JP4974312B2 - Screw with a slope at the bottom of the female thread valley - Google Patents

Description

Detailed Description of the Invention

INDUSTRIAL APPLICABILITY The present invention is a nut that is excellent in improving earthquake resistance and safety, and is used for joining residential building structural members and fastening automobile parts, and greatly shortening the tightening work time.

Bolts and nuts are widely used for joining civil engineering structures, automobiles, construction machinery, and the like. Among them, various types of loosening prevention products are fastened particularly where safety is required, and some loosening prevention nuts are standardized by JISB1156.

Japanese Patent Application Laid-Open No. 2005-121154 requires tertiary processing and quaternary processing, has a high manufacturing cost, and mass production is difficult

Japanese Patent Application No. 2005-76969 is a product that prevents looseness by the frictional resistance of the screw surface, but it cannot be expected to prevent looseness due to slippage of the screw surface.

The public utility Showa 59-86408 has a nut bottom inclination angle of 30 degrees, and the screw restraint force is 365 N in the analysis result, which is approximately 60% stronger than the standard nut, but the self lock nut vibration test of the NAS3354 standard meets the standard content. I have not done

JIS standard screws use various means to increase and stabilize the screw axial force when tightening bolts and nuts, but it is difficult to make the friction coefficient the same due to the inherent nature of the screws, resulting in unstable tightening. In recent years, the situation has not been solved. More stable conclusions are required by the industry.

It has been clarified that the load applied to each screw thread at the time of screw tightening is applied to the first screw thread on the fastening side by the metric element analysis and research by public institutions. For this reason, it has been found that the stress concentration part at the time of screw fastening is the starting point of fracture.Further, when the screw surface is fastened, surface slippage occurs and screw looseness occurs.

Problems to be solved by the invention

The purpose of the present invention is to provide a nut that disperses the stress concentration generated in the screw part during screw fastening, and has excellent fracture and fatigue resistance, and also exhibits a loosening prevention effect by the same fastening method as a hexagon nut. is there

A finite element model is shown in FIG. Here is M8X1.25 bolt. A nut fastening body that meshes with only five threads was selected as an analysis target. The bolt is center axis X. Bound in the Y direction, giving freedom around the Z axis. The nut was fully constrained on all sides. The fastened plate is X. The rotation around the Y direction and the Z axis was constrained. The material of the bolt, nut and member to be fastened was SS400, Young's modulus 186 GPa, Poisson's ratio 0.3, and friction coefficient 0.25.
In the analysis, the bolt, nut fastening body and the plate to be fastened are fastened with a constant torque of 18 Nm, and the plastic strain and the radial direction acting on the bolt when the inclination angle of the bottom valley slope of the nut is changed from 23 degrees to 40 degrees. Sought binding force

FIG. 5 shows the plastic strain distribution of the bolt. The combination of the hex nut and the bolt hardly causes plastic strain, but in the case of the combination with the present invention product, plastic strain is generated around the screw thread contact portion of the bolt as shown in FIG. It was also found that this plastic strain increases as it approaches the bolt head (first thread) and then gradually decreases. FIG. 6 shows the amount of plastic deformation of this thread for the product of the present invention.

FIG. 6 shows that the amount of plastic deformation of the first thread is the largest.
Focusing on the first thread, we investigated the amount of plastic deformation and radial force of the first thread.

FIG. 7 shows the restraining force and plastic strain in the radial direction.
In the nut valley slope part 23 degrees, the restraining force in the radial direction is almost the same as that of the hexagon nut, but the restraining force suddenly increased from 24 degrees and the maximum restraining force was exhibited at 25 degrees.

At an angle of 25 ° or more at the bottom of the nut valley bottom, the restraining force decreases as the angle increases, and the plastic strain is approximately the same value as the hexagonal nut when the angle of the product is 23 ° to 24 °, but 25 ° Shows the maximum value. Furthermore, it was found that the plastic strain is smaller as the angle becomes larger in the inclined part of the bottom of the nut valley of 25 degrees or more like the restraining force.

The relationship between the radial restraint force in FIG. 7 and the plastic strain of the first screw thread shows the maximum restraint force at 25 ° at the bottom of the nut valley slope as shown in FIG. occured. On the other hand, the amount of plastic deformation suddenly decreased at 24 degrees at the bottom of the nut valley bottom, which was almost the same as the hexagon nut, and exhibited a restraining force 1.5 times that of the hexagon nut.

Means for solving the problem

The nut according to the present invention is configured by a thread having an inclined portion on the pressure flank surface on which a load is applied when fastened, and having a screw size larger than the basic screw size.

