Abstract: An ignition apparatus for an internal combustion engine, which is controlled by a control unit, includes a connector, an ignition coil assembly, an igniter and a capacitor. The connector is electrically connected with the control unit, and includes an input terminal, which is electrically connected with the control unit to receive an ignition signal outputted by the control unit. The connector also includes a ground terminal, which is connected with a ground. The igniter includes a switching device that switches a coil current supplied to the ignition coil assembly based on the ignition signal received from the control unit through the connector. The igniter also includes a Zener diode that serves as a protection element of the switching device. The capacitor is provided in parallel with the Zener diode between the input terminal and the ground terminal to form a parallel circuit.

Abstract: An ignition apparatus for an internal combustion engine, which is controlled by a control unit, includes a connector, an ignition coil assembly, an igniter and a capacitor. The connector is electrically connected with the control unit, and includes an input terminal, which is electrically connected with the control unit to receive an ignition signal outputted by the control unit. The connector also includes a ground terminal, which is connected with a ground. The igniter includes a switching device that switches a coil current supplied to the ignition coil assembly based on the ignition signal received from the control unit through the connector. The igniter also includes a Zener diode that serves as a protection element of the switching device. The capacitor is provided in parallel with the Zener diode between the input terminal and the ground terminal to form a parallel circuit.

Abstract: An ignition coil for an internal combustion engine includes a core-coil assembly that includes an endless outer ring core, a straight core intersecting the interior of the outer ring core to form a closed magnetic circuit in cooperation with the outer ring core, and a primary coil and a secondary coil concentrically fitted within the outer ring core and supported by the straight core piercing through the primary coil; and an insulation casing that has a bottom at which a high-voltage terminal connected electrically to an ignition plug is retained, supports and accommodates the core-coil assembly therein so that the core-coil assembly is orthogonal to the axis of the plug hole of the engine, and contains a solid layer of insulating resin cast-molded for fixing the core-coil assembly thereto. The secondary coil is ball-shaped and has coil turns that are largest in number at the equator of the ball and gradually decrease toward the opposite poles of the ball.

Abstract: To facilitate mounting the ignition plug socket into a socket mounting hole formed in an engine body and additionally to prevent vibration of the mounted plug socket, a plurality of projections such as axially extending straight ribs or circumferentially extending annular ribs are formed on the outer circumferential surfaces of the plug socket body of the ignition plug socket.