WO2018029903A1 - Internal combustion engine piston and method for manufacturing internal combustion engine piston - Google Patents

Internal combustion engine piston and method for manufacturing internal combustion engine piston Download PDF

Info

Publication number
WO2018029903A1
WO2018029903A1 PCT/JP2017/014606 JP2017014606W WO2018029903A1 WO 2018029903 A1 WO2018029903 A1 WO 2018029903A1 JP 2017014606 W JP2017014606 W JP 2017014606W WO 2018029903 A1 WO2018029903 A1 WO 2018029903A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
combustion engine
internal combustion
conductive layer
low thermal
Prior art date
Application number
PCT/JP2017/014606
Other languages
French (fr)
Japanese (ja)
Inventor
高橋　智一
Original Assignee
日立オートモティブシステムズ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日立オートモティブシステムズ株式会社 filed Critical 日立オートモティブシステムズ株式会社
Publication of WO2018029903A1 publication Critical patent/WO2018029903A1/en

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/10—Pistons  having surface coverings
    • F02F3/12—Pistons  having surface coverings on piston heads
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/26—Pistons  having combustion chamber in piston head
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J1/00—Pistons; Trunk pistons; Plungers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to a piston for an internal combustion engine.
  • Patent Document 1 a piston of an internal combustion engine is known (for example, Patent Document 1).
  • the conventional piston has room for easy manufacture.
  • the piston of the internal combustion engine has a low heat conductive layer containing a layered silicate mineral in the piston head.
  • FIG. 1 schematically shows a cross section of a part of an engine taken along a plane passing through the axis of one cylinder of the first embodiment.
  • 1 is a perspective view of a piston according to a first embodiment. The cross section (henceforth an axial direction cross section) which cut the piston of 1st Embodiment with the plane which passes along the axis line is shown.
  • FIG. 3 is a perspective view of a piston after a casting process according to the first embodiment. The axial direction cross section of the piston after the casting process of 1st Embodiment is shown.
  • FIG. 3 is a perspective view of the piston after the material installation process of the first embodiment. The axial direction cross section of the piston after the material installation process of 1st Embodiment is shown.
  • FIG. 2 shows an axial cross-section of the piston during the sintering process of the first embodiment.
  • FIG. 3 is a perspective view of the piston after the sintering process of the first embodiment.
  • 2 shows an axial cross section of the piston after the sintering step of the first embodiment.
  • the axial direction cross section of the piston of 2nd Embodiment is shown.
  • FIG. 10 is a perspective view of a piston after a second material installation step of the second embodiment.
  • the axial direction cross section of the piston after the 2nd material installation process of 2nd Embodiment is shown.
  • FIG. 6 shows an axial cross section of a piston during a second sintering step of the second embodiment.
  • FIG. FIG. 10 is a perspective view of a piston after a second sintering step of the second embodiment.
  • FIG. 7 shows an axial cross section of the piston after the second sintering step of the second embodiment.
  • FIG. FIG. 5 is a perspective view of a preform of a forming material according to a third embodiment.
  • FIG. 10 is a perspective view of a piston according to a fourth embodiment.
  • FIG. 6 shows an axial cross section of a piston according to a fourth embodiment.
  • FIG. The axial direction cross section of the piston of other embodiment is shown.
  • the axial direction cross section of the piston of other embodiment is shown.
  • the internal combustion engine (engine) 100 of the present embodiment shown in FIG. 1 is a 4-stroke gasoline engine.
  • the engine 100 includes a piston 1, a cylinder block 101, a cylinder head 104, a connecting rod (connecting rod) 106, a crankshaft, a valve 107, an ignition device 108, and a combustion chamber 11.
  • the valve 107 has two intake valves and two exhaust valves.
  • the cylinder block 101 includes a cylindrical cylinder liner (cylinder sleeve) 102.
  • the inner peripheral side of the cylinder liner 102 functions as the inner wall of the cylinder 10.
  • the cylinder head 104 is installed in the cylinder block 101 so as to close the opening of the cylinder 10.
  • the cylinder head 104 is provided with a valve 107, a fuel injection nozzle, and an ignition device 108.
  • a crankshaft is rotatably installed on the cylinder block 101.
  • the piston 1 is accommodated in the cylinder 10 so as to be reciprocally movable.
  • the format of engine 100 is arbitrary.
  • the engine 100 may be a two-stroke engine or a diesel engine.
  • the fuel supply method may be an in-cylinder direct injection type that directly injects into the cylinder 10 (combustion chamber 11), or a port injection type that injects into the intake port.
  • the piston 1 has a piston main body 2 and a low heat conductive layer 3.
  • the piston body 2 is formed of an aluminum alloy (for example, Al-Si AC8A) as a material (raw material) for weight reduction and the like.
  • the piston 1 (piston body 2) has a bottomed cylindrical shape, and includes a piston head (crown portion) 4, a piston boss (apron portion) 5, and a piston skirt (skirt portion) 6.
  • the direction in which the axis of the piston 1 extends (the direction along the moving direction of the piston body 2 in the cylinder 10) is referred to as the axial direction.
  • the side of the piston head 4 with respect to the piston boss 5 and piston skirt 6 in the axial direction is called one side, and the opposite side is called the other side.
  • the piston head 4 has a crown surface portion 40 and a land portion 41.
  • the crown surface portion 40 is on one side in the axial direction of the piston head 4 and has a crown surface (top surface) 400.
  • the crown surface 400 is a flat surface extending perpendicularly to the axis of the piston 1 and has a substantially circular outline when viewed from one side in the axial direction.
  • the combustion chamber 11 is defined between the crown surface 400 and the cylinder head 104.
  • the combustion chamber 11 is a pent roof type.
  • the crown surface 400 is directly exposed to the combustion gas in the combustion chamber 11.
  • the piston body 2 includes a recess 401 on the combustion chamber 11 side (side facing the combustion chamber 11) of the piston head 4 (crown surface portion 40).
  • the concave portion 401 is substantially at the center of the crown surface 400 in the crown surface portion 40 and has a bottomed cylindrical shape (a shallow dish shape whose bottom surface is a flat surface).
  • the axis of the recess 401 substantially coincides with the axis of the piston 1 (within manufacturing error).
  • the land portion 41 extends from the outer peripheral side of the crown surface portion 40 to the other side in the axial direction.
  • a piston ring 7 is installed in the ring groove 410.
  • Inside the land portion 41 is an annular passage 411.
  • the passage 411 extends in the circumferential direction of the piston 1 and surrounds the recess 401 when viewed from the axial direction.
  • the passage 411 overlaps at least a part of the region where the ring groove 410 is formed in the axial direction.
  • the piston boss 5 and the piston skirt 6 extend from the piston head 4 (land portion 41) to the other side in the axial direction, and are on the opposite side of the combustion chamber 11 with respect to the piston head 4.
  • the inner peripheral sides of the piston skirt 6 and the piston boss 5 are hollow.
  • Each piston boss 5 has a pin boss 50.
  • Each pin boss 50 has a piston pin hole 51.
  • the piston pin hole 51 extends through the pin boss 50 in the radial direction of the piston 1.
  • the piston skirt 6 is sandwiched between the piston bosses 5 and 5 in the circumferential direction of the piston 1.
  • Both piston skirts 6 and 6 are connected by a piston boss 5.
  • the piston skirt 6 slides against the inner wall of the cylinder 10.
  • the piston pin end 51 is fitted into the piston pin hole 51.
  • the piston 1 is connected to one end side (small end portion) of the connecting rod 106 via a piston pin.
  • the other end side (large end portion) of the connecting rod 106 is connected to the crankshaft.
  • ⁇ Cooling water circulates in the passage 103 inside the cylinder liner 102.
  • An oil jet 105 is installed in the cylinder block 101.
  • the heat transferred from the combustion chamber 11 to the piston head 4 is released by being transferred to the cylinder liner 102 and the cooling water therein through the piston ring 7.
  • the heat is also released when oil adheres to and flows out from the inner peripheral side (back side) of the piston 1 or when oil flows through the passage 411. This adhesion and distribution of oil is performed, for example, by oil injection from the oil jet 105.
  • the passage 411 functions as a cooling passage (cooling channel).
  • the low thermal conductive layer 3 is a structure for reducing the thermal conductivity from the combustion chamber 11 to the piston body 2, and is located on one side in the axial direction of the piston head 4 (on the combustion chamber 11 side). It is formed on a part of the facing surface (crown surface 400). All of the low thermal conductive layer 3 is accommodated in the recess 401. As shown in FIGS. 2 and 3, the low thermal conductive layer 3 has a planar shape extending along the crown surface 400 (and the bottom surface of the recess 401). The thickness of the layer 3 (the depth of the recess 401) is arbitrary. There are voids (hollow portions) 33 inside the layer 3, and a plurality of voids 33 are dispersed. Gas (air) exists in the gap 33. A part of the plurality of voids 33 opens on the surface (crown surface 400) of the layer 3 on the combustion chamber 11 side.
  • the low heat conductive layer 3 includes a metal binder 31 and a layered silicate mineral.
  • the binder 31 includes aluminum.
  • Aluminum may be pure aluminum, an aluminum alloy, or may include both pure aluminum and an aluminum alloy.
  • the binder 31 may contain an additive in addition to aluminum.
  • the layered silicate mineral is expanded (vermiculite 32) when the meteorite 35 (which is a layered hydrous silicate mineral) is rapidly heated.
  • the air gap 33 is mainly inside the vermiculite 32.
  • a plurality of vermiculites 32 are dispersed inside the layer 3 together with the gaps 33, and the maximum external dimensions thereof are, for example, several mm.
  • the manufacturing method includes a casting process, a heat treatment process, a low thermal conductive layer forming process, and a machining process.
  • a prototype (intermediate workpiece) 2A of the piston body 2 as shown in FIGS. 4 and 5 is cast. Specifically, a molten aluminum alloy is poured into a mold and solidified. At this time, the inner periphery of the piston body 2 is formed, and the original 401A of the recess 401 and the passage 411 are formed.
  • the concave portion 401 may be formed or finished by machining.
  • heat treatment step heat treatment is performed.
  • the low thermal conductive layer 3 is formed on the prototype 4A (in the combustion chamber 11 side).
  • Layer 3 is formed as early as after the heat treatment step. (The heat treatment step is performed before the low thermal conductive layer forming step.)
  • the layer 3 is formed after the heat treatment step and before the machining step. In the machining process, the prototype on which the layer 3 is formed is machined by a lathe or the like.
  • the side of the piston head 4 facing the combustion chamber 11 is cut to form the crown surface 400. The entire surface of the piston head 4 on the combustion chamber 11 side is machined.
  • the piston pin hole 51 and the ring groove 410 are processed, and the outer diameter of the piston body 2 such as the outer periphery of the piston head 4 and the piston skirt 6 is finished. Thereby, the piston 1 as shown in FIGS. 2 and 3 is formed.
  • the low thermal conductive layer forming process includes a material preparation process, a material installation process, and a sintering process.
  • a material for forming the low thermal conductive layer 3 (hereinafter referred to as a forming material 36) is prepared.
  • the forming material 36 includes a metal powder and a layered hydrous silicate mineral powder.
  • the metal powder is aluminum powder 34.
  • the layered hydrous silicate mineral is meteorite 35 (hydrobiotite), in other words vermiculite before firing at high temperature.
  • the meteorite 35 is prepared and used as a powder having an average particle diameter of, for example, not less than 0.3 mm and not more than several mm.
  • a material 36 (mixed material that is a powder) is prepared by mixing aluminum powder 34 and meteorite 35 at a predetermined (weight or volume) ratio. In the mixed material, the meteorite 35 is dispersed in the aluminum powder 34.
  • the mixed forming material 36 is filled into the recess 401A of the prototype 2A (heat-treated). Specifically, the forming material 36 is put up to the upper end of the recess 401A. Note that the position of the forming material 36 in the recess 401A is arbitrary. Alternatively, after the aluminum powder 34 and the meteorite 35 are separately put into the recess 401A, they may be mixed in the recess 401A.
  • the filled forming material 36 (specifically, the aluminum powder 34) is sintered.
  • the principle of friction stir welding (joining) is used and sintering is performed using a rotating tool (tool) 8.
  • the tool 8 has a cylindrical shape, and the diameter D2 of the axial end 80 thereof is not less than the diameter D1 of the recess 401A, and is preferably slightly larger than the diameter D1.
  • the axis of the tool 8 is aligned with the central axis of the recess 401A.
  • the axial end 80 of the tool 8 is pressed against the forming material 36 (the axial pressing force is indicated by arrow B). ).
  • the tool 8 is rotated with the end portion 80 of the tool 8 pressed against the forming material 36.
  • the forming material 36 is sintered, and the low thermal conductive layer 3 made of a sintered body whose volume is smaller than the original is formed.
  • the sintering is completed (the low thermal conductive layer 3 is formed), the tool 8 is pulled up from the recess 401A.
  • a prototype 2B of the piston 1 as shown in FIGS. 9 and 10 is formed.
  • the prototype 401B of the recess 401 is formed on the prototype 4B of the piston head 4. Then, the said machining process is performed. A part of the low thermal conductive layer 3 is cut together with the prototype 4B of the piston head, and the crown surface 400 including the low thermal conductive layer 3 on the surface is finished into a flat surface.
  • the forming material 36 is mixed while being pressed by the rotating tool 8 and heated by frictional heat.
  • the aluminum powder 34 plastically flows, the oxide film on the surface of each powder 34 is broken, and the powder is sintered. Further, the volume of each meteorite 35 expands due to the heating. This is because the crystal water between the layers of the meteorite 35 is vaporized (evaporated) by rapid heating, so that the layers spread in an accordion shape and change into vermiculite 32 containing many air layers inside. Therefore, the low thermal conductive layer 3 is obtained by forming a plurality of voids 33 in each vermiculite 32 inside an aluminum sintered body (binder 31).
  • the air gap 33 contains air. A part of the plurality of voids 33 are opened on the surface of the layer 3 after the machining process.
  • the low heat conductive layer 3 is held on the piston head 4 by the recess 401.
  • the layer 3 faces the combustion chamber 11 and constitutes part of the wall of the combustion chamber 11.
  • the sintered body of the aluminum powder 34 in the layer 3 contains more minute voids (pores) than the piston body 2 formed by casting.
  • the void has a lower thermal conductivity than the solid. Therefore, the layer 3 as a whole has a lower thermal conductivity than the piston body 2.
  • the vermiculite 32 in the layer 3 is a low thermal conductivity material and has a lower thermal conductivity than the aluminum alloy that is the material (base metal) of the piston body 2.
  • the layer 3 as a whole (on average) has a lower thermal conductivity than the piston body 2.
  • vermiculite 32 (expanded meteorite 35). These voids 33 have extremely low thermal conductivity. Vermiculite 32 functions as a heat insulating material. Therefore, the layer 3 as a whole has a much lower thermal conductivity.
  • the aluminum powder 34 functions as a binder 31 by adhering to each other or the piston body 2, and holds the vermiculite 32 in the layer 3.
  • the layer 3 is between the combustion chamber 11 and the piston body 2 and functions as a heat insulating layer.
  • the layer 3 reduces the heat transfer from the gas in the combustion chamber 11 to the piston head 4 (piston body 2), so that the heat of the fuel (air mixture) supplied to the combustion chamber 11 is taken away by the piston body 2. Suppress. Therefore, a reduction in combustion efficiency can be suppressed and the thermal efficiency of engine 100 can be improved.
  • the low thermal conductive layer 3 is located on the crown surface 400 at least at a location corresponding to the fuel injection region (the location where the fuel collides and explodes and the temperature and pressure become highest and its surroundings). Preferably it is formed.
  • the layer 3 is formed at this location, heat transfer from the gas in the combustion chamber 11 to the piston head 4 (piston body 2) can be more effectively reduced.
  • the portion where the fuel adheres on the crown surface 400 quickly becomes high temperature and maintains a high temperature state. Therefore, the adhering fuel is quickly vaporized and burned, so that deterioration of exhaust gas characteristics can be suppressed. If the layer 3 is not formed on the crown surface 400 other than the above portion, it is possible to suppress the occurrence of knocking due to an unnecessarily high temperature at a portion other than the above portion.
  • the void 33 is formed by the evaporation of crystal water contained in the meteorite 35.
  • the crystal water is vaporized and expanded, and voids 33 are formed between the layers of the meteorite 35.
  • the sintering process functions as a void forming process.
  • the void 33 can be easily formed by mixing the vaporizing component (substance) in the forming material 36.
  • the layered hydrous silicate mineral (meteorite 35) having the property of expanding by heating as the forming material 36, the low thermal conductive layer 3 including the voids 33 can be easily provided on the piston head 4.
  • the aluminum powder 34 functions as the binder 31
  • the strength (hardness) of the bond inside the low thermal conductive layer 3 including the voids 33 is improved, and the chipping and collapse thereof are suppressed. Further, the bonding strength between the layer 3 and the piston body 2 is improved, and the force for holding the layer 3 in the piston head 4 (recess 401) is improved. Therefore, the function of the layer 3 can be maintained for a longer period.
  • additives sining aids and the like
  • the binder 31 is a metal (aluminum). Therefore, even if a relatively large gap 33 is formed, the strength of the layer 3 can be improved and the chipping and collapse can be more easily suppressed.
  • the binder 31 is the aluminum powder 34, the bonding force between the piston body 2 and the layer 3 formed of an aluminum alloy can be improved.
  • the aluminum powder 34 may be a pure aluminum powder or an aluminum alloy powder (for example, AC8A, which is the same as the base metal of the piston body 2).
  • the aluminum powder 34 may be granular aluminum powder.
  • the binder 31 is sintered, and the meteorite 35 is expanded by the heat at the time of sintering, whereby the gap 33 is formed. Since the sintering of the binder 31 and the formation of the voids 33 are performed simultaneously (in the same process), the manufacturing method is simplified. In other words, the low thermal conductive layer 3 including the voids 33 can be efficiently formed.
  • the piston head 4 has a recess 401. Therefore, even when sintering is performed by rotating the tool 8 using the principle of friction stir welding, the powder (formation material 36) is held on the piston head 4 and can be stirred by applying pressure to the powder. It is.
  • the diameter D2 of the tool 8 is not less than the diameter D1 of the recess 401.
  • the powder (forming material 36) can be prevented from jumping out from the radial gap between the end 80 of the rotating tool 8 and the recess 401.
  • Diameter D2 is larger than diameter D1. Therefore, since the layer 3 is formed while a part of the outer edge of the recess 401 is wound with the rotating tool 8, the bonding force between the layer 3 and the recess 401 can be improved.
  • sintering may be performed by, for example, a discharge plasma sintering method. Also in this case, sintering of the binder 31 and formation of the voids 33 are performed simultaneously.
  • the machining process is performed after the low thermal conductive layer forming process.
