JP3206332B2 - Member constituting combustion chamber of internal combustion engine and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member constituting a combustion chamber of an internal combustion engine to which deposits are unlikely to adhere, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Deposits adhere to the wall of a combustion chamber of an internal combustion engine when used for a long period of time. This deposit wears the cylinder liner, resulting in oil leakage and increased oil consumption. Further, the soot is seized on the wall surface of the combustion chamber, and the fuel becomes wet and adheres thereto. As a result, the amount of emission of unburned hydrocarbons and soot increases.

[0003] The cause of the deposit is that fuel adheres to the inside of the combustion chamber of the internal combustion engine, and the fuel is carbonized by incomplete combustion. Therefore, in order to prevent the fuel from adhering, it has been proposed to form a coating layer made of a specific ceramic material (JP-A-4-124443).
issue).

[0004]

The ceramic material used for the above-mentioned coating layer is silicon carbide or silicon nitride, which is generally known. Such conventionally known ceramic materials merely have water repellency and are insufficient in suppressing the deposition of deposits. Further, the coating layer made of this ceramic material is not sufficient in terms of resistance in the environment of a combustion chamber of an internal combustion engine.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a member constituting a combustion chamber of an internal combustion engine having a coating layer that reduces the adhesion of a deposit and effectively exerts a function of suppressing the accumulation of a deposit. .

[0006]

According to the present invention, an oxide gel is formed on a surface of a member constituting a combustion chamber of an internal combustion engine by using a metal alkoxide.
Subsequently, a method for producing a member constituting a combustion chamber of an internal combustion engine, which is provided with a ceramic coating layer containing a lithium element on the surface, which is characterized by applying a lithium alkoxide and calcining, is provided.

Further, according to the present invention, there is provided an internal combustion having a coating layer formed on a surface thereof by a sol-gel method from an alkoxide containing at least an alkoxide having an amino group and a metal alkoxide having a fluoroalkyl group. A member that constitutes a combustion chamber of an engine is provided.

Further, according to the present invention, a surface is provided with a coating layer formed by a sol-gel method from a metal alkoxide having a branched skeleton structure in which a part of an alkoxyl group is substituted by a fluoroalkyl group. There is provided a member constituting a combustion chamber of an internal combustion engine, characterized in that:

[0009]

According to the first aspect of the present invention, the lithium element exists as lithium ions in the ceramic coating layer. If the deposit adheres to the metal member,
Bonds are often formed by hydrogen bonds, and lithium ions cut off the hydrogen bonds. Therefore, by providing a ceramic coating layer containing a lithium element on a metal member, adhesion and deposition of the deposit on the member can be suppressed. Therefore, according to this method, more lithium element can be distributed on the surface of the ceramic coating layer, and the member having the ceramic coating layer formed by this method has a high effect of suppressing the deposition and deposition of the deposit.

According to the second aspect of the present invention, as the alkoxide constituting the coating layer, an alkoxide having a fluoroalkyl group-substituted alkoxide having a low affinity for an organic deposit and an alkoxide having an amino group having a high affinity for the deposit are used. By forming a coating film using the alkoxide having such a structure, the obtained coating film locally has a portion having a high affinity for the deposit on a surface having a low affinity for the deposit, and as a result, In addition, the adhesion of the deposit is suppressed as compared with the case where the entire surface has low affinity.

According to the third aspect of the present invention, as the alkoxide constituting the coating layer, a fluoroalkyl group-substituted alkoxide having a low affinity for an organic deposit is used. Used. By using such an alkoxide, a decrease in water repellency due to heating can be suppressed, and the heat resistance of the coating film can be increased.

[0012]

Supplementary explanation of means for solving the problem The ceramic coating layer containing lithium element is formed by using a so-called sol-gel method. The sol-gel method is a method in which an organic or inorganic compound of a metal is made into a solution, a hydrolysis / polycondensation reaction of the compound proceeds in the solution to solidify the sol as a gel, and an oxide solid is produced by heating the gel. is there. In the present invention, metal alkoxide and lithium alkoxide are used as raw materials.

