JP6173498B2 - Non-circular screw - Google Patents

Description

  One embodiment of the present invention relates to a screw. In particular, the present invention relates to a non-circular screw having a non-circular cross section of a shaft and / or a thread provided on the surface thereof.

  The screw is fastened to separate members by being inserted into the member while being rotated. In a screw intended to fasten the separate member, it is important to suppress loosening, that is, to suppress rotation of the screw in the direction opposite to that during insertion.

  As a screw that effectively suppresses loosening of a screw, a non-circular screw having a non-circular cross section of an axial center called taptite and / or a thread provided on the surface thereof is known. Specifically, in the non-circular screw, when the member is inserted into the member, the member is largely plastically deformed and elastically deformed at the portion of the screw thread having a long distance from the rotation center, and after the insertion is completed. Then, the elastically deformed member enters the screw thread portion having a short distance from the rotation center. Then, the member that has entered the portion of the screw thread whose distance from the rotation center is short becomes resistance against rotation of the non-circular screw in the direction opposite to that at the time of insertion (hereinafter referred to as “return resistance”). As a result, it is possible to suppress loosening in the non-circular screw.

  A screw that further suppresses loosening of a non-circular screw is disclosed in Patent Document 1. The non-circular screw disclosed in Patent Document 1 includes a plurality of notches in the ridge portion of the screw thread. In this case, after the insertion is completed, the elastically deformed member enters the plurality of cutout portions. Therefore, it is possible to provide a return resistance also in the plurality of cutout portions.

Japanese Patent No. 3909767

  The non-circular screw described in Patent Document 1 is characterized in that the flank angle of the return side flank surface of the non-circular screw is set smaller than the flank angle of the advance side flank surface. However, when set in this way, the looseness of the non-circular screw cannot be sufficiently suppressed.

  Specifically, the advancing flank surface is the surface where the frictional force with the member when the non-circular screw is inserted into the member is the largest. When the flank angle of the advancing flank is larger than the flank angle of the return flank, the area of the advancing flank is also larger than the area of the return flank. In this case, the frictional force at the time of inserting the non-circular screw becomes large, so that the insertion becomes difficult and the ratio of the plastic deformation of the member increases. Therefore, the ratio of the member which enters into the part of a screw thread with a short distance from a rotation center and a plurality of notch parts will decrease. As a result, in the non-circular screw described in Patent Document 1, it is difficult to sufficiently prevent loosening because a sufficient return resistance cannot be provided.

  In view of the above, an object of one embodiment of the present invention is to provide a non-circular screw capable of effectively suppressing loosening.

  The non-circular screw according to one aspect of the present invention is characterized in that the flank angle of the advancing flank surface of the screw thread provided with a plurality of notches in the ridge is smaller than the flank angle of the return flank surface. .

  In the non-circular screw of one embodiment of the present invention, the flank angle of the thread-advancing flank surface is smaller than the flank angle of the return-side flank surface. In this case, it is possible to provide a sufficient return resistance by reducing the frictional force between the member and the thread when the non-circular screw is inserted into the member. As a result, in the non-circular screw of one embodiment of the present invention, loosening can be effectively suppressed.

The figure which shows an example of a non-circular screw. The top view which shows an example of the head of the non-circular screw shown by FIG. The cross-sectional view which shows an example of the axial center and screw thread of the non-circular screw shown by FIG. The longitudinal cross-sectional view which shows an example of the thread of the non-circular screw shown by FIG.

1. Structure FIG. 1 is a diagram illustrating an example of a non-circular screw. The non-circular screw shown in FIG. 1 has a head 1 and a leg 2 that is suspended from the lower surface of the head. And the leg part 2 has the shaft center 21 whose lower end is hemispherical, and the screw thread 22 provided in the surface of the shaft spirally. In addition, AB line shown by FIG. 1 has shown the central axis of the non-circular screw.

  FIG. 2 is a top view showing an example of the head 1 shown in FIG. The head 1 shown in FIG. 2 includes a screw rotating tool engaging portion 11 on the upper surface. An example of the screw rotating tool is a driver.

