JP2005268386A - Ring type sintered magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a ring type sintered magnet having excellent shape accuracy with a manufacturing method of good productivity. <P>SOLUTION: The manufacturing method comprises the steps of forming a ring-shaped molded body by laminating, in the axial direction, a plurality of ring-shaped preliminary molded body 102 to which radial orientation is implemented, forming a ring-shaped sintered body 300 by sintering the ring-shaped molded body and coupling the ring-shaped preliminary molded bodies 102 with the sintering process, and dividing the ring-shaped sintered body 300. For example, a projected portion 103 is formed so that joining strength after the sintering process becomes weaker than that of the other boundaries at the particular boundary between the ring-shaped preliminary molded bodies 102 and the ring type sintered magnet 100 is formed with division at the boundary having the projected portion 103 of weak joining strength after the sintering process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radially oriented ring-type sintered magnet used for a small motor or the like and a method for manufacturing the same.

  A radial anisotropic ring magnet is applied as a motor using a permanent magnet. In order to obtain a small motor with high output and low inertia, a ring magnet that is long in the axial direction is used.

  In general, when a ring-shaped magnet that is long in the axial direction is magnetically shaped, there is a problem that the orientation magnetic field strength cannot be sufficiently obtained, the orientation rate of the magnetic powder is lowered, and high magnetic properties cannot be obtained.

  When the ring magnet is radially oriented, the magnetic flux that passes through the core of the mold that forms the magnetic powder in a ring shape is equal to the magnetic flux that passes through the inner diameter of the die, so the inner diameter of the ring magnet (the core diameter of the mold) Di, the outer diameter of the ring magnet (die inner diameter) is Dd, the height of the ring magnet (die height) is H, the magnetic flux density passing through the core of the mold is Bc, and the magnetic flux density passing through the inner diameter part of the die is Bd Then, the relationship of Formula (1) is established.

2 × π / 4 × Di ² × Bc = π × Dd × H × Bd (1)

  When a steel material such as S45C is used for the core of the mold, the saturation magnetic flux density is about 1.5T. Therefore, when Bc = 1.5 in the above equation (1) and the magnetic field necessary for the magnetic field orientation is 1.0T or more. Bd = 1.0, and the height H of the ring magnet that can be magnetically oriented shaped from the above equation (1) is expressed by equation (2).

H = 3Di ² / 4Dd (2)

  In general, when a ring magnet having an axial length equal to or greater than the value H in Expression (2) is magnetically formed, a decrease in orientation is a problem. In the present specification, a ring-shaped magnet having a long axial length means a case where the height H is larger than that of the above formula (2).

  Therefore, conventionally, a magnet having a short axial length that can be sufficiently formed by a magnetic field is manufactured and bonded with an adhesive or the like to manufacture a magnet having a required axial length.

  Conventionally, a method has been proposed in which a magnet molded body is formed within a range (axial length) in which magnetic field orientation can be performed, and the molded body is sequentially stacked in a mold to form a magnet having a required axial length (for example, Patent Document 1). reference).

  On the other hand, when the ring magnet compact is sintered, the compact shrinks by 20 to 30%, but the density in the compact is uneven, the difference in the sintering shrinkage between the orientation direction and the other direction, and the sintering. There is a problem that deformation does not occur evenly due to the effect of friction with the tray.

  In order to solve this problem, conventionally, a method has been proposed in which a ring magnet molded body is sintered together with a restraining jig and the deformation at the time of sintering is suppressed by being attached to the restraining jig (for example, Patent Documents). 2).

JP-A-2-281721 JP 2001-335808 A

  In the method of Patent Document 1, a required mold is set in a powder molding press incorporating an electromagnetic coil, and powder supply / filling (material is supplied to the mold), magnetic field molding (compression molding, demagnetization in a magnetic field). ), Demolding (removing the molded body from the mold), and taking out (removing the molded body from the magnetic field molding machine and storing it in the container) to sequentially manufacture the molded product, resulting in poor productivity. Furthermore, since all processes are performed in the magnetic field molding machine, there are many restrictions on each operation. Moreover, the lower the number of pressurizations, the more the orientation is disturbed and the magnetic properties are unavoidable. Furthermore, the boundary part of each layer has a problem that the magnetic properties are deteriorated due to the effect of the molded article in the lower layer.

  In addition, the method of the above-mentioned Patent Document 2 is inferior in productivity because it requires a constrained constraining jig, and it is necessary to set the constraining jig and the center position of the ring magnet molded body accurately. There is a problem. Further, during the sintering, the molded body is placed on a sintering jig (setter) and sintered, but the lower part of the molded body is inhibited from shrinkage due to friction with the setter, and the deformation becomes particularly large.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to manufacture a ring-type sintered magnet with good shape accuracy by a manufacturing method with high productivity.

