Die, metal mold, method of producing die, and method of producing green compact

Abstract

To provide a die less apt to be damaged even in the case of producing a green compact complicated in shape having a grooved recess.SOLUTION: A die comprises a cylindrical die body, an inner ring that tightens the die body, and an outer ring that tightens the inner ring. The die body comprises a plurality of first segments and a plurality of second segments alternately arranged around an axis of the die body. Each of the first segments, as viewed along the axis, comprises a first base portion in a block form and a head portion protruding toward the axis from the first base portion. Each of the second segments, as viewed along the axis, comprises a second base portion in a block form and a plate portion protruding toward the axis from the second base portion. The plate portion comprises a first portion sandwiched between two adjacent head portions and a second portion that is exposed from between the two head portions and extends toward the axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a die, a metal mold, a method for manufacturing a die, and a method for manufacturing a powder compact. [Background technology]

[0002] Patent Document 1 discloses a mold for forming a sintered molded product such as a rotor for a vane pump. The rotor is an annular member. The rotor has a plurality of groove-like recesses on its annular outer surface. The groove-like recesses extend along the axis of the rotor. Vanes are arranged in the recesses.

[0003] The mold of Patent Document 1 includes a die, an upper punch, and a lower punch. The die includes a die body having a cylindrical through hole that forms a molding space. A groove is formed on the circumferential surface of the through hole. A plate-shaped core is fitted into the groove. The core includes a plate portion disposed inside the groove and a protruding plate portion that protrudes into the mold hole. When a rotor is molded using this mold, a groove-shaped recess is formed in the rotor by the protruding plate portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-279709 Summary of the Invention [Problem to be solved by the invention]

[0005] In the die of Patent Document 1, when the rotor, which is a molded product to be sintered, is removed from the die, stress tends to concentrate near the boundary between the plate portion and the protruding plate portion of the plate-shaped core, which may damage the plate-shaped core, especially when the length of the rotor along the rotor axis is long.

[0006] An object of the present disclosure is to provide a die that is less likely to be damaged even when producing a powder compact having a complex shape with a groove-like recess, and a method for manufacturing the die.Another object of the present disclosure is to provide a mold including a die that is less likely to be damaged even when producing a powder compact having a complex shape with a groove-like recess. [Means for solving the problem]

[0007] The die disclosed herein is a die included in a mold for producing a powder compact, and includes a cylindrical die body having an axis and an annular outer peripheral surface, an inner ring tightening the die body from the outside to the inside, and an outer ring tightening the inner ring from the outside to the inside. The die body includes a plurality of first segments and a plurality of second segments arranged alternately around the axis. Each of the first segments, as viewed along the axis, includes a block-shaped first base portion forming a part of the outer peripheral surface of the die body and a head portion protruding from the first base portion toward the axis. Each of the second segments, as viewed along the axis, includes a block-shaped second base portion forming the remainder of the outer peripheral surface of the die body and a plate portion protruding from the second base portion toward the axis. The head portion protrudes toward the plate portion. The plate portion includes a first portion sandwiched between two adjacent head portions and a second portion exposed from the two head portions and extending toward the axis. [Effects of the Invention]

[0008] The die of the present disclosure can produce powder compacts of complex shapes having groove-like recesses, and is less likely to be damaged during production. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a mold according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of a die provided in the mold of FIG. [Figure 3]FIG. 3 is a schematic exploded perspective view of the die shown in FIG. [Figure 4] FIG. 4 is a schematic enlarged view of a part of the die body provided in the die shown in FIG. [Figure 5] FIG. 5 is a schematic configuration diagram of the vane pump according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Description of the embodiments of the present disclosure] <1> A die according to an embodiment of the present disclosure is provided in a mold for producing a powder compact, and includes a cylindrical die body having an axis and an annular outer peripheral surface, an inner ring tightening the die body from the outside to the inside, and an outer ring tightening the inner ring from the outside to the inside. The die body includes a plurality of first segments and a plurality of second segments arranged alternately around the axis. Each of the first segments, as viewed along the axis, includes a block-shaped first base portion forming a part of the outer peripheral surface of the die body and a head portion protruding from the first base portion toward the axis. Each of the second segments, as viewed along the axis, includes a block-shaped second base portion forming the remainder of the outer peripheral surface of the die body and a plate portion protruding from the second base portion toward the axis. The head portion protrudes toward the plate portion. The plate portion includes a first portion sandwiched between two adjacent head portions and a second portion exposed from the two head portions and extending toward the axis.

