DEVICE FOR PRODUCING OIL SUPPLY PIPE AND METHOD FOR PRODUCING OIL SUPPLY PIPE

Abstract

A method for producing an oil supply pipe in which occurrence of cracks can be prevented at the time of forming a threaded portion in a metal pipe is provided. A method for producing an oil supply pipe in which a first rotating shaft 13, a first circumferential surface 14, and one first ridge portion 15 are provided, and in which, using a first forming roller 11 having the first ridge portion 15 spirally provided to have a length of less than one turn in a circumferential direction of the first circumferential surface 14 and a second forming roller 21 having a second rotating shaft 23, a second circumferential surface 24, and a second ridge portion 25 and the second ridge portion 25 spirally provided in a circumferential direction of the second circumferential surface 24, a threaded portion formed of a spiral protrusion is formed in an inner circumferential surface of a metal pipe by inserting the metal pipe to the second forming roller 21, disposing the first rotating shaft 13 and the second rotating shaft 23 so that they are parallel to each other, and pressing a material forming the metal pipe between the second ridge portions 25 using the first ridge portion 15 while rotating the first forming roller 11 and the second forming roller 21 is provided.

Description

TECHNICAL FIELD

The present invention relates to a device for producing an oil supply pipe and a method for producing an oil supply pipe.

Priority is claimed on Japanese Patent Application No. 2021-122632, filed Jul. 27, 2021, the content of which is incorporated herein by reference.

BACKGROUND ART

An oil supply pipe through which a fuel is injected into a fuel tank for an automobile and the like at the time of supplying the fuel is attached to the fuel tank. This oil supply pipe may be called a fuel inlet pipe in some cases. The material of an oil supply pipe is generally a metal material such as ordinary steel and stainless steel and is also made of a resin these days. An oil supply pipe has a pipe main body and an enlarged pipe portion provided on one end side of the pipe main body. The other end of the pipe main body is connected to a fuel tank. An oil supply port is provided in the enlarged pipe portion. A threaded portion is provided inside the enlarged pipe portion. The threaded portion is a spiral convex portion which protrudes from an inner surface of the enlarged pipe portion. When an oil supply cap is installed in the oil supply port, the threaded portion of the oil supply cap is screwed into the threaded portion of the enlarged pipe portion.

In the related art, at the time of producing an oil supply pipe, after the pipe main body and the enlarged pipe portion are produced separately, the enlarged pipe portion is joined to one end side of the pipe main body through welding or the like. However, in recent years, in order to reduce the number of man-hours and the number of parts, an oil supply pipe obtained by integrally forming a pipe main body and an enlarged diameter portion has been proposed. Such oil supply pipes are produced by expanding and forming one end of a base pipe to form an enlarged pipe portion and forming a circumferential wall surface of the enlarged pipe portion to form a threaded portion.

As an example of a method for producing an oil supply pipe, FIG. 11 of the following Patent Document 1 illustrates a method for, at the time of forming a screw in a metal pipe, placing a metal pipe over core metal having a forming groove formed therein, when the metal pipe begins to rotate together with the core metal, pressing a ridge forming part of a forming roller which rotates in a direction opposite to that of the core metal against the metal pipe, and plastically deforming it to gradually form a screw part following the forming groove. In the method for forming a screw illustrated in FIG. 11 of Patent Document 1, two ridge forming parts 102a are provided in a forming roller 102. Furthermore, the metal pipe is partially recessed by pressing the ridge forming parts 102a from the outside of the metal pipe and a spiral convex portion is provided inside the pipe. As illustrated in FIG. 11 of Patent Document 1, the ridge forming parts 102a of the forming roller 102 partially overlap when viewed in an axial direction of a rotating shaft of the forming roller 102. More specifically, in FIG. 11 of Patent Document 1, the vicinity of a distal end portion of the upper ridge forming part 102a and the vicinity of a terminal end portion of the lower ridge forming part 102a overlap when viewed in the axial direction of the rotating shaft.