  The method for producing a ring-shaped sintered magnet according to the present invention includes a step of stacking a plurality of ring-shaped preforms having a radial orientation in the axial direction to form a ring-shaped molded body, and sintering the ring-shaped molded body. After sintering at a specific boundary between the ring-shaped preforms, including a ring-shaped sintered body, a step of joining the ring-shaped preforms together by sintering, and a step of dividing the ring-shaped sintered body The ring-shaped sintered magnet is produced by making the bonding strength of the lower than the bonding strength of the other boundary, and dividing at a boundary where the bonding strength is weak after sintering.

  According to the method for producing a ring-type sintered magnet of the present invention, since several ring-type sintered magnets integrated in the sintering process can be handled as one body, the following effects are obtained. That is, since several ring-type sintered magnets can be handled as one body, it can be efficiently transported between processes. In addition, since the inner and outer diameters of several ring-type sintered magnets can be integrally formed, the processing efficiency is improved. Further, since several ring-type sintered magnets can be integrally surface-treated, the processing efficiency is improved. Furthermore, a ring-shaped magnet sintered body with good shape accuracy can be obtained.

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

Embodiment 1 FIG.
(1) Configuration of Ring-Type Sintered Magnet of Embodiment 1 FIG. 1 is a perspective view showing a ring-type sintered magnet according to Embodiment 1 of the present invention. In FIG. 1, a ring-shaped sintered magnet 100 according to the present embodiment is formed by laminating a ring-shaped preform 102 made of radially oriented magnetic powder in the axial direction in a plurality of stages (in the figure, a three-stage configuration). The ring-shaped preforms 102 are bonded together by sintering. Here, the ring-shaped preforms 102 are sintered and integrated via the boundary 101. And in this Embodiment, the ring-shaped convex-shaped part 103 is formed in the upper surface of the ring-shaped preform 120 of the uppermost step part among the ring-shaped preforms 102 of several steps. Although not shown, it is preferable that the side surface of the convex portion 103 is tapered toward the tip.

(2) Method for Producing Ring-Type Sintered Magnet of Embodiment 1 The axial length of a radially oriented ring magnet that can be magnetically formed at one time is limited in order to form a required orientation magnetic field. In order to manufacture a radially oriented ring magnet having a long axial length, a ring-shaped preform 102 having an axial length capable of radial orientation is subjected to magnetic field orientation molding, and after taking it out of a mold, a plurality of the axially oriented preforms are stacked in the axial direction. The method of integrating by a sintering process is taken.

  In the method for manufacturing a ring-type sintered magnet according to the present embodiment, as shown in FIG. 2, the number of ring-shaped preforms 102 required for obtaining one ring-type sintered magnet is stacked. And the ring-shaped convex-shaped part 103 is provided in the upper end surface of the specific ring-shaped preform 120 among the multistage ring-shaped preforms 102. Then, sintering and heat treatment are performed in the state of FIG. 2, and the boundary between the ring-shaped preforms 102 is sintered and integrated to obtain a ring-shaped sintered body 300. The boundary of the ring-shaped preform 102 is integrated by sintering, but the boundary having the convex portion 103 has a smaller contact area between the ring-shaped preforms 102, so the bonding strength is smaller than the other boundaries. ing.

  Then, after finishing the inner and outer diameter parts of the sintered sintered ring-shaped sintered body 300 (state shown in FIG. 2), the ring-shaped sintered body 300 subjected to surface treatment for corrosion prevention is processed. When mechanical bending stress is applied to the boundary portion, as shown in FIG. 3, a ring-type sintered magnet 100 divided at the boundary portion having the convex portion 103 is obtained. Further, even if a mechanical external force is not applied, the specific boundary portion can be divided by an impact during magnetization only by applying a pulse magnetic field for magnetization.

  In addition, you may give the finishing process of the internal diameter part of the ring-shaped sintered compact 300 after parting. Further, since the ring-shaped sintered body 300 of the present embodiment has good shape accuracy as described below, the inner diameter portion can be bonded to the rotor shaft without finishing.

  4 is a cross-sectional view of one of the divided ring-type sintered magnets 100, and FIG. 5 is a cross-sectional view of the ring-type sintered magnet of FIG. As shown in FIG. 4, the thick line portion 105 in the figure is subjected to surface treatment, but the divided boundary portion (the end surface of the convex shape portion 103 or the end surface to which the convex shape portion 103 is connected) has a surface. It has not been processed. However, since all the areas that have not been surface-treated in the process of bonding to the rotor shaft 200 are covered with the adhesive (shaded portion in FIG. 5) 210, the corrosion of the ring-type sintered magnet 100 proceeds from there. There is no.

  Generally, when a molded body is subjected to a sintering treatment, the molded body is placed on a tray on which a spreader is spread and placed in a sintering furnace. The bedding powder is used to prevent the sintered body and the tray from joining. Further, it is used to reduce the friction between the compact (sintered body) and the tray during sintering shrinkage and suppress the sintering deformation. However, when sintering a ring-shaped molded body, the spread powder alone cannot suppress inhibition of sintering shrinkage due to friction with the tray, and deformation occurs due to sintering shrinkage, and the lower part of the molded body in contact with the tray is Defects such as deformation into an ellipse or an increase in dimensions may occur.

