JP5526161B2 - Spark plug manufacturing method and metal shell manufacturing method - Google Patents

Description

  The present invention relates to the manufacture of a spark plug, and more particularly to the manufacture of a metal shell used for a spark plug.

  The metal shell of the spark plug is manufactured by cutting each part of the metal shell from a forged body formed by forging (see, for example, Patent Document 1). Since there are many undulations in the contour line of the metal shell, the metal shell has been cut using a complete cutting tool formed with a cutting edge ridge along the contour line.

  FIG. 12 is an explanatory view showing a state of cutting of the metal shell 980 using the conventional general cutting tool 910. In the cutting of the metal shell 980, after fixing the metal shell 980, which is a workpiece, to the lathe spindle (not shown) and the center 960, the metal shell 980 is rotated around the rotation axis Cmd of the lathe spindle, By pressing the cutting tool 910 against the metal shell 980 from the direction orthogonal to the rotation axis Cmd, the shape of each part of the metal shell 980 is cut out.

  A plurality of cutting edge ridges 912 a to 912 d corresponding to the respective parts of the metal shell 980 are formed on the general cutting tool 910 by polishing the rake face 916. Each of the cutting edge ridges 912a to 912d is bent at a plurality of locations along each portion of the contour line OL of the metal shell 980. Relief surfaces 918a to 918d are formed in the general cutting tool 910 at positions corresponding to the cutting edge ridge sides 912a to 912d, respectively.

  In FIG. 12, the polished portion Pwt removed from the overall cutting tool 910 when the rake face 916 is polished is hatched. Since the rotary grindstone (not shown) for polishing the rake face 916 is cylindrical, the rake face 916 is a concave curved surface. Therefore, the blade edge heights of the cutting edge ridges 912a to 912d are in a state of being lowered from the rotation axis Cmd as the distance from the rotation axis Cmd increases. In the example of FIG. 12, the blade edge height of the cutting edge ridge side 912a is lowered by the distance Dec at maximum.

JP 2008-210681 A

  In the cutting tool used for cutting the metal shell of the spark plug, the cutting edge discharge direction is not stable because the rake face has a certain shape with respect to the edge of the cutting edge bent at multiple locations. There was a problem that the cutting waste was easily wound around the workpiece. In addition, as the edge of the cutting edge is further away from the rotation axis, there is a problem that the cutting edge height is lowered and the cutting accuracy is lowered.

  In view of the above-described problems, an object of the present invention is to provide a technique for improving the manufacturing efficiency of a spark plug.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1] The spark plug manufacturing method according to Application Example 1 includes a step of manufacturing a rod-shaped center electrode, a step of manufacturing an insulator configured to allow the insertion of the center electrode, and the insertion of the insulator. A spark plug manufacturing method comprising: a step of manufacturing a metal shell configured as described above; and a step of manufacturing a spark plug by assembling the center electrode, the insulator and the metal shell. The step of preparing a cutting edge ridge edge bent at a plurality of locations along at least a part of the contour line of the metal shell, and a cutting edge formed with a rake face corresponding to each portion of the cutting edge ridge edge. The material of the metal shell is cut using a cutting tool in which the height of the entire edge of the cutting edge is aligned with respect to the rotation axis for rotating the object to be cut and the blade portion is attached. To do. According to this application example, since the rake face is formed according to each part of the edge of the cutting edge bent at a plurality of places, the discharge direction of the cutting waste is stable, and curling of the cutting waste around the workpiece is suppressed. be able to. In addition, since the height of the entire area of the ridge edge of the cutting edge is aligned with the rotation axis, cutting accuracy can be improved as compared with a conventional complete cutting tool. As a result, the manufacturing efficiency of the metal shell can be improved, and consequently the manufacturing efficiency of the spark plug can be improved.

Application Example 2 The blade portion is a first and second blade portion in which cutting edge ridges having different shapes are formed, and the cutting tool includes the first and second blade portions. The first and second blade portions may be attached so that the height of the entire edge of each of the cutting blades is aligned with the rotation axis. According to this application example, cutting can be performed simultaneously on a plurality of parts of the metal shell.