The metal alkoxide is represented by the following formula M (OR) _n , wherein M is a metal, R is alkyl, and n is the oxidation number of the metal M. Various metals can be used as the metal M, and a metal corresponding to a target metal oxide is used. Examples of metals include, but are not limited to, Na, Cu, Ca, Sr, B
a, Zn, B, Al, Ga, Y, Si, Ge, Pb,
P, Sb, V, Ta, W, La, Nd and the like can be mentioned. As the alkyl, methyl, ethyl, propyl, butyl and the like can be used. Therefore, as metal alkoxides, NaOCH ₃ , Cu (OCH ₃ ) ₂ , Ca (OCH ₃ ) ₂ ,
Sr (OCH ₃ ) ₂ , Ba (OCH ₃ ) ₂ , Zn (OCH ₃ ) ₂ , B (OCH ₃ ) ₃ , Al (i-
OC ₃ H ₇ ) ₃ , Ga (OC ₂ H ₅ ) ₃ , Y (OC ₄ H ₉ ) ₃ , Si (OC ₂ H ₅ ) ₄ , Ge (OC _{2
H 5) 4, Pb (OC} 4 H 9) 3, PO (OCH 3) 3, Sb (OC 2 H 5) 3, VO (OC
_{2 H 5) 3, Ta (} OC 3 H 7) 5, W (OC 2 H 5) 6, La (OC 3 H 7) 3, Nd ((OC 2
H ₅ ) ₃ is exemplified.

The lithium alkoxide is not particularly limited. For example, LiOCH ₃ , LiOC ₂ H ₅ , LiOC ₃ H ₇ , LiOC ₄ H ₉
, Etc. are exemplified.

Water (for hydrolysis), alcohol (for preparing a homogeneous solution), acid or base (catalysis) is added to these metal alkoxides to prepare a solution. As the alcohol, for example, methanol, ethanol, propanol, butanol and the like are used. Examples of the acid used as the catalyst include hydrochloric acid, sulfuric acid, acetic acid, and hydrofluoric acid.
As the base, ammonia that can be removed by volatilization after the treatment is used. Further, a known additive such as acetylacetone may be added to the solution in the sol-gel method.

The metal alkoxide solution thus produced is applied to members constituting a combustion chamber of an internal combustion engine made of an iron or aluminum alloy, that is, a piston, a cylinder head, a suction valve head, and the like. As the coating method, a known coating method such as dipping, spin coating, spraying or the like can be used. The thickness of the coating film is not particularly limited, and is usually
It is 50-1000 nm. After this application, the applied film is dried and fired to obtain a ceramic coating film containing a lithium element.

Although the lithium element is uniformly dispersed in the ceramic coating film obtained by the above-described method, in order to enhance the effect of lithium ions for cutting the hydrogen bond between the deposit and the member, It is preferable that more lithium is present on the surface of the ceramic coating layer. Therefore, first, an oxide gel is formed on the surface of the metal member constituting the combustion chamber using various metal alkoxides, and then a solvent (eg, methanol) solution of lithium alkoxide is applied on the oxide gel and fired. Thereby, lithium can be effectively arranged on the surface of the ceramic coating film.

Amine generally has high affinity for organic substances and easily binds. Therefore, when a coating film is formed using a metal alkoxide having an amino group, the coating film has a high affinity for an organic deposit, and the deposit easily adheres to the coating film. On the other hand, fluoroalkyl groups have low affinity for deposits, and therefore, it has been conventionally performed to form coatings having high water repellency using alkoxides substituted by the fluoroalkyl groups. The present inventor has found that when a coating film is formed by mixing a fluoroalkyl group-substituted alkoxide having a low affinity for the deposit with an amine group-containing alkoxide having a high affinity for the deposit, the liposome having the parent deposit part locally is formed. A deposit coating film was obtained, and it was found that this coating film was able to suppress the adhesion of the deposit more than a coating film consisting only of the component of the sparse deposit. Examples of the alkoxide having an amino group used herein include an aminoalkylsilane represented by the following formula (RO) ₃ Si (CH ₂ ) _m NH ₂ . In the above formula, R is alkyl having 1 to 5 carbon atoms, and m is preferably 3 to 5. Further, the fluoroalkyl group-substituted alkoxide is obtained by substituting a part of the alkoxyl group with the fluoroalkyl group in the metal alkoxide. In the production of the coating film, the amount of the amino group-containing alkoxide to be mixed is preferably 30 mol% with respect to 70 mol% of the fluoroalkyl group-substituted alkoxide.

