Spark plug
AssigneeNgk Spark Plug Co., Ltd.
InventorsJumpei Isasa, Haruki Yoshida, Yutaka Yokoyama, Kuniharu Tanaka, Nobuyoshi Araki, Toshiki Kon
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Abstract
A spark plug includes an insulator made of an alumina sintered body containing Al2O3 as a principal component and additional components including; an Si component, a Ba component, an Mg component, a Ca component, an Sr component, and a rare earth element component. When the additional components are expressed as oxides including RSiO2, RBaO, RMgO, RCaO, RSrO, and RRE2O3, contents (mass %) of the sub-component satisfy expressions (1) to (6) as follows: (1) 1.0≦RSiO2≦5.0; (2) 0.5≦RBaO≦5.0; (3) 0≦RMgO≦0.18; (4) 0≦RMgO/RBaO≦0.36; (5) 0.3≦(RMgO+RCaO+RSrO)≦1.8; and (6) 0≦RRE2O3≦0.1.
Claims6
A spark plug comprising:
- an insulator having an axial bore extending in a direction of an axis;
- a center electrode provided at a front side of the axial bore;
- a metallic shell provided on an outer periphery of the insulator;
- and
- a ground electrode fixed to a front end of the metallic shell, wherein
- the insulator is made of an alumina sintered body containing Al2O3 as a principal component and further containing additional components including an Si component, a Ba component, an Mg component, a Ca component, an Sr component, a rare earth element component, and barium hexaaluminate, and
- when the additional components are expressed as oxides including RSiO2, RBaO, RMgO, RCaO, RSrO, and RRE2O3, contents (mass %) of the additional components satisfy expressions (1) to (6) as follows:
- 1.0≦RSiO2≦5.0 (1)
- 0.5≦RBaO≦5.0 (2)
- 0≦RMgO≦0.18 (3)
- 0≦RMgO/RBaOo≦0.36 (4)
- 0.3≦(RMgO+RCaO+RSrO)≦1.8 (5)
- 0≦RRE2O3≦0.1 (6).
Dependencies are inferred from the claim text.