JPH06102235B2 - Deformed screw and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deformed screw having a half thread angle of less than 15 ° and a method for rolling the same.

(Prior Art) For example, a trapezoidal screw or a square screw is generally used for a lead screw, a feed screw, or a screw jack of a lathe. This is because a large thread cross-sectional area can be taken to increase strength, and a large lead angle can be taken to achieve high-speed feed.

By the way, when comparing the trapezoidal screw and the square screw, in terms of strength, the square screw is superior to the trapezoidal screw, and in terms of the lead angle, the square screw with the half angle of the screw thread as approximately 0 is also found. It has the advantage of being larger than trapezoidal screws. On the other hand, in terms of cost, a trapezoidal screw that can be manufactured by rolling has a far greater advantage than a square screw that must be machined.

(Problems to be Solved by the Invention) That is, a trapezoidal screw and a square screw have advantages and disadvantages, and hitherto, no screw has both advantages.

In connection with this, there has been an attempt to ensure a relatively large strength and a lead by, for example, manufacturing a deformed screw having a small half-angle of a thread by rolling. However, if you try to roll a screw with a small half-width of the thread,
The amount of axial movement of the work piece due to the lead of the screw during rolling increases, which not only inevitably deteriorates the accuracy of the screw, but also causes damage to the screw thread. It is difficult for the material to flow smoothly along the tops of the die teeth,
There is a problem that a rolled thread is likely to have cracks (wrinkles) at the root, and JIS does not currently define a screw thread with a half angle of less than 15 ° that is close to a rectangle.

(Means for Solving the Problems) Therefore, the present invention is characterized in that in a deformed screw having a half-angle of the screw thread of less than 15 °, the root of the deformed screw has a concave circular arc portion.

In order to manufacture a deformed screw whose half angle of the screw thread is less than 15 °, a pair of thread-rolling flat dies each having a ridge of a die tooth with a convex arc shape are relatively moved, and positioning is performed between them. It is characterized in that the workpiece is subjected to a forced rotation driving force in synchronism with the movement of the rolling flat die to carry out the rolling.

In the above-described method for manufacturing a modified screw, the lead angle of the thread rolling flat die is set according to the circumference of the forced rolling diameter of the workpiece. However, the method of applying a forced rotation driving force to the workpiece is not particularly limited, but, for example, serrations or spline rolling dies are installed in parallel on the thread rolling flat die, and the serration or spline rolling is first performed. It is also possible to start the forming and to apply the force to the thread rolling, or to grasp one end of the workpiece with a chuck and transmit the rotating force synchronized with the thread rolling flat die to the chuck. Is also good.

(Operation) Since the profile bottom of the variant screw with the above configuration is an arcuate portion, stress concentration can be relieved and the half angle of the screw thread is 15
Large strength can be guaranteed even if it is as small as less than °. In addition, since the valley bottom is formed into an arc portion, the flow of the material of the valley bottom during the rolling process is promoted, and stable manufacturing by rolling is possible.

Further, in the method for manufacturing a deformed screw having the above configuration, the workpiece is forcibly rolled irrespective of the screw lower diameter, so that the axial movement amount of the workpiece becomes extremely small, while the die tooth Since the crest is an arc part, the material flow along the crest becomes smooth, and it becomes possible to roll deformed screws with a half angle of less than 15 ° of the screw thread with high accuracy without defects such as scratches. .

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing.

FIG. 1 shows the shape of the essential part of a modified screw according to the present invention. In the variant screw indicated by 1 in the figure, the half angle θ of the screw thread 2 is less than 15 °, the valley bottom 3 is an arc portion with a full radius R ₁ , and the crest portion is radiused with a small radius R ₂ . . The odd-shaped screw 1 having such a shape has a half-angle θ that is small and thus is as close as possible to a square screw shape. However, due to the presence of the full-arc portion, the corner portion 3a, which becomes a stress concentration portion in the valley bottom 3, The angle becomes gentle, and as a result,
The strength of the screw thread 2 is improved as a whole in combination with the increased thickness. As an example, the modified screw has
R ₁ = 0.5, R ₂ = 0.2, P (pitch) = 2.0 mm, H (mountain height) =
It consists of 1.3 mm specifications.

The deformed screw 1 can be manufactured by rolling, as shown in FIG. In FIG. 2, 11 is a thread rolling flat die, 12 is a serration rolling flat die,
Both of them are integrally incorporated in parallel with a rolling machine (not shown). These flat dies each include a biting tooth group 11a, 12a, a finishing tooth group 11b, 12b, and a relief tooth group 11c, 12c.In particular, the thread rolling flat die 11 has a starting end of the biting tooth group 11a. The serration screw rolling flat die 12 is positioned so as to be positioned in the middle of the biting tooth group 12a.

Further, as shown in FIG. 3, the thread rolling flat die 11 has its lead angle β set in accordance with the circumferential length πD ₁ of the rolling diameter D ₁ of the serrated portion. By the way, if it is a conventional thread rolling flat die, as shown in the figure,
Lead angle α is set in accordance with the circumferential length [pi] D ₂ of D _2.

Here, the tooth shape of the thread rolling flat die 11 is such that the crests are arcuate portions of the full radius following the tooth bottoms 3 of the variant screw 1, and the corners of the tooth bottoms are the crest angles of the variant screw 1. It is imprinted with a copy.

