# US 2014/0196680 A1 · Ceramic glow plug

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- Number: US 2014/0196680 A1
- Document ID: US20140196680A1
- Status: Published application
- Kind: A1
- Application number: 14/233,049
- Filed: 2012-09-25
- Published: 2014-07-17
- Earliest claimed: 2011-09-27
- Assignees: Ngk Spark Plug Co., Ltd.
- Applicants: Ngk Spark Plug Co., Ltd
- Inventors: Masahiro Torazawa
- Web page: https://patentgrep.com/patent/US20140196680A1

## CPC

- F02P 19/02: electric, e.g. layout of circuits of apparatus having glowing plugs
- F23Q 7/001: {Glowing plugs for internal-combustion engines}
- H05B 3/48: heating conductor embedded in insulating material
- H05B 2203/027: Heaters specially adapted for glow plug igniters
- F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00)
- F23Q: IGNITION (devices or installations peculiar to internal-combustion engines F02P; of cigarettes or tobacco A24F; compositions therefor, chemical igniters C06C); EXTINGUISHING-DEVICES
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

A ceramic glow pug has a structure in which a portion of an embedded resistor is exposed on a portion of a substrate and forms an exposed surface of an electrode taking-out portion. The resistor formed of an electrically conductive ceramic is embedded in the substrate formed of an electrically insulating ceramic, and a portion of the resistor is exposed on the surface of the substrate and has an exposed surface. The exposed surface and the embedded portion differ in stress acting on the substrate, which may decrease the breakage resistance in the vicinity of the electrode taking-out portion. The shape of the exposed surface is such that dimensions, in the axial and circumferential directions, fall within a range of 1.0 mm to 1.8 mm.

## Claims

### Claim 1

A ceramic glow plug comprising:
a ceramic heater composed of
a substrate formed of an electrically insulating ceramic and having a columnar shape extending in an axial direction, and
a resistor having a heat-generating element formed of an electrically conductive ceramic, embedded in a forward end portion of the substrate, and generating heat by resistance heating when energized, lead portions connected to opposite end portions of the heat-generating element and extending rearward in the axial direction, and an electrode taking-out portion extending in a radial direction from at least one of the lead portions and exposed on an outer circumferential surface of the substrate; and
a metallic tubular member in which the ceramic heater is held and which is in contact with an exposed surface of the electrode taking-out portion and electrically conducts with the exposed surface,
the ceramic glow plug being characterized in that dimensions, in the axial and circumferential directions, of the exposed surface of the electrode taking-out portion both fall within a range of 1.0 mm to 1.8 mm.

### Claim 2 (depends on 1)

A ceramic glow plug according to claim 1, wherein the ratio of a compressive residual stress in each of a specific region of the substrate which is separated 0.3 mm from a forward end of the exposed surface of the electrode taking-out portion and a specific region of the substrate which is separated 0.3 mm from a rear end of the exposed surface to a compressive residual stress in a portion of the substrate other than the specific regions is 50% or higher.

### Claim 3 (depends on 1)

A ceramic glow plug according to claim 1, wherein the dimension of the exposed surface of the electrode taking-out portion measured in the axial direction is smaller than that measured in the circumferential direction.

### Claim 4 (depends on 1)

A ceramic glow plug according to claim 1, wherein the shape of the exposed surface of the electrode taking-out portion does not have corner portions.

### Claim 5 (depends on 1)

A ceramic glow plug according to claim 1, wherein the ceramic heater is press-fitted into the tubular member.