[0011] When a powder compact is produced using the die according to the embodiment, the second portion of the plate portion forms a groove-like recess on the outer peripheral surface of the powder compact. Therefore, the die can produce a powder compact having a groove-like recess on the outer peripheral surface. Such a powder compact is, for example, a rotor for a vane pump.

[0012] In the die according to the embodiment, a die body including a plurality of first segments and a plurality of second segments arranged in an annular shape is doubly clamped from the outside of the die body by an inner ring and an outer ring. The die body is positioned inside the inner ring by shrink fitting. The inner ring is also positioned inside the outer ring by shrink fitting. That is, the die is manufactured by shrink fitting the inner ring to the outer periphery of the die body, and then shrink fitting the outer ring to the outer periphery of the inner ring. First, the die body including a plurality of first segments and second segments arranged in an annular shape is clamped by the inner ring, thereby applying compressive stress to the die body. The clamping by the inner ring supports the first segments and second segments to each other, maintaining a state in which the first segments and second segments are precisely positioned at desired positions. From this state, by clamping the inner ring by the outer ring, further compressive stress can be applied to the die body while maintaining the first segments and second segments precisely positioned. The doubly clamping by the inner ring and the outer ring improves the durability of the die body. The die of the embodiment manufactured in this manner has a cavity formed with high precision in a desired shape and is highly durable.

[0013] In the die according to the embodiment, the first base portion of the first segment and the second base portion of the second segment contact each other in a direction along the circumference centered on the axis of the die body, and the head portion of the first segment contacts a first portion of the plate portion of the second segment. Due to the large contact area between the first segment and the second segment and the fact that the first segment and the second segment are fastened together by the inner ring, even if stress acts on the plate portion during the production of a powder compact using the die, the stress is easily dispersed. As a result, excessive stress is less likely to concentrate near the boundary between the first and second portions of the plate portion, and the plate portion is less likely to be damaged. Here, the production of a powder compact in this specification includes both the operation of compressing powder inside the die of a metal mold and the operation of removing the powder compact from the die.

[0014] <2> the above <1> The die described in the above item 1 may include a coolant flow path formed by a circumferential groove disposed on at least one of the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring.

[0015] the above <2> According to the die described in the above, a cooling effect on the die body can be obtained by circulating a refrigerant through the refrigerant flow path during the production of a powder compact using the die. As a result, the temperature of the die body does not become too high, which tends to extend the life of the die body. In the double shrink-fit structure using the inner ring and the outer ring, a refrigerant flow path can be easily formed between the inner ring and the outer ring.

[0016] <3> the above <1> or <2> In the die described above, the first segment may have a uniform cross section at any position along the axis, and the second segment may have a uniform cross section at any position along the axis.

[0017] If the die body, which is an assembly, has specific locations where stress caused by clamping between the inner and outer rings locally concentrates, further stress may act on those specific locations during the production of a powder compact, potentially damaging those specific locations.In contrast, if the first and second segments that form the die body each have a uniform cross section at any position along the axis, it is less likely that a location where stress locally concentrates will be formed in the die body when the die body is clamped from the outer periphery by the inner and outer rings.

[0018] <4> the above <1> from <3> In the die described in any one of the above, the length of the die body along the axis may be 80 mm or more.

[0019] As described above, in the die according to the embodiment, localized stress is unlikely to act on the plate portion, and therefore, even if the length of the die body is 80 mm or more, the plate portion is unlikely to be damaged during the production of a powder compact, particularly when the powder compact is removed from the die body.

[0020] <5> the above <1> from <4> In the die described in any one of the above, the die body may be formed of a cemented carbide, and the inner ring and the outer ring may each be formed of a metal having higher toughness than the cemented carbide.

[0021] A die body made of a cemented carbide with high hardness is less likely to be damaged when the powder filled inside the die body is compressed and molded, and is also less likely to be damaged when the die body rubs against the powder compact when the powder compact is removed from the die.

[0022] When powder is compressed in the die, the powder packed inside the die body presses the die body from the inside. Because cemented carbide is brittle, there is a risk that the die body made of cemented carbide may be damaged. If the inner and outer rings that fasten the die body have high toughness, the internal stress acting on the die body can be alleviated. As a result, the die body is less likely to be damaged.

[0023] <6> the above <5> In the die described in the above, the metal may be copper or a copper alloy.

