Manufacturing method of casting core assembly and molding

Abstract

To reduce positional deviation between plural core bodies.SOLUTION: A casting core combination body 20 forms cavities in a casting upon molding the casting, and comprises: a base core 30 including base core bodies 34 for forming a part of the cavities of the casting; and combination core bodies 50, 60 including combination core bodies 56, 66 for forming the other part of the cavities of the casting. The base core bodies 34 have base core positioning parts 36, 37, the combination core bodies 56, 66 have the combination core bodies 56, 66, and in a state where the combination core positioning parts 56, 66 are contacted with the base core positioning parts 36, 37, the combination cores 50, 60 are combined with the base core 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This disclosure relates to a technique for assembling a plurality of cores to produce a core assembly for casting. [Background technology]

[0002] Patent Document 1 discloses a conventional core in which two port molding portions are molded integrally with the core body, and other port molding portions molded in a separate mold are bonded to the core body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jpn. Jpn. Published No. 56-020123 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not disclose how to bond other ports to the core body. There is a possibility that misalignment may occur between the port molding part molded integrally with the core body and the other port molding parts molded in a separate mold.

[0005] Therefore, an object of the present disclosure is to reduce positional misalignment between multiple core bodies. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a casting core combination is a casting core combination for forming a cavity in a casting when molding the casting, and comprises a base core including a base core body for forming a part of the cavity in the casting, and a combined core including a combined core body for forming another part of the cavity in the casting, wherein the base core body has a base core positioning portion, the combined core body has a combined core positioning portion, and the combined core is combined with the base core with the combined core positioning portion in contact with the base core positioning portion.

[0007] Also, in order to solve the above-mentioned problems, a manufacturing method for a molded product is a method for manufacturing a molded product having a cavity, the method comprising: (a) a base core including a base core body for forming a part of the cavity of the molded product; and a combined core, the combined core including a combined core body for forming another part of the cavity of the molded product, the combined core body being positioned and fitted into the base core body while the combined core is fixed to the base core to form a core combination, (b) placing the core combination in a mold, and (c) molding the molded product using the core combination and the mold. Effect of the Invention

[0008] According to the above-described casting core assembly, positional deviation between a plurality of core bodies can be reduced.

[0009] According to the above-described method for manufacturing a molded product, it is possible to manufacture a molded product with less misalignment between a plurality of core bodies and less misalignment of cavities. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view showing a casting core assembly. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4]FIG. 13 is an exploded perspective view showing the combined portion of the combination core body relative to the base core body. [Diagram 5] FIG. 13 is a plan view showing the combined portion of the combination core body relative to the base core body. [Figure 6] FIG. [Figure 7] FIG. 11 is a perspective view showing a state in which a casting core assembly is supported on an assembly auxiliary tool. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a casting core assembly according to an embodiment will be described.

[0012] 1 is a perspective view showing a casting core assembly 20. The casting core assembly 20 is a core for forming a cavity within a casting when forming the casting as a molded product. The casting core assembly 20 includes a base core 30 and combination cores 50 and 60.

[0013] The base core 30 includes a base core body 34 for forming a portion of the cavity of the casting. The combination core 50 includes a combination core body 54 that forms another portion of the cavity of the casting. The combination core 60 includes a combination core body 64 that forms yet another portion of the cavity of the casting. The cavity portion formed by the base core body 34 and the combination core bodies 54, 64 are continuous within the casting.

[0014] Of the base core 30, the base core body 34 has base core positioning portions 36, 37. Of the combined core bodies 54, 64, the combined core bodies 54, 64 have combined core positioning portions 56, 66. The combined core bodies 54, 64 are combined with the base core body 34 with the combined core positioning portions 56, 66 in contact with the base core positioning portions 36, 37. In other words, the base core 30 and the combined cores 50, 60 are combined with their portions that form cavities in contact with each other. As a result, the cavities in the casting are formed with high precision.

[0015] In this embodiment, the casting core combination 20 comprises multiple combined cores 50, 60. However, the casting core combination 20 may also be configured to have a single combined core. The multiple combined cores 50, 60 are combined with the base core 30 with the multiple combined core positioning portions 56, 66 in contact with the base core positioning portions 36, 37. In other words, the multiple combined cores 50, 60 are combined with the single base core 30 as a reference. As a result, the multiple combined cores 50, 60 can be combined with good positional precision.

[0016] Here, an example of a molded product produced using the casting core assembly 20 will be described.

[0017] Figure 2 is a perspective view of the casting 10. Figure 3 is a cross-sectional view of the casting 10. In Figure 3, a casting core assembly 20 and a mold 90 are shown.

[0018] The molded product 10 is formed into a cylindrical body as a whole. The molded product 10 has a main cavity 14 and branch cavities 15, 16, and 17 as cavities. The main cavity 14 is formed in the molded product 10 as a cylinder along the axial direction of the cylinder. Here, the main cavity 14 is a space that penetrates the molded product 10, but it may also be a cavity with a bottom.

[0019] The branch cavities 15, 16, and 17 are continuous from the main cavity 14 to the outside. Here, the branch cavity 15 is formed in the axial middle of the main cavity 14, from a part of the circumferential direction of the main cavity 14 to the outside. An extending tubular portion 11a extending outward is formed on the outer circumferential side of the part of the molded product 10 from which the branch cavity 15 extends. The branch cavity 15 opens outward through the extending tubular portion 11a. The branch cavity 16 is formed in the axial middle of the main cavity 14, from a part of the circumferential direction of the main cavity 14 to the outside. In the circumferential direction of the molded product 10, the branch cavity 16 is provided on the opposite side to the branch cavity 15. An extending tubular portion 11b extending outward is formed on the outer circumferential side of the part of the molded product 10 from which the branch cavity 16 extends. The branch cavity 16 opens outward through the extending tubular portion 11b. The branch cavities 15, 16 do not need to open outward through the extending tubular portions 11a, 11b. For example, the branch cavities 15, 16 may open directly to the outer circumferential surface of the tubular portion forming the main cavity 14. The branch cavity 17 is formed in the axially intermediate portion of the main cavity 14, from a portion of the circumferential direction of the main cavity 14 toward the outside of the main cavity 14. The branch cavity 17 does not open to the outside of the molded product 10, but passes through the peripheral wall of the molded product 10 toward the end of the molded product 10 (the lower end in Figs. 2 and 3). The branch cavity 17 opens to the main cavity 14 at the end of the molded product 10 (the lower end in Figs. 2 and 3). In other words, one end and the other end of the branch cavity 17 are continuous with the main cavity 14 at different positions in the axial direction, and the intermediate portion of the branch cavity 17 passes through the peripheral wall of the molded product 10. In this embodiment, two branch cavities 17 are formed between the branch cavities 15 and 16 in the circumferential direction of the molded product 10.

