Fastening member with friction coefficient stabilizer discharge function

Abstract

To provide a fastening member comprising a friction coefficient stabilizer discharge function capable of efficiently discharging a friction coefficient stabilizer remaining on a bearing surface to prevent rotational looseness, and capable of preventing reduction in axial force due to depression of an object to be fastened.SOLUTION: A fastening member having a flat bearing surface 11 formed with circumferential grooves 12 for discharging a friction coefficient stabilizer remaining on the bearing surface. The circumferential grooves 12 are formed so as to exist on an arbitrary radial line. It is preferable to form a width of the portion closer to the outer periphery to be wider than a width of the portion closer to the inner periphery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to fastening members such as bolts and nuts that are equipped with a friction coefficient stabilizer discharge function. [Background technology]

[0002] One method for stably generating a high axial force when fastening members such as bolts and nuts are tightened is to apply a friction coefficient stabilizer to the bearing surface and threaded parts to lower the friction coefficient, as described in Patent Document 1.

[0003] Patent Document 1 describes friction coefficient stabilizers such as low molecular weight polyethylene and synthetic resin emulsion dispersed in water, water-soluble alkyd resin dispersed in water, and water-dispersed urethane resin dispersed in water. In addition to these resin-based friction coefficient stabilizers, oil may also be used as a friction coefficient stabilizer, so in this specification, oil is included in the friction coefficient stabilizer. Such friction coefficient stabilizers contribute to improving the axial force during tightening, and are widely used for fastening machine parts, etc. The friction coefficient stabilizer gradually peels off during tightening and remains on the seating surface of the bolt or nut.

[0004] In fastening parts that receive a load perpendicular to the bolt axis, if the amount of movement of the fastened object exceeds the bolt's limit slippage (the maximum amount of slippage of the fastened object before slippage occurs on the bolt seating surface), the bolt will loosen. It is known that this limit slippage is advantageous when the friction coefficient of the seating surface is high. Friction coefficient stabilizers that remain on the seating surfaces of bolts and nuts reduce the friction coefficient of the seating surface, which is a factor in reducing the limit slippage. Therefore, while friction coefficient stabilizers contribute to improving the axial force during tightening, they become a factor in rotational loosening after tightening is complete.

[0005] According to the applicant's investigation, no prior patent documents were found that relate to the discharge of friction coefficient stabilizers remaining on the seating surface of fastening members. Patent Document 2 describes a fastening member having a groove formed on the seating surface for draining water, but this is a groove of a fixed width intended for the purpose of draining water, and is not considered to have a structure that can efficiently discharge friction coefficient stabilizers from the seating surface.

[0006] Patent Document 3 discloses that a number of triangular mountain-shaped protrusions are formed radially or spirally on the seating surface of the fastening member, and the tips of the triangular mountains are plastically deformed during fastening to increase the frictional force of the seating surface and prevent rotational loosening. However, this structure has a small contact area between the seating surface and the fastened object, so that the surface pressure of the fastened object becomes locally high after fastening, causing it to collapse, reducing the axial force and causing non-rotational loosening. In addition, the structure of Patent Document 3 may increase the torque required during fastening, making it difficult to obtain the required axial force, or may cause seizure or scratches on the fastened object during fastening, preventing normal fastening. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2002-323023 A [Patent Document 2] Japanese Utility Model Application Publication No. 54-38764 [Patent Document 3] Japanese Patent Application Publication No. 10-148093 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a fastening member equipped with a friction coefficient stabilizer discharge function that can efficiently discharge friction coefficient stabilizer remaining on the seating surface to prevent rotational loosening, while also preventing a decrease in axial force due to the collapse of the fastened objects. [Means for solving the problem]

[0009] In order to solve the above problems, The invention described in claim 1 is A fastening member having a circumferential groove formed on a flat bearing surface for discharging friction coefficient stabilizer remaining on the bearing surface, the circumferential groove being formed so that multiple grooves exist on any radial line. The circumferential groove is formed so that the width of the portion near the outer periphery is wider than the width of the portion near the inner periphery. The present invention is characterized in that: The circumferential groove may be a concentric groove.