[0024] Copper or copper alloys have excellent toughness. Therefore, a sufficient shrink-fitting effect can be obtained, making the die body, which is made of cemented carbide, less likely to be damaged. Copper or copper alloys have excellent thermal conductivity. When powder is compressed by the die, friction causes the temperature of the powder and the die body to rise. If the temperature of the die body rises, the life of the die body may be shortened. If the inner and outer rings are made of copper or copper alloy, the heat of the die body is dispersed between the inner and outer rings, preventing the temperature of the die body from becoming too high. As a result, the life of the die body is likely to be extended.

[0025] <7> the above <1> from <6> In any one of the dies described above, the powder compact may be a rotor of a vane pump.

[0026] the above <7> According to the die described in the above, rotors for vane pumps can be manufactured with high productivity.

[0027] <8> The mold according to the embodiment of the present disclosure is <1> from <7> and a lower punch and an upper punch fitted into the die.

[0028] the above <8> According to the die described in the above, a powder compact having a groove-shaped recess on the outer peripheral surface can be produced.

[0029] <9> A method for manufacturing a die according to an embodiment of the present disclosure includes the following steps: Step A: forming a cylindrical die body having an axis and an annular outer peripheral surface by alternately arranging a plurality of first segments and a plurality of second segments in an annular shape; Step B: shrink-fitting an inner ring onto the outer periphery of the die body; and Step C: shrink-fitting an outer ring onto the outer periphery of the inner ring. Each of the first segments, as viewed along the axis, includes a block-shaped first base portion forming a portion of the outer peripheral surface of the die body and a head portion protruding from the first base portion toward the axis. Each of the second segments, as viewed along the axis, includes a block-shaped second base portion forming the remainder of the outer peripheral surface of the die body and a plate portion protruding from the second base portion toward the axis. The width of the head portion is greater than the width of the first base portion. The plate portion includes a first portion sandwiched between two adjacent head portions and a second portion exposed from the two head portions and extending toward the axis.

[0030] According to the die manufacturing method of the embodiment, the die according to the embodiment can be manufactured. In the die manufacturing method of the embodiment, an inner ring is shrink-fitted to the outer periphery of a die body that combines a plurality of first segments and a plurality of second segments, and then an outer ring is shrink-fitted to the outer periphery of the inner ring. By dividing the shrink-fitting that tightens the die body into two steps, the first segments and the second segments can be accurately positioned in the desired positions and can be firmly integrated.

[0031] <10> The method for producing a powder compact according to an embodiment of the present disclosure comprises the steps of: <8> the step of preparing a mold described in the above, the step of filling the mold with raw material powder, the step of compressing the raw material powder into a powder compact, and the step of extracting the powder compact from the mold.

[0032] the above <10> According to the method for producing a powder molded body described in the above, a powder molded body having a groove-shaped recess on the outer circumferential surface can be produced. This powder molded body is, for example, a rotor for a vane pump.

[0033] [Details of the embodiments of the present disclosure] Specific examples of the mold, die, die manufacturing method, and powder compact manufacturing method of the present disclosure will be described below with reference to the drawings. The same reference numerals in the figures indicate the same or corresponding parts. The sizes of the components shown in each drawing are expressed for the purpose of clarity and do not necessarily represent the actual dimensions. The present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0034] <Embodiment 1> <Mold> The mold 100 shown in Fig. 1 is used to produce a powder compact. The mold 100 includes a cylindrical die 1, a lower punch 101, and an upper punch 102. The die 1 includes a through hole 10 that forms a molding space. In this example, the lower punch 101 and the upper punch 102 are cylindrical. A core (not shown) may be placed inside the through hole 10 of the die 1.

[0035] When a powder compact is produced using the mold 100 of FIG. 1 , a lower punch 101 is fitted into a first opening 11 of a through hole 10 in the die 1. The first opening 11 is an opening facing downward. Next, raw material powder is filled into a molding space surrounded by the inner peripheral surface of the through hole 10 and the upper surface of the lower punch 101. Thereafter, an upper punch 102 is fitted into a second opening 12 of the through hole 10, and the raw material powder is compressed between the lower punch 101 and the upper punch 102. A powder compact is produced by this compression. Once the powder compact has been produced, the upper punch 102 is removed from the die 1, and the lower punch 101 is moved upward to remove the powder compact from the die 1.

