An object of the present invention is to enhance the thermal efficiency of an engine, to provide a film having low thermal conductivity and low heat capacity and being free from separation, drop-off and the like and excellent in durability and reliability. According to the present invention, an engine combustion chamber structure, wherein an anodic oxide film having a thickness of from more than 20 μm to 500 μm and a porosity of 20% or more is formed on the inner surface of the engine combustion chamber, and a manufacturing method thereof are provided.

A piston having a piston crown with a combustion chamber, and a circumferential ring belt extending from the piston crown and having a plurality of ring grooves separated by piston lands. At least one of the piston lands, ring grooves or top surface of the crown is provided with a coating comprising hexagonal boron nitride. The coating can be made solely of hexagonal boron nitride, or can additionally include a resin. The coating can be a single layer coating or a multiple layer coating.

A piston having a piston crown with a combustion chamber, and a circumferential ring belt extending from the piston crown and having a plurality of ring grooves separated by piston lands. At least one of the piston lands, ring grooves or top surface of the crown is provided with a coating comprising hexagonal boron nitride. The coating can be made solely of hexagonal boron nitride, or can additionally include a resin. The coating can be a single layer coating or a multiple layer coating.

A heat insulating layer contains many hollow particles, a silicone-based resin binder, and silica nanoparticle. The percentage of the silica nanoparticles in the total amount of the resin binder and the silica nanoparticles is equal to or greater than 10% by volume and equal to or smaller than 55% by volume.

The present disclosure relates to a piston for an internal combustion engine. The piston comprises a cover which at least partially covers a piston basehead of the piston. A heat-isolating air gap is formed between the cover and the piston basehead, which is fluidically connected to a combustion chamber and/or an upper side of the cover facing away from the heat-isolating air gap. The fluidic connection permits a fluid exchange to take place between the heat-isolating air gap and the combustion chamber. In this way, a pressure gradient can be reduced between the combustion chamber and the heat-isolating air gap. As a result, the cover is/can be kept thin without being deformed during combustion.

A steel piston with an engineered coating is provided. A high thermal conductivity material, for example copper, is disposed on first regions of a combustion bowl to reduce hot spots in the piston. A low thermal conductivity material, for example a ceramic, is disposed on second regions of the combustion bowl to reduce loss of heat through the piston. The high thermal conductivity material disposed on the combustion bowl has a surface roughness (R.sub.a) of less than 5 μm to help reflect IR radiation and promote fuel flow. The low thermal conductivity material disposed on the combustion bowl has a surface roughness (R.sub.a) of less than 3 μm to promote fuel flow. The low thermal conductivity material is also disposed on the bowl rim and top ring land, and has a surface roughness (R.sub.a) of greater than 8 μm on the bowl rim and top ring land to retard gas flow.

A method for coating a piston of an internal combustion engine may include providing the piston, which may include a piston skirt and a piston crown with a fire land. The method may also include producing a ceramic suspension, which may include a solvent, a binder dissolved in the solvent, a plurality of hollow glass spheres distributed in the binder, and a plurality of ceramic particles distributed in the binder. The method may further include applying the ceramic suspension onto the piston and producing a coating on the piston via removing the solvent from the applied ceramic suspension. The coating may have a matrix formed by the binder in which the plurality of hollow glass spheres and the plurality of ceramic particles are arranged in a distributed manner.

A method for coating a piston of an internal combustion engine may include providing the piston, which may include a piston skirt and a piston crown with a fire land. The method may also include producing a ceramic suspension, which may include a solvent, a binder dissolved in the solvent, a plurality of hollow glass spheres distributed in the binder, and a plurality of ceramic particles distributed in the binder. The method may further include applying the ceramic suspension onto the piston and producing a coating on the piston via removing the solvent from the applied ceramic suspension. The coating may have a matrix formed by the binder in which the plurality of hollow glass spheres and the plurality of ceramic particles are arranged in a distributed manner.

A piston for an internal combustion engine may include a piston crown and a heat management coating. The heat management coating may be disposed on at least a region of an outer surface of the piston crown. The heat management coating may include a base layer and a functional layer. The base layer may be disposed between the piston crown and the functional layer, and may be adjoining the outer surface of the piston crown. The base layer may have a base layer matrix including a first polysilazane. The functional layer may have a functional layer matrix including a second polysilazane. The second polysilazane may be different from the first polysilazane.

A piston for an internal combustion engine may include a piston crown and a heat management coating. The heat management coating may be disposed on at least a region of an outer surface of the piston crown. The heat management coating may include a base layer and a functional layer. The base layer may be disposed between the piston crown and the functional layer, and may be adjoining the outer surface of the piston crown. The base layer may have a base layer matrix including a first polysilazane. The functional layer may have a functional layer matrix including a second polysilazane. The second polysilazane may be different from the first polysilazane.