CITATION LIST

Patent Document

[Patent Document 1]

• • Japanese Patent No. 3462427

SUMMARY OF INVENTION

Technical Problem

Problems when using the forming roller described in Patent Document 1 will be described with reference to FIGS. 9 to 11. FIG. 9 illustrates a schematic plan view and a schematic front view of a forming roller in the related art, FIG. 10 illustrates a schematic side view when the forming roller illustrated in FIG. 9 is rotated by 90°, and FIG. 11 illustrates a process diagram when a threaded portion is formed using a forming roller in the related art. As illustrated in FIGS. 9 and 10, two ridge portions 302a and 302b are provided on a circumferential surface of a cylindrical forming roller 301 and the vicinity of an end portion of one of the ridge portions 302a and the vicinity of an end portion of the other of the ridge portions 302b overlap when viewed in the axial direction of the rotating shaft of the forming roller 301. More specifically, as illustrated in FIG. 10, the vicinity of an end portion 302a₁ of the ridge portion 302a and the vicinity of an end portion 302b₁ of the ridge portion 302b overlap when viewed in the axial direction of the rotating shaft. If a threaded portion is formed in a metal pipe 401 in the same manner as in Patent Document 1 using such a forming roller 301, as illustrated in FIG. 11, a metal pipe 401 is simultaneously in contact with the vicinity of the end portion 302a₁ of one of the ridge portions 302a and the vicinity of the end portion 302b₁ of the other of the ridge portions 302b. Furthermore, the metal pipe 401 is simultaneously processed using these two ridge portions 302a and 302b. At a place M simultaneously processed using the two ridge portions 302a and 302b, the metal pipe 401 is pulled in a longitudinal direction thereof and a material is thinned. As a result, cracks starting from the thinned portion are likely to occur in the metal pipe after processing.

Particularly, when an enlarged diameter portion is formed by increasing a diameter of a base pipe and then a threaded portion is formed in an enlarged diameter portion, the material of the enlarged diameter portion is subjected to work hardening at a state in which the diameter of the base pipe has been increased. Thus, cracks are more likely to occur due to formation of the threaded portion.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a device for producing an oil supply pipe and a method for producing an oil supply pipe at the time of forming a threaded portion in a metal pipe.

Solution to Problem

In order to solve the above problems, the present invention employs the following constitution.

[1] A device for producing an oil supply pipe forms a threaded portion in a metal pipe by disposing a first forming roller on an outer circumferential surface side of the metal pipe, disposing a second forming roller on an inner circumferential surface side of the metal pipe, and subjecting the metal pipe to roll forming using the first forming roller and the second forming roller. The device includes: the first forming roller having a first rotating shaft, a first circumferential surface, and one first ridge portion spirally provided in a circumferential direction on the first circumferential surface to have a length of less than one turn; and the second forming roller having a second rotating shaft, a second circumferential surface, and a second ridge portions spirally provided in the circumferential direction on the second circumferential surface, in which the first rotating shaft and the second rotating shaft are disposed so that they are parallel to each other, and the first forming roller and the second forming roller are constituted to rotate.

[2] A method for producing an oil supply pipe is a method for forming a threaded portion in a metal pipe by disposing a first forming roller on an outer circumferential surface side of the metal pipe, disposing a second forming roller on an inner circumferential surface side of the metal pipe, and subjecting the metal pipe to roll forming using the first forming roller and the second forming roller. The method includes: using, as the first forming roller, a first forming roller having a first rotating shaft, a first circumferential surface, and one first ridge portion spirally provided in a circumferential direction on the first circumferential surface to have a length of less than one turn, and as the second forming roller, a second forming roller having a second rotating shaft, a second circumferential surface, and a second ridge portion spirally provided in the circumferential direction on the second circumferential surface, a preparation step of inserting the metal pipe into the second forming roller and disposing the first rotating shaft and the second rotating shaft so that they are parallel to each other; and a formation step of forming the threaded portion formed of a spiral protrusion in an inner circumferential surface of the metal pipe by pressing a material forming the metal pipe between the second ridge portions using the first ridge portion while rotating the first forming roller and the second forming roller.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a device for producing an oil supply pipe and a method for producing an oil supply pipe in which occurrence of cracks can be prevented at the time of forming a threaded portion in an enlarged diameter portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic front view illustrating a first forming roller and a second forming roller provided on a device for producing an oil supply pipe that is an embodiment of the present invention.

FIG. 2A is a schematic front view of the first forming roller of FIG. 1 when viewed from another angle.

