Nut structure

Abstract

To provide a nut structure capable of restraining a new nut from being installed on a bolt in a fastened member state by already installing a nut.SOLUTION: The nut 10 is mounted by screwing a nut body 14 to a shaft part 24 of a stud bolt 12. In the nut body 14, a protrusion 50 is formed on the top surface 22. A projection height d of the projection part 50 is made larger than a pitch p of a male screw of the stud bolt 12. Also. Even when the protrusion 50 receives a pressure exceeding the target pressure Pt corresponding to the target torque Tt, a state in which the protrusion height d is larger than the pitch p is maintained. For this reason, when the nut body side 14A is attached to the stud bolt 12 to which the nut body side 14B is attached, the nut body side 14B is seated on the protrusion 50 of the nut body side 14A, so that the rotation of the nut body side 14B is hindered, and the erroneous fastening can be detected.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a locking nut. The locking nut is made up of two nuts of the same shape, each of which has a convex portion and a concave portion formed on one axial surface. The two nuts are used as a locking nut by facing each other with the surfaces on which the convex portions and concave portions are formed, and by fitting the convex portion of one nut into the concave portion of the other nut and screwing it onto a bolt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-015392 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, in the fastening process where two parts are fastened by manually screwing a nut onto a bolt, a nut runner (automatic nut fastening machine) known as an electric torque wrench is often used. The nut runner screws the nut onto the bolt so that a preset tightening torque is obtained.

[0005] As a result, by using a nut runner in the fastening process, smooth fastening work can be achieved without being affected by individual differences such as the skill level (proficiency) of the worker, and fastening force can be made more precise and efficient with less variation than with hand fastening (manual work).In addition, by using a nut runner in the fastening process, it is possible to improve workability by shortening the work time and reducing the workload when fastening multiple nuts.

[0006] In the fastening process, when one or more attachment parts are fastened to the base, one of two fastened parts being the base and the other being the attachment part, a stud bolt is implanted in the base, and this stud bolt is inserted into a bolt hole formed in the attachment part, and a nut is screwed onto the stud bolt protruding from the bolt hole.

[0007] Conventionally, stud bolts of different lengths are arranged according to the mounting part and the position on the board where the mounting part is mounted, and the protruding height (length) of the stud bolt from the mounting part is often set to the length that can be screwed onto one nut (the length required for fastening). This makes it possible to prevent incorrect fastening (double nutting), where two nuts are attached to one stud bolt.

[0008] In recent years, standardization of parts has become commonplace in order to reduce costs, and stud bolts of the same length are sometimes used on the base. When multiple stud bolts of the same length are placed on the base, it can be difficult to determine whether the stud bolt to be worked on is already attached when using a nut runner for fastening work. For this reason, if the length of the stud bolt is long enough to attach multiple nuts, problems arise when using a nut runner for fastening work, such as incorrect fastening where two nuts are attached to one stud bolt.

[0009] The present invention has been made in consideration of the above-mentioned facts, and aims to provide a nut structure that can prevent another nut from being attached to a bolt when the bolt is already attached to the bolt and fastening the fastened member. [Means for solving the problem]

[0010] To achieve the above object, a nut structure according to a first aspect of the present invention includes a nut body having one axial side surface that serves as a seating surface, which is rotated while facing a fastened member to be screwed onto a bolt, and which fastens the fastened member to the bolt when the torque after the seating surface seats on the fastened member reaches a predetermined target torque, and a protrusion that is formed on the surface of the nut body opposite the seating surface and that protrudes in the opposite direction from the seating surface, and that maintains a protruding height that is greater than the pitch of the bolt even when pressure corresponding to a torque that exceeds the maximum value of the target torque is applied. [Effects of the Invention]

[0011] In the nut structure according to the first aspect of the present invention, the nut body, one axial side of which serves as a seating surface facing the fastened member, is rotated to screw onto the bolt, and the fastened member is fastened to the bolt when the torque after the seating surface seats on the fastened member reaches a preset target torque.

[0012] The nut body is also formed with a protrusion that protrudes in the opposite direction from the seating surface on the surface of the nut body opposite the seating surface. The protrusion is formed so that a protrusion height greater than the bolt pitch is maintained even when pressure corresponding to a torque exceeding the maximum value of the target torque is applied. The maximum value of the target torque is set for each nut body, and the target torque is set within a range that does not exceed the maximum value.

