Combustion chamber structure for engine
A combustion chamber structure for an engine includes a combustion chamber that is defined by a cylinder block, a cylinder head, and a piston. The cylinder head includes: a head body that has a lower surface opposing the combustion chamber; and a coat layer that covers the lower surface. The coat layer includes: a heat-insulating layer that is arranged in a region, which opposes a cavity, in the lower surface and has a lower thermal conductivity than the head body; a heat-shielding layer that is arranged to cover the lower surface and has a lower thermal conductivity than the head body and the heat-insulating layer; and a heat diffusion layer that is arranged between the heat-insulating layer and the heat-shielding layer and has a higher thermal conductivity. The heat diffusion layer includes a side end edge and an extending portion, each of which abuts the head body.
1. A combustion chamber structure for an engine, comprising:
a combustion chamber that is defined by a cylinder block, a cylinder head, and a piston, wherein
the cylinder head includes:
a head body that has a lower surface opposing the combustion chamber;
a heat-insulating layer that is arranged on the lower surface and has a lower thermal conductivity than the head body;
a heat-shielding layer that is arranged to cover the lower surface and has a lower thermal conductivity than the head body and the heat-insulating layer; and
a heat diffusion layer that is arranged between the heat-insulating layer and the heat-shielding layer and has a higher thermal conductivity than the heat-insulating layer and the heat-shielding layer, and
the heat diffusion layer includes an abutment portion that abuts the head body.
2. The combustion chamber structure for the engine according to claim 1 , wherein
the heat-insulating layer is arranged in a part of a radially-center region of the lower surface.
3. The combustion chamber structure for the engine according to claim 2 , wherein
the heat diffusion layer includes an extending portion that extends toward a radially outer side of an outer peripheral edge of the heat-insulating layer and/or toward a radially inner side of an inner peripheral edge of the heat-insulating layer, and the extending portion is the abutment portion that abuts the head body.
4. The combustion chamber structure for the engine according to claim 3 , wherein
in a radially-center region of an upper surface, the piston includes a cavity that is dented downward in a cylinder-axis direction, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the cavity.
5. The combustion chamber structure for the engine according to claim 4 , wherein
the cavity includes:
a bottom surface that is formed with the most dented portion in the cylinder-axis direction;
a raised surface that is raised radially outward and upward from the bottom surface; and
a peripheral edge portion that is an upper end edge of the raised surface, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the raised surface and the peripheral edge portion.
6. The combustion chamber structure for the engine according to claim 5 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
7. The combustion chamber structure for the engine according to claim 4 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
8. The combustion chamber structure for the engine according to claim 3 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
9. The combustion chamber structure for the engine according to claim 2 , wherein
in a radially-center region of an upper surface, the piston includes a cavity that is dented downward in a cylinder-axis direction, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the cavity.
10. The combustion chamber structure for the engine according to claim 9 , wherein
the cavity includes:
a bottom surface that is formed with the most dented portion in the cylinder-axis direction;
a raised surface that is raised radially outward and upward from the bottom surface; and
a peripheral edge portion that is an upper end edge of the raised surface, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the raised surface and the peripheral edge portion.
11. The combustion chamber structure for the engine according to claim 2 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
12. The combustion chamber structure for the engine according to claim 1 , wherein
the heat diffusion layer includes an extending portion that extends toward a radially outer side of an outer peripheral edge of the heat-insulating layer and/or toward a radially inner side of an inner peripheral edge of the heat-insulating layer, and the extending portion is the abutment portion that abuts the head body.
13. The combustion chamber structure for the engine according to claim 12 , wherein
in a radially-center region of an upper surface, the piston includes a cavity that is dented downward in a cylinder-axis direction, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the cavity.
14. The combustion chamber structure for the engine according to claim 13 , wherein
the cavity includes:
a bottom surface that is formed with the most dented portion in the cylinder-axis direction;
a raised surface that is raised radially outward and upward from the bottom surface; and
a peripheral edge portion that is an upper end edge of the raised surface, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the raised surface and the peripheral edge portion.
15. The combustion chamber structure for the engine according to claim 12 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
16. The combustion chamber structure for the engine according to claim 1 , wherein
in a radially-center region of an upper surface, the piston includes a cavity that is dented downward in a cylinder-axis direction, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the cavity.
17. The combustion chamber structure for the engine according to claim 16 , wherein
the cavity includes:
a bottom surface that is formed with the most dented portion in the cylinder-axis direction;
a raised surface that is raised radially outward and upward from the bottom surface; and
a peripheral edge portion that is an upper end edge of the raised surface, and
in the lower surface of the head body, the heat-insulating layer and the heat diffusion layer are arranged in a region that opposes the raised surface and the peripheral edge portion.
18. The combustion chamber structure for the engine according to claim 16 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
19. The combustion chamber structure for the engine according to claim 1 , wherein
outer peripheral edges of the heat-insulating layer and the heat diffusion layer extend to an outer peripheral edge of the combustion chamber or a portion near the outer peripheral edge of the combustion chamber.
20. The combustion chamber structure for the engine according to claim 1 , wherein
the heat-insulating layer is composed of a ceramic material,
the heat-shielding layer is composed of a heat-resistant silicone resin, and
the heat diffusion layer is composed of a copper-based material, a Corson alloy, beryllium copper, a fiber-reinforced aluminum alloy, or a titanium aluminum.