Casting cores

Abstract

To provide a core which is used in casting of a cast member having a cavity part filled with a granule therein while suppressing increase in the number of processes.SOLUTION: A frozen core 10 used in casting includes a body part 10a and projections 10b and 10c. The body part 10a has a mixture of a liquid and a granule, and is frozen and formed in a cavity part shape of a piston body part 2. Each of the projections 10b and 10c is formed of a porous member, and is formed as a discharge route of a vaporized liquid to the outside of the piston body part 2 from the cavity part in mold opening of the mold.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a core for casting, and more particularly to a core used in producing a cast member having an internal cavity filled with granular material. [Background technology]

[0002] Metal parts having an internal cavity are sometimes used. For example, Patent Document 1 discloses a piston used in an engine of a vehicle or the like, which has an internal cavity and is filled with granular material. By employing the piston disclosed in Patent Document 1, it is possible to reduce the inertial mass and improve fuel efficiency. Patent Document 1 also discloses that by filling the cavity of the piston with granular material, it is possible to increase the compression ratio while suppressing vibrations occurring in the piston.

[0003] Incidentally, when manufacturing a metal part that has a hollow portion inside and that is filled with granular material, one possible method is to place a core in the cavity of a mold, pour in molten metal, remove the core after the molten metal has solidified, and fill the hollow portion created by removing the core with granular material.

[0004] Patent Document 2 discloses the use of a core made of NaCl in casting. Patent Document 2 states that by using a core made of NaCl, the core can be easily removed by washing with water after the molten metal has solidified. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-186722 [Patent Document 2] Japanese Patent Application Publication No. 06-190532 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if a metal part having a cavity filled with granular material were manufactured using the method disclosed in Patent Document 2, it would be difficult to mass-produce the part, and the manufacturing costs would likely increase. That is, even if casting were performed using the core disclosed in Patent Document 2, it would be necessary to subsequently remove the core and then fill the cavity with granular material, which would likely increase the number of steps.

[0007] In addition to pistons used in engines, there are various other cast members that have a cavity inside and require granular material to be filled in the cavity.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a core that can be used when casting a cast member having a hollow portion filled with granular material inside, while suppressing an increase in the number of steps. [Means for solving the problem]

[0009] A casting core according to one aspect of the present invention is a core that is placed in a mold cavity when manufacturing a cast member having a hollow portion filled with granular material. The core according to this aspect comprises a main body and a protrusion. The main body contains a mixture of liquid and the granular material, and is a portion that is frozen in a state that forms the shape of the hollow portion. The protrusion is a portion that extends outward from the main body and contacts the mold, with a portion of the protrusion being in contact with the mixture and integral with the main body. In the core according to this aspect, the protrusion prevents the vaporized liquid from entering the mold when the mold is opened. From the part in contact with the mixture Discharged to the outside It becomes possible It is formed like this A plurality of holes .

[0010] The core according to the above embodiment has a main body formed by freezing a mixture of liquid and granular material, and a passageway through which the vaporized liquid is discharged to the outside. Having a plurality of holesWhen casting is performed using the core, the liquid in the main body vaporizes upon injection of molten metal, and the protrusions are formed when the mold is opened. Multiple holes in The vaporized liquid passes through the core and is discharged to the outside. That is, when casting is performed using the core according to the above embodiment, after the vaporized liquid is discharged when the mold is opened, granules remain in the cavity of the cast member. Therefore, when casting is performed using the above core, compared to when casting is performed using the core disclosed in Patent Document 2 (a core made of NaCl), there is no need to perform steps such as removing the core and then filling it with granules, which reduces the number of steps required to produce a cast member by casting and reduces production costs.

[0011] In the core according to the above aspect, the protrusion is Each The pore size is smaller than the particle size of the granules. The plurality of holes It may also be made of a porous material.

[0012] In the core according to the above embodiment, the protrusions are made of a porous material, so the vaporized liquid is discharged to the outside through the holes in the protrusions, while the granules remain within the hollows, making it advantageous for use in producing cast members having hollows filled with granules.