[0020] One example of the molded product 10 is a cylinder for a two-stroke engine. A two-stroke engine is an engine in which one cycle of stroke including intake / compression, combustion, exhaust, and scavenging is performed by one reciprocating movement of the piston. In a two-stroke engine, the intake port, scavenging port, and exhaust port opening on the inner peripheral wall of the cylinder space are opened and closed by the up and down movement of the piston. For this reason, the opening positions of the intake port, scavenging port, and exhaust port on the inner peripheral wall of the cylinder space can affect the operation timing of each of the above strokes.

[0021] Assuming that the molded product 10 is a cylinder for a two-stroke engine, for example, the main cavity 14 is a cylinder space that forms a space in which the cylinder reciprocates. The branch cavity 15 is a space that is connected to the cylinder space and forms an exhaust port that exhausts combustion gas to the outside. The branch cavity 16 is a space that is connected to the cylinder space and forms an intake port that introduces the mixture into the cylinder space. The branch cavity 16 that forms the intake port may be omitted. In this case, the absorption port may be formed in the crankcase. The branch cavity 17 is a space that is connected to the cylinder space at two different points in the axial direction of the cylinder space and forms a scavenging port that introduces the mixture into the cylinder space to scavenge. The molded product 10 may be formed with a passage (water jacket) 10c for flowing cooling water.

[0022] In the case where the molding 10 is a cylinder for a two-stroke engine as described above, the base core body 34 may form a part of the cylinder space which is the main cavity 14. At least one of the base core body 34 and the combined core bodies 54, 64 may form a scavenging port, and at least the other of the base core body 34 and the combined core bodies 54, 64 may form an exhaust port.

[0023] Here, the following example will be described: the base core body 34 forms a part (here, most of) the cylinder space which is the main cavity 14, and the exhaust port which is the branch cavity 15. The combined core body 54 forms a part of the cylinder space which is the main cavity 14, and the intake port which is the branch cavity 16. The combined core body 64 forms a part of the cylinder space which is the main cavity 14, and the scavenging port which is the branch cavity 17.

[0024] As described above, by combining the combined cores 50, 60 with the base core 30 with high positional accuracy, the opening positions of the intake port, the scavenging port and the exhaust port in the inner peripheral wall of the cylinder space are formed with high accuracy.

[0025] In particular, in a cylinder for a two-stroke engine, it is required to accurately position the upper edges of the openings of the exhaust port, intake port, and scavenging port in the axial direction of the cylinder space with respect to the upper edge of the cylinder space. The combined core bodies 54, 64 that form the intake port and scavenging port are positioned with respect to the base core body 34 including the portion that forms the exhaust port, so that the relative positional accuracy of each opening of the exhaust port, intake port, and scavenging port is improved. As a result, it is possible to accurately form the positions of the upper edges of the openings of the exhaust port, intake port, and scavenging port with respect to the upper edge of the cylinder space.

[0026] The surface of the molding 10 including the outward surface is formed by a mold 90 including a lower mold 92 and an upper mold 94. Mold surfaces are formed on opposing portions of the lower mold 92 and the upper mold 94 for forming the surface of the molding 10 including the outward surface. With the casting core combination 20 supported within the mold 90, molten metal for casting is poured into the space within the mold 90, thereby forming a molding 10 having a surface determined by the mold surfaces and the casting core combination 20.

[0027] The casting core combination 20 will be described in more detail. Fig. 4 is an exploded perspective view showing the combined portion of the combined core bodies 54, 64 relative to the base core body 34. Fig. 5 is a plan view showing the combined portion of the combined core bodies 54, 64 relative to the base core body 34.

[0028] As shown in Figures 1, 3, 4 and 5, the casting core combination 20 is constructed by combining a base core 30 and a plurality of combined core bodies 54, 64. For example, the casting core combination 20 that forms the desired shape is constructed by bonding the base core 30 and the plurality of combined core bodies 54, 64 with an adhesive. The base core 30 and the plurality of combined core bodies 54, 64 are combined in a portion that forms the main cavity 14. The base core 30 and the plurality of combined core bodies 54, 64 are each formed by hardening sand with resin in a core mold.

[0029] The base core 30 includes a baseboard 32 and a base core body 34. The base core body 34 includes a main cavity forming portion 35 and a branch cavity forming portion 38. The main cavity forming portion 35 is a portion that forms a part of the main cavity 14, and in this embodiment, is formed in a shape that is a partly recessed columnar shape. In the following description, the central axis side of the main cavity 14 may be referred to as the inner periphery side or inside, and the opposite side may be referred to as the outer periphery side or outside, based on the general cylindrical shape of the main cavity 14. A positioning hole 35h is formed in the center of the main cavity forming portion 35 along its axial direction. The lower end surface 35b of the main cavity forming portion 35 and the portion where the positioning hole 35h is formed can become a baseboard that is positioned in the mold 90. The branch cavity forming portion 38 is a portion that forms the branch cavity 15, and is formed in an elongated shape that extends radially outward from a part of the outer periphery of the main cavity forming portion 35. Here, the branch cavity forming portion 38 extends obliquely downward from a position near the top of the main cavity forming portion 35. A base board 32 is formed at the tip of the branch cavity forming portion 38. The base board 32 is a portion for supporting the base core 30 in the mold 90.

