JPS6155314A - 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 to form an engine combustion chamber and forming a catalyzer adhering area on an 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 external layer of the coating layer 18 is composed of ZrO2 layer and an adhering area to which ceramic material is adhered. 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, since the catalyzer can be improved in its durability, deleterious chemical products and unburnt elements can be surely reduced for a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention provides a piston that forms a combustion chamber of an internal combustion engine;
This is reflected in the combustion chamber wall structure in which a ceramic coating 71 layer, which serves as the catalyst bed for the oxidation catalyst, is formed on parts of the shilling head, intake and exhaust valves, etc.

(Prior Art) As a measure against exhaust emissions from diesel engines, a method has been proposed in which soot and unburned fuel generated during the combustion process are purified within the combustion chamber (for example, see Japanese Patent Laid-Open No. 59-41624, etc.). ).

As shown in Figure tpJ2, this is a coating layer 5 of oxidation catalyst formed on the crown of the piston 2 constituting the engine combustion chamber 1, the bottom of the Schilling Rad 3, the wall of the pre-chamber 4, etc. , incomplete combustion products generated during combustion form 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 metal part. Ceramics such as Z r O2, Al2
It is deposited on the surface of the thermal spray coating N6 such as 01 by vacuum evaporation, 4 or high frequency sputtering.

(rjJM, α to be solved by the invention) However, with the conventional combustion chamber wall structure formed in this way, it is difficult to sufficiently disperse the catalyst material in the surface layer portion of the ceramic covering +3jyJ6. 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 sometimes generate a large amount of soot when operating at low to medium speeds and high loads, so the soot adhering to the surface of the catalyst coating layer 5 cannot be sufficiently oxidized and a layer of soot is formed on the catalytic reaction surface. This tends to cause the problem of insufficient oxygen supply and rapid deterioration of conversion efficiency.

As a solution to this problem, CeO2 is used as a catalyst bed.
A coating layer is provided to make it possible to supply oxygen from the back side of the catalyst by utilizing the property of CeO2 to absorb oxygen in an oxidizing atmosphere and release oxygen in a reducing atmosphere (02 Straynow effect). has been proposed (1987-
186126), CeO2 has a weak bonding force with metals and other ceramic materials, and in particular, when a somewhat thick VLWI is formed to ensure sufficient heat insulation and oxygen supply as a catalyst bed, CeO2 has a weak bonding force with metals and other ceramic materials. There is a problem in that repeated expansion and contraction tends to cause peeling and cracking.

The present invention has been made with the aim of solving these conventional problems 7α.

(Means for solving the problem of 7 problems) In the present invention, firstly, a coating layer (of ceramics 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 is coated with ZrO2 powder by thermal spraying to form an r-Zr02 layer, and this ZrO2 layer is coated with CeO.
2 or a combination material of CeO2 and Al2O, and a noble metal compound with a decomposition temperature of 300'C or less, preferably nitric acid acidic nonitroquamium. The coating layer was impregnated with a solution of one or more metal compounds selected from the group consisting of /platinum, nitric acid-acidic palladium nitrate, or nitric acid-acidic rhodium nitrate, and after drying, the coating layer was heated and decomposed to form a catalyst-attached portion.

Secondly, at least the surface layer portion of the coating layer is also coated with Z
Zr spray coated with mixed powder of r02 and CeO2
Ce is added to the O□-CeO2 layer and this ZrO2-Ce02 layer.
O2 or Al□0. It is formed with an adhered part on which at least one ceramic material selected from the group consisting of The coating layer was impregnated with a solution of one or more metal compounds selected from the group consisting of palladium or nitric acid-acidic rhodium nitrate, dried, and then thermally decomposed to form a catalyst-attached portion.

(Function) In the above-mentioned catalyst adhesion part, the catalyst metal material is Z ro 2-Ce.
It has a large surface area because it is well dispersed in the porous JI1m of the ceramic coating layer such as the O2 layer.

Therefore, the oxygen supplying effect peculiar to QCeO2 is effective over a long period of time, and a high level of activity is maintained.