[0010] The invention described in claim 3, which has been made to solve the above problems, is a fastening member having a circumferential groove formed on a flat seating surface for discharging friction coefficient stabilizer remaining on the seating surface, characterized in that the circumferential groove is formed so that a plurality of grooves are present on any radial line, and the circumferential groove is a spiral groove. The width of the circumferential groove at the portion near the outer periphery can be formed wider than the width of the portion near the inner periphery. The radial cross section of the circumferential groove may be any one of a semicircular, rectangular, and semi-elliptical shape.The bearing surface is preferably a bearing surface for a bolt or a nut. Effect of the Invention

[0011] The fastening member of the present invention has a circumferential groove formed on the flat seating surface for discharging friction coefficient stabilizer remaining on the seating surface. In the final stage of fastening, the seating surface of the fastening member rotates while contacting the fastened object. The friction coefficient stabilizer applied to the seating surface is pressurized as the seating surface approaches the fastened object, and flows into the circumferential groove. At this time, the movement distance of the seating surface is longer and the area is larger in the outer periphery portion farther from the center of rotation than in the inner periphery portion closer to the center of rotation, so more friction coefficient stabilizer is pushed out and flows into the circumferential groove.

[0012] When radial grooves are formed on the seating surface as shown in Patent Document 2, the internal pressure in the portion of the radial groove near the outer periphery, where more friction coefficient stabilizer flows in during fastening, becomes higher than the internal pressure in the portion near the inner periphery, making it difficult for the friction coefficient stabilizer to be discharged from the outer periphery end of the seating surface. In contrast, the circumferential groove of the present invention allows more friction coefficient stabilizer to flow into the inside of the circumferential groove, and this effect can be enhanced by forming the portion near the outer periphery wider than the portion near the inner periphery in particular.

[0013] As a result, the fastening member of the present invention is able to lower the friction coefficient and increase the axial force during tightening due to the friction coefficient stabilizer, and the friction coefficient stabilizer is efficiently transferred from the seating surface into the circumferential groove during tightening, reducing the amount of friction coefficient stabilizer remaining on the seating surface and preventing the occurrence of rotational loosening. Moreover, since the seating surface of the fastening member of the present invention is flat except for the radial grooves, no depressions occur on the seating surface as in Patent Document 3, and a decrease in axial force due to non-rotational loosening can also be prevented. [Brief description of the drawings]

[0014] [Figure 1] 1A to 1C are a plan view, a cross-sectional view, and a bottom view showing a first embodiment of the present invention. [Diagram 2] 1A to 1C are a plan view, a cross-sectional view, and a bottom view showing a second embodiment of the present invention. [Diagram 3] 1A to 1C are diagrams showing cross-sectional shapes of various grooves. [Figure 4] FIG. 1 is a cross-sectional view showing a case where the present invention is applied to a nut. [Diagram 5] FIG. 2 is an explanatory diagram of a Junker type loosening tester used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments of the present invention will now be described. Fig. 1 is a diagram showing an embodiment in which the present invention is applied to a bolt. Although Fig. 1 shows a flanged bolt, the shape of the bolt body 10 is not particularly limited and may be, for example, a general hexagonal bolt.

[0016] A circumferential groove 12 is formed on the bolt bearing surface 11. A plurality of circumferential grooves are formed on any radial line, and in the embodiment shown in Fig. 1, there are two circumferential grooves 12. By forming a plurality of circumferential grooves 12 in this manner, the friction coefficient stabilizer adhering to any part of the bearing surface 11 can easily flow into the inside of the circumferential groove 12.

[0017] The portion of the seating surface 11 other than the circumferential groove 12 is a flat surface. Increasing the number of circumferential grooves 12 narrows the width of the flat surface, which may cause the seating surface 11 to collapse during tightening as in Patent Document 3, so it is preferable to keep the number of circumferential grooves 12 to five or less. With only one groove, the effect of discharging the friction coefficient stabilizer is insufficient.

[0018] The groove width of the circumferential groove 12 is wider on the outer periphery than on the inner periphery. In this embodiment, the width of the circumferential groove 12 on the outer periphery is 1.5 times the width of the circumferential groove 12 on the inner periphery. The movement distance of the seating surface is longer and the area is larger on the outer periphery portion farther from the center of rotation than on the inner periphery portion closer to the center of rotation, so more friction coefficient stabilizer is pushed out, but the cross-sectional area of ​​the circumferential groove 12 on the outer periphery is increased, so that the friction coefficient stabilizer can flow into the circumferential groove 12 without hindrance.

[0019] Circumferential groove The radial cross-sectional shape of 12 can be semicircular, rectangular, semi-elliptical, etc., as shown in Fig. 3. Note that the edge portion where the radial groove 12 intersects with the flat portion 14 preferably has a sharp shape in order to efficiently peel off the friction coefficient stabilizer applied to the seat surface 11.

[0020] In the first embodiment shown in FIG. Circumferential groove The shape of 12 is a concentric circle. However, it can also be a spiral groove as in the second embodiment shown in Fig. 2. In this case, it is formed so that multiple grooves exist on any radial line. It is also possible to combine a concentric groove or a spiral groove with a radial groove extending in the radial direction.

