JP2013087721A - Method of forming heat shield film and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a heat shield film on an inner wall of a combustion chamber of an internal combustion engine in a short time at a low cost.SOLUTION: A method of forming the heat shield film 23 on the inner wall of the combustion chamber 16 defined by a cylinder bore 12, a lower surface of a cylinder head 15 and a top of a piston 13 in the internal combustion engine 10 includes a step of plating the inner wall of the combustion chamber 16 with a plating solution containing hollow micro-capsules 25 made of metal or alloy, thereby forming a plated layer 24 and the heat shield film 23 including the micro-capsules 25 interposed in the plated layer 24 on the inner wall of the combustion chamber 16.

Description

  The present invention relates to a method for forming a thermal barrier film on the inner wall of a combustion chamber defined by a cylinder bore, a cylinder head lower surface and a piston top in an internal combustion engine, and a combustion chamber defined by a cylinder bore, cylinder head lower surface and piston top. It is related with an internal combustion engine provided with.

  There is known a technique for improving fuel efficiency by forming a heat shield layer on a combustion chamber wall of an internal combustion engine to reduce heat transfer from combustion gas in the combustion chamber.

  For example, as described in Patent Document 1 and the like, a ceramic piston head portion having a low thermal conductivity is attached to the top surface portion of an aluminum piston body with an air layer (gap) provided between the piston body and the piston body. This method is known.

JP-A-8-4585

  However, in the above-described method, the heat capacity of the ceramic piston head portion is large, and the temperature of the piston head portion can be high even during the intake stroke. For this reason, the charging efficiency does not increase, and there is a risk that the fuel consumption will deteriorate.

  It is also conceivable to form a thin thermal barrier film on the combustion chamber wall. However, in a known method (for example, thermal spraying or the like), it takes time to apply the heat shield film, and the heat shield film cannot be mass-produced at low cost.

  Therefore, an object of the present invention is to form a heat shield film on the combustion chamber wall of an internal combustion engine in a short time and at a low cost.

  In order to achieve the above-mentioned object, the present invention is a method of forming a thermal barrier film on the inner wall of a combustion chamber defined by a cylinder bore, a cylinder head lower surface and a piston top in an internal combustion engine, which is made of hollow metal or An inner wall of the combustion chamber is formed by plating the inner wall of the combustion chamber with a plating solution containing an alloy microcapsule, thereby forming a plating layer and a thermal barrier film including the microcapsule interposed in the plating layer. It is a formation method of the thermal barrier film characterized by forming in.

  The microcapsules may be manufactured from the same material as the main component of the plating solution.

  Further, the present invention provides an internal combustion engine including a combustion chamber defined by a cylinder bore, a cylinder head lower surface, and a piston top, and further includes a heat shield film formed on an inner wall of the combustion chamber, and the heat shield film includes the combustion chamber An internal combustion engine comprising a plating layer formed on an inner wall of a chamber and a hollow metal or alloy microcapsule interposed in the plating layer.

  According to the present invention, there is an excellent effect that the heat shield film can be formed on the combustion chamber wall of the internal combustion engine in a short time and at a low cost.

The internal combustion engine to which the thermal barrier film forming method according to one embodiment of the present invention is applied is shown, (a) is a schematic view of the internal combustion engine, and (b) is an enlarged view of part A of (a). It is explanatory drawing which shows an example of the method of making a microcapsule. It is explanatory drawing which shows the formation method of the thermal barrier film which concerns on one Embodiment of this invention. It is the schematic of the internal combustion engine which concerns on a modification.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1A, an internal combustion engine (in this embodiment, a direct injection diesel engine) 10 according to the present embodiment is reciprocated up and down in a cylinder bore 12 formed in a cylinder block 11 and in the cylinder bore 12. A piston 13 (sliding) and a cylinder head 15 attached to the upper part of the cylinder block 11 with a gasket 14 interposed therebetween are provided. A space surrounded by the cylinder bore 12, the lower surface of the cylinder head 15, and the top of the piston 13 forms a combustion chamber 16. The cylinder head 15 has an intake / exhaust port (intake port 17 and exhaust port 18) communicating with the combustion chamber 16, an intake valve 19 that opens and closes the intake port 17, an exhaust valve 20 that opens and closes the exhaust port 18, and fuel. A fuel injection valve (injector) 21 for injecting the combustion chamber 16 from above is provided. Further, a cavity (reentrant type cavity in the illustrated example) 13 b is recessed in the top surface 13 a of the piston 13.