Moreover, all of the above metal compound solutions 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.

Furthermore, the adhered part formed by thermal spraying a mixed powder of CeO2 and ZrO2 or by impregnating a CeO2-containing compound and drying and heating is more likely to contain metal or other materials than a thermally sprayed layer consisting only of CeO2. Since it has good adhesion to ceramic materials and strong bonding strength, it also improves mechanical strength and durability as a catalyst bed.

Examples of the present invention will be described below.

(Embodiment) FIG. 1 shows an embodiment 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, 1G is an injector, and 17 is a glow plug. Reference numeral 18 denotes an S layer having a thermally sprayed layer made of ZrO or ZrO2 and CeO2 and a catalyst-coated part, and as shown in the figure, each layer constituting the engine combustion chamber, such as the piston 12, Schilling Rad 13, swirl chamber 14, etc. It can be formed on the wall surface.

To explain the formation process of the coating layer 18 which becomes the heat insulating catalyst bed, for example, first, the surface to be coated of the piston crown portion 12A is cleaned and degreased, and then an appropriate surface roughness 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 on the surface to be coated to form Ni-A IM, and then ZrO, powder or a mixed powder of ZrO2 and CeO2 is sprayed on top of that to form Zro, Q or Z ro 2- CeO2
Form JrI. Recommended thickness is Ni-Al layer 30~200mm
ttm, Zr025 or Zr0x-CeO2N40-
It is 600x1m.

Thermal spray coating made of a mixture of Ni and Al is compatible with both metals such as aluminum alloys and ceramic materials, especially ZrO2, and has the effect of increasing the bonding strength of each, so it is suitable for forming the walls of the baking chamber. The durability of the ZrO2 layer or ZrO2Ce0z scraps on the metal surface can be further improved. When the object to be coated is an aluminum alloy, it is appropriate that the mixing ratio C of N1 and Al (by weight) is approximately 95% N and 5x Al.

Incidentally, as the thickness of each layer constituting the coating layer 18 increases, the heat insulating effect increases, and therefore the conversion efficiency of the catalyst deposited from the surface can be further increased. In this case, if the thickness of each layer exceeds a certain level, the durability may be impaired due to the temperature difference between the front and back of each layer and the increase in internal stress. , Al, Z
Intermediate layer sprayed with rO2 mixed powder (thickness 30~200 mm)
It is more desirable to provide p). Also, Zr0z-C
The eO2 layer may be composed of a lower layer with a relatively high ZrO2 content and an upper layer with a relatively high Cc○2 content.

Incidentally, it is desirable that the coating layer 18 has a thickness of at least about 100 ttm in order to ensure heat insulating properties, and from the viewpoint of preventing peeling, a thickness of about 111 m at the most is appropriate.

Next, when the surface layer part is a Z r O2 layer, C
A deposited portion is formed of a combination of eO2 or CeO2 and Al□03 (activated alumina). Although this may be done by thermal spray coating with each material, it is preferably applied by impregnating it with a liquid material, drying and decomposing it as follows.

That is, to deposit CeO2, the coating layer 18 is impregnated with a cerium nitrate aqueous solution, dried, and then thermally decomposed. Further, in order to deposit CeO2 and Al2O3, the coating layer 18 is impregnated with one or more materials of aluminum nitrate aqueous solution, boehmite alumina sol, or activated alumina mixed boehmite alumina sol and cerium nitrate aqueous solution simultaneously or sequentially. After drying, decompose by heating.

Alternatively, the Al. A liquid material containing ○ and cerium oxide powder mixed therein may also be used.

On the other hand, when the surface layer is a ZrO2-CeO2 layer,
A CeO2 or Al°03 deposited portion is formed.

This is also preferably applied by impregnating it with a liquid material, drying and thermally decomposing it as follows.

4. In other words, to deposit CeO2, cerium nitrate water,
The solution is impregnated into the BL layer 18, dried and then thermally decomposed.