[0021] In the embodiment described above, the present invention is applied to the bearing surface 11 of the bolt. However, as shown in Fig. 4, the present invention can also be applied in the same manner to the bearing surface 15 of a nut, which is a fastening member.

[0022] The fastening member of the present invention is used when fastening by applying a friction coefficient stabilizer to the bearing surface 11. As mentioned above, applying a friction coefficient stabilizer to the bearing surface 11 can reduce the friction coefficient of the bearing surface during fastening, and the axial force can be increased accordingly, but as mentioned above, this friction coefficient stabilizer can cause rotational loosening after fastening.

[0023] However, the fastener of the present invention uses the rotation of the bearing surface 11 during tightening to scrape off the friction coefficient stabilizer attached to the bearing surface and allow it to flow into the inside of the circumferential groove 12. This reduces the amount of friction coefficient stabilizer remaining between the bearing surface 11 and the fastened object after tightening is complete, making it possible to increase the friction coefficient of the bearing surface 11 compared to conventional cases in which the friction coefficient stabilizer remained as is, and by increasing the limit amount of slip, rotational loosening can be suppressed. In addition, because the fastener of the present invention has a wide flat portion 14 on the bearing surface 11, the bearing surface 11 does not collapse due to axial force, and non-rotational loosening can also be prevented. EXAMPLES

[0024] The following examples of the present invention will be described. In this embodiment, the axial force remaining rate of a bolt, which is a fastening member, was measured using a Junker loosening tester shown in Fig. 5. The Junker loosening tester is a device in which a bolt 22 to be tested is inserted into a fixing jig 24 on the underside of a base 20 and fixed with a nut 21, the neck of the bolt 22 is vibrated in a direction perpendicular to the axis by a vibration plate 25, and the axial force is measured by a load cell 26 provided between the base 20 and the fixing jig 24. Reference numeral 23 denotes a test hardened washer interposed between the vibration plate 25 and the bolt 22. The vibration plate 25 is subjected to vibration at 1000 times per minute by an eccentric disk 27 provided on one side of the vibration plate, and the amplitude is measured by a dial gauge 28 provided on the other side. The strain detected by the load cell 26 is input to a dynamic strain gauge 29 and a digital recorder 30 and recorded.

[0025] The bolt with the bearing surface of the present invention was set in the Junker type loosening tester, a resin-based friction coefficient stabilizer was applied to the bearing surface, and the bolt was subjected to a test with an amplitude of 0.34 mm ×1000 vibrations were applied. The bolt size was M8, and the shape of the bearing surface was as shown in Figure 1. When the axial force retention rate, which is the ratio of the axial force at the start of the test to the axial force after the test, was measured, the axial force retention rate of a conventional bolt with an entirely flat bearing surface was 62%, while the axial force retention rate of the bolt with the bearing surface of the present invention was 83%, confirming the excellent effect of the present invention. [Explanation of symbols]

[0026] 10 Bolt Body 11 Bolt bearing surface 12 Circumferential groove 14 Flat area 15 Nut bearing surface 20 Junker type looseness tester base 21 Nut 22 Bolts to be tested 23 Test hardened washer 24 Fixing jig 25 Diaphragm 26 Load Cell 27 Eccentric disk 28 Dial Gauge 29 Dynamic strain gauge 30 Digital Recorder

Claims

1. A fastening member having a circumferential groove formed in a flat seating surface for discharging a friction coefficient stabilizer remaining on the seating surface, wherein a plurality of the circumferential grooves are formed on an arbitrary radial line, and the circumferential groove is formed such that the width of a portion closer to the outer circumference is wider than the width of a portion closer to the inner circumference, and the fastening member has a function of discharging a friction coefficient stabilizer.

2. The fastening member having a function of discharging a friction coefficient stabilizer according to claim 1, wherein the circumferential groove is a concentric circular groove.

3. A fastening member having a circumferential groove formed in a flat seating surface for discharging a friction coefficient stabilizer remaining on the seating surface, wherein a plurality of the circumferential grooves are formed on an arbitrary radial line, and the circumferential groove is a spiral groove, and the fastening member has a function of discharging a friction coefficient stabilizer.

4. The fastening member having a function of discharging a friction coefficient stabilizer according to claim 3, wherein the circumferential groove is formed such that the width of a portion closer to the outer circumference is wider than the width of a portion closer to the inner circumference.

5. The fastening member having a function of discharging a friction coefficient stabilizer according to any one of claims 1 to 4, wherein a radial cross section of the circumferential groove is any one of a semi-circular shape, a rectangular shape, and a semi-elliptical shape.

6. The fastening member having a function of discharging a friction coefficient stabilizer according to any one of claims 1 to 5, wherein the seating surface is a seating surface of a bolt or a nut.

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