An ignition coil unit is attached to an engine body. The engine body includes a cylinder head having a plug hole and a head cover that covers the cylinder head by including an opening hole facing the plug hole. The ignition coil unit includes a coil unit that generates a high voltage and a cylindrical coupling unit that connects the coil unit with a spark plug. The coupling unit includes a flexible sealing section fitting to an outer peripheral surface of the high tension tower and a harder joint fitting to a tip of the sealing section. The sealing section includes an adhesion portion to tightly contact the head cover and a neck portion at least between the adhesion portion and the joint in a Z-axis direction. The neck portion is formed by partially constricting an outer peripheral surface of the sealing section radially inside.

An ignition device for generating a spark discharge at a spark plug based on a first voltage from a first supply and a second voltage from a second supply. The second voltage is higher than the first voltage. In the ignition device, a primary coil includes a center tap, a first terminal on a ground side of the center tap, and a second terminal on a first-supply side of the center tap, and a secondary coil is electromagnetically coupled to the primary coil and electrically connected to the spark plug. A first switch is configured to make or break an electrical connection between the first terminal and ground, a second switch is configured to make or break an electrical connection between the second supply and the center tap, and a third switch is configured to pass or interrupt a current from the second terminal to the first supply. A controller is configured to control an on/off state of each of the first to third switches.

Please substitute the new Abstract submitted herewith for the original Abstract: Energization abnormality of a switch element of an internal combustion engine ignition device is detected appropriately. To this end, in an internal combustion engine ignition device that includes an ignition coil and an ignition plug, the ignition coil includes a primary coil including a main primary coil and a sub primary coil and a secondary coil that generates secondary current in response to a voltage variation generated in the primary coil. The internal combustion engine ignition device includes a main switch element that performs energization/deenergization of the main primary coil in a first direction, a sub primary coil magnetic flux generation state switching unit capable of switching between a forward direction magnetic flux generation state in which energization of the sub primary coil in the first direction is performed and an opposite direction magnetic flux generation state in which energization of the sub primary coil in a second direction is performed, and an abnormality detection section that detects energization abnormality to the sub primary coil. The abnormality detection section is configured so as to detect energization abnormality on the basis of overlap between energization in the first direction and energization in the second direction of the sub primary coil.

Even when detecting the primary voltage of the primary coil side, without detecting the secondary voltage of the secondary coil side of high voltage, it is desired to provide a discharge state detecting apparatus of an internal combustion engine which can detect a spark discharge state with good accuracy, by reducing influences of the discharge current and the resistance component of the discharge path of the secondary coil side, which are generated in the primary voltage. A discharge state detecting apparatus of an internal combustion engine performs correction which reduces a signal component generated by the secondary current in the ignition coil from the primary voltage detected by the primary voltage detector, based on the detected secondary current, and outputs a primary voltage after correction; and determines a spark discharge state based on the primary voltage after correction.

A self-diagnosis method for an ignition coil includes receiving and confirming a current flag (C/F) signal through monitoring of primary current of an ignition coil; monitoring secondary current of the ignition coil upon receiving the C/F signal and confirming whether a fault flag (F/F) signal for determining whether misfire of the ignition coil occurs is input; and determining whether an abnormal signal of the ignition coil is generated based on the result of confirming the C/F signal and the F/F signal respectively.

A system for monitoring and cleaning a spark plug is disclosed. In one example, rim firing of a spark plug is detected according to characteristics of a voltage of a primary coil of an ignition coil. The system may institute spark plug cleaning after rim firing of a spark plug is detected.

An ignition device according to the present invention includes: an ignition plug, which includes a first electrode, a second electrode, and a dielectric body arranged between the electrodes; an AC power supply configured to generate an AC voltage to be applied between the electrodes; a thermal plasma detection portion configured to output a thermal plasma occurrence signal when thermal plasma has occurred between the electrodes; and an application time period determination portion configured to determine an application time period for the AC voltage during one cycle of the internal combustion engine in advance before the application, and when the thermal plasma occurrence signal is received while the AC voltage is being applied based on the application time period, change the application time period so as to shorten the application time period.

An ignition system for an engine is disclosed. The ignition system may have an igniter connected to selectively ignite a fuel mixture within the engine, at least one sensor configured to sense operation information of the engine and generate corresponding signals, and a controller in communication with the igniter and the at least one sensor. The controller may be configured to cause a first striking of the igniter to ignite the fuel mixture, make a determination that the fuel mixture has been ignited by the igniter based on the signals, and selectively cease striking of the igniter based on the determination.

An ignition apparatus includes a plasma device, a first circuit, a second circuit, and a control unit. The plasma device produces a plasma discharge in an air-fuel mixture before an arc discharge is produced. The first circuit causes an ignition plug to start the arc discharge. The second circuit energizes a primary coil in a direction opposite to the direction of the energization by the first circuit during the arc discharge, to maintain energization of the secondary coil in the same direction as the direction of the energization started by an operation of the first circuit, to cause continuation of the arc discharge. The control unit controls operations of the first circuit, the second circuit, and the plasma device.

A system for monitoring and cleaning a spark plug is disclosed. In one example, rim firing of a spark plug is detected according to characteristics of a voltage of a primary coil of an ignition coil. The system may institute spark plug cleaning after rim firing of a spark plug is detected.