JP6712966B2 - Spark plug - Google Patents

Description

The present invention relates to a spark plug, and more particularly to a spark plug that produces non-equilibrium plasma.

There is a spark plug that uses non-equilibrium plasma as a spark plug that ignites an air-fuel mixture taken into a combustion chamber of an internal combustion engine (Patent Document 1). In the spark plug disclosed in Patent Document 1, the tip of a rod-shaped center electrode is enclosed by a bottomed cylindrical insulator, and a metal shell holds the insulator from the outer peripheral side. When an AC voltage or a pulse voltage is applied between the center electrode and the metal shell a plurality of times, the spark plug generates plasma in a wide range on the surface of the insulator and ignites the air-fuel mixture.

JP, 2014-22341, A

However, in the technique disclosed in Patent Document 1, the electric field strength tends to be high in a portion where the distance between the center electrode and the insulator enclosed by the insulator is short, or in a portion of the center electrode where the surface curvature changes. The plasma is unevenly distributed in that portion, and the ignitability may be reduced.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide an ignition plug capable of suppressing uneven distribution of plasma.

In order to achieve this object, an ignition plug of the present invention comprises a first insulator having a bottomed tubular shape with a closed tip, and a tubular metal shell that holds the first insulator from the outer peripheral side. .. The first insulator includes a locking portion that projects outward in the radial direction and extends along the axis from the front end side to the rear end side. The metal shell includes a shelf portion that locks the locking portion of the first insulator from the tip side. A through hole having a plurality of openings is formed in the second insulator included in the first insulator, and a conductive member is arranged in the through hole. The terminal is electrically connected to the conductive member and insulated from the metal shell. The convex portion of the conductive member is arranged in the opening formed on the tip side of the locking portion of the first insulator among the plurality of openings.

According to the ignition plug of the first aspect, the through hole having the plurality of openings is formed in the second insulator contained in the first insulator, and the conductive member is arranged in the through hole. In the conductive member, a convex portion is arranged in the opening formed on the tip side of the locking portion of the first insulator among the plurality of openings. Since the convex portions in which the electric field is concentrated can be dispersed and arranged in the second insulator, uneven distribution of plasma generated in the first insulator can be suppressed.

According to the ignition plug of the second aspect, the second insulator is an assembly of a plurality of granular insulators filled in the bottomed cylinder of the first insulator. Since the through hole is a gap formed between a plurality of granular insulators, in addition to the effect of the first aspect, the number and size of the convex portions can be controlled by the shape and size of the insulator.

According to the ignition plug of the third aspect, the tip of the terminal is embedded in the rear end of the assembly and is electrically connected to the conductive member. Therefore, in addition to the effect of the second aspect, the terminal and the conductive member are connected. Can improve the contact.

According to the ignition plug of claim 4, since the second insulator is a porous body having through-holes having a plurality of openings, the second insulator has a convex shape depending on the shape and size of the through-holes in addition to the effect of the first aspect. The number and size of parts can be controlled.

According to the ignition plug of the fifth aspect, at least a part of the convex portion is located closer to the tip side than the tip of the metal shell. Therefore, in addition to the effect according to any one of claims 1 to 4, it is possible to improve the ignitability by generating plasma on the tip side of the metal shell rather than the tip.

It is one side sectional drawing of the ignition plug in 1st Embodiment of this invention. It is sectional drawing of a spark plug. It is sectional drawing of the spark plug in 2nd Embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided sectional view taken along the axis O of the ignition plug 10 according to the first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the ignition plug 10 near the tip thereof. is there. 1 and 2, the lower side of the drawing is referred to as the front end side of the ignition plug 10, and the upper side of the drawing is referred to as the rear end side of the ignition plug 10 (the same applies in FIG. 3). As shown in FIG. 1, the spark plug 10 includes a metal shell 20, a first insulator 30, a second insulator 40, and a terminal 50.

The metal shell 20 is a substantially cylindrical member fixed to a screw hole of an internal combustion engine (not shown), and is made of a conductive metal material (for example, low carbon steel). The metal shell 20 is connected from the rear end side to the front end side along the axis O in the order of the caulking portion 21, the tool engaging portion 22, the bending portion 23, the seat portion 24, and the body portion 25. A screw portion 26 is formed on the outer peripheral surface of the body portion 25.

