JP2019013942A - Self-drilling rivet fastening device - Google Patents

Abstract

To provide a self-drilling rivet fastening device for fastening a target member having poor ductility with a self-drilling type rivet so as not to cause a crack.SOLUTION: A self-drilling rivet fastening device (1) fastens a self-drilling rivet (10) having a large-diameter head (11) and a hollow leg (12) by driving the self-drilling rivet (10) into target members (41 and 42). A die comprises a die body (30) and a center pin (50). The die body (30) comprises an upper surface (31), a recessed part formed on the inner side of the upper surface, and a center pin hole (34) penetrating from a center part of the recessed part to a lower end part (37) thereof. The center pin (50) is supported so as to be movable in the axial direction within the center pin hole, and comprises a shaft part (52). A pin flange (53) can be provided at one end of the shaft part. A spring (55) presses the center pin upward. When fastening a self-drilling rivet, a target member enters the center pin hole by pressing the central pin. After the fastening, the center pin pushes out the fastened target member.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a self-piercing rivet fastening device that fastens a plurality of members to be fastened using a self-piercing rivet having a large-diameter head and hollow legs hanging from the head. . In particular, the present invention relates to a self-piercing rivet fastening device used when fastening a fastened member made of a material having poor spreadability such as a die-cast material.

  The self-piercing rivet has an advantage that a plurality of members to be joined can be easily joined simply by driving in a rivet without processing a hole for inserting a bolt or the like for fastening to the member to be fastened in advance.

  Self-drilling rivets are suitable for connecting aluminum body panels that are not suitable for welding. The weight of automobile bodies has been reduced, and aluminum bodies have also been adopted, and the demand for self-drilling rivets is increasing. In particular, the self-piercing rivet is driven so that the upper (punch side) fastened member penetrates, but the lower (receiving side) fastened member adjacent to the die does not penetrate and stays therein. Therefore, no rivet through-hole is formed on the surface of the receiving member to be fastened. Therefore, there is an advantage that the sealing performance to the receiving side fastening member is not impaired and the appearance is maintained as it is.

  When using a conventional self-piercing rivet fastening device using a die to fasten a fastened member such as a die-casting material, the tip of the leg of the self-piercing rivet is punched into the fastened member When the member to be fastened is deformed by the recessed portion of the die, the member to be fastened cannot withstand plastic deformation and cracking may occur. In particular, cracks often occur in the lower fastening member.

Patent Document 1 discloses a punch rivet setting die having a base body for a punch (self-piercing type) rivet setting tool. The recess formed in the base body has a bottom base and an annular wall around the base. An annular ridge is provided in the central region of the base of the recess to limit the material flow exiting radially outward from its inner region. Alternatively, instead of an annular ridge, a cavity is provided in the center of the base of the recess to limit the material flow exiting radially outward.
In Patent Document 1, since the material flow in the radial direction in the central region is limited, after the punch rivet is fastened, the lowermost workpiece is maintained in sufficient thickness, and the lowermost workpiece is cracked. It is difficult to occur.
However, the shape of the cavity of the mounting die of Patent Document 1 does not change even when fastening. Further, since the annular raised portion of the mounting die has a short axial length, its effect is limited.

Patent Document 2 discloses a die for an automatic drilling rivet fastening device. The die has a central pin that receives the central portion of the leg portion of the self-piercing rivet and a die body that is formed with a recess that guides the tip end of the leg portion of the self-piercing rivet to be deformed radially outward. A disc spring is provided to press the die body against the punch.
When the automatic perforating rivet is pressed by the punch, driven into the fastened member, and the tip of the leg begins to penetrate the fastened member on the receiving side, the disc spring shrinks, the die body moves downward, and the center pin moves It moves upward relative to the die body, and the center pin comes into contact with the lower surface of the receiving member to be fastened.
In Patent Document 2, since the center pin is located at the center position of the leg portion of the automatic drilling rivet, the tip of the leg portion of the automatic drilling rivet is greatly expanded and fastened in the radial direction. For this reason, the fastened member can be fastened with a sufficient binding force.

  However, in the automatic perforation rivet fastening device of Patent Document 2, when the automatic perforation rivet is fastened, the center pin pushes up the lower surface of the receiving-side member to be fastened at the center of the leg end of the automatic perforation rivet, and the automatic perforation rivet Acts to open the legs of the. When the member to be fastened is made of a material having poor spreadability, the receiving member to be fastened may be cracked.

  Therefore, there has been a demand for a self-piercing rivet fastening device that prevents the fastening member from cracking even when a fastened member having poor spreadability is fastened by a self-piercing rivet.

JP-T-2015-529562 International Publication WO03 / 061869

  An object of the present invention is to provide a self-piercing rivet fastening device that can fasten a fastened member having poor spreadability by a self-piercing rivet so that cracking does not occur.

