JP2005277180A - Magnet-manufacturing method, magnetic powder forming method and dry forming equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method that realizes the high filling density and high-speed manufacturing cycle of magnetic powders through dry forming in manufacturing magnets and forming magnetic powders or in the associated dry forming equipment. <P>SOLUTION: This method comprises the following two processes a filling process starts filling magnetic powders G in a mortar 3 with a magnetic field generation pattern 2 positioned above a dedicated filling depth and relatively moves the pattern 2 up to the filling depth for a mortar 3; filling the magnetic powders G and a forming process relatively moves the cope 1 within the mortar 3, when filling magnetic powders G is complete; and pressure-forming the magnetic powders G in the magnetic field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a magnet such as a ferrite magnet using a dry molding method, a method for molding a magnetic powder, and a dry molding apparatus used therefor.

Motors used for electrical appliances of automobiles and automobiles are required to have high performance, small size, and light weight. Such a motor is a DC motor, and an anisotropic ferrite magnet by dry molding is used as the magnet. The motor magnet is anisotropy so that the radial direction is the easy axis of magnetization.
This method of manufacturing an anisotropic ferrite magnet by dry molding is performed by applying a magnetic field to the mold (lower mold) and adding material to the mold (lower mold) when iron oxide fine powder having an average particle size of 1 μm or less is used as a material. At the time of pressure forming, pressure is applied while maintaining the orientation state along the direction of the magnetic flux lines, thereby providing polar anisotropy and improving product characteristics. For example, Patent Document 1 describes a method of manufacturing a ferrite magnet by dry molding as shown in FIG. 10, and describes the configuration and shape of the mold (upper mold 1, lower mold 2) and mortar mold 3. A combination optimized for satisfying the required characteristics has been proposed.

  The powder material is basically weighed using the space in the cavity. However, in order to handle fine powder with extremely poor fluidity, as described above, the assistance of filling with a magnetic field is indispensable. It is. Therefore, increasing the packing density to saturation, that is, minimizing the voids in the cavity is essential for the stability of the filling weight (reducing variation), and increasing the magnetic field strength is implemented as a direct means. Yes.

As a means for generating the magnetic field, a system is adopted in which a direct current is applied to the coil 5 surrounding the mold (the die 3) by the rectifier 4 using a thyristor. Further, after the press molding is completed, demagnetization is performed by applying a reversal magnetic field adjusted so as to cancel the residual magnetic flux of the product. At that time, a reversal current is applied by the rectifier 4.
Conventionally, after taking out the finished product, the lower die 2 moves to the filling depth position (the lowest position depth of the cavity (molding region)) until the material supply box 6 passes above the cavity in the die 3. Waiting. In this state, at the start of filling, a direct current is applied from the rectifier 4 to the coil 5 to generate a magnetic field in the lower die 2 of the ferromagnetic material, thereby attracting the magnetic powder G.
In terms of the magnetic circuit, the magnetic field strength increases when the upper and lower molds (upper mold 1 and lower mold 2) are close to each other, but the magnetic field used for the purpose of supplementing the filling is a single pole (N pole or S pole). Only the pole) is applied to the lower mold 2 so as to be in contact with the magnetic powder G.

JP 7-201558 A (page 3-4)

The following problems remain in the conventional technology.
Conventionally, to increase the packing density, a high direct current is applied to increase the magnetic field strength for assisting filling, but it is practically much stronger than the power supply current that obtains the magnetic field strength required for product characteristics. A direct current (2 to 3 times) is applied. However, if the high current output is cut off instantaneously due to the demagnetizing reversal current, the load (mainly heat generation) of the rectifier becomes large, so there is a limit to the operating capacity and it is difficult to increase the cycle speed. .

  The present invention has been made in view of the above-described problems, and provides a magnet manufacturing method, a magnetic powder molding method, and a dry molding apparatus capable of obtaining a high packing density of magnetic powder and a high-speed manufacturing cycle in dry molding. For the purpose.

  The present invention employs the following configuration in order to solve the above problems. That is, in the magnet manufacturing method of the present invention, the magnetic powder is filled into the die by starting the filling of the magnetic powder in the state where the lower mold that has generated the magnetic field is disposed above the predetermined filling depth position. However, the filling process in which the lower mold is moved relative to the die to the filling depth position, and the magnetic powder is applied in the magnetic field by moving the upper mold relatively in the die after the magnetic powder filling is completed. And a molding step of pressure molding.

