Abstract: The present disclosure generally pertains to devices and methods for generating thrust in vehicles, for instance in space applications. A heaterless, insertless hollow cathode utilizes AC and pulsed DC electric fields to ionize the propellant gas and generate a plasma plume. The cathode uses an argon microplasma generated in a quartz tube with a tungsten filament and brass ion collector. Free electrons are then drawn from the plasma plume and supplied to a thruster engine.

Abstract: A prechamber spark plug. The spark plug includes a housing, a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and a combustion chamber of an internal combustion engine; the through holes each having a hole center line; the cap including a recess at a region pointed towards the housing, the recess abutting the housing at a combustion-chamber-side end of the housing; a distance from an exit point of a through hole lying on the hole center line, to a recess, being in a range of 2 mm to 7 mm; and a first angle between a center axis of the prechamber spark plug and the hole center line being in a range of 30° to 70°. An internal combustion engine including such a prechamber spark plug is also described.

Abstract: A spark plug having a firing pad with minimal silicon diffusion and limited silicon oxidation at grain boundaries that can cause undesirable vertical cracking. In one embodiment, the firing pad has a multilayer structure having a base layer and a firing layer, wherein the base layer is a non-precious metal based material having silicon, and wherein the firing layer is a precious metal based material having yttrium in an amount of 0.1 to 0.5 wt %, inclusive. After at least 190 hours of isothermal treatment of at least 1000° C., an extent of vertical cracking from the sparking surface does not exceed 50% of a thickness of the firing pad or the firing layer.

Abstract: A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an intermediate layer located between the electrode tip and the electrode base, where the intermediate layer has a coefficient of thermal expansion (CTE) that is between that of the electrode base and the electrode tip and includes a whole area connection. In some examples, the whole area connection is non-uniform in thickness so that it is thicker in one section than it is in another section.

Abstract: An electrode material for a spark plug includes 22-46 wt % iron (Fe), inclusive, 20-40 wt % nickel (Ni), inclusive, 13-42 wt % cobalt (Co), inclusive, and one or more additional elements selected from aluminum (Al), titanium (Ti), chromium (Cr), boron (B), and niobium (Nb), wherein the electrode material has a coefficient of thermal expansion (CTE) from room temperature to 200° C. that is less than or equal to 11.0×10?6/° C. In another example, the electrode material includes greater than or equal to 32 wt % iron (Fe), greater than or equal to 36 wt % nickel (Ni), and one or more additional elements selected from aluminum (Al), chromium (Cr), and cobalt (Co). In advantageous embodiments, the electrode material includes greater than or equal to 22 wt % cobalt (Co). Replacing nickel with a higher percentage of cobalt can help reduce the coefficient of thermal expansion (CTE) of the electrode material.

Abstract: A prechamber spark plug that includes an internal reservoir, a flow passage portion, and a prechamber and is designed to operate efficiently across a wide variety of operating conditions and ranges. The internal reservoir includes upper and lower internal reservoir sections, the prechamber includes upper and lower prechamber sections, and the flow passage portion fluidly connects the lower internal reservoir section and the upper prechamber section so that burnt air/fuel gases can be exchanged therebetween. A ground electrode assembly with a ground electrode ring may be positioned in the prechamber such that it separates the upper and lower prechamber sections, whereas a modular prechamber cap may be used to define the shape and size of the lower prechamber section. In one example, the flow passage portion has a total cross-sectional area (AFC) and the internal reservoir has a total volume (VRES), and the ratio AFC:VRES is greater than or equal to 0.015 (1/mm).

Abstract: A ground electrode for a spark plug includes a ground electrode body arranged to face a center electrode of the spark plug. The ground electrode includes a discharge portion mounted on the ground electrode body to face the center electrode with a spark gap between the discharge portion and the center electrode. The discharge portion is made of a platinum-based alloy of platinum, rhodium, and nickel. A first mass percent of the rhodium contained in the platinum-based alloy of the platinum, the rhodium, and the nickel is within a first range from 2 wt % to 20 wt % inclusive. A second mass percent of the nickel contained in the platinum-based alloy of the platinum, the rhodium, and the nickel being within a second range from 2.5 wt % to 12 wt % inclusive.

