JP4683351B2 - Electrical resistance welding method for shaft-like parts - Google Patents

Description

  The present invention relates to an electric resistance welding method for a shaft-shaped component in which a welding projection of a shaft-shaped component such as a projection bolt is pressed only on one side of a steel plate component and a welding current is supplied in that state. In the following description, the projection bolt may be simply expressed as a bolt.

  The projection bolt, which is a shaft-like component described in Japanese Patent No. 4032313, has the shape shown in FIG. That is, as shown in FIG. 1B, reference numeral 1 denotes the entire projection bolt, and a shaft portion 2 on which a male screw is formed, and a diameter integrally formed with the shaft portion 2 and larger than the diameter of the shaft portion 2. The circular enlarged diameter portion 3 and the circular welding protrusion 4 formed at the center of the enlarged diameter portion 3 on the side opposite to the shaft portion 2 are arranged. The said enlarged diameter part 3 is what is called a flange, and the volt | bolt 1 is iron.

  The shaft portion 2 of the bolt 1 is held in the receiving hole 6 of the movable electrode 5, the welding protrusion 4 of the bolt 1 is pressed against the steel plate part 8 placed on the fixed electrode 7, and a welding current is passed in that state. Then, the welding projection 4 is welded to the steel plate part 8. The code | symbol 11 has shown the welding part. And the welding protrusion 4 shown here is made into the flat shape which has the taper surface 9 which inclined slightly, as shown to the same figure (B).

  The movable electrode 5 is advanced and retracted by an advancing / retreating drive means (not shown) such as an air cylinder, and the receiving hole 6 is provided on the center line of the movable electrode 5 at the center of the end face. And the permanent magnet 10 which hold | maintains the volt | bolt 1 in the back of the receiving hole 6 is arrange | positioned.

Further, in the welding method described in Japanese Patent Application Laid-Open No. 2008-44003, the projection bolt 1 is deformed from the one shown in FIG. 9B, and a circular cross-section member such as a pipe material is subjected to electric resistance welding. Yes. Here, in order to adapt to the pipe material, both sides of the enlarged diameter portion 3 and the welding projection 4 are cut into an oval shape. The projection bolt 1 having such a shape is welded in the manner shown in FIG. The longitudinal direction of the oval shape is the same as the axial direction of the pipe material. The pipe material 41 is supported by the V-block type fixed electrode 42, the movable electrode 5 holding the bolt 1 advances from the diameter direction of the pipe material 41, and the welding projection 4 is pressed against the cylindrical surface of the pipe material 41. The welding current is energized to complete the welding.

Japanese Patent No. 4032313 JP 2008-44003 A

  In welding like patent document 1 shown in FIG. 9, the three members of the enlarged diameter part 3, the welding protrusion 4 and the steel plate part 8 are sandwiched between the electrodes 5 and 7 and pressed, A welding current is applied. Since such a welding operation is performed, the welding projection 4 is pressed against the steel plate part 8 with a predetermined pressure, and at this time, the steel plate part 8 is stationary on the fixed electrode 7 without being deformed. Therefore, by setting the current value of the welding current and the energization time to a predetermined value, an appropriate shape of the welded portion 11 can be secured, and sufficient welding strength is obtained.

  In this way, the melted part 11 having a predetermined diameter and thickness is obtained because the enlarged diameter part 3 and the steel plate part 8 are sandwiched between the electrodes 5 and 7. It is difficult to dissipate heat, and therefore, the melting range of the welded portion 11 becomes appropriate over the diameter direction and the thickness direction.

  However, when a member having a heat dissipation prevention function such as the fixed electrode 7 does not exist on the back surface of the steel plate component 8 on the side opposite to the surface against which the welding projection 4 is pressed, that is, the welding projection 4 is a steel plate. When pressure is applied only to the surface of the component 8 and the back surface on the opposite side is exposed to the open space, a large amount of heat generated by energization is dissipated from the back surface of the steel plate component 8 to the open space. There is a problem that it becomes difficult to ensure the melted state of the welding protrusion 4 and the steel plate part 8 as prescribed, and an appropriate welded portion 11 cannot be obtained.

