JP2017096486A - Spherical seat bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical seat bolt in which the relationship between a fastening torque and a generated axial force shows stable linearity, and at the same time, caving-in or looseness of a fastened member hardly occurs.SOLUTION: A bearing surface 112 of a bolt 1 is a convex spherical surface, and a value of a spherical surface R on the convex spherical surface forms two stages from a head part side 11 of the bolt toward a screw part side 13 of the bolt.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bolt used for fastening an automobile or the like.

  Conventionally, a hexagon bolt with a flange shown in FIG. 5 has been frequently used at a fastening portion of each part of an automobile. In recent years, spherical seat bolts shown in FIG. 6 are being used in order to save space and light weight. The spherical seat bolt has a larger contact area on the seat surface than the hexagon bolt with flange, and the effect that the fastening member is less likely to be depressed or loosened is also obtained.

  When a spherical seat bolt is fastened, using a torque method that manages tightening based on the relationship between torque and axial force at the time of tightening, it is difficult to perform stable management due to variations in seat surface shape. For this reason, in many cases, a rotation angle method has been used in which the tightening is managed by the relationship between the rotation angle at the time of tightening and the axial force. Management by the rotation angle method is less affected by changes in the friction conditions, but is less efficient than management by the torque method, and management by the torque method is desirable if possible.

In order to grasp the conditions that enable management by the torque method in the dimensional relationship between the value of the spherical surface R of the spherical seat bolt and the value of the spherical surface R on the receiving side seating surface of the member to be fastened, the present inventors have conducted intensive research. The results are shown below. Under the fastening condition in which the value of the spherical surface R of the spherical seat bolt is larger than the value of the spherical surface R of the receiving side seating surface of the member to be fastened (hereinafter, this state is referred to as outer contact), the relationship between the tightening torque and the axial force It was found that linearity was observed (FIG. 7). Note that R ² shown in FIG. 7 is a determination coefficient used in statistics, and the closer the value is to 1, the smaller the difference between the approximate expression and the target data. The reason why the above-mentioned non-linearity appears is presumed to be that although the vicinity of the outer periphery of the seating surface is in contact at the beginning of tightening, the contact area increases in the axial direction as the axial force increases.

  On the other hand, when the value of the spherical surface R of the spherical seat bolt is smaller than the value of the spherical surface R on the receiving side seating surface of the member to be fastened (hereinafter, this state is referred to as inner contact), as shown in FIG. And the axial force show stable linearity. The reason for the above is presumed to be that the change in the contact area is slight even when the axial force increases because the vicinity of the axial center of the seating surface is in contact from the beginning of tightening.

  The inner contact condition shows stable linearity in the relationship between the torque and the axial force at the time of tightening, but there is a possibility that the member to be fastened is easily depressed or loosened due to the reduction of the contact area of the seating surface. 7 and 8, the values of the spherical surface R of the spherical seat bolt are 13.2 ± 0.1 mm and 12.6 ± 0.1 mm, respectively, and the spherical surface R on the receiving side seating surface of the member to be fastened is shown. The value is 13.0 ± 0.1 mm. The contact area of the seating surface in the case of FIG. 8 is about 40% smaller than that in the case of FIG.

  The present invention has been made in order to solve the above-described problems. A spherical seat bolt in which the relationship between the tightening torque and the generated axial force exhibits stable linearity and at the same time, the member to be fastened is not easily depressed or loosened. Is to provide.

  In the spherical seat bolt according to the present invention, the seat surface of the bolt is a convex spherical surface, and the value of the spherical surface R of the convex spherical surface becomes two steps as it goes from the head side of the bolt toward the screw portion side of the bolt. Yes.

  According to the present invention, it is possible to secure a sufficient contact area of the seating surface and prevent harmful effects caused by external contact.