FIG. 2B is a schematic plan view illustrating the first forming roller.

FIG. 3 is a cross-sectional view illustrating a main part of the device for producing an oil supply pipe that is an embodiment of the present invention.

FIG. 4 is a schematic front view illustrating a main part of an oil supply pipe obtained using a production device or a production method of an embodiment of the present invention.

FIG. 5 is a schematic partial cross-sectional view illustrating a threaded portion of an oil supply pipe that is an embodiment of the present invention.

FIG. 6 is a schematic plan view for explaining the method for producing an oil supply pipe that is an embodiment of the present invention.

FIG. 7 is a diagram illustrating a main part of an oil supply pipe that is an embodiment of the present invention and is a diagram for explaining a circumferential angle θ.

FIG. 8 is a diagram for explaining the method for producing an oil supply pipe, (a) is a diagram for explaining a comparative embodiment, and (b) is a diagram for explaining this embodiment.

FIG. 9 is a schematic plan view and a schematic front view illustrating a forming roller in the related art.

FIG. 10 is a schematic front view of the forming roller in the related art of FIG. 9 when viewed from another angle.

FIG. 11 is a schematic diagram for explaining a method for forming a threaded portion using a forming roller in the related art.

DESCRIPTION OF EMBODIMENTS

A device for producing an oil supply pipe and a method for producing an oil supply pipe that are embodiments of the present invention will be described below with reference to the drawings.

(Device for Producing Oil Supply Pipe)

A device for producing an oil supply pipe in an embodiment will be described.

FIG. 1 illustrates a first forming roller and a second forming roller provided in the device for producing an oil supply pipe in the embodiment. FIG. 2A illustrates a first forming roller rotated by 90° from a state in which it is illustrated in FIG. 1 and FIG. 2B illustrates a schematic plan view of the first forming roller. In addition, FIG. 3 illustrates a cross-sectional view of a main part of the device for producing an oil supply pipe.

A device 1 for producing an oil supply pipe in this embodiment includes a first forming roller 11 and a second forming roller 21 illustrated in FIG. 1. In the first forming roller 11 and the second forming roller 21, a first rotating shaft 13 of the first forming roller 11 and a second rotating shaft 23 of the second forming roller 21 are disposed parallel to each other and the first forming roller 11 and the second forming roller 21 are disposed away from each other. Furthermore, the first rotating shaft 13 of the first forming roller 11 and the second rotating shaft 23 of the second forming roller 21 are connected to drive parts (not shown), respectively. Each of the drive parts rotates the first forming roller 11 and the second forming roller 21.

As illustrated in FIG. 1, the first forming roller 11 is composed of a first roll main body 12 and the first rotating shaft 13. The first roll main body 12 has a cylindrical shape and has a circumferential surface including a first circumferential surface 14. In addition, one of the first ridge portions 15 is provided on the first circumferential surface 14.

As illustrated in FIGS. 1, 2A, and 2B, the first ridge portions 15 are ridges protruding from the first circumferential surface 14 and are spirally disposed in a circumferential direction of the first circumferential surface 14. One end 15a and the other end 15b are provided on the first ridge portion 15 in a longitudinal direction. A length from the one end 15a to the other end 15b of the first ridge portion 15, that is, a length of the first ridge portion 15 is shorter than a length of a spiral one turn around the first circumferential surface 14. That is to say, the first ridge portion 15 is provided spirally in the circumferential direction of the first circumferential surface 14 to have a length of less than one turn.

As illustrated in FIG. 2B, when the first forming roller 11 is viewed in a plan view (when viewed in the axial direction of the first rotating shaft 13), a circumferential angle θ_o (unit: rad) between the one end 15a and the other end 15b in the longitudinal direction of the first ridge portion 15 is less than one turn (more than 0 and less than 2π (more than 0° and less than 360°)). The circumferential angle θ_o is defined as follows. In a cross section of the first roll main body 12 orthogonal to the first rotating shaft 13, the circumferential angle θ_o of the first ridge portion 15 is defined using an angle formed by two straight lines SL1 and SL2, that is, the straight line SL1 connecting the one end 15a of the first ridge portion 15 and a center 13a of the first roll main body 12 and the straight line SL2 connecting the other end 15b of the first ridge portion 15 and the center 13a of the first roll main body 12. It is preferable that the circumferential angle θ_o be s≥π (rad) or more (180° or more) and 1.5π (rad) or less (270° or less).

