Patent Application
20210283678
This application claims the benefit and priority of Japanese Patent Application No. 2020-043901, filed Mar. 13, 2020, the entire disclosure of which is incorporated herein by reference.
The present disclosure relates to a self-piercing rivet (SPR) fastening method and fastening device; in particular to a SPR fastening method and fastening device having a through hole.
This section provides background information related to the present disclosure which is not necessarily prior art.
In recent years, a technique for mechanically joining a base metal using SPR has been used as an alternative technique to a direct joining technique such as spot welding. An SPR is a semi-cylindrical rivet having a chevron- or dish-shaped head and semi-cylindrical legs forming a cavity beneath the head. There is also an SPR in which a through hole is formed in the head, as described in FIGS. 1 and 2 of Patent Document 1. Patent Document 1 teaches that, by making the through hole stepped as shown in FIG. 2 of Patent Document 1, it is possible to prevent the shear debris of the member to be fastened from falling off when the SPR is driven into the member to be fastened.
The SPR is driven by the following procedure. First, the upper plate (for example, an aluminum plate) and the lower plate (for example, a high-strength steel plate) to be fastened are clamped by the die and the nose piece of the fastening device. When the SPR provided in the nose piece is punched, the legs of the SPR pierce and penetrate the upper plate. When the legs of the SPR penetrating the upper plate enter the lower plate and the lower surface of the lower plate comes into contact with the bottom of the die, the bottom of the die cavity pushes back the lower plate. As a result, the legs of the SPR receive a reaction force from the lower plate and open the legs in a ring shape in the lower plate without penetrating the lower plate. A mechanical interlock is formed by opening the legs of the SPR, and the upper plate and the lower plate are mechanically fastened. The die and nose piece separate from the member to be fastened and the fastening is completed.
The number of members to be fastened may be three or more. For example, in the case of three members, the upper plate and the intermediate plate are penetrated, and the lower plate is not penetrated. In the production of automobiles, an adhesive is often applied between the members to be fastened in order to improve the performance of Noise, Vibration, Harshness (NVH).
Japan Unexamined Patent Application Publication No. 2003-106316.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
According to the conventional method of fastening SPR using such an adhesive, it has been found that a phenomenon occurs in which the strength of the adhesive is not sufficiently exhibited.
The object of one aspect of the embodiments of the present disclosure is a fastening method and a fastening device for SPR in order to suppress the occurrence of such a phenomenon and thereby allow the adhesive applied between the members to be fastened to exert greater adhesive force.
By means of one aspect of the rivet fastening method according to one embodiment of the present disclosure, the method is equipped with a step of preparing at least two plates stacked via an adhesive layer, a step of preparing a rod-shaped punch having at least two openings and an air flow path communicating with the at least two openings, a step of preparing a self-piercing rivet having a through hole, and a step of punching the self-piercing rivet into the at least two plates with the punch so that one of the at least two openings of the punch faces the through hole of the self-piercing rivet.
By means of one aspect of the rivet fastening device according to one embodiment of the present disclosure, the device is equipped with at least two openings; a rod-shaped punch having an air flow path in which the at least two openings are communicated with each other; a tubular collet having an internal cavity through which the punch can be inserted and an air passage portion through which air can pass in the radial direction; a tubular nose piece that houses the collet; and a nose piece support portion that supplies a self-piercing rivet having a through hole and that supports the nose piece, the nose piece support portion having a first exhaust port for discharging air passing through the air passing portion of the collet to the outside; wherein the device is configured so that at the time of driving the self-piercing rivet, one of at least two openings in the punch faces the through hole of the self-piercing rivet.
By means of one aspect of the rivet fastening method according to one embodiment of the present disclosure, the method is equipped with a step wherein a self-piercing rivet having a through hole is driven by a rod-shaped punch, having at least two openings and an air flow path in which the at least two openings are communicated, into at least two plates stacked via an adhesive; wherein one of at least two openings in the punch is driven so as to face the through hole of the self-piercing rivet. Therefore, when the self-piercing rivet is driven, the air compressed in the internal cavity surrounded by the legs of the self-piercing rivet is exhausted to the outside through the through hole of the self-piercing rivet and the air flow path of the punch. Consequently, it is possible to prevent air from flowing out to the adhesive layer between the plate materials, so that the coating area of the adhesive at the fastening position can be secured, and the adhesive force of the adhesive can be further enhanced.
