JP4783459B2 - Ring type magnet manufacturing method, magnetic field forming apparatus, and ring type magnet manufacturing apparatus - Google Patents

Description

  The present invention relates to a ring magnet manufacturing method, a magnetic field forming apparatus, and a ring magnet manufacturing apparatus for manufacturing a radially oriented ring magnet.

  In a ring-type magnet applied to a small rotating machine, rare earth sintered magnets such as neodymium sintered magnets are used for miniaturization, high output and high efficiency. In order to obtain a high output, a ring-type magnet having a high residual magnetic flux density and a long axial length, in which the magnetic characteristics of the magnet are further improved, are used.

  As a method for manufacturing a ring-type magnet having a high residual magnetic flux density, there is a method disclosed in JP-A-6-267774. Here, a pulse alignment is used in which a counter magnetic field is generated by flowing a pulsed large current through coils disposed above and below a mold filled with magnetic powder to align the magnetic powder in the mold. Since a magnetic field larger than that of a direct current magnetic field is obtained, the orientation ratio can be improved, and a magnet having a high residual magnetic flux density can be manufactured.

  As a method for manufacturing a ring-type magnet having a long axial length, there are methods disclosed in JP-A-2-281721 and JP-A-10-55929. In this method, a magnetic powder as a raw material is filled in a cavity and subjected to pressure molding, and the obtained ring molded body is moved to a nonmagnetic portion of a die. Next, the process of filling the cavity of the magnetic part of the die after the transfer again with magnetic powder, press-molding, and then transferring the obtained ring molded body to the non-magnetic part is repeated any number of times. In this way, a multistage molding method for obtaining a molded article having a long axial length has been used.

  The multistage molding method is a complicated manufacturing method and has poor productivity. Therefore, there has been a method disclosed in Japanese Patent Application Laid-Open No. WO04-77647, in which a ring molded body having a short axial length is produced by orientation compression for each piece, and then a plurality of molded bodies are laminated and integrated by sintering. .

JP-A-6-267774 JP-A-2-281721 Japanese Patent Laid-Open No. 10-55929 Japanese Patent Laid-Open No. WO 04-77647

  In the pulse orientation disclosed in Japanese Patent Laid-Open No. 6-267774, the axial length is as very small as 2.0 mm with respect to the inner diameter of 15.4 mm of the ring molded body, as shown in the publication. When the length in the axial direction is increased, the strength of the orientation magnetic field is reduced, and a high orientation rate cannot be obtained. This is the same problem as in the case of direct current orientation in JP-A-2-281721 and JP-A-10-55929. Furthermore, in the case of pulse orientation, it is impossible to make the magnetic flux density uniform by controlling the flow of the magnetic field by a magnetic part of a die such as a die or a core like a DC magnetic field. For this reason, the magnetic field is strong only in the portion close to the coil, and the magnetic field is lowered in the middle portion between the coil and the coil, so that the variation in the orientation ratio becomes large and the magnetic characteristics vary.

  On the other hand, in the multistage molding method, a magnetic part and a non-magnetic part are provided in the mold, and the magnetic flux is guided to the magnetic powder arranged in the magnetic part, and is controlled so as not to flow into the molded body arranged in the non-magnetic part. . Therefore, the structure of the mold part is complicated. When applying pulse orientation to this method, it is not possible to arrange a pulse coil that needs to be close to the magnetic powder. In addition, eddy currents easily flow through magnetic molds (dies and cores), and the flow of magnetic flux cannot be controlled. Therefore, a ring magnet having a high residual magnetic flux density could not be manufactured by the multi-stage forming method due to pulse orientation.

  The method of integrating a plurality of short ring-shaped ring molded bodies disclosed in Japanese Patent Application Laid-Open No. WO 04-77647 by sintering is also DC-oriented, so that a magnet with high residual magnetic flux density could not be manufactured. .

  The present invention has been made to solve the above-described problems. A plurality of radially oriented magnets are manufactured with high productivity, and a ring-type sintered magnet with a long shaft length is manufactured with high productivity. For the purpose.

  The method for manufacturing a ring-type magnet according to the present invention includes a feeding process for feeding magnetic powder into a cavity of a mold having a ring-shaped cavity, and between each coil portion arranged in N stages (N is an integer of 3 or more). At least two or more molds are arranged in a magnetic field, an orientation process for radial orientation of magnetic powder in the mold by a counter magnetic field generated from adjacent coil portions, a pressurization process for pressurizing the magnetic powder in the mold, and orientation from the mold. Demolding and laminating process of demolding the pressed ring molded body and stacking a plurality of ring molded bodies, and a sintering process of sintering and integrating the stacked ring molded bodies Is.

  The magnetic field shaping apparatus according to the present invention is arranged in N stages (N is an integer of 3 or more), and is arranged between a coil section that generates a magnetic field facing each other from adjacent stages and an N stage coil section. And a mold having a cavity for storing magnetic powder that is radially oriented by the magnetic field generated by the coil portion.

  A ring-type magnet manufacturing apparatus according to the present invention includes a conveying mold having a cavity, a powder feeding unit for feeding magnetic powder to the cavity, and an orientation unit for applying a magnetic field for radial orientation of the magnetic powder fed to the cavity. A pressure unit that pressurizes the oriented magnetic powder, a reorientation / demagnetization unit that applies a magnetic field for reorienting the depressurized magnetic powder and a magnetic field for demagnetization, and molding from a conveyance mold A demolding unit for demolding the body, a laminating unit for laminating the demolded compact, and a magnetic field power source for supplying current to the orientation unit and the reorientation / demagnetization unit. The magnetic unit is arranged in N stages (N is an integer of 3 or more) and has a coil unit that generates a magnetic field facing each other from adjacent stages, and a transfer type is arranged between the N stage coil parts. Ru It has a field molding apparatus.