Application Example 3 In the rake face, a convex portion may be formed along an inclination direction of the rake face corresponding to at least one of the plurality of locations where the edge of the cutting edge is bent. According to this application example, the discharge direction of the cutting waste is further stabilized by the convex portion, and the winding of the cutting waste around the workpiece can be further suppressed.

Application Example 4 At least a part of the edge of the cutting edge may have a shape along a tapered portion of the metal shell that is inclined with respect to the axial direction of the metal shell. According to this application example, it is possible to improve the cutting accuracy of the tapered portion as compared with the conventional general-purpose cutting tool.

Application Example 5 A plurality of the cutting edge ridges are formed on the blade, and the used cutting edge ridge and unused are changed by changing the direction in which the blade is attached to the cutting tool. The edge of the cutting edge may be exchangeable. According to this application example, resource saving of the blade portion can be achieved.

[Application Example 6] A spark plug manufacturing method according to Application Example 6 includes cutting edge ridges bent at a plurality of locations along at least a part of a contour line of a metal shell of the spark plug, and each portion of the cutting edge ridge. A material for the metal shell using a cutting tool in which a blade portion formed with a corresponding rake face is mounted with the height of the entire edge of the cutting blade aligned with respect to the rotation axis for rotating the workpiece. It is characterized by cutting. According to this application example, since the rake face is formed according to each part of the edge of the cutting edge bent at a plurality of places, the discharge direction of the cutting waste is stable, and curling of the cutting waste around the workpiece is suppressed. be able to. In addition, since the height of the entire area of the ridge edge of the cutting edge is aligned with the rotation axis, cutting accuracy can be improved as compared with a conventional complete cutting tool. As a result, the manufacturing efficiency of the metal shell can be improved, and consequently the manufacturing efficiency of the spark plug can be improved.

Application Example 7 The manufacturing method of the metal shell in Application Example 7 is a manufacturing method of the metal shell used in the spark plug, and the cutting blade is bent at a plurality of locations along at least a part of the contour line of the metal shell. Prepare a blade part on which a ridge and a rake face corresponding to each part of the cutting edge are formed, and align the height of the entire area of the cutting edge with respect to the rotation axis that rotates the workpiece. Then, the material of the metal shell is cut using a cutting tool to which the blade portion is attached. According to this application example, since the rake face is formed according to each part of the edge of the cutting edge bent at a plurality of places, the discharge direction of the cutting waste is stable, and curling of the cutting waste around the workpiece is suppressed. be able to. In addition, since the height of the entire area of the ridge edge of the cutting edge is aligned with the rotation axis, cutting accuracy can be improved as compared with a conventional complete cutting tool. As a result, the manufacturing efficiency of the metallic shell can be improved.

  The form of this invention is not restricted to the form of the manufacturing method of a spark plug and a metal shell, For example, it is also possible to apply to various forms, such as a cutting tool, a blade part, and a cutting device. Further, the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be implemented in various forms without departing from the spirit of the present invention.

It is a fragmentary sectional view showing a spark plug. It is process drawing which shows the manufacturing method of a spark plug. It is process drawing which shows the manufacturing method of a metal shell. It is explanatory drawing which shows the mode of the cutting process of a metal shell. It is explanatory drawing which shows the structure of a cutting tool. It is explanatory drawing which shows the structure of a blade part. It is explanatory drawing which shows the cross-sectional structure of a blade part. It is explanatory drawing which shows the cross-sectional structure of a blade part. It is explanatory drawing which shows the structure of a blade part. It is explanatory drawing which shows the structure of a blade part. It is explanatory drawing which shows the structure of a blade part. It is explanatory drawing which shows the mode of the cutting process of the main metal fittings using the conventional general shape tool.

A. Embodiment:
A-1. Spark plug configuration:
FIG. 1 is a partial cross-sectional view showing a spark plug 100. FIG. 1 illustrates the external shape of the spark plug 100 on the right side of the drawing with the axis CA1 being the axis of the spark plug 100 as a boundary, and the cross-sectional shape of the spark plug 100 on the left side of the drawing. In the following description, the lower side of the spark plug 100 is referred to as “front end side”, and the upper side of the paper is referred to as “rear end side”.