  On the other hand, in welding as in Patent Document 2 shown in FIG. 10, when the welding projection 4 of the bolt 1 is pressed against the cylindrical surface of the pipe material 41 and a welding current is applied, the center of the welding projection 4 is obtained. As the melting progresses, the plate material softens and the welding projection 4 pushes the plate material toward the center of the pipe material 41. Due to the plastic deformation of the plate material, the plate material bulges toward the center side of the pipe material 41. This bulge is indicated by reference numeral 43. That is, since pressurization is performed from the outside of the cylindrical plate material, the plate material itself has high rigidity, so that the above-described pushing is started by heat softening of the plate material. In this way, the pressed plate material is dented inward in a state of being buckled by high-temperature softening, and plastic deformation is formed. Here, the same reference numeral 11 as the previous one is also written in the welded portion.

  When the pressure is applied to the pipe material 41 as described above, the cylindrical surface having high rigidity is pressed. Therefore, it is necessary to make the pressing force extremely high, and the pushing amount (dent amount) is made uniform. It becomes difficult to maintain.

  The present invention is provided in order to solve the above-described problems. Both the welding projection and the steel plate component are provided by using the elastic deformation imparted to the steel plate component while giving the welding projection a heat storage function. An object of the present invention is to provide an electric resistance welding method for a shaft-shaped part that secures a sufficient amount of metal melting and forms a sound weld.

The invention according to claim 1 includes a shaft portion, a circular enlarged portion formed integrally with the shaft portion and having a diameter larger than the diameter of the shaft portion, and a diameter-enlarged portion opposite to the shaft portion. A shaft-shaped part provided with a circular welding protrusion that is arranged in the center and performs a heat storage function by melting and semi-melting with energization of a welding current is prepared, and the shaft part of the shaft-shaped part is used as a pressure electrode. The shaft-shaped part is held in the pressure electrode by being inserted into the provided receiving hole, the shaft-shaped part is welded on one side, and the other side on the opposite side is supported by the support member and exposed to the open space. The plate electrode of the steel plate part is bent in the advance direction side of the pressurizing electrode by pushing the welding protrusion on only one side of the steel plate part and pushing the welding protrusion on the flat plate steel plate part. Then, the welding current is applied and a welding current is applied. Thermal storage heat of molten and semi-molten at the said other side so as to exceed the heat radiation amount to the open space, electric heating amount and volume of the fusion bonding projection welding current is set, released from the other side The heat dissipation to the space is performed from the surface area range of the other surface side corresponding to the melted area of the melted portion in the welding projection, and the welding projection as seen in the axial direction of the shaft-shaped component with respect to the thickness of the enlarged diameter portion The ratio of the height is set in a range from 1.3 in which the volume of the melted part and the semi-molten part in the welding protrusion can be secured to 3.0 in which the volume of the melted part and the semi-molten part in the welding protrusion is not excessive. It is a value that can fulfill the heat storage function in the welding projection, and the elastic restoring force due to the elastic deformation of the steel plate part acts against the melting portion and the semi-melting portion at the same time as melting and semi-melting in the welding projection. While melting the solidified part Prolongs the time required and promotes the expansion of the steel plate part in the thickness direction and the surface direction of the molten part, and then restores the steel plate part that was elastically deformed by solidification of the molten part and retraction of the pressure electrode An electric resistance welding method for a shaft-shaped part characterized in that:

  When the welding protrusion is pressed onto the steel plate component by the advancement of the pressurizing electrode, the surface of the steel plate component opposite to the pressurizing electrode is exposed to the open space, so the flat steel plate component is the plate material Is deformed elastically in the advancing direction of the pressure electrode in a state where is bent. When a welding current is applied in this state, the tip end side of the welding projection first enters a molten state, and the melting region expands as the energization time elapses. Synchronously with this, the surface portion of the steel plate part is also in a molten state. At that time, the diameter-expanded portion side of the melted portion of the welding protrusion gradually becomes a semi-molten state, and a softened layer is formed. Further, the softened layer gradually changes to become a solid part. The heat storage function in the welding protrusion is performed by the molten state or the semi-molten state as described above.

  As described above, the melted state and the semi-molten state of the welding protrusion form a state in which heat is stored in the welding protrusion during or immediately after energization of the welding current. In such a heat storage state, the elastic restoring force accompanying the elastic deformation described above acts on the molten part and the semi-molten part in the steel plate part, so the molten part expands in the thickness direction and surface direction of the steel plate part. To be promoted. Since this molten part is replenished with heat from the semi-molten part adjacent to it, the time required for solidification of the molten part becomes longer, thereby expanding the molten part to both the welding protrusion and the steel plate part. As a result, a welded part shape that provides sufficient welding strength is formed.

