WO2018097043A1

WO2018097043A1 - Metal fitting, rolling die, and method for forming male thread

Info

Publication number: WO2018097043A1
Application number: PCT/JP2017/041386
Authority: WO
Inventors: 慎泰長谷川
Original assignee: 日本特殊陶業株式会社
Priority date: 2016-11-25
Filing date: 2017-11-17
Publication date: 2018-05-31
Also published as: DE112017005987T5; CN110023003B; JP2018085265A; CN110023003A; JP6345222B2

Abstract

Through the present invention, a male thread is appropriately formed. A thread part provided to a cylindrical metal fitting according to the present invention includes a first thread formation portion and a second thread formation portion. The thickness of the second thread formation portion in a groove bottom thereof is greater than the thickness of the first thread formation portion in a groove bottom thereof. The thread height in the first thread formation portion is less than the thread height in the second thread formation portion. A roll forming die according to the present invention has a roll forming part including a groove part and a crest part. The groove depth in a first thread roll-forming portion of the roll forming part for forming a male thread in a first metal fitting portion where a metal fitting is thin is less than the groove depth in a second thread roll-forming portion in the roll forming part for forming a male thread in a second metal fitting portion where the metal fitting is thick. The metal fitting is caused to roll in relative fashion along the roll forming part in a state in which the roll forming die such as described above is pressed against the metal fitting, and a male thread is thereby formed in the metal fitting.

Description

Metal fittings, rolling dies, male thread forming method

The present specification relates to a technique for forming a male screw on a metal fitting.

Conventionally, cylindrical metal fittings are used in various devices such as a spark plug, a glow plug, and a sensor (for example, an oxygen concentration sensor). The fitting is formed with a male screw to be screwed into a female screw of a mounting hole (for example, a mounting hole provided in the internal combustion engine).

Japanese Patent Laying-Open No. 2015-141781

The male screw may be formed over a plurality of portions having different thicknesses in the metal fitting. When such a male screw is formed, a problem may occur. For example, a small unevenness may be formed on the top of the screw thread where the thickness is thin. This is because the thin portion can be greatly deformed toward the central axis, so that an amount of material necessary for forming the screw thread cannot be secured and an inappropriate screw thread is formed. *

The present specification discloses a technique capable of appropriately forming a male screw.

This specification discloses the following application examples, for example. *

[Application Example 1] A cylindrical metal fitting extending in the direction of the axis, and having a screw portion that is a portion in which an external thread extending in the direction of the axis is formed on the outer peripheral surface, and the screw portion is the screw portion The first screw forming portion, which is a part of the entire range, and the first screw forming portion are different in position in the direction of the axis, and the inside of the groove bottom of the male screw and the bracket A second screw forming portion having a groove thickness that is a thickness in a direction perpendicular to the axis between the first screw forming portion and a peripheral surface, and a second screw forming portion that is thicker than a groove thickness in the first screw forming portion. The screw height, which is the height from the groove bottom to the peak of the male screw, is smaller than the screw height at the second screw forming portion. *

According to this configuration, since the amount of material required for forming the thread of the first screw forming portion is small, the male screw of the thin first screw forming portion and the male screw of the thick second screw forming portion are Appropriately formed. *

[Application Example 2] The metal fitting according to Application Example 1, wherein a radius of curvature of the top of the male screw of the first screw forming portion is larger than a curvature radius of the top of the male screw of the second screw forming portion. Big, metal fittings. *

According to this configuration, the male screw of the thin first screw forming portion and the male screw of the thick second screw forming portion can be appropriately formed. *

Application Example 3 The outer peripheral surface of the first metal part of the cylindrical metal part extending in the direction of the axis and the first metal part have different positions in the direction of the axis, and the thickness in the direction perpendicular to the axis. A rolling die for forming a male screw extending in the direction of the axis on the outer peripheral surface of the second metal part with a thickness that is greater than the thickness of the first metal part, The rolling die has a rolling part including a groove part for forming a thread groove of the male screw and a thread part for forming a screw groove of the male screw, and among the rolling parts The groove depth, which is the depth from the top of the peak portion to the bottom of the groove portion at the first thread rolling portion that forms the male screw in the first metal fitting portion, is the second of the rolling portions. Rolling dies that are smaller than the groove depth at the second thread rolling part that forms the male screw in the metal part. *

According to this configuration, since the amount of material necessary for forming the thread of the first metal part is smaller than the amount of material necessary for forming the screw of the second metal part, the male part of the thin first metal part is The screw and the male screw of the thick second metal part can be appropriately formed. *

[Application Example 4] The rolling die according to Application Example 3, wherein the curvature radius of the bottom of the groove portion of the first thread rolling portion is the curvature radius of the bottom of the groove portion of the second thread rolling portion. Bigger than rolling dies. *

According to this configuration, the male screw of the thin first metal part and the male screw of the thick second metal part can be appropriately formed. *

[Application Example 5] A forming method of forming a male screw extending in the direction of the axis on the outer peripheral surface of a cylindrical metal fitting extending in the direction of the axis, wherein the portion of the metal fitting in which the male screw is formed is the male The first metal part, which is a part of a part of the entire range of the part where the screw is formed, differs from the first metal part in the direction of the axis and in a direction perpendicular to the axis. A second metal part having a thickness that is greater than a thickness of the first metal part, and the forming method includes the first screw rolling of the rolling die according to Application Example 3 or 4. Pressing the molded part against the first metal part of the metal fitting and the second thread rolling part of the rolling die against the second metal part of the metal fitting, respectively, Pressed against the first metal part, The first metal part and the second metal part are rotated by relatively rotating the metal parts along the rolling part of the rolling die in a state where the thread rolling part is pressed against the second metal part. Forming the male screw on a portion, and a forming method. *

According to this structure, a male screw can be appropriately formed in the first metal part and the second metal part. *

The technology disclosed in the present specification can be realized in various modes. For example, a metal fitting, a rolling die, a method of forming a male screw on a metal fitting using a rolling die, and a spark provided with the metal fitting. It can be realized in the form of a plug, a glow plug having a metal fitting, a sensor having a metal fitting, and the like.

It is sectional drawing of the ignition plug 100 as one Embodiment provided with a metal fitting. 3 is a flowchart showing an example of a method for forming a threaded portion 57 of the metal shell 50. FIG. 6 is a schematic view of formation of a screw portion 57. It is the schematic which shows a mode that a screw part is formed. It is the schematic of the reference example of the rolling die and the thread part formed in the metal shell. It is the schematic of embodiment with the rolling die and the thread part formed in a main metal fitting.