In order to achieve this object, a die of a self-piercing rivet fastening device according to the present invention includes a die body and a center pin that is movable in the axial direction in a center pin hole formed in the axial direction of the die body. The self-piercing rivet fastening device includes a pressing device that presses the center pin upward. When a self-piercing rivet is driven and fastened to the fastened member by punching, the material of the fastened member pushes the central pin downward, and the material of the fastened member enters the central pin hole after the central pin has moved. The member to be fastened is not enlarged more than necessary, and is difficult to break.
In addition, after completion of the fastening, the pressing device can push the center pin upward to push out the fastened member in the hole.

A first aspect of the present invention is a self-drilling rivet fastening device for driving a self-drilling rivet having a large-diameter head and hollow legs hanging from the head into a member to be fastened. There,
A nose for pressing the fastened member;
A punch for driving the self-piercing rivet into the fastened member;
A die for receiving the fastened member;
The die has an upper surface and a concave body formed on the inner side of the upper surface, and a die body in which a central pin hole penetrating downward from a central portion of the concave portion is formed;
A center pin supported in the center pin hole of the die body so as to be movable in the axial direction,
The central pin has a cylindrical shaft portion having an outer diameter matching the inner diameter of the central pin hole,
The self-piercing rivet fastening device further comprises a pressing device for pressing the central pin in the axial direction.

  When the self-piercing rivet fastening device includes a pressing device for pressing the central pin in the axial direction, the central pin can be held in the central pin hole of the die body while being pressed upward. When a large force is applied to the upper surface of the center pin, the center pin can move downward.

  It is preferable that the center pin is movable from a position below the bottom surface of the recess of the die body to a position above the bottom surface of the recess.

If the center pin is able to move downward until the top surface of the center pin is below the bottom surface of the concave portion of the die body, the center pin moves downward, so that it is fastened under the self-piercing rivet. The material of the member can enter the central pin hole.
If the center pin is movable upward until the top surface of the center pin is positioned above the bottom surface of the recess, the center pin moves upward to push the fastened member to be fastened from the die body. Can do.

The pressing device is a spring disposed below the center pin,
The spring applies an upward pressing force to the center pin,
When a downward pressing force stronger than the pressing force of the spring is applied to the upper surface of the central pin, the central pin moves downward until the upper surface is positioned below the bottom surface of the recess,
If the downward pressing force is not applied to the upper surface of the central pin, the central pin is pressed by the pressing force of the spring until the upper surface is positioned above the bottom surface of the recess. It is preferable to move upward.

  If the pressing device is a spring provided on the lower side of the center pin, the center pin can be easily pressed upward, and when the punch is subjected to the stress of driving a self-piercing rivet, the spring contracts and the center The pin can move downward.

When the fastened member is pushed by the self-piercing rivet and presses the upper surface of the central pin, the central pin moves downward and the fastened member can enter the central pin hole after the central pin has moved.
When the fastening of the self-piercing rivet is completed, the center pin is pushed upward by the pressing force of the spring, and the fastened member to be fastened can be pushed out from the die body.

  The pressing device is preferably a hydraulic device, a pneumatic device, or an electric device that is attached to the frame and presses the center pin.

  When the pressing device is a hydraulic device, a pneumatic device, or an electric device such as a motor, oil or air is supplied to the cylinder connected to the central pin, or the central pin is moved in the axial direction by the force of the motor or the like. it can. When the center pin is pressed by hydraulic pressure, pneumatic pressure, or an electric device, the movement of the center pin can be controlled more finely.

A second aspect of the present invention is a fastening method for fastening a self-piercing rivet,
The self-piercing rivet fastening device comprises a nose, a punch, and a die for receiving a fastened member,
The die has an upper surface and a concave body formed on the inner side of the upper surface, and a die body in which a central pin hole penetrating downward from a central portion of the concave portion is formed;
A center pin supported in the center pin hole of the die body so as to be movable in the axial direction;
Furthermore, the self-piercing rivet fastening device includes a pressing device for pressing the central pin in the axial direction, and the fastening method includes:
(a) disposing the fastened member on the upper surface of the die body;
(b) holding the fastened member by the nose;
(c) disposing the self-piercing rivet between the punch and the fastened member;
(d) Lowering the punch and pressing the self-piercing rivet against the fastened member, the fastened member moves downward, and the leg end of the self-piercing rivet is in the fastened member. Perforated and
(e) The material of the fastened member penetrates into the central pin hole, the central pin resists the pressing force of the pressing device, and the upper surface of the central pin is the bottom surface of the concave portion of the die body. The fastening method includes a step of lowering to a lower position and completing the fastening.

  When the punch presses the self-piercing rivet and the self-piercing rivet presses the material of the fastened member downward, the material of the fastened member enters the concave portion of the die body, and further pushes the central pin downward, to go into. The upper surface of the center pin is lowered to a position lower than the bottom surface of the concave portion of the die body. Self-drilling rivets are not expanded radially outward beyond necessity. Therefore, it is possible to prevent the member to be fastened from cracking.

(f) After completion of the fastening, the center pin is raised in the center pin hole by the pressing force of the pressing device, and the member to be fastened in the center pin hole can be pushed out.