  • the side facing the combustion chamber 11 of the piston head 4 is cut to form the crown surface 400. That is, the layer 3 is formed before the crown surface 400 is formed by cutting. Therefore, in the low thermal conductive layer forming step, there are few restrictions due to the shape of the crown surface 400, so that the operation of forming the layer 3 becomes easy. In other words, the layer 3 can be easily formed on the crown surface 400 having a complicated shape (see FIG. 20).
  • the low thermal conductive layer 3 has a first layer 301 on the other side in the axial direction (on the side of the piston body 2 or on the side opposite to the combustion chamber 11), and on one side in the axial direction (the combustion chamber 11).
  • the second layer 302 is provided on the second side. The surface of the second layer 302 faces the combustion chamber 11, and the surface (back surface) opposite to the combustion chamber 11 of the second layer 302 is in contact with the surface of the first layer 301.
  • the difference between layers can be determined by properties, shapes, functions, and the like.
  • the thickness of each layer 301, 302 is arbitrary.
  • the first layer 301 is a rough layer having more voids 33 than the second layer 302.
  • the second layer 302 is a dense layer with fewer gaps 33 than the first layer 301.
  • the ratio of the volume of the voids 33 (vermiculite 32) in the first layer 301 is larger than 50% as a whole (averaged over the entire first layer 301), preferably 70% or more, more preferably 90%. That is all (100% is acceptable).
  • the ratio of the volume of aluminum (binder 31) in the first layer 301 (including the minute voids inside the sintered body) as a whole is less than 50%, preferably 30% or less, more preferably 10%.
  • the ratio of the volume of the voids 33 (vermiculite 32) to the second layer 302 is less than 50% as a whole (averaged over the entire second layer 302), preferably 30% or less, more preferably 10%. It is as follows (it may be 0%).
  • the proportion of the volume of aluminum (binder 31) in the second layer 302 as a whole is greater than 50%, preferably 70% or more, more preferably 90% or more (or 100% may be used).
  • Other configurations are the same as those of the first embodiment.
  • the low thermal conductive layer forming process includes a material preparation process, a first material installation process, a first sintering process, a second material installation process, and a second sintering process.
  • a mixed material is prepared as the first forming material 361 by mixing the aluminum powder 34 (and additive if any) and the meteorite 35 in a first (weight or volume) ratio.
  • the volume ratio of the voids 33 (vermiculite 32) as a whole in the low heat conductive layer 3 after sintering is greater than 50%, preferably 70% or more, more preferably 90% or more. It is such a ratio.
  • a mixed material is prepared in which the aluminum powder 34 (and additive if any) and the meteorite 35 are mixed in a second (weight or volume) ratio.
  • the second ratio is such that the volume ratio of aluminum as a whole in the sintered layer 3 is greater than 50%, preferably 70% or more, more preferably 90% or more.
  • the average particle diameter of the meteorite 35 may be changed between the first forming material 361 and the second forming material 362.
  • the first forming material 361 is put into the recess 401A of the prototype 2A.
  • the first forming material 361 (specifically, the aluminum powder 34) is sintered by the same method as the sintering step of the first embodiment shown in FIG.
  • the first layer 301 is formed.
  • the second material installation step as shown in FIGS. 12 and 13
  • the second forming material 362 is put on the formed first layer 301 in the master 401B of the recess 401.
  • the second sintering step as shown in FIG.
  • the second forming material 362 (specifically, the aluminum powder 34) is sintered by the same method as the sintering step of the first embodiment. Thereby, the second layer 302 is formed.
  • the tool 8 is pulled up from the prototype 401C.
  • a prototype 2C of the piston 1 as shown in FIGS. 15 and 16 is formed.
  • a prototype 401C of the recess 401 is formed on the prototype 4C of the piston head 4.
  • a machining process is performed.
  • a part of the second layer 302 is cut together with the prototype 4C of the piston head 4.
  • a crown surface 400 including the second layer 302 on the surface is formed.
  • Other manufacturing steps of the piston 1 are the same as those in the first embodiment.
  • the volume ratio of aluminum in the low thermal conductive layer 3 is larger in the axial direction on the combustion chamber 11 side (second layer 302) than on the opposite side of the combustion chamber 11 (first layer 301).
  • the volume ratio of the gap 33 to the low thermal conductive layer 3 is smaller in the axial direction on the combustion chamber 11 side (second layer 302) than on the opposite side of the combustion chamber 11 (first layer 301).
  • Strength on the surface side is improved.
  • the numerical aperture of the voids 33 on the surface of the layer 3 is reduced. Thereby, the strength of the surface of the layer 3 is improved. Therefore, damage (chip and dropout) of the layer 3 can be suppressed. Since the back surface side of the layer 3 is surrounded by the piston body 2 (the bottom surface of the recess 401) and the surface side of the layer 3 (the ratio of the binder 31 is high), the risk of damage is small. Therefore, the durability of the layer 3 is improved. In addition, since the numerical aperture of the gap 33 on the surface of the layer 3 is reduced, the entry of unburned fuel from the combustion chamber 11 into the gap 33 is suppressed. Thereby, the deterioration of the exhaust gas performance is suppressed.
  • the ratio of the volume of aluminum in the low heat conductive layer 3 on the combustion chamber 11 side (second layer 302) in the axial direction is greater than 50%.
  • the strength on the surface side (combustion chamber 11 side) of the layer 3 can be secured to some extent, and the numerical aperture of the gap 33 to the combustion chamber 11 can be reduced to some extent. If the ratio is 70% or more, the strength can be improved and the numerical aperture can be further reduced. If the ratio is 90% or more, the above effect can be obtained more reliably.
  • the volume ratio of the voids 33 in the layer 3 is smaller than 50%.
  • the volume of the gap 33 does not occupy the majority, the strength on the surface side of the layer 3 can be secured to some extent, and the numerical aperture of the gap 33 to the combustion chamber 11 can be reduced to some extent. If the ratio is 30% or less, the strength can be improved and the numerical aperture can be further reduced. If the ratio is 10% or less, the above effect can be obtained more reliably.
  • the volume ratio of aluminum in the low thermal conductive layer 3 is smaller in the axial direction on the opposite side of the combustion chamber 11 (first layer 301) than on the combustion chamber 11 side (second layer 302).
  • the volume ratio of the gap 33 in the low thermal conductive layer 3 is larger in the axial direction on the opposite side of the combustion chamber 11 (first layer 301) than on the combustion chamber 11 side (second layer 302).
  • Thermal conductivity decreases.
  • the overall thermal conductivity of the low thermal conductive layer 3 can be effectively lowered to suppress a decrease in combustion efficiency.
  • Increasing the ratio of the void 33 (vermiculite 32) increases the risk of damage to the increased portion, but by suppressing the damage to the low thermal conductive layer 3 by making the above portion the back side of the low thermal conductive layer 3 Can do.
  • the volume ratio of the void 33 (vermiculite 32) occupying the low heat conductive layer 3 on the side opposite to the combustion chamber 11 (first layer 301) in the axial direction is greater than 50%.
  • the volume of the gap 33 occupies a majority, so that the thermal conductivity on the back side of the layer 3 can be lowered to some extent. If the ratio is 70% or more, the thermal conductivity can be further reduced. When the ratio is 90% or more, the thermal conductivity can be sufficiently lowered.
  • the proportion of the volume of aluminum in the layer 3 is smaller than 50%.
  • the thermal conductivity on the back surface side of the layer 3 can be lowered to some extent.
  • the thermal conductivity can be further reduced.
  • the thermal conductivity can be sufficiently lowered.
  • the low thermal conductive layer 3 includes a first layer 301 and a second layer 302 as a plurality of layers having different volume ratios of aluminum and voids 33 (vermiculite 32) in the axial direction. In this way, by combining a plurality of layers having different ratios of the binder 31 and the gap 33, the low thermal conductive layer 3 having desired characteristics as a whole can be obtained. As described above, it is possible to realize such characteristics that the thermal conductivity is low and damage and deterioration of exhaust gas performance can be suppressed.
  • the first sintering step may be omitted. That is, in the material installation step, the second forming material 362 is placed in the recess 401 subsequent to the first forming material 361, and the first forming material 361 and the second forming material 362 are layered in the recess 401. Thereafter, in the sintering process, as in the sintering process of the first embodiment, the end 80 of the tool 8 is pressed against the second forming material 362 and rotated. Thereby, the first forming material 361 (lower layer) and the second forming material 362 (upper layer) are mixed and heated, and a layer of a sintered body including the voids 33 due to expansion of the meteorite 35 is formed.
  • the low thermal conductive layer 3 is formed in which the volume ratio of aluminum and the gap 33 is different in the axial direction (the ratio of aluminum is larger on the combustion chamber 11 side than on the opposite side of the combustion chamber 11).
  • the said ratio may differ continuously in an axial direction, and may differ discontinuously.
  • the low thermal conductive layer 3 consisting essentially of two layers is formed. This method is particularly effective when the first forming material 361 contains almost no aluminum powder 34 and it is difficult to sinter the first forming material 361 alone.
  • the above method including the first sintering step is particularly effective when the aluminum powder 34 is present in the first forming material 361 to some extent.
  • first and second layers 301 and 302 By forming the first and second layers 301 and 302 (two sintered layers) independently of each other, it is possible to more accurately control the volume ratio of the aluminum and the voids 33 in each of the layers 301 and 302. In addition, by sequentially forming the plurality of layers 301 and 302, it is possible to easily increase the thickness of the layer 3 as a whole while efficiently forming the layers 301 and 302.
  • the third layer, the fourth layer, and the like may be formed in the same manner as the second layer 302. Other functions and effects are the same as those of the first embodiment.
  • a temporary molded body (preform 360) is prepared in which the first forming material 361 and the second forming material 362 (mixed material that is powder) are each set in a predetermined shape.
  • the preform 360 is a green compact obtained by pressing and compressing the forming material 36. It may be hardened with an adhesive or the like. As shown in FIG. 17, the preform 360 has a cylindrical shape.
  • the diameter D3 of the preform 360 of the first forming material 361 is slightly smaller than the diameter D1 of the original 401A of the recess 410.
  • the diameter D3 of the preform 360 of the second forming material 362 is slightly smaller than the diameter (the diameter of the end portion of the tool 8) D2 on the combustion chamber 11 side of the original 401B of the recess 401.
  • the diameters D3 of the preforms 360 of both materials 361 and 362 may be aligned.
  • the height (axis direction dimension) of the preform 360 can be set as appropriate. In the material installation process, when the forming materials 361 and 362 are put into the prototypes 401A and 401B of the recess 401, the preforms 360 are inserted and installed. Other manufacturing steps of the piston 1 are the same as those in the second embodiment.
  • the preformed forming material 36 (preform 360) is placed on the original 401A, 401B of the recess 401, so that the forming material 36 is placed in the original 401A, 401B while remaining in powder form, Installation work becomes easy.
  • Other functions and effects are the same as those of the second embodiment.
  • Only one of the both materials 361 and 362 may be used as the preform 360.
  • the preform 360 may be applied to the method for manufacturing the piston 1 of the first embodiment.
  • the piston 1 has a coating 9 on the surface (on the combustion chamber 11 side) of the low thermal conductive layer 3.
  • the coating 9 covers the entire surface of the layer 3 and the entire surface of the other portion (the portion surrounding the recess 401 or the low thermal conductive layer 3) on the crown surface 400.
  • the film 9 includes ceramics such as zirconia and cordierite.
  • Layer 3 and other piston 1 configurations are the same as those in the first embodiment.
  • the method for manufacturing the piston 1 of the present embodiment includes a film forming step.
  • the film forming process is performed after the machining process, and forms the film 9 on the surface of the crown surface 400 that has been cut (including the layer 3).
  • the ceramic 9 powder is used as a material, and the coating 9 is formed by, for example, plasma spraying the powder onto the crown surface 400.
  • Other manufacturing steps of the piston 1 are the same as those in the first embodiment.
  • the opening to the surface side (combustion chamber 11 side) of the gap 33 in the low thermal conductive layer 3 is covered with the coating 9.
  • the film 9 functions as a sealing layer that closes (seals) the opening of the gap 33.
  • the film 9 functions as a sealing layer that closes (seals) the opening of the gap 33.
  • the material of the film 9 only needs to have a certain degree of heat resistance and strength, and the thermal conductivity does not have to be lower than that of the aluminum alloy that is the material (base metal) of the piston body 2.
  • the ceramic (such as zirconia) of the coating 9 is a low thermal conductivity material and has a lower thermal conductivity than the material (aluminum alloy) of the piston body 2. Therefore, the film 9 has a lower thermal conductivity than the piston body 2.
  • the coating 9 is located between the combustion chamber 11 and the piston head 4 and functions as a heat insulating layer. Therefore, the thermal conductivity of the portion surrounding the layer 3 on the crown surface 400 can also be lowered, and further reduction in combustion efficiency can be achieved.
  • the coating 9 may be in a part of the crown surface 400 instead of the whole.
  • the coating 9 may cover only the surface of the layer 3 on the crown surface 400 and may not cover the surface of other portions. If the film 9 is not formed in the other part, it is possible to suppress the occurrence of knocking due to the other part becoming unnecessarily high temperature. Other functions and effects are the same as those of the first embodiment.
  • the film 9 may be an anodized film. That is, in the film formation step, the anodized film (surface) is formed on the crown surface 400 by anodizing aluminum (including the binder 31 of the layer 3 and the material of the piston body 2) of the crown surface 400 (including the low thermal conductive layer 3). Layer) may be formed. Due to the anodized film, the opening of the gap 33 on the surface of the layer 3 is closed or reduced. The anodizing process functions as a sealing treatment process. By reducing the opening of the gap 33, it is possible to suppress deterioration of exhaust gas performance and damage to the layer 3 as described above. In general, the thermal conductivity is lowered by oxidation.
  • the thermal conductivity is (average) lower on the anodized surface side (combustion chamber 11 side) of the layer 3 than on the side opposite to the combustion chamber 11.
  • a film 9 having a thermal conductivity lower than that of the low thermal conductive layer 3 (the portion that is not anodized) is formed on the crown surface 400 by anodic oxidation.
  • the thermal conductivity is lower on the anodized surface side of the layer 3 than on the side opposite to the combustion chamber 11. Therefore, the thermal conductivity of the layer 3 can be further reduced.
  • the thickness of the anodized film is preferably thin.
  • the layer 3 is a sintered body, the formation of the anodic oxide film does not proceed so much and the thickness can be suppressed to a certain extent, which is advantageous. Also in the portion other than the layer 3 on the crown surface 400 (portion surrounding the layer 3), the thermal conductivity is low on the anodized surface side (combustion chamber 11 side) as described above. As described above, the anodized film may be formed on a part of the crown surface 400 instead of the entire surface.
  • the coating 9 is applied to the piston 1 of the second embodiment (the coating forming step is applied to the manufacturing method of the piston 1 of the second embodiment), and the coating 9 covering the crown surface 400 including the second layer 302 is formed. May be. Further, the preform 360 of the third embodiment may be applied to the manufacturing method of the piston 1 of the present embodiment.
  • the outer peripheral edge of the recess 401 may be located on the inner side in the piston radial direction than the inner peripheral edge of the passage 411.
  • the crown surface 400 may have a recess such as a valve recess.
  • the piston 1 may have a shape in which a part of the crown surface 400 is raised toward the combustion chamber 11 side.
  • the low thermal conductive layer 3 includes a first layer 301 and a second layer 302.
  • the second layer 302 is on the ridge 402.
  • a part of the second layer 302 is cut together with the prototype 4C of the piston head 4.
  • the second layer 302 is cut while leaving the raised portion 402.
  • the crown surface 400 including the second layer 302 on the surface of the raised portion 402 is formed.
  • the coating 9 of the fourth embodiment may be formed on the crown surface 400.
  • a main body comprising an aluminum alloy and having a piston head and a piston skirt, the main body having a holding portion on the side facing the combustion chamber of the internal combustion engine, It includes a binder, which is a metal, and a layered silicate mineral, and has a low heat conductive layer in the holding portion.
  • a binder which is a metal, and a layered silicate mineral, and has a low heat conductive layer in the holding portion.
  • It has a film on the surface of the low thermal conductive layer, which closes the opening of the void in the low thermal conductive layer.
  • the film has a lower thermal conductivity than the low thermal conductive layer.
  • the film is an anodized film.
  • the binder includes aluminum.
  • the ratio of the volume of the binder to the low heat conductive layer is an axial direction along the moving direction of the main body in the cylinder of the internal combustion engine, and the combustion chamber side is larger than the opposite side of the combustion chamber.
  • the low thermal conductive layer has a plurality of layers having different volume ratios of the binder and the layered silicate mineral in the axial direction.
  • the proportion of the volume of the binder in the low thermal conductive layer is 90% or more.
  • the proportion of the volume of the layered silicate mineral in the low thermal conductivity layer is 90% or more.
  • (10) In one aspect of the method for producing a piston of an internal combustion engine, Forming a body having a piston head and a piston skirt from an aluminum alloy; Forming a holding portion on the side of the piston head facing the combustion chamber of the internal combustion engine; A step of installing a material in which the binder, which is a metal, and a layered hydrous silicate mineral are mixed in the holding unit; Pressing the installed material with a rotating tool, and forming a low thermal conductive layer on the holding portion. (11) In a more preferred embodiment, in the above embodiment, Forming a film on the surface of the low thermal conductive layer. (12) In another preferred embodiment, in any of the above embodiments, The film has a lower thermal conductivity than the low thermal conductive layer.
  • an anodized film is formed by anodization.
  • the diameter of the rotating tool is larger than the diameter of the holding part.
  • the binder includes aluminum powder.
  • the ratio of the volume of the binder to the low heat conductive layer is an axial direction along the moving direction of the main body in the cylinder of the internal combustion engine, and the combustion chamber side is larger than the opposite side of the combustion chamber.
  • a step of cutting the side of the piston head that faces the combustion chamber of the internal combustion engine is included.
  • the method includes a step of forming a film on the surface of the low thermal conductive layer.
  • Compressing the material and forming it into a predetermined shape In the step of installing the material on the holding unit, the molded material is installed on the holding unit.

