WO2018190167A1

WO2018190167A1 - Piston of internal-combustion engine, and method for manufacturing piston of internal-combustion engine

Info

Publication number: WO2018190167A1
Application number: PCT/JP2018/014067
Authority: WO
Inventors: 圭太郎宍戸
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2017-04-12
Filing date: 2018-04-02
Publication date: 2018-10-18
Also published as: JP2018178848A; CN110446845A

Abstract

According to the present invention, a piston of an internal-combustion engine includes a piston main body portion, an abrasion resistant ring, and an intermediate layer. The piston main body portion is formed from an aluminum alloy or a magnesium alloy, and includes a piston head and a skirt portion integral with the piston head. The abrasion resistant ring has a higher hardness than the piston main body portion, has a piston ring groove and is fixed to the piston head. The intermediate layer is disposed between the piston head and the abrasion resistant ring, and includes aluminum and an additive. The additive improves the wettability of the aluminum.

Description

Piston for internal combustion engine and method for manufacturing piston for internal combustion engine

The present invention relates to a piston for an internal combustion engine.

The piston of an internal combustion engine has a piston head, and a wear resistant ring is fixed to the piston head, and a piston ring groove is provided in the wear resistant ring. For example, in the piston manufacturing process disclosed in Patent Document 1, after a Niresist cast iron wear-resistant ring member is subjected to Alfin treatment, the wear-resistant ring member is set in a mold and the piston main body is cast, whereby the piston head A piston with a wear-resistant ring is manufactured.

JP-A-5-237632

This type of piston has room to improve the bondability between the wear-resistant ring and the piston body.

The piston of the internal combustion engine according to one embodiment of the present invention preferably has an intermediate layer containing aluminum between the piston body and the wear-resistant ring. The intermediate layer further includes an additive that improves the wettability of the aluminum.

Therefore, the piston of the internal combustion engine according to the embodiment of the present invention can improve the bondability between the wear resistant ring and the piston main body.

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. FIG. 2 is a perspective view of the piston of the first embodiment, showing a cross section cut by a plane passing through the axis of the piston. FIG. 3 shows an enlarged part of a piston head portion in the piston cross section of FIG. FIG. 3 is a diagram schematically showing a mold and a wear-resistant ring member installed in the mold in a step of casting the piston of the first embodiment, and shows a cross section cut by a plane passing through the axis of the wear-resistant ring member. FIG. 3 is a view of a wear-resistant ring member installed in a mold and a part of the mold as viewed obliquely in the process of casting the piston of the first embodiment. FIG. 3 is a cross-sectional view of a part of the alfin-treated abrasion resistant ring member according to the first embodiment, showing a cross section cut along a plane passing through the axis of the abrasion resistant ring member. FIG. 5 is a cross-sectional view of an intermediate material before forming a piston groove in a step of machining the piston of the first embodiment, taken along a plane passing through its axis, and shows a part of the piston head portion in an enlarged manner. It is a bar graph which shows the appearance rate of the joining defect of a wear-resistant ring and a piston main-body part according to the presence or absence of an additive. It is a schematic diagram of the instrument which tests the joining property of a wear-resistant ring and a piston main-body part. It is a photograph which shows the test result of bondability in case an additive is not included in the material of an intermediate | middle layer. It is a photograph which shows the test result of bondability in case an additive is included in the material of an intermediate | middle layer.

Hereinafter, modes for carrying out the present invention will be described with reference to the drawings.

[First embodiment]
First, the configuration will be described. An internal combustion engine (engine) 100 shown in FIG. 1 is a 4-stroke gasoline engine and is applied to a vehicle such as an automobile. The engine 100 includes a piston 1, a cylinder block 101, a cylinder head 104, a connecting rod (connecting rod) 105, a combustion chamber 106, a valve 107, an ignition device 108, and an oil jet 109. In the cylinder block 101, a crankshaft that is an output shaft of the engine is rotatably installed. The cylinder block 101 includes a cylindrical cylinder sleeve (cylinder liner) 102. The inner peripheral side of the cylinder liner 102 functions as an inner wall of the cylinder (cylinder bore) 10. The piston 1 is accommodated in the cylinder 10 so as to be reciprocally movable. The cylinder head 104 is installed in the cylinder block 101 so as to close the opening of the cylinder 10. As shown in FIG. 1, when the piston 1 is at the top dead center, a combustion chamber 106 is defined between the piston 1 and the cylinder head 104. The cylinder head 104 is provided with a valve 107, a fuel injection nozzle, and an ignition device 108. The valve 107 has two intake valves and two exhaust valves. The engine 100 includes a supercharging system such as turbocharging. Cooling water circulates in the passage 103 inside the cylinder liner 102. The oil jet 105 is installed in the cylinder block 101 so that its nozzle faces the back surface of the piston 1 (surface opposite to the combustion chamber 106).