[0013] In the core according to the above aspect, the protrusion may be formed of a columnar member, and one end may be disposed inside the main body.

[0014] In the core according to the above aspect, one end of the protrusion is disposed inside the main body, and the portion including the end is disposed so as to be in contact with the mixture, so that liquid vaporized by the heat of the molten metal is introduced into the protrusion from the portion and discharged from the portion extending out from the main body. Therefore, in the core according to the above aspect, the contact area between the main body and the protrusion is large, and the vaporized liquid can be discharged to the outside more smoothly when the mold is opened.

[0015] In the core according to the above aspect, the protrusion may have a frustum shape in which the area of ​​the one end is larger than the area of ​​the other end.

[0016] In the core according to the above embodiment, the protrusions have a frustum shape, which prevents the protrusions from falling off in the cast member after casting. Therefore, by casting using the core according to the above embodiment, it is possible to prevent the granular material from leaking out of the cavity in the cast member after casting.

[0017] In the core according to the above aspect, the protrusion may be formed of a columnar member and may penetrate the main body so that both ends are disposed outside the main body.

[0018] In the core according to the above aspect, the protrusion is arranged to penetrate the main body, thereby enabling a larger contact area between the main body and the protrusion, which makes it possible to more smoothly discharge the vaporized liquid when the mold is opened.

[0019] In the core according to the above embodiment, the protrusions penetrate the main body, so that both ends are located outside the main body. Therefore, in the cast member after casting, one end of the protrusion can abut against the metal portion (the portion where the molten metal has solidified). Therefore, in the cast member after production, the protrusions can function as reinforcing members that support the cavity.

[0020] In the core according to the above aspect, a plurality of the protrusions may be provided.

[0021] The core according to the above embodiment has multiple protrusions, which makes it possible to more stabilize the position and posture of the core when it is placed in the cavity, and also to more smoothly discharge vaporized liquid when the mold is opened.

[0022] In the core according to the above aspect, the amount of the granular material mixed in the main body portion may be specified so that the granular material is filled in the hollow portion in a range of 35% by volume or more and 55% by volume or less.

[0023] In the core according to the above embodiment, the liquid and granular material are mixed so that the filling rate of the granular material in the cavity is in the range of 35% to 55% by volume, which makes it possible to prevent the movement of the granular material within the cavity of the cast member after casting from being hindered. Therefore, when manufacturing the above-mentioned parts that constitute movable components, it is possible to reduce the weight of the cast member after casting and suppress vibration.

[0024] In the core according to the above aspect, the liquid may be water.

[0025] In the core according to the above aspect, water is used as the liquid for the main body, which makes it easy to procure, and even if it is discharged to the outside in a vaporized state, the environmental load can be kept small.

[0026] When water is used as the liquid, for example, a core frozen at a temperature of −40° C. or lower can be used to ensure a relatively long time for the water to evaporate upon contact with the molten metal during casting, which is advantageous in ensuring that the shape of the cavity in the cast member after casting is as designed. [Effects of the Invention]

[0027] By using the core according to each of the above aspects, it is possible to cast a cast member having a cavity filled with granular material inside while suppressing an increase in the number of steps. [Brief explanation of the drawings]

[0028] [Figure 1] 1A and 1B are perspective views showing the external shape of a frozen core according to an embodiment, in which FIG. 1A is a view from the side, and FIG. 1B is a view from the back side. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 1 is a flow diagram illustrating a method for forming a frozen core. [Figure 4] 1 is a flow diagram showing a method for manufacturing a piston using a frozen core according to an embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing a state in which a frozen core is placed in a cavity of a mold. [Figure 6] FIG. 10 is a cross-sectional view showing the state in which the mold is opened after the molten metal has solidified. [Figure 7] FIG. 2 is a cross-sectional view showing the structure of a cavity of a piston manufactured by casting and its surrounding area. [Figure 8] FIG. 10 is a cross-sectional view showing a partial configuration of a frozen core according to Modification 1. [Figure 9] FIG. 10 is a cross-sectional view showing a partial configuration of a frozen core according to Modification 2. [Figure 10] 10(a) is a cross-sectional view showing the structure of a protrusion member used in a frozen core according to Modification 3, and FIG. 10(b) is a cross-sectional view showing the structure of a protrusion member used in a frozen core according to Modification 4. FIG. [Figure 11] FIG. 10 is a perspective view showing the external shape of a frozen core according to Modification 5. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example of the present invention, and the present invention is not limited to the following embodiment except for its essential configuration.

