CN102324700B

CN102324700B - Plasma jet spark plug and manufacturing method thereof

Info

Publication number: CN102324700B
Application number: CN2011102442027A
Authority: CN
Inventors: 中村通; 加藤友聪
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2007-03-30
Filing date: 2008-03-28
Publication date: 2013-10-09
Anticipated expiration: 2028-03-28
Also published as: CN101276996A; JP4843076B2; JP2009224344A; CN101276996B; JP4413973B2; JP2009224345A; JP4944928B2; CN102324700A; JP4721237B2; JP2008277284A; KR101005694B1; KR20080089273A; JP2008277257A

Abstract

Disclosed is a plasma jet spark plug and a manufacturing method thereof. An electrode base material 33 structuring a grounding electrode 30 is arranged and connected to an engagement step part 57 of a main fitting 50 with an insulator 10 retained. At that time, a rare-metal chip 36 with a flange-like outwardly projecting part 37 is arranged at a communication part 31 beforehand. Then, if the rare-metal chip 36 is connected with the electrode base material 33 while being pressed toward a tip part 16 of the insulator 10, the gap between the grounding electrode 30 (the electrode base material 33) and the tip part 16 of the insulator 10 can be closed by the rare-metal chip 36, thus energy of plasma formed at a cavity 60 does not leak.

Description

Plasma jet spark plug and manufacture method thereof

The application is to be March 28, application number in 2008 the dividing an application for the application of " plasma jet spark plug and manufacture method thereof " that be 200810084898.X, denomination of invention the applying date.

Technical field

The present invention relates to a kind of plasma jet spark plug and manufacture method thereof, this spark plug is for generation of the air-fuel mixture in plasma and the ignition engine.

Background technology

Traditionally, for example the spark plug of automobile engine discharges to light air-fuel mixture by spark plug.In recent years, require internal combustion engine to have high output and low fuel consumption.In order to satisfy such requirement, known use plasma jet spark plug, because plasma jet spark plug provides the rapid diffusion of burning, and presents the high ignition performance that can light even have rare air-fuel mixture of higher ignition limit air-fuel ratio reliably.

This plasma jet spark plug has following structure: the insulator ring that is formed by pottery etc. around central electrode and and metal-back all-in-one-piece grounding electrode between spark-discharge gap, form the little volume discharge space that is called as the chamber thus.Apply high voltage to carry out sparkover to spark-discharge gap.Because the corresponding appearance of dielectric breakdown, can be under lower voltage action current.Like this, owing to also be subjected to the variation that energy is supplied with the discharge condition of influence, in the chamber, produce plasma.Because grounding electrode is positioned at the front of the insulator with chamber, therefore, grounding electrode has the hole that is called as the hole that is formed on wherein.Plasma is outwards launched by the hole, lights air-fuel mixture thus.

In addition, if between grounding electrode and insulator, have the gap, if and in the process of plasma by the hole emission, then the energy of plasma leaks in this gap, and leak in the gap that be communicated with aforementioned gap, between metal-back and the insulator, the energy of the plasma by hole emission reduces, and causes ignition performance to weaken thus.In order to address this problem, proposed a kind of plasma jet spark plug, wherein, insulator (housing) is configured to closely contact with grounding electrode (outer electrode), make and do not have gap (for example, with reference to TOHKEMY 2006-294257 communique) between insulator and the grounding electrode.In the disclosed plasma jet spark plug of this communique, grounding electrode and metal-back are integrally formed, make grounding electrode (part corresponding with grounding electrode of metal-back) correctly locate with respect to metal-back.Therefore, the management of the size of insulator will be enough to set up closely contact between insulator and grounding electrode.When keeping insulator by metal-back, the leading section butt grounding electrode of insulator.

In the manufacture process of plasma jet spark plug, owing to keep insulator by crimp by metal-back, therefore, insulator may produce displacement; Yet, be difficult to manage closely this displacement.Under some displaced condition, crimp external force can be applied to insulator against the mode of grounding electrode by the insulator leading section forcefully, may cause insulation breakdown.

Summary of the invention

Realized the present invention, be used for addressing the above problem, the purpose of this invention is to provide a kind of plasma jet spark plug, its be configured to reduce leak into insulator and be arranged in the gap between the grounding electrode in the place ahead of insulator and gap that be communicated with aforementioned gap, between metal-back and the insulator in the energy of plasma, and avoid insulator to collide grounding electrode forcefully.

To achieve these goals, according to a first aspect of the invention, provide a kind of plasma jet spark plug, it comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the axis hole; The chamber, it is formed in the leading section of insulator, and forms the shape of the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to described axial the place ahead, and have contact site and interconnecting part, this contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and this interconnecting part is used for setting up the connection between described chamber and the ambient atmosphere.In plasma jet spark plug, grounding electrode is not with respect to axially contacting with metal-back, but with respect to axially vertical radially contacting with metal-back, and be electrically connected with metal-back by the peripheral part that is engaged to metal-back.

According to a first aspect of the invention, under the leading section state of contact of the contact site of grounding electrode and insulator, grounding electrode is engaged to metal-back, has sealed the gap between the leading section that can be formed on grounding electrode and insulator thus and can be formed on gap between insulator and the metal-back.Therefore, if these gaps are not closed, during the plasma emission that then produces in the chamber, the energy of plasma can leak in the gap; Yet, according to the present invention, prevent that this energy from leaking, prevent that thus ignition performance from weakening.In addition, the contact site of grounding electrode contact with the leading section of insulator and grounding electrode and metal-back with respect to axially each other under the discontiguous state, grounding electrode is engaged to metal-back.The gap that is associated along axial setting between grounding electrode and metal-back has absorbed along axial assembly error, and this error can produce in the process that insulator is remained in the metal-back.Like this, in manufacture process, when the peripheral part of grounding electrode was engaged to metal-back, above-mentioned structure had avoided the contact site of grounding electrode to collide the leading section of insulator forcefully.Therefore, insulator can be owing to contact site collides the increase of the caused stress of leading section of insulator and breakage forcefully.

In plasma jet spark plug according to the present invention, grounding electrode contacts with the leading section of insulator.Here, term " contact " not only means the state that they contact with each other, and means the state that they abut against each other with more weak pressure.The leading section that means grounding electrode and insulator of " abutting against each other with more weak pressure " can not cause the mode of insulator damage to abut against each other with the size of the pressure that is associated between them.That is to say that the leading section of insulator can not collide grounding electrode forcefully, make the stress that in insulator, produces not increase.Particularly, the leading section of grounding electrode and insulator is enough to prevent from the leakage of the plasma of chamber emission with size, and needn't prevent that the pressure of the leakage of the combustion pressure that receives from the combustion chamber from abutting against each other.

According to a second aspect of the invention, provide a kind of plasma jet spark plug, it comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the axis hole; The chamber, it is formed in the leading section of insulator, and forms the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to axial the place ahead, and have contact site and interconnecting part, contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and interconnecting part is used for setting up the connection between described chamber and the ambient atmosphere.In plasma jet spark plug, grounding electrode is the composite component that is bonded together and forms by with electrode base metal and contact member.The electrode base metal is not with respect to axially contacting with insulator, but contacts with metal-back, and is electrically connected with metal-back by the peripheral part that is engaged to metal-back.Contact member has contact site.The part of electrode base metal and contact member form interconnecting part.

According to a second aspect of the invention, under the leading section state of contact of the contact site of grounding electrode and insulator, grounding electrode is engaged to metal-back, has sealed the gap between the leading section that can be formed on grounding electrode and insulator thus and can be formed on gap between insulator and the metal-back.Therefore, if these gaps are not closed, during the plasma emission that then produces in the chamber, the energy of plasma can leak in the gap; Yet, according to the present invention, prevented the leakage of this energy, thereby prevented that ignition performance from weakening.In addition, grounding electrode is the segmental member that is bonded together and forms by with electrode base metal and contact member.Therefore, in manufacture process, being used for the step that peripheral part with the electrode base metal joins the step of metal-back to and be used under the leading section state of contact of contact member and insulator contact member being joined to the electrode base metal can be separated from each other.The gap along axial between electrode base metal and the insulator leading section has absorbed along axial assembly error, and this error can produce in the process that insulator is remained in the metal-back.Like this, in manufacture process, when the peripheral part of grounding electrode was engaged to metal-back, above-mentioned structure had avoided grounding electrode to collide the leading section of insulator forcefully.Therefore, insulator can be owing to contact site collides the increase of the caused stress of leading section of insulator and breakage forcefully.

According to a third aspect of the invention we, except the structure of a second aspect of the present invention, the electrode base metal of grounding electrode has the most inboard inside protuberance that is positioned at respect to radially; The contact member of grounding electrode has outside protuberance, and the periphery of this outside protuberance is positioned at the radial outside in the week of inside protuberance; And outwards protuberance be arranged in inside protuberance with respect to axial rear.

According to a third aspect of the invention we, the outside protuberance of contact member be disposed in the electrode base metal inside protuberance with respect to axial rear, wherein, the electrode base metal is used to form grounding electrode.Like this, the outside protuberance of contact member is maintained between the leading section and the inside protuberance of electrode base metal of insulator.Therefore, even when using the engagement state that causes between contact member and the electrode base metal deterioration to occur owing to plasma jet spark plug is long-term, the electrode base metal also can prevent come off (the dropping) of contact member.

According to a forth aspect of the invention, except the structure of a second aspect of the present invention, the electrode base metal of described grounding electrode has the most inboard inside protuberance that is positioned at respect to radially; The contact member of grounding electrode has outside protuberance, and the periphery of this outside protuberance is positioned at the radial outside in the week of inside protuberance; And the peripheral part of grounding electrode is engaged to metal-back, make outside protuberance be arranged in inside protuberance with respect to axial the place ahead.