As shown in FIG. 2, the piston 1 has a piston main body 2 and a wear-resistant ring 3. The piston body 2 includes an aluminum alloy. This aluminum alloy is, for example, AC8A (specified in JIS H 5202, hereinafter the same). The piston main body 2 has a bottomed cylindrical shape, and integrally includes a piston head (crown portion) 4, a piston boss (apron portion) 5, and a piston skirt (skirt portion) 6. The piston head 4 has a crown surface portion 40 and a land portion 41 integrally. The cross section of the piston head 4 (crown surface portion 40) cut along a plane orthogonal to the moving direction of the piston 1 inside the cylinder 10 is substantially circular. A line passing through the center of the circle and parallel to the moving direction is referred to as an axis of the piston 1. The direction in which the axis extends (the above moving direction) is referred to as the axis direction. The crown surface portion 40 is on one side in the axial direction of the piston head 4. There is a crown surface (top surface) 400 on one side in the axial direction of the crown surface portion 40.

The land portion 41 extends from the outer peripheral side of the crown surface portion 40 to the other side in the axial direction. On the outer periphery of the land portion 41, there are three annular piston ring grooves (ring grooves) 411, 412, and 413. Each

ring groove

411, 412, 413 extends in the direction around the axis of the piston 1 (circumferential direction) and surrounds the entire circumference of the land portion 41. The

ring grooves

411, 412, 413 are arranged in this order from one side in the axial direction to the other side. Each

ring groove

411, 412, 413 is provided with a piston ring. The ring groove 411 is a top ring groove, and a top ring 71 is installed as a first pressure ring (compression ring). The ring groove 412 is a second ring groove, and a second ring 72 is installed as a second pressure ring. The ring groove 413 is an oil ring groove, and an oil ring 73 is installed as an oil control ring. An oil relief hole is opened at the bottom of the ring groove 413. The oil relief hole opens on the inner peripheral surface of the land portion 41. The top ring 71 and the second ring 72 are formed of, for example, high carbon steel, martensitic stainless steel, or the like, and are flat plate members having a substantially C shape in plan view in which a joint is formed at one place in the circumferential direction. The oil ring 73 has, for example, a three-piece structure in which two flat members are provided and a center ring is sandwiched between them.

Piston boss 5 and piston skirt 6 extend from piston head 4 (land portion 41) to the other side in the axial direction (opposite side of combustion chamber 15 with respect to 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 end of the piston pin 8 is fitted into the piston pin hole 51. The piston 1 is connected to one end side (small end portion) of the connecting rod 105 via the piston pin 8. The other end side (large end portion) of the connecting rod 105 is connected to the crankshaft.

As shown in FIG. 3, the wear-resistant ring 3 includes Ni-resist cast iron and is fixed to the inside of the piston head 4 (an installation site of the top ring 71 in the piston head 4). The wear-resistant ring 3 is an annular member that surrounds the outer periphery of the piston head 4. A line passing through the center of the circle of the ring and perpendicular to the plane including the ring is called the axis of the wear resistant ring 3. The axis of the wear-resistant ring 3 substantially coincides with the axis of the piston 1. The inner circumferential surface 31 of the wear-resistant ring 3 is a curved surface convex toward the axis of the wear-resistant ring 3 (inward in the radial direction), and a cross section cut by a plane passing through the axis is semicircular. Both side surfaces 32, 33 in the axial direction of the wear-resistant ring 3 have a planar shape perpendicular to the axis of the wear-resistant ring 3. The outer circumferential surface 34 of the wear-resistant ring 3 is cylindrical, and its outer diameter dimension (distance from the axis of the wear-resistant ring 3) substantially matches the outer diameter dimension of the piston head 4 (distance from the axis of the piston 1). . The outer peripheral surface 34 forms a part of the outer peripheral surface of the piston head 4 (is flush). A ring groove 411 is opened at the center of the outer peripheral surface 34 in the height direction (the axial direction of the wear resistant ring 3). The bottom surface of the ring groove 411 extends in the axial direction of the wear-resistant ring 3, and the inner surface other than the bottom surface of the ring groove 411 is substantially parallel to both side surfaces 32 and 33 in the axial direction of the wear-resistant ring 3.