  After the fastening is completed, the center pin is pushed upward by the pressing force of the pressing device in the center pin hole and rises, and when the member to be fastened in the center pin hole is pushed out, the member to be fastened is automatically removed from the fastening device. Can be removed.

When the self-piercing rivet is fastened by the self-piercing rivet fastening device of the present invention, deformation of the fastened member can be reduced, and cracking can be reduced even when fastening a fastened member with poor spreadability.
As a result, it is possible to provide a self-piercing rivet fastening device that can fasten a fastened member with poor spreadability without cracking.
In addition, by adjusting the pressing force and distance when the center pin is lowered, it is possible to adjust the way of opening the legs of the self-drilling rivet, and to be fastened with various thicknesses and materials with a small number of dies It can correspond to the conclusion of.

It is an enlarged view of the part which fastens the self-drilling type rivet of the conventional self-drilling type rivet fastening device. It is an expanded sectional view after fastening a to-be-fastened member by a self-drilling type rivet using the conventional die. 1 is a cross-sectional view of a part of a self-piercing rivet fastening device according to a first embodiment of the present invention. It is the perspective view which made a part of die | dye of FIG. 3 the cross section. It is sectional drawing before fastening a to-be-fastened member by a self-piercing type rivet using the die | dye of FIG. FIG. 6 is a cross-sectional view showing a stage where the punch presses the head of the self-piercing rivet slightly downward from the stage of FIG. 5. It is sectional drawing which shows the step which the punch pressed the head of the self-piercing type rivet further downward from the step of FIG. FIG. 8 is a cross-sectional view showing a stage where the punch presses the head of the self-piercing rivet further downward from the stage of FIG. 7. It is sectional drawing which shows the step which the punch pressed the head of the self-piercing type rivet further downward from the step of FIG. It is sectional drawing which shows the step which the fastening of the self-piercing type rivet was completed. FIG. 5 is a partial cross-sectional view of a self-piercing rivet fastening device according to a second embodiment. This is a simulation of the force applied to the self-piercing rivet and the member to be fastened when the fastening operation is completed using a conventional die. FIG. 5 is a simulation of a force applied to a self-piercing rivet and a member to be fastened when the fastening operation is completed using the die of FIG. 4. FIG.

Hereinafter, embodiments of a die used for a self-piercing rivet fastening device according to the present invention will be described in comparison with a conventional die with reference to the drawings.
FIG. 1 is an enlarged view of a portion for fastening a self-piercing rivet of a conventional self-piercing rivet fastening device. The self-piercing rivet fastening device 1 includes a C-shaped frame (not shown), and a conventional die 20 is fixed to the C-shaped frame. A nose 3 movable in the vertical direction is attached to the C-type frame, and a punch 4 for driving a self-piercing rivet 10 is attached.
The fastened members 41 and 42 can be clamped between the upper surface of the die 20 and the lower surface of the nose 3.

  The self-piercing rivet 10 has a large-diameter head 11 and a cylindrical leg 12 depending from the head 11. The lower end of the leg 12 is a leg tip 13 with a narrow width.

  The die 20 has a short cylindrical large diameter portion 24 and a cylindrical small diameter portion 26 therebelow. The upper end portion of the large diameter portion 24 is a flat upper surface 21, and a concave portion for deforming the leg portion 12 of the self-piercing rivet 10 is formed in the central portion of the upper surface 21. The concave portion includes a bottom surface 22 having a circular plane in the center and a curved surface 23 around the bottom surface 22.

  When fastened members 41, 42 are arranged on the die 20, and the self-piercing rivet 10 is driven by the punch 4 from above the fastened members 41, 42, the leg tip 13 of the self-piercing rivet 10 is The clamped member 41 on the punch side passes through, and the clamped member 42 on the receiving side adjacent to the die 20 does not penetrate and stays therein. The tip of the leg portion 12 of the self-piercing rivet 10 is deformed by the die 20 so as to expand the diameter outward in the radial direction. The fastened members 41 and 42 are connected to each other by the leg 12 and the head 11 that are open in the fastened member 42.

  FIG. 2 is an enlarged cross-sectional view after the fastened members 41 and 42 are fastened by the self-piercing rivet 10 using the conventional die 20. The nose 3 and the punch 4 are moving upward. When the self-piercing rivet 10 is driven by the punch 4, the leg portion 12 penetrates the punch-side fastened member 41 by the punch 4 and plastically deforms the receiving-side fastened member 42. The fastened member 42 is protruded downward by the leg 12, the protruding portion of the fastened member 42 is received in the recess, and the lower surface of the fastened member 42 hits the bottom surface 22 of the recess. When the fastened member 42 hits the bottom surface 22, it cannot move downward, so that the leg portion 12 of the self-piercing rivet 10 expands radially outward while pushing the fastened member 42 radially outward. Transforms into The leg tip 13 remains in the receiving member 42 adjacent to the die 20 without penetrating it. The fastened members 41 and 42 are connected to each other by the leg portion 12 and the head portion 11 having a diameter expanded in the fastened member 42.