Similarly, by means of one aspect of the riveting device according to one embodiment of the present disclosure, when the self-piercing rivet is driven, one of at least two openings of the punch is configured to face the through hole of the self-piercing rivet, thereby enabling further enhancement of the adhesive force of the adhesive.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Hereinbelow, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. By assigning the same or similar reference numbers to the same or similar members, duplicate description thereof is omitted. In order to explain the present invention in an easily comprehensible manner, the scale of the drawings is not constant.
Overall Configuration of the Rivet Fastening Device
First, the configuration of the rivet fastening device will be described with reference to
The control device 20 is a device for controlling the operation of the rivet driving device 30, the rivet supply device 40 and the C frame moving device 50. Although a single controller is illustrated in
The rivet driving device 30 is a device for driving the supplied rivet, and is equipped with an actuator (not shown). The actuator operates according to a command from the control device 20, and the operation of the actuator is converted into a linear reciprocating motion of the punch 102, which will be described later, and a rivet is driven.
The rivet supply device 40 is a device that supplies rivets to the rivet driving device 30. The rivet supply device 40 operates according to a command from the control device 20, and the rivet is supplied by utilizing the air pressure of compressed air.
The C-frame moving device 50 is a device for holding the member to be fastened at a predetermined position. The C-frame moving device 50 operates in accordance with a command from the control device 20, holds the member to be fastened at a predetermined position, and releases the member to be fastened when the rivet driving is completed. In some embodiments, the movement of the C-frame moving device is performed by a user.
Hardware Configuration of Control Device
Next, the hardware configuration of the control device will be described with reference to
The control device 20-1 is equipped with a processor 21 and a memory 22. The memory 22 stores a program for performing all or part of the punch 2 driving operation, the C frame moving operation, and the SPR supply operation; each operation is executed by the processor 21 reading and executing this program.
The processor 21 is, for example, a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor, a microcontroller, or a digital signal processor (DSP).
The memory 22 uses, for example, a semiconductor memory or a magnetic disk. More specifically, the memory 22 is random access memory (RAM), read only memory (ROM), flash memory, erasable programmable read only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), a solid-state drive (SSD) or a hard disk drive (HDD).
The processing circuit 23 is, for example, an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), a system-on-a-chip (SoC) or a system large-scale integration (LSI).
Each operation may be realized by any one device of the control device 20-1 or the control device 20-2, or may be realized by a plurality of devices combining the control device 20-1 and the control device 20-2.
Detailed Configuration of the Rivet Fastening Device
Next, the configuration of the rivet fastening device 10 will be described in more detail, mainly with reference to
As shown in
As shown in
The punch holder 103 slidably holds the punch 102. Although not shown, a housing (not shown) for housing the punch holder 103 is held by one end of the C frame 106. At the tip of the punch holder 103 are formed a concave groove 103a formed to match the shape of the protrusion 101f of the receiver 101, and a through groove 103b formed so as to face the through groove 101g of the receiver 101 when the punch holder 103 and the receiver 101 are fitted. The concave groove 103a extends the tip end portion of the punch holder 103 in the circumferential direction, for example, ¼ turn, and further extends along the axial direction toward the tip end portion of the punch holder 103. The protrusion 101f of the receiver 101 is guided from the groove at the tip of the punch holder 103, and slides along the axial direction, and is further rotated in the circumferential direction so that the state as shown in
The punch 102 is a rod-shaped member for driving the supplied SPR 204 into the members to be coupled 201 and 202. The SPR 204 is delivered until it abuts the rivet passage prevention wall 101c; when held by the rivet passage prevention wall 101c and the rivet holding member by a spring or the like (not shown), the punch 102 drives the SPR 204 into the bonded members 201 and 202. The driving operation of the punch 102 is performed by the rivet driving device 30.
As shown in
As shown in
These air flow paths 102a and 102b included in the punch 102 are flow paths for letting air passing through the through hole 204d of the SPR 204 escape. That is, when the SPR204 is driven, the air in the cavity 204c of the SPR204 is surrounded by the head 204a, the legs 204b, and the upper plate 201 of the SPR and is compressed to a high pressure, so that the air escapes from the through hole 204d of the SPR204. The air flow paths 102a and 102b of the punch 102 are flow paths for further releasing the air that has escaped from the through hole 204d of the SPR204 in this way.
