Screw structure

Abstract

The present invention enables generation of a locking effect by means of prevailing torque while reducing the proportion of a distribution load of a fastening axial force applied to a first screw thread.　In this screw structure comprising a bolt 1 and a nut 2, a female screw 20 of the nut 2 has: a first screw region 21; and a second screw region 22 in which flank surfaces 22a, 22b are formed in a protruding circular arc shape. In a state where the female screw 20 is being screwed into a male screw 10 of the bolt 1, in the first screw region 21, the compression-side flank surface 21a comes into contact with the male screw 10 while a gap is formed between the play-side flank surfaces 21b, 10b, and, in the second screw region 22, the compression-side and play-side flank surfaces 22a, 22b of the female screw 20 respectively come into contact with the compression-side and play-side flank surfaces 10a, 10b of the male screw 10.

Description

[Technical Field]

[0001] The present invention relates to a screw structure. [Background technology]

[0002] The applicant of the present application has been developing locking nuts for some time, and has disclosed a locking nut in which the flank surface of the female thread is a convex arc surface in Patent Document 1 listed below.

[0003] By making the flank surfaces convex arc surfaces, the play (gap) between the female thread of the nut and the male thread of the bolt is substantially eliminated, suppressing the relative movement of the nut with respect to the bolt in a vibration environment and reducing the occurrence of loosening of the nut. Furthermore, by bringing not only the compression side flank surfaces of the female thread and the male thread into contact with each other, but also the play side flank surfaces of the female thread and the male thread into contact with each other, a prevailing torque can be generated in the nut during the nut tightening operation, and this prevailing torque also produces an anti-loosening effect. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-105444 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when a nut is fastened to a bolt, the fastening axial force is distributed and applied to the multiple threads of the female thread that appear in the longitudinal cross section, and it is known that the proportion of the distributed load of the fastening axial force that is applied to the first thread of the female thread (the thread closest to the seating surface of the nut) is the largest.

[0006] When excessive axial force is applied, the first thread breaks first, and then the breakage progresses from there until all the female threads break. Also, even if the axial force is not strong enough to cause breakage, if the fastened nut is placed in a vibration environment, for example, the first thread, which bears a large distributed load, will also be subjected to the impact force from the vibration, causing slight deformation in the axial direction, which can significantly reduce the fastening axial force.

[0007] An object of the present invention is to reduce the proportion of the distributed load of the fastening axial force applied to the first thread, while generating an anti-loosening effect by prevailing torque. [Means for solving the problem]

[0008] The thread structure according to the present disclosure may include a first threaded member having a thread shank with a male thread formed on its outer peripheral surface, and a second threaded member having a threaded hole with a female thread formed on its inner peripheral surface to be threaded with the male thread. The female thread may have a first thread region and a second thread region. Preferably, when the male thread is threaded with the female thread, in the first thread region, the compression flank of the female thread contacts the compression flank of the male thread, but there is a gap between the play flank of the female thread and the play flank of the male thread. More preferably, the male thread and the female thread are configured such that in the second thread region, the compression flank and play flank of the female thread contact the compression flank and play flank of the male thread, respectively. Preferably, in the first thread region, the compression flank and play flank of the female thread are flat in longitudinal cross section. Preferably, in the second thread region, at least one of the compression flank surface and the play flank surface of the female thread has a convex arc shape in a longitudinal section.

[0009] Also, a threaded member having a thread according to the present disclosure has a first thread region and a second thread region. Preferably, in the first thread region, the compression flank and the clearance flank of the thread are flat in longitudinal cross section. Preferably, in the second thread region, at least one of the compression flank and the clearance flank of the thread has a convex arc shape in longitudinal cross section. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to reduce the proportion of the distributed load of the fastening axial force applied to the first thread, and also to generate an anti-loosening action due to the prevailing torque. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a longitudinal cross-sectional view of one embodiment of a screw structure according to the present disclosure; FIG. [Figure 2] FIG. 10 is a perspective view showing an example of a protrusion. [Figure 3] FIG. 10 is a perspective view showing another example of a protrusion. [Figure 4] 1 is a longitudinal cross-sectional view of one embodiment of a screw member according to the present disclosure. FIG. [Figure 5] 10A and 10B are longitudinal cross-sectional views illustrating press working for diameter-reducing deformation of a convex portion. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Embodiment of screw structure] The thread structure according to the present disclosure may include a first threaded member having a threaded shaft with a male thread formed on its outer circumferential surface, and a second threaded member having a threaded hole with a female thread formed on its inner circumferential surface to be threadedly engaged with the male thread. The female thread may have a first thread region and a second thread region.