  Since the steel plate component is flat, the plate itself is easily bent, the elastic deformation is reliably formed and an elastic reaction force can be ensured, and the elastic pressure force on the melting part and the semi-melting part is sufficiently applied. An appropriate welded portion shape is formed.

  The amount of heat generated by the welding current and the volume of the welding projection are set so that the amount of heat supplied to the melted portion by heat storage of the welding projection exceeds the amount of heat released from the other surface side of the steel plate part to the open space. . By doing so, the time required for solidification of the melted part is prolonged as described above, and the melted part expands to both the welding protrusion and the steel plate part.

  In addition, when the pressure electrode is retracted after the melted portion is solidified, the plate material of the steel plate component that has been elastically deformed can be restored and returned to the shape of the predetermined steel plate component. Steel plate parts are secured.

  The invention according to claim 2 is the electric resistance welding method for a shaft-like part according to claim 1, wherein the flat plate-like steel plate part includes a plate material which is regarded as a substantially flat plate which is slightly curved.

  For example, in the case of a steel plate part such as a roof panel of an automobile, the shape may be almost a flat plate having a curvature radius of 3000 mm. In such a shape, a plate material that is substantially regarded as a flat plate is a counterpart member for welding. The above-described welding process can be performed as expected even for such a steel plate part having a small curvature. Note that when the shaft-shaped part is directly resistance-welded to the roof panel, minute irregularities are formed on the surface and the appearance quality is deteriorated. Therefore, actually, the slightly curved shape arranged along the roof panel is reduced. A shaft-like component is welded to a reinforcement (reinforcing member) from one side by electric resistance welding.

The height of the welding projection viewed in the axial direction of the shaft-like part with respect to thickness before Symbol enlarged section that is set to a value that can play a heat storage function by melting and half-melted in the fusion bonding projection.

  By setting the height dimension of such a welding protrusion, a sufficient heat storage function is exhibited.

The ratio of the height of the welding projection viewed in the axial direction of the shaft-like part with respect to thickness before Symbol enlarged portion, Ru der 1.3 to 3.0.

  A sufficient heat storage function is exhibited by setting the height dimension of such a welding projection as in the above ratio.

  The present invention is an invention of an electrical resistance welding method for a shaft-shaped component as described above, but as is clear from the examples described below, the initial melted part and the dimensions and the like of each part of the welding projection were specified. It can exist as an invention of a part shape of “electrical resistance welding shaft-like part or projection bolt”.

It is a side view which shows the shape and dimension of a volt | bolt. It is the side view and perspective view which show the state welded. It is sectional drawing which shows a welding process. It is sectional drawing which shows a welding completion state. It is sectional drawing which shows the site | part division of the welding projection part. It is sectional drawing which shows the fusion | melting at the time of welding, and a semi-molten state. It is sectional drawing which shows the welding to another steel plate component. It is a side view of the inclined welding state. It is sectional drawing and a side view which show a prior art. It is sectional drawing which shows other prior art.

  Next, an embodiment for carrying out the electric resistance welding method for a shaft-shaped part of the present invention will be described.

  1 to 8 show a first embodiment.

  There are various types of shaft-shaped components, but the shaft-shaped components in this embodiment are projection bolts.

  First, the projection bolt will be described.

  The iron bolt 12 to be welded in this embodiment includes a shaft portion 13 on which a male screw is formed, and a circular flange-like shape that is formed integrally with the shaft portion 13 and has a diameter larger than the diameter of the shaft portion 13. The enlarged diameter portion 14 and the circular welding protrusion 15 disposed at the center of the enlarged diameter portion 14 on the opposite side to the shaft portion 13 are configured. And the welding protrusion 15 shall fulfill | perform the heat storage function by fusion | melting and semi-melting with energization of welding current. On the end face of the welding protrusion 15, an initial melting portion 17 having a taper portion 16 with a small inclination angle θ that becomes lower on the outer peripheral side is formed. A top portion 18 is formed at the center of the tapered portion 16.

  The dimensions of each part of the bolt 12 are as follows. The diameter D1 of the shaft portion 13 is 9 mm, the diameter D2 of the enlarged diameter portion 14 is 13.5 mm, the diameter D3 of the welding projection 15 is 11 mm, the thickness T1 of the enlarged diameter portion 14 is 1.1 mm, and the initial melting portion 17 is included. The total height H1 of the welding projection 15 is 2.5 mm, the height H2 of the initial melting portion 17 is 0.5 mm, the height H3 of the portion excluding the initial melting portion 17 of the welding projection 15 is 2 mm, and the taper portion 16 The inclination angle θ is 10 degrees.

