JPS6155313A - Combustion chamber wall structure of internal-combustion engine - Google Patents

Abstract

PURPOSE:To surely reduce deleterious chemical products and unburnt fuel elements by fixing a ceramic coating layer on a metallic wall forming an engine combustion chamber and providing an aluminum oxide adhering area with a catalyzer adhering area. CONSTITUTION:A metallic wall forming an engine combustion chamber 11 is provided with a ceramic coating layer 18 which serves as an adiabatic catalytic floor. The at least external layer of the coating layer 18 is composed of ZrO2 layer and an aluminum oxide adhering area formed on the ZrO2 layer. A precious metallic compound solution having less than 300 deg.C of decomposition temperature is impregnated into the ceramic coating layer 18, and then decomposed under superheating after drying to make a catalyzer adhering area. Consequently deleterious chemical products and unburnt elements can be surely reduced for a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a piston forming a combustion chamber of an internal combustion engine;
This invention relates to a combustion chamber wall structure in which a ceramic coating layer serving as a catalyst bed of an oxidation catalyst is formed on a part of a shilling head, an intake/exhaust valve, etc.

(Prior art) As a measure against exhaust emissions from diesel engines, soot and unburned fuel generated during the combustion process are purified within the combustion chamber. Some proposals have been made (for example, Japanese Patent Application Laid-Open No. 59-41624,
(See Utility Model Application Publication No. 58-186126, etc.).

As shown in Fig. 2, an oxidation catalyst coating layer 5 is formed on the crown part of the piston 2 constituting the engine combustion chamber 1, the bottom surface of the sill and throat 3, and the wall surface of the hollow chamber 4. The incompletely combusted products generated during combustion are deposited on the catalyst coating layer 5.
It is designed to oxidize upon contact with.

The catalyst coating layer 5 is an adiabatic catalyst bed (carrier) formed on the surface of the metal part (piston 2) as shown in FIG. 3 to prevent the reaction temperature and conversion efficiency from decreasing due to heat transfer to the gold part. Ceramics such as ZrO2, Al20i
, CaO2 or the like is deposited on the surface of the thermally sprayed coating layer 6 by vacuum deposition or high frequency sputtering.

(Problems to be Solved by the Invention) However, with the conventional combustion chamber wall structure formed in this manner, it is difficult to sufficiently disperse the catalyst material in the surface layer portion of the ceramic coating layer 6. As a result, the surface area that comes into contact with reactants such as soot decreases early, resulting in a durability problem in that the initial performance as a catalyst cannot be maintained over a long period of time. In particular, diesel engines generate a large amount of soot when operating at low to medium speeds and high loads, so when the catalyst coating layer 5 deteriorates, the soot attached to its surface cannot be sufficiently oxidized, and a layer of soot forms on the catalytic reaction surface. formation, resulting in insufficient oxygen supply and further deterioration of conversion efficiency.

This invention was made with the aim of solving such conventional problems.

(Means for solving the problem α) In the present invention, a ceramic coating layer serving as a heat insulating catalyst bed is provided on the metal wall surface constituting the engine combustion chamber, and at least the surface layer of the coating layer is coated with ZrO2 powder. Spray coated Z
It consists of an rO2 layer and an alumina-adhered part formed by impregnating this ZrO2 layer with an alumina-containing solution, drying it, and then decomposing it under heat. nonitronoaminoplatinum,
A solution of one or more metal compounds selected from the group consisting of nitric acid-acidic palladium nitrate or nitric acid-acidic rhodium nitrate was impregnated into the coating layer, dried, and then thermally decomposed to form a catalyst-attached portion.

(Function) According to the above structure, since the catalytic metal material is well dispersed in the porous mm consisting of Zr○2JVI and the alumina adhered portion, it has a surprisingly large surface area, and therefore maintains high activity for a long period of time. .

Further, all of the above metal compound solutions constituting the catalyst-adhered portion decompose at a low temperature of 300° C. or lower. Therefore, in addition to being easy to process, there is no risk that the engine components made of aluminum alloy or the like to be machined will be thermally damaged during the thermal decomposition process.

