Abstract: A spark plug for an internal-combustion engine comprises an attachment fitting 2, an insulator 3, a center electrode 4 and an earth electrode 5 . While fixed to the attachment fitting 2, the earth electrode 5 has a convex part 510 formed by projecting toward the center electrode 4 a part of the opposed surface 51, which faces the center electrode 4, of the earth electrode and a concave part 520 formed toward the opposed surface 51 from the earth electrode's back surface 52 which is the reverse side of the opposed surface 51 of the earth electrode 5 . The convex part 510 is disposed so that the extension of a shaft center of the convex part 510 may pass through the area in which the concave part 520 is formed. A relation of S1>=s is realized when an area of an opening of the concave part 520 is set to S1 and an average cross-section area of a cross section of the convex part 510 perpendicular to an axial direction of the spark plug is set to s.

Abstract: A protruding length L1 that is a distance between an inner circumference of a flow path through which fluid flows on an axis of a temperature sensor disposed in the flow path and the center of said temperature sensitive device is 50 mm or more. A protruding location that is a distance between an inner circumferential surface of the flow path and the center of said temperature sensitive device on a cross section extending perpendicular to the axis of said flow path through the center of said temperature sensitive device is defined as L1?. A flow path width that is a distance between intersections of the axis of the temperature sensor with the inner circumferential surface of said flow path when the temperature sensor is projected onto said cross section is defined as D1. A relation of L1?/D1 is specified as a function of the value of D1, thereby reducing heat transfer in an exhaust temperature sensor and enabling the temperature to be measured accurately.

Abstract: A temperature sensor including a temperature sensitive device which is disposed in a flow path through which fluid flows and whose electric characteristic changes as a function of temperature of the fluid in the flow path, signal lines connected at top end sides thereof to said temperature sensitive device through electrode wires and at base end sides thereof to lead wires for connection with an external circuit, a sheath member retaining the signal lines therein, and a holding member which holds an outer circumferential surface of said sheath member directly or indirectly through another member. The resonance (primary) frequency at a top end of the temperature sensor against acceleration in a radius direction of the temperature sensor is 480 Hz or less, thereby reducing the transmission of vibration to the top end of the temperature sensor to avoid the breakage of the temperature sensitive device and the disconnection of the electrode wires 502102 even when the temperature sensor resonates.

Abstract: The temperature sensor 1 is equipped with a temperature sensitive device 2 to be disposed inside an exhaust pipe of an internal combustion engine, signal lines 31 connected at a top end side to the temperature sensitive device 2 and at a rear end side to leads for connection with an external circuit, an inner member 18 having a sheath pin 3 in which the signal lines 31 are disposed, and an outer member 13 disposed to cover at least a portion of an outer periphery of the inner member 18. The outer member 13 includes a fixed portion (rib 6) to be fixed to an upper wall of the exhaust pipe, a retainer portion 132 retaining the inner member 18, and an extending portion 131 formed closer to a top end side than the retainer portion 132.

Abstract: A total amount of NOX that flows into an NOX catalyst between the time that air-fuel ratio control ends and the time that the air-fuel ratio control starts the next time, is obtained. A total stored amount, which is the sum of an oxygen stored amount and an stored amount in the NOX catalyst before the air-fuel ratio control started, is calculated based on the amount of reducing agent that has flowed into the NOX catalyst during the air-fuel ratio control. The oxygen stored amount is calculated by extrapolating a relationship between the total amount of NOX and the total stored amount. The relationship is established beforehand by executing the air-fuel ratio control with at least two levels.

Abstract: A spark plug for an internal combustion engine is disclosed having a metal shell having an outer periphery formed with a mounting thread, a porcelain insulator fixedly secured to the metal shell on a central axis thereof, a center electrode retained within the porcelain insulator along a central axis thereof with a distal end located outside the porcelain insulator, and a ground electrode joined to the metal shell and having an end associated with the distal end of the center electrode to define therebetween a spark discharge gap. The ground electrode includes a facing surface intersecting the central axis of the center electrode and having a width equal to or less than 1.6 mm.