  The spark plug 100 includes a center electrode 10, an insulator 20, a metal shell 30, and a ground electrode 40. In the present embodiment, the axis CA1 of the spark plug 100 is also the axis of each member of the center electrode 10, the insulator 20, and the metal shell 30.

  The center electrode 10 of the spark plug 100 is a rod-shaped electrode body. In the present embodiment, the center electrode 10 is made of a nickel alloy mainly composed of nickel such as Inconel (registered trademark). The outer surface of the center electrode 10 is electrically insulated from the outside by an insulator 20. The tip side of the center electrode 10 protrudes from the tip side of the insulator 20. The rear end side of the center electrode 10 is electrically connected to the rear end side of the insulator 20. In the present embodiment, the rear end side of the center electrode 10 is electrically connected to the rear end side of the insulator 20 through the seal body 16, the ceramic resistor 17, the seal body 18, and the terminal fitting 19.

  The insulator 20 of the spark plug 100 is a cylindrical insulator. In this embodiment, the insulator 20 is formed by firing an insulating ceramic material such as alumina. The insulator 20 includes a shaft hole 28 that is a through hole along the axis CA1. The center hole 10 is accommodated in the shaft hole 28.

  The metal shell 30 of the spark plug 100 is a cylindrical metal body. In the present embodiment, the metallic shell 30 is a nickel-plated low carbon steel metal body. In other embodiments, the metal shell 30 may be a zinc-plated low-carbon steel metal body or an unplated (non-plated) nickel alloy metal body. The metal shell 30 is caulked and fixed to the outer surface of the insulator 20 while being electrically insulated from the center electrode 10. The metal shell 30 is formed with an end surface 31, a mounting screw part 32, a body part 34, a groove part 35, a tool engaging part 36, and a crimping part 38 in order from the front end side to the rear end side.

  The end surface 31 of the metal shell 30 is formed on the front end side of the metal shell 30. In the present embodiment, the end surface 31 is a hollow circular surface. A ground electrode 40 is joined to the end face 31. The insulator 20 and the center electrode 10 protrude from the center of the end surface 31.

  The mounting screw portion 32 of the metal shell 30 is a cylindrical portion having a thread formed on the outer surface. In the present embodiment, the spark plug 100 can be attached to the internal combustion engine 200 by screwing the attachment screw portion 32 of the metal shell 30 into the screw hole 210 of the internal combustion engine 200.

  The body portion 34 of the metal shell 30 is a hook-shaped portion that protrudes from the groove portion 35 in the outer peripheral direction. The body portion 34 compresses the gasket 50 between the internal combustion engine 200.

  The groove part 35 of the metal shell 30 is formed between the body part 34 and the tool engaging part 36. The groove portion 35 is a portion that bulges in the outer circumferential direction when the metal shell 30 is caulked and fixed to the insulator 20.

  The tool engaging portion 36 of the metal shell 30 is a hook-shaped portion that protrudes from the groove portion 35 in the outer peripheral direction. The tool engaging portion 36 has a shape that engages with a tool (not shown) for attaching the spark plug 100 to the internal combustion engine 200.

  The caulking portion 38 of the metal shell 30 is a part that is plastically processed so as to be in close contact with the insulator 20 when the metal shell 30 is caulked and fixed to the insulator 20. In this embodiment, powder talc (talc) is sealed in a region between the caulking portion 38 of the metal shell 30 and the insulator 20.

A-2. Spark plug manufacturing:
FIG. 2 is a process diagram showing a method for manufacturing the spark plug 100. When manufacturing the spark plug 100, the process of manufacturing the center electrode 10 (process P110), the process of manufacturing the insulator 20 (process P120), and the process of manufacturing the metal shell 30 (process P130) are performed. The center electrode 10, the insulator 20, and the metal shell 30 are prepared. Details of the method of manufacturing the metal shell 30 will be described later.