[0013] When a nut body is threaded onto a bolt using a nut runner, the torque required to rotate the nut body is low until the seating surface of the nut body seats on the fastened member, etc., but increases once the seating surface seats. The nut runner stops rotating when the torque required to rotate the nut body after the nut body seats reaches the target torque. At this time, the protruding portion of the nut body is not subjected to pressure.

[0014] On the other hand, when a new nut body is threaded onto a bolt that already has a nut body attached, the seating surface of the new nut body abuts against the protruding portion of the existing nut body. In this case, because the protruding height of the protruding portion is greater than the bolt pitch, even if an attempt is made to rotate the new nut body further, the protruding portion of the already attached nut body will hinder the rotation.

[0015] As a result, if a nut body is already attached to the bolt, the new nut body will not rotate even if the torque to rotate it increases, and the nut runner can detect that the nut body has stopped rotating, thereby preventing incorrect tightening of the nut body. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic side view of the nut and stud bolt according to the embodiment. [Figure 2] (A) is a schematic diagram of the nut body as viewed from the side, (B) is a schematic diagram of the main parts of the stud bolt as viewed from the side, and (C) is a schematic diagram of the side view showing a state in which a new nut body is being installed by placing it on top of an already installed nut body. [Figure 3] FIG. 10 is a diagram showing an outline of the change in torque on the nut body over time. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The nut 10 according to this embodiment is attached to a stud bolt 12 serving as a bolt. The nut 10 includes a nut body 14, and the nut body 14 is attached to the stud bolt 12.

[0018] Fig. 1 shows a schematic side view of the nut 10 and stud bolt 12 according to this embodiment. Fig. 2(A) shows a schematic side view of the nut body, Fig. 2(B) shows a schematic side view of the main parts of the stud bolt, and Fig. 3(C) shows a schematic side view of an example of two nut bodies attached to a stud bolt. In the drawings, the axial direction of the stud bolt 12 is indicated by arrow S. In the following description, the direction intersecting the axial direction of the stud bolt 12 is defined as lateral.

[0019] 1 and 2(A), the nut body 14 of the nut 10 has an outer shape that is a substantially hexagonal column, and the nut body 14 is a hexagonal nut. The nut body 14 (nut 10) has an inner hole 16 with a predetermined inner diameter (nominal diameter) formed in the axial center, and the inner hole 16 has a female thread engraved on the inner peripheral surface.

[0020] The nut body 14 may be a type 2 (type 2 nut), but is preferably a type 1 (type 1 nut) in which one axial side is chamfered to clearly define the seating surface. The nut body 14 is also integrally formed with a disk-shaped flange 18 on one axial side (seat side), making the nut body 14 a flanged nut. The surface of the nut body 14 facing the flange 18 in the axial direction serves as a seating surface 20, and the surface opposite the seating surface 20 serves as a top surface 22.

[0021] As shown in Figure 1, the stud bolt 12 has a generally cylindrical shank 24 with a predetermined outer diameter, and the shank 24 has a general configuration with a male thread engraved on the outer periphery. The stud bolt 12 uses a nut body 14 that has an inner hole 16 with an inner diameter (the same nominal diameter) that corresponds to the outer diameter of the shank 24, and the nut body 14 is screwed onto the shank 24.

[0022] In this embodiment, the nut 10 and stud bolt 12 are used to fasten two fastened members together, and the two fastened members are a base 26 and an attachment part 28 attached to the base 26. The stud bolt 12 is implanted in a predetermined position in the base 26. The stud bolt 12 is disposed in the base 26 in a known configuration, such as by embedding the head in the base 26 and allowing the shank 24 to protrude from the base 26.

[0023] A configuration in which one or more mounting parts 28 can be attached to the base 26 can be applied, and the multiple mounting parts 28 may have different shapes, functions (types), etc. When multiple mounting parts 28 are attached to the base 26, stud bolts 12 are implanted at positions corresponding to the mounting positions of each of the mounting parts 28. In addition, bolt holes 30 are formed through the mounting parts 28, and the shanks 24 of the stud bolts 12 are inserted into the bolt holes 30, and the mounting part 28 is positioned relative to the base 26 by inserting the shanks 24 of the stud bolts 12 into the bolt holes 30.