  The magnetic powder molding method of the present invention starts filling the die with the magnetic powder in a state where the lower die generating the magnetic field is arranged above the predetermined filling depth position, while filling the magnetic powder. A filling process in which the lower die is moved relative to the die to the filling depth position, and molding in which the magnetic powder is pressure-molded by moving the upper die relatively into the die in a state where filling of the magnetic powder is completed. And a process.

  The dry molding apparatus of the present invention is a dry molding apparatus for dry-molding magnetic powder, a lower mold and an upper mold that can move relative to the die, and a powder filling mechanism that fills the die with magnetic powder from above. And a magnetic field generation mechanism that generates a magnetic field from the lower mold, and the lower mold is disposed above a predetermined filling depth position at the start of filling, and the lower mold is relative to the die to the filling depth position while filling. And a mold moving mechanism for moving the mold.

  In these magnet manufacturing methods, magnetic powder molding methods, and dry molding apparatuses, the lower mold is disposed above a predetermined filling depth position (minimum position depth of the molding region) at the start of filling, so that Even if the magnetic field applied to the mold is low, the magnetic powder can be reliably attracted because the lower mold is close to the magnetic powder. Furthermore, by moving the lower mold relative to the die to the filling depth position while filling, the magnetic powder can be filled in the die at a high filling density while maintaining a state where the magnetic powder is strongly attracted. it can.

In the magnet manufacturing method of the present invention, it is preferable that the upper end of the lower mold protrudes from the upper end surface of the die and enters the magnetic powder to be filled at the start of filling.
In the dry molding apparatus of the present invention, the powder filling mechanism includes a material supply unit that stores magnetic powder and can fill the magnetic powder into the die from the lower opening, and the mold moving mechanism pushes the upper end of the lower mold at the start of filling. It is preferable to protrude from the upper end surface of the die and enter the magnetic powder in the material supply unit.

  In these magnet manufacturing methods and dry molding apparatuses, the lower die is brought into contact with the magnetic powder directly by protruding the upper end of the lower die from the upper end surface of the die and entering the magnetic powder at the start of filling. It can be reliably sucked and filled.

The magnet manufacturing method of the present invention is characterized in that the magnetic powder is a ferrite magnetic powder having an average particle diameter of 1 μm or less.
This magnet manufacturing method is particularly suitable when a ferrite magnetic powder having an average particle size of 1 μm or less is used as the magnetic powder.

  The magnetic powder molding method of the present invention includes a filling step in which a magnetic powder is filled into a filling region in a die from above, and an upper die is relatively moved into the die in a state where the filling of the magnetic powder is completed. A filling step in which a magnetic field is generated in a filling region in the die, and the magnetic field strength is set to be maximized in the vicinity of the upper end surface of the die at the start of filling. The position where the magnetic field intensity is maximized is lowered below the filling region while filling.

  In this magnetic powder molding method, a magnetic field is generated in the filling region in the die, and the magnetic field strength is set so as to be maximized in the vicinity of the upper end surface of the die at the start of filling. Since the position where the magnetic field intensity is maximum is lowered below the filling region while being further filled with magnetic powder, the magnetic powder is filled to the bottom of the filling region with high density while being strongly attracted.

In the dry molding apparatus of the present invention, the magnetic field generating mechanism is applied to the coil according to the coil wound around the die, the ferromagnetic part provided in the lower mold, and the upper end position of the lower mold at the start of filling. And a rectifier capable of changing the direct current.
In this dry molding apparatus, by setting the direct current according to the upper end position of the lower mold so that the necessary and sufficient magnetic field strength is obtained, the power consumption of the rectifier can be reduced and the manufacturing cycle can be speeded up. .

The present invention has the following effects.
That is, according to the magnet manufacturing method, the magnetic powder molding method and the dry molding apparatus according to the present invention, the lower mold that generates the magnetic field at the start of filling is disposed above the predetermined filling depth position, and the filling is performed. Since the lower mold is moved to the filling depth position, the magnetic powder can be filled in the die with a high filling density, and the applied current for generating the magnetic field is lowered while maintaining the high attractive force of the magnetic powder. be able to. Further, according to the method for molding magnetic powder of the present invention, a magnetic field is generated in the filling region in the die, and the magnetic field strength is set to be maximum near the upper end surface of the die at the start of filling. Since the position where the magnetic field strength becomes maximum is lowered below the filling region while filling, the magnetic powder can be efficiently and strongly attracted into the filling region from the initial filling to the completion of filling, and can be filled with high density.
As a result, high quality magnetic powder can be molded, and the production cycle can be increased while maintaining good product characteristics such as magnets.