[0030] In the following, a core used for casting a piston to be incorporated into an engine of a vehicle or the like will be described as an example.

[0031] [Embodiment] 1. Structure of frozen core 10 The structure of a core (frozen core) 10 used in casting will be described with reference to FIGS.

[0032] As shown in FIGS. 1(a) and 1(b), the freezing core 10 according to this embodiment comprises a main body 10a and two protrusions 10b and 10c. The main body 10a is formed by freezing a mixture of a liquid (e.g., water) and granular material (e.g., metal or ceramic granular material). The main body 10a has a generally cylindrical exterior shape with a hole 10d in the center. The main body 10a is formed to fit the shape of the cavity to be formed inside the piston and is set to a size slightly smaller than the piston to be manufactured. The top surface 10e of the main body 10a is formed in a shape that fits the top surface of the piston to be manufactured.

[0033] As shown in FIG. 1(b), two rear recesses 10f, 10g are provided on the rear surface of the main body 10a (the surface opposite the top surface 10e) between the portions corresponding to the skirts of the piston to be manufactured. The two rear recesses 10f, 10g are located on both sides of the hole 10d. Furthermore, a portion of each of the protrusions 10b, 10c extends from each of the rear recesses 10f, 10g toward the side opposite the top surface 10e.

[0034] 2. Internal structure of frozen core 10 The internal structure of frozen core 10 will be described with reference to Fig. 2. Note that Fig. 2 illustrates rear surface recess 10f and protrusion 10b partially extending from rear surface recess 10f, but the portion of protrusion 10c partially extending from rear surface recess 10g also has the same structure.

[0035] 2, in the freezing core 10 according to this embodiment, a portion of the columnar porous member (e.g., porous ceramics or porous metal) constituting the protrusion 10b is inserted inside the main body 10a, and the remaining portion extends from the rear surface recess 10f toward the opposite side from the top surface 10e. Note that in this embodiment, the porous member constituting the protrusion 10b has a cylindrical shape, and an outer end surface (other end) 10h located outside the main body 10a and an inner end surface (one end) 10i located inside the main body 10a are both formed in a circular shape with approximately the same area.

[0036] 2, in the frozen core 10 according to this embodiment, the porous member constituting the protrusion 10b is positioned so that the inner end surface 10i does not reach the top surface 10e of the main body 10a. However, the inner end surface 10i of the protrusion 10b may be positioned so that it is exposed to the outside from the top surface 10e of the main body 10a.

[0037] Furthermore, the protrusions 10b are in contact with the mixture that constitutes the main body 10a at the portions that have entered the main body 10a.

[0038] 3. Method for forming frozen core 10 A method for forming the frozen core 10 will be described with reference to FIG.

[0039] (Kneading step) A liquid (e.g., water) and granular material (e.g., metal or ceramic granular material) are kneaded (step S1). In this case, the ratio of the liquid to the granular material is adjusted so that the granular material accounts for 35% by volume or more and 55% by volume or less of the volume of the hollow portion in the piston after production.

[0040] (Porous member preparation step) As described above, a columnar porous member made of porous ceramics or porous metal is prepared (step S2). In this embodiment, as described with reference to FIG. 1(b), two porous members are prepared to form the frozen core 10 having two protrusions 10b, 10c.

[0041] (Setting Step) The two porous members prepared in step S2 above are set in a mold (step S3). The mold used in step S3 has a cavity that matches the external shape of the frozen core 10 to be formed.