  The top portion 18 is finished to have a sharp shape by machining, a slightly rounded shape by die molding, or the like, and the current density at the initial energization is almost the same. This also applies to the case of a circular flat surface portion 21 having a slight diameter, as shown in FIG.

  Next, the electric resistance welding state of the bolt will be described.

  As shown in FIG. 2 (A), a receiving hole 20 into which the shaft portion 13 of the bolt 12 is inserted is provided in the pressure electrode 19 that is operated by advancing / retreating drive means such as an air cylinder (not shown). . The receiving hole 20 is opened from the end face side in a state of being coaxial with the axis of the pressure electrode 19. When the shaft portion 13 is inserted into the receiving hole 20, the enlarged diameter portion 14 comes into close contact with the end face of the pressure electrode 19. In order to maintain this close contact and prevent the bolt 12 from falling, a permanent magnet 22 is fixed to the back of the receiving hole 20.

  A flat steel plate component 23 is supported by a support jig 24 that is a support member, and the support jig 24 is disposed at a location away from the axis of the pressurizing electrode 19. The bolt 12 is welded to one side 25 which is the surface of the steel plate part 23, and there is nothing in contact with the other side 26 which is the back side of the steel plate part 23, and it is exposed to the open space 27. Reference numeral 28 denotes a transformer, which is connected to the pressure electrode 19 and the steel plate part 23. The plate thickness T2 of the steel plate component 23 used here is 1 mm.

  FIG. 2B is a plan view of the steel plate part 23. The steel plate part 23 is supported by the four support jigs 24, and the support jigs 24 are arranged just at the corners of the square. The relative positions of the pressure electrode 19 and the support jig 24 so that the central portion of the bolt 12 supported by the pressure electrode 19, that is, the top portion 18 of the taper portion 16 presses the center portion of the four support jigs 24. Is set. Thus, when the top part 18 pressurizes the place furthest from each support jig 24, the steel plate component 23 is elastically deformed in the advance direction side of the pressurizing electrode 19. Due to this elastic deformation, the plate material itself of the steel plate component 23 is bent into a curved shape.

  It is also possible to perform welding by changing the position of the top 18 to the position indicated by reference numerals 18a and 18b. In this case, since it is close to the support jig 24, the amount of elastic deformation is smaller than in the case of the central portion.

  2 (A) and 2 (B) is a flat plate in which the plate material of the steel plate component 23 has a completely flat surface such as a horizontal surface, but is as if it has a curved radius of, for example, 3000 mm, like a roof panel of an automobile. The bolt 1 may be welded to the steel plate part 23 close to. This case is shown in FIG. 2 (D) and FIG. 2 (E), which is an EE cross-sectional view thereof. The roof panel 44 is supported by the support jig 24 in an inverted state, with the lower side in the figure being the upper side of the vehicle body and the upper side being the indoor side of the vehicle body. FIG. 2D is a cross-sectional view taken along a plane orthogonal to the front-rear direction of the automobile. The plate material is indicated by a thick line, and the thickness of the plate is not shown. The roof panel 44 has a remarkably large radius of curvature and has a completely flat plate appearance. The curvature radius is, for example, 3000 mm to 4000 mm.

  Since such a roof panel 44 is an outer plate, when the bolts 1 are directly welded, irregularities are generated on the outer surface, and therefore, bolt welding is usually performed on a reinforcement (reinforcing member) 45 disposed on the inside. The lean reinforcement 45 has the same curved shape as that of the roof panel 44 and is arranged along the inside of the roof panel 44. The end portion of the reinforcement 45 is joined to the roof panel 44 by spot welding. Reference numeral S indicates this spot weld. A structural adhesive 46 is filled between the roof panel 44 and the reinforcement 45 to prevent the roof panel 44 from vibrating membrane during traveling.

  The roof panel 44 and the reinforcement 45 seen in FIG. 2 (E) extend in a direction perpendicular to the paper surface of FIG. 2 and have a slight curvature in that direction.