There is an intermediate layer 30 between the wear-resistant ring 3 and the piston head 4. The intermediate layer 30 is in contact with the entire range of the inner peripheral surface 31 of the wear-resistant ring 3 and the entire range of both side surfaces 32 and 33 in the axial direction. The intermediate layer 30 does not cover the outer peripheral surface 34 and the ring groove 411 of the wear resistant ring 3. The average thickness of the intermediate layer 30 is 1 mm or less, and more preferably, the maximum value of the thickness of the intermediate layer 30 is 1 mm or less. The intermediate layer 30 includes an aluminum alloy and an additive. The aluminum alloy is, for example, AC3A (specified in JIS H。5202, hereinafter the same). The additive includes sodium Na. The proportion of the mass of Na in the intermediate layer 30 is 9 ppm or more and 1% or less. Note that the additive may contain a substance other than Na.

Hereinafter, a method for manufacturing the piston 1 will be described. The manufacturing process of the piston 1 includes a wear-resistant ring member forming process, an alfin treatment process, a casting process, a heat treatment process, and a machining process. In the wear-resistant ring member forming step, the base material of the wear-resistant ring 3 (the wear-resistant ring member 3A) is formed using Ni-resist cast iron as a material. As shown in FIG. 6, the shape of the wear-resistant ring member 3A is the shape of the wear-resistant ring 3 before the outer peripheral side (the outer peripheral surface 34 and the ring groove 411) is formed by machining. The outer peripheral surface 34A of the wear resistant ring member 3A is cylindrical, and its outer diameter dimension (distance from the axis of the wear resistant ring member 3A) is slightly larger than the outer diameter dimension of the piston head 4. The shape of the inner peripheral surface 31A of the wear resistant ring member 3A is the same as the shape of the inner peripheral surface 31 of the wear resistant ring 3. Both side surfaces 32A, 33A in the axial direction of the wear resistant ring member 3A are slightly radially outward from both side surfaces 32, 33 in the axial direction of the wear resistant ring 3.

In the Alfin treatment process, first prepare the mixed material. The mixed material includes an aluminum alloy AC3A and an additive (Na). The ratio of the mass of Na in the mixed material is 9 ppm or more and 1% or less. With this mixed material, the surface of the wear resistant ring member 3A is alfined. That is, the wear resistant ring member 3A is immersed in the molten mixed material, and the surface of the wear resistant ring member 3A is covered with the mixed material. As a result, as shown in FIG. 6, a molecular bond is generated between AC3A and Niresist cast iron, and an alloy film 30A containing a compound of AC3A and Niresist cast iron is formed on the surface. This film 30A contains Na. Hereinafter, the wear resistant ring member 3A on which the film 30A is formed is referred to as a member 300.

In the casting process, the prototype (intermediate material) of the piston body 2 is cast by the gravity casting method, and the wear resistant ring member 3A is cast into the intermediate material. As shown in FIG. 4, the mold includes a lower mold 91, an upper mold 92, and a core 93. The lower mold 91 has a cylindrical portion 910. The cylindrical portion 910 functions as a mold for the outer periphery of the intermediate material. A stepped portion 911 is provided at the upper end of the cylindrical portion 910. The upper die 92 closes the opening of the lower die 91 (cylindrical portion 910) and functions as a die on the crown surface portion 40 side of the intermediate material. As shown in FIG. 5, the core 93 is a sand mold (sand core), and functions as a mold on the inner circumference and the other side in the axial direction of the intermediate material. First, the core 93 is installed in the lower mold 91. Thereafter, the member 300 is installed on the step portion 911 of the lower mold 91. In this state, the axis of the wear resistant ring member 3A substantially coincides with the axis of the cylindrical portion 910. Both

side surfaces

32A and 33A in the axial direction of the wear-resistant ring member 3A extend substantially horizontally and are substantially orthogonal to the axis of the cylindrical portion 910. Further, the upper mold 92 is installed on the lower mold 91. The member 300 is sandwiched between the lower mold 91 (step 911) and the upper mold 92. In this way, the molten metal, for example, the molten aluminum alloy AC8A, is introduced into the space 94 formed by the molds 91 to 93 and the like through the gate 90. By solidifying the molten metal, the intermediate material in which the wear-resistant ring member 3A is cast on the outer peripheral side of the piston head 4 (original mold) is formed. The alloy film 30A between the intermediate material (the prototype of the piston head 4) and the wear resistant ring member 3A is a future intermediate layer 30.

