JP2005349458A - Casting, cast piston, and method for producing casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting whose surface is exposed to hollow parts formed by casting, to provide a method for producing the same, and to provide a cast piston having excellent cooling efficiency and having high reliability. <P>SOLUTION: The piston 1 is a casting in which oil galleries 20 are formed by casting. The piston 1 is provided with wire gauze 21, and each wire gauze 21 covers the surface of a piston body 11 regulating the oil gallery 20. Cooling oil is passed through each oil gallery 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to a cast product, a cast piston, and a method of manufacturing the cast product. More specifically, the present invention relates to a cast product, a cast piston, and a cast product in which a hollow portion for circulating cooling oil is formed. It relates to a manufacturing method.

  Regarding a conventional piston, for example, Japanese Patent Laid-Open No. 5-69240 discloses a piston for a diesel engine in which a cooling oil passage is formed along a wear-resistant ring in which a ring groove is formed (Patent Document 1). . In the piston disclosed in Patent Document 1, a cooling oil passage is formed in a space defined by a wear ring and a cooling oil ring welded to the wear ring.

Japanese Patent Laid-Open No. 11-82738 discloses a piston that does not require a complicated structure and improves the cooling efficiency of the ring groove of the wear-resistant ring (Patent Document 2). Even in the piston disclosed in Patent Document 2, a cooling oil passage is formed in a space defined by a wear-resistant ring and a hollow metal ring welded to the wear-resistant ring.
JP-A-5-69240 Japanese Patent Laid-Open No. 11-823838

  However, in the piston disclosed in Patent Document 1, the cooling oil ring portion separates the aluminum alloy that is the piston base material and the cooling oil that circulates through the cooling oil passage. For this reason, the heat transfer coefficient between both falls, and the problem that the expected cooling efficiency is not obtained generate | occur | produces. Further, in the piston disclosed in Patent Document 2, in order to improve the cooling efficiency of the ring groove, the inner circumferential surface of the wear-resistant ring that defines the cooling oil passage is formed in an uneven shape. However, since there is a continuous hollow metal ring between the aluminum alloy forming the piston and the cooling oil circulating in the cooling oil passage, the cooling efficiency is similar to that of the piston disclosed in Patent Document 1. Decrease is a problem.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, and to provide a cast product in which the surface of the casting is exposed in a hollow portion formed by casting and a manufacturing method thereof. Another object of the present invention is to provide a highly reliable casting piston having excellent cooling efficiency.

  The cast product according to the present invention is a cast product in which a hollow portion is formed by casting. The cast product includes a metal net. The mesh body covers the surface of the casting that defines the hollow portion.

  According to the cast product configured in this manner, the net-like body prevents the molten metal from entering the hollow portion during the casting process of the cast product. Thereby, the structure which the surface of the casting which prescribes | regulates a hollow part is exposed to the hollow part from between the mesh | network of a mesh body can be obtained.

  A casting piston according to the present invention includes a piston main body having an outer peripheral surface, and a wear-resistant ring embedded in the piston main body along a circumferential direction of the outer peripheral surface and formed with a ring groove, and receives the combustion pressure of the internal combustion engine. And a casting piston that receives heat. The piston body is formed with a hollow portion through which a cooling fluid flows adjacent to the wear-resistant ring. The casting piston further includes a metal net. The mesh body covers the surface of the piston body that defines the hollow portion.

  According to the casting piston configured as described above, the net-like body prevents the molten metal from entering the hollow portion during the casting process of the casting piston. Thereby, the surface of the piston main body that defines the hollow portion can be exposed to the hollow portion from between the meshes of the mesh body. With such a configuration, the cooling fluid flows in the hollow portion while being in direct contact with the surface of the piston body. As a result, the cooling efficiency of the piston main body and the wear-resistant ring by the cooling fluid can be improved, and as a result, the reliability of the piston can be improved.