With the flat die with the above configuration, the work W is now between these
Is supported by both centers 13 and 13, and the flat die is relatively moved as indicated by an arrow A. Then, the serration-rolling flat die 12 bites on the workpiece W to start serration rolling, and then the thread-rolling flat die 11 bites on the workpiece W to start screw rolling.

The thread rolling proceeds with the serration groove that has already been allocated as the starting point of action, and the lead angle β of the thread rolling flat die 11
Is set in accordance with the circumference of the rolling diameter of the serration portion, the thread rolling flat die 11 causes a slip with respect to the workpiece W, and as a result, a screw having a predetermined lead angle α is gradually produced. Will be created.

Moreover, due to the rotation constraint, the axial movement amount of the workpiece W becomes extremely small during the rolling process as shown by the solid line A in FIG. 4, and as a result, the movement direction returns to the original "walking distance". "L _a also becomes small, no bruise, so accuracy to better profiled screw 1 is obtained. Incidentally, when the thread rolling flat die alone is used for rolling without using the serration rolling flat die 12, as shown by a broken line B in FIG. 4, the axial movement amount of the workpiece W is extremely large. Therefore, the walking distance L _B also becomes large, and it is not possible to obtain a highly accurate deformed screw.

Further, by making the crests of the thread rolling flat die 11 into full-round arc portions, the material flow of the workpiece W along the crests during the rolling becomes smooth, and the valley bottom 3 of the deformed screw 1 is formed.
No defects such as peeling will occur in.

In the above embodiment, the serration rolling was used to forcibly roll the workpiece W, but instead of this, for example, the fifth
The means shown in the figure can be used. In FIG. 5, reference numeral 21 denotes a pair of tool supporting bases for supporting the thread rolling flat die 11, which is slidably attached to the vertical guide member 22 and is relatively moved (in a direction perpendicular to the paper surface) by a driving means (not shown). You can do it. Reference numeral 23 denotes a main shaft having a center 24, which can support the workpiece W between the center 24 and a tailstock 25 provided so as to face the center 24. Spindle 23
A synchronous pinion 26 is rotatably mounted on the synchronous pinion 26, and a chuck 27 capable of gripping one end of the workpiece W is fixed to the synchronous pinion 26. Meanwhile, the tool support base
21 includes a synchronous rack 28, 2 which can be meshed with the synchronous pinion 26.
8 is installed.

That is, when the tool support base 21 relatively moves, its driving force is transmitted as a rotational force to the chuck 27 via the synchronous rack 28 and the synchronous pinion 26, and the workpiece W is forcibly rotated. Here, the lead angle of the thread rolling flat die 11 is set in accordance with the rolling diameter of the chucking portion as in the above embodiment.

As a result, during the rolling, the thread rolling flat die 11 tries to rotate the workpiece W with the screw lower diameter, but the workpiece W is forcibly rolled with the chucking portion diameter. The same operation as that of the first embodiment is reproduced, and the same effect can be obtained.

(Effects of the Invention) As described in detail above, in the deformed screw according to the present invention, since the valley bottom is an arc portion, stress concentration can be relaxed and the half angle of the screw thread is small. Anyway,
A large strength can be guaranteed. Further, due to the shape of the bottom of the arc, the flow of the material during rolling can be promoted, and stable manufacturing by rolling can be realized.

Further, when the deformed screw is manufactured by rolling, a forced rotational driving force is applied to the work piece, so that the axial movement amount of the work piece becomes extremely small, and there is no damage and the accuracy is high. It enables the production of excellent profile screws. Also at this time,
Since the peak of the die tooth is a full radius arc, the material flow along the peak becomes smooth, and it is possible to suppress the occurrence of defects such as peeling, and overall durability and
It is possible to manufacture highly reliable irregular shaped screws.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the shape of an essential part of a modified screw according to the present invention, and FIG. 2 is a perspective view schematically showing an example of a manufacturing mode of the modified screw according to the present invention. The figure is an explanatory view showing the conditions for setting the lead angle of the thread rolling flat die shown in FIG.
FIG. 4 is a graph showing the amount of axial movement of the workpiece by the manufacturing method shown in FIG. 2 in comparison with the case of conventional rolling, and FIG. It is sectional drawing which shows an example and its manufacturing apparatus. 1 ... Deformed screw 2 ... Thread 3 ... Valley bottom θ: Half angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Igawa 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Shinobu Kaneko 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation ( 72) Inventor Mitsuo Saito, 3-12 Kamiyama, Kamo-cho, Toyohashi-shi, Aichi, Osu G Co., Ltd. (72) Yoshihiro Umebayashi, 3-12, Kamiyama, Kamo-cho, Toyohashi-shi, Aichi (56) References JP-A 61-52951 (JP, A) JP-A 60-72630 (JP, A) Actual development JP-A 62-87248 (JP, U)

Claims (3)

[Claims] 1. A deformed screw characterized in that the half angle of the screw thread is less than 15 ° and the root has a concave circular arc portion. 2. A method for producing a deformed screw having a half-angle of a screw thread of less than 15 °, wherein a pair of thread-rolling flat dies each having a ridge of a die tooth having a convex arc are relatively moved. The method for producing a deformed screw is characterized in that the workpiece positioned during this time is subjected to rolling by applying a forced rotation driving force in synchronism with the movement of the rolling flat die. 3. A method for manufacturing a deformed screw according to claim 2, wherein the lead angle of the thread rolling flat die is set in accordance with the circumference of the forced rolling diameter of the workpiece. .