JP6668989B2 - Self-piercing rivet joining method and self-piercing rivet joining device - Google Patents

Description

  The present invention relates to a joining method and a joining apparatus using self-piercing rivets, and for example, self-piercing between base materials made of different materials having different strengths, such as a combination of an aluminum alloy plate and a high-tensile steel plate (including an ultra-high-tensile steel plate). The present invention relates to a joining method using a rivet joint structure and a joining device used for the method.

  A joining method using a self-piercing rivet (also referred to as a self-piercing rivet or a punch rivet) which is a self-piercing type and does not penetrate a base material to the back surface side has been known for a long time, and particularly, outside a car. When joining with self-piercing rivets on board panels, etc., as part of quality control, it is necessary to control the head of self-piercing rivets after driving so that it is almost flush with the surface of the base material on the driving side Have been. As means for that purpose, Patent Documents 1 and 2 disclose techniques for measuring the height position of the head of the self-piercing rivet after driving each time.

JP 2008-173688 A JP-A-2004-306115

  According to the techniques disclosed in Patent Documents 1 and 2, when the die and the punch that are responsible for driving the self-piercing rivet are both supported by a common so-called C-shaped frame, more or less at the moment when the self-piercing rivet is driven. Since the C-shaped frame elastically bends and deforms, even if a measurement method taking into account the bending and deformation of the C-type frame is adopted (especially paragraph [0013] of Patent Document 1 and paragraph [0005] of Patent Document 2) ].), The speciality in joining base materials of dissimilar materials having different mechanical strengths is not taken into consideration, and there is still room for improvement.

  For example, a combination of plate materials as a base material to be joined by a self-piercing rivet is configured as an upper plate and a lower plate, and the self-piercing rivet is driven in from the upper plate while the lower plate is in contact with the die. In this case, since the concave portion is formed in the die in advance, the self-piercing rivet is plastically deformed so that the self-piercing rivet expands in a flared skirt shape with the driving of the self-piercing rivet. A part of the upper plate and the material of the lower plate punched out by the piercing rivet are plastically flowed, and they are pushed into the concave portion of the die while filling into the inside of the self-piercing rivet, and are filled.

  If, for example, an aluminum alloy plate is used for the lower plate, and an ultra-high tensile strength steel plate whose tensile strength exceeds 1000 MPa is used for the upper plate, the self-piercing rivets used therefor also have relatively high hardness. Must be used. With the adoption of this high-hardness self-piercing rivet, the material that did not fit in the recess of the die grows as a bulge on the back surface of the lower plate, and the plate material after the self-piercing rivet is driven up from the die, As a result, there is a problem that the head position of the self-piercing rivet after driving cannot be accurately measured. The cause of the self-floating plate material after the self-piercing rivet driving will be described later.

  The present invention has been made in view of such a problem, and employs a high-tensile steel plate or an ultra-high-tensile steel plate having a large tensile strength as a plate-like base material (member to be joined) to be joined by self-piercing rivets. The present invention also provides a self-piercing rivet joining technique that can accurately measure the position of a self-piercing rivet after driving.

  In the self-piercing rivet joining method according to the present invention, the punch for driving the self-piercing rivet is driven forward and backward by a punch driving mechanism, and the punch driving mechanism determines the position of the driven self-piercing rivet. Assuming that it has a function of measuring based on the displacement of the punch, the self-piercing rivet is set in a state where the base material joined by driving the self-piercing rivet is separated from the die by a predetermined floating amount. Was measured.

  According to the present invention, even if a phenomenon occurs in which the base material after self-piercing rivet driving is self-floating, the self-piercing rivet is kept in a state where the base material is separated from the die by a set floating amount equal to or more than the self-floating amount. By measuring the position of the self-piercing rivet, the position of the self-piercing rivet can be accurately measured while avoiding the influence of the self-flying amount.

