High-temperature molding die

Abstract

This high-temperature molding die comprises: an outer mold including a holding surface; and an inner mold including an outer surface at least a part of which is adjacent to the holding surface, and an inner surface that defines a molding chamber. When the temperature of the outer mold and the inner mold before high-temperature molding is T, the temperature rise accompanying the high-temperature molding is ΔT, the thermal expansion coefficient of the inner mold in a temperature region from the temperature T to a temperature T+ΔT is α, and the thermal expansion coefficient of the outer mold is β, the relationship of a formula (1) is satisfied.　Formula: (1) α>β.

Description

Mold for high temperature molding

[0001] The present invention relates to a mold for forming a workpiece at high temperatures.

[0002] During high-temperature molding using a mold, thermal expansion can make it difficult to remove the workpiece from the mold. During high-temperature molding, the mold not only thermally expands, but also becomes larger than its initial dimensions due to elastic deformation caused by the molding load. When the high-temperature environment is removed by cooling after molding, if the amount of thermal contraction and elastic deformation of the mold is greater than the amount of thermal contraction of the workpiece, the workpiece cannot be removed from the mold. For this reason, a tapered mold structure is known in which the mold has a two-layer structure consisting of an inner mold and an outer mold, the inner mold is split, and the inner mold and outer mold are fitted together at a taper (see, for example, Patent Document 1).

[0003] However, tapered dies require machining into a tapered shape during production, which makes it difficult to achieve precision and tends to result in high machining costs. Furthermore, it may be necessary to actually assemble the inner and outer dies and perform a finish machining process to fit them together. In this case, it is essential to use and store the adjusted inner and outer dies as a set. Therefore, in forming devices that use multiple dies to perform hot forming, there is a problem of increased effort in managing and storing the dies.

[0004] Patent No. 3050866

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a mold for high-temperature molding that is easy to remove the workpiece from and easy to manage.

[0006] A high-temperature molding die according to one aspect of the present invention comprises an outer die including a holding surface, an inner die including an outer surface at least partially adjacent to the holding surface, and an inner surface that defines a molding chamber, and satisfies the relationship of the following formula (1), where T is the temperature of the outer die and the inner die before high-temperature molding, ΔT is the temperature rise associated with high-temperature molding, α is the thermal expansion coefficient of the inner die in the temperature range from temperature T to temperature T + ΔT, and β is the thermal expansion coefficient of the outer die. (1) (1) α>β

[0007] According to the present invention, it is possible to provide a mold for high-temperature forming that is easy to remove the workpiece and easy to manage.

[0008] FIG. 1 is a schematic diagram of a molding apparatus to which a high-temperature molding die according to the present invention is applied. FIG. 2 is a cross-sectional view showing a high-temperature molding die according to a first embodiment of the present invention, which has a molding chamber with a rectangular cross section. FIG. 3 is a cross-sectional view showing a high-temperature molding die according to a modified example of the first embodiment, which has a molding chamber with a circular cross section. FIG. 4 is a cross-sectional view showing a high-temperature molding die according to a modified example of the first embodiment, in which a partition plate is arranged within the molding chamber. FIG. 5 is a cross-sectional view showing a high-temperature molding die according to a second embodiment, in which a molding chamber with a rectangular cross section is partitioned by a split inner mold. FIG. 6 is a cross-sectional view showing a high-temperature molding die according to a modified example of the second embodiment, in which a molding chamber with a circular cross section is partitioned by a split inner mold. FIG. 7 is a cross-sectional view showing a high-temperature molding die according to a modified example of the second embodiment, which uses a split inner mold with different thermal expansion coefficients. FIG. 8 is a cross-sectional view showing a high-temperature molding die according to a modified example of the second embodiment, in which a partition plate is arranged within the molding chamber. FIG. 9 is a cross-sectional view showing a high-temperature molding die according to a third embodiment, in which a molding chamber with a rectangular cross section is partitioned by two split inner mold layers. Fig. 10 is a cross-sectional view showing a high-temperature molding die using a split inner die having a different thermal expansion coefficient, which is a modified example of the third embodiment. Fig. 11 is a cross-sectional view showing a high-temperature molding die using a split inner die having a different thermal expansion coefficient, which is a modified example of the third embodiment. Fig. 12A is a top view showing a modified outer die. Fig. 12B is a cross-sectional view taken along line XIIB-XIIB of Fig. 12A. Fig. 13A is a top view showing a modified outer die. Fig. 13B is a cross-sectional view taken along line XIIIB-XIIIB of Fig. 13A.

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. The mold according to the present invention is a mold for high-temperature forming used at high temperatures of several hundred degrees Celsius, and is used for processes such as sintering, which involves heating and pressurizing sintered materials such as powders or solid pieces of metals or ceramics; die casting, which involves pressure-molten metal forming; and diffusion bonding, which involves joining different materials or the same materials together. That is, the mold is a high-temperature forming mold used to produce high-precision molded products by pressing a heated workpiece contained in the mold to transfer the shape of the inner wall surface of the mold to the workpiece. Furthermore, the mold according to the present invention can also diffusion-bond different materials or the same materials together without using a press.

[0010] 1 is a longitudinal cross-sectional view schematically showing a molding apparatus 1 used for molding sintered products, etc., and illustrates a preferred application of a mold 2 for high-temperature molding according to the present invention. The mold 2 has a molding chamber 20 for molding a workpiece MP. The mold 2 has a two-layer structure consisting of at least an inner mold and an outer mold in the direction from the molding chamber 20 toward the outside. The mold structure will be described in detail below.