It is a figure which shows the spherical seat bolt of a present Example. It is an enlarged view of the A section in FIG. It is the figure which showed the ratio of the contact area of the seat surface in each condition. It is a figure which shows the relationship between the tightening torque and axial force in the spherical seat bolt of a present Example. It is a figure which shows the conventional hexagon bolt with a flange. It is a figure which shows the conventional spherical seat bolt. It is a figure which shows the relationship between the tightening torque and axial force in the conventional spherical seat bolt. It is a figure which shows the relationship between the tightening torque and axial force in the spherical seat bolt of internal contact conditions.

  Examples of the present invention are shown below. FIG. 1 shows a spherical seat bolt of this embodiment, and FIG. 2 is an enlarged view of part A in FIG.

  The spherical seat bolt 1 of this embodiment includes a head portion 11 that receives power from a tightening tool (not shown), a shaft portion 12 connected to the head portion 11, and a screw portion 13. The head portion 11 is provided with an engaging portion 111 that engages with the tightening tool and a spherical portion 112 that serves as a seating surface. In this embodiment, the shape of the engaging portion 111 is a hexagonal hole, but it may be a hexalobular hole or a twelve-square hole.

  As shown in FIG. 2, the spherical surface portion 112 is composed of a large diameter portion 112a and a small diameter portion 112b. The value of the spherical surface R in the large-diameter portion 112a is set so as not to exceed the value of the spherical surface R on the receiving side seating surface of the fastened member and not to be too low. For example, when the value of the spherical surface R on the receiving side seating surface of the member to be fastened is 13.0 ± 0.1 mm, the value of the spherical surface R in the large diameter portion 112a is 12.8 ± 0.1 mm.

  The value of the spherical surface R in the small diameter portion 112b is desirably a value that is 1 to 3% smaller than the value of the spherical surface R in the large diameter portion 112a. In addition, the range h of the small diameter portion 112b in the head 11 is desirably 5 to 20% with respect to the nominal diameter of the bolt 1. By setting the small-diameter portion 112b as described above, in the unlikely event that an unexpected external force acts on the fastening body, it becomes possible to reduce the seat surface displacement and rattling, and by cold forging It is possible to reduce the burden on the mold when the head 11 is processed.

  FIG. 3 shows the ratio of the seating surface contact area in this embodiment and the inner hit / outer hit conditions. When the spherical surface R on the bolt side is 12.6 mm, it corresponds to the inner contact condition, 12.8 mm + 12.6 mm corresponds to the present embodiment, and 13.2 mm corresponds to the outer contact condition. It is the ratio to the contact area of the seating surface under conditions. The contact area of the bearing surface in the bolt of the present embodiment is not less than the inner hit condition and not more than the outer hit condition. Also, as shown in FIG. 4, the relationship between the tightening torque and the axial force in the spherical seat bolt of the present embodiment shows stable linearity, and can be appropriately managed by the torque method. That is, according to the bolt of the present embodiment, it is possible to reduce the risk of occurrence of depression and loosening by securing the contact area of the seating surface as much as possible within a range where tightening does not become unstable due to external contact. It is.

DESCRIPTION OF SYMBOLS 1 Spherical seat bolt 11 Bolt head 111 Tool engaging part 112 in a bolt head Spherical part 112a Large diameter part 112b in a spherical part Small diameter part 12 in a spherical part 12 Bolt shaft part 13 Bolt screw part

Claims (4)

  A spherical seat bolt, wherein the seat surface of the bolt is a convex spherical surface, and the value of the spherical surface R of the convex spherical surface is two steps from the head side of the bolt toward the screw portion side of the bolt.   2. The spherical seat bolt according to claim 1, wherein the convex spherical surface is constituted by a small diameter portion having a small value of the spherical surface R and a large diameter portion having a large value of the spherical surface R. 3.   3. The spherical seat bolt according to claim 1, wherein the small diameter portion is disposed on a head side of the convex spherical surface, and the large diameter portion is disposed on a screw portion side of the convex spherical surface.   4. The spherical seat bolt according to claim 1, wherein the value of the spherical surface R in the small diameter portion is a value that is 1 to 3% smaller than the value of the spherical surface R in the large diameter portion.

Images