Powder molding apparatus and method for manufacturing powder compact

Abstract

To provide a manufacturing method of a powder molded body and the like which can reduce the cost required for a removal process of an annular molded body that is associated with a spherical molded body (or molded body which has a portion of a spherical base containing an equator and whose outer diameter becomes maximum at the equator).SOLUTION: Pressing surfaces of an upper punch 10 and a lower punch 20 are formed by: first pressing surfaces S11, S21 consisting of a hemispherical surface or a hemispherical surface that lacks a latitude range of θ11, θ21=0.01° to 3.0° from the equator; and circular second pressing surfaces S12, S22 connected to the outer peripheral edge of the first pressing surfaces S11, S21. The second pressing surfaces S12, S22 of at least one of the upper punch 10 and the lower punch 20 are formed so as to be gradually farther away from the plane including the equator of the hemispherical surface to at least the middle as it goes outward in the radial direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a technique for producing a powder compact using a die. [Background technology]

[0002] Conventionally, in order to obtain a spherical sintered body to be used as a ball for a ball bearing, etc., a method has been proposed in which a raw material powder is filled into a space formed by a lower punch and a molding die, and the raw material powder filled into the space is compressed by an upper punch and a lower punch to produce a substantially spherical powder compact (see, for example, Patent Document 1). In order to reduce the density difference between the center and the outer periphery of the spherical powder compact, a method has been proposed in which the positions of the pressing surfaces of the inner punch and the outer punch surrounding the inner punch that constitute the lower punch (and upper punch) are shifted when the raw material powder is filled, and then aligned when the powder is compressed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6100556 [Patent Document 2] JP 2021-154674 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the powder compact is composed of a spherical compact originating from the approximately hemispherical pressing surfaces of the upper punch and the lower punch, and an annular compact originating from the gaps at the outer peripheries of the pressing surfaces of the upper punch and the lower punch and extending annularly along the equator of the spherical compact in one piece. Therefore, in order to obtain a spherical sintered body, a process is required to remove the annular compact from the spherical compact, which can be costly.

[0005] Therefore, the present invention aims to provide a method for producing a powder compact which can reduce the costs required for the process of removing annular compacts associated with spherical compacts (or compacts having a spherical truncated portion including the equator and with the outer diameter at the equator being the maximum). [Means for solving the problem]

[0006] The powder molding apparatus of the present invention is A powder molding apparatus including an upper punch, a lower punch, and a molding die having through holes into which the upper punch and the lower punch are inserted from above and below, The pressing surfaces of the upper punch and the lower punch are 、 red A hemisphere missing the latitude range of 0.01° to 3.0° from the road or A first pressure surface formed by a spherical zone; a second annular pressure surface continuous with an outer peripheral edge portion of the first pressure surface, The second pressing surface of at least one of the upper punch and the lower punch is formed so as to become gradually farther from a plane including the equator of the hemisphere at least partway as it moves radially outward.

[0007] The method for producing a powder compact of the present invention is a method for producing a powder compact using the powder molding apparatus having the above-mentioned configuration, a powder filling step of filling a space defined by the forming die and the lower punch inserted from below into the through hole of the forming die with powder; a pressurizing step of pressing the powder filled in the space by bringing the upper punch and the lower punch, which are inserted from above into the through hole of the molding die, relatively close to each other; The method includes a molded body removal process in which the upper punch is pulled upward from the through hole of the molding die by displacing the upper punch and the molding die relatively, and the lower punch is raised relative to the molding die by displacing the lower punch and the molding die relatively.

[0008] According to the powder molding apparatus having the above-mentioned configuration and the method for manufacturing a powder compact using the same, the powder is compressed by the upper punch and the lower punch inserted from above and below into the through hole of the molding die. This realizes a state in which a powder compact integrally composed of a spherical compact (or a compact having a spherical truncated part including an equator, the outer diameter of which is maximum at the equator) and an annular compact is present in the space defined by the pressure surface of the upper punch, the pressure surface of the lower punch, and the side of the through hole of the molding die.

