JP6488967B2 - Powder filling apparatus and method for producing rare earth sintered magnet using the same - Google Patents

Description

  The present invention relates to an apparatus for filling powder into a cavity of a powder molding apparatus (hereinafter referred to as “molding apparatus”), and more particularly to a powder filling apparatus used for manufacturing a rare earth sintered magnet.

Permanent magnets (hereinafter simply referred to as “magnets”) are used as magnet pieces of various shapes. Rare earth magnets have excellent magnetic properties and are widely used. As rare earth sintered magnets, two types of rare earth / cobalt magnets and rare earth / iron / boron magnets are widely used in various fields. A rare earth / iron / boron magnet includes an Nd ₂ Fe ₁₄ B type compound as a main phase, and a part of Fe may be replaced with another transition metal element (hereinafter referred to as “T”). In addition, part or all of Nd may be expressed as another light rare earth element (hereinafter sometimes referred to as “RL”), or a light rare earth element and a heavy rare earth element (hereinafter referred to as “RH”). .) May be substituted. Rare earth elements are denoted as “R”. RL other than Nd is, for example, Pr, and RH is, for example, Dy or Tb. Furthermore, a part of B can be replaced by C (carbon). Hereinafter, a rare earth sintered magnet having an Nd ₂ Fe ₁₄ B type compound as a main phase is referred to as an “RTB-based sintered magnet”. Note that the RTB-based sintered magnet may contain a trace amount of added elements in addition to the above elements.

  The magnet piece of the RTB-based sintered magnet is manufactured, for example, by the following method. In the present specification, a magnet that is not magnetized is also called a magnet.

  An RTB-based alloy powder having a desired composition is prepared. Hereinafter, the alloy powder for sintered magnet is referred to as “magnetic powder”. A compact having a desired shape is obtained by press molding magnetic powder in a magnetic field, and a sintered compact is obtained by sintering the compact. If necessary, the sintered body is subjected to an additional heat treatment. Before or after the heat treatment, it is machined into magnet pieces of the desired size and shape. Thereafter, the magnet pieces are cleaned to remove grinding powder and grinding liquid generated by machining and adhering to the magnet surface.

  In order to improve the manufacturing efficiency of the magnet piece of the RTB-based sintered magnet and the yield of the material, a molded body having a shape close to the shape of the final magnet piece (sometimes referred to as “net shape”). Attempts have been made to fabricate.

JP 2000-248301 A JP 2002-160096 A

  However, for example, sintered magnet pieces used in motors for power sources of automobiles and motors for industrial equipment, for which demand has been increasing in recent years, are small and long (for example, length 30 mm × width 10 mm × thickness). 5 mm), and it is difficult to produce a molded body close to the net shape for such a shape.

  As will be described in detail later with reference to the drawings, this is because, for example, in the conventional filling method described in Patent Documents 1 and 2, it is difficult to uniformly fill the cavity of the molding apparatus with magnetic powder. . Magnetic powders for rare earth sintered magnets have low fluidity, so various filling methods have been studied, but the technology for producing molded bodies close to the net shape for the above shapes is still in practical use. It has not been.

  Therefore, conventionally, a molded body larger than the final magnet piece was produced, the large molded body was sintered, and the obtained sintered body was cut. For example, when producing a small and long magnet, make a molded body whose length in the long direction is close to the net shape, and cut the molded body or sintered body in the width direction and the thickness direction. The net-shaped magnet piece was obtained. As described above, among the three dimensions of the long rectangular magnet piece, the molded body or the sintered body was cut for the dimensions in two directions, so that the yield and throughput were reduced.

  The present invention has been made in order to solve the above-described problems. A powder filling apparatus and a rare earth sintering using the powder filling apparatus that make it possible to manufacture a small and thin sintered magnet piece more efficiently than in the past. The main object is to provide a method of manufacturing a magnet.

  A powder filling apparatus according to an embodiment of the present invention includes a feeder box, a support frame, a movable frame, a guide bar fixed to the support frame and extending in a first direction, and the movable frame extending linearly along the guide bar. The feeder box has an upper opening, a lower opening smaller than the upper opening, and a side wall extending from the upper opening to the lower opening. The movable frame is supported so as to be movable along the guide rod, and the movable frame has two action rods arranged to face each other with the feeder box interposed therebetween, and the movable frame When the reciprocating motion is performed, the two action rods alternately hit the feeder box, and the feeder box is reciprocated.

  In one embodiment, the lower opening has a rectangular shape, and a length in the first direction is larger than a length in a second direction orthogonal to the first direction.

  In one embodiment, the apparatus further includes a plurality of pins fixed to the guide rod and arranged in the first direction in a space between the upper opening and the lower opening. Among the plurality of pins, the center pin is longer than the pins at both ends.

