JP4413973B2 - Plasma jet ignition plug and method for manufacturing the same - Google Patents

Description

  The present invention relates to a plasma jet ignition plug for an internal combustion engine that forms plasma and ignites an air-fuel mixture, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, spark plugs that ignite an air-fuel mixture by spark discharge are used as ignition plugs of engines that are internal combustion engines for automobiles, for example. In recent years, there has been a demand for higher output and lower fuel consumption of internal combustion engines, as a spark plug with high ignitability that can be ignited reliably even for a lean mixture with a fast combustion spread and a higher ignition limit air-fuel ratio, Plasma jet spark plugs are known.

  Such a plasma jet ignition plug has a small volume discharge called a cavity in which a spark discharge gap between a center electrode and a ground electrode integrated with a metal shell is surrounded by an insulator made of ceramics or the like. It has a structure that forms a space. Then, a high voltage is applied to the spark discharge gap to cause a spark discharge, and a current can flow at a relatively low voltage due to the dielectric breakdown that occurs at this time. To generate a plasma in the cavity. Since a ground electrode is arranged on the tip side of the insulator in which the cavity is formed, a hole called an orifice is provided in the ground electrode, and plasma is ejected to the outside through this orifice and mixed. Qi is ignited.

By the way, in the process in which plasma is ejected from the orifice, if there is a gap between the ground electrode and the insulator, the plasma has in the gap or between the metal shell and the insulator communicating with the gap. Energy may leak out. In such a case, there is a possibility that the amount of plasma energy ejected from the orifice is reduced and the ignitability is lowered. Therefore, a plasma jet ignition plug is proposed in which an insulator (housing) is provided in close contact with a ground electrode (external electrode), and there is no gap between the insulator and the ground electrode (for example, Patent Document 1). reference.). In the plasma jet ignition plug of Patent Document 1, the ground electrode and the metal shell are integrally formed, and the ground electrode (portion corresponding to the ground electrode) is accurately positioned with respect to the metal shell. Therefore, the size of the insulator may be controlled, and when the insulator is held by the metal shell, the tip of the insulator is in contact with the ground electrode.
JP 2006-294257 A

  However, in the manufacturing process of the plasma jet spark plug, the insulator is crimped and held by the metal shell, so that it may be displaced. However, it is difficult to strictly manage the displacement, and depending on the state of the displacement, A load may be applied so that the tip of the insulator is strongly pressed against the ground electrode, and the insulator may be damaged.

  The present invention has been made in order to solve the above-described problems, and includes a gap between an insulator and a ground electrode disposed on the tip side thereof, and a gap between a metal shell communicating with the gap and the insulator. An object of the present invention is to provide a plasma jet ignition plug and a method of manufacturing the same that can reduce the energy of plasma leaking to the earth while preventing the insulator from being in strong contact with the ground electrode. .

In order to achieve the above object, a plasma jet ignition plug according to a first aspect of the present invention has a center electrode and an axial hole extending in the axial direction, and the distal end surface of the central electrode is accommodated on the distal end side in the axial hole. And an insulator that holds the center electrode, and a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode at the tip of the insulator, A metal shell that surrounds and holds the periphery of the insulator perpendicular to the axial direction in the radial direction, and is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is annular with the distal end portion of the insulator And a ground electrode having a contact portion in which the opening of the cavity is inside itself when viewed from the axial direction, and a communication portion for communicating the inside of the cavity with outside air, the ground electrode Is While having the communication part and being in non-contact with the insulator in the axial direction, the outer metal is in contact with the metal shell, and its outer edge is joined to the metal shell to electrically connect with the metal shell. and the electrode base material to which it is connected, a part of the communicating portion, and Ri electrode der composed of a composite member which contact with the members are joined with the contact portion, the electrode base metal of the ground electrode, the diameter And the contact member of the ground electrode has an outer protrusion located on the outer side in the radial direction with respect to the inner protrusion, and the outer protrusion. The portion is arranged on the rear end side in the axial direction with respect to the inner protrusion while being overlapped with the inner protrusion in the axial direction .

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, at least a part of the inner peripheral wall of the communication portion of the ground electrode is a noble metal member made of a noble metal. It is formed.

The plasma jet spark plug according to claim 3, in addition to the configuration of the invention according to claim 1 or 2, wherein the said tip portion of the insulator, the engagement portion into which the contact portion is engaged is It is provided.

According to a fourth aspect of the present invention, there is provided a plasma jet spark plug manufacturing method including a center electrode and an axial hole extending in an axial direction, and the front end surface of the central electrode is accommodated on the front end side in the axial hole. An insulator that holds the center electrode, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode at the front end of the insulator, and the insulator A metal shell that surrounds and holds a radial periphery perpendicular to the axial direction, and is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and annularly contacts the distal end portion of the insulator. A contact portion where the opening of the cavity is inside itself when viewed from the axial direction, and a ground electrode having a communication portion that communicates the inside of the cavity and the outside air with the outside air, ,in front An electrode base material that has a communication portion and an inner protrusion that is an innermost portion in the radial direction, and is in non-contact with the insulator in the axial direction, while being in contact with the metal shell A plasma jet, which is an electrode made of a composite member in which a contact member having a part of the communication portion, the contact portion, and an outer protrusion located outside the inner protrusion in the radial direction is joined. A spark plug manufacturing method, wherein the insulator holding the center electrode is held by the metal shell, and the contact member is disposed at the tip of the insulator after the insulator holding step. In the member arranging step, in the axial direction, the inner projecting portion of the electrode base material is overlapped with the outer projecting portion of the contact member, and the inner projecting portion is disposed closer to the distal end side in the axial direction than the outer projecting portion. Of the electrode base material An arrangement step including an electrode base material placement step of placing the electrode base material closer to the tip end side in the axial direction than the tip end portion of the insulator while placing the contact member in the communication portion; and A ground electrode joining step for joining an outer edge portion of the electrode base material to the metal shell; and after the ground electrode joining step, the contact member and the electrode while contacting the contact member with the tip portion of the insulator A contact member joining step for joining the base material.

Also, a manufacturing method for the plasma jet spark plug according to claim 5, in addition to the configuration of the invention according to claim 4, wherein the said tip portion of the insulator, the contact portion of the ground electrode is engaged A mating engagement portion is provided , and the contact portion is engaged with the engagement portion.

  In the plasma jet ignition plug according to the present invention, the ground electrode is in contact with the tip of the insulator, but the term “contact” here is not only in a state of being in contact with each other but also relatively weak. This includes a state in which both abut against each other with a pressing force. "A state where both are in contact with each other with relatively weak pressing force" means a drag that does not cause damage to the insulator while the ground electrode and the tip of the insulator are in contact with each other. It means that there is. That is, the tip of the insulator does not come into strong contact with the ground electrode, and the stress of the insulator with respect to the ground electrode does not increase. The degree of drag will be described more specifically. It is only necessary to maintain the contact state with the pressing force necessary to prevent leakage of the plasma energy ejected from the cavity. It does not prevent even the leakage of the combustion pressure received from.

In the plasma jet ignition plug according to the first aspect of the present invention, the contact portion of the ground electrode is joined to the metal shell while being in contact with the tip portion of the insulator, and between the ground electrode and the tip portion of the insulator. In addition, a gap that may occur between the insulator and the metal shell is closed. For this reason, when the plasma formed in the cavity is ejected, the plasma energy may leak into the gap if the gap is not closed. Since such leakage of energy is prevented, it is possible to prevent a decrease in ignitability. The ground electrode is a composite member in which an electrode base material and a contact member are joined. For this reason, at the time of manufacture, the process of joining the outer edge part of an electrode base material to a metal shell, and the process of joining to an electrode base material, making a contact member the front-end | tip part of an insulator can be divided. The gap between the electrode base material in the axial direction and the tip of the insulator serves to absorb axial assembly tolerances that may occur when the insulator is held by the metal shell. For this reason, when joining the outer edge portion of the ground electrode to the metal shell, it is possible to avoid making the contact portion strongly contact the tip portion of the insulator, and strongly contact the contact portion to the tip portion of the insulator. As a result, the insulator does not break due to increased stress.