According to a forth aspect of the invention, the outside protuberance of contact member be disposed in contact member inside protuberance with respect to axial the place ahead, and in the outside protuberance location contact member by use, contact member and electrode base metal are joined together.This off-axis that can prevent contact member is arranged.

According to a fifth aspect of the invention, the structure of any one in first to fourth aspect of the present invention, the precious metal components that at least a portion of the internal perisporium of the interconnecting part of grounding electrode is made by noble metal forms.

In order in the chamber, to produce plasma, between grounding electrode and central electrode, apply high-energy.Therefore, plasma has high-energy, causes the consumption of grounding electrode.According to a fifth aspect of the invention, at least a portion of the internal perisporium of the interconnecting part of grounding electrode is formed by precious metal components, has reduced the consumption by the caused grounding electrode of high-energy of plasma thus.

According to a sixth aspect of the invention, the structure of any one in first to the 5th aspect of the present invention, the leading section of insulator has the junction surface that engages with contact site.

According to a sixth aspect of the invention, the contact site of grounding electrode engages with the junction surface of the leading section of insulator, can prevent that thus the off-axis of contact member from arranging.In addition, the closely contact each other at the interface between them of contact site and junction surface, sealed the gap between the leading section that can be formed on grounding electrode and insulator thus and can be formed on gap between insulator and the metal-back, these gaps are positioned at the radial outside at interface.

According to a seventh aspect of the invention, provide a kind of manufacture method of plasma jet spark plug, plasma jet spark plug comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the axis hole; The chamber, it is formed in the leading section of insulator, and forms the shape of the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to axial the place ahead, and have contact site and interconnecting part, this contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and this interconnecting part is used for setting up the connection between chamber and the ambient atmosphere.This manufacture method comprises: insulator keeps step, is used for keeping insulator at metal-back, keeps central electrode in insulator; Deposition step, be used for after insulator keeps step, with ground electrode arrangement the leading section of insulator with respect to axial the place ahead, and with respect to axially not contacting with metal-back, and make the contact site that is arranged on the grounding electrode contact with the leading section of insulator; And the engaging ground electrode step, be used for contact site keep with the insulator state of contact under join the peripheral part of grounding electrode to metal-back.

In the manufacture method of according to a seventh aspect of the invention plasma jet spark plug, with engaging ground electrode before the metal-back, insulator is maintained in the metal-back.Therefore, in the maintenance process, there is not the object of the leading section of pressing insulator, can prevents the breakage of insulator thus.Insulator is maintained in the metal-back by crimp usually.When grounding electrode is engaged to metal-back, can absorb the assembly error that is associated with respect to the position of the leading section of insulator by adjusting grounding electrode.

In addition, when arranging grounding electrode, the contact site of grounding electrode contacts with the leading section of insulator.When keeping this state, grounding electrode is engaged to metal-back, has sealed the gap between the leading section that can be formed on grounding electrode and insulator thus and can be formed between insulator and the metal-back and the gap that is communicated with aforementioned gap.When using the plasma jet spark plug of so making, during the plasma emission that in the chamber, produces, can reduce the energy that leaks in these gaps, thereby prevent that ignition performance from weakening.

According to an eighth aspect of the invention, except the structure of a seventh aspect of the present invention, grounding electrode is by precious metal components being joined to the composite component that the electrode base metal forms, the part of electrode base metal and precious metal components formation interconnecting part; Manufacture method also comprises the precious metal components engagement step, is used for joining precious metal components to the electrode base metal, and the precious metal components engagement step is before deposition step; And in the engaging ground electrode step, the peripheral part with the electrode base metal under the contact site maintenance at least one in being arranged on electrode base metal and precious metal components and the leading section state of contact of insulator joins metal-back to.

When using the plasma jet spark plug of so making, in order in the chamber, to produce plasma, between grounding electrode and central electrode, apply high-energy.Therefore, plasma has high-energy, causes the consumption of grounding electrode.According to an eighth aspect of the invention, make plasma jet spark plug by using grounding electrode, before deposition step, this grounding electrode forms by precious metal components being joined to the electrode base metal, has reduced the consumption by the caused grounding electrode of high-energy of plasma thus.

According to a ninth aspect of the invention, provide a kind of manufacture method of plasma jet spark plug, plasma jet spark plug comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the described axis hole; The chamber, it is formed in the leading section of insulator, and forms the shape of the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to axial the place ahead, and have contact site and interconnecting part, this contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and this interconnecting part is used for setting up the connection between chamber and the ambient atmosphere.Grounding electrode is the composite component that is bonded together and forms by with electrode base metal and contact member.The electrode base metal has the most inboard inside protuberance that is positioned at respect to radially, and with respect to axially not contacting with insulator, but contact with metal-back.Contact member has contact site and outside protuberance, and the periphery of this outside protuberance is positioned at the radial outside in the week of inside protuberance.The part of electrode base metal and contact member constitute interconnecting part.Manufacture method comprises: insulator keeps step, is used for keeping insulator at metal-back, keeps central electrode in insulator; Deposition step, it has: the contact member deposition step is used for contact member being arranged in the leading section of insulator after insulator keeps step; Electrode base metal deposition step, be used for the electrode base metal be arranged in insulator leading section with respect to axial the place ahead, contact member is arranged in the interconnecting part of electrode base metal simultaneously, make the inside protuberance of electrode base metal be disposed in contact member outside protuberance with respect to axial the place ahead; And the engaging ground electrode step, be used for joining the peripheral part of the electrode base metal of grounding electrode to metal-back; The contact member engagement step is used under the leading section state of contact of contact member and insulator contact member and electrode base metal bond being in the same place after the engaging ground electrode step.

According to a ninth aspect of the invention, grounding electrode is the composite component that is bonded together and forms by with electrode base metal and contact member; Contact member has outside protuberance; And the electrode base metal is engaged to metal-back, makes outside protuberance be maintained between the leading section of the inside protuberance of electrode base metal and insulator.Thus, can prevent come off (the dropping) of contact member.In addition, after the electrode base metal bond is arrived the step of metal-back, under the leading section state of contact of contact member and insulator, contact member is engaged to the electrode base metal, has sealed the gap between the leading section that can be formed on grounding electrode and insulator thus and can be formed between insulator and the metal-back and the gap that is communicated with aforementioned gap.That is to say, engaging ground electrode step and contact member engagement step can be separated from each other, wherein, the engaging ground electrode step is used for joining the peripheral part of electrode base metal to metal-back, and the contact member engagement step is used for joining contact member to the electrode base metal under the leading section state of contact of contact member and insulator.As under the situation aspect above-mentioned of the present invention, with the electrode base metal bond before the metal-back, insulator is maintained in the metal-back; Therefore, absorb along axial assembly error, this error can occur in the process that insulator is remained in the metal-back, prevents the breakage of insulator thus.

According to the tenth aspect of the invention, provide a kind of manufacture method of plasma jet spark plug, this plasma jet spark plug comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the axis hole; The chamber, it is formed in the leading section of insulator, and forms the shape of the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to axial the place ahead, and have contact site and interconnecting part, this contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and interconnecting part is used for setting up the connection between chamber and the ambient atmosphere.Grounding electrode is the composite component that is bonded together and forms by with electrode base metal and precious metal components.The electrode base metal has and is positioned at respect to described the most inboard inside protuberance radially.Precious metal components has outside protuberance, and the periphery of this outside protuberance is positioned at the radial outside in the week of inside protuberance.The part of electrode base metal and precious metal components constitute interconnecting part.This manufacture method comprises: insulator keeps step, is used for keeping insulator at metal-back, keeps central electrode in insulator; Electrode base metal deposition step, the contact site that is used for the electrode base metal is arranged to be arranged on the electrode base metal contacts with the leading section of insulator; The engaging ground electrode step is used for after electrode base metal deposition step, joins the peripheral part of the electrode base metal of grounding electrode to metal-back; The precious metal components deposition step, be used for precious metal components is arranged in the interconnecting part of electrode base metal, make that the inside protuberance of the outside protuberance of precious metal components and electrode base metal is overlapping, and be disposed in the electrode base metal inside protuberance with respect to axial the place ahead; And the precious metal components engagement step, be used for precious metal components and electrode base metal bond are in the same place.

According to the tenth aspect of the invention, under the leading section state of contact of electrode base metal and insulator, the electrode base metal is engaged to metal-back, has sealed the gap between the leading section of grounding electrode and insulator thus reliably.Because therefore precious metal components and the electrode base metal bond that is fixed on the metal-back, do not comprise moving element, are conducive to engaging process thus.Can overlay by the outside protuberance with precious metal components on the inside protuberance of electrode base metal and locate precious metal components, prevent that thus the off-axis of precious metal components from arranging.As under the situation aspect above-mentioned of the present invention, before the electrode base metal was engaged to metal-back, insulator was maintained in the metal-back; Therefore, the assembly error of absorbent insulation body prevents the breakage of insulator thus.