[0009] The second pressing surface of at least one of the punches is configured to move away from the equator of the hemispherical surface corresponding to the first pressing surface as it moves radially outward. As a result, in the integral compact, a relatively large stress remains in a portion corresponding to the annular continuous portion of the first pressing surface and the second pressing surface, i.e., in the annular continuous portion of the spherical compact and the annular compact.

[0010] In the compact removal step, the annular compact is kept at least partially restrained from the pressed state against the side surface of the through hole of the molding die, so that a force is applied so that the molding die restrains the annular compact. As a result, the annular compact is not lifted by the upper punch, and the annular compact can be separated from the spherical compact almost at the same time as the spherical compact is removed from the molding die. This makes it possible to reduce the cost required for the step of removing the annular compact from the spherical compact. [Brief description of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram illustrating a configuration of a powder molding apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 4 is an explanatory diagram showing the configuration of an outer upper punch according to one embodiment of the present invention. [Diagram 3] FIG. 4 is an explanatory diagram illustrating the configuration of an outer lower punch according to one embodiment of the present invention. [Figure 4] 1A to 1C are explanatory diagrams illustrating a method for producing a powder compact according to the present invention. [Diagram 5] FIG. 2 is a diagram illustrating the method for producing a powder compact of the present invention (continued). [Figure 6] FIG. 4 is an explanatory diagram of the powder compact after removal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (composition) 1 includes an upper punch 10, a lower punch 20, and a molding die 24 having a substantially cylindrical through hole into which the upper punch 10 and the lower punch 20 are inserted from above and below. The upper punch 10 is composed of a substantially cylindrical inner upper punch 11 and a substantially cylindrical outer upper punch 12 having an inner diameter substantially the same as that of the inner upper punch 11. The lower punch 20 is composed of a substantially cylindrical inner lower punch 21 and a substantially cylindrical outer lower punch 22 having an inner diameter substantially the same as that of the inner lower punch 21.

[0013] The powder molding apparatus is equipped with an inner upper punch actuator 110, an outer upper punch actuator 120, an inner lower punch actuator 210, an outer lower punch actuator 220 and a molding die actuator 240 for driving the inner upper punch 11, the outer upper punch 12, the inner lower punch 21, the outer lower punch 22 and the molding die 24, respectively, up and down.

[0014] The powder molding apparatus includes a control device 40. The control device 40 is configured with a computer, an arithmetic processing device (CPU, processor, processor core, etc.), a storage device (memory such as ROM and RAM, HDD, SSD, etc.), an I / O circuit, etc. The control device 40 is configured to execute a task by reading out necessary data and a program (software) from the storage device and executing arithmetic processing according to the program on the data. The task includes control processing of the operation of each of the inner upper punch actuator 110, the outer upper punch actuator 120, the inner lower punch actuator 210, the outer lower punch actuator 220, and the molding die actuator 240, as well as control processing of the operation of a raw material powder supply device (not shown).

[0015] 2 shows a state in which the pressing surface of the inner upper punch 11 and the pressing surface of the outer upper punch 12 are aligned to form the original pressing surface of the upper punch 10. The pressing surface of the upper punch 10 is called the first pressing surface S 11 and the first pressure surface S 11 The second pressing surface S is an annular surface extending radially outwardly from the outer peripheral edge of the 12 The present invention is composed of the following:

[0016] First pressure surface S 11 is the center O 1 Of the hemispherical surface of radius r (target radius of powder compact), the distance from the equator to the 11 The first pressure surface S is formed by a curved surface that is missing a latitudinal range of 0.01° to 3.0° (preferably 0.01° to 2.0°, and more preferably 0.01° to 1.0°). 11 The latitude range θ may be formed of a hemispherical surface that does not have any missing parts. For example, the missing parts of the hemispherical surface may have an uneven structure like a crown along the circumferential direction, and the latitude range θ may be formed according to the longitude of the hemispherical surface. 11 may vary intermittently or continuously.

