fastening structure
By combining washers with small screws using a sloping surface design, the problems of loosening and high processing costs in fastening structures are solved, achieving the effect of not easily loosening under vibration conditions and reusable bolts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NIPPON PLARAD CO
- Filing Date
- 2023-11-21
- Publication Date
- 2026-06-23
AI Technical Summary
Existing fastening structures are ineffective in preventing loosening, have high processing costs, are prone to jamming due to vibration, and the bolt threads are easily damaged, making them difficult to reuse.
The washer with an inclined surface is combined with a small screw. The coefficient of friction of the inclined surface is less than that of the flat surface. The front end of the screw is curved. The screw axis is parallel to the nut axis, which avoids jamming and reduces processing costs.
It achieves the effect of not easily loosening under vibration conditions, avoiding jamming, and the bolt thread is not damaged, allowing for reuse and reducing processing costs.
Smart Images
Figure CN122270637A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fastening structure using nuts and bolts. Background Technology
[0002] In the past, various methods were used to prevent loosening, such as using spring washers, using double nuts, and using cotter pins to pass through the nut and bolt. However, these methods were not very effective and could cause loosening due to vibration, or the mechanisms and processes were complex and expensive.
[0003] In response, relevant locking pin mechanisms have been proposed. One method involves pressing the locking pin into a hole on the inner surface of the nut to open the inner surface and generate anti-loosening pressure. Another method involves creating a through-hole at an angle slightly away from the inner surface of the nut, inserting a locking pin slightly longer than the insertion hole with a sharpened tip, and then manually screwing the nut onto the external thread of the bolt until it reaches the washer. Finally, using a wrench or other commercially available tool, the nut is tightened forcefully, thereby securing the object sandwiched between the two washers. Upon further tightening, the locking pin is squeezed by the washer, and the tip of the locking pin is tightly engaged with the external thread, thus compressing the external thread and generating an anti-loosening effect. Upon further forceful tightening, the tip of the locking pin bites into the external thread like a stake, further enhancing the anti-loosening effect (for example, see Patent Documents 1 and 2).
[0004] The structures described in Patent Documents 1 and 2 are fixed by spreading the inner surface of the nut or by having the front end of the locking pin bite into the bolt's threaded rod. As a result, the threaded rod (threaded portion) will be damaged, and even if the nut is loosened for maintenance, it cannot be reused.
[0005] To address this, a fastening structure is proposed that prevents loosening in the fastened state, allows for easy unscrewing during maintenance, and enables the reuse of bolts and nuts. This fastening structure secures the object to the mounting component by having the shank of a bolt used for mounting the object pass through a mounting hole in the mounted component and protrude its front end. A small screw, mounted on a nut, is screwed into the front end with appropriate torque via a washer, thereby fixing the object to the mounted component. The washer has an inclined surface on a first side facing the nut, while a flat surface on a second side opposite the first side. The inclined surface gradually decreases in height towards the tightening direction of the nut. The small screw is screwed into the nut with its axis orthogonal to the inclined surface, and the front end of the small screw protrudes in contact with the inclined surface. The coefficient of friction of the inclined surface is less than that of the second surface of the washer (for example, see Patent Document 3).
[0006] In this way, the small screw is screwed into the nut with its axis orthogonal to the inclined surface located on the first side of the washer, thus avoiding damage to the bolt's threaded portion and allowing for reuse. Furthermore, even if the nut attempts to loosen due to vibration, the small screw will attempt to move upwards along the inclined surface because the coefficient of friction on the inclined surface is lower than that on the second surface. This generates a force that presses the washer against the component being mounted, thus preventing the nut from easily loosening. Existing technical documents Patent documents
[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-293793 Patent Document 2: Japanese Patent Application Publication No. 2011-179679 Patent Document 3: Japanese Patent Application Publication No. 2018-138814 Summary of the Invention The problem the invention aims to solve
[0008] However, the structure of the aforementioned Patent Document 3 has the following concerns: (i) The washer has the same number of inclined surfaces as the small screws (i.e., a large number), which increases the cost due to these processes. (ii) Because the screws need to be inclined, the threaded holes for the screws need to be machined to be inclined relative to the nut axis, which also increases the cost. (iii) The tip of the small screw contacts the inclined surface of the washer at a right angle, but if the small screw is screwed in forcefully, it will slightly sink into the inclined surface. When the nut tries to turn to the loose side (counterclockwise) due to vibration, the (slightly sunken tip) small screw may get stuck on the inclined surface of the washer and cannot rotate smoothly. In other words, there is a problem such as jamming, which causes the washer to rotate with the nut.
