Molding apparatus and molding method

Abstract

To reduce a pressure difference in the axial direction of a workpiece with a relatively simple structure.SOLUTION: The forming apparatus (1) includes a die (2) having a through hole (H) extending in an axial direction, a first punch (3) inserted into the through hole (H) from one side in the axial direction in a state of being movable in the axial direction, a second punch (4) inserted into the through hole (H) from the other side in the axial direction so as to face the first punch (3) and defining a forming chamber (MR) of a workpiece (W) together with the die (2) and the first punch (3), a base (5) fixedly supporting the second punch (4), and a cushion member (6) disposed between the die (2) and the base (5) and elastically compressed and deformed by receiving an axial force acting on the die (2) as the workpiece (W) is pressed by the first punch (3).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a technique for compression molding a workpiece using a molding device including a die and a punch. [Background technology]

[0002] A molding apparatus described in Patent Document 1 below is known. The molding apparatus in Patent Document 1 is a powder molding press that compresses and molds raw material powder, and includes a cylindrical die with a through hole and an upper punch and a lower punch that are inserted into the through hole so as to face each other. The upper punch and the lower punch are provided so as to be independently movable on the axis of the through hole so that the raw material powder in the through hole can be compressed from above and below. In other words, the molding apparatus in Patent Document 1 is a so-called biaxial molding machine that molds a workpiece using a pair of independently movable punches. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-130193 Summary of the Invention [Problem to be solved by the invention]

[0004] A biaxial molding machine such as that in Patent Document 1 can compress the workpiece from both axial sides, making it less likely for a pressure difference to occur in the workpiece in the axial direction, and has the advantage of being able to ensure higher molding accuracy than a uniaxial molding machine in which only the punch on one side can move.

[0005] However, because a pair of punches in a double-screw molding machine must be moved axially independently, a separate movement mechanism must be provided for each punch, which can lead to a problem of a complex structure.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a molding device and molding method that can reduce the axial pressure difference of the workpiece with a relatively simple structure. [Means for solving the problem]

[0007] In order to solve the above problem, a molding device according to one aspect of the present invention comprises a die having a through hole extending in the axial direction, a first punch which is inserted into the through hole from one side in the axial direction while being movable in the axial direction, a second punch which is inserted into the through hole from the other side in the axial direction so as to face the first punch and which, together with the die and the first punch, defines a molding chamber for the workpiece, a base which fixedly supports the second punch, and a cushion member which is arranged between the die and the base and which elastically compresses and deforms in response to the axial force acting on the die as the first punch presses the workpiece.

[0008] When the forming device begins forming, the first punch presses one end of the workpiece in the axial direction, clamping the workpiece between the first and second punches. The outer periphery of the workpiece is then pressed against the inner periphery of the die, generating friction between the two. This friction increases as the first punch continues to press. As the friction increases, the force exerted by the first punch disperses from the workpiece to the die, making it more difficult for the pressure to reach the other end of the workpiece (the end closest to the second punch). This results in a lower pressure at the other end of the workpiece than at the one end, creating an axial pressure difference within the workpiece. This pressure difference can hinder the processing of the other end of the workpiece.

[0009] In contrast, in the present invention, an elastically compressible cushion member is disposed between the die and the base, thereby reducing the pressure difference in the workpiece that accompanies the increase in frictional force. In other words, as the frictional force increases, the load transmitted from the first punch to the die via the workpiece increases. The die, which receives this load, crushes the cushion member, causing it to elastically compress and deform. This allows the die to move toward the base, causing the second punch, fixed to the base, to move toward the first punch relative to the die, increasing the pressure at the other end of the workpiece. This reduces the pressure difference, allowing the other end of the workpiece to be machined more efficiently, improving the machining accuracy of the workpiece.

[0010] Furthermore, according to the present invention, in which an elastically compressible and deformable cushion member is provided between the die and the base, there is no need to provide a mechanism for independently moving the first punch and the second punch as in, for example, a conventional double-screw molding machine, and the structure of the molding device can be simplified.