In the heat treatment process, heat treatment is performed. Thereby, the property of the cast intermediate material is improved and adjusted to an appropriate strength and hardness.

In the machining process, the intermediate material is machined with a lathe. As shown in FIG. 7, the piston head 4 is cut to form a crown surface 400. Further, the outer diameter of the piston main body 2 such as the outer periphery of the piston head 4 and the piston skirt 6 is finished. A part (outer peripheral side) of the wear resistant ring member 3A is cut together with the outer circumference of the piston head 4 to form a prototype 3B of the wear resistant ring 3. In other words, the outer peripheral surface of the piston head 4 including the outer peripheral surface 34 of the prototype 3B as a part thereof is finished. Further, the piston pin hole 51 and the ring grooves 411 to 413 are formed by cutting (the ring groove 411 is formed in the master 3B). Thereby, the piston 1 (the wear resistant ring 3 and the piston main body 2) as shown in FIGS. 2 and 3 is completed. Note that the ring groove 411 may be formed in the wear-resistant ring member 3A before the casting process (after the alfin treatment process).

Next, the function and effect will be described. When the engine 100 is in operation, the crown surface 400 of the piston 1 is exposed to the combustion gas inside the combustion chamber 106. The piston 1 reciprocates in the cylinder 10 by receiving the combustion pressure generated in the combustion chamber 106 during the expansion stroke on the crown surface 400. This reciprocating movement is converted into a rotational motion by the connecting rod 105 and output to the crankshaft. Here, since the piston main body 2 includes the aluminum alloy AC8A, it is possible to reduce the weight of the piston 1 and improve the heat dissipation. The piston rings 71 to 73 and the piston skirt 6 slide against the inner wall of the cylinder 10. The heat transferred from the combustion chamber 106 to the piston head 4 is released by being transferred to the cylinder liner 102 and the cooling water therein through the piston ring 71 and the like. The heat is also released when oil adheres to the inner peripheral side (back side) of the piston 1 and flows out. This oil adhesion is performed by, for example, the injection of oil from the oil jet 109.

The combustion pressure in the combustion chamber 106 is high because the engine 100 includes the supercharging system. In addition, if the engine 100 is intended to reduce fuel consumption and output, the temperature of the combustion chamber 106 increases. When the load (in-cylinder load) acting on the piston 100 is increased in this way, the piston ring 71 and the like are also required to have high wear resistance, and the piston ring 71 and the like having high hardness are used. For example, since the high hardness piston ring 71 collides with the inner wall of the ring groove 411, the inner wall of the ring groove 411 is likely to be worn or deformed. On the other hand, the ring groove 411 is formed in the wear-resistant ring 3. The wear-resistant ring 3 formed from Ni-resist cast iron has higher hardness (Rockwell hardness, Vickers hardness, etc.) than the piston body 2 formed from the aluminum alloy AC8A, and is excellent in wear resistance even at high temperatures. Therefore, wear and deformation of the inner wall of the ring groove 411 can be suppressed, and gas leakage and oil leakage through the outer periphery of the piston 1 can be suppressed. The material of the wear-resistant ring 3 is not limited to Ni-resist cast iron, but may be any material that has higher hardness than the piston body 2 and excellent wear resistance. In the present embodiment, since the wear resistant ring 3 is made of Ni-resist cast iron, the linear expansion coefficient of the wear resistant ring 3 is close to that of aluminum (alloy AC8A), and an increase in thermal stress during engine operation can be suppressed.

As a pretreatment for the casting process of the piston 1, the wear resistant ring member 3A is immersed in a mixed material containing an aluminum alloy AC3A (alphine treatment). Thereby, the alloy film 30A is formed. Therefore, in the casting process, the wettability of the wear resistant ring member 3A (member 300) with the aluminum alloy AC8A that is the material of the piston main body 2 is improved. Compared to the case without the film 30A, the surface tension of the molten aluminum alloy AC8A in contact with the wear resistant ring member 3A (film 30A) is lowered. Since the adhesion between the molten metal and the wear resistant ring member 3A (member 300) is improved, the wear resistant ring member 3A is more firmly cast inside the piston main body 2.

