Insert nuts and fastening structures

Abstract

In particular, the retention force of the insert nut after it has moved due to the rotation of the bolt, that is, the retention force in the direction of removal, should be kept high. [Solution] The insert nut 2 is embedded in the base member 3, with some exceptions, and is fastened with a bolt 1 for fixing mating members 4 and 5 to the base member. The main part consists of a flange portion 20 that forms an insertion opening 21 for inserting the bolt 1, and a cylindrical portion 22 that is integrated with the flange portion and has a female thread 24 on its inner circumference that engages with the male thread of the bolt. The cylindrical portion 22 also has a knurled surface 26 formed by an inclined groove 27 on its outer circumference, and the groove directions of the female thread 24 and the inclined groove 27 are formed to be opposite to each other in the bolt insertion direction.

Description

Technical Field

[0001] The present invention relates to a fastening structure in which an insert nut inserted into a base member and a mating member are fixed to the base member by the insert nut and a bolt.

Background Art

[0002] FIG. 9 shows a fastening structure disclosed in Patent Document 1, where (a) is a diagram of the state before fastening and (b) is a diagram of the state after fastening. In this fastening structure, the first relay bus bar 31 of the relay bus bar 3 constituting the mating member and the first high-voltage bus bar 71 are fixed to the resin base member (first fixing portion) 1 by a nut (first nut) 41 and a bolt 42. Among these, the nut 41 is an insert nut press-fitted into a fitting portion 11 provided in the base member 1. An insertion hole 311 for inserting a bolt is provided in the first relay bus bar 31, and an insertion hole 711 for inserting a bolt is provided in the first high-voltage bus bar 71. The first high-voltage bus bar 71 and the first relay bus bar 31, which are mating members, are provided such that the insertion holes 311 and 711 are coaxial with the female thread of the nut 41, and the bolt 42 is screwed into the female thread of the nut 41 to be fastened to the base member 1 via the nut 41.

[0003] That is, in this fastening structure, as shown in (a), with a gap between the base member 1 and the first relay bus bar 31 (without deforming or moving the base member and the mating member), the nut is forcibly moved in the removal direction by rotating the bolt to absorb the gap. In this structure, if the first high-voltage bus bar and the first relay bus bar, which are mating members, are forcibly pulled into the base member, there is a risk of forced deformation or damage to the mating members and the base member, and further, there is a risk that the force to return to the initial position acts and the bolt loosens. However, such problems can be solved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, in the fastening structure described above, the mating members (the first high-voltage busbar and the first relay busbar) are positioned by the movement of the insert nut relative to the base member, or by the fastening of the bolt and insert nut relative to the base member. If the insert nut is subjected to an impact or vibration in the direction of dislodgement, it may overcome the holding force in the direction of dislodgement (the gripping force of the resin) and loosen, or it may even move further in the direction of dislodgement.

[0006] Therefore, the objective of the present invention is to provide a configuration in which an insert nut is moved to absorb the gap between a base member and a mating member without deforming the base member or the mating member, and in particular, to maintain a high holding force of the insert nut after it has moved due to the rotation of the bolt, that is, a holding force in the direction of removal. Other objectives will be clarified in the following description. [Means for solving the problem]

[0007] To achieve the above objective, the invention of claim 1, as specified by reference to the drawings, is an insert nut (2) that is embedded in a base member (3) except for a portion and fastened with a bolt (1) for fixing mating members (4, 5) to the base member, comprising a flange portion (21) forming an insertion opening for inserting the bolt, and a cylindrical portion (22) integrated with the flange portion and having a female thread on its inner circumference that engages with the male thread of the bolt, and further comprising a knurled surface (26) formed on the outer circumference of the cylindrical portion and consisting of an inclined groove (27), and characterized in that the groove directions of the female thread (24) and the inclined groove are formed to be opposite to each other in the bolt insertion direction.