  The fastened member 42 is pushed outward in the radial direction by the enlarged leg portion 12. When the fastened member 42 is made of a material with poor spreadability, cracks are likely to occur near the curved surface 23 of the die 20.

(First embodiment)
FIG. 3 is a cross-sectional view showing the die of the self-piercing rivet fastening device 1 according to the first embodiment of the present invention and a part of the C-shaped frame 45 that supports the die. A C-type frame 45 is used in the self-piercing rivet fastening device 1. In the C-type frame 45, an upper horizontal arm portion, a vertical arm portion, and a lower horizontal arm portion are integrated. Only the lower horizontal arm portion is shown in FIG. A fastening mechanism is attached to the upper horizontal arm portion. A die is attached to the lower horizontal arm portion of the C-shaped frame 45.
The fastening mechanism attached to the upper horizontal arm portion has a nose 3 so that the fastened member can be pressed on the die. Further, the punch 4 is provided, and the self-piercing rivet 10 can be driven into a fastened member disposed on the die. In FIG. 3, nose 3 and punch 4 are not shown.

  The self-piercing rivet 10 has a large-diameter head 11 and a cylindrical leg 12 depending from the head 11. The lower end of the leg 12 is a leg tip 13 with a narrow width. The material of the self-piercing rivet 10 is selected according to the material of the member to be fastened, and aluminum, aluminum alloy, steel, stainless steel or the like is used.

FIG. 4 is a perspective view, partly in section, of the die of the self-piercing rivet fastening device 1 of the present invention shown in FIG. Hereinafter, the die will be described in detail with reference to FIGS. 3 and 4.
The die includes a die body 30 and a center pin 50 slidably received in the center pin hole 34 of the die body 30. The die body 30 includes a large-diameter large-diameter portion 35 and a small-diameter portion 36 smaller in diameter than the substantially cylindrical large-diameter portion 35 below the large-diameter portion 35.

  The large diameter portion 35 is made of a hard material such as high speed tool steel so that the leg portion 12 of the rivet 10 can be deformed. The large-diameter portion 35 of the die body 30 is axisymmetric about the central axis. The upper end portion is a flat upper surface 31, and a concave portion for deforming the leg portion 12 of the self-piercing rivet 10 is formed in the central portion of the upper surface 31. The concave portion is composed of a circular flat bottom surface 32 at the center and a curved surface 33 curved around the bottom surface 32. In addition to this, the recess can take various shapes.

  A die body hole 46 having a circular cross section is formed in the lower horizontal arm portion of the C-shaped frame 45. The small-diameter portion 36 of the die body 30 is accommodated in the die body hole 46, and the large-diameter portion 35 protrudes above the die body hole 46. The inner diameter of the die body hole 46 is equal to or slightly larger than the outer diameter of the small diameter portion 36 of the die body 30. The small-diameter portion 36 of the die body 30 is accommodated in the die body hole 46 and fixed so as not to move relative to the C-shaped frame 45 by screws (not shown) or the like.

The small diameter portion 36 of the die body 30 is substantially cylindrical, and the lower end portion 37 is a flat surface.
A central pin hole 34 having a circular cross section is formed at the center of the bottom surface 32 of the upper surface of the die body 30. The central pin hole 34 penetrates from the upper surface 31 of the die 30 to the lower end portion 37.

A central pin 50 is disposed in the central pin hole 34 so as to be slidable in the axial direction. The center pin 50 has a cylindrical shaft portion 52 and a pin flange 53 having a diameter larger than that of the shaft portion 52 formed at one end portion of the shaft portion 52. The pin flange 53 may not be provided.
An upper end portion of the shaft portion 52 of the center pin 50 is a flat upper surface 51. The outer diameter of the pin flange 53 is larger than the inner diameter of the central pin hole 34. When the center pin 50 is slid into the center pin hole 34, the pin flange 53 of the center pin 50 comes into contact with the lower end portion 37 of the die body 30 and stops.

A spring 55 is disposed between the bottom of the die body hole 46 of the C-shaped frame 45 and the lower surface of the pin flange 53 of the center pin 50, and applies an upward force to the center pin 50. When the pin flange 53 of the center pin 50 is not provided, the upper end portion of the spring 55 comes into contact with the lower end portion of the center pin 50.
A stopper 56 is formed in the lower part of the center pin 50. When the pin flange 53 abuts against the stopper 56, the center pin 50 cannot move downward. The stopper 56 may not be provided.
3 and 4, the center pin 50 is in the lowest lowered position. In the lowered position, the upper surface 51 of the central pin 50 is located below the bottom surface 32 of the recess of the die body 30, and there is a gap between the pin flange 53 and the lower end portion 37 of the die body 30.

When the center pin 50 is moved upward in the center pin hole 34, the upper surface of the pin flange 53 comes into contact with the lower end portion 37 of the die body 30, and the center pin 50 stops. This position is the home position of the center pin 50.
When the center pin 50 does not have the pin flange 53, the upper end of the spring 55 contacts the lower end 37 of the die body 30, and the center pin 50 stops.
The length of the shaft portion 52 of the central pin 50 is longer than the length from the bottom surface 32 to the lower end portion 37 of the concave portion of the die body 30. Therefore, at the home position of the center pin 50, the upper surface 51 of the center pin 50 is located above the bottom surface 32 of the recess.