  After preparing the center electrode 10, the insulator 20, and the metal shell 30, the spark plug 100 is completed through a process (process P180) of assembling these components to manufacture the spark plug 100. Specifically, in the step of assembling the parts of the spark plug 100 (process P180), the center electrode 10 is inserted into the insulator 20, and the insulator 20 is inserted into the metal shell 30. Thereafter, the metal shell 30 is caulked and fixed to the insulator 20, and the ground electrode 40 joined to the metal shell 30 is bent, whereby the spark plug 100 is completed.

  FIG. 3 is a process diagram showing a method for manufacturing the metal shell 30. When manufacturing the metal shell 30, first, forging (process P132) is performed. Specifically, using a cold forging machine, a cylindrical low carbon steel material (for example, S10C or S15C of JIS standard) that is a material of the metal shell 30 is pressed in multiple times, and the metal shell 30 Create a forged body molded into the original shape.

  After forging (process P132), cutting (process P134) is performed. Specifically, the shape of each part of the metal shell 30 is cut out by cutting the outer periphery and inner periphery of the forged body created by the forging process (process P132) with a lathe. Details of the cutting process (process P134) will be described later.

  After cutting (process P134), the ground electrode 40 is welded to the metal shell 30 (process P136). In the present embodiment, the ground electrode 40 when welding to the metal shell 30 is a wire extending straight unlike a finished product.

  After the ground electrode 40 is welded to the metal shell 30 (process P136), a threading process (process P137) for forming a thread on the mounting screw portion 32 of the metal shell 30 is performed. Thereafter, when the metal shell 30 is plated (P138), the metal shell 30 is completed.

  FIG. 4 is an explanatory diagram showing a state of cutting (process P134) of the metal shell 30. FIG. In the cutting process (process P134), after fixing the metal shell 30, which is a workpiece, to the lathe spindle (not shown) and the center 760, the cutting tool is rotated while rotating the metal shell 30 about the rotation axis Cmd of the lathe spindle. The shape of each part of the metal shell 30 is cut out by pressing 500 against the metal shell 30 from a direction orthogonal to the rotation axis Cmd.

  FIG. 5 is an explanatory diagram showing the configuration of the cutting tool 500. 5 shows a front view of the cutting tool 500 as viewed from the rotation axis Cmd side, and an upper view of the cutting tool 500 in a positional relationship corresponding to the front view is shown in the upper part of FIG.

  The cutting tool 500 is a tool used for cutting, and is also called a “bite”. The cutting tool 500 includes a holding part 510, a blade part 530, and a fixing screw 580.

  In the present embodiment, the cutting tool 500 includes two holding portions 510. In another embodiment, the number of holding parts 510 included in the cutting tool 500 may be one, or may be three or more.

  In the present embodiment, the cutting tool 500 includes four blade portions 530. In another embodiment, the number of blade portions 530 provided in the cutting tool 500 may be one or a plurality other than four.

  In the description of the present embodiment, the reference numeral “530” is used when the blades in the cutting tool 500 are indicated without being individually specified, and the English letter is added to “530” when the specific blade is indicated individually. Use the attached code. In the embodiment of FIG. 4, reference numerals “530a”, “530b”, “530c”, and “530d” are used when the four blade portions are individually shown.

  In the description of the present embodiment, the symbol “580” is used when the fixing screw in the cutting tool 500 is indicated without being individually specified, and when the specific fixing screw is indicated individually, it corresponds to the fixing screw. The code | symbol which attached | subjected the alphabetic character of the code | symbol used for a blade part to "580" is used. In the embodiment shown in FIG. 4, the symbols “580a”, “580b”, “580c”, and “580d” are used when four fixing screws are individually shown.

  The holding part 510 of the cutting tool 500 is a member that holds the blade part 530, and is also called “shank”. The holding portion 510 has an engagement groove 514 that engages with the blade portion 530, and the blade portion 530 is fixed to the engagement groove 514 using a fixing screw 580. The opposite side of the engaging groove 514 in the holding portion 510 is gripped by a lathe feed table (not shown).