  According to the method for manufacturing a ring magnet of the present invention, a plurality of radially oriented magnets can be manufactured with high productivity.

  According to the magnetic field forming apparatus of the present invention, a plurality of radially oriented magnets can be manufactured with high productivity.

  According to the ring-type magnet manufacturing apparatus of the present invention, a ring-type sintered magnet having a long axial length can be manufactured with high productivity.

It is a perspective view which shows the example of the ring type magnet manufactured by the manufacturing method of the ring type magnet of this invention. It is a figure which shows the basic composition of the manufacturing apparatus of the ring type magnet by Embodiment 1. FIG. FIG. 3 is a cross-sectional view illustrating a conveyance mold used in the first embodiment. It is a figure explaining the structure and operation | movement of the powder supply unit of Embodiment 1. FIG. It is a figure explaining the structure and operation | movement of the powder supply unit of Embodiment 1. FIG. FIG. 4 is a diagram illustrating the configuration and operation of the alignment unit according to the first embodiment. FIG. 4 is a diagram illustrating the configuration and operation of the alignment unit according to the first embodiment. FIG. 3 is a circuit diagram showing a magnetic field power supply and a coil according to the first embodiment. FIG. 3 is a diagram illustrating a current waveform generated by the magnetic field power supply according to the first embodiment. FIG. 3 is a diagram illustrating a flow of magnetic flux generated in the alignment unit of the first embodiment. 2 is a diagram illustrating a configuration of a pressure unit according to Embodiment 1. FIG. FIG. 4 is a diagram illustrating the configuration and operation of the reorientation / demagnetization unit according to the first embodiment. It is a figure which shows the structure and operation | movement of the mold release unit of Embodiment 1. FIG. It is a figure which shows the structure and operation | movement of the demolding unit of Embodiment 1, and a lamination | stacking unit. FIG. 3 is a diagram illustrating a sintering process of a ring molded body according to the first embodiment. It is a figure which shows the other basic composition of the manufacturing apparatus of the ring type magnet by Embodiment 1. FIG. It is a figure which shows the basic composition of the manufacturing apparatus of the ring type magnet by Embodiment 2 of this invention. 6 is a diagram illustrating the configuration and operation of an orientation / pressure unit according to Embodiment 2. FIG. FIG. 10 is a diagram showing a configuration of an orientation / pressure unit of another example of the second embodiment. The conveyance type structure by Embodiment 3 of this invention is shown. It is a figure which shows the structure of the orientation unit by Embodiment 4 of this invention.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing an example of a ring magnet obtained by molding and sintering by the method for manufacturing a ring magnet of the present invention. As a ring-type magnet obtained by the manufacturing method of the present invention, as shown in FIG. 1 (a), there is one in which a ring molded body 1a formed into a cylindrical shape is laminated and sintered to be integrated. Also, as shown in FIG. 1B, ring molded bodies 1b having periodic irregularities on the outer peripheral surface or the inner peripheral surface are stacked so that the irregularities are skewed by a predetermined angle, and are sintered and integrated. There is. In addition, in FIG.1 (b), although the outer peripheral surface has the periodic unevenness | corrugation 1c, the ring magnet which has an unevenness | corrugation on an inner peripheral surface can also be manufactured.

  FIG. 2 is a diagram showing a basic configuration of a ring-type magnet manufacturing apparatus according to the present embodiment. The manufacturing apparatus according to the present embodiment includes a conveyance mold 10, a powder feeding unit 100 for supplying magnetic powder to the cavity of the conveyance mold 10, an alignment unit 110 for applying a magnetic field to the conveyance mold 10 supplied with magnetic powder, and an alignment A pressure unit 120 for pressing the magnetic powder, a reorientation / demagnetization unit 130 for applying a magnetic field for reorienting the depressurized magnetic powder and a magnetic field for demagnetizing, and a ring mold from the conveying mold 10 The demolding unit 140 for demolding, the laminating unit 150 for laminating the demolded ring molded body, and the magnetic field power source 200 for supplying current to the coils of the orientation unit 110 and the reorientation / demagnetization unit 130 are configured. In addition, in order to move the conveyance type | mold 10 between each unit, you may provide a belt conveyor etc. (it abbreviate | omits in a figure). Further, the entire unit may be blocked from air and purged with an inert gas such as nitrogen.

  FIG. 3 is a cross-sectional view showing the conveyance mold 10 used in the present embodiment. The conveyance mold 10 includes a core 11, a die 12 disposed around the core 11, and a lower punch 15 and an upper punch 16 disposed between the core 11 and the die 12, and includes the core 11, the die 12, and the lower punch. 15 and an upper punch 16 and has a cavity 17 which is a ring-shaped space filled with magnetic powder. An O-ring presser base (presser base) 18 is disposed below the die 12, and an O-ring (friction body) 19 is fixed by the die 12 and the O-ring presser 18. Further, the lower punch 15 is held by friction with the O-ring 19 fixed to the O-ring presser 18. Further, the core 11 is held by the friction of the O-ring 19 disposed between the lower punch 15 and the core 11. The upper punch 16 is set in a state where the cavity 17 is filled with magnetic powder.

