JPH0957384A - Method for rolling female screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the excellent accuracy of females screws without leaving an imperfect threaded part by arranging dies having the inner circumferential surface of the prescribed surface on the outer circumferential side of a cylinder part, and pressing the cylindrical part from the inner circumferential side to the dies by a pressing member of the prescribed shape to achieve the plastic working. SOLUTION: A rolling equipment 3 is arranged so that the axis S of notation of a ball screw 30 agrees with the center axis of a cylindrical part 10, and a roller 33 is advanced in the cylindrical part 10 while being revolved around the center axis of the cylindrical part 10. The locus of the roller 33 becomes spiral, and the roller 33 presses the inner circumferential surface of the cylindrical part 10 toward a female screw part 22 of a die 2 while being rotated spirally from a base part of the cylindrical part 10 toward the tip. Because the pitch of the ball screw 30 is same as that of the female screw part 22, the roller 33 is advanced while being surely and spirally rotated along the female screw part 22, and a female screw 11 of the same pitch as that of the female screw part 22 is rolled on the cylindrical part 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an internal thread by plastic working on the inner peripheral surface of a cylindrical portion provided on a metal plate material.

[0002]

2. Description of the Related Art In general, a female screw is formed on a block material by cutting by rotating a tap. However, in order to form the female screw in the tubular portion provided on the plate material, the cutting process is not preferable because the wall thickness becomes thin. Therefore, as a method of forming a female screw in a cylindrical portion provided on a metal plate material, first, a cylindrical portion is formed in the plate material by pressing, and a die having a male screw of a predetermined shape is arranged in the cylindrical portion from the outer periphery. A method is known in which a roller is pressed to plastically process the inner peripheral surface of the cylindrical portion into an inverted shape of the male screw of the die to form a female screw.

For example, in order to form an oil inlet of a cylinder head cover made of an iron plate, first, an iron plate 100 is subjected to a cylindrical portion 10 as shown in FIG.
Form one. In the sheet metal stamping, a number of pressing steps that are approximately proportional to the length of the tubular portion 101 are performed, and a punching step of punching the bottom of the tubular portion 101 is also performed. Next, the maximum outer diameter is the cylindrical part 1.
A die 200 smaller than the inner diameter of 01 is placed in the tubular portion 101. On the outer peripheral surface of the die 200, a male screw portion 201 having a predetermined shape is formed by reversing the intended female screw.

A roller 300 revolving around the central axis of the tubular portion 101 is arranged on the outer periphery of the tubular portion 101,
The roller 1 is axially moved toward the iron plate 100 while rolling the roller 300 while pressing 1 from the outer peripheral side toward the die 200 in the radial direction. As a result, the inner peripheral surface of the cylindrical portion 101 is shaped in the inverted shape of the male screw portion 201 of the die 200, and a female screw is formed by rolling.

[0005]

However, when the roller 300 is pressed from the outer periphery by the roller 300 to perform rolling, the shape of the outer peripheral surface is the same as that of the roller 300 and the accuracy is easily ensured. However, although it is pressed by the die 200 on the inner peripheral surface, it is difficult to transfer the shape of the die 200 as it is, and it is often difficult to secure the accuracy of the intended internal thread. For example, if the radius of curvature of the root of the male thread of the die 200 is smaller than the radius of curvature of the cross section of the peripheral edge of the roller 300, it may be difficult for the inner peripheral surface of the tubular portion 101 to abut the root of the male thread. .

Therefore, when the male screw member such as the cap is screwed, the screwing precision is low, and there is a problem that it is hard to fit and easily loosens. Further, when the roller 300 is pressed from the outer periphery and rolled, the roller 30 is rolled in a portion near the iron plate 100.
Rolling becomes difficult due to interference between 0 and the iron plate 100. Therefore, an incomplete thread portion remains at the base of the tubular portion 101. Therefore, the length of the tubular portion must be made longer than necessary in order to secure a necessary length of female screw. Then, more pressing steps are required at the time of sheet metal pressing of the tubular portion 101, resulting in a large number of steps.