The caulking portion 21 and the bending portion 23 are portions for fixing the metal shell 20 to the first insulator 30. The tool engagement portion 22 is a portion for engaging a tool such as a wrench when the screw portion 26 is coupled to an internal combustion engine (not shown). The seat portion 24 is a portion that is located on the rear end side of the body portion 25 and that protrudes radially outward in an annular shape. An annular gasket 55 is arranged between the seat portion 24 and the body portion 25. When the screw portion 26 is coupled to the internal combustion engine, the gasket 55 is sandwiched between the seat portion 24 and the internal combustion engine and seals the gap between the screw hole (not shown) and the screw portion 26. The body portion 25 has a shelf portion 27 that is formed on the inner circumference and that protrudes inward in the radial direction.

The first insulator 30 is a bottomed cylindrical member made of alumina or the like, which has excellent mechanical properties and insulation at high temperatures. The first insulator 30 has a hole 31 formed along the axis O, which is open at the rear end and closed at the front end. In the present embodiment, the hole 31 has a circular cross section. The hole portion 31 has a step portion 32, which projects inward in the radial direction, formed on the tip end side. The inner diameter of the hole portion 31 on the tip side of the step portion 32 is set smaller than the inner diameter of the hole portion 31 on the rear end side of the step portion 32. The step portion 32 is inclined so that the inner diameter becomes gradually smaller toward the tip end side.

The first insulator 30 includes a cylindrical body portion 33 that extends in the axis O direction, an annular protrusion 34 that extends radially outward from the center of the body portion 33 in the axis O direction, and a locking portion 35. And a leg portion 36 connected to the front end side of the body portion 33 via the intermediary portion. The outer diameter of the leg portion 36 is set to be smaller than the outer diameter of the body portion 33, and the outer diameter of the locking portion 35 is reduced toward the distal end side.

The first insulator 30 is inserted into the metal shell 20. A packing 39 (see FIG. 2) is interposed between the locking portion 35 of the first insulator 30 and the shelf portion 27 of the metal shell 20. The packing 39 is an annular plate member formed of a metal material such as a mild steel plate that is softer than the metal material forming the metal shell 20.

Between the body portion 33 on the rear end side of the overhanging portion 34 of the first insulator 30 and the tool engaging portion 22 of the metal shell 20, a pair of ring members 56, such as talc sandwiched between the ring members 56, is formed. Filler 57 is disposed. When the caulking portion 21 of the metal shell 20 is caulked inward in the radial direction toward the first insulator 30, the first insulator 30 causes the shelf portion 27 of the metal shell 20 via the ring member 56 and the filler 57. Is pressed towards. As a result, the metal shell 20 fixes the first insulator 30 via the packing 39, the ring member 56, and the filler 57.

As shown in FIG. 2, the leg portion 36 (see FIG. 1) of the first insulator 30 is connected to the first portion 37 connected to the tip side of the locking portion 35 and the tip side of the first portion 37. And a second portion 38. The outer diameters of the first portion 37 and the second portion 38 are set to be the same along the axis O direction. The outer diameter of the second portion 38 is set to be smaller than the outer diameter of the first portion 37. The body portion 25 of the metal shell 20 is arranged on the outer side in the radial direction of the first portion 37, and the tip end side of the first metal portion 37 and the second portion 38 project more toward the tip end side than the tip end 28 of the metal shell 20. The first portion 37 and the second portion 38 on the tip side of the boundary 11 between the locking portion 35 and the first portion 37 are present outside the space sealed by the packing 39 (open space).

The second insulator 40 is housed in the hole 31 (bottomed cylinder) of the first insulator 30. In the present embodiment, the second insulator 40 is composed of an aggregate 42 of a plurality of granular insulators 41 filled in the hole 31. The aggregate 42 is arranged on the tip side of the step portion 32 in the hole portion 31. The insulator 41 is formed in a granular shape from alumina, magnesia, zirconia, mullite, silicon nitride, etc., which are excellent in insulation and heat resistance at high temperatures. The aggregate 42 is composed of one kind or a plurality of kinds of these particles. The triaxial average diameter of the insulator 41 (particles) is about 0.1 to 5 mm.

The aggregate 42 has a gap 43 formed between the insulators 41 arranged randomly in the hole 31. The gap 43 forms a continuous through-hole (through-hole) like a mesh in a three-dimensional manner from the rear end to the front end of the assembly 42. The triaxial average diameter of the gap 43 is about 0.1 to 5 mm. A portion of the gap 43 formed in the aggregate 42 that faces the hole 31 forms a plurality of openings 44. The openings 44 are uniformly formed in the portion of the aggregate 42 facing the hole 31.

The conductive member 45 is arranged in the gap 43 of the assembly 42. The conductive member 45 is a member having conductivity, and for example, a metal containing one kind or plural kinds of Pd, Au, Ag, Sn, Ni and the like, a low melting point metal containing In, Ga and the like is used. The portion of the conductive member 45 arranged in the opening 44 forms a convex portion 46. The conductive member 45 may be densely filled in the gap 43, or may be partially filled in the gap 43 as long as the terminal 50 and the convex portion 46 are electrically connected. ..

The convex portion 46 closes a part or the whole of the opening 44 and is in contact with the hole 31. The convex portions 46 are uniformly arranged on the aggregate 42. The convex portion 46 exists at least on the tip side (lower side in FIG. 2) of the boundary 11 between the locking portion 35 and the leg portion 36 (see FIG. 1). In the present embodiment, a part of the convex portion 46 is located closer to the tip side than the tip 28 of the metal shell 20.

The terminal 50 is formed in a rod shape by using a conductive metal material (for example, a nickel-based alloy or stainless steel). In the terminal 50, the tip 51 is embedded in the rear end of the assembly 42, and the tip 51 and the conductive member 45 are in contact with each other. The terminal 50 has a flange portion 52 protruding radially outward from the tip portion 51. Since the outer dimension of the collar portion 52 is larger than the inner diameter of the hole portion 31 on the tip side of the step portion 32, when the collar portion 52 is abutted against the step portion 32, the depth of the tip portion 51 embedded in the assembly 42 is increased. Is decided.

In the present embodiment, the tip portion 51 is formed in a conical shape, and the outer diameter of the tip portion 51 is reduced toward the rear end side in the axis O direction. Since the front end portion 51 having a reduced outer diameter is embedded in the rear end portion of the assembly 42, the front end portion 51 and the conductive member 45 are not separated from each other as compared with the case where the end surface of the front end portion 51 is perpendicular to the axis O. The contact area can be widened. As a result, the contact between the terminal 50 and the conductive member 45 can be improved.

It returns to FIG. 1 and demonstrates. The terminal fitting 54 is a rod-shaped member to which a high voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel). The tip side of the terminal fitting 54 is arranged in the hole 31 of the first insulator 30. A conductive seal material 53 is arranged between the terminal fitting 54 and the terminal 50. The terminal 50 and the terminal fitting 54 are electrically connected to each other in the hole 31 by the sealing material 53.

As the sealing material 53, for example, one obtained by firing a mixture of glass powder and conductive powder is used. As the glass powder, for example, B ₂ O ₃ —SiO ₂ system, BaO—B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —CaO—BaO system, SiO ₂ —ZnO—B ₂ O ₃ system, SiO ₂ —. B ₂ O ₃ -Li powders such as ₂ O system and _{SiO 2 -B 2 O 3 -Li 2} O-BaO systems.

Examples of the conductive powder include powders made of a semiconductive oxide, a metal and a nonmetal conductive material, and the like. Examples of the semiconductive oxide include SnO ₂ . Examples of the metal include Zn, Sb, Sn, Ag and Ni. Examples of the non-metal conductive material include amorphous carbon (carbon black), graphite, silicon carbide, titanium carbide, titanium nitride, tungsten carbide and zirconium carbide. These conductive powders may be used alone or in combination of two or more.

The spark plug 10 is manufactured, for example, by the following method. First, after filling the mixture of the raw material powder of the conductive member 45 and the insulator 41 into the hole 31 of the first insulator 30, the mixture is pre-compressed using a compression rod (not shown). The mixing ratio of the raw material powder of the conductive member 45 and the insulator 41 is determined in consideration of the filling rate occupied by the insulator 41 when the holes 31 are densely filled with the insulator 41.

Then, the terminal 50 is inserted into the hole 31. After transferring the first insulator 30 into the furnace and heating the first insulator 30 to a temperature at which, for example, the raw material powder of the conductive member 45 forms a liquid phase, the first insulator 30 is connected to the terminal 50 until the flange 52 hits the step 32. Apply a load in the direction of the axis O. As a result, the conductive member 45 is compressed/sintered, and the conductive member 45 is bonded to the second insulator 40 formed of the aggregate 42 of the insulators 41. The conductive member 45 forms a three-dimensional mesh-shaped conductive path.

After transferring the first insulator 30 to the outside of the furnace, the raw material powder of the sealing material 53 is put in through the holes 31 and filled around the terminals 50. After pre-compressing the raw material powder of the sealing material 53 filled in the holes 31 with a compression rod (not shown), the first insulator 30 is transferred into the furnace, and, for example, the raw material powder of the sealing material 53. Heat to a temperature above the softening point of. After heating, the terminal fitting 54 is inserted into the hole 31 of the first insulator 30, and the raw material powder of the sealing material 53 is axially compressed by the tip of the terminal fitting 54. As a result, the raw material powder of the sealing material 53 is compressed and sintered, and the sealing material 53 is formed inside the first insulator 30. After transferring the first insulator 30 to the outside of the furnace, the metal shell 20 is attached to the outer periphery of the first insulator 30 to obtain the spark plug 10.

In the spark plug 10, the convex portion 46 is mainly covered by the first portion 37 and the second portion 38 of the first insulator 30. In the spark plug 10, when an AC voltage or a pulse voltage is applied a plurality of times between the terminal fitting 54 and the metallic shell 20, the electric field strength of the convex portion 46 increases. Since the radial thickness of the second portion 38 is smaller than the radial thickness of the first portion 37, the spark plug 10 mainly generates plasma on the surface of the second portion 38 and ignites the air-fuel mixture. ..

Since the convex portions 46 in which the electric field is concentrated are arranged in the hole portions 31 in a distributed manner, uneven distribution of plasma generated in the second portion 38 can be suppressed. As a result, plasma can be generated in a wide range on the surface of the second portion 38. Therefore, even when the air-fuel mixture has uneven concentration or when the air-fuel mixture is thin, a flame can be generated and ignitability can be improved. Further, since plasma can be generated in a wide range, active species such as ozone and negative ions can be efficiently generated.

The second insulator 40 is an assembly 42 of a plurality of granular insulators 41 filled in the first insulator 30, and the conductive member 45 is arranged in the gap 43 formed between the insulators 41. The number and size of the convex portions 46 can be controlled by the shape and size of the insulator 41.

Since the convex portion 46 is uniformly formed in the portion of the first insulator 30 where the second insulator 40 is disposed, facing the hole portion 31, the convex portion 46 is formed uniformly on the surface of the first insulator 30, particularly the surface of the second portion 38. Plasma can be generated uniformly. As a result, the ignition probability can be increased as compared with the case where the plasma is unevenly distributed.

Since the aggregate 42 is formed by filling the plurality of insulators 41 in the bottomed cylinder of the first insulator 30, and the conductive member 45 is arranged in the gap 43 of the aggregate 42, the convex of the conductive member 45 is formed. The groove 46 contacts the hole 31. If there is a gap between the convex portion 46 and the hole portion 31, a discharge is generated between the convex portion 46 and the hole portion 31, the potential of the second portion 38 decreases, and the amount of plasma generated decreases. Although there is a point, since the convex portion 46 contacts the hole portion 31, this problem can be solved. Therefore, the decrease in the potential of the second portion 38 can be prevented and the amount of plasma generated can be secured.

The holes 31 of the first insulator 30 are filled with a plurality of insulators 41 to form an aggregate 42 depending on the shape of the holes 31. Since the conductive member 45 is arranged in the assembly 42, the degree of freedom in designing the shape of the conductive member 45, that is, the hole 31 can be increased. For example, the cross section of the hole 31 may be polygonal or the inner size of the hole 31 may be increased toward the tip side, while the outer shape of the first insulator 30 may be formed in a shape corresponding to the hole 31. .. Thereby, since the surface area of the first insulator 30 can be increased without changing the volume of the first insulator 30, the amount of plasma generated can be increased.

A front end portion 51 of the terminal 50 is embedded in a rear end portion of the assembly 42 and is electrically connected to the conductive member 45. As a result, the contact area between the tip 51 and the conductive member 45 can be increased as compared with the case where the tip 51 of the terminal 50 is not embedded in the assembly 42. Therefore, the contact between the terminal 50 and the conductive member 45 can be improved.

Since at least a part of the convex portion 46 exists on the tip side of the tip 28 of the metal shell 20, the tip portion of the metal shell 20 on the tip side, that is, in the space near the center of the combustion chamber (not shown). Plasma can be generated in the. As a result, the ignitability can be improved.

Next, a second embodiment will be described with reference to FIG. In the first embodiment, the case where the second insulator 40 including the aggregate 42 of the plurality of granular insulators 41 is provided has been described. On the other hand, in the second embodiment, the case where the second insulator 61 is made of the porous body 62 having the through pores 63 will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 3 is a cross-sectional view of the spark plug 60 in which the vicinity of the tip of the spark plug 60 according to the second embodiment is enlarged and shown.

The second insulator 61 of the spark plug 60 is a porous body 62 and is housed in the hole 31 (bottomed cylinder) of the first insulator 30. The porous body 62 is arranged on the tip side of the hole portion 31 with respect to the step portion 32. The porous body 62 is a rod-shaped member formed of alumina, magnesia, zirconia, mullite, cordierite, silicon nitride, or the like, which has excellent insulating properties and heat resistance at high temperatures. In the porous body 62, through holes 63 having a plurality of openings 64 are randomly formed in a three-dimensional mesh shape. The through-holes 63 are connected from the rear end to the tip of the porous body 62, and the openings 64 are uniformly formed on the side surface and the end surface (portion facing the hole 31) of the porous body 62. The biaxial average diameter of the opening 64 is about 0.5 to 1 mm.

A conductive member 65 is arranged in the through-hole 63 of the porous body 62. As the conductive member 65, a metal having conductivity or a low melting point metal is used. A portion of the conductive member 65 arranged in the opening 64 forms a convex portion 66. The convex portions 66 block a part or the whole of each of the openings 64 and are uniformly arranged in the porous body 62. The porous body 62 has a groove-shaped recess 67 at the rear end.

The terminal 70 is formed of a conductive metal material (for example, a nickel-based alloy or stainless steel) in a rod shape. An engaging portion 71 that engages with the concave portion 67 of the porous body 62 of the terminal 70 projects from the tip. The terminal 70 has a flange 72 that abuts the step 32 and projects outward in the radial direction with respect to the engaging portion 71. Since the engaging portion 71 engages with the concave portion 67 of the porous body 62, the contact area between the terminal 70 and the conductive member 65 can be increased as compared with the case where the engaging portion 71 is omitted. As a result, the contact between the terminal 70 and the conductive member 65 can be improved.

The spark plug 60 is manufactured by the following method, for example. First, a porous body 62 larger than the hole 31 of the first insulator 30 is prepared, and the porous body 62 is immersed in a molten conductive member 65 (molten metal) so that the through-holes 63 of the porous body 62 have a conductive member. Insert 65. The porous body 62 is taken out of the molten metal, and after the conductive member 65 in the porous body 62 is hardened, the porous body 62 is ground to a size that can be inserted into the hole 31 of the first insulator 30.

Next, after inserting the porous body 62 into the hole 31 of the first insulator 30, the terminal 70 is inserted into the hole 31 and the engaging portion 71 of the terminal 70 is engaged with the recess 67 of the porous body 62. Next, as in the first embodiment, after the conduction between the terminal 70 and the terminal fitting 54 is secured by the sealing material 53, the metallic shell 20 is assembled to the outer periphery of the first insulator 30 to obtain the spark plug 60.

Since the second insulator 61 of the spark plug 60 is the porous body 62 in which the through pores 63 having the plurality of openings 64 are formed, the number and size of the convex portions 66 depend on the shape and size of the through pores 63. Can be controlled. Since the convex portions 66 on which the electric field is concentrated are arranged in a dispersed manner, it is possible to suppress uneven distribution of plasma generated in the second portion 38. As a result, plasma can be generated over a wide range of the surface of the second portion 38, as in the first embodiment.

The engaging portion 71 of the terminal 70 engages with the recess 67 formed at the rear end of the second insulator 61 (porous body 62), and the terminal 70 is fixed to the first insulator 30 via the seal material 53. .. This can prevent the second insulator 61 (porous body 62) from rotating in the hole 31 due to vibration or the like.

Since the convex portion 66 is arranged in the opening 64 having a biaxial average diameter of about 0.5 to 1 mm, and the convex portion 66 is uniformly formed on the porous body 62, the first insulator 30, especially Plasma can be uniformly generated on the surface of the second portion 38. As a result, the ignition probability can be increased as compared with the case where the plasma is unevenly distributed.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the spirit of the present invention. It can be easily guessed.

In the first embodiment, after the mixture of the raw material powder of the conductive member 45 and the insulator 41 is filled in the hole 31 of the first insulator 30, the first insulator 30 is heated to heat the insulator 41 and the conductive member 45. Although the case of joining and has been described, the present invention is not limited to this. For example, after filling the holes 31 of the first insulator 30 with the plurality of insulators 41, the first insulator 30 is heated to bake the insulator 41, and the aggregates 42 of the insulators 41 are provided in the holes 31. To fix. Then, the molten conductive member 45 is injected into the hole 31 and the conductive member 45 is cured in the gap 43 of the assembly 42, whereby the conductive member 45 can be arranged in the assembly 42.

In the first embodiment, the case where the diameter of the second insulator 40 is the same in the direction of the axis O has been described, but the present invention is not necessarily limited to this. It is naturally possible to make the diameter of the portion arranged on the distal end side of the leg portion 36 larger than the diameter of the root portion of the second insulator 40. By appropriately setting the diameter of the leg portion 36 and the diameter of the second insulator 40, the surface area and the radial thickness of the leg portion 36 are set, and the amount of plasma generated around the leg portion 36 is set appropriately. it can.

In the second embodiment, the case where the three-dimensional mesh-shaped through pores 63 are formed in the rod-shaped porous body 62 has been described, but the present invention is not necessarily limited to this. For example, a porous body in which a plurality of first holes intersecting with the axis O and second holes parallel to the axis O are formed in a rod-shaped insulator can be given. Both ends of the first hole are opened at the side surface of the insulator, and the second hole is opened at the rear end of the insulator and communicates with the first hole. Also in this case, by arranging the conductive member in the first hole and the second hole, it is possible to achieve the same effect as that of the second embodiment.

In each of the above embodiments, the case where the hole 31 having a circular cross section is formed in the first insulator 30 has been described, but the present invention is not limited to this. It is naturally possible to make the cross-sectional shape of the hole 31 a polygon such as a triangle or a quadrangle.

In each of the above-described embodiments, when the leg portion 36 on the tip side of the locking portion 35 of the first insulator 30 has a diameter of the second portion 38 on the tip side smaller than the diameter of the first portion 37 on the base. However, the present invention is not limited to this. Naturally, it is possible to make the diameter of the leg portion 36 the same along the direction of the axis O. Further, it is naturally possible to make the diameter of the portion of the leg portion 36 of the first insulator 30 projecting from the metallic shell 20 to the tip side larger than the diameter of the portion of the leg portion 36 existing inside the metallic shell 20. Is.

In each of the above embodiments, the case where the first insulator 30 is formed of one member has been described, but the present invention is not necessarily limited to this. It is naturally possible to divide the first insulator 30 into a plurality of members and join the members by bonding or screws to form the first insulator 30.

10,60 Spark plug 20 Metal shell 27 Shelf 28 Tip 30 First insulator
31 Hole 35 Locking Part 40,61 Second Insulator 41 Insulator 42 Assembly 43 Gap (Through Hole)
44,64 Opening 45,65 Conductive member 46,66 Convex part 50,70 Terminal 51 Tip part 62 Porous body 63 Through hole (through hole)
O axis

Claims (5)

A hole portion, which extends along the axis from the front end side to the rear end side and projects outward in the radial direction, is provided with a hole portion whose rear end is open and whose front end is closed is formed along said axis line. A bottomed cylindrical first insulator,
A spark plug comprising: a shell that locks the locking portion of the first insulator from the tip end side; and a tubular metal shell that holds the first insulator from the outer peripheral side,
A second insulator included in the first insulator and having a through hole having a plurality of openings facing the hole ;
A conductive member arranged in the through hole,
A terminal electrically connected to the conductive member and insulated from the metal shell,
The conductive member includes a convex portion arranged in an opening formed on the tip side of the locking portion of the first insulator among the plurality of openings ,
The spark plug , wherein the convex portion is a part of the conductive member . The second insulator is an assembly of a plurality of granular insulators filled in the bottomed cylinder of the first insulator,
The spark plug according to claim 1, wherein the through hole is a gap formed between the plurality of granular insulators. The spark plug according to claim 2, wherein a front end portion of the terminal is embedded in a rear end portion of the assembly and is electrically connected to the conductive member. The spark plug according to claim 1, wherein the second insulator is a porous body having through pores having a plurality of openings. The spark plug according to any one of claims 1 to 4, wherein at least a part of the convex portion is located closer to a tip side than a tip of the metal shell.

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