  In the internal combustion engine (direct injection type diesel engine) 10 shown in FIG. 1A, for example, fuel is injected into the combustion chamber 16 from the fuel injection valve 21 when the piston 13 is positioned near the compression top dead center. The fuel in the chamber 16 self-ignites and burns. A plurality of nozzle holes 22 are provided at the tip of the fuel injection valve 21, and each nozzle 22 is configured so that the fuel injected from the nozzle 22 near the compression top dead center of the piston 13 is directed toward the lip 13c of the cavity 13b. It is oriented.

  In the present embodiment, a heat shield film (heat shield layer) 23 for suppressing heat transfer from the combustion gas in the combustion chamber 16 to the piston 13 is formed on the top of the piston 13 forming the combustion chamber 16. More specifically, as shown in FIGS. 1A and 1B, the thermal barrier film 23 is formed on the top surface 13a of the piston 13 and a part of the cavity 13b (in the illustrated example, in the vicinity of the lip portion 13c of the cavity 13b). The top of the piston 13 is plated using a plating solution containing a microcapsule 25 made of a hollow metal or alloy. Therefore, the thermal barrier film 23 of the present embodiment includes a plated layer 24 formed on the top of the piston 13 and microcapsules 25 interposed in the plated layer 24. That is, the heat shield film 23 of the present embodiment functions as a heat shield layer (heat shield air layer) formed by the internal space of the microcapsule 25.

  Next, a method for forming the thermal barrier film 23 according to the present embodiment will be described with reference to FIGS.

[1] Preparation of Microcapsule There are various methods for making the microcapsule 25. An example of the method for making the microcapsule 25 is shown in FIG. That is, the method for making the microcapsule 25 is not limited to the method described below.

  In this embodiment, it is assumed that nickel plating is used, and the microcapsules 25 are made of nickel.

  First, as shown in FIG. 2A, the nickel child particles are driven into the resin-made mother particles by impact force. That is, the child particles are jetted onto the mother particles at a high speed. Thereafter, as shown in FIG. 2 (b), the combined body of the mother particles and the child particles is heated, and as shown in FIG. The microcapsule 25 is made of nickel.

  The particle size R of the microcapsule 25 is, for example, about 0.1 to 20 μm. In addition, the child particles that form the outer shell of the microcapsule 25 are assumed to be of nanoparticle size.

  Note that the reason why the microcapsules 25 are made of nickel in the present embodiment is that nickel plating is often used in electroless plating described later. In the case of plating other than nickel plating, the child particles are also changed according to the type of plating. That is, it is preferable to manufacture the microcapsule 25 using the same material as the main component of the plating solution.

  However, the material of the microcapsule 25 is not limited to the same material as the main component of the plating solution, and various materials (for example, materials having a melting point higher than that of the main component of the plating solution) can be used. is there.

[2] Formation of Thermal Barrier Film Electroless plating is used to adhere the nickel microcapsules 25 prepared in [1] above to the aluminum alloy piston 13 (to-be-plated body).

  For example, as shown in FIG. 3, electroless plating is a solution (electroless plating solution) in which a metal salt (M; Ni in the present embodiment) and a reducing agent (Red) coexist in the plating tank 26. An object to be plated is immersed to form a film on the surface of the object to be plated. Electrons released by oxidation (Ox) of the reducing agent (Red) are transferred to metal ions, and metal is deposited on the surface of the object to be plated. A film is formed.

