Internal combustion engine and method of producing same
An internal combustion engine in which an anodic oxidation coating film is formed on all or a portion of a wall that faces a combustion chamber, wherein the anodic oxidation coating film has a structure that is provided with a bonding region in which each of hollow cells forming the coating film is bonded to the adjacent hollow cells, and a nonbonding region in which three or more adjacent hollow cells are not bonded to each other, and wherein a porosity of the anodic oxidation coating film is determined by a first void present in the hollow cell and a second void that forms the nonbonding region.
1. An internal combustion engine, comprising:
an anodic oxidation coating film formed on all or a portion of a wall facing a combustion chamber of the internal combustion engine, the anodic oxidation coating film having a structure provided with a bonding region and a nonbonding region, each of hollow cells forming the coating film in the bonding region being bonded to the adjacent hollow cells, and three or more adjacent hollow cells in the nonbonding region being not bonded to each other, and
a porosity of the anodic oxidation coating film in the anode oxidation coating film being determined by a first void present in the hollow cell and a second void forming the nonbonding region.
2. The internal combustion engine according to claim 1 , wherein the thickness of the anodic oxidation coating film is in the range from 100 to 500 μm.
3. The internal combustion engine according to claim 1 , wherein the porosity is in the range from 15 to 40%.
4. The internal combustion engine according to claim 1 , wherein the ratio φ/d, where φ is an average pore diameter of the first void present in the hollow cell and d is an average cell diameter of the hollow cell, is in the range from 0.3 to 0.6.
5. The internal combustion engine according to claim 1 , wherein the surface of the anodic oxidation coating film has been subjected to a sealing treatment with boiling water or steam or to a coating treatment with a thin film that lacks pores or to both treatments.
6. The internal combustion engine according to claim 5 , wherein the thin film comprises an inorganic sealant.
7. The internal combustion engine according to claim 1 , wherein the anodic oxidation coating film is an alumite coating film.
8. The internal combustion engine according to claim 7 , wherein the microVickers hardness of the anodic oxidation coating film is in the range from 110 to 400 HV0.025.
9. A method of producing an internal combustion engine by forming an anodic oxidation coating film on all or a portion of a wall facing a combustion chamber in the internal combustion engine, comprising:
forming an anode by immersing all or a portion of the wall in an acidic electrolytic bath, forming a cathode within the acidic electrolytic bath, and then applying between the two electrodes a voltage adjusted to the range of 130 to 200 V for the maximum, and performing electrolysis at a heat removal rate adjusted to the range from 1.6 to 2.4 cal/s/cm 2 ; and
producing, on the surface of all or a portion of the wall, an anodic oxidation coating film having a structure provided with a bonding region and a nonbonding region, each of hollow cells in the bonding region being bonded to the adjacent hollow cells, and three or more adjacent hollow cells in the nonbonding region being not bonded to each other.
10. The method of producing an internal combustion engine according to claim 9 , further comprising:
a first step of forming an intermediate of the anodic oxidation coating film; and
a second step of adjusting a porosity determined by a first void present in the hollow cell and a second void forming the nonbonding region, by widening voids of the intermediate of the anodic oxidation coating film by carrying out a pore widening treatment using acid on all or a portion of the wall provided on the surface of the intermediate of the anodic oxidation coating film.
11. The method of producing an internal combustion engine according to claim 9 , wherein the temperature of the acidic electrolyte is adjusted to the range from −5 to 5° C.
12. The method of producing an internal combustion engine according to claim 9 , wherein the thickness of the anodic oxidation coating film is adjusted to the range from 100 to 500 μm.
13. The method of producing an internal combustion engine according to claim 9 , further comprising:
a step of performing, after the formation of the anodic oxidation coating film, a sealing treatment with boiling water or steam or a coating treatment with a thin film that lacks pores or both treatments.
14. The method of producing an internal combustion engine according to claim 13 , characterized in that the thin film comprises an inorganic sealant.
15. The method of producing an internal combustion engine according to claim 9 , wherein the anodic oxidation coating film is an alumite coating film.