  Instead of the steel plate component 23 shown in FIGS. 2A and 2B, the bolt 12 may be welded to a steel plate closed cross-section structure 29 shown in FIG. The closed cross-section structure 29 is obtained by spot welding a bending member 31 having a hat-shaped cross section to a flat plate 30, and the internal space of the closed cross-section structure 29 is the above-described open space 27. A location where the bolt 12 is pressed is a flat plate material. Such a closed cross-section structure 29 is generally employed in a frame member of a floor plate of an automobile body, a pillar, or the like.

  Various welding conditions in the state shown in FIG. 2 (A) are as follows. The pressurizing force of the pressure electrode 19 is 15 kgf, the current value of the welding current is 8000 amperes, and the energization time is 3 cycles (1 cycle is 1/60 second).

  Next, the welding process will be described.

  3 (A) to 3 (D) and FIG. 4 show a changing process of welding that occurs in the welding protrusion 15 and the steel plate part 23. FIG. 3 (A) shows a state in which the pressure electrode 19 (not shown in FIG. 3) has advanced and the top 18 of the welding projection 15 is in contact with one side 25 of the steel plate part 23. . As shown in FIG. 5B, the pressurization electrode 19 further advances, and the advancement of the pressurization electrode 19 stops at a place where a predetermined pressure is applied. In this state, the steel plate part 23 is elastically deformed in a state where the plate material is bent in the pressurizing direction of the pressurizing electrode 19 by the pressurizing force of the pressurizing electrode 19. When energization of the welding current is started in this state, a slight melting of the welding projection 15 and the steel plate part 23 is first started from the top 18. The melted or welded part is indicated by reference numeral 32.

  As shown in FIG. 3C, the steel plate part 23 is elastically deformed, and thus the elastic reaction force acts as an elastic restoring force. An arrow line 33 indicates this elastic restoring force. When energization is further continued in this state, the melting part 32 spreads over almost the entire area of the initial melting part 17. Since the elastic restoring force 33 is acting, expansion of the melting part 32 is promoted.

  Next, when the energization is interrupted, or when the energization is interrupted after the energization is slightly continued, as shown in FIG. 4D, the melted portion 32 is moved into the same figure (C ) And the welding is finished.

  As shown in FIG. 4, after cooling, when the welding portion 32 is solidified and the pressure electrode 19 is retracted, the steel plate part 23 that has been elastically deformed is restored to a flat state. That is, it returns to the above-mentioned complete flat plate shape. In this embodiment, a gap 35 is formed between the enlarged diameter portion 14 and the single-sided side 25 in the state of completion of welding in FIG.

  FIG. 5 is a cross-sectional view showing the regions of the respective parts for easy understanding.

  Next, the heat storage function will be described.

  As described above, the front end side of the welding projection 15, that is, the initial melting portion 17 is in a molten state, and in synchronization with this, the one side 25 of the steel plate part 23 is also in a molten state. In that case, the diameter-expanded part 14 side of the fusion | melting part 32 of the welding protrusion 15 will be in a semi-molten state gradually, and a softening layer is formed. Further, the softened layer gradually changes to become a solid part. The heat storage function in the welding protrusion 15 is achieved by the molten state or the semi-molten state as described above.

  As described above, the melted state and the semi-molten state of the welding projection 15 form a state in which heat is stored in the welding projection 15 during energization of the welding current or immediately after energization. In such a heat storage state, the steel plate part 23 has the elastic restoring force 33 accompanying the elastic deformation described above acting on the melting part 32 and the semi-melting part 36 in a reaction force, so that the melting part 32 is in the thickness direction of the steel sheet part. And expansion in the surface direction is promoted. Since the melted portion 32 is replenished with heat from the semi-molten portion 36 adjacent to the melted portion 32, the time required for solidification of the melted portion 32 is lengthened. A welded part shape is formed that expands to both parts 23 and provides sufficient welding strength.

  Control of the heat generation amount of the welding current and the welding protrusion 15 so that the heat supply to the melting part 32 due to heat storage of the welding protrusion 15 exceeds the heat radiation amount from the other surface side 26 of the steel plate part 23 to the open space 27. The volume is set. By doing so, the time required for solidification of the melting part 32 is prolonged as described above, and the melting part 32 expands to both the welding protrusion 15 and the steel plate part 23.

