Internal-combustion engines – Combustion chamber – Having coating or liner
Reexamination Certificate
1999-05-27
2001-07-10
Pyon, Harold (Department: 1772)
Internal-combustion engines
Combustion chamber
Having coating or liner
C123S668000, C123S188800, C123S188300, C251S368000, C428S447000, C428S450000, C427S307000, C427S309000, C427S385500, C427S387000, C427S388100
Reexamination Certificate
active
06257217
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to combustion chamber components for internal combustion engines having a water and oil repellent coating and a process for formation of the coating.
With regard to the aforementioned combustion chamber components, cylinder heads, pistons, the valve seat parts of fuel injection valves, etc. can be cited as examples. The reason for these parts to have a water and oil repellant coating is to suppress the accumulation of deposits on their surface due to the oxidation of adhered fuel by making the surfaces resistant to the adhesion of fuel.
With regard to pistons having a water and oil repellant coating, those disclosed in Japanese Patent Application Laid-open No. 8-105352 are known in the art, and with regard to valve seat parts for fuel injection valves having a water and oil repellant coating, those disclosed in Japanese Patent Application Laid-open No. 9-112392 are known.
However, since conventional water and oil repellent coatings are poor in terms of their thermal durability in the thermal environment of the combustion chamber, the effect of suppressing the accumulation of deposits is not well maintained and, in addition, adhesion to the combustion chamber components is inadequate, which is a problem.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide the aforementioned combustion chamber components having a water and oil repellent coating in which the effect of suppressing the accumulation of deposits is well maintained and which has good adhesive power.
In order to achieve the aforementioned objective in accordance with the present invention, a combustion chamber component for an internal combustion engine having a water and oil repellent coating is provided which has a water and oil repellent coating on its surface, the coating being formed from an organosilicon compound represented by the formula Rf—R
1
—Si(NH)
3/2
wherein Rf denotes a perfluoroalkyl group having 1 to 10 carbon atoms and R
1
denotes a divalent hydrocarbon group having 2 to 10 carbon atoms.
The combustion chamber components are formed from, for example, at least one type of material chosen from steel, cast iron, malleable Al alloy and Al casting alloy. Since it is possible to cause chemical bonding between the surface of the combustion chamber components and the organosilicon compound of the invention, the coating of the invention exhibits excellent adhesive power. Furthermore, the coating of the invention has good water and oil repellent properties as well as good thermal durability in the thermal environment of the combustion chamber, thus maintaining the effect of suppressing the accumulation of deposits over long periods.
In the aforementioned general formula Rf corresponds to CF
3
—, C
4
F
9
—, C
8
F
17
—, etc. which may have straight or branched chains. With regard to R
1
, it corresponds, for example, to an alkylene group such as —C
2
H
4
— or —C
3
H
6
— in which the two terminal carbons are joined by single bonds, etc.
Another objective of the present invention is a process in which a water and oil repellent coating can be formed efficiently.
In order to achieve the objective in accordance with the present invention, a process for the formation of a water and oil repellent coating is provided which comprises the following steps:
(1) cleansing the surface of a combustion chamber component for an internal combustion engine using at least one of a washing material and an organic solvent,
(2) maintaining the combustion chamber component at a temperature in the range from 100° C. to 500° C. for about 1 minute or more, and thereafter cooling the combustion chamber component to 50° C. or less and
(3) forming a coating on the surface of the combustion chamber component from an organosilicon compound represented by the formula Rf—R
1
—Si(NH)
3/2
wherein Rf denotes a perfluoroalkyl group having 1 to 10 carbon atoms and R
1
denotes a divalent hydrocarbon group having 2 to 10 carbon atoms.
By carrying out steps (1) and (2), various types of substances such as organic compounds attached to the surface of the combustion chamber component are removed and, furthermore, OH groups are generated on the surface of the combustion chamber component, thus increasing the OH density.
In step (3), the OH groups which are present on the surface of the combustion chamber component at a high density react directly with the organosilicon compound, and thus a coating is formed on the surface of the combustion chamber component which adheres to the surface via chemical bonding. It is possible to enhance the operability by employing an immersion method for the formation of such a coating.
Thus, in accordance with the process of the invention, a water and oil repellent coating can be formed efficiently in a small number of steps.
Since the coating formed by the present process is extremely thin (preferably 10 nm or less), even with the formation of a coating on the combustion chamber components the fit and functioning of, for example, fuel injection valves (e.g., the slidability of operating rods, the ability to seat valve bodies, etc.) is not degraded. Therefore, it becomes unnecessary to mask those parts for which the fit is important during the coating formation, and thus it is effective in terms of increasing the efficiency of the coating.
With regard to the washing materials in process step (1), it does not matter which type of washing material is used as long as the surfaces of the aforementioned parts can be cleansed, but it is preferable to use a detergent, which provides for enhancement of thermal durability and solvent resistance of the coating. With regard to the organic solvents, those which have a strong power to dissolve and are volatile including, for example, alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and hydrocarbon-containing solvents such as toluene, xylene and hexane, etc. can be employed.
In process step (2), when the heating temperature is less than 100° C., the residual washing material and/or organic solvent from the preceding step cannot be completely removed and, furthermore, organic substances which could not be removed in the preceding step cannot be thermally decomposed. On the other hand, when the heating temperature exceeds 500° C., there is a possibility of damaging the physical properties of the materials which are required for the aforementioned parts and causing deformation of their shape. The reason for setting the minimum value for the heating time at about 1 minute or more is that at least approximately 1 minute is required to remove moisture. It is preferable for the heating time to be at least 1 hour. If the temperature to which the aforementioned components are cooled exceeds 50° C., when the aforementioned components are subjected to a treatment at room temperature (about 20° C., the same applies below) with a solution of an organosilicon compound in accordance with the invention, the solution is converted into a foam, which makes it very difficult to form a uniform coating.
An alternative embodiment of the present invention includes a process for the formation of a water and oil repellent coating in which the heating and cooling of the aforementioned step (2) are omitted. This is a simplified process, but the efficiency of formation of the coating is high.
Another embodiment in accordance with the present invention includes a process for the formation of a water and oil repellent coating in which in the aforementioned step (2), the surfaces of the aforementioned parts are pickled instead of employing the aforementioned heating and cooling step.
This pickling step is carried out using an acid, in order to remove the organic substances remaining on the surface of the aforementioned parts and roughen the surface so as to increase the density of the OH groups. With regard to the acid to be used in the pickling step, there are no particular restrictions. Hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, acetic acid, etc. can be cited as examples. There
Hasegawa Masaaki
Hayakawa Hiroyoshi
Kohyama Katsuhiko
Kuki Yoshihiro
Yamazaki Hideharu
Arent Fox Plotkin Kintner Kahn PLLC.
Honda Giken Kogyo Kabushiki Kaisha
Pyon Harold
Tsoy Elena
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