[0030] Base core positioning portions 36, 37 are formed on the outer periphery of the main cavity forming portion 35. Base core positioning portion 36 is formed on the portion of the outer periphery of the main cavity forming portion 35 opposite the branch cavity forming portion 38. The two base core positioning portions 37 are formed on the outer periphery of the main cavity forming portion 35 in two portions between the base core positioning portion 36 and the branch cavity forming portion 38.

[0031] The combination core 50 includes a base board 52 and a combination core body 54. The base board 52 is a portion for supporting the combination core 50 in the mold 90. The combination core body 54 includes a main cavity forming portion 55 and a branch cavity forming portion 58. The main cavity forming portion 55 is a portion that forms the main cavity 14 together with the main cavity forming portion 35. A combination core positioning portion 56 is formed in the main cavity forming portion 55.

[0032] The branch cavity forming portion 58 extends downward from the lower portion of the outer peripheral portion of the main cavity forming portion 55, and then extends further outward from that downward extension. The inner surface of the branch cavity forming portion 58 is formed into an arc-shaped surface that is located on a downward extension of the outer peripheral surface of the main cavity forming portion 55. The branch cavity forming portion 58 extends obliquely upward toward the outside. A baseboard 52 is provided at the tip of the branch cavity forming portion 58.

[0033] The combination core 60 includes a baseboard 62 and a combination core body 64. The baseboard 62 is a portion for supporting the combination core 60 in the mold 90. The combination core body 64 includes a main cavity forming portion 65 and a branch cavity forming portion 68. The main cavity forming portion 65 is a portion that forms the main cavity 14 together with the main cavity forming portion 35. A combination core positioning portion 66 is formed in the main cavity forming portion 65.

[0034] The branch cavity forming portion 68 extends downward from the lower outer circumferential portion of the main cavity forming portion 65 in an arc shape that is convex toward the outer circumferential side. The lower end of the branch cavity forming portion 68 faces the inner circumferential side, and its tip face is formed in an arc-shaped surface located on a downward extension of the outer circumferential surface of the main cavity forming portion 65. The baseboard 62 is provided at the lower end of the branch cavity forming portion 68.

[0035] The two combination cores 60 have a mirror-symmetric shape with respect to an imaginary plane passing through the central axis of the main cavity forming portion 35. The base core positioning portion 37 in which the two combination cores 60 are positioned also has a mirror-symmetric shape with respect to the imaginary plane.

[0036] The main cavity forming portions 35, 55, 65 are combined to form a cylindrical core portion for forming the main cavity 14. In this state, the branch cavity forming portions 38, 58, 68 are arranged so as to protrude from the cylindrical core portion. In this way, a casting core combination 20 for forming the main cavity 14 (cylinder space) and branch cavities 15, 16, 17 (exhaust port, scavenging port, intake port) in the casting 10 is manufactured.

[0037] The following description focuses on the configuration for positioning the combination core bodies 54, 64 relative to the base core body 34.

[0038] The base core positioning parts 36, 37 and the combined core positioning parts 56, 66 are positioned relative to each other while being in contact with each other at least in a predetermined positioning direction P. The predetermined positioning direction P is, for example, the axial direction of the main cavity forming part 35. The axial direction of the main cavity forming part 35 is also the central axial direction of the main cavity 14 (cylinder space). In this case, the base core body 34 and the combined core bodies 54, 64 are positioned in the axial direction of the main cavity 14 (cylinder space), so that the opening of the port to the space is accurately positioned in the axial direction of the main cavity 14 (cylinder space). The predetermined positioning direction P may be the direction of gravity. In this case, the base core body 34 and the combined core body 54, 64 can be easily assembled by placing one of them on the other and applying a load due to gravity. The base core positioning portions 36, 37 and the combination core positioning portions 56, 66 may be positioned in a direction other than at least the predetermined positioning direction P, for example, in the circumferential direction of the main cavity forming portion 35.

[0039] One of the combined core positioning portions 56, 66 and the base core positioning portions 36, 37 is a positioning recess, and the other is a positioning convex portion. The positioning convex portion fits into the positioning concave portion, so that the combined core positioning portions 56, 66 and the base core positioning portions 36, 37 are positioned relative to each other in a state of contact with each other. In this embodiment, an example is described in which the combined core positioning portion 56 as a positioning convex portion fits into the base core positioning portion 36 as a positioning concave portion. Also, an example is described in which the combined core positioning portion 66 as a positioning convex portion fits into the base core positioning portion 37 as a positioning concave portion. At least one of these concave-convex relationships may be an inverse relationship.

[0040] The combination core positioning portion 56 and the base core positioning portion 36 will now be described.

[0041] The base core positioning portion 36 is formed in a shape in which a portion of the outer periphery of the main cavity forming portion 35 is recessed. The base core positioning portion 36 includes a first recess 36A and a second recess 36B. The second recess 36B is recessed on the rear side of the first recess 36A, and the height and width of the second recess 36B are smaller than the height and width of the first recess 36A.

[0042] More specifically, the first recess 36A includes a pair of outer guide side surfaces 36Aa and a pair of receiving surfaces 36Ab. The pair of outer guide side surfaces 36Aa are formed so as to face inward from the outer peripheral surface of the main cavity forming portion 35. The lower ends of the pair of outer guide side surfaces 36Aa are formed in a shape that faces in a direction approaching each other downward. The pair of receiving surfaces 36Ab are formed on a surface (here, a plane) that connects the inner sides of the pair of outer guide side surfaces 36Aa. The pair of receiving surfaces 36Ab face the outer peripheral side of the main cavity forming portion 35.