  Since the ring-shaped sintered body of the present embodiment has several ring-shaped preforms stacked in the axial direction, deformation is caused by sintering shrinkage only at the bottom stage, and the upper part has good shape accuracy. It becomes a ring shape. Therefore, for example, if the inner diameter of the lowermost ring-shaped preform is reduced and formed so as to ensure a machining allowance sufficient for finishing even if shrinkage deformation occurs, the machining allowance increases only in the lowermost stage. However, as a whole, a ring-type sintered magnet with good shape accuracy can be obtained.

As described above, the following effects (a) to (d) are obtained by integrally handling several ring-type sintered magnets integrated in the sintering process.
(A) Since several ring-type sintered magnets can be handled integrally, it can be efficiently transported between processes.
(B) Since several ring-type sintered magnets can be integrally processed with an inner diameter and an outer diameter, the processing efficiency is improved.
(C) Since several ring-type sintered magnets can be integrally surface-treated, the processing efficiency is improved.
(D) A ring-shaped magnet sintered body with good shape accuracy is obtained.

  In the above configuration, the convex portion 103 formed on the upper end surface of the ring-shaped preform is not limited to the shape shown in the figure, and if the shape reduces the contact area at the boundary of a specific ring-shaped preform, It doesn't matter what it is. For example, a ring shape having a circular cross section, a convex shape dotted in the circumferential direction, and the like are conceivable. Further, the shape is not limited to a convex shape, and may be a concave shape in order to reduce the contact area. Furthermore, not only the upper end surface of the ring-shaped preform, but also a convex or concave shape may be formed on the lower end surface of the ring-shaped preform. Furthermore, convex or concave shapes may be formed on both the upper end surface and the lower end surface of the ring-shaped preform.

(3) Specific Manufacturing Process of Ring-Type Sintered Magnet of Embodiment 1 Next, a specific manufacturing process of the ring-type sintered magnet of the present embodiment will be described. As the permanent magnet material, a neodymium alloy containing Nd, Dy, Fe and B is used. The neodymium alloy is subjected to hydrogen storage treatment and fine pulverization using a jet mill to obtain fine powder having an average particle size of about 5 μm. Using this as a raw material, a one-stage ring-shaped preform is formed.

  FIG. 6 shows a configuration of a manufacturing apparatus for forming a ring-shaped preform. This manufacturing apparatus includes a belt conveyor 2 that conveys a conveyance mold 10, a powder supply / filling unit 3 that measures and supplies magnetic powder into a cylindrical cavity of the conveyance mold 10, and a conveyance mold 10. Magnetic field of magnetic powder by a punch set unit 4 for setting the upper punch to pressurize the magnetic powder in the cavity of the mold and a state where the upper punch is set and ready for pressure forming. A magnetic field forming unit 5 for performing pressure forming, a demolding unit 6 for extracting the ring-shaped preform formed by magnetic field press-molding from the conveying mold 10, and an extra attached to the extracted ring-shaped preform. The compact body de-dusting unit 7 for removing magnetic powder, the stacking unit 8 for stacking the ring-shaped preform formed by magnetic field pressure molding, and the magnetic powder adhering to the conveying mold 10 are removed. And a mold removing powder / die set unit 9 to be set in the transport state the conveying molds 10.

  As shown in FIG. 7, the conveying mold 10 includes a pallet 10a that moves on the belt conveyor 2, a first holder 10b that holds a lower mold portion, a core 10d on a pillar, a lower punch 10e, A core 10d is disposed at the center, and a lower punch 10e and a die 10f that forms a cavity 10h to which magnetic powder is supplied together with the core 10d, and an upper punch 10g held by a second holder 10j are provided.

  FIG. 8 is a cross-sectional view showing the shape of the upper punch 10g. As will be described later, the upper punch 10g serves to pressurize the magnetic powder in the cavity from above. The upper punch 10g of the present embodiment has a flat bottom end surface as shown in FIG. 8 (a) and a recess g1 formed as shown in FIG. 8 (b). As shown in FIG.8 (c), there exists a thing in which the taper-shaped recessed part g2 is formed. The upper punch 10g in FIG. 8A is for forming a ring-shaped preform 102 having a flat upper end surface, and the upper punch 10g in FIG. 8B has a convex portion on the upper end surface. The upper punch 10g in FIG. 8C is for forming a ring-shaped preform having a tapered convex portion on the upper end surface.

