JP2005268387A - Ring type sintered magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ring type sintered magnet having excellent shape accuracy which can be inserted into a rotor shaft without processing an internal diameter of the ring type sintered magnet. <P>SOLUTION: The manufacturing method comprises the steps of forming a plurality of ring-shaped preliminary molded bodies to which radial alignment has been implemented, forming the ring-shaped molded body by laminating, in a plurality of stages, the ring-shaped preliminary molded bodies in the axial direction, and forming a ring type sintered magnet by sintering the ring-shaped molded bodies. The ring-shaped preliminary molded bodies are formed with the equal internal diameter and the ring-shaped preliminary molded bodies having the internal diameter which is larger than the equal internal diameter. The ring-shaped preliminary molded body having larger internal diameter is placed as the body of the lowest stage and the ring-shaped preliminary molded bodies having the equal internal diameter are stacked thereon. These molded bodies are placed on a sintering tray and sintered with the ring-shaped preliminary molded body having the larger internal diameter placed as the body of the lowest stage. <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.

  For example, a ring magnet with a long shaft length can be obtained by repeating a process in which a molded ring magnet molded in a mold is moved to a non-magnetic part of the die, and then the cavity is filled with magnetic powder and molded. A method of forming a molded body has been proposed (see Patent Document 1).

JP-A-2-281721

  However, 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 (magnetic material is supplied to the mold), magnetic field molding (compression molding in a magnetic field). , Demagnetization), 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 manufacture the molded product. Productivity will be worse. Furthermore, since all the processes are performed in the magnetic field molding machine, there are many restrictions on each operation. In particular, it is difficult to uniformly supply and fill the magnetic powder in the cavity. For this reason, a density distribution occurs in the ring-shaped molded body. Furthermore, the lower the number of pressurizations, the greater the density difference in the vertical direction within the molded body.

  When the ring-shaped molded body is sintered, the molded body shrinks by 20 to 30%, and the density in the sintered body becomes uniform. However, if there is a density difference in the ring-shaped molded body, sintering shrinkage occurs so that the difference disappears after sintering. That is, the shrinkage rate is large in a portion having a low density in the molded body, and the shrinkage rate is small in a portion having a high density. Therefore, if there is a density difference in the ring-shaped molded body as described above, there is a problem that warpage and deformation occur during sintering, and the size and shape accuracy of the ring-shaped sintered body deteriorate.

  In addition, the sintering shrinkage is inhibited by friction with the sintering tray on which the ring-shaped molded body is mounted during sintering, so that the shrinkage becomes non-uniform and the ring-shaped sintered body is deformed. There is.

  Furthermore, a radially oriented ring magnet is used by being inserted into a ferromagnetic rotor shaft. However, if the shape accuracy of the ring-shaped sintered body is poor, not only does it require a great number of man-hours for inner diameter processing but also for processing. It was necessary to allow for more stock allowance, which caused high costs.

  The present invention has been made to solve the conventional problems as described above, and can be inserted into the rotor shaft without processing the inner diameter of the ring-type sintered magnet, and the ring type has excellent shape accuracy. An object is to provide a sintered magnet.

  The ring-type sintered magnet of the present invention is a ring-type sintered magnet composed of a plurality of stages in which a plurality of ring-shaped preforms with radial orientation are stacked in the axial direction and the respective ring-shaped preforms are bonded together by sintering. A magnet is characterized in that the inner diameter of the step at the axial end of the ring-type sintered magnet is larger than the inner diameter of the other steps.

  The method for manufacturing a ring-shaped sintered magnet according to the present invention includes a step of forming a plurality of ring-shaped preforms with radial orientation, and a ring-shaped molding by stacking a plurality of ring-shaped preforms in the axial direction. A ring-shaped sintered body having the same inner diameter in the step of forming a ring-shaped preform, and a step of forming a ring-shaped sintered magnet having a plurality of stages by sintering the ring-shaped molded body In the step of forming a preform and a ring-shaped preform having an inner diameter larger than the inner diameter, and stacking the ring-shaped preform, the ring-shaped preform having a larger inner diameter is placed at the bottom, and the above-mentioned In the step of stacking ring-shaped preforms having the same inner diameter and sintering the ring-shaped preform, the ring-shaped preform having a larger inner diameter is placed on the sintering tray in a state where it is in the lowest stage. That.

