Method for producing molded article

Abstract

This method for producing a molded article comprises: a supply step for supplying a compound that contains a thermosetting resin and a magnet powder into a mold space of a mold unit; and a molding step for compressing the compound which has been heated inside the mold unit and molding the compound into a molded article. The mold unit is provided with a first communication path for communication with the mold space. The first communication path has a cross-sectional shape that allows the passage of particles with a size that is the median diameter of the magnet powder or greater but that inhibits the passage of particles with a size more than 20 times the median diameter of the magnet powder.

Description

Method for manufacturing a molded body 【0001】 The present disclosure relates to a method for manufacturing a molded body. 【0002】 As a permanent magnet, there is a bonded magnet. For example, since the crystal structure of an Sm—Fe—N-based permanent magnet is liable to deteriorate at a high temperature (about 500° C.), it is difficult to manufacture a sintered magnet from an Sm—Fe—N-based permanent magnet. Therefore, an Sm—Fe—N-based permanent magnet is used as a raw material for an anisotropic bonded magnet that can be manufactured by heating at a low temperature at which the crystal structure is maintained (thermosetting of a thermosetting resin mixed with magnet powder). Further, for example, in addition to an Sm—Fe—N-based permanent magnet, anisotropic bonded magnets using magnets such as Nd—Fe—B-based permanent magnets (neodymium-iron-boron-based permanent magnets) are known. 【0003】 As a raw material for a bonded magnet, a compound containing magnet powder (a large number of magnet powders made of a permanent magnet) and a thermosetting resin is used. In the manufacture of an anisotropic bonded magnet, the compound is supplied into a mold. While applying a magnetic field generated by a coil to the compound in the mold, the compound is compressed by the mold, whereby a molded body is molded from the compound. Each magnet particle (magnetic domain in each magnet particle) in the molded body is magnetized and oriented along the magnetic field. The molded body is demagnetized, the demagnetized molded body is cured by heating, and by magnetizing the cured molded body, an anisotropic bonded magnet is obtained. 【0004】 Japanese Patent No. 7298804 【0005】 The residual magnetic flux density (Br), which is one of the magnetic properties of a bonded magnet, is improved by an increase in the filling rate of magnet particles in a molded body. For this reason, it is conceivable to manufacture a molded body by pressurizing a compound at a high pressure, but the pressure applied to the magnet powder becomes high, and deformation of the powder shape or the like occurs, whereby the magnetic properties are liable to deteriorate. 【0006】 Therefore, the present disclosure describes a method for manufacturing a molded body that can increase the density of a molded body that becomes a bonded magnet while suppressing a decrease in magnetic properties. 【0007】A method for manufacturing a molded article according to one aspect of the present disclosure is: [1] "A manufacturing method for a molded article comprising: a supply step of supplying a compound containing magnetic powder and a thermosetting resin into the molding space of a mold unit; and a molding step of compressing the heated compound in the mold unit to mold a molded article from the compound, wherein the mold unit is provided with a passage that communicates with the molding space, and the passage has a cross-sectional shape that allows particles larger than or equal to the median diameter of the magnetic powder to flow through, and prevents the flow of particles larger than 20 times the median diameter of the magnetic powder." 【0008】 The mold unit used in the molding process of this manufacturing method for molded articles is provided with a connecting passage that communicates with the molding space. This connecting passage has a cross-sectional shape that allows particles larger than or equal to the median diameter of the magnetic powder to flow through. Therefore, a portion of the compound (a portion of the magnetic powder and thermosetting resin) that is pressurized during the molding process can enter the connecting passage from the molding space within the mold unit. This improves the fluidity of the compound in the molding space when the compound is pressurized, and increases the density of the magnetic powder in the molded article within the molding space. In addition, when the compound is pressurized, some of the compound can escape (enter) the connecting passage from the molding space. Therefore, the pressure applied to the magnetic powder can be reduced, and damage to the magnetic powder due to pressurization can be suppressed. This connecting passage has a cross-sectional shape that inhibits the flow of particles larger than 20 times the median diameter of the magnetic powder. Therefore, when the compound is pressurized during the molding process, it is possible to appropriately pressurize the compound while suppressing excessive outflow of the compound from the molding space into the communication passage. In this way, this method of manufacturing a molded body makes it possible to increase the density of the molded body that becomes a bonded magnet while suppressing a decrease in magnetic properties. 【0009】The above method for manufacturing a molded article may also be [2] "the mold unit comprises a concave mold having a recess, and a punch inserted into the recess and providing a bottom portion of the recess for pressurizing the compound in the molding space, wherein the passage is formed by the gap between the inner wall surface of the recess and the outer surface of the punch inserted into the recess, and the gap width between the inner wall surface of the recess and the outer surface of the punch is greater than or equal to the median diameter of the magnetic powder and less than or equal to 20 times the median diameter of the magnetic powder, as described in [1] above." In this case, the gap between the inner wall surface of the recess and the outer surface of the punch can form a passage through which the compound can enter when it is pressurized during the molding process. 