[0013] Preferably, when the male thread is threadedly engaged with the female thread, the compression flank of the female thread contacts the compression flank of the male thread in the first thread region, but there is a gap between the play flank of the female thread and the play flank of the male thread.More preferably, the male thread and the female thread are configured so that, in the second thread region, the compression flank and play flank of the female thread contact the compression flank and play flank of the male thread, respectively.

[0014] The phrase "a state in which the male thread is threaded into the female thread" includes not only a state in which the first and second screw members are fastened together, but also a state in the middle of a fastening operation in which no fastening torque is being generated.

[0015] The first threaded member is typically a bolt having a threaded shank. The threaded shank is typically a solid shaft, but may also have a tubular structure. The first threaded member may be a conventional bolt manufactured according to required standards. The male thread has a predetermined thread profile defined by a predetermined thread pitch and predetermined crest and root diameters of the male thread. Both the compression side and clearance side flank surfaces of the male thread may be flat in longitudinal cross section.

[0016] The second threaded member is typically a nut having a threaded hole. The first and second thread regions each have a predetermined axial length. Preferably, the first and second thread regions each have an axial length greater than one pitch of the female thread. More preferably, the first and second thread regions each have an axial length greater than two pitches of the male thread. The first and second thread regions are provided at different axial positions. The first and second thread regions may be arranged axially consecutively, or a third thread region may be provided between the first and second thread regions. The female thread preferably has thread profiles in which the first and second thread regions have different thread profiles so that the above-mentioned contact state occurs at the flank surfaces.

[0017] Preferably, in the first thread region, the compression flank and the clearance flank of the female thread are flat in longitudinal cross section. Preferably, in the second thread region, at least one of the compression flank and the clearance flank of the female thread has a convex arc shape in longitudinal cross section. More preferably, in the second thread region, both the compression flank and the clearance flank of the female thread have a convex arc shape in longitudinal cross section.

[0018] Preferably, the second threaded member has a main body and a protrusion axially protruding from the end face of the main body and having an outer diameter smaller than that of the main body, and the threaded hole is provided across the main body and the protrusion. The main body may be hexagonal nut-shaped or cylindrical nut-shaped. The protrusion may be cylindrical or truncated cone-shaped, or may have a structure having multiple blocks aligned in the circumferential direction and a thin-walled connecting portion connecting adjacent blocks, similar to the locking nut disclosed in Japanese Patent No. 3272265. "Having an outer diameter smaller than that of the main body" means that the average radial thickness from the outer periphery of the main body to the inner periphery of the thread is smaller than the average radial thickness from the outer periphery of the protrusion to the inner periphery of the thread. A protrusion that is thinner than the main body undergoes slight radial outward deformation due to reaction forces acting on both flank surfaces when the female thread is threaded onto the male thread, thereby suppressing seizure.

[0019] Preferably, at least a portion of the first thread region of the female thread is provided on the main body. Preferably, at least a portion of the second thread region of the female thread is provided on the convex portion. According to this, when the second threaded member is threaded onto the first threaded member from the main body side, only the first thread region, which has play with the male thread, engages with the male thread at the beginning of the tightening operation, allowing the second threaded member to be smoothly threaded. When the second threaded member of the female thread begins to engage with the male thread, the compression side and play side flank surfaces of the female thread of the second thread region come into contact with the male thread, and a large prevailing torque is generated due to the frictional resistance. However, because the entire first thread region is threaded with the male thread at that point, the second threaded member can be threaded into the first threaded member by rotating the second threaded member relative to the first threaded member with a tightening torque greater than the prevailing torque.

[0020] Preferably, a portion of the second thread region of the female thread is provided on the main body, and the portion of the second thread region provided on the convex portion has a smaller diameter than the portion of the second thread region provided on the main body when the female thread is not threaded onto the male thread. This structure can be obtained by deforming the convex portion radially inward to reduce its diameter after forming the female thread. When the female thread is threaded onto the male thread, the portion of the second thread region provided on the convex portion is slightly deformed radially outward, so that when the female thread is threaded onto the male thread, the portion of the second thread region provided on the convex portion has the same diameter as the portion of the second thread region provided on the main body.