  The conveyance mold 10 is first sent to the powder supply / filling unit 3. FIG. 9 is a cross-sectional view for explaining the powder supply / filling unit and its operation. In the magnetic powder measuring step of FIG. 9 (a), a magnetic powder such as a neodymium alloy having a constant weight is used by using a vibration feeder and a weight meter. 11 is weighed and stored in the container 3c. 9 (b) and 9 (c), a funnel-shaped powder feeding jig 3a that guides the magnetic powder 11 to the cavity 10h of the conveying mold 10 and a blade-shaped jig (stirring the magnetic powder 11 supplied to the cavity). (Not shown) is set on the die 10f of the conveyance mold 10, and the container 3c is moved to the position of the powder feeding jig 3a, rotated and tilted, and the magnetic powder 11 in the container 3c is supplied to the powder feeding jig 3a. To do. Next, the powder feeding jig 3a is vibrated by the vibration mechanism 3b to transfer all the magnetic powder 11 on the powder feeding jig 3a into the cavity 10h, and the blades of the blade-like jig are rotated to rotate the magnetic powder in the cavity 10h. While stirring 11, the blade is raised to fill the magnetic powder in the cavity. By rotating the blade and filling the magnetic powder 11, the cavity in the magnetic powder in the cavity or the bridge of the magnetic powder 11 is broken, and the magnetic powder 11 is uniformly filled in the cavity 10 h.

  The conveyance mold 10 in which the magnetic powder 11 is filled in the cavity 10 h is sent to the punch set unit 4. As shown in FIG. 10, the punch set unit 4 includes a hand 4a that catches the upper punch 10g and a moving mechanism (not shown) that moves the hand 4a up and down and moves the caught upper punch 10g. With this punch set unit 4, the transport mold 10 can be set in a state in which the magnetic powder in the cavity can be pressurized with the upper punch 10 g.

  First, as shown in FIG. 10A, the pallet 10a is conveyed to the stage of the punch set unit 4 and positioned at a specified position. And as shown in FIG.10 (b), the hand 4a descend | falls and catches the upper punch 10g. Next, as shown in FIG. 10 (c), the hand 4a lifts the upper punch 10g and moves toward the lower die, and as shown in FIG. 10 (d), the hand 4a descends to place the upper punch 10g into the core 10d. The upper punch 10g is released, and the upper punch 10g fits into the cavity. Since the diameter of the upper end of the core 10d is 0.2 mm smaller than the diameter in the cavity and a taper of 3 ° is given, the position of the pallet 10a and the hand 4a is displaced by less than 0.1 mm when the upper punch is inserted. Even if it exists, the defect that the upper punch 10g cannot be inserted into the core 10d does not occur. Next, after releasing the upper punch 10g, the hand 4a rises and moves to the original position.

  Next, the conveyance mold is sent to the magnetic field forming stage. 11 is a cross-sectional view illustrating the configuration and operation of the magnetic field forming unit, FIG. 12 is a cross-sectional view illustrating the structure of the pressurizer, and FIG. 13 is a view illustrating the configuration of the back core.

  As shown in FIG. 6, the magnetic field forming stage transfers the transfer mold 10 on which the upper punch 10g is set from the pallet 10a on the belt conveyor 2 to the magnetic field forming unit 5, and after the magnetic field forming on the belt conveyor 2. A transfer mechanism 5h for returning to the pallet 10a is provided. As shown in FIG. 11, the magnetic field forming unit 5 includes upper and lower electromagnetic coils 5a (fixed to a frame) that generate an alignment magnetic field for aligning magnetic powder, an upper electromagnetic coil 5a, and an upper punch 10g. It is driven by a compression molding mechanism 5b that raises and lowers a pressurizer 5c that pressurizes, a vertical drive mechanism that raises and lowers an upper frame including the upper electromagnetic coil 5a and the compression molding mechanism 5b, a ring-type elastic member 5j, and an air cylinder (not shown). And a back yoke 5d in contact with the die 10f.

  As shown in FIG. 12, the pressurizer 5 includes a punch pressurizing unit 5e that pressurizes the upper punch, a movable rod 5f that moves so as to be recessed into the punch pressurizing unit 5e, a back surface of the movable rod 5f, and a punch press. A spring 5g is provided between the inner surface of the pressure portion 5e and presses the movable rod 5f against the core 10d.

  As shown in FIG. 13, the back yoke 5d is a pair of ferromagnetic bodies having semicircular recesses that fit into the outer diameter of the die 10f. The back yoke 5d is installed so that the center of the thickness thereof coincides with the center of the thickness of the die 10f, and moves in the direction of the die 10f and comes into contact therewith.

  When the transport mold 10 is transported from the punch set unit 4 to the magnetic field forming unit 5 by the belt conveyor 2, the mold part is moved from the pallet 10a by the transfer mechanism 5h together with the holder 10b as shown in FIG. It is transferred to the forming part of the magnetic field forming unit 5. Next, as shown in FIG. 11B, the vertical drive mechanism is activated, the electromagnetic coil 5a and the pressurizer 5c are lowered, the upper and lower frames are fixed by the chucking function, and the upper frame The die 10f is fixed by a ring-type elastic member 5j attached to the lower part. Thereafter, the back yoke 5d approaches from both sides of the die 10f and comes into close contact with the outer peripheral portion of the die 10f. Next, a current flows through the electromagnetic coil 5a to generate a radial orientation magnetic field, and as shown in FIG. 11 (c), the pressurizer 5c is lowered, the upper punch 10g is pressurized, and the magnetic powder in the cavity is removed. By performing compression molding, a radially oriented ring-shaped preform is obtained. The compression molding pressure is 10 to 100 MPa, preferably 40 MPa, and the orientation magnetic field is 1 T or more.