According to an eleventh aspect of the invention, provide a kind of manufacture method of plasma jet spark plug, this plasma jet spark plug comprises: central electrode; Insulator, it has vertically the axis hole that extends, and in the mode of the front end face that holds central electrode in the leading section of axis hole central electrode is remained in the axis hole; The chamber, it is formed in the leading section of described insulator, and forms the recess that the front end face by the wall of axis hole and central electrode limits; Metal-back, its with respect to axially vertical radially from outer ring around with keep insulator; And grounding electrode, its be arranged in insulator leading section with respect to axial the place ahead, and have contact site and interconnecting part, this contact site contacts with the leading section ring-type of insulator, make when from end on observation, the opening in chamber is positioned at the inboard of contact site, and this interconnecting part is used for setting up the connection between chamber and the ambient atmosphere.Grounding electrode is the composite component that is bonded together and forms by with electrode base metal and contact member.The electrode base metal does not axially contact with insulator with respect to described, but contacts with metal-back.Contact member has contact site.The part of electrode base metal and contact member constitute interconnecting part.This manufacture method comprises: insulator keeps step, is used for keeping insulator at metal-back, keeps central electrode in insulator; Electrode base metal deposition step is used for after insulator keeps step, the electrode base metal is arranged in insulator leading section with respect to axial the place ahead; The engaging ground electrode step is used for joining the peripheral part of the electrode base metal of grounding electrode to metal-back; The contact member deposition step is used for contact member is arranged in the interconnecting part of electrode base metal, and makes contact member along moving axially, so that contact site contacts with the leading section of insulator; And the contact member engagement step, be used under the leading section state of contact of contact site maintenance and insulator, joining contact member to the electrode base metal.

According to an eleventh aspect of the invention, at first, the electrode base metal is engaged to metal-back; Then, in the time of in the interconnecting part that contact member is arranged in the electrode base metal, contact member is adjusted at the appropriate location so that it contacts with the leading section of insulator; Under this state, contact member is engaged to the electrode base metal.By this step, can seal the gap between the leading section of grounding electrode and insulator reliably, and need not consider the position of electrode base metal.As under the situation aspect above-mentioned of the present invention, before the electrode base metal was engaged to metal-back, insulator was maintained in the metal-back; Therefore, the assembly error of absorbent insulation body prevents the breakage of insulator thus.

According to a twelfth aspect of the invention, except the of the present invention the 7th to the tenth any one structure on the one hand, the leading section of insulator have be arranged on grounding electrode on the junction surface that engages of contact site, and contact site engages with the junction surface.

According to a twelfth aspect of the invention, the contact site of grounding electrode engages with the junction surface of the leading section that is arranged on insulator, grounding electrode and insulator can relative to each other be located reliably thus, and can seal the gap between the leading section of grounding electrode and insulator more reliably.

Description of drawings

Fig. 1 is the partial sectional view according to the plasma jet spark plug of the first embodiment of the present invention;

Fig. 2 is the amplification view of leading section of the plasma jet spark plug of first embodiment;

Fig. 3 is the figure of a part of manufacture process that the plasma jet spark plug of first embodiment is shown;

Fig. 4 is the amplification view according to the leading section of the plasma jet spark plug of the variation of first embodiment;

Fig. 5 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Fig. 6 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Fig. 7 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Fig. 8 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Fig. 9 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Figure 10 is the amplification view according to the leading section of the plasma jet spark plug of another variation of first embodiment;

Figure 11 is the amplification view of the leading section of plasma jet spark plug according to a second embodiment of the present invention;

Figure 12 is the figure of a part of manufacture process that the plasma jet spark plug of second embodiment is shown;

Figure 13 is the amplification view according to the leading section of the plasma jet spark plug of the variation of second embodiment;

Figure 14 is the amplification view according to the leading section of the plasma jet spark plug of another variation of second embodiment;

Figure 15 is the amplification view according to the leading section of the plasma jet spark plug of another variation of second embodiment;

Figure 16 is the amplification view of leading section of the plasma jet spark plug of a third embodiment in accordance with the invention;

Figure 17 is the figure of a part of manufacture process that the plasma jet spark plug of the 3rd embodiment is shown;

Figure 18 is the amplification view according to the leading section of the plasma jet spark plug of the variation of the 3rd embodiment;

Figure 19 is the amplification view according to the leading section of the plasma jet spark plug of another variation of the 3rd embodiment;

Figure 20 is the amplification view according to the leading section of the plasma jet spark plug of another variation of the 3rd embodiment;

Figure 21 is the amplification view of leading section of the plasma jet spark plug of a fourth embodiment in accordance with the invention;

Figure 22 is the figure of a part of manufacture process that the plasma jet spark plug of the 4th embodiment is shown;

Figure 23 is the amplification view according to the leading section of the plasma jet spark plug of the variation of the 4th embodiment;

Figure 24 is the amplification view according to the leading section of the plasma jet spark plug of another variation of the 4th embodiment; And

Figure 25 is the amplification view according to the leading section of the plasma jet spark plug of another variation of the 4th embodiment.

Embodiment

First embodiment

With the plasma jet spark plug 100 that illustrates with reference to the accompanying drawings according to the first embodiment of the present invention.At first, the structure of plasma jet spark plug 100 will be described with reference to Fig. 1 and 2.Fig. 1 shows the plasma jet spark plug 100 of first embodiment in the mode of partial cross section.Fig. 2 is the cutaway view that shows the leading section of plasma jet spark plug 100 with magni-scale.In the explanation hereinafter, the direction of the axes O of the plasma jet spark plug 100 among Fig. 1 is called as vertical direction, and the downside of the plasma jet spark plug among Fig. 1 100 is called as the front side of plasma jet spark plug 100, and the upside of the plasma jet spark plug 100 among Fig. 1 is called as the rear side of plasma jet spark plug 100.

The plasma jet spark plug of first embodiment shown in Figure 1 comprises: insulator 10; The metal-back 50 that keeps insulator 10; Be maintained at central electrode 20 in the insulator 10 along the direction of axes O; Be welded to the grounding electrode 30 of the leading section 65 of metal-back 50; And be arranged on metal terminal 40 on the rearward end of insulator 10.

As everyone knows, insulator 10 is formed by sintering by aluminium oxide etc., and is the tubular insulating component with the axis hole 12 that extends along the direction of axes O.Insulator 10 has flange part 19 and back stem portion 18, and flange part 19 is positioned at the substantial middle with respect to the direction of axes O, and has big external diameter, and back stem portion 18 is positioned at the rear of flange part 19.The outer circumference surface of the rearward end of back stem portion 18 is undulatory, is used for increasing the leakage distance between metal-back 50 and the metal terminal 40.Insulator 10 also has preceding stem portion 17 and shank 13, and this preceding stem portion 17 is positioned at the place ahead of flange part 19, and has the external diameter less than back stem portion 18, and this shank 13 is positioned at the place ahead of preceding stem portion 17, and has the external diameter less than preceding stem portion 17.In addition, insulator 10 also has the stage portion 14 between shank 13 and preceding stem portion 17.

The corresponding part of inner circumference portion with shank 13 of axis hole 12 is formed diameter less than the electrode accommodation section 15 of the diameter of the corresponding other parts of the inner circumference portion with preceding stem portion 17, flange part 19 and back stem portion 18 of axis hole 12.Electrode holds 15 and keeps central electrode 20.As shown in Figure 2, the diameter of the part in the place ahead that is positioned at electrode accommodation section 15 of axis hole 12 further reduces, so that it is as front end minor diameter 61.Front end minor diameter 61 is at leading section 16 place's openings of insulator 10.The leading section 16 of insulator 10 has the junction surface, top 62 of ring-type, and this junction surface, top 62 is around the opening of front end minor diameter 61, and forms recess.The outside protuberance 37 of noble metal electrode head 36 with explanation engages with junction surface, top 62 after a while.

Central electrode 20 is the cylindric electrode bars that formed by nickel alloys such as for example INCONEL (trade (brand) name) 600 or 601, and have by the material that has excellent heat conductivity as copper etc. form metal-cored 23.The circular electrode top 25 that is formed by the alloy that mainly contains noble metal and tungsten (W) is soldered to the leading section 21 of central electrode 20, makes electrode tip 25 and central electrode 20 be integral.In first embodiment, " central electrode " comprises the electrode tip 25 that is soldered to central electrode 20.

As shown in Figure 1, the diameter of the part that the rear end towards central electrode 20 of central electrode 20 is arranged increases, and forms flange shape thus.The stepped area of the electrode accommodation section 15 of the flange part butt axis hole 12 of central electrode 20, central electrode 20 is positioned at electrode accommodation section 15 thus.As shown in Figure 2, the circumference of the front end face 26 of the leading section 21 of central electrode 20 (more specifically, join the circumference of front end face 26 of the electrode tip 25 of central electrode 20 at leading section 21 places of central electrode 20) stage portion between electrode accommodation section 15 and front end minor diameter 61 of butt axis hole 12, electrode accommodation section 15 has different diameters with front end minor diameter 61.By adopting this structure, the wall of the front end minor diameter 61 of axis hole 12 and 26 restrictions of the front end face of central electrode 20 form the tubular at the bottom of the confining zone and have the discharge space of little volume.In plasma jet spark plug 100, pass the spark-discharge gap that is formed between grounding electrode 30 and the central electrode 20 and carry out sparkover, and the path of sparkover extends through discharge space.This discharge space is called as chamber 60.When sparkover, in chamber 60, produce plasma, and plasma is from 66 emissions forward of opening of leading section 16.Chamber 60 can surrounding electric poles accommodation section 15 the rear that is positioned at front end minor diameter 61 and the mode with part of the diameter bigger than front end minor diameter 61 form.

As shown in Figure 1, central electrode 20 is electrically connected with metal terminal 40 via conductive seal material 4 in preceding stem portion 17, and this conductive seal material is the mixture of metal and glass, and is arranged in the axis hole 12.Sealing substance 4 is fixed on central electrode 20 and metal terminal 40 in the axis hole 12, sets up simultaneously to be electrically connected between central electrode 20 and metal terminal 40.Metal terminal 40 extends back in axis hole 12, and the rearward end 41 of metal terminal 40 is outstanding to the outside of insulator 10 from the rear end of insulator 10.The high-voltage cable (not shown) is connected to rearward end 41 via the plug (not shown), and high voltage is applied to rearward end 41 from the igniter (not shown).

