Combustion chamber structure for diesel engine

Patent metadata

Field	Value
Publication number	US-9938887-B2
Application number	US-201415310147-A
Country	US
Kind code	B2
Filing date	May 22, 2014
Priority date	May 22, 2014
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A direct injection diesel engine includes a piston having a reentrant cavity and a multi-hole fuel injection nozzle disposed on a center line of the cavity. The cavity is formed by a lip portion defining a smallest diameter at a position below a piston crown surface and a raised portion formed at a center of the bottom and shaped like a frustum of a cone. A conical surface of the raised portion is formed to have an angle pointing to a spray point of the fuel injection nozzle at a piston top dead center position. The height position of a top surface is substantially equal to the height position of the lip portion. This structure is to promote the oxidation of soot by utilizing the air in the central part of the cavity.

First claim

The invention claimed is:

1. A combustion chamber structure in a diesel engine including a piston having a crown surface formed with a reentrant cavity, and a multi-hole fuel injection nozzle disposed on a center line of the cavity, wherein
a lip portion defining a minimum diameter in an entrance portion of the cavity is located below an opening brim,
a spray center axial line extending from a spray point of the fuel injection nozzle is oriented to point to a position slightly below the lip portion at a position at or near a top dead center,
a height position of a top of a raised portion formed centrally in a bottom of the cavity is set substantially equal to a height position of the lip portion, and
a conical surface of the raised portion is formed at one of an angle pointing to the spray point of the fuel injection nozzle at a piston position at the top dead center, and an angle steeper than the angle pointing to the spray point, to form a region where an excess air rate is highest, on a center line of the raised portion.

2. The combustion chamber structure as claimed in claim 1 , wherein the conical surface is inclined to have the angle pointing to the spray point of the fuel injection nozzle at the piston position of the top dead center.

3. The combustion chamber structure as claimed in claim 1 , wherein a distance from the crown surface of the piston to the lip portion in an axial direction of the piston is greater than or equal to 10 percent and smaller than or equal to 37 percent with respect to a distance from the crown surface of the piston to the bottom of the cavity.

4. The combustion chamber structure as claimed in claim 1 , wherein the fuel injection nozzle includes a first injection hole group pointing to a lower level and a second injection hole group pointing to a higher level higher than the lower level, and
a spray center axial line of the first injection hole group extending from the spray point points to a position below the lip portion at a position at or near the top dead center, and a spray center axial line of the second injection hole group points to a position above the lip portion.

Assignees

• Nissan Motor

Inventors

• Uehara Isshou
• Hasegawa Manabu
• Tsuji Naohide

Classifications

• F02B23/0642

  the depth of the combustion space being much smaller than the diameter of the piston, e.g. the depth being in the order of one tenth of the diameter · CPC title

• F02B23/0672

  Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis (the surrounding wall being exactly vertical F02B23/0696) · CPC title

• F02B23/06 Primary

  the combustion space being arranged in working piston (F02B23/04 takes precedence) · CPC title

• F02B23/0621

  Squish flow · CPC title

• F02B23/0669

  having multiple fuel spray jets per injector nozzle · CPC title