[0024] The stud bolt 12 is inserted into the bolt hole 30 of the mounting part 28, and the nut body 14 is screwed onto the shank 24 that protrudes on the side opposite the base 26. As a result, the mounting part 28 is fastened and fixed to the base 26 by the axial force generated in the shank 24 of the stud bolt 12.

[0025] On the other hand, a nut runner (automatic nut fastening machine) 40 that functions as an electric torque wrench can be used to screw (fasten) the nut body 14 onto the stud bolt 12 (shank 24). A controller 42 is connected to the nut runner 40, and the controller 42 controls the operation of a motor (not shown) in the nut runner 40, which uses the torque of the motor to rotate the nut body 14 attached to the socket.

[0026] The controller 42 includes a microcomputer (not shown) in which a CPU, a ROM, a RAM, and a non-volatile memory are connected via a bus to enable data exchange. The controller 42 realizes the torque control function for the nut runner 40 by having the CPU read out a torque control program stored in the ROM or memory and executing it using the RAM as a work memory.

[0027] The nut runner 40 is provided with a sensor (not shown) that detects the rotation angle (rotation angle) of the nut body 14, the rotation time (operating time), and the torque (rotational torque and tightening torque) that rotates the nut body 14.

[0028] The controller 42 controls the operation of the motor while acquiring the rotation angle of the nut body 14, the rotation time (operation time), the torque for rotating the nut body 14, and the like, which are detected by each of the sensors in the nut runner 40. Note that the nut runner 40 may detect the rotation angle of a rotating shaft rotated by the motor instead of detecting the rotation angle of the nut body 14. Known configurations can be applied to the basic configurations of such a nut runner 40 and controller 42.

[0029] Incidentally, the nut 10 has a protrusion 50 formed on the nut body 14 as a protruding portion. The protrusion 50 protrudes to a predetermined height from the periphery of the inner hole 16 on the top surface 22 of the nut body 14 toward the side opposite the seating surface 20. When the nut body 14 receives pressure toward the seating surface 20, the protrusion 50 is suppressed from undergoing plastic deformation or elastic deformation, and the predetermined height is maintained, even if the pressure exceeds a preset pressure.

[0030] Next, the fastening of the base body 26 and the attachment part 28 using the nut 10 and the stud bolt 12 will be described. In the nut 10, a target tightening torque Tt [N·m] is set for the nut body 14. If the lower limit of the target torque Tt in the nut body 14 is a [N·m] and the upper limit as the maximum value of the target torque Pt is b [N·m], the lower limit a and the upper limit b are determined by the structure (structural dimensions) of the nut body 14, such as the nominal diameter (inner diameter of the inner hole 16), the material, etc.

[0031] In addition, the nut body 14 generates an axial force [N] corresponding to the target torque Tt by being rotated at the target torque Tt while seated on the attachment part 28, etc., and the attachment part 28, etc. generates a target pressure Pt [N / m 2 From this, the target torque Tt of the nut body 14 used to fasten the base body 26 and the attachment part 28 is set within the range of lower limit value a to upper limit value b (a≦Tt≦b) depending on the base body 26, the attachment part 28, and their strengths, etc.

[0032] The torque (rotational torque) T [N·m] required to rotate the nut body 14 to thread onto the stud bolt 12 is low until the seating surface 20 of the nut body 14 seats on the mounting part 28 or the like. Furthermore, when the seating surface 20 of the nut body 14 seats on the mounting part 28 or the like, the torque T required to rotate the nut body 14 increases and functions as the tightening torque at which final tightening begins. When final tightening begins, an axial force [N] corresponding to the tightening torque (torque T) is generated between the nut body 14 and the stud bolt 12.

[0033] When the nut body 14 is attached to the stud bolt 12 and a new nut body 14 is screwed onto the stud bolt 12, the seating surface 20 of the new nut body 14 abuts against the protrusion 50, and the protrusion 50 receives pressure from the new nut body 14 according to the torque T.