A. Embodiment: A-1. Configuration of Spark Plug 100: FIG. 1 is a cross-sectional view of a spark plug 100 (also referred to as a spark plug 100) as an embodiment including a metal fitting. In the drawing, a center axis CL (also referred to as “axis line CL”) of the spark plug 100 and a flat cross section including the center axis CL of the spark plug 100 are shown. Hereinafter, the direction parallel to the central axis CL is also referred to as “direction of the axis CL”, or simply “axis direction” or “front-rear direction”. A direction perpendicular to the axis CL is also referred to as a “radial direction”. The circumferential direction of the circle centered on the axis CL is also referred to as “circumferential direction”. Of the directions parallel to the central axis CL, the lower direction in FIG. 1 is referred to as the front end direction Df or the front direction Df, and the upper direction is also referred to as the rear end direction Dfr or the rear direction Dfr. The tip direction Df is a direction from the terminal fitting 40 described later toward the center electrode 20. 1 is referred to as the front end side of the spark plug 100, and the rear end direction Dfr side in FIG. 1 is referred to as the rear end side of the spark plug 100. *

The spark plug 100 includes a cylindrical insulator 10 having a through-hole 12 (also referred to as a shaft hole 12) extending along the axis CL, a center electrode 20 held on the tip side of the through-hole 12, and the through-hole 12. The terminal metal fitting 40 held on the rear end side, the resistor 73 disposed between the center electrode 20 and the terminal metal fitting 40 in the through-hole 12, and the center electrode 20 and the resistor 73 are brought into contact with these. A conductive first seal portion 72 that electrically connects the

members

20 and 73, and a conductive second seal that contacts the resistor 73 and the terminal fitting 40 to electrically connect the

members

73 and 40. Part 74, cylindrical metal shell 50 fixed to the outer peripheral side of insulator 10, one end is joined to front end surface 55 of metal shell 50, and the other end faces center electrode 20 through gap g. And a ground electrode 30 arranged in this manner. *

A large-diameter portion 14 having the largest outer diameter is formed at the approximate center in the axial direction of the insulator 10. A rear end side body portion 13 is formed on the rear end side from the large diameter portion 14. A front end side body portion 15 having an outer diameter smaller than that of the rear end side body portion 13 is formed on the front end side of the large diameter portion 14. A further reduced diameter portion 16 and a leg portion 19 are formed in this order toward the distal end side further on the distal end side than the distal end side body portion 15. The outer diameter of the reduced outer diameter portion 16 gradually decreases toward the front direction Df. In the vicinity of the reduced outer diameter portion 16 (in the example of FIG. 1, the front end side body portion 15), a reduced inner diameter portion 11 is formed in which the inner diameter gradually decreases in the front direction Df. The insulator 10 is preferably formed in consideration of mechanical strength, thermal strength, and electrical strength. For example, the insulator 10 is formed by firing alumina (other insulating materials can also be used). is there). *

The center electrode 20 is a metal member, and is disposed at the end on the front direction Df side in the through hole 12 of the insulator 10. The center electrode 20 has a substantially cylindrical rod portion 28 and a first tip 29 joined to the tip of the rod portion 28 (for example, laser welding). The rod portion 28 includes a head portion 24 that is a portion on the rear direction Dfr side, and a shaft portion 27 that is connected to the front direction Df side of the head portion 24. The shaft portion 27 extends in the forward direction Df parallel to the axis line CL. A portion on the front direction Df side of the head portion 24 forms a flange portion 23 having an outer diameter larger than the outer diameter of the shaft portion 27. The surface on the front direction Df side of the flange portion 23 is supported by the reduced inner diameter portion 11 of the insulator 10. The shaft portion 27 is connected to the front direction Df side of the flange portion 23. The first chip 29 is joined to the tip of the shaft portion 27. Note that the first chip 29 may be omitted. *

The rod portion 28 includes an outer layer 21 and a core portion 22 disposed on the inner peripheral side of the outer layer 21. The outer layer 21 is formed of a material (for example, an alloy containing nickel as a main component) that has better oxidation resistance than the core portion 22. Here, the main component means a component having the highest content rate (weight percent (wt%)). The core portion 22 is formed of a material having higher thermal conductivity than the outer layer 21 (for example, pure copper, an alloy containing copper as a main component, etc.). The first chip 29 is formed using a material (for example, a noble metal such as iridium (Ir) or platinum (Pt)) that is more durable against discharge than the shaft portion 27. A part of the center electrode 20 on the tip side including the first tip 29 is exposed from the shaft hole 12 of the insulator 10 to the front direction Df side. The core portion 22 may be omitted. *

The terminal fitting 40 is a rod-shaped member extending in parallel with the axis CL. The terminal fitting 40 is formed using a conductive material (for example, a metal containing iron as a main component). The terminal fitting 40 includes a cap mounting portion 49, a flange portion 48, and a shaft portion 41, which are arranged in order in the front direction Df. The shaft portion 41 is inserted into a portion on the rear direction Dfr side of the shaft hole 12 of the insulator 10. The cap mounting portion 49 is exposed outside the shaft hole 12 on the rear end side of the insulator 10. *

In the shaft hole 12 of the insulator 10, a resistor 73 for suppressing electrical noise is disposed between the terminal fitting 40 and the center electrode 20. The resistor 73 is formed using a conductive material (for example, a mixture of glass, carbon particles, and ceramic particles). A first seal portion 72 is disposed between the resistor 73 and the center electrode 20, and a second seal portion 74 is disposed between the resistor 73 and the terminal fitting 40. These

seal portions

72 and 74 are formed using a conductive material (for example, a mixture of metal particles and the same glass as that included in the material of the resistor 73). The center electrode 20 is electrically connected to the terminal fitting 40 by the first seal portion 72, the resistor 73, and the second seal portion 74. *

The metal shell 50 is a cylindrical member having a through hole 59 extending along the axis CL. The insulator 10 is inserted into the through hole 59 of the metal shell 50, and the metal shell 50 is fixed to the outer periphery of the insulator 10. The metal shell 50 is formed using a conductive material (for example, a metal such as carbon steel containing iron as a main component). A part of the insulator 10 on the front direction Df side is exposed outside the through hole 59. Further, a part of the insulator 10 on the rear direction Dfr side is exposed outside the through hole 59. *

The metal shell 50 has a tool engaging part 51 and a body part 52. The tool engaging portion 51 is a portion into which a spark plug wrench (not shown) is fitted. The trunk portion 52 is a portion including the front end surface 55 of the metal shell 50. On the outer peripheral surface of the body portion 52, a screw portion 57 for screwing into a mounting hole of an internal combustion engine (for example, a gasoline engine) is formed. The screw portion 57 is a portion where a male screw extending in the direction of the axis line CL is formed, and has a spiral thread and a spiral thread groove (not shown).

On the outer peripheral surface between the tool engaging portion 51 and the body portion 52 of the metal shell 50, a flange-shaped flange portion 54 protruding outward in the radial direction is formed. An annular gasket 90 is disposed between the threaded portion 57 and the flange portion 54 of the body portion 52. The gasket 90 is formed by, for example, bending a metal plate member, and is crushed and deformed when the spark plug 100 is attached to the engine. Due to the deformation of the gasket 90, the gap between the spark plug 100 (specifically, the surface on the front direction Df side of the flange portion 54) and the engine is sealed, and leakage of combustion gas is suppressed. The gasket 90 may be omitted. In this case, the flange portion 54 may directly contact a portion (for example, an engine head) that forms a mounting hole for the spark plug 100 of the engine. *

The body portion 52 of the metal shell 50 is formed with a reduced inner diameter portion 56 whose inner diameter gradually decreases toward the distal end side. The front end side packing 8 is sandwiched between the reduced inner diameter portion 56 of the metal shell 50 and the reduced outer diameter portion 16 of the insulator 10. In this embodiment, the front end side packing 8 is, for example, a plate ring made of iron (other materials (for example, metal materials such as copper) can also be used). *

A thin caulking portion 53 is formed on the rear end side of the metal shell 50 from the tool engaging portion 51. Further, a thin buckled portion 58 is formed between the flange portion 54 and the tool engaging portion 51.

