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US 9,425,585 B2Granted
Insulator and spark plug
AssigneeNgk Spark Plug Co., Ltd.
InventorsKengo Fujimura, Toshimasa Saji, Hirokazu Kurono, Toshitaka Honda
Life of this patent
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Abstract
An insulator used in a spark plug having improved strength and dielectric strength performance. The insulator comprises a sintered compact whose main constituent is alumina. In the sintered compact, a content ratio of a rare earth element (R. E.) and a group 2 element (2A) satisfies 0.1≦R. E./2A ≦1.4, and the content ratio of the R. E. and barium oxide (BaO) satisfies 0.2≦BaO/R. E.≦0.8. At least one virtual rectangular frame of 7.5 μm×50 μm surrounding crystals containing the rare earth element lies within a region of 630 μm×480 μm in any cross section of the sintered compact.
Claims9
An insulator used in a spark plug, said insulator comprising:
- a sintered compact comprising alumina as a main constituent, a rare earth element, silicon, and a plurality of group 2 elements including barium oxide,
- wherein the group 2 elements are listed in the periodic table of elements based on IUPAC Recommendation 1990,
- wherein a first content ratio of the rare earth element to the group 2 elements, in terms of an oxide represented by mass percentage, satisfies a range from 0.1 to 1.4,
- wherein a second content ratio of the barium oxide to the rare earth element, in terms of an oxide represented by mass percentage, satisfies a range from 0.2 to 0.8,
- wherein a third content ratio of the silicon to a sum of the silicon and the group 2 elements, in terms of an oxide represented by mass percentage, is less than 0.60,
- wherein an average particle diameter of particles of the alumina is less than or equal to 8 μm,
- wherein an average particle diameter of crystals containing the rare earth element is less than or equal to 5 μm,
- wherein at least one virtual rectangular frame of 7.5 μm×50 μm surrounding the crystals containing the rare earth element lies within a region of 630 μm×480 μm in any cross section of the sintered compact,
- wherein, in the rectangular frame, an occupancy ratio of an area of the crystals containing the rare earth element to an area of the rectangular frame is greater than or equal to 5%,
- wherein the rectangular frame is equally divided into three regions in a direction of a long side of the rectangular frame,
- wherein each of the regions has a regional occupancy ratio defined by an area within the region of the crystals containing the rare earth element to an area of the region, and
- wherein a ratio of a maximum of the regional occupancy ratios to a minimum of the regional occupancy ratios is less than or equal to 5.5%.
9 more elements
A spark plug comprising:
- an insulator including a sintered compact, the sintered compact comprising alumina as a main constituent, a rare earth element, silicon, and a plurality of group 2 elements including barium oxide,
- wherein the group 2 elements are listed in the periodic table of elements based on IUPAC Recommendation 1990,
- wherein a first content ratio of the rare earth element to the group 2 elements, in terms of an oxide represented by mass percentage, satisfies a range from 0.1 to 1.4,
- wherein a second content ratio of the barium oxide to the rare earth element, in terms of an oxide represented by mass percentage, satisfies a range from 0.2 to 0.8,
- wherein a third content ratio of the silicon to a sum of the silicon and the group 2 elements, in terms of an oxide represented by mass percentage, is less than 0.60,
- wherein an average particle diameter of particles of the alumina is less than or equal to 8 μm,
- wherein an average particle diameter of crystals containing the rare earth element is less than or equal to 5 μm,
- wherein at least one virtual rectangular frame of 7.5 μm×50 μm with surrounding the crystals containing the rare earth element lies within a region of 630 μm×480 μm in any cross section of the sintered compact,
- wherein, in the rectangular frame, an occupancy ratio of an area of the crystals containing the rare earth element to an area of the rectangular frame is greater than or equal to 5%,
- wherein the rectangular frame is equally divided into three regions in a direction of a long side of the rectangular frame,
- wherein each of the regions has a regional occupancy ratio defined by an area within the region of the crystals containing the rare earth element to an area of the region, and
- wherein a ratio of a maximum of the regional occupancy ratios to a minimum of the regional occupancy ratios is less than or equal to 5.5%.
9 more elements
An insulator used in a spark plug, said insulator comprising:
- a sintered compact comprising alumina as a main constituent, a rare earth element, silicon, and a plurality of group 2 elements including barium oxide,
- wherein the group 2 elements are listed in the periodic table of elements based on IUPAC Recommendation 1990,
- wherein a first content ratio of the rare earth element to the group 2 elements, in terms of an oxide represented by mass percentage, satisfies a range from 0.1 to 1.4,
- wherein a second content ratio of the barium oxide to the rare earth element, in terms of an oxide represented by mass percentage, satisfies a range from 0.2 to 0.8,
- wherein a third content ratio of the silicon to a sum of the silicon and the group 2 elements, in terms of an oxide represented by mass percentage, is less than 0.60,
- wherein at least one virtual rectangular frame of 7.5 μm×50 μm surrounding the crystals containing the rare earth element lies within a region of 630 μm×480 μm in any cross section of the sintered compact,
- wherein, in the rectangular frame, an occupancy ratio of an area of the crystals containing the rare earth element to an area of the rectangular frame is greater than or equal to 5%,
- wherein the rectangular frame is equally divided into three regions in a direction of a long side of the rectangular frame,
- wherein each of the regions has a regional occupancy ratio defined by an area within the region of the crystals containing the rare earth element to an area of the region, and
- wherein a ratio of a maximum of the regional occupancy ratios to a minimum of the regional occupancy ratios is less than or equal to 5.5%.
7 more elements
Dependencies are inferred from the claim text.