As long as such an object is achieved, the shape of the flow path provided in the punch 102 and the position where the flow path is provided can take various forms. For example, one flow path may extend in the punch 102 in an oblique shape or an L shape. Further, the air flow path 102b in
As shown in
As shown in
The receiver 101, the punch holder 103, and the nose piece 104 can integrally move linearly along the axial direction of the nose piece 104 by a driving means (not shown), such as a compression coil spring.
The die 105 is a member that supports the upper plate 202 and the lower plate 201. The die 105 has a cavity 105a at its head having a diameter larger than the outer diameter of the leg portion 204b of the SPR 204 so that the leg portion 204b can be opened when the SPR 204 is driven.
One end of the C frame 106 holds the die 105, as shown in
Operation
Next, the operation of the rivet fastening device 10 will be described with reference to the flowchart of
First, in step 801, the C frame 106 is positioned, and the member to be fastened overlapped with the adhesive is clamped by the nose piece 104 and the die 105. At this time, the punch holder 103, the nose piece 104, and the receiver 101 to which the punch holder 103 and the nose piece 104 are attached are integrally lowered, and the members to be fastened are clamped by the nose piece 104 and the die 105.
Next, in step 802, SPR204 is supplied to the receiver 101. The SPR204 is sent out from the supply device using the air pressure of compressed air, passes through the passage 101b, is fed to a position where it abuts the rivet passage prevention wall 101c, and is held by the rivet passage prevention wall 101c and a rivet holding member (not shown).
Next, in step 803, the punch 102 is pressed by a predetermined force and speed, and the SPR 204 is driven into the member to be fastened. In order to shorten the waiting time until the adhesive is cured, it is common to drive the SPR into the member to be fastened at the step in which the adhesive is not cured.
Next, in step 804, the member to be fastened is released from the nose piece 104 and the die 105.
Operation
Next, the operation according to the embodiment of the present disclosure will be described with reference to
Here, as explained earlier, since the collet 107 is formed by fitting the collet pieces 107a and 107b, and the fitted portions are not in close contact with each other, the air that is compressed, is highly pressurized and flows out from the openings 102b1 and 102b2 can pass through the fitting portions of the collet pieces 107a and 107b in the radial direction. The air that has passed through the fitting portions of the collet pieces 107a and 107b moves along the outer groove 107d as shown by the bold arrow in
Further, as shown by the bold arrow in
The air that has moved along the external groove 107d is also discharged to the external space from the exhaust port a of the receiver 101, as shown by the bold arrow in
In order to confirm the effect of the SPR fastening method according to the embodiment of the present disclosure, a cross peeling test was performed according to the following procedures.
First, a 40 mm×125 mm upper plate (590 Mpa high-tensile material; plate boldness 1.6 mm) and a 40 mm×125 mm lower plate (590 Mpa high-tensile material; plate boldness 1.6 mm) were prepared.
Next, press oil was applied to an overlap space of 40 mm×40 mm; then adhesive was applied so as to achieve a boldness of 1 mm, and the layers were laminated in a cross shape as shown in
Subsequently, SPR (SPR560F0C0-4Y1) was driven into the center of the overlap space using the rivet fastening device of the present disclosure.
The adhesive was then cured at 170° C. for 20 minutes.
Next, a tensile load was applied to the plate material fastened using a tensile tester at a tensile speed of 15 mm/min, and the maximum load until the fastened portion became broken was measured. In Working Example 1, an example in which the adhesive is heated and cured is shown, but there is also a type of adhesive that cures without applying heat. Therefore, the adhesive may be cured without heating to perform a cross-peeling test, and the type of adhesive may be other type.
The SPR was driven and a cross peeling test was performed under the same conditions as in Working Example 1,
The SPR was driven and a cross peeling test was performed under the same conditions as in Working Example 1,
In order to verify the effects of the Working Examples, the SPR was driven under the same conditions as in Working Example 1, except that punching was performed with a normal punch that does not have an air flow path instead of punch 102, and the cross-peeling test was performed three times.
Test Results
Table 1 and
In
From the test results in Table 1, comparing the average value of the working examples and the average value of the comparative examples with respect to the maximum adhesive peeling load, an increase of [(4.036-3.844)/3.844]×100≈5% was observed.
