Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: A ground electrode of an igniter plug has inlets for supplying cooling fluid therethrough to a first space formed between an insulator and the ground electrode, and first outlets located forward of the inlets and radially outward of the inner circumference of a ground electrode forward-end portion and adapted to discharge the cooling fluid therethrough. A second space communicating with the first space and having a second outlet for discharging the cooling fluid therethrough is formed between a forward end surface of the insulator and a surface of the ground electrode which faces the forward end surface.

Abstract: A spark plug includes a tip joined to a center electrode. The coefficient of linear thermal expansion of the center electrode is greater than that of the tip. The tip has a gap-forming portion having a maximum width of 1.2 mm or greater and forming a gap in cooperation with the ground electrode and a to-be-joined portion joined to the center electrode. At a position A which is shifted 0.1 mm from the forward end of the outer surface of the fusion portion toward the forward end side, the width of the to-be-joined portion measured on the cross section is smaller than the width of the gap-forming portion. The to-be-joined portion satisfies Dtw/Dw?1.1, where Dtw represents the width of the to-be-joined portion at the position A, and Dw represents the width of the fusion portion at the forward end of the outer surface thereof.

Abstract: A spark plug is provided with a ground electrode, a noble metal tip made of a Pt alloy, and a relieving layer tip made of a Pt alloy which has a linear expansion coefficient between that of the ground electrode and that of the noble metal tip.

Abstract: A technique of reducing occurrence of multiple discharge in a spark plug provided. The spark plug has a main ground electrode and three auxiliary ground electrodes. The position at which first auxiliary ground electrode is joined to a metallic shell is located opposite the position at which main ground electrode is joined to the metallic shell, with respect to a center electrode. The positions at which second and third auxiliary ground electrodes are joined to the metallic shell are located opposite to each other with respect to the center electrode. When the width of first auxiliary ground electrode is represented by W, the shortest distance between second auxiliary ground electrode and third auxiliary ground electrode is represented by T, and a distance which is a component of the shortest distance T in a direction orthogonal to first auxiliary ground electrode is represented by Tp, a relation W?Tp is satisfied.

Abstract: A spark plug comprises an insulator having a axial hole penetrating in a direction of an axis, a central electrode provided on the front end side of the axial hole, a tubular metal shell that holds the insulator, and a ground electrode including a surface layer and a core material that is surrounded by the surface layer and has a larger thermal conductivity than that of the surface layer. The metal shell of the spark plug has a protruding portion in which at least a part of the metal shell protrudes toward the front end side in the direction of the axis. The ground electrode has an end surface at one end portion thereof joined to the inside of the protruding portion and the other end portion thereof facing the central electrode.

Abstract: An electrode-attached insulator having an insulator provided with an axial hole extending in the direction of an axis and a center electrode which is disposed on a distal-end side of the axial hole and has a front end portion that is exposed from a front end of the insulator. The electrode-attached insulator includes a locking member having a collar portion which is locked on a step portion. The center electrode and the locking member are joined together in the axial hole.

Abstract: A spark plug including: a center electrode; an insulator; a metal shell; a ground electrode; and an electrode chip. The electrode chip is joined to the ground electrode in a state in which the electrode chip is engaged in a recess portion formed in the ground electrode. The electrode chip is formed by previously welding a chip body portion containing a noble metal and a chip holding portion containing Ni before the electrode chip is joined to the ground electrode. A first molten bond is formed by welding the chip body portion and the chip holding portion. The first molten bond is placed in the recess portion so as not to be exposed to an outside environment in a state in which the electrode chip is engaged in the recess portion and joined to the ground electrode.

Abstract: A ground electrode of an igniter plug has inlets for supplying cooling fluid therethrough to a first space formed between an insulator and the ground electrode, and first outlets located forward of the inlets and radially outward of the inner circumference of a ground electrode forward-end portion and adapted to discharge the cooling fluid therethrough. A second space communicating with the first space and having a second outlet for discharging the cooling fluid therethrough is formed between a forward end surface of the insulator and a surface of the ground electrode which faces the forward end surface.