[0011] Preferably, the cushion member includes a rod-shaped cushion pin extending in the axial direction between an end face of the die on the other side in the axial direction and the base spaced apart from the end face in the axial direction.

[0012] In this embodiment, the rod-shaped cushion pin is elastically compressed and deformed in the axial direction in response to the load applied from the die during compression molding, thereby allowing the cushion pin to apply a sufficient reaction force (output load) to the die, thereby firmly supporting the die in the early stages of compression molding and appropriately allowing the die to move as the compression molding progresses.

[0013] Preferably, the molding device further includes a stopper that restricts the amount of movement of the die that moves to the other side in the axial direction in response to compressive deformation of the cushion member.

[0014] In this embodiment, the stopper can prevent the cushion member from being compressed and deformed beyond its allowable limit, and the shape of the workpiece, i.e., the molded product, can be stabilized after compression molding.

[0015] Preferably, the molding apparatus further includes a heater for heating the die, and the cushion member is made of a carbon fiber reinforced carbon composite material.

[0016] Carbon fiber reinforced carbon composites have the characteristics of having a large output load per unit area during elastic deformation and not changing significantly in mechanical properties even under high temperature conditions. In this embodiment, by applying a cushion member made of such a carbon fiber reinforced carbon composite to a hot forming apparatus, it is possible to appropriately perform hot forming while reducing the pressure difference in the axial direction of the workpiece.

[0017] A molding method according to another aspect of the present invention is a method for compression molding a workpiece using a molding device including a die having a through hole extending in an axial direction, a first punch inserted into the through hole from one side in the axial direction, a second punch inserted into the through hole from the other side in the axial direction so as to face the first punch, a base that fixedly supports the second punch, and a cushion member disposed between the die and the base, wherein the workpiece is inserted into a molding space that is a space between the first punch and the second punch in the through hole, and the first punch is pushed in a first direction from the first punch toward the second punch to compress the first punch. The method includes a first step of clamping the workpiece between the punch and the second punch and bringing the outer surface of the workpiece into contact with the inner surface of the die to generate a frictional force between them; a second step of continuing to push the first punch to increase the frictional force, thereby moving the die together with the first punch in the first direction and compressively deforming the cushion member between the moving die and the base; and a third step of increasing the pressure in the workpiece in the vicinity of the second punch by moving the second punch relative to the die in a second direction opposite to the first direction as the cushion member is compressed and deformed.

[0018] This molding method invention can also provide the same effects as the molding apparatus invention described above. [Effects of the Invention]

[0019] As described above, the forming apparatus and forming method of the present invention can reduce the pressure difference in the axial direction of the workpiece with a relatively simple structure. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view showing the overall configuration of a molding device according to one embodiment of the present invention. [Figure 2] 10A and 10B are diagrams illustrating a state in which a cushion member is elastically compressed and deformed. [Figure 3] 10 is a schematic cross-sectional view showing an upper punch being pushed downward as compression molding begins. FIG. [Figure 4] 10 is a schematic cross-sectional view showing how the deformation amount of the workpiece increases as the upper punch continues to push. FIG. [Figure 5] 10 is a schematic cross-sectional view showing a state in which the die moves downward together with the upper punch and the cushion member is compressed. FIG. [Figure 6] FIG. 10 is a schematic cross-sectional view showing a state in which the die has moved downward until it abuts against a stopper. [Figure 7] FIG. 2 is a schematic cross-sectional view showing a state after compression molding is completed. [Figure 8] FIG. 2 is an explanatory diagram showing the operation of each stage of compression molding arranged side by side. DETAILED DESCRIPTION OF THE INVENTION