  FIG. 14 is a cross-sectional view showing a state of magnetic flux in the radial orientation. The magnetic field generated by the upper coil 5a becomes a magnetic flux, passes through the pressurizer 5c, which is a ferromagnetic material, enters the movable rod 5f, which is also a ferromagnetic material, and the magnetic field generated by the lower coil 5a is strong. It enters the core 10d through the holder 10d which is a magnetic body. The lower punch 10e and the upper punch 10g are nonmagnetic materials.

  As shown in FIG. 14, the magnetic flux indicated by the broken-line arrow passes through the movable rod 5f and the core 10d, which are ferromagnetic materials, passes through the cavity 10h of the die 10f, which is a ferromagnetic material, in the radial direction, and radially enters the cavity 10h. An orientation magnetic field is formed.

  The radially oriented ring-shaped preform is returned by the transfer mechanism 5h onto the pallet 10a together with the conveyance mold.

  In the magnetic field shaping stage, the strength of the orientation magnetic field at the time of magnetic field shaping can be controlled by the magnitude of the current flowing through the electromagnetic coil 5a. The orientation rate of each ring-shaped preform (step) can be controlled by adjusting the current of the electromagnetic coil 5a every time each ring-shaped preform (step) is formed. Thereby, the ring-shaped preform (step part) which has the predetermined magnetic characteristic demonstrated in Embodiment 1-3 can be shape | molded.

  Next, the conveyance mold is sent to a demolding stage. FIG. 15: is sectional drawing (b) which shows the structure of a mold release unit, and the top view (a) seen from the direction of AA. The demolding unit includes a molded body pressurizing mechanism including an air cylinder 6a for pressing the ring-shaped preform 102 and an upper punch abutting portion 6d, a table 6c for pushing the die 10f upward, an air cylinder 6b, and the like. A die push-up mechanism.

  FIG. 16 is a cross-sectional view for explaining the demolding process. As shown in FIG. 16A, the pallet 10a on which the conveyance mold including the ring-shaped preform 102 is placed is conveyed to the demolding unit 6 by the belt conveyor 2 and stops at a specified position. The air cylinder 6a lifts the pallet 10a, the upper punch 10g hits the upper punch abutting portion 6d, and the ring-shaped preform 102 is pressurized. The applied pressure is 0.1 to 1 MPa. Next, as shown in FIG. 16B, the air cylinder 6b operates, the table 6c lifts the die 10f, and the ring-shaped preform 102 is extracted from the die 10f. Next, as shown in FIG. 16C, the air cylinder 6 a is lowered and the pallet 10 a is placed on the belt conveyor 2. The belt conveyor 2 moves the pallet 10a to the position where it is placed on the second holder 10j placed on the pallet 10a when the die 10f supported by the table 6c is lowered, and the table pressurizing cylinder 6b is moved. In operation, the table 6c is lowered and the die 10f is placed on the second holder 10j.

  In the process of extracting the ring-shaped preform 102 from the conveying mold 10, the upper part of the ring-shaped preform 102 extracted from the conveying mold 10 and the lower part of the ring-shaped preform 102 in the conveying mold 10 Since there is a difference in internal stress, cracks are likely to occur at the boundary between the extracted upper portion of the ring-shaped preform 102 and the lower portion in the conveying mold 10. Since the preformed body 102 is extracted from the die 10f in a pressurized state, the internal stress difference between the upper part and the lower part of the ring-shaped preformed body 102 is reduced, and the generation of cracks is prevented.

  Next, the conveyance mold 10 is sent to the compact de-dusting unit 7. 17 and 18 are cross-sectional views illustrating the configuration and operation of the compact de-dusting unit. The compact de-dusting unit 7 includes a table 7a and an elevating mechanism including an air cylinder 7b for elevating and lowering the table 7a, a nozzle 7c for injecting nitrogen gas, and a dust suction duct for sucking magnetic powder and iron powder and collecting them in a dust collector. 7d. By removing excess magnetic powder adhering to the ring-shaped pre-formed body 102 with the compact de-dusting unit 7, the ring-shaped pre-formed body 102 is prevented from being tilted or displaced in the next stacking process. can do.

  As shown in FIG. 17 (a), the transport mold 10 after demolding is transferred to the compact de-dusting unit 7 by the belt conveyor 2 and stopped at a specified position, and the air cylinder 7b is activated to raise the table 7a. To do. Then, as shown in FIG. 17B, the lower punch 10e is supported by the table 7a and ascends, and the ring-shaped preform 102 is extracted from the core 10d. At this time, the ring-shaped preform 102 is extracted while the magnetic powder adhering to the outer periphery of the core 10d is scraped off, so that the magnetic powder adheres to the inner peripheral end surface portion of the ring-shaped preform 102. At this time, the upper punch 10g is also extracted and placed on the second holder 10j.