Although an amino group-containing alkoxide is used as a substance having a high affinity for the deposit, it is considered that a substance having a high affinity for the deposit can be used in addition to the amino group. Examples of such substances include phenyl group-containing alkoxides and alkoxides having etheric oxygen.

The alkoxide having a branched structure is represented by the following formula:

Embedded image The fluoroalkylsilane represented by these is illustrated. In the above formula, R is alkyl having 1 to 3 carbons, and n is 3 to 10. If n is less than 3, the initial contact angle of the obtained coating film is undesirably too small. If n exceeds 10, the heat resistance during isothermal heating will decrease.

[0021]

EXAMPLE 1 160 g of tetraethoxysilane, 426.5 g of ethanol, and 50 g of acetylacetone were placed in a 1-liter beaker, and then placed in a beaker.
Stir and mix for minutes. Then 83 g of water and 0.1 N
An aqueous hydrochloric acid solution was added, and the mixture was stirred and mixed for 2 hours. The mixture was transferred to a sealed container and left at 25 ° C. for 24 hours. Immerse the piston in the solution obtained in this way and pull up at a speed of 30 mm
The piston was pulled up at / min to form a wet coating film of a metal oxide gel on the piston surface. Next, a piston having this coating film was treated with 50 g of ethoxylithium and 426.
5 g, 50 g of acetylacetone, 83 g of water, and a 0.1 N hydrochloric acid aqueous solution were immersed in the liquid, and pulled up at a pulling rate of 30 mm / min to form a wet coating film of lithium alkoxide on the oxide gel. Next, the whole was baked at 250 ° C. for 1 hour to form a coating film of lithium-containing ceramic on the surface having a thickness of 200 nm.

The piston obtained in Example 1 and an untreated piston were subjected to a durability test using a Toyota in-line four-cylinder gasoline engine at a constant rotation speed and a constant load at which deposits were observed up to 1000 hours. Then, the thickness of the deposit on the top surface of the piston was measured. The result is shown in FIG. From this figure, the piston produced in Example 1 it is clear that significantly less deposition thickness of the deposit as compared to the piston untreated.

Example 2 30 mol of ethanol, 0.9 mol of tetraethoxysilane, (0.1-x) mol of fluoroalkylsilane (CF ₃ (CF ₂ ) ₇
After mixing C ₂ H ₄ Si (OCH ₃ ) ₃ ) and 10 mol of water to produce a homogeneous solution, add x mol of aminoalkylsilane ((C _{2
H 5 O) 3 SiC 3 H} 6 NH 2) was added and the solution was obtained and stirred for 5 hours. The piston was immersed in this solution to form a wet coating on the piston top surface. After drying, the coating film was baked at 200 ° C. for 1 hour to form a coating film.

The piston thus manufactured was assembled in an engine and subjected to a 250-hour endurance test in the same manner as described above to measure the thickness of the deposit on the top surface of the piston. The results are shown in Figure 6. The deposit thickness is different depending on the site of the top surface, thus measuring the film thickness of 23 points of the piston top face, showing the maximum and minimum values of the value in FIG. As is clear from this figure, in the case of the fluoroalkylsilane alone, there was a portion where no deposit was deposited, but about 70 μm.
There was also a deposit thickness of about m. on the other hand,
Uncoated pistons with no coating have a deposit on the entire top surface and a thickness of 120-250 μm
It was about. In addition, aminoalkylsilane alone
Deposits between 100 and 220 μm thick were deposited, almost the same as the untreated piston. In the composite system of fluoroalkylsilane and aminoalkylsilane, the deposit thickness is small, and the effect of this composite is recognized. From FIG. 2 , this effect was remarkable in the composite system of 70% fluoroalkylsilane and 30% aminoalkylsilane.

