Ceramic glow plug

Patent metadata

Field	Value
Publication number	US-9644597-B2
Application number	US-201214233049-A
Country	US
Kind code	B2
Filing date	Sep 25, 2012
Priority date	Sep 27, 2011
Publication date	May 9, 2017
Grant date	May 9, 2017

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.

First claim

The invention claimed is:

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,
wherein the ratios of compressive residual stress in each of a specific region of the substrate which is 0.3 mm forward in the axial direction from a forward end of the exposed surface of the electrode taking-out portion and a specific region of the substrate which is 0.3 mm rearward in the axial direction from a rear end of the exposed surface to a compressive residual stress in a portion of the substrate other than the specific regions are 50% or higher.

2. The 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.

3. The 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.

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

Assignees

• Ngk Spark Plug Co

Inventors

• Torazawa Masahiro

Classifications

• H05B3/03

  Electrodes · CPC title

• F02N19/00

  Starting aids for combustion engines, not otherwise provided for · CPC title

• H05B3/46

  heating conductor mounted on insulating base · CPC title

• H05B2203/027

  Heaters specially adapted for glow plug igniters · CPC title

• F23Q7/001

  Glowing plugs for internal-combustion engines · CPC title