[0042] (Filling step) The mixture formed by kneading in step S1 is filled into the cavity of the mold in which the porous member is set (step S4). Note that the mixture filled into the cavity comes into contact with a part of the porous member set in the mold in step S3.

[0043] (Freezing Step) The mold filled with the mixture in step S4 is frozen to form the frozen core 10 (step S5). The freezing to form the frozen core 10 is carried out, for example, at a temperature of −40° C. or lower for about 5 hours.

[0044] 4. Manufacturing method of piston using frozen core 10 A method for manufacturing a piston (cast member) using the frozen core 10 formed as described above will be described with reference to FIGS.

[0045] (Preparation Step) The frozen core 10 formed as described above is prepared (step S11).

[0046] (Mold Clamping Process) The frozen core 10 is placed in the cavity of the mold and mold clamping is performed (Step S12). Specifically, as shown in FIG. 5, the frozen core 10 is placed in the cavity 20a formed by combining the segments 21 to 24, and the mold 20 is clamped. Of the segments 21 to 24 that make up the mold 20, segment 22 is provided with two recesses 20b, 20c into which the protrusions 10b, 10c of the frozen core 10 can be inserted. The bottom surfaces of the recesses 20b, 20c are flat so as to abut against the outer end surfaces 10h, 10j of the protrusions 10b, 10c. In this way, by inserting the protrusions 10b, 10c of the frozen core 10 into the recesses 20b, 20c, the position and orientation of the frozen core 10 in the cavity 20a can be determined.

[0047] (Pouring Step) After clamping the mold 20, molten metal (e.g., molten aluminum alloy) is poured into the cavity 20a from a sprue (not shown) of the mold 20 (step S13). In this step, the temperature of the molten metal at the time of pouring is approximately 800°C. The molten metal poured into the cavity 20a begins to solidify from the portion in contact with the frozen core 10.

[0048] On the other hand, after the molten metal is poured into the main body 10a of the frozen core 10, the temperature gradually rises to around 0° C., and then remains at around 0° C. for a short time. After remaining at around 0° C. for a short time, the temperature of the main body 10a of the frozen core 10 rises, and the liquid begins to evaporate.

[0049] (Mold Opening Step) After a predetermined time has elapsed for the molten metal to solidify, the mold 20 is opened, and the vaporized liquid (the liquid contained in the main body 10a of the frozen core 10) is discharged to the outside (step S14). Specifically, as shown in FIG. 6 , the liquid contained in the main body 10a of the frozen core 10 is vaporized by the injection of the molten metal, passes through the protrusions 10b and 10c, and is discharged to the outside from the piston main body 2 (the portion where the molten metal has solidified) (arrows A1 and A2). Note that in casting using the frozen core 10 according to this embodiment, the protrusions 10b and 10c are formed to protrude through the back surface 2c of the piston head 2a, which is on the opposite side from the top surface 2b. Therefore, even if the protrusions 10b and 10c remain, they do not affect engine combustion.

[0050] Here, the frozen core 10 according to this embodiment is configured so that the protrusions 10b and 10c remain after casting, but it is acceptable for some of them to melt when the molten metal is poured in. However, it is necessary to ensure a path for discharging the vaporized liquid.

[0051] In this way, the casting of a piston using frozen core 10 is completed. The configuration of the cavity and its surroundings in the piston after the casting is completed will be described with reference to Fig. 7. Note that Fig. 7 only shows cavity 2d into which part of protrusion 10b is inserted and its surroundings, but cavity 2d into which part of protrusion 10c is inserted and its surroundings also have a similar configuration.

[0052] As shown in Figure 7, the piston 1 manufactured by casting using the frozen core 10 of this embodiment has a piston main body portion (metal portion) 2, granular material 3 filled in the hollow portion 2d of the piston main body portion 2, and protrusion portions 10b, 10c that remain partially protruding from the above-mentioned back surface portion 2c of the piston main body portion 2 (see Figure 6).