[0011] The forming apparatus 1 includes an upper punch 11 that presses the workpiece MP in the forming chamber 20, and a lower punch 12 that receives the workpiece MP to be pressed. An upper backing 13 that applies a pressing force is attached to the upper punch 11. The lower punch 12 may use a backing that receives the press load, or, as shown in FIG. 1, may be attached with a lower backing 14 that is supported by a cushion mechanism that controls the load applied to the workpiece. The forming apparatus 1 also includes heating means for the mold 2. The heating means may be, for example, an electric heating or induction heating device for the mold 2, or a heating furnace that houses the forming apparatus 1.

[0012] In the case of high-temperature molding using the mold 2 as described above, in which the workpiece MP is pressed against the inner wall surface of the molding chamber 20, the mold 2 thermally expands and becomes larger than its initial dimensions due to elastic deformation caused by the molding load of the press. Upon cooling after molding, the dimensions of the mold 2 and the workpiece MP become smaller than in the high-temperature environment. However, if the amount of thermal contraction of the mold 2 is greater than the amount of thermal contraction of the workpiece MP, the workpiece MP cannot be removed from the mold 2.

[0013] One way to solve this problem is to use a tapered mold, but as mentioned above, this requires a matched finish, which is problematic as it requires time and effort in mold management. In this invention, by providing a difference in thermal expansion coefficients between the constituent materials of the inner and outer molds, we provide a mold 2 for high-temperature molding that makes it easy to achieve precision and remove the workpiece MP and also simplifies the time and effort required for mold management. Various specific examples of such a mold 2 are described below.

[0014] 2 is a horizontal cross-sectional view showing a high-temperature molding die 2A according to a first embodiment of the present invention, which has a molding chamber with a rectangular cross-section. The die 2A has a molding chamber 20 with a rectangular cross-section that accommodates a workpiece MP that will ultimately become a molded product. The die 2A is composed of an outer die 3 and an inner die 4 whose periphery is surrounded by the outer die 3.

[0015] The outer mold 3 has a rectangular frame shape in cross section and a rectangular inner wall surface 301 that serves as a holding surface for the inner mold 4. The inner mold 4 includes an outer surface 401 adjacent to the inner wall surface 301 of the outer mold 3 and an inner surface 402 that defines the molding chamber 20. The inner wall surface 301 surrounds the four sides of the inner mold 4. The inner mold 4 also has a rectangular frame shape in cross section. Examples of mold materials that constitute the outer mold 3 and the inner mold 4 include metallic materials, non-metallic materials, composite materials of metallic and non-metallic materials, cermet materials, and ceramic materials. Examples of metallic materials include cemented carbide, tool steel, aluminum alloys, copper alloys, and magnesium alloys. Examples of non-metallic materials include graphite, plastic-formed carbon, CFRP, and carbon composites. Examples of cermet materials include titanium carbonitride, and examples of ceramic materials include alumina, silicon nitride, and zirconia.

[0016] Of the mold materials listed above, a material that has greater thermal expansion and contraction than the material that makes up the outer mold 3 in a specified temperature range is selected as the material that makes up the inner mold 4. Here, the temperature of the outer mold 3 and inner mold 4 before high-temperature molding is T, and the temperature rise that accompanies high-temperature molding is ΔT. Temperature T is also the temperature at the time the molded product is removed from the mold 2A. ΔT is the temperature difference between the time of high-temperature molding and the time the molded product is removed. Also, the thermal expansion coefficient of the inner mold 4 in the temperature range from temperature T to temperature T+ΔT is α, and the thermal expansion coefficient of the outer mold 3 is β. In this case, the mold 2A satisfies the relationship of the following formula (1): (1) α>β

[0017] Furthermore, the outer dimension of the inner mold 4 in the direction along one center line CL passing through the center of the molding chamber 20 is defined as A, and the inner dimension of the outer mold 3 is defined as B. In this case, it is desirable that the mold 2A satisfy the relationship of the following formula (2): (2) α×A×ΔT>β×B×ΔT

[0018] According to the above-described mold 2A, as shown in Equation (1), the thermal expansion coefficient α of the inner mold 4 is greater than the thermal expansion coefficient β of the outer mold 3. Therefore, during hot forming, where high-temperature molding is performed, the inner mold 4 expands inward while its periphery is constrained by the outer mold 3. Therefore, when a workpiece MP (FIG. 1) is placed in the molding chamber 20 and heated and pressed, the pressing force of the workpiece MP against the inner surface 402 of the inner mold 4 is increased. This allows the inner shape of the molding chamber 20 to be effectively transferred to the workpiece MP, enabling highly accurate molding. Furthermore, during hot forming, the inner mold 4 presses against the outer mold 3, forming a tight fit, which has the advantage of improving the strength of the mold 2A.

[0019] On the other hand, in the cold state after the mold is cooled, the inner mold 4 experiences a greater degree of thermal shrinkage than the outer mold 3. That is, as shown in Equation (2), the outer dimension A of the inner mold 4 is greater than the inner dimension B of the outer mold 3 in terms of the amount of thermal expansion and contraction within the temperature range ΔT. That is, when the temperature is lowered from a hot state to a cold state, the inner mold 4 shrinks more than the outer mold 3. This makes it easier to form a gap between the outer surface 401 of the inner mold 4 and the inner wall surface 301 of the outer mold 3, facilitating the release of the inner mold 4 from the outer mold 3. If the thermal expansion coefficient α of the inner mold 4 is set smaller than the thermal expansion coefficient of the workpiece MP, the workpiece MP will shrink more than the inner mold 4 within the molding chamber 20. Therefore, even with a non-split inner mold 4, the molded product of the workpiece MP can be easily removed from the inner mold 4.