  As shown in FIG. 18A, in the process of extracting the ring-shaped preform 102 from the core 10d, when the upper surface of the ring-shaped preform 102 slightly protrudes from the core 10d, the upper punch 10g is removed, and the nozzle 7c. Then, nitrogen gas is blown out to blow off the magnetic powder adhering to the surface of the ring-shaped preform 102 and sucked by the suction duct 7d. Thereafter, as shown in FIG. 18 (b), the ring-shaped preform 102 is further pulled out upward. However, it is not always necessary to completely extract from the core 10d.

  19, 20, and 21 are diagrams for explaining the configuration and operation of the stacking unit 8. The stacking unit 8 includes a chucking mechanism having a hand 8a for chucking the ring-shaped preform 102, a table 8b for stacking the ring-shaped preform 102, and a hand 8a (not shown). A mechanism for moving the table up and down, and a rotating mechanism for rotating the table 8b. An electromagnetic chuck may be used as the chucking mechanism.

  First, as shown in FIG. 19 (a), the hand 8a of the chucking mechanism is moved immediately above the ring-shaped preform 102 extracted from the core 10d. Then, as shown in FIG. 19B, the hand 8a is lowered and the ring-shaped preform 102 is chucked with the hand 8a. The chucking force is 0.1 to 4N. Next, as shown in FIG. 20 (a), the hand 8a is raised and moved so that the center of the hand 8a is directly above the table 8b, and the hand 8a is lowered as shown in FIG. 20 (b). Then, the ring-shaped preform 102 is placed on the table 8b. Further, similarly, as shown in FIGS. 35A and 35B, the second-stage and third-stage ring-shaped preforms 102 are stacked on the first-stage ring-shaped preform 102. To do.

  In order to obtain the ring-shaped sintered magnet of the first embodiment shown in FIG. 1, as shown in FIG. 21 (a), a ring-shaped convex portion is formed on the upper end surface of the third-stage ring-shaped preform 102. Stack what is formed. That is, as shown in FIG. 8 above, a ring-shaped concave shape is formed on the upper punch 10g at a rate of one for every three conveyance molds ((b) or (c) in FIG. 8). When is used, a ring-shaped molded body having the above-described configuration is obtained. The concave shape of the upper punch 10g is preferably formed with a taper as shown in FIG. If the concave shape is tapered as shown in FIG. 8C, the ring-shaped preform 102 is unlikely to be damaged such as cracks when the ring-shaped preform 102 is released from the upper punch 10g. .

  A ring-shaped molded body having such a configuration cannot be obtained by a molding method in which a mold is fixed to a molding machine as in the conventional method. As shown in FIG. 21 (b), the ring-shaped preforms 102 having flat end surfaces similar to those of the first stage may be stacked after the fourth stage.

  Here, when the height of the ring-shaped preform 102 varies, unnecessary force is applied to the ring-shaped preform 102 (when the height is high) during stacking, and the ring-shaped preform 102 Crushed. Alternatively, the hand 8a may release the ring-shaped preform 102 in the air and be destroyed by the impact of dropping. However, in this embodiment, since the weight of the ring-shaped preform 102 formed at one time is measured in a constant amount in the magnetic powder measuring step of the powder supply / filling unit 3, the ring-shaped preform is measured. The height of the body 102 is constant, and no unnecessary force or impact force is applied to the ring-shaped preform 102 during stacking.

  When the stacking process is completed, the transfer molds 10b, 10d, and 10e are returned to the pallet by the transfer mechanism 12, and transferred to the mold de-dusting / mold set unit 9 that performs the next process. The mold powder removal / mold set unit 9 includes a powder removal mechanism for removing the magnetic powder adhering to the conveyance mold 10 and each part of the conveyance mold 10 in an initial state in which the magnetic powder can be supplied in the powder supply / filling unit 3. And a set mechanism for setting.

  The powder removal mechanism has a nozzle that can inject nitrogen gas onto each part of the transport mold, and a suction mechanism for sucking and collecting the magnetic powder blown off by the nitrogen gas. The setting mechanism is a mechanism that lifts the die 10f placed on the second holder 10j and moves it onto the lower punch 10e placed on the first holder 10b after the stacking process is completed. By the powder removal mechanism and the set mechanism, the steps up to the molding and stacking of the next cycle can be performed smoothly.

  The ring-shaped molded body obtained by stacking the ring-shaped preforms 102 is transferred to a sintering / heat treatment furnace, sintered and heat-treated at a predetermined temperature, and the ring-shaped sintered body shown in FIG. Can be obtained. Thereafter, the process until assembling to the rotor shaft shown in FIG. 5 is as described above.