【0010】 The above method for manufacturing a molded article may also be [3] "the mold unit comprises a concave mold having a recess, and a punch inserted into the recess and providing pressure on the compound in the molding space at the bottom of the recess, wherein the connecting passage is a hole provided in the concave mold, and the inner diameter of the hole, or the inner diameter in the short direction of the hole having a cross-section with a short direction and a long direction, is greater than or equal to the median diameter of the magnet powder and less than or equal to 20 times the median diameter of the magnet powder, as described in [1] above." In this case, when the compound is pressurized during the molding process, the compound can enter the connecting passage provided in the concave mold from the molding space. 【0011】 The above method for manufacturing a molded article may also be [4] "the method for manufacturing a molded article according to any one of [1] to [3] above, wherein the communication passage connects the molding space with the space outside the mold unit." In this case, when the compound is pressurized during the molding process, the gas in the communication passage is easily discharged to the outside of the mold unit. As a result, in this method for manufacturing a molded article, when the compound is pressurized during the molding process, it is possible to easily allow the compound to enter the communication passage. 【0012】The above method for manufacturing a molded article may also be [5] "the method for manufacturing a molded article according to any one of [1] to [4] above, wherein in the molding step, the compound is compressed while a magnetic field is applied to the compound, and the connecting passage extends from the molding space along the direction of the magnetic field." In this case, this method for manufacturing a molded article makes it possible to obtain a molded article in which the easy magnetization axes of the magnetic domains in the magnet particles are oriented along the direction of the magnetic field. Furthermore, the connecting passage extends from the molding space along the direction of the magnetic field applied to the compound. As a result, when the compound is pressurized in the molding step, the compound moves along the direction of the magnetic field and enters the connecting passage from the molding space. Therefore, around the connection point with the connecting passage in the molding space, the flow direction of the magnet powder is less likely to be disturbed in directions other than along the magnetic field. As a result, a molded article can be obtained in which the degree of orientation of the easy magnetization axes of the magnet particles is high around the connection point with the connecting passage in the molding space. 【0013】 The above method for manufacturing a molded article may also be [6] "the method for manufacturing a molded article according to [5] above, wherein the communication passage includes a first communication passage and a second communication passage, and the first communication passage and the second communication passage extend in opposite directions from the molding space along the direction of the magnetic field." In this case, this method for manufacturing a molded article makes it possible to obtain a molded article in which the degree of orientation of the easy magnetization axes of the magnet particles is high at both end faces of the molded article in the direction of the magnetic field. 【0014】 The above method for manufacturing a molded article may also be [7] "the method for manufacturing a molded article according to any one of [1] to [6] above, wherein the magnet powder includes an Sm-Fe-N permanent magnet, and the median diameter of the Sm-Fe-N permanent magnet is 3 μm." In this case, the method for manufacturing a molded article makes it possible to increase the density of the molded article while suppressing a decrease in magnetic properties in a molded article using an Sm-Fe-N permanent magnet. 【0015】 According to one aspect of this disclosure, it is possible to increase the density of the molded body that becomes a bonded magnet while suppressing a decrease in magnetic properties. 【0016】Figure 1 is a front view showing an example of a manufacturing apparatus used in a method for manufacturing a molded article according to an embodiment. Figure 2(a) is a side view showing the first connecting passage of the mold unit. Figure 2(b) is a side view showing the second connecting passage of the mold unit. Figure 3 is a front view showing an example of a manufacturing apparatus used in a method for manufacturing a molded article according to a modified example. Figure 4 is a top view of the mold unit as seen from the upper punch side. 【0017】 The following describes exemplary embodiments with reference to the drawings. In each drawing, the same or equivalent elements are denoted by the same reference numerals, and redundant explanations are omitted. 【0018】 (Overall configuration of the manufacturing apparatus) The manufacturing apparatus 1 shown in Figure 1 compresses the compound 2 in the mold unit K to form a molded body 2A that will become a bond magnet. The manufacturing apparatus 1 is equipped with a compression mechanism 10 and a magnetic field generation mechanism 20. The compression mechanism 10 is equipped with a first pressurizing mechanism 11, a second pressurizing mechanism 12, and a mold unit K. The mold unit K has a concave mold K1 and an upper punch (punch) K2. The concave mold K1 is provided with a recess K1a. A molding space R for molding the molded body 2A is provided at the bottom of the recess K1a of the concave mold K1. The compound 2 is supplied to the molding space R. Hereinafter, in the mold unit K, the extending direction (depth direction) of the recess K1a provided in the concave mold K1 is defined as the Z-axis direction, one direction perpendicular to the Z-axis direction is defined as the X-axis direction, and the direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction. The upper punch K2 is inserted into the recess K1a of the concave shape K1 along the Z-axis direction. 