Further, as in the invention according to claim 1 , if the outer protrusion of the contact member is arranged closer to the rear end side in the axial direction than the inner protrusion of the electrode base material constituting the ground electrode, the outer protrusion of the contact member Can be sandwiched between the tip of the insulator and the inner protrusion of the electrode base material. That is, even when the plasma jet ignition plug is used for a long period of time and the joining state between the contact member and the electrode base material is deteriorated, the contact base member can be prevented from falling off (dropping out).

In addition, since high energy is supplied between the ground electrode and the center electrode in order to generate plasma in the cavity, the inner peripheral wall of the communication portion of the ground electrode as in the invention according to claim 2 If at least a part of these is made of a noble metal member, the consumption of the ground electrode due to the high energy of plasma can be reduced.

Further, as in the invention according to claim 3 , if the contact portion of the ground electrode is engaged with the engagement portion of the tip portion of the insulator, the axial displacement of the ground electrode can be prevented. In addition, the mating surfaces of the contact portion and the engaging portion are in close contact, and the gap between the ground electrode located on the radially outer side of the mating surface and the tip of the insulator or between the insulator and the metal shell. Possible gaps are closed.

Holding to insulation insulator of the metal shell is usually carried out by crimping, it may occur assembly seen with tolerances that time.

On the other hand, as in the invention according to claim 4 , the ground electrode is a composite member in which the electrode base material and the contact member are joined, the contact member is provided with an outer protrusion, and the outer protrusion is an inner protrusion of the electrode base material. If the electrode base material is joined to the metal shell, the contact member can be prevented from falling off (dropping out). Further, if the contact member is subsequently brought into contact with the tip of the insulator and joined to the electrode base material, the gap between the electrode base material, that is, the ground electrode and the tip of the insulator, or the insulation communicating with the gap is provided. A gap that may occur between the insulator and the metal shell can be closed. That is, the ground electrode joining step of joining the outer edge portion of the electrode base material to the metal shell and the contact member joining step of joining the contact member to the electrode base material while making the contact member the tip of the insulator can be separated. it can. In addition, since the insulator is held by the metal shell before the electrode base material is joined to the metal shell, the axial assembly tolerance that may occur when the insulator is held by the metal shell is absorbed, and the insulator is broken. Ru is prevented.

Further, as in the invention according to claim 5 , if the contact portion of the ground electrode is engaged with the engaging portion provided at the tip portion of the insulator, it is between the ground electrode and the tip of the insulator. Positioning can be performed reliably, and the gap between the ground electrode and the tip of the insulator can be more reliably closed.

[First Embodiment]
Hereinafter, a first embodiment of a plasma jet ignition plug embodying the present invention will be described with reference to the drawings. First, with reference to FIG. 1 and FIG. 2, the structure of the plasma jet ignition plug 100 as an example is demonstrated. FIG. 1 is a partial cross-sectional view of a plasma jet ignition plug 100 according to the first embodiment. FIG. 2 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 100 according to the first embodiment. In FIG. 1, the axis O direction of the plasma jet ignition plug 100 is the vertical direction in the drawing, the lower side is the front end side (front), and the upper side is the rear end side (rear).

  The plasma jet spark plug 100 according to the first embodiment shown in FIG. 1 is generally held in the insulator 10, a metal shell 50 that holds the insulator 10, and the insulator 10 in the direction of the axis O. The center electrode 20, the ground electrode 30 welded to the front end portion 65 of the metal shell 50, and the terminal metal fitting 40 provided at the rear end portion of the insulator 10 are configured.

  The insulator 10 is a cylindrical insulating member that is formed by firing alumina or the like and has an axial hole 12 in the direction of the axis O as is well known. A flange portion 19 having the largest outer diameter is formed substantially at the center in the direction of the axis O, and a rear end side body portion 18 is formed on the rear end side. The rear end side outer peripheral surface of the rear end side body portion 18 is subjected to uneven processing called corrugation for increasing the creeping distance between the metallic shell 50 and the terminal fitting 40. Further, a distal end side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 on the front end side from the flange portion 19, and a further outer diameter than the front end side body portion 17 on the front end side of the front end side body portion 17. A small leg length 13 is formed. A step portion 14 having a step shape is formed between the leg length portion 13 and the front end side body portion 17.

  The inner peripheral portion of the leg long portion 13 of the shaft hole 12 is formed as an electrode housing portion 15 having a diameter smaller than the inner peripheral portions of the front end side body portion 17, the flange portion 19 and the rear end side body portion 18. A center electrode 20 is held inside the electrode housing portion 15. As shown in FIG. 2, the shaft hole 12 is formed as a tip small-diameter portion 61 with the inner circumference further reduced in diameter on the tip side of the electrode housing portion 15. The tip small diameter portion 61 opens at the tip portion 16 of the insulator 10. In addition, an annular tip engaging portion 62 surrounding the periphery of the opening of the tip small-diameter portion 61 is formed in the tip portion 16 of the insulator 10 as a recess, and an outer protrusion 37 of a noble metal tip 36 described later is engaged. ing.

  The center electrode 20 is a cylindrical electrode rod formed of a nickel-based alloy such as Inconel (trade name) 600 or 601 and has a metal core 23 made of copper or the like having excellent thermal conductivity. A disc-shaped electrode tip 25 made of an alloy containing precious metal or W (tungsten) as a main component is welded to the tip 21 of the center electrode 20 so as to be integrated with the center electrode 20. In the first embodiment, the electrode chip 25 integrated with the center electrode 20 is also referred to as “center electrode”.

  Further, as shown in FIG. 1, the rear end side of the center electrode 20 is enlarged in a bowl shape, and this bowl-shaped portion is brought into contact with a stepped portion of the electrode housing portion 15 in the shaft hole 12. The center electrode 20 is positioned in the electrode housing portion 15. As shown in FIG. 2, the distal end surface 26 of the distal end portion 21 of the center electrode 20 (more specifically, the distal end surface 26 of the electrode tip 25 joined integrally with the central electrode 20 at the distal end portion 21 of the central electrode 20). ) Is in contact with a step portion between the electrode housing portion 15 and the tip small-diameter portion 61 having different diameters. With this configuration, a small discharge space having a bottomed cylindrical shape surrounded by the inner peripheral surface of the tip small diameter portion 61 of the shaft hole 12 and the tip surface 26 of the center electrode 20 is formed. In the plasma jet spark plug 100, spark discharge is performed in the spark discharge gap formed between the ground electrode 30 and the center electrode 20, and the path of the spark discharge passes through this discharge space. . This discharge space is referred to as a cavity 60, and plasma is formed in this cavity 60 during spark discharge, and is ejected forward from the opening 66 of the tip end portion 16. The cavity 60 may be configured to include a part of the electrode housing portion 15 whose diameter is larger than the inner diameter of the tip small diameter portion 61 on the rear end side with respect to the tip small diameter portion 61.

  Further, as shown in FIG. 1, the center electrode 20 is connected to the terminal fitting 40 in the distal end side body portion 17 via the conductive seal body 4 made of a mixture of metal and glass provided in the shaft hole 12. And are electrically connected. The center electrode 20 and the terminal fitting 40 are fixed in the shaft hole 12 while being conducted in the shaft hole 12 by the seal body 4. The terminal fitting 40 extends rearward in the shaft hole 12, and the rear end portion 41 projects outward from the rear end of the insulator 10. A high voltage cable (not shown) is connected to the rear end portion 41 via a plug cap (not shown), and a high voltage is applied from an ignition device (not shown).

  Next, the metal shell 50 will be described. The metal shell 50 is a cylindrical metal fitting for fixing the plasma jet ignition plug 100 to an engine head (not shown) of the internal combustion engine. The metal shell 50 surrounds the periphery of the insulator 10 in the radial direction perpendicular to the direction of the axis O in a portion extending from the long leg portion 13 of the insulator 10 to the front end side of the rear end side body portion 18. The insulator 10 is held. The metal shell 50 is made of a low carbon steel material, and a mounting portion 52 is formed from approximately the center to the tip side. A male screw-like thread is formed on the outer peripheral surface of the mounting portion 52, and is screwed into a female screw formed in a mounting hole (not shown) of the engine head. The metal shell 50 places importance on heat resistance and may use stainless steel, Inconel (trade name), or the like.

