An ignition system includes: a step-up transformer having a primary side and a secondary side; an electric energy source which is able to be connected to the primary side; a spark gap, which is designed to carry a current transferred to the secondary side by the step-up transformer. The step-up transformer has a bypass for transferring electric energy from the electric energy source to the secondary side. The bypass is designed to support a decaying electrical signal in the secondary coil of the high-voltage generator as of a predefined time, or as of a predefined intensity of the current being reached.

A method for checking electrodes of a spark gap of an ignition system for a combustion chamber of an internal combustion engine with an externally provided ignition includes generating a spark at the spark gap in an operating state without ignition of an ignitable mixture in the combustion chamber; ascertaining a parameter or characteristic function representing the spark current, the spark voltage, and/or the spark duration; comparing the parameter or the characteristic function to a reference; adapting an energy for a voltage buildup for a further spark generation for the mixture ignition and/or for maintaining an ignition spark for the mixture ignition, in particular for a future ignition process, as a function of a difference between the parameter or the characteristic function and the reference.

An ignition apparatus for an internal combustion engine includes: a spark plug; a first ignition coil and a second ignition coil; a battery; a booster circuit that boosts a voltage supplied from the battery; a power transistor that conducts and interrupts a primary current flowing to a primary coil included in the first ignition coil; a MOSFET that applies and interrupts the voltage boosted by the booster circuit to a primary coil included in the second ignition coil; and an ECU that starts electric discharge by the spark plug by controlling the power transistor, and repeatedly applies and interrupts the voltage boosted by the booster circuit by the MOSFET so that the electric discharge that is started is maintained.

An ignition apparatus for an internal combustion engine includes: a spark plug; a first ignition coil and a second ignition coil; a battery; a booster circuit that boosts a voltage supplied from the battery; a power transistor that conducts and interrupts a primary current flowing to a primary coil included in the first ignition coil; a MOSFET that applies and interrupts the voltage boosted by the booster circuit to a primary coil included in the second ignition coil; and an ECU that starts electric discharge by the spark plug by controlling the power transistor, and repeatedly applies and interrupts the voltage boosted by the booster circuit by the MOSFET so that the electric discharge that is started is maintained.

Described is a method for controlling an internal combustion engine, wherein an ignition control device is prompted by control signals of an engine control device to activate an ignition device by means of which an ignition of a fuel-air mixture in a cylinder of the internal combustion engine is affected. It is provided according to this disclosure, that the engine control device communicates a target ignition angle or information about an operating condition of the internal combustion engine to the ignition control device, and the ignition control device sets an operating parameter of the ignition device in dependence on the target ignition angle or the information about the operating condition of the internal combustion engine.

An ignition device includes a spark plug, a measurement value detector, an electrical breakdown determiner, an AC voltage applying section, and a first changing section. The measurement value detector includes primary and secondary coils, and detects at least one measurement value among an ignition coil, a primary current, a primary voltage, a secondary current, and a secondary voltage. The electrical breakdown determiner determines whether a discharge has become an electrical breakdown state based on the measurement value. The AC voltage applying section applies an AC voltage of a first predetermined frequency that causes voltage resonance to the primary coil. The first changing section changes the frequency of the AC voltage to a second predetermined frequency that can maintain the electrical breakdown state and is lower in frequency than the first predetermined frequency when it is determined that the discharge has become the electrical breakdown state.

A plasma generating device that improves plasma generating efficiency can further accommodate changes in plasma generating state because of changes in conditions of surroundings and the like. The plasma generating device is provided with an electromagnetic wave radiating device, which has an electromagnetic wave generating device that oscillates electromagnetic waves and a radiating antenna that radiates electromagnetic waves oscillated by the electromagnetic wave generating device, and a control device that controls the electromagnetic wave radiating device. The electromagnetic wave radiating device is provided with a power detector that detects traveling wave power output by the electromagnetic wave generating device and reflected wave power reflected from the radiating antenna, and the control device automatically controls the oscillation pattern for the electromagnetic waves on the basis of the proportion of the value for the reflected wave power to the value for the traveling wave power detected by the power detector.

A plasma generating device that improves plasma generating efficiency can further accommodate changes in plasma generating state because of changes in conditions of surroundings and the like. The plasma generating device is provided with an electromagnetic wave radiating device, which has an electromagnetic wave generating device that oscillates electromagnetic waves and a radiating antenna that radiates electromagnetic waves oscillated by the electromagnetic wave generating device, and a control device that controls the electromagnetic wave radiating device. The electromagnetic wave radiating device is provided with a power detector that detects traveling wave power output by the electromagnetic wave generating device and reflected wave power reflected from the radiating antenna, and the control device automatically controls the oscillation pattern for the electromagnetic waves on the basis of the proportion of the value for the reflected wave power to the value for the traveling wave power detected by the power detector.

In a laser ignition device which is mounted in an internal combustion engine and at least includes a laser spark plug equipped with an optical window which protects an optical device from high temperature and high pressure generated in a combustion chamber and a prechamber cap equipped with a cylindrical prechamber, a prechamber throat portion that is a bottomed cylinder with a sectional area smaller than that of the prechamber, and a plurality of prechamber spray holes which communicate with a combustion chamber on a side of a closed end of the prechamber throat portion, the prechamber cap is arranged between the optical window and the combustion chamber. A converging point FP is located inside the prechamber to ignite an air-fuel mixture delivered into the prechamber, thereby jetting combustion flames from the prechamber into the combustion chamber to fire the internal combustion engine. The center axis AX.sub.F of the prechamber is oriented horizontally eccentrically from the center axis AX.sub.S of the prechamber throat portion.

In an ignition coil for an internal combustion engine, a resistor is disposed in a tower insertion hole of a high-voltage tower section. A coil spring is inserted in the tower insertion hole. An inner diameter of a proximal end side portion of the tower insertion hole is larger than an outer diameter of a maximum outer diameter portion of the resistor. An inner diameter of the distal end side portion of the tower insertion hole is larger than an outer diameter of a proximal end side portion of the coil spring, and is smaller than the outer diameter of the maximum outer diameter portion. In a state where the coil spring is pulled out from the tower insertion hole, the maximum outer diameter portion is restrained by the distal end side portion of the tower insertion hole, and a gap is formed between the resistor and a high-voltage cap.