DIRECT INJECTION DIESEL ENGINES

• US 20130036998A1
• Filed: 01/26/2011
• Published: 02/14/2013
• Est. Priority Date: 01/29/2010
• Status: Active Grant

• Current Assignee: Ricardo UK Limited (Ricardo PLC)
• Original Assignee: Ricardo UK Limited (Ricardo PLC)
• Inventors: Conicella, Fabrizio, Cornwell, Richard
• Granted Patent: US 8,770,168 B2
• Time in Patent Office: Days
• US Class Current: 123/193.6
• CPC Class Codes: F02B 2275/14 Direct injection into combustion chamber
• CPC Class Codes: F02B 23/0669 having multiple fuel spray jets per injector nozzle
• CPC Class Codes: F02B 23/0672 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 Class Codes: F02B 23/0693 the combustion space consisting of step-wise widened multiple zones of different depth
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A piston for a four valve direct injection diesel engine defines a combustion chamber comprising a recess (10) in the piston crown, which is rotationally symmetrical about the axis of the piston in axial cross-section and is defined by a base and a side wall. A generally conical projection (5) is upstanding from the base. The recess (10) includes a lower toroidal portion (8) and an upper portion (10), whose diameter progressively increases towards the piston crown. The upper and lower portions of the recess are separated by an annular, arcuate lip (12) extending into the recess. The included angle of the conical projection (5) is between 104° and 108°, the maximum depth of the recess (10) is between 13% and 22% of the diameter of the piston, the conical projection (5) merges with the base of the recess along a circular line whose diameter is between 38% and 44% of the diameter of the piston, the diameter of the lip (12) is between 54% and 59% of the diameter of the piston, the line of minimum diameter of the lip (12) is situated at a distance between 5% and 10% of the diameter of the piston from the plane of the piston crown and the diameter of the upper portion (10) of the recess increases from 54% to 59% of the diameter of the piston at the line of minimum diameter of the lip to between 72% and 76% of the diameter of the piston at the line where the side wall of the recess intersects the plane of the piston crown.

Claims

1. A piston for a four valve direct injection diesel engine, the piston defining a combustion chamber comprising:

a recess formed in a piston crown, the recess being rotationally symmetrical about an axis of the piston in axial cross-section and defined by a base and a side wall,

a substantially conical or frusto-conical projection upstanding from the base, the recess including a lower toroidal portion furthest from the piston crown and an upper portion closest to the piston crown whose diameter progressively increases towards the piston crown,

the upper and lower portions being separated by an annular lip of arcuate shape in axial cross-section extending into the recess,

an included angle of the conical or frusto-conical projection between 104° and

108°

,

the maximum depth of the recess from the base to a plane of the piston crown between 13 and 22% of the a diameter of the piston,

the substantially conical or frusto-conical projection merging with the base along a circular line whose diameter is between 38 and 44% of the diameter of the piston,

a diameter of the annular lip between 54 and 59% of the diameter of the piston,

a line of minimum diameter of the annular lip situated at a distance of between 5 and 10% of the diameter of the piston from the plane of the piston crown, and

a diameter of the upper portion of the recess increasing from 54 to 59% of the diameter of the piston at the line of minimum diameter of the annular lip to between 72 and 76% of the diameter of the piston at the line,

the side wall of the recess intersecting the plane of the piston crown.

2. The piston as claimed in claim 1, wherein the included angle of the substantially conical or frusto-conical projection is substantially 106°

.

3. The piston as claimed in claim 1, wherein a portion of the side wall which defines the upper portion of the recess is concave in axial cross-section.

4. A direct injection diesel engine including:

a cylinder block defining at least one cylinder which is closed by a cylinder head and reciprocably receives a respective piston, the piston including;

a recess formed in a piston crown, the recess being rotationally symmetrical about an axis of the piston in axial cross-section and defined by a base and a side wall,

a substantially conical or frusto-conical projection upstanding from the base, the recess including a lower toroidal portion furthest from the piston crown and an upper portion closest to the piston crown whose diameter progressively increases towards the piston crown,

the upper and lower portions being separated by an annular lip of arcuate shape in axial cross-section extending into the recess,

an included angle of the conical or frusto-conical projection between 104° and

108°

,

the maximum depth of the recess from the base to a plane of the piston crown between 13 and 22% of a diameter of the piston,

the substantially conical or frusto-conical projection merging with the base along a circular line whose diameter is between 38 and 44% of the diameter of the piston,

a diameter of the annular lip between 54 and 59% of the diameter of the piston,

a line of minimum diameter of the annular lip situated at a distance of between 5 and 10% of the diameter of the piston from the plane of the piston crown, and

a diameter of the upper portion of the recess increasing from 54 to 59% of the diameter of the piston at the line of minimum diameter of the annular lip to between 72 and 76% of the diameter of the piston at the line,

the side wall of the recess intersecting the plane of the piston crown,

wherein the cylinder is configured to communicate with two inlet valves and two exhaust valves in the cylinder head,

wherein the inlet valves are arranged to induce swirl of the inflowing air in the cylinder substantially about the cylinder axis,

wherein the cylinder head includes a fuel injector which is situated substantially on the cylinder axis and includes a plurality of fuel injection orifices,

wherein the orifices are arranged so that the fuel jets through them extend at an angle which diverges from the surface of the projection by 15 to 19°

,

wherein the fuel jets impinge firstly on the arcuate side wall of the lower portion of the recess.