JP2014222056A - Method for forming heat insulation layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an excellent heat insulation layer on a wall surface of a component forming a combustion chamber of an engine.SOLUTION: A method for forming a heat insulation layer includes a first resin application step (step S2) for forming a first resin layer 11 by applying silicone resin 22 on a top surface of a piston 1, a particle adhesion step (step S3) for attaching hollow particles 20 on a surface of the first resin layer 11, and a second resin application step (step S4) for forming a second resin layer 12 containing the hollow particles 20 by applying the silicone resin 22 on the hollow particles 20. Further, after the particle adhesion step and the second resin application step, steps similar to the steps are repeatedly carried out twice, and thus, a third resin layer 13 and a fourth resin layer are formed (step S7). Thereby, a heat insulation layer 10 containing the first to fourth resin layers 11-14 is formed.

Description

  The present invention relates to a method for forming a heat insulating layer on a part wall surface forming a combustion chamber of an engine.

  In recent years, on the premise of a combination of a high compression ratio of the engine and leaner mixture, a part of the combustion chamber is insulated to reduce cooling loss at an extremely high geometric compression ratio, while a high engine A technique for improving the illustrated thermal efficiency of the engine and significantly improving the fuel consumption performance by increasing the expansion ratio (high compression ratio) has been studied. Patent Document 1 discloses a technique useful for insulating a combustion chamber. Specifically, the wall surface forming the combustion chamber is coated with a resin containing hollow particles to reduce the thermal conductivity of the wall surface and to insulate the combustion chamber.

JP 2012-172619 A

  In Patent Document 1, a general method as a coating method (a method for forming a heat insulating layer), that is, a hollow particle is mixed with a resin and stirred to form a paint, and this paint is applied to the wall surface of the combustion chamber. A method of baking a coating film after forming a film is disclosed. However, it is actually difficult to form a good heat insulating layer only by following such a method. That is, in the process of mixing and stirring the hollow particles in the resin, the hollow particles collide with each other, or the hollow particles collide with the stirring member, and many hollow particles are crushed. Moreover, when spraying resin etc., many hollow particles are crushed by collision between hollow particles or collision between hollow particles and a wall surface. Such crushing of the hollow particles is one of the causes of reducing the heat insulation effect.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for forming a better heat insulating layer on a part wall surface forming a combustion chamber of an engine.

  In order to solve the above problems, the present invention is a method of forming a heat insulating layer on a part wall surface forming a combustion chamber of an engine, wherein the resin layer is formed by applying a resin to the part wall surface. A resin application step, a particle adhesion step of attaching hollow particles to the surface of the resin layer, and a second resin application step of forming a resin layer containing the hollow particles by applying a resin on the hollow particles, After the first resin application step, the particle adhesion step and the second resin application step are repeated a plurality of times in this order.

  According to this method, since there is no step of mixing and stirring the hollow particles in the resin liquid, the hollow particles are not crushed by collision between the hollow particles due to the stirring or collision between the hollow particles and the stirring member. Therefore, it becomes possible to ensure more favorable hollow particles in the heat insulating layer finally formed.

  The method further includes a heating step of heating the resin layer, and the heating step is performed after the first resin application step, before the particle adhesion step, and / or after the particle adhesion step, before the second resin application step, and It is preferable to carry out after the final second resin coating step.

  According to this method, it is possible to increase the gasoline resistance and hardness of the heat insulating layer by heating (baking) the resin. Moreover, since the resin layers are individually heated, the solvent evaporates after the formation of a plurality of resin layers (that is, after the final second resin coating step is completed) as compared with the case of heating the whole at once. By being easy, the total heating time can be shortened.

  In this case, the metal layer forming step of performing the heating step at least after the final second resin coating step and forming a metal layer on the resin layer formed in the final second resin coating step after the heating step. It is preferable to further contain.

  According to this method, it becomes possible to further increase the gasoline resistance and hardness of the surface of the heat insulating layer (resin layer), which contributes to improving the durability of the heat insulating layer.

  As described above, according to the present invention, it becomes possible to secure more favorable hollow particles in the finally formed heat insulating layer. Therefore, a better heat insulating layer having a low thermal conductivity can be formed.

It is sectional drawing of the piston which has the heat insulation layer formed based on the formation method of the heat insulation layer which concerns on this invention. It is process drawing explaining the formation method (formation method of the heat insulation layer concerning this invention) of the heat insulation layer shown in FIG.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

(Insulation layer structure)
FIG. 1 is a sectional view showing a piston having a heat insulating layer formed based on the method for forming a heat insulating layer according to the present invention. As shown in the figure, the piston 1 includes a heat insulating layer 10 on a top surface (wall surface) forming a combustion chamber of the engine. The heat insulating layer 10 includes a first resin layer 11 formed over the entire top surface of the metal base material of the piston 1, a second resin layer 12 formed in order on the upper surface of the first resin layer 11, It consists of three resin layers 13 and a fourth resin layer 14. In this example, the metal base material of the piston 1 is, for example, an aluminum alloy AC8A for casting.