The schematic explanatory drawing which shows an example of the riveting gun used for the self-piercing rivet joining method which concerns on this invention. FIG. 2 is a process explanatory view showing a step of driving a self-piercing rivet by the rivet driving gun shown in FIG. 1. FIG. 5 is an enlarged cross-sectional view after driving a self-piercing rivet when an ultra-high tensile strength steel plate is used for an upper plate and an aluminum alloy plate is used for a lower plate. FIGS. 3A and 3B show details of a die using a ring lifter as a push-up member, wherein FIG. 3A is a longitudinal sectional view and FIG. 3B is a bottom view of FIG. FIG. 5 is an explanatory process diagram showing stepwise a self-piercing rivet driving process performed by using the die shown in FIG. 4 as the first embodiment of the self-piercing rivet joining method according to the present invention. 4A and 4B are diagrams showing details of another die having a different ring lifter driving method from that shown in FIG. 4, wherein FIG. 4A is a longitudinal sectional view and FIG. 4B is a bottom view of FIG. FIG. 7 is a process explanatory view showing stepwise a self-piercing rivet driving process performed by using the die shown in FIG. 6 as a second embodiment of the self-piercing rivet joining method according to the present invention. FIG. 6 is a longitudinal sectional view showing details of still another die having a different ring lifter driving system from that shown in FIG. 4. FIG. 9 is a process explanatory view showing stepwise a self-piercing rivet driving process performed by using the die shown in FIG. 8 as a third embodiment of the self-piercing rivet joining method according to the present invention.

  1 to 5 show a more specific embodiment for carrying out the self-piercing rivet joining method according to the present invention. In particular, FIG. 1 shows an example of a riveting gun 1 as a self-piercing rivet joining device, and FIG. 3 shows the details of the self-piercing rivet driving by the rivet driving gun 1.

  As shown in FIG. 1, the rivet driving gun 1 is formed by using a so-called C-shaped frame 2 as a base body. For example, a solid cylindrical die 3 is provided at one end on the open side of the C-shaped frame 2 via a die post 4. A punch drive unit 5 as a punch drive mechanism including a punch 11 (see FIG. 2) described later is mounted on the other end of the C-shaped frame 2 on the open side. Thereby, the C-shaped frame 2 functions as a common support that supports both the die 3 and the punch 11.

  The punch driving unit 5 includes a cylindrical body 6, a power transmission mechanism 7 connected to an upper end of the body 6, a servomotor 8 as a rotary drive source mounted on the power transmission mechanism 7, A rotary encoder 9 as a rotation detector attached to the servomotor 8. The punch drive unit 5 is fixedly supported at the other open end of the C-shaped frame 2 so that the punch 11 and the body 6 are located on the same axis as the die 3. A bracket 10 is attached to an intermediate portion of the C-shaped frame 2, and the riveting gun 1 is, for example, a teaching-playback type industrial robot (hereinafter simply referred to as a robot) via the bracket 10. It is supported by the tip of the arm 11.

  The power transmission mechanism 7 accommodates, for example, a speed reduction mechanism and a toothed belt transmission mechanism, and the rotational driving force of the servomotor 8 is reduced and transmitted to the body 6 side. A ball screw, for example, is accommodated and disposed in the body 6 as a rotation displacement-linear motion displacement conversion mechanism, and the ball screw receives a rotational force from the power transmission mechanism 7 and rotates the screw shaft. The nut member screwed to the screw shaft is driven forward and backward in the longitudinal direction of the body portion 6. A punch 11 shown in FIG. 2 is connected to a nut member that is driven forward and backward, and an annular nose piece 12 that functions as a plate holder is mounted on the outer periphery of the tip of the punch 11 so as to be relatively movable. The nosepiece 12 is urged downward by a compression coil spring (not shown).

  The servo motor 8 and the rotary encoder 9 are connected to the controller 13 so that the speed (rotational speed of the rotary shaft of the servo motor 8) and the stroke of the punch 11 driven forward and backward can be arbitrarily set. 9, the position of the punch 11 can be monitored.

  The rivet driving gun 1 shown in FIG. 1 is provided with a rivet feeder for supplying a self-piercing rivet into the nose piece 12 at the tip of the punch 11 before the self-piercing rivet is driven by the riveting gun 1. However, in order to avoid complicating the drawing, illustration of elements other than the rivet supply tube 14 is omitted in FIG.

  Then, based on the autonomous function of the robot, the riveting gun 1 performs an approaching operation on the base material to be joined, and when the riveting gun 1 is positioned at a predetermined position, the self-piercing rivet setting operation is performed. FIG. 2 shows a general basic operation of the rivet driving. In FIG. 2, the upper plate W1 as a base material (member to be joined) to be riveted is, for example, a mild steel plate or an aluminum alloy plate, and the lower plate W2 is, for example, a high-tensile steel plate.