【0019】The first pressurizing mechanism 11 and the second pressurizing mechanism 12 are positioned opposite each other along the Z-axis direction, separated by a predetermined distance. The first pressurizing mechanism 11 is a device that moves the upper punch K2 along the Z-axis direction. The upper punch K2 is connected to the first pressurizing mechanism 11. The first pressurizing mechanism 11 may be a hydraulic mechanism. The second pressurizing mechanism 12 is a device that moves the concave mold K1 along the Z-axis direction. The concave mold K1 is connected to the second pressurizing mechanism 12. The first pressurizing mechanism 11 moves the upper punch K2 towards the second pressurizing mechanism 12. The second pressurizing mechanism 12 moves the concave mold K1 towards the first pressurizing mechanism 11. As a result, the compound 2 in the molding space R is compressed by the upper punch K2 and the concave mold K1. Alternatively, the compression mechanism 10 may compress the compound 2 by moving the upper punch K2 using the first pressurizing mechanism 11 while the concave mold K1 is fixed. 【0020】 The magnetic field generating mechanism 20 applies a magnetic field to the compound 2 within the mold unit K. The magnetic field generating mechanism 20 comprises a first coil 21 and a second coil 22. The first coil 21 and the second coil 22 are positioned to sandwich the mold unit K. The magnetic field generating mechanism 20 further includes a power supply mechanism. The power supply mechanism is electrically connected to the first coil 21 and the second coil 22, respectively. The direction and absolute value of the first current generated in the first coil 21 and the direction and absolute value of the second current generated in the second coil 22 are freely controlled by the power supply mechanism. The power supply mechanism is not shown in the figure. 【0021】A magnetic field H is combined from the magnetic field generated in the first coil 21 and the magnetic field generated in the second coil 22. The combined magnetic field H may be applied to the compound 2 in the mold unit K. Alternatively, the magnetic field H generated by only one of the coils, the first coil 21 and the second coil 22, may be applied to the compound 2 in the mold unit K. For example, the direction of the magnetic field H may be perpendicular to the opposing direction (Z-axis direction) of the first pressurizing mechanism 11 and the second pressurizing mechanism 12. However, the direction of the magnetic field H is not limited. The direction of the magnetic field H may be changed by changing the arrangement of the first coil 21 and the second coil 22. In this embodiment, as an example, the first coil 21 and the second coil 22 are arranged so as to sandwich the mold unit K in the X-axis direction. In this embodiment, as an example, the direction of the magnetic field H applied to the compound 2 in the mold unit K is the X-axis direction. 【0022】 Furthermore, the manufacturing apparatus 1 may include a heating section for heating the compound 2 inside the mold unit K. The heating section for heating the compound 2 may be a heater or the like. 【0023】 When molding compound 2, the manufacturing apparatus 1 compresses the heated compound 2 in the mold unit K using the compression mechanism 10 while applying a magnetic field H to the compound 2 using the first coil 21 and the second coil 22. Each magnetic particle in compound 2 is magnetized and rotated by the magnetic field H, and the easy magnetization axis of the magnetic domain in each magnetic particle is oriented along the magnetic field H. In other words, each magnetic particle in compound 2 is oriented so that its magnetization direction is approximately parallel to the magnetic field H. If each magnetic particle is a single crystal grain (single magnetic domain), the magnetization direction of each magnetic particle is the same as the direction in which the easy magnetization axis of each magnetic particle extends. The thermosetting resin is cured by the heat applied to compound 2, forming a molded body 2A (magnetic molded body) containing magnetic particles (multiple magnetic particles) oriented along the magnetic field H and cured material of the thermosetting resin. In other words, a molded body 2A made of cured material of compound 2 is formed. The magnetization direction of the entire molded body 2A is substantially or perfectly parallel to the direction of the magnetic field H applied to the compound 2 by the first coil 21 and the second coil 22. 【0024】(Compound) Compound 2 contains magnetic powder and thermosetting resin. The magnetic powder is, for example, Nd-Fe-B magnet (Nd ２ Fe １４ (Alloys such as B), samarium-iron-nitrogen magnets (Sm ２ Fe １７ N ３ It may be an alloy such as (or a ferrite magnet). Compound 2 may contain, in addition to the magnet powder and thermosetting resin, components such as a curing agent, a curing accelerator (curing catalyst), a silane coupling agent, a wax (lubricant), a flame retardant, and an organic solvent. Compound 2 may further contain a thermoplastic resin in addition to the thermosetting resin. The temperature of the compound itself supplied into the mold unit K may be room temperature. Compound 2 supplied into the mold unit K may be in the form of a powder, tablet, or paste. 【0025】 (Details of the mold unit) The concave mold K1 is provided with a first connecting passage (connecting passage, hole) T1 and a second connecting passage (connecting passage, hole) T2. One end of the first connecting passage T1 communicates with the molding space R. The other end of the first connecting passage T1 communicates with the space outside the mold unit K. In other words, the first connecting passage T1 is a hole provided in the concave mold K1 that connects the molding space R and the space outside the mold unit K. Similarly, one end of the second connecting passage T2 communicates with the molding space R. The other end of the second connecting passage T2 communicates with the space outside the mold unit K. In other words, the second connecting passage T2 is a hole provided in the concave mold K1 that connects the molding space R and the space outside the mold unit K. 