JP6036368B2 - Thermal insulation structure for engine combustion chamber and method for manufacturing the same - Google Patents

Description

  The present invention relates to a heat insulating structure in which a heat insulating layer is formed on the surface of a base material of a component constituting an engine combustion chamber, and a method for manufacturing the same.

In the 1980s, as a method for increasing the thermal efficiency of the engine, it was proposed to provide a heat insulating layer in a portion facing the engine combustion chamber (see, for example, Patent Document 1), and thereafter, a heat insulating layer made of a ceramic sintered body, or zirconia insulation layer made of thermally sprayed layer containing a (ZrO ₂₎ particles has been proposed to have a low thermal conductivity.

  However, the use of a ceramic sintered body causes problems such as generation of cracks due to thermal stress and thermal shock, and generation of cracks. For this reason, in particular, those in which a heat insulating layer made of a ceramic sintered body is applied to a portion having a relatively large area such as the top surface of the piston, the inner peripheral surface of the cylinder liner, and the lower surface of the cylinder head has reached practical use. Not in.

  On the other hand, the sprayed layer itself has been used for the trochoidal surfaces of cylinder liners and rotary engines, but it is intended to improve wear resistance and not to improve heat resistance. In order to make the thermal spray layer a heat insulating layer, it is preferable to spray a low thermal conductive material mainly composed of zirconia as described above, but the zirconia-based layer is inferior in adhesion between particles as compared with the cermet-based layer. Therefore, there is a problem that cracks are likely to occur due to fatigue due to thermal stress or repeated stress.

In order to solve such a problem, for example, Patent Document 2 proposes a heat insulating thin film including a particulate first heat insulating material, a film-shaped second heat insulating material, and a reinforcing fiber material. Yes. In Patent Document 2, it is described that the second heat insulating material has a function of bonding the first heat insulating material. As the particulate first heat insulating material, hollow ceramic beads, hollow glass beads, silica Examples thereof include a heat insulating material having a fine porous structure mainly composed of (silicon dioxide, SiO ₂ ), silica airgel, and the like. The film-like second heat insulating material includes ceramics such as zirconia (ZrO ₂ ), silicon, titanium, and zirconium, ceramics mainly composed of carbon and oxygen, and high-strength and high-heat-resistant ceramic fibers. Illustrated. Further, it is described that the second heat insulating material is coated or bonded to the base material.

In addition, Patent Document 3 describes a SiO ₂ ceramic layer including a hollow portion. Specifically, the hollow portion is formed by hollow inorganic compound particles formed by forming a layer containing a spherical resin whose surface is coated with an inorganic compound and then heating the layer to burn off the spherical resin. It is configured. In Patent Document 3, by heating the SiO ₂ ceramic layer, the resin in each particle is thermally decomposed and gasified, and the gas generated by the thermal decomposition of the organosilicon compound is extracted from the film. This prevents a decrease in film strength due to residual gas.

International Publication No. 89/039030 Pamphlet JP 2009-243352 A JP 2010-077092 A

  Patent Document 2 only describes that the second heat insulating material is coated or bonded to the base material, but does not describe in detail how to obtain the heat insulating thin film. In view of the fact that a ceramic material is used as the second heat insulating material, it is estimated that the heat insulating thin film is similar to a ceramic sintered body. Moreover, patent document 2 is not disclosing about effectively suppressing the deformation | transformation by cracking pressure etc. and generation | occurrence | production of a crack.

On the other hand, when the thin film of the SiO ₂ ceramic layer of Patent Document 3 is provided on the base material surface of the engine combustion chamber made of an aluminum alloy, the thermal expansion coefficient differs greatly. May occur. In addition, since the degassed portion as described above is in communication with the surface, problems such as infiltration of fuel occur.

Therefore, it is conceivable to use a silicone resin as a material having a small difference in thermal expansion coefficient from the aluminum alloy, instead of using the entire heat insulating layer as a SiO ₂ ceramic layer. However, since the silicone resin generally has a low hardness, if the wall surface of the engine combustion chamber is covered with the silicone resin, the heat insulating layer may be deformed by the pressure from the compression stroke to the time of combustion. When the heat insulating layer is deformed, the compression ratio changes, which greatly affects the engine performance. Further, when the heat insulating layer is exposed to this pressure fluctuation cycle for a long period of time, cracks may be generated in the heat insulating layer, and there is a possibility that the fuel may enter the uncured portion in the film.