If the circumferential angle θ_o (unit: rad) becomes 2π or more, another portion of the first ridge portion 15 is positioned before in an axial direction the first rotating shaft 13 from the one end 15a of the first ridge portion 15. In other words, there are places on the first circumferential surface 14 in which the first ridge portions 15 are adjacent to each other. Thus, during forming of the metal pipe, different places of the first ridge portions 15 are simultaneously in contact with the metal pipe and processed. As a result of being restrained by two different places of the first ridge portions 15 at the place which has been processed simultaneously by different places of the first ridge portions 15, the metal pipe is pulled from both sides in the longitudinal direction thereof. Thus, the material is thinned and cracks starting from the thinned portion are likely to occur in the metal pipe after processing. In order to prevent such problems, the circumferential angle θ_o (unit: rad) needs to be less than 2π.

Also, as illustrated in FIG. 1, a distance in a direction of the first rotating shaft 13 between the one end 15a and the other end 15b of the first ridge portion 15 is defined as a step P_o of the first ridge portion 15. When two parallel straight lines extending in circumferential direction (leftward/rightward direction on the paper surface) while being orthogonal to the direction of the first rotating shaft 13 (upward/downward direction on the paper surface) from the one end 15a and the other end 15b of the first ridge portion 15 are drawn, the step P_o is the shortest distance between the parallel straight lines. The details of the step P_o of the first ridge portion 15 will be described later.

Furthermore, FIG. 3 illustrates a shape of the first ridge portion 15 when viewed in a cross-sectional view. The first ridge portion 15 has a base portion 15d protruding from the first circumferential surface 14 and a top portion 15c whose distal end is arcuate when viewed in a cross-section view. A radius of curvature R_o of the top portion 15c of the first ridge portion 15 will be described later.

Next, as illustrated in FIGS. 1 and 3, the second forming roller 21 is composed of a second roll main body 22 having the second rotating shaft 23 and a second circumferential surface 24 and one second ridge portion 25. As illustrated in FIG. 1, the second roll main body 22 has a cylindrical shape. An outer diameter of the second roll main body 22 is an outer diameter which is smaller than an outer diameter of the first roll main body 12. There is the second rotating shaft 23 at a center of a lower surface of the second roll main body 22. Furthermore, a circumferential surface of the second roll main body 22 is the second circumferential surface 24. One second ridge portion 25 is provided on the second circumferential surface 24.

As illustrated in FIG. 1, second ridge portions 25 are ridges protruding from the second circumferential surface 24 and are spirally disposed in the circumferential direction of the second circumferential surface 24 at a constant pitch P_i (unit: mm). A length from one end to the other end of the second ridge portion 25, that is, a length of the second ridge portion 25 is longer than a length of a spiral one turn around the second circumferential surface 24, for example, a length of three turns. That is to say, the second ridge portion 25 is spirally provided over one or more perimeters on the second circumferential surface 24. Details of a distance between adjacent second ridge portions 25, that is, a pitch P_i (unit: mm) will be described later.

FIG. 3 illustrates a shape of the second ridge portion 25 when viewed in a cross-sectional view. The second ridge portion 25 has a base portion 25d protruding from the second circumferential surface 24 and a top portion 25c whose distal end is arcuate when viewed in a cross-sectional view. A radius of curvature R_i of the top portion 25c of the second ridge portion 25 will be described later.

Also, as relative positions of the first forming roller 11 and the second forming roller 21 in a direction of each rotating shaft, as illustrated in FIG. 3, it is preferable to adjust the relative positions of the first forming roller 11 and the second forming roller 21 so that the first ridge portions 15 are positioned between the second ridge portions 25.

(Method for Producing Oil Supply Pipe)

A method for producing an oil supply pipe in this embodiment will be described below.

First, a metal pipe 2 to be processed by the method for producing an oil supply pipe in this embodiment will be described. The oil supply pipe is, for example, a fuel oil supply pipe through which a fuel is injected into a fuel tank of an automobile. The oil supply pipe has a pipe main body and an enlarged pipe portion provided on one end side of the pipe main body. The other end of the pipe main body is configured to be connected to the fuel tank. An oil supply port is provided in the enlarged pipe portion. A threaded portion which protrudes spirally is provided inside the enlarged pipe portion. Such an oil supply pipe is produced by increasing a diameter the one end side of the base pipe to form the enlarged pipe portion and forming a circumferential wall surface of the enlarged pipe portion to form a threaded portion.