  Hereinafter, an embodiment of a magnet manufacturing method, a magnetic powder molding method, and a dry molding apparatus according to the present invention will be described with reference to FIGS. 1 to 6.

The magnet produced by the manufacturing method of the present embodiment is an arcuate dry-formed ferrite magnet (so-called anisotropic segment magnet) having a circular arc cross section and having anisotropy in the radial direction. It is manufactured using a molding apparatus.
As shown in FIGS. 1 to 3, this dry molding apparatus fills a molding region K in a die (die) 3 with a magnetic powder G and performs dry molding in a magnetic field. A lower mold 2 and an upper mold 1 that can move relative to the mortar mold 3, a powder filling mechanism 8 that fills the mortar mold 3 with magnetic powder G from above, and a magnetic field that generates a magnetic field in the lower mold 2. A generating mechanism 9, a mold moving mechanism 10 such as a hydraulic cylinder device that moves the lower mold 2 and the upper mold 1 relative to the die 3, and a pair of rectangular parallelepiped shapes that apply a magnetic field in the radial direction of the molding region K And a ferromagnetic body 11.

The upper die 1 is composed of an upper punch 1a made of a ferromagnetic material and an upper nonmagnetic material portion 1b provided on the lower side of the upper punch 1a facing the forming region K. The lower die 2 is composed of a lower punch (ferromagnetic part) 2a made of a ferromagnetic material and a lower non-magnetic part 2b provided on the upper side of the lower punch 2a facing the forming region K. ing. In the present embodiment, since the lower mold 2 is fixed to a frame (not shown), the mold moving mechanism 10 relatively moves the position of the lower mold 2 by moving the mortar mold 3 and the upper mold 1. Let
The molding region K is formed so as to be surrounded by the upper nonmagnetic body portion 1b, the lower nonmagnetic body portion 2b, and the mortar die 3 so that the convex upper surface thereof is on the lower side.

  In addition, the lower non-magnetic body portion 2b and the upper non-magnetic body portion 1b are set so that the central portion is thicker than both end portions. By making the cross-sectional shapes of the lower non-magnetic body portion 2b and the upper non-magnetic body portion 1b in this way, the orientation near the end of the magnet molded body is directed more toward the center and the degree of radial orientation becomes better, and magnetic characteristics It is for improving. In addition, since there is a nonmagnetic material having a low magnetic permeability between the lower punch 2a and the upper punch 1a made of a ferromagnetic material and the magnetic powder G, a sudden change in magnetic flux can be avoided, and at the time of firing. Cracking is prevented and yield is improved.

Furthermore, the lower non-magnetic part 2b is provided with a flat part in the vicinity of the central part to prevent the central part from becoming too thick. Note that the cross-sectional shape of the lower non-magnetic part 2b is configured such that the upper edge and the lower edge are each arc-shaped and are eccentric, or the upper edge and the lower edge have different radii of curvature. Also good. The same applies to the upper nonmagnetic part 1b.
The upper nonmagnetic body portion 1b and the lower nonmagnetic body portion 2b are not essential, but in order to obtain better orientation, it is preferable to provide at least the lower nonmagnetic body portion 2b. If the part 1b is provided, the orientation is further improved. In addition, by providing these non-magnetic materials, the lifetime of the upper punch 1a and the lower punch 2a is extended.

  The constituent materials of the lower nonmagnetic body portion 2b and the upper nonmagnetic body portion 1b are not particularly limited, and are usually appropriately selected from nonmagnetic stainless steel, nonmagnetic stellite, and the like. Further, the upper punch 1a, the lower punch 2a, and the orientation ferromagnetic material 11 may be made of a magnetic material such as S45C. The mortar mold 3 may be made of a nonmagnetic cemented carbide material or the like.

The powder filling mechanism 8 includes a material supply box (material supply unit) 6 that accommodates the magnetic powder G and can be filled into the die 3 from the lower opening, and the die surface (upper end surface) of the die 3. And a box moving mechanism 12 such as a hydraulic cylinder device for moving the material supply box 6 so as to be able to advance and retreat.
As the magnetic powder G, ferrite magnetic powder having an average particle diameter of 1 μm or less is used.
The magnetic field generation mechanism 9 includes a coil 5 disposed so as to surround the die 3 and a rectifier 4 that applies a direct current to the coil 5. This rectifier 4 uses a thyristor and can change the current value and the current direction of the direct current. In particular, the rectifier 4 can change the applied current so that the required magnetic field strength can be obtained according to the position of the lower mold 2 at the start of filling.
The pair of orientation ferromagnetic materials 11 are provided on both sides in the circumferential direction of the molding region K via the die 3 respectively.

