Ceramic heater and glow plug
First Claim
1. A ceramic heater comprising a substrate formed of an electrically insulative ceramic, and a resistor element buried in the substrate, wherein the resistor element includes a single heat-generating portion formed of an electrically conductive ceramic and folded into a U-like shape, and a pair of lead portions which are joined to opposite end portions of said heat-generating portion, the end portion facing rearward with respect to a direction of an axis XA, and which extend straight rearward with respect to the direction of the axis XA, the ceramic heater being characterized in thatsaid resistor element includes intermediate portions located between said heat-generating portion and said lead portions;
- when, on cross section S1 and S2 of said ceramic heater taken along a plane perpendicular to said axis XA at a front end side point P1 and a rear end side point P2, which are arbitrary two different points on said axis XA, imaginary circumscribed circles CG1 and CG2 are drawn such that the imaginary circumscribed circles CG1 and CG2 circumscribe and contain two cross sections HS1a and HS1b and two cross sections HS2a and HS2b, respectively, of said resistor element appearing on the cross section S1 and S2, respectively, diameter CL1 and CL2 of the circumscribed circles CG1 and CG2 satisfy a relation CL1<
CL2; and
the total cross sectional area HS1S of the two cross sections HS1a and HS1b of said resistor element and the total cross sectional area HS2S of the two cross sections HS2a and HS2b of said resistor element satisfy a relation HS1S<
HS2S; and
wherein said ceramic heater is inserted into and held in a tubular member formed of metal such that a front end portion of said ceramic heater is exposed;
each of said intermediate portions has a portion having a thickness tXVex equal to or less than ⅔
a maximum thickness tXVmax of said resistor element; and
a portion of said resistor element whose thickness is 2 (tXVmax)/3 is exposed from said tubular member formed of metal.
2 Assignments
0 Petitions
Accused Products
Abstract
A ceramic heater (12) includes a substrate (60) and a resistor element (30) buried in the substrate (60). The resistor element (30) includes a heat-generating portion (33), lead portions (31), and intermediate portions (40) located between the heat-generating portions (33) and the lead portions (31). The intermediate portions (40) are formed such that, when cross sections at arbitrary two points P1 and P2 along the axis XA direction are compared, both the diameter CL of an imaginary circumscribed circle CG containing cross sections of the resistor element 30 and the total cross sectional area HS of the cross sections become small in the front end side cross section as compared with those in the rear end side cross section.
77 Citations
9 Claims
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1. A ceramic heater comprising a substrate formed of an electrically insulative ceramic, and a resistor element buried in the substrate, wherein the resistor element includes a single heat-generating portion formed of an electrically conductive ceramic and folded into a U-like shape, and a pair of lead portions which are joined to opposite end portions of said heat-generating portion, the end portion facing rearward with respect to a direction of an axis XA, and which extend straight rearward with respect to the direction of the axis XA, the ceramic heater being characterized in that
said resistor element includes intermediate portions located between said heat-generating portion and said lead portions; -
when, on cross section S1 and S2 of said ceramic heater taken along a plane perpendicular to said axis XA at a front end side point P1 and a rear end side point P2, which are arbitrary two different points on said axis XA, imaginary circumscribed circles CG1 and CG2 are drawn such that the imaginary circumscribed circles CG1 and CG2 circumscribe and contain two cross sections HS1a and HS1b and two cross sections HS2a and HS2b, respectively, of said resistor element appearing on the cross section S1 and S2, respectively, diameter CL1 and CL2 of the circumscribed circles CG1 and CG2 satisfy a relation CL1<
CL2; andthe total cross sectional area HS1S of the two cross sections HS1a and HS1b of said resistor element and the total cross sectional area HS2S of the two cross sections HS2a and HS2b of said resistor element satisfy a relation HS1S<
HS2S; andwherein said ceramic heater is inserted into and held in a tubular member formed of metal such that a front end portion of said ceramic heater is exposed; each of said intermediate portions has a portion having a thickness tXVex equal to or less than ⅔
a maximum thickness tXVmax of said resistor element; anda portion of said resistor element whose thickness is 2 (tXVmax)/3 is exposed from said tubular member formed of metal. - View Dependent Claims (2, 3, 4, 5)
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6. A ceramic heater comprising a substrate formed of an electrically insulative ceramic, and a resistor element buried in the substrate, wherein the resistor element includes a single heat-generating portion formed of an electrically conductive ceramic and folded into a U-like shape, and a pair of lead portions which are joined to opposite end portions of said heat-generating portion, the end portion facing rearward with respect to a direction of an axis XA, and which extend straight rearward with respect to the direction of the axis XA, the ceramic heater being characterized in that
said resistor element includes intermediate portions located between said heat-generating portion and said lead portions; -
when, on cross section S1 and S2 of said ceramic heater taken along a plane perpendicular to said axis XA at a front end side point P1 and a rear end side point P2, which are arbitrary two different points on said axis XA, imaginary circumscribed circles CG1 and CG2 are drawn such that the imaginary circumscribed circles CG1 and CG2 circumscribe and contain two cross sections HS1a and HS1b and two cross sections HS2a and HS2b, respectively, of said resistor element appearing on the cross section S1 and S2, respectively, diameter CL1 and CL2 of the circumscribed circles CG1 and CG2 satisfy a relation CL1<
CL2; andthe total cross sectional area HS1S of the two cross sections HS1a and HS1b of said resistor element and the total cross sectional area HS2S of the two cross sections HS2a and HS2b of said resistor element satisfy a relation HS1S<
HS2S, wherein a relation θ
2>
θ
1 and a relation L1>
L2 are satisfied, where θ
1 represents an angle formed between said axis XA and each of radially outer side outlines of said intermediate portions which outlines determine a width of said intermediate portions, L1 represents a length of said intermediate portions as measured along the direction of said axis XA, θ
2 represents a largest angle among angles formed between said axis XA and radially outer side outlines of said intermediate portions which outline determine a thickness of said intermediate portions, and L2 represents a length of the outlines of said intermediate portions forming the largest angle, as measured along the direction of said axis XA. - View Dependent Claims (7, 8, 9)
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Specification