  As shown in FIG. 2A, the die 3 is pressed against the lower surface of the lower plate W2 of the upper plate W1 and the lower plate W2 positioned in a state of being overlapped in advance, and is arranged to face the die 3. The nose piece 12 is lowered, and the upper plate W1 and the lower plate W2 are lightly pressed and restrained by the nose piece 12 and the die 3. At this time, a self-piercing rivet 15 is supplied to the tip of the punch 11 in advance and is suction-supported.

  Here, the self-piercing rivet 15 has a shape similar to a full tubular rivet, and includes a flat head portion 15a and a hollow cylindrical shaft portion 15b. The die 3 is formed with a concave portion 3a serving as a dish-shaped or concave pressing restraining surface corresponding to the size of the self-piercing rivet 15 to be driven, and a substantially conical projecting portion 3c is formed at the center thereof. Have been.

  Subsequently, as shown in FIG. 2B, the punch 11 arranged opposite to the die 3 together with the nose piece 12 is lowered, and the self-piercing rivet 15 is driven from the upper plate W1 side. The self-piercing rivet 15 is driven into the upper plate W1 and the lower plate W2 by a self-piercing method as the name implies, and a part of the upper plate W1 and a part of the lower plate W2 are directed toward the recess 3a side of the die 3 as the driving progresses. It will be plastically deformed to swell.

  Then, as shown in FIG. 3C, the self-piercing rivet 15 eventually penetrates the upper plate W1 but does not penetrate the lower plate W2, and the tip of the shaft portion 15b is spread outward to the lower plate W2. When the bite and the head 15a are substantially flush with the upper plate W1, fastening as a rivet joint, that is, fastening and joining between the upper material W1 and the lower plate W2 by the self-piercing rivet 15, is completed. The lower plate W2 is inevitably formed with a convex portion P1 having a concave central portion as a joining mark or a fastening mark by the self-piercing rivet 15 in a form in which the shape of the concave portion 3a of the die 3 is transferred. Become.

  In this case, the position of the head 11a of the self-piercing rivet 15 in contact with the leading end surface of the punch 11 in the vertical stroke direction of the punch 11 (the position of the head 15a with respect to the upper surface of the die 3). The position of the upper surface) can be detected from the output of the rotary encoder 9 shown in FIG. 1, and when the driving of the self-piercing rivet 15 is completed, the position data of the lowest position of the punch 11 is peak-held and captured. By comparing with the set reference value, it is possible to judge whether or not the driving quality of the self-piercing rivet 15 is good or not, or to store the data as quality assurance of all the driving positions.

  FIG. 2 shows an example in which the upper plate W1 is, for example, a mild steel plate or an aluminum alloy plate, and the lower plate W2 is, for example, a high-tensile steel plate. An ultrahigh-strength steel plate having a thickness of about 1.6 mm at 1180 MPa and an aluminum alloy plate having a thickness greater than that of the upper plate W1 (a thickness of approximately 2.8 mm) are adopted as the lower plate W2. FIG. 3 shows an example in which the self-piercing rivet 15 is used for joining. In FIG. 3, a projection 3c as shown in FIG. 2 is formed in the recess 3a of the die 3 in order to prevent the occurrence of a crack in the projection P1 unavoidably formed on the lower plate W2 side. No type is used.

  As shown in the figure, especially when an ultra-high tensile strength steel plate having a tensile strength exceeding 1000 MPa is used for the upper plate W1 and an aluminum alloy plate softer than the upper plate W1 is used for the lower plate W2, the lower plate is used. A bulge P2 formed by overflowing the material of the lower plate W2 into a corner formed by the protrusion P1 inevitably formed on the W2 side and the back surface of the lower plate W2, that is, the base of the protrusion P1. It was found to be formed along the circumferential direction. When the bulging portion P2 is formed, the entire base material is relatively pushed up from the die 3 by a predetermined amount α together with the punch 11, and although the joining quality by the self-piercing rivet 15 does not matter, the driving is performed. The position of the head 15a of the self-piercing rivet 15 cannot be accurately measured.

