# US 10,770,868 B1 · Spark plug that suppresses pre-ignition and misfires

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- Number: US 10,770,868 B1
- Document ID: US10770868B1
- Status: Granted
- Kind: B1
- Application number: 16/841,991
- Filed: 2020-04-07
- Granted: 2020-09-08
- Earliest claimed: 2019-05-07
- Assignees: Ngk Spark Plug Co., Ltd.
- Applicants: Ngk Spark Plug Co., Ltd.
- Inventors: Tatsuya Gozawa
- Web page: https://patentgrep.com/patent/US10770868B1

## CPC

- H01T 13/20: characterised by features of the electrodes or insulation
- F02B 19/12: with positive ignition (engines with non-timed positive ignition, and with incandescent chambers F02B9/08)
- F02B 19/18: Transfer passages between chamber and cylinder
- F02P 13/00: Sparking plugs structurally combined with other parts of internal-combustion engines ({connection of ignition coil to spark plug connector F02P3/02;} with fuel injectors F02M57/06 {; spark plug connector per se H01T13/04 – H01T13/06; predominant aspects of sparking plug, see H01T13/40 – H01T13/44})
- F02P 15/00: Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 {and combined with layout of ignition circuits (not combined F02B, F02C, F02G, F02K)}
- H01T 13/54: having electrodes arranged in a partly-enclosed ignition chamber
- H01T 13/34: characterised by the mounting of electrodes in insulation, e.g. by embedding
- Y02T 10/12: Improving ICE efficiencies
- 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)
- F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G)
- F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A spark plug wherein both pre-ignition and misfires are suppressed. The spark plug includes a center electrode; a ground electrode; a cylindrical insulator; a metal shell that accommodates the insulator therein; and a cover portion that covers a front end portion of the center electrode and a facing portion of the ground electrode to form a pre-chamber. The insulator includes an outer peripheral surface exposed to the pre-chamber, the cover portion includes a portion exposed to the pre-chamber, and the metal shell includes a portion exposed to the pre-chamber. When a surface area of the outer peripheral surface is a first surface area A (mm2), and a total surface area of the portion of the cover portion and the portion of the metal shell is a second surface area B (mm2), the spark plug satisfies a relational expression 1:0.10<A/B<0.70.

## Claims

### Claim 1

A spark plug comprising:
a center electrode:
a ground electrode that includes a facing portion facing a front end portion of the center electrode and forms a discharge gap between the facing portion and the front end portion of the center electrode;
a cylindrical insulator that accommodates the center electrode therein with the front end portion of the center electrode being exposed from a front end of the insulator;
a metal shell that accommodates the insulator therein; and
a cover portion that covers, from a front end side of the spark plug, the front end portion of the center electrode and the facing portion of the ground electrode to form a pre-chamber,
the cover portion including an injection hole that is a through hole,
wherein the insulator includes an outer peripheral surface that is exposed to the pre-chamber,
the cover portion includes a portion that is exposed to the pre-chamber,
the metal shell includes a portion that is exposed to the pre-chamber, and
wherein when a surface area of the outer peripheral surface of the insulator is a first surface area A (mm2), and a total surface area of the portion of the cover portion and the portion of the metal shell is a second surface area B (mm2), a relational expression 1 below is satisfied:
0.10<A/B<0.70.

### Claim 2 (depends on 1)

The spark plug according to claim 1, wherein when a volume of the pre-chamber is a pre-chamber volume C (mm3), a relational expression 2 below is satisfied:
0.50<C/B<2.10.

### Claim 3 (depends on 1)

The spark plug according to claim 1, wherein a relational expression 3 below is satisfied:
0.15<A/B<0.55.

### Claim 4 (depends on 2)

The spark plug according to claim 2, wherein a relational expression 4 below is satisfied:
0.80<C/B<1.90.

### Claim 5 (depends on 4)

The spark plug according to claim 4, wherein a relational expression 5 below is satisfied:
1.10<C/B<1.80.

### Claim 6 (depends on 2)

The spark plug according to claim 2, wherein a relational expression 3 below is satisfied:
0.15<A/B<0.55.