Spark plug production method, spark plug production device and assembly inspection method

A spark plug production device for producing a spark plug which includes an assembly which is composed of a tubular metallic shell having a ground electrode at its forward end and an insulator having an axial hole and holding a terminal electrode in the axial hole such that a portion of the terminal electrode on its base end side is exposed from the axial hole, the assembly being assembled such that the metallic shell covers an outer circumferential surface of a forward end portion of the insulator, the spark plug production device comprising:

• a pressure container which has an opening and into which a portion of the assembly on its forward end side is inserted through the opening;
• a sealing section which brings an insulating member into contact with an outer circumferential surface of a base end portion of the terminal electrode over the entire circumference of the base end portion in a state in which an axial line of the assembly and an axial line of the opening coincide with each other, and presses the assembly so as to close the opening by the assembly;
• a pressurizing section which pressurizes an interior of the pressure container;
• and
• a voltage application section which applies a predetermined voltage between the terminal electrode and the metallic shell,
• wherein the pressure container accommodates the portion of the assembly on its forward end side such that a gap formed between an outer circumferential surface of the insulator and an inner circumferential surface of the metallic shell on the forward end side of the assembly is disposed in the pressure container.