[0085] Furthermore, a portion of support plate 16 is exposed, protruding into space 31 within cap 9. Therefore, when support plate 16 expands due to welding heat, the exposed portion bulges into space 31 within cap 9, as shown by the two-dot chain line. This expansion and deformation into space 31 mitigates the abnormally strong contact between the inner circumference of through-hole 17 and the outer circumference of guide pin 20, thereby reducing wear on the inner surface of the through-hole to zero or to a level that effectively causes no damage. This is effective in improving the durability of support plate 16. This phenomenon is believed to be due to the internal stress within support plate 16 caused by thermal expansion being reduced by the dispersed expansion into the space.

[0086] Industrial applicability

[0087] As described above, the electrode according to the present invention, in a resistance welding electrode that houses an advance / retract member composed of a guide pin and a sliding member, prevents the advance / retract member from tilting even if a portion of a steel plate member contacts the guide pin, and allows elastic deformation of the steel plate between the guide pin and the clamping mechanism of a robotic device. Therefore, the electrode can be used in a wide range of industrial fields, including automotive body welding processes and sheet metal welding processes for household appliances.

[0088] Label Description

[0089] 1: Electrode body; 2: Steel plate component; 3: Projection welding nut; 5: Threaded hole; 7: Lower hole; 8: Main cylindrical portion; 9: Cap portion; 11: Cylindrical portion; 13: End component; 15: Guide hole; 16: Support plate; 17: Through hole; 19: Corner portion; 20: Guide pin; 21: Inclined portion; 22: Sliding component; 23: Advance and retreat component; 24: Vent; 29: Inlet; 30: Air passage; 31: Space; 32: Gap; 33: Exhaust passage; 37: Stationary inner end face; 38: Movable end face; 39: Compression coil spring; 44: Robot device; 45: Clamping mechanism; OO: Center axis of electrode; O1-O1: Center axis of lower hole.

Claims

1. A resistance welding electrode, characterized in that: The electrode body on which the steel plate member is placed is composed of at least a main cylindrical portion and a cap portion integrated with the main cylindrical portion. The cap portion is composed of a cylindrical portion with a circular cross section integrated with the main cylindrical portion and an end member that functions as a cover member of the electrode body, and the steel plate member is placed on the end member. A guide pin with a circular cross section protruding from the end member is integrated with a sliding member slidably inserted into a guide hole formed in the main cylindrical portion to form an advance and retreat member. The end portion of the steel plate component is firmly held by a clamping mechanism of a robot device. A lower hole is formed in the steel plate member, and when the steel plate member is placed on the electrode body, the guide pin relatively passes through the lower hole. The front end portion of the guide pin is formed with an inclined portion whose diameter gradually decreases toward the front end of the guide pin. A through hole with a circular cross section is provided on a support plate made of synthetic resin material and arranged in the inner part of the cap, through which the guide pin passes. The outer diameter of the guide pin and the inner diameter of the through hole are set so that the guide pin can move forward and backward while the outer peripheral surface of the guide pin can rub against the inner peripheral surface of the through hole, thereby constituting that the advancing and retreating member does not substantially tilt relative to the central axis of the electrode. The resistance welding electrode is constructed as follows: after the inner circumference of the lower hole of the steel plate component contacts the inclined portion through the action of the robot device, when the steel plate component is placed on the end component while the inner circumference of the lower hole rubs against the inclined portion due to its own weight, the guide pin does not substantially perform an inclined displacement, and the steel plate component between the guide pin and the clamping mechanism undergoes elastic deformation in the bending direction or the elongation direction, and the guide pin relatively penetrates the lower hole while the steel plate component is placed on the end component.

2. The resistance welding electrode according to claim 1, wherein An air vent for supplying cooling air to the guide hole is provided in the main cylindrical portion, and an air passage is formed in the sliding member, which leaves a ventilation gap when the guide pin moves forward and backward while the outer peripheral surface of the guide pin rubs against the inner peripheral surface of the through hole. The support plate is in a disk shape, and its outer diameter is set smaller than the inner diameter of the cylindrical portion of the cap, so that a portion of the support plate is exposed in a state of protruding into the space inside the cap.

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