Diesel engine piston and diesel engine

Patent metadata

Field	Value
Publication number	US-11795868-B2
Application number	US-202117798367-A
Country	US
Kind code	B2
Filing date	May 7, 2021
Priority date	May 19, 2020
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

This piston for a diesel engine includes: a bottom portion that has a deepest combustion chamber bottom in the combustion chamber; a circumferential protrusion that is provided around an entire circumference of a circumferential wall between the bottom portion and a top surface of the piston and protrudes toward an intersection (P 0 ) of a center line of the piston and the top surface in a cross-sectional view that includes the center line; an inclination portion that inclines closer to the top surface toward an outer side in a radial direction from the circumferential protrusion; and a rising portion that rises from the inclination portion toward the top surface.

First claim

The invention claimed is:

1. A piston for a diesel engine that has a combustion chamber in which fuel is injected directly from a fuel injection nozzle, comprising:
a bottom portion that has a deepest combustion chamber bottom in the combustion chamber;
a central protrusion which is provided in a center of the piston in a radial direction and protrudes from a side of the bottom portion toward the fuel injection nozzle;
an inner bottom curved portion that connects the bottom portion and the central protrusion and is continuously curved along an entire length in a cross-sectional view,
a circumferential protrusion that is provided around an entire circumference of a circumferential wall between the bottom portion and a top surface of the piston and protrudes toward an intersection P 0 of a center line of the piston and the top surface in the cross-sectional view that includes the center line;
an outer bottom curved portion that connects the bottom portion and the circumferential protrusion and is curved toward an outer side of the combustion chamber with respect to the intersection P 0 in the cross-sectional view,
an inclination portion that inclines closer to the top surface toward an outer side in a radial direction from the circumferential protrusion; and
a rising portion that rises from the inclination portion toward the top surface,
wherein fuel injection from the fuel injection nozzle is performed at a portion of the inclination portion near the circumferential protrusion by lowering the piston,
wherein the fuel injection from the fuel injection nozzle is performed at a portion of the outer bottom curved portion near the circumferential protrusion when the piston is at a top dead point, and
wherein, in the cross-sectional view, when a shortest distance between the center line and the rising portion is L 0 , a distance between an intersection of an extension line of the inclination portion and an extension line of the rising portion and the top surface is H 1 , a shortest distance between the intersection P 0 and the circumferential protrusion is L 1 , and an angle formed between a straight line orthogonal to the center line and the extension line of the inclination portion is A 1 , the following conditions (1) and (2) are satisfied:
when L0 is 100, L0:H1:L1=100:9±5:83±5, and   (1)

20 degrees ≤A1≤40 degrees, and  (2)

wherein, in the cross-sectional view, when a longest distance between the intersection P 0 and the outer bottom curved portion is L 2 , and a distance between the top surface and the combustion chamber bottom is H 0 ,
L 0 :L 2 :H 0 =100:90±5:48±5 is satisfied.

2. The piston for a diesel engine according to claim 1 , wherein, in the cross-sectional view, when an angle formed between a straight line parallel to the center line and the extension line of the rising portion is A 2 , clockwise rotation with respect to the straight line parallel to the center line is a positive angle, and counterclockwise rotation with respect to the straight line parallel to the center line is a negative angle,
−10 degrees ≤A 2 ≤10 degrees is satisfied.

3. The piston for a diesel engine according to claim 1 ,
wherein, in the cross-sectional view, a radius of curvature of the inner bottom curved portion is larger than a radius of curvature of the outer bottom curved portion.

4. The piston for a diesel engine according to claim 3 , wherein, in the cross-sectional view, when a shortest distance between the top surface and the central protrusion is H 2 ,
L 0 :H 2 =100:10±8 is satisfied.

5. The piston for a diesel engine according to claim 1 , wherein, in the cross-sectional view, when a distance between the intersection P 0 and the intersection of the extension line of the inclination portion and the extension line of the rising portion is L 3 ,
L 1 <L 2 <L 3 is satisfied.

6. The piston for a diesel engine according to claim 1 , wherein, when the combustion chamber is divided by a line that connects the intersection P 0 and an apex of the circumferential protrusion in the cross-sectional view, a side of the top surface of the divided combustion chamber is a first combustion chamber, and a side of the bottom portion of the divided combustion chamber is a second combustion chamber,
fuel injection from the fuel injection nozzle is performed toward the second combustion chamber at −15 to 5 degrees after a top dead point, is performed toward the circumferential protrusion at 0 to 15 degrees after a top dead point, and is performed toward the first combustion chamber at 5 to 30 degrees after a top dead point.

7. The piston for a diesel engine according to claim 6 , wherein, when a volume of the first combustion chamber is a first volume V 1 , and a volume of the second combustion chamber is a second volume V 2 ,
45/55≤V 2 /V 1 ≤55/45 is satisfied.

8. The piston for a diesel engine according to claim 1 , wherein an outer diameter of the piston is 90 mm or more.

9. A diesel engine comprising:
a cylinder; and
a piston according to claim 1 which is provided to be movable in an axial direction of the cylinder.

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Onoda Naoki
• Ito Akira
• Shimazu Tomohiro
• Mimura Satoru
• Kuribara Takashi

Classifications

• F02B23/0672 Primary

  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

• F02B23/0651

  the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space · CPC title

• F02B23/0669

  having multiple fuel spray jets per injector nozzle · CPC title

• F02B23/0696 Primary

  W-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 wall · CPC title

• F02F3/26

  having combustion chamber in piston head (the surface thereof being covered F02F3/14) · CPC title