[0036] One of the features of the die 100 of this example is the configuration of the die 1. The configuration of the die 1 is closely related to the shape of the powder compact produced by the die 100. The shape of the powder compact depends on the application of the powder compact. Therefore, before describing the die 1, the application of the powder compact produced by the die 100 will be mentioned. The application of the powder compact described in this example is a rotor 95 of a vane pump 9 shown in FIG. 5.

[0037] The vane pump 9 is a pump that pumps fluids such as oil or water. The vane pump 9 of this example includes a cylindrical cam ring 90 having an internal space 90s, and a rotor 95 disposed inside the cam ring 90. In this example, the shape of the internal space 90s as viewed along the central axis 90c of the cam ring 90 is circular. Unlike this example, the shape of the internal space 90s as viewed along the central axis 90c may be elliptical. An intake port and an exhaust port (not shown) are connected to the internal space 90s.

[0038] The rotor 95 includes a rotor body 96 and a plurality of vanes 97. The rotor body 96 is a cylindrical sintered body having a rotation axis 96c. The sintered body is manufactured by sintering a powder compact manufactured using a mold 100 shown in FIG. 1. When the vane pump 9 is in operation, the rotor body 96 rotates in the direction of rotation indicated by the white arrow. The rotor body 96 includes a plurality of groove-like recesses 96g on the outer peripheral surface 96b of the rotor body 96. The recesses 96g extend in a direction along the rotation axis 96c and are arranged radially relative to the rotation axis 96c. When viewed along the rotation axis 96c, the bottoms of the recesses 96g are circular. A vane 97 is disposed in each recess 96g.

[0039] The vane 97 is a plate-shaped member extending in a direction parallel to the rotational axis 96c. The vane 97 may be a sintered body or a melt-cast body. The vane 97 is fitted into the recess 96g so as to be movable in a direction parallel to the depth of the recess 96g. The direction parallel to the depth is the direction from the opening of the recess 96g in the outer peripheral surface 96b toward the rotational axis 96c. The vane 97 advances toward the inner peripheral surface 90a of the cam ring 90 due to centrifugal force and other factors associated with the rotation of the rotor body 96. The tip of the vane 97 contacts the inner peripheral surface 90a. With this configuration, the internal space 90s is divided into multiple small spaces aligned in the rotational direction of the rotor body 96. Each small space is surrounded by two vanes 97, 97 that are adjacent to each other in the rotational direction of the rotor body 96, the outer peripheral surface 96b of the rotor body 96, and the inner peripheral surface 90a of the cam ring 90.

[0040] The rotation axis 96c of the rotor body 96 is eccentric from the central axis 90c of the internal space 90s of the cam ring 90. Therefore, each of the small spaces lined up in the rotation direction of the rotor body 96 has a different volume. By configuring the vane pump 9 so that fluid is sucked into the vane pump 9 at the position of the small space with a larger volume and discharged from the vane pump 9 at the position of the small space with a smaller volume, the vane pump 9 can pump the fluid.

[0041] As described above, in this example, a powder molded body, which is a precursor of the rotor body 96 of the vane pump 9 shown in Fig. 5, is manufactured using the die 100 shown in Fig. 1. The shape of this powder molded body is substantially the same as the shape of the rotor body 96 after sintering. Hereinafter, each part of the powder molded body will be described using the same reference numerals as each part of the rotor body 96.

[0042] Thailand The configuration of the die 1 that determines the shape of the powder compact will be described with reference to FIGS. 2 to 4. FIG. 2 is a bottom view of the die 1 shown in FIG. 1. As shown in FIG. 2, the die 1 includes a cylindrical die body 2 having an axis 20, an inner ring 3 that clamps the die body 2 from the outside to the inside, and an outer ring 4 that clamps the inner ring 3 from the outside to the inside. One of the features of this die 1 is the configuration of the die body 2. Another feature of the die 1 of this example is that the die body 2 is doubly clamped.

[0043] [Die body] The die body 2 is a cylindrical body having an axis 20. This cylindrical die body 2 has an annular outer peripheral surface 21 and an irregularly shaped inner peripheral surface 22. The inner peripheral surface 22 determines the shape of the through hole 10 that forms the molding space. The contour shape of the inner peripheral surface 22 as viewed along the axis 20 is uniform along the axis 20. In other words, the contour shape of the inner peripheral surface 22 remains the same regardless of the position on the axis 20 at which the die body 2 is cut along a plane perpendicular to the axis 20.