[0017] Second pressure surface S 12 The second pressure surface S is configured to be continuously or intermittently farther from the plane including the equator of the hemisphere (equatorial plane) as it moves radially outward. As shown in FIG. 2, the second pressure surface S 12 is the angle θ with respect to the equatorial plane 14 The second pressure surface S is a curved surface that is approximately a truncated cone. 12 The angle θ that the inner periphery of the 14 is preferably within an angle range of 20° to 85° (preferably 45° to 85°, and more preferably 65° to 75°).

[0018] Second pressure surface S 12 The first pressure surface S may be formed of an annular convex curved surface, an annular concave curved surface, or a combination thereof. 11 and the second pressure surface S 12 The continuous part S of10 The second pressure surface S may be a flat surface parallel to the equatorial plane or a substantially flat convex curved surface. 12 is the continuous part S 10 From the center O 1 , and then may maintain an equal distance to the equatorial plane thereafter, or may gradually approach the equatorial plane.

[0019] The pressing surface of the inner upper punch 11 is a first pressing surface S 11 The pressing surface of the outer upper punch 12 is the first pressing surface S 11 The outer part of the hemisphere (latitude θ 11 ~θ 11 +θ 12 (part) and the second pressure surface S 12 It is composed of θ 12 For example, the radius rcos(θ 11 +θ 12 ) and the first pressing surface S of the outer upper punch 12 11 The radial spacing r{cosθ 11 -cos(θ 11 +θ 12 The ratio of the first pressing surface S of the outer upper punch 12 is, for example, in the range of 0.985:0.014 to 0.602:0.397, and preferably in the range of 0.940:0.059 to 0.788:0.211. 11 The radial spacing r{cosθ 11 -cos(θ 11 +θ 12 )} and the second pressure surface S 12 The ratio of the radial spacing of to is, for example, within the range of 32:1 to 1:8, may be within the range of 5:1 to 1:5, and is preferably within the range of 3:1 to 1:3.

[0020] 3 shows a state in which the pressing surface of the inner lower punch 21 and the pressing surface of the outer lower punch 22 are aligned to form the original pressing surface of the lower punch 20. The pressing surface of the lower punch 20 is the first pressing surface S 21 and the first pressure surface S 21 The second pressing surface S is an annular surface extending radially outwardly from the outer peripheral edge of the 22 The present invention is composed of the following:

[0021] First pressure surface S 21 is the center O 1 Of the hemispherical surface of radius r (target radius of powder compact), the distance from the equator to the 21 The second pressure surface S is formed by a curved surface that is missing a latitudinal range of 0.01° to 3.0° (preferably 0.01° to 2.0°, and more preferably 0.01° to 1.0°). 21 The latitude range θ may be formed of a hemispherical surface that does not have any missing parts. For example, the missing parts of the hemispherical surface may have an uneven structure like a crown along the circumferential direction, and the latitude range θ may be formed according to the longitude of the hemispherical surface. 21 may vary intermittently or continuously. 21 =θ 11 It is preferable that:

[0022] Second pressure surface S 22 The second pressure surface S is configured to be continuously or intermittently farther from the plane including the equator of the hemisphere (equatorial plane) as it moves radially outward. As shown in FIG. 3, the second pressure surface S 22 is the angle θ with respect to the equatorial plane 24 The second pressure surface S is a curved surface that is approximately a truncated cone. 22 The angle θ that the inner periphery of the 24 is preferably within an angle range of 20° to 85° (preferably 45° to 85°, and more preferably 65° to 75°). 24 =θ 14 It is preferable that:

[0023] Second pressure surface S 22The first pressure surface S may be formed of an annular convex curved surface, an annular concave curved surface, or a combination thereof. 21 and the second pressure surface S 22 The continuous part S of 20 The second pressure surface S may be a flat surface parallel to the equatorial plane or a substantially flat convex curved surface. 22 is the continuous part S 20 From the center O 2 , and then may maintain an equal distance to the equatorial plane thereafter, or may gradually approach the equatorial plane.