  FIG. 6 is an enlarged cross-sectional view of the stage shown in FIG. At this stage, the melted portion 32 painted black is formed over both the initial melted portion 17 and the steel plate part 23, and a semi-molten portion 36 is gradually formed adjacent to the enlarged portion 14 toward the enlarged diameter portion 14 side. By forming the melted part 32 and the semi-molten part 36 in this way, a heat storage function is imparted to the welding protrusion 15. The semi-molten portion 36 is present in a layered state, although no boundary line appears in the fluidized portion 36A in FIG. 6 where the satin is hatched and the softened portion 36B where only the satin is applied. .

  The fluidized part 36 </ b> A is assimilated to the molten part 32 by the action of the elastic restoring force 33 of the steel plate part 23. At the time of assimilation, the softening part 36B cannot flow due to hardening accompanying cooling, and remains a function of supplying heat. As described above, a heat storage function is performed on the welding protrusion 15 by replenishing heat from the melting part 32 itself and the semi-melting part 36, and the melting part 32 further expands in the thickness direction of the steel plate part 23. This enlarged region 37 is indicated by a two-dot chain line 38. By promoting the melting up to the region indicated by the two-dot chain line, the welded portion dimension in the thickness direction of the steel plate part 23 is increased, so that the welding strength can be increased.

  Since the elastic restoring sword 33 is acting on the steel plate part 23 in replenishing the heat quantity from the melting part 32 itself and the semi-melting part 36 as described above, the welding protrusion 15 and the steel plate part 23 having fluidity and deformability. This metal part is enlarged to the enlarged region 37. In other words, since the amount of heat is replenished, the time required for solidification of the melting part 32 is prolonged, and the melting region expands from the melting part 32 toward the two-dot chain line 38.

  The welding strength of the bolt 12 welded through the above process was measured. The measurement was performed by fixing the steel plate part 23 with a jig and pulling the shaft portion 13 of the bolt 12 in the axial direction. As a result, when the traction force of the shaft portion 13 reached 253 kgf, the plate portion of the steel plate component 23 was broken into a circle together with the welded portion 32 and was torn off from the steel plate component 23 and separated. That is, the fusion | melting part 32 and the steel plate component 23 were united, the circular fracture | rupture was formed, and the steel plate component 23 was in the state with the hole. Alternatively, as a result of hitting the bolt 12 with a hammer in the bending direction, the bolt 12 is inclined by about 45 degrees with respect to the steel plate part 23, and the semicircular portion of the steel plate part 23 remains with the molten portion 32 and the steel plate part 23 being integrated. It broke. Since sufficient welding strength can be ensured in this way, it has been confirmed that, for example, mounting the heat exchanger of the air conditioner to the dash panel of the automobile with the bolts 12 can be realized with high reliability.

  Next, the dimensional state of each part of the bolt will be described.

  An appropriate range is set for the height, diameter, and the like of the welding protrusion 15 in order to exhibit the heat storage function.

  In the embodiment, the ratio of the height H1 of the welding projection 15 as viewed in the axial direction of the bolt 12 to the thickness T1 of the enlarged diameter portion 14 is 2.3. This ratio is desirably 1.3 to 3.0. If the ratio is less than 1.3, the height of the welding protrusion 15 is too low to sufficiently secure the volume of the melted part 32 or the semi-molten part 36, and there is a risk of insufficient heat supplementation. Moreover, when this ratio exceeds 3.0, the height of the welding protrusion 15 is too high, and the volume of the fusion | melting part 32 and the semi-molten part 36 becomes excessive, and it is necessary to make energization time unusually long for thermal storage. Is economically disadvantageous. Further, when the volume of the melted part 32 or the semi-molten part 36 becomes excessive, the amount of deformation in the axial direction of the welding projection 15 becomes excessive, and therefore the distance from the surface of the steel plate part 23 to the tip of the shaft part 13 is uneven. This is not preferable in terms of component accuracy.

  In the embodiment, the inclination angle θ is 10 degrees. The inclination angle θ is desirably 7 degrees to 15 degrees. If this angle is less than 7 degrees, the shape of the initial melted portion 17 is too flat, and it becomes difficult to increase the current density of the top portion 18, and reliable start of initial melting cannot be obtained. If this angle exceeds 15 degrees, the current density of the top portion 18 increases, but the shape of the initial melted portion 17 becomes too thick, the volume of the initial melted portion 17 becomes excessive, and melting does not proceed smoothly. There is.