  The reason why the formation of the bulging portion P2 causes the entire base material to be pushed up by a predetermined amount α can be explained as follows. In other words, when an ultra-high tensile strength steel plate is used for the upper plate W1 and an aluminum alloy plate softer than the upper plate W1 is used for the lower plate W2, the self-piercing rivet 15 for joining them is also high in hardness. Is required. For this reason, the shaft portion 15b of the self-piercing rivet 15 is less likely to expand in diameter, and the plastic flow of a part Wn of the upper plate W1 punched by the self-piercing rivet 15 becomes slow. As is clear from the comparison, the material on the side Wn of the punched upper plate W1 and the material on the lower plate W2 side does not sufficiently enter the inside of the self-piercing rivet 15 (the inside of the shaft portion 15b). A phenomenon occurs in which a part of the material to be filled in the concave portion 3a overflows.

  When the riveting gun 1 having the C-shaped frame 2 as a base as shown in FIG. 1 is used, since the C-shaped frame 2 bears all the reaction force accompanying the driving of the self-piercing rivet 15, the self-piercing The moment the rivet 15 is driven, more or less flexural deformation (elastic deformation) occurs in the C-shaped frame 2 itself. As a result, when the driving of the self-piercing rivet 15 is completed and the flexural deformation of the C-shaped frame 2 is restored, the material that cannot be accommodated in the concave portion 3a of the die 3 becomes the bulging portion P2 on the back surface of the lower plate W2. It is presumed that the material grows as a whole and pushes up the whole base material from the die 3 and pushes back even the punch 11. Here, if the floating amount α in FIG. 2 which pushes up the entire base material due to the formation of the bulging portion P2 at the time of driving the self-piercing rivet 15 as described above is defined as the self-lifting amount, the self-lifting amount α Is about 0.2 to 0.3 mm.

  Therefore, in the present embodiment, the position of the head 15a of the driven self-piercing rivet 15 is determined after the formation of the bulging portion P2 which is inevitable depending on the combination of the upper plate W1 and the lower plate W2. It provides a method of measuring accurately, and details are shown in FIGS.

  FIG. 4 is an enlarged schematic view of a die 20 instead of the die shown in FIGS. 1 to 3, and FIG. 5 shows a stepwise driving process of the self-piercing rivet 15 using the die 20 of FIG.

  4A is a cross-sectional explanatory view of the die 20, and FIG. 4B is a bottom view of FIG. 4A. As shown in these figures, the die post 21 supporting the die 20 is shown in FIG. A retainer 22 is fixed to the outer periphery, and a compression coil spring (hereinafter simply referred to as a spring) 23 is mounted on the retainer 22 so as to be extrapolated to the die 20. Further, an annular ring lifter 24 similar to a washer is mounted on the upper surface of the spring 23 as a push-up member.

  The spring 23 has a winding diameter that does not interfere with the die 20 or the die post 21 when the spring 23 expands and contracts, and the upper surface of the ring lifter 24 and the upper surface of the die 20 when the ring lifter 24 is unloaded. The lift limit position L1 of the ring lifter 24 is mechanically restricted by a stopper (not shown) so that the distance between the ring lifter 24 and the set lift-up amount S is a preset lift amount. That is, even if the ring lifter 24 repeats the descending operation and the ascending operation with the expansion and contraction of the spring 23, the spring 23 is compressed by a predetermined amount so as to always return to the ascending limit position L1, which is a constant height position. In this state (the spring 23 is not in the free length state), the ascending limit position L1 of the ring lifter 24 is set.

  Note that the set lift-up amount S, which is the distance between the upper surface of the ring lifter 24 and the upper surface of the die 20, is more than the self-floating amount α based on the bulging portion P2 formed inevitably as described above. Is set to a large value.

  FIG. 5A shows a state immediately after the self-piercing rivet 15 is driven into the base material composed of the upper plate W1 and the lower plate W2 using the die 20 with the ring lifter 24 of FIG. Is shown. In addition, reference numeral L1 in the figure indicates the ascending limit position level of the ring lifter 24, and reference numeral L2 indicates the position of the die 20 in a state where the C-shaped frame 2 supporting the die 20 and the die post 21 in FIG. The top level is shown.