  The present invention has been made in view of the above problems, and its purpose is to absorb the difference in thermal expansion coefficient between the engine parts and the base material to prevent the occurrence of cracks and delamination, and to penetrate the fuel. It is to obtain a heat insulating structure of an engine combustion chamber member having a heat insulating layer that can prevent the above, and to easily obtain such a heat insulating structure.

  In order to achieve the above object, the present invention uses a silicone resin and hollow particles as a material of a heat insulating layer used for a heat insulating structure of a member facing an engine combustion chamber, and a metal foil layer is formed on the surface of the heat insulating layer. Was provided.

Specifically, in the heat insulating structure of a member facing the engine combustion chamber according to the present invention, a heat insulating layer is provided on the combustion chamber wall surface of the member facing the combustion chamber of the engine, and the heat insulating layer includes a silicone resin and a hollow shape. comprising a resin layer having a surface layer comprising a base layer and Si-based oxide formed on the surface of the base layer and the hollow particles comprise particles and a metal foil layer formed on a surface of said surface layer, said surface The pencil hardness of the surface of the layer is HB or higher .

According to the heat insulating structure of the member facing the combustion chamber of the engine according to the present invention, the heat insulating layer includes a resin layer including a silicone resin having a low thermal conductivity and hollow particles exhibiting an air heat insulating effect. The effect is obtained, which is advantageous for reducing the cooling loss of the engine. Furthermore, since the thermal expansion of the engine member is absorbed by the resin layer containing the silicone resin, it is possible to prevent the occurrence of cracks in the heat insulating layer and the peeling. Moreover, since the metal foil layer is provided on the surface of the resin layer, the resin layer can be protected from combustion pressure and fuel. That is, deformation of the heat insulating layer due to combustion pressure (deformation of the resin layer portion) is prevented by the metal foil layer. Further, the penetration of fuel into the resin layer and the dissolution of the resin layer are prevented by the metal foil layer. Moreover, the metal foil layer has a smaller specific heat capacity than the silicone resin. For this reason, the surface temperature of the heat insulation layer follows the change of the combustion chamber gas temperature with good responsiveness, that is, the temperature difference between the surface temperature of the heat insulation layer and the combustion chamber gas temperature tends to be small, and as a result, the cooling loss is suppressed. Is done. Furthermore, if the surface of the heat insulating layer is locally hot, that portion may become an ignition source for abnormal combustion or may cause thermal damage to the silicone resin, but the metal foil layer is hotter than the silicone resin. Since the conductivity is high and the thermal diffusibility is good, the surface temperature of the heat insulating layer is prevented from being locally increased. Moreover, since the surface hardness of the resin layer is high because the pencil hardness of the surface layer is equal to or higher than HB, it is possible to prevent deformation and cracks in the resin layer due to combustion pressure and the like.

  In the heat insulating structure of the engine combustion chamber according to the present invention, the metal foil layer has an Al-containing layer containing Al (aluminum) on the surface side in contact with the resin layer, and the surface in contact with the resin layer of the Al-containing layer includes: It is preferable that a roughening treatment is performed.

  In this case, the roughening treatment is preferably at least one of blast treatment and anodizing treatment.

  If it does in this way, an unevenness | corrugation will be formed in the surface which contact | connects the resin layer of a metal foil layer, and the adhesiveness of a metal foil layer and a resin layer can be improved. In addition, when anodizing is used, a reactive group (OH group) that can be bonded to an organic group or the like of the silicone resin is generated on the surface, so that the adhesion between the metal foil layer and the resin layer can be improved. The peeling of the foil layer can be prevented.

  In the heat insulation structure for an engine combustion chamber according to the present invention, the heat insulation layer is preferably formed with a substantially uniform thickness so as to follow the shape of the combustion chamber wall surface of the member.

  If it does in this way, the local excessive heat insulation and the heat | fever contraction resulting from the difference in the heat insulation performance by the difference in the thickness of a heat insulation layer can be prevented.

  In the engine combustion chamber according to the present invention, the resin layer has a thickness of 60 μm or more and 200 μm or less, includes hollow particles of 20 vol% or more and 60 vol% or less, and the average particle diameter of the hollow particles is 15 μm or more and 25 μm or less. Preferably there is.

  If the thickness of the resin layer is 60 μm or more, the required heat insulating properties can be obtained, while if it is 200 μm or less, the shrinkage of the resin layer at the high temperature of the engine and the generation of outgas from the resin layer can be suppressed. The resin layer can be prevented from peeling off. For this reason, the thickness of the resin layer is preferably 60 μm or more and 200 μm or less.