Then, metal-back 50 will be described.Metal-back 50 is for the tubular hardware that plasma jet spark plug 100 is fixed to the engine head (not shown) of internal combustion engine.Metal-back 50 remains on insulator 10 in its tubular hole 59 thus around the zone of the leading section from shank 13 to back stem portion 18 of insulator 10.Metal-back 50 is formed by mild steel, and has the roughly axial installation portion 52 that extends of middle section from metal-back 50 forward.External screw thread is formed on the outer circumference surface of installation portion 52, and engages with internal thread on the wall of the installing hole (not shown) that is formed on engine head.Consider thermal endurance, stainless steel, INCONEL (trade (brand) name) etc. can be used for forming metal-back 50.

Flange shape sealing 54 is formed on the rear side of installation portion 52.The annular shim 5 that forms by bent plate is mounted to the zone between sealing 54 and installation portion 52.When plasma jet spark plug 100 is installed to the installing hole (not shown) of engine head, pad 5 is extruded between the face of being located 55 and is out of shape, between them, provide sealing to flow out by installing hole to prevent burning gases thus, this is located the preceding directed face that face 55 is sealings 54, also is near the surface of the engine head the opening of installing hole.

Tool engagement portion 51 is formed on the rear side of sealing 54, and unshowned plug wrench is mounted to tool engagement portion 51.The crimp portion 53 of thin band wall is arranged on the rear side of tool engagement portion 51.The bend 58 of thin band wall is arranged between tool engagement portion 51 and the sealing 54.

Endless loop member

6,7 is inserted in the outer circumference surface of back stem portion 18 of the inner peripheral surface from tool engagement portion 51 to crimp portion 53 of metal-back 50 and insulator 10; In addition, the space between the

endless loop member

6,7 is filled with the powder of talcum 9.

As shown in Figure 2, the inner peripheral surface of installation portion 52 has stage portion 56.The stage portion 14 of insulator 10 is placed on the stage portion 56 via annular seal filler 80.As shown in Figure 1, when the end of crimp portion 53 during with radially aduncate mode crimp, press insulator 10 forward via

circle member

6,7 and talcum 9.In this crimp process, bend 58 is heated, and is accompanied by applying of compression stress and dilatancy increases the compression travel of crimp portion 53 thus.By this step, 19 the part from stage portion 14 to flange part of insulator 10 is maintained at the crimp portion 53 and stage portion 56 of metal-back 50, and insulator 10 is kept integratedly by metal-back 50 thus.Airtight and watertight padding 80 provides the airtight sealing between metal-back 50 and the insulator 10, prevents that thus burning gases from passing through tubular hole 59 and flowing out.

Then, explanation is arranged in grounding electrode 30 in the leading section 65 of metal-back 50.Grounding electrode 30 shown in Figure 2 is the composite components that are bonded together and form by the noble metal electrode head 36 with the electrode base metal 33 of nickel alloy and noble metal.Grounding electrode 30 is formed discoid, and have be formed on its radially central authorities intercommunicating pore (interconnecting part 31).Noble metal electrode head 36 is disposed in the radially inner side of electrode base metal 33, and is engaged to electrode base metal 33.

Step junction surface 57 on the inner peripheral surface of the peripheral part 35 of grounding electrode 30 (being the peripheral part 35 of electrode base metal 33) and the leading section 65 that is formed on metal-back 50 engages; Under the state that so engages, laser welding is stood at the interface between peripheral part 35 and the step junction surface 57, and thus, grounding electrode 30 and metal-back 50 are joined together.

Electrode base metal

33 and 36 cooperations of noble metal electrode head form the interconnecting part 31 of grounding electrode 30.Interconnecting part 31 has be used to the opening of setting up the connection between chamber 60 and the ambient atmosphere.The part that is engaged to metal-back 50 of term " peripheral part " expression grounding electrode 30.In first embodiment, grounding electrode 30 is formed discoid; Like this, the radially outer circumference portion of grounding electrode 30 is corresponding with " peripheral part ".Even when described grounding electrode 30 does not form when discoid, the outer radial periphery portion of grounding electrode 30 also is engaged to metal-back 50.

The noble metal electrode head 36 of first embodiment forms tubular, and constitutes the part of interconnecting part 31; Particularly, it forms the inner peripheral wall 70 of interconnecting part 31.Noble metal electrode head 36 has from the outer circumference surface of the rearward end of noble metal electrode head 36 with flange shape outstanding outside protuberance 37 radially outward.Electrode base metal 33 forms discoid, and its radially central authorities have the hole, this bore portion ground constitutes interconnecting part 31.The same with noble metal electrode head 36, electrode base metal 33 has from the leading section of the wall in the hole of electrode base metal 33 with flange shape radially inside outstanding inside protuberance 34.The outside protuberance 37 of noble metal electrode head 36 is arranged in the rear of the inside protuberance 34 of electrode base metal 33.Because even this structure when deterioration appears in the joint between electrode base metal 33 and the noble metal electrode head 36, can prevent that also noble metal electrode head 36 from dropping forward.

The leading section 16 of insulator 10 has junction surface, top 62, and this junction surface, top 62 is formed in the recess of the front end face of insulator 1, and engages with the outside protuberance 37 of noble metal electrode head 36.Junction surface, top 62 forms ring-type in the mode around the opening 66 in chamber 60.The outside protuberance 37 of noble metal electrode head 36 engages with junction surface, top 62, contacts with leading section 16 ring-types of insulator 10 thus.Outwards the part that engages and contact with leading section 16 ring-types of insulator 10 with junction surface, top 62 of protuberance 37 is contact sites 38.When observing from the direction of axes O, the opening 66 in chamber 60 is positioned at the inboard of contact site 38.The noncontact portion 39 of electrode base metal 33 is arranged on the rear side of electrode base metal 33, and under the situation that does not contact leading section 16 towards the leading section 16 of insulator 10.Gap between the leading section 16 of noble metal electrode head 36 sealing grounding electrodes 30 and insulator 10 and gap that be communicated with aforementioned gap, between metal-back 50 and insulator 10 leading sections 16, and set up connection between chamber 60 and the ambient atmosphere.When the plasma that produces in chamber 60 was outwards launched, this structure prevented that the energy of plasma from leaking into the gap between the leading section 16 of gap between the leading section 16 of grounding electrode 30 and insulator 10 and metal-back 50 and insulator 10.Noble metal electrode head 36 is corresponding with " contact member " and " precious metal components " among the present invention.

In the manufacture process of the plasma jet spark plug 100 of the structure like this of first embodiment, for the gap between the gap between the leading section 16 that seals grounding electrode 30 and insulator 10 and insulator 10 and the metal-back 50, to prevent that the energy of plasma leaks in these gaps when the plasma emission, before joining grounding electrode 30 to metal-back 50, insulator 10 is maintained in the metal-back 50.Then, will be with reference to the manufacture method of figure 3 explanation plasma jet spark plugs 100.Fig. 3 partly illustrates the manufacture process of the plasma jet spark plug 100 of first embodiment.

In the manufacture process of plasma jet spark plug 100, insulator 10 is inserted in the tubular hole 59 of the metal-back 50 that has prepared in an independent step, wherein, under the state that central electrode 20 (having the electrode tip 25 that joins central electrode 20 to) and metal terminal 40 are installed, in an independent step, prepare insulator 10.The stage portion 14 of insulator 10 is placed on via airtight and watertight padding 80 on the stage portion 56 in tubular hole 59 of metal-back 50.Under this state, the crimp portion 53 (referring to Fig. 1) of metal-back 50 is by crimp, thus, 19 the part from stage portion 14 to flange part of insulator 10 is maintained at the stage portion 56 of crimp portion 53 and metal-back 50, like this, insulator 10 is remained on (insulator maintenance step) in the metal-back 50 integratedly.

Then, the tubular noble metal electrode head 36 with outside protuberance 37 is arranged in the place ahead (the contact member deposition step in the deposition step) of the leading section 16 of insulator 10 towards the mode of insulator 10 with outside protuberance 37.At this moment, noble metal electrode head 36 is arranged in outside protuberance 37 towards the position at the junction surface, top 62 of the leading section 16 of insulator 10.In addition, the circular electrode base metal 33 with the outstanding hole of inside protuberance 34 be arranged in inside protuberance 34 noble metal electrode head 36 outside protuberance 37 the place ahead and inwardly protuberance 34 and outwards the mode that overlaps each other with respect to the direction of axes O of protuberance 37 be arranged in the place aheads (the electrode base metal deposition step of deposition step) of insulator 10 leading sections 16.The peripheral part 35 of electrode base metal 33 is assembled and joins to the step junction surface 57 of metal-back 50.At this moment, the noncontact portion 39 of electrode base metal 33 maintains not leading section 16 state of contact with insulator 10.Insert the mode of the position restriction between the junction surface, top 62 of the inside protuberance 34 of electrode base metals 33 and insulator 10 with outside protuberance 37 and arrange noble metal electrode head 36.

