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. The protrusion 50 is plastically deformed by receiving a pressure corresponding to a set torque in which the torque applied to the nut body 14 is larger than the torque when the seating surface 20 is seated on the fitting 28 and is set lower than the target torque. Therefore, when the nut body 14A part is attached to the stud bolt 12 to which the nut body 14B part is attached, the angle until reaching the set torque after detecting the seating becomes larger than the angle in the nut body 14A part, so that 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 has seated 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 protrudes in the opposite direction from the seating surface, and which is plastically deformed when the torque applied to the nut body is greater than the torque when the seating surface seats on the fastened member and corresponds to a set torque that is set lower than the target torque. [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 undergoes plastic deformation when the torque applied to the nut body is greater than the torque when the seating surface seats on the fastened member and is subjected to pressure corresponding to a set torque that is set lower than the target torque.

[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] In contrast, 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, increasing the torque required for rotation, and plastically deforming the protruding portion of the existing nut body when the set torque is reached. Also, the new nut body plastically deforms the protruding portion of the existing nut body, causing the seating surface to seat on the existing nut body, and rotation is stopped when the torque required for rotation reaches the target torque.

[0015] As a result, if a nut body is already attached to the bolt, the time it takes for the new nut body to reach the target torque from the set torque will be longer and the number of rotations (or rotation angle) will increase, so by having the nut runner detect at least one of these changes, incorrect tightening of the nut body can be prevented. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic configuration diagram of a nut and a stud bolt according to the embodiment, as viewed from the side. [Figure 2] (A) and (B) are schematic diagrams from the side showing the state in which a new nut body is attached on top of an already attached nut body, where (A) shows the state in which the new nut body is seated on the already attached nut body, and (B) shows the state in which the new nut body is seated on the protrusion. [Figure 3] FIG. 10 is a diagram showing an outline of the change in angle of the nut body with respect to 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. Fig. 1 shows a schematic side view of the nut 10 and stud bolt 12 according to this embodiment. In the drawing, the axial direction of the stud bolt 12 is indicated by an arrow S. In the following description, the direction intersecting the axial direction of the stud bolt 12 is defined as the side.

[0018] 1, 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.

[0019] 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.

[0020] 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 formed with an inner hole 16 whose inner diameter (the nominal diameter is the same) corresponds to the outer diameter of the shank 24, and the nut body 14 is screwed onto the shank 24.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The nut 10 has a protrusion 50 formed on the nut body 14 as a protruding portion. The protrusion 50 protrudes from the periphery of the inner hole 16 on the top surface 22 of the nut body 14 toward the side opposite to the seating surface 20. When the protrusion 50 receives pressure toward the seating surface 20 side on the nut body 14, the pressure reaches a preset pressure Ps [N / m 2 ], elastic deformation is possible, but when the pressure reaches the set pressure Ps, the strength is such that plastic deformation (crushing) occurs.

[0029] 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, the target torque Tt [N·m] of the tightening torque for the nut body 14 is set according to the structure (structural dimensions) such as the nominal diameter of the nut body 14 (the inner diameter of the inner hole 16), the material, etc., and also according to the base body 26, the mounting parts 28, and their strengths, etc.

[0030] In the nut body 14, the torque (rotation torque) T [N·m] required for rotation to be screwed onto the stat bolt 12 is a low value until the seating surface 20 of the nut body 14 seats on the mounting parts 28, etc. Also, in the nut body 14, when the seating surface 20 seats on the mounting parts 28, etc., the torque T required for rotation increases and functions as the tightening torque at which final tightening starts. Between the nut body 14 and the stat bolt 12, when final tightening starts, an axial force [N] corresponding to the tightening torque (torque T) is generated.

[0031] On the other hand, in the nut body 14, when a new nut body 14 is screwed onto the stat bolt 12 in a state where it is attached to the stat bolt 12, when the seating surface 20 of the new nut body 接触する comes into contact with the protrusion 50, the protrusion 5 reacts to the new nut body 14. In the nut body 14, when the protrusion 50 receives the set pressure Ps, plastic deformation occurs in the protrusion 50.

[0032] In the nut body 14, the set pressure Ps is higher than the pressure (seating pressure) Pc when the seating surface 20 of the nut body 14 contacts the mounting part 28 and lower than the target pressure Pt [N / m 2 according to the target torque Tt (Pc < Ps < Pt). Also, if the torque T at the time of seating of the nut body 14 is defined as the seating torque Tc and the torque T at which an axial force (equal) corresponding to the set pressure Ps for the protrusion 50 is generated is defined as the set torque Ts, the set torque Ts is set to a value larger than the seating torque Tc and smaller than the target torque Tt (Tc < Ts < Tt).

[0033] For the appropriate range of the set torque Tt, when the minimum value is a [N·m] and the maximum value is b [N·m], it is not less than the minimum value a and not more than the maximum value b (a ≤ Tt ≤ b).

[0034] Generally, the seating torque Tc is set to about 10% to 40% of the target torque Tt (0.1Tt≦Tc≦0.4Tt). Furthermore, 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. For this reason, when the rotation of the nut body 14 is stopped at the set torque Tt, the detected torque T may exceed the set torque Tt (overshoot). Taking this overshoot into consideration, the seating torque Tc is set to about 10% to 70% of the target torque Tt (0.1Tt≦Tc≦0.7Tt).