  Further, when the content of the hollow particles in the resin layer is 20 vol% or more, since the air layer is contained in the resin layer in a large amount, the required heat insulating properties can be obtained. On the other hand, when the content is 60 vol% or less, the hollow particles It is possible to secure a sufficient amount of resin necessary to connect the two, and to form a durable film. For this reason, it is preferable that content of the hollow particle in a resin layer shall be 20 vol% or more and 60 vol% or less.

  Further, if the average particle diameter of the hollow particles is 15 μm or more, the amount of air contained in the particles can be increased, while if it is 25 μm or less, the amount of particles that can be contained with respect to the thickness of the resin layer is increased. And the required amount of air layer can be obtained. For this reason, a required heat insulation characteristic can be acquired if the average particle diameter of a hollow particle is the range. Furthermore, when the average particle diameter of the hollow particles is 25 μm or less, the surface roughness of the resin layer can be reduced, the surface temperature can be prevented from rising locally, and abnormal combustion of the engine and heat loss of the resin layer can be prevented. Therefore, the average particle diameter of the hollow particles is preferably 15 μm or more and 25 μm or less.

  In the heat insulating structure of the engine combustion chamber according to the present invention, it is preferable that the surface in contact with the heat insulating layer of the member facing the engine combustion chamber is subjected to at least one roughening treatment of blast treatment and anodization treatment. .

  If it does in this way, since an unevenness | corrugation is formed in the surface which contact | connects the heat insulation layer of the said member, the adhesiveness of the member and resin layer which face the combustion chamber of an engine can be improved. In addition, when anodization is used, reactive groups (OH groups) that can be bonded to organic groups of the silicone resin are generated, so that the adhesion between the member facing the combustion chamber of the engine and the resin layer can be improved. It can prevent that a heat insulation layer peels from an engine member.

The method for manufacturing a heat insulating structure for an engine combustion chamber according to the present invention is directed to a method for manufacturing a heat insulating structure for an engine combustion chamber in which a heat insulating layer is provided on a combustion chamber wall surface of a member facing the combustion chamber of the engine. forming a resin layer containing the combustion chamber wall surface and a silicone-based resin and hollow particles, a step of forming the metal foil into the same shape as the surface shape of the resin layer, the metal on the surface of the resin layer A step of adhering the foil, and a step of curing at least the surface side of the resin layer by heat treatment after adhering the metal foil .

According to the method for manufacturing a heat insulation structure for an engine combustion chamber according to the present invention, the heat insulation as described above is high and the cooling loss of the engine can be suppressed, and cracks and peeling due to the difference in the coefficient of thermal expansion with the engine member. In addition, it is possible to obtain a heat insulating layer that can prevent fuel penetration and the like. Since the manufacturing method according to the present invention is not complicated as described above and does not require a special apparatus or the like, the heat insulating layer can be easily obtained. In addition, before the step of bonding the metal foil to the surface of the resin layer, the metal foil is bonded to the resin layer after the metal foil is bonded to the resin layer by providing a step of forming the metal foil into the same shape as the surface shape of the resin layer. There is no need to process the metal foil, and processing of the metal foil is facilitated by performing it before bonding.

  In the method for manufacturing a heat insulating structure for an engine combustion chamber according to the present invention, the metal foil includes an Al layer on the side bonded to the resin layer, and before the step of bonding the metal foil to the surface of the resin layer, the Al It is preferable to further include a step of roughening the layer.

  If it does in this way, the adhesiveness of metal foil with respect to a resin layer can be improved, and peeling of metal foil can be prevented.

  In the method for manufacturing a heat insulating structure for an engine combustion chamber according to the present invention, a step of roughening the surface of the member before the step of forming the resin layer on the combustion chamber wall surface of the member facing the combustion chamber of the engine. Is preferably further provided.

  If it does in this way, since the adhesiveness of the member and resin layer which faces the combustion chamber of an engine can be improved, peeling of a resin layer can be prevented.

  According to the heat insulating structure for an engine combustion chamber member and the method for manufacturing the same according to the present invention, the heat insulating layer absorbs the difference in coefficient of thermal expansion from the member facing the engine combustion chamber to prevent cracks and peeling. Infiltration of fuel can be prevented, and a heat insulating structure having such a heat insulating layer can be easily obtained.