  Regarding the material of the conveyance mold 10, the die 12, the lower punch 15 and the upper punch 16 are nonmagnetic materials such as stainless steel, and nonmagnetic super steel is used for a portion requiring hardness. The core 11 is made of a combination of a magnetic material such as iron and super steel in a portion requiring hardness. As the magnetic material of the core 11, a material having a high saturation magnetic flux density such as permendur may be used. Further, when the ring molded body is small (when the axial length is 10 mm or less), a strong and uniform orientation magnetic field can be easily obtained. Therefore, all members including the core 11 may be made of a nonmagnetic material. Further, by using an insulating material such as ceramic or a high electrical resistance material as the material of each member of the transport mold 10, eddy current can be reduced and the effect of stabilizing the magnetic field distribution can be obtained.

Next, the powder supply unit 100 will be described. In the powder supply unit 100, the work of setting the upper punch 16 by measuring and supplying the magnetic powder 20 to the cavity 17 of the conveyance mold 10 is performed. FIG. 4 is a diagram showing a state of powder feeding of the magnetic powder 20 in the powder feeding unit 100. The magnetic powder 20 weighed to a predetermined weight by a measuring instrument (not shown) is supplied to the cavity 17 through the powder feed port 101 and the funnel 102 set on the cavity 17 of the conveyance mold 10. The powder feeding port 101 and the funnel 102 vibrate slightly when the magnetic powder is supplied, and the magnetic powder 20 can be uniformly filled in the cavity 17. By providing movable blades (not shown) in the cavity 17 and rotating and vibrating when supplying the magnetic powder, more uniform powder supply is possible. The packing density of the magnetic powder 20 is desirably 2 to ³ g / cm ³ . If the packing density is too low, the magnetic powder 20 is biased to a region where the orientation magnetic field is strong in the cavity 17 when an orientation magnetic field is applied, and the orientation varies when compressed and the magnetic properties deteriorate. If the packing density is too high, the frictional force between the magnetic powders becomes large, and even if an orientation magnetic field is applied, it becomes difficult to orient and magnetic properties are deteriorated. After the magnetic powder 20 is filled, the upper punch 16 is set on the cavity 17 by the hand 103 as shown in FIG.

  Next, the orientation unit 110 will be described. In the orientation unit 110, an operation of applying a magnetic field to the conveyance mold 10 in which the magnetic powder 20 is supplied and the upper punch 16 is set is performed. In this example, an alternating magnetic field is applied to the magnetic powder filled in the cavity 17 of the transport mold 10. First, the difference between application of a DC magnetic field and application of an AC magnetic field will be described. In the case of a DC magnetic field, the magnetic field is always applied during the period in which the magnetic powder is being pressurized. Therefore, a large current of the order of several hundreds A is applied to the DC magnetic field coil during a period of about 10 to 30 seconds. A coil for a DC magnetic field has a coil turn number of several hundred T, and a coil having a large cross-sectional area is used to suppress heat generation due to its electrical resistance. In many cases, a coil cooling mechanism is attached. That is, the DC magnetic field coil having a large coil size such as an inner diameter of 200 mm, an outer diameter of 600 mm, and an axial length of 200 mm is used. For this reason, the magnetic field cannot be concentrated in the cavity 17 of the small-sized conveyance mold 10 and the orientation magnetic flux density cannot be increased. In addition, operations such as setting and removal of the conveyance mold 10, powder supply, and demolding are made difficult.

  On the other hand, in the case of an alternating magnetic field, the magnetic field power supply configuration will be described in detail later, and the current flow period is a few ms. Therefore, even if a current with a peak value of 10 kA flows, the amount of heat generated is larger than that of the direct current magnetic field. Is about 1/100. Therefore, when the outer diameter of the ring molded body is up to about 50 mm, the AC magnetic field coil may have a coil size of an outer diameter of 50 mm and an axial length of about 20 mm. Thus, since the coil for alternating current magnetic fields can be made small, the structure of the orientation unit as shown below becomes possible.

  6 and 7 are diagrams illustrating the configuration and operation of the alignment unit 110 according to the present embodiment. The orientation unit 110 of the present embodiment includes a coil unit 111 arranged in a plurality of stages (N stages, where N is an integer of 3 or more), and a coil driving unit 115 that relatively approaches or separates each coil part 111. Become. The coil unit 111 includes a coil 112 that generates a magnetic field and a coil holding unit 113 that holds the coil 112. The coils 112 arranged in a plurality of stages are arranged so that their coil centers are substantially coaxial, and are connected by winding so that the directions of currents are opposite between adjacent coils. In the example of the figure, the coil part 111 has shown the case where it comprises with 4 steps | paragraphs. The coil drive unit 115 is configured such that each coil unit 111 can be relatively moved by combining a linear guide, a ball screw, a servo motor, and the like.

  The operation of the alignment unit 110 of the present embodiment will be described with reference to FIGS. First, as shown in FIG. 6, the interval between the coil portions 111 is widened by the coil driving portion 115, and the conveyance mold 10 is set between the coil portions 111 by the hand 118. FIG. 7A shows a state in which the conveyance mold 10 is set between the coil portions 111. In this example, three conveyance molds 10 can be set. Then, as shown in FIG. 7B, the coil driving unit 115 narrows the interval between the coil units 111 and fixes the coil unit 111.