  As shown in FIG. 5A, by pressing the die 20 against the lower plate W2, the ring lifter 24 is relatively pressed down by the base material so as not to hinder the driving of the self-piercing rivet 15. Further, as described above, the driving of the self-piercing rivet 15 causes the C-shaped frame 2 of FIG. 1 supporting the die 20 and the die post 21 to bend and deform. Therefore, in FIG. 5A, the state in which the die 20 and the die post 21 are pushed down is exaggerated as compared with FIG. 5B.

  FIG. 5B shows a state after the driving of the self-piercing rivet 15 is completed and the bending deformation of the C-shaped frame 2 in FIG. 5A is restored. As described above, the bulging portion P2 is formed on the lower plate W2 side when the deformation is restored. Due to the restoration of the flexural deformation of the C-shaped frame 2 and the formation of the bulging portion P2, the punch 11 is slightly pushed back together with the upper plate W1 and the lower plate W2 as the base materials.

  FIG. 5C shows a state in which the formation of the bulging portion P2 as described above is allowed, and the upper plate W1 and the lower plate W2, which are the base materials, are forcibly lifted up by the ring lifter 24. ing. At the time of this lift-up, the punch 11 is once moved upward by a predetermined stroke together with the nose piece 12, and the ring lifter 24 is moved by the force of the spring 23 with the lift operation of the punch 11. Then, the upper plate W1 and the lower plate W2, which are the base materials, are lifted up by the amount S and floated from the die 20.

  The set lift-up amount S by which the ring lifter 24 pushes up the upper plate W1 and the lower plate W2 as the base material is, as described above, the self-lift amount α based on the inevitable formation of the bulging portion P2. Is also set to a large value, the lower plate W2 including the projection P1 is always separated from the die 20. The rising stroke of the punch 11 is preset in the controller 13 shown in FIG. Naturally, the force of the spring 23 pushing up the ring lifter 24 is set in advance to a size that can sufficiently oppose the own weight of the upper plate W1 and the lower plate W2, which are the base materials.

  When the upper plate W1 and the lower plate W2, which are the base materials, are lifted up by the set lift-up amount S in this manner, the punch 11 once moved upward together with the nosepiece 12 as shown in FIG. It is lowered again and brought into contact with the head 15a of the self-piercing rivet 15 after driving. In this case, in order to prevent the descending punch 11 from pushing back the ring lifter 24, the punch 11 is lowered at a lower speed and with a lower load than at the time of driving the self-piercing rivet. Note that the stroke, speed, and the like for lowering the punch 11 again are preset in the controller 13 described above.

  When the punch 11 comes into contact with the head 15a of the self-piercing rivet 15 and stops, the position data indicated by the rotary encoder 9 shown in FIG. It is stored as height position data. Further, by comparing the taken height position data of the self-piercing rivet 15 with a preset reference value (a reference value in consideration of the set lift-up amount S), the driving quality of the self-piercing rivet 15 (after driving) The quality of the head 15a of the self-piercing rivet 15 and the level of the upper plate W1 are determined in real time, or the data is stored and recorded as data for quality assurance of all hit points.

  In addition, while the set lift-up amount S by the ring lifter 24 is reflected in the acquired height position data of the self-piercing rivet 15, the set lift-up amount S is such that the bulging portion P2 is inevitably formed. Is set in advance so as to have a value larger than the self-flying height α based on. For this reason, when it is desired to acquire the height position data of the self-piercing rivet 15 in which the set lift-up amount S by the ring lifter 24 is not reflected, it is necessary to simply obtain the height setting data from the measured self-piercing rivet 15 position data. What is necessary is to reduce the value of the lift-up amount S.

  As described above, according to the present embodiment, the set lift-up amount S by the ring lifter 24 as the push-up member is set to a value larger than the self-floating amount α based on the inevitable formation of the bulging portion P2. On the other hand, the height of the head 15a of the self-piercing rivet 15 is measured after the base material after the self-piercing rivet driving is lifted up by the set lift-up amount S described above. It is possible to accurately measure the position of the head 15a of the self-piercing rivet 15 after driving without being affected by the bulging portion P2 inevitably formed on the lower surface of the plate W2 and the bending deformation of the C-shaped frame 2. It becomes possible.