  In one embodiment, the drive device has a swing motor fixed to the support frame.

  In one embodiment, the powder filling device further includes a shutter for the lower opening of the feeder box.

  In one embodiment, the feeder box further includes a bottom plate, and the bottom plate is formed of a fluororesin.

  A method of manufacturing a rare earth sintered magnet according to an embodiment of the present invention includes a step of preparing a magnetic powder for a rare earth magnet, and supplying a predetermined amount of the magnetic powder to the feeder box of any of the above powder filling apparatuses. A step of arranging the powder filling device such that the lower opening of the feeder box supplied with the magnetic powder is positioned on a cavity of the molding device; and the movable frame of the powder filling device By reciprocating the feeder box, filling the cavity with the magnetic powder, uniaxially pressing the magnetic powder in the cavity, and forming the molded body, And obtaining a sintered body by sintering the body.

  In one embodiment, the reciprocating motion is performed 300 times or more and 1200 times or less per minute.

  In one embodiment, the step of producing the molded body includes a step of applying an orientation magnetic field in the first direction.

  In one embodiment, the method includes a step of cutting the sintered body into a plurality of sintered body pieces along a direction corresponding to the first direction. In some embodiments, this cutting step is the only cutting step for shaped bodies and sintered bodies.

  According to the powder filling apparatus of the embodiment of the present invention and the method of manufacturing a rare earth sintered magnet using the same, it is possible to manufacture a small and thin sintered magnet piece more efficiently than in the past.

(A)-(d) is a schematic diagram for demonstrating the manufacturing process of the rare earth sintered magnet by embodiment of this invention. (A)-(c) is a schematic diagram of the shaping | molding apparatus 100 used for the manufacturing method of the rare earth sintered magnet by embodiment of this invention, (a) followed the AA 'line of (c). It is sectional drawing, (b) is sectional drawing along the BB 'line of (c), (c) is a top view of the state except the upper punch 12U. It is a typical top view of powder filling device 200 by an embodiment of the present invention. (A) And (b) is typical sectional drawing of the powder filling apparatus 200, (a) is sectional drawing along the 4A-4A 'line in FIG. 3, (b) is FIG. It is sectional drawing along the 4B-4B 'line in the inside. (A) And (b) is a typical top view for demonstrating the reciprocating motion of the movable frame 80 in the powder filling apparatus 200, (a) is the state which the feeder box 60 moved upwards in the figure. (B) shows the state where the feeder box 60 has moved downward in the figure. (A)-(c) is an optical image which shows the mode of the magnetic powder which filled the three cavities 10 which the shaping | molding apparatus 100 has using the powder filling apparatus of the reference example. It is an optical image which shows the crack in the sintered compact obtained by sintering the molded object produced using the powder filling apparatus of a reference example. (A)-(c) is an optical image which shows the mode of the magnetic powder filled into the three cavities 10 which the shaping | molding apparatus 100 has using the powder filling apparatus 200 of embodiment. (A)-(e) is a schematic diagram for demonstrating the manufacturing process of the conventional rare earth sintered magnet.

  Hereinafter, a powder filling apparatus according to an embodiment of the present invention and a method for producing a rare earth sintered magnet using the same will be described with reference to the drawings.

  First, a conventional process for manufacturing a rare earth sintered magnet will be described with reference to FIGS. Here, the rare-earth sintered magnet piece 4P (see FIG. 9 (e)) to be finally produced has a relationship of length L, width W, and thickness T such that L ≧ 2W ≧ T, and W Is 5 mm or less. According to the embodiment of the present invention, such a small and long magnet piece 4P can be manufactured more efficiently than in the past.

  As shown in FIG. 9A, a compact 1P is produced using magnetic powder for an R—Fe—B based sintered magnet. Of the dimensions of the molded body 1P, the length Lp1 is close to the length L of the magnet piece 4P. Since the volume shrinks when the molded body is sintered, the length Lp1 of the molded body 1P is determined so that the length of the sintered body 4P becomes L. The width Wp1 and the thickness Tp1 of the molded body 1P are determined in consideration of the cutting margin (the volume that becomes powder (processing waste) by cutting) so that a plurality of sintered bodies 4P can be obtained after sintering. When the molded body 1P is produced by press molding, for example, an orientation magnetic field is applied in the direction indicated by the arrow M (thickness Tp1 direction). The pressing direction is the length Lp1 direction, and the molded body 1P is produced by a so-called right-angle molding method.