Piston body 2 contains aluminum alloy AC8A. That is, the piston main body 2 has aluminum as a main component, like the alloy film 30A (intermediate layer 30). Thereby, since the adhesiveness between the piston main body 2 (molten metal) and the membrane 30A is further improved, better bonding can be obtained between the piston main body 2 and the wear resistant ring member 3A.

The alloy film 30A (intermediate layer 30) only needs to contain aluminum. For example, silicon Si may not be contained (pure aluminum may be used). In the present embodiment, the film 30A (intermediate layer 30) is made of an aluminum alloy AC3A and contains silicon Si. Thus, the melting point of the metal for the alfin processing (mixed material) becomes low because the aluminum that is the metal for the alfin processing contains Si. Therefore, better bonding can be obtained between the piston main body 2 and the wear resistant ring member 3A. That is, when the melting point of the alfin processing metal is high, in the casting process of the piston main body 2, the film 30A is partially solidified and is difficult to be combined with the piston main body 2 (molten metal). On the other hand, by lowering the melting point of the metal for alfin treatment, even if the temperature of the member 300 is lowered in the casting process, the film 30A maintains a highly fluid (molten) state, and has the above-mentioned bowl shape. Hard to become. Therefore, the adhesion between the piston main body 2 (the molten metal) and the membrane 30A is further improved, so that a better bond can be obtained between the piston main body 2 and the wear resistant ring member 3A.

The thickness of the alloy film 30A (intermediate layer 30) is 1 mm or less. Therefore, the joint strength between the piston body 2 and the wear resistant ring member 3A can be improved. For example, if the member 300 is installed in the mold 91 and is gripped with a tool (scissors or the like), the gripped part of the membrane 30A is marked, and the joint property may be deteriorated at this part. If the thickness of the film 30A (intermediate layer 30) is 1 mm or less, such inconvenience can be remarkably suppressed. This inventor discovered this.

Alloy film 30A (intermediate layer 30) contains sodium Na as an additive to the metal for alfin processing. Na has a function of improving the wettability of the aluminum alloy AC3A, that is, the wettability of the film 30A. Therefore, in the casting process, the wettability of the wear resistant ring member 3A (member 300) with the aluminum alloy AC8A that is the material of the piston main body 2 is further improved. Compared with the case where the film 30A does not contain Na, the surface tension of the film 30A in contact with the molten aluminum alloy AC8A is lowered. Since the adhesion between the molten metal and the wear resistant ring member 3A (member 300) is improved, the wear resistant ring member 3A is more firmly cast inside the piston main body 2.

Figure 8 shows an example in which Na was added to the metal for AC3A for the alphin treatment that covers the wear resistant ring member 3A in the alphin treatment process (the mass ratio of Na is 9 ppm to 12 ppm) and an example in which Na was not added to the AC3A. The rate of occurrence of poor bonding between the wear-resistant ring 3 and the piston main body 2 (occurrence rate of individuals in which defects were recognized in the penetrant inspection after machining) is shown. In the case where Na was not added, the appearance rate of bonding failure was 25%, whereas in the case where Na was added, the appearance rate was about 2%.

10 and 11 show experimental results in which a molten metal 13 of an aluminum alloy AC8A, which is a material of the piston main body 2, is poured into the test piece 14 of the wear resistant ring member 3A (member 300). The test piece 14 in FIG. 10 is covered with an alfin-treating metal AC3A to which Na is not added. The test piece 14 in FIG. 11 is covered with AC3A to which Na is added (the mass ratio of Na is 28 ppm). As shown in FIG. 9, the test piece 14 was placed on the pedestal 12 in a state of being inclined at a predetermined angle, and the molten metal 13 of AC8A was poured onto the pedestal 12 from above. The molten metal 13 solidified while flowing in the direction indicated by the arrow 11. Compared to the example of FIG. 10, in the example of FIG. 11, the joining area of the molten metal 13 in the test piece 14 is about 60% larger. As described above, since the alloy film 30A (intermediate layer 30) of the wear resistant ring member 3A contains Na, the adhesion between the molten metal of the piston body 2 and the wear resistant ring member 3A (member 300) is improved. Occurrence of poor bonding of the wear resistant ring 3 can be suppressed.