[0020] As described above, the mold 2A utilizes the difference in thermal expansion coefficient between the inner mold 4 and the outer mold 3 to improve molding accuracy and remove the workpiece MP. This eliminates the need for finish machining, as is required with tapered molds. This eliminates the need to manage and store the inner mold 4 and outer mold 3 as a set, making mold management easier.

[0021] 3 is a cross-sectional view showing a high-temperature molding die 2B, a modified example of the first embodiment, which includes a molding chamber 20 that is circular in horizontal cross section. The die 2B is composed of an outer die 3 having a frame shape with a circular cross section and an inner die 4 that is surrounded by the outer die 3. The inner die 4 includes a cylindrical outer surface 401 adjacent to the cylindrical inner wall surface 301 of the outer die 3, and a cylindrical inner surface 402 that defines the molding chamber 20.

[0022] In the mold 2B, the relationship between the thermal expansion coefficient α of the inner mold 4 and the thermal expansion coefficient β of the outer mold 3 is as shown in Equation (1) above. Furthermore, the relationship between the outer dimensions of the inner mold 4 and the inner dimensions of the outer mold 3 along the center line CL passing through the center of the molding chamber 20, i.e., the relationship between the amount of thermal expansion and contraction in the temperature range ΔT when the diameter of the inner mold 4 is A and the inner diameter of the outer mold is B, is as shown in Equation (2) above. Even in a mold with a circular cross section like the mold 2B, by satisfying the relationships of Equation (1) and (2), the inner mold 4 shrinks more than the outer mold 3 in the cold state. Therefore, the ease of removing the molded product of the workpiece MP from the mold 2B can be improved.

[0023] FIG. 4 is a cross-sectional view showing a high-temperature molding die 2C according to another modification of the first embodiment. The structure of the outer die 3 and inner die 4 of the die 2C is the same as that of the die 2A shown in FIG. 2 . The only difference is that a partition plate 5 is disposed within the molding chamber 20 of the inner die 4. FIG. 4 shows an example in which two partition plates 5 are disposed at equal intervals along the center line CL. The two partition plates 5 divide the molding chamber 20 into three small chambers 20A. A workpiece MP is loaded into each small chamber 20A, and high-temperature molding is performed. In other words, the die 2C can simultaneously produce three molded products in one molding run.

[0024] [Second Embodiment] Figure 5 is a horizontal cross-sectional view showing a high-temperature molding die 2D according to the second embodiment, in which a rectangular cross-sectional molding chamber 20 is defined by a split inner die. The die 2D is composed of an outer die 3 and an inner die 4A surrounded by the outer die 3. The inner die 4A has an outer surface 401 adjacent to the inner wall surface 301 of the outer die 3 and an inner surface 402 that defines the rectangular cross-sectional molding chamber 20. This is similar to the die 2A of the first embodiment. The die 2D differs from the die 2A of the first embodiment in that the inner die 4A of the die 2D is a split die formed by an assembly of a pair of first split dies 41 and a pair of second split dies 42. The split inner die 4A facilitates removal of the molded product from the inner die 4A after high-temperature molding of the workpiece MP.

[0025] The pair of first split molds 41 are mold halves each having a rectangular cross section and are arranged opposite each other across the center line CL of the molding chamber 20. The pair of second split molds 42 are mold halves each having a rectangular cross section and are arranged in a direction intersecting the center line CL, more specifically, in a direction perpendicular to the center line CL. One second split mold 42 is arranged adjacent to one end 411 of the first split mold 41 and closes the space between the pair of one ends 411. The other second split mold 42 is arranged adjacent to the other end 412 of the first split mold 41 and closes the space between the pair of other ends 412.

[0026] The first split mold 41 and the second split mold 42 are made of the same mold material. That is, the thermal expansion coefficient of the first split mold 41 and the second split mold 42 in the temperature range from temperature T to temperature T+ΔT is α. The thermal expansion coefficient of the outer mold 3 is β, and the relationship α>β is set as shown in formula (1). Regarding the amount of thermal expansion and contraction, the mold 2D satisfies the relationship of the following formula (3), where A1 is the dimension of the first split mold 41 along the center line CL and A2 is the dimension of one of the second split molds 42 along the center line CL. (3) α×A1×ΔT+2×(α×A2×ΔT)>β×B×ΔT

[0027] According to the mold 2D of the second embodiment, an inner mold 4A is used, which is made up of a pair of first split molds 41 and a pair of second split molds 42. In the temperature range of ΔT, the amount of thermal expansion and contraction of the total outer dimension A1 + 2 × A2 of the split mold pair constituting the inner mold 4A is greater than the amount of thermal expansion and contraction of the inner dimension B of the outer mold 3. This improves the molding accuracy of the workpiece MP, and also allows the inner mold 4A, which is made up of the split mold pair, to be reliably released from the outer mold 3. This also makes it easier to remove the molded product from the inner mold 4A.

[0028] FIG. 6 is a horizontal cross-sectional view of a high-temperature molding die 2E, a modified example of the second embodiment, in which a molding chamber 20 having a circular cross section is partitioned by a split inner die 4B. The die 2E is composed of an outer die 3 having a circular cross-sectional frame shape and an inner die 4B having a circular cross-sectional frame shape surrounded by the outer die 3. The split inner die 4B is composed of arc-shaped segments formed by dividing a cylinder having its center at the center of the molding chamber 20 into multiple segments in the circumferential direction. FIG. 6 illustrates an inner die 4B divided equally into four segments in the circumferential direction. The inner die 4B includes a cylindrical outer surface 401 adjacent to the cylindrical inner wall surface 301 of the outer die 3 and a cylindrical inner surface 402 that partitions the molding chamber 20. The inner die 4B may be divided into three or fewer segments, five or more segments, or even equally.