  Next, the manufacturing method of the dry-type ferrite magnet by the dry-type molding apparatus will be described below with reference to FIGS.

  First, as shown in FIG. 1A, after completion of the pressure molding, the rectifier 4 was adjusted so as to cancel the residual magnetic flux in the direction opposite to the direct current applied during the pressure molding. A reversal current is applied to the coil 5 to generate a reversal magnetic field, and a demagnetization process is performed. Then, as shown in FIG. 1B, the die 3 is moved downward with respect to the lower die 2 and the upper die 1 by the die moving mechanism 10, and the magnet compact S after the pressure forming is moved to the die 3. It protrudes above the mortar surface (upper end surface). Further, as shown in FIG. 1C, only the upper mold 1 is moved upward, and the magnet compact S is removed (knock-out) as shown in FIG. 3A.

  Next, in the state where the upper die 1 is retracted upward, the material supply box 6 is moved over the die surface of the die 3 to the position immediately above the lower die 2 by the box moving mechanism 12 as shown in FIG. Move. At this time, the lower die 2 is in a state of being retracted below the mortar surface of the die 3 so as not to hinder the movement of the box moving mechanism 12. In a state where the lower opening of the material supply box 6 is completely located immediately above the lower mold 2, the movement of the material supply box 6 is stopped and, as shown in FIG. The lower die 2 is moved upward relative to the die 3 by moving 3 downward, and the upper end of the lower die 2 protrudes from the die surface of the die 3 to form the magnetic powder G in the material supply box 6. Let it enter. In this state, by applying a predetermined direct current to the coil 5 and applying a magnetic field to the lower mold 2 by the rectifier 4, a strong magnetic field is generated in the lower mold 2 to attract the magnetic powder G.

  Further, with the magnetic field applied to the lower mold 2, the lower mold 2 is moved downward relative to the mortar mold 3 by moving the mortar mold 3 upward as shown in FIG. As shown in FIG. 4B, the lower mold 2 is lowered while attracting the magnetic powder G until reaching a predetermined filling depth position. That is, by moving the lower die 2 upward at the start of filling, the magnetic field strength is maximized in the vicinity of the die surface of the die 3 (near the die surface of the filling region), and then the lower die 2 is lowered. As a result, the position where the magnetic field intensity becomes maximum while being filled with the magnetic powder G is lowered below the filling region. Thereby, the magnetic powder G is filled with high density into the molding region (filling region) K in the die 3 (filling step).

Next, as shown in FIG. 4C, the material supply box 6 is retracted and retracted from the molding region K, and as shown in FIGS. 5A, 5B, and 5C, the mold moving mechanism 10 is moved. Thus, the upper die 1 is lowered and the magnetic powder G is pressure-molded under a predetermined pressure condition in the molding region K between the lower die 2 and the die 3 to form a magnet compact S (molding step). At this time, a magnet molded body S in which the anisotropic direction is aligned with the radial direction of the molding region K is obtained by an orientation magnetic field generated in the pair of orientation ferromagnetic bodies 11 by applying a predetermined direct current to the coil 5. .
Thereafter, the magnet molded body S is taken out in the same manner as described above with reference to FIGS. By sintering the magnet molded body S, an arc-shaped anisotropic ferrite magnet is obtained.

In the present embodiment, the lower mold 2 is placed close to the magnetic powder G even when the magnetic field applied to the lower mold 2 is low by arranging the lower mold 2 above a predetermined filling depth position at the start of filling. Therefore, the magnetic powder G can be reliably attracted. In particular, the lower die 2 is directly brought into contact with the magnetic powder G by projecting the upper end of the lower die 2 from the mortar surface of the die 3 and entering the magnetic powder G, so that the lower die 2 can be sucked and filled more reliably. Can do. Further, by moving the lower die 2 relative to the die 3 to the filling depth position while filling, the magnetic powder G is increased in the die 3 while the magnetic powder G is strongly attracted. Can be filled with density.
In addition, by setting the direct current according to the upper end position of the lower mold 2 so that the necessary and sufficient magnetic field strength is obtained, the power consumption of the rectifier 4 can be reduced and the manufacturing cycle can be speeded up.