  Specifically, transportable molds are sequentially transported to the powder feeding / filling stage, magnetic field forming stage, demolding stage, powdering stage, and stacking stage to produce a radially oriented ring-shaped compact and transport it. A ring-shaped molded body is obtained by stacking a plurality of ring-shaped preforms molded using a mold in the axial direction on a stacking stage. The inner diameter of the lowermost ring-shaped preform is set to be larger than the inner diameters of the other stages. And a ring-shaped sintered compact is obtained by sintering and heat-processing a ring-shaped molded object. In the sintering, the ring-shaped preform formed at the bottom at the time of molding is sintered at the bottom.

  According to the ring-type sintered magnet of the present invention, the inner diameter of the step at the axial end of the ring-type sintered magnet is larger than the inner diameter of the other steps, so that the inner diameter of the ring-type sintered magnet is finished. Even if it does not give, it can insert in the rotor shaft of a motor, etc., and can adhere.

  In addition, according to the method for manufacturing a ring-type sintered magnet of the present invention, since the lowermost ring-shaped preform is in contact with the sintering tray during sintering, deformation due to sintering shrinkage is large. Therefore, even if the deformation is slightly larger than the other ring-shaped preforms, the ring-shaped sintered magnet can be attached to the rotor shaft without finishing the inner diameter part. Can be inserted and glued.

  In addition, since each process is accurately and efficiently processed on individual stages, deformation during sintering is small, and steps other than the lowest step can be inserted and bonded to the rotor shaft without processing the inner diameter.

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

Embodiment 1 FIG.
(1) Configuration and Manufacturing Method of Ring-Type Sintered Magnet of Embodiment 1 As described above, a radially oriented ring-shaped magnet has an axial length that can be magnetically formed at one time to form a required orientation magnetic field. Limited. Therefore, in the present invention, in order to produce a radially oriented ring magnet having a long axial length, axially shaped ring-shaped preforms capable of radial orientation are individually magnetically oriented and removed from the mold. After that, a plurality of rings are stacked in the axial direction to form a ring-shaped molded body, and the ring-shaped molded body is integrated by a sintering process to form a ring-shaped sintered body.

  Fig.1 (a) is sectional drawing which shows the ring-shaped molded object of this Embodiment 1 manufactured by said method. FIG. 1 (b) shows the cross-sectional shape (AA line cross-sectional shape) of the second, third, and fourth-stage ring-shaped preforms, and FIG. 1 (c) shows the lowermost (first stage). The cross-sectional shape (BB cross-sectional shape) of this ring-shaped preform is shown.

  FIG. 2A is a cross-sectional view of a ring-type sintered magnet obtained by sintering the ring-shaped formed body of FIG. 1 at 1080 ° C. and then performing heat treatment at 550 ° C. to 900 ° C. FIG. 2 (b) shows the cross-sectional shape (A-A line cross-sectional shape) of the second, third, and fourth stage ring-type sintered magnets, and FIG. The cross-sectional shape (BB line cross-sectional shape) of this ring-type magnet sintered compact is shown.

  FIG. 3A is a cross-sectional view of a permanent magnet rotor obtained by finishing the outer diameter portion of the ring-type sintered magnet of FIG. 2 and then bonding it to the rotor shaft. FIG. 3B shows the cross-sectional shapes of the second, third, and fourth stage ring magnet portions of the permanent magnet rotor of FIG. 3A, and FIG. 3C shows FIG. The cross-sectional shape of the ring-shaped magnet portion of the lowermost stage (first stage) of the permanent magnet rotor is shown.

  As shown in FIG. 1, the outer diameters and axial lengths of all the ring-shaped preforms 102 are the same, but the inner diameter of the lowermost ring-shaped preform 102 is the same as that of the other ring-shaped preforms 102. It is formed larger than the inner diameter. As shown in FIG. 1, four ring-shaped preforms 102 are stacked on a sintering tray in which alumina spherical particles (bed powder) having an average particle size of 80 μm are spread with a thickness of 0.1 mm or more. Place in the state of 1 and put into a sintering / heat treatment furnace. If it heat-processes at 550-900 degreeC after sintering at 1080 degreeC, the ring magnet sintered compact 120 shown in FIG. 2 will be obtained.