[0024] The pressing surface of the inner lower punch 21 is the first pressing surface S 21 The pressing surface of the outer lower punch 22 is the first pressing surface S 21 The outer part of the hemisphere (latitude θ 21 ~θ 21 +θ 22 (θ 22 =θ 12 It is preferable that the portion of the second pressure surface S 22 It is composed of θ 22 For example, the radius rcos(θ 21 +θ 22 ) and the first pressing surface S of the outer lower punch 22 21 The radial spacing r{cosθ 21 -cos(θ 21 +θ 22 The ratio of the first pressing surface S of the outer lower punch 22 is, for example, in the range of 0.985:0.014 to 0.602:0.397, and preferably in the range of 0.940:0.059 to 0.788:0.211. 21 The radial spacing r{cosθ 21 -cos(θ 21 +θ 22 )} and the second pressure surface S 22The ratio of the radial spacing of to is, for example, within the range of 32:1 to 1:8, may be within the range of 5:1 to 1:5, and is preferably within the range of 3:1 to 1:3.

[0025] (function) The function of the powder molding apparatus having the above-mentioned configuration, and further the procedure of the method for producing a powder compact using the same, will be described below.

[0026] (Powder filling process) As shown in FIG. 4(1), in the powder filling step, the position of the pressing surface of the inner lower punch 21 is controlled to be lower than the position of the pressing surface of the outer lower punch 22. The position of the upper end of the outer lower punch 22 inserted into the through hole of the molding die 24 and the position of the upper end of the molding die 24 are controlled to be approximately the same. In this state, the powder P is filled into the space defined by the inner surface of the outer lower punch 22 and the pressing surface of the inner lower punch 21 by the powder supplying device. The powder P may be a ceramic powder, a metal powder, or a mixed powder thereof. As shown in FIG. 4(1), the pressing surface of the inner upper punch 11 and the pressing surface of the outer upper punch 12 may be aligned to form a continuous pressing surface of the upper punch 10.

[0027] In addition to the space (first powder filling space) defined by the inner side surface of the outer lower punch 22 and the pressing surface of the inner lower punch 21, the powder P may also be filled in a space (second powder filling space) defined by the pressing surface of the outer lower punch 22 and the side surface of the through hole of the forming die 24. In this case, the position of the upper end of the outer lower punch 22 may be controlled to be relatively lower than the position of the upper end of the forming die 24.

[0028] (First preliminary process) 4(2), the forming die 24 is driven to move upward relative to the outer lower punch 22. Furthermore, the upper punch 10 is driven to move downward, and the upper punch 10 is inserted into the through hole of the forming die 24 from above.

[0029] (Second preliminary process) Next, as shown in Fig. 4(3), the inner lower punch 21 is driven upward relative to the outer lower punch 22 so that the pressing surface of the inner lower punch 21 approaches the pressing surface of the outer lower punch 22. This causes the powder P to be transferred upward by the inner lower punch 21. The inner upper punch 11 is driven upward relative to the outer upper punch 12 so that the pressing surface of the inner upper punch 11 moves away from the pressing surface of the outer upper punch 12. As a result, as shown in Fig. 4(3), a state is realized in which the powder P is filled in the space defined by the pressing surface of the inner upper punch 11, the inner surface and pressing surface of the outer upper punch 12, the side surface of the through hole of the molding die 24, the pressing surface of the inner lower punch 21, and the inner surface and pressing surface of the outer lower punch 22.