  By sintering the molded body 1P, a sintered body 2P shown in FIG. 9B is obtained. The length Lp2, the width Wp2, and the thickness Tp2 of the sintered body 2P are respectively smaller than the length Lp1, the width Wp1, and the thickness Tp1 of the molded body 1P due to shrinkage accompanying the sintering. The length Lp1 of the molded body 1P is set so that the length of the sintered body 2P becomes the length L of the net shape. In this specification, the net shape dimensions do not necessarily coincide with each other accurately, and include net shape dimensions that are subjected to processing such as polishing. However, a large piece so that the magnet piece is cut into a plurality of portions is not included.

  Next, as shown in FIG. 9C, the sintered body 3P having a width W of net shape is obtained by cutting the sintered body 2P along the thickness direction. The cutting is performed using, for example, a wire saw device or an outer peripheral blade.

  Subsequently, as shown in FIG. 9 (d), the sintered body 3P is cut along the width direction, whereby the thickness becomes the thickness T of the net shape, and the net shape sintered body (magnet piece) 4P. Is obtained.

  Due to the two cutting operations described with reference to FIGS. 9C and 9D, a part of the sintered bodies 2P and 3P becomes powder (working waste). Moreover, the rare earth sintered body is a material that is difficult to cut, the time required for cutting is relatively long, and defects such as chipping are likely to occur. Thus, the cutting process reduces throughput and yield.

  As shown in FIG. 9E, the magnet piece 4P has dimensions (length L, width W, thickness T) close to a net shape. However, the side surfaces 4Pa and 4Pb of the magnet piece 4P are surfaces formed by cutting and may have saw marks (grinding marks). When the surface treatment (for example, plating, chemical conversion treatment or painting) is performed on the magnet piece 4P, the saw mark can be a cause of coating failure, and therefore, machining such as polishing and chamfering is performed on the side surfaces 4Pa and 4Pb. There is a case to receive. The machining process after the cutting process is also a factor that decreases the throughput and the yield.

  On the other hand, in the method for manufacturing a sintered magnet according to the embodiment of the present invention, the thin plate-like molded body 1E shown in FIG. 1 (a) is produced, so that the number of times of cutting the sintered body can be reduced. it can. Therefore, the small and thin sintered magnet piece 3E can be manufactured more efficiently than before.

  With reference to Fig.1 (a)-(d), the manufacturing process of the sintered magnet by embodiment is demonstrated. Here, the magnet piece 3E to be finally manufactured (see FIG. 1D) has, for example, a length L, a width W, and a thickness T of L, similarly to the magnet piece 4P shown in FIG. The relationship of ≧ 2W ≧ T is satisfied, and W is 5 mm or less.

  In the process of the sintered magnet according to the embodiment of the present invention, a thin plate-shaped molded body 1E shown in FIG. Of the dimensions of the molded body 1E, the length L1 is close to the length L of the magnet piece 3E, and the width W1 is close to the width W of the magnet piece 3E. The length L1 and the width W1 of the molded body 1E are determined so that the length of the sintered body 3E becomes L and the width W in consideration of volume shrinkage due to sintering. The thickness T1 of the molded body 1E is determined in consideration of the cutting margin (volume that becomes powder (working waste) by cutting) so that a plurality of sintered bodies 3E can be obtained after sintering. When the molded body 1E is produced by press molding, for example, an orientation magnetic field is applied in the direction indicated by the arrow M (thickness T1 direction).

  By sintering the molded body 1E, a sintered body 2E shown in FIG. 1B is obtained. The length L and width W of the sintered body 2E are the dimensions of the net shape of the sintered body 3E. The thickness T2 of the sintered body 2E is determined in consideration of the cutting margin so that a plurality of sintered bodies 3E can be obtained due to shrinkage accompanying the sintering and smaller than the thickness T1 of the molded body 1E.

  Next, as shown in FIG. 1C, by cutting the sintered body 2E along the width direction, the thickness becomes the net shape thickness T, and the net shape sintered body (magnet piece) 3E. Is obtained.

  As shown in FIG. 1D, the magnet piece 3E has dimensions (length L, width W, thickness T) close to a net shape. Of the side surfaces 3Ea and 3Eb of the magnet piece 3E, only the side surface 3Eb is formed by cutting.

  As can be seen by comparing the conventional manufacturing process described with reference to FIG. 9 and the manufacturing process according to the embodiment described with reference to FIG. 1, according to the manufacturing process according to the embodiment, the number of times the sintered body is cut is reduced. Reduced to one time. As a result, since only the side surface 3Eb of the magnet piece 3E is a surface formed by cutting, the machining process caused by the saw mark is also reduced.

  Thus, according to the embodiment of the present invention, the magnet piece 3E can be manufactured more efficiently than before.

  The press molding step in the method for producing a rare earth sintered magnet according to the above-described embodiment can be performed using, for example, the molding apparatus 100 shown in FIG. A powder filling apparatus according to an embodiment of the present invention for supplying magnetic powder to the molding apparatus 100 will be described in detail later.

