Abstract: A spark plug includes a center electrode extending along an axial line, a ground electrode, and a noble metal tip. A center axis of the noble metal tip is displaced from a center axis of the ground electrode toward a base-end side in the axial line. The ground electrode includes an outer layer and an inner layer, and a distal end of the inner layer is closer to the axial line than a base end of the ground electrode. An overlap area between the inner layer and the noble metal tip occupies a ratio of 25% or more in a projective plane defined by projecting, along the center axis, a plane of the ground electrode viewed from a distal-end face on a cross section of the ground electrode in which a maximum cross-sectional area of the inner layer is achieved, among cross sections orthogonal to the center axis.

Abstract: A spark plug includes a center electrode extending in an axial direction; an insulator formed externally of the outer circumference of the center electrode; a metallic shell formed externally of the outer circumference of the insulator and having a ledge which supports the insulator; and a ground electrode joined to the metallic shell. The insulator has a support portion which faces the ledge. A “frontward direction” is defined as the direction parallel to the axial direction toward a spark portion formed between the center electrode and the ground electrode. The insulator has a diameter reduction portion whose outside diameter reduces along the frontward direction from the support portion, and a diameter increase portion whose outside diameter increases along the frontward direction from the front end of the diameter reduction portion. This restrains the generation of leak current while maintaining heat resistance of the spark plug.

Abstract: A corner of a distal end of a ground-electrode-side noble metal tip of a spark plug is taken as a first corner; a corner of a leading end of a center-electrode-side noble metal tip is taken as a second corner; a corner formed at a starting point where a diameter of the center electrode is reduced is taken as a third corner; a corner of the ground electrode is taken as a fourth corner; a corner closest to the third corner of the corners on the distal end of the ground-electrode-side noble metal tip is taken as a fifth corner; a length of a virtual flying spark path defined between the first corner and the second corner is taken as L1; a length of a virtual flying spark path defined between the third corner and the fourth corner is taken as L2; a length of a virtual flying spark path defined between the third corner and the fifth corner is taken as L3; and L2 or L3, whichever is shorter, is taken as L4, the spark plug fulfills a relational expression of L4/L1?1.1.

Abstract: An ignition apparatus which facilitates improvement in energy efficiency as well as materializing an excellent ignitability through effectively utilizing energy used for inductive discharge as a blowout power. The ignition apparatus is used for an ignition plug that includes a center electrode, a ground electrode and a cavity surrounding at least a portion of a clearance formed between the two electrodes to thereby form a discharge space. The ignition apparatus includes a voltage application portion which applies voltage to the clearance and a power supply portion which supplies electric power to the clearance. In addition, a capacitance portion for storing a capacitance is provided, in parallel with the ignition plug, in a voltage application path of the voltage application portion.

Abstract: A plasma jet ignition plug exhibiting high plasma generation efficiency while restraining occurrence of preignition. P1 represents the position of a rear end of a region of a metallic shell ledge, the region being in contact with an insulator. P2 represents the position of a rear end of a region of the insulator ledge, the region being in contact with the center electrode. Front end surfaces of the metallic shell, the insulator, and center electrode, an imaginary plane S1 which is perpendicular to the axis and contains position P1, and an imaginary plane perpendicular to the axis and contains position P2 are disposed in this order from front side to rear side along the axis. The axial distance A from the front end surface of the insulator to imaginary plane S1 and axial distance B from the imaginary plane S1 to imaginary plane S2 satisfy 0.5×A?B.

Abstract: A plasma jet ignition plug including a wire-wound resistor for restraining the radiation of noise while allowing application of a sufficiently large current for generation of plasma to a spark discharge gap at the time of ignition. The wire-wound resistor having an inductance of 1 ?H to 100 ?H inclusive and a resistance of 1? or less, and is provided on at least one of a center electrode and a ground electrode. The wire-wound resistor restrains current which is generated by the influence of stray capacitance present in the plasma jet ignition plug, thereby reducing noise.

Abstract: A plasma jet spark plug capable of preventing a channeling progress and having excellent heat conduction. The plasma jet spark plug comprised of: a ceramic insulator having a small diameter portion which assumes a linear shape in an axial direction, and a center electrode has an outer diameter increasing in the order of a frontmost portion, a step portion, a front end portion and a body portion.

Abstract: A current of sufficient size to form plasma at ignition of a plasma jet ignition plug flows to a spark discharge gap while suppressing noise occurrence. There is provided an ignition apparatus of a plasma jet ignition plug, which includes a resistor R1, with one end connected to a diode D1 disposed between the plasma jet ignition plug 100 and a high-voltage generation circuit 210 and with the other end electrically connected to a center electrode 40 of the plasma jet ignition plug 100, and a capacitor C1, with one end connected to the center electrode 40 of the plasma jet ignition plug 100 and with the other end grounded.

Abstract: A plasma jet ignition plug including an insulating body having an axial hole therethrough. A center electrode is inserted into the axial hole. A cavity portion is defined by the insulating body and center electrode, with the leading end of the axial hole as an opening end. A decreasing diameter portion decreasing in diameter toward a leading end side is formed on the axial hole, the leading end of the decreasing diameter portion is positioned closer to the leading end side than the leading end face of the center electrode. The inside diameter of the leading end of the decreasing diameter portion is made smaller than the outside diameter of the leading end face of the center electrode.