  Preferably, the casting constituting the piston main body is present only on the opposite side of the hollow portion with the mesh body interposed therebetween. According to the casting piston configured as described above, the casting projecting into the hollow portion from between the meshes of the mesh body does not hinder the flow of the cooling fluid flowing in the hollow portion. For this reason, it can prevent that the cooling efficiency of the piston main body by the cooling fluid and a wear-resistant ring falls.

  The method for manufacturing a cast product according to the present invention includes a step of placing a metal network having a hollow shape in a mold, a molten metal poured into the mold, and a position in a hollow shape portion of the network. And a step of producing a cast product in which the hollow portion is formed.

  According to the casting product manufacturing method configured as described above, the molten metal poured into the mold cannot pass through the mesh of the mesh body, and a hollow portion is formed in the hollow shape portion of the mesh body. can do. Thereby, the structure which the surface of the casting was exposed to the hollow part can be obtained, without using a core.

  Preferably, in the step of producing a cast product, when a cast product is produced by a gravity casting method, an oxide film of a molten metal generated at a boundary with an atmosphere in a mold is captured by a network and an oxide film is formed. A step of controlling the position. According to the method of manufacturing a cast product thus configured, a molten metal oxide film that can be a starting point of cracks and defects is formed at a position where stress concentration of the cast product is likely to occur or at a position processed after the casting process. Can be prevented.

  As described above, according to the present invention, it is possible to provide a cast product in which the surface of the casting is exposed in a hollow portion formed by casting and a method for manufacturing the same. Moreover, according to this invention, the reliable casting piston excellent in cooling efficiency can be provided.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a piston according to an embodiment of the present invention. In the figure, a piston and a cylinder constituting a direct injection type diesel engine are shown. FIG. 2 is a cross-sectional view showing the piston in FIG.

  Referring to FIGS. 1 and 2, the diesel engine includes a cylinder 2 having a cylinder wall 2b and a piston 1 enclosed in a space surrounded by the cylinder wall 2b. The piston 1 is a cast piston manufactured by a casting process, and includes a piston main body 11 formed of, for example, an aluminum alloy. The cylinder 2 is made of cast iron or aluminum alloy, for example.

  The piston body 11 includes a head portion 4 and a skirt portion 3 that is connected to the head portion 4 and connected to a connecting rod (not shown). The head portion 4 has a top surface 1a facing a cylinder head (not shown). The head portion 4 is formed with a lip portion 17 having a shape recessed from the top surface 1a and constituting a combustion chamber. The piston 1 reciprocates in the cylinder 2 by receiving the combustion pressure generated in the combustion chamber.

  3 is an enlarged cross-sectional view of a range surrounded by a two-dot chain line III in FIG. Referring to FIGS. 1 to 3, head portion 4 further includes an outer peripheral surface 1 b extending to face cylinder wall 2 b. A wear-resistant ring 10 is embedded in the piston body 11. The wear-resistant ring 10 extends in a ring shape along the circumferential direction of the outer peripheral surface 1 b so as to surround the lip portion 17. The wear ring 10 is made of a material having excellent wear resistance, and is made of, for example, Ni-resist (high nickel austenitic cast iron).

  The wear-resistant ring 10 is formed with a ring groove 12 that opens toward the outer peripheral surface 1b and extends along the circumferential direction of the outer peripheral surface 1b. A ring groove 13 and an oil ring groove 14 extending along the circumferential direction of the outer peripheral surface 1b are formed on the outer peripheral surface 1b. The ring grooves 12 and 13 and the oil ring groove 14 are formed spaced apart from each other, and are formed side by side from a position close to the top surface 1a in the order of the ring groove 12, the ring groove 13, and the oil ring groove 14. ing.

  An upper piston ring 5 and a lower piston ring 6 are fitted in the ring grooves 12 and 13, respectively. The oil ring 7 is fitted in the oil ring groove 14. The upper piston ring 5 is disposed at a position that is the most severe condition against wear. Therefore, the wear resistance of the piston 1 can be ensured by providing the wear-resistant ring 10 at that position. In this embodiment, the piston is provided with three rings. However, one ring may be provided, or two rings may be provided.