  A hook-shaped seal portion 54 is formed on the rear end side of the attachment portion 52. An annular gasket 5 formed by bending a plate is inserted into a portion between the seal portion 54 and the attachment portion 52. When the plasma jet ignition plug 100 is attached to the engine head mounting hole (not shown), the gasket 5 is formed between the seat surface 55 which is the surface facing the tip of the seal portion 54 and the peripheral portion of the opening of the mounting hole. By being sandwiched and deformed and sealed between the two, the outflow of combustion gas through the mounting hole is prevented.

  A tool engaging portion 51 into which a plug wrench (not shown) is fitted is formed on the rear end side of the seal portion 54. A thin caulking portion 53 is provided on the rear end side from the tool engagement portion 51, and a thin buckling portion 58 is also provided between the tool engagement portion 51 and the seal portion 54. And annular ring members 6, 7 are interposed between the inner peripheral surface from the tool engaging portion 51 to the caulking portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10, Further, a powder of talc (talc) 9 is filled between the ring members 6 and 7.

  As shown in FIG. 2, a stepped step portion 56 is formed on the inner peripheral surface of the mounting portion 52, and the step portion 14 of the insulator 10 is supported on the step portion 56 via an annular packing 80. Has been. As shown in FIG. 1, the insulator 10 is pressed toward the distal end side through the ring members 6, 7 and the talc 9 by crimping the end of the crimping portion 53 inwardly. The buckling portion 58 is heated during the caulking, and is deformed so as to swell with the addition of the compressive force, thereby earning a compression stroke of the caulking portion 53. As a result, a portion between the stepped portion 14 and the flange portion 19 of the insulator 10 is sandwiched between the crimped portion 53 and the stepped portion 56 of the metal shell 50, and the insulator 10 is integrated with the metal shell 50. Retained. And the gas tightness between the metal shell 50 and the insulator 10 is maintained by the packing 80, and the outflow of combustion gas through the cylindrical hole 59 is prevented.

  Next, the ground electrode 30 disposed at the distal end portion 65 of the metal shell 50 will be described. The ground electrode 30 shown in FIG. 2 is an electrode made of a composite member in which an electrode base material 33 made of a nickel-based alloy and a noble metal tip 36 made of a noble metal are integrally joined. The ground electrode 30 has a disk shape, and a communication hole (communication portion 31) is formed in the center in the radial direction. The noble metal tip 36 is disposed on the radially inner peripheral side and joined to the electrode base material 33. The outer edge portion 35 of the ground electrode 30 (that is, the outer edge portion 35 of the electrode base material 33) is engaged with an engagement step portion 57 in which the inner peripheral surface of the distal end portion 65 of the metal shell 50 is formed in a step shape. The mating surfaces of the two are laser welded, and the ground electrode 30 and the metal shell 50 are joined together. The communication portion 31 of the ground electrode 30 is constituted by the electrode base material 33 and the noble metal tip 36, and is used for communicating the inside of the cavity 60 with the outside air via the ground electrode 30 disposed on the tip side of the insulator 10. With an opening. Here, the “outer edge portion” refers to a portion where the ground electrode 30 is joined to the metal shell 50, and in the first embodiment, the ground electrode 30 has a disk shape, so The edge portion corresponds to the “outer edge portion”. However, even when the ground electrode 30 is not in the shape of a disk, the outer edge portion becomes a joint portion with the metal shell 50 when viewed in the radial direction.

  The noble metal tip 36 of the first embodiment has a cylindrical shape, and an inner peripheral wall 70 of the communication part 31 is formed as a part of the communication part 31. The noble metal tip 36 includes an outer protrusion 37 that protrudes in a bowl shape with its outer peripheral surface facing radially outward on the rear end side in the axis O direction. The electrode base material 33 has a disk shape, and has a hole constituting the communication portion 31 at the center in the radial direction. Similarly to the noble metal tip 36, the electrode base material 33 is provided with an inner protrusion 34 that protrudes in a bowl shape with the inner peripheral surface of its own hole directed radially inward, on the tip side in the axis O direction. . The outer protrusion 37 of the noble metal tip 36 is arranged on the rear end side in the axis O direction with respect to the inner protrusion 34 of the electrode base material 33 constituting the ground electrode. With such a configuration, it is possible to prevent the noble metal tip 36 from slipping forward in the direction of the axis O even when a failure occurs in the joining between the electrode base material 33 and the noble metal tip 36.

  Further, a tip engaging portion 62 having a tip formed as a recess is provided at the tip 16 of the insulator 10 so that the outer protrusion 37 of the noble metal tip 36 is engaged. The tip engaging portion 62 is formed in an annular shape surrounding the periphery of the opening 66 of the cavity 60. The outer projecting portion 37 of the noble metal tip 36 is engaged with the tip engaging portion 62 and is in annular contact with the distal end portion 16 of the insulator 10. A portion of the outer protrusion 37 that is engaged with the tip engaging portion 62 and is in annular contact with the tip 16 of the insulator 10 is a contact portion 38. When viewed from the direction of the axis O, the opening 66 of the cavity 60 is inside the contact portion 38. On the other hand, the non-contact portion 39 provided behind the electrode base material 33 and facing the tip portion 16 of the insulator 10 is not in contact with the tip portion 16 of the insulator 10. The noble metal tip 36 closes a gap between the ground electrode 30 and the tip 16 of the insulator 10 and a gap between the metal shell 50 communicating with the gap and the tip 16 of the insulator 10. The interior of 60 is in communication with outside air. With this configuration, when the plasma formed in the cavity 60 is ejected outward, the energy of the plasma is between the ground electrode 30 and the tip 16 of the insulator 10 or between the insulator 10 and the metal shell 50. Leakage into the gap between them is prevented. The noble metal tip 36 corresponds to the “contact member” and the “noble metal member” in the present invention.

  In the process of manufacturing the plasma jet ignition plug 100 of the first embodiment having such a configuration, as described above, the tips of the ground electrode 30 and the insulator 10 are provided so as to prevent leakage of energy during plasma ejection. 16, the insulator 10 is held before the ground electrode 30 is joined to the metal shell 50 in order to close the gap between the insulator 10 and the metal shell 50. Hereinafter, a method for manufacturing the plasma jet ignition plug 100 will be described with reference to FIG. FIG. 3 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 100 according to the first embodiment.

  In the manufacturing process of the plasma jet ignition plug 100, the center electrode 20 (electrode tip 25 is joined) produced in the same process in the cylindrical hole 59 of the metal shell 50 produced in another process in advance. The insulator 10 in which the terminal fitting 40 is integrally assembled is inserted. The step portion 14 of the insulator 10 is supported on the step portion 56 of the cylindrical hole 59 of the metal shell 50 via the packing 80. In this state, the caulking portion 53 (see FIG. 1) of the metal shell 50 is caulked, and the portion between the step portion 14 and the flange portion 19 of the insulator 10 is sandwiched between the main portion 50 and the main portion 50, thereby The insulator 10 is integrally held by the metal fitting 50 (insulator holding step).

  Next, the noble metal tip 36 formed in a cylindrical shape having the outer protrusion 37 is disposed closer to the distal end side in the axis O direction than the distal end portion 16 of the insulator 10 with the outer protrusion 37 side facing the insulator 10 side. (Contact member arranging step in the arranging step). At this time, the noble metal tip 36 is disposed at a position where the outer protrusion 37 faces the tip engaging portion 62 of the tip portion 16 of the insulator 10. Further, the disc-shaped electrode base material 33 having a hole in which the inner protrusion 34 is formed has the inner protrusion 34 and the outer protrusion 37 of the noble metal tip 36 with the inner protrusion 34 facing forward in the direction of the axis O. It arrange | positions so that it may overlap with the axis line O direction, and it arrange | positions from the front-end | tip part 16 of the insulator 10 at the front end side (electrode base material arrangement | positioning process in an arrangement | positioning process). Then, the outer edge portion 35 of the electrode base material 33 is engaged so as to be fitted into the engagement step portion 57 of the metal shell 50 having a step shape. At this time, the non-contact portion 39 of the electrode base material 33 is maintained in a non-contact state with the tip portion 16 of the insulator 10. As for the noble metal tip 36, the outer projection 37 is sandwiched between the inner projection 34 of the electrode base material 33 and the tip engaging portion 62 of the insulator 10, and the arrangement position is regulated.