[0008] In contrast, the invention of claim 3 is a fastening structure for fixing mating members (4, 5) to a base member (3) with a nut and a bolt, wherein the nut has a flange portion (21) forming an insertion opening for inserting the bolt, a cylindrical portion (22) integrated with the flange portion and having a female thread on its inner circumference that engages with the male thread of the bolt, and a knurled surface (26) formed on the outer circumference of the cylindrical portion and consisting of an inclined groove (27), and is an insert nut (2) embedded in the base member with part or all of the flange portion exposed, and the bolt is driven through a through hole provided in the mating member and screwed into the female thread of the insert nut embedded in the base member, so that the insert nut moves while rotating in the same direction as the rotation direction of the bolt relative to the base member and is pulled toward the mating member.

[0009] In each of the above inventions, the base member is a resin-made mounting member for fixing the mating member, which is the mounting member. The mating member is a mounting member fixed to the base member, and is not limited to a single member but may consist of multiple members. Depending on when the insert nut is inserted into the base member, there are methods such as inserting it during the molding of the base member, or inserting it after molding using a press-fit or hot-press-fit method, and any of these methods may be used. [Effects of the Invention]

[0010] In the invention of claim 1, the insert nut has knurling, particularly consisting of inclined grooves provided on the outer circumference of the cylindrical portion, and is embedded in the base member with part or all of the flange portion exposed. Therefore, when used in a fastening structure such as that of claim 3, the insert nut moves easily as shown in the example, rotating in the same direction as the bolt rotation operation and being pulled towards the mating member. Furthermore, it is easier to prevent it from loosening or moving in the direction of detachment due to vibrations such as shocks after movement.

[0011] In the invention of claim 2, the knurling has numerous inclined grooves formed at equal intervals in the same direction, and is formed continuously from one end to the other of the cylindrical portion, so that, for example, the insert nut can easily rotate with movement in the direction of removal relative to the base member.

[0012] In the invention of claim 3, as a fastening structure in which a mating member is fastened to a base member with a nut and bolt, in particular, the insert nut moves so as to be pulled toward the mating member while rotating in the same direction as the rotation direction of the bolt relative to the base member due to the inclined grooves that constitute the knurling, so that if there is a gap between the base member and the mating member, the movement of the nut can be adjusted to absorb the gap. At the same time, after the movement, the inclined grooves that constitute the knurling maintain a high holding force against pulling the insert nut toward the mating member, making it easier to prevent the insert nut from unintentionally loosening or coming off even when vibrations such as shocks are applied.

[0013] In the invention of claim 4, the knurling is formed by numerous inclined grooves that are equally spaced and in the same direction, or by the groove directions of the female thread and the inclined grooves being opposite to each other in the bolt insertion direction, making it easier for the insert nut to move in a direction that protrudes from the base member with rotation when the bolt is rotated.

[0014] In the invention of claim 5, if the inclined grooves constituting the knurling are inclined at a gradient of 15 degrees or more compared to flat knurling or straight knurling, the resistance to the insert nut embedded in the base member can be maintained at a predetermined level, and unintentional dislodgement due to impact or vibration in the dislodgement direction can also be prevented. In this regard, the inventors created insert nuts with the same groove width and depth as the inclined grooves, and varied the gradient of the inclined grooves relative to the straight grooves, as schematically shown in Figure 7(a), and compared the dislodgement resistance in a usage manner similar to the example form. The results showed that it is preferable for the gradient to be greater than 15 degrees and less than 75 degrees. This is because the smaller the gradient and the closer it is to a straight groove, the easier it is to loosen or shift in the dislodgement direction, and if the gradient is greater than 75 degrees, the load when moving the insert nut by bolt rotation operation tends to become excessive.

[0015] In the invention of claim 6, if the knurling is divided and formed by a circumferential groove with a number of inclined grooves arranged in the circumferential direction, the insert nut will have stronger resistance to coming loose at the location of the circumferential groove, and at the same time, it will be easier to prevent inadvertent loosening or movement in the direction of coming loose due to impact or vibration. [Brief explanation of the drawing]