[0021] A preferred embodiment of the molding apparatus of the present invention will be described below with reference to the drawings. The molding apparatus of the present invention is an apparatus for compression molding a workpiece in a molding chamber. Compression molding can be performed in either a hot or cold environment. The workpiece can be, for example, a pre-sintered body, a powder, or a laminated body of forged parts. The molding apparatus pressurizes the workpiece in the molding chamber to form the workpiece. For example, if the workpiece is a pre-sintered body, the molding apparatus performs main sintering to increase the density and strength of the pre-sintered body by compression molding the pre-sintered body. If the workpiece is a powder, the molding apparatus compression molds the powder to produce a molded product (sintered body) in which the powder is integrated. If the workpiece is a laminated body of parts, such as forged parts, the molding apparatus compression molds the laminated body to produce a molded product (jointed body) in which the parts are diffusion-bonded to each other.

[0022] (1) Equipment configuration FIG. 1 is a schematic cross-sectional view showing the overall configuration of a molding apparatus 1 according to one embodiment of the present invention. The molding apparatus 1 of this embodiment is an apparatus for hot compression molding a workpiece W, which is a workpiece material, and includes a die 2, an upper punch 3, a lower punch 4, a base 5, a cushion member 6, a stopper 7, and a heater 8. While various types of workpieces W can be used, in this embodiment, the workpiece W is a pre-sintered compact (green compact) obtained by preforming a powder, such as a metal powder or a ceramic powder, through heating or other processes. Note that the state shown in FIG. 1 is the state before compression molding of the workpiece W, and in this state, a gap exists between the workpiece W and the die 2. In FIG. 1, this gap is exaggerated compared to the actual size. Also, FIG. 1 shows an example in which the molding apparatus 1 is installed so that the upper punch 3 and the lower punch 4 are aligned in this order from top to bottom. However, this is merely an example and is not intended to limit the orientation of the molding apparatus 1.

[0023] The die 2 is a cylindrical mold with its axis X extending in the vertical direction. That is, the die 2 has a through hole H extending in the axial direction (here, the vertical direction) that is parallel to the axis X. In this embodiment, the through hole H is a circular straight hole. The die 2 has a cylindrical inner peripheral surface 2a that defines the through hole H.

[0024] The upper punch 3 is inserted from above into the through hole H of the die 2. In this embodiment, the upper punch 3 is a cylindrical member having an outer diameter that is approximately the inner diameter of the die 2, i.e., the diameter of the through hole H. The upper punch 3 is supported so as to be movable in the axial direction (up and down direction) via a pressing mechanism 10, with at least its lower portion inserted into the through hole H. The pressing mechanism 10 applies a downward pressing force to the upper punch 3 during compression molding, thereby moving the upper punch 3 downward toward the lower punch 4. The upper punch 3 corresponds to the "first punch" in this invention. The direction in which the pressing mechanism 10 presses the upper punch 3, i.e., downward, corresponds to the "first direction" in this invention.

[0025] The lower punch 4 is inserted into the through hole H of the die 2 from below. In this embodiment, the lower punch 4, like the upper punch 3, is a cylindrical member having an outer diameter that is similar to the inner diameter of the die 2, i.e., the diameter of the through hole H. The lower punch 4 is fixedly supported with at least its upper portion inserted into the through hole H. The lower punch 4 corresponds to the "second punch" in this invention. The direction in which the reaction force from the lower punch 4 acts, i.e., upward, corresponds to the "second direction" in this invention.

[0026] The lower punch 4 is arranged to face the upper punch 3 in the axial direction (vertical direction) with the workpiece W in the through hole H sandwiched therebetween. As a result, the lower punch 4, together with the die 2 and the upper punch 3, form a forming chamber MR for forming the workpiece W. The forming chamber MR is a space surrounded by the inner peripheral surface 2a of the die 2, the lower end surface 3a of the upper punch 3, and the upper end surface 4a of the lower punch 4. The workpiece W is formed into a shape corresponding to the forming chamber MR by compression molding.

