JP2016156400A5 - - Google Patents

Description

As these measures, for example, a male screw member having a pilot part as described in Patent Document 1 has been proposed. The male screw member is provided with a guide screw thread having a diameter smaller than that of the normal screw thread on the tip side of the shaft portion where the normal screw thread is formed, and a cylindrical guide further on the tip side than the guide screw thread. It was. The guide thread has an outer diameter that is equal to or smaller than the inner diameter of the female thread, and the cylindrical guide ( guide having a cylindrical outer peripheral surface) is larger than the root diameter of the guide thread and is a guide screw. It has a configuration that has a diameter equal to or smaller than the outer shape of the mountain.
When screwing into the female screw member and tightening, it is inserted while the inclination is corrected by the cylindrical guide at the tip, then the guide screw part is inserted, and the guide screw thread is engaged with the female screw thread of the female screw member. Then, it is guided to be screwed with the normal thread while adjusting the pitch.

In order to achieve the above object, the present invention includes a head and a shaft portion, and the shaft portion has a normal thread portion formed with a normal screw thread for fastening with a female screw member, and the normal screw portion. The guide screw portion provided on the tip end side of the shaft portion and having a guide screw thread having a smaller diameter and the same pitch than the normal screw thread, and the outer peripheral surface provided on the tip end side of the guide screw portion is a cylindrical guide. In a male screw member having
The unthreaded region located between the guiding thread and the guide, characterized in that the formation of the axial gap between the tip and the guide of the guiding thread.
Thus, by forming an axial gap between the tip of the guide screw thread and the guide, there is no wedge-shaped step between the tip of the guide screw thread and the guide. The processing stress generated between the guides can be reduced as much as possible.
Also, by providing an axial clearance between the guide screw thread and the guide, the guide entry amount until the guide screw thread engages with the inlet of the female screw member can be increased, and the outer diameter of the guide can be increased. The effect that the inclination at the time of bolt insertion can be made as small as possible without increasing the dimensional accuracy is also obtained. The shorter the cylindrical guide, the greater the effect of the amount of entry.

According to the present invention, machining stress generated between the guiding thread and a cylindrical guide when rolling can be alleviated as much as possible, it is possible to improve the productivity prolong tool life.

The pilot portion 30 is provided on the distal end side of the shaft portion with respect to the normal screw portion 22, and includes a guide screw portion 26 in which guide screw threads 25 having the same pitch (P) as the normal screw thread 21 are formed, and a guide screw portion 26. Furthermore, it has a cylindrical guide 24 ( guide with a cylindrical outer peripheral surface) provided on the distal end side.
The guide thread 25 has a diameter smaller than that of the normal thread 21 and a height lower than that of the normal thread 21. In the transition region 28 where the normal thread 21 moves to the guide thread 25, the guide thread 25 To the normal thread 21 is provided with a transition thread 27.

FIG. 1C is an enlarged cross-sectional view of the normal thread 21, the transition thread 27, and the guide thread 25 cut along a plane passing through the central axis N1.
The normal thread 21 is a JIS standard metric thread, and the cross-sectional shape is a chevron having an arcuate top 21a, and the flank surfaces 21b and 21c serving as inclined surfaces are thread center lines perpendicular to the central axis N1. It is inclined symmetrically with respect to M. In this example, the thread angle θ is 60
The left and right flank angles are θ / 2 and both are 30 °.
The guide thread 25 also has a cross-sectional shape including a top portion 25a having the same radius of curvature as that of the normal thread 21 and flank surfaces 25b and 25c having the same thread angle θ, but the thread height h5 is a normal thread. It is lower than the peak height h1 of the peak 21 and is set to about 0.2 to 0.3 times the normal thread 21.
The valley diameter of the guide thread 25 is the same as the valley diameter of the normal thread 21, but the shape of the outer peripheral surface of the valley section 25 d is different from the round-shaped valley section 21 d of the normal thread 21, and is a linear cylinder. It is a surface.