Abstract

Provided is an internal combustion engine piston which can be manufactured more easily. The internal combustion engine piston comprises: a main body section made of an aluminum alloy and having a piston head and a skirt part disposed on the piston head; a low-heat-conduction layer holding part disposed on the side of the piston head nearer to the combustion chamber of the internal combustion engine; and a low-heat-conduction layer held by the low-heat-conduction layer holding part. The low-heat-conduction layer includes a mixed material comprising a binder formed from a metal material and a laminar hydrous silicate mineral.

Description

内燃機関のピストン、及び内燃機関のピストンの製造方法Piston for internal combustion engine and method for manufacturing piston for internal combustion engine
　本発明は、内燃機関のピストンに関する。 The present invention relates to a piston for an internal combustion engine.
　従来、内燃機関のピストンが知られている（例えば特許文献１）。 Conventionally, a piston of an internal combustion engine is known (for example, Patent Document 1).
特開２００８－２８６１７８号公報JP 2008-286178 A
　従来のピストンでは、製造を容易化する余地があった。 The conventional piston has room for easy manufacture.
　本発明の一実施形態に係る内燃機関のピストンは、層状ケイ酸塩鉱物を含む低熱伝導層を、ピストンヘッドに有する。 The piston of the internal combustion engine according to one embodiment of the present invention has a low heat conductive layer containing a layered silicate mineral in the piston head.
　よって、ピストンの製造の容易化を図ることができる。 Therefore, the manufacture of the piston can be facilitated.
第1実施形態の1つのシリンダの軸線を通る平面でエンジンの一部を切った断面を模式的に示す。1 schematically shows a cross section of a part of an engine taken along a plane passing through the axis of one cylinder of the first embodiment. 第1実施形態のピストンの斜視図である。1 is a perspective view of a piston according to a first embodiment. 第1実施形態のピストンをその軸線を通る平面で切った断面（以下、軸線方向断面）を示す。The cross section (henceforth an axial direction cross section) which cut the piston of 1st Embodiment with the plane which passes along the axis line is shown. 第1実施形態の鋳造工程後のピストンの斜視図である。FIG. 3 is a perspective view of a piston after a casting process according to the first embodiment. 第1実施形態の鋳造工程後のピストンの軸線方向断面を示す。The axial direction cross section of the piston after the casting process of 1st Embodiment is shown. 第1実施形態の材料設置工程後のピストンの斜視図である。FIG. 3 is a perspective view of the piston after the material installation process of the first embodiment. 第1実施形態の材料設置工程後のピストンの軸線方向断面を示す。The axial direction cross section of the piston after the material installation process of 1st Embodiment is shown. 第1実施形態の焼結工程時のピストンの軸線方向断面を示す。2 shows an axial cross-section of the piston during the sintering process of the first embodiment. 第1実施形態の焼結工程後のピストンの斜視図である。FIG. 3 is a perspective view of the piston after the sintering process of the first embodiment. 第1実施形態の焼結工程後のピストンの軸線方向断面を示す。2 shows an axial cross section of the piston after the sintering step of the first embodiment. 第2実施形態のピストンの軸線方向断面を示す。The axial direction cross section of the piston of 2nd Embodiment is shown. 第2実施形態の第2材料設置工程後のピストンの斜視図である。FIG. 10 is a perspective view of a piston after a second material installation step of the second embodiment. 第2実施形態の第2材料設置工程後のピストンの軸線方向断面を示す。The axial direction cross section of the piston after the 2nd material installation process of 2nd Embodiment is shown. 第2実施形態の第2焼結工程時のピストンの軸線方向断面を示す。FIG. 6 shows an axial cross section of a piston during a second sintering step of the second embodiment. FIG. 第2実施形態の第2焼結工程後のピストンの斜視図である。FIG. 10 is a perspective view of a piston after a second sintering step of the second embodiment. 第2実施形態の第2焼結工程後のピストンの軸線方向断面を示す。FIG. 7 shows an axial cross section of the piston after the second sintering step of the second embodiment. FIG. 第3実施形態の形成材料のプリフォームの斜視図である。FIG. 5 is a perspective view of a preform of a forming material according to a third embodiment. 第4実施形態のピストンの斜視図である。FIG. 10 is a perspective view of a piston according to a fourth embodiment. 第4実施形態のピストンの軸線方向断面を示す。FIG. 6 shows an axial cross section of a piston according to a fourth embodiment. FIG. 他の実施形態のピストンの軸線方向断面を示す。The axial direction cross section of the piston of other embodiment is shown. 更に他の実施形態のピストンの軸線方向断面を示す。The axial direction cross section of the piston of other embodiment is shown.
　以下、本発明を実施するための形態を、図面に基づき説明する。 Hereinafter, modes for carrying out the present invention will be described with reference to the drawings.
　［第1実施形態］
  まず、構成を説明する。図1に示す本実施形態の内燃機関（エンジン）100は、4ストローク・ガソリンエンジンである。エンジン100は、ピストン1と、シリンダブロック101と、シリンダヘッド104と、コネクティングロッド（コンロッド）106と、クランクシャフトと、バルブ107と、点火装置108と、燃焼室11とを備える。バルブ107は2つの吸気バルブと2つの排気バルブを有する。シリンダブロック101は、円筒状のシリンダライナ（シリンダスリーブ）102を備える。シリンダライナ102の内周側はシリンダ10の内壁として機能する。シリンダヘッド104は、シリンダ10の開口を塞ぐようにシリンダブロック101に設置される。シリンダヘッド104には、バルブ107と、燃料の噴射ノズルと、点火装置108とが設置される。シリンダブロック101にはクランクシャフトが回転可能に設置される。ピストン1は、シリンダ10の内部に、往復移動可能に収容される。なお、エンジン100の形式は任意である。例えば、エンジン100は2ストロークエンジンでもよいしディーゼルエンジンでもよい。燃料の供給方式は、シリンダ10（燃焼室11）内に直接噴射する筒内直噴式でもよいし、吸気ポートに噴射するポート噴射式でもよい。 [First embodiment]
First, the configuration will be described. The internal combustion engine (engine) 100 of the present embodiment shown in FIG. 1 is a 4-stroke gasoline engine. The engine 100 includes a piston 1, a cylinder block 101, a cylinder head 104, a connecting rod (connecting rod) 106, a crankshaft, a valve 107, an ignition device 108, and a combustion chamber 11. The valve 107 has two intake valves and two exhaust valves. The cylinder block 101 includes a cylindrical cylinder liner (cylinder sleeve) 102. The inner peripheral side of the cylinder liner 102 functions as the inner wall of the cylinder 10. The cylinder head 104 is installed in the cylinder block 101 so as to close the opening of the cylinder 10. The cylinder head 104 is provided with a valve 107, a fuel injection nozzle, and an ignition device 108. A crankshaft is rotatably installed on the cylinder block 101. The piston 1 is accommodated in the cylinder 10 so as to be reciprocally movable. The format of engine 100 is arbitrary. For example, the engine 100 may be a two-stroke engine or a diesel engine. The fuel supply method may be an in-cylinder direct injection type that directly injects into the cylinder 10 (combustion chamber 11), or a port injection type that injects into the intake port.
　図2及び図3に示すように、ピストン1は、ピストン本体2と低熱伝導層3を有する。ピストン本体2は、軽量化等のため、アルミニウム合金（例えばAl-Si系のAC8A）を材料（素材）として形成される。ピストン1（ピストン本体2）は、有底筒状であり、ピストンヘッド（冠部）4と、ピストンボス（エプロン部）5と、ピストンスカート（スカート部）6とを有する。ピストン1の軸心が延びる方向（シリンダ10内におけるピストン本体2の移動方向に沿う方向）を軸線方向という。軸線方向でピストンボス5やピストンスカート6に対しピストンヘッド4の側を一方側といい、その反対側を他方側という。 As shown in FIGS. 2 and 3, the piston 1 has a piston main body 2 and a low heat conductive layer 3. The piston body 2 is formed of an aluminum alloy (for example, Al-Si AC8A) as a material (raw material) for weight reduction and the like. The piston 1 (piston body 2) has a bottomed cylindrical shape, and includes a piston head (crown portion) 4, a piston boss (apron portion) 5, and a piston skirt (skirt portion) 6. The direction in which the axis of the piston 1 extends (the direction along the moving direction of the piston body 2 in the cylinder 10) is referred to as the axial direction. The side of the piston head 4 with respect to the piston boss 5 and piston skirt 6 in the axial direction is called one side, and the opposite side is called the other side.
　ピストンヘッド4は、冠面部40とランド部41を有する。冠面部40は、ピストンヘッド4の軸線方向一方側にあり、冠面（頂面）400を有する。冠面400は、ピストン1の軸心に直交して広がる平面状であり、軸線方向一方側からみて略円形の輪郭を有する。図1に示すように（ピストン1が上死点にあるとき）、冠面400とシリンダヘッド104との間に、燃焼室11が区画される。燃焼室11はペントルーフ型である。冠面400は燃焼室11内の燃焼ガスに直接暴露される。ピストン本体2は、ピストンヘッド4（冠面部40）の燃焼室11側（燃焼室11に臨む側）に凹部401を備える。凹部401は、冠面部40において冠面400の略中央にあり、有底円筒状（底面が平面である浅皿状）である。凹部401の軸心はピストン1の軸心と実質的に（製造誤差の範囲内で）一致する。 The piston head 4 has a crown surface portion 40 and a land portion 41. The crown surface portion 40 is on one side in the axial direction of the piston head 4 and has a crown surface (top surface) 400. The crown surface 400 is a flat surface extending perpendicularly to the axis of the piston 1 and has a substantially circular outline when viewed from one side in the axial direction. As shown in FIG. 1 (when the piston 1 is at top dead center), the combustion chamber 11 is defined between the crown surface 400 and the cylinder head 104. The combustion chamber 11 is a pent roof type. The crown surface 400 is directly exposed to the combustion gas in the combustion chamber 11. The piston body 2 includes a recess 401 on the combustion chamber 11 side (side facing the combustion chamber 11) of the piston head 4 (crown surface portion 40). The concave portion 401 is substantially at the center of the crown surface 400 in the crown surface portion 40 and has a bottomed cylindrical shape (a shallow dish shape whose bottom surface is a flat surface). The axis of the recess 401 substantially coincides with the axis of the piston 1 (within manufacturing error).
　ランド部41は冠面部40の外周側から軸線方向他方側に延びる。ランド部41の外周には、環状の溝（リング溝）410が3つある。リング溝410にはピストンリング7が設置される。ランド部41の内部には、環状の通路411がある。通路411は、ピストン1の周方向に延び、軸線方向から見て凹部401を取り囲む。通路411は、軸線方向で、リング溝410が形成された領域の少なくとも一部と重なる。 The land portion 41 extends from the outer peripheral side of the crown surface portion 40 to the other side in the axial direction. There are three annular grooves (ring grooves) 410 on the outer periphery of the land portion 41. A piston ring 7 is installed in the ring groove 410. Inside the land portion 41 is an annular passage 411. The passage 411 extends in the circumferential direction of the piston 1 and surrounds the recess 401 when viewed from the axial direction. The passage 411 overlaps at least a part of the region where the ring groove 410 is formed in the axial direction.
　ピストンボス5及びピストンスカート6は、ピストンヘッド4（ランド部41）から軸線方向他方側に延び、ピストンヘッド4に対し燃焼室11の反対側にある。ピストンスカート6及びピストンボス5の内周側は中空である。ピストンボス5は、ピストン1の径方向両側に一対ある。各ピストンボス5はピンボス50を有する。各ピンボス50はピストンピン穴51を有する。ピストンピン穴51は、ピンボス50を貫通してピストン1の径方向に延びる。ピストンスカート6は、ピストン1の径方向両側に一対ある。ピストンスカート6は、ピストン1の周方向で両ピストンボス5,5に挟まれる。両ピストンスカート6,6はピストンボス5によって連結される。ピストンスカート6はシリンダ10の内壁に対し摺動する。ピストンピン穴51にはピストンピンの端部が嵌合する。ピストン1は、ピストンピンを介してコンロッド106の一端側（小端部）に連結される。コンロッド106の他端側（大端部）はクランクシャフトに連結される。 The piston boss 5 and the piston skirt 6 extend from the piston head 4 (land portion 41) to the other side in the axial direction, and are on the opposite side of the combustion chamber 11 with respect to the piston head 4. The inner peripheral sides of the piston skirt 6 and the piston boss 5 are hollow. There are a pair of piston bosses 5 on both radial sides of the piston 1. Each piston boss 5 has a pin boss 50. Each pin boss 50 has a piston pin hole 51. The piston pin hole 51 extends through the pin boss 50 in the radial direction of the piston 1. There are a pair of piston skirts 6 on both radial sides of the piston 1. The piston skirt 6 is sandwiched between the piston bosses 5 and 5 in the circumferential direction of the piston 1. Both piston skirts 6 and 6 are connected by a piston boss 5. The piston skirt 6 slides against the inner wall of the cylinder 10. The piston pin end 51 is fitted into the piston pin hole 51. The piston 1 is connected to one end side (small end portion) of the connecting rod 106 via a piston pin. The other end side (large end portion) of the connecting rod 106 is connected to the crankshaft.
　シリンダライナ102の内部の通路103には冷却水が循環する。シリンダブロック101にはオイルジェット105が設置される。燃焼室11からピストンヘッド4に伝わった熱は、ピストンリング7を介してシリンダライナ102及びその内部の冷却水に伝わることで放出される。また、上記熱は、ピストン1の内周側（裏側）にオイルが付着し流出したり、通路411内をオイルが流通したりすることでも、放出される。このオイルの付着や流通は、例えばオイルジェット105からのオイルの噴射により行われる。通路411は冷却通路（クーリングチャネル）として機能する。 ¡Cooling water circulates in the passage 103 inside the cylinder liner 102. An oil jet 105 is installed in the cylinder block 101. The heat transferred from the combustion chamber 11 to the piston head 4 is released by being transferred to the cylinder liner 102 and the cooling water therein through the piston ring 7. The heat is also released when oil adheres to and flows out from the inner peripheral side (back side) of the piston 1 or when oil flows through the passage 411. This adhesion and distribution of oil is performed, for example, by oil injection from the oil jet 105. The passage 411 functions as a cooling passage (cooling channel).
　低熱伝導層3は、燃焼室11からピストン本体2への熱伝導性を低めるための構造体であり、ピストンヘッド4における軸線方向一方側（燃焼室11の側）にあって、燃焼室11に臨む表面（冠面400）の一部に形成される。低熱伝導層3の全部は凹部401に収容される。図2及び図3に示すように、低熱伝導層3は、冠面400（及び凹部401の底面）に沿って広がる平面状である。層3の厚さ（凹部401の深さ）は任意である。層3の内部には空隙（中空部）33があり、複数の空隙33が分散している。空隙33には気体（空気）が存在する。複数ある空隙33の一部は、層3の燃焼室11側の表面（冠面400）に開口する。 The low thermal conductive layer 3 is a structure for reducing the thermal conductivity from the combustion chamber 11 to the piston body 2, and is located on one side in the axial direction of the piston head 4 (on the combustion chamber 11 side). It is formed on a part of the facing surface (crown surface 400). All of the low thermal conductive layer 3 is accommodated in the recess 401. As shown in FIGS. 2 and 3, the low thermal conductive layer 3 has a planar shape extending along the crown surface 400 (and the bottom surface of the recess 401). The thickness of the layer 3 (the depth of the recess 401) is arbitrary. There are voids (hollow portions) 33 inside the layer 3, and a plurality of voids 33 are dispersed. Gas (air) exists in the gap 33. A part of the plurality of voids 33 opens on the surface (crown surface 400) of the layer 3 on the combustion chamber 11 side.
　低熱伝導層3は、金属のバインダー31及び層状ケイ酸塩鉱物を含む。バインダー31はアルミニウムを含む。アルミニウムは、純アルミニウムであってもよいし、アルミニウム合金であってもよいし、純アルミニウムとアルミニウム合金の両方を含んでもよい。また、バインダー31は、アルミニウムの他に添加物を含んでもよい。層状ケイ酸塩鉱物は、（層状の含水ケイ酸塩鉱物である）蛭石35が急加熱されることで膨張したもの（バーミキュライト32）である。空隙33は主にバーミキュライト32の内部にある。バーミキュライト32は空隙33と共に層3の内部に複数分散しており、その最大外形寸法は例えば数mmである。 The low heat conductive layer 3 includes a metal binder 31 and a layered silicate mineral. The binder 31 includes aluminum. Aluminum may be pure aluminum, an aluminum alloy, or may include both pure aluminum and an aluminum alloy. The binder 31 may contain an additive in addition to aluminum. The layered silicate mineral is expanded (vermiculite 32) when the meteorite 35 (which is a layered hydrous silicate mineral) is rapidly heated. The air gap 33 is mainly inside the vermiculite 32. A plurality of vermiculites 32 are dispersed inside the layer 3 together with the gaps 33, and the maximum external dimensions thereof are, for example, several mm.
　以下、本実施形態のピストン1の製造方法を説明する。製造方法は、鋳造工程、熱処理工程、低熱伝導層形成工程、及び機械加工工程を含む。鋳造工程で、図4及び図5に示すようなピストン本体2の原型（中間加工材）2Aを鋳造する。具体的には、アルミニウム合金の溶湯を金型に流し込み、凝固させる。このとき、ピストン本体2の内周が形成され、凹部401の原型401A及び通路411が形成される。なお、凹部401を機械加工により形成又は仕上げてもよい。熱処理工程で、熱処理を行う。これにより、鋳造された原型2Aの性質を改善して適当な強度・硬さに調整する。低熱伝導層形成工程で、原型4A（における燃焼室11側）に低熱伝導層3を形成する。層3は、早くとも上記熱処理工程後に形成される。（熱処理工程は低熱伝導層形成工程の前に行われる。）本実施形態では、上記熱処理工程後、機械加工工程前に、層3を形成する。機械加工工程で、層3が形成された原型を旋盤等により機械加工する。低熱伝導層形成工程の後、ピストンヘッド4のうち燃焼室11に臨む側を切削加工し、冠面400を形成する。ピストンヘッド4における燃焼室11側の表面の全部は、機械加工される。また、例えば、ピストンピン穴51やリング溝410を加工するとともに、ピストンヘッド4やピストンスカート6の外周等、ピストン本体2の外径を仕上げる。これにより図2及び図3に示すようなピストン1が形成される。 Hereinafter, a method for manufacturing the piston 1 of the present embodiment will be described. The manufacturing method includes a casting process, a heat treatment process, a low thermal conductive layer forming process, and a machining process. In the casting process, a prototype (intermediate workpiece) 2A of the piston body 2 as shown in FIGS. 4 and 5 is cast. Specifically, a molten aluminum alloy is poured into a mold and solidified. At this time, the inner periphery of the piston body 2 is formed, and the original 401A of the recess 401 and the passage 411 are formed. The concave portion 401 may be formed or finished by machining. In the heat treatment step, heat treatment is performed. This improves the properties of the cast prototype 2A and adjusts it to an appropriate strength and hardness. In the low thermal conductive layer forming step, the low thermal conductive layer 3 is formed on the prototype 4A (in the combustion chamber 11 side). Layer 3 is formed as early as after the heat treatment step. (The heat treatment step is performed before the low thermal conductive layer forming step.) In this embodiment, the layer 3 is formed after the heat treatment step and before the machining step. In the machining process, the prototype on which the layer 3 is formed is machined by a lathe or the like. After the low thermal conductive layer forming step, the side of the piston head 4 facing the combustion chamber 11 is cut to form the crown surface 400. The entire surface of the piston head 4 on the combustion chamber 11 side is machined. Further, for example, the piston pin hole 51 and the ring groove 410 are processed, and the outer diameter of the piston body 2 such as the outer periphery of the piston head 4 and the piston skirt 6 is finished. Thereby, the piston 1 as shown in FIGS. 2 and 3 is formed.
　低熱伝導層形成工程は、材料準備工程と、材料設置工程と、焼結工程とを含む。材料準備工程で、低熱伝導層3を形成するための材料（以下、形成材料36という。）を準備する。形成材料36は、金属粉末と層状の含水ケイ酸塩鉱物の粉末とを含む。金属粉末はアルミニウム粉34である。層状の含水ケイ酸塩鉱物は蛭石35（加水黒雲母）、言い換えると高温で焼成する前のバーミキュライトである。蛭石35は例えば0.数mm以上、数mm以下の平均粒径を有する粉末に調製して用いる。粒径の測定には、例えばJIS Z8801の試験用ふるいを用いることができる。平均径としてメジアン径（d50）を用いることができる。アルミニウム粉34と蛭石35とを所定の（重量又は体積）比率で混ぜ合わせた材料36（粉体である混合材料）を準備する。混合材料において蛭石35はアルミニウム粉34の中に分散している。 The low thermal conductive layer forming process includes a material preparation process, a material installation process, and a sintering process. In the material preparation step, a material for forming the low thermal conductive layer 3 (hereinafter referred to as a forming material 36) is prepared. The forming material 36 includes a metal powder and a layered hydrous silicate mineral powder. The metal powder is aluminum powder 34. The layered hydrous silicate mineral is meteorite 35 (hydrobiotite), in other words vermiculite before firing at high temperature. The meteorite 35 is prepared and used as a powder having an average particle diameter of, for example, not less than 0.3 mm and not more than several mm. For the measurement of the particle size, for example, a test sieve of JIS Z8801 can be used. The median diameter (d50) can be used as the average diameter. A material 36 (mixed material that is a powder) is prepared by mixing aluminum powder 34 and meteorite 35 at a predetermined (weight or volume) ratio. In the mixed material, the meteorite 35 is dispersed in the aluminum powder 34.