  In the description of the present embodiment, the reference numeral “514” is used when the engagement grooves in the holding portion 510 are indicated without being individually specified, and when the specific engagement grooves are indicated individually, the engagement grooves are used. The code | symbol which attached | subjected the alphabetic character of the code | symbol used for the blade part engaged to "514" is used. In the embodiment of FIG. 4, when the four engagement grooves are individually shown, the symbols “514a”, “514b”, “514c”, and “514d” are used.

  In the present embodiment, two blade portions 530 are held by one holding portion 510. In another embodiment, one blade portion 530 may be held by one holding portion 510, and three or more blade portions 530 may be held by one holding portion 510.

  The blade part 530 of the cutting tool 500 is a cutting edge configured to be detachable from the holding part 510, and is also referred to as “tip”, “slow away tip”, or “insert”.

  As a material of the blade part 530, for example, a cemented carbide, cermet, or ceramics can be used. Further, a surface film having high hardness and wear resistance may be coated on these surfaces. When manufacturing the blade part 530 used for this embodiment, first, material powder is shape | molded and the molded object is sintered. Then, when the sintered body is processed into a desired shape and a film is formed on the surface, the blade portion 530 is completed.

  As shown in FIGS. 4 and 5, the blade portion 530 is formed with a cutting edge ridge 532, a rake face 536, and a flank face 538. In the description of the present embodiment, when the cutting edge ridge, the rake face, and the flank face are indicated without specifying the blade portion, the symbols “532”, “536”, and “538” are used, respectively. When indicating the edge of the cutting edge, rake face, and flank face in a specific blade part, the alphabetical characters used for the blade part are indicated by the symbols “532”, “536”, and “538”, respectively. use. For example, the cutting edge 530a, the rake face 536a, and the flank 538a are formed in the blade part 530a.

  As shown in FIG. 4, the cutting edge ridge 532 of the blade 530 is bent at a plurality of locations along at least a part of the contour line OL of the metal shell 30. In the present embodiment, the contour line OL of the metallic shell 30 has a plurality of tapered portions TP that are inclined with respect to the rotation axis Cmd that is the axial direction of the metallic shell 30. In the present embodiment, the four cutting edge ridge sides 532a to 532d have different shapes.

  In the present embodiment, the cutting edge ridge side 532a of the blade part 530a has a shape along the contour line OL extending from the caulking part 38 of the metal shell 30 to the rear end side of the tool engaging part 36. In the present embodiment, the rear end side of the tool engaging portion 36 in the metal shell 30 is a tapered portion TP, and the cutting edge ridge side 532a has a shape along the tapered portion TP in part.

  In the present embodiment, the cutting edge ridge 532 b of the blade part 530 b has a shape along the contour line OL extending from the front end side of the tool engaging part 36 of the metal shell 30 to the rear end side of the body part 34. In the present embodiment, the front end side of the tool engaging portion 36 and the rear end side of the body portion 34 of the metal shell 30 are tapered portions TP, and the cutting edge ridge side 532b is partially shaped along the tapered portion TP. Have.

  In the present embodiment, the cutting edge ridge 532 c of the blade portion 530 c has a shape along the contour line OL extending from the distal end side of the body portion 34 of the metal shell 30 to the rear end side of the mounting screw portion 32. The rear end side of the mounting screw portion 32 in the metal shell 30 is a tapered portion TP, and the cutting edge ridge side 532c has a shape along the tapered portion TP in part.

  In the present embodiment, the cutting edge ridge side 532d of the blade portion 530d has a shape along the contour line OL extending from the distal end side of the mounting screw portion 32 of the metal shell 30 to the end surface 31. The front end side of the mounting screw portion 32 in the metal shell 30 is a tapered portion TP, and the cutting edge ridge side 532d has a shape along the tapered portion TP in part.

  As shown in FIG. 5, the cutting tool 500 is provided with a blade portion 530 with the entire height of the cutting edge ridge 532 aligned with respect to the rotation axis Cmd. That is, in the present embodiment, the cutting tool 500 is provided with four blade portions 530a to 530d with the height of each of the four cutting edge ridges 532a to 532d aligned with the rotation axis Cmd. Yes. As shown in FIG. 5, the rake face 536 and the flank face 538 of the blade part 530 are formed in accordance with each part of the cutting edge ridge 532.