It is sectional drawing which shows the engine structure which concerns on embodiment of this invention. It is sectional drawing which shows the heat insulation structure of the engine combustion chamber member which concerns on this invention. It is an expanded sectional view showing the heat insulation layer of the heat insulation structure concerning the present invention. (A)-(c) is a figure which shows the method of manufacturing the heat insulation structure of the engine combustion chamber member based on this invention in order of a process. (A)-(c) is a figure which shows the processing method of metal foil in order of a process.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its method of application, or its application.

  In the present embodiment, the heat insulating structure of the engine combustion chamber member is employed in the engine shown in FIG.

<Engine features>
In the direct injection engine E shown in FIG. 1, reference numeral 1 is a piston, reference numeral 3 is a cylinder block, reference numeral 5 is a cylinder head, reference numeral 7 is an intake valve for opening and closing the intake port 9 of the cylinder head 5, and reference numeral 11 is an exhaust port 13. An exhaust valve that opens and closes, reference numeral 15 denotes a fuel injection valve. The combustion chamber of the engine is formed by the top surface of the piston 1, the cylinder block 3, the cylinder head 5, and the valve head surfaces of the intake and exhaust valves 7 and 11 (surfaces facing the combustion chamber). A cavity 17 is formed on the top surface of the piston 1. Note that the illustration of the spark plug is omitted.

  By the way, it is known that the thermal efficiency of the engine increases theoretically as the geometric compression ratio is increased and the excess air ratio of the working gas is increased. However, in practice, as the compression ratio is increased and the excess air ratio is increased, the cooling loss increases. Therefore, the improvement of the thermal efficiency due to the increase in the compression ratio and the excess air ratio reaches its peak.

  That is, the cooling loss depends on the heat transfer rate from the working gas to the engine combustion chamber wall, the heat transfer area, and the temperature difference between the gas temperature and the wall temperature. For this reason, in the engine combustion chamber, a heat insulating structure using a heat insulating layer made of a material having a lower thermal conductivity than the metal base material of the engine component is configured.

<Insulation structure>
So, below, the heat insulation structure which concerns on this embodiment is demonstrated.

  The heat insulation structure of the engine combustion chamber member according to the present embodiment is configured by forming a heat insulation layer on the top surface of a piston, which is a component constituting the engine combustion chamber. Such a heat insulating structure of the engine combustion chamber member will be described with reference to FIG.

  As shown in FIG. 2, a heat insulating layer 21 is formed on the top surface 19a (surface facing the engine combustion chamber) of the piston main body 19 as an engine member. A concave portion corresponding to the cavity 17 is formed at the center of the top surface 19a of the piston main body 19, and the heat insulating layer 21 is formed with a substantially uniform thickness so as to follow the shape of the top surface 19a.

  The heat insulating layer 21 includes a resin layer 27 as a heat insulating layer body and a metal foil layer 29 that covers the surface of the resin layer 27. The resin layer 27 includes a low thermal conductivity base layer 23 that covers the entire top surface 19 a of the piston body 19, and a high-hardness surface layer 25 that covers the entire surface of the base layer 23. For convenience of explanation, the drawing is drawn so that the base layer 23 and the surface layer 25 are in contact with each other with a boundary. However, as will be apparent from the following description, the surface layer 25 has a degree of oxidation of the silicone resin. The surface continuously decreases from the surface toward the inside and continues to the base layer 23, and there is actually no clear boundary between the layers 23 and 25. This also applies to FIG.

  In FIG. 2, the engine combustion chamber member is described as the piston main body 19. However, the invention is not limited to this, and the heat insulating layer 21 may be provided on a member constituting another engine combustion chamber such as a cylinder head.

  The piston body 19 in this example is made of an aluminum alloy that has been subjected to T6 treatment. The top surface 19a of the piston body 19 on which the heat insulating layer 21 is formed is subjected to at least one roughening treatment of blast treatment and anodizing treatment (alumite treatment). Thereby, irregularities are formed on the top surface 19 a of the piston body 19. Moreover, when an alumite process is used, the reactive group (OH group) couple | bonded with the organic group etc. of a silicone resin will be produced | generated. For this reason, the adhesiveness of the piston main body 19 and the resin layer 27 in the heat insulation layer 21 can be improved, and as a result, the heat insulation layer 21 can be prevented from peeling from the piston main body 19.