In order to improve the wettability of the alloy film 30A, it is also conceivable to apply a flux to the surface of the film 30A instead of adding Na to the film 30A. However, the surface of the die 91 or the like used in the gravity casting method is usually coated with a heat insulating coating agent. For this reason, the film 30A (AC3A, which is an alfin processing metal) covering the wear resistant ring member 3A installed in the mold 91 or the like maintains a molten high temperature state. Therefore, even if a flux is applied to the surface of the film 30A, the flux evaporates at a high temperature and is difficult to apply. On the other hand, in this embodiment, the flux is not applied to the surface of the film 30A, but an additive (Na) is included in the material of the film 30A. Therefore, in the casting process, the wettability of the film 30A can be improved even if the wear resistant ring member 3A (member 300) installed in the mold 91 or the like is in a high temperature state. The casting method of the piston 1 is not limited to the gravity casting method, and may be a low pressure casting method or the like. Further, the specific configuration of the mold is not limited to that of the present embodiment.

Note that the additive of the alloy film 30A (intermediate layer 30) may be any surface active element of aluminum (alloy) that is the material of the film 30A, that is, an element that reduces the surface tension of the molten aluminum (alloy). Not limited to Na. Specifically, in addition to Na, bismuth Bi, barium Ba, lithium Li, lead Pb, thallium Tl, strontium Sr, and antimony Sb can function as the above elements. By adding at least one of these to the material of the film 30A (intermediate layer 30), the wettability of the film 30A can be improved. In this embodiment, the additive contains Na. Na is highly effective in reducing the surface tension of molten aluminum among the above elements. Therefore, sufficient wettability can be easily obtained with a smaller amount of additive.

The mass ratio of the additive, Na, in the intermediate layer 30 (alloy film 30A) is 9 ppm or more. By setting the lower limit of the Na ratio as described above, the wettability of aluminum (alloy AC3A), that is, the wettability of the membrane 30A is sufficiently improved, and the wear resistance between the material of the piston body 2 (AC8A) The wettability of the ring member 3A (member 300) can be sufficiently improved. This inventor discovered this.

The mass ratio in the intermediate layer (alloy film 30A) of Na as an additive is 1% or less. By setting the upper limit of the ratio of Na as described above, it is possible to suppress a situation in which the structure of the intermediate layer 30 is chemically changed and becomes brittle. This inventor discovered this. As a result, it is possible to suppress a decrease in the bondability between the piston body 2 and the wear resistant ring 3.

[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. In the casting process, the molten magnesium alloy is poured into a mold (where the wear resistant ring member 3A is disposed). Thereby, the intermediate material of the piston main body 2 is cast. Therefore, the piston main body 2 includes a magnesium alloy. The mixed material in the Alfin treatment step contains pure aluminum and sodium Na as an additive. Therefore, the intermediate layer 30 includes pure aluminum and an additive (Na). Other configurations and manufacturing steps are the same as those in the first embodiment.

Next, the function and effect will be described. Since the piston body 2 includes a magnesium alloy, the weight of the piston 1 can be reduced. The wear-resistant ring 3 formed from Ni-resist cast iron has a higher hardness than the piston main body 2 formed from a magnesium alloy. Therefore, wear and deformation of the inner wall of the ring groove 711 can be suppressed. In the casting process, the alloy film 30A formed by Alfin treatment reduces the surface tension of the molten magnesium alloy in contact with the wear resistant ring member 3A, and the adhesion between the molten metal and the wear resistant ring member 3A (member 300). Will improve. The film 30A (intermediate layer 30) is made of pure aluminum and does not contain silicon Si. Therefore, the embrittlement (decrease in material strength) of the structure of the piston main body 2 that can occur when Si is mixed with magnesium in the piston main body 2 can be suppressed. In the casting process, the addition of Na to the film 30A reduces the surface tension of the film 30A in contact with the molten magnesium alloy, and improves the adhesion between the molten metal and the wear resistant ring member 3A (member 300). Other functions and effects are the same as those of the first embodiment.