[0030] (Pressure process) 4(4), the outer upper punch 12 is driven downward and / or the outer lower punch 22 is driven upward so that the outer upper punch 12 and the outer lower punch 22 approach each other. Also, in order to form the original pressing surface of the upper punch 10, the inner upper punch 11 is driven downward relative to the outer upper punch 12 so that the pressing surface of the inner upper punch 11 approaches the pressing surface of the outer upper punch 12. Similarly, in order to form the original pressing surface of the lower punch 20, the inner lower punch 21 is driven upward relative to the outer lower punch 22 so that the pressing surface of the inner lower punch 21 approaches the pressing surface of the outer lower punch 22.

[0031] As a result, as shown in FIG. 4(4), the first pressing surface S of the upper punch 10, which is substantially hemispherical, 11 (See FIG. 2) and the substantially hemispherical first pressing surface S of the lower punch 20 21 A spherical compact Q is formed in a substantially spherical space defined by the second pressing surface S of the upper punch 10 (see FIG. 3). 12 (See FIG. 2) and the second pressing surface S of the lower punch 20 22(see FIG. 3) and the side surface of the through hole of the forming die 24, an annular molded body R is formed in the annular space defined by the through hole of the forming die 24. At this time, the annular molded body R is integrally connected to the spherical molded body Q over the entire circumference along its equator.

[0032] (Molded body removal process) As shown in Fig. 5 (5), the forming die 24 is driven downward until the position of the upper end of the forming die 24 is slightly higher than the position of the lower end of the upper punch 10. Furthermore, as shown in Fig. 5 (6), the lower inner punch 21 is driven upward and the upper punch 10 is driven upward so that the position of the upper end of the lower inner punch 21 is approximately the same as the position of the upper end of the forming die 24. At this time, the amount of upward displacement of the inner punch 21 and the amount of upward displacement of the upper punch 10 are the same.

[0033] As a result, as shown in FIG. 5(6), the spherical compact Q is separated from the annular compact R and is sandwiched or supported in the vertical direction by the pressing surface of the inner lower punch 21 and the pressing surface of the upper punch 10. At this time, the annular compact R is in contact with the upper end of the side surface of the through hole of the forming die 24 and the pressing surface of the outer lower punch 22 (second pressing surface S 22 ) and remains in its original position.

[0034] Then, as shown in Fig. 5(7), the upward movement of the lower inner punch 21 is stopped, while the upper punch 10 is further driven upward. As a result, as shown in Fig. 5(7), the spherical molded body Q is taken out while being supported by the pressing surface of the lower inner punch 21.

[0035] (Action and effect) According to the powder molding apparatus exhibiting the above-mentioned functions and the method for producing a powder compact using the same, the powder P is compressed by the upper punch 10 and the lower punch 20 inserted from above and below into the through hole of the molding die 24 (see FIG. 4(4)). This realizes a state in which a powder compact integrally composed of a spherical compact Q and an annular compact R is present in the space defined by the pressure surface of the upper punch 10, the pressure surface of the lower punch 20, and the side surface of the through hole of the molding die 24.

[0036] The second pressing surface S of the upper punch 10 12 and the second pressing surface S of the lower punch 20 22 As each of the first pressure surfaces S 11 , S 21 Therefore, in the integrally molded body, the first pressing surface S 11 , S 21 and the second pressure surface S 12 , S 22 A continuous circular part S of 10 , S 20 In other words, a relatively large stress remains in the annular continuous portion of the spherical compact Q and the annular compact R.

[0037] In the compact removal step, the annular compact R is kept at least partially restrained from the pressure contact state with the side surface of the through hole of the molding die 24, so that the molding die 24 exerts a force to restrain the annular compact R. As a result, the annular compact R is not lifted by the upper punch 10 (outer upper punch 12), and the annular compact R can be separated from the spherical compact Q almost at the same time as the spherical compact is removed from the molding die (see FIG. 5 (5)). FIG. 6 shows the spherical compact Q and the annular compact R removed in a separated state. This makes it possible to reduce the cost required for the step of removing the annular compact R from the spherical compact Q.