[0027] The base 5 is a pedestal (backing) disposed below the die 2. The base 5 fixedly supports the lower punch 4. That is, the base 5 supports the lower punch 4 in a state in which the lower punch 4 cannot move relative to the base 5. The upper surface 5a of the base 5 is spaced downward from the lower end surface 2b of the die 2. This upper surface 5a functions as a reference surface during compression molding.

[0028] The cushion member 6 is disposed between the die 2 and the base 5. The cushion member 6 includes a plurality of cushion pins 61 disposed around the lower punch 4. The plurality of cushion pins 61 are, for example, disposed so as to be aligned at equal intervals in the circumferential direction along the outer periphery of the lower punch 4. Each cushion pin 61 is, for example, a rod-shaped body with a circular cross section, having an axis extending parallel to the axial direction (up-down direction) of the die 2. Each cushion pin 61 is disposed so that each axial end portion thereof contacts the lower end surface 2b of the die 2 and the upper surface 5a of the base 5, respectively.

[0029] The cushion member 6 or cushion pins 61 support the die 2 while undergoing elastic compressive deformation during compression molding. To achieve this function of the cushion pins 61, a relatively high-strength and high-elasticity material is selected as the material for the cushion pins 61, that is, an elastic body with both high yield strength and elastic limit. There are no particular restrictions on the material for the cushion pins 61 as long as it has such properties, but in this embodiment, a carbon fiber reinforced carbon composite material is used as the material for the cushion pins 61. Note that hereinafter, the carbon fiber reinforced carbon composite material will be abbreviated as C / C composite material where appropriate.

[0030] The C / C composite material from which the cushion pin 61 is made is a composite material in which carbon is reinforced with carbon fiber, in other words, a composite material with carbon fiber as the reinforcement and carbon as the base material (matrix). Such C / C composite material has a large output load per unit area during elastic deformation and can function as a high-output elastic spring. Another feature of C / C composite material is that its mechanical properties do not change significantly even under high-temperature conditions such as those during hot forming.

[0031] 2 is a diagram showing how the cushion pin 61 is elastically compressed and deformed. As shown in this figure, the cushion pin 61 is elastically compressed and deformed by an axial compression load F, that is, a downward pressing force applied from the die 2 during compression molding. If the amount of compression at this time is ΔL, then the output load of the cushion pin 61 is proportional to the amount of compression ΔL. More specifically, if the axial length of the cushion pin 61 before compression is L, the cross-sectional area is S, and the compression elastic modulus is E, then the output load (=F) of the cushion pin 61 when it is compressed and deformed by ΔL is expressed by the following formula (1):

[0032] F = (ΔL / L) × S × E ‥‥Equation (1)

[0033] C / C composite materials have the characteristic that their compressive elastic modulus changes depending on the orientation of the carbon fibers. When evaluated in a compression test, an example was found to have a compressive elastic modulus E of approximately 2.0 GPa. The axial length L and cross-sectional area S of the cushion pin 61 are adjusted in advance, taking into account the value of the compressive elastic modulus E, so that the desired output load can be generated according to the molding device 1.

[0034] Returning to FIG. 1 , the stopper 7 is a member that restricts the amount of downward movement of the die 2 during compression molding. The stopper 7 is disposed outside the cushion member 6 and between the die 2 and the base 5. In the initial state of FIG. 1 before the upper punch 3 is pressed, a predetermined gap G is formed between the lower end surface 2b of the die 2 and the stopper 7. During compression molding, the die 2 can move downward a distance equivalent to this gap G. In other words, the stopper 7 limits the amount of movement of the die 2 during compression molding to the distance equivalent to the gap G.

[0035] The heater 8 is a device that heats the die 2 and the like to increase the molding temperature during compression molding. The heater 8 in this embodiment includes a furnace body 81 and a heat source (not shown) that increases the internal temperature of the furnace body 81. Inside the furnace body 81, the die 2, upper punch 3, lower punch 4, cushion member 6, and the like are arranged. In other words, the molding device 1 in this embodiment is a hot molding device that compression molds the workpiece W inside the furnace body 81, which has been heated to a high temperature.