[0043] The second recess 36B includes a pair of guide side surfaces 36Ba, a back surface 36Bb, and a main positioning surface 36Bc. The pair of guide side surfaces 36Ba are located inside the pair of outer guide side surfaces 36Aa and face inward from the receiving surface 36Ab. The pair of guide side surfaces 36Ba face each other apart in the circumferential direction of the main cavity forming portion 35 of the base core body 34. The pair of guide side surfaces 36Ba are formed so as to gradually narrow toward the back side of the second recess 36B. When the pair of guide side surfaces 36Ba are used as a reference, the pair of receiving surfaces 36Ab extend outward from the wider side of the pair of guide side surfaces 36Ba. The back surface 36Bb is formed as a surface connecting the back sides of the pair of guide side surfaces 36Ba, here a flat surface.

[0044] The pair of guide side surfaces 36Ba and the rear surface 36Bb extend from the upper end to just before the lower end of the main cavity forming portion 35. A main positioning surface 36Bc is formed so as to connect the lower sides of the pair of guide side surfaces 36Ba and the lower side of the rear surface 36Bb. The main positioning surface 36Bc intersects (here, perpendicular to) a predetermined positioning direction P. Using the main positioning surface 36Bc as a reference, a surface that intersects with the main positioning surface 36Bc (for example, the receiving surface 36Ab or the pair of guide side surfaces 36Ba) may be regarded as a secondary positioning surface. By providing a main positioning surface and a secondary positioning surface that intersects with the main positioning surface, positioning can be performed in two or more different directions.

[0045] The combination core positioning portion 56 corresponds to the base core positioning portion 36 and is formed into a shape that can be fitted into the base core positioning portion 36 .

[0046] More specifically, the combination core positioning portion 56 includes a first protrusion 56A corresponding to the first recess 36A and a second protrusion 56B corresponding to the second recess 36B. The first protrusion 56A is formed in a convex shape that can be fitted into the first recess 36A, and has a pair of side surfaces corresponding to the pair of outer guide side surfaces 36Aa and a contact surface corresponding to the receiving surface 36Ab. The first protrusion 56A is fitted into the first recess 36A in a state of contact with the pair of outer guide side surfaces 36Aa and the receiving surface 36Ab.

[0047] The second protrusion 56B is formed in a protruding shape that can be fitted into the second recess 36B, and protrudes from a circumferentially intermediate position on the inner surface of the first recess 36A, which is located at an upper position. The second protrusion 56B has a pair of side surfaces corresponding to the pair of guide side surfaces 36Ba, a surface 56Bb corresponding to the rear surface 36Bb, and a main abutment surface 56Bc corresponding to the main positioning surface 36Bc. The pair of side surfaces are inclined in the same direction as the pair of guide side surfaces 36Ba. The protruding dimension of the second protrusion 56B relative to the first protrusion 56A is smaller than the depth dimension of the second recess 36B based on the receiving surface 36Ab. Therefore, when the second protrusion 56B is fitted into the second recess 36B, a gap S is provided between the inner peripheral surface 56Bb of the second protrusion 56B and the rear surface 36Bb (see FIG. 5). Furthermore, the primary abutment surface 56Bc intersects (here, perpendicular to) a predetermined positioning direction P, and with the second convex portion 56B fitted into the second concave portion 36B, the primary positioning surface 36Bc and the primary abutment surface 56Bc can come into contact with each other in the predetermined positioning direction P. Using the primary abutment surface 56Bc as a reference, other surfaces (each surface of the first convex portion 56A, a pair of side surfaces of the second convex portion 56B, and surface 56Bb) that intersect with the primary abutment surface 56Bc may be understood as secondary abutment surfaces.

[0048] The combination core positioning portion 66 and the base core positioning portion 37 will be described.

[0049] The base core positioning portion 37 is formed in a shape in which part of the outer periphery of the main cavity forming portion 35 is recessed. Here, the base core positioning portion 37 is formed at two locations between the base core positioning portion 36 and the branch cavity forming portion 38 in the circumferential direction of the main cavity forming portion 35.

[0050] The base core positioning portion 37 includes a pair of guide side surfaces 37a and a receiving surface 37b. The pair of guide side surfaces 37a are formed so as to face inward from the outer peripheral surface of the main cavity forming portion 35. The pair of guide side surfaces 37a are opposed to each other at a distance in the circumferential direction of the main cavity forming portion 35 in the base core body 34. The pair of guide side surfaces 37a are formed so as to gradually narrow toward the back side of the base core positioning portion 37. The receiving surface 37b is formed as a surface connecting the back sides of the pair of guide side surfaces 37a, and here is formed as an arc-shaped surface that is convex outward. The pair of guide side surfaces 37a and the receiving surface 37b extend from the upper end to just before the lower end of the main cavity forming portion 35. A main positioning surface 37c is formed so as to connect the lower side of the pair of guide side surfaces 37a and the lower side of the receiving surface 37b. The main positioning surface 37c intersects (here, perpendicular to) the predetermined positioning direction P. Using the main positioning surface 37c as a reference, a surface intersecting the main positioning surface 37c (for example, the receiving surface 37b or the pair of guide side surfaces 37a) may be regarded as a sub-positioning surface.

[0051] The combination core positioning portion 66 corresponds to the base core positioning portion 37 and is formed into a shape that allows it to be fitted into the base core positioning portion 37 .

[0052] More specifically, the combination core positioning portion 66 is formed in a convex shape that can be fitted into the base core positioning portion 37, and has a pair of side surfaces 66a corresponding to the pair of guide side surfaces 37a, a back surface 66b corresponding to the receiving surface 37b, and a main contact surface 66c corresponding to the main positioning surface 37c. The pair of side surfaces 66a are inclined in the same direction as the pair of guide side surfaces 37a. The back surface 66b is formed as a surface (here, an arc-shaped surface) that connects the inner sides of the pair of side surfaces 66a. A shallow groove 37bg extending along the axial direction of the main cavity forming portion 35 is formed in 37b. The groove 37bg can be used as a space for retaining adhesive. The main contact surface 66c intersects (here, perpendicular to) the predetermined positioning direction P. Then, with the combination core positioning part 66 fitted into the base core positioning part 37, the pair of side surfaces 66a may contact the pair of guide side surfaces 37a, the rear surface 66b may contact the receiving surface 37b, and further the primary abutment surface 66c may contact the primary positioning surface 37c, all at the same time. Using the primary abutment surface 66c as a reference, the other surfaces (the rear surface 66b, the pair of side surfaces 66a) that intersect with the primary abutment surface 66c may be understood as secondary abutment surfaces.