Abstract: A spark plug includes a plug cover provided at a tip end portion of a housing to cover an auxiliary combustion chamber where an electrical discharge gap is located. The plug cover has a curved surface portion. The curved surface portion includes an outer curved surface convexly curved outward. The curved surface portion has an inclined injection hole formed therein to allow communication between the auxiliary combustion chamber and an outside. The inclined injection hole is opened to be inclined, relative to a plug axial direction, outward in a plug radial direction toward a tip end side. In a cross section including a central axis of the inclined injection hole and along the plug axial direction, a tangent line of a portion of the outer curved surface that overlaps an extended line of the central axis of the inclined injection hole is orthogonal to the extended line.

Abstract: A spark plug includes a housing, a porcelain insulator, a center electrode, a ground electrode, and a prechamber-defining portion. The prechamber-defining portion has a prechamber formed therein. The prechamber-defining portion has a plurality of spray holes. At least one of the spray holes is an upstream spray hole which is arranged upstream of a plug center axis in a gas flow within a main combustion chamber and designed such that and an angle which an extension in an opening direction makes with an inner wall surface of the prechamber is selected to be larger than 90°. A spark gap is formed upstream of a plug center axis in the gas flow within the main combustion chamber.

Abstract: A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an electrode base that at least partially surrounds a heat dissipating core, an electrode tip that is formed on the electrode base and includes a precious metal-based material, and a thermal coupling zone that directly thermally couples the electrode tip to the heat dissipating core. In some examples, the electrode tip is formed on an electrode base that has been cut or severed to expose a portion of the heat dissipating core, such that the electrode tip is formed directly on the heat dissipating core using additive manufacturing.

Abstract: A spark plug having a center electrode that includes a columnar noble metal tip at one end thereof, and a ground electrode that forms a spark gap between the ground electrode and a circular discharge surface of the tip. In the tip, a mass % of Pt is largest and a content percentage of Ni is more than or equal to 0 mass % and less than or equal to 40 mass %. In each of both a cross-section of the tip parallel to the discharge surface and a cross-section of the tip perpendicular to the discharge surface, particles each having an aspect ratio of more than or equal to 1 and less than or equal to 10 occupy more than or equal to 70% of observed particles in an area extending from an outline of the cross-section by a distance of 10% of a diameter of the discharge surface.

Abstract: The present disclosure relates to electrodes for biosensors. An electrode is made from a stack including (A) a layer made from ruthenium metal, a ruthenium-based alloy, nickel metal, or a nickel-based alloy; and (B) a layer made from a conductive metal or conductive metal alloy or carbon. The resulting electrode stack has physical and electrical property advantages when compared with existing pure metal electrodes.

Abstract: In a spark plug, a noble metal tip includes an Ir-alloy material and has a circular-columnar shape that has a predetermined outer diameter and is formed by the Ir-alloy material being stretched. The spark plug generates discharge between the noble metal tip and a ground electrode that is arranged to oppose an outer peripheral surface of the noble metal tip. The Ir-alloy material includes crystal grains of an Ir alloy having an average aspect ratio that is adjusted to be equal to or greater than 1.3 and equal to or less than 4.8. The average aspect ratio is an average value of aspect ratios of the crystal grains each being a value obtained by a length of the respective crystal grains in an axial direction of the noble metal tip being divided by a length of the respective crystal grains in a direction perpendicular to the axial direction.

Abstract: A spark plug has a central electrode and a ground electrode. The central electrode has an electrode base material part and a noble metal chip of a cylindrical shape and is welded on the electrode base material part. A spark discharge is generated between the noble metal chip of the central electrode and the ground electrode when supplying a predetermined voltage to the spark plug. An intermediate region is formed on an overall surface between the electrode base material part and the noble metal chip. The intermediate region has a primary measurement part and a secondary measurement part. Components of the noble metal chip in the primary measurement area have a first average ratio of not less than 40 wt %, and components of the noble metal chip in the secondary measurement area have a second average ratio of not more than 80 wt %.