[0021] [Embodiment of the screw member] A screw member according to the present disclosure includes a screw having a first threaded region and a second threaded region. Preferably, in the first thread region, the compression flank and the clearance flank of the thread are flat in longitudinal cross section. Preferably, in the second thread region, at least one of the compression flank and the clearance flank of the thread has a convex arc shape in longitudinal cross section. The thread of the threaded member may be a male thread or a female thread.

[0022] Preferably, in the second thread region, both the compression flank surface and the clearance flank surface of the female thread have a convex arc shape in longitudinal cross section.

[0023] Preferably, the screw member is a nut having a nut body and a protrusion that protrudes axially from an end face of the nut body and has an outer diameter smaller than that of the nut body. In this case, the thread is a female thread provided on the inner periphery of a threaded hole that is provided across the nut body and the protrusion.

[0024] Preferably, at least a part of the first thread region of the female thread is provided on the nut body, and at least a part of the second thread region of the female thread is provided on the protrusion.

[0025] Preferably, a (other) part of the second thread region of the female thread is provided in the nut body. Preferably, the part of the second thread region provided in the convex portion has a smaller diameter than the part of the second thread region provided in the nut body. [Example]

[0026] Hereinafter, preferred embodiments of the screw member and screw structure according to the present disclosure will be described with reference to the drawings. Screw member.

[0027] FIG. 1 shows one embodiment of a screw member and screw structure according to the present disclosure. The screw structure includes a bolt 1, which is a first screw member, and a locking nut 2, which is a second screw member. The bolt 1 has a threaded shaft with a male thread 10 formed on its outer circumferential surface. The nut 2 has a threaded hole with a female thread 20 formed on its inner circumferential surface, which screws onto the male thread 10. A commercially available conventional bolt can be used as the bolt 1.

[0028] As also shown in Figure 4, the female thread 20 of the nut 2 has a first thread region 21 arranged on the seat surface side (the bottom surface of the nut in the illustrated example) and a second thread region 22 arranged axially farther from the seat surface than the first thread region 21.

[0029] When the male thread 10 is threaded into the female thread 20, in the first thread region 21, the compression flank surface 21a of the female thread 20 contacts the compression flank surface 10a of the male thread 10, but there is a gap between the play side flank surface 21b of the female thread 20 and the play side flank surface 10b of the male thread 10. Furthermore, when the male thread 10 is threaded into the female thread 20, in the second thread region 22, the compression flank surface 22a and the play side flank surface 22b of the female thread 20 contact the compression flank surface 10a and the play side flank surface 10b of the male thread 10, respectively.

[0030] In the first thread region 21, the compression flank surface 21a and the clearance flank surface 21b of the female thread 20 are flat in longitudinal cross section.

[0031] In the second thread region 22, both the compression flank surface 22a and the clearance flank surface 22b of the female thread 20 have a convex arc shape in longitudinal cross section. In Fig. 4, the convex arc-shaped flank surfaces 22a, 22b seen at the back of the cross section are shown shaded. Note that either the compression flank surface 22a or the clearance flank surface 22b may have a convex arc shape in longitudinal cross section, while the other may be flat in longitudinal cross section.

[0032] The nut 2 has a nut body 2A having a seat surface and a protrusion 2B that protrudes in the axial direction from the top of the nut body 2A and has an outer diameter smaller than that of the nut body 2A. A screw hole having a female thread 20 penetrates the nut body 2A and the protrusion 2B.

[0033] A first thread region 21 of the female thread 20 is provided at the bottom of the nut body 2A, and a second thread region 22 is provided from the top of the nut body 2A to the protrusion 2B.

[0034] The outer peripheral shapes of the nut body 2A and the protrusions 2B are not particularly limited, but in one embodiment, as shown in FIG. 2, the nut body 2A is configured in a hexagonal nut shape, and the protrusions 2B are configured in a truncated cone shape. The protrusions 2B have a maximum outer diameter at their bottoms. They have a minimum outer diameter at the center of the hexagonal nut side of the nut body 2A. The maximum outer diameter of the protrusions 2B is smaller than the minimum inner diameter of the nut body 2A. This makes the protrusions 2B more easily deformed in the radial direction than the nut body 2A.

[0035] As shown in FIG. 3, the protrusion 2B may include multiple blocks aligned in the circumferential direction. Preferably, adjacent blocks are connected and integrated by connecting portions that are thinner than the radial thickness of the blocks themselves. For example, by forming multiple vertical grooves on the outer periphery of the protrusion 2B, a structure in which multiple blocks are connected by connecting portions can be obtained. However, if a slit is provided between adjacent blocks in the radial direction to structurally separate the multiple blocks, the radial deformability of each block becomes too large, and the effect of the arc-shaped flank surface becomes limited.