  The laser beam is irradiated around the circumferential direction aiming at the mating surface between the outer edge portion 35 of the electrode base material 33 and the engagement step portion 57 of the metal shell 50, and the electrode base material of the metal shell 50 and the ground electrode 30 is irradiated. 33 is welded (ground electrode joining step). At this time, the noble metal tip 36 is in an unfixed state. In the next step, the noble metal tip 36 is pressed toward the rear end side in the axis O direction, and the outer protrusion 37 is engaged with the tip engaging portion 62 of the insulator 10 to be positioned. Thereby, the axial shift of the noble metal tip 36 is prevented. Furthermore, when the noble metal tip 36 is pressed to the tip end side in the axis O direction, the noble metal tip 36 and the tip engaging portion 62 are brought into close contact (contact) state, and between the noble metal tip 36 and the tip portion 16 of the insulator 10. The gap and the gap between the electrode base material 33 constituting the ground electrode 30 and the tip 16 of the insulator 10 are closed. Then, with the noble metal tip 36 being held down, laser light is irradiated aiming at the mating surface between the noble metal tip 36 and the electrode base material 33, and the two are welded around the circumference (contact member joining step). The noble metal tip 36 is integrated with the electrode base material 33 to form the communication portion 31.

  In this way, the ground electrode 30 is joined to the distal end portion 65 of the metal shell 50, and the plasma jet ignition plug 100 shown in FIG. 1 is completed. As described above, before the ground electrode 30 is joined to the metal shell 50, the insulator 10 is caulked and held on the metal shell 50, so that there is nothing that abuts the tip 16 of the insulator 10 during caulking. The tip 16 of the insulator 10 does not receive a strong pressing force from the outside. Further, at the time of manufacturing, when the metal fitting 50 is caulked, the position of the tip portion 16 of the insulator 10 may be displaced in the direction of the axis O, that is, the assembly tolerance may be increased. Even in such a case, the tolerance can be absorbed by the gap in the direction of the axis O between the electrode base material 33 and the tip 16 of the insulator 10 when the electrode base material 33 is joined to the metal shell 50.

  Further, a gap that may be generated between the electrode base material 33 of the ground electrode 30 and the tip end portion 16 of the insulator 10 causes the noble metal tip 36 having a part of the communication portion 31 and the contact portion 38 to be connected to the tip end portion 16 of the insulator 10. It can be blocked by bringing it into contact. Therefore, the plasma energy does not leak into the gap, and the ignitability can be prevented from being lowered. Further, since the noble metal tip 36 is located at the position where the outer protrusion 37 overlaps the inner protrusion 34 of the electrode base material 33 in the axis O direction, the noble metal tip 36 is joined after the electrode base material 33 is arranged in the manufacturing process. Until the noble metal tip 36 is not dropped. Even when the plasma jet ignition plug 100 is used for a long period of time and the joining state between the noble metal tip 36 and the electrode base material 33 is deteriorated, the noble metal tip 36 is prevented from falling off.

  The plasma jet ignition plug 100 according to the first embodiment can be variously modified. For example, as in the plasma jet ignition plug 101 shown in FIG. 4, the tip engaging portion may not be formed at the tip portion 116 of the insulator 110. When the noble metal tip 191 is joined to the electrode base material 33, it is pressed to the rear end side in the direction of the axis O, and laser welding is performed while the contact portion 120 of the noble metal tip 191 is in contact with the tip portion 116 of the insulator 110. The gap between the electrode 171 (electrode base material 33) and the tip 116 of the insulator 110 can be closed.

  Further, as in the plasma jet ignition plug 102 shown in FIG. 5 and the plasma jet ignition plug 103 shown in FIG. 6, the length of the noble metal tips 192 and 193 in the direction of the axis O is increased or decreased. Also good. If it does in this way, the joint part of the noble metal tip 192,193 and the electrode base material 33 will become step shape. Then, when the noble metal tips 192 and 193 and the electrode base material 33 are laser-welded while the contact portions 121 and 122 of the noble metal tips 192 and 193 are brought into contact with the tip portion 116 of the insulator 110, the axis line with respect to the mating surfaces of the two It becomes easy to irradiate laser light from an angle that intersects O with an acute angle. In this way, laser light can be prevented from entering the gap between the mating surfaces of the noble metal tips 192 and 193 and the electrode base material 33, and more reliable joining can be performed.

  Further, like the plasma jet ignition plug 104 shown in FIG. 7, the shape of the outer protrusion 131 of the noble metal tip 194 is tapered so that the diameter increases toward the rear end side in the axis O direction, and the noble metal tip 194 contacts. The portion 123 may be brought into contact with the distal end portion 116 of the insulator 110. In this case, by providing a taper portion 132 that overlaps the outer protrusion 131 and the axis O direction in the hole of the electrode base material 184, until the noble metal tip 194 is joined after the electrode base material 184 is disposed in the manufacturing process. The noble metal tip 194 will not fall out.

  Similarly, when a noble metal tip having such a tapered outer protrusion is used, a noble metal tip 195 such as a plasma jet ignition plug 105 shown in FIG. 8 or a plasma jet ignition plug 106 shown in FIG. 9 is used. , 196 may be lengthened or shortened in the axial direction. That is, if the joining portion of the noble metal tips 195 and 196 and the electrode base material 184 is stepped, the contact portions 124 and 125 of the noble metal tips 195 and 196 are brought into contact with the tip portion 116 of the insulator 110, It is possible to easily irradiate the laser beam from the angle that intersects the axis O with an acute angle with respect to the mating surface that is irradiated with the laser beam at the time of welding, so that more reliable bonding can be performed.

  Further, as in the plasma jet ignition plug 107 shown in FIG. 10, the outer periphery of the noble metal tip 197 protrudes radially outward from the inner protrusion 34 of the electrode base material 33 without forming the outer protrusion. If it is in the state, it is possible to prevent the noble metal tip 197 from falling off as in the first embodiment. Of course, as in the first embodiment, after the electrode base material 33 is joined to the metal shell 150, the noble metal tip 197 is pressed toward the rear end side in the axis O direction, and the contact portion 126 of the noble metal tip 197 is insulated. The electrode base material 33 and the noble metal tip 197 may be joined while being brought into contact with the tip portion 116 of the metal. Alternatively, in the ground electrode joining step, the outer periphery 35 of the electrode base material 33 is attached to the metal shell 150 while the electrode base material 33 is pressed to the rear end side in the axis O direction and the noble metal tip 197 is brought into contact with the tip portion 116 of the insulator 110. The engagement step 157 may be joined. In this way, the arrangement position of the electrode base material 33 can be made closer to the insulator 110 side, so that the mating portion between the engagement step portion 157 of the metal shell 150 and the outer edge portion 35 of the electrode base material 33 is stepped. As described above, more reliable joining can be performed.

  In the modified examples shown in FIGS. 7 to 10, the ground electrodes 174 and 177 (not shown in FIGS. 8 and 9) may be joined to the metal shell 50 in the same process as in the first embodiment. In this way, when the insulator 110 is held by the metal shell 50 due to the gap between the electrode bases 174, 184, 198 (non-contact portions 140, 141, 142) and the tip portion 116 of the insulator 110. It serves to absorb the assembly tolerances in the direction of the axis O. Therefore, the gap between the tip portion 116 and the ground electrodes 174 and 177 can be closed with the noble metal tips 194 to 197 while preventing the tip portion 116 of the insulator 110 from receiving a strong pressing force from the outside. . 4, 5, 7, and 8, the inner peripheral walls of the noble metal tips 191, 192, 194, and 195 are the inner peripheral walls 71, 72, 74, 75 may be configured. Further, like the plasma jet ignition plugs 103, 106 and 107 shown in FIGS. 6, 9 and 10, the inner peripheral walls of the noble metal tips 193, 196 and 197 are part of the inner peripheral walls 73, 76 and 77 of the communicating portion. It may be configured.