Embodiment 2. FIG.
FIG. 22 is a cross-sectional view showing a ring-shaped sintered body obtained by the method for manufacturing a ring-type sintered magnet according to Embodiment 2 of the present invention. FIG. 23 shows that the inner and outer diameter parts of the sintered ring-shaped sintered body (FIG. 22) are finished and then bent at the boundary of the ring-shaped sintered body subjected to surface treatment for corrosion prevention. It is sectional drawing of the ring type sintered magnet which applied stress and was parted by the boundary part.

  As shown in FIG. 22, the lowermost ring-shaped preform 102B of the ring-shaped molded body for obtaining this ring-shaped sintered body 301 is smaller in thickness than the other ring-shaped preforms 102, and is formed on the upper end surface. A ring-shaped convex portion 103 is formed. The lowermost ring-shaped preform 102B that is in contact with the sintering tray through the spread powder is deformed by the shrinkage of the sintering in the sintering process, or the shrinkage is reduced. The molded body is not deformed and shrinks uniformly. Therefore, a ring-shaped sintered body with good shape accuracy can be obtained except for the sintered body of the lowermost ring-shaped preform 102B.

  Since the ring magnet requires a great amount of man-hours for the finishing process in the subsequent process, even if the dummy ring-shaped preform 102B is placed in the lowest stage and sintered in this way, the total man-hours can be reduced. The manufacturing method according to the embodiment can also reduce the cost. In the manufacturing method of the present embodiment, since a large number of ring-type sintered magnets 100 are obtained for one dummy sintered body (sintered body of the ring-shaped preform 102B), the dummy sintered body is obtained. The loss for producing the ring-shaped preform 102B for use is reduced as a whole, and a cost merit is obtained.

Embodiment 3 FIG.
FIG. 24 is a cross-sectional view showing a ring-shaped sintered body obtained by the method for manufacturing a ring-type sintered magnet according to Embodiment 3 of the present invention. Alumina powder 104 having an average particle diameter of 1 to 100 μm is dispersed at a specific boundary of the ring-shaped preform 102 for obtaining the ring-shaped sintered body 302 of FIG. 24 in a thickness of 1 to 100 μm. The alumina powder 104 is dispersed in a region that is 1/2 or less of the area of the boundary surface.

  The ring-shaped preform is manufactured by the same manufacturing method as described in the first embodiment. For example, in order to obtain the ring-shaped sintered body 302 of FIG. After forming and stacking 102, a small amount of alumina powder 104 is sprayed on the upper end surface of the third stage ring-shaped preform 102. The dispersion amount is adjusted so that the dispersed alumina powder 104 covers 1/2 or less of the area of the upper end surface of the ring-shaped preform 102. When the particle diameter and thickness of alumina become 100 μm or more, the boundary will not be joined, so it should be less than that. In addition, when the particle size and thickness of alumina are 1 μm or less, the boundary bonding strength does not decrease, so it is more than that. And the ring-shaped sintered compact 302 shown in FIG. 24 with a small joining strength of a specific boundary is obtained by sintering the ring-shaped molded object which sprayed the alumina powder to the specific boundary in this way.

  As described above, according to the present embodiment, a specific boundary can be joined in a simple process without forming a convex shape portion or a concave shape portion on the end surface of the ring-shaped preform as in the above embodiment. A ring-shaped sintered body with low strength can be manufactured.

  In the present embodiment, other ceramic particles such as magnesia may be used instead of the alumina powder.

Embodiment 4 FIG.
FIG. 25 is a cross-sectional view showing a ring-shaped sintered body obtained by the method for manufacturing a ring-type sintered magnet according to Embodiment 4 of the present invention. At the specific boundary of the ring-shaped preform 102 for obtaining the ring-shaped sintered body 303 of FIG. 25, there are burrs generated during magnetic field molding and magnetic powder adhering to the inner diameter side when the molded body is extracted from the core. It exists as it is.

  In the manufacturing method of the ring-shaped preform described in the first embodiment, when a ring-shaped preform that forms a specific boundary (a ring-shaped preform at a lower stage of the specific boundary) is formed, FIG. It does not carry out the pulverization process shown, and sends it to the stacking process of the next stage. By treating in this way, there are burrs or extra magnetic powder at a specific boundary of the ring-shaped molded body, so that the boundary does not adhere, and if it is sintered, the bonding strength of the specific boundary is small A ring-shaped sintered body 303 is obtained.

  As described above, according to the present embodiment, a specific boundary can be obtained without forming a convex portion or a concave portion on the axial end surface of the ring-shaped preform 102, or without spraying ceramic powder. A ring-shaped sintered body 303 having a low bonding strength can be manufactured.