Also, should I use aluminum nitrate water to deposit Al2O?
It is impregnated with either Ja, boehmite alumina sol or activated alumina mixed boehmite alumina sol, or two or more materials, and is heated and decomposed after drying. Of course, CeO2 and A I 203 may be combined in wL deposition, and in this case, a mixture of cerium oxide powder in the A+203-based liquid material may be used.

Then, this ceramic coating layer 18 is preferably impregnated with an aqueous solution of nonitronium/platinum acidified with nitric acid, palladium nitrate acidified with nitric acid, or ronium nitrate acidified with nitric acid, dried and then thermally decomposed to form a catalyst-attached portion. Since the aqueous solution of the metal compound permeates the porous coating layer, the surface area of the catalyst-attached portion becomes extremely large. However, as the water evaporates during the drying process, the solute, the gold compound, moves to the surface of the coating layer, so the distribution density of the catalyst is higher in the surface layer, which is more likely to come into contact with the combustion gas.

The coating layer 18 and the catalyst thus formed on the piston crown portion 12A and the like absorb soot particles and unburned fuel in the combustion gas that is ejected from the swirl chamber 14 into the main combustion chamber 11 through the nozzle hole 15 during combustion. oxidizes them on contact. When I was two,
As mentioned above, the surface area of the catalyst is extremely large, and the coating layer 1
Since the catalyst is attached to the layer 8'cA, an efficient oxidation effect can be obtained, and the exhaust gas purification effect lasts for a long period of time. In addition, ZrO2-CeO2 layer or Ce
The conversion efficiency is slightly increased due to the release of oxygen from the 02 layer. In other words, CeO2 absorbs oxygen during the intake to compression stroke, when the intake air is rich in oxygen, and releases it during the combustion process, when oxygen is lacking, making the catalyst extremely active.

Next, we conducted a test to specifically demonstrate the above-mentioned effects, so we will discuss the details and results.

Five types of tests were conducted for each basic piston specification, but each test was conducted on a 4-cylinder 2000cc
This is done using a pre-chamber (vortex chamber) type diesel engine, and as a general rule, a coating layer with catalyst is formed only on the piston crown.
The amount of smoke generated under + operating conditions was measured, and the test results were expressed as a percentage reduction from the amount of smoke generated by the same type of engine without a catalyzed coating layer.

In addition, all pistons with catalysts used in the test were subjected to burner flame blowing for 100 hours using the method (gas burner flame and cold air are alternately blown onto the catalyst coating layer in a 1-minute cycle) before being assembled into the engine. Durability treatment was applied.

Test 1 The specifications of the piston etc. used in this test are as follows.

Piston A (Example 1-1) The crown surface was degreased with chloroform and acetone,
After sandblasting, N i:A 1=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 catalyst bed. The spraying thickness of each part is Ni-Al layer 50p, N1-Al-
The ZrO2 layer is 50p and the SZrO2 layer is 400p. The ceramic adhesion area was impregnated several times with an aqueous solution of cerium nitrate containing 10% by weight of CeO2 and dried.
Heating at 90°C for 2 hours, the final temperature was 0,51? Ce of r
It is coated with O2.

As a catalyst, 5 cc of an aqueous dinitronoaminoplatinum solution containing 0.02 gr/cc of platinum was impregnated into the above coating layer in 10 batches of 0.5 cc each, and then dried <+'! 2, then heated in an electric furnace at 250°C for 1 hour to coat 6 pistons B with 0 and 1 gr of platinum.
(Example 1-2) The same as Example 1-1 except that a nitric acid-acidic palladium nitrate aqueous solution was used to form the catalyst-adhered portion in place of the nitric acid-acidic sinitroplatinum aqueous solution.

Piston C (Example 1-3) The same as Example 1-1 except that a nitric acidic noni-diaminoplatinum aqueous solution was filled with a nitric acidic ronium nitrate aqueous solution to form the catalyst adhering portion.

Schilling Head (Example 1-4/Outside Table) A coating layer was formed on the combustion chamber wall portion of the shilling head in the same manner as in Example 1-1, and 0.1 gr of platinum was deposited per cylinder.

