Abstract: Provided is an ignition control device capable of suppressing wear of an ignition plug due to occurrence of a re-strike without adding a component.

Abstract: An ignition control system performs discharge generation control, in which a discharge spark is generated, once or a plurality of times during a single combustion cycle. The ignition control system successively calculates an approximate energy density based on a secondary current and a discharge path length. During a predetermined period after blocking of a primary current is performed during a single combustion cycle, the ignition control system calculates an integrated value by integrating the discharge path length at this time, based on the approximate energy density being greater than a predetermined value. The ignition control system performs the discharge generation control again based on the calculated integrated value being less than a first threshold.

Abstract: In at least some implementations, an ignition system for a combustion engine includes a controller, an ignition circuit, and a wire providing two-way communication between the ignition circuit and the controller. The ignition circuit may include a charge capacitor that is discharged to cause an ignition event. The ignition circuit may be an inductive discharge ignition circuit including a coil and may then also include a second wire that provides electrical power to the coil.

Abstract: A plasma generator is disclosed. In an embodiment a plasma generator includes a piezoelectric transformer subdivided into an input region and an output region in a longitudinal direction, wherein the piezoelectric transformer comprises an output-side end face facing away from the input region, wherein the plasma generator comprises a passive load arranged permanently in front of the output-side end face, and wherein the plasma generator is configured to generate non-thermal atmospheric-pressure plasma.

Abstract: An electronic ignition system for an internal combustion engine. The system includes an ignition coil provided with at least a primary winding and a secondary winding, a switch connected to the primary winding and drivable to be in an opened and/or closed position according to a value of a driving signal, a control unit associated to the switch and configured to drive the switch to be in the open position and/or closed position according to the value of the driving signal (G). The system may also include current detection means associated with the secondary winding, in which the control unit is associated with the detection means for receiving a signal representative of at least a current value in the secondary winding, and configured to control the switch according to said signal.

Abstract: An internal combustion engine ignition system includes: a primary coil provided with a center tap; a third switching element that interrupts and conducts a primary current flowing from a voltage application unit to the center tap; a first switching element connected to one end on a first winding side; a second switching element connected to the other end on a second winding side; an ignition control circuit that controls operation of each of the above switching elements, thereby performing discharge generation control that allows an ignition plug to generate a spark discharge, and thereby interrupting and conducting the primary current flowing to the second winding to perform discharge maintenance control that maintains the spark discharge generated in the ignition plug; and a current circulation path that circulates a current flowing from the second winding to the second switching element.

Abstract: A garden tool includes a gasoline engine and a power source, the gasoline engine including a fuel supply system and an ignition system. The garden tool may further include a control system with at least one sensor used for collecting a working condition signal of the gasoline engine and a controller used for receiving the working condition signal and controlling the fuel supply system and/or the ignition system according to the working condition signal received. The power source may provide a power supply for the fuel supply system, the ignition system, and the control system through the controller.

Abstract: An ignition system includes a controller which controls two stages—to provide current to a spark plug. The stages include a first transformer including a first primary winding and a first secondary winding and a second transformer including a second primary winding and a second secondary winding. A switch is electrically connected between a supply high side and the high side of the first primary winding. A second switch is electrically connected between the first primary winding and the power supply low side supply. A third switch is connected between the junction of the switch and high side end of the first inductor and a point between the low side of the second primary winding and low side supply. A fourth switch is located between the low side of the second primary winding and the point. A fifth switch is located between the point and low side supply.

Abstract: An ignition coil includes a first winding, a second winding, and a third winding. A first switch is electrically connected to the first winding. A battery is electrically connected to the first winding. A booster is electrically connected to the battery. A second switch is electrically connected to the third winding. A drive device drives the first switch and the second switch. The drive device turns the first switch from on-state to off-state to allow a secondary current to flow through the second winding, turns the second switch from off-state to on-state to supply an output of the booster to the third winding, and superimpose a second current to the second winding. When a third winding current becomes equal to or greater than a predetermined value, the booster controls such that power generated by the third winding current and an output voltage of the booster is restricted to constant power.