[0044] When the powder is compressed and when the powder compact is removed from the die body 2, strong stress acts on the die body 2. To prevent damage to the die body 2 during such stresses, the die body 2 is made of a material with excellent strength. The die body 2 is made of a material such as cemented carbide, for example.

[0045] The die body 2 of this example is composed of a plurality of first segments 5 and a plurality of second segments 6 arranged alternately around the axis 20. The number of first segments 5 is the same as the number of second segments 6. The length of the first segments 5 along the axis 20 is the same as the length of the second segments 6. The die body 2 is doubly fastened from the outside by the inner ring 3 and the outer ring 4. Therefore, the first segments 5 and the second segments 6 support each other, and the die body 2 does not come apart.

[0046] The first segment 5 in this example has a uniform cross section along the axis 20. In other words, the cross-sectional shape of the first segment 5 is the same regardless of the position on the axis 20 at which the first segment 5 is cut along a cross section perpendicular to the axis 20. As shown in FIG. 4 , each first segment 5 viewed along the axis 20 includes a block-shaped first base portion 50 that forms part of the outer peripheral surface 21 of the die body 2, and a head portion 55 that protrudes from the first base portion 50 toward the axis 20.

[0047] When viewed along the axis 20, the first base portion 50 has a general fan shape including an arc portion that forms part of the outer peripheral surface 21 of the die body 2. The width of the first base portion 50 gradually narrows toward the axis 20. Here, the width of the first base portion 50 is the length of the first base portion 50 along the circumferential direction of the die body 2. The circumferential direction of the die body 2 is the direction along an imaginary circle centered on the axis 20 when the die body 2 is viewed along the axis 20.

[0048] When viewed along the axis 20, the head portion 55 has a general fan shape including an arc portion that forms part of the inner circumferential surface 22 of the die body 2. The width of the head portion 55 gradually increases with increasing distance from the axis 20. The width of the head portion 55 near the boundary between the first base portion 50 and the head portion 55 is greater than the width of the first base portion 50. Therefore, when the first segment 5 is viewed along the axis 20, the head portion 55 protrudes in the circumferential direction beyond the first base portion 50. In other words, the head portion 55 protrudes toward the plate portion 65 of the second segment 6, which will be described later.

[0049] The second segments 6 in this example have a uniform cross section along the axis 20. In other words, the cross-sectional shape of the second segments 6 is the same regardless of the position on the axis 20 at which the second segments 6 are cut along a cross section perpendicular to the axis 20. When viewed along the axis 20, each second segment 6 includes a block-shaped second base portion 60 that forms the remainder of the outer peripheral surface 21 of the die body 2, and a plate portion 65 that protrudes from the second base portion 60 toward the axis 20.

[0050] The second base portion 60, as viewed along the axis 20, includes an arcuate portion that constitutes the remainder of the outer peripheral surface 21 of the die body 2. The second base portion 60 has a generally rectangular shape with two side surfaces extending parallel to the arcuate portion. Each side surface is in surface contact with the first base portion 50 that faces it.

[0051] As shown in Fig. 3, the plate portion 65 has a thin plate shape. As shown in Fig. 4, the width of the plate portion 65 as viewed along the axis 20 is smaller than the width of the second base portion 60. The width of the plate portion 65 is the length of the plate portion 65 along the circumferential direction of the die body 2. The width of the second base portion 60 is the length of the second base portion 60 along the circumferential direction of the die body 2. The width of the plate portion 65 may be uniform in the protruding direction of the plate portion 65, or may change gradually or in steps.

[0052] The plate portion 65 includes a first portion 65A sandwiched between two adjacent head portions 55, 55, and a second portion 65B exposed from the two head portions 55, 55 and extending toward the axis 20. An end portion 65E of the second portion 65B is circular when viewed along the axis 20. The width of the second portion 65B excluding the circular end portion 65E is uniform in the protruding direction of the plate portion 65. The width of the first portion 65A is uniform in the protruding direction of the plate portion 65. The width of the second portion 65B excluding the circular end portion 65E is slightly smaller than the width of the first portion 65A.

[0053] The length L1 of the first portion 65A and the length L2 of the second portion 65B along the protruding direction of the plate portion 65 satisfy, for example, the following formula. 0.3≦L1 / (L1+L2)≦0.7 If L1 / (L1+L2) is 0.3 or more, the first portion 65A supported by the head portion 55 is not too short compared to the second portion 65B exposed from the head portion 55, so that the stress acting on the boundary between the first portion 65A and the second portion 65B does not become too high. If L1 / (L1+L2) is 0.7 or less, a recess 96g with sufficient depth can be formed in the powder compact. L1 / (L1+L2) may be 0.4 or more and 0.6 or less.