[0034] As shown in Figure 2(B), the male thread of the stud bolt 12 is formed with a predetermined pitch p [mm]. Also, as shown in Figure 2(A), the protrusion 50 has a protruding height d [mm] from the top surface 22. Furthermore, in the nut body 14, the protruding height d of the protrusion 50 is greater than the pitch p of the stud bolt 12 (d>p).

[0035] In addition, in the nut body 14, the protrusion 50 is pressed against the pressure Pb [N / m 2 ], the protrusion height d remains greater than the pitch p. That is, even when the protrusions 50 are subjected to a pressure exceeding the upper limit (pressure Pb) of the target pressure Pt, plastic deformation is suppressed. The protrusions 50 may be elastically deformable, and in this case, may be formed with a protrusion height and material (Young's modulus) that maintains the protrusion height d (protrusion height after elastic deformation) greater than the pitch p (d>p) even when the protrusions 50 are subjected to a pressure exceeding the pressure Pb and elastically deform.

[0036] The controller 42 is set with a target torque Tt and a seating torque Tc for the nut body 14 of the nut 10. When the seating torque Tc is detected, the controller 42 controls the nut runner 40 so that the detected torque T reaches the target torque Tt (final tightening).

[0037] Between the nut runner 40 and the controller 42, a delay in control by the controller 42 based on the torque (actual measurement value) detected in the nut runner 40 may occur. As a result, when the nut body 14 rotates, the actual torque may exceed the detected torque T (overshoot). It is preferable that the controller 42 perform torque control taking this overshoot into consideration.

[0038] Figure 2(C) shows a schematic side view of two nut bodies 14 attached to one stud bolt 12. Figure 3 shows a diagram of the change in torque (tightening torque) T over time detected by the controller 42 when the nut body 14 is screwed onto the stud bolt 12.

[0039] In addition, Figure 2(C) shows an outline of the installation of one of the two nut bodies 14 (hereinafter referred to as nut body 14A) when the other nut body 14 (hereinafter referred to as nut body 14B) is already attached to the stud bolt 12.

[0040] In addition, the controller 42 stops the rotation of the nut body 14 (14A, 14B) when it determines that the torque T detected in the nut runner 40 reaches the target torque Tt, or when it determines that there has been a change in the torque T or an abnormality has occurred in the rotation of the nut body 14.

[0041] When the attachment part 28 is fastened to the base 26 by the nut body 14A and the stud bolt 12, the nut body 14A is rotated by the nut runner 40. As a result, the seating surface 20 of the nut body 14A seats on the attachment part 28, causing the torque T to increase and reach the target torque Tt, and the controller 42 detects that the nut body 14A has seated on the attachment part 28 (seating at the required pressure), and stops the rotation of the nut body 14. As a result, the base 26 and the attachment part 28 are fastened together with an axial force corresponding to the target torque Tt (see the solid lines in FIGS. 1 and 3).

[0042] At this time, as shown by the solid line in Fig. 3, if the change in torque T is gradual until it reaches the target torque Tt (no change in torque T that is perceived as abnormal is detected), the controller 42 determines that the nut body 14 (14A) has been properly fastened. In other words, if the slope of the change in torque T (torque change rate) after seating of the nut body 14 is detected is lower than a preset slope (threshold value), the controller 42 determines that the base 26 and the attachment part 28 have been fastened and fixed by the nut body 14 with an appropriate tightening torque.

[0043] In contrast, when the nut body 14B is attached while the nut body 14A is already attached to the stud bolt 12, the nut body 14B rotated by the nut runner 40 causes the protrusion 50 of the nut body 14A to abut against the seating surface 20. This causes the controller 42 to detect that the nut body 14B is seated. Thereafter, the controller 42 causes the nut body 14B to continue rotating until the torque T reaches the target torque Tt.

[0044] Here, in the nut body 14 (14A, 14B), the protrusion height d of the protrusions 50 is set to be larger than the pitch p of the stud bolts 12 (d>p). Furthermore, even when the protrusions 50 are subjected to a pressure exceeding the pressure corresponding to the target torque Tt (target pressure Pt), plastic deformation and elastic deformation of the protrusions 50 are suppressed, and the protrusion height d is maintained.