  FIG. 3 is a cross-sectional view showing an example of the shaft center 21 and the thread 22 of the non-circular screw shown in FIG. FIG. 3 shows one spiral of the screw thread 22 provided on the surface of the shaft 21. Also, the direction of the arrow (clockwise) shown in FIG. 3 is the direction of rotation when the non-circular screw is inserted into the member.

  The shaft center 21 shown in FIG. 3 has a circular cross-sectional shape. The cross-sectional shape of the shaft center 21 is not limited to a circle. For example, the cross-sectional shape of the shaft center 21 may be a polygonal shape or a rice ball shape.

  The screw thread 22 shown in FIG. 3 has a ridge portion 221 whose outer periphery is shaped like a rice ball, and a plurality of notches 222 provided in the ridge portion 221. In addition, the dotted line shown in FIG. 3 shows the outer periphery of the ridge part deleted by providing a plurality of notch parts 222. Moreover, the shape of the outer periphery of the ridge part 221 is not limited to the rice ball shape, and may be any shape as long as it is non-circular. For example, the outer periphery of the ridge portion 221 may have a polygonal shape.

  In addition, in the thread 22 shown in FIG. 3, the angle θ <b> 1 formed by the ridge portion 221 and the portion on the insertion rotation direction side of each of the plurality of notches 222 is the opposite side (each of the plurality of notches 222. Is smaller than the angle θ2 formed by the ridge portion 221 and the portion on the anti-insertion rotation direction side). In addition, the dashed-dotted line shown by FIG. 3 has shown the tangent of the location of the insertion rotation direction side of the notch part 222, and the location of the other side.

  FIG. 4 is a longitudinal sectional view showing an example of the thread 22 of the non-circular screw shown in FIG. The screw thread 22 shown in FIG. 4 has a leading flank surface 223, a return flank surface 224, and a top surface 225 parallel to the surface of the axis 21. In FIG. 4, two steps of the ridge portion 221 are shown. Further, the top surface 225 may not be provided in the screw thread 22 shown in FIG. That is, you may deform | transform so that it may become the shape which sharpened the vertex of the screw thread.

  Further, in the thread 22 shown in FIG. 4, the flank angle θ3 of the advance side flank surface 223 is smaller than the flank angle θ4 of the return side flank surface 224. 4 indicates a straight line perpendicular to the top surface 225, and a two-dot chain line indicates a straight line parallel to the advance side flank surface 223 and the return side flank surface 224.

2. Effect In the non-circular screw disclosed in the present specification, the flank angle θ3 of the advance side flank surface 223 is smaller than the flank angle θ4 of the return side flank surface 224. That is, when inserted into the member, the area of the leading flank surface 223 having the largest frictional force is smaller than the area of the return flank surface 224. For this reason, it is possible to relatively easily insert the non-circular screw into the member, and to reduce the rate of plastic deformation of the member. As a result, a member that is elastically deformed at the time of insertion enters a relatively large amount in the portion of the screw thread 22 and the plurality of notches 222 that are short from the rotation center. As a result, in the non-circular screw disclosed in the present specification, it is possible to provide a sufficient return resistance and sufficiently suppress loosening.

  Further, in the non-circular screw disclosed in the present specification, the angle θ1 formed by the ridge portion 221 and the portion on the insertion rotation direction side of each of the plurality of notches 222 is different from the opposite portion and the ridge portion 221. It is smaller than the angle θ2 formed. That is, the outside angle of the angle θ1 is larger than the outside angle of the angle θ2. In this case, the member that is elastically deformed at the time of insertion enters more in the outer angle portion of the angle θ1 than in the outer angle portion of the angle θ2. The return resistance is not a member that enters the outer angle portion of the angle θ2, but a member that enters the outer angle portion of the angle θ1. Therefore, in the non-circular screw disclosed in this specification, the return resistance of the non-circular screw can be sufficiently provided, and the looseness can be sufficiently suppressed.

