Spark plug

Patent metadata

Field	Value
Publication number	US-9853423-B1
Application number	US-201715646559-A
Country	US
Kind code	B1
Filing date	Jul 11, 2017
Priority date	Jul 13, 2016
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa−Sb corresponds to 35% or more of Sa.

First claim

What is claimed is:

1. A spark plug comprising:
a center electrode; and
a ground electrode disposed so as to form a gap between the center electrode and the ground electrode,
wherein at least one of the center electrode and the ground electrode includes an electrode body, an electrode tip having a discharge surface that faces the gap, and a welded portion formed between the electrode body and the electrode tip and containing a component of the electrode body and a component of the electrode tip,
the electrode tip includes:
a tip body comprising a side surface extending in a direction that intersects the discharge surface, and an opposite surface which is disposed on an opposite side of the discharge surface, at least a part of which is in contact with the welded portion and a part of which is a non-contact portion not in contact with the welded portion and
a cover layer that covers at least the side surface of the tip body,

the tip body comprises iridium (Ir) or an alloy containing iridium (Ir) as a main component,
the cover layer comprises an intermetallic compound (IrAl) of iridium (Ir) and aluminum (Al) and having a thickness of 50 μm or less,
the electrode body comprises an alloy containing 50% by weight or more of nickel (Ni), and
wherein “Sa” is defined as an area of a section through the tip body along a plane located near but not intersecting the welded portion, and parallel to the discharge surface,
wherein “Sb” is defined as an area of a projection of the non-contact portion of the opposite surface on the section in a direction perpendicular to the discharge surface, and
wherein Sa−Sb corresponds to 35% or more of Sa.

2. The spark plug according to claim 1 ,
wherein Sa−Sb corresponds to 45.7% or more of Sa.

3. The spark plug according to claim 1 ,
wherein “Sc” is defined as an area of an exposed portion of a surface of the electrode tip, and
Sa−Sb corresponds to 7% or more of Sc.

4. The spark plug according to claim 1 ,
wherein a content of aluminum (Al) in the welded portion in a vicinity of a boundary between the tip body and the welded portion is 10% by mass or less.

5. The spark plug according to claim 4 ,
wherein the content of aluminum (Al) in the welded portion in a vicinity of a boundary between the tip body and the welded portion is 5% by mass or less.

Assignees

• Ngk Spark Plug Co

Inventors

• Sumoyama Daisuke
• Nakada Takuto
• Shibata Tsutomu
• Kikai Takaaki

Classifications

• H01T13/10

  by bayonet-type connection · CPC title

• H01T13/32

  characterised by features of the earthed electrode · CPC title

• H01T13/38

  Selection of materials for insulation · CPC title

• H01T13/39 Primary

  Selection of materials for electrodes · CPC title

• H01T13/20 Primary

  characterised by features of the electrodes or insulation · CPC title