In a spark plug, a cylindrical metal shell is provided whose inner wall has a ledge portion on which an insulator rests through its seat portion. The insulator has an axial bore in which a center electrode is placed whose front end has a heat-resistant metal tip. A ground electrode is provided to form a spark gap with the noble metal tip of the center electrode. The insulator forms an insulator nose which measures less than 15 mm in length. The heat-resistant metal tip measures less than 0.8 mm in diameter. A space between an outer surface of the center electrode and an inner wall of a front open end of the axial bore is defined to be more than 0.1 mm in width.

Spark plug for an internal combustion engine

A power-saving type of ignition apparatus is provided with a spark plug of which electrodes (30, 40) are regulated in their shapes to lower an amount of energy required for its ignition. To face to a tip (31) of a center electrode (30) extending from a mounting bracket (10), a cylindrical protrusion (41) is built on one surface (43) of an earth electrode (40). The protrusion extends toward the center electrode to form a discharge gap (50) between the protrusion and the tip of the center electrode. Both of the tip of the center electrode and the protrusion of the earth electrode are 2.3 [mm] or less in each diameter (D1, D2), thus an amount of energy required for ignition being limited to 17 [mJ] or less.

Spark plug and ignition apparatus using same

Provided is an igniter for internal combustion engines that improves combustion efficiency and suppresses power consumption by detecting an ion current, recognizing the combustion state of an internal combustion engine, and performing overlapping discharge in accordance with this combustion state.
An igniter for internal combustion engines comprises a ion current resistance (150) that is connected to both ends of a high voltage diode (50) and does not create a short circuit for an output point of a voltage doubler circuit (20), and that has a resistance that does not interfere with detection operations of an ion current detection circuit (100), wherein the ion current detection circuit (100), after the overlapping discharge ends, detects an ion current by applying, to a spark plug (60) via a secondary coil (32) and the ion current resistance (150), a voltage for ion current detection having a polarity opposite to the voltage output from the secondary coil (32) and the voltage doubler circuit (20).

Igniter for internal combustion engines

PURPOSE:To reduce quenching action of a flame nucleus so as to improve ignitability by providing a secondary voltage control circuit, which places duration time of an induction component of a spark discharge and spark energy in a specific condition, while specifying a diameter in a point end part of a center electrode of a spark plug. CONSTITUTION:In this spark plug 1, a firing part, which is a point end of a center electrode 11, is made of platinum alloy or iridium to provide 0.3 to 0.6mm diameter. An ignition circuit 2 is constituted of an ignition coil 3, distributor 4, switching circuit 5 and a secondary voltage circuit 6. Here, the secondary voltage control circuit 6 is constituted such that duration time of an induction component of a spark discharge is 1.0msec or less and 0.2msec or more with spark energy 20millijoule or less and 5.0millijoule or more, when an engine speed is 1000rpm or less, to reduce the spark energy while shortening the duration time according to increasing the engine speed further with generated voltage by the ignition coil maintainable.

Oshima Takafumi

Papers

Ignition device for internal combustion engine