  Further, in the non-circular screw disclosed in the present specification, the plurality of notches 222 are provided at substantially equal intervals, and an integral multiple of the intervals is not the circumference of one spiral of the thread 22. . In other words, in the non-circular screw disclosed in the present specification, the plurality of notches 222 are not in the same position in the adjacent upper and lower stages. For example, looking at whether or not the notch 222 overlaps with the AB line shown in FIG. 1 in the direction perpendicular to the paper surface, although it does not overlap in the first, fourth to sixth stages, it is 2, 3, 7 from the top. At the stage, they overlap. In short, in the non-circular screw shown in FIG. 1, as a whole, the position of the notch 222 is shifted downward and shifted to the right. In this case, it is possible to achieve both equal quality of the non-circular screw and mass production at low cost for the following reasons.

  In a non-circular screw, the distance between the outer periphery of the thread and the central axis changes. Here, if a plurality of notches are provided at the same position in the adjacent upper and lower stages in a flow operation, the notch is provided only at a position where the distance between the outer periphery of the screw thread and the central axis is long. A circular screw and a non-circular screw having a notch provided only at a position where the distance between the outer periphery of the screw thread and the central axis is short can be manufactured. However, the characteristics of the two non-circular screws are greatly different. On the other hand, it is possible to manufacture a non-circular screw in a state where the position where the notch is provided is specified instead of the flow work, but in that case, an increase in manufacturing cost and a decrease in throughput are inevitable. .

  On the other hand, like the non-circular screw disclosed in the present specification, a plurality of notches 222 are provided at substantially equal intervals, and an integral multiple of the intervals is equal to one spiral of the thread 22. When the circumference does not reach, even in the flow operation, the notches 222 can be provided in a balanced manner at positions where the distance between the outer periphery of the screw thread 22 and the central axis is long and short. As a result, it is possible to achieve both a uniform quality of the non-circular screw and a mass production at low cost.

  Moreover, in the non-circular screw disclosed in this specification, in order to achieve both fastening of separate members and suppression of loosening, about 3 to 7 pieces per one spiral of the screw thread 22 are provided. The notch 222 is preferably provided. In other words, the interval at which the plurality of notch portions 222 are provided is shorter than the circumference of one third of the spiral of the screw thread 22 and more than the circumference of one seventh of the helix of the screw thread 22. Is also preferably long.

  Further, in the non-circular screw disclosed in the present specification, a top surface 225 is provided on the screw thread 22. In this case, even if a person has touched the leg 2, the skin is not damaged, which is preferable.

  Moreover, in the non-circular screw disclosed in this specification, the lower end of the shaft center 21 is hemispherical. In this case, it is preferable because both the easy insertion into the member and the prevention of damage to the lower end of the shaft center 21 during the insertion can be achieved.

DESCRIPTION OF SYMBOLS 1 Head 2 Leg 11 Screw rotation tool engaging part 21 Axis center 22 Screw thread 221 Ridge part 222 Notch part 223 Advance side flank surface 224 Return side flank surface 225 Top surface

Claims (4)

A head having a screw rotating tool engaging portion on the upper surface;
A leg portion suspended from the lower surface of the head,
The legs are
The axis,
A screw thread helically provided on the surface of the shaft,
The thread is
A ridge having a non-circular outer periphery;
A plurality of notches provided in the ridge,
The flank angle of the advance side flank surface of the thread is smaller than the flank angle of the return side flank surface ,
Before SL plurality of cutout portions are schematic provided at equal intervals on the ridge,
The integral multiple of the interval is not the circumference of one spiral of the thread,
The thread is a non-circular screw having a top surface parallel to the surface of the axis. In claim 1,
The angle formed between each of the plurality of cutout portions on the insertion rotation direction side and the ridge portion is smaller than the angle formed between the portion on the anti-insertion rotation direction side of each of the plurality of cutout portions and the ridge portion. Non-circular screw. In claim 1 or claim 2 ,
The non-circular screw, wherein the interval is shorter than the circumference of one third of the spiral of the thread and longer than the circumference of one seventh of the spiral of the thread. In any one of Claims 1 thru | or 3 ,
A non-circular screw having a hemispherical lower end.

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