JP6676113B2 - Male thread member - Google Patents

Description

  The present invention relates to a male screw member having a pilot portion at a distal end for guiding screwing to a female screw member.

  2. Description of the Related Art Conventionally, in mass production processing such as assembly of an automobile, when fastening a male screw member, a fastening device capable of performing high-speed rotation to improve workability has been used as a fastening device. In some fastening parts, the working posture is unstable, and the male screw member may not be able to be formed at right angles to the mating female screw member. Due to work under adverse conditions where the tightening is fast and may be performed diagonally, biting and burning occur between the male screw member and the female screw member.

As these countermeasures, for example, a male screw member having a pilot portion as described in Patent Document 1 has been proposed. This male screw member is provided with a guide screw thread having a smaller diameter than the normal screw thread on the distal end side of the shaft portion where the normal screw thread is formed, and a configuration having a cylindrical guide further on the distal end side than the guide screw thread. Had become. The guide thread has an outer diameter equal to or smaller than the inner diameter of the female thread, and the cylindrical guide (the guide whose outer peripheral surface is cylindrical) is larger than the root diameter of the guide thread, and The diameter is equal to or smaller than the outer shape of the mountain.
When screwing into the female thread member and tightening, the tip 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 engages with the female thread of the internal thread member. It is guided so as to be screwed with a normal thread while adjusting the pitch.

Japanese Patent No. 3739012

  However, in the past, since the tip of the guide screw thread was connected to and connected to the cylindrical guide, there was a wedge-shaped step between the root of the cylindrical guide and the tip of the guide screw thread. However, there is a problem that stress concentrates on a portion corresponding to the wedge-shaped step, and the tool life is short.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a screw member having a shape capable of reducing working stress generated between a guide screw thread and a cylindrical guide during rolling as much as possible.

In order to achieve the above object, the present invention includes a head portion and a shaft portion, wherein the shaft portion has a normal thread portion forming a normal thread for fastening with a female thread member, and A guide screw portion provided on the tip end side of the shaft portion and having a guide screw thread having a smaller diameter than the normal thread and having the same pitch, and an outer peripheral surface further provided on the tip end side of the guide screw portion and further having a cylindrical outer shape. A guide whose diameter is smaller than the inner diameter of the internal thread member,
Providing a threadless region between the guide screw thread and the guide, forming an axial gap between the tip of the guide screw thread and the guide,
The outer peripheral surface of the root portion of the guide screw thread is generally a cylindrical surface having the same diameter as the root diameter of the screw thread and having a smaller diameter than the outer peripheral surface of the guide.
Thus, by forming an axial gap between the tip of the guide screw thread and the cylindrical guide, a wedge-shaped step is eliminated between the tip of the guide screw thread and the cylindrical guide. The processing stress generated between the guide screw thread and the cylindrical guide can be reduced as much as possible.
Further, by providing a gap in the axial direction between the guide screw thread and the cylindrical guide, the amount of entry of the cylindrical guide until the guide screw thread engages with the inlet of the female screw member 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 of the outer diameter of the shape guide is obtained. The shorter the cylindrical guide, the greater the effect of the amount of penetration.

The dimensional tolerance of the outer diameter of the guide screw thread can be set in a range from the center to the lower limit value of the dimensional tolerance range of the inner diameter standard of the internal thread member that meshes with the normal thread which is a metric thread of JIS standard .
The gap between the outer diameter of the guide thread and the inner diameter of the internal thread member has a plus gap and a minus gap.However, even if the dimensional tolerances are the same, the plus gap can be made narrower than before so that the guide thread can be more securely The pitch can be adjusted by engaging with the threads of the female thread member. Also, even if a minus gap occurs and a part of the guide screw thread is caught on the thread of the internal thread member, the portion on the opposite side by 180 ° is separated from the internal thread by the amount of the hook, so that the inclination can be made without interference. Is absorbable.
Further, in the present invention, the top cross-sectional shape of the guide screw thread is the same as the top cross-sectional shape of the normal screw thread, and the thread angle of the guide screw thread is the same as the thread angle of the normal screw thread. Can be.
By making the shape of the top and the flank surface of the guide screw thread the same as the shape of the top and the flank surface of the guide screw thread, the guide screw can be securely engaged with the female screw thread and the pitch can be adjusted. Further, since the flank surface of the guide screw thread is continuous with the flank surface of the normal screw thread, it is possible to smoothly guide the guide screw thread from the guide screw thread to the normal screw thread.

ADVANTAGE OF THE INVENTION According to this invention, the working stress which arises between a guide screw thread and a cylindrical guide at the time of rolling can be eased as much as possible, and tool life can be prolonged and productivity can be improved.