  More preferably, the length of the shaft portion 52 of the center pin 50 is equal to the length from the upper surface 31 to the lower end portion 37 of the die body 30. Therefore, the upper surface 51 of the central pin 50 is flush with the upper surface 31 of the die body 30 at the home position of the central pin 50. When the fastened members 41 and 42 are disposed on the die body 30 in a state where the central pin 50 is at the home position, it is convenient that the fastened members 41 and 42 are not bent.

Before the self-piercing rivet 10 is fastened, the center pin 50 is in the raised home position by the spring force of the spring 55.
When the self-piercing rivet 10 is fastened, when the self-piercing rivet 10 is drilled into the fastened members 41, 42, the material of the fastened members 41, 42 moves downward, enters the recess, Further, when the upper surface 51 of the center pin 50 is pushed, the center pin 50 descends in the center pin hole 34. At the stage where the fastening is completed, the center pin 50 is lowered to or near the lowered position.
When conditions such as the material and size of the self-piercing rivet 10 and the materials and thickness of the fastened members 41 and 42 are changed, the spring force of the spring 55 is adjusted. The center pin 50 is pushed by the spring 55 and positioned at the home position before fastening, and the center pin 50 moves down to the lowered position against the pressing force of the spring 55 at the time of fastening. The central pin 50 pushes out the fastened members 41 and 42 in the central pin hole 34 by the pressing force of 55.

With reference to FIGS. 5 to 10, a process of driving the self-piercing rivet 10 into the fastened members 41 and 42 using the self-piercing rivet fastening device according to the first embodiment of the present invention will be described.
In FIG. 5, the fastened members 41 and 42 are placed on the upper surface 31 of the die body 30 with the central pin 50 in the home position.

In the illustrated example, the receiving-side fastened member 42 is thicker than the punch-side fastened member 41. The fastened member 41 and the fastened member 42 are made of a soft material such as aluminum or a hard material such as steel. The fastened member 41 on the punch side may be made of a material such as carbon or resin. Even if the receiving-side fastened member 42 is made of a material that is hard and has poor spreadability, the fastened member 42 can be thickened and fastened without cracking by using the die of the present invention.
The fastened members 41 and 42 are pressed by the nose 3, the self-piercing rivet 10 is disposed on the fastened member 41 in the opening of the nose 3, and the punch 4 is disposed thereon.

The upper surface 31 of the die body 30 and the upper surface 51 of the shaft portion 52 of the center pin 50 are preferably in the same plane. Both the upper surface 31 of the die body 30 and the upper surface 51 of the center pin 50 are in contact with the lower surface of the lower fastening member 42.
The upper surface 51 of the shaft portion 52 of the central pin 50 may be positioned lower than the upper surface of the die body 30. In that case, the upper surface 51 of the shaft portion 52 of the center pin 50 does not support the lower surface of the fastened member 42.
Although the lower part of the center pin 50 is not shown in FIG. 5, the center pin 50 is in the home position.

FIG. 6 shows a stage where the punch 4 slightly presses the head 11 of the self-piercing rivet 10 downward. The spring 55 (not shown) is slightly bent. A leg tip 13 of the self-piercing rivet 10 enters the upper fastening member 41. The portions of the fastened members 41 and 42 below the self-piercing rivet 10 have moved slightly downward.
The lower surface of the fastened member 42 remains in contact with the upper surface 51 of the center pin 50. The center pin 50 is pushed downward by the fastened member 42 and moved slightly downward.
There is still a space between the lower surface of the fastened member 42 and the curved surface 33 and the bottom surface 32 of the die body 30. The pin flange 53 of the center pin 50 is slightly separated from the lower end portion 37 of the die body 30.

FIG. 7 shows a stage where the punch 4 presses the head 11 of the self-piercing rivet 10 further downward. Until the leg tip 13 of the self-piercing rivet 10 passes through the upper fastening member 41, the fastening member 41 enters. The leg tip 13 extends slightly outward. The portions of the fastened members 41 and 42 under the self-piercing rivet 10 have moved further downward.
While the lower surface of the fastened member 42 is in contact with the upper surface 51 of the center pin 50, the center pin 50 is pushed further downward. The upper surface 51 of the shaft portion 52 of the central pin 50 is lowered to the same plane as the bottom surface 32 of the die body 30.
A part of the lower surface of the fastened member 42 is in contact with the bottom surface 32 of the die body 30. There is still a space between the lower surface of the fastened member 42 and the curved surface 33 of the die body 30.

FIG. 8 shows a stage where the punch 4 presses the head 11 of the self-piercing rivet 10 further downward. The leg tip 13 passes through the upper fastened member 41, and the inner part of the leg tip 13 of the fastened member 41 is cut into a circular cross section. The lower part of the self-drilling rivet 10 of the fastened members 41 and 42 is further moved downward. The leg tip 13 has not yet entered the fastened member 42.
The center pin 50 is pushed further downward and moved downward. The upper surface 51 of the shaft portion 52 of the central pin 50 is at a position lower than the bottom surface 32 of the die body 30.

