US 6,274,971 B1 · Spark plug and method of manufacturing the same

Abstract

A glaze layer formed on the surface an alumina-based insulator of a resistor spark plug contains SiO2 (18 to 35% by weight), B2O3 (25 to 40% by weight), ZnO (10 to 25% by weight), BaO (7 to 20% by weight), Na2O (3 to 9% by weight), and K2O (3 to 9% by weight). Since the difference between the coefficients of linear expansion of the glaze and that of the alumina-based insulating material is relatively small, the glaze layer is less susceptible to cracks and the like. Also, since the glaze has a softening point lower than that of conventional lead-silicate-glass-based glaze, the glost-firing temperature can be as low as 800° to 950° C. Therefore, even in the case where glost firing is performed concurrently with a glass sealing step, a center electrode and a terminal metal piece are less susceptible to oxidation. Further, even though the content of the alkali metal component is high, a good insulating performance is obtained so that excellent flashover resistance is attained.

Claims30

Dependent claims

A spark plug comprising:

a center electrode;
a metallic shell disposed so as to surround the center electrode;
a ground electrode, one end of the ground electrode being connected to the metallic shell, while the other end of the ground electrode facing the center electrode;
an insulator disposed between the center electrode and the metallic shell such that the insulator covers the outer surface of the center electrode;
and
a glaze layer mainly formed of oxides and adapted to cover at least a portion of the surface of the insulator, wherein
glaze which forms the glaze layer predominantly comprises Si, B, Zn, and Ba, and two co-added alkali metal components selected from among Na, K, and Li, wherein the amount of Si is 18 to 35% by weight as reduced to SiO2, the amount of B is 25 to 40% by weight as reduced to B2O3, the amount of Zn is 10 to 25% by weight as reduced to ZnO, the amount of Ba is 7 to 20% by weight as reduced to BaO, and the amount of each of the two co-added alkali metal components is 3 to 9% by weight as reduced to Na2O, K2O, or Li2O.

4 more elements

A spark plug comprising:

a center electrode;
a metallic shell disposed to surround the center electrode;
a ground electrode having ends, one end of the ground electrode being connected to the metallic shell, the other end of the ground electrode facing the center electrode;
an insulator disposed between the center electrode and the metallic shell, the insulator covering an outer surface of the center electrode;
and
a glaze layer formed to cover at least a portion of a surface of the insulator, wherein
glaze which forms the glaze layer predominantly comprises Si, B, Zn, and Ba, as well as at least one component selected from Ti and Zr, wherein the amount of Si is 20 to 38% by weight as reduced to SiO2, the amount of B is 20 to 35% by weight as reduced to B2O3, the amount of Zn is 15 to 25% by weight as reduced to ZnO, the amount of Ba is 10 to 23% by weight as reduced to BaO, and the amount of Ti and Zr is 2 to 10% by weight as reduced to TiO2 or ZrO2;
and the glaze further comprises at least one alkali component selected from among Na, K, and Li in a total amount of 12% by weight or less as reduced to their oxides, wherein the Pb content is not greater than 0.1% by weight as reduced to PbO.

5 more elements

A spark plug comprising:

a center electrode;
a metallic shell disposed to surround the center electrode;
a ground electrode having ends, one end of the ground electrode being connected to the metallic shell, the other end of the ground electrode facing the center electrode;
an insulator disposed between the center electrode and the metallic shell, the insulator covering an outer surface of the center electrode;
and
a glaze layer formed to cover at least a portion of a surface of the insulator, wherein
glaze which forms the glaze layer predominantly comprises Si, B, Zn, and Ba, as well as at least one component selected from Ti and Zr, wherein the amount of Si is 20 to 40% by weight as reduced to SiO2, the amount of B is 20 to 35% by weight as reduced to B2O3, the amount of Zn is 15 to 25% by weight as reduced to ZnO, the amount of Ba is 10 to 23% by weight as reduced to BaO, and the amount of Ti and Zr is 2 to 10% by weight as reduced to TiO2 or ZrO2, where the Zr content as reduced to ZrO2 is not greater than 3.4% by weight;
and the glaze further comprises at least one alkali component selected from among Na, K, and Li in a total amount of 12% by weight or less as reduced to their oxides, wherein the Pb content is not greater than 0.1% by weight as reduced to PbO.

5 more elements

A spark plug comprising:

a center electrode;
a metallic shell disposed to surround the center electrode;
a ground electrode having ends, one end of the ground electrode being connected to the metallic shell, the other end of the ground electrode facing the center electrode;
an insulator disposed between the center electrode and the metallic shell, the insulator covering an outer surface of the center electrode;
and
a glaze layer formed so as to cover at least a portion of a surface of the insulator, wherein
glaze which forms the glaze layer predominantly comprises Si, B, Zn, and Ba, as well as at least one component selected from Ti and Zr, wherein the amount of Si is 20 to 40% by weight as reduced to SiO2, the amount of B is 20 to 35% by weight as reduced to B2O3, the amount of Zn is 15 to 25% by weight as reduced to ZnO, the amount of Ba is 10 to 23% by weight as reduced to BaO, and the amount of Ti and Zr is 2 to 10% by weight as reduced to TiO2 or ZrO2, where the Ti content as reduced to TiO2 is not greater than 1.5% by weight;
and the glaze further comprises at least one alkali component selected from among Na, K, and Li in a total amount of 12% by weight or less as reduced to their oxides, wherein the Pb content is not greater than 0.1% by weight as reduced to PbO.

5 more elements

A spark plug comprising:

a center electrode;
a metallic shell disposed to surround the center electrode;
a ground electrode having ends, one end of the ground electrode being connected to the metallic shell, the other end of the ground electrode facing the center electrode;
an insulator disposed between the center electrode and the metallic shell, the insulator covering an outer surface of the center electrode;
and
a glaze layer formed to cover at least a portion of a surface of the insulator, wherein
glaze which forms the glaze layer predominantly comprises Si, B, Zn, and Ba, as well as at least one component selected from Ti and Zr, wherein the amount of Si is 20 to 40% by weight as reduced to SiO2, the amount of B is 20 to 35% by weight as reduced to B2O3, the amount of Zn is 15 to 25% by weight as reduced to ZnO, the amount of Ba is 10 to 23% by weight as reduced to BaO, and the total amount of Ti and Zr is 2 to 10% by weight as reduced to TiO2 or ZrO2, where the ratio between the Ti content WTi as reduced to TiO2 and the Zr content WZr as reduced to ZrO2, i.e., WTi/WZr is 0.2 to 10;
and the glaze further comprises at least one alkali component selected from among Na, K, and Li in a total amount of 12% by weight or less as reduced to their oxides, wherein the Pb content is not greater than 0.1% by weight as reduced to PbO.

5 more elements

Dependencies are inferred from the claim text.

Spark plug and method of manufacturing the same

Life of this patent

Spark plug and method of manufacturing the same

Life of this patent

Abstract

Claims30