Whole circumference along the interface between the step junction surface 57 of the peripheral part 35 of electrode base metal 33 and metal-back 50 is shone this interface with laser beam, and the electrode base metal 33 with metal-back 50 and grounding electrode 30 welds together (engaging ground electrode step) thus.At this moment, noble metal electrode head 36 is in the on-fixed state.In next step, noble metal electrode head 36 is pressed backward, makes outside protuberance 37 engage with the junction surface, top 62 of insulator 10, locatees noble metal electrode head 36 thus.By this step, prevent that the off-axis of noble metal electrode head from arranging.In addition, because noble metal electrode head 36 is pressed backward, therefore, noble metal electrode head 36 closely contacts each other with junction surface, top 62, sealed the gap between the leading section 16 of noble metal electrode head 36 and insulator 10 thus and partly constitute the electrode base metal 33 of grounding electrode 30 and the leading section 16 of insulator 10 between the gap.When the noble metal electrode head remains on pressured state, whole circumference along the interface between noble metal electrode head 36 and the electrode base metal 33 is shone this interface with laser beam, thus noble metal electrode head 36 and electrode base metal 33 is welded together (contact member engagement step).Noble metal electrode head 36 and electrode base metal 33 form interconnecting part 31.

By above-mentioned steps, grounding electrode 30 is engaged to the leading section 65 of metal-back 50, has finished plasma jet spark plug shown in Figure 1 100 thus.As mentioned above, before grounding electrode 30 was engaged to metal-back 50, insulator 10 was maintained in the metal-back 50 by crimp; Therefore, in the crimp process, do not have the leading section 16 of object butt insulator 10, make the leading section 16 of insulator 10 avoid bearing strong external pressure thus.In manufacture process, when insulator 10 was maintained in the metal-back 50 by crimp, the leading section 16 of insulator 10 can produce along the displacement of the direction of axes O; That is to say that assembly error can increase.Even in this case, electrode base metal 33 is being joined in the step of metal-back 50, this assembly error also can be absorbed by the gap along the direction of axes O between the leading section 16 of electrode base metal 33 and insulator 10.

In addition, can be by the gap between the leading section 16 of the electrode base metal 33 that makes noble metal electrode head 36 and the leading section 16 of insulator 10 contact to seal can be formed on grounding electrode 30 and insulator 10, noble metal electrode head 36 has a part and the contact site 38 of interconnecting part 31.Therefore, the energy of plasma does not leak in the above-mentioned gap, can prevent that thus ignition performance from weakening.In addition, because it is overlapping with respect to the direction of axes O with the inside protuberance 34 of electrode base metal 33 that noble metal electrode head 36 is arranged to outside protuberance 37, therefore, join in the manufacture process of noble metal electrode head 36 in the layout with electrode base metal 33, noble metal electrode head 36 can not drop.Even when because the long-term use of plasma jet spark plug 100 when causing engagement state between noble metal electrode head 36 and the electrode base metal 33 deterioration to occur, also can prevent dropping of noble metal electrode head 36.

The plasma jet spark plug 100 of first embodiment can be with various other shape distortion.For example, as under the situation of plasma jet spark plug shown in Figure 4 101, the leading section 116 of insulator 110 can not have the junction surface, top.In the engaging process that carries out noble metal electrode head 191 and electrode base metal 33, by being pressed backward with noble metal electrode head 191 so that the contact site 120 of noble metal electrode head 191 carries out laser welding with the mode that the leading section 116 of insulator 110 contacts, can be with the gap between the leading section 116 of enough gratifying state sealing grounding electrode 171 (electrode base metal 33) and insulator 110.

In addition, under the situation as the plasma jet spark plug 102 that illustrates respectively at Fig. 5 and Fig. 6 and plasma jet spark plug 103, noble metal electrode head 192,193 the length along the direction of axes O can be lengthened out or shorten.This to noble metal electrode head 192,193 and electrode base metal 33 between borderline region the step geometry is provided.With noble metal electrode head 192,193 contact site 121,122 and leading section 116 state of contact of insulator 110 under in the process of laser welding noble metal electrode head 192,193 and electrode base metal 33, the step geometry is conducive to laser beam and is applied to interface between them with the acute angle with respect to axes O.This prevent laser beam pass noble metal electrode head 192,193 and the contact-making surface of electrode base metal 33 between the gap, set up more reliable engagement state thus.

As under the situation of plasma jet spark plug shown in Figure 7 104, the taper that the outside protuberance 131 of noble metal electrode head 194 can diameter increases backwards forms.In this case, the hole of electrode base metal 184 has the taper portion 132 overlapping with respect to axes O with outside protuberance 131.Thus, join in the manufacture process of noble metal electrode head 194 in the layout with electrode base metal 184, noble metal electrode head 194 can not drop.

Even have in use under the situation of noble metal electrode head of outside protuberance of taper, as Fig. 8 of the plasma jet spark plug 105 that illustrates respectively and plasma jet spark plug 106 and shown in Figure 9, noble metal electrode head 195,196 the length along the direction of axes O can be lengthened out or shorten.This to noble metal electrode head 195,196 and electrode base metal 184 between borderline region the step geometry is provided.With noble metal electrode head 195,196 contact site 124,125 and leading section 116 state of contact of insulator 110 under in the process of laser welding noble metal electrode head 195,196 and electrode base metal 184, the step geometry is conducive to laser beam and is applied to interface between them with the acute angle with respect to axes O.This can set up more reliable engagement state.

Plasma jet spark plug 107 as shown in figure 10 is the same, and noble metal electrode head 197 can not have outside protuberance, as long as the periphery of noble metal electrode head 197 is positioned at the radial outside of the inside protuberance 34 of electrode base metal 33.Even in this case, similar with first embodiment, also can prevent dropping of noble metal electrode head 197.Certainly, can carry out engaging process with the similar mode of first embodiment; Particularly, after electrode base metal 33 is engaged to metal-back 150, pressed backward at noble metal electrode head 197, with the contact site 126 of keeping noble metal electrode head 197 with when the leading section 116 of insulator 110 contacts, electrode base metal 33 and noble metal electrode head 197 are joined together.As selection, can carry out the engaging ground electrode step, make electrode base metal 33 pressed backward and noble metal electrode head 197 with when the leading section 116 of insulator 110 contacts, the peripheral part 35 of electrode base metal 33 is engaged to the step junction surface 157 of metal-back 150.By this step, electrode base metal 33 can be arranged by more close insulator 110; Like this, can provide the step geometry to the borderline region between the peripheral part 35 of the step junction surface 157 of metal-back 150 and electrode base metal 33.Therefore, because previously mentioned reason can be set up more reliable engagement state.

In above-mentioned variation shown in Figure 10, grounding electrode 174,177 (not shown among Fig. 8 and Fig. 9) can be by being engaged to metal-back 50 with the similar step of first embodiment at Fig. 7.Gap between the leading section 116 of these step permission electrode base metal 174,184,198 (noncontact portions 140,141,142) and insulator 110 absorbs along the assembly error of the direction of axes O, and this assembly error can produce in the process that insulator 110 is remained on metal-back 50.Like this, avoid bearing under the state of strong external pressure at the leading section 116 of insulator 110, the gap between leading section 116 and the grounding electrode 174,177 can be sealed by noble metal electrode head 194,195,196,197.As at Fig. 4 under the situation of plasma jet spark plug 101 to 105 shown in Figure 8, noble metal electrode head 191,192,193,194,195 inner peripheral wall can be as the inner

peripheral walls

71,72,73,74,75 of interconnecting part.As under the situation of Fig. 9 and plasma jet spark plug 106 shown in Figure 10 and 107, noble metal electrode head 196,197 inner peripheral wall can partly constitute the inner peripheral wall 76,77 of interconnecting part.

In first embodiment, outwards protuberance 37 is arranged on the tubular noble metal electrode head 36 with flange shape.Yet outwards protuberance 37 needn't form continuous flange shapely, also can only form protuberance.This is equally applicable to the inside protuberance 34 of electrode base metal 33.Outwards protuberance 37 and inwardly the shape of protuberance 34 have no particular limits, as long as when noble metal electrode head 36 and electrode base metal 33 are bonded together, outwards protuberance 37 and inside protuberance 34 overlap each other with respect to the direction of axes O.

Second embodiment

Then, with the plasma jet spark plug 200 that illustrates with reference to the accompanying drawings according to a second embodiment of the present invention.At first, the structure of plasma jet spark plug 200 will be described with reference to Figure 11.Figure 11 is the cutaway view that the leading section of plasma jet spark plug 200 is shown with magni-scale.

The plasma jet spark plug 200 of second embodiment is with plasma jet spark plug 100 difference structurally of first embodiment: grounding electrode 230 forms different shapes, and the leading section 216 of insulator 210 does not have the junction surface, top.Like this, the structure of the leading section of plasma jet spark plug 200 will be described here, will omit or be briefly described similar other architectural feature with first embodiment.

As shown in figure 11, similar with first embodiment, be arranged in grounding electrode 230 in the leading section 65 of metal-back 50 and be the composite component that is bonded together and forms by with electrode base metal 233 and noble metal electrode head 236.Grounding electrode 230 forms discoid, and its radially central authorities have intercommunicating pore (interconnecting part 231).Noble metal electrode head 236 forms cylindric.Electrode base metal 233 forms discoid, and its radially central authorities have the hole, this bore portion ground constitutes interconnecting part 231.Noble metal electrode head 236 and electrode base metal 233 the outer circumference surface of noble metal electrode head 236 under the state of the circumference wall in the hole of electrode base metal 233 being in the same place by laser welding at the interface each other.Noble metal electrode head 236 constitutes the interconnecting part 231 of grounding electrode 230 with the hole of electrode base metal 233.Interconnecting part 231 via by the inner peripheral wall 78 of interconnecting part 231 around intercommunicating pore set up being communicated with between chamber 60 and the ambient atmosphere.