Valve center (Example 1-5/Not shown) 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 1-1.

As for the nitric acidic dinitrosyaminoplatinum aqueous solution, 1 ce (platinum 0.02) Br) was used per pulp set.

Piston D (Comparative Example 1-1) Same as Example 1-1 except for the beans that do not have a CeO2 deposited part.

Piston E (Comparative Example 1-2) Same as Example 1-2 except that no CeO2 adhered portion was provided.

Piston F (Comparative Example 1-3) Same as Example 1-3 except that no CeO□ adhered portion was provided.

The results of Test 1 are shown in Table 1. As shown in Table 1, the smoke reduction rate according to the present invention reached a maximum of 64% when applied only to the piston crown and after durability treatment. In addition, although it is not listed above, Example 1 in which burner flame spraying was subjected to 100-hour durability treatment according to the law in the same way as the piston.
A test was conducted under the same operating conditions using a -4.5 (N+)79' head and a valve set with pistons A and hHh, and as a result, an excellent performance with a smoke reduction rate of 76% was obtained.

This is because, as mentioned above, the effective surface area of the catalyst deposited part is extremely large, and oxygen release from the CeO2 deposited part is effective. 6 Test 2 Specifications of the piston etc. used in this test is as follows.

Piston A (Example 2-1) As the ceramic adhered part, Al□O1 was used instead of CeO2.
Boehmite alumina sol containing 3% by weight as Ce
Example 1-1 was the same as in Example 1-1 except that a mixed solution with an aqueous cerium nitrate solution containing 3% by weight was used as 02.

The adhered part is formed by impregnating and drying the mixed solution in several parts and then heating it at 290°C for 2 hours, and finally has a 0.
5 gr of Al2O,-CeO2 was deposited.

Piston B (Example 2-2) Same as Example 2-1 except for 7α in which a nitric acidic palladium nitrate aqueous solution was used to form the catalyst adhering portion instead of nitric acidic nonitronium/platinum.

Piston C (Example 2-3) This is the same as Example 2-1 except that a nitric acidic rhodium nitrate aqueous solution was used to form the catalyst adhering portion instead of the nitric acidic dinitrodiaminoplatinum.

Piston D (Example 2-4) This is the same as Example 2-1 except that an aluminum nitrate aqueous solution was used to form the ceramic adhered portion instead of the boehmite alumina sol.

Piston E (Example 2-5) Al20. 1.5% by weight of activated alumina powder with an average particle size of 1 ttTrl was mixed into a boehmite alumina sol containing 1.5% by weight to form an alumina slurry containing approximately 1.5% by weight of Al2O□3. This example is the same as Example 2-1 except that it is adopted as Example 2-1.

Piston F (Example 2-6) Boehmite alumina sol containing 1.5% by weight as Al20p and CeO2 powder having a bi-average particle size of 1tl'm were mixed into 1.
The process is the same as Example 2-1 except that 5% by weight of the mixture was used to form the ceramic adhered part.

Piston G (Example 2-7) In Example 2-1, after impregnating only the boehmite alumina sol and drying and heating, this activated alumina adhered part was impregnated with a cerium nitrate aqueous solution and drying and heating, and Al2
Example 2-1 was the same as Example 2-1 except that adhered portions were formed of 0.25 gr each of CeO1 and CeO2.

Piston I-1 (Example 2-8) Instead of 5 cc of nitric acid acidic nonitrodiaminoplatinum aqueous solution,
The same aqueous solution and nitric acid paranoum nitrate water solution Hatani 2, 5
A mixed solution of cc was used to form the catalyst-adhesive portion. It is the same as Example 2-1 except for V.

Schilling Head (Example 2-9/Outside Table) A VI layer was formed on the combustion chamber wall portion of the Schilling head in the same manner as in Example 2-1, and white tO per air segment was obtained.

1 gr was applied.

Valve set (Example 2-10/Not shown) 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 2-1.

