Abstract: An electric tool system includes an electric tool device and a camera device. The electric tool device has a drive unit and an electric tool communication unit. The drive unit performs tightening work of tightening a tightening component to a work target. The electric tool communication unit performs communication with outside. The camera device has a fixing unit, an image capturing unit, and a camera communication unit. The fixing unit is removably attached to the electric tool device. The image capturing unit captures an image of at least the work target. The camera communication unit performs communication with the outside.

Abstract: A spark plug for an internal combustion engine includes a tubular housing, a tubular insulator held inside the housing, a center electrode held inside the insulator, a ground electrode disposed so as to form a spark discharge gap with the center electrode, and a plug cover fixed to a distal end portion of the housing so as to form an auxiliary combustion chamber with the housing. The plug cover is formed with at least one through hole for communicating between inside of the auxiliary chamber and outside of the plug cover. The ground electrode is formed so as to project from an inner surface of the plug cover toward the inside of the auxiliary combustion chamber.

Abstract: A spark plug for an internal combustion engine includes a tubular housing, a tubular insulator held inside the housing, a center electrode held inside the insulator, a ground electrode disposed so as to form a spark discharge gap with the center electrode, and a plug cover fixed to a distal end portion of the housing so as to form an auxiliary combustion chamber with the housing. The plug cover is formed with at least one through hole for communicating between inside of the auxiliary chamber and outside of the plug cover. The ground electrode is formed so as to project from an inner surface of the plug cover toward the inside of the auxiliary combustion chamber.

Abstract: A spark plug for an internal combustion engine is provided which is equipped with an inward top end protrusion. The inward top end protrusion extends inwardly from a top end of a cylindrical housing within which a porcelain insulator is disposed. The porcelain insulator has a center electrode disposed therein. The inward top end protrusion is at least partially located to be closer to the top of the spark plug than a top end of the porcelain insulator is in an axial direction of the spark plug. This enhances the strength of an electric field surrounding the center electrode, which facilitates the ease with which an electron is emitted by the center electrode and thus permits an initial required voltage at the spark plug to be decreased, thereby resulting in an increase in service life of the spark plug.

Abstract: A spark plug includes a center electrode having an end portion, and an earth electrode having an opposing portion opposed to the end portion via a gap. The end portion has an end-projecting portion. The opposing portion has an opposing-projecting portion opposed to the end-projecting portion. The end-projecting portion and the opposing-projecting portion have non-projection direction opposing surfaces which are parallel to and opposed to each other with a minimum distance and in a direction other than a projection direction. A first opposing area of a portion which includes the non-projection direction opposing surfaces and where the end-projecting portion and the opposing-projecting portion are opposed to each other with the minimum distance is larger than a second opposing area obtained when a plane of the end-projecting portion and a plane of the opposing-projecting portion, which are orthogonal to the projection direction, are opposed to each other in the projection direction.

Abstract: A spark plug includes a center electrode having an end portion, and an earth electrode having an opposing portion opposed to the end portion via a gap. The end portion has an end-projecting portion. The opposing portion has an opposing-projecting portion opposed to the end-projecting portion. The end-projecting portion and the opposing-projecting portion have non-projection direction opposing surfaces which are parallel to and opposed to each other with a minimum distance and in a direction other than a projection direction. A first opposing area of a portion which includes the non-projection direction opposing surfaces and where the end-projecting portion and the opposing-projecting portion are opposed to each other with the minimum distance is larger than a second opposing area obtained when a plane of the end-projecting portion and a plane of the opposing-projecting portion, which are orthogonal to the projection direction, are opposed to each other in the projection direction.

Abstract: A spark plug for an internal combustion engine is provided which is equipped with an inward top end protrusion. The inward top end protrusion extends inwardly from a top end of a cylindrical housing within which a porcelain insulator is disposed. The porcelain insulator has a center electrode disposed therein. The inward top end protrusion is at least partially located to be closer to the top of the spark plug than a top end of the porcelain insulator is in an axial direction of the spark plug. This enhances the strength of an electric field surrounding the center electrode, which facilitates the ease with which an electron is emitted by the center electrode and thus permits an initial required voltage at the spark plug to be decreased, thereby resulting in an increase in service life of the spark plug.