[0053] An example of a method for producing a molding 10 having cavities 14, 15, 16, and 17 will be described using a casting core assembly 20 as an example of a core assembly.

[0054] This manufacturing method includes the steps of (a) forming a casting core assembly 20, (b) placing the casting core assembly 20 in a mold, and (c) molding the casting 10.

[0055] In step (a), the combination cores 50, 60 are fixed to the base core 30 with the combination core bodies 54, 64 positioned and fitted to the base core body 34, thereby forming the casting core combination 20.

[0056] In this case, an assembly auxiliary tool 100 as shown in Figures 6 and 7 may be used. Figure 6 shows a state in which the base core 30 is supported by the assembly auxiliary tool 100, and Figure 7 shows a state in which the base core 30 and combined cores 50, 60 are supported by the assembly auxiliary tool 100.

[0057] The combination aid 100 is a member formed from resin or the like, and includes a main support portion 110 and sub-support portions 120 and 130. The main support portion 110 and the sub-support portions 120 and 130 are supported in a fixed positional relationship on a base 102 that extends in a plane.

[0058] The main support part 110 is configured to be able to support at least a portion of the base core 30 in a placed state. Here, the main support part 110 comprises a first main support part 112 and a second main support part 114. The first main support part 112 comprises a columnar part 113 and a rod-shaped part 113p erected in the center of the upper surface of the columnar part 113. The second main support part 114 is provided at a part of the periphery of the first main support part 112. A groove-shaped recess 115 is formed in the second main support part 114.

[0059] The main cavity forming portion 35 of the base core 30 is supported by the first main support portion 112. Specifically, the lower surface of the main cavity forming portion 35 is placed on the upper surface of the cylindrical portion 113. As a result, the main cavity forming portion 35 is positioned in the positioning direction P on the first main support portion 112. Also, the rod-shaped portion 113p is inserted into the positioning hole 35h of the main cavity forming portion 35. As a result, the main cavity forming portion 35 is also positioned in a direction intersecting the positioning direction P. Also, the base board 32 provided at the end of the branch cavity forming portion 38 is placed on the recess 115 while being fitted into the recess 115. As a result, rotation of the base core 30 around the rod-shaped portion 113p is prevented. As a result, the base core 30 is supported at a fixed position by the main support portion 110.

[0060] The auxiliary support portions 120, 130 are configured to be able to support the portions of the multiple combination cores 50, 60 extending from the base core 30 when portions of the combination cores 50, 60 are positioned on the base core 30 supported by the main support portion 110.

[0061] Specifically, the auxiliary support part 120 is provided on the opposite side of the second main support part 114 with respect to the first main support part 112. A positioning recess 122 is formed in the auxiliary support part 120. The positioning recess 122 has a pair of side surfaces that face each other and are spaced apart in the circumferential direction centered on the first main support part 112, and a bottom surface between the pair of side surfaces. With the combined core positioning part 56 of the combined core 50 positioned in the base core positioning part 36 of the base core 30, the base board 52 of the combined core 50 is placed on the bottom surface between the pair of side surfaces. As a result, the portion of the combined core 50 that extends from the base core 30 is supported by the auxiliary support part 120.

[0062] The auxiliary support 130 is provided around the outside of the first main support 112, between the second main support 114 and the auxiliary support 120. A positioning recess 132 is formed in the auxiliary support 130. The positioning recess 132 has a pair of side surfaces that face each other at a distance in the circumferential direction centered on the first main support 112, and a bottom surface between the pair of side surfaces. With the combined core positioning portion 66 of the combined core 60 positioned on the base core positioning portion 37 of the base core 30, the baseboard 62 of the combined core 60 is placed on the bottom surface between the pair of side surfaces. As a result, the portion of the combined core 60 that extends from the base core 30 is supported by the auxiliary support 130. When the combined core 60 is supported hanging down with the combined core positioning portion 66 positioned on the base core positioning portion 37, it is not essential that the bottom surface supports the baseboard 62.

[0063] An example of an operation for forming a casting core combination 20 using the above-mentioned combination auxiliary tool 100 will be described.

[0064] The rod-shaped portion 113p is inserted into the positioning hole 35h of the main cavity forming portion 35 so that the lower surface of the main cavity forming portion 35 comes into contact with the upper surface of the columnar portion 113. Also, the base board 32 provided at the end of the branch cavity forming portion 38 is fitted into the recess 115. Thereby, the base core 30 is placed on the main support portion 110 (step a1).

[0065] At this time, adhesive B supplied from a tube Ba or the like may be applied to the base core positioning parts 36, 37 or the combination core positioning parts 56, 66 (see FIG. 6). A cyanoacrylate-based jelly adhesive may be used as the adhesive B. The application location may be, for example, the surface of the base core positioning parts 36, 37 closer to the main cavity forming part 35.

[0066] Next, the main cavity forming portions 55, 65, which are parts of the combined cores 50, 60, are positioned in the main cavity forming portion 35 of the base core 30 above the main support portion 110 (step a2).

[0067] Then, the baseboards 52, 62 extending from the base core 30 of the combination core positioning parts 56, 66 are positioned and supported by the auxiliary support parts 120, 130 (step a2, see FIG. 7).

[0068] The base core 30 and the combined cores 50, 60 are supported on the assembly auxiliary tool 100 until the adhesive B hardens. When the adhesive B hardens, the casting core combination 20 is formed.

[0069] The casting core combination 20 manufactured as described above is placed in a mold 90 (see FIG. 3). That is, by fixing the lower end surface 35b and positioning hole 35h of the main cavity forming portion 35 to the cylindrical portion 92a of the mold 90, the base core body 34 and the combined core bodies 54, 64 are positioned away from the mold surface.