[0029] Specifically, the inner mold 4B is composed of a pair of first arc-segmented molds 45 that face each other along one center line CL that passes through the center of the molding chamber 20, and a pair of second arc-segmented molds 46 that are arranged facing each other across the center line CL. The annular inner mold 4B is configured in such a manner that the pair of second arc-segmented molds 46 close two circumferential gaps between the pair of first arc-segmented molds 45, respectively.

[0030] The first arc-segmented mold 45 and the second arc-segmented mold 46 are made of the same mold material. That is, the thermal expansion coefficient of the first arc-segmented mold 45 and the second arc-segmented mold 46 in the temperature range from temperature T to temperature T+ΔT is α. The thermal expansion coefficient of the outer mold 3 is β, and the relationship α>β is set as shown in formula (1). Regarding the amount of thermal expansion and contraction, the mold 2E satisfies the relationship of formula (5) below, where A3 is the distance between the first arc-segmented molds 45 on the center line CL and A4 is one dimension (thickness) of the first arc-segmented mold 45 along the center line CL. (5) α×(A3+2×A4)×ΔT>β×B×ΔT

[0031] 6, when the inner mold 4B is configured by combining the first arc-shaped segmented mold 45 and the second arc-shaped segmented mold 46, the amount of thermal expansion and contraction of the outer dimension A3 + 2 × A4 of the inner mold 4B is greater than the amount of thermal expansion and contraction of the inner dimension B of the outer mold within the temperature range ΔT. This improves the molding accuracy of the workpiece MP, and also enables the inner mold 4B, which is made up of a segmented mold pair, to be reliably released from the outer mold 3. Furthermore, because the inner mold 4B is segmented, it is easy to remove the molded product from the inner mold 4B.

[0032] FIG. 7 is a horizontal cross-sectional view of a high-temperature molding die 2F, a modified example of the second embodiment, using a split inner die 4A with a different thermal expansion coefficient. The structure of the outer die 3 and split inner die 4A of the die 2F is the same as that of the die 2D shown in FIG. 5 . The difference is that the thermal expansion coefficients of the first split die 41 and the second split die 42 are different. For example, depending on the shape of the molded product, i.e., the shape of the molding chamber 20, the amount of thermal expansion and contraction along the center line CL may differ significantly from that in the direction perpendicular to the center line CL. In this case, adjusting the thermal expansion coefficients of the first split die 41 and the second split die 42 in the split inner die 4A can improve the ease of removal of the molded product.

[0033] Regarding the amount of thermal expansion and contraction, when the thermal expansion coefficient of the first split mold 41 is α1 and the thermal expansion coefficient of the second split mold 42 is α2 in the temperature range from temperature T to temperature T+ΔT, the mold 2F satisfies the relationship of the following formula (4): (4) α1×A1×ΔT+2×(α2×A2×ΔT)>β×B×ΔT (where α1>β, α2>β).

[0034] Figure 8 is a cross-sectional view showing a high-temperature molding die 2G according to another modification of the second embodiment. The structure of the outer die 3 and the split inner die 4A of the die 2G is the same as that of the die 2D shown in Figure 5. The only difference is that two partition plates 5 are disposed within the molding chamber 20 of the inner die 4A. The two partition plates 5 divide the molding chamber 20 into three small chambers 20A. A workpiece MP is loaded into each small chamber 20A, and high-temperature molding is performed. In other words, the die 2G can simultaneously produce three molded products in one molding run.

[0035] In the mold 2G, the thermal expansion coefficient of the contents in the molding chamber 20 may be taken into consideration. In the mold 2G, the contents are the partition plate 5 and the workpiece MP loaded into the small chamber 20A. If the thermal expansion / contraction of the contents along the center line CL is smaller than that of the first split mold 41 along the center line CL, this may hinder the release of the inner mold 4A from the outer mold 3. For example, if the thermal contraction of the contents is smaller than that of the first split mold 41 when transitioning from a hot state to a cold state, the contents may press the second split mold 42 against the inner wall surface 301 of the outer mold 3. In this case, it is desirable to set the thermal expansion / contraction of the inner mold 4A, including the contents, to be larger than that of the outer mold. In other words, the thermal expansion / contraction of the contents may be taken into consideration in addition to the thermal expansion / contraction of the first split mold 41 along the center line CL.

[0036] Here, when the coefficient of thermal expansion of the partition plate 5 is δ, the coefficient of thermal expansion of the workpiece MP loaded in the small chamber 20A is ε, the dimension of the partition plate 5 along the center line CL is D, the dimension of the small chamber 20A along the center line CL is E, the number of parallel partition plates 5 is N1, and the number of parallel chambers 20A is N2, the configuration may further satisfy the relationship of the following formula (3-1) in addition to the above formula (3). (3-1) 2×(α×A2×ΔT)+δ×D×ΔT×N1+ε×E×ΔT×N2>β×B×ΔT

[0037] [Third Embodiment] Figure 9 is a cross-sectional view showing a high-temperature molding die 2H according to a third embodiment, in which a molding chamber 20 having a rectangular cross section is partitioned by two layers of split inner molds. The die 2H is composed of an outer mold 3 and an inner mold 4C whose periphery is surrounded by the outer mold 3. The inner mold 4C is a split frame body and has a two-layer structure consisting of a first inner mold layer 40A and a second inner mold layer 40B whose periphery is surrounded by the first inner mold layer 40A. The die 2H is a configuration in which an additional split inner mold is placed inside the inner mold 4A of the die 2D shown in Figure 5.