　材料設置工程で、図6及び図7に示すように、混合された形成材料36を、（熱処理が行われた）原型2Aの凹部401Aに充填する。具体的には、凹部401Aの上端部まで形成材料36を入れる。なお、凹部401Aのどの位置まで形成材料36を入れるかは任意である。また、凹部401Aにアルミニウム粉34と蛭石35とを別々に入れた後、凹部401A内でこれらを混ぜ合わせてもよい。 In the material installation step, as shown in FIGS. 6 and 7, the mixed forming material 36 is filled into the recess 401A of the prototype 2A (heat-treated). Specifically, the forming material 36 is put up to the upper end of the recess 401A. Note that the position of the forming material 36 in the recess 401A is arbitrary. Alternatively, after the aluminum powder 34 and the meteorite 35 are separately put into the recess 401A, they may be mixed in the recess 401A.
　焼結工程で、充填された形成材料36（具体的にはそのうちのアルミニウム粉34）を焼結する。本実施形態では、図8に示すように、摩擦撹拌溶接（接合）の原理を利用し、回転する工具（ツール）8を用いて焼結を行う。工具8は円柱状であって、その軸線方向端部80の直径D2は凹部401Aの直径D1以上であり、好ましくは直径D1よりも若干大きい。工具8の軸線と凹部401Aの中心軸とを合わせる。工具8をその軸線の周りに回転駆動した状態で（軸線周りの回転を矢印Aで示す。）、工具8の軸線方向端部80を形成材料36に押し当てる（軸線方向の押し付け力を矢印Bで示す）。又は、工具8の端部80を形成材料36に押し付けた状態で、工具8を回転させる。これにより形成材料36が焼結され、当初よりも体積が減少した焼結体からなる低熱伝導層3が形成される。焼結が完了する（低熱伝導層3が形成される）と、工具8を凹部401A内から引き上げる。これにより図9及び図10に示すようなピストン1の原型2Bが形成される。ピストンヘッド4の原型4Bに凹部401の原型401Bが形成される。その後、上記機械加工工程を行う。ピストンヘッドの原型4Bとともに低熱伝導層3の一部を切削加工し、低熱伝導層3を表面に含む冠面400を平面状に仕上げる。 In the sintering process, the filled forming material 36 (specifically, the aluminum powder 34) is sintered. In this embodiment, as shown in FIG. 8, the principle of friction stir welding (joining) is used and sintering is performed using a rotating tool (tool) 8. The tool 8 has a cylindrical shape, and the diameter D2 of the axial end 80 thereof is not less than the diameter D1 of the recess 401A, and is preferably slightly larger than the diameter D1. The axis of the tool 8 is aligned with the central axis of the recess 401A. With the tool 8 rotated around its axis (rotation around the axis is indicated by arrow A), the axial end 80 of the tool 8 is pressed against the forming material 36 (the axial pressing force is indicated by arrow B). ). Alternatively, the tool 8 is rotated with the end portion 80 of the tool 8 pressed against the forming material 36. As a result, the forming material 36 is sintered, and the low thermal conductive layer 3 made of a sintered body whose volume is smaller than the original is formed. When the sintering is completed (the low thermal conductive layer 3 is formed), the tool 8 is pulled up from the recess 401A. As a result, a prototype 2B of the piston 1 as shown in FIGS. 9 and 10 is formed. The prototype 401B of the recess 401 is formed on the prototype 4B of the piston head 4. Then, the said machining process is performed. A part of the low thermal conductive layer 3 is cut together with the prototype 4B of the piston head, and the crown surface 400 including the low thermal conductive layer 3 on the surface is finished into a flat surface.
　次に、作用効果を説明する。焼結工程で、回転する工具8により形成材料36が押圧されつつ混ぜられ、摩擦熱により加熱される。アルミニウム粉34が塑性流動し、各粉34の表面の酸化膜が破れ、粉体が焼結する。また、各蛭石35の体積が上記加熱により膨張する。これは、蛭石35の層間の結晶水が急加熱により気化（蒸発）することで層間がアコーディオン状に広がり、内部に多くの空気層を含むバーミキュライト32に変化することに由来する。よって、低熱伝導層3は、アルミニウムの焼結体（バインダー31）の内部に、各バーミキュライト32における空隙33が複数形成されたものとなる。空隙33には空気が含まれる。機械加工工程後の層3の表面には、複数ある空隙33の一部が開口する。 Next, the function and effect will be described. In the sintering process, the forming material 36 is mixed while being pressed by the rotating tool 8 and heated by frictional heat. The aluminum powder 34 plastically flows, the oxide film on the surface of each powder 34 is broken, and the powder is sintered. Further, the volume of each meteorite 35 expands due to the heating. This is because the crystal water between the layers of the meteorite 35 is vaporized (evaporated) by rapid heating, so that the layers spread in an accordion shape and change into vermiculite 32 containing many air layers inside. Therefore, the low thermal conductive layer 3 is obtained by forming a plurality of voids 33 in each vermiculite 32 inside an aluminum sintered body (binder 31). The air gap 33 contains air. A part of the plurality of voids 33 are opened on the surface of the layer 3 after the machining process.
　低熱伝導層3は凹部401によりピストンヘッド4に保持される。層3は燃焼室11に面し、燃焼室11の壁の一部を構成する。層3におけるアルミニウム粉34の焼結体は、鋳造によるピストン本体2よりも、微少な空隙（気孔）を多く含む。空隙は固体よりも熱伝導率が低い。よって、層3は全体として熱伝導率がピストン本体2よりも低くなる。また、層3中のバーミキュライト32は、低熱伝導性材料であり、ピストン本体2の素材（母材金属）であるアルミニウム合金よりも、熱伝導率が低い。よって、層3は全体として（平均的に）熱伝導率がピストン本体2よりも更に低くなる。また、層3の内部には、バーミキュライト32（膨張した蛭石35）による比較的大きな空隙33が複数ある。これらの空隙33は、熱伝導率が極めて低い。バーミキュライト32は断熱材として機能する。よって、層3は全体として熱伝導率がより一層低くなる。アルミニウム粉34は、互いに又はピストン本体2と接着することでバインダー31として機能し、バーミキュライト32を層3に保持等する。層3は、燃焼室11とピストン本体2との間にあって、断熱層として機能する。層3は、燃焼室11内のガスからピストンヘッド4（ピストン本体2）への熱伝達を低下させ、燃焼室11に供給された燃料（混合気）の熱がピストン本体2に奪われるのを抑制する。よって、燃焼効率の低下を抑制し、エンジン100の熱効率の向上を図ることができる。 The low heat conductive layer 3 is held on the piston head 4 by the recess 401. The layer 3 faces the combustion chamber 11 and constitutes part of the wall of the combustion chamber 11. The sintered body of the aluminum powder 34 in the layer 3 contains more minute voids (pores) than the piston body 2 formed by casting. The void has a lower thermal conductivity than the solid. Therefore, the layer 3 as a whole has a lower thermal conductivity than the piston body 2. The vermiculite 32 in the layer 3 is a low thermal conductivity material and has a lower thermal conductivity than the aluminum alloy that is the material (base metal) of the piston body 2. Thus, the layer 3 as a whole (on average) has a lower thermal conductivity than the piston body 2. Further, inside the layer 3, there are a plurality of relatively large voids 33 made of vermiculite 32 (expanded meteorite 35). These voids 33 have extremely low thermal conductivity. Vermiculite 32 functions as a heat insulating material. Therefore, the layer 3 as a whole has a much lower thermal conductivity. The aluminum powder 34 functions as a binder 31 by adhering to each other or the piston body 2, and holds the vermiculite 32 in the layer 3. The layer 3 is between the combustion chamber 11 and the piston body 2 and functions as a heat insulating layer. The layer 3 reduces the heat transfer from the gas in the combustion chamber 11 to the piston head 4 (piston body 2), so that the heat of the fuel (air mixture) supplied to the combustion chamber 11 is taken away by the piston body 2. Suppress. Therefore, a reduction in combustion efficiency can be suppressed and the thermal efficiency of engine 100 can be improved.
　筒内直噴式のエンジン100では、低熱伝導層3は、冠面400において、少なくとも燃料の噴射領域に対応した箇所（燃料が衝突・爆発し、温度や圧力が最も高くなる部位及びその周辺）に形成されることが好ましい。この箇所に層3を形成することで、燃焼室11内のガスからピストンヘッド4（ピストン本体2）への熱伝達をより効果的に低下させることができる。また、層3によりピストン本体2への熱吸収が抑制されることから、冠面400において燃料が付着する箇所が速やかに高温になるとともに、高温状態を維持する。よって、付着した燃料が速やかに気化・燃焼するため、排ガス特性の悪化を抑制できる。なお、冠面400において上記箇所以外に層3を形成しなければ、上記箇所以外の部位で不必要に高温となってノッキングが発生する事態を抑制できる。 In the in-cylinder direct injection type engine 100, the low thermal conductive layer 3 is located on the crown surface 400 at least at a location corresponding to the fuel injection region (the location where the fuel collides and explodes and the temperature and pressure become highest and its surroundings). Preferably it is formed. By forming the layer 3 at this location, heat transfer from the gas in the combustion chamber 11 to the piston head 4 (piston body 2) can be more effectively reduced. Further, since heat absorption to the piston main body 2 is suppressed by the layer 3, the portion where the fuel adheres on the crown surface 400 quickly becomes high temperature and maintains a high temperature state. Therefore, the adhering fuel is quickly vaporized and burned, so that deterioration of exhaust gas characteristics can be suppressed. If the layer 3 is not formed on the crown surface 400 other than the above portion, it is possible to suppress the occurrence of knocking due to an unnecessarily high temperature at a portion other than the above portion.
　空隙33は、蛭石35に含まれていた結晶水が気化することによって形成されたものである。焼結工程では、結晶水が気化して膨張し、蛭石35の層間に空隙33が形成される。焼結工程は空隙形成工程として機能する。このように、気化する成分（物質）を形成材料36に混在させることによって、空隙33を容易に形成することができる。加熱により膨張する性質を備えた層状の含水ケイ酸塩鉱物（蛭石35）を形成材料36に用いることで、空隙33を含む低熱伝導層3をピストンヘッド4に容易に設けることができる。蛭石35の粒径が0.数mm以上、数mm以下であり比較的大きいことに加え、これが更に膨張するため、比較的大きな空隙33が形成される。よって、低熱伝導層3の全体として、熱伝導率がより低くなるため、上記効果を向上できる。なお、加熱により層と層の間が押し広げられて膨張する無機層状物質として、鉱物以外に、人工物である熱膨張性黒鉛を用いてもよい。蛭石35を用いることで、材料を安価にすることができる。 The void 33 is formed by the evaporation of crystal water contained in the meteorite 35. In the sintering process, the crystal water is vaporized and expanded, and voids 33 are formed between the layers of the meteorite 35. The sintering process functions as a void forming process. In this way, the void 33 can be easily formed by mixing the vaporizing component (substance) in the forming material 36. By using the layered hydrous silicate mineral (meteorite 35) having the property of expanding by heating as the forming material 36, the low thermal conductive layer 3 including the voids 33 can be easily provided on the piston head 4. In addition to the relatively large particle size of the meteorite 35 being not less than 0.3 mm and not more than several mm, this further expands, so that a relatively large gap 33 is formed. Therefore, since the thermal conductivity of the low thermal conductive layer 3 as a whole becomes lower, the above effect can be improved. In addition to minerals, heat-expandable graphite, which is an artificial material, may be used as the inorganic layered substance that expands by being expanded between layers by heating. By using the meteorite 35, the material can be made inexpensive.
　アルミニウム粉34がバインダー31として機能することにより、空隙33を含む低熱伝導層3の内部における結合の強度（硬さ）が向上し、その欠けや崩れが抑制される。また、層3とピストン本体2との接合の強度が向上し、層3をピストンヘッド4（凹部401）に保持する力が向上する。よって、層3の機能をより長期にわたり維持できる。なお、形成材料36に、蛭石35とバインダー31以外に、添加物（焼結助剤等）を混ぜてもよい。バインダー31は金属（アルミニウム）である。よって、比較的大きな空隙33が形成されても、層3の強度を向上し、その欠けや崩れをより容易に抑制できる。なお、アルミニウム粉34の代わりに他の金属（マグネシウム等）の粉末を用いてもよい。この場合、回転する工具8の押圧による焼結が可能なものであれば都合がよい。また、耐熱性や耐久性が高いものが好ましい。本実施形態では、バインダー31がアルミニウム粉34であるため、アルミニウム合金で形成されたピストン本体2と層3との接合力を向上させることができる。なお、アルミニウム粉34は、純アルミニウムの粉末であってもよいし、アルミニウム合金（例えばピストン本体2の母材金属と同じAC8A）の粉末であってもよい。アルミニウム粉34は粒状アルミニウム粉であってもよい。 Since the aluminum powder 34 functions as the binder 31, the strength (hardness) of the bond inside the low thermal conductive layer 3 including the voids 33 is improved, and the chipping and collapse thereof are suppressed. Further, the bonding strength between the layer 3 and the piston body 2 is improved, and the force for holding the layer 3 in the piston head 4 (recess 401) is improved. Therefore, the function of the layer 3 can be maintained for a longer period. In addition to the meteorite 35 and the binder 31, additives (sintering aids and the like) may be mixed into the forming material 36. The binder 31 is a metal (aluminum). Therefore, even if a relatively large gap 33 is formed, the strength of the layer 3 can be improved and the chipping and collapse can be more easily suppressed. In place of the aluminum powder 34, another metal (magnesium or the like) powder may be used. In this case, any material that can be sintered by pressing the rotating tool 8 is convenient. Moreover, a thing with high heat resistance and durability is preferable. In the present embodiment, since the binder 31 is the aluminum powder 34, the bonding force between the piston body 2 and the layer 3 formed of an aluminum alloy can be improved. The aluminum powder 34 may be a pure aluminum powder or an aluminum alloy powder (for example, AC8A, which is the same as the base metal of the piston body 2). The aluminum powder 34 may be granular aluminum powder.
　焼結工程では、バインダー31が焼結されるとともに、焼結時の熱によって蛭石35が膨張することで空隙33が形成される。バインダー31の焼結と空隙33の形成とが同時に（同じ工程で）行われるため、製造方法が簡素化される。言い換えると、空隙33を含む低熱伝導層3を効率的に形成できる。ピストンヘッド4には凹部401がある。よって、摩擦撹拌溶接の原理を利用して工具8の回転により焼結を行う場合でも、ピストンヘッド4に粉体（形成材料36）を保持しつつ粉体に圧力を加えて撹拌できるため、有利である。工具8の直径D2は凹部401の直径D1以上である。よって、回転する工具8の端部80と凹部401との間の径方向隙間から粉体（形成材料36）が飛び出してしまうことを抑制できる。直径D2は直径D1よりも大きい。よって、回転する工具8で凹部401の外縁の一部を巻き込みながら層3が形成されるため、層3と凹部401との接合力を向上させることができる。なお、摩擦撹拌溶接の原理を利用した上記方法以外に、例えば放電プラズマ焼結法により焼結を行ってもよい。この場合も、バインダー31の焼結と空隙33の形成とが同時に行われる。 In the sintering process, the binder 31 is sintered, and the meteorite 35 is expanded by the heat at the time of sintering, whereby the gap 33 is formed. Since the sintering of the binder 31 and the formation of the voids 33 are performed simultaneously (in the same process), the manufacturing method is simplified. In other words, the low thermal conductive layer 3 including the voids 33 can be efficiently formed. The piston head 4 has a recess 401. Therefore, even when sintering is performed by rotating the tool 8 using the principle of friction stir welding, the powder (formation material 36) is held on the piston head 4 and can be stirred by applying pressure to the powder. It is. The diameter D2 of the tool 8 is not less than the diameter D1 of the recess 401. Therefore, the powder (forming material 36) can be prevented from jumping out from the radial gap between the end 80 of the rotating tool 8 and the recess 401. Diameter D2 is larger than diameter D1. Therefore, since the layer 3 is formed while a part of the outer edge of the recess 401 is wound with the rotating tool 8, the bonding force between the layer 3 and the recess 401 can be improved. In addition to the above method using the principle of friction stir welding, sintering may be performed by, for example, a discharge plasma sintering method. Also in this case, sintering of the binder 31 and formation of the voids 33 are performed simultaneously.
　低熱伝導層形成工程後に機械加工工程を行う。ピストンヘッド4に低熱伝導層3を形成した後に、ピストンヘッド4のうち燃焼室11に臨む側を切削加工して冠面400を形成する。すなわち、冠面400を切削加工により形成する前に、層3を形成する。よって、低熱伝導層形成工程において、冠面400の形状による制約が少ないため、層3を形成する作業が容易となる。言い換えると、複雑な形状の冠面400にも層3を容易に形成できる（図20参照）。 The machining process is performed after the low thermal conductive layer forming process. After the low thermal conductive layer 3 is formed on the piston head 4, the side facing the combustion chamber 11 of the piston head 4 is cut to form the crown surface 400. That is, the layer 3 is formed before the crown surface 400 is formed by cutting. Therefore, in the low thermal conductive layer forming step, there are few restrictions due to the shape of the crown surface 400, so that the operation of forming the layer 3 becomes easy. In other words, the layer 3 can be easily formed on the crown surface 400 having a complicated shape (see FIG. 20).
　［第2実施形態］
  まず、構成を説明する。以下、第1実施形態と共通する部材や構造については第1実施形態と同じ符号を付して、説明を省略する。図11に示すように、低熱伝導層3は、軸線方向他方側（ピストン本体2の側、又は燃焼室11と反対の側）に第1層301を有し、軸線方向一方側（燃焼室11の側）に第2層302を有する。第2層302の表面は燃焼室11に臨み、第2層302の燃焼室11と反対側の面（裏面）は第1層301の表面に接する。一般に、層の違いは、性状、形状、機能等によって判別可能である。各層301,302の厚さは任意である。第1層301は、第2層302に比べ、空隙33が多い粗な層である。第2層302は、第1層301に比べ、空隙33が少ない密な層である。第1層301に占める空隙33（バーミキュライト32）の体積の割合は、全体として（第1層301全体で平均して）、50%より大きく、好ましくは70%以上であり、より好ましくは90%以上である（100％でもよい）。第1層301に占めるアルミニウム（バインダー31）の体積（焼結体の内部の微少な空隙を含む）の割合は、全体として、50%より小さく、好ましくは30%以下であり、より好ましくは10%以下である（0％でもよい）。第2層302に占める空隙33（バーミキュライト32）の体積の割合は、全体として（第2層302全体で平均して）、50%より小さく、好ましくは30%以下であり、より好ましくは10%以下である（0％でもよい）。第2層302に占めるアルミニウム（バインダー31）の体積の割合は、全体として、50%より大きく、好ましくは70%以上であり、より好ましくは90%以上である（100％でもよい）。他の構成は第1実施形態と同じである。 [Second Embodiment]
First, the configuration will be described. Hereinafter, members and structures common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted. As shown in FIG. 11, the low thermal conductive layer 3 has a first layer 301 on the other side in the axial direction (on the side of the piston body 2 or on the side opposite to the combustion chamber 11), and on one side in the axial direction (the combustion chamber 11). The second layer 302 is provided on the second side. The surface of the second layer 302 faces the combustion chamber 11, and the surface (back surface) opposite to the combustion chamber 11 of the second layer 302 is in contact with the surface of the first layer 301. In general, the difference between layers can be determined by properties, shapes, functions, and the like. The thickness of each layer 301, 302 is arbitrary. The first layer 301 is a rough layer having more voids 33 than the second layer 302. The second layer 302 is a dense layer with fewer gaps 33 than the first layer 301. The ratio of the volume of the voids 33 (vermiculite 32) in the first layer 301 is larger than 50% as a whole (averaged over the entire first layer 301), preferably 70% or more, more preferably 90%. That is all (100% is acceptable). The ratio of the volume of aluminum (binder 31) in the first layer 301 (including the minute voids inside the sintered body) as a whole is less than 50%, preferably 30% or less, more preferably 10%. % Or less (may be 0%). The ratio of the volume of the voids 33 (vermiculite 32) to the second layer 302 is less than 50% as a whole (averaged over the entire second layer 302), preferably 30% or less, more preferably 10%. It is as follows (it may be 0%). The proportion of the volume of aluminum (binder 31) in the second layer 302 as a whole is greater than 50%, preferably 70% or more, more preferably 90% or more (or 100% may be used). Other configurations are the same as those of the first embodiment.