  As shown in FIGS. 2A to 2C, the molding apparatus 100 includes a die 22 having a through hole 22a forming the cavity 10, an upper punch 12U for pressing the magnetic powder filled in the cavity 10, and A lower punch 12L. The through hole 22a of the die 22 has an opening having a length T1 and a width W1. The depth of the cavity 10 is adjusted by the position of the lower punch 12L. The molding apparatus 100 is a uniaxial molding apparatus, for example, a hydraulic press or an electric molding machine.

  The molding apparatus 100 can produce three molded bodies 1E shown in FIG. Of course, the molding apparatus 100 may make three or more (for example, four) molded bodies, or three or less (for example, two). As shown in FIG. 2C, three cavities 10 extending in the T1 direction are arranged in parallel. An orientation magnetic field (for example, 0.8 T to 4.0 T) is applied to the magnetic powder in the cavity 10 by the magnetic field generator 32.

The pressing pressure and pressing time are appropriately set by preliminary studies so that a molded body having a predetermined density can be obtained. The density of the compact can be, for example, 4.0 g / cm ³ (about 53% of the true density) when an RTB-based sintered magnet having a true density of about 7.5 g / cm ³ is manufactured. .

  The die 22, the lower punch 12L, and the upper punch 12U are formed of a cemented carbide (for example, a WC-Ni-based cemented carbide). The pressurizing surfaces of the lower punch 12L and the upper punch 12U are preferably mirror-finished surfaces. If the pressing surfaces of the lower punch 12L and the upper punch 12U are mirror surfaces, it is possible to prevent the orientation of the magnetic powder particles from being disturbed by friction with the pressing surface when molding while applying an orientation magnetic field. it can. In particular, the effect is remarkable in the right-angle molding method.

  After the molded body having a predetermined density is obtained as described above, the entire molded body is positioned above the uppermost end of the through hole 22a in a state where the molded body is pressed by the lower punch 12L and the upper punch 12U. Until then, the die 22 is lowered relative to the upper punch 12U and the lower punch 12L. At this time, in order to prevent cracking of the molded body and separation of a part of the molded body, the upper punch 12U is held down by the upper punch 12U or the upper punch 12U is slightly lifted to release the pressure and maintain the pressure. In this state, the die 22 is lowered and the formed body is extracted.

  Then, a sintered compact is obtained by sintering a molded object, and additional heat processing is performed as needed. These steps are performed by a known method. For example, sintering is performed by heat treatment at 1050 ° C. for 2 hours under an argon atmosphere. In this way, a sintered body 2E is obtained. The sintered body 2E is cut into a plurality of magnet pieces 3E as described above with reference to FIG. Then, if necessary, it is subjected to mechanical processing such as polishing and chamfering, surface treatment is performed, magnetized, and magnet pieces are obtained. Magnetization may be performed, for example, in a motor manufacturing factory.

  Conventionally, the filling of the magnetic powder into the cavity has been performed by, for example, a scraping method described in Patent Document 2. That is, the relative position of the pressing surface (upper surface) of the lower punch 12L with respect to the cavity 10 is adjusted, the volume of the cavity 10 is regulated, and the magnetic powder surface (upper surface) is flush with the surface of the die 22. Was filling. However, as in the powder filling device described in Patent Document 2, it is difficult to uniformly fill the thin plate-like cavity 10 illustrated here with magnetic powder only by causing the collision member to collide with the powder container. . Further, according to the scraping method, it is difficult to accurately control the amount of the magnetic powder filled in the cavity 10, and the variation in mass between the compacts is large.

  Therefore, in the press molding step of the manufacturing method of the present embodiment, the magnetic powder quantified in advance is supplied to the powder filling device, and the supplied magnetic powder is reliably filled in the cavity 10 with high accuracy (for example, 1 g or less). Since the amount of magnetic powder that does not fill the cavity 10 by adhering to the inner wall of the powder filling device is constant, it is sufficient to supply the amount to the powder filling device by that amount. As described above, by reliably filling the quantified magnetic powder into the cavity 10, it is possible to reduce the mass variation between the molded bodies.

  With reference to FIGS. 3-5, the powder filling apparatus 200 by embodiment of this invention is demonstrated. The illustrated powder filling apparatus 200 is suitably used for filling a quantified magnetic powder into a cavity for producing a thin plate-shaped molded body, but can be used for other purposes as well.

  FIG. 3 shows a schematic plan view of the powder filling apparatus 200, and FIGS. 4A and 4B show schematic cross-sectional views of the powder filling apparatus 200. 4A is a cross-sectional view taken along line 4A-4A 'in FIG. 3, and FIG. 4B is a cross-sectional view taken along line 4B-4B' in FIG.