  FIG. 6 is an explanatory diagram showing the configuration of the blade portion 530a. A through hole 531a into which the fixing screw 580a is inserted is formed at the center of the blade portion 530a. On the periphery of the blade portion 530a, a cutting edge ridge 532a is formed in series over the cutting edge range Rcb. In the present embodiment, the blade portion 530a has three cutting edge ridges 532a. By changing the direction in which the blade portion 530a is attached to the engagement groove 514a of the holding portion 510, the used cutting edge 532a is changed. The blade edge 532a and the unused cutting edge 532a can be exchanged.

  FIG. 7 is an explanatory diagram showing a cross-sectional configuration of the blade portion 530a. In FIG. 7, the cross section of the blade part 530a seen from arrow F7 of FIG. 6 was illustrated. As shown in FIG. 7, the blade portion 530a is formed with a rake face 536a with a rake angle corresponding to each part of the cutting edge ridge 532a, and escapes with a clearance angle corresponding to each part of the cutting edge ridge 532a. A surface 538a is formed.

  As shown in FIG. 6, in this embodiment, a series of cutting edge ridges 532a in the cutting edge range Rcb are bent at three locations. That is, the series of cutting edge ridge sides 532a has three bent portions Pc.

  FIG. 8 is an explanatory diagram showing a cross-sectional configuration of the blade portion 530a. In FIG. 8, the cross section of the blade part 530a seen from the arrow F8 of FIG. 6 was illustrated. As shown in FIGS. 6 and 8, the rake face 536a of the blade part 530a is formed with a convex part 534a along the inclination direction of the rake face 536a, corresponding to the bent part Pc of the cutting edge 532a. Yes. In the present embodiment, as shown in FIG. 6, the blade portion 530a has two convex portions 534a.

  FIG. 9 is an explanatory diagram showing the configuration of the blade portion 530b. A through hole 531b into which the fixing screw 580b is inserted is formed at the center of the blade portion 530b. On the periphery of the blade portion 530b, a cutting edge ridge 532b is formed in a series over the cutting edge range Rcb. In this embodiment, the blade portion 530b is formed with two cutting edge ridges 532b. By changing the direction in which the blade portion 530b is attached to the engaging groove 514b of the holding portion 510, the used cutting edge 532b is changed. The blade edge 532b and the unused cutting edge 532b can be exchanged. As with the blade portion 530a, the blade portion 530b is formed with a rake face 536b with a rake angle corresponding to each part of the cutting edge ridge side 532b, and with a clearance angle corresponding to each part of the cutting edge ridge side 532b. A surface 538b is formed.

  As shown in FIG. 9, in this embodiment, a series of cutting edge ridge sides 532b in the cutting edge range Rcb are bent at two locations. That is, a series of cutting edge ridge sides 532b have two bent portions Pc. On the rake face 536b of the blade part 530b, similarly to the blade part 530a, a convex part 534b is formed along the inclination direction of the rake face 536b corresponding to the bent part Pc of the cutting edge 532b. In the present embodiment, as shown in FIG. 9, the blade portion 530b has convex portions 534b formed at two locations.

  FIG. 10 is an explanatory diagram showing the configuration of the blade portion 530c. A through hole 531c into which the fixing screw 580c is inserted is formed at the center of the blade portion 530c. On the periphery of the blade portion 530c, a cutting edge ridge side 532c is formed in series over the cutting edge range Rcb. In the present embodiment, the blade portion 530c is formed with two cutting edge ridges 532c. By changing the direction in which the blade portion 530c is attached to the engaging groove 514c of the holding portion 510, the used cutting edge 532c is changed. The blade edge 532c and the unused cutting edge 532c can be exchanged. As with the blade portion 530a, the blade portion 530c is formed with a rake face 536c with a rake angle corresponding to each part of the cutting edge ridge side 532c, and escapes with a clearance angle corresponding to each part of the cutting edge ridge edge 532c. A surface 538c is formed.