  During the electroless plating, if the nickel microcapsules 25 prepared in [1] above are floated (mixed) in the electroless plating solution, nickel is formed on the surface of the object to be plated by the above reaction. When the film is formed, the microcapsule 25 is also taken in, and a bubble layer (heat shielding film 23) as shown in FIG. 1B can be formed on the piston 13 (to-be-plated body).

  The thickness T of the heat shield film 23 is, for example, about 50 to 100 μm.

  Note that the plating method is not limited to electroless plating, and may be plating of other methods (for example, electroplating). The kind of plating is not limited to nickel plating, and plating other than nickel plating may be used.

  In short, according to the present embodiment, the plating layer 24 is plated by plating the top of the piston 13 forming the combustion chamber 16 using a plating solution containing hollow metal or alloy microcapsules 25. Since the heat shield film 23 including the microcapsules 25 interposed in the plating layer 24 is formed on the top of the piston 13, the heat shield film 23 can be formed on the piston 13 (the counterpart member) in a short time and at a low cost. It becomes.

  That is, in this embodiment, since the top of the piston 13 that forms the combustion chamber 16 is plated using a plating solution containing hollow metal or alloy microcapsules 25, it is shorter than spraying or the like. The heat shield film 23 can be formed on the piston 13 (the counterpart member) at a low cost in time. In addition, since the thermal barrier film 23 of the present embodiment functions as a thermal barrier layer (thermal barrier air layer) formed by the internal space of the microcapsule 25, the main component of the plating solution and the material of the microcapsule 25 are used. It is not necessary to adopt a low thermal conductivity. Therefore, various materials can be used as the main component of the plating solution and the material of the microcapsule 25.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various other embodiments can be adopted.

  For example, in the above-described embodiment, the heat shielding film 23 is formed on the top of the piston 13, but this is not a limitation, and as shown in FIG. 4, the lower surface of the cylinder head 15 forming the combustion chamber 16 or the cylinder bore It is also possible to form a thermal barrier film 23 on the substrate 12. When the thermal barrier film 23 is formed on the lower surface of the cylinder head 15, as shown in FIG. 4, the thermal barrier film 23 may be formed only on the portion of the lower surface of the cylinder head 15 that faces the combustion chamber 16. Although not shown, the heat shield film 23 may be formed on the entire lower surface of the cylinder head 15. Further, when the heat shield film 23 is formed on the cylinder bore 12, it is conceivable that the surface of the heat shield film 23 is subjected to a surface treatment such as honing.

  In the above-described embodiment, the heat shield film 23 is formed on a part of the top surface 13 a and the cavity 13 b of the piston 13. However, the present invention is not limited to this, and the heat shield film 23 is formed on the top of the piston 13. In this case, as shown in FIG. 4, a heat shielding film 23 may be formed on the entire top surface 13 a and the cavity 13 b of the piston 13.

  The internal combustion engine 10 is not limited to a diesel engine, and may be a gasoline engine or the like. Further, the internal combustion engine 10 is not limited to a direct injection type, and may be a spark ignition type.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder bore 13 Piston 15 Cylinder head 16 Combustion chamber 23 Thermal insulation film 24 Plating layer 25 Microcapsule

Claims (3)

  A method of forming a thermal barrier film on the inner wall of a combustion chamber defined by a cylinder bore, a cylinder head lower surface and a piston top in an internal combustion engine, using a plating solution containing hollow metal or alloy microcapsules Forming a heat shielding film including a plating layer and the microcapsules interposed in the plating layer on the inner wall of the combustion chamber by plating the inner wall of the combustion chamber. Method.   The method for forming a thermal barrier film according to claim 1, wherein the microcapsule is manufactured from a material that is the same material as the main component of the plating solution.   An internal combustion engine having a combustion chamber defined by a cylinder bore, a cylinder head lower surface, and a piston top, includes a heat shield film formed on an inner wall of the combustion chamber, and the heat shield film is formed on an inner wall of the combustion chamber. An internal combustion engine comprising: a plated layer; and a hollow metal or alloy microcapsule interposed in the plated layer.