JP7460078B2 - Bolt caulking structure and caulking method - Google Patents

Description

The present invention relates to a structure and method for caulking a bolt to a metal plate.

Bolts that are caulked and fixed to a metal plate are called caulking bolts, and have been known from the past as shown in Patent Document 1 and Patent Document 2. These caulking bolts are firmly fixed to the metal plate by inserting the shaft into a prepared hole in the metal plate and caulking with a die and punch, and by causing the metal material to plastically flow on the head seat and the upper end of the shaft. It is something that will be done.

The member to be attached to the caulking bolt is usually inserted into the shaft of the caulking bolt and fixed with a nut. At this time, the inner diameter of the attachment hole formed in the member to be attached needs to be larger than the outer diameter of the thread of the bolt shaft. As a result, the mounting positions of the attached members relative to the caulking bolts vary slightly, and for example, when a link mechanism is constructed using the caulking bolts as a fulcrum, there is a risk that the operation thereof will vary.

It is also possible to form a step for positioning on the upper part of the shaft of the caulking bolt, but the diameter of the step must be larger than the thread diameter, resulting in wasted bolt material. This is not desirable for mass-produced products because it increases the cost of the bolt.

JP2017-155860A Japanese Patent Application Publication No. 2018-200095

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bolt caulking structure and a caulking method that can solve the above-mentioned conventional problems and improve the positioning accuracy of a member to be attached without increasing the cost of the bolt.

The bolt caulking structure of the present invention, which has been made to solve the above problems, is a bolt caulking structure in which a caulking bolt is caulked and fixed to a flat metal plate in which a pilot hole is formed, and the shank of the caulking bolt is is formed with a screw thread whose upper end is located directly below the head seat surface, and a protrusion for preventing rotation is formed on the head seat surface of the caulking bolt. The protrusion is pressed into the surface of the metal plate, and a part of the metal material that has plastically flowed due to caulking covers the outer periphery of the upper end of the screw thread, and a cylindrical positioning step is formed on the back side of the head seat. This step is used to position a member attached to the step .

It is preferable that the thread includes a complete thread portion and an incomplete thread portion at its upper end, the end point of the incomplete thread portion is within 3 pitches from the head seat, and the outer periphery of the incomplete thread portion is covered by the step portion.

Furthermore, the bolt crimping method of the present invention, devised to solve the above-mentioned problems, is a bolt crimping method in which a crimped bolt, with the upper end of the thread formed on the shank located directly below the head seat, is crimped and fixed to a flat metal plate in which a pilot hole is formed, using a die and punch, and is characterized in that a die is used which has a recess formed on the upper part with a diameter larger than the diameter of the pilot hole formed in the metal plate, and during crimping, a rotation-preventing protrusion formed on the head seat of the crimped bolt is pressed into the surface of the metal plate, and the metal material around the edge of the pilot hole is caused to plastically flow into the recess of the die, thereby forming a cylindrical positioning step on the back side of the head seat , and this step is used to position the attached member to be attached to this step .

In addition, the bolt caulking method of the present invention, which has been made to solve the above problems, is a caulking bolt in which the upper end of the thread formed on the shaft portion is located directly below the head bearing surface. A bolt caulking method in which a die and a punch are used to caulk and fix a bolt to a flat metal plate. By pushing the anti-rotation protrusion formed on the head seat of the bolt into the surface of the metal plate and causing the metal material around the pilot hole to plastically flow into the gap between the center hole of the die and the shaft part. , a cylindrical step for positioning is formed on the back side of the head seat surface , and this step is used to position a member to be attached to the step .

According to the present invention, the metal material on the periphery of the pilot hole formed in the metal plate is made to plastically flow into the recess of the die or the gap between the center hole of the die and the shaft portion, so that the metal material on the back side of the head seat surface is A cylindrical step can be formed on the surface. Since this stepped portion can be formed with high precision by a recess or a center hole formed in the die, by using it as a stepped portion for positioning the member to be attached, it is possible to improve the accuracy of positioning the member to be attached. Also, it does not increase the cost of bolts.

Furthermore, if the outer periphery of the incompletely threaded part is covered by the stepped part, the pull-out strength of the caulking bolt will be increased, and a complete thread will be formed right below the stepped part, so the nut can be tightened. It becomes possible to screw in to just below the step. Therefore, even when the thickness of the member to be attached is thin, reliable attachment is possible.