[0038] The first inner mold layer 40A of the inner mold 4C is formed by an assembly of a pair of first split molds 41 and a pair of second split molds 42. The pair of first split molds 41 are arranged opposite each other across the center line CL of the molding chamber 20. The pair of second split molds 42 are arranged in a direction perpendicular to the center line CL. One second split mold 42 is arranged adjacent to one end 411 of the first split mold 41 and closes the space between the pair of one ends 411. The other second split mold 42 is arranged adjacent to the other end 412 of the first split mold 41 and closes the space between the pair of other ends 412.

[0039] The second inner mold layer 40B defines the molding chamber 20. The second inner mold layer 40B is formed by an assembly of a pair of third split molds 43 and a pair of fourth split molds 44, which are arranged along the inner surface 402 of the area defined by the first inner mold layer 40A. The pair of third split molds 43 are mold halves each having a rectangular cross section and are arranged opposite each other across the center line CL of the molding chamber 20. The pair of second split molds 42 are mold halves each having a rectangular cross section and are arranged in a direction perpendicular to the center line CL. One fourth split mold 44 is arranged adjacent to one end 431 of the third split mold 43 and closes the space between the pair of ends 431. The other fourth split mold 44 is arranged adjacent to the other end 432 of the third split mold 43 and closes the space between the pair of ends 432. The outer surface 403 of the second inner mold layer 40B abuts against the inner surface 402 of the first inner mold layer 40A. The inner surface 404 of the second inner mold layer 40B becomes the inner wall surface that defines the molding chamber 20.

[0040] In the hot mold 2H, the first inner mold layer 40A, whose outward expansion is restricted by the outer mold 3, expands inward, pushing the second inner mold layer 40B inward. In the direction of extension of the center line CL, one end 431 and the other end 432 of the third split mold 43 of the second inner mold layer 40B abut against the fourth split mold 44. In the direction intersecting the center line CL, the side surface of the second inner mold layer 40B abuts against the inner surface 402 of the first inner mold layer 40A. Therefore, with the mold 2H equipped with a split inner mold 4C having a two-layer structure, the dimensions inside the molding chamber 20 are as designed, and there are no gaps between the split molds, which has the advantage of suppressing the occurrence of burrs.

[0041] In the mold 2H, the first split mold 41 and the second split mold 42 both have a coefficient of thermal expansion α in the temperature range from temperature T to temperature T+ΔT. The third split mold 43 and the fourth split mold 44 both have a coefficient of thermal expansion γ in the temperature range from temperature T to temperature T+ΔT. Note that α = γ may also be true. The thermal expansion coefficient of the outer mold 3 is β, and the relationship α > β is set as shown in formula (1). Regarding the amount of thermal expansion, the mold 2H is set to satisfy the relationship of formula (6) or (7) below, where A1 is the dimension of the first split mold 41 along the center line CL, A2 is one dimension of the second split mold 42 along the center line CL, C1 is the dimension of the third split mold 43 along the center line CL, and C2 is one dimension of the fourth split mold 44 along the center line CL. (6) α×A1×ΔT + 2×(α×A2×ΔT)>β×B×ΔT (where α>γ) (7) 2×(α×A2×ΔT) + γ×C1×ΔT + 2×(γ×C2×ΔT)>β×B×ΔT (where α<γ)

[0042] According to the mold 2H, the inner mold 4C has a multi-layer structure in which a first inner mold layer 40A, consisting of a pair of first split molds 41 and a pair of second split molds 42, is enclosed within a second inner mold layer 40B, consisting of a pair of third split molds 43 and a pair of fourth split molds 44. Furthermore, taking into account the difference in thermal expansion coefficients between the first inner mold layer 40A and the second inner mold layer 40B, the total outer dimensions of the inner mold 4C are set larger than the inner dimensions of the outer mold 3 with respect to the amount of thermal expansion and contraction within the temperature range ΔT. This improves molding accuracy and ensures that the inner mold 4C, formed from two split mold layers, can be reliably released from the outer mold 3. Note that, in the third embodiment, a partition plate 5 may be placed in the molding chamber 20 to partition multiple small chambers 20A, as in the modified example of the second embodiment shown in FIG. 8. This allows multiple molded products to be produced simultaneously in a single molding run.

[0043] Figure 10 is a cross-sectional view showing a modified example of the third embodiment, a high-temperature molding die 2I equipped with an inner die 4C formed using split dies with different thermal expansion coefficients. The structure of the outer die 3 and split inner die 4C of the die 2I is the same as that of the die 2H shown in Figure 9. The difference is that the thermal expansion coefficients of the first split die 41 and the second split die 42 of the first inner die layer 40A are different. The thermal expansion coefficients of the third split die 43 and the fourth split die 44 of the second inner die layer 40B are the same value, γ.

[0044] Regarding the amount of thermal expansion and contraction, the mold 2I is set to satisfy the following relationships: (6-1) or (7-1), which are obtained by rewriting the above equations (6) and (7) as follows: where the thermal expansion coefficient of the first split mold 41 is α1 and the thermal expansion coefficient of the second split mold 42 is α2 in the temperature range from temperature T to temperature T + ΔT. (6-1) α1 × A1 × ΔT + 2 × (α2 × A2 × ΔT) > β × B × ΔT (where α1 > γ) (7-1) 2 × (α2 × A2 × ΔT) + γ × C1 × ΔT + 2 × (γ × C2 × ΔT) > β × B × ΔT (where α1 < γ). Note that even in this modification, a partition plate 5 may be disposed in the molding chamber 20 to partition multiple small chambers 20A, as in the modification of the second embodiment shown in FIG. 8. This allows multiple molded products to be produced simultaneously in a single molding run.