  In the embodiment, the ratio of the diameter D3 of the welding protrusion 15 to the diameter D1 of the shaft portion 13 is 1.2. This ratio is desirably 1.0 to 1.6. When this ratio is less than 1.0, a sufficient volume of the welding protrusion 15 necessary for the heat storage function cannot be secured. Furthermore, if this ratio is less than 1.0, the volume is insufficient and the welding protrusion 15 is melted in the early stage, so that only the diameter-expanded portion 14 becomes annular and separates from the welding protrusion 15. A malfunction occurs. When this ratio exceeds 1.6, the diameter of the welding protrusion 15 becomes excessive, the volume of the melting part 32 and the semi-melting part 36 becomes excessive, and it is necessary to abnormally lengthen the energization time for heat storage. , Economically disadvantageous. Further, if the volume of the melted part 32 or the semi-molten part 36 becomes excessive, the amount of deformation in the axial direction of the welding projection 15 becomes excessive, so that the distance from the surface of the steel plate part 23 to the tip of the shaft part 13 is uneven. This is not preferable in terms of component accuracy.

  Next, another modification will be described.

  In the example shown in FIG. 7, a steel plate aggregate 39 is arranged below the steel plate part 23. In this case, the open space 27 exists below the aggregate 39. Thus, when the steel plate part 23 and the aggregate 39 are piled up, since the heat dissipation to the open space 27 is reduced, the amount of heat stored in the welding projection 15 is increased or decreased by shortening the energization time or the like. .

  In the case described in FIG. 8, when the bolt 12 is inclined and pressed against the steel plate part 23 for any reason, the corner of the welding protrusion 15 hits one side 25 and the outer peripheral edge of the enlarged diameter portion 14. The part is not in contact with the single side 25. Since the height of the welding protrusion 15 is set to be large in this way, there is an effect that it is possible to avoid energizing the end edge portion of the enlarged diameter portion 14 even if the bolt 12 is inclined.

  The operational effects of the first embodiment described above are as follows.

  When the welding protrusion 15 is pressed against the steel plate part 23 by the advancement of the pressurizing electrode 19, the surface of the steel plate part 23 opposite to the pressurizing electrode 19 is exposed to the open space 27. The steel plate part 23 is elastically deformed in the advancing direction of the pressure electrode 19 in a state where the plate material is bent. When a welding current is applied in this state, the tip end side of the welding projection 15 is first in a molten state, and the melting region expands as the energization time elapses. In synchronization with this, the surface portion of the steel plate part 23 is also in a molten state. At that time, the diameter-expanded portion 14 side of the melted portion of the welding protrusion 15 gradually becomes a semi-molten state, and a softened layer is formed. Further, the softened layer gradually changes to become a solid part. The heat storage function in the welding protrusion 15 is achieved by the molten state or the semi-molten state as described above.

  As described above, the melted state and the semi-molten state of the welding projection 15 form a state in which heat is stored in the welding projection 15 during energization of the welding current or immediately after energization. In such a heat storage state, in the steel plate part 23, the elastic restoring force accompanying the elastic deformation described above is acting on the melting part 32 and the semi-melting part 36 in a reaction force, so that the melting part 32 is in the thickness direction of the steel plate part 23. And expansion in the surface direction is promoted. Since the melted portion 32 is replenished with heat from the semi-molten portion 36 adjacent to the melted portion 32, the time required for solidification of the melted portion 32 is lengthened. A welded part shape is formed that expands to both parts 23 and provides sufficient welding strength.

  Since the steel plate component 23 has a flat plate shape, the plate material itself is easily bent, the elastic deformation is surely formed and an elastic reaction force can be secured, and the elastic pressure force on the melting portion 32 and the semi-melting portion 36 is sufficient. And an appropriate welded part shape is formed.

  The amount of heat generated by the welding current and the volume of the welding protrusion are set so that the heat supply to the melting part 32 due to the heat storage of the welding protrusion 15 exceeds the heat radiation from the other surface side 26 of the steel plate part 23 to the open space 27. Is set. By doing so, the time required for solidification of the melting part 32 is prolonged as described above, and the melting part 32 expands to both the welding protrusion 15 and the steel plate part 23.

  Further, when the pressure electrode is retracted after the melting part 32 is solidified, the plate material of the steel plate component 23 that has been elastically deformed is restored to a complete flat plate shape and returns to the shape of the predetermined steel plate component 23. Thus, the steel plate part 23 having a normal shape is secured.

  The plate-like steel plate component 23 includes a plate material that is slightly curved and is regarded as a substantially flat plate.