[0053] The granules 3 fill the cavity 2d to a volumetric extent of 35% to 55% of the volume of the cavity 2d, and are movable within the cavity 2d. As described above, the protrusions 10b, 10c are formed from a porous material, and the pore diameter is set to be larger than the size of the liquid molecules in the main body 10a of the frozen core 10 and smaller than the particle size of the granules 3. Therefore, after the mold 20 is opened and the vaporized liquid is discharged from the main body 10a of the frozen core 10 to the outside, the granules 3 are prevented from leaking out of the cavity 2d.

[0054] 5.Effects The frozen core (core) 10 according to this embodiment includes a main body 10a formed by freezing a mixture of liquid and granular material and protrusions 10b and 10c that serve as paths for the vaporized liquid to be discharged to the outside. When casting is performed using this frozen core 10, the liquid in the main body 10a is vaporized by the injection of molten metal, and the vaporized liquid is discharged to the outside through the protrusions 10b and 10c when the mold is opened. That is, when casting is performed using the frozen core 10 according to this embodiment, after the vaporized liquid is discharged when the mold is opened, the granular material 3 remains in the cavity 2d of the piston main body 2. Therefore, compared to casting using the core disclosed in Patent Document 2 (a core made of NaCl), casting using the frozen core 10 does not require steps such as core removal and subsequent filling with granular material. This reduces the number of steps required to produce the piston 1 by casting, thereby reducing manufacturing costs.

[0055] Furthermore, in the frozen core 10 according to this embodiment, the protrusions 10b, 10c are made of a porous material, so the vaporized liquid is discharged to the outside through the holes in the protrusions 10b, 10c, while the granules 3 remain within the cavity 2d. This makes it advantageous for use in manufacturing a piston 1 having a cavity 3 filled with granules 3.

[0056] Furthermore, in the frozen core 10 according to this embodiment, portions of the protrusions 10b, 10c (portions on the inner end face 10i side) are arranged in a state in which they penetrate into the interior of the main body 10a, and therefore the liquid vaporized by the heat of the molten metal is introduced into the protrusions 10b, 10c from around the penetrated portions of the protrusions 10b, 10c and is discharged to the outside of the piston main body 2. Therefore, in the frozen core 10, the contact area between the main body 10a and the protrusions 10b, 10c is wide, and the vaporized liquid can be discharged to the outside more smoothly when the mold is opened.

[0057] Furthermore, the frozen core 10 according to this embodiment is provided with two protrusions 10b, 10c, which makes it possible to more stabilize the position and posture of the frozen core 10 when it is placed in the cavity 20a, and also allows the vaporized liquid to be discharged more smoothly when the mold is opened. The number of protrusions on the frozen core can also be three or more. In this case, the same effects as those described above can be obtained.

[0058] Furthermore, in the frozen core 10 according to this embodiment, the mixture ratio of the liquid and the granular material in the main body 10a is set so that the filling rate of the granular material 3 in the hollow portion 2d of the piston main body 2 is in the range of 35% to 55% by volume, which makes it possible to prevent the movement of the granular material 3 from being hindered within the hollow portion 2d in the completed piston 1. This makes it possible to reduce the weight of the piston 1 and suppress vibration.

[0059] Furthermore, in the frozen core 10 according to this embodiment, water is used as the liquid in the main body 10a, which makes it easy to obtain, and even if it is discharged to the outside in a vaporized state, the environmental impact can be kept small.

[0060] In addition, when water is used as the liquid, for example, by using a core frozen at a temperature of -40°C or below, the time until the water comes into contact with the molten metal during casting and evaporates can be secured to a certain extent, which is advantageous in ensuring that the shape of the hollow portion 2d in the completed piston 1 is as designed.

[0061] As described above, by using the frozen core 10 according to this embodiment, it is possible to cast the piston 1 having the hollow portion 2d therein filled with the granular material 3 while suppressing an increase in the number of steps.

[0062] [Variation 1] The configuration of the frozen core 40 according to Modification 1 will be explained using Fig. 8. Note that Fig. 8 shows only a portion of the frozen core 40, but the overall external shape is the same as the frozen core 10 according to the above embodiment. Furthermore, the frozen core 40 according to this modification has the same configuration as the frozen core 10 according to the above embodiment, except for the shape of the protrusions 40b.