The metal pipe 2 to be processed in the production method in this embodiment is the enlarged pipe portion obtained by increasing the diameter of the one end side of the base pipe. Metal materials such as ordinary steel and stainless steel can be exemplified as a material of the metal pipe 2 (the enlarged pipe portion). Furthermore, in this embodiment, a threaded portion 3 is formed in the metal pipe 2 (the enlarged pipe portion) through a production method which will be described later.

FIG. 4 illustrates an exterior form of the oil supply pipe obtained through the production device and the production method of this embodiment, that is, the metal pipe 2 having the threaded portion 3. A spiral groove portion 3a is formed in an outer circumferential surface 2a of the metal pipe 2 illustrated in FIG. 4. Furthermore, FIG. 5 illustrates a schematic partial cross-sectional view for explaining the threaded portion 3 of the metal pipe 2. A depth of the spiral groove portion 3a formed on the outer circumferential surface 2a side is deeper than a wall thickness t (unit: mm) of the metal pipe 2. Thus, a spiral protrusion 4 corresponding to the spiral groove portion 3a is provided on an inner circumferential surface 2b of the metal pipe 2. The threaded portion 3 is formed using the spiral protrusion 4.

The details of a radius of curvature R (unit: mm) of a top portion 4c of the protrusion 4 constituting the threaded portion 3 and a height h (unit: mm) of the protrusion 4 will be described later. A total length of the spiral protrusion 4 (groove portion 3a) is longer than a length of one turn of the outer circumferential surface 2a of the metal pipe 2. A distance between the adjacent spiral protrusions 4, that is, a pitch P (unit: mm) of the threaded portion 3 will be described later.

In the method for producing an oil supply pipe in this embodiment, a preparation step and a formation step are sequentially performed. Each of the steps will be described in detail below.

In the preparation step, the metal pipe 2 is inserted into the second forming roller 21. In addition, the forming rollers 11 and 21 are disposed so that the first rotating shaft 13 and the second rotating shaft 23 are parallel. That is to say, the first forming roller 11 is disposed on the outer circumferential surface 2a side of the metal pipe 2 and the second forming roller 21 is disposed on the inner circumferential surface 2b side of the metal pipe 2. Furthermore, as illustrated in FIG. 3, relative positions of the first forming roller 11 and the second forming roller 21 are adjusted so that the first ridge portion 15 of the first forming roller 11 is located between the second ridge portions 25 of the second forming roller 21.

FIG. 6 illustrates a state in which the metal pipe 2 is inserted into the second forming roller 21 and the first forming roller 11 is disposed on the outer circumferential surface 2a side of the metal pipe 2 in the preparation step. The inner circumferential surface 2b of the metal pipe 2 is disposed to be opposite to the second forming roller 21. On the other hand, the outer circumferential surface 2a of the metal pipe 2 is disposed to be opposite to the first forming roller 11. An outer diameter in which the second ridge portions 25 of the second forming roller 21 are included is approximately the same size as an inner diameter of the metal pipe 2 or slightly smaller than the inner diameter of the metal pipe 2.

Subsequently, in the formation step, the metal pipe 2 is subjected to roll forming by pressing a material forming the metal pipe 2 between the second ridge portions 25 aligned in parallel on the second circumferential surface 24 of the second forming roller 21 using the first ridge portion 15 while rotating the first forming roller 11 and the second forming roller 21.

