JP6456813B2 - Spark plug manufacturing equipment - Google Patents

Description

  The present invention relates to a spark plug manufacturing apparatus.

  The spark plug is installed in the engine by being screwed and fixed to the cylinder head. Therefore, a screw is formed on the outer surface of the metal shell of the spark plug.

Japanese Patent Laid-Open No. 4-300041

  In the spark plug manufacturing apparatus disclosed in Patent Document 1, the feed speed of a die for performing a rolling process on a workpiece having a portion serving as a metal shell is fast until the die sufficiently bites into the workpiece, and the die sufficiently bites into the workpiece. From this point, the accuracy of screw formation is prevented from deteriorating by slowing down. However, when a hollow cylindrical workpiece is applied to such a manufacturing apparatus, the inner diameter may be reduced due to deformation and crushing of the workpiece. Further, even when the die feed rate is constant, the inner diameter may be reduced due to deformation and crushing of the workpiece. For this reason, when a rolling process using a die is performed on a hollow cylindrical workpiece, a technique capable of forming a screw portion on the outer surface of the workpiece while suppressing a reduction in the inner diameter of the workpiece is desired. It was.

  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.

を満たす前記送り速度で前記ダイスを前記軸中心に向けて送ることを特徴とする。この形態によれば、３ダイス式によりワークを３点で支持するため、２ダイス式と比べてダイスがワークと接触することによってワークを支持する支持点の間におけるワークの円弧長さが３分の２になることから、ダイスがワークを内径側に押す力を分散させることができる。このため、中空円筒状のワークの内径が縮小することを抑制しつつそのワークの外側面にねじを形成することができる。また、この形態によれば、数式Iを満たすよう、送り速度の平均ｆ、長さｔおよび距離Ｐを調整することによって、より一層精度よくワークの内径縮小を抑制することおよびワークの外側面におけるねじ形成を両立できる。 (1) According to one aspect of the present invention, a spark plug manufacturing apparatus is provided. The spark plug manufacturing apparatus includes a die for forming a screw on an outer surface of a hollow cylindrical workpiece having a portion serving as a metal shell, and a screw is formed on the die by feeding the die toward the axial center of the workpiece. In the spark plug manufacturing apparatus comprising: a die instructing unit, wherein the die is a three-die type and a screw is formed on the outer surface, and the die instructing unit is configured to form the screw on the outer surface. The average feed speed of the dies from when the dies are fed toward the axis center until the stagnation is defined as f (mm / rev), and the thickness of the workpiece in the direction orthogonal to the axial direction of the workpiece is t. (Mm) and the pitch of the screw formed on the workpiece is P (mm), the following formula I

The die is fed toward the axis center at the feed speed that satisfies the condition. According to this embodiment, since the workpiece is supported at three points by the three-die type, the arc length of the workpiece between the support points for supporting the workpiece is 3 minutes compared to the two-die type when the die contacts the workpiece. Therefore, the force by which the die pushes the work toward the inner diameter side can be dispersed. For this reason, it is possible to form a screw on the outer surface of the work while suppressing a reduction in the inner diameter of the hollow cylindrical work. Further, according to this embodiment, by adjusting the average feed speed f, the length t, and the distance P so as to satisfy the formula I, the inner diameter reduction of the workpiece can be suppressed more accurately and the outer surface of the workpiece can be reduced. Both screw formation can be achieved.

  (2) In the spark plug manufacturing apparatus according to the above aspect, the dice instruction unit may cause the dice to be sent to the work by decreasing the feed speed every time the dice rotates once. According to this form, it is easy to increase the thread on the outer surface of the workpiece by increasing the feed speed at the initial stage of screw formation, and the inner diameter of the workpiece is reduced by reducing the feed speed at the end of screw formation. Can be suppressed. As a result, it is possible to suppress the inner diameter reduction of the workpiece with higher accuracy and to form the screw on the outer surface of the workpiece.

  (3) In the spark plug manufacturing apparatus according to the above aspect, when the die is sent toward the axial center of the workpiece, the die instructing unit is configured to perform the first rotation after the die contacts the workpiece. You may control so that a feed rate may be 0.9 mm / rev or more. According to this aspect, since the dice are fed at a predetermined speed or more in the initial stage of screw formation, the thread can be formed high.