Use 1 cc (white * 0.02 gr) of nitric acidic nonitrodiaminoplatinum aqueous solution for each valve set.

Piston E (Comparative Example 2-1) A +203 Same as Example 2-1 except that no CeO2 adhered portion was provided.

Piston J (Comparative Example 2-2) Same as Example 2-1 except that the catalyst-attached portion was formed by depositing 0.1+rr of platinum by vacuum deposition.

Piston K (Comparative Example 2-3) Same as Example 2-1 except for α, in which a chloroplatinic acid aqueous solution was used to form the catalyst part in place of the nitric acidic nonitrodiaminoplatinum aqueous solution.

Piston L (Comparative Example 2-4) Instead of the nitric acid-acidic palladium nitrate aqueous solution, a hydrochloric acid-acidic palladium chloride aqueous solution was used to form the catalyst-adhered portion. It is the same as Example 2-2 except for V.

Piston M (Comparative Example 2-5) Same as Example 2-3 except that a hydrochloric acid-acidic rhodium chloride aqueous solution was used to form the catalyst adhering portion instead of the nitric acid-acidic rhodium nitrate aqueous solution.

The results of Test 2 are shown in Table 2, 1. The best smoke reduction rate is 71 when this invention is applied only to the piston.
%, and when the shilling head and valve set of Example 2-9.10 were combined with piston A, the smoke reduction rate of b reached 83%.

<Table 2-1> Test 3 The specifications of the piston, etc. used in this test are as follows.

Piston A (Example 3-1) After removing B from the crown surface with chloroform and acetone and sandblasting, Ni:A I=95
:5 (weight ratio, same below) mixed powder, Ni:A
1:Zr02=33:2:65 (r) Mixed powder, ZrO, powder, and ZrO2:Ce02=20:
The mixed powder of No. 80 was sequentially plasma sprayed to form a coating layer that would become a catalyst bed.

The spraying thickness of each part is Ni-AtN30ttm, N1-Al
-Z ro 2 layers 50 tnnSZ ro 2 layers 200
ttm, ZrO2ceo2 layer 400 μm.

The ceramic adhered part was impregnated with a cerium nitrate aqueous solution containing 10% by weight as CeO2 in several steps and dried, heated at 290'C for 2 hours, and finally
It is coated with gr CeO2.

As a catalyst, the above coating layer was impregnated with 5 cc of a dinitronoaminoplatinum aqueous solution acidified with nitric acid containing 0.02 gr/cc of platinum in 10 doses of 0.5 cc each and dried, and then heated at 250°C in an electric furnace. After heating for 1 hour, platinum 0,
1 gr was deposited.

Piston B (Example 3-2) This is the same as Example 3-1 except that a nitric acidic dinitrodiaminoplatinum aqueous solution was replaced with a nitric acidic dinitrodiaminoplatinum aqueous solution for forming the catalyst-adhered portion.

Piston C (Example 3-3) This is the same as Example 3-1 except that a nitric acidic ronium nitrate aqueous solution was used to form the catalyst-adhered portion instead of the nitric acidic noni-diaminoplatinum aqueous solution.

Cylinder head (Example 3-4/Outside table) A coating layer was formed on the wall portion of the m-burning chamber of the cylinder head in the same manner as in Example 3-1, and platinum O0Igr was deposited on each cylinder.

Valve set (Example 3-5/Not shown) 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 3-1.

Use 1 cc (0.02 gr of platinum) of nitric acidic dinitrodiaminoplatinum aqueous solution for each valve set.

Piston D (Comparative Example 3-1) Same as Example 3-1 except that no CeO2 adhered portion was provided.

Piston E (Comparative Example 3-2) Same as Example 3-2 except that no CeO2 adhered portion was provided.

Piston F (Comparative Example 3-3) Same as Example 3-3 except that no CeO2 adhered portion was provided.

The results of Test 3 are shown in Table 3. As shown in the table, the best smoke reduction rate according to the present invention reached 67%. In addition, as a result of testing under the same operating conditions with the sill head and valve cent of Example 3-4.5 combined with piston A, the smoke reduction rate was 78%.6 Table 3> Test 4 The specifications of the piston etc. used in this test are as follows.

