Spark plug

Patent metadata

Field	Value
Publication number	US-9831638-B2
Application number	US-201715473685-A
Country	US
Kind code	B2
Filing date	Mar 30, 2017
Priority date	Mar 31, 2016
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

The spark plug has a shaft shaped center electrode, insulator, terminal fitting, ground electrode and resistor. The insulator has an axially penetrating shaft hole, and the center electrode is held in a tip end side of the shaft hole. The terminal fitting has a shaft and a terminal part. The shaft is held in a base end side of the shaft hole. The terminal part is projected from a base end of the shaft hole to a base end side of the spark plug. The ground electrode faces the center electrode in a tip end side of the shaft hole. The resistor is disposed between the center electrode and the terminal fitting in the shaft hole. An axial length L of the resistor is 15 mm≦L≦22.5 mm. An axial length T of the shaft satisfies a relation of 1.25≦T/L.

First claim

What is claimed is:

1. A spark plug comprising:
a center electrode which has an elongated shaft shape;
an insulator which has a shaft hole penetrated therein in an axial direction, and the center electrode is held in a tip end side of the shaft hole;
a terminal fitting which has a shaft and a terminal part, and the shaft is held in a base end side in the shaft hole, and the terminal part is projected from a base end of the shaft hole to a base end side of the spark plug in the axial direction;
a ground electrode which faces the center electrode in the tip end side of the shaft hole; and
a resistor which is disposed between the center electrode and the terminal fitting in the shaft hole,
wherein a length L of the resistor in the axial direction is 15 mm≦L≦22.5 mm,
wherein a length T of the shaft in the axial direction and the length L of the resistor are in a relation of 1.25≦T/L.

2. The spark plug as set forth in claim 1 , wherein the length L of the resistor is 15.5 mm≦L≦21.5 mm.

3. The spark plug as set forth in claim 1 , wherein the length T of the shaft and the length L of the resistor are in a relation of 1.29≦T/L≦2.6.

4. The spark plug as set forth in claim 1 , wherein the resistor includes a substrate to which a conductive material is added; and
the substrate includes a filled material and a glass material.

5. The spark plug as set forth in claim 4 , wherein the conductive material includes carbon.

Assignees

• Denso Corp

Inventors

• Watanabe Tomoyuki
• Araki Hiroshi

Classifications

• H01T13/41 Primary

  with interference suppressing or shielding means · CPC title

• H01T13/32

  characterised by features of the earthed electrode · CPC title

• H01T13/39

  Selection of materials for electrodes · CPC title

• H01T13/20

  characterised by features of the electrodes or insulation · CPC title