Example 3 29 mol of ethanol, 0.9 mol of tetraethoxysilane, 0.1 mol of fluoroalkylsilane (CF ₃ (CF ₂ ) ₇ C ₂ H ₄
Solution (A) was obtained by mixing Si (OCH ₃ ) ₃ ), 9 mol of water and 0.01 mol of hydrochloric acid. A solution B was obtained in the same manner using CF ₃ (CF ₂ ) ₇ CH (C ₂ H ₅ ) CH ₂ Si (OCH ₃ ) ₃ as the fluoroalkylsilane. These solutions were stirred at room temperature for one day to obtain treatment solutions A and B.

A degreased quartz glass was immersed in these treatment solutions, pulled up at a pulling rate of 60 mm / min to form a wet coating film, dried, and baked at 200 ° C. for 1 hour to form a coating film. . When the contact angle of each coating film was measured, it was about 110 °. The quartz glass having these coating films was placed in a furnace at 350 ° C., heated at an isothermal temperature, and the change in the contact angle was examined. The results are shown in Figure 3. A treatment using a fluoroalkylsilane (CF ₃ (CF ₂ ) ₇ C ₂ H ₄ Si (OCH ₃ ) ₃ ) having the same content of the fluoroalkyl silane in each processing solution but having no branched structure Liquid A
Coating A formed by a treatment liquid B using a fluoroalkylsilane having a branched structure (CF ₃ (CF ₂ ) ₇ CH (C ₂ H ₅ ) CH ₂ Si (OCH ₃ ) ₃ ) In the case of the film B, there was a difference in the decrease in the contact angle due to the isothermal heating at 350 ° C.
In the case of the coating film A, the decrease was smaller than that of the coating film A, and the heat resistance was better.

[0027]

The member constituting the combustion chamber of the internal combustion engine according to the present invention has a novel coating layer on the surface thereof.
As a result, it has a high effect of suppressing the accumulation of deposits, and has characteristics that can sufficiently withstand the environment of the combustion chamber.

[Brief description of the drawings]

FIG. 1 is a graph showing a deposit amount in a durability test of a piston having a coating layer manufactured in Example 1 .

FIG. 2 is a graph showing a deposit amount in a durability test of a piston having a coating film manufactured in Example 2 .

FIG. 3 is a graph showing heat resistance of a coating film manufactured in Example 3 .

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Yokoishi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-61-64887 (JP, A) JP-A-54- 43129 (JP, A) JP-A-55-125343 (JP, A) JP-A-62-240454 (JP, A) JP-A-57-41446 (JP, A) JP-A-4-124443 (JP, A) JP-A-7-246365 (JP, A) JP-A-4-136181 (JP, A) JP-A-64-68477 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 3/00-3/26 C23C 18/00-18/12

Claims (3)

(57) [Claims] 1. A ceramic coating layer containing a lithium element, wherein an oxide gel is formed using metal alkoxide on a surface of a member constituting a combustion chamber of an internal combustion engine, and then lithium alkoxide is applied and fired. A method for producing a member constituting a combustion chamber of an internal combustion engine having a surface thereof. 2. A combustion chamber for an internal combustion engine, comprising a coating layer formed on a surface of an alkoxide containing at least an alkoxide having an amino group and a metal alkoxide having a fluoroalkyl group by a sol-gel method. Constituent members. 3. An internal combustion engine, wherein a coating layer formed by a sol-gel method from a metal alkoxide having a branched skeleton structure in which a part of an alkoxyl group is substituted by a fluoroalkyl group is provided. A member that constitutes the combustion chamber of the engine.