Abstract: Disclosed is a spark plug capable of suppressing high-frequency noise by improving the material of an electrical connection part between a center electrode and a metal terminal within an axial hole of an insulator. A spark plug has an electrical connection part arranged in an axial hole of an insulator to establish electrical connection between a center electrode and a metal terminal. The electrical connection part includes a conductor having a first crystal phase formed of a Fe-containing oxide and a second crystal phase formed of a conductive metal oxide of perovskite crystal structure.

Abstract: A spark plug having a resistor disposed within a through hole of an insulator and between a center electrode and a metal terminal so as to be spaced apart from the center electrode in a direction of an axial line; and a conductive glass seal layer provided between the resistor and the center electrode and electrically connecting the resistor and the center electrode to each other, the conductive glass seal layer has a diameter of 3.9 mm or less, and a joined surface of the conductive glass seal layer and the resistor has a convex shape toward the center electrode side. A length ? from a rear end to a front end of the joined surface and a maximum length ? of the conductive glass seal layer in the direction of the axial line meets a relation of ?/??0.4.

Abstract: A spark plug including an insulator containing not less than 92 mass % and not greater than 96 mass % of Al component in terms of oxide, wherein the insulator is formed from an alumina sintered body comprising alumina crystal and a grain boundary phase present between crystal grains of the alumina crystal. Assuming that mass contents of an Si component, an Mg component, a Ba component, and a Ca component in terms of oxide are represented by MSiO2, MMgO, MBaO, and MCaO, respectively, and a sum of MSiO2, MMgO, MBaO, and MCaO is represented by Mt, the grain boundary phase contains these components so as to satisfy conditions (1) to (4) as follows: (1) 0.17?MSiO2/Mt?0.47; (2) 0.005?MMgO/Mt?0.07; (3) 0.29?MBaO/Mt?0.77; (4) 0.03?MCaO/Mt?0.19.

Abstract: A resistor element of a spark plug containing ZrO2, wherein a target region is defined by a rectangular region where the size in the direction perpendicular to an axial line is 1800 ?m and the size in the direction of the axial line is 2400 ?m. In the case where the target region is divided into a plurality of square regions having lengths of 200 ?m on a side, a transverse line-shaped region is defined by a region in a line shape that is constituted of nine square regions arranged in the direction perpendicular to the axial line. A first type region is defined by the square region where a proportion of an area of ZrO2 is 25% or more, and a second type region is defined by the square region where a proportion of an area of ZrO2 is less than 25%.

Abstract: A spark plug including an insulator containing not less than 92 mass % and not greater than 96 mass % of Al component in terms of oxide, wherein the insulator is formed from an alumina sintered body comprising alumina crystal and a grain boundary phase present between crystal grains of the alumina crystal. Assuming that mass contents of an Si component, an Mg component, a Ba component, and a Ca component in terms of oxide are represented by MSiO2, MMgO, MBaO, and MCaO, respectively, and a sum of MSiO2, MMgO, MBaO, and MCaO is represented by Mt, the grain boundary phase contains these components so as to satisfy conditions (1) to (4) as follows: (1) 0.17?MSiO2/Mt?0.47; (2) 0.005?MMgO/Mt?0.07; (3) 0.29?MBaO/Mt?0.77; (4) 0.03?MCaO/Mt?0.19.

Abstract: A spark plug includes an insulator made of an alumina sintered body containing Al2O3 as a principal component and additional components including; an Si component, a Ba component, an Mg component, a Ca component, an Sr component, and a rare earth element component. When the additional components are expressed as oxides including RSiO2, RBaO, RMgO, RCaO, RSrO, and RRE2O3, contents (mass %) of the sub-component satisfy expressions (1) to (6) as follows: (1) 1.0?RSiO2?5.0; (2) 0.5?RBaO?5.0; (3) 0?RMgO?0.18; (4) 0?RMgO/RBaO?0.36; (5) 0.3?(RMgO+RCaO+RSiO)?1.8; and (6) 0?RRE2O3?0.1.

