Abstract: A spark plug has a tubular ground electrode, an insulator, and a center electrode. The insulator has an insulator protruding portion protruding to a tip end side in a plug axial direction with respect to the ground electrode. The center electrode 4 has an exposed portion exposed through a tip end of the insulator protruding portion. The exposed portion of the center electrode has a first part covering the insulator protruding portion from the tip end side in the plug axial direction, and a second part extending from the first part to a base end side in the plug axial direction and covering the entire circumference of an outer peripheral surface of the insulator protruding portion from an outer peripheral side in a plug radial direction.

Abstract: In a spark plug for an internal combustion engine, a cylindrical insulator is arranged radially inside a cylindrical ground electrode, and includes an insulator protruding portion protruding further toward a distal end side in an axial direction than a distal end of the ground electrode. A center electrode is held radially inside the insulator, and includes an exposed portion exposed from a distal end of the insulator protruding portion. The spark plug generates a discharge from the exposed portion to the ground electrode, in a discharge gap formed along a surface of the insulator protruding portion. At least one of the exposed portion and the insulator protruding portion includes a flow inlet that is open on an outer circumferential surface thereof, a flow outlet that is open toward the discharge gap, and a communication passage communicating between the flow inlet and the flow outlet.

Abstract: In a spark plug for an internal combustion engine, a discharge gap is formed between a central electrode and a ground electrode in an axial direction of the spark plug. An insulator of a cylindrical shape has an axial hole and an insulator front end part. The axial hole is formed in the insulator, into which the central electrode is arranged and supported. The insulator front end part projects further toward a front side of the insulator in the axial direction of the spark plug than a location of an opening part formed at a front end side of the axial hole. The discharge gasp is formed in an auxiliary combustion chamber. The outer peripheral side of the auxiliary combustion chamber is covered with the insulator front end part.

Abstract: A spark plug for an internal combustion engine includes a housing, an insulator, and a center electrode. The center electrode includes an inside electrode portion and an outside electrode portion. The housing includes a ground electrode projecting from a distal end portion of the housing toward the distal end side of the plug at a part in a plug circumferential direction. The outside electrode portion projects along a surface of the insulator tip in a direction away from a boundary with the inside electrode portion and includes a projection, which is capable of causing an electrical discharge between the ground electrode and the outside electrode portion. The projection is formed in a region in the plug circumferential direction. The projection and the ground electrode are located at positions different from each other in the plug circumferential direction.

Abstract: An ignition apparatus of an internal combustion engine is provided with an ignition plug, an AC (alternating current) voltage application unit configured to apply AC voltage to the center electrode of the ignition plug, and an application voltage control unit that controls an operation of the AC voltage application unit. The application voltage control unit is configured to control the AC voltage application unit to apply the center electrode with a first AC voltage having an amplitude smaller than that of a required voltage of the ignition plug in a first period which is before an ignition timing, and to apply the center electrode with a second AC voltage having an amplitude smaller than that of the first AC voltage or to stop applying the center electrode with the AC voltage during a second period which is before the ignition timing after the first period has elapsed.

Abstract: A spark plug for an internal combustion engine includes a housing, an insulator, and a center electrode. The center electrode includes an inside electrode portion and an outside electrode portion. The housing includes a ground electrode projecting from a distal end portion of the housing toward the distal end side of the plug at a part in a plug circumferential direction. The outside electrode portion projects along a surface of the insulator tip in a direction away from a boundary with the inside electrode portion and includes a projection, which is capable of causing an electrical discharge between the ground electrode and the outside electrode portion. The projection is formed in a region in the plug circumferential direction. The projection and the ground electrode are located at positions different from each other in the plug circumferential direction.

Abstract: In a spark plug for an internal combustion engine, a discharge gap is formed between a central electrode and a ground electrode in an axial direction of the spark plug. An insulator of a cylindrical shape has an axial hole and an insulator front end part. The axial hole is formed in the insulator, into which the central electrode is arranged and supported. The insulator front end part projects further toward a front side of the insulator in the axial direction of the spark plug than a location of an opening part formed at a front end side of the axial hole. The discharge gasp is formed in an auxiliary combustion chamber. The outer peripheral side of the auxiliary combustion chamber is covered with the insulator front end part.