[0045] As a result, the nut body 14B tilts (see FIG. 2(C)), and the protrusions 50 of the nut body 14A hinder the nut body 14B from engaging with the female threads in the inner hole 16 and the male threads of the shank 24 of the stud bolt 12. Because the rotation of the nut body 14B is hindered by the protrusions 50 of the nut body 14A, the torque T required to rotate the nut body 14B increases.

[0046] This causes the torque T detected by the controller 42 to rise sharply (the rate of change of the torque T increases) as shown by the dashed line in Fig. 3. By detecting the sharp rise in the torque T (a change exceeding a preset rate of change), the controller 42 determines that, for example, erroneous fastening of the nut body 14B has occurred (detects erroneous fastening), and stops the rotation of the nut body 14B.

[0047] Therefore, since the nut body 14 is formed with a protrusion 50 whose protruding height d is greater than the pitch p of the stud bolt 12, the nut 10 can detect incorrect tightening using the controller 42, and the nut 10 can prevent incorrect tightening from occurring.

[0048] In the above-described embodiment, it has been described that the misfastening is detected from the change (change rate) of the torque T (tightening torque) in the nut body 14 in which the protrusion 50 is formed. However, misfastening is not limited to the change in torque, and it is also possible to apply the change in the rotation angle of the nut body (the change in the rotation angle is small), the time from when the torque is seated until the target torque is reached, and the like.

[0049] For example, when the torque T reaches a predetermined torque (for example, the lower limit value a of the target torque Tt), the controller controls the nut runner so that the nut 10 (nut body 14) rotates. At this time, in the controller 42, since the nut body 14 is rotated at a preset rotation speed by the nut runner 40, an overshoot occurs in the torque change due to the high rotation speed (see the solid line in FIG. 3). At this time, it is assumed that the controller 42 rotates the nut body 14 at a constant rotation speed set so that the torque T does not exceed a predetermined torque c (a < c < b) (see the solid line in FIG. 3).

[0050] Here, when the nut body 14B is screwed while the nut body 14A is attached to the stud bolt 12, even if the rotation of the nut body 14B is stopped at the lower limit value c due to the sudden change in the torque T, a large overshoot occurs, and the detected torque T greatly exceeds the predetermined torque c. From this, for the nut body 14B stacked on the nut body 14A, the torque c detected by the occurrence of an overshoot is set as a threshold value with respect to the target torque (for example, the lower limit value a). Thereby, in the controller 42, when the torque c is detected, it can be determined that a misfastening has occurred in which the nut body 14B is fastened on top of the nut body 14A.

[0051] Furthermore, torque detection time anomalies can also be used to detect erroneous fastening. For example, the time from when torque rises to when it reaches a target torque (e.g., lower limit a) differs between nut body 14A, which is installed first, and nut body 14B, which is installed after nut body 14A is installed. For example, for nut body 14A, the time when seating is detected is t1, and the time when lower limit a is reached is t2. For nut body 14B, which is placed on top of nut body 14A, the time when seating is detected is t3, and the time when lower limit a is reached is t4.

[0052] In this case, the time difference (t4-t3) is shorter than the time difference (t2-t1) ((t2-t1)>(t4-t3)). Therefore, by setting a threshold value for the time from when seating is detected (when the torque rise is detected) until a predetermined torque is reached in the nut body 14, it becomes possible to determine whether erroneous tightening has occurred and to prevent erroneous tightening from occurring. [Explanation of symbols]

[0053] 10 nuts 12 stud bolts 14(14A, 14B) Nut body 20 seating surface 22 Top surface (opposite side from the seating surface) 24 Shaft 26 Base (part to be fastened) 28 Mounting parts (fastened parts) 40 Nutrunner 42 Controller 50 Projection (protrusion)

Claims

[Claim 1] a nut body having one side surface in the axial direction as a seating surface, the seating surface being rotated in opposition to a fastened member to be screwed onto the bolt, and the fastened member being fastened to the bolt when the torque after the seating surface is seated on the fastened member reaches a predetermined target torque; a protrusion formed on a surface of the nut body opposite to the seating surface in a direction opposite to the seating surface, the protrusion maintaining a protruding height greater than the pitch of the bolt even when pressure corresponding to a torque exceeding the target torque is applied; Nut structure including:

Images