If rolling is performed from the tip end side of the tubular portion 101 toward the base, a mechanism for moving the roller 300 in the radial direction is not required, and the rolling device is simplified.
However, if the material is rolled from the tip side toward the root, it becomes difficult for the material to flow at the root, and the extra thickness removed by the rolling is accumulated in the root, resulting in bulging. Further, since the cylindrical portion 101 is pressed from the outer peripheral side, the diameter of the cylindrical portion 101 is reduced, and there is a situation in which excess thickness is likely to occur.
Therefore, if it is attempted to roll from the root portion toward the end portion in order to avoid this, a mechanism for moving the roller 300 in the radial direction is required, and there is a problem that the rolling device becomes complicated.

Since the formed female screw is engaged with the die 200, the die 200 can be pulled out by rotating the die 200 or by pulling the die 20.
It is necessary to configure 0 as a divided body, which requires man-hours for removing the die 200. The present invention has been made in view of such circumstances, and an object thereof is to ensure high accuracy of an internal thread without leaving an incomplete threaded portion.

[0009]

The features of the internal thread forming method of the present invention which solves the above-mentioned problems are that an internal thread is formed inside a cylindrical portion formed in a part of the plate material in which the central axis direction is substantially perpendicular to the plate material. A method of forming, wherein a die having an inner peripheral surface of a predetermined shape is arranged on the outer peripheral side of the cylindrical portion, and the cylindrical portion is pressed from the inner peripheral side toward the die by a pressing member of a predetermined shape to perform plastic working. Is to form a female screw on the inner peripheral surface of the tubular portion.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a female screw is formed inside a tubular portion formed in a part of a plate material in an axial direction substantially at right angles to the plate material. The tubular portion can be formed by sheet metal pressing or the like. Then, a die is arranged on the outer circumference of the cylindrical portion, a pressing member is arranged on the inner circumference, and the pressing member presses the cylindrical portion toward the outer peripheral side, whereby a female screw is formed by plastic working. At this time, since the diameter of the tubular portion is expanded at least in the valley portion of the female screw, excess thickness is less likely to occur and overhang molding is prevented. Since the pressing is performed from the inner peripheral side, interference between the pressing member and the plate material does not occur, and the generation of the incomplete screw portion is avoided. Further, since the internal thread is formed along the surface shape of the pressing member, the accuracy of the internal thread is high.

On the outer peripheral surface pressed by the die,
Since it is not necessary to exactly follow the shape of the die, particularly high accuracy is not required if the surface shape of the die is a shape that follows the internal thread. The pressing by the pressing member is performed by a method in which a male screw shape of an inverted shape of an intended female screw is held on the surface and is radially pressed by a die divided by a plane including the central axis of the cylindrical portion, or a roller is cylindrically processed. For example, a method of rolling by pressing the tubular portion in the radial direction while revolving around the axis of the portion and moving in the axial direction is adopted.

[0012]

EXAMPLES The present invention will be described in more detail below with reference to examples. First, as shown in FIG. 3, the tubular portion 10 is formed on the iron plate material 1 by sheet metal pressing. The axial direction of the tubular portion 10 is perpendicular to the plate material 1. Next, the die 2 shown in FIGS. 1 to 3 is prepared and arranged on the outer peripheral side of the tubular portion 10.
The die 2 has a substantially cylindrical shape as a whole, and is composed of a head portion 20 having an outer peripheral surface tapered toward the tip and a neck portion 21 extending from the head portion 20, and the inner peripheral surface of the head portion 20 has a tip. The internal threaded portion 22 is formed by a predetermined distance from. As shown in FIG. 2, the die 2 has a three-divided structure that is cut along a plane that includes the central axis and intersects with each other at an angle of 120 °, and the diameter can be expanded by dividing the die.