FIG. It is a front view of a caulking bolt. It is a bottom view of a caulking bolt. FIG. 3 is a longitudinal cross-sectional view of the caulking bolt. It is a sectional view showing a caulking process. It is a sectional view showing a caulking process. It is a front view showing a caulking structure. FIG. 3 is a partial cross-sectional view showing a state in which a member to be attached is attached. 10A to 10C are cross-sectional views showing a crimping step according to another embodiment. 10A to 10C are cross-sectional views showing a crimping step according to another embodiment.

An embodiment of the present invention will be described below.
First, the crimp bolt used in the embodiment will be described with reference to Figures 1 to 4. In these figures, 10 is the head of the crimp bolt, and 11 is the shaft. The head 10 is disk-shaped, and a rotation-preventing protrusion 13 is formed on the head seat 12. In this embodiment, the rotation-preventing protrusion 13 has eight radial arms 14 arranged at equal intervals, and the tip 15 of each arm 14 is beveled at an angle. Between the bases of each arm 14 is an arc-shaped connection 16, and the minimum diameter of the arc-shaped connection 16 is larger than the outer diameter of the shaft 11. In this embodiment, the thickness of the head 10 (the distance from the top surface of the head 10 to the head seat 12) is 1.5 mm, and the thickness of the arms 14 is 0.5 mm.

The shaft portion 11 is formed with a thread whose upper end is located directly below the head seat 12. The thread includes a complete thread portion 17 and an incomplete thread portion 18 formed at its end. Most of the threads of mass-produced bolts are formed by a rolling method using a rolling die, but the end of the rolled thread inevitably has an incomplete thread portion 18. The incomplete thread portion 18 is formed at the end of the complete thread portion 17 and is a portion with a lower thread height than the complete thread portion 17. The incomplete thread portion 18 on the head side is located directly below the head seat 12, and the portion below it is the complete thread portion 17. In this embodiment, the upper end of the thread, i.e., the incomplete thread portion 18, is within a range of three pitches from the head seat 12. If the position of the upper end of the thread is further away from the head seat 12, the metal material does not flow sufficiently between the threads, so there is a risk of a decrease in pull-out strength when crimped.

The caulking bolt described above is caulked and fixed to a flat metal plate 30 using a die 20 and a punch 21, as shown in FIG. A pilot hole is formed in the metal plate 30 in advance. Naturally, the inner diameter of the pilot hole needs to be slightly larger than the outer diameter of the thread of the shaft portion 11 of the caulking bolt. Note that in the state shown in FIG. 5, the lower surface of the anti-rotation protrusion 13 is in contact with the upper surface of the metal plate 30.

The die 20 is placed on the back surface of the metal plate 30, and a recess 31 having a diameter larger than the diameter of the prepared hole is formed on the upper surface, that is, the surface in contact with the metal plate 30. This recess 31 is formed so as to surround the outer periphery of the shaft portion 11 of the caulking bolt, and its length in the vertical direction is preferably about 1 to 2 pitches from the top surface of the die. Further, it is preferable that the inner diameter of the recess 31 be larger than the outer diameter of the thread formed on the shaft portion 11 by about 0.2 to 5 mm. The specific size of the recess 31 can be determined as appropriate depending on the material and thickness of the metal plate 30.

A cylindrical pad 22 and a punch 21 that moves up and down inside the pad 22 are arranged above the metal plate 30, and the punch 21 is rapidly lowered as shown in FIG. 6 to direct the head 10 of the caulking bolt toward the metal plate 30. Type it in. At the same time, the anti-rotation protrusion 13 formed on the head seat surface 12 is pushed into the surface of the metal plate 30, and the head seat surface 12 of the caulking bolt is brought into close contact with the upper surface of the metal plate 30. Further, the metal material around the pilot hole formed in the metal plate 30 plastically flows toward the incompletely threaded portion 18 directly below the head seat surface 12 and flows into the recess 31 of the die 20, as shown in FIG. A cylindrical stepped portion 40 is formed on the back side of the head seat.

In the caulking structure shown in FIG. 7, the metal material on the surface of the metal plate 30 flows between the arms 14 of the anti-rotation protrusions 13, thereby producing an excellent anti-rotation effect and increasing the idling torque. Can be done. Further, since the metal material around the pilot hole flows between the threads of the incompletely threaded portion 18 directly below the head seat surface 12, the pullout load in the axial direction can also be increased. Note that the stepped portion 40 may reach not only the upper part of the incompletely threaded part 18 but also the upper part of the completely threaded part 17.