In the formation step, finally, the first forming roller 11 and the second forming roller 21 are rotated in directions opposite to each other while pressing the material of the metal pipe 2 to the second forming roller 21 side using the first ridge portion 15 in a state in which the one end 15a of the first ridge portion 15 is brought into contact with the outer circumferential surface 2a of the metal pipe 2. The metal pipe 2 rotates in the same direction of rotation as the direction of rotation of the second forming roller 21. Furthermore, the metal pipe 2 is pressed in sequence between the second ridge portions 25 using the first ridge portion 15 by rotating the first forming roller 11 while pressing the first ridge portion 15 to the outer circumferential surface 2a. The pressing of the metal pipe 2 using the first ridge portion 15 continues until the other end 15b of the first ridge portion 15 is in contact with the metal pipe 2. Thus, the spiral groove portion 3a is formed in the outer circumferential surface 2a of the metal pipe 2. An amount of pressing of the first ridge portion 15 is larger than the wall thickness t of the metal pipe 2. As a result, the threaded portion 3 formed of the spiral protrusion 4 is formed in the inner circumferential surface 2b of the metal pipe 2. Here, although a case in which the first forming roller 11 and the second forming roller 21 are rotated in opposite directions has been described as an example, the present invention is not limited thereto. In addition, they may be rotated in the same direction in some cases.

In the spiral protrusion 4 (groove portion 3a) forming the threaded portion 3, as illustrated in FIG. 7, a circumferential angle θ (unit: rad) from one end 4a to the other end 4b exceeds 2π (exceeds 360°). An upper limit of the circumferential angle θ may be 380° or less or 370° or less. The circumferential angle θ is defined as follows. The circumferential angle θ of the spiral protrusion 4 forming the threaded portion 3 is defined by an angle formed by two straight lines SL3 and SLA, that is, a straight line SL3 connecting the one end 4a of the protrusion 4 and a center of the metal pipe 2 and a straight line SL4 connecting the other end 4b of the protrusion 4 and a center of the metal pipe 2 in a cross section orthogonal to the longitudinal direction of the metal pipe 2.

FIG. 8 illustrates a method for forming a threaded portion of a comparative embodiment and a method for forming a threaded portion of this embodiment.

In the formation method of the comparative embodiment illustrated in FIG. 8(a), a forming roller 301 illustrated in FIG. 9 is used as a first forming roller. Two first ridge portions 301a and 301b are provided on a first circumferential surface 314 of the first forming roller 301. Thus, at the time of forming the metal pipe 2, processing is performed in a state in which the two first ridge portions 301a and 301b are simultaneously in contact with the metal pipe 2 at a place in which the first ridge portions 301a and 301b are adjacent. As a result of constraining the material at the two places, that is, the adjacent first ridge portions 301a and 301b, the metal pipe 2 is pulled from both in the longitudinal direction thereof at a place which has been subjected to processing simultaneously using the two first ridge portions 301a and 301b. Thus, the material is thinned and cracks are likely to occur in the metal pipe 2 after processing starting from the thinned portion.

On the other hand, in the formation method of this embodiment illustrated in FIG. 8(b), the first forming roller 11 illustrated in FIG. 1 is used. One of the first ridge portions 15 is provided on a first outer circumferential surface 14 of the first forming roller 11 in a spiral shape in the circumferential direction to have a length of less than one turn. Thus, at the time of forming the metal pipe 2, the one end 15a of the first ridge portion 15 is first in contact with the metal pipe 2 and the other end 15b is finally in contact with the metal pipe 2. That is to say, the metal pipe 2 is not processed using different parts of the first ridge portion 15 at the same time. For this reason, the stress applied to the metal pipe 2 during processing is reduced and an amount of thinning of the material can be reduced compared to the comparative embodiment. Thus, generation of cracks is prevented. Therefore, even when the metal pipe 2 is made of stainless steel which is more prone to cracking than ordinary steel, cracking due to the formation of the threaded portion 3 can be prevented.

A more preferable form of the method for producing an oil supply pipe of this embodiment will be described below.

In the above embodiment, in the formation step, it is preferable to adjust rotational speeds of the first forming roller 11 and the second forming roller 21 so that an absolute value v (=|v_o/v_i|) of a ratio between a rotational speed v_o (unit: rad/second) of the first forming roller 11 and a rotational speed vi (unit: rad/second) of the second forming roller 21 satisfies the following Expression (1). Thus, as illustrated in FIG. 3, a clearance C between the first ridge portion 15 and the second ridge portion 25 is neither excessively large nor excessively small, preventing the metal pipe 2 from breaking at the time of forming the groove portion 3a.