[0045] 11 is a cross-sectional view showing a high-temperature molding die 2J, another variation of the third embodiment, including an inner die 4C formed using split dies with different thermal expansion coefficients. The outer die 3 and split inner die 4C of the die 2J are identical in structure to the die 2H shown in FIG. 9. The differences are that the thermal expansion coefficients of the first split die 41 and the second split die 42 of the first inner die layer 40A are different, the thermal expansion coefficients of the third split die 43 and the fourth split die 44 of the second inner die layer 40B are different, and two partition plates 5 are provided in the molding chamber 20.

[0046] In mold 2J, the thermal expansion coefficient of first split mold 41 in the temperature range from temperature T to temperature T+ΔT is assumed to be α1, the thermal expansion coefficient of second split mold 42 is α2, the thermal expansion coefficient of third split mold 43 is γ1, and the thermal expansion coefficient of fourth split mold 44 is γ2. In this case, mold 2J is set so that the amount of thermal expansion and contraction satisfies the relationship of equation (6-2) or (7-2), which is obtained by rewriting the above equations (6) and (7) as follows: (6-2) α1×A1×ΔT + 2×(α2×A2×ΔT)>β×B×ΔT (where α1×A1>γ1×C1+2×γ2×C2) (7-2) 2×(α2×A2×ΔT) + γ1×C1×ΔT + 2×(γ2×C2×ΔT)>β×B×ΔT (where α1×A1<γ1×C1+2×γ2×C2)

[0047] As yet another modification of the third embodiment, a high-temperature molding die may be used in which the thermal expansion coefficients of the first and second split dies 41 and 42 in the temperature range from temperature T to temperature T+ΔT are set to the same value (α), the thermal expansion coefficient of the third split dies 43 is set to γ1, and the thermal expansion coefficient of the fourth split dies 44 is set to γ2 (γ1 ≠ γ2). Also, by placing a partition plate 5 in the molding chamber 20 to separate the small chambers 20A, multiple molded products can be produced simultaneously in a single molding run.

[0048] [Modifications of Outer Mold] Next, modifications of the outer mold 3 will be described. In the above embodiment, the outer mold 3 completely surrounds the inner mold 4 on all four sides. The outer mold 3 does not have to be a completely surrounding type as described above, and it is sufficient that it has a holding surface that holds the inner mold 4.

[0049] Fig. 12A is a top view showing a high-temperature molding die 2K having an outer die 3A according to a modified example, and Fig. 12B is a cross-sectional view taken along line XIIB-XIIB in Fig. 12A. The die 2K is composed of an outer die 3A and an inner die 4D held by the outer die 3A. The outer die 3A includes an outer die base 31 formed of a rectangular parallelepiped having a substantially square shape when viewed from above, and restricting plates 32 erected from the outer die base 31. The restricting plates 32 are rectangular parallelepipeds with a rectangular cross section, and erected from the central regions of the four sides of the outer die base 31. The inner surfaces of the restricting plates 32 are holding surfaces 32A that hold the inner die 4.

[0050] The inner mold 4D is formed by a pair of first split molds 41A and a pair of second split molds 42A, and defines the molding chamber 20. The outer surfaces of the first split mold 41A and the second split mold 42A are adjacent to the holding surfaces 32A of the correspondingly arranged regulating plates 32. The first split mold 41A and the second split mold 42A are each smaller in size than the regulating plates 32, and spacers 6 that fill the size difference between them are disposed at the four corners of the inner mold 4D.

[0051] In the mold 2K, the thermal expansion coefficient of the first split mold 41A and the second split mold 42A of the inner mold 4D in the temperature range from temperature T to temperature T+ΔT is defined as α, and the thermal expansion coefficient of the outer mold 3A is defined as β. In this case, the relationship α > β is set as shown in formula (1). The relationship of the mold 2D shown in Figure 5 can be applied mutatis mutandis to the amount of thermal expansion and contraction. That is, when the dimension of the first split mold 41A is defined as A1, the dimension of one of the second split molds 42A is defined as A2, and the dimension between the holding surfaces 32A of a pair of opposing regulating plates 32 is defined as B, the mold 2K satisfies the relationship of formula (3) above.

[0052] Fig. 13A is a top view showing a high-temperature molding die 2L having an outer die 3B according to another modified example, and Fig. 13B is a cross-sectional view taken along line XIIIB-XIIIB in Fig. 13A. The die 2L is composed of an outer die 3B and an inner die 4E held by the outer die 3B. The outer die 3B includes an outer die base 310 formed of a rectangular parallelepiped that is approximately square in top view, and restriction rods 33 erected from the outer die base 310. The restriction rods 33 are cylindrical, and two restriction rods 33 erect from each of the four sides of the outer die base 310.

[0053] The inner mold 4E is formed by a pair of first split molds 41B and a pair of second split molds 42B, and defines the molding chamber 20. The outer surfaces of the first split molds 41B and the second split molds 42B are adjacent to the inner peripheral surfaces of the correspondingly arranged restriction rods 33. In this modification, the inner peripheral surfaces of the restriction rods 33 are the holding surfaces of the inner mold 4E.

[0054] In the mold 2L, the thermal expansion coefficient of the first split mold 41B and the second split mold 42B of the inner mold 4E in the temperature range from temperature T to temperature T+ΔT is defined as α, and the thermal expansion coefficient of the outer mold 3B is defined as β. In this case, the relationship α > β is set as shown in formula (1). The relationship of the mold 2D shown in Figure 5 can be applied mutatis mutandis to the amount of thermal expansion and contraction. That is, when the dimension of the first split mold 41B is defined as A1, the dimension of one of the second split molds 42B is defined as A2, and the dimension between the inner peripheral surfaces of a pair of opposing restriction rods 33 is defined as B, the mold 2L satisfies the relationship of formula (3) above.