  FIGS. 6 and 7 are views showing a second embodiment of the self-piercing rivet joining method according to the present invention, in which parts common to those of the first embodiment shown in FIGS. It is. 6A is a cross-sectional explanatory view of the die 20, and FIG. 6B is a bottom view of FIG. 6A. FIG. 7 shows stepwise the driving process of the self-piercing rivet 15 using the die 20 of FIG.

  In the second embodiment, as shown in FIG. 6, the ring lifter 24 is positively moved up and down by a fluid pressure actuator 29 typified by an air cylinder. More specifically, a holder 26 is guided and supported at a lower portion of the die post 25 so as to be able to move up and down, and a bar-shaped retainer 27 is disposed in an escape hole 25 a penetrating the die post 25 in the radial direction. The retainer 27 is connected and supported by the holder 26, and a pair of left and right tie bars 28 are erected from both ends of the retainer 27, and the ring lifter 24 is connected and supported on the upper ends of the tie bars 28.

  An output rod of a fluid pressure actuator 29 typified by, for example, an air cylinder as a direct acting actuator is connected to the holder 26, and when the fluid pressure actuator 29 is in a contracted state, the upper surface of the ring lifter 24 is Is set to be flush with the upper surface of the die 20 or to stand by at a lower limit position where the height is slightly lower than the upper surface of the die 20.

  FIG. 7 shows stepwise the driving process of the self-piercing rivet 15 using the ring lifter 24 driven by the fluid pressure actuator shown in FIG. 6, and FIGS. 5 (a) to 5 (d) as they are.

  As shown in FIG. 7A, in addition to the stage where the self-piercing rivets 15 are driven into the upper plate W1 and the lower plate W2, which are the base materials, as shown in FIG. Until the bending deformation is restored and the bulging portion P2 is formed in the lower plate W2, the ring lifter 24 is at the lower limit position L2.

  As shown in FIG. 7 (c), after the punch 11 is moved up by a predetermined stroke together with the nose piece 12 after the driving of the self-piercing rivet 15, the extension operation of the fluid pressure actuator 29 shown in FIG. Based on this, the ring lifter 24 lifts up, pushing up the upper plate W1 and the lower plate W2, which are the base materials. In the lift-up state of the ring lifter 24, the set lift-up amount S, which is the distance between the upper surface of the ring lifter 24 and the upper surface of the die 20, is similar to that of the first embodiment. The value P2 is set in advance to a value larger than the self-flying height α based on the inevitable formation of P2.

  Then, in such a lift-up state, as shown in FIG. 7D, the punch 11 is lowered again together with the nose piece 12, and is brought into contact with the head 15a of the self-piercing rivet 15 after being driven. The height position will be measured.

  In the second embodiment, the same effects as those in the first embodiment can be obtained.

  8 and 9 are views showing a third embodiment of the self-piercing rivet joining method according to the present invention, in which parts common to those of the second embodiment shown in FIGS. It is.

  In the third embodiment, as shown in FIG. 8, an electromagnet 31 is used as a direct-acting actuator for moving the ring lifter 24 up and down instead of the fluid pressure actuator 29 of FIG. More specifically, a holder 30 guided and supported so as to be able to move up and down below the die post 25 is made of a permanent magnet, and an electromagnet 31 is fixedly arranged adjacent to the lower side of the holder 30. As is clear from the comparison between FIG. 9B and FIG. 9C described later, the electromagnet 31 can reverse the upper and lower polarities of the electromagnet 31 by switching the energizing direction. . In the state shown in FIG. 8, the holder 30 is attracted to the electromagnet 31, whereby the upper surface of the ring lifter 24 is flush with the upper surface of the die 20, or the lower end of which is slightly lower than the upper surface of the die 20. It is set to wait at a position.

  FIG. 9 shows stepwise the driving process of the self-piercing rivet 15 using the electromagnet-driven ring lifter 24 shown in FIG. 8, wherein (a) to (d) of FIG. 7 (a) to 7 (d) as they are.

  As shown in FIG. 9 (a), in addition to the stage where the self-piercing rivets 15 are driven into the upper plate W1 and the lower plate W2, which are the base materials, as shown in FIG. Until the bending deformation is restored and the bulging portion P2 is formed in the lower plate W2, the ring lifter 24 is at the lower limit position. That is, the electromagnet 31 is in a state of holding the holder 30.