【0026】The first communication passage T1 and the second communication passage T2 extend from the molding space R along the direction of the magnetic field H applied to the compound 2. The direction of the magnetic field H applied to the compound 2 is the direction of the magnetic field H at the part of the compound 2 among the magnetic field H generated by the magnetic field generation mechanism 20. Extending along the direction of the magnetic field H can also be rephrased as extending parallel or substantially parallel to the direction of the magnetic field H (magnetic flux). In other words, in this embodiment, the first communication passage T1 and the second communication passage T2 extend along the X-axis direction. The first communication passage T1 and the second communication passage T2 extend from the molding space R in opposite directions along the direction of the magnetic field H. In this embodiment, the first communication passage T1 extends from the molding space R along the X-axis direction toward the first coil 21. In this embodiment, the second communication passage T2 extends from the molding space R along the X-axis direction toward the second coil 22. 【0027】 As shown in Figures 1 and 2(a), the first connecting passage T1 is a hole whose cross-sectional shape (cross-section perpendicular to the X-axis direction) is cut along a direction perpendicular to the extending direction of the first connecting passage T1, and which has a short side direction and a long side direction. In this embodiment, the cross-sectional shape of the first connecting passage T1 is rectangular. In this embodiment, the short side L11 of the cross-section of the first connecting passage T1 is the side that extends along the Z-axis direction, and the long side L12 of the cross-section of the first connecting passage T1 is the side that extends along the Y-axis direction. The length of the short side L11 of the first connecting passage T1 is defined as the first short side length d11, and the length of the long side L12 of the first connecting passage T1 is defined as the first long side length d12. The first short side length d11 is the inner diameter in the short side direction of the first connecting passage T1 (hole) whose cross-section has a short side direction and a long side direction. The length of the first long side d12 is the inner diameter in the longitudinal direction of the first connecting passage T1 (hole), which has a cross-sectional shape with both a short side and a long side. 【0028】Similarly, as shown in Figures 1 and 2(b), the second passage T2 is a hole whose cross-sectional shape (cross-section perpendicular to the X-axis direction) is cut along a direction perpendicular to the extending direction of the second passage T2, and which has a short side and a long side. In this embodiment, the cross-sectional shape of the second passage T2 is rectangular. In this embodiment, the short side L21 of the cross-section of the second passage T2 is the side that extends along the Z-axis direction, and the long side L22 of the cross-section of the second passage T2 is the side that extends along the Y-axis direction. The length of the short side L21 of the second passage T2 is defined as the second short side length d21, and the length of the long side L22 of the second passage T2 is defined as the second long side length d22. The second short side length d21 is the inner diameter in the short side direction of the second passage T2 (hole) whose cross-section has a short side and a long side. The length of the second long side d22 is the inner diameter in the longitudinal direction of the second connecting passage T2 (hole), which has a cross-sectional shape with both a short side and a long side. 【0029】 Each of the first passage T1 and the second passage T2 has a cross-sectional shape that allows particles larger than or equal to the median diameter of the magnetic powder contained in compound 2 to flow, while inhibiting the flow of particles larger than 20 times the median diameter of the magnetic powder. Inhibiting flow here means preventing particles larger than 20 times the median diameter of the magnetic powder from passing through. In other words, particles larger than or equal to the median diameter of the magnetic powder, and 20 times or less the median diameter of the magnetic powder, can enter the first passage T1 and the second passage T2 from the molding space R. For example, if the magnetic powder contains an Sm-Fe-N permanent magnet, the median diameter of the Sm-Fe-N permanent magnet may be 3 μm. Although the first passage T1, etc., is described as having a cross-sectional shape that inhibits the flow of particles larger than 20 times the median diameter of the magnetic powder, it may also have a cross-sectional shape that inhibits the flow of particles larger than 30 times the median diameter of the magnetic powder. More preferably, the cross-sectional shape is such that it inhibits the flow of particles larger than 20 times the median diameter of the magnetic powder, and even more preferably, it is such that it inhibits the flow of particles larger than 10 times the median diameter of the magnetic powder. 【0030】Specifically, in this embodiment, the first short side length d11 (inner diameter in the short direction of the hole) of the first connecting passage T1 is greater than or equal to the median diameter of the magnet powder, and less than or equal to 20 times the median diameter of the magnet powder. Similarly, in this embodiment, the second short side length d21 (inner diameter in the short direction of the hole) of the second connecting passage T2 is greater than or equal to the median diameter of the magnet powder, and less than or equal to 20 times the median diameter of the magnet powder. 【0031】 As shown in Figure 2(a), the length of the first long side d12 of the first connecting passage T1 may be the same as the width of the molding space R in the Y-axis direction. As shown in Figure 2(b), the length of the second long side d22 of the second connecting passage T2 may be the same as the width of the molding space R in the Y-axis direction. However, the length of the first long side d12 of the first connecting passage T1 and the length of the second long side d22 of the second connecting passage T2 are not limited to being the same as the width of the molding space R in the Y-axis direction. At least one of the length of the first long side d12 and the length of the second long side d22 may be greater than or less than the width of the molding space R in the Y-axis direction. 