In this die 2, a shaft member (not shown) is inserted into the neck portion 21, and a ring member (not shown) having a tapered inner peripheral surface is arranged on the outer periphery of the head 20,
The ring member (not shown) and the head portion 20 are engaged with each other to reduce the diameter and integrate the three-part structure. Then, the bolt is inserted into the bolt hole 23 provided in the neck portion 21 and fastened to the shaft member, and in the state where the integral structure is fixed, it is coaxially arranged on the outer periphery of the tubular portion 10 as shown in FIG.

At this time, the female screw portion 22 of the head portion 20 is replaced by the cylindrical portion 1.
It is located on the outer periphery of 0. The minimum inner diameter of the female screw portion 22 is made slightly larger than the outer diameter of the tubular portion 10, and the tubular portion 10 is arranged in the head portion 20 without resistance. In this state, the rolling device 3 shown in FIG. 4 rolls the inner peripheral surface of the tubular portion 10 to form a female screw. This rolling device 3 includes a rotatable ball screw 30.
A bearing device 31 for rotatably holding the ball screw 30, a U-shaped holding member 32 fixed to the tip of the ball screw 30, and a roller 33 rotatably supported by the holding member 32. ing. The pivot shaft of the roller 33 is provided parallel to and eccentric to the rotation shaft of the ball screw 30, and the roller 33 revolves around the rotation shaft S of the ball screw 30 and can rotate about its own pivot shaft. Is configured.

The rolling device 3 includes a rotating shaft S of the ball screw 30.
Are arranged so as to coincide with the central axis of the tubular portion 10, and the roller 33 is driven by the rotation of the ball screw 30 to move forward in the tubular portion 10 while revolving around the central axis of the tubular portion 10. Therefore, the locus of the roller 33 has a spiral shape, and the roller 33 spirally rotates from the base portion of the cylindrical portion 10 toward the tip thereof, while the inner peripheral surface of the cylindrical portion 10 is rotated by the female screw portion 2 of the die 2.
Press toward 2.

Since the ball screw 30 and the female screw portion 22 have the same pitch, the roller 33 surely moves forward along the female screw portion 22 while spirally rotating, and the cylindrical portion 10 has the female screw portion. The female screw 11 having the same pitch as 22 is rolled. Here, the radius of curvature of the valley portion of the female screw portion 22 of the die 2 is R = 1.5 mm, and the radius of curvature of the tip cross section of the peripheral edge portion of the roller 33 is R = 1.677 mm. Therefore, when the roller portion 33 presses the cylindrical portion 10 against the female screw portion 22, the radius of curvature of the roller 33 is accurately transferred to the inner peripheral surface of the cylindrical portion 10 as shown in FIG. A gap 24 is formed between the surface and the valley portion of the female screw portion 22. The gap 24 allows the material flow at the time of rolling, and further prevents the occurrence of defects due to the obstruction of the material flow. Since the cylindrical portion 10 is required to have the accuracy of the internal thread 11 on the inner peripheral surface, and the shape of the outer peripheral surface does not need to have accuracy, the existence of the gap 24 causes no problem.

After the rolling of the female screw 11 is completed, the rotation axis S of the ball screw 30 is slightly eccentric from the central axis of the cylindrical portion 10 to disengage the roller 33 from the female screw 11 without interference. The rolling device 3 can be removed from the tubular portion 10. In the die 2, the bolt (not shown) is removed from the bolt hole 23, and the shaft member (not shown) is pulled out from the neck portion 21.
By moving a ring member (not shown) toward the tip of the head 20, the divided portion divided into three is opened. As a result, the diameter of the die 2 is expanded and the engagement with the tubular portion 10 is released, so that the die 2 can be removed from the tubular portion 10.

