Spark plug and method for producing the same

Patent metadata

Field	Value
Publication number	US-9705292-B2
Application number	US-201615245583-A
Country	US
Kind code	B2
Filing date	Aug 24, 2016
Priority date	Sep 1, 2015
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

A spark plug comprising a center electrode, a ground electrode disposed on the center electrode across a gap, and a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, the tip has a discharge layer and a relieving layer, the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer, the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined, and 0.81≦A/B≦1.21 is satisfied when an average cross-sectional area of the discharge layer is A mm 2 and an average cross-sectional area of the relieving layer is B mm 2 , and a method for producing the spark plug.

First claim

Having described the invention, the following is claimed:

1. A spark plug comprising:
a center electrode;
a ground electrode disposed opposite to the center electrode with a gap therebetween; and
a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, wherein
the tip has a discharge layer and a relieving layer,
the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer,
the diffusion layer has a gradient composition in which a Pt content increases and/or a Ni content decreases from the ground electrode side toward the relieving layer side,
the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined,
the clad diffusion layer has a gradient composition in which a Pt content increases and/or a Ni content decreases from the relieving layer side toward the discharge layer side,
0.81≦A/B≦1.21 is satisfied when an average cross-sectional area of a plurality of cross-sections of the discharge layer obtained when the discharge layer is cut along planes parallel to the opposed surface is A mm 2 and an average cross-sectional area of a plurality of cross-sections of the relieving layer obtained when the relieving layer is cut along planes parallel to the opposed surface is B mm 2 , and
C>D is satisfied when a thickness of the clad diffusion layer is C μm and a thickness of the diffusion layer is D μm.

2. A spark plug according to claim 1 , wherein the discharge layer has a total content of Pt and Rh of not less than 90 mass %.

3. A spark plug according to claim 1 , wherein the discharge layer has a total content of Pt and Rh of not less than 90 mass %.

4. A method for producing a spark plug having a center electrode;
a ground electrode disposed opposite to the center electrode with a gap therebetween; and
a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, wherein
the tip has a discharge layer and a relieving layer,
the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer,
the diffusion layer has a gradient composition in which a Pt content increases and/or a Ni content decreases from the ground electrode side toward the relieving layer side,
the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined,
the clad diffusion layer has a gradient composition in which a Pt content increases and/or a Ni content decreases from the relieving layer side toward the discharge layer side,
0.81≦A/B≦1.21 is satisfied when an average cross-sectional area of a plurality of cross-sections of the discharge layer obtained when the discharge layer is cut along planes parallel to the opposed surface is A mm 2 and an average cross-sectional area of a plurality of cross-sections of the relieving layer obtained when the relieving layer is cut along planes parallel to the opposed surface is B mm 2 , and
C>D is satisfied when a thickness of the clad diffusion layer is C μm and a thickness of the diffusion layer is D μm;
the method comprising:
joining the relieving layer and the opposed surface to each other by means of solid phase diffusion joining after the discharge layer and the relieving layer are joined to each other by means of solid phase diffusion joining to form the tip.

5. A method for producing a spark plug according to claim 4 , wherein the discharge layer has a total content of Pt and Rh of not less than 90 mass %.

Assignees

• Ngk Spark Plug Co

Inventors

• Gozawa Tatsuya
• Sumoyama Daisuke
• Shibata Tsutomu

Classifications

• H01T21/02 Primary

  of sparking plugs · CPC title

• H01T13/39

  Selection of materials for electrodes · CPC title

• H01T13/32 Primary

  characterised by features of the earthed electrode · CPC title