Annular ring members

61 and 62 are inserted between the inner peripheral surface of the metal shell 50 from the tool engaging portion 51 to the caulking portion 53 and the outer peripheral surface of the rear end side body portion 13 of the insulator 10. ing. Further, the talc 70 powder is filled between the

ring members

61 and 62. In the manufacturing process of the spark plug 100, when the crimping portion 53 is bent inward and crimped, the buckling portion 58 is deformed outward (buckling) with the addition of compressive force, and as a result, the metal shell 50 And the insulator 10 are fixed. The talc 70 is compressed during the caulking process, and the airtightness between the metal shell 50 and the insulator 10 is improved. The packing 8 is pressed between the reduced outer diameter portion 16 of the insulator 10 and the reduced inner diameter portion 56 of the metal shell 50, and seals between the metal shell 50 and the insulator 10. *

The ground electrode 30 is a metal member, and includes a rod-shaped main body portion 37 and a second chip 39 attached to the distal end portion 34 of the main body portion 37. The other end portion 33 (also referred to as a base end portion 33) of the main body portion 37 is joined to the distal end surface 55 of the metal shell 50 (for example, resistance welding). The main body portion 37 extends from the base end portion 33 joined to the metal shell 50 in the distal direction Df, bends toward the central axis CL, and reaches the distal end portion 34. The second tip 39 is fixed to a portion on the rear direction Dfr side of the tip portion 34 (for example, laser welding). The second tip 39 of the ground electrode 30 and the first tip 29 of the electrode 20 form a gap g. That is, the second tip 39 of the ground electrode 30 is disposed on the front direction Df side of the first tip 29 of the center electrode 20 and is opposed to the first tip 29 via the gap g. The second chip 39 is formed using a material (for example, a noble metal such as iridium (Ir) or platinum (Pt)) that is more durable against discharge than the main body portion 37. Note that the second chip 39 may be omitted. *

The main body portion 37 includes an outer layer 31 and an inner layer 32 disposed on the inner peripheral side of the outer layer 31. The outer layer 31 is made of a material (for example, an alloy containing nickel as a main component) that has better oxidation resistance than the inner layer 32. The inner layer 32 is formed of a material having higher thermal conductivity than the outer layer 31 (for example, pure copper, an alloy containing copper as a main component, etc.). The inner layer 32 may be omitted. *

A-2. Formation of Threaded Part 57: FIG. 2 is a flowchart showing an example of a method for forming the threaded part 57 of the metal shell 50 (FIG. 1). 3A and 3B are explanatory diagrams of S100 in FIG. In this embodiment, the screw part 57 is formed by using a pair of rolling dies 210 and 220. FIG. 3A is a schematic view of the metal shell 50x and the rolling dies 210 and 220 before the screw portion 57 is formed, as viewed in the front direction Df. FIG. 3B is a schematic view of the metal shell 50x and the rolling dies 210, 220 viewed in a direction perpendicular to the central axis of the metal shell 50x (here, the same as the axis CL in FIG. 1). . *

The rolling dies 210 and 220 are cylindrical tools extending along the respective

central axes

210c and 220c. The rolling dies 210 and 220 are arranged side by side so that the

central axes

210c and 220c are parallel to each other. The rolling dies 210 and 220 are rotatable around the

central axes

210c and 220c, respectively. A known drive unit (for example, an electric motor) for rotating the rolling dies 210 and 220 is connected to the rolling dies 210 and 220 (not shown). Formed on the outer

peripheral surfaces

210s and 220s of the rolling dies 210 and 220 are rolling

portions

300a and 300b for forming the screw portions 57, respectively. The rolling

parts

300a and 300b include a spiral groove part for forming a spiral thread of the screw part 57 and a spiral thread part for forming a spiral thread groove of the screw part 57. Have. In the present embodiment, the position of the first rolling die 210 is fixed. The second rolling die 220 is movable with respect to the first rolling die 210 in a direction perpendicular to the central axis 220c. A known moving device (for example, a linear slide mechanism) that moves the second rolling die 220 in a direction perpendicular to the central axis 220c is connected to the second rolling die 220 (not shown). *

In S100 (FIG. 2), the rolling dies 210 and 220 rotate in the same direction in a sufficiently separated state. The metal shell 50x is disposed between the rolling dies 210 and 220. The central axis CL of the metal shell 50x is parallel to the

central axes

210c and 220c of the rolling dies 210 and 220. The metal shell 50x is supported by a support (not shown) so as to be rotatable about the central axis CL. Then, the outer peripheral surface of the body portion 52x of the metal shell 50x (the body portion 52x before the screw portion 57 is formed) contacts the outer peripheral surface 210s of the first rolling die 210 (that is, the rolled portion 300a). Thus, the metal shell 50x moves toward the first rolling die 210 perpendicular to the axis CL. Then, the second rolling die 220 moves toward the metal shell 50x, and the outer peripheral surface 220s (that is, the rolled portion 300b) of the second rolling die 220 is pressed against the body 52x of the metal shell 50x. . Thereby, the metal shell 50x is sandwiched between the rolling dies 210 and 220, and the rolling

portions

300a and 300b of the rolling dies 210 and 220 are pressed against the body 52x of the metal shell 50x. *

In this manner, the rolling dies 210 and 220 are rotated in a state where the rolling

parts

300a and 300b are pressed against the body part 52x of the metal shell 50x (S110 (FIG. 2)). 3C and 3D are explanatory diagrams of S110 in FIG. FIG. 3C is a schematic view of the metal shell 50x and the rolling dies 210 and 220 viewed in the front direction Df, as in FIG. 3A. FIG. 3D is a schematic view of the metal shell 50x and the rolling dies 210 and 220 viewed in the direction perpendicular to the central axis CL of the metal shell 50x, as in FIG. 3B. As shown in the drawing, the metal shell 50x is sandwiched between the rolling dies 210 and 220 and rotates according to the rotation of the rolling dies 210 and 220 (the direction of rotation of the metal shell 50x is determined by the rolling dies). The direction of rotation of 210 and 220 is opposite). Thereby, the screw part 57 is formed in the trunk | drum 52x of the metal shell 50x. Then, the process of FIG. 2 ends. *

When viewed from the rolling part 300a, the metal shell 50x appears to rotate along the rolling part 300a. Similarly, when viewed from the rolled part 300b, the metal shell 50x appears to rotate along the rolled part 300b. Thus, the metal shell 50x relatively rotates along the rolled

portions

300a and 300b. *

FIG. 4 is a schematic diagram illustrating a state in which a thread portion is formed on the workpiece 400 by the rolled portion 300x. In the drawing, a cross section of the rolled portion 300x and the workpiece 400 is shown. The rolling part 300x and the workpiece 400 are obtained by modeling the rolling part 300a of the rolling die 210 and the body 52x of the metal shell 50x shown in FIG. The cross section shown in FIG. 4 corresponds to a cross section including the central axis 210c of the rolling die 210 and the central axis CL of the metal shell 50x in FIG. The shape of the workpiece 400 changes in the order of FIGS. 4 (A) to 4 (F). *

As shown in FIG. 4A, the rolled part 300x has a peak part 310 for forming a thread groove of a male screw and a groove part 320 for forming a screw thread of a male screw. . In the cross section, the crests 310 and the grooves 320 are alternately arranged. *