Abstract: A method for manufacturing a spark plug. The method includes: furnishing an insulator; introducing into the insulator a material mixture that is configured to constitute a resistor paste, the material mixture containing ZrO2 and SiO2; heating the insulator and the material mixture present therein to a temperature T of at least 870° C., so that ZrO2 and SiO2 in the material mixture react at least partly to ZrSiO4.

Abstract: An electrode material includes a composite including a core wire that is composed of a nickel base material containing 96% by mass or more of Ni and a covering that covers an outer peripheral surface of the core wire and that does not cover but exposes an end face of the core wire. The covering is composed of a nickel alloy containing 10% by mass or more and 30% by mass or less of Cr and 0.1% by mass or more and 6% by mass or less of Al. The composite has a specific resistance of less than 50 ??·cm.

Abstract: A spark plug electrode includes an electrode base body made of a first material and an ignition element made of a second material and forming an ignition surface for a spark plug. The electrode base body and the ignition element are integrally joined to each other via a welding seam. A mixing rate for the first or second materials is less than 15 weight percent in a half of the welding seam adjacent to the ignition element. A method for manufacturing a spark plug electrode includes: providing an electrode base body and an ignition element; carrying out a welding process joining the electrode base body and the ignition element while forming a welding seam, where a welding beam guided over the surface of the spark plug electrode by tilting a reflection element, thereby producing a welding seam at a joining point between the electrode base body and the ignition element.

Abstract: A prechamber sparkplug includes a housing having a nozzle with a prechamber formed therein, and each of a first set and a second set of electrode prongs within the prechamber. The second set of electrode prongs downwardly depend from attachment points to the housing, and form, together with the first set of electrode prongs, spark gaps within the prechamber. Each of the anode-cathode pairs formed by the sets of electrode prongs is spaced radially inward a clearance distance from the prechamber wall to position the spark gaps in a flow of swirled gases. The flow of swirled gases displaces a flame kernel formed at the spark gaps to inhibit quenching.

Abstract: A spark plug includes: a center electrode; a ground electrode that is provided such that a gap for spark discharge is formed between the center electrode and the ground electrode; and a plug cover covering the center electrode and the ground electrode from a front side to form an auxiliary chamber, the plug cover being provided with a through hole, wherein 60% or more of the auxiliary chamber is present in a sphere. The sphere t has a center at a midpoint of a line segment connecting the center electrode and the ground electrode at a shortest distance on an axial line of the center electrode and is in contact with a point located closest from the center on an inner open end of the through hole is imagined.

Abstract: The present invention provides a method of manufacturing a spark plug which is capable of securing a bonding strength at the middle of a chip while suppressing an occurrence of scattering. The method of manufacturing the spark plug having a ground electrode to which a bonding surface of a chip is welded, has a machining process of machining the ground electrode such that an area located inside an edge of a welding-planned part where the chip is welded on the ground electrode and including a center of the welding-planned part is rougher than a section except the area of the welding-planned part, and a bonding process of bonding the chip to the welding-planned part of the ground electrode after undergoing the machining process by resistance welding.

Abstract: A spark plug includes a center electrode held inside an insulator, a ground electrode that is provided on a housing holding the insulator and faces the center electrode, and a composite chip formed on at least one of the electrodes. In the composite chip, a core having a mount integral with an electrode base material is formed from a Ni alloy material, and a surface layer having a discharge portion covering a protrusion end surface of the core and a side surface coating covering a side surface is formed from a Pt alloy material. The coating thickness S of the side surface coating in the radial direction, the outer diameter D1 of the discharge portion, and the coating length L1 of the side surface coating in the axial direction satisfy: S?D1/20+L1/10?0.005 mm.