Abstract: An ignition control apparatus applied to an internal combustion engine including a spark plug includes an in-cylinder pressure acquisition section, a frequency signal transmitting section which transmits a frequency signal having a predetermined frequency to a switching element, and a weak discharge generating section which causes the frequency signal to be transmitted during an intake stroke and controls the frequency signal such that a weak discharge is generated at the spark plug a plurality of times. The weak discharge generating section controls the frequency signal so as to cause a duty ratio of the switching element to be changed in accordance with the in-cylinder pressure, such that the frequency of generating weak discharges during a time period in which the frequency signal is transmitted becomes higher than a predetermined frequency.

Abstract: An electronic ignition system for an internal combustion engine. The system includes an ignition coil provided with at least a primary winding and a secondary winding, a switch connected to the primary winding and drivable to be in an opened and/or closed position according to a value of a driving signal, a control unit associated to the switch and configured to drive the switch to be in the open position and/or closed position according to the value of the driving signal (G). The system may also include current detection means associated with the secondary winding, in which the control unit is associated with the detection means for receiving a signal representative of at least a current value in the secondary winding, and configured to control the switch according to said signal.

Abstract: An ignition control apparatus of the present embodiment controls operation of an ignition plug provided so as to ignite an air-fuel mixed gas.

Abstract: The systems and methods that warm-up a virtual machine are provided. An application byte code is generated from an application source code for an application that processes time-sensitive messages using a virtual machine. The virtual machine is configured to interpret the application byte code. A warm-up data is received by the virtual machine. The warm-up data is configured to emulate one or more time-sensitive messages processed by the virtual machine. From the warm-up data, the virtual machine generates application machine-readable code from the application byte code, and stores the application machine-readable code. After the virtual machine generates the application machine-readable code, a computing device that includes the virtual machine is placed in a real-world environment and begins to receive the time-sensitive messages. The virtual machine processes the time-sensitive messages using the generated application machine-readable code.

Abstract: In an ignition device, a second circuit energizes a primary coil from its negative side in a first direction to thereby maintain energization of a second coil in a second direction during spark discharge started by a first circuit. The maintained energization continuously supplies energy to a spark plug, thus performing a continuation of the spark discharge. The first direction is opposite to a direction of energization of the primary coil carried out by the first circuit, and the second direction is the same as a direction of energization of the second coil that has been started based on the first circuit. A humidity detection unit detects humidity of intake air into an engine. The control section controls the first circuit to advance start timing of the spark discharge generated by the first circuit in accordance with an increase in the humidity of the intake air.

Abstract: The ignition system has an electromagnetic wave oscillator which oscillates electromagnetic waves, a control device that controls the electromagnetic wave oscillator, a plasma generator which integrates a booster circuit containing a resonant circuit capacitive coupled with the electromagnetic wave oscillator, and a discharge electrode which discharges a high voltage generated by the booster circuit. The plasma generator includes a plurality of discharge electrodes arranged so as to be exposed within the combustion chamber of the internal combustion engine.

Abstract: An ignition device at least equipped with a DC power source, an ignition coil unit, a spark plug, an ignition switch, and an auxiliary power source, wherein the auxiliary power source is at least equipped with a discharge energy accumulating means, a discharge switch, and a discharge driver. The ignition device is further equipped with a secondary-current feedback controlling means comprising a secondary current detecting means for detecting a secondary current flowing during the ignition coil unit discharge period, and a secondary current feedback control circuit-for determining an upper limit and a lower limit for the secondary current from binary threshold values, and driving so as to open and close the discharge switch on the basis of the determination results. Furthermore, energy is introduced from the auxiliary power source without switching the polarity of the secondary current.

Abstract: An ignition plug wire for an internal combustion engine has an elongated conductor with a programmable capacitor module disposed in-line with the elongated conductor. The programmable capacitor module is configured to step up or convert the ignition voltage normally supplied by an ignition coil to a plasma voltage. An inventive ignition plug if configured such that the anode enclosed within the insulator includes or is replaced by a voltage converting module designed to convert the ignition voltage into a plasma voltage. The voltage converting module consists of a semiconductor circuit, a composite semiconductor material, or a capacitor.