Examples of the present invention will be described below.

(Example) Fig. mi shows an example in which the present invention is applied to a swirl chamber type diesel engine.

In the figure, 10 is a shilling, 11 is a main combustion chamber, 12 is an aluminum alloy piston, 13 is a shilling head, 14
1 is a swirl chamber, 15 is a nozzle hole that communicates the main combustion chamber 11 and the swirl chamber 14, 16 is an injector, and 17 is a glow plug. 18 is a coating having a ZrO2 sprayed layer and a catalyst deposited part.
With scraps, piston 12, Schilling Rad 1 as shown.
3. It can be formed on each wall surface of the engine combustion chamber, such as the swirl chamber 14.

To explain the process of forming the coating layer 18 which becomes the heat insulating catalyst bed, for example, first, the surface to be coated on the piston crown portion 12 is cleaned and degreased, and then an appropriate surface hardness is imparted by sandblasting. This is an effective treatment for further strengthening the bonding force with the coating material.

Next, preferably, a mixed powder of Ni and Al is sprayed onto the surface to be coated to form a Ni-Al layer, and then ZrO is further applied on top of the Ni-Al layer.
2 powder to form a ZrO2 layer.

Recommended thickness is Ni-Al, I[30~200ttm, Zr
○Two layers: 40 to 600 II Ml.

Thermal spray coating made of a mixture of Ni and Al is compatible with both metals such as aluminum alloys, ceramic materials, and especially ZrO2, and has the effect of increasing the bonding strength of each, so it can be used on metal surfaces that make up the combustion chamber walls. Zr○2N above
Contributes to improved durability. When the object to be coated is an aluminum alloy, the mixing ratio (weight ratio) of Ni and Al is 195% N and 195% Al.
Approximately 5% is appropriate.

Note that as the thickness of each layer constituting the above-mentioned coating layer becomes thicker, the heat insulation effect increases, and therefore, there are benefits such as the ability to further increase the conversion efficiency of the catalyst deposited from the surface. In this case, if the thickness of each layer exceeds a certain level, durability may be impaired due to the temperature difference between the surface cracks of each layer and the increase in internal stress. thermal spraying of powder)rj(
) It is more desirable to provide 30 to 200 knots). Incidentally, it is desirable that this coating layer 18 has a thickness of at least about 100p in order to ensure heat insulation properties.
From the perspective of preventing peeling, a maximum thickness of about 1 m10 is appropriate.

Next, activated alumina is deposited on the II layer or Z ro Jjij. This includes one or more of aluminum nitrate aqueous solution, boehmite alumina sol, or activated alumina mixed boehmite alumina sol6! : After drying, decompose by heating.

Then, this ceramic coated JV118 is impregnated with an aqueous solution of dinitronoaminoplatinum acidified with nitric acid, palladium nitrate acidified with nitric acid, or rhodium nitrate acidified with nitric acid, dried and then thermally decomposed to form a catalyst-attached portion. Since the aqueous solution of the metal compound No. 111 penetrates into the porous coating, the surface area of the catalyst-attached portion becomes extremely large. However, as the water evaporates during the drying process, the metal compound, which is the solute, moves to the surface of the coating layer, so the distribution density of the catalyst is greater in the surface layer, which is more likely to come into contact with the combustion gas.

The layer 18 and the catalyst thus formed on the piston crown portion 12A etc. are used to remove soot particles and unburned fuel in the combustion gas that is ejected from the vortex chamber 14 to the main combustion chamber 11 through the nozzle hole 15 during combustion. oxidizes these on contact with. At this time,
As mentioned above, the surface area of the catalyst is extremely large, and the coating layer 1
Since the catalyst is adhered to the deep layer of the exhaust gas, an efficient oxidation effect can be obtained, and the exhaust purification effect lasts for a long period of time.

Next, a test was conducted to determine the smoke reduction rate when this invention was applied, and the contents and results will be described.