  As shown in FIG. 10, in this embodiment, a series of cutting edge ridges 532c in the cutting edge range Rcb are bent at three locations. That is, a series of cutting edge ridge sides 532c have three bent portions Pc. On the rake face 536c of the blade part 530c, similarly to the blade part 530a, a convex part 534c is formed along the inclination direction of the rake face 536c corresponding to the bent portion Pc of the cutting edge 532c. In the present embodiment, as shown in FIG. 10, the blade portion 530c has convex portions 534c formed at two locations.

  FIG. 11 is an explanatory diagram showing the configuration of the blade portion 530d. A through hole 531d for inserting the fixing screw 580d is formed in the center of the blade portion 530d. On the periphery of the blade portion 530d, a cutting edge ridge side 532d is formed in series over the cutting edge range Rcb. In the present embodiment, the blade portion 530d has three cutting edge ridges 532d, and the used cutting edge is changed by changing the direction in which the blade portion 530d is attached to the engagement groove 514d of the holding portion 510. The blade edge 532d and the unused cutting edge 532d can be exchanged. Like the blade part 530a, the blade part 530d is formed with a rake face 536d with a rake angle corresponding to each part of the cutting edge ridge side 532d, and escapes with a clearance angle corresponding to each part of the cutting edge ridge side 532d. A surface 538d is formed.

  As shown in FIG. 11, in this embodiment, a series of cutting edge ridge sides 532d in the cutting edge range Rcb are bent at four locations. That is, a series of cutting edge ridge sides 532d have four bent portions Pc. On the rake face 536d of the blade part 530d, similarly to the blade part 530a, a convex part 534d is formed along the inclination direction of the rake face 536d corresponding to the bent part Pc of the cutting edge 532d. In the present embodiment, as shown in FIG. 11, the blade portion 530d has convex portions 534d formed at two locations.

A-3. effect:
According to the spark plug manufacturing method described above, the rake face 536 is formed in accordance with each part of the cutting edge ridge 532 bent at the plurality of bent parts Pc. It is possible to suppress the winding of the cutting waste around the cutting body. Further, since the height of the entire area of the cutting edge ridge 532 is aligned with respect to the rotation axis Cmd, cutting accuracy can be improved as compared with the conventional general cutting tool 910. As a result, the manufacturing efficiency of the metal shell 30 can be improved, and as a result, the manufacturing efficiency of the spark plug 100 can be improved.

  Further, in order to perform the cutting (process P134) using the cutting tool 500 in which the heights of the entire cutting edge ridges 532a to 532d are aligned with the rotation axis Cmd and the plurality of blade portions 530a to 530d are attached, Cutting can be performed simultaneously on a plurality of parts of the metal shell 30.

  Further, the rake surfaces 536a to 536d of the blade portions 530a to 530d correspond to the bent portions Pc of the respective cutting blade ridge sides 532a to 532d, and the convex portions 534a to 536d along the inclination direction of the rake surfaces 536a to 536d. Since 534d is formed, the discharge direction of the cutting waste is further stabilized by the convex portions 534a to 534d, and the winding of the cutting waste around the workpiece can be further suppressed.

  Further, since the height of the cutting edge ridge side 532 corresponding to the taper portion TP of the metal shell 30 is also aligned with the rotation axis Cmd, the taper portion TP is compared with the conventional general cutting tool 910. Cutting accuracy can be improved.

  The blade portion 530 is formed with a plurality of cutting edge ridges 532. By changing the direction in which the blade portion 530 is attached to the engagement groove 514, the used cutting edge ridge 532 and the unused cutting edge 532 are changed. Since the blade edge 532 can be replaced, resource saving of the blade portion 530 can be achieved.

B. Other embodiments:
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement with a various form within the range which does not deviate from the meaning of this invention.

  For example, in the above-described embodiment, the blade portion 530 in which the cutting edge ridges 532 are formed at two or three places is used for the cutting process (process P134). The blade part formed in one place may be used, and the blade part in which the cutting edge edge is formed in four or more places may be used.