  As shown in FIG. 3, the powder filling apparatus 200 includes a feeder box 60, a support frame 70, a movable frame 80, and a swing motor 90. The feeder box 60, the support frame 70, and the movable frame 80 of the powder filling apparatus 200 are made of, for example, stainless steel or aluminum.

  The feeder box 60 has a structure in which three feeder box portions 60p corresponding to the three cavities 10 of the die 22 shown in FIG. 2 are integrated. Each feeder box portion 60 p has an upper opening 62 to which magnetic powder is supplied and a lower opening 64 for discharging the magnetic powder toward the cavity 10. The upper opening 62 is larger than the lower opening 64, and the side surface from the upper opening 62 to the lower opening 64 has at least two inclined side walls (the side walls parallel to the T1 direction and / or the W1 direction are inclined). Are). The size of the upper opening 62 and the angle of the inclined side wall are appropriately set depending on the number and size of the cavities, the size of the molding device, and the like, and are, for example, about 2 to 10 times that of the lower opening 64. It is preferable that the angle is set so that the magnetic powder is smoothly guided to the lower opening 64 along the side wall (for example, 1 to 5 degrees). As shown in FIGS. 4A and 4B, the lower opening 64 has the same size as the opening of the cavity 10 (T1 × W1). However, the lower opening 64 does not necessarily have the same size as the cavity 10, and the feeder box 60 reciprocates as will be described later, so the lower opening 64 is made smaller by that amount. Also good.

  As shown in FIGS. 3 and 4, the feeder box 60 is supported so as to be movable in the T1 direction (longitudinal direction of the rectangular cavity) along the guide bar 72 fixed to the support frame 70. . That is, the guide bar 72 is fixed to the support frame 70 and extends in the T1 direction (first direction). Further, as shown in FIG. 4A, the guide bar 72 is disposed so as to penetrate the side wall of the feeder box portion 60p. That is, the hole 60a is provided in the side wall in the T1 direction of the feeder box portion 60p, and the guide rod 72 is inserted into the hole 60a. The guide bar 72 is fixed to the support frame 70 with screws, for example.

  A swing motor 90 is fixed to the support frame 70. The head portion 92 of the swing motor 90 is fixed to the movable frame 80. The head portion 92 of the swing motor 90 reciprocates linearly in the vertical direction in FIG. Therefore, the movable frame 80 reciprocates linearly in the vertical direction in FIG. 3 together with the head portion 92 of the swing motor 90. As long as the movable frame 80 can be reciprocated linearly, another drive device may be used instead of the swing motor 90. The reciprocating speed and the movable range are preferably variable.

  Here, the movable frame 80 has two action bars 84a and 84b arranged to face each other with the feeder box 60 interposed therebetween. The action rods 84a and 84b are fixed to the movable frame 80 via the connecting portion 83a and the connecting portion 83b, respectively.

  When the lower opening 64 is arranged so as to coincide with the cavity 10, the working bar 84 a and the working bar 84 b are configured to have a gap (for example, 1 to 2 mm) between the outer wall of the feeder box 60. Yes. When the movable frame 80 is reciprocated linearly by the swing motor 90, the action bars 84 a and 84 b alternately collide with the outer wall of the feeder box 60. The action bars 84 a and 84 b reciprocate the feeder box 60 along the guide bar 72. For example, the reciprocating speed of the head unit 92 is, for example, 700 times per minute. The movable range of the reciprocating motion of the head unit 92 is set to 10 mm, for example. The reciprocating motion of the movable frame 80 will be described later with reference to FIG.

  A pin 74 is fixed to the guide rod 72 with a screw, for example. Here, the four pins 74 are arranged at approximately equal intervals over the length T1 in the longitudinal direction of the opening of the cavity 10. Since the pin 74 is fixed to the support frame 70 via the guide rod 72, the pin 74 does not move even if the movable frame 80 and the feeder box 60 reciprocate in the T1 direction. Accordingly, the pin 74 reciprocates relative to the feeder box 60, that is, relative to the magnetic powder supplied into the feeder box 60 in the T1 direction. As a result, the magnetic powder in the feeder box 60 is agitated and uniformly falls into the cavity 10 from the lower opening 64 and filled. The pin 74 is made of, for example, stainless steel.

  Here, as schematically shown in FIG. 4A, the center two bottles 74 are preferably longer than the two at both ends. By arranging the pins 74 in this way, it is possible to suppress the magnetic powder from being biased and filled at the end of the cavity 10 in the T1 direction.

  Since the place where the quantified magnetic powder is supplied to the feeder box 60 is away from the molding apparatus 100, the magnetic powder remains until the powder filling apparatus 200 is disposed at a predetermined position on the die 22 of the molding apparatus 100. In order not to fall, it is preferable that the powder filling apparatus 200 further includes a shutter 94 for the lower opening, as shown in FIGS. 4A and 4B, for example. The shutter 94 can be opened and closed by using a known device such as an air cylinder or an actuator. For example, a shutter opening / closing mechanism described in JP-A-2006-15540 or JP-A-2004-130333 can be employed.