  As shown in FIG. 9C, after the punch 11 is moved up by a predetermined stroke together with the nose piece 12 after the self-piercing rivet 15 is driven, the energizing direction of the electromagnet 31 is switched to the opposite direction. Thus, the upper and lower polarities of the electromagnet 31 are reversed. Due to the polarity reversal of the electromagnet 31, the electromagnet 31 and the holder 30 repel each other. At this time, the ring lifter 24 lifts up together with the holder 30 for the first time, and the upper plate W1 and the lower plate W2 will be pushed up. In the lift-up state of the ring lifter 24, the set lift-up amount S, which is the distance between the upper surface of the ring lifter 24 and the upper surface of the die 20, is similar to that of the first embodiment. The value P2 is set in advance to a value larger than the self-flying height α based on the inevitable formation of P2.

  Then, in such a lift-up state, as shown in FIG. 9D, the punch 11 is lowered again together with the nose piece 12, and is brought into contact with the head 15a of the self-piercing rivet 15 after the driving. The height position will be measured.

  In the third embodiment, the same effects as in the first and second embodiments can be obtained. However, in order to simplify the structure because there are few ancillary devices such as piping and wiring, the first embodiment is most advantageous.

  Further, in the first to third embodiments, an example in which an ultra-high-strength steel plate is used as an upper plate serving as a base material and an aluminum steel plate is used as a lower plate also serving as a base material has been described as an example. The combination of the base materials is not limited to the combination of the ultra-high-strength steel sheet and the aluminum steel sheet, and a three-layered base material may be adopted. In short, the present invention can be applied to a case where a relatively hard material is used as the self-piercing rivet to be driven into the upper and lower plates due to the difference in strength between the upper and lower plates made of different materials.

  Further, the ring lifter 24 used as the push-up member in the first to third embodiments is merely an example, and it goes without saying that another shape can be used as long as the same function is exhibited. No.

1. Riveting gun 2. C-type frame (support)
5. Punch drive unit (punch drive mechanism)
8 Servo motor 9 Rotary encoder 11 Punch 15 Self-piercing rivet 20 Die 23 Compression coil spring 24 Ring lifter (push-up member)
P2: bulging portion S: set lift-up amount (set floating amount)
W1: Upper plate (base material)
W2: Lower plate (base material)
α: Self-floating amount

Claims (6)

At least two plate-shaped base materials having different strengths are overlapped with each other, and the die is brought into contact with the base material having the lower strength, and the support is common to the die from the base material having the higher strength toward the die. A method of joining base materials together in the form of a rivet joint by driving a self-piercing rivet with a punch supported by
The punch is driven forward and backward by a punch drive mechanism,
The punch drive mechanism has a function of measuring the position of the driven self-piercing rivet based on the displacement of the punch,
A self-piercing rivet joining method, wherein the position of the self-piercing rivet is measured while the base material joined by driving the self-piercing rivet is separated from the die by a predetermined floating amount.   2. The set floating amount is set to a value larger than a self floating amount in which a base material in contact with the die floats from the die due to plastic flow after the self-piercing rivet is driven. Self-piercing rivet joining method. While the punch is once separated from the self-piercing rivet after driving the self-piercing rivet,
After the base material joined by driving the self-piercing rivet is separated from the die by a set floating amount, a punch is again brought into contact with the self-piercing rivet to measure the position of the self-piercing rivet. 3. The method for joining self-piercing rivets according to item 2. The support on which the die and the punch are supported is a C-shaped frame,
A die is supported at one end of the C-shaped frame,
4. The self-piercing rivet joining method according to claim 3, wherein a punch located on the same axis as the die is supported at the other end of the C-shaped frame together with a punch driving mechanism.   The self-piercing rivet according to any one of claims 1 to 4, wherein the low-strength base material is an aluminum alloy plate, and the high-strength base material is a high-tensile steel plate or an ultra-high-tensile steel plate. Joining method. A self-piercing rivet joining apparatus used in the self-piercing rivet joining method according to claim 4,
A self-piercing rivet joining apparatus, characterized in that a push-up member is provided on the die side for causing the base material joined by driving the self-piercing rivet to separate from the die by a set floating amount.

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