JP2015096634A - Method of forming heat-shielding film for internal engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a heat-shielding film for internal engines which can prevent occurrence of cracking of an anode oxide film when the temperature of a combustion chamber becomes high.SOLUTION: A method of forming a heat-shielding film for an internal engine is based on forming an anode oxide film on members constituting a wall surface of a combustion chamber of an internal engine and includes a step of forming an alumite film on the surface of a member and a step of subjecting the alumite film to a sealing treatment at such a temperature that the member undergoes thermal expansion.

Description

  The present invention relates to a method for forming a thermal barrier film for an internal combustion engine.

  Conventionally, a technique for forming a thermal barrier film on a member constituting a wall surface of a combustion chamber of an internal combustion engine is known. For example, Patent Document 1 discloses a technique for forming an anodized film made of alumite on a member constituting a wall surface of a combustion chamber whose base material is aluminum or an alloy thereof. By forming a thermal barrier film such as an anodized film on the member constituting the wall surface of the combustion chamber, the heat insulating property on the wall surface of the combustion chamber is improved. As a result, the thermal efficiency of combustion in the internal combustion engine can be improved.

JP2013-060620A

  By the way, when the anodic oxide film is exposed to a high temperature in the combustion chamber of the internal combustion engine, a crack may be generated by being pulled by thermal expansion of a member constituting the wall surface of the combustion chamber. As a result, the combustion gas and the members constituting the wall surface of the combustion chamber are in direct contact with each other, which may impair the heat insulation in the internal combustion engine.

  The present invention has been made to solve the above-described problems, and a method for forming a thermal barrier film for an internal combustion engine that can prevent the occurrence of cracks in the anodized film when the combustion chamber becomes hot. The purpose is to provide.

In order to achieve the above object, the first invention provides
A method for forming a thermal barrier film of an internal combustion engine, wherein an anodized film is formed on a member constituting a wall surface of a combustion chamber of the internal combustion engine,
Forming an alumite film on the surface of the member;
Performing a sealing treatment on the alumite film at a temperature at which the member causes thermal expansion;
It is characterized by providing.

  According to the first invention, it is possible to prevent the anodized film from being divided by the thermal expansion of the members constituting the wall surface of the combustion chamber. As a result, the intrusion of combustion gas and fuel into the alumite film can be suppressed. Moreover, it can prevent that the heat insulation of an anodized film is impaired.

It is a figure showing the thermal barrier film in this Embodiment. It is a figure for demonstrating the temperature which performs a sealing process. It is the figure showing about the film-forming process of an anodized film, and the anodized film when the inside of an engine becomes a high temperature field. It is a figure for demonstrating the sealing agent structure 1. FIG. It is a figure for demonstrating the sealing agent structure 2. FIG.

Embodiment 1 FIG.
Hereinafter, a method for forming a thermal barrier film for an internal combustion engine according to the present embodiment will be described with reference to FIGS. 1, 2, and 3.

  FIG. 1 is a view showing a heat shield film formed on a member constituting a wall surface of a combustion chamber of an internal combustion engine. FIG. 1A shows a member (hereinafter referred to as a member 10) constituting the wall surface of the combustion chamber of the internal combustion engine. The member 10 is made of an aluminum alloy as a base material. On the surface of the member 10, an anodized film 20 is formed as a heat shield film. Hereinafter, the anodized film 20 will be described.

  As shown in FIG. 1, the anodic oxide film 20 is composed of an alumite film 14 and a sealing agent 16. The anodized film 14 is a porous film formed by anodizing an aluminum alloy that is a base material of the member 10. A barrier layer 12 is formed between the alumite film 14 and the member 10.

  The sealing agent 16 seals the communication hole A formed inside the anodized film 14, suppresses the intrusion of combustion gas and fuel into the anodized film 14, and the heat insulating property of the anodized film 20 is impaired. It is provided for the purpose of preventing this. As the sealing agent 16, a material (preferably polysilazane or polysiloxane) in which a heat-resistant material such as silica acts as a main component after coating and curing is used. In addition, only the crack portion may be made of a material having a low elastic coefficient for stress relaxation due to thermal expansion. Furthermore, the roughness of the surface of the anodized film 20 can be improved by applying the sealing agent 16. Furthermore, the strength of the anodized film 20 can be improved. Thus, the sealing agent 16 is applied to maintain the performance of the anodized film 20 and improve the reliability of the anodized film 20.

  By the way, during engine operation, the temperature in the combustion chamber rises and the member 10 causes thermal expansion. At this time, the anodized film 20 may be cracked due to the thermal expansion of the member 10. This will be described below with reference to FIG. In the present specification, the temperature around the member 10 causing the member 10 to thermally expand is expressed as a high temperature field.

  FIG. 1B is a diagram showing changes in the anodic oxide film 20 caused during engine operation. FIG. 1B shows a state in which cracks occur in the anodized film 20 when the combustion chamber changes to a high temperature field during engine operation. This crack is generated when the anodized film 20 is pulled by the thermally expanded aluminum alloy when the combustion chamber becomes a high temperature field. This is caused by the fact that the coefficient of thermal expansion of alumite is about 1/5 that of an aluminum alloy. Due to the occurrence of this crack, the alumite film 14, the barrier layer 12, and the sealing agent 16 are divided at the same time. As a result, the performance of the anodized film 20 cannot be maintained.

  Therefore, in the present embodiment, in the film forming process for forming the anodic oxide film 20 on the member 10, the sealing process is performed in which the temperature is set to a high temperature field and the sealing agent 16 is applied to the alumite film 14. Thereby, even when the combustion chamber becomes a high temperature field during the engine operation, the performance of the anodized film 20 can be maintained. Hereinafter, the sealing process will be described in detail with reference to FIGS. 2 and 3.