[0009] The function of this structure is to allow the small screw to slide upward along the inclined surface of the washer, increasing the axial force of the bolt, so that it will not loosen even when subjected to vibration. However, due to the aforementioned jamming phenomenon, this function may often fail.
[0010] The purpose of this invention is to provide a fastening structure that can avoid the aforementioned jamming phenomenon and reduce processing costs. Problem Solving Methods
[0011] This invention is a fastening structure characterized by fixing the object to be mounted by passing the bolt of a bolt used for mounting the object through a mounting hole in the mounted component and having its front end protruding, and screwing a small screw installed in a nut into the front end via a washer, wherein the object is fixed to the mounted component, and the washer has an inclined surface on a first side facing the nut, while a flat surface on a second side opposite to the first side, the inclined surface being formed such that its height gradually decreases towards the tightening direction of the nut, and the small screw with a curved front end is screwed into the nut with its thread axis parallel to the axis of the nut, the front end of the small screw protruding from the nut and contacting the inclined surface, the coefficient of friction of the inclined surface being less than that of the second surface of the washer.
[0012] In this way, the threaded hole for the small screw is easy to machine, and the bolt shank (threaded portion) can be reused without damaging it. Furthermore, even if the nut or bolt attempts to loosen due to vibration, the difference in friction coefficient between the inclined surface and the second surface of the washer causes the movement of the small screw to press the washer against the installed component, making it less prone to loosening. In addition, when the nut attempts to loosen (counterclockwise) due to vibration, the curved tip of the small screw prevents it from getting stuck and allows it to slide easily. Therefore, the (slightly recessed) small screw getting stuck on the inclined surface of the washer and unable to rotate smoothly (i.e., the jamming phenomenon that causes the washer to rotate with the nut) is avoided.
[0013] In this case, the curved surface of the tip of the small screw can be spherical. Furthermore, the spherical shape is preferably such that, when the tip is pressed against the inclined surface of the washer and gradually tightened, the shape of the tip changes and gradually flattens, completely conforming to the inclined surface of the washer at the point when the small screw is tightened with a specified maximum force. In this way, the average surface pressure of the tip face of the small screw decreases at the point when the small screw is fully tightened.
[0014] Furthermore, the surface roughness of the inclined surface is preferably smoother than that of the second surface, the inclined surface being machined using standard machining, while the second surface is rough-machined. Additionally, one or more inclined surfaces may be formed around the center hole of the washer along the circumferential direction.
[0015] Furthermore, this invention can be applied not only to fastening structures where an object is installed using a nut and a washer, but also to fastening structures where an object is fixed to a component using a headed bolt. In other words, this invention also includes a fastening structure characterized by using a headed bolt to fix an object to a component, with a washer disposed adjacent to the head of the bolt on the bolt's thread. The washer has an inclined surface on a first side facing the head of the bolt, while a second side opposite the first surface is flat. The inclined surface gradually decreases in height towards the tightening direction of the bolt. A small screw with a curved tip is screwed into the head of the bolt with its thread axis parallel to the axis of the nut. The tip of the small screw protrudes from the nut and contacts the inclined surface. The coefficient of friction of the inclined surface is less than that of the second surface of the washer. The effects of the invention
[0016] The threaded hole for the small screw of this invention is simple to machine and can be reused without damaging the bolt shank (threaded portion). Furthermore, even if the nut or bolt attempts to loosen due to vibration, the difference in friction coefficient between the inclined surface and the second surface of the washer allows the movement of the small screw to press the washer against the installed component, preventing it from loosening. In addition, it avoids the jamming phenomenon where the small screw gets stuck on the inclined surface of the washer and cannot rotate smoothly when the nut attempts to loosen (counterclockwise) due to vibration. Attached Figure Description
[0017] Figure 1 This is a cross-sectional view showing the fastening structure of the present invention. Figure 2 yes Figure 1 Enlarged view of part A in the image. Figure 3 This is a perspective view of the gasket used in the fastening structure of the present invention, viewed from above. Figure 4 (a) is an illustration of the surface pressure distribution at the initial point (at contact) when the tightening load is small, and (b) is an illustration of the surface pressure distribution at the point (at tightening) when fully tightened. Figure 5 This is a cross-sectional view showing another embodiment. Detailed Implementation
[0018] The embodiments of the present invention will be described below.