  The piston main body 11 is formed with an oil gallery 20 that is positioned inside the wear-resistant ring 10 and extends in an annular shape. The oil gallery 20 is formed in a space surrounded by the inner peripheral surface 10c of the wear-resistant ring 10 and the surface 11a of the piston main body 11 connected to the inner peripheral surface 10c. The oil gallery 20 is located approximately between the wear-resistant ring 10 and the lip portion 17. The piston main body 11 is formed with an oil supply hole 15 communicating with the oil gallery 20 and an oil discharge hole (not shown) communicating with the oil gallery 20 in a cross section different from the cross section shown in FIG. The surface 11a of the piston body 11 is covered with a wire mesh 21 formed of a metal such as stainless steel. The casting that constitutes the piston main body 11 exists only on the opposite side of the oil gallery 20 with the metal mesh 21 in between, and the casting that constitutes the piston main body 11 exists in a space surrounded by the inner peripheral surface 10c and the surface 11a. do not do.

  In addition, in this Embodiment, although the above-mentioned structure was demonstrated as a preferable form, the casting which comprises the piston main body 11 may protrude from the mesh | network of the metal mesh 21. FIG.

  FIG. 4 is a perspective view partially showing the wear-resistant ring and the wire mesh shown in FIG. In the drawing, the piston main body 11 in FIG. 3 is shown in a transparent manner in order to represent the shape of the wear-resistant ring and the wire mesh. 3 and 4, the wire mesh 21 is bent in a substantially C shape, and both ends thereof are connected to the upper end and the lower end of the inner peripheral surface 10c along the circumferential direction of the wear-resistant ring 10, respectively. ing. The metal mesh 21 is formed in a mesh shape in which openings 30 having a square shape are arranged in a lattice pattern. The length of one side of the opening 30 is, for example, 0.5 mm. A surface 11 a of the piston body 11 surrounding the oil gallery 20 is exposed to the oil gallery 20 through the opening 30.

  Cooling oil is supplied to the oil gallery 20 through the oil supply hole 15 in order to cool the wear ring 10 and the piston body 11. The supplied cooling oil is circulated through the oil gallery 20 and then discharged to the outside through an oil discharge hole (not shown). At this time, since the surface 11a of the piston body 11 is exposed to the oil gallery 20, the cooling oil circulates inside the oil gallery 20 while directly contacting the surface 11a.

  When the value (the diagonal length of the opening 30 in FIG. 4) at which the opening size of the wire mesh 21 is the largest is L, the opening size L is preferably 0.2 mm or more and 1.0 mm or less. By setting the opening dimension L to 0.2 mm or more, an area where the surface 11a is exposed to the oil gallery 20 can be secured. By setting the opening dimension L to 1.0 mm or less, it is possible to prevent the molten metal from passing through the mesh of the metal mesh 21 during the piston 1 casting process described later.

  FIG. 5 is a first modified example of the wire mesh shown in FIG. 4, and is a plan view showing an enlarged surface of the wire mesh. Referring to FIG. 5, in this modification, the wire net 21 is formed in a mesh shape in which openings 31 having a rectangular shape are arranged in a lattice shape. In this case, the diagonal length of the opening 31 is the opening dimension L of the wire mesh 21.

  FIG. 6 is a perspective view showing a second modification of the wire mesh shown in FIG. FIG. 7 is an enlarged plan view showing the surface of the wire mesh shown in FIG. With reference to FIG. 6 and FIG. 7, in the present modification, the wire net 21 is formed in a mesh shape in which openings 32 having a rhombus shape are continuously arranged. In this case, the larger one of the two diagonal lengths obtained from the opening 32 is the opening dimension L of the wire mesh 21.

  FIG. 8 is a third modification of the wire mesh shown in FIG. 4, and is a plan view showing the surface of the wire mesh in an enlarged manner. Referring to FIG. 8, in the present modification, the wire net 21 is formed in a mesh shape in which circular openings 33 are continuously arranged. In this case, the diameter of the opening 33 is the opening dimension L of the wire mesh 21. Note that the shape of the mesh of the wire mesh 21 is not limited to the shape described with reference to FIGS. 4 to 8 and may be other shapes such as a polygon or an ellipse.