1A and 1B show an external thread member according to an embodiment of the present invention, in which FIG. 1A is an overall front view, FIG. 1B is an enlarged view near a cylindrical guide and a guide screw portion, and FIG. 1C is an ordinary screw shown in FIG. FIG. 9D is a partially enlarged cross-sectional view of a thread, a transition thread, and a guide thread, and FIG. FIG. 2 is a diagram illustrating a dimensional relationship between a male screw member and a female screw member in FIG. 1. It is a figure which shows the dimension relationship of a guide screw thread, a screw hole, and a cylindrical guide. (A) to (C) are diagrams schematically showing a process from a state in which the external thread member of FIG. 1 starts to enter the screw hole to a tightening state. It is a figure showing the tip part of the male screw member concerning other embodiments.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.
FIG. 1 shows a male screw member according to an embodiment of the present invention.
In the drawing, reference numeral 1 denotes the entire male screw member, and the male screw member 1 includes a head portion 10 and a shaft portion 20. The shaft portion 20 includes a normal screw portion 22 having a normal screw thread 21 formed therein. And a pilot section 30 provided on the tip end side of the shaft section.
The shape of the head 10 is illustrated as a hexagonal shape with a flange in the figure, but is not particularly limited, and various shapes of the head shape can be applied.

The pilot portion 30 is provided on the distal end side of the shaft portion with respect to the normal screw portion 22, and has a guide screw portion 26 formed with a guide screw thread 25 having the same pitch (P) as the normal screw thread 21. And a cylindrical guide 24 (a guide whose outer peripheral surface is cylindrical) provided on the distal end side.
The guide screw thread 25 has a smaller diameter than the normal screw thread 21 and a lower thread height than the normal screw thread 21, and a transition region 28 where the normal screw thread 21 transitions to the guide screw thread 25 includes a guide screw thread 25. A transition thread 27 is provided which continuously transitions from the normal thread 21 to the normal thread 21.

FIG. 1C is an enlarged 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 metric thread according to JIS, and the cross-sectional shape is a mountain shape having an arc-shaped apex 21a, and the flank surfaces 21b and 21c serving as inclined surfaces are thread center lines orthogonal to the center axis N1. It is symmetrically inclined with respect to M. In this example, the thread angle θ is 60
° (left and right flank angles are θ / 2, both 30 °).
The guide screw thread 25 also has a cross-sectional shape having a top 25a having the same radius of curvature as the normal screw thread 21 and flank surfaces 25b and 25c having the same screw thread angle θ. It is lower than the peak height h1 of the peak 21 and is set to be about 0.2 to 0.3 times the normal thread 21.
Although the root diameter of the guide screw thread 25 is the same as the root diameter of the normal screw thread 21, the shape of the outer peripheral surface of the root thread 25 d is different from the radius-shaped root 21 d of the normal screw thread 21. Surface.

The transition screw thread 27 also has a cross-sectional shape including a top 25a having the same radius of curvature as the normal screw thread 21 and flank surfaces 27b and 27c having the same screw thread angle θ. The height of the top 27 a gradually increases toward the crest 21 and is connected to the top 21 a of the normal thread 21.
In this embodiment, the transition from the guide thread 25 to the normal thread 21 transitions between 1.5 pitches and 2 pitches. If the transition length is extremely short, the normal thread 21 will try to fit before the oblique correction is performed, so that galling is likely to occur. If the transition length is too long, it is disadvantageous because it leads to an increase in weight from the viewpoint of weight reduction.
The guide screw thread 25 is set to a length of about 2.5 to 4 pitches, and the tip side of the guide screw thread 25 is reduced in height while maintaining the shape of the top 25a and the screw thread angle θ. It converges to the valley part 25d of the shape. By avoiding incomplete ridges, the pitch can easily be matched with the female thread pitch, and the mechanism does not cause galling. This thread shape greatly affects the oblique screwing characteristics. When the thread is incomplete, the outer diameter does not increase and it is impossible to reach the target outer diameter. The rising range from the tip 25e to the regular height h5 of the guide screw thread 25 is such that it rises over about 0.2 to 0.4 pitch.

