Ceramic glow plug

• US 9,644,597 B2
• Filed: 09/25/2012
• Issued: 05/09/2017
• Est. Priority Date: 09/27/2011
• Status: Active Grant

• Current Assignee: NGK Spark PLUG Company Limited
• Original Assignee: NGK Spark PLUG Company Limited
• Inventors: Torazawa, Masahiro
• Primary Examiner(s): McMahon, Marguerite
• Assistant Examiner(s): KIM, JAMES JAY
• Application Number:
  US14/233,049
• Publication Number:
  US 20140196680A1
• Time in Patent Office: 1,687 Days
• Field of Search: 123145 A, 219277, 219544
• CPC Class Codes: F02P 19/02 electric, e.g. layout of circuits of apparatus having glowing plugs
• CPC Class Codes: F23Q 7/001 Glowing plugs for internal-combustion engines
• CPC Class Codes: H05B 2203/027 Heaters specially adapted for glow plug igniters
• CPC Class Codes: H05B 3/48 heating conductor embedded in insulating material

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

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.