Abstract: In a spark plug for an internal combustion engine, a cylindrical insulator is arranged radially inside a cylindrical ground electrode, and includes an insulator protruding portion protruding further toward a distal end side in an axial direction than a distal end of the ground electrode. A center electrode is held radially inside the insulator, and includes an exposed portion exposed from a distal end of the insulator protruding portion. The spark plug generates a discharge from the exposed portion to the ground electrode, in a discharge gap formed along a surface of the insulator protruding portion. At least one of the exposed portion and the insulator protruding portion includes a flow inlet that is open on an outer circumferential surface thereof, a flow outlet that is open toward the discharge gap, and a communication passage communicating between the flow inlet and the flow outlet.

Abstract: A spark plug has a tubular ground electrode, an insulator, and a center electrode. The insulator has an insulator protruding portion protruding to a tip end side in a plug axial direction with respect to the ground electrode. The center electrode 4 has an exposed portion exposed through a tip end of the insulator protruding portion. The exposed portion of the center electrode has a first part covering the insulator protruding portion from the tip end side in the plug axial direction, and a second part extending from the first part to a base end side in the plug axial direction and covering the entire circumference of an outer peripheral surface of the insulator protruding portion from an outer peripheral side in a plug radial direction.

Abstract: An ignition control system includes a spark plug including a cylindrical ground electrode, a cylindrical insulator having a protruding portion held inside the ground electrode and protruding toward a tip side the spark plug relative to the ground electrode, and a center electrode held inside the insulator and exposed from the insulator, an ignition coil including a primary coil and a secondary coil, and a primary current control unit performing creeping discharge control for generating a creeping discharge along a surface of the insulator, and air discharge transition control for stopping the creeping discharge occurring in the spark plug after the creeping discharge control is performed, and cutting off primary current after a discharge stop period ends, in one combustion cycle of the engine.

Abstract: An ignition apparatus of an internal combustion engine is provided with an ignition plug, an AC (alternating current) voltage application unit configured to apply AC voltage to the center electrode of the ignition plug, and an application voltage control unit that controls an operation of the AC voltage application unit. The application voltage control unit is configured to control the AC voltage application unit to apply the center electrode with a first AC voltage having an amplitude smaller than that of a required voltage of the ignition plug in a first period which is before an ignition timing, and to apply the center electrode with a second AC voltage having an amplitude smaller than that of the first AC voltage or to stop applying the center electrode with the AC voltage during a second period which is before the ignition timing after the first period has elapsed.

Abstract: An ignition apparatus includes a spark plug and an ignition coil. The spark plug has a plug terminal protruding proximalward from an insulator. The ignition coil includes a coil main body, which includes a primary coil and a secondary coil, and a helical spring that electrically connects the secondary coil and the plug terminal. The plug terminal is made of a material that is both electrically conductive and magnetic. The plug terminal includes a terminal main body, which has an outer diameter greater than an inner diameter of the spring, and a terminal extension portion that has an outer diameter less than the inner diameter of the spring and extends proximalward from the terminal main body. A distal end portion of the spring abuts the terminal main body. The terminal extension portion is inserted and arranged in the spring. Between an outer circumferential surface of the terminal extension portion and an inner circumferential surface of the spring, there is interposed an insulating member.

Abstract: An ignition apparatus includes a spark plug and an ignition coil. The spark plug has a plug terminal protruding proximalward from an insulator. The ignition coil includes a coil main body, which includes a primary coil and a secondary coil, and a helical spring that electrically connects the secondary coil and the plug terminal. The plug terminal is made of a material that is both electrically conductive and magnetic. The plug terminal includes a terminal main body, which has an outer diameter greater than an inner diameter of the spring, and a terminal extension portion that has an outer diameter less than the inner diameter of the spring and extends proximalward from the terminal main body. A distal end portion of the spring abuts the terminal main body. The terminal extension portion is inserted and arranged in the spring. Between an outer circumferential surface of the terminal extension portion and an inner circumferential surface of the spring, there is interposed an insulating member.