を満たす前記送り速度で前記ダイスを前記軸中心に向けて送ることを特徴とする。この形態におけるスパークプラグの製造方法は、前記形態のスパークプラグの製造装置と同様に、３ダイス式によりワークを３点で支持するため、２ダイス式と比べてダイスがワークと接触することによってワークを支持する支持点の間におけるワークの円弧長さが３分の２になることから、ダイスがワークを内径側に押す力を分散させることができる。このため、中空円筒状のワークの内径が縮小することを抑制しつつそのワークの外側面にねじを形成することができる。また、この形態によれば、数式Ｉを満たすよう、送り速度の平均ｆ、長さｔおよび距離Ｐを調整することによって、より一層精度よくワークの内径縮小を抑制することおよびワークの外側面におけるねじ形成を両立できる。 (4) Another embodiment of the present invention is a method for manufacturing a spark plug. The spark plug manufacturing method includes a die indicating step of forming a screw on the outer surface of the workpiece in a three-die manner by sending a die toward the axial center of a hollow cylindrical workpiece having a portion serving as a metal shell. In the method for manufacturing a plug, the die instructing step may include calculating an average of feed speeds of the dies until the stagnation after the dies are fed toward the axis center when forming a screw on the outer surface of the workpiece. When f (mm / rev) is set, the thickness of the workpiece in a direction orthogonal to the axial direction of the workpiece is t (mm), and the pitch of the screw formed on the workpiece is P (mm), Formula I

The die is fed toward the axis center at the feed speed that satisfies the condition. In the spark plug manufacturing method according to this embodiment, the workpiece is supported at three points by the three-die type, similarly to the spark plug manufacturing apparatus of the above-described mode, so that the die comes into contact with the workpiece as compared with the two-die type. Since the arc length of the workpiece between the support points that support the workpiece becomes two thirds, the force by which the die pushes the workpiece toward the inner diameter side can be dispersed. For this reason, it is possible to form a screw on the outer surface of the work while suppressing a reduction in the inner diameter of the hollow cylindrical work. Further, according to this embodiment, by adjusting the average feed speed f, the length t, and the distance P so as to satisfy the formula I, the inner diameter reduction of the workpiece can be suppressed more accurately and the outer surface of the workpiece can be reduced. Both screw formation can be achieved.

  The form of the present invention is not limited to an apparatus for manufacturing a spark plug. For example, various forms such as a spark plug mounted on an internal combustion engine, an internal combustion engine system including the internal combustion engine, a vehicle mounted with the internal combustion engine system, and the like. It is also possible to apply to. 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 explanatory drawing which shows the partial cross section of a spark plug. It is process drawing which shows the manufacturing method of a spark plug. It is explanatory drawing which shows the manufacturing apparatus of the spark plug of this embodiment. It is a perspective view which shows arrangement | positioning of dice | dies. It is explanatory drawing which showed the state when the dice cut into the workpiece | work. It is the perspective view which showed the state when the dice are cutting into the workpiece | work. It is the graph which showed the internal diameter of the workpiece | work in the position away from the end surface of the metal shell by the predetermined distance.

A. First Embodiment A1. Configuration of Spark Plug FIG. 1 is an explanatory view showing a partial cross section of a spark plug 100. FIG. 1 illustrates the external shape of the spark plug 100 on the left side of the drawing with respect to the axis CA, which is the axis of the spark plug 100, and the cross-sectional shape of the spark plug 100 on the right side of the drawing with respect to the axis CA. ing. In the present embodiment, the lower side in FIG. 1 of the spark plug 100 is referred to as “front end side”, and the upper side in FIG. 1 is referred to as “rear end side”. FIG. 1 shows XYZ axes orthogonal to each other. The XYZ axes in FIG. 1 correspond to the XYZ axes in the other drawings. An axis CA shown in FIG. 1 is an axis along the Z axis.

  The spark plug 100 includes a center electrode 10, a terminal fitting 20, an insulator 30, a metal shell 40, and a ground electrode 50. In the present embodiment, the axis CA of the spark plug 100 is also the axis of each member of the center electrode 10, the terminal fitting 20, the insulator 30 and the metal shell 40.

  The spark plug 100 has a spark discharge gap (spark discharge gap) formed between the center electrode 10 and the ground electrode 50 on the tip side. The spark plug 100 is configured to be attachable to the internal combustion engine 90 in a state where the tip end side where the spark discharge gap is formed protrudes from the inner wall 91 of the combustion chamber 92. When a high voltage (for example, 10,000 to 30,000 volts) is applied to the center electrode 10 with the spark plug 100 attached to the internal combustion engine 90, spark discharge occurs in the spark discharge gap. The spark discharge generated in the spark discharge gap realizes ignition of the air-fuel mixture in the combustion chamber 92.