[0036] (2) Molding method Next, the specific procedure for compression molding the workpiece W will be described. Before this compression molding begins, the heater 8 has already heated the die 2 and the workpiece W has been placed in the molding chamber MR. At this point, the workpiece W assumes a cylindrical shape with an outer peripheral surface Wa that is slightly smaller than the inner peripheral surface 2a of the die 2. When compression molding begins, the pressing mechanism 10 first pushes the upper punch 3 downward, causing the upper punch 3 to press the upper end of the workpiece W downward. As a result, as shown in FIG. 3, the workpiece W is sandwiched between the upper punch 3 and the lower punch 4 (see arrows A1 and A2), causing the workpiece W to undergo compression deformation. In other words, the axial length of the workpiece W decreases by the amount that the upper punch 3 moves downward from its initial position in contact with the upper end of the workpiece W before molding. Note that the heater 8 (FIG. 1) is omitted from FIG. 3. This also applies to FIG. 4 and subsequent figures described below.

[0037] In this embodiment, in the initial state before the upper punch 3 starts to push, there is a gap between the outer peripheral surface Wa of the workpiece W and the inner peripheral surface 2a of the die 2, so when the upper punch 3 starts to push, the outer peripheral surface Wa of the workpiece W is not constrained. Therefore, as the pushing of the upper punch 3 progresses and the axial length of the workpiece W decreases, the workpiece W gradually deforms so as to expand in the radial direction. Specifically, the workpiece W deforms so that the central portion in the axial direction bulges first, resulting in a drum-like shape.

[0038] The outer peripheral surface Wa of the workpiece W, which has been deformed into a drum shape as described above, first comes into contact with the inner peripheral surface 2a of the die 2 at its axial center. From the moment this contact occurs, the outer peripheral surface Wa of the workpiece W begins to be constrained (see arrow A3), and a frictional force is generated between the outer peripheral surface Wa of the workpiece W and the inner peripheral surface 2a of the die 2.

[0039] In this state, the upper punch 3 is further pressed, increasing the amount of deformation of the workpiece W. Then, as shown in FIG. 4, the contact area between the outer peripheral surface Wa of the workpiece W and the inner peripheral surface 2a of the die 2 increases. This increases the restraining force on the outer peripheral surface Wa of the workpiece W (see arrow A4), and also increases the frictional force between the workpiece W and the die 2. Due to this increase in frictional force, the pressing force acting from the upper punch 3 is dispersed from the workpiece W to the die 2 (see arrow A5), making it difficult for the pressure to be transmitted to the bottom of the workpiece W. As a result, a significant pressure difference occurs in the axial direction inside the workpiece W. In other words, a situation arises in which the pressure at the bottom of the workpiece W is smaller than the pressure at the top.

[0040] Meanwhile, as the frictional force increases, the downward load (arrow A5) transmitted from the upper punch 3 to the die 2 via the workpiece W increases. This increases the compressive load acting from the die 2 on the cushion member 6. As a result, as shown in FIG. 5, the cushion member 6 undergoes elastic compressive deformation, and the die 2 moves downward together with the upper punch 3 by an amount corresponding to the amount of deformation (see arrow A6). That is, each cushion pin 61 of the cushion member 6 elastically deforms in a direction that reduces its axial length, and the die 2 moves downward accordingly.

[0041] The downward movement of the die 2 as described above changes the relative positional relationship between the die 2 and the lower punch 4. That is, while the die 2 moves downward, the position of the lower punch 4, which is fixed to the base 5, remains unchanged, so the lower punch 4 moves upward relative to the die 2. This increases the pressure on the lower part of the workpiece W near the lower punch 4, and processing of that lower part progresses. Specifically, in the state shown in FIG. 4, where the cushion member 6 was barely compressed and deformed, the pressure on the lower part of the workpiece W did not increase easily, and processing of that lower part did not progress sufficiently, resulting in a relatively large gap between the lower part of the workpiece W and the die 2. In contrast, in the state shown in FIG. 5, where the pressure on the lower part of the workpiece W increases due to the upward relative movement of the lower punch 4, the lower part of the workpiece W is processed so that it expands radially, and the gap between the lower part of the workpiece W and the die 2 is reduced (see region R1). In this way, the upward relative movement of the lower punch 4 advances processing of the lower part of the workpiece W.