Abstract: A spark plug includes an insulator, a center electrode, a metallic shell, and a ground electrode. The insulator contains not less than 90.0 mass % and not greater than 98.1 mass % of Al2O3 with respect to a total mass of elements, as reduced to oxides, contained in the insulator, and has a porosity not greater than 5%. Assuming that a porosity of the insulator after a heat treatment is B, a difference (B?A) of the porosities before and after the heat treatment is not greater than 3.5%. In the heat treatment, the insulator is placed in a furnace, and a temperature in the furnace is increased from a room temperature to 1400° C. at a temperature increase rate of 7° C./min and is held at 1400° C. for 30 minutes, and thereafter, the temperature is decreased from 1400° C. to 400° C. at a temperature decrease rate of 10° C. or less per 5 minutes and is decreased to the room temperature.

Abstract: A connection portion connecting a center electrode and a terminal metal fixture together in a through hole of the insulator includes a resistor and a magnetic substance structure including a magnetic substance and a conductor and being disposed on a leading end side or a rear end side of the resistor while being positioned away from the resistor. The connection portion further includes a first conductive sealing portion, a second conductive sealing portion and a third conductive sealing portion. The first conductive sealing portion is disposed on a leading end side of a first member and is in contact therewith. The second conductive sealing portion is disposed between the first member and a second member and is in contact with the first and second members. The third conductive sealing portion is disposed on a rear end side of the second member and is in contact therewith.

Abstract: A connection portion connecting a center electrode and a terminal metal fixture together in a through hole of the insulator includes a resistor and a magnetic substance structure including a magnetic substance and a conductor. The connection portion further includes a first conductive sealing portion, a second conductive sealing portion and a third conductive sealing portion. The first conductive sealing portion is disposed on a leading end side of a first member and is in contact therewith. The second conductive sealing portion is disposed between the first member and a second member and is in contact with the first member and the second member. The third conductive sealing portion is disposed on a rear end side of the second member and is in contact therewith.

Abstract: A spark plug with an insulator that includes: a first portion having a first inner diameter with a front end of a trunk portion of a metal terminal disposed therein; a second portion having a second inner diameter larger than the first inner diameter, and including a portion 1 mm or more forward of a rear end of the insulator; and a third portion disposed between the first portion and the second portion and having a third inner diameter larger than the first inner diameter and smaller than the second inner diameter. The trunk portion of the metal terminal includes: a front trunk portion and a rear trunk portion with a front end of the rear trunk portion positioned forward of a rear end of the third portion of the insulator, the rear trunk portion having an outer diameter larger than the outer diameter of the front trunk portion.

Abstract: A spark plug with an insulator that includes: a first portion having a first inner diameter with a front end of a trunk portion of a metal terminal disposed therein; a second portion having a second inner diameter larger than the first inner diameter, and including a portion 1 mm or more forward of a rear end of the insulator; and a third portion disposed between the first portion and the second portion and having a third inner diameter larger than the first inner diameter and smaller than the second inner diameter. The trunk portion of the metal terminal includes: a front trunk portion and a rear trunk portion with a front end of the rear trunk portion positioned forward of a rear end of the third portion of the insulator, the rear trunk portion having an outer diameter larger than the outer diameter of the front trunk portion.

Abstract: A connection portion connecting a center electrode and a terminal metal fixture together in a through hole of the insulator includes a resistor and a magnetic substance structure including a magnetic substance and a conductor and being disposed on a leading end side or a rear end side of the resistor while being positioned away from the resistor. The connection portion further includes a first conductive sealing portion, a second conductive sealing portion and a third conductive sealing portion. The first conductive sealing portion is disposed on a leading end side of a first member and is in contact therewith. The second conductive sealing portion is disposed between the first member and a second member and is in contact with the first and second members. The third conductive sealing portion is disposed on a rear end side of the second member and is in contact therewith.

Abstract: A connection portion connecting a center electrode and a terminal metal fixture together in a through hole of the insulator includes a resistor and a magnetic substance structure including a magnetic substance and a conductor The connection portion further includes a first conductive sealing portion, a second conductive sealing portion and a third conductive sealing portion. The first conductive sealing portion is disposed on a leading end side of a first member and is in contact therewith. The second conductive sealing portion is disposed between the first member and a second member and is in contact with the first member and the second member. The third conductive sealing portion is disposed on a rear end side of the second member and is in contact therewith.