  When the ring-shaped molded body 110 is sintered, dimensional shrinkage of 20 to 30% occurs. At this time, the lower part of the ring-shaped molded body 110 is deformed by being inhibited from contraction due to friction with the sintering tray and the spread powder. Further, due to the frictional imbalance (difference in frictional force depending on the direction) between the sintering tray and the spread powder, the ring-shaped sintered body 120 does not have a similar shape to the ring-shaped molded body 110, and FIG. As described above, the ring-shaped sintered body is deformed into an elliptical shape.

  In the ring-shaped molded body 110 stacked as shown in FIG. 1, sintering deformation is likely to occur in the lowermost ring-shaped preform 102, and the other stages of the ring-shaped molded body 102 contract relatively uniformly. It occurs and there is almost no deformation due to friction with the sintering tray and the powder. 2B and 2C show a cross section of the ring magnet sintered body after sintering shrinkage. As shown in FIG. 2 (c), the lowermost cross section is deformed into an ellipse shape because the sintering shrinkage is inhibited by friction, but the other stages are uniformly sintered and contracted. The shape is good and close to a perfect circle.

  After finishing the outer diameter of the ring-shaped sintered body 120 of FIG. 2 to form the ring-shaped sintered magnet 100, the ring-shaped sintered magnet 100 is inserted into the rotor shaft 200 and bonded thereto, as shown in FIG. A permanent magnet rotor is obtained. Looking at the cross section of the lowermost sintered body as shown in FIG. 3C, the inner diameter portion is elliptical, but the inner diameter in the minor axis direction after sintering is larger than the rotor shaft dimension. The ring-type sintered magnet 100 is smoothly inserted into the rotor shaft 200 and fixed with an adhesive. The inner diameter of the lowermost ring-shaped preform 102 is set to a dimension that can be smoothly inserted into the rotor shaft 200 without finishing and can secure a sufficient thickness of the adhesive layer even if deformation occurs during sintering.

Further, the inner diameter of the ring-shaped preform 102 at the other stage is larger than the inner diameter in the minor axis direction of the lowermost stage and has a shape close to a perfect circle, so that it can be smoothly inserted into the rotor shaft 200 and the thickness of the adhesive layer Is also ensured uniformly over the entire circumference.

  Further, as will be described later, each ring-shaped preform 102 is individually high-precision and high-quality using a dedicated device for each of the powder feeding / filling stage, the magnetic field forming stage, the demolding stage, and the dedusting stage. Since it is processed and manufactured efficiently, a ring-shaped preform 102 having a uniform density in the molded body and a uniform radial orientation can be obtained. Then, the ring-shaped preforms 102 are formed by stacking the ring-shaped preforms 102 that have been uniformly magnetically molded in this way, and the ring-shaped preform 110 is sintered. In a stage other than the lowest stage where there is no influence of friction, uniform sintering shrinkage occurs, and the ring-shaped sintered body 120 (ring-type sintered magnet 100) having a similar shape accuracy to the ring-shaped molded body 110 is obtained. can get. Accordingly, steps other than the lowest step can be inserted and bonded to the rotor shaft 200 without finishing the inner diameter portion.

  Further, the end surface portion of the ring-shaped sintered body that has been finished before the ring-type sintered magnet 100 is bonded to the rotor shaft 200 may be used. Further, a method of finishing the outer diameter portion of the ring-shaped sintered body 120 on the basis of the center of the rotor shaft 200 after inserting and bonding the ring-shaped sintered body 120 that has not been finished at all is used. May be.

  By configuring in this way, the ring-shaped sintered body can be inserted and bonded to the rotor shaft 200 without finishing the inner diameter portion of the ring-shaped sintered body. A rotor can be manufactured. Since the processing of the inner diameter portion of the ring-shaped sintered body accounts for 50% or more of the total number of processing steps, a large cost reduction can be realized by eliminating the inner diameter processing step.

  Also, if the outer diameter part of the ring-shaped sintered body is processed after bonding to the rotor shaft, it is possible to prevent the center of the rotor shaft and the outer diameter center of the ring-shaped sintered body from being misaligned during assembly. A magnet rotor can be obtained, and a motor with a small cogging torque can be manufactured.

(2) 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. 4 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. 5, the conveyance 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.