Abstract: A spark plug includes a housing, an isolator arranged in the housing, and a ground electrode arranged on a front surface of the housing on a combustion chamber side. The spark plug further includes a central electrode, a terminal stud, and a resistance element all of which are arranged in the isolator. The resistance element is spatially arranged between the central electrode and the terminal stud and connects the central electrode to the terminal stud. The ground electrode forms a spark gap together with the central electrode. The resistance element contains a resistance material that contains conductive particles and non-conductive particles. At least 80% of the non-conductive particles have a maximum diameter of 20 ?m.

Abstract: Disclosed is a spark plug in which a first electrode has a tip joined to an electrode base through a fusion zone. In a cross section of the first electrode taken along a center axis, an interface of the fusion zone and a tip includes a first region, a second region and a base point present on at least one side of the cross section. The base point is a point connection of the first and second regions and is located farthest away from the imaginary straight line in the direction parallel to the center axis. The base point is positioned so as to satisfy a condition of 0.1?X/W?0.4 where W is a length of the interface in a direction perpendicular to the center axis; and X is a distance between the base point and the center axis.

Abstract: A spark plug that can suppress pre-ignition of a combustible air-fuel mixture that has flowed into the sub-chamber. The spark plug includes a ground electrode that joins to a metal shell and forms a spark gap; and a cap member that covers a center electrode and the ground electrode and forms a sub-chamber. A first fused portion that joins the metal shell and the cap member is located on the front-end side relative to the spark gap. At least a part of a first facing portion at which the metal shell and the cap member face each other is located on the sub-chamber side relative to the first fused portion. The first fused portion is not formed in an inner peripheral surface of the metal shell and an inner peripheral surface of the cap member.

Abstract: A spark plug having excellent ignitability including a rod-shaped center electrode; a ground electrode that includes a facing portion facing a front end portion of the center electrode and forms a discharge gap between the facing portion and the front end portion of the center electrode; an insulator; a metal shell; and a cover portion that covers, from a front end side of the spark plug, the front end portion of the center electrode and the facing portion of the ground electrode to form a pre-chamber and includes injection holes that are through holes.

Abstract: A spark plug having a shell with a ground electrode recess. A ground electrode having an insertion end, a firing end, and a round cross-sectional profile toward the insertion end is inserted into the ground electrode recess of the shell. An attachment portion surrounds at least a portion of the ground electrode and includes a solidified bonding material at a connection interface between the ground electrode and the shell. In some implementations, the ground electrode can have a copper core that extends further into the shell, past the distal end of the insulator. In some embodiments, the ground electrode has a sheath surrounding the copper core that has aluminum and a high weight percentage of nickel.

Abstract: In a spark plug for an internal combustion engine, a discharge gap is formed between a central electrode and a ground electrode in an axial direction of the spark plug. An insulator of a cylindrical shape has an axial hole and an insulator front end part. The axial hole is formed in the insulator, into which the central electrode is arranged and supported. The insulator front end part projects further toward a front side of the insulator in the axial direction of the spark plug than a location of an opening part formed at a front end side of the axial hole. The discharge gasp is formed in an auxiliary combustion chamber. The outer peripheral side of the auxiliary combustion chamber is covered with the insulator front end part.

Abstract: A spark plug including a ground electrode including a base material, a tip having a discharge surface, and a melt portion interposed over an entire area between the tip and the base material and joining the tip to the base material; and a center electrode with a spark gap formed between the center electrode and the discharge surface. The tip has, in an inner area surrounded by an outer peripheral portion of the tip, a thin portion in which a distance between the discharge surface and the melt portion is shorter than a distance between the discharge surface and the melt portion in the outer peripheral portion. The thin portion extends from a part of the outer peripheral portion to a part other than the part of the outer peripheral portion.

Abstract: In a spark plug for an internal combustion engine, an insulator is held inside a housing such that a proximal end thereof projects in an axial direction. A center electrode is held inside the insulator such that a distal end thereof projects. A terminal fitting is connected to the proximal end of the insulator and provided such that electricity is conducted between the center electrode and the terminal fitting. A ground electrode forms a spark discharge gap between the distal end of the center electrode and the ground electrode. A first gap is formed between the proximal end of the insulator and the terminal fitting, a second gap is formed between a proximal end of the housing and the insulator, and at least one of the first gap and the second gap is filled with a filler.