[0042] The upper punch 3 continues to push until the die 2 abuts against the stopper 7. That is, as the upper punch 3 continues to push, the compressive load acting from the die 2 on the cushion member 6 increases, and the amount of compressive deformation of the cushion member 6 increases. This allows the die 2 to move further downward, and eventually, as shown in FIG. 6, the lower end surface 2b of the die 2 abuts against the stopper 7. After this, the die 2 can no longer move downward, so most of the load from the upper punch 3 is received by the upper part of the workpiece W, and the pressure on the upper part of the workpiece W rises again. Then, processing progresses also on the upper part of the workpiece W, and the gap between the upper part of the workpiece W and the die 2 decreases (see region R2).

[0043] As the processing of the top and bottom of the workpiece W progresses as described above, the material eventually fills the upper and lower corners of the molding chamber MR with almost no gaps. As a result, as shown in Figure 7, the workpiece W is compressed almost uniformly within the molding chamber MR, and a molded product MP is formed that accurately replicates the shape of the molding chamber MR. The molded product MP has a higher density and strength than the workpiece W before processing. In other words, by continuing to push the upper punch 3 until the state shown in Figure 7 is achieved, compression molding that increases the density and strength of the workpiece W is completed, and a molded product MP with a shape that corresponds to the molding chamber MR is produced.

[0044] FIG. 8 is an explanatory diagram showing the various stages of the compression molding process, arranged side by side. Stages (A), (B), (C), (D), and (E) in FIG. 8 correspond to FIGS. 1, 3, 4, 5, and 6, respectively. Stages (A) through (C) are stages in which the workpiece W is clamped between the upper punch 3 and the lower punch 4, bringing the outer peripheral surface Wa of the workpiece W into contact with the inner peripheral surface 2a of the die 2 and generating friction between them. These stages correspond to the "first step" in this invention. Stages (D) and (E) are stages in which the process of compressing the cushion member 6 by moving the die 2 downward together with the upper punch 3 due to increased friction and the process of increasing the pressure below the workpiece W by moving the lower punch 4 upward relative to the workpiece W are simultaneously performed. These stages correspond to the "second step" and "third step" in this invention.

[0045] (3) Effects As described above, the molding device 1 of this embodiment includes the die 2, the upper punch 3 and the lower punch 4 inserted into the through hole H of the die 2 so as to face each other in the axial direction (vertical direction), the base 5 that fixedly supports the lower punch 4, and the elastically compressible and deformable cushion member 6 that is arranged between the die 2 and the base 5. Such a configuration has the advantage that it is possible to reduce the pressure difference in the axial direction of the workpiece W with a relatively simple structure, and to improve the processing accuracy of the workpiece W.

[0046] When the upper end of the workpiece W is pressed by the upper punch 3 as forming begins, the outer peripheral surface Wa of the workpiece W is pressed against the inner peripheral surface 2a of the die 2, generating a frictional force between the two. This frictional force increases as the upper punch 3 continues to press, but the greater the frictional force, the more easily the pressing force acting from the upper punch 3 is dispersed from the workpiece W to the die 2 (see arrow A5 in Figure 4), making it more difficult for the pressure to be transmitted to the bottom of the workpiece W. As a result, the pressure at the bottom of the workpiece W becomes smaller than the pressure at the top, creating an axial (vertical) pressure difference inside the workpiece W. This pressure difference can hinder the processing of the bottom of the workpiece W.