Abstract: A catalyst monitoring system diagnoses deterioration of an NOX catalyst (18) which is arranged in an exhaust passage (12) of an internal combustion engine (10). An NOX sensor (25) is arranged downstream of the NOX catalyst (18). An output integrated value of the NOX sensor (25) is calculated by integrating an output from the NOX sensor (25) during at least a period near the end of air-fuel ratio control. Deterioration of the NOX catalyst (18) is diagnosed based on the output integrated value of the NOX sensor (25).

Abstract: A storage reduction NOx catalyst is disposed in an exhaust passage for an internal combustion engine. A NOx sensor is disposed upstream of the NOx catalyst. An inflow NOx amount, which is the amount of NOx that has flown into the NOx catalyst, is calculated by accumulating the output of the NOx sensor. A total storage amount, which is the sum of the amounts of oxygen and NOx stored in the NOx catalyst, is calculated based on an output generated by an exhaust gas sensor disposed downstream of the NOx catalyst when rich spike is being executed. The deterioration of the NOx catalyst is determined based on the inflow NOx amount and the total storage amount.

Abstract: A small-sized spark plug is provided which ensures the stability in the location of production of sparks between center and ground electrodes. The center and ground electrodes have joined thereon cylindrical members such as noble metal chips which are opposed to each other through a spark gap. The cylindrical members are so oriented to have longitudinal center lines extend parallel in misalignment with each other. This orientation results in shorter and longer intervals between end surfaces of the cylindrical members. The sparks are concentrated between portions of edges of cylindrical members located apart the shorter interval, thereby resulting in the stability in the location of production of the sparks.

Abstract: A spark plug according to the invention includes a metal shell, a hollow insulator, a center electrode, and a ground electrode. The insulator has a first end protruding into a combustion chamber of an engine and a second end opposite to the first end in the lengthwise direction of the insulator. The insulator increases in outer diameter from the edge of the inner surface thereof at the first end to a reference plane that is defined to extend perpendicular to the lengthwise direction of the insulator and away 0.1 mm from the edge of the inner surface of the insulator toward the second end of the same in the lengthwise direction. Further, a first volume V1, which is the volume of a portion of the insulator between the edge of the inner surface of the insulator and the reference plane, is in the range of 0.15 to 0.38 mm3.

Abstract: A spark plug having a length for an internal combustion engine is provided which is designed to keep the ignitability of a gaseous fuel high to decrease a rise in voltage required by the spark plug to discharge, thereby prolonging the service life of the spark plug. The spark plug includes noble metal chips joined to a ground electrode and a center electrode to define a spark gap therebetween. At least one of the noble metal chips has a length of 0.3 mm or more and includes a portion whose sectional area traversing a lengthwise direction of the spark plug is greater than an area of a top end surface, thereby ensuring a higher degree of ignitability of the fuel and minimizing the rate of the rise in the required voltage.

Abstract: A spark plug is provided which ensures the reliability of a weld between a noble metal chip and a ground electrode as well as higher durability and ignitability of fuel. The ground electrode is joined to a metal shell, after which the noble metal chip is laser-welded to the ground electrode. The laser welding is achieved by emitting laser beams around an interface between the noble metal chip and the ground electrode outside a given angular range within which the metal shell will be an obstruction to the traveling of the laser beams. Specifically, the laser beams are emitted without any optical interference with the metal shell. This permits the angle between the orientation of each of the laser beams and the surface of the ground electrode to be minimized regardless of the metal shell, thus ensuring a desired depth of the fused portions in the noble metal chip.

Abstract: A spark plug for an internal combustion engine is disclosed having a metal shell having an outer periphery formed with a mounting thread, a porcelain insulator fixedly secured to the metal shell on a central axis thereof, a center electrode retained within the porcelain insulator along a central axis thereof with a distal end located outside the porcelain insulator, and a ground electrode joined to the metal shell and having an end associated with the distal end of the center electrode to define therebetween a spark discharge gap. The ground electrode includes a facing surface intersecting the central axis of the center electrode and having a width equal to or less than 1.6 mm.