  The piston 1 as a cast product in the embodiment of the present invention is a cast product in which an oil gallery 20 as a hollow portion is formed by casting. The piston 1 includes a metal net 21 as a metal net. The metal mesh 21 covers the surface 11 a of the piston body 11 as a casting that defines the oil gallery 20. The oil gallery 20 is supplied with cooling oil as a cooling fluid.

  In the present embodiment, the case where the cast product according to the present invention is applied to the piston 1 constituting the diesel engine has been described. However, the present invention is not limited to this and can be applied to various products produced by casting. Is possible. Further, it can be applied not only to a piston of a diesel engine but also to a piston of a gasoline engine. Further, in the present embodiment, the oil gallery 20 is formed adjacent to the wear-resistant ring 10, but the oil gallery 20 may be formed inside the piston main body 11 with a space from the wear-resistant ring 10. . In this case, the wire mesh 21 is formed so as to cover the surface of the piston body 11 surrounding the oil gallery 20. In the cast product according to the present invention, the wear-resistant ring 10 does not necessarily have to be formed.

  A piston 1 as a casting piston in an embodiment of the present invention is a casting piston that includes a piston body 11 having an outer peripheral surface 1b, receives the combustion pressure of a diesel engine as an internal combustion engine, and receives heat. The piston main body 11 is formed with an oil gallery 20 as a hollow portion through which cooling oil as a cooling fluid flows. The piston 1 further includes a wire net 21 as a net-like body. The wire mesh 21 covers the surface 11 a of the piston body 11 that defines the oil gallery 20.

  The piston 1 further includes a wear-resistant ring 10 that is embedded in the piston body 11 along the circumferential direction of the outer peripheral surface 1b and in which a ring groove 12 is formed. The oil gallery 20 extends in an annular shape adjacent to the wear-resistant ring 10.

  FIG. 9 is a cross-sectional view showing a mold for manufacturing the piston in FIG. Then, the manufacturing method of the piston shown in FIG. 1 is demonstrated. Referring to FIG. 9, in the present embodiment, piston 1 is manufactured by a gravity casting method (a method in which molten metal is poured into a mold by natural gravity) using a mold 41 having a cavity 51 having a predetermined shape. The mold 41 is formed with a gate 42 and a riser 43 that communicate with the cavity 51 from different positions.

  First, the wear-resistant ring base 53 to which the wire mesh 21 is fixed so as to form the hollow space 54 is set at a predetermined position in the cavity 51. Next, molten metal 52, for example, a molten aluminum alloy, which is a material of the piston body 11 is poured into the cavity 51 from the gate 42. At this time, the molten metal 52 is filled around the wire mesh 21, but cannot pass through the mesh of the wire mesh 21 due to its surface tension. For this reason, the molten metal 52 does not enter the hollow space 54 but fills the cavity 51 in a state of surrounding the molten metal 52.

  FIG. 10 is an enlarged cross-sectional view showing a range surrounded by a two-dot chain line X in FIG. Referring to FIG. 10, when pouring molten metal 52, cavity 51 is in an air atmosphere. For this reason, the molten metal 52 reacts with oxygen in the air atmosphere, and an oxide film is formed on the liquid surface 52 a of the molten metal 52. On the other hand, as the pouring of the molten metal 52 proceeds, the height of the liquid level 52a gradually rises and eventually reaches a position where the metal mesh 21 is set. At this time, the oxide film of the molten metal 52 located immediately below the wire mesh 21 and formed on the liquid surface 52 a comes into contact with the wire mesh 21. Then, all the oxide films formed over the entire liquid surface 52 a are attracted to the wire mesh 21 and gather around the wire mesh 21.

  Thus, the metal mesh 21 also functions as a filter for the oxide film of the molten metal 52, and can prevent an oxide film from being formed at a position where the lip portion 17 is processed in a subsequent process. The reliability of the piston 1 can be improved by preventing the formation of an oxide film serving as a starting point of cracks and defects on the lip portion 17 that is susceptible to stress concentration due to combustion pressure. Further, when the lip portion 17 is processed in the subsequent process, it is possible to prevent the processed surface from being chipped.