[0038] (Another embodiment of the present invention) In the above embodiment, the upper punch 10 is composed of the inner upper punch 11 and the outer upper punch 12, but in another embodiment, the upper punch 10 may be composed as a single punch in which the inner upper punch 11 and the outer upper punch 12 are integrated together. In this case, the inner upper punch actuator 110 and the outer upper punch actuator 120 are composed as a single upper punch actuator.

[0039] In the above embodiment, the lower punch 20 is composed of the inner lower punch 21 and the outer lower punch 22, but in another embodiment, the lower punch 20 may be composed as a single punch in which the inner lower punch 21 and the outer lower punch 22 are integrated together. In this case, the inner lower punch actuator 210 and the outer lower punch actuator 220 are composed as a single lower punch actuator.

[0040] The inner upper punch 11 may be composed of a generally columnar central punch and one or more annular upper punches arranged coaxially so as to surround the central punch. In this case, in the second preliminary step (see FIG. 4(3)), a state is realized in which the position of the pressing surface of the central punch is the highest, and the position of the pressing surface of the annular upper punch is higher than the position of the pressing surface of the outer upper punch 12 (further, the position of the pressing surface of the inner annular upper punch is higher than the position of the pressing surface of the outer annular upper punch). Then, in the pressing step (see FIG. 4(4)), the central punch may be driven downward relative to the annular upper punch so that the pressing surface of the central punch approaches the pressing surface of the annular upper punch. Furthermore, when multiple annular upper punches are present, the inner annular upper punch may be driven downward relative to the outer annular upper punch).

[0041] The inner lower punch 21 may be composed of a generally columnar central lower punch and one or more annular lower punches arranged coaxially so as to surround the central lower punch. In this case, in the second preliminary step (see FIG. 4(3)), a state is realized in which the position of the pressing surface of the central lower punch is the lowest and the position of the pressing surface of the annular lower punch is higher than the position of the pressing surface of the outer lower punch 22 (furthermore, the position of the pressing surface of the inner annular lower punch is lower than the position of the pressing surface of the outer annular lower punch). Then, in the pressing step (see FIG. 4(4)), the central lower punch may be driven upward relative to the annular lower punch so that the pressing surface of the central lower punch approaches the pressing surface of the annular lower punch. Furthermore, when multiple annular lower punches are present, the inner annular lower punch may be driven upward relative to the outer annular upper punch.

[0042] In the above embodiment, the second pressing surface S of the upper punch 10 12 and the second pressing surface S of the lower punch 20 22 As each of the above moves radially outward, 1 The equatorial plane containing and centered on O 2 In the above embodiment, the second pressing surface S of the upper punch 10 is gradually farther from each of the equatorial planes including the equator plane. 12 and the second pressing surface S of the lower punch 20 22 Only one of the two approaches the center O 1 The equatorial plane or center O 2 In this case, the second pressing surface S of the upper punch 10 may be gradually moved away from the equatorial plane including the second pressing surface S of the upper punch 10. 12 and the second pressing surface S of the lower punch 20 22 The other of these is the center O 1 The equatorial plane or center O 2 The punch may be formed so as to extend along an equatorial plane including the punch head, at least partially approach the equatorial plane, or at least protrude beyond the equatorial plane in a direction approaching the opposing punch.

[0043] Instead of the spherical molded body Q, the annular molded body R may be separated from a molded body having a spherical truncated part including the equator, with the outer diameter being maximum at the equator. For example, the annular molded body R connected to the equator of the intermediate part may be separated from a molded body having a shape in which a semispherical, spherical crown, semi-elliptical, conical, truncated conical or cylindrical upper part, a semispherical, spherical crown, semi-elliptical, conical, truncated conical or cylindrical upper part having an upper surface (flat) with the same diameter as the lower surface (flat) of the upper part, a spherical truncated intermediate part including the equator, and a semispherical, spherical crown, semi-elliptical, conical, truncated conical or cylindrical lower part having an upper surface with the same diameter as the lower surface (flat) of the intermediate part may be connected coaxially in this order from above. In this case, the pressing surface of the upper punch 10 is a first pressing surface S having a substantially spherical band shape. 11 and the second pressure surface S 12 In addition, the first pressure surface S 11 Similarly, the pressing surface of the lower punch 20 is a first pressing surface S having a substantially spherical band shape. 21 and the second pressure surface S 22 In addition, the first pressure surface S 21 and a pressure surface having a shape corresponding to the shape of the lower portion, which is continuous with the inner peripheral edge of the pressure surface.