  The center electrode 10 is an electrode having conductivity. The center electrode 10 has a rod shape extending in the direction of the axis CA. The outer surface of the center electrode 10 is electrically insulated from the outside by an insulator 30. The tip side of the center electrode 10 protrudes from the tip side of the insulator 30.

  The terminal fitting 20 is a terminal for receiving power supply, and is electrically connected to the center electrode 10. The rear end side of the center electrode 10 is electrically connected to the rear end side of the insulator 30 through the terminal fitting 20.

  The insulator 30 is an insulator having electrical insulation. The insulator 30 has a cylindrical shape extending about the axis CA. In this embodiment, the insulator 30 is produced by baking an insulating ceramic material (for example, alumina). The insulator 30 has a shaft hole 39 that is a through hole extending in the direction of the axis CA. In the shaft hole 39, the center electrode 10 is held on the axis CA with the center electrode 10 protruding from the tip side of the insulator 30.

  The metal shell 40 is a conductive metal body. The metal shell 40 has a cylindrical shape extending in the direction of the axis CA. In the present embodiment, the metal shell 40 is a member obtained by performing nickel plating on a low carbon steel formed into a cylindrical shape. A threaded portion 42 for attaching the spark plug 100 to the combustion chamber 92 of the internal combustion engine is formed on the outer surface on the front end side of the metal shell 40.

  An end face 44 is formed on the front end side of the metal shell 40. From the center of the end surface 44, the insulator 30 together with the center electrode 10 protrudes in the + Z-axis direction (tip direction). A ground electrode 50 is joined to the end face 44.

  The ground electrode 50 is an electrode having conductivity. The ground electrode 50 has a rod shape, and one end is joined to the end face 44 of the metal shell 40. The ground electrode 50 extends in the + Z-axis direction from the end surface 44 of the metal shell 40 and is then bent toward the axis CA. In the present embodiment, the material of the ground electrode 50 is a nickel alloy containing nickel (Ni) as a main component.

A2. Manufacturing Method of Spark Plug FIG. 2 is a process diagram showing a manufacturing method of the spark plug 100. When manufacturing the spark plug 100, the manufacturer of the spark plug 100 produces the metal shell 40P, which is the metal shell 40 being manufactured (process P100). In the present embodiment, the metallic shell 40P is manufactured by pressing and cutting. In the present embodiment, the threaded portion 42 is not formed on the metal shell 40P.

  After the metal shell 40P is manufactured (process P100), a welding process (process P110) is performed on the metal shell 40P. The welding process (process P110) is a process in which the ground electrode 50P, which is the ground electrode 50 being manufactured, is welded to the end face 44 of the metal shell 40P. In the present embodiment, the ground electrode 50P is not bent and has a shape extending straight. In the present embodiment, the cross section perpendicular to the Z-axis direction of the ground electrode 50P is a rectangular cross section.

  After performing the welding process (process P110), the metal shell 40P is threaded to form the threaded portion 42 on the outer surface 42P of the metal shell 40P (process P120). Thereafter, the metal shell 40P is subjected to surface processing (plating) (process P130). Thereby, the metallic shell 40 is completed.

  After the metal shell 40 is completed (process P130), the metal shell 40 is assembled with other members (the center electrode 10, the terminal metal fitting 20, the insulator 30, etc.) (process P140). Thereby, the spark plug 100 is completed. In the present embodiment, in the step (step P140) in which another member is assembled to the metal shell 40, the ground electrode 50P is bent.

A3. Configuration of Spark Plug Manufacturing Device FIG. 3 is an explanatory view showing the spark plug manufacturing device 200 of the present embodiment used in the threading step (step P120) in which the threaded portion 42 is formed on the metal shell 40P. Spark plug manufacturing apparatus 200 includes holding unit 210, dice 220a, 220b, and 220c, and dice instruction unit 230.

  In this embodiment, in the welding process (process P110), a workpiece W is a member in which the ground electrode 50P, which is the ground electrode 50 being manufactured, is welded to the end face 44 of the metal shell 40P.