  The conveyance mold 10 is first sent to the powder supply / filling unit 3. FIG. 6 is a cross-sectional view for explaining the powder feeding / filling unit and its operation. In the magnetic powder measuring step of FIG. 6 (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. 6 (b) and 6 (c), a funnel-shaped jig 3a that guides the magnetic powder 11 to the cavity 10h of the conveyance mold 10 and a blade-shaped jig that stirs 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. 7, 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. 7A, 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.7 (b), the hand 4a descend | falls and catches the upper punch 10g. Next, as shown in FIG. 7 (c), the hand 4a lifts the upper punch 10g and moves toward the lower mold, and as shown in FIG. 7 (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. 8 is a cross-sectional view illustrating the configuration and operation of the magnetic field forming unit, FIG. 9 is a cross-sectional view illustrating the structure of the pressurizer, and FIG. 10 is a view illustrating the configuration of the back core.

  As shown in FIG. 4, 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. 8, the magnetic field forming unit 5 includes upper and lower electromagnetic coils 5a (fixed to the 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. 9, the pressurizer 5 includes a punch pressurizing portion 5e that pressurizes the upper punch, a movable rod 5f that moves so as to be recessed into the punch pressurizing portion 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. 10, 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 conveyance mold 10 is conveyed from the punch set unit 4 to the magnetic field forming unit 5 by the belt conveyor 2, as shown in FIG. 8A, the mold part is transferred from the pallet 10a by the transfer mechanism 5h together with the holder 10b. It is transferred to the forming part of the magnetic field forming unit 5. Next, as shown in FIG. 8B, the vertical drive mechanism is activated, the electromagnetic coil 5a and the pressurizer 5c are lowered, the upper and lower frames are fixed to each other 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. 8C, 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. 11 is a cross-sectional view showing the state of magnetic flux in 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. 11, the magnetic flux indicated by the broken-line arrow passes through the movable rod 5f, which is a ferromagnetic material, and the core 10d, passes through the cavity 10h of the die 10f, which is a ferromagnetic material, in the radial direction, and is radial into 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.

  Next, the conveyance mold is sent to a demolding stage. FIG. 12 is a cross-sectional view (b) showing the configuration of the demolding unit and a plan view (a) viewed from the direction 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. 13 is a cross-sectional view for explaining the demolding process. As shown in FIG. 13 (a), the pallet 10a on which the conveying 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. 13B, 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. 13C, 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. FIG.14 and FIG.15 is sectional drawing explaining the structure and operation | movement of a molded object powdering 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. 14 (a), the conveying 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. 14B, 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. 15A, 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. 15 (b), the ring-shaped preform 102 is further extracted upward. However, it is not always necessary to completely extract from the core 10d.

  16, 17, and 18 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. 16A, the hand 8a of the chucking mechanism is moved immediately above the ring-shaped preformed body 102 extracted from the core 10d. Then, as shown in FIG. 16B, 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. 17 (a), the hand 8a is raised, 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. 17 (b). Then, the ring-shaped preform 102 is placed on the table 8b.

  Further, as shown in FIGS. 18A and 18B, the second, third, and fourth stage ring-shaped preforms 102 are stacked on the first stage ring-shaped preform 102. To do. Here, in order to obtain the ring-shaped molded body shown in FIG. 1, the transport metal is set so that the inner diameter of the lowermost ring-shaped preform 102 is larger than the inner diameter of the other ring-shaped preform 102. The dimensions of the core 10d and the upper and lower punches 10g and 10e of the mold 10 are different from the dimensions of the core 10d and the upper and lower punches 10g and 10e of the conveying mold 10 for forming the ring-shaped preform 102 of the other stage. Thus, since each process of a manufacturing process is processed with the said individual unit using multiple types of conveyance metal mold | dies 10, it becomes possible to manufacture the structure of the ring-shaped molded object shown in FIG. On the other hand, a ring-shaped molded body having such a configuration cannot be obtained by a molding method in which a mold is fixed to a magnetic field molding machine as in the conventional method.

  In the stacking process, if the height of the ring-shaped preforms 102 varies, unnecessary force is applied to the ring-shaped preforms 102 (when the height is high), and the ring-shaped preforms 102 are stacked. The molded body 102 is 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 110 shown in FIG. 1 obtained by stacking the ring-shaped preforms 102 is transferred to a sintering / heat treatment furnace and sintered and heat-treated at a predetermined temperature, as shown in FIG. A ring-shaped sintered body 120 can be obtained.

Embodiment 2. FIG.
FIG. 19 is a cross-sectional view showing a ring-shaped molded body according to Embodiment 2 of the present invention, and FIG. 20 is a cross-sectional view showing a ring-type sintered magnet according to Embodiment 2 of the present invention.