  Next, the production method of the magnet and the molding method of the magnetic powder according to the present invention will be specifically described with reference to examples.

  With the manufacturing method of the present embodiment, several types of magnet molded bodies S are produced by changing the direct current output (hereinafter referred to as rectifier output) of the rectifier 4 at the time of filling, and the die in the filling region of the die 3 at the start of filling. FIG. 6 shows the magnetic field strength in the vicinity of the surface (magnetic field strength at the time of filling in the present invention: x mark in the figure) and product characteristics (magnetic characteristics) (▽ mark in the figure). Also shown in FIG. 6 is the magnetic field strength immediately before molding (marked with ■ in the figure) that affects the product characteristics. This magnetic field strength immediately before molding is a magnetic field strength immediately before pressurizing the magnetic powder G filled with the upper die 1, that is, in a state where the upper die 1 is lowered to the die surface position of the die 3 after filling. As a comparative example, the magnetic field strength when filling with the lower die 2 position at the start of filling lowered to the filling depth position (conventional magnetic field strength during filling: ◇ in the figure) as a comparative example. ) Is also shown in FIG.

  As can be seen from FIG. 6, the magnetic field strength immediately before forming (marked with ■ in the figure) required for saturation of the product characteristics (marked with ▽ in the figure) is the case where the output of the rectifier is 50% or more. Further, the conventional magnetic field strength during filling when the output of the rectifier is 100% (marked in the drawing) is the same as the magnetic field strength during filling of the present invention when the output of the rectifier is 50% (marked in the drawing). Therefore, in the manufacturing method of the present invention, when the output of the rectifier is 50%, the same magnetic field density at the time of filling as in the case of the conventional rectifier output of 100% can be obtained. It has been. That is, according to the present invention, even if the rectifier output at the time of filling is 50%, the magnetic field strength necessary for product characteristics and filling density can be obtained, so that the burden on the rectifier 4 is greatly reduced by halving the rectifier output. It can be reduced and the product cycle can be accelerated.

Next, FIG. 7 shows a magnetic field strength simulation result when filling is performed by a conventional method with a rectifier output of 100% at the start of filling. In addition, FIG. 8 shows the magnetic field strength simulation result when filling is performed by the conventional method with a rectifier output of 50%. Further, FIG. 9 shows a magnetic field strength simulation result when filling is performed by the method of the present invention with 50% rectifier output (new filling). As can be seen from these figures, in the case of the method of the present invention with a rectifier output of 50%, a magnetic field strength of 250 mT (actual measurement 270 mT) similar to that of the conventional rectifier output of 100% is obtained in the vicinity of the die surface in the filling region. ing.
By adopting the present invention in this way, the press operation speed of the dry molding apparatus can be improved by a factor of three compared to the conventional case, and the productivity can be improved by a factor of three. Moreover, the power consumption of the rectifier 4 can be reduced to 1/2, and the power consumption per product can be suppressed to 1/6 ((1/2) × (1/3) = 1/6). did it.

  The technical scope of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, in the present invention, the magnetic powder G is not limited to the above-described ferrite magnetic powder, but can be applied to rare earth magnetic powder. The rare earth magnetic powder can be applied to R-TM-B magnetic powder (R is one or more rare earth elements, TM is Fe, or Fe and Co), and R-Co magnetic powder. Here, R has a concept including Y, and includes one or more of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, and Y. Selected. Further, in order to improve the coercive force, one or more elements such as Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, Ag and Ga are used. Two or more kinds may be contained. The R—Co based magnetic powder contains R, one or more elements selected from Fe, Ni, Mn, and Cr, and Co. In this case, it preferably further contains one or more elements selected from Cu or Nb, Zr, Ta, Hf, Ti and V, and particularly preferably from Cu and Nb, Zr, Ta, Hf, Ti and V. Containing one or more selected elements. Among these, in particular, an intermetallic compound of Sm and Co, preferably an Sm ₂ Co ₁₇ intermetallic compound, is the main phase, and a subphase mainly composed of SmCo ₅ is present at the grain boundary.

