JP4661367B2 - Friction spot welding method and apparatus - Google Patents

Description

  The present invention belongs to a technical field related to a friction point joining method and apparatus for friction spot joining a first metal member and a second metal member having a melting point higher than that of the first metal member using a rotary tool.

  2. Description of the Related Art In recent years, aluminum alloy materials and the like have come to be widely used in automobile bodies and the like for the purpose of weight reduction, for example, and members made of aluminum alloy materials and members made of iron or steel materials, for example. Opportunities to join are increasing. Since it is difficult to join such members made of different metal materials by welding, rivet joining is usually performed, but this rivet joining increases the cost.

Therefore, a friction point joining method is used as a method capable of joining members made of different metal materials at low cost. In this method, for example, as shown in Patent Document 1, a first metal member made of an aluminum alloy material or the like and a second metal member made of a steel material or the like having a melting point higher than that of the first metal member are overlapped. Generated by rotating the rotating tool and pressing the first metal member with the tip of the rotating tool that rotates about the axis centered from the first metal member side against the combined workpiece. By softening and plastically flowing the first metal member with the frictional heat, the two metal members are solid-phase bonded (bonding in a solid phase state without melting) at a temperature equal to or lower than the melting point.
JP 2005-34879 A

  By the way, in the above-mentioned friction point joining method, the plating layer (zinc plating layer is formed as a rust prevention measure in steel materials) existing at the joining boundary surface of both members is discharged from the joint, or the oxide film is removed. It is advantageous to ensure the high joint strength by breaking or exposing the new surfaces of both metal members. For this purpose, the first metal member into which the rotary tool is pushed is sufficiently softened and plastically flowed. There is a need.

  In this regard, the present inventors have found that the step of pressing the rotary tool against the first metal member is preferably divided into a plurality of steps from the viewpoint of the pressing force (pressing force) on the first metal member. . In other words, the rotary tool is moved forward and backward in the axial direction of the rotary tool with respect to the workpiece and pressed against the first metal member, and the pressing force at the time of pressing can be changed by a supply current or voltage. A motor is provided, and in the first first pressing step, the rotating tool is pressed against the first metal member with a relatively low pressure by the pressing motor while rotating the rotating tool around the axis of the rotating tool. Let This is because if a sudden high pressure is applied to the first metal member, there is a high possibility that the first metal member that has not yet been softened will be sheared and destroyed. (1) The metal member is sufficiently softened. Then, after the first metal member is sufficiently softened, in the next second pressing step, a high pressure is applied to the first metal member to promote plastic flow. If it does in this way, a plastic flow will be performed satisfactorily and a high joint strength will be obtained, without the 1st metal member carrying out shear fracture.

  As described above, the pressing force in the first pressing step is preferably set to a low value that allows the first metal member to be sufficiently softened without shear fracture. However, if this pressing force is too low, problems occur. There is a case. That is, the frictional resistance value generated in the mechanism for moving the rotating tool, that is, the moving resistance value of the rotating tool is not stable, and varies depending on the influence of the gap amount, grease, etc. between the movable part and the fixed part. For this reason, in the first pressing step, even if the current of the pressing motor is controlled so as to achieve the low pressing force, the pressing force actually acts on the first metal member depending on the magnitude of the movement resistance value. Time to do will vary. As a result, if the pressing motor is controlled to press the rotary tool against the first metal member for a predetermined time with the low pressure, the pressure is actually pressed against the first metal member with the pressure. When the time to do varies considerably with respect to the predetermined time, and when it becomes considerably short with respect to the predetermined time, the first metal member is not sufficiently softened, and there is a high possibility of shear fracture in the second pressing step. In addition, even if shear failure is not caused, the bonding strength varies. On the other hand, if the predetermined time is lengthened, the first metal member is sufficiently softened even if the actual pressing time with the applied pressure varies considerably with respect to the predetermined time. However, in automobile manufacturing factories and the like, it is required to complete joining within a limited time, and it is extremely difficult to lengthen the predetermined time.

  This invention is made | formed in view of such a point, The place made into the objective is the viewpoint of the pressurization force with respect to a 1st metal member as mentioned above, the process which presses a rotary tool with respect to a 1st metal member. When performing friction point welding by dividing into a plurality of processes, by appropriately setting the applied pressure in the first first pressing process, the welding can be performed as soon as possible, and a stable high bonding strength can be obtained. Is to be able to.

To achieve the above object, in the present invention, a first pressure against first metal member in the first pressing step, so as to be larger than the moving resistance of the rotating tool, the first pressing step, the rotating While the tool is rotated around the axis of the rotary tool at a predetermined rotational speed, the shoulder portion and the pin portion of the rotary tool are moved between the first metal for a predetermined time by the pressing motor with the first pressurizing force. In the step of pressing and contacting the member, the first pressure is set to 2.45 kN or more and 3.43 kN or less, the predetermined rotation speed is set to 1500 rpm or more and 3500 rpm or less, and the predetermined time is set to 0.2. It was set to be not less than 2 seconds and not more than 2.0 seconds .

  Specifically, according to the first aspect of the present invention, the shaft of the rotary tool that rotates about the axis with respect to the workpiece in which the first metal member and the second metal member having a melting point higher than that of the first metal member are overlapped. By pushing the distal end, which is one end in the central direction, from the side of the first metal member, and softening and plastically flowing the first metal member by frictional heat generated by the rotation of the rotary tool and the pressing operation against the first metal member. The present invention is directed to a friction spot joining method in which both the metal members are friction spot joined.