Abstract: An ignition control device comprises: a first switching element having a power source side terminal connected to an other end side of a primary coil and a first ground side terminal connected to a ground side; a second switching element having a second ground side terminal connected to the other end side of the primary coil; a third switching element having a third power source side terminal connected to the second power source side terminal in the second switching element, and a third ground side terminal connected to the ground side; and an energy storage coil. The energy storage coil is an inductor interposed in an electric power line connecting a non-ground side output terminal in a DC power source and the third power source side terminal in the third switching element, and stores energy from the turning on of the third switching element.

Abstract: A display device including a display area. The display area having a plurality of pixel circuits, a peripheral area including a scanning circuit, a plurality of first scanning lines, a plurality of second scanning lines, and a plurality of third scanning lines. Each of the plurality of pixel circuits includes a write transistor, a drive transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a capacitor, and a light emitting element. Duration of a conductive state of the third switching transistor is variably controlled by changing a width of the input pulse and duration of a conductive state of the fourth switching transistor is variably controlled by changing the width of the input pulse.

Abstract: A method for actuating a spark plug, in which the spark plug is assigned a first ignition coil and second ignition coil.

Abstract: A control apparatus of an engine ignition spark plug includes a switch having a control terminal and an output terminal connected to an external transformer. The switch assumes a closed state for supplying energy to the transformer, and an open state for the transformer to supply energy to the spark plug. A measuring module measures a time duration where, in the open state, a voltage at the output terminal of the switch decreases from a first value to a second value. A detecting module detects an operating condition of the spark plug based on comparing the measured time duration to a time threshold, and to generate a detecting signal based on the comparing.

Abstract: An ignition apparatus which facilitates improvement in energy efficiency as well as materializing an excellent ignitability through effectively utilizing energy used for inductive discharge as a blowout power. The ignition apparatus is used for an ignition plug that includes a center electrode, a ground electrode and a cavity surrounding at least a portion of a clearance formed between the two electrodes to thereby form a discharge space. The ignition apparatus includes a voltage application portion which applies voltage to the clearance and a power supply portion which supplies electric power to the clearance. In addition, a capacitance portion for storing a capacitance is provided, in parallel with the ignition plug, in a voltage application path of the voltage application portion.

Abstract: The ignition device for the internal combustion engine includes: an ignition plug including a first electrode and a second electrode opposed to each other via a predetermined gap, for generating in the predetermined gap a spark discharge for igniting a combustible mixture in a combustion chamber of the internal combustion engine; an ignition coil including a primary coil and a secondary coil, for generating a high voltage in the secondary coil by supplying or stopping a primary current flowing through the primary coil, and then applying the generated high voltage to the first electrode; and a control unit for driving the ignition coil for a plurality of times within a single ignition process, and changing a primary voltage for driving the ignition coil within the single ignition process.

Abstract: A method of improving the combustion of a spark-ignition internal combustion engine. Such engines have at least one cylinder, each cylinder having a compression chamber and operated such that an air-fuel mixture introduced into the combustion chamber is ignited to cause a combustion event. An antenna is placed within the combustion chamber, and is used to apply electromagnetic energy to the combustion.

Abstract: An internal combustion engine 100 includes a cylinder 102 that defines a combustion chamber 196 causing a premixed gas to be combusted, a piston 120 that defines the combustion chamber 196 together with the cylinder 102, and reciprocates in the cylinder 102, and an active species generator 150 that generates active species. The internal combustion engine 100 promotes combustion of the mixed gas by the active species generated by the active species generator 150. The piston 120 includes an active species generation chamber 194 that is formed therein and open to a top surface of the piston 120, and in which the active species generator 150 generates the active species.

Abstract: The plasma ignition device includes an ignition plug, a breakdown discharge circuit configured to apply a high voltage to the ignition plug to cause a breakdown discharge in a discharge space in the ignition plug, and a plasma discharge circuit configured to accumulate electric energy supplied from a power supply and applies the accumulated electric energy to the ignition plug as a current to bring a gas in the discharge space into a plasma state so that the gas in the plasma state is injected to a combustion chamber of an combustion engine during the breakdown discharge in order to cause ignition. The plasma discharge circuit includes an energy accumulating section, and an energy supplying section configured to supply the electric energy to the energy accumulating section during a short time period immediately before the breakdown discharge circuit applies the first voltage to the ignition plug.