The lower surface of the fastened member 42 is in contact with the bottom surface 32 of the die body 30. There is still a space between the lower surface of the fastened member 42 and the curved surface 33 of the die body 30.
In the stage of FIG. 8, the punch 4 has moved considerably downward from the stage of FIG. 7, but the leg tip 13 of the self-piercing rivet 10 has not entered the lower fastened member 42. The center pin 50 is pushed downward by the self-drilling rivet 10, and a part of the material of the fastened member 42 enters the center pin hole 34 by pushing down the center pin 50. Therefore, the material of the fastened member 42 has not moved much in the lateral direction.

FIG. 9 shows a stage where the punch 4 presses the head 11 of the self-piercing rivet 10 further downward. The leg tip 13 breaks through the punched member 41 and enters the receiving member 42 on the receiving side.
At this stage, since the bottom surface 32 of the die body 30 is located below the leg tip 13 via the thin portion of the fastened member 41, the leg 12 cannot move much downward. Therefore, the leg tip 13 spreads outward in the radial direction. The center pin 50 has not moved much downward from the stage of FIG.
The bottom surface 32 of the die body 30 is in contact with the lower surface of the fastened member 42. A little space still remains between the lower surface of the fastened member 42 and the curved surface 33 of the die body 30.

  FIG. 10 shows a stage where the fastening of the self-piercing rivet 10 is completed. The lower surface of the pin flange 53 contacts the stopper 56, and the center pin 50 is in the lowered position. The position of the self-piercing rivet 10 in the axial direction is not much different from that in FIG. 9, but the punch 4 presses the head 11 of the self-piercing rivet 10 further downward. The upper surface of the head 11 of the self-piercing rivet 10 is substantially flush with the upper surface of the fastened member 41.

On the inside of the leg portion 12 of the self-piercing rivet 10, a space is provided between the lower surface of the head 11 and the upper surface of the fastened member 41.
When the fastened member 41 is made of a thick and soft metal material, this space tends to be small.
The leg tip 13 of the self-piercing rivet 10 further spreads outward in the radial direction, and the fastened member 41 and the fastened member 42 are fastened.

  After the self-piercing rivet 10 is fastened, the punch 4 moves upward, and the nose 3 holding the fastened members 41 and 42 also moves upward. When the force for pressing the fastened members 41 and 42 from above is lost, the spring 55 presses the center pin 50 upward. The center pin 50 pushes the fastened member 42 in the center pin hole 34 upward. The fastened members 41 and 42 thus fastened are pushed out above the die body 30.

  In the first embodiment, when the self-piercing rivet 10 is fastened, the central pin 50 moves downward, and the fastened member 42 on the receiving side enters the central pin hole 34 portion. Therefore, the fastened member 42 does not greatly expand in the radial direction. The leg portion 12 of the self-piercing rivet 10 has a diameter that is smaller than when the conventional die 20 is used. A strong tensile stress is not generated in the fastened member 42. Therefore, even if the receiving-side fastened member 42 is made of a hard material, cracks are unlikely to occur.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 11 is a cross-sectional view showing a die of a self-piercing rivet fastening device according to a second embodiment of the present invention and a part of a C-shaped frame 45 that supports the die. In the second embodiment, as in the first embodiment, the die has a die body 30 and a center pin 50 that is movably supported in the center pin hole 34 of the die body 30.
In the first embodiment, the center pin 50 is pressed upward by the spring 55. In the second embodiment, oil is supplied to the space between the bottom of the die body hole 46 and the lower surface of the pin flange 53 by the pump 58, and the pin flange 53 of the center pin 50 is pushed up by hydraulic pressure. Alternatively, air can be supplied instead of oil by a pump, and the pin flange 53 of the center pin 50 can be pushed up by air pressure.
In the second embodiment, oil or air is supplied to the space sealed by the die body hole 46 and the pin flange 53, so the pin flange 53 is necessary.
Alternatively, the central pin 50 can be moved up and down by using an electric device such as a motor instead of the hydraulic device or the pneumatic device.

In the second embodiment, before the punch 4 is driven, oil is supplied to the space between the bottom of the die body hole 46 and the lower surface of the pin flange 53 so that the center pin 50 is positioned at the raised home position. To. In order to drive the self-piercing rivet 10, oil is removed as the punch 4 is lowered so that the central pin 50 is lowered to the lowered position.
When the self-piercing rivet 10 is fastened, the pump 58 can be controlled so that the central pin 50 descends at a constant speed to the lowered position. Alternatively, the central pin 50 is controlled to descend at a programmed speed, and the lowering distance of the central pin is reduced in the initial stage of fastening, and the deformation of the fastened member 42 is increased in the latter half of the stage. The descending distance can be increased.
Alternatively, the center pin 50 can be lowered before the self-piercing rivet 10 is driven.

