JP2006086055A - Main body fitting for spark plug and manufacturing method of spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide main body fittings keeping high accuracy and lengthen the life of a mold. <P>SOLUTION: In a first process, by extrusion-molding a first cylindrical work W1 in the axis direction, a second work W2 comprising a small diameter part 6 and a large diameter part 7 coaxially integrated with the small diameter part 6 is formed. In a second process, by extrusion-molding the second work W2 in the axial direction, the whole outer circumferential surface of the large diameter part 7 is made parallel to the axial direction and the cross sections vertical each other in the axial direction form a hexagon, and a third work W3 forming a first axial hole 18b pierced from the opposite side to the small diameter part 6 and positioning the tip part having a distance from the small diameter part 16 to form a large diameter corner part 18 is formed in the large diameter part 7. In a third process, by extrusion-molding the third work W3 in the axial direction, a remaining part 19b other than a main part 19a of the large diameter corner part 18 is swelled in the diameter direction and a fourth work W4 forming a flange part 29b directly connecting the remaining part 19b to the small diameter part 16 is formed, while the shape of the main part 19a on the opposite side to the small diameter part 16 of the large diameter corner part 18 is held. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spark plug metal shell and a spark plug manufacturing method.

  As shown in FIG. 9, a general spark plug 100 includes a cylindrical metal shell 90 shown in FIG. As shown in FIG. 9, a cylindrical insulator 91 extending in the axial direction of the metal shell 90 and having both ends protruding from both ends of the metal shell 90 is fixed in the metal shell 90. Further, the tip of the rod-shaped center electrode 92 protrudes from the tip of the insulator 91, the rear end of the center electrode 92 is electrically connected to the terminal 94 in the insulator 91, and the terminal 94 extends from the rear end of the insulator 91. It is protruding. On the other hand, one end of the ground electrode 93 is fixed to the metal shell 90, and a discharge gap is formed between the other end of the ground electrode 93 and the center electrode 92.

  The metal shell 90 constituting this type of spark plug is generally manufactured by a manufacturing method including the following steps using a mold.

  First, in the first step, a columnar first workpiece (not shown) is extruded in the axial direction. As a result, as shown in FIG. 11A, a second workpiece 62 is formed that includes a small diameter portion 62a and a large diameter portion 62b that is coaxial with the small diameter portion 62a on one end side of the small diameter portion 62a. A shallow shaft hole 62h is recessed in the end surface on the other end side of the small diameter portion 62a, and a shaft hole 62c for forming a first shaft hole 63c described later is recessed in the end surface on one end side of the large diameter portion 62b. Established.

  In the second step, the second workpiece 62 is extruded in the axial direction. Thus, as shown in FIG. 11B, the first shaft hole 63c is formed in the large diameter portion 62b from one end side, and the small diameter portion 62a is defined as the small diameter portion 63a. The tip of the first shaft hole 63c is located at a distance from the small diameter portion 63a. Thus, the third work 63 is formed with the large diameter portion 62b as a cylindrical large diameter cylindrical portion 63d. A shaft hole 63h deeper than the shaft hole 62h is recessed in the end surface on the other end side of the small diameter portion 63a.

  Next, in the third step, the third work 63 is extruded in the axial direction. As a result, as shown in FIG. 11 (c), the second shaft hole 64e is formed from one end side in the large diameter cylindrical portion 63d while maintaining the diameter of the first shaft hole 63c. The second shaft hole 64e has a smaller diameter than the first shaft hole 63c. In this way, the fourth workpiece 64 is formed by using the small diameter portion 63a as the small diameter cylindrical portion 64a whose one end is cylindrical. A shaft hole 64h deeper than the shaft hole 63h is recessed in the end surface on the other end side of the small diameter cylindrical portion 64a.

  Further, in the fourth step, the fourth work 64 is extruded in the axial direction. As a result, as shown in FIG. 11 (d), while maintaining the diameter of the first shaft hole 63c, the outer peripheral surface on one end side of the large-diameter cylindrical portion 63d is squeezed into the large-diameter corner portion 65f, and the small-diameter cylindrical portion 64a. Is a small diameter cylindrical portion 65a. The large-diameter corner portion 65f has a hexagonal cross section perpendicular to the axial direction. Thus, the other end side of the large-diameter corner portion 65f is a flange portion 65g that is directly continuous with the small-diameter cylindrical portion 65a, and the fifth workpiece 65 is formed. A shaft hole 65h deeper than the shaft hole 64h is recessed in the end face on the other end side of the small diameter cylindrical portion 65a.

  Thereafter, in the fifth step, the fifth work 65 is extruded in the axial direction, and the second shaft hole 64e is extended to the other end side as shown in FIG. 11 (e). Thereby, the small diameter cylinder part 65a is made into the small diameter cylinder part 66a extended to the other end side, and the 6th workpiece | work 66 is obtained. A shaft hole 66h deeper than the shaft hole 65h is recessed in the end surface on the other end side of the small-diameter cylindrical portion 66a.