  The resin layer 27 is formed to have a thickness of 60 μm or more and 200 μm or less. If the thickness of the resin layer 27 is 60 μm or more, the required heat insulation characteristics can be obtained. On the other hand, if the thickness is 200 μm or less, the resin layer 27 contracts at a high temperature of the engine, and outgas generation from the resin layer 27 occurs. It can suppress and can prevent peeling of the resin layer 27. For this reason, the thickness of the resin layer 27 is preferably 60 μm or more and 200 μm or less.

  Further, as shown in FIG. 3, the resin layer 27 is a layer mainly composed of a silicone-based resin including hollow particles 31 of an inorganic oxide. That is, the base layer 23 of the resin layer 27 includes a large number of hollow particles 31 dispersed in a base material (matrix) 33 made of a silicone resin having a three-dimensional cross-linked structure. The base layer 23 is a low thermal conductivity layer because the base material 33 is composed of a silicone resin having a low thermal conductivity, and the air contains a low amount of thermal conductivity due to the inclusion of the hollow particles 31. Yes.

On the other hand, the surface layer 25 has a large number of hollow particles 31 dispersed in the base material 35. The base material 35 is made of a silicone resin, but at least part of the base material 35 is oxidized to form a Si base. It is an oxide (for example, SiO ₂ ). In particular, the oxidation degree of the silicone resin is high on the surface of the base material 35, and the oxidation degree is lower as the base layer 23 is approached. Thus, the surface layer 25 is a layer having high heat resistance and high hardness because the base material 35 is mainly composed of Si-based oxide, and further includes the hollow particles 31, so that heat conduction is achieved. The nature is also low. The surface layer 25 is formed, for example, by oxidizing a silicone resin by heat treatment. Here, it is an aluminum alloy that is a material of the piston body 19, and if the resin layer 27 formed on the surface of the piston body 19 is processed at an extremely high temperature, the mechanical strength of the piston body 19 may be reduced. For example, it is preferable to perform heat treatment at about 180 ° C. Furthermore, it is preferable to perform the heat treatment for about 65 hours so that the oxidation of at least the surface silicone resin in the resin layer 27 proceeds. Thereby, the oxidation of the silicone resin occurs at least partially, and the surface layer 25 having a pencil hardness of HB or higher can be formed.

As the inorganic oxide hollow particles 31, it is preferable to employ ceramic hollow particles containing a Si-based oxide component (for example, SiO ₂ ) such as fly ash balloon, shirasu balloon, silica balloon, and airgel balloon. . Each material and particle size are as shown in Table 1.

For example, the chemical composition of the fly ash _{balloons, SiO 2; 40.1~74.4%, Al} 2 O 3; 15.7~35.2%, Fe 2 O 3; 1.4~17.5%, MgO; 0.2 to 7.4%, CaO; 0.3 to 10.1% (the above is mass%). The chemical composition of the Shirasu _{balloon, SiO 2; 75~77%, Al} 2 O 3; 12~14%, Fe 2 O 3; 1~2%, Na 2 O; 3~4%, K 2 O; 2~ 4%, IgLoss; 2 to 5% (the above is mass%). The average particle diameter of the hollow particles 31 is preferably 15 μm or more and 25 μm or less, and the content in the resin layer 27 is preferably 20 vol% or more and 60 vol% or less.

  If the content of the hollow particles 31 in the resin layer 27 is 20 vol% or more, the resin layer 27 contains a large amount of air layer, so that the required heat insulating properties can be obtained. On the other hand, if the content is 60 vol% or less, the hollow particles Since the amount of the resin necessary to connect the 31 can be secured, a durable film can be formed. Therefore, the content of the hollow particles 31 in the resin layer 27 is preferably 20 vol% or more and 60 vol% or less.

  In addition, when the average particle diameter of the hollow particles 31 is 15 μm or more, the amount of air contained in the particles can be increased. On the other hand, when the average particle size is 25 μm or less, the amount of particles that can be contained with respect to the thickness of the resin layer 27. And a necessary amount of air layer can be obtained. For this reason, when the average particle diameter of the hollow particles 31 is within the range, necessary heat insulation characteristics can be obtained. Further, when the average particle diameter of the hollow particles 31 is 25 μm or less, the surface roughness of the resin layer 27 can be reduced, the local increase in the surface temperature can be prevented, and abnormal combustion of the engine and heat loss of the resin layer 27 can be prevented. Can do. Therefore, the average particle diameter of the hollow particles 31 is preferably 15 μm or more and 25 μm or less.

  As the silicone resin used in the present embodiment, for example, a silicone resin composed of a three-dimensional polymer having a high degree of branching represented by methyl silicone resin and methylphenyl silicone resin can be preferably used. Specific examples of the silicone resin include polyalkylphenylsiloxane.