　以下、本実施形態のピストン1の製造方法を説明する。低熱伝導層形成工程は、材料準備工程と、第1材料設置工程と、第1焼結工程と、第2材料設置工程と、第2焼結工程とを含む。材料準備工程では、第1形成材料361として、アルミニウム粉34（及び、あれば添加物）と蛭石35とを第1の（重量又は体積の）比率で混ぜ合わせた混合材料を準備する。第1の比率は、焼結後の低熱伝導層3に全体として占める空隙33（バーミキュライト32）の体積の割合が50％より大きくなり、好ましくは70％以上となり、より好ましくは90％以上となるような比率である。第2形成材料362として、アルミニウム粉34（及び、あれば添加物）と蛭石35とを第2の（重量又は体積の）比率で混ぜ合わせた混合材料を準備する。第2の比率は、焼結後の層3に全体として占めるアルミニウムの体積の割合が50％より大きくなり、好ましくは70％以上となり、より好ましくは90％以上となるような比率である。なお、第1形成材料361と第2形成材料362とで、蛭石35の平均粒径を変えてもよい。 Hereinafter, a method for manufacturing the piston 1 of the present embodiment will be described. The low thermal conductive layer forming process includes a material preparation process, a first material installation process, a first sintering process, a second material installation process, and a second sintering process. In the material preparation step, a mixed material is prepared as the first forming material 361 by mixing the aluminum powder 34 (and additive if any) and the meteorite 35 in a first (weight or volume) ratio. In the first ratio, the volume ratio of the voids 33 (vermiculite 32) as a whole in the low heat conductive layer 3 after sintering is greater than 50%, preferably 70% or more, more preferably 90% or more. It is such a ratio. As the second forming material 362, a mixed material is prepared in which the aluminum powder 34 (and additive if any) and the meteorite 35 are mixed in a second (weight or volume) ratio. The second ratio is such that the volume ratio of aluminum as a whole in the sintered layer 3 is greater than 50%, preferably 70% or more, more preferably 90% or more. The average particle diameter of the meteorite 35 may be changed between the first forming material 361 and the second forming material 362.
　第1材料設置工程で、第1実施形態の材料設置工程と同様、図6及び図7に示すように、原型2Aの凹部401Aに第1形成材料361を入れる。第1焼結工程で、図8に示す第1実施形態の焼結工程と同じ方法により、第1形成材料361（具体的にはアルミニウム粉34）を焼結する。これにより、図9及び図10に示すように、第1層301が形成される。第2材料設置工程で、図12及び図13に示すように、凹部401の原型401Bにおいて、形成された第1層301の上に、第2形成材料362を入れる。第2焼結工程で、図14に示すように、第1実施形態の焼結工程と同じ方法により、第2形成材料362（具体的にはアルミニウム粉34）を焼結する。これにより第2層302が形成される。焼結が完了する（第2層302が形成される）と、工具8を原型401C内から引き上げる。これにより図15及び図16に示すようなピストン1の原型2Cが形成される。ピストンヘッド4の原型4Cに凹部401の原型401Cが形成される。その後、機械加工工程を行う。ピストンヘッド4の原型4Cとともに第2層302の一部を切削加工する。これにより、図11に示すように、第2層302を表面に含む冠面400が形成される。ピストン1の他の製造工程は第1実施形態と同じである。 In the first material installation process, as in the material installation process of the first embodiment, as shown in FIGS. 6 and 7, the first forming material 361 is put into the recess 401A of the prototype 2A. In the first sintering step, the first forming material 361 (specifically, the aluminum powder 34) is sintered by the same method as the sintering step of the first embodiment shown in FIG. As a result, as shown in FIGS. 9 and 10, the first layer 301 is formed. In the second material installation step, as shown in FIGS. 12 and 13, the second forming material 362 is put on the formed first layer 301 in the master 401B of the recess 401. In the second sintering step, as shown in FIG. 14, the second forming material 362 (specifically, the aluminum powder 34) is sintered by the same method as the sintering step of the first embodiment. Thereby, the second layer 302 is formed. When the sintering is completed (the second layer 302 is formed), the tool 8 is pulled up from the prototype 401C. As a result, a prototype 2C of the piston 1 as shown in FIGS. 15 and 16 is formed. A prototype 401C of the recess 401 is formed on the prototype 4C of the piston head 4. Thereafter, a machining process is performed. A part of the second layer 302 is cut together with the prototype 4C of the piston head 4. Thereby, as shown in FIG. 11, a crown surface 400 including the second layer 302 on the surface is formed. Other manufacturing steps of the piston 1 are the same as those in the first embodiment.
　次に、作用効果を説明する。低熱伝導層3に占めるアルミニウムの体積の割合が、軸線方向で、燃焼室11側（第2層302）の方が燃焼室11の反対側（第1層301）よりも大きい。又は、低熱伝導層3に占める空隙33の体積の割合が、軸線方向で、燃焼室11側（第2層302）の方が燃焼室11の反対側（第1層301）よりも小さい。このように、低熱伝導層3の裏面側（燃焼室11の反対側）よりも表面側（燃焼室11側）で、バインダー31の比率が高い、又は空隙33の比率が低いため、層3の表面側の強度が向上する。表面側で空隙33の比率が低いため、層3の表面における空隙33の開口数が減少する。これによって、層3の表面の強度が向上する。よって、層3の損傷（欠けや脱落）を抑制できる。層3の裏面側は、ピストン本体2（凹部401の底面）及び層3の（バインダー31の比率が高い）表面側によって包囲されるため、損傷リスクが少ない。よって、層3の耐久性の向上が図られる。また、層3の表面における空隙33の開口数が減少するため、燃焼室11から空隙33内へ未燃焼の燃料が侵入することは抑制される。これによって、排ガス性能の悪化が抑制される。 Next, the function and effect will be described. The volume ratio of aluminum in the low thermal conductive layer 3 is larger in the axial direction on the combustion chamber 11 side (second layer 302) than on the opposite side of the combustion chamber 11 (first layer 301). Alternatively, the volume ratio of the gap 33 to the low thermal conductive layer 3 is smaller in the axial direction on the combustion chamber 11 side (second layer 302) than on the opposite side of the combustion chamber 11 (first layer 301). Thus, since the ratio of the binder 31 is higher or the ratio of the voids 33 is lower on the front surface side (combustion chamber 11 side) than the back surface side (opposite side of the combustion chamber 11) of the low thermal conductive layer 3, Strength on the surface side is improved. Since the ratio of the voids 33 is low on the surface side, the numerical aperture of the voids 33 on the surface of the layer 3 is reduced. Thereby, the strength of the surface of the layer 3 is improved. Therefore, damage (chip and dropout) of the layer 3 can be suppressed. Since the back surface side of the layer 3 is surrounded by the piston body 2 (the bottom surface of the recess 401) and the surface side of the layer 3 (the ratio of the binder 31 is high), the risk of damage is small. Therefore, the durability of the layer 3 is improved. In addition, since the numerical aperture of the gap 33 on the surface of the layer 3 is reduced, the entry of unburned fuel from the combustion chamber 11 into the gap 33 is suppressed. Thereby, the deterioration of the exhaust gas performance is suppressed.
　具体的には、軸線方向における燃焼室11側（第2層302）で、低熱伝導層3に占めるアルミニウムの体積の割合が50%より大きい。このようにバインダー31の体積が過半を占めることで、層3の表面側（燃焼室11側）の強度をある程度確保し、また燃焼室11への空隙33の開口数をある程度減少できる。上記割合が70%以上であれば、上記強度を向上し、上記開口数をより減少できる。上記割合が90%以上であれば、より確実に上記効果が得られる。同様に、軸線方向における燃焼室11側（第2層302）で、層3に占める空隙33の体積の割合が50%より小さい。このように空隙33の体積が過半を占めないことで、層3の表面側の強度をある程度確保し、燃焼室11への空隙33の開口数をある程度減少できる。上記割合が30%以下であれば、上記強度を向上し、上記開口数をより減少できる。上記割合が10%以下であれば、より確実に上記効果が得られる。 Specifically, the ratio of the volume of aluminum in the low heat conductive layer 3 on the combustion chamber 11 side (second layer 302) in the axial direction is greater than 50%. Thus, by occupying the majority of the volume of the binder 31, the strength on the surface side (combustion chamber 11 side) of the layer 3 can be secured to some extent, and the numerical aperture of the gap 33 to the combustion chamber 11 can be reduced to some extent. If the ratio is 70% or more, the strength can be improved and the numerical aperture can be further reduced. If the ratio is 90% or more, the above effect can be obtained more reliably. Similarly, on the combustion chamber 11 side (second layer 302) in the axial direction, the volume ratio of the voids 33 in the layer 3 is smaller than 50%. Thus, since the volume of the gap 33 does not occupy the majority, the strength on the surface side of the layer 3 can be secured to some extent, and the numerical aperture of the gap 33 to the combustion chamber 11 can be reduced to some extent. If the ratio is 30% or less, the strength can be improved and the numerical aperture can be further reduced. If the ratio is 10% or less, the above effect can be obtained more reliably.
　低熱伝導層3に占めるアルミニウムの体積の割合が、軸線方向で、燃焼室11の反対側（第1層301）の方が燃焼室11側（第2層302）よりも小さい。又は、低熱伝導層3に占める空隙33の体積の割合が、軸線方向で、燃焼室11の反対側（第1層301）の方が燃焼室11側（第2層302）よりも大きい。このように、低熱伝導層3の表面側（燃焼室11側）よりも裏面側（燃焼室11の反対側）で、空隙33の比率が高い、又はバインダー31の比率が低いため、裏面側の熱伝導率が低下する。低熱伝導層3の全体の熱伝導率を効果的に低くして、燃焼効率の低下を抑制できる。空隙33（バーミキュライト32）の比率を高くすると、その高くした部分の損傷のリスクが高くなるが、上記部分を低熱伝導層3の裏面側としたことにより、低熱伝導層3の損傷を抑制することができる。 The volume ratio of aluminum in the low thermal conductive layer 3 is smaller in the axial direction on the opposite side of the combustion chamber 11 (first layer 301) than on the combustion chamber 11 side (second layer 302). Alternatively, the volume ratio of the gap 33 in the low thermal conductive layer 3 is larger in the axial direction on the opposite side of the combustion chamber 11 (first layer 301) than on the combustion chamber 11 side (second layer 302). Thus, since the ratio of the gaps 33 is higher or the ratio of the binder 31 is lower on the back side (opposite side of the combustion chamber 11) than on the front side (combustion chamber 11 side) of the low thermal conductive layer 3, Thermal conductivity decreases. The overall thermal conductivity of the low thermal conductive layer 3 can be effectively lowered to suppress a decrease in combustion efficiency. Increasing the ratio of the void 33 (vermiculite 32) increases the risk of damage to the increased portion, but by suppressing the damage to the low thermal conductive layer 3 by making the above portion the back side of the low thermal conductive layer 3 Can do.
　具体的には、軸線方向における燃焼室11と反対側（第1層301）で、低熱伝導層3に占める空隙33（バーミキュライト32）の体積の割合が50%より大きい。このように空隙33の体積が過半を占めることで、層3の裏面側の熱伝導率をある程度低くできる。上記割合が70%以上であれば、上記熱伝導率をより低くできる。上記割合が90%以上であれば、上記熱伝導率を充分に低くできる。同様に、軸線方向における燃焼室11と反対側（第1層301）で、層3に占めるアルミニウムの体積の割合が50%より小さい。このようにアルミニウムの体積が過半を占めないことで、層3の裏面側の熱伝導率をある程度低くできる。上記割合が30%以下であれば、上記熱伝導率をより低くできる。上記割合が10%以下であれば、上記熱伝導率を充分に低くすることができる。 Specifically, the volume ratio of the void 33 (vermiculite 32) occupying the low heat conductive layer 3 on the side opposite to the combustion chamber 11 (first layer 301) in the axial direction is greater than 50%. As described above, the volume of the gap 33 occupies a majority, so that the thermal conductivity on the back side of the layer 3 can be lowered to some extent. If the ratio is 70% or more, the thermal conductivity can be further reduced. When the ratio is 90% or more, the thermal conductivity can be sufficiently lowered. Similarly, on the side opposite to the combustion chamber 11 in the axial direction (first layer 301), the proportion of the volume of aluminum in the layer 3 is smaller than 50%. Thus, since the volume of aluminum does not occupy the majority, the thermal conductivity on the back surface side of the layer 3 can be lowered to some extent. When the ratio is 30% or less, the thermal conductivity can be further reduced. When the ratio is 10% or less, the thermal conductivity can be sufficiently lowered.
　低熱伝導層3は、軸線方向で、アルミニウムと空隙33（バーミキュライト32）との体積の比率が異なる複数の層として、第1層301と第2層302を有する。このように、バインダー31と空隙33との比率が異なる層を複数組み合わせることにより、全体として所望の特性を有する低熱伝導層3とすることができる。上記のように、熱伝導率が低く、損傷や排ガス性能の悪化を抑制できる、といった特性を実現可能である。 The low thermal conductive layer 3 includes a first layer 301 and a second layer 302 as a plurality of layers having different volume ratios of aluminum and voids 33 (vermiculite 32) in the axial direction. In this way, by combining a plurality of layers having different ratios of the binder 31 and the gap 33, the low thermal conductive layer 3 having desired characteristics as a whole can be obtained. As described above, it is possible to realize such characteristics that the thermal conductivity is low and damage and deterioration of exhaust gas performance can be suppressed.
　なお、第1焼結工程を省略してもよい。すなわち、材料設置工程で、第1形成材料361に引き続いて第2形成材料362を凹部401に入れ、第1形成材料361と第2形成材料362とを凹部401内で層状に重ならせる。その後、焼結工程で、第1実施形態の焼結工程と同様、工具8の端部80を第2形成材料362に押し当てて回転させる。これにより第1形成材料361（下層）と第2形成材料362（上層）がそれぞれ混ぜられて加熱され、蛭石35の膨張による空隙33を含む焼結体の層が形成される。アルミニウムと空隙33の体積の比率が軸線方向で異なった（燃焼室11側の方が燃焼室11の反対側よりもアルミニウムの比率が大きい）低熱伝導層3が形成される。上記比率は軸線方向で連続的に異なってもよいし非連続的に異なってもよい。上記比率の相違に着目すると、実質的に2層からなる低熱伝導層3が形成される。この方法は、第1形成材料361にアルミニウム粉34がほとんど含まれず第1形成材料361の単独での焼結が難しい場合に特に有効である。一方、第1焼結工程を含む上記方法は、第1形成材料361にアルミニウム粉34がある程度存在する場合に特に有効である。第1,第2層301,302（2層の焼結層）を互いに独立に形成することで、各層301,302に占めるアルミニウム及び空隙33の体積の割合を、より正確にコントロール可能である。また、複数の層301,302を順次形成することで、各層301,302を効率的に形成しつつ、全体としての層3の厚さを容易に増大させることができる。第2層302と同様にして第3層,第4層等を形成してもよい。他の作用効果は第実施形態と同じである。 Note that the first sintering step may be omitted. That is, in the material installation step, the second forming material 362 is placed in the recess 401 subsequent to the first forming material 361, and the first forming material 361 and the second forming material 362 are layered in the recess 401. Thereafter, in the sintering process, as in the sintering process of the first embodiment, the end 80 of the tool 8 is pressed against the second forming material 362 and rotated. Thereby, the first forming material 361 (lower layer) and the second forming material 362 (upper layer) are mixed and heated, and a layer of a sintered body including the voids 33 due to expansion of the meteorite 35 is formed. The low thermal conductive layer 3 is formed in which the volume ratio of aluminum and the gap 33 is different in the axial direction (the ratio of aluminum is larger on the combustion chamber 11 side than on the opposite side of the combustion chamber 11). The said ratio may differ continuously in an axial direction, and may differ discontinuously. When attention is paid to the difference in the ratio, the low thermal conductive layer 3 consisting essentially of two layers is formed. This method is particularly effective when the first forming material 361 contains almost no aluminum powder 34 and it is difficult to sinter the first forming material 361 alone. On the other hand, the above method including the first sintering step is particularly effective when the aluminum powder 34 is present in the first forming material 361 to some extent. By forming the first and second layers 301 and 302 (two sintered layers) independently of each other, it is possible to more accurately control the volume ratio of the aluminum and the voids 33 in each of the layers 301 and 302. In addition, by sequentially forming the plurality of layers 301 and 302, it is possible to easily increase the thickness of the layer 3 as a whole while efficiently forming the layers 301 and 302. The third layer, the fourth layer, and the like may be formed in the same manner as the second layer 302. Other functions and effects are the same as those of the first embodiment.
　［第3実施形態］
  本実施形態のピストン1の構成は、第2実施形態と同じである。本実施形態のピストン1の製造方法を説明する。材料準備工程で、第1形成材料361及び第2形成材料362（粉体である混合材料）をそれぞれ所定の形状に固めた仮の成形体（プリフォーム360）を用意する。プリフォーム360は、形成材料36を加圧して圧縮することにより固めた圧粉体である。なお、接着剤等により固めてもよい。図17に示すように、プリフォーム360は円柱状である。第1形成材料361のプリフォーム360の直径D3は、凹部410の原型401Aの直径D1よりわずかに小さい。第2形成材料362のプリフォーム360の直径D3は、凹部401の原型401Bのうち燃焼室11側の直径（工具8の端部の直径）D2よりわずかに小さい。なお、両材料361,362のプリフォーム360の直径D3を揃えてもよい。プリフォーム360の高さ（軸線方向寸法）は、適宜設定可能である。材料設置工程で、凹部401の原型401A,401Bに形成材料361,362をそれぞれ入れる際、それらのプリフォーム360を挿入して設置する。ピストン1の他の製造工程は第2実施形態と同じである。 [Third embodiment]
The configuration of the piston 1 of the present embodiment is the same as that of the second embodiment. A method for manufacturing the piston 1 of the present embodiment will be described. In the material preparation step, a temporary molded body (preform 360) is prepared in which the first forming material 361 and the second forming material 362 (mixed material that is powder) are each set in a predetermined shape. The preform 360 is a green compact obtained by pressing and compressing the forming material 36. It may be hardened with an adhesive or the like. As shown in FIG. 17, the preform 360 has a cylindrical shape. The diameter D3 of the preform 360 of the first forming material 361 is slightly smaller than the diameter D1 of the original 401A of the recess 410. The diameter D3 of the preform 360 of the second forming material 362 is slightly smaller than the diameter (the diameter of the end portion of the tool 8) D2 on the combustion chamber 11 side of the original 401B of the recess 401. The diameters D3 of the preforms 360 of both materials 361 and 362 may be aligned. The height (axis direction dimension) of the preform 360 can be set as appropriate. In the material installation process, when the forming materials 361 and 362 are put into the prototypes 401A and 401B of the recess 401, the preforms 360 are inserted and installed. Other manufacturing steps of the piston 1 are the same as those in the second embodiment.
　次に、作用効果を説明する。材料設置工程で、予め成形された形成材料36（プリフォーム360）を凹部401の原型401A,401Bに設置することにより、形成材料36を粉末状のまま原型401A,401Bに設置する場合に比べ、設置作業が容易となる。他の作用効果は第2実施形態と同じである。なお、両材料361,362のいずれかのみをプリフォーム360としてもよい。例えば、材料準備工程で形成材料36を加圧して圧縮する際、第1形成材料361における蛭石35の比率が高いことで第1形成材料361を固めることが困難なときは、第2形成材料362のみプリフォーム360に成形してもよい。また、第1実施形態のピストン1の製造方法にプリフォーム360を適用してもよい。 Next, the function and effect will be described. In the material installation process, the preformed forming material 36 (preform 360) is placed on the original 401A, 401B of the recess 401, so that the forming material 36 is placed in the original 401A, 401B while remaining in powder form, Installation work becomes easy. Other functions and effects are the same as those of the second embodiment. Only one of the both materials 361 and 362 may be used as the preform 360. For example, when pressurizing and compressing the forming material 36 in the material preparation step, if it is difficult to harden the first forming material 361 due to the high ratio of the meteorite 35 in the first forming material 361, the second forming material Only 362 may be formed into the preform 360. Further, the preform 360 may be applied to the method for manufacturing the piston 1 of the first embodiment.
　［第4実施形態］
  まず、構成を説明する。図18及び図19に示すように、ピストン1は、低熱伝導層3の（燃焼室11側の）表面に皮膜9を有する。皮膜9は、冠面400において、層3の表面の全部と、他の箇所（凹部401ないし低熱伝導層3を取り囲む部分）の表面の全部とを覆う。皮膜9は、例えばジルコニアやコージェライト等のセラミックスを含む。層3その他のピストン1の構成は第1実施形態と同じである。本実施形態のピストン1の製造方法は、皮膜形成工程を含む。皮膜形成工程は、機械加工工程後に行われ、切削加工された（層3を含む）冠面400の表面に皮膜9を形成する。例えば上記セラミックスの粉末を材料とし、この粉末を冠面400にプラズマ溶射する等により皮膜9を形成する。ピストン1の他の製造工程は第1実施形態と同じである。 [Fourth embodiment]