Abstract: A resonance inductor is connected with a charging path through which an ignition condenser is charged; a first switching device controls charging of the ignition condenser; discharging of the ignition condenser is controlled by a second switching device whose collector terminal is connected with the other end of the primary coil of an ignition coil unit and whose emitter terminal is connected with the negative-polarity terminal of the ignition condenser; a clamp diode is connected between the one end of the primary coil and the collector terminal of the second switching device.

Abstract: An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

Abstract: A plasma ignition system is described herein that can produce plasma ionization around a spark plug gap using a single power circuit for the spark and plasma ionization. The system results in fewer components and higher reliability, allowing the system to be more easily integrated with existing ignition circuitry or in new ignition system designs. The plasma ignition system adds a one-way current path between the primary and secondary windings of the high voltage transformer. This allows energy stored within the capacitor after the creation of the spark to flow out of the capacitor, across the one-way current path, and through the spark plug gap. Thus, the plasma ignition system provides a dramatically better ignition spark with relatively little increase in components. The system does so without requiring a secondary power supply circuit to generate the current for producing plasma ionization.

Abstract: There is provided an internal-combustion engine that allows plasma to be used safely, efficiently, and in a manner conducive to resource conservation. An internal-combustion engine having an intake valve for opening and closing a combustion chamber, the internal-combustion engine comprising a valve-driving mechanism for driving the intake valve; and a plasma-generating device positioned within a region containing gas used for combustion during a combustion stroke, the plasma-generating device being composed of an antenna and a microwave-generating device, wherein the plasma-generating device composed of the antenna and the microwave-generating device generates plasma at a timing intimately associated with a state of openness of the intake valve in response to the driving of the valve by the valve-driving mechanism.

Abstract: A power circuit, which supplies plasma energy to a spark plug, includes a DC/DC converter which charges a tank capacitor, a voltage limiting circuit which restricts an output voltage of the converter to a predetermined value, a PJ capacitor which is connected to the output side of the converter and is charged by the tank capacitor, and a high breakdown voltage switch which is connected between the PJ capacitor and the DC/DC converter and controls a charging time period of the PJ capacitor in response to operating conditions of an internal combustion engine; and the power circuit switches a voltage limiting value of the tank capacitor for charging the PJ capacitor in synchronization with a driving signal of the high breakdown voltage switch.

Abstract: A method of improving the combustion of a spark-ignition internal combustion engine. Such engines have at least one cylinder, each cylinder having a compression chamber and operated such that an air-fuel mixture introduced into the combustion chamber is ignited to cause a combustion event. An antenna is placed within the combustion chamber, and is used to apply electromagnetic energy to the combustion.

Abstract: A system, in one embodiment, includes a combustion-based system having a combustion chamber. The system also includes an ignition control system. The ignition control system includes an ignition device coupled to the combustion chamber, control circuitry having an energy storage device configured to supply energy to the ignition device to produce an ignition event having a desired energy level, and a controller configured to obtain a target voltage across the energy storage device and to discharge an ignition energy from the energy storage device after obtaining the target voltage, wherein the ignition control system is configured to supply the ignition energy to the ignition device to produce the ignition event.

Abstract: A method for controlling a radio-frequency plasma generator including a supply circuit with a switch controlled by at least one control pulse train, for applying an intermediate voltage at a control frequency on an output to which is connected a resonator for generating a spark between two electrodes when a high voltage level is applied to the output. The method receives first and second measurement signals respectively representative of the operation of a combustion engine and of the type of spark generated; and real-time adjusts, based on the received measurement signals, at least one parameter selected from at least the intermediate voltage level, the control frequency, and the duration of the control train, to promote branching of the spark generated.

Abstract: An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

Abstract: A control method for a spark-ignited internal combustion engine includes generating plasma by interacting an electric field generated in a combustion chamber by electric field generation means with spark discharge caused by a spark plug, and igniting an air-fuel mixture, wherein the electric field generated by the electric field generation means is set to an intensity weaker than that of an electric field generated by the spark plug when the spark discharge is caused, and set to an intensity at which discharge into the combustion chamber is disabled, and the air-fuel mixture can be securely ignited and combusted at an intended ignition timing and at a position of the spark plug.