  A method for manufacturing a spark plug metal shell including the same steps as described above is known in Patent Document 1. In this manufacturing method, since the large-diameter corner portion 65f, the flange portion 65g, and the small-diameter cylindrical portion 66a are formed by extrusion molding, productivity superior to cutting can be exhibited.

  As shown in FIG. 10, the sixth workpiece 66 obtained in this manner is formed into a shaft hole 89 by communicating the second shaft hole 64 e and the shaft hole 66 h with a drill. Further, the sixth workpiece 66 is cut on the outer peripheral surface on one end side of the large-diameter corner portion 65f and on the flange portion 65g side to form thin portions 83 and 84 in those portions, and the remaining large-diameter portion. The corner portion 65f is left as a clamping portion 81 that can be clamped by a spanner or the like. A male screw 86 is formed on the outer peripheral surface of the small diameter cylindrical portion 66a of the sixth work 66. The metal shell 90 thus obtained is inserted into the shaft hole 89 with the insulator 91 assembled with the center electrode 92 shown in FIG. 9 and the like, and the thin portion 83 is caulked to the shaft side to thereby form the insulator 91 and the like. Be united. Further, the outer electrode 93 is fixed to the tip of the small-diameter cylindrical portion 66a of the metal shell 90 by welding or the like. Thus, the spark plug 100 is obtained.

  However, when the metal shell 90 is manufactured in this way, the large-diameter corner portion 65f is formed by drawing in the fourth step, so there is a limit in the accuracy of the large-diameter corner portion 65f. On the other hand, the manufacturing method of the metal shell for spark plugs of patent document 2 is proposed.

  This manufacturing method also uses a mold. First, in a first step, a cylindrical first workpiece (not shown) is extruded in the axial direction. As a result, as shown in FIG. 12A, a second workpiece 72 is formed that includes a small diameter portion 72a and a large diameter portion 72b that is coaxial with the small diameter portion 72a on one end side of the small diameter portion 72a. A shallow conical shaft hole 72h is recessed in the end surface on the other end side of the small diameter portion 72a, and a conical shape for forming a first shaft hole 73c described later on the end surface on one end side of the large diameter portion 72b. The shaft hole 72c is recessed.

  In the second step, the second workpiece 72 is extruded in the axial direction. As a result, as shown in FIG. 12B, the outer peripheral surface on one end side of the large diameter portion 72b has a hexagonal shape in a cross section perpendicular to the axial direction, and the large diameter portion 72b is viewed from the side opposite to the small diameter portion 72a. A first shaft hole 73c is formed. Thus, one end side of the large diameter portion 72b is a large diameter corner portion 73d, and the small diameter portion 72a is a small diameter portion 73a. The tip of the first shaft hole 73c is located at a distance from the small diameter portion 73a. A cylindrical intermediate portion 73e is formed between the large-diameter corner portion 73d and the small-diameter portion 73a. The cylindrical intermediate portion 73e forms an outer diameter intermediate between the opposite-side dimension of the large-diameter corner portion 73d and the outer diameter of the small-diameter portion 73a. In this way, the third work 73 is formed. A shaft hole 73h deeper than the shaft hole 72h is recessed in the end surface on the other end side of the small diameter portion 73a.

  Next, in the third step, the third work 73 is extruded in the axial direction. As a result, the intermediate portion 73e is expanded in the radial direction to form a flange portion 74f as shown in FIG. At this time, the first shaft hole 73c is formed in the same manner as in the second step, and extends in the axial direction to the inside of the flange portion 74f. Thus, the large diameter corner portion 73d becomes the large diameter corner portion 74d, and the small diameter portion 73a also becomes the small diameter portion 74a. Thus, the fourth work 74 is formed. A shaft hole 74h deeper than the shaft hole 73h is recessed in the end surface on the other end side of the small diameter portion 74a.

  Further, in the fourth step, the fourth work 74 is extruded in the axial direction. Accordingly, as shown in FIG. 12D, the second shaft hole 75e is formed from one end side while maintaining the shapes of the first shaft hole 73c, the large diameter corner portion 74d, and the flange portion 74f. The second shaft hole 75e has a smaller diameter than the first shaft hole 73c. In this way, the fifth workpiece 75 is formed by using the small diameter portion 74a as the small diameter cylindrical portion 75a whose one end is cylindrical. A shaft hole 75h deeper than the shaft hole 74h is recessed in the end face on the other end side of the small diameter cylindrical portion 75a.

  Thereafter, in the fifth step, the space between the second shaft hole 75e and the shaft hole 75h of the fifth work 75 is punched out in the same manner as the sixth work 66 obtained by the general manufacturing method shown in FIG. As a result, as shown in FIG. 12E, a shaft hole 76h in which the second shaft hole 75e and the shaft hole 75h are integrated is formed, and the small diameter cylindrical portion 75a is defined as the small diameter cylindrical portion 76a. In this way, the sixth workpiece 76 which is the final forged product is formed. The sixth workpiece 76 maintains the shapes of the first shaft hole 73c, the large-diameter corner portion 74d, and the flange portion 74f.

  The sixth workpiece 76 is processed in the same manner as the sixth workpiece 66 of FIG. 11 having the shaft hole 89 (see FIG. 10). As shown in FIG. 10, the thin portions 83 and 84, the sandwiching portion 81, and A male screw 86 is formed. Further, the metallic shell 90 obtained in this way is made the spark plug 100 of FIG. 9 by the same general manufacturing method.