Abstract: A spark plug having a metal shell and an insulator, wherein a stepped portion that includes a rear-end-side facing surface that retains an insulator either directly or via another member is provided at an inner periphery of a metal shell. The stepped portion includes a first convex portion that includes the rear-end-side facing surface, a second convex portion that is disposed on a front end side of the first convex portion and that is adjacent to the first convex portion, and a connection portion that connects the first convex portion and the second convex portion to each other.

Abstract: The spark plug includes an insulator, a metal shell, and a buffering member. The buffering member is filled in a space that is enclosed by an inner peripheral surface of the metal shell and an outer peripheral surface of the insulator. 3 mm2?L×T is satisfied in a case where: a length in a direction of an axial line of a filled portion filled with the buffering member is defined as a filling length L; a thickness, of a screw portion of the metal shell, that is half a difference left after subtraction of the inner diameter of the metal shell from the pitch diameter of the screw portion is defined as an effective thickness; and a minimum value of the effective thickness of a portion, of the screw portion, present rearward of an inner diameter reduction portion of the metal shell is defined as a minimum thickness T.

Abstract: A firing tip for a corona igniter is provided. The firing tip includes a base formed of metal, such as nickel, and rivets formed of precious metal, such as iridium. The base includes indentations, and the rivets are disposed in the indentations of the base. The rivet has a melting point and/or wear resistance greater than the base. Typically, the indentations of the base include a concave surface and the rivets have a cylindrical shape matching the shape of the indentations. The rivets can be sharpened to a point. The rivets can include a first piece formed of precious metal and a second piece formed of nickel or nickel alloy, wherein an end of the first piece is welded to an end of the second piece, and the second piece is welded to the base. Alternatively, the rivets can be formed entirely of the precious metal.

Abstract: A spark plug includes: an insulator with an axial hole; a center electrode held in a front end side of the axial hole; a cylindrical metal shell disposed around the insulator and having a seal part brought into contact with an outer circumferential surface of the insulator; a ground electrode arranged to form a gap with the center electrode; and a cap connected to a front end part of the metal shell to define therein an auxiliary combustion space in which the gap is formed, the cap having at least one through hole formed to provide communication between the auxiliary combustion space and the outside, wherein the condition (B/A)?0.25 is satisfied where A represents a volume of an imaginary space defined at a position frontward of the seal part; and B represents a volume of parts of the ground and center electrodes located in the imaginary space.

Abstract: A spark plug for an internal combustion engine includes a housing, an insulator, a center electrode, a ground electrode, and a plug cover. The housing has a cylindrical shape. The insulator is held on an inner side of the housing. The insulator has a cylindrical shape. The center electrode is held on an inner side of the insulator. The ground electrode forms a discharge gap with the center electrode. The plug cover, together with the housing, configures an auxiliary combustion chamber in which the discharge gap is arranged. The plug cover includes a spray hole that communicates between the inside and outside of the plug cover. The ground electrode is connected to a plurality of locations on an auxiliary-chamber inner wall surface that includes surfaces of the housing and the plug cover that are exposed to the auxiliary combustion chamber.

Abstract: A spark plug includes a ground electrode that is curved to oppose a tip end surface of a center electrode. A predetermined virtual plane that passes through a center axis of the spark plug along the curved ground electrode faces a flow direction of airflow. The ground electrode includes a main body including: an opposing surface on a first side facing the tip end surface of the center electrode; and a sloped surface on a second side opposite the first side. The main body satisfies 10 [°]?Dg?70 [°], 1.0 [mm]?Th, and 1.5 [mm]?Wd, where Dg is a slope angle of the sloped surface relative to the opposing surface, Th is a thickness of the main body in an insertion direction of the center electrode, and Wd is a width of the ground electrode in a direction perpendicular to the virtual plane.