Abstract: A plasma power supply circuit includes a DC/DC converter connected to a DC power supply and outputting a DC voltage, a voltage limit circuit limiting an output voltage from the DC/DC converter to a predetermined value, a PJ capacitor connected to an output end of the DC/DC converter and charged with electric energy used to generate a plasma in a discharge space of the spark plug, and a high-voltage switch connected between the PJ capacitor and the DC/DC converter and controlled to switch ON and OFF so that a charge period of the PJ capacitor is controlled according to running conditions of the internal combustion engine. Hence, the plasma ignition device can prevent damage on an electronic component incorporated therein even at the occurrence of a short and lessen damage on the internal combustion engine caused by an erroneous plasma jet ejection, wearing of the spark plug, and power consumption.

Abstract: Disclosed is a spark plug arc intensifier system that influences the arc of the spark plug at any given performance of the gasoline engine. The intensifier system consists of a microcomputer that applies an additional signal to the lead-in wire coming from the transformer coil of the engine to influence the intensity of arc of the spark plug. This system results in a complete burning of the air/fuel mixture that is prevalent at the time of combustion. This system then results in a cleaner environment, less fuel consumption and a more powerful performance of the engine.

Abstract: To provide a plasma ignition system that can prevent damage on an internal combustion engine due to erroneous ejection of a plasma jet, and further, even when the required voltage of an ignition plug becomes lower, can prevent erroneous ignition by the charged voltage of a PJ capacitor. A plasma power supply circuit of the plasma ignition system includes a voltage-limiting circuit having a first set voltage having an absolute value lower relative to the discharge voltage of the ignition coil, and a second set voltage having an absolute value higher relative to the discharge voltage of the ignition coil, and the first set voltage and the second set voltage are selectively switched according to an operation condition of the internal combustion engine.

Abstract: A plasma power supply circuit includes a DC/DC converter connected to a DC power supply and outputting a DC voltage, a voltage limit circuit limiting an output voltage from the DC/DC converter to a predetermined value, a PJ capacitor connected to an output end of the DC/DC converter and charged with electric energy used to generate a plasma in a discharge space of the spark plug, and a high-voltage switch connected between the PJ capacitor and the DC/DC converter and controlled to switch ON and OFF so that a charge period of the PJ capacitor is controlled according to running conditions of the internal combustion engine. Hence, the plasma ignition device can prevent damage on an electronic component incorporated therein even at the occurrence of a short and lessen damage on the internal combustion engine caused by an erroneous plasma jet ejection, wearing of the spark plug, and power consumption.

Abstract: An engine spark ignition device for internal combustion engines having electrical coupling of the firing spark plug wire to the non-firing spark plug wires. The device is for use with an engine having a plurality of spark plug wires connected between a distributor and a spark plug disposed in the engine cylinder and comprises identical elongated electrically conductive semi-circular plates which enclose identical elongated electrically conductive planar plates having apertures therein that intersect to form spaces for receiving the spark plug wires. The interaction between firing spark plug wires and non-firing spark plug wires results in more efficient and cleaner combustion in the combustion chambers.

Abstract: The plasma ignition device includes an ignition plug, a breakdown discharge circuit configured to apply a high voltage to the ignition plug to cause a breakdown discharge in a discharge space in the ignition plug, and a plasma discharge circuit configured to accumulate electric energy supplied from a power supply and applies the accumulated electric energy to the ignition plug as a current to bring a gas in the discharge space into a plasma state so that the gas in the plasma state is injected to a combustion chamber of an combustion engine during the breakdown discharge in order to cause ignition. The plasma discharge circuit includes an energy accumulating section, and an energy supplying section configured to supply the electric energy to the energy accumulating section during a short time period immediately before the breakdown discharge circuit applies the first voltage to the ignition plug.