  According to this manufacturing method, since the large-diameter corner portion 74d is formed by extrusion rather than drawing in the second step, the amount of deformation of the workpiece is reduced, and the processing can be performed without difficulty. For this reason, according to this manufacturing method, a more accurate spark plug metal shell can be obtained.

European Patent Application Publication No. EP0036050A1 JP-A-4-329287

  However, when the metal shell is manufactured by the manufacturing method disclosed in Patent Document 2, the accuracy of the flange portion is not yet sufficient, and the life of the mold for shaping the shape is short.

  The present invention has been made in view of the above-described conventional situation, and it is an object to be solved to obtain a metal shell that maintains high accuracy and to extend the life of a mold.

  The inventor has intensively studied to solve the above problems. And in the manufacturing method of patent document 2, in order to form the flange part with the largest diameter in a metal shell, the intermediate part is formed between the large diameter corner | angular part and the small diameter part with respect to a workpiece | work. However, it came to mind that the amount of deformation of the workpiece was large and the accuracy of the flange portion was not sufficient.

  Further, in the manufacturing method disclosed in Patent Document 2, the workpiece has a complicated step between the large-diameter corner portion and the intermediate portion and between the intermediate portion and the small-diameter portion, and the complex of the mold for shaping the same shape is required. It was discovered that the mold was damaged at many points by the pressure of the workpiece that was deformed by extrusion molding against a large step. Thus, the inventors have completed the following invention.

The spark plug metal shell manufacturing method according to the present invention includes a second part comprising a small-diameter part and a large-diameter part coaxially and integrally formed with the small-diameter part by extruding a cylindrical first workpiece in the axial direction. A first step of forming a workpiece;
By extruding the second workpiece in the axial direction, all the outer peripheral surfaces of the large-diameter portion are formed in a polygonal shape with cross sections parallel to the axial direction and perpendicular to each other in the axial direction. A third shaft hole having a large diameter corner portion is formed by drilling the diameter portion from the opposite side of the small diameter portion to form a first shaft hole having a tip located at a distance from the small diameter portion in the large diameter portion. A second step of forming a workpiece;
By extruding the third work piece in the axial direction, the remaining portion of the large diameter corner portion excluding the main portion while maintaining the shape of the main portion on the opposite side of the small diameter portion. And a third step of forming a fourth work in which the remaining portion directly forms a flange portion that continues to the small diameter portion.

  In the manufacturing method of the present invention, in the first step, a cylindrical first workpiece is extruded in the axial direction. Thereby, the 2nd workpiece | work consisting of a small diameter part and the large diameter part which is coaxial and united with this small diameter part is formed.

  Subsequently, in the second step, the second workpiece is extruded in the axial direction. As a result, all the outer peripheral surfaces of the large diameter portion are parallel to the axial direction and form polygons with cross sections perpendicular to each other in the axial direction. Further, the first shaft hole is formed in the large diameter portion from the side opposite to the small diameter portion. Since the first shaft hole forms a flange portion in a third step to be described later, the tip is located at a distance from the small diameter portion. Thus, the third workpiece is formed with the large diameter portion as the large diameter corner portion.

  Thereafter, in the third step, the third workpiece is extruded in the axial direction. The large-diameter corner portion is composed of a main portion opposite to the small-diameter portion and a remaining portion excluding the main portion, and the first shaft hole is located at a distance from the small-diameter portion and the tip is located. Thus, if the third workpiece is extruded in the axial direction, the material at the tip of the first shaft hole swells in the radially outward direction. Thereby, the remaining portion is expanded in the radial direction while maintaining the shape of the head portion, and the remaining portion forms a flange portion directly continuing to the small diameter portion. Thus, the fourth work is formed.

  The phrase “the flange portion is directly continuous with the small diameter portion” means that there is no intermediate portion such as the intermediate portion disclosed in Patent Document 2 between the flange portion and the small diameter portion, and both are adjacent to each other.

  For this reason, according to this manufacturing method, in the third step, the large-diameter corner portion is not drawn, and the large-diameter corner portion is formed only by extrusion molding. Processing can be performed without difficulty.

  In particular, according to this manufacturing method, in the third step, the flange portion is formed by expanding the remainder of the large-diameter corner portion whose diameter difference from the flange portion after expansion is smaller than the conventional intermediate portion. For this reason, the amount of deformation of the work is smaller than when the flange portion is formed by forming the intermediate portion. That is, since the remaining portion forming the flange portion is previously installed with the same diameter as the main portion of the large-diameter corner portion and this remaining portion is expanded, the amount of deformation in one process is prevented from increasing. For this reason, a flange part can be formed more accurately.

  Moreover, according to this manufacturing method, since the 3rd workpiece | work does not have an intermediate part, the metal mold | die of a 2nd process does not shape a complicated level | step difference.

  Therefore, according to the manufacturing method of the present invention, it is possible to obtain a metal shell maintaining high accuracy and to prolong the life of the mold.