As illustrated in FIG. 4B, the rolled part 300 x is pressed toward the workpiece 400. On the cross section, the tops 311 of the plurality of crests 310 are in contact with the surface 490 of the workpiece 400. From this state, the rolled part 300x is further pressed toward the workpiece 400 (FIG. 4C). Thereby, each top 311 of the plurality of peak portions 310 bites into the surface 490 of the workpiece 400. On both sides of the apex 311 (the left side and the right side of the apex 311 in the figure), a part of the workpiece 400 (specifically, the part pushed away by the crest 310 of the rolled part 300x) faces the rolled part 300x. The protrusion 430 is formed. On the cross section, one groove part 320 of the rolled part 300x is sandwiched between two adjacent peak parts 310. Therefore, in one groove part 320, the two convex parts 430 of the workpiece 400 are raised toward the bottom 321 of the groove part 320. A concave portion 440 is formed between the two convex portions 430. *

The rolled portion 300x is further pressed toward the workpiece 400 (FIG. 4D). The crest 310 of the rolling unit 300x further bites into the workpiece 400. The convex part 430 of the workpiece 400 further protrudes toward the bottom 321 of the groove part 320. Thereby, one peak part 410z which has the two convex parts 430 and the recessed part 440 between these convex parts 430 is formed in one groove part 320 of the rolling part 300x. The When the rolled portion 300x is further pressed toward the workpiece 400 (FIG. 4E), the convex portion 430 further approaches the bottom 321 of the groove portion 320. Since the space of the groove part 320 is smaller as it is closer to the bottom 321, the concave part 440 becomes smaller as the convex part 430 approaches the bottom 321. *

When the rolled portion 300x is further pressed toward the workpiece 400 (FIG. 4F), the convex portion 430 reaches the bottom 321 of the groove portion 320. The concave portion 440 is buried in the two convex portions 430. Thereby, the groove part 320 of the rolling part 300x forms the peak part 410 of the same shape as the groove part 320. Moreover, the peak part 310 of the rolling part 300x forms a groove part 420 having the same shape as the peak part 310. As described above, the peak portion 310 and the groove portion 320 of the rolled portion 300x are pressed against the workpiece 400, whereby the workpiece 400 is plastically deformed, and the groove portion 420 and the peak portion 410, that is, the screw portion is formed on the workpiece 400. The *

A-3. Screw part of reference example: FIG. 5 is a schematic view of a reference example of a rolling die and a screw part formed on a metal shell. FIG. 5A shows a cross section of the body 52x of the metal shell 50x before the thread portion is formed and the rolling die 210z of the reference example. This cross section is a cross section including the central axis CL of the metal shell 50x and the central axis (not shown) of the rolling die 210z. In the drawing, only a portion of the body 52x of the metal shell 50x closer to the rolling die 210z than the center axis CL and a portion of the rolling die 210z closer to the metal shell 50x are shown. *

As described with reference to FIG. 1, the reduced inner diameter portion 56 is formed in the through hole 59 of the metal shell 50x. A shelf 59b having a substantially constant inner diameter is formed on the front direction Df side of the reduced inner diameter portion 56, and a leading hole 59c having an inner diameter slightly larger than the shelf 59b is formed on the front direction Df side of the shelf 59b. Is formed. On the rearward direction Dfr side of the reduced inner diameter portion 56, an inner hole portion 59a having a substantially constant inner diameter is formed. The inner diameter of the middle hole portion 59a is larger than the inner diameters of the leading hole portion 59c and the shelf portion 59b.

A target portion 57x in the drawing is a portion of the body portion 52x where a screw portion is to be formed. The target portion 57x extends from the middle of the middle hole portion 59a to the middle of the leading hole portion 59c. The outer diameter of the target portion 57x is substantially constant over the entire target portion 57x. The thickness Ta of the metal shell 50x in the middle hole portion 59a is thinner than both the thickness Tb in the shelf portion 59b and the thickness Tc in the tip hole portion 59c. Thus, the target portion 57x includes the first metal fitting portion 57xa having a thickness Ta and the second metal fitting portion 57xb having a thickness Tb and Tc that are thicker than the first thickness Ta. Contains. The second metal part 57xb is a part different from the first metal part 57xa in the position in the direction parallel to the axis CL. The thickness is a thickness in a direction perpendicular to the axis CL (that is, a direction in which a straight line perpendicular to the axis CL extends, in this case, the radial direction). *

A rolling portion 300z is provided on the outer peripheral surface of the rolling die 210z of the reference example. The rolling part 300z has a spiral peak 310 and a spiral groove 320 extending in a direction parallel to the axis CL. In the cross-sectional view of FIG. 5A, a plurality of peak portions 310 and a plurality of groove portions 320 are alternately repeated along a direction parallel to the axis CL. In the reference example, the same peak portion 310 and the same groove portion 320 are provided over the entire rolled portion 300z. Here, the rolling portion 300z is pressed against the target portion 57x of the metal shell 50x, so that the crest portion 310 and the groove portion 320 form a screw portion in the target portion 57x of the metal shell 50x. *

FIG. 5B shows a cross section (a cross section including the axis CL) of the body portion 52z of the metal shell 50z in which the screw portion is formed. As shown in the drawing, a screw portion 57z is formed on the outer peripheral surface of the body portion 52z. In the reference example of FIG. 5B, the groove portion 420 (FIG. 4F, etc.) having a shape corresponding to the shape of the peak portion 310 of the rolled portion 300z (FIG. 5A) over the entire screw portion 57z. ) Is formed. *

The thicknesses T1, T2, and T3 in the figure are all thicknesses in the radial direction (that is, the direction orthogonal to the axis CL) between the bottom 421 of the groove 420 and the inner peripheral surface 59s of the metal shell 50z (ie, the direction perpendicular to the axis CL) Also referred to as groove thicknesses T1, T2, T3). Here, the bottom 421 of the groove 420 is a portion of the outer surface of the groove 420 that is closest to the axis CL. The groove thickness T1 at the middle hole portion 59a is thinner than both the groove thickness T2 at the shelf portion 59b and the groove thickness T3 at the leading hole portion 59c. The screw portion 57z includes a first screw forming portion 57za having a groove thickness T1 and a second screw forming portion 57zb having a groove thickness T2 and T3 having a groove thickness larger than the groove thickness T1. The second screw forming portion 57zb is a portion having a position different from the first screw forming portion 57za in the direction parallel to the axis CL. In the reference example of FIG. 5B, the first screw forming portion 57za corresponds to the first metal fitting portion 57xa of FIG. 5A, and the second screw forming portion 57zb is the second metal fitting of FIG. 5A. This corresponds to the portion 57xb. *

As shown in the drawing, the thick second screw forming portion 57zb is formed with a crest 410 (FIG. 4F) having a shape corresponding to the shape of the groove 320 of the rolled portion 300z (FIG. 5A). Yes. However, the thin first screw forming portion 57za is formed with the peak portion 410z having the convex portion 430 and the concave portion 440 at the top as described with reference to FIG. The reason for this is as follows. *

As shown in FIG. 5A, when the rolling portion 300z of the rolling die 210z is pressed against the target portion 57x of the metal shell 50x, the cylindrical target portion 57x is deformed by the force from the rolling die 210z. obtain. For example, the target portion 57x can be bent toward the central axis CL. When the target portion 57x is deformed toward the central axis CL, that is, in a direction away from the rolled portion 300z, the peak portion 310 of the rolled portion 300z cannot sufficiently bite into the target portion 57x. As a result, as shown in FIG. 4E, a peak portion 410z having a convex portion 430 and a concave portion 440 at the top can be formed. The small convex part 430 is easy to deform | transform by contacting another member (for example, other metal fittings). If the convex part 430 deform | transforms, malfunctions may arise, such as the friction between the screw parts 57z of the metal shell 50z and female threads, such as an attachment hole, becoming large. *