The internal thread 11 thus formed is
It was formed from the root portion of the tubular portion 10 with the plate material 1 and had no incomplete threaded portion and was highly accurate. According to the female screw forming method of the present embodiment, a mechanism for moving the roller 33 in the radial direction is not necessary, and the radius of rotation of the roller 33 can be smaller than that of the conventional method of pressing from the outer circumference. The structure of the manufacturing apparatus can be simplified.

Further, a highly accurate internal thread can be formed from the root to the tip of the tubular portion 10 and no incomplete thread portion remains. Therefore, the length of the tubular portion can be minimized, and an increase in the pressing process can be prevented. Further, in this embodiment, since the internal thread is formed while expanding the diameter of the cylindrical portion 10, it is possible to prevent the excess thickness from being generated and to prevent the over-expansion molding.

In the present embodiment, the method of forming the female screw by rolling with the roller 33 has been described, but the present invention is not limited to this, and a split die having a male screw portion on the surface is formed in the cylindrical portion 10. It is also possible to form a female screw by arranging it and expanding it to press it radially. In addition, a split die with a male thread part with the same pitch as the die 2 on the surface,
It is also possible to plastically process the female screw by screwing it into the tubular portion 10.

In this embodiment, the roller 3 is used as a pressing member.
Although 3 is used, a protrusion or a rod member may be used instead of the roller 33, and the female screw may be plastically worked by moving the female screw while pressing it against the cylindrical portion similarly to the roller 33. that's all,
Although the embodiments of the present invention have been described, it should be noted that the embodiments of the present invention have various embodiments of the following various technical matters in addition to the technical matters described in the claims. I'll do it. (1) A method of forming an internal thread inside a tubular portion formed in a part of the plate material such that the central axis direction is substantially perpendicular to the plate material, the inner peripheral surface having a predetermined shape on the outer peripheral side of the tubular portion. And a pressing member having a center of rotation that is eccentric from the central axis of the tubular portion, and the center of the tubular portion is abutted against the inner peripheral surface of the tubular portion. A method for forming a female screw, characterized in that a female screw is formed on the inner peripheral surface of the cylindrical portion by revolving with respect to the shaft and moving in the axial direction. (2) The female screw forming method according to the above (1), wherein the pressing member is a roller and the female screw is formed by rolling.

[0022]

According to the female screw forming method of the present invention, it is possible to easily form a highly accurate female screw from the base portion to the tip of the tubular portion, and improve the screwing precision with the male screw member such as the cap. . In addition, it is possible to prevent the incomplete thread portion from remaining. Further, since the die is located on the outer peripheral side of the tubular portion, the engagement with the tubular portion can be easily released by the division even after the female screw is formed. Since the pressing member is located inside the cylindrical portion, the movement distance required to press the inner peripheral surface can be short. For these reasons, the female screw forming device can be made compact, which is advantageous in terms of space and cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a die used in an example of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view of an essential part in a state in which a die is arranged in a tubular part in one embodiment of the present invention.

FIG. 4 is an explanatory cross-sectional view showing how an internal thread is formed in one embodiment of the present invention.

FIG. 5 is an enlarged explanatory view of a main part of FIG.

FIG. 6 is an explanatory view showing a conventional internal thread forming method.

[Explanation of symbols]

1: Plate material 2: Dice
3: Rolling device 10: Cylindrical part 11: Female thread 2
2: Female screw part 33: Roller (pressing member)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Takagi 5-1037 Sangencho, Toyota City, Aichi Prefecture

Claims (1)

[Claims] 1. A method of forming an internal thread inside a tubular portion formed in a part of the plate material so that the central axis direction is substantially perpendicular to the plate material, wherein an internal thread of a predetermined shape is formed on the outer peripheral side of the tubular part. It is possible to form a female screw on the inner peripheral surface of the cylindrical portion by disposing a die having a peripheral surface and pressing the cylindrical portion from the inner peripheral side toward the die with a pressing member having a predetermined shape to perform plastic working. Characteristic female screw forming method.