  The coil 112 of each coil unit 111 is supplied with a current from the magnetic field power supply 200 and generates an orientation magnetic field. FIG. 8 is a circuit diagram showing the magnetic field power supply 200 and each coil 112 (112a, 112b, 112c, 112d). A magnetic field power supply 200 shown in FIG. 8 includes a power supply 201 for charging a capacitor, a booster circuit 202, a large-capacitance capacitor 203, a switch 204 such as a thyristor (SCR), an antiparallel diode 205 of the switch 204, a switch A control circuit 206 for controlling 204 is provided. Each coil 112 is connected to the magnetic field power supply 200 as a load in series so that the winding directions of adjacent coils are opposite. In the example of FIG. 9, four coils 112a, 112b, 112c, and 112d are connected in series, and the coils 112a and 112b, the coils 112b and 112c, and the coils 112c and 112d are connected so that the winding directions are opposite. Yes. When the switch 204 is turned on while the capacitor 203 is charged, a current flows from the capacitor 203 to the coil 112. Resonance occurs between the capacitance of the capacitor 203 and the inductance of the coil 112, and an alternating current that gradually attenuates as shown in FIG. 9 is generated, and the orientation magnetic field is also attenuated according to the alternating current. The AC magnetic field to be applied may be 2 to 3 cycles. The attenuation rate of the amplitude in one period may be 90 to 50%. The current may be forcibly stopped after a predetermined number of alternating magnetic fields.

  FIG. 10 is a diagram showing the flow of magnetic flux generated in the alignment unit 110 of the present embodiment. Each coil 112 is wound and connected so that adjacent coils have opposite current directions. Therefore, the magnetic flux directed in the axial direction from each coil 112 flows in a direction opposite to each other between adjacent coils. The opposing magnetic fluxes change the direction of the magnetic flux in the radial direction near the middle of each coil 112. Therefore, a radial orientation magnetic field is applied to the cavity 17 of the transfer mold 10 arranged between the coils 112. Further, these magnetic fluxes indicated by arrows in FIG. 10 are gradually attenuated in accordance with the above-described decaying alternating current.

  In the case of a conventional pulse magnetic field, a phenomenon occurs in which magnetic powder for a high coercive force magnet (inherent coercive force of 1200 kA / m (15 kOe) or more) is not easily oriented, but an alternating magnetic field that attenuates is applied as in this embodiment. By doing so, the magnetic powder for the high coercive force magnet can also be sufficiently oriented. Magnetic powder for a high coercive force magnet has a high coercive force, and is magnetized in a powder state, and aggregates in the cavity. By applying an alternating magnetic field, the above-mentioned aggregation can be prevented, and therefore the orientation is improved.

  In the case of the present embodiment, the magnetic field applied to the magnetic powder is an alternating magnetic field that attenuates, so that demagnetization can be performed simultaneously. In the case of a conventional DC magnetic field or pulsed magnetic field, demagnetization is performed by applying a magnetic field opposite to the direct current magnetic field or pulsed magnetic field. In this embodiment, such demagnetization is not performed. It may be easy to handle after orientation. It should be noted that the conventional demagnetization with a DC magnetic field requires a time of 10 seconds or more including the current rise and fall times.

  Next, the connection between the coils 112 will be described. When the coils 112 are connected in parallel, there may be a difference in flowing current due to a difference in the coil shape and a difference in inductance based on a difference in arrangement. Therefore, it is preferable to connect the coils 112 in series. There are also the following effects. The resonance frequency f of the capacitance C of the capacitor and the inductance L of the coil is expressed by the following formula (1).

f = 1 / 2π (C · L) ^1/2 (1)

  Here, when the series connection and the parallel connection are compared, the inductance becomes larger in the case of the series connection, so that the resonance frequency becomes lower. The members requiring mechanical strength such as the transfer mold 10 and the coil driving unit 115 may be made of a conductive material such as a metal, but the conductive material easily generates an eddy current due to an oscillating magnetic field therein. However, when the coils are connected in series, the resonance frequency is lowered, and the generation of eddy current can be suppressed even with a conductive material.

  The magnetic powder 20 filled in the cavity 17 of the transfer mold 10 is oriented in the radial direction by the magnetic field generated by the coil 112. In the present embodiment, four coils 112 are connected in series and driven by one magnetic field power source 200. By passing a current using a magnetic field power source with a capacitor capacity of 2000 μF and a charging voltage of 3700 V to three transfer molds 10 that can form a ring molded body having an outer diameter of 40 mm, an inner diameter of 35 mm, and an axial length of 20 mm, In the cavity 17 of the transfer mold 10, a magnetic flux having a magnetic flux density of 5T can be generated. The coil 112 has an outer diameter of 50 mm, an inner diameter of 20 mm, an axial length of 15 mm, and a number of turns of 30T.

  As the magnetic field power source 200, a general magnetized power source can be used. When a 2000 μF capacitor is charged to 3700 V, a charge of about 8 [C] is stored in the capacitor. If the charging capacity of the capacitor charging unit is 4000 V and 0.53 A, the capacitor can be charged in 15 seconds. When the capacitor charging unit is configured with a simple step-up transformer (200 V: 4000 V), the power supplied to the primary side (low voltage side) is 200 V, 10.6 A, which indicates that a relatively small power supply is sufficient. In the power supply facility of the magnetic field power supply 200, an excessive facility is not required. The time can be further shortened by increasing the capacitor charging unit. In the above description, four examples of the coil unit 111 are shown, but the number is not limited to four.

  Next, the pressure unit 120 will be described. The pressurizing unit 120 presses the magnetic powder of the transport mold 10 oriented by the orientation unit 110 with the upper punch 16 and the lower punch 15. That is, the conveyance mold 10 filled with the magnetic powder oriented by the orientation unit 110 is set in the pressure unit 120. FIG. 11 is a diagram showing the configuration of the pressure unit 120 of the present embodiment. In the figure, the upper punch 16 and the lower punch 15 are pressurized by a pressurizer 121, and the pressurizer 121 is driven in the direction of the arrow by a pressurization drive unit 122. The upper punch 16 and the lower punch 15 relatively approach the die 12 from above and below to press the magnetic powder in the cavity 17. At this time, the core 11 is supported by the core support portion 123 so as not to move with respect to the die 12. The lower punch 15 is fixed by the friction of the O-ring 19, but since a force larger than that is applied to the lower punch 15 by the presser 122, the magnetic powder is pressed without any problem.