[0070] The cylindrical core portion formed by the main cavity forming portions 35, 55, 65 is placed on top of the cylindrical portion 92a protruding from the lower die 92. The cylindrical portion 94a protruding from the upper die 94 is disposed so as to be continuous with the upper part of the cylindrical core portion. Thus, the main cavity 14 in the molding 10 is formed by the cylindrical portion 92a of the lower die 92, the cylindrical core portion of the casting core assembly 20, and the cylindrical portion of the upper die 94.

[0071] Molten metal is then poured into the mold 90. The molten metal cools and solidifies, forming a molded product 10 whose surface shape is transferred to the mold surface shape and the surface shape of the casting core assembly 20.

[0072] The molded product 10 may have an inner peripheral surface around the main cavity 14 machined. This allows the inner peripheral surface forming the cylindrical space to be machined into a smooth surface. The inner peripheral surface around the main cavity 14 may have linear unevenness caused by the boundaries between the cylindrical portion 92a of the lower die 92, the cylindrical portion of the core assembly 20, and the cylindrical portion of the upper die 94. In addition, since the boundaries of the main cavity forming portions 35, 55, and 65 exist in the cylindrical portion of the core assembly 20, the inner peripheral surface around the main cavity 14 may have unevenness caused by the boundaries. Since the unevenness caused by these boundaries is formed in the portion that is machined after die molding, the unevenness can be made less noticeable.

[0073] With the casting core combination 20 configured in this manner, the combined cores 50, 60 are combined with the base core 30 with the combined core positioning portions 56, 66 of the combined core bodies 54, 64 in contact with the base core positioning portions 36, 37 of the base core body 34. As a result, the position of the combined core bodies 54, 64 is determined with the base core body 34 as the reference. This makes it possible to reduce misalignment between the base core body 34 and the combined core bodies 54, 64. This improves the surface shape precision of the molding 10 produced using the casting core combination 20.

[0074] Furthermore, the positions of the multiple combined core bodies 54, 64 are determined with respect to one base core body 34. For this reason, it is possible to reduce positional deviation of the multiple combined core bodies 54, 64 with respect to the base core body 34 as a reference, which also improves the surface shape precision of the molded product 10.

[0075] Furthermore, since the base core positioning portions 36, 37 and the combined core bodies 54, 64 contact each other in a predetermined positioning direction P, the combined core bodies 54, 64 can be positioned with high positioning accuracy in the positioning direction P using the base core body 34 as a reference.

[0076] Furthermore, the base core positioning parts 36, 37 are positioning recesses and have a pair of guide side surfaces 36Ba, 37a that gradually narrow towards the back. For this reason, when the combination core positioning parts 56, 66, which are positioning protrusions, are fitted into the base core positioning parts 36, 37, the combination core positioning parts 56, 66 are smoothly guided by the pair of guide side surfaces 36Ba, 37a towards the back of the base core positioning parts 36, 37. This allows the combination core bodies 54, 64 to be positioned easily and accurately around the main cavity forming part 35 of the base core 30.

[0077] The base core positioning portion 36, which is a positioning recess, has a pair of receiving surfaces 36Ab that extend outward from the wider side of the pair of guide side surfaces 36Ba. The combined core positioning portion 56, which is a positioning protrusion, is fitted into the base core positioning portion 36 with a gap S provided between the innermost surface 36Bb on the inner side of the pair of guide side surfaces 36Ba and in contact with the pair of receiving surfaces 36Ab. For example, if the innermost surface 36Bb and the receiving surface 36Ab are designed to contact the combined core positioning portion 56 at the same time, one of the innermost surface 36Bb and the receiving surface 36Ab may come into contact first and the other may not come into contact due to manufacturing errors, etc. In particular, when the innermost surface 36Bb comes into contact with the combined core positioning portion 56, the contact area is small, so that the combined core body 54 may wobble relative to the base core body 34. Therefore, by configuring the pair of receiving surfaces 36Ab extending outward from the wider sides of the pair of guide side surfaces 36Ba to have preferential contact with the combined core positioning portion 56, the combined core positioning portion 56 can be easily positioned relative to the base core positioning portion 36 without any rattling.

[0078] Furthermore, the molding 10 is a cylinder having a main cavity 14 and branch cavities 15, 16, 17, with the base core body 34 forming a part of the main cavity 14, and each of the combined core bodies 54, 64 being combined with the base core body 34 to form the other part of the main cavity 14 and at least some of the branch cavities 15, 16, 17. Therefore, the core bodies 54, 64 which form the branch cavities 16, 17 are combined with the base core body 34 which forms a part of the main cavity 14 as a reference. Therefore, the other branch cavities 16, 17 are formed with good positional accuracy with respect to the main cavity 14. Because the branch cavity 15 is formed by the base core body 34, the positional accuracy of the branch cavity 15 with respect to the main cavity 14 is good.

[0079] Furthermore, if the molding 10 is a cylinder for a two-stroke engine, the base core positioning parts 36, 37 and the combined core positioning parts 56, 66 come into contact with each other in the central axial direction P of the cylinder space, and at least one of the base core 30 and the combined cores 50, 60 forms a scavenging port, and at least the other forms an exhaust port, then the scavenging port and the exhaust port can be formed with good positional accuracy in the direction P with respect to the cylinder space. This provides good timing for exhaust, scavenging, etc., associated with the movement of the piston.

[0080] By manufacturing a molding 10 using such a casting core combination 20, it is possible to produce a molding 10 in which the cavity formed by the base core 30 and the cavities formed by the combined cores 50, 60 are formed with little misalignment from the designed positions.

[0081] When forming the casting core combination 20, by using the above-mentioned assembly auxiliary tool 100, the combined core positioning portions 56, 66 can be easily assembled with high precision to the base core 30 on the main support portion 110 and the secondary support portions 120, 130.