[0035] Here, the strength of the protrusions 50 can be such that they do not undergo plastic deformation when subjected to pressure corresponding to a torque T of 0.1Tt or less, but undergo plastic deformation when subjected to pressure corresponding to a torque of 0.7Tt or more. The strength of the protrusions 50 may also be set according to the target torque Tt.

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

[0037] Figures 2(A) and 2(B) show side views of an outline of two nut bodies 14 attached to one stud bolt 12, and Figure 3 shows a diagram of an outline of the change over time in the angle θ detected by the controller 42.

[0038] 2(A) and 2(B) show an outline of the state in which one of the two nut bodies 14 (hereinafter referred to as nut body 14A) is already attached to the stud bolt 12, and the other nut body 14 (hereinafter referred to as nut body 14B) is then attached. Also, Fig. 2(A) shows a state in which the seating surface 20 of the nut body 14B is seated on the top surface 22 of the nut body 14A, and Fig. 2(B) shows a state in which the seating surface 20 of the nut body 14B is in contact with the protrusion 50 of the nut body 14A (seated state on the protrusion 50).

[0039] The controller 42 also detects the angle θ [°] corresponding to the rotation angle of the nut body 14 from when the torque T detected in the nut runner 40 reaches the seating torque Tc until when it reaches the target torque Tt. Note that when the nut runner 40 rotates the nut body 14 at a constant rotation speed (the change in the rotation angle is constant), it is also possible to use the time [sec] or the like from when the torque T reaches the set torque Ts until it reaches the target torque Tt.

[0040] In this embodiment configured as described above, when fastening and fixing the attachment part 28 to the base 26 using the nut body 14A and the stud bolt 12, the nut body 14A is rotated using the nut runner 40. As a result, when the seating surface 20 of the nut body 14A seats on the attachment part 28, the controller 42 detects the seating torque Tc and detects that the nut body 14A has seated on the attachment part 28.

[0041] Thereafter, when the nut body 14 is further rotated by the nut runner 40, the torque T (tightening torque) increases, and when the torque T reaches the target torque Tt, the rotation of the nut body 14 is stopped. As a result, the base body 26 and the attachment part 28 are fastened and fixed with an axial force according to the target torque Tt (see FIG. 1).

[0042] 3, the tightening time ta of the nut body 14A is ta=t2-t1, where t1 is the time from when the nut body 14 starts rotating (time t=0) until it seats, and t2 is the time until it reaches the target torque Tt. Also, the angle θ from when the nut body 14A seats on the mounting part 28 until it reaches the target torque Tt is represented by angle θa.

[0043] On the other hand, when the nut body 14B is attached to the stud bolt 12 while the nut body 14A is already attached, the nut body 14B is rotated using the nut runner 40. In this case, as shown in Fig. 2(B), the seating surface 20 of the nut body 14B first seats (comes into contact with) the protrusion 50 of the nut body 14A. This allows the controller 42 to detect the seating torque Tc.

[0044] As the nut body 14B is further rotated, the torque T increases and reaches the set torque Ts, and the axial force generated by the nut body 14B causes the protrusion 50 of the nut body 14A to plastically deform. After this, as shown in Fig. 2(A), the seating surface 20 of the nut body 14B seats on the top surface 22 of the nut body 14A, and as the nut body 14B is further rotated, the torque T detected by the controller 42 increases toward the target torque Tt.

[0045] 3, the time t3 from when the nut body 14B starts rotating (time t=0) until it seats on the protrusion of the nut body 14A, and the time t4 until it reaches the target torque Tt, and the tightening time tb of the nut body 14B are expressed as tb=t4-t3. Also, the angle θ from when the nut body 14B seats on the nut body 14A until it reaches the target torque Tt is expressed as angle θb.

[0046] Here, the angle θb of the nut body 14B is larger than the angle θa of the nut body 14A (θb>θa). Therefore, by setting a threshold value in advance for the angle difference Δθ between the angles θa and θb in the controller 42, it is possible to determine whether or not the nut body 14 being fastened by the nut runner 40 is likely to cause erroneous fastening, based on the angle θa of the nut body 14A (or a reference value obtained from the average value of the angles θa, etc.) and the threshold value.

[0047] Therefore, in the nut 10 in which the protrusion 50 is formed on the nut body 14, erroneous tightening can be detected by the controller 42, and the nut 10 can be prevented from being erroneously tightened.

[0048] In this embodiment, erroneous tightening is determined from the difference in angle change. However, time t may also be used to determine erroneous tightening. That is, the tightening time tb of the nut body 14B is longer than the tightening time ta of the nut body 14A. Therefore, the controller 42 may set a threshold value in advance for the time difference Δt between the tightening times ta and tb (Δt = tb - ta). In this way, the controller 42 may determine whether the nut body 14 being tightened by the nut runner 40 is likely to cause erroneous tightening based on the tightening time ta of the nut body 14A (or a reference value obtained from the average tightening time ta, etc.) and the threshold value. [Explanation of symbols]

[0049] 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 protruding portion formed on a surface of the nut body opposite to the seating surface in a direction opposite to the seating surface, the protruding portion being plastically deformed when the torque applied to the nut body is greater than the torque when the seating surface seats on the fastened member and is subjected to pressure corresponding to a set torque set lower than the target torque; Nut structure including:

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