The test was conducted using a 4-air In 2000cc pre-chamber (vortex chamber) type diesel engine, and as a general rule, a coating layer with catalyst was formed only on the piston crown, and the output was 5 fi.
The amount of smoke generated under the operating conditions of 1 kg/2400 rpIll was measured, and the test results showed that the
(The amount of smoke generated is expressed as a percentage compared to the amount of smoke generated by the same type of engine without layers.

In addition, the specifications of the catalytic pistons used in the test are as follows, but before installing them into the 8!1 section, burner flame spraying was carried out. A 100-hour durability treatment was carried out with spraying (spraying alternately with a 1-minute cycle).

Piston A (Example 1) Degrease the crown surface with chloroform and acetone,
After sandblasting, Ni:Al”95:5
(weight ratio, same below) mixed powder, N i:A l:Z
A mixed powder of r○2=33:2:65 and ZrO2 powder were sequentially plasma sprayed to form a coating layer that would become a C catalyst bed. The spraying thickness of each part is Ni Al layer 50ρ, Ni
Al Zroz layer 50ttm1ZrC)zJVi40
It is 0um.

The alumina-adhered area was impregnated with boehmite alumina sol containing 3% by weight as alumina in several parts, dried, heated at 290°C for 2 hours, and finally 0.3 gr
It is coated with alumina.

As a catalyst, the coating layer was impregnated with 5 cc of an aqueous dinitrodiaminoplatinum solution containing 0.02 gr/cc of platinum in 10 doses of 0 and 5 cc each, and dried, and then impregnated with 5 cc of dinitrodiaminoplatinum aqueous solution containing 0.02 gr/cc of platinum in an electric furnace at 250°C. After heating for a period of time, 0.1 gr of platinum was deposited.

Piston B (Example 2) Piston B is the same as Example 1 except that a nitric acidic palladium nitrate aqueous solution was used to form the catalyst adhering portion instead of the nitric acidic dinitrodiaminoplatinum.

Piston C (Example 3) This is the same as Example 1 except that a nitric acidic rhodium nitrate aqueous solution was used to form the catalyst adhering portion instead of the nitric acidic nonitronoaminoplatinum.

Piston D (Example 4) Example 1 except that an aluminum nitrate aqueous solution was used to form the alumina adhered portion instead of the boehmite alumina sol.
It is similar to

Piston E (Example 5) Boehmite alumina sol similar to Example 1 with average particle size I
Example 1 except that an alumina slurry containing 3% by weight of alumina by mixing 511% of active alumina powder of Inn and diluting this twice with water was used to form the alumina adhered part. It is similar to

Piston F (Example 6) Example except that instead of nitric acid acidic nonitronoamino platinum aqueous solution "fL5CC", a mixed solution of the same aqueous solution and nitric acid acidic nitric acid (radium aqueous solution wave valley 2.5 cc) was used to form the catalyst adhesion part. It is the same as 1.

Schilling head (Example 7/Outside table) A coating layer was formed on the combustion chamber wall portion of the shilling head in the same manner as in Example 1, and 0.1 gr of platinum was deposited per cylinder.

Pulp Set (Example 8/Outside Table) Platinum was deposited on the combustion chamber side surfaces of the heat-resistant alloy intake valve and exhaust valve in the same manner as in Example 1. Nitric acidic dinitrodiaminoplatinum aqueous solution was added at 1 cc (1 cc) per valve cent.
0.02 gr of platinum) for historical use.

Piston G (Comparative Example 1) Same as Example 1 except that no alumina deposited portion was provided.

Piston H (Comparative Example 2) Six pistons I (Comparative Example 3) Same as Example 1, except that the catalyst coating part was formed by depositing 0 and 1 gr of platinum by vacuum evaporation.6 Piston I (Comparative Example 3). This example is the same as Example 1 except that a chloroplatinic acid aqueous solution was used to form the catalyst-attached portion instead of the diaminoplatinum aqueous solution.

Piston J (Comparative Example 4) This is the same as Example 2 except that a hydrochloric acid-acidic paranoum chloride aqueous solution was used to form the catalyst-attached portion instead of the nitric acid-acidic palladium nitrate aqueous solution.

