# US 10,120,015 B2 · Method for inspecting insulator for spark plug

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- Number: US 10,120,015 B2
- Document ID: US10120015B2
- Status: Granted
- Kind: B2
- Application number: 15/008,740
- Filed: 2016-01-28
- Published: 2016-08-04
- Granted: 2018-11-06
- Earliest claimed: 2015-01-30
- Assignees: Ngk Spark Plug Co., Ltd.
- Applicants: Ngk Spark Plug Co., Ltd.
- Inventors: Kazumichi Hirose; Yoshiaki Hashiguchi; Shou Nakama
- Web page: https://patentgrep.com/patent/US10120015B2

## CPC

- G01R 31/1263: {of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation}
- H01T 13/60: of electrical properties
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H)

## Abstract

A method for inspecting an insulator for a spark plug to determine whether or not the insulator has a defect, the spark plug extending in an axial direction, includes a voltage applying step of applying a voltage between a first electrode disposed in an axial hole in the insulator and a second electrode disposed near an outer peripheral surface of the insulator. The voltage applying step is performed while a gap between a front end of the first electrode and an inner peripheral surface of the insulator that faces the front end of the first electrode in a radial direction is filled with a first insulating material without leaving a hollow space.

## Claims

### Claim 1

A method for inspecting an insulator for a spark plug to determine whether or not the insulator has a defect, the spark plug extending in an axial direction, the method comprising:
a voltage applying step of applying a voltage between a first electrode disposed in an axial hole in the insulator and a second electrode disposed near an outer peripheral surface of the insulator,
wherein the voltage applying step is performed while a gap between a front end of the first electrode and an inner peripheral surface of the insulator that faces the front end of the first electrode is filled with a first insulating material without leaving a hollow space; and
wherein, in the voltage applying step, a front distal tip of the first electrode is located in the axial hole.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the voltage applying step is performed while a back portion of the first electrode is covered with a second insulating material.

### Claim 3 (depends on 2)

The method according to claim 2, wherein a front end of the second insulating material is on a front side of a position of a back end of a metal shell when the metal shell is attached to an outer periphery of the insulator.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the first insulating material is insulating liquid.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the insulating liquid has a boiling point of 0 degrees Celsius or more and 100 degrees Celsius or less.