  The feeder box 60 is reciprocated on the die 22 of the molding apparatus 100. In order to reduce the frictional resistance between the upper surface of the die 22 and the bottom surface of the feeder box 60, the feeder box 60 preferably further includes a bottom plate 96 formed of a material having a low coefficient of friction. As the material having a low friction coefficient, a fluororesin (for example, PTFE) is preferable. The bottom plate 96 made of PTFE has excellent slidability in a state where the magnetic powder does not enter between the upper surface of the die 22 and the lower surface of the bottom plate 96 so as to be in contact with the upper surface of the die 22 without a gap. The thickness of the bottom plate 96 is, for example, 2 mm or more and 10 mm or less.

  With reference to FIG. 3 and FIG. 5, the filling operation | movement by the powder filling apparatus 200 by embodiment of this invention is demonstrated. 5 (a) and 5 (b) are schematic plan views for explaining the reciprocating motion of the movable frame 80 in the powder filling apparatus 200. FIG. 5 (a) shows the feeder box 60 at the upper side in the figure. FIG. 5B shows a state where the feeder box 60 has moved downward in the figure.

  As shown in FIG. 3, the powder filling device 200 is set on the die 22. At this time, for example, the powder filling apparatus 200 is set so that the lower opening 64 coincides with the opening of the cavity 10.

  When the switch of the swing motor 90 is turned on, the head portion 92 of the swing motor 90 reciprocates linearly in the T1 direction (vertical direction in the figure). As shown in FIG. 5A, when the head portion 92 moves upward in the drawing, the movable frame 80 fixed to the head portion 92 also moves upward, and the action rod 84 b collides with the outer wall of the feeder box 60. The head portion 92 moves further upward to the upper limit of the movable range, and the action bar 84b moves the feeder box 60 upward.

  Next, as shown in FIG. 5B, when the head portion 92 moves downward in the figure, the movable frame 80 fixed to the head portion 92 also moves downward, and the action rod 84 a moves to the outer wall of the feeder box 60. collide. The head portion 92 moves further downward to the lower limit of the movable range, and the action bar 84a moves the feeder box 60 downward.

  In this way, the action bars 84 a and 84 b reciprocate the feeder box 60 along the guide bar 72. The impact force when the action rods 84a and 84b collide with the outer wall of the feeder box 60 vibrates the feeder box 60, for example, shakes off the magnetic powder adhering to the side wall of the feeder box. Further, since the pin 74 fixed to the guide rod 72 does not move, the magnetic powder in the feeder box 60 reciprocates linearly in the vertical direction. Thereby, the magnetic powder in the feeder box is agitated to prevent the magnetic powder from agglomerating and uniformly distributed. Further, as described with reference to FIG. 4A, by arranging a pin 74 longer than both ends in the center among the four pins 74, the magnetic powder is placed at the end of the cavity 10 in the T1 direction. Uneven filling can be suppressed.

  The head portion 92 of the swing motor 90 reciprocates 700 times per minute, for example. Meanwhile, the magnetic powder in the feeder box 60 is uniformly filled into the cavity by its own weight while receiving vibration and stirring action as described above. Although the speed and the movable range of the reciprocating motion of the head unit 92 depend on the size of the feeder box 60, for example, the speed is not less than 300 times and not more than 1200 times per minute, and the movable range (T1 direction) is It is preferably set in the range of T1 × 0.85 mm to T1 × 1.3 mm. If the movable range is too narrow, the magnetic powder may not be sufficiently supplied into the cavity. Conversely, if the movable range is too wide, the magnetic powder remains in the feeder box, and the magnetic powder is supplied into the cavity with high accuracy. Because there is a fear that it cannot be done.

  3 and 5, the orientation magnetic field is applied in a direction parallel to the direction in which the feeder box 60 reciprocates. However, the orientation magnetic field may be applied in a direction perpendicular to the feeder box 60.

  Next, an experimental example is shown and the powder filling apparatus 200 by embodiment of this invention is demonstrated.

  As magnetic powder, magnetic powder for RTB-based sintered magnet was prepared. The composition of the RTB-based sintered magnet is expressed by RT- (M) -B, where R is a rare earth element including Y and necessarily includes Nd, and T is Fe or Fe and Co and / or Ni. M is an additive element (for example, at least one of Al, Ti, Cu, V, Cr, Ni, Ga, Zr, Nb, Mo, In, Sn, Hf, Ta, and W), and B is boron or It is a mixture of boron and carbon.