  The first resin layer 11 is formed of only a silicone resin, and is formed with a substantially constant thickness on the entire upper surface of the metal base material.

  Each of the second to fourth resin layers 12 to 14 is formed of a plurality of hollow particles 20 and a silicone resin 22 that holds the hollow particles 20. As shown in the figure, the hollow particles 20 of the resin layers 12 to 14 are held by the silicone resin 22 in a state of being spread along the lower resin layer. As shown in FIG. 1, the upper surface of the first resin layer 11 and the lower surface of the silicone resin 22 in the second resin layer 12 thereon, and the upper surface of the silicone resin 22 in the second resin layer 12 and the upper surface thereof. The lower surface of the silicone resin 22 in the third resin layer may be partially non-contact, and in such a form, the non-contact part (part A) will form a heat insulating air layer, This is advantageous in terms of ensuring heat insulation.

  Here, as the silicone resin of each of the resin layers 11 to 14, for example, a silicone resin made of a three-dimensional polymer having a high degree of branching, represented by methyl silicone resin and methylphenyl silicone resin, is suitable. Specifically, polyalkylphenylsiloxane and the like are suitable.

The hollow particles 20 included in the second to fourth resin layers 12 to 14 are ceramics containing Si-based oxide components (for example, SiO ₂ ) such as fly ash balloons, shirasu balloons, silica balloons, and airgel balloons. System hollow particles are preferred. Each material and particle size are as shown in Table 1.

For example, the chemical composition of the fly ash balloons are _{mass%, SiO 2; 40.1~74.4%,} AI 2 O 3; 15.7~35.2%, Fe 2 O 3; 1.4~17 0.5%, MgO; 0.2 to 7.4%, CaO; 0.3 to 10.1%. The chemical composition of the shirasu balloons, in _{mass%, SiO 2; 75~77%,} AI 2 O 3; 12~14%, Fe 2 O 3; 1~2%, Na 2 O; 3~4%, K 2 O: 2-4%, IgLoss: 2-5%.

  The average particle diameter of the hollow particles is preferably 5 μm or more and 30 μm or less, and the content in each of the resin layers 12 to 14 is preferably 20 vol% or more and 60 vol% or less. If this is within this range, the amount of particles that can be contained with respect to the thickness of each resin layer 12-14 can be increased while increasing the amount of air contained in the hollow particles to some extent, This is because the necessary heat insulating properties can be obtained satisfactorily.

  Moreover, the heat insulation layer 10 is formed so that the thickness may be 60 micrometers or more and 200 micrometers or less. This is because the heat insulation layer 10 can be prevented from shrinking and outgassing from the heat insulation layer 10 at a high temperature of the engine while preventing the heat insulation layer 10 from peeling off while ensuring the necessary heat insulation properties. It is.

(Method of forming heat insulation layer)
The heat insulation layer 10 mentioned above can be formed based on the method shown in FIG.

  In this method, a piston 1, which is a base material, a silicone resin liquid (simply referred to as silicone resin 22), and hollow particles 20 are prepared (step S1). First, the silicone resin 22 is applied to the top surface of the piston 1. Thus, the first resin layer 11 is formed (step S2). As a coating method of the silicone resin 22, a coating method such as spray coating, dip coating, or screen printing can be applied. In this example, the process of step S2 corresponds to the first resin coating process of the present invention.

  Next, the first resin layer 11 formed in step S2 is appropriately heated to calcinate the first resin layer 11 (step S3), and then hollow particles are formed on the surface of the first resin layer 11. 20 is attached (step S4). The hollow particles 20 are attached using the viscosity of the silicone resin 22 (first resin layer 11). Therefore, the temporary baking in step S3 is performed within a range in which the silicone resin 22 of the first resin layer 11 maintains a viscosity that allows the hollow particles 20 to adhere. For example, it is preferable to heat at 180 ° C. for about 3 to 5 hours.

  Next, the second resin layer 12 containing the hollow particles 20 is formed by applying the silicone resin 22 on the hollow particles 20 (step S5), and further, the second resin layer 12 is temporarily fired ( Step S6). The method for applying the silicone resin 22 in step S5 and the method for temporary baking in step S6 are the same as those in steps S2 and S3. In this example, the processes of steps S4 and S5 correspond to a particle adhesion process and a second resin application process, respectively.