On the other hand, the outer peripheral surface of the cylindrical guide 24 is basically cylindrical, and its distal end portion has an arcuate round shape, so that insertability into the female screw member 110 is ensured. The shape of the tip may be not only a round shape but also a cut shape as shown in FIG. In addition, the axial length L of the cylindrical guide 24 is set to a length of about 0.25 to 0.20 of the nominal diameter (outer diameter) d of the normal screw portion 22. It has an appropriate length. The outer diameter d1 of the cylindrical guide 24 is larger than the root diameter d2 of the guide screw thread 25, and a step 24b is formed between the outer diameter d1 of the guide screw thread 25 and the cylindrical flat valley part 25d. A threadless region 29 is formed between the distal end 25 e of the guide screw thread 25 and the root end of the cylindrical guide 24, and a shaft is provided between the distal end 25 e of the guide screw thread 25 and the cylindrical guide 24. A gap g in the direction is formed.
As described above, since the axial gap g is formed between the tip of the guide screw thread 25 and the cylindrical guide 24, a wedge-shaped step is formed between the tip of the guide screw thread 25 and the cylindrical guide 24. Therefore, the working stress generated between the guide thread 25 and the cylindrical guide 24 during rolling can be reduced as much as possible, and the life of the rolling tool can be increased.
From the viewpoint of increasing the life of the rolling tool, it is preferable that the gap g is large. However, if the gap g is increased, the length of the guide thread 25 is shortened, and from the viewpoint of pitch adjustment, the gap g is preferably small.
Also, if the gap g is too small, even if there is a threadless region 29, the stepped portion 24b between the root of the cylindrical guide 24 and the cylindrical valley portion 25d of the guide screw portion 26 and the guide screw 25 at the time of rolling.
The gap g is preferably about 0.1 to 0.2 mm because the processing stress between the top ends 25e of the first and second ends increases.

2 and 3 show the dimensional relationship between the female screw member 110, the guide screw thread 25, and the cylindrical guide 24. FIG.
The outer diameter d5 of the guide screw thread 25 is set between the center and the lower limit of the standard range of the inner diameter of the female screw member 110 (FIG. 3), and after the cylindrical guide 24 is inserted into the female screw member 110, the female screw pitch is changed. It plays the role of adjusting the pitch with. This pitch adjustment prevents the subsequent thread 21 from sticking or seizing.
More specifically, the dimensional tolerance of the outer diameter d5 of the guide screw thread 25 is set in the range of the lower limit from the center of the standard range (dimensional tolerance) of the female screw member 110. When compared with the median value, the outer diameter of the guide screw thread 25 is set to be smaller than the inner diameter D of the female screw member 110.
On the other hand, the outer diameter d1 of the cylindrical guide 24 is smaller than the inner diameter D of the female screw member 110. Actually, α set in the range between the lower limit value of the inner diameter standard and the lower limit value of the inner diameter of the internal thread member-α [mm] is set to about 0.5 [mm]. Insertion into the screw member 110 corrects the inclination. If the height of the guide screw thread 25 is set, it is about 0.2 to 0.3 times the normal screw thread 21.

Next, with reference to FIG. 4, a description will be given of the work of tightening the screw member of the present embodiment.

In the tightening operation, first, the cylindrical guide 24 of the pilot portion 30 is inserted into the screw hole 112 of the female screw member 110. Since the outer diameter d1 of the cylindrical guide 24 is smaller than the inner diameter D of the female screw member 110, the cylindrical guide 24 is inserted into the screw hole 112 while being guided by the inner peripheral surface of the screw hole 112, and The shaft portion 20 of the member 1 and the female screw member 110 are aligned.
However, since there is a gap between the cylindrical guide 24 and the inner peripheral surface of the screw hole 112, the tip 25 e of the guide screw thread 25 engages with the screw thread 114 of the female screw member 110 at the entrance of the screw hole 112. The tip end 24a of the cylindrical guide 24 engages with the inner periphery of the screw hole 112 at an angle of 180 ° opposite to the engaging portion and is inclined. The smaller the gap between the cylindrical guide 24 and the screw hole 112 is, the smaller the inclination can be, but it is necessary to increase the dimensional accuracy.

In the present invention, an axial gap g is formed between the cylindrical guide 24 and the tip 25e of the guide screw thread 25, so that the cylindrical guide 24 enters the screw hole 112 as much as possible. To reduce the inclination. Therefore, even when the dimensional accuracy of the outer diameter of the cylindrical guide 24 is the same, the inclination when the male screw member 1 is inserted can be made as small as possible, and the initial inclination can be corrected smoothly.
Further, in the present embodiment, the guide screw thread 25 gradually rises from the tip to a predetermined thread height, so that the guide screw thread 25 does not engage with the thread 114 at the entrance of the screw hole 112 for a predetermined amount from the tip. As a result, the guide screw portion 26 is inserted by a predetermined amount, and the inclination correcting effect is enhanced.
In particular, the valley 25d of the guide screw thread 25 has a cylindrical surface, and the cylindrical valley 25d is engaged with the inner peripheral surface of the female screw member 110, so that the inclination is corrected.

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 tolerance is the same, the plus gap becomes narrower than in the past, and the guide screw thread 25 is more securely inserted into the female hole 112 in 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, the guide thread 25 can be more securely engaged with the thread 114 of the female thread member 110, and the pitch can be accurately adjusted. it can. Further, since the flank surfaces 25b and 25c of the guide screw thread 25 and the flank surfaces 27b and 27c of the transition screw thread 27 are continuous with the flank faces 21b and 21c of the normal screw thread 21, the guide screw thread 25 and the normal screw thread 21 Will be guided smoothly. Therefore, the cylindrical guide 24 and the guide screw thread 25 can be guided stably, and the length of the pilot portion 30 can be made shorter and the weight can be reduced.