[0063] 8, the frozen core 40 according to this modification has a truncated cone-shaped protrusion 40b. The protrusion 40b is made of a porous material, similar to the protrusions 10b and 10c of the frozen core 10 according to the above embodiment.

[0064] A portion of the protrusion 40b, including the outer end surface 40h with a small diameter (diameter D1), extends outward from the main body 40a, while the remaining portion, including the inner end surface 40i with a large diameter (diameter D2), penetrates into the main body 40a. On the back surface 40f of the main body 40a, the portion from which the protrusion 40b extends is the extension portion 40k, which has an inner diameter D3. The portion of the protrusion 40b corresponding to the extension portion 40k is the intermediate portion 40l, and the outer diameter of the intermediate portion 40l is approximately the same as the inner diameter of the extension portion 40k. This prevents the granular material filled in the cavity of the cast piston from leaking out of the cavity.

[0065] In this modification, D3 is larger than D1, and D2 is larger than D3. This prevents the protrusions 40b from falling off the main body 40a when, for example, setting the frozen core 40 in the cavity of the mold. Furthermore, even after casting, it is possible to prevent the protrusions 40b from falling off the piston main body (metal part).

[0066] Furthermore, the frozen core 40 according to this modification has the same configuration as the frozen core 10 according to the above embodiment, except for the shape of the protrusions 40b, and can therefore achieve the same effects as above.

[0067] [Variation 2] The configuration of the frozen core 50 according to Modification 2 will be explained using Fig. 9. Note that Fig. 9 shows only a portion of the frozen core 50, but the overall external shape is the same as the frozen core 10 according to the above embodiment. Furthermore, the frozen core 50 according to this modification has the same configuration as the frozen core 10 according to the above embodiment, except for the manner in which the protrusions 50b penetrate into the main body 50a.

[0068] 9, in the frozen core 50 according to this modification, the protrusion 50b is formed of a cylindrical porous material, as in the frozen core 10 according to the above embodiment. In this modification, the top end face 50i of the protrusion 50b (the end face that will be located on the top surface side of the piston head after casting) is disposed so as to reach approximately the same height as the top surface 50e of the main body 50a. However, the top end face 50i of the protrusion 50b may extend so as to be located away from the top surface 50e of the main body 50a.

[0069] The frozen core 50 according to this modification, which includes the protrusions 50b shown in Fig. 9, allows vaporized liquid to be more smoothly discharged to the outside when the mold is opened during casting of the piston. Specifically, the protrusions 50b are arranged so as to reach the top surface 50e of the main body 50a, so that vaporized liquid over a wide range in the height direction of the main body 50a (indicated by arrow B) is captured by the protrusions 50b, and the captured liquid is discharged to the outside from the portion exposed from the piston main body, including the outer end surface 50h. Therefore, casting using the frozen core 50 according to this modification makes it difficult for liquid to remain in the cavity of the piston, allowing the granular material to move more easily within the cavity, which is advantageous for producing a piston (cast member) with reduced vibration.

[0070] Furthermore, when a piston is manufactured by casting using frozen core 50 according to this modification, top end surface 50i of protrusion 50b abuts against the piston main body (metal portion). Therefore, in the manufactured piston, protrusion 50b also functions as a reinforcing member that supports the cavity of the piston.

[0071] The frozen core 50 of this modified example differs from the frozen core 10 of the above embodiment only in the arrangement of the protrusion portion 50b relative to the main body portion 50a, and the other configurations are the same, so that the same effects as those of the frozen core 10 of the above embodiment can be obtained.

[0072] [Variation 3] Among the configurations of the frozen core according to Modification 3, the configuration of the protruding member 60 that constitutes the protruding portion will be described with reference to FIG. 10(a).