  When the preliminary firing of the second resin layer 12 is completed, the same processing as the processing of the above steps S4 to S6 is repeated twice, thereby enclosing the hollow particles 20 in the silicone resin 22 and temporarily firing the third resin layer. 13 and the fourth resin layer 14 are formed (step S7). In this example, the processes of steps S3 and S6 correspond to the heating process of the present invention.

  Thus, when the first to fourth resin layers 11 to 14 that have been pre-fired are formed on the top surface of the piston 1, that is, the heat-insulating layer 10 that has been pre-fired as a whole is formed. The heat insulating layer 10 is heated and fired. When the heat insulating layer 10 is thus baked, the surface of the silicone resin 22 in the heat insulating layer 10 is modified to Si-based oxide, and the heat insulating layer 10 having gasoline resistance is completed.

  According to such a method for forming the heat insulating layer 10, since there is no step of mixing and stirring the hollow particles in the silicone resin (resin liquid) as in the prior art, collision between the hollow particles 20 due to the stirring, The hollow particles 20 are not crushed by the collision between the hollow particles 20 and the stirring member. Therefore, more favorable hollow particles 20 can be secured in the heat insulating layer 10 to be finally formed, and thereby, a better heat insulating layer 10 having a low thermal conductivity can be formed.

  Further, according to this method, there is an advantage that the total firing time required for forming the heat insulating layer 10 can be shortened. In other words, according to the above method, since the resin layers 11 to 14 having a relatively small thickness are subjected to temporary firing each time, the time required for temporary firing of the individual resin layers 11 to 14 can be shortened. In addition, since the resin layers 11 to 14 are pre-baked in advance as described above, the time required for final main baking can be shortened. Therefore, compared with the case where the whole is fired at once after all the resin layers 11 to 14 are formed, the total firing time required for forming the heat insulating layer 10 can be shortened, and the heat insulating layer 10 is efficiently formed. can do.

  Moreover, according to the method of performing temporary baking for each of the resin layers 11 to 14 as described above, the heat insulating layer 10 is formed in comparison with the case where the resin layers 11 to 14 are formed and then heated all at once and fired. It becomes possible to suppress the thermal distortion which arises. Therefore, it is also possible to suppress crushing of the hollow particles 20 due to thermal strain, and it is possible to secure more favorable hollow particles 20 in this respect.

  Moreover, according to the method of repeating temporary firing for each resin layer while sequentially forming the resin layer on the top surface of the piston 1 as described above, the state in which the hollow particles 20 are spread along the lower resin layer is somewhat stable. In this state, the next (upper) resin layer is formed. Therefore, it is suppressed that the hollow particle 20 is biased to a specific position. Therefore, according to the above method, the hollow particles 20 can be arranged with a more uniform density in the heat insulating layer 10, and thereby, an advantage that a good heat insulating effect can be expected to be obtained in the heat insulating layer 10 as a whole. is there.

  In the method of forming the heat insulating layer 10 described above, a pretreatment may be performed on the top surface of the piston 1 in order to improve the adhesion of the silicone resin 22. As the pretreatment, for example, an alumina layer (aluminum oxide) is formed by performing an alumite treatment on the top surface of the piston 1, or a chemical conversion treatment (for example, zinc phosphate treatment) is performed on the top surface of the piston 1. Is preferred. According to this method, the first resin layer 11 can be stably formed on the top surface of the piston 1, and as a result, the durability of the heat insulating layer 10 can be improved. In particular, the alumina layer obtained by the alumite treatment is porous, and it is advantageous in that the OH group is easily adsorbed on the surface, and the adhesion with the silicone resin is increased.

(Modification of heat insulation layer)
In the heat insulation layer 10 shown in FIG. 1, a metal layer such as plating may be further formed on the surface thereof. According to this configuration, it is possible to improve the gasoline resistance and rigidity of the surface of the heat insulating layer 10, and contribute to the improvement of the durability of the heat insulating layer 10.

  For example, such a heat insulating layer 10 is subjected to the following plating process (corresponding to the metal layer forming step of the present invention) after the process of step S8 of the method shown in FIG. It can be obtained by carrying out an etching treatment step, a catalytic metal application step, and an electroless plating treatment step.

-Etching process In this process, the non-processed part other than the heat insulation layer 10 of the piston 1 is masked with a masking agent, and the heat insulation layer 10 is etched. As the etchant, for example, a mixed acid of nitric acid and hydrofluoric acid (nitric acid 200 mL / L, hydrofluoric acid 200 mL / L) can be used, and the processing time is preferably about 1 minute at room temperature. By this etching process, fine protrusions are formed on the surface of the heat insulating layer 10.