  Moreover, according to this manufacturing method, since it can process without difficulty, a material with higher rigidity can be used for a workpiece | work. Thereby, the intensity | strength of the metal shell for spark plugs can be improved, and the intensity | strength of a spark plug can be improved by extension.

  In the manufacturing method of the present invention, the fourth workpiece is extruded in the axial direction, thereby forming a second shaft hole communicating with the first shaft hole in the small diameter portion to form a fifth work. It is preferable to include a fourth step. Thereby, a shaft hole can be drilled by the same extrusion molding as in other steps. For this reason, it is possible to perform the process of drilling the shaft hole with an integrated facility such as a progressive die, and it is possible to shorten the machining time and the machining cost.

  In the manufacturing method of the present invention, by forming the first shaft hole with a diameter larger than that of the second shaft hole, it is possible to form the stepped portion that supports the insulator with the spark plug metal shell.

  The metal shell obtained by the above method for manufacturing a spark plug metal shell can be used for manufacturing a spark plug.

  Hereinafter, a method for manufacturing the spark plug metal shell 90 (see FIG. 10) according to Examples 1 to 3 will be described with reference to the drawings. These production methods of Examples 1 to 3 embody the production method of the present invention.

  In Example 1, first, in the first step, a columnar first workpiece W1 shown in FIG. 1 is prepared. Here, FIG. 1A shows a front view of the first workpiece W1, and FIG. 1B shows a bottom view thereof. The first workpiece W1 is carbon steel (S25C, S35C, etc.).

  And the 1st workpiece | work W1 is extrusion-molded using the metal mold | die P1 for extrusion molding shown to Fig.2 (a). The mold P1 includes a die 1, a punch 2, a pin 3, and a sleeve 4.

  A cavity C1 extending in the axial direction is provided in the die 1. The cavity C1 has a smaller diameter on the front end side (lower side in FIG. 2A) than the rear end side, and a tapered step is formed between the front end side and the rear end side. The die 1 is provided with a punch 2 that can be raised and lowered at the rear end side of the cavity C1, and a pin 3 and a sleeve 4 are provided at the front end side of the cavity C1.

  In this mold P1, the first work W1 is inserted into the cavity C1 from the rear end side of the mold P1 with the punch 2 raised, and then the punch 2 is lowered. Thus, the first workpiece W1 is extruded forward in the axial direction.

  Thereby, the small diameter part 6 and the large diameter part 7 are formed, and the 2nd workpiece | work W2 is formed. In the second workpiece W2, the small diameter portion 6 and the large diameter portion 7 are coaxial and integrated. A shaft hole 6a concentric with the axis passing through the center of the front end face is formed, and a shaft hole 7a concentric with the axis passing through the center of the rear end face is formed. Here, FIG. 2B represents a plan view of the second workpiece W2, and FIG. 2C represents a bottom view thereof.

  Next, in the second step, the second workpiece W2 is extrusion-molded using the extrusion mold P2 shown in FIG. The mold P2 includes a die 11, a punch 12, a pin 13, and sleeves 10 and 14.

  A cavity C2 extending in the axial direction is provided in the die 11. The cavity C2 has a smaller diameter on the front end side (lower side in FIG. 3A) than the rear end side, and a step perpendicular to the axis is formed between the front end side and the rear end side. The rear end side of the cavity C2 has a hexagonal shape in which all inner peripheral surfaces are parallel to the axial direction and are perpendicular to each other in the axial direction. The die 11 is provided with a punch 12 and a sleeve 10 on the rear end side of the cavity C2 so as to be able to be raised and lowered, and a pin 13 and a sleeve 14 are provided on the front end side of the cavity C2.

  In the mold P2, the second work W2 is inserted into the cavity C2 from the rear end side of the mold P2 with the punch 12 and the sleeve 10 raised, and then the punch 12 and the sleeve 10 are lowered. Thus, the second workpiece W2 is extruded backward in the axial direction.

  Thereby, all the outer peripheral surfaces of the large-diameter portion 7 of the second workpiece W2 are formed in a hexagonal shape with cross sections parallel to the axial direction and perpendicular to each other in the axial direction. Further, the first shaft hole 18 b is formed in the large diameter portion 7 from the side opposite to the small diameter portion 6. The first shaft hole 18b has a distal end located at a distance from the small-diameter portion 16 formed by deforming the small-diameter portion 6 in order to form the flange portion 29b in a third step described later. In this way, the large diameter portion 7 is used as the large diameter corner portion 18, and the third workpiece W3 is formed. In the third workpiece W3, the small-diameter portion 16 and the large-diameter corner portion 18 are directly and coaxially continuous, and a first shaft hole 18b is formed concentrically with an axis passing through the center of the rear end surface. A shaft hole 16a deeper than the shaft hole 6a is formed concentrically with the shaft center passing through the center of the tip surface of the third workpiece W3. Here, FIG. 3B shows a plan view of the third workpiece W3, and FIG. 3C shows a bottom view thereof.

