CERAMIC HEATER AND GLOW PLUG

• US 20100213188A1
• Filed: 03/20/2007
• Published: 08/26/2010
• Est. Priority Date: 03/21/2006
• Status: Abandoned Application

• Current Assignee: NGK Spark PLUG Company Limited
• Original Assignee: NGK Spark PLUG Company Limited
• Inventors: Nishihara, Hiroshi, Konishi, Masahiro
• Application Number:
  US12/160,487
• Publication Number:
  US 20100213188A1
• Time in Patent Office: Days
• US Class Current: 219/544
• CPC Class Codes: F23Q 2007/004 Manufacturing or assembling methods
• 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 3/141 Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
• CPC Class Codes: H05B 3/48 heating conductor embedded in insulating material

Abstract

There are provided a ceramic heater in which a defect, such as generation of a gap at the interface between a heat-generating resistor and an insulating substrate, is unlikely to occur in the course of manufacture or use, and a glow plug using the ceramic heater. A ceramic heater 110 includes an insulating substrate 111 extending in the direction of an axis AX and a heat-generating resistor 115, which has a heat-generating portion 116, two lead portions 117, 117 and two lead lead-out portions 118a and 118b. The ceramic heater 110 satisfies an expression a≧0.15(b+c) in a section of the ceramic heater perpendicular to the direction of the axis AX, where a represents a minimum gap a between the pair of lead portions 117, 117 on the minimum-gap-associated imaginary straight line, and b and c represent dimensions of the pair of lead portions 117, 117.

Claims

1. A ceramic heater extending in an axial direction and adapted to generate heat from its front end portion upon energization, comprising:

an insulating substrate formed from an insulating ceramic and extending in the axial direction; and

a heat-generating resistor formed from a conductive ceramic and embedded in the insulating substrate, wherein the heat-generating resistor includes;

a heat-generating portion embedded in a front end portion of the insulating substrate, having such a form as to extend frontward from a rear side, change direction, and then again extend rearward, and generating heat upon energization,

a pair of lead portions connected to respective rear ends of the heat-generating portion and extending rearward in the axial direction, and

a pair of lead lead-out portions connected to the respective lead portions, extending radially outward, and exposed outward; and

the ceramic heater satisfies an expression a≧

0.15(b+c) in any cross section of the ceramic heater which is taken perpendicular to the axial direction and in which the lead portions are present, where;

of imaginary straight lines which pass through the center of the cross section and along which a gap a between the lead portions is measured, an imaginary straight line associated with a minimum gap a is defined as a minimum-gap-associated imaginary straight line; and

b and c are dimensions of the respective lead portions as measured on the minimum-gap-associated imaginary straight line.

4. A glow plug comprising a ceramic heater according to claim 1.

2. A ceramic heater assuming the form of a cylindrical column extending in an axial direction and adapted to generate heat from its front end portion upon energization, comprising:

an insulating substrate formed from an insulating ceramic and assuming the form of a cylindrical column extending in the axial direction; and

a heat-generating resistor formed from a conductive ceramic and embedded in the insulating substrate, wherein the heat-generating resistor includes;

a heat-generating portion embedded in a front end portion of the insulating substrate, having such a form as to extend frontward from a rear side, change direction, and then again extend rearward, and generating heat upon energization,

a pair of lead portions connected to respective rear ends of the heat-generating portion and extending rearward in the axial direction, and

a pair of lead lead-out portions connected to the respective lead portions, extending radially outward, and exposed outward; and

the ceramic heater satisfies an expression 2≦

D≦

10 and an expression a≦

D−

(b+c)−

0.2 in any cross section of the ceramic heater which is taken perpendicular to the axial direction and in which the lead portions are present, where;

D (mm) is a diameter of the insulating substrate;

of imaginary straight lines which pass through the center of the cross section and along which a gap a (mm) between the lead portions is measured, an imaginary straight line associated with a minimum gap a (mm) is defined as a minimum-gap-associated imaginary straight line; and

b (mm) and c (mm) are dimensions of the respective lead portions as measured on the minimum-gap-associated imaginary straight line.

3. A ceramic heater according to claim 2, further satisfying an expression a≧

0.15(b+c).

5. A glow plug comprising a ceramic heater according to claim 2.