[0019] Figure 1 This is a cross-sectional view showing the fastening structure of the present invention. Figure 2 yes Figure 1 Enlarged view of part A in the image.
[0020] like Figure 1 and Figure 2 As shown, the fastening structure of the present invention is as follows: the bolt 1a of the bolt 1 used to install the object (not shown) to the mounting member 2 passes through the mounting hole of the mounting member 2 and the front end protrudes, and the object is fixed to the mounting member 2 by applying a nut 4 via a washer 3 at the front end.
[0021] like Figure 3 As shown, the washer 3 has a central hole 3a through which the screw 1a passes. Furthermore, on the first surface 3A opposite to the nut 4, an inclined surface 3b is formed along the circumferential direction of the central hole 3a. On the other hand, the second surface 3B is a flat surface. Additionally, the inclined surface 3b can be single or multiple, and the number of inclined surfaces is independent of the number of small screws 5 described below. Figure 3 The example below shows the case where there are two inclined surfaces 3b.
[0022] The inclined surface 3b is continuous with the wall surface 3c that rises from the end of the nut 4 on the tightening direction side. These surfaces 3b and 3c are orthogonal. The inclined surface 3b is inclined relative to the second surface 3B at an angle of about θ = 3 to 20°, and is at least above the lead angle of the nut (or bolt) thread.
[0023] Furthermore, the first surface 3A (inclined surface 3b) and the second surface 3B of the washer 3 change the coefficient of friction by altering their surface roughness. The inclined surface 3b is smoother than the second surface 3B, resulting in a lower coefficient of friction. For example, the inclined surface 3b is machined using a normal process, while the second surface 3B is machined using a rough process.
[0024] A threaded hole 4a is formed around the central hole of the nut 4, corresponding to the inclined surface 3b, for the small screw 5 to be screwed in, such that the thread axis in the nut 4 is parallel to the nut axis. The small screw 5 is screwed into the threaded hole 4a of the nut 4, with its front end 5b protruding from the nut 4 and contacting the inclined surface 3b. The front end 5b of the small screw 5 is a curved surface (e.g., spherical) with the most prominent central part and has an arc.
[0025] Here, if the front end of the small screw is flat, the largest outer diameter portion (=edge) contacts the inclined surface 3b at approximately a right angle, so the edge of the small screw 5 that is embedded in it is easy to get stuck on the inclined surface 3b. However, as shown in this invention, if the front end is curved and has an arc, the front end portion (arc portion) of the small screw 5 will be slightly concave, and the inclined surface side will also slightly sink into the inclined surface 3b due to the arc portion. However, by adjusting the size of the arc, even if a slight concavity occurs on the inclined surface 3b, it will not get stuck due to the arc and will slide easily.
[0026] Thus, by making the front end of the small screw 5 curved and arc-shaped, the necessity for the small screw 5 to make right-angle contact with the inclined surface 3b of the washer 3 disappears. The small screw 5 does not need to be tilted relative to the nut 4, so the threaded hole 4a into which the small screw 5 is screwed can be set with its axis parallel to the axis of the nut 4. As a result, it has the significant advantage of maintaining the function of not loosening while significantly reducing the processing cost.
[0027] In other words, with this structure, when the nut 4 attempts to loosen in the direction of rotation (counterclockwise) due to vibration, the small screw 5 will move upward along the inclined surface 3b of the washer 3, thus increasing the distance between the upper surface of the nut 4 and the second surface 3B of the washer 3. At this point, because the coefficients of friction of the first and second surfaces 3A and 3B of the washer 3 are different, the relative sliding between the inclined surface 3b of the washer 3 (with the lower coefficient of friction) and the tip of the small screw 5 will occur first, i.e., before the sliding between the second surface 3B and the mounted component 2. Even with slight sliding, the distance will increase, and the second surface 3B of the washer 3 will press more forcefully against the seat surface (mounted component 2), making it more difficult to slide.