The deformation of the target portion 57x increases at a thin portion of the target portion 57x. For example, in the reference example of FIG. 5A, the first metal part 57xa can be deformed more toward the central axis CL than the second metal part 57xb. As a result, when an appropriate peak 410 is formed in the second metal part 57xb, an inappropriate peak 410z may be formed in the first metal part 57xa. *

By adjusting the rolling conditions, an appropriate peak portion 410 can be formed in the first metal part 57xa. For example, the force for pressing the rolling die 210z against the metal shell 50x may be increased. Further, the time for rotating the rolling die 210z in a state where the rolling die 210z is pressed against the metal shell 50x may be lengthened. However, in these cases, the rolled part 300z is pressed too strongly against the second metal part 57xb, or the rolled part 300z is pressed too long against the second metal part 57xb. As a result, problems such as the surface of the screw part formed in the second metal part 57xb being scraped off may occur. *

As described above, when the screw portion is formed in the target portion 57x including a plurality of portions having different thicknesses, a problem may occur. Therefore, in the present embodiment, the rolling dies 210 and 220 (FIG. 3) are configured so that a lower screw thread is formed in a portion having a small thickness compared to a portion having a large thickness. *

A-4. Screw part of embodiment: FIG. 6 is a schematic view of an embodiment of a rolling die and a screw part formed on a metal shell. FIG. 6A shows a cross section of the body 52x of the metal shell 50x before the thread portion is formed and the rolling die 210 of the embodiment. The illustrated cross section includes a central axis CL of the metal shell 50x and a central axis (not illustrated) of the rolling die 210. The configuration of the metal shell 50x is the same as the configuration of the metal shell 50x in FIG. An inward direction Di in the figure is a direction toward the inner peripheral side in the radial direction centering on the axis CL. An outward direction Do in the figure is a direction toward the outer peripheral side in the radial direction. *

Unlike the reference example of FIG. 5, in the rolling part 300a of the rolling die 210, the first screw rolling part 3aa for forming a male screw on the first metal part 57xa and the male screw on the second metal part 57xb are provided. The configuration of the groove is different from the second thread rolling portion 3ab to be formed. In the second thread rolling portion 3ab, a peak portion 310 and a groove portion 320 are provided as in the reference example of FIG. On the other hand, in the first thread rolling portion 3aa, a groove 350 that is shallower than the groove 320 is provided instead of the groove 320 (hereinafter, the groove 320 is also referred to as a deep groove 320 and the groove 350 is also referred to as a shallow groove 350). . The peak portion 310 of the first thread rolling portion 3aa is the same as the peak portion 310 of the second screw rolling portion 3ab. *

FIG. 6B shows a cross section (a cross section including the axis CL) of the trunk portion 52 of the metal shell 50 in which the screw portion 57 is formed. In the present embodiment, a groove 420 (such as FIG. 4F) having a shape corresponding to the shape of the crest 310 of the rolled portion 300a is formed over the entire screw portion 57. The groove thicknesses T1, T2, and T3 in the figure are the same as the groove thicknesses T1, T2, and T3 described with reference to FIG. The screw portion 57 includes a first screw forming portion 57a having a groove thickness T1 and a second screw forming portion 57b having a groove thickness T2 and T3 having a groove thickness larger than the groove thickness T1. The second screw forming portion 57b is a portion that is different in position in a direction parallel to the axis CL from the first screw forming portion 57a. In the embodiment of FIG. 6 (B), the first screw forming portion 57a corresponds to the first metal fitting portion 57xa of FIG. 6 (A), and the second screw forming portion 57b is the second metal fitting of FIG. 6 (A). This corresponds to the portion 57xb. *

As shown in the drawing, the second screw forming portion 57b is formed with a peak portion 410 (FIG. 4F) having a shape corresponding to the shape of the deep groove portion 320 of the rolled portion 300a. In the first screw forming portion 57a, a peak portion 450 having a shape corresponding to the shape of the shallow groove portion 350 of the rolled portion 300a is formed. As will be described later, the peak portion 450 is lower than the peak portion 410 (hereinafter, the peak portion 410 is also referred to as the high peak portion 410 and the peak portion 450 is also referred to as the low peak portion 450). *

FIG. 6C is a cross-sectional view of the deep groove portion 320, the shallow groove portion 350, and the peak portion 310 of the rolling portion 300 a of the rolling die 210. In the drawing, enlarged views of a portion including the deep groove portion 320 and a portion including the shallow groove portion 350 in the cross section of the rolled portion 300a illustrated in FIG. 6A are shown. The configuration of the peak portion 310 and the deep groove portion 320 is the same as the configuration of the peak portion 310 and the groove portion 320 shown in FIG. On the other hand, the bottom 351 of the shallow groove portion 350 is located closer to the top 311 of the peak portion 310 than the bottom 321 of the deep groove portion 320. *

When rolling the threaded portion, as shown in FIG. 3B, the rolled portion 300a contacts the target portion 57x. In this state, the top 311 of the peak portion 310 is in contact with the target portion 57x of the metal shell 50x. A straight line 57 </ b> L in FIG. 6C is a straight line passing through the plurality of vertices 311 on the cross section, and indicates the outer peripheral surface of the target portion 57 x in contact with the plurality of vertices 311. 6C shows the axis CL (not shown) of the metal shell 50x and the target portion in a state where the top 311 of the peak 310 is in contact with the target portion 57x of the metal shell 50x for rolling the screw portion. A cross section including a top 311 in contact with 57x is shown. The directions Di and Do in the figure indicate the direction toward the inner peripheral side and the direction toward the outer peripheral side in the radial direction around the central axis CL of the metal shell 50x in such a state. The bottom 321 of the groove part 320 is a part on the outermost side Do side of the outer surface of the groove part 320. Similarly, the bottom 351 of the groove part 350 is a part of the outer surface of the groove part 350 on the outermost direction Do side. Further, the top 311 of the peak portion 310 is a portion of the outer surface of the peak portion 310 closest to the inner direction Di. *

The first depth D1 in the figure is the depth from the top 311 of the peak portion 310 to the bottom 351 of the shallow groove portion 350. The second depth D2 is a depth from the top 311 of the peak portion 310 to the bottom 321 of the deep groove portion 320. In the present embodiment, the first depth D1 is smaller than the second depth D2. These depths D1 and D2 are distances in the outward direction Do from the straight line 57L passing through the plurality of apexes 311 on the cross section to the

bottoms

351 and 321. That is, the depths D1 and D2 are depths in a direction orthogonal to the axis CL (not shown) of the metal shell 50x that contacts the plurality of apexes 311 in the cross section of FIG. In addition, the cross section of the rolling die 210 in FIG. 6A also shows the same cross section as the cross section in FIG. *

FIG. 6D is a cross-sectional view of the

ridges

410 and 450 formed by the

groove portions

320 and 350 and the ridge portion 310 of the rolling die 210 (FIG. 6C) and the groove portion 420. In the drawing, enlarged views of a part including the high peak part 410 and a part including the low peak part 450 in the cross section of the screw part 57 shown in FIG. 6B are shown. The configuration of the high peak portion 410 and the groove portion 420 is the same as the configuration of the peak portion 410 and the groove portion 420 shown in FIG. On the other hand, the top 451 of the low mountain portion 450 is located closer to the bottom 421 of the groove 420 than the top 411 of the high mountain portion 410. *

Note that the bottom 421 of the groove 420 is a portion of the outer surface of the groove 420 on the innermost direction Di side. The bottom 421 is formed by the top 311 of the crest 310 of the rolling die 210 (FIG. 6C). Further, the top 411 of the high mountain portion 410 is a portion of the outer surface of the high mountain portion 410 that is closest to the outward direction Do. The top 411 of the high mountain portion 410 is formed by the bottom 321 of the deep groove portion 320 of the rolling die 210. Similarly, the apex 451 of the low mountain portion 450 is the portion of the outer surface of the low mountain portion 450 that is closest to the outer direction Do. The top 451 of the low peak portion 450 is formed by the bottom 351 of the shallow groove portion 350 of the rolling die 210.