[0082] Furthermore, if at least a portion of the portion where the combined core body 54, 64 and the base core body 34 are positioned and fitted together (for example, the combined portion between the base core positioning portions 36, 37 and the combined core positioning portions 56, 66) is formed in a portion that will be machined after molding of the molded product 10 (for example, the inner surface of the cylinder space), the uneven portion caused by the combination can be made less noticeable by the machining process.

[0083] The molded product 10 does not have to be a cylinder for a two-stroke engine. The molded product 10 may be a cylinder that is not for a two-stroke engine. The molded product 10 may be another part that constitutes an engine. The molded product is not limited to an engine part, and may be another molded product, for example, a casting.

[0084] The formation examples of the branch cavities 15, 16, 17 by the base core body 34 and the combined core bodies 54, 64 are not limited to the examples described in the above embodiments. For example, all of the branch cavities 15, 16, 17 may be formed by the combined core body. Also, the scavenging port or the intake port may be formed by the base core body, and other ports may be formed by the combined core body.

[0085] The configurations described in the above embodiment and modifications can be combined as appropriate as long as they are not mutually inconsistent.

[0086] The present disclosure includes the following aspects.

[0087] A first aspect is a casting core combination for forming a cavity in a casting when molding the casting, the casting core combination comprising: a base core including a base core body for forming a part of the cavity of the casting; and a combination core including a combination core body for forming another part of the cavity of the casting, the base core body having a base core positioning portion, the combination core body having a combination core positioning portion, and the combination core being combined with the base core with the combination core positioning portion in contact with the base core positioning portion.

[0088] With this casting core combination, the combined core is combined with the base core with the combined core positioning portion of the combined core body in contact with the base core positioning portion of the base core body. Therefore, the position of the combined core body is determined with reference to the base core body. This makes it possible to reduce misalignment between the base core body and the combined core body.

[0089] A second aspect is the casting core combination according to the first aspect, which includes a plurality of the combination cores, and the plurality of combination cores are combined with the base core with the combination core positioning portion of each of the plurality of combination cores in contact with the base core positioning portion. In this case, the positions of the plurality of combination core bodies are determined with reference to the base core body. This makes it possible to reduce positional deviation between the base core body and the plurality of combination core bodies.

[0090] In a third aspect, in the casting core combination according to the first or second aspect, the base core positioning portion and the combined core positioning portion come into contact with each other at least in a predetermined positioning direction, whereby the combined core body can be positioned with high positioning accuracy in the predetermined positioning direction with respect to the base core body.

[0091] A fourth aspect is a casting core combination according to any one of the first to third aspects, in which one of the combined core positioning portion and the base core positioning portion is a positioning recess and the other is a positioning protrusion, the positioning recess has a pair of guide side surfaces spaced apart in the circumferential direction of the base core body, and the pair of guide side surfaces gradually narrow toward the back side of the positioning recess. In this case, when the positioning protrusion is fitted into the positioning recess, the positioning protrusion is guided by the pair of guide side surfaces. This allows the combined core to be positioned easily and accurately in the circumferential direction of the base core.

[0092] A fifth aspect is the casting core combination according to the fourth aspect, wherein the positioning recess has a pair of receiving surfaces extending outward from the wider sides of the pair of guide side surfaces, and the positioning protrusion fits into the positioning recess while contacting the pair of receiving surfaces with a gap provided between the positioning recess and the rear side of the pair of guide side surfaces. This allows the combination core to be positioned with good positional accuracy relative to the base core body.

[0093] A sixth aspect is a casting core combination according to any one of the first to fifth aspects, in which the casting is a cylindrical body, the cavities being a main cavity within the cylindrical body and a branch cavity continuing to the outside of the main cavity, the base core body forming a part of the main cavity, and each of the combined core bodies combining with the base core body forming the other part of the main cavity and at least a part of the branch cavity. In this case, the combined core body forming at least a part of the branch cavity is combined with the base core body forming a part of the main cavity as a reference. Therefore, the other branch cavities are formed with good positional accuracy relative to the main cavity.

[0094] A seventh aspect is a casting core combination according to the sixth aspect, wherein the casting is a cylinder for a two-stroke engine, the main cavity is a cylinder space within the cylinder, the base core positioning part and the combined core positioning part are in contact with each other in the central axial direction of the cylinder space, at least one of the base core body and the combined core body forms a scavenging port connected to the cylinder space as the branch cavity, and at least another of the base core body and the combined core body forms an exhaust port connected to the cylinder space as the branch cavity. This makes it possible to form a scavenging port and an exhaust port in the cylinder with good positional accuracy in the central axial direction of the cylinder space.

[0095] An eighth aspect is a method for producing a molded product having a cavity, comprising: (a) a base core including a base core body for forming a part of the cavity of the molded product; and a combination core, the combination core including a combination core body for forming another part of the cavity of the molded product, the combination core body being positioned and fitted into the base core body while the combination core is fixed to the base core to form a core combination, (b) placing the core combination in a mold, and (c) molding the molded product using the core combination.

[0096] According to this manufacturing method for moldings, the combination core is assembled to the base core with the combination core body positioned and fitted to the base core body. Therefore, the position of the combination core body is determined based on the base core body. By manufacturing a molding using this core assembly, it is possible to manufacture a molding in which the cavity formed by the base core and the cavity formed by the combination core are formed with little misalignment.

[0097] A ninth aspect is a method for producing a molded product according to the eighth aspect, wherein in step (a), (a1) at least a part of the base core is placed on a main support part, (a2) a part of the combined core is positioned on the base core above the main support part, and (a3) ​​a part of the combined core extending from the base core is supported by a sub-support part.

[0098] This makes it possible to easily assemble the combination core to the base core on the main support portion and the sub-support portion with high accuracy.

[0099] A tenth aspect is a manufacturing method for a molded product according to the eighth or ninth aspect, in which at least a part of the portion where the combined core body and the base core body are positioned and fitted together is formed in a part that is machined after molding of the molded product. This makes it possible to make at least a part of the portion where the combined core body and the base core body are positioned and fitted together inconspicuous by the machining.