[0036] As shown in FIG. 5 , the protrusion 2B is pressed from the radially outward direction, so that portions 22a', 22b' of the second thread region 22 provided on the protrusion 2B may be smaller in diameter than portions 22a, 22b of the second thread region 22 provided on the nut 2A body when the female thread 20 is not threaded onto the male thread 10. Although the male threads of commercially available bolts have manufacturing tolerances, by reducing the diameter of the female thread provided on the inner circumference of the protrusion 2B, the compression side and clearance side flank surfaces 22a', 22b' of the second thread region 22 can be reliably brought into contact with the compression side and clearance side flank surfaces of the male thread when the female thread is threaded onto the male thread. Furthermore, the magnitude of the generated prevailing torque can be adjusted by adjusting the amount of diameter-reducing deformation of the protrusion 2B.

[0037] The thread structure of this embodiment can prevent stress concentration on the first thread of the female thread 20 of the female thread nut 2 while suppressing seizure, thereby improving resistance to axial force. Furthermore, even if the bearing surface pressure disappears instantaneously in a vibration environment, the male thread and female thread are in contact on both flank surfaces, preventing axial vibration of the female thread relative to the male thread and providing a high anti-loosening effect.

Claims

1. A screw structure including a first screw member having a screw shaft with a male thread formed on an outer peripheral surface thereof, and a second screw member having a screw hole with a female thread formed on an inner peripheral surface thereof, the second screw member having a female thread that screws into the male thread, the internal thread has a first thread region and a second thread region; A thread structure in which the male thread and the female thread are configured such that, when the male thread is threadedly engaged with the female thread, in a first thread region, the compression flank surface of the female thread contacts the compression flank surface of the male thread, but there is a gap between the play side flank surface of the female thread and the play side flank surface of the male thread, and in a second thread region, the compression flank surface and the play side flank surface of the female thread contact the compression flank surface and the play side flank surface of the male thread, respectively. In the first thread region, the compression flank and the clearance flank of the female thread are flat in longitudinal cross section; In the second thread region, at least one of a compression flank surface and a clearance flank surface of the female thread has a convex arc shape in a longitudinal cross section. Screw structure.

2. The screw structure according to claim 1, In the second thread region, both the compression side flank surface and the play side flank surface of the female thread have a convex arc shape in longitudinal cross section. Screw structure.

3. The screw structure according to claim 1 or 2, the second screw member has a main body and a protrusion that protrudes in the axial direction from an end face of the main body and has an outer diameter smaller than that of the main body, and the screw hole is provided across the main body and the protrusion, At least a portion of the first threaded region of the internal thread is provided on the body; At least a portion of the second thread region of the female thread is provided on the protruding portion. Screw structure.

4. The screw structure according to claim 3, a portion of the second threaded region of the internal thread is provided on the body; a portion of the second thread region provided on the protrusion has a smaller diameter than a portion of the second thread region provided on the main body when the female thread is not threaded onto the male thread; Screw structure.

5. A screw structure including a first screw member having a screw shaft with a male thread formed on an outer peripheral surface thereof, and a second screw member having a screw hole with a female thread formed on an inner peripheral surface thereof, the second screw member having a female thread that screws into the male thread, the internal thread has a first thread region and a second thread region; A thread structure in which the male thread and the female thread are configured such that, when the male thread is threadedly engaged with the female thread, in a first thread region, the compression flank surface of the female thread contacts the compression flank surface of the male thread, but there is a gap between the play side flank surface of the female thread and the play side flank surface of the male thread, and in a second thread region, the compression flank surface and the play side flank surface of the female thread contact the compression flank surface and the play side flank surface of the male thread, respectively. the second screw member has a main body and a protrusion that protrudes in the axial direction from an end face of the main body and has an outer diameter smaller than that of the main body, and the screw hole is provided across the main body and the protrusion, At least a portion of the first threaded region of the internal thread is provided on the body; At least a portion of the second thread region of the female thread is provided on the protruding portion. Screw structure.

6. The screw structure according to claim 5, a portion of the second threaded region of the internal thread is provided on the body; a portion of the second thread region provided on the protrusion has a smaller diameter than a portion of the second thread region provided on the main body when the female thread is not threaded onto the male thread; Screw structure.

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