$\begin{array}{cc}{\theta }_o/\theta \ge v\ge \left({\theta }_o/\left(P\theta \right)\right)·\left(2R+t/2\right)& \left(1\right)\end{array}$

In the foregoing Expression (1), θ (unit: rad) is a circumferential angle from the one end 4a to the other end 4b in the longitudinal direction of the spiral protrusion 4 forming the threaded portion 3, θ_o (unit: rad) is a circumferential angle from the one end 15a to the other end 15b in the longitudinal direction of the first ridge portion 15, R (unit: mm) is a radius of curvature (unit: mm) of the top portion 4c of the spiral protrusion 4, t (unit: mm) is a wall thickness of the metal pipe 2, and P is a pitch (unit: mm) of the threaded portion 3.

Also, with regard to the wall thickness t (unit: mm) of the metal pipe 2, it is preferable that a radius of curvature R_i (unit: mm) of a top portion 25a of the second ridge portion 25 be within a range in which the following Expression (2) is satisfied.

$\begin{array}{cc}{R}_i\ge \left(3/4\right)·t& \left(2\right)\end{array}$

In addition, with regard to the wall thickness t (unit: mm) of the metal pipe 2 and the radius of curvature R (unit: mm) of the top portion 4c of the spiral protrusion 4, it is preferable that a radius of curvature R_O (unit: mm) of the top portion 15c of the first ridge portion 15 be within a range in which the following Expression (3) is satisfied.

$\begin{array}{cc}{R}_o\ge R-2t& \left(3\right)\end{array}$

Moreover, with regard to the wall thickness t (unit: mm) of the metal pipe 2, it is preferable that the clearance C (unit: mm) between the first ridge portion 15 and the second ridge portion 25 be within a range in which the following Expression (4) is satisfied.

$\begin{array}{cc}C\ge \left(3/2\right)·t& \left(4\right)\end{array}$

When Expressions (2) to (4) are satisfied, the clearance C between the first ridge portion 15 and the second ridge portion 25 does not become extremely large or extremely small and the metal pipe 2 is prevented from breaking at the time of forming the groove portion 3a.

Also, a shape of the first ridge portion 15 is determined using a design value of the spiral protrusion 4 to be formed. Therefore, a step P_o of the first ridge portion 15 may be set so that the following Expression (5) is satisfied. Furthermore, it is preferable that a length r_oθ_o of the first ridge portion 15 when the first forming roller 11 is viewed from in a plan view (refer to FIG. 2B) be set so that the following Expression (6) is satisfied.

$\begin{array}{cc}{P}_o=\left(\theta /2\pi \right)·P& \left(5\right)\end{array}$ $\begin{array}{cc}\left(\theta /2\right)·\left(D-2h+4t\right)\ge r_o{\theta }_o\ge \left(\theta /2\right)·\left(D-2h+t\right)& \left(6\right)\end{array}$

In Expressions (5) and (6), θ is a circumferential angle (unit: rad) from the one end 4a to the other end 4b in the longitudinal direction of the spiral protrusion 4 forming the threaded portion 3. Furthermore, in Expression (5), P is a pitch (unit: mm) of the threaded portion 3. In addition, in Expression (6), D is an outer diameter (unit: mm) of the metal pipe 2, h is a height (unit: mm) of the spiral protrusion 4, t is a wall thickness of the metal pipe 2, θ_o (unit: rad) is a circumferential angle (unit: rad) from the one end 15a to the other end 15b of the first ridge portion 15 at a center of the first roll main body 12, and r_o is a straight line distance from the center of the first roll main body 12 to the first circumferential surface 14, that is, a radius (unit: mm) of the first roll main body 12.

Also, it is preferable that the pitch P_i of the second ridge portion 25 be set so that the following Expression (7) is satisfied on the basis of the design value of the spiral protrusion 4 (threaded portion 3) to be formed, the shape of the first ridge portion 15, and the rotational speeds of the first forming roller 11 and the second forming roller 21.

$\begin{array}{cc}{P}_i=\left(\theta /{\theta }_o\right)·\mathrm{vP}& \left(7\right)\end{array}$

In Expression (7), θ is a circumferential angle (unit: rad) from the one end 4a to the other end 4b in the longitudinal direction of the spiral protrusion 4 forming the threaded portion 3. θ_o (unit: rad) is a circumferential angle (unit: rad) from the one end 15a to the other end 15b of the first ridge portion 15 in the first roll main body 12. v is an absolute value (|v_o/v_i|) of a ratio between a rotational speed v_o (unit: rad/second) of the first forming roller 11 and a rotational speed v_i (unit: rad/second) of the second forming roller 21. P is a pitch (unit: mm) of the threaded portion 3.