  In the above-described embodiment, the blade portions 530a to 530d on which the convex portions 534a to 534d are formed are used for the cutting process (process P134). However, in other embodiments, the convex portions are formed on the rake face. You may use the blade part which is not.

DESCRIPTION OF SYMBOLS 10 ... Center electrode 16 ... Sealing body 17 ... Ceramic resistance 18 ... Sealing body 19 ... Terminal metal fitting 20 ... Insulator 28 ... Shaft hole 30 ... Main metal fitting 31 ... End surface 32 ... Mounting screw part 34 ... Trunk part 35 ... Groove part 36 ... Tool Engagement part 38 ... crimping part 40 ... ground electrode 50 ... gasket 100 ... spark plug 200 ... internal combustion engine 210 ... screw hole 500 ... cutting tool 510 ... holding part 514, 514a-514d ... engagement groove 530, 530a-530d ... blade Portions 531a to 531d ... Through holes 532, 532a to 532d ... Cutting edge ridges 534a to 534d ... Projections 536, 536a to 536d ... Rake faces 538, 538a to 538d ... Flanks 580, 580a to 580d ... Fixing screws 760 ... Center 910 ... Total shape tool 912a ... Edge of cutting edge 916 ... Rake face 918a, 918d Flank 960 ... center 980 ... metal shell CA1 ... axis Cmd ... rotational axis OL ... contour TP ... tapered portion Pc ... bent portion Rcb ... cutting range Dec ... distance Pwt ... polishing site

Claims (7)

Producing a rod-shaped center electrode;
Producing an insulator configured to allow insertion of the center electrode;
Producing a metal shell configured to be able to insert the insulator;
A process for producing a spark plug by assembling the center electrode, the insulator and the metal shell,
The process of producing the metallic shell includes
Preparing a cutting edge formed with cutting edge ridges bent at a plurality of locations along at least a part of the contour line of the metal shell, and a rake face corresponding to each part of the cutting edge ridge;
The material of the metal shell is cut using a cutting tool in which the height of the entire edge of the cutting edge is aligned with respect to the rotation axis for rotating the workpiece, and the blade is attached. Spark plug manufacturing method. It is a manufacturing method of the spark plug according to claim 1,
The blade portions are first and second blade portions in which cutting edge ridges having different shapes are formed,
The first and second blade portions are attached to the cutting tool such that the heights of the entire edges of the respective cutting blade edges of the first and second blade portions are aligned with the rotation axis. A method of manufacturing a spark plug characterized by the above. A method of manufacturing a spark plug according to claim 1 or claim 2,
In the spark plug according to the present invention, a convex portion is formed along the inclined direction of the rake face corresponding to at least one of the plurality of locations where the edge of the cutting edge is bent. Production method. A method for manufacturing a spark plug according to any one of claims 1 to 3,
At least a part of the edge of the cutting edge has a shape along a tapered portion of the metal shell that is inclined with respect to the axial direction of the metal shell. A method for manufacturing a spark plug according to any one of claims 1 to 4,
A plurality of the cutting edge ridges are formed in the blade part, and by changing the direction in which the blade part is attached to the cutting tool, a used cutting edge ridge and an unused cutting edge ridge A method for manufacturing a spark plug, characterized in that it can be replaced.   A cutting part having a cutting edge ridge that is bent at a plurality of locations along at least a part of the contour line of the metal shell of the spark plug, and a rake face corresponding to each part of the cutting edge is formed. A method for manufacturing a spark plug, comprising: cutting a material of the metal shell using a cutting tool attached with the entire height of the edge of the cutting edge aligned with respect to a rotation axis for rotating the metal shell. A method of manufacturing a metal shell used for a spark plug,
Preparing a cutting edge formed with cutting edge ridges bent at a plurality of locations along at least a part of the contour line of the metal shell, and a rake face corresponding to each part of the cutting edge ridge;
The material of the metal shell is cut using a cutting tool in which the height of the entire edge of the cutting edge is aligned with respect to the rotation axis for rotating the workpiece, and the blade is attached. A method of manufacturing a metal shell.

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