  After the self-piercing rivet 10 is fastened, oil or air is supplied to the space between the bottom of the die body hole 46 and the lower surface of the pin flange 53 to raise the central pin 50 and fasten from the central pin hole 34 The member 42 can also be extruded.

In the second embodiment, the movement of the central pin 50 can be controlled regardless of the pressure applied to the upper surface of the central pin 50.
Further, the movement of the center pin 50 can be controlled more precisely as compared with the first embodiment in which the center pin 50 is pushed down against the pressing force of the spring 55.

  Also in the second embodiment of the present invention, when the self-piercing rivet 10 is fastened, the central pin 50 moves downward, and the receiving-side fastened member 42 enters the central pin hole 34 portion. Therefore, the fastened member 42 is not greatly deformed radially outward, and a strong tensile stress is not generated in the fastened member 42. Therefore, the receiving-side fastened member 42 is unlikely to crack.

(Traditional die simulation)
The self-piercing rivet 10 is used when the fastened members 41 and 42 are fastened using a conventional die and when the fastened members 41 and 42 are fastened using the die of the first embodiment of the present invention. And the result of having simulated the internal stress of the to-be-fastened members 41 and 42 is demonstrated.
FIG. 12 is a result of simulating the internal stresses of the self-piercing rivet 10 and the fastened members 41, 42 when fastening the fastened members 41, 42 using the conventional die 20 (FIG. 1). .
FIG. 13 shows a self-drilling rivet 10 and a fastened member 41 when fastened members 41 and 42 are fastened using a die in which the die body 30 and the central pin 50 according to the first embodiment of the present invention are combined. , 42 is the result of simulation of internal stress.

The clamped member 42 on the receiving side is thicker than the clamped member 41 on the punch side.
A white portion indicates that the internal stress is large. The dark and dark part indicates that the internal stress is negative and the absolute value is large. The middle gray portion indicates that the internal stress is positive or negative and small.

  FIG. 12 is a simulation of a stage in which the fastened members 41 and 42 are disposed on the conventional die 20 shown in FIG. 1 and fastened by the self-piercing rivet 10. Nose 3 and punch 4 are indicated by a two-dot chain line.

  When the self-piercing rivet 10 is driven by the punch 4, the leg portion 12 breaks the upper fastening member 41 and enters the receiving fastening member 42. The fastened member 42 is pushed downward, and the portion of the fastened member 42 pushed downward enters the recess of the die 20. When the fastened member 42 hits the bottom surface 22, it cannot move downward. Since the leg portion 12 cannot move downward, the diameter is increased radially outward. Therefore, the fastened member 42 also spreads outward in the radial direction.

After the self-piercing rivet 10 is fastened, both the head 11 and the leg 12 of the self-piercing rivet 10 have very high internal stress. The leg portion 12 has a high internal stress.
The to-be-fastened member 41 on the punch side is pulled by the self-piercing rivet 10 near the fastening portion, resulting in a negative internal stress. The round part cut out by the leg part 12 of the fastened member 41 on the punch side and entered into the leg part 12 is pulled outward in the radial direction by the leg part 12 whose diameter is increased, resulting in a negative internal stress. .

Regarding the receiving-side fastened member 42, the internal stress is high under the leg tip 13 of the self-piercing rivet 10 due to strong pressure from the leg tip 13.
A portion of the fastened member 42 that contacts the curved surface 23 is subjected to negative internal stress.

  Since the fastened member 42 cannot move much downward, a high internal stress is applied to the legs 12 of the self-piercing rivet 10. Therefore, a high internal stress is generated in the portion of the fastened member 42 at the tip of the leg tip 13, and the fastened member 42 may be cracked.

(Simulation of the first embodiment)
FIG. 13 is a simulation of a stage in which the self-piercing rivet 10 is driven into the fastened members 41 and 42 using the die according to the first embodiment of the present invention, and the fastening is completed.

  In the first embodiment, a die composed of a die body 30 and a center pin 50 is used. When the self-piercing rivet 10 is driven into the fastened members 41 and 42, the central pin 50 moves downward in the central pin hole 34, and the fastened member 42 on the receiving side enters the upper part of the central pin hole 34.

In the first embodiment, the internal stress of the head 11 of the self-piercing rivet 10 is lower than when the conventional die 20 of FIG. 12 is used. When the conventional die 20 is used, the internal stress of the leg portion 12 is high, but in the first embodiment, the internal stress of the leg portion 12 is high only in part.
The to-be-fastened member 41 on the punch side is pulled by the self-piercing rivet 10 near the fastening portion, resulting in a negative internal stress. The round part cut out by the leg part 12 of the fastened member 41 on the punch side and entered into the leg part 12 is pulled outward in the radial direction by the leg part 12 whose diameter is increased, and negative internal stress is generated. However, the portion where the negative internal stress is larger than the conventional one becomes narrower.
With respect to the receiving-side fastened member 42, the internal stress of the portion below the leg tip 13 of the self-piercing rivet 10 is lower than that of the conventional member in FIG.

