Spark plug and method for manufacturing spark plug

Patent metadata

Field	Value
Publication number	US-9843166-B2
Application number	US-201514839022-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Sep 16, 2014
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A spark plug includes: a metallic shell having a through hole extending in a direction of an axis; a cap covering an opening in the metallic shell; a melt portion formed between the cap and the metallic shell to join the cap and the metallic shell to each other; and a gap extending from a specific space which is surrounded by the metallic shell and the cap to the melt portion and interposed between the metallic shell and the cap.

First claim

The invention claimed is:

1. A spark plug comprising:
a metallic shell having a through hole extending in a direction of an axis and having an opening at an open end;
a cap that is located at a front side of the spark plug and covers the opening in the metallic shell; and
a melt portion provided between the cap and the metallic shell, said melt portion joining the cap and the metallic shell to each other, wherein
the cap and the metallic shell form a specific space surrounded by an inner surface of the cap and the inner peripheral surface of the metallic shell,
the cap has a projection that extends from the peripheral edge of the cap into the specific space so as to form a gap between the metallic shell and the projection of the cap defining a channel communicating with the specific space and the melt portion, and
the melt portion is exposed to the specific space so as to exhaust gas generated by welding into the gap.

2. The spark plug according to claim 1 , wherein the gap includes:
a first gap portion disposed between the interior surface of the metallic shell and the projection of the cap; and
a second gap portion disposed between the interior surface of the metallic shell and a recess in the projection of the cap, wherein the second gap portion is larger than the first gap portion in at least one dimension.

3. The spark plug according to claim 2 , wherein
the metallic shell has a first surface which is not perpendicular to the axis, and
the cap has a second surface which faces the first surface of the metallic shell to provide the first gap and the second gap.

4. The spark plug according to claim 1 , wherein the gap is annular.

5. The spark plug according to claim 1 , wherein the gap is provided at a plurality of positions in a circumferential direction when being seen from the direction of the axis.

6. A method for manufacturing a spark plug, the method comprising the steps of:
placing a cap on a metallic shell that has a through hole extending in a direction of an axis and has an opening at an open end thereof, said cap having an inner surface and a projecting portion extending from an inner peripheral edge of the cap so as to form an annular gap between the projection and the inner surface of the shell, the cap and the metallic shell forming a specific space surrounded by an inner surface of the cap and the inner peripheral surface of the metallic shell; and
welding the cap to the shell so that the projection of the cap extends into the open end of the metallic shell volume, such that the gap defines a channel between the specific space and a melt portion formed by the welding, wherein
the melt portion is exposed to the specific space so as to exhaust gas generated by welding into the gap,
the annular gap includes:
a first gap portion which communicates between the melt portion and the specific space; and
a second gap portion which communicates between the specific space and the melt portion at the location of recesses in the cap projection, wherein because of the recesses the second gap is larger than the first gap, and
the step of welding the cap to the metallic shell further comprises the sub-steps of:
welding a specific portion whose position in a circumferential direction is different from that of a specific second gap, of a boundary between the cap and the metallic shell which communicates with the annular gap; and
after welding the specific portion, welding a portion whose position in the circumferential direction is the same as that of the specific second gap, of the boundary.

7. The spark plug according to claim 1 , wherein the cap has at least one communication hole which provides communication between the specific space and an outside of the cap.

Assignees

• Ngk Spark Plug Co

Inventors

• Okazaki Koji
• Takahashi Kei
• Mori Kazuhiko

Classifications

• H01T13/20 Primary

  characterised by features of the electrodes or insulation · CPC title

• H01T13/08

  Mounting, fixing or sealing of sparking plugs, e.g. in combustion chamber · CPC title

• H01T13/467

  in parallel connection · CPC title

• H01T13/54

  having electrodes arranged in a partly-enclosed ignition chamber · CPC title