Claims
- 1. A spark plug for use in an internal combustion engine comprising:
- a pair of electrodes, each made of base metal;
- a noble metal tip portion provided on one of said electrodes to define a spark discharge gap between said noble metal tip portion and the other one of said electrodes; and
- recess means formed in a surface of said noble metal tip portion defining said spark discharge gap, and radially extending to divide said noble metal tip portion into a plurality of sections,
- wherein said noble metal tip portion includes a tip layer made of noble metal, and a thermal stress-relieving layer disposed between said noble metal tip layer and said one electrode, and
- wherein said recess means axially extends toward said one electrode.
- 2. A spark plug as in claim 1 wherein said recess means is in a cross shape dividing said noble metal tip layer into four substantially equal portions.
- 3. A spark plug as in claim 1 wherein said recess means is in a substantially Y shape, dividing said noble metal tip portion into three substantially equal portions.
- 4. A spark plug for use in an internal combustion engine comprising:
- a pair of electrodes, each made of base metal;
- a noble metal tip portion provided on one of said electrodes to define spark discharge gap between said noble metal tip portion and the other one of said electrodes; and
- recess means formed in a surface of said noble metal tip portion defining said spark discharge gap, and radially extending to divide said noble metal tip portion into a plurality of sections,
- wherein said noble metal tip portion includes a tip layer made of noble metal, and a thermal stress-relieving layer disposed between said noble metal tip layer and said one electrode,
- wherein said recess means axially extends toward said one electrode, and wherein
- said one of said electrodes is a central electrode and said other one of said electrodes is an earth electrode;
- said noble metal tip portion is flared at an outer periphery thereof against said earth electrode; and
- said recess means extends in a depth direction towards said central electrode and is progressively increased in a width thereof towards said spark discharge gap defining surface of said noble metal tip portion.
- 5. A spark plug as in claim 4 wherein a surface profile of said recess means is cross-shaped.
- 6. A spark plug as in claim 4 wherein a surface profile of said recess means is Y-shaped.
Priority Claims (4)
Number |
Date |
Country |
Kind |
1-343737 |
Dec 1989 |
JPX |
|
1-343738 |
Dec 1989 |
JPX |
|
2-147997 |
Jun 1990 |
JPX |
|
2-310094 |
Nov 1990 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 08/25,385, filed on Mar. 2, 1993, which was abandoned upon the filing hereof which is a CIP of application Ser. No. 07/634,351, filed Dec. 26, 1990, now U.S. Pat. No. 5,202,601.
US Referenced Citations (6)
Foreign Referenced Citations (5)
Number |
Date |
Country |
57-145288 |
Sep 1982 |
JPX |
59-33949 |
Aug 1984 |
JPX |
3225784 |
Oct 1991 |
JPX |
3225783 |
Oct 1991 |
JPX |
2027797 |
Feb 1980 |
GBX |
Continuations (1)
|
Number |
Date |
Country |
Parent |
25385 |
Mar 1993 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
634351 |
Dec 1990 |
|