[0044] The powder molding apparatus may include an upper punch (or an inner upper punch and an outer upper punch) having the same cross-sectional shape as the upper punch 10 (or an inner upper punch 11 and an outer upper punch 12) and defining an approximately semicylindrical open space extending in a direction perpendicular to the cross-sectional shape, a lower punch (or an inner lower punch and an outer lower punch) having the same cross-sectional shape as the lower punch 20 (or an inner lower punch 21 and an outer lower punch 22) and defining an approximately semicylindrical open space extending in a direction perpendicular to the cross-sectional shape, and a molding die having a through hole penetrating in the vertical direction. The through hole of the molding die has a pair of inner surfaces facing each other so as to define the end faces of the cylinder and a pair of inner surfaces facing each other so as to sandwich the cylinder in the radial direction, the approximately cylindrical open space defined by the upper punch and the lower punch.

[0045] According to the powder molding apparatus, a cylindrical compact is formed in place of the spherical compact Q, and a pair of linear compacts, each of which is substantially linear (or has a substantially trapezoidal or sectoral cross section) and extends in a direction parallel to the central axis of the cylindrical compact at positions symmetrical to each other across the central axis of the cylindrical compact, are formed in place of the annular compact R. The cylindrical compact and the pair of linear compacts are integral until halfway through (see FIG. 4(4)), but then the cylindrical compact and the pair of linear compacts are separated from each other by the same principle as that by which the spherical compact Q and the annular compact R are separated from each other. This reduces the manufacturing cost of the cylindrical compacts (see FIG. 5(5)). [Explanation of symbols]

[0046] 10. Upper punch 11. Inside upper punch 12. Outer upper punch 20. Lower punch 21. Inside lower punch 22. Lower outer punch 24. Forming die 40. Control device 110...Inner upper punch actuator 120...Outer upper punch actuator 210...Inner lower punch actuator 220...Outer lower punch actuator 240...Molding die actuator P‥Powder Q‥Spherical molded object R: Ring-shaped molded body S 10 ...Continuous portion of the first and second pressing surfaces of the upper punch S 11 ...First pressing surface of the upper punch S 12 ...Second pressing surface of upper punch S 20 ...Continuous portion of the first and second pressing surfaces of the lower punch S 21 ...First pressing surface of the lower punch S 22 ...The second pressure surface of the lower punch.

Claims

1. A powder molding apparatus including an upper punch, a lower punch, and a molding die having through holes into which the upper punch and the lower punch are inserted from above and below, The pressing surfaces of the upper punch and the lower punch are A first pressure surface is formed of a hemisphere or a spherical zone missing a latitude range of 0.01° to 3.0° from the equator; a second annular pressure surface continuous with an outer peripheral edge portion of the first pressure surface, The second pressing surface of at least one of the upper punch and the lower punch is formed so as to become gradually farther from a plane including the equator of the hemisphere at least partway toward the outside in the radial direction. Powder molding equipment.

2. 2. The powder molding apparatus according to claim 1, The angle that the inner peripheral edge of the second pressure surface makes with respect to a plane including the equator of the hemisphere is within an angle range of 20° to 85°. Powder molding equipment.

3. 3. The powder molding apparatus according to claim 1, The lower punch is composed of an inner lower punch having an inner portion of the first pressure surface as at least a part of its pressure surface, and an outer lower punch surrounding the inner lower punch having an outer portion of the first pressure surface and the second pressure surface as its pressure surface. Powder molding equipment.