  In the first embodiment, the outer protrusion 37 is provided in a bowl shape on the cylindrical noble metal tip 36, but it does not necessarily have to be continuous in a bowl shape and may have a protrusion shape. The same applies to the inner protrusion 34 of the electrode base material 33. When the noble metal tip 36 and the electrode base material 33 are integrated, the outer protrusion 37 and the inner protrusion 34 overlap in the axis O direction. It is sufficient to be positioned so that

[Second Embodiment]
Next, a plasma jet ignition plug 200 according to a second embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 200 will be described with reference to FIG. FIG. 11 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 200 of the second embodiment.

  The plasma jet ignition plug 200 of the second embodiment and the plasma jet ignition plug 100 of the first embodiment are structurally different in that the shape of the ground electrode 230 is different and the insulator 210 The tip engaging portion 216 is not formed with a tip engaging portion. Therefore, the structure of the tip portion of the plasma jet ignition plug 200 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

  As shown in FIG. 11, the ground electrode 230 disposed at the distal end portion 65 of the metal shell 50 is a composite in which an electrode base material 233 and a noble metal tip 236 are integrally joined, as in the first embodiment. The electrode is made of a member. The ground electrode 230 has a disk shape, and a communication hole (communication portion 231) is formed in the center in the radial direction. The noble metal tip 236 has a cylindrical shape. On the other hand, the electrode base material 233 has a disk shape and has a hole constituting the communication portion 231 at the center in the radial direction. The noble metal tip 236 is laser-welded to the electrode base material 233 at the joint portion of both surfaces with the outer peripheral surface facing the inner peripheral surface of the hole of the electrode base material 233. The noble metal tip 236 constitutes a communication portion 231 of the ground electrode 230 together with a hole in the electrode base material 233. The communication portion 231 communicates the inside of the cavity 60 with the outside air through a communication hole surrounded by the inner peripheral wall 78 of the communication portion 231 on the tip side of the insulator 10.

  Further, the outer edge portion 235 of the ground electrode 230 (that is, the outer edge portion 235 of the electrode base material 233) is engaged with the engagement step portion 57 provided at the distal end portion 65 of the metal shell 50, and laser welding is performed in this state. The metal shell 50 is integrally joined. The contact portion 127 provided on the rear end side of the noble metal tip 236 is in contact with the front end portion 216 of the insulator 210. When viewed from the direction of the axis O, the opening 66 of the cavity 60 is connected to the contact portion 127. Inside. The noble metal tip 236 having a contact portion and a part of the communication portion blocks a gap between the tip portion 216 of the insulator 210 and the ground electrode 230. On the other hand, the non-contact portion 143 provided behind the electrode base material 233 and facing the tip portion 216 of the insulator 210 is not in contact with the tip portion 216 of the insulator 210. With this configuration, as in the first embodiment, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred between the ground electrode 230 and the tip 216 of the insulator 210. And the gap between the metal shell 50 communicating with the gap and the insulator 210 are prevented from leaking. The noble metal tip 236 corresponds to the “contact member” and the “noble metal member” in the present invention.

  Next, the manufacturing method of the plasma jet ignition plug 200 of 2nd Embodiment is demonstrated with reference to FIG. FIG. 12 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 200 according to the second embodiment.

  As shown in FIG. 12, also in the plasma jet spark plug 200 of the second embodiment, the insulator 210 in which the center electrode 20 and the terminal fitting 40 (see FIG. 1), which have been previously prepared in separate steps, are assembled together. Similarly, the metal shell 50 manufactured in a separate process is integrally held by crimping (insulator holding process).

  Next, the disc-shaped electrode base material 233 having a hole is disposed on the front end side of the front end portion 216 of the insulator 210 (electrode base material disposing step). In this step, the outer edge portion 235 of the electrode base material 233 is engaged so as to be fitted into the engaging step portion 57 of the metal shell 50 having a step shape. At this time, the electrode base material 233 is maintained in a non-contact state with the tip 216 of the insulator 210. In this state, laser light is emitted around the circumferential direction aiming at the mating surface between the outer edge portion 235 of the electrode base material 233 and the engagement step portion 57 of the metal shell 50, and the metal shell 50 and the ground electrode 230 are irradiated. Welding with the electrode base material 233 is performed (ground electrode joining step).

  And the noble metal chip | tip 236 formed in the cylinder shape is inserted in the hole of the electrode base material 233, and is arrange | positioned at the communication part 231 (contact member arrangement | positioning process). The noble metal tip 236 is in an unfixed state, and is pressed toward the rear end side in the axis O direction in the next step, and constitutes a gap between the noble metal tip 236 and the tip portion 216 of the insulator 210, and the ground electrode 230. The gap between the electrode base material 233 and the tip 216 of the insulator 210 and the gap between the metal shell 50 and the insulator 210 communicating with the gap between the tip 216 of the insulator 210 are closed. . Then, with the noble metal tip 236 being held down, laser light is irradiated aiming at the mating surface between the noble metal tip 236 and the electrode base material 233, and the two are welded around the circumference (contact member joining step). The noble metal tip 36 is integrated with the electrode base material 33 to form the communication portion 31. Thus, the ground electrode 230 is joined to the front-end | tip part 65 of the metal shell 50, and the plasma jet ignition plug 200 of the second embodiment is completed.

  Also in the second embodiment, since the insulator 10 is caulked and held on the metal shell 50, the ground electrode 230 is joined to the metal shell 50, and the insulator 210 is not easily damaged during the manufacturing process. A contact portion 127 is defined as a gap that may be generated between the electrode base material 233 of the ground electrode 230 and the tip portion 216 of the insulator 210, or a gap that may be generated between the metal shell 50 communicating with the gap and the insulator 210. And it can block with the noble metal tip 236 which constitutes a part of communication part 231, and it can prevent a fall of ignitability.

  The plasma jet ignition plug 200 of the second embodiment can be variously modified. For example, as in the case of the plasma jet ignition plug 201 shown in FIG. 13 and the plasma jet ignition plug 202 shown in FIG. Alternatively, the mating portion with the electrode base material 33 may be stepped. In this way, when laser welding is performed while the contact portions 128 and 129 of the noble metal tips 291 and 292 are in contact with the tip portion 216 of the insulator 210, the mating surfaces of the noble metal tips 291 and 292 and the electrode base material 33 are used. Laser light is prevented from entering the gaps, and more reliable bonding can be performed.

  Further, like a plasma jet ignition plug 203 shown in FIG. 15, a flange-like outer protrusion 247 that protrudes radially outward is provided on the outer periphery of the cylindrical noble metal tip 293 at the front end side in the axis O direction. Also on the 283 side, a stepped tip mounting portion 244 whose diameter is increased on the tip side in the axis O direction may be provided in the hole of the electrode base material 283. In this way, as described above, the tip mounting portion 244 adjusts the arrangement position of the noble metal tip 293 in the direction of the axis O and closes the gap between the electrode base material 283 and the tip portion 216 of the insulator 210. Axis misalignment can be prevented. Further, when the noble metal tip 293 having such an outer protrusion 247 is used, the adjustment of the arrangement position of the noble metal tip 293 in the direction of the axis O is limited (when the outer protrusion 247 abuts the tip mounting portion 244, Therefore, the arrangement position adjustment by the electrode base material 283 may also be performed. Further, the engagement step portion 257 of the metal shell 250 may be provided so as to protrude toward the front end side in the axis O direction from the position where the ground electrode 273 is disposed when the ground electrode 273 is engaged with the engagement step portion 257. . In this way, when joining the engaging step portion 257 and the outer edge portion 245 of the electrode base material 283, it is easy to irradiate the laser beam from an angle that intersects the axis O with an acute angle, thereby performing more reliable joining. be able to. As in the modification of the first embodiment, the inner peripheral wall of the noble metal tip 292 constitutes the inner peripheral walls 161 and 162 of the communicating portion, as in the plasma jet ignition plugs 202 and 203 shown in FIGS. May be. Further, like the plasma jet ignition plug 201 shown in FIG. 13, the inner peripheral wall of the noble metal tip 291 may constitute a part of the inner peripheral wall 160 of the communicating portion.

[Third Embodiment]
Next, a plasma jet ignition plug 300 according to a third embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 300 will be described with reference to FIG. FIG. 16 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 300 according to the third embodiment.