  The holding unit 210 holds the workpiece W. The holding part 210 holds the workpiece W by being inserted from the + side in the Z-axis direction into the cylinder of the metallic shell 40P having a cylindrical shape extending in the axis CA direction. The holding unit 210 can move the work W to the position in the Z-axis direction where the dice 220a, 220b, and 220c are arranged by descending to the − side in the Z-axis direction while holding the work W.

  FIG. 4 is a perspective view showing the arrangement of the dies 220a, 220b, and 220c. In FIG. 4, only the dice 220a, 220b, and 220c are shown for easy understanding. The dies 220a, 220b, and 220c are arranged at intervals of 120 degrees as viewed from the axis CA. The dice 220a, 220b, and 220c are configured to be rotatable about respective central axes ax, bx, and cx that are parallel to each other. The central axes ax, bx, cx are also parallel to the axis CA. On the outer surface of the dies 220a, 220b, and 220c, there are a peak portion that protrudes outward from the respective central axes ax, bx, and cx and a valley portion that is recessed toward the central axes ax, bx, and cx directions. They are arranged alternately in the axial direction. The dies 220a, 220b, and 220c form the threaded portion 42 by cutting into the outer side surface 42P on the front end side of the metal shell 40P in the workpiece W. In the description of the present embodiment, the symbol “220” is used to collectively refer to each of the three dice.

Returning to FIG. 3, the die instructing unit 230 feeds the die 220 toward the axis center of the workpiece W and causes the die 220 to form the screw portion 42. When forming the screw portion 42 on the outer side surface 42P of the workpiece W, the die instruction unit 230 calculates the average feed speed of the die 220 from when the die 220 is fed toward the axis center of the workpiece W until it stops. (Mm / rev), when the thickness of the workpiece W in the direction orthogonal to the axial direction of the workpiece W is t (mm), and the pitch of the screw portions 42 formed on the workpiece W is P (mm), The die 220 is fed toward the axis center of the workpiece W at a feed rate that satisfies the following formula I. The state in which the die 220 is stagnated is a state in which the die 220 continues to rotate but cannot be fed toward the axis center of the workpiece W.

  The grounds for defining in this way will be described. The inventors of the present invention have conducted a number of experiments, and in forming the screw portion 42 on the outer surface 42P of the hollow cylindrical workpiece W using the three dies 220, the average f of the feed speed, the workpiece W, and the like. It has been found that there is a relationship between the wall thickness t and the distance P. That is, when forming the threaded portion 42 on the outer side surface 42P of the hollow cylindrical workpiece W by rolling, if the ratio of the wall thickness t to the distance P exceeds 1.5 times, rolling becomes difficult. I found it. If the ratio of the wall thickness t to the distance P exceeds 1.5 times, the thread at the threaded portion 42 tends not to rise. On the other hand, if the rotational speed at which the die 220 is fed toward the axis center of the workpiece W in order to improve the rise of the thread, the workpiece W is likely to crack or generate burrs. For this reason, if the ratio of the wall thickness t to the distance P exceeds 1.5 times, rolling becomes difficult.

  In rolling with a die, it is considered that a thread portion is formed on the outer surface of the workpiece by moving a part of the workpiece pressed in contact with the peak portion of the die to the trough side of the die. At this time, if the feed speed of the die is slow, a sufficient biasing force for moving a part of the workpiece in contact with the crest of the die to the trough side of the die cannot be obtained. There is a tendency that the inner diameter of the workpiece is reduced as the height decreases. When the die feed speed is high, the die is moved toward the center of the workpiece faster than the part of the workpiece pressed in contact with the peak of the die moves to the trough side of the die. There is a tendency that the ridges of the are deformed by being pushed from the workpiece. For this reason, it is effective to control the average feed speed f of the dies within a predetermined range in a hollow cylindrical workpiece in which the ratio of the thickness t to the distance P is 1.5 times or less. The inventor found out.

  From these findings, the present inventors, based on Formula I, send the dice 220 toward the axis center of the workpiece W to suppress the reduction of the inner diameter of the hollow cylindrical workpiece W while reducing the workpiece. It has been found that the screw portion 42 can be formed on the outer surface of W.

  In the present embodiment, the dice instruction unit 230 decreases the feed speed of the dice 220 and sends the dice 220 to the work W every time the dice 220 rotates once.

