IGNITION SYSTEM

• US 20140174416A1
• Filed: 12/19/2013
• Published: 06/26/2014
• Est. Priority Date: 12/20/2012
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: OKABE, Shinichi, NAKASE, Yoshihiro, SUGIURA, Akimitsu, ABE, Yuya
• Granted Patent: US 9,331,458 B2
• Time in Patent Office: Days
• US Class Current: 123/608
• CPC Class Codes: F02P 9/007 by supplementary electrical discharge in the pre-ionised electrode interspace of the sparking plug, e.g. plasma jet ignition
• CPC Class Codes: H01T 13/20 characterised by features of the electrodes or insulation
• CPC Class Codes: H01T 13/50 having means for ionisation of gap H01T13/52 takes precedence
• CPC Class Codes: H01T 13/52 characterised by a discharge along a surface

Abstract

An ignition system for an internal combustion engine includes a discharge portion of the center electrode in which a part thereof is surrounded by a bottom portion and a tubular tip portion of the center dielectric, the part of the discharge portion and the tubular tip portion are projected into a combustion chamber of the internal combustion engine from a substantially annular tip portion of the ground electrode that opens to the combustion chamber at a distal end of the ground electrode, a diameter-changing portion formed by reducing a diameter of a part of the tubular tip portion in a radial direction gradually as approaching toward a tip thereof, and a thin-walled portion formed by reducing a thickness of the tip of the tubular tip portion.

Claims

1. An ignition system for an internal combustion engine comprising:

a substantially shaft-like center electrode that has a length with a base end and a tip end in both ends thereof;

a substantially bottomed cylindrical center dielectric disposed coaxially with the center electrode;

a substantially cylindrical ground electrode disposed coaxially with the center dielectric with a discharge gap having a predetermined distance therebetween;

a power source that applies a high voltage between the center electrode and the ground electrode;

a discharge portion of the center electrode in which a part thereof is surrounded by a bottom portion of the center dielectric;

a tubular tip portion of the center dielectric;

the part of the discharge portion and the tubular tip portion are projected into a combustion chamber of the internal combustion engine from a substantially annular tip portion of the ground electrode that opens to the combustion chamber at a distal end of the ground electrode;

a diameter-changing portion formed by reducing a diameter of a part of the tubular tip portion in a radial direction gradually as approaching toward a tip thereof; and

a thin-walled portion formed by reducing a thickness of the tip of the tubular tip portion.

2. The ignition system for the internal combustion engine according to claim 1, wherein,

a substantially cylindrical discharge space is formed by a part of an outer peripheral surface of the tubular tip portion, a bottom end formed by enlarging a base end side of the tubular tip portion in a radial direction, and an inner circumferential surface of a tubular portion of the ground electrode;

and

when measured from an inner bottom surface of the bottom end, a length to a distal end of the discharge portion is defined as a discharge portion length L₁₀₀, a length to a distal end of the discharge space is defined as a discharge space length L₁₃₀, and a length to the diameter-changing portion is defined as a thin-walled end position length L₂₀₀, a relationship of L₁₃₀<

L₂₀₀<

L₁₀₀ is satisfied.

3. The ignition system for the internal combustion engine according to claim 1, wherein,

a substantially cylindrical discharge space is formed by a part of an outer peripheral surface of the tubular tip portion, a bottom end formed by enlarging a base end side of the tubular tip portion in a radial direction, and an inner circumferential surface of a tubular portion of the ground electrode;

and

when measured from an inner bottom surface of the bottom end, a length to a distal end of the discharge portion is defined as a discharge portion length L₁₀₀, a length to a distal end of the discharge space is defined as a discharge space length L₁₃₀, and a length to the diameter-changing portion is defined as a thin-walled end position length L₂₀₀, a relationship of 3 mm<

=L₂₀₀<

=10 mm is satisfied.

4. The ignition system for the internal combustion engine according to claim 1, wherein,

when an outer diameter of the tubular tip portion is defined as φ

D₁₁₁, a thickness thereof is defined as T₁₁₁, an outer diameter of the thin-walled portion is defined as φ

D₂₀₀, and a thickness thereof is defined as T₂₀₀, relationships of D₂₀₀<

D₁₁₁ and 0.2T₁₁₁<

T₂₀₀<

0.9T₁₁₁ are satisfied.

5. The ignition system for the internal combustion engine according to claim 1, wherein,

when an outer diameter of the tubular tip portion is defined as φ

D₁₁₁, a thickness thereof is defined as T₁₁₁, an outer diameter of the thin-walled portion is defined as φ

D₂₀₀, and a thickness thereof is defined as T₂₀₀, a relationship of 0.4 mm<

=T₂₀₀<

=1.8 mm is satisfied.

6. The ignition system for the internal combustion engine according to claim 1, wherein,

a frequency of the voltage supplied from the power supply is more than 80 kHz, and less than 850 kHz.

7. The ignition system for the internal combustion engine according to claim 2, wherein,

a volume of the discharge space is 300 mm³ or less.

8. The ignition system for the internal combustion engine according to claim 3, wherein,

a volume of the discharge space is 300 mm³ or less.