  The metal foil layer 29 is made of a metal material having a high thermal conductivity. Examples of the metal include gold, silver, and nickel, but are not limited thereto. Further, the metal foil layer 29 has an Al-containing layer 30 made of Al or an Al alloy on the side in contact with the resin layer 27 (lower layer side). The Al-containing layer 30 is provided by performing vapor deposition or plating on one surface of the nickel foil or the like. In addition, the Al-containing layer 30 can be obtained by stacking and rolling an Al foil or an Al alloy foil on one surface of the nickel foil or the like. Moreover, the side (lower layer side) in contact with the resin layer 27 of the Al-containing layer 30 is subjected to a roughening treatment. As the roughening treatment, for example, a blast treatment or an anodizing treatment (alumite treatment) is performed. Can be used. Thereby, irregularities are formed on the lower layer side of the Al-containing layer 30, and adhesion with the resin layer 27 can be improved. Further, when anodizing is used, an OH group is generated on the lower layer side of the Al-containing layer 30, and the OH group can react and bond with the organic group of the silicone resin in the resin layer 27. Adhesion with the layer 27 can be improved. As a result, the adhesion between the metal foil layer 29 and the resin layer 27 can be improved, and the metal foil layer 29 can be prevented from peeling off from the resin layer 27.

  As described above, the heat insulating layer 21 has a high heat resistance, a small heat capacity and a high thermal conductivity, and a surface layer 25 having a high heat resistance and a high hardness mainly composed of a Si-based oxide. The low thermal conductivity base layer 23 mainly composed of a silicone resin is protected. Therefore, even if the heat insulating layer 21 is exposed to extremely severe heat and pressure environments, the base layer 23 is prevented from being deformed or damaged by the metal foil layer 29 and the surface layer 25 having increased hardness, and the silicone resin having low thermal conductivity. And the hollow particles 31 having an air insulation effect exhibit excellent heat insulation performance. Further, since the difference in thermal expansion between the metal foil layer 29 and the surface layer 25 and the piston main body 19 is absorbed by the low-hardness silicone resin of the base layer 23, the occurrence of cracks and peeling are prevented.

  Furthermore, since the specific heat capacity of the metal foil layer 29 is smaller than that of the silicone resin, the surface temperature of the heat insulating layer 21 follows the change in the gas temperature in the engine combustion chamber with good responsiveness. Thereby, the temperature difference between the surface temperature of the heat insulating layer 21 and the combustion chamber gas temperature tends to be small, and as a result, cooling loss is suppressed. In addition, since the metal foil layer 29 has higher thermal conductivity and better thermal diffusivity than the silicone resin, the surface temperature of the heat insulating layer 21 is prevented from being locally increased. Thereby, abnormal combustion of the engine is prevented, and heat loss of the silicone resin is also prevented.

<Method of manufacturing a heat insulating structure>
Next, the manufacturing method of the heat insulation structure which concerns on this embodiment is demonstrated, referring FIG. 4 (a)-(c) and FIG. 5 (a)-(c). 4 (a) to 4 (c) are views showing a method of manufacturing a heat insulating structure for an engine combustion chamber member according to the present invention in the order of steps. 5 (a) to 5 (c) are diagrams showing the processing method of the metal foil used for the production in the order of steps.

  In the following, a method of forming the heat insulating layer 21 on the top surface of the piston main body 19 will be described. However, the heat insulating layer may be formed on other engine members such as a cylinder block by the same method as that for the piston main body 19. it can.

First, a piston body 19 that is an engine member and a heat insulating layer material are prepared. About the piston main body 19, stain | pollution | contamination, such as fats and oils and fingerprints adhering to the surface which should form the heat insulation layer, is removed by a degreasing process. In addition, a resin material 27a obtained by stirring and mixing a silicone resin and hollow particles is prepared as a heat insulating layer material. If necessary, a thickener or a dilution solvent is added to adjust the viscosity of the resin material 27a. Here, in order to increase the adhesion between the piston main body 19 and the resin material 27a, particularly the silicone resin, it is preferable to subject the top surface 19a to which the resin layer material of the piston main body 19 is applied to a roughening treatment. As the roughening treatment, for example, blasting such as sand blasting is preferably performed. For example, the blasting process can be performed using an air blasting apparatus, using alumina having a particle size of # 30 as an abrasive, and processing conditions of a pressure of 0.39 MPa, a time of 45 seconds, and a distance of 100 mm. In addition, when not only this but the piston main body 19 consists of Al alloys, you may improve the adhesive force of the piston main body 19 and the resin material 27a containing silicone resin by performing an alumite process. For example, the alumite treatment can be performed using an oxalic acid bath under a treatment condition of a bath temperature of 20 ° C., a current density of 2 A / dm ² , and a time of 20 minutes.