The peripheral part 235 of grounding electrode 230 (that is the peripheral part 235 of electrode base metal 233) engages with step junction surface 57 in the leading section 65 that is formed on metal-back 50; Under the state that so engages, laser welding is stood at the interface between peripheral part 235 and the step junction surface 57, and grounding electrode 230 and metal-back 50 are joined together thus.The contact site 127 that is arranged on the rear end of noble metal electrode head 236 contacts with the leading section 216 of insulator 210.When observing from the direction of axes O, chamber 60 open 66 inboards that are positioned at contact site 127.Have the part of interconnecting part 231 and the noble metal electrode head 236 of contact site 127 and seal the leading section 216 of insulators 210 and the gap between the grounding electrode 230.The noncontact portion 143 of electrode base metal 233 is arranged on the rear side of electrode base metal 233, and under the situation that does not contact leading section 216 towards the leading section 216 of insulator 210.Similar with first embodiment, when the plasma that produces in chamber 60 was outwards launched, this structure prevented that the energy of plasma from leaking into the gap between the leading section 216 of grounding electrode 230 and insulator 210 and gap that be communicated with aforementioned gap, between metal-back 50 and the insulator 210.Noble metal electrode head 236 is corresponding with " contact member " and " precious metal components " among the present invention.

Then, the manufacture method of the plasma jet spark plug 200 of second embodiment will be described with reference to Figure 12.Figure 12 partly illustrates the manufacture process of plasma jet spark plug 200.

As shown in figure 12, even in the manufacture process of the plasma jet spark plug 200 of second embodiment, insulator 210 is remained in the metal-back 50 that has prepared in an independent step integratedly by crimp, wherein, under the state that central electrode 20 and metal terminal 40 (referring to Fig. 1) are installed, in an independent step, prepare insulator 210 (insulator maintenance step).

Then, the circular electrode base metal 233 with hole is disposed in the place ahead (electrode base metal deposition step) of the leading section 216 of insulator 210.In this step, the peripheral part 235 of electrode base metal 233 is mounted to the step junction surface 57 of metal-back 50, and engages with the step junction surface 57 of metal-back 50.At this moment, electrode base metal 233 is maintained at not leading section 216 state of contact with insulator 210.Under this state, whole circumference along the interface between the step junction surface 57 of the peripheral part 235 of electrode base metal 233 and metal-back 50 is shone this interface with laser beam, thus the electrode base metal 233 with metal-back 50 and grounding electrode 230 be bonded together (engaging ground electrode step).

Then, tubular noble metal electrode head 236 is inserted in the hole of electrode base metal 233, and is disposed in (contact member deposition step) in the interconnecting part 231.Noble metal electrode head 236 is in the on-fixed state.In next step, noble metal electrode head 236 is pressed backward, seals the gap between the leading section 216 of the electrode base metal 233 of gap between the leading section 216 of noble metal electrode head 236 and insulator 210, grounding electrode 230 and insulator 210 and gap that be communicated with gap between the leading section 216 of electrode base metal 233 and insulator 210, between metal-back 50 and the insulator 210 thus.When noble metal electrode head 236 remains on pressured state, whole circumference along the interface between noble metal electrode head 236 and the electrode base metal 233 is shone this interface with laser beam, thus noble metal electrode head 236 and electrode base metal 233 is welded together (contact member engagement step).Noble metal electrode head 236 and electrode base metal 233 form interconnecting part 231.By above-mentioned steps, grounding electrode 230 is engaged to the leading section of metal-back 50, has finished the plasma jet spark plug 200 of second embodiment thus.

Even in a second embodiment, after insulator 210 was maintained at metal-back 50 by crimp, grounding electrode 230 was engaged to metal-back 50; Therefore, in manufacture process, insulator 210 can not occur damaged.In addition, can can be formed on the gap between the leading section 216 of the electrode base metal 233 of grounding electrode 230 and insulator 210 by noble metal electrode head 236 sealings that have contact site 127 and partly constitute interconnecting part 231, and be communicated with aforementioned gap, can be formed on the gap between metal-back 50 and the insulator 210, can prevent that thus ignition performance from weakening.

The plasma jet spark plug 200 of second embodiment can be with various other shape distortion.For example, similar with first embodiment, under the plasma jet spark plug 201 that does not illustrate as distributing at Figure 13 and Figure 14 and the situation of plasma jet spark plug 202, noble metal electrode head 291,292 the length along the direction of axes O can lengthen or shorten, with to noble metal electrode head 291,292 and electrode base metal 233 between the zone on border the step geometry is provided.With noble metal electrode head 291,292 contact site 128,129 and leading section 216 state of contact of insulator 210 under in the process of laser welding noble metal electrode head 291,292 and electrode base metal 33, the step geometry prevents that laser beam from passing noble metal electrode head 291,292 contact-making surface and the gap between the electrode base metal 233, thereby sets up more reliable engagement state.

In addition, as under the situation of plasma jet spark plug shown in Figure 15 203, tubular noble metal electrode head 293 can have flange shape outside protuberance 247, and this outside protuberance 247 is radially outward outstanding from the outer circumference surface of the leading section of noble metal electrode head 293.In addition, electrode base metal 283 can have step-like top installation portion 244, and this top installation portion 244 is formed on bigger step-like in the aperture of front side on the wall in hole of electrode base metal 283.Because this structural feature, similar with first embodiment, can arrange gap between the leading section 216 of the position enclosed-electrode base metal 283 of noble metal electrode head 293 and insulator 210 by adjusting along the direction of axes O, and top installation portion 244 can prevent that the off-axis of noble metal electrode head 293 from arranging.Owing to use the noble metal electrode head 293 with this outside protuberance 247, arrange that along the axes O direction adjustment of the position of noble metal electrode head 293 is restricted (when the outside protuberance 247 butt top installation portions 244, outwards protuberance 247 can not be further mobile backward), therefore, it is more feasible using the electrode base metal 283 of the position that is used for adjustment noble metal electrode head 293 in addition.In addition, with from the position that engages with step junction surface 257 of grounding electrode 273 forward outstanding mode step junction surface 257 that metal-back 250 is set be more feasible.In the process that the peripheral part 245 with step junction surface 257 and electrode base metal 283 is bonded together, this step junction surface 257 is conducive to laser beam with the acute angle effect with respect to axes O, sets up more reliable engagement state thus.Similar with the variation of first embodiment, as under Figure 14 and plasma jet spark plug 202 shown in Figure 15,203 situation, the inner peripheral wall of noble metal electrode head 292 can be as the inner peripheral wall 161,162 of interconnecting part.In addition, as under the situation of plasma jet spark plug shown in Figure 13 201, the inner peripheral wall of noble metal electrode head 291 can partly constitute the inner peripheral wall 160 of interconnecting part.

The 3rd embodiment

Then, will the plasma jet spark plug 300 of a third embodiment in accordance with the invention be described with reference to the accompanying drawings.At first, the structure of plasma jet spark plug 300 will be described with reference to Figure 16.Figure 16 is the cutaway view that shows the leading section of plasma jet spark plug 300 with magni-scale.

Similar with second embodiment, the plasma jet spark plug 300 of the 3rd embodiment is with plasma jet spark plug 100 difference structurally of first embodiment: grounding electrode 330 forms different shapes, and the leading section 316 of insulator 310 does not have the junction surface, top.Therefore, the structure of the leading section of plasma jet spark plug 300 will be described here, with omission or brief description and similar other architectural feature of first embodiment.

As shown in figure 16, being arranged in grounding electrode 330 in the leading section 65 of metal-back 50 is the composite components that are bonded together and form by with electrode base metal 333 and noble metal electrode head 336.Grounding electrode 330 forms discoid, and its radially central authorities have intercommunicating pore (interconnecting part 331).Noble metal electrode head 336 and electrode base metal 333 form discoid (ring-type) respectively, and its radially central authorities have the hole respectively.The thickness of noble metal electrode head 336 is littler than the thickness of electrode base metal 333.Electrode base metal 333 has step-like top installation portion 334, and this top installation portion 334 is formed on bigger step-like of rear side diameter on the wall in hole of electrode base metal 333.The peripheral part 337 that noble metal electrode head 336 is arranged to noble metal electrode head 336 engages with top installation portion 334, and the back side of noble metal electrode head 336 (with the vertical surface of thickness direction) flushes with the back side of electrode base metal 333.The peripheral part 337 of noble metal electrode head 336 is laser-welded to electrode base metal 333.Noble metal electrode head 336 constitutes the interconnecting part 331 of grounding electrode 330 with the hole of electrode base metal 333.

The peripheral part 335 of grounding electrode 330 (that is, the peripheral part 335 of electrode base metal 333) engages with the step junction surface 57 of the leading section 65 of metal-back 50, makes the side that is engaged to noble metal electrode head 336 of grounding electrode 330 to insulator 310.In addition, under leading section 316 state of contact of grounding electrode 330 and insulator 310, grounding electrode 330 is laser-welded to metal-back 50, and grounding electrode 330 and metal-back 50 are welded together thus.Leading section 316 by grounding electrode 330 and insulator 310 contacts with each other, and has sealed the gap between the leading section 316 of grounding electrode 330 and insulator 310, and gap that be communicated with aforementioned gap, between metal-back 50 and the insulator 310.Noble metal electrode head 336 and electrode base metal 333 towards the leading section 316 of insulator 310 and the part that contacts with the leading section 316 of insulator 310 jointly as contact site 320.The noncontact portion 340 of metal-back 50 and electrode base metal 333 does not contact each other with respect to the direction of axes O.Similar with first and second embodiment, when the plasma that produces in chamber 60 was outwards launched, this structure prevented that the energy of plasma from leaking into the gap between the leading section 316 of grounding electrode 330 and insulator 310.Noble metal electrode head 336 is corresponding with " precious metal components " among the present invention.