Piston A (Example 4-1) As the ceramic adhered part, Al2O was used instead of CeO2,
This is the same as Example 3-1 except that . Al2
The part to which O, is adhered is formed by impregnating and drying boehmite alumina sol containing 3% by weight as Al2O in several parts, then heating at 290'C for 2 hours, and finally
, 3 gr Al□0. was coated with.

Piston B (Example 4-2) A nitric acidic paranoum nitrate aqueous solution was used to form the catalyst-attached portion instead of the nitric acidic dinitronamitsu platinum. It is the same as Example 4-1 except for α.

Piston C (Example 4-3) Same as Example 4-1 except that a nitric acidic rhodium nitrate aqueous solution was used to form the catalyst adhering portion instead of nitric acidic dinitrosyamin/platinum.

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

Piston E (Example 4-5) Boehmite alumina sol was mixed with 3% by weight of activated alumina powder with an average particle size of 1μI11, and this was diluted twice with water to obtain an alumina slurry containing 3% by weight of Al2O. Example 4-1 is the same as Example 4-1 except that Example 4-1 was adopted for forming the ceramic adhered portion.

Piston F (Example 4-6) Instead of 5 cc of nitrodiaminoplatinum aqueous solution, 2.5 cc of the same aqueous solution and 2.5 cc of nitrodiaminoplatinum aqueous solution
This example is the same as Example 4-1, except that a mixed liquid of cc was used to form the catalyst-attached portion.

Schilling Head (Example 4-7/Outside Table) A coating layer was formed on the combustion chamber wall portion of the shilling head in the same manner as in Example 4-1, and 0.1 gr of platinum was deposited per cylinder.

Valve set (Example 4-8/Not shown) 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 4-1.

Use 1 cc (0.02 gr of platinum) of nitric acid acidic dinitronamitsu platinum aqueous solution for each valve set.

Piston G (Comparative Example 4-1) Same as Example 4-1 except that the Al2O adhered portion was not provided.

Piston (Comparative Example 4-2) Same as Example 4-1 except that the catalyst-attached portion was formed by depositing 0.1 gr of platinum by vacuum deposition.

Piston knife (Comparative Example 4-3) This is the same as Example 4-1 except that a chloroplatinic acid aqueous solution was used to form the catalyst-adhered portion instead of the nitric acid acidic nonitrodiamide 7 platinum aqueous solution.

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

Piston K (Comparative Example 4-5) Same as Example 4-3 except that a hydrochloric acid-acidic rhodium chloride aqueous solution was used to form the catalyst adhesion portion instead of the nitric acid-acidic rhodium nitrate aqueous solution.

The results of Test 4 are shown in Table 4, 1. The smoke reduction rate by applying this invention only to the piston is the best, 69
%, and when the shilling head and valve cent of Example 4-7.8 were combined with piston A, the smoke reduction rate was 82%.

Test 5 The specifications of the piston, etc. used in this test are as follows.

Piston A (Example 5-1) Boehmite alumina sol containing 3% by weight as Aho instead of CeO2 and CeO2 as the ceramic adhered part
Example 3-1 is the same as Example 3-1, except that a mixed solution with an aqueous cerium nitrate solution containing 3% by weight of cerium nitrate was used. The part to be Xf is formed by impregnating and drying the mixed solution several times, heating it at 290'C for 2 hours, and finally
, 5 gr of Al203-CeO2 was deposited.

Piston B (Example 5-2) This is the same as Example 5-1 except that a nitric acid-acidic palladium nitrate aqueous solution was used to form the catalyst-adhered portion instead of nitric acid-acidic dinitrolaffinoplatinum.

Piston C (Example 5-3) Same as Example 5-1 except that a nitric acid-acidic rhodium nitrate aqueous solution was used to form the catalyst adhering portion instead of the nitric acid-acidic dinitrorahminoplatinum.