【0032】 The concave mold K1 may be composed of a die having a recess K1a. Alternatively, the concave mold K1 may be composed of a die having a through hole and a lower punch inserted into one end of the through hole of the die. In this case, the recess K1a of the concave mold K1 may be formed by the inner wall surface of the through hole provided in the die and the tip surface (the tip surface in the insertion direction) of the lower punch. If the concave mold K1 has a lower punch, the first communication passage T1 and the second communication passage T2 may be provided in the die. If the concave mold K1 has a lower punch, the lower punch may be connected to the second pressurizing mechanism 12. 【0033】The concave mold K1 may be composed of a first mold member K11 and a second mold member K12. The first connecting passage T1 may be provided between the first mold member K11 and the second mold member K12. For example, a groove K11a extending along the X axis may be provided on the surface of the first mold member K11 to which the second mold member K12 is superimposed. The first connecting passage T1 may be formed by the inner wall surface of the groove K11a provided in the first mold member K11 and the outer surface of the second mold member K12 superimposed on the first mold member K11 so as to cover the groove K11a. Similarly, the second connecting passage T2 may be provided between the first mold member K11 and the second mold member K12. For example, a groove K11b extending along the X axis may be provided on the surface of the first mold member K11 to which the second mold member K12 is superimposed. The second connecting passage T2 may be formed by the inner wall surface of a groove K11b provided in the first mold member K11 and the outer surface of the second mold member K12 superimposed on the first mold member K11 so as to cover the groove K11b. When removing the molded body 2A, the first mold member K11 and the second mold member K12 may be separated to remove the hardened material that has entered the first connecting passage T1 (first connecting passage hardened material 3A) and the hardened material that has entered the second connecting passage T2 (second connecting passage hardened material 3B). 【0034】 (Method for manufacturing a molded body) The method for manufacturing a molded body 2A according to this embodiment includes at least a supply step and a molding step. (Supply step) In the supply step, the compound 2 is supplied into the molding space R of the mold unit K. For example, with the upper punch K2 withdrawn from the concave mold K1, the compound 2 is supplied into the molding space R of the concave mold K1. Thereafter, the upper punch K2 is inserted into the recess K1a of the concave mold K1. 【0035】 (Molding Process) In the molding process, a molded body 2A is formed from the compound 2 by the manufacturing apparatus 1. During the molding process, the manufacturing apparatus 1 applies a magnetic field H to the heated compound 2 in the mold unit K using the magnetic field generating mechanism 20, while compressing the compound 2 in the mold unit K using the first pressurizing mechanism 11 and the second pressurizing mechanism 12. As a result, the thermosetting resin contained in the compound 2 undergoes thermal curing, forming a molded body 2A made of the cured compound 2 within the molding space R. 【0036】 In the molding process, the compound 2 in the molding space R is pressurized, causing a portion of the compound 2 (magnet powder and a portion of the thermosetting resin) to enter the first and second connecting passages T1 and T2 from the molding space R. The compound 2 that enters the first connecting passage T1 hardens due to the thermosetting of the thermosetting resin contained in the compound 2, becoming the first connecting passage hardened product 3A. The compound 2 that enters the second connecting passage T2 hardens due to the thermosetting of the thermosetting resin contained in the compound 2, becoming the second connecting passage hardened product 3B. The first connecting passage hardened product 3A and the second connecting passage hardened product 3B are each connected to the molded body 2A. In a later process, the first connecting passage hardened product 3A and the second connecting passage hardened product 3B may be removed from the mold unit K together with the molded body 2A, for example, and separated from the molded body 2A. 【0037】 The molded body 2A formed in the molding process may be a completed anisotropic bonded magnet. The overall magnetization direction of the anisotropic bonded magnet is substantially or perfectly parallel to the direction of the magnetic field H applied to the compound 2 by the magnetic field generating mechanism 20 of the manufacturing apparatus 1, the overall magnetization direction of the molded body 2A, and the magnetization direction of each magnet particle in the bonded magnet. 【0038】 A bonded magnet may be manufactured by performing the following steps on a molded body 2A manufactured by the method described above. In the method for manufacturing a bonded magnet, a demagnetization step may be performed in which the molded body 2A is demagnetized by applying a magnetic field (reverse magnetic field) to the molded body 2A that is in the opposite direction to the magnetic field H applied in the molding step described above. This demagnetization may be performed in the manufacturing apparatus 1 before the molded body 2A is removed from the mold unit K, or it may be performed after the molded body 2A is removed from the mold unit K. After the demagnetization step, a thermosetting step may be performed. In the thermosetting step, the molded body 2A is heated to a temperature above the thermosetting temperature of the thermosetting resin. As a result, the thermosetting of the thermosetting resin in the molded body 2A progresses further. In the method for manufacturing a bonded magnet, a magnetization step may be performed after the demagnetization step. In the magnetization step, a magnetic field in the same direction as the magnetic field H used in the molding step described above may be applied to the molded body 2A. As a result, the molded body 2A is magnetized, and the molded body 2A becomes an anisotropic bonded magnet. 