As described above, according to the device 1 for producing an oil supply pipe of this embodiment, the first forming roller 11 is disposed on the outer circumferential surface 2a side of the metal pipe 2 and only one of the first ridge portions 15 spirally provided to have a length of less than one turn is provided on the first forming roller 11. Therefore, at the time of processing the metal pipe 2, the one end 15a and the other end 15b in the longitudinal direction of the first ridge portion 15 is not in contact with the metal pipe 2 at the same time. Thus, there is no concern that the material of the metal pipe 2 will be significantly thinned as in the related art. This prevents the metal pipe 2 from cracking.

Also, according to the method for producing an oil supply pipe of this embodiment, the threaded portion 3 is formed by processing the material forming the metal pipe 2 using one of the first ridge portions 15 spirally provided to have a length of less than one turn in the formation step. Therefore, the strain applied to the threaded portion 3 can be reduced compared to the method in the related art, thereby more reliably preventing the occurrence of cracks.

Particularly, even when the material of the enlarged diameter portion (metal pipe 2) is subjected to work hardening when the enlarged diameter portion obtained by increasing the diameter of the base pipe (for example, increasing the diameter by 1.5 times or more from the original diameter) is the metal pipe 2, as in this embodiment, the thinning of the metal pipe material during the formation of the threaded portion 3 can be reduced. Thus, the occurrence of cracks due to the formation of the threaded portion 3 can be prevented.

REFERENCE SIGNS LIST

• • 1 Method for producing oil supply pipe
  • 11 First forming roller
  • 12 First roll main body
  • 13 First rotating shaft
  • 14 First circumferential surface
  • 15 First ridge portion
  • 15 a One end
  • 15 b Other end
  • 15 c Top portion
  • 21 Second forming roller
  • 22 Second roll main body
  • 23 Second rotating shaft
  • 24 Second circumferential surface
  • 25 Second ridge portion
  • 25 a Top portion
  • 2 Metal pipe
  • 2 a Outer circumferential surface
  • 2 b Inner circumferential surface
  • 3 Threaded portion
  • 4 Spiral protrusion
  • 4 a One end
  • 4 b Other end
  • 4 c Top portion

Claims

1. A device for producing an oil supply pipe which forms a threaded portion in a metal pipe by disposing a first forming roller on an outer circumferential surface side of the metal pipe, disposing a second forming roller on an inner circumferential surface side of the metal pipe, and subjecting the metal pipe to roll forming using the first forming roller and the second forming roller, the device comprising: the first forming roller having a first rotating shaft, a first circumferential surface, and one first ridge portion spirally provided in a circumferential direction on the first circumferential surface to have a length of less than one turn; andthe second forming roller having a second rotating shaft, a second circumferential surface, and a second ridge portions spirally provided in the circumferential direction on the second circumferential surface,wherein the first rotating shaft and the second rotating shaft are disposed so that they are parallel to each other, andthe first forming roller and the second forming roller are constituted to rotate.

2. A method for producing an oil supply pipe which is a method for forming a threaded portion in a metal pipe by disposing a first forming roller on an outer circumferential surface side of the metal pipe, disposing a second forming roller on an inner circumferential surface side of the metal pipe, and subjecting the metal pipe to roll forming using the first forming roller and the second forming roller, the method comprising: using, as the first forming roller, the first forming roller having a first rotating shaft, a first circumferential surface, and one first ridge portion spirally provided in a circumferential direction on the first circumferential surface to have a length of less than one turn, andas the second forming roller, the second forming roller having a second rotating shaft, a second circumferential surface, and a second ridge portion spirally provided in the circumferential direction on the second circumferential surface,a preparation step of inserting the metal pipe into the second forming roller and disposing the first rotating shaft and the second rotating shaft so that they are parallel to each other; anda formation step of forming the threaded portion formed of a spiral protrusion in an inner circumferential surface of the metal pipe by pressing a material forming the metal pipe between the second ridge portions using the first ridge portion while rotating the first forming roller and the second forming roller.