And, in advance, the tip portion of the rotary tool is a shoulder portion facing the workpiece, and a pin portion that is located on the axis of the rotary tool and projects from the shoulder portion to the workpiece side with a smaller diameter than the shoulder portion. And an annular recess provided in the shoulder portion around the pin portion, and the rotary tool is moved forward and backward in the axial direction of the rotary tool with respect to the workpiece and the first metal An initial pressing motor is provided that can press the member and change the pressing force at the time of pressing, and the rotating motor moves the rotating tool to an initial position that is close to the first metal member. After the moving step and the initial moving step, the rotating tool rotates around the axis of the rotating tool, and the rotation in the initial moving step is performed by the pressing motor. A first pressing step in which the shoulder portion and the pin portion of the rotating tool are pressed against the first metal member with a first pressing force larger than the movement resistance value of the tool, and the rotation after the first pressing step. While the tool is rotated about the axis of the rotary tool, the shoulder portion and the pin portion of the rotary tool are attached to the first metal member by the pressing motor with a second pressing force larger than the first pressing force. look including a second pressing step of pushing, the first pressing step, while the rotating tool is rotated at a predetermined rotational speed about the axis of the rotary tool, by the pressing motor, in the first pressure, A step of pressing and contacting a shoulder portion and a pin portion of the rotary tool with respect to the first metal member for a predetermined time, wherein the first pressing force is set to 2.45 kN or more and 3.43 kN or less, The predetermined speed is Is set below 1500rpm above 3500 rpm, the predetermined time is assumed to be set to 2.0 seconds or less 0.2 seconds or more.

  With the above configuration, in the initial movement step, the rotary tool moves to the initial position that is the proximity position of the first metal member. After that, in the first pressing step, the rotary tool is rotated by the pressing motor while rotating. The shoulder portion and the pin portion of the rotary tool are pressed against the first metal member with a first pressurizing force larger than the movement resistance value of the first metal member, thereby softening the first metal member. Thereafter, in the second pressing step, the shoulder portion and the pin portion of the rotating tool are pushed into the first metal member by the pressing motor while the rotating tool rotates with a second pressing force larger than the first pressing force, Thereby, a 1st metal member carries out plastic flow, and both metal members are friction point joined. Here, since the first pressing force in the first pressing step is larger than the movement resistance value of the rotating tool, the first pressing step rotates immediately after the first pressing step regardless of the magnitude of the movement resistance value. The shoulder part and the pin part of the tool are pressed against the first metal member. Thereby, even if the pressing motor is controlled to press the rotary tool against the first metal member for a predetermined time with the first pressing force, the first pressing force is actually applied to the first metal member. The operating time is substantially the same as the predetermined time and is stable. As a result, even if the predetermined time is not lengthened, the first metal member is sufficiently softened, and the plastic flow of the first metal member is satisfactorily and stably performed in the second pressing step. And since the front-end | tip part of a rotary tool is comprised by the shoulder part, the pin part, and the cyclic | annular recessed part, the 1st metal member which plastically flows at a 2nd press process flows out from the part facing a rotary tool to the outside. The pressure applied by the rotating tool is concentrated on the portion facing the rotating tool. Therefore, the bonding can be performed as soon as possible, and a stable high bonding strength can be obtained.

Here, if the first pressurizing force becomes too large, the first metal member may be sheared and destroyed. However, the predetermined time which is the first pressurizing force, the rotational speed of the rotary tool, and the pressing time with respect to the first metal member is set. By setting each within the scope of the present invention, the first metal member can be favorably softened without being sheared and broken, so that a stable and high joint strength can be reliably obtained. become.

According to a second aspect of the invention, in the first aspect of the invention, after the second pressing step, a third pressing force smaller than the second pressurizing force is applied by the pressing motor while rotating the rotary tool around the axis of the rotating tool. The pressure tool further includes a third pressing step in which the shoulder portion and the pin portion of the rotary tool are pressed against the first metal member with pressure.

  By doing so, it is possible to prevent the rotary tool from entering too deeply into the first metal member, and it is possible to prevent the first metal member from being excessively thin and torn, and the rotary tool can be By continuing to press against the member at a position where the first metal member is not pushed too thin, a good plastic flow can be obtained over a long period of time, thereby further stabilizing the bonding strength. be able to.

In the invention of claim 3, in the invention of claim 1 or 2 , the first metal member is made of an aluminum alloy material, the second metal member is made of a steel material, and the mating surface portions of the two metal members are subjected to friction. Solid phase bonding is performed by point bonding.

  This makes it possible to easily obtain a bonded metal member that has a high bonding strength and can be used for an automobile or the like at a low cost.

According to a fourth aspect of the present invention, at one end in the axial direction of the rotary tool that rotates about the axis with respect to a workpiece in which the first metal member and the second metal member having a higher melting point than the first metal member are overlapped. By pushing a certain tip from the side of the first metal member and softening and plastically flowing the first metal member by frictional heat generated by the rotation of the rotary tool and the pressing operation against the first metal member, both the metal members It is invention of the friction point joining apparatus which carries out friction point joining.