  The magnetic powder for the R—Fe—B based sintered magnet is produced by a known method (for example, see Japanese Patent Publication No. 6-6728 (Japanese Patent Laid-Open No. Sho 63-33505)). The entire disclosure of Japanese Patent Publication No. 6-6728 is incorporated herein by reference.

  Here, the magnetic powder was prepared as follows.

  Nd 23.0 mass%, Pr 6.5 mass%, Dy 3.0 mass%, Al 0.1 mass%, Co 2.0 mass%, Ga 0.08 mass%, Cu 0.1 mass%, B 0.98 mass%, balance Fe The composition was adjusted so as to have the following composition, and an alloy flake having a thickness of 0.2 mm to 0.3 mm was produced by a strip casting method.

  Next, this alloy flake was filled in a container and accommodated in a hydrogen treatment apparatus. Then, the hydrogen treatment apparatus was filled with hydrogen gas having a pressure of 50 kPa, so that hydrogen was occluded in the alloy flakes and then released. By performing such a hydrogen treatment, the alloy flakes were embrittled and coarsely pulverized powder having a size of about 0.15 mm to 2 mm was produced.

  After adding 0.05% by weight of zinc stearate as a grinding aid to the coarsely pulverized powder produced by the above hydrogen treatment and mixing, a median diameter (D50) of 4 μm is obtained by carrying out a grinding process with a jet mill device. A fine powder was prepared.

  258 g ± 1 g of the above fine powder was weighed to prepare each molded body.

  The size of the cavity 10 was T1 = 75 mm and W1 = 12 mm. In addition, L1 of the molded object obtained was 70 mm.

The specific configuration of the powder filling apparatus 200 used in the experiment is as follows.
Feeder box 60 Upper opening 76mm x 64mm
Lower opening 76mm x 8mm
Height (depth) 120mm
Inner wall inclination angle T1 direction 0 degree, W1 direction 3 degrees
Both ends 95mm
Pin spacing 11mm
Head 92 reciprocating speed: 720 times / min
Movable range: 10mm

  For comparison, a powder filling apparatus of a reference example was prepared.

  The powder filling apparatus of the reference example is replaced with a mechanism (such as the movable frame 80 and the driving apparatus 90) for reciprocating the feeder box 60 in the powder filling apparatus 200 described above, one air vibrator on each of the upper and lower outer walls of the feeder box. (Made by Netter) was arranged. In addition, it does not have a pin (the pin 74 in the powder filling apparatus 200). The frequency of vibration of the air vibrator was 800 times / minute.

The pressing conditions and sintering conditions are as follows.
Uniaxial press Pressure: 0.4 ton / cm ² Pressurization time: 8 seconds Orientation magnetic field 1T (Tesla)
Sintering temperature: 1080 ° C for 6 hours

  With reference to FIGS. 6A to 6C and FIGS. 7A and 7B, the results of using the powder filling apparatus of the reference example will be described.

  6A to 6C are optical images showing the state of the magnetic powder filled in the three cavities 10 of the molding apparatus 100 using the powder filling apparatus of the reference example. FIGS. 6A to 6C are optical images of a lump of magnetic powder obtained by lowering the die 22 without pressing after filling three cavities, respectively. The horizontal direction of each optical image is the T1 direction. FIG. 6B corresponds to the central cavity, and FIGS. 6A and 6C correspond to the cavities on both sides.

  As is clear from FIGS. 6A to 6C, the way of filling the magnetic powder in the T1 direction is different in the three cavities. For example, the shape of the upper end of the mass of magnetic powder is different in three cavities. The upper end of the mass of the magnetic powder in FIG.

  In addition, the density variation in the mass of magnetic powder is large. In an optical image, a dark portion has a high density, and a light portion has a low density. It can be seen that there is a variation in density in each of FIGS. Further, the density variations in FIGS. 6A to 6C are also different.

  When the magnetic powder in such a non-uniform filling state is uniaxially pressed, the molded body is cracked or buckled. For example, as shown in FIG. 6 (a), when pressing a magnetic powder lump whose upper right side is clearly high, if the appropriate pressure is applied to the right magnetic powder in the cavity, The applied pressure will be insufficient. This is because the magnetic powder for rare earth sintered magnets has low fluidity, and the magnetic powder does not move easily even if the pressing surface of the punch is a mirror surface. As a result, the obtained sintered body is cracked on the left side where the pressure is insufficient, as shown in FIGS. 7 (a) and 7 (b). In FIG. 7A, the portion surrounded by a circle (the left side of the sintered body) is a portion where cracks are generated, and FIG. 7B is an enlarged view thereof. Even when no cracks are confirmed in the molded body, cracks may be confirmed after sintering. In addition, if the conditions under which an appropriate pressure is applied to the left magnetic powder in the cavity are selected, an excessive pressure is applied to the right magnetic powder, and buckling occurs on the right side of the compact.