[0047] In contrast, in this embodiment, an elastically compressible and deformable cushion member 6 is disposed between the die 2 and the base 5, thereby reducing the pressure difference on the workpiece W that accompanies the increase in frictional force described above. That is, when the frictional force increases, the downward load transmitted from the upper punch 3 to the die 2 via the workpiece W increases, and the die 2 that receives this load crushes the cushion member 6, causing the cushion member 6 to undergo elastic compressive deformation. This allows the die 2 to move downward, i.e., move closer to the base 5, so that the lower punch 4 fixed to the base 5 moves upward relative to the die 2, increasing the pressure on the lower part of the workpiece W. This reduces the pressure difference described above, allowing the lower part of the workpiece W to be machined further, thereby improving the machining accuracy of the workpiece W.

[0048] Furthermore, according to this embodiment, in which an elastically compressible cushion member 6 is provided between the die 2 and the base 5, there is no need to provide a mechanism for independently moving the upper punch 3 and the lower punch 4, as in conventional biaxial molding machines, thereby simplifying the structure of the molding apparatus 1. In other words, if a mechanism similar to the pushing mechanism 10 for the upper punch 3 is also applied to the lower punch 4, the lower punch 4 can be moved axially (up and down) independently of the upper punch 3, thereby reducing the pressure difference in the workpiece W. However, this configuration would result in a complex and large-sized apparatus. In contrast, this embodiment employs a configuration in which the lower punch 4 is moved relative to the upper punch 3 by compressive deformation of the cushion member 6, eliminating the need for a pushing mechanism for the lower punch 4 and allowing for a simplified and compact apparatus. In other words, this embodiment achieves pseudo-biaxial molding without providing a separate pushing mechanism for the lower punch 4.

[0049] It is also possible to use a hydraulic or gas-pressure floating rod instead of the cushion member 6. That is, a floating rod supported by a hydraulic or gas-pressure support mechanism that sinks when subjected to pressure exceeding a specified value is used instead of the cushion member 6. Supporting the die 2 with such a floating rod allows the die 2 to move downward when the load from the die 2 increases, as in the above embodiment. However, this method requires the use of hydraulic or gas pressure, which again complicates the device and makes it difficult to apply to hot forming equipment. Furthermore, the overall volume of the floating rod and its supporting mechanism tends to be large, making it difficult to arrange multiple floating rods side by side with small spacing. Therefore, it is difficult to apply floating rods to so-called multi-row forming, in which workpieces are simultaneously compression-molded using multiple dies arranged side by side.

[0050] In contrast, according to this embodiment, which uses a cushion member 6 made of an elastic material, the cushion member 6 can be applied to hot forming equipment without any problems, depending on the material selected for the cushion member 6. For example, the C / C composite material (carbon fiber reinforced carbon composite material) used as the material for the cushion member 6 in this embodiment is suitable for hot forming because its mechanical properties do not change significantly even under high temperature conditions. Furthermore, when the cushion member 6 is used for multi-row forming, multiple cushion members 6 can be arranged close to each other, which reduces the distance between adjacent dies. In other words, the cushion member 6 can also be suitably applied to multi-row forming.

[0051] Moreover, in this embodiment, the cushion member 6 has a plurality of rod-shaped cushion pins 61 extending in the axial direction (vertical direction) between the lower end surface 2b of the die 2 and the upper surface 5a of the base 5. With this configuration, the rod-shaped cushion pins 61 are each elastically compressed and deformed in the axial direction in response to the load acting from the die 2 during compression molding, thereby allowing each cushion pin 61 to apply a sufficient reaction force (output load) to the die 2. This makes it possible to firmly support the die 2 in the early stages of compression molding while appropriately allowing movement of the die 2 as compression molding progresses.

[0052] In this embodiment, a stopper 7 that restricts the amount of downward movement of the die 2 is provided between the die 2 and the base 5. With this configuration, the stopper 7 can prevent the cushion pins 61 (cushion members 6) from being compressed and deformed beyond the allowable amount, and can stabilize the shape of the workpiece W, i.e., the molded product MP, after compression molding.