And in this invention, the front-end | tip part of the said rotary tool is located on the axial center of the said rotary tool and the shoulder part which opposes the said workpiece | work, and protrudes from the shoulder part to the workpiece | work side by a smaller diameter than a shoulder part. A rotation drive means configured to rotate the rotation tool around the axis of the rotation tool, and the rotation tool. A pressing motor capable of moving forward and backward in the axial direction of the rotary tool with respect to the workpiece and pressing the first metal member and changing a pressing force at the time of pressing; and the rotation driving means and the pressing motor. An initial movement step of moving the rotary tool to an initial position that is a proximity position of the first metal member by the pressing motor; After the initial movement step, the rotation tool rotates the rotation tool around the axis of the rotation tool, and the pressing motor causes the first movement resistance value to be larger than the movement resistance value of the rotation tool in the initial movement step. A first pressing step in which a shoulder portion and a pin portion of the rotating tool are pressed against the first metal member with a pressing force, and after the first pressing step, the rotating tool is used to attach the rotating tool to the rotating tool. A second pressing step of pressing the shoulder portion and the pin portion of the rotating tool into the first metal member with the second pressing force larger than the first pressing force by the pressing motor while rotating around the axis; It is configured to perform the above first pressing step, while the rotating tool is rotated at a predetermined rotational speed about the axis of the rotary tool, in the pressing motor In this step, the shoulder portion and the pin portion of the rotating tool are pressed against the first metal member for a predetermined time with the first pressure force, and the first pressure force is 2.45 kN or more. It is set to 3.43 kN or less, the predetermined rotation speed is set to 1500 rpm or more and 3500 rpm or less, and the predetermined time is set to 0.2 second or more and 2.0 seconds or less .

  According to the present invention, the same effect as that attained by the 1st aspect can be attained.

As described above, according to the friction point joining method and apparatus of the present invention, the rotating tool is rotated around the axis of the rotating tool after the initial moving step of moving the rotating tool to the initial position by the pressing motor. A first pressing step in which the shoulder portion and the pin portion of the rotary tool are pressed and contacted with the first metal member by the pressing motor with a first pressurizing force larger than the movement resistance value of the rotary tool in the initial movement step. After the first pressing step, the rotating tool shoulder is rotated with the second pressing force larger than the first pressing force by the pressing motor while rotating the rotating tool around the axis of the rotating tool. given the parts and pin together to perform a second pressing step of pushing the first metal member, said first pressing step, the rotating tool about the axis of the rotary tool A process of pressing and contacting the shoulder part and the pin part of the rotating tool with respect to the first metal member for a predetermined time with the first pressurizing force by the pressing motor while rotating at a rotation number, The first applied pressure was set to 2.45 kN or more and 3.43 kN or less, the predetermined rotation speed was set to 1500 rpm or more and 3500 rpm or less, and the predetermined time was set to 0.2 seconds or more and 2.0 seconds or less . Thus, even if the pressing motor is controlled to press the rotary tool against the first metal member for a predetermined time with the first pressing force, the first pressing force is actually applied to the first metal member. The working time is substantially the same as the predetermined time, and even if the predetermined time is not lengthened, the first metal member is sufficiently softened, and the plastic flow of the first metal member is good and stable in the second pressing step. As a result, It is possible to perform fast bonding unless coming, stable and high bonding strength can be obtained. Further, the first metal member can be softened satisfactorily without being sheared and broken, so that a stable and high bonding strength can be reliably obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a friction point welding apparatus 1 according to an embodiment of the present invention. As will be described later, the friction point welding apparatus 1 includes a first metal member W1 (see FIG. 7) and a second metal member W2 (see FIG. 7) having a melting point higher than that of the first metal member W1. As a main component, a joining gun 10 and a robot 40 having the joining gun 10 on the wrist are included. As the robot 40, a general-purpose 6-axis vertical articulated robot is preferably used.

  In the present embodiment, the first and second metal members W1 and W2 are members constituting the body of the automobile. The first metal member W1 is made of an aluminum alloy material (aluminum alloy plate), and the second metal member W2 is used. Is made of a steel material (steel plate), but is not limited thereto. The surface of the second metal member W1 is provided with a galvanized layer Z (see FIG. 8) as a rust prevention measure.

  2 and 3, the joining gun 10 includes a mounting box 11 for the robot 40, an L-shaped arm 12 extending downward from the lower surface of the mounting box 11, and the arm 12. A body case 13 attached to the side surface of the mounting box 11 above, a pressing motor 14, and a rotating motor 15. A rotary tool 16 that is one of a pair of joining tools is provided at the lower end of the main body case 13, while the rotary tool 16 and the axis of the rotary tool 16 are provided at the tip of the arm 12. Opposing in the X direction (vertical direction), a receiving member 17 which is the other of the welding tools is provided. The receiving member 17 contacts the second metal member W2 of the work in which the first metal member W1 and the second metal member W2 are overlapped, and receives the work. A tip end portion (lower end portion) which is one end portion in the axial center X direction of the rotary tool 16 rotating around X is pushed from the first metal member W1 side.

  As shown in FIG. 4, a screw shaft (elevating shaft) 24 and a spline shaft (rotating shaft) 25 extending in the vertical direction in parallel with each other are provided in the main body case 13 so as to be rotatable around respective axis centers. ing. The upper ends of the shafts 24 and 25 penetrate the upper lid member 21 and reach the upper cover 22, where the driven pulleys 26 and 27 are assembled to the shafts 24 and 25, respectively. As shown in FIGS. 3 and 5, the upper lid member 21 and the upper cover 22 protrude from the upper part of the main body case 13 to the side of the main body case 13, and are pressed against the lower surface of the protruding portion of the upper cover member 21. The motor 14 and the rotation motor 15 are fixed. The front end portions (upper end portions) of the output shafts 14a and 15a of both the motors 14 and 15 pass through the upper lid member 21 and reach the upper cover 22, where drive pulleys 14b and 15b are connected to the output shafts 14a and 15a. Each is assembled. Drive transmission belts 28 and 29 are respectively wound between the drive pulleys 14b and 15b and the driven pulleys 26 and 27, and the screw shaft 24 is rotated by the rotation of the pressing motor 14. 5, the spline shaft 25 is rotationally driven in the direction C of FIG.