4. 4. The powder molding apparatus according to claim 3, The upper punch is composed of an inner upper punch having an inner portion of the first pressing surface as at least a part of its pressing surface, and an outer upper punch surrounding the inner upper punch having an outer portion of the first pressing surface and the second pressing surface as its pressing surface. Powder molding equipment.

5. A method for producing a powder compact using the powder molding apparatus according to claim 1 or 2, comprising the steps of: a powder filling step of filling a space defined by the forming die and the lower punch inserted from below into the through hole of the forming die with powder; a pressurizing step in which the upper punch and the lower punch, which are inserted from above into the through hole of the forming die, are brought relatively close to each other to pressurize the powder filled in the space, thereby forming a spherical molded body by the first pressing surfaces of the upper punch and the lower punch, and forming an annular molded body that is continuous with the spherical molded body via an annular continuous portion by the second pressing surfaces of the upper punch and the lower punch and a side surface of the through hole of the forming die; a compact removal step in which the upper punch is pulled upward from the through hole of the forming die by relatively displacing the upper punch and the forming die, and the lower punch is raised relative to the forming die by relatively displacing the lower punch and the forming die, thereby separating the spherical compact from the annular compact at the continuous portion; Includes A method for producing a powder compact.

6. A method for producing a powder compact using the powder molding apparatus according to claim 3, comprising the steps of: a powder filling step of positioning a pressing surface of the inner lower punch relatively lower than a pressing surface of the outer lower punch, and filling a space defined by an inner surface of the outer lower punch inserted from below into the through hole of the forming die and the pressing surface of the inner lower punch with powder; a pressurizing step of pressing the powder filled in the space by bringing the upper punch and the lower punch, which are inserted from above into the through hole of the forming die, relatively close to each other and bringing the pressurizing surface of the inner lower punch relatively close to the pressurizing surface of the outer lower punch so that the pressurizing surface of the lower punch is formed, thereby forming a spherical molded body by the first pressurizing surfaces of the upper punch and the lower punch, and forming an annular molded body that is continuous with the spherical molded body via an annular continuous portion by the second pressurizing surfaces of the upper punch and the lower punch and a side surface of the through hole of the forming die; a compact removal step of relatively displacing the upper punch and the forming die to pull the upper punch upward from the through hole of the forming die, and relatively displacing the inner lower punch and the outer lower punch to raise the pressure surface of the inner lower punch higher than the pressure surface of the outer lower punch, thereby separating the spherical compact from the annular compact at the continuous portion. A method for producing a powder compact.

7. A method for producing a powder compact using the powder molding apparatus according to claim 4, comprising the steps of: a powder filling step of positioning a pressing surface of the inner lower punch relatively lower than a pressing surface of the outer lower punch, and filling a space defined by an inner surface of the outer lower punch inserted from below into the through hole of the forming die and the pressing surface of the inner lower punch with powder; a pressurizing step of pressing the powder filled in the space by bringing the upper punch and the lower punch, which are inserted from above into the through hole of the forming die, relatively close to each other, bringing the pressurizing surface of the inner lower punch relatively close to the pressurizing surface of the outer lower punch so that the pressurizing surface of the lower punch is formed, and bringing the pressurizing surface of the inner upper punch relatively close to the pressurizing surface of the outer upper punch so that the pressurizing surface of the upper punch is formed, thereby forming a spherical molded body by the first pressurizing surfaces of the upper punch and the lower punch, and forming an annular molded body that is continuous with the spherical molded body via an annular continuous portion by the second pressurizing surfaces of the upper punch and the lower punch and a side surface of the through hole of the forming die; a compact removal step of relatively displacing the upper punch and the forming die to pull the upper punch upward from the through hole of the forming die, and relatively displacing the inner lower punch and the outer lower punch to raise the pressure surface of the inner lower punch higher than the pressure surface of the outer lower punch, thereby separating the spherical compact from the annular compact at the continuous portion. A method for producing a powder compact.

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