Abstract: An ignition plug includes a main metal fitting; an earth electrode having one end fixed to the main metal fitting and including, in a part of the other end, an inclined portion inclined toward the center axis line of the main metal fitting; an earth electrode-side chip joined to the inclined portion; and a center electrode having one end exposed from the main metal fitting. The ignition plug includes: a pedestal which has an elliptic cylindrical shape, is disposed so as to have a minor axis directed toward the earth electrode-side chip, and has an end surface forming an inclined surface inclined along the minor axis with respect to the center axis line; and a center electrode-side chip laser-welded to the inclined surface. The earth electrode-side chip and the center electrode-side chip face each other.

Abstract: A spark plug electrode assembly and method of manufacturing a spark plug assembly having an inner and outer electrode component, one of which or both being formed using metal injection molding (MIM). Forming at least one of the inner or outer electrode components with MIM allows for the creation of a mechanical lock and a metallurgical bond at an interface between the components such that the components may be joined without a weld.

Abstract: A spark plug includes a tip extending in a first direction and an electrode base metal having an extending portion extending in the first direction and connected to the tip through a fusion zone. In a section taken along the first direction and containing a center axis of the tip, in a case where two ends of the interface between the extending portion and the fusion zone are located at the same position with respect to the first direction, the linear distance between the ends is denoted by A, or, in a case where one end is located forward of the other end, the distance from the one end to an intersection between a straight line passing the one end and extending perpendicularly to the center axis and the outline of the fusion zone is denoted by A. The interface length B satisfies a relational expression B/A?1.2.

Abstract: The spark plug includes: an insulator having an axial hole formed along an axial line; and a metal terminal provided on a rear side of the axial hole of the insulator. The metal terminal has, at a rear end portion thereof, a bottom surface facing rearward and a projection projecting rearward from an outer edge of the bottom surface, and a mark is provided to at least a part of the bottom surface. The Vickers hardness of the projection is 100 HV or higher. A rear end surface of the projection is positioned on a rear side with respect to a rear end of the mark. An area of the rear end surface is 3 mm2 or greater.

Abstract: In a spark plug, a discharge gap is formed between a ground electrode and a central electrode. The ground electrode has a rod-shaped part and an opposing part. The opposing part faces the central electrode, and has a flat surface part and a slope surface part. The slope surface part is formed on a part of the opposing part in an extending direction of the ground electrode, and formed on the opposing part and gradually separated from the central electrode along a width direction of the opposing part. The spark plug has a ratio V/W within a range of 0.5<V/W<2.0. V indicates a length of the opposing part measured in a gap formation direction in which the central electrode, the discharge gap and the opposing part are arranged in order. W indicates a length of the opposing part in the ground electrode width direction.

Abstract: An internal combustion engine includes a spark plug which protrudes into a combustion chamber. The spark plug has a central electrode and a ground electrode, and is configured such that a spark is generated between the central electrode and the ground electrode by electrical discharge. The spark plug has a vortex generator that separates an air flow near the ground electrode from the ground electrode and generates a vortex at a downstream side. The central electrode and the ground electrode are placed in a manner such that a spark or a flame deformed by an air flow flowing between the central electrode and the ground electrode enters the trailing vortex, or the spark penetrates through the inside of the trailing vortex.

Abstract: A spark plug includes: a cylindrical mounting bracket attachable to an internal combustion engine; a center electrode that is held by the mounting bracket in an insulated manner and has a first end portion exposed and extended from a first end portion of the mounting bracket; a ground electrode that has a first end side joined to the first end portion of the mounting bracket and has a surface of the second end side extended to be opposed to the first end portion of the center electrode; a convex portion that protrudes from a base material of the ground electrode on the surface of the ground electrode toward the center electrode, has a surface protruded outward, and has surfaces without corners; and a precious metal layer formed on the surface of the convex portion.

Abstract: A spark plug including a center electrode with a tip welded to a front end portion with a fused portion therebetween. The front end portion contains Ni, Cr, and at least one element selected from a group B consisting of Mn, Si, Al, Ti, rare earth elements, Hf, and Zr. Ni is present in the largest proportion, and Cr is present in the second largest proportion and in an amount of 12% by mass or more. The at least one element selected from the group B is present in a total amount of 0.1% by mass or more. The front end portion satisfies f/e?0.15 and m/e?0.015, where f is the Fe content, e is the sum of the Cr, Si, and Al contents, and m is the Mo content.