  Next, the reorientation / demagnetization unit 130 will be described. The reorientation / demagnetization unit 130 applies a magnetic field for reorientation or a magnetic field for demagnetization to the magnetic powder pressurized by the pressure unit 120. FIG. 12 is a diagram for explaining the configuration and operation of the reorientation / demagnetization unit 130 of the present embodiment. The configuration and operation of the reorientation / demagnetization unit 130 are almost the same as those of the orientation unit 110 described above. For the reorientation, an AC attenuation magnetic field having the same strength as that of the orientation is applied. When the orientation of the magnetic powder is disturbed by the pressurization of the pressure unit 120 or when the orientation unit 110 is not sufficiently demagnetized, the unit 130 performs reorientation and demagnetization. If it is not necessary to perform reorientation or demagnetization, the unit 130 can be omitted.

  In the present embodiment, the magnetic field power source of the coil of the reorientation / demagnetization unit 130 and the magnetic field power source 200 of the coil of the orientation unit 110 can be shared. In that case, the coil of the orientation unit 110 and the coil of the reorientation / demagnetization unit 130 are alternately energized. For example, in an installation with a coil charging time of 15 seconds, the coils of both units are alternately energized for 15 seconds at 30-second intervals. In other words, the coil of the orientation unit 110 is energized for 15 seconds, and in the subsequent 15 seconds, the conveyance mold 10 is taken out from the alignment unit 15 and a new conveyance mold 10 is mounted, and at the same time, the coil of the reorientation / demagnetization unit 130 is energized. .

  Next, the demolding unit 140 and the laminated unit 150 will be described. The demolding unit 140 is for demolding the ring molded body 30 that has been oriented and pressurized from the conveying mold 10, and the laminating unit 150 is for laminating the demolded ring molded body 30. 13 and 14 are diagrams showing the configuration and operation of the demolding unit 140 and the laminated unit 150. FIG. First, the conveyance mold 10 is set in the mold removal unit 140. Then, as shown in FIG. 13A, the die 12 is moved downward by the die presser 143 while the core 11 and the lower punch 15 are held by the core support 141 and the punch support 142. Subsequently, as shown in FIG. 13B, the core 11 is moved downward by the core presser 145 while the lower punch 15 is held by the punch support portion 142. Thereafter, as shown in FIG. 14, when the core presser 145 is raised, the ring molded body 30 can be taken out by the electromagnetic chuck 151. In the lamination unit 150, a predetermined number of the ring molded bodies 30 taken out from the demolding unit 140 are laminated. Then, the laminated ring molded body 30 is sintered by the heater 161 in a vacuum or an inert gas shown in FIG. 15, so that the layers of the ring molded bodies 30 are joined and integrated. Become a mold magnet.

  Next, the processing capability of each unit shown in FIG. 2 will be described. First, the processing time of the alignment unit 110 will be described. Compared with the charging time of the magnetic field power supply 200 and the mounting and dismounting time of the transfer mold 10 to and from the alignment unit 110, the longer time (the energization time can be ignored in several ms) is the time required for alignment. In the case of this example, the charging time of the magnetic field power supply 200 is 15 seconds, the mounting and removing time of the transfer mold 10 is 20 seconds, and the magnetic powder of the three transfer molds 10 can be oriented in the longer 20 seconds. (Tact time: 6.6 seconds / 1 piece).

  In the powder supply unit 100, the pressurizing unit 120, the demolding unit 130, and the stacking unit 140, each unit is necessary so that each tact time is matched with the processing time of the orientation unit 110 (re-orientation / demagnetization unit 130). Determine the number. In the case of this example, since the powder supply unit 100 requires 15 seconds for weighing and 30 seconds for filling 15 seconds, it is composed of five powder supply units (tact time: 6 seconds / 1 piece). The pressurizing unit 120 requires 20 seconds per time for mounting, pressurizing, and taking out the conveyance mold 10, and is composed of three units (tact time: 6.6 seconds / 1 piece). The demolding unit 130 also requires 20 seconds per time for mounting, demolding, and taking out the transport mold 10, and is composed of three units (tact time: 6.6 sec / 1 unit). When three ring molded bodies 30 are laminated to form one ring magnet, 20 seconds are required for the magnetic field molding process of this example for each ring magnet.

  On the other hand, in the case of conventional multi-stage molding, the energization time requires a rise and fall time of current, and 30 seconds per layer (corresponding to one of the present invention). Furthermore, since pressure, powder supply and lamination time are continuously required in a state where a magnetic field is applied, 60 seconds per layer are required for orientation and compression. Three times longer time is required to stack three layers. Therefore, it takes 180 seconds for each ring magnet.

  Thus, according to the present embodiment, a long-axis ring magnet having a high residual magnetic flux density can be manufactured with high productivity. In addition, since the decaying AC magnetic field is used, the orientation ratio of the magnetic powder of the high coercive force material can be improved, and orientation and demagnetization can be performed at a time. As a result, the time required for orientation can be shortened and productivity can be improved.

  The case where an alternating magnetic field is applied to the magnetic powder in the orientation unit 110 and the reorientation / demagnetization unit 130 has been described above. However, depending on the type of magnetic powder, for example, in the case of a magnetic powder having a low coercive force, a pulsed magnetic field is used. May be added. In this case, the pulse magnetic field may be repeatedly applied 2 to 3 times.