【0039】As described above, in the method for manufacturing the molded body 2A, a mold unit K is used in the molding process. The concave mold K1 of the mold unit K is provided with a first communication passage T1 and a second communication passage T2 that communicate with the molding space R. The first communication passage T1 and the second communication passage T2 have a cross-sectional shape that allows particles of the magnetic powder contained in the compound 2 that are larger than or equal to the median diameter to flow through. Therefore, a portion of the compound 2 (a portion of the magnetic powder and thermosetting resin) that is pressurized in the molding process can enter the first communication passage T1 and the second communication passage T2 from the molding space R in the mold unit K. As a result, when the compound 2 is pressurized, the fluidity of the compound in the molding space R is improved, and the density of the magnetic powder in the molded body 2A in the molding space R can be increased. In addition, when the compound 2 is pressurized, the compound 2 can escape (enter) from the molding space R into the first communication passage T1 and the second communication passage T2. Therefore, the pressure applied to the magnetic powder can be reduced, and damage to the magnetic powder can be suppressed. The first passage T1 and the second passage T2 have a cross-sectional shape that inhibits the flow of particles larger than 20 times the median diameter of the magnetic powder contained in the compound 2. Therefore, when the compound 2 is pressurized during the molding process, the compound 2 can be appropriately pressurized while suppressing excessive outflow of the compound 2 from the molding space R into the first passage T1 and the second passage T2. In this way, the manufacturing method of the molded body 2A can increase the density of the molded body 2A that becomes a bonded magnet while suppressing a decrease in magnetic properties. 【0040】 The first and second communication passages T1 and T2, which communicate with the molding space R, are provided in the concave mold K1. As a result, when the compound 2 in the molding space R is pressurized by the upper punch K2, it can enter the first and second communication passages T1 and T2 provided in the concave mold K1. 【0041】The first communication passage T1 and the second communication passage T2 communicate with the molding space R and the space outside the mold unit K, respectively. In this case, when the compound 2 is pressurized in the molding process, the gas (air) in the first communication passage T1 and the second communication passage T2 is easily discharged outside the mold unit K. Thereby, in this method for manufacturing the molded body 2A, when the compound is pressurized in the molding process, the compound 2 can easily enter the first communication passage T1 and the second communication passage T2. 【0042】 In the molding process, the compound 2 is compressed while applying a magnetic field H to the compound 2. In this case, in the method for manufacturing the molded body 2A, a molded body 2A in which the easy magnetization axis of the magnetic domains in the magnet particles is oriented along the magnetic field H can be obtained. Further, the first communication passage T1 and the second communication passage T2 extend from the molding space R along the direction of the magnetic field H applied to the compound 2 in the molding process. Thereby, when the compound 2 is pressurized in the molding process, the compound 2 moves along the magnetic field H, and the compound 2 enters the first communication passage T1 and the second communication passage T2 from the molding space R, respectively. Therefore, around the connection portion with the first communication passage T1 in the molding space R and around the connection portion with the second communication passage T2 in the molding space R, the flow direction of the magnet powder is not easily disturbed in a direction other than the direction along the magnetic field H. Thereby, around the connection portion with the first communication passage T1 in the molding space R and around the connection portion with the second communication passage T2 in the molding space R, a molded body 2A with a high degree of orientation of the easy magnetization axis of the magnet particles can be obtained. 【0043】The first communication path T1 and the second communication path T2 extend in opposite directions from the molding space R along the direction of the magnetic field. In this case, in the method for manufacturing the molded body 2A, a molded body 2A having a high degree of orientation of the easy magnetization axis of the magnet particles can be obtained at both end faces of the molded body 2A itself in the direction of the magnetic field. Further, as shown in FIGS. 2(a) and 2(b), the first long side length d12 of the first communication path T1 and the second long side length d22 of the second communication path T2 may be the same as the width of the molding space R in the Y-axis direction. In this case, in the method for manufacturing the molded body 2A, a molded body 2A having a portion with a high degree of orientation of the easy magnetization axis of the magnet particles over the entire region in the Y-axis direction can be obtained at both end faces of the molded body 2A itself in the direction of the magnetic field. 【0044】 The compound 2 contains an Sm—Fe—N-based permanent magnet as the magnet powder. In this case, in the method for manufacturing the molded body 2A, in the molded body 2A using the Sm—Fe—N-based permanent magnet, the density of the molded body 2A can be increased while suppressing a decrease in magnetic properties. 