  Returning to FIG. 4, the elevating block 31 is screwed to the screw portion 24 a of the screw shaft 24, and the rotating cylinder 35 is splined to the spline portion 25 a of the spline shaft 25. The rotating cylinder 35 is rotatably provided inside an elevating cylinder 33 integrally coupled to the elevating block 31 via a coupling member 32. The screw shaft 24, the lifting cylinder 33 and the rotating cylinder 35 are disposed concentrically with each other. Hereinafter, the integrated body of the elevating block 31, the coupling member 32, and the elevating cylinder 33 is referred to as an elevating body 30.

  A cylindrical downward projecting portion 13a is formed on the lower surface of the main body case 13, and a lower cover 23 is provided at the lower end portion of the downward projecting portion 13a. The lower end portions of the elevating cylinder body 33 and the rotating cylinder body 35 penetrate the lower cover 23 and protrude downward. The rotating cylinder 35 on the inner side protrudes downward longer than the lifting cylinder 33 on the outer side, and the attachment member 36 is fixed to the lower end portion of the rotating cylinder 35. A base end portion, which is an end portion on the opposite side of the distal end portion of the rotary tool 16, is attached to the attachment member 36 in a detachable (exchangeable) manner. The axis X of the attached rotary tool 16 is on the extension of the axis of the spline shaft 25. An extendable bellows member 34 is disposed between the lower cover 23 and the lower end of the elevating cylinder 33 to protect the outer surface of the elevating cylinder 33 from contamination outside the main body case 13. .

  With the above configuration, when the screw shaft 24 is rotationally driven in the direction A in FIG. 5 by the rotation of the pressing motor 14, the elevating body 30 is lowered by screwing with the screw portion 24 a, and the elevating cylinder in the elevating body 30. The rotary cylinder 35 housed in 33 and the rotary tool 16 attached to the lower end of the rotary cylinder 35 via the attachment member 36 are lowered together. Conversely, when the screw shaft 24 is rotationally driven in the direction B of FIG. 5 by the rotation of the pressing motor 14, the elevating body 30 is lifted by screwing with the screw portion 24a, and the rotary cylinder 35 and the rotary tool 16 are moved. Rise together. As a result, the pressing motor 14 moves the rotary tool 16 forward and backward in the direction of the axis X of the rotary tool 16 with respect to the workpiece positioned between the rotary tool 16 and the receiving member 17 as will be described later. It will be configured. The pressing motor 14 is configured to press the rotary tool 16 against the first metal member W1 of the workpiece, and the pressing force at the pressing is changed by a current supplied to the pressing motor 14. Can be done.

  When the spline shaft 25 is driven to rotate in the direction C in FIG. 5 by the rotation of the motor 15 for rotation, the rotating cylinder 35 is splined with the spline portion 25a regardless of the movement of the elevating body 30 as described above. The rotating tool 16 that rotates in the same C direction as the spline shaft 25 by the coupling and is attached to the rotating cylinder 35 also rotates in the same C direction as the spline shaft 25 around the axis X of the rotating tool 16. Thus, the rotation motor 15 constitutes a rotation drive unit that rotates the rotation tool 16 around the axis X of the rotation tool 16. In addition, the rotation motor 15 can change the number of rotations around the axis X of the rotation tool 16 by a current supplied to the rotation motor 15.

  The pressing motor 14 is preferably a servo motor that can easily control and detect the rotation angle, and the rotation motor 15 can be a servo motor that can also easily control and detect the rotation angle, or control of the rotation speed. An easy induction motor is preferred.

  FIG. 6 shows an enlarged front end portion of the rotary tool 16. A tip portion of the rotary tool 16 is a lower end surface (whose contour is circular) of a cylindrical body portion 16a, a shoulder portion 16b facing the workpiece (first metal member W1), and the rotary tool. A pin portion 16c that is located on the axis X of 16 and has a smaller diameter than the shoulder portion 16b from the shoulder portion 16b and protrudes toward the workpiece side (lower side) by a predetermined length h; It is comprised by the annular recessed part 16d provided in the shoulder part 16b. In the present embodiment, the bottom surface of the annular recess 16d is inclined so that the amount of recesses decreases toward the outside in the radial direction, and the annular recess 16d has a conical shape centered on the axis X of the rotary tool 16. It is recessed. As specific dimensions of the rotary tool 16, for example, the diameter of the shoulder portion 16b is 10 mm, the diameter of the pin portion 16c is 2 mm, the protruding length h of the pin portion 16c is 0.3 mm to 0.35 mm, and the annular recess 16d The inclination angle θ of the bottom surface with respect to the shoulder portion 16b is 5 ° to 7 °.

  As shown in FIG. 1, the robot 40 is connected to a control panel 50 via a harness 51. The joining gun 10 is connected to the control panel 50 via harnesses 52, 54, 55 and a repeater 53. The rotation unit (current value supplied to the motor) of the pressing motor 14 and the rotation motor 15 is controlled by a control unit 50a built in the control panel 50. Thus, the control unit 50 a constitutes a control unit that controls the pressing motor 14 and the rotation motor 15.

  In order to perform friction point joining of the first metal member W1 and the second metal member W2 by the friction point joining apparatus 1, first, as illustrated in FIG. The workpiece overlaid with the metal member W2 as the lower plate is gripped and fixed by gripping means (not shown). Subsequently, by the operation of the robot 40, the joining gun 10 is brought close to one of the plurality of joining portions P to be joined in the workpiece, and the rotary tool 16 is positioned above the one joining portion P. 17 is positioned below the joint P. Next, the entire joining gun 10 is moved upward to bring the receiving member 17 into contact with the lower surface of the second metal member W2.