[0054] In the die body 2, which is formed by combining a plurality of first segments 5 and a plurality of second segments 6, an inner peripheral surface 22 is formed by the surface of the head portion 55 facing the axis 20 and the circumferential surface of the second portion 65B of the plate portion 65. The surface of the head portion 55 facing the axis 20 forms an outer peripheral surface 96b (FIG. 5) of the powder compact. The circumferential surface of the second portion 65B forms a recess 96g (FIG. 5) of the powder compact.

[0055] In this example, the first base portion 50 of the first segment 5 and the second base portion 60 of the second segment 6 are in contact with each other in the circumferential direction around the axis 20 of the die body 2, and the head portion 55 of the first segment 5 and the first portion 65A of the plate portion 65 of the second segment 6 are in contact with each other. The die body 2 is fastened by the inner ring 3 and the outer ring 4, which will be described later, and therefore cannot be disassembled into the first segment 5 and the second segment 6.

[0056] As described above, the contact area between the first segment 5 and the second segment 6 is relatively large. Therefore, even when the die body 2 is tightened, the stress caused by the tightening is easily dispersed. This stress dispersion prevents damage to the first segment 5 and the second segment 6. Furthermore, because the contact area between the first segment 5 and the second segment 6 is relatively large, the stress acting on the second portion 65B of the plate portion 65 when compressing the powder in the die 100 and when releasing the powder compact from the die 1 is also easily dispersed. Therefore, excessive stress is less likely to act near the boundary between the first portion 65A and the second portion 65B of the plate portion 65, and the plate portion 65 is less likely to be damaged.

[0057] Furthermore, in this example, the first segment 5 and the second segment 6 have a uniform cross section along the axis 20, and therefore there is no significant difference in the force with which the first segment 5 and the second segment 6 press against each other at any position along the axis 20. Therefore, when the die body 2 is clamped by the inner ring 3 and the outer ring 4 and when a powder compact is produced, localized stress concentrations are unlikely to occur in the die body 2.

[0058] Furthermore, to prevent damage to the die body 2, the first segment 5 in this example includes a first notch 59, and the second segment 6 includes a second notch 69. The shapes of the first notch 59 and the second notch 69 are, for example, C-chamfered or R-chamfered. The first notch 59 of the first segment 5 is formed in a portion facing a second corner located at the joint between the second base portion 60 and the plate portion 65 of the second segment 6. The first notch 59 prevents the head portion 55 of the first segment 5 from contacting the second corner, thereby preventing stress from acting on the second corner. Meanwhile, the second notch 69 of the second segment 6 is formed in a position facing a first corner located at the joint between the first base portion 50 and the head portion 55 of the first segment 5. The second notch 69 prevents the second base portion 60 of the second segment 6 from contacting the first corner, thereby preventing stress from acting on the first corner.

[0059] In the die body 2 having the configuration of this example, the plate portion 65 is less likely to be damaged, so the length L of the die body 2 shown in FIG. 3 can be increased. The length L is the length of the die body 2 along the axis 20 (see FIG. 2). The length L may be, for example, 80 mm or more, 100 mm or more, or 120 mm or more. Although the plate portion 65 is less likely to be damaged, the longer the length L, the higher the possibility of the plate portion 65 being damaged. Therefore, the upper limit of the length L is, for example, 150 mm. The length of the powder compact produced by such a die body 2 is 0.35 to 0.8 times the length L.

[0060] [Inner and outer rings] As shown in FIG. 2 , the inner ring 3 is a cylindrical member that houses the die body 2 therein. The inner peripheral surface 32 of the inner ring 3 is in contact with the outer peripheral surface 21 of the die body 2. As shown in the manufacturing method of the die 1 described later, the die body 2 is fitted into the inner ring 3 by shrink fitting. The outer diameter of the die body 2 before fitting into the inner ring 3 is larger than the inner diameter of the inner ring 3. The die body 2 fitted into the inner ring 3 by shrink fitting is clamped by the inner ring 3 from the outside to the inside.

