Inspection method of spark plug and manufacturing method of spark plug

Abstract

A method for inspecting a spark plug and a method for manufacturing a spark plug, capable of more reliably distinguishing flashover and breakdown discharge during the inspection of the insulation performance of an insulator, and improving the yield. The spark plug (1) has: an insulator (2) having a shaft hole extending in the direction of the axis (CL1); a center electrode (5) inserted through the front end side of the shaft hole (4); and a body fitting (3) being Arranged on the outer periphery of the insulator, the spark plug has an annular space (29) opened on the front end side formed by the outer peripheral surface of the insulator and the inner peripheral surface of the metallic shell. The spark plug checks the insulation performance of the insulator based on whether the insulator is electrically damaged when a voltage is applied to the center electrode. During the inspection, when a voltage is applied to the center electrode, the range including at least the center electrode, the insulator, and the annular space is photographed from the front end side in the axial direction, and the presence or absence of electrical damage is judged from the obtained photographed image.

Description

technical field [0001] The present invention relates to a method of inspecting a spark plug used in an internal combustion engine and a method of manufacturing the spark plug. Background technique [0002] A spark plug is attached to an internal combustion engine (engine), etc., and is used to ignite the air-fuel mixture in the combustion chamber. Generally, a spark plug has: an insulator having a shaft hole extending in the axial direction; a center electrode inserted through the front end side of the shaft hole; a metal shell provided on the outer periphery of the insulator; and a ground electrode fixed to the The front end of the body fitting. In addition, a spark discharge gap is formed between the front end of the ground electrode and the center electrode. By applying a high voltage to the center electrode (spark discharge gap), a spark discharge is generated in the spark discharge gap to realize the discharge of the mixed gas, etc. the ignition. [0003] However, wh...

AI Technical Summary

Problems solved by technology

However, there is no significant difference between the waveform of the applied voltage when the flashover occurs and the waveform of the applied voltage when the breakdown discharge occurs, and it is impossible to determine whether the flashover or the breakdown discharge has occurred in the above method.

Therefore, there is a possibility that a product that flashes over when a voltage is applied but actually has no problem with its insulation performance may have to be handled as a defective product, resulting in a decrease in yield

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