  Then, with the receiving member 17 in contact with the lower surface of the second metal member W2, the screw shaft 24 is driven to rotate in the direction A in FIG. From the upper side, the rotary tool 16 is moved in the axial center X direction (lower side) and moved to the initial position which is the proximity position of the first metal member W1 (initial movement step). This initial position is a position where the tip of the pin portion 16c of the rotary tool 16 is slightly separated from the upper surface of the first metal member W1. In this initial movement step, the rotary tool 16 may be rotated around the axis X of the rotary tool 16 by the motor 15 for rotation, or may not be rotated. It is made to rotate at the same rotation speed (1st rotation speed) as a 1st press process so that it can transfer to 1 press process immediately.

  Subsequently, as shown in FIG. 8, the rotation tool 15 is rotated around the axis X of the rotation tool 16 at the first rotation speed by the rotation motor 15, and the rotation in the initial movement step is performed by the pressing motor 14. The shoulder portion 16b and the pin portion 16c of the rotary tool 16 are brought into pressure contact with the first metal member W1 for a first predetermined time with a first pressure greater than the movement resistance value of the tool 16 (first pressing step). ).

  The pressure applied to the first metal member W1 of the rotary tool 16 is determined by the current value supplied to the pressing motor 14, so that the control unit 50a uses the current supplied to the pressing motor 14 as the first pressing step. Then, it controls so that it may become the electric current value corresponding to the said 1st pressurizing force during the said 1st predetermined time. Further, since the rotation speed of the rotary tool 16 is determined by the current value supplied to the rotation motor 15, the control unit 50a uses the current supplied to the rotation motor 15 as the first pressing step (and the initial movement step). Then, it controls so that it may become the electric current value corresponding to the said 1st rotation speed.

  The moving resistance value is determined by the frictional resistance generated in the mechanism that moves the lifting cylinder 33 (rotary tool 16), which is constituted by the screw shaft 24, the lifting body 30, and the like. It is not stable and varies due to the influence of the gap amount, grease, etc. between the movable part and the fixed part. For this reason, when the first applied pressure is less than or equal to the movement resistance value, the time until the first applied pressure actually acts on the first metal member W1 varies depending on the magnitude of the movement resistance value, and the first metal member The time for actually pressing W1 with the first applied pressure varies considerably with respect to the first predetermined time. However, in the present embodiment, since the first pressing force is set to be larger than the movement resistance value, the rotary tool is rotated with the first pressing force immediately after the start of the first pressing step regardless of the magnitude of the movement resistance value. The 16 shoulder portions 16b and the pin portion 16c are pressed against the first metal member W1, and the time during which the first pressure force actually acts on the first metal member W1 is substantially the same as the first predetermined time. ,Stabilize.

The first pressure is greater than the maximum value of the variation range of the moving resistance, to set the inclusive 2.45kN 3.43kN. Further, the first rotational speed, to set below 1500rpm than 3500 rpm. Further, the first predetermined time, to set to 2.0 seconds or less 0.2 seconds or more. With respect to the first pressurizing force, the first rotation speed, and the first predetermined time, the rotary tool 16 has a part of the bottom surface of the annular recess 16d (the portion on the deep axis X side) with respect to the first metal member W1. It sets so that it may be pushed to such an extent that the peripheral part of the shoulder part 16b and the pin part 16c may contact the 1st metal member W1, without contacting the 1st metal member W1.

  In the first pressing step, the peripheral portion of the shoulder portion 16b and the pin portion 16c are pressed and contacted with the first metal member W1 while rotating around the axis X of the rotary tool 16, so that the two contacts are made. Friction heat is generated at the part, and this frictional heat is quickly diffused to the part between the two contact parts of the work (the part where the bottom surface of the annular recess 16d is not in contact), and eventually to the entire joint P. The whole part (joint part P) facing the shoulder part 16b in the first metal member W1 is softened well. Further, the galvanized layer Z applied to the surface of the second metal member W1 is also softened at the joint P. Thus, by setting the first pressurizing force, the first rotation speed, and the first predetermined time within the preferable ranges, the first metal member W1 can be favorably softened without being sheared. Become.

  Next, as shown in FIG. 9, while the rotary tool 16 is rotated around the axis X of the rotary tool 16 at the second rotational speed by the rotary motor 15, the pressing motor 14 causes the first applied pressure to be higher than the first applied pressure. The shoulder portion 16b and the pin portion 16c of the rotary tool 16 are pushed into the first metal member W1 for a second predetermined time with a large second pressure (second pressing step). In the second pressing step, the applied pressure increases, so that the shoulder portion 16b and the pin portion 16c of the rotary tool 16 gradually enter the first metal member W1, and the entire bottom surface of the annular recess 16d, that is, the pin portion 16c. The entire shoulder portion 16b including the annular recess 16d contacts the first metal member W1. Along with this, in addition to the softening of the first metal member W1, plastic flow (see symbol Q) is performed. Since this plastic flow is provided with an annular recess 16d in the shoulder portion 16b (particularly, the annular recess 16d has a conical shape), the first metal member W1 that plastically flows flows in the vertical direction, Outflow from the portion immediately below the rotary tool 16 (joint portion P) is suppressed. Moreover, the second recessed pressure is concentrated on the joint P by the annular recess 16d, and the plastic flow of the first metal member W1 is promoted. Further, the softened galvanized layer Z is pushed out from the joint P at the joint interface between the two metal members W1 and W2, so that the new surface of the second metal member W2 is exposed and is not shown in the drawings. When the oxide film formed on the surface of the first metal member W1 is broken at the joint P by the oxygen, the new surface of the first metal member W1 is exposed.