  After preparing the piston main body 19 and the resin agent 27 as described above, the resin material 27a is applied to the top surface 19a of the piston main body 19 using a spray or a brush as shown in FIG. Subsequently, the resin material 27a on the top surface 19a of the piston body 19 is preliminarily dried by hot air drying, an infrared heater, or the like. When the thickness of the resin material 27a does not reach the desired thickness, application and preliminary drying are repeated until the desired thickness is reached (overcoat coating), and the thickness is adjusted to the desired thickness. Alternatively, the resin material 27a is placed on the top surface 19a of the piston body 19, and the resin material 27a is pressed against the top surface 19a of the piston body 19 by a molding die having a molding surface that follows the shape of the piston top surface 19a. You may spread over. As described above, the thickness of the resin material 27a can be adjusted. In the present embodiment, the thickness is adjusted to 60 μm or more and 200 μm or less for the above reason.

  Next, as shown in FIG. 4B, a metal foil 29a is bonded to the surface of the formed resin material 27a. At this time, it can adhere | attach by pressing using the type | mold of the same shape as the shape of the top surface 19a of a roller or the piston main body 19. FIG.

  Prior to this bonding, the metal foil 29a is previously formed into the surface shape of the resin material 27a (the shape of the top surface 19a of the piston body 19). The forming method is not particularly limited. For example, as shown in FIGS. 5A and 5B, the metal foil 29 a made of, for example, nickel and having a thickness of about 1 μm to 5 μm, and the top surface 19 a of the piston main body 19. An upper die 39a and a lower die 39b corresponding to the shapes are prepared, and the metal foil 29a is formed into the shape of the top surface 19a of the piston main body 19 (surface shape of the resin material 27a) by an ordinary press forming method. At this time, it is preferable that the surface of the lower mold 39b is roughened, and in this way, the lower surface of the metal foil 29a (the surface to be bonded to the resin material 27a) is roughened and bonded to the resin material 27a. Can be improved.

Thereafter, as shown in FIG. 5C, an Al-containing layer 30 containing Al is formed by performing a process such as vapor deposition of Al or an Al alloy on the lower surface of the molded metal foil 29a. In vapor deposition, for example, using a resistance heating type vacuum vapor deposition apparatus, a pure Al film can be obtained by processing for 2 minutes in a high vacuum (10 ⁻⁴ Pa or less), whereby the Al-containing layer 30 can be obtained. . In addition, you may use other methods, such as a plating method, for formation of Al content layer 30. Furthermore, it is preferable to perform an alumite treatment on the formed Al-containing layer 30, and in this way, the adhesion between the metal foil 29a and the resin material 27a can be further improved, and peeling of the metal foil 29a can be prevented. . The alumite treatment can be performed, for example, using an oxalic acid bath, under a bath temperature of 20 ° C., a current density of 2 A / dm ² , and a treatment condition of 5 minutes. Note that the Al-containing layer 30 may be roughened by performing a blasting process such as sandblasting in addition to the anodizing process. The blasting process can be performed, for example, using a microblasting apparatus, using alumina having a particle size of # 3000 as an abrasive, and processing conditions of a pressure of 0.1 MPa, a time of 45 seconds, and a distance of 100 mm.

  As described above, after processing the metal foil 29a and bonding the metal foil 29a to the resin material 27a, as shown in FIG. 4C, the resin material 27a is heated at about 180 ° C. for about 65 hours. Heat treatment is performed. The heat treatment is not particularly limited as long as it can be cured by oxidizing at least the surface portion of the silicone resin in the resin material 27a and the temperature and time do not soften the Al alloy piston main body 19. At this time, since heat is transmitted from the surface of the resin material 27a to the inside, the resin material 27a has a temperature gradient in which the temperature gradually decreases from the surface toward the inside. Since the surface of the resin material 27a is heated to a temperature equal to or higher than the oxidation temperature of the silicone resin, the silicone resin on the surface is oxidized to produce a Si oxide. That is, on the surface side of the resin material 27a, the surface layer 25 in which the hollow particles 31 are dispersed in the cured base material 35 mainly composed of the Si-based oxide shown in FIG. 3 is formed.