  In the large-diameter corner portion 18, the opposite side dimension of the hexagon that is a cross-sectional shape perpendicular to the axial direction is substantially equal to the diameter of the large-diameter portion 7 of the second workpiece W2. In other words, the hexagonal inscribed circle is substantially equal to the diameter of the large-diameter portion 7 of the second workpiece W2. Of the large-diameter corner portion 18, a portion that is located on the opposite side of the small-diameter portion 16 and later becomes a clamping portion corresponds to the main portion 19a, and a portion that is deformed except for the main portion 19a corresponds to the remaining portion 19b.

  According to the second step, since the third workpiece W3 does not have a conventional intermediate portion, the mold P2 in the second step does not form a complicated step.

  Then, in the third step, the third workpiece W3 is extrusion-molded using an extrusion molding die P3 shown in FIG. The mold P3 includes a die 21, an inner punch 22, an outer punch 25, a pin 23, and sleeves 20 and 24.

  A cylindrical cavity C3 extending in the axial direction is provided in the die 21. A cavity C4 extending in the axial direction is provided in the outer punch 25. The cavity C4 has a larger diameter on the front end side (lower side in FIG. 4A) than the rear end side, and a tapered step is formed between the front end side and the rear end side. The outer punch 25 is provided with an inner punch 22 and a sleeve 20 on the rear end side of the cavity C4 so as to be raised and lowered, and the die 21 is provided with a pin 23 and a sleeve 24 on the front end side of the cavity C3.

  In this mold P3, after the small diameter portion 16 of the third workpiece W3 is inserted into the cavity C3 with the die 21 and the outer punch 25 separated, the outer punch 25 is lowered. Then, the inner punch 22 and the sleeve 20 are lowered into the first shaft hole 18b of the third workpiece W3.

  The large-diameter corner portion 18 includes a main portion 19a opposite to the small-diameter portion 16 and a remaining portion 19b excluding the main portion 19a. The first shaft hole 18b is spaced from the small-diameter portion 16 at a distal end. Therefore, if the third workpiece W3 is extruded in the axial direction in this way, the material at the tip of the first shaft hole 18b swells in the radially outward direction. Thereby, among the large-diameter corner portion 18 of the third workpiece W3, the remaining portion 19b is expanded in the radial direction while maintaining the shape of the main portion 19a, and the remaining portion 19b forms a flange portion 29b that is directly connected to the small-diameter portion 16. . Thus, the fourth work W4 is formed. In the fourth workpiece W4, the small diameter portion 16 and the flange portion 29b are coaxially adjacent to each other, and the flange portion 29b and the large diameter corner portion 28 are coaxially integrated with a tapered step. The fourth workpiece W4 is formed with a first shaft hole 28b concentrically with an axis passing through the center of the rear end face. Further, the shape of the shaft hole 16a obtained in the second step concentrically with the axis passing through the center of the tip surface of the fourth workpiece W4 is maintained. Here, FIG. 4B shows a plan view of the fourth workpiece W4, and FIG. 4C shows a bottom view thereof.

  According to the third step, the flange portion 29b is formed only by extrusion molding inside the large-diameter corner portion 18 without performing the drawing process of the large-diameter corner portion 18 as in Patent Document 1, and thus the large-diameter corner portion is formed. The accuracy of the part 18 can be maintained.

  In particular, in this manufacturing method, the flange portion 29b is formed by expanding the large-diameter corner portion 18 whose diameter difference from the expanded flange portion 29b is smaller than that of the conventional intermediate portion, so that the intermediate portion is formed. Thus, it is possible to form the flange portion 29b with higher accuracy than the formation of the flange portion 29b with less deformation of the third workpiece W3.

  In addition, in the first shaft hole 28b of the fourth workpiece W4 obtained in the third step, the processing trace of the first shaft hole 18b drilled in the second step remains. This processing trace can be hidden by subsequent plating without any problem in accuracy.

  Next, in the fourth step, the fourth workpiece W4 is extrusion-molded using an extrusion molding die P4 shown in FIG. The mold P4 includes a die 31, an inner punch 32, an outer punch 35, a pin 33, and sleeves 30 and 34.

  A cylindrical cavity C5 extending in the axial direction is provided in the die 31. A cavity C6 extending in the axial direction is provided in the outer punch 35. The cavity C6 has a larger diameter on the front end side (lower side in FIG. 5A) than the rear end side, and a tapered step is formed between the front end side and the rear end side. The outer punch 35 is provided with an inner punch 32 and a sleeve 30 on the rear end side of the cavity C6 so as to be raised and lowered, and the die 31 is provided with a pin 33 and a sleeve 34 on the front end side of the cavity C5.

  In this mold P4, after inserting the small diameter portion 16 of the fourth workpiece W4 into the cavity C5 with the die 31 and the outer punch 35 separated, the outer punch 35 is lowered. Then, the inner punch 32 and the sleeve 30 are lowered into the first shaft hole 28b of the fourth workpiece W4.