  The second applied pressure is preferably set to 3.92 kN or more and 5.88 kN or less. The second rotation speed is preferably set to 2000 rpm or more and less than 3000 rotations. Further, the second predetermined time is preferably set to 1.0 second or more and 2.0 seconds or less. The second applied pressure, the second rotation speed, and the second predetermined time are set so that the rotary tool 16 is not pushed deeper than the predetermined insertion position into the first metal member W1. The predetermined insertion position is a position where the first metal member W1 becomes excessively thin and can be torn off when the rotary tool 16 enters deeper than the insertion position.

  The end of the second pressing step may end the joining at the joint P, but in this embodiment, after the second pressing step, as shown in FIG. While rotating the tool 16 around the axis X of the rotating tool 16 at a third rotational speed, the shoulder portion 16b and the pin of the rotating tool 16 are rotated by the pressing motor 14 with a third pressing force smaller than the second pressing force. The part 16c is pressed against the first metal member W1 for a third predetermined time (third pressing step). In this 3rd press process, by making pressure force smaller than a 2nd press process, the rotary tool 16 is not pushed deeply into the 1st metal member W1 rather than the said predetermined insertion position, and the 2nd press process was complete | finished. It will continue to be pressed at the time position. This prevents the first metal member W1 from being excessively thin and torn and maintains the same temperature as in the second pressing step, and good plastic flow is performed for a long time. . By the end of the third pressing step, the joining at one joining portion P is finished.

  The third pressure is preferably set to be 0.49 kN or more and 1.47 kN or less than the first pressure. The third rotation speed is preferably set to 1500 rpm or more and 3500 rotations or less. Furthermore, it is preferable that the third predetermined time is set to 0.5 seconds or more and 2.5 seconds or less. The third pressing force, the third rotation speed, and the third predetermined time continue to press the rotary tool 16 against the first metal member W1 at the position when the second pressing step is completed, and the first metal member W1. Each is set so that plastic flow occurs.

  In the third pressing step, the metal material extruded by the rotary tool 16 becomes a burr R and rises on the surface of the first metal member W1, and the galvanized layer Z is further extruded from the joint P, and is oxidized. The coating is further destroyed, and the exposed range of the new surfaces of both metal members W1 and W2 is expanded (the range indicated by x in FIG. 10). As a result, the mating surface portions of both metal members are solid-phase bonded by friction point bonding, and the bonding strength is stably increased.

  In the vicinity of the joint P in the galvanized layer Z, a metal mixture layer Y of the metal of the first metal member W1 and the metal of the galvanized layer Z is generated.

  When the joining at the one joining portion P is completed, the rotary tool 16 is raised by rotating the screw shaft 24 in the direction B in FIG. 5 by the pressing motor 14, and the entire joining gun 10 is moved downward. It is moved and moved horizontally to the position of the next joint P, and thereafter, the same operation as described above is repeated to perform the joint at the next joint P, and in this way, the friction point joint ( Solid phase bonding) is performed.

  In the joint P after the completion of the friction spot welding, as shown in FIG. 11, the marks of the shoulder portion 16b and the pin portion 16c remain on the surface of the workpiece (first metal member W1), and the shoulder portion 16b There is a burr R around it.

  Here, in the first pressing step, the first pressurizing force, the first rotation speed, and the first predetermined time can be variously changed to favorably soften the first metal member W1 without causing shear fracture. A softening test was conducted to check whether or not.

  The first metal member W1 is a 6000 series aluminum alloy plate (not containing Cu) having a thickness of 1.4 mm, and the second metal member W2 is a steel plate (galvanized) having a thickness of 1.0 mm; The results of the above softening test are shown in FIGS. 12 (a) to 12 (c). Moreover, the result of the said softening test at the time of changing the 1st metal member W1 to the 6000 series aluminum alloy plate which contained Cu less than 1% is shown to Fig.13 (a)-(c).

  In the figure, a circle mark indicates a case where the first metal member W1 is softened well without shear fracture, and a cross mark indicates that the first metal member W1 is shear broken to cause an internal defect or the rotary tool 16 Or the case where the softening is insufficient due to insufficient frictional heat. Then, in the graph of the relationship between the first predetermined time and the first rotation speed for each applied pressure, the range where the ◯ mark exists is the “appropriate area”, and the range where the X mark due to shear fracture exists is the “shear fracture” The area where “x” is present due to insufficient softening is defined as “the area with insufficient residual heat”. In the softening test, as shown in FIG. 8, the annular recess 16d of the rotary tool 16 is not in contact with the first metal member W1, that is, the peripheral portion of the shoulder portion 16b and the pin portion 16c are in the first state. If the first metal member W1 is in contact with the first metal member W1, it can be said that the first metal member W1 has been softened well without undergoing shear fracture. Never do. Further, when the entire shoulder portion 16b including the pin portion 16c and the annular recess 16d comes into contact with the first metal member W1, the first metal member W1 is sheared and broken. Furthermore, if only the pin portion 16c is in contact with the first metal member W1, it can be said that the softening is insufficient, and the first metal member W1 will be sheared and destroyed in the subsequent second pressing step. .

  As a result of the softening test, the first applied pressure is preferably set to 2.45 kN or more and 3.43 kN or less, the first rotational speed is preferably set to 1500 rpm or more and 3500 rpm or less, and the first predetermined time is It turns out that it is good to set it to 0.2 second or more and 2.0 second or less. However, depending on the material of the first metal member W1, the combination of the first pressure, the first rotation speed, and the first predetermined time needs to fall within the “appropriate region”.