-Catalyst metal provision process In this process, the catalyst metal for electroless plating is provided to the surface of the heat insulation layer 10 of the piston 1. More specifically, after the piston 1 is immersed in a catalyst liquid containing a Pd—Sn complex, an activation promotion process is performed. As a catalyst liquid, for example, a mixed solution of 50 mL / L of acidic palladium / tin colloid type catalyst treating agent (product CRP catalyst manufactured by Okuno Pharmaceutical Co., Ltd.) and 250 mL / L of 35% hydrochloric acid (Pd-Sn colloidal catalyst) Can be used. The bath temperature is preferably 35 ° C. and the immersion time is preferably about 6 minutes. Thereby, the Pd—Sn complex adheres to the Si-based oxide derived from the silicone resin 22 and the Si-based oxide derived from the hollow particles 20 on the surface of the heat insulating layer 10.

  In the activation promotion treatment, a mixed solution of 100 mL of concentrated sulfuric acid, 5 g of an accelerator (product accelerator X manufactured by Okuno Pharmaceutical Co., Ltd.) and water can be used as an activation bath. The bath temperature is preferably 35 ° C and the immersion time is preferably about 3 minutes. Thereby, tin chloride dissolves and a catalytic metal made of metal Pd is generated on the Si-based oxide by an oxidation-reduction reaction. That is, the catalyst metal is supported on the Si-based oxide.

Electroless plating treatment step In this step, the piston 1 with the catalytic metal applied to the heat insulating layer 10 is washed with water to remove excessively attached sulfuric acid and the like, and then immersed in an electroless Ni plating bath. As the plating bath, for example, an electroless Ni—P alloy plating solution (Okuno Pharmaceutical Co., Ltd. product top Nicolone LPH-LF) 250 mL / L can be used. The bath temperature is 90 °, and the immersion time is preferably about 12 minutes (aim for a plating film thickness of 3 μm). In this case, the plating metal deposition rate is 12 to 18 μm / h. By this electroless plating treatment, a Ni—P alloy is deposited with the catalyst metal Pd as a nucleus, and a plating film is formed on the surface of the heat insulating layer 10. In this case, as described above, the fine protrusions are formed on the surface of the heat insulating layer 10 by the etching process, so that the plating film is firmly fixed to the surface of the heat insulating layer 10 by the anchor effect.

  The heat insulating layer 10 and the method for forming the heat insulating layer 10 and the method for forming the heat insulating layer 10 described above are examples of preferred embodiments of the heat insulating layer and the method for forming the heat insulating layer according to the present invention. The structure and the specific method for forming the heat insulating layer can be changed as appropriate without departing from the scope of the present invention.

  For example, in the above-described embodiment, an example in which the heat insulating layer 10 according to the present invention is formed on the top surface of the piston 1 as a part that forms the combustion chamber of the engine has been described. Other than the top surface, specifically, it can be formed on a cylinder head (combustion chamber forming surface), an intake valve, an exhaust valve, an intake port, an exhaust port, and the like.

  Moreover, in the said embodiment, although temporary baking (step S3, S6) is performed for every resin layers 11-14, you may perform temporary baking at timings other than this. For example, you may make it perform temporary baking for every two resin layers. However, from the viewpoint of reducing the total firing time, it is preferable to perform temporary firing for each of the resin layers 11 to 14 as in the above embodiment.

DESCRIPTION OF SYMBOLS 1 Piston 10 Heat insulation layer 11 1st resin layer 12 2nd resin layer 13 3rd resin layer 14 4th resin layer 20 Hollow particle 22 Silicone resin

Claims (4)

A method of forming a heat insulating layer on a part wall surface forming a combustion chamber of an engine,
A first resin application step of forming a resin layer by applying a resin to the component wall surface;
A particle attaching step for attaching hollow particles to the surface of the resin layer;
A second resin coating step of forming a resin layer containing the hollow particles by coating a resin on the hollow particles,
After implementing a 1st resin application | coating process, the particle adhesion process and the 2nd resin application | coating process are repeatedly implemented in this order several times, The formation method of the heat insulation layer characterized by the above-mentioned. In the formation method of the heat insulation layer of Claim 1,
A heating step of heating the resin layer;
The heating step is performed after the first resin application step, before the particle adhesion step, and / or after the particle adhesion step, before the second resin application step, and / or after the final second resin application step. A method for forming a heat insulating layer. In the formation method of the heat insulation layer of Claim 2,
The heating step is performed at least after the final second resin coating step,
The method for forming a heat insulating layer, further comprising a metal layer forming step of forming a metal layer on the resin layer formed in the final second resin coating step after the heating step. In the formation method of the heat insulation layer according to any one of claims 1 to 3,
The method for forming a heat insulating layer, wherein the resin is a silicone resin.

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