FIG. 3 is a cross-sectional view of the main part configuration showing the operation of the dry molding apparatus from pressure molding to magnet molding removal in the magnet manufacturing method, magnetic powder molding method and dry molding apparatus according to one embodiment of the present invention. In one Embodiment which concerns on this invention, it is a top view which shows the principal part structure of the dry-type molding apparatus in the state which removed the upper mold | type. In one Embodiment which concerns on this invention, it is sectional drawing of the principal part structure which shows operation | movement of the dry-type shaping | molding apparatus after taking out a magnet molded object to the time of a filling start. In one Embodiment which concerns on this invention, it is sectional drawing of the principal part structure which shows operation | movement of the dry-type shaping | molding apparatus from the filling start to the completion of filling. In one Embodiment which concerns on this invention, it is sectional drawing of the principal part structure which shows operation | movement of the dry-type shaping | molding apparatus after completion of filling to the time of pressure molding. In the Example which concerns on this invention, it is a graph which shows the magnetic field intensity just before shaping | molding at the time of changing a rectifier output, the magnetic field intensity at the time of filling, and a product characteristic. It is a graph which shows the magnetic field intensity | strength simulation result at the time of filling with 100% of rectifier outputs in the prior art example which concerns on this invention. In the prior art example which concerns on this invention, it is a graph which shows the magnetic field strength simulation result at the time of filling with 50% of rectifier outputs. In the Example which concerns on this invention, it is a graph which shows the magnetic field strength simulation result at the time of filling with 50% of rectifier outputs. In the prior art example which concerns on this invention, it is sectional drawing of the principal part structure which shows the state of the dry-type molding apparatus at the time of filling.

Explanation of symbols

  1 Upper mold, 2 Lower mold, 2a Lower punch (ferromagnetic part), 3 Die mold (die), 4 Rectifier, 5 Coil, 6 Material supply box (material supply part), 8 Powder filling mechanism, 9 Magnetic field generation mechanism 10 type moving mechanism, G magnetic powder, K molding area

Claims (8)

The filling of the magnetic powder into the die is started in a state where the lower die that has generated the magnetic field is disposed above the predetermined filling depth position, and the lower die is placed at the filling depth position while filling the magnetic powder. A filling step of moving relative to the die until
A magnet manufacturing method comprising: a molding step in which an upper die is relatively moved into the die in a state where the magnetic powder is completely filled, and the magnetic powder is pressure-molded in a magnetic field.   2. The method of manufacturing a magnet according to claim 1, wherein at the start of filling, the upper end of the lower mold protrudes from the upper end surface of the die and enters the magnetic powder to be filled. 3.   The method for producing a magnet according to claim 1, wherein the magnetic powder is a ferrite magnetic powder having an average particle diameter of 1 μm or less. The filling of the magnetic powder into the die is started in a state where the lower die that has generated the magnetic field is disposed above the predetermined filling depth position, and the lower die is placed at the filling depth position while filling the magnetic powder. A filling step of moving relative to the die until
A molding method of magnetic powder, comprising: a molding step of pressure-molding the magnetic powder by relatively moving the upper die into the die in a state where the filling of the magnetic powder is completed. A filling step of filling magnetic powder into the filling region in the die from above;
A molding step of pressure-molding the magnetic powder by relatively moving the upper die into the die in a state where the filling of the magnetic powder is completed,
The filling step generates a magnetic field in a filling region in the die and sets the magnetic field strength to be maximum in the vicinity of the upper end surface of the die at the start of filling, and the magnetic field strength while filling the magnetic powder. A method for forming a magnetic powder, characterized in that the position at which the maximum value is reduced is lowered below the filling region. A dry molding apparatus for dry molding magnetic powder,
A lower mold and an upper mold that can move relative to the die; and
A powder filling mechanism for filling the magnetic powder from above into the die;
A magnetic field generating mechanism for generating a magnetic field from the lower mold,
A mold moving mechanism that disposes the lower mold above a predetermined filling depth position at the start of filling, and moves the lower mold relative to the die to the filling depth position while filling; A dry-type molding apparatus comprising: The powder filling mechanism includes a material supply unit that accommodates the magnetic powder and can fill the die with the magnetic powder from a lower opening;
The dry molding according to claim 6, wherein the mold moving mechanism causes the upper end of the lower mold to protrude from the upper end surface of the die and enter the magnetic powder in the material supply unit at the start of the filling. apparatus. The magnetic field generating mechanism includes a coil wound around the die;
A ferromagnetic portion provided in the lower mold;
The dry molding apparatus according to claim 6 or 7, further comprising a rectifier capable of changing a direct current applied to the coil in accordance with an upper end position of the lower mold at the start of the filling.

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