  Next, the bonding strength when the first metal member W1 and the second metal member W2 were friction point bonded by the bonding method described in the above embodiment was examined.

  That is, first, a first metal member W1 made of a 6000 series aluminum alloy plate (not containing Cu) with a plate thickness of 1.4 mm and a second metal plate made of a steel plate (galvanized) with a plate thickness of 1.0 mm. As shown in FIG. 14, the metal member W2 was subjected to friction point bonding at the position of the joint P at the center of the cross in a state where the metal member W2 was overlapped and clamped in a cross shape. As joining conditions at this time, as shown in Table 1, No. 1-No. 6 to 6 ways.

  Next, a tensile test for measuring the peel strength was performed on those subjected to the friction spot bonding under the above-mentioned respective bonding conditions. Specifically, the first metal member W1 is pulled in the direction of the upward arrow M1, the second metal member W2 is pulled in the direction of the downward arrow M2, and the tensile force (when the metal members W1, W2 are separated from each other) The peel strength was examined. The measurement results of the peel strength are also shown in Table 1.

  From the above measurement results, No. 1-No. 3 and no. 4-No. The difference in the peel strength is different from that of No. 6, but this is mainly due to the difference in the second pressing force, and the one with the larger second pressing force (No. 1 to No. 3) is more plastic. It is considered that the flow strength was sufficiently promoted to increase the peel strength, that is, the bonding strength. Moreover, if the joining conditions in the second and third pressing steps are the same, the joining strength is stable even if the joining conditions in the first pressing step are changed within the “appropriate region”. This is thought to be because the first metal member W1 was softened well in the first pressing step.

  Therefore, in the present embodiment, after the initial movement step in which the rotary tool 16 is moved to the initial position by the pressing motor 14, the rotating tool 16 is rotated around the axis of the rotating tool 16 by the rotating motor 15. The shoulder portion 16b and the pin portion 16c of the rotary tool 16 are pressed and brought into contact with the first metal member W1 by the motor 14 with a first pressing force larger than the movement resistance value of the rotary tool 16 in the initial movement step. Therefore, regardless of the magnitude of the movement resistance value, immediately after the start of the first pressing step, the shoulder portion 16b (peripheral portion) and the pin portion 16c of the rotary tool 16 with respect to the first metal member W1 with the first pressure force. It will be pressed. As a result, the time during which the first pressurizing force actually acts on the first metal member W1 is substantially the same as the first predetermined time and is stable. As a result, even if the first predetermined time is not lengthened, the first metal member W1 is sufficiently softened, and the plastic flow of the first metal member W1 is satisfactorily and stably performed in the second pressing step. On the other hand, if the first pressurizing force becomes too large, the first metal member W1 may be sheared and broken. In the present embodiment, the first pressurizing force is set to 2.45 kN or more and 3.43 kN or less. At the same time, according to the material of the first metal member W1, the rotary tool 16 has a part of the bottom surface of the annular recess 16d with respect to the first metal member W1. The first metal member W1 is shear-fractured by setting so that the peripheral portion of the shoulder portion 16b and the pin portion 16c are pushed to the extent that they contact the first metal member W1 without contacting the first metal member W1. It can be softened well without causing it to occur. In addition, the annular recess 16d at the tip of the rotary tool 16 prevents the first metal member W1 that plastically flows in the second pressing step from flowing out from the portion immediately below the rotary tool 16, and the second additive. The pressure is concentrated on the portion immediately below the rotary tool 16. As a result, the bonding can be performed as soon as possible, and a stable and high bonding strength can be reliably obtained.

  Further, in the present embodiment, after the second pressing step, the rotating tool 16 is rotated around the axis of the rotating tool 16 by the rotating motor 15 and the third pressure smaller than the second pressing force is applied by the pressing motor 14. Since the shoulder portion 16b and the pin portion 16c of the rotary tool 16 are pressed and brought into contact with the first metal member W1 by the applied pressure, the rotary tool 16 enters deeper than the predetermined insertion position with respect to the first metal member W1. As a result, it is possible to prevent the first metal member W1 from being excessively thin and torn, and a good plastic flow can be obtained over a long period of time, thereby further stabilizing the bonding strength. be able to.

  INDUSTRIAL APPLICABILITY The present invention is useful for a friction point joining method and apparatus for friction spot joining of a first metal member and a second metal member having a melting point higher than that of the first metal member using a rotary tool. This is useful when the step of pressing the tool against the first metal member is divided into a plurality of steps from the viewpoint of the pressure applied to the first metal member.

It is a side view showing a schematic structure of a friction spot welding device concerning an embodiment of the present invention. It is a side view which expands and shows the joining gun of the friction point joining apparatus of FIG. It is a front view which expands and shows the joining gun of the friction point joining apparatus of FIG. It is sectional drawing which shows the internal structure of the main body case of a joining gun. It is the VV sectional view taken on the line of FIG. It is a fragmentary sectional view which shows the front-end | tip part of a rotary tool. It is a schematic perspective view which shows a mode that a 1st metal member and a 2nd metal member are piled up and a friction point joining is carried out with a rotary tool. It is sectional drawing which shows the state which the rotary tool is pressing with respect to the 1st metal member at the 1st press process. It is sectional drawing which shows the state which the rotary tool is pressing with respect to the 1st metal member at the 2nd press process. It is sectional drawing which shows the state which the rotary tool is pressing with respect to the 1st metal member at the 3rd press process. It is sectional drawing which shows the state of the junction part after friction point joining is completed. It is a figure which shows the result of a softening test in case a 1st metal member is a 6000 series aluminum alloy plate which does not contain Cu. It is a figure which shows the result of a softening test in case a 1st metal member is a 6000 series aluminum alloy plate containing Cu. It is a perspective view which shows the state which is performing the tensile test for measuring peeling strength with respect to what performed the friction point joining by superimposing the 1st metal member and the 2nd metal member on the cross shape.