  FIG. 2 is a diagram for explaining the temperature at which the sealing process is performed. The vertical axis in FIG. 2 indicates the temperature change of the piston. Here, the piston is used as a specific example of the member 10. The horizontal axis in FIG. 2 indicates changes in engine speed. FIG. 2 shows a solid line showing the relationship between the temperature change of the piston and the engine speed.

  In the solid line shown in FIG. 2, the point at which the piston temperature reaches the maximum value is displayed as the maximum output point. FIG. 2 shows the temperature at which the aluminum alloy softens (hereinafter referred to as the Al alloy softening temperature). Here, in this Embodiment, the sealing agent application temperature which is a temperature which performs a sealing process is set by the temperature between Al alloy softening temperature and a maximum output point. This is because the aluminum alloy is sealed without being softened and at a temperature equal to or higher than the maximum temperature assumed in the combustion chamber of the engine. Next, the film forming process for performing the sealing process at the sealing agent application temperature will be described with reference to FIG. In addition, the temperature of the member 10 can be raised to the sealing agent application temperature by placing the member 10 in a high temperature environment.

  FIG. 3 is a diagram illustrating the film forming process of the anodic oxide film 20 and the anodic oxide film 20 when the inside of the engine is in a high temperature field. FIG. 3A is a diagram showing an anodic oxide film 20 formed by a conventional technique. In the conventional technique, anodization is performed in a room temperature field, and an alumite film 14 is formed on the member 10. Here, the normal temperature field refers to the temperature around the member 10 at which the aluminum alloy does not cause thermal expansion.

  Next, a sealing treatment is performed in a room temperature field, and a sealing agent 16 is applied to the alumite film 14.

  FIG. 3A shows a state in which cracks occur in the anodized film 20 formed by the conventional technique when the combustion chamber becomes a high temperature field during engine operation. In the prior art, the performance of the anodized film 20 cannot be maintained due to the occurrence of this crack.

  FIG. 3B is a diagram for explaining a method of forming the anodic oxide film 20 of the present embodiment. In the present embodiment, anodization is performed in a room temperature field, and an alumite film 14 is formed on the member 10. Next, by placing the member 10 on which the alumite film 14 is formed in an environment of a high temperature field, the member 10 causes thermal expansion, and the alumite film 14 is cracked. Next, the sealing agent 16 is applied to the alumite film 14 in which the crack has occurred. Thereby, the sealing agent 16 is also impregnated into the cracked portion of the alumite film 14.

  Thus, by impregnating the sealing agent 16 in the cracked portion of the alumite film 14 and performing the sealing treatment, the combustion chamber became a high temperature field during engine operation, causing the member 10 to thermally expand. Sometimes, the structure of the anodized film 20 can be maintained. For this reason, the division | segmentation of the anodic oxide film 20 by the thermal expansion of the member 10 can be prevented. As a result, the intrusion of combustion gas and fuel into the alumite film 14 can be suppressed. Moreover, it can prevent that the heat insulation of the anodic oxide film 20 is impaired.

[Sealing agent composition 1]
Further, in order to maintain the performance of the anodized film 20 even when the combustion chamber becomes a high temperature field, a configuration in which the thermal expansion coefficient of the sealing agent is equivalent to the thermal expansion coefficient of the aluminum alloy (hereinafter referred to as sealing) There is a method of taking the composition 1). Below, the sealing agent structure 1 is demonstrated with reference to FIG.

  FIG. 4 is a diagram for explaining the sealant configuration 1. A sealing agent 160 having a thermal expansion coefficient equivalent to that of the aluminum alloy of the member is sealed in the anodic oxide film 20 shown in FIG. FIG. 4 shows how the member 10 causes thermal expansion during engine operation. FIG. 4 shows a state in which the alumite film 14 is cracked by being pulled by the thermal expansion of the member 10. However, the sealing agent 160 maintains its structure even when pulled by the thermal expansion of the member 10. This is because the sealing agent 160 has a thermal expansion coefficient equivalent to that of the member 10. Thus, even when the combustion chamber becomes a high temperature field during engine operation, the sealing agent 160 does not crack.

[Sealing agent composition 2]
In addition, in order to maintain the performance of the anodized film 20 even when the combustion chamber is at a high temperature, a layer having a thermal expansion coefficient equivalent to that of an aluminum alloy is provided between the sealing agent and the alumite film (hereinafter referred to as “aluminum alloy”). There is a method of taking a sealing agent composition 2. The sealant configuration 2 will be described with reference to FIG.

  FIG. 5 is a diagram for explaining the sealant configuration 2. In the anodic oxide film 20 having the sealing agent structure 2 shown in FIG. 5, an intermediate layer 18 is provided between the sealing agent 16 and the alumite film 14. The intermediate layer 18 has a thermal expansion coefficient equivalent to that of the aluminum alloy. The intermediate layer 18 is provided for the purpose of reducing the difference in thermal expansion between the alumite film 14 and the sealing agent 16. Thereby, it can prevent that the sealing agent 16 is pulled by the thermal expansion of the member 10, and is divided.

10 Member 12 Barrier layer 14 Anodized film 16 Sealing agent 20 Anodized film

Claims (1)

A method for forming a thermal barrier film of an internal combustion engine, wherein an anodized film is formed on a member constituting a wall surface of a combustion chamber of the internal combustion engine,
Forming an alumite film on the surface of the member;
Performing a sealing treatment on the alumite film at a temperature at which the member causes thermal expansion;
A method for forming a thermal barrier film for an internal combustion engine.

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