Abstract: An ignition plug providing excellent ignition performance that can be maintained over a long period of time by restraining channeling. The ignition plug includes a ceramic insulator having an axial bore, a center electrode inserted into the axial bore, a metallic shell, and a ground electrode fixed to the metallic shell, and has a cavity defined by an inner circumferential surface of the axial bore and the forward end surface of the center electrode. The axial bore includes a first straight portion and a diameter-reducing portion. As viewed on a section which contains an axis (CL1) of the ignition plug, a relational expression ??10 is satisfied, where ? (°) is an acute angle formed by a straight line orthogonal to the axis (CL1) and the outline of the diameter-reducing portion.

Abstract: It is an object of the present invention to provide a spark plug that can be produced at low cost and secure compatibility between ignition performance and durability. The spark plug according to the present invention includes a center electrode and a ground electrode having an inner surface facing the center electrode, characterized in that; the ground electrode has a protrusion and a hole; the protrusion protrudes from the inner surface by a protruding length A of 0.4 to 1 mm and has a first straight portion with a projected first straight portion area S1 of 1.5 to 3 mm2; the hole has an opening at an outer surface of the ground electrode, a second straight portion, a bottom portion and a transition portion; the opening is formed in such a manner that the ratio (S2/S1) of a projected opening area S2 of the opening to the projected first straight portion area S1 is not less than 1.2; and the transition portion is in the form of a taper portion.

Abstract: An overhead image-reading apparatus includes a one-dimensional image sensor having imaging elements arranged in parallel to each other and is configured to change an angle between an optical axis of a light source and a medium to be read during reading of the medium, and the apparatus includes a correcting unit that corrects distortion in a main-scanning direction in read image data of the medium read by the apparatus.

Abstract: A spark plug including: a rod-shaped center electrode; an insulator; a metal shell; a ground electrode joined to the metal shell and bent toward the center electrode; a noble metal tip joined to an end portion of the ground electrode and opposing a leading end portion of the center electrode via a gap; and a bulge portion. A part of the noble metal tip is embedded in the ground electrode, and another part of the noble metal tip protrudes from a distal end surface of the ground electrode. A relationship A?0.25 mm is satisfied where A (mm) is a protruding length of the noble metal tip from the distal end surface. The bulge portion covers a center part of a boundary between the noble metal tip and the end surface in a width direction.

Abstract: A spark plug (1) including a center electrode (5), an insulator (2), a metal shell (3), and a ground electrode (27). Spark discharge is provided substantially along a direction of an axis (CL1) in a spark discharge gap (33). The ground electrode includes a narrowed width portion (42) having a substantially uniform width smaller than an outer diameter of a tip end surface (5F) of the center electrode, and a widened width portion (41) having a width larger than the width of the narrowed width portion. When viewed from a tip end side, a base end of the narrowed width portion is offset from the tip end surface of the center electrode toward the root side of the ground electrode. The base end of the narrowed width portion is offset from a center of the spark discharge gap toward the tip end side of the spark plug.

Abstract: A plasma jet ignition plug including an insulating body having an axial hole therethrough. A center electrode is inserted into the axial hole. A cavity portion is defined by the insulating body and center electrode, with the leading end of the axial hole as an opening end. A decreasing diameter portion decreasing in diameter toward a leading end side is formed on the axial hole, the leading end of the decreasing diameter portion is positioned closer to the leading end side than the leading end face of the center electrode. The inside diameter of the leading end of the decreasing diameter portion is made smaller than the outside diameter of the leading end face of the center electrode.

Abstract: An ignition plug that maintains excellent ignition performance over a long period of time through effective prevention of channeling. The ignition plug includes an insulator having an axial bore, a center electrode inserted into the axial bore, a metallic shell disposed externally of the outer circumference of the insulator, and a ground electrode fixed to a front end portion of the metallic shell. A cavity is defined by the wall surface of the axial bore and the front end surface of the center electrode. The ground electrode includes a body whose distal end portion is disposed away from the front end of the insulator, and a protrusion protruding from the body.

Abstract: A spark plug having improved durability having a ground electrode comprised of a ground electrode base member and a noble metal tip. A center axis of the noble metal tip slants in relation to the center axis of the ground electrode base member at angle ? which satisfies a relation 2°???25°.

Abstract: A plasma jet spark plug for igniting an air-fuel mixture in a conventional combustion device such as an internal combustion engine.

Abstract: A plasma jet spark plug having increased capacitive discharge current, and thus improved plasma generation efficiency. The plasma jet spark plug includes an insulating body having an axial hole, a center electrode, a metal shell, and a cavity portion formed by the inner peripheral surface of the insulating body and the leading end face of the center electrode. A conductive layer formed from a conductive material is provided on at least one portion of at least one of: (a) a surface on the insulating body outer peripheral surface opposed to the inner peripheral surface of the metal shell, the conductive layer electrically connected to a ground electrode; and (b) a surface on the insulating body inner peripheral surface opposed to the outer peripheral surface of the center electrode, the conductive layer electrically connected to the center electrode.

Abstract: A plasma jet ignition plug that reliably prevents current leakage with restraint on variation in the position of a ground electrode relative to an insulator and on overheat of the ground electrode, for stable generation of plasma. The plug includes an insulator having an axial bore extending in the direction of an axis CL1, a center electrode inserted in the axial bore, a metallic shell disposed externally of the outer circumference of the insulator, and a ground electrode fixed to the metallic shell, and has a cavity defined by the wall surface of the axial bore and the front end surface of the center electrode. Supports intervene between the insulator and the ground electrode. A space formed radially outward of the supports and a space formed radially inward of the support communicate with each other.