  In the first embodiment, when the self-piercing rivet 10 is driven into the fastened members 41 and 42 and fastened, the central pin 50 moves downward, and the central pin hole 34 portion after the central pin 50 has moved. In addition, the material of the fastened member 42 moves. The material of the fastened member 42 does not spread so much outward in the radial direction. The material inside the leg 12 of the self-piercing rivet 10 is not pulled too much radially outward and the internal stress is not increased. The leg portion 12 is not expanded outward in the radial direction more than necessary. The internal stress in the portion of the fastened member 42 below the leg tip 13 is reduced, and the lower fastened member 42 is unlikely to crack.

  To summarize the simulation results, when the conventional die 20 shown in FIG. 12 is used, a strong stress is generated in the head 11 and the leg 12 of the self-drilling rivet 10, and a strong negative stress is applied to the receiving member 42 to be fastened. Occur. On the other hand, when the die of the first embodiment shown in FIG. 13 is used, the portion where the strong stress is generated in the head 11 and the leg 12 of the self-piercing rivet 10 is reduced, and the receiving member 42 to be fastened is received. There are almost no portions where strong negative stress is generated. As described above, even in the simulation, in the first embodiment, the leg portion 12 is not expanded beyond the radial direction more than necessary, the internal stress of the leg tip 13 is reduced, and the lower fastening member 42 is cracked. It was confirmed that is difficult to occur. The same effect can be obtained in the second embodiment.

1 Self-piercing rivet fastening device
3 Nose
4 punch
10 Self-drilling rivets
11 head
12 legs
13 Leg tip
20 dies (conventional)
21 Top view
22 Bottom
23 Curved surface
24 Large diameter part
26 Small diameter part
30 die body
31 Top view
32 Bottom
33 Curved surface
34 Center pin hole
35 Large diameter part
36 Small diameter part
37 Bottom edge
41 Fastened member (punch side)
42 Fastened member (receiving side)
45 C-type frame
46 Die body hole
50 center pin
51 Top view
52 Shaft
53 pin flange
55 Spring
56 Stopper
58 Pump

Claims (6)

A self-piercing rivet fastening device for driving and fastening a self-piercing rivet having a large-diameter head and hollow legs hanging from the head into a member to be fastened,
A nose for pressing the fastened member;
A punch for driving the self-piercing rivet into the fastened member;
A die for receiving the member to be fastened,
The die has an upper surface and a concave body formed on the inner side of the upper surface, and a die body in which a central pin hole penetrating downward from a central portion of the concave portion is formed;
A center pin supported in the center pin hole of the die body so as to be movable in the axial direction,
The central pin has a cylindrical shaft portion having an outer diameter matching the inner diameter of the central pin hole,
The self-piercing rivet fastening device further comprises a pressing device for pressing the central pin in the axial direction. The self-piercing rivet fastening device according to claim 1,
The center pin is a self-piercing rivet fastening device in which an upper surface of the center pin is movable from a position below the bottom surface of the concave portion of the die body to a position above the bottom surface of the concave portion. A self-piercing rivet fastening device according to claim 1 or 2,
The pressing device is a spring disposed below the center pin,
The spring applies an upward pressing force to the center pin,
When a downward pressing force stronger than the pressing force of the spring is applied to the upper surface of the central pin, the central pin moves downward until the upper surface is positioned below the bottom surface of the recess,
If the downward pressing force is not applied to the upper surface of the central pin, the central pin is pressed by the pressing force of the spring until the upper surface is positioned above the bottom surface of the recess. Self-drilling rivet fastening device adapted to move upward. A self-piercing rivet fastening device according to claim 1 or 2,
The pressing device is a self-piercing rivet fastening device that is a hydraulic device, a pneumatic device, or an electric device that presses the center pin upward. A fastening method for fastening a self-piercing rivet by a self-piercing rivet fastening device, the self-piercing rivet fastening device comprising a nose, a punch, and a die for receiving a member to be fastened,
The die has an upper surface and a concave body formed on the inner side of the upper surface, and a die body in which a central pin hole penetrating downward from a central portion of the concave portion is formed;
A center pin supported in the center pin hole of the die body so as to be movable in the axial direction;
Furthermore, the self-piercing rivet fastening device includes a pressing device for pressing the central pin in the axial direction, and the fastening method includes:
(a) disposing the fastened member on the upper surface of the die body;
(b) holding the fastened member by the nose;
(c) disposing the self-piercing rivet between the punch and the fastened member;
(d) Lowering the punch and pressing the self-piercing rivet against the fastened member, the fastened member moves downward, and the leg end of the self-piercing rivet is in the fastened member. Perforated and
(e) The material of the fastened member penetrates into the central pin hole, the central pin resists the pressing force of the pressing device, and the upper surface of the central pin is the bottom surface of the concave portion of the die body. A fastening method comprising the steps of lowering to a lower position and completing the fastening. The fastening method according to claim 5, further comprising:
(f) A fastening method in which, after completion of the fastening, the center pin is raised in the center pin hole by the pressing force of the pressing device, and the fastened member in the center pin hole is pushed out.