Spark plug and mounting structure of the same
AssigneeNgk Spark Plug Co., Ltd.
InventorTakahiro Suzuki
Life of this patent
Estimating the term…
Abstract
The spark plug has a top end portion of a main metal shell that is almost cylindrical on an outer circumferential face without having a plug attaching external thread screwed into the cylinder head. Further, the plug hole formed in the cylinder head has a top end counterpart corresponding to the top end portion of the main metal shell. And in the mounting structure of the spark plug into the cylinder head (plug hole), the clearance amount (φD−φd) satisfies a relation φD−φd≦0.15 (unit: mm) where the outer diameter of the top end portion of the main metal shell is φd and the hole diameter of the top end counterpart of the plug hole is φD.
Claims17
A spark plug adapted to be mounted in a plug hole formed in a cylinder head, said spark plug comprising:
- a central electrode extending in an axial direction thereof;
- an insulator having a tip end portion which surrounds said central electrode;
- and
- a main metal shell provided around said insulator, said main metal shell having a flange portion with a plug bearing surface at a tip end of said flange portion, and said main metal shell having a top end portion which extends in an axial direction thereof from said plug bearing surface to a tip end side of the main metal shell,
- wherein the top end portion of said main metal shell is formed into a substantially cylindrical shape having an outer circumferential face on which no external thread is provided, and the outer diameter of the top end portion satisfying a following relation,
- φD−φd≦0.15
- where φd (unit:
- mm) defines the outer diameter of said top end portion of said main metal shell, and φD (unit:
- mm) denotes the inner diameter of a top end counterpart of said plug hole where is in confront with said top end portion.
A mounting structure comprising:
- a spark plug including, a central electrode extending in an axial direction thereof,
- an insulator having a tip end portion which surrounds said central electrode, and
- a main metal shell provided around said insulator, said main metal shell having a flange portion with a plug bearing surface at a tip end of said flange portion, and said main metal shell having a top end portion which extends in an axial direction thereof from said plug bearing surface to a tip end side of the main metal shell;
- and
- a cylinder head having plug hole with a top end counterpart which receives the top end portion of said main metal shell,
- wherein the top end portion of said main metal shell is formed into a substantially cylindrical shape having an outer circumferential face on which no external thread is provided, and the top end portion of said main metal shell and the top end counterpart of said plug hole satisfies a following relation,
- ΦD−Φd≦0,15
- where Φd (unit:
- mm) defines the outer diameter of said top end portion, and ΦDD (unit:
- mm) denotes the inner diameter of the top end counterpart.
Dependencies are inferred from the claim text.