  Although the silicone resin inside the heat insulating material layer is also cross-linked by the heating, the temperature does not rise so as to oxidize the silicone resin due to the temperature gradient, and the above-described three-dimensional cross-linked silicone type shown in FIG. The base layer 23 in which the hollow particles 31 are dispersed using the resin as a base material 33 is formed. Further, the base layer 23 is in a state of being bonded to the piston body 19 through the silicone resin having the three-dimensional crosslinked structure in the course of the crosslinking of the silicone resin.

  As described above, the heat insulating layer 21 including the resin layer 27 including the base layer 23 and the surface layer 25 and the metal foil layer 29 illustrated in FIG. 3 is formed on the top surface 19 a of the piston body 19.

  As a method of heating the surface of the resin material 27a, the surface of the metal foil 29a may be directly heated by a flame, or may be heated by an infrared heater or the like.

  In order to suppress oxidation of the internal silicone resin while oxidizing the silicone resin on the surface of the heat insulating material layer, the piston main body 19 may be cooled from the inside of the piston skirt by water cooling or air cooling. Further, before the surface of the heat insulating material layer is heated, the whole heat insulating material layer may be heated to a temperature lower than the oxidation temperature of the silicone resin to advance the crosslinking of the silicone resin.

1 Piston 3 Cylinder block (Engine member)
5 Cylinder head (engine member)
7 Intake valve (engine parts)
11 Exhaust valve (engine member)
19 Piston body (Engine member)
19a Top surface 21 Heat insulation layer 23 Base layer 25 Surface layer 27 Resin layer 27a Resin material 29 Metal foil layer 29a Metal foil 30 Al-containing layer 31 Hollow particles 33 Base layer base material (silicone resin)
35 Base material 39a upper mold 39b lower mold having Si-based oxide of surface layer

Claims (9)

An engine combustion chamber heat insulating structure in which a heat insulating layer is provided on a combustion chamber wall surface of a member facing the engine combustion chamber,
The heat insulating layer is provided on the surface of the surface layer including a base layer including a silicone resin and hollow particles, a Si oxide provided on the surface of the base layer, and a surface layer including the hollow particles, and the surface layer. A metal foil layer ,
The heat insulation structure for an engine combustion chamber, wherein the surface layer has a pencil hardness of HB or more . The metal foil layer has an Al-containing layer containing Al on the surface side in contact with the surface layer,
The heat insulation structure for an engine combustion chamber according to claim 1, wherein a surface of the Al-containing layer in contact with the surface layer is subjected to a roughening treatment.   The heat insulation structure for an engine combustion chamber according to claim 2, wherein the roughening treatment is at least one of a blast treatment and an anodizing treatment.   The heat insulation structure for an engine combustion chamber according to any one of claims 1 to 3, wherein the heat insulation layer is formed with a substantially uniform thickness so as to follow the shape of the combustion chamber wall surface of the member. body. The resin layer has a thickness of 60 μm or more and 200 μm or less, and includes the hollow particles of 20 vol% or more and 60 vol% or less,
5. The heat insulation structure for an engine combustion chamber according to claim 1, wherein an average particle diameter of the hollow particles is 15 μm or more and 25 μm or less. The engine combustion according to any one of claims 1 to 5 , wherein a surface of the member in contact with the heat insulating layer is subjected to at least one roughening treatment of blast treatment and anodizing treatment. Room insulation structure. A method for manufacturing a heat insulating structure for an engine combustion chamber in which a heat insulating layer is provided on a combustion chamber wall surface of a member facing the engine combustion chamber,
Forming a resin layer containing the silicone resin and the hollow particles on the combustion chamber wall of the member;
Forming a metal foil into the same shape as the surface shape of the resin layer;
A step of bonding the metal foil to the surface of the resin layer,
And a step of curing at least the surface side of the resin layer by heat treatment after the metal foil is bonded . A method for producing a heat insulating structure for an engine combustion chamber. The metal foil includes an Al layer on the side bonded to the resin layer,
The engine combustion chamber according to claim 7 , further comprising a step of roughening the surface of the Al layer before the step of bonding the metal foil to the surface of the resin layer. Manufacturing method of heat insulation structure. The engine combustion according to claim 7 or 8 , further comprising a step of subjecting the surface of the member to a roughening treatment before the step of forming the resin layer on the combustion chamber wall surface of the member. A method for manufacturing a heat insulating structure of a room.

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