【0045】 As described above, the embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments. For example, in the above embodiments, the cross-sectional shape of the communication path such as the first communication path T1 provided in the concave K1 is not limited to a rectangular shape having a short side and a long side, and may be other shapes (for example, circular, elliptical, square, etc.). For example, the communication path may be a hole having a circular cross-sectional shape. In this case, it is sufficient that the inner diameter of the communication path (hole) is not less than the median diameter of the magnet powder contained in the compound 2 and not more than 20 times the median diameter of the magnet powder. Further, the cross-sectional shape and size of the communication path may be different from each other at each position in the extending direction. Even in these cases, the communication path provided in the concave K1 only needs to have a cross-sectional shape that allows particles having a size not less than the median diameter of the magnet powder contained in the compound 2 to flow through and inhibits the flow of particles having a size greater than 20 times the median diameter of the magnet powder. 【0046】The concave mold K1 is not limited to having two connecting passages, a first connecting passage T1 and a second connecting passage T2. The number of connecting passages in the concave mold K1 may be one or three or more. The first connecting passage T1 and the second connecting passage T2 are not limited to extending along the direction of the magnetic field H. The first connecting passage T1 and the second connecting passage T2 may extend in a direction intersecting the magnetic field H. The first connecting passage T1 and the second connecting passage T2 only need to communicate with the molding space R, and do not need to communicate with the space outside the mold unit K. In other words, the end of the first connecting passage T1 opposite to the end communicating with the molding space R may be closed. The end of the second connecting passage T2 opposite to the end communicating with the molding space R may be closed. 【0047】 (Modification) Next, a modification of the method for manufacturing a molded body will be described. In this modification, the mold unit M shown in Figure 3 is used instead of the mold unit K according to the embodiment. The compression mechanism 10A of the manufacturing apparatus 1A used in this modification is equipped with the mold unit M shown in Figure 3 instead of the mold unit K according to the embodiment. The mold unit M differs from the mold unit K according to the embodiment in the configuration of the communication passage T. As shown in Figure 3, the mold unit M has a concave mold M1 and an upper punch (punch) M2. The concave mold M1 is provided with a recess M1a. A molding space R is provided at the bottom of the recess M1a of the concave mold M1. Compound 2 is supplied to the molding space R. Hereinafter, in the mold unit M, the extending direction (depth direction) of the recess M1a provided in the concave mold M1 will be defined as the Z-axis direction, one direction perpendicular to the Z-axis direction will be defined as the X-axis direction, and the direction perpendicular to the Z-axis direction and the X-axis direction will be defined as the Y-axis direction. The upper punch M2 is inserted into the recess M1a of the concave mold M1 along the Z-axis direction. 【0048】 Similar to the mold unit K in the embodiment, the mold unit M has an upper punch M2 connected to the first pressurizing mechanism 11 and a concave mold M1 connected to the second pressurizing mechanism 12. The first pressurizing mechanism 11 moves the upper punch M2 toward the second pressurizing mechanism 12. The second pressurizing mechanism 12 moves the concave mold M1 toward the first pressurizing mechanism 11. As a result, the compound 2 in the molding space R of the concave mold M1 is compressed, and a molded body 2A is formed. 【0049】 As shown in Figures 3 and 4, the mold unit M is provided with a connecting passage T. The connecting passage T is formed by the gap between the inner wall surface M1b of the recess M1a provided in the concave mold M1 and the outer surface M2a of the upper punch M2 inserted into the recess M1a. The inner wall surface M1b of the recess M1a is a cylindrical wall surface rising from the outer edge of the bottom surface M1c of the recess M1a. The inner wall surface M1b of the recess M1a can also be called the inner circumferential surface of the recess M1a. The outer surface M2a of the upper punch M2 is the surface facing the inner wall surface M1b of the recess M1a when the upper punch M2 is inserted into the recess M1a of the concave mold M1. The outer surface M2a of the upper punch M2 is a cylindrical wall surface that connects to the outer edge of the tip surface M2b in the insertion direction of the upper punch M2. The outer surface M2a of the upper punch M2 can also be called the outer circumferential surface of the upper punch M2. 【0050】 In this embodiment, the recess M1a provided in the concave mold M1 has a rectangular cross-section in the direction perpendicular to the Z-axis direction. The upper punch M2 inserted into the recess M1a of the concave mold M1 has a rectangular cross-section in the direction perpendicular to the Z-axis direction. Therefore, the connecting passage T extends along the Z-axis direction and has a rectangular frame shape in the direction perpendicular to the Z-axis direction that surrounds the upper punch M2. 【0051】 The passage T has a cross-sectional shape that allows particles larger than or equal to the median diameter of the magnetic powder contained in compound 2 to flow, while obstructing the flow of particles larger than 20 times the median diameter of the magnetic powder. In other words, particles larger than or equal to the median diameter of the magnetic powder, and 20 times or less the median diameter of the magnetic powder, can enter the passage T from the molding space R. 【0052】 Specifically, as described above, the passage T is formed by the gap between the inner wall surface M1b of the recess M1a and the outer surface M2a of the upper punch M2. The gap width d between the inner wall surface M1b of the recess M1a and the outer surface M2a of the upper punch M2 is greater than or equal to the median diameter of the magnet powder, and less than or equal to 20 times the median diameter of the magnet powder. The gap width d that forms this passage T is the length between the inner wall surface M1b of the recess M1a and the outer surface M2a of the upper punch M2 in the direction in which they face each other. 