Abstract: There is obtained an ignition apparatus, for an internal combustion engine, that can make a predetermined output current flow in a stable manner so that the combustion state of the internal combustion engine can always be maintained in a good condition, even in the case where the voltage of the power source connected with the energy storing coil fluctuates.

Abstract: An apparatus and method for igniting combustible materials in a combustion chamber of a combustion engine using corona discharge plasma from a coaxial cavity resonator. This system and method uses a coaxial cavity resonator in a body adapted to mate with a combustion chamber of a combustion engine. The coaxial cavity resonator is coupled with an energy shaping means that develops the appropriate waveform for triggering radio frequency oscillations in the coaxial cavity resonator. A connection means on the apparatus allows for the apparatus to accept an electrical ignition stimulus from an electronic ignition control system. The coaxial cavity resonator develops corona discharge plasma at a discharge electrode when a sustained radio frequency oscillation results in a standing wave in the coaxial cavity resonator. The corona discharge plasma developed near the discharge electrode ignites the combustible materials in the combustion chamber of the combustion engine.

Abstract: The present invention refers to an apparatus for raising the spark energy in capacitive ignition systems comprising at least one charge winding (L1) which via a first rectifier device (D1) charges a charge capacitor (C1) connected to the primary winding of an 5 ignition voltage transformer in order to provide said primary winding with energy for generation of a spark characterized in that additionally a second rectifier device (D2) and a switching device (Q2) are arranged in such a way that the switching device periodically can short circuit the charge winding and thereby increase the charge of the charge capacitor at low engine speeds.

Abstract: An ignition control device for controlling a multi-spark operation comprises: a secondary electric energy generator generating an electric energy to reignite an air fuel-mixture associated with an internal combustion engine during the multi-spark operation; a switching element capable of controlling the supplying of the electric energy to a primary coil of an ignition coil, the controlling causing a secondary current in a secondary coil of the ignition coil; an ignition timing signal generator generating an ignition timing signal based on a driving state of the engine; a multi-spark period setting element setting a multi-spark period of the multi-spark operation based on the ignition timing signal; and an ignition control element setting an amount of electric power supplied to the secondary electric energy generator based on the multi-spark period before the performing of the multi-spark operation is started, and for controlling the switching element.

Abstract: A spark plug circuit for, and a method of, reducing or preventing the corrosion of a spark plug electrodes in an internal combustion engine. The circuit and method provide a positive voltage across the center electrode/ground electrode gap, which repels positively charged corrosion mechanisms, such as calcium and phosphorus ions.

Abstract: A method of maintaining electronic medical records, comprising the steps of receiving a medical transaction record, encrypted with an encryption key relating to a patient association of the file, accessing the encrypted medical transaction record according to a patient association; and further encrypting the encrypted accessed medical transaction record with an encryption key associated with an intended recipient of the medical record. The system and method according to the present invention presents a new business model for the creation, maintenance, transmission, and use of medical records, allowing financial burdens to be reallocated, for example more optimally or equitably, to decrease overall societal cost, or simply to provide a successful business model for a database proprietor. Secure entrusted medical records are held in trust by an independent third party on behalf of the patient, serving the medical community at large.

Abstract: The present invention refers to an apparatus for raising the spark energy in capacitive ignition systems comprising at least one charge winding (L1) which via a first rectifier device (D1) charges a charge capacitor (C1) connected to the primary winding of an 5 ignition voltage transformer in order to provide said primary winding with energy for generation of a spark characterised in that additionally a second rectifier device (D2) and a switching device (Q2) are arranged in such a way that the switching device periodically can short circuit the charge winding and thereby increase the charge of the charge capacitor at low engine speeds.

Abstract: A plasma ignition system includes an ignition plug attached to an engine and a high-voltage supply. The plug includes a center electrode serving as a positive pole, a ground electrode serving as a negative pole, and an insulating member insulating the center electrode from the ground electrode and defining a discharge space therein. At least a part of a surface of the center electrode faces the space, and at least a part of a surface of the ground electrode faces the discharge space. The plug puts gas in the space into a plasma state and injects the gas into the engine as a result of application of high voltage and supply of a large current to the plug by the high-voltage supply. The center electrode has a recess portion opposed to the space and recessed in a direction opposite to an injection direction.