Piston D (Example 5-4) 6-piston E (Example 5-5), which is the same as Example 5-1 except for Hiro, in which an aluminum nitrate aqueous solution was used to form the ceramic adhesion part instead of boehmite alumina sol 1.5% of activated alumina powder with an average particle size of 1ρ was added to a boehmite alumina sol containing 1.5% by weight as AI20.
An alumina slurry containing 3% by weight of Al□Os was used for forming the ceramic adhered portion. Same as Example 5-1 except for Hiroshi.

Piston F (Example 5-6) CeO2 powder with an average particle size of 1f (rIl) was added to boehmite alumina sol containing 1.5% by weight as Al2O2.
The procedure is the same as in Example 5-1 except that the mixture containing gL in an amount of % was used to form the first part of the ceramic coating.

Piston G (Example 5-7) In Example 5-1, only the boehmite alumina sol was first impregnated and dried and heated, and then the activated alumina adhered part was impregnated with a cerium nitrate aqueous solution and dried and heated to form Al□
It is the same as Example 5-1 except that the adhered portions were formed of 0.25 gr each of ◯ and Ce◯2.

Piston H (Example 5-8) Instead of 5 cc of nitric acid acidic nonitronoamino platinum aqueous solution,
The same aqueous solution and nitric acid acidic paranoum nitrate aqueous solution Hatani 2.5 c
The procedure was the same as in Example 5-1 except for the fish in which the mixed solution of c was used to form the catalyst-attached portion.

Schilling nozzle (Example 5-9/Outside table) VIWI was applied to the combustion chamber wall of the silling throat in the same manner as in Example 5-1.
0°Igr of platinum was deposited on each cylinder.

Valve set (Example 5-10/Not listed) 11i Platinum was deposited on the combustion chamber side surfaces of the preheated alloy intake valve and exhaust valve in the same manner as in Example 5-1.

Use 1 cc (0.02 platinum Hr) of nitric acidic dinitrodiaminoplatinum aqueous solution for each valve set.

Piston ■ (Comparative Example 5-1) Same as Example 5-1 except that the Al□03CeO2 adhered portion was not provided.

Piston J (Comparative Example 5-2) Same as Example 5-1 except that the catalyst-attached portion was formed by depositing 0.1 gr of platinum by vacuum evaporation.

Piston K (Comparative Example 5-3) Same as Example 5-1 except that a chloroplatinic acid aqueous solution was used to form the catalytic wave @ portion in place of the nitric acidic dinitrodiaminoplatinum aqueous solution.

Piston L (Comparative Example 5-4) Same as Example 5-2 except that a hydrochloric acid-acidic palladium chloride aqueous solution was used to form the catalyst-adhered portion instead of the nitric acid-acidic palladium nitrate aqueous solution.

Piston M (Comparative Example 5-5) Same as Example 5-3 except that a hydrochloric acid acidic ronium chloride aqueous solution was used to form the catalyst adhering portion instead of the η°1 acidic ronium nitrate aqueous solution.

The results of Test 5 are shown in Table 5, 1. The best smoke reduction rate when this invention is applied only to the piston is 73.
Furthermore, when the silling head and valve set of Example 5-9.10 were combined with piston A, the smoke reduction rate reached 85%.

Table 5-1> Table I56 summarizes the materials and results for typical examples and comparative examples of each of the above tests.

From this table, firstly, if the material of the adhered part is the same, it is considered as 7. It can be seen that the combination of rO2 and CeO2 is superior to that of ZrO2 alone. This is mainly due to the 02 storage effect of CeO2, as is clear from the comparison with the comparative example which does not have a ceramic adhered part.

Second, if we focus on the material of the adhered part, Al□03 is better than CeO2, but the combination of CeO□ and ALO is better than Al□03 from the perspective of smoke reduction. I know that there is. This means that Al□O0 has better properties as a catalyst bed than CeO2, and the combination of CeO2 and Al□O1 has better properties than Al□03, giving better catalyst surface area or dispersibility. Suggests. Further, it has been shown that the combination of A I20 and CeO2 brings about a synergistic effect in combination with the above characteristics and the 02 Strano effect of CeO2. In addition,
In this way, CeO
Those employing □ generally exhibit a superior smoke reduction rate, but since CeO2 is expensive, it is not necessarily advantageous from a cost perspective.