[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. For example, the engine format is arbitrary. The engine is not limited to a 4-stroke engine and may be a 2-stroke engine. It is not limited to a spark ignition engine (gasoline engine), but may be a compression ignition engine (diesel engine). The fuel supply method may be an in-cylinder direct injection type that directly injects into the cylinder (combustion chamber), or a port injection type that injects into the intake port. An engine mounted on a ship or the like is not limited to a vehicle. The intermediate layer of the present invention can be applied to any piston that has a high in-cylinder load during combustion and has a wear-resistant ring. The shape of the piston (piston body) is arbitrary. For example, an annular passage for circulating a cooling medium may be provided inside the piston head and on the inner peripheral side of the wear-resistant ring. In this case, a part of the wear-resistant ring may be used as the outer peripheral wall of the annular passage. As in this case, the intermediate layer of the present invention may be provided only on a part of the surface of the wear-resistant ring between the piston head and the wear-resistant ring.

[Technical ideas that can be grasped from the embodiment]
The technical idea (or technical solution, the same applies hereinafter) that can be understood from the embodiment described above will be described below.
(1) A piston of an internal combustion engine according to the present technical idea, in one aspect thereof, includes an aluminum alloy or a magnesium alloy, a piston main body having a piston head and a skirt portion integral with the piston head, and the piston main body. A wear-resistant ring having a higher hardness and having a piston ring groove, the wear-resistant ring being fixed to the piston head, and between the piston head and the wear-resistant ring, and wetting of aluminum and the aluminum And an intermediate layer containing an additive for improving the properties.
(2) In a more preferred embodiment, in the above embodiment, the additive contains at least one of sodium, bismuth, barium, lithium, lead, thallium, strontium, and antimony.
(3) In another preferred embodiment, in any of the above embodiments, the additive comprises sodium.
(4) In still another preferred embodiment, in any one of the above embodiments, the mass ratio of the additive sodium in the intermediate layer is 9 ppm or more.
(5) In still another preferred embodiment, in any one of the above embodiments, the mass ratio of sodium as the additive in the intermediate layer is 1% or less.
(6) In still another preferred embodiment, in any of the above embodiments, the intermediate layer has a thickness of 1 mm or less.
(7) In still another preferred embodiment, in any one of the above embodiments, the piston main body portion includes an aluminum alloy.
(8) In still another preferred embodiment, in any of the above embodiments, the intermediate layer includes silicon.
(9) In still another preferred embodiment, in any one of the above embodiments, the piston main body portion includes a magnesium alloy.
(10) In still another preferred embodiment, in any of the above embodiments, the intermediate layer does not contain silicon.
(11) Further, according to one aspect of the manufacturing method of the piston of the internal combustion engine of the present technical idea, the piston includes a piston head and a piston main body having a skirt portion integrated with the piston head, and the piston head. A wear-resistant ring cast into the body, and forming a base material for the wear-resistant ring with a material having a hardness higher than that of the piston main body, and an additive for improving aluminum and the wettability of the aluminum The step of covering the surface of the base material of the wear-resistant ring with the mixed material in a molten state, and the base material of the wear-resistant ring whose surface is covered with the mixed material are arranged in the casting mold of the piston main body portion A step of pouring a molten aluminum alloy or magnesium alloy into the casting mold in which the base material of the wear-resistant ring is disposed; And forming a grayed groove.
(12) In a more preferred embodiment, in the above embodiment, the additive contains at least one of sodium, bismuth, barium, lithium, lead, thallium, strontium, and antimony.
(13) In another preferred embodiment, in any of the above embodiments, the additive comprises sodium.
(14) In still another preferred embodiment, in any one of the above embodiments, the mass ratio of sodium as the additive in the mixed material is 9 ppm or more.
(15) In still another preferred embodiment, in any one of the above embodiments, a mass ratio of the additive sodium in the mixed material is 1% or less.
(16) In still another preferred embodiment, in any one of the above embodiments, the thickness of the layer formed of the mixed material between the piston head and the wear-resistant ring is 1 mm or less.
(17) In still another preferred aspect, in any one of the aspects, the piston main body is formed of the aluminum alloy.
(18) In still another preferred embodiment, in any of the above embodiments, the mixed material includes silicon.
(19) In still another preferred aspect, in any one of the aspects, the piston main body is formed of the magnesium alloy.
(20) In still another preferred embodiment, in any of the above embodiments, the mixed material does not contain silicon.

In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

This application claims priority based on Japanese Patent Application No. 2017-0799015 filed on Apr. 12, 2017. The entire disclosure including the specification, claims, drawings, and abstract of Japanese Patent Application No. 2017-0799015 filed on April 12, 2017 is incorporated herein by reference in its entirety.