It is a perspective view which shows the ring type sintered magnet by Embodiment 1 of this invention. It is sectional drawing which shows the ring-shaped sintered compact by Embodiment 1 of this invention. It is sectional drawing which shows the state which divided the ring-shaped sintered compact by Embodiment 1 of this invention. It is sectional drawing which shows the ring-type sintered magnet by Embodiment 1 of this invention. It is sectional drawing which shows the state which attached the ring type sintered magnet by Embodiment 1 of this invention to the rotor shaft. It is a top view which shows the structure of the manufacturing apparatus of the ring type sintered magnet by Embodiment 1 of this invention. It is the top view and sectional drawing which show the structure of the conveyance metal mold | die in FIG. It is sectional drawing which shows the shape of the upper punch by Embodiment 1 of this invention. It is sectional drawing explaining the structure and operation | movement of a powder supply and filling unit. It is sectional drawing explaining the structure and its operation | movement of a punch set unit. It is sectional drawing explaining the structure and its operation | movement of a magnetic field shaping | molding unit. It is sectional drawing which shows the structure of a pressurizer. It is a top view (a) which shows composition of a back yoke, (c), an AA sectional view (b), and a BB sectional view (d). It is sectional drawing which shows the state of the magnetic flux in radial orientation. It is sectional drawing (b) which shows the structure of a mold release unit, and the top view (a) seen from the arrow direction of AA. It is sectional drawing for demonstrating the operation | movement in a mold removal unit. It is sectional drawing explaining the structure and operation | movement of a molded object powdering unit. It is sectional drawing explaining the operation | movement in a molded object powder removal unit. It is sectional drawing explaining the structure and operation | movement of a stacking unit. It is sectional drawing explaining the structure and operation | movement of a stacking unit. It is sectional drawing explaining the structure and operation | movement of a stacking unit. It is sectional drawing of the ring-shaped sintered compact by Embodiment 2 of this invention. It is sectional drawing which shows the ring-type sintered magnet obtained by parting the ring-shaped sintered compact of Embodiment 2 of this invention. It is sectional drawing of the ring-shaped sintered compact by Embodiment 3 of this invention. It is sectional drawing of the ring-shaped sintered compact by Embodiment 4 of this invention.

Explanation of symbols

2 belt conveyors, 3 powder supply / filling units, 4 punch set units,
5 Magnetic field forming unit, 6 Demolding unit, 7 Molded body de-dusting unit,
8 stacking unit, 9 mold de-dusting / mold set unit, 10 transport mold
100 ring-type sintered magnet, 101 boundary, 102 ring-shaped preform,
103 Convex part.

Claims (8)

A ring-shaped sintered magnet in which a plurality of ring-shaped preforms subjected to radial orientation are stacked in the axial direction, and the ring-shaped preforms are bonded together by sintering,
A ring-shaped sintered magnet, wherein a convex-shaped portion or a concave-shaped portion is formed on at least one axial end surface of the ring-shaped sintered magnet. A step of stacking a plurality of ring-shaped preforms with radial orientation in the axial direction to form a ring-shaped molded body, and sintering the ring-shaped molded body to form a ring-shaped sintered body. A step of bonding the compacts together by sintering, and a step of dividing the ring-shaped sintered body,
A ring-type sintered magnet is prepared by making the bonding strength after sintering weaker than the bonding strength of other boundaries at a specific boundary between the ring-shaped preforms, and dividing at a boundary where the bonding strength is weak after sintering. A method for manufacturing a ring-type sintered magnet, characterized by comprising: A dummy ring-shaped preform is installed at the lowest stage of the ring-shaped molded body, and the bonding strength after sintering at the boundary between the dummy ring-shaped preform and the upper ring-shaped preform is another boundary. 3. The ring-type sintered magnet according to claim 2, wherein the ring-type sintered magnet is produced by cutting at a boundary where the bonding strength is weak after sintering, and making the ring-type sintered magnet lower than the bonding strength of the ring-shaped sintered magnet. Method. Forming a convex shape or concave shape on at least one end face of the ring-shaped preform that faces the specific boundary, and dividing it at the boundary where the convex shape portion or concave shape portion is formed after sintering. A manufacturing method of a ring type sintered magnet according to claim 2 or 3, wherein a magnetized magnet is produced. A ceramic particle having a particle diameter of 1 to 100 μm and a thickness of 1 to 100 μm is formed at a specific boundary between the ring-shaped preforms, and is divided at the boundary after sintering to produce a ring-type sintered magnet. The method for producing a ring-type sintered magnet according to claim 2 or 3. After removing the burrs generated at the time of compression molding or demolding at the specific boundary between the ring-shaped preforms or the magnetic powder adhering to the specific boundary, the ring-shaped preforms are stacked and sintered. The method for producing a ring-type sintered magnet according to claim 2 or 3, wherein the ring-type sintered magnet is created by dividing at the boundary. 7. The ring-shaped sintered body integrated by sintering is subjected to finish processing on at least one of an outer diameter portion and an inner diameter portion, and then divided at a boundary where the bonding strength is weak. The manufacturing method of the ring-type sintered magnet of any one of these. The ring-shaped sintered magnet according to claim 7, wherein the ring-shaped sintered body having been subjected to the finishing process is subjected to a surface treatment for preventing corrosion and then divided at a boundary where the bonding strength is weak. Method.

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