[0073] As shown in Figure 10(a), the protruding member 60 used to form the frozen core according to this modification has a cylindrical peripheral wall 60c that surrounds a hollow portion 60a, and an end wall 60b that closes one opening of the cylinder formed by the peripheral wall 60c. The peripheral wall 60c and the end wall 60b are integrally formed or joined without any gaps. In this modification, the other opening of the cylinder formed by the peripheral wall 60c is left as an opening 60d.

[0074] As shown in the enlarged portion of Figure 10(a), the peripheral wall 60c and the end wall 60b are provided with a plurality of holes 60e. The diameter of the holes 60e is set to be larger than the size of the liquid molecules contained in the main body and smaller than the particle size of the granular material. There are no particular restrictions on the material that can be used to form the peripheral wall 60c and the end wall 60b, but porous metals, porous ceramics, etc. can also be used.

[0075] The frozen core formed using the protrusion member 60 shown in Figure 10(a) can also achieve the same effects as the frozen core 10 according to the above embodiment. Furthermore, because the protrusion member 60 has a hollow portion 60a, it can be made lighter than when a solid protrusion is used.

[0076] [Variation 4] Among the configurations of the frozen core according to Modification 4, the configuration of the protruding member 70 that constitutes the protruding portion will be described with reference to FIG. 10(b).

[0077] As shown in Fig. 10(b), the protruding member 70 used to form the frozen core according to this modification has a cylindrical member 71 and a porous member 72. The cylindrical member 71 is made of metal or ceramics and has a hollow portion. 71a The porous member 72 has a cylindrical shape surrounding the hollow portion 71a of the cylindrical member 71. The porous member 72 is made of porous metal or porous ceramics, and is disposed in a part of the hollow portion 71a of the cylindrical member 71. The inner peripheral surface of the cylindrical member 71 and the outer peripheral surface of the porous member 72 are joined together so that there is almost no gap between them.

[0078] When forming a frozen core using the protrusion member 70 shown in Figure 10(b), the side of the protrusion member 70 on which the porous member 72 is arranged is inserted into the main body, and the other side is extended from the main body.

[0079] Here, the pore diameter of the porous member 72 is set to be larger than the size of the liquid molecules contained in the main body portion and smaller than the particle size of the granular material.

[0080] 10(b) can also achieve the same effects as the frozen core 10 according to the above embodiment. Furthermore, in the protruding member 70, the porous member 72 is not disposed in part of the hollow portion 71a of the cylindrical member 71, so the weight can be reduced compared to when protruding members are made of solid porous members.

[0081] [Variation 5] The configuration of a frozen core 80 according to Modification 5 will be described using Fig. 11. Note that the frozen core 80 according to this modification is the same as that of the above embodiment except for the number and arrangement of the protrusions 80b, 80c, 80m, and 80n, and therefore the following description will focus on the differences from the above embodiment.

[0082] 11, like the frozen core 10 according to the above embodiment, the frozen core 80 according to this modified example also has two protrusions 80b, 80c protruding from the back surfaces 80f, 80g of the main body 80a. In addition to the two protrusions 80b, 80c, the frozen core 80 according to this modified example has two more protrusions 80m, 80n.

[0083] The protrusions 80m, 80n are provided so as to partially protrude downward from bottom surfaces 80p, 80r of skirt-corresponding portions 80o, 80q of the main body 80a that correspond to the skirt of the piston after casting. When an imaginary line Ln1 connecting the protruding ends of the protrusions 80b and 80c and an imaginary line Ln2 connecting the protruding ends of the protrusions 80m and 80n are imagined, the protrusions 80b, 80c, 80m, and 80n are arranged so that the imaginary line Ln1 and the imaginary line Ln2 are substantially perpendicular to each other in a plan view.

[0084] The frozen core 80 of this modified example is configured to have four protrusions 80b, 80c, 80m, and 80n, so that when the frozen core 80 is placed in the cavity of the mold, the posture and position of the frozen core 80 within the cavity can be more reliably maintained.

[0085] Furthermore, the frozen core 80 of this modified example is the same as the frozen core 10 of the above embodiment, except for the number of protrusions 80b, 80c, 80m, and 80n formed, and therefore can obtain the same effects as the frozen core 10 of the above embodiment.