1 piston 2 piston body 3 wear ring 30 intermediate layer 411 piston ring groove 6 piston skirt (skirt part) 100 engine (internal combustion engine)

Claims

A piston of an internal combustion engine,
A piston main body including an aluminum alloy or a magnesium alloy, the piston main body having a piston head and a skirt portion integral with the piston head;
A wear-resistant ring having a higher hardness than the piston main body and having a piston ring groove, the wear-resistant ring fixed to the piston head,
A piston for an internal combustion engine having an intermediate layer between the piston head and the wear-resistant ring and containing aluminum and an additive for improving the wettability of the aluminum.
The piston of the internal combustion engine according to claim 1,
The internal combustion engine piston, wherein the additive includes at least one of sodium, bismuth, barium, lithium, lead, thallium, strontium, and antimony.
The piston of the internal combustion engine according to claim 2,
A piston for an internal combustion engine, wherein the additive comprises sodium.
The piston of the internal combustion engine according to claim 3,
The piston of an internal combustion engine, wherein a mass ratio of the additive sodium in the intermediate layer is 9 ppm or more.
The piston of the internal combustion engine according to claim 3,
The piston of an internal combustion engine, wherein a mass ratio of the additive sodium in the intermediate layer is 1% or less.
The piston of the internal combustion engine according to claim 1,
The piston of an internal combustion engine, wherein the intermediate layer has a thickness of 1 mm or less.
The piston of the internal combustion engine according to claim 1,
A piston for an internal combustion engine, wherein the piston body includes an aluminum alloy.
The piston of the internal combustion engine according to claim 7,
The piston of an internal combustion engine, wherein the intermediate layer includes silicon.
The piston of the internal combustion engine according to claim 1,
The piston main body portion includes a magnesium alloy and is a piston of an internal combustion engine.
The piston of the internal combustion engine according to claim 9,
The piston of an internal combustion engine, wherein the intermediate layer does not contain silicon.
A method of manufacturing a piston for an internal combustion engine,
The piston is
A piston body having a piston head and a skirt portion integral with the piston head;
With a wear-resistant ring cast into the piston head,
The manufacturing method includes:
Forming the base material of the wear-resistant ring with a material having higher hardness than the piston main body, and
Covering the surface of the base material of the wear-resistant ring with a mixed material containing aluminum and an additive for improving the wettability of the aluminum and in a molten state;
Placing the base material of the wear-resistant ring, the surface of which is covered with the mixed material, in a casting mold of the piston body part;
Pouring a molten aluminum alloy or magnesium alloy into the casting mold in which the base material of the wear-resistant ring is disposed;
Forming a piston ring groove in the base material of the wear-resistant ring,
A method for manufacturing a piston of an internal combustion engine.
In the 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 additive includes at least one of sodium, bismuth, barium, lithium, lead, thallium, strontium, and antimony.
The method for manufacturing a piston of an internal combustion engine according to claim 12,
The method for manufacturing a piston of an internal combustion engine, wherein the additive contains sodium.
The method for manufacturing a piston of an internal combustion engine according to claim 13,
The method for producing a piston of an internal combustion engine, wherein a mass ratio of the additive sodium in the mixed material is 9 ppm or more.
The method for manufacturing a piston of an internal combustion engine according to claim 13,
The method for manufacturing a piston of an internal combustion engine, wherein a ratio of mass of the additive sodium in the mixed material is 1% or less.
In the manufacturing method of the piston of the internal-combustion engine according to claim 11,
A method for manufacturing a piston of an internal combustion engine, wherein a thickness of a layer formed of the mixed material between the piston head and the wear-resistant ring is 1 mm or less.
In the manufacturing method of the piston of the internal-combustion engine according to claim 11,
A method for manufacturing a piston of an internal combustion engine, wherein the piston main body is formed of the aluminum alloy.
The method for manufacturing a piston of an internal combustion engine according to claim 17,
The method for manufacturing a piston of an internal combustion engine, wherein the mixed material includes silicon.
In the manufacturing method of the piston of the internal-combustion engine according to claim 11,
A method for manufacturing a piston of an internal combustion engine, wherein the piston body is formed of the magnesium alloy.
The method for manufacturing a piston of an internal combustion engine according to claim 19,
The method for manufacturing a piston of an internal combustion engine, wherein the mixed material does not contain silicon.