[0016] [Figure 1] The above shows a single insert nut; (a) is a perspective view showing the appearance of the insert nut, and (b) is a partially broken perspective view thereof. [Figure 2] (a) is a schematic enlarged view illustrating the inclined grooves that make up the knurling of the insert nut described above. [Figure 3] (a) is a schematic perspective view showing modified example 1 of the above insert nut, and (b) is a partially broken perspective view showing modified example 2 of the above insert nut. [Figure 4] The diagram shows the relationship between the base member having the insert nut, the mating first and second mounting members, and the bolt. (a) is a top view thereof, and (b) is an enlarged cross-sectional view of (a) along the line C1-C1. [Figure 5] The above shows the bolt being rotated and screwed into the insert nut; (a) is a top view thereof, and (b) is an enlarged cross-sectional view of (a) along the line C2-C2. [Figure 6] The above shows the state in which the bolt is rotated to move the insert nut toward the mating member, with (a) being a top view and (b) being an enlarged cross-sectional view of (a) along the C3-C3 line. [Figure 7] Figure 1 is a schematic perspective view showing the relationship between the components in a partially broken state. [Figure 8] (a) is a schematic perspective view showing the relationship between members in the state of Figure 2 with some parts broken, and (b) is a schematic perspective view showing the relationship between members in the state of Figure 3 with some parts broken. [Figure 9] The fastening structure of Patent Document 1 is shown, with (a) and (b) representing Figure 6(a) and (b) disclosed in Patent Document 1.

Best Mode for Carrying Out the Invention

[0017] Hereinafter, the optimal mode of the present invention will be described with reference to the drawings. In this description, after the insert nut and its modified examples are described in detail with reference to FIGS. 1 to 3, the fastening structure shown in FIGS. 4 to 8 will be clarified.

[0018] (Embodiment Example) FIGS. 1(a) and (b) show a single insert nut to which the present invention is applied. This insert nut 2 is of the type that is inserted or embedded during the resin molding of the base member 3, and as shown in FIG. 4, it is buried in the resin base member 3 except for a part, and is fastened to the bolt 1 for fixing the first and second attachment members 4 and 5, which are mating members, to the base member 3. The material is made of stainless steel (SUS) with high rigidity and excellent corrosion resistance, but other metals such as brass can also be used.

[0019] Structurally, it consists of a flange portion 20 that forms an insertion port 21 for inserting the bolt 1, and a cylindrical portion 22 that is integrated with the flange portion 20 and forms an internal thread 24 that engages with the external thread 13 of the bolt 1 on the inner circumference. Among these, the flange portion 20 is formed in a donut shape, and the upper and lower edge portions 20a and 20b are chamfered. The flange portion 20 is inserted or embedded during the resin molding of the base member 3, and in that inserted state, a part of the upper portion protrudes from the base member 3, and the protruding upper surface serves as a receiving surface for receiving the attachment members 4 and 5.

[0020] The cylindrical portion 22 protrudes integrally from the lower surface of the flange portion 20, and the lower end 23 is formed in a substantially L-shaped cross section. The lower end 23 is formed with a large-diameter portion on the inside, and a disk-shaped bottom plate 25 that closes the lower end of the cylindrical portion is engaged and held in the large-diameter portion. Note that the bottom plate 25 may be configured to close the tip side of the cylindrical portion 22 with a lid-like or cap-like wall portion like an existing socket nut in addition to the engagement and holding configuration.

[0021] Furthermore, female threads 24 that engage with the male threads 13 of the bolt 1 are continuously formed on the inner circumference of the flange portion 20 and the cylindrical portion 22. In this example, the thread direction is right-hand thread (configured to be screwed in when the nut is fixed and the bolt is turned clockwise). The outer circumference of the cylindrical portion 22 is provided with knurling 26, which is made up of numerous inclined grooves 27. In this example, the groove directions of the female threads 24 and the inclined grooves 27 that make up the knurling 26 are formed to be opposite to each other in the bolt insertion direction. That is, if the female threads 24 are right-hand threads (threads from the left to the upper right), the groove shape of the inclined grooves 27 is in the opposite direction, i.e., the groove shape upper right direction, i.e., the groove shape is in the opposite direction, i.e., the groove shape is in the opposite direction, i.e., the groove shape is in the left to the upper right direction.