[0028] The greater the inclination angle of the inclined surface 3b, the greater the force applied to the second surface 3B of the washer 3 against the seat surface, thus further increasing the friction and making it even more difficult to rotate. In other words, the nut 4 will never loosen.
[0029] As an example, under the conditions that bolt 1 is 36mm in diameter (M36), 5 times the diameter (180mm) in length, bolt axial force (=tightening force) is 350kN, and the inclination depth of the inclined surface 3b of washer 3 is 0.6mm, if the tightening force is set to 100, then the force (=axial force, or rotational torque) used to (forcefully) loosen nut 4 is 196% (approximately 2 times).
[0030] When the diameter of bolt 1 is set to 64mm and the axial force is set to 1150kN (other conditions are the same), the force required to loosen it is 153% (1.5 times). The force required to loosen the previous nut 4 varies depending on the inclination depth of the inclined surface 3b on the washer 3 (the height of the wall 3c). The deeper the inclination, the greater the force required (loosening rotation torque or axial force).
[0031] It takes 153 to 196% of the force to loosen it, which means that nut 4 will not loosen. The reason is that bolts are usually tightened at 60 to 90% of their yield point. If nearly twice the loosening torque (or axial force) is applied, the bolt will break (before it loosens).
[0032] Nevertheless, nut 4 typically needs to be easily loosened for maintenance, etc. In other words, any nut requires the opposite performance: it must never loosen on its own, but it is desirable to loosen it easily when loosened.
[0033] This fastening structure perfectly meets the previous requirements. Due to the relationship between nut 4 and washer 3, nut 4 will never loosen naturally even under vibration. On the other hand, if it is necessary to loosen nut 4 for maintenance, it can be easily loosened, for example, with a manual wrench. That is to say, after loosening the small screw 5 with a manual wrench, even if the tightness of nut 4 is slightly higher than when it was initially tightened, it can be easily loosened.
[0034] In other words, based on this fastening structure, through the relationship between the nut 4 (small screw 5) and the washer 3 (inclined surface 3b), the nut 4 will not loosen naturally even when subjected to vibration, etc. However, when it is necessary to loosen the nut 4 for maintenance, it can be easily unscrewed, for example, with a manual wrench.
[0035] Furthermore, in paragraph 0050 of Patent Document 3, a strategy is disclosed for making the axis of the small screw parallel to the thread axis of the nut. To make the front end of the small screw hemispherical, the beveled side of the washer also fits against the hemispherical portion of the small screw. In addition to making the front end of the small screw hemispherical, a concave groove with a semi-circular cross-section along the inclined surface is carved into the inclined surface. This achieves the same effect even when the small screw is perpendicular, without requiring an angled tilt. This is because carving a concave groove with a semi-circular cross-section along the inclined surface increases the contact area between the front end of the small screw and the concave groove of the inclined surface, thereby reducing (equalizing) the contact surface pressure. Otherwise, assuming the inclined surface is flat, the surface pressure at the front end of the small screw would increase sharply, causing the front end to be crushed.
[0036] However, this method of carving a semi-circular groove in the washer is not only costly, but also inevitably creates a gap (loosening) between the inner diameter of the washer and the diameter of the screw. Therefore, when installing the screw, the washer may shift relative to the nut's axis due to this loosening. This shift means that the center of the groove on the washer side may always be offset from the center of the screw. Furthermore, in the case of offset, the hemispherical tip of the screw may interfere with the side of the groove, leading to malfunction.
[0037] In contrast, in this invention, the inclined surface of the washer is flat. Therefore, even if the inner diameter of the washer is offset relative to the central axis of the nut, the tip of the small screw only moves on the plane, thus avoiding interference with the concave groove as in the structure of Patent Document 3. A more significant difference lies in the fact that the curvature of the small screw tip is an R-shape (slightly spherical) so large that it cannot be identified as a hemisphere. This R dimension is determined by stress and strain precisely calculated using Hertz's equations in physics. Specifically, designed so that when the spherical tip of the small screw is pressed against the washer surface and gradually tightened, (since the small screw is an elastic body) the shape of the spherical tip changes and gradually flattens, completely conforming to the plane of the inclined surface at the point when the small screw is tightened with the specified maximum force. As a result, at the point of full tightening, the average surface pressure on the tip of the small screw is reduced (equalized).
