Combustion chamber structure of engine

Patent metadata

Field	Value
Publication number	US-11092107-B2
Application number	US-201816641758-A
Country	US
Kind code	B2
Filing date	Aug 23, 2018
Priority date	Aug 28, 2017
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

An engine combustion chamber structure includes a combustion chamber of an engine and a fuel injection valve. The fuel injection valve injects fuel toward a cavity in a crown face of a piston. The cavity includes a first cavity provided in a radially central region of the crown face with a first bottom having a first depth, a second cavity provided in an outer side of the first cavity with a second bottom having a second depth being smaller than the first depth, a connecting portion, and a standing wall region disposed further in a radially outer side than the second bottom of the second cavity. The second bottom is provided lower than an upper end, of the connecting portion. A lower section of the standing wall region is provided further in a radially inner side than an upper edge of the standing wall region.

First claim

The invention claimed is:

1. An engine combustion chamber structure comprising:
a combustion chamber of an engine, the combustion chamber being formed by a lower face of a cylinder head, a cylinder, and a crown face of a piston; and
a fuel injection valve that injects fuel into the combustion chamber, wherein
the crown face of the piston is provided with a cavity,
the fuel injection valve injects fuel toward the cavity and is disposed at or near a radial center of the combustion chamber,
the cavity includes
a protruding hill portion provided lust below the fuel injection valve,
a first cavity that is provided in a radially central region of the crown face and includes a first bottom having a first depth from the crown face in a cylinder axial direction and a first inner end provided in a radially innermost of the first cavity and adjoining a lower end of the hill portion, the first inner end and the first bottom connected by a continuously concave curved face gradually becoming lower toward a radially outer side,
a second cavity that is provided in the crown face to be in an outer side of an outer circumference of the first cavity and includes a second bottom having a second depth in the cylinder axial direction, the second depth from the crown face being smaller than the first depth,
a connecting portion that connects the first cavity to the second cavity, and
a standing wall region disposed further in the radially outer side than the second bottom of the second cavity,

the second bottom is provided lower than an upper end, regarding the cylinder axial direction, of the connecting portion, and
a lower section of the standing wall region is provided further in a radially inner side than an upper edge of the standing wall region.

2. The engine combustion chamber structure according to claim 1 , wherein
the first cavity includes, in a cross-section including a cylinder axis,
a first section having an arc shape and located farthermost from the fuel injection valve, a second section provided between the first section and the connecting portion, and a third section extending from the first section toward a radially inner side, and
the second section and the third section each has an arc shape, and a radius of the arc decreases from the second section to the first section and increases from the first section to the third section.

3. The engine combustion chamber structure according to claim 1 , wherein
the fuel injection valve includes an injection hole to inject fuel, and
the injection hole has an injection axis along which fuel is injected toward the connecting portion at a predetermined crank angle.

4. The engine combustion chamber structure according to claim 3 , further comprising
a fuel injection controller that controls fuel injection performed by the fuel injection valve, wherein
the fuel injection controller causes the fuel injection valve to perform at least a main injection performed at a timing when the piston is near a top dead center of compression and a pilot injection at a timing earlier than the timing of the main injection, and
the injection hole has an injection axis along which fuel is injected toward the connecting portion at a crank angle at which the pilot injection is performed.

5. The engine combustion chamber structure according to claim 4 , wherein
the fuel injection controller performs the pilot injection in an operating range where the engine operates under a middle load.

6. The engine combustion chamber structure according to claim 3 , wherein
the cavity includes a tapered region extending from the upper end of the connecting portion to the second bottom of the second cavity, and
the tapered region has a face having an inclination along the injection axis.

7. The engine combustion chamber structure according to claim 3 , further comprising
a fuel injection controller that controls fuel injection performed by the fuel injection valve, wherein
the fuel injection controller performs a pilot injection in an operating range where the engine operates under a middle load.

8. The engine combustion chamber structure according to claim 1 , wherein
the crown face of the piston is provided with an annular flat portion disposed further in the radially outer side than the cavity,
the connecting portion has a convex shape formed of a curved face having a first radius in a cross-section along the cylinder axial direction,
the second cavity has, in the cross-section along the cylinder axial direction, a concave shape formed of a curved face having a second radius in a region between the second bottom and the standing wall region, and a convex shape formed of a curved face having a third radius in a region between the upper edge of the standing wall region and the annular flat portion, and
a sum of the first radius and the second radius is larger than a first distance, and a sum of the second radius and the third radius is set to be equal to or less than a second distance where the first distance is a distance along the cylinder axial direction between a center of the first radius and a center of the second radius and the second distance is a distance along a cylinder radial direction between the center of the second radius and a center of the third radius.

9. The engine combustion chamber structure according to claim 6 , wherein
the tapered region has a face having the same inclination as the inclination of the injection axis from a horizontal line along the radial direction.

Assignees

• Mazda Motor

Inventors

• Kim Sangkyu
• Sumimoto Takashi
• Shimo Daisuke
• Harada Tomonori
• Okada Shintaro
• Takuma Shuji

Classifications

• F02B23/0693

  the combustion space consisting of step-wise widened multiple zones of different depth · CPC title

• F02F3/12

  on piston heads · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title

• F02F3/26

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

• F02D13/0219

  by shifting the phase, i.e. the opening periods of the valves are constant · CPC title