  On the other hand, when the powder filling apparatus 200 of the embodiment was used, it was possible to uniformly fill the three cavities with the magnetic powder.

  8A to 8C are optical images showing the state of the magnetic powder filled in the three cavities 10 of the molding apparatus 100 using the powder filling apparatus 200 of the embodiment. FIGS. 8A to 8C are optical images of a lump of magnetic powder obtained by lowering the die 22 without pressing after filling three cavities, respectively. The horizontal direction of the optical image is the T1 direction. FIG. 8B corresponds to the central cavity, and FIGS. 8A and 8C correspond to the cavities on both sides.

  As is clear from FIGS. 8A to 8C, the manner of filling the magnetic powder in the T1 direction is almost the same in all three cavities. That is, the shape of the upper end of the lump of magnetic powder has a highly symmetrical shape that is slightly higher at the center and slightly lower at both ends. Further, since the density of each optical image is small, it can be seen that the variation in density in the magnetic powder lump is small.

  No cracks or buckling occurred in the molded body produced using this powder filling apparatus 200, and no cracks were observed after sintering.

  As described above, by using the powder filling apparatus according to the embodiment of the present invention, it is possible to mass-produce a thin plate-like molded body. As a result, the manufacturing process described with reference to FIG. 1 can be adopted, and the number of times of cutting the sintered body can be reduced to one. As a result, the machining process after the cutting process is also reduced. Therefore, according to the method for manufacturing a rare earth sintered magnet according to the embodiment of the present invention, a small and long magnet piece can be manufactured more efficiently than in the past.

  Of course, the powder filling apparatus according to the embodiment of the present invention is not limited to the production of a molded body having the above-described shape, and can also be used to produce a molded body having another shape. Since the powder filling apparatus according to the embodiment of the present invention can fill the cavity with the quantified magnetic powder with high accuracy, it is possible to suppress the variation in the mass of the molded body as compared with the conventional scraping method. .

  The present invention is suitably used for the production of rare earth sintered magnets, particularly for the production of small and long magnet pieces.

DESCRIPTION OF SYMBOLS 10 Cavity 12U Upper punch 12L Lower punch 22 Dies 22a Through-hole 32 Magnetic field generator 60 Feeder box 62 Upper opening 64 Lower opening 70 Support frame 72 Guide rod 74 Pin 80 Movable frame 84a, 84b Acting rod 90 Oscillating motor ( Drive device)
92 Head unit 100 Molding device 200 Powder filling device

Claims (10)

A feeder box, a support frame, a movable frame, a guide bar that is fixed to the support frame and extends in the first direction, and a drive device that reciprocates the movable frame linearly along the guide bar;
The feeder box has an upper opening, a lower opening smaller than the upper opening, and a side wall extending from the upper opening to the lower opening, and is movable along the guide bar. Is supported as
The movable frame has two action bars arranged to face each other with the feeder box interposed therebetween,
A powder filling apparatus configured to reciprocate the feeder box when the movable frame is reciprocated, so that the two action bars alternately hit the feeder box.   2. The powder filling apparatus according to claim 1, wherein the lower opening has a rectangular shape, and a length in the first direction is larger than a length in a second direction orthogonal to the first direction.   The powder filling apparatus according to claim 1, further comprising a plurality of pins fixed to the guide rod and arranged in the first direction in a space between the upper opening and the lower opening.   The powder filling apparatus according to any one of claims 1 to 3, wherein the driving device has a swing motor fixed to the support frame.   The powder filling apparatus according to claim 1, further comprising a shutter for the lower opening of the feeder box.   The powder filling apparatus according to claim 1, wherein the feeder box further includes a bottom plate, and the bottom plate is formed of a fluororesin. Preparing magnetic powder for rare earth magnets;
A step of supplying a predetermined amount of the magnetic powder to the feeder box of the powder filling apparatus according to claim 1;
Disposing the powder filling device on the cavity of the molding device so that the lower opening of the feeder box supplied with the magnetic powder is positioned;
Reciprocating the feeder frame by reciprocating the movable frame of the powder filling device, and filling the cavity with the magnetic powder;
Producing a compact by uniaxially pressing the magnetic powder in the cavity;
And a step of obtaining a sintered body by sintering the molded body.   The method for producing a rare earth sintered magnet according to claim 7, wherein the reciprocating motion is performed 300 times or more and 1200 times or less per minute.   The method for producing a rare earth sintered magnet according to claim 7 or 8, wherein the step of producing the compact includes a step of applying an orientation magnetic field in the first direction.   The method for producing a rare earth sintered magnet according to claim 7, comprising a step of cutting the sintered body into a plurality of sintered body pieces along a direction corresponding to the first direction.