[0022] Furthermore, the knurled surface 26 has numerous inclined grooves 27 formed at equal intervals in the same direction. Here, the depth of each inclined groove 27 is a fairly shallow groove of about 0.2 to 0.6 mm. The groove width is about 0.3 to 0.8 mm. It is preferable that the groove depth and width be set to be at least less than 1 mm. Each inclined groove 27 is formed continuously from one end to the other end of the cylindrical portion 22. These configurations allow the insert nut 2 to move in the direction of removal without requiring excessive stress, and to move with rotation while embedded in the base member 3. This movement is intended to absorb the gap as the insert nut 2 moves from Figure 5 to Figure 6. At the same time, after the movement as shown in Figure 6, a predetermined holding force is maintained by the gripping force of the resin, preventing it from loosening or moving unintentionally in the direction of removal due to impact or vibration. In other words, as shown in Figures 5 and 6, the initial movement can be performed without excessive rotational resistance, and in the moved state shown in Figure 6, a predetermined holding force is maintained so that it does not easily move, loosen, or move in the direction of detachment. The present invention was completed after repeated studies to satisfy these conflicting operational requirements.

[0023] In addition, although the numerous inclined grooves 27 described above are formed on the entire outer circumference of the cylindrical portion 22, they may also be formed on only a part of the outer circumference of the cylindrical portion. In that case, however, it is preferable that they be inclined at a gradient of 15 degrees or more compared to flat knurling or straight knurling. These are to maintain a predetermined frictional resistance so that the insert nut 2 embedded in the base member 3 does not loosen or move in the direction of coming out when used as shown in Figure 6, as described above.

[0024] Regarding the gradient of the inclined groove 27, the inventors created insert nuts 2 with the same groove width and depth as schematically shown in Figure 2, and varied the gradient of the inclined groove 27 relative to the straight groove to 10 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 75 degrees, as schematically shown in the same figure. They then compared the resistance to coming out after gap absorption in a usage manner similar to the example form, as shown in Figure 6. The results showed that the gradient was less than 15 degrees and approached the straight groove, making it relatively easy to move or loosen, which posed a design problem. It was also found that when the gradient was greater than 60 degrees, an increasingly larger load was required when moving from Figure 5 to Figure 6. From these findings, it is preferable to set the gradient of the inclined groove 27 to be between 15 degrees and 60 degrees.

[0025] (Modification 1) Figure 3(a) shows an example of a modified insert nut 2. In this insert nut 2, the knurling 26 is divided vertically or horizontally by a circumferential groove 28 that divides the numerous inclined grooves 27 into upper and lower or front and back sections. In this circumferential groove 28, the depth of the groove is relatively shallow, about 0.2 to 0.6 mm, similar to the inclined grooves 27. The groove width is set to about 0.5 to 1.5 mm. If the groove width is larger than 1.5 mm, excessive stress tends to be required when moving to absorb the gap G in Figure 5, so it is preferable to form it relatively narrow, at 1.5 mm or less, to avoid this.

[0026] (Modified example 2) Figure 3(b) shows a modified example in which the bottom plate 25 is omitted from the insert nut 2. This insert nut 2 lacks the lower end 23 of the approximately L shape in Figure 1, and the inner diameter of the flange portion 20 and the cylindrical portion 22 is penetrated vertically. Such a structure is suitable for cases where the insert nut 2 is a hot-press-fit type inserted into the base member 3 after the base member is formed, or an expansion type in which the tip portion is expanded after it is driven into the base member.

[0027] (Fastening Structure) Figures 4 to 8 show fastening structures in which the mounting member (mating member) is fixed to the base member (the member to be mounted), which is an example of the use of the insert nuts described above. Next, the fastening structure of the example form will be described in detail with reference to these. Figures 7 and 8 are schematic external views to facilitate understanding of the main parts of Figures 4 to 6.