  As a result, the second shaft hole 36b is formed, the small diameter portion 16 and the flange portion 29b become the small diameter portion 36 and the flange portion 39b, and the large diameter corner portion 28 and the first shaft hole 28b maintain their shapes, and the fifth workpiece. W5 is formed. The small-diameter portion 36 of the fifth workpiece W5 has a shape extending to the front end side with respect to the small-diameter portion 16 of the fourth workpiece W4, and a second shaft hole 36b is formed on the rear end side thereof. Further, the flange portion 39b of the fifth workpiece W5 has a first shaft hole 28b on the rear end side thereof, and a second shaft hole 36b communicating with the first shaft hole 28b is formed on the front end side thereof. ing. The remaining shape of the fifth workpiece W5 is the same as that of the fourth workpiece W4. A shaft hole 36a that is deeper than the shaft hole 16a is formed concentrically with the axis passing through the center of the tip surface of the fifth workpiece W5. Here, FIG.5 (b) represents the top view of the 5th workpiece | work W5, and FIG.5 (c) represents the bottom view.

  In the fourth step, the second shaft hole 36b and the shaft hole 36a are formed by the same extrusion molding as in the third step. For this reason, it is possible to perform up to the fourth step by an integrated facility such as a progressive die, and it is possible to shorten the processing time and the processing cost.

  In the fourth step, the second shaft hole 36b has a smaller diameter than the first shaft hole 28b. In other words, the first shaft hole 28b has a larger diameter than the second shaft hole 36b. Thereby, the 5th workpiece | work W5 can form the step part which supports the insulator 91 (refer FIG. 9).

  Then, in the fifth step, the fifth workpiece W5 is extrusion-molded using the extrusion molding die P5 shown in FIG. The mold P5 includes a die 41, an inner punch 42, an outer punch 45, a pin 43, and sleeves 40 and 44.

  A cylindrical cavity C7 extending in the axial direction is provided in the die 41. A cavity C8 extending in the axial direction is provided in the outer punch 45. The cavity C8 has a larger diameter on the front end side (lower side in FIG. 6A) than the rear end side, and a tapered step is formed between the front end side and the rear end side. The outer punch 45 is provided with an inner punch 42 and a sleeve 40 on the rear end side of the cavity C8 so as to be raised and lowered, and the die 41 is provided with a pin 43 and a sleeve 44 on the front end side of the cavity C7.

  In this mold P5, after the small diameter portion 36 of the fifth workpiece W5 is inserted into the cavity C7 in a state where the die 41 and the outer punch 45 are separated from each other, the outer punch 45 is lowered. Then, the inner punch 42 and the sleeve 40 are lowered into the first shaft hole 28b of the fifth workpiece W5.

  As a result, a second shaft hole 46b deeper than the second shaft hole 36b is formed, the small diameter portion 36 becomes the small diameter portion 46, and the large diameter corner portion 28, the first shaft hole 28b and the flange portion 39b maintain their shapes. A sixth work W6 is formed. The small diameter portion 46 of the sixth workpiece W6 has a shape extending to the tip side from the small diameter portion 36 of the fifth workpiece W5. The remaining shape of the sixth workpiece W6 is the same as that of the fifth workpiece W5. A shaft hole 46a that is deeper than the shaft hole 36a is formed concentrically with the axis passing through the center of the tip surface of the sixth workpiece W6. Here, FIG. 6B shows a plan view of the sixth workpiece W6, and FIG. 6C shows a bottom view thereof.

  In the fifth step, the second shaft hole 46b and the shaft hole 46a are formed by the same extrusion molding as in the fourth step. For this reason, it is possible to carry out up to the fifth step by an integrated facility such as a progressive die, and it is possible to shorten the processing time and the processing cost. In addition, the 4th process and 5th process in Example 1 correspond to the 4th process of this invention.

  Finally, the sixth workpiece W6 is taken out from the mold P5 and processed in the same manner as the sixth workpiece 66 in FIG. 11 having the shaft hole 89 (see FIG. 10) and the sixth workpiece 76 in FIG. As shown, thin portions 83 and 84, a clamping portion 81 and a male screw 86 are formed. Further, the metallic shell 90 obtained in this way is made the spark plug 100 of FIG. 9 by the same general manufacturing method.

  Therefore, according to the manufacturing method of the first embodiment, it is possible to obtain the metal shell 90 maintaining high accuracy and to extend the life of the mold P2.

  Moreover, according to this manufacturing method, since it can process without difficulty, a material with higher rigidity can be used for a workpiece | work. Thereby, the intensity | strength of the metal shell 90 can be improved and the intensity | strength of the spark plug 100 can be improved by extension.

  In the first embodiment, the sleeve 4 on the tip side of the mold P1 is fixed relatively to the mold P1 during extrusion molding. As the punch 2 is lowered, the pin 3 is slightly raised from the rear end surface of the sleeve 4 to form the shaft hole 6a. Similarly, at the time of extrusion molding, the sleeve 14 on the front end side of the mold P2 is also fixed relatively to the mold P2, and the sleeve 24 on the front end side of the mold P3 is also fixed relatively to the mold P3. The sleeve 34 on the tip side of the mold P4 is also fixed relatively to the mold P4, and the sleeve 44 on the tip side of the mold P5 is also fixed relatively to the mold P5. The sleeves 4, 14, 24, 34, 44 are independent of the pins 3, 13, 23, 33, 43 and the molds P1, 2, 3, 4, 5 after extrusion. It is possible to rise. On the other hand, in the first embodiment, the sleeves 10, 20, 30, and 40 on the rear end sides of the molds P2 to P5 may not be in contact with the rear end surfaces of the works W3 to W6.