Abstract: An ignition plug having a metallic shell with a through hole extending therethrough in an axial direction, an insulator fitted into the through hole of the metallic shell and having an axial hole extending in the axial direction, and a center electrode fitted into the axial hole of the insulator. The ignition plug further includes a cap member which covers a front end opening of the metallic shell, provided on a front end side thereof where the center electrode is disposed, to thereby form an ignition chamber at the front end portion of the metallic shell, and a ground electrode disposed within the ignition chamber and facing a circumferential surface of the center electrode directly or indirectly.

Abstract: An ignition plug having a center electrode, an insulator holding the center electrode in an axial bore, and a ground electrode disposed in contact with a front end portion of the insulator and having a through-hole whose center coincides with the axis of the center electrode. A semiconductor layer in contact with the center electrode and the ground electrode is formed in a portion of the surface of the insulator.

Abstract: A spark plug is provided with a ground electrode, a noble metal tip made of a Pt alloy, and a relieving layer tip made of a Pt alloy which has a linear expansion coefficient between that of the ground electrode and that of the noble metal tip.

Abstract: A spark plug including a ground electrode which has an excellent heat sinking ability. The ground electrode includes a core material therein. Heat received from a combustion chamber during a drive of an internal-combustion engine can be conducted to the core material. More effective heat sinking ability can be achieved because of the core material.

Abstract: An ignition plug having a center electrode, an insulator holding the center electrode in an axial bore, and a ground electrode disposed in contact with a front end portion of the insulator and having a through-hole whose center coincides with the axis of the center electrode. A semiconductor layer in contact with the center electrode and the ground electrode is formed in a portion of the surface of the insulator.

Abstract: A spark plug including: a center electrode; an insulator; a metal shell; a ground electrode; and an electrode chip. The electrode chip is joined to the ground electrode in a state in which the electrode chip is engaged in a recess portion formed in the ground electrode. The electrode chip is formed by previously welding a chip body portion containing a noble metal and a chip holding portion containing Ni before the electrode chip is joined to the ground electrode. A first molten bond is formed by welding the chip body portion and the chip holding portion. The first molten bond is placed in the recess portion so as not to be exposed to an outside environment in a state in which the electrode chip is engaged in the recess portion and joined to the ground electrode.

Abstract: A spark plug including a ground electrode which has an excellent heat sinking ability. The ground electrode includes a core material therein. Heat received from a combustion chamber during a drive of an internal-combustion engine can be conducted to the core material. More effective heat sinking ability can be achieved because of the core material.

Abstract: An ignition device for an internal combustion engine comprising: an ignition coil comprising a primary winding and a secondary winding, the ignition coil generating an igniting high voltage in the secondary winding by turning off a primary current flowing in the primary winding; an ignition switching unit; a spark plug connected to an igniting high voltage generation end of the secondary winding; a reverse current prevention unit series-connected on a current-conduction path of the discharge current connecting the secondary winding to the spark plug; a voltage application unit connected to an other end of the secondary winding opposite to the igniting high voltage generation end; an ionic current detection unit; and an ionic current detection switching unit series-connected on a current-conduction path of the ionic current-detecting voltage connecting the voltage application unit to the other end.

Abstract: A misfiring detection apparatus including a comparison unit 22 and a time counting unit 24 which accumulates periods of time during which the ion current flowing between the center electrode 10a and the ground electrode 10b of a spark plug 10 exceeds a predetermined current value; and an ECU 26 which judges that misfiring has occurred when a total of the accumulated periods is not greater than a predetermined value. The ion current is thus determined as a cumulative value of ion current generation periods. Therefore, even when the ion current contains a discharge noise component, the discharge noise component having a short duration accounts for only a small portion of the cumulative value, so that the influence of the discharge noise component on misfiring detection can be reduced. As a result, misfiring detection can be performed with improved accuracy.

Abstract: An ignition device for an internal combustion engine comprising: an ignition coil comprising a primary winding and a secondary winding, the ignition coil generating an igniting high voltage in the secondary winding by turning off a primary current flowing in the primary winding; an ignition switching unit; a spark plug connected to an igniting high voltage generation end of the secondary winding; a reverse current prevention unit series-connected on a current-conduction path of the discharge current connecting the secondary winding to the spark plug; a voltage application unit connected to an other end of the secondary winding opposite to the igniting high voltage generation end; an ionic current detection unit; and an ionic current detection switching unit series-connected on a current-conduction path of the ionic current-detecting voltage connecting the voltage application unit to the other end.