[0028] This fastening structure is an example of fixing a first mounting member 4 and a second mounting member 5, which are mating members, to a base member 3, which is the member to be mounted, using an insert nut 2 and a bolt 1. Here, as described above, the insert nut 2 has a female thread 24 provided on the inner circumference of the flange portion 20 and the cylindrical portion 22 that screws into the male thread 13 of the bolt 1, and a knurled surface 26 made up of numerous inclined grooves 27 provided on the outer circumference of the cylindrical portion 22 excluding the flange portion 20, and is inserted into the base member 3 in an embedded state with a part of the flange portion 20 exposed. Reference numeral 33 indicates a vertical hole located directly below the insert nut 2, which was formed during the insert molding of the base member 3. On the other hand, the bolt 1 has a circular flange portion 12 integrally between the head 10 and the male thread 13, and as shown in Figure 5, the flange portion 12 abuts against the second mounting member 5 when the male thread 13 is screwed into the female thread 24 of the insert nut 2. The head 10 is hexagonal and can be rotated with a wrench or spanner. Furthermore, the head 10 has a hexagonal socket 11, allowing it to be rotated using a hex wrench. The flange 12 distributes the pressure applied to the second mounting member 5, which is the tightening point. As shown in Figure 6, the male thread 13 is long enough so that it does not touch the bottom plate 25 of the insert nut when fully screwed into the female thread 24 of the insert nut. In this fastening structure, the first and second mounting members 4 and 5 are integrally fixed in an overlapping state between the flange 12 of the bolt 1 and the flange 20 of the insert nut 2.

[0029] More specifically, in this fastening operation, for example, as shown in Figures 4 and 7, the first mounting member 4 and the second mounting member 5 are superimposed with their through holes 4a and 5a aligned, and while maintaining this state, the through holes 4a and 5a are positioned on the female threads 24 of the insert nut 2 relative to the base member 3. Here, the base member 3 integrally comprises a mounting plate 30 positioned on the lower side, a base 31 protruding from the upper surface of the mounting plate 30, and a pair of restricting walls 32 protruding from opposing sides of the base 31. The mounting plate 30 extends front to back and has mounting holes 34 provided near the front and rear ends, and is attached to the target equipment side via the mounting holes 34 and bolts, etc. The base 31 is positioned between the restricting walls 32 with the first mounting member 4 and the second mounting member 5 superimposed. At this time, each through hole 4a and 5a is positioned so that it is on the female threads 24 of the insert nut 2. In this example, the first mounting member 4 and the second mounting member 5 are supported at the height shown in the figure by components not shown, and their downward movement is restricted.

[0030] Next, as shown in Figures 5 and 8(a), the bolt 1 is positioned so that the male thread 13 passes through the through holes 5a and 4a and fits into the female thread 24 of the insert nut 2 from the insertion opening 21, and the bolt 1 is rotated from this position. In this operation, the bolt 1 is rotated using, for example, a hex wrench (not shown) that fits onto the head 10, while the male thread 13 is screwed into the female thread 24. In the state shown in the figure, the insert nut 2 maintains its embedded state from when it was molded, and a predetermined gap G is created between the original first mounting member 4 and the flange portion 20 of the insert nut.

[0031] Next, Figures 6 and 8(b) show the completed fastening state, where the insert nut 2 has moved upward until it has absorbed the gap G due to the rotation of the bolt 1. In this structure, the inclined groove 27, which constitutes the knurling 26 of the insert nut 2, prevents the rotation of the bolt 1 from becoming excessively large. At the same time, even if the insert nut 2 is subjected to a predetermined amount of impact or vibration in the state shown in the figure, the inclined groove 27 prevents it from easily loosening or moving in the direction of coming out.

[0032] (Operation) Next, we will describe the main operation of the fastening structure described above. (1) In this structure, the first and second mounting members 4 and 5 are fastened to the base member 3 with nuts and bolts. In particular, the insert nut 2 moves towards the first and second mounting members 4 and 5 without requiring excessive load, rotating in the same direction as the rotation direction of the bolt 1 relative to the base member 3 by the inclined groove 27 which constitutes the knurling 26. This allows the insert nut 2 to adjust and absorb any unnecessary gap G between the base member 3 and the first mounting member 4 by moving. At the same time, the inclined groove 27 which constitutes the knurling 26 maintains a high holding force to prevent the insert nut 2 from unintentionally loosening or coming out after movement, and also prevents the insert nut 2 from unintentionally loosening or moving in the direction of coming out even when subjected to impact or vibration.