  For this reason, at the time of extrusion molding, the sleeves 4, 14, 24, 34, 44 and the pins 3, 13, 23, 33, 43 are not displaced with respect to the respective molds P1, 2, 3, 4, 5, There is no variation on the lower surface of each workpiece W2-6. Further, the lower surfaces of the punches 12, 22, 32, and 42 allow the upper surfaces of the workpieces W3 to 6 to be raised (so-called backward extrusion molding). Then, after the extrusion molding, the workpieces W2 to W6 can be taken out by the sleeves 4, 14, 24, 34, and 44.

  In the manufacturing method of Example 2, in the third step, the third workpiece W3 is extrusion-molded by using the mold P13 shown in FIG. Other steps are the same as those in the first embodiment.

  The mold P13 includes a die 121, a punch 122, a pin 123, and sleeves 120 and 124.

  A cavity C13 extending in the axial direction is provided in the die 121. In the cavity C13, the front end side (the lower side in FIG. 7) has a smaller diameter than the rear end side, and a step 121a orthogonal to the axis is formed between the front end side and the rear end side. The die 121 is provided with a punch 122 and a sleeve 120 on the rear end side of the cavity C13 so as to be raised and lowered, and a pin 123 and a sleeve 124 are provided on the front end side of the cavity C13.

  The sleeve 120 includes a first cylindrical portion 120b located on the rear end side, and a second cylindrical portion 120c having a step 120a on the front end side of the first cylindrical portion 120b and concentric with the first cylindrical portion 120b and having a small diameter. Become. The step 120 a is in contact with the upper surface of the die 121. A cavity C <b> 14 extending in the axial direction is provided in the sleeve 120. A tapered surface 120d is formed at the distal end of the second cylindrical portion 120c and is located on the rear end side with respect to the step 121a of the die 121 so that the distal end side has a larger diameter than the rear end side. Note that an urging spring (not shown) having an urging force on the distal end side is provided at the rear end of the sleeve 120.

  In the mold P13, after the third workpiece W3 is inserted into the cavity C13 from the rear end side of the mold P13 with the punch 122 and the sleeve 120 raised, the sleeve 120 is first lowered. Accordingly, the step 120 a of the sleeve 120 can be brought into contact with the upper surface of the die 121, and the tapered surface 120 d can be positioned on the rear end side of the step 121 a of the die 121. Then, the punch 122 is lowered. Thus, the third work W3 is extruded backward in the axial direction.

  Thereby, the 4th work W4 'similar to the 4th work W4 obtained at the 3rd process of Example 1 can be obtained. Further, the fourth work W4 'obtained in this way has the same effect as the fourth work W4 obtained by the third step of the first embodiment. Other functions and effects are the same as those of the first embodiment.

  In the manufacturing method of Example 3, in the third step, the third workpiece W3 is extrusion-molded using the mold P23 shown in FIG. Other steps are the same as those in the first embodiment.

  The mold P23 includes a lower mold 221, a constraining mold 225, a plurality of split molds 226, a punch 222, a pin 223, and sleeves 220 and 224.

  A cavity C23 extending in the axial direction is provided in the lower mold 221. Each split mold 226 is provided with a cavity C24 extending in the axial direction. The cavity C24 has a larger diameter on the front end side (lower side in FIG. 8) than the rear end side, and a tapered step is formed between the front end side and the rear end side.

  Further, a constraining mold 225 is provided on the rear end side of each split mold 226, and a biasing spring 227 having a biasing force on the front end side is provided on the rear end side of the constraining mold 225. Inside the constraining die 225, the punch 222 and the sleeve 220 are provided so as to be raised and lowered, and the lower die 221 is provided with a pin 223 and a sleeve 224 on the tip side of the cavity C23.

  The inner surface on the front end side of the constraining die 225 is an inclined surface F1 whose rear end side is close to the axis. A plurality of split molds 226 are arranged around the axis. An inclined surface F2 that is aligned with the inclined surface F1 is formed on the outer peripheral surface of each split mold 226. Each split mold 226 forms a cavity C24 in a state where the split mold 226 is in contact with the rear end surface of the lower mold 221. Further, the constraining die 225 urges each split die 226 toward the tip side by the urging force of the urging spring 227.

  In the mold P23, the constraining mold 225, the punch 222, and the sleeve 220 are raised, and the third work W3 is placed in the cavity C23 of the lower mold 221 in a state where each split mold 226 is divided in the axial direction and the outer side. After insertion from the rear end side of the mold P23, the restraint mold 225 is first lowered. As a result, each split mold 226 is biased toward the axis. Thereafter, the punch 222 and the sleeve 220 are lowered.

  As a result, a fourth work W4 ″ that is the same as the fourth work W4 obtained in the third step of the first embodiment can be obtained. The fourth work W4 ″ obtained in this way is the third work W4 ″ obtained in the first embodiment. The same effect as the fourth work W4 obtained by the process is achieved.