On the other hand, the dimensional tolerance of the outer diameter d 5 of the guiding thread 25, which are set from the center of the inner diameter standard range of the female screw member 110 in a range of lower limit value, the outer diameter d 5 and the female screw of the guiding thread 25 The gap between the inner diameters D of the member 110 is a plus gap and a minus gap. However, even if the dimensional tolerances are the same, the plus gap is narrower than before, and the guide thread 25 is more reliably fitted into the screw hole 112. The pitch can be reliably adjusted by engaging with the thread 114 of the member 110.
In particular, since the guide thread 25 has the same top shape and thread angle as the normal thread 21, it is possible to more reliably engage the thread 114 of the female thread member 110 and to adjust the pitch accurately. it can. Furthermore, since the flank surfaces 25b, 25c of the guide thread 25 and the flank surfaces 27b, 27c of the transition thread 27 are continuous with the flank surfaces 21b, 21c of the normal thread 21, the normal thread 21 from the guide thread 25 is obtained. Will be guided smoothly. Therefore, the cylindrical guide 24 and the guide screw thread 25 can be stably guided, and the pilot portion 30 can be made shorter and lighter than the conventional one.

In the above embodiment, the dimensional tolerance of the outer diameter d5 of the guide screw thread 25 is set from the center of the dimensional tolerance range of the inner diameter D of the female screw member 110 to the lower limit value range. The outer diameter may be set to be equal to or smaller than the inner diameter D of the female screw member 110, or may be equal to or larger than the inner diameter D of the female screw member 110.
In the above embodiment, the guide thread 25 has the same top cross-sectional shape as that of the normal thread 21 and the flank surface having the same thread angle. However, the guide thread 25 is not completely the same and has some differences. In some cases, it may be an incomplete thread shape.
Moreover, in the said embodiment, although the range which the guide screw thread 25 converges is 1.5-2 pitches, it is not limited to this range, It may be short and becomes long. May be.
The tip of the guide screw thread 25 has a shape that gradually decreases from a predetermined height and converges to the cylindrical surface of the valley while maintaining the top cross-sectional shape. The shape does not necessarily have to maintain the top cross-sectional shape, and may be, for example, an incomplete thread shape.

DESCRIPTION OF SYMBOLS 1 Male thread member 10 Head part 20 Shaft part 21 Normal thread 21a Top part, 21b, 21c Frank surface 22 Normal thread part 24 Cylindrical guide, 24b Step, 24e Tip 25 Guide thread 25a Top part, 25d Valley part, 25e Tip 26 Guide screw portion 27 Transition screw thread 29 Unthreaded region 30 Pilot portion 50 Tip guide portion 110 Female thread member, 112 thread hole, 114 thread D D female thread inner diameter M thread center line N1 center axis d Normal thread 21 Outer diameter (nominal diameter)
d1 Cylindrical guide outer diameter d2 Guide thread root diameter g Clearance θ Thread angle

Claims (6)

A head portion and a shaft portion, wherein the shaft portion is formed with a normal thread portion that forms a normal screw thread for fastening with the female screw member, and the normal screw thread is provided on the front end side of the shaft portion with respect to the normal screw portion. In a male screw member having a guide screw portion formed with a guide screw thread having a smaller diameter and the same pitch, and a guide having a cylindrical outer peripheral surface provided on the distal end side of the shaft portion of the guide screw portion,
Externally threaded member, characterized in that the formation of the axial gap between the unthreaded area provided, and the tip of the guiding thread and the guide between the guide thread and the guide.   The male screw member according to claim 1, wherein a dimensional tolerance of the diameter of the guide screw thread is set in a range from a center of a dimensional tolerance range of an inner diameter of the female screw member to a lower limit value.   The male thread member according to claim 1 or 2, wherein the guide thread has a flank surface having the same top cross-sectional shape and the same thread angle as the normal thread.   4. The transition thread transitioning from the normal thread to the guide thread has a flank surface having the same top cross-sectional shape and the same thread angle as the normal thread. The male screw member described in 1. The outer peripheral surface of the trough portion of the guiding thread is the same diameter as the root diameter of the regular thread, male thread according to any one of claims 1 to 4 has a smaller diameter cylindrical surface of the guide Element. The tip of the guide thread, while maintaining a top cross-sectional shape, according to any one of claims 1 to 5 gradually decreases from the predetermined height has a shape which converges to the outer peripheral surface of the valley Male thread member.

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