[0033] (2) In this structure, the knurling 26 has many inclined grooves 27 formed at equal intervals in the same direction, and is formed continuously from one end to the other of the cylindrical portion 22, and the groove directions of the female thread 24 and the inclined grooves 27 are formed to be in different directions from each other in the bolt insertion direction, so that, for example, the insert nut 2 can move in the removal direction without requiring an excessive load as a rotational operation on the base member 3.

[0034] (3) In this structure, if the inclined grooves 27 constituting the knurling 26 are inclined at a gradient of 15 degrees or more compared to flat knurling or straight knurling as shown in Figure 2, or if the gradient is set to be between 15 degrees and 60 degrees, the insert nut 2 can be moved to absorb the gap without requiring excessive load on the rotation of the bolt, and after movement, it is possible to prevent unintentional loosening or movement in the direction of detachment caused by shock or vibration. (4) Furthermore, if the knurling 26 is formed by dividing a number of inclined grooves 27 with circumferential grooves 28 provided in the circumferential direction, as in the modified example 1 of Figure 3(a), the insert nut 2 will have stronger resistance to coming loose at the location of the circumferential grooves 28, and at the same time, it will be easier to prevent inadvertent loosening caused by shocks or vibrations, as well as inadvertent movement in the direction of coming loose.

[0035] As described above, the present invention only needs to have the configuration specified in the claims, and the details can be modified in various ways as needed, as shown in the modified examples. For example, the mating member is not limited to a configuration consisting of a first mounting member and a second mounting member as shown in the example form, but may also consist of a single mounting member or a configuration consisting of three or more mounting members. [Explanation of symbols]

[0036] 1. Bolt (10 is the head, 12 is the flange, 13 is the male thread) 2. Insert nut (20 is the flange portion, 21 is the insertion hole, 24 is the female thread) 3. Base component (30 is the fixing part, 31 is the base part, 31a is the top surface) 4. First mounting member (mating member) 5. Second mounting member (mating member) 25...Bottom wall 26...knurling 27...Slanted groove 28..Circumferential groove G·····Gap

Claims

1. An insert nut that is embedded in the base member except for a portion, and fastened with a bolt for fixing the mating member to the base member, It consists of a flange portion that forms an insertion opening for inserting the bolt, and a cylindrical portion that is integrated with the flange portion and has a female thread on its inner circumference that engages with the male thread of the bolt. Furthermore, the insert nut is characterized by having knurling formed by inclined grooves on the outer circumference of the cylindrical portion, and by being formed so that the groove directions of the female thread and the inclined grooves are opposite to each other in the bolt insertion direction.

2. The insert nut according to claim 1, characterized in that the knurling has a large number of inclined grooves formed at equal intervals in the same direction, and is formed continuously from one end to the other of the cylindrical portion.

3. A fastening structure in which a mating member is fixed to a base member with nuts and bolts, The nut has a flange portion forming an insertion opening for inserting the bolt, a cylindrical portion integrated with the flange portion and having a female thread on its inner circumference that engages with the male thread of the bolt, and a knurled groove formed on the outer circumference of the cylindrical portion, and is an insert nut that is embedded in the base member with part or all of the flange portion exposed. The fastening structure is characterized in that the bolt is screwed into the female thread of the insert nut, which is embedded in the base member and passes through a through hole provided in the mating member, so that the insert nut moves while rotating in the same direction as the rotation direction of the bolt relative to the base member and is pulled toward the mating member.

4. The fastening structure according to claim 3, characterized in that the knurling is formed by numerous inclined grooves at equal intervals and in the same direction, and the groove directions of the female thread and the inclined grooves are in different directions from each other in the bolt insertion direction.

5. The fastening structure according to claim 3 or 4, characterized in that the inclined grooves constituting the knurling are inclined at a gradient of 15 degrees or more and 60 degrees or less compared to flat knurling or straight knurling.

6. The fastening structure according to claim 5, characterized in that the inclined grooves constituting the knurling are divided and formed by circumferential grooves provided on the outer circumference excluding the flange portion.

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