Abstract: A spark plug for an internal combustion engine is provided which has a center electrode and a ground electrode. The ground electrode includes an upright portion extending in a lengthwise direction of the spark plug and an extension bent from the upright portion in a radial direction of the spark plug. The extension has a slant surface which is shaped to be inclined away from the center electrode downstream in a flow of air-fuel mixture within a combustion chamber when the spark plug is mounted in the engine. This results in an increase in in distance by which a starting point on the ground electrode where a spark is created is moved on the slant surface, thereby increasing a length of time the spark is moved downstream and then blown out to increase the probability of successful ignition of the air-fuel mixture.

Abstract: A spark plug comprising: a first electrode including a tip containing 1r as a main material, and a base member to which the tip is joined; and a second electrode opposed to the tip with a spark gap therebetween. The number of crystal grains appearing in a range of 0.25 mm2 on an arbitrary cross-section of the tip in a first direction connecting the tip and the second electrode within the spark gap, is not less than 20. When a length of each of the crystal grains in the first direction is denoted by Y, and a length of each of the crystal grains in a second direction perpendicular to the first direction is denoted by X, 5 ?m?X?100 ?m and Y/X?1.5 are satisfied.

Abstract: Provided is a spark plug capable of ensuring fouling resistance with a simple configuration. An insulator includes a step portion formed on an outer circumferential surface thereof. A center electrode is arranged in an axial hole of the insulator. A cylindrical metal shell having a shelf portion formed on an inner circumferential surface thereof is arranged radially outside the insulator. The insulator further includes a front end portion located frontward of the step portion. An outer circumferential surface of the front end portion has an arithmetic average roughness of 0.5 ?m or smaller in a circumferential direction. A recess is formed with a depth of 3 to 20 ?m in at least part of an end surface and the outer circumferential surface of the front end portion so as to extend from the front toward the rear.

Abstract: A ceramic porous body has an alumina porous body made up by binding aggregate alumina particles to each other, the aggregate alumina particles being bound to each other by a compound including gadolinium silicate, lanthanum silicate or yttrium silicate synthesized from a silicate mineral and at least one rare-earth oxide selected from Gd2O3, La2O3, and Y2O3, and an inorganic porous film formed on the alumina porous body.

Abstract: Disclosed is a spark plug having a ground electrode in which a weld zone is formed a tip and electrode base. The weld zone has: a back region exposed at an opposite surface of the electrode base; a joint region at which the tip is joined; and a connection region connects the joint region and the back region without being exposed at side surfaces of the electrode base. In a cross section of the ground electrode taken through the side surfaces of the electrode base along a plane passing through the centers of the top and bottom surfaces of the tip, a value of a width of the top surface of the tip being divided by a width of the facing surface of the electrode base is greater than 0.3, and a maximum width of the connection region is larger than a width of the back region.

Abstract: Disclosed is a production method of a spark plug in which a ground electrode has an electrode base and a tip welded to a surface of the electrode base via a weld metal. The production method includes an image capture step, an image analysis step and an inspection step. The image capture step is to capture image data about the surface of the electrode base to which the tip has been welded. The image analysis step is to perform analysis of the image data, thereby detecting an edge of the electrode base and an edge of the weld metal, determining a center point of a contour of the weld metal and then detecting an edge of the tip in a specific area of the image data. The inspection step is to inspect a welding position of the tip based on the detected edges of the electrode base and the tip.

Abstract: When one of a center chip and a ground chip of a spark plug is defined as a first chip and another one is defined as a second chip, a discharge starting ridge line, which is a straight ridge line that forms a boundary between two surfaces having different normal line directions, is formed in a portion closest to the second chip in the first chips, and a distance from the discharge starting ridge line to the second chip is configured to be equal at a portion where the first chip and the second chip are opposed to each other.