  In addition, by providing a switching means that can reverse the energization direction of the coil 112 by connecting the positive and negative poles of the pulse power source that generates the pulse magnetic field to both ends of the coil 112, the pulse magnetic field whose polarity is alternately reversed is provided. May be applied. By applying a pulsed magnetic field whose polarity is alternately reversed, agglomeration of magnetic powder having a high coercive force can be prevented in the same manner as when an alternating magnetic field is applied, and as a result, the orientation is improved.

  When a pulse magnetic field is applied to the magnetic powder, the demagnetization may be an alternating magnetic field that attenuates. In addition, when applying a pulse magnetic field that reverses the above polarity alternately, the connection between the pulse power source and the coil 112 is switched, and a current less than that of the first time is applied. A pulse magnetic field having a magnetic field strength of about 1/20 may be applied. By using a pulse magnetic field as compared with an alternating magnetic field, the configuration of the power supply is simplified.

  FIG. 16 is a diagram showing another basic configuration of the ring-type magnet manufacturing apparatus according to the present embodiment. As shown in FIG. 16, the orientation unit 110 and the reorientation / demagnetization unit 130 of FIG. In this case, the magnetic powder of the transport mold 10 is oriented by the orientation / demagnetization unit 160 and then pressurized by the pressure unit 120, and then returns to the orientation / demagnetization unit 160 to be reoriented or demagnetized. . Thereafter, the demolding unit 140 and the laminating unit 150 perform demolding and lamination of the ring molded body. With this configuration, the number of units can be reduced. Further, since the magnetic field power source 200 needs to supply current only to the coils of the orientation / demagnetization unit 160, the entire manufacturing apparatus has a simple configuration, and the equipment cost can be reduced.

  Next, the manufacturing process of the ring magnet according to the present embodiment will be described in detail. The manufacturing process of the ring magnet includes a raw material alloy casting process, a pulverization process, a forming process in a magnetic field, and a sintering / heat treatment process. More specifically, the composition of the magnet is Nd: 30 wt%, B: 1 wt%, Dy: 3 wt%, Fe: remaining wt%. In the raw material alloy casting step, the raw material alloy is produced by mixing the magnet raw materials having the above composition by high frequency melting. In the pulverization step, the raw material alloy is pulverized by a hydrogen embrittlement treatment and a jet mill to obtain a magnetic powder having an average particle size of 4 μm. Next, in the magnetic field forming step, the magnetic powder is subjected to orientation and pressurization to align the direction of the magnetic crystal by applying the magnetic field in the magnetic field forming step of the present embodiment to the ring-shaped body 30. Then, the ring molded body is subjected to sintering and heat treatment processes at 1080 ° C., 900 ° C., and 600 ° C. in vacuum to obtain a ring sintered body.

  In the case of the present embodiment, the conveyance mold 10 has a cavity height of 30 mm and a die height of 40 mm so that a ring molded body 30 having a height of 15 mm can be formed. Using this conveying mold 10, three ring molded bodies having a height of 15 mm having a circular outer periphery and an uneven portion on the inner periphery of the ring are produced. Then, by stacking and sintering the three ring molded bodies 30 in the height direction, the ring mold according to the present embodiment has a 35 mm height after sintering, the ring outer periphery is circular, and the ring inner periphery has uneven portions. Sintered magnets can be manufactured. In addition, when the magnet height is low, a ring-shaped sintered magnet may be manufactured by sintering one ring molded body 30.

  As a result of measuring the magnetic characteristics of the test piece cut by wire cutting from the ring magnet manufactured in the present embodiment (attenuating AC magnetic field), the residual magnetic flux density 1.3T (13.0 kG) intrinsic coercive force 1560 kA / m (19.5 kOe) and an orientation ratio of 94.5% were obtained. In the normal DC orientation method, the residual magnetic flux density is 1.25T (12.5.kG), the intrinsic coercive force is 1520 kA / m (19.0 kOe), and the orientation ratio is 91.4%. Has improved.

  In the above description, the production of the ring-type magnet has been described as an example. However, the orientation unit 110 and the reorientation / demagnetization unit 130 are generally applicable when producing a radially oriented magnet regardless of the shape of the magnet. be able to. The same applies to the following embodiments.

Embodiment 2. FIG.
FIG. 17 is a diagram showing a basic configuration of a ring magnet manufacturing apparatus according to Embodiment 2 of the present invention. In the present embodiment, the orientation / pressure unit 170 in which the functions of the orientation unit 110, the pressure unit 120, and the reorientation / demagnetization unit 130 of the first embodiment are combined is installed.

  FIG. 18 is a diagram for explaining the configuration and operation of the orientation / pressure unit 170 of the present embodiment. The orientation / pressure unit 170 of the present embodiment includes a coil unit 111 arranged in a plurality of stages and a coil driving unit 115 that relatively approaches or separates each coil unit 111. The coil unit 111 includes a coil 112 that generates a magnetic field and a coil holding unit 113 that holds the coil 112. Each coil 112 is arranged substantially coaxially, and is connected by winding so that adjacent coils have opposite directions of current. Furthermore, a pressurizer 171 is installed in the coil unit 111 as a pressurizing mechanism that pressurizes the upper punch 16 or the lower punch 15 of the conveyance mold 10 installed between the coil units 111.

  Next, the operation of the present embodiment will be described. The transfer die 10 is mounted between the coil portions 111 in the same manner as in the first embodiment, and then the coil drive portion 115 narrows the interval between the coil portions 111 so that the transfer die 10 is sandwiched between the coil portions 111. become. Next, as described in Embodiment 1, an alternating current is applied to each coil 112 from the magnetic field power supply 200 to apply an alternating orientation magnetic field to the transfer mold 10. The AC magnetic field to be applied may be 2 to 3 cycles. Further, an alternating magnetic field having an amplitude attenuation rate of 90 to 50% may be applied. The current may be forcibly stopped after a predetermined number of alternating magnetic fields.