[0038] In other words, the structure described in paragraph 0050 of Patent Document 3 is a method of reducing surface pressure by increasing the contact area of the tip of the small screw from the beginning. However, in this invention, the tip of the small screw makes "point contact" with the washer surface at the initial point (when in contact) when the tightening load is relatively small (see reference). Figure 4 (a)), but at the point of full tightening (when tightened), the front end is almost flat, and the surface pressure between it and the washer decreases (see reference). Figure 4 (b) The physical difference between the two is significant. In this case, the flat side of the washer will also be slightly concave, but the amount of concavity is calculated using Hertz's equation. After repeated practical experiments, the curvature R of the tip of the small screw was finally determined so that when the nut attempts to loosen and move, the small screw can slide smoothly upward along the inclined surface of the washer.
[0039] As described above, embodiments of the present invention have been explained with reference to the accompanying drawings; however, various additions or modifications can be made without departing from the spirit of the invention. For example, in the described embodiment, a fastening structure utilizing the relationship between a nut and a washer is configured, but... Figure 5 As shown, this method can also be applied to fastening structures utilizing the relationship between the head 1b of the headed bolt 1 and the washer 3. In this case, a small screw 5 with a spherical front end 5b is screwed into the threaded hole 1c with its thread axis parallel to the axis of the bolt 1, and the front end 5b of the small screw 5 contacts the inclined surface 3b. In this case, the head 1b of the headed bolt 1 is not limited to a hexagonal cross-section, but can also be a circular cross-section. Symbol Explanation
[0040] 1: Bolt; 1a: Screw; 1b: Head; 1c: Threaded hole; 2: Installed component; 3: Washer; 3A: First surface; 3a: Center hole; 3B: Second surface; 3b: Inclined surface; 3c: Wall surface; 4: Nut; 4a: Threaded hole; 5: Small screw; 5a: Threaded part; 5b: Front end.
Claims
1. A fastening structure, characterized in that, The object is fixed to the component being mounted by passing the bolt of a bolt through the mounting hole of the component being mounted and making its front end protrude. A small screw, which is mounted on a nut, is screwed into the front end via a washer, and the washer has an inclined surface on a first side facing the nut, while the second side opposite the first side is a flat surface. The inclined surface is formed such that its height gradually decreases in the tightening direction of the nut. The small screw, whose front end is curved, is screwed into the nut with its thread axis parallel to the axis of the nut. The front end of the small screw protrudes from the nut and contacts the inclined surface. The coefficient of friction of the inclined surface is less than that of the second surface of the washer.
2. The fastening structure according to claim 1, wherein the curved surface of the front end of the small screw is spherical.
3. The fastening structure according to claim 2, wherein the spherical shape is as follows: when the front end is pressed against the inclined surface of the washer and gradually tightened, the shape of the front end changes and gradually becomes flat, and at the point when the small screw is tightened with a specified maximum force, it is completely in contact with the inclined surface of the washer.
4. The fastening structure according to claim 1, wherein the surface roughness of the inclined surface is smoother than that of the second surface, the inclined surface is machined normally, and the second surface is rough machined.
5. The fastening structure according to claim 1, wherein the inclined surface is formed in one or more circumferential directions around the central hole of the washer.
6. A fastening structure, characterized in that, A headed bolt is used to fix the object to the component to be installed. A washer is disposed adjacent to the head of the bolt on the bolt shank. The washer has an inclined surface on a first side facing the head of the bolt, and a flat surface on a second side opposite to the first side. The inclined surface is formed such that its height gradually decreases in the tightening direction of the bolt. A small screw with a curved front end is screwed into the head of the bolt with its thread axis parallel to the axis of the nut. The front end of the small screw protrudes from the nut and contacts the inclined surface. The coefficient of friction of the inclined surface is less than that of the second surface of the washer.