[0053] (4) Variations Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in the following manner, for example.

[0054] In the above embodiment, the cushion member 6 including a plurality of rod-shaped cushion pins 61 extending in the axial direction is disposed between the die 2 and the base 5. However, the form of the cushion member is not limited to this, and for example, a cushion member consisting of an integral cylindrical body surrounding the lower punch 4 may also be used.

[0055] In the above embodiment, a molding device 1 was used to perform actual sintering of a workpiece W consisting of a pre-sintered body (compressed powder body) by compression molding. However, the molding device of the present invention can also be used for applications such as sintering powder by compression molding and diffusion bonding laminates made by stacking forged parts, sintered parts, etc.

[0056] In the above embodiment, an example of applying the present invention to a hot forming apparatus 1 including a heater 8 has been described, but the present invention can be applied not only to hot forming apparatuses but also to cold forming apparatuses in the same manner.

[0057] In the above embodiment, a C / C composite material (carbon fiber reinforced carbon composite material) is used as the material for the cushion member 6. However, the material for the cushion member 6 is not limited to a C / C composite material as long as it can elastically compress and deform in response to the load received from the die 2 during molding. For example, in addition to the above C / C composite material, hot die steel, cemented carbide (tungsten-based sintered alloy), cermet, graphite, ceramics, etc. can be used as the material for the cushion member for hot molding. Furthermore, in addition to the above C / C composite material, cutting tool materials such as carbon fiber reinforced plastic (CFRP), graphite, cermet, etc., and various alloy steels such as powder high-speed steel and cemented carbide (tungsten-based sintered alloy) can be used as the material for the cushion member for cold molding. [Explanation of symbols]

[0058] 1 Molding equipment 2 Die 3 Upper punch (first punch) 4. Lower punch (second punch) 5. Bass 6 Cushion material 61 cushion pin 7 Stopper 8 Heater H through hole MR molding room W Work (workpiece)

Claims

1. a die having an axially extending through-hole; a first punch that is inserted into the through hole from one side in the axial direction while being movable in the axial direction; a second punch inserted into the through hole from the other axial side so as to face the first punch and defining a forming chamber for the workpiece together with the die and the first punch; a base that fixedly supports the second punch; a cushion member disposed between the die and the base, the cushion member elastically compressing and deforming in response to the axial force acting on the die as the first punch presses the workpiece.

2. The molding apparatus according to claim 1, A molding apparatus, wherein the cushion member includes a rod-shaped cushion pin extending in the axial direction between an end face on the other side of the axial direction of the die and the base spaced apart from the end face in the axial direction.

3. 3. The molding apparatus according to claim 1 or 2, The molding device further includes a stopper that restricts the amount of movement of the die that moves to the other side in the axial direction as the cushion member is compressed and deformed.

4. 3. The molding apparatus according to claim 1 or 2, Further comprising a heater for heating the die; The cushion member is made of a carbon fiber reinforced carbon composite material.

5. A method for compression molding a workpiece using a molding device including: a die having a through hole extending in an axial direction; a first punch inserted into the through hole from one side in the axial direction; a second punch inserted into the through hole from the other side in the axial direction so as to face the first punch; a base that fixedly supports the second punch; and a cushion member disposed between the die and the base, a first step of inserting the workpiece into a forming space, which is a space between the first punch and the second punch in the through hole, and pressing the first punch in a first direction from the first punch toward the second punch to clamp the workpiece between the first punch and the second punch and bringing an outer peripheral surface of the workpiece into contact with an inner peripheral surface of the die to generate a frictional force therebetween; a second step of moving the die together with the first punch in the first direction by continuing the pushing movement of the first punch to increase the frictional force, thereby compressively deforming the cushion member between the moving die and the base; a third step of increasing the pressure in the workpiece near the second punch by moving the second punch relative to the die in a second direction opposite to the first direction as the cushion member compresses and deforms.

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