Spark plug with specific measured parameters
AssigneeDenso Corporation
InventorsToshikazu Shimizu, Yasushi Kawashima
Life of this patent
Estimating the term…
Abstract
A spark plug has an insulator having a through hole extending in an axial direction thereof and an insulator leg portion at an end thereof, a resistor disposed in the through hole, a central electrode disposed in the through hole to face a central electrode side end face of the resistor and protruding from an insulator end face of the insulator leg portion, and a housing holding the insulator. A length between the insulator end face and the central electrode side end face of the resistor is equal to or larger than 1.5 times as large as a length of the insulator leg portion in the axial direction. Accordingly, temperature at a contact portion between the resistor and the central electrode is prevented from being increased, resulting in long life of the spark plug.
Claims21
A spark plug for an internal combustion engine, comprising:
- an insulator having a through hole extending in an axial direction of the insulator and an insulator leg portion at a first end portion in the axial direction;
- a resistor disposed in the through hole and formed from a resistive material by welding;
- a central electrode disposed in the through hole to face a central electrode side end face of the resistor and protruding from an insulator end face of the insulator leg portion;
- a housing holding the insulator therein and having a screw portion for being attached to the internal combustion engine;
- and
- an earth electrode fixed to the housing and facing the central electrode to define a spark gap therebetween,
- wherein a first length between the insulator end face and the central electrode side end face of the resistor is equal to or larger than 1.5 times as large as a second length of the insulator leg portion in the axial direction.
A spark plug for an internal combustion engine, comprising:
- an insulator having a through hole extending in an axial direction of the insulator;
- a central electrode disposed in the through hole and protruding from an insulator first end face of the insulator in the axial direction;
- a terminal electrode disposed in the through hole to be electrically connected to the central electrode and protruding from an insulator second end face of the insulator in the axial direction;
- a housing holding at least part of the insulator on a central electrode side;
- and
- an earth electrode fixed to the housing and facing the central electrode to define a spark gap therebetween,
- wherein an entire length of the insulator between the insulator first and second end faces in the axial direction is equal to or larger than 90 mm;
- wherein a length between the insulator second end face and an end face of the housing on an insulator second end face side is equal to or larger than 40 mm;
- and
- wherein a projection area of the insulator second end face is in a range of 80 mm.sup.2 to 200 mm.sup.2.
A spark plug for an internal combustion engine, comprising:
- an insulator having a through hole extending in an axial direction of the insulator;
- a central electrode disposed in the through hole and protruding from an insulator first end face of the insulator in the axial direction;
- a cylindrical housing disposed on an outer circumference surface of the insulator and having a polygonal attachment portion for being rotated when the spark plug is attached to the internal combustion engine, and a sleeve portion on a side of the polygonal attachment portion opposite the insulator first end face, the sleeve portion being for forming a ring-shaped space with the outer circumference surface of the insulator by caulking;
- an earth electrode fixed to the housing and facing the central electrode with a spark gap therebetween;
- and
- a powdery layer filling the ring-shaped space,
- wherein a length of the powdery layer in the axial direction is in a range of 5 mm to 8 mm;
- and
- wherein a length of the polygonal attachment portion in the axial direction is in a range of 10 mm to 15 mm.
A spark plug for an internal combustion engine, comprising:
- an insulator having a through hole extending in an axial direction of the insulator;
- a central electrode disposed in the through hole and protruding from an insulator first end face of the insulator in the axial direction;
- a cylindrical housing disposed on an outer circumference surface of the insulator and having a polygonal attachment portion for being rotated when the spark plug is attached to the internal combustion engine, and a sleeve portion on a side of the polygonal attachment portion opposite the insulator first end face, the sleeve portion being for forming a ring-shaped space with the outer circumference surface of the insulator by caulking;
- an earth electrode fixed to the housing and facing the central electrode with a spark gap therebetween;
- and
- a powdery layer filling the ring-shaped space,
- wherein the sleeve portion is caulked by cold-caulking and hot-caulking.
Dependencies are inferred from the claim text.