  In general, it has been considered that if the die feed rate is relatively low and constant, the inner diameter of the workpiece can be prevented from being reduced. However, as a result of many experiments conducted by the present inventor, when three dies are fed toward the axial center of a hollow cylindrical workpiece, the die feed speed is not constant, but the initial stage of screw formation. In the stage, it has been found that it is more effective to feed the die to the workpiece W while increasing the die feeding speed relatively and then decreasing the die feeding speed. This is because at the initial stage of screw formation, it is easy to increase the thread by increasing the die feed rate, and at the end of screw formation, it is possible to suppress the reduction of the inner diameter of the workpiece by reducing the die feed rate. it is conceivable that.

  For this reason, the dice instruction | indication part 230 suppresses the internal diameter reduction | decrease of the workpiece | work W more accurately by reducing the feed speed of the die | dye 220 and sending the three dice | dies 220 to the workpiece | work W every time the die | dye 220 makes one rotation. And the formation of the threaded portion 42 on the outer side surface 42P of the workpiece W can be achieved.

  In the present embodiment, when the die 220 is fed toward the axis center of the workpiece W, the die instructing unit 230 has a feed speed in the first rotation after the die 220 contacts the workpiece W of 0.9 mm / rev. Control to be

  The present inventor conducted a number of experiments, and when the die was fed to a workpiece satisfying that the ratio of the thickness t to the distance P was 1.5 times or less, the feed speed in the first rotation was set to 0. It has been found that it is effective to set it to 9 mm / rev or more. This is because the die feed rate at the initial stage of screw formation is constant in order to increase the screw thread of the screw part formed on the workpiece satisfying that the ratio of the thickness t to the distance P is 1.5 times or less. This is considered necessary.

  For this reason, when the die 220 is fed toward the axis center of the workpiece W, the die instructing unit 230 is set so that the feed speed in the first rotation after the die 220 contacts the workpiece W becomes 0.9 mm / rev or more. Therefore, when the screw part 42 is formed on the outer surface of the workpiece W, the thread can be formed high.

  FIG. 5 is an explanatory view showing a state when the die 220 is cut into the workpiece W. FIG. FIG. 6 is a perspective view showing a state when the die 220 is cut into the workpiece W. FIG. In FIG. 5, only the workpiece W, the holding unit 210, and the die 220 are shown for easy understanding. In FIG. 6, only the workpiece W and the dies 220a, 220b, and 220c are shown for easy understanding. The workpiece W in FIGS. 5 and 6 is in a state of being moved by the holding unit 210 to the position in the Z-axis direction where the die 220 is disposed. When the die 220 is cut into the outer surface 42P of the metal shell 40P in the workpiece W in this state, a threaded portion 42 is formed in the metal shell 40P.

  FIG. 7 shows the workpiece W after the thread portion 42 is formed on the outer surface of the workpiece W under various conditions at a position away from the end surface 44 of the metal shell 40 by a predetermined distance on the negative side in the Z-axis direction. 3 is a graph showing an inner diameter of a workpiece W. The vertical axis in FIG. 7 represents the relative value of the inner diameter of the workpiece W after the threaded portion 42 is formed according to each condition, where the inner diameter of the workpiece W before processing is 1.

  A black square indicates the inner diameter of the workpiece W before the thread portion 42 is formed. The black circle indicates the inner diameter of the workpiece W after the threaded portion 42 is formed by using the spark plug manufacturing apparatus 200 of the present embodiment that sends the three dies 220 based on Formula I. The black triangles indicate the inner diameter of the workpiece W after the threaded portion 42 is formed by using the spark plug manufacturing apparatus of the reference example for feeding two dies.

  In the spark plug manufacturing apparatus 200 of the present embodiment, the feed speed of the dice 220 decreases each time the dice 220 rotates once, and the dice 220 is sent to the workpiece W. On the other hand, in the spark plug manufacturing apparatus of the reference example, the die feeding speed is constant, and the die is fed to the workpiece W.

  The average f of the feed speed of the die 220 in the spark plug manufacturing apparatus 200 of the present embodiment is higher than the average of the die feed speed in the spark plug manufacturing apparatus of the reference example. Therefore, the spark plug manufacturing apparatus 200 of the present embodiment is less than the spark plug manufacturing apparatus of the reference example with respect to the total number of rotations of the dies in forming the screw portion 42.