Piston K (Comparative Example 5) Instead of the nitric acid-acidic ronium chloride aqueous solution, a hydrochloric acid-acidic ronium chloride aqueous solution was used to form the catalyst-attached portion. It is the same as Example 3 except for σ.

The test results are shown in Table 1. As shown in the table, the smoke reduction rate according to the present invention reached a maximum of 71% when applied only to the piston crown and after durability treatment.

Although it is not listed above, the burner flame blower f
Example 7 subjected to 100 hours of durability treatment using the 't coating method.
．． As a result of testing under the same operating conditions using a No. 8 shilling head and pulp set in combination with Piston A, an extremely excellent smoke reduction rate of 79% was obtained.

This is because, as mentioned above, the effective surface area of the catalyst-coated portion according to the present invention is extremely large and is less susceptible to deterioration.

Specifically, the surface area of the catalyst-attached portion is as shown in Table 2. This surface area measurement is a durable road]! l! The coating layers of the completed pistons A, F, and G were peeled off, and the CO adsorption method was applied to each coating layer.

A comparison between piston A, which has an alumina deposited part, and e-ston F, which does not have the same deposited part, confirms that the alumina deposited part greatly contributes to the dispersion of the catalyst and the increase in surface area. Further, the piston G has a catalyst deposited thereon by vacuum deposition, and it is clear that a sufficient surface area cannot be obtained by deposition.

Regarding piston I in Table 1, the smoke reduction rate is not good despite having an alumina-coated part, but this is because the decomposition temperature of the chloroplatinic acid impregnated into the coating layer is extremely high. This indicates that the formation of the adhered portion is insufficient, and the same is true for the pistons J and K. Incidentally, Table 3 shows the decomposition temperatures of the noble metal compounds used in the test.

<Table 1><Table2><Table13> (Effects of the invention) In summary, according to the present invention, the alumina adhered portion formed by the impregnation method on the catalyst bed based on Zro2N,
The catalyst is impregnated with a compound solution of a catalyst material that decomposes at a relatively low temperature, then dried and thermally decomposed to ensure good dispersibility.The catalyst has a large effective surface area, which improves the activity and durability of the catalyst. Therefore, it is possible to achieve the effect that harmful products such as soot and unburned fuel components generated during the combustion process of an internal combustion engine can be reliably reduced over a long period of time.

Further, a t-metal compound forming the catalyst adhesion part of the present invention,
Specifically, nitric acidic dinitronoaminoplatinum, nitric acidic nitrate baradium, or nitric acidic rhodium nitrate can all be decomposed at a relatively low temperature of 300°C or less,
Therefore, workability and productivity are good, and there is no risk of adverse thermal effects on parts to be coated made of aluminum alloy, etc., so that a highly reliable catalyzed combustion chamber wall surface sliding structure can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment to show an example of an application of the present invention, FIG. 2 is a m-cross-sectional view of a conventional example, and FIG. 3 is an enlarged view of the main part thereof. 11... Main combustion chamber, 12... Piston, 13...
To the cylinder, 14... Vortex chamber, 18... Ceramics coating layer.

Claims (1)

[Scope of Claims] 1. A ceramic coating layer serving as a heat insulating catalyst bed is provided on the metal wall surface constituting the engine combustion chamber, and at least the surface layer of the coating layer is coated with ZrO_2 powder by thermal spraying.
and an alumina-adhered part formed by impregnating this ZrO_2 layer with a solution containing alumina, drying and decomposing it by heating, and impregnating the coating layer with a solution of a noble metal compound having a decomposition temperature of 300°C or less. A combustion chamber wall structure for an internal combustion engine, characterized in that a catalyst-adhered portion is formed by overheating and decomposition after drying. 2. The combustion chamber wall surface during the internal combustion period according to claim 1, wherein the coating layer includes a Ni-Al layer formed by thermally spraying a mixed powder of Ni and Al on the metal wall surface side. structure. 3. Between the ZrO_2 layer and the Ni-Al layer, Ni and Al
The combustion chamber wall structure for an internal combustion engine according to claim 2, further comprising an intermediate layer formed by thermal spray coating of a mixed powder of ZrO_2 and ZrO_2.