From FIG. 1, the basic dimensions of the metric thread are 1, 2, 3, 4 and the product of the present invention is 9, 10, 12, 13. 10 and 12 are inclined from 24.5 to 27 degrees from the axis, and the thread dimensions of 9, 10, 11, and 13 are designed to be 0.17 mm to 0.45 mm larger than the standard dimension.

With respect to the inclination angle of 10 to 12 in FIG. 1, at 23 degrees from the finite element method analysis, the bolt restraint force is 240 N, which is almost the same as that of the hexagon nut, and the effect of preventing loosening cannot be expected.
At 24 degrees, the restraint force is 330 N, and the bolt restraint force is 1.4 times that of the hexagon nut, and a slack prevention effect can be expected. Also, the plastic deformation amount is not 0.003, which is plastic deformation.

With respect to the inclination angle of 10 to 12 in FIG. 1, the bolt restraint force is 480 N at 25 degrees from the finite element method analysis, and the restraint effect is expected to be about twice as strong as the hexagon nut.

According to FIG. 2 of Japanese Utility Model Laid-Open No. 59-086408, the inclination angle of 5 to 6 is set to 30 degrees with respect to the pressure side flank surface of the screw reference dimension lines 1, 2, 3, 4 and the present invention. The angle is different, and is fundamentally different from the product of the present invention expanded by 0.17 mm or more from the screw basic dimension.

According to Japanese Patent Application No. 2007-77810 in FIG. 3, the inclination angle of 7 to 8 is set to 27 to 37 degrees on the pressure side flank surface of the screw reference dimension lines of 1, 2, 3, and 4. The part is a position 0.05 mm to 0.12 mm below the screw reference line, which is greatly different from the enlarged design of the screw reference line of the present invention.

An embodiment of a nut according to the present invention will be described in detail with reference to the drawings.

From Fig. 1, the 9, 10, 12, and 13-shaped threads that are 0.17mm to 0.45mm larger than the metric screw reference dimensions are related to the metric screw reference bolt dimensions. Bolts are easily inserted by enlarging the angle, and the tilt angle is set so that the slack prevention effect is exhibited even when the bolt dimension is from the maximum value to the minimum value of JIS class 2.

As shown in FIG. 1, the inclination angle of 10 to 12 is set from 24.5 degrees to 27 degrees, and by using this angle, the load received at the time of screw fastening is distributed among the screw threads.

The invention's effect

The nut of the present invention receives a load in the entire thread that meshes when the bolt is engaged, while the metric thread concentrates a lot of stress on the first thread, and has excellent destructive and earthquake resistance. Other slack prevention products require many processes, but because the product of the present invention is mass-produced in the same manufacturing process as the hexagon nut, the manufacturing cost can be kept low.

By providing an angle of inclination at the bottom of the nut screw thread valley, in the tensile test, even if a load that is 1.8 times the JIS standard value is applied, the screw does not stretch, and the load is dispersed and received. Excellent earthquake resistance

The performance evaluation of the locking nut is verified by the NAS3354 standard (American Aerospace Administration standard). In the verification test at a public organization, the product of the present invention is normally fastened after 30,000 rotations, and the locking effect is verified. The

Thread shape of the product of the present invention Thread shape of Japanese Utility Model Sho 59-086408 Thread shape of Japanese Patent Application No. 2007-77810 Finite element model Plastic strain distribution Plastic strain of each thread Radial restraint force and plastic strain Relationship between plastic strain and radial restraint force Figure of fitting between second-class precision bolt and product of the present invention Radial restraint force

1 JIS Standard Metric Screw Reference Line Position 2 JIS Standard Metric Screw Reference Line Position 3 JIS Standard Metric Screw Reference Line Position 4 JIS Standard Metric Screw Reference Line Position 5 Japanese Utility Model Laid-Open No. Sho 59-086408 Valley bottom inclination angle 7 Japanese Patent Application No. 2007-77810 Valley bottom inclination angle 8 Japanese Patent Application No. 2007-77810 Valley bottom inclination angle 9 Invention product thread 10 Invention invention valley screw thread, bottom inclination angle 11 Thread position 12 expanded from the screw reference line Invention product thread, valley bottom inclination angle 13 Invention product thread

Claims (4)

In a nut engaged with a metric screw bolt, the cross-sectional shape of the bottom of the nut is inclined from 24.5 degrees to 27 degrees toward the pressure flank side with respect to the axis , and the inner diameter dimension of the nut And a nut with a trough diameter expanded from the metric thread standard dimension   The steel nut according to claim 1, wherein the slope of the cross-sectional shape of the valley bottom is 24.5 to 25 degrees.   The steel nut according to claim 1, wherein a slope of a cross-sectional shape of the bottom of the valley is set to 25 degrees. The steel nut according to claim 1, wherein the slope of the cross-sectional shape of the bottom of the valley is 24.5 degrees.

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