  The plasma jet ignition plug 300 according to the third embodiment is also different from the plasma jet ignition plug 100 according to the first embodiment in terms of the shape of the ground electrode 330 and the tip 316 of the insulator 310. This is different in that no joint is formed. Therefore, as described above, the structure of the tip portion of the plasma jet ignition plug 300 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

  As shown in FIG. 16, the ground electrode 330 disposed at the distal end portion 65 of the metal shell 50 is an electrode made of a composite member in which an electrode base material 333 and a noble metal tip 336 are integrally joined. The ground electrode 330 has a disk shape and has a communication hole (communication portion 331) at the center in the radial direction. Each of the noble metal tip 336 and the electrode base material 333 has a disk shape (annular shape), and a hole is formed in the radial center. The noble metal tip 336 is thinner than the electrode base material 333. The electrode base material 333 has a tip mounting portion 334 whose rear end side in the axis O direction is enlarged in a step shape on the inner peripheral side of the hole. The outer edge 337 of the noble metal tip 336 is engaged with the tip mounting portion 334 so that the surface of the electrode base material 333 is aligned with the surface of the electrode base material 333 (referred to as a surface orthogonal to the disk-shaped (annular) thickness direction). A noble metal tip 336 is arranged. The outer edge 337 of the noble metal tip 336 is laser welded to the electrode base material 333. The noble metal tip 336 constitutes a communication portion 331 of the ground electrode 330 together with a hole of the electrode base material 333.

  Further, the ground electrode 330 has the surface on which the noble metal tip 336 is bonded facing toward the insulator 310, and the outer edge portion 335 (that is, the outer edge portion 335 of the electrode base material 333) is engaged with the distal end portion 65 of the metal shell 50. The step 57 is engaged. Further, the ground electrode 330 is laser-welded to the metal shell 50 in contact with the tip 316 of the insulator 310, and both are integrally joined. That is, the gap between the ground electrode 330 and the tip 316 of the insulator 310 and the gap between the metal shell 50 communicating with the gap and the insulator 310 are in contact with each other. It is blocked. Of the portions of the noble metal tip 336 and the electrode base material 333 that face the tip portion 316 of the insulator 310, the portion that contacts the tip portion 316 is a contact portion 320. On the other hand, the non-contact part 340 of the electrode base material 333 and the metal shell 50 are not in contact with each other in the direction of the axis O. With this configuration, as in the first and second embodiments, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred to the ground electrode 330 and the tip 316 of the insulator 310. Leakage into the gap between the two is prevented. The noble metal tip 336 corresponds to the “noble metal member” in the present invention.

  Next, the manufacturing method of the plasma jet ignition plug 300 of 3rd Embodiment is demonstrated with reference to FIG. FIG. 17 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 300 according to the third embodiment.

  As shown in FIG. 17, also in the plasma jet ignition plug 300 of the third embodiment, the insulator 310, in which the center electrode 20 and the terminal fitting 40 (see FIG. 1), which are previously prepared in separate steps, are integrally assembled. Similarly, the metal shell 50 manufactured in a separate process is integrally held by crimping (insulator holding process).

  Next, the outer edge portion 337 of the noble metal tip 336 is engaged with the tip attachment portion 334 of the electrode base material 333. At this time, the surface of the electrode base material 333 and the surface of the noble metal tip 336 are aligned. In this state, laser light is irradiated toward the mating surface between the noble metal tip 336 and the electrode base material 333, and the ground electrode 330 in which the noble metal tip 336 is integrally joined with the electrode base material 333 is produced (noble metal member joining). Process). The noble metal tip 336 forms a communication portion 331 together with the hole of the electrode base material 333.

  And this ground electrode 330 is arrange | positioned in the front end side rather than the front-end | tip part 316 of the insulator 310 (arrangement | positioning process). At this time, the ground electrode 330 is disposed such that the side where the noble metal tip 336 is exposed (the side where the electrode base material 333 and the board surface are aligned) is directed to the tip 316 side of the insulator 310 and the thickness direction is aligned with the axis O direction. Is done. Then, the ground electrode 330 is pressed toward the rear end side in the axis O direction, and the contact portion 320 and the tip portion 316 are brought into contact with each other, so that the gap between the ground electrode 330 and the tip portion 316 of the insulator 310 is closed. Can be removed. In this state, the laser beam makes a round in the circumferential direction and irradiates the target surface of the outer edge portion 335 of the ground electrode 330 (that is, the outer edge portion 335 of the electrode base material 333) and the engagement step portion 57 of the metal shell 50. Then, the two are welded (ground electrode joining step). In this way, the ground electrode 330 is joined to the distal end portion 65 of the metal shell 50, and the plasma jet ignition plug 300 of the third embodiment is completed.

  Also in the third embodiment, the insulator 10 is caulked and held on the metal shell 50, and then the ground electrode 330 is joined to the metal shell 50, so that the insulator 310 is not easily damaged during the manufacturing process. Since the ground electrode 330 is pressed against the insulator 310 when the ground electrode 330 is joined to the metal shell 50, no gap is generated between the ground electrode 330 and the tip 316 of the insulator 310. . For this reason. When the plasma formed in the cavity 60 is ejected outward, the plasma energy is prevented from leaking into the gap between the ground electrode 330 and the tip portion 316 of the insulator 310, and the ignitability is reduced. Can be prevented.

  The plasma jet ignition plug 300 according to the third embodiment can be variously modified. For example, like the metal shell 350 of the plasma jet ignition plug 301 shown in FIG. 18, the surface of the engagement step portion 357 on the front side in the axis O direction when the ground electrode 330 is engaged with the engagement step portion 357. The position may be the rear end side in the axis O direction with respect to the position of the surface of the ground electrode 330 on the front side in the axis O direction. In this way, similarly to the above, when joining the engaging step portion 357 and the outer edge portion 335 of the ground electrode 330, it is easy to irradiate the laser beam from an angle that intersects the axis O with an acute angle, and more reliable joining is achieved. It can be carried out. Further, although not shown, the position of the surface of the engagement step portion 357 on the tip side in the axis O direction when the ground electrode 330 is engaged with the engagement step portion 357 is the surface of the ground electrode 330 on the tip side in the axis O direction. It is good also as a front end side of an axis O direction rather than the position.

  Further, like the plasma jet ignition plug 302 shown in FIG. 19 and the plasma jet ignition plug 303 shown in FIG. 20, a noble metal tip 392 constituting the communication portion 341 of the ground electrode 372 is formed in a cylindrical shape, and the axis O A hook-shaped outer protrusion 342 that protrudes radially outward may be provided on the outer periphery on the tip side in the direction. Further, on the electrode base material 382 side, a stepped tip mounting portion 344 having a diameter enlarged at the front end side in the axis O direction is provided in the hole of the electrode base material 382. That is, the noble metal tip 392 can be positioned with respect to the electrode base material 382. In this way, the electrode base material 382 and the noble metal tip 392 can be easily joined.

  Further, the noble metal tip 392 has a configuration in which a part of the noble metal tip 392 protrudes from the surface of the electrode base material 382 toward the rear end side in the axis O direction when the noble metal tip 382 is joined. At the time of joining 372, the protruding portion may be brought into contact with the tip 316 of the insulator 310. In this way, the contact area between the ground electrodes 372 can be made smaller than when the entire surface of the ground electrode 372 is brought into contact with the tip 316 of the insulator 310 to close the gap between the two, and the contact surface for closing the gap. The smoothness of the (contact portion 321) can be easily managed.

  Further, the ground electrode 372 is engaged with the engagement step portions 358 and 357, such as the engagement step portion 358 of the metal shell 351 shown in FIG. 19 and the engagement step portion 357 of the metal shell 350 shown in FIG. The position of the engagement step portions 358 and 357 at the front end side in the axis O direction of the engagement step portions 358 and 357 is positioned on the rear end side in the axis O direction from the position of the surface on the front end side in the axis O direction of the ground electrode 330. Or it is good to make it be the front side of the axis O direction. In this way, as described above, the laser is used when joining the engaging step portions 358 and 357 and the outer edge portion 345 of the ground electrode 372 while the contact portion 321 of the noble metal tip 392 is in contact with the tip portion 316 of the insulator 310. Light can be easily irradiated from an angle that intersects the axis O with an acute angle, and more reliable bonding can be performed.