FIG. 5 shows an example in which a distal end guide portion 50 that is inclined so as to gradually taper is provided at the distal end of the cylindrical guide 24.
The tip guide portion 50 is configured to be inclined in a truncated cone shape. In the illustrated example, the inclination angle β is 90 °, and the tip diameter is about １ ／ of the diameter of the cylindrical guide 24. The inclination angle β is not limited to 90 °, and the inclined surface is not limited to a straight line and may be a curved line such as an arc. If the tip guide portion 50 is provided in this manner, although the weight increases, even when the screw hole and the screw shaft are misaligned at the time of insertion into the screw hole, the tip guide portion 50 can search for the screw hole. Can be drilled, and the hole searchability is improved. Although the entry angle becomes large, the pitch is automatically adjusted by the subsequent cylindrical guide 24 and guide screw thread 25, so that the convenience is high.
In the above embodiment, the length L in the axial direction of the cylindrical guide 24 is set to about 0.25 to 0.20 of the nominal diameter (outer diameter) d of the normal screw portion 22. The axial length of the cylindrical guide 24 is made longer than that of the above-described embodiment for inclination correction by the priority of the searchability. This length is preferably about 0.35 to 0.6 times the nominal diameter (outer diameter) d of the normal screw portion 22.

In the above-described embodiment, the dimensional tolerance of the outer diameter d5 of the guide screw thread 25 is set to a range from the center of the dimensional tolerance range of the inner diameter D of the female screw member 110 to the lower limit value. 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 set to be equal to or larger than the inner diameter D of the female screw member 110.
Further, in the above embodiment, the guide screw thread 25 has the same top cross-sectional shape as the normal screw thread 21 and the shape having the flank face with the same screw thread angle, but is not completely the same and has some differences. Alternatively, in some cases, the shape may be an incomplete thread shape.
Further, in the above embodiment, the range in which the guide screw thread 25 gradually converges is set to 1.5 to 2 pitches, but is not limited to this range and may be short or long. You may.
Further, the guide thread 25 tip, while maintaining the top cross-sectional shape, but has a shape which converges to a cylindrical surface of the valley portion gradually decreases from a predetermined height, the convergence intermediate stage of the guiding thread 25 of the The shape does not necessarily have to maintain the top cross-sectional shape, and may be, for example, a shape of an incomplete thread.

1 Male Thread Member 10 Head 20 Shaft 21 Normal Thread 21a Top, 21b, 21c Frank Surface 22 Normal Thread 24 Cylindrical Guide, 24b Step, 24e Tip 25 Guide Thread 25a Top, 25d Valley, 25e Tip 26 Guide screw part 27 Transition screw thread 29 No screw area 30 Pilot part 50 Tip guide part 110 Female screw member, 112 Screw hole, 114 Screw D Internal diameter of female screw member M Thread center line N1 Center axis d Normal screw thread 21 Outer diameter (nominal diameter)
d1 Outer diameter of cylindrical guide d2 Root diameter g of guide screw thread Gap θ Thread angle

Claims (5)

A head portion and a shaft portion, wherein the shaft portion is provided with a normal thread portion forming a normal thread portion for fastening with an internal thread member, and the normal thread portion provided on a tip end side of the shaft portion with respect to the normal thread portion. A guide screw portion having a smaller diameter and a guide screw thread of the same pitch is formed, and a guide having a cylindrical outer peripheral surface provided on the tip end side of the guide screw portion and having an outer diameter smaller than the inner diameter of the female screw member. In the male screw member having,
Providing a threadless region between the guide screw thread and the guide, forming an axial gap between the tip of the guide screw thread and the guide,
A male screw member, wherein the outer peripheral surface of the root portion of the guide screw thread is a cylindrical surface having the same diameter as the root diameter of the normal screw thread and smaller in diameter than the outer peripheral surface of the guide. The dimensional tolerance of the diameter of the guide screw thread is set to a range from the center to the lower limit value of the dimensional tolerance range of the inner diameter standard of the internal thread member that meshes with the normal thread which is a JIS standard metric thread . Screw member.   The male screw member according to claim 1, wherein the guide screw thread has a flank surface having the same top cross-sectional shape and the same screw thread angle as a normal screw thread.   4. The transition thread which transitions from the normal thread to the guide thread has a flank face having the same top cross-sectional shape and the same thread angle as the normal thread. The male screw member according to 1.   The tip according to any one of claims 1 to 4, wherein a tip of the guide screw thread is gradually reduced from a predetermined height and converges on a cylindrical surface of the cylindrical valley while maintaining a top cross-sectional shape. The external thread member described.