Then, the manufacture method of the plasma jet spark plug 300 of the 3rd embodiment will be described with reference to Figure 17.Figure 17 partly shows the manufacture process of plasma jet spark plug 300.

As shown in figure 17, even in the manufacture process of the plasma jet spark plug 300 of the 3rd embodiment, insulator 310 is remained in the metal-back 50 that has prepared in an independent step integratedly by crimp, wherein, under the state that central electrode 20 and metal terminal 40 (referring to Fig. 1) are installed, in an independent step, prepare insulator 310 (insulator maintenance step).

Then, the peripheral part 337 of noble metal electrode head 336 engages with the top installation portion 334 of electrode base metal 333.At this moment, the back side of electrode base metal 333 is flushed each other with the back side of noble metal electrode head 336.Under this state, with the interface between laser beam irradiation noble metal electrode head 336 and the electrode base metal 333, noble metal electrode head 336 and electrode base metal 333 are joined together thus, to form grounding electrode 330 (precious metal components engagement step).Noble metal electrode head 336 constitutes the interconnecting part 331 of grounding electrode 330 with the hole of electrode base metal 333.

Then, the grounding electrode 330 that so forms is disposed in the place ahead (deposition step) of the leading section 316 of insulator 310.At this moment, be arranged in such a way grounding electrode 330: a side of exposing noble metal electrode head 336 of grounding electrode 330 (side that the back side of noble metal electrode head 336 flushes with the back side of electrode base metal 333) is towards the leading section 316 of insulator 310, and the thickness direction of grounding electrode 330 overlaps with the direction of axes O.Grounding electrode 330 is pressed backward, so that contact site 320 contacts with the leading section 316 of insulator 310, seals the gap between the leading section 316 of grounding electrode 330 and insulator 310 thus.Under this state, along the peripheral part 335 of grounding electrode 330 (namely, the peripheral part 335 of electrode base metal 333) and the whole circumference at the interface between the step junction surface 57 of metal-back 50 shine this interface with laser beam, thus metal-back 50 and grounding electrode 330 are welded together (engaging ground electrode step).By this step, grounding electrode 330 is engaged to the leading section 65 of metal-back 50, has finished the plasma jet spark plug 300 of the 3rd embodiment thus.Even in the 3rd embodiment, after insulator 310 was maintained at metal-back 50 by crimp, grounding electrode 330 was engaged to metal-back 50; Therefore, in manufacture process, insulator 310 can not occur damaged.Therefore step owing to carrying out grounding electrode 330 is joined to metal-back 50 under the state that is pressed towards insulator 310 at grounding electrode 330, can not form the gap between the leading section 316 of grounding electrode 330 and insulator 310.Like this, when the plasma that produces in chamber 60 is outwards launched, can avoid the energy of plasma to leak into gap between the leading section 316 of grounding electrode 330 and insulator 310, prevent that thus ignition performance from weakening.

The plasma jet spark plug 300 of the 3rd embodiment can also be with various other shape distortion.For example, as under the situation of the metal-back 350 of plasma jet spark plug shown in Figure 180 301, when grounding electrode 330 engaged with step junction surface 357, the front end face at step junction surface 357 can be positioned at the rear of the leading flank of grounding electrode 330.Similar with above-mentioned laser beam welding, in the process that the peripheral part 335 with step junction surface 357 and grounding electrode 330 is bonded together, this structural feature is conducive to laser beam with the acute angle effect with respect to axes O, thereby sets up more reliable engagement state.In addition, though not shown, when grounding electrode 330 engaged with step junction surface 357, the front end face at step junction surface 357 can be positioned at the place ahead of the leading flank of grounding electrode 330.

In addition, shown in Figure 19 and 20 that plasma jet spark plug 302 and plasma jet spark plug 303 are shown respectively, the noble metal electrode head 392 that partly constitutes the interconnecting part 341 of grounding electrode 372 can form tubular, and can have flange shape outside protuberance 342, this outside protuberance 342 is radially outward outstanding from the outer circumference surface of the leading section of noble metal electrode head 392.In addition, electrode base metal 382 has step-like top installation portion 344, and this top installation portion 344 is formed on the wall in hole of electrode base metal 382, makes that the aperture of front side is bigger.That is to say that electrode base metal 382 is configured to noble metal electrode head 392 can be with respect to electrode base metal 382 location.This structural feature is conducive to the joint between electrode base metal 382 and the noble metal electrode head 392.

In addition, noble metal electrode head 392 is configured to when noble metal electrode head 392 is engaged to electrode base metal 382, part noble metal electrode head 392 is outstanding backwards from the back side of electrode base metal 382, and joining grounding electrode 372 to metal-back 351, in 350 the process, it is more feasible making the leading section 316 of protuberance contact insulator 310.The leading section 316 that contacts insulator 310 with the whole back side of grounding electrode 372 is compared with the situation in the gap between the leading section 316 of sealing grounding electrode 372 and insulator 310, this way can reduce the contact area between the leading section 316 of grounding electrode 372 and insulator 310, is conducive to be fit to the flatness management of the contact-making surface (contact site 321) of closing gap thus.

In addition, as under the situation of metal-back shown in Figure 19 351 and metal-back 350 shown in Figure 20, step junction surface 358,357 is configured to when grounding electrode 372 engages with step junction surface 358,357, and the place ahead or rear that step junction surface 358,357 front end face are positioned at the leading flank of grounding electrode 330 are more feasible.Similar with above-mentioned laser beam welding, under leading section 316 state of contact of the contact site 321 of noble metal electrode head 392 and insulator 310 with step junction surface 358,357 and the process that is bonded together of the peripheral part 345 of grounding electrode 372 in, this structural feature is conducive to laser beam with respect to the effect of axes O acute angle, thereby sets up more reliable engagement state.Similar with the variation of first embodiment, under the situation as the plasma jet spark plug 302,303 that illustrates respectively at Figure 19 and Figure 20, the inner peripheral wall of noble metal electrode head 392 can be as the inner peripheral wall 164 of interconnecting part.As selection, as in plasma jet spark plug shown in Figure 180 301, the inner peripheral wall of noble metal electrode head 336 can partly constitute the inner peripheral wall 163 of interconnecting part.In addition, under the situation as the plasma jet spark plug 302,303 that illustrates respectively at Figure 19 and Figure 20, only noble metal electrode head 392 can have contact site 321, and the noncontact portion 347 of electrode base metal 382 can be not the two contacts with metal-back 351,350 and insulator 310.As selection, as under the situation of plasma jet spark plug shown in Figure 180 301, noble metal electrode head 336 and electrode base metal 333 can have contact site 320, and the noncontact portion 340 of electrode base metal 333 can not contact with metal-back 350 with respect to the direction of axes O.

The 4th embodiment

Then, will the plasma jet spark plug 400 of a fourth embodiment in accordance with the invention be described with reference to the accompanying drawings.At first, the structure of plasma jet spark plug 400 will be described with reference to Figure 21.Figure 21 is the cutaway view that shows the leading section of plasma jet spark plug 400 with magni-scale.

Similar with the second and the 3rd embodiment, the plasma jet spark plug 400 of the 4th embodiment is with plasma jet spark plug 100 difference structurally of first embodiment: grounding electrode 430 forms different shapes, and the leading section 416 of insulator 410 does not have the junction surface, top.Like this, the structure of the leading section of plasma jet spark plug 400 will be described here, with omission or brief description and similar other architectural feature of first embodiment.

As shown in figure 21, the grounding electrode 430 that is arranged in the leading section 465 of metal-back 450 is the composite components that are bonded together and form by with electrode base metal 433 and noble metal electrode head 436.Grounding electrode 430 forms discoid, and its radially central authorities have intercommunicating pore (interconnecting part 431).Noble metal electrode head 436 and electrode base metal 433 form discoid (ring-type) respectively, and its radially central authorities have the hole respectively.The thickness of noble metal electrode head 436 is littler than the thickness of electrode base metal 433.Electrode base metal 433 has step-like top installation portion 434, and bigger step-like of lateral apertures is formed on the wall in hole of electrode base metal 433 before the top installation portion 434.The peripheral part 437 that noble metal electrode head 436 is arranged to noble metal electrode head 436 engages with top installation portion 434, and the front of noble metal electrode head 436 flushes with the front of electrode base metal 333.The peripheral part 437 of noble metal electrode head 436 is laser-welded to electrode base metal 433.Noble metal electrode head 436 constitutes the interconnecting part 431 of grounding electrode 430 with the hole of electrode base metal 433.In plasma jet spark plug 400, the inner peripheral wall of the part of the inner peripheral wall of electrode base metal 433 and noble metal electrode head 436 constitutes the inner peripheral wall 166 of interconnecting part 431.

The peripheral part 435 of grounding electrode 430 (that is, the peripheral part 435 of electrode base metal 433) engages with the step junction surface 457 of the leading section 465 of metal-back 450, make grounding electrode 430 a side that is engaged to noble metal electrode head 436 forwards.In addition, under leading section 416 state of contact of grounding electrode 430 and insulator 410, grounding electrode 430 is laser-welded to metal-back 450.Contact with each other by grounding electrode 430 front end 416 with insulator 410, sealed the gap between the leading section 416 of grounding electrode 430 and insulator 410.A part that contacts with leading section 416 insulator 410 electrode base metal 433 is as contact site 420.Electrode base metal 433 also has noncontact portion 440 in its side towards metal-back 450.Noncontact portion 440 does not contact with metal-back 450 with respect to the direction of axes O.Similar with the 3rd embodiment, when the plasma that produces in chamber 60 was outwards launched, this structure prevented that the energy of plasma from leaking into the gap between the leading section 416 of grounding electrode 430 and insulator 410.Noble metal electrode head 436 is corresponding with " precious metal components " of the present invention.