  As in the modification of the first embodiment, the inner peripheral wall of the noble metal tip 392 constitutes the inner peripheral wall 164 of the communicating portion, as in the plasma jet ignition plugs 302 and 303 shown in FIGS. Also good. Further, like the plasma jet ignition plug 301 shown in FIG. 18, the inner peripheral wall of the noble metal tip 336 may constitute a part of the inner peripheral wall 163 of the communicating portion. Further, like the plasma jet ignition plugs 302 and 303 shown in FIGS. 19 and 20, only the noble metal tip 392 includes the contact portion 321, and the non-contact portion 347 of the electrode base material 382 is the metal shell 351, 350 in the axis O direction. In addition, it may be configured not to contact both the insulator 310 and the insulator 310. Further, like the plasma jet ignition plug 301 shown in FIG. 18, both the noble metal tip 336 and the electrode base material 333 are provided with a contact part 320, and the non-contact part 340 of the electrode base material 333 is connected to the metal shell 350 in the axis O direction. It is good also as a structure which does not contact.

[Fourth Embodiment]
Next, a plasma jet ignition plug 400 according to a fourth embodiment will be described with reference to the drawings. First, the structure of the plasma jet ignition plug 400 will be described with reference to FIG. FIG. 21 is an enlarged cross-sectional view of the tip portion of the plasma jet ignition plug 400 according to the fourth embodiment.

  Similar to the above, the plasma jet ignition plug 400 of the fourth embodiment is also different from the plasma jet ignition plug 100 of the first embodiment in that the ground electrode 430 has a shape and the tip of the insulator 410 has a tip. The difference is that the engaging portion is not formed. Therefore, the structure of the tip portion of the plasma jet ignition plug 400 will be described here, and the other portions are the same, and the description thereof will be omitted or simplified.

  As shown in FIG. 21, the ground electrode 430 disposed at the tip 465 of the metal shell 450 is an electrode made of a composite member in which an electrode base material 433 and a noble metal tip 436 are integrally joined. The ground electrode 430 has a disk shape, and a communication hole (communication portion 431) is formed in the center in the radial direction. The noble metal tip 436 and the electrode base material 433 are each formed in a disc shape (annular shape) and have a hole in the center in the radial direction. The noble metal tip 436 is thinner than the electrode base material 433. The electrode base material 433 has a tip mounting portion 434 whose diameter is expanded stepwise on the tip side in the axis O direction on the inner peripheral side of its own hole. The noble metal tip 436 is disposed so that the outer edge portion 437 of the noble metal tip 436 is engaged with the tip attachment portion 434 and the board surface of the electrode base material 433 is aligned with its own board surface. The noble metal tip 436 is laser-welded at the outer edge portion 437 to the electrode base material 433, and constitutes a communication portion 431 of the ground electrode 430 together with a hole in the electrode base material 433. In the plasma jet ignition plug 400, a part of the inner peripheral wall of the electrode base material 433 and the inner peripheral wall of the noble metal tip 436 constitute the inner peripheral wall 166 of the communication portion 431.

  In addition, the ground electrode 430 has the surface on which the noble metal tip 436 is bonded facing forward in the direction of the axis O, and the outer edge portion 435 (that is, the outer edge portion 435 of the electrode base material 433) is engaged with the tip portion 465 of the metal shell 450 The step 457 is engaged. Further, the ground electrode 430 is laser-welded to the metal shell 450 in a state where the ground electrode 430 is in contact with the tip 416 of the insulator 410. That is, the gap between the ground electrode 430 and the tip portion 416 of the insulator 410 is closed by being in contact with each other. A portion where the electrode base material 433 contacts the tip 416 of the insulator 410 is a contact portion 420. On the other hand, the electrode base material 433 has a non-contact portion 440 on the surface facing the metallic shell 450 and does not contact the metallic shell 450 in the axis O direction. With this configuration, as in the third embodiment, when the plasma formed in the cavity 60 is ejected outward, the plasma energy is transferred between the ground electrode 430 and the tip portion 416 of the insulator 410. Leakage into the gap is prevented. The noble metal tip 436 corresponds to the “noble metal member” in the present invention.

  Next, the manufacturing method of the plasma jet ignition plug 400 of 4th Embodiment is demonstrated with reference to FIG. FIG. 22 is a diagram illustrating a part of the manufacturing process of the plasma jet ignition plug 400 according to the fourth embodiment.

  As shown in FIG. 22, also in the plasma jet ignition plug 400 of the fourth embodiment, the insulator 410, in which the center electrode 20 and the terminal fitting 40 (see FIG. 1) previously produced in separate steps are assembled together, is provided. Similarly, the metal shell 450 manufactured in another process is integrally held by crimping (insulator holding process).

  Next, the disc-shaped electrode base material 433 having a hole is disposed on the distal end side from the distal end portion 416 of the insulator 410 (electrode base material disposing step). In this step, the outer edge portion 435 of the electrode base material 433 is engaged so as to be fitted into the engagement step portion 457 of the metal shell 450 having a step shape. Further, the electrode base material 433 is pressed toward the tip portion 416 of the insulator 410, and the gap between the electrode base material 433 and the tip portion 416 of the insulator 410 is closed. As it is, the laser beam is irradiated around the circumferential direction aiming at the mating surface between the outer edge portion 435 (see FIG. 21) of the electrode base material 433 and the engagement step portion 457 of the metal shell 450. In order to facilitate adjustment of the arrangement position of the electrode base material 433, the engagement step portion 457 protrudes toward the front end side in the axis O direction from the position when the electrode base material 433 is disposed in the engagement step portion 457. The laser beam is irradiated from an angle that intersects the axis O at an acute angle. Thereby, the metal shell 450 and the electrode base material 433 of the ground electrode 430 are more reliably joined (ground electrode joining step).

  Then, the noble metal tip 436 formed in a cylindrical shape is inserted into the hole of the electrode base material 433 and arranged in the communication portion 431 (noble metal member arranging step). In this state, the laser beam is irradiated around the circumferential direction aiming at the mating surface between the noble metal tip 436 and the electrode base material 433, and the two are welded (noble metal member joining step). The noble metal tip 436 is integrated with the electrode base material 433 to form a communication portion 431. In this way, the ground electrode 430 is joined to the distal end portion 465 of the metal shell 450, and the plasma jet ignition plug 400 of the fourth embodiment is completed.

  Also in the fourth embodiment, the insulator 410 is caulked and held on the metal shell 450, and then the ground electrode 430 is joined to the metal shell 450, so that the insulator 410 is not easily damaged during the manufacturing process. Further, since the ground electrode 430 is pressed to the insulator 410 side when the ground electrode 430 is joined to the metal shell 450, a gap is not generated between the ground electrode 430 and the tip 416 of the insulator 410. It is possible to prevent ignitability from being lowered.

  The plasma jet ignition plug 400 of the fourth embodiment can be variously modified. For example, like the metal shell 451 of the plasma jet ignition plug 401 shown in FIG. 23, the surface on the distal end side of the engagement step portion 458 in the axis O direction when the ground electrode 430 is engaged with the engagement step portion 458. This position may be on the rear end side of the position of the surface on the front end side of the ground electrode 430. By doing so, similarly to the above, when joining the engagement step portion 458 and the outer edge portion 435 of the ground electrode 430, it is possible to easily irradiate the laser beam from an angle intersecting the axis O with an acute angle, and more reliable joining. It can be performed.

  Further, like the plasma jet ignition plug 402 shown in FIG. 24, the ground electrode 472 may not include a noble metal tip. Furthermore, in the plasma jet ignition plugs of the third and fourth embodiments, the metal shell is provided with a mounting step portion. However, like the plasma jet ignition plug 403 shown in FIG. You may not provide a step part. Even in these cases, when the contact portions 421 and 422 of the ground electrodes 472 and 473 are joined to the metal shells 452 and 453, if the ground electrode 472 is pressed against the tip portion 416 side of the insulator 410, the ground electrode 472 It is possible to prevent a gap from being generated between 473 and the tip portion 416 of the insulator 410. In the plasma jet ignition plugs 402 and 403, the inner peripheral walls of the ground electrodes 472 and 473 that do not include the noble metal tip constitute the inner peripheral walls 167 and 168 of the communication portion.

