# US 8,770,777 B2 · Spark plug

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- Number: US 8,770,777 B2
- Document ID: US8770777B2
- Status: Granted
- Kind: B2
- Application number: 13/816,567
- Filed: 2011-09-16
- Published: 2013-06-06
- Granted: 2014-07-08
- Earliest claimed: 2010-10-01
- Assignees: Ngk Spark Plug Co., Ltd.
- Applicants: Haruki Yoshida; Toshitaka Honda; Akira Suzuki
- Inventors: Haruki Yoshida; Toshitaka Honda; Akira Suzuki
- Web page: https://patentgrep.com/patent/US8770777B2

## CPC

- H01T 13/02: Details
- H01T 13/05: combined with interference suppressing or shielding means
- H01T 13/20: characterised by features of the electrodes or insulation
- H01T 13/34: characterised by the mounting of electrodes in insulation, e.g. by embedding
- H01T 13/41: with interference suppressing or shielding means
- H01T 21/02: of sparking plugs
- H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H)

## Abstract

A spark plug having excellent load life performance even when the spark plug receives an impact or vibration. The spark plug includes an accommodated portion of a metallic terminal, which is accommodated in an axial hole of an insulator, having a plurality of bent portions formed as a result of proper bending of the accommodated portion. The bent portions are in close vicinity to an inner circumferential surface of the insulator at three or more locations, and are present without localizing in the radial direction of the axial hole.

## Claims

### Claim 1

A spark plug comprising:
an insulator having an axial hole extending in a direction of an axis;
a center electrode held at one end of the axial hole;
a metallic terminal which has an accommodated portion accommodated in the axial hole and which is held at the other end of the insulator; and
a connecting portion which electrically connects the center electrode and the metallic terminal within the axial hole, wherein:
the side of the axial hole where the metallic terminal is held is defined as a rear end side with respect to the direction of the axis;
a connection member which constitutes the connecting portion is provided between an outer circumferential surface of a forward end portion of the accommodated portion and an inner circumferential surface of the insulator; and
in sectional images orthogonal to the axis which are captured at intervals of 0.5 mm from a rear end of the accommodated portion toward a forward end thereof up to a rear end position where the connection member is present,
on a sectional image Sn at the n-th section, n being a natural number, counted from the rear end of the accommodated portion,
a center of the accommodated portion is defined as a point an, a center of the axial hole is defined as a point On, a line which passes through the points an and On is defined as a line Ln, a diameter of the axial hole is represented by 2Rn, a diameter of the accommodated portion is represented by 2rn, a distance between the point an and the point On is represented by Haon, and the point an which satisfies a relation Haon≧0.8(Rn−rn) is defined as a point An,
on the sectional image S1,
a line which is obtained by rotating a line L1 by 45° about the point O1 is defined as a line L1+, a line which is obtained by rotating the line L1 by −95° about the point O1 is defined as a line L1−, four areas which are surrounded by a plane X+ containing the line L1+ and the axis, a plane X− containing the line L1− and the axis, and the inner circumferential surface of the insulator are areas T1, T2, T3, and T4, respectively, and
when successive points Am to A(m+k), m and k being natural numbers, are present in a specific area selected from the areas T1, T2, T3, and T4, a group containing these points Am to A(m+k) is defined as a group Bm,y, where y is a natural number and means that the group is the y-th group counted from the rear end side of the accommodated portion,
wherein the maximum value of y is at least 3, and at least two of the groups Bm,y are present in two areas which are selected from the areas T1 to T4 and which are located at symmetrical positions.

### Claim 2 (depends on 1)

A spark plug according to claim 1, wherein an inter-bend distance D, which is a distance along the direction of the axis between a sectional image containing a point As, which is the first point An counted from the rear end of the accommodated portion, and a sectional image containing a point Ae, which is the last point An counted from the rear end of the accommodated portion, is 5 mm or greater.

### Claim 3 (depends on 1)

A spark plug according to claim 1 wherein the groups Bm,y are present in at least three areas selected from the areas T1 to T4.

### Claim 4 (depends on 1)

A spark plug according to claim 1, wherein the maximum value of y is at least 4.

### Claim 5 (depends on 1)

A spark plug according to claim 1, wherein the groups Bm,y are present in all the areas T1 to T4.

### Claim 6 (depends on 1)

A spark plug according to claim 1, wherein the maximum value of y is at least 5.

### Claim 7 (depends on 1)

A spark plug according to claim 1, wherein an intermediate-diameter portion diameter, which is a diameter of the axial hole at a position where the forward end portion is disposed, is 2.9 mm or less.

### Claim 8 (depends on 1)

A spark plug according to claim 1, wherein the inter-bend distance D is 7 mm or greater.

### Claim 9 (depends on 1)

A spark plug according to claim 1, wherein the inter-bend distance D is 10 mm or greater.