The first height Ha in the drawing is the height from the bottom 421 of the groove 420 to the top 451 of the low peak 450. The second height Hb is a height from the bottom 421 of the groove 420 to the top 411 of the high mountain portion 410. In the present embodiment, the first height Ha is smaller than the second height Hb. These heights Ha and Hb are heights in a direction perpendicular to the axis CL of the metal shell 50. The first height Ha is approximately the same as the first depth D1 (FIG. 6C), and the second height Hb is approximately the same as the second depth D2. As described above, the depths D1 and D2 in FIG. 6C correspond to the thread heights Ha and Hb of the thread portion. *

Also in this embodiment, when the rolling part 300a of the rolling die 210 (FIG. 6A) is pressed against the target part 57x of the metal shell 50x, as in the reference example of FIG. 5A, the target part 57x. (In particular, the thin first metal part 57xa) can bend toward the central axis CL. Therefore, the amount of biting into the first metal part 57xa of the peak 310 of the rolling die 210 may be smaller than the amount of biting into the second metal part 57xb of the peak 310. Here, as described in FIGS. 6A and 6C, the depth D1 of the shallow groove portion 350 of the first thread rolling portion 3aa is equal to the depth of the deep groove portion 320 of the second thread rolling portion 3ab. It is smaller than 2 depth D2. Therefore, the raised part of the first metal part 57xa (the part corresponding to the convex part 430 in FIG. 4E) can easily reach the bottom 351 of the shallow groove part 350 (FIG. 6C). Thereby, the low peak part 450 of the shape corresponding to the shape of the shallow groove part 350 is easily formed in the first metal part 57xa. Further, the thick second metal part 57xb is less likely to bend than the thin first metal part 57xa. Therefore, the high mountain part 410 having a shape corresponding to the shape of the deep groove part 320 is easily formed in the second metal part 57xb. As described above, in this embodiment, a small concave portion such as the concave portion 440 in FIG. 4E is formed in each of the peak portion 450 of the first screw formation portion 57a and the peak portion 410 of the second screw formation portion 57b. Is suppressed from being formed. *

In the present embodiment, the height of the screw thread is different between the first screw forming portion 57a and the second screw forming portion 57b of the screw portion 57 (FIG. 6B). However, the first screw forming portion 57a and the second screw forming portion 57b respectively form different portions of one continuous screw portion 57 (that is, one continuous male screw). Therefore, between the first screw forming portion 57a and the second screw forming portion 57b, the screw pitch is the same, and the screw thread angle is also the same. *

6A and 6C, the deep groove portion 320 and the shallow groove portion 350 are formed on the outer peripheral surface 210s of the rolling die 210 (FIGS. 3A and 3B). It is formed by one spiral groove that rotates around the central axis 210c. The depth of the groove is different between the first thread rolling portion 3aa and the second screw rolling portion 3ab. It is preferable that the depth of the groove changes smoothly at a boundary portion (for example, a portion corresponding to the reduced inner diameter portion 56) between the first screw rolling portion 3aa and the second screw rolling portion 3ab. In this case, the thread height of the thread portion 57 of the metal shell 50 can be smoothly changed between the first screw forming portion 57a and the second screw forming portion 57b. However, the depth of the groove of the rolling die 210 may change stepwise. In this case, the thread height of the thread portion 57 of the metal shell 50 changes in a stepped manner between the first screw forming portion 57a and the second screw forming portion 57b. Further, in the present embodiment, when forming the screw portion, the metal shell 50x rotates around the rolling portion 300a one or more times in a state where it is in contact with the rolling portion 300a of the rolling die 210. That is, the outer peripheral surface 210s of the rolling die 210 (that is, the rolled portion 300a) forms a screw portion in the metal shell 50x over the entire circumference. However, only a part of the entire circumference of the rolling part 300a of the rolling die 210 may form a screw part on the metal shell 50x. In this case, the rolling part 300a may be formed only on a part of the entire circumference of the outer peripheral surface 210s of the rolling die 210. *

The configuration of the rolling die 210 has been described above. The configuration of the second rolling die 220 is the same as the configuration of the first rolling die 210. *

As described above, in the present embodiment, as shown in FIG. 6A, the target portion 57x where the screw portion of the metal shell 50x before the screw portion is formed is the first metal portion 57xa and the first metal portion 57xa. 2 metal parts 57xb. The first metal part 57xa is a part of the range of the position in the direction parallel to the axis line CL in the entire range of the target part 57x. In the first metal part 57xa, the thickness in the direction orthogonal to the axis CL is the first thickness Ta. The second metal part 57xb is a part having a position different from the first metal part 57xa in the direction parallel to the axis CL. The wall thicknesses Tb and Tc at the second metal part 57xb are thicker than the wall thickness Ta at the first metal part 57xa. *

The rolling portion 300a of the rolling die 210 includes a first thread rolling portion 3aa for forming a male screw on the first metal fitting portion 57xa and a second screw for forming a male screw on the second metal fitting portion 57xb. A thread rolling portion 3ab. In the first thread rolling portion 3aa, as described with reference to FIG. 6C, the depth from the top 311 of the peak portion 310 to the bottom 351 of the groove portion 350 is the first depth D1. In the second thread rolling portion 3ab, the depth from the top 311 of the peak portion 310 to the bottom 321 of the groove portion 320 is the second depth D2. And the 1st depth D1 in 1st screw rolling part 3aa is smaller than the 2nd depth D2 in 2nd screw rolling part 3ab. Therefore, the amount of material necessary for forming the thread (ridge 450 (FIG. 6D)) to be formed by the groove 350 of the first thread rolling portion 3aa is the groove 320 of the second thread rolling portion 3ab. Is less than the amount of material required for forming the thread (the thread 410 (FIG. 6D)). That is, the thread (the thread 450 (FIG. 6D) of the first metal part 57xa. ) Is less than the amount of material necessary for forming the thread (peak portion 410 (FIG. 6D)) of the second metal part 57xb. Even when the first metal part 57xa of the target part 57x is bent more than the second metal part 57xb at the time of formation, the first screw rolling part 3aa is appropriately connected to the first metal part 57xa with a male screw. And the second thread rolling portion 3ab is the second metal fitting portion. The 57Xb, suitably, to form a male screw.

