Patent ID: 9644597
Date: 2017-05-09
CPC Classifications: F02P,F23Q,H05B

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, 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.