JPH0210808Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to improvements in threaded parts such as bolts and nuts for fastening hard members together using threaded means.

(Prior art) Generally, fastening using threaded parts is performed by rotating either the male threaded part or the female threaded part, but in this case, the appropriate tightening force is achieved by tightening with a constant torque as low as possible. If the torque coefficient value is large, the friction coefficient will also be large, which will reduce the tightening force (axial force) relative to the tightening torque, making it impossible to obtain sufficient fastening and causing screws to loosen or fall out. .

Also, especially in the case of screws with flat and wide bearing surfaces,
The friction coefficient of the bearing surface is large, and the degree of finish and quality of the surface treatment of the threaded parts greatly influences the variation in the torque coefficient value. In addition, chips from the fastened parts and peeling debris from the plating of the threaded parts, etc. They tend to become interposed between fastening members, further increasing the coefficient of friction and causing seizure, making it difficult to obtain an appropriate tightening force.

However, conventional general threaded parts have a flat bearing surface that makes surface contact with the fastened member, and when the torque coefficient of this threaded part is replaced by a friction coefficient ratio, 40% is due to the threaded part, and 40% is due to the lead angle of the screw. 10 things
%, and 50% is due to the seat surface, and the friction coefficient of the seat surface accounts for one-half of the total.

However, in recent years, screw parts with a flanged head with a wide bearing surface have been widely used, and the tightening of these parts has come to be performed by work robots, making them even more stable. There is a demand for threaded parts that can provide a high level of tightening force.

(Purpose of the invention) Therefore, in order to improve the drawbacks of the prior art described above, the present invention aims to reduce the coefficient of friction of the tightening seat surface of a threaded part, thereby making it possible to obtain an appropriate tightening force with a small tightening torque. The purpose is to provide the following.

(Structure of the invention) The screw component of the present invention that achieves the above object is different from steel screw components with a flat and wide tightening seat surface that makes even surface contact with the fastened member. The main feature is that a large number of small diameter recesses are bored throughout the area to reduce the frictional contact surface.

(Example) Below, the screw component of the present invention will be explained based on the illustrated example. First, FIGS. 1 and 2 are views of a first embodiment applied to a hexagonal bolt 1, in which a head 2 for receiving a tool is formed in a hexagonal shape, and a shaft 3 extends from below the neck of the head 2. A threaded portion 4 having a male thread is provided continuously thereto. A large number of small diameter recesses 6 are provided on the seat surface 5 where the head 2 comes into surface contact with a member to be fastened (not shown) during tightening, and the small diameter recesses are similar to dimples formed on the surface of a golf ball. It has a semi-spherical shape and is scattered at almost uniform depth.

Next, FIGS. 3 and 4 are views of a second embodiment applied to a flanged bolt 7, in which a flange portion 10 is formed between a head 8 and a threaded portion 9, and the flange portion 10 is As in the first embodiment, a large number of small diameter recesses 12 are provided on the seat surface 11 that makes surface contact with the member to be fastened during tightening.

Furthermore, FIGS. 5 and 6 are views of a third embodiment applied to a seated nut 13, in which a seat surface with a diameter smaller than the width across flats is specially provided so as to come into surface contact with the member to be fastened during tightening. 14 is provided with a large number of small diameter recesses 15 similar to those described above.

In each of the above embodiments, the small-diameter recess has a hemispherical shape, but the recess may have an elliptical, rectangular, or other shape at its opening end.

(Effects of the invention) Next, the effects of the invention along with its operation will be explained as follows.

1. The torque coefficient due to the bearing surface that occurs when tightening a screw is smaller due to the reduced frictional contact surface due to the small diameter recess compared to the high-strength fastened member. Therefore, even with the same tightening torque, the axial force is lower than before. becomes larger, the tightening force increases, and the surface pressure load per unit area increases, resulting in a strong fastening.

2 For example, when the width of the bearing surface is different, such as a hexagonal bolt with a flange and a regular hexagonal bolt,
Conventionally, the tightening torque setting was changed in order to obtain the appropriate tightening force when the flange diameter was different even though the screw diameter was the same, but with the threaded parts of this application, the seating surface It is possible to adjust the load area to the same tightening torque.

Therefore, it is possible to reduce the number of times to replace tightening tools, and to increase the number of locations to be tightened by the same work robot, which facilitates management of tightening torque and helps improve work efficiency.

3. Chips of the fastened member, peeled off plating, etc. generated by friction and pressure during tightening are stored in the small diameter recess, so it is possible to prevent an increase in friction and seizure.

4 In high-strength fastening using lubricating oil, etc.,
The small diameter recess functions as a kind of oil dam and can prevent the oil film from running out.

[Brief explanation of the drawing]

Fig. 1 is a front view of a hexagonal bolt according to a first embodiment of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a front view of main parts of a flanged bolt according to a second embodiment, and Fig. 4 is a front view of a hexagonal bolt according to a first embodiment of the present invention. FIG. 5 is a front view of the seat nut according to the third embodiment, and FIG. 6 is a plan view thereof. Explanation of symbols, 1...Hexagonal bolt, 2, 8...Head, 3...Shaft, 4,9...Threaded part, 5, 11,
14... Seat surface, 6, 12, 15... Small diameter recess, 7
... Bolt with flange, 10 ... Flange part, 1
3...Zatsuki Natsuto.

Claims (1)

[Scope of utility model registration request] For steel screw parts that have a flat and wide tightening seat surface that makes even surface contact with the fastened member, numerous small-diameter recesses are drilled throughout the entire tightening seat surface to reduce frictional contact surfaces. Screw parts characterized by: