JP2018200789A - Spark plug - Google Patents

Abstract

To provide a spark plug capable of suppressing plasma uneven distribution.SOLUTION: The spark plug includes a first insulator having a closed end and a bottomed cylindrical shape and a cylindrical main body metal fitting for holding the first insulator from the outer peripheral side. The main body metal fitting includes a shelf for locking the locking part of the first insulator from the head end side; the second insulator included in the first insulator has an open hole including a plurality of openings, and a conductive member is arranged in the open hole; a terminal is electrically connected to the conductive member and is insulated from the main body metal fitting; and a convex portion of the conductive member is arranged in an opening formed on the head end side from the locking part of the first insulator among the plurality of openings.SELECTED DRAWING: Figure 1

Description

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

  As an ignition plug for igniting an air-fuel mixture sucked into a combustion chamber of an internal combustion engine, there is one using non-equilibrium plasma (Patent Document 1). In the spark plug disclosed in Patent Document 1, the bottom of the rod-shaped center electrode is enclosed by a bottomed cylindrical insulator, and the metal shell holds the insulator from the outer peripheral side. When an AC voltage or a plurality of pulse voltages are applied between the center electrode and the metal shell, the spark plug generates plasma over a wide area on the surface of the insulator and ignites the mixture.

JP 2014-22341 A

  However, in the technique disclosed in Patent Document 1, there is a tendency that the electric field strength of a portion where the distance between the central electrode wrapped with the insulator and the insulator is short or a portion of the central electrode where the curvature of the surface changes is high. The plasma is unevenly distributed in the portion, and the ignitability may be reduced.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a spark plug that can suppress the uneven distribution of plasma.

  In order to achieve this object, a spark plug of the present invention includes a bottomed cylindrical first insulator having a closed tip, and a cylindrical metal shell that holds the first insulator from the outer peripheral side. . The first insulator includes a locking portion that protrudes 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 for locking the locking portion of the first insulator from the tip side. The second insulator included in the first insulator has a through hole having a plurality of openings, and a conductive member is disposed 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 disposed in an opening formed on the distal end side of the plurality of opening portions with respect to the locking portion of the first insulator.

  According to the spark plug of the first aspect, a through-hole having a plurality of openings is formed in the second insulator included in the first insulator, and the conductive member is disposed in the through-hole. The conductive member has a convex portion disposed in an opening formed on the distal end side of the plurality of openings with respect to the engaging portion of the first insulator. Since the convex portions where the electric field concentrates can be distributed and arranged in the second insulator, uneven distribution of plasma generated in the first insulator can be suppressed.

  According to the spark plug of the second aspect, the second insulator is an aggregate 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 spark plug of claim 3, since the tip of the terminal is embedded in the rear end of the assembly and is electrically connected to the conductive member, in addition to the effect of claim 2, the terminal and the conductive member Can be improved.

  According to the spark plug of claim 4, since the second insulator is a porous body having through holes having a plurality of openings, in addition to the effects of claim 1, the second insulator has a convex shape depending on the shape and size of the through holes. The number and size of the parts can be controlled.

  According to the spark plug of the fifth aspect, at least a part of the convex portion is present on the front end side of the front end of the metal shell. Therefore, in addition to the effect of any one of the first to fourth aspects, plasma can be generated on the front end side of the front end of the metal shell, and the ignitability can be improved.

It is a half sectional view of the spark plug in the first embodiment of the present invention. It is sectional drawing of a spark plug. It is sectional drawing of the ignition 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-side cross-sectional view with the axis O of the spark plug 10 according to the first embodiment of the present invention as a boundary, and FIG. 2 is an enlarged cross-sectional view of the spark plug 10 showing the vicinity of the tip of the spark plug 10. is there. 1 and 2, the lower side of the drawing is referred to as the leading end side of the spark plug 10, and the upper side of the drawing is referred to as the rear end side of the spark plug 10 (the same applies to 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 formed of a conductive metal material (for example, low carbon steel). The metal shell 20 is connected 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 along the axis O from the rear end side to the front end side. The body portion 25 has a thread portion 26 formed on the outer peripheral surface.

  The caulking portion 21 and the bending portion 23 are portions for fixing the metal shell 20 to the first insulator 30. The tool engaging 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 projects annularly outward in the radial direction. An annular gasket 55 is disposed between the seat portion 24 and the body portion 25. The gasket 55 is sandwiched between the seat portion 24 and the internal combustion engine when the screw portion 26 is coupled to the internal combustion engine, and seals a gap between the screw hole (not shown) and the screw portion 26. As for the trunk | drum 25, the shelf part 27 which protrudes to an inner side of radial direction is formed in the inner periphery.

  The first insulator 30 is a bottomed cylindrical member formed of alumina or the like that is excellent in mechanical properties and insulation at high temperatures. The first insulator 30 is formed with a hole 31 along the axis O that is open at the rear end of the first insulator 30 and closed at the front end. In the present embodiment, the hole 31 has a circular cross section. As for the hole part 31, the step part 32 which protrudes to an inner side of radial direction is formed in the front end side. The inner diameter of the hole portion 31 on the front end side with respect to the step portion 32 is set smaller than the inner diameter of the hole portion 31 on the rear end side with respect to the step portion 32. The stepped portion 32 is inclined so that the inner diameter gradually decreases toward the distal end side.

  The first insulator 30 includes a cylindrical body portion 33 extending in the axis O direction, an annular projecting portion 34 projecting 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 distal end side of the trunk portion 33. The outer diameter of the leg part 36 is set smaller than the outer diameter of the trunk | drum 33, and the outer diameter of the latching | locking part 35 is reduced in diameter toward the front 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 formed of a metal material such as a mild steel plate that is softer than the metal material constituting the metal shell 20.

  A pair of ring members 56 and a talc or the like sandwiched between the ring members 56 between the body 33 on the rear end side of the projecting portion 34 of the first insulator 30 and the tool engaging portion 22 of the metal shell 20. Filler 57 is disposed. When the crimping portion 21 of the metal shell 20 is crimped radially inward toward the first insulator 30, the first insulator 30 is connected to the shelf 27 of the metal shell 20 via the ring member 56 and the filler 57. Is pressed toward. 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 distal end side of the locking portion 35 and the distal end side of the first portion 37. A second portion 38. The first portion 37 and the second portion 38 have the same outer diameter across the direction of the axis O. The outer diameter of the second part 38 is set smaller than the outer diameter of the first part 37. The body portion 25 of the metal shell 20 is disposed outside the first portion 37 in the radial direction, and the distal end side and the second portion 38 of the first portion 37 protrude from the distal end side of the metal shell 20 toward the distal end side. The first part 37 and the second part 38 on the tip side of the boundary 11 between the locking part 35 and the first part 37 exist outside the space sealed by the packing 39 (open space).

  The second insulator 40 is accommodated in the hole 31 (bottomed tube) 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 assembly 42 is disposed on the distal end 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, or the like that is excellent in insulation and heat resistance at high temperatures. The aggregate 42 is composed of one or more of these particles. The triaxial average diameter of the insulator 41 (particles) is about 0.1 to 5 mm.

  The assembly 42 has a gap 43 formed between the insulators 41 randomly arranged in the hole 31. The gap 43 forms a through-hole (through-hole) that is three-dimensionally continuous like a mesh 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 assembly 42 that faces the hole 31 constitutes a plurality of openings 44. The opening 44 is uniformly formed in the portion of the assembly 42 facing the hole 31.

  A conductive member 45 is disposed in the gap 43 of the assembly 42. The conductive member 45 is a conductive member. For example, a metal containing one or more of Pd, Au, Ag, Sn, Ni, etc., a low melting point metal containing In, Ga, or the like is used. A portion of the conductive member 45 disposed in the opening 44 constitutes a convex portion 46. As long as the conductive member 45 is electrically connected between the terminal 50 and the convex portion 46, the gap 43 may be densely filled, or a part of the gap 43 may be filled. .

  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 distal end side (lower side in FIG. 2) from 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 exists on the tip side of the tip 28 of the metal shell 20.

  The terminal 50 is formed in a rod shape from a conductive metal material (for example, nickel-based alloy or stainless steel). The tip 50 of the terminal 50 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 52 protruding outward in the radial direction with respect to the tip 51. Since the outer dimension of the flange portion 52 is larger than the inner diameter of the hole portion 31 on the distal end side than the step portion 32, when the flange portion 52 is brought into contact with the step portion 32, the depth of the distal end portion 51 embedded in the assembly 42 is increased. Is decided.

  In this Embodiment, the front-end | tip part 51 is formed in the cone shape, and the outer diameter of the front-end | tip part 51 is reducing as it goes to the rear end side of the axis line O direction. Since the front end portion 51 whose outer diameter is reduced is embedded in the rear end portion of the assembly 42, the front end portion 51 and the conductive member 45 can be 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.

  Returning to FIG. The terminal fitting 54 is a rod-like member to which a high voltage cable (not shown) is connected, and is formed of a conductive metal material (for example, low carbon steel). The distal end side of the terminal fitting 54 is disposed in the hole 31 of the first insulator 30. A conductive sealing material 53 is disposed between the terminal fitting 54 and the terminal 50. The terminal 50 and the terminal fitting 54 are electrically connected in the hole 31 by the sealing material 53.

As the sealing material 53, for example, a material obtained by firing a mixture of glass powder and conductive powder is used. Examples of the glass powder include 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, and 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 powder made of a semiconductive oxide, a metal, a non-metallic conductive material, and the like. An example of the semiconductive oxide is SnO ₂ . Examples of the metal include Zn, Sb, Sn, Ag, and Ni. Examples of the nonmetallic 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 by the following method, for example. 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 insulator 41 is densely filled in the hole 31.

  Next, the terminal 50 is inserted into the hole 31. After the first insulator 30 is transferred into the furnace, for example, the first insulator 30 is heated to a temperature at which the raw material powder of the conductive member 45 forms a liquid phase, the terminal 50 is connected to the terminal 50 until the flange portion 52 hits the step portion 32. Apply a load in the direction of axis O. As a result, the conductive member 45 is compressed and sintered, and the conductive member 45 is coupled to the second insulator 40 including the aggregate 42 of the insulators 41. The conductive member 45 forms a three-dimensional network-like conductive path.

  After the first insulator 30 is transferred to the outside of the furnace, the raw material powder of the sealing material 53 is put through the hole 31 and filled around the terminal 50. After pre-compressing the raw material powder of the sealing material 53 filled in the hole 31 using a compression rod (not shown), the first insulator 30 is transferred into the furnace, for example, the raw material powder of the sealing material 53 Heat to a temperature higher than the softening point. After the 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 compressed in the axial direction 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 the first insulator 30 is transferred to the outside of the furnace, the metal shell 20 is assembled 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 with 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 plurality of pulse voltages are applied between the terminal fitting 54 and the metal 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 mixture. .

  Since the convex portions 46 on which the electric field concentrates are distributed in the holes 31, the uneven distribution of plasma generated in the second portion 38 can be suppressed. As a result, plasma can be generated over a wide range of 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 the ignitability can be improved. Moreover, since plasma can be generated in a wide range, active species such as ozone and negative ions can be generated efficiently.

  The second insulator 40 is an aggregate 42 of a plurality of granular insulators 41 filled in the first insulator 30, and the conductive member 45 is disposed 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 facing the hole portion 31 of the first insulator 30 where the second insulator 40 is disposed, the convex portion 46 is formed on the surface of the first insulator 30, particularly the second portion 38. Plasma can be generated uniformly. As a result, the ignition probability can be increased compared to the case where plasma is unevenly distributed.

  A plurality of insulators 41 are filled in the bottomed cylinder of the first insulator 30 to form an aggregate 42, and the conductive member 45 is disposed in the gap 43 of the aggregate 42. The shape portion 46 contacts the hole portion 31. If there is a gap between the convex portion 46 and the hole portion 31, a discharge occurs between the convex portion 46 and the hole portion 31, and the potential of the second portion 38 decreases to reduce the amount of plasma generated. Although there is a point, since the convex portion 46 contacts the hole portion 31, this problem can be solved. Therefore, it is possible to prevent the potential of the second portion 38 from decreasing and to secure the amount of plasma generated.

  A plurality of insulators 41 are filled in the hole 31 of the first insulator 30, and an aggregate 42 depending on the shape of the hole 31 is formed. 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 portion 31, can be increased. For example, the cross section of the hole 31 can be made polygonal, or the inner dimension of the hole 31 can be increased toward the tip side, while the outer shape of the first insulator 30 can be made to a shape corresponding to the hole 31. . Thereby, since the surface area of the 1st insulator 30 can be enlarged without changing the volume of the 1st insulator 30, the production amount of plasma can be increased.

  The terminal 50 has a front end 51 embedded in the rear end of the assembly 42 and is electrically connected to the conductive member 45. Thereby, compared with the case where the front-end | tip part 51 of the terminal 50 is not embedded in the aggregate | assembly 42, the contact area of the front-end | tip part 51 and the electrically-conductive member 45 can be enlarged. 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 front end side of the front end 28 of the metal shell 20, a space closer to the front end side than the front end 28 of the main metal shell 20, that is, the center of the combustion chamber (not shown). Plasma can be generated. As a result, the ignitability can be improved.

  Next, a second embodiment will be described with reference to FIG. In 1st Embodiment, the case where the 2nd insulator 40 which consists of the aggregate | assembly 42 of the some granular insulator 41 was provided was demonstrated. On the other hand, in the second embodiment, a case where the second insulator 61 is composed of a porous body 62 having through-holes 63 will be described. In addition, about the part same as the part demonstrated in 1st Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | 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.

  The second insulator 61 of the spark plug 60 is a porous body 62 and is accommodated in the hole 31 (bottomed tube) of the first insulator 30. The porous body 62 is disposed on the distal end side of the step portion 32 in the hole portion 31. The porous body 62 is a rod-shaped member formed of alumina, magnesia, zirconia, mullite, cordierite, silicon nitride, or the like that is excellent in insulation 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-hole 63 is connected from the rear end to the front end of the porous body 62, and the opening 64 is uniformly formed on the side surface and the end surface (portion facing the hole portion 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 disposed in the through-hole 63 of the porous body 62. The conductive member 65 is made of conductive metal, low melting point metal, or the like. A portion of the conductive member 65 arranged in the opening 64 constitutes a convex portion 66. The convex portion 66 closes a part or the whole of the opening 64 and is uniformly disposed in the porous body 62. The porous body 62 has a recess 67 formed in a groove shape at the rear end.

  The terminal 70 is formed in a rod shape from a conductive metal material (for example, a nickel base alloy, stainless steel, or the like). As for the terminal 70, the engaging part 71 engaged with the recessed part 67 of the porous body 62 protrudes from the front-end | tip. In the terminal 70, the collar portion 72 that abuts on the step portion 32 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 the molten conductive member 65 (molten metal), and the conductive member is inserted into the through-holes 63 of the porous body 62. Add 65. After the porous body 62 is taken out from the molten metal and the conductive member 65 in the porous body 62 is cured, the porous body 62 is ground and processed to a size that can be inserted into the hole 31 of the first insulator 30.

  Next, after the porous body 62 is inserted 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 ensured by the sealing material 53, the metal 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 a porous body 62 in which through holes 63 having a plurality of openings 64 are formed, the number and size of the convex portions 66 are determined depending on the shape and size of the through holes 63. Can be controlled. Since the convex portions 66 where the electric field concentrates are arranged in a distributed manner, uneven distribution of plasma generated in the second portion 38 can be suppressed. 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 is engaged with a 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. . Accordingly, the second insulator 61 (porous body 62) can be prevented from rotating in the hole 31 due to vibration or the like.

  Since the convex part 66 is arrange | positioned in the opening part 64 whose biaxial average diameter is about 0.5-1 mm, and the convex part 66 is uniformly formed in the porous body 62, the 1st 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 compared to the case where plasma is unevenly distributed.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made 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. However, the present invention is not necessarily limited to this. For example, after the holes 31 of the first insulator 30 are filled with a plurality of insulators 41, the first insulator 30 is heated to fire the insulators 41, and the aggregate 42 of the insulators 41 in the holes 31. To fix. Next, the conductive member 45 can be disposed in the assembly 42 by injecting the molten conductive member 45 into the hole 31 and curing the conductive member 45 in the gap 43 of 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 thereto. Of course, it is possible to make the diameter of the portion disposed on the distal end side of the leg portion 36 larger than the diameter of the base 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 appropriately set. it can.

  In the second embodiment, the case where the three-dimensional mesh-like through-holes 63 are formed in the rod-like porous body 62 has been described. However, the present invention is not necessarily limited thereto. For example, a porous body in which a plurality of first holes intersecting the axis O and second holes parallel to the axis O are formed in a rod-like insulator can be given. Both ends of the first hole open on the side surface of the insulator, and the second hole opens at the rear end of the insulator and communicates with the first hole. Also in this case, the same effects as those of the second embodiment can be realized by disposing the conductive members in the first hole and the second hole.

  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. However, the present invention is not necessarily limited thereto. Of course, the cross-sectional shape of the hole 31 may be a polygonal shape such as a triangle or a quadrangle.

  In each of the above-described embodiments, when the leg portion 36 on the distal end side of the locking portion 35 of the first insulator 30 has a smaller diameter of the second portion 38 on the distal end side than the diameter of the first portion 37 at the root. However, the present invention is not necessarily limited to this. Of course, it is possible to make the diameter of the leg part 36 the same over the direction of the axis O. In addition, it is naturally possible to make the diameter of the portion of the leg portion 36 of the first insulator 30 that protrudes from the metal shell 20 to the front end side larger than the diameter of the portion of the leg portion 36 that exists inside the metal shell 20. It is.

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

DESCRIPTION OF SYMBOLS 10,60 Spark plug 20 Main metal fitting 27 Shelf part 28 Tip 30 First insulator 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 portion 50, 70 Terminal 51 Tip 62 Porous body 63 Through-hole
O axis

Claims (5)

A bottomed cylindrical first insulator having a locking portion extending from the front end side to the rear end side along the axis and projecting outward in the radial direction;
A spark plug comprising: a shelf that locks the locking portion of the first insulator from a tip side; and a cylindrical metal shell that holds the first insulator from an outer peripheral side,
A second insulator that is included in the first insulator and has a through hole having a plurality of openings;
A conductive member disposed in the through hole;
A terminal electrically connected to the conductive member and insulated from the metal shell,
The electrically conductive member is a spark plug including a convex portion disposed in an opening formed on a distal end side of the locking portion of the first insulator among the plurality of openings. The second insulator is an aggregate of a plurality of granular insulators filled in a 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 tip 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-holes 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 present on a front end side of a front end of the metal shell.

Images