  After the molten metal 52 is cooled, the obtained casting piston is taken out from the mold 41. An oil gallery 20 is formed in a hollow space 54 surrounded by the wear-resistant ring base 53 and the wire mesh 21. Finally, necessary processing is performed on the cast piston to complete the piston 1 shown in FIG.

  The manufacturing method of the piston 1 as a cast product according to the embodiment of the present invention includes a step of disposing a metal mesh 21 as a metal net having a hollow space 54 as a hollow shape in the mold 41, And the step of pouring molten metal 52 into the piston 1 in which the oil gallery 20 as a hollow portion is formed in the hollow space 54 portion of the wire mesh 21.

  According to the piston 1 and the manufacturing method thereof according to the embodiment of the present invention configured as described above, the cooling oil circulates in the oil gallery 20 while being in contact with the surface 11a exposed to the oil gallery 20. For this reason, the cooling efficiency of the piston main body 11 is improved, and it is possible to effectively cool the periphery of the wear-resistant ring 10 that is close to the combustion chamber and has the largest temperature rise. For example, assuming that a stainless steel plate is interposed between the piston body 11 made of aluminum and the oil gallery 20 and the heat transfer coefficient between aluminum and stainless steel is 100%, in this embodiment, in this case, The cooling efficiency can be improved by about 1%. That is, in practice, the cooling efficiency can be improved in the range of 1% to 7%. Thereby, it can prevent that the lubricating oil supplied to the sliding surface of the piston 1 and the cylinder 2 deteriorates, and can reciprocate the piston 1 stably.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a side view which shows the piston in embodiment of this invention. It is sectional drawing which shows the piston in FIG. It is sectional drawing which expands and shows the range enclosed by the dashed-two dotted line III in FIG. FIG. 4 is a perspective view partially showing a wear-resistant ring and a wire net shown in FIG. 3. It is a 1st modification of the wire mesh shown in FIG. 4, Comprising: It is a top view which expands and shows the surface of the wire mesh. It is a perspective view which shows the 2nd modification of the wire mesh shown in FIG. It is a top view which expands and shows the surface of the wire mesh shown in FIG. FIG. 5 is a third modification of the wire mesh shown in FIG. 4, and is a plan view showing an enlarged surface of the wire mesh. It is sectional drawing which shows the casting_mold | template for manufacturing the piston in FIG. It is sectional drawing which expands and shows the range enclosed with the dashed-two dotted line X in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Piston, 1b outer peripheral surface, 10 Wear-resistant ring, 11 Piston main body, 11a surface, 12 Ring groove, 20 Oil gallery, 21 Wire net, 41 Mold, 52 Molten metal, 54 Hollow space.

Claims (5)

A cast product in which a hollow portion is formed by casting,
A cast product comprising a metal net that covers the surface of a casting that defines the hollow portion. A piston body having an outer peripheral surface;
A wear-resistant ring embedded in the piston body along the circumferential direction of the outer peripheral surface and having a ring groove formed thereon,
A casting piston that receives the combustion pressure of the internal combustion engine and receives heat,
In the piston body, a hollow portion through which a cooling fluid flows is formed adjacent to the wear-resistant ring,
A cast piston, further comprising a metal net that covers a surface of the piston body defining the hollow portion.   The casting piston according to claim 2, wherein a casting that constitutes the piston main body exists only on the opposite side of the hollow portion with the mesh body interposed therebetween. Placing a metal net having a hollow shape in a mold; and
And a step of pouring molten metal into the mold and producing a cast product in which a hollow part is formed in a hollow part of the mesh body.   The step of producing the cast product includes capturing the oxide film of the molten metal generated at the boundary with the atmosphere in the mold by the network when producing the cast product by a gravity casting method. The manufacturing method of the casting of Claim 4 including the process of controlling the position formed.

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