【0053】When viewed along the Z-axis, the gap width d forming the communication passage T in all parts around the upper punch M2 (over the entire circumference) may be greater than or equal to the median diameter of the magnetic powder, and less than or equal to 20 times the median diameter of the magnetic powder. 【0054】 However, when viewed along the Z-axis, the gap width d forming the communication passage T in a portion of the area around the upper punch M2 may be greater than or equal to the median diameter of the magnetic powder, and less than or equal to 20 times the median diameter of the magnetic powder. In this case, in other portions of the area around the upper punch M2, the gap width d forming the communication passage T may be less than the median diameter of the magnetic powder. This allows the compound 2 to enter the communication passage T in a portion of the communication passage T, while preventing the compound 2 from entering the communication passage T in other portions of the communication passage T. 【0055】 When molding a molded body 2A using a mold unit M, when the compound 2 is pressurized during the molding process, a portion of the compound 2 enters the communication passage T from the molding space R. For example, the hardened compound 2 that has hardened in the communication passage T (communication passage hardened material 3C) may be removed from the concave mold M1 together with the molded body 2A while still connected to it. After that, the communication passage hardened material 3C may be separated from the molded body 2A. 【0056】 In this way, the gap between the inner wall surface M1b of the recess M1a of the concave mold M1 and the outer surface M2a of the upper punch M2 forms a passage T through which the compound 2 can enter when it is pressurized during the molding process. As a result, in the manufacturing method of the molded body 2A using the mold unit M, the density of the molded body 2A that becomes a bonded magnet can be increased while suppressing a decrease in magnetic properties, similar to the manufacturing method of the molded body 2A using the mold unit K according to the embodiment. 【0057】 In the above embodiments and modifications, it is not necessary to apply a magnetic field when compressing the compound 2 to form the molded body 2A. In this case, the manufacturing apparatus 1, 1A does not need to be equipped with a magnetic field generating mechanism 20. 【0058】2...Compound, 2A...Molded body, d...Gap width, d11...First short side length (inner diameter in the short side direction), d21...Second short side length (inner diameter in the short side direction), K, M...Mold unit, K1, M1...Concave mold, K1a, M1a...Concave, M1b...Inner wall surface, K2, M2...Upper punch (punch), M2a...Outer surface, R...Molding space, T...Connecting passage, T1...First connecting passage (connecting passage), T2...Second connecting passage (connecting passage), H...Magnetic field.

Claims

1. A method for manufacturing a molded article, comprising: a supply step of supplying a compound containing magnetic powder and a thermosetting resin into the molding space of a mold unit; and a molding step of compressing the heated compound in the mold unit to mold a molded article from the compound, wherein the mold unit is provided with a passage that communicates with the molding space, and the passage has a cross-sectional shape that allows particles larger than or equal to the median diameter of the magnetic powder to flow through, and inhibits the flow of particles larger than 20 times the median diameter of the magnetic powder.

2. The method for manufacturing a molded article according to claim 1, wherein the mold unit comprises a concave mold having a recess, and a punch inserted into the recess and pressurizing the compound in the molding space provided at the bottom of the recess, the communication passage is formed by the gap between the inner wall surface of the recess and the outer surface of the punch inserted into the recess, and the width of the gap between the inner wall surface of the recess and the outer surface of the punch is greater than or equal to the median diameter of the magnetic powder and less than or equal to 20 times the median diameter of the magnetic powder.

3. The method for manufacturing a molded article according to claim 1, wherein the mold unit comprises a concave mold having a recess, and a punch inserted into the recess and pressurizing the compound in the molding space provided at the bottom of the recess, the communication passage being a hole provided in the concave mold, and the inner diameter of the hole, or the inner diameter in the short direction of the hole having a cross-section with a short direction and a long direction, is greater than or equal to the median diameter of the magnet powder and less than or equal to 20 times the median diameter of the magnet powder.

4. The method for manufacturing a molded article according to claim 1, wherein the communication passage connects the molding space with the space outside the mold unit.

5. The method for manufacturing a molded article according to claim 3, wherein in the molding step, the compound is compressed while a magnetic field is applied to the compound, and the communication passage extends from the molding space in the direction of the magnetic field.

6. The method for manufacturing a molded article according to claim 5, wherein the communication passage includes a first communication passage and a second communication passage, and the first communication passage and the second communication passage extend in opposite directions from the molding space along the direction of the magnetic field.

7. The method for manufacturing a molded article according to any one of claims 1 to 6, wherein the magnetic powder comprises an Sm-Fe-N permanent magnet, and the median diameter of the Sm-Fe-N permanent magnet is 3 μm.

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