[0061] The outer ring 4 is a cylindrical member that houses the inner ring 3. The inner peripheral surface 42 of the outer ring 4 is in contact with the outer peripheral surface 31 of the inner ring 3. As shown in the manufacturing method of the die 1 described later, the inner ring 3 is fitted into the outer ring 4 by shrink fitting. The outer diameter of the inner ring 3 before fitting into the outer ring 4 is larger than the inner diameter of the outer ring 4. The inner ring 3 fitted into the outer ring 4 by shrink fitting is tightened by the outer ring 4 from the outside to the inside. The outer peripheral surface 41 of the outer ring 4 is the outer peripheral surface of the die body 2.

[0062] As described above, in the die 1 of this example, the die body 2, which is made up of a combination of a plurality of first segments 5 and a plurality of second segments 6, is doubly clamped from the outside of the die body 2 by the inner ring 3 and the outer ring 4. Therefore, the first segments 5 and the second segments 6 support each other, and the die body 2 does not come apart.

[0063] The inner ring 3 and the outer ring 4 are formed, for example, from a metal that has higher toughness than the die body 2. When powder is compressed using the mold 100 (FIG. 1), the powder filled inside the die body 2 presses the die body 2 from the inside. The die body 2, which is formed from a cemented carbide, is brittle and easily damaged, but if the inner ring 3 and the outer ring 4 that fasten the die body 2 have high toughness, the inner stress acting on the die body 2 from the inside can be counteracted by the inner ring 3 and the outer ring 4. As a result, the die body 2 is less likely to be damaged.

[0064] The metal forming the inner ring 3 and the outer ring 4 is, for example, copper or a copper alloy. Copper or a copper alloy has excellent toughness. Therefore, the die body 2 formed from a cemented carbide alloy is less likely to be damaged. Copper or a copper alloy has excellent thermal conductivity. When the powder is compressed by the die 1, friction causes the temperature of the powder and the die body 2 to rise. If the temperature of the die body 2 becomes too high, the life of the die body 2 may be shortened. If the inner ring 3 and the outer ring 4 are formed from copper or a copper alloy, the heat of the die body 2 is dispersed to the inner ring 3 and the outer ring 4, and the temperature of the die body 2 does not become too high. As a result, the life of the die body 2 is likely to be extended.

[0065] As shown in FIG. 3 , the outer ring 4 of this example has a circumferential groove 45 on its inner peripheral surface 42. The circumferential groove 45 of this example is a spiral groove that spirals around the inner peripheral surface 42 from the first end face to the second end face of the outer ring 4. By fitting the inner ring 3 inside this outer ring 4, a refrigerant flow path 15 is formed, which is a space surrounded by the outer peripheral surface 31 of the inner ring 3 and the circumferential groove 45 of the outer ring 4. By flowing a refrigerant through the refrigerant flow path 15, the die body 2 can be cooled during the production of a powder compact. As a result, the temperature of the die body 2 does not become too high, which tends to extend the life of the die body 2.

[0066] Unlike this example, the circumferential groove that forms the refrigerant flow path 15 may be formed on the outer peripheral surface 31 of the inner ring 3. In this case, the space surrounded by the circumferential groove formed on the outer peripheral surface 31 of the inner ring 3 and the inner peripheral surface 42 of the outer ring 4 functions as the refrigerant flow path 15. Alternatively, circumferential grooves may be formed on both the outer peripheral surface 31 of the inner ring 3 and the inner peripheral surface 42 of the outer ring 4. In this case, the space surrounded by the circumferential groove of the inner ring 3 and the circumferential groove of the outer ring 4 functions as the refrigerant flow path 15.

[0067] <Die manufacturing method> The die 1 is manufactured by carrying out the following steps in order. Step A: A step of forming a cylindrical die body 2 having an axis 20 and an annular outer surface 21 by arranging a plurality of first segments 5 and a plurality of second segments 6 alternately in a ring shape. Step B: A step of shrink-fitting the inner ring 3 onto the outer periphery of the die body 2. Process C: A process of shrink-fitting the outer ring 4 onto the outer periphery of the inner ring 3.

[0068] In the manufacturing method of the die 1 of this example, after performing step A to form a die body 2 consisting of a plurality of first segments 5 and a plurality of second segments 6 arranged in an annular shape, step B is performed to shrink-fit an inner ring 3 onto the outer periphery of the die body 2. By clamping the die body 2 with the inner ring 3 and applying compressive stress to the die body 2, the first segments 5 and the second segments 6 support each other, maintaining the first segments 5 and the second segments 6 precisely positioned in their desired positions. From this state, by clamping the inner ring 3 with the outer ring 4 in step C, further compressive stress can be applied to the die body 2 while maintaining the first segments 5 and the second segments 6 precisely positioned. The doubly clamped structure between the inner ring 3 and the outer ring 4 improves the durability of the die body 2. The die 1 of this embodiment manufactured in this manner has a cavity precisely formed in a desired shape and is highly durable.