  Further, if only the punch 222 is replaced in the mold P23 using each split mold 226, the fourth step and the fifth step in the first embodiment can also be performed. Other functions and effects are the same as those of the first embodiment.

  In addition, the 3rd process of the said Example 1, a 4th process, a 5th process, and each metal mold | die P3-5 in the said Example 3 and P23 are the small diameters of the workpiece | work W3-5 in the state which inserted the workpiece | work W3-5. A portion perpendicular to the axial direction is divided between the portions 16 and 36 and the large-diameter corner portion 18 or the flange portions 29b and 39b. The position of this division may be the position of the tip in the step between the flange portions 29b, 39b and the large diameter corner portion 18.

  In the above, the present invention has been described with reference to the first to third embodiments. However, the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the spirit of the present invention. Absent.

  The present invention is applicable to a spark plug metal shell and a spark plug manufacturing method.

FIG. 4A is a front view of a first work, and FIG. 5B is a bottom view of the first work in the manufacturing method according to the first embodiment. FIG. 4A is a sectional view of the mold and the second workpiece in the first step, FIG. 5B is a plan view of the second workpiece, and FIG. FIG. FIG. 4A is a sectional view of a mold and a third work in the second step, FIG. 5B is a plan view of the third work, and FIG. 5C is a bottom surface of the third work. FIG. According to the manufacturing method of Example 1, FIG. (A) is a sectional view of the mold and the fourth workpiece in the third step, FIG. (B) is a plan view of the fourth workpiece, and (c) is the bottom surface of the fourth workpiece. FIG. According to the manufacturing method of Example 1, FIG. (A) is a sectional view of the mold and the fifth workpiece in the fourth step, FIG. (B) is a plan view of the fifth workpiece, and (c) is the bottom surface of the fifth workpiece. FIG. According to the manufacturing method of Example 1, FIG. (A) is a sectional view of the mold and the sixth workpiece in the fifth step, FIG. (B) is a plan view of the sixth workpiece, and (c) is the bottom surface of the sixth workpiece. FIG. It is sectional drawing of the metal mold | die and 4th workpiece | work in a 3rd process in connection with the manufacturing method of Example 2. FIG. It is sectional drawing of the metal mold | die and 4th workpiece | work in a 3rd process in connection with the manufacturing method of Example 3. FIG. It is a side view of a partial cross section of a spark plug according to a conventional manufacturing method. It is a side view of a partial cross section of a metal shell according to a conventional manufacturing method. FIG. 4A is a side view and a plan view of a partial cross section of the second workpiece, FIG. 5B is a side view and a plan view of a partial cross section of the third workpiece, and FIG. FIG. 4D is a side view and a plan view of a partial cross section of the fifth workpiece, FIG. 4E is a side view and a plan view of a partial cross section of the sixth workpiece, and FIG. FIG. FIG. 4A is a side view and a plan view of a partial cross section of the second workpiece, FIG. 5B is a side view and a plan view of a partial cross section of the third workpiece, and FIG. FIG. 4D is a side view and a plan view of a partial cross section of the fifth workpiece, FIG. 4E is a side view and a plan view of a partial cross section of the sixth workpiece, and FIG. FIG.

Explanation of symbols

90 ... metal shell 100 ... spark plug W1 ... first workpiece 6, 16, 36, 46 ... small diameter portion 7 ... large diameter portion W2 ... second workpiece 18b, 28b ... first shaft hole 18, 28 ... large diameter corner portion W3 ... 3rd work 19a ... Head part 19b ... Remaining parts 29b, 39b ... Flange part W4 ... 4th work 36b, 46b ... 2nd shaft hole W5 ... 5th work

Claims (4)

A first step of forming a second workpiece comprising a small-diameter portion and a large-diameter portion coaxially and integrally with the small-diameter portion by extruding a cylindrical first workpiece in the axial direction;
By extruding the second workpiece in the axial direction, all the outer peripheral surfaces of the large-diameter portion are formed in a polygonal shape with cross sections parallel to the axial direction and perpendicular to each other in the axial direction. A third shaft hole having a large diameter corner portion is formed by drilling the diameter portion from the opposite side of the small diameter portion to form a first shaft hole having a tip located at a distance from the small diameter portion in the large diameter portion. A second step of forming a workpiece;
By extruding the third work piece in the axial direction, the remaining portion of the large diameter corner portion excluding the main portion while maintaining the shape of the main portion on the opposite side of the small diameter portion. And a third step of forming a fourth work in which the remaining portion directly forms a flange portion that is continuous with the small-diameter portion, and a method for manufacturing a spark plug metal shell.   A fourth step of forming a fifth work by forming a second shaft hole communicating with the first shaft hole in the small-diameter portion by extruding the fourth work piece in the axial direction; The manufacturing method of the metal shell for spark plugs of Claim 1 characterized by the above-mentioned.   The method for manufacturing a metal shell for a spark plug according to claim 2, wherein the first shaft hole has a larger diameter than the second shaft hole.   A spark plug manufacturing method comprising manufacturing a spark plug from the metal shell obtained by the method for manufacturing a spark plug metal shell according to any one of claims 1 to 3.

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