[0100] The above description is illustrative in all respects, and the present invention is not limited thereto. It is understood that countless variations not illustrated can be assumed without departing from the scope of the present invention. [Explanation of symbols]

[0101] 10 Molded object 14 Main cavity 15, 16, 17 Branch Cavity 20 Casting core assembly 30 Base core 34 Base core body 35 Main cavity forming part 36, 37 Base core positioning part 36Ab, 37b receiving surface 36Ba, 37a Guide side 36Bb back side 36Bc, 37c Primary locating surfaces 38 Branch cavity formation part 50, 60 combination core 54, 64 Combination core body 55, 65 Main cavity forming part 56, 66 Combination core positioning part 56Bb side 56Bc, 66c Main contact surface 58, 68 Branch cavity formation part 62 Baseboard 66a side 90 type 100 Combination aid 110 Main support part 120, 130 Sub-support part P Positioning direction

Claims

1. 1. A casting core combination for forming a cavity including a main cavity in a casting and another cavity connected to the main cavity when molding the casting, comprising: a base core including a base core body for forming a portion of a cavity of the casting; a combination core including a combination core body for forming another portion of the cavity of the casting; Equipped with The base core body has a base core positioning portion, The combination core body has a combination core positioning portion, A casting core combination, wherein the combination core positioning portion is formed in a shape that can fit into the base core positioning portion from the radial outside of the main cavity while in contact with the base core positioning portion in the axial or circumferential direction relative to the main cavity.

2. A casting core assembly as claimed in claim 1, The base core positioning portion is a positioning recess, and the combination core positioning portion is a positioning protrusion, The combination core positioning portion includes a portion that forms a part of the main cavity.

3. A casting core combination according to claim 1 or claim 2, the base core has, in addition to the base core positioning portion, a main cavity forming portion for forming the main cavity, and a branch cavity forming portion for forming a first branch cavity extending radially outward from the main cavity, a combination core for casting, wherein the combination core has, in addition to the combination core positioning portion, a branch cavity forming portion for forming a second branch cavity extending radially outward from the main cavity.

4. A casting core combination according to any one of claims 1 to 3, a casting core combination, wherein the combination core positioning portion is formed in a shape that can be fitted into the base core positioning portion from the radially outside while in contact with the base core positioning portion in the axial and circumferential directions relative to the main cavity.

5. A casting core combination according to any one of claims 1 to 4, A casting core combination, wherein the combination core positioning portion has a groove that forms a space for retaining adhesive.

6. A casting core combination as claimed in claim 1, One of the combination core positioning portion and the base core positioning portion is a positioning concave portion, and the other is a positioning convex portion, The positioning recess has a pair of guide side surfaces spaced apart in a circumferential direction of the base core body, The pair of guide side surfaces gradually narrow toward the back side of the positioning recess, The positioning recess has a pair of receiving surfaces extending outward from the wider sides of the pair of guide side surfaces, The positioning protrusion has a shape that gradually narrows toward the inside in the radial direction, a casting core assembly in which the positioning protrusion and the positioning recess are in contact with each other with a gap provided in the radial direction, thereby positioning them relative to each other in the circumferential direction of the main cavity.

7. A casting core combination according to claim 1, claim 2 or claim 6, the casting is a cylinder for a two-stroke engine, the other cavity being a branch cavity that is continuous with the outside of the main cavity; the main cavity being a cylinder space within the cylinder, The base core positioning portion and the combination core positioning portion are in contact with each other in the central axial direction of the cylinder space, A casting core combination, wherein at least one of the base core body and the combined core body forms a scavenging port connected to the cylinder space as the branch cavity, and at least one other of the base core body and the combined core body forms an exhaust port connected to the cylinder space as the branch cavity.

8. A method for producing a molded article having a cavity including a main cavity and another cavity continuous with the main cavity, comprising the steps of: (a) a base core including a base core body for forming a part of a cavity of the molding, and a combination core, the combination core including a combination core body for forming another part of the cavity of the molding, the base core body having a base core positioning portion, the combination core body having a combination core positioning portion, the combination core positioning portion being in contact with the base core positioning portion in an axial direction relative to the main cavity and being fitted into the base core positioning portion in a direction intersecting the axial direction to form a core combination, (b) placing the core assembly in a mold; (c) A method for producing a molded article, comprising using a mold and the core combination to mold the molded article.

9. A method for producing the molded product according to claim 8, comprising: In the step (a), the combined core and the base core are each supported by a combination auxiliary tool so that the axial direction is in the up-down direction, and the combined core is fixed to the base core in a state in which the combined core and the base core are aligned with each other relative to the combination auxiliary tool, thereby forming the core combination body.

10. A method for producing the molded product according to claim 9, comprising the steps of: In the step (a), (a1) placing at least a portion of the base core on a main support portion of the assembly auxiliary tool; (a2) positioning a portion of the combination core on the base core above the main support portion; (a3) A method for manufacturing a molding, in which a portion of the combination core extending from the base core is supported by a sub-support portion of the combination auxiliary tool.

11. A method for producing a molded product according to any one of claims 8 to 10, comprising: A method for manufacturing a molded product, wherein at least a portion of the portion where the combination core body and the base core body are positioned and fitted together is formed in a portion that will be machined after molding of the molded product.

12. 1. A casting core combination for forming a cavity including a main cavity in a casting and another cavity connected to the main cavity when molding the casting, comprising: a base core including a base core body for forming a portion of a cavity of the casting; a combination core including a combination core body for forming another portion of the cavity of the casting; Equipped with The base core body has a concave base core positioning portion, The combination core body has a convex combination core positioning portion, The base core has a main cavity forming portion for forming the main cavity in addition to the base core positioning portion, The combination core has a branch cavity forming portion for forming another cavity extending from the main cavity to the radially outer side of the main cavity in addition to the combination core positioning portion, The base core positioning portion is a positioning recess, and the combination core positioning portion is a positioning protrusion, The combination core positioning portion includes a portion that forms a part of the main cavity.

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