Moreover, in this embodiment, the structure of the

groove parts

350 and 320 differs between the 1st thread rolling part 3aa of the rolling die 210, and the 2nd thread rolling part 3ab. Accordingly, the rolling conditions (for example, the strength of the pressing force of the rolling die and the length of time for pressing the rolling die) are set between the first metal part 57xa and the second metal part 57xb of the metal shell 50x. You do not have to change it. In addition, the formation of the screw portion of the first metal part 57xa and the formation of the screw part of the second metal part 57xb may not be divided into separate steps. That is, using the rolling die 210, it is possible to simultaneously form screw portions in the first metal part 57xa and the second metal part 57xb. *

In the present embodiment, as shown in FIG. 6C, the bottom 351 of the shallow groove portion 350 and the bottom 321 of the deep groove portion 320 are each rounded. FIG. 6C shows a first curvature radius R1 of the bottom 351 of the shallow groove portion 350 and a second curvature radius R2 of the bottom 321 of the deep groove portion 320 in the cross section of FIG. 6C. As illustrated, the first radius of curvature R1 is larger than the second radius of curvature R2. Therefore, the male screw of the first metal part 57xa and the male screw of the second metal part 57xb can be appropriately formed using the rolling die 210. Further, the rolling die 210 having the shallow groove portion 350 and the deep groove portion 320 can be easily prepared. *

The configuration of the second rolling die 220 is the same as that of the first rolling die 210. Therefore, by using the first rolling die 210 and the second rolling die 220, male screws can be appropriately formed on the first metal part 57xa and the second metal part 57xb. *

2, 3, and 6, when the screw portion 57 is formed in the metal shell 50 x, first, the first screw rolling portion 3 aa of the rolling portion 300 a of the rolling die 210 is the main body. The second metal part 57ab is pressed against the first metal part 57xa of the metal part 50x, and the second thread rolling part 3ab is pressed against the second metal part 57xb (FIG. 2: S100, FIG. 3 (A), FIG. 3 (B)). The same applies to the rolling part 300b of the second rolling die 220. Then, in a state where the corresponding portions of the rolling

parts

300a, 300b of the rolling dies 210, 220 are pressed against the metal parts 57xa, 57xb, along the rolling

parts

300a, 300b of the rolling dies 210, 220, The metal shell 50x is relatively rotated (FIG. 2: S110, FIG. 3C, FIG. 3D). Thereby, a male screw is appropriately formed in each metal part 57xa, 57xb. *

As shown in FIG. 6B, the screw portion 57 of the metal shell 50 includes a first screw forming portion 57a and a second screw forming portion 57b. The first screw forming portion 57 a is a portion of the partial range of the entire range of the screw portion 57 in the position range in the direction parallel to the axis line CL. In the first screw forming portion 57a, the groove thickness which is the thickness in the direction perpendicular to the axis CL between the bottom 421 of the male screw groove 420 and the inner peripheral surface 59s of the metal shell 50 is the first groove thickness T1. It is. The second screw forming portion 57b is a portion that is different in position in a direction parallel to the axis CL from the first screw forming portion 57a. The groove thicknesses T2 and T3 at the second screw forming portion 57b are thicker than the groove thickness T1 at the first screw forming portion 57a. *

As shown in FIG. 6D, in the first screw forming portion 57a, the screw height that is the height from the bottom 421 of the groove 420 to the top 451 of the peak 450 is the first height Ha. In the second screw forming portion 57b, the screw height from the bottom 421 of the groove 420 to the top 411 of the peak 410 is the second height Hb. And the 1st height Ha in the 1st screw formation part 57a is smaller than the 2nd height Hb in the 2nd screw formation part 57b. *

According to this configuration, the amount of material necessary for forming the screw thread (the low thread part 450 (FIG. 6D)) of the first screw forming part 57a is the same as the screw thread (the high thread part 410) of the second screw forming part 57b. (FIG. 6 (D)) is smaller than the amount of material required for forming the first metal part 57xa (FIG. 6 (A)) than the second metal part 57xb. Even if it bends, by using a rolling die having groove portions having different depths (for example, a rolling die 210 having a shallow groove portion 350 and a deep groove portion 320 in FIG. 6A), a thin first die is used. The male screw of the first screw forming portion 57a and the male screw of the thick second screw forming portion 57b can be appropriately formed.

Moreover, in this embodiment, as shown to FIG 6 (D), the top 451 of the low mountain part 450 and the top 411 of the high mountain part 410 are each rounded. FIG. 6D shows a first radius of curvature Ra of the top 451 of the low peak 450 and a second radius of curvature Rb of the top 411 of the high peak 410 in the cross section of FIG. 6D. . As shown in the figure, the first curvature radius Ra is larger than the second curvature radius Rb. Accordingly, the radius of curvature of the bottom of the groove portion of the rolling die for forming the low peak portion 450 (for example, the first radius of curvature R1 of the bottom 351 of the shallow groove portion 350 in FIG. 6C) and the high mountain portion 410 are formed. By adjusting the curvature radius of the bottom of the groove portion of the rolling die for the purpose (for example, the second curvature radius R2 of the bottom 321 of the deep groove portion 320 in FIG. 6C), the thin first screw forming portion 57a And the male screw of the thick second screw forming portion 57b can be appropriately formed. *

The first curvature radius Ra of the top 451 of the low peak portion 450 is substantially the same as the first curvature radius R1 of the bottom 351 of the shallow groove portion 350 (FIG. 6C) that forms the low peak portion 450. In addition, the second curvature radius Rb of the top 411 of the high mountain portion 410 is substantially the same as the second curvature radius R2 of the bottom 321 of the deep groove portion 320 (FIG. 6C) that forms the high mountain portion 410. *

B. Modifications: (1) As the configuration of the rolling dies, various other configurations can be adopted instead of the configurations of the rolling dies 210 and 220 described with reference to FIG. For example, in the cross section of FIG. 6C, the

bottoms

321 and 351 of the

groove portions

320 and 350 may be V-shaped without being rounded. Further, the

bottoms

321 and 351 may include flat portions (for example, a portion parallel to the axis CL of the metal shell 50x in a state where the rolling die is in contact with the metal shell 50x to form a screw portion).

In the embodiment of FIG. 6C, the top 311 of the peak portion 310 is rounded in the cross section of FIG. Alternatively, the apex 311 may form a V-shaped corner. Further, the top 311 may include a flat portion (for example, a portion parallel to the axis CL of the metal shell 50x in a state where the rolling die contacts the metal shell 50x to form a screw portion). *

Further, the rolling dies may be various rolling dies such as flat dies and planetary dies instead of the cylindrical dies such as the rolling dies 210 and 220 in FIG. When a cylindrical die is used, the screw portion may be formed by pressing three or five dies (generally, two or more dies) against the metal shell 50x. *

In general, a rolling die has a rolling part including a groove part for forming a male thread thread and a thread part for forming a male screw thread groove. And as a structure of a rolling part, the depth of the groove part in the 1st thread rolling part which forms a male screw in the thin part of a metal fitting is the 2nd screw rolling part which forms a male screw in a thick part of a metal fitting Various configurations can be employed such that the depth is smaller than the depth of the groove portion. In any case, the rolling dies can be manufactured by various methods such as cutting, grinding and forging. *

(2) As the configuration of the screw portion of the metal fitting, other various configurations can be adopted instead of the configuration of the screw portion 57 described in FIG. For example, in the cross section of FIG. 6D, the

peaks

411 and 451 of the

peak portions

410 and 450 may be rounded to form V-shaped corners. The

apexes

411 and 451 may include flat portions (for example, portions parallel to the axis CL). *

In the embodiment of FIG. 6D, the bottom 421 of the groove 420 is rounded in the cross section of FIG. Alternatively, the bottom 421 may be V-shaped. Further, the bottom 421 may include a flat portion (for example, a portion parallel to the axis CL). *