[0055] In the above embodiments, the molding chamber 20 has been described as having a rectangular or circular horizontal cross section, but the cross-sectional shape is not limited to these. The cross-sectional shape of the molding chamber 20 is appropriately set depending on the contour of the molded product. Therefore, the cross-sectional shape of the inner mold exemplified in the above embodiments is appropriately set depending on the contour of the molded product.

[0056] Furthermore, the mold according to the present invention also allows molding without using a press. For example, in the second embodiment, when a plurality of workpieces MP are arranged in the molding chamber 20 along the center line CL or along a direction perpendicular to the center line CL and the mold 2D and the workpieces MP are heated, the workpieces MP are pressed and diffusion-bonded by the thermally expanded second split mold 42 (when arranged along the center line CL) or the thermally expanded first split mold 41 (when arranged along the perpendicular direction). In this case, the relationship of the above formula (3) is satisfied, so that the inner mold 4A can be reliably released from the outer mold 3, and the molded product can be easily removed from the inner mold 4A.

[0057] [Summary of the Invention] The specific embodiments described above include inventions having the following configurations.

[0058] A high-temperature molding die according to one aspect of the present invention comprises an outer die including a holding surface, an inner die including an outer surface at least partially adjacent to the holding surface, and an inner surface that defines a molding chamber, and satisfies the relationship of the following formula (1), where T is the temperature of the outer die and the inner die before high-temperature molding, ΔT is the temperature rise associated with high-temperature molding, α is the thermal expansion coefficient of the inner die in the temperature range from temperature T to temperature T + ΔT, and β is the thermal expansion coefficient of the outer die. (1) (1) α>β

[0059] According to this embodiment, the thermal expansion coefficient α of the inner mold is greater than the thermal expansion coefficient β of the outer mold. Therefore, when a workpiece is placed in the molding chamber and heated and pressed, the pressing force of the workpiece against the inner wall surface of the inner mold is increased, resulting in highly accurate molding. In other words, the inner shape of the molding chamber can be accurately transferred to the workpiece. Meanwhile, when the temperature is lowered from hot to cold, the inner mold experiences a greater degree of thermal shrinkage than the outer mold. This facilitates the creation of a gap between the inner and outer molds, facilitating their release from the outer mold. Furthermore, since the difference in thermal expansion coefficients between the inner and outer molds is utilized to improve molding accuracy and facilitate the removal of the workpiece, there is no need for the in-place finishing process of the inner and outer molds, as is required with tapered molds. This eliminates the need to manage and store the inner and outer molds as a set, simplifying mold management.

[0060] In the above-described high-temperature molding die, when the holding surface is an inner wall surface surrounding the inner mold, and the outer dimension of the inner mold in a direction along the center line passing through the center of the molding chamber is A and the inner dimension of the outer mold is B, it is desirable to satisfy the relationship of the following formula (2): (2) α×A×ΔT>β×B×ΔT

[0061] According to this embodiment, the outer dimensions of the inner mold are larger than the inner dimensions of the outer mold with respect to the amount of thermal expansion and contraction within the temperature range ΔT. Therefore, when hot, the inner mold presses against the outer mold, forming an interference fit, improving the strength of the mold. On the other hand, when the temperature is lowered from hot to cold, the inner mold shrinks more than the outer mold, allowing the inner mold to be reliably released from the outer mold.

[0062] In the above-described high-temperature molding die, the inner mold is preferably a split-type inner mold formed by an assembly of a plurality of split molds.

[0063] According to this embodiment, since the inner mold is of a split type, the molded product after the workpiece is molded at high temperature can be easily released from the inner mold.

[0064] In the above-described high-temperature molding die, the multiple split dies may include a pair of first split dies arranged opposite each other across the center line of the molding chamber, and a pair of second split dies arranged opposite each other so as to intersect the center line and be adjacent to one end and the other end of the pair of first split dies, and may be configured to satisfy the relationship of the following formula (3), where A1 is the dimension of the first split dies along the center line, and A2 is the dimension of one of the second split dies along the center line: (3) α×A1×ΔT+2×(α×A2×ΔT)>β×B×ΔT

[0065] According to this aspect, the inner mold is composed of a pair of first split molds and a pair of second split molds. With respect to the amount of thermal expansion and contraction in the temperature range of ΔT, the total outer dimensions of the split mold pair constituting the inner mold are greater than the inner dimensions of the outer mold. This improves molding accuracy and allows the inner mold composed of the split mold pair to be reliably released from the outer mold.

[0066] In the above-described high-temperature molding die, when the thermal expansion coefficient of the first split die is α1 and the thermal expansion coefficient of the second split die is α2 in the temperature range from temperature T to temperature T+ΔT, the following formula (4) may be satisfied: (4) α1×A1×ΔT+2×(α2×A2×ΔT)>β×B×ΔT (where α1>β, α2>β).

[0067] According to this aspect, even if the inner mold is composed of a pair of a first split mold and a second split mold and the thermal expansion coefficients of the two are different, the molding accuracy can be improved and the inner mold consisting of the split mold pair can be reliably released from the outer mold.

[0068] In the above-described high-temperature molding die, the plurality of split dies may be arc-shaped split dies formed by dividing a cylindrical inner die having a circular center at the center of the molding chamber into a plurality of parts in the circumferential direction, and may include a pair of arc-shaped split dies facing each other along the center line of the molding chamber, and may be configured to satisfy the relationship of the following formula (5), where A3 is the distance between the pair of arc-shaped split dies on the center line and A4 is the dimension of one of the arc-shaped split dies along the center line. (5) (5) α×(A3+2×A4)×ΔT>β×B×ΔT

[0069] According to this aspect, when the inner mold is constructed by combining arc-shaped split molds, the outer dimensions of the inner mold are larger than the inner dimensions of the outer mold in terms of the amount of thermal expansion and contraction within the temperature range of ΔT. This increases molding accuracy and allows the inner mold consisting of the split mold pair to be reliably released from the outer mold.