Abstract: A spark plug is provided which ensures the reliability of a weld between a noble metal chip and a ground electrode as well as higher durability and ignitability of fuel. The ground electrode is joined to a metal shell, after which the noble metal chip is laser-welded to the ground electrode. The laser welding is achieved by emitting laser beams around an interface between the noble metal chip and the ground electrode outside a given angular range within which the metal shell will be an obstruction to the traveling of the laser beams. Specifically, the laser beams are emitted without any optical interference with the metal shell. This permits the angle between the orientation of each of the laser beams and the surface of the ground electrode to be minimized regardless of the metal shell, thus ensuring a desired depth of the fused portions in the noble metal chip.

Abstract: A spark plug is provided which ensures the reliability of a weld between a noble metal chip and a ground electrode as well as higher durability and ignitability of fuel. The ground electrode is joined to a metal shell, after which the noble metal chip is laser-welded to the ground electrode. The laser welding is achieved by emitting laser beams around an interface between the noble metal chip and the ground electrode outside a given angular range within which the metal shell will be an obstruction to the traveling of the laser beams. Specifically, the laser beams are emitted without any optical interference with the metal shell. This permits the angle between the orientation of each of the laser beams and the surface of the ground electrode to be minimized regardless of the metal shell, thus ensuring a desired depth of the fused portions in the noble metal chip.

Abstract: A spark plug according to the present invention includes a metal shell, an insulator, a cylindrical center electrode, a first ground electrode, and a second ground electrode. The first ground electrode is aligned with the center electrode in the axial direction of the center electrode to form a first spark gap, across which normal sparks are discharged when the insulator is not fouled with carbon. The second ground electrode is aligned with the center electrode in the radial direction of the center electrode to form a second spark gap, across which side sparks are discharged when the insulator is fouled with carbon. The spark plug has an improved structure where dimensional parameters A, T, B, C, L, D, and E are specified to be in suitable ranges that are determined through experimental investigation. The improved structure ensures a high ignition capability and a long service life of the spark plug.

Abstract: A spark plug is composed of a main metal fitting having a cylindrical structure, an insulator disposed inside the cylindrical main metal fitting, a center electrode fitted in the insulator in a manner that a front end portion of the center electrode projects outward over one end of the insulator, and a grounding electrode mounted to the main metal fitting and having one end portion opposing to the front end portion of the center electrode through a discharge gap therebetween. The front end portion of the center electrode includes a conical portion having a tapered surface having a taper angle of less than 80°, and a columnar portion formed to a top end portion of the conical portion so as to have a diameter in a range of 0.4 mm to 0.8 mm.

Abstract: Carbon fouling adhered on an insulator tip of a spark plug of the present invention is burnt down by a leak current during an inductive discharge period, due to a promoted ionization before beginning a capacitive discharge, in such an arrangement of a central electrode that a border portion of a body and narrowed portion is positioned in an insulator. The carbon burning-down effect is further improved by a narrow projection provided with an earth electrode, due to increased inductive energy and extended inductive discharge time period. This is because an electric field in a discharge gap is raised, thereby decreasing a discharge voltage and suppressing an energy emitted from a coil during the capacitive discharge.

Abstract: A spark plug according to the invention includes a metal shell, a hollow insulator, a center electrode, and a ground electrode. The insulator has a first end protruding into a combustion chamber of an engine and a second end opposite to the first end in the lengthwise direction of the insulator. The insulator increases in outer diameter from the edge of the inner surface thereof at the first end to a reference plane that is defined to extend perpendicular to the lengthwise direction of the insulator and away 0.1 mm from the edge of the inner surface of the insulator toward the second end of the same in the lengthwise direction. Further, a first volume V1, which is the volume of a portion of the insulator between the edge of the inner surface of the insulator and the reference plane, is in the range of 0.15 to 0.38 mm3.

Abstract: A spark plug according to the present invention includes a metal shell, an insulator, a cylindrical center electrode, a first ground electrode, and a second ground electrode. The first ground electrode is aligned with the center electrode in the axial direction of the center electrode to form a first spark gap, across which normal sparks are discharged when the insulator is not fouled with carbon. The second ground electrode is aligned with the center electrode in the radial direction of the center electrode to form a second spark gap, across which side sparks are discharged when the insulator is fouled with carbon. The spark plug has an improved structure where dimensional parameters A, T, B, C, L, D, and E are specified to be in suitable ranges that are determined through experimental investigation. The improved structure ensures a high ignition capability and a long service life of the spark plug.