The reason for which the maximum adhesive peeling load increased in this manner is described with reference to
It is considered that this laterally extending line is due to the compressed air in the internal cavity 204c of the SPR204 flowing out to the adhesive layer. That is, in the comparative examples, SPR204 was punched with a normal punch without the provision of an air flow path; therefore, the air compressed in the internal cavity 204c cannot flow out of the through hole 204d at the head of the SPR204. Consequently, the compressed air tries to move by searching for a portion having a relatively low pressure other than the through hole 204d, but it is the adhesive layer that has not yet hardened between the plates that acts as such a relatively low-pressure portion.
As shown in
Based on the above principle, it is considered that a white line was formed on the adhesive-coated surface in
As described above, by increasing the maximum adhesive peeling load, it becomes possible to exhibit the original expected performance of the adhesive. That is, by increasing the maximum adhesive peeling load, the plate material does not peel off even if it is pulled by a tensile force that has conventionally caused peeling, so that the adhesive state can be maintained. As a result, the noise, vibration, and harshness (NVH) performance of the adhesive can be maintained.
Further, by maintaining the adhesive strength of the adhesive, the redundancy of the joint can be maintained, which leads to improvement of the safety and reliability of the joint. That is, since the fastened state by the adhesive and the fastened state by the SPR are maintained, the safety and reliability of the fastened portion are improved.
Hereinbelow, modified embodiments obtained by modifying the embodiments according to the present disclosure are described with reference to
As shown in
As shown in
As shown in
Further, in some embodiments, the collet 107″ is inserted into the nose piece 104 so that the through groove 104a of the nose piece 104′ and the through groove 107k of the collet 107″ overlap. By arranging in this way, the air flowing out through the through groove 107k can be effectively discharged to the external space of the nose piece 104′.
In addition, in some embodiments, the winding direction of the spiral through groove of the nose piece 104′ is opposite to the winding direction of the spiral through groove 107k of the collet 107″. By reversing the direction of the spiral in this way, when the collet 107″ is inserted into the nose piece 104′, the through groove of the nose piece 104′ and the through groove 107k of the collet 107″ always intersect. Therefore, the air flowing out through the through groove 107k can be effectively discharged to the external space of the nose piece 104′ regardless of the insertion direction of the collet 107″.
In this way, air can be bled more effectively at the time of fastening, so that it is possible to expect that the adhesive will be prevented from flowing out at the fastening position, the coating area of the adhesive will be secured, and the maximum adhesive peeling load will be increased.
Machine fastening using SPR is performed on two or more plate materials, and, in many cases, dissimilar materials such as steel plates and aluminum plates are fastened. The shape of the SPR stud is that of a bag shape, and when fastening two materials, a cylindrical claw (leg) penetrates the upper plate material, penetrates into the second plate, and the tip of the claw (leg) expands to fasten the upper plate and the lower plate. Here, the amount of expansion of the claws (legs) is referred to as “interlock,” and securing this interlock is an extremely important factor in this fastening method (SPR). In addition, an adhesive is often applied between the materials to be fastened, with the aim of improving the robustness of the fastened structure and preventing electrolytic corrosion. Therefore, securing the coating area of the adhesive is also an important factor.
In the conventional SPR fastening method, a phenomenon occurs thought to be that the strength of the adhesive is not sufficiently exhibited. Regarding this point, the present invention has found the following two points as more specific problems in the prior art, and has resolved them.
1. When there is adhesive between the plates and SPR fastening is performed, it becomes difficult to secure the interlock due to accumulation of adhesive.
2. When there is adhesive between the plates and SPR fastening is performed, since the rivet shape is bag-shaped, the rivet penetrates the material to be fastened while air is mixed in, and the air bursts at the time of fastening, generating places where the adhesive of the fastening interface cannot be applied. As a result, it becomes impossible to secure 100% of the adhesive area.
The present invention solves the above problems mainly by processing the head part of the rivet (hole for air to escape during cold forging) and providing an air flow path in the fastening mechanism including the punch, so that it is possible to secure the amount of interlock and the fastening area at the same time. As a result, according to the present invention, it is possible to secure the fastening strength by securing the interlock, and it is possible to secure the robustness of the mechanical fastening joint using the adhesive by securing the fastening area.
It should be noted that the present invention can be implemented by combining, modifying, or omitting the components of the disclosed embodiments within the scope of the invention.