First, the configuration will be described. As shown in FIGS. 18 and 19, the piston 1 has a coating 9 on the surface (on the combustion chamber 11 side) of the low thermal conductive layer 3. The coating 9 covers the entire surface of the layer 3 and the entire surface of the other portion (the portion surrounding the recess 401 or the low thermal conductive layer 3) on the crown surface 400. The film 9 includes ceramics such as zirconia and cordierite. Layer 3 and other piston 1 configurations are the same as those in the first embodiment. The method for manufacturing the piston 1 of the present embodiment includes a film forming step. The film forming process is performed after the machining process, and forms the film 9 on the surface of the crown surface 400 that has been cut (including the layer 3). For example, the ceramic 9 powder is used as a material, and the coating 9 is formed by, for example, plasma spraying the powder onto the crown surface 400. Other manufacturing steps of the piston 1 are the same as those in the first embodiment.
　次に、作用効果を説明する。低熱伝導層3内の空隙33の表面側（燃焼室11側）への開口は、皮膜9により覆われる。皮膜9は空隙33の開口を閉塞（封孔）する封孔層として機能する。開口が覆われることで、空隙33の内部で対流が起きにくくなるため、層3の断熱性が向上する。また、燃焼室11から空隙33内へ未燃焼の燃料が侵入することが抑制されるため、排ガス性能の悪化が抑制される。また、空隙33の開口が皮膜9により覆われることで、層3の表面における空隙33による凹凸が減少する。よって、層3の表面の強度を向上し、層3の損傷を抑制できる。なお、皮膜9の材料は耐熱性と強度を一定程度有していればよく、ピストン本体2の素材（母材金属）であるアルミニウム合金よりも熱伝導率が低くなくてもよい。本実施形態では、皮膜9のセラミックス（ジルコニア等）は、低熱伝導性材料であり、ピストン本体2の素材（アルミニウム合金）よりも熱伝導率が低い。よって、皮膜9は、ピストン本体2よりも熱伝導率が低くなる。皮膜9は、燃焼室11とピストンヘッド4との間にあって、断熱層として機能する。よって、冠面400における層3を取り囲む部分の熱伝導率をも低くし、燃焼効率の低下の更なる抑制を図ることができる。なお、皮膜9は冠面400の全部でなく一部の範囲にあってもよい。例えば、皮膜9は、冠面400における層3の表面のみを覆い、他の箇所の表面を覆わなくてもよい。上記他の箇所に皮膜9を形成しなければ、上記他の箇所が不必要に高温となってノッキングが発生する事態を抑制できる。他の作用効果は第1実施形態と同じである。 Next, the function and effect will be described. The opening to the surface side (combustion chamber 11 side) of the gap 33 in the low thermal conductive layer 3 is covered with the coating 9. The film 9 functions as a sealing layer that closes (seals) the opening of the gap 33. By covering the opening, it becomes difficult for convection to occur inside the gap 33, so that the heat insulation of the layer 3 is improved. Further, since unburned fuel is prevented from entering the gap 33 from the combustion chamber 11, deterioration of exhaust gas performance is suppressed. Further, since the opening of the gap 33 is covered with the film 9, the unevenness due to the gap 33 on the surface of the layer 3 is reduced. Therefore, the strength of the surface of the layer 3 can be improved and damage to the layer 3 can be suppressed. Note that the material of the film 9 only needs to have a certain degree of heat resistance and strength, and the thermal conductivity does not have to be lower than that of the aluminum alloy that is the material (base metal) of the piston body 2. In the present embodiment, the ceramic (such as zirconia) of the coating 9 is a low thermal conductivity material and has a lower thermal conductivity than the material (aluminum alloy) of the piston body 2. Therefore, the film 9 has a lower thermal conductivity than the piston body 2. The coating 9 is located between the combustion chamber 11 and the piston head 4 and functions as a heat insulating layer. Therefore, the thermal conductivity of the portion surrounding the layer 3 on the crown surface 400 can also be lowered, and further reduction in combustion efficiency can be achieved. The coating 9 may be in a part of the crown surface 400 instead of the whole. For example, the coating 9 may cover only the surface of the layer 3 on the crown surface 400 and may not cover the surface of other portions. If the film 9 is not formed in the other part, it is possible to suppress the occurrence of knocking due to the other part becoming unnecessarily high temperature. Other functions and effects are the same as those of the first embodiment.
　皮膜9は陽極酸化皮膜であってもよい。すなわち、上記皮膜形成工程で、（低熱伝導層3を含む）冠面400のアルミニウム（層3のバインダー31やピストン本体2の素材）を陽極酸化させることにより、冠面400に陽極酸化皮膜（表面層）を形成してもよい。陽極酸化皮膜により、層3の表面における空隙33の開口が閉塞され又は小さくなる。陽極酸化の工程は、封孔処理工程として機能する。空隙33の開口が小さくなることで、上記と同様、排ガス性能の悪化や層3の損傷を抑制できる。また、一般に、酸化によって熱伝導率は低くなる。このため、層3の陽極酸化された表面側（燃焼室11側）で、燃焼室11と反対側よりも、熱伝導率が（平均的に）低くなる。言い換えると、陽極酸化により、冠面400に、低熱伝導層3（の陽極酸化されない部分）よりも熱伝導率が低い皮膜9が形成される。また、陽極酸化皮膜中のポーラスによっても、層3の陽極酸化された表面側で、燃焼室11と反対側よりも、熱伝導率が低くなる。よって、層3の熱伝導率を更に低くすることができる。なお、陽極酸化皮膜中のポーラスが大きくなりすぎないためには、陽極酸化皮膜の厚さは薄いほうがよい。この点、層3は焼結体であるため、陽極酸化皮膜の形成はそれほど進まず、その厚さはある程度薄く抑えられることから、好都合である。冠面400における層3以外の箇所（層3を取り囲む部分）でも、上記と同様、陽極酸化された表面側（燃焼室11側）で、熱伝導率が低くなる。陽極酸化皮膜が冠面400の全部でなく一部の範囲に形成されてもよいことは、上記と同様である。 The film 9 may be an anodized film. That is, in the film formation step, the anodized film (surface) is formed on the crown surface 400 by anodizing aluminum (including the binder 31 of the layer 3 and the material of the piston body 2) of the crown surface 400 (including the low thermal conductive layer 3). Layer) may be formed. Due to the anodized film, the opening of the gap 33 on the surface of the layer 3 is closed or reduced. The anodizing process functions as a sealing treatment process. By reducing the opening of the gap 33, it is possible to suppress deterioration of exhaust gas performance and damage to the layer 3 as described above. In general, the thermal conductivity is lowered by oxidation. For this reason, the thermal conductivity is (average) lower on the anodized surface side (combustion chamber 11 side) of the layer 3 than on the side opposite to the combustion chamber 11. In other words, a film 9 having a thermal conductivity lower than that of the low thermal conductive layer 3 (the portion that is not anodized) is formed on the crown surface 400 by anodic oxidation. In addition, due to the porosity in the anodized film, the thermal conductivity is lower on the anodized surface side of the layer 3 than on the side opposite to the combustion chamber 11. Therefore, the thermal conductivity of the layer 3 can be further reduced. In order to prevent the porosity in the anodized film from becoming too large, the thickness of the anodized film is preferably thin. In this respect, since the layer 3 is a sintered body, the formation of the anodic oxide film does not proceed so much and the thickness can be suppressed to a certain extent, which is advantageous. Also in the portion other than the layer 3 on the crown surface 400 (portion surrounding the layer 3), the thermal conductivity is low on the anodized surface side (combustion chamber 11 side) as described above. As described above, the anodized film may be formed on a part of the crown surface 400 instead of the entire surface.
　第2実施形態のピストン1に上記皮膜9を適用（第2実施形態のピストン1の製造方法に上記皮膜形成工程を適用）し、第2層302を含む冠面400を覆う皮膜9を形成してもよい。また、本実施形態のピストン1の製造方法に第3実施形態のプリフォーム360を適用してもよい。 The coating 9 is applied to the piston 1 of the second embodiment (the coating forming step is applied to the manufacturing method of the piston 1 of the second embodiment), and the coating 9 covering the crown surface 400 including the second layer 302 is formed. May be. Further, the preform 360 of the third embodiment may be applied to the manufacturing method of the piston 1 of the present embodiment.
　［他の実施形態］
  以上、本発明を実施するための形態を、図面に基づき説明したが、本発明の具体的な構成は、実施形態に限定されるものではなく、発明の要旨を逸脱しない範囲の設計変更等があっても本発明に含まれる。ピストン1（ピストン本体2）の形状は任意である。また、上述した課題の少なくとも一部を解決できる範囲、または、効果の少なくとも一部を奏する範囲において、特許請求の範囲および明細書に記載された各構成要素の任意の組み合わせ、または、省略が可能である。例えば、凹部401の形状や位置は上記に限らず任意である。凹部401の外周縁は通路411の内周縁よりもピストン径方向で内側にあってもよい。冠面400にバルブリセス等の凹部を有してもよい。図20に示すように、冠面400の一部が燃焼室11側に隆起した形状のピストン1であってもよい。低熱伝導層3は、第1層301及び第2層302を有する。第2層302は隆起部402にある。第2実施形態の低熱伝導層形成工程後の機械加工工程において、ピストンヘッド4の原型4Cとともに第2層302の一部を切削加工する。隆起部402を残して第2層302を切削加工する。これにより、第2層302を隆起部402の表面に含む冠面400が形成される。更に、図21に示すように、上記冠面400に、第4実施形態の皮膜9を形成してもよい。 [Other Embodiments]
As mentioned above, although the form for implementing this invention was demonstrated based on drawing, the specific structure of this invention is not limited to embodiment, The design change etc. of the range which does not deviate from the summary of invention are included. Even if it exists, it is included in this invention. The shape of the piston 1 (piston body 2) is arbitrary. In addition, any combination or omission of each constituent element described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect is achieved. It is. For example, the shape and position of the recess 401 are not limited to the above and are arbitrary. The outer peripheral edge of the recess 401 may be located on the inner side in the piston radial direction than the inner peripheral edge of the passage 411. The crown surface 400 may have a recess such as a valve recess. As shown in FIG. 20, the piston 1 may have a shape in which a part of the crown surface 400 is raised toward the combustion chamber 11 side. The low thermal conductive layer 3 includes a first layer 301 and a second layer 302. The second layer 302 is on the ridge 402. In the machining step after the low thermal conductive layer forming step of the second embodiment, a part of the second layer 302 is cut together with the prototype 4C of the piston head 4. The second layer 302 is cut while leaving the raised portion 402. Thereby, the crown surface 400 including the second layer 302 on the surface of the raised portion 402 is formed. Furthermore, as shown in FIG. 21, the coating 9 of the fourth embodiment may be formed on the crown surface 400.
　［実施形態から把握しうる他の態様］
  以上説明した実施形態から把握しうる他の態様（又は技術的解決策。以下同じ。）について、以下に記載する。
(1) 内燃機関のピストンは、その1つの態様において、
  アルミニウム合金を含み、ピストンヘッド及びピストンスカートを有する本体であって、前記ピストンヘッドのうち内燃機関の燃焼室に臨む側に保持部がある本体と、
  金属であるバインダー及び層状ケイ酸塩鉱物を含み、前記保持部にある低熱伝導層とを有する。
(2) より好ましい態様では、前記態様において、
  前記低熱伝導層の表面にあり、前記低熱伝導層内の空隙の開口を閉塞する皮膜を有する。
(3) 別の好ましい態様では、前記態様のいずれかにおいて、
  前記皮膜は前記低熱伝導層よりも熱伝導率が低い。
(4) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記皮膜は陽極酸化皮膜である。
(5) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記バインダーはアルミニウムを含む。
(6) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記低熱伝導層に占める前記バインダーの体積の割合が、前記内燃機関のシリンダ内における前記本体の移動方向に沿った軸線方向で、前記燃焼室側の方が前記燃焼室の反対側よりも大きい。
(7) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記低熱伝導層は、前記軸線方向で、前記バインダーと前記層状ケイ酸塩鉱物との体積の比率が異なる複数の層を有する。
(8) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記軸線方向における前記燃焼室側で、前記低熱伝導層に占める前記バインダーの体積の割合が９０パーセント以上である。
(9) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記軸線方向における前記燃焼室と反対側で、前記低熱伝導層に占める前記層状ケイ酸塩鉱物の体積の割合が９０パーセント以上である。
(10) 内燃機関のピストンの製造方法は、その1つの態様において、
  ピストンヘッドとピストンスカートとを有する本体をアルミニウム合金で形成する工程と、
  前記ピストンヘッドのうち内燃機関の燃焼室に臨む側に保持部を形成する工程と、
  金属であるバインダーと層状の含水ケイ酸塩鉱物とを混合した材料を前記保持部に設置する工程と、
  前記設置された材料を、回転する工具により押圧し、前記保持部に低熱伝導層を形成する工程とを含む。
(11) より好ましい態様では、前記態様において、
  前記低熱伝導層の表面に皮膜を形成する工程を有する。
(12) 別の好ましい態様では、前記態様のいずれかにおいて、
  前記皮膜は前記低熱伝導層よりも熱伝導率が低い。
(13) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記皮膜を形成する工程では、陽極酸化により陽極酸化皮膜を形成する。
(14) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記回転する工具の直径は前記保持部の直径よりも大きい。
(15) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記バインダーはアルミニウム粉を含む。
(16) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記低熱伝導層に占める前記バインダーの体積の割合が、前記内燃機関のシリンダ内における前記本体の移動方向に沿った軸線方向で、前記燃焼室側の方が前記燃焼室の反対側よりも大きい。
(17) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記低熱伝導層を形成する工程の後、前記バインダーと前記含水ケイ酸塩鉱物とを前記材料と異なる比率で混合した別の材料を前記保持部に設置する工程と、
  前記設置された別の材料を、回転する工具で押圧し、前記保持部に別の低熱伝導層を形成する工程とを有する。
(18) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記低熱伝導層を形成する工程の後、前記ピストンヘッドのうち内燃機関の燃焼室に臨む側を切削加工する工程を有する。
(19) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記切削加工する工程の後、前記低熱伝導層の表面に皮膜を形成する工程を有する。
(20) さらに別の好ましい態様では、前記態様のいずれかにおいて、
  前記材料を圧縮し所定の形状に成形する工程を有し、
  前記材料を前記保持部に設置する工程では、前記成形された前記材料を前記保持部に設置する。 [Other aspects that can be grasped from the embodiment]
Other aspects (or technical solutions; the same applies hereinafter) that can be understood from the embodiment described above will be described below.
(1) In one aspect of the piston of the internal combustion engine,
A main body comprising an aluminum alloy and having a piston head and a piston skirt, the main body having a holding portion on the side facing the combustion chamber of the internal combustion engine,
It includes a binder, which is a metal, and a layered silicate mineral, and has a low heat conductive layer in the holding portion.
(2) In a more preferred embodiment, in the above embodiment,
It has a film on the surface of the low thermal conductive layer, which closes the opening of the void in the low thermal conductive layer.
(3) In another preferred embodiment, in any of the above embodiments,
The film has a lower thermal conductivity than the low thermal conductive layer.
(4) In still another preferred embodiment, in any of the above embodiments,
The film is an anodized film.
(5) In still another preferred embodiment, in any of the above embodiments,
The binder includes aluminum.
(6) In still another preferred embodiment, in any of the above embodiments,
The ratio of the volume of the binder to the low heat conductive layer is an axial direction along the moving direction of the main body in the cylinder of the internal combustion engine, and the combustion chamber side is larger than the opposite side of the combustion chamber.
(7) In still another preferred embodiment, in any of the above embodiments,
The low thermal conductive layer has a plurality of layers having different volume ratios of the binder and the layered silicate mineral in the axial direction.
(8) In still another preferred embodiment, in any of the above embodiments,
On the combustion chamber side in the axial direction, the proportion of the volume of the binder in the low thermal conductive layer is 90% or more.
(9) In still another preferred embodiment, in any of the above embodiments,
On the opposite side of the combustion chamber in the axial direction, the proportion of the volume of the layered silicate mineral in the low thermal conductivity layer is 90% or more.
(10) In one aspect of the method for producing a piston of an internal combustion engine,
Forming a body having a piston head and a piston skirt from an aluminum alloy;
Forming a holding portion on the side of the piston head facing the combustion chamber of the internal combustion engine;
A step of installing a material in which the binder, which is a metal, and a layered hydrous silicate mineral are mixed in the holding unit;
Pressing the installed material with a rotating tool, and forming a low thermal conductive layer on the holding portion.
(11) In a more preferred embodiment, in the above embodiment,
Forming a film on the surface of the low thermal conductive layer.
(12) In another preferred embodiment, in any of the above embodiments,
The film has a lower thermal conductivity than the low thermal conductive layer.
(13) In still another preferred embodiment, in any of the above embodiments,
In the step of forming the film, an anodized film is formed by anodization.
(14) In still another preferred embodiment, in any of the above embodiments,
The diameter of the rotating tool is larger than the diameter of the holding part.
(15) In still another preferred embodiment, in any of the above embodiments,
The binder includes aluminum powder.
(16) In still another preferred embodiment, in any of the above embodiments,
The ratio of the volume of the binder to the low heat conductive layer is an axial direction along the moving direction of the main body in the cylinder of the internal combustion engine, and the combustion chamber side is larger than the opposite side of the combustion chamber.
(17) In still another preferred embodiment, in any of the above embodiments,
After the step of forming the low thermal conductive layer, a step of installing another material in which the binder and the hydrous silicate mineral are mixed in a ratio different from that of the material in the holding unit;
Pressing the another installed material with a rotating tool to form another low thermal conductive layer on the holding portion.
(18) In still another preferred embodiment, in any of the above embodiments,
After the step of forming the low thermal conductive layer, a step of cutting the side of the piston head that faces the combustion chamber of the internal combustion engine is included.
(19) In still another preferred embodiment, in any of the above embodiments,
After the cutting step, the method includes a step of forming a film on the surface of the low thermal conductive layer.
(20) In still another preferred embodiment, in any of the above embodiments,
Compressing the material and forming it into a predetermined shape,
In the step of installing the material on the holding unit, the molded material is installed on the holding unit.
　本願は、２０１６年８月１２日出願の日本特許出願番号２０１６－１５８３６６号に基づく優先権を主張する。２０１６年８月１２日出願の日本特許出願番号２０１６－１５８３６６号の明細書、特許請求の範囲、図面及び要約書を含む全ての開示内容は、参照により全体として本願に組み込まれる。 This application claims priority based on Japanese Patent Application No. 2016-158366 filed on August 12, 2016. The entire disclosure including the specification, claims, drawings and abstract of Japanese Patent Application No. 2016-158366 filed on August 12, 2016 is incorporated herein by reference in its entirety.
１００　エンジン（内燃機関）、１１　燃焼室、１　ピストン、２　ピストン本体、３　低熱伝導層、３１　バインダー、３２　バーミキュライト（層状ケイ酸塩鉱物）、４　ピストンヘッド、４０１　凹部（保持部）、６　ピストンスカート 100 engine (internal combustion engine), 11 combustion chamber, 1 piston, 2 piston body, 3 low heat conduction layer, 31 binder, 32 vermiculite (layered silicate mineral), 4 piston head, 401 recess (holding part), 6 piston skirt