[0070] In the above-described high-temperature molding die, the multiple split dies are arranged along an inner wall surface partitioned by the pair of first split dies and the pair of second split dies, and further include a pair of third split dies and a pair of fourth split dies that partition the molding chamber, the pair of third split dies are arranged opposite each other across the center line of the molding chamber, and the pair of fourth split dies are arranged opposite each other so as to intersect with the center line and be adjacent to one end and the other end of the pair of third split dies, respectively, and the configuration may be such that the relationship of the following formula (6) or (7) is satisfied, where γ is the thermal expansion coefficient of the third split dies and the fourth split dies in the temperature range from temperature T to temperature T+ΔT, C1 is the dimension of the third split dies along the center line, and C2 is one dimension of the fourth split dies along the center line. (6) α×A1×ΔT + 2×(α×A2×ΔT)>β×B×ΔT (where α>γ) (7) 2×(α×A2×ΔT) + γ×C1×ΔT + 2×(γ×C2×ΔT)>β×B×ΔT (where α<γ)

[0071] According to this aspect, the inner mold has a multi-layer structure in which an inner mold consisting of a pair of third and fourth split molds is disposed within an outer mold consisting of a pair of first split molds and a pair of second split molds. Furthermore, taking into account the difference in thermal expansion coefficients between the outer and inner molds, the total outer dimensions of the inner mold are set larger than the inner dimensions of the outer mold for the amount of thermal expansion / contraction in the temperature range ΔT. This improves molding accuracy and allows the inner mold consisting of the first to fourth split molds to be reliably released from the outer mold.

[0072] The above-described high-temperature molding die may further include a partition plate disposed inside the molding chamber to divide the molding chamber into a plurality of compartments.

[0073] According to this aspect, one molding chamber can be divided into a plurality of compartments by the partition plates, thereby improving the production efficiency of molded products.

Claims

1. A high-temperature molding die comprising an outer die including a retaining surface, and an inner die including an outer surface at least partially adjacent to the retaining surface and an inner surface partitioning a molding chamber, wherein the temperature of the outer die and the inner die before high-temperature molding is T, the temperature rise associated with high-temperature molding is ΔT, the thermal expansion coefficient of the inner die in the temperature range from temperature T to temperature T+ΔT is α, and the thermal expansion coefficient of the outer die is β, satisfying the relationship of the following formula (1). (1) α>β 2. The high-temperature molding die according to claim 1, wherein the holding surface is an inner wall surface surrounding the inner die, and the relationship of the following formula (2) is satisfied when the outer dimension of the inner die in the direction along the center line passing through the center of the molding chamber is A and the inner dimension of the outer die is B. (2) α×A×ΔT>β×B×ΔT 3. A high-temperature molding die according to claim 2, wherein the inner die is a split-type inner die formed by an assembly of a plurality of split dies.

4. A high-temperature molding die according to claim 3, wherein the plurality of split dies include a pair of first split dies arranged opposite each other across the center line of the molding chamber, and a pair of second split dies arranged opposite each other so as to intersect with the center line and be adjacent to one end and the other end of the pair of first split dies, and the high-temperature molding die satisfies the relationship of the following formula (3), where A1 is the dimension of the first split dies along the center line, and A2 is one dimension of the second split dies along the center line. (3) α×A1×ΔT+2×(α×A2×ΔT)>β×B×ΔT 5. A high-temperature molding die according to claim 4, which satisfies the relationship of the following formula (4) when the thermal expansion coefficient of the first split die is α1 and the thermal expansion coefficient of the second split die is α2 in the temperature range from temperature T to temperature T+ΔT: (4) α1×A1×ΔT+2×(α2×A2×ΔT)>β×B×ΔT (where α1>β, α2>β).

6. A high-temperature molding die according to claim 3, wherein the plurality of split dies are arc-shaped split dies obtained by dividing a cylindrical inner die having a circular center at the center of the molding chamber into a plurality of parts in the circumferential direction, and include a pair of arc-shaped split dies facing each other along the center line of the molding chamber, and the high-temperature molding die satisfies the relationship of the following formula (5), where A3 is the distance between the pair of arc-shaped split dies on the center line, and A4 is one dimension of the arc-shaped split dies along the center line. (5) α×(A3+2×A4)×ΔT>β×B×ΔT 7. A high-temperature molding die as claimed in claim 4, wherein the multiple split dies are arranged along an inner wall surface partitioned by the pair of first split dies and the pair of second split dies, and further include a pair of third split dies and a pair of fourth split dies which partition the molding chamber, the pair of third split dies are arranged opposite each other across the center line of the molding chamber, and the pair of fourth split dies are arranged opposite each other so as to intersect with the center line and be adjacent to one end and the other end of the pair of third split dies, respectively, wherein the thermal expansion coefficient of the third split die and the fourth split die in the temperature range from temperature T to temperature T+ΔT is γ, the dimension of the third split die along the center line is C1, and one dimension of the fourth split die along the center line is C2, satisfying the relationship of the following formula (6) or (7). (6) α×A1×ΔT+2×(α×A2×ΔT)>β×B×ΔT (where α<γ) (7) 2×(α×A2×ΔT)+γ×C1×ΔT+2×(γ×C2×ΔT)>β×B×ΔT (where α>γ) 8. A high-temperature molding die according to any one of claims 1 to 7, further comprising a partition plate disposed inside the molding chamber for dividing the molding chamber into a plurality of compartments.

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