Then, the manufacture method of the plasma jet spark plug 400 of the 4th embodiment will be described with reference to Figure 22.Figure 22 partly shows the manufacture process of plasma jet spark plug 400.

As shown in figure 22, even in the manufacture process of the plasma jet spark plug 400 of the 4th embodiment, insulator 410 is remained in the metal-back 50 that has prepared in an independent step integratedly by crimp, wherein, under the state that central electrode 20 and metal terminal 40 (referring to Fig. 1) are installed, in an independent step, prepare insulator 410 (insulator maintenance step).

Then, the circular electrode base metal 433 with hole is disposed in the place ahead (electrode base metal deposition step) of the leading section 416 of insulator 410.In this step, the peripheral part 435 of electrode base metal 433 is mounted to the step junction surface 457 of metal-back 450, and engages with the step junction surface 457 of metal-back 450.In addition, electrode base metal 433 is pressed towards the leading section 416 of insulator 410, thus the gap between the leading section 416 of enclosed-electrode base metal 433 and insulator 410.Under this state, shine this interface along the whole circumference at the interface between the step junction surface 457 of the peripheral part 435 of electrode base metal 433 and metal-back 450 with laser beam.For the adjustment of the position that is conducive to electrode base metal 433, step junction surface 457 is formed when electrode base metal 433 is arranged in the step junction surface 457, and it is outstanding forward that step junction surface 457 surpasses the electrode base metal 433 that is arranged.Like this, laser beam is with the acute angle effect with respect to axes O.This makes metal-back 450 engage (engaging ground electrode step) more reliably with the electrode base metal 433 of grounding electrode 430.

Then, tubular noble metal electrode head 436 is inserted in the hole of electrode base metal 433, and is disposed in (contact member deposition step) in the interconnecting part 431.Under this state, shine this interface along the whole circumference at the interface between noble metal electrode head 436 and the electrode base metal 433 with laser beam, noble metal electrode head 436 and electrode base metal 433 are welded together (precious metal components engagement step) thus.Noble metal electrode head 436 and electrode base metal 433 form interconnecting part 431.By above-mentioned steps, grounding electrode 430 is engaged to the leading section 465 of metal-back 450, has finished the plasma jet spark plug 400 of the 4th embodiment thus.

Even in the 4th embodiment, after insulator 410 was maintained at metal-back 450 by crimp, grounding electrode 430 was engaged to metal-back 450; Therefore, in manufacture process, the breakage of insulator 410 can not appear.Therefore step owing to carrying out grounding electrode 430 is joined to metal-back 450 under the state that is pressed towards insulator 410 at grounding electrode 430, can not form the gap between the leading section 416 of grounding electrode 430 and insulator 410.Therefore, can prevent that ignition performance from weakening.

The plasma jet spark plug 400 of the 4th embodiment can also be with various other shape distortion.For example, as under the situation of the metal-back 451 of plasma jet spark plug shown in Figure 23 401, when grounding electrode 430 engaged with step junction surface 458, the front end face at step junction surface 458 can be positioned at the rear of the leading flank of grounding electrode 430.Similar with above-mentioned laser beam welding, in the process that the peripheral part 435 with step junction surface 458 and grounding electrode 430 is bonded together, this structural feature is conducive to laser beam with the acute angle effect with respect to axes O, thereby sets up more reliable engagement state.

In addition, as under the situation of plasma jet spark plug shown in Figure 24 402, grounding electrode 472 can not have the noble metal electrode head.In addition, in the plasma jet spark plug of third and fourth embodiment, metal-back has the step installation portion.Yet as under the situation of plasma jet plasma jet spark plug 403 shown in Figure 25, metal-back 453 can not have the step installation portion.Even at plasma jet spark plug 402, in 403, when under following state, carrying out grounding electrode 472,473 and during the engaging process of metal-back 452,453, at grounding electrode 472,473 and the leading section 416 of insulator 410 between can not form the gap: grounding electrode 472,473 are pressed towards the leading section 416 of insulator 410, so that contact site 421,422 contacts with leading section 416.In plasma jet spark plug 402,403, the inner peripheral wall that does not have the grounding electrode 472,473 of noble metal electrode head is used as the inner peripheral wall 167,168 of interconnecting part.

When the plasma jet spark plug of explanation first to the 4th embodiment, all mention the noble metal electrode head of tubular or ring-type.In the plasma jet spark plug of third and fourth embodiment, seal the gap between the leading section of grounding electrode and insulator by the noble metal electrode head that uses the electrode base metal or be engaged to the electrode base metal.Therefore, the noble metal electrode head needn't necessarily form tubular or ring-type.That is to say, in third and fourth embodiment, if the electrode base metal forms ring-type at least, and the electrode base metal be engaged to metal-back when the leading section of insulator contacts, then can be formed on gap between the leading section of electrode base metal and insulator with enough gratifying state sealings.Therefore, if the noble metal electrode head as the part of interconnecting part is engaged to the electrode base metal, make that the flashing discharge (namely between noble metal electrode head and central electrode, dielectric breakdown resistance between noble metal electrode head and the central electrode is lower than the dielectric breakdown resistance between electrode base metal and the central electrode), then the noble metal electrode cephalopodium enough uses.

In the plasma jet spark plug of first to the 4th embodiment, contact site is arranged towards the inner peripheral wall of grounding electrode.In the plasma jet spark plug of first and second embodiment, have the gap between the leading section of grounding electrode and insulator, but this gap is not communicated with the chamber, the inhibition point fire performance weakens on the maximum possible degree thus.Yet contact site is not limited to above-described embodiment with respect to the radial position of grounding electrode.For example, contact site can be positioned at the radially zone line of grounding electrode.That is to say that the gap between the leading section of grounding electrode and insulator can be communicated with the chamber.Even in this case, also can seal in the gap side radially outward of contact site, between grounding electrode and the insulator leading section, and gap that be communicated with aforementioned gap, between metal-back and the insulator.Yet, consider that the restriction point fire performance weakens, the volume in gap between the leading section of grounding electrode and insulator, that be communicated with the chamber is more little, just more preferred.

In the plasma jet spark plug of first and second embodiment, by the gap between noble metal electrode head sealing grounding electrode and the insulator.Therefore, the electrode base metal needn't necessarily form ring-type; That is to say that the noble metal electrode capitiform becomes tubular or the ring-type that is enough to closing gap.That is to say that the electrode base metal can be the member that is fit to support in the mode that the noble metal electrode head contacts with the leading section of insulator the noble metal electrode head.In addition, first to the 4th embodiment uses the noble metal electrode head as contact member; Yet the metal electrode head of the electric conducting material except noble metal also can be used as contact member.

When the plasma jet spark plug of explanation first to the 4th embodiment, all mention for the so-called hot bending limit that insulator is remained on metal-back.Yet the maintenance method is not particularly limited.For example, can adopt the crimp that does not heat; It is the clod wash limit.In addition, under the situation of not using talcum, can be by directly or by airtight and watertight padding etc. pressing the end of the crimp portion of insulator to keep insulator indirectly.In addition, can keep insulator by the method except crimp.Yet, if the maintenance method that adopts comprises the step of pressing insulator forward, consider the breakage that prevents insulator, press step preferably as do not having under according to the situation of manufacture process of the present invention to carry out under the state of leading section of object butt insulator.

Claims

1. plasma jet spark plug, it comprises:

Central electrode (20);

Insulator (310,410), it has vertically the axis hole (12) that extends, and in the mode of the front end face that holds described central electrode (20) in the leading section of described axis hole (12) described central electrode (20) is remained in the described axis hole (12);

Chamber (60), it is formed in the leading section (316,416) of described insulator (310,410), and forms the shape of the recess that the front end face by the wall of described axis hole (12) and described central electrode (20) limits;

Metal-back (350,351,450,451,452,453), its with respect to described axially vertical radially from outer ring around with keep described insulator (310,410); And

Grounding electrode (330,372,430,472,473), it is arranged in described insulator (310,410) described leading section (316,416) with respect to described axial the place ahead, and have contact site (320,321,420,421,422) and interconnecting part (331,341,431), described contact site (320,321,420,421,422) with the described leading section (316 of described insulator (310,410), 416) ring-type contact, make that the opening (66) of described chamber (60) is positioned at the inboard of described contact site, described interconnecting part (331 when from described end on observation, 341,431) for the connection of setting up between described chamber (60) and the ambient atmosphere;

Wherein, described grounding electrode (330,372,430,472,473) with respect to described axially not with described metal-back (350,351,450,451,452,453) contact, but with respect to described axially vertical radially with described metal-back (350,351,450,451,452,453) contact, and by being engaged to described metal-back (350,351,450,451, the peripheral part of described grounding electrode 452,453) and described metal-back (350,351,450,451,452,453) be electrically connected, between the leading section of described insulator and described grounding electrode, have the gap.

2. plasma jet spark plug according to claim 1 is characterized in that, wherein, described grounding electrode (300,372,430) is by with electrode base metal (333,382,433) and contact member (336,392,436) be bonded together and the composite component that forms described grounding electrode (30,171,174,177,230,273,330,372,430,472,473) described interconnecting part (31,231,331,341,431) at least a portion of internal perisporium is formed by described contact member, and described contact member is made by noble metal.

3. plasma jet spark plug according to claim 1 and 2 is characterized in that, described insulator (10,110,210,310,410) leading section (16,116,216,316,416) have and described contact site (38,120～129,220,320,321,420,421,422) junction surface of Jie Heing (62).