Claims (20)

  1. 　内燃機関のピストンであって、
    　アルミニウム合金で形成された本体部であって、ピストンヘッドと、前記ピストンヘッドに設けられたスカート部と、を有する本体部と、
    　前記ピストンヘッドのうちの、前記内燃機関の燃焼室側に設けられた低熱伝導層保持部と、
    　前記低熱伝導層保持部に保持される低熱伝導層と
    　を備え、
    　前記低熱伝導層は、金属材料から形成されたバインダーと、層状の含水ケイ酸塩鉱物と、の混合材料を含む
    　内燃機関のピストン。     A piston of an internal combustion engine,
    A main body formed of an aluminum alloy, the main body having a piston head and a skirt provided on the piston head;
    Of the piston head, a low thermal conductive layer holding part provided on the combustion chamber side of the internal combustion engine;
    A low thermal conductive layer held by the low thermal conductive layer holding unit,
    The piston of an internal combustion engine, wherein the low heat conductive layer includes a mixed material of a binder formed of a metal material and a layered hydrous silicate mineral.
  2. 　請求項１に記載の内燃機関のピストンであって、
    　前記低熱伝導層の表面に設けられ、前記低熱伝導層の空隙を閉塞する被膜を備える
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 1,
    A piston for an internal combustion engine, comprising a coating provided on a surface of the low thermal conductive layer and closing a gap in the low thermal conductive layer.
  3. 　請求項２に記載の内燃機関のピストンであって、
    　前記被膜は、前記低熱伝導層よりも熱伝導率が低く、かつ、前記低熱伝導層よりも比熱が小さい
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 2,
    The piston of an internal combustion engine, wherein the coating film has a lower thermal conductivity than the low thermal conductive layer and a specific heat smaller than that of the low thermal conductive layer.
  4. 　請求項２に記載の内燃機関のピストンであって、
    　前記被膜は、陽極酸化被膜である
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 2,
    The coating film is an anodized film piston of an internal combustion engine.
  5. 　請求項１に記載の内燃機関のピストンであって、
    　前記バインダーは、アルミニウム粉である
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 1,
    The binder is an aluminum powder piston of an internal combustion engine.
  6. 　請求項１に記載の内燃機関のピストンであって、
    　前記低熱伝導層において、前記バインダーの混合比率が、前記内燃機関のシリンダ内における前記本体部の移動方向に沿った軸線方向において、前記燃焼室側の方が前記燃焼室とは反対側よりも高い
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 1,
    In the low heat conduction layer, the mixing ratio of the binder is higher on the combustion chamber side than on the opposite side of the combustion chamber in the axial direction along the moving direction of the main body in the cylinder of the internal combustion engine. Piston for internal combustion engine.
  7. 　請求項６に記載の内燃機関のピストンであって、
    　前記低熱伝導層は、前記軸線方向において、前記バインダーと前記層状の含水ケイ酸塩鉱物との混合比率が異なる複数の層を備える
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 6,
    The piston of an internal combustion engine, wherein the low heat conductive layer includes a plurality of layers having different mixing ratios of the binder and the layered hydrous silicate mineral in the axial direction.
  8. 　請求項６に記載の内燃機関のピストンであって、
    　前記低熱伝導層は、前記軸線方向における前記燃焼室側の表面の前記バインダーの比率が90パーセント以上である
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 6,
    The piston of an internal combustion engine, wherein the low heat conductive layer has a ratio of the binder on the surface on the combustion chamber side in the axial direction of 90% or more.
  9. 　請求項６に記載の内燃機関のピストンであって、
    　前記低熱伝導層は、前記軸線方向における前記燃焼室とは反対側の端部の前記層状の含水ケイ酸塩鉱物の混合比率が90パーセント以上である
    　内燃機関のピストン。     A piston for an internal combustion engine according to claim 6,
    The piston of an internal combustion engine, wherein the low heat conductive layer has a mixing ratio of the layered hydrous silicate mineral of 90% or more at the end opposite to the combustion chamber in the axial direction.
  10. 　内燃機関のピストンの製造方法であって、
    　アルミニウム合金で形成された本体部であって、ピストンヘッドと前記ピストンヘッドに設けられたスカート部とを有する本体部と、前記ピストンヘッドのうちの、前記内燃機関の燃焼室側に設けられた低熱伝導層保持部と、を備えるピストンを用意する工程と、
    　金属材料から形成されたバインダーと、層状の含水ケイ酸塩鉱物と、の第1の混合材料を前記低熱伝導層保持部に設置する設置工程と、
    　前記混合材料を回転するツールで押圧し、前記低熱伝導層保持部に低熱伝導層を形成する低熱伝導層形成工程と、
    　を備える内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine,
    A main body formed of an aluminum alloy, the main body having a piston head and a skirt provided on the piston head, and a low heat provided on the combustion chamber side of the internal combustion engine of the piston head. A step of preparing a piston comprising a conductive layer holding part;
    An installation step of installing a first mixed material of the binder formed of a metal material and the layered hydrous silicate mineral in the low thermal conductive layer holding unit;
    A low thermal conductive layer forming step of pressing the mixed material with a rotating tool and forming a low thermal conductive layer on the low thermal conductive layer holding part,
    A method for manufacturing a piston of an internal combustion engine.
  11. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記低熱伝導層形成工程の後、前記低熱伝導層の表面に被膜を設ける被膜形成工程を備える
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    The manufacturing method of the piston of an internal combustion engine provided with the film formation process which provides a film on the surface of the said low heat conductive layer after the said low heat conductive layer formation process.
  12. 　請求項１１に記載の内燃機関のピストンの製造方法であって、
    　前記被膜は、前記低熱伝導層よりも熱伝導率が低く、かつ、前記低熱伝導層よりも比熱が小さい
    　内燃機関のピストンの製造方法。     It is a manufacturing method of the piston of the internal-combustion engine according to claim 11,
    The method for manufacturing a piston of an internal combustion engine, wherein the coating film has a lower thermal conductivity than the low thermal conductive layer and a lower specific heat than the low thermal conductive layer.
  13. 　請求項１１に記載の内燃機関のピストンの製造方法であって、
    　前記被膜形成工程は、陽極酸化処理により陽極酸化被膜を形成する工程を備える
    　内燃機関のピストンの製造方法。     It is a manufacturing method of the piston of the internal-combustion engine according to claim 11,
    The said film formation process is a manufacturing method of the piston of an internal combustion engine provided with the process of forming an anodized film by an anodizing process.
  14. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記ツールの直径は、前記低熱伝導層保持部の直径よりも大きい
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    The diameter of the tool is larger than the diameter of the low thermal conductive layer holding part.
  15. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記バインダーは、アルミニウム粉である
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    The said binder is aluminum powder. The manufacturing method of the piston of an internal combustion engine.
  16. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記低熱伝導層は、前記バインダーの混合比率が、前記内燃機関のシリンダ内における前記本体部の移動方向に沿った軸線方向において、前記燃焼室側の方が前記燃焼室とは反対側よりも高い
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    In the low heat conductive layer, the mixing ratio of the binder is higher on the combustion chamber side than on the opposite side of the combustion chamber in the axial direction along the moving direction of the main body in the cylinder of the internal combustion engine. A method for manufacturing a piston of an internal combustion engine.
  17. 　請求項１６に記載の内燃機関のピストンの製造方法であって、
    　前記低熱伝導層形成工程の後、前記バインダーと前記層状の含水ケイ酸塩鉱物との混合比率が前記第1の混合材料とは異なる第2の混合材料を前記低熱伝導層保持部に設置する第2の設置工程と、
    　前記第2工程で設置された前記第2の混合材料を回転するツールで押圧し、前記低熱伝導層保持部に2層目の低熱伝導層を形成する第2の低熱伝導層形成工程と、
    　を備える
    　内燃機関のピストンの製造方法。     A method for manufacturing a piston of an internal combustion engine according to claim 16,
    After the low thermal conductive layer forming step, a second mixed material having a mixing ratio of the binder and the layered hydrous silicate mineral different from the first mixed material is installed in the low thermal conductive layer holding unit. 2 installation processes;
    Pressing the second mixed material installed in the second step with a rotating tool, a second low thermal conductive layer forming step of forming a second low thermal conductive layer in the low thermal conductive layer holding portion,
    A method for manufacturing a piston of an internal combustion engine.
  18. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記低熱伝導層形成工程の後、前記ピストンヘッドの冠面を切削加工する加工工程を備える
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    The manufacturing method of the piston of an internal combustion engine provided with the process process which cuts the crown surface of the said piston head after the said low heat conductive layer formation process.
  19. 　請求項１８に記載の内燃機関のピストンの製造方法であって、
    　前記加工工程の後、前記低熱伝導層の表面に被膜を設ける被膜形成工程を備える
    　内燃機関のピストンの製造方法。     A method for manufacturing a piston of an internal combustion engine according to claim 18,
    The manufacturing method of the piston of an internal combustion engine provided with the film formation process which provides a film on the surface of the said low heat conductive layer after the said process process.
  20. 　請求項１０に記載の内燃機関のピストンの製造方法であって、
    　前記第1の混合材料を圧縮し、所定の形状に成形する成形工程を備え、
    　前記設置工程は、前記成形工程によって成形された前記第1の混合材料を前記低熱伝導層保持部に設置する工程を備える
    　内燃機関のピストンの製造方法。     A method of manufacturing a piston for an internal combustion engine according to claim 10,
    Compressing the first mixed material, comprising a molding step of molding into a predetermined shape,
    The installation step includes a step of installing the first mixed material molded in the molding step on the low thermal conductive layer holding portion. A method for manufacturing a piston of an internal combustion engine.
PCT/JP2017/014606 2016-08-12 2017-04-10 Internal combustion engine piston and method for manufacturing internal combustion engine piston WO2018029903A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2016-158366 2016-08-12
JP2016158366A JP2018025164A (en) 2016-08-12 2016-08-12 Piston for internal combustion engine and method for manufacturing piston for internal combustion engine