Some of the various embodiments disclosed in the present specification will be summarized below.
The rivet fastening method according to Appendix 1 is equipped with a step of preparing at least two plates (201, 202) stacked via an adhesive layer;
a step of preparing a rod-shaped punch having at least two openings (102a1, 102b1, 102b2) and an air flow path (102a, 102b) through which the at least two openings are communicated;
a step of preparing a self-piercing rivet (204) with a through hole (204d); and
a step of driving the self-piercing rivet into the at least two plates with the punch so that one of the at least two openings in the punch (102a1) faces the through hole of the self-piercing rivet.
By means of the rivet fastening method according to Appendix 1, air compressed in the internal cavity surrounded by the legs of the self-piercing rivet when the self-piercing rivet is driven can be exhausted to the outside through the through hole of the self-piercing rivet and the air flow path of the punch. Therefore, it is possible to prevent air from flowing out to the adhesive layer between the plate materials, so that the coating area of the adhesive at the fastening position can be secured, and the adhesive force of the adhesive can be further enhanced.
The rivet fastening method according to Appendix 2 is the rivet fastening method described in Appendix 1,
further comprising a step of placing at least two stacked plates on the die;
wherein the step of preparing the self-piercing rivet is a step of preparing the self-piercing rivet on the side of at least two stacked plates opposite to the die.
The rivet fastening method according to Appendix 2 can be configured so that the plate material can be supported by the die, and so that, by arranging the die on the opposite side of the plate material from the self-piercing rivet, the legs of the self-piercing rivet can be opened in the die when the self-piercing rivet is driven.
The rivet fastening device according to Appendix 3 is equipped with a rod-shaped punch having at least two openings (102a1, 102b1, 102b2) and an air flow path (102a, 102b) through which the at least two openings are communicated;
a tubular collet (107) having an internal cavity (107e) through which the punch can be inserted and an air passing portion (107h, 107i, 107k) through which air can pass in the radial direction; and
a nose piece support portion (101) that supplies a tubular nose piece (104) for housing the collet and a self-piercing rivet (204) having a through hole (204d), and which supports the nose piece, the nose piece support portion (101) having a first exhaust port (101a) for discharging air passing through the air passing portion of the collet to the outside;
the device configured so that when driving the self-piercing rivet, one of at least two openings (102a1) of the punch is opposed to the through hole of the self-piercing rivet.
By means of the rivet fastening device according to Appendix 3, when driving a self-piercing rivet, the air in the cavity (204c) of the self-piercing rivet can be exhausted to the outside via, in order, self-piercing rivet through hole (204d), air flow paths (102a, 102b) in the punch, at least two openings (102a1, 102b1, 102b2), collet air passages (107h, 107i, 107k), and first exhaust port (102a) of the nose piece support portion. Therefore, it is possible to suppress the outflow of air to the adhesive layer between the plate materials, so that the coating area of the adhesive at the fastening position can be secured, and the adhesive strength of the adhesive can be further enhanced.
The rivet fastening device according to Appendix 4 is the rivet fastening device according to Appendix 3, wherein the collet consists of at least two collet pieces (107a, 107b), and the air passing portion is equipped with a gap in a portion of the two or more collet pieces to which the first collet piece and the second collet piece are connected.
According to the rivet fastening device according to Appendix 4, air from at least two openings in the punch can be more efficiently caused to flow out of the collet through the gaps where the first and second collet pieces of the collet are connected to bleed air. so that air bleeding can be performed more effectively.
The rivet fastening device according to Appendix 5 is the rivet fastening device according to Appendices 3 or 4, wherein the air passing portion is equipped with a through groove (107k).
By means of the rivet fastening device according to Appendix 5, the air flowing out from at least two openings of the punch can be more efficiently guided to the outside of the collet through the through groove (107k), and the air can be bled more effectively.
The rivet fastening device according to Appendix 6 is the rivet fastening device according to any one of Appendices 3 to 5, wherein the nose piece has a second exhaust port (104a) for exhausting air passing through the collet to the outside.
By the rivet fastening device according to Appendix 6, the air flowing out to the outer groove 107d of the collet can be effectively discharged to the outer space of the nose piece through the second exhaust port (104a), and the air can be bled more effectively.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-043901 | Mar 2020 | JP | national |