  For example, in the case of a steel plate part 23 such as a roof panel of an automobile, the shape may be almost a flat plate having a curvature radius of 3000 mm. In such a shape, a plate material that is substantially regarded as a flat plate is a counterpart member for welding. The above-described welding process can be performed as expected even for such a steel plate part 23 having a small curvature. In addition, if the bolt 12 is directly resistance-welded to the roof panel 44, minute irregularities are formed on the surface and the appearance quality is deteriorated. Therefore, actually, a slight curved shape arranged along the roof panel 44 is used. The bolt 12 is welded from one side to the reinforcement (reinforcing member) 45 by electric resistance welding.

  The height of the welding projection 15 as viewed in the axial direction of the bolt 12 with respect to the thickness of the diameter-expanded portion 14 is set to a value that can perform a heat storage function by melting and semi-melting in the welding projection 15.

  By setting the height dimension of the welding protrusion 15 as described above, a sufficient heat storage function is exhibited.

  The ratio of the height of the welding protrusion 15 viewed in the axial direction of the projection bolt 12 to the thickness of the enlarged diameter portion 14 is 1.3 to 3.0.

  A sufficient heat storage function is exhibited by setting the height dimension of such a welding projection as in the above ratio.

  As described above, according to the electrical resistance welding method for a shaft-shaped part of the present invention, the welding protrusion is provided with a heat storage function, and the welding protrusion and the steel sheet part are made of elastic deformation imparted to the steel sheet part. It can secure a sufficient amount of metal melting on both sides to form a sound weld, so it can be used in a wide range of industrial fields such as the process of welding projection bolts to the body of automobiles and the sheet metal welding process of home appliances. .

DESCRIPTION OF SYMBOLS 12 Projection bolt, shaft-shaped component 13 Shaft part 14 Expanded part 15 Welding protrusion 16 Tapered part 17 Initial melting part 18 Top part 19 Pressurizing electrode 20 Receiving hole 23 Steel plate part 25 One side 26 Other side 27 Open space 32 Melting part , Welded portion 33 elastic restoring force 36 semi-melted portion 36A fluidized portion 36B softened portion 37 enlarged region 44 roof panel 45 lean reinforcement

Claims (2)

A shaft portion, a circular enlarged diameter portion integrally formed with the shaft portion and having a diameter larger than the diameter of the shaft portion, and a center of the enlarged diameter portion opposite to the shaft portion and welding Prepare a shaft-shaped part with a circular welding projection that performs heat storage function by melting and semi-melting with current application,
The shaft part of the shaft-shaped part is inserted into a receiving hole provided in the pressure electrode to hold the shaft-shaped part on the pressure electrode,
A plate-shaped steel plate component exposed on an open space with a shaft-shaped component welded to one side and the other side opposite to the other side is supported by a support member. Pressing the welding protrusion only on one side of the component to cause the steel plate component to undergo elastic deformation in a state where the plate material of the steel plate component is bent to the advance direction side of the pressure electrode,
Then energize the welding current,
The energization heat generation amount of welding current and the volume of the welding projection are set so that the heat storage heat amount of melting and semi-melting in the welding projection caused by this energization exceeds the heat radiation amount from the other surface side to the open space. ,
The heat dissipation from the other surface side to the open space is performed from the area range of the surface on the other surface side corresponding to the melting area of the melting portion in the welding projection,
The ratio of the height of the welding protrusion as seen in the axial direction of the shaft-shaped part to the thickness of the diameter-expanded part is 1.3 in the welding protrusion from 1.3 that can secure the volume of the molten part and the semi-molten part in the welding protrusion. It is a value that can fulfill the heat storage function in the welding protrusion set in the range of 3.0 so that the volume of the melted part and the semi-molten part is not excessive,
At the same time as melting and semi-melting at the welding protrusion, the elastic restoring force due to the elastic deformation of the steel plate parts is reacted toward the molten and semi-molten parts, and the solidification time of the molten part is lengthened and melted. Promote the expansion of steel sheet parts in the thickness direction and surface direction,
Thereafter, the steel part that has been elastically deformed by solidifying the melted part and retreating the pressure electrode is restored, and an electric resistance welding method for a shaft-like part.   The electric resistance welding method for a shaft-shaped part according to claim 1, wherein the plate-shaped steel sheet part includes a plate material that is slightly curved and is substantially regarded as a flat plate.

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