  Next, the coil moving unit 115 further narrows the interval between the coil units 111. Thereby, the pressurizer 171 provided in the coil unit 111 applies pressure to the upper punch 16 and the lower punch 15 of the transport mold 10, and the magnetic powder filled in the cavity 17 of the transport mold 10 is compressed. When the pressurization of the magnetic powder is completed, the interval between the coil portions 111 is widened by the coil driving portion 115, and the conveyance mold 10 can be taken out.

  The magnetic field for orientation may be applied at the following timing. An alternating current is supplied from the magnetic field power source to each coil 112 in a state where the transport die 10 is sandwiched between the coil portions 111. Subsequently, the coil driving unit 115 operates to narrow the interval between the coil units 111, and pressurizes the magnetic powder through the pressurizer 171 and the upper and lower punches 16 and 15. Subsequently, an alternating current is supplied to each coil 112, and then the above pressurization is repeated. You may make it repeat a magnetic field application and pressurization 2-5 times in such a procedure.

  In the above description, the case where an AC magnetic field is applied to the magnetic powder has been described, but the magnetic field to be applied may be a pulsed magnetic field. Further, a plurality of pulse magnetic fields may be continuously applied. In the case of a pulsed magnetic field or when demagnetization is insufficient, an alternating magnetic field that attenuates for demagnetization may be applied last. Further, the demagnetization may be performed by applying a pulse magnetic field having a polarity opposite to that of the pulse magnetic field in the case of orientation and having an amplitude of 1/3 to 1/20.

  In the above description, an example in which the magnetic powder is pressurized through the pressurizer 171 by driving the coil driving unit 115 is shown. However, as shown in FIG. 172 may be provided to drive the pressurizer 171 and the coil driving unit 115 may be configured to adjust the position in an auxiliary manner. Servo motors are well suited for pressurizing power, but the same effect can be obtained with hydraulic pressure. Alternatively, the coil driving unit 115 may hold the conveyance die 10 so that the upper punch 16 moves downward and the lower punch 15 moves upward relative to the die 12.

Embodiment 3 FIG.
FIG. 20 shows a conveyance type structure according to Embodiment 3 of the present invention. On the base 40, the die 12, the lower punch 15, and the core 11 are mounted. The base 40 is provided with a plurality of through holes 41 in the lower portion on which the lower punch 15 is mounted, and is provided with a through hole 42 in the lower portion on which the core 11 is mounted. At the time of pressurization, the lower punch 15 is pushed by a pressurizer or the like through the through hole 41. At the time of mold removal, it is necessary to push the die 12 from above while holding the lower punch 15 and the core 11. The lower punch 15 is held by a holder (not shown) through the through hole 41. The core 11 is also held by a holder (not shown) through the through hole 42. An elastic member such as a rubber material may be inserted between the side surface of the lower punch 15 and the base 40 so that the lower punch 15 does not fall after the magnetic powder is compressed, and the friction force may prevent the fall. The same effect can be obtained even if a spring is inserted between the base 40 and the lower punch 15. The upper punch 16 is set thereon after the cavity 17 is filled with magnetic powder.

Embodiment 4 FIG.
FIG. 21 is a diagram showing the structure of an alignment unit according to Embodiment 4 of the present invention. In the present embodiment, the core 11 of the transport mold 10 is composed of the magnetic body 11a and the nonmagnetic body 11b. That is, in the core 11, the magnetic body 11 a is disposed at a position corresponding to the vicinity of the center of the cavity 17 in the axial direction, and the non-magnetic body 11 b is disposed at a position corresponding to the vicinity of both ends of the cavity 17 in the axial direction. When the entire core 11 is made of a magnetic material, the flow of magnetic flux is as indicated by the dotted arrows in FIG. 21, and the magnetic flux density is strong at both ends in the axial direction of the cavity and weak near the center in the axial direction of the cavity. On the other hand, in the core 11 of the present embodiment, the magnetic flux passes through the magnetic body 11a having a small magnetic path resistance, and thus the flow is as indicated by the solid line arrow in FIG. Therefore, the magnetic flux density that is low near the center in the axial direction of the cavity 17 increases, and a uniform magnetic flux density distribution in the axial direction is obtained in the cavity 17. As a result, the variation in the orientation rate of the magnetic powder filled in the cavity 17 is reduced, and the magnetic characteristics of the ring magnet are stabilized. In addition, when the entire core 11 is made of a magnetic material, the magnetic powder concentrates at both ends in the axial direction where the magnetic flux density is strong during orientation, resulting in a difference in the density of the molded body, and sintering strain occurring after sintering. It was. In the case of the present embodiment, the low magnetic flux density increases in the vicinity of the center of the cavity 17 in the axial direction, and a uniform magnetic flux density distribution is obtained in the axial direction in the cavity 17, so that no difference occurs in the density of the molded body. Sintering strain can be reduced, and the shape accuracy of the sintered body can be improved.