  A ring-shaped sintered body 120a (ring-type sintered magnet 100a) in FIG. 20 is obtained by sintering the ring-shaped molded body 110a shown in FIG. 19 at 1080 ° C. and heat-treating at 550 to 900 ° C. The outer diameter part and end face part of the bonded body are finished. The inner diameter portion is not finished.

  The ring-shaped molded body of FIG. 19 is manufactured by the same manufacturing method described in the first embodiment. However, the inner diameter of the lowermost ring-shaped preform 102 is the same as the inner diameter of the other ring-shaped preform 102, and the inner and outer diameters are formed with the same dimensions over the entire axial length. The ring-shaped formed body 110a formed in this way is mounted on a sintering tray on which a spread powder is spread, and is put into a sintering furnace. The bedding powder is laid on a sintering tray so that alumina spherical particles having an average particle diameter of 80 μm have a thickness of 0.1 mm or less (different from the first embodiment).

  In such a state, the ring-shaped molded body 110a mounted on the sintering tray shrinks in size due to sintering. However, the shrinkage of the lower part of the ring-shaped molded body 110a that is in contact with the sintering tray and the spread powder is hindered by the influence of friction. In the case of the second embodiment, since the thickness of the bed powder layer is thin, the influence of friction is greater than that in the case of the first embodiment, and the lowermost ring-shaped preform 102 is deformed into an elliptical shape. In addition, since the shrinkage (shrinkage rate) is also reduced, the inner diameter of the lowermost ring-shaped preform 102 is formed larger than the inner diameter of the other ring-shaped preform 102 as in the first embodiment. Even if not, the ring-shaped sintered body (the inner diameter portion is not finished) can be smoothly inserted into the rotor shaft and bonded. In addition, since the friction between the sintering tray and the spread powder is large, the lowermost sintered body generates a difference in contraction amount in the axial length direction even in the stage, and becomes a tapered shape 130 having a large inner diameter dimension on the end face side. The taper surface serves as a guide surface when the ring magnet is inserted into the rotor shaft, and it is possible to suppress the occurrence of defects such as defects during assembly.

It is sectional drawing which shows the ring-shaped molded object 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 of the permanent magnet rotor which attached the ring type sintered magnet of FIG. 2 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 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 which shows the ring-shaped molded object by Embodiment 2 of this invention. It is sectional drawing which shows the ring type sintered magnet by Embodiment 2 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 stack units, 9 mold de-dusting / mold set unit, 10 transport mold,
100, 100a Ring-type sintered magnet, 102 Ring-shaped preform,
110, 110a Ring-shaped molded body, 120 Ring-shaped sintered body, 130 Tapered shape.

Claims (4)

A ring-shaped sintered magnet composed of a plurality of stages in which a plurality of ring-shaped preforms subjected to radial orientation are stacked in the axial direction, and the ring-shaped preforms are joined together by sintering,
A ring-type sintered magnet, characterized in that the inner diameter of the step at the axial end of the ring-type sintered magnet is larger than the inner diameter of the other steps. A ring-shaped sintered magnet composed of a plurality of stages in which a plurality of ring-shaped preforms subjected to radial orientation are stacked in the axial direction, and the ring-shaped preforms are joined together by sintering,
A ring-type sintered magnet characterized in that the inner diameter of the ring-type sintered magnet is tapered toward the end in the axial direction. The ring-shaped sintered magnet according to claim 1 or 2, wherein a finishing process after sintering is not performed on an inner diameter portion of the ring-shaped sintered magnet. A step of forming a plurality of ring-shaped preforms with radial orientation, a step of stacking the ring-shaped preforms in a plurality of stages in the axial direction to form a ring-shaped formed body, and firing the ring-shaped preform. And a step of forming a ring-type sintered magnet composed of a plurality of stages,
In the step of forming the ring-shaped preform, a ring-shaped preform having the same inner diameter and a ring-shaped preform having an inner diameter larger than the same inner diameter are formed.
In the step of stacking the ring-shaped preforms, the ring-shaped preform having a large inner diameter is placed at the bottom, and the ring-shaped preforms having the same inner diameter are stacked thereon,
In the step of sintering the ring-shaped formed body, the ring-shaped sintered magnet is mounted on a sintering tray in a state where the ring-shaped preform having a large inner diameter is in the lowest stage.

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