Third, Comparative Example B has the same coating layer and 1 part of the ceramic coating as in the example except that a chloroplatinic acid aqueous solution was used to form the catalyst coating part. The reason for the poor results is thought to be that the decomposition temperature of the impregnated chloroplatinic acid is extremely high, resulting in insufficient formation of the catalyst adhesion area. The same applies to those employing palladium or hydrochloric acid acidified ronium chloride. Incidentally, Table 7 shows the decomposition temperatures of the noble metal compounds used in the test.

Table 6> Table 7> Next, for Test 2.4.5, the catalyst surface area of a representative sample was measured, and the results are shown in Table I52, 2, Table 4, and Table 7, respectively. It is shown in 2 of Table 5. The surface area was measured by peeling off the coating layer of each piston that had been subjected to durability treatment, and using the Hiiragi Co adsorption method on each coating layer.

This measurement result also supports the favorable properties of Ceo 2' A I□○ and the deposited portion as a catalyst bed.

In addition, piston J of 2 in Table 2 and 2 of Table 5 and piston 4
Piston G in Table 2 has a catalyst deposited by vacuum deposition, and it is clear that a sufficient surface area cannot be obtained by vapor deposition.

<Table 2-2> Table 4-2> Table 5-2> Material of adherend of piston A: CeO2A 120° (effects of the invention) In summary, according to the present invention, Zr02 layer or Z
ro 2-Ceo Catalyst deposition with a large effective surface area by impregnating a catalyst bed based on two layers with a compound solution of a catalyst material that decomposes at a relatively low temperature, and then drying and thermally decomposing it to ensure good dispersibility. Since the catalyst is provided with a portion, the durability of the catalyst can be increased, and therefore, 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.

In particular, those provided with a ZrO2 layer, a CeO2 layer, or a C
e Ceramics coating by impregnation method with O2-containing solution.
When deposited on arfI, the bonding strength and reliability of CeO2 to other ceramic or metal materials can be increased. Therefore, while ensuring sufficient heat insulation required for the catalyst bed through a relatively thick coating layer, CeO
Harmful products in the combustion gas can be reduced as much as possible by taking advantage of the 02 Strano effect specific to 2.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention to show an example of a 3-meter portion, FIG. 2 is a vertical 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...
Schilling head, 14... Vortex chamber, 18... Ceramics coating layer 6

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.
layer and this ZrO_2 layer with CeO_2 or CeO_2
and a deposited part on which one or more ceramic materials selected from the group consisting of a combination material with Al_2O_3 are deposited, and the coating layer is impregnated with a solution of a noble metal compound having a decomposition temperature of 300°C or less and dried. A combustion chamber wall structure for an internal combustion engine, characterized in that a catalyst-adhered portion is formed by post-superheat decomposition. 2. The combustion chamber wall surface of an internal combustion engine 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 thermally spraying a mixed powder of ZrO_2 and ZrO_2. 4. 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 a ZrO_2-CeO_2 layer by thermal spraying with a mixed powder of ZrO_2 and CeO_2; ZrO_2
The layer CeO_2 is formed with a deposited part on which one or more ceramic materials selected from the group consisting of CeO_2 and Al_2O_3 are deposited, and the coating layer is impregnated 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. 5. The internal combustion period according to claim 4, wherein the coating layer is provided through a Ni-Al layer formed by thermally spraying a mixed powder of Ni and Al on the metal wall side. Combustion chamber wall structure. 6. The method according to claim 5, which includes an intermediate layer formed by spray coating a mixed powder of Ni, Al, and ZrO_2 between the ZrO_2-CeO_2 layer and the Ni-Al layer. Combustion chamber wall structure of internal combustion engine.