DESCRIPTION OF SYMBOLS 1 Friction point joining apparatus 10 Joining gun 14 Pressing motor 15 Rotating motor (rotation drive means)
16 Rotating tool 16b Shoulder portion 16c Pin portion 16d Annular recess 50a Control unit (control means)
W1 1st metal member W2 2nd metal member X The axis of the rotary tool

Claims (4)

The tip of the first metal member and the second metal member having a melting point higher than that of the first metal member are overlapped with each other, and the tip portion that is one end in the axial direction of the rotary tool that rotates about the axis is disposed on the first metal. Friction point at which the two metal members are friction point joined by being pushed in from the side of the member and softening and plastically flowing the first metal member by frictional heat generated by rotation of the rotary tool and pressing operation on the first metal member A joining method,
In advance, a shoulder portion facing the workpiece, a tip portion of the rotating tool, a pin portion that is located on the axis of the rotating tool and projects from the shoulder portion to the workpiece side with a smaller diameter than the shoulder portion, And an annular recess provided in the shoulder portion around the pin portion, and the rotary tool is moved forward and backward in the axial direction of the rotary tool with respect to the workpiece and is moved to the first metal member. A pressing motor that can be pressed and can change the pressing force at the time of pressing is provided,
An initial moving step of moving the rotary tool to an initial position which is a proximity position of the first metal member by the pressing motor;
After the initial movement step, while rotating the rotary tool around the axis of the rotary tool, the pressing motor causes the pressing tool to have a first pressure greater than the movement resistance value of the rotary tool in the initial movement step. A first pressing step of pressing and contacting a shoulder portion and a pin portion of the rotary tool against the first metal member;
After the first pressing step, while rotating the rotary tool around the axis of the rotary tool, the shoulder portion of the rotary tool with the second pressing force larger than the first pressing force is applied by the pressing motor. the pin portion seen including a second pressing step of pushing the first metal member above,
In the first pressing step, the shoulder portion and the pin portion of the rotating tool are moved by the pressing motor with the first pressing force while rotating the rotating tool around the axis of the rotating tool at a predetermined rotation speed. , A step of pressing and contacting the first metal member for a predetermined time,
The first pressing force is set to 2.45 kN or more and 3.43 kN or less,
The predetermined rotational speed is set to 1500 rpm or more and 3500 rpm or less,
The said predetermined time is set to 0.2 second or more and 2.0 second or less, The friction point joining method characterized by the above-mentioned . In the friction point joining method according to claim 1 ,
After the second pressing step, the shoulder portion and the pin portion of the rotating tool are moved to the first position with a third pressing force smaller than the second pressing force by the pressing motor while rotating the rotating tool around the axis of the rotating tool. A friction point joining method, further comprising a third pressing step of pressing and contacting one metal member. In the friction point joining method according to claim 1 or 2 ,
The first metal member is made of an aluminum alloy material,
The second metal member is made of a steel material,
A friction point joining method, wherein the mating surface portions of the two metal members are solid-phase joined by friction spot joining. The tip of the first metal member and the second metal member having a melting point higher than that of the first metal member are overlapped with each other, and the tip portion that is one end in the axial direction of the rotary tool that rotates about the axis is disposed on the first metal. Friction point at which the two metal members are friction point joined by being pushed in from the side of the member and softening and plastically flowing the first metal member by frictional heat generated by rotation of the rotary tool and pressing operation on the first metal member A joining device,
The tip of the rotary tool has a shoulder portion facing the workpiece, a pin portion located on the axis of the rotary tool and projecting from the shoulder portion to the workpiece side with a smaller diameter than the shoulder portion, and the pin It is composed of an annular recess provided in the shoulder part around the part,
Rotation driving means for rotating the rotary tool around the axis of the rotary tool;
A pressing motor capable of changing the applied pressure at the time of pressing while causing the rotating tool to move forward and backward in the axial direction of the rotating tool with respect to the work and pressing the first metal member;
Control means for controlling the rotation driving means and the pressing motor,
The control means includes
An initial moving step of moving the rotary tool to an initial position which is a proximity position of the first metal member by the pressing motor;
After the initial movement step, the rotation tool rotates the rotation tool around the axis of the rotation tool, and the pressing motor causes a first resistance greater than the movement resistance value of the rotation tool in the initial movement step. A first pressing step of pressing and contacting a shoulder portion and a pin portion of the rotary tool against the first metal member with a pressing force;
After the first pressing step, the rotating tool rotates the rotating tool around the axis of the rotating tool, and the rotating motor rotates the rotating tool with a second pressing force larger than the first pressing force. And a second pressing step of pressing the shoulder portion and the pin portion of the tool into the first metal member .
In the first pressing step, the shoulder portion and the pin portion of the rotating tool are moved by the pressing motor with the first pressing force while rotating the rotating tool around the axis of the rotating tool at a predetermined rotation speed. , A step of pressing and contacting the first metal member for a predetermined time,
The first pressing force is set to 2.45 kN or more and 3.43 kN or less,
The predetermined rotational speed is set to 1500 rpm or more and 3500 rpm or less,
The friction point joining apparatus , wherein the predetermined time is set to 0.2 seconds or more and 2.0 seconds or less .

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