[0069] In the manufacturing method of the die 1 of this example, shrink fitting for fastening the die body 2 is performed in two steps. Therefore, by forming a circumferential groove 45 on at least one of the outer peripheral surface 31 of the inner ring 3 and the inner peripheral surface 42 of the outer ring 4, the refrigerant flow path 15 can be formed between the inner ring 3 and the outer ring 4 simply by shrink fitting the outer ring 4 onto the outer periphery of the inner ring 3. [Explanation of symbols]

[0070] 1 die 10 through hole, 11 first opening, 12 second opening, 15 refrigerant flow path 2 die body, 20 axis, 21 outer peripheral surface, 22 inner peripheral surface 3 Inner ring, 31 Outer surface, 32 Inner surface 4 outer ring, 41 outer peripheral surface, 42 inner peripheral surface, 45 circumferential groove 5 First Segment 50 first base portion, 55 head portion, 59 first notch portion 6 Second Segment 60 second base portion, 65 plate portion, 69 second notch portion 65A first part, 65B second part, 65E end 9. Vane Pump 90 cam ring, 90a inner circumferential surface, 90c center shaft, 90s internal space 95 rotor 96 rotor body, 96b outer peripheral surface, 96c rotating shaft, 96g recess 97 Vane 100 molds 101 Lower Punch, 102 Upper Punch L, L1, L2 length

Claims

1. A die provided in a mold for producing a powder compact, a cylindrical die body having an axis and an annular outer circumferential surface; an inner ring tightening the die body from the outside to the inside; an outer ring tightening the inner ring from the outside to the inside, the die body includes a plurality of first segments and a plurality of second segments arranged alternately around the axis; Each of the first segments, viewed along the axis, comprises: a block-shaped first base portion that forms a part of the outer circumferential surface of the die body; a head portion protruding from the first base portion toward the axis, Each of the second segments, viewed along the axis, a block-shaped second base portion that forms the remainder of the outer circumferential surface of the die body; a plate portion protruding from the second base portion toward the axis, The head portion protrudes toward the plate portion, The plate portion is a first portion sandwiched between two adjacent head portions; and a second portion exposed from the two head portions and extending toward the axis. Thailand.

2. The die of claim 1 , further comprising a coolant flow path formed by a circumferential groove disposed on at least one of an inner circumferential surface of the outer ring and an outer circumferential surface of the inner ring.

3. the first segment has a uniform cross section at any position along the axis; 3. A die according to claim 1 or claim 2, wherein the second segment has a uniform cross section anywhere along the axis.

4. 3. A die according to claim 1 or claim 2, wherein the length of the die body along the axis is 80 mm or more.

5. the die body is made of cemented carbide; The die according to claim 1 or 2, wherein the inner ring and the outer ring are each formed of a metal having higher toughness than the cemented carbide.

6. The die of claim 5 , wherein the metal is copper or a copper alloy.

7. 3. The die according to claim 1, wherein the powder compact is a rotor of a vane pump.

8. The die according to claim 1 or claim 2; A lower punch and an upper punch fitted into the die are provided. Mold.

9. a step A of forming a cylindrical die body having an axis and an annular outer circumferential surface by alternately arranging a plurality of first segments and a plurality of second segments in an annular manner; a step B of shrink-fitting an inner ring onto the outer periphery of the die body; and a step C of shrink-fitting an outer ring onto the outer periphery of the inner ring, Each of the first segments, viewed along the axis, comprises: a block-shaped first base portion that forms a part of the outer circumferential surface of the die body; a head portion protruding from the first base portion toward the axis, Each of the second segments, viewed along the axis, a block-shaped second base portion that forms the remainder of the outer circumferential surface of the die body; a plate portion protruding from the second base portion toward the axis, The width of the head portion is greater than the width of the first base portion, The plate portion is a first portion sandwiched between two adjacent head portions; and a second portion exposed from the two head portions and extending toward the axis. Die manufacturing method.

10. providing a mold according to claim 8; filling the mold with raw material powder; compressing the raw material powder into a powder compact; and removing the powder molded body from the die. A method for manufacturing a powder compact.

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