Embodiment 5 FIG.
In the orientation unit 110 or the reorientation / demagnetization unit 130 described in the first embodiment or the orientation / pressure unit 170 described in the second embodiment, the generated magnetic flux of the coil unit 111 located in the middle is It passes through the two conveying molds 10 positioned. However, the magnetic flux generated by the coil portions 111 located at both upper and lower ends passes only through one conveyance mold 10 located at the lower or upper portion thereof. When passing through the two conveyance molds 10, the magnetic part of the core 11 becomes two places, the magnetic path resistance decreases, and the magnetic flux density increases. However, when passing through one conveyance mold 10, the magnetic part of the core 11 becomes one place, and the magnetic path resistance becomes larger than when passing through two magnetic parts, and the magnetic flux density is lowered accordingly. Therefore, in the present embodiment, the number of turns of the coil 112 of the coil unit 111 located at both ends (upper end or lower end) is set to be greater than the number of turns of the coil 112 of the coil unit 111 located in the middle. The magnetic flux density of 111 can be made uniform. For example, by increasing the number of turns of the coil 112 at both end positions by 5 to 20% with respect to the number of turns of the coil 112 at the intermediate position, the magnetic flux density passing through each conveyance mold 10 can be made uniform.

  The present invention can be widely applied to the production of a radially oriented magnet. For example, the present invention is applied to the production of a magnet used for a rotor of a motor.

Claims (20)

A powdering step of feeding magnetic powder into the cavity of the mold having a ring-shaped cavity;
At least two or more of the molds are arranged between the coil parts arranged in N stages (N is an integer of 3 or more), and the magnetic powder in the mold is radially oriented by the opposing magnetic field generated from the adjacent coil parts. An alignment process;
A pressurizing step of pressurizing the magnetic powder in the mold;
Demolding / lamination step of demolding the ring molded body oriented / pressed from the mold and laminating a plurality of the ring molded bodies,
A sintering step of sintering and integrating the laminated ring molded body. At least two or more of the above-mentioned molds are arranged between each coil part arranged in N stages (N is an integer of 3 or more), and the above-described pressure is applied by the opposing magnetic field generated from the adjacent coil part. The manufacturing method of the ring-type magnet of Claim 1 provided with the reorientation and demagnetizing process which reorientate or demagnetize with respect to magnetic powder. The method of manufacturing a ring magnet according to claim 1, wherein the orientation step and the pressurization step are combined into an orientation / pressurization step, and the orientation and the pressurization are repeated alternately. The manufacturing method of the ring type magnet according to claim 1, further comprising a coil driving unit that relatively approaches or separates each of the coil units, and the mold is disposed between the coil units. 2. The method for manufacturing a ring magnet according to claim 1, wherein each of the coil portions includes a coil arranged substantially coaxially, and is wound and connected so that the directions of current are opposite between adjacent coils. The method for manufacturing a ring magnet according to claim 5, wherein the coils are connected in series. 6. The method of manufacturing a ring magnet according to claim 5, wherein the number of turns of the coil located at both ends is greater than the number of turns of the coil located in the middle. The method for manufacturing a ring magnet according to claim 1, wherein each of the coil portions generates an alternating magnetic field. The method for manufacturing a ring magnet according to claim 8, wherein the amplitude of the alternating magnetic field attenuates with time. The method of manufacturing a ring magnet according to claim 1, wherein each of the coil portions generates a pulsed magnetic field whose polarity is alternately switched. The method of manufacturing a ring magnet according to claim 10, wherein the intensity of the pulse magnetic field attenuates with time. The mold includes a core, a die disposed around the core, and a lower punch and an upper punch disposed between the core and the die, and is surrounded by the core, the die, the lower punch, and the upper punch. The method of manufacturing a ring magnet according to claim 1, wherein the method is a conveyance type having a cavity. In the transfer mold, a presser base is disposed below the die, a friction body is fixed by the die and the presser base, the lower punch is held by the friction body, and the core is held by friction of the friction body. The ring-type magnet manufacturing method according to claim 12. The ring-type magnet according to claim 12, further comprising a base on which the die, the lower punch, and the core are mounted, wherein the lower die of the base and the lower portion of the core are provided with through holes. Production method. The ring type according to claim 12, wherein in the core, a magnetic body is disposed at a position corresponding to the vicinity of the center in the axial direction of the cavity, and a non-magnetic body is disposed at a position corresponding to the vicinity of both ends of the cavity in the axial direction. Magnet manufacturing method. Coil portions that are arranged in N stages (N is an integer of 3 or more) and generate magnetic fields that face each other from adjacent stages;
A magnetic field forming apparatus including a mold having a cavity for storing magnetic powder that is arranged one by one between the N-stage coil portions and is radially oriented by the magnetic field. The magnetic field shaping apparatus according to claim 16, further comprising a pressurizing mechanism that pressurizes the magnetic powder accommodated in the cavity. A conveying mold having a cavity, a powder feeding unit for feeding magnetic powder to the cavity, an orientation unit for applying a magnetic field for radial orientation of the magnetic powder fed to the cavity, and the oriented magnetic powder are added. A pressing unit for pressing, a reorientation / demagnetizing unit for applying a magnetic field for reorienting the depressurized magnetic powder and a magnetic field for demagnetizing, and a demolding unit for demolding the molded body from the conveying mold And a magnetic field power source for supplying a current to the orientation unit and the reorientation / demagnetization unit.
The orientation unit and the reorientation / demagnetization unit have coil portions that are arranged in N stages (N is an integer of 3 or more) and generate magnetic fields facing each other from adjacent stages. An apparatus for manufacturing a ring magnet comprising a magnetic field forming device arranged one by one between the N-stage coil portions. 19. The apparatus for manufacturing a ring magnet according to claim 18, wherein the orientation unit and the reorientation / demagnetization unit are combined into an orientation / demagnetization unit, and the orientation / demagnetization unit includes the magnetic field shaping device. The said orientation unit and the said pressurization unit are made into an orientation and pressurization unit, and the said magnetic field shaping | molding apparatus was equipped with the pressurization mechanism which pressurizes the magnetic powder accommodated in the said cavity of the said conveyance type | mold. Ring magnet manufacturing equipment.

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