Abstract: A spark plug includes an insulator having an axial hole, a center electrode inserted into a forward portion of the axial hole, a terminal electrode inserted into a rear portion of the axial hole, and an interelectrode insert which contains glass and electrically conductive carbon and is disposed in the axial hole between the center electrode and the terminal electrode. The interelectrode insert has a resistance of 1.0 k? to 3.0 k?, and the interelectrode insert has a carbon content of 1.5% by mass to 4.0% by mass at a forward portion located forward of a center point between the rear end of the center electrode and the forward end of the terminal electrode. Furthermore, the forward portion is lower in resistance than a rear portion of the interelectrode insert located rearward of the center point.

Abstract: Provided is a terminal fitting that includes a first terminal fitting having a first electric wire holding section for holding an electric wire, a first attachment section to be attached to an attachment target object, and a protruding section provided on the first attachment section, and a second terminal fitting piece having a second electric wire holding section for holding an electric wire, a second attachment section to be attached to the attachment target object, and a hole section provided in the second attachment section, the first attachment section and the second attachment section being overlapped with each other in a state that the protruding section is inserted into the hole section.

Abstract: The present invention provides a connection terminal (1) which includes terminal members (2, 3) having cylindrical wire connecting parts (21, 31) to which conductors of electric wires are inserted and the conductors are electrically connected, and flat plate shaped attaching parts (22, 32) continuous to the wire connecting parts.

Abstract: A spark plug having a resistor disposed within a through hole of an insulator and between a center electrode and a metal terminal so as to be spaced apart from the center electrode in a direction of an axial line; and a conductive glass seal layer provided between the resistor and the center electrode and electrically connecting the resistor and the center electrode to each other, the conductive glass seal layer has a diameter of 3.9 mm or less, and a joined surface of the conductive glass seal layer and the resistor has a convex shape toward the center electrode side. A length ? from a rear end to a front end of the joined surface and a maximum length ? of the conductive glass seal layer in the direction of the axial line meets a relation of ?/??0.4.

Abstract: A spark plug includes an insulator having an axial hole, a center electrode inserted into a forward portion of the axial hole, a terminal electrode inserted into a rear portion of the axial hole, and an interelectrode insert which contains glass and electrically conductive carbon and is disposed in the axial hole between the center electrode and the terminal electrode. The interelectrode insert has a resistance of 1.0 k? to 3.0 k?, and the interelectrode insert has a carbon content of 1.5% by mass to 4.0% by mass at a forward portion located forward of a center point between the rear end of the center electrode and the forward end of the terminal electrode. Furthermore, the forward portion is lower in resistance than a rear portion of the interelectrode insert located rearward of the center point.

Abstract: A resistor element of a spark plug containing ZrO2, wherein a target region is defined by a rectangular region where the size in the direction perpendicular to an axial line is 1800 ?m and the size in the direction of the axial line is 2400 ?m. In the case where the target region is divided into a plurality of square regions having lengths of 200 ?m on a side, a transverse line-shaped region is defined by a region in a line shape that is constituted of nine square regions arranged in the direction perpendicular to the axial line. A first type region is defined by the square region where a proportion of an area of ZrO2 is 25% or more, and a second type region is defined by the square region where a proportion of an area of ZrO2 is less than 25%.

Abstract: A spark plug having an insulator with a through hole formed therein in a direction of an axis, a center electrode disposed in a front side of the through hole, a metal terminal disposed in a rear side of the through hole, an electrical connection part arranged in the through hole to establish electrical connection between the center electrode and the metal terminal and a metal shell holding therein the insulator. The electrical connection part has a conductor including a conductive material and at least one kind of Fe-containing oxide material. The Fe-containing oxide material contains at least FeO. The conductor satisfies a relationship of 0.06?S1/(S1+S2)?0.46 where, in a cross section taken along the axis, S1 is an area occupied by the conductive material and S2 is an area occupied by the Fe-containing oxide material.