  At each value in the black circle, the average f of the feed speed of the die 220 and the rotation speed from when the die 220 is fed toward the axis center of the workpiece W until it stagnates are the same. The variation in the values in the black circles is due to the difference in the number of rotations that can be rotated after the dice 220 stagnate in forming the screw portion 42. At each value in the black triangle, the number of rotations until the stagnation after the dice in forming the screw portion 42 are fed toward the axis center of the workpiece W and the number of rotations rotated after the stagnation is the same are the same. . The variation in the values in the black triangles is due to the difference in the die feed speed.

  From the results shown in FIG. 7, the following was confirmed. That is, in the spark plug manufacturing apparatus of the reference example in which two dies are fed, it was not confirmed that the inner diameter of the workpiece W exceeded a relative value of 0.985. On the other hand, in the spark plug manufacturing apparatus 200 of the present embodiment that sends three dies 220 based on Formula I, the inner diameter of the workpiece W is a relative value of 0. Exceeded 985. Therefore, when forming the screw part 42 with respect to the hollow cylindrical workpiece W, the spark plug manufacturing apparatus 200 of the present embodiment can suppress the inner diameter reduction of the workpiece W as compared with the spark plug manufacturing apparatus of the reference example. Was confirmed.

  According to the embodiment described above, since the workpiece W is supported at three points by the three-die type, the workpiece between the support points that support the workpiece W by contacting the workpiece W with the die 220 as compared with the two-die type. Since the arc length of W is two-thirds, the force by which the die 220 pushes the workpiece W toward the inner diameter side can be dispersed. For this reason, the screw part 42 can be formed on the outer surface of the workpiece W while suppressing the reduction of the inner diameter of the hollow cylindrical workpiece W. Further, according to this embodiment, by adjusting the average f, the length t, and the distance P of the feed speed so as to satisfy the mathematical formula, the inner diameter reduction of the workpiece W can be suppressed more accurately and the outer surface of the workpiece W The screw portion 42 can be formed at the same time.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above-described effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Center electrode 20 ... Terminal metal fitting 30 ... Insulator 39 ... Shaft hole 40 ... Main metal fitting 40P ... Main metal fitting 42 ... Screw part 42P ... Outer surface 44 ... End surface 50 ... Ground electrode 50P ... Ground electrode 90 ... Internal combustion engine 91 ... Inner wall 92 ... Combustion chamber 100 ... Spark plug 200 ... Manufacturing apparatus 210 ... Holding part 220 ... Dies 220a, 220b, 220c ... Dies 230 ... Dice instruction part CA ... Axis W ... Workpieces ax, bx, cx ... Central axis

Claims (4)

A die for forming a screw on the outer surface of a hollow cylindrical workpiece having a portion to be a metal shell, and a die indicating portion for feeding the die toward the axial center of the workpiece to form the screw on the die. In the spark plug manufacturing apparatus provided,
The die is a three-die type, and the screw is formed on the outer surface.
The dice instruction unit
When forming the screw on the outer surface, the average of the feed speed of the die until the die stagnate after being sent toward the axis center is f (mm / rev),
The thickness of the workpiece in a direction orthogonal to the axial direction of the workpiece is t (mm),
When the pitch of the screw formed on the workpiece is P (mm), the following formula I

An apparatus for manufacturing a spark plug, wherein the die is fed toward the axis center at the feed speed satisfying The spark plug manufacturing apparatus according to claim 1,
The die instructing unit is a spark plug manufacturing apparatus that reduces the feeding speed and sends the die to the workpiece every time the die rotates once. A spark plug manufacturing apparatus according to claim 1 or 2,
The die instructing unit is configured such that when the die is fed toward the axial center of the workpiece, the feeding speed in the first rotation after the die contacts the workpiece becomes 0.9 mm / rev or more. Spark plug manufacturing equipment to control. In the method for manufacturing a spark plug comprising a die instruction step toward the axial center of the hollow cylindrical workpiece to form a Flip sleep on an outer surface of the workpiece in three dice formula send a die having a portion to be a metal shell,
The dice instruction process includes
When forming the screw on the outer surface of the workpiece, the average of the feed speed of the die from when the die is fed toward the axis center until it stagnates is f (mm / rev),
The thickness of the workpiece in a direction orthogonal to the axial direction of the workpiece is t (mm),
When the pitch of the screw formed on the workpiece is P (mm), the following formula I

A method for manufacturing a spark plug, wherein the die is fed toward the axis center at the feed speed satisfying the following condition.

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