[0086] [Other variations] In the above embodiment and modified examples 1 and 2, frozen cores 10, 40, and 50 having two protrusions 10b, 10c, 40b, and 50b are used, and in modified example 5, frozen core 80 having four protrusions 80b, 80c, 80m, and 80n is used, but the present invention is not limited to this. For example, it is also possible to use a frozen core having one, three, or five or more protrusions.

[0087] Furthermore, in the above embodiments, the mixture ratio of the liquid to the granular material in the main body 10a, 40a, 50a, 80a of the frozen core 10, 40, 50, 80 is specified so that the granular material 3 in the completed piston 1 is in the range of 35% to 55% by volume of the volume of the cavity 2d, but the present invention is not limited to this. For example, the mixture ratio of the liquid to the granular material in the main body of the frozen core may be specified so that the granular material is less than 35% by volume or more than 55% by volume of the volume of the cavity.

[0088] In addition, in the above embodiments, water is used as the liquid to form the main body 10a, 40a, 50a, 80a of the frozen core 10, 40, 50, 80, but the present invention is not limited to this. For example, alcohol or an alcohol-water solution may also be used.

[0089] In the above-described embodiments, the protrusions 10b, 10c, 40b, 50b, 80b, 80c, 80m, and 80n are arranged in a state where they partially penetrate into the main body 10a, 40a, 50a, and 80a, but the present invention is not limited to this. If the protrusions are arranged so that they partially contact the mixture that constitutes the main body, they can be used as a path for discharging liquid that has evaporated due to the heat of the molten metal to the outside.

[0090] In the above-described embodiments, the freeze-thaw cores 10, 40, 50, and 80 are used to cast a piston 1 to be incorporated into an engine of a vehicle or the like. However, the present invention is not limited to this. For example, the freeze-thaw cores can be used to manufacture cast parts that are automobile components, such as axle knuckles, connecting rods, cranks, tire wheels, cylinder blocks, intake manifolds, motor housings, and gear cases. In addition to automobile parts, the freeze-thaw cores can also be used to manufacture cast parts for railway vehicles, such as wheels, motors, and inverter cases; cast parts used in infrastructure, such as water pumps, piping, and heat sinks; machine tool frames, such as robot arms; and building materials. [Explanation of symbols]

[0091] 2d cavity 3 granules 10,40,50,80 Frozen Neutrons 10a,40a,50a,80a Main body 10b, 10c, 40b, 50b, 80b, 80c, 80m, 80n protrusions 60,70 protruding parts

Claims

1. A casting core to be placed in a cavity of a mold when producing a cast member having a hollow portion filled with granular material, a main body portion having a mixture of a liquid and the particulate material and frozen in a state having the shape of the hollow portion; a protrusion extending outward from the main body and in contact with the mold, with a portion of the protrusion being in contact with the mixture and integral with the main body; Equipped with the protrusion has a plurality of holes formed so that the vaporized liquid can be discharged to the outside from a portion in contact with the mixture when the mold is opened. Middle child.

2. The core according to claim 1, The protrusion is made of a porous member having a plurality of pores, each pore size of which is smaller than the particle size of the granular material. Middle child.

3. The core according to claim 1 or 2, The protrusion is formed of a columnar member, and one end is disposed inside the main body. Middle child.

4. The core according to claim 3, The protrusion has a frustum shape in which the area of ​​the one end is larger than the area of ​​the other end. Middle child.

5. The core according to claim 1 or 2, The protrusion is formed of a columnar member and penetrates the main body so that both ends are disposed outside the main body. Middle child.

6. The core according to any one of claims 1 to 5, The protrusions are provided in plurality. Middle child.

7. The core according to any one of claims 1 to 6, The amount of the granular material mixed in the main body is specified so that the granular material is filled in the hollow portion in a range of 35% by volume or more and 55% by volume or less. Middle child.

8. The core according to any one of claims 1 to 7, The liquid is water. Middle child.

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