Further, the cylindrical step portion 40 formed by the recess 31 of the die 20 has a larger diameter than the shaft portion 11 of the caulking bolt, and has a highly accurate cylindrical shape. For this reason, as shown in FIG. 8, a mounting hole 51 with an inner diameter corresponding to the cylindrical step 40 is formed in the member 50 to be mounted, and by fitting into the step 40, the mounting position of the member 50 to be mounted is determined. It can be determined with high accuracy. Further, since the stepped portion 40 is not formed on the shaft portion of the bolt, but is formed by plastically flowing the metal material of the metal plate 30, the material cost of the bolt does not increase.

Furthermore, even when fastening the attached member 50 with the nut 51, since the fully threaded portion 17 is formed in the entire portion of the shaft portion 11 below the stepped portion 40, the nut 51 cannot be tightened sufficiently deeply. can. Therefore, the nut 51 can be reliably tightened even when the attached member 50 is thin.

In the above embodiment, the metal material around the edge of the pilot hole is plastically flowed into the recess 31 of the die 20 during crimping to form a cylindrical positioning step 40 on the back side of the head seat. In another embodiment shown in Figures 9 and 10, a die 20 with a center hole 32 slightly larger in diameter than the diameter of the pilot hole formed in the metal plate 30 is used, and the metal material around the edge of the pilot hole is plastically flowed into the gap 33 between the center hole 32 of the die 20 and the bolt shaft 11 during crimping to form a cylindrical positioning step 40 on the back side of the head seat. That is, in this embodiment, the gap 33 is used instead of the recess 31 of the die 20, but the formed step 40 has the same shape as in Figure 7.

Although the present invention has been described based on the illustrated embodiment as described above, the specific shape and size of the caulking bolt and the stepped portion 40 are not limited to this embodiment, and various modifications are possible. Needless to say.

REFERENCE SIGNS LIST 10 Head 11 Shaft 12 Head seat 13 Rotation-preventing projection 14 Arm 15 Tip 16 Arc-shaped connection 17 Completely threaded portion 18 Incompletely threaded portion 20 Die 21 Punch 22 Pad 30 Metal plate 31 Recess 32 Center hole 33 Gap 40 Step 50 Mounted member 51 Nut

Claims (4)

A bolt crimping structure in which a crimp bolt is crimped and fixed to a flat metal plate having a pilot hole formed therein,
The shank of the crimp bolt is formed with a screw thread whose upper end is located directly below the head seat,
A protrusion for preventing rotation is formed on the head seat of the crimp bolt,
The anti-rotation projection is pressed into the surface of the metal plate by crimping,
A bolt crimping structure characterized in that a portion of the metal material that has been plastically flowed by crimping covers the outer periphery of the upper end of the thread, forming a cylindrical positioning step on the back side of the head seat , and this step is used to position the attached workpiece attached to this step . The thread includes a fully threaded portion and an incompletely threaded portion at its upper end, the end point of the incompletely threaded portion is within 3 pitches from the head seat surface, and the outer periphery of the incompletely threaded portion is covered by the stepped portion. 2. The bolt caulking structure according to claim 1, wherein: A method for crimping a bolt, in which a crimp bolt having an upper end of a thread formed on a shaft portion and located directly below a head seat surface is crimped and fixed to a flat metal plate having a pilot hole formed therein, using a die and a punch,
A method of crimping a bolt, characterized in that a die having a recess formed on the upper part with a diameter larger than the diameter of a pilot hole formed in a metal plate is used, and during crimping, a rotation-preventing protrusion formed on the head seat of the crimping bolt is pressed into the surface of the metal plate, and the metal material around the edge of the pilot hole is caused to plastically flow into the recess of the die, thereby forming a cylindrical positioning step on the back of the head seat , and this step is used to position the attached member to be attached to this step . A method for crimping a bolt, in which a crimp bolt having an upper end of a thread formed on a shaft portion and located directly below a head seat surface is crimped and fixed to a flat metal plate having a pilot hole formed therein, using a die and a punch,
A method of crimping a bolt, characterized in that a die with a central hole larger in diameter than the diameter of a pilot hole formed in a metal plate is used, and during crimping, a rotation-preventing protrusion formed on the head seat of the crimping bolt is pressed into the surface of the metal plate, and the metal material on the periphery of the pilot hole is caused to plastically flow into the gap between the central hole of the die and the shank, thereby forming a cylindrical positioning step on the back side of the head seat , and this step is used to position the attached member to be attached to this step .

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