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.

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; 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, wherein 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 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, and as 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; 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.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0014] 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.

[0015] FIG. 2A is a schematic front view of the first forming roller of FIG. 1 when viewed from another angle.

[0016] FIG. 2B is a schematic plan view illustrating the first forming roller.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 ?.

[0022] 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.

[0023] FIG. 9 is a schematic plan view and a schematic front view illustrating a forming roller in the related art.

[0024] FIG. 10 is a schematic front view of the forming roller in the related art of FIG. 9 when viewed from another angle.

[0025] 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

[0026] 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)

[0027] A device for producing an oil supply pipe in an embodiment will be described.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 ?.sub.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 2? (more than 0? and less than 360?)). The circumferential angle ?.sub.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 ?.sub.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 ?.sub.o be s?? (rad) or more (180? or more) and 1.5? (rad) or less (270? or less).

[0033] If the circumferential angle ?.sub.o (unit: rad) becomes 2? 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 ?.sub.o (unit: rad) needs to be less than 2?.

[0034] 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.sub.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.sub.o is the shortest distance between the parallel straight lines. The details of the step P.sub.o of the first ridge portion 15 will be described later.

[0035] 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.sub.o of the top portion 15c of the first ridge portion 15 will be described later.

[0036] 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.

[0037] 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.sub.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.sub.i (unit: mm) will be described later.

[0038] 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.sub.i of the top portion 25c of the second ridge portion 25 will be described later.

[0039] 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)

[0040] A method for producing an oil supply pipe in this embodiment will be described below.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In the spiral protrusion 4 (groove portion 3a) forming the threaded portion 3, as illustrated in FIG. 7, a circumferential angle ? (unit: rad) from one end 4a to the other end 4b exceeds 2? (exceeds 360?). An upper limit of the circumferential angle ? may be 380? or less or 370? or less. The circumferential angle ? is defined as follows. The circumferential angle ? 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] A more preferable form of the method for producing an oil supply pipe of this embodiment will be described below.

[0055] 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.sub.o/v.sub.i|) of a ratio between a rotational speed v.sub.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.

[00001]$\begin{array}{cc}{?}_o/??v?\left({?}_o/\left(P?\right)\right).Math.\left(2R+t/2\right)& \left(1\right)\end{array}$

[0056] In the foregoing Expression (1), ? (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, ?.sub.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.

[0057] Also, with regard to the wall thickness t (unit: mm) of the metal pipe 2, it is preferable that a radius of curvature R.sub.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.

[00002]$\begin{array}{cc}{R}_i?\left(3/4\right).Math.t& \left(2\right)\end{array}$

[0058] 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.sub.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.

[00003]$\begin{array}{cc}{R}_o?R-2t& \left(3\right)\end{array}$

[0059] 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.

[00004]$\begin{array}{cc}C?\left(3/2\right).Math.t& \left(4\right)\end{array}$

[0060] 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.

[0061] 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.sub.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.sub.o?.sub.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.

[00005]$\begin{array}{cc}{P}_o=\left(?/2?\right).Math.P& \left(5\right)\end{array}$$\begin{array}{cc}\left(?/2\right).Math.\left(D-2h+4t\right)?r_o{?}_o?\left(?/2\right).Math.\left(D-2h+t\right)& \left(6\right)\end{array}$

[0062] In Expressions (5) and (6), ? 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, ?.sub.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.sub.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.

[0063] Also, it is preferable that the pitch P.sub.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.

[00006]$\begin{array}{cc}{P}_i=\left(?/{?}_o\right).Math.\mathrm{vP}& \left(7\right)\end{array}$

[0064] In Expression (7), ? 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. ?.sub.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.sub.o/v.sub.i|) of a ratio between a rotational speed v.sub.o (unit: rad/second) of the first forming roller 11 and a rotational speed v.sub.i (unit: rad/second) of the second forming roller 21. P is a pitch (unit: mm) of the threaded portion 3.

[0065] 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.

[0066] 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.

[0067] 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

[0068] 1 Method for producing oil supply pipe [0069] 11 First forming roller [0070] 12 First roll main body [0071] 13 First rotating shaft [0072] 14 First circumferential surface [0073] 15 First ridge portion [0074] 15a One end [0075] 15b Other end [0076] 15c Top portion [0077] 21 Second forming roller [0078] 22 Second roll main body [0079] 23 Second rotating shaft [0080] 24 Second circumferential surface [0081] 25 Second ridge portion [0082] 25a Top portion [0083] 2 Metal pipe [0084] 2a Outer circumferential surface [0085] 2b Inner circumferential surface [0086] 3 Threaded portion [0087] 4 Spiral protrusion [0088] 4a One end [0089] 4b Other end [0090] 4c Top portion