  In the plasma jet spark plugs of the first to fourth embodiments described above, the noble metal tip has been described as an example of a cylindrical or annular shape. Among them, in the plasma jet ignition plugs of the third and fourth embodiments, the gap between the ground electrode and the tip of the insulator is closed using the electrode base material or the noble metal tip joined to the electrode base material. For this reason, the noble metal tip is not necessarily cylindrical or annular. That is, in the third and fourth embodiments, at least the electrode base material has an annular shape, and it is sufficient that the electrode base material is joined to the metal shell while being in contact with the tip of the insulator. It is possible to close gaps that may occur. Therefore, the noble metal tip is joined to the electrode base material as a part of the communication portion, and a spark discharge is performed between the noble metal tip and the center electrode (that is, the dielectric breakdown resistance between the electrode base material and the center electrode). The dielectric breakdown resistance value between the noble metal tip and the center electrode is lower than the value).

  In the plasma jet ignition plugs of the first to fourth embodiments, the contact portion is provided on the radially inner wall side of the ground electrode. And even if there is a gap between the ground electrode and the tip of the insulator as in the plasma jet ignition plug of the first and second embodiments, the gap is not in communication with the inside of the cavity. It was configured to prevent the decrease in ignitability as much as possible. However, the installation position of the contact portion in the radial direction of the ground electrode is not limited to the above embodiment, and for example, the contact portion may be provided in the central portion in the radial direction of the ground electrode. That is, the gap may be communicated with the inside of the cavity between the ground electrode and the tip of the insulator. Even in such a case, it is possible to close the gap between the ground electrode in the portion where the contact portion exists and the tip of the insulator, and between the metal shell and the insulator communicating with the gap. it can. However, from the viewpoint of preventing a decrease in ignitability, when there is a gap communicating with the inside of the cavity between the ground electrode and the tip of the insulator, it is preferable that the volume of the gap is smaller.

  Similarly, in the plasma jet spark plugs of the first and second embodiments, the noble metal tip is used to close the gap between the ground electrode and the tip of the insulator, so that the electrode base material is not necessarily used. It is not necessary to have an annular shape, and it is sufficient that the noble metal tip has a cylindrical shape or an annular shape. In other words, the electrode base material may be a member that supports the noble metal tip so that the noble metal tip is in contact with the tip of the insulator. Furthermore, although the noble metal tip is used as the contact member, a metal tip made of a conductive member other than the noble metal may be used as the contact member.

  In the description of the plasma jet ignition plug according to the first to fourth embodiments, the structure by the so-called heat caulking has been described with respect to the method of holding the insulator by the metal shell, but this holding method is not limited at all. There is nothing. For example, it may be crimped by cold working without heating, or without using talc, either directly or indirectly through packing, etc., the end of the crimped portion presses the insulator, and the insulator May be held. Furthermore, the method is not limited as long as the insulator can be held regardless of caulking. However, when the insulator is pressed toward the tip end side in the direction of the axis O by caulking or the like as a holding method, there is nothing that comes into contact with the tip portion of the insulator as in the manufacturing process according to the present invention. If the caulking is held with the metal shell in the state, it is preferable in terms of the effect of preventing breakage of the insulator.

It is a fragmentary sectional view of plasma jet ignition plug 100 of a 1st embodiment. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 100 of 1st Embodiment was expanded. It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 100 of 1st Embodiment. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 101 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 102 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 103 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 104 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 105 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 106 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 107 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 200 of 2nd Embodiment was expanded. It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 200 of 2nd Embodiment. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 201 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 202 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 203 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 300 of 3rd Embodiment was expanded. It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 300 of 3rd Embodiment. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 301 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 302 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 303 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 400 of 4th Embodiment was expanded. It is a figure which shows a part of manufacturing process of the plasma jet ignition plug 400 of 4th Embodiment. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 401 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 402 as a modification was expanded. It is sectional drawing to which the front-end | tip part of the plasma jet ignition plug 403 as a modification was expanded.

DESCRIPTION OF SYMBOLS 10 Insulator 12 Shaft hole 20 Center electrode 26 Tip surface 30 Ground electrode 31 Communication part 33 Electrode base material 34 Inner protrusion 35 Outer edge part 36 Precious metal tip 37 Outer protrusion part 38 Contact part 50 Metallic fitting 60 Cavity 61 Tip small diameter part 66 Opening 70 inner wall 100 plasma jet spark plug

Claims (5)

And the middle heart electrode,
Having an axial hole extending in the axial direction, accommodating the distal end surface of the central electrode on the distal end side in the axial hole, and an insulator for holding the central electrode;
At the tip of the insulator, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode as wall surfaces;
A metal shell that surrounds and holds a radial circumference perpendicular to the axial direction of the insulator;
The insulator is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is in annular contact with the distal end portion of the insulator, so that the opening of the cavity is located inside itself when viewed from the axial direction. A grounding electrode having a contact portion and a communication portion for communicating the inside of the cavity with the outside air,
The ground electrode is
While having the communication part and being in non-contact with the insulator in the axial direction, the outer metal is in contact with the metal shell, and its outer edge is joined to the metal shell to electrically connect with the metal shell. A connected electrode base material;
Some of the communicating portion, and Ri electrode der composed of a composite member which contact with the members are joined with the contact portion,
The electrode base material of the ground electrode has an inner protrusion that is a part located on the innermost side in the radial direction, and the contact member of the ground electrode is located on the outer side in the radial direction than the inner protrusion. Having an outer protrusion located,
The plasma jet ignition plug , wherein the outer protrusion is disposed on the rear end side in the axial direction with respect to the inner protrusion while being overlapped with the inner protrusion in the axial direction . The plasma jet ignition plug according to claim 1, wherein at least a part of an inner peripheral wall of the communication portion of the ground electrode is formed of a noble metal member made of a noble metal. The plasma jet ignition plug according to claim 1 or 2 , wherein an engagement portion with which the contact portion engages is provided at the tip portion of the insulator. A center electrode;
Having an axial hole extending in the axial direction, accommodating the distal end surface of the central electrode on the distal end side in the axial hole, and an insulator for holding the central electrode;
At the tip of the insulator, a cavity formed in a concave shape with the inner peripheral surface of the shaft hole and the tip surface of the center electrode as wall surfaces;
A metal shell that surrounds and holds a radial circumference perpendicular to the axial direction of the insulator;
The insulator is disposed closer to the distal end side in the axial direction than the distal end portion of the insulator, and is in annular contact with the distal end portion of the insulator, so that the opening of the cavity is located inside itself when viewed from the axial direction. A grounding electrode having a contact portion and a communication portion for communicating the inside of the cavity with the outside air,
The ground electrode is
An electrode base material that has the communication portion and an inner protrusion that is a portion located on the innermost side in the radial direction, and is in non-contact with the insulator in the axial direction, but in contact with the metal shell When,
Plasma jet ignition, which is an electrode composed of a composite member in which a part of the communication part, the contact part, and a contact member having an outer protrusion located outside the inner protrusion in the radial direction are joined together A method of manufacturing a plug,
An insulator holding step for holding the insulator holding the center electrode on the metal shell;
A contact member disposing step of disposing the contact member at the tip of the insulator after the insulator holding step; and the inner protrusion of the electrode base material overlapping the outer protrusion of the contact member in the axial direction. However, the electrode base material is placed on the insulator while the contact member is disposed at the communication portion of the electrode base material so that the inner protrusion is disposed on the tip end side in the axial direction with respect to the outer protrusion. An arrangement step of arranging an electrode base material arrangement step to be arranged closer to the tip side in the axial direction than the tip portion of
A ground electrode joining step for joining an outer edge of the electrode base material of the ground electrode to the metal shell;
A plasma jet ignition comprising a contact member joining step for joining the contact member and the electrode base material while bringing the contact member into contact with the tip of the insulator after the ground electrode joining step. Plug manufacturing method. An engagement portion that is engaged with the contact portion of the ground electrode is provided at the tip of the insulator.
The method of manufacturing a plasma jet ignition plug according to claim 4 , wherein the contact portion is engaged with the engagement portion.

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