Publications (1)

Publication Number Publication Date
WO2018029903A1 true WO2018029903A1 (en) 2018-02-15

Family

ID=61161838

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2017/014606 WO2018029903A1 (en) 2016-08-12 2017-04-10 Internal combustion engine piston and method for manufacturing internal combustion engine piston

Country Status (2)

Country Link
JP (1) JP2018025164A (en)
WO (1) WO2018029903A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6965853B2 (en) * 2018-09-03 2021-11-10 マツダ株式会社 Premixed compression ignition engine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005076471A (en) * 2003-08-28 2005-03-24 Toyota Motor Corp Piston and internal combustion engine
JP2013213446A (en) * 2012-04-02 2013-10-17 Toyota Motor Corp Internal combustion engine and method for manufacturing the same
WO2015016122A1 (en) * 2013-08-01 2015-02-05 日立オートモティブシステムズ株式会社 Method for manufacturing piston for internal combustion engine, and piston for internal combustion engine
JP2015193915A (en) * 2014-03-27 2015-11-05 スズキ株式会社 Anode oxidation treatment method and internal combustion engine structure

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005076471A (en) * 2003-08-28 2005-03-24 Toyota Motor Corp Piston and internal combustion engine
JP2013213446A (en) * 2012-04-02 2013-10-17 Toyota Motor Corp Internal combustion engine and method for manufacturing the same
WO2015016122A1 (en) * 2013-08-01 2015-02-05 日立オートモティブシステムズ株式会社 Method for manufacturing piston for internal combustion engine, and piston for internal combustion engine
JP2015193915A (en) * 2014-03-27 2015-11-05 スズキ株式会社 Anode oxidation treatment method and internal combustion engine structure

Also Published As

Publication number Publication date
JP2018025164A (en) 2018-02-15

Similar Documents

Publication Publication Date Title
US10634091B2 (en) Multi-layered piston crown for opposed-piston engines
US10718291B2 (en) Cylinder liner for an internal combustion engine and method of forming
US8813734B2 (en) Heat-insulating structure
JP2020076409A (en) Piston made using additive manufacturing process
US20170234216A1 (en) Composite thermal barrier coating
US20090260594A1 (en) In-cylinder fuel-injection type internal combustion engine, piston for in-cylinder fuel-injection type internal combustion engine and process for manufacturing piston for in-cylinder fuel-injection type internal combustion engine
EP3440331B1 (en) Piston with thermally insulating insert and method of construction thereof
WO2018029903A1 (en) Internal combustion engine piston and method for manufacturing internal combustion engine piston
WO2018147188A1 (en) Piston for internal combustion engine and manufacturing method therefor
WO2015029117A1 (en) Internal combustion engine
WO2018198786A1 (en) Internal-combustion engine piston, and method for controlling cooling of internal-combustion engine piston
WO2018037616A1 (en) Piston for internal combustion engine and method for manufacturing piston for internal combustion engine
WO2018173548A1 (en) Piston of internal combustion engine and manufacturing method therefor
JP6065389B2 (en) Thermal insulation structure and manufacturing method thereof
WO2018116753A1 (en) Piston for internal combustion engine, method for manufacturing piston for internal combustion engine, and structure
US20190107045A1 (en) Multi-layer thermal barrier
JP2014105619A (en) Piston
WO2018190167A1 (en) Piston of internal-combustion engine, and method for manufacturing piston of internal-combustion engine
WO2018131356A1 (en) Piston for internal combustion engine
JPS6128822B2 (en)
JPH0357818A (en) Heat insulating structure of subchamber
JP6343974B2 (en) Piston of internal combustion engine
JP6343975B2 (en) Piston for internal combustion engine and method for manufacturing the same
JPH01317678A (en) Structure of cylinder liner and production thereof
JPS6142468A (en) Production of cylinder head

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 17838979

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 17838979

Country of ref document: EP

Kind code of ref document: A1