Further, the thread portion may be a double thread instead of the single thread. A single thread is a screw composed of one spiral thread and a spiral thread, and a double thread is two spiral threads and two spiral screws. It is a screw composed of a groove. In general, the screw portion may be an N-thread formed of a spiral N number (N is an integer of 1 or more) and a spiral N number of screw grooves. The rolling portion of the rolling die is configured to form a spiral N number of threads and a spiral number of N thread grooves. *

Generally, a thin first screw forming portion and a thick second screw forming portion (for example, a first screw forming portion 57a having a small groove thickness and a second screw forming portion 57b having a large groove thickness shown in FIG. 6B). ) Include various configurations in which the screw height from the bottom of the groove portion to the top of the crest at the first screw forming portion is smaller than the screw height at the second screw forming portion. Can be adopted. If such a configuration is adopted as a configuration of one continuous screw portion, by using the various rolling dies described above, a male screw of a thin first screw forming portion and a male screw of a thick second screw forming portion are used. Can be formed appropriately. *

The thick second screw forming portion may be a portion away from the thin first screw forming portion, or may be a portion connected to the thin first screw forming portion instead. In any case, in order to properly attach the screw portion of the metal fitting to the female screw of the attachment hole, the thread valley diameter is approximately the same between the thin first screw forming portion and the thick second screw forming portion. Is preferred. And as a thin 1st screw formation part, you may employ | adopt the part with a larger internal diameter compared with a thick 2nd screw formation part. *

(3) As a method of forming the threaded portion on the metal fitting, various methods can be adopted instead of the method described with reference to FIGS. For example, the start of rotation of the rolling dies 210, 220 (that is, the start of relative rotation of the metal shell 50x with respect to the rolling dies 210, 220) is before pressing the rolling dies 210, 220 against the metal shell 50x. It may be after the rolling dies 210 and 220 are pressed against the metal shell 50x. *

(4) The metal fitting having the threaded portion may be a cylindrical metal fitting of other various devices instead of the metal shell 50 of the spark plug 100. For example, a cylindrical fitting of a device such as a spark plug, a glow plug, a gas sensor (for example, an oxygen concentration sensor) attached to a power system having an internal combustion engine (for example, a system including an internal combustion engine, an intake pipe, and an exhaust pipe) The above-described screw portion may be applied. *

As mentioned above, although this invention was demonstrated based on embodiment and a modification, embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

8 ... front end side packing, 10 ... insulator, 11 ... reduced inner diameter part, 12 ... through hole (shaft hole), 13 ... rear end side body part, 14 ... large diameter 15: distal end body part, 16 ... reduced outer diameter part, 19 ... leg part, 20 ... center electrode, 21 ... outer layer, 22 ... core part, 23 ..鍔, 24 ... head, 27 ... shaft, 28 ... bar, 29 ... first chip, 30 ... ground electrode, 31 ... outer layer, 32 ... Inner layer, 33 ... proximal end, 34 ... tip, 37 ... main body, 39 ... second chip, 40 ... terminal fitting, 41 ... shaft, 48 ...鍔 part, 49 ... cap mounting part, 50, 50x, 50z ... metal shell, 51 ... tool engaging part, 52, 52x, 52z ... trunk, 53 ... caulking part, 54 ... collar part, 55 ... tip surface, 56 ... reduced inner diameter part, 57, 57z ... screw part, 57a ... first screw forming part, 57b ... second screw forming part, 57x ... Target part, 57xa ... First bracket part 57xb ... second metal fitting part, 57za ... first screw forming part, 57zb ... second screw forming part, 58 ... buckling part, 59 ... through hole, 59a ... in Hole, 59b ... shelf, 59c ... tip hole, 59s ... inner peripheral surface, 61 ... ring member, 70 ... talc, 72 ... first seal part, 73. .. Resistor, 74 ... second seal part, 90 ... gasket, 100 ... ignition plug, 210 ... first rolling die, 210c ... center axis, 210s ... outer peripheral surface , 220 ... second rolling die, 220c ... center axis, 220s ... outer peripheral surface, 210z ... rolling die, 300a, 300b, 300x, 300z ... rolling part, 3aa ... 1st thread rolling part, 3ab ... 2nd thread rolling part, 310 ... mountain part, 311 ... top, 320 ... deep groove part, 321 ... bottom, 350 ... shallow Groove, 351 ... Bottom, 400 ... Workpiece, 410 ... Takayama, 411 ... Top, 10z ... mountain, 420 ... groove, 421 ... bottom, 430 ... convex, 440 ... concave, 450 ... low peak, 451 ... top, 490 ... Surface, g ... gap, CL ... center axis (axis), Df ... tip direction (front direction), Dfr ... rear end direction (rear direction),

Claims

A cylindrical metal fitting extending in the direction of the axis,

It has a threaded portion that is a part in which a male thread extending in the direction of the axis is formed on the outer peripheral surface,

The screw portion is

A first screw forming part which is a part of a part of the whole range of the screw part;

The position of the axial direction is different from the first screw forming portion, and the groove thickness which is the thickness in the direction perpendicular to the axial line between the groove bottom of the male screw and the inner peripheral surface of the metal fitting is the A second screw forming portion that is thicker than the groove thickness in the first screw forming portion;

Including

The screw height that is the height from the groove bottom to the top of the male screw at the first screw forming portion is smaller than the screw height at the second screw forming portion.

Hardware.
The metal fitting according to claim 1,

The radius of curvature of the top of the male screw of the first screw forming portion is larger than the radius of curvature of the top of the male screw of the second screw forming portion,

Hardware.
The outer peripheral surface of the first metal part of the cylindrical metal part extending in the direction of the axis is different from the first metal part in the position in the direction of the axis, and the thickness is the thickness in the direction perpendicular to the axis. A rolling die for forming a male screw extending in the direction of the axis on the outer peripheral surface of the second metal part thicker than the thickness of the first metal part by rolling,

The rolling die has a rolling part including a groove part for forming a thread of the male screw and a thread part for forming a screw groove of the male screw,

The groove depth which is the depth from the top of the peak portion to the bottom of the groove portion in the first screw rolling portion that forms the male screw in the first metal fitting portion of the rolling portion is the rolling Smaller than the groove depth at the second thread rolling portion that forms the male screw in the second metal part of the portion,

Rolling dies.
The rolling die according to claim 3,

The curvature radius of the bottom of the groove portion of the first thread rolling portion is larger than the curvature radius of the bottom of the groove portion of the second thread rolling portion,

Rolling dies.
A forming method of forming a male screw extending in the direction of the axis on the outer peripheral surface of a cylindrical metal fitting extending in the direction of the axis,

The portion of the metal fitting on which the male screw is formed is

A first metal part which is a part of a part of the entire range of the part where the male screw is formed;

A second metal part having a thickness different from a position of the first metal part in the direction of the axis, and a thickness that is a thickness in a direction perpendicular to the axis is larger than a thickness of the first metal part,

Including

The forming method includes:

5. The first thread rolling part of the rolling die according to claim 3 or 4 is used as the first metal part of the metal fitting, and the second screw rolling part of the rolling die is used as the second metal part of the metal fitting. Pressing each part,

The first thread rolling portion is pressed against the first metal fitting portion, and the second screw rolling portion is pressed against the second metal fitting portion, along the rolling portion of the rolling die. Forming the male screw in the first metal part and the second metal part by rotating the metal parts relatively;

Forming method.